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ANNUAL REPORT

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FACULTY OF

MATERIALS AND EARTH SCIENCES

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Annual Report 2003

Faculty 11 Materials and Earth Sciences

Materials Science: Petersenstraße 23 • L2 01 • 64287 Darmstadt

Phone 06151/16 53 77 • Fax 06151/16 55 51 http://www.tu-darmstadt.de/fb/ms/

Earth Sciences:

Schnittspahnstraße 9 • B2 01/02 • 64287 Darmstadt Phone 06151/16 25 71 • Fax 06151/16 65 39

http://www.tu-darmstadt.de/fb/geo/

for further information contact: Dr. Joachim Brötz, Phone 06151/16-4392; e-mail: broetz@tu-darmstadt.de

Dr. Wieland Weise, Phone 06151/16-6250; e-mail: weise@e-mat.tu-darmstadt.de

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1. PREFACE 4 2. MATERIALS SCIENCE

Physical Metallurgy 7 Ceramics Group 15

Electronic Material Properties 18 Surface Science 21

Thin Films 25 Dispersive Solids 28 Structure Research 33

Chemical Analytics 40 Theoretical Materials Science 43

Materials Modelling 46

Collaborative Research Centre (SFB) 48 Reports of Research Activities 51

Diploma Theses 89 PhD Theses 91

Habilitations 92 3. EARTH SCIENCES

Institute of Applied Earth Sciences

Physical Geology and Global Cycles 93 Hydrogeology 97 Engineering Geology 98 Applied Sedimentology 100 Georesources and geohazards 102

Geomaterials Science 104 Technical Petrology 106 Environmental Mineralogy 110

Institute of Geography Human Geography 112

Reports of Research Activities 114 Diploma and Magister Theses 140

PhD Theses 141

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Preface by Hartmut Fuess,

Dean of the Faculty of Materials and Earth Sciences

The present situation in teaching and research in Germany is characterized by uncertainty, controversial discussions and contradictory suggestions. Here, we shall not resume the various suggestions by individual politicians and the Federal Government, but only make a few remarks concerning Darmstadt University of Technology, and hence the Faculty, directly. The State of Hesse is currently preparing a law which will grant almost full autonomy to the University, and thus strengthen the position of the President considerably. Control will mainly be exercised by the University Council including ten external personalities from science and industry. This new and extremely powerful role of the University Administration calls for a reorganization of the interrelations between the various faculties and the central authorities: the envisaged autonomy must be shared by all faculties to a great extent. Fruitful discussions on this matter are expected for the time ahead. Turning to the Materials and Earth Sciences, where considerable progress can be scored. The Collaborative Research Centre (SFB) “Electric Fatigue of Functional Materials“ under the chairmanship of Professor Jürgen Rödel, which took off in 2003, looks back to its first year of successful operation. The Research Project “Solar Cells“, which was initiated by Professor Wolfram Jaegermann, proved to be another major acquisition in 2003, funded by the Federal Ministry of Economy. Both activities lead to an increase of external funds in 2003, totalling over six million Euros for Materials Science, as documented in Fig. 1.

Fig. 1: Breakdown of external funds raised for Materials Science at Darmstadt University of Technology during the past seven years.

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On 18 October 2003, the Institute of Materials Science organized a one day exhibition entitled “The World of Materials“, which demonstrated the multifarious uses of materials to a group of over 400 interested visitors. The Institute of Applied Earth Sciences concentrated its research efforts in projects on water supplies in the Ebro region and on environmental research. Professor Matthias Hinderer was granted an extension of funds for research within the International Continental Drilling Project jointly conducted with partner institutions in Freiburg and Hanover. Professor Stephan Weinbruch participated in the Research Training Group of the University of Mainz entitled “Trace Analysis of Element Species“ and in the Research Group “Saharan Mineral Dust Experiment“, which was recently approved by the German Research Foundation (DFG). Over and above that, he was actively involved in the Collaborative Research Centre (SFB) “The Tropospheric Ice Phase“, inaugurated together with the universities of Frankfurt and Mainz and the Max Planck Institute for Chemistry in Mainz. An even closer cooperation between these institutions and Darmstadt University of Technology within the framework of a Rhine-Main Research Centre solely devoted to the Earth Sciences is now being actively discussed. Jürgen Eckert from the Institute for Solid State and Materials Research in Dresden was appointed Professor of Physical Metallurgy from 1 October 2003, following the retirement of Professor Hans Eckart Exner on 30 September 2003 which was celebrated by an official act in the University’s Georg-Christoph-Lichtenberg-Haus on 14 October 2003, prior to the Materials Day organized by Professor Holger Hanselka and Professor Jürgen Rödel within the frame of the Rhine-Main Materials Research Network MatForm on 15 October 2003.

Fig. 2: Number of freshers in the Natural and Engineering Sciences at Darmstadt University of Technology during the past twenty-four years.

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Despite having been offered a chair at Hanover University, Professor Matthias Hinderer resolved to stay at Darmstadt University of Technology. He was promoted to a C4 post and elected Director of the Institute of Applied Earth Sciences for the period from 2003 to 2005. Three young colleagues, Dr. Andreas Klein (Surface Science), Dr. Branko Stahl (Thin Films) and Dr. Imre Demhardt (Anthropogeography) obtained their Habilitation in 2003. The situation of first year undergraduates in Materials Science remained fairly constant during the past years; on the other hand, a considerable increase in the number of freshers can be stated for the Applied Earth Sciences, as demonstrated in Fig. 2. This year saw the highest number of Diplomas in Materials Science wheras the Doctorates varies little over the years, as appears from Fig. 3. Noteworthy is the relatively large number of successful final exams in Geography; a possible sign of the demand of this discipline in our university.

Fig. 3: Number of graduates in Materials and Earth Sciences at Darmstadt University of Technology during the past four years. The German Science Council visited the University on 28 and 29 October 2003. After discussions with members of all faculties, this organization decided to work out a proposal for restructuring the various departments. Such a proposal might not, however, entail immediate actions, bearing in mind the ongoing discussions referred to above, which are closely associated with budgeting problems. This year, the annual prize for the best Diploma in Materials Science went to Jürgen Ell (Surface Science). Professor Hartmut Fuess was awarded an honorary doctorate in Chemical Sciences by Bratislava University of Technology; Professor Jürgen Rödel was elected a Fellow of the American Ceramic Society.

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Institute of Materials Science

Physical Metallurgy The emphasis of the research and teaching activities in the Division of Physical Metallurgy is on the correlation between the basic mechanisms and processes governing phase formation, microstructure development, processing methods and the resulting structural and functional properties of metallic materials. The main focus of the research is to qualitatively and quantitatively describe the properties of the materials as well as their performance in technological applications on the basis of phase formation-microstructure-property relations. This includes attempts to predict the influence of process variables on materials properties during and after solidification, solid state reaction, densification, heat treatment, forming and shaping. Modelling and numerical simulation of casting processes, recrystallization, sintering, forging, sheet drawing, and chip formation, as well as microstructure-based modelling of mechanical properties reaching from uniaxial deformation to fatigue testing are covered. In all cases, experimental results are linked with theoretical considerations in order to rationalize the correlation between processing, testing and modelling and to derive guidelines for further optimization of the properties of the materials. New methods for the quantitative description of microstructure and surface morphology are investigated and strategies for the development of new materials with improved properties are developed. The ongoing work in the Physical Metallurgy Division deals with titanium, aluminium and magnesium-based light alloys, steel, solders, precious and hard metals, superalloys, fibre strengthened aluminum, soldering alloys, and other multicomponent alloys. Fatigue, wear, corrosion and their complex interactions are investigated. Progress in the area of microstructure-based processing for properties was achieved in the fields of titanium alloys for artificial joints, new alloys for electrical contacts, lead free solders and functionally graded materials. Improvements in the understanding of solidification, remelting, ion implantation, nucleation and recrystallization phenomena lead to optimization of alloys for a variety of applications. Besides these activities, the research in Physical Metallurgy will be broadened by the appointment of Prof. Jürgen Eckert (formerly Leibniz-Institute for Solid State and Materials Research Dresden) as new Head of the Division following the retirement of Prof. Hans Eckart Exner. This implements new activities in the area of metastable metallic materials, such as for example bulk metallic glasses, nanostructured materials and advanced composites, for structural applications as new high strength-high elasticity materials as well as for use as functional materials with promising properties for magnetic applications, catalysis, hydrogen storage or as electrode materials. The activities in the area of metastable phase formation by solidification as well as through solid state processing will be further strengthened and the investigations on the developing microstructures and the

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properties of these new materials will be linked with the ongoing research on well-established metallic materials already in use. Teaching covers lectures on mechanical properties of engineering materials and fundamentals of deformation and fracture, phase formation, phase diagrams and phase transformations, solidification and heat treatment mechanisms, solid state processing and quantitative image analysis for the characterization of microstructures. Extensive laboratory exercises on all levels are offered to facilitate and intensify the technical understanding in these topics and to improve the practical skills for investigating metallic materials. Cooperation with other groups in the Institute and with other Departments of Darmstadt University of Technology, particularly with those of Mechanical Engineering, Technical Mechanics, Chemistry, and Physics, as well as with other universities and research laboratories in Germany (Aachen, Berlin, Chemnitz, Dresden, Dortmund, Göttingen, Kaiserslautern, Karlsruhe, Jülich, Ulm etc.), within Europe (Austria, Denmark, France, Italy, Poland, Romania, Slovak Republic, Switzerland, The Netherlands, UK etc.) and abroad (Australia, China, India, Japan, Korea, Russia, South Africa, Ukraine, USA and others) as well as with industry (Acheson, Adam Opel AG, Daimler-Chrysler, Degussa-Hüls, H.C. Starck, Heraeus, Hirschvogel, Liquidmetal Inc., Umicore, among others) give opportunities for scientific and personal exchange. Participation in national and international conferences, seminars and workshops facilitates exchange of ideas and scientific communication, which aids the actuality of teaching and research, fosters collaborations and promotes exchange of scientists and students.

Staff Members Head Prof. Dr.-Ing. Jürgen Eckert (since October 1, 2003) Prof. Dr. mont. Dr. h.c. Hans Eckart Exner (until September 30,

2003) Research Associates Dr.-Ing. Bhaskar Dutta PD Dr.-Ing. Clemens Müller PD Dr. rer.nat. Markus Rettenmayr Technical Personnel Ulrike Kunz Heinz Lehmann Petra Neuhäusl Claudia Wasmund Secretary Christine Hempel PhD Students Dipl.-Ing. Martin Buchmann Dipl.-Ing. Christian Dindorf Dipl.-Ing. Thorsten Keller Dipl.-Ing. Arne Kriegsmann Dipl.-Ing. Steffen Landua Dipl.-Ing. Peter Marx

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Dipl.-Ing. Michael Nimz Dipl.-Ing. Klaus Wintrich Dipl.-Ing. Uwe Zeigmeister Dipl.-Ing. Guoping Zhao Diploma Students Christoph Betz Fanny Juigner Dirk Wittig Guest Scientists Dr. Radhakrishnan Sumathi

Research Projects Bulk Metallic Glasses and Composites (EU-MCF, 2002-2006)* Characterization of Chip Formation at Short Time Loading during High Speed Cutting (DFG, 1998-2004) Crack Propagation and Crack Closure in Microstructures with Graded Deformation (2002-2005) Fatigue Strength Improvement of High-Strength Magnesium Wrought Alloys Regarding Their Mechanochemical Behavior (Adam Opel, Rüsselsheim, 2002-2005) Formation, Structure and Properties of Magnetic Bulk Metallic Glasses (DFG-NSFC, 2002-2004)* High Temperature Properties of Platinum Materials (OMG / umicore, Hanau, 2002-2004) Microstructural and Mechanical Properties of Ramified Sheet Structures (project submitted as part of DFG-SFB) Nd-base Alloys (DFG, 2001-2004)* Optimization of Abrasive and Wear Behavior of Tool Surfaces through Selective Surface Hardening (joint research project submitted with AIF) Partition Coefficients in Multicomponent Alloys (DAAD, 2000-2004) Solutal Melting (DFG, 2002-2004) Storage and Permeability of Hydrogen in Metals (Daimler-Chrysler, Ulm, 2000-2003) (* managed via the Leibniz-Institute for Solid State and Materials Research Dresden)

