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Deutsche Tagung fur ¨ Forschung mit Synchrotronstrahlung, Neutronen und ¨ Ionenstrahlen an Großgeraten 2006

¨ Hamburg, Universitat 04.-06. Oktober 2006 Programm und Abstracts

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Deutsche Tagung fur ¨ Forschung mit Synchrotronstrahlung, Neutronen und ¨ Ionenstrahlen an Großgeraten 2006 ¨ Hamburg, Universitat 04.-06. Oktober 2006 Programm und Abstracts

¨ Hrsg.: A. Schreyer, R. Willumeit, R. Rohlsberger, L. Incoccia-Hermes, K. Griewatsch

Komitee Forschung mit Neutronen

Komitee Erforschung kondensierter Materie

KFS

mit nuklearen Sonden und Ionenstrahlen KOMITEE Forschung mit Synchrotronstrahlung

Impressum: Herausgeber: A. Schreyer, R. Willumeit, R. R¨ ohlsberger, L. Incoccia-Hermes, K. Griewatsch Deutsche Tagung f¨ ur Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großger¨ aten 2006 Programm und Abstracts Universit¨at Hamburg Oktober 2006 Veranstalter: Deutsches Elektronen-Synchrotron DESY und GKSS Forschungszentrum Geesthacht GmbH Programmkomitee: H. Schober, O. Pietsch, H. Hofs¨ass, A. Schreyer, R. R¨ ohlsberger

c GKSS Forschungszentrum Geesthacht GmbH, 2006

Alle Rechte vorbehalten.

Mit freundlicher Unterst¨ utzung durch

ESRF

Vorwort Die Nutzung von Großger¨ aten zur Erforschung der kondensierten Materie hat in den letzten Jahren zu einer Vielzahl von herausragenden Forschungsergebnissen gef¨ uhrt. Experimente mit Neutronen, Synchrotron- und Ionenstrahlung bieten komplement¨ are M¨ oglichkeiten, die Eigenschaften der Materie in all ihren Facetten auszuleuchten. Die SNI2006 stellt ein gemeinsames Forum f¨ ur die Pr¨ asentation neuester Erkenntnisse, f¨ ur den Ideenaustausch und die weitere Vernetzung der Methoden dar. Eine spezielle Veranstaltung widmet sich der allgemeinverst¨ andlichen Darstellung der Forschung f¨ ur ¨ die Offentlichkeit. Die Tagung findet auf Initiative der Kommission Erforschung kondensierter Ma” terie mit Großger¨ aten“ (KEKM), der Dachorganisation der Komitees f¨ ur Forschung mit Neutronen (KFN), Synchrotronstrahlung (KFS) und nuklearen Sonden und Ionenstrahlen (KFSI) statt. Sie kn¨ upft an fr¨ uhere BMBF-Statusseminare (Helgoland 1986, Kloster Seeon 1997) an und soll die Komplementarit¨ at der Methoden deutlich machen und den wissenschaftlichen Austausch befl¨ ugeln. Die SNI2006 bietet ein Forum f¨ ur ein breites Spektrum von Disziplinen und deren Vernetzung. Folgende Themenbereiche werden abgedeckt: Weiche Materie Nanstrukturen und Grenzfl¨ achen Mikroskopie und Tomographie Struktur und Dynamik Chemische Prozesse und Phasen¨ uberg¨ ange Teilchen und Kerne

Magnetismus Biologische Systeme und Medizin Materialien/Werkstoffe Methoden und Instrumentierung Materie unter extremen Bedingungen

Ein H¨ ohepunkt der Tagung wird ein Senatsempfang am Abend des 05.10.2006 im Hamburger Rathaus sein, bei dem der Hamburger Senator f¨ ur Wissenschaft und Gesundheit, J¨ org Dr¨ ager und Schleswig-Holsteins Minister f¨ ur Wissenschaft, Wirtschaft und Verkehr Dietrich Austermann sowie eine/e VertreterIn des BMBF Grußworte sprechen werden. Die wichtige Rolle der Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großger¨ aten wird anschließend in einem popul¨ arwissenschaftlichen Vortrag beispielhaft von Helmut Dosch aufgezeigt werden. Im Anschluss daran laden der Senat der Stadt Hamburg und die SNI2006 zu einem Buffet und geselligem Zusammensein ein. Wie der Zufall will, findet die SNI2006 exakt 20 Jahre nach dem ersten nationalen Treffen der Pioniere auf Helgoland statt. Mit rund 500 erwarteten Teilnehmern wird die SNI2006 die bisher wohl gr¨ oßte nationale wissenschaftliche Tagung dieses wachsenden Forschungsgebiets werden. Die Organisatoren begr¨ ußen Sie hier in Hamburg und w¨ unschen Ihnen aufregenden Diskussionen, viele neuen Ideen, interessante neuen Kollaborationspartner und vor allem viel Spaß. Willkommen in Hamburg!

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8:00

Mittwoch, 4. Oktober 2006 Registrierung

Donnerstag, 5. Oktober 2006 8:30

Freitag, 6. Oktober 2006 8:30

Plenarvortr¨ age: Butz, Pyzalla 9:30 10:00 10:30 11:00

9:40 Begr¨ ußung Plenarvortrag: Zabel Kaffeepause

9:40 Parallelsitzungen: Instrumentierung, Weiche Materie, Materialien

10:40 11:10

Parallelsitzungen: Mikroskopie/Tomographie, Dynamik, Nanostrukturen und Grenzfl¨ achen 12:30

Parallelsitzungen: Biologie, Magnetismus, Materialien, Weiche Materie 10:40

Kaffeepause

11:10

Parallelsitzungen: Methoden und Instrumentierung S, N, SNI 12:30

Mittagspause

Plenarvortr¨ age: M¨ uller,Braun

13:00

Kaffeepause Parallelsitzungen: Biologie, Magnetismus, Chemische Prozesse

12:30 Mittagspause

Mittagspause

Postersitzung B Magnetismus, Nano/Grenzfl¨ achen, Weiche Materie, extreme Bedingungen, Materialien, Teilchen und Kerne

14:00 Postersitzung A Instrumentierung, Biologie, Struktur/Dynamik, Chem. Prozesse, Mikroskopie/Tomographie

15:30

15:30 SNI f¨ ur Neugierige Salditt, Kuhs, Dollinger

Plenarvortr¨ age: Meyer,Fink

17:00

Parallelsitzungen: Magnetismus, Struktur, Nanostrukturen und Grenzfl¨ achen

18:00

16:00

Schlusswort Bustransfer zu DESY und GKSS Besichtigungen von DESY und GKSS

Bustransfer ins Rathaus

17:30

Senatsempfang im Rathaus Grußworte: Dr¨ ager/Austermann Vortrag: Dosch

19:00 Verleihung Wolfram-Prandl-Preis

Plenarvortr¨ age: Feldhaus, Neuhaus, Altarelli, Trautmann 14:55

16:30

19:30

13:35

19:30 Buffet

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19:00

R¨ uckkehr/Ankunft am Bahnhof bzw. Flughafen

Mittwoch, 4. Oktober 2006, vormittags 8:00

¨ Offnung des Tagungsb¨ uros, Registrierung

Plenarsitzung, H¨ orsaal ESA A 9:30 10:00

10:30

Begr¨ ußung Hartmut Zabel (Ruhr-Universit¨ at Bochum) Magnetische Schichtsysteme: Tiefe Einblicke mit polarisierter Neutronenreflexion und resonanter magnetischer R¨ ontgenstreuung

M-PV1

Kaffeepause

Parallelsitzungen 11:00

11:30

11:50

12:10

12:30

M-V1

Dynamik ESA B Michael Krisch (ESRF) Inelastic x-ray scattering from phonons: status and perspectives M-V5

Gerd Schneider (BESSY) Nano-Tomography and Spectromicroscopy with the new BESSY X-Ray Microscope M-V2 Th. Schmidt (Universit¨ at W¨ urzburg) SMART - an aberration corrected spectromicroscope for surface characterization with high resolution M-V3 Christoph Greubel (Univ.d.Bundeswehr) Untersuchung der Dynamik von DNA Reparaturfaktoren in lebenden Zellen am Rasterionenmikroskop SNAKE M-V4

Philippe Wernet (BESSY) Wasser in neuem Licht – R¨ ontgenspektroskopie liefert neue Erkenntnisse zur Nahordnung in Wasser M-V6 Walter Schirmacher (TU M¨ unchen) Collective excitations in a molten transition metal M-V7 Peter Fouquet (ILL) Combining neutron and helium spin echo: A powerful tool to clarify surface effects in confined systems M-V8

Mikroskopie und Tomographie Michael Schulz (TU M¨ unchen) Neutron Imaging Methods at FRM-II

ESA A

Mittagspause (bis 14:00)

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Nanostrukturen und Grenzfl¨ achen ESA J Wolfgang Bolse (Universit¨ at Stuttgart) Instabilit¨ at und Selbstorganisation bei der Bestrahlung von Schichtpaketen mit hochenergetischen Ionen M-V9 Daniel Schwen (Universit¨ at G¨ ottingen) Electronic properties of graphite-like ion tracks in insulating tetrahedral amorphous carbon M-V10 Olaf Magnussen (Universit¨ at Kiel) Transmission surface x-ray diffraction studies of solid-liquid and liquid-liquid interfaces M-V11 Jochen Stahn (ETH Z¨ urich) Antiphase magnetic proximity effect in perovskite superconductor / ferromagnet multilayers M-V12

Mittwoch, 4. Oktober 2006, nachmittags Postersitzung A 14:00

ESA Westfl¨ ugel (Foyer und Raum 221) : Instrumentierung und Methoden, Mikroskopie und Tomographie ESA Ostfl¨ ugel (Foyer und Raum 221) : Struktur und Dynamik, Chemische Prozesse und Phasen¨ uberg¨ ange, Biologische Strukturen und Medizin Foyer vor H¨ orsaal ESA B : Großger¨ ate stellen sich vor

Plenarsitzung, H¨ orsaal ESA A 16:30

Andreas Meyer (DLR K¨ oln): Structure and dynamics of undercooled metallic melts

M-PV2

17:00

Rainer Fink (Universit¨ at Erlangen): Zone-plate based microspectroscopy with soft x-rays

M-PV3

Parallelsitzungen 17:40

18:00

18:20

18:40

Magnetismus ESA A Wolfgang Kuch (FU Berlin) Time, layer, and spatially resolved magnetic domain imaging of layered magnetic structures by x-ray magnetic circular dichroism photoelectron emission microscopy M-V13 Christian Stamm (BESSY) Ultraschnelle Magnetisierungsdynamik untersucht mit Femtosekunden-R¨ ontgenpulsen M-V14 Klaus Habicht (HMI) Time-resolved SANS studies of field induced ordering in Ferrofluids M-V15

Struktur ESA B Susan Schorr (HMI) Neutron diffraction study of the multinary chalcogenides CuFe1−x Znx SnS4 - a potential photovoltaic material M-V17 Stefan Kowarik (Universit¨ at T¨ ubingen) Real-time observation of structural and orientational transitions in organic semiconductor growth M-V18 Manfred Deicher (Univ. des Saarlandes) Electrical and structural properties of DX defects in CdTe M-V19

A. Michels (Universit¨ at des Saarlandes) Dipolar correlations in nanocomposites M-V16

Kurt Walther (GFZ Potsdam) Neutronographische Texturanalyse zur Absch¨ atzung statischer bzw. dynamischer Deformationsanteile in Carrara-Marmor (Appenin) M-V20

Plenarsitzung, H¨ orsaal ESA A 19:00

Verleihung des Wolfram-Prandl Preises, Vortrag des Preistr¨ agers (bis 19:30)

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Nanostrukturen und Grenzfl¨ achen ESA J Gernot Buth (FZ Karlsruhe) Structural Aspects of Porphyrins as Biomimetic Antennas M-V21 Dietmar Schwahn (FZ J¨ ulich) Inhibition of Calcium Phosphate Formation in the Presence of the Protein Fetuin-A M-V22 J¨ org Zegenhagen (ESRF) Photoelektronen Spektroskopie mit harter R¨ ontgenstrahlung f¨ ur chemisch sensitive Strukturanalyse und Valenzbandspektroskopie M-V23 Reinhard Neder (Universit¨ at W¨ urzburg) Structure determination of nanoparticles using the pair distribution function M-V24

Donnerstag, 5. Oktober 2006, vormittags Plenarsitzung, H¨ orsaal ESA A 8:30

Tilman Butz (Universit¨ at Leipzig): Nukleare Sonden und Ionenstrahlen f¨ ur die Zukunft

D-PV4

9:00

Anke Pyzalla (MPI f¨ ur Eisenforschung): Applications of Synchrotron Radiation, Neutrons and Ions in Engineering Material Science

D-PV5

Parallelsitzungen 9:40

10:00

10:20

10:40 11:10

11:30

11:50

12:10

12:30

Instrumentierung SNI ESA A Hermann Franz (DESY) PETRA III: a new high brilliance synchrotron radiation source at DESY D-V25 Reinhard Neumann (GSI) Materialforschung mit energiereichen Schwerionen bei der GSI D-V26 Alan Tennant (HMI) New High Field Magnet for Neutron Scattering at Hahn-Meitner Institute D-V27

Weiche Materie ESA B Maikel C. Rheinst¨ adter (ILL) Using Neutron Spectroscopy to Study Collective Dynamics of Biological and Model Membrane Systems D-V28 Roland Steitz (HMI) Swelling kinetics and structural changes of polyelectrolyte multilayers in contact with aqueous solution and water vapor D-V29 Christian Gutt (DESY) Dynamics of soft matter surfaces investigated with X-ray photon correlation spectroscopy D-V30

Materialien und Werkstoffe ESA J Heinz-G¨ unter Brokmeier (TU Clausthal) Kristallographische Textur industrierelevanter Komponenten D-V31 Bernd Hasse (TU Berlin) Bestimmung von Spannungsfeldern mit hoher Ortsaufl¨ osung D-V32 Ulrich A. Glasmacher (Univ. Heidelberg) Phase Transitions in Solids Stimulated by Simultaneous Exposure to High Pressure and Relativistic Heavy Ions D-V33

Instrumentierung N ESA B Wolfgang Treimer (HMI) Neutron Tomography: Status Quo and Future Developments D-V38 Christian Gr¨ unzweig (PSI) Neutron phase contrast imaging using a grating interferometer D-V39 Adrian R¨ uhm (MPI Stuttgart/FRM-II) N-REX + - The New Neutron / X-Ray Reflectometer for Materials Science at FRM II D-V40 Ulf Garbe (GKSS) High Gain Focusing Optics for Stress and Local Texture Measurement at the FRM-II Materials Science Diffractometer D-V41

Instrumentierung SNI ESA J Christoph Hugenschmidt (TU M¨ unchen) Positron Experiments and Instrumentation at the FRM-II Positron Source D-V42 Elke Pl¨ onjes (DESY) Wavefront Studies at the Free-Electron Laser FLASH D-V43 Yuri Shvyd’ko (APS) Progress in the Development of New Optics for Very High Resolution Inelastic X-Ray Scattering Spectroscopy D-V44 Jochen Krempel (ILL) Von Einstein zum Kilogramm D-V45

Kaffeepause Instrumentierung S ESA A Lothar Str¨ uder (MPI M¨ unchen) High Speed Semiconductor Detectors for Experiments at LCLS and XFEL D-V34 Christian Schroer (TU Dresden) Hard X-Ray Microscopy based on Refractive X-Ray Lenses D-V35 Tilo Baumbach (ANKA) Synchrotron-Radiation Computed Laminography - A New Method for the Tree-Dimensional Imaging of Flat Objects D-V36 Axel Bernhard (Universit¨ at Karsruhe) Supraleitende Undulatoren an ANKA D-V37 Mittagspause vor Ort (bis 13:00)

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Donnerstag, 5. Oktober 2006, nachmittags Postersitzung B 13:00

ESA Westfl¨ ugel (Foyer und Raum 221) : Magnetismus, Nanostrukturen und Grenzfl¨ achen ESA Ostfl¨ ugel (Foyer und Raum 221) : Weiche Materie, Werkstoffe und Materialien, Materie unter extremen Bedingungen, Teilchen und Kerne Foyer vor H¨ orsaal ESA B : Großger¨ ate stellen sich vor

Plenarsitzung (¨ offentlich): SNI f¨ ur Neugierige, H¨ orsaal ESA A 15:30

16:00

16:30

Tim Salditt (Institut f¨ ur R¨ ontgenphysik, Universit¨ at G¨ ottingen) Neues Licht f¨ ur mehr Sicht: R¨ ontgenblick im Nanokosmos

D-NV1

Werner F. Kuhs (Abteilung Kristallographie, Universit¨ at G¨ ottingen) Kristalle aus Gas und Wasser: Gashydrate als Herausforderung f¨ ur Wissenschaft und Technik

D-NV2

G¨ unther Dollinger (Institut f¨ ur Angewandte Physik und Messtechnik, Universit¨ at der Bundeswehr M¨ unchen) Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen

D-NV3

Senatsempfang im Hamburger Rathaus 17:00

Bustransfer ins Rathaus

18:00

Grußworte J¨ org Dr¨ ager, Ph.D., Senator f¨ ur Wissenschaft und Gesundheit der Freien und Hansestadt Hamburg Dietrich Austermann, Minister f¨ ur Wissenschaft, Wirtschaft und Verkehr des Landes Schleswig-Holstein Vortrag Prof. Dr. Helmut Dosch, Direktor am Max-Planck Institut f¨ ur Metallforschung, Stuttgart Die Eroberung des Nanokosmos - Von der Grundlagenforschung zu neuen Technologien

19:30

Buffet

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D-AV1

Freitag, 6. Oktober 2006, vormittags Plenarsitzung, H¨ orsaal ESA A 8:30

Martin M¨ uller (Universit¨ at Kiel): Struktur und Dynamik biologischer Materialien

F-PV6

9:00

Wolfgang Braun (Paul-Drude Institut): In-situ R¨ ontgenbeugungsuntersuchungen epitaktischer Kristallwachstumsprozesse

F-PV7

Parallelsitzungen 09:40

10:00

10:20

10:40 11:10

11:30

11:50

12:10

Biologische Systeme ESA A L. T. Wasserthal (UniErlangen) Synchroton videography and tomography combined with physiological measurements for analysis of circulation and respiration dynamics in insects F-V55 S. Fiedler (EMBL Hamburg) Concepts and highlights in structural biology at EMBL-Hamburg: Towards future applications at PETRA-III F-V56 A. Marx (MPG Hamburg) Structure of the Protein Kinase MARK/Par-1 : Catalytic and UBA Domain F-V57

Magnetismus ESA B K. Theis-Br¨ ohl (Univ. Bochum) Exchange bias instability in a bilayer with an ion beam imprinted stripe pattern of FM/AFM interfaces F-V52 C. M. Schneider (FZ J¨ ulich) A View on Fast Magnetization Dynamics: Studies by XPEEM F-V53 Thomas Diederich (DESY) Antiferromagnetic coupling between the oxide layers in Fe/Feoxide superlattices F-V54

Kaffeepause Biologische Systeme ESA A Thomas Nawroth (Universit¨ at Mainz) Indirect Radiation Therapy of Cancer by Neutrons and Synchrotron Radiation F-V58 Himadri Shikhar Gupta (MPI Golm) Nanostructure and mechanics in hierarchical biocomposites F-V59 Volker Sch¨ unemann (TU Kaiserslautern) Inelastic Nuclear Resonant Scattering as a Local Probe for the Dynamics of Iron-Sulfur Proteins F-V60 Ingo K¨ oper (MPI f¨ ur Polymerforschung) Festk¨ orperunterst¨ utzte Modellmembranen F-V61

Materialien ESA C P. Klaus Pranzas (GKSS) Untersuchung von nanokristallinen Metallhydrid - Wasserstoffspeichermaterialien mit Hilfe der Neutronen- und R¨ ontgenkleinwinkelstreuung F-V49 K. Nikolowski (TU Darmstadt) Combined neutron and synchrotron diffraction study of Li(Ni,Co)O2 in Li-ion batteries at different charging states F-V50 Bernd Leiss (Univ. G¨ ottingen) Neutron Texture Analyses of Rocks - Recent Applications and Perspectives F-V51

Magnetismus ESA B Arno Hiess (ILL) Die magnetischen und supraleitenden Eigenschaften von UPd2 Al3 - mikroskopische Einblicke durch Streumethoden F-V66 Dimitri Argyriou (HMI) Melting of the magneto-electric state in TbMnO3 F-V67 Peter Wochner (MPI f¨ ur Metallforschung) Orbital Polaron Lattice Formation in Lightly Doped La1−x Srx MnO3 F-V68 Hans-Henning Klauss (TU Braunschweig) Magnetism and Superconductivity in Electron Doped Cuprates: A Muon Spin Relaxation Study on Thin Films of La2−x Cex CuO4 F-V69

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Weiche Materie ESA J W. Ensinger (Univ. Marburg) Degradation of polyimide (Kapton) induced by irradiation with swift heavy ions F-V46 A. Radulescu (FZ J¨ ulich) Multilevel structures formed by partially crystalline polymers in solution: from fundamentals to applications F-V47 Marion Kuhlmann (DESY) Tomographic small-angle x-ray scattering of nanostructured softmatter materials F-V48

Chemische Prozesse ESA J G¨ otz Eckold (Universit¨ at G¨ ottingen) Zeitaufgel¨ oste Phononenspektroskopie F-V62 Jan-Dierk Grunwaldt (ETH Z¨ urich) Time-resolved and operando XAS studies on heterogeneous catalysts in liquid phase and in supercritical fluids F-V63 Reinhard Denecke (Universit¨ at Erlangen) Surface reactions studied by in-situ x-ray photoelectron spectroscopy F-V65 Tobias Panzner (Universit¨ at Siegen) Coherence experiments with white synchrotron radiation F-V64

Freitag, 6. Oktober 2006, nachmittags 12:30 13:35

Mittagspause

Plenarsitzung, H¨ orsaal ESA A 13:35

14:00

14:25

14:40

14:55

Josef Feldhaus (DESY) Current research at FLASH

F-PV8

J¨ urgen Neuhaus (FRM-II) Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II)

F-PV9

Massimo Altarelli (European XFEL Project Team, DESY) The European X-Ray Free-Electron Laser Facility in Hamburg

F-PV10

Christina Trautmann (GSI) The Future FAIR accelerator facility for Antiprotons and Ion Research

F-PV11

Verleihung der Posterpreise und Schlusswort (Andreas Schreyer, GKSS)

15:30

Bustransfer zu DESY und GKSS (Besichtigungen)

16:00

Besichtigungen von DESY und GKSS

19:00

R¨ uckkehr/Ankunft am Bahnhof bzw. Flughafen

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Programm der Postersitzungen Postersitzung A: Mittwoch, d. 4. 10. 2006, 14:00 - 16:30 Flu ¨ gelbau ESA - West Methoden und Instrumentierung Mikroskopie und Tomographie

M-P1 – M-P96 M-P97 – M-P114

Flu ¨ gelbau ESA - Ost Struktur und Dynamik Chemische Prozesse und Phasen¨ uberg¨ange Biologische Systeme und Medizin

M-P115 – M-P167 M-P168 – M-P180 M-P181 – M-P213

Postersitzung B: Donnerstag, d. 5. 10. 2006, 13:00 - 15:30 Flu ¨ gelbau ESA - West Magnetismus Nanostrukturen und Grenzfl¨achen Weiche Materie

D-P214 – D-P266 D-P267 – D-P320 D-P321 – D-P360

Flu ¨ gelbau ESA - Ost Materie unter extremen Bedingungen Materialien und Werkstoffe Teilchen und Kerne

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D-P361 – D-P368 D-P369 – D-P411 D-P412 – D-P415

Allgemeine Hinweise

Tagungsort Die Tagung findet im Hauptgeb¨ aude der Universit¨ at Hamburg statt. Das Geb¨ aude liegt zentral, gegen¨ uber dem Bahnhof Dammtor. Adresse: Edmund-Siemers-Allee 1, D-20146 Hamburg. Ein Stadtplan der n¨ aheren Umgebung sowie ein Netzplan der Hamburger U- und SBahnen befindet sich in dem Eventkalender“ in Ihrer Konferenztasche. ”

Tagungsbu ¨ ro Das Tagungsb¨ uro ([email protected]) befindet sich im Hauptgeb¨ aude der Universit¨ at und ist t¨ aglich ge¨ offnet: am Mi., den 04.10. von 8:00 bis 19:30 Uhr am Do., den 05.10. von 8:00 bis 15:30 Uhr am Fr., den 06.10. von 8:00 bis 15:30 Uhr

Mittagessen Die Teilnehmer haben die M¨ oglichkeit, das Mittagessen in den nahegelegenen Mensen einzunehmen, siehe Umgebungsplan auf Seite 12. Am Donnerstag wird am Tagungsort f¨ ur die Konferenzteilnehmer ein Imbiss angeboten.

Vortr¨ age In den H¨ ors¨ alen steht je ein Computer mit angeschlossenem Beamer und ein OverheadProjektor zu Ihrer Verf¨ ugung. Eigene Laptops k¨ onnen angeschlossen werden. Bitte u ufen Sie die Wiedergabe Ihres Vortrages rechtzeitig vor der Sitzung. ¨berpr¨

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¨ Offentliche Veranstaltung und Rahmenprogramm

SNI fu ¨ r Neugierige Am Nachmittag des 05.10.2006 wird eine ¨ offentliche Sitzung mit allgemeinverst¨ andlichen Vortr¨ agen zu den Themen der SNI stattfinden. Alle Interessierten sind eingeladen! Termin: 05.10.2006, 15:30 Uhr, Hauptgeb¨ aude der Universit¨ at Hamburg 15:30 Tim Salditt (Institut f¨ ur R¨ ontgenphysik, Universit¨ at G¨ ottingen): Neues Licht f¨ ur mehr Sicht: R¨ ontgenblick im Nanokosmos 16:00 Werner F. Kuhs (GZG, Abteilung Kristallographie, Universit¨ at G¨ ottingen): Kristalle aus Gas und Wasser: Gashydrate als Herausforderung f¨ ur Wissenschaft und Technik 16:30 G¨ unther Dollinger (Institut f¨ ur Angewandte Physik und Messtechnik, Universit¨ at der Bundeswehr M¨ unchen): Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen

Senatsempfang im Hamburger Rathaus Ein H¨ ohepunkt der Tagung wird der Senatsempfang im Hamburger Rathaus sein, bei dem J¨ org Dr¨ ager, Ph.D., Senator f¨ ur Wissenschaft und Gesundheit der Freien und Hansestadt Hamburg, und Dietrich Austermann, Minister f¨ ur Wissenschaft, Wirtschaft und Verkehr des Landes Schleswig-Holstein sowie eine/e VertreterIn des BMBF Grußworte sprechen werden. Die Bedeutung der Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen wird in einem popul¨ arwissenschaftlichen Vortrag verdeutlicht werden. Im Anschluss daran laden der Senat der Stadt Hamburg und die SNI2006 zu einem Buffet und geselligem Zusammensein ein.

Besichtigung der Helmholtz-Zentren DESY (Hamburg) oder GKSS (Geesthacht) Die Konferenzteilnehmer und ihre Begleitung haben die M¨ oglichkeit, im Anschluss an die Konferenz wahlweise DESY (Hamburg) oder GKSS (Geesthacht) zu besichtigen. Alle Kosten daf¨ ur sind im Konferenzbeitrag enthalten. Eine Anmeldung bis sp¨ atestens 04.10.2006 ist erforderlich. Die Anzahl der Teilnehmer ist aus organisatorischen Gr¨ unden begrenzt. Termin: 06.10.2006, 15:30-19:00 Uhr Abfahrt um 15:30 Uhr vom Tagungsort R¨ uckfahrt zum Hauptbahnhof oder Flughafen mit Ankunft um 19:00 Uhr

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Lageplan

Mensa Studierendenhaus (Hauptmensa) Mensa Campus Mensa Philosophenturm

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¨ Abstracts: Plenarvortrage

Plenarvortrag

Mi., 10:00–10:30

M-PV1

Magnetische Schichtsysteme: tiefe Einblicke mit polarisierter Neutronenreflexion und resonanter magnetischer R¨ ontgenstreuung Hartmut Zabel1 1

Lehrstuhl f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, D44780 Bochum K¨ unstliche magnetische Stapelschichten sowie laterale magnetische Anordnungen haben in den letzten Jahren v¨ ollig neue M¨ oglichkeiten er¨ offnet, Spinstrukturen und Spintransport auf der Nanometerskala zu untersuchen, zu manipulieren und f¨ ur gezielte Anwendungen Maß zu schneidern. Dabei spielt die Grenzfl¨ ache zwischen ferromagnetischen und paramagnetischen, antiferromagnetischen, ferroelektrischen, halbleitenden oder supraleitenden Schichten eine herausragende Rolle. Beispielhaft ist die Austauschasymmetrie, die beim Wachstum von ferromagnetischen Schichten auf antiferromagnetischen Substraten beobachtet wird. Hier f¨ uhrt die Austauschwechselwirkung an der Grenzfl¨ ache sowohl zu einer Verschiebung als auch zu einer Verbreiterung der ferromagnetischen Hysterese. Bei Reduzierung der lateralen Dimension durch lithographische Methoden kann man zus¨ atzlich auf die ferromagnetischen und antiferromagnetischen Dom¨ anengr¨ oßen Einfluss zu nehmen. Mit polarisierter Neutronenreflexion im diffusen nicht-spekul¨ aren Bereich kann die Spinunordnung an den inneren Grenzfl¨ achen und die Dom¨ anenbildung w¨ ahrend der Ummagnetisierung beobachtet werden, w¨ ahrend resonante magnetische R¨ ontgenstreuung elementspezifisch die Bestimmung der magnetischen Hysterese sowohl in der ferro- wie auch in der antiferromagnetischen Schicht erlaubt. Die Kombination dieser beiden Methoden hat inzwischen zu einer weitgehenden Aufkl¨ arung der Grenzfl¨ achenprozesse gef¨ uhrt, die fast f¨ unfzig Jahre lang die Magneti¨ ker plagte. Ahnlich kompliziert ist die Situation der Heusler-Legierungsschichten, die wegen ihrer theoretisch vorausgesagten hundertprozentigen Spinpolarisation als ferromagnetische Elektrode in Spinventilen besonders geeignet w¨ aren. Jedoch ist die hohe Polarisation an die geordnete L21-Struktur gekn¨ upft, die in Grenzfl¨ achenn¨ ahe zu Tunnelbarrieren nur schwer realisiert werden kann. Zur Optimierung der Polarisation muss unabh¨ angig das chemische, strukturelle und magnetische Profil der Heuslerschichten als Funktion von Wachstumsparametern und Schichtdicken charakterisiert werden. Dies gelingt nur durch die Kombination von polarisierter Neutronenreflexion und resonanter magnetischer R¨ ontgenstreuung. In diesem Vortrag werden die Streumethoden kurz vorgestellt und an Hand von aktuellen Beispielen zu magnetischen Heteroschichten diskutiert. Diese Arbeiten werden dankenswerterweise durch die DFG (SFB 491) and das BMBF (05KS4PCA and 03ZA6BC1) unterst¨ utzt.

Plenarvortrag

Mi., 16:30–17:00

M-PV2

Structure and Dynamics of Undercooled Metallic Melts Andreas Meyer1 1

Deutsches Zentrum f¨ ur Luft und Raumfahrt, Institut f¨ ur Raumsimulation, 51170 K¨ oln

We investigate the atomic motion in multicomponent melts on a Ni-, Zr-, Ti- and Albasis with quasielastic neutron scattering in order to clarify the microscopic transport mechanisms. The high-resolution energy and momentum information emerging from quasielastic neutron scattering experiments allows to study the interplay between structure, viscous flow and atomic diffusion. Our results reveal non-trivial mechanisms of mass transport in these systems. However, in spite of a pronounced chemical short range order on intermediate length scales, the mass transport in these systems is dominated by packing effects like in other hard-sphere like liquids. In a recent experiment we succeeded to process liquid droplets of 6-8 mm in diameter in an electromagnetic levitation device on the neutron time-of-flight spectrometer ToF-ToF of the FRM-II [1]. This containerless processing of the samples not only gives access to experiments on high temperature and chemically reactive liquids, but also allows for undercooling the samples several 100 K below their liquidus. The undercooling and the corresponding slowing down of dynamics allows for a stringent test of theoretical descriptions of dynamics in liquid matter. [1] A. Meyer, S. St¨ uber, D. Holland-Moritz, O. Heinen, T. Unruh, to be published

Plenarvortrag

Mi., 17:00–17:30

M-PV3

Zone-plate based Microspectroscopy with soft x-rays Rainer Fink1 1

Physikalische Chemie II, Univ. Erlangen, Egerlandstraße 3, 91058 Erlangen

With the advance in the fabrication of micro zone plates focusing of x-rays down to about 20 nm has been demonstrated [1]. Taking advantage of the high brilliance of 3rd generation synchrotron sources, high-resolution spectroscopy can be combined with high spatial resolution. Scanning-transmission microspectroscopy offers many different applications with lateral resolutions well below 50 nm routinely in an easy-to use experiment. The operation of the microscope in either He atmosphere or in vacuum allows the investigation of thin solid films and liquid films in wet cells. The BMBF funded PolLux project, which is presently under commissioning at the Swiss Light Source (SLS, Paul Scherrer Institut, Villigen) will be a microspectroscopy facility which offers a wide variety of experimental possibilities in the photon energy range from 260 to 1100 eV. PolLux is an interferometrically controlled STXM based on the ALS polymer STXM design [2]. We make particular use of the high stability of the stored electron beam at the SLS, which is a prerequisite for high spatial resolution. Steering of the beam will even allow one to perform XMCD experiments with fast switching of the helicity or time-resolved experiments (although the instrument is installed at a bending magnet beamline). Several applications of STXM shall be discussed in this contribution. Emphasis will be lying on the investigation of so-called soft matter samples, which were prepared as thin films either by dip- or spin coating. The materials used range from functionalized π-conjugated molecules, molecular magnets, liquid crystal films, and block copolymers. The near-edge x-ray absorption fine structure (NEXAFS) is used to explore the structure-dependent electronic structure of nanostructured selforganized films, which in some cases form small nanosized crystals. Other examples to be discussed will be biologically relevant samples (e.g. human hair, insect eyes), which are sometimes difficult to image in routinely used transmission electron microscopy. Present STXM highlights concern the investigation of the magnetization dynamics in magnetic nanostructures using time-resolved NEXAFS. In these systems, STXM is superior compared to commonly used XPEEM studies [3]. This project is funded by the BMBF under contract 05 KS4WE1/6. [1] Weilun Chao, B.D. Harteneck1, J.A. Liddle, E.H. Anderson, and D.T. Attwood, Nature 435 (2005) 1210 [2] A.L.D. Kilcoyne, T. Tyliszczak et al., J. Synchrotr. Rad. 10(2003) 125 [3] A. Puzic A, B. Van Waeyenberge, K.W. Chou et al., J. Appl. Phys. 97(10) (2005) 10E704

Plenarvortrag

Do., 08:30–09:00

D-PV4

Nukleare Sonden und Ionenstrahlen f¨ ur die Zukunft Tilman Butz1 1

Universit¨ at Leipzig, Fakult¨ at f¨ ur Physik und Geowissenschaften, Linn´estr.5, 04103 Leipzig

Nukleare Sonden, das sind instabile Kerne und Teilchen, werden f¨ ur die Erforschung der Struktur und Dynamik in kondensierter Materie gerne dann eingesetzt, wenn es um h¨ ochste Empfindlichkeit geht. Der Einsatz basiert auf der Detektion der emittierten Teilchen und γ-Strahlung. Strahlen von stabilen Ionen werden sowohl f¨ ur die Analytik als auch f¨ ur die Materialbearbeitung und auch f¨ ur strahlenbiologische Fragestellungen eingesetzt. Daneben gibt es auch Einrichtungen wie ISOLDE/CERN, die radioaktive Ionenstrahlen (RIB) erzeugen. In dem vorliegenden Beitrag wird u ¨ber neueste Entwicklungen auf den folgenden Teilgebieten berichtet: a) neue Quellen: RIB am CERN f¨ ur gest¨ orte Winkelkorrelation (PAC), EmissionsChanneling, Photolumineszenz, Deep Level Transient Spectroscopy, Tracerdiffusion; Synchrotron-basierte PAC (SRPAC)unter Ausnutzung der Polarisation; gepulste Positronenquellen; low-energy Myonen am PSI; b) neue Detektoren: Szintillatoren mit exzellenter Energie- und Zeitaufl¨ osung; Szintillatoren f¨ ur SRPAC bei 60 KeV; ortsaufl¨ osende Detektoren f¨ ur Emissions-Channeling; c) neue Spektrometer: voll-digitale PAC-Spectrometer, geeignet unter anderem f¨ ur gestreckte Kaskaden“ mit mehreren prompten γ-Quanten; ” d) neue Datenanalyseverfahren.

Plenarvortrag

Do., 13:00–15:30

D-PV5

Applications of Synchrotron Radiation, Neutrons and Ions in Engineering Material Science Anke Rita Pyzalla1 1

Max-Planck-Institut f¨ ur Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 D¨ usseldorf, Germany Neutron diffraction techniques have become an established technique in engineering material science. Neutron small angle scattering and neutron diffraction are valuable tools for material characterization and the development of new materials. In addition neutron diffraction, in particular residual stress analyses and neutron tomography reveal unique information due to allowing a non-destructive testing of components. Neutron diffraction and tomography thus can play an important role for the optimization of manufacturing processes. The availability of synchrotron radiation has strongly expanded the spectrum of techniques available for investigating material microstructures, their development and also their degradation under thermal and mechanical loading. A multitude of different approaches e.g. using diffraction methods for the analyses of residual stresses give complementary information to those obtained by neutron diffraction. The high brilliance at modern synchrotron radiation sources further provides new insight in-situ into very localized and time-dependent phenomena, e.g. into the growth of individual crystallites in a polycrystalline material and the nucleation and into the development of voids in materials subjected to loading at high temperatures. In addition to several examples showing the impact of investigations using neutrons and synchrotron radiation on material and component development in engineering material science, an example will be presented which highlights the complementarity of the three probes (neutrons, synchrotron radiation and ions) in an investigation of an ancient nanomaterial.

Plenarvortrag

Fr., 08:30–09:00

F-PV6

Struktur und Dynamik biologischer Materialien ¨ller1 Martin Mu 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, 24098 Kiel

Ein Merkmal nahezu aller biologischen Materialien ist ihre hierarchische Strukturierung u ¨ber viele L¨ angenskalen. Auf mesoskopischer Ebene findet sich fast immer eine Verbundstruktur mit kristallinen Regionen, die in eine weichere, ungeordnete Matrix eingebettet sind. Diese Matrix wiederum ist typischerweise f¨ ur Wasser zug¨ anglich. Der Wassergehalt beeinflußt erheblich die mechanischen Eigenschaften von Biomaterialien; im speziellen Fall von Holz ist das von erheblicher technischer Bedeutung. Wir untersuchen die strukturellen Ver¨ anderungen biologischer Materialien wie Zellulosefasern, Seide und Holz in situ unter mechanischer Belastung mit Mikro–R¨ ontgenstrahlen an Synchrotronstrahlungsquellen. Mit einer neuartigen Probenumgebung k¨ onnen wir den Wassergehalt der Proben variieren. Unsere Ergebnisse erlauben es, erstmals mikroskopische Modelle f¨ ur die unterschiedlichen Verformungsmechanismen trockener und feuchter Biomaterialien zu entwickeln. Hierbei spielt die weiche Matrix eine entscheidende Rolle. Um lokale Information u ¨ber Molek¨ ule in ungeordneten Bereichen zu gewinnen, wenden wir Neutronenspektroskopie an. Damit messen wir u. a. Anregungen adsorbierten Wassers in orientierten Zellulosefasern, die Informationenen u ¨ber die Anisotropie ihrer Umgebung liefern. Experimente an selektiv deuterierten Seidenfasern wurden erfolgreich mit Zugversuchen kombiniert. Die erhaltenen Phononenspektren bei verschiedenen Dehnungen geben einen direkten Hinweis darauf, daß die ungeordneten Molek¨ ule einen großen Teil der makroskopischen Dehnung erm¨ oglichen. Die vorgestellten Ergebnisse an Biomaterialien sind ein Beispiel daf¨ ur, wie durch die Komplementarit¨ at verschiedener Sonden ein umfassendes Modell der Struktur und Eigenschaften komplexer Proben erhalten werden kann.

Plenarvortrag

Fr., 09:00–09:30

F-PV7

In-situ-R¨ ontgenbeugungsuntersuchungen epitaktischer Kristallwachstumsprozesse Wolfgang Braun1 , Klaus H. Ploog1 1

Paul-Drude-Institut f¨ ur Festk¨ orperelektronik, Berlin

Die R¨ ontgenbeugung ist ein nahezu ideales Werkzeug, um Mechanismen des Kristallwachstums zu studieren. Dabei spielt die geringe Wechselwirkung des R¨ ontgenstrahls mit Materie eine entscheidende Rolle, erlaubt sie doch einerseits eine zerst¨ orungsfreie Messung, andererseits oft die Vernachl¨ assigung von Mehrfachstreuung in der mathematischen Analyse. Zur Untersuchung d¨ unner Schichten und Oberfl¨ achen sind wir jedoch auf Synchrotronstrahlung angewiesen, um trotz der geringen Wechselwirkung ausreichende Signalst¨ arken zu erreichen. Die Kombination einer MolekularstrahlEpitaxie(MBE-)anlage mit einem Diffraktometer ist besonders viel versprechend, da in der MBE Schichten auf einkristallinen Substraten direkt aus den konstituierenden Elementen aufgebaut werden. Dadurch wird die Physik des Kristallwachstumsprozesses so einfach wie m¨ oglich gehalten. Durch die Variation des Einfallswinkels der R¨ ontgenstrahlung kann die Wechselwirkungstiefe von einigen ˚ Angstr¨ om bis zu vielen Mikrometern ver¨ andert werden, was einerseits extrem oberfl¨ achenempfindliche Messungen erlaubt, andererseits eine Analyse dicker Schichtstapel erm¨ oglicht. Die R¨ ontgenbeugung arbeitet dabei als Frequenzfilter im Realraum, wodurch Strukturen mit unterschiedlichen Korrelationsl¨ angen separiert werden k¨ onnen. Das Paul-Drude-Institut betreibt ein eigenes Strahlrohr bei BESSY, an dem wechselweise eine von drei MBE-Anlagen in einem Sechskreis-Diffraktometer betrieben werden kann. Die Energie des monochromatischen Prim¨ arstrahls kann zwischen 6 und 12 keV variiert werden. Dadurch ergibt sich eine breit angelegte Palette sowohl in der m¨ oglichen Wahl der untersuchten Materialsysteme als auch der anwendbaren Beugungsmethoden. Wir stellen verschiedene Beispiele vor, so unter anderem die Wachstumskinetik verschiedener III-V-Halbleiteroberfl¨ achen, das Wachstum ferromagnetischen Manganarsenids auf Galliumarsenid und die Untersuchung des Ordnungszustandes von epitaktischem Eisensilizid auf GaAs.

Plenarvortrag

Fr., 13:35–14:00

F-PV8

Current research at FLASH Josef Feldhaus1 1

DESY, Notkestraße 85, D-22607 Hamburg

The free-electron laser at DESY in Hamburg (FLASH) is the first free-electron laser (FEL) built for the vacuum-ultraviolet (VUV) and soft X-ray region. In the present configuration the FEL can be tuned to any wavelength between approximately 50 nm and 13 nm by changing the electron beam energy from approximately 350 MeV to 700 MeV. The FEL has been operated at various wavelengths, the radiation pulses were characterised in terms of pulse energy, spectral distribution and coherence, and they have been used for a variety of experiments. Saturated intensities in the 10 100 µJ range have been reached with pulse durations of 10 - 50 fs. At these intensities strong second and third harmonic radiation with some 0.5 % of the main peak has been observed. FLASH has started regular user operation in summer 2005. Currently 16 science projects involving approximately 200 scientists from 11 countries are sharing 20 weeks of beamtime per year. The remaining time is used for work on the accelerator to improve and extend the operation of the FEL. In order to make efficient use of the FEL beam, it can be switched between four experimental stations by movable mirrors. A synchronised optical laser system is available for pump-probe experiments. Diagnostics has been implemented to monitor the pulse energy and its timing with respect to the optical laser. The science projects focus currently on four different areas: (i) interaction of the ultra-intense FEL pulses with matter, including multiphoton excitation of atoms, molecules and clusters, creation and characterisaton of dense plasmas, and imaging of small objects; (ii) femtosecond time-resolved experiments; (iii) investigation of extremely dilute samples such as mass selected clusters and highly charged ions; (iv) investigation of solids and surfaces. The current status of the facility is reviewed and examples of first user experiments are presented.

Plenarvortrag

Fr., 14:00–14:25

F-PV9

Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) ¨rgen Neuhaus1 Ju 1

Forschungsneutronenquelle Heinz Maier-Leibnitz, TU M¨ unchen, D-85747 Garching

Starting in May 2005 the FRM II has conducted its first year of routine operation. Right from the beginning a comprehensive number of beam tube instruments were available for external users. These instruments are exclusively operated by external collaboration groups from universities, Max-Planck institutes and large scale facilities. From the available beam time 2/3 is distributed via a biannual proposal selection procedure (http://user.frm2.tum.de). Access for European users is provided through the NMI3 consortium in the FP6 frame work program. Four different sources (cold, thermal, hot, fast) provide intense neutron beams via 10 horizontal beam tubes to the experimental and neutron guide hall. In addition, the inclined beam tube SR11 serves as a high intensity positron source with a flux of moderated positrons up to 5 × 108 e+ /s. Today 15 instruments are operational, two more will follow by the end of 2006. With the installation of the J¨ ulich Center of Neutron Science JCNS the suite of first generation instruments at the FRM II will be completed especially for applications of SANS, high resolution spectroscopy and reflectometry. A major effort is put to improve the user service for sample environment, especially for extreme conditions. Already available are cooling liquid free cryostats (top loader and cooling head), high temperature furnaces (2000 ◦ C) and high magnetic fields (15 T at 50 mK on the cold three-axis spectrometer Panda). A cooling liquid free magnet up to 7.5 T with flexible core (room temperature, 100 mm) is in the commissioning phase. First high pressure experiments (Paris-Edinburgh cell) could be performed successfully. Gas pressure cells are under construction. In house developments focus on the very low temperature equipment in the mK range. First experiments with a 3 He cooling system have been performed, the de-mixing chamber is in the commissioning phase.

Plenarvortrag

Fr., 14:25–14:40

F-PV10

The European X-ray Free-Electron Laser Facility in Hamburg Massimo Altarelli1 1

European XFEL Project Team - DESY, Notkestr. 85, 22607 Hamburg

In the quest for more brilliant x-ray sources, a number of projects worldwide are pursuing the realization of a source of extremely brilliant (peak brilliance ∼ 1033 photons/s/mm2 /mrad2 /0.1 %BW), ultra-short (∼ 100 fs) pulses of spatially coherent x-rays with wavelengths down to 0.1 nm, and to exploit them for revolutionary scientific experiments in a variety of disciplines spanning physics, chemistry, materials science and biology. In the US and in Japan, Free-Electron Lasers (FEL) are being developed based on room-temperature linear accelerators (Linacs). In Europe, the superconducting linear accelerator technology developed within the TESLA collaboration, and successfully applied to produce laser-like radiation in the UV and soft x-ray range at the FLASH facility at DESY, is adopted for the international facility to be built in Hamburg. The most important advantage of the superconducting technology is the possibility to produce up to 30000 pulses per second, instead of 60 or 120 foreseen in the Japanese and American projects, respectively. In the European facility, it is foreseen that electron bunches, accelerated to 17.5 GeV in a ∼ 1.7 km long linac, pass through long (up to 200 m) undulators, where they generate bursts of coherent x-rays via the process known as SASE (Self-Amplified Spontaneous Emission). Commissioning with first beam of the facility is expected to take place in 2013. An initial contingent of 5 photon beamlines with 10 experimental stations is foreseen, where experiments exploiting the high intensity, the coherence and the time structure of the new source are going to be performed. A brief illustration of some of the potential experiments is presented. The possibility to investigate the structure of macromolecules with atomic resolution without the need for crystallization; the study of molecular configuration rearrangements during chemical reactions down to the sub-ps scale; the dynamics of fluctuations on unprecedented time and length scales; the experimental access to regions of the phase diagram of materials so far only found in astrophysical environments or under conditions unfavourable for accurate experiments are some of the examples discussed.

Plenarvortrag

Fr., 14:40–14:55

F-PV11

The future FAIR accelerator facility for Antiprotons and Ion Research Christina Trautmann1 1

Gesellschaft f¨ ur Schwerionenforschung, Planckstr.1, 64291 Darmstadt

The future international accelerator Facility for Antiproton and Ion Research (FAIR) will deliver relativistic beams of both stable and unstable heavy nuclei of highest intensities. The central part of FAIR consists of two superconducting synchrotrons which will accelerate heavy ion beams up to uranium for experiments at energies up to 35 GeV per nucleon, and for the production of radioactive ion beams and antiprotons. The existing GSI accelerators UNILAC and SIS will serve as injector. A complex system of storage rings is equipped with beam cooling, internal targets, and deceleration facilities. The presentation provides information about the current concept and design status with special focus on future installations and possibilities for research activities in atomic physics, material science, biophysics and other interdisciplinary fields.

Fig. 1: Scheme of the planned FAIR facility

Abstracts: SNI fur ¨ Neugierige

SNI f¨ ur Neugierige

Do., 15:30–16:00

D-NV1

Neues Licht f¨ ur mehr Sicht: R¨ ontgenblick im Nanokosmos Tim Salditt1 , Christian Fuhse1 , Christoph Ollinger1 1

Inst. f¨ ur R¨ ontgenphysik, Friedrich-Hund-Platz 1, 37077 G¨ ottingen

Unsere Kenntnis der Nanostruktur biologischer und unbelebter Materie h¨ angt entscheidend von den experimentellen Methoden ab, die uns zur Untersuchung zur Verf¨ ugung stehen. Die Beobachtung funktioneller Mechanismen auf molekularer Ebene erfordert Methoden mit einer r¨ aumlichen und zeitlichen Aufl¨ osung, die h¨ aufig u ¨ber die heute vorhandenen M¨ oglichkeiten weit hinausgehen. Unsere Bilder der molekularen Welt entsprechen daher streckenweise noch eher einem Cartoon. Die unterschiedlichen Beschr¨ ankungen der Sonden hoher r¨ aumlicher Aufl¨ osung (optisches Licht, Elektronen, R¨ ontgen, Neutronen, Rasterkraftmikroskopie, Kernspinresonanz) werden sich auch in Zukunft nicht durch einfache experimentelle oder theoretische Ans¨ atze aufheben lassen. So kann niemand erwarten, dass Methoden, die z. B. zur Strukturuntersuchung von Kristallen geeignet sind, sich morgen auf Strukturuntersuchung biologischer Zellen anwenden lassen. Dennoch haben Entwicklungen gerade in der Optik gezeigt, dass lange als unvermeidbar geltende Beschr¨ ankungen durchaus durch neue experimentelle Ans¨ atze umgangen werden k¨ onnen. Dieser Vortrag behandelt die Weiterentwicklung von Quellen, Optik und Untersuchungsmethoden, um mit R¨ ontgenstrahlung zu Abbildungen des Nanokosmos zu gelangen. Die Vision Molekularer Filme“ wird besonders auch durch das XFEL-Projekt ” greifbar, mit dem in wenigen Jahren in Hamburg Laserstrahlung im Bereich harter R¨ ontgenstrahlung realisiert werden soll.

SNI f¨ ur Neugierige

Do., 16:00–16:30

D-NV2

Kristalle aus Gas und Wasser: Gashydrate als Herausforderung f¨ ur Wissenschaft und Technik Werner F. Kuhs1 1

GZG Abt. Kristallographie, Universit¨ at G¨ ottingen

Gashydrate sind kristalline Verbindungen aus Wasser und Gas. Riesige Mengen solcher eis¨ ahnlichen methanhaltigen Substanzen lagern im Meeresboden und im arktischen Permafrost. Ihr geologisches Risikopotenzial bei einer Zersetzung ist erheblich; vor dem Hintergrund knapper Energievorr¨ ate stellen sie aber auch eine wichtige Kohlenwasserstoff-Ressource dar. Ob und wie Gashydrate als Energiequelle genutzt werden k¨ onnen steht allerdings noch dahin. Im technischen Bereich sind sie ebenfalls von großer Bedeutung; viele hundert Millionen Euro werden jedes Jahr ausgegeben, um die Bildung von Gashydraten in Erd¨ ol- und Erdgas-Pipelines zu verhindern. Eine Reduzierung der genannten Unsicherheiten, Risiken und Kosten kann letztendlich nur u ¨ber ein besseres Verst¨ andnis des molekularen Geschehens gelingen. Obschon Gashydrate seid fast 200 Jahren bekannt sind, hat sich ein breites und vertieftes wissenschaftliches Interesse erst in den letzten 20 Jahren gebildet; von einem wirklichen Verst¨ andnis dieser Substanzen sind wir allerdings noch weit entfernt. Der Vortrag soll wichtige Ergebnisse aktueller Untersuchungen an Gashydraten greifbar machen und die Bedeutung der Großforschungseinrichtungen bei der Beantwortung der zahlreichen offenen Fragen beleuchten. Insbesondere Neutronenstreuexperimente haben hier den Wissenschaftlern entscheidende Einblicke in die Struktur und Dynamik sowie die Bildungsund Zersetzungsvorg¨ ange von Gashydraten gew¨ ahrt.

SNI f¨ ur Neugierige

Do., 16:30–17:00

D-NV3

Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen ¨nther Dollinger1 , Christoph Dollinger2 Gu 1

Universit¨ at der Bundeswehr M¨ unchen, 85577 Neubiberg – 2 Technische Universit¨ at M¨ unchen, 85748 Garching Mikroskopie“ bedeutet nichts anderes als etwas kleines Betrachten“. Urspr¨ unglich ” ” war mit Mikroskopie“ die optische Abbildung kleiner Gegenst¨ ande gemeint, die mit ” bloßem Auge nicht beobachtbar sind. Inzwischen wurden aber eine ganze Reihe von Mikroskopen entwickelt, die Eigenschaften von kleinen Objekten sichtbar machen, die der optischen Mikroskopie verborgen bleiben. Ziel des Vortrages ist es, zwei neuartige Mikroskope zu beschreiben, die mit hochenergetischen Protonen beziehungsweise mit Positronen arbeiten. Protonen sind ionisierte Wasserstoffatome, die mit großen Teilchenbeschleunigern auf hohe Energien beschleunigt werden und die wir zur Abbildung der Verteilung von Wasserstoff in Mikrostrukturen verwenden. Positronen sind Teilchen, die wir in unserer Welt selten antreffen. Positronen sind ein Teil dessen, was man als Antimaterie“ bezeichnet; sie sind die Antiteilchen der Elektronen. Das hat kata” strophale Konsequenzen f¨ ur die Positronen, wenn sie auf normale Materie geschossen werden: Wenn ein Positron mit den Elektronen der Materie in Kontakt tritt, vernichten sich das Positron und eines der Elektronen in einem R¨ ontgenblitz innerhalb sehr kurzer Zeiten. Das interessante ist, dass uns dieser Vernichtungsprozess u ¨ber atomare Leerstellen in der Materie berichtet. Ein Positronen-Mikroskop erlaubt es uns also, die Verteilung von atomaren Leerstellen abzubilden. Wir wollen versuchen, diese wunderbare Welt der neuartigen Mikroskope n¨ aher zu beleuchten: Wie erh¨ alt man mit solchen exotischen Teilchen mikroskopische Abbildungen? Aus welchen Teilen bestehen diese neuartigen Mikroskope? Was sieht“ man mit ” diesen Mikroskopen?

Abstracts: Abendvortrag

Senatsempfang

Do., nach 18:00

D-AV1

Die Eroberung des Nanokosmos: Von der Grundlagenforschung zu neuen Technologien Helmut Dosch1 1

Max-Planck-Institut f¨ ur Metallforschung, Stuttgart

Ohne raffinierte High-Tech Materialien geht in den modernen Industriestaaten heute nichts mehr. Maßgeschneiderte Materialsysteme sind die Grundbausteine f¨ ur alle modernen Technologien, angefangen von Information und Kommunikation, Medizin und Gesundheitswesen, Energie- und Umwelt bis hin zu Mobilit¨ at und Transport. Im Alltag bedienen wir uns von morgens bis abends Spitzenprodukten aus den Denkstuben der Festk¨ orperforscher und Materialwissenschaftler. Und der Ideenvorrat der Grundlagenforscher f¨ ur die Zukunft ist nicht schlecht, er reicht von Einzelelektronen-Transistoren, organischen Lasern, Quanten- und Lichtcomputern, magnetischer Elektronik, die mit dem Elektronenspin arbeitet, Datenspeichermedien in Stecknadelkopf-Gr¨ oße, staubkorn-kleinen Chips ( smart dust“) bis hin zu neuen superharten Materialien, die Stahl ” weich wie Butter aussehen lassen. Diese Zukunftsvisionen lassen sich nur verwirklichen, wenn wir die analytischen Technologien bereitstellen, mit denen man die neuen Strukturen, Ph¨ anomene und Funktionen im Nanokosmos mit hoher Pr¨ azision ertasten kann. Den Synchotronstrahlungs-, Neutronen- und Ionenquellen kommt hier eine Schl¨ usselrolle zu, da sie eine zerst¨ orungsfreie dreidimensionale Analyse der Nanostrukturen unter realistischen Umwelt- und Technologiebedingungen bzw. hochpr¨ azise Nanostrukturierung erm¨ oglichen. Revolution¨ are neue Einblicke in den Nanokosmos lassen neue R¨ ontgen- und Neutronenquellen erwarten, welche von Linearbeschleunigern gespeist werden. Mit dem Europ¨ aischen R¨ ontgenlaser X-FEL wird es bespielsweise erstmals m¨ oglich werden, direkt zu beobachten, wie chemische Bindungen entstehen und brechen, wie Medikamente wirken und Nanomaschinen funktionieren. Der Vortrag entf¨ uhrt Sie in einer allgemeinverst¨ andlichen Sprache in eine bislang verborgene, unsichtbare Dimension des Nanokosmos.

¨ Abstracts: Vortrage

Mikroskopie und Tomographie

Vortrag: Mi., 11:00–11:30

M-V1

Neutron Imaging Methods at FRM-II ¨cherl2 , Elbio Calzada1 , Klaus Lorenz1 , Martin Michael Schulz1 , Thomas Bu 1 ¨hlbauer , Burkhard Schillinger1 Mu 1

FRM-II, Munich and Physics E21, Munich – 2 Institut f¨ ur Radiochemie, M¨ unchen

The research reactor FRM-II hosts two facilities for neutron imaging offering several different spectra and radiations for different imaging methods. The beam tube of the ANTARES facility faces the cold source and offers standard neutron radiography as well as computed tomography with very high spatial resolution. Using a Cd filter, the epithermal part of the spectrum can be used for better penetration. A B4C filter blocks nearly all cold to epithermal neutrons. With a gamma scintillation screen, the gamma radiation emitted from the reactor vessel and beam nozzle can be used for high-energy gamma imaging. Several pin hole apertures can be used for phase contrast imaging. Additional switchable lead filters and a monocrystalline Bismuth filter serve as gamma filters to suppress the remaining gamma background that is still detected by the neutron scintillation screen, a polycrytalline Bismuth filter can shift the spectrum to cold neutrons around 6˚ A. When the neutron shutter is closed, a 300 kV X-ray tube can be rotated into the beam close to the neurton shutter, rendering an X-ray beam with virtually the same geometry as the neutron beam. X-ray and neutron images can be superimposed without a registering process. The NECTAR facility is the only neutron imaging facility world-wide situated at a beam tube with a uranium converter plate inside the reactor vessel delivering an unmoderated fission spectrum of fast neutrons. Thermal neutrons are suppressed with Cd filters, fast neutron radiography and tomography can be performed on thick samples. The talk will describe the setup of the facilities and show examples for each imaging method available.

Fig. 1: Cold neutron radiography of an oil-filled pump

Fig. 2: The same pump seen with reactor gammas

Mikroskopie und Tomographie

Vortrag: Mi., 11:30–11:50

M-V2

Nano-Tomography and Spectromicroscopy with the new BESSY X-Ray Microscope Gerd Schneider1 , Peter Guttmann1 , Stefan Rehbein1 , Stefan Heim1 , Diane Eichert1 1

BESSY m.b.H., Albert-Einstein-Str. 15

X-ray microscopy is a powerful imaging technique with many applications in materials, environmental and life sciences. Among many scientific questions in life sciences, the cell nucleus which is a vital and complex organelle is still a mystery. How the DNA it contains and its associated proteins are arranged and packaged to fit within this approx. 10 micron diameter organelle is unknown. The normal cellular contingent of DNA is 105-fold longer than the nuclear diameter. Some DNA compaction (6-fold) can be accounted for by its wrapping around nucleosomes. The nucleosomal fiber is itself probably folded to yield a thicker fiber of 30 nm thickness, providing 7-fold more compaction. How this “30 nm fiber” is folded to achieve the further necessary compaction is unknown. Other questions of packaging concern how much “free” space for diffusion is available in the nucleus. The interaction of x-rays is element specific, therefore, x-ray nano-tomography can be used to quantify the packing density of organic material. However, different proteins or molecular structures cannot be distinguished directly in x-ray microscope images. This problem is solved by the availability of specific fluorescent probes detectable by fluorescence microscopy. Thus the two imaging modalities are complementary. Since fluorescence and x-ray microscopy permit analysis of whole cells, it is possible to investigate the same cell in both microscopes. These correlative studies are ideally suited to x-ray microscopy because of its ability to image cells in 3D. We expect to develop a widely applicable technique that, as applied to nuclear structure, will yield significant new insights. 3D x-ray microscopy - pioneered at BESSY has found numerous applications worldwide. To further improve 3D x-ray imaging towards sub-10 nm spatial resolution and to increase the usable photon energy range by phase contrast methods, progress has to be made in x-ray optics, instrumentation and theory. In the talk, the current status and future aspects of x-ray microscopy at 3rd generation electron storage rings and the upcoming Free Electron Lasers with their fs-pulses will be discussed.

Mikroskopie und Tomographie

Vortrag: Mi., 11:50–12:10

M-V3

SMART - an aberration corrected spectromicroscope for surface characterization with high resolution Th. Schmidt1 , F. Maier1 , U. Groh1 , E. Umbach1 , H. Marchetto2 , P. ´vesque2 , T. Ska `la2 , H.-J. Freund2 , R. Fink3 , SMART Collaboration4 Le 1

Exp. Physik 2, Uni W¨ urzburg – 2 Fritz-Haber-Institut, Berlin – 3 Phys. Chemie 2, Uni 4 Erlangen – U W¨ u, FHI, U Erl., TU Darmstadt, TU Clausthal, Carl Zeiss NTS GmbH

With the availability of high flux beamlines at third-generation synchrotron radiation sources spectromicroscopy has developed into one of the most promising techniques. Combining high-brilliance synchrotron radiation with a parallel imaging LEEM (low energy electron microscope) or PEEM (photoemission electron microscope) allows a comprehensive characterization of surfaces, adsorbates, and ultrathin films. One of the most challenging projects in this field is the SMART [1] (Spectro-Microscope with Aberration correction for Resolution and Transmission enhancement), aiming at a lateral resolution of 2 nm and an energy resolution of 100 meV which can only be achieved by aberration correction and energy filtering. Regarding aberration correction pioneering work has been done: the tetrode mirror [2] is the first and only working aberration corrector which simultaneously compensates for both, the spherical and chromatic aberrations of the electron lens system. The quality of our magnetic OMEGA filter - a second-order aberration-corrected energy filter - is demonstrated by the absolute energy resolution of 100 meV at a pass energy of 15 keV, yielding in an unusual resolving power of 150.000. Utilizing different sources (linearly or circularly polarized x-rays, UV-light, electron gun, etc.) the SMART excels as a versatile instrument with a variety of contrast mechanisms by imaging photoemitted (XPEEM, UV-PEEM) and reflected electrons (LEEM, MEM). Thus it enables the spatially resolved study of morphology, chemical distribution, electronic state, molecular orientation, magnetization, work function, structural properties, atomic steps, etc. Within seconds the instrument can be switched from microscopy to two further methods [3]: (a) laterally resolved spectroscopy from small object areas with the size of the lateral resolution (nano-XPS, nano-AES, nano-NEXAFS, etc.) and (b) laterally resolved and energy filtered imaging of angular distributions: nano-PED (Photoelectron diffraction), Fermi surface/valence band mapping, LEED (low energy electron diffraction), etc. This variety of complementary probing tools enables a comprehensive characterization of, e.g., deposited nano-objects, nano-structured surfaces, and due to the possibility of real-time observation of processes like crystal growth, chemical surface reactions, and surface phase transitions. First experiments on the growth properties of organic thin films, their dependence on the substrate, and the internal structure of microcrystallites of organic molecules show the potential of the instrument and will be briefly presented in the talk. Project funded by the BMBF, contract 05 KS4 WWB/4; [1] R. Fink et al., J. Electr. Spectrosc. 84 (1997) 231; [2] D. Preikszas, H. Rose, J. Electr. Micr. 1 (1997) 1; [3] Th. Schmidt et al., Surf. Rev. Lett. 9 (2002) 223.

Mikroskopie und Tomographie

Vortrag: Mi., 12:10–12:30

M-V4

Untersuchung der Dynamik von DNA Reparaturfaktoren in lebenden Zellen am Rasterionenmikroskop SNAKE ¨nther Dollinger1 , Andreas Christoph Greubel1 , Volker Hable1 , Gu ¨cken2 , Hilmar Strickfaden3 , Steffen Dietzel3 , ThoHauptner2 , Reiner Kru mas Cremer3 , Guido Drexler4 , Anna Friedl4 1

LRT2, Universit¨ at der Bundeswehr, 85577 Neubiberg – 2 Physik Department E12, TU M¨ unchen, 85748 Garching – 3 Biologie Department II, LMU M¨ unchen, M¨ unchen – 4 Radiobiologisches Institut, LMU M¨ unchen, M¨ unchen Mit dem Rasterionenmikroskop SNAKE (Supraleitendes Nanoskop f¨ ur angewandte kernphysikalische Experimente) am M¨ unchener 14 MV Tandembeschleuniger k¨ onnen Ionenstrahlen auf einen Durchmesser von weniger als einem Mikrometer fokussiert werden. Mikroschlitze beschneiden den Strahl und pr¨ aparieren so ein Objekt. Dieses wird mittels einer supraleitenden Multipollinse verkleinert in die Fokalebene abgebildet. Die Strahlposition dort kann mittels einer elektrostatischen Ablenkeinheit variiert werden. Da f¨ ur Zellbestrahlungsexperimente die Kontrolle der applizierten Energiedosis essentiell ist, wurde hierzu eine Einzelionenpr¨ aparation realisiert. Mittels eines Choppers wird der Strahl elektrostatisch so weit abgelenkt, dass kein Ion mehr die Fokalebene und somit die Zellprobe erreicht, sobald diese mit der gew¨ unschten Anzahl von Ionen bestrahlt wurde. Der hierf¨ ur n¨ otige Ionennachweis geschieht in Transmissionsgeometrie hinter der senkrecht montierten Zellprobe mit einem Szintilationsdetektor. Durch die Kopplung der Strahlablenkung und der Einzelionenpr¨ aparation ist es m¨ oglich die Zellprobe in beliebigen geometrischen Mustern zu bestrahlen. Ebenso ist die gezielte Bestrahlung einzelner Zellen oder Zellkerne m¨ oglich. Der derzeitige Gegenstand biologischer Studien ist die Dynamik von mittelbar oder unmittelbar an der DNA Reparatur beteiligten Proteinen oder Proteinmodifikationen. Zellproben wurden zu verschiedenen Zeitpunkten nach der Bestrahlung fixiert und der Doppelstrangbruchmarker γ–H2AX sowie das Protein 53BP1 mittels Immunofluoreszenztechniken angef¨ arbt. Als Antwort auf die durch Ionenbestrahlung induzierten Doppelstrangbr¨ uche akkumulieren diese beiden Faktoren an den Schadensorten, sie bilden sogenante Foci. Die Abweichung dieser Foci vom bestrahlten Muster korrelliert mit der Bewegung des gesch¨ adigten Chromatins. Unsere Daten sind mit einer Diffusionsbewegung vertr¨ aglich. Weitergehende Studien zur Abh¨ angigkeit der Diffusionskonstante von der Sch¨ adigungsdichte und des aktuellen Zellzyklus der Zellen sind in ¨ Bearbeitung. Die zeitliche Anderung der Focigr¨ oße der betrachteten Reparaturfaktoren zeigt ein komplexes Verhalten. Einem anf¨ anglichen Anstieg der Focigr¨ oße bis etwa zwei Stunden nach Bestrahlung folgt ein steiler Abfall mit anschließendem Plateau.

Dynamik

Vortrag: Mi., 11:00–11:30

M-V5

Inelastic X-ray scattering from phonons: status and perspectives Michael Krisch1 1

European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cedex, France

Inelastic x-ray scattering (IXS) with meV energy resolution has become a powerful spectroscopic tool in the study of phonon dispersion in condensed matter. The most important aspects distinguishing IXS from the well-established coherent inelastic neutron scattering (INS) techniques are the absence of kinematic limitations and the possibility to study very small sample quantities (down to 10−5 mm3 ). This has opened up new possibilities in research fields ranging from biology to geophysics. The aim of the contribution is to illustrate the present capabilities of IXS and to discuss future perspectives.

Dynamik

Vortrag: Mi., 11:30–11:50

M-V6

Wasser in neuem Licht — R¨ ontgenspektroskopie liefert neue Erkenntnisse zur Nahordnung in Wasser Philippe Wernet1 1

BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin

So gew¨ ohnlich fl¨ ussiges Wasser auch erscheinen mag so außergew¨ ohnlich sind doch seine Eigenschaften. Ein fluktuierendes Netzwerk aus Wasserstoffbr¨ uckenbindungen (WBB) verkn¨ upft die außergew¨ ohnlich mobilen Wassermolek¨ ule und bestimmt seine Struktur und seine Eigenschaften. Da WBB aber permanent brechen und neu geformt werden, ist die Struktur fl¨ ussigen Wassers ¨ außerst unzug¨ anglich und bis heute umstritten. Uns gelang k¨ urzlich ein neuer Einblick in die Nahordnung von Wasser mit Hilfe R¨ ontgenspektroskopischer Verfahren [1-4]. Die Anwendung von Synchrotronstrahlung mit Energien zwischen 500 und 10000 eV und der Nachweis von Elektronen bzw. Photonen erm¨ oglichte es, Wasser mit Informationstiefen zwischen 1 ˚ A und 1 mm zu untersuchen. Einblicke in die Struktur von Wasser wurden aus Absorptionsspektroskopie mit weicher [1] und Raman Streuung mit harter R¨ ontgenstrahlung [3] gewonnen. Diese elementspezifischen, symmetrie-sensitiven, lokalen und ultra-schnellen Methoden geben Aufschluss u ¨ber die St¨ arke und die Anzahl der WBB eines Molek¨ uls zu seinen n¨ achsten Nachbarn. So konnten wir die Nahordnung in fl¨ ussigem Wasser aus Vergleichen mit bekannten Modellsystemen n¨ amlich der Oberfl¨ ache und dem Innern von Eis ermitteln [1]. Danach bildet die Mehrzahl der Molek¨ ule lediglich 2 starke WBB aus, eine auf der Sauerstoffund eine auf der Wasserstoffseite. Die Molek¨ ule in fl¨ ussigem Wasser ordnen sich also in Ringen und Ketten und nicht, wie bisher angenommen und vergleichbar dem Innern von Eis, tetraedrisch an. Unser asymmetrisches Modell steht in krassem Widerspruch zum allgemein akzeptierten Wissen. Bei genauerer Betrachtung stellt sich jedoch heraus, dass dieses Wissen auf molekulardynamischen Simulationen basiert und dass unsere neuen Erkenntnisse im Einklang mit etablierten experimentellen Ergebnissen aus der Neutronen- und R¨ ontgenstreuung sind [5]. In diesem Beitrag werden die Methoden eingef¨ uhrt, die Erkenntnisse werden dargestellt und mit Ergebnissen aus der Neutronen- und R¨ ontgenstreuung und mit molekulardynamischen Simulationen verglichen. Untersuchungen zu Eis, zu fl¨ ussigem Wasser bei Raumtemperatur [1], nahe des Siedepunktes [2] und bis in den u ¨berkritischen Bereich [4] werden vorgestellt. Ein Ausblick f¨ uhrt zu neuesten Anstrengungen zur Untersuchung der Dynamik in Wasser wobei ultra-kurze Laserpulse verwendet werden, um spezifische Anregungen zu erzeugen deren Auswirkungen auf die Struktur dann stroboskopisch mit ultra-kurzen R¨ ontgenpulsen abgefragt werden. [1] Ph. Wernet et al., Science 304 (2004) 995. [2] A. Nilsson et al., Science 308 (2005) 793a. [3] U. Bergmann et al., Phys. Rev. B 66 (2002) 092107. [4] Ph. Wernet et al., J. Chem. Phys. 123 (2005) 154503. [5] A. K. Soper, J. Phys.: Condens. Matter 17 (2005) S3273.

Dynamik

Vortrag: Mi., 11:50–12:10

M-V7

Collective excitations in a molten transition metal Walter Schirmacher1,2 , Harald Sinn2 , Ayman Said2 1

Phys. Dept. E13, TU M¨ unchen. D-85747 Garching, Germnay – 2 Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, We report inelastic X-ray scattering measurements of the atomic collective excitations of an early transition metal, namely liquid titanium at T=2020 K. The data show well defined sound excitations with a low damping constant comparable to the damping observed in liquid alkaline metals. Calculations of the spectrum of density fluctuations as a function of the excitation wave number based on G¨ otzes self-consistent mode coupling approach were carried out. The calculations were performed on the knowledge of the static structure factor and number density of liquid titanium only, no adjustable parameters were used. A remarkable agreement between the prediction of mode-coupling theory and experiment is observed.

Dynamik

Vortrag: Mi., 12:10–12:30

M-V8

Combining neutron and helium spin echo: A powerful tool to clarify surface effects in confined systems Peter Fouquet1 , Andrew P. Jardine2 , Holly Alexandrowicz2 , John Ellis2 , William Allison2

Hedgeland2 ,

Gil

1

Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2 Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, U.K. We present a new approach to gain a microscopic understanding of surface contributions to the dynamics of molecules confined in mesoporous materials. In mesoporous confinements a large fraction of molecules interacts with the wall of the matrix changing the overall dynamics significantly [1]. At present, however, the understanding of the surface contribution is very limited and almost exclusively based on volume measurements. In our approach we combine neutron spin-echo spectroscopy (NSE) to measure the diffusion of molecules confined in mesoporous matrices with increasing pore size and helium spin-echo spectroscopy (HeSE) [2,3] to measure the diffusion of molecules adsorbed on surfaces which are structurally similar to the walls of the confining matrices. Both techniques work at typical diffusional ps to ns time scales and on molecular lenth scales. Using additionally state-of-the-art molecular dynamics (MD) simulations we get a detailed microscopic picture of the surface diffusion. As a prototype study for our approach we have measured the diffusion of benzene molecules on HOPG and exfoliated graphite surfaces as well as in activated carbon fibers. The dynamics of the benzene molecules on the graphite surfaces differ strongly from the widely assumed jump diffusion model (Fig. 1). With the aid of MD calculations we were able to interpret the dynamics in terms of a 2d liquid with rather low friction and we could clarify the important role of rotational activation. [1] C. Alba-Simionesco et al., Eur. Phys. J. E 12 (2003) 19. [2] A.P. Jardine et al., Science 304 (2004) 1790. [3] P. Fouquet et al., Rev. Sci. Instrum. 76 (2005) 053109.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 11:00–11:30

M-V9

Instabilit¨ at und Selbstorganisation bei der Bestrahlung von Schichtpaketen mit hochenergetischen Ionen Wolfgang Bolse1 1

Institut f¨ ur Strahlenphysik, Universit¨ at Stuttgart

Energetische Ionen sind ein Werkzeug mit einzigartigen Eigenschaften zur Erzeugung von Nano- und Submikrometerstrukturen auf oder in der N¨ ahe der Oberfl¨ ache von Festk¨ orpern. Bei seiner Abbremsung wird ein großer Teil der kinetischen Energie des Ions nahezu instantan in ein hochlokalisiertes Volumen von nm-Dimensionen (zumindest in lateraler Richtung) im Festk¨ orper deponiert. Die dabei erreichte Energiedichte u ¨bersteigt bei weitem die Bindungsenergien im Festk¨ orper und resultiert in einer nano-skaligen Zone mit extremen Nicht-Gleichgewichtsbedingungen. Da dies in einer kalten Umgebung stattfindet, k¨ uhlt die angeregte Zone innerhalb weniger 10 bis 100 ps wieder ab. Derart intensive, hochlokalisierte und extrem kurze Festk¨ orperanregungen werden von keiner anderen Methode zur Materialmodifikation erreicht. Einzelne Ionen k¨ onnen daher dazu verwendet werden, Nicht-Gleichgewichtsstrukturen mit neuartigen physikalischen Eigenschaften direkt auf einer nm-Skala zu erzeugen, die dann als Ausgangsbasis f¨ ur funktionelle Nano-Strukturen dienen. Einzelionenbestrahlung ist aber nicht der einzige Weg zur Erzeugung von von Nano- bzw. Submikrometerstrukturen mit energetischen Ionen. Erh¨ oht man die Ionenfluenz und damit die Dichte der durch ¨ Ioneneinschl¨ age modifizierten Bereiche, so f¨ uhrt die Wechselwirkung und der Uberlapp dieser Zonen oft zu Oberfl¨ acheninstabilit¨ aten und Selbstorganisationseffekten, in deren Folge großfl¨ achige und oft periodische, nanometrische Muster und Strukturen entstehen, deren Eigenschaften weit u ¨ber eine einfache Superposition der Einzelioneneffekte hinaus gehen. In diesem Beitrag sollen einige k¨ urzlich erzielte Ergebnisse zu Instabilit¨ aten und Selbstorganisationsprozessen in D¨ unnschichtsystem unter Bestrahlung mit hochenergetischen Ionen (MeV/amu) und ihre potentielle Anwendung zur Herstellung großfl¨ achiger Anordnungen von maßgeschneiderten Nano- und Submikrometerstrukturen diskutiert werden.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 11:30–11:50

M-V10

Electronic properties of graphite-like ion tracks in insulating tetrahedral amorphous carbon Daniel Schwen1 , Anne-Katrin Nix1 , Carsten Ronning1 , Johann Krauser2 , ¨ss1 Christina Trautmann3 , Hans Hofsa 1

II. Physikalisches Institut, Universit¨ at G¨ ottingen, Germany – 2 Hochschule Harz, 3 Wernigerode, Germany – Gesellschaft f¨ ur Schwerionenforschung, Darmstadt, Germany We investigated the formation of quasi one-dimensional conducting filaments in diamond like carbon (DLC) films by swift heavy ion irradiation. Various DLC films with thicknesses of several 100 nm were grown using mass separated ion beam deposition on highly conducting Si, Fe and Ni substrates. After deposition the films were irradiated with 1 GeV 238 U ions with fluences between 109 and 1011 ions/cm2 . Due to their high electronic energy loss of about 30 keV/nm the swift heavy ions graphitize the predominantly (80 %) sp3 -bound carbon film along their trajectories yielding conducting nanowires embedded in an insulating matrix. Using atomic force microscopy (AFM) with conducting cantilevers and applied bias voltage the presence of conducting tracks was confirmed and their conductivities were determined to be several orders of magnitude higher than of the host matrix. Temperature dependent electrical measurements were performed on the irradiated samples at 300 K - 10 K with fields up to 5 V/µm. We will discuss the results with respect to contact resistances and possible one-dimensional conduction mechanisms within the tracks.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 11:50–12:10

M-V11

Transmission surface x-ray diffraction studies of solid-liquid and liquidliquid interfaces Olaf Magnussen1 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, Olshausenstr. 40, 24098 Kiel Deeply buried interfaces between condensed phases, such as solid-liquid and liquidliquid interfaces, are ubiquitous in nature as well as of great importance in many technological processes, ranging from fuel cells to plating for microelectronics applications. The high brilliance of modern synchrotron sources allows studies of the atomicscale interface structure in-situ under realistic conditions. This will be illustrated by studies of Au(111) and liquid Hg electrodes in aqueous electrolytes. Specifically, grazing-incidence diffraction studies during homoexitaxial gold electrodeposition will be presented that reveal a noticeable more compressed reconstructed Au surface layer during Au deposition as compared to Au-free electrolyte [1]. Contrary to the Au-free case, the surface compression increases with decreasing potential in Au-containing solution. Second, it will be shown by in-situ x-ray reflectivity measurements that liquid Hg electrodes exhibit stratification into atomic layers at the interface to simple salt solutions [2]. This surface layering is even more pronounced than that found in previous studies at the liquid Hg / vapour interface [3]. [1] Ayad, J. Stettner, O.M. Magnussen, Phys. Rev. Lett. 94 (2005) 066106. [2] O. M. Magnussen, B. M. Ocko, I. Sloutkin, J. Baumert, I. Kuzmenko, and M. Deutsch, in preparation. [3] O. M. Magnussen, B. M. Ocko, M. J. Regan, K. Penanen, P. S. Pershan, and M. Deutsch, Phys.Rev.Lett. 74 (1995) 4444.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 12:10–12:30

M-V12

Antiphase magnetic proximity effect in perovskite superconductor / ferromagnet multilayers Jochen Stahn1 , Justin Hoppler2 , Christof Niedermayer1 , Jacques Chakhalian3 , Georg Cristiani3 , Hans-Ulrich Habermeier3 , Bernhard Keimer3 , Christian Bernhard2 1

Laboratory for Neutron Scattering, ETH Z¨ urich – 2 Physics department, Universit´e de Fribourg, Switzerland – 3 Max Planck Institute for Solid State Research, Stuttgart, Germany Materials with strongly correlated charge carriers are promising candidates for new electronic devices because their charge carrier mobility is linked to its spin degree of freedom and its exchange coupling to magnetic ions. Superconducting materials are also very attractive since their charge carriers are condensed in a macroscopic quantum state, the phase of which can be easily manipulated, for example, by an externally applied magnetic field. Based upon these considerations, heterostructures made from perovskite-oxides, such as cuprate high Tc superconductors and ferromagnetic manganite compounds that exhibit the so-called colossal magneto resistance effect seem to be ideal candidates for novel devices. Our neutron reflectometry measurements on YBa2 Cu3 O7 /La2/3 Ca1/3 MnO3 multilayers have revealed detailed, microscopic information about the magnetization profile as a function of in-plane and out-of-plane wave vectors. [1] We observed characteristic differences between the nuclear and the magnetic scattering profiles which in combination with XMCD [2] results allowed us to identify an antiphase magnetic proximity coupling where FM moment is induced in YBCO that is oriented antiparallel to the one in LCMO. We also observed an anomalous enhancement of the off-specular reflection in the SC state which suggests a strong mutual interaction between the SC and the FM order parameters. [1] J. Stahn et.al., Phys. Rev. B 71 (2005) 140509. [2] J. Chakhalian et.al., Nature Physics 2 (2006) 244.

Magnetismus

Vortrag: Mi., 17:40–18:00

M-V13

Time, layer, and spatially resolved magnetic domain imaging of layered magnetic structures by x-ray magnetic circular dichroism photoelectron emission microscopy Wolfgang Kuch1 , Keiki Fukumoto1 , Jan Vogel2 , Julio Camarero3 , Fabien ¨rgen Kirschner4 Romanens2 , Stefania Pizzini2 , Marlio Bonfim2 , Ju 1

Freie Universit¨ at Berlin, Institut f¨ ur Experimentalphysik, Arnimallee 14, D-14195 Berlin – 2 Laboratoire Louis Neel, CNRS, 25 avenue des Martyrs, F-38042 Grenoble, France – 3 Universidad Aut´ onoma de Madrid, E-28049 Madrid, Spain – 4 Max-PlanckInstitut f¨ ur Mikrostrukturphysik, Weinberg 2, D-06120 Halle Magnetic structures consisting of ferromagnetic layers separated by ultra-thin nonmagnetic spacer layers exhibit many new and interesting effects. The fundamental investigation of the magnetization dynamics of such layered magnetic structures calls for a method capable of delivering microscopic magnetic information about each of the magnetic layers separately. X-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM) is such a technique. It combines the layer-resolved visualization of magnetic domain patterns at surfaces and in buried layers with a timeresolved stroboscopic measurement of the magnetization reversal dynamics, taking advantage of the time structure of the synchrotron radiation. Using this time-resolved, layer-selective microscopic technique we observed evidence for the importance of a local magnetic interlayer coupling mediated by magnetostatic stray fields emanating from domain walls. During the fast magnetization reversal, stray fields from domain walls in the hard magnetic layer can lead to a locally enhanced domain nucleation and thus to a faster switching of the soft magnetic layer. The images show furthermore that the speed of domain wall motion is influenced by the domain wall energy, leading to a lower velocity when domains are small. This becomes apparent as a delay in the nucleation of reversed domains.

Magnetismus

Vortrag: Mi., 18:00–18:20

M-V14

Ultraschnelle Magnetisierungsdynamik untersucht mit Femtosekunden-R¨ ontgenpulsen ¨rr1 , WolfChristian Stamm1 , Niko Pontius1 , Torsten Kachel1 , Hermann Du gang Eberhardt1 1

BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin

Die Entmagnetisierung eines d¨ unnen ferromagnetischen Films auf der fs-Zeitskala ist ein momentan noch nicht ausreichend verstandenes, grundlegendes Problem. Bisherige Experimente verwendeten fs-Pulse eines Lasers als Anregung wie auch als Sonde zur Messung der Magnetisierung. Diese ergaben eine Zeitkonstante von weniger als 1 ps f¨ ur die Entmagnetisierung [1]. Fragen nach dem Transfer von Drehmoment aus dem magnetischen System an das Gitter blieben jedoch offen: Die Spin-Gitter Relaxationszeit ¨ von 50-100 ps [2] ist zu lange, um eine Anderung der Magnetisierung auf der sub-ps Zeitskala zu erkl¨ aren. Wir verwenden Synchrotronstrahlung f¨ ur einen neuen, alternativen Ansatz zur Untersuchung der Magnetisierungsdynamik. Die R¨ ontgen-Absorptionsspektroskopie erlaubt uns, element-spezifische Messungen an d¨ unnen Filmen durchzuf¨ uhren. Messungen des Zirkular-Dichroismus geben Aufschluss u ¨ber die magnetischen Momente der Probe. ¨ Uber die Summenregeln ist es sogar m¨ oglich, die beiden Beitr¨ age zur Magnetisierung in Festk¨ orpern — das Orbital- und das Spinmoment der Elektronen — getrennt zu bestimmen. Dies erm¨ oglicht einen Einblick in den Transfer von Drehmoment zwischen den einzelnen Freiheitsgraden w¨ ahrend der fs Entmagnetisierung. Unser Experiment verwendet einen sogenannten laser pump – x-ray probe“ Auf” bau. Der magnetische Film wird mit einem fs-Laserpuls angeregt, und danach durch einen R¨ ontgenpuls mit variabler Zeitverz¨ ogerung gemessen. Die Zeitaufl¨ osung ist durch die zeitliche Struktur der verwendeten Synchrotronstrahlung gegeben. Die Dauer eines einzelnen R¨ ontgenpulses liegt normalerweise bei etwa 50 ps, in speziellen Betriebsschichten (low-alpha [3]) kann sie bis auf wenige ps verk¨ urzt werden. Noch k¨ urzere R¨ ontgenpulse von maximal 150 fs Dauer werden durch die Methode des Femtoslicings bei BESSY erzeugt [4]. Diese Zeitstruktur zusammen mit den Eigenschaften der Synchrotronstrahlung (einstellbare Photonenenergie und variable Polarisation) sind ein ideales Werkzeug f¨ ur unsere Problemstellung. Dadurch konnten wir zum ersten Mal die Entmagnetisierung eines 30 nm dicken Ni-Films innerhalb von 300 fs mittels R¨ ontgenZirkulardichroismus nachweisen. [1] E. Beaurepaire et al., Phys. Rev. Lett. 76 (1996) 4250. [2] A. Vaterlaus et al., Phys. Rev. Lett. 67 (1991) 3314. [3] J. Feikes et al., Proceedings of EPAC Lucerne (2004) 1954. [4] K. Holldack et al., Phys. Rev. ST Accel. Beams 8 (2005) 040704.

Magnetismus

Vortrag: Mi., 18:20–18:40

M-V15

Time-resolved SANS studies of field induced ordering in Ferrofluids Albrecht Wiedenmann1 , Uwe Keiderling1 , Klaus Habicht1 , Margerita ¨hler2 Russina1 , Roland Ga 1

Hahn- Meitner Institut , Glienickerstr. 100, 14109 Berlin, Germany – 2 Institut LaueLangevin, BP 85X, F-38042 Grenoble Cedex We report on real-time stroboscopic investigations of the kinetics of field induced ordering processes in concentrated Co-ferrofluids by means of SANS. Ordering of the magnetic particles was forced by an alternating magnetic field of frequency f(s) with a maximum amplitude of Hmax=±200 Gs. We applied for the first time the TISANE method where a fast chopper of frequency f(e) was synchronized to f(s) and adjusted to a data acquisition frequency f(d) of the detector.A considerable gain in intensity and resolution was obtained by this technique where a large frame overlap and high repetition rates could be achieved. Up to about f(s)=1300 Hz the SANS scattering patterns oscillated as a function of time from isotropic at H=0 to strongly anisotropic at Hmax. The observed threshold frequency is far below the resolution limit of the TISANE technique which must therefore result from the characteristic time needed for re-orientation of the magnetic particle moments. In a conventional stroboscopic SANS experiment when the data acquisition was triggered by a signal from the ac-field the periodic response was detected only up to about f(s)=600 Hz. With increasing frequency the oscillations are smeared out by the different flight times corresponding to the wavelength resolution of the velocity selector of 0.1 [2]. [1] R. G¨ ahler, R. Golub ILL Scientific council April (1999) SC 99-1, page 73 [2] A. Wiedenmann, U. Keiderling, K. Habicht, M. Russina, R. G¨ ahler sbm. PRL

Magnetismus

Vortrag: Mi., 18:40–19:00

M-V16

Dipolar correlations in nanocomposites A. Michels1 , C. Vecchini2 , O. Moze2 , K. Suzuki3 , P. K. Pranzas4 , J. ¨ller1,6 Kohlbrecher5 , J. Weissmu 1

Technische Physik, Universit¨ at des Saarlandes, Saarbr¨ ucken, Germany – 2 CNR-INFM S3 National Research Center, Physics Department, University of Modena and Reggio Emilia, Italy – 3 Department of Materials Engineering, Monash University, Melbourne, Australia – 4 GKSS Research Center, Geesthacht, Germany – 5 Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland – 6 Institut f¨ ur Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe, Germany

We present results for the magnetic-field, temperature, and neutron-polarization dependence of the recently observed dipole-field-induced spin disorder in the soft magnetic Fe-based nanocomposite Nanoperm (Fe89 Zr7 B3 Cu1 ). The mismatch of the saturation-magnetization values between the nanosized Fe particles (particle size: 12 nm) and the amorphous magnetic matrix gives rise to a dipolar stray field around each crystallite which induces spin disorder at the nanoscale and manifests itself as a pronounced clover-leaf-shaped angular anisotropy in the magnetic small-angle neutron scattering cross section (see figure below). We provide an analysis of the spindependent magnetic neutron scattering cross section of a multicomponent and multiphase nanocrystalline ferFig. 1: (a) Field dependence romagnet which entails anisotropic contributions that of difference-intensity data of give rise to enhanced magnetic scattering at angles θ = Nanoperm at T = 298 K. The total SANS cross section 45◦ relative to the direction of an applied magnetic dΣ/dΩ at µ0 H = 1.5 T has field. The clover-leaf-shaped anisotropy is observed in been subtracted from the respective dΣ/dΩ at the lower field. the scattering patterns over a wide range of applied (b) Temperature dependence of magnetic fields (∼ 30 − 290 mT) and momentum transdifference-intensity data. fers (0.08 nm−1 ≤ q ≤ 0.6 nm−1 ) and persists up to T = 693 K, i.e., several hundred degrees Kelvin higher than the Curie transition temperature of the amorphous matrix phase (TCam ∼ = 345 K). Analysis of the radiallyaveraged spin-misalignment scattering cross section suggests that the characteristic wavelength of the dipole-field-induced spin disorder is temperature independent and of the order of at least 80 nm, in other words, dipolar correlations evolve on a length scale larger than the mean particle size. Measurements with a polarized incident neutron beam indicate that the dipole-field-associated spin-misalignment scattering contributes only very little to the polarization dependence.

Struktur

Vortrag: Mi., 17:40–18:00

M-V17

Neutron diffraction study of the multinary chalcogenides CuFe1−x Znx SnS4 - a potential photovoltaic material Susan Schorr1 , Hans-Joachim Hoebler2 , Michael Tovar3 1

Hahn-Meitner-Institute Berlin, Dep. Solar Energy Research, Glienicker Str. 100, 14109 Berlin – 2 Institute of Mineralogy, Crystallography and Materials Science, University Leipzig, Scharnhorststr. 20, 04275 Leipzig – 3 Hahn-Meitner-Institute Berlin, Dep. Structural Research, Glienicker Str. 100, 14109 Berlin The multinary chalcogenides Cu2 FeSnS4 (stannite) and Cu2 ZnSnS4 (kesterite) have newly attracted attention as possible photovoltaic materials [1] since the availability of indium is an object of discussion regarding the large-scale production of CuInSe2 solar cells. Their both structures are are topologically identical, but assigned to different space groups due to a different distribution of the cations Cu+ , Zn2+ and Fe2+ . The stannite structure is consistent with the I-42m symmetry, with Fe located at at the origin (2a) and Cu at 4d (0, 21 , 14 ) [2]. In the kesterite structure, one Cu atom occupies the 2a (0,0,0) position, with Zn and the remaining Cu ordered at 2c (0, 12 , 14 ) and 2d (0, 41 , 43 ) respectively, leading to the spacegroup I-4 [2]. In both structures Sn is located at 2b (0,0, 12 ). The elements Cu and Zn are neighbours in the periodic table, Cu+ and Zn2+ have the same number of electrons, i. e. they have equal atomic form factors (f (Cu+ )=f (Zn2+ )). Hence these both cations are not distinguishable by conventional X-ray diffraction. The problem can be solved using neutron diffraction, because of the different neutron scattering lengths of Cu and Zn (bCu =7.718 fm, bZn =5.67 fm). Thus the investigation of the restructure process of the cation substructure in the stannite-kesterite join, CuFe1−x Znx SnS4 , is a prime example to demonstrate the power of neutron diffraction in structural research of complex materials. Neutron powder diffraction experiments were performed at the Hahn-Meitner-Institute Berlin at the high resolution powder diffractometer E9 (λ=1.79 ˚ A). Structural parameters and cation site occupancies were determined by Rietveld analysis of the data. From the latter the average neutron scattering length (bav (exp)) of the cation sites was obtained, providing the information about the cation restructure process. Based on a cation distribution model a theoretical average neutron scattering lengths (bav (calc)) was calculated. The condition bav (exp)=bav (calc) could be fullfilled by modelling the cation distribution. Surprisingly the evaluated Cu+ and Zn2+ distribution in kesterite (Cu2 ZnSnS4 ) is random on the sites 2c and 2d, which is in disagreement to literature [2, 3]. This may be caused by the Cu-Zn differentiation problem in X-ray diffraction as described above. The crossover from stannite (x=0) to kesterite (x=1) in CuFe1−x Znx SnS4 was found as a three-stage process of cation restructure involving Cu+ , Zn2+ and Fe2+ . The Sn4+ cation does not take part in this process. The knowledge about the metal distribution in CuFe1−x Znx SnS4 multinary compounds provides a basis for further studies, i. e. about defect compounds. [1] H. Katagiri, Thin Sol. Films 480-481 (2005) 426. [2] Hall et al., Can. Mineral. 16 (1978) 131. [3] Bonazzi et al., Can. Mineral. 41 (2003) 639 and references within.

Struktur

Vortrag: Mi., 18:00–18:20

M-V18

Real-time observation of structural and orientational transitions in organic semiconductor growth Stefan Kowarik1,2 , Alexander Gerlach1,2 , Stefan Cavalcanti3 , Oleg Konovalov3 , Frank Schreiber1

Sellner1 ,

Leide

1

T¨ ubingen University, Institute for Applied Physics, 72076 T¨ ubingen, Germany – Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3 ESRF, 38053 Grenoble, France 2

We use in-situ and real-time X-ray scattering during growth of the organic semiconductor diindenoperylene to study the kinetically controlled evolution of the film structure with time. We manage to produce movies of the changes in reflectivity and grazing incidence diffraction in a relatively broad q range, i.e. beyond simple anti-Bragg-point time scans during organic molecular beam deposition [1]. These measurements yield structural and morphological information for a range of film thicknesses. We identify a transition from layer by layer growth to rapid roughening [2] after 9 MLs for high temperature growth, subtle changes of the molecular tilt angle, a dynamic change of the in-plane unit cell dimensions, and competition between standing up and lying down phases for low temperature growth. Importantly the real-time measurements also reveal dynamic growth phenomena such as transient structures during growth which would be missed in simple post-growth measurements.

Fig. 1: Real-time evolution of the specular reflectivity during diindenoperylene growth.

Struktur

Vortrag: Mi., 18:20–18:40

M-V19

Electrical and structural properties of DX defects in CdTe ¨rker1 , Jo ¨ rg Kronenberg1 , Manfred Deicher1 , Herbert Muhammed Tu 1 1 Wolf , Karl Johnston , Thomas Wichert1 , ISOLDE Collaboration2 1 2

Technische Physik, Universit¨ at des Saarlandes, D-66041 Saarbr¨ ucken, Germany – CERN, CH-1211 Geneva 23, Switzerland

In some semiconductors the achievable doping levels are limited by the formation of intrinsic defects which leads to the effect of electrical “self-compensation” of dopants. In AlGaAs and CdTe, donors are electrically compensated by the formation of so-called DX centers. In the case of In donors in CdTe and In concentrations exceeding 1018 cm−3 , these DX centers are created. A characteristic feature of DX centers is the so-called “persistent photoconductivity (PPC)”, a metastable state of the DX-center, that is formed by illumination at low temperatures thereby increasing the carrier concentration. The DX-center and the PPC effect are theoretically explained by the “large lattice relaxation model” [1]. In this model, the DX center is formed by the relaxation of the In donor towards an interstitial lattice site thereby generating a neighboring Cd vacancy. Then, the PPC effect consists in a relaxation of the In donor back to a substitutional lattice site resulting in an electrically reactivation of the donor. In this model, the lattice relaxation involves changes of the In-Te distance of more then 1 ˚ A thereby locally breaking the cubic symmetry of the CdTe lattice. Such a lattice perturbation should create an electric field gradient (EFG) observable by perturbed angular correlation spectroscopy (PAC). Using the probe 111 In/111 Cd, an EFG assigned to the DX defect has been reported characterized by νQ = 21 MHz and η = 0 [2]. This assignment is based on theoretical calculations of the respective EFG. At the same time, these calculations predict a short lived stability of the DX center even after the decay of 111 In to 111 Cd, the isotope at which the actual PAC measurements take place. We performed PAC measurements using 111 In/111 Cd and simultaneously measured the conductivity of the same samples as a function of temperature with and without illumination. Below 150 K, the samples showed a PPC effect that was accompanied by an increase of about 20 % of the carrier concentration. But, this effect is not accompanied by any changes of the observed EFG. Possible explanations of the observed EFG, originally assigned to the DX center will be discussed. We will also present first results on the experimental detection of DX centers in CdTe by PAC using the radioactive isotope 117 Cd decaying to 117 In; this isotope is both a donor in CdTe and a PAC probe atom. In this type of experiment, the DX centers including In donors are formed after the decay of 117 Cd and are still present during the PAC measurement performed at an excited nuclear state of 117 In. This work has been supported by the Bundesministerium f¨ ur Bildung und Forschung (BMBF) under Contract No. 05 KK1TSB/5. [1] C.H. Park and D.J. Chadi, Phys. Rev. B 52 (1995) 11884. [2] S. Lany, H. Wolf, and Th. Wichert, Phys. Rev. Lett. 92 (2004) 225504.

Struktur

Vortrag: Mi., 18:40–19:00

M-V20

Neutronographische Texturanalyse zur Absch¨ atzung statischer bzw. dynamischer Deformationsanteile in Carrara-Marmor (Appenin) ¨k1,2 Kurt Walther1 , Alexander Frischbutter1 , Christian Scheffzu 1

GeoForschungsZentrum Potsdam, Section 5.3, Telegrafenberg, 14473 Potsdam, Germany – 2 Frank Laboratory of Neutron Physics, JINR Dubna, 141980 Dubna, Russia Die vorgestellte Texturmessung erfolgte am Neutronendiffraktometer SKAT des Forschungsreaktors IBR-2 in Dubna (RUS) mit der Flugzeitmethode. Im westlichen Teil der Toskana sind im Bereich des Apennin m¨ achtige Kalkformationen triasischen bis jurasischen Alters am S-Rand des Alpenbogens deformiert worden. Teil dieser m¨ achtigen Flyschsedimente, abgelagert in der Tethys, sind auch die tiefjurassischen (200 Mill. Jahre) Ausgangsgesteine der Carrara-Marmore. Die bereits vor 2000 Jahren zu Zeiten des Augustus intensiv abgebauten Gesteine streichen in einem weit nach Osten auslaufenden Gebirgsbogen des Apennin (Apuanische Alpen) in einem geologischen Fenster umgeben von terti¨ aren Folgen aus. Ihre Deformation erfolgte im wesentlichen zu terti¨ arer Zeit (Eoz¨ an 40 Mill. Jahre) im Zusammenhang mit der Auffaltung von nach Osten j¨ unger werdenden Faltenb¨ ogen. Den st¨ arksten Hebungsphasen im Mioz¨ an vor etwa 15 Mill. Jahren folgt im Pleistoz¨ an eine magmatisch-intrusive und vulkanische Entwicklung im s¨ udlich an das Apennin grenzende Latium. Die Struktur der Carrara-Marmore wird in der Fachliteratur einer kontaktmetamor¨ phen Uberpr¨ agung im Bereich dieser granitischen Intrusionen (um 2 Mill. Jahre und j¨ unger), das heißt einer im wesentlichen durch statische Rekristallisation gepr¨ agten Formung zugeschrieben. Die Ergebnisse der durchgef¨ uhrten Texturanalyse (Fasertextur mit G¨ urteltendenz, Abb. 1) belegen jedoch zus¨ atzlich eine deutliche kristallographische Vorzugsorientierung der Kalzitminerale, - auch f¨ ur eine Probe von einer makroskopisch massigen Gesteinsvariante. Damit kann zus¨ atzlich auch eine dynamische Deformationskomponente belegt werden, wie sie in Anbetracht der in den alpiden Faltenbau einbezogenen Formation auch zu erwarten war. Vor allem diese Deformationsanteile beeinflussen letztlich nicht unwesentlich die Brauchbarkeit des Gesteins als Werkstoff.

Abb. 1: Experimentelle Kalzit-(0006)-Polfigur

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 17:40–18:00

M-V21

Structural Aspects of Porphyrins as Biomimetic Antennas Gernot Buth1 , Myriam Linke-Schaetzel2 , Christopher E. Anson3 , Teodor Silviu Balaban2 1

Forschungszentrum Karlsruhe, Institut f¨ ur Synchrotronstrahlung (ISS), Hermannvon-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen – 2 Forschungszentrum Karlsruhe, Institut f¨ ur Nanotechnologie (INT) – 3 Universit¨ at Karlsruhe (TH), Institut f¨ ur Anorganische Chemie, Engesserstr. 15, D-76131 Karlsruhe Light-harvesting occurs in some photosynthetic bacteria with great efficiency, sometimes even at 100 m under the water surface. These photon sponges have organelles called chlorosomes, which act as light-harvesters and which agglomerate bacteriochlorophyll c as the main pigment molecule [1]. The advent of the ANKA Synchrotron source [2] made possible collection of X-ray diffraction data on quite small crystals of several self-assembling porphyrins which are equipped with the same recognition groups as the natural bacteriochlorophyll. The solved crystal structures allow an unprecedented insight into the supramolecular organization of such antenna systems [3]. Below is shown a stack of a porphyrin which crystallizes into two different modifications and which can pack in different ways [3]. In another example, a conformational switching between energy and electron transfer will be presented [4]. X-ray crystallography allows to understand the structural implications and thus programming of the self-assemblies for a certain function, as for instance light-harvesting. It is hoped that this knowledge will bear fruit in the construction of efficient biomimetic solar cells. [1] [2] [3] [4]

T. S. Balaban, Acc. Chem. Res. 38 (2005) 612. H. O. Moser, Journal of Alloys and Compounds 328 (2001) 42. T. S. Balaban et al., Chem. Eur. J. 11 (2005) 2267. M. Linke Schaetzel et al., Chem Eur J. 12 (2006) 1931.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 18:00–18:20

M-V22

Inhibition of Calcium Phosphate Formation in the Presence of the Protein Fetuin-A Alexander Heiss2 , Dietmar Schwahn1

Hitoshi

Endo1 ,

Willi

Jahnen-Dechent2 ,

1

IFF - FZ J¨ ulich, 52425 J¨ ulich – 2 IZKF BioMAT, Universit¨ atsklinik, Pauwelsstrasse 30, 52074 Aachen Fetuin-A / α2 -HS glycoprotein is a liver derived serum protein [1]. It strongly accumulates in bone due to its affinity for the mineral phase[2] and a direct impact on bone metabolism was reported [3]. However, the prime physiological role of fetuin-A apparently is the systemic inhibition of calcium phosphate mineral deposition in extracellular fluids [4]. Clinical studies conducted in humans demonstrated that reduced fetuin-A serum levels in dialysis patients correlate with the extent of soft tissue calcification and mortality [5]. Thus the lack of fetuin-A has serious pathobiochemical consequences. SANS is a rather new experimental technique in this field of biomineralization, it delivers detailed structural information about mineral-protein composites by applying contrast variation method which is done by proper varying the H2 O/D2 O composition of the aqueous solution [6]. The formation and maturation of the mineral particles in the presence of fetuin proceeds in a two-stage process. During the first stage particles of about 250 ˚ A radius of gyration were observed for about 5 hours immediately after mixing. Between 5 and 10 hours the particles slowly increased their size to the order of 500 ˚ A representing the second stage. From 10 to 24 hours (the experimental endpoint) we observed stable particles. The structure of the mineral-organic particles of the second stage was further analyzed by the method of contrast variation [6]. The partial scattering functions were derived by the “singular value decomposition” method. The self-term PP,P represents a bimodal distribution of the fetuin-A attributed to the mineralized particles (at low Q) and the fetuin-A monomers (at high Q). All self-terms show Porods Q−4 power law indicating compact particles with a sharp interphase. The positive cross-term PP,M suggests a mineral core covered by a protein layer. We found an octacalcium phosphate core and a dense protein monolayer, which protects the mineral from further growth until sedimentation takes place. So, inhibition of mineral deposition is based on the stabilization of 1000 ˚ A sized colloidal particles. We thank German Science Foundation for financial support within the priority program “Principles of Biomineralization”. [1] K.O. Pedersen, Nature 3914 (1944) 575. [2] J.T. Triffitt et al., Nature 262 (1976) 226. [3] M. Szweras et al., J. Biol. Chem. 277 (2002) 1999. [4] C. Sch¨ afer et al., J. Clin. Invest. 112 (2003) 357. [5] M. Ketteler et al., Lancet 361 (2003) 828. [6] H. Endo, D. Schwahn , H. C¨ olfen, J. Chem. Phys. 120 (2004) 9410.

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 18:20–18:40

M-V23

Photoelektronen Spektroskopie mit harter R¨ ontgenstrahlung f¨ ur chemisch sensitive Strukturanalyse und Valenzbandspektroskopie ¨ rg Zegenhagen1 , Tien-Lin Lee1 , Sebastian Thieß1 , Christof Kunz2 , RoJo bert L. Johnson2 1

European Synchrotron Radiation Facility, Grenoble, France – 2 Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg Das Gebiet der Photoelektronen Spektroskopie (PS) mit harter R¨ ontgenstrahlung (Hard X-Ray Photoelectron Spektroscopie, HAXPES) ist durch die Verf¨ ugbarkeit von Synchrotronstrahlungsquellen der dritten Generation zug¨ anglich geworden. Man ben¨ otigt eine brilliante Anregungsquelle, da die Wirkungsquerschnitte f¨ ur die Elektronenanregung ann¨ ahernd mit der dritten Potenz der Photonenenergie abfallen. Ein zentraler Vorteil der HAXPES Technik ist die große Ausdringtiefe von Elektronen hoher kinetischer Energie. Mit Photoelektronen im 10 keV Energiebereich werden Informationstiefen im 10 nm Bereich erreicht, ideal um die St¨ arken der PS auf heutzutage interessante Nano-Strukturen anzuwenden. Zudem kann mit R¨ ontgenmonochromatoren im harten R¨ ontgenbereich eine exzellente Energieaufl¨ osung erzielt werden (ca. 1 meV bei 15 keV). Jedoch ist es zur Zeit noch nicht erwiesen, dass eine entsprechende Aufl¨ osung vom Elektronenspektrometer erzielt werden kann. (Kommerzielle Spektrometer erreichen zur Zeit maximal 10 keV und eine Aufl¨ osung von 50-100 meV). Ein weiterer Vorteil ergibt sich durch die Kombination von HAXPES mit R¨ ontgeninterfrenzfeldern (X-ray Standing Waves, XSW) wodurch atomare Strukturen element-spezifisch und auch chemisch spezifisch (d.h. gem¨ aß des Bindungszustandes der Atome eines Elementes) abgebildet werden k¨ onnen. Der Stand des Gebietes ist zur Zeit am besten in Ref. 1 dokumentiert, den Proceedings des ersten HAXPES Workshops in Grenoble 2003. Wir werden in unserem Beitrag u ¨ber die Messung von Wirkungsquerschnitten von schwach gebundenen Elektronenniveaus im harten R¨ ontgenbereich bis ca. 15 keV berichten, die wir mit einem kommerziellen Elektronenspektrometer (PHI 10-360) und einer speziellen von uns konstruierten Retardierungslinse analysiert haben. Wir werden weiterhin schildern wie die Kombination von HAXPES und XSW es erlaubt nachzuweisen, dass ultra-d¨ unne Schichten des Supraleiters YBa2 Cu3 O7 auf SrTiO3 in Form von perowskitischen Cu(Y,Ba)-oxid Einheitszellen wachsen und welchen Atomen in der SrTiO3 Einheitszelle die verschiedenen Regionen des SrTiO3 Valenzbandes zugeordnet werden k¨ onnen. Im Rahmen der laufenden BMBF F¨ orderperiode ist inzwischen zusammen mit der Industrie ein Spektrometer im Bau, das f¨ ur die Spektroskopie im harten R¨ ontgenbereich optimiert ist. [1] HAXPES 2003, proceedings of the workshop on Hard X-ray Photoelectron Spectroscopy, ESRF, Grenoble September 11-12, 2003, Editors: J¨ org Zegenhagen and Christof Kunz; Nuclear Instruments and Methods in Physics Research, section A, Vol. 547, No. 1 (2005).

Nanostrukturen und Grenzfl¨ achen

Vortrag: Mi., 18:40–19:00

M-V24

Structure determination of nanoparticles using the pair distribution function Reinhard Neder1 , Vladimir Korsunkiy1 1

Institut f¨ ur Mineralogie, Am Hubland 97074 W¨ urzburg

PDFs of interatomic distances G(R) are obtained by Fourier transformation of powder diffraction pattern [1]. The PDF peak positions correspond to interatomic distances and the peak intensity is proportional to the number of corresponding distances. This allows the modelling of the real atomic mutual arrangement in extremely small (13 nm) nanoparticles [1,2], whose structure cannot be investigated with the standard methods like Rietveld fitting of powder diffraction intensities. By the use of high intensity high energy synchrotron radiation (λ=0.1 ˚ A, E=100-120keV), one can reliably obtain highly resolved PDFs. This is due to the possibility to precisely measure the very weak scattering up to a very high diffraction vector qmax =4πsinΘ/λ=30 ˚ A−1 . Our measurements were carried out at the beam line BW5 at HASYLAB DESY in Hamburg [1]. The PDFs of both, polycrystalline and nanocrystalline ZnSe show sharp peaks, characteristic of interatomic distances in a crystal. The PDF of crystalline ZnSe does show these up to very large R, while in the PDF of nanocrystalline ZnSe, equivalent peaks have already disappeared at R>30 ˚ A due to the finite nanoparticle size. This allows to estimate the particle size as being ca. 30 ˚ A. The modelling of the PDF shows that the nanoparticles have the zincblende structure but with several defects. Small (D=18 ˚ A) CdS nanoparticles have a quasi-amorphous structure and the two types of S atoms the internal inorganic and the external belonging to the organic ligands define two quite distinct CdSCd angles (109 and 100◦ ) between the Cd-S (2.52 ˚ A) bonds. In the RDF, the two peaks produced by distances between heavy Cd atoms (at 3.85 and 4.11 ˚ A) correspond to these different bond angles. In the PDF of composite nanoparticles consisting of a CdSe core and a ZnS shell, interatomic distances characteristic for both components were observed directly. In the diffraction pattern, however, only very broad and overlapping peaks are observed due to the small particle size and structural defects. [1] V.I. Korsounski, R.B. Neder, at all, J.Appl.Cryst. 36 (2003) 1389. [2] V.I. Korsunskiy, , R.B. Neder, J.Appl.Cryst. 38 (2005) 1020.

Methoden und Instrumentierung

Vortrag: Do., 09:40–10:00

D-V25

PETRA III: a new high brilliance synchrotron radiation source at DESY ¨ hlsberger1 , Horst Hermann Franz1 , Ulrich Hahn1 , Olaf Leupold1 , Ralf Ro 1 1 1 Schulte-Schrepping , Oliver Seeck , Joachim Spengler , Markus Tischer1 , Edgar Weckert1 , Thomas Wroblewski1 1

Deutsches Elektronen Synchrotron DESY, Notkestr. 85 22607 Hamburg

In 2003 DESY has decided to reconstruct its 2.3 km long PETRA storage ring into a third generation synchrotron radiation source called PETRA III from mid 2007 on. A technical design report has been published in spring 2004 (http://petra3.desy.de). PETRA III will be operated at a particle energy of 6 GeV and its emittance will be 1 nmrad which is a world record low value for a high energy storage ring. The storage ring current will be 100 mA (in top-up mode) in the beginning. Due to these parameters PETRA III will be the most brilliant storage ring based X-ray source enabling a wealth of new experimental techniques like sub 100 nm focusing or experiments exploiting coherent photons. In total 14 insertion device beamlines will be available for experiments. Planning and R&D for PETRA III is in an advanced stage and the first components for the new storage ring sections have already been ordered. The scientific program of the phase I beamlines has been decided on and detailed planning in collaboration with the user community is ongoing. The presentation will give an overview about the scientific possibilities of PETRA III and report on the status.

Methoden und Instrumentierung

Vortrag: Do., 10:00–10:20

D-V26

Materialforschung mit energiereichen Schwerionen bei der GSI Reinhard Neumann1 1

Gesellschaft f¨ ur Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt

Die GSI verf¨ ugt mit Hochladungsinjektor HLI, Linearbeschleuniger UNILAC und Schwerionensynchrotron SIS u ¨ber Großger¨ ate, mit denen sich Ionenstrahlen s¨ amtlicher Elemente des Periodensystems (am SIS in allen Ladungszust¨ anden bis hin zu nacktem Uran) erzeugen lassen. Die Energien betragen 1,4 MeV/u am HLI, etwa 4 bis 12 MeV/u am UNILAC und ca. 50 MeV/u bis 1 GeV/u (f¨ ur leichtere Ionen bis 2 GeV/u) am SIS. Am Anfang der Pr¨ asentation steht eine kurze Darstellung der an diesen Beschleunigern betriebenen Strahlpl¨ atze f¨ ur Material- und Festk¨ orper-Untersuchungen, sowie der in-situ und in Laboren außerhalb der Strahlpl¨ atze vorhandenen Analysetechni¨ ken. Es folgt dann ein Uberblick der im GSI-Bereich Materialforschung in Kooperation mit zahlreichen in- und ausl¨ andischen Partnern bearbeiteten Themenschwerpunkte: (1) Ein breites grundlagenorientiertes Arbeitsgebiet betrifft Schwerionen-induzierte Ver¨ anderungen wie Punktdefekte oder Phasen¨ uberg¨ ange in Festk¨ orpern, zum Beispiel bei gleichzeitiger Anwendung von Druck oder tiefer Temperatur. So wurden erstmals in einer Diamantstempelzelle unter hohem Druck befindliche Festk¨ orper betrahlt, wobei der SIS-Ionenstrahl aufgrund seiner hohen kinetischen Energie mehrere Millimeter Diamant durchlief. Weitere Arbeitsgebiete sind sowohl grundlagen- als auch in erheblichem Maß anwendungsorientiert: (2) Energiereiche Schwerionen erzeugen lange sog. latente Spuren, durch deren Auf¨ atzung Nanoporen entstehen. Durch Bestrahlung einer Polymerfolie mit nur einem Schwerion erh¨ alt man auf diese Weise eine EinzellochMembran, die zum Studium von Materialtransport wie z. B. biologischer Molek¨ ule besonders geeignet ist. (3) Materialabscheidung in solchen Kan¨ alen erm¨ oglicht auch die Erzeugung von Nanodr¨ ahten, die je nach den verwendeten Abscheideparametern poly- oder einkristallin sein k¨ onnen. Zu den an Nanodr¨ ahten untersuchten Eigenschaften geh¨ oren elektrischer Widerstand, thermische Instabilit¨ at und m¨ ogliche, durch die eingeschr¨ ankte Geometrie bewirkte Quanteneffekte. (4) Die Schwerionen-Mikrosonde am UNILAC dient der Bestrahlung von Objekten, wie elektronische Schaltkreise oder biologische Zellen. Diese Sonde zeichnet sich durch die F¨ ahigkeit aus, einzelne Schwerionen einschließlich Uran auch bei maximaler UNILAC-Energie von 12 MeV/u mit einer Pr¨ azision von ca. 0,5 Mikrometer zu plazieren. So werden u.a. in Zusammenarbeit mit dem GSI-Bereich Biophysik einzelne Zellkerne in einer Zellkultur bestrahlt mit anschließender Beobachtung, wie sich getroffene und nicht bestrahlte Zellen u ¨ber gr¨ oßere Zeitspannen verhalten.

Methoden und Instrumentierung

Vortrag: Do., 10:20–10:40

D-V27

New High Field Magnet for Neutron Scattering at Hahn-Meitner Institute M. Steiner1 , A. Tennant1 , F. Mezei1 , P. Smeibidl1 1

Hahn-Meitner Institut, Glienicker Str. 100, D-14109 Berlin, Germany

The Berlin Neutron Scattering Center BENSC at the Hahn-Meitner-Institute as a user facility for structural research with neutrons and synchrotron radiation has a special emphasis on experiments under high magnetic field. For over 10 years HMI has developed experience in special neutron sample environment at low temperatures and high magnetic fields. Neutron scattering is uniquely suited to study magnetic properties on a microscopic length scale. This is because neutrons have comparable wavelengths and, due to their magnetic moment, they interact with the atomic magnetic moments. Magnetic interactions and magnetic phenomena depend on thermodynamical parameters like magnetic field, temperature and pressure. Therefore special efforts are made in HMI’s neutron research to offer outstanding sample environment equipment. We are running eight different magnet systems up to the highest static, vertical field for neutron scattering of 17.5 T worldwide. Combined with systems for low and high temperatures as well as high pressure, these magnets can be used at several neutron instruments. For the future a dedicated instrument for neutron scattering at extreme fields is under construction (Extreme Environment Diffractometer, ExED). The TOF technique permits the access of a broad range of Q-values or d-spacing domains under scattering angle access strongly restricted to forward and backward directions by the use of highest field magnets above 30 T. Both cold and thermal neutrons are delivered to the instrument by a new multispectral extraction system and a ballistic guide and give rise to a very broad wavelength spectrum of 0.7 ˚ A < λ < 20 ˚ A. For this instrument the existing superconducting magnets as well as a future hybrid system can be used. The highest fields, above 30 T will be produced by the planned series-connected hybrid magnet system, designed and constructed in collaboration with the National High Magnetic Field Laboratory, Tallahassee, FL. This will be a horizontal magnet system with coned ends at both sides. Results of present neutron scattering experiments and examples for future research possibilities at very high fields will be given.

Weiche Materie

Vortrag: Do., 09:40–10:00

D-V28

Using Neutron Spectroscopy to Study Collective Dynamics of Biological and Model Membrane Systems ¨dter1 , Tilo Seydel1 , Wolfgang Ha ¨ussler2 , Tim Salditt3 Maikel C. Rheinsta 1

Institut Laue-Langevin, B.P. 156, 6 rue Jules Horowitz, 38042 Grenoble, France – FRM-II, Technische Universit¨ at M¨ unchen, 85747 Garching, Germany – 3 Institut f¨ ur R¨ ontgenphysik, Friedrich-Hund Platz 1, 37077 G¨ ottingen, Germany

2

While most spectroscopic techniques, as, e.g., nuclear magnetic resonance or dielectric spectroscopy probe macroscopic responses, neutron and within some restrictions also x-ray scattering experiments give the unique access to microscopic dynamics at length scales of intermolecular or atomic distances. Only recently, it has become possible to study collective dynamics of planar lipid bilayers using neutron spectroscopy techniques [1]. We determined the dispersion relation of the coherent fast picosecond density fluctuations on nearest neighbor distances of the phospholipid acyl chains in the gel and in the fluid phases of a DMPC bilayer and could shed light on the evolution of structure and dynamics in the range of the gel-fluid main phase transition. By combining different neutron scattering techniques, namely three-axis, backscattering and spin-echo spectroscopy, we present measurements of short and long wavelength collective fluctuations in biomimetic and biological membranes in a large range in momentum and energy transfer, covering time scales from about 0.1 ps to almost 1 µs and length scales from 3 ˚ A to about 0.1 µm [1-4]. Because of optimized setups and sample preparation, inelastic neutron scattering experiments supply for the first time sufficiently strong coherent inelastic signals for quantitative analysis. The measurements offer a large window of length and time scales to test and refine theoretical models of dynamics of biomimetic and biological membranes. From a smectic hydrodynamic theory, the long wavelength dispersion relation give direct access to the elasticity parameters of the membranes in the fluid phase [3], i.e., the bilayer bending rigidity κ and the compressional modulus B of the stacks. [1] M.C. Rheinst¨ adter, C. Ollinger, G. Fragneto, F. Demmel, T. Salditt, Phys. Rev. Lett. 93, 108107 (2004). [2] Maikel C. Rheinst¨ adter, Tilo Seydel, Franz Demmel, Tim Salditt, Phys. Rev. E 71, 061908 (2005). [3] Maikel C. Rheinst¨ adter, Wolfgang H¨ außler, Tim Salditt, submitted. [4] Maikel C. Rheinst¨ adter, Tilo Seydel, Tim Salditt, submitted.

Weiche Materie

Vortrag: Do., 10:00–10:20

D-V29

Swelling kinetics and structural changes of polyelectrolyte multilayers in contact with aqueous solution and water vapor Roland Steitz1 , John E. Wong2 , Regine v. Klitzing3 1

Hahn-Meitner-Institut, SF1, Glienicker Str. 100, D-14109 Berlin – 2 TU Berlin, Stranski-Laboratorium, Straße des 17. Juni 112, D-10623 Berlin – 3 ChristianAlbrechts-Universit¨ at Kiel, Ludewig-Meyn-Strasse 8, D-24118 Kiel The sequential layer-by-layer adsorption of polyanions and polycations to build polyelectrolyte multilayers has triggered enormous interest in their potential uses in a wide range of fields, from photonic to pharmaceutical applications. This is due to the ease of preparation, the possibility to control film thickness with Angstrom precision and because the macroscopic properties can be influenced by the chemical composition of the polymers [1]. The detailed mechanism of film formation and the manipulation of the films by external means are current topics of active research. Experimental studies have shown that the main driving force for the assembly of multilayer films is the electrostatic attraction between the oppositely charged polyelectrolyte chains and the concomitant release of counter ions. We have found that a minimum charge density of ca. 60 % of the fully charged chains is necessary for obtaining stable films [2]. We will show that the conformation of the solvent swollen films - prior to drying - is determined by the initial adsorption conditions [3], but can be altered ex-situ by exposure to a liquid phase of very high ionic strength. Recently, it has been observed that the swelling depends on outermost layer [4, 5]. The water uptake of the outer layers is more pronounced, which leads to the assumption, that they are more loosely packed than the inner layers near the template [5]. A neutron reflectivity study of this effect in addition indicated the existence of two kinds of water, bound with different strength within the films. Beside unexpected two-step kinetics of swelling, the reflectivity curves of the layers against vacuum before and after re-hydration in D2 O vapor did not agree. It was only after subsequent re-hydration in saturated H2 O vapor that the initial and final reflectivity curves against vacuum superimposed. We will discuss our findings in the context of polyion complex formation, interdigitation and film imperfections. [1] G. Decher, Science 277, 1232 (1997) [2] R. Steitz, W. Jaeger, R. v. Klitzing, Langmuir 17, 4471 (2001) [3] R. Steitz, V. Leiner, R. Siebrecht, R. v. Klitzing, Colloids Surfaces A 163, 63 (2000) [4] B. Schwarz, M. Sch¨ onhoff, Langmuir 18, 2964 (2002) [5] J. E. Wong, F. Rehfeldt, P. H¨ anni, M. Tanaka, and R. v. Klitzing, Macromolecules, 37, 7285 (2004)

Weiche Materie

Vortrag: Do., 10:20–10:40

D-V30

Dynamics of soft matter surfaces investigated with X-ray photon correlation spectroscopy Christian Gutt1 , Robert Fendt2 , Simone Streit2 , Tuana Ghaderi2,3 , Anders Madsen4 , Metin Tolan2 , Sunil K. Sinha3 1

Hasylab at Desy, Notkestrasse 85, 22603 Hamburg – 2 Experimentelle Physik Ia, Universit¨ at Dortmund – 3 University of California at San Diego, CA 92039, USA – 4 European Synchrotron Radiation Facility (ESRF), Grenoble, France X-ray photon correlation spectroscopy is used to study the dynamics of soft matter surfaces. We present results of capillary wave dynamics on bulk liquid surfaces, thin wetting films on solid substrates and the 2-dimensional slow dynamics of gold cluster on polymer surfaces. We present a formalism for resolution effects in XPCS experiments based on the theory presented in reference [1]. This formalism enables us to explain experimentally observed transitions between homodyne and heterodyne correlation functions and to explain the excess damping usually found for propagating waves. XPCS experiments from thin vapour deposited wetting films on solid substrates showed the absence of capillary wave dynamics on length scales even below the thickness dependent van der Waals cutoff. Instead of capillary wave dynamics we found a static surface morphology with a peculiar 1/q3 power law behaviour. The speckle structure from the diffuse scattering in plane scattering and the reflectivities depend on the conditions of sample preparation. The dynamic structure factor of gold particles moving on the surface of thin polymer films has been measured. Above the glass transition of the polymer we found the dynamic structure factor of the gold clusters to follow the peculiar form f(q,t) ∼ exp(-(t/τ )α ) with an exponent α= 3/2 that is a faster than exponential decay of the correlation function. The relaxation times scales 1/q thus pointing to hyperdiffusive motion. Moreover aging phenomena are observed. [1] S. K. Sinha, M. Tolan, A. Gibaud, Phys. Rev. B 57, 2740 (1998)

Materialien/Werkstoffe

Vortrag: Do., 09:40–10:00

D-V31

Kristallographische Textur industrierelevanter Komponenten ¨nter Brokmeier1 Heinz-Gu 1

IWW - Technische Universit¨ at Clausthal / GKSS-Forschungszentrum, Max-PlanckStr, 21502 Geesthacht In der materialkundlichen Beschreibung von realen Komponenten (Bauteilen oder Halbzeugen) sind zerst¨ orungsfreie Pr¨ ufungen bez¨ uglich Bauteilfehlern, anisotroper Eigenschaften und Restspannungen von großer Bedeutung f¨ ur deren Einsatz. F¨ ur anisotropes Verhalten ist in vielen F¨ allen die Gesamtheit der Mikrostruktur inklusiv der Vorzugsorientierung, der das Bauteil aufbauenden Kristalle, verantwortlich. Die Standardverfahren zur Bestimmung kristallographischer Texturen (Texturtyp, Textursch¨ arfe und Einfluss auf die Anisotropie der Eigenschaften) arbeiten zerst¨ orend mittels Laborr¨ ontgenanlagen [1] und Elektronenstrahlen (EBSD-Verfahren) [2]. Im Falle von grobk¨ ornigen Materialien, wo große Probenvolumina zur Erreichung der Kornstatistik ben¨ otigt werden, kommt die Neutronenbeugung zum Einsatz [3]. Im Gegensatz dazu kann die Texturuntersuchung von Bauteilen und Halbzeugen zerst¨ orungsfreies Messen erforderlich machen, insbesondere wenn Restspannungen an identischen Proben untersucht werden m¨ ussen. Messungen im inneren kompakter Proben erfordert eine Messsonde mit hoher Eindringtiefe. Hierf¨ ur sind thermische Neutronen und harten R¨ ontgenstrahlen mit Eindringtiefen im cm-Bereich (z. B. 100 keV-R¨ ontgen: Mg 3,40 cm, Cu - 0,20 cm; Neutronen: Mg - 6,10 cm, Cu - 0,85 cm). Die Anforderungen an das Texturexperiment sind je nach Probenmaterial und geometrie sehr unterschiedlich. Untersuchungen an Niobrohren unterschiedlicher Qualit¨ aten wurden durchgef¨ uhrt um Texturinhomogenit¨ aten u ¨ber den Umfang von 84mm dicken Rohren mit Wandst¨ arken von 4 mm zu ermitteln. Die Bestimmung von kristallographischen Texturen an Standardzugproben dient der direkten Korrelation von Materialeigenschaften (Spannungs-Dehnungs-Messungen, Streckgrenze, Bruchdehnung etc.) mit der Textur an identischen Probenbereichen. Messungen an einer Stahlwelle, an einer Raketend¨ use und an TiAl-Turbinenschaufeln wurden wahlweise mit Neutronen oder harten R¨ ontgenstrahlen durchgef¨ uhrt. Die Auswahlkriterien waren die Eindringtiefe des Strahles, das Streuverhalten des Materials, die Probengeometrie und die Korngr¨ oßenverteilung. [1] L. Spieß et al., Moderne R¨ ontgenbeugung, Teubner (2005). [2] H.J. Bunge und R. A. Schwarzer, Advanced Engineering Materials 3 (2001) 25. [3] V. Jung und H.-G. Brokmeier, Crystal Research and Technology 35 (2000) 321.

Materialien/Werkstoffe

Vortrag: Do., 10:00–10:20

D-V32

Bestimmung von Spannungsfeldern mit hoher Ortsaufl¨ osung Bernd Hasse1 , Mustafa Kocak2 , Walter Reimers1 1

TU Berlin, Institut f¨ ur Materialwissenschaften und –technologien, Sekr. BH18, ErnstReuter-Platz 1, 10587 Berlin – 2 GKSS, Max-Planck-Str. 1, 21502 Geesthacht Am Messplatz G3 am HASYLAB/DESY [1] wurden mit dem MAXIM Verfahren Eigenspannungen am Beispiel von Reibr¨ uhr- und Laserschweißn¨ ahten ortsaufgel¨ ost unter Verwendung des sin2 Ψ-Verfahrens [2] untersucht. Im Rahmen des sin2 Ψ-Verfahrens werden Beugungsmessungen im Hinblick auf die Bestimmung von Eigenspannungen unter verschiedenen Einfallswinkeln Ψ durchgef¨ uhrt. Ψ ist dabei der Winkel zwischen Oberfl¨ achennormale und Beugungsvektor. Die MAXIM-Methode am Messplatz G3 am HASYLAB erlaubt die simultane Untersuchung einer Probenoberfl¨ ache (bis zu 12 x 4 mm2 ) mit einer Ortsaufl¨ osung von bis zu 13 x 13 µm2 . Das Ergebnis einer solchen Messung mit diesem Aufbau ist dann eine Karte mit Eigenspannungswerten als Funktion der Position im oberfl¨ achennahen Probenbereich. Bei einer R¨ ontgenwellenl¨ ange zur Erfassung von Netzebenenabst¨ anden von 1.78 ˚ A betr¨ agt die Eindringtiefe in Magnesium und Aluminium etwa 10 bis 20 µm. Um Spannungsfelder auch im Innern einer Probe messen zu k¨ onnen, m¨ ussen Messungen mit h¨ oherenergetischer R¨ ontgenstrahlung durchgef¨ uhrt werden. Diese steht am Messplatz HARWI-2 zur Verf¨ ugung, wo dann in Verbindung mit einem neuen Detektorsystem ebenfalls ortsaufgel¨ oste Beugungsmessungen m¨ oglich sein werden. Der zur Auswertung erforderliche Algorithmus wird dann entsprechend angepasst. [1] Th. Wroblewski et al., Nucl. Inst. Met. Phys Res. A 428 (1999) 570. [2] E. Macherauch et al., Z. f. angew. Physik 13 (1961) 305.

Materialien/Werkstoffe

Vortrag: Do., 10:20–10:40

D-V33

Phase Transitions in Solids Stimulated by Simultaneous Exposure to High Pressure and Relativistic Heavy Ions Ulrich A. Glasmacher1 , Maik Lang2 , Hans Keppler3 , Falko Langenhorst4 , ¨nther A. Reinhard Neumann2 , Dieter Schardt2 , Christina Trautmann2 , Gu Wagner5 1

Geologisch-Pal¨ aontologisches Institut, Ruprecht-Karls Universit¨ at Heidelberg, Heidelberg, Germany – 2 Gesellschaft f¨ ur Schwerionenforschung (GSI), Darmstadt, Germany – 3 Bayerisches Geoinstitut, Universit¨ at Bayreuth, Bayreuth, Germany – 4 Institut f¨ ur Geowissenschaften, Friedrich-Schiller-Universit¨ at, Jena, Germany – 5 Forschungsstelle Arch¨ aometrie der Heidelberger Akademie der Wissenschaften am Max-Planck-Institut f¨ ur Kernphysik, Heidelberg, Germany In many solids, heavy ions of high kinetic energy (MeV-GeV) produce long cylindrical damage trails with diameters of order 10 nm (see e. g. [1]). Up to now, almost no information was available [2] how solids cope with the simultaneous exposure to these energetic projectiles and to high pressure. We report the first experiments where relativistic heavy ions from the SIS heavy-ion synchrotron at GSI were injected through several mm of diamond into solid samples pressurized up to 18 GPa (180 kbar) in a diamond anvil cell. We used ions with kinetic energies up to 70 GeV which traversed completely one of the two diamond anvils and penetrated the sample enclosed in the high-pressure cell with an energy loss value sufficiently high for damage creation [3,4]. In several solids, such as synthetic graphite and natural zircon, the combination of pressure and ion beams triggered drastic structural changes not caused by the applied pressure or the ions alone [5]. The modifications comprise long-range amorphization of graphite rather than individual track formation, and in the case of zircon the decomposition into nanocrystals and nucleation of the high-pressure phase reidite. In contrast, for other materials, e. g., dark mica, no significant influence of the pressure on the ion-track formation could be observed. [1] Nucl. Instrum. Methods Phys. Res., Sect. B 245 (2006), contain the Proceedings of the “Sixth International Symposium on Swift Heavy Ions in Matter (SHIM 2005)”. [2] C. Trautmann, S. Klaum¨ unzer and H. Trinkaus, Phys. Rev. Lett. 85, 36483651 (2000). [3] M. Lang, U.A Glasmacher, R. Neumann, C. Trautmann, D. Schardt and G.A. Wagner, Appl. Phys. A 80, 691-694 (2005). [4] http://www.srim.org/SRIM/SRIM2003.htm [5] U.A. Glasmacher, M. Lang, H. Keppler, F. Langenhorst, R. Neumann, D. Schardt, C. Trautmann, G.A. Wagner, Phys. Rev. Lett. (2006), in press.

Methoden und Instrumentierung

Vortrag: Do., 11:10–11:30

D-V34

High Speed Semiconductor Detectors for Synchrotron Experiments at LCLS and XFEL ¨der1 Lothar Stru 1

MPI Halbleiterlabor, Otto-Hahn-Ring 6, 81739 M¨ unchen

Silicon Drift Detector type detectors (SDDs, pnCCDs, CDDs and active pixel sensors(APS), DEPFETs) have been developed as high speed spectrometers for energies from 50 eV up to 50 keV in a single photon counting mode as well in an integration mode. They show high energy and high position resolution as well as high quantum efficiency for X-rays. Their full well capacities exceed 106 electrons per pixel. The read noise close to room temperature is less than 10 electrons (rms) leading to Fano limited energy measurements at readout speeds of 108 pixels per second. Pixel sizes of 20 × 20 µm2 have been realized on 500 µm thick fully depleted silicon as well as pixel sizes up to 1 cm2 . Typical formats being experimentally evaluated are 256 × 256 or 512 × 512 with pixel sizes from 35 µm2 to 75 µm2 . The minimum sensitive detector thickness is 50 µm, a maximum detector thickness is technologically limited to 1.5 mm. Special designs have been proposed for synchrotron applications complying with the time structure (bunch structure) conditions of the recently approved XFEL to be built at DESY and the LCLS at SLAC. The X-ray imagers are based on the concepts of (non-controlled) controlled drift detectors (CDD) and fully depleted pnCCDs. They are dedicated for X-ray imaging from the kHz to the MHz range. A detector system which satisfies the LCLS (X-FEL at SLAC) specifications is presented on the basis of fully depleted pnCCDs with a format of 1024 × 1024 combined with a pixel size of 50 µm and a readout rate of 500 Hz. Subsystems are already operational and show the full agreement with the performance specified and required by the synchrotron light user. The presentation will include the discussion of the user requirements and specifications, a detailed concept of the LCLS detection system and measured properties of such a system. A conceptual study of the XFEL detector system based on the controlled drift detectors will be given. The present concept of the XFEL approach uses controlled drift detectors to be read out with 1 MHz having a drift path of 2.6 cm per subunit. It includes integrated FETs on the CDD and dedicated preamplifiers, ADCs and data buffers for each individual channel. First experimental results from the CDD detectors will be shown.

Methoden und Instrumentierung

Vortrag: Do., 11:30–11:50

D-V35

Hard X-Ray Microscopy based on Refractive X-Ray Lenses Christian Schroer1 , Jens Patommel1 , Pit Boye1 , Jan Feldkamp1 , Bruno Lengeler2 , Manfred Burghammer3 , Christian Riekel3 1

Institut f. Strukturphysik, TU Dresden, D-01062 Dresden – 2 II. Physikalisches Institut, RWTH Aachen, D-52056 Aachen – 3 ESRF, B.P. 220, F-38043 Grenoble Cedex, France

At synchrotron radiation sources, parabolic refractive x-ray lenses allow one to built both full field and scanning microscopes in the hard xray range [1]. The latter microscope can be operated in transmission, fluorescence, and diffraction mode, giving chemical, elemental, and structural contrast. For scanning microscopy, a small and intensive microbeam is required. Parabolic refractive x-ray lenses with a focal distance in the centimeter range, so-called nanofocusing lenses (NFLs, Fig. 1(a)), can generate hard x-ray nanobeams in the range of 100 nm and below, even at short distances, i. e., 40 to 70 m from the source [2,3]. Recently, a 47nm×55nm beam with 1.7·108 ph/s at 21 keV (monochromatic, Si 111) was generated using silicon NFLs in crossed geometry (Fig. 1(b)) at a distance of 47 m from an undulaFig. 1: (a) nanofocusing refractive x-ray tor source (ID13) at the European Synchrotron lenses (NFLs) made of Si. (b) Hard x-ray nanoprobe based on two crossed NFLs. Radiation Facility [3]. This beam is not diffraction limited, and smaller beams may become available in the future. Lenses made of more transparent materials, such as boron or diamond, could yield an increase in flux of one order of magnitude and have a larger numerical aperture. For these NFLs, diffraction limits below 20 nm are conceivable [2]. Using adiabatically focusing lenses [4], the diffraction limit can in principle be pushed below 5 nm. The fundamental limit to focusing with refractive optics is discussed [4]. [1] [2] [3] [4]

B. C. C. C.

Lengeler, et al., J. Phys. D: Appl. Phys. 38 (2005) A218. G. Schroer, et al., Appl. Phys. Lett. 82 (2003) 1485. G. Schroer, et al., Appl. Phys. Lett. 87 (2005) 124103. G. Schroer, B. Lengeler, Phys. Rev. Lett. 94 (2005) 054802.

Methoden und Instrumentierung

Vortrag: Do., 11:50–12:10

D-V36

Synchrotron-Radiation Computed Laminography - A New Method for the Tree-Dimensional Imaging of Flat Objects Lukas Helfen1,2 , Tilo Baumbach1 , Petra Pernot2 , Petr Mikulik3 1

ANKA / Institute for Synchrotron Radiation, Forschungszentrum Karlsruhe GmbH, P.O. Box 36 40, D-76021 Karlsruhe, Germany – 2 European Synchrotron Radiation Facility, F-38043 Grenoble – 3 Masaryk University, Kotlarska 2, 61137 Brno, The Czech Republic In the paper the methodical development and first instrumental realization of computed laminography with synchrotron radiation is described. Synchrotron radiation computed Laminography, in the following called SRCL, combines tomosynthesis principles with the specific advantages of synchrotron radiation, such as high brilliance (allowing contrast improvement by working with monochromatic radiation), high partial coherence (enabling to use phase contrast enhancement due to Fresnel diffraction), high spatial resolutions with electronic detector systems with fast read-out and high dynamic range. CT consists in the acquisition of a series of projection radiographs for different rotation angles around the tomographic axis, which is set perpendicular to the transmitted beam direction. By applying suitable reconstruction algorithms, a 3d image of the sample volume can be reconstructed, providing that the entire sample width was imaged. Since the field of view of digital 2D detectors is limited CT has to accept a compromise between spatial resolution and maximum lateral object width a limitation, which often hinders applications of CT for non-destructive testing of micro systems, e.g. the inspection of the bump bonds of flip-chip bonded micro devices. Contrary to computed tomography, for flat objects the resolution realizable by SRCL does not depend on theobject size. By some simple modification of the scanning geometry and adaptation of tomosynthesis reconstruction algorithms, SRCL enables non-destructively imaging of the 3D-structure of flat, laterally extended objects such as devices of micro system technology. In the talk we discuss the novel instrumental set-up, based on a new concept also compared to laboratory tomosynthesis set-ups. By a series of first experimental examples we show the feasibility of the method for imaging with both, white and monochromatic radiation and high spatial resolution down to submicron scale. The comparison to phantom samples demonstrates the methodical and instrumental feasibilities, the selected examples illustrate the methods potential for non-destructive testing and quality assurance.

Methoden und Instrumentierung

Vortrag: Do., 12:10–12:30

D-V37

Supraleitende Undulatoren an ANKA Axel Bernhard1 , Sara Casalbuoni2 , Michael Hagelstein2 , Barbara Kostka2 , Robert Rossmanith2 , Theo Schneider3 , Matthias Weißer4 , Daniel Wollmann1 , Erhard Steffens4 , Tilo Baumbach1,2 1

LAS, Universit¨ at Karsruhe – 2 Institut f¨ ur Synchrotronstrahlung, Forschungszentrum Karlsruhe, ANKA – 3 Institut f¨ ur Technische Physik, Forschungszentrum Karlsruhe – 4 Physikalisches Institut, Friedrich-Alexander-Universit¨ at Erlangen Supraleitende In-Vakuum-Undulatoren mit kleinem Gap und kurzer Periodenl¨ ange bieten wegen ihres im Vergleich zu Permanentmagnetundulatoren gleicher Periodenl¨ ange h¨ oheren erreichbaren Magnetfeldes die M¨ oglichkeit, an Speicherringen mittlerer Energie hochbrillante Undulatorstrahlung bis in den harten R¨ ontgenbereich zu erzeugen. Ihre rein elektrische Durchstimmbarkeit ohne mechanische Verstellung ist ein weiterer Vorzug. Seit einem Jahr wird an ANKA der weltweit erste supraleitende Undulator an einem Speicherring betrieben. Die Installation dieses SCU14 stellt einen wesentlichen Meilenstein einer seit mehr als zehn Jahren an ANKA verfolgten Entwicklung dar: Erstmals konnte die Kompatibilit¨ at supraleitender In-Vakuum-Undulatoren mit dem Speicherringbetrieb nachgewiesen und eine Reihe von Experimenten zur Charakterisierung der erzeugten Strahlung und zu W¨ armeeintr¨ agen in die Kaltmasse durch den gespeicherten Elektronenstrahl durchgef¨ uhrt werden. Nach diesem erfolgreichen Test wird an ANKA eine zweite Generation supraleitender Insertion Devices entwickelt. Diese neue Generation umfasst supraleitende Undulatoren mit elektrischer Feldfehlerkompensation (shimming), elektrisch kontrollierbarer Polarisation sowie supraleitende Hybrid-Undulatoren/Wiggler auf der Basis elektrischer Vervielfachung der Periodenl¨ ange. ¨ Dieser Beitrag gibt einen Uberblick u ¨ber die Betriebserfahrungen und Experimente mit dem SCU14 sowie u ¨ber die Entwicklung neuartiger supraleitender Insertion Devices an ANKA.

Methoden und Instrumentierung

Vortrag: Do., 11:10–11:30

D-V38

Neutron Tomography: Status Quo and Future Developments Wolfgang Treimer1,2 , Markus Strobl1,2 , Hilger1,2 , Ingo Manke2,3

Nikolay Kardjilov2 ,

Andre

1

University of Applied Sciences (TFH), FB II, 13353 Berlin – 2 Hahn Meitner Institut, SF3, 14106 Berlin – 3 Technical University Berlin, 10623 Berlin

In the last decade neutron tomography has become an important part in neutron physics due to a number of applications in material research, non-destructive testing, material design, material testing, archeology, biological systems, imaging of rapid processes, etc. The main developing work on this subject was done by improving geometry, spatial resolution, szintillator materials and detectors, based on the main imaging contrast of attenuation of neutrons by materials. Experimental conditions, small or large samples, low or high absorbing materials, possible activation of parts of the sample, etc., demand very often different techniques or imaging signals, which are not based on attenuation contrast. In the last few years a number new imaging signals such as time resolved CT, energy dispersive contrast CT, phase contrast CT, refraction contrast CT (which is topological also a phase contrast), small angle scattering contrast CT , CT with monochromatic neutrons were investigated and carefully proved to be suited for neutron tomography [1] [6].(see Fig.1). Other, new techniques will be developed and applied to condensed matter physics. The wave nature and the spin of Fig. 1: 3D reconstruction of a part of the neutron will bring further CT- techniques such as Fouriera vent tube with sediCT and polarized neutron CT , which will enlarge the field of ments, monochromatic neutrons l=0.528nm application of n-Ct [7], [8]. The future of neutron tomography, however, will belong to such new techniques and therefore interact with neutron scattering (as well as x-ray scattering ) methods in a very sustainable and fruitful way. [1] W. Treimer, et al, Appl. Phys. Lett. (2003) 83, 2 [2] M. Strobl, et al, Physica B (2004) 350, 155-158 [3] M. Strobl, et al, Appl. Phys. Lett. (2004) 85 [4] W. Treimer, et al, IEEE (2005) 52, 1 [5] N. Kardjilov, et al Nucl. Instr. Meth. A (2005) 542 ,16 [6] M. Strobl et al, Nucl. Instr. Meth. A (2005) 542 383 [7] W. Treimer et al , Nucl. Instr. Meth. A (2005) 542 367 [8] W. Treimer, et al, Applied Solid State Physics, (2005) Vol 45, 407

Methoden und Instrumentierung

Vortrag: Do., 11:30–11:50

D-V39

Neutron phase contrast imaging using a grating interferometer ¨nzweig1,2 , Franz Pfeiffer1 , Oliver Bunk1 , Ian Johnson1 , Christian Gru Xavier Donath1 , Gabriel Frei1 , Eberhard Lehmann1 , Hennrik Rønnow1,2 , Christian David 1

Paul Scherrer Institut, 5232 Villigen PSI, Switzerland – 2 ETH-Z¨ urich, Switzerland

Today the majority of radiographic imaging applications is based on the attenuation of the radiation inside the object. However, the imaging of the phase shift induced by the object can provide substantially new and otherwise not accessible information. In the case of x-rays, phase contrast imaging yields an increased contrast for biological samples, and thus is of potential interest for medical applications [1,2]. Neutron phase measurements, on the other hand, have a long and distinguished history in the exploration of the fundamental properties of quantum mechanics [3]. Thus, a combination of phase sensitive measurements with a neutron imaging approach has the potential of providing two- or even three-dimensionally resolved spatial information on the quantum mechanical interactions of massive particles with matter. Here we report how a setup consisting of three transmission gratings can yield quantitative differential neutron phase contrast images [4]. As opposed to existing techniques, the method requires only little spatial and chromatic coherence. Since separate phase and attenuation images are obtained simultaneously, our method provides additional information through neutron phase-sensitive imaging, but yet is fully compatible with conventional neutron radiography. The high efficiency of our method, compared to the other existing methods (pinhole geometry, crystal interferometer and analyzer crystal), reduces the measurement time for 3D neutron phase contrast tomography by more than two orders of magnitude and opens up the way for imaging the phase shifts induced by other than the nuclear interaction as shown in Fig. 1. [1] R. Fitzgerald, Physics Today 53, 7, 23-27 (2000). [2] F. Pfeiffer, O. Bunk, T. Weitkamp, and C. David, Nature Physics 2, 258-261 (2006). [3] H. Rauch and S.A. Werner, Neutron Interferometry, Oxford University Press, Oxford (2000). [4] F. Pfeiffer, C. Gr¨ unzweig, O. Bunk, G. Frei, E. Lehmann, and C. David, accepted for publication in Phys. Rev. Lett. (2006).