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Publications Bab, M.A.; Damonte, L.C.; Mendoza-Zélis, L.A.; Deledda, S.; Eckert, J.; Nanocrystalline ZrN Particles Embedded in Zr-Fe-Cu-Al-Ni Amorphous Matrix, in: Supercooled Liquids, Glass Transition and Bulk Metallic Glasses, (Hrsg. T. Egami, A.L. Greer, A. Inoue, S. Ranganathan). Mater. Res. Soc. Symp. Proc. 754 (2003) 211-214. ���������� ���������� �������� ��Eckert, J.; Co-Based Soft Magnetic Bulk Amorphous Ferromagnets Prepared by Powder Consolidation, Phys. Stat. Sol. (a) 199 (2003) 299-304. Borrego, J.M.; Conde, A.; Roth, S.; Eckert, J.; Soft Magnetic Properties of FeCoSiAlGaPCB Amorphous Alloys, J. Magn. Magn. Mater. 254-255 (2003) 444-446. Calin, M.; Eckert, J.; Schultz, L.; High-Strength Cu-Ti-Rich Bulk Metallic Glasses and Nano-Composites, Z. Metallkde. 94 (2003) 615-620. Calin, M.; Eckert, J.; Schultz, L.; Improved Mechanical Behavior of Cu-Ti-Based Bulk Metallic Glass by in situ Formation of Nanoscale Precipitates, Scripta Mater. 48 (2003) 653-658. Damonte, L.C.; Mendoza-Zélis, L.A.; Deledda, S.; Eckert, J.; Effect of Preparation Conditions on the Short-Range Order in Zr-Based Bulk Glass-Forming Alloys, Mater. Sci. Eng. A343 (2003) 194-198. Daniel, B.S.S.; Heilmaier, M.; Bartusch, B.; Kanzow, J.; Günther-Schade, K.; Rätzke, K.; Eckert, J.; Faupel, F.; Free Volume Evolution in Bulk Metallic Glass during High Temperature Creep, in: Supercooled Liquids, Glass Transition and Bulk Metallic Glasses, (Hrsg. T. Egami, A.L. Greer, A. Inoue, S. Ranganathan). Mater. Res. Soc. Symp. Proc. Proc. 754 (2003) 293-298. Das, J.; Güth, A.; Klauß, H.-J.; Mickel, C.; Löser, W.; Eckert, J.; Roy, S.K.; Schultz, L.; Effect of Casting Conditions on Microstructure and Mechanical Properties of High-Strength Zr73.5Nb9Cu7Ni1Al9.5 In-Situ Composites, Scripta Mater. 49 (2003) 1189-1195. Das, J.; Löser, W.; Kühn, U.; Eckert, J.; Roy, S.K.; Schultz, L.; High-Strength Zr-Nb-(Cu, Ni, Al) Composites with Enhanced Plasticity, Appl. Phys. Lett. 82 (2003) 4690-4692. Deledda, S.; Eckert, J.; Schultz, L.; Crystallization Behavior of Mechanically Alloyed Zr-Cu-Al-Ni Glass Composites Containing Second-Phase ZrC Particles, in: Supercooled Liquids, Glass Transition and Bulk Metallic Glasses, (Hrsg. T. Egami, A.L. Greer, A. Inoue, S. Ranganathan). Mater. Res. Soc. Symp. Proc. Proc. 754 (2003) 385-390. Dindorf, C.; Müller, C.; Corrosion and Fatigue Behavior of the Magnesium Die-Cast Alloy AZ91 hp after Surface Treatment, in K.U. Kainer (ed.) „Magnesium, Proc. of the 6th Int. Conf. Magnesium Alloys and their Applications”, Wiley-VCH, Weinheim, Germany, ISBN 3-527-30975-6 (2003) 271-278. Dutta B., Palmiere, E.J.; Effect of Prestrain and Deformation Temperature on the Recrystallisation Behaviour of Nb-microalloyed Steels, Metallurgical Transactions 34A (2003), 1237-1247.

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Eckert, J.; Bartusch, B.; Gebert, A.; The Effect of Nanosized Y2O3 as a Second Phase in Mechanically Alloyed Mg-Y-Cu Glass Matrix Composites, J. Metastable and Nanocrystalline Materials 15-16 (2003) 37-42. Eckert, J.; He, G.; Das, J.; Löser, W.; Nanostructured Composites in Multicomponent Alloy Systems, Mater. Trans. 44 (2003) 1999-2006. Eckert, J.; Perner, O.; Fuchs, G.; Nenkov, K.; Müller, K.-H.; Häßler, W.; Fischer, C.; Holzapfel, B.; Schultz, L.; High Critical Fields and Currents in Mechanically Alloyed MgB2, in: Advances in Solid State Physics, Vol. 43, (Hrsg. B. Kramer), Springer Verlag, Berlin (2003) 703-718. Eckert, J.; Schurack, F.; Schultz, L.; Synthesis and Mechanical Properties of High Strength Aluminum-Based Quasicrystalline Composites, J. Metastable and Nanocrystalline Materials 15-16 (2003) 245-252. Exner, E.; Rettenmayr , M; Komplexe Grenzflächengeometrien bei Phasenumwandlungen, in Sonderbände der Praktische Metallographie G. Petzow (ed.) vol. 34, Progress in Metallography, A. Kneissl, F. Jeglitsch (eds.), MatInfo Werkstoffinformationsgesellschaft, Frankfurt (2003) 3-14. Fischer, C.; Rodig, C.; Häßler, W.; Perner, O.; Eckert, J.; Nenkov, K.; Fuchs, G.; Wendrock, H.; Holzapfel, B.; Schultz, L.; Preparation of MgB2 Tapes using a Nanocrystalline Partially Reacted Precursor, Appl. Phys. Lett. 83 (2003) 1803-1805. Fuchs, G.; Drechsler, S.L.; Müller, K.-H.; Handstein, A.; Shulga, S.V.; Behr, G.; Gümbel, A.; Eckert, J.; Nenkov, K.; Narozhnyi, V.N.; Schultz, L.; Eschrig, H.; Otani, S.; Rosner, H.; Pickett, W.E.; A Comparative Study of MgB2 and other Diborides, J. Low-Temp. Phys. 131 (2003) 1159-1163. Grahl, H.; Roth, S.; Eckert, J.; Schultz, L.; Stability and Magnetic Properties of Fe-Based Amorphous Alloys with Supercooled Liquid Region, J. Magn. Magn. Mater. 254-255 (2003) 23-25. Gümbel, A.; Perner, O.; Eckert, J.; Fuchs, G.; Nenkov, K.; Müller, K.-H.; Schultz, L.; High Density Nanocrystalline MgB2 Bulk Superconductors with Improved Pinning, IEEE Trans. Appl. Supercond. 13 (2003) 3064-3067. Häßler, W.; Rodig, C.; Fischer, C.; Holzapfel, B.; Perner, O.; Eckert, J.; Nenkov, K.; Fuchs, G.; Low Temperature Preparation of MgB2 Tapes using Mechanically Alloyed Powder, Supercond. Sci. Technol. 16 (2003) 281-284. He, G.; Eckert, J.; Dai, Q.L.; Sui, M.L.; Löser, W.; Hagiwara, M.; Ma, E.; Nanostructured Ti-Based Multi-Component Alloys with Potential for Biomedical Applications, Biomaterials 24 (2003) 5115-5134. He, G.; Eckert, J.; Löser, W.; Schultz, L.; Ductile Dendritic Phase Reinforced Ti-Base Bulk Metallic Glass-Forming Alloys, in: Supercooled Liquids, Glass Transition and Bulk Metallic Glasses, (Hrsg. T. Egami, A.L. Greer, A. Inoue, S. Ranganathan). Mater. Res. Soc. Symp. Proc. Proc. 754 (2003) 327-333.

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He, G.; Eckert, J.; Löser, W.; Schultz, L.; Novel Ti-Base Nanostructure-Dendrite-Composite with Enhanced Plasticity, Nature Mater. 2 (2003) 33-37. He, G.; Eckert, J.; Löser, W.; Stability, Phase Transformation and Deformation Behavior of Ti-Base Metallic Glass and Composites, Acta Mater. 51 (2003) 1621-1631. He, G.; Löser, W.; Eckert, J.; In-Situ Formed Ti-Cu-Ni-Sn-Ta Nanostructure-Dendrite Composite with Large Plasticity, Acta Mater. 51 (2003) 5223-5234. He, G.; Löser, W.; Eckert, J.; Microstructure and Mechanical Properties of the Zr66.4Cu10.5Ni8.7Al8Ti6.4 Metallic Glass-Forming Alloy, Scripta Mater. 48 (2003) 1531-1536. He, G.; Löser, W.; Eckert, J.; Schultz, L.; Phase Transformation and Mechanical Properties of Zr-Base Bulk Glass-Forming Alloys, Mater. Sci. Eng. A352 (2003) 179-185. He, G.; Zhang, Z.F.; Löser, W.; Eckert, J.; Schultz, L.; Effect of Ta on Glass Formation, Thermal Stability and Mechanical Properties of a Zr52.25Cu28.5Ni4.75Al9.5Ta5 Bulk Metallic Glass, Acta Mater. 51 (2003) 2383-2395. Hillert, M. ; Rettenmayr, M.; Deviations From Local Equilibrium at Migrating Phase Interfaces, Acta Materialia 51 (2003) 2803-2809. Kühn, U.; Eckert, J.; Mattern, N.; Radtke, N.; Schultz, L.; Microstructure and Mechanical Properties of Slowly Cooled Zr66.4Nb6.4Cu10.5Ni8.7Al8.0 with Ductile bcc Phase, in: Supercooled Liquids, Glass Transition and Bulk Metallic Glasses, (Hrsg. T. Egami, A.L. Greer, A. Inoue, S. Ranganathan). Mater. Res. Soc. Symp. Proc. Proc. 754 (2003) 333-338. Kumar, G.; Eckert, J.; Löser, W.; Roth, S.; Schultz, L.; Effect of Al on Microstructure and Magnetic Properties of Mould-Cast Nd60Fe40-xAlx Alloys, Scripta Mater. 48 (2003) 321-325. Kumar, G.; Eckert, J.; Roth, S.; Löser, W.; Schultz, L.; Ram, S.; Effect of Microstructure on the Magnetic Properties of Mold-Cast and Melt-Spun Nd-Fe-Co-Al Amorphous Alloys, Acta Mater. 51 (2003) 229-238. Kumar, G.; Eckert, J.; Roth, S.; Müller, K.-H.; Schultz, L.; Coercivity Mechanism in Mold-Cast Nd60FexCo30-xAl10 Bulk Amorphous Alloys, J. Alloys & Compounds 348 (2003) 309-313. Kunz, U.; Thomas, S.; Vulpius, W.; Müller, C.; Einfluss eines Deformationsgradienten auf Rekristallisation und Kornwachstum in Titan Grad 2, in A. Kneißl, F. Jeglitsch (eds.), Fortschritte in der Metallographie, Werkstoff-Informationsgesellschaft, Frankfurt, Germany, ISBN 3-88355-313-1 (2003) 251-258. Müller, C.; Burghardt, B.; Crack Propagation and its Computation in Graded Microstructures of a Near-α-Titanium Alloy, accepted for publication in Proc. of 10th World Conference on Titanium, Hamburg (2003). Müller, C.; Burghardt, B.; Exner, E.; Methode zur Berechnung der Rissausbreitung in Gradientengefügen, in A. Kneißl, F. Jeglitsch (eds.), Fortschritte in der Metallographie,

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Werkstoff-Informationsgesellschaft, Frankfurt, Germany, ISBN 3-88355-313-1 (2003) 389-398. Müller, C.; Rodríguez, R.; Influence of Shot Peening on the Fatigue and Corrosion Behavior of the Die Cast Magnesium Alloy AZ91 hp, in L. Wagner (ed.), Shot Peening, Wiley-VCH, Weinheim, Germany, ISBN 3-527-30537-8 (2003) 271-278. Palmiere, E.J.; Dutta, B.; Strain-induced Precipitation of Nb(CN) in Low Carbon Steels : Modelling and Experimental Validation, Proceedings of the THERMEC' 2003, Madrid, Spain (2003). Rettenmayr, M.; Reply: Discussion on Local Equilibrium at Solid/Liquid Interfaces During Melting, Scripta Materialia 48 (2003) 315-319. Rettenmayr, M.; Song, X.; Modelling Microstructure Evolution During Annealing of an Inhomogeneously Deformed Material, Materials Science and Technology 19 (2003) 173-177. Rettenmayr, M; Oechsle, M.; Zeuner, S.; Krebs, W.; Eigenschaften von dispersionsverfestigten Platinwerkstoffen, Glas-Ingenieur 13 (2003) 52-58. Saage, G.; Roth, S.; Eckert, J.; Schultz, L.; Low Magnetostriction Crystalline Ribbons Prepared by Melt Spinning and Reactive Annealing, J. Magn. Magn. Mater. 254-255 (2003) 26-28. Schurack, F.; Eckert, J.; Schultz, L.; AlMnCe Quasicrystalline Composites – Phase Formation and Mechanical Properties, Philos. Mag. 83 (2003) 807-825. Schurack, F.; Eckert, J.; Schultz, L.; Synthesis and Mechanical Properties of Mechanically Alloyed Al-Cu-Fe Quasicrystalline Composites, Philos. Mag. 83 (2003) 1287-1305. Schurack, F.; Eckert, J.; Schultz, L.; Synthesis and Mechanical Properties of Quasicrystalline Al-Based Composites, in: Quasicrystals: Structure and Physical Properties, (Hrsg. H.-R. Trebin). Wiley-VCH Publications, Weinheim (2003) 551-569. Schwabe, D.; Sumathi, R.R.; Wilke, H.; A Combined Experimental and Numerical Effort to Simulate the Large Interface Deflection of YAG and to Study the Parameters for Growth with Flat Interface, in print, J. Crystal Growth (2003). Scudino, S.; Eckert, J.; Kühn, U.; Schultz, L.; Formation of Quasicrystals in Zr-Ti-Nb-Cu-Ni-Al Melt-Spun and Ball-Milled Multicomponent Alloys, J. Metastable and Nanocrystalline Materials 15-16 (2003) 67-72. Scudino, S.; Eckert, J.; Kühn, U.; Schultz, L.; Formation of Quasicrystals by Partial Devitrification of Ball-Milled Amorphous Zr57Ti8Nb2.5Cu13.9Al7.5, Appl. Phys. Lett. 83 (2003) 2345-2347. Song, X.; Rettenmayr, M.; Liu, G.; 3D Simulation Study of Inhomogeneous Microstructure and its Evolution, Image Analysis & Stereology 22 (2003) 163-169.

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Song, X.; Rettenmayr, M.; Liu, G.; 3D Visual Simulation Study of Inhomogeneous Microstructure and its Evolution, Proceedings of International Conference on Stereology (2003). Song, X.; Rettenmayr, M.; Study on the Effects of a Deformation Gradient on Re-crystallization in a Material Containing Precipitates, Scripta Materialia 48 (2003) 1123-1128. Subba Rao, R.V.; Wolff, U.; Baunack, S.; Eckert, J.; Gebert, A.; Corrosion Behaviour of the Amorphous Mg65Y10Cu15Ag10 Alloy, Corrosion Science 45 (2003) 817-832. Subba Rao, R.V.; Wolff, U.; Baunack, S.; Eckert, J.; Gebert, A.; Stability of the Mg65Y10Cu15Ag10 Metallic Glass in Neutral and Weakly Acidic Media, J. Mater. Res. 18 (2003) 97-105. Sumathi, R.R.; Senthil Kumar, M.; Kumar, J.; Barium Titanate as a Good Insulator for InP and GaN MIS Device Applications, Proceedings of the International School on Crystal Growth of Technologically Important Electronic Materials (ISCGTIEM-2003), Mysore, India, Allied Publishers Limited, 184-188. Sun, L.L.; Wang, W.K.; Wang, L.M.; Kikegawa, T.; Wu, Q.; Zhang, J.; Fan, C.Z.; Eckert, J., L. Schultz, L.; Structural Evaluation of Fe60Co10Zr8Mo5Nb2B15 Metallic Glass under High Pressure, Phys. Rev. B 68 (2003) 052302-1-052302-4. Sun, Z.G.; Löser, W.; Eckert, J.; Müller, K.-H.; Schultz, L.; Effect of Cooling Rate on Microstructure and Magnetic Properties of Nd60Fe30Al10 Hard Magnetic Alloys, J. Magn. Magn. Mater. 261 (2003) 122-130. Tamirisakandala, S.; Yellapregada, P.V.R.K.; Medeiros, S. C.; Frazier, W.G.; Malas, J.C.; Dutta, B.; High Speed Deformation Processing of a Titanium Alloy, Advanced Engineering Materials 5 (2003) 667-669. Thomas, S.; Jung, S.; Nimz, M.; Müller, C.; Groche, P.; Exner, E.; Models and Experiments Describing Deformation, Roughness and Damage in Metal Forming, in K. Hutter, H. Baaser (eds.), Deformation and Failure in Metallic Materials, Springer Verlag, Berlin, Germany, ISBN 3-540-00848-9 (2003) 323-343. Zhang, Z.F.; Eckert, J.; Schultz, L.; Difference in Compressive and Tensile Fracture Mechanisms of Zr59Cu20Al10Ni8Ti3 Bulk Metallic Glass, Acta Mater. 51 (2003) 1167-1179. Zhang, Z.F.; Eckert, J.; Schultz, L.; Tensile and Fatigue Fracture Mechanisms of a Zr-Based Bulk Metallic Glass, J. Mater. Res. 18 (2003) 456-465. Zhang, Z.F.; He, G.; Eckert, J.; Schultz, L.; Fracture Mechanisms in Bulk Metallic Glassy Materials, Phys. Rev.Lett. 91 (2003) 045505-1-045505-4. Zhang, Z.F.; Wang, Z.G.; Eckert, J.; What Types of Grain Boundaries can be Passed Through by Persistent Slip Bands?, J. Mater. Res. 18 (2003) 1031-1034.

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Ceramics Group The emphasis in the ceramics group is on the correlation between microstructure and mechanical as well as functional properties. A number of processing methods are available in order to accomplish different microstructure classes, to determine their specific properties in an experiment and to rationalize these with straightforward modelling efforts. Thereby a materials optimization is afforded, which allows effective interplay between processing, testing and modelling. The scientific effort can be grouped as follows:

1. Sintering of oxides Sintering of ceramics is approached using a continuum mechanical description, which affords inclusion of laminate stresses as arise in sintering of thin films and cosintering of several layers. In order to determine the constitutive equations for the sintering bodies, dilatometry and a new hot forging apparatus are used. This equipment together with a substantial modelling effort allows measurement of sintering stresses and viscosities and thereby predictions of shrinkage and curvature in multilayer structures. Materials under consideration are ZrO2, Al2O3, as well as LTCC materials. 2. Mechanical properties of ceramics and composites: Work on mechanical properties is geared towards an improved understanding of fracture strength, fracture toughness, R-curve behaviour and subcritical crack growth. Recently, an additional focus was placed on microcracking coupled with efforts on finite element modelling and damage evolution on the grain size level. Materials under consideration are ZrO2, Al2O3, Al2TiO5 and Al2O3/Cu. 3. Ferroelectric materials: Two scientific questions are of interest for this group. Reliability of piezoceramics for applications as actuator materials is under investigation. An increasing number of electrical cycles leads to a progressive loss of obtainable strain and polarisation in these materials. Point defects are speculated to contribute to the electrical fatigue effect. In order to investigate the reduced domain – boundary mobility, acoustic emission is used for polycrystalline ceramics. In parallel, Barkhausen pulses and acoustic emission studies are performed on single crystals used as model systems. The second branch is concerned with mechanical properties of ferroelastic materials. Crack propagation depends on crack – and specimen geometry and is experimentally determined and correlated. These investigations consider both a thermodynamic crack equilibrium as well as subcritical crack growth. The process zone in ferroelastic materials is investigated using a liquid crystal display, an approach which was recently developed in our group. Besides mechanically loaded cracks, electrically driven cracks – as appearing in multilayer actuators -are also investigated. Electric cyclic loading without any mechanical preload is also studied as it has been shown to provide a mechanical driving force for crack propagation also. Materials under consideration are PZT as well as PMN-PT.

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Staff Members Head

Prof. Dr. Jürgen Rödel

Research Associates Dr. Doru Lupascu

Dr. Ludwig Weiler Dr. Ruzhong Zuo

Technical Personnel

Emil Aulbach Herbert Hebermehl

Secretaries

Roswita Geier Gisela Völzke

Marion Bracke

PhD Students

Dipl.- Ing. Nina Balke Dipl.-Ing. Jens Eichler Dipl.-Phys. Alain Brice Kounga Dipl.-Ing. Ulrich Stiefel Dipl.-Ing. Cyril Verdier

Dipl.-Phys. Susan Galal Yousef Dipl.-Phys. Thorsten Schlegel Dipl.-Ing. Thomas Utschig M. Sc. Ilona Westram

Diploma Students Nina Balke Claire Fouquet

Antje Winkelmann

Guest Scientists

Dr. Rong-jun Xie Dr. Yong Zhang

Research Projects Sintering of ceramic films (DFG, 2000-2005) Electrical fatigue in actuators (DFG 2001-2003) Crack growth in ferroelectrics driven by cyclic electric loading (DFG and NSFC, 2002-2004) Defects in ferroelectrics (DFG, 2002-2005) Crack propagation in ferroelectrics: Crack opening displacement and effect of stress state (DFG, TU Karlsruhe, Dr. Fett, 2000-2003) Processing and thermo-mechanical properties of AIN-Al matrix composites (Phase II) (VW-Foundation, Prof. Jayaram, Bangalore, India, 2002-2004) Functional metal-ceramic composites (Freudenberg, 2002-2003) Processing of textured ceramic actuators with high strain (SFB 595) Model experiments to describe the interaction between ferroelectric domains and agglomerates (SFB 595) Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics (SFB 595)

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Publications Verdier, C.; Lupascu, D. C.; Rödel, J.; Unipolar Fatigue of Ferroelectric Lead-Zirconate-Titanate, J. Eur. Ceram. Soc., 23 [9] (2003) 1409-1415. Karastamatis, T.; Lupascu, D. C.; dos Santos e Lucato, S. L.; Rödel, J.; Lynch, C. S.; R-Curves of Lead Zirconate Titanate, J. Eur. Ceram. Soc., 23, (2003) 1401-08. dos Santos e Lucato, S. L.; Bahr, H. A.; Pham, V. B.; Lupascu, D. C.; Balke, H.; Rödel, J.; Bahr, U.; Crack Deflection in Piezoelectric Ceramics, J. Eur. Ceram. Soc., 23, (2003) 1147-1156. Lupascu, D. C.; Aulbach, E.; Rödel, J.; Mixed electromechanical fatigue in lead zirconate titanate, J. Appl. Phys., 93 [9] (2003) 5551-56. Zuo, R.; Aulbach, E.; Bordia, R. K. Rödel, J.; Critical Evaluation of Hot Forging Experiments: Case Study in Alumina, J. Am. Ceram. Soc., 86 [7] (2003) 1099-1105. Zuo, R.; Aulbach, E.; Rödel, J.; Experimental Determination of Sintering Stresses and Sintering Viscosities, Acta Materialia, 51 (2003) 4563-74. Zuo, R.; Aulbach, E.; Rödel, J.; Viscous Poisson’s Coefficient Determined by Discontinuous Hot Forging, J. Mat. Res., 18 [9] (2003) 2170-76. Kounga Njiwa, A. B., Fett, T., Lupascu, D. C., Rödel, J.; Crack-Tip Toughness of a Soft PZT, J. Am. Ceram. Soc, 86 [11] (2003) 1973-75. Wiederhorn, S. M., Dretzke, A., Rödel, J.; Near the Fatigue Limit in Glass, Int. J. of Fract., 121 (2003) 1-7. dos Santos e Lucato, S., Bahr, H.-A.; Pham, V.-B.; Lupascu, D. C.; Balke, H.; Rödel, J.; Bahr, U.; Crack Propagation and Deflection in Partially Electroded Ferroelectrics; J. Mechanics and Physics of Solids 50, (2002) 2333-35 and 51, (2003) 977. Emmel, T, Stiefel, U., Gross, D., Rödel, J.; Damage and Failure of Ceramic Metal Composites in: "Deformation and Failure in Metallic Materials",; Eds.: K. Hutter, H. Basler, Springer Verlag Berlin (2003) 203 – 221.