Fig. 1: Conventional neutron radiograph (a) and retrieved phase image (b) of Cupper and Titanium metal rods. The white scale bar corresponds to 5 mm. Due to similar neutron capture cross sections and incoherent scattering lengths, a difference in attenuation of the neutron beam in the rods is hardly recognized (a). In the phase image it is interesting that Ti has a brighter colour compared to the background whereas Cu appears darker. This is due to the negative neutron scattering length density of Ti and consequently a negative phase shift [π] is measured in the material.

Methoden und Instrumentierung

Vortrag: Do., 11:50–12:10

D-V40

N-REX + The New Neutron / X-Ray Reflectometer for Materials Science at FRM II ¨hm1,2 , Max Nu ¨lle1 , Felix Maye1,2 , Janos Major1 , Helmut Dosch1 Adrian Ru 1

Max-Planck-Institut f¨ ur Metallforschung, Stuttgart – Heinz Maier-Leibnitz, FRM II, Garching

2

Forschungsneutronenquelle

In the framework of the Max Planck initiative “Materials and Solid-State Research at the New Neutron Source FRM II” a novel neutron/X-ray-contrast reflectometer for materials science, N-REX + , is currently being commissioned at FRM II. It enables the simultaneous characterization of samples with both neutrons and X-rays, which is especially interesting for in-situ studies of time-dependent processes. Another focus lies on the further development of the spin-echo resolved grazing incidence scattering (SERGIS) technique, as well as its utilization in a routine manner for the study of in-plane correlations on surfaces, interfaces and thin films. Complementary to conventional angle-resolved diffraction techniques, this novel spin-encoded real-space method is well suited for the study of length scales from the nanometer up into the micron range. No in-plane collimation of the beam is required, so that a remarkably high neutron flux is available at the detector for all in-plane length-scales to be examined. Systems to be investigated at N-REX + with this new characterization method range from self-assembled and artificial nanostructures over rough and modulated surfaces and interfaces to polymers and biological membranes. First experimental results demonstrating the diverse capabilities of the instrument will be presented.

Methoden und Instrumentierung

Vortrag: Do., 12:10–12:30

D-V41

High Gain Focusing Optics for Stress and Local Texture Measurement at the Materials Science Diffractometer STRESS-SPEC at FRM-II Ulf Garbe1 , Joana Rebelo-Kornmeier2 , Andreas Ostermann3 , Michael Hofmann3 1

GKSS Forschungszentrum, Max-Planck-Str. 1, D-21502 Geesthacht – 2 HMI, BENSC, Glienickerstr. 100, D-14109 Berlin – 3 FRM-II, TU M¨ unchen, Lichtenbergstr. 1, D85747 Garching In response to the development of new materials and the application of materials and components in new technologies the direct measurement, calculation and evaluation of textures and residual stresses has gained worldwide significance in recent years. Nondestructive analysis for phase specific residual stresses and textures is only possible by means of diffraction methods. In order to cater for the development of these analytical techniques the new Materials Science Diffractometer STRESS-SPEC has been installed recently at the new reactor FRM-II to be equally applied to texture or residual stress analyses by virtue of its flexible configuration and high neutron flux at the sample position [1]. The results of our first user experiments show that small gauge volumes down to 1x1x1 mm3 can be easily used for residual stress measurements. However, with measurement points deeply embedded in components the primary slit has to be positioned far away from the scattering center thus causing a poor definition of the nominal gauge volume. Here we present the results of simulations where the primary slit is replaced by a parabolic focussing guide which provides a good definition of a small gauge volume even deep within components and a substantial flux increase at the sample position.

In addition the combination of intensity increase provided by the focussing guide together with the extension of the existing PSD-detector will enable local texture measurements [3] in a short timescales and also 3-D texture mapping is realistic. Currently even with the high flux of STRESS-SPEC the measuring time per pole figure amounts up to 14 hours using a gauge volume of 2x2x2 mm3 . Simulations are presented to demonstrate the possible gains using two or three position sensitive detectors, all installed at the same position in 2θ with different χ angles. In this way more orientations are detected at the same time. Together with the focussing guide due to the neutron flux increase and the reduced number of necessary sample orientations local texture measurements with high spatial resolution will be possible. [1] M. Hofmann, R. Schneider, G.A. Seidl, J. Rebelo-Kornmeier, R.C. Wimpory, U. Garbe and H.-G. Brokmeier, Physica B, in press. [2] C. Schanzer, P. B¨ oni, U. Filges, T. Hils, Nucl. Instr. and Meth. A 529 (2004) 6368. [3] C.S.Choi, H.J. Prask S.F. Trevino, J. Appl. Cryst. 12, (1979) 327-331.

Methoden und Instrumentierung

Vortrag: Do., 11:10–11:30

D-V42

Positron Experiments and Instrumentation at the Positron Source at the FRM-II Christoph Hugenschmidt1,2 , Thomas Brunner2 , Jakob Mayer2 , Christian Piochacz1 , Martin Stadlbauer1 , Klaus Schreckenbach1,2 1

ZWE FRM II, Technische Universit¨ at M¨ unchen, Lichtenbergstraße 1, 85747 Garching, Germany – 2 Physik-Department E21, Technische Universit¨ at M¨ unchen, James-FranckStrasse, 85748 Garching, Germany The in-pile positron source NEPOMUC (Neutron Induced Positron Source Munich) of the Munich research reactor FRM-II delivers a low-energy positron beam of highest intensity. The primary kinetic energy of the positrons can be varied in the range between 15 eV and 1 keV. The maximum yield of positrons was up to 5·108 moderated positrons per second. New instruments for beam diagnostics have been implemented for the determination of the positron intensity and for positron beam profile measurements. In the present arrangement of NEPOMUCs instrumentation the mono-energetic positron beam is magnetically guided to various experiments: a coincident Doppler broadening spectrometer (CDBS), a PAES (positron induced Auger electron spectroscopy) analysis chamber and a multi-purpose beam port. An overview of the current status of the positron beam facility is given and first experimental results are presented. Future developments such as beam brightness enhancment and the production of a Positronium-beam are discussed as well.

Methoden und Instrumentierung

Vortrag: Do., 11:30–11:50

D-V43

Wavefront Studies at the Free-Electron Laser FLASH ¨ njes1 , Marion Kuhlmann1 , Sven Toleikis1 , Philippe Zeitoun2 , Elke Plo Julien Gautier2 , Thierry Lefrou2 , Denis Douillet2 , Pascal Mercere3 , Guillaume Dovillaire4 , Marta Fajardo5 1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 Laboratoire d’Optique Appliquee, ENSTA, Chemin de la Huniere, F-91761 Palaiseau cedex, France – 3 Synchrotron SOLEIL, L’Orme des Merisiers - Saint-Aunin - BP 48, 91192 Gif-surYvette Cedex, France – 4 Imagine Optic, 18 rue Charles de Gaulle, Orsay France 91400, France – 5 Centro de Fisica dos Plasmas, Institutio Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal The Free-Electron Laser in Hamburg (FLASH) is operated in the “self-amplified spontaneous emission” (SASE) mode and delivers sub-picosecond radiation pulses, with gigawatt peak powers. At present, lasing has been observed down to about 13 nm in the fundamental, the shortest wavelength ever achieved with a free electron laser. User experiments started in August 2005 and were carried out between 45 nm and 13 nm. For these wavelengths, FEL pulse intensities from typical 5 µJ up to more than 50 µJ have been obtained with pulse lengths between 20 and 50 fs. FEL wavefronts observations have been recorded using a Hartmann sensor (by Imagine Optic). The Hartmann principle is based on a pinhole array, which divides the incoming beam into a large number of sub-rays monitored in intensity and position of individual spots. The identification of the local slope of the incident wavefront makes the aberrations from a perfect spherical wavefront visible. Ray tracing backwards accesses the beam focal point in size and position. The intense and coherent vacuum-ultraviolet FEL beam of various repetition rates leads to unique requirements for the wavefront sensor setup. The wavefront studies were carried out in the context of commissioning of the experimental stations. A further goal is to provide an online diagnostic tool for experiments which need to determine beam parameters which can vary with the shot to shot characteristic of the FEL, e.g. the focal spot size. We report measurements of the metrology of flat and curved mirrors at FLASH beamlines. The effects of solid and gaseous filters are selectively described in the wavelength regime of 10 nm to 32 nm. The use of wavefront measurements to provide reliable machine parameter is discussed. The wavefront sensor proved to be a valuable tool to determine the FEL beam quality and the performance of optical elements, filters and diagnostic tools.

Methoden und Instrumentierung

Vortrag: Do., 11:50–12:10

D-V44

Progress in the Development of New Optics for Very High Resolution Inelastic X-Ray Scattering Spectroscopy ¨ter3 , Michael Lerche4,1 , Yuri Shvyd’ko1 , Ulrich Kuetgens2 , Hans Dierk Ru Ahmet Alatas1 , Jiyong Zhao1 1

Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA – 2 Physikalisch-Technische Bundesanstalt (PTB), D-38116 Braunschweig, Germany – 3 Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg, D-22761 Germany – 4 University of Illinois at Urbana-Champaign, IL 61801, USA Inelastic x-ray scattering (IXS) spectroscopy with meV resolution is one of the major techniques for studying vibrational dynamics in solids, liquids, and biological molecules. X-ray monochromators and analyzers with meV-resolution are the main optical components of the spectrometers. Single-crystal and multiple-crystal techniques for the meVmonochromatization and the spectral analysis of x-rays have been developed during the last decades. These techniques have a basic general property: the higher the required energy-resolution, the higher indexed Bragg reflections have to be used, and thus photons of higher energy E are needed. By this reason, photons with E > 20 keV are typically used in IXS experiments. This tendency is, however, in dissonance with the increasing demand for more spectral flux in IXS experiments and the fact that undulator based synchrotron radiation sources generate less photons in the high-energy spectral range. Using high-energy photons allows IXS spectroscopy only at high-energy machines like ESRF, APS, and SPring-8, but not at future powerful medium-energy facilities such as DIAMOND, SOLEIL, NSLS-II, etc., and future X-FELs including the European X-FEL in Hamburg. To overcome these problems, and thus to broaden the potential of the IXS spectroscopy, a concept of an IXS spectrometer with meV and sub-meV resolution has been proposed for x-rays in the medium-energy spectral range (5-10 keV). It is based on a principle of monochromatization and spectral analysis, which exploits the effect of angular dispersion in asymmetric Bragg diffraction. One of its beneficial features is that higher energy-resolutions are achieved at lower(!) photon energies, typically E < 10 keV, a tendency, which is consistent with better performance of x-ray undulators at these energies. The realization of the monochromatization principle requires an arrangement of three crystals, playing the role of a collimator (C), a dispersive element (D), and a wavelength selector (W) in a three bounce CDW monochromator. The CDW monochromator combined with a paraboloidal mirror could be used as a high-resolution analyzer of scattered radiation from a sample. We will present the design of the CDW monochromator, and the results of the first tests of the CDW monochromator for 9.1 keV x-rays. Two CDW monochromators are used in the experiments, with the second one as an analyzer, to measure the effect of monochromatization. A 2.2 meV spectral bandwidth is demonstrated.

Methoden und Instrumentierung

Vortrag: Do., 12:10–12:30

D-V45

Von Einstein zum Kilogramm Jochen Krempel1,2,3 , Michael Jentschel1 , Giovanni Mana4 , Peter Becker2 1

Institut Laue-Langevin, 38042 Grenoble Cedex 9, France – 2 PhysikalischTechnische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany – 3 LudwigMaximilians-Universit¨ at M¨ unchen, Am Coulombwall 1, 85748 Garching, Germany – 4 Istituto Nazionale di Ricerca Metrologica, str. delle cacce 91, 10135 Torino, Italy Am Hochflussreaktor des ILL k¨ onnen Proben in unmittelbarer N¨ ahe des Reaktorkernes in einen Neutronenfluss von 5·1014 n s−1 cm−2 gebracht werden. Die beim Neutroneneinfang entstehende Gammastrahlung kann mit dem GAMS Doppelkristallspektrometer gemessen werden. Das Messprinzip basiert auf zwei Silizium-Einkristallen deren relativer Winkel durch optische Interferometrie bestimmt wird. Es k¨ onnen Energien im Bereich von 20 keV bis 8 MeV mit einer relativen Unsicherheit von 10−7 gemessen werden. Die Energieaufl¨ osung liegt im ppm-Bereich und es besteht die M¨ oglichkeit zur absoluten Kalibration. Dies erlaubt neben Untersuchungen von Kern¨ uberg¨ angen[1] die Bestimmung der Neutronen-Bindungsenergie. Mit Hilfe von Ionenmassenmessungen kann so die Neutronenmasse bestimmt werden[2]. Ebenso ist es m¨ oglich die Masse¨ Energie-Aquivalenz E = mc2 experimentell zu verifizieren[3]. Mit dem derzeitigen Umbau des Instruments wird das Aufl¨ osungsverm¨ ogen und die Genauigkeit stark verbessert. Es ist geplant die Molare Planckkonstante mit einer Unsicherheit von 1 · 10−8 zu bestimmen und somit einen Beitrag zur Neudefinition des Kilogramms zu leisten. [1] C. Granja et al., Phys. Rev. C 70, 034316 (2004) [2] E.G. Kessler et al., Phys. Lett. A255 (1999) 221 [3] S. Rainville et al., Nature, Vol. 438 (2005)

Weiche Materie

Vortrag: Fr., 09:40–10:00

F-V46

Degradation of polyimide (Kapton) induced by irradiation with swift heavy ions D. Severin1 , W. Ensinger1,2 , C. Trautmann3 , G. Walter3 , R. Neumann3 1

Philipps-University Marburg – 2 Darmstadt University of Technology – 3 Gesellschaft f¨ ur Schwerionenforschung, Darmstadt

Polyimide (Kapton) is a highly radiation and thermally resistant polymer. For this reason, it is one of the preferred insulating materials in technical devices exposed to high-dose radiation. This not only the case for high-energy photons, but also for swift heavy ions. The latter might be a problem in the heavy ion synchrotron in the future ion-beam facility FAIR at GSI, with its very high ion fluxes (10E12 ions/pulse) at high energies (10 GeV/u). In order to simulate long-term use of Kapton in such devices, foils were exposed to beams of various ions at ∼10 MeV/u [1]. Ion beam induced material degradation was investigated by means of UV/Vis-spectroscopy for light transmission, by IR-spectroscopy for structural degradation, by dielectric spectroscopy for changes in electrical properties, and by mechanical strength measurements. It turns out that the data obtained by the different techniques can be scaled by the total absorbed dose. Up to a dose of about 1 MGy, the material modifications are less pronounced. However, above this threshold the properties decay significantly. Surprisingly, the dielectric spectroscopy data do not follow this trend. This method seems to be sensitive for a different degradation process. The figure shows degradation of Kapton exposed to beams of various ionic species. The change of the different material properties is normalized to pristine Kapton. The threshold behaviour, shown by the different characterization techniques, can well be seen. The underlying physical and chemical processes, such as bond scission and carbonization, are discussed. [1] D. Severin, W. Ensinger, R. Neumann, C. Trautmann, G. Walter, I. Alig, S. Dudkin, Nucl. Instr. and Meth. B 236 (2005) 456-460

Fig. 1: Results of dielectric relaxation, IR, UV/Vis and tensile strength measuremsnts, of Kapton foil, as a function of radiation dose

Weiche Materie

Vortrag: Fr., 10:00–10:20

F-V47

Multilevel structures formed by partially crystalline polymers in solution: from fundamentals to applications - a combined USANS, focusing-SANS and conventional SANS study Aurel Radulescu1 , Dietmar Schwahn1 , Michael Monkenbusch1 , Emmanuel Kentzinger1 , Lewis J. Fetters2 , Dieter Richter1 1 Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, 52425 J¨ ulich – 2 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca NY 14853-1301, USA

Under wintry conditions, middle distillate fuels can clog the filters by precipitating large waxy crystals and thereby prevent engine operations. The copolymers consisting of crystalline and amorphous segments can interact favorably with waxes (long-chain Cn H2n+2 alkanes or simply Cn ) and modify the crystal morphology to smaller units. The wax-copolymer interaction in solution is rather complex and is not yet fully understood. Because the morphology of the common wax-copolymer aggregates strongly depends on the precipitation temperatures of both components, a good knowledge of the copolymer self-assembling behavior in solution is required first of all. Therefore, these copolymers are also of much interest in basic research. Several polymer architectures with a combination of crystalline and amorphous sequences have been studied for determination of their self-assembly and wax crystal modification properties. We report here the case of the poly(ethylene-butene) random copolymers and syndiotactic-polypropylene -block -poly(ethylene-co-propylene) diblock copolymers. Their self-assembling or common aggregation with waxes yields in hydrocarbon solutions complex morphologies with characteristic lengths covering four orders of magnitude, from 10 µm to 1 nm. These morphologies evolving either separately or as hierarchical multilevel structures could be fully analysed by three small-angle neutron scattering techniques namely, the conventional pin-hole SANS, the focusing-mirror SANS and the double-crystal diffractometry (USANS) covering a Q range from 3x10−5 - 0.2 ˚ A−1 . Microscopy techniques have been complementarily used in order to visualize the morphologies formed.

Weiche Materie

Vortrag: Fr., 10:20–10:40

F-V48

Tomographic small-angle x-ray scattering of nanostructured soft-matter materials Marion Kuhlmann1 , Stephan Volker Roth1 , Rainer Gehrke1 , Christian ¨ chel3 , Armando Almendarez-Camarillo3 , Norbert G. Schroer2 , Ulrich No 3 Stribeck 1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 Institut f¨ ur Strukturphysik, TU Dresden, D-01062 Dresden, Germany – 3 University Hamburg, Institute TMC, Bundesstr. 45, D-20146 Hamburg, Germany Scanning microscopy is performed in combination with small angle x-ray scattering (SAXS), exploiting the SAXS contrast inside the sample. This is especially useful for samples, where classical absorption tomography fails. The result is an invasive but non-destructive analytic tool to determine the local microstructure on the nanometre scale inside a specimen. The tomographic reconstruction yields the SAXS pattern in the direction of the rotation axis at each location of a virtual slice through a sample. In case of rotationally symmetric specimen the full reciprocal space information can be reconstructed [1]. These reconstructed SAXS patterns can be analysed in order to track the variations of the nanostructure inside the sample. Many nanostructured soft-matter materials exhibit rotational symmetry, e.g. natural fibres, polymer fibres, wood. The method is demonstrated by data from polyethylene rods made by injection moulding [2], a freeze dried arabidopsis flower stalk, and rat tail collagen. The experiments were performed at the beamline BW4 at the DORIS III storage ring of HASYLAB / DESY. The monochromatic synchrotron radiation was focused by parabolic refractive lenses made of beryllium [3]. In case of a polyethylene rod a spatial resolution of ≈80 µm has been resolved in the reconstructed slice. A 2D detector at distances >1800 mm allowed to cover a q-range from 0.06 nm−1 to 2 nm−1 . The primary, the directly transmitted, and the scattered intensity were measured for projections of slices through the specimen over a full rotation of the sample to allow for tomographic reconstruction. Currently, single pattern acquisition times are of 20 s up to 360 s, this leads to days of required beamtime for one tomogram. Technical developments are discussed to minimize such limitations. [1] C.G. Schroer et al., Appl. Phys. Lett. 88, (2006) 164102 [2] N. Stribeck et al., Macromol. Chem. Phys. 205, (2004) 1445 [3] B. Lengeler et al., J. Phys. D: Appl. Phys. 38, (2005) A218

Materialien/Werkstoffe

Vortrag: Fr., 09:40–10:00

F-V49

Untersuchung von nanokristallinen Metallhydrid-Wasserstoffspeichermaterialien mit Hilfe der Neutronen- und R¨ ontgenkleinwinkelstreuung ¨ senberg1 , Gu ¨nter P. Klaus Pranzas1 , Martin Dornheim1 , Ulrike Bo 2 3 3 Goerigk , Stephan Volkher Roth , Rainer Gehrke , Andreas Schreyer1 1

Institut f¨ ur Werkstoffforschung, GKSS Forschungszentrum, Max-Planck-Str. 1, 21502 Geesthacht – 2 Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, Postfach 1913, 52425 J¨ ulich – 3 HASYLAB, Notkestr. 85, 22603 Hamburg Nanokristalline Leichtmetallhydride werden f¨ ur die reversible Speicherung von Wasserstoff eingesetzt. Eines der interessantesten Speichermaterialien ist das Magnesiumhydrid, das eine Wasserstoffspeicherkapazit¨ at von bis zu 7.6 Gewichtsprozenten besitzt. Die Wasserstoff-Absorptions- und Desorptionskinetik von MgH2 ist bekannt, ebenso die Zyklier- und thermische Stabilit¨ at. Die Sorptionseigenschaften werden durch die Verwendung von Metalloxid-Katalysatoren, wie Fe3 O4 , Nb2 O3 und TiO2 , deutlich ver¨ bessert. Allerdings wurden strukturelle Anderungen w¨ ahrend dieser Prozesse sowie die Funktion und Verteilung verschiedener Additive bisher kaum untersucht. ¨ In dieser Arbeit wurden Anderungen in der Struktur Hochenergie-gemahlener Metallhydride w¨ ahrend der Absorption und Desorption von Wasserstoff ohne und unter Zusatz von Additiven mit Hilfe der Neutronen- (SANS/USANS) und R¨ ontgen(ultra)kleinwinkelstreuung (SAXS/USAXS) untersucht. Die SANS/USANS-Experimente wurden an den Instrumenten SANS-2 und DCD der Geesthachter Neutronenforschungseinrichtung (GeNF) durchgef¨ uhrt, SAXS/USAXS Messungen am BW4 Instrument am Hamburger Synchrotronstrahlungslabor (HASYLAB). Um Informationen u ¨ber die Funktion und Verteilung verschiedener Metalloxid-Additive zu erhalten, wurden zus¨ atzlich Anomale SAXS (ASAXS) Untersuchungen unter Verwendung verschiedener Energien nahe der Absorptionskanten der Katalysator-Metalle am B1/JUSIFA Instrument am HASYLAB vorgenommen. Gr¨ oßenverteilungen von Inhomogenit¨ aten mit Dimensionen zwischen 1 nm und bis zu 20 µm wurden als Funktion des Wasserstoffgehalts und der Anzahl der durchgef¨ uhrten Zyklen berechnet, um den Einfluss des Zyklierens auf die Mikrostruktur zu bestimmen und um Informationen u ¨ber den Hydridbildungsmechanismus zu erhalten. Die Resultate weisen auf eine Kornvergr¨ oberung und das Aufbrechen von Partikeln mit Radien gr¨ oßer 10 µm mit fortschreitendem Zyklierprozess hin. Signifikante Effekte auf die Mikrostruktur wurden ebenfalls bei der Verwendung verschiedener MetalloxidKatalysatoren und Mischhydride erhalten, sowie bei der Variation der Mahlparameter. Unterschiede in den aus den SANS und SAXS Streukurven berechneten Gr¨ oßenverteilungen lassen auf die Verteilung des Wasserstoffs zur¨ uckschließen. Bei den ASAXSUntersuchungen wurde f¨ ur die Additive Fe3 O4 and TiO2 eine energieabh¨ angige Streuung gefunden. Die Ergebnisse tragen zu einem besseren Verst¨ andnis der Sorptionsmechanismen in nanokristallinen Leichtmetallhydriden bei und liefern n¨ utzliche Informationen f¨ ur die Entwicklung dieses neuen Typs von Wasserstoffspeichermaterialien.

Materialien/Werkstoffe

Vortrag: Fr., 10:00–10:20

F-V50

Combined neutron and synchrotron diffraction study of Li(Ni,Co)O2 in Liion batteries at different charging states Kristian Nikolowski1 , Helmut Ehrenberg1 , Natascha Bramnik1 , Anatoliy ¨ lzel1 , Carsten Baehtz2 Senyshyn1 , Markus Ho 1

Institute for Materials Science, Darmstadt University of Technology, Petersenstr. 23, D-64287 Darmstadt, Germany – 2 HASYLAB, Notkestr. 85, D-22607 Hamburg, Germany LiCoO2 with a cation-ordered rocksalt superstructure is the standard cathode material in Li-ion batteries for high-energy applications. The partial replacement of Co by other 3d-transitional metals is an intensively studied approach to enhance thermal stability of this cathode material, to reduce costs or to improve cycle stability. The effect of annealing temperature on the structure and the electrochemical properties of Ni-substituted material was previously reported [1]. In addition, a model for the conditioning of Li(Ni,Co)O2 during the first charge-discharge cycles was proposed based on in situ synchrotron diffraction at beamline B2, HASYLAB, Germany [2]. The advantages of this synchrotron study, in situinvestigation and high angular resolution, are now combined with the benefits of neutron diffraction: Li-ions become visible, the occupation factor of the oxygen site can be refined and Ni versus Co can be distinguished. In a first step two series of Li1−x (Ni0.8 Co0.2 )O2 samples are studied by ex situ neutron powder diffraction at SPODI, FRM II. One sample has a low degree of cation disorder and shows good electrochemical properties, another sample has a high degree of disorder and a poor Li-extraction and Li-reinsertion behaviour. Both samples are studied as-prepared, charged to x = 0.5 and after one complete charge-discharge cycle. These experiments contribute to establish in situ neutron diffraction on Li-ion batteries as a complementary tool to our in situ synchrotron diffraction studies [3]. [1] T. Gross, Th. Buhrmester, K. G. Bramnik, N. N. Bramnik, K. Nikolowski, C. Baehtz, H. Ehrenberg, H. Fuess, Structure-intercalation relationships in LiNiy Co1−y O2 , Solid State Ionics 176 (2005) 1193-1199. [2] H. Ehrenberg, K. Nikolowski, N. Bramnik, C. Baehtz, T. Buhrmester, T. Gross, Conditioning of Li(Ni,Co)O2 cathode materials for rechargeable batteries during the first charge-discharge cycles, Adv. Eng. Mater. 7 (2005) 932-935. [3] K. Nikolowski, C. Baehtz, N. N. Bramnik, H. Ehrenberg, A Swagelok-type in situ cell for battery investigations using synchrotron radiation, J. Appl. Cryst. 38 (2005) 851-853.

Materialien/Werkstoffe

Vortrag: Fr., 10:20–10:40

F-V51

Neutron Texture Analyses of Rocks – Recent Applications and Perspectives Bernd Leiss1 , Klaus Ullemeyer2 , Jens Walter3 1

Geowissenschaftliches Zentrum der Universit¨ at G¨ ottingen (GZG), Abteilung Strukturgeologie und Geodynamik, Goldschmidtstr. 3, 37077 G¨ ottingen – 2 Geologisches Institut, Universit¨ at Freiburg, Albertstr. 23B, 79104 Freiburg – 3 MineralogischPetrologisches Institut der Universit¨ at Bonn, Aussenstelle am Forschungszentrum J¨ ulich, MIN/ZFR, D-52425 J¨ ulich Analyses of the crystallographic preferred orientations (CPO, textures) of mineral phases contribute significantly to the quantitative characterisation of the anisotropic physical rock properties, as well as to the understanding of the mechanisms of fabric development. Most rocks in the Earths crust and mantle are relatively coarse-grained and are composites of several mineral phases, usually of low crystal symmetry. In addition, geological structures are often heterogenous and show complicated structures due to polyphase deformation. Thus, volume-related texture analyses of rocks require (a) the measurement of large sample volumes, (b) high d -resolution in the diffraction patterns, and (c) the measurement of large sample series. Due to low absorption in matter, neutrons are especially suitable for diffraction experiments of large sample volumes. Both the SKAT time-of-flight diffractometer at the IBR-2 reactor in Dubna and the SV-7 instrument at the FRJ-2 reactor in J¨ ulich enabled the measurement of large sample volumes up to 50x50x50 mm3 . While the SKAT instrument offers a high resolution of ∆d/d = 0.5 % to the best, the long measuring periods of the SV-7 instrument allowed the measurement of large sample series. Many innovating projects could be realized, e.g: (1) The systematic structure-related analysis of carbonate rocks revealed new texture types and allowed a differentiated interpretation of the deformation history and the deformation mechanisms of rocks, as well as the understanding of weathering processes. (2) First quantitative textures analysis of granites showed CPOs for the quartz and plagioclase phase. In addition to new ideas on the fabric development in granites, the results are important for predicting anisotropic crack. development, for the safety of repositories, and for the initiation of fluid pathways for geothermal power plants. (3) The texture analysis of rock salt from salt dome structures showed unexpected results, which will strongly contribute to the understanding of the mechanisms of salt diapirism and, therefore, for the development of concepts of radioactive waste repositories in Germany. (4) The quantitative correlation of experimentally determined and texture-derived anisotropic elastic rock properties is helpful for the understanding of seismic cross sections. (5) Correlation of shape preferred orientations and CPOs of lava flows in dependence on viscosity, temperature, chemical composition and degree of crystallization may contribute to the understanding of emplacement mechanisms of lava flows. – The above examples demonstrate the importance of neutron texture analyses for the geoscience community. Due to increasing requests for beam time, it is essential to provide measuring capabilities in the future, and to refine and further develop neutron diffraction instruments for rock texture analyses.

Magnetismus

Vortrag: Fr., 09:40–10:00

F-V52

Exchange bias instability in a bi-layer with an ion beam imprinted stripe pattern of FM/AFM interfaces ¨ hl1 , B.P. Toperverg1 , M. Wolff1 , H. Zabel1 , U. Ru ¨cker2 K. Theis-Bro 1

Department of Physics, Ruhr-University Bochum, D-44780 Bochum – 2 Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich GmbH, D-52425 J¨ ulich We have investigated the magnetization arrangement in an in-plane stripe pattern with alternating exchange bias domains. The stripe pattern was produced by ion bombardment induced magnetic patterning, which changed locally the exchange bias direction at the ferromagnet/ antiferromagnet interface, but not the ferro- or antiferromagnetic properties of the Co70 Fe30 and Mn83 Ir17 layers, respectively. For the analysis of the magnetic domain structure evolution along the hysteresis loop we used a combination of experimental techniques: magneto-optical Kerr effect (MOKE), Kerr microscopy, polarized neutron reflectometry (PNR), and off-specular scattering of polarized neutrons with polarization analysis. Instead of a perfect antiparallel alignment we found that the magnetization in neighboring stripes is periodically canted with respect to the stripe axis so that the net magnetization of the ferromagnetic film turns almost perpendicular to the stripes. At the same time the projection of the magnetization vector onto the stripe axis has a periodically alternating sign. In Fig.1 the longitudinal MOKE hysteresis loop and in Fig. 2 specular PNR curves are displayed. In this measurements the non-spin-flip-reflectivities are almost degenerate and the spin asymmetry is SA≈0. The experimental observations are explained and quantitatively described within the frame of a phenomenological model. The model defines conditions which can be used for tailoring nano- and micro-patterned EB systems with different types of magnetic order. We gratefully acknowledge financial support by the DFG via SFB 491 and BMBF 03ZA6BC1.

Fig. 1: MOKE hysteresis loop (line) and results of fits to the PNR data (symbols).

Fig. 2: PNR measurements taken in the antiparallel state of the sample.

Magnetismus

Vortrag: Fr., 10:00–10:20

F-V53

A View on Fast Magnetization Dynamics: Studies by XPEEM C. M. Schneider1 , M. Bolte2 , A. Krasyuk3 , A. Oelsner3 , S. A. Nepijko3 , H.-J. ¨ nhense3 Elmers3 , G. Scho 1

IFF, FZ J¨ ulich GmbH, D-52425 J¨ ulich, Germany – 2 Inst. f. Ang. Physik u. Zentrum f. Mikrostrukturforschung, Univ. Hamburg, D-20355 Hamburg, Germany – 3 Inst. f. Physik, Univ. Mainz, Staudinger Weg 7, D-55099 Mainz, Germany Understanding the microscopic mechanisms governing fast magnetic switching processes is of high fundamental interest as well as of vital technological importance. A macrospin picture often fails to adequately describe the situation in extended systems. A detailed study of the magnetization dynamics in complex magnetic materials thus requires a real-space mapping of the magnetization distribution in the ground state and of its time evolution. Imaging these transient magnetization distributions on a subnanosecond time scale is an experimental challenge, which can be successfully addressed by time-resolved x-ray photoemission microscopy (XPEEM). XPEEM is known as an extremely versatile tool to image static domain patterns, combining element selectivity with strong magnetic contrast and high lateral resolution. The choice of different magnetic contrast modes with circularly or linearly polarized light provides access to both ferro- and antiferromagnetically ordered structures. The technique can be extended into the sub-nanosecond time-domain by exploiting the intrinsic time structure of the synchrotron light [1-3]. We investigated the magnetodynamic behavior of small Permalloy platelets using a stroboscopic approach with synchronized magnetic field pulses (pump) via coplanar waveguides. The time resolution is limited by the width of the soft x-ray pulse (probe) and can be varied via the operation mode of the storage ring between 10 and 70 ps. Starting from well-defined Landau ground state domain patterns we observed a variety of reversal modes and magnetodynamic phenomena, depending on the timescale and -structure of the magnetic field pulse. For nanosecond field pulses we mainly found coherent and incoherent rotation events [4, 5]. Incoherent magnetization rotation occurs, if the exciting pulse field Hp points opposite to the sample magnetization M. It is associated with sizable magnetic stray fields, proving the importance of the magnetization torque in these fast processes. The picture changes, if we apply sub-ns magnetic field pulses. In addition to domain wall motion and rotation events, we find also collective excitations of the magnetization. These modes have frequencies in the GHz regime and are determined by the shape of the platelets. Exciting the magnetic system close to the resonance frequency of one of these modes leads to an interesting self-trapping process of the modes [6]. [1] A. Krasyuk et al., Appl. Phys. A 76 (2003) 836. [2] J. Vogel et al., Appl. Phys. Lett. 82 (2003) 2299. [3] S.-B. Choe et al., Science 304 (2004) 420. [4] C. M. Schneider et al., Appl. Phys. Lett. 85 (2004) 2562. [5] G. Sch¨ onhense et al., Adv. Imaging Elec. Phys. 142 (2006) 157. [6] A. Krasyuk et al., Phys. Rev. Lett. 95 (2005) 207201.

Magnetismus

Vortrag: Fr., 10:20–10:40

F-V54

Antiferromagnetic coupling between the oxide layers in Fe/Fe-oxide superlattices ¨ hlsberger1 Thomas Diederich1 , Sebastien Couet1 , Ralf Ro 1

Hasylab am DESY, Notkestr. 85, 22607 Hamburg

We have studied the magnetic structure of multilayer systems consisting of Fe and native Fe-oxide. The Fe layers have been produced by magnetron sputtering. Native oxide layers on the Fe were prepared by subsequent dosage of oxygen into the chamber. The samples have been analysed in-situ by nuclear resonant scattering (NRS) of synchrotron radiation. Ultrathin layers of 57 Fe are used to probe the magnetic structure of the Fe and the Fe-oxide layers with very high depth resolution. Surface oxide layers coupled to the metallic Fe appeared to be non-magnetic at room temperature. After deposition of another Fe layer one observes a magnetically ordered component in the Fe-oxide layer that increases with growing thickness of the iron capping layer. This results in a relatively high magnetization of these buried oxide layers [1]. In an Fe/Fe-oxide superlattice we discovered an antiferromagnetic (AFM) alignment of the oxide layers [2]. This became evident by a strong superstructure (half-order) Bragg peak in the nuclear resonant reflectivty of a Fe/57 Fe-oxide multilayer. If an external magnetic field of 1 T is applied this peak vanishes. These observations point to a pure magnetic origin of the superstructure and hence to an antiferromagnetically ordered spin arrangement within the lattice of the Fe-oxide layers. Quite remarkably, the coupling angle between the metallic iron and the component in the oxide that participates in the AFM order is about 90◦ . This suggests the existence of a spin-flop phase that is stabilized by the magnetization of the metallic Fe layers. The spin-flop transition, i. e., a sudden reorientation of the layer moments upon application of an external field has in fact been found. Such an antiferromagnetic coupling has so far only been observed for multilayers consisiting of ferromagnetic layers separated by non-magnetic spacer layers that mediated the interaction between the neighbouring ferromagnetic layers. This is in contrast to our system where the metallic iron layers seem to mediate the coupling between the oxide layers. [1] G.S.D. Beach et al. Phys. Rev. Lett. 91 (2003) 267201. [2] Th. Diederich et al., in preparation

Biologische Systeme und Medizin

Vortrag: Fr., 09:40–10:00

F-V55

Synchrotron x-ray-videography and -tomograpy combined with physiological measurements for analysis of circulation and respiration dynamics in insects (Drosophila and Calliphora). Lutz Thilo Wasserthal1 , Peter Cloetens3 , Rainer Fink2 1

Universit¨ at Erlangen, Lehrstuhl f¨ ur Zoologie I, Staudtstr. 5, D-91058 Erlangen – Universit¨ at Erlangen, Lehrstuhl f¨ ur Physikalische Chemie II, Egerlandstr. 3, D-91058 Erlangen – 3 ESRF, 6 rue Jules Horowitz, F-38043 Grenoble 2

Despite their small size, higher flies (fruitflies and blowflies) have a sophisticated respiratory gas exchange system based not only on diffusion as generally assumed - but also on mechanical ventilation of the tracheal system [1]. The mechanism has largely been ignored, as the ventilatory movements are invisble from outside. The periodic volume changes of the air sacs and of heart pulses are visualised by x-ray videos in Drosophila and Calliphora respectively. Intratracheal pressure pulses measured in the mesothorax coincide with pulsations of the air sacs in the head and with anterograde pulses of the heart shown in x-ray-videos. Parallel measurements of pressure pulses with x-ray videos of heart pulsations reveal that the enlarged conical heart chamber in the anterior abdomen is the main motor of periodic hemolymph shift between anterior body and abdomen. It works as a pressure pump during forward (anterograde) pulsations and as a suction pump during backward (retrograde) pulses. [1] L.T.Wasserthal, Int. J. Insect Morph. and Embryol. 28 (1999) 111-129.

Biologische Systeme und Medizin

Vortrag: Fr., 10:00–10:20

F-V56

Concepts and highlights in structural biology at EMBL-Hamburg: towards future applications at PETRA-III Stefan Fiedler1 , Manfred Weiss1 , Manfred Roessle1 , Dmitri Svergun1 , Christoph Hermes1 , Matthias Wilmanns1 1

European Molecular Biology Laboratory, Hamburg Unit c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany An important development in structural biology is the investigation of macromolecular complexes of increasing size such as the molecular architecture of muscle sarcomeres. At the EMBL Hamburg Unit it has been possible to determine the structure of the N-terminal assembly complex of titin, the largest gene product of the human genome, which comprises up to 38,000 residues in its largest isoform. Structural proteomics projects like the Mtb initiative, coordinated by our institute, form another trend. This initiative is targeting proteins from the Mycobacterium tuberculosis and is aiming to identify novel lead compounds to combat tuberculosis. Such projects call for high-throughput techniques and integrated approaches including X-ray crystallography and X-ray small angle scattering. These developments are reflected in our concept for an Integrated Life Science Centre built and operated by the EMBL at PETRA-III, the planned 3rd generation synchrotron on the DESY site in Hamburg. The centre will comprise two beamlines for Macromolecular X-ray crystallography (MX) and one for Small Angle X-ray Scattering (SAXS) all linked through a joint sample preparation and storage facility. One of the MX beamlines will be dedicated to experimental phase determination over a broad energy range, the other optimised for measurements of protein crystals with micrometer size scattering volume. The main focus of the SAXS beamline will be the study of protein solutions with ultra-small volume or concentration and kinetic experiments. The beamlines will be integrated into a highly automated pipeline ranging from biophysical and biochemical protein characterisation to high throughput crystallisation, automated crystal mounting, centering, data collection and data interpretation allowing large numbers of samples to be investigated. The automation of most of these steps is being tested and implemented already at the existing facilities at the DORIS storage ring. We expect to make the facilities successively available to the international scientific community with the planned beginning of user operation of PETRA-III in 2009.

Biologische Systeme und Medizin

Vortrag: Fr., 10:20–10:40

F-V57

Structure of the Protein Kinase MARK/Par-1: Catalytic and UBA Domain Saravanan Panneerselvam1 , Alexander Marx1 , Eva-Maria Mandelkow1 , Eckhard Mandelkow1 1

Max-Planck Unit for Structural Molecular Biology, Notkestrasse 85, 22607 Hamburg

MAP/Microtubule affinity regulating kinases (MARKs) are Ser/Thr kinases that phosphorylate the microtubule-associated proteins tau, MAP2 and MAP4 [1]. Phosphorylation of the neuronal MAP tau at serine S262 leads to detachment of tau from the surface of microtubules and to destabilization of microtubules [2]. Phosphorylated tau can aggregate and form filamentous structures. Formation of paired helical filaments (PHFs) and neurofibrillary tangles is a hallmark of Alzheimer disease. The closely related kinase Par-1 is important for the development of cell polarity [3]. The human kinome contains four MARK isoforms. A stable fragment of MARK2, containing the catalytic and the ubiquitin-associated (UBA) domain, was identified by limited proteolysis. Structures of the wild type construct and of two mutants, K82R and T208A/S212A, were determined by x-ray crystallography using synchrotron radiation of DORIS at DESY, Hamburg [4]. Mutation of K82 to arginine inhibits the kinase activity by interference with nucleotide binding. T208 is the primary phosphorylation site in the activation loop which controls access of the substrate. S212 was also found to be phosphorylated in MARK2 from brain. These two residues were mutated to alanine to mimic the unphosphorylated state. All three constructs crystallized in space group P61, in two distinct, but similar crystal forms, which differ by the length of the c-axis: 106.0 ± 0.37 ˚ A (sd, n = 15) for the double mutant, 99.7 ± 0.23 ˚ A (n = 8) for the K82R mutant (both forms observed for the wild type). The catalytic domain exhibits the typical bi-lobed structure with the cleft wide opened. Two molecules form a symmetric dimer, with the catalytic clefts facing each other in the center of the dimer. The UBA domain is attached via a taut linker to the large lobe of the kinase domain and leans against a hydrophobic patch on the distal side of the small lobe. The UBA structure is unusual in that the orientation of its third helix is inverted, relative to previous structures. Data were collected at the X13 Consortium beamline at HASYLAB (DESY, Hamburg). We thank W.Rypniewski, M.Perbandt, and J. M¨ uller for help with the beamline facilities and for stimulating discussions. [1] G. Drewes et al., Cell 89 (1997) 297 [2] J. Biernat et al., Neuron 11 (1993) 153 [3] J. Pellettieri and G. Seydoux, Science 298 (2002) 1946 [4] S. Panneerselvam et al., Structure 14 (2006) 173

Biologische Systeme und Medizin

Vortrag: Fr., 11:10–11:30

F-V58

Indirect Radiation Therapy of Cancer by Neutrons and Synchrotron Radiation Thomas Nawroth1a , Heinz Decker1b , Christian Meesters1b , Bruno Pairet1b , ¨hler3b , Peter Boesecke4a , Christoph Alexiou2 , Roland P. May3a , Roland Ga 4b 4c ´raldine Le Duc Alberto Bravin , Ge 1

Gutenberg-Universit¨ at: a) Biochemistry, Becherweg 30, b) Molecular Biophysics, Welder-Weg 23; D-55099 Mainz, Germany – 2 Klinik f¨ ur Hals- Nasen-, Ohrenkranke HNO; Universit¨ atsklinik, Waldstraße 1, D-91054 Erlangen – 3 ILL Institut Lange Langevin: a) Large Scale Structure group LSS, b) NeutroGraph; BP156, F-38042 Grenoble – 4 ESRF European Synchrotron Radiation Facility: a) ASAXS beamline ID01, b) Medical beamline ID17, c) BioMedical Facility BMF; BP220, F-38043 Grenoble, France

Fig. 1: Indirect radiation therapy inactivates cancer cells by secondary radiation products of short range upon specific absorption at the local target. The target is a biocompatible DTPAcomplex, which can be enriched by magnetic nanoparticles References: (1) T. Nawroth, M. Rusp, R.P. May; Physica B 350(2004), e635-638 (2) T. Nawroth, G. Le Duc, St. Corde, R.P. May, P. Boesecke, A. Bravin; ESRF User meeting proceedings (2006, 3 contributions) (3) WEB: www.mpsd.de/irt

Indirect radiation therapy of cancer IRT inactivates tumors cells by secondary products evolving from an incorporated target upon specific absorption of external radiation (fig.1). We have developed those methods using biocompatible heavy metal complexes of Lanthanides, e.g. Gadolinium- to Lutetium-DTPA. The heavy metals are applied as key-formulations reversibly braking the blood-brain barrier (BBB), or in targetnanoparticles, i.e. magnetic target liposomes (1) and target-Ferrofluids. As external radiation we use synchrotron X-ray radiation at the K-edge of absorption and neutrons, which are completely absorbed at locally injected 157 Gd (Gd-NCT, black target). The long term project is an institutional and international cooperation (Germany, Spain, France; at ESRF and ILL). During three years it shall proceed from the current animal tests and cell culture experiments to the first human applications, i.e. a novel adjuvant cancer therapy.

Biologische Systeme und Medizin

Vortrag: Fr., 11:30–11:50

F-V59

Nanostructure and mechanics in hierarchical biocomposites: applications of synchrotron X - ray microfocus scanning and in - situ diffraction and scattering Himadri Shikhar Gupta1 , Oskar Paris1 , Wolfgang Wagermaier1 , Markus Rueggeberg1 , Chenghao Li1 , Ingo Burgert1 , Manfred Burghammer2 , Sergio S. Funari3 , Christian Riekel2 , Peter Fratzl1 1

Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany – 2 ESRF, Grenoble, France – 3 Beamline A2, HASYLAB-DESY, Notkestrasse 85, Hamburg, Germany Biological connective tissues like bone or wood are natural composite materials which are hierarchically structured from the nanometer level to macroscopic length scales [1, 2]. As a result, spatial variation and optimization of structural and mechanical properties occurs at all levels, including the length scale of 0.1 µm - 10 µm. To obtain information at this level on the micrometer level variation in the average nanostructural properties, structural and chemical techniques like small angle X - ray scattering (SAXS), wide - angle X - ray diffraction (WAXD) and X - ray fluorescence (XRF) can be combined with micron sized beams, scanning setups, and thin sample sections to generate two-dimensional spatial maps of nanostructural variations over sizes up to 50 to 100 µm. Complementary to the high spatial resolution available with a synchrotron X - ray microbeam, time - resolved in - situ mechanical testing enables us to track temporal variations at the molecular and supramolecular level induced, for example, by the application of mechanical stress. In this contribution, we report some recent work carried out by our group along these two lines. High resolution (1 µm) scanning X ray diffraction and scattering enabled us to reconstruct the 3 - dimensional crystallite orientation in the individual lamellae of compact human osteonal bone, revealing a right - handed spiralling fiber pattern [3]. Variations in the mineral particle size and resolution could be studied at the level of individual bone packets. Two - dimensional maps of the total SAXS intensity provided much higher contrast at the lamellar level than microradiography measurements. The fibrillar level mechanics of parallel fibered bone revealed a shearing mechanism at the nanometer level, between stiff fibers and an intervening extrafibrillar matrix [4]. We highlight SAXS and WAXD measurements of wood and bone obtained recently at the newly commissioned SAXS/WAXS/XRF beamline at BESSY, specially designed for scanning microbeam experiments on biological samples. [1] [2] [3] [4]

O. Paris et al, Cell. Mol. Biol. 46 (2000) 993. P. Fratzl et al, J. Mater. Chem. 14 (2004) 2115. W. Wagermaier et al, Biointerphases 1 (2006) 1. H. S. Gupta et al, Nano Lett. 5 (2005) 2108.

Biologische Systeme und Medizin

Vortrag: Fr., 11:50–12:10

F-V60

Inelastic Nuclear Resonant Scattering as a Local Probe for the Dynamics of Iron-Sulfur Proteins ¨nemann1 Volker Schu 1

TU Kaiserslautern, Fachbereich Physik, Erwin-Schr¨ odinger-Str. 56, 67663 Kaiserslautern Iron-sulfur proteins serve mainly as electron transfer proteins but act sometimes also as oxygen sensors or as enzymes. In both cases the dynamic properties of the ironsulfur centers are related to protein function. In electron transfer proteins they tune electron transfer rates. In sensor proteins as well as in iron enzymes dynamic properties influence the binding of molecules to the active iron site. The dynamic properties of these iron sites are conventionally studied by vibrational spectroscopy like Infrared (IR) or Resonance Raman (RR) spectroscopy. Inelastic nuclear resonant scattering is complementary to these methods because this technique is site selective and does not rely on optical selection rules. Therefore iron vibrations can also be detected if IR or RR fails as in the case of reduced rubredoxins which have a single tetrahedral sulfur coordinated iron site. The applicability of inelastic nuclear resonant scattering to reduced rubredoxin has been recently shown independently by two groups [1,2]. In this contribution inelastic nuclear resonant scattering experiments applied to proteins with more complicated iron sites like the 4Fe-4S site of ferredoxin will be discussed. These experiments may put the basis for future studies on the dynamics of even more complex iron sulfur centers like those in hydrogenases, enzymes which are involved in biological hydrogen production. [1] Y. Xiao et al., J. Am. Chem. Soc. 127 (2005) 14596. [2] A.X. Trautwein et al. Hyperfine Interact accepted.

Biologische Systeme und Medizin

Vortrag: Fr., 12:10–12:30

F-V61

Festk¨ orperunterst¨ utzte Modellmembranen ¨ per1 Ingo Ko 1

Max Planck Institut f¨ ur Polymerforschung, Ackermannweg 10, 55128 Mainz

Festk¨ orperunterst¨ utzte Modellmembranen (tethered membranes, tBLM) stellen ein wichtiges Modellsystem zur Untersuchung von Membranen und Membranproteinen dar. Eine tBLM besteht aus einer Lipid Doppelschicht, deren proximale Schicht kovalent an eine Festk¨ orperoberfl¨ ache angebunden ist. Meist wird als Substrat Gold gew¨ ahlt, was die Charakterisierung mittels elektrochemische Methoden zul¨ asst. Wir haben in den letzten Jahren ein Baukastensystem entwickelt, mit dessen Hilfe verschiedene Membranarchitekturen realisiert werden k¨ onnen [1-2]. Die Lipid-Doppelschichten erlauben den funktionellen Einbau von Membranproteinen [3]. Die Funktion der Eingebauten Proteine kann somit in einer quasi-nat¨ urlichen und sehr stabilen Platform untersucht werden. Anwendungsm¨ oglichkeiten liegen im Bereich der Biosensorik, wo einzelne modifizierte Ionenkan¨ ale als Detektionseinheiten mit hoher Selektivit¨ at verwendet werden sollen. Die molekulare Architektur der Membranen konnte mit Hilfe von Neutronenreflektivit¨ at aufgekl¨ art werden. Die am AND/R Spektrometer (NIST, Gaithersburg, MD) erhaltenen Ergebnisse geben wertvolle Hinweise f¨ ur m¨ ogliche Verbesserungen des Systems. [1] I. K¨ oper et al., Advances in Planar Lipid Bilayers, Vol. 3, (2006) 37-53. [2] V. Atanasov et al., Bioconjugated Chemistry (2006, in press). [3] V. Atanasov et al., Biophysical Journal, 89(3)(2005)1780.

Abb. 1: schematische Darstellung einer tBLM. Die proximale Schicht ist kovalent u ¨ ber eine Spacer-Gruppe an ein Substrat angebunden. Membraneproteine, z.B. Ionenkan¨ ale k¨ onnen funktionell eingebaut werden.

Chemische Prozesse und Phasen¨ uberg¨ ange

Vortrag: Fr., 11:10–11:30

F-V62

Zeitaufgel¨ oste Phononenspektroskopie ¨ tz Eckold1 , Friedrich Gu ¨thoff1 , Marcel Petri1 , Klaudia Hradil1 , HelGo 2 mut Schober , Frederic Descamps2 , Harald Schneider1 1 2

Institut f¨ ur Physikalische Chemie, Universit¨ at G¨ ottingen, D-37077 G¨ ottingen – Institut Laue-Langevin, F-38042 Grenoble

Phononen bilden auf direkte Weise die interatomaren Kr¨ afte in Kristallen ab. Dementsprechend sind sie besonders geeignet, um Ver¨ anderungen innerhalb fester Systeme aufgrund von chemischen Umwandlungen, Phasen¨ uberg¨ angen etc. zu charakterisieren. Am Beispiel von Silber-Alkalihalogeniden als Modellsystemen wird gezeigt, dass Entmischungsprozesse und ihre Mechanismen durch die zeitliche Ver¨ anderung von Phononenspektren eindeutig verfolgt werden k¨ onnen, was durch strukturelle Untersuchungen allein nicht m¨ oglich ist. Mit stroboskopischen Methoden k¨ onnen nicht nur zeitabh¨ angige Aufspaltungen und Frequenzverschiebungen von Phononen aufgrund der Phasentrennung beobachtet werden, sondern dar¨ uber hinaus mit dem neuen Dreiachsenspektrometer PUMA auch erstmals die Linienbreiten und Lebensdauern von Gitterschwingungen, die sich im Laufe der Entmischung deutlich ver¨ andern. Zudem ist es gelungen, auch am Flugzeitspektrometer IN5 ein stroboskopisches Datenerfassungssystem zu installieren, das es erlaubt, an Pulverproben die Ver¨ anderungen der Phononenzustandsdichte w¨ ahrend der Phasentrennung auf einer Sekunden-Zeitskala zu beobachten. Abbildung 1 zeigt die Ver¨ anderung des Flugzeitspektrums einer Ag0.5 Na0.5 Br-Probe bei zyklischer Temperaturvariation zwischen der homogenen Phase bei 350 ◦ C und der Entmischungstemperatur von 100 ◦ C. Deutlich zu erkennen ist die breite Intensit¨ atsverteilung bei hohen Temperaturen (t< 0 und t > 180 s), w¨ ahrend nach dem Abschrecken auf die Entmischungstemperatur (t=0) innerhalb weniger Sekunden sch¨ arfer strukturierte Spektren entstehen. Die quantitative Auswertung sowohl der Einkristall- als auch der Pulverdaten erlaubt eine detaillierte Charakterisierung des Entmischungsprozesses auf atomarer Ebene.

Abb. 1: Zeitliche Entwicklung der Phononenzustandsdichte (Flugzeitspektren integriert u ¨ ber alle Streuwinkel) von Ag0.5 Na0.5 Br w¨ ahrend zyklischer Temperaturvariation zwischen 350 ◦ C und 100 ◦ C

Chemische Prozesse und Phasen¨ uberg¨ ange

Vortrag: Fr., 11:30–11:50

F-V63

Time-resolved and operando XAS studies on heterogeneous catalysts in liquid phase and in supercritical fluids up to 200 bar Jan-Dierk Grunwaldt1 , Alfons Baiker1 1

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hoenggerberg, HCI, CH-8093 Zurich Catalyst characterization during preparation, activation and under reaction conditions is important for a targeted catalyst development. X-ray absorption spectroscopy is a valuable tool for this, since it is element-specific, information both on amorphous and crystalline materials can be gained and it can be used in situ under reaction conditions. In order to mimic the conditions of a catalyst under reaction conditions, the in situ cell should operate as closely as possible to the reaction conditions found in a catalytic reaction [1]. Mostly, in situ spectroscopic studies on heterogeneous catalysts are reported at normal pressure and in gas phase. However, many heterogeneously catalysed reactions are performed in liquids or even at elevated pressure [2]. Although the study of such reactions is equally important, in situ studies in these areas are only seldomly reported. The potential of XANES and/or EXAFS are discussed in these areas focusing on Pd- and Pd-Bi-catalysed selective oxidation of alcohols to the corresponding aldehydes. Starting with investigations in liquid phase [3], we recently succeeded in deriving structure-performance relationships even under the demanding conditions of supercritical fluids [4,5]. [1] J.-D. Grunwaldt, M. Caravati, S. Hannemann, A. Baiker, Phys. Chem. Chem. Phys. 6 (2004) 3037. [2] J. D. Grunwaldt and A. Baiker, Phys. Chem. Chem. Phys. 7 (2005) 3526. [3] C. Keresszegi, J.-D. Grunwaldt, T. Mallat, A. Baiker, J. Catal. 222 (2004) 268 [4] J.-D. Grunwaldt, M. Caravati, M. Ramin, A. Baiker, HASYLAB Highlight Research Report, Newsletter 08-2004. [5] J.-D. Grunwaldt, M. Caravati, A. Baiker, J. Phys. Chem. B, in press.

Chemische Prozesse und Phasen¨ uberg¨ ange

Vortrag: Fr., 11:50–12:10

F-V64

Surface reactions studied by in-situ x-ray photoelectron spectroscopy ¨nkenschuh1 , Thomas Reinhard Denecke1 , Christian Papp1 , Barbara Tra 1 1 1 ¨ck Fuhrmann , Regine Streber , Hans-Peter Steinru 1

Lehrstuhl f¨ ur Physikalische Chemie II, Universit¨ at Erlangen-N¨ urnberg, Egerlandstr. 3, 91058 Erlangen Employing high-flux and high-resolution synchrotron radiation from BESSY II, surface reactions can be studied in situ using a combination of high-resolution X-ray photoelectron spectroscopy (XPS) and a supersonic molecular beam set-up [1]. By continuously measuring C 1s or O 1s core level spectra with total times per spectrum of only a few seconds, surface reactions such as CO adsorption and CO oxidation with preadsorbed atomic oxygen as well as dissociative adsorption of methane and its subsequent dehydrogenation have been studied. From a quantitative analysis it is possible to determine the time- and coverage-dependent occupation of different adsorption sites or the population of certain surface species, which can be distinguished by in-situ high-resolution XPS. This includes the identification of step and terrace species and sites on regularly stepped surfaces [2] as well as the identification of different hydrocarbons by their specific vibrational fine structure [3]. The majority of the experiments rely on the use of a supersonic molecular beam for various reasons. The spatially confined beam allows for a relatively high particle flux (equivalent to pressure) on the sample, while keeping UHV conditions in the rest of the chamber. Secondly, the confined beam can be switched on and off precisely by a moveable flag. Finally, activated processes, like the dissociative adsorption of methane, can be facilitated by using highly energetic molecules provided by a supersonic molecular beam [3]. Using all these properties, a variety of surface reactions can be studied. We will present examples from our recent investigations. Supported by the DFG (STE 620/4-3). [1] R. Denecke, Appl. Phys. A 80 (2005) 977. [2] B. Tr¨ ankenschuh, N. Fritsche, T. Fuhrmann, C. Papp, J.F. Zhu, R. Denecke, H.-P. Steinr¨ uck, J. Chem. Phys. 124 (2006) 074712. [3] T. Fuhrmann, M. Kinne, B. Tr¨ ankenschuh, C. Papp, J.F. Zhu, R. Denecke, H.-P. Steinr¨ uck, New J. Phys. 7 (2005) 107.

Chemische Prozesse und Phasen¨ uberg¨ ange

Vortrag: Fr., 12:10–12:30

F-V65

Coherence experiments with white synchrotron radiation Tobias Panzner1 , Wolfram Leitenberger2 , Gudrun Gleber1 , Tushar Sant1 , Ullrich Pietsch1 1

Festk¨ orperphysik, Universit¨ at Siegen – 2 Institut f¨ ur Physik, Universit¨ at Potsdam

The third-generation X-ray source BESSYII (Berlin, Germany) provides a certain portion of coherent x-ray radiation which can be used for static and dynamic speckle analysis. Since about three years our group follows the concept of using “white” radiation for coherence experiments. Exploiting the exponentially decaying part of the BESSYII emission spectrum (critical energy 1 keV) we can use energies between 5 < E < 20 keV with sufficient coherent flux. Various experiments were performed to test and to measure the coherence properties at the white-beam bending-magnet beamline (EDR). We measured static speckles from plane and surface patterend semiconductor and polymer surfaces under grazingincidence over a wide energy range simultaneous. In this scattering geometry the Fourier-back transformation is influenced by the incindence spectrum which already contains features of Fresnel diffraction of the coherent beam at the incident pinhole. This apparatus function has been measured at the samples site for different incidence conditions and was simulated in terms of Lommel formalism. Knowing this function one is able to deconvolute measured reciprocal space maps by the apparatus function to receive the speckle pattern of the measured surface. On the other hand one can consider this function as input for reconstruction of the true sample surface. Using this setup we performed first XCPS studies at polymer surfaces. On time scale of several 10 seconds we detected the dynamics of molecular movement initiated by laser light at the surface of light-sensitive azopolymer film. Considering the apparatus function one can discriminate between static features due to Fresnel scattering from incident pinhole and dynamic speckles induced by the light. Both show different autocorrelation function as well. The features can be observed simulataneous over a broad energy band which help to distinguish between diffusion and not-diffusion controlled processes.

Magnetismus

Vortrag: Fr., 11:10–11:30

F-V66

Die magnetischen und supraleitenden Eigenschaften von UPd2 Al3 − mikroskopische Einblicke durch Streumethoden Arno Hiess1 1

Insitut Laue Langevin, BP 156, 38042 Grenoble Cedex 9, France

Information u ¨ber das Wechselspiel zwischen Supraleitung und Magnetismus ist der Schl¨ ussel zum Verst¨ andnis einer Reihe bedeutsamer Materialien, beispielsweise der Hochtemperatur- und Schwere-Fermionen-Supraleiter. Ein ausgezeichnetes Beispiel ist der magnetische Supraleiter UPd2 Al3 , der bei tiefen Temperaturen die Koexistenz von Supraleitung und antiferromagnetischer Ordnung zeigt. Diese intermetallische Verbindung ist - neben Hochtemperatursupraleitern - eine der am besten mit Streumethoden untersuchten supraleitenden Materialien, lassen doch die Beobachtungen einzigartige R¨ uckschlsse auf beide elektronischen Eigenschaften zu. In meinem Beitrag gebe ich ¨ einen Uberblick der experimentellen Untersuchungen der vergangenen Jahre: Magnetische R¨ ontgenstreuung an d¨ unnen Schichten beleuchtet die r¨ aumliche Ausdehnung der magnetischen Ordnung in Abh¨ angigkeit der Temperatur. Dreiachsenspektroskopie bei tiefen Temperaturen und in hohen Magnetfeldern zeigt den Einfluss der Supraleitung auf die impuls- und energieabh¨ angige Magnetisierungsdynamik, Neutronen Spin Echo Spektroskopie erlaubt Einblicke in die Fermifl¨ achentopologie des supraleitenden Zustands. Ich danke meinen vielen in den verschiedenen Ver¨ offentlichungen genannten Kollegen f¨ ur die langj¨ ahrige erfolgreiche Zusammenarbeit. [1] A. Hiess, N. Bernhoeft, S. Langridge, C. Vettier, M. Huth, M. Jourdan, H. Adrian, G. H. Lander, Physica B 259-261 (1999) 631-633; N. Bernhoeft, A. Hiess, S. Langridge, A. Stunault, D. Wemeille, C. Vettier, G. H. Lander, M. Huth, M. Jourdan, H. Adrian, Physical Review Letters 81 (1998) 3419-3422 [2] for a review see: A. Hiess, N. Bernhoeft, N. Metoki, G. H. Lander, B. Roessli, N. K. Sato, N. Aso, Y. Haga, Y. Koike, T. Komatsubara, and Y. Onuki, accepted for publication in J. Phys: Cond. Matt. (topical review, 2006) and references therein. [3] E. Blackburn, A. Hiess, N. Bernhoeft, G. H. Lander and N. K. Sato, accepted for publication in Phys. Rev. B [4] E. Blackburn, A. Hiess, M. C. Rheinst¨ adter, W. H¨ außler, N. Bernhoeft and G. H. Lander, submitted to Phys. Rev. Lett. Abb. 1: Magnetisierungsdynamik des magnetischen Supraleiters UPd2 Al3 am antiferromagnetischen Zonenzentrum Q = (0 0 als Funktion der Temperatur (links) und des Magnetfeldes (rechts). Neutronenzhlrate entsprechend der Farbscala oben links. Die superleitende Tsc = 2 K und magnetische TmN = 14 Kbergangstemperatur sind durch Pfeile gekennzeichnet. Kleine Punkte geben die Messpunkte an. Die Messung erfolgte am kalten Dreiachsenspektrometer IN14 des ILL mit kf = 1.15 AA [2,3].

Magnetismus

Vortrag: Fr., 11:30–11:50

F-V67

Melting of magneto-electric state in TbMnO3 with c−axis aligned magnetic field Dimitri Argyriou1 , N. Aliouane1 , J. Strempfer2 , I. Zegkinoglou2 , M. v. Zimmermann3 1

Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2 Max-PlanckInstitut f¨ ur Festk¨ orperforschung, Heisenbergstraße 1, 70569,Stuttgart, Germany – 3 HASYLAB at DESY, Notkestr. 85, 22065 Hamburg, Germany

TbMnO3 is an example of a multiferroic materials where magnetism and ferroelectricity are strongly coupled. This particular material exhibits a novel flop of the electric polarization P from from P || c to P || a with magnetic field when field is applied parallel to the a− or b−axis. Recently it was shown that as TbMnO3 is cooled in a ∼10 Tesla magnetic field aligned along the c−axis, the ferroelectric phase (P || c) exhibits a reiterant behavior, with a paraelectric phase appearing at intermediate temperatures.[1] We have performed in-field neutron and X-ray diffraction measurements on a TbMnO3 single crystal and find that an applied field parallel to the c−axis destabilizes the incommensurate magnetic modulation of Mn-spins in preference of a simple commensurate antiferromagnetic ordering (see fig. 1). The reiterant behavior of the ferroelectric state arises from the magneto-structural coupling of Tb-spins as they order incommensurately. [1] T. Kimura et. al., Phys. Rev. B 71, 224425 (2005).

Fig. 1: Scans along (1,k,0) as a function of temperature from a TbMnO3 single crystal cooled in a H || c=12T magnetic field. The incommensurate reflections due to Mn ordering are labeled as q M n , while incommensurate reflections from Tb spin ordering are labeled as q T b . The commensurate (010) reflection is also indicated. The data shows that the disapperance of the q M n reflections coincides with the melting of the ferroelectric phase, while the ordering of Tb spins at lower temperature with its reiterant behavior.

Magnetismus

Vortrag: Fr., 11:50–12:10

F-V68

Orbital Polaron Lattice Formation in Lightly Doped La1−x Srx M nO3 ¨diger Klingeler1 , PasJochen Geck1,2 , Peter Wochner2 , Sven Kiele1,3 , Ru 1,4 4 ¨chner1 cal Reutler , Alex Revcolevschi , Bernd Bu 1

Leibniz-Institut f¨ ur Festk¨ orper- und Werkstoffforschung IFW Dresden, Helmholtzstr. 20, 01069 Dresden – 2 Max-Planck-Institut f¨ ur Metallforschung, Heisenberg Str. 3, 70569 Stuttgart – 3 Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg – 4 Laboratoire de Physico-Chimie de l’Etat Solide, Universit´e de Paris-Sud, 91405 Orsay Cedex, France

During the last 20 years there have been tremendous efforts worldwide to unravel the physics behind the doping induced changes in magnetic transition metal oxides. The physics of doped manganites has become one of the main foci in this field. In these materials not only are the spins and the charges important, but also the so-called orbital degree of freedom plays a central role for the physical properties. This is already documented by the insulating ground state of undoped LaMnO3 , which does not only display antiferromagnetic (AFM) order but also antiferro-orbital order, meaning that the spatial distribution of the 3d electrons alternates from one Mn site to the next. Doping of this correlated magnet with holes results in a large number of intriguing physical phenomena. The most prominent is the colossal magnetoresistance effect, i. e., the enormous suppression of the electrical resistivity in applied magnetic fields. By Fig. 1: Orbital polaron model for the resonant x-ray scattering at the Mn K-edge on FMI phase of La7/8 Sr1/8 MnO3 . A top view of the different ab planes along the La7/8 Sr1/8 MnO3 , we show that an orbital poc axis is shown. The hatched cross (z=0) laron lattice (OPL) develops at the metal-insulaand the gray bars (z=0.5) mark the ortor transition of this compound [1]. This orbital bital polaron and charge stripes in the ab planes, respectively. reordering explains consistently the unexpected coexistence of ferromagnetic and insulating properties at low temperatures, the quadrupling of the lattice structure parallel to the MnO2 planes, and the observed polarization and azimuthal dependencies. The OPL is a clear manifestation of strong orbital-hole interactions, which play a crucial role for the colossal magnetoresistance effect and the doped manganites in general. [1] J. Geck et al., Phys. Rev. Lett. 95 (2005) 236401.

Magnetismus

Vortrag: Fr., 12:10–12:30

F-V69

Magnetism and Superconductivity in Electron Doped Cuprates A Muon Spin Relaxation Study on Thin Films of La2−x Cex CuO4 Hans-Henning Klauss1 , Hubertus Luetkens2 , Yoshinari Krockenberger3 , Andreas Winkler4 , Lambert Alff4 , Michio Naito5 , Elvezio Morenzoni2 , Thomas Prokscha2 , Andreas Suter2 , Jochen Litterst1 1

TU Braunschweig, Inst. f. Physik d. Kondensierten Materie – 2 Paul-Scherrer-Institut, Villigen, Switzerland – 3 MPI f. Festk¨ orperforschung, Stuttgart – 4 TU Darmstadt, 5 Institut f. Materialwissenschaften – NTT Basic Research Laboratory, Atsugi, Japan Unconventional superconductivity in strongly correlated electron systems like high temperature superconductors and heavy fermion systems is always in competion with magnetically ordered ground states. Muon spin relaxation (µSR) provides an ideal tool to examine long and short range magnetic order as well as the superconducting order parameter in these systems. In high-TC -cuprates it is used intensively to study e.g. the interplay of nanoscale stripe order and superconductivity in hole doped cuprates[1]. Similar studies of electron doped systems like (Nd,Pr)2−x Cex CuO4 are disturbed by the presence of the magnetic rare earth elements. La2−x Cex CuO4 , not containing a magnetic rare earth, can only be prepared as thin films. We studied the magnetic and superconducting properties of this system for different x ranging from long range antiferromagnetism to the pure superconducting state on thin films with 60 to 300 nm thickness by means of state-of-the-art low-energy muon spin rotation (LE-µSR). The results show that optimally doped samples (x ≈ 0.10) with the highest TC = 28 K still exhibit a nanoscale coexistence of a magnetic surface layer with bulk superconductivity in the film. In an externally applied magnetic field, the superconducting films show Meissner screening with a magnetic penetration depth of the order of 250 to 300 nm. These measurements provide a clear differentiation between volume and filamentary surface superconductivity. The temperature dependence of the magnetic penetration depth can be used to characterize the symmetry of the order parameter. The results on these films will be compared with similar µSR studies on bulk samples of (Nd,Pr)2−x Cex CuO4 [2]. [1] H.-H. Klauss, J. Phys: Cond. Mat. 16 (2004), S4457. [2] D. Baabe et al., Phys. Rev. B 69 (2004), 134512. Work supported in part by BMBF under contract 05 KK4MBA/2.

Abstracts: Poster Postersitzung A: Mittwoch, 4. 10. 2006, 14:00 - 16:30 Flugelbau ESA - West ¨ Methoden und Instrumentierung Mikroskopie und Tomographie

M-P1 – M-P97 –

M-P96 M-P114

Flugelbau ESA - Ost ¨ Struktur und Dynamik ¨ Chemische Prozesse und Phasenuberg ange ¨

M-P115 – M-P167 M-P168 – M-P180

Biologische Systeme und Medizin

M-P181

–

M-P213

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P1

Optimization of the Cairo Fourier Diffractometer Facility for the Polarized Neutron Diffraction Measurements Ihab Abdel-Latif1 , Vitaly Trounov2 1

Reactor Physics Dept., NRC, Atomic Energy Authority, Abou Zabaal – 2 Petersburg Nuclear Physics Institute, Gatchina, 188350, Petersburg, Russia The present work deals with the calculations of the polarized neutron diffraction option for the Cairo Fourier Diffractometer Facility CFDF. The CFDF is based on the reverse time of flight RTOF diffraction method using Fourier chopper. The Neutron flux incident on the sample is 106 neutrons.cm−2 .s−1 in the case of non-polarized neutron diffraction, (in the present time). The polarized neutron PN possibility will decrease the intensity incident on the sample ∼ 2x105 neutrons.cm−2 .s−1 with resolution of 5x10−3 . The PN option enable studying the magnetic structure and spin density of the magnetic materials besides suppressing the incoherent contributions in the diffraction pattern.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P2

A Combined Fabry-Perot Interferometer for Moessbauer Radiation And Visible Laser Light Birk Andreas1 , Yuri Shvyd’ko2 , Ulrich Kuetgens1 , Peter Becker1 1

Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany – 2 Argonne National Laboratory, Advanced Photon Source, Argonne, IL 60439, U.S.A. By x-ray interferometry the lattice constant of silicon can be used as a length standard in the subnanometer regime. The relative uncertainties are typically not smaller than 10−8 [1]. The limiting factor is the variation of the lattice constant due to wanted or unwanted dopands and the isotopic mixture ratio. In order to define a better standard on this length scale we aim to use the wavelength of 57 Fe Moessbauer radiation λM =0.086 nm (photon energy EM =14.4125 keV) and to trace it back to the SI system. The relative spectral width of the Moessbauer radiation and thus the uncertainty in the wavelength is as small as 3×10−13 . For this purpose we are developing a Fabry-Perot interferometer (FPI) based on two sapphire crystals which are cut and tempered properly for backscattering of the Moessbauer radiation [2,3]. The crystals are also used as cavity of an optical FPI. By scanning the mirror spacing it is possible to compare the wavelength of an iodine-stabilized laser at 532 nm with that of the Moessbauer radiation. The crucial requirements and the current layout of the setup as well as the remaining obstacles will be discussed in this presentation. [1] P. Becker and G. Mana, Metrologia 31, 203 (1994). [2] Yu. V. Shvyd’ko et al., Phys. Rev. Lett. 90, 013904 (2003). [3] Yu. V. Shvyd’ko, X-Ray Optics: High energy-resolution Applications. Berlin, Heidelberg, New York: Springer, 2004.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P3

Soft x-ray dispersive electron spectroscopy and near-edge absorption finestructure ¨ ll1 , R. D.R. Batchelor1 , Th. Schmidt1 , Ch. Jung2 , R. Follath2 , A. Scho Fink3 , M. Knupfer4 , E. Umbach1 1

Exp.Physik II, Univ. W¨ urzburg, D-97074 W¨ urzburg – 2 BESSY Gmbh, Phys, D3 12489, Berlin – Physikalische Chemie II, Universit¨ at Erlangen, D-91058 Erlangen – 4 IFW Dresden, D-01171 Dresden The technique of energy dispersive NEXAFS is well established in the hard x-ray region, but its application using soft x-rays is much less common [1]. By combining the photon energy dispersion of a monochromator and utilising the imaging properties of a hemispherical electron analyser orthogonal to the photon dispersion, energy dispersive electron spectroscopy is possible. To realise this multiplex technique, a small spot size of a state-of-art synchrotron beamline and a modern electron energy analyser with 2D imaging detectors are needed. We present the design for such an upgrade of the existing UFF UE52-PGM beamline and present results of a pilot experiment utilising the low angular divergence of a PGM which is operated at low Cf f values. Data for various edges will be presented illucidating the complex nature of the electronic excitations responsible for the near edge fine structure. Besides the common photoemission and Auger lines and the known participator and spectator decay channels the extensive, quasi-3-dimensional data sets show that other excitations, such as ”shake-up”, play an important role in both, the normal and resonant Auger processes. The detailed analysis also allows the identification of valence band features and demonstrates that orbitals other than the LUMO have a substantial contribution to the NEXAFS spectra. As an example of the method we show data for a C60 film below. The map is built up from a collage of maps with a narrower energy range taken at discrete photon energies. The inset displays a NEXAFS spectrum obtained by integrating along the electron energy axis and is in excellent agreement with published data. [1] K. Amemiya, H. Kondoh, T. Yokoyama, T. Ohta, J. Electron Spectr. Rel. Phen.124 (2002) 151.

Fig. 1: Resonant excitation at the carbon edge for a thin film of C60. The displayed “map” consists of a collage of individual maps with a narrower energy range taken at discrete photon energies. The inset shows a NEXAFS spectrum obtained by integrating along the kinetic energy scale.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P4

Microdiffraction Imaging of Semiconductor Materials ¨bbert1 , Petr Mikulik3 , Lukas Helfen2 , Petra Tilo Baumbach1 , Daniel Lu 2 Pernot , Christoph Landesberger4 , Juergen Schreiber5 , Stacia Keller6 , Steven P. Den Baars6 , Jose Baruchel2 1

ANKA / Institute for Synchrotron Radiation, Forschungszentrum Karlsruhe GmbH, P.O. Box 36 40, D-76021 Karlsruhe, Germany – 2 European Synchrotron Radiation Facility, F-38043 Grenoble – 3 Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic – 4 Fraunhofer Institute for Reliability and Microintegration, D-80686 Munich, Germany – 5 Fraunhofer Institute for Nondestructive Testing, D-01326 Dresden, Germany – 6 University of California, Santa Barbara, California 93106 We report on a method for microstructural characterization and quality control of single-crystalline materials and epitaxial devices in microelectronics and micro system technology. The parallel-beam X-ray microdiffraction imaging technique realizes spatial resolution on a µm scale. The method is based on a combination of x-ray rocking curve analysis and digital X-ray diffraction topography. Back projection and multi peak analysis of local rocking curves allow full field mapping of microdiffraction properties. Segmentation procedures and 2D and 3D reconstruction of characteristic parameters provide convenient means to monitor the local crystalline quality in semiconductor microstructures. The development and production of highly perfect semiconductor materials and their application in components in various branches of microelectronics and micro system technology require information on their structural perfection. Of crucial importance are structural properties and their relations to technological steps. Moreover, the investigation of structure-property relationships for the components, from semiconductor substrate up to the final component, e. g. the completed laser or integrated circuit, and beyond to the entire device, e. g. the single photon counting pixel detector arrays, the finished PCB-unit or hybrid circuit, is needed. We demonstrate the principles of imaging and reconstruction of the full field microdiffraction imaging method and its instrumental realization. We illustrate the potential for technologically relevant applications by examples of non-destructive testing for Thin Chip technology - Vertical System Integration by vertical interchip bonding Wafer technology - macrodefects and dislocation density mapping in GaAs and InP GaN - technology - virtual substrates for blue laser diodes by GaN Epitaxial Lateral Overgrowth on sapphire and SiC Flip-Chip technology strain and damage induced by the interconnection technology Direct converting x-ray detectors - strain and defect analysis and others.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P5

Synchrotronstrahlung und Untersuchung von Proteinen mittels Zirkulardichroismus-Spektroskopie im fernen UV ¨rtel1 , Ben Schuler2 , Gerd Reichardt3 , Olgica Bakajin4 , Jan Peter Baumga Lengefeld1 , Avinash Kane4 , Armin Hoffmann2 , Robert Seckler1 1

Universit¨ at Potsdam, Physikalische Biochemie, Karl-Liebknecht-Str. 24, 14476 Golm – Universit¨ at Z¨ urich, Biochemisches Institut, Winterthurerstrasse 190, CH-8057 Z¨ urich – 3 BESSY, Albert-Einstein-Str. 15, 12489 Berlin – 4 Lawrence Livermore National Laboratory, BioSecurity and Nanosciences Laboratory, Livermore, CA USA 2

Zirkulardichroismus-Spektroskopie (CD) im fernen UV ist eine etablierte Methode zur Untersuchung von Proteinen. Aus einem Spektrum l¨ asst sich der Sekund¨ arstrukturgehalt eines Proteins berechnen. Mit Hilfe der stopped-“ oder continous-flow“ Tech” ” nik kann zudem der Faltungszustand des Proteins zeitaufgel¨ ost abgebildet werden. Der hierzu ben¨ otigte Spektralbereich im fernen UV (300 bis 130 nm) legt es nahe, Synchrotronstrahlung als Lichtquelle zu nutzen. Bei BESSY II konnte bereits eine Messkammer in Betrieb genommen werden. Sie dient unter anderem dazu, den Vorteil der Synchrotronstrahlung f¨ ur die Methodik zu sondieren und aufzuzeigen. Ein Vorteil der Synchrotronstrahlung liegt im erweiterten Spektralbereich bis 130 nm – in Laborger¨ aten liegt die untere Grenze bei 170 nm. Die Ergebnisse zeigen, dass der erweiterte Bereich nur durch die Pr¨ aparation ¨ außerst d¨ unner Schichten oder getrockneter Proben zug¨ anglich wird. Bei den Techniken f¨ ur zeitaufgel¨ oste Messungen sind zudem die geringe Divergenz und der hohe Photonenfluss der Synchrotronstrahlung von Vorteil. Sie erlauben es die Zeitaufl¨ osung zu verbessern und das Probenvolumen wesentlich zu verkleinern. Dies wird am Beispiel erster erfolgreicher Messungen, mit dem von uns entwickelten Mikromixer, dargestellt [1]. Die Messungen zeigen jedoch auch, dass derzeit bei BESSY II kein f¨ ur die Methode optimal geeigneter Experimentierplatz zur Verf¨ ugung steht. Eine L¨ osung f¨ ur die Zukunft k¨ onnte deshalb ein f¨ ur CD dediziertes Strahlrohr bei BESSY II sein. [1] A. Hoffmann et al., eingereicht bei PNAS, Mai 2006

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P6

Wafer contamination analysis and speciation as well as reference-free nanolayer characterization employing X-ray spectrometry ¨ller1 , Burkhard Beckhoff1 , Rolf Fliegauf1 , Michael Kolbe1 , Matthias Mu Beatrix Pollakowski1 , Jan Weser1 , Gerhard Ulm1 1

Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin, Germany

Monochromatized synchrotron radiation has been used for the non-destructive investigation of wafer surface contamination and nanolayered materials by X-ray spectrometry in different beam geometries: varying the incident angle from close to zero degrees, i.e. total-reflection geometry (T), over grazing incidence (GI) to conventional X-ray fluorescence (XRF). In TXRF geometry only the surface is analyzed, whereas GIXRF and XRF provide information from subsurface layers respectively the bulk of a sample. The Physikalisch-Technische Bundesanstalt operates XRF equipment at a plane grating monochromator beamline for undulator radiation in its laboratory at BESSY II. The absolute lower levels of detection for TXRF of light elements range between 100 fg and 1 pg with respect to a measuring time of 1000 s. For the explicit purpose of the semiconductor industry, PTB can handle 25 mm through 300 mm silicon wafers in its XRF and TXRF instrumentation [1] ensuring reference-free quantitation by calibrated components [2]. Near-edge X-ray absorption fine structure (NEXAFS) investigations in conjunction with TXRF are able to contribute to the speciation of low Z and organic compounds. TXRF-NEXAFS experiments [1,3] of contaminants have been performed at the K absorption edges of light elements and the L absorption edges of transition metals. Reference-free quantification in X-ray fluorescence analysis requires the accurate knowledge of all experimental values both in the excitation and detection channels as well as of the fundamental parameters involved. The experimental data are accessible through calibrated devices such as photodiodes, diaphragms and energy-dispersive detectors. Besides the instruments’ contributions, the relative uncertainties of the XRF analytical results are also affected by the tabulated fundamental parameters of the elements, some of which only have estimated uncertainties. The layer thickness obtained for transition metals as well as silicon dioxide layers by reference-free XRF has been compared to the thicknesses determined by X-ray reflectometry. Both methods showed the same results within the frame of their respective uncertainties [4]. For the speciation of nanolayer compositions, grazing incidence XRF (GIXRF or GIXF) allows for different penetration depths by varying the incident angle. At a given incident angle, GIXRF can be combined with NEXAFS revealing the depth profile of the chemical layer structure. [1] [2] [3] [4]

B. Beckhoff et.al, ECS Proc. 2003-3 (2003) 120 F. Scholze et al., Microchim. Acta (2006) online G. Pepponi et al., Spectrochim. Acta B 58 (2003) 2245 M. Kolbe et al., Spectrochim. Acta B 60 (2005) 505

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P7

Die TGM-Beamline an der Synchrotronstrahlungsquelle DELTA ¨ ring1,2 , Carsten Westphal1,2 Ulf Berges1,2 , Sven Do 1 2

DELTA, Universit¨ at Dortmund, Maria-Goeppert-Mayer Str. 2, 44221 Dortmund – Experimentelle Physik I, Universit¨ at Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Die ehemalige TGM3-Beamline des BESSYI wurde am 1,5 GeV Elektronenspeicherring DELTA der Universit¨ at Dortmund wieder aufgebaut. Diese Dipolbeamline nutzt Synchrotronstrahlung zwischen 6 und 200 eV, um Fermi-Fl¨ achen zu vermessen und Photoelektron-Spektroskopie im Valenzband-Bereich zu betreiben. Das Design von BESSYI wurde beibehalten, insbesondere das optische Layout. Das Vakuum-System wurde komplett neu konstruiert, nur die Spiegel-, Monochromator- und Spaltkammern wurden wieder verwendet. Wegen der h¨ oheren thermischen Last an DELTA aufgrund der h¨ oheren Elektronenstrahlenergie musste eine Wasserk¨ uhlung in die erste Spiegelkammer integriert werden. Das f¨ uhrte zu einem komplett neuen Design der Vakuumkammer. An DELTA befindet sich diese Kammer innerhalb der Strahlenschutzmauer, was eine Motorisierung aller Achsen der Spiegelkammer zus¨ atzlich erfordert. Das Monochromator-Kontrollsystem inklusive des Motors wurde komplett durch ein neues System ersetzt, das zu dem neuen Beamlinekontrollsystem an DELTA paßt. Erste Experimente zur Charakterisierung der Beamline werden zur Zeit durchgef¨ uhrt. Die Leistung der Beamline und erste Ergebnisse werden pr¨ asentiert.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P8

Die PGM-Beamline am Undulator U55 bei DELTA ¨ ring1,2 , Carsten Westphal1,2 Ulf Berges1,2 , Sven Do 1 2

DELTA, Universit¨ at Dortmund, Maria-Goeppert-Mayer Str. 2, 44221 Dortmund – Experimentelle Physik I, Universit¨ at Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Eine VUV-Beamline f¨ ur linear polarisierte Synchrotronstrahlung von einem Permanentmagnetundulator wird am DELTA, der 1.5 GeV Synchrotronstrahlungsquelle der Universit¨ at Dortmund, betrieben. Diese Beamline im PGM-Design deckt einen Energiebereich von 55 bis 1500 eV ab. Die berechnete Fokusgr¨ oße am Experiment betr¨ agt 70 µm (h) x 30 µm (v). Der gemessene Photonenfluss liegt in der Gr¨ oßenordnung von 1012 Photonen / s / 100 mA / 0.1 % BW bei 400 eV, 200 µm Austrittsspaltbreite und einem cff-Wert von 2. Die Beamline kann auch in einem hochaufl¨ osenden Modus betrieben werden mit einer berechneten Energieaufl¨ osung von bis zu 30.000. Verschiedene Messungen bez¨ uglich der Energieaufl¨ osung, des Photonenflusses und der Strahlstabilit¨ at, die zu einer Charakterisierung der Beamline f¨ uhren, werden pr¨ asentiert. Auch die Instrumentierung der Beamline wird diskutiert.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P9

Status der Synchrotron-Licht-Quelle DELTA ¨ ring1,2 , Christian Sternemann1,2 , Metin Tolan1,2 , Ulf Berges1,2 , Sven Do 1 Thomas Weis , Carsten Westphal1,2 , Klaus Wille1 1 2

DELTA, Universit¨ at Dortmund, Maria-Goeppert-Mayer Str. 2, 44221 Dortmund – Experimentelle Physik I, Universit¨ at Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Der Dortmunder Elektronenbeschleuniger DELTA ist eine 1,5 GeV Synchrotronstrahlungsquelle an der Universit¨ at Dortmund. Sie wird an 3000 Stunden im Jahr betrieben, 2000 Stunden davon als Strahlzeit f¨ ur Synchrotronstrahlungsnutzer und 1000 Stunden f¨ ur die Maschinenphysik, Optimierung und Wartung. Der Status der Synchrotronstrahlungsquelle wird pr¨ asentiert mit besonderer Betonung auf den Betrieb, die Kommissionierung und den Aufbau der Beamlines und Insertion-Devices. Zwei UndulatorBeamlines f¨ ur Photonen im VUV-Bereich (von 5 bis 400 eV (U250) und zwischen 55 und 1500 eV (U55)), zwei Dipol-Beamlines (zwischen 6 und 200 eV und f¨ ur weiße Synchrotronstrahlung mit einer kritischen Energie von 2.2 keV) und einer WigglerBeamline zwischen 4 und 20 keV an einem supraleitenden asymmetrischen Wiggler (SAW, Feldst¨ arke 5,3 T, kritische Energie 7,9 keV) werden zur Zeit betrieben. Eine weitere Beamline am SAW wird kommissioniert, die den Energiebereich von 20 keV bis hinunter zu 2 keV abdecken wird. Eine dritte Beamline am SAW wird zur Zeit aufgebaut. Verschiedene Dipol-Beamlines sind zur Zeit noch in Planung. Die Beamlines werden von verschiedenen Universit¨ aten (Dortmund, Wuppertal und Siegen) und vom Forschungszentrum J¨ ulich betrieben.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P10

ThALES - towards the next generation cold three axis spectrometer at ILL Martin Boehm1 , Stephane Roux1 , Arno Hiess1 , Jiri Kulda1 1

Institut Laue Langevin, 6, rue Jules Horowitz, BP 156, 38042 Grenoble, France

Das kalte Neutronen Dreiachsenspektrometer IN14 am Institut Laue Langevin (ILL, Grenoble, Frankreich) gilt seit u ¨ber 20 Jahren als weltweit f¨ uhrend zur Untersuchung magnetischer Wechselwirkungen. Der Energiebereich von etwa 2 bis 15 meV erlaubt die Untersuchung geordneter Systeme mit ihren Spinwellen sowie - mit in den letzten Jahren zunehmender Bedeutung - exotischer“ Spinsysteme, die direkten Einblick ” in deren Quantenwelt erlauben. Der oft niederdimensionale Charakter der Wechselwirkungen (1D oder 2D Systeme) bedingt jedoch in vielen F¨ allen im Impuls- und Energieraum breite und deswegen intensit¨ atsschwache Kontinua, deren experimentelle Nachweis schwierig ist. Auch kleine Spinquantenzahlen (Spin 1/2 Systeme) und durch die Verwendung extremer Probenumgebungen (hohe Dr¨ ucke, hohe magnetische Felder, Temperaturen < 1K) reduzierte Probenvolumina f¨ uhren zu geringen - oftmals zu zu geringen - Z¨ ahlraten. Die kontinuierliche Entwicklung der letzten Jahrzehnte auf dem Gebiet der Neutronenoptik bringt neue Perspektiven f¨ ur Dreiachsenspektrometer. Im Rahmen des so genannten Millenium Programms“ des Institut Laue Langevin wurden bereits die thermische ” Neutronen Dreiachsenspektrometer IN8 und IN20 erneuert. F¨ ur das Prim¨ arspektrometer werden nun doppelfokusierende Monochromatoren erfolgreich eingesetzt, f¨ ur das Sekund¨ arspektrometer stehen neuartige Mehrfachanalysatorensysteme (FlatCone, IMPS) zur Verf¨ ugung. Das Projekt ThALES - Three Axis Low Energy Spectroscopy -, zielt darauf ab durch ¨ Ubertragung dieser neutronenoptischen Konzepte die n¨ achste Generation kalter Neutronen Dreiachsenspektrometer am ILL zu implementieren. ThALES verfolgt im besonderen die folgenden instrumentellen Schwerpunkte: - Die Erh¨ ohung der Z¨ ahlraten um eine Gr¨ oßenordnung durch Einbindung modernster Neutronenleitertechnologie (elliptische m=3 Supermirrors), doppelfokusierende Monochromatoren sowie neuer Mehrfachanalysatorensysteme. - Eine effiziente Option f¨ ur polarisierte Neutronen, die in Verbindung mit erh¨ ohten Z¨ ahlraten dringend ben¨ otigte inelastische Experimente mit polarisierten kalten Neutronen erm¨ oglicht. - Eine Vergr¨ oßerung des dynamischen Bereiches zu thermischen Energien (E=25 meV) durch Modifikationen des prim¨ aren Spekrometers. - Die Optimierung des Spetrometers f¨ ur extreme Probenumbegung, v. a. durch die Verwendung nichtmagnetischer Materialien in der Experimentierzone. In unserem Beitrag werden wir die Erfolge der bisherigen Umbaumaßnahmen der thermische Neutronen Dreiachsenspektrometer beleuchten, die instrumentellen Aspekte des Projekts ThALES vorstellen und den Einfluss f¨ ur die Untersuchung der dynamischen Eigenschaften magnetischer System erl¨ autern.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P11

Neues TDC-Modul f¨ ur das MCA-System des GKSS-Forschungszentrums Geesthacht ¨ rg Burmester1 , Jo ¨ rn Plewka1 , Robert Kulcke1 , Burkhard Wenzel1 , OliJo ver Frank1 1

GKSS-Forschungszentrum Max-Planck-Str.1 21502 Geesthacht

Durch das st¨ andige Streben nach g¨ oßeren Z¨ ahlraten, h¨ oheren Aufl¨ osungen und kompakterer Hardware f¨ ur Detektoren, bei der Elektronikabteilung (TEL) des GKSSForschungszentrum Geesthacht, konnte ein neues TDC-Modul entwickelt werden, daß f¨ ur zuk¨ unftige Meßaufgaben ger¨ ustet ist. Besondere Highlights: 5 multihitf¨ ahige TDC-Kan¨ ale; 1 ADC-Kanal (Abtasten der Pulsform f¨ ur Analyse); Peakz¨ ahlrate bis 200 Mevents/s f¨ ur 100 Events; kontinuierliche Z¨ ahlrate ca. 5 MEvents/s; Zeitliches Aufl¨ osungsverm¨ ogen ≤ 40 ps; frei u ¨ber Software einstellbarer Eingangskomparator; positive wie negative Flankenerkennung; Pulsbreitenerkennung/auswertung (Gammaunterdr¨ uckung); Onchip Pulsanalyse (Pulsformanalyse); Datenerfassung Listmode (Raid-System); PC-Anbindung u ¨ber cPCI, Ethernet oder Glasfaser. An der Geesthachter Neutron Facility (GeNF) werden mehrere Experimente betrieben, die alle mit einer Experimentsteuerung angesteuert werden, die in LabVIEW programmiert ist. Hierbei ist hervorzuheben, daß es sich um eine dynamisch ans Experiment anpassbare Software handelt. Es k¨ onnen Motoren frei definiert werden, die alle u ¨ber eine Inidatei initialisiert werden. So k¨ onnen Grenzen, Freigaben etc. vordefiniert ¨ werden, um evtl. Kollisionen sehr einfach und effizient zu verhindern. Uber eine graphische Oberfl¨ ache k¨ onnen Position etc. angezeigt werden. So erh¨ alt man sehr schnell einen Gesamt¨ uberblick u ¨ber die Stellung aller Achsen und Schalter etc. Die Experimentablaufsteuerung erfolgt u ¨ber eine Scriptsprache, welche gr¨ oßtm¨ ogliche Flexibilit¨ at bietet. R¨ uckfragen bitte an Dipl. Ing. J¨ org Burmester GKSS-Forschungszentrum Geesthacht Abteilung TEL Max-Planck Str. 1 21502 Geesthacht Tel.: +49(0)4152/872733 Fax: +49(0)4152/872727 email: [email protected]

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P12

Resonant Inelastic X-ray Scattering of Transition Metals and Transition Metal Compounds Wolfgang Caliebe1 , Edmund Welter1 , Pavel Machek2 1

Hasylab am Desy, Notkestraße 85, 22607 Hamburg – 2 Institute of Organic and Analytical Chemistry, Justus Liebig Universit¨ at We used a Johann spectrometer [1] to measure emission spectra of different transition metals (TM) and transition metal compounds (TMC) while tuning the excitation energy through the K-absorption edge. The energy resolution of the spectrometer is better than 1 eV, while the energy resolution of the exciting x-ray beam is about 2 eV. The emission lines excited above threshold show significant differences for different compounds in case of Kβ1,3 and Kβ2,5 fluorescence lines, while there are just minor differences for Kα1,2 fluorescence lines. The spectra excited close to threshold show significant differences, and allow to separate transitions, which cannot be separated with conventional x-ray absorption spectroscopy. We observe significant resonant enhancement at the Cr K-edge, which allows to observe charge-transfer excitations in K2 CrO4 with an excitation energy of ≈3.3 eV, which is not observed off-resonance. Additional observations are better separations of (weak) quadrupolar transitions in the near-edge region from the dominating dipolar transition. [1] E. Welter et al., J. Synchrotron Rad. 12 (2005) 448

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P13

Instrumentierung in der Neutronenleiterhalle-II bei BENSC ´rine Pappas1 , Ferenc Mezei1,2 Daniel Clemens1 , Judith Peters1 , Cathe 1

Hahn-Meitner-Institut Berlin, Abt. Methoden & Instrumente, Glienicker Str. 100, D-14109 Berlin – 2 Los Alamos National Laboratory, MS H805, Los Alamos, NM 87545, USA BENSC hat in den letzten Jahren die Instrumentierung in der neu gebauten zweiten Neutronenleiterhalle (NLH-II) am BER-II vorangetrieben. Das Projekt ersetzt vollst¨ andig den seit 1992 betriebenen Neutronenleiter 4 (NL4) durch ein modernes Leitersystem, bei dem erstmals eine multispektrale Extraktion verwirklicht wurde, deren Optik von zwei Moderatoren ausgeht. Die Endpositionen liegen in der neuen NLH-II. Weitgehend mit Superspiegeln beschichtet, gliedert sich das System in drei Neutronenleiter von bis zu ca. 80 m L¨ ange auf. Die Altinstrumente des NL4 erhalten im Fall des Reflektometers V6 eine nahezu unver¨ anderte Strahlposition, w¨ ahrend das Spin-Echo-Spektrometer SPAN eine endst¨ andige Position in der Mitte der NLH-II einnimmt, f¨ ur die ein polarisierender Leiter eingerichtet wird. Um sich gezielt den Forschungsschwerpunkten widmen zu k¨ onnen, die sich in der j¨ ungeren Vergangenheit unter den BENSC-Nutzern herausgebildet haben, errichten wir zwei neue Instrumente in der NLH-II: eine zweite Kleinwinkelstreuanlage (VSANS) mit einer Ausrichtung auf Fragestellungen der Weichen Materie und das hochaufl¨ osende Pulverdiffraktometer EXED. VSANS erschließend Impuls¨ ubertr¨ age bis 10−3 nm−1 und eine Aufl¨ osung, die unter 5 % liegt. EXED nutzt das erweiterte Wellenl¨ angenband von 0.07 – 2 nm, das sich aus der multispektralen Extraktion ergibt. Ein fensterlos mit dem Neutronenleiter verbundenes Choppersystem erlaubt das einst von Bouras vorgeschlagene Flugzeitmeßprinzip zu realisieren, womit Aufl¨ osungen bis 3 ×10−4 erreicht werden k¨ onnen. Als Basis f¨ ur den Einsatz eines Hochfeldmagneten, der nur kleine Zugangsfenster erlaubt ist EXED ideal ausgelegt, auch weil es sich in einem von magnetisierbaren Materialien frei gehaltenen Hallenbereich befindet. Wir berichten u ¨ber den Stand der Neuinstrumentierung am NL4 und einige Leistungsmerkmale.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P14

Konzept f¨ ur pump-probe Experimente mit synchronisierten Laser- und VUV-FEL Pulsen ¨hling4 , Rolf Fru ¨ke2 , RoStefan Cunovic3 , Markus Drescher1 , Ulrike Fru land Kalms1 , Maria Krikunova1 , Theophilos Maltezopoulos4 , Norbert ¨ller3 , Marek Wieland1 , Thomas Wilhein2 Mu 1

Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg, Luruper Chaussee 149, 22761 Hamburg – 2 Institut f¨ ur X-Optik, FH Koblenz, S¨ udallee 2, 53424 Remagen – 3 Fakult¨ at f¨ ur Physik, Universit¨ at Bielefeld, Universit¨ asstr. 25, 33615 Bielefeld – 4 HASYLAB, DESY, Notkestr. 85, 22603 Hamburg Die Kombination von hoher durchstimmbarer Photonenenergie, hoher Intensit¨ at und kurzer Zeitstruktur macht den VUV-FEL FLASH am Hasylab, DESY besonders interessant zur Realisierung zeitaufgel¨ oster Experimente nach dem pump-probe Prinzip. Photochemische Reaktionen k¨ onnen mit einem simultan angebotenen Laserpuls in Gang gesetzt, und mit dem VUV-Puls abgefragt werden. Im Gegensatz zur konventionellen Femtochemie lassen sich atomare Innerschalenzust¨ ande anregen und so elementspezifische Informationen zur molekularen Dynamik gewinnen. Hierf¨ ur wird eine Apparatur f¨ ur pump-probe Experimente in der Gasphase und in Fl¨ ussigkeiten aufgebaut. Die derzeit mit diesem Konzept prinzipell erreichbare zeitliche Aufl¨ osung entspricht allerdings noch nicht den Pulsbreiten der Laser- und FEL-Pulse von ca. 100 fs bzw. ca. 30 fs, sondern ist durch eine Puls-zu-Puls Variation der relativen Verz¨ ogerung beider Pulse gegeben, die nach der in der Regel notwendigen Summation u ¨ber viele Einzelpulse eine zeitliche Unsch¨ arfe von mehreren 100 fs erwarten l¨ asst. Der hier verfolgte L¨ osungsansatz basiert auf der simultanen Messung dieser Verz¨ ogerung f¨ ur jeden Puls und die anschließende Sortierung der Daten des Pump-Probe Experiments gem¨ aß dieser Referenzmessung. Es wurde dazu ein Einzelschuß-Kreuzkorrelator aufgebaut, der eine unmittelbare zeitliche Korrelation der Laser- und FEL Pulse erlaubt. Das physikalische Prinzip fußt auf der atomaren Photoionisation in einem intensiven Laserfeld. ¨ Ein r¨ aumlich/zeitlicher Uberlapp beider Pulse in einem Edelgas f¨ uhrt zur Ausbildung energetischer Seitenb¨ ander im Spektrum der Photoelektronen. Durch eine spezielle Geometrie wird die Zeitachse auf eine Ortskoordinate projeziert, so dass mit einem abbildenden Elektronenspektrometer Information u ¨ber die Dauer des FEL-Pulses sowie seine zeitliche Lage relativ zum Laserfeld gewonnen werden kann. Die Wirksamkeit des physikalischen Mechanismus sowie die Funktion des Kreuzkorrelators konnten am FLASH nachgewiesen werden. Da der FEL-Strahl das Gasphasen-Target praktisch ungemindert passiert, kann der Kreuzkorrelator in Serie mit einem absorbierenden pump-probe-Experiment an einer Festk¨ orperoberfl¨ ache oder einer Fl¨ ussigkeit betrieben werden.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P15

From IRIS to HIRES Franz Demmel1 , Felix Fernandez-Alonso1 , Mark Telling1 1

ISIS Facility, Chilton, OX11 0QX, UK

IRIS was for long time the standard in high resolution spectroscopy combined with a large dynamic range. After twenty years of success it is time to pursue new horizons in high resolution back scattering techniques. With the OSIRIS spectrometer an ultimate aim towards high intensity was already achieved. We propose to extend the techniques to a high energy resolution spectrometer HIRES with silicon analysers. In contrast to the back scattering spectrometer at the SNS the primary spectrometer would use a pulse shaping chopper in combination with a coupled hydrogen moderator. Besides a higher flux, in comparison with a poisoned moderator, an inherent advantage is the flexibility in changing the pulse width. Trading resolution against intensity will provide a powerful and flexible tool in high resolution spectroscopy.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P16

The new MAGS beamline: an instrument for hard x-ray diffraction at Bessy Esther Dudzik1 , Ralf Feyerherm1 1

Hahn-Meitner-Institut Berlin/Bessy, Albert-Einstein-Str. 15, 12489 Berlin, Germany

To complement its existing neutron instrumentation, the Hahn-Meitner-Institute Berlin has set up a new beamline for hard x-ray diffraction at BESSY which is now in user operation. The beamline uses a 7 T multipole wiggler source to provide a high-intensity focussed monochromatic beam with photon fluxes in the 1012 (s 100 mA)−1 range at photon energies from about 4 to 30 keV (with lower fluxes up to about 70 keV). It has active bendable optics to provide flexible horizontal and vertical focussing and to compensate the large heat load from the wiggler. The experimental endstation consists of a six-circle Huber diffractometer which can be used with an additional (polarisation) analyser. Two closed-cycle cryostats can be used for temperature ranges of 7 to 800 K and 4 to 300 K, respectively; a 5 T magnet is under construction. There are two detectors: a low energy Canberra Ge diode for energy-resolved detection, and a compact scintillation detector. The beamline is intended for single-crystal diffraction and (resonant) magnetic scattering experiments, and the study of ordering phenomena and phase transitions, as well as for the study of thin films, micro-, and nanostructures in materials science. First experimental results prove that the beamline MAGS is a versatile tool for structural investigations in a variety of different research areas ranging from basic solid state physics to applications in materials science.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P17

Influence of finite resolution on the results of surface-XPCS measurements Robert Fendt1 , Christian Gutt2 , Aymeric Robert3 , Anders Madsen3 , Metin Tolan1 1

Fachbereich Physik, Universit¨ at Dortmund, Germany – 2 HASYLAB, Hamburg, Ger3 many – European Synchrotron Radiation Facility (ESRF), Grenoble, France Surface-sensitive X-ray photon correlation spectroscopy (SXPCS) is a powerful technique for in-situ measurements of the dynamics of fluctuating surfaces. Unlike dynamic light scattering (PCS), which is usually done using visible light, there is virtually no bulk-scattering and – in principle – no limitation preventing investigations on nanometer scale. However, recent experimental results clearly show that assuming Fraunhofer-like scattering is an over-simplification in the case of XPCS, yielding the need for a more thorough theoretical treatment [1-3].

In the case of low-viscosity liquids, which is considered here, one expects propagating capillary waves“ on the liquid’s surface which yield an oscillating behaviour of ” the measured correlation function, i. e. for a homodyne setup, Ghom (~ q, τ ) = 1 + C cos2 (ω(~ q )τ ) exp(−2Γ(~ q )τ ) with the contrast 0 < C ≤ 1. However, under special circumstances, a heterodyne“ function Ghet (~ q , τ ) = 1 + C cos(ω(~ q )τ ) exp(−Γ(~ q )τ ) is ” observed [4-6]. This behaviour can be understood as a resolution effect in the sense that a finite experimental resolution dq > 0 enables the specular reflection from the surface to serve as a static reference signal [2, 3]. Finite resolution also modifies the observed oscillation frequency and damping constant. This is in good agreement with our experimental data [1-4, 6]. In order to investigate the influence of resolution and sample properties in a systematic way, ethanol-water mixtures have been studied by SXPCS [4]. Recent experiments [6] showed that the direct dependence of dq on sample properties (if any) is at most rather weak (the main influence being the surface tension of the liquid). However, the sample setup strongly influences the stability of the measurement, yielding e. g., a possible heterodyne correlation function from water surfaces. Recent results show clearly homodyne correlation functions from water for stable conditions, which changes only when the scattered intensity fluctuates (i. e., the specular position is unstable). This strongly supports the conjecture that heterodyne mixing with reference beams will be possible in the future for SXPCS. [1] [2] [3] [4] [5] [6]

M. Sprung et al.: ESRF 2004, unpub. T. Gadheri: PHD thesis, University of Dortmund, 2006 C. Gutt, T. Gadheri et al.: to be publ. 2006 R. Fendt et al.: ESRF 2005, unpub. C. Gutt et al.: PRL 91, 076104 (2003) R. Fendt et al.: ESRF 2006, unpub.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P18

Charakterisierung der inhomogenen Verteilung von inhalierten metallhaltigen Aerosolpartikeln am Beispiel von Uranbergarbeitern ¨ chel1 Joachim Feuerborn1 , Arndt Kno 1

Inst. f. Anorg. u. Angew. Chemie, Universit¨ at Hamburg

Das Schicksal inhalierter metallhaltiger St¨ aube im menschlichen Organismus ist von großer Bedeutung f¨ ur die Arbeitsmedizin. Zur Absch¨ atzung des gesundheitlichen Risikos aktuell eingesetzte biokinetische Modelle gehen von einer homogenen Verteilung der inhalierten Partikel aus, da bisher f¨ ur diesbez¨ ugliche Untersuchungen nur Bulkanalysen gr¨ oßerer Gewebebereiche verf¨ ugbar sind. Auf der Basis der R¨ ontgenmikrosonde mit Synchrotronstrahlung am HASYLAB wurde ein Analysenverfahren zur ortsabh¨ angigen Bestimmung der Elementgehalte von mit Partikeln belasteten Geweben entwickelt und am Beispiel von Gewebeproben (Lymphknoten-, Lungen-, Leber- und Nierengeweben) des pathologischen Archivs der SDAG Wismut prototypisch angewandt. Von zentraler Bedeutung war dabei die Entwicklung von Einzelelementfolien als Tr¨ agermaterial und quasi-interner Standard zur Quantifizierung der vorliegenden Elementgehalte. Die Untersuchungen zeigten erwartungsgem¨ aß eine inhomogene Verteilung der Elemente mit unterschiedlichen Verteilungsmustern. Vor allem Lungen- und Lymphknotenproben wiesen hohe punktuelle Belastungen auf. Uran wurde im Vergleich zu anderen Elementen nicht nur seltener, sondern auch in geringeren H¨ ochstkonzentrationen gefunden, als es die mineralogische Zusammensetzung der St¨ aube erwarten l¨ asst. Zur Aufkl¨ arung dieses Urandefizits wurden an nat¨ urlichen Uranmineralen Auslaugungsversuche in lungen¨ ahnlichen Fl¨ ussigkeiten durchgef¨ uhrt. In lymph¨ ahnlicher Fl¨ ussigkeit zeigten die Minerale ein sehr unterschiedliches L¨ oslichkeitsverhalten, wobei Pechblenden tendenziell langsamer als Uranylminerale ausgelaugt wurden. In lysosom¨ ahnlicher L¨ osung konnten aufgrund von R¨ uckf¨ allungen keine gr¨ oßeren Anteile gel¨ osten Urans detektiert werden. Durch R¨ ontgenabsorptionsuntersuchungen am HASYLAB wurde das unterschiedliche L¨ oslichkeitsverhalten mit der jeweils vorliegenden Bindungsform korreliert, der Mechanismus der Uranmobilisierung aufgekl¨ art, der Umsetzungsgrad in lysosom¨ ahnlicher Fl¨ ussigkeit bestimmt sowie die entstandenen F¨ allungsprodukte weitgehend als Uranylphosphate charakterisiert. Die Ergebnisse erm¨ oglichen, das bisher verwendete ICRP-Lungenmodell wesentlich zu verfeinern und das Gef¨ ahrdungspotential inhalierter uranhaltiger Staubpartikel reali¨ stischer abzusch¨ atzen. Eine Ubertragung des Verfahrens auf andere, hinsichtlich inhalierter St¨ aube arbeitsmedizinisch relevante Fragestellungen bietet sich an.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P19

A robotic sample changing system for a macromolecular biology beamline of the EMBL Hamburg Stefan Fiedler1 , Uwe Ristau, Thomas Gehrmann, Doris Jahn, Bernd Robrahn, Alexander Popov, Christoph Hermes 1

European Molecular Biology Laboratory, Hamburg Unit c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany The EMBL Hamburg Unit has developed a sample changing system for macromolecular crystallography (MX) based on an ADEPT six-axis industry robot serving an existing diffractometer on the fixed wavelength BW7b beamline at DORIS storage ring. The main design considerations have been simplicity (e.g. all sample movements are performed by the robot, in particular those in liquid nitrogen), compatibility (e.g. compatible with the EMBL/ESRF baskets for SPINE sample holders), flexibility (e.g. the system can automatically load baskets into its main dewar) and reliability (e.g. robot grippers are heated to reduce problems related to ice formation). The use of an industry robot requires also the application of industrial safety standards even when installed in a scientific environment. We have implemented a safety system in conformity with the European regulations. The progress in automating the sample changing, the sample centering and the data acquisition process makes a remote access to the instruments increasingly attractive. We have integrated the sample changing robot into the TINE control system developed by DESY. Until recently, the repeated change of samples on a diffractometer was one of the bottlenecks in the macromolecular crystallography pipeline. However, it is only a small step in the whole process of high throughput MX. Its possible integration into a wider concept for the planned structural biology beamlines at the future PETRA-III synchrotron will be discussed.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P20

Elemental Analysis of Aerosols with SR-TXRF: Direct Calibration with Pico-droplets (pL) Generated by Ink-Jet Printers Ursula Fittschen1 , Stephan Hauschild1 , Christina Streli2 , Gerhard Lammel3 , Peter Wobrauschek2 , Florian Meirer2 , Giancarlo Pepponi4 , ¨ rster1 , Gerald Falkenberg5 , Jose ´ Broekaert1 Stephan Fo 1

Department Chemie, Universit¨ at Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg – 2 Atominstitut der ¨ osterreichischen Univerit¨ aten, Technische Universit¨ at Wien, Stadionallee 2, A-1020 Wien – 3 Max Planck Institut f¨ ur Meterologie, Bundesstraße 53, D-20146 Hamburg – 4 ITC-irst, Via Sommarive 18, I-38050 Povo (Trento) – 5 Hamburger Synchrotronstrahlungslabor at Deutsches ElektronenSynchrotron DESY, Notkestr. 85, D-22603 Hamburg The impact of the chemical composition of airborne particles and its particle size dependence on air quality and on climate has become apparent in recent years [1]. Particle sources and sinks are strongly related to their size and so is the chemical composition [2]. A number of metals and also non-metals like P, S, Cl and Br undergo chemical transformations typically on the time scale of hours. These requirements translate to 10−1 pg and even less of trace elements to be determined. TXRF is a very sensitive method for element determinations which has been successfully used for size-resolved aerosol analysis [3]. Even more sensitive is SR-XRF. Its combination with size-resolved aerosol sampling is promising, as already shown in Ref. [4]. An accurate and reliable calibration of SR-TXRF of aerosol samples collected is necessary but difficult: The addition of standard solution with micropipettes may suffer from destroying the sample spots or lines as a result of the relatively high amount of liquid. Here we present the results of a study into the suitability of a calibration in aerosol sample analysis by SR-TXRF using pico-droplets (i.e. 5-130 pL), generated by inkjet printers. The procedure could be made compatible to aerosol particle sampling using a Berner impactor. In the latter the aerosol particles are collected in different complex patterns on the impaction stages. The diameter of the dried droplets ranges from 50-200 µm for ink droplets printed on hydrophobic surfaces. The reliability of the dosing of standard solution was satisfactory and enables a spotting of well-defined absolute amounts of standard in the picogram range and below. Further, it was shown that a printing according to a given pattern in the micrometer range can easily be done with the aid of common computer software. [1] J. E. Penner et al., Thierd Assessment Report of the Intergovernmental Panel on Climate Change 2001 (J. T. Houghton et al., eds.), Cambridge University Press, Cambridge, UK, pp. 289-348 [2] K. R. Spurny, CRC Press, Boca Raton, USA, 486 pp. [3] B. Schneider, Spectrochim. Acta, Part B 44, (1989), 519-524 [4] N. Bukowiecki et al., Environ. Sci. Technol. 39 (2005), 5754-5762

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P21

Multifragment Imaging of Photon and Ion induced Processes Lutz Foucar1 , Achim Czasch1,2 , Ottmar Jagutzki1,2 , Klaus Ullmann1,2 , Da¨ ßler1 , Till Jahnke1 , Reinhard niel Wald2 , Lothar Schmidt1 , Sven Scho ¨ rner1 , Horst Schmidt-Bo ¨ cking1 Do 1

Institut f¨ ur Kernphysik, Universit¨ at Frankfurt, Max-von-Laue-Str.1,60438 Frankfurt, FRG – 2 Roentdek GmbH, Im Vogelshaag 8, 65779 Kelkheim Correlated many-particle dynamics in Coulombic systems, which is one of the unsolved fundamental problems in physics, can now be experimentally investigated with unprecedented completeness and precision. The recent development of the COLTRIMS reaction microscope (COLd Target Recoil Ion Momentum Spectroscopy) [1,2] provides a coincident multi-fragment imaging technique for eV and sub-eV particle detection. In its completeness it is as powerful as the bubble chamber in high energy physics. The technique is widely applied for single but also for multiple photon absorption processes. More and more complex fragmentation systems are being investigated. The multi-channel plate detectors with delay-line anode read out are ideally suited for multi-hit detection. However, pile-up effects in the fast read-out electronics are presently the bottle neck of the system. Fast transient recorders (ADCs), which digitize the in-coming signals on a sub-nanosecond scale, can be used to overcome this problem. Using standard fitting algorithms multi-hit signals can be separated as two pulses even if the two signals are separated by only two nanoseconds. Additionally the test experiments showed that the internal detector and electronic timing can thus be improved to yield a timing resolution of well below 100 picoseconds. In combination with improved readout electronics the COLTRIMS imaging technique is prepared for the next step multiple fragmentation processes of large molecules. Acknowledgements: We acknowledge the great help of C.L. Cocke, M. Prior and many other colleagues as well as the support of BMBF, DFG and by Roentdek GmbH. [1] J. Ullrich et al., J. Phys. B: At.Mol.Opt.Phys. 30:2917, (1997) [2] R. D¨ orner et al. , Physics Reports 330:95, (2000)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P22

The Wide Angle Spin Echo Spectrometer Project WASP at ILL Peter Fouquet1 , Bela Farago1 , Catherine Pappas2 , Phillip M. Bentley2 , Ferenc Mezei2 1

Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2 Hahn-MeitnerInstitut, Glienicker Str. 100, 14109 Berlin, Germany This presentation will give an overview of design and projected performance of the new ILL spin echo spectrometer WASP (Wide Angle SPin echo spectrometer). At present, ILL offers two spin-echo only spectrometers to the user community specialized in high signal (IN11) and high resolution (IN15), respectively. The aim of the project is to increase the detection and acceptance angle of the high signal spectrometer IN11 by changing the design of the magnetic coils. The design of WASP profits from the experience gained with the novel spectrometer SPAN which has recently been commissioned at the Hahn-Meitner Institute in Berlin, Germany [1]. In the SPAN/WASP design nearly perfect 360o field symmetry is achieved by replacing the conventional collinear NSE field solenoids by a pair of anti-Helmholtz solenoids placed above and below the neutron beam plane. Furthermore, careful field analysis revealed that within this design a near perfect cos2 field shape [2] can be created along the neutron trajectories, so that field correction can be minimized. We will present improvements on field optimization calculations using Biot-Savart field calculations and Monte Carlo raytracing calculations. Very recently we have incorporated genetic algorithms into our design package. Using this tool we have been able to accelerate the rather complex coil design with typically more than 10 free parameters. [1] C. Pappas et al.i, Physica B 297 (2001) 14. [2] C.M.E. Zeyen et al., IEEE Trans. Magn. 24 (1988) 1540. [3] P.M. Bentley et al., Physica B, accepted.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P23

The IR/VUV Pump-Probe Facility at the VUV FEL FLASH ¨hling1 , Markus Drescher2 , Oliver Grimm1 , Oleg Kozlov3 , Elke Ulrike Fru 1 ¨ njes , Jo ¨ rg Rossbach1 , Evgeny Saldin1 , Evgeny Schneidmiller1 , Mikhail Plo 1 Yurkov 1

Desy, Hamburg – 2 Uni Hamburg, Hamburg – 3 JINR, Dubna, Moscow Region

An electromagnetic undulator generating infrared radiation in the range of 1-200 microns will be installed at the FLASH facility, the VUV FEL at DESY, Hamburg, in spring 2007. The device will use the spent electron beam from the FEL undulators and thus allow pump-probe experiments using infrared and vacuum ultraviolet radiation with almost perfect, natural synchronisation. Intensities in the few picosecond long infrared pulses are up to 10 MW peak (30 uJ), the 20-50 femtosecond long VUV pulses are in the GW level (up to 100 uJ). The basic layout and parameters of the device have been reported previously. This paper gives a summary of more detailed radiation generation calculations, including effects of tolerances and magnetic properties of the undulator. The transmission characteristic of the new infrared beam line is presented. A first VUV-pump/ FIR-probe experiment will diagnose the longitudinal structure of the VUV pulses.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P24

Infrared Synchrotron Ellipsometry for analysis of laterally patterned organic thin films Michael Gensch1 , Ulrich Schade2 , Markus Raschke3,5 , Leonid Ionov4 , Klaus-Jochen Eichhorn4 , Karsten Hinrichs1 , Manfred Stamm4 , Norbert Esser1 1

ISAS - Institute for Analytical Sciences, Department Berlin, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 2 Berliner Elektronenspeicherring-Gesellschaft f¨ ur Synchrotronstrahlung mbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany – 3 Max Born Institute Nichtlineare Optik Kurzzeitspektroskopie, Max-Born Str. 2A, 12489 Berlin, Germany – 4 Leibniz Institut f¨ ur Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden – 5 Department of Chemistry, University of Washington, Seattle, WA 981951700, USA A specially designed infrared spectroscopic ellipsometer is presented that enables the investigation of sample areas of less than 1 mm2 with monolayer sensitivity. This sensitivity is achieved for films on metallic as well as on semiconducting substrates by utilizing infrared synchrotron radiation at BESSY II [1]. Measurement principle and performance of the instrument are discussed for selected examples and the recent upgrades of the set-up are introduced. It is shown how thickness, structure and composition of patterned nanofilms can be derived from the analysis of the infrared ellipsometric parameters [2]. These parameters are of technological relevance to understand the functionality of e. g. stimuli responsive 1D polymer brush gradient films [3], biomedical array sensors, or monomolecular films for solar cell applications. Furthermore, infrared optical constants as determined from microfocus IR ellipsometry allow for a detailed analysis of the results from other techniques, e. g. scanning nearfield infrared microscopy (SNIM) [4]. [1] U. Schade, A. R¨ oseler, E.H. Korte, F. Bartl, K.P. Hofmann, T. Noll, W.B. Peatman, Rev. Sci. Instr. 73 (2002) 1568. [2] K. Hinrichs, M. Gensch, and N. Esser, Appl. Spectrosc. 59 (2005) 272A. [3] L. Ionov, A. Sidorenko, K.J. Eichhorn, M. Stamm, and S. Minko, Langmuir 21 (2005) 8711. [4] M.B. Raschke , L. Molina, T. Elsaesser, D.H. Kim, W. Knoll, and K. Hinrichs, ChemPhysChem 6 (2005) 2197.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P25

Neutron Pathfinder Karin Griewatsch1 , Ana Claver2 1

IEAP, Universit¨ at Kiel, Leibnizstraße 19, 24118 Kiel – J¨ ulich, 52425 J¨ ulich

2

IFF, Forschungszentrum

Are you planning a neutron experiment and wonder which would be the right instrument? Or you are just curious about the possibilites in neutron research? You want an overview of one instrument type in Europe? Then you should visit the new website, which was built up by NMI3 and KFN in cooperation with the neutron centres. The basis of the ”Neutron Pathfinder” is a database with 150 European neutron instruments. You decide yourself how detailed you want to search. • instruments for certain fields of work (Science Pathfinder) • instruments that allow a specific experiment (Experiment Pathfinder) • instruments of a certain type (Instrument Pathfinder) • methods • facilities http://www.neutron-eu.net/pathfinder

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P26

Perspektiven monochromatischer Neutronenpulverbeugung f¨ ur intensit¨ atslimitierte Experimente mit D20 am ILL Thomas Hansen1 , Paul F. Henry1 , Henry E. Fischer1 , Jacques Torregrossa1 1

Institut Max von Laue-Paul Langevin, BP 156, 38042 Grenoble Cedex 9, Frankreich

Angesichts immer leistungsf¨ ahigerer Flugzeit-Diffraktometer beleuchten wir die Rolle konventioneller Zweiachsendiffraktometer f¨ ur Experimente, die eher durch Intensit¨ at als denn durch Aufl¨ osung limitiert werden. D20 bietet die h¨ ochste Intensit¨ at f¨ ur Neutronenpulverbeugungsexperimente. Der Fluss an der Probe erreicht bis zu 108 n/s/cm2 bei λ ≈ 1.3 ˚ A. Der station¨ are, gekr¨ ummte lineare ortsempfindliche Detektor deckt 153.6◦ (2θ) mit 1536 Kan¨ alen ab, was in-situ Beugungsexperimente erm¨ oglicht. 4 vertikal fokussierende Monochromatoren, 14 take-off Winkel, sowie optionale Soller Kollimatoren im Prim¨ arstrahl erm¨ oglichen die Wahl optimaler Abdeckung des reziproken Raumes, geeigneter Aufl¨ osung, Wellenl¨ ange und Fluss. Dadurch kann D20 unterschiedlichen Bed¨ urfnissen kristallographischer Komplexit¨ at und der Geschwindigkeit eines zu beobachtenden Ph¨ anomens gerecht werden. Neu sind ein oszillierender Radialkollimator und die M¨ oglichkeit mit polarisierten Neutronen zu arbeiten, womit neue experimentelle M¨ oglichkeiten geschaffen wurden. Weitere Ausbaum¨ oglichkeiten, wie etwa ein gr¨ oßerer, zweidimensional aufl¨ osender Detektor, werden kritisch diskutiert. Die kontinuierliche und simultane Aufzeichnung vollst¨ andiger Pulverdiffraktogramme ist erforderlich f¨ ur die Untersuchung von Phasendiagrammen in Abh¨ angigkeit variabler Parameter wie z.B. Temperatur (Thermodiffraktometrie). One-shot Experimente erlauben die Verfolgung struktureller Ver¨ anderungen in Feststoffen in situ w¨ ahrend einer chemischen Reaktion. Die Hochtemperatursynthese von Ti3 SiC2 wurde z. B. so untersucht. Dabei wurde ein Reaktionsmechanismus mit zwei Schritten mit Zeitkonstanten von 500 ms and 5 s gefunden. Eine Serie von Diffraktogrammen von nur 400 ms Dauer quantifizierte die kurzlebigen intermedi¨ aren Phasen und zeigte strukturelle ¨ Anderungen im Vorfeld der Z¨ undung. Schnellere, zyklische Ph¨ anomene sind mit stroboskopischer Datenerfassung beobachtbar. Die Zeitaufl¨ osung ist dabei nur durch die Flugzeit der Neutronen durch Probe und Detektorgas bestimmt, etwa 10 µs f¨ ur thermische Neutronen. Die hohe Intensit¨ at erm¨ oglicht neben parametrischer Beugung aber auch die Untersuchung sehr kleiner Proben oder die sehr pr¨ azise Bestimmung von Intensit¨ aten, wie sie f¨ ur differentielle Experimente n¨ otig ist. So k¨ onnen Dr¨ ucke u ¨ber 10 GPa mit Paris-Edinburgh“ Zellen in situ erzielt werden. Statistisch ausreichende, saubere und ” vollst¨ andige Diffraktogramme k¨ onnen in weniger als 10 Minuten von Proben mit 5 mm Durchmesser und 0.7 mm H¨ ohe in einem TiZr-Gasket und zwischen Stempeln aus WC oder BN erhalten werden. Auch hochaufgel¨ oste Pulverdiffraktogramme k¨ onnen mit D20 bei h¨ ochstem take-off Winkel mit einem Germanium-Monochromator in wenigen Minuten erhalten werden. Dieses erlaubt unter anderem hochaufgel¨ oste Pulverbeugung an extrem kleinen Proben von weniger als 10 mg.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P27

Analytical applications of X-ray micro fluorescence ¨ der1 , Markus Kra ¨mer1 , Alex von Bohlen1 Roland Hergenro 1

ISAS-Institute for Analytcal Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund

The increased interest in spatial resolved X-ray fluorescence chemical analysis in medicine, biology, and material sciences demands, special, new instrumental solutions. Submicrometer resolution combined with high sensitivity and monochromatic excitation over a wide range of energies can only be realized in a reasonable measuring time when applying synchrotron radiation as an exciatation source. A typical application field is the analysis of objects of cultural heritage. The material composition of outstanding archaeological finds from the city area of Dortmund was characterized by using SREDXRF. As an example object, a decoration plate of a buckler used by the Germans living in the 4th century AC in this area which is made of a silver plate decorated with silver pearls and gold foils, is presented. The pearls and foils were fixed with a tin solder onto the silver base. The provenance of the materials was deduced to be Scandinavia by regarding the historical background. Other applications fields that will be demonstarted and discussed are from material science and biology. Here, X-ray fluorescence spectroscopy with high spectral resolution due to a wavelength dispersice spectrometer [1]in the low energy regime (< 2 keV) is used to deduce chemical binding states from chemical shift measurements. [1] A. von Bohlen, R. Hergenr¨ oder, C. Sternemann, M. Paulus, M. Radtke and H. Riesemeier, Instrumentation Science & Technology, 2005, 33, 137-150

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P28

X12 a new MAD beamline at EMBL Hamburg Christoph Hermes1 , Thomas Gehrmann1 , Doris Jahn1 , Emiliano Piselli1 , Bernd Robrahn1 , Tim Siambanis1 , Manfred Weiss1 1

EMBL, Notkestr. 85, 22603 Hamburg

In October 2005 EMBL officially opened for user-operation a new energy-tunable beamline for applications in Protein Crystallography. It receives 1 mrad of white Synchrotron radiation from a bending magnet at the DORIS III storage ring. Key optical elements of the beamline are a bespoke fixed-exit double crystal monochromator (DCM) and a vertically focusing X-ray mirror with dynamically adjustable radius. These elements will be described in detail. X-ray diffraction data are collected using a MAR desktop beamline equipped with a large CCD detector, an automatic sample changer and a fluorescence detector. Beamline control is achieved with a program written in Labview and aiming at optimal user-friendliness via an intuitive graphical interface to allow, for instance, very rapid changes of the X-ray energy. Examples of data collected on this beamline will be shown.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P29

The A- and Gi-SAXS dedicated SAXS instrument at BESSY 7T wiggler Armin Hoell1 , Ivo Zizak1 , Sylvio Haas1 , Dragomir Tatchev2 , John Banhart1 1

Hahn-Meitner Institute Berlin, Department of Materials, D-14109 Berlin – 2 Institute of Physical Chemistry, Bulgarian Academy of Sciences, BG-1113 Sofia, Bulgaria The SAXS instrument (7T-WLS-SAXS), on the high brilliance wiggler beamline at BESSY, has been designed to perform two advanced scattering techniques, ASAXS [1] and GISAXS [2]. It has been installed at the monochromatic beam of the 7T wiggler at BESSY. The SAXS instrument runs in timesharing with a magnetic scattering experiment. Therefore, the detector chamber is based on an air cushion system (Fig. 1) to be removable. The X-ray energy can be varied between 4.5 keV and 26 keV using a double crystal monochromator with Si 111 crystals. The photon flux at the sample position is in the order of magnitude of 109 s−1 to 1011 s−1 , depending on optics and slits settings. The beam can be focused by the two mirrors and the sagitally curvable 2nd monochromator crystal. The SAXS chamber is equipped with a position sensitive 2D gas detector (20 cm * 20 cm). A MAR CCD detector with 16.5 cm diameter is available also. One of the two 2D detectors is directly mounted at a vacuum flange at the end of the scattering beam path. The sample - detector distance can continuously be varied between about 74 cm and 374 cm. An edge welded bellow system with an inner diameter of 25 cm is stretched between the beam diagnostics chamber and the beamstop chamber (Fig. 1). To realize all lengths between 18 cm and 318 cm the bellow system is divided into two pieces, whereby the longer part can move down into the optical bench (Fig. 1b) on its own rail system. The advantage of using an edge welded bellow system in comparision to other instruments [3, 4] is that the sample detector distance can vary continuously, while having easy access to the detector. The whole scattering beam path with the optical bench can be tilted up to 3.2◦ with respect to the horizontal that is used in case of GISAXS. The sample environments are not directly fixed to the described detector chamber. Different sample environments are available or can be installed, like sample changers under vacuum or normal air conditions, a high temperature furnace (up to 1000 ◦ C), and a GISAXS furnace to be used in reflection geometry. [1] A. Hoell, F. Bley, A. Wiedenmann, J. P. Simon, A. Mazuelas, P. Boesecke: Scripta Mater. 44 (2001) 2234. [2] A. Naudon, and D. Thiaudiere, J. Appl. Cryst. 30 (1997) 822. [3] H.-G. Haubold, K. Gruenhagen, M. Wagener, H. Jungbluth et al: Rev. Sci. Instrum. 60 (1989) 1943. [4] S. Lequien, L. Goirand, and F. Lesimple: Rev. Sci. Instrum. 66 (1995) 1725.

Fig. 1: Sketches of the two main configurations of the SAXS chamber are shown. The sample is positioned in the front of the big valve. The sample-detector distance can be varied between 750 mm and 3750 mm as shown in the picture. Four z-stages are used to align the optical bench and to lift up the ◦ detector support by up to 3 in case of GISAXS. The instrument is based on an air cushion system.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P30

Triple Axis Spectrometer PUMA at FRM II: Characterisation, current Status and Perspectives ¨rgen Neuhaus2 , Go ¨ tz Eckold1 Klaudia Hradil1 , Harald Schneider1 , Ju 1

IPC, Universit¨ at G¨ ottingen – 2 ZWE FRM II, TU M¨ unchen

The triple axis spectrometer PUMA with a view on the thermal source of FRM II is built up within a cooperation of the University of G¨ ottingen and the Physics Department E13 of the Technical University of Munich. After the commissioning phase and first “friendly user” experiments, the instrument is now available to the user community within the proposal system of the FRM II. An overload factor of ∼2 already for the first proposal rounds reveals the high demand and acceptance of the instrument. The main characteristics of PUMA can be summarised as follows: high neutron flux on sample position; flexible and straightforward change of components as collimation, monochromators/analysers; Eularian cradle for flexible scattering plane adjustment; equipment for time resolved measurements; diverse and powerful sample environment. At present, PG(002) and Cu(220) monochromators and PG(002) as analyser, manufactured at IPC, are provided, covering an energy transfer range up to 80 meV. A multi analyser/detector option is under construction which allows survey measurements in (Q, ω) space and provides new features for time-resolved measurements of excitations. The high quality of the Cu(220) is displayed by the beam profiles at sample position (figure 1). Phonon measurements for larger energy transfers proved the high flux at sample position. Beside the standard sample environment of FRM II a closed-cycle cryostat (3-300K), a cryo furnace (3-800K), a high temperature furnace (-1300K) for the Eularian cradle and a high-pressure cell Paris-Edinburgh type VX3 (10 GPa) is available. In the context of this contribution, characteristics, current status of the instrument and a survey of the first measurements on PUMA will be presented. This project has been funded by the German Federal Ministry of Education and Research under contract no. 03EC6GO1

Fig. 1: CCD picture of the beam −1 profile, ki = 4.5 ˚ A . (left) horizontal/vertical focussed; (right) flat Cu(220) monochromator

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P31

Strukturpulverdiffraktometer SPODI - Status, Spezifikationen und Messungen ¨ lzel1 , Anatoliy Senyshyn1 , Ralph Gilles2 , Hans Boysen3 , HartMarkus Ho mut Fuess1 1

Technische Universit¨ at Darmstadt, Materialwissenschaften, Petersenstrasse 23, 64287 Darmstadt – 2 Technische Universit¨ at M¨ unchen, Forschungsneutronenquelle FRM II, Lichtenbergstrasse 1, 85747 Garching – 3 Ludwig-Maximilians Universit¨ at M¨ unchen, Department f¨ ur Geo- und Umweltwissenschaften, Am Coulombwall 1, 85747 Garching Das Strukturpulverdiffraktometer SPODI am FRM II ist ein Gemeinschaftsprojekt zwischen TU Darmstadt, LMU M¨ unchen und TU M¨ unchen. Es zeichnet sich insbesondere durch hohe Aufl¨ osung bei hohem Fluss, flexible Auswahl von Wellenl¨ angen sowie ¨ eine mannigfaltige Probenumgebung aus. In diesem Beitrag soll ein Uberblick zum gegenw¨ artigen Status des Instruments und seine Spezifikationen gegeben werden sowie eine Auswahl von Messungen pr¨ asentiert werden. Die Detektorbank mit 80 vertikal ortsempfindlichen Detektoren (aktive L¨ ange > 300 mm) erm¨ oglicht die Integration der Daten entlang der Debye-Scherrer-Ringe. Somit kann hochaufl¨ osende Pulverdiffraktometrie bei hohen Intensit¨ aten erzielt werden. Weiterhin gew¨ ahrt die Darstellung der 2-dimensionalen Daten eine schnelle Charakterisierung bzgl. Kristallinit¨ at und Textur. Die Standard-Probenumgebung umfasst einen Closed-Cycle Kaltkopf-Kryostaten (3 K bis 300 K) sowie einen Vakuum-Hochtemperaturofen (300 K bis 2100 K). Gegenw¨ artig erfolgt die Inbetriebnahme einer Hochdruckzelle vom Typ Paris-Edinburgh VX3 (bis 10 GPa) und einer Materialzugpr¨ ufmaschine (bis 100 kN). Die Anwendungsfelder von SPODI werden durch die Einbindung der Kleinwinkelstreu-Apparatur mit einem Bildplattendetektor (MAR 345) noch erweitert werden. Als Beispiele erster Experimente seien Strukturuntersuchungen an Hydriden oder Seltenerd-Gallaten genannt. Diverse Experimente am SPODI dienten zur Bestimmung thermischer Auslenkungsparameter in verschiedenen Systemen. Ein weiteres Anwendungsfeld liegt in der Untersuchung magnetischer Phasen¨ uberg¨ ange. Dieses Projekt wird durch das Bundesministerium f¨ ur Bildung und Forschung finanziert.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P32

Application of ultrasound to multi crystal neutron diffractometer Eugene Iolin1 , Leonid Rusevich1 , Markus Strobl2 , Wolfgang Treimer2 , Pavul Mikula3 1

Institute of Physical Energetic, Riga, Latvia – 2 Hahn-Meitner Institute, Berlin, Germany – 3 Nuclear Physics Institute, Re near Prague, Czech Republic It is known that high frequency ultrasound increases the intensity by quasi elastic scattering in single crystals accompanied by a loss of the impulse resolution. It was supposed (E.I., 1989) that resolution losses could be avoided by exciting ultrasound with the same frequency in single crystal monochromator and analyzer of a diffractometer. Neutron absorbed (emitted) N ultrasonic phonons in monochromator and resonantly emitted (absorbed) the same N ultrasonic phonons in analyzer. We realized such experiment with a double crystal, DC, diffractometer with Si(111) crystals (neutron wavelength 0.523 nm) and observed ∼ 60 % intensity increase in the peak of the instrumental curve. Simultaneously a strong improvement of the ultrasonic phonon satellite (-5
Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P33

CCD-Calibration for Accurate High Resolution Crystal Structure Analysis Simone K.J. Johnas1 , Edgar Weckert1 1

HASYLAB at DESY, Notkestr. 85, 22607 Hamburg

Hard X-rays, about 25 keV and higher, are of advantage for high resolution crystal structure analysis, up to about 0.5 ˚ A resolution, because of minimization of systematic errors like absorption of the X-rays in the crystal and extinction. For crystals of large unit cells only 2D-CCD-detectors enable to collect the necessary intensity data within reasonable time. Presently available CCD-detectors are optimized for photon energies of about 12 keV, where photons are almost totally stopped by the fluorescence phosphor independent of the incident angle. For higher photon energies a smaller portion of the diffracted photons is absorbed within the phophor leading to systematic errors of the measured intensities as a function of the angle of incidence on the detector surface. This is due to the different path lengths of the photons in the phosphor, see Fig.1. This effect can account for a factor of more than 2, and needs to be corrected especially in the case of accurate structure determination like charge density structures. A generaly applicable correction procedure based on reference data sets of well known compounds will be presented as well as the influence of this correction on various high resolution data sets and the derived structural parameters.

Fig. 1: Scheme in which way the diffraction angle affects the absorption path of the incoming photon in the pixel at a given wavelength.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P34

Der neue 2D Kleinwinkeldetektor des Flugzeitspektrometers FOCUS, SINQ ¨ssle2 , Lothar Holitzner3 , Niklaus Schlumpf3 , Fanni Juranyi1,2 , Thierry Stra 3 ¨l Mesot2 , Rolf Urs Greuter , Thomas Gahl3 , Stefan Janssen3 , Joe Hempelmann1 1

Physikalische Chemie, Universit¨ at des Saarlandes, 66123 Saarbr¨ ucken, Deutschland – Labor f¨ ur Neutronenstreuung, PSIETHZ, 5232 Villigen PSI, Schweiz – 3 Paul Scherrer Institut, 5232 Villigen PSI, Schweiz 2

FOCUS [1] ist ein Flugzeitspektrometer f¨ ur kalte Neutronen an der Spallationsquelle SINQ (Paul Scherrer Institut, Schweiz). Es ist ein gemeinsames Projekt des PSI und der Universit¨ at des Saarlandes. Ein Drittel der Messzeit steht Benutzern aus deutschen Institutionen zur Verf¨ ugung. FOCUS ist ein Spektrometer mit direkter Geometrie. Der gepulste, monochromatische Strahl (2-15 ˚ A, 20-0.35 meV Einfallsenergie) wird durch 2 Chopper und einen doppeltfokussierenden Monochromator erzeugt. Das Instrument kann ¨ außerst flexibel an die experimentellen Anforderungen angepasst werden und stellt dar¨ uberhinaus vielseiti¨ ge Probenumgebungen (Dilutionkryostaten, Magnetkryostaten, Ofen, Druckzellen) zur Verf¨ ugung. Die gestreuten Neutronen wurden bis jetzt in 375 3 He-Detektoren in einem Winkelbereich von 10 bis 135 Grad erfasst. Der neue 2D Kleinwinkeldetektor [2] wird die bestehenden Detektoren komplement¨ ar erg¨ anzen. Er ist aus 70 ortsempfindlichen 3 He Detektoren aufgebaut. Die Ortsaufl¨ osung liegt bei ca. 1.5 cm x 1.5 cm. Die Gesamtfl¨ ache von 70 cm (vertikal) und ca. 90 cm (horizontal) deckt einen Winkelbereich von 2 bis 20 Grad ab. Es besteht die M¨ oglichkeit, den neuen Detektor in folgenden Betriebsarten zu nutzen: a) Zusammenfassen der Pixel entlang der Debye-Scherrer Ringe (constant 2Θ), um damit den Q-E Bereich zu erweitern. b) Integration u ¨ber Flugzeit f¨ ur in situ SANS Messungen. c) Hohe Orts- und Zeitaufl¨ osung f¨ ur Messungen an anisotropen Proben (insbesondere Einkristallen). Thematisch wird der neue Detektor insbesondere f¨ ur magnetische Untersuchungen und Diffusionsexperimente einen wesentlichen Beitrag liefern. Dar¨ uberhinaus wird er in situ Strukturanalyse im Nanometerbereich erm¨ oglichen. Die ersten Testmessungen werden ab Juli 2006 durchgef¨ uhrt. [1] S. Janssen, J. Mesot, L. Holitzner, A. Furrer, R. Hempelmann, Physica B 234236 (1997) 1174; http://sinq.web.psi.ch/sinq/instr/focus [2] F. Juranyi, L. Holitzner, N. Schlumpf, U. Greuter, T. Gahl, S. Janssen, J. Mesot, R. Hempelmann, J. Neutr. Res. (accepted)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P35

Proposal for a Novel Structured Pulse Engineering Spectrometer (SPES) Reinhard Kampmann1 , Martin Haese-Seiller1 , Valery Kudryashov1 , Andreas Schreyer1 1

GKSS-Forschungszentrum, Abteilung WFN, Max-Planck-Str. 1, 21502 Geesthacht

A novel ToF-system has been developed for the new structured pulse engineering spectrometer (SPES) proposed by the GKSS-Research Centre for measuring both textures and residual stresses. The chopper device of SPES is distinguished by two features: On the one hand it allows for very high transmission of typically more than 5 % due to the low resolution of its base pulses and on the other hand for very high resolution (∆d/d < 2 · 10−3 ) resulting from a novel pulse structuring technique. The transmission of this chopper device is thus comparable to multi-burst techniques such as realized in the pulse overlap ToF diffractometer (POLDI) at PSI and in Reverse-ToF instruments at GKSS or in Gatchina/St. Petersburg which are designed for the analysis of residual stresses. In contrast to these instruments, however, the SPES-chopper will allow for measurements without pulse overlap and will, thus, offer excellent conditions for the determination of position, shape and absolute intensity of peaks in highly symmetric materials. Due to this chopper performance and the integration of a large and high resolution 2D-detector system SPES will offer new perspectives for the combined analysis of textures and strain fields. Finally, complex sample environments will be made available for very different engineering applications.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P36

Horizontal TOF-neutron reflectometer REFSANS at FRM-II Munich: potential and first experimental results Reinhard Kampmann1 , Martin Haese-Seiller1 , Valery Kudryashov1 , Bert Nickel2 , Christian Daniel3 , Wilhelm Fenzl2 , Andreas Schreyer1 , Erich ¨dler2 Sackmann3 , Joachim Ra 1

GKSS-Forschungszentrum Geesthacht GmbH, Max-Planck-Str. 1, D-21502 Geesthacht – 2 Lehrstuhl f¨ ur Experimentelle Physik/Biophysik, Sektion Physik, Ludwig-Maximilians-Universit¨ at, D-80539 M¨ unchen – 3 Physik-Department E22, TUM¨ unchen, D-85748 Garching The reflectometer REFSANS allows to perform comprehensive analyses of vertical and lateral surface and interface structures by means of specular and off-specular neutron reflectivity as well as small-angle neutron scattering at grazing incidence (GISANS). All measurements can be performed on the air-water interface (horizontally aligned sample). REFSANS has been put into operation as from autumn 2005. Its performance is demonstrated on the one hand by results of first reflectivity and GISANS measurements. On the other hand its capability of adjusting both the wavelength and the angular resolution and even the scattering geometry to very different experimental demands is presented. On this basis the potential of this novel instrument for measuring weak off-specular scattering, GISANS and extremely low specular reflectivity including the case of a strongly incoherently scattering substrate is discussed.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P37

Magneto-optics in the vicinity of the 2p and 3p edges of 3d transition metals Armin Kleibert1 , Volkmar Senz1 , Karl-Heinz Meiwes-Broer1 , Joachim Bansmann2 , Peter M. Oppeneer3 1

Institut f¨ ur Physik, Universit¨ at Rostock, D-18051 Rostock, Germany – 2 Abt. Oberfl¨ achenchemie und Katalyse, Universit¨ at Ulm, D-89069 Ulm, Germany – 3 Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden Soft x-ray based experimental techniques are powerful and very sensitive methods to investigate the properties of systems with low dimensions such as ultrathin films or clusters. During the last decade, resonantly enhanced magnetic dichroism occuring after excitation of 2p core level electrons of the 3d transition metals has received much attention. X-ray magnetic circular dichroism (XMCD) is one of the most prominent phenomena within this filed of research, since it enables element-specific investigations of the magnetic spin and orbital moments when measuring the respective x-ray absorption spectra. However, all magneto-optical properties of a material are determined by one and the same dielectric tensor and thus, it should be possible to obtain the same information when from measuring the reflectivity. Experiments using the reflectivity instead of photoabsorption especially profit from the much larger probing depth of about 20-100 nm when compared to the commonly applied total electron yield detection with a probing depth of 2-4 nm. Reflectivity measurements are hence attractive investigation methods on buried layer in complex magnetic structures as, e. g., spin valves. In this contribution we will focus on the transverse magneto-optical Kerr-effect (TMOKE) and its different capabilities at the 2p and 3p edges of 3d transition metal samples, respectively. On the one hand, we will present results that have been obtained in in situ experiments at the 2p edges of ultrathin cobalt films using reflectivity as well as conventional XMCD experiments [1]. On the other hand, we will present measurements of the T-MOKE at the 3p edges of capped iron films and we will demonstrate how to obtain the full set of optical constants in this energy regime where highly circularly polarized radiation is usually not available. The elements of the dielectric tensor taken from the T-MOKE experiments at the 3p edges will then be compared to the corresponding data in the vicinity of the 2p core levels. The results will be discussed with respect to future experiments on magnetic nanostructures. [1] A. Kleibert, V. Senz, J. Bansmann, and P. M. Oppeneer, Phys. Rev. B 72, 144404 (2005)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P38

X-Ray Tomographic Imaging Of Atoms - Crystal Views From Inside P. Korecki1 , M. Tolkiehn2 , D.V. Novikov2 , G. Materlik3 , M. Szymonski1 1

M. Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland – 2 Hamburger Synchrotronstrahlungslabor Hasylab at DESY, Hamburg,Germany – 3 Diamond Light Source Limited, Chilton, Oxfordshire, United Kingdom Most x-ray methods for crystal structure investigations are based on diffraction phenomena and sample the information in the reciprocal space using an external far-field detector. In principle, transformation from reciprocal to real-space can be made using a Fourier transformation. However, such a direct back transform is often hindered by the lack of phase information in the recorded intensity data and the inversion algorithms are ambiguous. An alternative approach for atomic resolution imaging involves measuring the x-ray wave field intensity directly at atomic sites. Such a measurement is performed in the x-ray standing waves technique [1] or in atomic resolution x-ray holography [2]. The absorption cross-section in these methods is modulated by x-ray diffraction, which results in an angular dependent absorption fine structure. This angular fine structure can be inverted to real space by using Fourier or holographic reconstruction. In recent works [3,4] it was demonstrated that the patterns of the angular fine structure in x-ray absorption recorded using white x-rays have a simple real-space interpretation. For a white x-ray beam, the variations of the wave field, formed by interference of the incident beam with the waves scattered on single atoms, cancel out by energy integration for all directions, except for the nearly forward scattering components, coinciding with the incident beam. In this contribution we shall describe the directional fine structure in white x-ray absorption and a tomographic approach for crystal structure retrieval. We shall also demonstrate an application of tomographic algorithm to experimental x-ray absorption data recorded for GaP crystal. This work was supported by Volkswagen Foundation, Federal Republic of Germany. The access to synchrotron radiation was supported by the European Community. [1] J. Zegenhagen, Surf. Sci. Rep.18, (1993) 199 [2] R. Fitzgerald, Physics Today 54, (2001) 21 [3] P. Korecki and G. Materlik, Phys. Rev. Lett. 86, (2001) 2333 [4] P. Korecki , M. Tolkiehn, D. V. Novikov , G. Materlik, M. Szymonski, Phys. Rev. Lett 96, (2006) 035502

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P39

Neue Entwicklungen in der Neutronenoptik Thomas Krist1 1

Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin

Am HMI werden neutronenoptische Komponenten wie Polarisatoren und Analysatoren, Kollimatoren und fokussierende Elemente gebaut und getestet. Es wurden polarisierende bender hergestellt, die aus Si-wafers mit Dicken zwischen 0.15 mm und 0.25 mm bestehen. Diese bender wurden mit Neutronen bei Wellenl¨ angen von 0.24 nm und 0.475 nm getestet, wobei 42 - 60 % der spin up Komponente mit Polarisationen von u ¨ber 95 % durch die bender transmittiert wurden. Es wurde auch ein polarisierender bender ohne absorbierende Schichten gebaut, der einen Neutronenstrahl in zwei polarisierte Strahlen aufspaltet, die den bender unter unterschiedlichen Winkeln verlassen. Mit einem Kollimator hinter diesem bender kann dann insbesondere die in Flugrichtung transmittierte Komponente herausgefiltert werden. F¨ ur eine Wellenl¨ ange von 0.475 nm wurden eine maximale Transmission von 50 % der gew¨ unschten Komponente und eine Polarisation von mehr als 98 % erreicht. Damit steht ein Festk¨ orper-Transmissionspolarisator zur Verf¨ ugung, der einen beliebig breiten Strahl u ¨ber eine Strecke von weniger als 100 mm polarisiert, ohne die Flugrichtung der Neutronen zu ¨ andern. Ferner wurden Spin-Analysatoren in der Bauform einer radialen cavity gebaut, die es erlauben, in zwei Dimensionen einen Winkelbereich von 5 Grad zu analysieren. Es wurden auch Festk¨ orper-Kollimatoren hergestellt. Dabei bestanden die Kanalw¨ ande entweder aus rein absorbierenden Schichten oder waren zus¨ atzlich dazu mit einer reflektierenden Schicht versehen worden. Mit deren Hilfe kann eine rechteckige Transmissionsfunktion erreicht werden, im Gegensatz zur dreieckigen Form bei Kollimatoren mit rein absorbierenden W¨ anden. Hiermit konnten Kollimationen bis herab zu 0.14 Grad erreicht werden. Die Transmissionen lagen bei u ¨ber 95 % der theoretisch erwarteten Werte. Durch Einf¨ ugung von Abstandshaltern in einen derartiges Bauteil konnten radiale Kollimatoren realisiert werden. K¨ urzlich wurde eine Festk¨ orperlinse getestet, die einen Neutronenstrahls mit der Divergenz eines mit Ni-58 beschichteten guides von einer H¨ ohe von 20 mm in einem Abstand von 36 mm hinter dem Linsenende auf 2 mm FWHM fokussierte. Das entspricht einer Flusserh¨ ohung um einem Faktor 3 im Fokusmaximum in Vergleich zum Fluss an dieser Stelle ohne Linse.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P40

New 2D-detector for the time-of-flight SANS-instrument YuMo @ IBR-2 ´ Gabriel2 , Valentin I. Alexander I. Kuklin1 , Akhmed Kh. Islamov1 , Andre 1 3 ¨ tz Eckold Gordeliy , Go 1

Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia – 2 EMBL Grenoble, 6, rue Jules Horowitz, BP-181 F-38042 Grenoble Cedex 9, France – 3 Institute of Physical Chemistry, University of G¨ ottingen, D-37077 G¨ ottingen, Germany

As a result of an international co-operation, a new two-dimensional position sensitive detector was developed for small angle diffraction at the time-of-flight instrument YuMo @ IBR-2. Based on the wire matrix and delay-line technology, this detector provides a spatial resolution better than 4 mm. The sensitive area is 580 x 580 mm2 . The body of the detector is made from aluminium providing an effective thickness of 40 mm which is filled with 3 He up to a pressure of 10 bar. Thus, the device is optimised for neutrons with wavelengths between 0.7 and 6 ˚ A that are available at the YuMo instrument. As a unique feature, the detector exhibits a central hole of 70 mm diameter for the direct beam as shown in the figure below. This is particularly useful if a two detector system is used that covers a large range of wave vector transfers simultaneously without the need of changing distance between sample and detector. In this contribution we report on the first test results of this detector under real experiment conditions. The performance of detector along with electronics and data acquisition allows to accept integrated count rates of more than 1.7 MHz. With this new device, the field of application of YuMo is extended to anisotropic phenomena that become more and more important in the future. This project has been funded by the German Federal Ministry of Education and Research under contract no. 03DU03G2.