Lupascu, D. C.; Utschig, T.; Shur, V. Ya.; Shur, A. G.; The dynamics of domain walls determined from acoustic emission measurements; Ferroelectrics 290, (2003) 207-219.

dos Santos e Lucato, S.; Crack-growth-Velocity-Dependent R-Curve Behavior in Lead Zirconate Titanate; J. Am. Ceram Soc. 86 (2003) 1037 – 1039. Sadowski, T., Neubrand, A.; Thermal Shock Crack Propagation in Functionally Graded Strip; Proc. Int. Symp. „Brittle Matrix Composites 7“, (2003) 81 – 90.

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Electronic Material Properties The division Electronic Materials has been founded to introduce the aspect of functional materials and their properties into the Institute of Materials Science. Research concentrates on the characterization of various classes of materials suited for implementation in information storage and organic electronics. Three major research topics are presently addressed: ��Electronic properties of organic semiconductors, ��Charge transport and polarization in organic dielectrics, and ��Photo- and photostimulated luminescence in inorganic phosphors. In the field of organic semiconductors a worldwide interest exists in the use of organic semiconductors in novel electronic devices, such as displays and organic electrical circuits. Already commercialized applications are multicolor displays of a digital camera and of a car radio consisting of vacuum-deposited layers of functional small organic molecules. Applications reaching further into the future will be simple organic circuits based on semiconducting polymers, which will be positioned in communication electronics such as circuits on chip cards, barcodes and maybe one day in an electronic newspaper where the information is continuously renewed via local area networks (LAN). The activities of the group are concerned with the characterization of organic materials properties. Two major aspects are addressed: the first one is the detection and characterization of electronic traps in organic semiconductors and their correlation to charge transport properties, such as carrier mobility. For this purpose thermally stimulated current and luminescence measuring equipment and a laser spectroscopy setup utilized for time-of-flight and site-selective spectroscopy are available. The latter serves the understanding of the limits of electronic conduction in highly ordered and intentionally disordered organic semiconductors. Experimental techniques for device fabrication and characterization for small molecules and polymers are installed. In the field of polymer electrets present research comprises the characterization of surface charge distribution, charge stability, and charge transport properties of fluoropolymers, as well as their applications in acoustical transducers. Present investigations of charge transport and polarization in organic dielectrics are directed towards the basic understanding of polarization buildup and stabilization in PVDF, which is scientifically interesting as a model ferroelectric polymer. The available equipment includes poling devices such as corona and high voltage setups, and a thermally stimulated current setup to investigate the energetic trap structure in dielectrics as well as the thermal charging and discharging under high electric fields. Techniques to study the charge transport in dielectric films such as the laser-induced-pressure-pulse method (LIPP) to determine the spatial distribution are planed. The field of photo- and photostimulated luminescent materials (phosphors) is concerned with the synthesis and characterization of suited inorganic compounds. Such materials are utilized as wavelength converters in fluorescent lamps and in scintillating and information storing crystals. Challenges are the sensibilization of such phosphors in respect to the radiation energy, which can range from ultraviolet over hard γ-rays to thermal neutrons. Present work on x-ray storage is focussed on materials which exhibit needle-like growth,

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needed for improved resolution in medical imaging. Another research topic are quantum cutters, which are materials that emit two light-particles (photons) upon the absorption of one high energy photon. Such materials are foreseen to be essential components in future high efficiency energy-saving lamps, which will function without mercury and so have a low environmental impact. With respect to teaching the group is involved in the topic of electronic properties of organic and inorganic materials. The understanding of electrical, optical, dielectric and magnetic matter and their relation to structural properties such as crystalline and amorphous phases are the main subjects. The intention is to give students the intellectual tools at hand to utilize the relation between function and structure to design specific materials and devices for special properties and applications. Staff Members Head

Prof. Dr. Heinz von Seggern

Research Associate Dr. Roland Schmechel Dr. Wieland Weise

Prof. Dr. Sergei Fedosov Dr. Zhongming Hu Dr. Vladimir Nikitenko Dr. Vladimir Pankratow

Technical Personnel

Gabriele Andreß Sabine Hesse

Bernd Stoll

Secretary

Gerlinde Dietrich

PhD Students

Dipl.-Phys. Marcus Ahles Dipl.-Phys. Torsten Finnberg Dipl.-Ing. Arne Fleißner Dipl.-Ing. Holger Heil

Dipl.-Ing. Aline Hepp Dipl. Phys. Frederik Neumann Dipl.-Ing. Jörg Zimmermann

Diploma Students

Torsten Keith

Sven Kiesewetter

Guest Scientist Dr. Andrey Kadashchuk

Research Projects Charge Storage and Piezoelectricity of Porous and Cellular Electret Films (VW-Stiftung, 2001-2004) Development of Functional Polymers for Integrated Organic Circuits (PODOS), (BMBF Project with Siemens, 2001-2004) Photo-induced charge transfer in the novel low bandgap polymer semiconductors and their use in photovoltaic devices (EU Project 2001-2003)

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Injectionlaser (EU-Project 2002-2004) Interface alignment in organic field effect transistors (2002-2004) Fatigue of semiconductor components (DFG, 2003-2006) Phenomenological modelling of bipolar carrier transport in organic semiconducting devices under special consideration of injection, transport and recombination phenomenae (DFG, 2003-2006) Development of interfacial layers for organic electrodes (Merck, 2004-2006) Investigation of fast scintillators (Siemens, (2004-2005) Piezoelectric sensor materials based on porous polymers (AiF, 2004-2006, DKI)

Publications Heil, H.; Finnberg, T.; von Malm, N.; Schmechel, R.; von Seggern, H.; The infuence of mechanical rubbing on the field-effect mobility in polyhexylthiophene, J. Appl. Phys. 93 (2003) 1636-1641.

Hepp, A.; von Malm, N.; Schmechel, R.; von Seggern, H.; Effects of Process Parameters on Trap Distributions, Synthetic Metals 138 (2003) 201-207.

Nikitenko, V.R.; Heil, H.; von Seggern, H.; Space charge limited current in regioregular poly-3-hexyl-thiophene , J.Appl. Phys. 94, (2003) Hepp, A.; Heil, H.; Weise, W.; Ahles, M.; Schmechel, R.; von Seggern, H.; Light-Emitting Field-Effect Transistor Based on a Tetracene Thin Film, Phys. Rev. Let. 91, (2003) 157406-1 Arkhipov, V.I.; von Seggern, H.; Emilianova, E.V.; Injection versus space charge limited currents in organic light emitting diodes, Appl. Phys. Let. 83, (2003) 5074 Schlapp, M., Bulur, E., von Seggern, H., Photo-stimulated luminescence of calcium co-doped BaFBr:Eu2+ x-ray storage phosphors, J. Phys. D: Appl. Phys. 36 (2003), 103-108. Moses, D.; Schmechel, R.; Heeger,A.J.; Effects of structural disorder and temperature on the distribution of exciton binding energy in poly(phenylene vinylene) films, Synthetic Metals 139 (2003) 807-810.

Weise, W.; Investigation of the Anisotropy of Hemi-dodecahedron Noise Source Radiation, J. Sound Vib. 270, (2003) 137-147

Weise, W.; Measurement Uncertainties for Sound Field Levels in Rooms, Building Acoustics 10, (2003) 281-287

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Surface Science The surface science division of the institute of materials science uses advanced surface science techniques to investigate surfaces and interfaces of materials and materials combinations of technological use. For this purpose integrated UHV-systems have been built up which combine different surface analytical tools (photoemission, electron diffraction, ion scattering, scanning probe techniques) with the preparation of thin films and interfaces in cluster tools. The main research interest is directed to devices using novel polycrystalline compound semiconductors and interfaces between dissimilar materials. The perspectives of energy converting devices as e. g. solar cells are of special interest. In addition, the fundamental processes involved in chemical and electrochemical device engineering are investigated. The main research areas are: • Electrochemical Interfaces

The aim of this research activity is the better understanding of electrochemical interfaces and contact formation. In addition, empirically derived (electro)chemical processing steps as the controlled modification and structuring of materials is investigated and further optimized. In the center of our interest are semiconductors and ion conductors.

• Van der Waals semiconductor heterojunctions and multilayers

The aim of this research acitivity is the testing and development of 2D-semiconductors (layered chalcogenides) for optoelectronic devices. In addition, van der Waals layers are investigated as passivating layers for 3D semiconductors and as buffer layers of lattice mismatched materials combinations. Furthermore the decisive factors, which govern the electronic properties of heterojunctions, are studied.

• Thin film solar cells

The aim of this research activity is the testing and development of novel materials and materials combinations for photovoltaic applications. In addition, the interfaces in microcrystalline thin film solar cells are to be characterized on a microscopic level to understand and to further improve the empirically based optimisation of solar cells.

• Surface analysis

The UHV-surface science equipment and techniques using different and versatile integrated preparation chambers is used for cooperative service investigations.

For the experiments we use integrated UHV-preparation and analysis-systems (UPS, (M)XPS, LEISS, LEED), spectromicroscopy (PEEM) coupled with UHV-STM/AFM. We further apply synchrotron radiation (SXPS, spectromicroscopy), scanning probe methods (STM, AFM), and electrochemical measuring techniques. UHV-preparation chambers dedicated for MBE, CVD, PVD sputtering, close spaced sublimation (CSS) and (electro)chemical treatment are available.

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The member of the group are involved in basic courses of the department’s curriculum and offer special courses on the physics, chemistry and engineering of semiconductor devices and solar cells, on surface and interface science, and on thin film and surface technology.

Staff Members Head

Prof. Dr. Wolfram Jaegermann

Research Associates Dr. Andreas Klein Dr. Jochen Fritsche Dr. Stefan Oelting

Dr. Thomas Mayer Dr. Ralf Hunger Dr. Andreas Thißen

Technical Personnel

Dipl.-Ing. Erich Golusda Dipl.-Ing. Gabi Haindl

Christina Spanheimer

Secretary

Marga Lang

PhD Students

Dipl.-Ing. David Ensling Dipl.-Ing. Yvonne Gassenbauer Dipl.-Ing. Rainer Fritsche Dipl.-Ing. Daniel Kraft Dipl.-Ing. Frank Säuberlich Qihui Wu Dipl.-Ing. Bengt Jäckel

Dipl.-Ing. Thomas Schulmeyer Dipl.-Ing. Ulrich Weiler Dipl.-Ing. Elmar Wisotzki

Diploma Students Jürgen Ell Hicham Kouaici Robert Schafranek Konrad Schwanitz

Bettina Späth Sebastian Taeger Sebastian Weber

Humboldt Fellow

Dr. Mikhail Lebedev

DAAD Dr. Javier Fernandez

Research Projects Nanostructuring of epitaxial layers of layered compounds with scanning probe methods. (DFG 2002 – 2003)

Interfaces and inhomogeneities of polycristalline CdTe thin film solar cells (BMBF, 1999-2002) Dedicated preparation-, transfer and spectrometersystem for the analysis of materials modifications and –synthesis at solid-liquid-interfaces with synchrotron radiation (BMBF, 2001-2004) ZnO for Thin Film Solar cells; Materials and Interface Research (BMBF, 2001-2003) Photovoltage optimization of II-VI compound thin film solar cells (BMBF, 2001-2004)

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Silicon-organic pigment material hybrids for photovoltaic application (VW-Stiftung, , 2002 – 2005) High performance CdTe thin film solar cells (2003 – 2005) Interface modification of semiconductor heterostructures by electronic processing (2003 – 2004) Intercalnet (2003 – 2006)

Publications Liu, G.; Schulmeyer, T.; Thißen, A.; Klein, A.; Jaegermann, W.; In situ preparation and interface characterization of TiO2 /Cu2 S heterointerface; Appl. Phys. Lett. 82, (2003) 2269-2271. Kraft, D.; Thißen, A.; Broetz, J.; Flege, S.; Campo, M.; Klein, A.; Jaegermann, W.; Characterization of tellurium layers for back contact formation on close to technology treated CdTe surfaces; J. Appl. Phys. 94, (2003) 3589-3598. Liu, G.; Klein, A.; Thißen, A.; Jaegermann, W.; Electronic properties and interface characterization of phthalocyanine and Ru-polypyridine dyes on TiO2 surface; Surf. Sci., 539, (2003) 37-48. Lebedev, M.; Mayer, T.; Jaegermann, W.; Sulfur adsorption at GaAs(100) from solution: Role of the solvent in surface chemistry; Surf. Sci., 547 (2003) 171-183. Sakurai, K.; Hunger, R.; Tsuchimochi, N.; Baba, T.; Matsubara, K.; Fons, P.; Yamada, A.; Kojima, T.; Deguchi, T.; Nakanishi, H.; Niki, S.; Properties of CuInGaSe2 solar cells based upon an improved three stage process; Thin Solid Films 431-432 (2003) 6-10. Säuberlich, F.; Fritsche, J.; Hunger, R.; Klein, A.; Properties of sputtered ZnO films and its interfaces with CdS; Thin Solid Films 431 (2003) 378-381. Kraft, D.; Weiler, U.; Thißen, A.; Tomm, Y.; Klein, A.; Jaegermann, W.; Alternative back contacts for CdTe solar cells: a photoemission study of the VSe2/CdTe and TiSe2/CdTe interface formation; Thin Solid Films 431-432 (2003) 382-386. Hunger, R.; Sakurai, K.; Yamada, A.; Fons, P.; Iwata, K.; Matsubara, K.; Niki, S.; In situ deposition rate monitoring during the three-stage-growth process of Cu(In,Ga)Se2 absorber films; Thin Solid Films 431-432 (2003) 16-21. Fritsche, J.; Schulmeyer, T.; Thißen, A.; Klein, A.; Jaegermann, W.; Interface modifications of CdTe thin film solar cells by CdCl2 –activation; Thin Solid Films 431-432 (2003) 267-271.

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Liu, G.; Schulmeyer, T.; Brötz, J.; Klein, A.; Jaegermann, W.; Interface properties and band alignment of Cu2 S/CdS thin film solar cells; Thin Solid Films 431-432 (2003) 477-482. Schulmeyer, T.; Fritsche, J.; Thißen, A.; Klein, A.; Jaegermann, W.; Campo, M.; Beier, J.; Effect of in situ UHV CdCl2 -activation on the electronic properties of CdTe thin film solar cells; Thin Solid Films 431-432 (2003) 84-89. Kraft, D.; Späth, B.; Thißen, A.; Klein, A.; Jaegermann, W.; Chemical and electronic properties of metal/Sb2Te3/ CdTe contacts for CdTe thin film solar cells studied by photoelectron spectroscopy; MRS Symp. Proc. 763 (2003) B3.3 Säuberlich, F.; Klein, A.; Band alignment at oxide semiconductor interfaces; MRS Symp. Proc. 763 (2003) B9.10 Ensling, D.; Hunger, R.; Kraft, D.; Mayer, T.; Jaegermann, W.; Pulse Plating of Pt on n-GaAs (100) Wafer Surfaces: Synchrotron Induced Photoelectron Spectroscopy and XPS of Wet Fabrication Processes; Nucl. Instr. and Meth. B 200 (2003) 432-438

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Thin Films The scientific program of the Thin Films Division combines the synthesis, the characterization with the determination of the properties and the theoretical modeling/simulation of nanostructured materials. Nanostructured materials with structural features in the nanometer range can be found in the form of clusters, thin films, multilayers and nanocrystalline materials often expressed by their dimensionality of 0, 1, 2 and 3. The ultimate goal of the research program is to achieve a better understanding of the fundamental atomistic processes and properties of materials which are dominated by grain boundaries and interfaces. In selecting the materials and the properties, the potential for technological applications is considered. The materials investigated include metals, amorphous and crystalline alloys, semiconductors, oxide, nitride and carbide ceramics in the form of clusters, thin films, multilayers and bulk nanocrystalline materials. Most synthesis techniques are based on vapor phase processes such as Molecular Beam Epitaxy (MBE), Chemical Vapor Deposition (CVD) and DC- and RF- Magnetron Sputtering for thin films and multilayers and Chemical Vapor Synthesis (CVS) for clusters and nanocrystalline materials. The high quality and reproducibility of the materials are achieved by establishing clean conditions such as ultra-high vacuum environments, computer control of the synthesis parameter and in-situ analysis techniques such as Reflection High Energy Electron Diffraction (RHEED) or Aerosol Mass Spectrometry. The characterization of the materials is performed in part in collaboration with research groups in the Materials Science Department and other institutions using modern analytical methods. These include X-Ray Diffraction (XRD), High Resolution Scanning Electron Microscopy (HRSEM) and Transmission Electron Microscopy (HRTEM), Electron MicroProbe Analysis (EMPA), Secondary Ion Mass Spectroscopy (SIMS), Atomic Force and Scanning Tunneling Microscopy (AFM/STM), Mössbauer Spectroscopy (MS) and Depth-sensitive Conversion Electron Mössbauer Spectroscopy (DCEMS), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS), nitrogen adsorption and in cooperation with several national and international research facilities, e.g. Small Angle Neutron Scattering (SANS) and Extended X-ray Adsorption Fine Structure (EXAFS). In addition, several accelerator facilities are used for ion beam analysis, such as Rutherford Backscattering Spectroscopy (RBS) or Nuclear Reaction Analysis (NRA), of thin film structures and nanocrystalline materials after ion implantation and ion beam modification. A wide range of optical, electronic, magnetic, mechanical and catalytic properties of these materials are investigated. For example, the giant and tunneling magnetoresistance effects (GMR, TMR) and atomic transport in multilayers and in nanocrystalline materials, have been studied intensively. An understanding of the atomistic processes can be deduced from the knowledge of the detailed microstructure and of the structure/property relationships leading to optimized engineering properties for applications. These include materials for resistive gas sensors based on semiconducting oxides, catalysts and calorimetric gas sensors based on noble metals on nanocrystalline oxides and motion sensors for automotive applications based on the GMR-effect in multilayers and granular thin films. Atomic scale computer simulations are in the focus of the materials modeling activities. The main tool is the Molecular Dynamics (MD) method. Large scale computer simulations of several million of atoms can be performed on the recently installed 18-processor parallel cluster computer (DAMASCOS). The development of reactive analytical potentials allows

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the simulation of a variety of elemental and compound systems. Total energy calculations within the density functional theory are used for materials characterization, kinetic Monte-Carlo methods for studying materials processes on time scales, which are not accessible by the MD-method. In late 2002, the research efforts in atomistic simulations have been concentrated in an independent “Junior-Professorship - Materials Modeling”. Besides the teaching of mandatory undergraduate and graduate courses, the Thin Films Division offers several elective courses for students of Materials Science, Physics, Chemistry and Engineering:

• Synthesis of novel high-technology materials; • Modification and analysis of materials using ion beam techniques; • Magnetic properties of novel nanostructured materials; • Phase transformations in solids; • Introduction to high resolution scanning electron microscopy.

Staff Members Head

Prof. Dr.-Ing. Horst Hahn

Research Associates Sarbari Bhattacharya Ph. D. PD Dr. Markus Winterer

Dr. Adam G. Balogh, C. Sc. Dr. Mohammad Ghafari Dr. Branko Stahl

Technical Personnel

Jürgen Schreeck

Secretaries

Renate Hernichel Marion Bracke

PhD Students

Dipl.-Ing. Mete Berber Dipl.-Ing. Joachim Brehm Dipl.-Ing. Jörg Ebert Dipl.-Ing. Sebastian Gottschalk Dipl.-Ing. In-Kyum Lee Dipl.-Ing. Michael Schallehn Dipl.-Ing. Johannes Seydel

Dipl.-Ing. Wolfram Berky Dipl.-Ing. Yong-San Cho Dipl.-Ing. Jens Ellrich Dipl.-Ing. Andrew Johnson Dipl.-Phys. Marcel Müller Dipl.-Ing. Holger Schmitt Dipl.-Ing. Hermann Sieger

Diploma Students Robert Barunovic Richard Finckh Pierre A. Huhn

Thorsten Enz Bernd Bethlehem

Guest Scientists

Dr. Subramshu Bhattacharya, Indian Institute of Technology, Madras, India Prof. A. Raghurama Raju, Jawaharlal Nehru Center, Bangalore, India Velegelati Kishor, Indian Institute of Technology, Madras, India Kranthi Kumar, Indian Institute of Technology, Madras, India R. Maculewicz, German Polish Lithuanian Dialoque, University of Poznan, Poland Prof. Mariana Calin, Polytechnical University Bukarest, Romania Swaraj Basu, Indian Institute of Technology, Madras, India

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Research Projects

Critical Behavior of FeBO3-layers and particles close to the Néel-temperature (DFG 2001-2003)

Functionalization and modification of nanoparticles in the gas phase (DFG 2002-2004)

Synthesis and characterization of magnetic Fe-Pt nanoparticles and their self-organized two dimensional arrangement (DFG 2002-2003)

Atomistic computer simulation of elemental processes during gliding of grain boundaries (DFG 2001-2003)

Defect evolution, grain growth and phase transitions in nanocrystalline ceramics under heavy ion irradiation (GSI 2001-2004)

Cooperation project: Materials Science using neutron diffraction (HMI 1997-2003)

Innovatec – guest professorship for innovative studies at German universities, (DAAD 2002-2003)

“Klares Sigma”, Basis of synthesis of Indium-tinoxide nanoparticles (BMBF 1999 – 2003)

Defect structure and diffusion in ferroelectric materials (SFB 595 2003 – 2006)

Atomistic computer simulation of defect migration in metal oxides (SFB 595 2003 – 2006)

Publications Schallehn, M.; Winterer, M.; Weirich, T.; Keiderling, U.; Hahn, H.; In-Situ Preparation of Polymer Coated Alumina Nanopowders by Chemical Vapor Synthesis, Chem. Vap. Dep., 9 (2003), 40-44. Voegeli, W.; Albe, K.; Hahn, H.; Simulation of grain growth in nanocrystalline nickel induced by ion irradiation, Nucl. Instr. Meth. B 202 (2003) 230-235. Srdic, V. V.; Winterer, M.; H. Hahn; Sintering of nanocrystalline Zirconia prepared by chemical vapor synthesis at different temperatures, Proceedings of 10th International Ceramics Congress – Part B, 2, (2003) 145-151. H. Hahn; Unique Features and Properties of Nanostructured Materials, Adv. Eng. Mat.5, (2003) 1-8. M. Winterer, Hahn, H.; Nanoceramics by chemical vapour synthesis, Z. Metallkd, 94, 10 (2003), 1084 – 1090. B. Stahl, E. Kankeleit, G. Walter; Implantation Induced Phase Formation in Stainless Steel; Nucl. Inst. Meth. B 211 (2003) 227-238. B. Stahl, J. Ellrich, R. Theissmann, M. Ghafari, S. Bhattacharya, H. Hahn, N. S. Gajbhiye, D. Kramer, R.N. Viswanath, J. Weissmüller, H. Gleiter; Electronic Properties of 4 nm FePt particles; Phys. Rev. B 67, (2003) 014422 ff.

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Dispersive Solids The research of the Dispersive Solids group is based on the development of strategies for producing novel inorganic, oxidic, and non-oxidic materials. The main focus is the synthesis of ceramics with properties which exceed the present state of the art. Synthesis methods like the sol-gel-technology, polymer pyrolysis and chemical vapour deposition (CVD) are used and continuously further developed. Moreover molecular, oligomeric, and polymeric ceramic precursors as well as inorganic materials derived therefrom are synthesized and characterized. Further emphasis is put on the transformation of the precursors into ceramic components (for example layers, fibers, bulk materials, composites, membranes) and the characterization of their chemical and physical materials properties. The aim of our research activities is to correlate those properties with the composition and structure of the molecular precursors. The present projects include the following four main topics: materials synthesis, properties, modelling, and processing & applications. In 2003 the group has organized or co-organized the following symposia and workshops: • DKG und DGM Gemeinschaftsausschuss Hochleistungskeramik, 8th group meeting

Polymerkeramik, Darmstadt, July 15th.

• EUROMAT 2003, Advanced Nitrides, Lausanne, September 1st – 5th.

• Materials Week 2003, coordination of symposium, Munich, September 18th – 21st.