Fig. 1: 2D-detector for the YuMo instrument

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P41

Horizontal Reflectometer at the IBR2-Reactor Dubna V. Lauter-Pasyuk1,2 , H. Lauter2 1

TU M¨ unchen, Germany – 2 ILL, Grenoble, France

The IBR-2 reactor is a high-flux long-pulse reactor. After the refurbishment the IBR2 reactor will be equipped with a cold moderator, which will be optimized for the horizontal reflectometer. A long flight-path is available to get a wavelength resolution of ∼2 % for the interesting regions of the broad wavelength distribution and thus for the broad q-range. Moreover an inclined flight-path is foreseen, favorable for a horizontal reflectometer. Direct view on the cold moderator, but not on the core, and full use of the cold moderator surface allows maximizing the flux. The background can be kept on a very low level due to experience with the actual reflectometer REMUR. Larmor precession of the neutrons will be used for angular encoding. This is a new method [1] which allows to tailor the angular resolution without changing the cross section of the beam. The two-dimensional detector will be of the same type, which gave recently interesting results for the fast neutron background. The scientific case is given by the study of fluid samples, which require a horizontal sample surface, ranging from surfactants, liquid polymers to biological membranes and solutions of pharmaceutics. Particular attention will be given to off-specular scattering and GISANS, so to lateral correlations of the samples in the two orthogonal directions of the sample plane and with its depth sensitivity. Application of these techniques gives also access to an extremely broad range of lateral correlations. The use of polarized neutrons allows also developing magnetic scattering from e.g. magnetic fluids in TOF within the Larmor precession field at small external magnetic fields. The Larmor precession research project has been supported by the European Commission under the 6th Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract n◦ : RII3-CT-2003505925. [1] H.J. Lauter, B.P. Toperverg, V. Lauter-Pasyuk, A. Petrenko, V. Aksenov, Physica B 350, e759 (2004)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P42

Innovative upgrading of the SANS instrument D11 at the ILL ¨hler1 P. Lindner1 , R. Schweins1 , K. Lieutenant1 , R. Ga 1

Institut Laue-Langevin, 6, rue Jules Horowitz, F-38042 Grenoble CEDEX 9, France

Significant flux gains of 40 % - 140 % can be obtained at D11 for the whole range of collimation distances with a new guide design, recently confirmed by MC simulations [1]. The 39 metres of straight glass guides with constant cross section 30 x 50 mm (width x height) will be replaced with a guide system with a diverging section, widening the guide width over the first metres by about 50 % and a focusing section over the last few metres. The changes are going to be realised in the period 2007-2008 and in conjunction with the ongoing Millennium Project “New Detector Tank” which concerns the development of a larger and faster SANS detector for D11 [2]. The new detector will be installed in a new detector tank with increased diameter and length, thus increasing the dynamic range and the resolution by 100 % each, allowing for about 6 times higher count-rates than at present and extending the range of momentum transfer Q both to higher Q as well as to lower Q, including the option of installing a multi-beam USANS. [1] K. Lieutenant, P. Lindner, R. G¨ ahler (2006) manuscript in preparation [2] P. Lindner R. Schweins (2006) ILL Technical Report ILL06 LI 02T

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P43

PANDA- cold neutron three-axes spectrometer at FRM-II Peter Link1 , Astrid Schneidewind2 , Dirk Etzdorf1 , Michael Loewenhaupt2 1

Forschungsneutronenquelle Heinz Maier-Leibnitz, TU M¨ unchen – Festk¨ orperphysik, TU Dresden

2

Institut f¨ ur

After a year of operation we report about the performance of the cold TAS - PANDA. Emphasis will be laid on the specific instrument design properties, which make PANDA to one of the most intense cold TAS world-wide. Using Gold foil activation combined with a calibrated monitor we measured a flux of 1.9 · 107 n/cm2 /s (ki =1.5 ˚ A−1 , 180 mm 7 2 −1 ˚ L-N2 cooled Be Filter) and 5.5 · 10 n/cm /s (ki =2.662 A , 60 mm PG Filter) at the sample position having the PG002 monochromator horizontally flat and vertically focused. Data obtained during the commissioning time and about 20 user experiments show that PANDA fulfills the expectations from the design studies. The experiments profited of both the high flux and the flexibility of PANDA. High resolution studies in the classical cold neutron TAS regime with kf <1.5 ˚ A−1 , as well as studies at higher −1 incident energy (ki up to 4 ˚ A ) have been carried out successfully. Fig. 1 shows inelastic data of CeBiPt at T=2.8 K (kf =1.2 ˚ A−1 ; Be-filter on ki ) (G. Goll et al., private communication). For comparison a Vanadium standard measured with the identical set-up has been normalized to the amplitude of the incoherent elastic signal. Fig. 2 shows CEF excitations observed at energy transfers of 6.6meV and 7.7 meV (M. Frontzek et al., private communication). Further development of the instrument in the near future will also be addressed.

Fig. 1: inelastic data of CeBiPt (kf =1.2˚ A−1 ) fitted with a superposition of a Gaussian peak and a quasielastic Lorentzian; data from Vanadium normalized to the same amplitude is shown for comparison.

Fig. 2: CEF excitations of a single crystalline sample of T b2 P dSi3 , the two peaks at 6.6 meV and 7.6 meV have been fitted by Gaussians.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P44

The new Materials Science Synchrotron-Beamline HARWI II T. Lippmann1 , F. Beckmann1 , R.V. Martins1 , L. Lottermoser1 , T. Dose1 , H.U. Ruhnau1 , A. Schreyer1 1

Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht

The decision of the Helmholtz-Zentrum Geesthacht / Germany to build up and operate Materials Science beamlines at DESY in Hamburg has now lead to the reconstruction and completion of the first of these beamlines, HARWI II, located at the second generation source DORIS. Thus, the expertise of the Institute for Materials Science operating the research reactor FRG 1, i. e. mainly uses neutron scattering for materials science investigations, will in future be complemented by synchrotron experiments. These benefit from the availability of both high-energy and high-brilliant synchrotron sources. HARWI II is dedicated to investigations of large samples. Global texture analyses, stress and strain measurements and global imaging will be typical experiments. A new high-field wiggler was installed and two in-vacuum monochromators are envisaged. The first, a horizontal double-Laue type, provides a beam of 10 by 10 mm2 size up to 250 keV and is already in use, whereas the vertical monochromator (20 to 150 keV) for a beam of 10 mm (height) and up to 70 mm (width) will be soon installed. In addition, the beamstop at the rear end of the vacuum tank also provides a small part of the ’white’ beam via a pinhole of 0.7 mm in diameter. The optical elements are completed by various slits, shutters, beam filters and beam intensity monitors, which are all located in an optics hutch made of concrete. In contrast, the experiment areas downstream are ’conventional’ lead hutches. In the first hutch a large materials science diffractometer will carry heavy samples and sample environments up to 600 kg weight. Moreover, a conventional Eulerian cradle can be mounted on top of the instrument and two detector arms allow measurements in the vertical using either a point detector or a 2D–detector. The scattering setup is completed by a ’detector portal’, which allows to position two additional 2D–detectors independently at any place in the hutch in a distance up to 10 m away from the sample. The sample tower (including the heavy load) can be moved outside the beam and two large tables can be independently installed using elevators. The first table of 3 m length and 1.5 m width is dedicated to user equipments, the second one permanently carries a tomography setup. In a second experimental area the Geoforschungszentrum Potsdam is operating a press for high–pressure experiments. Results of first experiments will be presented in further contributions to this conference. The beamline is now available to external users.

Fig. 1: Scheme of the HARWI II Beamline

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P45

Combining non-specular X-ray scattering and X-ray absorption spectroscopy - A new method for surface science ¨tzenkirchen-Hecht1 , Patrick Keil2 , Ronald Frahm1 Dirk Lu 1

Fachbereich C - Experimentalphysik, Bergische Universit¨ at Wuppertal, Gauß-Str. 20, 42097 Wuppertal – 2 Max-Planck Institut f¨ ur Eisenforschung - Adhesion and Thin Films, Max-Planck-Str. 1, 40237 D¨ usseldorf The atomic structure and the chemical composition of buried interfaces is of high interest for many applications e.g. in multilayered samples such as oxidized metals, optic and microelectronic devices. Due to the various functions of modern materials, nondestructive testing methods are highly desirable. We will show that the combination of grazing incidence non-specular X-ray scattering with X-ray absorption spectroscopy enables surface-sensitive structural investigations yielding many details of thin films or multilayered systems. More specifically, investigations of buried interaces are are feasible. Our new approach makes use of the distinct off-specularly scattered intensities which appear for grazing angles in the vicinity of the critical angle of total reflection. Extensive work in the past has shown that the intensity of this so-called Yoneda-peak is related to lateral surface inhomo-geneities such as roughness, and that a quantitative calculation is possible in many cases using sophisticated mathematical models such as the distorted wave born approximation. Since the angular position of the Yoneda-peak is strongly correlated with the density of the X-ray scattering materials, different interfaces can be selected by the choice of the scattering angle. Therefore, by measuring the X-ray absorption fine structure for given, well defined incidence and exit angles, it is possible to study the atomic short range order and the chemical state of a chosen element. By analyzing the spectra measured for well defined model systems such as noble metal thin films, we will first show that a quantitative description of the measured data is possible. In a second step, structural investigations of different samples will be presented. In the case of oxidized copper, a detailed insight into the structure of the multilayered oxide film is accessible. For metallic double layers (copper on gold) prepared by evaporation or sputtering, the Cu atoms at the Cu-air (vacuum)-interface can be separated from those in the inner Cu-Au interface in an unambiguous way.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P46

Time-resolved X-ray absorption spectroscopy - recent advances and new applications ¨tzenkirchen-Hecht1 , Bernd Griesebock1 , Ronald Frahm1 Dirk Lu 1

Fachbereich C - Experimentalphysik, Bergische Universit¨ at Wuppertal, Gauß-Str. 20, 42097 Wuppertal Time-resolved X-ray absorption spectroscopy (QEXAFS) yields structural information during fast chemical decomposition reactions, thin film deposition, solid-state reactions, phase transformations etc. This presentation will outline the technical developments of the QEXAFS technique, its current state and the most challenging results. More specifically, we will present results obtained using a cam-driven oscillating doublecrystal monochromator (DCM) with a channel-cut crystal. This DCM has been used at various synchrotron radiation sources worldwide, e.g. at HASYLAB, the ESRF, LURE, ANKA and the APS. Depending on the available photon flux and sample quality, repetition rates of about 100 Hz can be realized for XANES measurements, while the acquisition of full EXAFS spectra with a scan range of more than 1 keV and a repetition rate of 10 Hz are feasible. Using cryogenic cooling, the silicon crystal can cope with the full heat load from third generation undulator sources. Excellent data quality can be obtained. Since a fast sequential energy scanning technique is used, the detection of fluorescence radiation or surface sensitive techniques such as reflection mode EXAFS can be applied, and a reference sample can be monitored simultaneously with each measurement. This permits to detect even very small changes of the edge position - and thus the chemical valency of the species of interest - with a high accuracy. XANES-microtomography with a lateral resolution in the micrometerscale becomes feasible by combining the fast scanning monochromator with refractive X-ray lenses for beam focusing. Furthermore, the combination of time-resolved Xray absorption spectroscopy (Quick-XANES) with additional techniques such as UVVis, Raman-spetroscopy or differential scanning calorimetry (DSC) is feasible. We will different applications of the new technique ranging from solution chemistry to heterogeneous catalysis and biological sample systems.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P47

Johann Spectrometer for High Resolution X-ray Spectroscopy ¨ggmann2 , Pavel Machek1 , Edmund Welter2 , Wolfgang Caliebe2 , Ulf Bru 3 1 ¨nter Dra ¨ger , Michael Fro ¨ ba Gu 1

Institut f¨ ur Anorganische und Analytische Chemie, Justus-Liebig-Universit¨ at Gießen, Heinrich-Buff-Ring 58, 35392 Gießen, Germany – 2 Hamburger Synchrotron Strahlungslabor (HASYLAB) am Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany – 3 Martin-Luther-Universit¨ at HalleWittenberg, FB Physik, Friedemann-Bach-Platz, 606108 Halle(Saale), Germany We present a vacuum Johann spectrometer for inelastic x-ray scattering and high resolution fluorescence spectroscopy that has been installed at the DORIS III storage ring in HASYLAB. The spectrometer utilizes spherically bent crystals with a maximum size of 150 mm and cylindrically bent crystals as dispersive optical elements. Standard radius of curvature of the crystals is 1000 mm, however, the design of the spectrometer also facilitates measurements with smaller and larger bending radii. Up to four crystals are mounted on a revolving crystal changer and thus it is possible to change crystals without breaking the vacuum. The spectrometer works at fixed Bragg angle, the energy transfers are obtained by varying the incident photon energy. The measurements are preferably performed in a dispersive set-up with a sample located inside a Rowland circle and with a position sensitive detector on the circumference. The vacuum in the spectrometer tank is typically 10-6 mbar. The sample chamber is separated from the tank vacuum either by 25 um Kapton windows which allow to measure samples under ambient conditions or by two gate valves. The spectrometer is currently installed at wiggler beamline W1 whose working range is 4-10.5 keV and the typical flux at the sample of 5x1010 photons/s/mm2 . The capabilities of the spectrometer are illustrated by resonant inelastic experiments on 3d transition metals and rare earth compounds, and by the chemical shift measurements on chromium compounds.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P48

3D Mikro R¨ ontgenfluoreszenzspektroskopieein neues analytisches Instrument Wolfgang Malzer1 , Kanngießer1 1

Yvonne

¨ hn1 , Ho

Ioanna

Mantouvalou1 ,

Birgit

Institut f¨ ur Atomare Physik, Technische Universit¨ at Berlin

R¨ ontgenstrahlung hat die geeignete Energie um Strukturuntersuchungen und Materialver¨ anderungen im Mikro- und Nanometerbereich durchzuf¨ uhren. Das letztere ist erst seit der Einf¨ uhrung von effizienten R¨ ontgenoptiken und dem Nutzen von Synchrotronstrahlung m¨ oglich geworden. Die Herstellung neuer R¨ ontgenoptiken f¨ ur die Mikro R¨ ontgenfluoreszenzanalyse (Mikro-RFA) stellt den essentiellen Teil eines effektiven Mikro-R¨ ontgenspektrometers dar. Der durch die neuen R¨ ontgenoptiken erzeugte Anregungsspot im Mikrometerbereich wurde bis jetzt benutzt, um lokale Elementanalysen durch zweidimensionales Abrastern u ¨ber die Probenoberfl¨ ache durchzuf¨ uhren. Allerdings waren die so gewonnenen Informationen nicht explizit tiefenabh¨ angig. Wir haben die M¨ oglichkeiten der Mikro-RFA um eine Tiefenanalyse erweitert. Dies wird durch einen konfokalen Aufbau erm¨ oglicht, bei dem eine R¨ ontgenoptik sowohl im Anregungskanal asl auch im Detektionskanal verwendet wird. Dadurch wurde eine dreidimensionale Mikro-R¨ ontgenfluoreszenzspektroskopie geschaffen, die eine zerst¨ orungsfreie 3D Analyse hinsichtlich der Elementverteilung und des chemischen Zustands einer Probe erlaubt. Der Aufbau wurde zum ersten Mal am Speicherring BESSY realisiert. Die Grundlagen einer vollen Quantifizierungsroutine, in der eine Entfaltung der r¨ aumlichen Intesit¨ atsverteilung des Mikrovolumens integriert ist, sind bereits geschaffen. Das große Potential dieser Methode wird anhand sehr unterschiedlicher Untersuchungen im Bereich der Materialwissenschaften, der Arch¨ aometrie und der Biowissenschaften gezeigt. Als Ausblick werden erste Untersuchungen gezeigt, in denen der konfokale Aufbau auf die Nutzung von Protonenstrahlen u ¨bertragen wurde.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P49

Micro X-Ray Fluorescence Spectroscopy at the new µspot beamline at BESSY Wolfgang Malzer1 , Birgit Kanngießer1 , Heinrich Riesemeier2 , Martin Radtke2 , Gundolf Weseloh3 , Alexei Erko4 1

Institut f¨ ur Atomare Physik, Technische Universit¨ at Berlin – 2 Bundesanstalt f¨ ur Ma3 terialforschung und -pr¨ ufung, Berlin – MPI for Colloids and Interfaces, Potsdam – 4 BESSY, Berlin The µspot beamline is a new beamline at BESSY dedicated to X-ray spectroscopy and to scanning small and wide angle scattering. As a special feature for micro X-ray spectroscopy a confocal setup of two special X-ray optics is part of the experimental environment. The characteristics of the new beamline, the instrumentation and the experimental environment will be described. Emphasis is laid upon the confocal setup and its potentials. Results of the first application experiments will be presented. Applications in life science, geology, art and archaeology, materials science, and other application fields of X-ray spectroscopy are encouraged and welcome. User operation will start in the second half of this year.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P50

HU Research and Training Beamline at BESSY II Recardo Manzke1 , Thorsten Zandt1 , Reichardt2 , Wolfgang Eberhardt2

Christoph

Janowitz1 ,

Gerd

1

Humboldt-Universit¨ at zu Berlin, Institut f¨ ur Physik, Newtonstr. 15, 12489 Berlin – 2 Berliner Elektronenspeicherring-Gesellschaft f¨ ur Synchrotronstrahlung m.b.H., Albert-Einstein-Str. 15, 12489 Berlin Application of highly brilliant synchrotron radiation in a wide photon energy range from infrared up to x-rays leads to an ever increasing number of important results in all scientific fields, e.g. atomic, solid-state and surface physics, chemistry, life sciences, nano-spectroscopy, materials and structural research, lithography, and radiometry. This permanently growing scientific impact stands in close interrelation with the rapid development of new and more efficient sources of synchrotron radiation as well as steadily improving and changing experimental end stations, but also with a continuously prospering demand for well-trained young scientists. In order to meet in parts the demands, our team of the Humboldt university started, in close collaboration with BESSY, with the implementation of the HU Research and Training Beamline at BESSY II. On this beamline it is planned to introduce and continuously qualify students and young scientists into the fascinating possibilities of synchrotron radiation research. It is intended to offer practical training complemented by theoretical courses, both at the university and at the synchrotron. The close neighbourhood of BESSY II, a source of synchrotron radiation of the 3. generation, to the scientific campus of the Humboldt University in Berlin-Adlershof offers here a unique opportunity. Beyond training and courses the beamline will be open to young scientists for their master and doctoral thesis. The Research and Training Beamline will consist of a 5m-normal incidence monochromator (5m-NIM) of high resolution and at beginning of two experimental end station, one for high-resolution angle-resolved photoemission (HIRE-PES) and another for photoemission microscopy (PEEM). The 5m-NIM will be installed at the dipole magnet DIP3-1B. The performance are a photon energy range from 10 to 40 eV and a resolving power (E/∆E) of at least 20 000, i.e. a resolution of 1 meV at 20 eV photon energy. In this contribution we will present the performances and technical realizations of the HU Research and Training Beamline as well as the concepts of the future education.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P51

Angle Resolved Photoemission Spectroscopy at VUV-FEL ¨ nke Harm1 , Kai Martin Marczynski1 , Matthias Kallaene1 , Tim Riedel1 , So 1 1 Rossnagel , Lutz Kipp 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, D-24098, Germany Free Electron Lasers (FELs) are new kinds of light sources that can generate very brilliant ultrashort and coherent photon pulses. Employing 38 eV FEL radiation delivered by the VUV-FEL beamline PG2 at HASYLAB we performed angle resolved photoemission spectroscopy (ARPES) measurements on layered crystals. Electronic structure and space charge effects were investigated as a function of FEL pulse intensity. ARPES spectra were taken on a single shot basis using a hemispherical analyzer with a multichannel detector capable of detecting energy and angle of the photoelectrons in parallel. This work is supported by Innovationsfond des Landes Schleswig- Holstein.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P52

The Future High Energy Materials Science Beamline at Petra 3 R.V. Martins1 , T. Lippmann1 , F. Beckmann1 , H.-U. Ruhnau1 , A. Schreyer1 1

GKSS-Research Centre Geesthacht GmbH, Institute for Materials Science, 21502 Geesthacht, Germany The high energy materials science beamline will be among the first fourteen beamlines planned to be operational in 2009 at the new third generation synchrotron light source Petra 3 at DESY, Germany. The operation and funding of this beamline is assured by GKSS. 70 % of the beamline will be dedicated to materials science. The remaining 30 % are reserved for physics and are covered by DESY. The materials science activities will be concentrating on three intersecting topics which are industrial, applied, and fundamental research. The beamline will combine three main features: Firstly, the high flux, fast data acquisition systems, and the beamline infrastructure will allow to carry out complex and highly dynamic in-situ experiments. Secondly, a high flexibility in beam shaping will be available, fully exploiting the high brilliance of the source. Thirdly, the beamline will provide the possibility to merge in one experiment different analytical techniques such as diffraction and tomography. For the insertion device a five meter long in-vacuum or cryogenically cooled in-vacuum undulator is under discussion. It will have a main energy of 120 keV, tunable in the range from 50 to 300 keV and optimized for sub-micrometer focussing. The aim is to be highly flexible in beam shaping and focussing down to spot sizes far below 1 micrometer. The implementation of a Kirkpatrick-Baez microfocussing X-ray mirror system (KB-mirrors), Compound Refractive Lenses (CRLs), a fixed exit monochromator, and a single-bounce monochromator is planned. Two experimental hutches will be available. In the first one a high resolution microstructure and strain mapper and a diffractometer for physics experiments is foreseen. Furthermore space for user provided experiments and optics will be available. In the 12 m long second experimental hutch a diffractometer for loads up to 1 t and a smaller, high precision diffractometer, and a detector portal are projected. Furthermore, a tomography setup will be placed at the end of this hutch.

Fig. 1: Sketch of the projected layout for the high energy beamline at Petra 3.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P53

Advances in small-angle neutron scattering on D22: Biology, Soft Matter, Physics and Materials Roland May1 , Charles Dewhurst1 , Stefan Egelhaaf2 , Isabelle Grillo1 1

Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2 Institut f¨ ur Physik der Kondensierten Materie, Universit¨ atsstraße 1, 40225 D¨ usseldorf, Germany Small-angle neutron scattering (SANS) has been one of the most successful techniques provided by the ILL. Based on the success of D11, another dedicated SANS instrument, D22, was designed and implemented in the second guide hall of the ILL. It started full operation in 1996. The project of a third instrument, D33, is on its way. The sample-to-detector distance range of D22 is 1.05 to 18 m. The detector has an area of roughly 1 m2 and can be moved laterally by 50 cm, considerably increasing the simultaneous momentum-transfer range. D22 is probably the SANS instrument with the highest flux at the sample position. It reached its full performance only about two years ago, when a detector consisting of a vertical array of 128 linear sensitive Reuter-Stokes tubes of 8 mm diameter was installed; each of those has a dead-time of 2 µs. The whole detector can therefore accept a uniform load of more than 6 MHz at 10 % dead-time loss, a performance improvement of a factor of 60. The high flux (> 108 cm−2 s−1 ) at optimal conditions for the standard ∆λ/λ of 10 % can now be fully used, while formerly the limited detector count rate often forced one to over-collimate the incoming beam. This is of interest when the signal is small compared to a huge (often incoherent) background. The gain is particularly important for time-resolved experiments, which are becoming more and more popular in Soft Matter and Biology. The number of total counts that is required for a given statistics in every time frame (that can be ≤ 50 ms) is accumulated with much less repetitions if the count rate is not limited by the detector, thus wasting less precious sample material. Another example is the observation of inelastic SANS, like the temperature-dependent scattering from silicon (Cheung et al.), where the reduction of counts due to chopping the beam needs to be counterbalanced by a high flux. The high flux is also advantageous in the case of weakly scattering samples. One prominent example is the measurement of the scattering from the vortex lattice of the topical superconductor MgB2 , where Cubitt et al. were able to observe scattering from a crystal of less than 100 µg. The treatment of SANS data has made a considerable step forward at the ILL with the development of the Grasp suite, available at http://www.ill.fr/lss/grasp. After successful tests that employed an improvised polariser and a Mezei spin flipper, e.g. on ferrofluids and fusion-reactor steels, we are about to install a transmission polariser in the selector bunker, a permanent-magnet guide field along the collimation, and a radio-frequency spin flipper.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P54

Electron Emission channeling spectrometer using X-ray CCD detectors ¨ss1 Velimir Milinovic1 , Carsten Ronning1 , Hans Hofsa 1

II. Physikalisches Institut, Universit¨ at G¨ ottingen, Friedrich-Hund-Platz 1, 37077 G¨ ottingen We present a new spectrometer developed for electron emission channeling studies at the ISOLDE isotope spearator facility at CERN using an energy- and position sensitive CCD detector originally developed for imaging of soft X-rays in X-ray astronomy telescopes [1]. The lattice sites of impurity atoms in crystalline materials can be determined with high precision and high sensitivity using the emission channeling technique [2]. This spectroscopic method provides valuable information on the structure, the diffusion behavior and the defect interaction of impurity atoms in crystalline solids. In the emission channelingC technique, radioactive impurity atoms are ion implanted and the emission distribution of decay particles around different crystallographic directions are measured. Isotopes emitting conversion electrons with well-defined energies in the range of several 10 keV up to several 100 keV are particular well-suited for such studies, because such electrons exhibit pronounced channeling effects (enhanced emission intensity) along crystallographic axes and planes if the emitter atoms are located within the respective atom rows and planes. The measurement of electron channeling spectra requires the energy- and angle-resolved detection of conversion electrons with an angular precision of typically 0.1 deg. Instead of using conventional semiconductor detectors, the use of the CCD detector significantly improves the quality of the measured emission distributions and will drastically reduce the acquisition time. It is demonstrated that the X-ray CCD detector is an excellent detector for conversion electrons with extremely low noise and an good energy resolution [3]. Possible applications of the new spectrometer for electron channeling spectroscopy are outlined. [1] L. Strueder, et al. Rev. Sci. Instrum. 68, 4271 (1997) [2] H. Hofs¨ ass, G. Lindner, Phys. Rep. 201, 121 (1991) [3] H. Hofs¨ ass, et al., Nucl. Instr. Meth. A 512 (2003) 378

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P55

Neutron Spin-Echo Spectrometer Developments at the JCNS Michael Monkenbusch1 , Olaf Holderer1 , Ralf Biehl1 , Michael Ohl1 , Dieter Richter1 1

IFF, Forschungszentrum J¨ ulich, D-52425 J¨ ulich

The J¨ ulich Centre of Neutron Science (JCNS) will supply two neutron spin-echo spectromteres to the user community. These ultra-high resolution spectrometers are located at the new FRMII reactor and at the new MW-spallation source in Oak-Ridge. The FRMII instrument is an enhanced version of the FRJ2-NSE which was in operation at the FRJ2-DIDO reactor since 1996. With new electronics, improved correction elements and adjustment degrees of freedom it benefits from increased flux at the FRMII and better neutron extraction allowing the usage of neutrons from 4.5 ˚ A to 16 ˚ A or longer if the intensity is sufficient. The flux gain on the sample due to reactor power and larger beam cross section will be in the range of a factor of 10. With a maximum field integral of 0.5 Tm, Fourier times beyond 200 ns will be accessible at 13 ˚ A wavelength. The scattering angle range extends from 2◦ to 90◦ . It is planned that the instrument will be operational at the FRMII end of 2006. With a somewhat longer time horizon we are constructing a NSE instrument at the SNS spallation source in Oak Ridge. Using short fully compensated superconducting main solenoids it allows for a magnetically shielded enclosure necessary for stable and undisturbed operation. The design field integral is 1.5 Tm, using a broad band of incoming neutrons a dynamical range of 1 : 106 will be achieved and a maximum Fourier time at 18 ˚ A is one of the design goals.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P56

Depth dependent studies of magnetic and superconducting properties with polarized low energy muons Elvezio Morenzoni1 , Thomas Prokscha1 , Andreas Suter1 , Hubertus Luetkens1,2 , Dimitry Eshchenko1,3 , Ted Forgan4 , Hugo Keller3 , Jochen ¨nter Schatz5 , Gerard Nieuwenhuys6 Litterst2 , Gu 1

Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland – 2 IMNF, TU Braunschweig, Braunschweig, Germany – 3 Physik Institut, U. Z¨ urich, Z¨ urich, Switzerland – 4 School of Physics and Astronomy, U. of Birmingham, Birmingham, U.K. – 5 Fakult¨ at f¨ ur Physik, U. Konstanz, Konstanz, Germany – 6 Kamerling Onnes Laboratory, Leiden U., Leiden, The Netherlands Positive muons with 100 % spin polarization and whose energy can be continuously varied from 0.5 to 30 keV represent a novel extension of the µSR technique allowing depth dependent µSR-studies of thin films and multilayered structures in the range from ∼ 1 nm to ∼ 200 nm [1]. They act as a non-destructive microscopic probe for local investigations and provide unique information about magnetic and superconducting properties. A new beam line, specially designed to maximize the low energy muon flux, and an upgraded apparatus for µSR spectroscopy have been recently built and commissioned at PSI [2]. It has been supported by contributions of BMBF, EPSCR and various universities. The new set-up provides an intensity increase by almost a factor of ten with respect to the past and will contribute to the realization of the full potential offered by the use of polarized positive muons as nanoprobes. In this talk we will give an introduction of the method and present some experiments recently performed. Experiments include depth dependent studies of thin films, single layers and heterostructures of magnetic and superconducting materials. Specifically, the measurement of the value of the local magnetic field as a function of position below a surface on a scale of a few nm has been used to map non-conventional and conventional superconductors in the Meissner and vortex state, to study oxygen isotope effects on the magnetic penetration depth, or to quantify non-local effects in superconductors [3,4,5]. In multilayered structures (ferromagnetic/nonmagnetic/ferromagnetic) low energy muons probe the oscillating conduction electron spin polarization responsible for the interlayer exchange coupling [6] and in thin ferromagnetic/superconducting/ferromagnetic hybrid structures they are used to characterize coexistence and coupling of a spin density wave with bulk superconductivity [7]. [1] E. Morenzoni et al., Phys. Rev. Lett., 72, 2793 (1994) [2] T. Prokscha et al., Physica B 374-375, 460-464 (2006) [3] T. Jackson et al., Phys. Rev. Lett., 84, 4958 (2000) [4] A. Suter et al., Phys. Rev. Lett. 92, 087001 (2004) [5] R. Khasanov et al., Phys. Rev. Lett. 92, 057602 (2004) [6] H. Luetkens et al., Phys. Rev. Lett. 91, 017204 (2003) [7] A. Drew et al., Phys. Rev. Lett. 95, 197201 (2005)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P57

Absolute determination of resonant Raman scattering cross sections for silicon ¨ller1 , Birgit Kanngießer2 , Burkhard Beckhoff1 , Gerhard Matthias Mu Ulm1 1

Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin – 2 Technische Universit¨ at Berlin, Hardenbergstr. 36, 10623 Berlin The resonant Raman scattering (RRS) of X-rays in the vicinity of the K-absorption edge of silicon was studied. The investigation was carried out at the plane grating monochromator beamline for undulator radiation of the PTB laboratory at BESSY II in Berlin. Cross sections were determined absolutely [1] for a wide energy range of incident photons with small relative uncertainties employing calibrated instrumentation avoiding any reference samples. The experimentally determined values differ clearly from the theoretical ones found in the literature. This work was motivated by the disturbing continuous background a substrate or a matrix element can produce in total reflection x-ray fluorescence analysis (TXRF) and x-ray fluorescence analysis (XRF). That background can affect dramatically the lower limits of detection for trace elements with fluorescence lines below the resonant absorption edge of a matrix or a substrate element. One example is the detection of Al and Mg on silicon wafers, where the incident radiation with photon energy below the silicon K-edge is resonantly scattered at the silicon 2p electrons. For reference-free quantitative analysis by either TXRF or XRF the knowledge of the cross sections for the RRS is important for the correct background calculation. [1] M. M¨ uller, B. Beckhoff, G. Ulm, and B. Kanngießer, Phys. Rev. A (2006) accepted [2] C.Streli et al., Spectrochim. Acta B 58 (2003) 2113 [3] M. Kolbe, B. Beckhoff, M. Krumrey, G. Ulm, Spectrochim. Acta B 60 (2005) 505

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P58

X-Ray Refraction Computed Tomography for NDE of lightweight materials ¨ller1 , Axel Lange1 , Michael Harwardt1 , Manfred P. Bernd R. Mu 1 ¨rgen Goebbels1 , Joachim Bamberg2 , Hentschel , Bernhard Illerhaus1 , Ju Falco Heutling2 1

Federal Institute for Materials Research and testing (BAM); Berlin; Germany – 2 MTU Aero Engines; Munich; Germany X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structural elements causing phase related effects like refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity (1 · 10−5 ). The extraordinary contrast of inner surfaces is far beyond absorption effects. Scanning of specimens results in 2D-imaging of closed and open pore surfaces and crack surface density of ceramics and foams. Crack orientation and fibre/matrix debonding in plastics, polymers and ceramic composites after cyclic loading and hydro thermal aging can be visualized. In most cases the investigated inner surface and interface structures correlate to mechanical properties. For the exploration of Metal Matrix Composites (MMC) and other micro structured materials the refraction technique has been improved by a 3D Synchrotron Refraction Computed Tomography (SR-CT) test station. The specimen is situated in an X-ray beam between two single crystals. Therefore all sample scattering is strongly suppressed and interpreted as additional attenuation. Asymmetric cut second crystals magnify the image up to 50 times revealing nano meter resolution. The refraction contrast is several times higher than true absorption and results in images of cracks, pores and fibre debonding separations below the spatial resolution of the detector. The technique is an alternative to other attempts on raising the spatial resolution of CT machines. The given results yield a much better understanding of fatigue failure mechanisms in light weight materials for applications of high safety requirements.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P59

Photoemission Spectroscopy Using Flash ¨ hlisch1 , Mitsuru Nagasono1 , Alexander Fo 1 1 Pietzsch , Wilfried Wurth 1

Edlira Suljoti1 ,

Annette

Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg

The vacuum ultraviolet free electron laser (FEL) Flash is a self amplified spontaneous emission (SASE) type 4th generation light source with high peak brilliance (1012 ∼1013 photons/pulse), short pulses (20∼200 fs) and high coherence. The photon energy regime is 30∼200 eV. We present first results of photoelectron spectroscopy for gases and solids using Flash The experiments were carried out with our transportable spectroscopy UHV system at the monochromator beamline PG2. Operation mode of the VUV-FEL was single bunch or 8 bunch-train with a repetition rate of 2 Hz. The analyzer chamber of the system is equipped with a hemispherical electron analyzer, SES2002, which is rotatable around the optical axis of the FEL beam. In this study, the analyzer was fixed at magic angle with respect to the polarization vector of the FEL. The detector of the electron analyzer was synchronized with the FEL, so that photoelectron spectra could be detected for individual pulses or for a bunch-train. Incoming photon flux was measured by a MCP placed between the undulator device and the experimental hall. For the gas study, the intensity of the transmitted FEL beam was measured with fluorescence intensity of a Ce-Yag crystal using a CCD synchronized with the FEL. For the solid study, sample current was measured. High-harmonics of the VUV-FEL were cut by an Al filter with thickness of 700 nm. Gases were dosed by a nozzle with 0.2 mm diameter. Samples were He atoms and N2 molecules for gas phase experiments and a Cu single crystal for solid experiments. The photoelectron yield differs for each bunch because the photon flux of the FEL has a broad intensity distribution due to its statistical nature. The photoelectron yield of He is a linear function of the photon flux, but that of N2 shows a saturation effect. This is due to a difference of the photoionization cross section between He and N2 . The N2 photoelectron spectrum at high flux differs from that at low flux. This may be related to differences in partial cross-section. In the Cu crystal photoelectron spectra at high photon flux we observed photoelectrons with higher kinetic energy than the incoming photon energy. This is considered to be due to the coulomb repulsion among photoelectrons which are emitted simultaneously from the Cu.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P60

Planar set of refractive lenses for hard X-ray micro spectroscopy and imaging ¨rgen Mohr1 , Volker Vladimir Nazmov1 , Elena Reznikova1 , Arndt Last1 , Ju Saile1 1

PO. 3640, 76021 Karlsruhe

X-ray planar refractive lenses from SU-8 polymer and nickel have been developed during the last four years at the IMT / FZK, Karlsruhe. The lenses are manufactured using the LI-thography and electroplating-G steps of the LIGA-technique. By perpendicular respectively 45◦ -tilted X-ray patterning linear respectively crossed lenses can be formed to obtain a linear or a point-like focal spot. The set designed for crossed parabolic lenses structured in the SU-8 polymer includes 17 parallel rows of a large number of lens elements with different curvature radii and apertures. The possibility of mechanically removing elements allows adapting the lenses of the set to any experimental requirements. For example, synchrotron radiation with different photon energies can be focussed on identical focal distance. Due to the low atomic number of the atoms of SU-8 polymer, the transparency of the lenses is ∼ 0.7 with a maximal efficiency in the range of 12-30 keV. Together with X-ray lenses with a parabolic shape, using E-beam writing, lenses with mosaic and quasi-parabolic shapes are created, to increase the photon flux (4 times) and increase focal depth (50 times), respectively. For the previous testing experiments, the linear lenses formed the focal line of 105 nm width at 15.85 keV, and the cross lenses provided 0.4 x 0.8 µm2 focus spot at 28 keV. The very large demagnification by means of the crossed lenses resulted in an intensity gain of more than 50000. In comparison with Be-lenses, the very compact arrangement of crossed SU-8 micro structure lens elements provides a focal distance of several millimetres that allows focusing X-rays from synchrotron radiation sources of different generations to a nanoscale beam. The cross lenses were used for X-ray imaging of micro objects with a spatial resolution of less than 0.3 µm in phase contrast mode. A magnification up to 150 was achieved. The results of the lens characterisation at ANKA and at ESRF are presented together with examples of lens applications like X-ray µ-spectroscopy and magnified X-ray imaging.

Fig. 1: Row of crossed parabolic lenses

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P61

Towards measured pole figures error reduction Dmitry Nikolayev1 1

Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, 141980, Moscow region, Russia Pole figures are the source of the primary information in the conventional quantitative texture analysis. Therefore it is very important to measure pole figures with highest possible accuracy. The main sources of errors are the number of grains that are in reflecting position, beam intensity, instrumental function, signal background ratio etc. [1,2]. Instead of traditional way of neutron texture measurements, it is possible to measure quantities that are averages along circles of pole figures. These functions have smaller then pole figures experimental errors, cold be measured faster, from one hand, and could be used for pole figures and orientation distribution function reconstruction from the other. Results of the first such experiments that are fulfilled at SKAT difractometer (Dubna) [3] are presented as well as ways how pole figures cold be reconstructed from these functions. The present work is supported by INTAS grant No 03-51-6092. References [1]. D.I. Nikolayev et al. Solid State Phenomena Vol. 105, July 2005, Trans Tech Publications Proc. of ITAP 2, Metz , France, pp. 77-82 [2]. D.I. Nikolayev et al. Materials Science Forum Vols. 495-497, Sep. 2005, Trans Tech Publications Proc. of ICOTOM 14, pp. 307-312 [3] K. Ullemeyer et al. Nucl. Instr. And Meth. A 1998, Vol. 412 , p.80-88

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P62

Current state of diffraction data analysis software at beamline F1, Hasylab/DESY Carsten Paulmann1 , Thomas Malcherek1 1

Mineralogisch-Petrographisches Institut, Grindelallee 48, 20146 Hamburg, Germany

Since spring 2005 the beamlines F1 and D3 at Hasylab/DESY are equipped with new Marresearch GmbH CCD detectors with an active diameter of 165 mm and a resolution of 2048x2048 pixels (2x2 binning). The combination of bright X-ray sources with 2D area detector systems not only allows fast Bragg data collections (eg. charge density studies) but also greatly facilitates studies of disordered crystals which may show weak diffuse scattering ranging from broad and structured intensity up to weak commensurate or incommensurate satellite reflections. Currently indexing, integration and correction of the single crystal diffraction data collected at F1/D3 is based on the XDS package [1] which is mainly tailored for the evaluation of standard Bragg data collections on well-ordered samples. Analysis of diffraction data from disordered samples requires more advanced data processing and visualisation features covering non-integer indexed positions in reciprocal space (modulated structures, twinning) as well as a complete pixel-wise data processing in case of short-range ordered samples exhibiting broad diffuse scattering. To aid this process a range of software tools (C, F90, Perl) has been developed which provides advanced possibilities of viewing and processing CCD-based diffraction data of disordered samples. The tools include scripts to view individual image frames, to overlay a spot prediction based on the orientation matrix obtained by XDS or to search for the position of particular diffraction positions in a sequence of rotation frames. Furthermore, special emphasis has been put on possibilities for a post data collection processing (scaling, binning, data format conversion, averaging, background subtraction). Another set of software tools aims at the reciprocal space reconstruction from raw image data with interfaces to different common data formats (ASCII, Igor, Kuplot). This set is currently tailored to MarCCD/XDS data but an extension to other experimental setups (eg. Bruker-Nonius) is in progress. All programs are mainly command line driven in order to allow for simple generation of automated scripts and cross-network use. [1] W. Kabsch, J. Appl. Cryst. 26 (1993) 795

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P63

The x-ray diffraction endstation of beamline BL9 at DELTA Michael Paulus1 , Christof Krywka1 , Christian Sternemann1 , Martin Volmer1 , Metin Tolan1 1

Experimentelle Physik I, DELTA, Universit¨ at Dortmund, Maria-Goeppert-Mayer Str. 2, 44227 Dortmund DELTA is a synchrotron source located at the University of Dortmund, Germany, and is operated a 1.5 GeV with a maximum electron current of 120 mA and lifetimes of about 10 hours. The beamline BL9 is attached to a superconducting asymmetric wiggler which supplies radiation in the energy range between 5 keV and 30 keV. The incident radiation is monochromatized by means of a Si311 double crystal monochromator with sagittally bend second monochromator crystal. The experimental endstation of BL9 is equipped with a Huber six-circle diffractometer and is dedicated to (grazing incidence) x-ray diffraction and x-ray reflectivity studies on solid surfaces and thin films. Recently, the endstation was extended to perform small and wide angle x-ray scattering experiments making use of a MAR345 image plate scanner. Moreover, a spectrometerin Rowland geometry is accessible to perform resonant inelastic x-ray scattering experiments. The different setups will be described in detail and key applications will be presented with focus on small angle x-ray scattering, texture analysis and reflectivity studies.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P64

Das Neutronendiffraktometer RESI am FRM II – Erste wissenschaftliche Ergebnisse ¨ rn Pedersen1 , Friedrich Frey2 , Wolfgang Scherer3 , Gu ¨nther Seidl1 Bjo 1

FRM II, TUM, 85747 Garching – 2 Inst. f. Kristallographie und Angewandte Mineralogie, LMU M¨ unchen – 3 Institut f¨ ur Physik, Uni Ausgburg, 86135 Augsburg RESI (Reciprocal Space Investigator) ist ein vielseitiges Diffraktometer mit thermischen Neutronen. Es wurde f¨ ur viele unterschiedliche Problemstellungen entwickelt. Die Schwerpunkte liegen dabei bei: • Strukturen mit großen Zellen und niedriger Symmetrie (chemische Strukutur, (kleine) Proteine) ¨ • Messung von (unbekannten) Uberstrukturen • fehlgeordnete Kristalle (diffuse Streuung) Die ersten Messungen haben gezeigt, das RESI f¨ ur diese Probleme ein geeignetes Ger¨ at ist. An ausgesuchten Ergebnissen soll dies dargestellt werden. Die Verwendung eines Online-image-plate-Detektors er¨ offnet gerade im Bereich der unbekannten Strukturen neue M¨ oglichkeiten. Besondere Vorteile sind hier der große dynamische Bereich und das geringe intrinsische Rauschen des Detektors. Die Gammasensitivit¨ at ist durch geeignete Abschirmungen leicht beherrschbar.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P65

BRISP - a new thermal neutron Brillouin scattering spectrometer W.-C. Pilgrim1 , F. Barocchi2 , A Cunsolo3,4 , F. Formisano3,4 , T. Gahl6 , E. Guarini2 , A. Orecchini3,4 , C. Petrillo5 , F. Sacchetti5 , J.-B. Suck7 1

Institute of Physical Chemistry, Philipps-University of Marburg, Germany – 2 INFMUnit` a di Ricerca di Firenze, Italy – 3 INFM-OGG Grenoble, France – 4 Institut LaueLangevin, Grenoble, France – 5 INFM-Unit` a di Ricerca di Perugia, Italy – 6 Paul Scherrer Institut, Villigen, Switzerland – 7 Technical University Chemnitz, Germany BRISP is an Italian-German thermal neutron BRIllouin SPectrometer project, financed by INFM (Italy) and BMBF (Germany). This TOF spectrometer is designed for inelastic scattering experiments where wide energy ranges at small momentum transfer are desired. The extension of the Q-ω-plane allows to address a number of longstanding questions which were yet hampered due to kinematic restrictions of conventional neutron spectrometers. The new possibilities range from detailed investigations of magnetic dynamics in condensed matter to a study of fluid dynamics in systems close to their liquid-vapour critical points. Collective density excitations at low Q can be measured in glasses and fluids where the sound velocity reaches values up to 4000 m/s. The instrument components are now completely installed at the HFR at the ILL in Grenoble and the 1x2 m2 two-dimensional position-sensitive detector and related electronics [1] have meanwhile been completed. First experiments were carried out (see Fig. 1) demonstrating the capability of this new instrument and confirming the calculated predictions [2] for the energy resolution. Results [3] will be presented. BRISP will be available in autumn 2006. [1] P. van Esch, T. Gahl, B. Guerard, Nucl. Instr. Methods A 526/3 (2004) 493 [2] D. Aisa et al., Nucl. Instr. Meth. A 544/3 (2005) 620 [3] F. Sacchetti et al. Physica B: Condensed Matter (accepted)

Fig. 1: S(Q,ω)-spectra of liquid Pb, measured with an incoming energy of 79.9 meV. Measured energy resolution is also shown (2.7 meV, dashed line).

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P66

SALSA, das roboterbetriebene Neutronen Spannungsdiffraktometer am ILL Thilo Pirling1 1

Institut Laue-Langevin, 6, rue Jules Horowitz, BP156, F-38042 Grenoble, France

Im Juni 2005 nahm das neue Spannungsdiffraktometer SALSA am Institut Laue-Langevin in Grenoble seinen Betrieb auf. SALSA steht f¨ ur Strain Analyser for Large Scaled Applications, was nicht bedeutet, dass nur große Proben gemessen werden k¨ onnen. Die Bandbreite reicht von oberfl¨ achennahen Messungen bis zu scans in 1,5 m langen Komponenten. Bei der Konstruktion wurde besonderen Wert gelegt auf gr¨ oßtm¨ ogliche Flexibilit¨ at, sowie auf maximalen Neutronenfluss und optimalen Untergrund. Ein interaktives 3D-Kamersystem vereinfacht die Probenjustierung. Erstmals wurde f¨ ur ein derartiges Instrument ein Roboter zur Probenmanipulation entwickelt. Es handelt sich um ein Hexapod, ¨ ahnlich einem Flugsimulator, Abb. 1: SALSA das gleichzeitig Translations- und Rotationsbewegungen im Bereich ± 300 mm bzw. ± 30◦ bietet. Dabei betr¨ agt die maximale Last 1000 kg bei einer Positioniergenauigkeit zwischen 10 µm und 50 µm, abh¨ angig von Last und aktueller Position. Eine besondere Mechanik erweitert den Arbeitsbereich auf 1,5 m und 360◦ omega-Rotation. Die Strahloptik besteht aus computergesteuerten Spaltblenden, sowie Radialkollimatoren. Damit l¨ asst sich die Optik optimal an das Messproblem anpassen und erm¨ oglicht sowohl effiziente Messungen in großen Proben, als auch hochaufl¨ osende Oberfl¨ achenmessungen. Die optischen Komponenten sind austauschbar und der Einbau auch anderer Optiken ist leicht m¨ oglich. Die Wellenl¨ ange kann stufenlos zwischen 0,13 nm und 0,24 nm variiert werden und der doppelfokussierende Si-Monochromator sorgt f¨ ur hohe Intensit¨ at bei gleichzeitig guter Aufl¨ osung. Erste Ergebnisse demonstrieren die Leistungsf¨ ahigkeit und Bandbreite SALSAs. Die Messzeit wurde gegen¨ uber dem Vorg¨ angerinstrument D1A um einen Faktor 10 verk¨ urzt. Beispiele sind die Kartographierung von Schweißn¨ ahten, Messungen in 55 mm dicken Stahlstrukturen, oberfl¨ achennahe Messungen bis 30 µm an oberfl¨ achenbehandelten TiLegierungen. Sogar Einkristallmessungen sind in begrenztem Maße m¨ oglich, was besonders interessant ist, wenn sich der Kristall im Innern des Werkst¨ ucks befindet.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P67

Quantitative gas-phase experiments with femtosecond soft X-ray free-electron laser pulses at FLASH Mathias Richter1 , Andrei Sorokin1,2 , Sergey Bobashev2 , Kai Tiedtke3 1

Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany – 2 Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia – 3 Deutsche Elektronen-Synchrotron, Notkestr. 85, 22603 Hamburg, Germany Recent progress in the development of powerful vacuum-ultraviolet radiation and soft X-ray (XUV) sources such as higher harmonics generation sources and free-electron lasers (FELs) has allowed to extend the study of ultra-fast and non-linear effects on the interaction of highly intense electromagnetic radiation with matter considerably from the optical regime to the spectral range above atomic ionization thresholds. In this context, we present first results of pulse resolved gas-phase experiments obtained at the new XUV-FEL facility FLASH in Hamburg. Emphasis was laid on the determination of absolute photon numbers per pulse with the help of a calibrated setup [1] which allows the investigation of non-linear effects by quantitative measurements. In our contribution, we will discuss the competition between direct and sequential multiphoton ionization, e.g. in molecular nitrogen [2], and the influence of Coulomb explosion and space charge on ion time-of-flight spectra (see, e.g., Fig. 1). Moreover, a new method for the determination of spot size and beam waist on focused XUV-FEL beams will be presented which is based on a saturation effect upon atomic photoionization [3]. [1] M. Richter et al., Appl. Phys. Lett. 83 (2003) 2970. [2] A.A. Sorokin et al., submitted to J. Phys. B. [3] A.A. Sorokin et al., submitted to Appl. Phys. Lett.

Fig. 1: Two single-shot ion time-of-flight spectra of neon obtained from two subsequent FEL pulses, respectively, with 750 (red) and 150,000 (blue) ions generated within the first pulse.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P68

Von Mikrofokus bis USAXS - Neue M¨ oglichkeiten der Kleinwinkelstreuung an BW4 / HASYLAB ¨ hrmann1 , Martin Dommach1 , Marion Stephan V. Roth1 , Ralph Do Kuhlmann1 , Christian Schroer2 , Bruno Lengeler3 , Harald Walter4 , Peter ¨ller-Buschbaum5 , Rainer Gehrke1 Mu 1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Deutschland – 2 Institut f¨ ur Strukturphysik, TU Dresden, D-01062 Dresden, Deutschland – 3 II. Physik. Inst., Physikzentrum Melaten, RWTH Aachen, D-52074 Aachen, Deutschland – 4 CSEM SA, Badenerstrasse 569, CH-8048 Z¨ urich, Schweiz – 5 Physik-Department E13, TU M¨ unchen, James-Franck-Str. 1, D-85748 Garching, Deutschland Der R¨ ontgenwigglermessplatz BW4 am Hamburger Synchrotronstrahlungslabor (HASYLAB) ist ausgelegt f¨ ur Ultrakleinwinkelstreuung (U-KWS) im Bereich der Materialforschung [1]. Nach zehn Jahren erfolgreichem Betrieb wurde im Jahre 2003 damit begonnen, den Messplatz grundlegend aufzur¨ usten, um neuen Anforderungen seitens der Nutzer im Bereich der KWS gerecht zu werden. Anhand von Standardproben und neuen Experimenten beschreiben wir im Detail die Aufr¨ ustung der U-KWS-Kamera, die zur Verf¨ ugung stehenden KWS-Aufbauten und den derzeitigen Status des BW4Messplatzes. Die wesentlichen Verbesserungen sind [2]: 1. Die maximale Kleinwinkelstreuaufl¨ osung in Transmission bedingt durch die Gr¨ oße des Prim¨ arstrahlf¨ angers ist dmax > 1 µm bei einem Abstand von Probe zu Detektor von 13 m. 2. Bei Kleinwinkelstreuung unter streifendem Einfall k¨ onnen Strukturl¨ angen gr¨ oßer als 7 µm aufgel¨ ost werden. 3. Zur Erweiterung des Kleinwinkelstreubereiches zu gr¨ oßeren q-Werten k¨ onnen nun auch k¨ urzere Abst¨ ande zwischen Probe und Detektor zwischen 1.1 m und 4 m realisiert werden. Die dazu n¨ otige Optimierung von Intensit¨ at und Aufl¨ osung wird durch ein neuartiges, portables, piezogetriebenes Blendenmodul gew¨ ahrleistet. 4. Ein neuer Mikrofokusaufbau wurde mithilfe von refraktiven Berylliumlinsen realisiert. Derzeitig betr¨ agt die kleinstm¨ ogliche Strahlgr¨ oße 30x17 µm2 . Diese neue Option er¨ offnet die M¨ oglichkeit, Rasterr¨ ontgenmethoden wie Mikrokleinwinkelstreuung (µKWS) in Transmission [3] und unter streifendem Einfall einzusetzen [4]. Insbesondere bei KWS unter streifendem Einfall kann damit die Probengr¨ osse um zwei Gr¨ ossenordnungen reduziert werden.

[1] A. Endres, U. Lode, G.v. Krosigk, M. Bark, S. Cunis, R. Gehrke and W. Wilke, Rev. Sci. Instr. 68 (1997) 4009 [2] http://www-hasylab.desy.de/facility/experimental stations/BW4/BW4.htm [3] C. Schroer et al., Appl. Phys. Lett. 88 (2006) 164102 [4] S.V. Roth et al., Appl. Phys. Lett. 88 (2006) 021910

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P69

The microfocus SAXS / WAXS beamline at PETRA III - design and layout Stephan V. Roth1 , Rainer Gehrke1 , Horst Schulte-Schrepping1 , Ralph ¨ hlsberger1 , Hermann Franz1 , Edgar Weckert1 Ro 1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

Starting in 2007, the new high-brilliance third generation synchrotron radiation source PETRA III at HASYLAB / Hamburg will be constructed. PETRA III as a third generation synchrotron sources allows to realize new experimental methods using microand nanofocused x-ray beams. Hence, among the first beamlines to be built at PETRA III is the microfocus small- and wide-angle x-ray scattering beamline µSAXS/WAXS. This beamline will exploit the excellent photon beam properties of the low emittance source PETRA III to provide micro- and nanofocused beams with ultra-high intensity and resolution in real and reciprocal space. Based on the first concept for the µSAXS/WAXS beamline proposed in [1], we redefined the layout of the beamline incorporating on-axis compound-refractive optics. The new design foresees dedicated microand nano-focus end-stations being both dedicated to transmission as well as grazing incidence experiments. The beam dimensions range from 100x7 µm2 and 40x3 µm2 for a microfocus to approximately 100x100 nm2 for a nanofocus. Optics under consideration for nanofocusing include waveguides [2], Fresnel-zone plates [3], Beryllium compound refractive lenses and planar Silicon refractive lenses [4]. Additionally, a 1:1 imaging layout for combining USAXS with a moderately microfocused beam is currently discussed. The microSAXS/WAXS beamline is planned to exploit one of a high-β canted 2 m undulator pair. The energy range of the beamline is foreseen as 8-25keV. In combination with Si(111) crystals, this demands a very high stability and precise positioning. To suppress higher harmonics, a planar double-mirror with low incidence angle compatible with the large energy range of the beamline will be used. We will present the current layout of the µSAXS/WAXS beamline and discuss the different micro- and nanofocusing options possible. Furthermore, we will review the implications of this new beamline with respect to in-situ experiments as well as brilliancedemanding novel methods like µGISAXS [5] and µSAXS tomography [6]. [1] R. Gehrke et al., in K. Balewski et al., PETRA III: A Low Emittance Synchrotron Radiation Source, Technical Design Report, ISSN 0418-9833 (2004), pp. 318-329 [2] C. Riekel, Rep. Prog. Phys. 63 (2000) 233 [3] C. David et al., Spectrochimica Acta Part B 59 (2004) 1505 [4] B. Lengeler et al., J. Phys. D: Appl. Phys. 38 (2005) A218 [5] S.V. Roth et al., Appl. Phys. Lett. 88, 021910 (2006) [6] C. Schroer et al., Appl. Phys. Lett. 88 (2006) 164102

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P70

Investigations on spatial grain patterns for identification of manufactured, polycrystalline products by imaging diffraction ´ Rothkirch1 Andre 1

Hasylab/Desy, Notkestr. 85, 22607 Hamburg

Manufactured goods are supposed to look the same and be of reproducible quality and same attributes, thus they are very similar and are hard to classify/identify. Grain spatial distributions in materials are assumed to be non-reproducible (i.e. given by chance) implying a variation between goods of a same production charge with respect to their grain pattern and orientation and thus offering a possible feature for individual sample identification. Such identification would, within given limits, allow the individual handling of goods, i.e. to use the “built in fingerprint” for certification purposes (e.g. to use it as a seal to proof origin of highly valuable spare parts, to track/prevent the non-intended use or shipping of goods in terms of export control etc.). A “proof of concept” has been made for the discrimination of goods by 2D grain patterns. 20 EURCent coins have been chosen as test sample(s) and diffraction images have been taken. Several measurements of a single sample were done to define a basis for pattern comparison and to determine limits for sample adjustment accuracy. Measurements by interchanging coins, including remounting the sample holder, have been made to account for sample mounting accuracy and to perform a comparison of different coins. Methods being used will be presented and comparison results of different coins will be given.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P71

An autocorrelator and versatile delay line for the VUV FEL at TTF ¨ rn Siemer1 , Helmut Zacharias1 , Marco Rutkowski1 , Rolf Mitzner1 , Bjo 2 2 Matthias Neeb , Tino Noll , Wolfgang Eberhardt2 1

Physikalisches Institut, Wilhelm-Klemm Str. 10, 48149 M¨ unster – 2 BESSY GmbH, Albert EInstein Str. 15, 12489 Berlin In order to do jitter-free X-ray pump and probe experiments at the VUV FEL (FLASH) at DESY / Hamburg as well as to characterize the temporal structure of its high power pulses a novel autocorrelator has been designed for the XUV up to photon energies of 200 eV. The design is based on geometrical beamsplitting of the incomming FEL beam by a sharp mirror edge into two branches. Due to the limited reflection and the strong absorption of optical components an all-reflective geometry with grazing incidence angles at the mirrors has been chosen. The actual design represents a compromize between size and delay range of the delay line on the one hand and efficiency on the other hand. Thus it allows the handling of high power pulses and guarantees a high efficiency (50 %) up to 200 eV. The total delay is about 25 ps with a femtosecond resolution. The main challenge arises from the strict requirements regarding the motional resolution of the mirror movements as well as the mechanical stability of the entire autocorrelator. To fulfil the requirements on the motional accuracy elastic deformation (flexure) is used to control the movements. The intrinsic stabilization of the delay line is achieved by optimizing the stiffness. A further advantage of the autocorrelator design is the lack of any angle deviation or shift of the beam direction. Thus the autocorrelator can be integrated permanently into one of the FEL beamlines at the TTF2. First test experiments at the FEL are planned end of 2006 utilizing two photon photo emission from noble gases to measure the temporal length of the FEL pulses at 40 eV.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P72

Resonante Kernstreuung an der ESRF ¨ffer1 Rudolf Ru 1

ESRF, BP 220, F-38043 Grenoble Cedex

Resonante Kernstreuung mit Synchrotronstrahlung, erstmals in Hamburg 1984 nachgewiesen, entwickelte sich mit dem Aufkommen von Synchrotronstrahlungsquellen der dritten Generation im harten R¨ ontgenbereich von einer exotischen Technik zu einer versatilen Spektroskopie auf verschiedenen Gebieten. Untersuchungen magnetischer und elektronischer - statisch und dynamisch - Eigenschaften als auch schneller und langsamer struktureller Dynamik unter extremen Bedingungen sind geradezu pr¨ adestiniert f¨ ur diese zeitaufgel¨ oste und isotopenspezifische Spektroskopie. Dies ist der einmaligen Kombination der herausragenden Eigenschaften einerseits der Synchrotronstrahlung und andererseits des M¨ ossbauereffektes zu verdanken. An Hand von einigen typischen Experimenten, durchgef¨ uhrt an der ESRF, wollen wir exemplarisch die St¨ arken der Spektroskopie darlegen. (1) Magnetische (P,T)-Phasendiagramme von hochkorrelierten Elektronensystemen wie z.B. SmS, SmAl2 , SmB6 , UNiSn, U(Inx Sn1−x )3 . (2) Magnetisches Verhalten von exchanged-coupled“ d¨ unnen Schichten. ” (3) Magnetische Eigenschaften und strukturelle Dynamik von d¨ unnen Schichten, Monolagen und nanostrukturierten Materialien wie z. B. Magnetismus, Diffusion und Phononen von Eisen auf Wolfram. (4) Diffusion von Eisen in geordneten Legierungen, amorphen und nanokristallinen Systemen. (5) Glasdynamik wie z. B. VDOS und α- und β-Relaxation in schwachen und starken Glasformern.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P73

The High Magnetic Field µSR Project at PSI - Status and Prospects Robert Scheuermann1 , Alexey Stoykov1 , Alex Amato1 , Dierk Herlach1 , Hubertus Luetkens1 1

Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland

Positive muons are very sensitive probes which have a large variety of applications in condensed matter research and chemistry. With a magnetic moment larger than any nuclear moment, the muons are used to probe extremely small local magnetic fields, their spatial distribution and their temporal fluctuations, in any form of matter. The positive muon carries an elementary electric charge and can therefore be considered as a light proton, which makes it particularly useful for studying electronic quantum effects in matter. All these studies are performed with the µSR (muon spin rotation/relaxation/resonance) technique which utilizes the parity-violating decay of muons from a highly spin-polarized beam. To cope with the increasing demand of the users, the sample environment has recently been widely extended. However, and partly due to the specificity of the µSR technique, the increasing demand on high magnetic fields (i.e., >> 1 Tesla), which has been observed among the µSR users at PSI, could not be fulfilled due to the lack of a dedicated facility. This fact has triggered the high-field µSR project at PSI. A detailed scientific case [1] summarizes the outcome of a workshop held in January 2002 with 50 participants from 15 countries. Taking into account technical restrictions and wishes expressed by the users led to the main design specifications of the planned instrument for transverse field µSR: Maximum magnetic field: Hmax ≈ 10 T. Field homogeneity / stability ∆H/H < 10 ppm. Time resolution F W HM < 300 ps. In order to fulfill the requirements for the desired time resolution a new detector system has to be developed. The small spiraling radius of the relativistic decay positrons (e.g., 1 cm for a 30 MeV positron in a field of 10 T) requires that the scintillators are placed close to the sample and cover the full solid angle. To enhance the time resolution the length of the light guides has to be minimized, which makes it necessary that the photon detectors are capable to operate in high magnetic fields. A collaboration between PSI and JINR (Dubna, Russia) aims towards the development of an advanced microchannel photodiode (AMPD) operating in Geiger mode with improved gain and time resolution. The even more challenging specifications of the magnet cannot be met by any commercially available system. In order to decide on a suitable magnet design, GEANT4 simulations of the evolution of the muon spin polarization and of the measured asymmetry (with a certain detector geometry) are under way. Furthermore, a dedicated new surface muon beamline providing a highly parallel beam with small diameter and small momentum bite and 90◦ spin rotation is necessary to ensure optimum performance of the new instrument. [1] A. Amato, PSI Bericht Nr. 05-11 (ISSN 1019-0643)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P74

IN12-UFO: Innovative techniques for future triple-axis spectroscopy Wolfgang Schmidt1 , Karin Schmalzl1 , Michael Ohl1 1

Forschungszentrum J¨ ulich, IFF, 52425 J¨ ulich, Germany

The IN12 instrument is operated by the Research Centre at J¨ ulich in collaboration with CEA Grenoble at the Institute Laue Langevin in Grenoble. As a triple-axis spectrometer for cold neutrons it is dedicated for high-resolution studies of low-energy excitations. To meet further challenges as a state-of-the-art instrument IN12 is currently being upgraded with a multi-analyser option. IN12 will then be equipped with a 2-dimensional position sensitive detector and an array of fifteen analysers which can be rotated and positioned individually in order to map the scattered beam on a user-chosen path in Q-ω-space. We refer to this set-up as IN12-UFO (Universal Focusing Option). The innovative flexibility of the analyser array is realized by a non-magnetic drive mechanism where all relevant parameters are controlled by a laser-based optical absolute encoding system. This is a completely new technique in neutron scattering instrumentation that will drastically enhance the reliability and reproducibility of the multi-analyser. The positioning mechanics consists of parallel rails with variable distance which allows to position the individual analysers so that a) there are no gaps or overlaps as seen from the sample (optimum coverage) and b) all reflected beams from the analysers meet at one single focus point on their way to different spots on the detector surface. The focus point is controlled by a movable diaphragm and provides the only opening between analyser and detector shielding to prevent cross-talk and to keep the background low. We will present further details of this set-up, point out its potential for future neutron instrumentation and demonstrate its flexibility and multiplex advantages for specific physical applications.

Fig. 1: IN12-UFO - a typical configuration: Shown are the flight paths between sample, analysers and detector with sample at (0,0) and the horizontal axis as the direction of the incident beam. All units are in cm. The rails of the array are shown by the dashed lines. The border lines of each analyser are drawn in different colours to demonstrate coverage and divergence. Each colour also represents a different energy.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P75

The soft x-ray analytics facility WERA at ANKA Stefan Schuppler1 , Eric Pellegrin1 , Peter Nagel1 , Christian Pinta1 , Bernd Scheerer1 , Dirk Fuchs1 1

Forschungszentrum Karlsruhe, IFP

User operations have just started at WERA, IFP’s new beamline for soft x-ray spectroscopy and microscopy in the photon energy range 90 - 1500 eV at the ANKA synchrotron radiation facility. Emphasizing versatility, WERA facilitates combinatory studies of electronic and magnetic structure, in particular of strongly correlated, thinfilm, and nanoscale materials. Available methods include photoemission (PES), x-ray absorption (NEXAFS), as well as photoemission electron microscopy (PEEM). The experimental chambers are interconnected in UHV and accessible from various sample preparation chambers, including pulsed-laser deposition (PLD) of epitaxial thin films. Further endstations such as for magnetic dichroism (SXMCD) are planned as part of a long-term cooperation with outside user groups. Salient features of beamline and endstation layout, performance, and first experimental results will be presented.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P76

The future High Resolution Diffraction Beamline at PETRA III Oliver H. Seeck1 1

Hasylab am DESY, Notkestrasse 85, 22603 Hamburg, Germany

In the coming years the existing storage ring PETRA at DESY (Hamburg, Germany) will be completely reconstructed. From 2009 on it will serve as dedicated third generation synchrotron radiation source, called PETRA III. Compared to existing third generation sources, such as ESRF and APS, the brilliance of the photon beams will be a factor of 2 to 4 higher. Especially, the collimation of the beam and the coherence properties will be extraordinary. At PETRA III, 14 independent undulators will be installed at 9 sections. 5 sections will be shared by two undulators with a canting angle of 5mrad. This separation is sufficient to install independent front end equipment (such as shutters, collimators) but too small to build up two fully independent experiments. Therefore, one experiment at a sharing section has to be artificially offset by some offset optics. The High Resolution Diffraction Beamline (HighRes) will share a section with the Magnetic Resonant Scattering Beamline. HighRes will be the offset beamline with a vertical offset of approximately 1.5m. It will cover a photon energy range from 5.4 keV to 30 keV. The x-ray beam will be delivered in three different modes regarding the requirements of the users. At 10 keV, in the raw mode the beam will have a size of (2×1) mm2 (FWHM) and a divergence of ±(10×6) µrad2 , with the notation (horizontal×vertical). The collimation mode will deliver (1×0.5) mm2 (FWHM) and a divergence of ±(3×0.2) µrad2 . At the focussing mode the beamsize will be (300×15) µm2 (FWHM) with a divergence of ±(15×5) µrad2 . The flux at the sample will be >1012 ph/s at an energy resolution of 0.2 eV. HighRes will be presented including timetable, design, and equipment. Ray tracing calculations will be shown to demonstrate the stability of the beam and its capability to perform high ~ q –resolution investigations.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P77

SRPAC: basic features and first applications ¨rck3 , A.I. Chumakov1,4 , C. Strohm1,3 , I. Sergueev1 , T. Asthalter2 , U. van Bu 1 4 3 ¨ffer , G.V. Smirnov , W. Petry R. Ru 1

European Synchrotron Radiation Facility ESRF, F-38043 Grenoble, France – Physikalische Chemie II, Universit¨ at Stuttgart, D-70569 Stuttgart, Germany – 3 Physik-Dept. E13, Technische Universit¨ at M¨ unchen, D-85748 Garching, Germany – 4 Russian Research Center “Kurchatov Institute”, 123182 Moscow, Russia 2

Nuclear resonant scattering (NRS) of synchrotron radiation (SR) has become an established field in solid state research, involving mainly two methods: nuclear forward scattering (NFS) and nuclear inelastic scattering (NIS) [1]. Presently a third method is being developed, nuclear incoherent scattering observed on the time scale. This method is essentially a synchrotron radiation based analogue of Time Differential Perturbed Angular Correlations (TDPAC) [2]. By contrast to TDPAC, in Synchrotron Radiation based Perturbed Angular Correlations (SRPAC) the intermediate nuclear level is not excited from above, via a cascade of preceding nuclear transitions after decay of a radioactive parent, but from below from the ground state during spatially incoherent, single-nucleus resonant scattering of SR [3]. In both methods the interference of indistinguishable paths via an intermediate nuclear level split by magnetic dipole and/or electric quadrupole interaction allows one to investigate hyperfine interactions and spin dynamics. SRPAC can be applied to all nuclei with isomeric states with energies attainable by SR. SRPAC can also be considered as an extension of M¨ ossbauer spectroscopy or NFS into domains where these methods break down due to a vanishing Lamb-M¨ ossbauer factor: for relatively low-energy transitions (e.g. 57 Fe, 119 Sn) in very soft matter like melts and liquids, or for relatively high-energy transitions (e.g. 61 Ni, 67 Zn) in solid matter e.g. at room temperature. The basic features of SRPAC have been described recently [4]. SRPAC has been successfully applied so far using the 14.4 keV transition of 57 Fe for the investigation of rotational dynamics in glass-formers [4,5], in plastic crystals [6,7], and of probes confined to one-dimensional channels [8]. The feasibility at high energies has been demonstrated for the 67.4 keV-transition of 61 Ni [9]. The combination of SRPAC in hard matter and NIS has been used for a site-specific determination of a phonon DOS [10]. [1] NRSSR, eds. E. Gerdau and H. de Waard, Hyperfine Interact. 123/124 (1999), 125 (2000). [2] see e.g. T. Butz, Z. Naturforsch. 51a (1996) 396. [3] A.Q.R. Baron et al., Europhys. Lett. 34 (1996) 331. [4] I. Sergueev et al., Phys. Rev. B 73 (2006) 024203. [5] I. Sergueev et al., in preparation. [6] T. Asthalter et al., J. Phys. Chem. Solids 66 (2005) 2271. [7] T. Asthalter et al., J. Phys. Chem. Solids 67 (2006) in press. [8] T. Asthalter et al., in preparation. [9] O. Leupold et al., in preparation. [10] M. Seto et al., Phys. Rev. Lett. 91 (2003) 185505.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P78

NeRo-The New Reflectometer at GeNF Danica Solina1 , Dieter Lott1 , Ursula Tietze1 , Oliver Frank1 , Vincent Leiner1 , Andreas Schreyer1 1

GKSS Forschungszentrum GmbH, Max-Planck Str. 1; D-21502 Geesthacht, Germany

2005 saw the opening of the new NEutron ReflectOmeter (NERO) at the GKSS research centre in Geesthacht, Germany for the investigation of magnetic and non-magnetic systems as well as soft matter nano-structures. NERO operates with a monochromatic beam of neutrons of wavelength 0.433 nm with a resolution better than 2 %. An angular range of 20◦ < θ < 100◦ allows for both reflectometry and high angle diffraction measurements to be made on NERO. NERO has both a position sensitive detector and a pencil detector installed for flexibility when making specular and diffuse measurements. NERO has been designed to accommodate heavy sample environments such as cryofurnaces and various kinds of magnets. Polarization analysis is available for the investigation of magnetic nano-structures. A super mirror stack with a wide angular acceptance range will be available in 2006 for time efficient measurements of magnetic diffuse reflectivity. Further information and proposal forms can be obtained online at http//:genf.gkss.de.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P79

AMOR a versatile time-of-flight polarized neutron reflectometer at SINQ/PSI Jochen Stahn1 , Mark Koennecke1 , Thomas Gutberlet1 1

Lab. f. Neutron Scattering, ETHZ PSI, 5232 Villigen PSI, Switzerland

AMOR the apparatus for multi-option reflectometry at SINQ/PSI is a multi purpose state of the art reflectometer adaptable to the experimental demands of surface and interface studies in various fields of research. Phenomena to be challenged may relate to growth, wetting, absorption, adhesion, (inter-)diffusion, corrosion, nanocrystals, surface magnetism, magnetic excitation, thin film super-conductivity, polymer films, biomembranes, Langmuir films and more [1,2]. Measurements with polarized or unpolarized neutrons in white beam time-of-flight mode (1.3 ˚ A < λ < 13 ˚ A) and optionally in monochromatic θ-2θ mode can be performed. Most of the components are riding on an 8 m optical bench so that the chopper detector distance can be varied in order to give an optimal sample illumination and resolution (∆q/q = 0.5-10 %). The scattering plane is oriented vertically to allow also measurements at liquid surfaces. The inclination angle and thereby the accessible qrange is adjusted by tilting a deflection mirror and/or the sample. A flexible software control of the θ-2θ-movement around axis that are not mechanically coupled has been implemented. The standard mode of the instrument is time-of-flight, which has been opened for user operation in Oct. 2002. Two single detector tubes can be operated alternatively with an area detector. The area detector system allows coverage of off-specular reflectivity to map reasonable space in qz and qx . Polarized neutrons are provided via a polarizing supermirror of FeVCo/Ni to perform full spin polarized and analyzed reflectometry measurements. The flexibility of the instrument also allows for large sample environments, such as cryomagnets, evaporation chambers, furnaces or Langmuir troughs. Experiments at AMOR have included measurements of polymers at air-water interfaces, adsorption of model membrane systems to polymer cushions, structural fluctuations and dynamics in block co-polymers, magnetic multilayer systems of FM/AM/FM multilayers or HTSC/AM layer systems, diffusion in intermetallic layers. Results and performance of AMOR will be presented and discussed. [1] D. Clemens et al., Physica B 276-278 (2000) 140. [2] M. Gupta et al., Pramana J. Phys. 63 (2004) 57.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P80

High-Speed Chopper f¨ ur Experimente mit Neutronen und Synchrotronstrahlung Hermann Stelzer1 , Ralf Greven1 , Franz Janßen1 , Marko Leyendecker1 , Bernd Lindenau1 , Stephan Polachowski1 1

Forschungszentrum J¨ ulich GmbH, Zentralabteilung Technologie, D-52425 J¨ ulich

Extrem schnell rotierende Chopper mit Drehzahlen, die das rotierende Material auf Grund der Fliehkraft bis zur Materialfestigkeit belasten, werden zunehmend bei der Instrumentierung von Experimenten mit Neutronen und Synchrotronstrahlung ben¨ otigt. Bei den Neutronenstreuexperimenten handelt es sich i.d.R. um rotierende Scheibenchopper oder zylindrische Fermi-Chopper, die auch in Reihe hintereinander angeordnet werden k¨ onnen und die gew¨ unschten Neutronen selektieren. Im Falle der Synchrotronstrahlung dienen so genannte R¨ ontgenpuls-Selektoren dazu, aus rhytmisch pulsierender Strahlung die gew¨ unschten Anteile heraus zu filtern. Besonders geeignet f¨ ur sehr schnell rotierende Chopper sind ber¨ uhrungslos, reibungsfrei und damit v¨ ollig wartungsfrei im Vakuum betreibbare Magnetlagerungen, in denen die Chopper verschleißfrei rotieren k¨ onnen. Bevorzugt zum Einsatz kommen permanentmagnetische Lagerungen, die sich durch besonders geringen Leistungsverbrauch und geringe W¨ armeentwicklung auszeichnen. Neben der Lagerung spielt die Antriebstechnik der Chopper eine wichtige Rolle, da die Phasenstabilit¨ at vor allem bei hintereinander angeordneten Neutronenchoppern von ¨ erheblicher Bedeutung ist. Bei den Synchrotron-Selektoren werden Offnungszeiten von 500 ns bei einer Phasenstabilit¨ at von ±2 ns und einer Drehzahl von 60.000 Upm erreicht. Dies entspricht bei Verwendung von dreiseitigen Scheiben, deren Verformung auf Grund der Fliehkraft bereits bei der Fertigung Ber¨ ucksichtigung findet, Puls-Frequenzen von 3 kHz. Vorgestellt wird die permanentmagnetische Lagertechnik an Hand von Beispielen erst k¨ urzlich in Betrieb gegangener bzw. noch in Bau befindlicher Neutronenchopper, z.B. f¨ ur ILL/Frankreich, PSI/Schweiz, SNS/USA und FZJ/Deutschland sowie R¨ ontgenpulsSelektoren z.B. f¨ ur ESRF/Frankreich, APS/USA und KEK/Japan.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P81

A double monochromator device for the CONRAD imaging instrument at HMI Berlin Markus Strobl1,2 , Nicolay Treimer1,2 , Ingo Manke1

Kardjilov1 ,

´ Andre

Hilger1 ,

Wolfgang

1

Hahn Meitner Institut, Glienickerstr. 100, 14109 Berlin – 2 TFH Berlin, Luxemburger Str. 10, 13353 Berlin Besides the disadvantage of lower flux densities, imaging with monochromatic radiation, in our case neutrons, offers a number of advantages especially in the case of various energies available. Avoiding beam hardening effects allows more sensitive and accurate quantitative measurements and in the latter case energy selective and energy dispersive techniques can be applied opening new fields of application. Here we want to introduce the first neutron double monochromator device for that purpose installed at the imaging beam line CONRAD. CONRAD is the new cold neutron radiography and tomography instrument at the Hahn Meitner Institute in Berlin which recently started operation as a part of the Berlin Neutron Scattering Centre (BENSC). It includes two measurement positions of which the first one directly at the end of the NL1b neutron guide was used to install a flexible monochromator device as an additionally available insert. While the CONRAD instrument uses in standard operation the full cold spectrum of the lower part of the guide, a first PCG(002) monochromator with a mosaic spread of app. 2 degrees is placed in the upper beam part deflecting neutrons downwards. The initial lower beam part is blocked by a shutter and on a linear manipulation table behind it the second corresponding graphite crystal is installed. Hence, while both crystals can be rotated to chosen Bagg angles, the second one can be positioned along the original beam direction in order to reflect the monochromatic beam from the first crystal into the initial beam path of the CONRAD instrument. This construction enables to choose a monochromatic beam with wavelengths between 0.25 nm and 0.65 nm for high resolution imaging at the second measurement position of CONRAD app. 5 m downstream. First measurements and results concerning operational parameters, tests of methods ranging from energy selective radiography to stress mapping, first quantitative analyses and application perspectives will be presented.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P82

The new V12a double crystal diffractometer at HMI and neutron imaging ´ Hilger1 Markus Strobl1,2 , Wolfgang Treimer1,2 , Andre 1

Hahn Meitner Institut, Glienickerstr. 100, 14109 Berlin – 2 TFH Berlin, Luxemburger Str. 10, 13353 Berlin

Double crystal diffractometers (DCD) are widely used for structural investigations at the limit between macroscopic and microscopic inner structures of sample materials. Operating in an ultra small angle neutron scattering (USANS) q-range between 10−4 nm−1 and 10−1 nm−1 structures between 50 nm and nearly 100 micrometer can be resolved. Hence the DCD connects the resolvable ranges of small angle neutron scattering (SANS) instruments and neutron tomography facilities. However, the DCD does not only link the resolvable size ranges but can also be operated to yield both, q-space information on microscopic structures combined with real space information in the range of macroscopic inner structures. This method was developed in recent years at the V12 DCD at HMI by introducing refraction and USANS contrast for tomography. The new V12 DCD set-up has now been optimised to exploit all the opportunities of USANS, refraction and USANS contrast tomography and conventional attenuation contrast tomography with an intense monochromatic neutron beam. The new contrast methods will be introduced as well as the final set-up of the V12 instrument. Additionally several examples and results achieved by the new techniques and instrument will be given.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P83

Insertion Devices for the PETRA III Storage Ring ¨uer1 , Uwe Englisch1 , Markus Tischer1 , Miriam Barthelmeß1 , Martin Bra 1 1 ¨ger , Jochen Skupin Joachim Pflu 1

Deutsches Elektronen-Synchrotron (DESY), HASYLAB, Notkestr. 85, 22603 Hamburg, Germany The PETRA ring at DESY, presently used as a booster ring, will be reconstructed and converted to a dedicated 3rd generation light source in the years 2007/2008 [1]. One octant of the machine will be completely remodeled for installation of 14 undulator beamlines with unprecedented brilliance, particularly suited for experiments with small or diluted samples requiring small beam size or extreme focusing conditions. PETRA III will operate in top-up mode at an energy of 6 GeV with a beam current of 100 mA. The first stored electron beam is expected for the end of 2008, first photon beam and start of beamline commissioning in early 2009. The emittance of the new storage ring will be brought down to 1 nmrad by means of 20 permanent magnet damping wigglers [2]. In the remodeled octant 8 straight sections will be available for installation of 5 m long insertion devices (IDs). To enlarge the number of independently operable beamlines, five of these sections will be used for two 2 m long undulators with a 5 mrad bend in-between. Furthermore, the straight section at the beginning of the octant provides space for installation of a 20 m long undulator. There will be 7 different undulator types, the majority of which are conventional, planar hybrid undulators of 2 m and 5 m length with two different period lengths. In addition, five special undulators have been assigned, including a quasi-periodic undulator with shifted higher harmonics and an APPLE2 device for circularly and elliptically polarized radiation in the VUV region. Furthermore, two hard X-ray IDs for 30 and 100 keV photons and the 20 m undulator are in the design phase. A common development of undulators has been started for PETRA III and the European XFEL [3], the other large future project at DESY to be realized until 2012. Aside from minor differences the undulator requirements in both projects have a lot in common regarding their magnetic properties, mechanical stability, and precision of the motion control system. First devices, which will be available in the near future, are expected to meet the more demanding requirements regarding specification and performance of either project. [1] K. Balewski et al. (Ed.), PETRA III Technical Design Report, DESY 2004035 (2004); http://petra3.desy.de [2] M. Tischer et al., Damping Wigglers for the PETRA III Light Source, JACoW conference proceedings PAC 2005 (2005), 2446-2448 [3] M. Altarelli et al. (Ed.), The European X-Ray Free-Electron Laser XFEL, Technical Design Report (2006), in preparation; http://xfel.desy.de

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P84

Upgrading of the SKAT texture diffractometer at the IBR-2 pulsed neutron source in Dubna, Russia Klaus Ullemeyer1 , Jan H. Behrmann1 1

Geologisches Institut, Universit¨ at Freiburg, Albertstr. 23B, 79104 Freiburg

The TOF texture diffractometer SKAT [1] at the IBR-2 pulsed neutron source of the Frank Laboratory of Neutron Physics in Dubna is operated by German scientists and mainly used by Earth scientists due to advantages (in particular, high resolution) for texture investigations on polyphase rock samples. The pulse repetition rate of 5 s−1 at IBR-2 reactor limits the maximum accessible range of lattice spacings d to about 4.9 ˚ A. This may be sufficient for texture analyses on many polyphase rocks composed of high-symmetrical constituents, however, successful texture analyses on rocks containing low-symmetrical constituents may be hampered. Hence, we intend to expand accessible d -range, which may be achieved by decreasing the scattering angle 2Θ. We consider construction of a multidetector system with the detectors located at 2Θ = 65◦ . Accessible d -range extends to about 6.5 ˚ A, giving access to more non-overlapped Bragg reflections. Deterioration of resolution by about 15-20 % appears to be acceptable. In addition, the single-axis sample goniometer will be expanded by two more scanning axes, allowing more complex sample movements and the recording of orientational data for alternative methods of quantitative texture analysis. [1] Ullemeyer et al., Nucl. Instr. Meth. Phys. Res. A412 (1998), 80.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P85

Die Metrology Light Source - der neue Elektronenspeicherring der PTB Gerhard Ulm1 , Guido Brandt1 , Rolf Fliegauf1 , Arne Hoehl1 , Roman Klein1 , ¨ller1 , Klaus Bu ¨rkmann-Gehrlein2 , Joachim Rahn2 Ralph Mu 1

Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin – 2 BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin Die Physikalisch-Technische Bundesanstalt (PTB), das nationale Metrologie-Institut der Bundesrepublik Deutschland, errichtet in Berlin-Adlershof einen NiederenergieElektronenspeicherring, die Metrology Light Source (MLS), in direkter Nachbarschaft zu BESSY II. Die MLS wird als dedizierte Anlage von der PTB haupts¨ achlich f¨ ur die Radiometrie im UV, EUV und VUV genutzt werden und damit BESSY I ersetzen. Ferner wird es m¨ oglich sein, durch Sonderbetrieb mit kurzen Elektronen-Bunchen intensive koh¨ arente Synchrotronstrahlung im FIR/THz-Bereich zu erzeugen. Mit dem Aufbau der Speicherringanlage in einem neuen Geb¨ aude wurde im Mai 2006 begonnen, das Commissioning der MLS soll im 2. Quartal 2007 beginnen, Nutzerbetrieb ist ab Januar 2008 vorgesehen. Die MLS wurde von der BESSY GmbH nach Vorgaben durch die PTB geplant, die BESSY GmbH u ¨berwacht und steuert auch den Aufbau und wird auch den Betrieb verantworten. Als Injektor wird ein 100 MeV-Mikrotron dienen, der Ring wird einen Umfang von 48 m haben und bei Elektronenenergien im Bereich zwischen 200 MeV und 600 MeV betrieben werden [1]. Die Spektren der Ablenkmagnete (mit charakteristischen Photonenenergien zwischen 12 eV und 314 eV) und eines Undulators erg¨ anzen perfekt die R¨ ontgenspektren von BESSY II. F¨ ur die Radiometrie wird die MLS im Bereich des VIS, UV, EUV und VUV als berechenbare Strahlungsquelle genutzt werden, der hierf¨ ur erforderliche Sonderbetrieb (meist bei kleinen gespeicherten Elektronenstr¨ omen und bei unterschiedlichen Elektronenenergien) ist bei einer kleinen Anlage eher problemlos m¨ oglich als an großen Nutzereinrichtungen. Monochromatisierte Synchrotronstrahlung hoher spektraler Reinheit vom UV bis ca. 300 eV Photonenenergie wird f¨ ur die Kalibrierung von Detektoren und f¨ ur Reflektometrie verf¨ ugbar sein. Einen besonderen Schwerpunkt werden Arbeiten zur Entwicklung der EUV-Lithographie darstellen. Ein Ziel ist, im Rahmen der sich im Aufbau befindlichen europ¨ aischen Metrologie ein Kompetenzzentrum f¨ ur Radiometrie darzustellen, erweitert in den R¨ ontgenbereich durch die Messm¨ oglichkeiten der PTB bei BESSY II. Eine weitere Zielrichtung ist, quantitative Analytik mit Synchrotronstrahlung vom THz- bis in den VUV-Bereich zu entwickeln. Grunds¨ atzlich ist eine Nutzung durch Externe nicht ausgeschlossen, Erweiterungsm¨ oglichkeiten durch zus¨ atzliche Strahlrohre sind gegeben. [1] R. Klein et al., Proc. of EPAC 2004, Lucerne, Switzerland (2004) 2290.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P86

Metrologie mit Synchrotronstrahlung im PTB-Laboratorium bei BESSY II Gerhard Ulm1 , Burkhard Beckhoff1 , Alexander Gottwald1 , Roman Klein1 , ¨ller1 , Mathias Richter1 , Frank Scholze1 , ReiMichael Krumrey1 , Ralph Mu ner Thornagel1 1

Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin

Die Physikalisch-Technische Bundesanstalt (PTB) nutzt seit mehr als 20 Jahren Synchrotronstrahlung f¨ ur die Metrologie, insbesondere f¨ ur die Radiometrie [1]. Bei BESSY II betreibt die PTB ein Laboratorium mit gegenw¨ artig 10 Messpl¨ atzen an 4 AblenkmagnetStrahlrohren und an einem Undulator-Strahlrohr. Monochromatisierte Strahlung hoher spektraler Reinheit steht vom UV bis in den R¨ ontgenbereich (10 keV) zur Verf¨ ugung. Harte R¨ ontgenstrahlung eines 7 T-Wellenl¨ angenschiebers wird bis zu 60 keV genutzt. BESSY II wird als berechenbare Strahlungsquelle, als prim¨ ares Strahlernormal, genutzt, um Strahlungsquellen und energiedispersive Detektoren (z. B. Si(Li)-Detektoren) zu kalibrieren. Herausragende Beispiele dieser Art der Nutzung sind die Kalibrierungen von Teleskopen f¨ ur Sonnenmissionen und von Detektoren f¨ ur die R¨ ontgenastronomie [2]. Hochgenaue Kalibrierungen von Detektoren, z. B. von Photodioden, werden vom UV bis in den R¨ ontgenbereich durchgef¨ uhrt, indem diese Detektoren in monochromatisierter Strahlung mit einem Kryoradiometer als prim¨ ares Empf¨ angernormal verglichen werden [3]. Basierend auf diesen absolut kalibrierten Detektoren werden fundamentale und angewandte Untersuchungen zur R¨ ontgenfluoreszenzanalyse [4] und Studien der biologischen Wirksamkeit von R¨ ontgenstrahlen durchgef¨ uhrt [5]. Ein weiteres wesentliches Arbeitsgebiet ist die Reflektometrie vom UV- bis in den R¨ ontgenbereich. Hier stellen zur Zeit Arbeiten zur Entwicklung der EUV-Lithographie einen besonderen Schwerpunkt dar, der im Rahmen mehrerer Kooperationen mit Industrieunternehmen und Forschungseinrichtungen bearbeitet wird [6]. Außerdem wird R¨ ontgenreflektometrie zur Bestimmung von Schichtdicken im nm-Bereich durchgef¨ uhrt [7]. Der neue, zur Zeit im Aufbau befindliche dedizierte Niederenergie-Elektronenspeicherring der PTB, die Metrology Light Source (MLS), wird die Messm¨ oglichkeiten im UV- und VUV-Bereich wesentlich verbessern und bis in den THz-Bereich hinein erweitern [8]. [1] [2] [3] [4] [5] [6] [7] [8]

G. Ulm, Metrologia 40 (2003) S101. M. Richter et al., Adv. in Space Research 37 (2006) 265. A. Gottwald et al., Metrologia 43 (2006) S125. B. Beckhoff et al., Solid State Phenom. 92 (2003) 89. M. Krumrey et al., Radiat. Environ. Biophys. 43 (2004) 1. R. Klein et al., Microelectr. Eng. 83 (2006) 707. M. Krumrey et al., Thin Solid Films 459 (2004) 241. R. Klein et al., Proc. of EPAC 2004, Lucerne, Switzerland (2004) 2290.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P87

The Variable Polarization XUV Beamline at PETRA III Jens Viefhaus1 1

HASYLAB bei DESY, Notkestr. 85, 22607 Hamburg

The 6 GeV energy of the storage ring PETRA III (DESY, Hamburg) together with its very low emittance of 1 nm rad makes it an excellent facility to host a Variable Polarization XUV Beamline. The high brilliance and flux of the beamline provided in a broad photon energy range (200 eV to 3000 eV) will open up completely new scientific opportunities in fields like: A. Spectromicroscopy B. High resolution photoelectron spectroscopy C. Soft X-Ray scattering D. Magnetic studies E. Gas phase targets F. Surface Chemistry Key absorption edges of practically all important elements lie in the range of photon energies provided by the beamline which creates the possibility to uniquely determine the element-specific local electronic structure in complex materials by exploiting atomic resonances. In the future polarization-dependent studies with soft X-rays will play a key role in enhancing our knowledge of the structure of matter. The source of the beamline will be a 5 m APPLE-II-type undulator (65.6 mm period) allowing full polarization control by the user. The undulator can operate over the whole photon energy range in the first harmonic thereby simultaneously providing high flux and complete polarization. Using current technology it is possible to achieve a spectral resolving power of more than 10000 at 1 keV with an extremely high flux (more than 1012 photons/sec) focused on the sample. Special attention will be paid to provide both small focal spot size as well as high photon flux required by the different user communities. Together with the main source parameters a detailed layout of the beamline will be presented. User operation of the beamline will start in 2009 right after the startup phase of PETRA III.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P88

Probenumgebungen f¨ ur Neutronenstreuexperimente in Kombination mit in situ Gasadsorption unter kontrollierten PVT-Bedingungen Dirk Wallacher1 , Astrid Brandt1 1

Hahn-Meitner-Institut GmbH, Berlin

Das Interesse an Neutronenstreuexperimenten in Kombination mit in situ Gasadsorptionsverfahren hat in den letzten Jahren stark zugenommen. Gasadsorptionsmessungen geh¨ oren zu den Standardmethoden zur Charakterisierung grenzfl¨ achenbestimmter, d. h. nanostrukturierter Materialien. Insbesondere wird diese Methode zur Bestimmung der Porengr¨ oßenverteilung von nanopor¨ osen Medien eingesetzt. Erg¨ anzend dazu bietet vor allem die Neutronenkleinwinkelstreuung eine einzigartige M¨ oglichkeit, zus¨ atzliche Informationen u ¨ber die Porenstruktur und Defekte in mesopor¨ osen Materialien zu gewinnen. Neben ihrer Bedeutung bei der stetigen Weiterentwicklung dieser Materialien tragen solche Vergleichsexperimente auch zum Verst¨ andnis des Adsoptionsverhaltens und damit zur theoretischen Modellierung der auf Gasadsorption basierenden Standardcharakterisierungsverfahren bei. Weiter sind Studien zur Struktur und Dynamik von Adsorbaten in eingeschr¨ ankten Geometrien, die Untersuchung der Einfl¨ usse von Feuchtigkeit auf biologische Materialien sowie die Erforschung von Materialien zur Interkalation von Wasserstoff weitere interessante Anwendungsgebiete f¨ ur Neutronenstreuexperimente in einer Probenumgebung mit der M¨ oglichkeit einer Gasexposition bzw. Gasadsorption unter definierten PVT (Druck-Volumen-Temperatur)-Bedingungen. Bedingt durch diese mannigfaltigen Anwendungsaspekte sind die Anforderungen an die jeweilige experimentelle Umgebung und Technik sehr unterschiedlich. Das Berliner Zentrum f¨ ur Neutronenstreuung (BENSC) am Hahn-Meitner-Institut ist im Rahmen des 2006 angelaufenen ADSO-SE (Adsorption Sample Environment) Projekts bem¨ uht, Probenumgebungen f¨ ur einen m¨ oglichst großen Teil der nachgefragten Anforderungen an derartige Neutronenexperimente zur Verf¨ ugung zu stellen. Dazu geh¨ oren verschiedene Probenst¨ abe f¨ ur die vorhandenen Orange-Kryostaten, die zusammen mit einem automatisierten Gasverteilungssystem die M¨ oglichkeit zur volumetrischen Bef¨ ullung einer Probenzelle u ¨ber Kapillaren im Temperaturbereich von 2 K-450 K und bei Dr¨ ucken von bis zu 200 bar zul¨ asst. Um Neutronenuntersuchungen trotz der teilweise sehr zeitaufw¨ andigen, volumetrischen Kondensationsmethoden sehr effizient zu gestalten, werden M¨ oglichkeiten zur gleichzeitigen Pr¨ aparation mehrer Proben in Verbindung mit einem Probenwechsler vorgestellt. Weiter sind im Zusammenhang mit dem ADSO-SE die Entwicklung von geregelten Feuchtigkeitszellen kombiniert mit einer gravimetrischen Messung der aufgenommen Feuchtigkeitsmenge, die Bereitstellung von Durchflusskontrollierten Zellen mit konstanter Druckumgebungen sowie der Aufbau einer Wasserstoffgeeigneten Hochdruckzelle f¨ ur Dr¨ ucke bis ca. 10 kbar vorgesehen.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P89

Konstruktion eines Textur/Pulver-Flugzeitdiffraktometers am FRM-II ¨fer1 Jens M. Walter1 , Harald Conrad2 , Wolfgang Scha 1

Mineralogisch-Petrologisches Institut der Universit¨ at Bonn, Aussenstelle am Forschungszentrum J¨ ulich, MIN/ZFR, D-52425 J¨ ulich – 2 Institut f¨ ur Festk¨ orperfoschung, Forschungszentrum J¨ ulich, D-52425 J¨ ulich Auch nach Beendigung der Messm¨ oglichkeiten am J¨ ulicher Forschungsreaktors FRJ-2 besteht insbesondere bei den Geowissenschaften und der Festk¨ orperchemie ein großer Bedarf an einem Textur- und Pulverneutronendiffraktometer, das auf eine mittlere Aufl¨ osung und hohe Intensit¨ at optimiert ist. Die Osthalle am FRM-II in M¨ unchen kann hier aufgrund des ca. 35 m langen Flugweges der Neutronen besonders den experimentellen Anforderungen an die geplanten Probenumgebungen einen idealen Experimentierplatz auf der Basis der Flugzeitmethode liefern. Das Textur/Pulver-Diffraktometer soll allgemein f¨ ur die Materialwissenschaften ausgelegt werden und dabei als Texturdiffraktometer auf die Anforderungen geowissenschaftlicher Fragestellungen optimiert werden. Aufgrund der vorgesehenen horizontalen Strahlteilung des SR5 mit dem J¨ ulicher TOPAS wird in der Konzeption von einer Ausgangsstrahlgeometrie von 48 x 48 mm ausgegangen. Dieser wird mittels eines Strahlkompressors f¨ ur die Puls-Chopper komprimiert und anschließend wieder dekompri¨ miert. Nach dem Puls-Chopper sind noch jeweils ein Band und ein Uberlapp-Chopper geplant. Bei einer Flugl¨ ange von 10 m zwischen Puls-Chopper und Detektoren ergibt sich bei einer Aufl¨ osung von ∆d/d ≤ 5x10−3 eine Pulsfrequenz von 200 Hz und ein Wellenband von 2 ˚ A, das an die entsprechend ben¨ otigten d -Werte anpassbar ist. Das ∆L/L erlaubt damit eine Probengr¨ oße von 2,5 cm im Durchmesser, was eine Voraussetzung f¨ ur die u ¨blicherweise grobk¨ ornigen polyphasen geologischen Proben ist. F¨ ur Pulvermessungen im mm3 -Bereich ist ein vom Puls-Chopper weiter fokussierender Leiter geplant, der mit dem dekomprimierenden Leiter alternierend eingebaut werden kann. Die ortsaufl¨ osenden Detektoren befinden sich dabei in R¨ uckstrahlung auf einem Debye-Scherrer Kegel. Als zweiter Probenort soll eine Hochdruckzelle f¨ ur extreme Bedingungen (25 GPa, 3000 K) im Strahl plaziert werden k¨ onnen. Das Flugzeit-Multidetektorsystem ist auf minimale Probenrotationen ausgelegt, so dass auch experimentelle Probenumgebungen, wie Scherzellen, uniaxiale Lastrahmen, HT/HP-Autoklaven und zus¨ atzlich Radiographieuntersuchungen m¨ oglich werden. Die Pulverdiffraktometrie soll in den Bereichen 0,3 - 1500 K und bis 7 Tesla durchgef¨ uhrt werden k¨ onnen.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P90

The structure of liquids studied by resonant x-ray emission and absorption spectroscopy in the soft x-ray range Markus Weigand1 , Oliver Fuchs1 , Florian Maier1 , Eberhard Umbach1 , ¨ r3 , Michael Zharnikov2 , Michael Grunze2 , Lothar Weinhardt3 , Marcus Ba 3 4 Clemens Heske , Jonathan Denlinger 1

Exp. Physik II, Universit¨ at W¨ urzburg, D-97074 W¨ urzburg – 2 Angew. Physikal. Chemie, Universit¨ at Heidelberg, D-69120 Heidelberg – 3 Dept. of Chemistry, University of Nevada, Las Vegas, NV 89154-4003, USA – 4 Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA We have used resonant x-ray emission spectroscopy and x-ray absorption spectroscopy in the soft x-ray range to study liquids. Employing these techniques to liquids is a technically challenging task requiring a third-generation synchrotron source combined with a high-efficiency grating spectrometer, and, last but not least, a liquid cell with an ultra-thin window separating the liquid from the vacuum. Recently several groups have started experiments with custom-made static cells. To overcome the problems of these designs with beam-induced effects like gas bubbles and the precipitation of material on the window, we have developed a flow-through liquid cell. In our design the liquid in the probing volume is exchanged several times per second thus avoiding such effects. Furthermore, it allows a fast switching of the investigated liquid, a change of the concentration of a solved component, and the variation of the temperature within the probed volume. With this cell we have investigated the structure of various liquids including H2 O, D2 O, NaOH, NaOD, acetic acid, and various aqueous solutions under well-defined conditions. Our high-resolution spectra reveal details on the hydrogen bonding network of water and its temperature-dependence. These spectra allow a direct determination of the number of intact hydrogen bonds per molecule as a function of temperature. Moreover, the different dynamics of H2 O and D2 O lead to pronounced isotope effects, which are also present in the spectra of OH− and OD− ions. The technical design of a new XES spectrometer and of the flow-through liquid cell as well as new results on various liquids will be presented. (financed by BMBF under contract no. 05KS4WWA/6 und 05KS4VHA/4)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P91

R¨ ontgen-Gitterinterferometrie: Funktionsweise und Anwendungen Timm Weitkamp1 , Christian David2 , Ana Diaz2 , Oliver Bunk2 , Franz Pfeiffer2 , Marco Stampanoni2 , Eric Ziegler3 , Luca Peverini3 1

Inst. f. Synchrotronstrahlung / ANKA, Forschungszentrum Karlsruhe, Postfach 36 40, D-76021 Karlsruhe – 2 Paul Scherrer Institut, CH-5232 Villigen PSI – 3 European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Gitter-Interferometrie f¨ ur harte R¨ ontgenstrahlung ist eine relativ junge Entwicklung [1,2]. Sie erm¨ oglicht quantitative Phasen-Tomographie und -radiographie [3] mit Strahlung von begrenzter Koh¨ arenz bei großen Gesichtsfeldern [4]. Im Vergleich zu anderen interferometrischen Methoden zeichnet sie sich weiterhin durch einen einfachen Aufbau (Abb. 1) mit hoher mechanischer Stabilit¨ at aus. Durch eine geeignete Erweiterung des Aufbaus kann ein Gitter-Interferometer auch effizient mit Strahlung aus herk¨ ommlichen R¨ ontgenr¨ ohren (etwa einer Drehanode) und sogar mit Neutronen benutzt werden [4,5,6]. Außer f¨ ur Radiographie und Tomographie ist die Methode u. a. zur Charakterisierung von Wellenfronten und/oder r¨ ontgenoptischen Bauelementen geeignet [7]. Die Pr¨ asentation zeigt die Funktionsweise eines Gitterinterferometers auf, stellt dessen Leistungsmerkmale in den Kontext bereits existierender Phase-imaging-Methoden und zeigt Demonstrationsbeispiele f¨ ur Anwendungen. [1] C. David, B. N¨ ohammer, H. H. Solak, and E. Ziegler, Appl. Phys. Lett. 81 (2002) 3287. [2] A. Momose, S. Kawamoto, I. Koyama, Y. Hamaishi, K. Takai, and Y. Suzuki, Jpn. J. Appl. Phys. 42 (2003) L866. [3] T. Weitkamp, A. Diaz, C. David, F. Pfeiffer, M. Stampanoni, P. Cloetens, Opt. Express 13 (2005) 6296. [4] F. Pfeiffer, T. Weitkamp, O. Bunk, and C. David, Nature Physics 2 (2006) 258. [5] F. Pfeiffer et al., in Vorbereitung. [6] C. David, F. Pfeiffer, and T. Weitkamp, Europ. Patentantrag EP05012121, Eingangsdatum 6. Juni 2005. [7] T. Weitkamp, B. N¨ ohammer, A. Diaz, C. David, and E. Ziegler, Appl. Phys. Lett. 86 (2005) 054101.

Abb. 1: Gitterinterferometrische Radiographie. Links: Schematischer Aufbau. Mitte: Detail eines rekonstruierten Phasenbildes (Bein einer Spinne). Rechts: Nichtinterferometrisches Bild derselben Probe.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P92

The FLASH high-resolution monochromator beamline ¨ fer1 , Michael Martins1 , Jon Tobias Hoeft1 , Martin Beye1 , Michael Wellho Florian Sorgenfrei1 , Wilfried Wurth1 1

Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg, Luruper Chaussee 149, 22761 Hamburg FLASH at DESY is the first SASE Free electron laser user facility dedicated to delivering extremely short VUV laser pulses of 20-200 fs duration with very high radiation energy in the range of few ten microjoules per pulse. It is a powerful tool for molecular and cluster dynamics investigations, ionization and fragmentation experiments. The intrinsic energy resolution of the VUV-FEL is in the order of 1 %, which is not sufficient for quite a number of applications. To make this machine available for a broader range of questions two high resolution monochromator beamlines were prospected of which one is in operation since June 2005. The layout of the monochromator follows the design of Follath and Senf [1] employing a plane grating monochromator using collimated light with an SX700 pre-mirror grating optic. For all optical components Diamond-Like-Carbon (DLC) coatings are used to withstand the high power density of FLASH. The monochromator is equipped with two gratings (200 and 1200 lines/mm) to cover the energy range from 20 eV to 1000 eV photon energy. Hence, the monochromator covers the whole energy range from the first harmonic up to the fifth harmonic of FLASH. In particular for experiments on non linear processes in the soft x-ray region the statistical nature of the SASE process is critical. Even when the total intensity of two different FEL puls is similar, the peak intensity might differ significantly. However, for non-linear processes the peak intensity and not the integrated intensity of the FEL pulses is important. Thus, a special monochromator option exists to use the zeroth order from the monochromator grating for experiments and to analyse FEL pulses in first order. The zeroth order, which normally is absorbed in the beamdump, can be used in a dedicated zeroth order beamline PG0 simultaneously with the first order in PG2. First experiments have been performed using this unique setup on the photoemission of rare gas atoms. The photoelectron spectra have been measured using time-of-flight (TOF) photo-electron spectrometers. In the linear region in both channels the same FEL spectrum should be measured. Thus, in the case of a simple electronic structure, e. g. the He 1s, the photoelectron spectrum can be used as a probe to measure the SASE spectrum of each FEL puls. This method will also be suitable as an online diagnostic tool for the upcoming X-FEL. [1] R.Follath and F.Senf, Nucl.Instrum.Methods A390, 388 (1997)

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P93

Status und zuk¨ unftige experimentelle Weiterentwicklung der XAFS Spektroskopie am DORIS III Speicherring Edmund Welter1 , Wolfgang Drube1 , Karen Rickers-Appel1 1

Hamburger Synchrotronstrahlungslabor am Deutschen Elektronen Synchrotron, Notkestraße 85, 22607 Hamburg, Germany Derzeit werden am HASYLAB am Speicherring DORIS III drei Messpl¨ atze f¨ ur R¨ ontgenabsorptionsspektroskopie (XAFS) betrieben. Die Hauptanwendungen kommen aus den Bereichen Katalyse, Materialforschung und Umweltforschung. Insbesondere im Bereich der Katalyse werden auch immer wieder Experimente von industriellen Nutzern durchgef¨ uhrt. Die Messpl¨ atze A1 und E4 sind gut ausgebucht, der Messplatz X1 ist stark u ¨berbucht; die Hauptgr¨ unde daf¨ ur sind der grosse Energiebereich (7-100 keV) und die sehr gute Infrastruktur f¨ ur in-situ Experimente. Um die Nachfrage der Nutzer zu befriedigen und den X1 zu entlasten wurde in den letzten 12 Monaten der Messplatz C1 in einen XAFS Messplatz umgebaut. Dort kann mit Hilfe eines neuartigen Doppelkristall-Monochromators der Energiebereich 2,4 44 keV abgedeckt werden. Ausserdem steht die f¨ ur in-situ Experimente notwendige Infrastruktur zur Verf¨ ugung. Am Messplatz A1 soll ein fokussierender Spiegel eingebaut werden, um den Fluss etwa um den Faktor 10 zu erh¨ ohen und um den Arbeitsbereich nach unten bis zur Schwefel K-Kante bei 2.4 KeV auszuweiten. Nach Fertigstellung dieser Umbauten wird der E4 geschlossen werden. Wir werden die aktuellen M¨ oglichkeiten f¨ ur XAFS Experimente darstellen und dabei insbesondere den neuen Messplatz C1 vorstellen. Ausserdem soll die zuk¨ unftige Perspektive der XAFS Spektroskopie nach der Inbetriebnahme von PETRA 3 vorgestellt werden. Den meisten XAFS Anwendungen ist gemeinsam, dass sie keine hohe Brillianz ben¨ otigen. Auch wenn es eine Reihe spezieller Anwendungen gibt, die von den einzigartigen Eigenschaften einer modernen Drittgenerationsquelle profitiert, ist auch in Zukunft f¨ ur die Mehrzahl der XAFS Experimente der Einsatz eines Wigglers oder Ablenkmagneten an einer flussorientierten Quelle mit breitem kontinuierlichem Emissionspektrum und großem Strahldurchmesser wie DORIS III optimal. Nach der Inbetriebnahme von PETRA 3 k¨ onnte am DORIS Speicherring zus¨ atzlich ein Wigglermessplatz f¨ ur XAFS Messungen genutzt werden. Das Konzept eines solchen zuk¨ unftigen Messplatzes soll vorgestellt werden.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P94

Das Reflektometer ADAM Maximilian Wolff1,2 , Hartmut Zabel1 1

Ruhr-Universit¨ at Bochum – 2 Institut Laue-Langevin, Grenoble, Frankreich

Das von der Ruhr-Universit¨ at Bochum betriebene, winkeldispersive Reflektometer ADAM am Institut Laue-Langevin (ILL, Grenoble, Frankreich) bietet durch die Kombination von hohem Neutronenfluss, hervorragender Q-Aufl¨ osung und vollst¨ andiger Polarisationsanalyse weltweit einzigartige M¨ oglichkeiten f¨ ur die Untersuchung von Grenzfl¨ achen und D¨ unnschichtsystemen. Seit der Einweihung des Instrumentes vor 10 Jahren wurden zahlreiche Innovationen implementiert um stets auf dem neuesten Stand in der Neutronenreflekometrie zu bleiben bzw. das Potenzial vorher nicht realisierter technischer Neuentwicklungen zu testen. Beispielsweise wurde ein positionsempfindlicher Detektor mit effizienter Ausleseelektronik installiert der nicht nur diffuse Streuung sondern auch Kleinwinkelstreuung unter streifendem Einfall zug¨ anglich macht. Der Fluss wurde durch den Einbau eines neuen Monochromators optimiert. Die Polarisationsanalyse wurde u ¨ber den gesamten positionsempfindlichen Detektor ausgeweitet und auf kontaktfreie Spinflipper umgestellt. Außerdem stehen unterschiedlichste, auf das Instrument optimierte, Probenumgebungen wie Elektromagnet (bis 0.8 T), Kryostat (10 bis 400 K), Gasbeladungszellen, und verschiedene Scherzellen zur Verf¨ ugung. Die nachhaltigen Anstrengungen bei der Weiterentwicklung und Optimierung des ADAM Reflektometers haben zu zahlreichen wissenschaftlichen H¨ ohepunkten gef¨ uhrt. Um weiter Spitzenforschung im Bereich Neutronenreflektometrie betreiben zu k¨ onnen, neue Messemethoden zug¨ anglich zu machen und gegen¨ uber neueren Instrumenten konkurrenzf¨ ahig zu bleiben, planen wir die Neukonstruktion des Reflektometers mit dem Schwerpunkt in magnetischer Streuung. Das Instrument wird weltweit einzigartige M¨ oglichkeiten f¨ ur die Untersuchung magnetischer D¨ unnschichtsysteme bieten. Der Fluss des winkeldispersiven Reflektometers wird durch einen neuen Standort mit neuem Neutronenleiter und verbessertem Wellenl¨ angenfilter deutlich erh¨ oht. Wellenl¨ angen zwischen 4 bis 5 ˚ A werden flexibel mit einer Aufl¨ osung von 0.5 und 6 % angeboten. Ein großer, effizienter und optimiert abgeschirmter Fl¨ achendetektor erlaubt das simultane Messen von Reflektivit¨ at und Kleinwinkelstreuung (GISANS). F¨ ur die Polarisationsanalyse u ¨ber den gesamten positionsempfindlichen Detektor stehen ein 3 He Analysator und kontaktfreie Flipper zur Verf¨ ugung. Dar¨ uber hinaus ist eine 3D Polarisationsanalyse geplant. Ein fokusierender Leiter wird sehr kleine Proben (1 mm2 ) zug¨ anglich machen. Eine zus¨ atzliche Option bilden pump-probe Experimente f¨ ur inelastische Prozesse und ein Kryostat mit einem supraleitenden Magneten f¨ ur Felder bis 5 T. ¨ In unserem Beitrag geben wir einen kurzen Uberblick u ¨ber k¨ urzlich erzielte, bereits publizierte, Ergebnisse die an ADAM erzielt wurden und pr¨ asentieren die Charakteristika und das Layout des neu geplanten Instrumentes.

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P95

Micro X-ray diffraction imaging of bulk polycrystalline materials Thomas Wroblewski1 , Andre Rothkirch1 , Bernd Hasse2 , A Bjeoumikhov3 1

DESY-FS, Notkestr. 85, 22607 Hamburg – 2 Ernst-Reuter-Platz 1 – 3 IfG, Rudower Chaussee 29/31, 12489 Berlin The Materials X-ray Imaging (MAXIM) method allows the imaging of polycrystalline materials using the diffracted radiation. It applies a bundle of parallel tubes in front of a position sensitive detector (PSD). These tubes suppress cross fire of the radiation diffracted at different sample locations. Therefore, an image of the radiation diffracted in the direction parallel to the tubes is obtained. A dedicated instrument for MAXIM investigations was realized at HASYLAB beam line G3. The experimental setup consists of a micro channel plate (MCP) as collimator array in front of a directly illuminated CCD. The MCP currently used has a thickness of 4 mm and channels of 10 µm diameter with a centre to centre distance of 12.5 µm. The resulting angular acceptance is 2.5 mrad. The spatial resolution is given by this acceptance times the sample to CCD distance. At 5 mm (including the 4 mm MCP thickness) this resolution matches the pixel size of the CCD of 13 µm. The MAXIM technique has been applied in several investigations of materials including the determination of strain and texture but also dynamical effects like recrystallization have been studied. With the setup realized at beam line G3 the usable X-ray energy range is restricted to energies below 12 keV by the limited absorption of both the CCD and the MCP. Therefore, in most materials only the near surface region can be investigated. Furthermore, the MCP/CCD combination can only be used in the wide angle scattering regime. At small angles the CCD would move into the primary beam due to the small sample to detector distance required for high spatial resolution. Recently long bundles of glass capillaries became available opening the possibility to increase the sample to detector distance without loosing resolution. The polycapillaries used had a length of 300 mm and diameters of 30 µm and were arranged in a hexagonal array of 8distance between opposing sides. First successful studies were performed at HASYLAB beam line G3 using the diffractometer usually applied for MAXIM investigations. They included small angle scattering on polymers at 8 keV [3] and bulk diffraction on an Al-tube with a flat beam at 26 keV [4]. A dedicated instrument for bulk diffraction imaging and tomography (DITO) is planned at beam line W2 (HARWI II). Another possibility to investigate bulk properties is the application of neutrons. In this case capillary arrays of boron silicate showing a high absorption for neutrons can be applied in combination with a position sensitive neutron detector like a Li6 glass scintilator coupled to a position sensitive photomultiplier [5]. [1] T. Wroblewski, et al., Rev. Sci. Instrum. 66 (1995) 3560-3562 [2] T. Wroblewski, et al., Nucl. Instrum. Meth. A428 (1999) 570-582 [3] T. Wroblewski, A. Bjeoumikhov., Nucl. Instrum. Meth. A521 (2004) 571-575 [4] T. Wroblewski, A. Bjeoumikhov., Nucl. Instrum. Meth. A538 (2005) 771-777 [5] T. Wroblewski, et al., Nucl. Instrum. Meth. A423 (1999) 428-434

Methoden und Instrumentierung

Poster: Mi., 14:00–16:30

M-P96

Neutron strain scanning - Monte-Carlo based approach to the first millimeter Frederik Zilly1 , Robert Wimpory1 , Rainer Schneider1 , Klaus-Dieter Schotte2 1

Hahn-Meitner-Institut Berlin, Glienicker Straße 100, 14109 Berlin, Germany – Fachbereich Physik der Freien Universit¨ at Berlin, Institut f¨ ur Theoretische Physik, Arnimallee 14, 14195 Berlin, Germany 2

Neutrons usually are used for residual stress analysis starting from approx. 1 mm below the components surface. Their restriction for the near-surface regime is due to the limited size of the gauge-volume, the beam divergency and the geometrical effects when the gauge volume is touching the components surface and a wavelength gradient. Recently several successful approaches to explore the near surface region have been published. Here a full simulation of the neutron diffractometer is used for calibration of near-surface measurements. Detailed monte-carlo simulations of an angular dispersive neutron diffractometer for residual stress analysis are presented. Theoretical calculations validated by measurements of standard samples lead to correction terms for a partially filled gauge-volume. Geometrical effects of a shifted point of mass of the scattering volume due to a surface crossing the gauge volume can be numerically calculated. Absorption effects and a given wavelength distribution as well as the beam divergency and the slit distances are taken into account. The simulation is done using the McStas framework for neutron simulations. The reference system for the simulation is the E3 neutron diffractometer at the HMI Berlin. Geometrical and physical properties of the E3 are known and used as parameters for the simulation to ensure a maximum reliability of the simulation. The samples geometrical shape can be taken into account. Also, a phase-dependant orientation distribution function for the crystallites can be given as parameters for the simulation. This way, single crystals, powders and textured materials can be simulated using the same algorithms. The data analysis is done using the same tools as they are used for the E3 data produced by the CARESS environment, i.e. TVTueb. This way, it is easy to compare the data produced by the simulation with the experiments data. Experimental data of a simple with residual stress can be compared with a simulated powder sample of same shape. This way, when permorming a near-surface scan, where the gauge-volume is partially filled and the peak-shifts due to geometrical effects are high, the simulation helps to identify, which shift is due to geometrical effects. The remaining peak-shift can then be identified as a result of residual stress.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P97

New developments in synchrotron radiation based microtomography (SRµCT) at DESY and neutron tomography (NCT) at GKSS ¨rgen Vollbrandt1 , Felix Beckmann1 , Tilman Donath1 , Jens Fischer2 , Ju 1 1 Heinz-Werner Schmitz , Thomas Dose , Thomas Lippmann1 , Lars Lottermoser1 , Rene V. Martins1 , Andreas Schreyer1 1

GKSS-Research Center, Geesthacht, Germany – 2 Hannover Medical School, Hannover, Germany The GKSS-Research Center Geesthacht, Germany, is operating the user experiment for microtomography using synchrotron radiation at the storage ring DORIS 3 at DESY Hamburg. In the last two years the beamline W2 was rebuilt. The outstanding feature of this synchrotron radiation beamline HARWI 2 is the use of high energy X-rays from 20 to 250 keV for materials science experiments. The new features for microtomography at HARWI 2, new enhancements and applications using lower photon energies at the wiggler beamline BW2 will be given. Furthermore at the research reactor FRG-1 the neutron radiography facility GENRA 3 was recently extended by a setup for neutron tomography. First results performing SRµCT at HARWI 2 and NCT at GENRA 3 will be presented. The combination of neutron and synchrotron radiation techniques will give new insight into the three-dimensional behavior of samples in materials science.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P98

The new multipurpose tomography setup at the GKSS material science beamline at HASYLAB/DESY Oliver Brunke1 , Stefan Odenbach1 , Bernd Hasse2 , Felix Beckmann3 1

TU Dresden, Lehrstuhl f¨ ur Magnetofluiddynamik, 01062 Dresden – 2 TU Berlin, Institut f¨ ur Materialwissenschaften und Technologien, 10587 Berlin – 3 GKSSForschungszentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht State of the art tomography systems at synchrotron sources nowadays offer outstanding possibilities with respect to e.g. spatial resolution or density discrimination. Another important feature of synchrotron-based tomography is the reduction of the scanning time down to a few seconds for a whole tomographic dataset which is in principle possible due to the high brilliance of the source. CCD-detectors and computer hardware which are fast enough to fulfil the requirements become available nowadays and with this the developments of new setups begin to emerge. A reduction of the scanning time to short scanning periods offers new experimental possibilities e.g. for so called 4D which means in-situ time dependent dynamic tomography examinations. Furthermore, due to the reduction of the radiation dose, in-vivo biomedical studies will become available at synchrotrons sources. In order to achieve the possibilities for these dynamic studies we have developed a new multipurpose tomography system which is currently installed at the high energy material science beamline HARWI-2 at HASYLAB/DESY in Hamburg/Germany. The beam characteristics with a geometric cross section of up to 10x80 mm2 and the energy range of 20-200 keV offers a wide spectrum for the analysis of samples with a high diversity in absorption and geometry. The detector characteristics will allow scanning times of below 5 s for a complete dataset at about 20 microns spatial resolution using a monochromatic beam. The maximum spatial resolution is about 2 microns. A special feature of the system is the possibility to perform simultaneous spatially resolved diffraction and tomography measurements. Thus the system will allow the determination of e.g. the residual strain map and the 3D morphology of a sample during a single experimental scan. In our poster we will demonstrate the key features of our system as well as first preliminary results.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P99

In-situ Synchrotron Tomographie des partikelverst¨ arkten Verbundwerkstoffes AA6061 mit 22 % Al2O3 unter Kriechbedingungen Bettina Camin1 , Michael Huppmann1 , Anke Pyzalla2 , Marco di Michiel3 , Thomas Buslaps3 , Walter Reimers1 1

TU Berlin, Institut f¨ ur Werkstoffwissenschaften und -technologien, Metalle Werkstoffe, Sekr. BH18, Ernst-Reuter-Platz 1, 10587 Berlin – 2 Max-Planck-Institut f¨ ur Eisenforschung, D¨ usseldorf – 3 European Synchrotron Radiation Facility, Grenoble, Frankreich

Erh¨ ohte Temperatur und anliegende mechanische Spannung ist ein typisches Beanspruchungsprofil f¨ ur bewegte Bauteile in Motoren, Turbinen etc. Dieses Beanspru¨ chungsprofil f¨ uhrt zu Anderungen der Werkstoffmikrostruktur, die lebensdauerbegrenzend sein k¨ onnen. Um hier Verbesserungen zu erzielen, werden die metallischen Matrizes mit keramischen Hartpartikeln (MMC) verst¨ arkt. Die gezielte Optimierung der MMC hinsichtlich Anzahl der Partikel (Morphologie und Gr¨ oße) und Volumenanteil erfordert Informationen u ¨ber die Versagensmechanismen unter verschiedenen Last-Temperaturbedingungen. Hierzu liefert die in situ Synchrotron-R¨ ontgentomographie [1] entscheidende Beitr¨ age. Eine f¨ ur den Einsatz am Synchrotron entwickelte Miniatur-Kriechapparatur (Abb. 1) erm¨ oglicht in-situ-Messungen [2]. MitAbb. 1: In-situ Kriechapparatur tels Synchrotronstrahlung (Beamline ID15A, ESRF) k¨ onnen Materialvolumina bis zu 1 mm3 bei einer Aufl¨ osung bis zu 1 µm3 untersucht werden. Die zur Festigkeitssteigerung stranggepresste und anschließend w¨ armebehandelte Aluminiumlegierung AA6061 (AlMg1SiCu) wurde mit 22 % Al2 O3 partikelverst¨ arkt. Die Al2 O3 -Partikel (Gr¨ oße∼ 12 µm) besitzen eine irregul¨ are Form und sind in der metallischen Matrix homogen verteilt. Das stabile Aluminiumoxid wird in der Anwesenheit von Mg>1 % in der Matrix bzw. bei h¨ oheren Temperaturen instabil und bildet Al2 MgO4 (spinel). Diese Interface-Reaktion kann bei mechanischer und thermischer Belastung zur Losl¨ osung der Partikel von der Matrix f¨ uhren. Im Kriechversuch wurde AA6061 (22 % Al2 O3 ) mit verschiedenen Spannungen und Temperaturen beaufschlagt. Im Beanspruchungsprofil kleine Last/ hohe Temperatur tritt Porenbildung am Interface Partikel/ Matrix auf und f¨ uhrt zum Versagen. Demgegen¨ uber wird das Versagen im Beanspruchungsprofil hohe Last/ niedrige Temperatur eingeleitet durch Partikelbr¨ uche. [1] J. Baruchel et al., Hermes Science Publications, Paris 2000 [2] A. Pyzalla, B. Camin, T. Buslaps, M. di Michiel, H. Kaminski, A. Kottar, A. Pernack, W. Reimers, Science 308, 92 (2005)

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P100

Mikrotomographische Analyse und FE-Simulation von MMC-Verbundwerkstoffen unter Last Horst-Artur Crostack1 , Jens Nellesen1 , Gottfried Fischer2 , Siegfried Schmauder3 , Ulrich Weber3 , Felix Beckmann4 1

Universit¨ at Dortmund, Fakult¨ at Maschinenbau, Lehrstuhl f¨ ur Qualit¨ atswesen, D44221 Dortmund – 2 RIF e.V., Joseph-von-Fraunhofer-Str. 20, D-44227 Dortmund – 3 Universit¨ at Stuttgart, Institut f¨ ur Materialpr¨ ufung, Werkstoffkunde und Festigkeitslehre, Pfaffenwaldring 32, D-70569 Stuttgart – 4 GKSS-Forschungszentrum, MaxPlanck-Str. 1, D-21502 Geesthacht Gef¨ uge¨ anderungen wie Mikroverformungen und -sch¨ adigungen, die durch Zugbelastung verursacht werden, gehen dem makroskopischen Bruch eines Bauteils voraus. Um zum Verst¨ andnis dieser Prozesse beizutragen, werden Gef¨ ugebereiche von Zugproben auf verschiedenen Verformungsstufen mikrotomographisch abgebildet und das Verhalten dieser Gef¨ ugeausschnitte mit Hilfe der FE-Methode simuliert. Die Zugproben bestehen hierbei aus partikelverst¨ arkten Metallmatrixverbundwerkstoffen (wie bspw. Kobalt/Diamant oder Al/TiN), welche pulvermetallurgisch hergestellt werden. Tomogramme eines Teilvolumens des Zugprobenstegs werden aus Projektionsdaten rekonstruiert, die in verschiedenen Verformungszust¨ anden genommen werden. Zur Datenerhebung werden sowohl ein mit einer Mikrofokusr¨ ontgenr¨ ohre ausgestatteter Computertomograph als auch ein R¨ ontgentomographiemikroskop verwendet, das unter Verwendung monochromatischer Synchrotronstrahlung betrieben wird. Mit Hilfe von 3D-Datenverarbeitung werden die Tomogramme in 3D-Oberfl¨ achennetze u ¨berf¨ uhrt, die ausschließlich aus Dreiecken bestehen und die die Grenzfl¨ achen der Phasen des Verbundwerkstoffes beschreiben. Diese Netze werden anschließend hinsichtlich der Anzahl und Form der Dreiecke optimiert. Ausgehend von diesen Oberfl¨ achennetzen, welche als Keimfl¨ achen dienen, wird ein l¨ uckenloses, nur aus Tetraedern bestehendes 3D-FE-Netz aufgebaut. Die 3D-FE-Simulationen werden sowohl unter Verwendung von willk¨ urlichen als auch realistischen Randbedingungen durchgef¨ uhrt. Realistische Bedingungen werden mit Hilfe einer iterativen Korrespondenzanalyse zwischen Tomogrammen desselben Gef¨ ugebereiches in verschiedenen Verformungsstadien gewonnen. Die Effekte der Netzfeinheit und des Typs des finiten Elements (Tetraeder oder Hexaeder) auf die simulierten Spannungsverteilungen werden diskutiert. Das Auftreten und die Entwicklung von plastischen Zonen in der Matrix in Abh¨ angigkeit der außen aufgebrachten Verschiebungsfelder wird in den Simulationen studiert. Die Orte der errechneten maximalen Spannungen werden mit den im Tomogramm gefundenen Positionen der Rissentstehung verglichen.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P101

Quantitative synchrotron radiation based x-ray microtomography Tilman Donath1 , Felix Beckmann1 , Andreas Schreyer2 1

GKSS Research Center, Institute for Materials Research, GKSS at DESY, Notkestr. 85, 22607 Hamburg – 2 GKSS Research Center, Institute for Materials Research, MaxPlanck-Straße, 21502 Geesthacht X-ray microtomography (µCT) is a method for 3D imaging of objects at spatial resolution of around one micrometer. In µCT, the volume structure, more precisely, the distribution of the x-ray attenuation coefficient is reconstructed from 2D projection images. The unique properties of synchrotron radiation (SR), especially the small bandwidth available in monochromated beams, enable the precise determination of the attenuation coefficient in synchrotron radiation based microtomograhy (SRµCT). To make full use of the capabilities of SR radiation, the recorded data must be properly processed. New developments of the x-ray detector design and the reconstruction chain have been made. Especially, a new method for the determination of the center of rotation in the recorded data is presented [1]. Examples of quantitative measurements performed at the Hamburger Synchrotronstrahlungslabor (HASYLAB) at the Deutsches Elektronen-Synchrotron (DESY) are given. This contribution summarizes part of the first author’s PhD thesis. [1] T. Donath, F. Beckmann, and A. Schreyer. Automated determination of the center of rotation in tomography data. J. Opt. Soc. Am. A, 23(5):1048–1057, 2006.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P102

Mikroskopie mit niederenergetischen gepulsten Positronenstrahlen ¨ gel1 , Gu ¨nther Dollinger1 Werner Egger1 , Peter Sperr1 , Gottfried Ko 1

Institut f¨ ur Angewandte Physik und Messtechnik, Universit¨ at der Bundeswehr M¨ unchen, Werner-Heisenberg-Weg 39, D-85577 Neubiberg Positronen sind ideale Sonden zur zerst¨ orungsfreien Untersuchung von leerstellenartigen Defekten im Festk¨ orper. Aus Positronenlebensdauermessungen erh¨ alt man Information u ¨ber Art und Konzentration von Leerstellen, Leerstellenclustern und Versetzungen. Konventionelle Positronenannihilationsmethoden erlauben jedoch keine tiefenselektive Zuordnung der Defekte, da u ¨ber makroskopische Volumina gemittelt wird. Zudem beschr¨ ankt S¨ attigungseinfang der Positronen in einem Defekt die M¨ oglichkeit zur Bestimmung der Defektkonzentration. Diese Nachteile werden durch den Einsatz gepulster, niederenergetischer Positronenstrahlen zur Lebensdauermessung weitgehend beseitigt. Mit gepulsten Positronenstrahlen variabler Energie k¨ onnen Tiefenaufl¨ osungen im Nanometerbereich erzielt werden. Aus Tiefenprofilmessungen kann zudem selbst bei S¨ attigungseinfang die Defektkonzentration ermittelt werden. An der Universit¨ at der Bundeswehr in M¨ unchen wurden zwei gepulste Positronenstrahlsysteme zur Lebensdauermessung entwickelt: Die gepulste Positronenquelle PLEPS [1] zur Tiefenprofilierung von Defektverteilungen, sowie das Rasterpositronenmikroskop SPM [2] mit einer zus¨ atzlichen lateralen Aufl¨ osung von derzeit 2 µm. Mit beiden Systemen wurden unter anderem Defektverteilungen in der N¨ ahe von Rissoberfl¨ achen in Aluminiumlegierungen und in reinem Kupfer, die von Erm¨ udungsund Gewaltbr¨ uchen herr¨ uhren, erfolgreich untersucht [3,4]. Dabei konnte anhand der Positronenlebensdauer quantitativ zwischen Gewalt- und Erm¨ udungsbruch unterschieden werden: Neben hohen Vesetzungsdichten wurden in der N¨ ahe von Erm¨ udungsrissen auch Leerstellencluster nachgewiesen. Bei Gewaltbr¨ uchen wurde hingegen nur eine hohe Versetzungsdichte in Rissn¨ ahe beobachtet. Beide Strahlsysteme werden zur Zeit an die Hochflusspositronenquelle (NEPOMUC) am Forschungsreaktor FRM-II in M¨ unchen transferiert. Eine um den Faktor 104 erh¨ ohte Positronenstrahlintensit¨ at er¨ offnet einzigartige neue M¨ oglichkeiten zur Untersuchung der Defektstruktur in Rissn¨ ahe [5]. [1] W. Bauer-Kugelmann, P. Sperr, G. K¨ ogel, W. Triftsh¨ auser, Mater. Sci. Forum, 363-365 (2001), 529 [2] A. David, G. K¨ ogel, P. Sperr, W. Triftsh¨ auser, Phys. Rev. Lett. 87 (2001) 067402-1. [3] W. Egger, G. K¨ ogel, P. Sperr, W. Triftsh¨ auser, J. B¨ ar, S. R¨ odling, H. J. Gudladt, Z. Metallkunde, 94, (2003), 687 [4] A. Dupasquier, G. K¨ ogel, A. Somoza, Acta Mater., 52, (2004), 4707 [5] G. K¨ ogel, G. Dollinger, Appl. Surf. Science A 252 (2006), 3111

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P103

Texture Development in ECAP Processed Mg Si Alloys by Neutron Diffraction ¨nter Brokmeier2,3 , Bernd Schwebke2,3 , Andreas Weimin Gan1,2 , Heinz-Gu Schreyer2 , Mingyi Zheng1 , Xiaoguang Qiao1 , Shiwei Xu1 , Kun Wu1 1

School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001. P. R. China – 2 GKSS-Forschungszentrum, Geb03, Max-Planck Strasse 1, D-21502, Geesthacht – 3 Institute of Materials Science and Engineering, Clausthal University of Technology, Germany ECAP processing of the as-cast and the as-extruded Mg-Si alloys at different rotation routes A, B(c), and C from 1 pass to 8 passes was performed in the present work. Texture evolution of the deformed samples was measured by neutron diffraction at TEX-2 GKSS. ODF was calculated by series expansion method. For both as-cast and as-extruded Mg-Si alloys, results showed that route A processing, which the sample do not rotated between two passes, got the highest pole intensity in each pole figures; while route Bc processing, which the sample continuously rotated 90◦ between two passes, has the lowest pole density in each pole figures. As for the cast alloys, basal planes tilted about 10◦ around the normal direction after 1 pass deformation; and after 4 passes the intensity increased, but texture type has not changed; 8 passes deformation made the basal planes nearly parallel to the extrusion-transition direction though the pole intensity have not changed. Especially, similar as the Mg alloys rolling texture, which basal planes parallel to the extrusion direction, was formed after 8 passes route C deformation. As for the extruded Mg-Si alloys, two intensity peaks occurred after route B(c) processing, which attributed to the 45◦ back-and-forth shear deformation.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P104

Stereor¨ ontgenmikroskopie zur Untersuchung der Dynamik kolloidaler Systeme ¨rgen Thieme1 , Peter Guttmann2 Sophie-Charlotte Gleber1 , Ju 1

Institut f¨ ur R¨ ontgenphysik, Georg-August-Universit¨ at G¨ ottingen, Friedrich-HundPlatz 1, 37077 G¨ ottingen – 2 Institut f¨ ur R¨ ontgenphysik, Georg-August-Universit¨ at G¨ ottingen, c/o BESSY, Albert-Einstein-Str. 15, 12489 Berlin R¨ ontgenmikroskopie ist wegen ihrer hohen r¨ aumlichen und spektralen Aufl¨ osung ein wichtiges Instrument zur Untersuchung kolloidalen Systeme aus den Umweltwissenschaften in ihrer nat¨ urlichen w¨ assrigen Umgebung. Dabei k¨ onnen Proben von Dicken bis zu 10 µm in Transmission abgebildet werden bei einer Aufl¨ osung von derzeit 20 nm. Bei Aufnahmen mit R¨ ontgenlicht oberhalb und unterhalb einer Absorptionskante kann die jeweilige Elementverteilung in der Probe dargestellt werden. Besonders wichtig f¨ ur das Verst¨ andnis dieser Systeme ist ihr dynamisches Verhalten etwa bei Zugabe anderer Substanzen. Um die Dynamik direkt im R¨ ontgenmikroskop auszul¨ osen und beobachten zu k¨ onnen, sind spezielle Probenhalter entwickelt worden. Bei Aufnahmen unter verschiedenen Kippwinkeln kann mithilfe eines selbst entwickelten Programms zur stereoskopischen Darstellung Information u ¨ber die r¨ aumliche Anordnung kolloidaler Strukturen, z.B. Kollokalisation bestimmter Partikel, sowie u ¨ber deren dynamisches Verhalten gewonnen werden. Die f¨ ur die Tomographie ben¨ otigte Kryofixierung erlaubt diese Art der Untersuchungen nicht.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P105

Wie funktioniert und was kann das Schwerionen-Raster-Mikroskop bei GSI Markus Heiß1 , Bernd Fischer1 , Philippe Barberet1 , Guanghua Du1 1

Gesellschaft f¨ ur Schwerionenforschung, Abt. Materialforschung, Planckstr. 1, 64291 Darmstadt Der Charme eines Schwerionen-Raster-Mikroskops besteht, wie auch bei anderen Rastersonden-Mikroskopen darin, dass beliebig exotische Antworten eines Targets auf einen Ionenbeschuss zur Bilderzeugung verwenden k¨ onnen. Diese Vielfalt wird zus¨ atzlich durch die große Zahl verf¨ ugbarer Elemente erweitert, sodass das Schwerionen-RasterMikroskop speziell mit sehr schweren Ionen sogar als mechanisches Werkzeug verwendet werden kann. In der Pr¨ asentation wird die Funktion des Mikroskops in seiner einfachsten Form beschrieben und dargestellt, welche Anwendungen durch Hinzuf¨ ugen verschiedener Elemente m¨ oglich werden.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P106

Fokussierung harter R¨ ontgenstrahlung mit linearen Off-Axis-Reflexionszonenplatten Sebastian Kalbfleisch1 , Tim Salditt1 1

Institut f¨ ur R¨ ontgenphysik, Georg-August-Universit¨ at G¨ ottingen

F¨ ur viele hochaufl¨ osende Imaging-Experimente mit harter R¨ ontgenstrahlung ist die fokussierende Optik die entscheidende Komponente. Reflexionszonenplatten (RZP) bieten einen vielversprechenden Ansatz, das Prinzip der Fresnelsche Zonenplatten auf harte R¨ ontgenstrahlung zu u ¨bertragen ohne an die Grenzen der Strukturierung zu stoßen [1,2]. Die Off-Axis-Konstruktion trennt den Fokus r¨ aumlich von der spekul¨ ar reflektierten nullten Ordnung der Zonenplatte (Abb. 1). Damit wird die Untergrundstrahlung stark reduziert. Wegen des kleinen Totalreflexionswinkels liegen die Zonenbreiten einer RZP im Bereich einiger Mikrometer und sind daher einfach zu strukturieren. Simulationen zeigen, dass mit diesen Strukturgr¨ oßen Fokusdurchmesser im Bereich von unter 100 nm erreicht werden k¨ onnen (Abb. 2). Wir pr¨ asentieren Untersuchungen zur Auswirkung der Winkel- und Wellenl¨ angenakzeptanz sowie der Substratbeschaffenheit (Ebenheit) auf die Fokusgr¨ oße auf Grundlage von Simulationen, sowie erste experimentelle Ergebnisse mit Off-Axis-Zonenplatten. [1] A.G. Michette et al., Optics Comm. 245 (2005), 249-253 [2] Yu.A. Basov et al., Optics Comm. 109 (1994), 324-327

Abb. 1: Schematischer Strahlengang einer Off-Axis-Refelxionszonenplatte: Fokus und spekul¨ ar reflektierte nullte Ordnung sind r¨ aumlich getrennt.

Abb. 2: Simulation der Fokusgr¨ oße einer Off-Axis-Reflexionszonenplatte: Brennweite 10 cm, λ = 1.54 ˚ A, Halbwertsbreite 87 nm

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P107

Spectromicroscopy studies of colloid systems using cluster analysis Genoveva Mitrea1 , Juergen Thieme1 , Charlotte Gleber1 , Eva Pereiro Lopez2 1

Friedrich Hund Platz 1, 37077 Goettingen Germany – 2 ALBA Synchrotron Light Source, Apartado de Correos 68, 08193 Bellaterra, Barcelona, Spain We report results of first spectromicroscopy experiments that have been performed with the scanning transmission X-ray microscope (STXM) at the electron storage ring BESSY II in Berlin. This instrument has been designed especially for the use with the undulator U41, which supplies it with radiation in the range of 200-600 eV. This energy range has been chosen as the K-absorption edges of carbon, nitrogen and oxygen, as well as the L-absorption edges of potassium and calcium can be used for spectromicroscopy experiments. It is well-known within the field of X-ray microscopy as the so-called water window. The main goal of the STXM at BESSY II is to enable studies of colloidal systems from the environment and from material sciences directly in aqueous media. By finely tuning the energy of the used X-radiation around an absorption edge it is possible to first of all determine the distribution of that element within the sample. Secondly, just before the edge jump in absorption resonance, i.e. below the actual edge energy, resonance features can be observed representing chemical binding states. We have performed first spectromicroscopy experiments with colloidal systems from environmental as well as from material sciences. A soil science wise well-characterized sample from a Chernozem soil with 0.1 % humics has been used, because of its known high organic content (approx. 4 %). Sequences of images, so called stacks are recorded around the carbon edge in the fashion described above. This data set consists in N transmission images in (x, y) taken at N energies EN with P number of pixels each. The doses on each pixel applied when taking a stack is the same as when fixing the position of the X-ray spot on the sample and just taking a spectrum by tuning only the energy. The advantage is the availability of the chemical information within the whole image. The same (x, y, E) data set would have been obtained by acquiring a series of spectra of adjacent pixels. The data sets of the stacks obtained during the experiments have been analyzed using cluster analysis. This algorithm consists of a method of grouping pixels with similar experimentally determined spectra and then analyze the data according to these groups. A principal component analysis representation is priory applied to the data set for noise filtering and orthogonalizing it. Two cluster analysis methods have been involved, so that the pixels are grouped according to their Euclidian distance from a given cluster center, and respectively to their angular distribution with respect to the cluster center. We were able to localize the clay particles reach in potassium inside the soil colloids, as well as the organic domains reach in carbon. Spatially distinctive images of these domains are to be observed together with the corresponding spectra where potassium, respectively carbon absorption edges are lined out.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P108

Phase Sensitive Micro-Tomography With Asymmetric Bragg Reflection ¨bbert2 , Peter Scha ¨fer1 , Rolf Ko ¨ hler1 Peter Modregger1 , Daniel Lu 1

Institut f¨ ur Physik, Humboldt-Universit¨ at zu Berlin, Berlin, Germany – 2 Institut f¨ ur Synchrotronstrahlung, Forschungszentrum Karlsruhe, Germany Using phase information present in a beam after transmission through a sample offers the possibility of reducing the delivered dose while maintaining the visible contrast. Several phase sensivitive imaging techniques have been developed in recent years, among them in-line holography[1], which is now used on a routine base, and analyser based techniques[2] whose feasibility for medical imaging is currently under investigation. Although known for a long time imaging with asymmetric Bragg reflection as magnification optics[3] may be regarded as a further development of analyser based imaging providing two dimensional phase contrast while its two dimensional magnification yields the possibility of using thick fluorescence screens as x-ray to visual photon converter (i.e. commercial CCD-area detectors) thus enhancing detection efficiency at submicrometer resolution. Furthermore, imaging with asymmetric Bragg reflection provides a strong phase contrast and a large field of view on the sample. Recently, our group developed a full theoretical description of the imaging process (including the influences of Bragg reflection and free-space propagation)[4]. This enabled us to verify that a submicrometer resolution limit is achievable, to estimate the minimum detectable phase gradient present in the beam corresponding directly to the minimum detectable density variation in the sample and to understand the influences of beam divergence and dispersion effects. It also provides crucial information about future improvements of the experimental setup. In order to avoid artefacts during tomographic reconstructions phase retrieval algorithms have to be applied to the measured images. Several of these algorithms have been reported in literature differing in the underlying model of contrast formation (i.e. the presence of coherence, absorption or small angle scattering) and thus producing different kinds of quantative information about the sample. Our latest measurements at the ID-19/ESRF beamline will help to identify the most appropriate algorithm in case of magnifying analyser based imaging. Furthermore, we expect to directly measure the maximum achievable resolution limit in experiment for both two dimensional imaging and three dimensional reconstruction. [1] P. Cloetens, Ph.D. thesis, Vrije Universiteit Brussel (1999). [2] D. Chapman et al., Phys. Med. Biol. 42, 2015 (1997). [3] E. F¨ orster, et al., Krist. Tech. 15, 937 (1980). [4] P. Modregger, et al., Phys. Rev. B, submitted.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P109

Regenerated bone tissue and human tooth tissue studied with high resolution synchrotron-tomography ¨ber3 , M. Stiller2 , C. Apel3 , S. Zabler4 , T. A. Rack1 , C. Knabe2 , H. G. Gra Weitkamp1 , G. Weidemann5 , I. Manke4 , J. Goebbels5 1

Forschungszentrum Karlsruhe - ANKA – 2 Charit´e Berlin – 3 RWTH Aachen – 4 HahnMeitner-Institut Berlin – 5 Bundesanstalt f¨ ur Materialforschung und -pr¨ ufung

Fig. 1: Top: ceramic particles (Bioglass, white) as bone substitutes within upper jaw (red, sinus) of a sheep; 12 weeks after implantation. Bottom: deep carious lesion (red arrow) inside a human tooth - dentine in light gray, dental enamel in white.

High resolution synchrotron-tomography investigations on novel rapidly resorbable bone substitutes (ceramics like Bioglass, Cerasorb) and demineralised tooth tissue are reported. The measurements were performed with high spatial resolutions at the storage ring BESSY (BAMline). The use of monochromatic radiation and the application of subsequent 3d image analysis [1] enables us to separate different material phases in the volume data sets, e.g. tissue and ceramics in a reshaping jawbone (fig. 1, top). Quantitative determination of the formation and the structural changes of the bony tissue in a given defect plus the biodegradation of the bone substitute materials within animal and human biopsies 3, 4 and 6 months after implantation were performed. Parallel human tooth samples in different demineralisation stages were imaged as an loss of mineralized tissues (bone and tooth) is the first stage of caries and periodontitis (fig. 1, bottom). The demineralized tissue can be detected in the volume images due to it’s lower density. By quantitative analysis of the data one obtains information about the disease growing’s time-dependence. A comparison of nontreated infected teeth with treated ones (e.g. fluoridation) delivers information about the quality of different regeneration approaches. The aim of current and future research projects is to develop regenerative strategies by means of tissue engineering. [1] J. Ohser and F. M¨ ucklich, Statistical Analysis of Microstructures in Materials Science, John Wiley & Sons, 2000

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P110

Influence of Noise and Partial Coherence on Resolution in Coherent Diffractive Imaging Experiments Andreas Schropp1 , Christian Schroer2 , Ivan Weckert1 , Christian Mocuta3 , Hartmut Metzger3

Vartaniants1 ,

Edgar

1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 Institut f¨ ur Strukturphysik, TU Dresden, D-01062 Dresden, Germany – 3 ESRF, BP 220, F-38043 Grenoble Cedex, France Coherent X-ray diffraction imaging (CXDI) [1] is a suitable method to determine the structure of small, non-periodic objects up to a resolution on nanometer length scale. It can be considered as a microscopic technique providing information on physical properties of materials in a variety of scientific fields, e.g. whole-cell imaging [2] and mesoporous structures. The method, also named lensless imaging, is simply based on measuring of the Fraunhofer X-ray diffraction pattern of an object. Instead of using lenses or other optical components for image formation the structure of the object is reconstructed with the help of numerical algorithms which are able to recover the phase information in the diffraction pattern. From this view the numerical reconstruction is simply acting as a lens in an optical system. The achievable resolution of this method of structure determination depends in principle only on the used wavelength and the largest recorded diffraction angle. Nevertheless, the latter requirement is limited by the specific experimental arrangement, i.e. distance between sample and detector, detector size, signal to noise ratio, and especially by the total incoming coherent photon flux. As a result of a strong decrease of the diffracted photon intensity towards larger diffraction angles, i.e. I(q) ∼ q −3 , the amount of photons at large q-values determines the resolution. A systematic series of numerical simulations was carried out aiming to investigate the limitations in resolution due to a restricted number of incoming photons. In further simulations we considered additionally a second important factor which is the influence of partial coherent illumination. In this case, the visibility of the interference fringes is reduced which leads to a certain degree of smearing in the diffraction pattern. This effect is not taken into account by the numerical algorithms (HybridInput-Output Method [3]) that are usually used and thus, it can essentially affect the result of a reconstruction using a partially blurred data set. The results of these numerical simulations together with a comparison to the results of a CXD-experiment carried out at ID01 (ESRF) [4] will be presented on a poster. [1] J. Miao et al, Nature, 400, 342 (1999) [2] D. Shapiro et al., PNAS, 102, 15343 (2005) [3] J.R. Fienup, Appl. Opt. 21, 2758 (1982) [4] A. Schropp et al., Proceedings of the 8th International Conference on X-ray Microscopy (XRM2005), (2006) to be published

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P111

Applications in hard X-ray mapping and imaging at ANKA using planar sets of refractive crossed linear lenses from SU-8 polymer ¨rgen Mohr2 , Silvia Rolf Simon1 , Vladimir Nazmov2 , Elena Reznikova2 , Ju ´3 , Volker Saile2 Diabate 1

Institut f¨ ur Synchrotronstrahlung, Forschungszentrum Karlsruhe, Postfach 3640 DE-76021 Karlsruhe – 2 Institut f¨ ur Mikrostrukturtechnik, Forschungszentrum Karlsruhe, Postfach 3640 DE-76021 Karlsruhe – 3 Institut f¨ ur Toxikologie und Genetik, Forschungszentrum Karlsruhe, Postfach 3640 DE-76021 Karlsruhe Refractive planar X-ray lenses with linear parabolic profiles are fabricated from SU-8 polymer by direct deep X-ray lithography at the IMT beamlines of the ANKA storage ring at Forschungszentrum Karlsruhe. The lenses are usually arranged in crossed configuration for focussing in two directions and in several sets on a single support wafer in order to cover a wide energy range, e.g. from 5-30 keV. At the ANKA FLUO-TOPO beam line these lenses frequently have been tested and characterized[1,2], and furthermore they are regularly used for scanning and mapping applications using micrometer sized probe beams or full-field imaging applications. For scanning applications a probe beam size down to 500 nm FWHM could be realized employing a source demagnification by a factor of approx. 400. With this micro probe x-ray fluorescence mapping in two and three dimensions was applied to samples like environmental particles, bones and biological tissue, the excitation energies ranged between 5 and 28 keV. For applications in x-ray microscopy using absorption or phase contrast the x-ray lens was placed behind the micro- and nanoscaled objects in order to form an x-ray image on the recording CCD camera. The measured resolution of the images was 400 ± 50 nm that corresponded to the projection optical scheme with 18 mm focal distance of the lens 30 m remote from the source. The sensitivity of the imaging set-up to even low phase contrast (≈ 0.065) is demonstrated by visualizing details in human lungs cells with magnification of 50.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P112

X-ray spectromicroscopy - a tool for environmental sciences Juergen Thieme1 , Claudia Schmidt1 , Sophie-Charlote Gleber1 , Genoveva Mitrea1 , Eva Pereiro Lopez2 1

Institute for X-Ray Physics, University of Goettingen, Germany – 2 CELLS-ALBA, Barcelona, Spain X-ray spectromicroscopy is a powerful tool for addressing key questions in environmental sciences due to its high spectral and spatial resolution. As X-ray microscopy achieves a much higher resolution than its visible light counterpart due to the much shorter wavelength smallest structures around 20 nm in sizecan be seen. Imaging specimens directly in aqueous media is possible as well as performing spectromicroscopy studies by choosing an appropriate X-ray wavelength. Due to their surface activity, colloidal structures are involved in a variety of chemical and physical processes. Nutrients and toxicants can be bound and immobilized or transported, colloids can attach to microorganisms building up microhabitats, and organic matter as humic substances can flocculate due to interaction with metals. In this work, interest was focused on the appearance of colloidal structures from soils and groundwater aquifers, their distribution and the effect of changing chemical conditions in the aqueous environment. X-ray microscopy images reveal the morphology and its changes due to varied chemical conditions. With X-ray spectromicroscopy organic matter could be identified within structures of soil colloids and spectra have been analyzed for major components. Functional groups have been determined and mapped in relation to changes in the chemical condition. The role of different sulfur species in an entire soil profile has been assessed. Clay dispersions and microhabitats as well as humic substances have been imaged tomographically. The 3D reconstruction conveys the influence of oxidation on the morphology of humic substances as well as the internal structure of associations of bacteria and inorganic soil colloids.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P113

Coherent X-ray Diffraction Imaging Ivan Vartaniants1 1

HASYLAB at DESY, Notkestr. 85, D-22607 Hamburg, Germany

Coherent x-ray diffraction (CXD) imaging is a new experimental method for studying perfect and imperfect crystals. The method has become available by the recent development of high-brilliance third generation sources of synchrotron radiation (ESRF, APS, SPRING-8). The beams coherence volume being of the order of few microns can entirely enclose a nano-size object. Instead of incoherent averaging, a coherent sum of amplitudes produces a coherent diffraction pattern originating from the real space arrangement of the sample. If high-quality x-ray lenses were available as they are for electrons, such diffraction patterns could be transformed to magnified images directly. However such x-ray microscopes still suffer a lot from optics aberration and resolution is often limited to the pixel size of the CCD. In this talk it will be shown how the objective lens of the microscope can be replaced by a special iterative phase reconstruction procedure that inverts intensity measurements of the CXD pattern to real space image. The method is based on the fact that the diffraction pattern can be oversampled relative to its spatial Nyquist frequency so that the Fourier transform can be overdetermined in spite of missing phase information. In principle this method does not have any limitations on the available resolution. Several applications of the method will be given in the talk. It will be shown how 3D images of the interiors of Au nanocrystals that show 50 nm wide bands of contrast with 111 orientation can be obtained applying this technique [1]. The size of the objects can be further reduced to the size of the quantum dots samples if repetitive motive in the form of 2D crystal is used. It will be demonstrated that in the case of coherent illumination of these samples the correct shape and orientation of individual island can be obtained. In the case of partially coherent illumination the correct shape of the particle can be obtained only when the coherence of the incoming beam is reduced to match the size of the island [2]. In the last example experimental results of CXD scattering on the sample of specially fabricated GeSi islands of nanometer size and in a regular array embedded to Si substrate will be shown [3]. Two geometries of scattering that is grazing incidence diffraction (GID) and grazing incidence small angle x-ray scattering (GISAXS) were used. Applying a microfocuse coherent beam on our sample give rise to coherent diffraction pattern with Bragg spots and broad diffuse maxima in GID geometry. The GISAXS pattern has a typical shape resulting from the periodic array of identical islands. This diffraction pattern was used to reconstruct the average shape of the islands using a model independent phase retrieval algorithms. [1] G.J. Williams, et al., Phys. Rev.B 73(2006)094112. [2] I.A. Vartanyants, and I.K. Robinson, J. Synchrotron Rad. 10(2003) 409. [3] I.A. Vartanyants, et al., Phys Rev.B 71 (2005)245302.

Mikroskopie und Tomographie

Poster: Mi., 14:00–16:30

M-P114

Radiographie und Tomographie bei ANKA: die Strahllinie IMAGE ¨bbert1 , Alexander Rack1 , Rolf Timm Weitkamp1 , Lukas Helfen1 , Daniel Lu 1 1 Simon , Tilo de Castro 1

Institut f¨ ur Synchrotronstrahlung / ANKA, Forschungszentrum Karlsruhe, Postfach 36 40, D-76021 Karlsruhe An der Synchrotronstrahlungsquelle ANKA am Forschungszentrum Karlsruhe ist derzeit eine neue Beamline IMAGE f¨ ur bildgebende Verfahren wie Mikroradiographie und -tomographie im Bereich harter R¨ ontgen-Photonenenergien (7 bis 65 keV) in Planung. Die Beamline soll im Jahr 2009 in Betrieb gehen. IMAGE soll Strahlung von einem supraleitenden Insertion device erhalten. Verschiedene M¨ oglichkeiten der spektralen Filterung des Strahls (Multilayer-Monochromator, Kristall-Monochromator, weißer Strahl) bieten einerseits ausreichende Aufl¨ osung im reziproken Raum f¨ ur bildgebende Beugungsverfahren (z. B. Rocking-curve imaging), andererseits bei Bedarf hohen Fluss f¨ ur hohe Bildfolgen zur Verfolgung von Prozessen in Echtzeit. Bereits vor der Inbetriebnahme von IMAGE wird – voraussichtlich ab Anfang 2007 – an der Ablenkmagnet-Strahllinie TOPO-TOMO ein Messplatz f¨ ur Mikrotomographie bereitgestellt. Die Poster-Pr¨ asentation stellt den Planungsstand und einige wesentliche Anwendungsbereiche vor.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P115

Quantum entanglement in the fast proton conductor H3 OSbTeO6 Tyno Abdul-Redah1 , Aris C. Chatzidimitriou-Dreismann1 , Brigitte Hahn1 , Martin Lerch1 1

Institut f. Chemie, Str. d. 17. Juni 135, TU Berlin, Germany.

Due to the rapidly growing environmental and economical problems of natural energy resources in the near future, the development and optimization of fuel cells is one of the most pressing goals for science and technology today. A key process governing the efficiency of those cells is the ion mobility within the electrolyte being solid in the most common types. State of the art models of transport processes in super ion conductors are based on quantum molecular dynamics which do not take into account the existence of short-lived (i. e. atto-second) quantum entanglement and fast decoherence [1]. In recent years, an anomalous shortfall of neutron Compton scattering intensity has been observed in hydrogen-containing compounds and which has been attributed to the aforementioned quantum phenomena; cf. [2]. Here we present new experimental results, which indicate a strong anomalous shortfall of scattering intensity of the protons in the fast proton conductor H3 OSbTeO6 (pyrochlore-type). The displayed figure shows the measured (at T=298) ratio Rexp of scattering intensity of H of H3 OSbTeO6 relative to that of all heavier atoms (O, Sb, and Te), normalised with the expected value according to conventional theory, Rconv . An anomalous shortfall of Rexp in the range 20-30 % is found. These results suggest that the ion transport phenomenon in the electrolyte may be governed by a thus far unconsidered mechanism, i. e., by the quantum entanglement of the protons and by decoherence due to the interaction with the surrounding atoms. This experimental finding may have consequences for the theoretical description of transport processes of protons in solids. [1] C. A. Chatzidimitriou-Dreismann, Nachrichten aus der Chemie 52 (2004) 773. [2] C. A. Chatzidimitriou-Dreismann, et al., Phys. Rev. Lett. 79 (1997) 2839; Phys. Rev. Lett. 91 (2003) 057403.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P116

Is lithium hydride LiH or LiH0.5 ? This is just a question of time! Tyno Abdul-Redah1 1

Institut f. Chemie, Str. d. 17. Juni 135, TU Berlin, Germany.

The particles of a macroscopic condensed system are subject to continuous mutual interactions leading to quantum correlated states in which the particles become invisible. The survival time of these states in condensed matter is generally expected to be very short because of the fast and effective decoherence due to interaction with the remaining environment. However, it is indeed possible to measure their effects if the experimental technique is fast enough, e.g., using neutron Compton scattering (NCS) with scattering times < 10−15 s. Due to its low mass, hydrogen (H) is particularly suitable to be involved in those states. NCS experiments on various solid compounds like metal hydrogen systems have been done [1]. The effect manifests itself by a strong anomalous decrease of the scattering cross section of H with respect to the conventional expectation (see figure). In simple terms, as an example, the ionic hydride lithium hydride appears then as LiH0.5 rather than LiH in the subfemtosecond time scale of the experiment [2]. The anomaly varies among others with scattering time and with temperature depending on the chemical bond and the electronic environment of the hydrogen in the particular chemical compound. This effect cannot be explained in that way that the protons scatter as individual entities. New experimental results on solid LiH, LaHx , NbHx will be presented along with the dependence of the anomaly on the crystal structure as well as on the electronic environment of the proton. The importance of this effect for physics and chemistry will be outlined. [1] T. Abdul-Redah et al., Neutron News 15 (2004) 14. [2] T. Abdul-Redah et al. Physica B 350 (2004) 1035.

Fig. 1: Shown is the ratio of the experimentally determined relative neutron scattering cross section of hydrogen Rexp and the tabulated one Rtab versus scattering time for LiH at room temperature. Conventionally one expects Rexp /Rtab =1, but the data show a very strong reduction and also a strong scattering time dependence.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P117

Koh¨ arenzverlust und -transfer in molekularen Doppelspaltexperimenten Uwe Becker1 1

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin

Die Photoelektronenemission zweiatomiger homonuklearer Molek¨ ule ist ein Doppelspaltexperiment mit Einzelelektronen [1], das im Gegensatz zum klassischen Doppelspalt nicht auf der Unsch¨ arferelation, sondern auf der Inversionssymmetrie beruht. Ein weiterer Unterschied besteht im Auftreten der Interferenz, die im klassischen Doppelspaltexperiment im Ortsraum zutage tritt, im molekularen Doppelspaltexperiment hingegen experimentell nur im Impulsraum nachgewiesen werden kann. Dadurch treten bei letzterem Streuungen am Nachbaremitter zutage, die im klassischen Experiment verborgen bleiben. Diese Streuprozesse er¨ offnen Einblicke in die Energieabh¨ angigkeit der Koh¨ arenzph¨ anomene beim Doppelspaltexperiment. Solange die de-Broglie-Wellenl¨ ange des emittierten Elektrons gr¨ oßer ist als die Bindungsl¨ ange des emittierenden Molek¨ uls, u ¨berlagern sich alle Teilwellen gestreuter oder nicht gestreuter Elektronen immer nur ¨ von zwei getrennten Emissionszentren. Sie sind also koh¨ arente Uberlagerungen von Elektronenwellen, die von zwei r¨ aumlich getrennten Emissionszentren emittiert werden. Wenn die de-Broglie-Wellenl¨ ange jedoch k¨ urzer als die Bindungsl¨ ange des Molek¨ uls wird, findet ein Koh¨ arenztransfer-Prozeß statt. Die doppelspaltartige transversale ZweiZentren-Koh¨ arenz weicht einer EXAFS-artigen longitudinalen Ein-Zentren-Koh¨ arenz, die positions-sensitive Strukturinformationen enth¨ alt. Dieser Koh¨ arenztransfer-Prozeß findet ohne expliziten Symmetriebruch statt; er ist gewissermaßen ein symmetrisierter Vorl¨ aufer eines echten Symmetriebruchs. Ein echter Symmetriebruch bewirkt nicht nur einen Koh¨ arenztransfer, sondern einen Koh¨ arenzverlust. Dieser kann entweder durch eine ¨ außere St¨ orung wie Isotopensubstitution [2] oder aber durch eine innere St¨ orung wie koh¨ arente Anregung von verschiedenen Symmetriezust¨ anden durch Kurzzeitpulse erzeugt werden. Letzterer Effekt konnte k¨ urzlich mittels Anregung durch Pulse aus Higher Harmonic Generation (HHG) an H2 gezeigt werden [3] und soll f¨ ur Ne-Dimere am Freie-Elektronen-Laser bei DESY in Hamburg erstmals auch mittels direkter Photonenanregung anstelle von Elektronenr¨ uckstreuung im starken Laserfeld [4] nachgewiesen werden. Diese Arbeit wurde durch das Bundesministerium f¨ ur Bildung und Forschung (BMBF) unter dem F¨ orderkennzeichen 05 KS4EB1/3 gef¨ ordert. [1] [2] [3] [4]

R. P. Crease, Physics World Sep. (2002) D. Rolles et al., Nature 437, 711 (2005) M. F. Kling et al., Science 312, 246 (2006) H. Niikura et al., Nature 417, 917 (2002)

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P118

Ultrafast X-ray diffraction experiments at the linear accelerator based X-ray source SPPS Christian Blome1 , Thomas Tschentscher1 1

DESY, Notkestr. 85, 22607, Hamburg

The development of new X-ray sources like free electron lasers, 4th generation synchrotrons and laser driven plasmas will provide new opportunities for producing short pulses with short wavelength radiation. These ultrashort X-ray pulses offer a unique combination of spatial and temporal resolution and thus make it possible to directly observe atomic motion, for example during chemical reactions or phase transitions. Using the Sub-Picosecond Pulse Source in Stanford, USA the collaboration has applied optical pump X-ray probe techniques to various problems in physics with a time resolution of 100 fs. SPPS is the first linear accelerator based femtosecond multi keV X-ray source and stands in the forefront for research, in particular to conduct important RD work for accelerator concepts, X-ray optics, and experimental techniques for future X-ray FEL experiments. In this contribution we will give an overview of the activities at the SPPS. We will discuss preliminary results of the ionic to neutral phase transition in the typical mixed stack charge transfer compound TTF-CA. We compare results from the SPPS and discuss them in the context of the time resolved data from the ESRF, ID09 with 50 ps time resolution [1]. We present results of the non-thermal melting of a semiconductor after short pulse laser excitation [2] and first measurements of the detection of optical coherent phonons in laser excited Bismuth [3]. Beyond physics we discuss the crucial question how to time a linac based source with an optical pump laser [4]. [1] [2] [3] [4]

E. Collet et al., Science 300, 612-615, 2003 A.Lindenberg et al., Science 308, 392-395, 2005 K. Sokolowski-Tinten et al., Nature 422, 287-289, 2003 A. Cavalieri et al., Physical Review Letter 94, 1148011, 2005

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P119

Dewetting of thin solid films under swift heavy ion irradiation Thunu Bolse1 , Mirco Kreis1 , Hartmut Paulus1 , Klara Lyutovich2 , Wolfgang Bolse1 1

Institut f¨ ur Strahlenphysik, Universit¨ at Stuttgart – 2 Institut f¨ ur Halbleitertechnik, Universit¨ at Stuttgart

Incomplete wetting or dewetting plays an important role in thin film systems, be it for the growth of the film, its stability or chemical reactions and phase formation taking place at the interface. Dewetting usually occurs when the film is in its liquid state or at least near to its melting point (in case of glasses). Here we report about our recent observation that dewetting also may occur when a thin metal oxide film (NiO, Fe2 O3 , TiO2 , some tens of nm thicknes) grown on untreated Si-substrate is bombarded with swift heavy ions, even when the film is kept at liquid nitrogen temperature. Similar to what was observed in case of thin molten polymer films [1] we could identify heterogeneous and homogeneous nucleation taking place at the beginning of the dewetting process. Dewetting then proceeds by the formation and growth of circular holes with the removed material piling up in a rim around these holes. By coalescence of the holes narrow ridges are formed, which finally decay into small droplets because of the Rayleigh-Plateau instability. Different techniques like SEM, AFM and RBS were used to analyse the dewetting processes and nucleation mechanisms that occur during the ion bombardment. We have investigated the basic kinetics involved in these phenomena by studying the development of the dewetting patterns as a function of different ion species and energies and the applied fluences as well as their dependence on the film thicknes. [1] S. Herminghaus, et al., Science 282 (1998) 916

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P120

Extraordinary Negative Thermal Expansion in the Smallest Chiral Amino Acid, Alanine. `s3 , F. De ´noyer4 , H. N. Bordallo1 , D.N. Argyriou1 , J. Strempfer2 , M. Barthe J.-U. Hoffmann1 1

Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – HASYLAB- DESY, Hamburg – 3 Universit´e Montpellier II, cc 26 - 34095 -Montpellier cedex 05 France – 4 Universit´e Paris XI, Orsay, France 2

Amino acid construction consists of a carboxylic acid (-COOH) and an amino (-NH2 ) functional group attached to the same tetrahedral carbon atom, the α-carbon. Every amino acid, with the exception of glycine, comes in two forms, a left-handed (L) and a right-handed (D) version, which are identical mirror images of each other. However, protein chains cannot be formed from a mixture of D and L. We report on high resolution X-ray and neutron scattering diffraction as well as quasielastic neutron studies on crystalline L- and D-alanine over a wide temperature range. Our aim is to verify the possibility predicted by the Nobel Laureate A. Salam, that a phase transition, related to a break of the as Cα -H bond, occurs in alanine. While no change in the space group symmetry was observed, a negative thermal expansion, by discrete steps, along the c-axis is observed till the melting point. Additional anomalies are also noticed in the a and b lattice constants at 170 K. Moreover, the evolution of the mean-square displacement, obtained from the QENS, data shows a steadily increase on heating, but near 150 K and again near 200 K a deviation from the expected behavior is observed. The results suggest the excitation of new degrees of freedom, possibly due to a progressive conformational change of the NH3+ group. The ramifications of this study can be extremely interesting for the understanding of homochirality as well as a breakthrough in molecular mapping via non-traditional sources of information.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P121

Hydrogen in N-Methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering `s4 , T. Seydel2 , H. N. Bordallo1,2 , W. Kalceff3 , D.N. Argyriou1 , M. Barthe C. Fehr1 , F. Juranyi4,5 1

Hahn-Meitner-Institut, Glienicker Str., 100 Berlin 14109, Germany – 2 Institut LaueLangevin, BP 156 - 38042 Grenoble Cedex 9, France – 3 Department of Applied Physics, University of Technology Sydney, Australia – 4 Universit´e Montpellier II, cc 26 34095 -Montpellier cedex 05, France – 5 Physical Chemistry, Saarland University, 66123 Saarbrucken, Germany – 6 Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232Villigen, Switzerland A comparison with several molecular mechanics force fields widely used in molecular dynamics simulations of proteins, nucleic acids, and small molecules reveals systematic deviations from electronic structure calculations and protein structure statistics. These results point to the importance of understanding the anharmonic mode coupling of the amide group, present in the hydrogen bonds found in protein side chains and main chains. It is a non-trivial problem to choose a simplistic hydrogen bonded system that accurately mimics hydrogen bonds found in proteins. One of the long-standing building block models of the repeated peptide linkage of polypeptides and proteins is Nmethylacetamide,(CH3 CONHCH3 , hereafter NMA), a single amide containing methyl groups at both extremities. NMA, which is highly hygroscopic and melts just above room temperature (301 K), 0 undergoes a structural phase transition around room temperature (T =274 K), and 0 recent structural results support the idea of a glassy-type disorder below T , as well as 13 the occurrence of a second phase in the vicinity of 230-240 K. From C NMR studies, down to 200 K, the coexistence of typical broad lines with very narrow bands indicates that dynamic disorder is still observed well below the structural transition. In order to get further information on the relationship between local dynamics and the molecular structure of NMA, new QENS measurements were performed using FOCUS at PSI and IN10 at the ILL. Also, neutron diffraction measurements on the fully deutereted NMA, using the Fine Resolution Powder Diffractometer E9 at HMI and the High Resolution Powder Diffractomer (HRPD) at ISIS, were also carried out. Here we find that systematic deviation from the room temperature structure in the model system NMA influences the local dynamics, giving rise to a glass-type structure.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P122

Understanding the role of water in the superconductor Na0.28 CoO2 ·1.3H2 O using inelastic neutron scatering H. N. Bordallo1,2 , N. Jalarvo1 , N. Aliouane1 , J. Pieper1,3 , M.A. Adams4 , D.N. Argyriou1 1

Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – Institut Laue-Langevin, BP 156 - 38042 Grenoble Cedex 9, France – 3 Technische Universit¨ at Berlin, Institut f¨ ur Chemie Max-Volmer-Laboratorium f¨ ur Biophysikalische Chemie, Straße des 17. Juni 135 10623 Berlin, Germany – 4 4ISIS Pulsed Neutron Scattering Facility, Rutherford Appleton Laboratory,Chilton Didcot, Oxon, OX11 0QX, U.K 2

Sodium cobalt oxyhydrate Nax CoO2 ·yH2 O shows superconductivity with Tc =5 K for x=0.35 and y=1/3. In the same way that the two-dimensional nature of the copper oxide layers is thought to be important in this class of superconductors, the large separation of the cobalt oxide layers seems to be crucial in the superconducting behavior of Nax CoO2 ·yH2 O. Unlike the square lattice found in cuprates, cobalt oxide forms a triangular lattice. In order to understand the mechanisms of how the dynamics of the H-bond network is modified in the crystalline lattice as well as to get insight on the role of water in this new class of compounds a series of incoherent neutron scattering experiments were performed in Na0.7 CoO2 and Nax CoO2 ·yH2 O (x∼0.28, y∼1.3). Using quasi-elastic neutron scattering (QENS) we were able to distinguish the water chemically bound into the sodium cobalt oxyhydrate structure during the hydration process, from the physically bound or “glassy water”. Physically bound water is defined as the water that can hydrogen bond less strongly in the hydration shells around the Na ions. At room temperature the elastic incoherent structure factor (EISF), extracted from the neutron time-of-flight data, rules out single rotational-jump models, as well as isotropic rotational motions for the physically bound water molecule. Besides, high resolution QENS experiments, carried out on Na0.28 CoO2 ·1.3H2 O, using the high resolution neutron spectrometer IRIS at ISIS, show that at higher temperatures the water dynamics is well described by the random jump diffusion model with a mean residence time of 22 ps. Furthermore we show that the sodium ions have no influence on the rotational dynamics of the bulk-water molecules, however they introduce the disorder necessary to prevent total crystallization of the water below 240 K. This is reflected by the existence of a liquid-liquid transition involving water in Nax CoO2 ·yH2 O.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P123

Neutronenbeugungsuntersuchungen an den schnellen Anionenleitern O- und N-Mayenit (Ca12 Al14 O32 +O/N) ¨ lzel3 , Anatoly Senyshyn3 Hans Boysen1 , Martin Lerch2 , Markus Ho 1

Department f. Geo- und Umweltwissenschaften, Sektion Kristallographie, LMU M¨ unchen, Am Coulombwall 1, 85748 Garching – 2 Institut f¨ ur Chemie, TU Berlin, Str. d. 17. Juni 135, 10623 Berlin – 3 Strukturforschung, Technische Universit¨ at Darmstadt, Petersenstr. 23, 64287 Darmstadt und FRM II, Lichtenbergstr. 1, 85747 Garching Mayenit (Ca12 Al14 O33 ) ist ein schneller Sauerstoffionenleiter, der aus einem Calciumaluminat-Ger¨ ust besteht, in das 32 der 33 Sauerstoffionen fest eingebunden sind. Das 33. Sauerstoffion ist statistisch u ¨ber K¨ afige in der Struktur verteilt und kann sich bei Temperaturen um 1000 ◦ C leicht durch das Kristallgitter bewegen. Es kann gegen andere Ionen, u.a. Stickstoff ausgetauscht werden und er¨ offnet damit neue M¨ oglichkeiten zur Herstellung eines reinen Stickstoffionenleiters. Die Synthese von Ca12 Al14 O33 gelingt durch Festk¨ orperreaktion aus Al2 O3 und CaCO3 , wobei mehrmaliges Aufheizen auf etwa 1300 ◦ C mit anschließendem Vermahlen zur Bildung praktisch phasenreiner Proben n¨ otig ist. Die Darstellung einer stickstoffhaltigen Phase ist durch Ammonolyse m¨ oglich. Die hier untersuchte Probe enth¨ alt so viel Stickstoff, wie es dem formalen Austausch des 33. O durch 2/3 N entspricht (1 O2− → 2/3 N3− ). Am Pulverdiffraktometer SPODI (FRM2, Garching) wurden Neutronenbeugungsuntersuchungen am O-Mayenit und N-Mayenit bei Raumtemperatur, sowie temperaturabh¨ angige Messungen am O-Mayenit bis 1200 ◦ C durchgef¨ uhrt. Die freien“ Anionen ” (O, N) konnten eindeutig u ¨ber Differenz-Fourier Methoden lokalisiert werden. W¨ ahrend im Falle des O-Mayenits die auf Grund des Ladungsausgleichs erwartete Besetzung ge¨ funden wurde, zeigt sich beim N-Mayenit eine deutliche Uberbesetzung, deren Ursache noch nicht gekl¨ art ist. Ein Hinweis auf den Einbau von N in das Ger¨ ust kann aus den Daten nicht erhalten werden. Bei hohen Temperaturen nimmt in der reinen Sauerstoffprobe die scheinbare Besetzung des Zwischengitter-O ab, w¨ ahrend die atomaren Verschiebungsparameter stark ansteigen. Dies l¨ aßt sich mit signifikanten anharmoni¨ schen Beitr¨ agen zum Debye-Waller Faktor erkl¨ aren und damit verfeinern. Uber eine Analyse der daraus gewonnenen Aufenthaltswahrscheinlichkeiten lassen sich die Diffusionspfade und die effektiven Einteilchen-Potentiale bestimmen. Die Arbeiten werden im Rahmen des SPP 1136 durch die DFG (BO 1199/2-3, LE 781/10-4) unterst¨ utzt.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P124

Attosekunden-Verschr¨ ankung: Ein neuer Quanteneffekt der Neutronenstreuung C. A. C.-Dreismann1 , M. Krzystyniak1 , T. Abdul-Redah1 1

Institut f¨ ur Chemie, TU Berlin, D-10623 Berlin

Compton-Streuexperimente mit schnellen (sog. epithermischen) Neutronen an Protonen verschiedener fl¨ ussiger und fester Systeme haben k¨ urzlich neue Einsichten in die Dynamik kondensierter Materie erm¨ oglicht: Bisher unbekannte Prozesse werden sichtbar, die in wenigen hundert Attosekunden (as) ablaufen [1,2]. Auf dieser ultrakurzen Zeitskala gehen die Protonen in der Materie eine komplexe quantenmechanische Verschr¨ ankung mit den ihnen benachbarten Elektronen ein. Als Folge davon scheinen diese Protonen beim Streuprozess teilweise zu verschwinden“: Wasser zum Beispiel erscheint ” als H1,5 O anstatt H2 O [1]. Diese Experimente wurden an der gepulsten Spallationsquelle ISIS (Spektrometer Vesuvio, Rutherford Appleton Laboratory) durchgef¨ uhrt. Dieser u ¨berraschende Effekt wurde auch mit Hilfe einer unabh¨ angigen experimentellen Methode nachgewiesen, der Elektron-Proton Compton-Streuung [2]. Dadurch wurde auch gezeigt, dass dieser Effekt unabh¨ angig von der zugrunde liegenden fundamentalen Wechselwirkung (starke bzw. elektromagnetische) ist [3], und somit ein Verschr¨ ankungseffekt sein kann, wie theoretisch vorhergesagt. Der genannte Effekt steht im Widerspruch zur konventionellen Theorie der Neutronenstreuung, in der Verschr¨ ankung und Dekoh¨ arenz keine Rolle spielen [1,2]. Deshalb wurde er seit seiner Entdeckung von mehreren Seiten stark angegriffen. Nun gelang es Bruno Dorner (ILL, Grenoble) mit einer qualitativ neuen Auswertungsmethode [4], bisherige, am Metallhydrid NbH0.8 bei T = 293 K gewonnene Ergebnisse eindrucks¨ voll zu best¨ atigen; f¨ ur eine Ubersicht s. [4b]. Es ist wichtig zu bemerken, dass Dorners Methode nur die o.g. Peak-Separation voraussetzt, aber von jeglicher Annahme u ¨ber (a) die genaue Form der apparativen Aufl¨ osungsfunktion und (b) die spezifische Form eines Peaks v¨ ollig frei ist − es handelt sich hier um eine modell-freie Methode“ [4]. ” Eine weitere, unabh¨ angige Best¨ atigung des Effektes gelang Senesi et al. [5] mit Hilfe der sog. exakten“ Methode zur Analyse der am Vesuvio gewonnenen Flugzeitdaten. ” Dieser as-Effekt [1,2] d¨ urfte weitreichende Bedeutung auf ganz verschiedene Gebiete haben, wie z.B. der Neutronenphysik, Streuung an offenen Quantensystemen, kondensierte Materie, Molek¨ ulphysik und Dynamik chemischer Reaktionen. [1] C. A. Chatzidimitriou-Dreismann et al., Phys. Rev. Lett. 79 (1997) 2839; Physik in unserer Zeit, Juli 2004, S. 174 [2] C. A. Chatzidimitriou-Dreismann et al., Phys. Rev. Lett. 91 (2003) 057403 [3] Physics Today, (Sept. 2003) 9; Scientific American, (Okt. 2003) 20 [4] (a) B. Dorner, Nucl. Instr. Meth. B, im Druck (2006), online“” Version vom 2. Mai 2006; J. Neutron Research 13 (2005) 267; M. Krzystyniak et al., Phys. Rev. B 72 (2005) 174117 (b) C. A. Chatzidimitriou-Dreismann, Physik Journal 5 (Mai 2006) 16 [5] R. Senesi et al., Phys. Rev. B 72 (2005) 054119

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P125

Lifetime vibrational interference effects observed in the NO+ (A1 Π → X 1 Σ+ ) fluorescence after 1s−1 π ∗ resonance excitation Arno Ehresmann1 , Lutz Werner1 , Ph. V. Demkhin2 , M. P. Lemeshko2 , V. L. Sukhorukov2 , Karl-Heinz Schartner3 , Hans Schmoranzer4 1

Institute of Physics, University of Kassel, D-34132 Kassel, Germany – 2 Rostov State University of Transport Communications, 344038 Rostov-on-Don, Russia – 3 I Institute of Physics, Justus-Liebig-University Giessen, D-35392 Giessen, Germany – 4 Department of Physics, Kaiserslautern University of Technology, D-67653 Kaiserslautern, Germany Fluorescence spectroscopy experiments on simple molecules after excitation by monochromatized synchrotron radiation were mainly focused on outer-shell excitations of molecules (e.g. [1-3]), whereas the decay of inner shell excitations was investigated only scarcely (see e.g. [4]). The excitation of an inner shell electron in a molecule induces very complex relaxation processes, which are governed by the competition between autoionization and fragmentation of the molecule. In the present work we investigated aspects of the decay of the 1s−1 π ∗ resonances of NO by fluorescence spectroscopy, measuring dispersed VUV-fluorescence intensities (118 nm≤ λf l ≤ 143 nm) to investigate the influence of liftime vibrational interference (LVI). In recent studies we successfully investigated the C(v 0 ) → X(v 00 ) fluorescence in the −1 ∗ N+ π resonance [5-6]. Due to the vibrational spacing of the 2 ion excited via the 1s ∗ N2 state of about 230 meV, which is about twice as large than its natural linewidth the LVI between the excitation pathways via different 1s−1 π ∗ (vr ) vibrational levels was found to be not of significance. In contrast the vibrational spacing of 195 meV of the N∗ O state is only about 1.5 times larger than its natural width and in the case of the NO∗ the vibrational spacing is already smaller than the natural width. For the N∗ O state LVI effects has been observed by [7] and it is expected that a very pronounced vibrational interference will be investigated in the case of the NO∗ de-excitation. [1] H. Liebel et al. J. Phys. B: At. Mol. Opt. Phys. 35 (2002) [2] Y. Hatano Phys. Rep. 313 (1999) [3] E. D. Poliakoff Vacuum Ultraviolet Photoionization and Photodissociation of Molecules and Clusters edited by Ng C Y (World Scientific, Singapore)(1991) [4] A. Marquette et al. Phys. Rev. A 35 (2000) 022513 [5] A. Ehresmann et al. J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 283 [6] A. Ehresmann et al. J. Phys. B: At. Mol. Opt. Phys. 39 (2006) L119 [7] T. X. Carroll et al. Phys. Rev. Lett. 58(9) (1987) 867

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P126

Dynamics of Ionic Liquids by means of QENS Jan Peter Embs1 , Fanni Juranyi2 , Rolf Hempelmann1 1

FR 8.1 Physikalische Chemie, Universit¨ at des Saarlandes, 66041 Saarbr¨ ucken – Laboratory for Neutron Scattering, PSI and ETH Z¨ urich, CH-5232 Villigen-PSI, Switzerland 2

Ionic liquids (IL), i.e. ionic melts with melting points below 373 K, have attracted considerable attention in recent years as solvents for a variety of applications including electrodeposition, batteries, catalysis, separations and organic synthesis [1,2]. A quasielastic neutron scattering study has been performed by Triolo et al. [3] in collaboration with F. Juranyi on [bmim][PF6 ]. Recently, we have performed an experiment on [N-butyl-N-methyl-pyrrolidinium] bis-(trifluoromethylsulfonyl) imide ([BMPyrr] Tf2 N). The typical spectra can be described as a superposition of an elastic component, a comparatively narrow and a very broad Lorentzian. The Q-dependence of their line widths and of the elastic incoherent structure factor (EISF), i.e. the ratio elastic intensity / total intensity indicate localized side chain motion, see Fig. 1. Investigations on fully protonated [N-alkyl-N-methyl-pyrrolidinium] Tf2 N (here, alkyl means ethyl, butyl, octyl, etc.) samples using our cold neutron time-of-flight spectrometer FOCUS are in progress now. [1] M.J. Earle and K.R. Seddon, Pure Appl. Chem. 72 (2000) 1391 [2] T. Welton, Chem. Rev. 99 (1999) 2071 [3] A. Triolo, O. Russina, V. Arrighi, F. Juranyi, S. Janssen and M.C. Gordon, J. Chem. Phys. 119 (2003) 8549

Fig. 1: Left : widths (FWHM) of the three components, right : EISF both as function of Q.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P127

The amorphous state seen in synchrotron light Hermann Franz1 , Andreas Schoeps1 , Karel Saksl1 , Gerd Wellenreuther1 , ¨rck3 , Ilya Sergueev4 Ying Wang2 , Jianzhong Jiang2 , Uwe van Bu 1

Deutsches Elektronen Synchrotron DESY, Notkestr. 85 22607 Hamburg – 2 Zhejinag University, Hangzhou, P.R. China – 3 Technical University Munich, Garching, Germany – 4 European Synchrotron Radiation Facility, ESRF, Grenoble, Cedex, France The transition from the liquid to the amorphous state is still a matter of controversial debate. Many different experimental methods and numerical simulations have been applied to shine light onto this problem. We used synchrotron radiation to study both structure and dynamics of amorphous systems in particular in the vicinity of the glass-liquid-transition. The contribution will discuss the results of our investigation on model systems ranging from amorphous metals to simple organic glass-formers. We investigated the structure of amorphous systems using a combination of techniques including reverse MonteCarlo methods, slow relaxations near the calorimetric glass transition by fast diffraction experiments and fast dynamics near the mode-coupling glass transition temperature by nuclear resonant scattering techniques. Also effects of extreme conditions like high pressure and geometrical confinement will be discussed. Moreover new ideas on the conditions for glass formation in metallic systems will be presented.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P128

Quasikristalle – Neutronendiffraktion am Ger¨ at RESI des FRMII ¨ rn Pedersen2 , Ines Kaiser-Bischoff1 , Peter Gille1 Friedrich Frey1 , Bjo 1

LMU M¨ unchen, Department f¨ ur Geo- und Umweltwissenschaften, Sektion Kristallographie, Theresienstrasse 41, 80333 M¨ unchen – 2 TU M¨ unchen, Forschungsneutronenquelle FRM-II, Lichtenbergstrasse 1, 85747 Garching Quasikristalle (QK) zeigen eine langreichweitige Ordnung mit zumindest partiell fehlender Translationsperiodizit¨ at und mit neuen nicht-kristallographischen“ Symmetri” en. Beugungsbilder zeigen neben einigen starken Reflexen dicht“ liegende, meist sehr ” schwache Reflexe an Positionen, die keinem rez. Gitter zugeordnet werden k¨ onnen. Sehr oft treten zus¨ atzlich komplexe diffuse Streuerscheinungen auf, die mit phononenund phasonenartigen Fehlordnungserscheinungen verkn¨ upft sind. Quasikristalline Ord¨ nungen treten insbesondere in tern¨ aren Legierungen mit Al und Ubergangsmetallen (z.B. Cu, Fe, Co, Ni) auf, prominente Beispiele sind die dekagonale Phasen (2D QK) in den Systemen Al-Ni-Co oder Al-Cu-Co. H¨ oherdimensionale“ Strukturanalysen mittels ” Diffraktion basieren bis dato ausschließlich auf R¨ ontgendaten, die allerdings eine Kontrastierung der Co-Ni oder Co-Cu Verteilung nicht erlauben. Erste Messungen wurden daher mittels Neutronendiffraktion am Ger¨ at RESI durchgef¨ uhrt, unter Verwendung eines IP-Fl¨ achendetektors (hoher dynamischer Messbereich). Die Abbildungen zeigen IP-Neutronen-Daten von d-Al-Ni-Co, insbesondere 5-z¨ ahlige Symmetrien, und die Koexistenz von starken und schwachen Reflexen (Abb.1), sowie diffuse Schichten senkrecht zur dekagonalen Achse (Abb.2). Nach Aufnahme vollst¨ andiger Datens¨ atze (Juli 2006) sind h¨ oherdimensionale kombinierte Neutronen-R¨ ontgenStrukturverfeinerungen (Kooperation ETH Z¨ urich - Prof. Steurer) vorgesehen.

Abb. 1: Ausschnitt aus der dekagonalen hk0-Ebene (d-AlNi-Co)

Abb. 2: Diffuse Schichten (d-Al-Ni-Co)

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P129

Determination of structural disorder in superionic AgCuSe and AgCuS Hartmut Fuess1 , Michael Knapp1,2 , Daria Mikhailova1 , Anatoliy Senyshyn1 , Dmytro Trots1,∗ 1

Institute for Materials Science, University of Technology, Petersenstr. Darmstadt, Germany – 2 CELLS, P.O.B 68, 08193 Barcelona, Spain

23, 64287

Recently the high values of ionic conductivity and ionic thermoelectromotive force [1] renovate the practical interest for the ternary superionic (SI) compounds AgCuSe and AgCuS. In order to explain correlations between crystal structure and high-ionic conductivity, the time-average structure of AgCuSe and AgCuS was investigated by synchrotron (B2, HASYLAB/DESY) and neutron elastic coherent scattering (SPODI, FRM-II) in a wide temperature range. The model with cations disordered between tetrahedral (8c) and octahedral (32f) sites yields a temperature dependence for the parameters of the average structure without any anomalies. Within this model, it is likely that cations jump in skewed <100> directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. Note that diffraction results on a number of SI compounds [2] imply that ionic conductivity can be sensitive to details of the cation redistribution between available interstitial sites vs. temperature. Taking this into account, we can propose a correlation between the results of the electrochemical measurements [1], which revealed only a relatively modest increase in ionic conductivity with temperature within SI-AgCuSe, and our diffraction results, which show no pronounced cation redistribution. This gives strong support for the validity of the model [3]. Nevertheless, due to the limited number of observed Bragg reflections from SI AgCuSe and AgCuS the correlations between parameters are very strong. Therefore, a detailed analysis of diffuse scattering is mandatory. Hence, the results on the average structure are a base for further reverse Monte Carlo (RMC) modelling. This modelling will be done with the RMCpow software [4], which is a development of the RMC method intended specially for powdered crystalline materials [5]. These investigations are now in progress. Financial support from the Bundesministerium fuer Bildung und Forschung is gratefully acknowledged. ∗

e-mail: [email protected]

[1] S. Miyatani, J. Phys. Soc. Jpn. 34 (1973) 423; M.H. Balapanov et al., Physics of the Solid State 45 (2003) 634. [2] S. Hull, Rep. Prog. Phys. 67 (2004) 1233. [3] D. Trots et al., EPJ B, accepted. [4] A. Mellergard et al., Acta Crystallogr. A55 (1999) 783. [5] D. Keen et al., J. Phys.: Condens. Matter. 17 (2005) S15.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P130

Resonant X-ray spectroscopy for atom specific electronic structure and dynamics ¨ hlisch1 , Mitsuru Nagasono1 , Sethuraman Vijayalakshmi1 , Alexander Fo Franz Hennies1 , Edlira Suljoti1 , Annette Pietzsch1 , Wilfried Wurth1 1

Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg, Luruper Chaussee 149, 22761 Hamburg In complex systems, composed from many atomic units, it is of equal importance to determine the time scales of dynamic processes and to have control at which atomic site a dynamic process was initiated. Using third generation synchrotron radiation facilities, resonant X-ray spectroscopy allows to create atomically localized excited states and to monitor their dynamics in comparison to the ultra fast time scale of the transient core-hole resonance in autoionization or resonant inelastic X-ray scattering. With this core-hole-clock method, charge transfer between adsorbed atoms and the substrate has been investigated. Monitoring Coster-Kronig decay channels, charge transfer dynamics of only 320±90 attoseconds could be determined for Sulphur adsorbed on the Ru(0001) surface extending the core-hole-clock method into the range of attoseconds. The influence of orbital overlap and the surface electronic structure of the substrate has also been studied and fundamental aspects of autoionization and the electron localization in matter have been performed. Due to the symmetry selection rules of resonant inelastic X-ray scattering, ultra fast atomic motion can be investigated, which changes the molecular symmetry during the transient core-excited state.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P131

Koh¨ arenzexperimente mit weisser Synchrotronstrahlung Gudrun Gleber1 , Tobias Panzner1 , Wolfram Morawetz2 , Andreas Pucher2 , Ullrich Pietsch1 1

Leitenberger2 ,

Knut

Universit¨ at Siegen, Siegen – 2 Universit¨ at Potsdam, Potsdam

Speicherringe der dritten Generation stellen teilkoh¨ arente Strahlung zur Verf¨ ugung, welche eine neue Art von Experimenten erm¨ oglicht, sogenannte R¨ ontgen Photonen Korrelations Spektroskopie (x-ray photon correlation spectroscopy XPCS). XPCSExperimente erm¨ oglichen den Einblick in statische oder dynamische Eigenschaften von Proben in der Gr¨ oßenordnung von Nanometern. ¨ Ublicherweise werden XPCS-Experimente mit monochromatischer Strahlung durchgef¨ uhrt. Um auf diese Weise Informationen aus dem gesamten, reziproken Raum aufzunehmen, muss schrittweise der Einfallswinkel ver¨ andert werden, was jedoch den beleuchteten Bereich auf der Probe und damit auch das Beugungsmuster ¨ andert. Durch die Verwendung eines polychromatischen Strahls, wie er von der EDR-beamline (EDR: energy dispersive reflectometry) bereit gestellt wird, sind wir in der Lage dieselben In¨ ¨ formationen ohne Anderung des Einfallswinkels und damit ohne Anderung des beleuchteten Bereiches auf der Probe zu erhalten. Dies stellt einen großen Vorteil f¨ ur die Oberfl¨ achenrekonstruktion aus dem gemessenen Beugungsmuster dar. Auf Grund der Tatsache, dass ein Energiespektrum Einblick in unterschiedliche Bereiche der Probe liefert, nutzen wir diese Technik um langsame Prozesse in Polymeren zu beobachten. Auf diesem Poster wollen wir den aktuellen Stand der statischen und dynamischen Messungen mit einem energiedispersiven System pr¨ asentieren.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P132

Synchrotron X-ray diffraction study of chemical bonds in crystals under external electric field Semen Gorfman1 , Vladimir Tsirelson2 , Oleg Schmidt1 , Marcus Schmidt3 , Horst Bormann3 , Ullrich Pietsch1 1

University of Siegen, Siegen, Germany – 2 Mendeleev University of Chemical Technology, Moscow, Russia – 3 Max-Plank Institute for Chemical Physics of Solids, Dresden, Germany The physical properties of crystals such as dielectric polarization and piezoelectricity are well studied on macroscopic level. They are described by the tensors of dielectric susceptibilities and piezoelectric constants. In most cases their atomistic origin is not clear. The evaluation of the structural origin of these phenomena requires insitu measurement of the microscopic structural response under influence of an external perturbation. One possible experiment of this type is to monitor the change of X-ray diffraction intensities by a crystal under a permanent external electric field. Because the effect is small (∆I/I<0.01) it has to be measured by means of the synchrotron radiation [2]. The shifts of diffraction peak positions are related to the change of crystal lattice parameters (converse piezoelectric effect). The variations of Bragg intensities are associated with the change of the fractional atomic positions (dielectric polarization). From one side electric field induced atomic displacements may be related to crystal dielectric properties. From other side they are directly connected to features of electron density and chemical bonding in studied crystal. Thus the microscopic information, derived from electron density may be related to crystal physical properties through the electric field induced structural changes, measured in synchrotron diffraction experiment. Recently [1], we applied this strategy to investigate the site selective response in α-GaPO4 to a permanent external electric field. Here we have shown that the response of a crystal rather depends on the pseudoatomic charges of consistent atoms then to the strength of chemical bond. Therefore the PO4 with stronger bond deforms a little bit stronger compared with the GaO4 tertrahedra with smaller bond strength due to the higher pseudoatomic charge of P atom compared with Ga one. This outcome can be verified by inspection of other semi-covalent ternary compounds such as ZnSiP2 or similar chalcopyrite compounds. These are iso-structural to ZnS structure and contain two different bonds with different bond strength and pseudoatomic charges. The chalcopyrite ZnSiP2 crystals were grown by chemical transport reactions and prepared for synchrotron diffraction studies under external electric field. The electron density in this crystalline compound is investigated on the basis of density functional theory. The strength Zn-P and Si-P chemical bonds are studied and the pseudoatomic charges of Zn, P and Si atoms are determined. On the basis of the previous results the reaction of ZnSiP2 crystals to an external electric field is predicted. [1] S.V. Gorfman, V.G. Tsirelson, A. Pucher, W. Morgenroth, U. Pietsch. Acta Cryst. A62 (2006) 1-10. [2] S. V. Gorfman, V.G. Tsirelson, U. Pietsch. Acta Cryst. A61 (2005) 387-396.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P133

Microheterogeneous atomic structure of liquid Cu-Sn alloys S. Gruner1 , I. Kaban1 , R. Kleinhempel1 , W. Hoyer1 1

Chemnitz University of Technology, Institute of Physics, D-09107 Chemnitz

In the solid state, Cu-Sn alloys exhibit a number of intermetallic phases. Structuresensitive properties such as the dynamic viscosity and the electrical conductivity show a non-monotonous composition dependence with maxima at the compound’s composition. Assuming that the interactions between the atoms in these alloys are basically unchanged when heating to the liquid state, on can expect signs of cluster formation similar to the corresponding intermetallic phases in the liquid state. Thus, a detailed study on the structure of liquid Cu-Sn alloys over the entire concentration range is presented in this work. The samples under investigation have been prepared from granules of the pure elements Cu and Sn (purity 99.999 %). The X-ray diffraction experiments have been performed using a high-temperature θ-θ-Diffractometer at the TU Chemnitz as well as at the BW5 experimental station [1] at HASYLAB at DESY, Hamburg. Neutron diffraction has been done at the SLAD diffractometer [2] at the Neutron Research Laboratory NFL Studsvik, Sweden. The course of the analysis of the diffraction data followed two major techniques: (i) the coherently scattered X-ray intensities for numerous samples over the whole composition range were evaluated with the model of micro-inhomogeneous structure as proposed by Il’inskii and co-workers [3]; (ii) samples with selected compositions were investigated by means of X-ray and neutron scattering at a temperature near the liquidus line. The results of these scattering experiments have been used to derive partial correlation functions by using the reverse Monte Carlo (RMC) method [4]. Partial co-ordination numbers as well as short-range ordering parameters have been calculated. Using the example of the Cu6 Sn5 alloy it was shown by comparison with partial structure factors determined from neutron scattering using isotopic substitution [5] that simultaneous RMC-modelling of two total structure factors obtained from X-ray and neutrondiffraction yield reliable pair correlation functions. Both, the evaluation following Il’inskii’s model as well as the RMC modelling suggest a heterogeneous structure and confirm the existence of clusters of the Cu3 Sn-stoichiometry. [1] H. F. Poulsen, J. Neuefeind, H.-B. Neumann, J. R. Schneider, M. D. Zeidler, J. Non-cryst. solids 188 (1995) 63 [2] A. Wannberg et. al., J. Neutron Res. 8 (1999) 133 [3] A. G. Il’inskii, L. E. Mikhajlova, A. V. Romanova, A. V. Rosenfeld, W. Hoyer, Magnetic and Electronic Properties of Materials, vol. 2, Naukova Dumka Kiev 1990, p. 75 [4] R. L. McGreevy, L. Pusztai, Mol. Simul. 1 (1988) 359 [5] J. E. Enderby, D. M. North, P. A. Egelstaff Phil. Mag. 14 (1966) 961

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P134

Rare-earth site distribution in R(PO3 )3 (R=La, Nd, Er, Yb) glasses by Reverse Monte Carlo simulations Uwe Hoppe1 1

Universit¨ at Rostock, Institut f¨ ur Physik, 18051 Rostock

(R2 O3 )x (P2 O5 )1−x glasses with x=0.25 possess comparably great fractions of rareearth ions R3+ . Determination of their mutual order is important to understand special glass properties and is also a challenging work because the relevant distances are already outside of the short-range order. Results of several approaches based on neutron diffraction are presented in the literature. On the other hand, the R-R correlations possess most weight in x-ray scattering data but extraction of the desired information is difficult. The approach used is a combination of total x-ray and neutron diffraction data by means of the Reverse Monte Carlo (RMC) method. Results of glasses with four different R3+ ions are presented where effects of the decrease of the ionic radius in the order La, Nd, Er, and Yb become visible. The RMC method generates three-dimensional atomic configurations which reflect main features of the short-range order of the metaphosphate glasses due to use of reasonable constraints in addition to the total x-ray and neutron structure factors. Twofold corner-connected PO4 tetrahedra forming chain and cyclic structures surround the R3+ sites. The terminal oxygen corners of the PO4 tetrahedra coordinate the rareearth ions. The main results for further analysis are the R-R partial structure factors and pair distribution functions. The assumption of a random packing of R-centered spheres with minimum separation of 0.63 nm reproduces the first sharp diffraction peak. But for reproducing the detailed features of the R-R pair distributions the description of the medium-range order of the R sites needs a more specific model. Starting form the structure of the monoclinic crystal Yb(PO3 )3 a hexagonal order of R sites is suggested (c/a=0.87). This model yields broad R-R first-neighbour peaks (8 neighbours) and the second-neighbour peak lies in the right position (12 neighbours). In addition to this model some short R-R distances (0.45 nm) occur. This peak reflects R sites which share terminal oxygen neighbours. This effect is very small for glasses with R=Yb but it increase with increasing radii of the rare-earth ions. The number of neighbours correlates excellently with the R-O coordination numbers and the numbers of the terminal oxygens which is available for coordination of an R site.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P135

Growth Mode of ZnPc on Passivated and Bare Silicon Substrates Sindu John Louis1 , Daniel Lehmann1 , Marion Friedrich1 , Dietrich R.T. Zahn1 1

Chemnitz University of Technology, Semiconductor Physics, D-09107 Chemnitz, Germany Zinc Phthalocyanine (ZnPc) has been identified as an excellent candidate, because of its flexibility in varying electrical and optical behaviour and its own benefit as an organic semiconductors. It is known that the fashion of ZnPc molecular stacking, affects its electrical and photoconductivity, which depends on the degree of π-π interaction between the adjacent molecules. Being planar and exhibiting structural self organisation, the molecular orientation depends mainly on the growth mode of the first few layers, which in turn depends on the inter molecular interaction and on molecule-substrate interaction. Thin films of ZnPc are prepared by Organic Molecular Beam Deposition (OMBD) in ultra high vacuum condition on hydrogen passivated and bare silicon (111) oriented substrates. Spectroscopic ellipsometry and transmission measurements are carried out using Variable Angle Spectroscopic Ellipsometer (VASE) in the NIR-Vis-UV range from 0.75 eV to 5 eV. For the optically anisotropic ZnPc films, the complex dielectric function, film thicknesses and the surface roughness were determined. The average molecular tilt angle of the ZnPc with respect to the substrate is calculated. The results are confirmed with infrared reflection measurements. Both the dielectric function as well as the tilt angle of the ZnPc molecule is found to be strongly dependent on the substrate used. The kind of orientation adopted by the first few layers is found to be preserved in thicker films.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P136

X-ray diffraction, neutron diffraction and EXAFS study of amorphous Ge15 Te85 ´ va ´ri2 , W. Hoyer1 , E. Welter3 I. Kaban1 , P. Jo 1

Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany – 2 Research Institute for Solid State Physics and Optics, H-1525 Budapest, POB 49, Hungary – 3 Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg, Germany The atomic structure of amorphous Ge15 Te85 has been studied by X-ray and neutron diffraction and X-ray absorption spectroscopy at the Ge K-edge. Neutron diffraction experiments were carried out with the liquid and amorphous materials diffractometer SLAD at NFL, Studsvik. The incident wavelength of neutrons was 1.11 ˚ A. The scattered intensity was measured between 0.4 ˚ A−1 and 10.4 ˚ A−1 . X-ray diffraction experiments were carried out at the BW5 experimental station at HASYLAB, Hamburg. The energy of the radiation was 125 keV (0.101 ˚ A). Scattered intensities were measured between 0.5 ˚ A−1 and 20 ˚ A−1 . EXAFS measurements at the Ge K-edge (11103 eV) were carried out at the beam line A1 of HASYLAB in transmission mode using a Si (111) double-crystal monochromator. The ionization chambers were filled with N2 -Ar mixture. The pressure inside the sample chamber was of the order of 10−2 mbar. The diffraction measurements were modelled simultaneously with EXAFS data by the reverse Monte Carlo (RMC) simulation technique. Combination of the three independent measurements allowed separation of the partial pair correlation functions gGeT e (r) and gT eT e (r) and estimation of the corresponding coordination numbers. ˚ The mean Ge-Te and Te-Te distance obtained in the present study are rGeT e = 2.60 A and rT eT e = 2.79 ˚ A, and the coordination numbers: NT eT e = 1.64 and NGeT e = 3.53. It is assumed that the structure of amorphous Ge15 Te85 consists of GeTe3/2 and GeTe4/2 units bridged through the net of Te atoms.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P137

Synchrotron- und Neutronenstreuung an Sc-(N)-dotiertem Zirkoniumdioxid Ines Kaiser-Bischoff1 , Hans Boysen1 , Friedrich Frey1 , Martin Lerch2 , Jens¨ rn Pedersen5 , Markus Ho ¨ lzel6 , Uwe Hoffmann3 , Carsten Paulmann4 , Bjo Anatoliy Senyshyn6 1

LMU M¨ unchen, Department f¨ ur Geo- und Umweltwissenschaften, Sektion Kristallographie, Am Coulombwall 1, 85748 Garching – 2 TU Berlin, Institut f¨ ur Chemie, Strasse des 17. Juni 135, 10623 Berlin – 3 BENSC/Uni T¨ ubingen, HMI, Glienickerstrasse 100, 14109 Berlin – 4 Hasylab/Uni Hamburg, DESY, Notkestrasse 85, 22607 Hamburg – 5 TU M¨ unchen, Forschungsneutronenquelle FRM-II, Lichtenbergstrasse 1, 85747 Garching – 6 TU Darmstadt, Materialwissenschafen, Petersenstrasse 23, 64287 Darmstadt ZrO2 , dotiert mit Sc2 O3 , geh¨ ort zu den Materialien mit den h¨ ochsten Sauerstoffionenleitf¨ ahigkeiten. In Abh¨ angigkeit vom Dotiergehalt (Sc/N) bilden sich Strukturen mit ¨ geordneten Leerstellenverteilungen. Diese rhomboedrischen Uberstrukturen lassen sich von der bei hohen Temperaturen realisierten Fluoritphase (Fm3m) ableiten, die eine statistische Verteilung der Leerstellen und N/O zeigt. Ziel der Untersuchungen ist, ¨ die Ordnungsprinzipien der Uberstrukturen und den Einfluss der Co-Dotierung mit Stickstoff zu verstehen, sowie die Anionendiffusion zu charakterisieren. W¨ ahrend kubisch-stabilisierte ZrO2 -Phasen (z.B. mit Y2 O3 ) eine charakteristische diffuse Streuung bei RT zeigen, die durch rhomboedrische Nahordnung bewirkt wird, ¨ wird diese bei Zr0.82 Sc0.18 O1.91 erst bei hohen Temperaturen nach dem Ubergang in die kubische Phase beobachtet (Ger¨ at E2/HMI). ¨ Zur Bestimmung der Uberstrukturen wurden verschiedene Proben mit Synchrotron(Ger¨ at F1/Hasylab) und Neutronenstreuung (Ger¨ at RESI/FRM2) untersucht. W¨ ahrend die tern¨ are Probe (Zr-Sc-O) mit ca. 10mol% Sc2 O3 die β-Phase (R-3) zeigt [1], f¨ uhrt die ¨ Co-Dotierung mit Stickstoff zu einer anderen Uberstruktur. In der Literatur wird die ¨ Uberstruktur im System Zr-Mg-O-N mit der β’-Phase beschrieben [2], die ein ¨ ahnliches Reflexmuster wie Zr-Sc-O-N zeigt. Zus¨ atzliche Reflexe deuten eventuell auf eine andere ¨ Uberstruktur oder vielfache Zwillinge hin. Neutronenpulvermessungen am Ger¨ at SPODI/FRM2 konnten hingegen bei RT mit der β’-Phase verfeinert werden. Im Gegensatz zum System Mg-Zr-O-N zeigt sich hier keine N/O-Ordnung. Zur Charakterisierung der Anionendiffusion wurden Hochtemperatur-Pulvermessungen am Ger¨ at SPODI (FRM2) durchgef¨ uhrt. Die Diffusion findet haupts¨ achlich entlang der <100>-Richtungen statt, mit einer Potentialschwelle von ca. 1.5 eV bei 1700 ◦ C. [1] K. Wurst, D.J.M. Bevan, J. Mohyla, M. Hofmann und E. Schweda, Solid State Sciences, 5 (2003) 1491. [2] M. Lerch, H. Boysen, and P.G. Radaelli, J. Phys. Chem. Solids 58 (10) (1997) 1557.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P138

Na2 O - Fe2 O3 - SiO2 glasses: Inhomogeneous distribution of Fe in channels Florian Kargl1,2 , Andreas Meyer2 , Michael Marek Koza3 1

Department of Applied Science, Chalmers University of Technology, 41296 G¨ oteborg, Schweden – 2 Deutsches Zentrum f¨ ur Luft und Raumfahrt, Institut f¨ ur Raumsimulation, 51170 K¨ oln – 3 Institute Laue-Langevin, 38042 Grenoble, Frankreich We report on the investigation of ternary sodium iron-silicate glasses by means of neutron spectroscopy and diffraction. Being of outstanding importance for geosciences, iron bearing silicate glasses and melts show a number of unique features [1]. Adding Fe2 O3 to a binary alkali silicate melt leads to an increase in melt viscosity. This increase depends not only on the amount of Fe2 O3 , but also on the conditions of synthesis. For instance, under normal conditions of synthesis Fe is predominantly built into the structure as Fe3+ . Depending on melt composition, temperature, and atmosphere Fe can also exist in the reduced form Fe2+ . We demonstrate that a partial Fe-Fe structure factor can be directly obtained in these multicomponent system. Neutrons scattered on Fe3+ couple to its unpaired electron spin moment. Quasielastic neutron scattering allows to separate nuclear from magnetic scattering contributions in sodium iron silicates. The results were corroborated by experiments using polarization analysis. The partial Fe-Fe structure factor determined by means of magnetic scattering features a correlation peak around 0.9 ˚ A−1 . A correlation peak in the nuclear elastic structure factor observed at the same position in binary alkali silicate melts was shown to reflect a network of percolation channels for fast alkali ion diffusion [2]. The addition of a second network forming component, Al2 O3 , leads to a drastic increase in viscosity and a disruption of the channel structure. This is evidenced by vanishing of this correlation peak in the nuclear elastic structure factor [3]. Considering the total nuclear structure factor consisting of ten different partial structure factors the position of Al with respect to the other components cannot be unambiguously determined. In the sodium iron-silicates the position of the correlation peak is Fe concentration independent. However, the peak height scales with the total Fe3+ content. The experiments indicate an inhomogeneous distribution of Fe. They further suggest that the Fe atoms are located on Na equivalent positions rather than on those equivalent to Si. [1] Y. Bottinga, D. B. Dingwell, and P. Richet, edts., 6th Silicate Melt Workshop, Chem. Geol. 174, (2001) 1; Y. Bottinga, D. B. Dingwell, P. Richet, and M. Toplis edts., 7th Silicate Melt Workshop, Chem. Geol. 213, (2004) 1. [2] A. Meyer, J. Horbach, W. Kob, F. Kargl, and H. Schober, Phys. Rev. Lett. 93, (2004) 027801. [3] F. Kargl and A. Meyer, Chem. Geol. 213, (2004) 165.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P139

Charge Ordering in transition metal oxides with low d-level occupation ¨ lzel3,4 , A. Senyshyn3,4 , A. Cousson5 , F. A. C. Komarek1 , M. Isobe2 , M. Ho 5 5 1 Bouree , G. Andre , W.-D. Stein , T. Lorenz1 , M. Braden1 1

II. Physikalisches Institut, Uni K¨ oln, Z¨ ulpicher Str. 77, 50937 K¨ oln – 2 Institute 3 for Solid State Physics, The University of Tokyo – Darmstadt University of Technology, Institute for Material Science, Petersenstrasse 23, D-64287 Darmstadt – 4 Munich University of Technology, FRM-II, Lichtenbergstr. 1, D-85747 Garching – 5 LaboratoireLeon Brillouin, CEA/CNRS, F91191 Gif-Sur Yvette Cedex, France We present a structural study of three different transition metal oxide systems by means of neutron and single crystal X-ray diffraction. We found charge ordering in the Y1−x Cax TiO3 titanate system and in the K2 V8 O16 hollandite system and confirm the charge order in the LiV2 O5 vanadate to persist to low temperatures. Having one electron in the 3d shell, the rare earth titanates RTiO3 represent an interesting system to study the complex interplay of magnetic and structural degrees of freedom. In addition we have analysed the metal-insulator (MI) transitions driven by hole doping when trivalent R-ions get replaced by divalent earth-alkaline ions. Upon cooling Ca-doped YTiO3 system exhibits a structural first-order phase transition accompanied by cossover phenomena in structural and magnetic properties. In contrast to most transtion metal oxides, we find the metallic phase to be stabilized at low temperature. For Ca-concentrations around 35-50 % we find first evidence for static charge ordering in the insulating phases. The vanadate family of oxides AV2 O5 shows a variety of lowdimensional phenomena originating from their peculiar crystal structures. These transition metal oxides are quasi two dimensional (2D) materials with layers formed by VO5 square pyramids while the A ions are situated between the layers as intercalants and act as electron donors. For A=Li the vanadium ions are nominally in a mixed-valence state with an average valency of +4.5. Thus, vanadium 4+ zigzag chains are separated by non-magnetic 5+ zigzag chains turning this system quasi onedimensional (1D). We were able to confirm the persistence of charge ordering of LiV2 O5 down to 2 K by single crystal neutron diffraction. The hollandite K2 V8 O16 room-temperature structure is tetragonal and consists of octahedral VO6 double-chains running along the c-direction. The potassium ions align in the free space between these vanadium oxide double-chains and form chains in c-direction parallel to the VO6 double-chains. The vanadium ions in this compound possess an average valency of 3.75+. K2 V8 O16 exhibits a metalinsulator (MI) transition at 175 K. Concomitantly with the MI-transition there is a phase transition from the tetragonal to a monoclinic structure. We performed single crystal X-ray diffraction measurements and were able to solve the complex, distorted structure below 175 K for the first time. It turned out that there is a dimerization of the vanadium ions in one of the two vanadium chains forming the VO6 double-chain and a zig-zag-chain formation in the neighbouring vanadium chain. Furthermore, the analyses of the bond distances in terms of bond-valence sums point to charge ordering in this complex distorted structure.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P140

Energy-dispersive X-ray reflectivity for real-time growth studies of organic thin films Stefan Kowarik1,2 , Alexander Gerlach1,2 , Frank Schreiber1 , Wolfram Leitenberger3 , Ullrich Pietsch4 1

T¨ ubingen University, Institute for Applied Physics, 72076 T¨ ubingen, Germany – Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3 Potsdam, Institute for Physics, 14469 Potsdam, Germany – 4 Siegen University, Department of Physics, 57068 Siegen, Germany 2

We employ energy-dispersive as well as angle-dispersive X-ray reflectivity to study the growth and structure of the organic semiconductors rubrene and pentacene in in situ and real time. Following the surface morphology of rubrene films during organic molecular beam deposition, we find relatively smooth films (surface roughness below ∼15 ˚ A for thicknesses up to at least 600 ˚ A) and a significant delay before the onset of roughening. This anomalous roughening in the beginning and crossover to normal roughening later during growth may be related to conformational changes of rubrene in the early stages of growth. Studying pentacene in real-time during growth with energy-dispersive reflectometry we can follow the growth oscillations for a wide range in q-space including the anti-Bragg point. These growth oscillations give a detailed picture of the crossover from layer-by-layer growth for the first pentacene monolayers to roughening for thicker films. Finally, we discuss the chances and limitations of energy dispersive as compared to conventional angle-dispersive measurements [1]. [1] S. Kowarik et al., PCCP 8 (2006) 1834

Fig. 1: Following the evolution of the X-ray reflectivity during pentacene thin film growth with energy dispersive measurements allows to determine the growth mode.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P141

Komplimentarit¨ at von inelastischen Streuexperimenten mit Neutronen und Synchrotronstrahlung Michael Marek Koza1 , Michael Krisch2 1

Institut Laue Langevin, 6 rue Jules Horowitz, 38042 GRENOBLE, France – 2 European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 GRENOBLE, France Das Verst¨ andnis dynamischer Eigenschaften von Materialien mit komplexem strukturellen Aufbau stellt eine grosse Herausforderung f¨ ur experimentelle Untersuchungen dar. Als Beispiele f¨ ur strukturell–komplexe Materialien seien hier amorphe Werkstoffe, Zeolite, Clatrate, Hydrat–Clatrate und gef¨ ullte Skutterudite genannt [1,2,3]. Das hohe Interesse, die dynamischen Charakteristika dieser Materialien zu verstehen, gr¨ undet sich auf deren anwendungsbezogene Einsatzbereiche. So finden diese Materialien ihre Anwendung als Isolator–, Katalysator–, Filter–, Energiespeicher– oder Thermoelektrische–Werkstoffe. Damit spielen thermische Eigenschaften und folglich die mikroskopische Dynamik eine sehr wichtige Rolle f¨ ur deren Anwendung und Anwendbarkeit. Die Schwierigkeit, detailierte Erkenntnisse u ¨ber deren mikroskopische Dynamik zu gewinnen, hat mannigfaltige Gr¨ unde. So sind die oben aufgef¨ uhrten Systeme in der Regel nicht als Einkristalle herstellbar, womit eine umfassende experimentelle Untersuchung ~ im Sinne von Gitterdynamik im vierdimensionalem Q–ω Phasenraum unterbunden wird. Im Falle der offenen Netzwerk–Systeme sind die GastWirt Wechselwirkungen sehr komplex und theoretisch weder vollst¨ andig verstanden noch einheitlich beschreibbar. In einigen F¨ allen verhindert die Gr¨ oße der offenen Netzwerke selbst eine umfassende theoretische Beschreibung der Dynamik des Gitters. Wir werden an den Beispielen von amorphem Eis, Hydrat-Clatraten und gef¨ ullten Skutteruditen zeigen, dass die Nutzung von inelastischen Streuexperimenten mit Neutronen und Synchrotronstrahlung einen entscheidenden Schritt zum Verst¨ andnis der Dynamik dieser Systeme darstellt. Wir werden ferner diskutieren, dass die Anwendung beider Sonden, Neutronen und Synchrotronstrahlung, eine Notwendigkeit ist, um eine detailgetreue Beschreibung der mikroskopischen Dynamik zu erhalten. Dies ist durch die Komplimentarit¨ at beider Sonden in Bezug auf die Ausleuchtung des Q–ω Phasenraums und die Energieaufl¨ osung zu erkl¨ aren. [1] M.M. Koza et al., Phys. Rev. B 69 (2004) 24204; Phys.Chem.Chem.Phys. 7, (2005) 1423; Phys. Rev. Lett 94 (2005) 125506. [2] B. Chazallon et al. Phys.Chem.Chem.Phys. 4 (2002) 4809; J. Baumert et al. 68 (2003) 174301. [3] R. Viennois et al. Phys.Chem.Chem.Phys. 7 (2005) 1617; G.J. Long et al, Phys. Rev B 71 (2005) 140302(R).

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P142

Anomalous neutron Compton scattering: convolution approximation vs. model-free approach Maciej Krzystyniak1 , Tyno Abdul-Redah1 , Aris Chatzidimitriou-Dreismann1 1

Technische Universit¨ at Berlin, Institut f¨ ur Chemie, Sekr. C2, Straße des 17. Juni 135, 10623 Berlin A shortfall of the scattering intensity from protons has been observed in liquids (water, benzene, etc.) and solids (metal hydrogen systems, organic polymers, etc) using neutron Compton scattering (NCS). However, the conventional NCS data reduction scheme [1], used to obtain the scattering intensities, based on the convolution approximation (CA) of the nuclear momentum distribution with the instrument resolution function was severely criticized. It was claimed that it is the way the energy resolution function is incorporated in the data reduction scheme that leads to an underestimation of the scattering intensity. In the present work the CA approximation is compared to a newly proposed model-free approach that is independent of the form of the momentum distribution and the resolution function [2 - 4]. The new data reduction scheme is shown to lead to the same results as for the experimental data published earlier and treated with the CA approximation thus refuting the criticisms claiming the way the data reduction is performed responsible for the effect under consideration. [1] J. Mayers, T. Abdul-Redah, J. Phys: Condens. Matter 16, 4811 (2004) [2] B.Dorner, Journal of Neutron Research 13, 267 (2005) [3] M. Krzystyniak and C. A. Chatzidimitriou-Dreismann, Phys. Rev. B 72, 174117 (2005) [4] M. Krzystyniak and C. A. Chatzidimitriou-Dreismann, Journal of Neutron Research, in press

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P143

SAXS-studies on structure function relationships of thiamine diphosphatedependent enzymes ¨ nig1 Stephan Ko 1

Institut f¨ ur Biochemie, Fachbereich Biochemie/Biotechnologie, Martin-LutherUniversit¨ at Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale) A dozen of thiamine diphosphate-dependent enzymes have been investigated by means of small-angle X-ray solution scattering with synchrotron radiation. As a result of this it became obvious that SAXS is the method of choice to determine the oligomer state of enzymes in aqueous solutions. Furthermore it was possible to study the influence of a number of specific ligands, like substrates, activators, inhibitors, cofactors, and pH on the oligomerisation state and stability of enzymes in solution. Recently, the availability of corresponding programs allows the calculation of three-dimensional structure models of the enzymes directly from experimental scattering patterns ab initio without any further prerequisites. Comparison of these models to crystal structure models demonstrated the general reliability of these procedures. Furthermore it is possible to compare both kinds of structure models and to draw conclusions on the spatial arrangement of enzymes in aqueous solutions. Together with kinetic studies and protein crystal structure analysis, the SAXS is a powerful method to elucidate structure function relationships of enzymes.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P144

Time-Resolved Structural Investigation of Excimer Evolution in Organic Molecules Henrik Till Lemke1 , Tine Ejdrup1 , Nerijus Rusteika1 , Peter Hammershøj1 , Theis Ivan Sølling1 , Niels Harrit1 , Klaus Bechgaard1 , Robert Feidenhans’l1 , Martin Meedom Nielsen1 1

Centre for Molecular Movies, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark Excited aromatic molecules like pyrene, perylene and pentacene can relax to a short lived (≈100 ps) excited dimer state (excimer) that decays radiatively. Although this state is well characterised by time resolved optical spectroscopy the structural change upon dimerization remains unknown. We employ pump laser probe X-ray experiments in order to investigate structural changes during excimer evolution. X-ray pulses are either obtained from Kα secondary radiation from a plasma source or as synchrotron radiation from individual electron bunches at the ESRF. Using grazing incidence diffraction on polycrystalline thin films we can achieve a high excitation density within the probed volume and thus enhance the scattering signal. We have demonstrated a preferential uniaxial alignment of crystallites along the substrate surface, resembling a 2D-powder, as well as bi-axial alignment on substrates with friction deposited PTFE alignment layers. This enables us to take advantage of the grazing incidence scattering geometry to enhance the scattering signal. Results for this first time-resolved structural observations of transient excimers are reported.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P145

Linear instabilities in early transition metal oxide structures Thomas Malcherek1 , Ulrich Bismayer1 , Carsten Paulmann1 1

Mineralogisch-Petrographisches Institut, Universit¨ at Hamburg, Grindelallee 48, D20146 Hamburg Early transition metals (e.g. M = Ti, V, Nb, Ta) frequently exhibit out-of-center distortions within the octahedral coordination environment of common oxide structures. Given an appropriate structural topology of trans-corner connected octahedra, the distortions may align to form chains of alternating short and long metal-oxygen bonds at low temperatures. Depending on symmetry, the formation of such chains may give rise to ferroelectric, antiferroelectric or antipolar ground states. Compounds of this type often show characteristic diffuse scattering extending along reciprocal space planes upon transformation to their high temperature paraphase. In the perovskites BaTiO3 and KNbO3 such effects have been related to dynamic long range correlations of Ti-displacements parallel to h100i of the cubic paraphase by first principle computational methods [1]. Synchrotron radiation provides the means to efficiently study the weak scattering effects associated with these linear displacement correlations as well as their temperature dependence. Several examples of planar diffuse scattering effects in structure types containing trans-corner connected chains of MO6 -octahedra are being presented. The effects are discussed in relation to structural phase transitions occuring in these oxide compounds. [1] R. Yu et al., Phys. Rev. Lett. 74 (1995) 4067.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P146

Amorphization of Quasicrystalline Zr-Ti-Ni-Cu ¨nzer1 , Thomas Stefan Mechler1 , Gerhard Schumacher1 , Siegfried Klaumu 1 1 1 Zumkley , Nelia Wanderka , Michael-Peter Macht , Christian Abromeit1 1

Hahn-Meitner-Institut Berlin, Glienicker Straße 100, D-14109 Berlin

Au, Xe and Kr ions in the energetic range of 300-600 MeV were used to study the stability of quasicrystalline Zr-Ti-Ni-Cu under irradiation with swift heavy ions. Irradiation experiments have been performed at room temperature and at liquid nitrogen temperature at ISL. Prior to irradiation and after each fluence step the structure of the material was analyzed by means of X-ray diffraction. The X-ray measurements have been performed at room temperature under Bragg-Brentano geometry. Some specimens have also been analyzed by conventional and High Resolution Electron Microscopy (TEM and HRTEM, respectively) in the non-irradiated condition and after irradiation to moderate fluence steps. The structure of the specimens was completely quasicrystalline prior to irradiation. The relative decrease of the relative amount of the quasicrystalline phase under irradiation was determined by measuring the relative changes in X-ray peak intensity. Irradiation with 600 MeV Au ions lead to complete amorphization of the specimens already at fluence of 1x1013 cm−2 . At lower fluences amorphous tracks inside the quasicrystals were visualized by the use of HRTEM. The track diameter near the surface determined by HREM was 12 nm. This value is in agreement with the value determined from X-ray diffraction measurements. Amorphization induced by 350 MeV Au ions and 600 MeV Au ions was assigned to the electronic energy loss while amorphization by 300 MeV Kr ions is predominantly due to the nuclear energy loss. Within the experimental uncertainty, there was no difference in amorphization between 350 MeV Au ions and 600 MeV Au ions. Irradiation at liquid nitrogen temperature results in slower amorphization compared to room-temperature irradiation. This result is in qualitative agreement with predictions of thermal spike models.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P147

Ionen im Licht von Synchrotronstrahlung ¨ller1 Alfred Mu 1

Institut f¨ ur Atom- und Molek¨ ulphysik, Universit¨ at Giessen

F¨ ur aussagekr¨ aftige Messungen absoluter Wirkungsquerschnitte von Clustern oder Biomolek¨ ulen in Wechselwirkungsprozessen mit Photonen oder Elektronen ist eine Massenselektion und damit die Ionisierung der zu untersuchenden Spezies notwen¨ dig. Durch die Uberlagerung sauber charakterisierter Strahlen ionisierter Atome, Mo¨ lek¨ ule oder Cluster mit Synchrotronstrahlung unter definierten Uberlapp-Bedingungen ist es m¨ oglich, partielle Ionisations- und Aufbruchprozesse in Photon-Ion Wechselwirkungen quantitativ zu studieren. Messungen mit ineinander verlaufenden Ionen- und Photonen-Strahlen werden weltweit in mehreren Synchrotronstrahlungs-Laboratorien durchgef¨ uhrt. Ein Messbeispiel ist in Abbildung 1 dargestellt [1]. F¨ ur den Einsatz an PETRA III wird ein flexibles Konzept f¨ ur ein Ionenstrahl-Spektrometer vorgeschlagen [2], das es unter anderem zus¨ atzlich zu den existierenden M¨ oglichkeiten erlauben wird, erstmals Messungen differentieller Elektronenemission mittels Elektronen-Imaging bzw. hochaufl¨ osender Elektronenspektroskopie durchzuf¨ uhren. Im neuen Experimentaufbau wird die M¨ oglichkeit vorgesehen, einen elektrostatischen Ionen-Speicherring zu integrieren. [1] S.W. J. Scully, E. D. Emmons, M. F. Gharaibeh, R. A. Phaneuf, A. L. D. Kilcoyne, A. S. Schlachter, S. Schippers, A. M¨ uller, H. S. Chakraborty, M. E. Madjet, J. M. Rost, Phys. Rev. Lett. 94 (2005) 065503 [2] A. M¨ uller, S. Schippers, J. Ullrich, A. Wolf, M. Martins, R. D¨ orner, L. Schmidt, E. R¨ uhl, R. Flesch, Projektskizze zur F¨ orderperiode 2007-2010 der BMBF-Verbundforschung

Abb. 1: Absolute Wirkungsquerschnitte f¨ ur die Photoionisation von C+ 60 Ionen. Angedeutet sind die Beitr¨ age zweier kollektiver Schwingungsmoden der Gesamtheit aller quasi-frei beweglichen Elektronen im Gitter der 60 KohlenstoffIonenr¨ umpfe [1].

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P148

Struktur und Dynamik von Wasser in Pflanzenzellw¨ anden ¨ller1 , Ingo Grotkopp1 , Fanni Juranyi2 , Christoph Czihak3,4 , Gero Martin Mu 3 Vogl , Helmut Schober4 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, 24098 Kiel – SINQ, Paul–Scherrer–Institut, CH–5232 Villigen PSI, Schweiz – 3 Institut f¨ ur Mate¨ rialphysik, Universit¨ at Wien, Strudlhofgasse 4, A–1070 Wien, Osterreich – 4 Institut Laue–Langevin, B. B. 156, F–38042 Grenoble Cedex 9, Frankreich 2

¨ Uber viele einzigartige Eigenschaften von Wasser wurde in den letzten Jahrzehnten berichtet. Wasser, das in den ungeordneten Bereichen von Zellulose, dem Hauptbestandteil von Pflanzenzellw¨ anden, adsorbiert, zeigt Fl¨ ussigkeitsdynamik unter dem Gefrierpunkt. Allerdings sind weder die strukturellen Eigenschaften von Wasser in Zellulose noch die Natur des Phasen¨ ubergangs in eine feste Phase komplett verstanden. Unsere Streuexperimente mit Neutronen k¨ onnen helfen, ein Modell f¨ ur die Struktur und Dynamik von Wasser in Zellw¨ anden unter 0 ◦ C zu entwickeln. Beim Abk¨ uhlen friert ein zunehmender Anteil der Wassermolek¨ ule in einem graduellen, heterogenen Glas¨ ubergang zu einer neuen Art amorphen Eises ein. Der Rest wird unterk¨ uhlt und bleibt bis hinunter zu 200 K fl¨ ussig, allerdings mit einer stark verlangsamten Dynamik. In Modellen der Wasseradsorption in Zellulose wird angenommen, daß jeweils 1–3 Wassermolek¨ ule in bestehende Wasserstoffbr¨ uckenbindungen eingef¨ ugt werden. In einer neuen Untersuchung mit inelastische Neutronenstreuung von Wasser in orientierten Zellulosefasern konnten wir finden, daß die dynamischen Eigenschaften des adsorbierten Wassers ¨ ahnlich anisotrop wie seine Umgebung ist. Dies k¨ onnte erkl¨ aren, warum sich keine ausgedehnten Netzwerke kristallinen Eises in Pflanzenzellw¨ anden ausbilden.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P149

Improved growth of Fe/V-superlattices due to H-assistance Gregor Nowak1 , Arndt Remhof1 , Andreas Liebig2 , Moreno Marcellini2 , ¨ rgvin Hjo ¨ rvarsson2 , Hartmut Zabel1 Kurt Westerholt1 , Bjo 1

Institut f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, Germany – 2 Department of Physic, University Uppsala, Regementsv¨ agen 1, 75121 Uppsala, Sweden We studied the influence of hydrogen on the growth of sputter deposited V single layers and on [Fe(2ML)/V(16ML)]×30 superlattices. We show that the high structral quality achieved previously [1] can be further improved by using hydrogen enriched Argon (pAr =7 mbar)as process gas during sputter deposition. At each chosen hydrogen pressure of up to 2×10−6 mbar we prepared a series of samples at substrate temperatures between 270 ◦ C and 320 ◦ C. The structural characterization was carried out by x-ray diffraction at the wiggler beamline W1.1 at the Hamburg synchrotron laboratory (HASYLAB). Three trends are observed. The mosaicity decreases, the interface quality increases (Fig. 1), and the transport measurements of 240 ˚ A thick V single layers grown in H-enriched sputter gas reveal a 53 % higher residual resistivity ratio of 14.2 in comparison to V-layers grown without H-enrichment (Fig. 2). The residual resistivity ratio is a direct measure of the Cooper pairs coherence length which we could increase due to the H-enrichment by 25 % to 232 ˚ A in V. The Cooper pair coherence length is mainly limited by scattering on structural and chemical defects which could be reduced in the H-enrich sputter process. We attribute this effects to an increased surface mobility of the metal atoms in the presence of hydrogen during the sputtering process [2]. This project was funded by the DFG under contract-Nr. RE 2203-1/1 [1] P. Isberg et al., Vacuum, 48 (1997) 483. [2] Horch et al., Nature, 398 (1999) 132.

Fig. 1: X-ray radial scans of the Fe/V superlattices.

Fig. 2: Transport measurements for 26 nm thick V single layers.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P150

Methyl rotational potentials and guest molecule dynamics in water clathrates of methyl halides ¨rgen Allgaier1 , Werner Press2 , Arnaud Desmedt3 , Michael Prager1 , Ju ¨ rg Pieper4 , John Tse5 , DeAlexandra Buchsteiner4 , Margarita Russina4 , Jo 5 6 nis Klug , Marie Plazanet 1

IFF, Forschungszentrum J¨ ulich, 52425 J¨ ulich, Germany – 2 Inst. f¨ ur Experimentalphysik, Universit¨ at Kiel, Germany – 3 LPCM, Universite de Bordeaux 1, France – 4 Hahn-Meitner Institut, Berlin, Germany – 5 Steacie Institute of Molecular Science, NRC of Canada, Ontario, Canada – 6 Institut Laue-Langevin, Grenoble, France The CH3 X water clathrates, X=F,Cl,Br, assume the cubic I structure of clathrates as the natural methane clathrate [1]. The interaction with the cage is significantly different to the methane case due to the presence of a dipole moment and a tendency to form hydrogen bonds. By changing the guest molecule these properties can be changed and allow new insight on the guest-host interaction. Such tuning of the interaction is not possible with the symmetric methane molecule. The clathrate structure with CH3 I guest molecules is cubic II. Rotational potentials of methyl groups were obtained from high resolution neutron tunneling spectroscopy. They give information on the potential energy surface of the cage with e.g. different adsorption sites and on disorder of the hydrogen bond network of the cage. Quasielastic spectra allow to study in addition to methyl rotation the rotational and translational dynamics, often called rattling, of the whole molecule in the cage. Beside of the published results on CH3 I [2] and CH3 F [3] clathrates we will present new results on the chlorine and bromine compounds. [1] C. Gutt et al, J. Chem. Phys. 113,4713(2000) [2] M. Prager et al, J. Phys.: Condens. Matter 16,7045(2004) [3] M. Prager et al, Phys. Chem. Chem. Phys. 7,1228(2005)

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P151

Fehlordnung von C2 -Hanteln in der Hochtemperaturmodifikation von K2 C2 Uwe Ruschewitz1 , Winfried Kockelmann2 , Bodo Zibrowius3 1

Institut f¨ ur Anorganische Chemie, Universit¨ at zu K¨ oln, Greinstraße 6, D-50939 K¨ oln – 2 Rutherford Appleton Laboratory, ISIS Facility, Chilton, OX11 0QX, UK – 3 MaxPlanck-Institut f¨ ur Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 M¨ ulheim an der Ruhr Von den meisten Alkali- und Erdalkalimetallacetyliden (AI2 C2 mit AI = Li, Na, K und AII C2 mit AII = Ca, Sr, Ba) sind kubische Hochtemperaturmodifikationen bekannt, ¨ die durch fehlgeordnete C2 -Hanteln charakterisiert sind. Uber die Natur der Fehlordnung gab es jedoch bislang nur wenige Informationen. K¨ urzlich konnten wir f¨ ur K2 C2 mit Hilfe der 13 C-Festk¨ orper-NMR-Spektroskopie zeigen, dass eine dynamische Fehlordnung mit einer Zeitkonstante deutlich kleiner als 4·10−6 s vorliegt [1]. Um die Natur dieser dynamischen Fehlordnung detaillierter zu untersuchen, wurden Neutronenbeugungsexperimente am ROTAX-Diffraktometer (ISIS/RAL, UK) an K2 C2 und isotypem Na2 C2 bei verschiedenen Temperaturen oberhalb der Phasenumwandlungstemperatur durchgef¨ uhrt. Es sind zwei grundlegende Modelle denkbar: das Pauling-Modell mit einer freien Rotation der C2 -Hanteln um ihren Schwerpunkt und das Frenkel -Modell mit Austauschprozessen zwischen verschiedenen Lagen, die in der kubischen Symmetrie zul¨ assig sind. Rietveld-Verfeinerungen ergeben sowohl f¨ ur Na2 C2 als auch f¨ ur K2 C2 eine bessere Anpassung f¨ ur das Frenkel -Modell. Dabei wurden die besten Verfeinerungsergebnisse f¨ ur Austauschprozesse zwischen Lagen gefunden (s. Abb. 1), bei denen die C2 -Hanteln auf die Fl¨ achen des W¨ urfels der umgebenden Alkalimetallionen zeigen (Orientierung entlang [100]). [1] B. Zibrowius et al., Phys. Chem. Chem. Phys. 6 (2004) 5237.

Abb. 1: M¨ ogliche Modelle f¨ ur die dynamische Fehlordnung von C2 -Hanteln in HT-K2 C2 .

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P152

Relation between the excess density of states and Brillouin spectra in glasses Walter Schirmacher1 , Giancarlo Ruocco2 , Tullio Scopigno2 1

Phys. Dept. E13, TU M¨ unchen, D-5747 Garching, Germany – 2 Dipt. di Fisica, Universit’a La Sapienza, I00185 Roma, Italy Using a theory developed recently by one of us, based on a model in which the shear modulus exhibits a random spatial variation due to the disorder, we derive relations between the excess of the density of vibrational states and the position and width of the Brillouin peak observed in inelastic X-ray, neutron and light scattering. Comparing these relations with results of molecular-dynamics simulations and experiments gives good agreement with the theory.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P153

X-ray diffraction study of BiB3 O6 crystals in an external electric field Oleg Schmidt1 , Semen Gorfman1 , Wolfgang Morgenroth2 , Ullrich Pietsch1 1

Solid state physics department, Siegen University, Germany – 2 Department for Inorganic Chemistry, University of G¨ ottingen, Germany, Department of Chemistry, Aarhus, Denmark and HASYLAB at DESY, Hamburg, Germany The application of a permanent external electric field to a single crystal induces deformations, visible on both atomic and macroscopic levels. Microscopic deformations are associated with displacements of atomic positions in a fixed unit cell [1], and result in dielectric polarization of a media. In addition non-centrosymmetrical crystals are deformed under electric field, showing thus converse piezoelectric effect. The information about atomic displacements within a unit cell is obtained from Bragg diffraction intensities. Macroscopic deformation can be simultaneously quantified from angular positions of diffraction maxima. In the present work we performed X-ray diffraction study of monoclinic BiB3 O6 crystal under external electric field. This crystal is interesting because of its extraordinary piezoelectric effect, at least 10 times stronger than in α-quartz. For the first time the piezoelectric constants of BiB3 O6 were measured by means of a Michelson interferometer [2]. We have determined piezoelectric constants from shifts of rocking curves by means of synchrotron X-ray diffraction experiment. The measurements were performed with three differently oriented samples of BiB3 O6 parallel to (100), (010), (001) Miller planes using the four circle HUBER diffractometer at the D3 beamline at HASYLAB. External high voltage was applied via two silver contacts deposited on the opposite sample faces. The peak shift and intensity variation of more than 100 reflections were measured. We used the following equation to calculate eight independent constants of the piezoelectric tensor dijk . Hk Hk Hk + dijk Ei Yj + Rijk Ei Yj H2 H H This equation relates the tensor dijk , the antisymmetric rotation tensor Rijk and the electric field vector Ei with the observed peak shift ∆θ. Hi is the scattering vector and Yi is the Y-axis of the diffractometer in a crystal Cartesian system as the basic system. We compare the calculated piezoelectric constants to those, obtained in the work [2]. To get an information about structural reasons for observed physical properites of BiB3 O6 we measured electric field induced diffraction intensity variations. With the measured data qualitative statements are made concerning atomic displacements related to high piezoelectric properties. The authors acknowledge the support of DFG (priority program 1178) and L. Bohat´ y, P. Becker (University of Cologne) for providing the samples of BiB3 O6 . [1] Gorfman, S., Tsirelson, V., Pietsch, U. Acta. Cryst. A61, p. 387-396 (2005) [2] Hauss¨ uhl, S., Bohat´ y, L., Becker, P. Appl. Phys. A82, p. 495-502 (2006) ∆θ(H) = tan θdijk Ei Hj

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P154

FLASH - The Free Electron Laser at DESY Siegfried Schreiber1 , Josef Feldhaus1 1

DESY, Notkestr. 85, 22603 Hamburg

FLASH is a free electron laser user facility at DESY providing laser-like radiation in the VUV and soft X-ray wavelenth regime. The facility unique in the world recently achieved a world record with lasing at a wavelength of 13.1 nm. A low emittance electron beam is accelerated with superconducting accelerating structures of the TESLA type to an energy of 700 MeV. In a 24 m long undulator system laser-like radiation is geneated via the SASE process, a single-pass high-gain amplification starting from noise. The pulsed radiation is fully coherent with a peak brilliance several orders of magnitudes higher than 3rd generation synchrotron radiation sources. The pulse length is in the order of 25 to 50 fs allowing many experiments in different scientific fields, for instance time resolved observation of chemical reactions with atomic resolution.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P155

Structures of the Metal Oxyhalides M OX (M = Ti, V and X = Cl, Br) at Low Temperature ¨ nleber1 , Luka ´ˇ Andreas Scho s Palatinus2 , Sander van Smaalen1 1

Lehrstuhl f¨ ur Kristallographie, Universit¨ at Bayreuth, BGI Geb¨ aude, Bayreuth, Germany – 2 Laboratoire de Cristallographie, EPF Lausanne, BSP-Dorigny, Lausanne, Switzerland The metal(III) oxyhalide M OX structures with M = Ti, V and X = Cl, Br [1] are isostructural with FeOCl at room temperature: they are built by slabs consisting of a M2 O2 bilayer enclosed by layers of X atoms. Their symmetry is orthorhombic, space group P mmn. Two phase transitions have been observed in TiOCl and TiOBr upon cooling, suggesting the presence of a spin-Peierls state [2,3]. In VOCl only one phase transition is observed [4]. We have performed temperature dependent single crystal X-ray diffraction experiments down to T = 10 K at beam line D3, HASYLAB-DESY, Germany. The aim of the experiments was to explore the phase transitions and to develop precise and detailed structural models for the low temperature and intermediate temperature phases of these compounds. The low temperature phases of TiOCl and TiOBr are twofold superstructures of the room temperature phases [5,6]. They show a dimerization of the Ti atoms along the [010] direction in accordance with spin-Peierls magnetic ordering. The intermediate phases are incommensurately modulated with temperature dependent modulation wave vectors [7,8]. The analysis of the variations of the structural parameters will be presented as function of temperature. The results are compared and set into relation to the various degrees of magnetic order in these compounds, which are responsible for the phase transitions. Therefore the knowledge of the superstructures is important, because it sheds further light on the nature of the phase transitions in the M OX compounds. [1] H. Sch¨ afer et al., Z. Anorg. Allg. Chemie 295 (1958) 268. [2] A. Seidel et al., Phys. Rev. B 67 (2003) 020405. [3] T. Sasaki et al., arXiv:cond-mat 0501691 (2005) unpublished. [4] A. Wiedenmann et al., J. Phys. C: Solid State Phys. 16 (1983) 5339. [5] M. Shaz et al., Phys. Rev. B 71 (2005) 100405(R). [6] L. Palatinus et al., Acta Crystallogr. C 61 (2005) i47. [7] S. van Smaalen et al., Phys. Rev. B 72 (2005) 020105(R). [8] A. Sch¨ onleber et al., Phys. Rev. B (2006) in press.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P156

¨ Resonante Beugung im weichen R¨ ontgenbereich an Ubergangsmetalloxiden ¨ßler-Langeheine1 , Justina Schlappa1 , Chun Fu Chang1 , HolChristian Schu ger Ott1 , Arata Tanaka2 , Maurits W. Haverkort1 , Zhiwei Hu1 , L. Hao Tjeng1 1

II. Physikalisches Institut, Universit¨ at zu K¨ oln, Z¨ ulpicher Str. 77, 50937 K¨ oln – Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, 739-8530, Japan 2

Resonante Beugung verbindet spektroskopische und strukturelle Informationen. Gera¨ de im Bereich der Ubergangsmetall L2,3 Resonanzen im weichen R¨ ontgenbereich zeigt sich, daß die Methode extrem empfindlich auf den elektronischen Zustand des streuenden Ions ist. Resonante Beugung ist somit die ideale Methode, um Ordnungsph¨ anomene ¨ in Ubergangsmetalloxiden wie orbitale Ordnung oder Ladungsordnung, also periodische Modulationen des elektronischen Zustandes, zu untersuchen. Deren Rolle wird in Zusammenhang mit der Erkl¨ arung von Ph¨ anomenen wie Kollossalem Magnetwiderstand oder Hochtemperatur-Supraleitung intensiv untersucht. Sr-dotiertes La2 NiO4 ist ein System, in dem streifenf¨ ormige Ladungsordnung auftritt, ¨ und das wegen seiner strukturellen Ahnlichkeit zu den Kuprat-Supraleitern besonders interessiert. F¨ ur diese Verbindung konnten wir durch die Kombination von resonanter Beugung und einer quantitativen mikroskopischen Modellierung ein umfassendes mikroskopisches Bild der Ladungsordnung, insbesondere der Symmetrie der dotierten L¨ ocher, gewinnen [1]. Ein anderes von uns untersuchtes System ist Magnetit (Fe3 O4 ), f¨ ur das der Charakter der Tieftemperaturphase seit langem diskutiert wird. Wir konnten anhand des Resonanzverhaltens von zwei Beugungsreflexen, die charakteristisch sind f¨ ur die beiden dominierenden zus¨ atzlichen Gittermodulationen, die in der Tieftemperaturphase auftreten, deren elektronischen Charakter untersuchen und sie mit Ladungsordnung und orbitaler Ordnung identifizieren. [1] C. Sch¨ ußler-Langeheine et al., Phys. Rev. Lett. 95, 156402 (2005).

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P157

High-frequency dynamics in metallic glasses Tullio Scopigno1 , Jens-Boie Suck2 , Albergamo3 , Giancarlo Ruocco1

Roberta

Angelini1 ,

Francesco

1

INFM CRS-SOFT and Dipartimento di Fisica, Universita´ di Roma La Sapienza, I-00185, Roma, Italy – 2 Institute of Physics, University of Technology Chemnitz, D-09107 Chemnitz, Germany – 3 European Synchrotron Radiation Facility, F-38043 Grenoble, Cedex, France Using inelastic X-ray scattering we studied the collective atomic dynamics in the glassy alloy Ni33 Zr67 in the first pseudo-Brillouin-zone. This energy-, h ¯ ω, and momentum-, Q, region is of primary importance for the investigation of collective modes in disordered systems. For metallic glasses it had not been accessible up to now. Using IXS this Q-region could now be explored and key properties such as the dispersion of collective excitations (see Fig. 1) and the damping of the acoustic modes[1] be determined. We discuss these results in the general context of recently proposed models for the damping of acoustic modes in glasses. We demonstrate the existence of well defined (in the Ioffe-Regel sense) acoustic-like excitations also well above the boson peak energy in this moderately fragile glass and the importance of the Boson peak intensity for the damping mechanism. [1] T. Scopigno et al. Phys. Rev. Lett. 96 (2006) 135501

Fig. 1: Dispersion curve

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P158

Molekularer Ursprung der Reißfestigkeit von Seidenfasern Tilo Seydel1 , Imke Diddens2 , Nadine Hauptmann2 , Gesa Helms2 , Malte Ogurreck2 , Igor Krasnov2 , Shin-Gyu Kang2 , Michael Marek Koza1 , Sergio ¨ller2 S. Funari3 , Martin Mu 1

Institut Laue–Langevin, B. B. 156, F–38042 Grenoble Cedex 9, Frankreich – 2 Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, 24098 Kiel – 3 HASYLAB bei DESY, Notkestraße 85, 22603 Hamburg Die Gr¨ unde f¨ ur die starke Dehnbarkeit und die hohe Reißfestigkeit der Seide der Seidenraupe Bombyx mori sind trotz umfassender Forschung auch heute noch nicht hinreichend gekl¨ art. Zwar kennt man die chemische Zusammensetzung von Seide, jedoch ist offenbar die komplexe Morphologie mit kristallinen und amorphen Bereichen entscheidend f¨ ur die mechanischen Eigenschaften. W¨ ahrend Kristalle sich sehr gut mit R¨ ontgendiffraktion untersuchen lassen, ist die inkoh¨ arente inelastische Neutronenstreuung (INS) auf lokale Eigenschaften von Molek¨ ulen und damit auch auf die Dynamik ungeordneter Bereiche sensitiv. Wir haben entsprechende Streckexperimente in situ sowohl erstmals am Neutronenspektrometer IN6 (ILL) als auch an der Synchrotron–Beamline A2 (HASYLAB) durchgef¨ uhrt. Beim INS–Experiment wurde eine Deuterierungstechnik zur Maskierung der kristallinen Bereiche von Seide angewandt, wie sie bereits f¨ ur Zellulosefasern beschrieben wurde [1]. Die so erhaltenen Phononenspektren amorpher Seide bei verschiedenen Dehnungen der Seidenfasern geben einen direkten Hinweis darauf, daß die ungeordneten Molek¨ ule einen großen Teil der makroskopischen Dehnung erm¨ oglichen. Im komplement¨ aren Experiment mit R¨ ontgenstrahlung wurde umgekehrt gefunden, daß die kristallinen Bereiche jeweils unter der makroskopischen mechanischen Spannung gehalten werden, sich aber z. B. in feuchter Seide nur um 1.5 % bei einer makroskopischen Dehnung von 20 % unter Zug dehnen. [1] M. M¨ uller et al., Macromolecules 33 (2000) 1834-1840.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P159

Angular Dispersion and other Effects in X-Ray Bragg Diffraction in Asymmetric Backscattering Geometry ¨ter4 , Yuri Shvyd’ko1 , Michael Lerche2,1 , Ulrich Kuetgens3 , Hans Dierk Ru Ahmet Alatas1 , Jiyong Zhao1 1

Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA – 2 University of Illinois at Urbana-Champaign, IL 61801, USA – 3 PhysikalischTechnische Bundesanstalt (PTB), D-38116 Braunschweig, Germany – 4 Institut f¨ ur Experimentalphysik, Universit¨ at Hamburg, D-22761 Germany Almost 100 years after discovery and extensive and accurate studies, covered in a great number of publications, little remains unknown and unobserved related to Bragg diffraction of x rays. However, unexplored areas concealing a wealth of new knowledge still exist even in such a very well charted terrain. Such a surprisingly untried area, opening new physical effects and perspectives of applications, is Bragg diffraction in backscattering from asymmetrically cut perfect crystals. We observe three effects in the Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals, predicted theoretically in [1]. First, exact Bragg backscattering takes place not at normal incidence to the reflecting atomic planes. Second, a well collimated (' 1 µrad) beam is transformed after the Bragg reflection into a strongly divergent beam (230 µrad) with reflection angle dependent on x-ray wavelength – an effect of angular dispersion. The asymmetrically cut crystal thus behaves like an optical prism, dispersing an incident collimated polychromatic beam. The dispersion rate is ' 8.5 mrad/eV. Third, parasitic Bragg reflections accompanying Bragg backreflection are suppressed. These effects offer radically new means for monochromatization of x-rays not limited by the intrinsic width of the Bragg reflection. These and other applications of the observed effects will be discussed in another paper submitted to the conference [2]. [1] Yu. Shvyd’ko, X-Ray Optics – High-Energy-Resolution Applications, vol. 98 of Optical Sciences, Springer, Berlin Heidelberg New York, 2004. [2] Yu. Shvyd’ko, U. Kuetgens, H. D. R¨ uter, M. Lerche, A. Alatas, J. Zhao, “Progress in the Development of New Optics for Very High Resolution Inelastic X-Ray Scattering Spectroscopy” submitted to SNI-2006

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P160

Adsorption geometry of large organic molecules studied by NIXSW: Snphthalocyanine and NTCDA on Ag(111) ¨ ren Hansen1 , Florian Pollinger1 , Jo ¨ rg Stanzel1 , Christoph Stadler1 , So ¨ ll1 , Christian Kumpf1 , Eberhard Umbach1 Achim Scho 1

Experimentelle Physik II, Universit¨ at W¨ urzburg, Am Hubland, 97074 W¨ urzburg

The properties of organic thin films largely depend on the balance between moleculemolecule and molecule-substrate interactions and can often be tuned by changing the preparation conditions like temperature or coverage. This is also the case for 1,4,5,8Naphthalenetetracarboxylic dianhydride (NTCDA) and the family of phthalocyanines (Pc) which are frequently studied as adsorbates on various surfaces. Here we present results obtained for SnPc, a non-planar representative of the phathalocyanines, and its adsorption on the Ag(111) surface in a coverage up to one monolayer. We used a combination of the synchrotron-based NIXSW (normal incident x-ray standing wave) method and SPA-LEED (spot profile analysing low energy electron diffraction) to study the vertical and lateral adsorption geometry. Various different adsorption phases where found, depending on coverage and substrate temperature, and tow phases were investigated in detail. In the incommensurate monolayer structure at room temperature (RT) with one molecule per unit cell it adsorbs in a tin-down geometry, where the Sn is closer to the uppermost silver atoms than the N and C atoms. In the commensurate submonolayer structure at 150K with two molecules per unit cell a mixed structure with both, tin-up and tin-down geometries is found. The latter is only stable at low temperatures and the corresponding RT structure is disordered. Furthermore, the phenyl rings lie always closer to the surface than the porphyrine N atoms, an effect, which is even stronger for the LT phase than for the RT phase. This bending is an important information which clearly shows a strong interaction between the phenyl rings of the molecule and the substrate. In the case of NTCDA/Ag(111) the so-called relaxed monolayer was studied by NIXSW and a significant vertical distortion of the molecule is found upon adsorption. The core level shift of the carboxylic oxygen and the anhydride oxygen was used to determine the individual atom heights above the silver surface. The carboxylic oxygen at the corners of the molecule is significantly bended downwards, whereas the anhydride oxygen in the bridge position is at the same height as the naphthalene core. For all the analysis non dipolar effects of the photo electrons are taken into account. In the case of SnPc/Ag(111) a multilayer is investigated to determine the asymmetry parameter of the non dipolar contributions to the photoemission yield. In the case of NTCDA/Ag(111) a comparison of O KLL and O1s data allows the determination of this asymmetry parameter and the portion of electron induced Auger processes.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P161

Erzeugung ultrakurzer Synchrotronpulse durch C. Stamm1 , T. Kachel1 , N. Pontius1 , R. Mitzner2 , T. Quast1 , K. Holldack1 , ¨rr1 , W. Eberhardt1 S. Khan1 , H.A. Du 1

BESSY mbH, 12489 Berlin, Germany – M¨ unster, 48149 M¨ unster, Germany

2

Physikalisches Institut der Universit¨ at

Experimentelle Techniken zur Untersuchung ultraschneller dynamischer Prozesse in Festk¨ orpern, Fl¨ ussigkeiten und Gasen waren bislang weitgehend auf den Gebrauch ultrakurzer optischer Laserpulse begrenzt, mit denen Details dieser Vorg¨ ange stroboskopartig abgebildet werden k¨ onnen. Hierbei sind jedoch die beobachtbaren physikalischen Aspekte auf den Bereich eingeschr¨ ankt, der mit spektroskopischen Methoden im optischen Wellenl¨ angenbereich zug¨ anglich ist. Eine weitreichende und vielversprechende Erweiterung dieser Technik verspricht der Gebrauch von ultrakurzen R¨ ontgenpulsen, der die hohe Zeitaufl¨ osung mit dem enormen Potential der R¨ ontgenspektroskopie kombiniert, die z.B. Element- und Ortsspezifit¨ at sowie die Untersuchung magnetischer Ph¨ anomene erlaubt. Die bisherige Pulsdauer von an Synchrotronstrahlungsquellen erzeugter R¨ ontgenstrahlung liegt jedoch mit typischerweise 50 ps zwei bis drei Gr¨ oßenordnungen u ¨ber der erforderlichen Zeitaufl¨ osung. Am Berliner Elektronenspeichering BESSY ist w¨ ahrend der vergangenen zwei Jahre ein Konzept realisiert worden, das die Erzeugung von R¨ ontgenpulsen von ∼150 fs Dauer, durchstimmbarer Photonenenergie (ca. 400 bis 1200 eV) und variabler Polarisation erm¨ oglicht [1,2]. Beim sogenannten Femto-Slicing“ [3] wird ein Elektronenpa” ket des Speicherrings in einem ersten Undulator ( Modulator“) mit einem optischen ” fs-Laserpuls u ¨berlagert. Eine Scheibe“ von Elektronen im Wechselwirkungsbereich, ” die im wesentlichen der L¨ ange des Laserpulses entspricht, wird dabei energiemoduliert und in einer energiedispersiven Strecke vom Hauptb¨ undel absepariert. In einem zweiten Undulator ( Radiator“) strahlt die Elektronenscheibe einen R¨ ontgenpuls etwa gleicher ” Dauer ab, der f¨ ur Experimente genutzt werden kann. Es werden der Aufbau des Femto-Slicing-Experimentes und beispielhaft experimentelle Ergebnisse pr¨ asentiert, die die erzeugten Femtosekundenr¨ ontgenpulse erfolgreich in einem laser-pump & x-ray-probe“-Experiment nachweisen und das Potential der ” Technick demonstrieren. Die Femto-Slicing-Einrichtung beim BESSY wird in K¨ urze f¨ ur externe Nutzer offenstehen. [1] K. Holldack et al., Phys. Rev. ST Accel. Beam 8 (2005) 040704. [2] K. Holldack et al., Phys. Rev. Lett. 96 (2006) 054801. [3] R. W. Schoenlein, Science 287 (2000) 2240.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P162

Dynamics of gold nanoparticles on the surface of thin polymer films Simone Streit1 , Henning Sternemann1 , Christian Gutt2 , Virginie Chamard3 , Aymeric Robert4 , Metin Tolan1 1

Exp. Physik I, Universit – 2 DESY (HASYLAB), Notkestr. 85, 22607 Hamburg, Germany – 3 LTPCM, 1130 rue de la piscine, 38402 St Martin d’H`eres, France – 4 ESRF, BP 220, 38043 Grenoble Cedex, France We present surface x-ray photon correlation spectroscopy (XPCS) measurements of the dynamic structure factor S(q, τ ) of gold nanoparticles moving on the surface of thin polystyrene films. Above the glass transition of the polymer the dynamic structure factor follows the peculiar form S(q, τ ) ∼ exp[−(2Γτ )α ]. Depending on the sample composition and age, the exponent α ranges between 0.7 and 1.9. A dispersion relation from q = 0.1 to 0.6 nm−1 is obtained, thus probing dynamics in the nanometer regime. The relaxation time τ scales as q −1 in contrast to the q −2 behavior of simple Brownian diffusive motion. This type of correlation function is due to a power law distribution of particle velocities which has also been observed in other aging bulk soft matter systems. The special form of the dynamic structure factor characterizes a hyperdiffusive or ballistic motion of the gold clusters.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P163

Diffusion in Al4 Ni melts, by inelastic neutron scattering ¨ber1 , Andreas Meyer1 , Tobias Unruh2 Sebastian Stu 1

Deutsches Zentrum f¨ ur Luft und Raumfahrt, Institut f¨ ur Raumsimulation, 51170 K¨ oln – 2 Forschungsneutronenquelle Heinz Maier-Leibnitz, TU M¨ unchen We report on inelastic neutron scattering measurements on Al4 Ni melts with different isotopic compositions. The experiments were performed at the new time-of-flight instrument of the neutron source Heinz Maier-Leibnitz in Garching, yielding an exceptionally good signal-to-background ratio. AlNi melts exhibit a strong non-linear dependence of the Ni self diffusion on stoichiometric composition. By measuring Al4 Ni samples with three different Ni isotopic compositions (natural Ni, 58 Ni, and 60 Ni), we are able to derive the three partial structure factors. The amplitude as well as the time scale of diffusive atomic motion exhibit a strong dependence on coherent, respectively incoherent contributions to scattering, and secondly, their oscillations are in phase with the static structure factor. This data set allows a detailed investigation of the diffusion mechanism in AlNi melts. The experimental results are compared with Molecular Dynamics computer simulations.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P164

Diffuse neutron scattering from a kagom´ e antiferromagnet Martin Valldor1 , Werner Schweika2 1

IPKM, TU-Braunschweig, D-38106 Braunschweig, Germany – 2 Forschungszentrum J¨ ulich, D-52425 J¨ ulich, Germany A new type of magnetic metal oxides has recently been discovered, containing a net of tetrahedrally coordinated Co. The transition metal sublattice forms perfect kagom´e type layers and the interlayer coupling situation is geometrically frustrated. In the stoichiometry Y0 .5Ca0 .5BaCo4 O7 [1], this frustration together with an unusual spin state of the inter-layers Co causes the layers to magnetically decouple. Although susceptibility measurements indicate strong antiferromagnetic coupling between spins, the magnetic part neutron diffraction data, separated through polarization, shows no longrange order down to 1.2 K [2]. The observed diffuse peak indicates an ordering tendency towards chiral ground state, a spin structure of Heisenberg spins in layers p pa staggered called (3)x (3). This coplanar spin structure exhibits degeneracy with local chiral disorder even at very low temperatures. Studies of this complex magnetic state give clues to unique spin ordering effects close to their ground state. [1] M.Valldor cond-mat/0605063 (2006) [2] M.Valldor et al. submitted (2006)

Fig. 1: Co substructure forming kagom´ e layers

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P165

Opening of the SC Gap observed in Neutron Spectroscopy Frank Weber1,2 , Rolf Heid1 , Andreas Kreyssig3 , Lothar Pintschovius1 , Dmitry Reznik1,4 , Wilfried Reichardt1 , Oliver Stockert5 , Klaudia Hradil6 1

Forschungszentrum Karlsruhe, Institut f¨ ur Festk¨ orperphysik, D-76021 Karlsruhe, Germany – 2 Physikalisches Institut, Universit¨ at Karlsruhe (TH), D-76128 Karlsruhe, Germany – 3 Institut f¨ ur Festk¨ orperphysik, TU Dresden, D-01062 Dresden, Germany (present adress: Ames Laboratory, USA) – 4 Laboratoire L´eon Brillouin, C.E. Saclay, F-99191 Gif-sur-Yvette, France – 5 Max-Planck-Institut f¨ ur Chem. Physik fester Stoffe, D-01187 Dresden, Germany – 6 Institut f¨ ur phys. Chemie, Universit¨ at G¨ ottingen, Aussenstelle FRM II, D-85747 Garching, Germany It was previously noted that acoustic phonons in YNi2 B2 C [1] and LuNi2 B2 C [2] with wavevectors q ≈ (0.5,0,0) undergo strong changes of their lineshapes upon entering the superconducting (SC) state. However, no convincing interpretation of the data could be given. Here, we present inelastic neutron scattering data on YNi2 B2 C (Tc = 15 K). We made a systematic study of the already known phonon anomaly in the (100)-direction as well as of a so far unexplored anomaly at the zone boundary in the (110)-direction (Mpoint). Our data unambiguously show that the superconductivity-induced changes of the spectral function of phonons with a strong electron-phonon coupling can extremely well be understood in the framework of a theory proposed by Allen et al. [3]. The analysis yields the temperature dependent SC energy gap with high accuracy. As a consequence, even deviations from BCS like behavior can be assessed with confidence. Further, we found that the Sc gap extracted from the phonon data for q=(0.5,0,0) and q=(0.5,0.5,0), respectively, differs by a factor 1.4. This is a direct proof for the long discussed anisotropy of the SC energy gap in borocarbides (e.g., Ref. [4]). A prerequisite for the observation of the gap anisotropy is to select phonons for which the dominant coupling to the quasiparticles stems from a relatively small part of the Fermi surface. Our choice was guided by DFT calculations [5] which predict both the phonon frequencies and linewidths very well. [1] [2] [3] [4] [5]

Kawano et al., PRL. 77, 4628 (1996), Stassis et al., PRB 55, R8678 (1997), Allen et al., PRB 56, 5552 (1997), Izawa et al., PRL 89, 137006 (2002), Reichardt et al., J. Superconductivity, 10.1007 (2005)

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P166

Statistical model of radiation damage within an atomic cluster irradiated by VUV photons from FEL. Beata Ziaja-Motyka1 , A. R. B. de Castro ¨ ller1 Mo 1

1

, Edgar Weckert1 , Thomas

HASYLAB, DESY, Notkestrasse 85, 22607 Hamburg

Boltzmann equations are applied for modelling the radiation damage in samples irradiated by photons emitted from free electron laser (FEL). This statistical approach is used to model the evolution of a spherically symmetric xenon cluster consisting of 1000 atoms irradiated with FEL photons at VUV energies. Simulation parameters follow those set in the first cluster experiments performed at FLASH at DESY HAMBURG. Predictions obtained with this theoretical model are then compared to the experimental data. The results obtained demonstrate the potential of the Boltzmann method for describing the complex and non-equilibrium dynamics of samples exposed to FEL radiation. In particular, this approach work also well for large samples, for which the standard simulation methods become inefficient.

Struktur und Dynamik

Poster: Mi., 14:00–16:30

M-P167

Kornrotation in nanokristallinen Schichten w¨ ahrend der Bestrahlung mit schnellen schweren Ionen ¨nzer1 , Walter Assmann2 , Ivo Zizak1 , Nora Darowski1 , Siegfried Klaumu ¨rgen Gerlach3 Ju 1

Hahn-Meitner-Institut, Albert-Einstein-Str. 15, 12489 Berlin, Germany – 2 LudwigMaximillian Universit¨ at, Am Coulombwall 1, 85748 Garching, Germany – 3 Institut f¨ ur Oberfl¨ achenmodifizierung, Permoserstr. 15, D-04318 Leipzig, Germany Nach der Bestrahlung der d¨ unnen, nanokristallinen Ti und TiN Schichten mit schnellen ¨ schweren Ionen wurde eine Anderung der Orientierungsverteilung gemessen. Die ca. 1 µm dicken Schichten wurden auf Silizium aufgedampft und anschließend mit 350 MeV Au Ionen bis zu 2 × 1015 ions/cm2 am HMI Ionenbeschleuniger (ISL) bestrahlt. Um die Einfl¨ usse der Oberfl¨ achenenergie und der Ionenbestrahlung trennen zu k¨ onnen, wurden die Schichten unter 30◦ zur Probennormale bestrahlt. Die Textur der Schichten wurde f¨ ur unterschiedliche Fluenzen an der BESSY Synchrotronsstrahlungsquelle gemessen. In unbestrahlten Schichten wurde, wie erwartet, eine zylindersymmetrische Verteilung der Orientierungen gemessen. Im Fall der bestrahl¨ ten Proben wurden zwei Anderungen beobachtet: i) Die zylindrische Symmetrie wurde gebrochen, und die Textur wandelte sich mit zunehmender Fluenz von einer Faser-Textur in eine Mosaik-Textur um. Die Orientierung der neuen Textur hing sehr stark von der Ionen-Richtung ab. ii) Die Orientierungsverteilung rotierte proportional zur Ionenfluenz bis zum Bruch der Zylindersymmetrie in der Richtung weg von dem Ionenstrahl. Die Rotation war, ¨ f¨ ur Winkel bis etwa 50◦ , umkehrbar durch Anderung der Bestrahlungsrichtung. ¨ Eine m¨ ogliche Erkl¨ arung f¨ ur die beobachtete Anderung der Symmetrie ist eine Wechselwirkung der Ionen mit dem Kristallgitter. Beachtet man jedoch die Rotation und die Umkehrbarkeit des Effektes, so k¨ onnen diese nur durch die Wechselwirkung zwischen Ionen und isotropem Material beschrieben werden. ¨ Da diese Anderungen in grobkristallinen Materialien nicht beobachtet wurden, nehmen wir an, dass die Ionen mit den amorphen Korngrenzen wechselwirken. Der Anteil der Atome, die sich in nanokristallinen Materialien in den Korngrenzen befinden liegt im Prozentbereich. Werden amorphe, statt nanokristalline, d¨ unne Schichten mit schnellen, schweren Ionen bestrahlt, fließen sie in Richtung der Bestrahlung plastisch[1,2]. Die amorphen Korngrenzen in nanokristallinen Schichten k¨ onnten auf die gleiche Art fließen. Dabei w¨ urden die K¨ orner von dem umgebenden Material mitgetragen. Die Rotation der K¨ orner ergibt sich dann daraus, dass die Fließgeschwindigkeit an der Oberfl¨ ache gr¨ oßer ist als in der N¨ ahe des Substrates. [1] H. Trinkaus and A.I. Ryazanov, Physical Review Letters 74 (1995) 5072 [2] S. Klaum¨ unzer, Mater.Sci.For. 97 (1992) 623

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P168

Surface oxidation of metals using oxygen ion beams Nikolai Alov1 1

Lomonosov Moscow State University, 119992 Moscow, Russia

Surface oxidation of Mo, W, Nb and Ta using oxygen ion beams was investigated by Xray photoelectron spectroscopy (XPS). Irradiation by oxygen ion beams was carried out at room temperature with ion energy of 1-5 keV, dose of 1015 -1018 cm−2 and direction normal to surface. XPS analysis of oxidized metal surfaces was performed in situ using Leybold LHS-10 electron spectrometer. The fitted XPS spectra of Mo 3d and W 4f core levels show that the metal oxidation states 4+, 5+ and 6+ are present in oxide films. At the initial stage of irradiation the rapid oxidation of Mo and W surface layers was observed. At higher dose, which depends on the energy of oxygen ions and the kind of metal, the oxidation of surface layers reaches saturation and the surface composition remains almost unchanged with increasing irradiation dose. The fitted XPS spectra of Nb 3d and Ta 4f core levels show that the metal oxidation states 2+, 4+ and 5+ are present in oxide films. At the initial stage of irradiation the rapid oxidation of Nb and Ta surface layers was observed. However, at higher dose, which depends on the energy of oxygen ions and the kind of metal, the population of Nb2+, Nb4+, Ta2+ and Ta4+ reaches a maximum and then begins to decrease. The population of Nb5+ and Ta5+ continues to increase and the entire oxide films will consist of only Nb5+ and Ta5+. Using XPS data the absolute values of fundamental parameters of low-energy oxygen ion interaction with metal surfaces (reaction and sputtering cross-sections) were calculated.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P169

in-situ powder diffraction - Monitoring chemical reactions Carsten Baehtz1 , Kristian Nikolowski2 , Natascha Bramnik2 , Helmut Ehrenberg2 , Dominic Stuermer2 , Fabian Raif3 , Michael Bron3 , Peter Claus3 1

HASYLAB, Notkestr. 85, 22607 Hamburg, Germany. – 2 Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany. – 3 ErnstBerl Institut FB Chemie, Petersenstr. 20, 64287 Darmstadt, Germany. The last few years have seen an increasing interest in in-situ powder diffraction experiments. Such experiments benefit from the advantages of the usage of synchrotron radiation like a high angular resolution of the instrument to detect small changes in lattice parameter, free choice of wavelength to reduce absorption effects of the sample as well as its environment and the high intensity of the beam giving a high time resolution by a good data quality suitable for Rietfeld refinements. At beamline B2@DORIS, HASYLAB two dedicated sample environments for specialised in-situ investigations are in user service. A special design of a coin cell allows observing the cycling behaviour of secondary lithium ion batteries during the charge - discharge process [1,2]. Result on the cathode materials LiNiO2 and LiCoO2 and their phase behaviour will be reported. A new furnace working in capillary geometry is dedicated for diffraction experiments under controlled atmosphere like oxygen, hydrogen or noble gas up to 5 bars. Herby chemical synthesis of catalysts or inorganic substances, phase identification under reaction conditions and material characterisation under controlled atmosphere are possible. Both sample environments are also suitable for EXAFS-investigation. [1] C. Baehtz et al, Solid State Ionics 176 (2005) 1647. [2] K. Nikolowski et al, J. Appl. Cryst. 38 (2005) 851.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P170

Time-resolved views onto gas hydrate formation and decomposition using neutron diffraction Andrzej Falenty1 , Thomas Hansen2 , Werner F. Kuhs1 1

Universit¨ at G¨ ottingen GZG, Abteilung Kristallographie, Germany – 2 Institut LaueLangevin, Grenoble, France The kinetics of formation/decomposition processes of gas hydrates is a complicated multi-phase process, details of which are still largely unknown. Clearly, a better understanding of these processes will help to answer a number of unsolved geoscientific questions and may enable a wide range of new industrial and scientific applications in the field of gas hydrates. Time-resolved neutron diffraction on D20 at ILL/ Grenoble proved to be of crucial importance to unravel the transformation of ice particles into gas hydrates taking place in a multistage process [1,2,3] The reaction starts with nucleation-and-growth and later changes to a diffusion controlled formation. Similarly, the decomposition reaction of gas hydrates back into ice was followed by time-resolved neutron diffraction. Here, a complication arises at lower temperatures due to the intermediate formation of defective, stacking-faulty ice (resembling so-called ice Ic) [4]. Thus, treating the diffraction data calls for a proper description of the stacking faults in the defective ice formed. We shall report on the progress made in describing the decomposition reaction followed by time-resolved neutron diffraction and helped by in-house work using physico-chemical methods and scanning electron microscopy. [1] D.K. Staykova, W. F. Kuhs, A. N. Salamatin, and T. Hansen (2003) Formation of Porous Gas Hydrates from Ice Powders: Diffraction Experiments and Multistage Model. J. Phys. Chem. B 107, 10299-10311 [2] G. Genov, W. F. Kuhs, D. K. Staykova, E. Goreshnik, and A. N. Salamatin (2004) Experimental studies on the formation of porous gas hydrates. Am. Miner. 89, 12281239 [3] W.F. Kuhs, D.K. Staykova, A.N.Salamatin (2006) Formation of methane hydrate from polydisperse ice powders. J.Phys.Chem. B xxx (in press) [4] W. F. Kuhs, G. Genov, D. K. Staykova, and T. Hansen (2004) Ice perfection and onset of anomalous preservation of gas hydrates. Phys. Chem. Chem. Phys. 6, 4917-4920

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P171

2D-Mapping of the catalyst structure inside a fixed-bed reactor: Partial oxidation of methane over a Rh/Al2 O3 -catalyst Jan-Dierk Grunwaldt1 , Stefan Hannemann1 , Pit Boye2 , Christian G. Schroer2 , Alfons Baiker1 1

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hoenggerberg, HCI, CH-8093 Zurich – 2 Department of Structural Physics, TU Dresden, D-01062 Dresden In situ X-ray absorption spectroscopy is a well-suited technique to gain information on the structure of heterogeneous catalysts. In certain cases a variation of the catalyst structure can occur inside a catalytic reactor as a result of temperature or concentration gradients. This requires spatially resolved molecular information on a microscale. Here, we have used a position sensitive X-ray camera to record XANES spectra from inside the catalytic reactor with a spatial resolution on the scale of a few micrometers [1]. The catalytic performance was determined simultaneously using mass spectrometric analysis. Partial oxidation of methane over Rh/Al2 O3 catalyst is used as an example. For recording locally resolved the absorption of the sample inside the catalytic microreactor, a CCD camera was installed behind the in situ cell and X-ray absorption images were recorded around the Rh K-edge (23220 eV) as shown in the Figure. In total, 170 absorption images were taken that allowed the reconstruction of the full Rh K-edge XANES spectra at each pixel (a corresponding movie can be downloaded at [2]). The measurements uncovered tremendous changes of the structure of the Rh particles along the catalyst bed within less than 100 micrometer. The shape and position of the gradient strongly depended on temperature and flow [3]. [1] J.-D. Grunwaldt et al., J. Phys. Chem. B 110 (2006) 8674. [2] http://www.baiker.ethz.ch/people/Scistaff/Grunwaldt/ESI [3] J.-D. Grunwaldt et al., in preparation.

Fig. 1: X-ray absorption of Rh/Al2 O3 inside the microreactor at different energies during the partial oxidation of methane (cf. refs. [1,2])

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P172

Phase transition of β − MoTe2 studied by temperature-dependent angleresolved photoemission spectroscopy Robert Heimburger1 , Thorsten Zandt, Recardo Manzke 1

Humboldt-Universit¨ at zu Berlin, Institut f¨ ur Physik, Newtonstr. 15, 12489 Berlin

The β-type of the polymorph material MoTe2 grown by chemical vapor transport at temperatures above 900◦ C shows a layered structure which can be described as stacked sandwiches of the tree layers Te-Mo-Te. Therefore, the crystals exhibit distinct twodimensional behavior. At room temperature β − MoTe2 has a monoclinic crystal structure. The Te atoms are placed around the metal atom in a slightly distorted octahedron and therefore the metal atoms form zigzag-chains along the crystallographic x2 direction. By cooling below 250K, β − MoTe2 undergoes a phase transition, where the monoclinic angle of the high temperature phase changes from 93◦ 55” to 90◦ , resulting in an orthorhombic structure. In this contribution we present a detailed temperature dependent study of electronic band structure of β − MoTe2 performed by angle-resolved photoemission spectroscopy (ARPES). The measurements were carried out at the BUS undulator beamline at BESSY II supplemented by data taken with HeI radiation. It results that the dispersions of the valence bands along the different high-symmetric directions of the Brillouin zone are extremely weak except for the bands very close to the Fermi level. These bands reveal close insight into the low temperature and phase transition behavior of quasitwo dimensional materials like β − MoTe2 . The experimental findings will be compared with additional tight-binding band structure calculations.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P173

Studying Chemical Processes by Pulse Radiolysis Eberhard Janata1 1

Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin

Studying Chemical Processes by Pulse Radiolysis E. Janata Hahn-Meitner-Institut Berlin GmbH, Bereich Solarenergieforschung Glienicker Str. 100, 14109 Berlin The impact of a pulse of high-energy electrons creates electron-hole pairs in solids, or forms a number of reducing or oxidizing species in solutions. Electrons and holes can move and recombine independently or are trapped by structural defects or impurities. In solution, the species created can reduce or oxidize additives nearly instantaneously, which may be the starting point for a sequence of chemical reactions. These processes can be detected in solids, such as glasses or glassy-crystalline materials, and in solutions in situ by means of optical methods. Conductometric methods are also applicable, either simultaneously with the optical or as stand-alone methods. After a short introduction to the pulse radiolysis apparatus of the 4 MeV van de Graaff accelerator facility ELBENA at the Hahn-Meitner-Institut, three examples are given. Firstly, the formation and disappearance of a short-lived thallium-silver cluster in aqueous solution is discussed. Secondly, the concentration of nitrous oxide in aqueous solutions of different contents of NaCl or LiCl is measured, thus representing a kinetic method for the determination of the salting-out effect. Thirdly, optical emission and absorption spectra of a bariumsilicate glass are compared with the results obtained with a fused quartz.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P174

Low energy XAS at the S K-edge for in situ catalyst characterization Anderas Jentys1 , Hendrik Dathe1 , Johannes Lercher1 1

TU M¨ unchen, Department Chemie

XANES on the S K-edge is a powerful technique for studying sulphur species present on catalytic materials. The possibility of following the oxidation state of sulphur in situ during the reactions reveals new insights into the formation sulfur species on solid catalysts. The design of the reaction chamber and the sealing against the vacuum is shown in Figure 1. The sample chamber is inserted into a modified 6-way cross, which can be directly attached to the equipment used at the ANKA XAFS beamline. The in situ cell is applicable for experiments in the temperature range between 303 and 673 K at a maximum pressure of Fig. 1: Experimental 1 bar. The sample is placed inside the reaction chamber and setup for time resolved sealed against the vacuum to minimize absorption and scatlow energy XAS (H = Heating; T = Thermocoutering of the gas phase with a 0.0075 mm Kapton window. ple; S = Sample; K = The cell allows experiments in transmission and fluorescence Kapton window) mode. Reaction gas mixtures containing H2 , O2 , SO2 , H2 S were tested in absence as well as in presence of water. Sucessful examples for the use of low energy XAS for the SOx trapping under oxidizing conditions using novel metal organic framework materials and the characterization of novel hydro-isomerization catalysts will be presented.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P175

The influence of subsurface carbon on the selectivity in the hydrogenation reaction of 1-pentyne over Pd catalysts ¨vecker1 , Spiros Axel Knop-Gericke1 , Detre Teschner1 , Michael Ha ¨ gl1 , Arran S. Zafeiratos1 , Hermann Sauer1 , Elaine Vass1 , Robert Schlo 2 2 3 Canning , David Jackson , James McGregor 1 Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin – 2 WestCHEM, Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, UK – 3 University of Cambridge, Department of Chemical Engineering, New Museums Site, Pembroke Street, Cambridge CB2 RA, UK

The hydrogenation of 1-pentyne over various palladium catalysts was studies under different conditions. X-ray Photoelectron Spectroscopy (XPS) measurements performed at the synchrotron radiation facility BESSY in Berlin at 0.9 mbar in a mixed atmosphere of hydrogen and 1-pentyne show significant amounts of subsurface carbon and a Pd-C surface phase builds up in the early stage of the reaction in the regime of selective hydrogenation. These species inhibit the emergence of bulk-dissolved hydrogen to the surface, which is reactive, but unselective. Carbon laydown was also observed by Tapered Element Oscillating Microbalance (TEOM) and by catalytic pulse experiments with greater laydown occurring in the selective regime. The effect of carbon dissolution in the crystal lattice near the surface was evidence by High-Resolution Transmission Electron Microscopy (HRTEM). In alkyne hydrogenation the active phase of palladium catalysts is a Pd-C surface phase in the regime of selective hydrogenation. As self-hydrogenation (hydrogen from dissociated 1-pentyne) was shown to be unselective as well, only surface hydrogen from the gas phase is available to generate the alkene. A model of the palladium surface during 1-pentyne hydrogenation is suggested. The contribution shows, that the application of synchrotron radiation to perform X-ray photoelectron spectroscopy under reaction conditions, is a very powerful tool for the characterization of heterogeneous catalytic processes especially in combination with other methods.

Fig. 1: Model of the palladium surface during 1pentyne hydrogenation

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P176

Schaltverhalten modulierter Ferroelektrika J. Leist1 , H. Gibhardt1 , K. Hradil1 , H. Schneider1 , G. Eckold1 1

Institut f¨ ur Physikalische Chemie, Universit¨ at G¨ ottingen

Der Einfluss eines elektrischen Feldes auf die ferroelektrische lock-in Umwandlung in K2 SeO4 bei Tc =93 K wurde mit elastischer und inelastischer Neutronenstreuung am ¨ Dreiachsenspektrometer PUMA, sowie mit γ-Diffratometrie untersucht. Ahnlich wie bei anderen Verbindungen des Typs A2 BX4 wurde bei Anwendung gen¨ ugend hoher elektrischer Felder eine intermedi¨ are Phase beobachtet, die durch ein diffuses Satellitenspektrum charakterisiert ist und dementsprechend weder eine wohldefinierte Modulation noch ein geordnetes Solitonengitter aufweist. Mit Hilfe stroboskopischer Methoden konnte die Kinetik der Phasenumwandlung auf einer Millisekunden-Zeitskala beobachtet werden. Dabei wurden die Ver¨ anderungen der Satelliten erster und dritter Ordnung w¨ ahrend eines gepulsten Feldes mit der Amplitude 8 kV/cm und Frequenzen bis zu 200 Hz detektiert. Die Abbildung zeigt den zeitlichen Verlauf des inkommensurablen Volumenanteils bei verschiedenen Temperaturen. Die Zeitkonstanten der Umwandlung liegen zwischen 0.2 und 1.2 ms und sind damit etwa eine Gr¨ oßenordnung kleiner als im isostrukturellen Rb2 ZnCl4 [1]. Dar¨ uber hinaus ist es gelungen, das Phason als Elementaranregung der inkommensurablen Phase bis nahe Tc zu verfolgen. Interessanterweise wird seine Dispersion vom außeren elektrischen Feld nahezu nicht beeinflusst. Die obere Grenze f¨ ¨ ur ein m¨ ogliches Phason-Gap zu 0.2 THz abgesch¨ atzt werden. [1] G. Eckold, M. Hagen, U. Steinberger, Phase Transitions 67 (1998) 219.

Abb. 1: Zeitabh¨ angigkeit des incommensurablen Volumenanteils bei ν = 100 Hz.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P177

Solid-Liquid Interface Analysis using the SoLiAS experimental station Thomas Mayer1 , Ralf Hunger1 , Andreas Thißen1 , Wolfram Jaegermann1 1

Fachgebiet Oberfl¨ achenforschung, Institut f¨ ur Materialwissenschaft, TU Darmstadt, Petersenstr. 23, 64287 Darmstadt Electrochemical processes like electrocatalysis, wet surface cleaning and etching, thin film deposition, and corrosion are ubiquitous in modern life und usually exhibit a considerable degree of scientific complexity. The SoLiAS experimental station (SolidLiquid-Interface Analysis System), is dedicated to the analysis of such processes using 3rd generation synchrotron light forstate-of-the-art photoemission and X-ray absorption spectroscopy. Specific preparational facilities have been established within SoLiAS in order to bridge the pressure and environmental gap: A purpose-designed atmospheric pressure inert gas cell for ex-situ emersion experiments (cf. Fig. 1) allows for high quality spectra even after transfer from the electrolyte. In addition, a low-temperature-adsorption stage is used for the preparation of model electrolytes by vacuum adsorption of electrolyte species under defined conditions (cf. Fig. 2). In this contribution, the capabilities of the SoLiAS end station are presented and illustrated with scientific projects from the course of four years of user operation. This includes projects from applied fields as photovoltaic solar energy conversion, electrocatalysis in fuel cells, and high density Li-ion batteries to projects from fundamental research of electrolyte electronic structure, solvation effects, and nanostrutured film formation, which have been conducted within our group and in collaboration with project partners from the international electrochemistry community. The broad range of research fields demonstrates the flexibility and versatility of the system.

Fig. 1: Electrochemical conditioning of a Pt/Ru nanoparticle catalyst in the SoLiAS system prior to emersion and analysis.

Fig. 2: Schematic setup of the SoLiAS system.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P178

Untersuchung der Kristallisationskinetik von [N i(tren)]SnS3 mit in-situ EDXRD in Abh¨ angigkeit von den Edukten Marie-Eve Ordolff1 , Nicole Pienack1 , Wolfgang Bensch1 1

Inst. f. Anorg. Chemie, Universit¨ at Kiel, Olshausenstr. 40, 24098 Kiel

In den letzten Jahrzehnten wurden unter solvothermalen Bedingungen viele neue por¨ ose Materialien dargestellt. Neben den typischen oxidischen Verbindungen wurden in großem Umfang Materialien auf Sulfidbasis unter diesen Bedingungen synthetisiert. Besonders interessante Stoffklassen stellen die Thiostannate und antimonate dar, bei denen in die ¨ Kristallstruktur Ubergangsmetalle integriert sind. Die Schwierigkeit bei der gezielten Darstellung solcher Materialien besteht darin, dass u ¨ber die Reaktionsmechanismen nur sehr wenig bekannt ist und somit die Synthesen nicht gezielt geplant werden k¨ onnen. Durch Untersuchung mit energiedispersiver insitu-R¨ ontgenbeugung (EDXRD) kann das Wachstum der kristallinen Produkte ebenso wie gegebenenfalls vorhandener kristalliner Precursoren und Zwischenprodukte verfolgt werden. [1]

An dem Modellsystem [Ni(tren)]SnS3 wurde der Einfluss verschiedener Edukte auf den Reaktionsverlauf untersucht. Die Synthese wurde in 2 mL einer 50 %igen, w¨ assrigen L¨ osung von Tris-2-aminoethylamin (tren) mit Ni, Sn und S als Edukte durchgef¨ uhrt. In weiteren Versuchen wurde statt elementarem Zinn das Chlorid SnCl2 ·2 H2 O und statt Nickel [Ni(tren)H2 OCl]Cl eingesetzt. In Abh¨ angigkeit der verwendeten Edukte konnte ¨ eine drastische Anderung der Reaktionsgeschwindigkeit beobachtet werden. Ein Einfluss auf den Reaktionsverlauf und die Produktbildung wurde ebenfalls festgestellt. Die detaillierten Ergebnisse dieser in-situ-EDXRD-Experimente werden auf dem Poster pr¨ asentiert. [1] M.Behrens, S.Scherb, C.N¨ ather, W.Bensch, Z. Anorg. Allgem. Chem., 629 (2003) 1367.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P179

Untersuchungen zur Laserdesorption am System NO/ HOPG mittels des VUV-FEL (FLASH) ¨ rn Siemer1 , Carsten Thewes1 , Helmut Marco Rutkowski1 , Tim Hoger1 , Bjo 1 Zacharias 1

Physikalisches Institut, Wilhelm Klemm Str. 10, 48149 M¨ unster

Zur Untersuchung katalytischer Reaktionen an Oberfl¨ achen wurden am FLASH Untersuchungen zur Laserdesorption am System NO/ HOPG gemacht. Hierbei wurden die NO Molek¨ ule mittels des VUV Laserstrahls von der Oberfl¨ ache desorbiert und konnten dann in einem zweiten Schritt mit einen weiteren Laser zustandsselektiv nachgewiesen werden. Es konnten sowohl die Geschwindigkeitsverteilungen der Molek¨ ule als auch der Desorptionsyield gegen¨ uber der Intensit¨ at des Desorptionslasers bestimmt werden. Theoretisches Ans¨ atze zur Modellierung des Desorptionssignales in Abh¨ angigkeit des Desorptionslaser werden aktuell erarbeitet und sollen hier pr¨ asentiert werden. Zudem konnten auch weitere Adsorbate wie z.B. Wasserstoff direkt als Ionen nachgewiesen werden.