Staff Members Head

Prof. Dr. Ralf Riedel

Research Associates Dr. Ralf Hauser Dr. Robert Kolb Dr. Christoph Konetschny Dr. Isabel Kinski

Dr. Edwin Kroke Dr. Saifun Nahar-Borchert Dr. Andreas Zerr Dr. Yanping Zhou

Technical Personnel

Dipl.-Ing. Claudia Fasel Dipl.-Chem. Ildiko Balog

Secretary

Su-Chen Chang

PhD Students

Dipl.-Ing. Susanne Deuchert Dipl.-Min. Michael Eberhardt M. Tech. Rahul Harshe Dipl.-Ing. Frank Hönack Dipl.-Ing. Elisabeta Horvath-Bordon

Dipl.-Ing. Alexander Klonczynski Dipl.-Chem. Verena Liebau Dipl.-Ing. Marcus Schwarz

Diploma Student Friedericke Halstrick Thomas Locherer Florian Maurer Herwig Schiefer

Frieder Scheiba Uwe Zeigmeister

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Humboldt Fellow Dr. Dusan Galusek, Institute of Inorganic Chemistry, Slovak Academy of Sciences, Slovaky

Guest Scientists

Prof. Dr. Corneliu Balan, Politehnica, Univ. of Bucharest, Romania Dr. Jinwang Li, Institute of Chemical Metallurgy Chinese Academy of Sciences, Beijing, China Dr. Mathilda Zemanova, University of Bratislava, Slowakei B. Tech. Rajneesh Verma, Institute of Technology, Banaras Hindu University, India Dr. Adel Francis, Central Metallurgical Research and Development Institute, Cairo, Egypt Gaelle Vagnon, Ecole Nationale Supérieure de Chimie et de Physique de Bordeaux, France

Research Projects High pressure synthesis of SiCN-materials (DeBeers, Johannesburg, South Africa, since 2000) Electrical properties of precursor-derived ceramics in the system Si-O-C (Robert Bosch GmbH, Stuttgart, since 1996) Precursorkeramik (DFG-SPP): Synthesis and high-temperature stability of amorphous ceramics in the system Si-B-C-N from polymeric preliminary stages and their application for carbon-fibres coatings about the fluid-coating-method (DFG, with Prof. Dr. U. Klingebiel, Inorganic Chemistry, Univ. Göttingen; Prof. Dr. R. Gadow, Fertigungstechnologie keramischer Bauteile, Univ. Stuttgart; Dr. H.-J. Kleebe, Materialforschung, Univ. Bayreuth, since 1997) Precursorkeramik (DFG-SPP): Molecular design of preceramic polymers using quantum mechanical method: synthesis of novel metallocarbodiimide-polymers and -gels (DFG, Priv.-Doz. Dr. J. Woltersdorf, MPI, Halle, since 1997). Precursorkeramik (DFG-SPP): Novel nitrogen rich ceramic materials in the binary system C/N (DFG, since 1997) Precursorkeramik (DFG-SPP): Oxidation und corrosion of Si-(B)-C-N materials from polymeric precursors (DFG, Prof. Dr. K. G. Nickel, Mineralogy, Petrology & Geochemistry, Univ. Tübingen, since 1998) Microstructure components for the information technology and more functional, high temperature stable sensors using preceramic polymer: Development of filled functionalized

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polysiloxane systems for the manufactur of microstructured ceramic prefabricated parts (Robert Bosch GmbH, Stuttgart, since 1999) Hochtemperaturstabilität von polymerbasierter SiOC Keramik (Robert Bosch GmbH, Stuttgart, since 1999) SiCO-ceramics with titanium containing fillers (since 1999) Synthesis of novel materials and improvement of the properties for the application as nitrogen-oxid storing catalytic converters of modern fuel-injection engines (UMICORE, Hanau, since 2000) Design and synthesis of polymeric precursors for multicomponent ceramic (JFCC, Nagoya, Japan) Inorganic Membranes (JFCC, Nagoya, Japan) Anorganic / organic hybrid materials and ceramics on the base of non-oxide carbodiimid-gels (DFG, since 2000) Superhard materials (scientific technologic cooperation with South Africa, since 2000) III-V-Group semiconductor materials (Merck, Darmstadt, since 2001) PACVD-synthesis and characterisation of Si(B)CN hard material films for tribological applications (DFG, since 2001) Nitridation of SiO2-glass in order to increase its high temperature stability (since 2002) Synthesis of Si3N4/SiC-nanocomposites from precursors prepared using a sol-gel process (since 2001)

Synthesis of novel nitrides of type A3-xBxN4 (A, B =Ti, Zr, Hf, C, Si, Pb; 0 < x < 3) in laser-heated diamond high-pressure anvil cell and their properties (DFG, since Nov. 2001 – Oct. 2003) Synthesis and thermal stability of ceramic materials in the quaternary system of Si-B-C-O (scholarship of the land Hessen, since Aug. 2002) Correlation of pyrolysis parameter, gas mixture and property profile of ceramic composites (Robert Bosch GmbH, Stuttgart, since Oct. 2002) Development of mechanical and oxidation resistant coatings for ceramic substrates (EADS, Munich, since Nov. 2002) Influence of Bi2O3-, GeO- and Al-fillers on the crystallization behaviour of polymer-derived SiOC-ceramics (Robert Bosch GmbH, Stuttgart, since Nov. 2002) Development of ceramic oxidation resistant coatings for Ni-based-alloys (Alstom, Mannheim, (since Nov. 2002)

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Synthesis and processing of amorphous Si(Al)OC bulk ceramics: high temperature properties and applications, (since 2000) Novel functional ceramics with substitution of anions in oxide systems, (DFG, SFB 595, project A4, since Jan. 2004) In-situ preperation of Al2O3-SiC composites, (scholarship of the Humboldt Society, 1st June 2003 – 31st May 2004)

Publications Riedel, R.; Horvath-Bordon, E.; Nahar-Borchert, S.; Kroke, E.; Molecular Chemical Concepts for the Synthesis of Novel Ceramics, Key Engineering Materials, 247 (2003) 121-128. Balan, C.; Riedel, R.; Sol-Gel Modelling Associated with the Rheology of Polymeric Precursors of Ceramic Materials, Appl. Rheol. 13 (2003) 251-258. Berger, C; Broszeit, E.; Falk, F.; Hoche, H.; Kroke, E.; Kroll, P. Probst, D.; Riedel, R.; Stafast, H.; Uhlitzsch, V.; Zhou, Y.; Plasma CVD of Si/C/N: Experimental and Theoretical Results, CVD-XVI/EUROCVD-14, Volume 1; Eds. Allendorf, M.; Maury, F.; Teyssandier, F.; The Electrochemical Society, Inc. Pennington, USA (2003) 646-652. Zerr, A.; Miehe, G.; Riedel R.; Synthesis of Cubic Zirconium and Hafnium Nitride Having Th3P4-Structure, Nature Materials 2 (2003) 185-189.

Nahar-Borchert, S.; Riedel, R.; Kroke, E.; Boury, B.; Corriu, R. J. P.; Synthesis and Characterization of Alkylene-Bridged Silsesquicarbodiimide Hybrid Xerogels, J. of Organometallic Chem., 686 (2003) 127-133. Hönack, F.; Riedel, R.; Influence of Ti-Based Fillers on the Thermal Decomposition and Phase Development of Polysiloxane Derived Materials, Advanced Engineering Materials 5 (2003) 122-124. Völger, K.W.; Kroke, E.; Gervais, C.; Saito, T.; Babonneau, F.; Riedel, R.; Iwamoto, Y.; Hirayama, T.; B/C/N Materials and B4C Synthesized by a Non-Oxide Sol-Gel Process, Chemistry of Materials 15 (2003) 755. Lowther, J.E.; Schwarz, M.; Kroke, E.; Riedel, R.; Electronic Structure Calculation of Cohesive Properties of Some Si6-zAlzOzN8-z Spinels, Journal of Solid State Chemistry 176 (2003) 549-555. Faulhaber, S.; Loeffler, L.; Hu, J.; Kroke, E.; Riedel, R.; Lange, F.F.; Synthesis of Nanocrystalline Aluminum-Gallium Nitride (AlxGa1-xN, x=0.1 – 0.5) with Oxide Precursors via Ammonolysis, Journal of Materials Research 18 (2003) 2350-2358.

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Lichtenberger, O.; Pippel, E.; Woltersdorf, J.; Riedel, R.; Formation of Nanocrystalline Titanium Carbonitride by Pyrolysis of Poly(titanylcarbo-diimide), Materials Chemistry and Physics 81 (2003) 195-201. Gervais, C.; Babonneau, F.; Ruwisch, L.; Hauser, R.; Riedel,.R; Solid State NMR Investigations of the Polymer Route to SiBCN Ceramics, Can. J. Chem./Rev. Can. Chim. 81 (11) (2003) 1359. Reschke, S.; Haluschka, C.; Riedel, R.���������� ��Galusek, D.; Polysilazane-Derived In-Situ Generated Homogeneous and Functionally Graded Ceramic Materials, Journal of the Europian Ceramic Society, 23 [11] (2003) 1963-70.

Patents Klonczynski, A.; Koehne, M.; Riedel, R.; Schiefer, H.; Harshe, R.; Erhöhung der Hoch-temperaturkriechbeständigkeit durch Al als Additiv, Deutsche Patentanmeldung mit der Firma Robert Bosch GmbH, 2003.

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Structure Research The central activity of the Structure Research group is the study of the correlation between materials properties and the corresponding crystal structure. The detailed characterization of structure and nanomorphology at an interatomic length scale requires different types of radiation. Therefore a variety of diffraction and microscopic techniques have been established in our group. In this background almost any structural defect or any type of material has successfully been studied, ranging from crystalline samples and amorphous solids to surfaces and interfaces. In addition, we operate two powder diffractometers at large scale facilities; one dedicated for experiments with synchrotron radiation at the HASYLAB laboratory in Hamburg, the other for neutron diffraction at the research reactor FRM-II in Munich. Among the main objectives in structure research is the selective improvement of novel but also already industrially applied materials. In this context materials for heterogeneous catalysis are investigated and optimised by systematic analysis of the respective structure-property relationship. Simultaneously, magnetic materials and ionic conductors play an important part in current research activities. Materials under present investigation are anode catalysts in PEM and direct methanol fuel cells, magnetic alloys, as well as complex oxides and pigments in collaboration with Merck, Darmstadt. Together with Umicore, Hanau, projects on three-way- and diesel catalysts are in progress. The funding of the research activities is based on the infrastructure provided by the university. The actual projects are mainly supported by public science organisations (BMBF, DFG) and to a large extend by cooperations with industry. These joint ventures proved to be beneficial to both partners in the past. The scientific staff is involved in basic teaching of the department’s curriculum and offers special courses in crystallography and X-ray diffraction. Additionally, more application-oriented topics, e.g. battery materials as well as spectroscopy and diffraction in applied catalysis, are presented in lectures.