Chemische Prozesse und Phasen¨ uberg¨ ange Poster: Mi., 14:00–16:30

M-P180

Phase behavior of aqueous dispersions of mixtures of ceramide, cholesterol and protonated fatty acid ´ Capitan2 , Se ´rgio S. Funari3 , Jesus Alvarez4 , Eurico Sofia L. Souza1 , M. Jose Melo1 1

Instituto de Tecnologia Qu´ımica e Biol´ ogica, Av. da Rep´ ublica-EAN, 2784-505 Oeiras, Portugal – 2 Instituto de estructura de la materia- CSIC. C/ Serrano 119, 28006Madrid, Spain – 3 Hasylab, DESY, Notkestrasse 85, D-22607 Hamburg, Germany – 4 Dpto. F´ısica de la materia condensada Universidad Aut´ onoma de Madrid, Cantoblanco. 28049 Madrid, Spain The lipid matrix of the stratum corneum (SC) of mammals is a mixture, whose main components are ceramides (Cer), cholesterol (Chol) and saturated fatty acids (FA). Probably because of being so unusual, and also due to the absence of applications of alike lipid blends in the industry, the physical-chemical properties of mixtures involving these classes of lipids have not been the object of systematic studies similar to those existing for ubiquitous lipids, such as cholines. Our objective in this work is the study of the thermotropic binary phase diagrams for the system containing C16 acyl ceramide and cholesterol, Cer16/Chol, at low ionic strength (100 mM) in excess water. Once obtained the binary phase diagram of Cer16/Chol we investigate the effect of the presence of palmitic acid FA16, ionized and protonated, in the thermotropism and structural properties of the mixture. The experiments including FA were done only for the relative Cer/Chol composition found in the SC lipid matrix (54:46 Cer16/Chol mole ratio), in this way crossing the composition equivalent to the Cer/Chol/FA relative abundances in the SC. From DSC we obtained the more plausible phase boundaries that were subsequently checked, and structurally characterized, by simultaneous SAXD and WAXD as a function of temperature. Ceramide systems are known to have metastable phases attributed to the strong interaction between headgroups. Pure Cer16 forms a lamellar phase that, as observed with other sphingolipids, suffers no thermal expansion until the phase transition, observed by DSC at 90 o C. In the region from 47-65 o C the chain structure gradually changes from ordered to relatively disordered. In the presence of Chol two new phases appear: one that can be ascribed to pure Chol in the monohydrate or anhydrous form, and other that may be interpreted as the result of Chol being dissolved in Cer16 lamellae. The analysis of the data allows the deduction of the thermotropic phase diagram for the Cer16/Chol system in excess water. From the DSC thermograms, and the SAX and WAX diffractograms of the mixtures between 54:46 Cer16/Chol and FA16 at two extreme pH values (corresponding to fully protonated and fully deprotonated FA16) we also deduce the phase behavior of these mixtures as a function of the FA16 molar fraction.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P181

Dynamic studies of an in situ molecular motor using synchrotron radiation Christopher Ashley1 , Maria Bagni2 , Giovanni Cecchi2 , Barbara Colombini2 , Sergio Funari3 , Peter Griffiths1 , Radek Pelc4 1

Univ. Lab. of Physiology, Parks Road, Oxford OX1 3PT, U.K. – 2 Dpt. di Scienze Fisiol., Universita degli Studi di Firenze, Florence I-50134, Italy. – 3 Gebaeude 25F, Hasylab at DESY, Notkestrasse 85, Hamburg D-22603, Germany – 4 Dept. of Microbiology, Czech Academy of Sciences, 142 20 Prague 4-Krc, Czech Republic. In higher animals, mechanical work is performed by translational molecular motors (protein macromolecules which transduce the free energy of ATP hydrolysis into linear motion). The most ubiquitous motor, myosin, achieves this by a multi-stage catalysis of ATP hydrolysis, powering cardiac and smooth muscle, all voluntary movement, and also adjustment of visual and aural acuity and myriad processes in intracellular physiology. Myosins form a class of at least 17 different forms of translational motor [1] Myosin II, present in all muscle tissue, is unique in that it forms helically-based filamentous aggregates. In striated muscles, these are arranged in a quasi-crystalline array, permitting structural events in the motor to be investigated dynamically by time-resolved X-ray diffraction. The X-ray pattern from skeletal muscle contains a strong axial reflection (M3) at a spacing corresponding to the third harmonic of the pitch of the myosin helix, which is sensitive to changes in myosin molecular structure. Upon activation, it undergoes changes in both intensity (IM 3 ) and in axial spacing (dM 3 ) [2]. We have studied the changes in M3 which accompany the motor power stroke in the microsecond time domain, and have attempted to relate these changes to the crystallographic structure of the myosin molecule. IM 3 changes reflect structural events in the S1 moiety of myosin, which projects from the surface of the myosin filament on a helical pitch and bears both the ATP catalytic site and the binding sites for the filamentous protein, actin (the ’track’ along which the myosin ’locomotive’ runs). Recent crystallographic work suggests that the motor mechanism is a tilting of the ’lever arm’ domain of S1, an a-helix chain of 9nm in length, linking the actin- and ATP-binding motor domain to the myosin filament backbone, producing 2-5 pN of force if isometric, or ca. 10 nm of translation if movement is permitted. dM 3 increases by ca. 1.5 % upon activation. This change is not explicable by structural events in S1. Instead, it may indicate a change in the myosin filament backbone structure, or the formation of a new axial unit cell due to the mismatch of actin and myosin filament helices. Recently, we examined this phenomenon further [3]. Our findings question the origin of this spacing change, suggesting that dM 3 is not an indicator of actin-S1 interaction, and allowing us to propose a new mechanism for dM 3 changes which could have important consequences for the prevailing models of the mechanism of contraction. [1] Sellers, J.R. Biochim. Biophys. Acta. 1496 (2000) 3. [2] Huxley, H.E.et al., J. Mol. Biol. 158 (1982) 63711. [3] Griffiths, P.J. et al., Biophys. J., 90 (2006) 975.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P182

Transiente Protein-Ligand-Wechselwirkungen im Verlauf von Enzymkatalysen im Shikimat-Reaktionsweg von M. tuberculosis Hans D. Bartunik1 , Gleb P. Bourenkov1 , Marc Bruning1 , Marcus Hartmann1 , Galina S. Kachalova1 1

Max-Planck-Arbeitsgruppen f¨ ur Strukturelle Molekularbiologie, MPG-ASMB c/o DESY, Notkestrasse 85, 22603 Hamburg Im Rahmen des XMTB-Strukturgenomik-Konsortiums untersuchten wir die StrukturFunktionsbeziehungen von Schl¨ usselenzymen des Shikimat-Reaktionswegs in Mycobacterium tuberculosis. Wir l¨ osten zun¨ achst die Kristallstrukturen der Enzyme und einer Reihe von Komplexen mit nat¨ urlichen Substraten und Kofaktoren. In einem weiteren Schritt untersuchten wir intermedi¨ are Zust¨ ande im Verlauf der katalytischen Reaktionen. F¨ ur zwei der Enzyme, Shikimat-Kinase (AroK) und EPSP-Synthase (AroA), konnte jeweils der gesamte Reaktionsweg im Kristall einschließlich der Bildung und der stufenweisen Freisetzung der Produkte bei hoher Aufl¨ osung verfolgt werden. F¨ ur ein weiteres Enzym, die Chorismat-Synthase (AroF), wurde einer der Zwischenschritte strukturmodelliert. Der Shikimat-Reaktionsweg ist essentiell f¨ ur die Synthese aromatischer Amino¨ auren in Mikroorganismen. Der Reaktionsweg existiert nicht in Mammalien. Diese Enzyme stellen daher potentielle Ziele f¨ ur die Entwicklung neuer Antibiotika dar. Die Reaktionsmechanismen der untersuchten Enzyme schließen konzertierte Konformations¨ anderungen ein, die vor allem im Falle von AroA hohe Komplexit¨ at aufweisen. Die beiden Substrate Shikimat-3-Phosphat (S3P) und PEP werden von der EPSPSynthase in sequentiellen Schritten gebunden. Die Wechselwirkung mit S3P induziert Bewegungen großer Amplitude, die f¨ ur die Bildung der PEP-Bindungsstelle erforderlich sind. Das nachfolgende Andocken von PEP liefert das Signal f¨ ur eine Schließbewegung der N- und C-terminalen Dom¨ anen. Die Reaktion setzt sich u ¨ber die Bildung eines tetraedrischen Intermediats, die Trennung in Enolpyruvylshikimat-3-Phosphat (EPSP) und Phosphat, sowie die Freisetzung der Produkte von einer partiell ge¨ offneten Konformation des Enzymmolek¨ uls fort. Die strukturelle Charakterisierung s¨ amtlicher Einzelschritte schafft eine Basis f¨ ur eine detaillierte Beschreibung des chemischen Mechanismus. Das Vorhaben wurde durch das Bundesministerium f¨ ur Bildung und Forschung, BMBF/PTJ, unter der Projektnummer BIO/0312992A gef¨ ordert.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P183

Large scale Protein dynamics studied by Neutron Spinecho Spectroscopy Ralf Biehl1 , Bernd Hoffmann2 , Michael Monkenbusch1 , Bela Farago3 , Rudolf Merkel2 , Dieter Richter1 1

Institut f¨ ur Festk¨ orperforschung, FZJ, Germany – 2 Institut f¨ ur Schichten und Grenzfl¨ achen, FZJ, Germany – 3 Institut Laue-Langevin, Grenoble, France During operation of proteins as universal nanomachines or involved in the transmission and amplification of signals, conformational changes are omnipresent. An intriguing combination of structure and flexibility facilitates their activity. Conformational changes can be triggered by small-amplitude, nanosecond protein domain motion. Understanding how conformational changes are initiated requires the characterization of protein domain motion on these timescales and on length scales comparable to protein dimensions. We present here examinations by Neutron Spinecho Spectroscopy of the internal dynamics of the unfolded globular protein ribonuclease A under thermal stress and the protein alcohol dehydrogenase in equilibrium.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P184

Chiral discrimination and structural analysis of RNA by Raman spectroscopy and x-ray crystallography Sarah Bolik1 , Benjamin Schulz1 , Michael Ruebhausen1 , Mathias Kramer2 , Markus Perbandt2 , Christian Betzel2 , V.E. Erdmann3 , Sven Klussmann4 1

Insitut f¨ ur Angewandte Physik, Universit¨ at Hamburg – 2 Institut f¨ ur Biochemie, Uni3 verist¨ at Hamburg – Institut f¨ ur Biochemie, Freie Universit¨ at Berlin – 4 Noxxon Pharma AG, Berlin Amino acids found in living organisms occur almost exclusively as L-enantiomers and nucleic acids as D-enantiomers. The origins of this pervasive homochirality have never been explained satisfactorily. Because there is no obvious biochemical reason for choosing one enantiomer over the other, numerous physical and biochemical mechanisms have been invoked to explain the phenomenon. Chirality is a fundamental aspect of chemical biology, and is of central importance in pharmacology. We have analysed the L- and the D- enantiomer of an RNA molecule with the sequence (r(CUGGGCGG)x r(CCGCCUGG)) by X-ray crystallography and Raman spectroscopy. The combined results of these experiments reveal new insights about the nature of chirality in nucleic acids. X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. Since electrons more or less surround atoms uniformly, it is possible to determine where atoms are located. This generally leads to an understanding of the material and molecular structure of a substance. This technique is widely used in chemistry and biochemistry to determine the structures of inorganic compounds, DNA/RNA, and proteins. X-ray diffraction is commonly carried out using single crystals of a material. Inelastic light scattering can reveal structural changes as well as changes in the electronic structure of the investigated system due to its coupling to electronic matrix elements. We use incident photons around 5 eV, where specific chromophores within the enantiomer exhibit a resonance. Spectra could be described by taking into account oscillation modes of the included bases. These modes are superpositions of modes originating from the different possible vibrations of atoms in the complex structured bases. We find that there is no sign of a structural difference in the spectra of L- and D-RNA. Nevertheless, small changes in the modes between the two forms enable us to calculate a Raman Difference Spectrum (RDS). The RDS is dependent on the incident photon energy. We suggest that electronic configuration between L- and D-RNA is different due to charge transfer effects that modify the electronic structure to which the Raman probe couples. We outline how to use this matrix element effect for the study of bio-organic matter.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P185

Die Aggregatstruktur bakterieller Pathogenit¨ atsfaktoren bestimmt ihre biologische Aktivit¨ at ¨ rg Howe1 Klaus Brandenburg1 , Manfred Roessle2 , Jo 1

Forschungszentrum Borstel, Parkallee 10 , 23845 Borstel – 2 European Molecular Biology Laboratory, Notkestr. 85, 22603 Hamburg Trotz der Verf¨ ugbarkeit von Antibiotika stellen Infektionskrankheiten eine zunehmende Bedrohung f¨ ur die menschliche Gesundheit weltweit dar. Dieses r¨ uhrt unter anderem von der Entstehung von Resistenzen her, die besonders auf den Mißbrauch von Antibiotika in der Tierzucht beruhen. In Gram-negativen Bakterien (u.a. Escherichia coli, Salmonella, Vibrio cholerae, Yersinia pestis) ist ein wichtiger Pathogenit¨ atsfaktor auf der Außenseite der ¨ außeren Membran lokalisiert, n¨ amlich das Endotoxin (chemisch: Lipopolysaccharid, LPS). Dieses wirkt in geringen Dosen positiv f¨ ur die menschliche Gesundheit, bei h¨ oheren Konzentrationen hingegen kann es das Sepsissyndrom ausl¨ osen, dem in Deutschland j¨ ahrlich ca. 60000 Menschen zum Opfer fallen. Dies h¨ angt unter anderem damit zusammen, daß viele Antibiotika zwar die Bakterien t¨ oten k¨ onnen, aber nicht die freiwerdenden Pathogenit¨ atsfaktoren wie LPS neutralisieren, die zu einem dramatischen Anstieg der Sekretion von Botenstoffen in Immunzellen f¨ uhren. Ein neuer therapeutischer Ansatz ist die Verwendung antimikrobieller Peptide (AMP) auf der Basis von LPS-Bindedom¨ anen von menschlichen und anderen LPS-Bindeproteinen wie Lactoferrin, Granulysin und anti-LPS-Faktor. Mit geeignet synthetisierten Peptiden konnten erhebliche Fortschritte in der F¨ ahigkeit zur LPS-Neutralisation, gemessen als Reduktion der Produktion von Botenstoffen, erreicht werden [1,2]. Ein maßgebener Parameter f¨ ur die Eigenschaft von LPS biologisch aktiv zu sein, ist der Typ seiner r¨ aumlichen Aggregatstruktur. Wir haben mit Synchrotronstrahlungs-Kleinwinkelbeugung gefunden, daß die Existsnz einer unilamellaren/nichtlamellaren dreidimensionalen Aggregatstruktur die Voraussetzung daf¨ ur ist, daß LPS hochaktiv ist [3]. In dem Maße, wie es durch AMP neutralisiert wird, wandelt sich seine r¨ aumliche Struktur in eine multilamellare Phase um. Dabei kommt der genauen Analyse dieser Phase (Zahl der Lamellen, Gr¨ oße der Aggregate, Bindungsenergie der einzelnen Monomere in den Aggregaten) eine besondere Bedeutung zu, um Aussagen u ¨ber die Neutralisierungsf¨ ahigkeit eines Peptides machen zu k¨ onnen. Zusammen mit der Verwendung anderer Techniken wie Titrationskalorimetrie und Gefrierbruch-Elektronenmikroskopie erlaubt uns die Analyse der LPS:Peptidkomplexe ein Verst¨ andnis der Prozesse auf molekularer Ebene, die zu der Reduzierung der toxischen Effekte der Pathogenit¨ atsfaktoren f¨ uhren. [1] J. Andr¨ a et al., Biochm. J. 385 (2005) 135. [2] J. Andr¨ a et al., Biochem. Pharmacol.68 (2004) 1297. [3] K. Brandenburg et al., Carbohydr. Res. 338 (2003) 2477.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P186

Water Dynamics in Phospholipid Model Membrane Systems Sebastian Busch1 , Fanni Juranyi2,3 , Thomas Gutberlet3 1

Physics Dept. E13, Technical University Munich, 85747 Garching, Germany – Physical Chemistry, University of the Saarland, 66123 Saarbruecken, Germany – 3 Lab. f. Neutron Scattering, PSI ETHZ, 5232 Villigen PSI, Switzerland

2

Biological membranes are characterized by a complex hierarchy of motions which is a fundamental prerequisite for their functionality on nature. Hydration of phospholipid bilayers and dynamics of water molecules at the membrane surfaces are of special importance in this context. The dynamical behavior in such membranes exhibits correlation times ranging from 10−12 s with the motion of alkyl chain defects up to 1 s corresponding to collective excitations of the bilayer. Due to the huge spread in correlation time and length quite different experimental approaches have been employed to study membrane dynamics ranging from light microscopy, dynamic light scattering, NMR, ESR, QENS, NSE and MD simulations [1-5]. To understand the dynamic behavior of water molecules in phospholipid membrane systems we have started to investigate the motions of water molecules in such systems by quasielastic neutron scattering. Rotational and translational motions of water molecules membrane bound and non-bound were described for phospholipids model membranes of DPPC below the main phase transition from fluid to gel state at different levels of low hydration [6]. Water diffusion constants below the bulk value of water were reported. We have extended these studies to phospholipids membranes at full hydration in the biological relevant fluid state. QENS measurements of alkyl chain deuterated DMPC at full hydration at different temperatures above and below the main phase transition were performed at the time-of-flight neutron spectrometer FOCUS at SINQ/PSI. The results show water diffusion within the phospholipids membranes similar to the diffusion of bulk water. The results and the corresponding measurements will be presented and discussed. [1] [2] [3] [4] [5] [6]

J. Seelig et al., Q. Rev. Biophys., 13 (1980) 19. W. Pfeiffer et al., Europhys Lett., 8 (1989) 201. S. Koenig et al., J. Phys. II France, 2 (1992) 1589. S. Koenig et al., Biophys. J., 68 (1995) 1871. M.C. Rheinstaedter et al., Phys. Rev. Lett. 93 (2004) 108107. S. Koenig et al., J. Chem. Phys., 100 (1994) 3307.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P187

News from the crystallographic structure of sea urchin spines of Heterocentrotus mammillatus S. Castorph1 , R. Hock2 , M. Baier2 1

Institute for X-Ray Physics, University of G¨ ottingen, Friedrich-Hund-Platz 1, 37077 G¨ ottingen – 2 Chair for Crystallography and Structural Physics, University of ErlangenN¨ urnberg, Staudtstr. 3, 91058 Erlangen Sea urchin spines consisting of high magnesian calcite are considered single crystals with the c-axis of calcite oriented parallel to the long spicule axis. As a biogenic carbonate mineral with a content of about 0.1 weight% proteins, an abnormal conchoidal fracture as compared to calcite and their sponge like interior structure, they have been attracting the interest of crystallographers [1,2,3]. We investigated spines of sea urchin Heterocentrotus mammillatus by powder diffraction and single crystal methods like the ordinary Laue technique on a Mo x-ray source and the high energy focussing Laue technique at energies of up to 65 KeV. For the detection of the single crystal diffraction patterns an image plate system was used. Chemically, spines were analysed by ICP Emission Spectroscopy. For powder diffraction measurements material from the outer dense shell of the spines and the inner sponge like calcitic stucture were prepared. The Mg content of the two radially separated regions of the spines is 9.4(4) and 7.6(4). Powder data from the inner part high magnesium calcite shows a superstructure with a modulation in [104] direction. Diffractograms from the shell material do not show superstructure reflections. Even so the diffractograms of the inner part material look at a first glance like those from ordinary high magnesian calcite, Rietveld fits within the R-3c model and a statistical Ca/Mg distribution are not satisfactory. To explain the superstructure, possible models for the symmetry of the biogenic calcitic material will be discussed and tested by Rietveld refinements. Namely a modified “inverse” µ-model according to Wenk et al. [4] with simultaneous ordering of cations and distortions in the carbonate groups and a tentative monoclinic variant of high magnesian calcite crystallised in C2/c with cation ordering in [104] sheets (in original calcite cell R-3c) together with distortions of the carbonate groups. Laue diffractograms with Mo radiation confirm the single crystalline nature previously reported, even so the term single crystal must be questioned in the light of the powder diffraction data. Diffuse scattering is observed in transmission and the variation of the Laue patterns after soaking samples in water and drying them at temperatures from 60 ◦ C up to 300 ◦ C were studied. Laue diffractograms measured with high energy in transmission nondestructively reveal the mosaicity of the spines as a function of position along the spicule axis. [1] [2] [3] [4]

C.D. West J. Paleontology 11 (1937) 458-459 U. Magdans H. Gies, Eur. J. Mineral. 16 (2004) 261-268 X. Su et al. J. Mat. Science 35 (2000) 5545-5551 H.R. Wenk et al. Phys. Chem. Minerals 17 (1991) 527-539

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P188

Protein Diffusion in Biological Cells Wolfgang Doster1 , Sebastian Busch1 , Stephane Longeville2 1

Technical University Munich, Physics department E 13, D-85748 Garching – 2 LLB CEA CRNS Saclay 91191, Gif-sur Yvette, France A characteristic of the interior of cells is the high total concentration of macromolecules. Such media are termed crowded rather than concentrated since no single macromolecular species occurs at high concentration. But taken together they occupy a signifcant fraction (20-30 %) of the total volume. This affects protein diffusion and protein association equilibria through excluded volume effects (highly non-ideal solutions). The goal of our project is to understand the effect of protein-protein interactions on molecular diffusion at high concentration. Our model of crowding in biological cells is hemoglobin diffusion inside erythrocytes. Using a combination of neutron spin echo and backscattering spectroscopy with low angle scattering, we analyse the effects of direct interactions and hydrodynamic interactions. Neutrons scattering allows probing molecular diffusion on a microscopic scale at high Q. The protein diffusion coefficients increase with decreasing Q indicating a cross-over from short-time self-diffusion to collective diffusion. Myoglobin solutions were investigated at various protein concentrations as well as hemoglobin diffusion in blood cells.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P189

Two-dimensional elemental mapping of liver tissue sections by micro-SRXRF Gerald Falkenberg1 , Osterode4

¨ ftberger2 , Romana Ho

Friedrich Wrba3 ,

Wolf

1

Deutsches Elektronensynchrotron DESY – 2 Medizin Universit¨ at Wien, Klinisches Institut f¨ ur Neurologie – 3 Medizin Universit¨ at Wien, Klinisches Institut f¨ ur Pathologie – 4 Medizin Universit¨ at Wien, Univ. Klinik f¨ ur Inner Medizin IV

The comparison of X-ray fluorescence elemental maps with biological structures in histological slices requires often the scanning of large areas in the millimetre range, but with microscopic resolution. To test whether large two-dimensional scans can be performed in an appropriate time with sufficient statistics we investigated normal liver tissue and liver tissue from patients with genetically disturbed iron metabolism (haemochromatosis, HC) in a continuous scanning mode by microscopic Synchrotron radiation induced X-ray fluorescence analysis (micro-SRXRF). Methods: micro-SRXRF measurements were performed at beamline L of DORIS III storage ring at HASYLAB/DESY in Hamburg. Slices of 10 µm thickness - imbedded in paraffin - were fixed on trace element free Ultralene foil for investigation. The white beam of the bending magnet was monochromatized by a double multilayer monochromator (NiC). The energy of the incoming beam was set to 17.5 keV for all measurements, and the monochromatic X-ray beam was focused by a polycapillary half-lens to a cross section of 15 µm providing a flux of 1011 photons/s. A Silicon multi-cathode X-ray Spectrometer VORTEX-EX (Radiant Detector Technologies) was employed in combination with a CANBERRA 2060 digital pulse processor. The system provided an excellent energy resolution of 160 eV (5.8 keV) for all count rates up to 80 000 cts/s. Several samples were scanned with 15 µm step size and 1 s sample time per pixel over different area sizes ranging up to 3 x 3 mm2 (40000 points, 11 h total scanning time). Element concentrations are calculated with a Fundamental Parameter code from normalized line intensities by comparison to an external reference sample (sputtered Ge film). Results: In normal liver tissue, after fixation and imbedding in paraffin, mean Fe, Cu and Zn concentrations were 152 ± 54, 20.1 ± 4.3 and 88.9 ± 19.5 µg/g sample weight, respectively. No substantial, characteristic differences in their distribution were found in the two-dimensional scans. In slices from patients with HC mean Fe, Cu and Zn concentrations were 1102 ± 53.9, 35.9 ± 14.6 and 27.2 ± 6.7 µg/g sample weight, respectively. Additionally, a significant decrease in phosphorus and sulphur concentrations existed. The increased Cu concentration around cirrhotic regenerations nodules is mostly associated with a lymphocytic infiltration in this region. Analyzing Fe in different sample regions reveals negative dependencies between Fe and Cu, Cu and Zn, but a positive dependence between Fe and Zn. Conclusion: In the continuous scanning mode elemental distribution in a near histological resolution (20 x light microscope) can be achieved in due time providing additional metabolic features.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P190

Integrated Life Science Centre at PETRA-III Stefan Fiedler1 , Gleb Bourenkov1 , Michele Cianci1 , Christoph Hermes1 , Victor Lamzin1 , Manfred Roessle1 , Dmitri Svergun1 , Matthias Wilmanns1 1

EMBL c/o DESY, Notkestrasse 85, 22603 Hamburg

Background: The EMBL-Hamburg Outstation operates five synchrotron radiation (SR) beamlines for applications in Macromolecular Crystallography (MX), one for Small Angle X-ray Scattering of Biological samples (BioSAXS) and one beamline for X-ray Absorption Spectroscopy of Biological samples (BioXAS) at the DORIS-III storage ring from DESY. During 2000-05, more than 1500 external projects from research groups across the world (about 85 % from Europe) have been carried out at the EMBLHamburg facilities. In addition, one of the largest high-throughput crystallization facilities is been commissioned at present and will become externally available later in 2006. Project: The European Molecular Biology Laboratory has recently made a proposal for an Integrated Life Science Centre at PETRA-III. It reflects the expressed needs by a large number of research groups from across Europe, requesting opportunities for the combined use or state-of-the-art SR beamlines and their integration into joint sample preparation and on-line data processing facilities. The proposed centre includes, at present: Two MX beamlines; the first one will be tuned for microfocusing to allow testing and data acquisition of extremely small crystals of biological macromolecules; the second one will be tuned for applications over a large energy range to allow data acquisition at the absorption edges of a broad range of different elements to allow experimental phase determination, and specific applications, such as structures at ultrahigh resolution, that require specific SR energy regimes. One BioSAXS beamline for large scale shape and quaternary structure analysis of individual macromolecules and functional complexes and for cutting edge applications such as ultra-fast kinetic studies. A joint sample preparation area and data processing area, allowing to provide a complete pipeline for structural biology experiments using synchrotron radiation. The recently built high-throughput crystallization facility will be integrated into this area. The Integrated Life Science Centre will be located at the last two straight sections at PETRA-III. The close proximity of tits components will allow to establish direct pipelines ranging from the preparation and characterization of samples, their transfer to SR beamlines, X-ray data acquisition and on-line data processing and interpretation, with options for remote experiment monitoring and operation. All endstations will be equipped with the state-of-the-art instruments to provide a user-friendly and highly automated experiment environment, permitting a high-throughput of experiments at the future PETRA-III beamlines. Our proposal has been approved and supported by two different reviewing panels and formally secured financial support is expected soon.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P191

Wie kontrollieren thermische Gleichgewichtsfluktuationen biologische Reaktionen? Dynamik-Funktions Beziehungen untersucht mit quasielastischer Neutronenstreuung ¨ rg Fitter1 Jo 1

Forschungszentrum J¨ ulich, IBI-2: Biologische Strukturforschung, D-52425 J¨ ulich

Biologische Makromolek¨ ule, wie z.B. Proteine die aus mehreren tausend Atomen bestehen, weisen eine strukturelle Komplexit¨ at auf, die sich auch in dynamischen Eigenschaften dieser Molek¨ ule widerspiegelt. Insbesondere thermische Gleichgewichtsfluktuationen im Piko- und Nanosekunden Zeitfenster sind essentiell um lokale Energiebarrieren in der komplexen Energielandschaft der Biomolek¨ ule zu u ¨berwinden. Diese Eigenschaften bestimmen direkt die Effizienz und Geschwindigkeit biokatalytischer Prozesse [1, 2]. Dar¨ uber hinaus tragen Strukturfluktuationen in diesem Zeitfenster wesentlich zur konformellen Entropie der Biomolek¨ ule bei. Im Falle von Protein-Liganden oder Protein-Protein Bindungen, aber auch im Falle von Proteinfaltungsprozessen spielt die Entropie¨ anderung h¨ aufig eine zentrale Rolle [2, 3]. Eine der wichtigsten Methoden zur Detektion und Charakterisierung dieser Strukturfluktuationen in Biomolek¨ ulen stellt die quasielastische Neutronenstreuung (QENS) dar (siehe Abb. 1). Das strategische Ziel unserer Studien ist es, die dynamischen und die biologisch relevanten Parameter unter m¨ oglichst identischen Probenbedingungen zu messen. Insbesondere Proteinl¨ osungen stellen dabei eine methodische Herausforderung f¨ ur Neutronenstreutechniken dar, da der Streubeitrag des Solvens (D2 O) selbst bei hochkonzentrierten L¨ osungen sehr hoch ist (∼ 80 %). Es wird anhand einiger Fallstudien demonstriert, welche Art von Strukturfluktuationen die biologischen Prozesse kontrollieren. [1] R.E. Lechner et al., Physica B, in press (2006) [2] Neutron Scattering in Biology: Techniques and Applications, Eds. J. Fitter, T. Gutberlet, and J. Katsaras, Springer Verlag, Heidelberg, 2006 [3] J. Fitter, Biophys. J., 84, 3924 (2003)

Abb. 1: Neutronenstreuspektren der α-Amylase im gefalteten und ungefalteten Zustand mit quasielastischem Streuanteil (grauer Fl¨ achenanteil). Die resultierenden elastisch inkoh¨ arenten Strukturfaktoren (A0 ) sind als Funktion des Impulstransfervektors Q dargestellt (nach [3]).

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P192

Interaction of long side chains Quinones and Hydroquinones with Model Membranes. ´rgio S. Funari1 , Maria Hanulova1 , Claudio di Vitta2 Se 1

HASYLAB at DESY, Notkestrase 85, 22603 Hamburg, Germany – 2 Institute of Chemistry, University of Sao Paulo, Sao Paulo, Brasil Quinones and hydroquinones present some biological activity. Generally speaking not much is known about and it is still not clear the relationship between doses and their effects. Moreover, the mechanism of action also is still speculative. Here we present the initial part of our study, i.e. the interaction of these compounds with model membranes. Two compounds were synthesized with side chains matching the acyl chain lenght of lipids forming model membranes. We present results from mixtures of these compounds with POPC, a zwitterionic lipid, using polarizing optical microscopy (POM) and X-ray scattering obtained simultaneously from small and wide angles at the soft condensed matter beam line A2 from HASYLAB at DESY. For each sample studied a temperature scan was carried out at typically 1-2 ◦ C/min. Due to the hydrophobicity of these compounds, they remain crystalline (needles) in water. Therefore mixtures of them with lipids could not be prepared by direct missing, but rather requiring a chloroform solution of both components, followed by solvent evaporation and posterior direct hydration. X-ray scattering near room temperature show patterns containing characteristics of lipid bilayers superimposed to typical patterns from crystals. It seems that at room temperature we have two phases, a solid crystal (quinone or hydroquinone) and a lipid liquid crystalline. Interestingly, they do not separate easily. Heating these samples to relatively high temperatures causes the melting of the crystals (above ca. 50 ◦ C, but depending on the sample composition). Cooling at 1-2 ◦ C/min does not produce an X-ray pattern of a two mixed phases system. However the pattern can be seen in the following day. The phase transitions and the mixing of phases are being investigated in more detail and shall be reported.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P193

Small-Angle X-Ray Scattering of Lipopolysaccharide-Peptide aggregates ¨ rg Howe1 , Manfred Roessle2 , Klaus Brandenburg1 Jo 1

Research Center Borstel, Division of Biophysics, Parkallee 10, D-23845 Borstel, Germany – 2 EMBL Outstation Hamburg, Notkestrasse 85, D-22603 Hamburg, Germany Bacterial endotoxin (Lipopolysaccharide, LPS) is the major component of the outer leaflet of the outer membrane in Gram-negative bacteria. It is composed of a hydrophobic moiety called lipid A and a hydrophilic saccharide part composed of different sugars, depending on the bacterial species. During cell division or cell death, LPS can be released from the membrane causing a variety of biological effects. The reaction may be beneficial at low concentrations, but can lead to patho-physiological effects at high concentrations like septic shock syndrome and multiorgan failure. Due to this fact, treatment of bacterial infections with conventional antibiotics without inactivating LPS has to be replaced by a medication that kills the bacteria and neutralizes LPS. One possible strategy for the development of new drugs is the use of antimicrobial peptides, which are derived from the binding epitopes of natural antimicrobial proteins. We used the endotoxin-binding protein of the horse-shoe crab Limulus polyphemus to synthesize peptides and tested them for their antimicrobial and endotoxin-neutralizing properties. LPS, as an amphipathic molecule, forms in aqueous solution three-dimensional aggregates. The three-dimensional aggregate structure was investigated using small-angle x-ray scattering. It was found that the biologically active form of the LPS molecules are cubic or unilamellar structures. We found that the best peptides for neutralizing LPS lead to a change in the LPS aggregate structure, from a cubic to a multilamellar arrangement of the molecules. Several other techniques are used to investigate the reaction of these peptides with the LPS, like freeze-fracture electron microscopy and Fourier-transform infrared spectroscopy to analyse the gel to liquid crystalline phase transition of the acyl chains of the LPS and the influence of the peptides. Complementary, isothermal titration calorimetry measurements were performed to get informations about the binding stoichiometry and binding enthalpies. Our results should lead to a better understanding of the mechanism of LPS neutralizing and lead to the estimation of necessary properties of peptides, which effectively kill bacteria and neutralize LPS.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P194

Lysozyme and Staphylococcal Nuclease solutions studied by small-angle xray scattering Christof Krywka1 , Christian Sternemann1 , Winter2 , Metin Tolan1 1 2

Nadeem Javid2 ,

Roland

Fachbereich Physik, DELTA, Universit¨ at Dortmund, D-44221 Dortmund – Fachbereich Physikalische Chemie, Universit¨ at Dortmund, D-44221 Dortmund

Ever since x-rays were employed for structure determination, small-angle x-ray scattering (SAXS) has retained its unique position among methods that allow to investigate structure on an Angstrom length scale. It is left with no competition when structure of partially or completely disordered particles is sought and its major advantage is the feasibility of in situ measurements, e.g., on protein molecules dissolved in their natural, aqueous environment at low concentration. The biological activity, thermodynamic stability along with the physical and chemical properties of proteins are strongly influenced by the structure of their aqueous microenvironment. Hence, understanding the effects of various types of cosolvents typical for cellular conditions on the structure and dynamics of proteins is crucial for a deeper insight into protein stability, folding, aggregation and fibrillation processes. The latter play an important role in many conformational diseases, such as Alzheimer, Huntington, Creutzfeldt-Jakob, and Parkinson. It was shown that the latter processes are in fact markedly influenced by the type and concentration of cosolvents. As a part of the human immune system, lysozyme breaks carbohydrate chains, destroying the structural integrity of bacteria cell wall and leading them to burst under their high internal osmotic pressure. The influence of the cosolvents tetrafluoroethylene, sodium chloride, and glycerol on the native state structure of lysozyme was studied using SAXS measurements on aqueous solutions of lysozyme at beamline BL9 of DELTA synchrotron, University of Dortmund. A wide range of concentrations of pure lysozyme as well as lysozyme in the presence of cosolvents, typical for conditions where unfolding sets in, was probed. For the higher concentrated samples, information about the intermolecular interaction potential could be obtained from analysis of the intermolecular structure factor. The biological function of staphylococcal nuclease is to catalyze the hydrolysis of the phosphate backbone of DNA and RNA. Unlike lysozyme, this protein can fold and unfold reversibly due to the lack of disulfide bonds or free sulfhydryl groups. This peculiarity opens up the possibility to studying the intermediate states of unfolding next to its native and denaturated state by applying a reversible condition that induces unfolding or refolding, such as temperature or pressure. For this reason, SAXS measurements were also performed on staphylococcal nuclease in a wide pressure and temperature range in the absence and presence of various cosolvents, using a home built high pressure cell, and subsequently analysis of the tertiary structure of the different conformational states was performed.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P195

Neuroimaging with neutrons and photons ¨hbacher1 , Gerald Falkenberg2 , Bernd Gru ¨newald3 , Ulrich Markus Ku 4 5 5 Schade , Martin Radtke , Heinrich Riesemeier , Jens Fischer6 , Felix Beckmann7 , Dietrich Behne1 , Antonios Kyriakopoulos1 1

Hahn-Meitner-Institut Berlin, Department Molecular Trace Element Research in the Life Sciences, Glienicker Str. 100, 14109 Berlin, Germany – 2 Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany – 3 Institut f¨ ur Neurobiologie, Freie Universit¨ at Berlin, 14195 Berlin, Germany – 4 Berliner Elektronenspeicherring-Gesellschaft f¨ ur Synchrotronstrahlung m. b. H. BESSY, 12489 Berlin, Germany – 5 Bundesanstalt f¨ ur Materialforschung und -pr¨ ufung, Unter den Eichen 87, 12200 Berlin, Germany – 6 Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625 Hannover, Germany – 7 GKSS-Research Center Geesthacht, Institute for Materials Research, Max-Planck-Strasse 1, D-21502 Geesthacht, Germany In this overview the concept of the complementary use of radiotracers produced with neutrons at the reactor of the Hahn-Meitner-Institut and photons produced at the synchrotron facilities BESSY and HASYLAB for 2D and 3D chemical imaging of metaland metalloid-containing proteins in specific tissues - in particular in the central nervous system - is discussed. Metals and metalloids are known to be involved in various cerebral metabolic processes. The determination of their spatial distribution within the brain in health and disease may help to identify their specific sites of action and to elucidate their biological roles [1]. Possibilities and limits of the synchrotron techniques are shown in relation to the application of radiotracers used for specific labeling of those metal- and metalloid containing proteins, which are then detectable, by autoradiography. Synchrotron radiation X-ray fluorescence analysis (SRXRF) allows the determination of the metal distribution in cryosections of tissues while synchrotron radiation-based Fourier transform infrared (SRFTIR) spectromicroscopy may provide information on the chemical composition of the sections of interest. These methods can therefore be used as valuable tools in studies on the role of metalloproteins in health and disease. The development of superior 3D imaging methods was an advance for histological structural analyses. Tomography, specifically X-ray tomography, is a 3D imaging method with the advantage to be non-destructive. In all cases, the use of synchrotron radiation offers the high spatial resolution necessary for the investigation of brain tissue. [1] M. K¨ uhbacher et al., X-Ray Spectrometry 34 (2005) 2: 112-117.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P196

Investigation of Native Starch Granules using Synchrotron Radiation Microdiffraction Henrik Till Lemke1 , Jean-Luc Putaux2 , Andreas Blennow3 , Manfred ¨ lln4 , Martin Mu ¨ller4 , Christian Burghammer5 , Ingo Grotkopp4 , Klaas Ko 5 Riekel 1

Niels Bohr Institute, Copenhagen – 2 CERMAV-CNRS, Grenoble, France – 3 Royal Veterinary and Agricultural University, Copenhagen – 4 Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel – 5 European Synchrotron Radiation Facility, Grenoble, France The hierarchical structure of single starch granules was investigated using scanning X-ray microdiffraction. Combined small- and wide-angle scattering experiments at the 1 µm level allowed spatially resolved investigation of the amylopectin microstructure and the lamellar superstructure at multiple length scales in fully hydrated potato granules of 50-100 µm diameter. The obtained fiber diffraction patterns showed changes in both orientation and intensity of characteristic reflections, which could be modeled by a ellipsoidal alignment of the lamellar structures around an eccentric origin. Investigation of starch granules from plants with selectively altered enzyme distribution in starch synthesis showed significant changes in crystallinity and lamellar distance. A kinetic study of the hydration process in dried starch granules suggests different time constants for the hydration of crystalline and amorphous regions.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P197

The interaction of antimicrobial peptides with model membranes investigated by small angle X-ray scattering Sebastian Linser1 , Sergio S. Funari2 , Regine Willumeit1 1 2

GKSS Research Center, Max-Planck-Str. 1, 21502 Geesthacht, Germany – Hasylab@DESY, Notkestr. 85, 22603 Hamburg, Germany

The uprising resistance of pathogenic bacteria is a severe problem in health care. To develop new antibiotic treatment, naturally occurring antimicrobial peptides and synthetic derivates might become potent agents. These peptides have a direct physical impact on the membranes of their target cells and display selectivity for bacteria and fungi in contrast to mammalian cells. In our work we tested the antibacterial activity of the synthetic peptide NK-CS and derivatives thereof against E. coli (Gram negative) and S. carnosus (Gram positive) bacteria as well as the hemolytic properties against human erythrocytes to determine the selectivity of the peptides. In parallel we investigated the interaction of the peptides with different model membranes, mimicking bacterial and human membranes, by small angle X-ray scattering (SAXS). The combination of these techniques gives an indication of the structure-function relationship of this peptide-lipid-system. Among the tested peptide, NK-CS was found to be the most potent antimicrobial peptide, while all derivatives showed less antibacterial selectivity and activity. Structural characterization of the interaction between the peptides and different model membranes revealed that the peptides showed no influence on phosphatidylcholine lipids, representing the membrane of erythrocytes, but for all tested peptides the inverse hexagonal phase transition of phosphatidylethanolamine lipids, standing for the main component of the bacterial membrane of E. coli, was significantly altered in a specific manner which can be correlated with the activity of the peptides. This phase transition temperature was increased by the peptides promoting a positive curvature of the membranes eventually leading to the disruption of the model membranes.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P198

D¨ unne Filme aus rekombinant hergestellter Spinnenseide untersucht mit R¨ ontgenstreuung unter streifendem Einfall E. Metwalli1 , C. Darko1 , U. Slotta2 , T. Scheibel2 , S.V. Roth3 , C.M. Papadakis1 1

Physikdepartment E13, Technische Universit¨ at M¨ unchen, James-Franck-Str. 1, 85747 Garching – 2 Department Chemie, Lehrstuhl f¨ ur Biotechnologie, Technische Universit¨ at M¨ unchen, Lichtenbergstr. 4, 85747 Garching – 3 HASYLAB at DESY, 22603 Hamburg F¨ ur die Biosensorik ist es wichtig, evtl. Konformations¨ anderungen von Proteinen bei ¨ der Absorption an festen Substraten zu charakterisieren. Wir untersuchen den Ubergang von der α-helix-reichen zu der β-Faltblatt-reichen Konformation, die in d¨ unnen Filmen aus rekombinant hergestellter Spinnenseide u.a. bei Behandlung mit Methanol auftritt. Filme aus Spinnenseide C12 wurden aus Hexafluoroisopropanol-L¨ osung auf SiOxSubstrate gegossen und mit Methanol oder Kaliumphosphat behandelt. Mit Zirkulardichroismus [1] und External Reflection Infrarotspektroskopie konnte der Konformations¨ ubergang quantifiziert werden. Oberfl¨ achendiffraktion (GIXD) an BW2 (HASYLAB) zeigte, dass nach der Behandlung die Kristallstruktur des beta-Faltblatts verst¨ arkt vorhanden ist (Abb. 1). Die Filme werden durch die Behandlung mit L¨ osungsmittel rauer, was wir mit Rasterkraftmikroskopie als auch R¨ ontgenkleinwinkelstreuung unter streifendem Einfall (GISAXS an BW4, HASYLAB) nachgewiesen haben. [1] D. Huemmerich, U. Slotta, T. Scheibel, Appl. Phys. A 82 (2006) 219.

Abb. 1: GIXD-Kurven von d¨ unnen Filmen aus rekombinant hergestellter Spinnenseide vor und nach der Behandlung mit Methanol.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P199

Biological X-ray Absorption Spectroscopy in the 21st Century: Towards automated Data-Collection and Analysis Wolfram Meyer-Klaucke1 1

EMBL Hamburg, Notkestr. 85, 22603 Hamburg, Germany

X-ray absorption spectroscopy allows the element specific characterization of metal sites in biological systems, yielding information about the types and distances of coordinating ligands as well as the oxidation state of the metal center. For multinuclear proteins, the metalmetal distance can also be determined. In fact, the method can be performed on samples in every state, including solutions and intact tissue. Energy dependent measurements of the absorption coefficient require a tunable X-ray source. Ideally, this is a synchrotron beamline equipped with a monochromator. The tremendous improvements in this field allow for a high degree of automation during the measurement. Increasingly, the data analysis becomes the bottle-neck. Recently, the first packages for automated data-reduction became available[1]. On the way is the automatic determination of metal binding motifs. These options open the window towards high-throughput biological XAS. Some recent ex-amples benefiting from these developments will be discussed in the second part of the presen-tation, focusing on the metal specificity in the metallo-beta lactamase superfamily[2] and pro-teins involved in metal regulation[3]. [1] Korbas, M., Fulla Marsa, D., Meyer-Klaucke, W. (2006) Kemp a program script for automated biological XAS data reduction, Rev Sci Instr, accepted Lippold, B, Meyer-Klaucke, W, Meyer, T, and Henkel, G (2005) Towards an automated quality control of XAS data. J Synchrotron Radiat 12, 45-52. [2] Schilling, O, Vogel, A, Kostelecky, B, Natal da Luz, H, Spemann, D, Spath, B, March-felder, A, Troger, W, and Meyer-Klaucke, W (2005) Zinc- and iron-dependent cytosolic metallo-beta-lactamase domain proteins exhibit similar zinc-binding affinities, independ-ent of an atypical glutamate at the metal-binding site. Biochem J 385, 145153. Schilling, O, Wenzel, N, Naylor, M, Vogel, A, Crowder, M, Makaroff, C, and MeyerKlaucke, W, Flexible metal binding of the metallo-beta-lactamase domain: glyoxalase II incorporates iron, manganese, and zinc in vivo. (2003) Biochemistry 42, 11777-11786 [3] Pohl, E, Haller, JC, Mijovilovich, A, Meyer-Klaucke, W, Garman, E, and Vasil, ML, (2003) Architecture of a protein central to iron homeostasis: crystal structure and spectroscopic analysis of the ferric uptake regulator. Mol Microbiol 47, 903-915.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P200

Indirect Radiation Therapy of Cancer by Neutron Capture at dense Gadolinium Targets (Gd-NCT) Thomas Nawroth1a , Heinz Decker1b , Moritz A. Konerding1c , Monika Rusp2 , ´raldine Le Duc3 , Ste ´phanie Corde4 , Roland Ga ¨hler5a , Roland P. May5b Ge 1

Gutenberg-Universit¨ at: a) Biochemistry Institute, Becherweg 30, b) Molecular Biophysics Institute, Welder-Weg 23, c) Institute of Anatomy and Cell Biology, Becherweg 13; D-55099 Mainz, Germany – 2 Technical University Munich TUM, Biophysics E22, Physics Department, James-Franck-Str., D-85747 Garching, Germany – 3 ESRF European Synchrotron Radiation Facility, BioMedical Facility BMF; BP220, F-38043 Grenoble, France – 4 Dep. Hemato-Cancerologie-Radiotherapie, CHRU clinics, B.M. 217X, F-38043 Grenoble Cedex9, France – 5 ILL Institut Lange Langevin: a) NeutroGraph tomography, b) Large Scale Structure group LSS; BP156, F-38042 Grenoble Neutron Capture Therapy NCT is an indirect radiation therapy of cancer, which inactivates tumors by secondary products evolving from an incorporated target upon specific absorption of external radiation. Early trials with Boron (B-NCT) were limited by the low physiological target concentration (1 mM) and the moderate cross section of 3843 barn. The change to 157 Gd with 254,000 barn cross section and highly concentrated biocompatible Gd-targets improves the method by 3 orders (Fig.1a). The Lanthanide-complex is applied in a key-formulation, which breaks the blood-brain barrier BBB reversibly, as in our synchrotron X-ray therapy project with Lu-Gd complexes at ESRF-ID17. The local deposition of the gamma photons arising after neutron capture is achived by a second Lanthanide (Er/Lu), which works as an internal radiation enhancer (gamma - Auger electron conversion, Fig.1b). The study is done with cold and thermal neutrons at the ILL- D22 and Neutrograph instruments. The biological tests are done in tight collaboration between ILL, ESRF with BioMedical Facility BMF. [1] T. Nawroth, M. Rusp, R.P. May; Physica B 350(2004), e635-638; [2] T. Nawroth, G. Le Duc, St. Corde, R.P. May, P. Boesecke, A. Bravin; ESRF User meeting proceedings (2006, 3 contributions); [3] WEB-site: www.mpsd.de/irt

Fig. 1: a) Neutron Capture Therapy NCT inactivates cancer cells by secondary radiation products after specific absorption of neutrons at a tumor-local target. The change from Boron (B-NCT) to Gadolinium (GdNCT) improves the method by 3 orders. b) A concentrated dual-Lanthanide target enhances the therapy effect by heteronuclear selfabsorption of the gamma radiation (1-8 MeV).

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P201

Indirect Radiation Therapy of Cancer with Synchrotron Radiation at the K-Edges of Heavy Metal Complexes and Target-Nanoparticles Thomas Nawroth1a , Heinz Decker1b , Christian Meesters1b , Bruno Pairet1b , ´phanie Corde4 , Peter Monika Rusp2 , Meritxell Costa Torres3 , Ste 5a 5b 5c ´raldine Le Duc , Alberto Bravin Boesecke , Ge 1

Gutenberg-Universit¨ at: a) Biochemistry, Becherweg 30, b) Molecular Biophysics, Welder-Weg 23; D-55099 Mainz, Germany – 2 Technical University Munich TUM, Biophysics E22, Physics Department, James-Franck-Str., D-85747 Garching, Germany – 3 Biophysics Unit, Biochemistry and Molecular Biology Department, Universidad Aut´ onoma de Barcelona, E-08193 Ballaterra, Spain – 4 Dep. Hemato-CancerologieRadiotherapie, CHRU clinics, B.M. 217X, F-38043 Grenoble Cedex9, France – 5 ESRF European Synchrotron Radiation Facility: a) ASAXS beamline ID01, b) BioMedical Facility BMF, c) Medical beamline ID17; BP220, F-38043 Grenoble, France

Indirect radiation therapy of cancer IRT inactivates tumors cells by secondary products evolving from an incorporated target upon specific absorption of therapeutic radiation, which is depicted as photon activation therapy PAT by Kedge target absorption of synchrotron radiation (fig.1). We apply biocompatible heavy metal complexes of Lanthanides, e.g. Gadolinium- to Fig. 1: Principles of indirect radiation Lutetium-DTPA in target-nanoparticles and in therapy IRT, i.e. photon activation key-formulations breaking the blood-brain bartherapy PAT, and direct radiation therapy RT with an incorporated Lutetium rier (BBB). The novel cancer therapy is optitarget. mised towards minmal body dose Qb (demage) at maximal healing dose Qt , specifically absorbed WEB: www.mpsd.de/irt at the local target material. With our materials using the heaviest Lanthanide Lutetium (EK = 63.31 keV) the relative therapeutic absorption At b = Qt /Qb can be up to 10 %, as calculated for an 1 cm target area covering a brain tumor in a human head (12 cm path); with Gadolinium an effect of At b=6.3 % is possible at EK = 50.24 keV. This lead to the imaging- therapy postulate for indirect radiation therapy: “An effective (adjuvant) cancer therapy target should be visible by in vivo contrast imaging (therapeutic imaging).” In animal tests with rats the imaging-therapy postulate was successfully verified. First therapy trials with rats bearing brain tumors are running.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P202

Structure of two-component lipid membranes on solid support: An X-ray reflectivity study Eva Novakova1 , Klaus Giewekemeyer1 , Tim Salditt1 1

Institut fuer Roentgenphysik, Universitaeat Goettingen, Friedrich-Hund-Platz 1, 37073 Goettingen, Germany Supported lipid bilayer systems serve as simple model for the much more complex biological counterparts, and are also interesting components for biotechnological applications, for example as bio-functionalized solid surfaces. We used X-ray refectivity to probe the structure of two-component lipid mixtures with varied surface charges, both in the fluid and gel phase, deposited on silicon by vesicle fusion. We investigated the effect of the bilayer charge on the water spacing between bilayer and silicon, as well as the detailed profile of mixed two-component bilayers. For this purpose, refectivity signal above background has been measured up to qz = 0.6 ˚ A−1 in the fluid phase and qz = 0.7 ˚ A−1 in the gel phase of the bilayers, using synchrotron radiation, while a range of at least qz = 0.3 ˚ A−1 and qz = 0.35 ˚ A−1 was exploitable in-house. We show that the resolution obtained in the density profile across the bilayer is high enough to distinguish two headgroup maxima in the profile if the sample is in the phase coexistence regime. The water layer between the bilayer and silicon is found to depend on the lipid surface charge density.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P203

Auto-Rickshaw: The EMBL Hamburg Automated Structure Determination Platform Santosh Panjikar1 , Venkataraman Parthasarathy1 , Victor S. Lamzin1 , Manfred S. Weiss1 , Paul A. Tucker1 1

EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany We present an automated crystal structure determination platform, Auto-Rickshaw. It contains several distinct computer coded decision-makers which invoke a number of macromolecular crystallographic software suites at different stages in the structure determination process. A large number of structure solution paths are encoded in the system and the optimal path is selected by the decision-makers as the structure solution evolves. The primary aim of the pipeline is to validate the crystallographic experiment at the synchrotron site while the crystal is still at or near the beamline. Thus, the system has been optimized for speed, so that typically within a few minutes the answer is provided whether the collected data will be of sufficient quality to allow successful structure determination. The platform has been installed on a 16-processor Linux cluster. Since January 2005, it is remotely accessible to the beamline users via a web-server. An overview of the Auto-Rickshaw pipeline with its design, functionality, some examples and the way this platform is used as a feedback system for X-ray data collection or validation of an X-ray experiment, will be presented.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P204

Structure of the prostaglandin D synthase from the parasitic nematode Onchocerca volvulus ¨ ppner2 , Jo ¨ rg Degen3 , Christian Betzel1 , Eva Markus Perbandt1 , Jana Ho Liebau4 1

Department of Biochemistry and Molecularbiology, University of Hamburg, Martin Luther King Platz 6, 20146 Hamburg, Germany – 2 Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine – 3 Center of Bioinformatics, University of Hamburg, Bundesstraße 43, 20146 Hamburg, Germany – 4 Institute of Zoo Physiology, Department of Molecular Physiology, Westf¨ alische Wilhelms-University of M¨ unster Onchocerciasis or river-blindness is a debilitating parasitic disease caused by the filarial worm, Onchocerca volvulus. Chemotherapeutic approaches to control parasite transmission and to treat onchocerciasis rely on drugs that only kill microfilariae and infectious larvae but not the adult parasites. So far this necessitates the continuous use of these microfilaricides until the adult worms die. Therefore, the development of drugs that also effectively kill the adult worms would greatly support the control and treatment of O. volvulus infections [1]. Furthermore, the potential development of drug-resistant strains of the nematode also demands the identification of alternative drug candidates to control the disease [2]. The long-term survival of the parasites in the host is remarkable and has initiated a search for parasite-derived molecules that are involved in the modulation of the host immune system. The glutathione-dependent prostaglandin D synthase (Ov-GST1) from O. volvulus is strongly in involved in this and belongs to the sigma class of the glutathione S-transferase (GST) family. It is located directly at the parasite-host interface. The data were collected at DESY/HASYLAB in Hamburg using synchrotron radiation. We analysed the three-dimensional structure of the enzyme complexed with glutathione at 2.0 ˚ A. The molecular architecture of the substrate binding site reveals significant differences to the vertebrate orthologs from human and rat. The putative substrate binding mode and its catalytic mechanism for the specific isomerization from PGH2 to PGD2 is proposed based on the structural insights. Knowing the three-dimensional shape and chemical nature of the enzyme binding pocket will aid in the discovery and design of novel anti-filarial compounds. [1] D.H. Molyneux et al., Trends Parasitol 19 (2003) 516-522. [2] N. Sangster, Parasitology 113 Suppl (1996) 201-216.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P205

Residual Stresses in the Exoskeleton of a Homarus americanus Lobster Haroldo Pinto1 , Helge Fabritius1 , Dierk Raabe1 , Anke Pyzalla1 1

Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 D¨ usseldorf, Germany Artificial tissues are being increasingly used in the replacement of damaged structural parts of the body. These artificial structures do not only require appropriated mechanical properties, but also biocompatibility and hemostatic properties. Therefore, the emulation of natural scaffolds represents an interesting possibility to combine good mechanical properties with biocompatibility. Natural extracellular skeletons often consist of ordered fibrous composites, which are hierarchically arranged in twisted plywoods structures. Generally, composite materials contain significant residual stresses due to differences in the physical properties of matrix and reinforcement. Also biological composites are, therefore, expected to have residual stresses, which are supposedly correlated to their formation process and function. The aim of these investigations is a first time characterization of the residual stress state in biocomposites, particularly in the cuticle of a lobster Homarus americanus, which is a hierarchically organized natural material. The structure of the exoskeleton and its residual stress state are revealed by electron microscopy and synchrotron X-ray diffraction studies.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P206

STRUCTURAL INVESTIGATIONS OF PRION PROTEIN AGGREGATION Lars Redecke1 , Marko Silvestric1 , Joachim Clos2 , Perter V. Konarev3 , Dimitri S. Svergun3 , Wolfram Meyer-Klaucke3 , Dessislava Georgieva1 , Nicolay Genov4 , Christian Betzel1 1

Universit¨ at Hamburg, Institut f¨ ur Biochemie und Lebensmittelchemie, MartinLuther-King Platz 6, 20146 Hamburg, Germany – 2 Bernhard-Nocht-Institut f¨ ur Tropenmedizin, Bernhard-Nocht Str. 74, 20359 Hamburg, Germany – 3 European Molecular Biology Laboratory, Outstation Hamburg, Notkestr. 85, 22607 Hamburg, Germany – 4 Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria Prion proteins are involved in a group of fatal neurodegenerative diseases including bovine spongiform encephalopathy (BSE) in cattle and Creutzfeld-Jakob disease (CJD) in humans. The posttranslational conversion of the prion protein from its normal cellular isoform (PrPC) into its misfolded infectious state (PrPSc), which accumulates in the central nervous system, is considered to act as a key event during the course of disease. However, the physiological functions of the cellular prion protein as well as the pathogenesis of neuronal cell death in prion diseases remain still enigmatic. Consequently, the detailed structural investigation of the conversion and aggregation process is required to elucidate the pathogenesis of prion diseases and to develop promising therapies. Since increased levels of oxidative stress have been linked to prion diseases, we investigated the metal-induced oxidation of human PrP (90-231) as well as of mouse PrP (89-230). A novel in vitro conversion assay based on aerobic incubation of PrP in the presence of elemental, redox-active metal pellets at pH 5 was established, resulting in aggregation of highly β-sheeted prion proteins. We show for the first time that discrete oligomeric species of elongated shape, approx. 25mers, 80mers, and 100mers, are formed on the pathway of oxidative PrP aggregation, which are well characterized regarding shape and size using small-angle X-ray scattering (SAXS) techniques. Considering that small oligomers of highly similar size have recently been reported to show the highest specific infectivity within TSE-infected brain tissues of hamsters, the novel oligomers observed in this study are interesting candidates as agent causing neurodegenerative and/or self-propagating effects. Moreover, extended X-ray absorption fine structure (EXAFS) measurements revealed that the generated high molecular mass aggregates coordinate Cu(II) and Zn(II) ions in a specific geometry, which indicates a structural influence of the metal ions during aggregate formation. Specific copper binding sites have been observed several fold within the N-terminal part of prion proteins. However, mammalian and avian prion proteins, which are not able to undergo the conversion process into an infectious isoform, have a considerably different N-terminal copper coordination, as it is additionally shown by comparative EXAFS analysis. These results provide new insights into the prion protein structure-function relationship and into the conversion process of PrP.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P207

Biological Small Angle X-ray Scattering at the European Molecular Biology Laboratory Hamburg - Present State and Future Plans for Petra III Manfred Roessle1 , Roy Klaering2 , Petr Konarev1 , Uwe Ristau2 , Bernd Robrahn2 , Maxim Pethoukov1 , Thomas Gehrmann2 , Stefan Fiedler2 , Christoph Hermes2 , Dmitri Svergun1 1

EMBL Hamburg BioSAXS Group Notkestr. 85 D-22603 Hamburg – 2 EMBL Hamburg X-ray Instrumentation Group Notkestr. 85 D-22603 Hamburg Small angle X-ray scattering (SAXS) is a versatile tool for structural investigation of biological molecules in solution, and became a rapidly growing field of research during the last years. In contrast with other methods in structural biology SAXS allows to study the overall structure of native particles in solutions and analyze structural changes in response to variations in external conditions such as temperature, pH etc. The BioSAXS station X33 at the EMBL Hamburg Outstation was subsequently upgraded to optimize performance for the scattering studies of macromolecular solutions. This upgrade includes changes in all components of the station, from major optical parts to the experimental stage and detector system. This recent technical upgrade of the BioSAXS station together with advantages in data analysis significantly enhanced resolution and reliability of structural models provided by the technique. The available software packages on the BioSAXS station cover all steps in data analysis ranging from semi-automatic data reduction, data analysis such as Guinier-approximation (PRIMUS) and indirect Fourier transformation (GNOM) up the ab inito low resolution model building (DAMMIN and GASBOR). Ab initio model building technique as well as rigid body modeling allows one to analyze the overall shape of the macromolecule based only on the scattering data, and taking advantage of already available high or low resolution structures. Semi-automatic modeling up to completely automatic rigid body modeling using distance constrains are possible with our present software packages (DAMMIN, GASBOR, MASSHA, SASREF and BUNCH). This software is freely available for the academic user community (ATSAS program suite) and widely used. The new BioSAXS beamline for Petra III will adequately exploit the exceptionally high brilliance of the Petra-III source to further improve the efficiency of structural analysis using the small-angle scattering technique accompanying new and fast analysis methods developed at the EMBL. The BioSAXS station will share the infrastructure for biological sample preparation and handling with the other EMBL beamlines and will lead towards a unique environment for cutting edge research and for large scale analysis of biological macromolecules in combined protein crystallographic - SAXS studies. [1] [2] [3] [4]

Svergun, D. I. et al. Rep. Progr. Phys. 66, (2003) Konarev, P. V., et al J. Appl. Crystallogr. 34, (2001) Vestergaard, B. et al Molecular Cell (2005) Roessle, M., et al Biomacromolecules 4, (2003)

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P208

Digital in-line holography with synchrotron radiation Axel Rosenhahn1 , Ruth Barth1 , Florian Staier1 , Xinyu Cao1 , Martina ¨rmann1 , Stefan Eisebitt2 , Michael Grunze1 Schu 1

Angewandte Physikalische Chemie, Universit¨ at Heidelberg, INF 253, 69120 Heidelberg – 2 BESSY m.b.H., Albert-Einstein-Str. 15, 12489 Berlin Digital in-line holography has been proven to be a highly useful microscopy technique that works without lenses and at the same time provides intrinsic three dimensional information [1-3]. The principle of such a holographic microscope goes back to the initial idea of D. Gabor of a new microscopic principle“ [4]. In this concept, coherent ” radiation is scattered by an object and its interference with the unscattered wavefront creates a diffraction pattern. As the unscattered background wave acts as reference, each of these holograms intrinsically contains three dimensional information about the investigated object. Both optically and nowadays digitally the scattering pattern can be reconstructed and information about the investigated object retrieved in real space [1]. In order to enhance the resolution of digital in-line holography it is straightforward to consider a decrease of the wavelength. Therefore, we use photons in the XUV region from 90 eV to about 350 eV, which includes the water window [5,6]. The feasibility to use this wavelength range for coherent scattering experiments has previously been proven [7,8,9]. We present results on XUV digital in-line holography using the classical Gabor geometry with a highly divergent beam. As the production of highly divergent XUV beams is a major challenge, possibilities and new point source designs are shown that help to successfully suppress direct beam transmission in order to avoid a beam block. To characterize the imaging properties, test samples with known properties as polymer beads and lithographic structures were used to analyze resolution and obtainable contrast. Additionally we show images of fibroblast cells to discuss future biological perspectives of the technique. In order to make this new imaging technique available to other users, the design of an experimental endstation exclusively dedicated to holographic imaging will be described [10]. [1] W. Xu et al., Proc. Natl. Acad. Sci. USA 98 (2001) 11301 [2] J. Garcia-Sucerquia et al., Appl. Optics 45 (2006) 836 [3] J. Garcia-Sucerquia et al., Opt. Lett. 31 (2006) 1211 [4] D. Gabor, Nature 161 (1948) 777 [5] S. Vogt et al., J. Struct. Biology 132(2) (2000) 123 [6] W. Meyer-Ilse et al., J. Microscopy 201(3) (2001) 395 [7] J.E. Trebes et al., Science 238 (1987) 517 [8] R.A. Bartels et al., Science 297 (2002) 376 [9] S. Lindaas et al., J. Opt. Soc. Am. A 13(9) (1996) 1788 [10] BMBF F¨ orderkennzeichen 05KS4VH1/5

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P209

Monitoring the degradation of spherical polymeric nanoparticles with scattering methods Thomas Siegemund1,2 , Bernd-Reiner Paulke3 , Herbert Schmiedel1 , Natalie ¨rtig2 Bordag2 , Steffen Lindert1 , Wolfgang Ha 1

University of Leipzig, Faculty of Physics and Earth Science, Institute of Experimental Physics I, Soft Matter Physics – 2 Univerity of Leipzig, Paul Flechsig Institut for Brain Research, Department of Neurochemistry – 3 Fraunhofer Institute for Applied Polymer Research For the delivery of drugs, the use of nanoparticles as carriers has been described as a promising approach. The transport of drugs to a single target and the protection from premature degradation allows to reduce dosis and side effects. Here, we prepared nanoparticles as carriers for the model drug thioflavin T that bind Alzheimers disease related fibrillar amyloid β-peptides (Aβ) in the brain. These polymer colloids are composed of a polystyrene core and a degradable PBCA [poly(butyl-2-cyanoacrylate)] shell with a diameter of 90-150 nm as shown by photon correlation spectroscopy. The enzymatic degradation of core-shell nanoparticles, as required in vivo, was shown after their treatment with porcine liver esterase, a non-specific esterase, and basic/acidic hydrolysis in vitro. Shells of nanoparticles were dose-dependently degraded while their polystyrene cores remained intact. Furthermore, we found a simple method with a satisfying accuracy for the determination of particle diameters based on their wavelengthdependent absorption. Additionally, we applied static and dynamic light scattering as useful tools to monitor the particle diameters during enzymatic degradation. Furthermore, we compare and verify our results by using small-angle neutron scattering. We measured the degradation-dependent changes in the neutron scattering density profile at the facilities of IBR-2 (Dubna, Russia) and BNC (Budapest, Hungary). This study was supported by the BMBF, grant 03DU03LE.

Fig. 1: Time-dependent degradation of HL-52 (core: perdeuterated polystyrene, shell: PBCA) in water and water:deuterium oxide (1:4) SANS measurement at the detector “Yellow Submarine” (BNC, Budapest)

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P210

The Use of Longer X-ray Wavelengths in Macromolecular Crystallography Manfred S. Weiss1 , Christoph Mueller-Dieckmann2 , Santosh Panjikar1 , Paul Tucker1 1

EMBL Hamburg Outstation, c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 ESRF, 6 Rue Jules Horowitz, F-38043 Grenoble Cedex, France

The use of longer X-ray wavelengths (λ = 1.5-3.0 ˚ A) in macromolecular crystallography has over the past few years become a tool for phase determination using the anomalous signal derived from the natively present sulfur and/or phosphorus atoms. In order to extract the maximum possible information contained in the data, it is essential, however, to apply a proper scaling protocol to the data. The best protocols in this respect take absorption into account implicitly. Nevertheless, there seems to be an optimal wavelength at which the anomalous signal-to-noise ratio is highest. In an extensive examination of 75 diffraction data sets collected at different wavelengths from ten different protein and DNA crystal systems, it was found that irrespective of the anomalously scattering substructure present, this optimal wavelength was around 2.0-2.1 ˚ A. A further use of a well measured long wavelength data set is in the unequivocal definition of the anomalously scattering substructure. Although a large percentage of proteins are crystallized in the presence of ions derived e.g. from NaCl, KCl, Na2 SO4 and Na3 PO4 only about 10-15 % of all PDB entries contain such ions as part of the structure coordinates. In order to further investigate this seeming contradiction, we examined the substructures of 23 different protein crystals using a wavelength of λ = 2.0 ˚ A. In all but two of the cases, we were able to identify additionally bound ions for these proteins. Our findings thus suggest that a data set collected at a longer wavelength appears to be essential in order to completely describe a protein structure.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P211

Towards automated BioXAS Gerd Wellenreuther1 , Wolfram Meyer-Klaucke1 1

EMBL Outstation Hamburg, Notkestr. 85, 22603 Hamburg

Automation of XAS data reduction and analysis is essential to cope with high-throughput data collection becoming available at an increasing number of synchrotron radiation centers. Recently, a flexible script called Kemp has been developed and introduced at the XAS beamline at EMBL Hamburg. It automatically processes fluorescence XAS data. The pipeline includes dead time correction, energy calibration, selection of fluorescence detector channels as well as the extraction of XANES and EXAFS [1]. In a second step, we introduced an universal algorithm for automated BioXAS data analysis. Only the EXAFS data and a range of possible coordinations and ligands (e. g. coordination number ranging from 3-6 and potential ligands being sulfur, nitrogen, oxygen or histidine) have to be provided. All permutations are fitted to the experimental data; the individual refinements are performed by DL EXCURV [2]. Models leading to unreasonable fit parameters are rejected based on a comparison with an internal database. In the next step, the most favorable structure is identified by the goodnessof-fit parameter. The results are summarized in a HTML-file containing all structural models as well as plots of the best fits. The entire process requires few seconds to minutes using single-scattering approximation and considerably longer when the multiple scattering algorithm is included. Initially, the program mainly provides assistance for the scientist analyzing BioXAS data. This will change once that the algorithm is implemented on a computer cluster allowing multiple-scattering analyses within minutes and the identification of standard metal binding motifs. On the long run this might open the door towards an online structure determination during an experiment. [1] Korbas, M., Fulla Marsa, D., and Meyer-Klaucke, W., submitted [2] S. Tomic et al, CCLRC Technical Report DL-TR-2005-001, ISSN 1362-0207(2005)

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P212

New insights into the molecular backgrounds of recessive X-linked ichthyosis; an X-ray and neutron scattering study ´1 , Mikhail A. Kiselev2 , Sergio S. Funari3 , Vasil M. Jarmila Zbytovska Garamus4 , Thomas Hauß5 , Siegfried Wartewig6 , Reinhard Neubert6 1

Faculty of Pharmacy, Charles University in Prague, Heyrovsk´eho 1203, 50005 Hradec Kr´ alov´e, Czech Republic – 2 Frank Laboratory of Neutron Physics, JINR, Dubna, Russia – 3 MPI of Colloids and Interfaces, Golm, *c/o HASYLAB, Hamburg, Germany – 4 GKSS Research Centre, Geesthacht, Germany – 5 HMI, Berlin, Germany – 6 Institute of Pharmaceutical Technology and Biopharmacy, Martin-Luther-University Halle-Wittenberg, Germany Stratum corneum (SC), the outermost skin layer consisting of corneocytes which are embedded in a lipid matrix, is responsible for the unique properties of the mammalian skin. An aberrant composition of the SC lipids affects the regular skin functions. In recessive X-linked ichthyosis (RXLI), decreased levels of cholesterol (CHOL) related to the increased levels of cholesterol sulphate (CS) have been described. Currently, the CS accumulation is considered to be the primary mechanism contributing to the pathologic skin features. However, it is not enough elucidated yet, if the decreased CHOL levels can also contribute to the abnormality of the RXLI skin. This study aims to elucidate the role of CHOL in the SC on the molecular level. A lipid model system mimicking the SC lipid composition has been developed. Small angle X-ray diffraction on multilamellar vesicles has been used to determine the lamellar repeat distance of the SC lipid membranes. This value decreases with the increasing CHOL content in the membrane. Small angle neutron scattering on unilamellar vesicles allowed calculating the membrane thickness parameter (dg ) and the average area per molecule of the membrane surface (A). An increase in the CHOL content in the membrane induces a decrease in dg and an increase in A. Neutron diffraction on multilamellar lipid films enabled us to obtain neutron scattering length density profiles of the model systems. The membrane thickness, thickness of the membrane hydration layer, thickness of the polar head groups as well as of the hydrocarbon chain regions have been determined [1]. In conclusion, the reduced CHOL levels are wrongfully neglected in the RXLI pathophysiology. Decreased CHOL concentration in the SC lipid membranes induces a decrease in the required fluidity of the hydrocarbon chains and changes in the internal membrane structure. Consequently, the SC lipid membranes become more rigid and fragile and the skin function is strongly affected. Financial support from the grants of the Federal State of Saxony-Anhalt (Project 3482A/1102L) and of the Ministry of Education of the Czech Republic (MSM 0021620822) as well as from HMI, GKSS and DESY is gratefully acknowledged. [1] Kiselev et al., Eur. Biophys. J. 34 (2005) 1030.

Biologische Systeme und Medizin

Poster: Mi., 14:00–16:30

M-P213

Computational studies of radiation damage in protein crystals Melanie Zehnder1 , Ivan Vartaniants1 , Edgar Weckert1 1

HASYLAB at DESY, Notkestrasse 85, 22607 Hamburg

Radiation damage limits the achievable resolution and data quality received from protein crystals in X-ray structure analysis. For a better quantitative understanding the damage produced by inelastic interaction of photons in the crystal is studied. Inelastic scattering of photons and the produced electrons are investigated by a Monte - Carlo approach. Two types of inelastic interactions are possible, photoelectric effect and Compton scattering. For small energies up to 30 keV the photoelectric effect is dominant. For higher X-ray energies Compton scattering becomes dominant. The photo electron carries nearly all the energy of the incoming photon, which is absorbed in the crystal. In most cases a low energetic Auger electron is created afterwards. For Compton scattering an outer shell interaction takes place and most of the energy is carried out from the crystal by the high-energetic photon. Typically the Compton electron has a much lower energy comparing to that of the photo electron. Electrons produce a higher damage comparing to photons due to a higher inelastic cross section. The Monte Carlo approach simulates the very early stages of the damage (first few picoseconds). In the simulation programme the ionization and excitation of ions are simulated, but no bond braking or recombination is studied. Different energies (from the keV range up to 100 keV) and crystal sizes (from the nanometer scale up to hundred micrometer scale) were studied by this approach. The investigations were done to explore the best ratio between diffracted intensity and damage produced for the given chemical composition. It is evaluated from the number of ions produced by the incoming photon and the subsequent cascade. This value can be calculated either per inelastic photon or per elastic photon. The simulation gives also information on the spatial distribution, the number of excited atoms in the crystal and the time of interaction.

Abstracts: Poster Postersitzung B: Donnerstag, 5. 10. 2006, 13:00 - 15:30 Flugelbau ESA - West ¨ Magnetismus ¨ Nanostrukturen und Grenzflachen

D-P214 – D-P266 D-P267 – D-P320

Weiche Materie

D-P321

–

D-P360

Materie unter extremen Bedingungen

D-P361

–

D-P368

Materialien und Werkstoffe

D-P369

–

D-P411

Teilchen und Kerne

D-P412

–

D-P415

Flugelbau ESA - Ost ¨

Magnetismus

Poster: Do., 13:00–15:30

D-P214

Characterisation of Polymer Membranes for Fuel Cell applications using Synchrotron Radiation Volker Abetz1 , Suzana Pereira Nunes1 , Mariela Leticia Ponce1 , Dominique ¨nter Goerigk2 , Sergio Funari2 , Jerusa Roeder Jesus1 Gomes1 , Gu 1 2

GKSS Forschungszentrum, Max Planck Str., D 21502 Geesthacht, Germany – Hasylab DESY, Notkerstraße 85, D-22067, Hamburg, Germany

The major disadvantages of Perfluorinated polymers in polymer electrolyte fuel cells (PEFCS), are their low proton conductivity over 100 ◦ C as well as their high cost. Polymers containing heterocyclic rings with basic character have been shown to be quite interesting for PEFCs application, since their ability to transport protons above 100 ◦ C [1, 2]. The presence of pyridine-like N sites may favour additional points for proton jumps, contributing to the proton conductivity. Previous ASAXS, WAXS and SAXS studies were performed on materials like sulfonated polymer matrix containing inorganic components (heteropolyacids, zirconium phosphates, sulfonated silica particles and zirconium oxides), to evaluate structural parameters like particles distribution, size and crystallinity for a better understanding of the correlation between structural and proton conducting properties of them. Detailed microstructure studies by SAXS and ASAXS have been done for fuel cell membrane materials based on: 1. Poly(ether ether ketones), polyoxadiazoles (POD) and polytriazoles (PT): effect of degree of sulfonation and distribution of sulfonic groups, on the channels structure between the hydrophobic and hydrophilic phases. The study was accompanied by proton conductivity measurements. High ionic conductivity values were obtained (order of magnitude of 10−3 S cm−1 at 50 ◦ C) for low sulfonated POD and PT. This result may be attributed to the presence of pyridinelike N sites [1]. 2. Nanocomposites: The previous work was continued including the use of metalorganic frameworks with a variety of functionalities on the surface of the pores or with guest molecules (e. g. conductive acids) and the use of sulfonated silica particles.

[1] [2] [3] [4]

R.F. Savinelli et al., US Patent D. Gomes et al., J. Polym. Sci. R.F. Savinelli et al., US Patent D. Gomes et al., J. Polym. Sci.

5,525,436 (1996) Part B, in press 5,525,436 (1996) Part B, in press

Magnetismus

Poster: Do., 13:00–15:30

D-P215

Field induced magneto-structural transition in multiferroic TbMnO3 Nadir Aliouane1 , D.N. Argyriou1 , J. Strempfer2 , I. Zegkinoglou2 , S. Landsgesell1 , M. v. Zimmermann3 1

Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2 Max-PlanckInstitut f¨ ur Festk¨ orperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany – 3 HASYLAB at DESY, Notkestr. 85, 22065 Hamburg, Germany We have used in-field neutron and X-ray single crystal diffraction to measure the incommensurability δ of the crystal and magnetic structure of multiferroic TbMnO3 . We show that the flop in the electric polarization at the critical field HC , for field H along the a− and b−axis coincides with a 1st order transition to a commensurate phase with propagation vector κ = (0, 14 , 0). In-field X-ray diffraction measurements show that the quadratic magneto-elastic coupling breaks down with applied field as shown by the observation of the 1st harmonic lattice reflections above and below HC .

Magnetismus

Poster: Do., 13:00–15:30

D-P216

Possible evidence for weak charge ordering near half doping in Na0.46 CoO2 D. Argyriou1 , O. Prokhnenko1 , K. Kiefer1 , C. Milne2 1

Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany

We have utilized neutron powder diffraction to probe the crystal structure of layered Nax CoO2 near the half doping composition of x =0.46. Our measurements show evidence of weak charge separation into stripes of Co+3.5+ and Co+3.5− ,  ∼0.06e below T 0 =150 K, pointing to the development of a weak charge density wave (CDW) that locks − in at a lower temperature. The pattern of charge ordering reflects the Na-ion potential which leads to a distortion of CoO6 octahedra depending on the CoO6 -Na coordination.

Magnetismus

Poster: Do., 13:00–15:30

D-P217

Role of the orbital-lattice interaction in multiferroic behavior M. Bastjan1 , A. Rusydi1 , G. Neuber1 , S. Singer1 , M. Ruebhausen1 , D.N. Argyriou2 , N. Aliouane2 , M. Kim3 , H. Barath3 , S.L. Cooper3 1

Insitut f¨ ur Angewandte Physik, Universit¨ at Hamburg – 2 Hahn Meitner Institut, Berlin 3 – University of Illinois at Urbana-Champaign, USA We have investigated the temperature dependence of the orbital, structural, and magnetic ordering in TbMnO3 by spectral ellipsometry, VUV reflectance, XAS, and Raman scattering in order to reveal the mechanism that leads to the symmetry breaking responsible for the multiferroic behavior. We find a pronounced redistribution of spectral weight below TN = 41 K in the optical spectra. We observe additional precursor effects in the spectra above TN . For incident photon energies of 1.91 eV in resonance with d - d transitions, we find a renormalization in the Raman spectra of the Jahn - Teller mode below TN and new soft mode below Tf , where TbMnO3 becomes multiferroic. In the VUV-reflectance spectra we analyze thermal difference spectra and find changes at the transition into the magnetic state at energies of 8,12, and 18 eV. The transition at 18 eV is most likely connected to the O2s-O2p transition. More details are revealed in the XAS spectra. We interpret our results as a strong evidence for the formation of an unconventional soft mode as a consequence of the interplay between the electronic correlations and the electron-phonon interaction.

Magnetismus

Poster: Do., 13:00–15:30

D-P218

Magnetic x-ray and neutron studies of magnetization profiles and interface roughness in multilayers with Heusler compounds Andre Bergmann1 , Johannis Grabis1 , Miriana Vadala1 , Alexei Nefedov1 , Max Wolff1 , Kurt Westerholt1 , Boris Toperverg2 , Hartmut Zabel1 1

Insitute of Experimental Physics, Ruhr-University Bochum, D-44780 Bochum, Germany – 2 Petersburg Nuclear Physics Institute, Gatchina, 188300 St. Petersburg, Russia Presently Heusler-alloys are intensively investigated as ferromagnetic (FM) electrodes in magnetic tunnel junctions [1] and as spin reservoir for spin-injection into semiconductor heterojunctions [2]. Due to a half metallic splitting of the d-band at EF , the spin polarization is predicted to be 100 %. The double Heusler compounds have a composition of the type X2 YZ, (X=Co,Ni; Y=Mn, Z=Si,Ge) and a L21 structure, consisting of 4 interpenetrating fcc lattices. Only compounds with perfect LRO exhibit the maximum FM saturation moment of 5µB /f.u. and half metallicity. Site disorder decreases the polarization, the average µB , and the Curie temperature. We have studied the structure and magnetism of the ferromagnetic Heusler compound Co2 MnGe in high-quality [Co2 MnGe/Au]n , [Co2 MnGe/V]n , and [Co2MnGe/Al2 O3 ]n -multilayers (ML) by hard x-ray scattering, soft x-ray resonant magnetic scattering (XRMS), and polarized neutron reflectivity (PNR) [3]. The diffuse hard x-ray scattering reveals that in [Co2 MnGe/Au]n at the interfaces correlated roughness dominates and interdiffusion is negligible, whereas in [Co2 MnGe/V]n the roughness is uncorrelated and dominated by interdiffusion. In [Co2 MnGe/Al2 O3 ]n ML the interfaces are very sharp. Energy analysis of the ML Bragg peaks at the L2 and L3 edges of Co and Mn reveals the element-specific magnetic moment density profile (MMDP) within the Co2 MnGe layers. We find that the MMDP of Co and Mn are definitely different. In addition they are more narrow than the chemical density profile and asymmetric with respect to the growth direction. We have also studied the interface quality and magnetization profile of [Co2 MnGe/V]n and [Co2 MnGe/Al2 O3 ]n multilayers via PNR using the ADAM reflectometers at the ILL. In the R+ map of [Co2 MnGe/V]n a half order antiferromagnetic (AF) Bragg peak occurs at temperatures below 30 K, indicative for weak AF N´eel coupling. In contrast, [Co2 MnGe/Al2 O3 ]n multilayers only show FM alignment of the Heusler layers. The diffuse scattering of the AF peak, as well as the specular intensities of all cross sections can be described by a domain state in remanence. [1] J. Schmalhorst et al., Phys. Rev. B 70 (2004) 024426 [2] X. Y. Dong et al., Appl. Phys. Lett. 86 (2005) 102107 [3] J. Grabis et al., Phys. Rev. B 72 (2005) 024438 (2005), J. Grabis et al., Phys. Rev. B 72 (2005) 024437; A. Bergmann et al., Phys. Rev. B 72 (2005) 214403; A. Bergmann et al., J. Phys. D: Appl. Phys. 39 (2006) 842 We gratefully acknowledge financial support by the DFG via SFB 491 and BMBF 05KS4PCA and 03ZA6BC1.

Magnetismus

Poster: Do., 13:00–15:30

D-P219

Investigation of multiferroic TbMnO3 and DyMnO3 in high magnetic fields ¨ rg Strempfer1 , Ioannis Zegkinoglou1 , NaBritta Bohnenbuck1 , Jo 2 dir Aliouane , Dimitri N. Argyriou2 , Sven Landsgesell2 , Martin v. Zimmermann3 1

Max-Planck-Institut f¨ ur Festk¨ orperforschung, Heißenbergstraße 1, 70569 Stuttgart – Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin – 3 HASYLAB, Notkestraße 85, 22603 Hamburg 2

TbMnO3 and DyMnO3 are improper ferroelectrics with a spontaneous polarization occurring below 28K and 18K, respectively. Both exhibit a polarization flop from P || c to P || a in an applied magnetic field. In order to study the interplay between magnetism, lattice distortions, and polarization we investigated the temperature and magnetic field dependence of structural superstructure reflections at the positions (0 δm l) and (0 2δm l) using x-ray diffraction. At zero field only second order superstructure reflections are observed whereas first order superstructure reflections appear in an applied magnetic field which increase linearly in intensity with magnetic field. This indicates that the quadratic magneto-elastic coupling breaks down in a magnetic field and a linear coupling is induced. In TbMnO3 , the polarization flop from P || c to P || a coincides with an incommensurate (IC) to commensurate (C) transition of the wave vector. This is not the case for DyMnO3 , where no wave vector change is observed at the critical magnetic field. The role of the IC to C phase transition will be discussed with respect to the polarization flop.

Magnetismus

Poster: Do., 13:00–15:30

D-P220

Investigation of Dilute Magnetic Semiconductor Multilayers with Polarized Neutron Reflectivity Heiko Braak1 , Amitesh Paul1 , Diana Rata1 , Reinert Schreiber1 , Daniel ¨nberg1 , Claus Schneider1 , Thomas Bru ¨ckel1 Buergler1 , Peter Gru 1

Institut f¨ ur Festkoerperforschung, Forschungszentrum J¨ ulich GmbH, D-52425 J¨ ulich, Germany In recent years, one of the remarkable achievements in spintronics was the observation of hole-mediated ferromagnetism in diluted III-V compounds. However, the growth of group-IV diluted ferromagnetic semiconductors (DMS) such as Mnx Ge1−x has also triggered strong interest in searching for higher ordering temperatures TC in Ge-based compounds [1]. Recently, we have reported [2] on the successful synthesis of a new DMS compound: Ge co-doped with Mn and Fe. The addition of Fe to Ge(Mn) enables to conserve epitaxial growth for higher total concentrations of the magnetic species, which results in an increase of TC . The alloy films are prepared by repeatedly growing Ge/Mn/Fe trilayers with various thicknesses of the Ge base layers. When the Ge thickness becomes comparable with the diffusion length of Mn and Fe in Ge, a material without detectable interfaces is formed as confirmed by X-ray reflectivity [3]. Magnetization and magnetotransport measurements reveal ferromagnetic ordering, but show two different TC (210 and above 300 K), which we relate to two magnetic phases [3]. Comparison of the temperature dependence of the anomalous Hall effect and the saturation magnetization for a [Ge(40 ˚ A)/Fe(2 ˚ A)/Mn(4 ˚ A)]22 sample shows that the contribution from the phase with TC > 300 K does not exceed ≈ 10 % of the total magnetization. Transmission electron microscopy shows the formation of precipitates depending on the preparation condition and the content of magnetic species. In order to have an unequivocal assignment of the magnetic phases to the precipitates and the matrix, respectively, more knowledge about the magnetic structure is required. Preliminary measurements were done on our polarized neutron beamline HADAS at FRJ-2. Nonspin-flip and spin-flip reflectivity spectra for the two samples, [Ge(40 ˚ A)/Fe(4 ˚ A)/Mn(2 ˚ A)]11 and [Ge(40 ˚ A)/Fe(2 ˚ A)/Mn(4 ˚ A)]11 , were taken at 50 and 250 K for various applied fields (Ha ). Significant contrast between magnetic moment parallel and antiparallel to Ha is visible only at 50 K and above 1.0 kOe, which corresponds to the saturation state of the sample with 4 ˚ A Fe. The sample with 4 ˚ A Mn shows similar contrast at somewhat lower fields when measured at 50 K, but this net magnetization is observable at higher fields even when measured at 250 K. So far, we could not obtain any element-specific insight in order to investigate the origin of the carrier-induced ferromagnetism, but we hope that this can be achieved by measuring at neutron sources with higher flux in the future. The present results are valuable guidelines for the optimized preparation of single-phase, homogenous Ge(Mn,Fe) DMS films with high TC and also provide useful feedback for future neutron measurements. [1] Y.D. Park et al., Science 295 (2002) 651. [2] H. Braak et al., Magn. Magn. Mater. 286 (2005) 46. [3] H. Braak, PhD thesis, Universit¨ at zu K¨ oln (2006).

Magnetismus

Poster: Do., 13:00–15:30

D-P221

Treatment of correlation effects within calculation of photoemission and magneto-optical spectra of solids S. Chadov1 , J. Minar1 , J. Braun1 , H. Ebert1 , A. Lichtenstein2 , M. Katsnelson3 1

Dept. Chemie und Biochemie, Physikalische Chemie, Universit¨ at at M¨ unchen, D81377 M¨ unchen, Germany – 2 Institute of Theoretical Physics, University of Hamburg, Germany – 3 University of Nijmegen, The Netherlands Correlation effects may have a rather pronounced impact on the electronic structure of transition metal systems that is reflected in their spectroscopic properties. Corresponding calculations have to account for this by going beyond the standard approach based on Local Spin Density Approximation (LSDA). We present a combination of LSDA and the Dynamical Mean-Field Theory (DMFT) that provides a basis for dealing with a wide range of solids. The LSDA+DMFT approach has been combined with the KKR (Korringa-Kohn-Rostoker) band structure method to allow a corresponding calculation of spectroscopic properties. This is demonstrated by results for the angleintegrated photo-emission spectra of the pure ferromagnets Fe, Co and Ni. Using the LSDA+DMFT approach instead of plain LSDA led to a very satisfying agreement with experiment when investigating the pure Fano-effect. This also applies when studying the so-called fundamental spectra for circular polarization. As corresponding calculations of magneto-optical spectra are computationally very demanding we used the LMTO- instead of the KKR-method in this case. Applications are presented for the magneto-optical Kerr-spectra of Ni and NiMnSb. In both cases a very satisfying agreement with experiment could be achieved by use of the LSDA+DMFT approach. This also applies for the compound US, for which a proper relativistic treatment is mandatory.

Magnetismus

Poster: Do., 13:00–15:30

D-P222

Correlation between magnetic fabric and chlorite preferred orientation in clay sediments: new insights from neutron diffraction analysis (TEX-2) Francesca Cifelli1 , Sabine Lenser2 , Massimo Mattei1 , Martin Chadima3 , ¨nter Brokmeier2 Heinz-Gu 1

Dipartimento Scienze Geologiche, Universit` a Roma TRE – 2 Institute of Materials Science and Engineering, Technische Universit¨ at Clausthal – 3 Institute of Geology, Academy of Sciences of the Czech Republic In poorly consolidated fine-grained sediments syn-deformation fabric may not be easily detected for their scarce potential in transmitting the differential stress accumulated during tectonic deformation. Hence, in some sedimentary basins where sediments show no evident pervasive tectonic structures conventional structural methods cannot be applied. The question is whether it is possible to find any qualitative, or even quantitative, record of deformation in these sediments, before brittle failure occurs. In this study, an integrated approach of magnetic and mineral fabric investigations is proposed as a possible alternative tool for detecting grain scale and regional deformation patterns in weakly deformed sediments, where macroscopic evidence of deformation is not visible. We first discriminated between the fabric arising from the ferrimagnetic fraction with that from the paramagnetic matrix in order to understand which minerals contribute to the susceptibility and which fraction is responsible for the orientation of the principal axes of the AMS ellipsoid. Results show the paramagnetic minerals, i.e. chlorite, are the main contributors to the magnetic susceptibility. The chlorite preferred orientations were then quantified by neutron pole figure measurements, using the TEX-2 in GKSS-Research Centre Geesthacht, Germany. Results show that neutron texture analysis represents a unique tool for mineral fabric investigation in clays. In fact, the high penetration of neutron beam and the possibility to utilize the same cylindrical specimen used for AMS analysis without any specimen preparation, make this method particularly suitable in detecting the mineral fabric in sediments, such as clays, whose original mineral fabric may be easily modified by specimen cutting and polishing. Magnetic results were compared with mineral results in order to independently determine the rock fabric and to establish a quantitative relationship between AMS and the preferred orientation of minerals carrying the magnetic fabric. Chlorite distribution is well correlated with the orientation of the high-field paramagnetic (HPF) and low-field (at room temperature RT and low temperature LT) AMS ellipsoids. The magnetic lineations (square symbols) are always perpendicular to the girdle distributions of the chlorite c-axes, which suggests that it is an apparent lineation. Therefore results indicate that the magnetic fabric is carried by chlorite and that its spatial arrangement has been modified in the strain field acting at regional scale and detected in other contiguous sediments. In this study, well show results from Neogene sedimentary sequences outcropping in the Rif chain (Morocco) and in Calabria (Southern Italy).

Magnetismus

Poster: Do., 13:00–15:30

D-P223

XAFS and neutron diffraction study of the the La1−x Sr(Ba)x CoO3 and La1−x Srx Co1−x/2 Nbx/2 O3 Vadim Efimov1 , Sergey Tiutiunnikov1 , Dmitriy Kochubey2 , Vladimir Kriventsov2 , Aleksandr Shmakov2 , Igor Troyanchuk3 , Alexey Kuzmin4 , Vadim Sikolenko5 , Serguei Molodtsov6 , Denis Vyalikh6 1

Joint Institute for Nuclear Research (JINR), 141980 Dubna, Moscow region, Russia – 2 Boreskov Institute of Catalysis, Lavrentiev prosp. 5, Novosibirsk, 630090, Russia – 3 Institute of Solid State and Semiconductor Physics, 220072 Minsk, Belarus – 4 Institute of Solid State Physics University of Latvia, 8 Kengaraga, Riga LV-1063, Latvia – 5 Hahn-Meitner-Institut Glienicker str. 100 Berlin D-14109 Germany – 6 Institut f. Festkoerperphysik Fachrichtung Physik TU Dresden 01062 Dresden, Germany The discovery of the colossal magnetoresistance (CMR) in the manganites with perovskite structure [1] has stimulated the research of the compounds exhibiting large magnetoresistance. The magnetic and transport properties of La1−x Srx CoO3 cobaltites with perovskite structure and manganites such as La1−x Srx MnO3 have common features [2]. In both systems the substitution of La with divalent ion Sr creates paramagnetic (x<0.2) to ferromagnetic (x>0.3) transition as the dopant concentration is increased. The Sr2+ and especially Ba2+ ionic radiuses is significantly greater than that of the La3+ ion, so it is possible to expect stabilization of the intermediate spin state of cobalt ions by substituting Sr2+ and especially Ba2+ ions for La3+ ones. However, at such heterovalent substitution Co4+ ions appear, leading to the ferromagnetic metallic ground state [3]. To prevent the Co4+ ion appearance, it is possible to introduce simultaneously Nb [4] ions, which at the presence of Co3+ ions will be in oxidizing state 5+. By simultaneously introducing Sr2+ and Nb5+ the cobalt ions keep their valence state and the electroconductivity of La1−x Srx Co1−x /2Nbx /2O3 solid solutions decreases with dopant concentration enhancement.Thus, the different nature of ferromagnetic interactions formation in the given systems is obvious [4]. In this work we present EXAFS and XANES measurements at the Co K-edge in La1−x Sr(Ba)x CoO3 and La1−x Srx Co1−x /2Nbx /2O3 (x = 0; 0.2; 0.3; 0.5) solid solutions. The sensitivity XANES and EXAFS to chemical composition, local lattice distortion, “chemical pressure” effect and to an overlapping mixture of low, intermediate and high spin states of Co3+ and Co4+ ions in these cobaltites was also considered. Crystal and magnetic structure of these cobaltites were precisely determined by high-resolution X-ray and Neutron diffraction methods. Correlations of the long-range structure parameters with local atomic and electronic structure ones and also with SQUID magnetization measurements was analyzed. The details of local atomic and electronic structure in cobaltites doped by Sr, Ba and Nb are presented and discussed. [1] P.M. Raccah and J.B. Goodenough, Phys. Rev. 155, 932 (1967). [2] G. Briceno et.al. Science 270, 273 (1995). [3] J. Wu, C. Leighton, Phys. Rev. B 67(17), 174408 (2003). [4] I.O. Troynchuk,et.al.,Phys. Stat. Sol.B 242, No. 6, pp. 49-51 (2005).

Magnetismus

Poster: Do., 13:00–15:30

D-P224

Symmetrieerniedrigung der magnetischen Struktur in CeCu2 (Si0,55 Ge0,45 )2 Enrico Faulhaber1 , Oliver Stockert2 , Astrid Schneidewind1 , Micha Deppe2 , Christoph Geibel2 , Frank Steglich2 , Michael Loewenhaupt1 1 2

TU Dresden; Institut f¨ ur Festk¨ orperphysik; Zellescher Weg 16; D-01062 Dresden – Max-Plank-Institut CPfS; N¨ othnitzer Str. 40; D-01187 Dresden

Das Schwer-Fermionen-System CeCu2 (Si1−x Gex )2 weist eine Vielzahl verschiedener Grundzust¨ ande auf, darunter Antiferromagnetismus und Supraleitung. Durch Variation ¨ der Germaniumkonzentration x kann der Ubergang von einem Antiferromagneten mit lokalen Momenten (x ≈ 1: TN ≈ 4,1 K) [1] hin zu einem antiferromagnetisch geordneten System itinieranter Momente (x ≈ 0: TN ≈ 0,7 K) [2] verfolgt werden. Dabei wird ein komplexes (x, T ) Phasendiagramm beobachtet, welches punktuell genauer untersucht wurde [3,4]. Insbesondere CeCu2 (Si0,55 Ge0,45 )2 nimmt eine Sonderstellung ein, da mehrere magnetisch geordnete Phasen gefunden wurden. Weiterhin liegen sowohl die Phasen¨ ubergangstemperaturen (TN ≈ 3 K, T1 ≈ 2,1 K, T2 ≈ 1,4 K) als auch das geordnete magnetische Moment (µord. ≈ 0,5 ·µB ) in einem experimentell gut zug¨ anglichem Bereich. Die Aufkl¨ arung der magnetischen Struktur dieses Systems ist von großer Bedeutung, da hiervon ausgehend auf die magnetische Struktur niedriger dotierter Proben, bis hin zu reinem CeCu2 Si2 , geschlossen wird. Bei tiefster Temperatur ordnet CeCu2 (Si0,55 Ge0,45 )2 inkommensurabel mit einer einfachen Modulation der Momentamplitude und einem Propagationsvektor τ = (0,273 0,273 0,51). Hierbei sind die magnetischen Momente orthogonal zum Propagationsvektor orientiert [5]. Vor kurzem wurde ein elastisches Neutronenstreuexperiment an CeCu2 (Si0,55 Ge0 , 45)2 am PANDA-Dreiachsen-Spektrometer am FRM-II in Garching durchgef¨ uhrt. Dabei wurden innerhalb der Tieftemperaturphase bei T = 50 mK zus¨ atzliche Satellitenreflexe nachgewiesen. Diese treten an Positionen auf, die nur durch eine Erniedrigung der Symmetrie der magnetischen Struktur verstanden werden k¨ onnen. Dabei wird die Innenzentrierung der magnetischen Struktur aufgehoben. Die neuen Erkenntnisse werden in Beziehung zu fr¨ uheren Ergebnissen diskutiert. [1] [2] [3] [4] [5]

A. Krimmel et al., Phys. Rev. B 55 (1997) 6416. F. Steglich et al., Phys. Rev. Lett. 43 (1979) 1892. G. Knebel et al., Phys. Rev. B 53 (1996) 11586. O. Trovarelli et al., Phys. Rev. B 56 (1997) 678. E. Faulhaber et al., J. Magn. Magn. Mater. 272 (2004) 44.

Magnetismus

Poster: Do., 13:00–15:30

D-P225

Antiferromagnetic-Ferromagnetic Phase Transition in Fe50 Pt50−x Rhx Thin Films Jochen Fenske1 , Dieter Lott1 , Gary J. Mankey2 , Prakesh Mani2 , Frank Klose3 , Wolfgang Schmidt4 , Andreas Schreyer1 1

GKSS Research Centre, Institute for Material Science – 2 MINT Center, The University of Alabama, Tuscaloosa, AL – 3 SNS, Oak Ridge Nat. Laboratory – 4 IN12, ILL, Grenoble, France In the last years perpendicular recording has been in the focus of scientific and technological interest on the search for materials to overcome the limitations in the storage density of conventional magnetic recording media. In order to reach the required high writing magnetic fields a soft underlayer is needed to provide a closure field during the writing process. An interesting candidate for such a magnetic underlayer is Fe50 Pt50−x Rhx . For certain compositions an antiferromagnetic (AF) state exists at lower temperatures which turns into a ferromagnetic (F) state at higher temperatures [1]. Used as a magnetic underlayer it can provide a closure field when heated lowering the write field. After the writing process the underlayer can be cooled again becoming AF and hence helps to stabilize the recording media via exchange interactions. The advantage of Fe50 Pt50−x Rhx compared to conventional underlayers like permalloy is that even thinner system may be sufficient to provide the same closure field. Neutron diffraction measurements were carried out to study the AF-F switching of thin films of Fe50 Pt50−x Rhx in dependence of temperature and magnetic field. Three kinds of AF ordering were observed, the (1/2 1/2 1/2), (0 0 1/2) and (1/2 1/2 3/2) depending on temperature and magnetic field. Both magnetization and neutron diffraction studies show the coexistence of an AF and F phase in a Fe50 Pt40 Rh10 . [1]P. A. Algarabel et al, Journal of Applied Physics, 79 (8) 4659(1996)

Magnetismus

Poster: Do., 13:00–15:30

D-P226

Multiferroic DyMnO3 studied by x-ray resonant magnetic scattering R. Feyerherm1 , E. Dudzik1 , N. Aliouane2 , D. N. Argyriou2 , O. Prokhnenko2 1

Hahn-Meitner-Institut, c/o BESSY, Albert-Einstein-Str. 15, 12489 Berlin – 2 HahnMeitner-Institut, Glienicker Str. 100, 14109 Berlin

Orthorhombic DyMnO3 exhibits incommensurate antiferromagnetic ordering of the Mn moments below TN,Mn = 39 K with a temperature dependent propagation vector q = 0.36 − 0.385 b∗ . Via quadratic magnetoelastic coupling this ordering is associated with a lattice modulation 2q. Below about Tf = 18 K, the value of q freezes in and a spontaneous ferroelectric polarisation occurs. Below about 6 K this polarisation is suppressed considerably [1]. In order to clarify the role of Dy in this sequence of phase transitions, we have studied the Dy magnetic ordering using x-ray resonant magnetic scattering at the Dy-L3 edge on a single crystal DyMnO3 . Recently, we have shown that below TN,Dy = 5 K, the Dy magnetic moments order in a commensurate structure with propagation vector 0.5b∗ . Simultaneous with the Dy magnetic ordering, an incommensurate lattice modulation with propagation vector 0.905b∗ evolves. The magnetic and structural nature of the corresponding Bragg reflections were demonstrated empolying linear polarisation analysis (see Figure). This behaviour was interpreted as resulting from a strong interference of Mn and Dy induced structural distortions in DyMnO3 [2]. New measurements show that in the temperature range 5 K < T < 16 K an induced ordered magnetic moment, significantly smaller than below 5 K, exists on the Dy with propagation vector 0.385b∗ , identical to the underlying Mn ordering. This temperature range apparently coincides with the one in which the spontaneous electric polarisation occurs, implying that the induced Dy ordering is directly related to ferroelectricity in DyMnO3 . The results are discussed in relation to neutron diffraction measurements on an isotope enriched powder sample 162 DyMnO3 that are presented in a separate contribution. [1] T. Kimura et al., Nature 426 (2003) 55; Phys. Rev. B 71 (2005) 224425. [2] R. Feyerherm et al., cond-mat/0603613, Phys. Rev B (2006), in press.

Fig. 1: Linear polarisation analysis of the Bragg reflections (0 2.5 4) and (0 2.905 3)

Magnetismus

Poster: Do., 13:00–15:30

D-P227

Tb2 PdSi3 : Untersuchungen des Koexistenzbereichs von lang- und kurzreichweitiger magnetischer Ordnung ¨nther Matthias Frontzek1 , Astrid Schneidewind1 , Andreas Kreyssig1 , Gu Behr2 , Michael Loewenhaupt1 1

TU Dresden, Institut f¨ ur Festk¨ orperphysik, D-01062 Dresden – 2 Leibniz-Institut f¨ ur Festk¨ orper- und Werkstoffforschung Dresden, D-01069 Dresden R2 PdSi3 (R = Seltene Erde) Verbindungen kristallisieren in einer hexagonalen AlB2 Struktur und werden seit ca. 15 Jahren untersucht. Das Zusammenspiel von magnetischer Austauschwechselwirkung und kristallelektrischem Feld auf dem hexagonalen Gitter f¨ uhrt zu einer großen Bandbreite von magnetischen Eigenschaften. Besonders die Verbindung Tb2 PdSi3 zeigt ein vielf¨ altiges magnetisches Phasendiagramm.

Mit dem neu aufgebauten PANDA-Spektrometer am FRM-II in Garching wurde das magnetische Phasendiagramm von Tb2 PdSi3 untersucht. Die antiferromagnetische Struktur im Nullfeld (TN = 23 K) mit einer Propagation τ1 = (0 0 1/16) koexistiert u ¨ber einen großen Magnetfeldbereich mit einer ferrimagnetischen Struktur mit kleinerer magnetischer Elementarzelle mit τ2 = (0 0 1/4)(s. Abb. 1). Zus¨ atzlich zu dieser langreichweitigen Ordnung wird im Nullfeld kurzreichweitige Ordnung unterhalb einer Temperatur von 8 K beobachtet. Diese kurzreichweitige Ordnung zeigt in Abh¨ angigkeit vom ¨ außeren Feld zwei weitere Phasen¨ uberg¨ ange in eine langreichweitige Ordnung. In unserem Beitrag werden erste Modelle der verschiedenen magnetischen Strukturen der einzelnen Phasen pr¨ asentiert. Dar¨ uberhinaus werden erste inelastische Messungen am System Tb2 PdSi3 vorgestellt.

Abb. 1: Entwicklung der magnetischen Intensit¨ at in Abh¨ angigkeit vom auße¨ ren Magnetfeld enlang der (00L)-Richtung bei T = 12 K

Magnetismus

Poster: Do., 13:00–15:30

D-P228

The magnetic structure of MnSi under applied field by polarized SANS Sergey Grigoriev1 , Sergey Maleyev1 , Alexey Okorokov1 , Yurii ¨ ni3 , Robert Chetverikov1 , Helmut Eckerlebe2 , Klaus Pranzas2 , Piter Bo Georgii3 1

Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg, 188350, Russia – GKSS Forschungszentrum, 21502 Geesthacht, Germany – 3 ZWE FRM-II/E21, Technische Universitat Munchen, 85747 Garching, Germany 2

The magnetic structure of the single crystal MnSi under applied field has been studied by small angle diffraction with polarised neutrons below TC = 28.7 K. Experiments have shown that in zero field the magnetic structure of MnSi consists of four lefthanded spiral domains oriented along four h111i axes. The magnetic field, applied along one of the h111i axes, produces the single domain helix oriented along the field at HC1 ≈ 80 mT at low temperatures. The magnetic mosaic of the spin structure changes with the magnetic field and has a maximum at HC1 . The integral intensity of the Bragg reflection shows a sharp minimum at Hin ≈ 160 mT attributed to the instability of the helix structure. When the field has a component perpendicular to the helix wavevector k , the wavevector rotates toward the field direction in the field range H < Hin . Additionally the second harmonic of the helix structure is induced by the perpendicular magnetic field at H < Hin . These three √features are well explained accounting for the presence of the spin wave gap ∆ ∼ Hin / 2 ' 11 µeV, which provides the stability of the spin wave spectrum with respect to the perpendicular magnetic field. Further increase of the field leads to the magnetic phase transition from conical to ferromagnetic state near HC2 ≈ 600 mT. The critical field HC2 is related to the spin of the spin wave stiffness A as gµHC2 = Ak2 . Our findings are in agreement with the recently developed theory [PRB, 73 (2006) 174402] for the cubic magnets with Dzyaloshinskii-Moria interaction, which relates the major parameters of the spin wave spectrum (such as the spin wave stiffness and the gap) with the features of the spin structure of MnSi being observed under applied magnetic field.

Magnetismus

Poster: Do., 13:00–15:30

D-P229

Magnetic excitations in a Dy/Y superlattice investigated with inelastic neutron scattering ¨nwald1,2 , Helena Tartakovskaya3 , Andrew Wildes1 , WolfAlexander Gru 4,1 gang Schmidt , Peter Link5 , Roger Ward6 , Andreas Schreyer2 1

Institut Laue-Langevin, Grenoble, France – 2 GKSS-Forschungszentrum, Geesthacht, Germany – 3 Institute of Magnetism, Kiev, Ukraine – 4 Forschungszentrum J¨ ulich, Germany – 5 TU M¨ unchen, Germany – 6 University of Oxford, United Kingdom Modern thin film growth techniques allow enormous flexibility in the choice of sample composition, making these materials of particular interest for the investigation of spin dynamics in structures of reduced dimensionality. While techniques as Brillouin light scattering and ferromagnetic resonance experiments are limited to specific regions in reciprocal space, inelastic neutron scattering provides, in principle, access to the whole Brillouin zone. We have shown that this technique can be used on multilayer samples [1]. These measurements are difficult, however, due to the small sample mass in superlattice structures. Rare earth elements are the best candidates for studying spin wave excitations in multilayer structures, since they exhibit the largest magnetic moment, and have the largest cross section for magnetic neutron scattering. Besides the novelty of measuring spin waves in artificially modulated structures, the experiments also provide new information on RKKY exchange coupling and its propagation across non-magnetic spacer layers. A new theory has been developed to describe the nature of the spin waves in a Dy/Y multilayer. The theory predicts discrete energy levels for spin waves propagating along the surface normal, with the number of discrete energy levels being derived from the number of magnetic atomic planes in a bi-layer. In the limit of an infinite number of atomic planes the dispersion of bulk Dy [2] is recovered. The new calculations show significant dependence of the energy eigenvalues on interdiffusion and interfacial roughness. To compare with new calculations on spin wave excitation eigenvalues, we present inelastic neutron scattering measurements of low energy magnetic excitations in a Dy/Y superlattice. The experimental data of constant-q scans show in some regions of reciprocal space double/multi-peak features, as predicted by the theory. Although measured with high resolution, these peaks are broad in width, which might be due to interdiffusion and roughness. However, these data give supporting evidence for the new theory of spin wave excitations in constrained magnetic multilayer structures. [1] A. Schreyer et al., J. Appl. Phys., 87 (2000) 5443 [2] R.M. Nicklow et al., Phys. Rev. Lett., 26 (1971) 140

Magnetismus

Poster: Do., 13:00–15:30

D-P230

Neutron TOF diffraction studies of Cr5−x Tix Te8 Zhong-Le Huang1 , Wolfgang Bensch1 , Winfried Kockelmann2 1

Institute of Inorganic Chemistry, CAU- Kiel, Germany – 2 Rutherford Appleton Laboratory, ISIS, Chilton, OX11 0QX, UK

The effect of substitution of Cr by Ti in Cr5 Te8 has been investigated with respect to its crystal structure, magnetic properties, and electronic structure [1]. The compounds Cr5−x Tix Te8 (x = 0, 0.5, 1, 1.5, 1.85, 2, 3, 4, 5) were synthesized at elevated temperatures followed by slow cooling the samples to room temperature. Three structural modifications are identified from X-ray powder diffraction data: monoclinic, space group F2/m for Cr5−x Tix Te8 (x = 0, 0.5, 1, 1.5, 1.85), trigonal supercell, space group P-3m1 for Cr5−x Tix Te8 (x = 2, 3), and trigonal basic cell, space group P-3m1 for Cr5−x Tix Te8 (x = 4, 5). The structures of all these phases are related to the NiAs structure with full and deficient metal layers stacking alternatively along the c axis. The irreversibility in the field-cooled/zero-field-cooled magnetization with low field depends strongly on the Ti concentration x. Four types of magnetic states are distinguished: reentrant ferromagnet for m-Cr5 Te8 , cluster-glass for m-Cr4.5 Ti0.5 Te8 and m-Cr4 TiTe8 , antiferromagnetic for m-Cr3.5 Ti1.5 Te8 , and spin-glass for tr-Cr3 Ti2 Te8 , tr-Cr2 Ti3 Te8 , and Cr0.25 TiTe2 . Here we report the neutron TOF studies (OSIRIS/ISIS, Rutherford Appleton Lab., UK) for m-Cr5 Te8 , m-Cr4 TiTe8 , m-Cr3.5 Ti1.5 Te8 , and tr-Cr3 Ti2 Te8 at temperatures from 1.5 K to temperatures above Tc. For the first two compounds, both FM and AFM Bragg peaks are observed at low temperatures, indicating the existence of long-range magnetic order. The set-in temperatures of FM/AFM peaks are 190/75 and 70/40 K for m-Cr5 Te8 and m-Cr4 TiTe8 , respectively. The magnetic moments of the FM phase are along the c-axis and those of the AFM phase are found in the ab-plane. For m-Cr3.5 Ti1.5 Te8 and Cr3 Ti2 Te8 , no magnetic Bragg scattering or background modulation were observed down to 1.5 K, indicating short-range magnetic correlations. The efforts to correlate the structural and magnetic properties and to understand the origin of the observed bulk magnetism from a microscopic point of view will be presented. [1] Zhong-Le Huang, W. Bensch, D. Benea, H. Ebert. J. Solid State Chem. 178 (2005) 2778.

Magnetismus

Poster: Do., 13:00–15:30

D-P231

Onset of spin-density-wave antiferromagnetism in Cr/V multilayers ¨ rgvin Hjo ¨ rvarsson3 , Andreas Hoser4,5 , Andreas Evgeny Kravtsov1,2 , Bjo 3 6 Liebig , Gary McIntyre , Alexei Nefedov7 , Florin Radu7 , Arndt Remhof7 , Flora Yakhou8 , Hartmut Zabel7 1

Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA – 2 Institute of Metal Physics, Ekaterinburg 620041, Russia – 3 Department of Physics, Uppsala University, SE-75121 Uppsala, Sweden – 4 Institut fuer Kristallographie, RWTH-Aachen, D-52056 Aachen, Germany – 5 Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Germany – 6 Institut LaueLangevin, B.P. 156, F-38042 Grenoble Cedex 9, France – 7 Institut fuer Experimentalphysik/Festkoerperphysik, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany – 8 European Synchrotron Radiation Facility, F-38000, Grenoble, France Spin-density wave (SDW) state in thin Cr films is known to be under influence of dimensional (film thickness) and proximity effects from neighboring layers. Here we report on a combined neutron and X-ray scattering study of these effects in a series of Cr/V superlattices with different Cr layer thicknesses. The neutron measurements have been performed at UNIDAS (Forschungszentrum J¨ ulich) and D10 (ILL) instruments, the synchrotron measurements at the ID20 beamline in ESRF. From the above experiments we provide a systematical description of the onset of the SDW state in the system. It was found that Cr/V superlattices are non-magnetic for Cr layers thinner than 120 ˚ A. At this thickness a commensurate SDW originates and as Cr thickness increases further a fraction of incommensurate SDW appears and expands. Finally the SDW becomes completely incommensurate. The Neel temperature and SDW period of the incommensurate SDW were found to scale with the Cr thickness as well. The research was supported by SFB 491 and INTAS project ref. No. 03-51-4778.

Fig. 1: Neutron scattering scans from the sample Cr(500˚ A)/V taken in the L direction around the Cr(010) position.

Magnetismus

Poster: Do., 13:00–15:30

D-P232

Approach to the Neutron Scattering Analysis of Magnetic Nanostructures. Wolfgang Kreuzpaintner1 , Helena Tartakovskaya1 , Andreas Schreyer1 1

GKSS Forschungszentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht

Elastic and inelastic Small Angle Neutron scattering on magnetic nanostructures, such as nanowires, nanodots or nanomatrices, is a most promising technique for obtaining information on structural and dynamical magnetic properties, which are essential for the further development of higher density magnetic data storage devices and new technologies like magnetic random access memory devices. The main problem nowadays still lies in producing specimens of large enough area or volume with sufficient filling fraction for achieving sufficient scattered neutron intensities. For multilayer systems these difficulties have already successfully been overcome and results on inelastic neutron scattering on e.g. Dy/Y superlattices have been reported [1]. We show approaches for also overcoming these difficulties in laterally nanostructured samples. Most promising are the use of holographic methods in combination with etching continous epitaxially grown layers (for nanowires and nanodots with an equal minimal lateral dimension and distance of 180 nm), the use of substrate shading by self organised periodic substrate surface structures during deposition (for nanowires with a basically infinite one dimensional expansion) as described in [2] and the use of self-assembly of CoPt3 Nanocrystals [3] for high volume filling fractions. Also we present the expectations for inelastic neutron scattering experiments which follow from the last theoretical results on inelastic neutron scattering in ordered systems of nanowires [4]. We show that a similar approach could be used in the case of three-dimensional ordered structures of CoPt3 nanospheres presented elsewhere [5]. In such systems two different types of spin wave excitations could be interesting for neutron experimental investigation. The first is the lowest uniform mode, which energy is about 0.07 meV, and the second is the set of non-uniform modes with much larger energy scale. The corresponding dispersion and dynamic structure factor of inelastic neutron scattering are calculated and presented here, showing that these modes are indeed accessible for inelastic neutron scattering experiments.

[1] A. Schreyer et al., J. Appl. Phys. 87 (2000) 5443 [2] M. Huth et al., Adv. Funct. Mater. 12 (2002) 333 [3] P. Beecher, A. J.Quinn, E. V. Shevchenko, H. Weller and G. Redmond, J. Phys. Chem. B 108 (2004) 9564 [4] E. V. Tartakovskaya, Phys. Rev. B 73 (2006) 092415 [5] F. Wiekhost, E. Shevchenko, H. Weller and J. K¨ otzler, Phys. Rev. B 67, (2003) 224416

Magnetismus

Poster: Do., 13:00–15:30

D-P233

Antiferromagnetic domains in RNi2 B2 C and GdNi2 Ge2 - characterization in reciprocal space and real space by neutron and x-ray diffraction A. Kreyssig1,2 , J. W. Kim2 , C. Detlefs3 , H. Klein3 , A. Dreyhaupt1 , L. Tan2 , B. Grenier4 , D. Wermeille2,5 , A. I. Goldman2 , M. Loewenhaupt1 1

Institut f¨ ur Festk¨ orperphysik, Technische Universit¨ at Dresden, Germany – 2 Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, USA – 3 European Synchrotron Radiation Facility, Grenoble, France – 4 Institut LaueLangevin, Grenoble, France – 5 Advanced Photon Source, Argonne, USA Magnetic domains are intensely investigated in ferromagnetic compounds according to their application as hard or soft ferromagnetic materials. Numerous methods are deployed to characterize the magnetic domain structure because of its strong influence on the relevant extrinsic magnetic properties. Mostly these techniques are based on measurements of the net magnetisation or on mapping of magnetic field inhomogeneities at the domain borders. Studies of domains in antiferromagnetic materials naturally request the usage of other signatures. In this presentation we will motivate at first the study of domains in antiferromagnetic materials. In general, the onset of antiferromagnetic order yields domains due to the lowering of symmetry by the propagation vector or the moment direction. These domains can play an important role, for instance, in the interplay between magnetism and superconductivity due to the pinning effect of domain borders on superconducting flux lines. Last but not least, the knowledge of the domain behavior is often necessary to determine the microscopic magnetic structure unambiguously. For both cases, we will present examples demonstrating different ways to characterize antiferromagnetic domains. In RNi2 B2 C compounds (R = rare earth), superconductivity and antiferromagnetic order can coexist. The antiferromagnetic domains are indirectly imaged through their attendant magnetoelastic distortions using x-ray topography at ESRF Grenoble. The results are discussed in relation to regularities in the domain arrangement proven by satellite reflections in neutron and x-ray diffraction patterns measured at ILL Grenoble and at Ames Laboratory. Consequences for the superconducting properties are discussed. In GdNi2 Ge2 , the second example, direct imaging of antiferromagnetic domains could be realised by x-ray resonant magnetic scattering and microscanning across the sample surface at APS Argonne. Domain imaging was essential to investigate the phase transition between the low-temperature spiral-like magnetic order and the high-temperature collinear magnetic structure in detail, because both magnetic structures would yield similar patterns in usual diffraction experiments due to domain averaging. We thank the groups of G. Behr and P. C. Canfield for the preparation of the high-quality single crystals. We acknowledge the financial support by the Deutsche Forschungsgemeinschaft through the SFB 463 and by the U. S. Department of Energy, Office of Science under contracts W-7405-ENG-82 and W-31-109-ENG-38.

Magnetismus

Poster: Do., 13:00–15:30

D-P234

Increased Curie-temperature in an osmate double perovskite by 5d-doping Yoshiharu Krockenberger1,2 , Kaylash Mogare2 , Manfred Reehuis2,3 , Martin Tovar3 , Andreas Winkler1 , Martin Jansen2 , Lambert Alff1 1

Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany – 2 Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany – 3 Hahn-Meitner-Institut (HMI), 10634 Berlin, Germany Within the group of ferrimagnetic double perovskites of the type A2 M N O6 (with A an alkaline earth, M a magnetic transition metal ion, and N a non-magnetic ion), a huge spread of magnetic transition temperatures is observed. We show for the example of the Cr-based double perovskites that increased band-filling by introducing elements with an increased number of 5d electrons leads to a strongly enhanced Curietemperature. Along this line the slightly rhombohedral compound Sr2 CrOsO6 has a Curie-temperature of about 750 K. The magnetic structure determined by neutron scattering and x-ray magnetic circular dichroism (XMCD) experiments confirms the existence of a sizable induced magnetic moment at the Os-site. This result is consistent with the picture that to a large extent spin-polarized electrons mediate a robust ferrimagnetic order in Sr2 CrOsO6 .

Magnetismus

Poster: Do., 13:00–15:30

D-P235

Magnetic coupling of NiO and CoO to Fe3 O4 investigated by X-PEEM Ingo Krug1 , Ulrich Hillebrecht1 , Claus M. Schneider1 1

Forschungszentrum J¨ ulich, Institut f¨ ur Festk¨ orperforschung (IFF)

Exchange coupling across ferromagnet-antiferromagnet-interfaces has gained great importance in magnetic storage and readout technology. Despite of widespread experimental and theoretical efforts, none of the present models provides an accurate description for a wider range of material systems. In order to separate and understand the microscopic details that lead to macroscopic effects like spin-flop coupling, coercivity enhancement and exchange bias, it is necessary to study quasi-ideal model systems. Therefore we investigated the exchange coupling of ultrathin films of NiO on CoO to high quality synthetic single crystals of magnetite. The films were grown epitaxially by in-situ Ox-MBE onto Fe3 O4 (111) substrates. We use Photoelectron Emission Microscopy (PEEM) in combination with polarized soft x-rays to simultaneously measure magnetization direction and spin-axis orientations in the ferrimagnet and the antiferromagnet, respectively, on a microscopic level(∆x = 50 − 100 nm). For CoO, we find the coupling to be of parallel (collinear) type (see Fig.1), as has also been observed for metallic (Co) ferromagnets in contact with NiO. In contrast, we observe 90◦ -coupling for NiO. This difference in behaviour is astonishing, since both substances have the same crystalline and similar magnetic structures. To detect small magnetic moments induced in the antiferromagnet by exchange coupling to the ferrimagnet, we employ a differential measurement technique based on 180◦ -domains present in the sample, achieving a magnetic signal to noise ratio better than 10−4 . From this approach we can further differentiate between the two AF materials: for NiO, there is hardly any induced moment present at the samples, whereas the CoO adlayers show a large induced ferromagnetic signal. These differences are analyzed within a model which takes into account magnetostrictive effects.

Fig. 1: Line profiles along the colored bars in the PEEM images of CoO/Fe3 O4 (111): (A) XMCDcontrast of the substrate. (B) CoXMCD, (coupling-induced moment at the interface), (C) CoO-XMLD contrast with p-polarized light, (D) CoO-XMLD-contrast with spolarized light. By the phase relation of XMCD and XMLD profiles, the coupling-type can be determined (in this case: parallel).

Magnetismus

Poster: Do., 13:00–15:30

D-P236

Layer-resolved magnetic domain imaging of antiferromagnetic/ferromagnetic layered systems by x-ray magnetic dichroism photoelectron emission microscopy Wolfgang Kuch1 , Francesco Offi2 , Liviu I. Chelaru2 , Jing Wang2 , Keiki ¨rgen Kirschner2 Fukumoto1 , Masato Kotsugi2 , Ju 1

Freie Universit¨ at Berlin, Institut f¨ ur Experimentalphysik, Arnimallee 14, D-14195 Berlin – 2 Max-Planck-Institut f¨ ur Mikrostrukturphysik, Weinberg 2, D-06120 Halle The magnetic coupling between an antiferromagnetic (AF) and a ferromagnetic (FM) film is interesting both for applications in magnetoresistive devices as well as for fundamental studies. In AF materials the direction of the atomic magnetic moments varies on the length scale of atomic distances, leading to zero net magnetization if averaged over a few lattice constants. Atomic-scale control and characterization of the AF-FM interface is thus essential for a fundamental understanding of the magnetic interaction between AF and FM materials. We present an x-ray magnetic circular (XMCD) and linear dichroism (XMLD) photoelectron emission microscopy (PEEM) study of single-crystalline bilayers and trilayers containing FeMn as antiferromagnetic layer on a Cu(001) single crystal surface. All systems show pronounced layer-by-layer growth, as confirmed by medium energy electron scattering during evaporation and scanning tunneling microscopy. This layer-by-layer growth provides the opportunity to controllably tune the interface roughness on the atomic scale by changing the atomic layer filling. Layer-resolved XMCD-PEEM magnetic domain images reveal an oscillatory magnetic interlayer coupling between two ferromagnetic layers across an antiferromagnetic FeMn spacer layer, as well as a modulation of the phase of this oscillation and the coupling strength as a function of the bottom interface roughness [1]. This proves the importance not only of the presence of atomic steps at the interface, but also of their detailed arrangement. Because of the three-dimensional non-collinear spin structure of FeMn films [2], the XMLD signal of the AF layer vanishes. However, it was possible to identify the tiny XMLD signal of the induced moments in the FeMn layer at the interface. These represent the first magnetic domain images of a metallic AF acquired with XMLD. [1] W. Kuch et al., Nature Materials 5 (2006) 128. [2] W. Kuch et al., Phys. Rev. Lett. 92 (2004) 017201.

Magnetismus

Poster: Do., 13:00–15:30

D-P237

Magnets with two order parameters and order parameters with two components ¨ bler1 , Andreas Hoser2,1 Ulrich Ko 1

IFF Forschungszentrum J¨ ulich, 52425 J¨ ulich – 2 Institut f¨ ur Kristallographie, RWTHAachen In the interpretation of the observed magnetic excitation spectra it is necessary to distinguish between the excitations for finite wave vector values, i.e. for q6=0 on the one hand and for q=0 on the other hand. The excitations with q6=0 are material specific non universal features on the length scale of the inter-atomic distance. On this length scale the short range Heisenberg interactions seem to be the relevant interactions. On the other hand, the spin dynamics at the stable fixed points T=Tc and T=0 shows universality. Universality is represented by power functions of temperature with exponents that do not depend on microscopic details such as spin structure and lattice symmetry. Under the continuous symmetry of the long range ordered state distinction between individual spins on a discrete lattice is no longer possible. The relevant interactions are at the Γ point of the Brillouin zone, i.e. at q=0. Continuum theories are more appropriate than atomistic models. Unfortunately, the long range interactions at q=0 are extremely small because they couple all spins of the sample. In many magnetic materials a magnetic excitation gap is observed at q=0. We show that in two dimensional (2D) magnets (K2 NiF4 ) and in one dimensional (1D) magnets (MnF2 ) the gap has identical temperature dependence as the order parameter. The gap, therefore, seems to be a second component of the order parameter. On the other hand, isotropic 3D magnets with integer spin also exhibit a magnetic excitation gap (LaVO3 ). From the different temperature dependencies of gap and order parameter (UO2 ) it can be concluded that the gap is a second order parameter. 3D magnets with half-integer spin have continuous excitation spectra. As a conclusion, it appears that in 2D and 1D magnets the order parameter has two components while in 3D magnets two distinguished order parameters can be identified. These observations cannot be explained assuming only short range Heisenberg interactions. The only known long range interactions are dipole-dipole interactions. In a classical treatment dipole-dipole interactions seem not to be able to explain a different behaviour for integer and half-integer spin values [1]. As a conclusion, a new type of long range interaction has to be found that is able to explain universality, long range magnetic order in two and one dimension and different universality classes for integer and half-integer spin values. [1] U. K¨ obler, A. Hoser, Physica B 362 (2005) 295.

Magnetismus

Poster: Do., 13:00–15:30

D-P238

Evolution of incommensurate magnetic order from A-type antiferromagnetism in N d1−x Yx M nO3 Sven Landsgesell1 , Oleksandr Prokhnenko1 , Nadir Aliouane1 , Dimitri Argyriou1 1

Hahn-Meitner-Institut Berlin GmbH (HMI), Glienicker Straße 100, 14109 Berlin

The evolution of spin- and orbital-ordered states for LnMnO3 with Ln=La - Ho has attracted significant attention in recent years. By lowering the Mn-O-Mn bond angle (by decreasing the ionic radius of Ln) the Neel-temperature decreases and at Ln = Tb the A-type antiferromagnet transforms to an incommensurate (IC) spin-spiral phase for Ln=Gd,Tb,Dy. The spin-spiral breaks both inversion and time reversal symmetry leading to a strong coupling between magnetism and ferroelectric polarization. In this work we study we investigate the evolution of the crystal and magnetic structure from the A-type phase to the IC spin spiral. This was achieved by systematically doping yttrium into NdMnO3 . By that the tolerance factors can be lowered to values similar to that for multiferroic TbMnO3 . One advantage of this appoach is that the tolerance factor can be tuned and that neodymiun and yttrium are not high neutron absopbing elements in sharp contrast to other rare earths like Gd, Dy and Eu. Compositions x = 0 to 0.5 in 0.1 steps have been prepared, neutron and x-ray powder diffraction patterns were measured at room temperature and 2K while the magnetic properties were measured with a SQUID magnetometer. It can be shown that by decreasing the tolerance factor that way, similar effects can be seen as with varying the ionic size of the rare earth ions. For example we found that for x = 0.4 and higher the incommensurate phase (δ = 0.2 -> 0.25) co-exist with the A-type antiferromagnetic phase. This suggests the transition from A-type to spin-spiral is discontinous.

Magnetismus

Poster: Do., 13:00–15:30

D-P239

Search for S = 1 Haldane chains in metallo-supramolecular assemblies M. Lommel1 , Y. Bodenthin1 , U. Pietsch1 , G. Schwarz2 , W. Haase3 , Z. Tomkowicz3,4 , D. G. Kurth2 1

University Siegen, FB7 Solid State Physics, D-57068 Siegen (Germany) – 2 Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam (Germany) – 3 Institute of Physical Chemistry, Darmstadt University of Technology, Petersenstrasse 20, D64287(Germany), – 4 Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krak´ ow (Poland) The physics of antiferromagnetic Heisenberg chains is an area of high interest since even at zero temperature quantum fluctuations suppress long range order. In 1983 Haldane concluded that for all integer spin values even a spin liquid ground state with a finite excitation gap is realized. [1] Since this time several Ni(II) metallo-organic systems have been clearly identified. Our aim was to elucidate the magnetic properties of metallo-supramolecular polyelectrolyte-amphiphile complexes (PAC) with Ni(II) as metal ion. [2] In PAC metal ions are coupled in a one-dimensional chain via metallosupramolecular coordination polyelectrolytes (MEPE), whereas amphiphile molecules serve as spacers between the MEPE chains. Ni(II)-PAC could be an molecular system realizing a Haldane quantum spin chain with S = 1. From the topology of the Ni(II)PAC compound one may expect that Ni(II) S = 1 spins coupled via MEPE fragments in a chain can interact with each other antiferromagnetical. First magnetization results reveal a Curie-Weiss behaviour with a small antiferromagnetic Weiss temperature of 1.3 K. These observations imply that one can realize the quantum Haldane situation by chemically engineering of the coupling strength between Ni-spins in a chain via increase of the antiferromagentic exchange interaction. Experiments on Fe(II)-PAC reveal the possibility to tune the magnetic properties of PAC by changing length of the ligand and amount of amphiphiles. Additionally previous element selective XMCD investigation elucidate an antiparallel oriented spinpolarization between iron and its sourrounding ligand leading to a magnetic coupling between neighbouring metal centres due to a superexchange interaction. The intention was to investigate the superexchange coupling between two Ni(II)-metal centres in PAC using x-ray magnetic linear dichroism (XMLD). We investigated a series of four different samples containing two different ligands each with two different metal to amphiphile ratios (1:6 and 1:2 metal to amphiphile ratios) at low temperature. The evaluation of the data was treated in terms of Zak’s formalism. All experiments were performed using the ALICE diffractometer of group Zabel, UniBochum at BESSY II. This project is supported by DFG Priority program 1137 Molecular Magnetism. [1] F. D.M. Haldane, Phys. Rev. Lett. 50 (1983) 1153 [2] D. G. Kurth, P. Lehmann, M. Sch¨ utte, Proc. Natl. Acad. Sci., USA, 97 (2000) 5704-5707

Magnetismus

Poster: Do., 13:00–15:30

D-P240

Magnetic properties of small, mass selected metal clusters Michael Martins1 , Leif Glaser1 , Matthias Reif1 , Sebastian Hankemeier1 , Wilfried Wurth1 1

Insitut f¨ ur Experimentalphysik, Universit¨ at Hamburg, Luruper Chaussee 149, D22761 Hamburg Size selected transition metal cluster allow to study the transition of the magnetic properties as a function of cluster size. Regarding possible applications these clusters have to be supported on a substrate or embedded in a matrix, where cluster-support interaction will influence their physical properties. To investigate the magnetic properties of such deposited clusters, x-ray magnetic circular dichroism (XMCD) is an ideal tool, due to its element selectivity and the capability to measure spin- and orbital moments independently. For iron cluster deposited on a remanently magnetized thin nickel film a strong size dependence of the spin- and orbital moments have been found [1,2]. The magnetic properties of the deposited clusters might be strongly influenced by the surface material. Thus, we have studied the magnetic properties of deposited, mass selected Crn and Run clusters on thin iron and nickel films. Crn clusters are of special interest, due to the anti-ferromagnetic coupling of chromium in the bulk. For Run -clusters in the gas phase a super-paramagnetic coupling is found, whereas this 4d element is non-magnetic in the bulk. Due to the anti-ferromagnetic coupling of Cr a complicated coupling scheme of the magnetic moments can be expected, e.g. already in a trimer for the third atom the spin will be frustated [3]. Thus we have started studies on chromium clusters in the size range from n=1 to n=13 deposited on ultrathin ferromagnetic nickel and iron films. Whereas for Cr cluster on Ni films no XMCD signal is found, Cr clusters on Fe films show a strong decrease of the magnetic moment by a factor of 4 with increasing cluster size. This effect can be interpreted in terms of a non-collinear coupling of the magnetic moments within the cluster and relative to the surface [4]. For Run clusters we have performed experiments on deposited atoms and dimers on Ni and Fe surfaces. XMCD-experiments on the 4d elements are much harder to perform, due to the small cross section of the M2,3 edges as compared to the corresponding L2,3 edges of the 3d metals. Whereas for Ru atoms on Ni(100) a ferromagnetic coupling is found, the Ru dimer on Ni(100) is non-magnetic. For Ru1,2 on a Fe surface the inverse behavior is found. [1] J.T. Lau, A. F¨ ohlisch, R. Nietubyc, M. Reif, W. Wurth, Phys.Rev.Lett.89 (2002) 057202 [2] J.T. Lau, A. F¨ ohlisch, M. Martins, R. Nietubyc, M. Reif, W. Wurth, New J. Phys. 4 (2002) 98.1 [3] T. Jamneala, V. Madhavan, M.F. Crommie, Phys. Rev. Lett. 87 (2001) 256804 [4] M. Reif, L. Glaser, M. Martins, W. Wurth, S. Lounis, S. Bl¨ ugel, in preparation

Magnetismus

Poster: Do., 13:00–15:30

D-P241

Real space observation of dipolar interaction in arrays of iron and permalloy elements Guido Meier1 , Markus Bolte1 , Rene Eiselt1 , Ulrich Merkt1 , Dong-Hyun Kim2 , Peter Fischer2 1

Institut f¨ ur Angewandte Physik und Zentrum f¨ ur Mikrostrukturforschung, Universit¨ at Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany – 2 Center for X-Ray Optics, Lawrence Berkeley National Lab, 1 Cyclotron Road, Mail Stop 2R0400, Berkeley, California 94720 Square lattice arrays of thin micro- and nanoelements of iron and permalloy are investigated by magnetic transmission x-ray microscopy. The influence of dipole interaction is analyzed by varying the interelement distance, the angle of the applied magnetic field, and the lattice configuration. For the iron squares the magnetostatic field caused by inter-element interaction leads to a substantial stabilization of the center elements of the array [1] comparable to the magnetization process previously found by numerical solution of the Landau-Lifshitz equation for magnetic dot arrays. Micromagnetic simulations show, that for high field strengths the dipolar interaction is collinear with the external field, while in the low-field-regime the strayfields have significant perpendicular components leading to a complex reversal mechanism. [1] Markus Bolte, Ren´e Eiselt, Guido Meier, Dong-Hyun Kim, and Peter Fischer, J. Appl. Phys. 99, 08H301 (2006).

Fig. 1: MTXM images of arrays of Fe microelements with (a) 200 nm, (b) 600 nm, (c) 800 nm, and (d) 2000 nm interelement spacing in a magnetic field of µ0 H = +8.7 mT. Its direction is indicated by the arrow. The inset in (d) is an enlarged zoom of one microelement of this array with the magnetization indicated by arrows.

Magnetismus

Poster: Do., 13:00–15:30

D-P242

Neutron Investigation of the antiferromagnetic State of Co2 SiO4 at HEiDi Martin Meven1 , Andrew Sazonov1 , Gernot Heger2 1

ZWE FRM-II TU M¨ unchen, Lichtenbergstraße 1, 85747 Garching – 2 Institut f¨ ur Kristallographie, J¨ agerstraße 17-19, 52056 Aachen Olivine, (Mg,Fe)2 SiO4 , is an important mineral of the upper Earth’s mantle. Well known natural olivine-type silicates are fayalite (Fe2 SiO4 , paramagnetic Fe2+ ions), forsterite (Mg2 SiO4 , diamagnetic Mg2+ ions) and kirschteinite (CaFeSiO4 , mixed diamagnetic/paramagnetic). A remarkable feature of the orthorhombic olivine-type structure (Pnma, no. 62) consists in two crystallographically non equivalent metal (M e) positions which yield one-dimensional chains of edge-sharing Me(1)O6 octahedra which are connected via Me(2)O6 octahedra. The magnetic properties of olivine compounds are quite complex. They are driven by different and competing super-exchange interactions. For instance, a complete replacement of paramagnetic Me(2) ions by diamagnetic ions should result in a onedimensional magnetic behaviour. Synthetic Co2 SiO4 also crystallizes in the olivine structure. Former investigations of the magnetization of Co2 SiO4 single crystals in dependence of crystal orientation and applied magnetic field were performed by W. Lottermoser and H. Fuess [1, 2]. At Tc ≈50 K an antiferromagnetic phase transition occurs. In the antiferromagnetic state at 20 K the Co(2) spins are collinear while the Co(1) spins are canted. To continue the investigation on the magnetical properties of Co2 SiO4 a large single crystal (≈ 300 mm3 ) was grown in a mirror furnace at Aachen. The single crystal diffractometer HEiDi at the hot source of the new neutron source Heinz Maier-Leibniz (FRM-II) was developed for very accurate structural investigations on single crystals and allows due to the short wavelengths between 1 ˚ A and 0.3 ˚ A to separate the magnetic contributions from nuclear contributions to determine magnetic spin densities. The combination with a closed cycle cryostat in the Eulerian cradle with a remarkable low Tmin of 2.2 K at the sample position makes the instrument a very good choice for detailed magnetic investigations at very low temperatures. A neutron diffraction data set of our Co2 SiO4 sample was taken on HEiDi at room temperature to characterize the sample quality. Cell parameters and atomic positions were very precisely determined with good agreement to data from literature [1, 2]. Temperature dependent measurements of magnetic reflections like (110) were performed from above Tc down to 2.2 K to observe their evolution in the antiferromagnetic phase. At 2.2 K a complete Bragg data set with nuclear and magnetic contributions was taken. A first result is the excellent agreement between the phase transition temperature found in former investigations [1, 2] and our measurement. Further results of our investigations of the antiferromagnetic state of Co2 SiO4 will be presented on this conference. [1] W. Lottermoser and H. Fuess, Phys. Stat. Sol. A 109, 589 (1988) [2] W. Lottermoser and H. Fuess, Phys. Chem. Min. 19, 46 (1992)

Magnetismus

Poster: Do., 13:00–15:30

D-P243

Calculation of spectroscopic properties of solids using the relativistic KKRmethod J. Minar1 , S. Chadov1 , S. Bornemann1 , H. Ebert1 , C. Sorg2 , H. Wende2 , K. Baberschke2 , M. Martins3 , W. Wurth3 , N. Brookes4 1

Department Chemie und Biochemie, Physikalische Chemie, Universit¨ at M¨ unchen, Germany – 2 Institut f¨ ur Experimentalphysik, Freie Universit¨ at Berlin, Germany – 3 Universit¨ at Hamburg, Institut f¨ ur Experimentalphysik, Hamburg, Germany – 4 ESRF, Grenoble, France The spin-polarized relativistic version of the Korringa-Kohn-Rostoker (SPR-KKR) method for the calculation of the electronic structure of solids supplies an extremely flexible and powerful basis to calculate a wide range of spectroscopic properties. We present an implementation of the SPR-KKR (Munich SPR-KKR package - available to interested users upon request: http://olymp.phys.chemie.uni-muenchen.de/ak/ebert/SPRKKR) together with recent applications to magnetic solids. As a first example results for the pure Fano-effect in the angle-integrated photo-emission of the ferromagnets Fe, Co and Ni is presented. It is demonstrated that this spin-orbit induced effect can be observed and discussed independent on the intrinsic spin polarization. Comparison between recent experimental results lead to a very satisfying agreement. In addition we present applications to the magnetic circular dichroism in X-ray absorption (XMCD). Corresponding results are presented for small transition metal clusters deposited on a metallic substrate. For Co on Pt(111) the calculated spin and orbital moments are found to reproduce the trend of the experimental results based on the XMCD sum rules very well. For Ru on Fe(001) the observed induced moment could be confirmed by the calculations. Investigations on the L2,3 -edge spectra of the pure elements Gd, Tb and Dy demonstrated the importance of correlated effects and allowed to identify the non-negligible quadrupolar contributions to the XMCD-spectra.

Magnetismus

Poster: Do., 13:00–15:30

D-P244

X-ray Resonant Magnetic Scattering on Diluted Magnetic Semiconductors Alexei Nefedov1 , Numan Akdogan1 , Rustam Khaibullin2 , Lenar Tagirov2,3 , Hartmut Zabel1 1

Institut f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, Bochum, Germany – 2 Kazan Physical-Technical Institute of RAS, Kazan, Russia – 3 Kazan State University, Kazan, Russia Diluted magnetic semiconductors (DMS) are key materials for spintronics, which are intended to manipulate both the spin and charge degree of freedom by coupling the spins of the magnetic ions and the charge carriers of the host semiconductors. Recently several oxide-based DMS have been reported to be robust, room temperature ferromagnets. In particular, the Co-doped TiO2 system, first reported to be ferromagnetic by Matsumoto [1], has received much attention. However, a consensus on the origin of the ferromagnetic coupling has not yet been reached. To clarify this situation we have studied in detail the magnetic properties of Co-doped TiO2 synthesized by ion implantation with doses of 0.25-1.50·1017 ions/cm2 using x-ray resonant magnetic scattering (XRMS) in a temperature range of 4.2-295 K. The XRMS experiments were carried out at BESSY II using the ALICE diffractometer [2]. Firstly, a two-component hysteresis curve was observed at the Co L3 edge (E=778 eV) for the sample implanted with the dose of 1.50·1017 ions/cm2 . However, variation of the photon energy leads to a change of the relative intensities of these two components and at the photon energy of E=780 eV only a one-component hysteresis curve has been observed. This allows to separate magnetic contributions from Co ions incorporated in TiO2 and contributions from Co metallic clusters. We found that the Curie temperature increases from 12 K for the lowest implantation dose (D=0.25·1017 ions/cm2 ) to above room temperature for samples implanted with a dose of 1.00·1017 ions/cm2 . Within our sensitivity no magnetic signal was found at the Ti edges, however at the O K edge a small, but clearly visible magnetic signal was observed. From this we infer that oxygen atoms which are close to Co atoms are polarized. This observation could imply that the ferromagnetism observed for Co-doped rutile (100)TiO2 samples is mediated by a superexchange mechanism through oxygen atoms. N. Akdogan acknowledges a fellowship through the International Max-Planck Research School “SurMat”. We gratefully acknowledge BMBF for the financial support through Contracts No. 05KS4PCA (ALICE diffractometer) and No. 05ES3XBA/5 (travel to BESSY). [1] Y. Matsumoto et al., Science 291 (2001) 854. [2] J. Grabis et al., Rev. Sci. Instr. 74 (2003) 4048.

Magnetismus

Poster: Do., 13:00–15:30

D-P245

Photons, neutrons and ions reveal epxitaxy, reversal mechanism and stoichiometry dependence of the blocking temperature of CoO/Fe exchange bias bilayers Gregor Nowak1 , Arndt Remhof1 , Florin Radu1 , Alexei Nefedov1 , Hans Werner Becker2 , Kurt Westerholt1 , Hartmut Zabel1 1

Institut f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, Germany – 2 Physik mit Ionenstrahlen, Ruhr-Universit¨ at Bochum, Germany The magnetic properties of CoO/Fe blayers are strongly influenced by the stoichiometry of the antiferromagnetic (AFM) CoO layer. We prepared stoichiometric and single crystalline CoO-films by an annealing step in UHV and compared them to as prepared samples. Especially the blocking temperature TB is sensitive to the oxygen concentration as shown by SQUID magnetometry (Fig. 1). While TB of stoichiometric, epitaxial CoO equals the Neel temperture of the bulk material, it is reduced by 40K in the superstoichiometric case. The annealed CoO films serve as a seed layer for the growth of epitaxial Fe films. The epitaxial relation between CoO and Fe was found to be of the Nishiyama-Wassermann [1,2] type (Fig. 2). Polarized neutron reflectometry (PNR) reveals the magnetic reversal mechanism. We observe a transition from domain wall movement to domain rotation within the first hysteresis after field cooling indicated by an strong increase of spin-flip scattering in the second half of the hysteresis loop [3]. This work was supported by the DFG via SFB 491. [1] Z. Nishiyama, Sci. Rep. Tohoku Univ. 23, (1934) 638. [2] G. Wassermann, Arch. Eisenh¨ uttenwesen 126 (1933) 647. [3] Florin Radu, Dissertation, Bochum 2005.

Fig. 1: Stochiometry dependence of the exchange bias field.

Fig. 2: In-plane rocking scans reveal the epitaxial relation between Fe and CoO.

Magnetismus

Poster: Do., 13:00–15:30

D-P246

Where are the limits of non-exponential relaxation ? Catherine Pappas1 , Robert Cywinski2 , Adrian Hillier3 , Pascal Manuel3 , Ian Campbell4 , Ferenc Mezei1 1

Hahn Meitner Institut Berlin, Germany – 2 Physics and Astronomy Department, Leeds, UK – 3 ISIS, Didcot UK – 4 Universit´e de Montpellier 2, France The fundamental question of the universality of the precursor features of a low temperature disordered phase cannot be easily answered. Non-exponential relaxation is found in glasses and spin glasses but not in disordered ferromagnets and antiferromagnets. According to an Griffithss argument, however, the paramagnetic phase above disordered ferromagnets should be anomalous showing non-exponential relaxation. We searched for this so-called Griffithss phase in the disordered system Au1−x Fex , by combining Neutron Spin Echo (NSE) spectroscopy and Muon Spin Relaxation (µSR). This system is spin glass for x<0.155 and a disordered ferromagnet for x>0.155. At the spin glass side, for x=0.14, the analysis of the strongly non-exponential relaxation leads to an excellent agreement between NSE and µSR, an unambiguous proof of the homogeneous character of the spin glass relaxation. A slight increase of the Fe concentration leads to the disordered ferromagnetic phase (x=0.16, 18) and an abrupt change of the relaxation seen by NSE, which becomes exponential. The µSR spectra on the other side remain non-exponential and at high temperatures they are very similar to those of the spin glass side of the phase diagram, as expected by the Griffithss argument. The puzzling discrepancy between NSE and µSR in the disordered ferromagnetic phase explains why neutron scattering and macroscopic magnetization measurements failed up to now to identify the Griffithss phase in disordered magnets. The observation of the Griffiths phase by muons and of the disordered ferromagnetic transition with neutrons provides a deeper link between theory and experiment and gives a natural explanation of the marked influence of strong disorder on the ferromagnetic and antiferromagetic second order phase transitions.

Magnetismus

Poster: Do., 13:00–15:30

D-P247

Influence of Nd-nanoparticles on hard magnetic properties of bulk amorphous alloys studied by small-angle neutrons scattering. ¨rgen Eckert3 Olivier Perroud1 , Albrecht Wiedenmann1 , Golden Kumar2 , Ju 1

Hahn-Meitner-Institut Berlin, Glienickerstr. 100, D-14109 Berlin, Germany – 2 NIMS, 1-2-1 Sengen, Tsukuba 305-0047, Japan – 3 TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt, Germany

Bulk amorphous Nd60 Fex Co30−x Al10 -alloys presents hard-magnetic properties for x>5. Some macroscopic investigations are reported [1], where two Curie temperatures (Tc1 ∼ 50 K and Tc2 ∼ 525 K) are observed. This samples exhibits a Fe-rich phase in micrometer scale, an amorphous matrix and some nanoparticles. The high coercivity were attributed to the pinning of magnetic domains with some Nd-nanoparticles in the Ferich phase. Small-angle neutron scattering with polarized neutrons (SANSPOL) allows to investigate and separate both nuclear and magnetic properties of a sample in the nanometer scale. An applied magnetic field of µ0 H=6 T doesnt saturated the sample and it follows, that the magnetic scattering contribution is weak compared to the nuclear one. Previous SANS experiments and high field measurement on Nd60 Fe20 Co10 Al10 -alloy have shown that the sample was not saturated [2,3] and confirm the presence of magnetic domains. The present measurements have been performed on the Nd60 Fe7.5 Co22.5 Al10 -alloy at temperatures between 5 K and 550 K and magnetic fields of µ0 H=1 T and 6 T. The scattering curves corroborate the presence of magnetic domains. The Nd-nanoparticles, which are paramagnetic above Tc1 , will act as pinning centers for the domains walls. This work is supported by the German Science Foundation (DFG) WI 1151/3-1. [1] G. Kumar et al., J. of Alloys and Compounds 248 309 (2003) [2] E. Garcia-Matres et al., Physica. B 350 e315-e318 (2004) [3] O. Perroud et al., Material Science and Engineering A, in press (2006)

Magnetismus

Poster: Do., 13:00–15:30

D-P248

Structural changes in cobalt-based ferrofluids under shear stress observed by small angle neutron scattering Loredana Mirela Pop1 , Stefan Odenbach1 , Martin Kammel2 , Albrecht Wiedenmann2 1

Technische Universit¨ at Dresden, 01062 Dresden, Germany – 2 Hahn Meitner Institute, Glienicker Str. 100, 14109 Berlin, Germany Long term stable colloidal suspensions of nanometer-sized magnetic particles in appropriate carrier liquids, ferrofluids show normal liquid behaviour coupled with superparamagnetic properties. Due to the possibility to change their physical properties by means of moderate magnetic fields, they can be used for an expanding number of applications like, for example, as a cooling medium in loudspeakers or as a sealing for rotary feedthroughs. Additional application fields concerning the use of ferrofluids in biomedical applications for cancer therapy are subject of actual research activities. In the presence of magnetic fields ferrofluids show an increase of their viscosity, the so called magnetoviscous effect, of several hundred percent compared to the viscosity without magnetic field. Due to a strong shear thinning in commercial ferrofluids, the viscosity changes diminish for technical useful shear rates to values not suitable for applications. Therefore, in the last years, a lot of experimental and theoretical studies have been done in order to explain the microscopic mechanisms of the magnetoviscous effect. As a result of these efforts, a model, based on numerical and experimental data, has been established. Chain formation of magnetic particles with strong particle particle interaction as well as structure destruction by means of shear influence are the essential processes for the understanding of the magnetoviscous phenomena. Since until now experimental data proving such a connection between the structure of ferrofluids and their viscous properties were missing the study of the microstructure of ferrofluids under shear for different magnetic field strengths and shear rates and its consequences on the magnetoviscous effect is in the focus of recent research. Using a specially designed rheometer, rheological as well as small angle neutron scattering investigations have been performed in the same experimental environment. The obtained results show a strong connection between structure formation in ferrofluids and their rheological behaviour. The evidence for a formation of chains and their deviation in a shear flow validates therefore the model of chain formation as an explanation for the magnetoviscous effect. Further information, concerning the local magnetisation of the sample in a shear flow relative to the direction of the chains, obtained from experiments using polarised neutrons, will be presented. Additionally, the possibility of combining X-Ray and neutron experiments will be discussed. Establishing a connection between the changes of the microstructure of ferrofluids, under the influence of a magnetic field, and their consequences on the macroscopical behaviour of these systems could allow an optimisation of the fluids. Based on the knowledge gained from experimental and theoretical studies, new applications can be developed, making ferrofluids an attractive medium for potential further research.

Magnetismus

Poster: Do., 13:00–15:30

D-P249

Forbidden magnetic reflections in UNiGa Karel Prokes1 , Ralf Feyerherm1 , Vladimir Sechovsky2 , Marian Mihalik3 1

Hahn-Meitner-Institute, SF-2, Glienickerstr. 100, 141 09 Berlin, Germany – Department of Electronic Structures, Charles University, 121 16 Prague 2, The Czech Republic – 3 Institute of Experimental Physics, SAS , Watsonova 47, Kosice, Slovakia 2

UNiGa crystallizes in the hexagonal ZrNiAl structure and undergoes a sequence of magnetic phase transitions in the 35 - 39.5 K temperature range. The ground-state antiferromagnetic (AF) structure is characterized by three propagation vectors q1 =(0, 0, 1/2), q2 =(0, 0, 1/3) and q3 =(0, 0, 1/6) corresponding to the c-axis (up-up-downup-down-down) stacking of U-moments that are ordered ferromagnetically within the hexagonal basal planes [1]. A strong uniaxial anisotropy keeps the moments aligned along c in all the magnetic structures. A magnetic field applied along the c axis induces a metamagnetic-like transition leading to a field-forced ferromagnetic stacking. This transition, which is of the first-order type with considerable hysteresis at T = 4.2 K and appears at Bc ≈ 0.8 T, splits into two steps for the temperature above 15 K. In the intermediate fields the structure of the (up-up-down) type was detected. The size of U-moments (1.35 µB at T = 4.2 K) is practically independent of the type of structure. A strong uniaxial anisotropy in this system locks the U moments along the c-axis (which is also the easy-magnetization axis). While low field applied at low temperatures along the hexagonal axis breaks the AF coupling and forces the U magnetic moments to align parallel, magnetic field applied perpendicular to the c axis has no significant influence on the low-field magnetic structure of UNiGa. Previous high-field magnetization studies at 4.2 K revealed that even magnetic fields as high as 35 T are not sufficient to tilt the moments significantly away from the hexagonal c axis. From these data one can roughly estimate the magnetic anisotropy field to be at least 300 T. It is therefore surprising that among the observed ground-state AF reflections are also reflections of the (0 0 +/- qn ) type, i.e. reflections for which is the projection of magnetic moment on the plane perpendicular to the scattering vector zero. There is no doubt that the ground state AF structure of UNiGa published in the literature on the basis of previous unpolarised and polarised neutron diffraction experiments is correct. The apparent disagreement between the experiment and theory calls for an explanation. In this contribution we describe combined results of neutron and X-ray diffraction performed on a good-quality single crystal to explain the possible reason for such an observation. [1] K. Prokes, E. Bruck, F. R. de Boer, M. Mihalik, A.A. Menovsky, P. Burlet, J.M. Mignot, L. Havela, V. Sechovsky, J. Appl. Phys. 79 (1996) 6396.

Magnetismus

Poster: Do., 13:00–15:30

D-P250

Magnetic Ordering in Multiferroic DyMnO3 O Prokhnenko1 , S. Landsgesell1 , D. Argyriou1 , L.C. Chapon2 1

Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2 ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, U.K.

DyMnO3 belongs to the family of the spin frustrated multiferroic perovskites which exhibit a strong coupling between magnetism and ferroelectricity. We have examined the magnetic and crystal structure of 163 DyMnO3 using neutron powder diffraction. We find that the Mn-spins order incommensurately with propagation vector q = (0, δ, 0), δ ∼ 0.37 at T > TN (M n)=38 K. The magnitude of δ varies as a function of temperature much the same way as it does in TbMnO3 . At lower temperature, TN (Dy) ∼6 K, we find that Dy spins order commensurately with propagation vectorq = (0, 1/2, 0), while the ordering of Mn-spins remain incommensurate. Surprisingly we find that as Dy-spins order the intensity of reflections that arise from Mn ordering decrease substantially in intensity. This may imply that Dy-spins also order with the same wavevector as Mn-spins and contributed to the corresponding Bragg reflections for T>TN (Dy). This hypothesis has been confirmed my resonant X-ray scattering presented in an other contribution to this conference.

Magnetismus

Poster: Do., 13:00–15:30

D-P251

Hydrogen induced changes of the magnetic moments in Fe/V superlattices ¨ rck2 , Martin Arndt Remhof1 , Gregor Nowak1 , Alexei Nefedov1 , Matts Bjo 2 2 1 ¨rnaste , Bjo ¨ rgvin Hjo ¨ rvarsson , Hartmut Zabel Pa 1

Institut f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, 44780 Bochum, Germany – 2 Department of Physics, Uppsala University, Box530, 75121 Uppsala, Sweden We report on the increase of the Fe magnetic moment within Fe/V superlattices upon H-uptake. At the Fe/V interface of pristine, ferromagnetically coupled Fe/V superlattices the V atoms acquire a magnetic moment, antiparallel aligned to the Fe moments [1]. Upon hydrogen loading the saturation magnetization was found to increase [2]. We employed element specific X-ray resonant magnetic scattering to investigate the response of the Fe and the V moments separately. An epitaxial [Fe(2ML)/V(16ML)]×30 superlattice was employed, ensuring a high number of V neighbors of each Fe atom. The soft x-ray measurements were carried out using the ALICE diffractometer at BESSY II in Berlin, Germany. The data clearly show a strong increase of the Fe moment upon H-loading (left panel). No change of the magnetic asymmetry at the V edge could be recognized (right panel). Our measurements confirm nicely the theoretical model by Uzdin et al. [3], predicting an increase of the Fe moment and a stable V moment in H loaded Fe/V superlattices. The authors are grateful for technical support by T. Kachel (BESSY). We would like to thank the DFG for financial support under contract RE 2203-1/1 as well as the INTAS project ref. nr. 03-51-4778 The soft x-ray work was supported by the BMBF under contracts O3ZA6BC2 and 05KS4PCA. Fig. 1: Magnetic asymmetry ratios measured on a [Fe(2)/V(16)]×30 superlattice in the vicinity of the Fe L-edges in reflection at the 2nd superlattice reflection prior (black) and after (red) hydrogen exposure. The spectra on the right panel were recorded on a [Fe(6ML)/V(16ML)] × 30 superlattice close to the V Ledges.

Magnetismus

Poster: Do., 13:00–15:30

D-P252

Fine-tuning the SDW in Cr/V heterostructures by hydrogen loading Arndt Remhof1 , Evgeny Kravtsov1 , Gregor Nowak1 , Alexei Nefedov1 , ¨ rgvin Hjo ¨ rvarsson2 , Andreas Hoser3 , Florin Radu1 , Andreas Liebig2 , Bjo 4 1 Luigi Paolasini , Hartmut Zabel 1

Department of Physics, Ruhr-University Bochum, D-44780 Bochum, Germany – Materials Physics, Department of Physics, Uppsala University, Box 530, SE-751 21 Uppsala, Sweden – 3 Institut f¨ ur Kristallographie, RWTH-Aachen, D-52056 Aachen, Germany and Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, D-52425, Germany – 4 European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38000 Grenoble, France 2

Spin-density wave (SDW) state in thin Cr films is known to be under influence of dimensionality (film thickness) and proximity effects from neighboring layers. Here we report on a combined neutron and X-ray scattering study of these effects of H loading on a [Cr(500ML)/V(14ML)]×4 superlattice. The neutron measurements have been performed at the Forschungszentrum J¨ ulich (UNIDAS) while the synchrotron measurements were carried out at the ESRF (ID20). Exposed to a hydrogen atmosphere of up to 1 bar, the sample takes up H quickly. As the dissolved H only resides in the V lattice, it does not influence directly the intrinsic properties of the Cr. It modifies the SDW state via the boundary conditions in proximity with the H-loaded V. It was found that H in the V layers favors the commensurate phase, shifting the commensurate-incommensurate phase coexistence to lower Temperatures. This research was supported by SFB 491 an by the INTAS project ref. nr. 03-51-4778.

Fig. 1: Neutron scattering scans taken in the L direction around the Cr(010) reflection in the H-loaded state (pH2 =100mbar) to explore the SDW polarization. Scans recorded at different temperatures are depicted with an offset in the vertical direction for clarity. The incommensurate phase can be identified by the two satellite reflections at L=±0.04, while the reflection at L=0 is indicative for the commensurate phase.

Magnetismus

Poster: Do., 13:00–15:30

D-P253

Experimental evidence of paired hole states in model high-Tc compounds Andrivo Rusydi1 , P. Abbamonte2 , M. Berciu3 , S. Smadici2 , H. Eisaki4 , Y. Fujimaki5 , S. Uchida5 , M. Ruebhausen1 , G. Sawatzky3 1

University of Hamburg, Hamburg – 2 University of Illinois, Urbana – 3 University of British Columbia, Vancouver – 4 AIST, Tsukuba – 5 University of Tokyo, Tokyo The distribution of holes in Sr14−x Cax Cu24 O41 (SCCO) is revisited with semi-emperical reanalysis of the x-ray absorption (XAS) data and exact-diagonalized cluster calculations. A new interpretation of the XAS data leads to much larger ladder hole densities than previously suggested. These new hole densities lead to a simple interpretation of the hole crystal (HC) recently reported with 1/3 and 1/5 wave vectors along the ladder. Our interpretation is consistent with paired holes in the rung of the ladders. Exact diagonalization results for a minimal model of the doped ladders suggest that the stabilization of spin structures consisting of 4 spins in a square plaquette as a result of resonance valence bond (RVB) physics suppresses the hole crystal with a 1/4 wave vector.

Magnetismus

Poster: Do., 13:00–15:30

D-P254

Magnetic short-range order in CaBaCo3 AlO7 and CaBaCo3 ZnO7 ¨ckel1 Yvonne Sanders1 , Werner Schweika1 , Martin Valldor2 , Thomas Bru 1

Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich GmbH, D-52425 J¨ ulich, Germany – 2 IPKM, TU-Braunschweig, D-38106 Braunschweig, Germany The new cobaltates CaBaCo3 AlO7 and CaBaCo3 ZnO7 have a common structure, in which Co-ions form kagom´e layers leading to high geometrical frustration among the strongly antiferromagnetically coupled Co-spins. The different ions Al and Zn in both compounds choose different sites; Zn prefers sites within the kagom´e layers, while Al occupies sites in between the kagom´e layers. We have performed neutron scattering experiments with polarization analysis to separate the diffuse magnetic scattering, which shows an asymmetric peak, indicating lowdimensional spin correlations. Despite the strong antiferromagnetic coupling between the Co-ions, evidenced from the large negative Curie-Weiss constant, both materials do not exhibit magnetic long-range order down to T=1.2K. The diffuse scattering is similar to predictions for the classical Heisenberg antiferromagnet on the kagom´e lattice, √ √which is supposed to select a ground state of staggered chirality, the so-called 3x 3 structure. For CaBaCo3 ZnO7 the non-magnetic Zn-ions cause spin dilution in the kagom´e layers, resulting in spin disorder among the Co-spins. The non-magnetic Al-ions on the interlayer sites cause a magnetic decoupling of the kagom´e layers and prohibit 3D spin order to take place. [1] M. Valldor, Solid State Sciences 6, 251 (2004); M. Valldor, J. Phys.: Condens. Matter 16, 9209 (2004).

Magnetismus

Poster: Do., 13:00–15:30

D-P255

Transport properties of magnetic tunnel junctions with Co2 MnSi electrode: influence of temperature-dependent interface magnetization and electronic band structure ¨mmerer1 , Oliver Schebaum1 , Jan Schmalhorst1 , Andy Thomas1 , Sven Ka 1 2 ¨tten , Gu ¨nter Reiss1 Marc D. Sacher , Andreas Hu 1

Thin Films and Nano Structures, Department of Physics, Bielefeld University, 33501 Bielefeld, Germany – 2 Institute for Nano-Technology, Research Center Karlsruhe, 76021 Karlsruhe, Germany The transport properties of Co2 MnSi / AlOx / Co-Fe magnetic tunnel junctions showing a tunnel magnetorestistance of 95 % at low temperatures are discussed with respect to temperature dependent magnetic moments at the Co2 MnSi / AlOx interface and electronic band structure effects. These junctions show a considerably larger temperature and bias voltage dependence of the tunneling magnetoresistance compared to Co-Fe-B / AlOx / Co-Fe-B junctions, although the effective spin polarization of Co2 MnSi (66 %) is larger than Co-Fe-B (60 %). With increasing atomic disorder of the interfacial Co2 MnSi its magnetic moments decrease and show a stronger temperature dependence. Even for the best achieved atomic ordering the corresponding spinwave parameters of Mn and Co at the Co2 MnSi / AlOx interface are significantly larger than expected for Co2 MnSi bulk and also larger than the spin wave parameters of Co and Fe at a Co-Fe-B / AlOx interface. The influence of enhanced interfacial magnon excitation in the Co2 MnSi / AlOx / Co-Fe junctions on their transport properties will be discussed.

Magnetismus

Poster: Do., 13:00–15:30

D-P256

Orbital correlations and magnetism in single layered manganites ¨ger2 , Y. Sidis3 , P. Link4 , K. Hradil5 , A. D. Senff1 , O. Schumann1 , F. Kru 6 7 Schneidewind , K. Habicht , W. Schmidt8 , M. Braden1 1

II. Physikalisches Institut, Universit¨ at K¨ oln – 2 Instituut Lorentz, Universitait Leiden 3 – Laboratoire Leon Brillouin, Saclay/France – 4 FRM II, TU M¨ unchen – 5 Institut 6 f¨ ur Physikalische Chemie, Universit¨ at G¨ ottingen – Institut f¨ ur Festk¨ orperphysik, TU Dresden – 7 Hahn Meitner Institut, Berlin – 8 Institut Laue Langevin, Grenoble/France The stable tetragonal crystal structure and the reduced electronic dimensionality in single layered manganites La1−x Sr1+x MnO4 open the way to a detailed study of the complex interplay of several degrees of freedom being relevant for all manganite-oxides [1] and which in the 3d perovskite manganites results in the colossal depression of the electric resistivity under magnetic field. The most studied compound of this family is the half-doped system La0.5 Sr1.5 MnO4 with an equal ratio of three- and four-valent Mn-ions, leading to a complex ordering of charges and orbitals below TCOO . At lowest temperatures this ordering is accompanied by an AFM ordering of the spins of the so-called CE-type, which is characterized by an AFM ordering of FM zigzag chains. Here we present our results of an inelastic neutron scattering study on the magnetic excitations of this complex ordered ground state [2]. We find a very anisotropic magnon spectrum with a steep dispersion along the direction of the FM zig-zag chains and only a weak AFM coupling between adjacent chains. We discus the observed spectrum in terms of linear spinwave theory, and based on a strong next-nearest neighbour exchange we stress the similarity of the magnetic excitation spectrum of the CE-type ordering with that in FM metallic perovskite manganites. To weaken the AFM interchain-coupling and the CE-type structure we studied the doping dependence of the CE-ordering in the region 0.4 ≤ x ≤ 0.6. For the underdoped compound x = 0.4 enhanced diffuse magnetic scattering indeed points to a pertubation of the magnetic coupling between adjacent chains. Although the sample remains insulating a strong FM response of 1.5µB /Mn at fields of 14T seems to somehow connect the single layered manganites with the 3d CMR-perovskites. Upon overdoping with Sr (x > 0.5), we do not observe a significant softening of the interchain coupling, but instead both the charge/orbital and the magnetic ordering get incommensurable, oncemore resembling the observations in the perovskite manganites. [1] D. Senff et al., Phys. Rev. B 71, 024425 (2005). [2] D. Senff et al., cond-mat 0512305, submitted to PRL.

Magnetismus

Poster: Do., 13:00–15:30

D-P257

Magnetismus an implantierten Fe-Atomen in Graphit Rainer Sielemann1 , Yoshio Kobayashi2 , Gunnlaugsson4 , Gerd Weyer4

Yutaka

Yoshida3 ,

Haraldur

1

Hahn-Meitner-Institut Berlin – 2 RIKEN, Japan – 3 Shizuoka Institute of Science and Technology, Japan – 4 University of Aarhus, Denmark

Magnetismus entsteht u ¨blicherweise durch die Wechselwirkung magnetischer Momente von Elektronen, wie z.B. in Materialien mit 3d Elektronen. Ein sehr aktuelles Forschungsfeld ist die Suche nach Stoffen, die normalerweise nicht magnetisch sind aber bei denen durch elektronische oder strukturelle Effekte Magnetismus entstehen kann. Beispiele hierf¨ ur sind organische Magnete oder verd¨ unnte magnetische Halbleiter. ¨ Sehr aktuell sind Hinweise, dass sich Oxyde von Ubergangsmetallen unter bestimmten Umst¨ anden magnetisch verhalten. Graphit als eine Form des Kohlenstoffs ist ein unmagnetisches Material und kristallisiert in einer Schichtstruktur mit sp2-hybridisierten Bindungen innnerhalb der Ebenen und einer van der Waals-artigen Bindung zwischen den Schichten. Das Material kann in hoher Reinheit mit Fremdatomkonzentrationen nicht h¨ oher als im ppm Bereich erhalten werden. Wenig ist bisher u ¨ber die mikroskopische Struktur einzelner Fremdatome bekannt. Eine Arbeit berichtet u ¨ber die Erzeugung von Magnetismus mittels Protonenbestrahlung [1]. Wir haben Eisenatome als 57Fe in sehr hoher Verd¨ unnung (ppm Bereich) in Graphit implantiert und an den Sonden M¨ ossbauereffekt (ME) gemessen. Die Experimente werden mit der In-Beam M¨ ossbauerspektroskopie (IBMS) am ISL Beschleuniger des HMI Berlin durchgef¨ uhrt [2]. Ein 6-Linienspektrum zeigt, dass bei Temperaturen unterhalb 52 K ein statisches Magnetfeld von 32 Tesla an den Sonden vorhanden ist. Die gleichzeitig gemessene Quadrupolaufspaltung (kombinierte Wechselwirkung) und Isomerieverschiebung weisen auf einen interstitiellen Gitterplatz hin. Experimente wurden an Highly Oriented Pyrolytic Graphite (HOPG) und polykristallinem Material ausgef¨ uhrt, Analysen der implantierten Schichten ergaben Frematomkonzentrationen im ppm Bereich. Das Zeitfenster des IBMS betr¨ agt ca. 1 Mikrosekunde. W¨ ahrend dieser Zeit k¨ onnen sich keine Ausscheidungen bilden. Die u ¨berraschende Entdeckung des magnetischen Verhaltens wird diskutiert, es kann dabei unterschieden werden zwischen der lokalen Struktur gemessen u ¨ber den M¨ ossbauereffekt und der Frage, ob es sich hier um eine langreichweitig geordnete Struktur handelt. Eine m¨ ogliche Ursache f¨ ur den Magnetismus k¨ onnten die um das Implantat entstehenden Defekte sein, die selbst magnetische Momente tragen [3] und mit dem Fe-Atom magnetisch koppeln. ¨ Uber weitere Experimente ausgef¨ uhrt am Massenseparator ISOLDE (CERN) und am ¨ ISL Berlin an Oxyden einiger Ubergangsmetalle wird berichtet. [1] P. Esquinazi et al., Phys. Rev. Lett. 91 (2003)227201 [2] R. Sielemann and Y. Yoshida, Hyp. Int. 68 (1991)119 [3] P.O. Lehtinen et al., Phys. Rev. Lett. 93 (2004)187202

Magnetismus

Poster: Do., 13:00–15:30

D-P258

Magnetismus in 214-Ruthenaten Paul Steffens1 , Olaf Schumann1 , Peter Link2 , Yvan Sidis3 , Wolfgang Schmidt4 , Jiri Kulda4 , Satoru Nakatsuji5 , Yoshiteru Maeno5 , Markus Braden1 1

II. Physikalisches Institut, Universit¨ at K¨ oln, Z¨ ulpicher Straße 77, 50937 K¨ oln – 2 FRM3 II, Technische Universit¨ at M¨ unchen, Lichtenbergstr. 1, 85747 Garching – Laboratoire L´eon Brillouin, F-91191 Gif-sur-Yvette Cedex, France – 4 Institut Laue Langevin, Rue Jules Horowitz, F-34802 Grenoble Cedex, France – 5 Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Die einfach geschichteten Ruthenate Ca2−x Srx RuO4 zeichnen sich durch vielf¨ altige interessante Eigenschaften aus: durch isovalente Ersetzung von Sr durch Ca geht aus dem unkonventionellen (Spin-Triplet-) Supraleiter Sr2 RuO4 der Mott-Isolator Ca2 RuO4 hervor. Dazwischen ergibt sich ein Phasendiagramm, das Bereiche sehr verschiedenen strukturellen, elektronischen und magnetischen Verhaltens vereint. Dabei exisitiert in den metallischen Phasen, die den großen Bereich 0.2
Abb. 1: Constant Energy Scans (E=2meV, T=1.5K) bei verschiedenen Magnetfeldern. Ohne Feld dominieren inkommensurabel antiferromagnetische Fluktuationen, bei B=6T hingegen ferromagnetische.

Magnetismus

Poster: Do., 13:00–15:30

D-P259

Investigation of Orbital and Magnetic Order in Ruthenates with Resonant X-Ray Diffraction J. Strempfer1 , I. Zegkinoglou1 , B. Bohnenbuck1 , C.S. Nelson2 , J.P. Hill3 , J.C. Lang4 , G. Srajer4 , Y. Maeno5 , C.T. Lin1 , B. Keimer1 1

MPI/FKF, Heisenbergstr. 1, 70569 Stuttgart – 2 NSLS/BNL, Upton, NY 11973, USA – 3 Department of Physics, BNL, Upton, NY 11973, USA – 4 APS/ANL, Argonne, IL 60439, USA – 5 Department of Physics, Kyoto University, Kyoto 606-8501, Japan Magnetic and orbital order in the 4d electron systems Ca2−x Srx RuO4 and RuSr2 GdCu2 O8 were investigated by resonant x-ray diffraction at the Ru LII and LIII absorption edges from single-crystals. A large resonance enhancement of the scattered signal is observed which is due to electric dipole transitions directly into the partly occupied 4d band. The Ca2−x Srx RuO4 compounds exhibit a rich phase diagram reaching from Sr2 RuO4 , the only known non-cuprate layered perovskite with superconducting properties (Tc = 1.5 K) to Ca2 RuO4 , an antiferromagnetically ordered Mott insulator (TN = 110 K), with an active orbital degree of freedom. Our investigations of Ca2 RuO4 revealed the existence of an orbitally ordered phase with a phase transition temperature of about 260 K [1], which lies well above the antiferromagnetic transition. The propagation vector of the orbitally ordered phase is the same as the one in the low-temperature antiferromagnetic state. The orbital order phase transition is observed also in the x=0.1 Sr-doped compound with a lower critical temperature. The ruthenocuprate system RuSr2 GdCu2 O8 is known for exhibiting both long-range magnetic order of the Ru magnetic moments (TN = 136 K) and superconductivity (Tc ≈ 35 K). Our investigations on a small single crystal allowed the precise determination of the direction of its magnetic moment from the azimuthal dependence of the magnetic scattering intensity. The moment direction was found to differ significantly from the (001) direction, revising conclusions drawn from powder neutron diffraction results. Finally, a possible interaction between the magnetic order and the onset of superconductivity was also investigated. [1] I. Zegkinoglou, J. Strempfer et al., Phys. Rev. Lett. 95 (2005) 136401

Magnetismus

Poster: Do., 13:00–15:30

D-P260

Neutronenbeugungsuntersuchungen zur druckabh¨ angigen magnetischen Struktur in CsCuCl3 ¨ßer1 , Ravil Sadykov2 , Andreas Hoser3 Norbert Stu 1

Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin – 2 Institute for High Pressure Physics RAS, 142190 Troitsk, Russia – 3 Institut f¨ ur Kristallographie, RWTH-Aachen Mittels Neutronenbeugung wurde die Spinanordnung des triangularen Antiferromagneten CsCuCl3 bis zu einem Druck von 23 kbar untersucht. Unter Normaldruck besitzt der hexagonale Perowskit CsCuCl3 in seiner magnetisch geordneteten Phase unterhalb von 10.65 K eine 120◦“Spinstruktur auf dem Dreiecksgitter in der ab-Ebene. L¨ angs ” der hexagonalen c-Richtung formt sich eine langwellige Spirale mit einem Drehwinkel von 5.1◦ zwischen benachbarten Spins [1]. Diese Spinstruktur kann n¨ aherungsweise durch eine Hamiltonfunktion beschrieben werden, die drei Austauschparameter J0, J1 und D enth¨ alt. Man nimmt eine antiferromagnetische Kopplung J1 benachbarter Spins in der ab-Ebene an. Entlang der c-Kette geht man von einer dominierenden ferromagnetischen Kopplung J0 aus, die in Konkurrenz zu einer antisymmetrischen (Dzyaloshinskii-Moriya) Wechselwirkung D steht. Letztere wird m¨ oglich durch die unterhalb von 423K auftretende Jahn Teller Verzerrung der Cl6 Oktaeder, die das Cu2+ Ion umgeben. Untersuchungen der Feldabh¨ angigkeit der magnetischen Struktur u. a. mit Neutronenbeugung haben darauf hingewiesen, dass thermische und quantenmechanische Fluktuationen bedeutsam in diesem Spin 12 System sind. Wenig bekannt ist u ¨ber die Druckabh¨ angigkeit. In diesem Beitrag stellen wir unsere Neutronenbeugungsmessungen vor, die an CsCuCl3 Einkristallen unter Druck bis zu 23 kbar durchgef¨ uhrt wurden. Als wesentliches Resultat erhalten wir eine starke Vergr¨ oßerung des Drehwinkels benachbarter Spins entlang der c-Achse mit zunehmendem Druck. Gleichzeitig beobachten wir eine Zunahme der Neel Temperatur. Dieses Verhalten wird qualitativ unter Ber¨ ucksichtung der im obigen Modell angenommenen Wechselwirkungen diskutiert. [1] K. Adachi, N. Achiwa and M. Mekata J. Phys. Soc. Japan 49 (1980) 545.

Magnetismus

Poster: Do., 13:00–15:30

D-P261

Neutron Diffraction Study of the Manganites Heavily Doped By Fe and Cr Iions I. O. Troyanchuk1 , M. V. Bushinsky1 , K. Baerner2 , H. Szymczak3 1

Joint Institute of Solid State and Semiconductor Physics, National Academy of Sciences – 2 IV. Physikalisches Institut Bunsenstrasse 13, D37073 G¨ ottingen, Germany – 3 Institute of Physics, National Academy of Science, al. Lotnikov 32/36, Warsaw, Poland At present there are many manganite systems studied in which manganese ions are substituted for other 3d- or diamagnetic ones. It is found that Cr and Fe ions have the strongest effect on magnetic properties, small additions of them can result in a change of the ground magnetic state. However the magnetic structure of manganites heavily doped by Cr and Fe is unknown. So we have performed neutron diffraction and magnetic studies for NdMn1−x Fex O3 and NdMn1−x Crx O3 manganites in a wide range of Fe and Cr dopants. Crystal structure of compound with x=0.5 has been refined in space groups Pnma and P21/n. However, the refinement in P21/n group did not improve significantly the reliability factors in comparison with the space group Pnma what points the absence of the Mn and Cr ions ordering. Oxygen octahedron around 3d-ions is rather elongated along one of the axes. This may be expected in the case of Jahn-Teller stabilization of dz2 orbitals of manganese ions. The angles O-Mn/Cr-O and O-Mn/Fe-O are close to 1520, what is much less than in manganites of lanthanum doped with alkaline earth. In NdMn0.5 Cr0.5 O3 the magnetic structure has been revealed consisting of both ferromagnetic and G-type antiferromagnetic components resulting from a 3d-ions magnetic moments ordering. Magnetic moments of Nd-ions are parallel to the ferromagnetic component. In NdMn0.5 Fe0.5 O3 only the antiferromagnetic G-type structure has been revealed whereas Nd-sublattice is not ordered. According to spectroscopic data both Cr and Fe ions in manganites adopt 3+ oxidative state. The magnetic moments of 3d-ions calculated from neutron diffraction data are much less than one can expect in the ionic model where the magnetic moments should be definitely localized. One can suppose the significant part of 3d-ions magnetic moments to be in the spin glass state and not contribute therefore into the coherent magnetic scattering of neutrons. Magnetic phase diagrams have been constructed for the both systems, interpreted assuming superexchange interactions Mn3+ -O-Cr3+ to be positive and Mn3+ -O-Fe3+ negative and taking into account the disordered arrangement of Mn and Cr ions in the crystal structure sublattice. The sign of Mn3+ -O-Mn3+ superexchange interaction is governed with a dynamic nature of Jahn-Teller effect. Magnetic phase separation phenomenon has been ascribed to the intrinsic chemical inhomogeneity of solid solutions.

Magnetismus

Poster: Do., 13:00–15:30

D-P262

Investigations on the coupling between multiferroic and structural properties of BaMnF4 J.R. Veira1 , D.N. Argyriou1 , K. Kiefer1 , U. Amann12 , J.-U. Hoffmann12 , H.N. Bordallo1 , R. Almairac3 , Th. Hangleiter4 1

Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin, Germany – 2 Universit¨ at T¨ ubingen, Institute of Applied Physics, 72070 T¨ ubingen, Germany – 3 Universit´e Montpellier II, F-34095 Montpellier Cedex 5, France – 4 University of Paderborn, Physics Departement, 33095 Paderborn, Germany

In recent years magnetoelectric multiferroics, especially rare-earth manganites like TbMnO3 attracted a lot attention [1]. With the coexistence of magnetic and dielectric order in the same phase interesting coupling effects can arise in those materials. We present investigations on BaMnF4 and BaMn1 − xZnx F4 . BaMnF4 is a well known material, being ferroelectric and antiferromagnetic at the same time for TN <26K [2], and is considered as a model system for the mechanisms underlying the multiferroic materials [3]. We (re)determined the magnetic phase diagram of BaMnF4 using magnetization and specific heat measurements and present data on the bulk magnetization of the Zn doped samples. From diffuse magnetic neutron scattering measurements we resolved the nature of the magnetic short range correlations occurring for T<70K and present exchange interactions for this ordering. BaMnF4 shows an incommensurate phase transition at T≈250K. We investigated the incommensurate structure and phase transition and show the influence of magnetic field and Zn doping on this transition. Finally taking measurements of the dielectric polarization in magnetic field into account we conclude about the coupling between multiferroic and structural properties in BaMnF4 . Our results suggest that the incommensurate phase is directly coupled to the ferroelectric properties and the main magnetic properties just follow the structure. A weak magnetoelectric coupling exists in BaMnF4 but different from the rare-earth manganites this coupling is more by-product than the driving force of the ferroelectric and magnetic properties. [1] M. Fiebig, J. of Phys. D: Appl. Phys. 38 (2005) R123 [2] J.F. Scott, Rep. Prog. Phys. 12 (1979) 1055 [3] C. Ederer. et al., condmat/0605042 (2006)

Magnetismus

Poster: Do., 13:00–15:30

D-P263

Field-Dependent Magnetic Small-Angle Neutron Scattering in Nanomaterials ¨ rg Weissmu ¨ller1,2 , Andreas Michels2 Jo 1

Institut f¨ ur Nanotechnology, Forschungszentrum Karlsruhe, Karlsruhe – 2 Technische Physik, Universit¨ at des Saarlandes, Saarbr¨ ucken When all spins in a ferromagnetic material are aligned in parallel by a sufficiently large applied magnetic field H, then magnetic small-angle neutron scattering (SANS) arises exclusively from the nonuniformity of the magnitude of the magnetization, due to inhomogeneous density or composition. Often, there is a significant, extra magnetic scattering when the field is insufficient to saturate the sample. In bulk samples with a nonuniform magnetic anisotropy, such as nanocrystalline materials, the extra scattering is large even when the sample is a single (macroscopic) magnetic domain, as exemplified by the figures below [1,2]. Here, the scattering originates not from the domain structure, but from the failure of the spins to align perfectly with the direction of the net magnetization. We shall discuss recent progress in understanding magnetic SANS from this spin misalignment, and in characterizing the underlying magnetic interaction terms by analysis of SANS data. The entire H- and q-dependence of d Sigma / d Omega can be understood quite generally in terms of materials parameters, saturation magnetization and exchange stiffness constant, and of the Fourier coefficients of the magnetic anisotropy field, which describe the spatial variation of the magnitude and direction of the anisotropy. By analysis of field-dependent SANS data in terms of this approach one can measure these quantities, which is more difficult or even impossible by other techniques. [1] J. Weissm¨ uller, A. Michels, J.G. Barker, A. Wiedenmann, U. Erb, and R.D. Shull, Phys. Rev. B 63 (2001), 214414/1. [2] J. Weissm¨ uller, A. Michels, D. Michels, A. Wiedenmann, C.E. Krill, H.M. Sauer, R. Birringer; Phys. Rev. B 69 (2004), 054402/1.

Fig. 1: Field-dependent SANS cross-sections of nanocrystalline Co (left; [1]) and Tb (right; [2]).

Magnetismus

Poster: Do., 13:00–15:30

D-P264

Lagenaufgel¨ oste Magnetisierung in d¨ unnen antiferromagnetischen Filmen ¨nter Kaindl1 , Walter So ¨ llinger2 , Eugen Weschke1 , Enrico Schierle1 , Gu 2 Gunther Springholz 1

Institut f¨ ur Experimentalphysik, Freie Universit¨ at Berlin, D-14195 Berlin – 2 Institut f¨ ur Halbleiter- und Festk¨ orperphysik, Johannes-Kepler-Universit¨ at, A-4040 Linz Reduzierte Ordnungsparameter an Oberfl¨ achen und modifizierte kritische Exponenten sind von theoretischer Seite schon lange bekannt [1]. Mit Hilfe resonanter magnetischer R¨ ontgenbeugung konnten wir dieses Ph¨ anomen an dem klassischen HeisenbergAntiferromagneten EuTe experimentell nachweisen. Die große Verst¨ arkung magnetischer Streuung an den M4,5 -Resonanzen der Lanthanide [2] erlaubt die Untersuchung sehr d¨ unner EuTe-Schichten, die mit hoher struktureller Qualit¨ at pr¨ apariert werden k¨ onnen [3]. Abb. 1 zeigt temperaturabh¨ angige magnetische Laue-Profile, gemessen an der Eu-M5 Resonanz bei hν ≈ 1128 eV mit p-polarisierter Synchrotronstrahlung. Der magnetische Braggreflex erscheint hier bei einem Streuwinkel von 2Θ ≈ 90◦ , d.h. fast genau am Brewsterwinkel. Das f¨ uhrt zu einer starken Unterdr¨ uckung der Ladungsstreuung und damit zu einem sehr hohen magnetischen Kontrast im k-Raum. Die hohe Qualit¨ at der magnetischen Daten erm¨ oglicht die Rekonstruktion der Magnetisierungsprofile und damit die Bestimmung der temperaturabh¨ angigen Magnetisierung der einzelnen ¨ Lagen, wie in Abb. 2 dargestellt. Die Ergebnisse sind in exzellenter Ubereinstimmung mit [1] und werden auch durch Monte-Carlo-Simulationen f¨ ur EuTe best¨ atigt. [1] K. Binder and P.C. Hohenberg, Phys. Rev. B 9, 2194 (1974). [2] E. Weschke et al., Phys. Rev. Lett. 93, 157204 (2004). [3] G. Springholz and G. Bauer, Appl. Phys. Lett. 19, 2399 (1993) .

Abb. 1: Temperaturabh¨ angige magnetische Laueprofile von 20 Lagen EuTe (blau). Ladungsstreuung oberhalb von TN (grau).

Abb. 2: Magnetisierung einzelner Lagen (Datenpunkte) und Monte-CarloRechnungen (farbig).

Magnetismus

Poster: Do., 13:00–15:30

D-P265

Lowering of the ordering temperature of FePt nanoparticles induced by He+ ion irradiation Ulf Wiedwald1 , Andreas Klimmer1 , Birgit Kern1 , Hans-Gerd Boyen1 , Paul Ziemann1 1

Abteilung Festk¨ orperphysik, Universit¨ at Ulm, Albert-Einstein-Allee 11, 89069 Ulm

Further reduction of the volume of magnetic nanostructures appears as a natural route towards the enhancement of information density stored by magnetic devices. To overcome thermal fluctuations an extremely large magnetic anisotropy energy density (∼ 107 J/m3 ) is required to stabilize the magnetization of a bit coding magnetic sphere. Chemically ordered FePt particles fulfil this need. Self assembled monolayers (SAM) of ligand-stabilized FePt nanoparticles can be prepared by means of colloidal chemistry [1]. It turns out, that the as-prepared FePt nanoparticles exhibit the lowanisotropy FCC phase, which has to be transformed into the FCT phase by annealing at temperatures larger 600 ◦ C. Such a heat treatment, however, is likely to result in the formation of larger agglomerates of the as-deposited particle ensembles thereby destroying the order of the particle array. Thus, a significant decrease of the ordering temperature would be desirable to maintain the quality of the SAM. One possibility to reduce the transition temperature is the creation of vacancies and interstitials by He+ ion irradiation as observed for FePt films [2]. Here, we make use of a micellar method [3,4] allowing the preparation of arrays of well separated and chemically pure FePt nanoparticles (diameter 3-10 nm) with adjustable interparticle distances of 18-100 nm. In a first experiment, 9 nm FePt nanoparticles were exposed to He+ ions at a dose of 1016 ions/cm2 . SEM images reveal that the irradiated particles are still located at the substrate surface as single units like the untreated ones. The magnetic properties of the particles are investigated by means of x-ray magnetic circular dichroism. The corresponding hysteresis loops of the particles after annealing at elevated temperatures show that as-prepared particles need to be annealed at 620 ◦ C for 30 min or higher to achieve room temperature hysteresis while the phase transformation for particles exposed to He+ ions already starts around 450 ◦ C. [1] S. Sun et al., Science 287, 1989 (2000) [2] H. Bernas et al., Phys. Rev. Lett. 91, 077203 (2003) [3] G. K¨ astle et al., Adv. Funct. Mater. 13, 853 (2003) [4] A. Ethirajan et al., submitted

Magnetismus

Poster: Do., 13:00–15:30

D-P266

NMR and XAS study of Fe-Mo double perovskites Dariusz A. Zajac1,2 , Czeslaw Kapusta1 , Marta Borowiec1 , Marcin Sikora1,3 , Vit Prochazka1,4 , Damian Rybicki1 , Clara I. Marquina5 , Jose M. de Teresa5 , Javier Blasco5 , Manuel R. Ibarra5 1

AGH University of Science and Technology, Faculty of Physics Applied Computer Science, av. Mickiewicza 30, 30-059 Cracow, Poland – 2 DESY Hasylab, Notkestrasse 85, 22 607 Hamburg, Germany – 3 European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France – 4 Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Prague 8, Czech Republic – 5 Universidad de Zaragoza, CSIC c/ Pedro Cerbuna 12, 50009 Zaragoza, Spain The results of molybdenum NMR and XAS measurements at the Fe and Mo K edges of the A2 FeMoO6 double perovskites (DP) (A2 =Sr2 ,SrBa,Ba2 ,Ca2 ) are reported. The information obtained on the individual site electronic and magnetic properties is analysed and discussed. The compounds studied belong to the family of materials exhibiting a huge negative magnetoresistance. Magnetoresistive properties of these compounds arise from their half-metallicity, i.e. only one spin direction being populated in the conduction band, which consists of overlapping spin down 3d Fe, 2p O and 4d Mo electron bands [1]. The molybdenum NMR measurements revealed the existence of a non-integer magnetic moment at Mo and Fe [2,3,4], which can be attributed to the DE-like interaction. The 95 Mo 97 Mo NMR measurements on Fe-Mo DP presented in this work show different values of the Mo hyperfine field and the corresponding Mo magnetic moment. This is attributed to a dependence of the Mo magnetic moment on the structural tolerance factor f related to the ionic radius of the alkaline earth. A similar dependence on f is also observed for TC . This indicates that the strength of magnetic interaction is related to the magnetic moment at the molybdenum site. X-ray absorption measurements in the XANES range provide the Fe and Mo K-edge energies correspond to intermediate valence states of Fe (Mo) between 2.5+ and 3+ (between 5+ and 6+) for all the investigated compounds, with opposite tendencies of the dependence on f. For the compounds Ba2 FeMoO6 and SrBaFeMoO6 a two-step feature of the absorption edge is observed. The step at higher energies is attributed to the iron valence states close to Fe3+ , whereas the lower energy one is attributed to an intermediate Fe valence, in analogy with the XAS spectrum of Fe3 O4 . XANES measurements at the Mo K edge show an intermediate valence state of Mo, similarly to that reported in [7]. A change of the edge energy with f is observed, with the opposite tendency to that obtained for Fe. The results of NMR measurements are compared to those of XANES study and a relation to bulk magnetic and electrical transport properties is discussed. [1] K.-I. Kobayashi, et al., Nature 395, 677 (1998), [2] Cz. Kapusta, et al., JMMM, 242-245, 701, (2002), [3] Cz. Kapusta, et al., JMMM, 272-276, e1619, (2004), [4] D. Zajac, PhD thesis, Cracow-Zaragoza 2006, [5] P.A. Algarabel, et al., JMMM, 226-230, 1089, (2001), [6] J. Linden, et al., Phys. Rev. B, 68, 174415, (2003), [7] J. Herrero-Martin, et al., J. Phys.: Condens. Matter, 16, 6877, (2004).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P267

Untersuchung der Punktdefekte und O-Diffusion in PZT Ferroelektrika Adam Georg Balogh1 , Sebastian Gottschalk1 1

Institut f¨ ur Materialwissenschaft, Technische Universit¨ at Darmstadt, Petersenstr. 23, 64287 Darmstadt F¨ ur die Ver¨ anderung der makroskopischen Eigenschaften in Ferroelektrika sind die Wechselwirkungen zwischen Punktdefekten und deren Agglomeraten mit den Dom¨ anenw¨ anden verantwortlich. Um die Erm¨ udungseigenschaften dieser technologisch wichtigen Materialien besser verstehen und voraussagen zu k¨ onnen, ist die systematische Untersuchung der Defektstruktur und der Diffusion (vor allen der Diffusion von O und O-Leerstellen) notwendig. Verschiedenartig dotierte (La, Nb, Fe, usw.) und zyklierte (erm¨ udete) PZT Proben wurden mit den Methoden der Positronenannihilation (Punktdefekte) und SIMS bzw. NRA (O-Diffusion) untersucht. Die Messung der Positronenlebensdauer und der Dopplerverbreiterung zeigt unterschiedliche Punktdefekte (Einzel- und Doppelleerstellen) in den Proben. Mit Hilfe der SIMS bzw. NRA Messungen werden die Diffusionskoeffiziente f¨ ur Volumen- und Korngrenzendiffusion bestimmt. Die Aktivationsenthalpie stimmt mit den Ergebnissen theoretischer Berechnungen gut u ¨berein. Aus diesen Ergebnissen erhoffen wir neue Kenntnisse u ¨ber die Erm¨ udungsmechanismen in zyklierten PZT Keramiken.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P268

Endotaxie von MnSb auf GaSb(001) Wolfgang Braun1 , Achim Trampert1 , Vladimir M. Kaganer1 , Bernd Jenichen1 , Dillip K. Satapathy2 , Klaus H. Ploog1 1 2

Paul-Drude-Institut f¨ ur Festk¨ orperelektronik, Hausvogteiplatz 5-7, 10117 Berlin – Paul Scherrer Institut, Swiss Light Source, CH-5232 Villigen PSI, Switzerland

MnSb weist eine hohe Curie-Temperatur auf, was es zu einem attraktiven Kandidaten f¨ ur Spininjektoren macht. Insbesondere das Wachstum auf GaSb scheint interessant, da Substrat und Film ein gemeinsames Element besitzen. Wir untersuchen die Molekularstrahlepitaxie von MnSb auf GaSb mittels In-Situ-R¨ ontgenbeugung. Im Gegensatz zu MnAs auf GaAs w¨ achst MnSb auf GaSb endotaktisch, d.h. zwischen den sich ausbildenden, am Wirtsgitter ausgerichteten MnSb-Kristallen wird GaSb aus dem Substrat gel¨ ost und rekristallisert an der Oberfl¨ ache. Bei h¨ oheren Temperaturen bilden sich MnSb-Kristalle mit ebener Grenzfl¨ ache zum Vakuum und n¨ aherungsweise halbkugelf¨ ormiger Gestalt innerhalb des Substrats, die sich entlang der GaSb-(111)-Ebenen ausrichten und in allen drei Raumrichtungen eine sehr geringe Gitterfehlanpassung aufweisen. Die strukturellen Daten sowie Magnetometrie belegen die im Rahmen der Messgenauigeit vollst¨ andige Phasenseparation zwischen MnSb und GaSb. Die nahezu perfekte Struktur sowohl der verwachsenden Kristalle als auch ihrer Grenzfl¨ achen machen das System zu einem interessanten Kandidaten f¨ ur selbstorganisierende SpinInjektorstrukturen.

Abb. 1: In-planeIntensit¨ atsprofile aufgenommen w¨ ahrend der Endotaxie von MnSb auf GaSb. Der Substratreflex besteht aus zwei verschieden breiten Komponenten, die bei h¨ oheren Temperaturen (blaue Kurve) verschmelzen. Die breite Komponente repr¨ asentiert dabei das w¨ ahrend der NiedertemperaturEndotaxie aus dem Substrat herausgel¨ oste Material.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P269

Thermal expansion coefficient of semiconductor multilayer lateral nanostructures ¨ rn Bru ¨ser1 , Victorina Poenariu1 , Ullrich Pietsch1 Bjo 1

Emmy-Noether-Campus, Walter-Flex-Str. 3, 57072 Siegen

The physical properties of III-V semiconductors, in particular lateral nanostructures, are of high interest because they are often used in electronic and optoelectronic devices. Under operation the devices may suffer from thermal expansion resulting in degradation or the creation of defects. The effects of thermal degradation are mainly investigated by trial-and error due to the luck of exact numerical data for the thermal expansion coefficient (TEC). Only values of bulk material are known which are transferred to thin layers or nanostructures without sufficient physical justification. On the other hand it has been shown that the value of TEC strongly depends on strain. Therefore its numerical value changes significantly for pseudomorphic strained layers compared to the relaxed ones [1]. We have performed synchrotron radiation experiment to measure the TEC for pseudomorphically strained semiconductor multilayers before and after lateral patterning. After lateral patterning throughout the whole multilayer we expect reduction of TEC due to partial relaxation of the strained component of the multilayer. The sample we investigate are highly strained InGaAs/GaAs and InGaP/InGaAs strain-balanced multilayers. In non-patterned structures the layers are pseudomorphically strained. Due to the large lattice mismatch between the layers their in-plane lattice parameter tends to adapt to the one of the substrate while the out-of-plane lattice constant increases/decreases. This induces elastic strain at the substrate-multilayer interface. In view of the fact that the thermal expansion coefficient is proportional to the lattice constant, there arises anisotropy of the thermal expansion coefficient. The aim of the experiment is to measure the thermal expansion coefficient at different temperatures. In order to determine the thermal expansion coefficient we measured the rocking curves of the symmetric 004 reflection at different temperatures between room temperature and about 400 ◦ C. This yields the variation of the out-of-plane lattice constants. Furthermore we measured the rocking curves of an asymmetric Bragg reflection or in-plane lattice parameters at different temperatures using synchrotron radiation. The change of both lattice parameters as function of temperature are interpreted in terms of linear elasticity theory using a generalized Keating potential. [1] U. Pietsch et. al., phys. stat. sol. (a) 118 (1990) 209.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P270

GaN and InN core level excitations studied by synchrotron ellipsometry ¨diger Goldhahn2 , Norbert Esser1,3 Christoph Cobet1 , Munise Rakel1,3 , Ru 1

ISAS - Institute for Analytical Sciences, Department Berlin, Albert-Einstein-Str. 9, D-12489 Berlin – 2 Institut f¨ ur Physik, TU Ilmenau, Weimarer Str. 32, D-98684 Ilmenau – 3 Institut f¨ ur Festk¨ orperphysik, TU Berlin, Hardenbergstr. 36, D-10623 Berlin An ellipsometric study on wurtzite InN, wurtzite GaN and zincblende GaN in a spectral region between 12 and 30eV using synchrotron radiation is presented. Especially for InN, relatively few experimental studies of the general optical/electronic properties have been carried out although the recently found small band gap value of 0.7 eV increases the number of possible applications for III-nitride alloys. In the VUV spectral range of 12-30eV the dielectric function is usually determined by electron energy loss rather than ellipsometry. But spectroscopic ellipsometry, however, has a superior spectral resolution and a Kramers-Kronig analysis requiring extrapolation to infinite energies is avoided. The direct determination of the complex dielectric function (DF) with ellipsometry provides full access on the linear optical response and gives valuable information about the electronic structure since the imaginary part is associated with the joint density of states. In the spectral region beyond the plasmon frequency the DF of InN and GaN is dominated by optical transitions between the In4d/Ga3dcore level and the p-like unoccupied (conduction) electron states. Thus the measured structures in the imaginary part give a characteristic view of the p-like conduction bands. The comparison between the experimental spectra and the calculated partial DOS by DFT-LDA shows an overall good agreement. By using linear polarized light in an ellipsometric measurement, the dielectric tensor components corresponding to the electric field vectors along the crystallographic axes, were separately examined. This allows a separation of direction dependent electronic contributions and thus a study of the anisotropy of the chemical bonds in hexagonal crystal structures. With an a-plane InN(1120) and a m-plane GaN(1100) film we observed a considerable polarisation dependence in the DF of hexagonal InN and GaN. That emphasizes the assumption of an anisotropy in the conduction band induced by direction dependent mixing of unoccupied p-orbitals in wurtzite crystals, yielding a pz-DOS different from the px+py-DOS. Low temperature measurements are used in order to determine the electron phonon coupling strength in GaN separately for the p-like conduction bands and the highest valence bands. At low temperature, finally, we could detect also the spin-orbit splitting of the d-bands in InN and GaN by means of synchrotron ellipsometry.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P271

Finite-size effects in the electrical resistance of single bismuth nanowires electrochemically deposited in ion track-etched membranes Thomas W. Cornelius1 , M. Eugenia Toimil-Molares1 , Shafqat Karim2 , Reinhard Neumann1 1

Gesellschaft f¨ ur Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt, Germany – 2 Fachbereich Chemie, Marburg University, Hans-Meerwein-Str., 35032 Marburg, Germany In recent years, nanowires attracted enormous interest due to their possible future applications. When the object size becomes comparable to intrinsic length scales electron mean free path and Fermi wavelength - classical and quantum size effects are expected [1]. Both are large in bismuth compared to conventional metals, making it an ideal material to study on the nanoscale. Polycarbonate foils were irradiated with single swift heavy ions at the UNILAC linear accelerator of GSI and subsequently etched in aqeuous sodium hydroxide. By this means, single-pore membranes were created in which single bismuth nanowires were deposited electrochemically [2]. Thereafter, the wires contacted electrically while left embedded in the template [3]. The mean size of the grains building up the wires was varied systematically by employing different deposition conditions. The specific electrical resistivity is a function of the wire crystallinity. It increases for wires fabricated at lower temperatures and higher potentials, i.e., consisting of smaller grains. These findings are in qualitative agreement with theoretical models about electron scattering at grain boundaries [4]. The wire resistance as a function of the temperature was recorded, revealing a non-monotonic behaviour. It rises, exhibits a maximum, and declines when cooling down from room temperature to 20 K. The resistance maximum shifts to higher temperatures for diminishing diameter and the maximum becomes the higher the smaller the mean grain size is. From the electrical resistance, the carrier mobility was deduced. While the mobility increases more than three orders of magnitude in bulk bismuth when cooling down from 300 to 4 K, it saturates for nanowires at low temperatures. Being a function of mean grain size and wire diameter the mobility is one to two orders of magnitude smaller for nanowires than for the bulk. [1] [2] [3] [4]

V.B. Sandormirskii, Sov. Phys. JETP 25 (1967) 101 T.W. Cornelius, et al., Nanotechnology 16 (2005) S246 M.E. Toimil-Molares, et al., Nanotechnology 15 (2004) S201 A.F. Mayadas, et al., Phys. Rev. B 1 (1970) 1382

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P272

Tiefenaufgel¨ oste Charakterisierung der ioneninduzierten Durchmischung von d¨ unnen Marker-Schichten mittels R¨ ontgenabsorption in Wellenleitergeometrie Nora Darowski1 , Ivo Zizak1 , Ajay Gupta2 , Alexei Erko3 1

Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin, Deutschland – 2 UGCDAE Consortium for Scientific Research, Khandwa Road, Indore, Indien – 3 BESSY, Albert-Einstein-Strasse 15, 12489 Berlin, Deutschland Gew¨ ohnlich erh¨ alt man in R¨ ontgenstreuexperimenten Informationen, die, aufgrund der großen Eindringtiefe, u ¨ber mehrere Mikrometer gemittelt sind. Durch Anregung einer stehenden Welle unter Ausnutzung des Effektes der Totalreflexion kann jedoch eine Tiefenselektion erreicht werden. Die Position der Wellenmaxima bez¨ uglich der ¨ Schichtstruktur kann durch Anderung des Einfallswinkels eingestellt werden. Die Tiefenaufl¨ osung kann weiter erh¨ oht werden, wenn Wellenleiterstrukturen, d.h. zwei Totalreflexionsschichten, verwendet werden. Die Kombination von R¨ ontgenfluoreszenz und R¨ ontgenreflektivit¨ at liefert detailierte strukturelle Informationen u ¨ber das zwischen den Totalreflexionsschichten eingeschlossene Material. Hier werden die Resultate einer tiefenaufgel¨ osten Wolfram-Fluoreszenzanalyse von Si/W/Si-Schichten vorgestellt. Die Vielfachschichten wurden am Ionenstrahllabor des Hahn-Meitner-Institutes mit 600 MeV Au Ionen bestrahlt und anschliessend an der Berliner Synchrotronstrahlungsquelle BESSY analysiert. EXAFS Messungen bei verschiedenen Werten des Impuls¨ ubertrages q, d.h. verschiedenen Intensit¨ atsverteilungen des Wellenfeldes im Schichtsystem, liefern Informationen aus verschiedenen Tiefen. Detailierte Informationen u ¨ber die verschiedenen Phasen, die als Resultat der Bestrahlung in verschiedenen Tiefen gebildet werden, k¨ onnen beim Verst¨ andins der IonenFestk¨ orper-Wechselwirkung sehr n¨ utzlich sein. Im Fall des betrachteten Materialsystems wurden folgende Resultate aus der gleichzeitigen Anpassung der Fluoreszenzund Reflektivit¨ atsdaten erhalten: Mit zunehmender Fluenz nimmt der Anteil der W-Si Bindungen, xW −Si , zu, gleichbedeutend mit einer voranschreitenden Durchmischung. Betrachtet man die W-Si Bindungsl¨ ange RW −Si , so muss man zwei Bereiche unterscheiden. F¨ ur niedrige Ionenfluenzen (5×1012 Ionen/cm2 ) ist RW −Si systematisch kleiner als f¨ ur große Fluenzen (2×1013 Ionen/cm2 ) und nimmt mit zunehmendem Abstand von der Marker-Schicht zu. Dabei sind k¨ urzere Bindungsl¨ angen charakteristisch f¨ ur W-reiche Phasen wie W5 Si3 oder W3 Si, w¨ ahrend l¨ angere Bindungsl¨ angen Si-reichen Phasen wie WSi2 zugeordnet werden. Im Fall hoher Fluenzen u ¨berwiegen W-Si Bindungen deutlich gegen¨ uber Metallbindungen und RW −Si zeigt keine signifikante Abh¨ angigkeit von q. Beides wird als Indiz f¨ ur vollst¨ andige Durchmischung angesehen. Alle Befunde stehen im Einklang mit den Vorhersagen des Thermal-Spike-Modells. Die vorgestellte experimentelle Methode ist nicht nur geeignet die Ionen-induzierte Durchmischung an Grenzfl¨ achen von Schichtstrukturen zu untersuchen sondern erm¨ oglicht dar¨ uber hinaus das tiefenaufgel¨ oste Studium verschiedener Diffusionsprozesse mit einer Aufl¨ osung im Sub-Nanometerbereich.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P273

Structure of silver nanoparticles in glasses and of nanoparticles-glass interfaces characterized by EXAFS ¨ rg Haug1 , Herbert Hofmeister2 , Manfred Dubiel1 , Reinhard Schneider1 , Jo Klaus-Dieter Schicke2 1

Martin Luther University of Halle-Wittenberg, Department of Physics, FriedemannBach-Platz 6, D-06108 Halle, Germany – 2 Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany Silver nanoparticles of 1.5 - 7 nm mean size formed in soda-lime glass by a combination of ion exchange and thermal processing have been studied using extended X-ray absorption spectroscopy (EXAFS) and high-resolution transmission electron microscopy to explore the structural characteristica of these nanoparticles and their interface to the glass matrix. The lattice parameters of particles show a slight lattice dilatation as well as a distinct size-dependent contraction that depends on the amount of iron oxide in the glasses. Temperature-dependent EXAFS spectra (10 K to 300 K) at the Ag K-edge evaluated on the basis of an anharmonic Einstein model indicate an increasing thermal expansion coefficient for Ag nanoparticles with decreasing size. By combination of dilatometric data of the matrix and EXAFS parameters of embedded nanoparticles their state of stress can be qualitatively explained. Averaged Ag-Ag coordination numbers derived from the respective particle sizes are used, together with the known Ag-O coordination number of matrix silver ions, to model the EXAFS-based coordination numbers of Ag species in the glass samples. With that a structural model of the particle-glass interface has been developed under the assumption of Ag-Ag interactions across the interface.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P274

Synchrotron-Aktivierung von Gold-Silikat-Gl¨ asern: XANES-Spektroskopie und Oxidationszust¨ ande Maik Eichelbaum1 , Klaus ¨ rner2 Riesemeier2 , Wolf Go 1 2

Rademann1 ,

Martin

Radtke2 ,

Heinrich

Institut f¨ ur Chemie, Humboldt-Univ., Brook-Taylor-Strasse 2, 12489 BERLIN – Bundesanstalt f¨ ur Materialforschung und -pr¨ ufung (BAM), 12489 BERLIN

Es ist uns gelungen, durch Aktivierung von Gold-Silikatgl¨ asern mit Synchrotronstrahlung ortsaufgel¨ ost Nukleationszentren auf nicht-thermischem Wege zu generieren, die im Verlauf einer anschließenden thermischen Behandlung zu Gold-Nanopartikeln definierter Gr¨ oße und Verteilung wachsen [1]. Um den Einfluss der Synchrotronstrahlung auf die Oxidationszahl zu untersuchen, haben wir Au-L3-XANES-Messungen durchgef¨ uhrt. Bei der Untersuchung von Gold-Nanopartikeln im ppm-Bereich hat sich die XANES-Spektroskopie insbesondere in der qualitativen Analyse von Oxidationszust¨ anden als sehr geeignete Methode bew¨ ahrt. Zum Vergleich wurden als Referenzmaterialien ein Goldfilm mit einer Schichtdicke von 40 nm auf Quarzglas, Gold(I)-cyanid sowie Gold(III)-oxid untersucht. Von einer mit Gold dotierten Glasprobe wurde ein XANES-Spektrum in einem mit Synchrotronstrahlung aktivierten Bereich aufgenommen. Dieses Spektrum sollte sich aus den Referenzspektren additiv zusammensetzen. Deshalb wurden die Spektren des Goldfilms und des Gold(III)-oxids in unterschiedlicher Gewichtung addiert und mit dem Glasprobenspektrum verglichen (Abb. 1). Als Ergebnis geht nun hervor, dass der Kantenbereich des Spektrums des Gold-Silikatglases und des reinen Goldfilms sehr gut u ¨bereinstimmen. Die white line bei 11922 eV deutet auf einen Gold(III)-Nebenanteil im Glas hin. Weiterhin wurde der Oxidationszustand in ultrad¨ unnen Gold(III)-dotierten Glasschichten (Sol-Gel-Methode) untersucht. Hierbei ¨ konnte erstmals mit Au-L3-XANES der Ubergang von dreiwertigem Gold zu elementaren Gold-Nanopartikeln nach einer thermischen Behandlung beobachtet werden. [1] M. Eichelbaum et al., Angew. Chem. 117 (2005) 8118-8122

Abb. 1: Normierte Au-L3-XANES-Spektren verschiedener Goldproben (durchgezogene Linien) und Spektren, die sich additiv aus den Referenzspektren zusammensetzen (gestrichelte Linien): a) Mit Synchrotronstrahlung aktiviertes Gold-Silikatglas; b) Au-Film; c) 0.2 Gold(III)oxid + 0.8 Au-Film; d) 0.6 Gold(III)oxid + 0.4 Au-Film; e) Gold(III)oxid.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P275

Formation of optically active gold nanoparticles in silicate glasses: SAXS studies on synchrotron activated growth Maik Eichelbaum1 , Klaus Rademann1 , Armin Hoell2 , Dragomir M. Tatchev1 , J. Banhart2 1

Institut f¨ ur Chemie, Humboldt-Univ., Brook-Taylor-Straße 2, 12489 Berlin – 2 HahnMeitner-Institut, Department of Structural Research, 14109 Berlin Gold clusters can be generated on demand in metal doped silicate glasses by a newly developed non-thermal activation process based on synchrotron radiation. Nanosized gold particles were obtained in soda lime silicate glasses containing 0.01 mol% Gold(III)chloride. Gold nanoparticles grow during annealing up to 30 min at 550 ◦ C in regions previously irradiated with 32 keV X-rays. The nanoparticles can be probed by their characteristic surface plasmon resonance in the UV/Vis spectrum [1]. In co-operation with Dr. Bernd L¨ ochel of the Anwenderzentrum f¨ ur Mikrosystemtechnologie (AZM), we also succeeded recently to write plasmonic microstructures into the glass by exposure through an x-ray mask. Small plasmonic metal clusters in transparent matrices could play an important role in optoelectronics. Our goal is the measurement of the optical characteristics of the so produced metal clusters as a function of the size, shape, topology and the dielectric environment as well as their optimization for the use in optoelectronic circuits. As a check of the cluster sizes and thus for the controlling of the optical characteristics of our materials it is necessary to understand the growth process of the metal particles. Therefore homogeneity, size distributions and thus the growth of the clusters were examined by (anomalous) small angle x-ray scattering ((A)SAXS) as a function of the temperature and duration of the thermal treatment of the glasses. After background subtraction, the scattering curves were fit with the spherical particle model by the maximum entropy method. Figure 1 shows the differential volume fraction size distributions for two annealing times. It can be seen that nanoparticle size and volume fraction increase with annealing time and that very sharp size distributions were achieved. [1] M. Eichelbaum et al., Angew. Chem. Int. Ed. 44 (2005) 7905

Fig. 1: Size distributions of Au particles in synchrotron activated gold ruby glass after different annealing times.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P276

Structural and electronic properties of highly ordered CuPc thin films on differently passivated vicinal silicon surfaces revealed by Near- Edge X-Ray Absorption Spectroscopy Gianina Gavrila1 , Stefan Seifert1 , Walter Braun2 , Dietrich R.T. Zahn1 1

Chemnitz University of Technology, Semiconductors Physics Department, D-09107 Chemnitz – 2 BESSY GmbH, Albert-Einstein-Straße 15, D-12489, Berlin Organic/inorganic interfaces have attracted considerable attention due to their potential technological applications and because of fundamental research interest. Currently research is not only limited to structural analysis but extended to intentional structural control aiming at the fabrication of molecule based nano-structures on inorganic substrates in order to take advantage of the anisotropic physical molecular properties, for instance, the anisotropic conductivity and the anisotropic light emission. One intriguing way of controlling the in-plane orientation of organic molecules on inorganic substrates is by designing the geometric structure of the substrate surface, e.g. by the steps and terraces of vicinal silicon. Near Edge X-ray Absorption Fine Structure (NEXAFS) investigations of CuPc deposition on hydrogen passivated vicinal Si(111)7x7 clearly reveal that CuPc molecules form structures aligned parallel to the step edges on the substrates with individual molecules laying flat on the terraces. On the other hand, on antimony (Sb)-passivated vicinal Si(111) surfaces the individual molecules are taking a standing upright geometry and the columns of CuPc lie predominantly parallel to the step edge direction. The influence of structural and molecular orientation on the electronic properties of such highly ordered CuPc thin films on differently passivated vicinal silicon surfaces is revealed by core-level and valence PhotoEmission Spectroscopy (PES). By comparison of NEXAFS and PES results with scanning tunneling microscopy images we can state that the two different chemical passivation techniques result in totally different electronic structures in the CuPc thin films on the well-defined vicinal silicon surfaces. This provides an interesting perspective for better control of the electronic properties of CuPc thin film on silicon surfaces with a view to applications.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P277

Absorption of π-conjugated molecules on Cu(111) and Ag(111) Alexander Gerlach1 , Stefan Sellner1 , Frank Schreiber1 , Norbert Koch2 , ¨ rg Zegenhagen3 Tien-Lin Lee3 , Jo 1

T¨ ubingen University, Institute for Applied Physics, 72076 T¨ ubingen, Germany – Humboldt University Berlin, Institute for Physics, Newtonstr. 15, 12489 Berlin, Germany – 3 ESRF, Rue Jules Horowity 6, BP220, 38043 Grenoble, France 2

We study the adsorption of different aromatic molecules such as phthalocyanines and perylene derivatives on Cu(111) and Ag(111) using the X-ray standing wave (XSW) technique. Element specific structural information of high precision is derived from the analysis of XSW yield measurements. Using the core-level photoelectron signals we show that the molecules adsorb in a lying-down configuration, but with different distances relative to the metal substrate. The binding distances between the aromatic ring structure and the metal substrate are generally found to be larger than covalent bond lengths. Furthermore, we discuss more subtle effects as e.g. deformations of the adsorbed molecules [1] that are related to the charge (re)distribution at the interface, which can be discussed in terms of rehybridization. We also discuss our approach of analyzing non-dipolar contributions to the XPS signal [2]. Finally, we discuss recent attempts to determine the bending of aromatic ring structures based on chemical shift in the XPS signal. [1] A. Gerlach et al, Phys. Rev. B 71 (2005) 205425 [2] F. Schreiber et al., Surf. Sci. Lett. 486 (2001) 519

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P278

Anomale R¨ ontgen-Kleinwinkelstreuung zur Analyse von Nanostrukturen in Chemie, Festk¨ orperphysik und Materialwissenschaften ¨nter Goerigk1 Gu 1

Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, c/o DESY-HASYLAB, Notkestr. 85, D-22603 Hamburg Mit R¨ ontgen-Kleinwinkelstreuung kann die Nanostruktur komplexer Materialien auf einer mesoskopischen L¨ angenskala zwischen 1 und einigen hundert Nanometern analysiert und mit makroskopischen Eigenschaften (Photoleitf¨ ahigkeit, Festigkeit, Protonenleitung,...) korreliert werden. Insbesondere gestattet die Anomale R¨ ontgen-Kleinwinkelstreuung unter Verwendung von Synchrotronstrahlung eine nach chemischen Elementen getrennte Analyse. In den letzten Jahren konnten durch eine verfeinerte Messtechnik und eine geeignete mathemetische Formulierung die rein-resonanten Streubeitr¨ age f¨ ur eine Reihe von Materialien aus Chemie, Festk¨ orperphysik und Materialforschung mit einem Anteil an der Gesamtstreuung von wenigen Prozent oder darunter abgetrennt werden. Neben der strukturellen Analyse der r¨ aumlichen Verteilung der einzelnen chemischen Komponenten k¨ onnen quantitative Informationen wie z.B. chemische Konzentrationen in den Nanophasen gewonnen werden. Dar¨ uberhinaus lassen sich die nicht-resonanten Streubeitr¨ age rekonstruieren und aus diesen strukturelle und quantitative Informationen u ¨ber die nicht-resonant streuenden Materialinhomogenit¨ aten (z.B. Hohlr¨ aume oder Wasserstoff-Cluster) gewinnen. Es werden verschiedene Beispiele aus Chemie, Festk¨ orperphysik und Materialwissenschaft vorgestellt. [1] G. Goerigk, and D.L. Williamson, J.Appl. Phys. 99, 084309 (2006)

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P279

Core level shifts in Cu/Ni Heterostructures Determined by High Kinetic Energy Photoelectron Spectroscopy Mihaela Gorgoi1 , Olof Karis2 , Svante Svensson2 , Gabriella Andersson2 , ¨fers1 , Moreno Marcellini2 , Marcel Mertin1 , Mike Sperling1 , Franz Scha Walter Braun1 , Wolfgang Eberhardt1 1

BESSY GmbH, Albert-Einstein-Str. 15, 12489, Berlin, Germany – 2 Department of Physics, Uppsala University, Regementsv¨ agen 1, SE-752 37 Uppsala, Sweden In the present work, results on different Cu/Ni heterostructures studied by high kinetic energy photoelectron spectroscopy are presented. Core level shifts are found as a function of the Cu layer thickness within the multilayer structure as well as a function of the interface type between the copper and nickel. The multilayer samples were grown on MgO(001). Each sample begins with a buffer layer composed of Fe, Pt, Cu and Ni in order to preserve the (001) orientation. While the thickness of the Ni layer was fixed at 5 ML, the thickness of the Cu layer varied. Three samples are studied for Cu thicknesses of 2 ML, 4 ML and 5 ML. The measured core level shifts are found to confirm theoretical calculations of these systems [1, 2]. The multilayer structures were subsequently heated and we have been able to study the destruction of the layered structures from the core photoelectron chemical shifts. Thus we have developed a new non destructive tool to study the quality of deeply buried interfaces. This study may therefore have considerable technical and commercial applicability. [1] W. Olovsson, E. Holmstr¨ om, J. Wills, P. James, I. A. Abrikosov, A. M. N. Niklasson, Phys. Rev. B 72 (2005) 155419. [2] W. Olovsson, E. Holmstr¨ om, I.A. Abrikosov, A.M.N. Niklasson, M. Gorgoi, O. Karis, S. Svensson, G. Anderson, M. Marcellini, W. Braun, W. Eberhardt, manuscript in preparation.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P280

High resolution grazing incidence diffraction on lateral nanostructures created by focused ion beam implantation on semiconductor surfaces Joerg Grenzer1 , Lothar Bischoff1 , Ullrich Pietsch2 1

Forschungszentrum Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, P.O.Box 51 01 19, D-01314 Dresden – 2 Institute of Physics, University of Siegen, Walter Flex 3, 57078 Siegen Ion beam implantation is one of the major technologies in the semiconductor industry. Although there have been a lot of technological applications, there is relatively little known about the structural changes of semiconductors after ion beam implantation at low doses. The focused ion beam implantation technique opens a way to manipulate the device structure locally, on a length scale of a few 10 nm. Of particular interest is the creation of lateral nanostructures by writing any pattern directly into the substrate. We report on the strain and defect analysis of two dimensional dot lattice structures that were produced in GaAs and Si (001) substrates using a 1014 cm−2 dose Ga+ focused ion beam at an energy of 25 keV. The spot size of the focused ion beam was below 50 nm. The structural analysis of the samples was performed utilizing the method of high resolution X-ray grazing-incidence diffraction at the ID01 and ID10 beam lines of the ESRF. X-ray grazing incidence diffraction is a scattering method which combines in-plane Bragg diffraction and out-of plane reflectivity under the condition of X-ray total external reflection from crystalline surfaces. The formation of an evanescent wave propagating parallel but close to the sample surface opens the possibility to probe crystalline surface structures. Moreover, it is possible to change the X-ray penetration depth by tuning the incidence angle in the vicinity of the critical angle αc (the angle at which the X-ray wave starts to penetrate the sample). The use of a laterally periodic wire structure generated on cubic materials makes possible a separate analysis of strain and damage profiles by measuring two symmetry-equivalent in-plane Bragg reflections. Additionally, periodic structure allows us to measure very low strain fields. We performed a detailed structural analysis of the implanted nanostructures that have a small modulation of the lattice constant only and do not possess any measurable density contrast. Therefore, such studies, operating at the resolution limit, are only possible using very high brilliant beam lines at 3rd generation synchrotrons.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P281

X-ray study of ion-induced surface ripples in Si Souren Grigorian1 , Joerg Grenzer2 , Andreas Biermanns1 , Ullrich Pietsch1 , Milan Sanyal3 , Tapas Chini3 , Satyajit Hazra3 1

Institute of Physics, University of Siegen,Walter Flex 3, 57078 Siegen, Germany – Institute of Ion Beam Physics and Materials Research,Bautzner Landstrasse 128, D-01328 Dresden, Germany – 3 Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India 2

Nanopattering at the metal and semiconductor surfaces by ion-beam irradiation has attracted significant technological interest due to possibility for the fabrication of novel nanodevices [1,2]. Recently has been shown, that structural features of the irradiated Si crystals and, especially, crystalline ripples can be studied at the 3rd generation synchrotron radiation sources [3]. In particular, the near-surface ripples pattern can be characterized by depth resolved x-ray grazing incidence diffraction (GID). The GID intensity profiles show the presence of satellite peaks on both sides of the main (220) Bragg peak. The appearance of satellite peaks confirms the existence of lateral undulation of the buried crystalline part of the sample. Additionally to the crystalline part, the amorphization process is very important to understand an amorphous-crystalline interfacial and a ripple formation mechanism. Amorphization features depending on the irradiation dose were probed by means of x-ray grazing amorphous scattering (GIAS). Two broad peaks of the GIAS profiles indicate short-range ordering of amorphous material of the irradiated samples. GIAS profiles taken under different azimuthal angles display a strong anisotropy of the amorphous scattering. A strong damage of crystalline structures takes place along particular crystallographic directions at low doses of irradiation. A complete, mostly uniform amorphization is eminent at high doses of irradiation. This mechanism can be used for a better understanding of the formation of subsurface amorphous-crystalline ripples. We would like to thank ID beamline staff for the support at ESRF. This work was supported by the DST-DAAD India-Germany Collaborative Program. [1] T. Aste and U. Valbusa, New Journal of Physics 7 (2005) 122. [2] C.Hofer, S. Abermann, C. Teichert, T. Bobek, H. Kurz, K. Lyutovich, E. Kasper Nuc. Inst. and Meth. in Phys. Res. B. 216 (2004) 178. [3] S. Hazra, T. K. Chini, and M. K. Sanyal, Grenzer J and Pietsch U Phys. Rev. B 70 (2004) 121307.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P282

Controlling Planar and Vertical Ordering in Three-Dimensional (In,Ga)As Quantum Dot Lattices by GaAs Surface Orientation Daniil Grigoriev1 , Martin Schmidbauer2 , Shahram Seydmohamadi3 , Zhiming ¨fer1 , Michael Hanke4 , Wang3 , Yuri Mazur3 , Gregory Salamo3 , Peter Scha ¨ hler1 Rolf Ko 1

Institut fur Physik, Humboldt-Universit¨ at zu Berlin, D-12489 Berlin, Germany – Institut f¨ ur Kristallz¨ uchtung, D-12489 Berlin, Germany – 3 Department of Physics, University of Arkansas, Fayetteville, Arkansas, 72701, USA – 4 Martin-LutherUniversit¨ at Halle-Wittenberg, D-06120 Halle/Saale, Germany 2

The process of self-organized growth of quantum dots (QD) in Stranski-Krastanow mode is affected not only by elastic properties of the substrate material, but also by physical properties of the surface. Thus, for GaAs (100) surface, due to the 2x4 reconstruction oriented along (01-1) direction the diffusion length in this direction is higher than for the elastically equal (011) direction. As a result, in the case of multilayer InGaAs QD structures under the certain growth conditions [1,2], QD are arranged in chains in (01-1) direction, demonstrating an excellent vertical correlation as well. The diffusion length, and so the type of ordering, could be effectively controlled by introducing the surface steps perpendicular to (01-1) direction, or, in other words, introducing so-called high-index surfaces with controlled miscut towards the (01-1) insurface direction. The surface steps on these surfaces play the role of potential barriers for the material transfer. In order to probe the 3D ordering of QD lattices x-ray diffuse scattering has been monitored three-dimensionally by a special multi-detection technique using a CCD detector [3]. The experiments have been carried out on beamlines W1 and BW2 at HASYLAB/DESY. The surfaces under investigation are GaAs (100) and GaAs (n11)B, where n is equal to 9, 7, 5, 4 and 3. The high index surfaces are tilted towards (111)B surface which forms B-type steps running along [011]-direction. In the talk we will demonstrate that all the samples under investigation show a complex 3D regular QD structure. Vertical ordering is mainly stress-determined, and the angle of the vertical inheritance varies non-monotonically between two limiting cases of (100) and (111)B surface orientation. Pplanar QD ordering is essentially determined by the surface anisotropy of material-transfer. We may contend that the planar ordering evolves from a linear one for (100) surface to an almost rectangular one for the (911)B surface through the set of rhombic- like unit cells and the angle of the rhombus opening angle θ, which depends linearly on the surface step density. The best regularity of the QD structure have been established for the (411)B surface. All the above-mentioned opens the way for controlled processing of highly ordered 3D QD structures with known parameters. [1] Wang et al., Appl.Phys. Lett. 84 (2004) 1931 [2] Yu. I. Mazur et al., Appl. Phys. Lett. 83, 987 (2003). [3] D Grigoriev et al., J. Phys. D: Appl. Phys. 38 (2005) A154A159

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P283

Novel Technique for Investigations of Spatially Ordered Magnetic Nanowires

Natalia Grigoryeva1 , Sergey Grigoriev2 , Helmut Eckerlebe3 , Klaus Pranzas3 , Andrey Eliseev4 , Alexey Lukashin4 , Kirill Napolskiy4 1

St-Petersburg State University, St-Petersburg, Russia, 198504 – 2 Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, Russia, 188300 – 3 GKSS Forschungszentrum, Geesthacht, Germany, 21502 – 4 Moscow State University, Moscow, Russia, 119899 A novel technique for investigations of spatially ordered nickel nanowires embedded into aluminum oxide films is proposed. The aluminum oxide films are considered to be a promising candidate for data storage devices. An aluminum plate is oxidized and the layer (∼ 200µm) of Al2 O3 is then exploited for producing of the hexagonal structure of pores. These pores are treated by C2 H2 O4 during 100 hours. Nickel is electro-chemically introduced inside these pores. The polarized SANS experiments were carried out at the SANS-2 scattering facility of the FRG-1 research reactor in Geesthacht (Germany). An external magnetic field of 1-300 mT was applied in the horizontal plane: perpendicular or parallel to the incident beam. For SAPNS, in general, the cross-section of polarized neutrons consists of nuclear and magnetic contributions, as well as a nuclear-magnetic interference scattering. We determine the total (nuclear and magnetic) scattering as: I(q) = (I(q, P0 ) + I(q, −P0 )). The polarisation dependent part of the scattering is determined as ∆I(q) = (I(q, P0 )I(q, −P0 )) of the intensities for neutrons polarized parallel (+) and anti-parallel (-) to the magnetic field. In our experiments the typical SANS curve contains also the Bragg peak corresponding to the scattering on the regular structure of pores in the aluminum oxide matrix. The introduction of nickel into the matrix does not shift the position of the Bragg peak what makes clear that the matrix was not destroyed by the introduction. The scattering in the small angle range and at the Bragg position increases significantly for the samples with Ni as compared to empty Al2 O3 matrix and it depends on the magnetic field. The field-dependent scattering intensity was extracted as IH (q) = I(q, H) − I(q, 0). The field dependent part IH (q) averaged over the Bragg peak demonstrates a complex hysteretic behavior, which is attributed to the formation of the spacially ordered system of magnetic nanowires. The positive nuclear-magnetic interference ∆I(q) was observed over the whole q-range under study but no or negative interference is visible at the Bragg peak. The interference term shows the correlations existing in system between nuclear and magnetic objects and it is proportional to the average magnetization of the system. In conclusion, the study demonstrates possibility of SAPNS for investigation of the spatially ordered magnetic nanowires embedded into diamagnetic matrix.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P284

Anomalous small-angle X-ray scattering investigation of Ru-Se catalysts supported on carbon Sylvio Haas1 , Armin Hoell1 , Gerald Zehl1 , Sebastian Fichter1 1

Hahn-Meitner-Institut Berlin, D-14109 Berlin

Carbon supported catalysts for use in fuel-cells based on ruthenium and selenium have been prepared at the Hahn-Meitner-Institut in the department solar energy research SE5. They are already tested to be promising catalysts. The aim behind this elements instead of the platinum is expense factor and the deposit of the materials. Another advantage of ruthenium and selenium is the possibility to use them in direct methanol fuel cells (DMFC). Platnium is not useable in this case. By studying the electrochemical behaviour and comparing it to the atomic structure analysed by using EXAFS, XANES, TEM and XRD, many open questions remain [1,2]. One of the main open question is the real nanostructure, which is up to now unclear. Particularly the selenium is important because the catalytic efficiency depends strongly on the content of the selenium and also most probably on its bonds to ruthenium and carbon. Up to now it is clear that most ruthenium form spherical particals with a diameters of about 1nm to 8 nm dispersed on the surface of the black pearls (carbon). Catalysts supported on porous materials like black perls (carbon) are a three phase system (support, voids and metal). The use of synchrotron radiation allows to seperate the scattering of the support from the one of the metal by taking advantage of the socalled anomalous or resonant behavior of the atomic scattering amplitude of an element near its absorption edge [3, 4]. A complete set of samples have been measured at the SAXS instrument (7T-WLSSAXS) at BESSY in Berlin. This means that we measured the final catalysts contains ruthenium, selenium and the support (carbon). We also measured the carbon support only and carbon samples which contains ruthenium only or selenium only on the support. To seperate the scattering of the metals from the strong scattering of the porous carbon particle, which have a diameter of about 50nm (internal surface ∼ 1800 m2 / g BET), combined measurments with X-ray energies near the Ru-K and Se-K X-ray absorption edges have been performed. The ASAXS measurement should help to localize the selenium which could mainly perform a shell surrounding the ruthenium or distributed somewhere in the samples. [1] M. Bron, P. Bogdanoff, S.Fichter, H.Tributsch; J. Electroanal. Chem. 578 (2005) 339 [2] M. Bron, P.Bogdanoff, S. Fichter, I. Dorbandt, M. Hilgendorff, H. Schulenburg, H. Tributsch; J. Electroanal. Chem. 500 (2001) 510 [3] H. Brumberger, D. Hagrman, J. Goodisman, K.D. Finkelstein; J. App. Cryst. 38 (2005) 147 [4] H. Brumberger, D. Hagrman, J. Goodisman, K.D. Finkelstein; J. App. Cryst. 38 (2005) 324

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P285

Structural research on weakly bonded clusters with synchrotron radiation Uwe Hergenhahn1 , Silko Barth1 , Volker Ulrich1 , Sanjeev Joshi1 1

Max-Planck-Institut f¨ ur Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching Results of structural research on a beam of free clusters are reported. We have carried out scans of the partial ion yield from H2 O clusters along the O K-edge. Since recently the NEXAFS spectrum of liquid water along the O K-edge was reported [1] and interpreted with far reaching conclusions on the local structure, it should be of great interest to compare to clusters. Results for the fragments from clusters show features of both hexagonal, four-fold coordinated and broken-bond, threefold coordinated structures in the interpretation of [1]. In NeAr heteroclusters, we can demonstrate a process of electronic relaxation by autoionization, which allows the identification of nearest neighbor relationships in noncovalently bonded systems from the kinetic energy of the autoionization electron. This process was predicted in theoretical work and termed ICD (Interatomic Coulombic Decay) [2]. Transitions of this type should exist in all or most van der Waals and hydrogen bridge bonded systems. [1] P. Wernet et al., Science 304 (2004) 995. [2] L.S. Cederbaum et al., Phys. Rev. Lett. 79 (1997) 4778; J. Zobeley et al., J. Chem. Phys. 115 (2001) 5076.

Fig. 1: Electron spectra from a coexpansion of Ne and Ar. When the beam is cooled sufficiently to allow formation of heteroclusters, a signal from autoionization of Ne 2s hole states into Ne 2p−1 Ar 3p−1 can be detected (left, bottom panel).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P286

Solid state and isotope effects in high–resolution NEXAFS spectra of large organic molecules ¨bner1 , Achim Scho ¨ ll1 , Rainer Fink2 , EberFlorian Holch1 , Dominique Hu hard Umbach1 1

Universit¨ at W¨ urzburg, Experimentelle Physik II – 2 Universit¨ at Erlangen, Physikalische Chemie II The interaction between most large organic molecules in the solid state is commonly believed to be solely due to electrostatic and van–der–Waals forces. An analysis of these intermolecular effects requires a comparison of high–quality spectroscopic data of gaseous and condensed organic molecules. We present high–resolution NEXAFS spectra of organic molecules with aromatic ring systems (naphthalene, NTCDA (1,4,5,8– naphthalene–tetracarboxylic acid dianhydride) and ANQ (acenaphthenequinone)) in the gas phase and solid state.

For the NTCDA and ANQ gas phase experiments a new experimental set–up has been used that allows the measurement of free molecules with high sublimation temperatures. A detailed Franck–Condon analysis of the vibronic fine structure of the NTCDA spectra at the C–K edge yields consistent results for both phases. In contrast, pronounced differences in the electronic features between gas phase and condensate can be demonstrated. This corroborates the results for ANQ that also suggest an involvement of the π ∗ –orbitals of the aromatic core in the intermolecular interaction. Our findings thus indicate that intermolecular forces can be much stronger than commonly believed and may cause the formation of intermolecular bonds. Moreover, we will present results of NEXAFS investigations on naphthalene and fully deuterated naphthalene in the gas phase [1]. The differences in the spectroscopic signatures of the two isotopes strongly suggest significant contributions of C–H (C–D) and C–C vibrational modes in contrast to theoretical results [2]. This is corroborated by a comparison with similar spectra of (deuterated) benzene, which allows the identification of at least two C–H (C–D) modes and one C–C mode. This work has been financially supported by the BMBF (projects 05KS4WWC/2, 05SF8WWA7 and 05KS1WWA5). Traveling benefits to perform the experiments at ELETTRA were provided by the EU through the VI Framework program for transnational access, under Contract No. RII3-CT-2004-506008 (IA-SFS). [1] D. H¨ ubner et al., Chem. Phys. Lett. 415 (2005) 188 [2] I. Minkov et al., J. Chem. Phys. 121 (2004) 5733

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P287

Long-range order in thin epitaxial Fe3 Si films grown on GaAs(001) Vladimir Kaganer1 , Bernd Jenichen1 , Jens Herfort1 , Dillip Satapathy1 , ¨ nherr1 , Wolfgang Braun1 , Klaus Ploog1 Hans-Peter Scho 1

Paul-Drude-Institut f¨ ur Festk¨ orperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

As-grown thin epitaxial Fe3 Si films fabricated by molecular beam epitaxy on GaAs(001) are studied by grazing incidence x-ray diffraction. The long-range order parameters of the films of different stoichiometry are determined by measuring fundamental and superlattice crystal truncation rods and comparing them to simulations in dynamical approximation. Two order parameters, associated with the degree of migration of Si atoms into different Fe sublattices, are obtained. A residual intermixing of the sublattices is found, even near complete stoichiometry. The relative positions of the Fe3 Si and GaAs lattices are determined. Fe atoms in Fe3 Si are located at the positions of the Ga atoms in GaAs, with an additional shift of 0.1±0.04 ˚ A of the tetragonally distorted Fe3 Si lattice normal to the interface. Figure 1 combines crystal truncation rod scans performed at different bulk reflections on one of the samples. The layer peak is fairly close to the substrate peak, indicating that the sample is nearly stoichiometric. The 004 and 022 reflections are not sensitive to disorder. The 002 and 222 reflections are influenced by disorder in the Fe(A,C) sublattice, and the 111, 311, and 113 reflections are sensitive to disorder in both sublattices Fe(B) and Fe(A,C). All measured curves were fitted simultaneously by dynamical diffraction calculations. We obtain the order parameters from the relative intensities of the layer peaks (with the substrate peak serving as an internal reference), the layer thickness from the oscillation period and the registry of the lattices from the phase of the oscillations. We find that the as-grown Fe3 Si layer is not fully ordered, although it is nearly stoichiometric. Approximately 30 % of Si has left its sublattice D and exchanged with the Fe(A,C) atoms. The Si atoms did not exchange with a Fe(B) atoms.

Fig. 1: Measured (thicker gray lines) and fitted (fine black lines) crystal truncation rods near different reciprocal lattice points. The fits of all curves are performed simultaneously with one and the same set of parameters. The coordinate L along the crystal truncation rods has its origin at the respective GaAs peak.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P288

Growth and Oxidation of Pd/ZnO(001) nanoparticles Nikolai Kasper1 , Andreas Stierle1 , Alexander Reicho1 , Philipp Nolte1 , Mitsuhiro Saito1 , Thomas Wagner1 , Helmut Dosch1 1

Max-Planck-Institut f¨ ur Metallforschung, Heisenbergstr. 3, D 70569 Stuttgart, Germany Understanding and controlling chemical reactions involving nanoparticles are important milestones for future nanotechnologies and for the enhanced performance of catalysts used in many applications. One key phenomenon is the oxidation behavior of metal nanoparticles under industrially and environmentally relevant conditions, which needs to be understood on a microscopic level. We report in this work the results of the in-situ synchrotron X-ray diffraction study of the high-pressure and high-temperature oxidation of Pd nanoparticles supported on ZnO(001) substrates. These particles grow as truncated triangular bi-pyramid, restricted by (111), (100) and (110) type of free faces [1]. We have observed the reversible changes of the morphology of the particle √ facets√vs. oxygen pressure (p O2 < √ √ 10−4 mbar), however neither ( 5 × 5)R27◦ nor ( 6 × 6) surface oxides have been found, which form during the oxidation of Pd(100) and Pd(111) single crystalline surfaces, respectively [2, 3]. The details of the bulk oxide formation have been obtained and compared with the results for Pd(100) [4] and Pd(111) [5] single crystalline surfaces and for Pd nanopaticles deposited on other types of substrates, such as α-Al2 O3 (001) and MgO(001) [6]. We demostrate that bulk PdO grows in the case of ZnO(001) - supported Pd nanoparticles at much lower pressures than for the other mentioned systems. We suggested that this feature is related to the polar nature of ZnO(001) surface. Financial support of this work is acknowledged from the European Union under contract no. NMP3-CT-2003-505670 (NANO2). [1] C.R. Henry, Surf.Sci.Rep. 31 (1998) 231; C.T. Cambell, Surf.Sci.Rep. 27 (1997) 1. [2] M. Todorova et al., Surf. Sci. 541 (2003) 101. [3] G. Zheng, E.I. Altman, Surf. Sci. 462 (2000) 151. [4] A.Stierle et al., J. Chem. Phys. 122 (2005) 044706; E. Lundgren et al., Phys. Rev. Lett. 92 (2004) 046101. [5] G. Ketteler, et al., J. of Am. Chem. Soc. 127 (2005) 18269. [6] N. Kasper et al., Surf. Sci., in print.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P289

Magnetic and structural properties of deposited 3d transition metal nanoparticles Armin Kleibert1 , Johannes Passig1 , Karl-Heinz Meiwes-Broer1 , Joachim Bansmann2 , Renate K. Gebhardt3 , Furkan Bulut3 , Mathias Getzlaff3 1

Institut f¨ ur Physik, Universit¨ at Rostock, D-18051 Rostock, Germany – 2 Abt. Oberfl¨ achenchemie und Katalyse, Universit¨ at Ulm, D-89069 Ulm, Germany – 3 Institut f¨ ur Angewandte Physik, Universit¨ at D¨ usseldorf, D-40225 Germany Free clusters and nanoparticles are not just small pieces of material with physical properties nearly identical to the bulk. Their electronic, optical and magnetic properties are clearly size-dependent with a non-linear behaviour between the two general limits given by the atomic and the bulk-like behaviour [1]. In this contribution we compare the magnetic properties of mass-filtered Fe, Co and FeCo nanoparticles being deposited onto different epitaxially grown thin films. The crystallographic structure and morphology of the particles have been determined independently by means of electron diffraction and high resolution transmission electron microscopy (HRTEM), respectively (cf. Fig. 1). The magnetic moments of the clusters have been measured in situ via X-ray absorption spectroscopy (XAS) as well as magnetic circular dichroism (XMCD) after deposition onto ferromagnetic films. Moreover we will discuss the presence of self-saturation effects in the nanoparticle spectra (cf. Fig. 2). [1] J. Bansmann et al., Surface Science Reports, 56 (2005) 189

Fig. 1: High resolution transmission image of an iron nanoparticle with a diamter of about 12nm,

Fig. 2: Top: comparison of a nanoparticle TEY spectra with a reference spectrum. Bottom: simulated spectrum confirming the presence of selfsaturation effects.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P290

Thin Film and Multilayer Analysis with Synchrotron Radiation Induced X-ray Standing Waves ¨mer1 , Alex von Bohlen1 , Christian Sternemann2,3 , Roland HerMarkus Kra ¨ der1 genro 1

ISAS - Institute for Analytical Sciences, Bunsen-Kirchhoff Str.11, 44139 Dortmund, Germany – 2 Experimentelle Physik E1a, University of Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund, Germany – 3 DELTA, University of Dortmund, Maria-GoeppertMayer-Str. 2, 44221 Dortmund, Germany With the help of X-ray standing waves (XSW) it is possible to characterize thin films, layered structures and surface depositions as well as element concentration distributions on a nanometer scale. XSW measurements are fast, easy and element specific. However, several elements can be observed simultaneously by an energy dispersive detector. The obtained curves represent a characterization in depth of the layer-structure and element distribution of the observed samples. XSW can be performed on conducting and nonconducting samples, and vacuum is not necessary in most cases. The existence of one or several reflecting interfaces is virtually the only condition to the sample. Thus samples can be characterized with little preparation. Synchrotron radiation as photon source for XSW measurements has several advantages: The photon flux is much higher than the flux from an X-ray tube, the photon energy can be chosen in a wide range from below 1 keV to more than 30 keV to utilize the energy most suitable for a certain kind of sample, and radiation is sufficiently monochromatic and longitudinally coherent enough to generate the desired X-ray Standing Waves. Various types of thin film and multilayer samples have been observed at DELTA synchrotron, Dortmund, using XSW. Together with several analyzing computer programs developed in the framework of this project, measurements and results of thickness, periodicity and element composition will be presented.

Fig. 1: Calculated XSW intensity field above a Si wafer for E=10 keV.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P291

Structure determination of very small semiconductor nanoparticles using synchrotron radiation Christian Kumpf1 , Franziska Niederdraenk1 , Pawel Luczak1 , Sanjeev Joshi1 , Reinhard Neder2 , Eberhard Umbach1 1

Experimentelle Physik II, Universit¨ at W¨ urzburg – 2 Lehrstuhl f¨ ur Mineralogie, Universit¨ at W¨ urzburg Semiconductor nanoparticles are of increasing interest for both, applied and fundamental research. Besides applications in material science, they are used as markers in biology and for cancer treatment. Nanoparticles in the diameter range from 1-5 nm are of particular interest in fundamental research since they represent a size scale between solid state and molecular physics which is difficult to investigate. The structural, electronic optical and magnetic properties of particles in this size range are very often not known and understood. Even a precise determination of basic geometrical parameters like the size and shape is difficult. Potentially, diffraction methods are able to provide complete structural information, but common analysis methods do not yield sufficiently precise results in the particle range below 5 nm. We present a new approach for the analysis of synchrotron radiation diffraction data (XRD) obtained from small particles. The experiments were performed at HASYLAB, Hamburg. The entire particle is modeled, and its diffraction pattern is computed using the Debye formula. This allows us to address not only fundamental parameters like size and crystal structure, but also shape, stress, relaxation effects, and stacking faults. In contrast to common analysis methods these essential structural features are explicitly taken into account as intrinsic parameters of the nanoparticle model. An ensembleaveraging is performed and hence the parameter distributions, most prominent the size distribution of the particles, can be determined. This is enabled by using a stochastic fit algorithm. Furthermore, we report on photoelectron spectroscopy experiments (PES) performed at BESSY, Berlin. The use of synchrotron radiation at different wavelength allows to vary the surface sensitivity of the measurement. Additionally core level shifts are utilized to identify different atomic species, for example atoms with different chemical bonds and in different coordinations. The combination of a quantitative analysis of chemically different species with that of their bulk- vs. surface sensitivity is utilized to determine the location of various atoms within the nanoparticle. This approach has been applied in detail to CdS particles resulting in an atomic model which is consistent with the XRD results. We believe that our two approaches enable a new access to detailed structural parameters of small nanoparticles and improve the knowledge about growth mechanism and particle formation.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P292

Triblock / diblock copolymer blend films: Structural analysis of spin-coated and solution-casted films with GISAXS ¨ rstgens1 , M.M. Abul Kashem1 , S. Stu ¨ber1 , S.V. Roth2 , P. Mu ¨llerV. Ko 1 Buschbaum 1 2

TU M¨ unchen Physik-Department E13, James-Franck-Str. 1, D-85748 Garching – HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg

Triblock copolymers are known to adopt nano-separated structures in case of immiscibility of the individual blocks. For the triblock copolymer styrene-isoprene-styrene of different block lengths highly ordered structures like lamellae, spheres or cylinders have been found. The different morphologies have a great impact on the mechanical properties of these materials. The system under investigation is a blend of styrene-b-isoprene-b-styrene (SIS) triblock copolymer with styrene-b-isoprene-(SI) diblock copolymer. Additional a naphtenic oil and an antioxidant are added components of the mixture. Polymer films were prepared from toluene solution on glass slides by two different procedures. On the one hand spin-coating technique was applied and on the other hand films were solution casted and dried. The obtained films differ markedly in thickness: 340 nm for the spin-coated film and 100 µm for the solution-casted film. Grazing incidence small angle scattering (GISAXS) has been chosen as it is a nondestructive probe allowing scattering with statistical information not only on the surface illuminated, but also on the bulk sample. The GISAXS measurements were performed at the beamline BW4 of the HASYLAB/DESY in Hamburg. Major goal of the comparison of thin and thick SIS/SI blend films is the separation of bulk and surface structures, where it has to be taken in account that the 2D GISAXS pattern is in fact the superposition of the bulk and the surface scattering signal. A typical indication of bulk structures with a powder like orientation is the occurrence of ring shaped intensity centered around the direct beam, which is most prominent for the solution casted sample. In contrast, the diffuse scattering from the thin spin-coated film is dominated by the presence of a side maxima close to the Yoneda peak, indicating a highly ordered surface structure. It is also weakly present in the scattering from the thick film. From the 2D detector pattern with a cut at constant scattering angle ψ =0 correlation with structures perpendicular to the surface can be obtained. In an outof-plane cut at constant exident angle af at the critical angle of polystyrene in-plane structures can be allocated. Additionally cake cuts centered around the direct beam have been performed which is equivalent to SAXS treatment of data. Model structures based on the scattering results for the spin-coated and the solutioncasted SIS/SI blend are presented.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P293

Innershell excitation of free nano particles ´ Lewinski2 , Peter Brenner2 , RoBurkhard Langer1,3 , Harald Bresch2 , Rene 2 2 man Flesch , Christina Graf , Tatiana Martchenko4 , Omair Ghafur4 , Marc ¨hl1 J. J. Vrakking4 , Eckart Ru 1

Institut f¨ ur Chemie und Biochemie, Freie Universit – 2 Institut f¨ ur Physikalische Chemie I, Universit¨ at W¨ urzburg, Am Hubland, 97074 W¨ urzburg – 3 Max-Born-Institut f¨ ur Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin – 4 FOM Institute AMOLF, Amsterdam, The Netherlands Using a continuous particle beam we have studied inner shell excitations in free nano particles when they were exposed to monochromatic synchrotron radiation. This approach goes beyond related work, where elastic light scattering has been studied in the vacuum ultraviolet regime [1,2]. It is also complementary to single, trapped nanoparticles that have been studied by synchrotron radiation in the soft x-ray regime [3]. Our particles were transferred into the gas phase by an aerosol generator. An additional differential mobilisation analyser (DMA) made it possible to generate a continuous beam of size selected nano particles that was focussed into the vacuum chamber by an aerodynamical lens. This approach allowed us to prepare free nano particles which were produced by colloidal chemistry. We have measured the total electron yield in order to characterise the electronic structure of nano particles in the region of their inner shell excitations. First experiments were performed on size selected NaCl nano particles (radius: 50-175 nm) in the region of the Cl 2p and the Na 1s excitation. Measurements in the region around the O 1s absorption threshold show that these particles contain only little water. In contrast, nanoscopic salt particles (Na2 SO4 ·10 H2 O) that contain chemically combined water show a significant absorption in this region which might be of interest to study the binding structure of such water. In addition, we have studied the influence of coatings to the electronic structure of free core-shell particles. Here we used ZnS particles (radius = 60 nm) with a 5 nm SiO2 shell. This work is supported by the Bundesministerium f¨ ur Bildung und Forschung (BMBF) grant no.: 05 KS4WW1/7 and the Deutsche Forschungsgemeinschaft (SFB 410-TP C8) [1] J.N. Shu, K.R.Wilson, M. Ahmed, S.R. Leone, C. Graf, E. R¨ uhl, J. Chem. Phys. 124, 034707 (2006). [2] J.N. Shu, K.R.Wilson, A.N. Arrowsmith, M. Ahmed, S.R. Leone, Nano Lett. 5, 1009 (2005). [3] M. Grimm, B. Langer, S. Schlemmer, T. Lischke, W. Widdra, D. Gerlich, U. Becker, R. Flesch, E. R¨ uhl, Phys. Rev. Lett. 96, 066801 (2006).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P294

Electronic Structure of Free and Supported Transition Metal Clusters Tobias Lau1 , Vicente Zamudio-Bayer1 , Leif Glaser2 , Theresa Schadow1 , Marlene Vogel1 , Jochen Rittmann1 , Wilfried Wurth2 , Bernd von ¨ ller1 Issendorff3 , Thomas Mo 1

TU Berlin, IAPF, PN 3-1, Hardenbergstraße 36, 10623 Berlin – 2 Universit¨ at Hamburg, Institut f¨ ur Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg – 3 AlbertLudwigs-Universit¨ at Freiburg, Fakult¨ at f¨ ur Physik, Stefan-Meier Straße 21, 79104 Freiburg Electron localization and correlation are important factors determining the electronic structure of 3d transition metals. In free 3d transition metal atoms, Coulomb interaction of the 2p core hole with the localized 3d electrons leads to multiplet splitting of the L2,3 absorption lines. In bulk transition metals, valence electrons are partially delocalized. In addition, multiplet splitting might be masked by line broadening. The issue of electron localization/delocalization and correlation in the transition from single atoms to bulk metals can ideally be addressed in the investigation of size-selected transition metal clusters. So far, however, the 3d multiplet structure in L2,3 X-ray absorption of deposited small metals clusters has not been observed neither on metal nor on HOPG substrates. We report here on the first study of the multiplet structure of small, mass selected chromium and cobalt clusters deposited on thin potassium films as well as on Cu(100). Potassium films were chosen as substrates, since 3d transition metal impurity atoms on alkali metal films show highly localized atomic configurations. A preliminary analysis of the experimental data suggests that the same atomic-like components might also be visible in small clusters. In addition to investigations on mass selcted, deposited clusters, first results on X-ray absorption spectroscopy on free transition metal clusters will be presented.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P295

Highly ordered self-organized copolymer-nanoparticle composite films studied by specular reflectometry and off-specular neutron scattering V. Lauter-Pasyuk1,2 , H. Lauter2 , M. Jernenkov2,3 , B. Toperverg4 , P. ¨ller-Buschbaum1 , W. Petry1 Mu 1

TU M¨ unchen, Germany – 2 ILL, Grenoble, France – 3 JINR, Dubna, Russia – 4 PNPI, Gatchina, Russia How to organize complex materials at the nano-scale is investigated with neutron grazing incidence techniques (specular reflection, off-specular scattering and grazing incidence small angle scattering). A “smart” method based on the principle of selforganization is employed to construct new nano-composite materials containing a high density of magnetic nano-particles arranged into well ordered regular block-copolymer lamellar structures. We investigated how the particle concentration and particle size affect the architecture of the composite film. New morphologies predicted theoretically [1] are obtained and explored in our studies. The creation of the nano-sheets was followed up to the destruction of the ordering of the nanoparticles and of the polymer lamellar structure. We show that the details of the internal structure of composite films are encoded in the two-dimensional map of the intensity scattered by the film and can be extracted via the quantitative data analysis. A dedicated theoretical approach based on the distorted-wave Born approximation (DWBA) is developed for the analysis of the full two-dimensional intensity. This approach will be applied to a wide range of technologically important systems and can be used to design novel composite architectures. This research project has been supported by the BMBF under the project No 03DU03MU. [1] R.B. Thompson et al., Science 292, 2469 (2001)

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P296

The dielectric function of zinc-tetraphenylporphyrin from near infrared to vacuum ultraviolet energy Daniel Lehmann1 , John Sindu1 , Ovidiu D. Gordan1 , Marion Friedrich1 , Christoph Cobet2,3 , Simona Silaghi3 , Norbert Esser3 , Walter Braun4 , Dietrich R.T. Zahn1 1

Institut f¨ ur Physik, TU Chemnitz, Reichenhainerstr. 70, 09107 Chemnitz, Germany – Institut f¨ ur Festk¨ orperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany – 3 ISAS Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 4 BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany 2

Zinc-meso-tetraphenylporphyrin (ZnTPP) layers are used in organic opto-electronic devices such as organic light emitting devices (OLEDs) and organic photovoltaic (OPV) solar cells as p-conducting active layer [1-2]. The dielectric properties of those layers are crucial for the functionality of opto-electronic devices. Here we present the dielectric function of ZnTPP in the range from 0.73 eV to 9.6 eV determined by Spectroscopic Ellipsometry. The layers for this study were grown by Organic Molecular Beam Deposition (OMBD) on silicon substrates. In the range from 0.73 eV to 5.0 eV the characterization was performed by Variable Angle Spectroscopic Ellipsometry (VASE). The results show an anisotropic behaviour. The tilt angle of the molecules with respect to the substrate was determined to be (29 ± 3)◦ . This was verified by infrared spectroscopy. Measurements in the range from 4.0 eV to 9.6 eV were performed at the Vacuum-Ultraviolet-Ellipsometry beamline at the synchrotron radiation source BESSY II. At an energy of 6.4 eV a strong absorption feature appears, which was not reported before. Measurements with synchrotron radiation in the VUV energy range are more sensitive for ultra-thin films due to the smaller wavelength. Results of ultrathin ZnTPP films investigated at BESSY II are presented. [1] K. Takahashi et al., Synthetic Met. 155 (2005) 51-55. [2] Y. Kim et al., Solid-State Electron. 48 (2004) 633-644.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P297

Der Einfluß von unoxidiertem Mg auf die Spinpolarisation der elektronischen Bandstruktur an der Fe(001)/MgO Grenzfl¨ ache ¨ller1 , Claus M. Schneider1 Frank Matthes1 , Martina Mu 1

Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, 52405 J¨ ulich

Wir berichten u ¨ber neue Ergebnisse zur Spinpolarisation an der Grenzfl¨ ache des Systems Fe(001)/MgO, die mittels spinaufgel¨ oster Valenzband-Photoemissionsspektroskopie an dem Undulatorstrahlrohr des Forschungszentrums J¨ ulich in Dortmund (DELTA) erzielt worden sind. Die durchgef¨ uhrten Untersuchungen zeigen eine deutliche ¨ Anderung der Spinpolarisation der elektronischen Bandstruktur, wenn die Zusammensetzung der MgO-Schicht von der idealen St¨ ochiometrie abweicht und sind von Bedeutung f¨ ur das grundlegende Verst¨ andnis von Systemen, die einen spinabh¨ angigen Widerstand in Schichtstrukturen mit einer Tunnelbarriere zeigen, den so genannten Tunnelmagnetowiderstandseffekt (TMR-Effekt). Das TMR-System Fe/MgO/Fe zeichnet sich vor allem durch seine Epitaxie aus, die theoretischen Modellen [1,2] zur Folge TMR¨ Anderungen bis zu mehreren 100 % erlaubt. Die ersten Messungen an entsprechenden Schichtstrukturen mit hohen TMR Werten (180 % bzw. 220 % bei Raumtemperatur) erfolgten 2004 in den Gruppen von Yuasa und Parkin[3,4]. Im Vordergrund der Diskussion stand dabei der Einfluß der Struktur und der Elektrodenmaterialien (Fe, FeCo). Aber auch die chemische Beschaffenheit der Grenzfl¨ ache ist von großer Bedeutung. So ließen schon 2001 mit R¨ ontgenstrahlung durchgef¨ uhrte oberfl¨ achenempfindliche Beugungsexperimente an der MgO/Fe Grenzfl¨ ache die m¨ ogliche Bildung einer FeO Zwischenschicht vermuten [5], die theoretischen Berechnungen zufolge zu einer Reduzierung des TMREffektes f¨ uhrt [1]. In unseren Messungen konnten wir nun eine starke Erh¨ ohung in der Spinpolarisation der elektronischen Bandstruktur an unteroxidierten“ MgO-Schichte ” nachweisen. F¨ ur die spinaufgel¨ osten Photoemissionsexperimente in DELTA wurden unter Ultrahochvakuumbedingungen 10 Monolagen dicke Eisenschichten epitaktisch auf einkristalline GaAs(100)-Substrate aufgedampft. Die Struktur der Eisenschicht wurde mit niederenergetischer Elektronenbeugung u ¨berpr¨ uft. Es folgte das Aufdampfen einer Monolage Magnesium, wobei durch Wahl eines geeigneten Sauerstoffpartialdruckes in der Anlage die Oxidation der Mg-Schicht eingestellt wurde. Das Verh¨ altnis von oxidiertem zu unoxidiertem Magnesium wurde durch Photoemissionsspektroskopie am Mg 2p Niveau bestimmt. Die daran durchgef¨ uhrten spinaufgel¨ osten Photoemissionsmessungen (n¨ ahere Beschreibung [7]) zeigen einen klaren Zusammenhang zwischen dem Anteil von unoxidiertem Magnesium und der gemessenen Spinpolarisation in der elektronischen Bandstruktur. So erh¨ ohte sich der Wert einer reinen Eisenschicht von 35 % auf 65 % bei einer Bedeckung mit einer Magnesiumschicht, die nur zu 60 % oxidiert war. Eine vollst¨ andige Oxidation der Magnesiumschicht reduzierte die Spinpolarization auf 35 %. [1]W.H. Butler et al.,PRB 63(2001) 054416. [2]J. Mathon et al.,PRB 63(2001) 220403. [3]S. Yuasa et al.,Nature Mat. 3(2004) 868. [4]S.S.P. Parkin et al.,Nature Mat. 3(2004) 862. [5] H.L. Meyerheim et al.,PRL 87(2001) 6102. [6] X.-G. Zhang et al.,PRB 68 (2003)92402. [7]F. Matthes et al.,JAP 95(2004) 7240

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P298

Phonon modes at the 2H–NbSe2 surface observed by surface sensitive inelastic X-ray scattering Bridget Murphy1 , Herwig Requardt2 , Jochim Stettner1 , Jorge Serrano2 , ¨ller1 , Werner Press1,3 Michael Krisch2 , Martin Mu 1

IEAP, CAU Kiel, Olshausenstraße 40, D-24098 Kiel, Germany – 2 ESRF, BP220, 38043 Grenoble Cedex, France – 3 ILL, BP156, 38042 Grenoble Cedex 9, France We have determined the dispersion of acoustic and optical surface phonon modes at the 2H–NbSe2 surface by inelastic x–ray scattering under grazing incidence conditions. Already, at room temperature, an anomaly is observed close to the charge density wave Q–vector position located at about one-third along the Γ-M direction of the Brillouin zone [1]. Our results indicate that the anomaly for the surface mode occurs at a lower energy than that measured in bulk sensitive geometry in the same experiment, showing evidence of a modified behaviour in the uppermost layers. Temperature–dependent softening is observed in both surface and bulk. We demonstrate that inelastic x–ray scattering in grazing incidence conditions provides a unique tool to selectively study either surface or bulk lattice dynamics in a single experiment. [1] B. M. Murphy, H. Requardt, J. Stettner, J. Serrano, M. Krisch, M. M¨ uller, W. Press, Phys. Rev. Lett. 95 (2005) 256104.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P299

Interface properties and electronic structure of ultrathin manganese oxide ´1 Mathias Nagel1 , Indro Biswas1 , Heiko Peisert1 , Thomas Chasse 1

Institut f¨ ur Physikalische und Theoretische Chemie, Universit¨ at T¨ ubingen, Auf der Morgenstelle 8, 72076 T¨ ubingen Transition metal oxides reveal interesting properties due to their high electronic correlation. Besides their electronic properties magnetic phenomena are of particular interest in layer systems which are already utilised in technical applications. As a consequence of the trend in miniaturising devices questions about the influence of the specific interface and the reduced dimensionality on the properties arise. The MnO/Ag(001) system is an interesting model system due to the high lattice mismatch (9 %). By choosing the optimal preparation method either pseudomorphic or relaxed growth of ultrathin MnO on Ag(001) can be obtained. This defined growth method gives the possibility to separately study the interface strain, the effect of the reduced dimensionality and the influence of the substrate. Ultrathin, epitaxial layers of MnO were prepared at Ag(001) with thicknesses of a few monolayers. The samples were characterised in situ by means of XPS, XES and XAS measurements. By combining these techniques a detailed understanding of the local geometry and the electronic structure of the evolving film can be obtained. The Mn L2,3 absorption edges of bulk and thin film samples were measured polarisation-dependent at ANKA. Atomic multiplet-ligand field simulations of the absorption edges were conducted using a code provided by F. de Groot. The parameters of the cubic and tetragonal distorted crystal field, respectively, were varied until a good correlation between experiment and theory was achieved. In pseudomorphically grown samples a tetragonal distortion of the MnO lattice is observed which decreases with increasing film thickness. In relaxed films the distortion is reduced but does not vanish completely. The valence band spectra of the films show significant differences compared to bulk samples as a consequence of the tetragonal distortion. Additionally a prominent difference between bulk and thin film samples appears in XES measurements. We gratefully acknowledge the support by E. Pellegrin, P. Nagel and S. Schuppler at the WERA beamline.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P300

Magnetometrie und Dom¨ anenstrukturanalyse magnetischer D¨ unnschichtsysteme mit Synchrotron-M¨ oßbauer-Reflektometrie und mit polarisierter Neutronenreflektometrie ´nes Lajos Nagy1 , La ´szlo ´ Bottya ´ n 1 , La ´szlo ´ Dea ´k1 , Olaf Leupold2,3 , De 1 4 ´rton Major , Johan Meersschaut , Aleksandr Petrenko5 , Rudolf Ma ¨ffer2 , Edit Szila ´gyi1 , Ferenc Tancziko ´1 Ru 1

KFKI Forschungsinstitut f¨ ur Teilchen- und Kernphysik, Pf. 49, H-1525 Budapest, Ungarn – 2 European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, Frankreich – 3 Jetzt bei DESY, Notkestraße 85, D-22607 Hamburg, Deutschland – 4 K.U. Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, B-3001 Leuven, Belgien – 5 Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141 980 Dubna, Moscow Region, Russland Antiferromagnetisch (AF) gekoppelte Multilagen sind sowohl f¨ ur Grundlagenforschung, als auch f¨ ur Technologie von großer Bedeutung. Die Orientierung der Magnetisierung der einzelnen Schichte und die Dom¨ anenstruktur spielen dabei eine wichtige Rolle. In diesem Beitrag soll gezeigt werden, wie diese Informationen durch die Anwendung von Synchrotron-M¨ oßbauer-Reflektometrie (SMR) und polarisierter Neutronenreflektometrie (PNR) zug¨ anglich gemacht werden k¨ onnen. Wir bringen auch Beispiele daf¨ ur, welche erg¨ anzende Information durch Rutherford-R¨ uckstreuung und Konversionselektronen-M¨ oßbauer-Polarimerie (CEMP) geliefert wird. Die Ausrichtung der Schichtmagnetisierung in AF-gekoppelten Multilagen kann aus der Intensit¨ at des SMR und/oder PNR AF-Reflexes bestimmt werden. Eine epitaktische MgO(001)/[57 Fe(2,6 nm)/Cr(1,3 nm)]20 Multilage wurde durch Molek¨ ulstrahlepitaxie (MBE) hergestellt; ihre Struktur wurde durch simultane Auswertung der R¨ ontgenreflektivit¨ atskurven und der Rutherford-R¨ uckstreuspektren bestimmt. Bei 295 K wurde ein S¨ attigungsfeld von 0,85 T entlang der leichten und 1,05 T entlang der schweren Achse gefunden. Die ¨ Multilage wies einen Bulk-Spin-Flop (BSF) Ubergang auf, wenn das zunehmende Magnetfeld entlang der leichten Achse, in der die Schichtmagnetisierungen lagen, 14 mT ¨ u ¨berschreitete. Dieser BSF-Ubergang wurde auch durch CEMP-Messungen nachgewiesen. Die Gr¨ oße der AF Dom¨ anen wurde der Breite der diffusen SMR oder PNR Reflektivit¨ atskurven entnommen. In erster N¨ aherung ist die Breite der diffusen Streukurve umgekehrt proportional zur Dom¨ anengr¨ oße: ∆qx = 1/ξ. Die prim¨ aren Dom¨ anen bilden sich, wenn das sinkende Magnetfeld den S¨ attigungsbereich verl¨ asst. Die native Dom¨ anengr¨ oße war in unserer Multilage ξ = 370 nm und blieb konstant, solange das Magnetfeld 200 mT nicht unterschritt. Die Dom¨ anengr¨ oße nahm spontan und unumkehrbar zu, wenn das Magnetfeld ab 200 mT weiter sank, und erreichte ξ = 800 nm ¨ in Remanenz (Dom¨ anenreifung). Der BSF-Ubergang rief eine weitere, explosionsartige Zunahme der Dom¨ anengr¨ oße bis zu ca. 100 µm hervor (Dom¨ anenvergr¨ oberung). Das sekund¨ are Dom¨ anenbild wurde erst in einem das S¨ attigungsfeld weit u ¨berschreitenden Magnetfeld gel¨ oscht. Dieser Effekt ist wahrscheinlich der Existenz kleiner, extrem stark gekoppelter Bereiche zuzuschreiben.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P301

Organic thin films and biomimetic surfaces ¨dler1 Bert Nickel1 , Joachim Ra 1

Ludwig-Maximilians-Universit¨ at, Geschwister-Scholl-Platz 1, 80539 M¨ unchen

Organic thin films exhibit semiconducting properties which make them suitable for field effect transistors, and, thus, plastic electronics. In this contribution, we will highlight how synchrotron diffraction can be used to access structure information [1,2,3] of such films [Fig. 1 a], and how this information can be linked to device function [Fig. 1 b]. In the second part, we will discuss the application of neutron and synchrotron beams to resolve the structure of solid-supported lipid membranes on various substrates [4,5]. The structural information is compared to functional properties such as selfdiffusion (membrane fluidity) or protein binding to such membranes. The diffraction experiments are complemented by fluorescent microscopy experiments on the same samples [Fig. 2]. In both parts, we will emphasis the need of these experiments in terms of instrumentation and facility infrastructure. Suggestions concerning infrastructure at FRM-2 will be presented. [1] N. Koch, I. Salzmann, A. Vollmer, H. Weiss, B. Nickel, J.P. Rabe, , Phys. Rev. Lett. 96 (2006)156803 [2] R. Ruiz, A. C. Mayer, G. G. Malliaras, B. Nickel et al., Appl. Phys. Lett. 85 (2004) 4926 [3] B. Nickel et al., Phys. Rev. B 70 (2004) 125401 [4] M. Hochrein, C. Reich, B. Krause, J. R¨ adler, B. Nickel, Langmuir 2 (2005)538 [5]C. Reich, M. Hochrein, B. Krause, B. Nickel, Rev. Sci. Inst. 76 (2005) 095103

Fig. 1: Organic field effect transistor. a) Morphology of the organic thin film (AFM). b) Device performance.

Fig. 2: Solid supported membranes. a) Schematic of the experimental setup. (b) Microscopy image (a phase-separating membrane front).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P302

Structure Determination of ZnO and CdSe/ZnS Core-Shell particles Franziska Niederdraenk1 , Pawel Luczak1 , Reinhard Neder2 , Christine ¨hl4 , Eberhard Barglik-Chory3 , Sofia Dembski4 , Christina Graf4 , Eckart Ru 1 Umbach 1

Experimentelle Physik II, Universit¨ at W¨ urzburg – 2 Mineralogisches Institut, Uni3 versit¨ at W¨ urzburg – Institut f¨ ur Physikalische Chemie, Universit¨ at W¨ urzburg – 4 Lehrstuhl f¨ ur Silicatchemie, Universit¨ at W¨ urzburg During the last 15 years, semiconductor nanoparticles have attracted more and more attention in both, fundamental and applied research. Some applications, e.g. in bioimaging or quantum electronics, are already under way. Yet, the basic knowledge is still far from complete, in particular for nanoparticles with diameters well below 5 nm. The size range between 1 and 5 nm is also of fundamental interest since it represents the transition regime between solid state, cluster, and molecular physics. One important aspect is the determination of precise geometric parameters like size, shape, crystallinity, lattice“ constants, and structural defects. In principle, powder dif” fraction methods can provide detailed structural information. However, the diffraction peaks become very broad for particle diameters fairly below 5 nm, and the analysis of the data is crucial. Commonly used approaches for a grain size evaluation like the Rietveld refinement or the Scherrer equation are based on periodic structures, an assumption which is often not sustainable for nanoparticles with diameters below 5 nm. Other more intricate parameters like relaxation effects or stacking faults cannot be considered at all. Here we use an alternative, more direct way for the data analysis. We model the entire particle and calculate the powder diffraction pattern using the Debye formula. In this way, all important parameters like size, shape, stacking faults, strain, etc. are intrinsically included in the calculated data. Furthermore, parameter distributions, e.g., the size distribution, can now be taken into account, which are essential since they are likely to occur in wet-chemically synthesized particles. We report on powder diffraction data with high signal-to-noise quality and low background measured at beamline BW2 at HASYLAB. The measured data are fitted using an evolutionary algorithm which includes the Debye method described above. Our results show that a stacking fault probability needs to be considered in most cases. This means that the particles are not necessarily single crystalline but consist of both zincblende- and wurtzite-like stacked layers. Distributions or probabilities are implemented by averaging the diffraction patterns of several different particles with different sizes, stacking sequences, or other parameters. Since the atomic model is highly flexible, the method can easily be expanded to core-shell particles by adding an outer layer consisting of different atoms with different lattice parameters. In our contribution we present several examples demonstrating the capability of our new data analysis method. Diffraction data for ZnO and CdSe/ZnS core-shell particles will be shown.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P303

Growth and Oxidation of Pd/α-Al2 O3 (0001) Nanoparticles studied with Synchrotron X-ray Diffraction Philipp Nolte1 , N. Kasper1 , A. Stierle1 , H. Dosch1 1

Max Planck Instute for Metals Research, Heisenbergstr. 3, 70569 Stuttgart

Supported transition metal nanoparticles are used as model catalysts. The oxidation of such systems is of great interest as not only the pure metal, but also its oxides can be involved in a catalytic process. In addition to bulk single crystal surfaces, the oxidation properties of nanoparticles can be expected to depend on the support, the orientation and the particle size. In-situ x-ray diffraction is an appropriate method to follow structural changes of oxygen induced phase transformations and simultaneously allows to bridge the pressure gap of UHV based surface analysis techniques. Pd nanoparticles were grown on α-Al2 O3 (0001) by electron beam evaporation in UHV and were studied with SXRD at the MPI-MF beamline at the synchrotron ANKA (FZ Karlsruhe). It was observed that the particles mainly grow (111)-oriented and epitaxially with a typical height of 2 nm and a lateral diameter of 4 nm in coexistence with particles in (110)-orientation. Oxidation experiments were performed in a temperature range between room temperature and 350 ◦ C. Applying UHV near oxygen pressures, it could be observed a reversible decrease of intensity and a broadening of the Pd Bragg peaks. At 350 ◦ C, the formation of bulk oxide could be observed at an oxygen pressure of 5 mbar. This indicates a structural change at the Pd particle surface at low oxygen pressures which acts as a kinetic barrier for the formation of the thermodynamically stable bulk oxide. Financial support of this work is acknowledged from the European Union under contract no. NMP3-CT-2003-505670 (NANO2).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P304

Mineralization of Calcium Carbonate in the Presence of Ovalbumin Exploration with Small Angle Neutron Scattering

an

Vitaliy Pipich1 , Matthias Balz2 , Wolfgang Tremel2 , Dietmar Schwahn1 1

IFF - FZ J¨ ulich, 52452 J¨ ulich – 2 Institut f¨ ur Anorganische Chemie, Johannes Gutenberg Universit¨ at Mainz, 55099 Mainz The mineralization of calcium carbonate in the presence of the protein ovalbumin was explored by time-resolved small angle neutron scattering. Information about the evolution of the mineral polymorphs as well as of the protein structure was obtained from measurements at different scattering contrasts achieved by a proper H2 O/D2 O composition of the aqueous solution. Because of the very different sizes of the mineral (µm) and the protein (30 ˚ A) the scattering from both could be distinguished. The intensity integrated over the small Q interval of “mineral” scattering versus time showed a peak after about 3 hours related to the amorphous phase, a minimum of the 74 % D2 O sample after about 4 hours due to the vaterite polymorph, whereas the lower intensity of the 82 % sample was attributed to the aragonite polymorph. The stable calcitic phase was not oberserved within the experimental time; it would give a minimum for the 74 % solution. The square root of Porods constant versus the D2 O content of√the solvent at given times support this interpretation. The matching conditions, i.e. P4 shifts with increasing mineralization to higher D2 O content. So one gets the following picture: The mineralization of CaCO3 followed Oswalds law by the formation of several polymorphs from the less stable amorphous polymorph to the more stable vaterite and aragonite. No calcite was observed within the experimental time of 12 hours. During the first 4 hours, when the amorphous polymorph is the dominating mineral, about 50 ovalbumin monomers aggregated to a Gaussian chain, which dissolved afterwards. This obervation gives a strong evidence about the interaction of the protein and amorphous mineral phase. Acknowledgements: We thank German Science Foundation for financial support within the priority program “Principles of Biomineralization”. [1] H.Endo, D.Schwahn, H.C¨ olfen, J. Chem. Phys. 120 (2004) 9410. [2] A.Heiss, H.Endo, W.Jahnen-Dechent, D.Schwahn (2005) (submitted) [3] S. Mann, S. (2001). Biomineralization; Principles and Concepts in Bioinorganic Materials Chemistry, Oxford University Press, Oxford, p 61-63. [4] D. Schwahn, M. Balz, M. Bartz, A. Fomenko, W. Tremel, J. Appl. Cryst. 36 (2003) 583. [5] D.Schwahn, M.Balz, W.Tremel, Physica B 350 (2004) E947

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P305

In-situ Oberfl¨ achenr¨ ontgenbeugung an sauerstoffinduzierten Rekonstruktionen auf Ag(111) Alexander Reicho1 , Andreas Stierle1 , Ioan Costina1 , Helmut Dosch1 1

Max-Planck-Institut f¨ ur Metallforschung, Heisenbergstraße 3, 70569 Stuttgart

Silber spielt eine wichtige Rolle als Katalysator f¨ ur Oxidationsreaktionen. Es wird z.B. f¨ ur die Epoxidation von Ethylen und die partielle Oxidation von Methanol zu Formaldehyd verwendet. Diese Reaktionen werden bei einer Temperatur von 500 bis 900 K und atmosph¨ arischem Sauerstoffdruck ausgef¨ uhrt. Ein grundlegendes Verst¨ andnis der katalytischen Aktivit¨ at von Silber erfordert die Kenntnis der Oberfl¨ achenstruktur der aktiven Phase auf atomarer Skala. Seit 1974 ist die Bildung einer sauerstoffinduzierten p(4×4) Rekonstruktion auf Ag(111) bekannt [1], welche f¨ ur die katalytische Aktivit¨ at von Silber verantwortlich gemacht wird [2,3]. In unserem Beitrag pr¨ asentieren wir Ergebnisse einer in-situ Oberfl¨ achenr¨ ontgenbeugungsuntersuchung (SXRD), die die G¨ ultigkeit verschiedener vorgeschlagener Strukturmodelle der p(4×4) Rekonstruktion in Frage stellt [2,4]. Weiterhin zeigen wir das gemessene Stabilit¨ atsdiagramm des O/Ag(111)-Systems, welches mit theoretischen Berechnungen verglichen wird [3]. Als ein Hauptresultat unserer SXRD Messungen k¨ onnen alle Strukturmodelle der p(4×4) Rekonstruktion, welche auf einer dreilagigen O-Ag-O Schicht des Bulkoxids Ag2 O beruhen, ausgeschlossen werden. Wir pr¨ asentieren ein nanostrukturiertes Ag12 O6 Adatommodell der p(4×4) Rekonstruktion, welches durch verschiedene experimentelle und theoretische Methoden bestimmt wurde [5] und im Einklang mit unseren SXRD Messungen steht. Dieses Modell besteht aus 2 Ag6 Dreiecken, die sich auf fcc und hcp Pl¨ atzen befinden. Diese Dreiecke sind durch 6 Sauerstoffatome pro Einheitszelle verbunden, wobei sich jeweils 2 Sauerstoffatome in den Gr¨ aben zwischen den Ag6 Dreiecken befinden. Außerdem haben wir mit Hilfe von in-situ SXRD das Stabilit¨ atsdiagramm des O/Ag(111)-Systems untersucht. Dabei konnten wir beobachten, dass die p(4×4) Rekonstruktion unter den katalytischen Bedingungen der Epoxidation von Ethylen stabil ¨ ist. Es k¨ onnte daher sein, dass diese Uberstruktur eine wichtige Rolle f¨ ur die katalytische Aktivit¨ at von Silber spielt. [1] [2] [3] [4] [5]

G. Rovida et al., Surf. Sci. 43 (1974) 230 A. Michaelides et al., Chem. Phys. Lett. 367 (2003) 344 W.X. Li et al., Phys. Rev. B 68 (2003) 165412 A. Michaelides et al., J. Vac. Sci. Technol. A 23 (2005) 1487 M. Schmid et al., Phys. Rev. Lett. 96 (2006) 146102

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P306

Surfen im k-Raum mit winkelaufl¨ osender Photoelektronen-Spektroskopie Kai Rossnagel1 , Lutz Kipp1 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel

Viele Eigenschaften kondensierter Materie k¨ onnen wir nur dann verstehen, wenn wir wissen, wie sich die am schw¨ achsten gebundenen Elektronen verhalten, also jene Elektronen nahe der Fermi-Energie. Eine seit l¨ angerem etablierte Methode zur Bestimmung der impulsaufgel¨ osten elektronischen Struktur an und unterhalb der Fermi-Energie ist die winkelaufl¨ osende Photoelektronen-Spektroskopie, die gerade in den letzten Jahren durch Fortschritte in der Spektrometerentwicklung noch stark an Leistungsf¨ ahigkeit gewonnen hat. Dies spiegelt sich in beeindruckender Weise in Sch¨ arfe, Detailreichtum und Vollst¨ andigkeit der aufgenommenen Daten wider. Anhand verschiedener Beispiele aus dem Reich der Schichtkristalle wird in diesem Vortrag die derzeitige Leistungsst¨ arke der winkelaufl¨ osenden Photoelektronen-Spektroskopie demonstriert, vor allem wenn sie mit Synchrotronstrahlung kombiniert wird.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P307

Combinatorial studies on metal / polymer gradient nanocomposites Stephan V. Roth1 , Harald Walter2 , Ralf Domnick3 , Olaf Leupold1 , Christian Schroer4 , Marion Kuhlmann1 , Bruno Lengeler5 , Rainer Gehrke1 , Pe¨ller-Buschbaum6 ter Mu 1

HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2 CSEM SA, Badenerstrasse 569, CH-8048 Z¨ urich, Switzerland – 3 identif GmbH, Ulrich-Schalk-Str. 3, D-91056 Erlangen, Germany – 4 Inst. f. Strukturphysik, TU Dresdesn, D-01062 Dresden, Germany – 5 II. Physik. Inst., Physikzentrum Melaten, RWTH Aachen, D52074 Aachen, Germany – 6 Physik-Department E13, TU M¨ unchen, James-Franck-Str. 1, D- 85748 Garching, Germany Nanostructuring of thin noble metal films is of utmost importance for many technological and biophysical areas, e.g. anti-counterfeiting and DNA scanning [1]. Usually a multilayer geometry is chosen consisting of noble metal layer / polymer / substrate. The optical properties of such multilayer systems depend crucially on the structure and morphology of the noble metal layer. They are determined by key parameters like deposition method or metal-polymer interaction affecting the self-assembly of the metal atoms. We advanced two-fold: Firstly, as polymer layer we chose a blend of deuterated polystyrene (dPS) and polyisoprene (PI) being already phase separated in thin film geometry. As metals, we chose Au and Cu which have different sticking coefficients on the two components of this blend. Secondly we installed a one-dimensional (1D) gradient in mass thickness of the noble metal layer during evaporation to allow for a combinatorial investigation of the nanostructure of the metal layer as a function of mass thickness. Microbeam grazing incidence small-angle x-ray scattering (µ GISAXS) is excellently suited for combinatorial investigations with high statistical significance [2,3]. The experiments were conducted at the beamline BW4 of HASYLAB using the novel µ focus option of BW4. A moderate micro-focus beam size of 32x17 µm2 (HxV) can be installed making use of Beryllium compound refractive lenses (Be CRLs). For the experiments a step size adapted to the microbeam size was used (∆y=40 µm). Along the gradient, the Cu mass thickness clearly changes. We present the results on two gradients, namely Au and Cu on dPS/PI-blend, and explain the results in terms of replication of the polymer blend nano-structure as a function of mass thickness. [1] G. Bauer, et al., Nanotechnology 14, (2003) 1289 [2] S.V. Roth et al., Appl. Phys. Lett. 82, (2003) 1935 [3] S.V. Roth et al., Appl. Phys. Lett. 88, (2006) 021910

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P308

Innerschalenanregung und elastische Lichtstreuung von freien, massenselektierten Nanopartikeln ¨hl1 , H. Bresch2 , B. Langer1,3 , R. Lewinski2 , P. Brenner2 , R. Flesch2 , E. Ru C. Graf2 , T. Martchenko4 , O. Ghafur4 , M.J.J. Vrakking4 1

Physikalische Chemie, Freie Universit¨ at Berlin, Takustr. 3, 14195 Berlin – 2 Institut f¨ ur Physikalische Chemie, Universit¨ at W¨ urzburg, Am Hubland, 97074 W¨ urzburg – 3 MaxBorn-Institut, Max-Born-Str. 2a, 12489 Berlin – 4 FOM Institut AMOLF, Amsterdam, Niederlande Es werden erste Resultate eines neuen experimentellen Ansatzes vorgestellt, mit dem freie, massenselektierte Nanopartikel in einem Strahl unter Nutzung von Synchrotronstrahlung untersucht werden. Die Pr¨ aparation der Nanopartikel erfolgt entweder aus L¨ osungen oder mit Hilfe von Methoden der Kolloidchemie, mit denen sich strukturierte Nanopartikel herstellen lassen. Die Partikel werden zun¨ achst durch einen Aerosolgenerator in die Gasphase gebracht, wobei die Gr¨ oßenselektion mit Hilfe eines differentiellen Mobilit¨ atsanalysators gelingt. Eine aerodynamische Linse erlaubt die Fokussierung des kontinuierlichen Teilchenstrahls im Hochvakuum auf die Synchrotronstrahlung. Die elektronische Struktur der freien Partikel wird im Bereich der Innerschalenanregung mittels totalen Elektronenausbeuten charakterisiert. Dadurch lassen sich freie Nanopartikel variabler Gr¨ oße ohne Kontakt zu einem Substrat unter Vermeidung von Strahlensch¨ aden im Bereich der Rumpfniveauanregung charakterisieren. Erste Experimente erfolgten an gr¨ oßenselektierten NaCl-Nanopartikeln (Radius: 50-175 nm) im Bereich der Cl 2p- und der Na 1s-Anregung. Der Bereich der O 1s-Absorption zeigt, dass die Partikel kaum Wasser enthalten. Nanoskopische Salzpartikel, die Kristallwasser enthalten (Na2 SO4 ·10 H2 O), liefern dagegen eine intensive O 1s-Absorption. Diese ist zur Untersuchung der Bindungsverh¨ altnisse des im Kristallgitter gebundenen Wassers von Interesse. Der Einfluss von ¨ außeren Beschichtungen auf die elektronische Struktur von freien Nanopartikeln wird an Core-Shell-Partikeln studiert. ZnS-Nanopartikel (r=60 nm), die mit einer 5 nm dicken SiO2 -Schale umgeben sind, wurden untersucht. Es werden Unterschiede in der elektronischen Struktur zwischen unbeschichteten und beschichteten ZnS-Partikeln diskutiert. Experimente zur winkelaufgel¨ osten, elastischen Lichtstreuung lassen sich am Nanopartikelstrahl bis in den weichen R¨ ontgenbereich durchf¨ uhren. Daraus k¨ onnen Strukturinformationen zur nanoskopischen Materie in Verbindung mit Simulationsrechnungen gewonnen werden. Ebenso l¨ asst sich mit dem Ansatz die spektrale Abh¨ angigkeit der optischen Eigenschaften nanoskopischer Materie im Bereich der Rumpfniveauauregung bestimmen.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P309

Static Speckle Experiments using White Synchrotron Radiation Tushar P. Sant1 , Tobias Panzner1 , Wolfram Leitenberger2 , Gudrun Gleber1 , Ullrich Pietsch1 1 2

Institute for Physics, University of Siegen, Walter Flex Str. 3, D-57068 Siegen. – Institute for Physics, University of Potsdam, Am Neuen Palais 10, D-14469 Potsdam.

We have performed static speckle experiments using white synchrotron radiation at EDR beamline at BESSY II. Static speckle pattern gives access to spatially resolved height function of the illuminated area at the atomic length scale [1]. It has been shown that for coherent scattering experiments in reflection geometry the knowledge of the illumination function incident on the sample is important for the reconstruction of the surface morphology from speckle data[1]. The coherent reflectivity has been recorded from the surface of technologically smooth GaAs wafer (Fig.1). Besides periodic oscillations which are caused by the scattering from incident pinhole other features appear in the measurement of the real surface of the sample. The illumination function calculated by means of Lommel formalism matches well with the measured function for the pin-hole diameter of 11.4 µm and will be used for further surface reconstruction from speckle maps. For further examination speckle map of reflection from a laterally periodic structure like GaAs grating is studied. Here the sample is illuminated with coherent as well as incoherent radiation by using pinholes of different diameters. Incoherent illumination confirms the existence of grating peaks. Under coherent illumination the grating peaks split into speckles which correspond to fluctuations on the sample surface. The surface morphology of the grating is reconstructed from this coherent scattering so as to determine local height fluctuations. [1] I. A. Vartanyants et.al., Phys. Rev. B 55 (1997) 13193.

Fig. 1: Measured coherent reflectivity from GaAs wafer

Fig. 2: Calculated and measured illumination function at 10keV

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P310

Ion track-etched nanopores in polymer foils Birgitta Schiedt1 , Javier Cervera2 , Ken Healy3 , Salvador Mafe4 , Alan P. Morrison3 , Reinhard Neumann1 , Gerard Pepy5 , Patricio Ramirez6 , Zuzanna Siwy7 , Christina Trautmann1 1

Gesellschaft f¨ ur Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt, Germany – 2 Dept. de Ci`encies Experimentals., Universitat Jaume I. Apdo. 224, E-12080 Castello, Spain – 3 Dept. of Electrical and Electronic Engineering, University College Cork, Ireland – 4 Dept. de Termodin` amica, Universitat de Val`encia, E-46100 Burjassot, Spain – 5 BNC, SzFKI, POB 45 Budapest, Hungary – 6 Dept. de Fisica Aplicada. Univ. Polit`ecnica de Val`encia, Camino de Vera s/n, E-46022 Valencia, Spain – 7 Department of Physics and Astronomy, University of California, Irvine, 2182 Frederick Reines Hall, Irvine, CA 92697 Track-etching has become an established method to create well-defined pores in polymer membranes with diameters down to a few nanometers. The irradiation of insulating materials with swift heavy ions of MeV to GeV energy creates damaged zones along the trajectories of the ions which can be attacked preferentially by a suitable etchant and are thus converted into pores. The number of pores in a membrane is given by the applied fluence, i.e. number of ions per surface area (typically between one single ion and 109 ions/cm2 ), while their size and shape is controlled via the time and conditions of etching. Cylindrical pores with diameters down to a few tens of nanometers or alternatively conical pores with a few nanometers opening on the small side can be produced. Structural analysis of cylindrical track-etched nanopores in polycarbonate has been performed by small angle x-ray scattering and revealed an excellent uniformity in pore size, if the samples have been exposed to UV light prior to the etching. Single pore membranes with a conical shape show ionic transport properties similar to biological channels (selectivity, rectification, fluctuations [1][2]). To better understand the underlying processes occurring in the system, model calculations based on the Nernst-Planck and Poisson equations have been performed, describing the transport phenomena (I-V curves at different concentrations) of conical pores in polyethyleneterephthalate [3]. These synthetic nanopores have the advantage of high stability, resistance against environmental conditions and easy-handling, which makes them a favourable system for applications in biosensing [4] and single-molecule (e.g. DNA) detection [5]. [1] P.Y. Apel et al., Nucl. Inst. Meth. B 184 (2001) 337. [2] Z. Siwy et al., Am. J. Phys. 72 (2004) 567. [3] J. Cervera et al., J. Chem. Phys. 124 (2006) 104706. [4] E.A. Heins et al., Nano Lett. 5 (2005) 1824. [5] A. Mara et al., Nano Lett. 4 (2004) 497.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P311

Characterization of InGaN/GaN nano-islands by grazing incidence x-ray diffraction Th. Schmidt1 , M. Siebert1 , J. I. Flege1 , S. Figge1 , T. Yamaguchi1 , D. Hommel1 , J. Falta1 1

Inst. of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen

InGaN quantum dots (QDs) embedded in GaN offer a great potential for applications in light emitting devices. Depending on the In concentration, a wide spectral range can be covered. In comparison to InGaN/GaN quantum-well based structures, InGaN quantum dots embedded in GaN are especially advantageous, e. g. because a smaller laser threshold is expected. In this context, information about the size, shape, chemical composition, and the strain state of such islands is necessary. Grazing incidence x-ray diffraction (GIXRD) is ideally suited for this purpose, as has already been shown for different material systems such as GaN/AlN [1], CdZnSe/ZnSe [2], or InGaAs/GaAs [3]. Here, we present the first grazing incidence x-ray characterization of InGaN/GaN nano-islands. GIXRD experiments were performed ex-situ in the so-called z-axis setup [4] at the BW1 undulator beamline at HASYLAB (Hamburg, Germany), using a focussed monochromatic beam at 10 keV photon energy. Reciprocal space maps were recorded in the vicinity of different reflections. InGaN/GaN(0001) samples were grown on sapphire (0001) substrates by metal-organic vapor pressure epitaxy (MOVPE) at our institute in Bremen. Samples with different InGaN deposition temperatures were investigated. For InGaN growth at T = 650◦ C, we find that the Inx Ga1−x N islands are virtually completely relaxed, and based on Vegard’s law, an In concentration of x ≈ 0.60 follows for these islands. For lower growth temperature (T = 600◦ C), broad reflections indicate the presence of small islands which are found to be coherently strained. In addition, samples grown by molecular beam epitaxy (MBE) on MOVPE templates were investigated. For an InGaN growth temperature of T = 450◦ C, fully relaxed islands are observed. The In concentration of these islands is as high as x ≈ 0.86. This value is found to be significantly reduced after MBE overgrowth with GaN cap layers. In comparison to as-grown QD layers, additional reflections occur for the overgrown samples. Especially for stacked QD layers, these reflections become intense. This is explained by the progressive formation of stacking faults and of regions with cubic crystal structure during MBE overgrowth. [1] V. Chamard et al., Appl. Phys. Lett. 79 (2001) 1971 [2] T. Passow, H. Heinke, Th. Schmidt, J. Falta, A. Stockmann, H. Selke, P. L. Ryder, K. Leonardi, and D. Hommel, Phys. Rev. B 64 (2001) 193311 [3] K. Zhang, J. Falta, Th. Schmidt, Ch. Heyn, G. Materlik, and W. Hansen, Appl. Phys. Lett. 72 (2000) 199 [4] M. Lohmann and E. Vlieg, J. Appl. Cryst. 26 (1993) 706

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P312

Heavy ion induced damage in alkali halide crystals irradiated at 8 and 300 K Kurt Schwartz1 , Alexander Volkov2 , Christina Trautmann1 , Kay-Obbe Voss1 , Maik Lang1 , Michael Sorokin2 , Reinhard Neumann1 1

Gesellschaft f¨ ur Schwerionenforschung (GSI), Planckstr. 1, D 64291 Darmstadt, Germany – 2 Russian Research Centre Kurchatov Institute, Kurchatov Sq. 1, 123182 Moscow, Russia Radiation damage in alkali halides induced by swift heavy ions is investigated by optical spectroscopy, optical bleaching, thermo-stimulated luminescence (TSL), and scanning force microscopy (SFM). Single crystals of LiF and NaCl were irradiated at the UNILAC linear accelerator of GSI with different heavy ions (from carbon to uranium) in the energy range between 50 and 2600 MeV. The irradiations were performed from 8 K up to room temperature (RT) using a cryostat that allows additionally in situ absorption and TSL measurements. The evolution of various color centers was studied as a function of ion fluence and irradiation temperature [1, 2]. The efficiency of F-center creation strongly depends on the energy loss of the ions and is related to electron-hole recombination processes [1, 2]. In LiF and NaCl crystals irradiated at 8 K primary hole centers were observed which are thermally annealed between 10 and 140 K. In LiF, crystals the ion induced damage changes the electronic structure of anion excitons [3]. On the surface of irradiated ionic crystals each ion produces a nanometric hillock [4]. The size (height and diameter) of the hillocks depends on the energy loss of the ion but is independent of the irradiation temperature (8 K, RT) which is in contrast to the creation of color centers. The efficiency of color center creation is related to local heating and thermally stimulated separation of primary color centers in ion tracks. Thermal spike calculations are performed to describe the heat propagation in the track [2]. [1] K. Schwartz, C. Trautmann, A.S. El-Said, R. Neumann, M. Toulemonde, W.Knolle, Phys. Rev. B 70 (2004) 184104. [2] K. Schwartz, A.E. Volkov, K.-O. Voss, M. Sorokin, C. Trautmann, R. Neumann, Nucl. Instr. Meth. B 245 (2006) 204. [3] A. Luschchik, A. Kotlov, Ch. Lushchik, V. Nagirnyi, K. Schwartz, E. Vasil´chenko, Annual Report DESY 2005, Hamburg, 2006, pp. 257 258. [4] C. M¨ uller, M. Cranney, A.. El-Said, N. Ishikawa, A. Iwase, M. Lang, R. Neumann, Nucl. Instr. Meth. B 191 (2002) 246.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P313

High-resolution PES and NEXAFS investigation of organic molecules and interfaces ¨ ll1 , Ying Zou1 , Thomas Schmidt1 , Rainer Fink2 , Eberhard Achim Scho Umbach1 1

Experimentelle Physik II, Universit¨ at W¨ urzburg – 2 Physikalische Chemie II, Universit¨ at Erlangen Metal-organic contacts are of fundamental interest and of crucial importance for all organic electronic applications. The bonding between the organic molecules of the active layer and the metal contact surface does not only have a key influence on the charge carrier transport through the interface but also on the morphology and structure of the organic film. By using high-resolution PES and NEXAFS spectroscopy we are able to characterize this interface in details that are not accessible by other techniques. As example, we present investigations on model molecules (PTCDA, NTCDA) in different adsoption states on Ag(111) and Au(111) surfaces. We find that the molecules interact much stronger with the Ag(111) surface, where PTCDA and NTCDA are chemisorbed which can clearly be derived by the high quality of the spectroscopic data. Moreover, the rich finestructures of the monolayer PES spectra exhibit substantial differences for the same molecule in different adsorption states. Changes in the relative intensity of satellite features can be interpreted in terms of different charge transfer screening probabilities due to differences in the interface coupling [1]. The bonding is assigned to the interaction of the molecular aromatic pi-system with Ag d-states and significant charge transfer from Ag into the NTCDA/PTCDA LUMO can be observed. In contrast, the investigated molecules show mainly physisorptive bonding to the Au(111) surface. In addition, the vibronic fine structure in high-resolution NEXAFS data, analysed in detail for NTCDA, reveals interesting information on the electron-vibron coupling in complex organic compounds [2]. This project is financed by the BMBF under contract 05KS4WWC/2. [1] A. Sch¨ oll et al., Journal of Physical Chemistry B 108, 14741 (2004). [2] A. Sch¨ oll et al., Physical Review Letters 93 (2004).