Staff Members Head

Prof. Dr. Dr. h.c. Hartmut Fueß

Research Associates

Dr. Carsten Bähtz Dr. Kirill Bramnik Dr. Joachim Brötz Dr. Thorsten Buhrmester Dr. Helmut Ehrenberg Dr. Ralph Gilles Dr. Michael Knapp Dr. Natalia Leyzerovich

Dr. Ian MacLaren Dr. Gerhard Miehe Dr. Christina Roth Dr. Hermann Pauly Dr. Andrei Skomorokhov Dr. Ralf Theissmann Dr. Michael Schlapp Dr. Hans Weitzel

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Technical Personnel

Dipl.-Ing. Heinz Mohren Jean Christophe Jaud

Dipl.-Ing. Bernhard Krimmer Ingrid Svoboda

Secretary

Maria Holzmann

PhD Students

Dipl.-Ing. Andreas Adams Dipl.-Chem. Lars Giebeler Dipl.-Ing. Astrid Gies Dipl.-Ing. Frank Haaß Dipl.-Ing. Markus Hölzel Dipl.-Ing. Markus Knoth Dipl.-Ing Thomas Locherer Dipl.-Phys. Mohamed Loukil

Dipl.-Ing. Nathalie Martz Dipl.-Ing. Marian Mazurek Dipl.-Ing. Alexander Morlang Dipl.-Phys. Vedran Rajevac Dipl.-Phys. Nizar Rammeh Dipl.-Ing. Ljubomira Schmitt Dipl.-Min. Kristin Schönau Dipl.-Chem. Emanuel Vollmar

Diploma Student

Ljubomira Erac Toni Groß

Kristian Nikolowski Björn Schwarz

Humboldt-fellows �� ��������������������� !���"#��$��!���!�� Prof. Dr. Ernesto Estevez Rams, Havana, Cuba

Guest Scientists

���$ ��� ���"��������%��� ��$�����������������������&'(��! Oznur Cakir, Univ. Ankara, Turkey �� ��'(�"���������%��� ��$�������������������n Republic Baris Emre, Univ. Ankara, Turkey Radovan Herchel, Univ. of Bratislava, Slovakian Republic �� �����$���)����%��� ��$�����������������������&'(��! Dr. Anouar Njeh, Univ. of Sfax, Tunisia Dr. Mustafa Öksüzoglu, Selcuk Univ. Konya, Turkey Lkhanaajev Nyam-Ochir, Univ. Ulaan Baatar, Mongolia �� ����)������&������%��� ��$�����������������������&'(��! Ouarsal Rachid, Univ. Fes, Marocco Yuruy Tyvanchuk, Univ. Lviv, Ukraine Grygoriy Dmytriv, Univ. Lviv, Ukraine

Research Projects Resonant and high-resolution powder diffraction on polycrystalline materials at HASYLAB in Hamburg (BMBF, 2001-2004) Chemical composition, nanomorphology and electrolytic activity of catalytic materials for direct methanol fuel cells (DFG, 1998-2004) Design and realisation of the new neutron structure powder diffractometer (SPODI) at the FRM-II (TU München) in Garching (BMBF, 1998-2004)

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Inelastic neutron scattering investigation of lattice dynamics in nitrided metals (BMBF, 2000-2004) Research and development of catalysts for engines operated with diesel fuels (UMICORE, 2000-2003) Development of novel interference pigment materials (Merck, 1999-2003) Function and dynamics of oxygen in Mo / V mixed oxides catalytic materials for partial oxidation of aldehydes (DFG in collaboration with Prof. Dr. H. Vogel, TUD and Prof. Dr. M. Martin, RWTH-Aachen, 2000-2004) Design and investigation of new oxygen storage systems to be used in three-way-catalysts (UMICORE, 2001-2004) Structural characterization of silicon monoxide SiO (DFG, 2000-2003) Lattice dynamics of superionic copper selenide (DFG, 2001-2003) In-situ studies of intercalation batteries (DAAD, 2002-2003, with the Universidad San Pablo, Madrid, Spain) Oxygen conductivity in rare earth / lanthanum - gallium oxides (DAAD, 2002/2003 with the Univ. of Lviv, Ukraine) Magnetic interactions and magnetostructural correlations (Humboldt cooperation 2003-2005, with Prof. Dr. Y. Elerman, University Ankara , Turkey) Ionic Fluids (Humboldt cooperation 2003-2005 with Prof. Dr. V. Balevicius, Vilnius University, Litauen ) Synthesis and properties of new (oxid)nitrid-ceramics: spinell-nitride and -sialone (DFG 2003-2005) Structural phase transitions and physical properties of Zintl-phases with NaTl-type structure (B32) at ambient condition (DFG 2003-2004)

Publications

Adla, A.; Fuess, H.; Trautmann, C.;Characterization of heavy ion tracks in polymers by transmission electron microscopy, J. Polym. Science B: Polymer Physics 41 (2003) 2892-2901. Ahmed, M.; Haase, W.; El-Saddek, M.; Elwahy, A.H.M.; Svoboda, I.; Fuess, H.; Crystal structure of 1,3-bis[3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridine-dione-9-yl] benzene; C40H48N2O4, Z. Kristallogr. NCS 218 (2003) 90-93.

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Balevicius, V.; Fuess H.; Ion induced hypercritical point in tetrahydrofuran/water solutions, J. Chem. Phys. Lett. 377 (2003) 530-536. ��������'��* ��+�&��'��� ��,�(�������* ��Fuess, H.; Anomalous structural changes in acetic acid/water solutions, Lithuan. Journ. of Phys. 43 (2003) 183-186. ������ ������� ��Ehrenberg, H.; Fuess ,H.; Linert, W.; Renz, F.;. Svoboda, I.; Spin crossover in iron(II) tris(2-(2-pyridyl)benzimidazole) complex monitored by variable temperature methods: synchrotron powder diffraction, DSC, IR spectra, Mössbauer spectra and magnetic susceptibility, Chem. Phys. 293 (2003) 375-395. Bo�a, R., Gembický, M.; Herchel, R.; Haase, W.; Jäger, L.; Wagner, C.; Ehrenberg, H.; Fuess, H.; Ferromagnetism in a dinuclear nickel(II) complex containing triethylenetetramine and tricyanomethanide, Inorg. Chem. 42 (2003) 6965-6967. Bramnik, K.G.; Ehrenberg, H.;. Dehn, J.K.; Fuess, H.; Preparation, crystal structure and magnetic properties of double perovskites M2MgReO6(M=Ca,Sr,Ba), Solid State Sci. 5 (2003) 235-241. Bramnik, K.G.; Ehrenberg, H., Theissmann, R.; Fuess, H., Morán, E.; Preparation and crystal structure of a new high-pressure phase (Vo0.5Re0.5)O2 with rutile-type structure, Z. Kristallogr., 218 (2003) 455-457. Bramnik, K.G.; Muessig, E.; Ehrenberg, H., Preparation, crystal structure, and magnetic studies of Na3Fe2Mo5O16, a new oxide containing Mo3O13 clusters, J. Solid State Chem. 176 (2003) 192-197. Danilkin, S.A.; Fuess, H.; Wipf, H.; Ivanov, A.; Gavriljuk, V.G.; Magnin, T.; Delafosse D.; Hydrogen vibrations in austenitic fcc Fe-Cr-Mn-Ni steels, Europhys. Lett. 63 (2003) 69-75. Danilkin, S.A.; Skomorokhov, A.N.; Hoser, A.; Fuess, H.; Rajevac, V.; Bickulova, N.N.; Crystal structure and lattice dynamics of superionic copper selenide Cu2-�Se, J. All. Comp. 361 (2003) 57-61. Elerman, Y.; Elmali, A .; Zeyrek, C.T.; Svoboda, I.; Fuess, H.; Crystal structure and magnetic properties of a new hetero-dinuclear CuIIMnII Schiff Base Complex, Z. Naturforsch., 58b (2003) 271-277. Ellouze, M.; Boujelben, W.; Cheikhrouhou, A.; Fuess, H.; Madar, R.; Structure, magnetic and electrical properties in the praseodynium deficient Pr0.8-x�xSr0.2MnO3 manganites oxides, J. All. and Comp. 352 (2003) 41-47. Ellouze, M.; Boujelben, W.; Cheikhrouhou, A.; Fuess, H.;. Madar, R.; Structure, ferromagnetism and magnetotransport properties in the barium-deficient Pr0.7Ba0.2�0.1MnO3 manganite oxides, J. Mag. Mag. Mater. 257 (2003) 319-326. Ellouze, M.; Boujelben, W.; Fuess H.; Rietveld refinement of x-ray powder data of Pr0.7Ba0.3MnO3, Powder Diffr. 18 (2003) 29-31. Elmali, A.; Dincer, I.; Elerman, Y., Ehrenberg, H.; Fuess, H.; Magnetic phase transitions in Pr1-xDyxMn2Ge2 and Ce1-xDyxMn2Ge2, J. Phys.: Condens. Matter 15 (2003) 653-661.

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Estevez-Rams, E.; Aragon-Fernandez, B.; Fuess, H., Penton-Madrigal, A.; Diffraction pattern of stacked layer crystals, Phys. Rev. B68 (2003) 64111-12. Franco, E.G.; Arico, E.; Linardi, M.; Roth, C.; Martz, N.; Fuess, H.;Synthesis and characterization of electrocatalyst powders for applications in PEM fuel cells, Mat. Sci. For 416-418 (2003) 4-10. Gierlowski, P.; Dynowska, E.; Abal'oshev, A.; Pelka, J.B.; Paszkowicz, W.; Kostrzenska, D.; Baehtz, C.; Knapp, M.; Structure of laser-modified YBa2Cu3O7-x thin films. J. Alloys Comp. 362 (2004) 293-296. Gilles, R.; Mukherji, D.; Del Genovese, D.; Strunz, P.; Barbier, B.; Kockelmann, W.: Rösler, J.; Fuess, H.; Misfit Investigations of Nickel-base Superalloys, Materials Science Forum 426-432 (2003) 821-826. Gowda, B.T.; D'souza, J.D.; Fuess, H.;35Cl NQR spectra of arylsulphonamides N-chloro and N,N-dichloro arylsulphonamides, Z. Naturforsch. 58a (2003) 220-224. Gowda, B.T.; Jyothi, K.; Paulus, H.; Fuess H.;35Cl NQR and structural studies on substituted amides, XyC6H5-yNHCOR (X=H or Cl; y= 0.1 or 2 and R = C(CH3)3, CHClCH3, C6H5 or 2-ClC6H4), Z. Naturforsch. 58a (2003) 225-230. Guangming, L.; Schulmeyer, T.; Brötz, J.; Klein, A.; Jaegermann, W.; Interface properties and band aliggnment of Cu2S/CdS thin film solar cells, Thin Solid Films, 431-432 (2003) 477-482. Haaß, F.; Adams, A. H.; Buhrmester, T.; Schimanke, G.; Martin, M.; Fuess, H.; X-ray absorption and x-ray diffraction studies on molybdenum doped vanadium pentoxide, Phys. Chem. Chem. Phys. 5 (2003) 4317-4324. Hartung, J.; Drees, S.; Greb, M.; Schmidt, P.; Svoboda, I.; Fuess, H., A. Murso, A. Stalke, D.; (Schiff-base)vanadium(v) complex-catalyzed oxidations of substituted bis(homoallylic) alcohols - stereoselective synthesis of functionalized tetrahydrofurans, Eur. J. Org. Chem. (2003) 2388-2408. Hartung, J.; Schwarz, M.; Svoboda, I.; Fuess, H.; Uncovering stereochemical relations in a compound with a stereogenic N,O-axis: methyl, 2-(4-methyl-2-thioxo-2,3-dihydrothiazol-3-yloxy)propanoate, Acta Cryst C 59 (2003) 0682-0684. Hartung, J.; Špehar, K.; Svoboda, I.; Fuess, H.; The N-O bond as an element of chirality: (P)-4-(p-chlorophenyl)-3 toluenesulfonyl)piperazino]ethoxy}thiazole-2(3H)-thione, Acta Cryst E 59 (2003) 01894-01895. Hashimoto, M.; Terao, H.; Fuess, H.; Svoboda, I.; Ehrenberg, H.; Crystal structure, hydrogen bonding, and 81Br NQR of low temperature phase of 4-aminopyridinium tetrabromoantimonate (III), Bull. Chem. Soc. Jpn, 76 (2003) 749-753. Hohl, A.; Wieder, T.;.van Aken, P.A.; Weirich, T.E., Denninger, G.; Vidal, M.; Oswald, S.; Deneke, C.; Mayer, J.; Fuess, H.; An interface clusters mixture model for the structure of amorphous silicon monoxide (SiO), J. Non Cryst. Sol. 320 (2003) 255-280.