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P314

Angle-scanned photoelectron diffraction applied to study the SiO2 /4HSiC(0001)-interface ¨rmann1 , Stefan Dreiner1 , Ulf Berges1 , Carsten Westphal1 Mark Schu 1

Universit¨ at Dortmund, Experimentelle Physik 1, Otto-Hahn-Straße 4, 44227 Dortmund Photoelectron diffraction is a surface sensitive technique which combines the chemical sensitivity of XPS with the possibility to conduct structure determinations. In this work angle-scanned photoelectron diffraction was applied to investigate the interface between ultrathin SiO2 films and 4H-SiC(0001). SiC is a semiconductor material with a large bandgap, which is, due to it’s properties, an attractive material for the application in semiconductor devices designed for operation at high temperatures, with high currents and high frequencies. The thermal oxidation of SiC surfaces leads to amorphous SiO2 films at the surface. The interface of these films to the SiC substrate is assumed to be an important source of defect states, which represent an obstacle for the application of SiC in MOS devices. At the U41-PGM beamline at BESSY 2 (Berlin), synchrotron radiation with high flux and sufficient spectral resolution was available. Thus it was possible to separate three components in the Si 2p XPS spectra corresponding to Si emitters in the SiC bulk, the SiO2 , and at the interface. Further, the O 1s signal from the silicon oxide layer and the C 1s signal from the SiC substrate were measured. Therefore experimental diffraction patterns are available which contain structural information about depths of the sample. For each of them a comparison with simulation calculations is presented, which provides information about the local atomic structure around the respective emitter. A model was found, in which the interface structure is very similar to ordered silicate layers on SiC as described by Bernhardt and coworkers [1]. Structural differences to ordered silicate layers were primarily found within the near-interface region of the oxide film. The size of locally ordered regions near the interface in the oxide film could be determined. [1] J. Bernhardt et al., Appl. Phys. Lett. 74, 1084 (1999)

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P315

Electronic structure of ultra-thin graphite layers on SiC(0001) Thomas Seyller1 , Konstantin Emtsev1 , Florian Speck1 , Lothar Ley1 , Petar Stojanov2 , Eric Huwald2 , John Riley2 , Robert Leckey2 1 2

Lehrstuhl f¨ ur Technische Physik, Universit¨ at Erlangen-N¨ urnberg, Germany – Department of Physics, La Trobe University, Australia

Graphene is a zerogap semiconductor with a linear dispersion of the π-bands at the zone boundary. There electrons and holes can be considered massless and transport should be governed by Diracs equation. Thus the mobility of 2D electron gases reach high values (15,000cm2 /Vs at 300K, 60,000 cm2 /Vs at 4K) [1-2]. Similar behaviour with smaller mobilities was observed for graphite/SiC(0001) [3]. It was suggested that such a system could open up a route towards graphene based electronics. This requires to understand the formation of thin graphite layers in detail. ◦ Graphite on SiC(0001) is grown by sublimation of √ Si at T > 1150 C. The first carbon √ 3×6 3) structure. Chen [4] characterized rich structure in the growth sequence is a (6 √ √ the (6 3 × 6 3) structure by STM and proposed a carbon nanomesh model which is incompatible with the weak substrate-overlayer interaction proposed by Forbeaux [5] based on undistorted π ∗ -bands. √ √ We have studied the occupied electronic states of the (6 3 × 6 3) structure and thin graphite layers √ by ARPES. Figure 1 compares the dispersion of the observed sur√ face states of the (6 3 × 6 3) structure with band structure calculations for graphite [6]. The observed σ-bands match the calculation quite well but the π-bands are not developed. Further results obtained at different coverages with graphite will be presented. The development of the electronic structure of ultra-thin graphite layers with increasing coverage is outlined.

[1] K. S. Novoselov et al., Nature 438 (2005) 197. [2] K. S. Novoselov et al., Science 306 (2004) 666. [3] C. Berger et al., Journal Of Physical Chemistry B 108 (2004) 19912. [4] W. Chen et al., Surface Science 595 (2005) 107. [5] I. Forbeaux et al., Phys. Rev. B 58 (1998) 16396. [6] R. Ahuja et al., Phys. Rev. B 51 (1995) 4813.

Fig. of the electronic states of the √ 1: Comparison √ (6 3 × 6 3) structure with the calculated band structure of graphite [6]. Note that the latter has been shifted downward in energy by 1eV in order to match the observed σ-bands to the calculation.

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P316

X-ray standing waves on GaN: crystal defects and non-dipole effects M. Siebert1 , Th. Schmidt1 , J. I. Flege1 , S. Figge1 , J. Zegenhagen2 , T.-L. Lee2 , D. Hommel1 , J. Falta1 1

Inst. of Solid State Physics, Univ. of Bremen, Germany – 2 ESRF, Grenoble, France

Magnesium and silicon are most commonly used as p-dopant and n-dopant material, respectively, in GaN based devices such as laser diodes. The incorporation of these dopants is known to lead to a variety of defects [1] which significantly decrease the performance of the devices. Hence, detailed knowledge about the interplay between dopant concentration and defect formation is required. The samples were grown by metal-organic vapor phase epitaxy on sapphire (0001) substrates. In order to determine the dopant incorporation sites, we performed x-ray standing wave measurements (XSW) in (0002) backscattering geometry at a photon energy of E=2390 eV at the beamlines BW 1 (HASYLAB/DESY) and ID 32 (ESRF). As secondary signals, Ga 2p photoelectrons, Mg KLL Auger electrons, and Si K fluorescence were recorded. In backscattering geometry, the intrinsic width of the rocking curve may exceed its defect induced broadening. Hence, the data can be evaluated directly applying the dynamical theory of diffraction. However, in 3 µm thick Mg doped GaN films, the defect induced broadening cannot be sufficiently compensated by choosing a backscattering setup. This could be compensated by an optimizing the sample design: A 3 µm thick high quality undoped GaN film was used to establish a standing wave field for the investigation of a 300-400 nm thin doped film deposited on top. By this approach, the width of the rocking curve can be significantly reduced. For XSW investigations using photoelectrons as secondary signal, contributions of non-dipole effects to the photoelectron yield need to be taken into account. In backscattering geometry, these effects become especially pronounced. For electrons emitted from an s state, the influence of nondipole contributions on the XSW-signal can be accounted for by applying calculated correction paramters [2]. However, such parameters are not yet available for other initial states, as required for the Ga 2p electrons used here. Therefore, we used a method that allows to determine non-dipole parameters with high precision, by comparing the XSW signal of Ga 2p photoelectrons and Ga LMM-Auger electrons from high quality undoped GaN films. In the setup we used, the difference of the kinetic energies of these two types of electrons is very small, hence both signals probe the same crystal volume. The parameters obtained from these experiments were then used for the data evaluation of XSW measurements of doped films with decreased crystal quality. The results confirm a prevalent incorporated of Mg on substitutional sites. With increasing dopant concentration, however, additional sites are occupated by Mg, which can be related to inversion domains. Different results have been obtained for Si doping, pointing to a general degradation of the crystal structure without a significant increase of non-substitutional Si atoms with increasing dopant concentration. [1] Z. Liliental-Weber et al., Physica B, 273–274 (1999) 124 [2] I. Vartanyants et al., Nucl. Instrum. Methods. Phys. Res. 547 (2005) 196

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P317

Korngrenzen- und Oberfl¨ achenmoden in Nanokristallen Jens-Boie Suck1 , Selcuk Mentese1 , Stefan Janssen2 1

Institut f¨ ur Physik, Technische Universit¨ at Chemnitz, D-09107 Chemnitz, Deutschland – 2 Labor f¨ ur Neutronenstreuung, Paul Scherrer Institut, CH-5232 Villingen PSI, Schweiz Die Vibrationsspektren nanokristalliner Materialien zeigen einen charakteristischen ¨ Uberschuss an niederenergetischen Moden (LEM). Wir haben die Energie- und zum ersten Mal auch die Wellenl¨ angenabh¨ angigkeit dieser atomaren Schwingungen im Falle des nano-abgeschreckten und des relaxierten Ni89 Hf11 f¨ ur zwei unterschiedliche Nanokristallgr¨ oßenverteilungen mit Hilfe unelastischer Neutronenstreuung untersucht. Unsere Ergebnisse zeigen neben den LEM (Fig.1), der bekannten Lokalisierung der Moden in den Nanokristalliten und der Kristallitgr¨ oßenabh¨ angigkeit der Intensit¨ at der LEM auch die Abnahme der LEM nach vorsichtiger Relaxation ohne sichtbares Kornwachstum. Wir konnten zeigen, daß diese herausgetemperte Intensit¨ at der LEM im Vergleich mit der verbleibenden niederenergetischen Intensit¨ at eine charakteristische Energie- und Wellenl¨ angenabh¨ angigkeit zeigt, die es zum ersten Mal erlaubt, diese den Korngrenzen zuzuordnenden Moden von den verbleibenden, vor allem Oberfl¨ achenmoden der Kristallite zu trennen.

Abb. 1: Totaler dynamischer Strukturfaktor des nc N i89 Hf11

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P318

Strain & domain formation in thin films of PbTiO3 A. Vlooswijk1 , A. Janssens2 , G. Rispens1 , G. Catalan1 , O. Seeck3 , G. Rijnders2 , D.H.A. Blank2 , B. Noheda1 1

Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands – 2 Mesa+ Institute for Nanotechnology, University of Twente, P.O. box 217, 7500 AE Enschede, The Netherlands – 3 HASYLAB- DESY, Notkestr. 85, D-22603 Hamburg, Germany PbTiO3 is a classical ferroelectric perovskite. In bulk form, it distorts tetragonally with ct > at below TC = 490 ◦ C and the ferroelectric polarization lies along the [001] direction. In thin film form, the polarization is preferred along the surface normal to facilitate the switching geometry, so substrates, such are SrTiO3 , are commonly chosen with lattice parameters close to at . Grazing Incidence Diffraction (GID) performed at the DORIS W1 beamline (HASYLAB) on thin layers of ferroelectric PbTiO3 has revealed that, on a well-chosen substrate with tensile misfit values, and for sufficiently thin (fully-strained) films, the polarization can tilt from the surface normal[1] without reaching the in-plane orientation. This is not only of fundamental interest since it has been predicted that this lowering of symmetry can improve functional properties like the piezoelectric and dielectric responses of the films[2]. The underlying substrate and the film thickness are the main parameters to control the strain state and orientation of an epitaxial thin film [3-5]. These effects can be used to tune and improve the physical properties of the film. Due to the presence of a high-symmetry phase at the growth temperatures, films of ferroelectric perovskites can release strain in the ferroelectric phase by forming periodic 90◦ domain patterns (with alternating in-plane and out-of-plane polarizations)[5]. Although this mechanism is known, a detailed characterization is still missing, in particular for weak tensile strain. Here we investigate the strain tunability and strain relaxation of thin films of ferroelectric PbTiO3 on different substrates and with different thickness. The films have been prepared using RHEED-assisted PLD (Reflection High-Energy Electron Diffraction assisted Pulsed Laser Deposition). The structural properties of the PbTiO3 films have been studied by x-ray diffraction. Reciprocal space maps have been measured around several main reflections, both in reflection and GID geometry at a lab diffractometer and at the DORIS W1 beamline at HASYLAB. Dielectric and Piezoelectric Force Microscopy (PFM) measurements have also been performed. Preliminary results indicate that tensile strain improves the piezoelectric response, as expected for a tilted polar phase[2,4]. [1] G. Catalan et al., Phys. Rev. Lett. 96 (2006) 127602 [2] E. Almahmoud, Phys. Rev. B 70 (2004) 220102(R) [3] N.A. Pertsev et al., Phys.Rev. Lett. 80 (1998) 1988 [4] C. Bungaro and K. M. Rabe, Phys. Rev. B 69 (2004) 184101 [5] W. Pompe et al., J. Appl. Phys. 74 (1993) 6012

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P319

Soft X-Ray studies on the system hafnium on Si(100) ¨chter1,2 , Mark Daniel Weier1,2 , Abner de Siervo3,4 , Christian Flu 1 1 1,2 ¨rmann , Stefan Dreiner , Ulf Berges , Marcelo Carazzolne4 , Schu Richard Landers3,4 , George Kleiman4 , Carsten Westphal1,2 1

Experimentelle Physik 1 - Universit¨ at Dortmund, Otto-Hahn-Str.4, D 44221 Dortmund, Germany – 2 DELTA - Universit¨ at Dortmund, Maria-G¨ oppert-Mayer-Str. 2, D 44227 Dortmund, Germany – 3 Laborat´ orio Nacional de Luz Sincrotron, C.P. 6192, 13084-971 Campinas, SP, Brazil – 4 Instituto de Fisica - Universidade Estadual de Campinas, C.P. 6165, 13083-970 Campinas, SP, Brazil Presently, there are many higk-k candidates discussed as a substitute for SiO2 as the gate dielectric in the silicon based CMOS (Complementary-MetalOxide-Semiconductors) technology. One of the most promising candidates is HfO2 [1]. The thermal stability of the new gate dielectric is one of the most difficult issues to solve. Recent publications [2] report the formation of hafnium silicide at the HfO2 interface at high temperature annealing. Due to this fact it is interessting to get more information about the the formation of HfSi on Si and to understand the structure and the interface of this system. In this work ultrathin films of HfSi on Si(100) were prepared and studied by X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The measurements were performed at the beamlines 5 and 11 at the synchrotron facility DELTA (Dortmund). The experimental results are compared to calculated patterns by an R-factor analysis. We present a possible model of the structure of HfSi on Si(100). [1] C.J. F¨ orst, C.R. Ashman, K. Schwarz and P. Bl¨ ochl, Nature 427, 53 (2004) [2] N. Miyata et al., Phys. Rev. B 71, 233302 (2005)

Nanostrukturen und Grenzfl¨ achen

Poster: Do., 13:00–15:30

D-P320

VUV Ellipsometry using Synchrotron Radiation with Sub-monolayer Resolution Dietrich R.T. Zahn1 , Ovidiu D. Gordan1 , Sascha Hermann1 , Daniel Lehmann1 , Cameliu Himcinschi1 , Christoph Cobet2,3 , Simona Silaghi3 , Walter Braun4 , Norbert Esser3 1

Institut f¨ ur Physik, TU Chemnitz, Reichenhainerstr. 70, 09107 Chemnitz, Germany – Institut f¨ ur Festk¨ orperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany – 3 ISAS Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 4 BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany 2

Ellipsometry is a non-destructive and very sensitive surface and thin film measurement technique which can detect the changes in the optical response produced by an overlayer on a smooth surface. Due to the long wavelengths of the spectral range accessible with most commercial ellipsometers it can, however, be difficult to separate the refractive index of the film and the film thickness. Consequently only the product of these parameters can be uniquely determined. The lower wavelength of the UV light should be even more sensitive for ultra-thin films. Still to our knowledge there is no investigation yet of organic monolayers using UV ellipsometry. Therefore the aim of this work is to show that sub-monolayer sensitivity can be achieved using in situ ellipsometry to monitor the evolution of the dielectric response of tris-(8-hydroxyquinoline)-aluminum(III) (Alq3 ) layers from ultra-low coverages to bulk-like layers. Alq3 was deposited under ultra-high vacuum conditions onto hydrogen passivated silicon and zinc oxide substrates. The characteristic Vacuum-Ultra-Violet (VUV) absorption lines of Alq3 were detected using synchrotron radiation as light source. In order to separate overlayer and substrate contributions to the effective dielectric function we use two different ways: analysis in terms of a conventional three phase model and a parameterfree approximation valid for ultra-thin films proposed by Aspnes [1]. In such ultra-thin films the absorption lines corresponding to molecular transitions of the Alq3 are found to be spectrally blue-shifted with respect to bulk-like layers. While it still remains to fully understand why the observed shift depends on the substrate, we proved for the first time that the dielectric response can be reliably obtained in the VUV range for strong absorbing materials even for sub-monolayer coverage. [1] D. Aspnes, Optical Properties of Solids-New Developments, ed B.Seraphin, Chap 15 (1976)

Fig. 1: Imaginary part of the dielectric function; comparison between the dielectric response for a sub-monolayer of Alq3 on H-Si(111) and on ZnO obtained from a model fit and calculated using the Aspnes approximation. The dielectric function for bulk Alq3 is also plotted. The calculated 2 from the Aspnes approximation is affected by the experimental noise of two different measurements.

Weiche Materie

Poster: Do., 13:00–15:30

D-P321

Aufkl¨ arung von Morphologien von Blockcopolymeren mit SAXS, TEM und AFM Volker Abetz1 , Adriana Boschetti-de-Fierro1 , Julio Albuerne1 , Daniel ´rgio S. Funari2 Fierro1 , Se 1

GKSS-Forschungszentrum Geesthacht GmbH, Institut f¨ ur Polymerforschung, MaxPlanck-Str. 1, 21502 Geesthacht – 2 HASYLAB beim DESY, Notkerstr. 85, 22603 Hamburg Wir haben Blockcopolymere aus Butadien, Styrol und Ethylenoxid durch sequentielle lebende anionische Polymerisation hergestellt und durch katalytische Hydrierung den Polybutadienblock in einen Polyethylenblock umgewandelt. Die Morphologie der erhaltenen Blockcopolymere vor bzw. nach der Hydrierung wurde mit Transmissionselektronenmikroskopie (TEM) und Rasterkraftmikroskopie (AFM) untersucht. In einigen F¨ allen konnte eine Morphologie nicht eindeutig identifiziert werden und aus diesem Grunde wurde R¨ ontgenkleinwinkelstreuung (SAXS) hinzugezogen. In manchen F¨ allen lieferten die verschiedenen Methoden u ¨bereinstimmende Ergebnisse, in anderen F¨ allen ergaben sich unterschiedliche Ergebnisse, welche in diesem Beitrag vorgestellt werden. Durch temperaturabh¨ angige SAXS-Messungen konnten auch reversible morphologische Ver¨ anderungen nachgewiesen werden, die teilweise mit der Kristallisation bzw. dem Schmelzen einzelner teilkristalliner Bl¨ ocke einherzugehen scheinen. Der Vortrag wird anhand dieser Beispiele deutlich machen, daß unterschiedliche und z. T. komplement¨ are Methoden notwendig sind, um sehr komplexe Strukturen aufkl¨ aren zu k¨ onnen, wie sie bei Blockcopolymeren auftreten k¨ onnen.

Weiche Materie

Poster: Do., 13:00–15:30

D-P322

Magnetic particles in supported polymer structure ¨llerM. M. Abul Kashem1 , L. Schulz1 , J. Perlich1 , S. V. Roth2 , P. Mu Buschbaum1 1

TU M¨ unchen, Physik-Department E13, James-Franck-Str. 1, D- 85747 Garching, Germany – 2 HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

A new class of composite materials is formed from the addition of magnetic particles in supported polymer nano-structures. The great potential of these composites are the substantial modification of the magnetic properties of polymers. The polymer nanostructures act as a template and enable a completely new arrangement of magnetic particles which is inaccessible with common magnetic materials [1]. The controlled incorporation of the magnetic particles (iron oxide) covered by polystyrene hairs yields to magnetic properties of the polymer composite. The polymer films containing particles are prepared by the spin-coating technique on the top of solid support. We use the diblock copolymer, polystyrene-block-polyisoprene, denoted by P(S-b-I), with a symmetric degree of polymerization of both monomer types. The nano-structures are created by additional preparation resulting in dewetting and micro-phase separation of P(S-b-I). Dewetting creates a drop-like structure of the polymer matrix. The self assembly process due to micro-phase separation inside such a superstructure produces an ordered nano-structure. Magnetic particles arrange themselves inside this nano-structured polymer matrix. Organization in a particular block is due to the selective affinity to one block in the diblock copolymer P(S-b-I). Such superstructure hosted nanoparticles are investigated with grazing incident small angle x-ray scattering (GISAXS) and atomic force microscopy (AFM). GISAXS experiments are carried out with synchrotron radiation at the beam line BW4 at HASYLAB, DESY, Hamburg. GISAXS gives us information (e.g., average statistics of length, height, and periodicity) of structures of nano- to micro- scale present inside the polymer films and on the surface [2]. Real space analysis by AFM provides us image of the structured surface in real space. Some of results of our investigation are presented. [1] V. Lauter-Pasyuk, H. J. Lauter, G. P. Gordeev, P. M¨ uller-Buschbaum, B .P. Toperverg, M. Jernenkov, W. Petry; Langmuir 19 (2003) 7783 [2] P. M¨ uller-Buschbaum; Anal. Bioanal. Chem. 376 (2003) 3

Weiche Materie

Poster: Do., 13:00–15:30

D-P323

Real time evolution of structural and morphological features in quenched polymers during heating Giovanni C. Alfonso1 , Fiorenza Azzurri1 , Matteo Alessi1 , Sergio S. Funari2 1

Department of Chemistry and Industrial Chemistry, University of Genova, Via Dodecaneso, – 2 HASYLAB at DESY, Notkestraße 85, D-22603 A simple experimental approach to gain information on structuring of polymeric materials in very fast cooling processes, mimicking solidification under processing conditions, has been recently developed in our laboratory. It consist in sandwiching a thin wire thermocouple type K (wire diameter 50 microns) between two thin films (ca. 200 micron thick) of the polymer and in recording its signal at fairly high sampling rate (5-10 readings/s) while the sample cools due to its immersion in a thermostatic liquid bath at a given constant temperature. The analysis of the cooling curve, T(t), is then carried out to obtain semi-quantitative information on the latent heat released by the crystallization of the sample. A set of experiments performed with i-PP, PVDF and HDPE at several quench temperatures indicate that crystallization takes place at increasingly higher undercooling and to a progressively lower extent on increasing cooling rate and that the sensitivity of crystallization to the imposed quench conditions decreases on increasing the intrinsic crystallization rate of the polymer, i.e. in the order i-PP>PVDF>HDPE. In general, samples obtained by quenching at rates of the order of several hundreds ◦ C/s contain metastable highly defective crystals which may undergo important structural and morphological reorganization before melting during a typical DSC scan aimed at establishing the correlation between crystallization conditions and characteristics of the semicrystalline state. In this context, the unique potential of simultaneous acquisition of SAXS/WAXD during heating provided by synchrotron facilities enables one to obtain an unambiguous picture of the evolution of crystals with different initial features. This will be demonstrated, for example, by comparing the reorganization and melting behaviour of i-PP samples quenched to various temperatures, from 20 to 90 ◦ C, and initially exhibiting different structures, from pure smectic to a mixture of smectic and α-monoclinic. The following observations can be made: - the weakly exothermal smectic-monoclinic transition takes place in the solid state and, upon heating, it begins at temperatures which are slightly lower for samples solidified at very high cooling rates. - the structural and morphological features of differently quenched samples progressively change during heating and, at temperatures around 120 ◦ C, the systems eventually attain an identical type and extent of ordering despite the appreciable differences in their initial state. This implies that, consistent with the recorded DSC signals, their behaviour in the melting range is independent from the initial morphology and structure and, therefore, it cannot be used to differentiate the state of order in products obtained under typical processing conditions.

Weiche Materie

Poster: Do., 13:00–15:30

D-P324

D¨ unne Filme aus kristallinen Diblockcopolymeren C. Darko1 , I. Botiz2 , G. Reiter2 , S.V. Roth3 , D.-M. Smilgies4 , C.M. Papadakis1 1

Physikdepartment E13, Technische Universit¨ at M¨ unchen, James-Franck Str. 1, 85747 Garching – 2 Institut de Chimie des Surfaces et Interfaces, CNRS, Mulhouse, Frankreich – 3 HASYLAB at DESY, 22063 Hamburg – 4 Cornell High Energy Synchrotron Source, Cornell University, Ithaca NY, USA In Blockcopolymeren mit einem kristallisierenden Block k¨ onnen sowohl die Kristallisation als auch die Mikrophasenseparation der beiden Bl¨ ocke die Strukturbildung bestimmen. In der Geometrie des d¨ unnen Films sind die Strukturen makroskopisch ausgerichte, und GIXD und GISAXS sind ideal geeignet, um einen großen L¨ angenskalenbereich zu untersuchen. Die Oberfl¨ achentexturen d¨ unner Filme aus lamellaren Poly(styrol-b-ethylenoxid) (PSb-PEO) Diblockcopolymeren (Blockmolmassen von 3000 g/mol) h¨ angen stark von der Kristallisationstemperatur ab (Abb. 1a,b). GIXD zeigt jedoch, dass bei allen untersuchten Kristallisationstemperaturen die PEO-Ketten senkrecht auf dem Substrat stehen (Abb. 1c). Die durch Kristallisation bzw. Mikrophasenseparation entstandenen mesoskopischen Strukturen bestehen bei allen Temperaturen aus Lamellen, deren Grenzfl¨ achen parallel zur Substratoberfl¨ ache liegen (Abb. 1d) und deren Dicke mit der Temperatur zunimmt.

Abb. 1: In der optischen Mikroskopie an PS-b-PEOFilmen bei Kristallisationstemperaturen Tx = 40 ◦ C (a) und 50 ◦ C (b) sind die wachsenden Kristallite sichtbar. (c) GIXD-Streukurve in der Filmebene bei Tx = 40 ◦ C. (d) 2D GISAXS-Streubild bei Tx=40 ◦ C bei einem Einfallswinkel von 0.15◦ .

Weiche Materie

Poster: Do., 13:00–15:30

D-P325

Thin Films of Multiferroic Oxides Christophe Daumont1 , Gustau Catalan1,2 , Caliebe3 , Beatriz Noheda1

Oliver Seeck3 ,

Wolgang

1

Solid State Chemistry, Material Science Centre, University of Groningen, Nijemborgh 4, 9747 AG Groningen, The Netherlands – 2 Departement of Earth Sciences, University of Cambridge, Dowing Street, Cambridge, CB2 3EQ, United Kingdom – 3 HASYLABDESY, Notkestr. 85, D-22603 Hamburg, Germany Multiferroics are materials that exhibit ferroelectricity and magnetism simultaneously. If these two properties are coupled, multiferroics offer the interesting possibility of manipulating electric properties by applying a magnetic field and vice versa, with potentially high impact in spintronics, memory, sensor, and other applications. Unfortunately, they are very rare and the existing ones only show large magnetoelectric (ME) coupling at low temperature. Although the search and design of new multiferroics are attracting much attention since the last couple of years, the mechanisms driving the coupling between ferroelectricity and magnetism are very diverse and still not well understood [1]. Among the multiferroics, the perovskite oxides are of great interest because their relatively simple structure allows easier access to the fundamental understanding of their ME coupling. Epitaxial growth of multiferroic films allows the tuning of the film properties, by means of strain imposed by the substrate. So strain provides an additional parameter to increase the temperature and magnitude of the ME coupling. Perovskites are well suited for that due to the availability of several perovskite substrates, such as SrTiO3 . Using Pulsed Laser Deposition (PLD), multiferroic BiFeO3 and TbMnO3 films with thicknesses of tens of nanometers have been epitaxially grown on SrTiO3 substrates [2],[3]. More recently, ultrathin films of BiFeO3 have also been reported down to 5nm[4], but the characterization of such thin layers by means of standard x-ray diffraction is not easy because of the limited diffracted intensity. As far as we know, there are no reports of TbMnO3 films with thicknesses below 100 nm. Growth and characterization of ultrathin film is also important in the context of multilayer growth. We report the successful growth of epitaxial ultrathin (5 nm) films of BiFeO3 and TbMnO3 on SrTiO3 single crystals via RHEED-assisted PLD. The structural characterization of these films has been done using synchrotron radiation at the DORIS W1 beamline at HASYLAB in grazing-incidence and reflection geometry. By characterizing these films as a function of temperature and thickness we expect to shed light into the effect of strain and the strain relaxation on the multiferroic properties of the layers. [1] N. M. Fiebig, J. Phys. D, R123 (2005); [2] J. Wang et al., Science 299, 1719 (2003); W. Eerenstein et al., Science 307, 1203 (205); [3] Y. M. Cui et al., APL 86, 203501 (2005) ; G. Xu et al., APL 86, 182905 (2005) ; X. Qi et al., APL 86, 071913 (2005); [4] H. B´ea et al., APL 88, 062502 (2006)

Weiche Materie

Poster: Do., 13:00–15:30

D-P326

Relationship between Crystalline Structure and Mechanical Behavior in Isotropic and Oriented Polyamide 6 ´rgio S. Nadya Dencheva1 , Zlatan Denchev1 , Maria Jovita Oliveira1 , Se Funari2 1

IPC Institute for Polymers and Composites, Department of Polymer Engineering, University of Minho, 4800-058 Guimar˜ aes, Portugal – 2 HASYLAB at DESY, Notkestrase 85, 22603 Hamburg, Germany The present study discusses the mutual relationship between the crystalline structure and the mechanical behavior in polyamide 6 (PA6) isotropic films and oriented cables prepared by compression molding or by consecutive extrusion and cold drawing. These samples were afterwards isothermally annealed in the 120-200o C range and than subjected to tensile tests at room temperature. 2D synchrotron WAXS and SAXS patterns were obtained before and after mechanical failure. The structural data obtained from these patterns (e.g., degree of crystallinity, d-spacing and long spacing values, orientation, content of α- and γ-PA6 polymorphs) were discussed in relation with the mechanical properties (e.g., Young modulus, yield stress and break strain) of the corresponding isotropic and oriented samples. It was demonstrated that annealing of isotropic PA6 in the 120-200o C range results in an increase in both Young modulus (from 730 to 1030 MPa) and of the yield stress values - from 40 to 50 MPa. These two findings were related to the proportional reduction of the d-spacing of the (002) plane for α-PA6 and of the (200) plane for the γ-PA6. The decrease of break strain values from 81 to 37 % as a function of annealing temperature was elucidated by analysing the corresponding 2D SAXS and WAXS patterns after mechanical failure. Stretching of samples annealed at 120o C resulted in extension of the amorphous domains whereas the crystalline ones did not orient. Samples annealed at 160 and 200o C showed significant anisotropy of the crystalline domains along the draw direction meaning that the amorphous phase did not absorb but transferred the stress to the crystalline phase. With the oriented PA6 samples, increasing the annealing temperature resulted in an increase of Young modulus from 990 to 3800 MPa, and of the yield stress in the 135-200 MPa range, the strain decreasing from 150 to <50 %. The main structural reason for this mechanical behaviour was related to the observed phase transition from γ- to α-PA6. This effect occurred upon annealing above 120o C, the less ductile and harder α-form becoming the predominant polymorph. In the framework of the crystal slip-governed plasticity, the increase of the stress and Young modulus values was again associated with the observed well-pronounced reduction of the inter-sheet distances of both polymorphs.

Weiche Materie

Poster: Do., 13:00–15:30

D-P327

Swift Ion Beams for Solid State Physics and Materials Science, Medicine and Science of Art Andrea Denker1 1

Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin

The effects of the electronic energy loss of fast ions in materials have gained increasing importance for modern science and technology over the past years. The research field includes, among others, permanent materials modification of solids by heavy ions. New, unexpected findings like the self organisation of the irradiated material have been observed. Besides the fundamental research concerning the interaction of ions with matter, ion beams are exploited in applied research, e.g. the study of radiation hardness of electronic compounds for aerospace. The high quality of ion beams from a cyclotron allows challenging novel applications and the elaboration of existing techniques: Hightech miniature filter production by heavy ion irradiation as well as eye tumour therapy profit from the high beamy stability, whereas materials analysis benefits from the low beam emittance. Different applications, ranging from high current irradiations to single ion track applications, will be presented. Examples from materials analysis using heavy ions for ERDA (Elastic Recoil Detection Analysis) of complex layered structures like solar cells as well as the non-destructive analysis of art objects, e.g. Egyptian coffin masks, by high energy PIXE (Proton Induced X-ray Emission) will be shown. The specific requirements for the accelerators will be discussed.

Weiche Materie

Poster: Do., 13:00–15:30

D-P328

Microspectroscopy of organic thin films ¨ rg Raabe2 , David Kilcoyne3 Rainer Fink1 , Gregor Bozek1 , Jo 1

Univ. Erlangen, Physikalische Chemie II, Egerlandstr. 3, D-91058 Erlangen – 2 Paul Scherrer Institut, SLS, WSLA/225, CH-5232 Villigen-PSI – 3 ALS, 1 Cyclotron Road, MS 7R0222, LBNL,Berkeley, CA 94720 - 8225 Zone-plate base scanning-transmission microspectroscopy offers manyfold different application with lateral resolutions well below 50 nm. The operation of the microscope in either He atmosphere or in vacuum allows the investigation of thin solid films and liquid films in wet cells. The BMBF funded PolLux project, which is presently under commissioning at the Swiss Light Source (Paul Scherrer Institut, Villigen) will be an easy to use microspectroscopy facility which offers a wide variety of experimental possibilities in the photon energy range from 260 to 1100 eV. Within this project, we have performed laterally resolved NEXAFS investigations of ultrathin organic films prepared either by vacuum sublimation or by dip- or spin-coating from solution. Particular emphasis was lying on structure-property relationships in thus prepared samples. The materials under investigation were ranging from supramolecular ligand stabilised assemblies with paramagnetic ions (which may also regarded as molecular magnets containing Fe and Mn ions), heteroaromates, metal-organic charge-transfer complexes, binary liquid films (see Fig. 1)and films from triblock copolymers. In all cases the NEXAFS contrast at the respective absorption edges was used for contrast improvement of the images or - in the case of multicomponent samples - to identify the different chemical species within the film. Nano- and microcrystalline growth is observed in many samples thus allowing to utilize the NEXAFS linear dichoism to monitor the molecular orientations. Due to the high photon flux density in the focussed beam radiation damage has been checked carefully. In contrast to other spectromicroscopies (e.g. XPEEM) illumination times in the millisecond range reduces damage significantly as demonstrated for the extremely sensity molecular magnets. This project is funded by the BMBF under contract 05 KS4WE1/6.

Fig. 1: STXM micrographs recorded at two different photon energies of a binary liquid crystal film prepared on 100 nm thick Si3 N4 -membranes (image size: 25 µm2 ) . Contrast reversal is the signature for the two different species.

Weiche Materie

Poster: Do., 13:00–15:30

D-P329

SANS experiments on confined polymers in microemulsions ¨rgen Allgaier1 , Dieter Henrich Frielinghaus1 , Simona Maccarrone1 , Ju 1 Richter 1

Forschungszentrum J¨ ulich GmbH, Institut f¨ ur Festk¨ orperforschung, D-52425 J¨ ulich, Germany It has been established that amphiphilic diblock copolymers increase the efficiency of surfactants in microemulsions (polymer boosting effect). These studies always considered large oil and water domains of size d compared to the typical polymer size Rg . Thus the confinement parameter Rg /d was small in these first studies. The ongoing studies of this paper consider medium and higher confinement, where small angle neutron scattering measurements reveal a new behaviour, which can be compared to computer simulations by T. Auth [1]. Microemulsions consist of immiscible oil and water, and a third component, the surfactant. The surfactant mediates between oil and water; thus a macroscopically homogenous phase is formed. Microscopically, domains of oil and water are formed with a surfactant film in between. The efficiency of a surfactant is measured by the minimum amount of surfactant needed to form a one-phase microemulsion. In previous studies [2] amphiphilic diblock copolymers proved to enhance the efficiency of surfactants dramatically (polymer boosting effect). By SANS experiments using contrast variation it was shown that the polymer decorated the film and the membrane bending rigidity is increased. Thus larger domain structures are formed with a better surface to volume ratio. The current studies focus on microemulsions with smaller domain sized d compared to the typical polymer size Rg . The variation of the ratio could be achieved by different polymers and the use of different oils, since the efficiency of the surfactant is oil dependent. At low confinement the result of the initial studies [2] is confirmed; at intermediate confinement a slightly higher sensitivity of the polymer effect is obtained, while at high confinement a reversed behaviour is observed. The theory of Auth [1] predicts a much more enhanced sensitivity at medium confinement and a reversed behaviour at larger confinement. These results are interesting for applications (enhanced polymer boosting) and interpretations of biological membranes (reversed behaviour). [1] T. Auth, PhD thesis, University Cologne, Cologne, Germany [2] B. Jakobs, T. Sottmann, R. Strey, J. Allgaier, L. Willner, D. Richter, Langmuir 15, 6707 (1999); H. Endo, M. Mihailescu, M. Monkenbusch, J. Allgaier, G. Gompper, D. Richter, B. Jakobs, T. Sottmann, R. Strey, I. Grillo, J. Chem. Phys. 115, 580 (2001)

Weiche Materie

Poster: Do., 13:00–15:30

D-P330

Investigation of mixed micelles of a bolamphiphile and SDS using protonated and deuterated SDS ¨ tz Milkereit1 , Vollkmar Vill1 , Vasil Garamus2 , Regine Sven Gerber1 , Go Willumeit2 1

University of Hamburg, Inst. of Organic Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany – 2 GKSS Research Centre, Max-Planck-Str. 1, 21502 Geesthacht, Germany

In this work we investigated the interaction of a carbohydrate-based bolaamphiphile with sodium dodecyl sulfate (SDS). SDS-mixtures in particular gained much interest in mixed surfactant systems, therefore much data is available that can be compared with results from our studies. It is known that SDS shows synergism in mixtures with non ionic surfactants. Experiments were carried out using deuterated and protonated SDS to obtain information about mixing with the bolaamphiphile and it0 s location in mixed micelles. The main feature, which has to be compared for both curves, is the position of the maximum. The position of the maximum is connected with the average distance between aggregates qmax ∼ 1/d1/3 which is determined by the concentration of aggregates. The constant value of qmax supports the idea that the concentration of aggregates, there we observe SDS and MDM (solution with protonated SDS) and there we can observe only MDM (solution with deuterated SDS), is the same. It means that we observe the same aggregates i.e., mixed micelles of SDS and MDM. It is well-known for non-ionic/ionic mixtures. Analysis of solutions with h-SDS and d-SDS gives the same parameters of aggregates. It points that the chosen model of one population of mixed micelles (without demixing within the micelle) is correct for the length scale l > π/q > 10 ˚ A. Aggregates are of a non-spherical (oblate) shape which is in accordance with pure SDS micelles . The total aggregation number is 30 % less than for pure SDS micelles but it should be taken into account that MDM molecules are significant larger than SDS ones. The observed slightly oblate shape shape of aggregates is in agreement with a preferably planar geometry of bola amphiphiles.

Fig. 1: a) Principal structure of bolaamphiphiles; b) investigated compound: 1,12-bis-[400 -O(α-D-glucopyranosyl)-β-Dglucopyranosyl]-dodecane (MDM)

Weiche Materie

Poster: Do., 13:00–15:30

D-P331

Template-directed formation of ordered colloidal assemblies Thomas Geue1 , Patrick Huber1 , Beate Reinhold2 , Knut Morawetz2 , Ullrich Pietsch3 , Marcus Textor4 1

Laboratory for Neutron Scattering, ETH Zurich PSI, CH-5232 Villigen, Switzerland – Institute of Physics, University of Potsdam, D-14415 Potsdam, Germany – 3 University of Siegen, FB7 Solid State Physics, D-57068Siegen, Germany – 4 Materials Science Dept., ETH Zurich, CH-8093 Zurich, Switzerland 2

The investigated ordered colloidal assemblies are three-dimensional periodic structures formed from small polystyrene spheres suspended in solution. These assemblies attract considerable attention when used as optical filters, switches and materials with photonic band gaps. Unluckily, a broad application of ordered colloidal assemblies is greatly restricted by numerous difficulties in the formation of large area ordered crystalline assemblies with uniform crystal orientation. We here present an approach using a holographically manufactured template made from a photopolymer which is pre-structured. The aim of these templates is to allow the growing of ordered colloidal assemblies by slow sedimentation to direct the crystallization of colloids towards bulky crystals and to allow a tailoring of the final lattice structure, orientation and size of the final colloidal assemblies. The understanding of the sedimentation process is hereby of great importance. Although there are optical [2,3] and confocal [4] microscopy well established as is-situ investigation techniques, both methods are limited. On the one hand optical microscopy is suitable investigating large particles in 2 dimensions while the confocal microscopy requires fluorescence labeled specimen for the observation. The methods are, moreover, more or less limited to describe surface phenomena only. To fully monitor the crystallization process in 3 dimensions, X-ray reflectometry and in-situ small angle X-ray scattering under grazing incidence as well as transmission geometry were used to describe the phenomena taking place on the formation of colloidal layering. These techniques are rarely used to investigated the formation of ordered colloidal assemblies so far [5]. [1] [2] [3] [4] [5]

Blaaderen, A. van, Ruel, R., Wiltzius, P. Nature, 385(1997) 321 Dushkin, C. D. et al.. Colloid Polym. Sci., 277 (1999) 914 Yin, Y. et al. J. Am. Chem. Soc., 123 (2001) 8718 Hoogenboom, J. P., Vergeer, P., Blaaderen, A. van J. Chem. Phys., 11 (2003) 3371 Narayanan, S., Wang, J., Lin, X.-M. Phys. Rev. Lett., 93 (2004) 135503

Weiche Materie

Poster: Do., 13:00–15:30

D-P332

Phasenverhalten mizellarer Systeme unter Druck H. Gibhardt1 , C.R. Haramagatti1 , A. Islamov2 , A. Kuklin2 , G. Eckold1 1

Institut f¨ ur Physikalische Chemie, Universit¨ at G¨ ottingen – 2 Frank Laboratory of Neutron Physics, JINR Dubna Mizellare L¨ osungen zeichnen sich durch eine Vielzahl von Anwendungen aus, die insbesondere durch die Aggregationseigenschaften von Tensidmolek¨ ulen hervorgerufen werden. Spezifische Wechselwirkungen zwischen einzelnen Molek¨ ulen und zwischen den Mizellen f¨ uhren zu komplexen Strukturen, die mit mikroskopischen Streumethoden, wie Neutronen-Kleinwinkelstreuung und Raman-Streuung, charakterisiert werden k¨ onnen. Am Beispiel von Alkyl-Trimethylammoniumbromid-L¨ osungen wurden Struktur und Dynamik in weiten Bereichen von Temperatur, Druck, Konzentration sowie unter dem Einfluss von Salz-Additiven untersucht, wobei insbesondere das Kristallisationsverhal¨ ten im Vordergrund stand. Der Ubergang von der fl¨ ussigen mizellaren L¨ osung in eine gelartige oder feste Phase bei hohem Druck oder tiefer Temperatur ist verkn¨ upft mit dem Verschwinden eines Korrelationspeaks in der Kleinwinkelstreuung, der die Aggregation der geladenen Mizellen charakterisiert. Gleichzeitig ver¨ andert sich aber auch die Konformation der Alkylketten, was sich in den Schwingungsspektren bemerkbar macht. Die Stabilit¨ atsbereiche von fl¨ ussigen L¨ osungen, gelartigen und festen Phasen konnten durch Kombination beider Untersuchungsmethoden detailliert bestimmt werden. Dabei ergab sich insbesondere bei hohen Tensidkonzentrationen und bei h¨ oheren Dr¨ ucken ein ausgepr¨ agtes Zwei-Phasengebiet. Dar¨ uber hinaus wurde in Systemen mit gen¨ ugend langen Alkylketten, wie z. B. C16 H33 , eine gelartige intermedi¨ are Phase beobachtet. Wie zeitabh¨ angige Experimente ergaben, ist die Kristallisationskinetik außerordentlich langsam mit charakteristischen Zeiten im Bereich von einigen Stunden. Dieses Projekt wurde vom Bundesministerium f¨ ur Bildung und Forschung unter dem F¨ orderkennzeichen 03-DU03G2 und vom Graduiertenkolleg GRK 782 gef¨ ordert.

Weiche Materie

Poster: Do., 13:00–15:30

D-P333

Struktur und mechanische Eigenschaften von Spinnenseide ´1 , Thorsten Vehoff1 , Tim Salditt1 Anja Gliˇ sovic 1

Institut f¨ ur R¨ ontgenphysik, Friedrich-Hund-Platz 1, 37077 G¨ ottingen

Spinnendseide, besonders die Seide der Rahmenf¨ aden, ist wegen ihrer ungew¨ ohnlichen Kombination aus Zugfestigkeit und Dehnbarkeit immer mehr ins Interesse der Wissenschaft ger¨ uckt [1]. Trotz der zunehmenden Forschung an Spinnenseide ist die Verkn¨ upfung der Struktur mit den mechanischen Eigenschaften weitgehend unverstanden [2]-[4]. Um diese Korrelation genauer zu untersuchen, wurde eine Kombination von Kraft-Dehnungs-Messungen und R¨ ontgenstreuung an einzelnen Spinnenf¨ aden (ca. 6 µm) bei unterschiedlichen Luftfeuchten an der Microfocus Beamline ID 13 der ES¨ RF in Grenoble durchgef¨ uhrt. Diese Methode erm¨ oglicht es die Anderungen des kristallinen Anteils der F¨ aden zu untersuchen [5]. Die so gefundenen Ver¨ anderungen der β-Faltblattkristallite werden vor dem Hintergrund der mechanischen Eigenschaften diskutiert. [1] [2] [3] [4] [5]

Vollrath et al., App. Phy. A 82 (2006) 205 Grubb et al., Macromolecules 30 (1997) 2860 Thiel et al., Biopolymers 41 (1997) 703 Gosline et al., J. Exp. Bio. 202 (1999) 3295 C. Riekel et al., Int. J. Bio. Mac. 29 (2001) 203

Weiche Materie

Poster: Do., 13:00–15:30

D-P334

Nasses und trockenes Holz — zwei sehr verschiedene Materialien ¨ lln1 , Henrik Lemke1 , Martin Dommach2 , Sergio Ingo Grotkopp1 , Klaas Ko 2 ¨ller1 S. Funari , Richard Davies3 , Manfred Burghammer3 , Martin Mu 1

Institut f¨ ur Experimentelle und Angewandte Physik, Universit¨ at Kiel, 24098 Kiel – HASYLAB bei DESY, Notkestr. 85, 22603 Hamburg – 3 ESRF, B. P. 220, F-38043 Grenoble Cedex, Frankreich

2

Durch den Wassergehalt von Holz lassen sich die mechanischen Eigenschaften von Holz drastisch ¨ andern. Bei nassem Holz, wie es ja auch der Baum verwendet, sind sowohl der Elastizit¨ atsmodul als auch die Bruchfestigkeit niedriger als bei trockenem oder leicht feuchtem Holz, wie wir es als Konstruktionsmaterial einsetzen. Auf mikroskopischer Ebene sind die Mechanismen, die zu diesen großen mechanischen Unterschieden f¨ uhren, noch nicht bekannt. Seit vielen Jahren wird R¨ ontgenstreuung zur Untersuchung der Mikro- und Nanostruktur von Holz eingesetzt; u. a. k¨ onnen die Gitterkonstanten der kristalline Zellulose– Mikrofibrillen und deren Orientierungsverteilung bestimmt werden. Es ist auch ein direkter Zugang zum sogenannten Mikrofibrillenwinkel (MFA) m¨ oglich, der als der Steigungswinkel der helikalen Anordnung der Mikrofibrillen in der Zellwand in Bezug auf die longitudinale Zellachse definiert ist. An Synchrotronstrahlungsquellen mit ihrer hohen Brillanz k¨ onnen Mikrostrahlen in den Streuexperimenten verwendet werden, die eine mikroskopische Ortsaufl¨ osung und damit Abrastern erm¨ oglichen. Wir kombinieren Streckexperimente an Nadelholz (Fichte und Kiefer) in situ mit R¨ ontgendiffraktion. Mit einer neuartigen Probenumgebung k¨ onnen wir den Wassergehalt der Proben kontrollieren. D¨ unne Holzfolien wurden am HASYLAB (A2) untersucht, einzelne Holzzellen am ESRF (Mikrofokus–Beamline ID13), um auch den Einfluß des Zellverbandes zu ermitteln. Unsere Ergebnisse erlauben es, erstmals ein mikroskopisches Modell f¨ ur die unterschiedlichen Verformungsmechanismen in trockenem und nassem Holz zu entwickeln. Hierin spielt die weiche Matrix aus ungeordnetem und f¨ ur Wasser zug¨ anglichen Material, in die die Mikrofibrillen im Sinne eines Verbundmaterials eingebettet sind, eine entscheidende Rolle.

Weiche Materie

Poster: Do., 13:00–15:30

D-P335

Influence of melittin on phase behaviour of lipids with various headgroups Maria Hanulova1 , Sergio S. Funari1 1

Hasylab at Desy, Notkestrasse 85, Hamburg, Germany

Melittin, a 26 amino acid peptide, is the toxin of bee venom with hemolytic and antibacterial activity. It binds to natural and model lipid membranes and at high molar ratios disrupts them. Using X-ray diffraction, we studied the influence of melittin on the phase behaviour of model lipid membranes composed of phospholipids with various headgroups: phosphatidylcholine, prevalent in membranes of red blood cells, phosphatidylethanolamine, main component of bacterial membranes, and phosphatidylglycerol, also important in bacterial membranes. We also studied lipid mixtures mimicking the composition of cell membranes. At lipid:protein ratios used in this study, 50 to 10000, the membrane is preserved, but melittin induces phase changes. In palmitoyloleoyl phosphatidylethanolamine, melittin induces two coexisting cubic phases and in palmitoyl-oleoyl phosphatidylcholine a phase separation in the lamellar phase.

Weiche Materie

Poster: Do., 13:00–15:30

D-P336

Dynamics of bicontinuous microemulsions on intermediate and short lengthscales ¨rgen Olaf Holderer1 , Henrich Frielinghaus1 , Michael Monkenbusch1 , Ju Allgaier1 , Dieter Richter1 , Bela Farago2 1

Institut f¨ ur Festk¨ orperforschung, Forschungszentrum J¨ ulich, 52425 J¨ ulich – 2 Institut Laue Langevin, Grenoble, BP 156, F38042 Grenoble Cedex 9, France Bicontinuous microemulsions, consisting of water, oil and a surfactant (C10E4), have been studied with neutron spin echo spectroscopy (NSE) and small angle neutron scattering (SANS). Addition of diblock copolymers (PEPX -PEOX ) or homopolymers (PEPX and PEOX , X=5 k or 10 kg/mol molecular weight) allows a tuning of the membrane properties such as the bending rigidity κ in such systems. The dynamics of bicontinuous microemulsions has been studied with NSE. On lenght scales of the order of the characteristic structural distance d (i.e. scattering angles ≈ qo = 2π/d) of the microemulsion, two contrasts for neutrons have been used: bulk contrast, where the dynamics of the oil/water difference is visible, and film contrast which reveals the surfactant layer fluctuations. Comparison with theoretical predicitons of the relaxation shed light on hydrodynamic interactions in bicontinuous microemulsions. On shorter length scales (i.e. larger scattering angles, q > 4q0 ), the bending modulus κ is obtained from a numerical integration of the intermediate scattering function S(q, t) of the Zilman-Granek model [1]. It is shown that the analysis of the dynamics gives a direct access to the ”bare” membrane bending moduls κ, which is compared to the renormalized one as obtained from SANS[2]. The difference between the two ways of determining κ is the renormalization factor, as predicted by theory. A decrease (increase) of the bending rigidity has been observed when homopolymers (diblock copolymers) have been added, in agreement with theoretical predictions. [1] A. Zilman, and R. Granek, Phys. Rev. Lett. 77 (1996) 4788. [2] O. Holderer et al., J. Chem. Phys. 122 (2005) 094908.

Weiche Materie

Poster: Do., 13:00–15:30

D-P337

Multicompartment-Hydrogele aus amphiphilen Poly(2-oxazolin) Triblockcopolymeren ¨dtke2 , T. Komenda2 , R. Jordan2 , K. R. Ivanova1 , T.B. Bonne1 , K. Lu 3 4 Mortensen , P.K. Pranzas , C.M. Papadakis1 1

Physikdepartment E13, Technische Universit¨ at M¨ unchen, 85747 Garching – Lehrstuhl f¨ ur Makromolekulare Stoffe, Department Chemie, Technische Universit¨ at M¨ unchen, 85747 Garching – 3 Danish Polymer Centre, Risø National Laboratory, DK4000 Roskilde, D¨ anemark – 4 Institut f¨ ur Werkstoffforschung, GKSS, 21502 Geesthacht 2

Amphiphile Copolymere finden u.a. Anwendung als Gelbildner oder Nanoreaktoren. In Blockcopolymeren aus Poly(2-oxazolin) kann die Wasserl¨ oslichkeit der Bl¨ ocke durch die Wahl der acylischen Seitengruppen kontrolliert eingestellt werden (Abb. 1a, Ref. 1). Wir untersuchen mizellare Hydrogele aus Triblockcopolymeren mit lipophilen, hydrophilen und fluorophilen Seitengruppen, die es erm¨ oglichen, Multicompartmentsysteme aus chemisch verschiedenen Mizellen zu bilden. Kleinwinkelneutronenstreumessungen mit Kontrastvariation zeigen, dass hydrophile/ lipophile und hydrophile/ fluorophile Diblockcopolymere in w¨ assriger L¨ osung KernSchale-Mizellen bilden, wobei erstere kugelf¨ ormig sind, letztere hingegen l¨ anglich, was auf den sterischen Anspruch bzw. die Steifigkeit der fluorophilen Seitengruppen zur¨ uckgef¨ uhrt werden kann. In w¨ assriger L¨ osung bilden diese Diblockcopolymere keine gemeinsamen Mizellen. Oberhalb einer Konzentration von ca. 10 Gew.Prozent bilden lipophile/ hydrophile/ fluorophile Triblockcopolymere Gele. Ihre Streukurven werden durch koexistierende kugelf¨ ormige lipophile und l¨ angliche, fluorophile Mizellkerne beschrieben, die von den hydrophilen Bl¨ ocken verbunden werden (Abb. 1b), was auf ein polymeres Multicompartment-Hydrogel hindeutet. [1] T.B. Bonne, K. L¨ udtke, R. Jordan, P. Stepanek, C.M. Papadakis, Coll. Polym. Sci. 282 (2004) 833. [2] T.B. Bonne, K. L¨ udtke, R. Jordan, C.M. Papadakis, eingereicht.

Abb. 1: a) Ein lipophiles/hydrophiles/fluorophiles Poly(2-oxazolin) Triblockcopolymer. b) SANS Streukurve eines Hydrogels (20 Gew.-prozent) und Fitkurven. Inset: Skizze des MulticompartmentHydrogels.

Weiche Materie

Poster: Do., 13:00–15:30

D-P338

Structure and crystallinity study in thin films of poly(3-hexylthiophene) Siddharth Joshi1 , Souren Grigorian1 , Ullrich Pietsch1 , Achmad Zen2 , Dieter Neher2 1

Festk¨ orperphysik, Universit¨ at Siegen, Siegen, Germany – 2 Institut f¨ ur Physik, Universit¨ at Potsdam, Potsdam, Germany Organic material devices have gained a lot of attention from last decade due to their application to polymeric electronic devices such as light-emitting diodes, Field-effect transistor(FETs), and photovoltaic cells (PVs). The special interest are focus on the low-cost devices based on polymeric materials prepared by simple solution processing. Regioregular poly(3-hexylthiophene) (P3HT) is one of the most promising polymer material for such purpose having high charge carrier mobility. Up-to now one of the fundamental problems in polymer transistors are to understand the relation between the surface morphology and the charge transport as they have relatively low chargecarrier mobility compared to inorganic semiconductor devices. Therefore our studies are focussed on the investigation of the structural order [1] and the degree of crystallinity of semicrystalline thin films (few nm) of low and high molecular weight of P3HTs using X-ray scattering techniques. For detailed studies grazing incidence X-ray diffraction [2,3] (GID) has employed to determine the vertical and lateral structures of films, additionally, X-ray reflectivity technique has been used to know the average thickness of such organic thin films using synchrotron radiation source. The degree of crystallinity was determined utilising Rulands method [4]. The present status of our calculations suggests that P3HT thin films having low molecular weight show a high degree of crystallinity compared to films with high molecular weight. This has been explained by the fact that crystalline parts of P3HT are embedded into the amorphous matrix. Temperature and concentration dependent study of the interplaner distances d of the P3HT thin films have shown that the d spacing increases with temperature and depending on layer thickness. In general, structural investigations at thin polymer films suffer from possible beam damage caused by probing high-intense synchrotron radiation. Therefore the content of structural investigations received from experiment might depend on the synchrotron radiation source for the experiment. [1] [2] [3] [4]

R. J. Kline, et. al., Nature materials, 5 (2006) 222. A. Zen, et al., Macromolecules, 39 (2006) 2162. A. Zen., et al., Adv. Funct. Mater. 14 (2004) 757. W. Ruland, Acta Cryst., 14 (1961) 1180.

Weiche Materie

Poster: Do., 13:00–15:30

D-P339

A simultaneous SWAXS/Shear/DSC study of a lipid model emulsion Daniel Kalnin1,4 , Olivier Schafer2 , Gerard Keller1 , Heinz Amenitsch3 , Michel Ollivon1 1

UMR 8612 CNRS, Equipe de Physico-Chimie des Syst`emes Polyphas´es, 92296 Chˆ atenay-Malabry, France – 2 CRN, Centre de Recherche Nestl´e, Vers-Chez-les-Blanc, 1000 Lausanne 26, Switzerland – 3 SAXS-Beamline 5.2, ELETTRA Sincrotrone, Trieste, 34012 Basovizza (TS), Italy – 4 current adress: WUR, Wageningen University and Research center, Agrotechnology Food Sciences, Physical-Chemistry of Foods Group, PO Box 8129, 6700 EV Wageningen, The Netherlands; mail : [email protected] The influence of shear on crystallization behavior of emulsified triacylglycerols (TAG) is investigated using a new micro-Couette device consisting of two coaxial quartz capillaries. The setup allows for simultaneous measurement of thermal and structural properties of micro samples under shear or in quiescent conditions. Small and wide angle X-ray diffraction is performed simultaneously with DSC measurements under or in the absence of shear. A structural study of lipids under shear was undertaken by Mazzanti et al. focussing on bulk lipids [1]. Hereafter, the crystallization behavior of a model emulsion consisting of palm oil stabilized with sodium caseinate (SC) is analyzed. The combination of the thermal and structural measurements allows for the determination of the molecular packing of lipids[2] even within emulsion droplets. In quiescent conditions where a detailed study recently showed the influence of the concentration of an emulsifier of the crystallisation behaviour[3], a lamellar phase of TAG of 2Lα type crystallizes first showing a d-spacing of 41 ˚ A on cooling. Its progressive transformation through a monotropic phase transition 2Lα 2Lβ is observed during the subsequent heating. However, under shear conditions, the more stable 2Lβ lamellar phase crystallizes first but partially with a smaller d-spacing of 37 ˚ A. A still liquid remaining moiety of the roplets crystallizes in the unstable 2Lα, alike in static conditions. It can be concluded that shear stress favors the formation of more stable polymorphs within emulsiondroplets of oil in water emulsions. [1] Mazzanti G. et al.: Modeling phase transitions during the crystallization of a multicomponent fat under shear, Phys. Rev. E 71(2005) 041607. [2] Kalnin et al.: Systematic investigation of lard polymorphism using combined DSC and time-resolved synchrotron X-ray diffraction, Eur. J. Lipid Sci. Technol. 107 (2005) 594-606. [3] Kalnin, D. et al.: Fat Crystallization in Emulsion: Influence of the emulsifier concentration on triacylglycerol crystal growth and polymorphism, Cryst. Growth Des. 4, 6 (2004) 1283-1293.

Weiche Materie

Poster: Do., 13:00–15:30

D-P340

Liquid-gas interfaces studied by x-ray reflectivity ¨hler1 , Michael Paulus1 , Metin Tolan1 Felix Lehmku 1

Experimentelle Physik Ia, Universit¨ at Dortmund, Maria-G¨ oppert-Mayer-Straße 2, 44227 Dortmund The polypropylene glycol 4000 (PPG4000) - isobutane interface was studied by x-ray reflectivity measurements. The interface was investigated under different pressures between 1.0 bar and 2.6 bar which is close to the condensation pressure of isobutane at the temperature of 289 K. While adsorption of molecular thin films of isobutane is expected for hydrophobic interacting systems like glycerol-isobutane or water-propane, the formation of isobutane films on PPG4000 surface is suppressed by the high miscibility of isobutane and PPG4000. Thus no evidence for the formation of isobutane films was found. The surface roughness of the substrate was estimated to vary between σN 2 = 4 ˚ A at 1 bar N2 and σ2.6 = 8 ˚ A at 2.6 bar isobutane pressure. This is explained by the change of surface tension of the PPG4000-isobutane mixture with isobutane pressure. Ideal solution of isobutane in PPG4000 regarding to Raoult’s Law [1] is assumed to describe the measurements. The surface tension γ is calculated with the capillary waves theory to confirm the ideal solution with theoretical models for surface tension behavior of binary liquid mixtures. The Parachor-method [2] and gradient theory [3] are applied. The measurements show very good agreement with the theoretical calculation. [1] P.W. Atkins, Kurzlehrbuch Physikalische Chemie, Spektrum Akademischer Verlag, Heidelberg (1993) [2] S. Sugden, J. Chem. Soc. Trans., 1924, 1177-1189 [3] V. Bongiorno, H.T. Davis, Phys. Rev. A, 12, 2213-2224 (1975)

Weiche Materie

Poster: Do., 13:00–15:30

D-P341

Kohlenhydrate: Steuerung der Aggregatbildung in Wasser durch Nutzung des Bausteins der Natur ¨ tz Milkereit1 , Sven Gerber1 , Vasil Garamus2 , Stephan Hauschild3 , MattGo ¨ rster3 , Volkmar Vill1 , Regine Willumeit2 hias Wulf1 , Stephan Fo 1

Inst. f. Organische Chemie, Universit¨ at Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg – 2 GKSS Forschungszentrum, Abt. WFS, Max-Planck-Straße 1, 21502 Geesthacht – 3 Inst. f. Physikalische Chemie, Universit¨ at Hamburg, Grindelallee 117, 20146 Hamburg Kohlenhydrate sind ein zentraler Bestandteil biologischer Strukturen. Die große Anzahl verschiedener Mono-, Di- sowie Oligosaccharide und die daraus resultierenden Verkn¨ upfungsm¨ oglichkeiten erm¨ oglichen es der Natur, aus einem großen Pool an Verbindungen zu sch¨ opfen [1]. Diese nat¨ urlichen Bausteine bieten die M¨ oglichkeit durch unterschiedliche Synthesevariationen eine große Strukturvielfalt zu verwirklichen. Es wurden Verbindungen mit unterschiedlichen Kohlenhydratkopfgruppen (Maltose, Melibiose, Lactose, Glucose), unterschiedlichen Ketten und Kettenl¨ angen (linear ges¨ attigt, linear unges¨ attigt, methyliert), Spacern (Ethanolamin, Serinol) und Bolastruktur synthetisiert. Durch diese systematische Variation der Molek¨ ulstruktur konnte der Zusammenhang zwischen Struktur und Aggregationsverhalten in verd¨ unnter L¨ osung mittels Neutronenkleinwinkelstreuung (SANS) und in Erg¨ anzung Dynamischer Lichtstreuung (DLS) untersucht werden. Ein Großteil der untersuchten Lipide bildet Micellen in w¨ assriger L¨ osung. Daraus konnte ein detailliertes Konzept f¨ ur die Micellbildung ¨ von Kohlenhydratamphiphilen abgeleitet werden. Die Anderung der micellaren Strukturen kann einem generellen Strukturkonzept angepasst werden. Die Art der Kopfgruppe und die Variation der hydrophoben Kette bestimmen die Form der Aggregate. Die Funktionalit¨ at biologisch relevanter Strukturen (z.B. methylierte Alkylketten in Pflanzen/Tieren, Bolastruktur) u ¨bertr¨ agt sich auch auf das Aggregationsverhalten in verd¨ unnter L¨ osung. [1] I. Ishizuka, T. Yamakawa, 1985. Glycolipids. In: H. Wiegandt (Ed.), New Comprehensive Biochemistry, vol. 10. Elsevier, 101.

Weiche Materie

Poster: Do., 13:00–15:30

D-P342

In-situ investigation of non-equilibrium flow on gradient surfaces. ¨ller-Buschbaum1 , P. Uhlmann2 , M. Stamm2 J.-F. Moulin1 , P. Mu 1

Technische Universit¨ at M¨ unchen, Physik Department E13, James-Franck-Str. 1, 85747 Garching (Germany) – 2 Leibniz Institut f¨ ur Polymerforschung Dresden e.V. (IPF), Hohe Str. 6, D- 01069 Dresden (Germany) To date, the development of microfluidic devices is limited by the lack of fundamental understanding of the physical phenomenon that take place at the interface between a complex fluid (e.g. a multicomponent polymer blend or solution) and a surface. Overcoming the phenomenological descriptions of the progression of fluid fronts, phase separation and ordering processes at surfaces would bring new opportunities to taylor the properties of a substrate in order to control the behaviour of complex fluids and therefore perform specific tasks (spatial control of chemical reactions, patterning). Our approach to these problems is a multidisciplinary one, involving groups with expertise in the field of sample preparation (generating a surface free energy gradient at the ad hoc lengthscale), characterisation (via real space microscopic techniques and scattering of X-rays and/or neutrons for the reciprocal space) and theoretical modelling. We have concentrated our attention on motion of liquids confined in geometries with gradually changing conditions, and more specifically on systems where the wall properties display a linear gradient. The properties studied can be either physical (such as the surface roughness) or chemical such as the composition. We will here report on the reciprocal space investigation of the fluid´s internal structure variations induced by the presence of the interface.

Weiche Materie

Poster: Do., 13:00–15:30

D-P343

Probing thin polymer films: A comparative GISAXS and GISANS investigation ¨ller-Buschbaum1 , S.V. Monkenbusch2 , R. Cubitt3 , M. Burghammer4 , P. Mu C. Riekel4 1

TU M¨ unchen, Physik-Department E13, James-Franck-Str.1, 85747 Garching (Germany) – 2 HASYLAB at DESY, Notkestr. 85, 22603 Hamburg (Germany) – 3 ILL, b.p. 156, 38042 Grenoble (France) – 4 ESRF, b.p. 220, 38043 Grenoble (France) Future generations of microelectronic devices will require both, ever-decreasing critical dimensions and shrinking tolerance on those dimensions. The rising costs and complexity associated with lithographically created structures at the nanometer length scale opened opportunities for alternative techniques. Following this track, self-assembly in physical systems can play a key role in future technological applications. Extremely promising candidates are nanostructured polymer films built up from diblock copolymers. The typical dimensions of the microphase separation structures are in the nanometer regime, yielding the desired nanostructured films [1]. These dimensions are determined by the fundamental properties of the diblock copolymer and can be adjusted by changing the total copolymer molecular weight while keeping the molecular weight ratio between the blocks constant. In the case of a thin film, the solid support is completely covered by the nanostructured polymeric layer. Alternatively, a superstructure can be imposed, replacing the thin film geometry. As a typical example, the initially continuous polymer film is replaced by an assembly of isolated polymer droplets, called nano-dots. Inside the host structure of these nano-dots, the microphase separation structure is present. Consequently, this type of system exhibits two characteristic lateral lengths, the first given by the microphase separation structure and the second resulting from the spacing of the nano-dots assembled upon the solid support. With the advanced scattering technique of grazing incidence small-angle scattering with synchrotron radiation and neutrons (GISAXS and GISANS) lateral lengths in a regime from molecular to micrometer-sized are covered [2]. Thus the addressed range is quite comparable to AFM or SEM, but the probed surface area is macroscopic instead of microscopic. [1] P.M¨ uller-Buschbaum et al.; J.Phys.Condens.Matter 17, S363 (2005) [2] P.M¨ uller-Buschbaum, et al.; Appl.Phys.Lett. 88, 083114 (2006)

Weiche Materie

Poster: Do., 13:00–15:30

D-P344

Instabilit¨ aten w¨ ahrend der Dampfbehandlung d¨ unner Diblockcopolymerfilme: Zeitaufgel¨ oste R¨ ontgenkleinweinkelstreuung unter streifendem Einfall C.M. Papadakis1 , D. Posselt2 , D.-M. Smilgies3 1

Physikdepartment E13, Technische Universit¨ at M¨ unchen, James-Franck-Str. 1, 85747 Garching – 2 IMFUFA, Roskilde University, DK-4000 Roskilde, D¨ anemark – 3 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, USA Diblockcopolymere bilden im d¨ unnen Film durch Selbstorganisation geordnete Morphologien. Wir untersuchen die Reaktion d¨ unner Filme aus lamellaren Poly(styrol-bbutadien) (P(S-b-B)) Diblockcopolymeren w¨ ahrend der Behandlung mit Toluoldampf mit zeitaufgel¨ oster R¨ ontgenkleinwinkelstreuung unter streifendem Einfall (GISAXS) an. Die Lamellen waren zun¨ achst entweder parallel oder senkrecht zur Substratoberfl¨ ache [1]. Die niedrigen Messzeiten an CHESS D-line (10 s) erm¨ oglichten Untersuchungen der Fr¨ uhstadien der Quellung. Die Reaktion auf Toluoldampf der beiden lamellaren Orientierungen ist grunds¨ atzlich verschieden. Stehen die Lamellen zun¨ achst senkrecht auf dem Substrat (Abb. 1), reagieren sie sofort auf den Dampf: Die Filme quellen w¨ ahrend der ersten Minuten, und es werden zus¨ atzlich andere Orientierungen beobachtet als die senkrechte. Beim Trocknen des Films stellt sich jedoch die rein senkrechte Orientierung wieder ein [2]. Sind die Lamellen zun¨ achst parallel zum Substrat, quellen sie w¨ ahrend der Dampfbehandlung zun¨ achst an. Nach einigen Minuten wird dieser Zustand jedoch instabil, was zu Undulationen der lamellaren Grenzfl¨ achen f¨ uhrt. Sp¨ ater werden die lamellaren Grenzfl¨ achen wieder glatt, und die Lamellen nehmen wieder ihre urspr¨ ungliche Dicke an. [1] P. Busch et al., D. Posselt, D.-M. Smilgies, B. Rheinl¨ ander, F. Kremer, C.M. Papadakis, Macromolecules 36 (2003) 8717. [2] D.-M. Smilgies, P. Busch, C.M. Papadakis, D. Posselt, Synchr. Rad. News 15 (2002) no. 5, p. 35.

Abb. 1: 2D GISAXS Streubilder eines Films mit senkrechten Lamellen vor und w¨ ahrend der Dampfbehandlung mit Toluol [2]. Lamellendicke 839 ˚ A, Einfallswinkel 0.20◦ .

Weiche Materie

Poster: Do., 13:00–15:30

D-P345

R¨ ontgenkleinwinkelstreuung unter streifendem Einfall von d¨ unnen, lamellaren Diblockcopolymerfilmen in der Bornschen N¨ aherung mit gest¨ orten Wellen C.M. Papadakis1 , P. Busch2 , M. Rauscher3 , D.-M. Smilgies2 , D. Posselt4 1

Physikdepartment E13, Technische Universit¨ at M¨ unchen, James-Franck-Str. 1, 85747 Garching – 2 Cornell University, Ithaca NY, USA – 3 MPI f¨ ur Metallforschung und Universit¨ at Stuttgart – 4 IMFUFA, Roskilde University, D¨ anemark Mit R¨ ontgenkleinwinkelstreuung unter streifendem Einfall (GISAXS) k¨ onnen d¨ unne Blockcopolymerfilme im Hinblick auf ihre mesoskopische Struktur und die Orientierung der phasenseparierten Dom¨ anen charakterisiert werden [1]. Durch die Wahl kleiner Einfallswinkel wird die Sensitivit¨ at f¨ ur die Filmstrukturen erh¨ oht, allerdings k¨ onnen die Streubilder nicht mehr durch die kinematische Theorie beschrieben werden. Wir haben den Streuquerschnitt f¨ ur lamellare Blockcopolymerfilme in der Bornschen N¨ aherung mit gest¨ orten Wellen berechnet, einer dynamischen Streutheorie [2]. Sowohl die parallele als auch die senkrechte Orientierung der Lamellen zur Substratoberfl¨ ache wurden berechnet und mit experimentellen Streubildern von d¨ unnen Filmen aus Poly(styrol-b-butadien) (PS-b-PB) Diblockcopolymeren verglichen. Die Streubilder von Filmen mit senkrechten Lamellen zeigen Bragg rods bei den vom Bragg-Gesetz her erwarteten Positionen. Filme mit parallelen Lamellen zeigen Intensit¨ atsmaxima entlang der Filmnormalen, deren Positionen durch die Beugung der R¨ ontgenstrahlung an der Filmoberfl¨ ache und durch Reflektion an der Film-Substrat-Grenzfl¨ ache erkl¨ art werden k¨ onnen (Abb. 1). Auf diese Art k¨ onnen die lamellare Orientierung im Film sowie die Lamellendicke genau bestimmt werden. [1] C.M. Papadakis, P. Busch, D. Posselt, D.-M. Smilgies, Adv. Solid State Phys. 44 (2004) 327. [2] P. Busch, M. Rauscher, D.-M. Smilgies, D. Posselt, C.M. Papadakis, J. Appl. Cryst., erscheint im Juni 2006.

Abb. 1: Intensit¨ atsprofile entlang der Filmnormalen eines PS-b-PB Films mit parallelen Lamellen der Dicke 197 ˚ A (d¨ unne, obere Linie). DWBAModellrechnung der diffusen Streuung (dicke Linie) sowie Beitr¨ age der f¨ uhrenden Terme (farbige, d¨ unne Linien). Es wurden zwei verschiedene Einfallswinkel gew¨ ahlt.

Weiche Materie

Poster: Do., 13:00–15:30

D-P346

A grazing incidence diffraction study of aqueous salt solutions and water Michael Paulus1 , Christian Gutt2 , Christof Krywka1 , Michael Sprung3 , Metin Tolan1 1

Experimentelle Physik I, DELTA, Universit¨ at Dortmund, Maria-Goeppert-Mayer Str. 2, 44227 Dortmund – 2 Deutsches Elektronen Synchrotron (Hasylab), Notkestraße 85, D-22607 Hamburg, Germany – 3 c/o 8ID/IMMY-XOR-CAT, APS/ANL, Argonne, IL, 60439, USA We report in-situ grazing incidence x-ray diffraction (GID) experiments to study aqueous solution-gas interfaces of the sodium halogenides NaCl, NaBr and NaI performed at ID10B, ESRF. The out-of-plane diffusely scattered signal yields information about the lateral structure of the investigated samples surface. The scattered signal can be used to test the simple capillary waves model down to nanometer length scales. Using the Distored Wave Born Approximation (DWBA) for the data analysis, a possible wave vector dependence of the surface tension can be determined. GID scans of the salt solutions (5 molar) and pure water were performed up to wave vector transfers parallel to the surface q|| of approximately two inverse angstroms. The measured data for the salt solutions and pure water are compared with theoretical calculations of the scattered signal based on the DWBA theory using both, a constant surface energy and a wave vector dependent surface energy based on the work of Mecke et al [1] . For a better description of the data, measurements of the bulk structure factors of all liquids were performed at the synchrotron source DELTA, BL9. The refinements of these measured structure factors were included into the calculations of the diffusely scattered signal. We observe for all liquids a reduction of the surface energy at short length scales. This effect seems to be similar for all liquids and will be explained in an alternative way by inclusion of lateral movements into the capillary waves model. [1] Mecke et al., Phys. Rev. E 59 (6) 6766 (1999)

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Poster: Do., 13:00–15:30

D-P347

GISAXS investigation of sol-gel templated nanocomposite films ¨ller-Buschbaum1 J. Perlich1 , Y. Cheng2 , J.S. Gutmann2,3 , S.V. Roth4 , P. Mu 1

TU M¨ unchen, Physik-Department LS E13, James-Franck-Str. 1, D-85748 Garching, Germany – 2 Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany – 3 Institute for Physical Chemistry, Johannes Gutenberg University, Jakob-Welder-Weg 10, D-55099 Mainz, Germany – 4 HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany We focus on the creation of nanostructured TiO2 thin films, which are of great interest for many applications, due to their electrical performance. The performance is strongly dependent on the morphology of the nanocomposite films, therefore it is very important to prepare the desired morphology with high reproducibility and homogeneously spread out over areas of cm2 . For the preparation of the TiO2 nanocomposite films we combine the amphilic diblock-copolymer PS-b-PEO, which acts as a templating agent, with an inorganic sol-gel chemistry [1]. First, the diblock copolymer is dissolved in 1.4-dioxane, which is a good solvent for both, the hydrophobic as well as the hydrophilic block of PSb-PEO. Afterwards, hydrochloric acid (HCl) and titanium tetraisopropoxide (TTIP) are added into the polymer solution as the source for the sol-gel process. Because HCl and TTIP are poor solvents for the hydrophobic block, a so-called good-poorsolvent pair induced phase separation leads to the formation of nanostructures by film preparation via spin-coating. The different morphologies can be controlled by the weight ratios of the solvents. In order to obtain crystalline TiO2 films as the final step calcination is conducted at higher temperature in air. For the investigation of the morphologies of the sol-gel templated nanocomposite films grazing incidence small angle x-ray scattering (GISAXS) is performed at the synchrotron beamline BW4 of the DESY HASYLAB facillity in Hamburg [2]. For the experiments a morderate micro-focussed beamsize of 30 x 60 µm2 is used, which also enables to investigate local gradients of the thin film morphology. The GISAXS experiments are conducted on various substrate materials with different surface roughnesses and variations in the morphology of the nanocomposite films. The GISAXS scattering patterns exhibit features clearly correlated to morphologies of ordered nanostructures, whereas the calcination may cause further ordering. It is also observed that the nanocomposite films on top of a surface with ordered nanoscale roughness influence the scattering patterns. In addition to the x-ray scattering, analytical methods as atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used for characterization. The results of AFM and SEM characterization are in good agreement with the GISAXS experiments. [1] Y.-J. Cheng, J. S. Gutmann, J. Am. Chem. Soc. 128(14) (2006) 4658-4674 [2] P. M¨ uller-Buschbaum, Anal.Bioanal.Chem. 376 (2003) 3

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Poster: Do., 13:00–15:30

D-P348

Influence of pH and alcohols on aggregation of nonionic surfactant C14E7 in heavy water solutions study by SANS method. Aldona Rajewska1,2 1

Institute of Atomic Energy, 05-400 Swierk - Otwock, Poland – 2 Joint Institute for Nuclear Research, Laboratory of Neutron Physics, 141980 Dubna, Russia The classic nonionic surfactant C14E7 (heptaethylene glycol monotetradecyl ether) were investigated at two constant concentrations of 0.17 %, 0.5 % in heavy water solutions at room temperature without and with add of alcohols ethanol and glycerol with used the small angle neutron scattering method. The influence of pH on aggregation in these solutions were investigated, too. All SANS measurements were performed on the time-of-flight spectrometer MURN of the pulsed reactor IBR-2, JINR, Dubna, Russia. Neutrons were used in wavelength range of 8 x 10−3 to 0.4 ˚ A−1 . For the measurements quartz cells of thickness 2 mm were used. They were sealed to prevent evaporation during the experiment. Up to 15 such cells were placed in a sample holder, and the temperature within the cells was kept constant in a range of ± 0.5 ◦ C by means of a thermostat. Conversion of the scattered intensities into absolute differential cross-sections was done by using an internal calibration standard (vanadium). For all samples D2 O was used as solvent in order to achieve good contrast conditions.

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Poster: Do., 13:00–15:30

D-P349

Small Angle X-ray Scattering Studies on Mesoporous Organic-Inorganic Proton-Conductors Based on 2,5-diaminobenzenesulfonic acid. Luis Antonio Sanchez de Almeida Prado1 , Suzana Pereira Nunes2 , Sergio S. Funari3 , Karl Schulte1 1

Technische Universit¨ at Hamburg-Harburg, Polymer Composites (AB 5-09), Denickestrasse 15, Geb. 2B, D-21073 Hamburg. – 2 GKSS, Forschungszentrum, Institut f¨ ur Polymerforschung, Max-Planckstrasse 1, D-21520, Geesthacht. – 3 HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg. The development of new inorganic materials with good thermal stability and high proton-conductivity gained an additional importance due to their potential application as additives for polyelectrolyte membranes for fuel cells. Recently, it was proved that the incorporation of mesoporous molecular sieves (MCM-41) caused an improvement of the methanol barrier properties of polyelectrolyte membranes for DMFC applications [1]. Even better results could be achieved after the surface modification of MCM-41 with proton-conducting groups derived from imidazole rings attached to organosiloxanes [1]. The use of sulphonated oxadiazole-based telechelics as modifiers of organically modified silicas (ormosils) containing C-Br bounds at the surface, lead to membranes with improved proton-conductivity and stability at temperatures higher than 373 K [2]. In the present communication, the very first results concerning the preparation and structural characterisation of sulphonated MCM-41 are presented. These organicinorganic materials were prepared by hydrolysis and condensation of a silica source and a sulphonated alkoxysilane (SAS). The aforementioned alkoxysilane was produced in situ via reaction between 2,5-diaminobenzenesulfonic acid and 3-glycidyloxypropyltrimethoxysilane (GLYMO). SAXS experiments were carried out at A2 beamline at HASYLAB (DESY) in order to confirm the formation of the MCM-41 mesophase. It was observed that the polycondensation of the sulphonated alkoxysilane did not produce any meso-structured material even in the presence of surfactant micelles as templates. However, the combination of the sodium metasilicate and the SAS enable the production of materials with a well-ordered hexagonal array of cylindrical pores (MCM-41), which were stable after the removal of the template by ethanol:heptane acidic mixtures. This extraction with acidic mixture leads to the partial removal of the sulphonated alkoxysilane moieties. On the other hand, the co-polymerisation between the SAS and tetramethoxysilane produced materials with less-ordered array of pores, although little extraction of AS could be observed after the removal of the template by the acidic ethanol:heptane mixture. New experiments are been currently carried out in order to optimize the reaction between sodium metasilicate and SAS aiming at developing of meso-structured materials with higher functionalization degrees. The authors acknowledge HASYLAB for the SAXS measurements (Project II-04-072). [1] C.S. Karthikeyan et al., J. Membrane Sci 254 (2005) 139. [2] D.Gomes et al., J. Polym. Sci. Polym. Phys. Ed. (2006) (submitted).

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Poster: Do., 13:00–15:30

D-P350

Molecular structure and mobility of spider dragline silk and adsorbed water Daniel Sapede1,2 , Tilo Seydel1 , V.Trevor Forsyth1 , M.Marek Koza1 , Ralf ¨ller3 , Fritz Vollrath4 , Christian Riekel2 Schweins1 , Martin Mu 1

Institut Laue-Langevin, B.P.156, F-38042 Grenoble – 2 European Synchrotron Radiation Facility, B.P.220, F-38043 Grenoble – 3 IEAP, Universit¨ at Kiel, D-24098 Kiel – 4 Dept.of Zoology, University of Oxford, U.K. Spider dragline silk is known for its outstanding mechanical properties which it obtains despite being spun at close to ambient temperature and pressure using water as a solvent. Our study using neutron diffraction, neutron backscattering and time-of-flight spectroscopy aims at elucidating the crucial role of adsorbed water to spider silk. As spider silk is currently only available in limited quantities from living spiders, a major challenge has been met in establishing the feasibility of neutron scattering experiments. Spider dragline silk is a semicrystalline biopolymer made out of an aminoacid sequence with dominating alanine and glycine molecules. From diffraction studies, a model of a fibrillar structure made out of small crystalline blocks in a matrix containing both partly oriented and unoriented amorphous material has been proposed. The crystalline fraction is composed basically out of poly(alanine) chains while the oriented amorphous fraction is glycine rich. This oriented material seems to be connected by a further fraction of random polymer chains. Although the aminoacid sequence in the polymer chains is being unravelled, our understanding of the link between primary structure and function remains limited. The mechanical properties of spider silk are strongly influenced by its water content and water-induced mobility at a molecular level. Thus in order to obtain its superior mechanical properties, the extruded fibre - which is spun from aqueous solution - has to be rapidly dried. X-ray small- and wide-angle scattering shows that the water content does not influence the fibrillar system. Apparently the water is absorbed by the random polymer chains whereas the crystallites are not accessible to the guest molecules. Since spider silk is exposed in nature to different humidity levels, it is interesting to note that the absorption of water is reversible. It seems that the polymer matrix mechanically behaves like a rubber when swollen with water. We present recent results from neutron small-angle scattering, neutron diffraction and neutron spectroscopic experiments on oriented spider dragline silk fibres as a function of temperature and humidity [1,2], as well as complementary synchrotron microbeam experiments. [1] D.Sapede, T.Seydel, V.T.Forsyth, M.M.Koza, R.Schweins, F. Vollrath, C. Riekel; Macromolecules 38, 8447 (2005). [2] D.Sapede; PhD Thesis, University Joseph Fourier, Grenoble (2006). (http://tel.ccsd.cnrs.fr/tel-00011700?langue=en)

Weiche Materie

Poster: Do., 13:00–15:30

D-P351

Structural and magnetic properties of polystyrene-b-polyisoprene diblock copolymer films with embedded Fe2 O3 nanoparticles L. Schulz1 , S. Valloppilly2 , S. V. Roth3 , M. Burghammer4 , C. Riekel4 , P. ¨ller-Buschbaum1 Mu 1

TU M¨ unchen, Physik-Department LS E13, James-Franck-Str. 1, 85747 Garching (Germany) – 2 TU M¨ unchen, Physik-Department LS E21, James-Franck-Str. 1, 85747 Garching (Germany) – 3 HASYLAB at DESY, Notkestr. 85, 22603 Hamburg (Germany) – 4 ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France) We investigate lamella-forming polystyrene-b-polyisoprene coploymer films with embedded Fe2 O3 nanoparticles. The used block copolymer is asymmetric and forms a microphase separation structure due to the incompatible block segments PS and PI. For the thin film preparation we apply two well-known techniques, spin-coating and solution-casting. From PS-b-PI/Fe2 O3 nanoparticles mixtures, dissolved in toluene, we are able to produce the desired thin polymer films on precleaned Si subtrates. Annealing induces further self-organisation. Various concentrations of nanoparticles result in different physical properties of the polymer matrices. Magnetic measurements indicate superparamagnetic behaviour of the nanoparticles at 300K and a ferromagnetic order at very low temperatures. In the ferromagnetic state the nanoparticles possess a constant coercivity irrespective of their volume fraction. Investigations with optical microscopy on macroscopic and atomic force microscopy (AFM) on microscopic length scale provide information about the surface. Structural composition, topography and distribution of the nanoparticles within the thin layers are obtained by grazing incidence small angle X-ray scattering (GISAXS) and X-ray reflectivity. GISAXS experiments are performed at beamline BW4 at HASYLAB/DESY in Hamburg and beamline ID13 at ESRF in Grenoble.

Weiche Materie

Poster: Do., 13:00–15:30

D-P352

Options for neutron backscattering spectroscopy on quasi-2D soft matter systems ¨dter1 , Tim Salditt2 Tilo Seydel1 , Maikel C. Rheinsta 1

Institut Laue-Langevin, B.P.156, F-38042 Grenoble – 2 Institut f¨ ur R¨ ontgenphysik, Friedrich-Hund-Platz 1, D-37077 G¨ ottingen Neutrons unlike x-rays are severely limited in source brilliance, and thus experiments concerning soft matter interfaces or quasi-twodimensional systems are often rendered impossible by this restriction. If, however, a sufficient scattering volume can be achieved, a wealth of new information can be obtained by high energy resolution neutron spectroscopy. Here we discuss a recent example.

Experiments carried out on model lipid membrane bilayer systems using the neutron backscattering technique [1-2] point to the new possibilities introduced by the availability of adequate lipid membrane samples. These samples consist of stacks of several thousand lipid membrane bilayers supported by silicon wafers. The mosaicity of the membrane stack is smaller than approx. 0.5◦ . By the cold neutron backscattering technique an energy resolution of 0.9 µeV FWHM can routinely be achieved whilst a wavevector transfer range of approx. 0.02 ˚ A−1
Weiche Materie

Poster: Do., 13:00–15:30

D-P353

In-situ Studies of Protein Resistance of Oligo(Ethylene Glycol) Self-Assembled Monolayers Maximilian Skoda1,2 , Frank Schreiber1 , Robert Jacobs2 , Reiner Dahint3 , Michael Grunze3 , Maximilian Wolff4 1

Universitaet T¨ ubingen, Institut f¨ ur Angewandte Physik, 72076 T¨ ubingen – 2 Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3 Universitaet Heidelberg, Institut f¨ ur Angewandte Physikalische Chemie, 69120 Heidelberg – 4 ILL, 38053 Grenoble, France The structure of the interface between organic matter, such as self-assembled monolayers (SAMs), and water is currently subject of intensive studies due to its importance for the understanding of surface-solvent and surface-surface interactions [1,2]. Our focus here are OEG-terminated SAMs which are used to make surfaces resistant to protein adsorption. We report our recent results from a Neutron Reflectivity (NR) study. The in-situ measurements reveal changes in the structure of water and the protein solution in the vicinity of the SAM upon changes in temperature. This study is complemented by Polarisation Modulated (PM) Fourier Transform Infrared Spectroscopy (FTIR) investigations, which help to shed light on the problem of the subtle interactions at the organic solid-liquid interface. The benefit of using IR along with NR is also that we are more sensitive to the defect structure of the organic interface, which has an impact on the interaction with water. [1] F. Schreiber, J. Phys.: Cond. Matter 16 (2004) R881 [2] D. Schwendel et al., Langmuir 19 (2003) 2284

Weiche Materie

Poster: Do., 13:00–15:30

D-P354

QENS and nuclear magnetic resonance studies of Q10-nanodispersions Christoph Smuda1 , Tobias Unruh1 1

Technische Universit¨ at M¨ unchen, Forschungsneutronenquelle Heinz Maier–Leibnitz FRM II, Lichtenbergstraße 1, 85747 Garching, Germany In recent years it has become evident that the development of new drugs alone is not sufficient to ensure progress in drug therapy. Today there are many drugs which in spite of their high pharmacological potential cannot be administered using standard formulations because of e.g. side effects, targeting problems or adverse release effects. Reasons can be: poor drug solubility in aqueous solutions, chemical instability of the drug, insufficient drug concentration due to poor absorption, rapid metabolism and elimination. A promising strategy to overcome these problems involves the development of suitable drug carrier systems. The in vivo-fate of the drug is no longer mainly determined by the properties of the drug, but by the carrier system, which should permit a controlled and localized release of the active drug according to the specific needs of the therapy [1]. We examine colloidal drug carrier systems like nanodispersions and solid lipid nanoparticles (SLN). The dispersions are prepared by high pressure homogenization of a predispersion of the molten lipid with water and emulsifiers. The heart-protecting drug ubidecarenone (coenzyme Q10) is of special interest due to its biological effects in the human body. Coenzyme Q10 is an antioxidant with very poor solubility in aqueous media and is naturally found throughout the body. High supercooling of Q10 and the formation of stable Q10-containing nanodispersions have been observed. The virtual insolubility of Q10 in water results in a very poor peroral bioavailability from conventional dosage forms. Processing into nanoparticles of supercooled melts lead to improved bioavailability [2]. Q10-nanodispersions were investigated by means of QENS and pulsed field gradient (PFG) nuclear magnetic resonance (NMR) for determination of self diffusion coefficients and internal motions like methyl group rotations. These methods provide complementary data: PFG-NMR allows the measurement of self diffusion coefficient of the nanoparticle and QENS the determination of the diffusion coefficient of the drug inside the nanoparticle. [1] W. Mehnert et al., Adv. Drug Del. Rev. 47 (2001) 165. [2] K. Westesen, Colloid Polym. Sci. 278 (2000) 608.

Weiche Materie

Poster: Do., 13:00–15:30

D-P355

Nanostructure Evolution and Nanostructure Gradients in Oriented Polymer Parts Norbert Stribeck1 1

Universit¨ at Hamburg, Institut TMC, Bundesstr. 45, 20146 Hamburg

The semicrystalline nanostructure of anisotropic samples made from commercial polymers is visualised from small-angle X-ray scattering (SAXS) data and compared to the information gathered by simultaneous two-dimensional wide-angle X-ray scattering (WAXS). The method is based on a combination of advanced experimental technique and novel methods of data analysis based on Fourier transformation theory. To-date manageable is the experimental and analytical effort for samples with fibre symmetry. From time-resolved experiments at a synchrotron source conclusions on the mechanisms of structure evolution can be drawn. Spatial resolution is achieved by tomographic reconstruction starting from a set of 7000 scattering patterns recorded while scanning a thick sample. As a result information is retrieved on the variation of nanostructure inside a fibre. Experiments have been performed using commercial grades of various polymers (PE, UHMWPE, PP, PVDF). Adequately evaluated and published are studies of PE and UHMWPE materials, which are presented. Concerning the mechanisms of structure evolution during quiescent crystallisation of polyethylene we have always found that the formation of crystallites is preceded by the formation of nanostructure (nanoforming) in the melt. the corresponding domains exhibit a very broad size distribution. We imagine regions that are discriminated by their entanglement density. Crystallisation is forcing the corresponding nanodomains to settle down. The places of settlement are random. Thus the population mechanism is described by R´enyi’s random car parking process. Even if the nanoformed domains are highly oriented lamellae, the crystallite orientation is isotropic. During secondary crystallisation the first lamellae can grow perfect and reorientation of crystallites is observed during this period. This principle is not valid for the nanodomains formed late. They populate the centres of the remnant white spots and, by doing so, are responsible for the ordered arrangement and the ultimate long period of the crystallised material, but their crystallites do not show preferential orientation. The SAXS microtomography of an injection moulded polyethylene rod demonstrates the method using a “fibre” which is thick enough for the spatial resolution that presently is accessible at HASYLAB, Hamburg. It is well-known that many fibres exhibit a core-shell structure and that the shell exhibits a regular and highly oriented nanostructure that is completely different from that found in the core. By means of filtered backprojection the studied material is virtually sliced into many small cubes (voxels) resulting in set of SAXS patterns related each to one of the voxels. Its analysis shows oriented lamellae stacks in a shell layer and extended chains in the central core of the fiber. We document zones of uni- and bimodal structure, variation of long periods, stack heights and lateral domain extension.

Weiche Materie

Poster: Do., 13:00–15:30

D-P356

QENS as a tool for studying pharmaceutical drug delivery systems Tobias Unruh1 , Christoph Smuda1 1

Technische Universit¨ at M¨ unchen, Forschungsneutronenquelle Heinz Maier–Leibnitz FRM II, Lichtenbergstraße 1, 85747 Garching, Germany Aqueous nanodispersions of liquid, liquid crystalline and solid lipids are under investigation as drug delivery systems for numerous therapeutic applications, such as intraveneous administration of poorly water soluble drugs [1]. The reason for using a drug carrier is most often to reduce side effects of drugs, to modify the drug release kinetics or to deliver the drug to a specific body site (drug targeting). Therefore the mobility of the drug molecules in the drug carrier and their interface cross over rates are of particular interest in order to understand the drug release behaviour of such systems. Moreover the dynamics of the carrier and especially of the stabilizer (emulsifier) molecules should mainly influence drug release rates and physico-chemical properties of the pharmaceutic formulation such as recrystallisation tendency (stability) of nanoscaled supercooled melts or the phase behaviour of lipid nanoparticles. In contrast to lots of publications on microscopic and mesoscopic structural investigations no investigations on the molecular dynamics of lipid drug delivery systems have been published so far. This might be due to the lack of experimental methods to investigate the interesting molecular dynamics within the highly complex native systems. Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy can not be used to determine e.g. the self-diffusion constant of molecules inside nanoscaled dispersed particles because of the spatially restricted diffusion in a nanoparticle, whereas relaxation time measurements by 13 C-NMR should reveal information on the molecular dynamics. In this contribution the potential of QENS in studying molecular mobilities in complex pharmaceutical systems will be outlined. First experimental results from nanodispersions of supercooled melts and phospholipid dynamics used as stabilizer in lipid nano dispersions will be presented. The measurements have been performed predominantly at the time-of-flight spectrometer TOFTOF at FRM II. [1] H. Bunjes, B. Siekmann, Microencapsulation, Editor: S. Benita, Marcel Dekker, New York, 213-268 (2005)

Weiche Materie

Poster: Do., 13:00–15:30

D-P357

SANSPOL study of organic magnetic fluids stabilized by different monocarboxylic acids Ladislau Vekas1 , Mikhail V. Avdeev2 , Doina Bica1 , Oana Marinica3 , Maria Balasoiu4 , Victor L. Aksenov2 , Vasyl M. Garamus5 , Andreas Schreyer5 1

Laboratory of Magnetic Fluids, CFATR, Romanian Academy, Timisoara Division, Timisoara, Romania – 2 Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna Moscow Reg., Russia – 3 National Center for Engineering of Systems with Complex Fluids, Univ. Politehnica, Timisoara, Romania – 4 National Institute for Nuclear Physics and Engineering, Bucharest, Romania – 5 GKSS Research Centre, Geesthacht, Germany A principle possibility to use biocompatible a short chain length monocarboxylic acid, myristic acid (MA), is considered [1]. As a first step, this surfactant is used to coat magnetite nanoparticles in non-polar organic liquids by the well-proven technology [2,3]. It results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by unsaturated oleic acid (OA). Parameters of the log-normal size distribution of magnetite particles are obtained by small-angle scattering of polarized neutrons (SANSPOL). The method reveals a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic radius (from 4 to 2.5 nm) and polydispersity (from 0.38 to 0.28) when MA is used instead of OA. These finding is in agreement also with magnetization and magneto-rheological analysis. One can conclude that monocarboxilic acids show different efficiency in dispersing different size-fractions of nanometric magnetite particles. While OA is proved to be highly efficient surfactant to stabilize nanomagnetite over the wide size interval of 2-20 nm, shorter acids (like MA) stabilize partially this interval dispersing in the carrier only a fraction of smaller particles. The size regulation effect is reported when MA/OA mixtures are used in stabilization procedure [4]. This research project has been supported by the European Commission under the 6th Framework Program through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract nr: RII3-CT-2003-505925, GKSS, Germany, as well as by the AEROSPATIAL research program of the Romanian Ministry of Education and Research, contract OALM nr.111/2004. M.V.Avdeev acknowledges the support from the INTAS Fellowship Grant for Young Scientists, Ref. N. 04-83-2582. [1] M.V.Avdeev, D.Bica, L.V´ek´ as, O.Marinica, M.Balasoiu, V.L.Aksenov, L.Rosta, V.M.Garamus, A.Schreyer, Submitted to J. Mag. Mag. Mater. (2006). [2] D.Bica, Rom. Rep. Phys. 47 (1995) 265-272. [3] L.V´ek´ as, et al., Progr. Colloid. Polym. Sci. 117 (2001) 104-109. [4] D.Bica, M.V.Avdeev, O.Marinica, V.M.Garamus, L.Vekas, In EUROMECH Coll. 470, February 2006, Dresden, Germany.

Weiche Materie

Poster: Do., 13:00–15:30

D-P358

Structural investigation on the mode of action of the antimicrobial peptide gramicidin S - a monolayer study ¨ckerl1 , Stefan Surber1 , Josef Lydia Woiterski1 , Ann Falk1 , Florian Ru ¨s1 , Carsten Selle1 Ka 1

Institut f¨ ur Experimentelle Physik I, Linnestr. 5, 04103 Leipzig

The antimicrobial function of the amphiphilic peptide gramicidin S (GS) is based on unspecific attack on the bacterial membrane integrity. The GS structure is a cyclic beta-sheet, cyclo(Val-Orn-Leu-DPhe-Pro)2. We present a study which aims to elucidate the fundamental non-specific interactions governing the phase behavior of both pure GS and mixtures from GS with phospholipids within Langmuir monolayers. In order to modulate electrostatic interactions between the basic peptide molecules, we investigated monolayers on buffers with pH values varied between 2 and 12 at room temperature and ionic strength of 0.19 M. The pressure-area isotherms recorded for GS monolayers demonstrated marked differences. The phase transition between two-dimensional liquid and solid phases was observed to appear at higher lateral pressures at decreased pH. Striking differences were found for the sizes and shapes of solid domains on the various subphases as observed by Brewster angle microscopy. The latter even occur in a pH region which is far below from the ornithin pK value indicating that a large pK shift of the basic ornithine (orn) residues compared to the bulk appears at the monolayer surface. This pH sensitive behavior is probably due to the high surface concentration of negative counterions present. Furthermore, the lateral pressure of GS monolayers at pH 7.5 and constant ionic strength was found to be dependent on the phosphate concentration. A possible qualtitative explanation is that divalent phosphate ions present at this pH might bind tightly to the cationic peptide inducing electrostatic repulsion. This could lead to an additional contribution to the lateral pressure which increases at higher phosphate concentrations. Tentatively, one could conclude that the negative surface charge of bacterial membranes can be enhanced by cationic peptides in the presence of divalent phosphate anions, resulting in membrane-destabilizing increased lateral pressure. To investigate structural properties of the antimicrobial peptide, synchrotron X-ray reflection (XR) and grazing incidence diffraction (GID) experiments were performed on GS monolayers at HASYLAB, DESY, Hamburg. By use of the latter technique, the lateral order within the film was studied while the reflectivity measurements provide information about the electron density profiles in the vertical direction of the monolayer. First results are be presented for GS monolayers on different buffers and at varied lateral surface pressures with and without phospholipids mimicking bacterial membranes.

Weiche Materie

Poster: Do., 13:00–15:30

D-P359

NS-SANS zur Erforschung grenzfl¨ achennaher Strukturen Maximilian Wolff1,2 , Marco Walz3 , Andreas Magerl3 , Hartmut Zabel1 1 3

Ruhr-Universit¨ at Bochum – Universit¨ at Erlangen-N¨ urnberg

2

Institut Laue-Langevin, Grenble, Frankreich –

Im Zusammenhang mit dem zunehmenden Interesse bei der Herstellung nanostrukturierer Materialien wird ein Verst¨ andnis der Selbstorganisation von Molek¨ ulen auf atomaren L¨ angenskalen immer wichtiger. Neutronenstreuung kann hier einen wichtigen Beitrag leisten da die Wellenl¨ ange und die Energie der Probe im Bereich der atomaren oder molekularen Abst¨ ande bzw. Relaxationszeiten liegen. Zus¨ atzlich erlaubt die hohe Durchdringungskraft von Neutronen f¨ ur viele Werkstoffe die Untersuchung von Proben in komplexen Probenumgebungen wie Scherzellen oder verborgene Grenzfl¨ achen. Scherung oder eine Grenzfl¨ ache kann Selbstorganisation in komplexen Polymersystemen induzieren. Scherinduzierte Ordnung ist das Resultat einer ¨ außeren Kraft die auf die Probe ausge¨ ubt wird. Um Information u ¨ber den Gleichgewichtszustand (Ruhezustand) zu erhalten erscheint es daher g¨ unstiger eine zur Scherung ¨ aquivalente Symmetriebrechung im System dadurch zu erreichen, dass die Probe in Kontakt mit einer festen Grenzfl¨ ache gebracht wird und dort die Grenzfl¨ achenstruktur bestimmt wird. Bisherige Studien beschr¨ anken sich meist auf das scherinduzierte Ordnen im Volumen. In unserer Pr¨ asentation werden wir die grenzfl¨ achennahe Kristallisation von Polymermizellen untersucht mit Kleinwinkelneutronenstreuung unter steifendem Einfall (NSSANS oder GISANS) detailliert diskutieren. Unsere Proben sind drei Blockpolymere (Pluronics), die in w¨ assriger L¨ osung zum Agglomerieren neigen. Als feste Grenzfl¨ achen wurden Siliziumwafer mit unterschiedlicher Affinit¨ at f¨ ur die Mizellenschale eingesetzt. Die wichtigsten Resultate lassen sich wie folgt zusammenfassen: (1) Die Kristallisation ist nahe einer attraktiven Grenzfl¨ ache verst¨ arkt, wohingegen sie in der N¨ ahe einer repulsiven unterdr¨ uckt wird. (2) Das epitaktische Wachstum der Kristallite beginnt an verschiedenen Keimen die schnell vernetzen. Dies resultiert in einer ausgepr¨ agten Textur, die zu Spannungen f¨ uhrt und eine Reduzierung der Korrelationsl¨ ange zur Folge hat. (3) Die Kristallisation derselben Phase aus unterschiedlichen Anfangszust¨ anden (z. B. niedrige/hohe Temperatur) kann zu unterschiedlichen Strukturen f¨ uhren. (4) Scherung kann die kristalline Struktur im Falle der attraktive Grenzfl¨ ache verst¨ arken, wohingegen sie im Falle der repulsiven zerst¨ ort wird.

Weiche Materie

Poster: Do., 13:00–15:30

D-P360

Investigation of micro mechanical cantilever sensors with micro-focus GISAXS Markus Wolkenhauer1 , Gina-Gabriela Bumbu1 , Yajun Cheng1 , Stephan V. Roth2 , Jochen S. Gutmann1,3 1

Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany – 2 Deutsches Elektronen Synchrotron (HASYLAB), Notkestr. 85, D-22603 Hamburg – 3 Institute for Physical Chemistry, Johannes Gutenberg University, JakobWelder-Weg 10, D-55099 Mainz Micro mechanical cantilevers covered with polymer brushes are of great interest for fundamental research and practical applications [1]. Used in fundamental research they allow an insight into the swelling behaviour of polymer brushes. Furthermore they can be used for a wide variety of sensor applications. In priciple a micro mechanical cantilever sensor consist of two main parts: the micromechanical cantilever that acts as a transducer element and a coating which can be highly specific for different molecules and produces specific response patterns for various analytes. As transducers OCTOSENSIS silicon microarrays (Micromotive, Germany) were used in order to investigate the swelling of polymer brushes. Each chip consists of eight rectangular cantilevers, with a length of 750 µm, width of 90 µm and thickness of 1 µm arranged at a pitch of 250 µm. Utilizing an atom transfer polymerisation (ATRP) “grafting from” technique polymer brushes were grown on the silanated array surface [2]. The quality of the coating, grafting density of the polymer brushes, layer thickness, uniformity of the layer are very important for the response of the sensor on an external stimulus. In our experiments we investigated the quality of the cantilever coatings, especially the quality of the gold layer and proofing the existence sharp boundaries between the polymer coated cantilevers and the ones gold coated. The experiments were carried out at the BW4 beamline using a micro-focus-GISAXS setup using a detector sample distance of 1.9 m and a 32x17 µm2 micro-focus beam [3]. The small beam parameters allowed to selectively analyze a single microcantilever with respect to coating uniformity, composition and thickness in a µ-GISAXS experiment. Our findings clearly correlate defects in the cantilever coatings to irregular behavior of the sensing element. [1] H.P Lang, M. Hegner, Ch. Gerber, Materials Today, 8 (2005) 30. [2] Bumbu GG, Kircher G, Wolkenhauer M, Berger R, Gutmann JS, Macromol. Chem. Phys. 205 (2004) 1713. [3] M. Wolkenhauer, G. G. Bumbu, Y. Cheng, S. V. Roth, J. S. Gutmann, APL, submitted

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P361

Ultrafast scattering from clusters with intense soft x-ray radiation from the FLASH FEL Christoph Bostedt1 , Ekatarina Eremina1 , Heiko Thomas1 , Matthias ¨ ller1 , Hubertus Wabnitz2 , Marion Kuhlmann2 , Elke Hoener1 , Thomas Mo 2 ¨ njes , Rubens de Castro2 , Tim Laarmann3 Plo 1

Technische Universit¨ at Berlin – 2 Deutsches Elektronensynchrotron DESY Hamburg – 3 Max Born Institut Berlin

The interaction of rare gas clusters with intense vacuum ultraviolett radiation from the DESY FEL operating at 100 nm wavelength has yielded many surprising results. For rare gas clusters unexpected high energy absorption was measured and thermionic electron emission was observed. Already at 1013 W/cm2 the clusters completely disintegrated in a coulomb explosion. These results indicate that for cluster in intense laser fields down to 100 nm very efficient energy absorption mechanisms exist. From a theoretical point of view new explanations for the observed energy absorption were suggested, including atomic corrections to the inverse Bremsstrahlung potentials or high intermediate charge states in the cluster. In fall 2005 the FLASH FEL source (DESY VUV-FEL) became operational, currently producing intense soft x-ray radiation with 32 nm wavelength and power densities of up to 1014 W/cm2 . In the talk first results of the laser cluster interaction at this reduced wavelength will be presented. The data show less efficient energy absorption from the laser field and no thermionic electrons. At this reduced wavelength scattering experiments at nanoparticles become feasible. We show first ultrafast single shot scattering data from large clusters. The results indicate that the particles stay in tact during exposure.

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P362

Multiphoton Ionisation and Excitation of Atoms and Fullerenes ¨ ster1 , Daniel Rolles2 , Jens Markus Braune1 , Sanja Korica1 , Axel Reinko 1 1 Viefhaus , Uwe Becker 1

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany – 2 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 4R0230, Berkeley, CA 94720, USA At the new VUV-FEL light-source at DESY/Hamburg we performed experiments at the monochromator beamline PG1 with a two chamber setup. In the front part of the combined apparatus a spherical multi-detector vacuum chamber with a set of time-offlight analysers at various angles with respect to the polarisation axis of the FEL was adjusted to the focus of the beamline. With this setup we performed angle resolved photoelectron spectroscopy measurements on various rare gases (He, Ne, Ar, Kr, Xe) as well as on the small molecules N2 and H2 . In the rear part - about one meter behind the focal point - C60 molecules are evaporated in an oven assembly. Ions generated by the FEL radiation were detected with an ion time of flight spectrometer. In both parts data were acquired simultaneously by recording analogue signals of micro channel plate detectors by means of a multi-channel digitizer card system and oscilloscope, respectively, recording traces which have time duration of a full FEL pulse train. An analysis of our recorded data shows clear indications for two-photon processes in both cases. For the photoelectron spectroscopy part we restrict the presentation of our results to experiments on neon only as it showed the strongest signals. Here, twophoton processes can be identified by analysis of either the dependency of the signal strength on the radiation intensity or the angular distribution of the signal. The former should reveal a non-linear behaviour, the latter gives rise to angular patterns different from a distribution of a dipole transition with momentum transfer of ∆l = 1 being governed by the well-known β-distribution (a 2nd order Legendre polynomial and the β-parameter). The observation of C60 ions can also gives hints about two-photon processes, since one would expect just intact Cq+ 60 ions (q = 1–3) for photon energies of 38 eV under single photon absorption conditions, whereas other traces of fragments, like q+ Cq+ 58 or C56 , require higher energies. This work was supported by the Bundesministerium f¨ ur Bildung und Forschung (BMBF) under promotion code no. 05 KS4EB1/3.

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P363

SANS investigation of the heavy-fermion compound CeRu2 Si2 G.P. Kopitsa1 , S.V. Grigoriev1 , V.M. Garamus2 , V.V. Runov1 , P. Lejay3 1

Petersburg Nuclear Physics Institute of RAS, 188300 Gatchina, Russia – 2 GKSS Research Centre D-21502 Geesthacht, Germany – 3 CRTBT-CNRS, 38042 Grenoble, France The theoretical studies [1 - 3] have shown that the orbital part of the magnetic scattering amplitude contains the term, which is singular at q → 0 and gives rise the small-angle neutron scattering on the conduction electrons in metals: Fsing = −ir

σ [q × p] , q2

(1)

where r =| γ | e2 /mc2 = 5.4 · 10−13 cm and γ = −1.91; p is the electron momentum. It was shown [1-3] that in metals the scattering cross section dΣ(q)/dΩ is proportional to (m/M )2 , where m is the effective mass of electrons (carriers) and M is the mass of the neutron. For ordinary metals this factor is of order 10−5 ÷ 10−6 and the neutron-electron scattering is negligibly small. However for heavy-fermion substances m ≈ 100me and (m/M )2 ∼ 10−2 . In such cases this scattering could be observed if one takes into account that dΣ(q)/dΩ is proportional to ϑ−1 for 2Eϑ  T and T /(ϑ2 E) for T  2Eϑ, where ϑ  1 is scattering angle and E is neutron energy. In this work [4], SANS experiments were carried out with CeRu2 Si2 single crystal in order to directly observe SANS on heavy fermion quasiparticles and to analyze the magnetic field effect on this scattering. The system CeRu2 Si2 is the archetypal heavy fermion compound with temperature Kondo TK ≈ 25 K, which has no additional complexity such as superconductivity, magnetic phase transitions, etc. at T ≤ 1 K. The SANS experiments were performed at the SANS-1 facility (reactor FRG1, GKSS Research Centre, Geesthacht, Germany), which operates in near point geometry. In these experiments the wavelengths λ1 = 8.1 and λ2 = 10.5 ˚ A were used. The measurements were carried out in the range of momentum transfer 7 · 10−3 < q < 2 · 10−1 ˚ A−1 and the magnetic fields 0 ≤ H ≤ 2.5 T at the temperatures T ≈ 1 and 290 K. In the course of SANS experiment we found, firstly, the additional small-angle scattering at q ≤ 0.04 ˚ A−1 which may be attributed to the contribution of the neutron-carrier scattering to the orbital part of the magnetic scattering amplitude in this system, as predicted in [3]. Secondly, it was found that the applied magnetic field results in both the increase of the observed scattering and its anisotropy with respect to the field direction. Moreover, measurements in the magnetic field reveal additional scattering for q > 0.04 ˚ A−1 , which is interpreted as magnetic scattering by spin-density fluctuations with a correlation radius Rc ≈ 30 ˚ A. [1] R.J.Elliott, Proc.Roy.Soc. 235 A (1956), 298 . [2] S.L.Ginzburg, S.V. Maleyev, Fiz.Tv.Tela 7 (1965), 3065 . [3] S.V. Maleyev, Usp. Fiz. Nauk, 172 (2002), 617 . [4] G.P. Kopitsa et al., JETP Letters 81 (2005), 556.

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P364

Inelastic neutron scattering on levitated liquid droplets ¨ber1 , Andreas Meyer1 , Sebastian Stu 2 3 Heinen , Tobias Unruh

Dirk Holland-Moritz2 ,

Oliver

1

Deutsches Zentrum f¨ ur Luft und Raumfahrt, Institut f¨ ur Raumsimulation, 51170 K¨ oln – 2 Institut f¨ ur Raumsimulation, DLR, 51170 K¨ oln – 3 Heinz Maier-Leibnitz Forschungsneutronenquelle, FRM-II, TU M¨ unchen, 85747 Garching Conventional neutron scattering experiments on metallic liquids are restricted to samples with a melting temperature that is well below 2000 K and that do not react with their sample holders made of e.g. alumina or SiC. We succeeded to process liquid droplets of 6-8 mm in diameter in an electromagnetic levitation device on the neutron time-of-flight spectrometer ToF-ToF of the FRM-II. This containerless processing of the samples not only gives access to experiments on high temperature and chemically reactive liquids, but also allows for undercooling the samples several 100 K below their liquidus. In addition, spectra at large q values can be measured with high accuracy that are otherwise dominated by Bragg scattering of the sample holders. We report on quasielastic neutron scattering experiments on liquid Ni as well as Ni and Zr rich alloys. More than 200 K undercooling and the resulting slowing down of dynamics allowed for a stringent test of theoretical descriptions of liquid dynamics in these systems.

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P365

Magnetic Properties of the Eu-Monochalcogenides at Extreme Pressures Kirsten Rupprecht1 , Wortmann1

Olaf

Leupold2 ,

Ulrich

Ponkratz3 ,

Gerhard

1

Department Physik, Universit¨ at Paderborn, D-33095 Paderborn – 2 HASYLAB, DESY, Notkestrasse 85, D-22607 Hamburg – 3 ESRF, F-38043 Grenoble Cedex The divalent Eu-chalcogenides EuX (X=O, S, Se, Te) are well-known model substances for Heisenberg magnetism because of the spin-only J=S=7/2 4f-moment of the Eu2+ ions and their simple NaCl structure. The variation of the magnetic ordering temperatures with pressure has been intensively studied in the NaCl phases up to 30 GPa using 151Eu-M¨ ossbauer and neutron spectroscopy [1, 2], delivering important information on the pressure dependence of the magnetic exchange interactions. Here we present for the first time systematic studies on EuO, EuS, EuSe and EuTe in their CsCl-type high-pressure phases up to 120 GPa using the 151Eu nuclear forward scattering (NFS) technique developed at the ESRF, where the present studies as well as previous studies on other Eu systems were performed [3]. The NaCl to CsCl phase transitions occur around 45, 20, 15 and 12 GPa for EuO, EuS, EuSe and EuTe, respectively. The samples were pressurized in a special diamond anvil cell designed to fit into the cryomagnet at ID22N. At each pressure we measured NFS spectra from 4 K up to 300 K to determine the magnetic ordering temperature TM, the saturation magnetic hyperfine field Bhf and the isomer shift SIS with respect to an applicable Eu reference absorber. The results on EuTe in the CsCl phase are already published [3]. In the CsCl-type high-pressure phases of EuSe, EuS and EuO we observe a further strong increase of the ferromagnetic ordering temperatures TC, reaching 300 K at 77 GPa for EuSe, 295 K at 120 GPa for EuS and 165 K at 75 GPa for EuO. For EuS the pressure dependent slope of TC denotes a saturation at the highest pressure in a strongly mixed valent state. In the case of EuO we found at even higher pressures a strong decrease of TC to 110 K at 92 GPa, a behaviour resembling that of EuO around 30 GPa in the NaCl phase [1]. This behaviour points to the onset of a mixed-valent state in CsCl-type EuO, which is also reflected by the isomer shift and the variation of Bhf. We discuss the present results in conjunction with models developed for magnetic and mixed-valent Eu systems, for instance for Eu metal at high pressures [4]. Work supported by the BMBF (grant no 05 KS4PPB/4) [1] M.M. Abd-Elmeguid and R.D. Taylor, Phys. Rev. B 42, 1048, (1990) [2] I.N. Goncharenko and I. Mirebeau, Phys. Rev. Lett. 80, 1082, (1998) and cited references [3] O. Leupold, K. Rupprecht, G. Wortmann, Structural Chemistry 14, 97, (2003) [4] J. R¨ ohler, Handbook of the Physics and Chemistry of Rare Earth, Vol. 10, 523, (1987)

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P366

MAX200x: XRD under High Pressure and High Temperature Conditions ¨ller2 , Hans-Josef Frank Schilling1 , Christian Lathe1,2 , Hans-Joachim Mu 2 Reichmann 1

GFZ Potsdam, Telegrafenberg, 14473 Potsdam, Germany. Notkestr. 85, 22603 Hamburg, Germany.

– 2 DESY-HASYLAB,

In-situ X-ray diffraction experiments under extreme pressure p and temperature T conditions at synchrotron beam lines become more and more important for Geosciences, Material Sciences, Chemistry and Physics. Especially for Geoscientists mineral reactions, phase transitions, as wheel as fluid rock interaction at enhanced p and T seem to have the potential to strongly influence and control the dynamic motions within the upper and lower mantle of the Earth. Around 25 GPa and 2000 K are required to simulate these processes in the laboratory. The new installed MAX200x (Fig. 1) is an excellent tool for these ambitious experiments. The MAX200x is operated in the double-stage compression mode, in which the first stage is the DIA-type apparatus with six anvils and the second stage consists of eight anvils. One corner each of all eight cubes Fig. 1: MAX200x surrounded from aluminium-lead-aluminium hutch at is truncated orthogonally to the spatial diagoDESY-HASYLAB. nal. The octahedral sample is compressed by the truncated corner of eight inner cubic anvils, which, in turn, is compressed by the outer first stage six anvils. Either tungsten carbide or cubic boron nitride is used for the second stage anvils. This system has a capability of generating pressures up to 25 GPa and temperatures exceeding 2000 K by a resistance furnace. The MAX200x is movable in y- and z-direction for ± 125 mm and can be rotated up to ± 15. For detecting the X-rays we use a high purity Germanium detector which is cooled by an electrical cooler. The Ge-detector is mounted on a goniometer which is adjusted to the centre of the press and can rotate from 0◦ up to 15◦ . It is assembled on a stepper motor driven table which can be displaced in z-, x-, and y-direction. For deformation experiments and viscosity studies under in situ conditions X-radiography is indispensable. Furthermore, to measure X-ray absorption as a tool for e.g. in situ density measurements of melts an ionization chamber is available [1]. First experimental results will be presented. [1] C. Lathe, F. Schilling, H.J. M¨ uller, H.J. Reichmann and J. Lauterjung, HASYLAB Annual Report (2005).

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P367

Kernstreuung von Synchrotronstrahlung unter hohem Druck: R¨ uckblick und Ausblick Gerhard Wortmann1 1

Department Physik, Universit¨ at Paderborn, D-33095 Paderborn

Seit dem ersten Nachweis [1] der nuklearen Streuung von Synchrotronstrahlung (SR) im Jahre 1985 durch Erich Gerdau und Mitarbeiter am HASYLAB (DESY, Hamburg) hat diese dem M¨ ossbauer-Effekt eng verwandte Methode unter Nutzung der SR-Quellen der 3. Generation einen großen Aufschwung genommen. Dabei erlaubt die elastische Kernvorw¨ artsstreuung (nuclear forward scattering, NFS) die Messung von Hyperfeinwechselwirkungen [2], so von magnetischen und elektrischen Felder, und die inelastische Kernstreuung (nuclear inelastic scattering, NIS) die lokale Phononen-Spektroskopie am M¨ ossbauerkern [3]. Da die SR auf Probengr¨ oßen von 10 Mikrometer und kleiner fokussiert werden kann, sind beide Methoden hervorragend f¨ ur Experimente unter hohen bis h¨ ochsten Dr¨ ucken geeignet. Unter der Verwendung von DiamantstempelHochdruckzellen wurden nach kurze Zeit NFS- und NIS Experimente in Druckbereichen h¨ oher 1 Mbar (100 GPa) durchgef¨ uhrt [4,5,6]. Die von der Paderborner Gruppe an der ESRF durchgef¨ uhrten NFS und NIS Experimente werden kurz vorgestellt, so die Unterdr¨ uckung des Magnetismus in LavesPhasen des Eisens [4], das ungew¨ ohnliche magnetische und gemischt-valente Verhalten der Eu(II)-Chalkogenide EuX (X = O, S, Se, Te) in den CsCl-Hochdruckphasen [4,7] und schließlich die Phononen-Spektroskopie an Eisen unter Dr¨ ucken wie im Inneren der Erde mit der geophysikalisch wichtigen Information u ¨ber die Schallgeschwindigkeiten [6,8]. Dann werden aktuelle Entwicklungen, wie sie zur Zeit an anderer Stelle vorangetrieben werden, vorgestellt, so die zus¨ atzliche Option der hohen Temperaturen, wie sie mit Laser-Heizung der Proben in den Hochdruckzellen erreicht werden kann. Zuk¨ unftige Entwicklungen der Kernstreuung unter extremen Bedingungen, wie sie an PETRA-III m¨ oglich werden, werden diskutiert. Gef¨ ordert durch das BMBF (05 KS4PPB/3-5). [1] [2] [3] [4] [5] [6] [7] [8]

E. Gerdau et al., Phys. Rev. Lett. 54 (1985) 835. J.B. Hastings et al., Phys. Rev. Lett. 66 (1991) 770. W. Sturhahn et al., Phys. Rev. Lett. 74 (1995) 3832. R. L¨ ubbers et al., Hyperfine Interactions 123/124 (1999) 529; ibid. 128 (2000) 115. R. L¨ ubbers et al., Science 287 (2000) 1250. H.-K. Mao et al., Science 292 (2001) 914. K. Rupprecht et al., ESRF Highlights 2005, p. 10. H. Giefers et al., ESRF Highlights 2004, p. 19.

Materie unter extremen Bedingungen

Poster: Do., 13:00–15:30

D-P368

X-ray diffraction in high magnetic fields at beamline BW5 M. v. Zimmermann1 , N.H. Andersen2 , J. Jensen3 , T.B.S. Jensen2 , R. Pinholt2 , A.B. Abrahamsen2 , K. Nørgaard Toft2 , P. Hedeg˚ ard2 , P.C. Canfield4 1

HASYLAB at DESY – 2 Materials Research Department at Risø National Laboratory, DK – 3 Niels Bohr Institute, DK – 4 Ames Laboratory, Iowa State University, USA The detailed balance of spin, charge, orbital and lattice degrees of freedom gives rise to highly unusual properties of correlated electron materials,which might be exploited for applications. The determination of all of these degrees of freedom is essential for the understanding of the unusual properties. The high energy diffraction at beamline BW5 at HASYLAB in Hamburg is a highly sensitive probe for structural distortions, enabling the determination of the lattice degree of freedom. In particular the recent installation of a 10 Tesla horizontal field magnet opens up unique possibilities to study the response of the lattice to the application of magnetic fields. In the presentation a recent examples of a high magnetic field study of rear earth nickel borocarbides will be presented. Here an increasing magnetic field leads to the stabilization of a spin density wave and induces quadrupolar ordering.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P369

Study on Preparation and Structural Analysis of Yb0.6 Sr0.4 Mnx Fe1−x O3 Ihab Abdel-Latif1 , Aisha Mostafa2 , Vitaly Trounov3 , Alex Kurbakov3 , Elena Tserkovna3 1

Reactor Physics Dept., NRC, Atomic Energy Authority, Abou Zabaal – 2 ) Physics Division, National Research Center, El-Dokky, Giza, Egypt – 3 Petersburg Nuclear Physics Institute, Gatchina, 188350, Petersburg, Russia The present work deals with studying the structure of Yb0.6 Sr0.4 Mnx Fe1−x O3 using X-ray and neutron diffraction methods. This compounds were prepared using solid state reaction from pure oxides (Yb2 O3 ∼99.9 %, Fe2 O3 ∼99.9 %, Mn2 O3 ∼99.999 % and SrO∼99.9 %). The sintering temperature was 1350 ◦ C for 30 h. The X-ray analysis showed that all samples have a single phase structure: The samples of Manganese concentration of x = 1 and 0.8 have a hexagonal structure of a space group P63cm (185). The lattice constant values are a=b=6.0618, 6.0493 ˚ A and c=11.3439, 11.3857 ˚ A, respectively. The structure changes from the hexagonal into orthorhombic for x=0.6 of Pnma (62) space group. The lattice parameters, (a, b, c) of x=0.6 sample, are 5.5725, 7.6576 and 5.4507 ˚ A, respectively.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P370

Study of pore structures in shungites by small-angle neutron scattering Mikhail V. Avdeev1 , Timur V. Tropin1 , Victor L. Aksenov1 , Laszlo Rosta2 , Vasyl M. Garamus3 , Natalia N. Rozhkova4 1

Joint Institute for Nuclear Research, Dubna, Russia – 2 Research Institute for Solid State Physics and Optics, Budapest, Hungary – 3 GKSS Research Center, Geesthacht, Germany – 4 Institute of Geology, Karelian Research Centre RAS, Petrozavodsk, Russia Shungites are carbon-rich rocks of Precambrian age widespread over Russian Karelia. In recent years they have been attracting much attention due to the prospects of their various industrial and biomedical applications [1]. A special attention to shungites is connected with the reported [2] presence of fullerenes in them. In the given work the analysis of the small-angle neutron scattering data for shungites from different deposits [3] is reported. It is shown that shungites have a complex pore structure at a nanoscale of 1-100 nm depending on their origin. Along with it, common features, in particular, two-level organization at the given scale can be observed. The absorption of heavy water by shungites is used to match the neutron scattering from open pores and to separate the information about the open and closed porosity in the samples. The revealed structural units are compared with the previous experimental results obtained by the complementary techniques. The work has been performed with the ISTCS support, project 2769. [1] Buseck PR, Galdobina LP, Kovalevski VV, Rozhkova NN, Valley JW, Zaidenberg AZ. Canadian Mineralogist 35 (1997) 1363. [2] Buseck PR, Tsipursky SJ, Hettich R. Science 257 (1992) 215. [3] Avdeev MV, Tropin TV, Aksenov VL, Rosta L, Garamus VM, Rozhkova NN. Carbon 44 (2006) 954.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P371

Chemische Bindung in Carbonitrid-Nanoschichten O. Baake1 , W. Ensinger1 , P. Hoffmann1 , A. Klein1 , B. Beckhoff2 , B. Pollakowski2 , G. Ulm2 , N. Fainer3 , M. Kosinova3 , V. Trunova3 1

Technische Universit¨ at Darmstadt – 2 Physikalisch-Technische Bundesanstalt, Berlin 3 – Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia Carbonitriden werden außergew¨ ohnliche mechanische, optische, elektronische und chemische Eigenschaften zugesprochen. Die Gr¨ unde daf¨ ur sind in der elektronischen Struktur ihrer chemischen Bindung sowie der atomaren Struktur des keramischen Netzwerks zu sehen. Insbesondere in der letzten Dekade wurden viele Versuche unternommen, Materialien wie BCx Ny und SiCx Ny herzustellen. F¨ ur die hier pr¨ asentierten Untersuchungen wurden Carbonitrid-Nanoschichten mit plasma-induzierter chemischer Gasphasenabscheidung (plasma-enhanced chemical vapour deposition PECVD) mit Prekursoren wie Trimethylammoniumboran, Hexamethyldisilazan and Bis(trimethylsilyl)carbodiimid hergestellt [1]. Nach der Synthese der Carbonitrid-Schichten wurde das amorphe Material durch Tempern bei 1000 ◦ C in nanokristallines umgesetzt. Synthese und Kristallisation sind bisher aber noch nicht genau verstanden. Es ist von großer Wichtigkeit, das entstandene Material chemisch zu charakterisieren. Zuerst sollten die chemischen Komponenten bestimmt werden, dann sollte die chemische Bindung bestimmt werden. Die Elementzusammensetzung wurde mit Elektronenstrahl-Mikroanalyse (EPMA) ermittelt. Die chemischen Bindungszust¨ ande von BCx Ny and SiCx Ny wurden zerst¨ orungsfrei mit TXRF-NEXAFS [2], XPS, TEM-EELS und Raman-Spektroskopie untersucht. Die TXRF-NEXAFS-Messungen wurden am Elektronenspeicherring BESSY II mit Synchrotron-Strahlung durchgef¨ uhrt. Die erhaltenen Spektren der Carbonitrid-Schichten wurden mit denen bin¨ arer Standardmaterialien, z.B. B4 C, BN, SiC, und Si3 N4 , verglichen. Damit konnte gezeigt werden, welche Bindungen durch diesen Vergleich identifizierbar waren und welche nicht mit denen der Standardmaterialien vergleichbar waren. [1] M L. Kosinova, N.I. Fainer et al., in M. Allendorf and Editors, Chemical Vapour Deposition, pp.709, Electrochemical Society Proceedings Series, Pennington, NJ, 2003 [2] G. Pepponi, B. Beckhoff, T. Ehmann, G. Ulm, C. Streli, L. Fabry, S. Pahlke, P. Wobrauschek, Analysis of organic contaminants on Si wafers with TXRF-NEXAFS. Spectrochim. Acta B 58, 2245-2253 (2003)

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P372

Use of neutron diffraction method for residual stress analysis of laser welded aluminium T-Joints for airframe applications Funda Seniz Bayraktar1 , Peter Staron2 , Manfred Horstmann3 , Mustafa Kocak4 , Andreas Schreyer5 1

GKSS Research Centre Geesthacht GmbH

Abstract. Welded structures should provide optimum weld microstructure, sound mechanical properties as well as control of residual stresses and distortions. Hence, in this study residual stresses in a laser beam welded T-joint of aerospace grade aluminium alloy were characterized using neutron diffraction. The figures 1 and 2 are schematically showing the welded airframe section and idealized panel used in this study, respectively. It is essential to understand the micro-mechanical properties of such new joint types for successful applications in future aircrafts. Welding start (run-in) and end (run-out) locations of the T-joints are generally considered as high risk areas with respect to solidification cracking and crack initiations under external loadings. However, there is lack of information both on residual stress and fatigue properties of such welds in open literature. Therefore, detailed analysis of welding induced residual stresses and fatigue crack propagation behaviours of such welds have to be conducted. These T-joints were used for the determination of residual stresses and fatigue crack propagation properties. Higher longitudinal tensile residual stresses are detected at the run-out locations than at the run-in locations. Measurements in the clip showed that there is a longitudinal tensile stress peak located about 8 mm from the weld seam. Fatigue crack propagation tests have shown that the weld seam is not necessarily the preferred crack path if the local design of the joints is optimised.

Fig. 1: Laser beam (LBW) welded airframe section. Currently stringers are welded in some part of the aircrafts. Welded clips are yet to be used.

Fig. 2: Idealized welded panel to conduct residual stress analysis on the LBW of clips in this study.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P373

Ultra high resolution heavy ion ERD and its application in the field of future microelectronic materials ¨nther Dollinger1 Andreas Bergmaier1 , Gu 1

Universit¨ at der Bundeswehr M¨ unchen, LRT 2, Werner-Heisenberg-Weg 39, D-85577 Neubiberg Ultra thin films with thicknesses smaller than 10 nm are now widely used e.g. in the field of microelectronics and neutron optics and there is ongoing research in the development of smart films in this fields. The physical properties of these films depend on stoichiometry, impurity content and surface and interface structures of the thin films. Therefore, there is a strong need for the elemental characterisation of those films where high accuracy and optimum depth resolution is required. In the last years the high resolution elastic recoil detection experiment at the Munich tandem accelerator, using a Q3D magnetic spectrograph was optimized for ultra thin films analysis. The talk will demonstrate the achievements in terms of depth resolution, sensitivity and accuracy. The potential of the method will be demonstrated on several applications where high resolution ERD is the most valuable tool for elemental profiling.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P374

Neutronenkleinwinkelstreuung an ausscheidungsgeh¨ arteten St¨ ahlen Michael Bischof1 , Peter Staron2 , Stefan Erlach3 , Harald Leitner1 , Elisabeth Eidenberger1 , Helmut Clemens1 1

Montanuniversit¨ at Leoben, Franz Josef-Straße 18, A-8700 Leoben – 2 GKSS Forschungszentrum, Max-Planck-Straße 1, D-21502 Geesthacht – 3 Materials Center Leoben Forschung GmbH, Franz Josef-Straße 13, A-8700 Leoben Die Neutronenkleinwinkelstreuung (SANS) hat sich als wertvolles Instrument zur Analyse von Inhomogenit¨ aten in technischen Werkstoffen etabliert. Derartige Inhomogenit¨ aten stellen beispielsweise auch die Ausscheidungen in Werkzeugst¨ ahlen dar. Deren Eigenschaften werden von nanometergroßen Sekund¨ arh¨ artekarbiden bzw. intermetallischen Ausscheidungen entscheidend gepr¨ agt. Eine umfassende Charakterisierung dieser Ausscheidungen ist deshalb von großer Bedeutung und eine kombinierte Anwendung von SANS, Transmissionselektronenmikroskopie (TEM) und Atomsondentomograpie (APT) hat sich diesbez¨ uglich als sehr hilfreich erwiesen [1]. SANS hat dabei den entscheidenden Vorteil, dass sowohl die Gr¨ oßenverteilung als auch die Volumenfraktion der Ausscheidungen mit hoher Genauigkeit erfasst werden k¨ onnen. W¨ ahrend des Streuexperimentes wird die Stahlprobe von einem starken Magnetfeld durchflossen. N¨ aherungsweise liegt somit ein System einer ferromagnetisch ges¨ attigten Matrix, in welcher nichtmagnetische Ausscheidungen eingebettet sind, vor. Streuphysikalisch wird dieses System deshalb u ¨blicherweise als einfaches 2-Phasen Modell behandelt. Es hat sich jedoch herausgestellt, dass f¨ ur eine korrekte Interpretation der SANS - Messungen unter Umst¨ anden zus¨ atzliche Streubeitr¨ age unterschiedlichen Ursprungs ber¨ ucksichtigt werden m¨ ussen. Diese stammen zum einen von magnetischen Inhomogenit¨ aten innerhalb der martensitischen Matrix, hervorgerufen durch deren magnetische Anisotropie. Zum anderen werden sie durch innere Streufelder, welche sich um die nichtmagnetischen Ausscheidungen bilden, verursacht [2]. Dar¨ uber hinaus hat auch der paramagnetische Restaustenit, der vor allem in abgeschreckten und kurz ausgelagerten St¨ ahlen vorliegt, großen Einfluß auf eine korrekte Auswertung der Teilchenverteilung. Die gezielte Kombination der oben genannten Methoden sowie die Notwendigkeit zur Korrektur der SANS - Daten wird anhand eines konkreten Beispieles dargestellt und die Vorteile, aber auch die Grenzen dieser Methode f¨ ur die Analyse von St¨ ahlen werden aufgezeigt. Im speziellen wird auch auf die Abh¨ angigkeit notwendiger Korrekturen von der vorangegangenen W¨ armebehandlung des Werkstoffes sowie auf einen Zusammenhang mit dessen magnetischen Eigenschaften eingegangen. [1] M. Bischof et al., Z. Metallkd. 96 (2005) 9, 1074-1080. [2] C. Vecchini et al., Appl. Phys. Lett. 87 (2005), 202509.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P375

Water dynamics in hardened cement paste - from Inelastic Neutron Scattering H. N. Bordallo1 , L.P. Aldridge, A. Desmedt 1

Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – Senior Fellow Materials Engineering Science ANSTO Australia A/Prof School of Civil and Environmental Engineering, UNSW2234, Australia – 3 LPCM UMR5803 CNRS Universit´e de Bordeaux I, F-33405 Talence, C´edex, France 2

Creep and shrinkage of concrete specimens occur during the loss and gain of water from cement paste. In order to better understand the role of water in concrete, a series of quasi-elastic neutron scattering (QENS) experiments were carried out on cement pastes with water/cement ratio varying between 0.32 and 0.6. The samples were cured for about 28 days in sealed containers so that the initial water content would not change. The QENS spectra differentiated between three different water interactions: water that was chemically bound into the cement paste, the physically bound or glassy water that interact with the surface of the gel pores in the paste and free or unbound water molecules that are in fact confined within the larger capillary pores of cement paste. The dynamics of the glassy water and free water in an extended time scale, from a hundred pico-seconds to a few nano-seconds, could be clearly differentiated from the data. Diffusive motion was characterized by diffusion constants, with significant reduction compared to the rate of diffusion for bulk water. This reduction of the water diffusion is discussed in terms of the interaction of the water with the calcium silicate gel and the ions present in the pore water. In addition, the short-time dynamics of the hydrogen atoms, mainly determine the inelastic part of the spectrum, was analysed. The spectrum of the hydrated OPC samples are very similar, and correlates well with molecular dynamics calculations for super-cooled water as well as with reconstructed density of states for hydrated calcium silicate pastes.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P376

Al und Cu Textur eines Al90 -Cu10 Verbundwerkstoffes ¨nter Brokmeier1 , Bernd Heinz-Gu Lippmann2 , Andreas Schreyer2

Schwebke1 ,

Ulf

Garbe2 ,

Thomas

1

IWW - Technische Universit¨ at Clausthal / GKSS-Forschungszentrum, Max-PlanckStr, 21502 Geesthacht – 2 GKSS-Forschungszentrum, Max-Planck-Institut, 21502 Geesthacht Die neue Materialforschungsbeamline Harwi-II am Speicherring Doris (HASYLABDESY) wurde benutzt, um die Textur von kalt stranggepresstem Al90 -Cu10 zu untersuchen. Die Texturanalyse von zweiphasigen Verbundwerkstoffen liefert Informationen u ¨ber das Verhalten des Matrixmaterials und des Verbundpartners in Abh¨ angigkeit von der thermomechanischen Behandlung, den Volumenanteilen und den Korngr¨ oßenverteilungen. Messtechnisch sind Reflex¨ uberlagerungen und geringe Volumenanteile von besonderer Bedeutung. W¨ ahrend der Verformung der Al90 -Cu10 Verbundprobe wird die relativ weiche Matrix aus Aluminium um die h¨ arteren Cu Partikel fließen. Dabei kann es zum Teil zu starken lokalen Texturen f¨ uhren. Die f¨ ur die globale Eigenschaft entscheidende Textur ist die mittlere Textur u ¨ber den Querschnitt des Strangpresslings, weshalb Neutronen oder harte R¨ ontgenstrahlen eingesetzt werden. Je nach Verformungsgrad werden auch die Cu-Partikel deformiert und bilden die typische Mikrostruktur mit lang gestreckten K¨ orner in Verformungsrichtung. F¨ ur die Messungen an Harwi-II stand ein Mar345 Imageplate Detektor zur Verf¨ ugung. Es wurden vollst¨ andige DebeyeScherrer Ringe der Reflexe Al (111), Al (200), Al (220), Cu (111), Cu (200) and Cu (220) f¨ ur die quantitative Texturanalyse benutzt. Dazu wurden insgesamt 19 einzelne Imageplate Aufnahmen in ω- Schritten von 5◦ verwendet. Die partielle Peak¨ uberlagerung von Cu (111) und Al (200) konnte u ¨ber Profilfitting getrennt werden. Reine FCC-Metalle entwickeln beim Strangpressen starke Doppelfasertexturen mit den Faserachsen <111> und <100>. Die St¨ arke der Faserachsen ist unter anderem abh¨ angig vom Metalltyp, vom Verformungsgrad und von der Korngr¨ oße. Metall-Matrix Verbundwerkstoffe zeigen eine gegenseitige Beeinflussung, die auch die diesem Experiment auftritt. Die mittels harter Synchrotronstrahlung gemessene Globaltextur zeigt f¨ ur beide Komponenten die bekannte Doppelfaser. Die Textur ist sowohl f¨ ur die Al-Matrix als auch f¨ ur das Cu deutlich schw¨ acher als f¨ ur vergleichbare einphasige Proben [1,2]. Im Falle des weicheren Aluminiums wird das homogene Fließen der Al-K¨ orner in Pressrichtung behindert, so dass sowohl die Kornl¨ angung als auch die Textursch¨ arfe weniger ausgepr¨ agt sind. Wie die Ergebnisse zeigen, wird dieses Verhalten schon bei 10 Vol.% Cu beobachtet. Der relativ geringe Cu Anteil f¨ uhrt dazu, dass es nur wenige Cu-Cu Grenzfl¨ achen gibt, trotzdem wird auch bei dem h¨ arteren Cu schon eine deutlich ausgepr¨ agte aber wesentlich schw¨ achere Textur beobachtet. Der innere Verformungsgrad der Cu-K¨ orner weicht deutlich vom makroskopischen Verformungsgrad von 96 % ab [2]. [1] H. Gertel, Diss., TU Clausthal 1992 [2] W. B¨ ocker, Diss., TU Clausthal 1992

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P377

High temperature texture investigation in steel ¨nter Brokmeier1 , Sang-Bong Yi2 , Jens Homeyer3 Heinz-Gu 1

IWW - Technische Universit¨ at Clausthal / GKSS-Forschungszentrum, Max-PlanckStr, 21502 Geesthacht – 2 IWW-Technische Universit¨ at Clausthal, Agricolastrasse 6, 38678 Clausthal-Zellerfeld – 3 Hasylab at DESY, Notkestr. 85, 22607 Hamburg In-situ experiments at high temperatures have been widely used for the study of phase transitions and the investigation of thermal expansion coefficients. Crystallographic texture analysis is in general a time consuming technique, that in-situ experiments are restricted by the total counting time. Recently developed methods and improvements in the instrumentation allow fast texture measurements. We have used hard X-rays of about 100 keV to measure the texture transition as well as the phase transition in a steel sample. The experiments were done at the high energy beam line BW5 at Hasylab (Desy-Hamburg/Germany). Using a MAR345 image plate detector one obtains a set of complete Debeye Scherrer cones each in 1 sec. At room temperature we found 100 % ferrite. During heating up till the austenite region we were able to investigate the thermal expansion, the texture at some fixed temperatures and the texture relation between ferrite and austenite. In In our case the Kurdjumov-Sachs model was found to describe the texture transition between ferrite and austenite. Furthermore, the program package MAUD offers the possibility to follow the phase transition, so that the composition at all temperatures can be documented during heating. It has to be pointed out that the texture influence on the quantitative phase analysis can be included by MAUD, so that even for strong crystallographic textures the relation ferrite/austenite can be given very well.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P378

Crystallographic texture investigations of Cu-Nb tubes for industrial applications ¨nter Brokmeier1 , Wenhai Ye1 , Waldemar Singer, Xenia Singer Heinz-Gu 1

IWW - Technische Universit¨ at Clausthal / GKSS-Forschungszentrum, Max-PlanckStr, 21502 Geesthacht – 2 DESY-MPL, Notke-Str.85, 22607 Hamburg Cu- Nb tubes are one of the candidates for the manufacturing of accelerator units for a linear collider. In order to produce an accelerator unit by hydro-forming the Cu-Nb tube is the pre-product which should have homogeneous textures around the perimeter. Beside the type of the initial materials such as the Cu and the Nb alloy and the production of the pure Cu and the pure Nb tubes the joining technique to form a Cu-Nb tube composite is of basic interest. The present investigation deals with co-extruded and explosive bonded material with a final wall thickness of about 4 mm (Cu 3 mm thick and Nb 1 mm thick). Non-destructive measurements were carried out on one hand to determine the texture inhomogeneity using thermal neutrons and on the other hand to study the strain gradient over the tube thickness using synchrotron radiation. This contribution will focus on the crystallographic texture. Therefore ring samples were cut samples with a diameter of 140 mm and a width of 15 mm. Due to the high penetration depth of thermal neutrons the average texture of both phases was measured. In order to get local textures around the perimeter of the Cu-Nb ring a Cd-slit for the incoming beam and a similar Cd-slit for the outgoing beam were used. In both phases typical textures types of fcc-Cu and bcc-Nb were found. By calculating the orientation distribution function using ISEM (iterative serious expansion method) one is able to compare quantitatively textures correlated to the processing technique, to describe texture variations along the perimenter and to study textures changes during thermo-mechanical treatments (heating, cooling etc.)

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P379

Texture of submicron Ni-Mn-Ga films studied by X-ray beam line of synchrotron source ¨llner4 , Volodymyr Chernenko1 , Stephen Doyle2 , Manfred Kohl3 , Peter Mu 5 6 Stefano Besseghini , Makoto Ohtsuka 1

Institute of Magnetism, Vernadsky str. 36-b, Kiev 03142, Ukraine – 2 ANKA, Forschungszentrum Karlsruhe, D-76021, Karlsruhe, Germany – 3 IMT, Forschungszentrum Karlsruhe, D-76021, Karlsruhe, Germany – 4 Department of Materials Science and Engineering, Boise State University, Boise, ID, USA – 5 CNR-IENI, Lecco 23900, Italy – 6 IMRAM, Tohoku University, Sendai 980-8577, Japan The ferromagnetic thermoelastic martensites exhibited by the single and polycrystalline Ni-Mn-Ga alloys have attracted much attention as potential multifunctional materials.It is a challenge to develop thin film technology for the production of microand nanocrystalline Ni-Mn-Ga martensites and to keep their functionality as in the bulk. In general, because the properties of polycrystalline thin films depend strongly on their microstructure, an important research area is concerned with the control of this microstructure, in particular the texture and internal stresses which develop during deposition and post-deposition annealing processes. As much as the feasibility of magnetomechanical activation in polycrystalline films is concerned, the crucial point is to get them in a crystallographic oriented (textured) form.The preferable orientation of one crystal axis in grains would give rise to the overall magnetic anisotropy of film as a prerequisite of its macroscopic magnetomechanical response. In metallic films, texture and martensitic transformation depend on the film thickness. In this work, we used an X-ray diffraction facility attached to the beam line generated by ANKA synchrotron source, FZK, Karlsruhe to study a texture and internal stress problem in Ni-Mn-Ga thin films magnetron-sputtered on alumina ceramic and molybdenum foil. Series of film/substrate composites with film thicknesses ranging from 0.1 to 5.0 micrometer were fabricated using two targets of different compositions. Films on substrates were vacuum annealed at 1073 K for 36 ks. The target compositions were designed to get in annealed films a 5-layered tetragonal and 7-layered orthorhombic martensitic phases, respectively. X-ray diffraction mapping was made at 300 and 423 K. An in-house made temperature controlled heating unit was designed to this aim. The selected values of temperatures assured our films to be either in martensitic or austenite cubic state. The texture measurements were performed using 2-teta scans at fixed fi and ki angles which were varied by the 10 deg. step in a range of 0 – 90 deg. A drastic change of intensity of 202 peak in martensitic phase and sharp changes in mutual intensities of 220 and 400 peaks in austenic phase as a function of ki was found while fi dependence was neglectful. An analysis of the results leads to the conclusion about different degree of 110-type fiber texture for the films of different thickness in both austenite and martensite states. The perpendicular magnetic anisotropy as a result of fiber texturing and particular microstructure of martensitic phase formed is proved experimentally for all the films.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P380

SANS/USANS investigations of SiO2 nanoclusters in different organic solutions Helmut Eckerlebe1 , P. Klaus Pranzas1 , Christian Eger2 , Manfred Pyrlik2 1

GKSS Forschungszentrum, Max-Planck-Str. 1, D-21502 Geesthacht – 2 hanse-chemie AG, Charlottenburger Str. 9, D-21502 Geesthacht Nanoscaled particles play an important role in various fields, e. g. as pigments and filler material in paints, coatings, castings, pottery or insulating materials. Using nanoscaled inorganic fillers new products can be developed and product properties can be optimized. In addition to particle size, the degree of agglomeration has an important influence on the properties of new materials. Hanse Chemie develops the technology to synthesize oxide nanoparticles in an aqueous environment and to transform the particles into organic reactive polymers retaining their monodispersed structure. Small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS) has been applied for the analysis of size and shape of nanoscaled SiO2 particles in different organic solvents. The mean radius of SiO2 particles of the measured samples is in the range of 8 to 40 nm. The size distribution and the corresponding volume fraction reveals that no agglomeration of SiO2 particles has taken place transferring these particles from aqueous environment into an organic reactive polymer matrix. The results of the SANS/USANS measurements are the basis for a patent application.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P381

R¨ ontgen- und Neutronenstreuung an levitierten metallischen Schmelzen Ivan Egry1 , Dirk Holland-Moritz2 1

Institut f¨ ur Raumsimulation, DLR, 51170 K¨ oln

Die atomare Struktur metallischer Schmelzen ist von grunds¨ atzlichem Interesse sowohl bez¨ uglich der makroskopischen physikalischen Eigenschaften der Fl¨ ussigkeit als auch f¨ ur die Einstellung gew¨ unschter Materialeigenschaften der bei der Erstarrung der Schmelzen gebildeten Festk¨ orper. Insbesondere erwartet man bei unterk¨ uhlten metallenen Schmelzen die Ausbildung einer Nahordnung bestehend aus ikosaedrischen Clustern. Die experimentelle Untersuchung fl¨ ussiger Metalle wird durch die hohen Temperaturen und die Reaktionsfreudigkeit der Schmelzen erschwert. Eine elegante L¨ osung sind tiegelfreie Verfahren, insbesondere die elektromagnetische Levitation. Diese Verfahren bieten zudem den Vorteil, dass sie eine tiefe Unterk¨ uhlung der Schmelze unter die Gleichgewichtsschmelztemperatur erlauben. In den letzten Jahren ist es gelungen, Levitations¨ ofen mit den Experimentiereinrichtungen an R¨ ontgen- und Neutronenquellen zu kombinieren und somit die unterk¨ uhlte Schmelze in situ durch Neutronen- und R¨ ontgenbeugung sowie durch R¨ ontgenabsorptionsspektroskopie zu untersuchen. In diesem ¨ Vortrag wird zun¨ achst ein Uberblick u ¨ber die experimentellen Techniken gegeben und anschliessend u ¨ber die erzielten Resultate berichtet.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P382

in situ Materialcharakterisierung mittels hochenergetischer Synchrotronstrahlung Helmut Ehrenberg1 , Kristian Nikolowski1 , Natascha Bramnik1 , Dmytro Trots1 , Dominic Stuermer1 , Kristin Schoenau1 , Hartmut Fuess1 , Carsten Baehtz2 , Herbert Vogel3 , Wolfgang Schmahl4 1

Materialwissenschaft, TU Darmstadt, Petersenstr. 23, 64287 Darmstadt – 2 Hamburger Synchrotronstrahlungslabor, Notkestr. 85, 22607 Hamburg – 3 Technische & Makromolekulare Chemie, TUD, Petersenstr. 20, 64287 Darmstadt – 4 Geo- und Umweltwissenschaften, LMU M¨ unchen, Theresienstr. 41, 80333 M¨ unchen

Das Durchdringungsverm¨ ogen hochenergetischer Synchrotronstrahlung erlaubt Diffraktionsexperimente an Materialien auch unter anwendungsnahen Einsatzbedingungen, die nur durch aufwendige Probenumgebungen realisierbar sind. Um diesbez¨ ugliche Fragestellungen aus den Sonderforschungsbereichen 459 Formged¨ achtnistechnik“ und 595 ” Elektrische Erm¨ udung von Funktionswerkstoffen“ sowie dem Schwerpunktprogramm ” 1091 Br¨ uckenschl¨ age zwischen realen und idealen Systemen in der Heterogenen Kata” lyse“ bearbeiten zu k¨ onnen, ist die Entwicklung hierf¨ ur optimierter Probenumgebungen notwendig. Diese Arbeiten erfolgen zur Zeit im Rahmen des Virtuellen“ HGF Insti” tuts VH-VI-102. Hierbei werden die komplement¨ aren Kompetenzen der Synchrotronstrahlungsquelle HASYLAB und der universit¨ aren Gruppen gemeinsam genutzt. Diese spezialisierten Probenumgebungen stehen auch im normalen Nutzerbetrieb am HASYLAB zur Verf¨ ugung. Anhand aktueller Ergebnisse wird erl¨ autert, wie aus strukturellen Details Wirkungs- bzw. Degradationsmechanismen abgeleitet werden und so u ¨ber ein grundlegendes Verst¨ andnis des Materialverhaltens verbesserte Werkstoffe entwickelt werden k¨ onnen. Dies gilt insbesondere beim Auftreten von unter Normalbedingungen instabilen Zwischenphasen oder besonders texturierten Zust¨ anden, die ex situ Verfahren nicht zug¨ anglich sind. Die direkte Beobachtung von Feststoffreaktionen erlaubt die Optimierung der Synthesebedingungen und Materialeigenschaften. Die Auswertung der grossen Anzahl von Diffraktogrammen, die bei Ver¨ anderung eines oder mehrerer Parameter aufgenommen werden, erfordert ebenfalls Fortschritte bei der Datenanalyse.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P383

In situ X-Ray Diffraction Study of the Growth of the Layer-Type Semiconductor WS2 Klaus Ellmer1 , Stephan Brunken1 , Rainald Mientus2 , Stefan Seeger1 1

Hahn-Meitner-Institut, Abt. Solare Energetik, Glienicker Str. 100, 14109 Berlin, Germany – 2 Opto-Transmitter-Umweltschutz-Technologie e.V., 12555 Berlin, K¨ openicker Str.325b Germany Transition metal dichalcogenides like WS2 are layer-type semiconductors with energy band gaps and absorption coefficients which make them candidates for absorber layers in thin film solar cells. In order to use the advantageous (weak) van der Waals bonding of the sulfur-terminated (001) lattice planes in these materials thin films have to be prepared with a strong (001) texture. By time-resolved energy-dispersive X-ray diffraction (EDXRD) at the beamline F3-HASYLAB, we found that the films always nucleate with the (001) planes, i.e. the van der Waals planes, parallel to the substrate surface. For high deposition rates and/or low substrate temperatures a texture crossover from the (001) to the (100) crystallite orientation occurs during the growth. High deposition rates, low substrate temperatures or low sputtering pressures lead to a significant lattice expansion of the crystallites in c direction (up to 3 %). This is most probably caused by a disturbed or turbostratic film growth induced by the energetic bombardment during film deposition. Reflected and neutralized energetic ions (Ar0 , S0 ) from the tungsten target and negative ions (S− ) accelerated in the cathode dark space constitute the main sources of the energetic bombardment leading to crystallographic defects. The energy of these particles can be tailored by (i) thermalization between target and substrate in the sputtering gas or (ii) by a reduction of the discharge or target voltage, respectively, by a high frequency excitation (13 or 27 MHz) of the plasma. Another thin film preparation route, which avoids ion-bombardment-induced defects, is the crystallization of an amorphous sulfur-rich WS3+x (0
Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P384

Eigenspannungsanalyse mittels Synchrotronstrahlung an lasergeschweißten Aluminiumblechen des Werkstoffes AA6056 ´ Vale ´ry Martins1 , Andreas Schreyer1 Torben Fischer1 , Rene 1

GKSS Forschungszentrum Geesthacht, Max Planck-Str. 1, 21502 Geesthacht

Die moderne Luftfahrtindustrie ist bestrebt in naher Zukunft auch bei tragenden Komponenten aufgrund von Kosten- und Gewichtsreduzierung Nietverbindungen durch geeignete Schweißverbindungen zu ersetzen. Neben dem Reibr¨ uhrschweißverfahren stellt besonders das Laserstrahlschweißen eine wichtige industrielle Anwendung dar. Seit den siebziger Jahren werden Laser zur Materialbehandlung in der metallverarbeitenden Industrie eingesetzt. Doch erst im letzten Jahrzehnt wurde das Laserstrahlschweißen auch f¨ ur die Luftfahrtindustrie interessant. Die Spannungen innerhalb eines Materials, insbesondere innerhalb einer Schweißnaht, lassen R¨ uckschl¨ usse auf die thermo-mechanische Vorgeschichte und Belastbarkeit des Materials zu. In diesem Zusammenhang werden mittels CO2 -Laser geschweißte Stoßn¨ ahte zwischen Aluminiumblechen auf Eigenspannungen untersucht. Die hierzu n¨ otigen Diffraktionsexperimente wurden an der neuen Beamline HARWI II (HArter R¨ ontgen WIggler) des GKSS-Forschungszentrums am HASYLAB am DESY durchgef¨ uhrt. Mit HARWI II steht den Materialwissenschaften ein Messplatz mit Synchrotronstrahlung im Energiebereich von 20 bis 250 keV und einem hohen Photonenfluss zur Verf¨ ugung. Dies erm¨ oglicht es, im Gegensatz zur Neutronenstreuung, die Probe mit einer hohen r¨ aumlichen Aufl¨ osung zu analysieren. F¨ ur die aktuellen Experimente wurde monochromatische Synchrotronstrahlung mit einer Energie von 83 keV verwendet. Die vorliegenden polykristallinen Proben bestehen aus der einphasigen Aluminiumlegierung AA6056. Die Gr¨ oße der Kristallite variiert zwischen etwa 200 µm im Basismaterial bis hin zu wenigen Mikrometern im Bereich der Schweißnaht. Die 3,2 mm starken Aluminiumbleche wurden in Transmissionsgeometrie vermessen. Ein Abstand von 7,6 m zwischen Probe und Detektor gew¨ ahrleistete eine sehr hohe Winkelaufl¨ osung f¨ ur die Bestimmung der Lage der Beugungsreflexe. Als Ergebnis ist ein sehr detaillierter Verlauf der im Material vorliegenden Spannungen zu erwarten. Es wurden sowohl die longitudinale als auch die transversale Komponente der Eigenspannung vermessen. Bei einer schrittweisen Reduzierung des Strahlquerschnitts von 6 x 0,2 mm2 auf 0,5 x 0,2 mm2 sinkt die Anzahl bestrahlter Kristallite deutlich. Ein weiterer Punkt der Untersuchung ist, wie sich dieser Umstand auf die G¨ ute der Messergebnisse auswirkt. Es zeigt sich, dass eine geringe Kornstatistik eine Modifizierung der Auswertungsverfahren erfordert.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P385

30 MeV Photons, Neutrons, Ions and Synchrotron Radiation for Reference Methods and Materials in Analytical Chemistry ¨ rner1 Wolf Go 1

Bundesanstalt f¨ ur Materialforschung und -pr¨ ufung FG I.4 Nuklearanalytik Unter den Eichen 87 12200 Berlin It is basic science, which initiates and exploits large size research devices. Nevertheless, the diffusion of applied research and development into this challenging experimental field is desirable. BAM has been using in house instrumental photon activation analysis (IPAA) for decades aiming at the certification of reference materials (CRMs) such as metals, ceramics, soils, plastics etc., especially for light elements or halogens. A unique feature of IPAA is its ability to analyze samples at kg level. This may be necessary for very inhomogeneous materials e.g. from recycling. Certification is a legal task of the institute. In the mid-nineties neutron activation (INAA) using the Hahn-Meitner-Reactor as well as in house ion bombardment broadened the basis of non-destructive chemical analysis being a valuable counterpart to methods needing chemical separation. Starting in 2002 synchrotron radiation based energy dispersive X-ray spectrometry (SR-EDXRS) was introduced at the BAMline (BESSY) for the first time into the certification scheme of a national metrological institute. In the meantime the SR-EDXRS evaluation procedure has become increasingly reliable. Moreover, the mentioned methods are operated in combination or for mutual supervision of quality. Thus, large size research devices have become efficient tools for certification in analytical chemistry and metrology. For the time to come there are ideas to further develop the spectrum of variants available: First, wave length dispersive X-ray spectrometry (SR-WDXRS) will replace the work intensive reconstitution method at high levels of element contents. Second, an irradiation facility at the neutron autoradiography site of beam tube NL 1a in the HMI is worthwhile to be installed. This low cost instrument would enable the analysis of samples at 100g-level with high representativity and would permit new type investigation in basic chemical metrology. Third, a highly efficient photon detector array with a sophisticated coincidence-anticoincidence logic would allow prompt gamma activation analysis (PGNAA) making the whole periodic system of elements accessible. This high cost device would be worth operating at accelerators, FRM II and BER II for nuclear spectrometry and instrumental chemical analysis.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P386

Untersuchung intermetallischer Phasenbildung in Nb3 Sn Supraleitern mittels Synchrotron-Tomographie und Neutronendiffraktion Astrid Haibel1 , Christian Scheuerlein2 , Rainer Schneider1 , Jens-Uwe Hoffmann1 , Robert Wimpory1 , Bella Lake1 , John Banhart1 , Alan Tennant1 1

Hahn-Meitner-Institut Berlin – 2 European Organization for Nuclear Research CERN, Geneva Tieftemperatur-Supraleiter aus Nb3 Sn werden h¨ aufig f¨ ur Anwendungen eingesetzt, bei denen Magnetfelder h¨ oher als 10 Tesla erreicht werden sollen. Allerdings ist Nb3 Sn, wie auch viele Hochtemperatur-Supraleiter, sehr spr¨ ode. Deshalb gestaltet sich die Herstellung solcher supraleitender Dr¨ ahte deutlich komplizierter als bei herk¨ ommlichen Magnetspulen. Zuerst werden die Subelemente Nb, Cu und Sn eingeh¨ ullt in eine Tantaldiffusionsbarriere und einen Kupfermantel extrudiert. Anschließend wird der Drahtquerschnitt durch Walzen und Ziehen auf einen Durchmesser kleiner 1 mm reduziert. Aus diesen Dr¨ ahten werden die Magnetspulen geformt. Erst die fertigen Spulen werden dann einer W¨ armebehandlung ausgesetzt, wobei sich aus den einzelnen Subelementen schließlich die supraleitende Phase bildet. W¨ ahrend dieser termischen Behandlung entstehen aus dem reinen Zinn und dem umgebenden Kupfer sukzessive verschiedene intermetallische Phasen (z.B. Cu6 Sn5 und Cu3 Sn) bevor sich schließlich Zinn und Niob zur supraleitenden Nb3 Sn-Phase verbinden. Abh¨ angig von der Temperatur und der Zeit der W¨ armebehandlung entstehen dabei zwei verschiedene Arten von Poren. Zum einen bilden sich sehr kleine Poren (etwa 1µm2 Querschnitt) ringf¨ ormig um die supraleitenden Filamente, zum anderen entstehen gr¨ oßere Poren direkt in den Zinn-Diffusionszentren. Diese Poren verringern die Homogenit¨ at der supraleitenden Adern und f¨ uhren zu lokalen Spannungen. Das erh¨ oht die Bruchwahrscheinlichkeit der Filamente, was zur Verringerung der kritischen Stromdichte f¨ uhren kann. Die Transformation von Nb und Sn in die supraleitende Phase Nb3 Sn und der Entstehungsmechanismus beider Porenarten wurde mittels Synchrotron-Tomographie (BESSY) untersucht. Die Tomographiedaten zeigen dabei deutlich die Porenentstehung und deren Diffusion aufgrund nicht optimierter Prozessparameter. Um den Phasenentstehungsprozess der supraleitenden Nb3 Sn-Phase in-situ zu analysieren, wurde die Neutronendiffraktion eingesetzt. Dabei wurden Diffraktogramme der Proben w¨ ahrend der gesamten W¨ armebehandlung im Temperofen aufgenommen. Die verschiedenen kristallographischen Strukturen aller Bestandteile und Phasen zeigen deutlich trennbare Peaks im Diffraktionsspektrum. Beide Messmethoden erg¨ anzen sich bei der Erforschung der Bildung supraleitender Nb3 Sn-Strukturen und erm¨ oglichen somit die Optimierung der Prozessparameter.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P387

In-situ investigation of superelasticity of NiTi under uniaxial load with hard x-rays Mahamudul Hasan1,2 , Wolfgang Schmahl1 , Klaus Hackl3 , Rainer Heinen3 , Jan Frenzel4 , Susanne Gollerthan4 , Gunther Eggeler4 , Martin Wagner4 , Jafar Khalil-Allafi5 1

Ludwig-Maximilian Universit¨ at, Department f¨ ur Geo- und Umweltwissenschaften, Sektion Kristallographie,Theresienstr. 41, 80333 M¨ unchen, Germany – 2 RuhrUniversit¨ at Bochum, Fakult¨ at f¨ ur Geowissenschaften,Universit¨ atsstr. 150, 44780 Bochum – 3 Ruhr-Universit¨ at Bochum, Institut f¨ ur Mechanik, Lehrstuhl f¨ ur Allgemeine Mechanik Universit¨ atsstr. 150, 44780 Bochum, Germany – 4 Ruhr-Universit¨ at Bochum, Institut f¨ ur Werkstoffe, Universit¨ atsstr. 150, 44801 Bochum, Germany – 5 Sahand University of Technology, Faculty of Materials Engineering, Tabriz, Iran We investigated the local textural evolution in a superelastic Ni50.7 Ti49.3 alloy under an applied uniaxial stress using high-energy synchrotron x-ray diffraction in transmission geometry. Texture information is identified from the intensity variations along Debye-Scherrer rings recorded on area detector diffraction images. The original textures of the cold rolled B2 austenite and that of the stress-induced B19’ martensite are quantitatively related to the features of the superelastic plateau in the stress-strain curve. The {110}A austenite plane normals are aligned in the rolling direction and {200}A is in the transverse direction. Due to the B2-B19’ lattice correspondence, the {110}A peak splits into four martensite peaks {020}M , {-111}M , {002}M and {111}M [1]. The stress-induced martensite is strongly textured due to twin variant selection in the stress field with {020}M aligned in the loading direction while the {002}M and {111}M maxima are at 67o and 75o from the loading direction. (B19’ unit cell settings: a = 2.87 ˚ A, b = 4.59 ˚ A, c = 4.1 ˚ A, γ = 96.2o ). A comparison between the experimental and recalculated distribution densities for the polycrystalline NiTi shows a reasonable agreement. In addition, we compare our experimental results with a micromechanical model which is based on total energy minimization [2] and we find again reasonable agreement. [1] W.W. Schmahl et al., Mat. Sci. Eng. A 378, (2004), 81. [2] K. Hackl, M. Schmidt-Baldassari, W. Zhang, Mat. Sci. Eng. A 378, (2004),503. Keywords: Texture evolution, superelasticity, stress-induced martensite, cold rolled B2 austenite, NiTi.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P388

X-ray tomography - a method for process and material optimization in micro powder injection moulding Richard Heldele1 , Michael Schulz1 1

Forschungszentrum Karlsruhe, Institut f¨ ur Materialforschung III, Postfach 3640, 76021 Karlsruhe Powder injection moulding is one of the most promising replication methods for the mass production of metal and ceramic micro parts. The material for injection moulding consists of thermoplastic binder components and inorganic filler with approximately equal volume fractions. Injection moulding of the feedstock leads to a green part that can be processed to a dense metal or ceramic micro part by debinding and sintering [1]. High shear rates in the injection moulding process can lead to separation of powder and binder causing anisotropic shrinkage during post-processing. The knowledge of introducing density gradients and defects would consequently allow the optimization of the feedstock, the moulding parameters and the validation of a simulation tool, as well. To determine the particle density and defect distribution in micro parts synchrotron radiation tomography in absorption mode was used. For the measurement, bending bars consisting of dispersed fused silica particles in a polymeric matrix were used. The experiments show that particle agglomerates and density variations in the micrometer range can be resolved. Additionally, various defects influencing the mechanical properties in the sintered state like flashes, disruptions or edge rounding in submillimeter sized green parts can be detected with this method [2]. The influence of process parameters on the flow behaviour of feedstock systems in micro dimensions will be the centre of further research. For better trade between contrast and photon transmission and resolution, different powder materials with selectable particle sizes or other tomography modes like phase contrast will be used. [1] German, R.M. et al., Princeton, N.J.: Metal Powder Industries Federation (1997). [2] Heldele, R., et al., Nucl. Instr. and Meth. B, 246(1) (2006) p. 211-216.

Fig. 1: Section of a measured micro bending bar (thickness: 55µm).

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P389

Phase distribution and texture analysis over a gamma-TAB/Ti64 friction weld Seung-Jun Jin1 , Heinz-Guenter Brokmeier1,2 , Sabine Lenser1 , Volker Ventzke3 , Mustafa Kocak3 , Jens Homeyer4 1

Institute of Materials Science and Engineering, Clausthal University of Technology, Germany – 2 GKSS Research Center, Department WFN, Geesthacht, Germany – 3 GKSS Research Center, Department WMF, Geesthacht, Germany – 4 Hasylab at DESY, Hamburg, Germany Titanium alloys are widely used for structural application, especially where high specific stiffness is required at elevated temperature. In the present investigation the friction welding process between two rods of Ti6Al4V alloy and of γ- TAB with 24.5mm φ and 80mm length are of basic interest. TiAl-based alloys have a high melting temperature, a good oxidation resistance and good strength at high temperatures. Ti6Al4V is one of the standard Ti-alloys, relatively cheap but limited in high temperature application up to 600 ◦ C. The microstructure of nominally γ-TAB can be single phase γ-TiAl, or in slightly leaner compositions, two-phased composition of tetragonal γ-TiAl and of hexagonal α2 -Ti3 Al. γ-TAB alloy had been developed at GKSS-Research Center Geesthacht for application in turbine construction was available for investigations. The Ti6Al4V alloy which is also two-phased, hexagonal α-Ti and cubic β-Ti, was available in addition. Among others the phase distribution in the weld and in the heat affected zone, describing the joining process is of great importance for the quality. High energy X-rays of 100keV were used to scan over the welding seam in order to investigate the phase composition. The measurements were carried out at the high energy beam line BW5 at HASYLAB with local resolution of 1x1mm slits and an overlapping z-scan of steps in 0.5mm. Two problems occur by this experiment: Firstly, the welded seam is smaller than 0.5mm and secondly the γ-TAB is rather coarse grained. The used Mar345 image plate detector covers a set of complete Debye-Scherrer ring able to calculate integrated sum diffraction pattern. The data analyses were carried out on MAUD (Material Analysis Using Diffraction) program doing phase analyses. Due to the sum diffraction pattern, the texture influence on quantitative phase analysis was reduced. In the basic material we have a two-phased system of hexagonal α-Ti (P 63 /mmc, about 82wt.%) and of cubic β-Ti (I m3m, about 18 wt.%) for Ti6Al4V and tetragonal γ-TiAl (P 4/mmm, about 98.2 wt.%) and hexagonal α2 -Ti3 Al (P 63 /mmc, about 1.8 wt.%) for γ-TAB. Inside the weld a small region of at least three crystallographic phases were observed. In addition crystallographic textures were measured using neutron synchrotron diffraction.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P390

The Effect of Crystal Orientation on the Oxidation Behavior of Iron Substrates Claudia Juricic1 , Haroldo Pinto2 , Thomas Wroblewski3 , Anke Pyzalla2 1

Vienna University of Tecnology, Institute of Material Science and Tecnology, Karlsplatz 13, 1040 Vienna, Austria – 2 Max-Planck Institute for Iron research, Max-Planck Str.1, 40237 D¨ usseldorf, Germany – 3 HASYLAB at DESY, Notkestr. 85, 22603 Hamburg, Germany Dense and adherent oxide layers protect metallic substrates by barring the diffusion between the corrosive environment and the reactant and, thus, by decreasing the corrosion rate. The integrity of protective oxide films is, however, strongly influenced by strain/stress generation in the oxides at high temperatures as well as at room temperature after cooling. The Pilling-Bedworth-Ratio (PBR), which is the ratio between the volume of the oxide and of the metal necessary for the oxide formation, has been often used to estimate strains in oxide layers. However, not even a qualitative connection exists between the PBR and the internal stresses in oxide layers. This is due to other factors affecting the strain state, such as cation diffusion mechanisms, lattice misfit between substrate and oxide in epitaxial layers, the formation of new oxides and gradients in the oxide composition of the layer. After oxidation and cooling the strain/stress state is also modified by additional stresses formed as a result of differences in the thermal properties of the oxide layer and metallic substrate. These cooling stresses are usually related to oxide spalling. The present work deals with the oxidation behavior of pure iron single and polycrystals. A systematic in-situ synchrotron diffraction study of the influence of crystal orientation, layer epitaxy and texture on the phase specific strain/stress state is carried out at 450 ◦ C and 650 ◦ C using the LIBAD-method. Above 570 ◦ C the third iron oxide phase, wuestite, becomes stable and grows between the substrate and magnetite. The effect of wuestite and higher oxidation rates at 650 ◦ C on layer morphology, texture and strain/stress state is also presented. Ex-situ diffraction experiments reveal the residual stresses in the epitaxial oxide layers after cooling.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P391

Texturanalyse an lasergeschweißten Al5083-Al6013-Blechen ¨nter Brokmeier1,2 , Volker Ventzke2 , Stefan Sabine Lenser1,2 , Heinz-Gu 2 2 Riekehr , Mustafa Kocak 1

Institut f¨ ur Werkstoffkunde und Werkstofftechnik, Technische Universit¨ at Clausthal, Germany – 2 GKSS-Forschungszentrum, Geesthacht, Germany Mit der Verf¨ ugbarkeit von Hochleistungslasern wird das Laserschweißen auch bei der Herstellung von Schweißverbindungen in naturharten und ausscheidungsgeh¨ arteten AlLegierungen angwendet. Dieses Verfahren erlaubt hohe Schweißgeschwindigkeiten unter Erzielung sehr schmaler N¨ ahte und verringert auf diese Weise den Verzug [1]. Die Arbeiten im Rahmen dieses Projekts tragen zum besseren Verst¨ andnis der Schweißabl¨ aufe und zur Optimierung der Prozessparameter dieses Verfahrens bei. Als Untersuchungsobjekt wurden gewalzte art¨ ahnliche Al-Bleche (AA5083H111 und AA6013T6) verwendet. Das feink¨ ornigere Al5083H111 wurde mit dem grobk¨ ornigeren Al6013T6 mittels eines 3.3 kW-Nd:YAG-Lasers in den Schweißgeschwindigkeiten 1,8 m/min und 2,6 m/min verschweißt. Zur Charakterisierung sowohl der Ausgangsbleche als auch der Schweißnaht wurden unter anderem Texturanalysen durchgef¨ uhrt. Unter der kristallographischen Textur eines polykristallinen Werkstoffes wird die Gesamtheit der Orientierungen der Kristallite eines Werkstoffs bezogen auf eine definierte Probenrichtung bezeichnet. Die Kenntnis der Textur einer Probe ist eine wichtige Voraussetzung f¨ ur die Untersuchung und Beschreibung texturmodifizierender Prozesse, wie Rekristallisation, Deformation oder Umformprozesse [2]. Außerdem hat die vorliegende kristallographische Textur einen Einfluss auf die Anisotropie der Materialeigenschaften (z.B. Festigkeit). Es wurden Untersuchungen am Vier-Kreis-Texturdiffraktometer TEX-2 beim FRG-1, GKSS-Forschungszentrum, Geesthacht bei einer Wellenl¨ ange von 1,239 ˚ A durchgef¨ uhrt. Neutronenbeugung wurde wegen der Grobk¨ ornigkeit von Al6013 verwendet. Vollst¨ andige Polfiguren der Reflexe (111), (200) und (220) wurden an insgesamt 5 Positionen der geschweißten Proben f¨ ur jede Schweißgeschwindigkeit gemessen. Die Texturinterpretation erfolgte aus der Berechnung der Orientierungsverteilungsfunktion (OVF) mittels der iterativen Reihenentwicklungsmethode. Die Legierung Al6013 besitzt als Haupttexturkomponenten eine st¨ arkere W¨ urfel-Lage und eine schw¨ achere Goss-Lage. Al5083 hat eine schwache Verformungstextur gepr¨ agt durch die typischen Texturlagen von fcc-Metallen. Bedingt durch den Schweißprozess liegen in der Schweißnaht eine moderate W¨ urfeltextur und eine schw¨ achere <100> Fasertextur in Schweißrichtung vor. Erg¨ anzende Untersuchungen wurden mittels EBSD und Synchrotronstrahlen durchgef¨ uhrt. [1] Aluminium Taschenbuch3, Aluminium-Verlag Marketing & Kommunikation GmbH, D¨ usseldorf, 16. Auflage (2003) [2] H.-J. Bunge, Z. Metallkunde B70 (1979) 411

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P392

Electronic structure of correlated systems from spectroscopic ellipsometry from FIR to VUV Dirk Menzel1 , Michael Marutzky1 , Ivan Jursic1 , Joachim Schoenes1 , Robert Troc2 1

Institut f¨ ur Physik der Kondensierten Materie, Technische Universit¨ at Braunschweig, Germany – 2 W. Trzebiatowski Institute of Low Temperature and Structure Research, Wroclaw, Poland Optical spectroscopy is a powerful tool to determine the physical properties of solids over a huge energy range from meV up to keV. Interesting excitations like phonons and from it the crystal symmetry, electronic transitions, Cooper-pair breaking energies in a superconductor, intraband transitions in a metal or core-level transitions, e.g., can be determined. In comparison to reflectivity measurements ellipsometric investigations have the advantage that they provide the full complex optical function with a high absolute acurracy without requiring a Kramers-Kronig transformation. In a metal, the reflectivity in the far-infrared is close to 100 % which makes ellipsometric measurements mandatory when the absolute values of the optical constants are needed very exactly. In the following we will describe two of the problems which we have studied with ellipsometry at two different synchrotrons. FeSi is a narrow band semiconductor with a gap of approx. 60 meV. It is intensively discussed whether FeSi is to be described in a correlated or in an itinerant picture as both experimental and theoretical results are contradictory so far. Another interesting phenomenon is the fact that the paramagnetic semiconductor FeSi turns into a ferromagnetic metal when it is doped with a few percent of Co. The gap of Fe1−x Cox Si as a feature of the electronic system is superposed by phonons as features of the lattice. So excitingly an electron-phonon coupling was observed in Raman spectra. We measured the optical conductivity as function of temperature and Co concentration at the IR-ellipsomter at ANKA in Karlsruhe. We observed four infrared phonons which remain visible even in the metallic regime. With increasing Co concentration the gap shifts to lower energies and crosses the phonons energetically. From the transverse and longitudinal frequencies of the optical phonons the Born and Szigeti effective charge are calculated. In order to study the 5f-compounds UN and UPtGe we focus on the UV range. In UN, the localization degree of the 5f-states is of special interesst. In the traditional model, the 5f-states are supposed to be relatively itinerant, in a more recent model both itinerant and localized 5f-states exist. UPtGe is a material with a complicated spin and crystal structure and anisotropic magnetic and electrical properties. We found UPtGe to be optically anisotropic from the FIR to the VUV. To make a study on the band structure of UN and UPtGe, ellipsometric measurements up to 32 eV at BESSY II in Berlin were made in order to find most of the electronic transitions. For UPtGe only very few band calculations exist, and so we experimentally determinend the electronic structure in dependence of the crystal direction.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P393

M¨ ossbauer Effect and SANS in F.C.C. FeNiC Alloys after Ultrasonic Impact Treatment Volodymyr Nadutov1 , Vasil Garamus2 , Regine Willumeit2 , Denis Semenov1 , Yevgenij Svystunov1 1

G.V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, Kyiv, Ukraine – 2 GKSS Research Centre, Geesthacht, Germany The ultrasonic surface treatment (UST) is an effective method improving mechanical properties of metal products and increasing the operation characteristics. The Invar Fe30.1 %Ni1.18 %C alloy after the UST was studied. The frequency of ultrasonic vibration of a sample was 1-3 kHz. The phase composition of the alloys was controlled by X-ray analysis. The transmission M¨ ossbauer spectroscopy and the smallangle neutron scattering (SANS) were used. The distribution of the hyperfine magnetic fields was obtained by using the Window method supplemented with procedure of the determination of the isomer shifts distribution function. The SANS experiments were performed at the SANS1 instrument at the FRG1 research reactor at GKSS Research Centre, Geesthacht, Germany. The neutron wavelength was 8.1 ˚ A. The range −1 of scattering vectors (0.005 < q < 0.25 ˚ A ) was obtained using four sample-to-detector distances (0.7 – 9.7 m). The experiments were carried out at room temperature in applied magnetic field of 2.5 T at a sample perpendicular to the neutron beam, which was polarized. From M¨ ossbauer data the UST causes the redistribution of C atoms in the f.c.c. FeNi-C alloys that results in modification of magnetic order; the UST in the considered mode does not change the phase composition of the Fe-Ni-C alloys that considerably differs from the effect of the impact low frequency loading causing the martensitic transformation. The SANS experiment did not reveal the effect UST. The SANS curve has shown −1 two slopes (Fig. 2). The analysis of large q part (q > 0.01 ˚ A ) by IFT method gives ˚ ˚ Rg = 155 A (the radius of equivalent sphere is 200 A). Dmax = 500 ˚ A. The analysis of −1 lowest q part (q < 0.01 ˚ A ) by slope I(q) q( −α) gives α=4.6 that points existence of some larger particles with fractal surface of diffuse type.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P394

PAC studies with Rare Earth probes in wide band gap semiconductors ´ de ´lec1 , Reiner Vianden1 , and ISOLDE collaboration Ronan Ne 1 2

2

Helmholtz Institut f¨ ur Strahlen- und Kernphysik der Universit¨ at Bonn, Germany – ISOLDE, CERN, Switzerland

The group III Nitrides as well as ZnO as wide band gap semiconductors have recently been subject to an enormous scientific research activity. The main efforts are devoted to the development of processes capable of producing a material quality that is adequate for advanced opto-electronic devices in the short wavelength region. However, due to their large band gap, these materials are not only suitable for blue and ultraviolet LED´s and laser diodes but also for high temperature and high power semiconductor devices. For the local doping of such planar devices, ion implantation is the most commonly used technique. Unfortunately, together with its advantages as a clean, controllable and reproducible technique, comes its main problem, which is the lattice damage caused by the ions. In order to achieve proper electrical activation of implanted dopants this damage has to be eliminated by an appropriate annealing procedure The PAC technique is excellently suited to provide information about the lattice vicinity of an implanted impurity. Therefore, in the past years the Rare Earth PAC probe 172Lu(172Yb) has been employed for the first time in wide band gap semiconductors. Results on the annealing of the implantation damage, the incorporation of the implanted ions and the temperature dependence of the observed EFG in AlN, InN and GaN will be presented and discussed.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P395

Disorder-induced diffuse scattering in mixed-cation scheelite-type compounds Carsten Paulmann1 , Thomas Malcherek1 , Rigo Peters2 , Klaus Petermann2 , Ulrich Bismayer1 1

Mineralogisch-Petrographisches Institut, Universit¨ at Hamburg, Grindelallee 48, D20146 Hamburg, Germany – 2 Institut f¨ ur Laserphysik, Universit¨ at Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany During the last decade, mixed-cation double tungstate and molybdate compounds gained special interest due to their optical properties. Especially scheelite-type compounds are favored as laser disc hosts due their uniaxial character and tunability. The average structure of these compounds is isotypical to scheelite (CaWO4 ) with space group I41 /a (Z=4) and lattice constants of a = 0.5282 and c = 1.1466 nm. Mixedcation occupation may also occur on the tetrahedrally coordinated W-position (4a) but the most interesting compounds are synthesised with mixed occupation at the strongly distorted dodecahedral Ca-positon (4b). With prominent absorption bands in the range of 940 - 980 nm, Yb3+ -doped NaGd(WO4 )2 offers optimum spectroscopic properties for diode pumping and currrent research concentrates on Yb3+ -activated tungstate crystals [1]. A statistical distribution of Na+ and Gd3+ was assumed earlier but recent X-ray powder investigations claimed evidence for weak superstructure peaks (doubling of a- and c-axis) pointing to local order at Wyckoff position 4b [2]. Single-crystal studies were performed at beamline F1 (Hasylab/DESY) using a Marresearch CCD-detector and a wavelength of 0.050 nm to reduce absorption. Bragg data collections were done with small distances (65 mm) and scan widths of 1◦ per frame whereas diffuse scattering studies were performed with thin-slicing (0.2◦ ) and a distance of 150 mm. The latter data were rescaled for the primary beam decay and corrected for background and sample-external scattering (beamstop). Very weak intensities for 00l-reflections with l=2n and hk0 with h,k=2n+1 give evidence for an at least local symmetry I-4 instead of I41 /a favored by incorporation of relatively small Yb3+ -ions which may lead to higher local ordering. Furthermore, reciprocal space reconstructions show weak diffuse intensities pointing out an incommensurate modulation with a vector parallel <430>* and a modulation wavelength of ca. 0.95a. No evidence was found for a modulation along c, in contrast to [2]. [1] P. Klopp et al., J. Appl. Phys. B 74 (2002) 185 [2] E. Zharikov et al., Inorg. Mater. 39 (2003) 151

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P396

In-situ Synchrotron X-ray Studies of Creep Damage in CuZn-alloys Anke Pyzalla1 , Augusta Isaac1 , Betina Camin2 , Andreas Kottar3 , Heinz Kaminski3 , Thomas Buslaps4 , Marco di Michiel4 , Walter Reimers3 1

Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 D¨ usseldorf, Germany – 2 Technical University Berlin, Ernst-Reuter Platz 1, 10587 Berlin, Germany – 3 Vienna University of Tecnology, Institute of Material Science and Tecnology, Karlsplatz 13, 1040 Vienna, Austria – 4 European Synchrotron Radiation Facility, ESRF, BP220, Grenoble, France The combination of tomography and diffraction experiments gives the unique opportunity to follow the development in the microstructure of materials and the subsequent changes in their texture and/or internal stress state due to external loading. Combined tomography and diffraction carried out continuously in-situ and during only one experiment significantly increases the understanding of microstructure changes during creep, where it is important to characterise the dynamics of void growth during all stages of the degradation process. We performed combined diffraction/ tomography experiments using white high energy synchrotron radiation, which aimed at determining in-situ the creep damage evolution and its correlation to texture development of CuZn-alloys. The results of the experiments reveal the development of creep voids and damage in CuZn-alloys with increasing creep time. The experiments also show an influence of loading conditions (temperature, stress) on void size, morphology, void orientation to the load axis and void growth mechanisms. We attempt to link creep damage, microstructure and microstrain development during the creep process.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P397

In-house Certification of a Reference Material by Neutrons, Ions, Synchrotron Radiation and ICP-IDMS ¨ rner1 , WolfHeinrich Riesemeier1 , Achim Berger1 , Klaus Ecker1 , Wolf Go 1 1 1 gang Pritzkow , Martin Radtke , Uwe Reinholz , Jochen Vogl1 1

BAM Unter den Eichen 87 12205 Berlin

The certification of reference materials (CRMs) is the core task of the department Analytical Chemistry; Reference Materials of the Federal Institute for Materials Research and Testing (BAM). They are used for quality assurance in chemical analytical laboratories. Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA), inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and X-ray fluorescence based on synchrotron radiation (SyXRF) have already successfully contributed to the BAM programme of certifying reference materials. With the thin film reference material Molybdenum implanted in Silicon for the first time the combination of these techniques, which are all available at the Division I.4 Nuclear Analysis , has been used to certify a reference material completely in-house. RBS was performed at the 2 MV tandem ion accelerator of BAM, INAA at the irradiation facilities (BER II reactor) of the Hahn-Meitner Institute in Berlin for neutron activation analysis. SyXRF was carried out at the Beamline of the BAM at the Berlin Synchrotron BESSY. While RBS, INAA and ICP-IDMS are accepted methods for certification, the use of SyXRF is quite new. To meet the requirements for the certification of reference materials, a new quantification method, based on Monte Carlo Simulations and pure element samples, has been established. This method is characterized by the minimization of the influence of the uncertainty of fundamental and geometric parameters and the elimination of the influence of the detector response. Drawbacks are the need to measure additional spectra and the required computing time if an iteration scheme must be applied. The measured values for the areal density of Mo are given here: ID-ICPMS INAA RBS SyXRF Mean value

3.43 3.38 3.56 3.47 3.46

(±0.04)E + 16atoms/cm2 (±0.05)E + 16atoms/cm2 (±0.03)E + 16atoms/cm2 (±0.03)E + 16atoms/cm2 (±0.07)E + 16atoms/cm2

(2 chips, 2 measurements each) (2 chips) (4 chips , 2 measurements each) (20 chips, 2 measurements each)

Additionally the property of SyXRF to measure non-destructive and fast, opened the possibility to analyse all available chips, to determine homogeneity. As a result of this measurements a number of chips with aberrant values have been excluded from further use. The work on the certification report is in progress.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P398

Structural Relaxation of Damage Structure in Creep-deformed Single Crystal Superalloy SC16 Measured by Means of X-Ray Diffraction Gerhard Schumacher1 , Nora Darowski1 , Ivo Zizak1 , Hellmuth Klin¨ ffer2 , Wolfgang Neumann3 gelho 1

Hahn-Meitner-Institut Berlin, Glienicker Straße 100, D-14109 Berlin – 2 Bundesanstalt f¨ ur Materialforschung und pr¨ ufung, Unter den Eichen 87, 12205 Berlin – 3 Institut f¨ ur Physik, Humboldt-Universit¨ at zu Berlin, Newtonstraße 15, 12489 Berlin Nickel base single crystal superalloys are widely used as structure materials in land base gas turbines as well as in air-craft turbines. Their excellent creep and fatigue properties at high temperatures are due to the special microstructure of the material consisting of cuboidal Gamma-prime-precipitates with L12 lattice structure which are coherently embedded in the Gamma fcc solid solution phase. The Gamma-Prime precipitates serve as obstacles for the dislocations produced during deformation. The stability of microstructure under creep-deformation is therefore important for the understanding of mechanical properties at high temperatures. We therefore studied the changes in microstructure in model single crystal superalloy SC16 during exposure at high, constant temperature after thermomechanical load at 1223 K to 15 % tensile creep strain in [001] direction under tensile load of 150 MPa. X-ray measurements have been performed using the 6-circle diffractometer at the KMC-2 beamline at BESSY using an X-ray energy of 8 kV. Measurements have been performed in the [100] direction, i.e., perpendicular to the axis of pre-strain. Structural relaxation of gamma prime crystal lattice at 1173K has been determined by measuring the position and linewidth of the 100 superlattice reflection. The lattice misfit between gamma and gamma prime phase has been determined by measurement of the 200 intensity profiles. Considerable changes in width and position of 100 superlattice reflection and in Gamma/Gamma-Prime lattice misfit were found. The results will be compared with measurements on the same material (15 % strain) measured in [001] direction, i.e., along the axis of creep-deformation [1]. The results are discussed in the frame of a dislocation model: Plastic deformation creates dislocations which arrange differently at differently oriented interfaces [2]. The stress induced by these dislocations partly relaxes during thermal treatment by rearrangement of dislocations. [1] G. Schumacher, N. Darowski, I. Zizak, H. Klingelh¨ offer, and W. Neumann, THERMEC2006, 5th int. conf. on processing and manufacturing of advanced materials, July 4-8 (2006) Vancouver, Canada, Materials Science Forum, in press. [2] W. Chen, N. Darowski, I. Zizak, G. Schumacher, H. Klingelh¨ offer and W. Neumann, Nucl. Instr. Meth. B 246 (2006) 201. Work supported by DFG Schu 1254/3-4 and Ne646/5-3

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P399

Mikrostruktur und Textur bei Scherverformungsversuchen an H¨ amatiterzen Heinrich Siemes1 , Birgit Klingenberg1 , Erik Rybacki2 , Michael Naumann2 , Jens Walter3 , Ekkehard Jansen3 , Karsten Kunze4 1

Institut f¨ ur Mineralogie und Lagerst¨ attenlehre, RWTH Aachen, D-52056 Aachen – Geoforschungszentrum Potsdam, Deformation und Rheologie, D-14473 Potsdam – 3 Mineralogisches Institut, Universit¨ at Bonn, Forschungszentrum J¨ ulich, D-52425 J¨ ulich – 4 Geologisches Institut, ETH Z¨ urich, CH-8092 Z¨ urich 2

Die Beziehungen zwischen der Mikrostruktur und der kristallografischen Vorzugsorientierung (Textur) von geb¨ anderten H¨ amatiterzen in Brasilien wurden in vielen Veroffentlichungen behandelt, z.B. [1,2]. Die elliptischen c-Achsen-Maxima liegen um den ¨ Pol der Foliation. Die Pole der Prismenfl¨ achen liegen auf Großkreisen und die Maxima auf diesen fallen mit der Lineation zusammen. Auf Grund von Stauchversuchen [3] und der bekannten Gleitsysteme [4] kann aber nur Scherverformung mit basalem Gleiten diese Textur hervorbringen. Bis jetzt wurden 6 H¨ amatitproben (Durchmesser 14 mm, L¨ ange 10 mm) mit einer 0,5 mm dicken Ag–Pd–Schutzh¨ ulle versehen, um die Bildung von Magnetit zu minimieren, und in ein Jacket aus Eisen oder aus Kupfer eingebracht, das die Probe vom Druckmedium Argongas trennt. Bei Temperaturen von 1000◦ C bis 800◦ C wurde in einer Torsionsapparatur [5] bei 400 MPa allseitigem Druck mit Torsionsraten von 6, 5 × 10−5 /s und 2, 5 × 10−5 /s in 30– und 70–Stunden Versuchen eine Scherverformung γmax = 4, 4 erreicht. Der H¨ amatit ist bei allen Temperaturen zu einem gleichf¨ ormigen polygonalen Korngef¨ uge rekristallisiert, das sich auch bei nat¨ urlich verformten Erzen findet. Die Korngr¨ oßen, die mit steigender Temperatur zunehmen, weisen dabei keine Unterschiede u ¨ber die Probenquerschnitte auf, obwohl die finite Scherverformung von Null im Zentrum der Probe bis zum maximalen Wert an der Peripherie variiert. Neutronentexturmessungen [6] im Probenbereich mit der st¨ arksten Verformung und EBSD-Messungen [7] ergaben f¨ ur die Polfigur des 0003Reflexes ein zentrales, elliptisches Maximum nahe dem Pol der Scherebene. Die H¨ ohe des 0003-Maximums nimmt dabei von 8,1 bis 11,2 mit steigender Temperatur zu. Der Texturindex bei der 1000◦ C-Probe steigt im Probenquerschnitt von 1,1 im Zentrum auf 3,8 an der Peripherie. Auf dem peripheren G¨ urtel der 11¯ 20-Polfigur befindet sich ein Maximum, das die Orientierung der Scherrichtung angibt. Die 10¯ 14-Polfigur, die zwei bananenf¨ ormige Maxima [8] unterschiedlicher Dichte und Ausdehnung aufweist, l¨ aßt auf den Schersinn schließen. Diese Polfiguren stimmen weitgehend mit Polfiguren nat¨ urlich verformter H¨ amatiterze u ¨berein. [1] Rosi`ere, C.A. et al. (2001) J. Struct. Geol. 23, 1429-1440. [2] Bascou, J., et al. (2002) Earth Planetary Sci. Let. 198, 77-92. [3] Siemes, H. et al. (2003) J. Struct. Geol. 25, 1471-1391. [4] Siemes, H. et al. (2006) Ore Geology Reviews, accepted. [5] Paterson, M.S., Olgaard, D.L.(2000) J. Struct. Geol. 22, 1341-1358. [6] Jansen, E. et al. (2000) J. Struct. Geol. 22, 1559-1564. [7] Kunze, K. et al. (1993) Textures Microstructures 20, 41-54. [8] Quade, H. (1988) Textures Microstructures, 8-9, 719-736

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P400

Microstructure and Residual Stress Formation in Oxide Layers Grown on High Niobium Containing γ-TiAl Based Alloy Pedro Silva1 , Haroldo Pinto1 , Alexander Kostka1 , Harald Chladil2 , Helmut Clemens2 , Anke Pyzalla1 1

Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 D¨ usseldorf, Germany – 2 Montanuniversit¨ at Leoben, Department Metallkunde und Werkstoffpr¨ ufung, 8700 Leoben, Austria Due to their low density, high mechanical strength and creep resistance at elevated temperatures titanium aluminides are considered as promising structural materials for high temperature applications in the aerospace and automotive sectors. The 3rd Generation of TiAl alloys (so called TNB alloys) are characterized by a high Nb-content. In particular, these high Nb containing alloys with the baseline composition Ti-(4245)Al-(5-10)Nb+X (at%) have attracted attention due to their combination of high creep strength, good ductility at room temperature and excellent oxidation resistance. The ternary Ti-Al-Nb system is known to enable the formation of a variety of mixed oxide scales depending on the chemical alloy composition and oxidation temperature. However, the phase composition is a decisive criterion for the shielding efficiency of these oxide layers, since a dense single protective Al2 O3 layer may deteriorate to a porous, less protective mixed oxide scale. Therefore, the knowledge about the mechanisms of oxide formation in these new alloys is essential for the determination of conditions necessary for the development of dense oxide layers with both mechanical integrity and diffusion barrier properties. The aim of this study is a characterization of oxide layers formed on γ-TiAl alloys with high Nb-contents after oxidation at 800 ◦ C. The microstructure of the oxide layers, the interface between the substrate and oxide layer as well as layer integrity are studied by synchrotron x-rays and electron microscopy. The results reveal the spatial arrangement of the different oxides within the nanostructured oxide layer. The oxide scales are quantitatively analyzed by Rietveld refinements. The phase specific residual stress state is evaluated using synchrotron X-ray diffraction at low incidence angles.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P401

Investigation of texture in deformed natural quartz vein from the Torridon area of NW Scotland using the FRM-II Stress-Spec neutron diffractometer H. Sitepu1 , U. Garbe2 , H.-G. Brokmeier3 , R.D. Law1 1

Department of Geosciences, Virginia Tech, Blacksburg 24061, USA – 2 GKSS-Research center, Max-Planck-Str., D-21502 Geestahacht, Germany – 3 Technical University Clausthal, Agricolastr. 2 Clausthal-Zellerfeld, Germany

Originally, X-ray texture goniometry and electron backscattered diffraction (EBSD) were used to measure pole figures of deformed quartz vein from Torridon area of NW Scotland and the Cambrian quartz mylonite; Stack of Glencoul, Assynt area of Moine thrust zone, NW Scotland. The X-ray results of Torridon sample showed that individual positions on the c-axis fabric skeleton are related by a common direction which is coincidence with this dominant a-axis point maximum. Thus, the crystallographic fabrics strongly support the bulk simple shear kinematic framework indicated by shear zone geometry. The crystal lattice preferred orientation results of Stack of Glencoul sample obtained from the EBSD are consistent with co-axial strain paths. The EBSD derived LPO was then used to predict elastic parameters for Cambrian quartz mylonite, from which 3 D seismic properties were derived. In the present study, we use the STRESS-SPEC material-science neutron diffractometer at FRM-II to measure simultaneously pole-figures of (110), (021), (111), (021), (112), (211) and (113) of the same Torridon and Stack of Glencoul samples. We will describe the bulk texture obtained from neutron diffraction, which is a very useful tool to study the bulk texture of large sample volume non-destructively because neutrons have small absorption coefficients for most materials.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P402

Characterization of friction stir welded aluminium matrix joints using synchrotron radiation Alicja Skrzypinska1 , Walter Reimers1 1

TU Berlin, Sekr. BH18, Institut f¨ ur Werkstoffwissenschaften und -technologien, Metallische Werkstoffe, Ernst-Reuter-Platz 1, 10587 Berlin

Friction Stir Welding is a solid state joining process, in which a cylindrical shouldered tool with a profiled pin is inserted into the joint line between two pieces of material. Frictional heat is created between the wear resistant pin and two work pieces, which are butted together and clamped onto a backing bar. The heat causes the materials to soften, without reaching melting point, and allows the rotating pin to traverse along the joint.

Fig. 1: 2D stress distribution image for aluminium phase in dissimilar joint of Al-MMC

In the study here presented the following friction stir weldings were investigated: Al reinforced by SiC (similar joints) and Al-SiC welded with Al (dissimilar joints). These materials are difficult to weld because of the irregular distribution of silicon carbide particles in the weld. These heterogeneity may also cause complicated residual stress distributions in cross-sections of the weld, so the study aims at the determination of the particle distributions and stress fields in these weldings.

In addition to conventional synchrotron x-ray diffraction measurements using point collimators, measurements with the capillary detector set up were performed at the diffractometer G3, HASYLAB [1]. Here with an area of 5mm x14mm can be investigated at one time with resolution of 13µm. As result a 2D image (Fig.1) with the near-surface stress distribution is obtained. Simultaneously the 2D-image shows the particle distribution. The differences in the particle distribution in dissimilar weldings with MMC on advancing and retreating side are presented and explained. Maximum tensile stresses of 220 MPa are formed in the weld zone. [1] Th. Wroblewski et. al., Nucl. Inst. Met. Phys Res., A 428 (1999) 570 The authors would like to acknowledge S. Dallkilic and G. Biallas of Deutsches Zentrum f¨ ur Luft- und Raumfahrt e.V. (DLR) in der Helmholtzgemeinschaft for sample preperation.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P403

Eigenspannungen in Laser-geschweißten Verbindungen von AA6056 Aluminium-Blechen P. Staron1 , W.V. Vaidya1 , M. Kocak1 , J. Hackius2 1

GKSS Forschungszentrum, Max Planck-Str. 1, D-21502 Geesthacht – 2 AIRBUS Germany, D-28183 Bremen Aluminiumlegierungen werden f¨ ur Leichtbaustrukturen in der Transportindustrie verwendet. Laserstrahl-Schweißen ist eine Verbindungstechnik, die besonders f¨ ur Aluminium geeignet ist, da der geringe lokale W¨ armeeintrag zu geringem Verzug f¨ uhrt. Dar¨ uber hinaus k¨ onnen hochfeste Verbindungen mit großen Prozeßgeschwindigkeiten hergestellt werden. Dennoch k¨ onnen in der Schweißzone lasergeschweißter Al-Bleche signifikante Eigenspannungen vorhanden sein. Ihre Gr¨ oße kann von der Legierungszusammensetzung und dem Legierungszustand abh¨ angen, sowie von den Schweißparametern, der Blechdicke oder der Einspannung w¨ ahrend des Schweißens. Eigenspannungen k¨ onnen einen sch¨ adlichen Einfluß auf das Einsatzverhalten von Schweißverbindungen im Hinblick auf Erm¨ udung und Korrosionseigenschaften haben. Daher werden h¨ aufig Spannungsarm-Gl¨ uhungen durchgef¨ uhrt um die schweißbedingten Eigenspannungen zu reduzieren. In dieser Arbeit werden der Einfluß des Materialzustandes (T4, T6) und die Effektivit¨ at verschiedener W¨ armebehandlungen zur Spannungsreduzierung (T6, T78) in 3.2 mm dicken AA6056 Al-Blechen mittels Neutronenbeugung und Beugung hochenergetischer R¨ ontgenstrahlung untersucht. Die Ergebnisse zeigen, daß Zugeigenspannungen in L¨ angsrichtung im geschweißten T6-Material wesentlich gr¨ oßer sind (180 MPa) als im geschweißten T4-Material (100 MPa). Die W¨ armebehandlungen T6 und T78 zur Spannungsreduzierung f¨ ur das geschweißte T4-Material f¨ uhren nicht zu einem nennenswerten Spannungsabbau.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P404

Study of the Ba N-edges in Ba8 Si46 with non-resonant inelastic x-ray scattering Henning Sternemann1 , Christian Sternemann1 , John S. Tse2 , Serge ¨ rgy Vanko ´ 4 , Andreas Schacht1 , Juha Aleksi Soininen5 , Desgreniers3 , Gyo Metin Tolan1 1

Dept. Phys. / DELTA, University of Dortmund, D-44221 Dortmund – 2 Dept. Phys. Engn. Phys., University of Saskatchewan, Canada – 3 Dept. Phys., University of Ottawa, Canada – 4 European Synchrotron Radiation Facility, Grenoble, France – 5 Div. X-ray Physics, Dept. Physical Sciences, University of Helsinki, Finland

Silicon clathrates are inclusion compounds with Silicon cagelike strutures in which guest atoms, e.g. Sodium, Potassium and Barium, can be enclathrated.Ba8 Si46 attracted a lot of interest in the recent years because it was found to be a superconductor with a transition temperature of 8.0 K [1]. This compound shows a strong charge transfer from Ba to the Si cages which is especially reflected in the empty d- and f -bands. The unoccupied partial density of states and thus the corresponding charge transfer of Ba8 Si46 can be studied utilizing non-resonant inelastic x-ray scattering (NRIXS). By making use of the momentum transfer dependence of the scattering cross section of the Ba NIV,V and NIII edges of the clathrate compound excitations to the empty states with different symmetries can be studied. For low momentum transfer q dipole transitions dominate the spectra whereas at higher momentum transfers multipole transitions can be observed. Therefore, by changing the magnitude of the momentum transfer different excitation channels can be probed. The Ba NIV,V and NIII absorption edges of Ba8 Si46 were measured within (low q) and far beyond (high q) the dipole limit. These measurements were carried out at the inelastic x-ray scattering beamline ID16 of the European Synchrotron Radiation Facility. The NRIXS spectra for low q show a well pronounced feature between 100 eV and 140 eV which can be related to a giant resonance (transitions from 4d to unoccupied f states) which is a well known phenomenon e.g. for atomic Ba [2]. At higher momentum transfer a strong structure appears between 90 (180) eV and 100 (190) eV for the Ba NIV,V (NIII ) edges. This structure can be assigned to the increasing contribution of non-dipole transitions to empty d and s (p and f ) states in case of the NIV,V (NIII ) spectra. These structures will be discussed with respect to the strong hybridization of Ba guests and Si host lattice. Moreover, the feasibility of NRIXS experiments at high pressure using a diamond anvil cell along with a Be gasket to study the Ba NIV,V (NIII ) edges beyond the dipole limit will be emphasized. Such experiments give rise to the study of charge transfer because in clathrate structures like Ba8 Si46 the charge transfer from the intercalated atom to the surrounding Si atoms and therewith the degree of ionization depends strongly on the cage size. [1] S. Yamanaka et al., Inorg. Chem. 39 (2000) 56. [2] J. P. Connerade et al., Phys. Rev. Lett. 48 (1982) 131.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P405

Structural characterization of LaMn1−x Pdx O3 -Perovskites by in-situ Synchrotron powder diffraction-experiments ¨rmer1 , C. Baehtz2 , L. Giebeler1 , H. Fuess1 D. Stu 1

Institute of Materials Science, Darmstadt University of Technology, D-64287 Darmstadt – 2 HASYLAB Hamburg, Notkestr. 85, D-22607 Hamburg, Germany Perovskite-type oxides have interesting catalytic properties e.g. for the total oxidation of hydrocarbons [1]. These catalytic properties can be improved, by replacing parts of the manganese by noble metals like palladium. In the past few years LaFeO3 perovskites doped with palladium were found to be a good alternative to Al2 O3 -supported Pt catalysts for automotive exhaust applications [2]. A furnace working in capillary geometry designated for diffraction experiments under controlled atmosphere was used to examine the formation of the Perovskite from the precursor, which was prepared by the Pechini method. The calcined perovskite was later once treated with oxygen and afterwards with hydrogen. Hereby a phase transformation is observed, which is also stable under oxygen atmosphere. Samples with different palladium content were investigated The aim of this experiment was to determine the structural changes during the catalyst preparation and catalysis. This work was financially supported by the virtual institute VH-VI-102, Development of in-situ characterization techniques for polycrystalline materials using high energy synchrotron radiation, of the Helmholtz Gemeinschaft. [1] M. A. Pe˜ na et al., Chem. Rev., 101, (2001) 1981-2017 [2] H. Tanaka et al., Top. Catal., 30/31, (2004) 389-396

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P406

Internal drift effects explaining anomalous diffusion profiles of Ag in CdTe ¨ rg Kronenberg1 , Herbert Wolf1 , Manfred Deicher1 , Frank Wagner1 , Jo 1 Karl Johnston , Thomas Wichert1 , ISOLDE Collaboration2 1 2

Technische Physik, Universit¨ at des Saarlandes, D-66041 Saarbr¨ ucken, Germany – CERN, CH-1211 Geneva 23, Switzerland

Anomalous concentration profiles have been observed upon diffusion of Ag in CdTe [1]. The diffusion experiments were performed with the radiotracers 111 Ag implanted at ISOLDE into one side of a typically 800 µm thick CdTe crystal at a depth of about 30 nm. The resulting diffusion profiles of Ag extending over the whole crystal critically depend on the respective external conditions during diffusion and on the sample pre-treatments (see figure): After diffusing the Ag dopant into the CdTe crystal at 800 K (60 min) under Cd pressure or vacuum the symmetrical concentration profiles show depletion layers of 100 or 300 µm below the surfaces of the crystal, whereby the depletion layers are much stronger pronounced in case of diffusion under Cd pressure. In contrast, the Ag concentration is increased at the surface and decreased in the interior of the crystal if the diffusion is performed under Te pressure. These anomalous Ag profiles are well described within a model based on an interaction of the Ag dopant atoms with the intrinsic defects of the Cd sublattice of CdTe taking into account the charge states of all participating defects. It turns out that the diffusion of Ag is significantly affected by an internal drift due to the electric field generated by the distribution of the charged defects. In addition, the influence of Cu, Au, and In on the diffusion of Ag in CdTe was investigated. Thus, evaporating a thin Cu layer on the 111 Ag implanted side of a CdTe single crystal and subsequent annealing at 550 K for 30 min effects that most of the Ag atoms were detected in a thin layer of only a few µm at the back of a 500 µm thick crystal. This work has been supported by the Bundesministerium f¨ ur Bildung und Forschung (BMBF) under Contract Nos. 05 KK1TSB/5 and CZE 03/002. [1] H. Wolf, F. Wagner, Th. Wichert, and ISOLDE Collaboration, Phys. Rev. Lett. 94 (2005) 125901.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P407

Micro focus X-ray diffraction on ion beam modified nuclear fuel Nico Wieschalla1,2 , Wroblewski3

Rainer Jungwirth1,2 ,

Winfried Petry1 ,

Thomas

1

Technische Universit¨ at M¨ unchen, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Lichtenbergstr. 1, 85747 Garching – 2 Technische Universit¨ at M¨ unchen, Physik Department, Institute E21, James-Franck-Strasse, 85748 Garching – 3 HASYLAB at DESY, Notkestr. 85, 22603 Hamburg

Irradiation damages caused by fission fragments in nuclear fuels can be simulated by bombardment with heavy ions. At conditions close to in-pile irradiation (comparable temperature and fission fragment density), it leads to a diffusion process in U-Mo/Al dispersion fuels between the spherical U-Mo grains and the surrounding Al-matrix like it takes places during in-pile irradiation [1]. The usage of high-density U-Mo/Al dispersion fuel for high burn up in research and test reactors seems to be limited by this unfavourable interdiffusion layer (IDL) [2,3]. Therefore it is of main interest to examine the formation of different phases in this IDL by micro focus diffraction at intense synchrotron sources. Detailed X-ray analysis of U1−x Mox (x=0.06, 0.1) fuel dissolved in an Al-Matrix will be presented. [1] N. Wieschalla et al, Proceedings of the 27th International Meeting on RERTR, Boston (USA) (2005) [2] M. K. Meyer et al, Journal of Nuclear Materials 304, 221 (2002). [3] F. Huet et al, Proceedings of the 25th International Meeting on RERTR, Chicago (USA) (2003).

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P408

Assessment of residual stresses in cracked Fracture Mechanics CT specimens. Robert Charles Wimpory1 , Kamran Nikbin2 1

Hahn-Meitner-Institut, Glienicker Straße 100, Berlin – 2 Imperial College London, SW7 2AZ, UK A major challenge facing life assessment of components operating at high temperatures is to understand how residual stresses and prior straining contribute to creep damage and crack growth failure. The efficiency of conventional steam and gas turbine power plants can be significantly improved by increasing the operating temperature, leading to reduced fuel consumption and lower levels of harmful emissions. With this trend towards higher operating temperatures and the competing need to extend the life of existing power plants, more accurate and reliable measurements and modelling of residual stresses are needed to improve predictions of component lifetimes. Failures in components are most likely to occur at or near weldments by fast fracture, creep or fatigue cracking. These regions can exhibit microstructural inhomogeneity as well as the presence of micro-cracks and residual stresses. Cracking normally occurs in the heat affected zone (HAZ) of these welds and cracks can grow significantly under service loads. Pilot creep crack growth tests on a type 316H stainless steel weldment have recently been carried out using compact tension (CT) specimen designs with specimens machined directly from a non-stress relieved weldment. The pilot creep crack growth tests showed anomalously short lives, with the crack path sometimes unexpectedly deviating away from the weld HAZ line at the centre of the specimen. It is believed that this anomalous behaviour can be related to the presence of residual stresses resulting from the welding process, which may significantly influence the creep crack growth rate behaviour in the CT specimen. In this paper a comparison of the residual strain and stresses and their subsequent re-distribution in Compact Tension specimens are presented. Results of Neutron Measurements from a number of EU neutron sources such as HMI, TUM/FRM II, ILL and ISIS were made following a Round Robin exercise in the collaborative VAMAS TWA 31 Creep/Fatigue Crack Growth of Welded Components programme. The data will contribute to quantifying the repeatability of measurements from different sources as well as identifying the role of residual stress in weldments and understanding their effects on creep and creep-fatigue crack growth behaviour in components. It is hoped that the final results and analyses will lead to recommendations for a code of practice for measuring crack growth in welded specimens.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P409

Synthesis, Crystal Structures, Metal Atom Distribution and Magnetic Properties of the monoclinic Compounds Cr5−x Tix Se8 (x ≈ 2, 3, 4) Joseph Wontcheu1 , Winfried Kockelmann2 , Wolfgang Bensch1 1

Institute of Inorganic Chemistry, University of Kiel, Olshausenstr. 40-60, 24098 Kiel, Germany – 2 Rutherford Appleton Laboratory, ISIS, Chilton, OX11 0QX, UK The non-stoichiometric chromium titanium selenides Cr5−x Tix Se8 (x ≈ 2, 3, 4) were prepared applying high-temperature solid-state reactions. The crystal structures have been refined with X-ray and neutron powder diffraction data with the Rietveld method. The samples crystallize in the non-conventional monoclinic space group F 2/m with four formula units per unit cell. The structures of all phases are related to the NiAstype structure with ordered metal vacancies in every second metal atom layer. The cation distributions on four inequivalent crystallographic sites were determined. The results showed a considerable disorder but they nevertheless revealed the site preference of Ti atoms for the 8h and 8i sites for the three investigated compounds. Based on the results these compounds are formulated as (Cr2.21 Ti1.79 )[Cr0.91 Ti0.03 ∆3.06 ]Se8 for Cr3.11 Ti1.82 Se8 , (Cr1.36 Ti2.64 )[Cr0.73 Ti0.19 ∆3.08 ]Se8 for Cr2.09 Ti2.83 Se8 , and (Cr0.22 Ti3.78 )[Cr0.63 Ti0.4 ∆2.89 ]Se8 for Cr0.85 Ti4.26 Se8 (note: () denotes atoms in the fully occupied layers, [] atoms in the partially layers and ∆ denotes the vacancies). The MSe6 octahedra share edges within layers and faces between layers. Consequently, long M-M separations occur within the layers and remarkably short M-M contacts result between M atoms in octahedra sharing faces. The irreversibility in the field-cooled/zero-field-cooled magnetization at 10 kOe depends strongly on the Ti concentration x. In all cases, χ(T) obeys the CurieWeiss law in the high-temperature range. The effective magnetic moments are 4.03, 3.91 and 3.90 µB per Cr atom for Cr3 Ti2 Se8 , Cr2 Ti3 Se8 and CrTi4 Se8 , respectively, slightly larger than the expected value 3.87 µB for spin-only Cr3+ . This is somewhat unusual for Cr3+ , but was frequently observed for chromium chalcogenides [1, 2]. [1] W. Bensch et al., J. Solid State Chem. 145 (1999) 235. [2] W. Bensch et al., J. Solid State Chem. 158 (2001) 198.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P410

Halogen Ion Implantation and Halogen Treatment as a Tool for improving the Oxidation Resistance of TiAl-Alloys at High Temperatures Hans-Eberhard Zschau1 , Bethge2

¨tze1 , Michael Schu

Horst Baumann2 ,

Klaus

1

DECHEMA e.V., Karl Winnacker Institut, Theodor-Heuss-Allee 25,D-60486 Frankfurt am Main, Germany – 2 Institut f¨ ur Kernphysik der Johann Wolfgang GoetheUniversit¨ at Frankfurt am Main, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany γ-TiAl-alloys are of increasing interest in gas turbine and automotive industries because of their good mechanical properties and of their about 50 % lower specific weight compared to the presently used Ni-based superalloys. However, due to the poor hightemperature oxidation resistance of TiAl above 750 ◦ C, the lifetime of components is limited. Indeed, under such conditions, a non protective mixture of TiO2 and Al2 O3 forms during oxidation. The formation of such a protective scale can be stimulated by the addition of small amounts of halogens, especially of fluorine. In this study the fluorine is applied in two ways: treatment with diluted HF and ion implantation. As first method the samples were treated with different aqueous HF solutions between 0.01 and 1.1 m.-% HF. The HF was applied as a drop which covers one side of the samples. After drying the specimens were oxidized at 10h/900 ◦ C/air. After treatment with 0.06 and 0.11 m.-% HF a dense and 0.8 µm thick protective alumina scale was formed at the surface. Non destructive Ion Beam Analysis was applied to determine the fluorine profile within the first 1.3 µm (PIGE) and to measure the elemental profiles of the main elements Ti, Al and O in the oxide layer down to the sub-surface region (RBS). From this it was revealed, that the F-maximum is located at the metal/oxide interface. The fluorine effect is connected with fluorine amounts of about 20 - 22 w.-% at the surface before oxidation. After the oxidation a maximum of the fluorine concentration was found within the metal/oxide interface region with values up to 1.1 w.-%. As a second method fluorine ion implantation was chosen. At 20 keV implantation energy (projected range of 34 nm) fluences between 1015 and 5x1017 F-ions cm−2 were implanted. After isothermal oxidation (12 h/900 ◦ C/air) a thin alumina scale was formed for fluences of 5x1016 and 1017 F-ions cm−2 . At longer oxidation times a fluence of 1017 gave the best results. The measured profiles of F, Ti, Al and O are similar to those obtained after HF treatment. The results proof the proposed mechanism of the fluorine effect. After finding the optimal parameters for both kinds of fluorine application the long time stability was studied until 1000h/900 ◦ C/air. In both cases a protective alumina scale was established. Further investigations concerned with the fluorine loss during heating. The technical exploitation of the fluorine effect is pointed out.

Materialien/Werkstoffe

Poster: Do., 13:00–15:30

D-P411

In-situ Charakterisierung der Phasen- und Texturentwicklung magnetrongesputterter d¨ unner Schichten mittels Synchrotronstrahlung Johannes von Borany1 , Norbert Schell1 , Valentina Cantelli1 , Manfred Beckers2 1

Institut f¨ ur Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, Postfach 51 01 19, 01314 Dresden, Germany – 2 Department of Physics, Chemistry and Biology, Link¨ oping University, 581 82 Link¨ oping, Sweden

Ein Schwerpunkt der Experimente am Materialforschungs-Meßplatz der ROssendorf BeamLine (ROBL) [1] bei der ESRF Grenoble sind in-situ (teilweise real-time) Untersuchungen zur Phasen- und Texturentwicklung von d¨ unnen Schichten w¨ ahrend der Abscheidung mittels Magnetronsputtern oder bei nachfolgenden Prozessschritten (Temperung, Ionenbestrahlung). Die eingesetzte Prozeßkammer mit zwei Magnetrons und einer separaten Ionenquelle erlaubt unter Neutral- oder Reaktivgas die Abscheidung von Schichten komplexer Zusammensetzung bei unterschiedlichen Temperaturen sowie deren Modifizierung durch die Ionenbestrahlung. Die r¨ ontgentechnische Charakterisierung konzentriert sich auf Streumethoden (Diffraktion, Reflektometrie, anomale Streuung etc.) und erlaubt gleichermaßen systematische Untersuchungen zum Einfluß von Abscheide- oder Prozeßparametern auf die Schichteigenschaften wie auch die Aufkl¨ arung der zugrunde liegenden physikalischen Ursachen. Der Beitrag veranschaulicht an einigen ausgew¨ ahlten Beispielen die Leistungsf¨ ahigkeit derartiger Untersuchungen. Dazu z¨ ahlen die Wachstumskinetik von epitaktischen Ti2 AlN-Hartstoffschichten (MAX-Phasen) auf MgO-Substraten, die Untersuchung der A1 −→ L10 Phasentransformation bei d¨ unnen magnetischen FePt-Schichten durch thermische Prozesse wie auch Ionenbestrahlung oder der Zusammenhang zwischen den strukturellen Eigenschaften und der Leitf¨ ahigkeit in d¨ unnen transparenten Indium-Zinn-Oxid (ITO)-Schichten. [1] http://www.fz-rossendorf.de/pls/rois/Cms?pNid=247

Teilchen und Kerne

Poster: Do., 13:00–15:30

D-P412

Fundamental physics with ultra cold neutrons UCN ¨ller1 , S. I. Altarev1 , A. Frei1 , E. Gutsmiedl1 , F.J. Hartmann1 , A.R. Mu 1 1 1 1 1 Paul , R. Picker , W. Schmid , D. Tortorella , O. Zimmer 1

Physik-Department E18, Technische Universit¨ at M¨ unchen, James-Franck-Strasse, 85748 Garching Ultracold Neutrons (UCN), i.e. neutrons with kinetic energies of less than 300 neV (corresponding to velocities of less than 7 m/s) can be created by down-scattering of cold neutrons in a solid-deuterium moderator. They may be stored in material or magnetic bottles and studied for times approaching the eta-decay lifetime of the neutron aun . From measurements of aun and eta-decay decay correlation coefficients, one may extract parameters that completely characterize the weak force and can search for deviations from the Standard Model and the unitarity of the quark mixing matrix. Measurement of the lifetime aun also provides information on the abundances of the light elements produced during the Big Bang. A general description of the experimental set-up for the miniD2 UCN source and the planned lifetime experiment PENELOPE, both for the FRM2 research reactor at Garching near Munich will be presented.

Teilchen und Kerne

Poster: Do., 13:00–15:30

D-P413

Search for scission neutrons using specific angular correlation in 235U fission induced by slow polarized neutrons Gevorg Danilyan1 , Peter Granz2 , Viacheslav Krakhotin1 , Valery Pavlov1 , Pavel Shatalov1 , Margarita Russina2 , Thomas Wilpert2 , Ernst Brakhman1 1

ITEP, B. Cheremushkinskaya 25, Moscow, 117218, Russia – Glienicker str. 100, D-14, 109, Berlin, Germany

2

BENSC - HMI,

The experimental data concerning scission (or pre-scission) neutrons are very contradictory - the relative part of these neutrons in the prompt fission neutrons varies from 1 % to 35 % due to arbitrary assumptions made in different analysis. To solve this problem we have used new alternative method to search for the scission neutrons. We have found the left-right asymmetry of prompt-fission-neutron (PFN) emission caused by sp-wave interference in entrance channel of the reaction and the P -odd asymmetry of the PFN emission caused by parity nonconservation at exit channel of the fission process. Both effects cannot reside in PFN evaporated by excited fission fragments. The scission (or pre-scission) neutrons are responsible for these effects.

Teilchen und Kerne

Poster: Do., 13:00–15:30

D-P414

Status of the neutron radiative decay research Rashid Khafizov1 1

Moscow 123182, Kurchatov sq., b. 1, RRC “Kurchatov Institute”

The report is dedicated to the investigation of the neutron radiative decay. The theoretical spectrum of radiative gamma quanta, calculated within the framework of the standard electroweak interaction model, is discussed. On the basis of a comparison drawn between neutron and muon decays, it is demonstrated that the study of radiative branches of elementary particle decay occupies a central place in the fundamental problem of searching for deviations from the standard electroweak model. Particular attention is paid to analyzing the results of the experiments conducted at ILL in 2002 [1] and at the second and third cycles at the FRMII reactor of the Technical University of Munchen [2] in 2005. [1] M. Beck et al, JETP Letters, v. 76(6), 2002, p. 332 [2] R.U. Khafizov et al. JETP Letters, v. 83(1), 2006, p. 5

Teilchen und Kerne

Poster: Do., 13:00–15:30

D-P415

Untersuchungen zum Nachweis von superschweren Elementen (SHE) mit hochenergetischer Synchrotron-Strahlung und R¨ ontgenfluoreszenz. Christian Schnier1 , Joachim Feuerborn1 , Klaus-Dieter Liss1 , Bong-Jun Lee1 1

GKSS-Forschungszentrum

Berechnungen der Bindungsenergien f¨ ur die K-Elektronen der SHE und die dazu geh¨ orenden charakteristischen R¨ ontgenlinien sind schon vor langer Zeit durchgef¨ uhrt worden. [1]. Danach k¨ onnen mit monochromatisierter Synchrotron-Strahlung im Energiebereich 130 keV bis u ¨ber 210 keV durch Anregung ihrer Fluoreszenz superschwere Elemente im Prinzip nachgewiesen werden. Z. B. hat die theoretisch vorausgesagte stabile Insel“ bei der Ordnungszahl Z=114 ” (A=298) f¨ ur die K-Elektronen die Bindungsenergie 200,21 keV. F¨ ur die charakteristischen Linien und die relativen Intensit¨ aten ergibt die Rechnung:K α2=160,01 keV;≈ 70 %; K α1=171,84 keV; 100 %; K β3=189,54 keV; ≈12 %; K β1=192,43 keV; ≈ 25 %; K β2=197,22 keV; ≈ 3 %; K β2=198,04 keV; ≈ 8 %. Der Nachweis eines SHE ist wahrscheinlich, wenn zwei oder mehr ungest¨ orte Linien mit passender Energie gefunden werden. Die Messungen wurden im Jahre 2004 durchgef¨ uhrt an der Beamline ID 15A des ESRF in Grenoble. Es wurden 20 sog. akzessorische Minerale bestrahlt. Die Auswahl war angeregt worden durch Befunde extremer Ungleichgewichte der Aktivit¨ aten in den nat¨ urlichen Zerfallsreihen von U-238, U-235 und Th-232, welche bisher nicht erkl¨ art werden konnten [2]. Jede Probe wurde mit den Prim¨ arenergien 185,6 keV, 205,6 keV und 227,2 keV bestrahlt, womit jeweils die Elemente bis Z=110, Z=115 und Z=119 nachgewiesen werden k¨ onnen. Eine große Schwierigkeit sind die St¨ orungen durch Summenpeaks (pile-ups) der Elemente in den Proben, die in den Energiebereich der SHE-Linien fallen. S¨ amtliche Kombinationen von deren Linien m¨ ussen bei der Auswertung ber¨ ucksichtigt werden, geordnet nach der relativen Intensit¨ at der Summenpeaks. Zur Unterdr¨ uckung der niederenergetischen Fluoreszenzlinien der leichteren Elemente (z. B. Y, Nb, SEE) und damit auch deren Summenpeaks mit den schweren Elementen (U, Th, Ta, Pb u.a.) waren vor den Detektoren Filter aus verschiedenen Metallen (ca.100µ bis 400µ) angebracht. Eine Unsicherheit besteht darin, daß ein gefundener Peak mehreren superschweren Elementen zugeordnet werden kann. In den nat¨ urlichen Mineralen sind nur geringste Spuren von SHE zu erwarten. Deswegen dauerten die Bestrahlungen mehrere Stunden trotz der hohen Intensit¨ at de Prim¨ arstrahls (bis ca.1011 Photonen/s auf 1,0x0,5 mm). In zwei der Proben fanden sich Hinweise auf SHE, abh¨ angig von den Meßparametern Anfangsenergie, Filter und Meßzeit: mit der Anfangsenergie 186,5 keV gab es Hinweise auf Z=110, 104. 101 und mit der Anfangsenergie 205,6 keV auf Z=114, 113,103,101,99. [1] Th. A. Carlson and C.W. Nestor: At. Data Nucl. Data Tables19 (1977) 153-173. [2] C. Schnier:, J.Radioanal. Nucl. Chemistry, 251 (2002), 191-196 and J. Radioanal. Nucl. Chemistry, 253 (2002), 209-216.

Index ¨ Autoren und ihre Beitrage: unterstrichen = Erstautor fett = Vortragender

Index Abbamonte, P. D-P253 Abdel-Latif, I. M-P1, D-P369 Abdul-Redah, T. M-P115, M-P116, M-P124, M-P142 Abetz, V. D-P214, D-P321 Abrahamsen, A.B. D-P368 Abromeit, C. M-P146 Abul Kashem, M.M. D-P292, D-P322 Adams, M.A. M-P122 Akdogan, N. D-P244 Aksenov, V.L. D-P357, D-P370 Alatas, A. M-P159, D-V44 Albergamo, F. M-P157 Albuerne, J. D-P321 Aldridge, L.P. D-P375 Alessi, M. D-P323 Alexandrowicz, G. M-V8 Alexiou, C. F-V58 Alff, L. D-P234, F-V69 Alfonso, G.C. D-P323 Aliouane, N. M-P122, D-P215, D-P217, D-P219, D-P226, D-P238, F-V67 Allgaier, J. M-P150, D-P329, D-P336 Allison, W. M-V8 Almairac, R. D-P262 Almendarez-Camarillo, A. F-V48 Alov, N. M-P168 Altarelli, M. F-PV10 Altarev, I. D-P412 Alvarez, J. M-P180 Amann, U. D-P262 Amato, A. M-P73 Amenitsch, H. D-P339 Andersen, N.H. D-P368 Andersson, G. D-P279 Andre, G. M-P139 Andreas, B. M-P2 Angelini, R. M-P157 Anson, C.E. M-V21 Apel, C. M-P109 Argyriou, D.N. M-P120, M-P121, M-P122, D-P215, D-P216, D-P217, DP219, D-P226, D-P238, D-P250, D-P262, F-V67 Ashley, C. M-P181

Assmann, W. M-P167 Asthalter, T. M-P77 Avdeev, M.V. D-P357, D-P370 Azzurri, F. D-P323 Baake, O. D-P371 Baberschke, K. D-P243 Baehtz, C. M-P169, D-P382, D-P405, F-V50 B¨ ar, M. M-P90 Baerner, K. D-P261 Bagni, M. M-P181 Baier, M. M-P187 Baiker, A. M-P171, F-V63 Bakajin, O. M-P5 Balaban, T.S. M-V21 Balasoiu, M. D-P357 Balogh, A.G. D-P267 Balz, M. D-P304 Bamberg, J. M-P58 Banhart, J. M-P29, D-P275, D-P386 Bansmann, J. M-P37, D-P289 Barath, H. D-P217 Barberet, P. M-P105 Barglik-Chory, C. D-P302 Barocchi, F. M-P65 Barth, R. M-P208 Barth, S. D-P285 Barthelmeß, M. M-P83 Barth`es, M. M-P120, M-P121 Bartunik, H.D. M-P182 Baruchel, J. M-P4 Bastjan, M. D-P217 Batchelor, D.R. M-P3 Baumann, H. D-P410 Baumbach, T. M-P4, D-V36, D-V37 Baumg¨ artel, P. M-P5 Bayraktar, F.S. D-P372 Bechgaard, K. M-P144 Becker, H.W. D-P245 Becker, P. M-P2, D-V45 Becker, U. M-P117, D-P362 Beckers, M. D-P411 Beckhoff, B. M-P6, M-P57, M-P86, D-P371 Beckmann, F. M-P44, M-P52, M-P97,

Index M-P98, M-P100, M-P101, M-P195 Behne, D. M-P195 Behr, G. D-P227 Behrmann, J.H. M-P84 Bensch, W. M-P178, D-P230, D-P409 Bentley, P.M. M-P22 Berciu, M. D-P253 Berger, A. D-P397 Berges, U. M-P7, M-P8, M-P9, D-P314, D-P319 Bergmaier, A. D-P373 Bergmann, A. D-P218 Bernhard, A. D-V37 Bernhard, C. M-V12 Besseghini, S. D-P379 Bethge, K. D-P410 Betzel, C. M-P184, M-P204, M-P206 Beye, M. M-P92 Bica, D. D-P357 Biehl, R. M-P55, M-P183 Biermanns, A. D-P281 Bischof, M. D-P374 Bischoff, L. D-P280 Bismayer, U. M-P145, D-P395 Biswas, I. D-P299 Bjeoumikhov, A. M-P95 Bj¨ orck, M. D-P251 Blank, D.H.A. D-P318 Blasco, J. D-P266 Blennow, A. M-P196 Blome, C. M-P118 Bobashev, S. M-P67 Bodenthin, Y. D-P239 Boehm, M. M-P10 B¨ oni, P. D-P228 Boesecke, P. M-P201, F-V58 B¨ osenberg, U. F-V49 Bohlen, A. von M-P27, D-P290 Bohnenbuck, B. D-P219, D-P259 Bolik, S. M-P184 Bolse, T. M-P119 Bolse, W. M-V9, M-P119 Bolte, M. D-P241, F-V53 Bonfim, M. M-V13 Bonne, T.B. D-P337

Borany, J. von D-P411 Bordag, N. M-P209 Bordallo, H.N. M-P120, M-P121, M-P122, D-P262, D-P375 Bormann, H. M-P132 Bornemann, S. D-P243 Borowiec, M. D-P266 Boschetti-de-Fierro, A. D-P321 Bostedt, C. D-P361 Botiz, I. D-P324 Botty´ an, L. D-P300 Bouree, F. M-P139 Bourenkov, G.P. M-P182, M-P190 Boye, P. M-P171, D-V35 Boyen, H.-G. D-P265 Boysen, H. M-P31, M-P123, M-P137 Bozek, G. D-P328 Braak, H. D-P220 Braden, M. M-P139, D-P256, D-P258 Br¨ auer, M. M-P83 Brakhman, E. D-P413 Bramnik, N. M-P169, D-P382, F-V50 Brandenburg, K. M-P185, M-P193 Brandt, A. M-P88, D-P323 Brandt, G. M-P85 Braun, J. D-P221 Braun, W. D-P268, D-P276, D-P279, D-P287, D-P296, D-P320, F-PV7 Braune, M. D-P362 Bravin, A. M-P201, F-V58 Brenner, P. D-P293, D-P308 Bresch, H. D-P293, D-P308 Broekaert, J. M-P20 Brokmeier, H.-G. M-P103, D-V31, DP222, D-P376, D-P377, D-P378, D-P389, D-P391, D-P401 Bron, M. M-P169 Brookes, N. D-P243 Br¨ uckel, T. D-P220, D-P254 Br¨ uggmann, U. M-P47 Br¨ user, B. D-P269 Bruning, M. M-P182 Brunke, O. M-P98 Brunken, S. D-P383 Brunner, T. D-V42

Index Buchsteiner, A. M-P150 B¨ ucherl, T. M-V1 B¨ uchner, B. F-V68 Buergler, D. D-P220 B¨ urck, U. van M-P77, M-P127 B¨ urkmann-Gehrlein, K. M-P85 Bulut, F. D-P289 Bumbu, G.-G. D-P360 Bunk, O. M-P91, D-V39 Burgert, I. F-V59 Burghammer, M. M-P196, D-V35, D-P334, D-P343, D-P351, F-V59 Burmester, J. M-P11 Busch, P. D-P345 Busch, S. M-P186, M-P188 Bushinsky, M.V. D-P261 Buslaps, T. M-P99, D-P396 Buth, G. M-V21 Butz, T. D-PV4 C.-Dreismann, C.A. M-P115, M-P124, M-P142 Caliebe, W. M-P12, M-P47, D-P325 Calzada, E. M-V1 Camarero, J. M-V13 Camin, B. M-P99, D-P396 Campbell, I. D-P246 Canfield, P.C. D-P368 Canning, A.S. M-P175 Cantelli, V. D-P411 Cao, X. M-P208 Capitan, M.J. M-P180 Carazzolne, M. D-P319 Casalbuoni, S. D-V37 Castorph, S. M-P187 Castro , A.R.B. de M-P166, D-P361 Castro, T. de M-P114 Catalan, G. D-P318, D-P325 Cavalcanti, L. M-V18 Cecchi, G. M-P181 Cervera, J. D-P310 Chadima, M. D-P222 Chadov, S. D-P221, D-P243 Chakhalian, J. M-V12 Chamard, V. M-P162 Chang, C.F. M-P156

Chapon, L.C. D-P250 Chass´e, T. D-P299 Chelaru, L.I. D-P236 Cheng, Y. D-P347, D-P360 Chernenko, V. D-P379 Chetverikov, Y. D-P228 Chini, T. D-P281 Chladil, H. D-P400 Chumakov, A.I. M-P77 Cianci, M. M-P190 Cifelli, F. D-P222 Claus, P. M-P169 Claver, A. M-P25 Clemens, D. M-P13 Clemens, H. D-P374, D-P400 Cloetens, P. F-V55 Clos, J. M-P206 Cobet, C. D-P270, D-P296, D-P320 Colombini, B. M-P181 Conrad, H. M-P89 Cooper, S.L. D-P217 Corde, S. M-P200, M-P201 Cornelius, T.W. D-P271 Costa Torres, M. M-P201 Costina, I. D-P305 Couet, S. F-V54 Cousson, A. M-P139 Cremer, T. M-V4 Cristiani, G. M-V12 Crostack, H.-A. M-P100 Cubitt, R. D-P343 Cunovic, S. M-P14 Cunsolo, A. M-P65 Cywinski, R. D-P246 Czasch, A. M-P21 Czihak, C. M-P148 Dahint, R. D-P353 Daniel, C. M-P36 Danilyan, G. D-P413 Darko, C. M-P198, D-P324 Darowski, N. M-P167, D-P272, D-P398 Dathe, H. M-P174 Daumont, C. D-P325 David, C. M-P91, D-V39 Davies, R. D-P334

Index De´ ak, L. D-P300 Decker, H. M-P200, M-P201, F-V58 Degen, J. M-P204 Deicher, M. M-V19, D-P406 Dembski, S. D-P302 Demkhin, P.V. M-P125 Demmel, F. M-P15 Den Baars, S.P. M-P4 Denchev, Z. D-P326 Dencheva, N. D-P326 Denecke, R. F-V65 Denker, A. D-P327 Denlinger, J. M-P90 D´enoyer, F. M-P120 Deppe, M. D-P224 Descamps, F. F-V62 Desgreniers, S. D-P404 Desmedt, A. M-P150, D-P375 Detlefs, C. D-P233 Dewhurst, C. M-P53 Diabat´e, S. M-P111 Diaz, A. M-P91 Diddens, I. M-P158 Diederich, T. F-V54 Dietzel, S. M-V4 D¨ ohrmann, R. M-P68 D¨ oring, S. M-P7, M-P8, M-P9 D¨ orner, R. M-P21 Dollinger, C. D-NV3 Dollinger, G. M-V4, M-P102, D-NV3, D-P373 Dommach, M. M-P68, D-P334 Domnick, R. D-P307 Donath, T. M-P97, M-P101 Donath, X. D-V39 Dornheim, M. F-V49 Dosch, H. D-AV1, D-V40, D-P288, D-P303, D-P305 Dose, T. M-P44, M-P97 Doster, W. M-P188 Douillet, D. D-V43 Dovillaire, G. D-V43 Doyle, S. D-P379 Dr¨ ager, G. M-P47 Dreiner, S. D-P314, D-P319

Drescher, M. M-P14, M-P23 Drexler, G. M-V4 Dreyhaupt, A. D-P233 Drube, W. M-P93 Du, G. M-P105 Dubiel, M. D-P273 Dudzik, E. M-P16, D-P226 D¨ urr, H. M-V14, M-P161 Eberhardt, W. M-V14, M-P50, M-P71, M-P161, D-P279 Ebert, H. D-P221, D-P243 Ecker, K. D-P397 Eckerlebe, H. D-P228, D-P283, D-P380 Eckert, J. D-P247 Eckold, G. M-P30, M-P40, M-P176, D-P332, F-V62 Efimov, V. D-P223 Egelhaaf, S. M-P53 Eger, C. D-P380 Eggeler, G. D-P387 Egger, W. M-P102 Egry, I. D-P381 Ehrenberg, H. M-P169, D-P382, F-V50 Ehresmann, A. M-P125 Eichelbaum, M. D-P274, D-P275 Eichert, D. M-V2 Eichhorn, K.-J. M-P24 Eidenberger, E. D-P374 Eisaki, H. D-P253 Eisebitt, S. M-P208 Eiselt, R. D-P241 Ejdrup, T. M-P144 Eliseev, A. D-P283 Ellis, J. M-V8 Ellmer, K. D-P383 Elmers, H.-J. F-V53 Embs, J.P. M-P126 Emtsev, K. D-P315 Endo, H. M-V22 Englisch, U. M-P83 Ensinger, W. D-P371, F-V46 Erdmann, V.E. M-P184 Eremina, E. D-P361 Erko, A. M-P49, D-P272 Erlach, S. D-P374

Index Eshchenko, D. M-P56 Esser, N. M-P24, D-P270, D-P296, D-P320 Etzdorf, D. M-P43 Fabritius, H. M-P205 Fainer, N. D-P371 Fajardo, M. D-V43 Falenty, A. M-P170 Falk, A. D-P358 Falkenberg, G. M-P20, M-P189, MP195 Falta, J. D-P311, D-P316 Farago, B. M-P22, M-P183, D-P336 Faulhaber, E. D-P224 Fehr, C. M-P121 Feidenhans’l, R. M-P144 Feldhaus, J. M-P154, F-PV8 Feldkamp, J. D-V35 Fendt, R. M-P17, D-V30 Fenske, J. D-P225 Fenzl, W. M-P36 Fernandez-Alonso, F. M-P15 Fetters, L.J. F-V47 Feuerborn, J. M-P18, D-P415 Feyerherm, R. M-P16, D-P226, D-P249 Fichter, S. D-P284 Fiedler, S. M-P19, M-P190, M-P207, F-V56 Fierro, D. D-P321 Figge, S. D-P311, D-P316 Fink, R. M-PV3, M-P3, M-V3, DP286, D-P313, D-P328, F-V55 Fischer, B. M-P105 Fischer, G. M-P100 Fischer, H.E. M-P26 Fischer, J. M-P97, M-P195 Fischer, P. D-P241 Fischer, T. D-P384 Fitter, J. M-P191 Fittschen, U. M-P20 Flege, J.I. D-P311, D-P316 Flesch, R. D-P293, D-P308 Fliegauf, R. M-P6, M-P85 Fl¨ uchter, C. D-P319 F¨ ohlisch, A. M-P59, M-P130

F¨ orster, S. M-P20, D-P341 Follath, R. M-P3 Forgan, T. M-P56 Formisano, F. M-P65 Forsyth, V.Trevor D-P350 Foucar, L. M-P21 Fouquet, P. M-V8, M-P22 Frahm, R. M-P45, M-P46 Frank, O. M-P11, M-P78 Franz, H. M-P69, M-P127, D-V25 Fratzl, P. F-V59 Frei, A. D-P412 Frei, G. D-V39 Frenzel, J. D-P387 Freund, H.-J. M-V3 Frey, F. M-P64, M-P128, M-P137 Friedl, A. M-V4 Friedrich, M. M-P135, D-P296 Frielinghaus, H. D-P329, D-P336 Frischbutter, A. M-V20 Fr¨ oba, M. M-P47 Frontzek, M. D-P227 Fr¨ uhling, U. M-P14, M-P23 Fr¨ uke, R. M-P14 Fuchs, D. M-P75 Fuchs, O. M-P90 Fuess, H. M-P31, M-P129, D-P382, D-P405 Fuhrmann, T. F-V65 Fuhse, C. D-NV1 Fujimaki, Y. D-P253 Fukumoto, K. M-V13, D-P236 Funari, S.S. M-P158, M-P180, M-P181, M-P192, M-P197, M-P212, D-P214, DP321, D-P323, D-P326, D-P334, D-P335, D-P349, F-V59 Gabriel, A. M-P40 G¨ ahler, R. M-V15, M-P42, M-P200, F-V58 Gahl, T. M-P34, M-P65 Gan, W. M-P103 Garamus, V.M. M-P212, D-P330, DP341, D-P357, D-P363, D-P370, D-P393 Garbe, U. D-V41, D-P376, D-P401 Gautier, J. D-V43

Index Gavrila, G. D-P276 Gebhardt, R.K. D-P289 Geck, J. F-V68 Gehrke, R. M-P68, M-P69, D-P307, F-V48, F-V49 Gehrmann, T. M-P19, M-P28, M-P207 Geibel, C. D-P224 Genov, N. M-P206 Gensch, M. M-P24 Georgieva, D. M-P206 Georgii, R. D-P228 Gerber, S. D-P330, D-P341 Gerlach, A. M-V18, M-P140, D-P277 Gerlach, J. M-P167 Getzlaff, M. D-P289 Geue, T. D-P331 Ghaderi, T. D-V30 Ghafur, O. D-P293, D-P308 Gibhardt, H. M-P176, D-P332 Giebeler, L. D-P405 Giewekemeyer, K. M-P202 Gille, P. M-P128 Gilles, R. M-P31 Glaser, L. D-P240, D-P294 Glasmacher, U.A. D-V33 Gleber, C. M-P107 Gleber, G. M-P131, D-P309, F-V64 Gleber, S.-C. M-P104, M-P112 Gliˇsovi´c, A. D-P333 Goebbels, J. M-P58, M-P109 Goerigk, G. D-P214, D-P278, F-V49 G¨ orner, W. D-P274, D-P385, D-P397 Goldhahn, R. D-P270 Goldman, A.I. D-P233 Gollerthan, S. D-P387 Gomes, D. D-P214 Gordan, O.D. D-P296, D-P320 Gordeliy, V.I. M-P40 Gorfman, S. M-P132, M-P153 Gorgoi, M. D-P279 Gottschalk, S. D-P267 Gottwald, A. M-P86 Grabis, J. D-P218 Gr¨ aber, H.G. M-P109 Graf, C. D-P293, D-P302, D-P308

Graf, H.-A. D-P323 Granz, P. D-P413 Grenier, B. D-P233 Grenzer, J. D-P280, D-P281 Greubel, C. M-V4 Greuter, U. M-P34 Greven, R. M-P80 Griesebock, B. M-P46 Griewatsch, K. M-P25 Griffiths, P. M-P181 Grigorian, S. D-P281, D-P338 Grigoriev, D. D-P282 Grigoriev, S. D-P228, D-P283, D-P363 Grigoryeva, N. D-P283 Grillo, I. M-P53 Grimm, O. M-P23 Groh, U. M-V3 Grotkopp, I. M-P148, M-P196, D-P334 Gr¨ unberg, P. D-P220 Gr¨ unewald, B. M-P195 Gr¨ unwald, A. D-P229 Gr¨ unzweig, C. D-V39 Gruner, S. M-P133 Grunwaldt, J.-D. M-P171, F-V63 Grunze, M. M-P90, M-P208, D-P353 Guarini, E. M-P65 G¨ uthoff, F. F-V62 Gunnlaugsson, H. D-P257 Gupta, A. D-P272 Gupta, H.S. F-V59 Gutberlet, T. M-P79, M-P186 Gutmann, J.S. D-P347, D-P360 Gutsmiedl, E. D-P412 Gutt, C. M-P17, M-P162, D-V30, D-P346 Guttmann, P. M-V2, M-P104 Haas, S. M-P29, D-P284 Haase, W. D-P239 Habermeier, H.-U. M-V12 Habicht, K. M-V15, D-P256 Hable, V. M-V4 Hackius, J. D-P403 Hackl, K. D-P387 H¨ artig, W. M-P209 Haese-Seiller, M. M-P35, M-P36

Index H¨ aussler, W. D-V28 H¨ avecker, M. M-P175 Hagelstein, M. D-V37 Hahn, B. M-P115 Hahn, U. D-V25 Haibel, A. D-P386 Hammershøj, P. M-P144 Hangleiter, Th. D-P262 Hanke, M. D-P282 Hankemeier, S. D-P240 Hannemann, S. M-P171 Hansen, S. M-P160 Hansen, T. M-P26, M-P170 Hanulova, M. M-P192, D-P335 Haramagatti, C.R. D-P332 Harm, S. M-P51 Harrit, N. M-P144 Hartmann, F.J. D-P412 Hartmann, M. M-P182 Harwardt, M. M-P58 Hasan, M. D-P387 Hasse, B. M-P95, M-P98, D-V32 Haug, J. D-P273 Hauptmann, N. M-P158 Hauptner, A. M-V4 Hauschild, S. M-P20, D-P341 Hauß, T. M-P212 Haverkort, M.W. M-P156 Hazra, S. D-P281 Healy, K. D-P310 Hedeg˚ ard, P. D-P368 Hedgeland, H. M-V8 Heger, G. D-P242 Heid, R. M-P165 Heim, S. M-V2 Heimburger, R. M-P172 Heinen, O. D-P364 Heinen, R. D-P387 Heiss, A. M-V22 Heiß, M. M-P105 Heldele, R. D-P388 Helfen, L. M-P4, M-P114, D-V36 Helms, G. M-P158 Hempelmann, R. M-P34, M-P126 Hennies, F. M-P130

Henry, P.F. M-P26 Hentschel, M.P. M-P58 Herfort, J. D-P287 Hergenhahn, U. D-P285 Hergenr¨ oder, R. M-P27, D-P290 Herlach, D. M-P73 Hermann, S. D-P320 Hermes, C. M-P19, M-P28, M-P190, M-P207, F-V56 Heske, C. M-P90 Heutling, F. M-P58 Hiess, A. M-P10, F-V66 Hilger, A. M-P81, M-P82, D-V38 Hill, J.P. D-P259 Hillebrecht, U. D-P235 Hillier, A. D-P246 Himcinschi, C. D-P320 Hinrichs, K. M-P24 Hj¨ orvarsson, B. M-P149, D-P231, D-P251, D-P252 Hock, R. M-P187 Hoebler, H.-J. M-V17 Hoeft, J.T. M-P92 H¨ oftberger, R. M-P189 Hoehl, A. M-P85 H¨ ohn, Y. M-P48 Hoell, A. M-P29, D-P275, D-P284 H¨ olzel, M. M-P31, M-P123, M-P137, M-P139, F-V50 Hoener, M. D-P361 H¨ oppner, J. M-P204 Hoffmann, A. M-P5 Hoffmann, B. M-P183 Hoffmann, B. M-P120, M-P137, DP262, D-P386 Hoffmann, P. D-P371 Hofmann, M. D-V41 Hofmeister, H. D-P273 Hofs¨ ass, H. M-V10, M-P54 Hoger, T. M-P179 Holch, F. D-P286 Holderer, O. M-P55, D-P336 Holitzner, L. M-P34 Holland-Moritz, D. D-P364, D-P381 Holldack, K. M-P161

Index Homeyer, J. D-P377, D-P389 Hommel, D. D-P311, D-P316 Hoppe, U. M-P134 Hoppler, J. M-V12 Horstmann, M. D-P372 Hoser, A. D-P231, D-P237, D-P252, D-P260 Howe, J. M-P185, M-P193 Hoyer, W. M-P133, M-P136 Hradil, K. M-P30, M-P165, M-P176, D-P256, F-V62 Hu, Z. M-P156 Huang, Z.-L. D-P230 Huber, P. D-P331 H¨ ubner, D. D-P286 H¨ utten, A. D-P255 Hugenschmidt, C. D-V42 Hunger, R. M-P177 Huppmann, M. M-P99 Huwald, E. D-P315 Ibarra, M.R. D-P266 Illerhaus, B. M-P58 Iolin, E. M-P32 Ionov, L. M-P24 Isaac, A. D-P396 Islamov, A.K. M-P40, D-P332 Isobe, M. M-P139 Issendorff, B. von D-P294 Ivanova, R. D-P337 Jackson, D. M-P175 Jacobs, R. D-P353 Jaegermann, W. M-P177 Jagutzki, O. M-P21 Jahn, D. M-P19, M-P28 Jahnen-Dechent, W. M-V22 Jahnke, T. M-P21 Jalarvo, N. M-P122 Janata, E. M-P173 Janowitz, C. M-P50 Jansen, E. D-P399 Jansen, M. D-P234 Janßen, F. M-P80 Janssen, S. M-P34, D-P317 Janssens, A. D-P318 Jardine, A.P. M-V8

Javid, N. M-P194 Jenichen, B. D-P268, D-P287 Jensen, J. D-P368 Jensen, T.B.S. D-P368 Jentschel, M. D-V45 Jentys, A. M-P174 Jernenkov, M. D-P295 Jiang, J. M-P127 Jin, S.-J. D-P389 John Louis, S. M-P135 Johnas, S.K.J. M-P33 Johnson, I. D-V39 Johnson, R.L. M-V23 Johnston, K. M-V19, D-P406 Jordan, R. D-P337 Joshi, S. D-P285, D-P291, D-P338 Jung, Ch. M-P3 Jungwirth, R. D-P407 Juranyi, F. M-P34, M-P121, M-P126, M-P148, M-P186 Juricic, C. D-P390 Jursic, I. D-P392 J´ ov´ ari, P. M-P136 Kaban, I. M-P133, M-P136 Kachalova, G.S. M-P182 Kachel, T. M-V14, M-P161 K¨ ammerer, S. D-P255 K¨ as, J. D-P358 Kaganer, V.M. D-P268, D-P287 Kaindl, G. D-P264 Kaiser-Bischoff, I. M-P128, M-P137 Kalbfleisch, S. M-P106 Kalceff, W. M-P121 Kallaene, M. M-P51 Kalms, R. M-P14 Kalnin, D. D-P339 Kaminski, H. D-P396 Kammel, M. D-P248 Kampmann, R. M-P35, M-P36 Kane, A. M-P5 Kang, S.-G. M-P158 Kanngießer, B. M-P48, M-P49, M-P57 Kapusta, C. D-P266 Kardjilov, N. M-P81, D-V38 Kargl, F. M-P138

Index Karim, S. D-P271 Karis, O. D-P279 Kasper, N. D-P288, D-P303 Katsnelson, M. D-P221 Keiderling, U. M-V15 Keil, P. M-P45 Keimer, B. M-V12, D-P259 Keller, G. D-P339 Keller, H. M-P56 Keller, S. M-P4 Kentzinger, E. F-V47 Keppler, H. D-V33 Kern, B. D-P265 Khafizov, R. D-P414 Khaibullin, R. D-P244 Khalil-Allafi, J. D-P387 Khan, S. M-P161 Kiefer, K. D-P216, D-P262 Kiele, S. F-V68 Kilcoyne, D. D-P328 Kim, D.-H. D-P241 Kim, J.W. D-P233 Kim, M. D-P217 Kipp, L. M-P51, D-P306 Kirschner, J. M-V13, D-P236 Kiselev, M.A. M-P212 Klaering, R. M-P207 Klaum¨ unzer, S. M-P146, M-P167 Klauss, H.-H. F-V69 Kleibert, A. M-P37, D-P289 Kleiman, G. D-P319 Klein, A. D-P371 Klein, H. D-P233 Klein, R. M-P85, M-P86 Kleinhempel, R. M-P133 Klimmer, A. D-P265 Klingeler, R. F-V68 Klingelh¨ offer, H. D-P398 Klingenberg, B. D-P399 Klitzing, R. von D-V29 Klose, F. D-P225 Klug, D. M-P150 Klussmann, S. M-P184 Knabe, C. M-P109 Knapp, M. M-P129

Kn¨ ochel, A. M-P18 Knop-Gericke, A. M-P175 Knupfer, M. M-P3 Kobayashi, Y. D-P257 Kocak, M. D-V32, D-P372, D-P389, D-P391, D-P403 Koch, N. D-P277 Kochubey, D. D-P223 Kockelmann, W. M-P151, D-P230, D-P409 K¨ obler, U. D-P237 K¨ ogel, G. M-P102 K¨ ohler, R. M-P108, D-P282 K¨ olln, K. M-P196, D-P334 K¨ onig, S. M-P143 Koennecke, M. M-P79 K¨ oper, I. F-V61 K¨ orstgens, V. D-P292 Kohl, M. D-P379 Kohlbrecher, J. M-V16 Kolbe, M. M-P6 Komarek, A.C. M-P139 Komenda, T. D-P337 Konarev, P.V. M-P206, M-P207 Konerding, M.A. M-P200 Konovalov, O. M-V18 Kopitsa, G.P. D-P363 Korecki, P. M-P38 Korica, S. D-P362 Korsunkiy, V. M-V24 Kosinova, M. D-P371 Kostka, A. D-P400 Kostka, B. D-V37 Kotsugi, M. D-P236 Kottar, A. D-P396 Kowarik, S. M-V18, M-P140 Koza, M.M. M-P138, M-P141, M-P158, D-P350 Kozlov, O. M-P23 Kr¨ amer, M. M-P27, D-P290 Krakhotin, V. D-P413 Kramer, M. M-P184 Krasnov, I. M-P158 Krasyuk, A. F-V53 Krauser, J. M-V10

Index Kravtsov, E. D-P231, D-P252 Kreis, M. M-P119 Krempel, J. D-V45 Kreuzpaintner, W. D-P232 Kreyssig, A. M-P165, D-P227, D-P233 Krikunova, M. M-P14 Krisch, M. M-V5, M-P141, D-P298 Krist, T. M-P39 Kriventsov, V. D-P223 Krockenberger, Y. D-P234, F-V69 Kronenberg, J. M-V19, D-P406 Kr¨ ucken, R. M-V4 Kr¨ uger, F. D-P256 Krug, I. D-P235 Krumrey, M. M-P86 Krywka, C. M-P63, M-P194, D-P346 Krzystyniak, M. M-P124, M-P142 Kuch, W. M-V13, D-P236 Kudryashov, V. M-P35, M-P36 K¨ uhbacher, M. M-P195 Kuetgens, U. M-P2, M-P159, D-V44 Kuhlmann, M. M-P68, D-V43, D-P307, D-P361, F-V48 Kuhs, W.F. M-P170, D-NV2 Kuklin, A.I. M-P40, D-P332 Kulcke, R. M-P11 Kulda, J. M-P10, D-P258 Kumar, G. D-P247 Kumpf, C. M-P160, D-P291 Kunz, C. M-V23 Kunze, K. D-P399 Kurbakov, A. D-P369 Kurth, D.G. D-P239 Kuzmin, A. D-P223 Kyriakopoulos, A. M-P195 L´evesque, P. M-V3 Laarmann, T. D-P361 Lake, B. D-P386 Lammel, G. M-P20 Lamzin, V. M-P190, M-P203 Landers, R. D-P319 Landesberger, C. M-P4 Landsgesell, S. D-P215, D-P219, D-P238, D-P250 Lang, J.C. D-P259

Lang, M. D-V33, D-P312 Lange, A. M-P58 Langenhorst, F. D-V33 Langer, B. D-P293, D-P308 Last, A. M-P60 Lathe, C. D-P366 Lau, T. D-P294 Lauter, H. M-P41, D-P295 Lauter-Pasyuk, V. M-P41, D-P295 Law, R.D. D-P401 Le Duc, G. M-P200, M-P201, F-V58 Leckey, R. D-P315 Lee, B.-J. D-P415 Lee, T.-L. M-V23, D-P277, D-P316 Lefrou, T. D-V43 Lehmann, D. M-P135, D-P296, D-P320 Lehmann, E. D-V39 Lehmk¨ uhler, F. D-P340 Leiner, V. M-P78 Leiss, B. F-V51 Leist, J. M-P176 Leitenberger, W. M-P131, M-P140, D-P309, F-V64 Leitner, H. D-P374 Lejay, P. D-P363 Lemeshko, M.P. M-P125 Lemke, H.T. M-P144, M-P196, D-P334 Lengefeld, J. M-P5 Lengeler, B. M-P68, D-V35, D-P307 Lenser, S. D-P222, D-P389, D-P391 Lerch, M. M-P115, M-P123, M-P137 Lerche, M. M-P159, D-V44 Lercher, J. M-P174 Leupold, O. D-V25, D-P300, D-P307, D-P365 Lewinski, R. D-P293, D-P308 Ley, L. D-P315 Leyendecker, M. M-P80 Li, C. F-V59 Lichtenstein, A. D-P221 Liebau, E. M-P204 Liebig, A. M-P149, D-P231, D-P252 Lieutenant, K. M-P42 Lin, C.T. D-P259 Lindenau, B. M-P80

Index Lindert, S. M-P209 Lindner, P. M-P42 Link, P. M-P43, D-P229, D-P256, D-P258 Linke-Schaetzel, M. M-V21 Linser, S. M-P197 Lippmann, T. M-P44, M-P52, M-P97, D-P376 Liss, K.-D. D-P415 Litterst, J. M-P56, F-V69 Loewenhaupt, M. M-P43, D-P224, D-P227, D-P233 Lommel, M. D-P239 Longeville, S. M-P188 Lorenz, K. M-V1 Lorenz, T. M-P139 Lott, D. M-P78, D-P225 Lottermoser, L. M-P44, M-P97 Luczak, P. D-P291, D-P302 L¨ ubbert, D. M-P4, M-P108, M-P114 L¨ udtke, K. D-P337 Luetkens, H. M-P56, M-P73, F-V69 L¨ utzenkirchen-Hecht, D. M-P45, M-P46 Lukashin, A. D-P283 Lyutovich, K. M-P119 Maccarrone, S. D-P329 Machek, P. M-P12, M-P47 Macht, M.-P. M-P146 Madsen, A. M-P17, D-V30 Maeno, Y. D-P258, D-P259 Maf´e, S. D-P310 Magerl, A. D-P359 Magnussen, O. M-V11 Maier, F. M-V3, M-P90 Major, J. D-V40 Major, M. D-P300 Malcherek, T. M-P62, M-P145, D-P395 Maleyev, S. D-P228 Maltezopoulos, T. M-P14 Malzer, W. M-P48, M-P49 Mana, G. D-V45 Mandelkow, E.-M. F-V57, F-V57 Mani, P. D-P225 Manke, I. M-P81, M-P109, D-V38 Mankey, G.J. D-P225

Mantouvalou, I. M-P48 Manuel, P. D-P246 Manzke, R. M-P50, M-P172 Marcellini, M. M-P149, D-P279 Marchetto, H. M-V3 Marczynski, M. M-P51 Marinica, O. D-P357 Marquina, C.I. D-P266 Martchenko, T. D-P293, D-P308 Martins, M. M-P92, D-P240, D-P243 Martins, R.V. M-P44, M-P52, M-P97, D-P384 Marutzky, M. D-P392 Marx, A. F-V57 Materlik, G. M-P38 Mattei, M. D-P222 Matthes, F. D-P297 May, R. M-P53, M-P200, F-V58 Maye, F. D-V40 Mayer, J. D-V42 Mayer, T. M-P177 Mazur, Y. D-P282 McGregor, J. M-P175 McIntyre, G. D-P231 Mechler, S. M-P146 Meersschaut, J. D-P300 Meesters, C. M-P201, F-V58 Meier, G. D-P241 Meirer, F. M-P20 Meiwes-Broer, K.-H. M-P37, D-P289 Melo, E. M-P180 Mentese, S. D-P317 Menzel, D. D-P392 Mercere, P. D-V43 Merkel, R. M-P183 Merkt, U. D-P241 Mertin, M. D-P279 Mesot, J. M-P34 Metwalli, E. M-P198 Metzger, H. M-P110 Meven, M. D-P242 Meyer, A. M-PV2, M-P138, M-P163, D-P364 Meyer-Klaucke, W. M-P199, M-P206, M-P211

Index Mezei, F. M-P13, M-P22, D-V27, D-P246 Michels, A. M-V16, D-P263 Michiel, M. di M-P99, D-P396 Mientus, R. D-P383 Mihalik, M. D-P249 Mikhailova, D. M-P129 Mikula, P. M-P32 Mikulik, P. M-P4, D-V36 Milinovic, V. M-P54 Milkereit, G. D-P330, D-P341 Milne, C. D-P216 Minar, J. D-P221, D-P243 Mitrea, G. M-P107, M-P112 Mitzner, R. M-P71, M-P161 Mocuta, C. M-P110 Modregger, P. M-P108 M¨ oller, T. M-P166, D-P294, D-P361 Mogare, K. D-P234 Mohr, J. M-P60, M-P111 Molodtsov, S. D-P223 Monkenbusch, M. M-P55, M-P183, D-P336, F-V47 Monkenbusch, S.V. D-P343 Morawetz, K. M-P131, D-P331 Morenzoni, E. M-P56, F-V69 Morgenroth, W. M-P153 Morrison, A.P. D-P310 Mortensen, K. D-P337 Mostafa, A. D-P369 Moulin, J.-F. D-P342 Moze, O. M-V16 M¨ uhlbauer, M. M-V1 M¨ uller, A. M-P147, D-P412 M¨ uller, B.R. M-P58 M¨ uller, H.-J. D-P366 M¨ uller, Martin M-P148, M-P158, MP196, D-P298, D-P334, D-P350, F-PV6 M¨ uller, Martina D-P297 M¨ uller, Matthias M-P6, M-P57 M¨ uller, N. M-P14, F-V58 M¨ uller, R. M-P85, M-P86 M¨ uller-Buschbaum, P. M-P68, D-P292, D-P295, D-P307, D-P322, D-P342, D-P343, D-P347, D-P351

Mueller-Dieckmann, C. M-P210 M¨ ullner, P. D-P379 Murphy, B. D-P298 Nadutov, V. D-P393 Nagasono, M. M-P59, M-P130 Nagel, M. D-P299 Nagel, P. M-P75 Nagy, D.L. D-P300 Naito, M. F-V69 Nakatsuji, S. D-P258 Napolskiy, K. D-P283 Naumann, M. D-P399 Nawroth, T. M-P200, M-P201, F-V58 Nazmov, V. M-P60, M-P111 N´ed´elec, R. D-P394 Neder, R. M-V24, D-P291, D-P302 Neeb, M. M-P71 Nefedov, A. D-P218, D-P231, D-P244, D-P245, D-P251, D-P252 Neher, D. D-P338 Nellesen, J. M-P100 Nelson, C.S. D-P259 Nepijko, S.A. F-V53 Neuber, G. D-P217 Neubert, R. M-P212 Neuhaus, J. M-P30, F-PV9 Neumann, R. D-V26, D-V33, D-P271, D-P310, D-P312, F-V46 Neumann, W. D-P398 Nickel, B. M-P36, D-P301 Niederdraenk, F. D-P291, D-P302 Niedermayer, C. M-V12 Nielsen, M.M. M-P144 Nieuwenhuys, G. M-P56 Nikbin, K. D-P408 Nikolayev, D. M-P61 Nikolowski, K. M-P169, D-P382, F-V50 Nix, A.-K. M-V10 N¨ ochel, U. F-V48 Nørgaard Toft, K. D-P368 Noheda, B. D-P318, D-P325 Noll, T. M-P71 Nolte, P. D-P288, D-P303 Novakova, E. M-P202

Index Novikov, D.V. M-P38 Nowak, G. M-P149, D-P245, D-P251, D-P252 N¨ ulle, M. D-V40 Odenbach, S. M-P98, D-P248 Oelsner, A. F-V53 Offi, F. D-P236 Ogurreck, M. M-P158 Ohl, M. M-P55, M-P74 Ohtsuka, M. D-P379 Okorokov, A. D-P228 Oliveira, M.J. D-P326 Ollinger, C. D-NV1 Ollivon, M. D-P339 Oppeneer, P.M. M-P37 Ordolff, M.-E. M-P178 Orecchini, A. M-P65 Ostermann, A. D-V41 Osterode, W. M-P189 Ott, H. M-P156 P¨ arnaste, M. D-P251 Pairet, B. M-P201, F-V58 Palatinus, L. M-P155 Panjikar, S. M-P203, M-P210 Panneerselvam, S. F-V57 Panzner, T. M-P131, D-P309, F-V64 Paolasini, L. D-P252 Papadakis, C.M. M-P198, D-P324, D-P337, D-P344, D-P345 Papp, C. F-V65 Pappas, C. M-P13, M-P22, D-P246 Paris, O. F-V59 Parthasarathy, V. M-P203 Passig, J. D-P289 Patommel, J. D-V35 Paul, A. D-P220 Paul, S. D-P412 Paulke, B.-R. M-P209 Paulmann, C. M-P62, M-P137, M-P145, D-P395 Paulus, H. M-P119 Paulus, M. M-P63, D-P340, D-P346 Pavlov, V. D-P413 Pedersen, B. M-P64, M-P128, M-P137 Peisert, H. D-P299

Pelc, R. M-P181 Pellegrin, E. M-P75 Pepponi, G. M-P20 Perbandt, M. M-P184, M-P204 Pereira Nunes, S. D-P214, D-P349 Pereiro Lopez, E. M-P107, M-P112 Perlich, J. D-P322, D-P347 Pernot, P. M-P4, D-V36 Perroud, O. D-P247 Petermann, K. D-P395 Peters, J. M-P13 Peters, R. D-P395 Pethoukov, M. M-P207 Petrenko, A. D-P300 Petri, M. F-V62 Petrillo, C. M-P65 Petry, W. M-P77, D-P295, D-P407 Peverini, L. M-P91 Pfeiffer, F. M-P91, D-V39 Pfl¨ uger, J. M-P83 Picker, R. D-P412 Pienack, N. M-P178 Pieper, J. M-P122, M-P150 Pietsch, U. M-P131, M-P132, M-P140, M-P153, D-P239, D-P269, D-P280, DP281, D-P309, D-P331, D-P338, F-V64 Pietzsch, A. M-P59, M-P130 Pilgrim, W.-C. M-P65 Pinholt, R. D-P368 Pinta, C. M-P75 Pinto, H. M-P205, D-P390, D-P400 Pintschovius, L. M-P165 Piochacz, C. D-V42 Pipich, V. D-P304 Pirling, T. M-P66 Piselli, E. M-P28 Pizzini, S. M-V13 Plazanet, M. M-P150 Plewka, J. M-P11 Pl¨ onjes, E. M-P23, D-V43, D-P361 Ploog, K.H. D-P268, D-P287, F-PV7 Poenariu, V. D-P269 Polachowski, S. M-P80 Pollakowski, B. M-P6, D-P371 Pollinger, F. M-P160

Index Ponce, M.L. D-P214 Ponkratz, U. D-P365 Pontius, N. M-V14, M-P161 Pop, L.M. D-P248 Popov, A. M-P19 Posselt, D. D-P344, D-P345 Prager, M. M-P150 Pranzas, K. D-P228, D-P283M-V16, D-P337, D-P380, F-V49 Press, W. M-P150, D-P298 Pritzkow, W. D-P397 Prochazka, V. D-P266 Prokes, K. D-P249 Prokhnenko, O. D-P216, D-P226, D-P238, D-P250 Prokscha, T. M-P56, F-V69 Pucher, A. M-P131 Putaux, J.-L. M-P196 Pyrlik, M. D-P380 Pyzalla, A. M-P99, M-P205, D-PV5, D-P390, D-P396, D-P400 P´epy, G. D-P310 Qiao, X. M-P103 Quast, T. M-P161 Raabe, D. M-P205 Raabe, J. D-P328 Rack, A. M-P109, M-P114 Rademann, K. D-P274, D-P275 Radtke, M. M-P49, M-P195, D-P274, D-P397 Radu, F. D-P231, D-P245, D-P252 Radulescu, A. F-V47 R¨ adler, J. M-P36, D-P301 Rahn, J. M-P85 Raif, F. M-P169 Rajewska, A. D-P348 Rakel, M. D-P270 Ram´ırez, P. D-P310 Raschke, M. M-P24 Rata, D. D-P220 Rauscher, M. D-P345 Rebelo-Kornmeier, J. D-V41 Redecke, L. M-P206 Reehuis, M. D-P234 Rehbein, S. M-V2

Reichardt, G. M-P5, M-P50 Reichardt, W. M-P165 Reichmann, H.-J. D-P366 Reicho, A. D-P288, D-P305 Reif, M. D-P240 Reimers, W. M-P99, D-V32, D-P396, D-P402 Reinhold, B. D-P331 Reinholz, U. D-P397 Reink¨ oster, A. D-P362 Reiss, G. D-P255 Reiter, G. D-P324 Remhof, A. M-P149, D-P231, D-P245, D-P251, D-P252 Requardt, H. D-P298 Reutler, P. F-V68 Revcolevschi, A. F-V68 Reznik, D. M-P165 Reznikova, E. M-P60, M-P111 Rheinst¨ adter, M.C. D-V28, D-P352 Richter, D. M-P55, M-P183, D-P329, D-P336, F-V47 Richter, M. M-P67, M-P86 Rickers-Appel, K. M-P93 Riedel, T. M-P51 Riekehr, S. D-P391 Riekel, C. M-P196, D-V35, D-P343, D-P350, D-P351, F-V59 Riesemeier, H. M-P49, M-P195, DP274, D-P397 Rijnders, G. D-P318 Riley, J. D-P315 Rispens, G. D-P318 Ristau, U. M-P19, M-P207 Rittmann, J. D-P294 Robert, A. M-P17, M-P162 Robrahn, B. M-P19, M-P28, M-P207 Roeder Jesus, J. D-P214 R¨ ohlsberger, R. M-P69, D-V25, F-V54 Rønnow, H. D-V39 Roessle, M. M-P185, M-P190, M-P193, M-P207, F-V56 Rolles, D. D-P362 Romanens, F. M-V13 Ronning, C. M-V10, M-P54

Index Rosenhahn, A. M-P208 Rossbach, J. M-P23 Rossmanith, R. D-V37 Rossnagel, K. M-P51, D-P306 Rosta, L. D-P370 Roth, S.V. M-P68, M-P69, M-P198, DP292, D-P307, D-P322, D-P324, D-P347, D-P351, D-P360, F-V48, F-V49 Rothkirch, A. M-P70, M-P95 Roux, S. M-P10 Rozhkova, N.N. D-P370 Ruebhausen, M. M-P184, D-P217, D-P253 R¨ ucker, U. F-V52 R¨ uckerl, F. D-P358 R¨ uffer, R. M-P72, M-P77, D-P300 Rueggeberg, M. F-V59 R¨ uhl, E. D-P293, D-P302, D-P308 R¨ uhm, A. D-V40 R¨ uter, H.D. M-P159, D-V44 Ruhnau, H.-U. M-P44, M-P52 Runov, V.V. D-P363 Ruocco, G. M-P152, M-P157 Rupprecht, K. D-P365 Ruschewitz, U. M-P151 Rusevich, L. M-P32 Rusp, M. M-P200, M-P201 Russina, M. M-V15, M-P150, D-P413 Rusteika, N. M-P144 Rusydi, A. D-P217, D-P253 Rutkowski, M. M-P71, M-P179 Rybacki, E. D-P399 Rybicki, D. D-P266 Sacchetti, F. M-P65 Sacher, M.D. D-P255 Sackmann, E. M-P36 Sadykov, R. D-P260 Said, A. M-V7 Saile, V. M-P60, M-P111 Saito, M. D-P288 Saksl, K. M-P127 Salamo, G. D-P282 Saldin, E. M-P23 Salditt, T. M-P106, M-P202, D-NV1, D-V28, D-P333, D-P352

Sanchez de Almeida Prado, L.A. D-P349 Sanders, Y. D-P254 Sant, T.P. D-P309, F-V64 Sanyal, M. D-P281 Sapede, D. D-P350 Satapathy, D.K. D-P268, D-P287 Sauer, H. M-P175 Sawatzky, G. D-P253 Sazonov, A. D-P242 Schacht, A. D-P404 Schade, U. M-P24, M-P195 Schadow, T. D-P294 Sch¨ afer, P. M-P108, D-P282 Sch¨ afer, W. M-P89 Sch¨ afers, F. D-P279 Schafer, O. D-P339 Schardt, D. D-V33 Schartner, K.-H. M-P125 Schatz, G. M-P56 Schebaum, O. D-P255 Scheerer, B. M-P75 Scheffz¨ uk, C. M-V20 Scheibel, T. M-P198 Schell, N. D-P411 Scherer, W. M-P64 Scheuerlein, C. D-P386 Scheuermann, R. M-P73 Schicke, K.-D. D-P273 Schiedt, B. D-P310 Schierle, E. D-P264 Schilling, F. D-P366 Schillinger, B. M-V1 Schirmacher, W. M-V7, M-P152 Schlappa, J. M-P156 Schl¨ ogl, R. M-P175 Schlumpf, N. M-P34 Schmahl, W. D-P382, D-P387 Schmalhorst, J. D-P255 Schmalzl, K. M-P74 Schmauder, S. M-P100 Schmid, W. D-P412 Schmidbauer, M. D-P282 Schmidt, C. M-P112 Schmidt, L. M-P21 Schmidt, M. M-P132

Index Schmidt, O. M-P132, M-P153 Schmidt, Th. M-V3, M-P3, D-P311, D-P313, D-P316 Schmidt, W. M-P74, D-P225, D-P229, D-P256, D-P258 Schmidt-B¨ ocking, H. M-P21 Schmiedel, H. M-P209 Schmitz, H.-W. M-P97 Schmoranzer, H. M-P125 Schneider, C. D-P220, D-P235, D-P297, F-V53 Schneider, G. M-V2 Schneider, H. M-P30, M-P176, F-V62 Schneider, R. M-P96, D-P273, D-P386 Schneider, T. D-V37 Schneidewind, A. M-P43, D-P224, D-P227, D-P256 Schneidmiller, E. M-P23 Schnier, C. D-P415 Schober, H. M-P148, F-V62 Sch¨ oll, A. M-P3, M-P160, D-P286, D-P313 Schoenau, K. D-P382 Schoenes, J. D-P392 Sch¨ onhense, G. F-V53 Sch¨ onherr, H.-P. D-P287 Sch¨ onleber, A. M-P155 Schoeps, A. M-P127 Sch¨ oßler, S. M-P21 Scholze, F. M-P86 Schorr, S. M-V17 Schotte, K.-D. M-P96 Schreckenbach, K. D-V42 Schreiber, F. M-V18, M-P140, D-P277, D-P353 Schreiber, J. M-P4 Schreiber, R. D-P220 Schreiber, S. M-P154 Schreyer, A. M-P35, M-P36, M-P44, M-P52, M-P78, M-P97, M-P101, M-P103, D-P225, D-P229, D-P232, D-P357, DP372, D-P376, D-P384, F-V49 Schroer, C. M-P68, M-P110, M-P171, D-V35, D-P307, F-V48 Schropp, A. M-P110

Sch¨ unemann, V. F-V60 Sch¨ urmann, M. M-P208, D-P314, D-P319 Sch¨ ußler-Langeheine, C. M-P156 Sch¨ utze, M. D-P410 Schuler, B. M-P5 Schulte, K. D-P349 Schulte-Schrepping, H. M-P69, D-V25 Schulz, B. M-P184 Schulz, L. D-P322, D-P351 Schulz, M. M-V1, D-P388 Schumacher, G. M-P146, D-P398 Schumann, O. D-P256, D-P258 Schuppler, S. M-P75 Schwahn, D. M-V22, D-P304, F-V47 Schwartz, K. D-P312 Schwarz, G. D-P239 Schwebke, B. M-P103, D-P376 Schweika, W. M-P164, D-P254 Schweins, R. M-P42, D-P350 Schwen, D. M-V10 Scopigno, T. M-P152, M-P157 Sechovsky, V. D-P249 Seckler, R. M-P5 Seeck, O.H. M-P76, D-V25, D-P318, D-P325 Seeger, S. D-P383 Seidl, G. M-P64 Seifert, S. D-P276 Selle, C. D-P358 Sellner, S. M-V18, D-P277 Semenov, D. D-P393 Senff, D. D-P256 Senyshyn, A. M-P31, M-P123, M-P129, M-P137, M-P139, F-V50 Senz, V. M-P37 Sergueev, I. M-P77, M-P127 Serrano, J. D-P298 Severin, D. F-V46 Seydel, T. M-P121, M-P158, D-V28, D-P350, D-P352 Seydmohamadi, S. D-P282 Seyller, T. D-P315 Shatalov, P. D-P413 Shmakov, A. D-P223

Index Shvyd’ko, Y. M-P2, M-P159, D-V44 Siambanis, T. M-P28 Sidis, Y. D-P256, D-P258 Siebert, M. D-P311, D-P316 Siegemund, T. M-P209 Sielemann, R. D-P257 Siemer, B. M-P71, M-P179 Siemes, H. D-P399 Siervo, A. de D-P319 Sikolenko, V. D-P223 Sikora, M. D-P266 Silaghi, S. D-P296, D-P320 Silva, P. D-P400 Silvestric, M. M-P206 Simon, R. M-P111, M-P114 Sindu, J. D-P296 Singer, S. D-P217 Singer, W. D-P378 Singer, X. D-P378 Sinha, S.K. D-V30 Sinn, H. M-V7 Sitepu, H. D-P401 Siwy, Z. D-P310 Skoda, M. D-P353 Skrzypinska, A. D-P402 Skupin, J. M-P83 Sk` ala, T. M-V3 Slotta, U. M-P198 Smaalen, S. van M-P155 Smadici, S. D-P253 Smeibidl, P. D-V27 Smilgies, D.-M. D-P324, D-P344, D-P345 Smirnov, G.V. M-P77 Smuda, C. D-P354, D-P356 Sølling, T.I. M-P144 S¨ ollinger, W. D-P264 Soininen, J.A. D-P404 Solina, D. M-P78 Sorg, C. D-P243 Sorgenfrei, F. M-P92 Sorokin, A. M-P67 Sorokin, M. D-P312 Souza, S.L. M-P180 Speck, F. D-P315

Spengler, J. D-V25 Sperling, M. D-P279 Sperr, P. M-P102 Springholz, G. D-P264 Sprung, M. D-P346 Srajer, G. D-P259 Stadlbauer, M. D-V42 Stadler, C. M-P160 Stahn, J. M-V12, M-P79 Staier, F. M-P208 Stamm, C. M-V14, M-P161 Stamm, M. M-P24, D-P342 Stampanoni, M. M-P91 Stanzel, J. M-P160 Staron, P. D-P372, D-P374, D-P403 Steffens, E. D-V37 Steffens, P. D-P258 Steglich, F. D-P224 Stein, W.-D. M-P139 Steiner, M. D-V27 Steinr¨ uck, H.-P. F-V65 Steitz, R. D-V29 Stelzer, H. M-P80 Sternemann, C. M-P9, M-P63, M-P194, D-P290, D-P404 Sternemann, H. M-P162, D-P404 Stettner, J. D-P298 Stierle, A. D-P288, D-P303, D-P305 Stiller, M. M-P109 Stockert, O. M-P165, D-P224 Stojanov, P. D-P315 Stoykov, A. M-P73 Str¨ assle, T. M-P34 Streber, R. F-V65 Streit, S. M-P162, D-V30 Streli, C. M-P20 Strempfer, J. M-P120, D-P215, D-P219, D-P259, F-V67 Stribeck, N. D-P355, F-V48 Strickfaden, H. M-V4 Strobl, M. M-P32, M-P81, M-P82, D-V38 Strohm, C. M-P77 Str¨ uder, L. D-V34 St¨ uber, S. M-P163, D-P292, D-P364

Index St¨ urmer, D. D-P405 Stuermer, D. M-P169, D-P382 St¨ ußer, N. D-P260 Suck, J.-B. M-P65, M-P157, D-P317 Sukhorukov, V.L. M-P125 Suljoti, E. M-P59, M-P130 Surber, S. D-P358 Suter, A. M-P56, F-V69 Suzuki, K. M-V16 Svensson, S. D-P279 Svergun, D. M-P190, M-P206, M-P207, F-V56 Svystunov, Y. D-P393 Szil´ agyi, E. D-P300 Szymczak, H. D-P261 Szymonski, M. M-P38 Tagirov, L. D-P244 Tan, L. D-P233 Tanaka, A. M-P156 Tanczik´ o, F. D-P300 Tartakovskaya, H. D-P229, D-P232 Tatchev, D. M-P29, D-P275 Telling, M. M-P15 Tennant, A. D-V27, D-P386 Teresa, J.M. de D-P266 Teschner, D. M-P175 Textor, M. D-P331 Theis-Br¨ ohl, K. F-V52 Thewes, C. M-P179 Thieme, J. M-P104, M-P107, M-P112 Thieß, S. M-V23 Thißen, A. M-P177 Thomas, A. D-P255 Thomas, H. D-P361 Thornagel, R. M-P86 Tiedtke, K. M-P67 Tietze, U. M-P78 Tischer, M. M-P83, D-V25 Tiutiunnikov, S. D-P223 Tjeng, L.H. M-P156 Toimil-Molares, M.E. D-P271 Tolan, M. M-P9, M-P17, M-P63, MP162, M-P194, D-V30, D-P340, D-P346, D-P404 Toleikis, S. D-V43

Tolkiehn, M. M-P38 Tomkowicz, Z. D-P239 Toperverg, B. D-P218, D-P295, F-V52 Torregrossa, J. M-P26 Tortorella, D. D-P412 Tovar, M. M-V17, D-P234 Tr¨ ankenschuh, B. F-V65 Trampert, A. D-P268 Trautmann, C. M-V10, D-V33, D-P310, D-P312, F-PV11, F-V46 Treimer, W. M-P32, M-P81, M-P82, D-V38 Tremel, W. D-P304 Troc, R. D-P392 Tropin, T.V. D-P370 Trots, D. M-P129, D-P382 Trounov, V. M-P1, D-P369 Troyanchuk, I. D-P223, D-P261 Trunova, V. D-P371 Tschentscher, T. M-P118 Tse, J. M-P150, D-P404 Tserkovna, E. D-P369 Tsirelson, V. M-P132 Tucker, P.A. M-P203, M-P210 T¨ urker, M. M-V19 Uchida, S. D-P253 Uhlmann, P. D-P342 Ullemeyer, K. M-P84, F-V51 Ullmann, K. M-P21 Ulm, G. M-P6, M-P57, M-P85, M-P86, D-P371 Ulrich, V. D-P285 Umbach, E. M-P3, M-V3, M-P90, MP160, D-P286, D-P291, D-P302, D-P313 Unruh, T. M-P163, D-P354, D-P356, D-P364 Vadala, M. D-P218 Vaidya, W.V. D-P403 Valldor, M. M-P164, D-P254 Valloppilly, S. D-P351 Vank´ o, G. D-P404 Vartaniants, I. M-P110, M-P113, M-P213 Vass, E. M-P175 Vecchini, C. M-V16

Index Vehoff, T. D-P333 Veira, J.R. D-P262 Vekas, L. D-P357 Ventzke, V. D-P389, D-P391 Vianden, R. D-P394 Viefhaus, J. M-P87, D-P362 Vijayalakshmi, S. M-P130 Vill, V. D-P330, D-P341 Vitta, C. di M-P192 Vlooswijk, A. D-P318 Vogel, H. D-P382 Vogel, J. M-V13 Vogel, M. D-P294 Vogl, G. M-P148 Vogl, J. D-P397 Volkov, A. D-P312 Vollbrandt, J. M-P97 Vollrath, F. D-P350 Volmer, M. M-P63 Voss, K.-O. D-P312 Vrakking, M.J. J. D-P293, D-P308 Vyalikh, D. D-P223 Wabnitz, H. D-P361 Wagermaier, W. F-V59 Wagner, F. D-P406 Wagner, G¨ unther A. D-V33 Wagner, M. D-P387 Wagner, T. D-P288 Wald, D. M-P21 Wallacher, D. M-P88 Walter, G. F-V46 Walter, H. M-P68, D-P307 Walter, J.M. M-P89, D-P399, F-V51 Walther, K. M-V20 Walz, M. D-P359 Wanderka, N. M-P146 Wang, J. D-P236 Wang, Y. M-P127 Wang, Z. D-P282 Ward, R. D-P229 Wartewig, S. M-P212 Wasserthal, L.T. F-V55 Weber, F. M-P165 Weber, U. M-P100 Weckert, E. M-P33, M-P69, M-P110,

M-P166, M-P213, D-V25 Weidemann, G. M-P109 Weier, D. D-P319 Weigand, M. M-P90 Weinhardt, L. M-P90 Weis, T. M-P9 Weiss, M. M-P28, M-P203, M-P210, F-V56 Weißer, M. D-V37 Weissm¨ uller, J. M-V16, D-P263 Weitkamp, T. M-P91, M-P109, M-P114 Wellenreuther, G. M-P127, M-P211 Wellh¨ ofer, M. M-P92 Welter, E. M-P12, M-P47, M-P93, M-P136 Wende, H. D-P243 Wenzel, B. M-P11 Wermeille, D. D-P233 Werner, L. M-P125 Wernet, P. M-V6 Weschke, E. D-P264 Weseloh, G. M-P49 Weser, J. M-P6 Westerholt, K. M-P149, D-P218, D-P245 Westphal, C. M-P7, M-P8, M-P9, D-P314, D-P319 Weyer, G. D-P257 Wichert, T. M-V19, D-P406 Wiedenmann, A. M-V15, D-P247, D-P248 Wiedwald, U. D-P265 Wieland, M. M-P14 Wieschalla, N. D-P407 Wildes, A. D-P229 Wilhein, T. M-P14 Wille, K. M-P9 Willumeit, R. M-P197, D-P330, DP341, D-P393 Wilmanns, M. M-P190, F-V56 Wilpert, T. D-P413 Wimpory, R. M-P96, D-P386, D-P408 Winkler, A. D-P234, F-V69 Winter, R. M-P194 Wobrauschek, P. M-P20

Index Wochner, P. F-V68 Woiterski, L. D-P358 Wolf, H. M-V19, D-P406 Wolff, M. M-P94, D-P218, D-P353, D-P359, F-V52 Wolkenhauer, M. D-P360 Wollmann, D. D-V37 Wong, J.E. D-V29 Wontcheu, J. D-P409 Wortmann, G. D-P365, D-P367 Wrba, F. M-P189 Wroblewski, T. M-P95, D-V25, D-P390, D-P407 Wu, K. M-P103 Wulf, M. D-P341 Wurth, W. M-P59, M-P92, M-P130, D-P240, D-P243, D-P294 Xu, S. M-P103 Yakhou, F. D-P231 Yamaguchi, T. D-P311 Ye, W. D-P378 Yi, S.-B. D-P377 Yoshida, Y. D-P257 Yurkov, M. M-P23 Zabel, H. M-PV1, M-P94, M-P149, DP218, D-P231, D-P244, D-P245, D-P251, D-P252, D-P359, F-V52 Zabler, S. M-P109 Zacharias, H. M-P71, M-P179 Zafeiratos, S. M-P175 Zahn, D.R.T. M-P135, D-P276, DP296, D-P320 Zajac, D.A. D-P266 Zamudio-Bayer, V. D-P294 Zandt, T. M-P50, M-P172 Zbytovsk´ a, J. M-P212 Zegenhagen, J. M-V23, D-P277, D-P316 Zegkinoglou, I. D-P215, D-P219, DP259, F-V67 Zehl, G. D-P284 Zehnder, M. M-P213 Zeitoun, P. D-V43 Zen, A. D-P338 Zhao, J. M-P159, D-V44

Zharnikov, M. M-P90 Zheng, M. M-P103 Ziaja-Motyka, B. M-P166 Zibrowius, B. M-P151 Ziegler, E. M-P91 Ziemann, P. D-P265 Zilly, F. M-P96 Zimmer, O. D-P412 Zimmermann, M. von D-P215, D-P219, D-P368, F-V67 Zizak, I. M-P29, M-P167, D-P272, D-P398 Zou, Y. D-P313 Zschau, H.-E. D-P410 Zumkley, T. M-P146

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8:00

Mittwoch, 4. Oktober 2006 Registrierung

Donnerstag, 5. Oktober 2006 8:30

Freitag, 6. Oktober 2006 8:30

Plenarvortr¨ age: Butz, Pyzalla 9:30 10:00 10:30 11:00

9:40 Begr¨ ußung Plenarvortrag: Zabel Kaffeepause

9:40 Parallelsitzungen: Instrumentierung, Weiche Materie, Materialien

10:40 11:10

Parallelsitzungen: Mikroskopie/Tomographie, Dynamik, Nanostrukturen und Grenzfl¨ achen 12:30

Parallelsitzungen: Biologie, Magnetismus, Materialien, Weiche Materie 10:40

Kaffeepause

11:10

Parallelsitzungen: Methoden und Instrumentierung S, N, SNI 12:30

Mittagspause

Plenarvortr¨ age: M¨ uller,Braun

13:00

Kaffeepause Parallelsitzungen: Biologie, Magnetismus, Chemische Prozesse

12:30 Mittagspause

Mittagspause

Postersitzung B Magnetismus, Nano/Grenzfl¨ achen, Weiche Materie, extreme Bedingungen, Materialien, Teilchen und Kerne

14:00 Postersitzung A Instrumentierung, Biologie, Struktur/Dynamik, Chem. Prozesse, Mikroskopie/Tomographie

15:30

15:30 SNI f¨ ur Neugierige Salditt, Kuhs, Dollinger

Plenarvortr¨ age: Meyer,Fink

17:00

Parallelsitzungen: Magnetismus, Struktur, Nanostrukturen und Grenzfl¨ achen

18:00

16:00

Schlusswort Bustransfer zu DESY und GKSS Besichtigungen von DESY und GKSS

Bustransfer ins Rathaus

17:30

Senatsempfang im Rathaus Grußworte: Dr¨ ager/Austermann Vortrag: Dosch

19:00 Verleihung Wolfram-Prandl-Preis

Plenarvortr¨ age: Feldhaus, Neuhaus, Altarelli, Trautmann 14:55

16:30

19:30

13:35

19:30 Buffet

19:00

R¨ uckkehr/Ankunft am Bahnhof bzw. Flughafen