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Jorík, V.; Ondrejkovi�����- ��*����������� � ��Ehrenberg, H.; X-Ray powder diffraction structural characterization of Iron(III) chloro-and bromo-complexes of triphenylphosphine oxide; Cryst. Res. Technol. 38 (2003) 174-181. Kraft, D.; Thissen, A.; Brötz, J.; Flege, S.; Campo, M.; Klein, A.; Jaegermann, W.; Characterization of tellurium layers for back contact formation on close to technology treated CdTe surfaces, J. Appl. Phys. 94 (2003) 3589-3598. Loukil, M.; Kabadou, A.; Svoboda, I.; Ehrenberg, H.; Ben Salah, A.; Fuess, H.; Crystal structure of ammonium tetrachloromercurate(II)monohydra (NH4)2HgCl4 . H2O, Z. Kristallogr., NCS 218 (2003) 29-30. Loukil, M.; Kabadou A,; Svoboda, I.; Salah, A.B.; Fuess, H.; Crystal structure of ammonium triiodomercurate(II) monohydrate NH4HgI3 . H2O, Z. Kristallogr. NCS 218 (2003) 269-270. Muessig, E.; Bramnik, K.G.; Ehrenberg, H., Structural investigation of the Na-Fe-Mo-O system, Acta Cryst. B 59 (2003) 611-616. Mukherji, D.; Gilles, R.; Barbier, B.; Del Genovese, D.; Hasse, B.;. Strunz, P.;Wroblewski, T.; Fuess, H.; Rösler, J.; Lattice misfit measurements in INCONEL 706 containing coherent γ ‘ and γ ‘‘precipitates, Scripta Materialia 48 (2003) 333-339. Mukherji, D.; Strunz, P.; Del Genovese, D.; Gilles, R.; Rösler, J.; Investigation of microstructural changes in Inconel 706 at high temperatures by in situ SANS, Metallurgical Transaction, 34 (2003) 2781-2791. Öksüzoglu, R.M.; Weirich, Th.E.; Fuess H.; Characterization of Co25Ag75 and (Co90Al10)28Ag72

granular films by electron diffraction, high resolution transmission

spectroscopic imaging, J. Electr. Micr., 52 (2003) 91-100. Rosemary, M.J.;, Suryanarayanan, V.;Ganapatireddy, P.; Maclaren, I. Baskaran, S.; Pradeep, T.; Ciprofloxacin@SiO2: Fluorescent nanobubbles, Proc. Indian Acad. Sci.115 (2003) 703-709. Roth, S.V.; Burghammer, M.; Gilles, R; Mukherji, Rösler, J.; Strunz, P.;Precipitate scanning in Ni-base γ/γ′ superalloys, Nuclear Instruments and Methods in Physics Research B, 200 (2003) 255-260. Ruschewitz, U.; Baehtz, C.; Knapp, M.; Zur Kinetik der Bildung von Na2PdC2 Z. Anorg. Allg. Chem., 629 (2003) 1581-1584. Savytskii, D.; Vasylechko, L.; Senyshyn, A.; Matkovskii, A.; Baehtz, C.; Sanjuán, M.L.; Bismayer, U.; Berkowski, M.; Low-temperature structural and Raman studies on rare-earth gallates, Phys. Rev. B 68 (2003) 024101. Schlapp, M., Bulur, E., von Seggern, H., Photo-stimulated luminescence of calcium co-doped BaFBr:Eu2+ x-ray storage phosphors, J. Phys. D: Appl. Phys. 36 (2003), 103-108.

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Sigmund, J.; Karova, K.; Miehe, G.; Saglam,.M.; Hartnagel,.H.L.; Fuess, H.; Investigation of a growth interruption under an As flux at AlSb/InAs interfaces with InSb bonds, J. Cryst. Growth, (2003) 526-531. Stir, M.; Traykova, T.; Nicula, R.; Burkel, E.; Baehtz, C.; Knapp, M.; Lathe, C.; In situ high-pressure and high-temperature diffraction experiments on pure and Ag-doped TiO2 nanopowders, Nucl. Instr. and Meth. B 199 (2003) 59-63. Strunz, P. Gilles, R.; Mukherji, D.; Wiedenmann, A.; Anisotropic SANS data evaluation: a faster approach, J. Appl. Cryst. 36 (2003) 854-859. Strunz, P.; Mukherji, D.; Gilles, R.; Rösler, J; Wiedenmann. A.; Small-Angle Neutron Scattering: a Tool for Microstructural Investigation of HighTemperature Materials, Materials Science Forum 426 – 432 (2003) 755-760. Suleiman, M.; Jisrawi, N.M.; Dankert, O.; Reetz, M.T.; Baehtz, C.;. Kirchheim, R.; Pundt, A.; Phase transition and lattice expansion during hydrogen loading of nanometer sized palladium clusters, J. All. Comp. 644 (2003) 356-357. Vashook, V.; Vasylechko, L.; Knapp, M.; Ullmann, H.; Guth, U.; Lanthanum doped calcium titanates: synthesis, crystal structure, thermal expansion and transport properties, J. Alloys Comp., 354 (2003) 13-23. Vasylechko, L.; Vashook, V.; Savytskii, D.; Niewa, R.; Knapp, M.; Ullmann, H.; Berkowski, M.; Matkovskii, A.; Bismayer, U.; Crystal structure, thermal expansion and conductivity of anisotropic La1-xSrxGa1-2xMg2xO3-y (x = 0.05, 0.1) single crystals, J. Solid State Chem., 172 (2003) 396-411. Zerr, A.; Miehe, G.; Riedel, R.; Synthesis of cubic zirconium and hafnium nitride having Th3 P4 structure. Nature materials 2 (2003)

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Chemical Analytics We are active in the following fields: • Corrosion phenomena

High temperature corrosion of iron- and nickel-based PM-ODS superalloys Corrosion of graphite tube assemblies in atomic absorption spectrometry Corrosion of metals in polymer technology Corrosion of vessel materials for ultratrace analysis Corrosion of medieval glasses

• PM-technology Investigations of the reduction process of MoO3 by hydrogen Surface chemistry of water atomized aluminium alloy powders Effect of trace impurities in hard metals

• Particle characterization Single particle characterization mainly by electron probe methods of - environmental particles - industrial aerosols for occupational health evaluation - wear particles in polymer technology (in co-operation with the DKI) - Diesel soot from Otto- and Diesel-engines (Prof. Hohenberg, Department of Mechanical Engineering)

• Process analytics Development of a fast and simple method for the determination of toxic metal traces in industrial waste waters Fast materials identification by X-ray fluorescence analysis including the Compton scattering and statistical principal component analysis (Merck, Darmstadt)

• Analytical methods development Development of a portable �-XRS with polycapillary optics and drift chamber detector for cultural and forensic applications

• Wear studies Study of the wear process of cutting of compacted graphite iron used for high compression Diesel motors (Production Engineering and Machine Tools, Department of Mechanical Engineering)

• Activation analytical techniques Particle induced gamma-ray emission, charged particle activation analysis and neutron activation analysis techniques for the determination of fluorine, boron and of other elements in human bone samples (IAEA Vienna)

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Staff Members Head Prof. Dipl.-Ing. Dr. techn. Hugo Ortner Scientific Dr. Christiane Brockmann Dr. Ing. Peter Hoffmann Staff Dr. Stefan Flege Dipl.-Ing. Gunther Kraft Technical Staff Dorothea Berres Brunhilde Thybusch Secretary Antje Pappenhagen Diploma-Thesis Olaf Baake Selma Temiz Students Seval Gülen Stefanie Tilger Christian Schmitt Ph-D.-Students Dipl.-Ing. Mike Böning Dipl.-Ing. Gunther Kraft Dipl.-Ing. Roy T. Fox Dipl.-Ing. Jamila Saroukh Dipl.-Ing. Burkard Höflich Guest Scientists Prof. Dr. hab. E. Bulska, Dr. B. Wagner (Department of Chemistry, University of Warsaw, Poland) Dr. Anatol Dedik (Institute of Technical Physics of the Ukrainian Academy of Sciences, Charkov, Ukraine)

Research Projects Quantification of wear in extruders for polymer production by continuous and time-resolved x-ray fluorescence analysis (AIF, Deutsches Kunststoffinstitut, 2000 – 2003) Analytical investigations on graphite corrosion in electrothermal atomic absorption spectrometry (in co-operation with the Institute for Analytical Chemistry, University of Warsaw and the Department of Chemistry, Federal University of Santa Catarina, Florianopolis, Brazil, since 1996) Single particle characterization of industrial aerosols for occupational health evaluation (National Institute of Occupational Health, Oslo, since 1998) Bulk- and topochemical investigations of trace contaminations in organic semiconductor materials (DFG, 1999 – 2003, in co-operation with the group for electronic properties of materials in our department) Investigation of contemporary forgeries of ancient coins (in cooperation with Dr. Reiff since 2002)

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Publications Ortner, H.M.: Characterization of Individual Aerosol Particles with Special Reference to Speciation Techniques, Book chapter in: Handbook of Elemental Speciation: Techniques and Methodology, Cornelis, R.; Crews, H.; Caruso J. and Heumann, K., eds., J. Wiley & Sons Ltd., (2003) 505 – 525 Ortner, H.M.: Scanning electron microscopy – the door to the microcosmos (in German) Editorial, GIT Labor-Fachzeitschrift, 8/2003, 769 Stadermann, F.J.; Ortner, H.M.: Characterization of interplanetary dust and material degradation of space-exposed surfaces (in German), GIT Labor-Fachzeitschrift 8/2003, 808 – 812 Rohr, U.; Ortner, H.M.; Weinbruch, St.: Topochemical speciation of intercalated palladium in graphite by valence bond x-ray spectrometry in the electron microprobe, Anal. Chem., 75, (2003) 6576 – 6585, Hoffmann; P.: Some special aspects of the influence of particulate and dissolved iron on the climate. 7th Analytical Russian-German-Ukrainian Symposium 2001, Baikalsk, Russia, Proceedings, (2003) 12-14, Heck, M.; Rehren, T.; Hoffmann, P.: The production of lead-tin yellow at Merovingian Schleitheim (Switzerland). Archeometry 45(1), (2003) 33-44. Schulz, O.; Flege, S.; Martin, M.: Cation Self and Impurity Diffusion in Poly-Crystalline La0.9Sr0.1Ga0.9Mg0.1O2.9; Proceedings of the Eighth International Symposium on Solid Oxide Fuel Cells (SOFC-VIII), 2003, Eds. S. C. Singhal and M. Dokiya, PV 2003-07, The Electrochemical Society, Pennington 2003, p.304-314. M. Heck, H.M. Ortner, S. Flege, U. Reuter, H. Schulz Archäometrische Untersuchung eines merowingerzeitlichen Tiegelfragmentes mit anhaftendem gelbem Glas. In A. Burzler, M. Höneisen, J. Leicht, B. Ruckstuhl, Das frühmittelalterliche Schleitheim – Siedlung, Gräberfeld und Kirche, Baudepartement des Kantons Schaffhausen, Kantonsarchäologie, 2002, Bd.1, S.36-41, Bd.2, S.8+81ff

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Theoretical Materials Science Teaching by this division addresses the atomistic foundations of materials science, including the concepts underlying their representation, from the theoretical physics point of view. Research focuses on materials modelling, being a powerful tool for materials development. Experimental results will be understood, and predictions of further observations given, in the light of theoretical evidence, both to aid the optimization of the properties or the performance of materials already in use and to guide the design of novel materials with properties, or behaviour, required in future engineering applications. Current investigations centre on the following classes of materials: Transition metals and related alloys For this class of materials, represented by Ta and Fe or, respectively, steels, the goal is examining their suitability for structural components of high-power spallation neutron sources that are exposed to the intense proton beam. Irradiation-induced hydrogen production under the operating conditions of the envisaged European spallation source is predicted to generate high internal concentrations of atomic hydrogen which, further enhanced by stress-driven hydrogen accumulation near microstructural cracks, may lead to a severe degradation of the mechanical properties of steel, whereas no noticeable deterioration is to be expected in the case of tantalum. High-temperature superconductors For this class of materials, typified by �.���/'�0� and �������/��/'�0�� in thin film or bulk form, great interest is directed towards investigating extended defects, e.g. low-angle grain and twin boundaries which are considered as weak-links between superconducting grains. There are two principal aims: (i) exploring the connection between the electromagnetic response (e.g. the current-voltage relation) and the characteristic defect morphology so as to obtain insight into constitutive parameters of superconducting films; (ii) searching for possibilities to improve the current-carrying capability of superconducting materials, which is limited by the above-mentioned types of defect. Preliminary studies of novel heterostructures involving superconductor strips with a single grain boundary defect, placed in open magnetic cavities, show that magnetic shielding here is a promising way forward. Organic semiconductors For this class of materials, represented by � �1� , emphasis is placed on real-time modelling of the charge transfer by injected carriers and thermally stimulated luminescence phenomena with the aim of extracting, in conjunction with experiments, information about the electronic structure of inherent traps, so as to assist technological exploitation and further materials development. Some of the most important features to be taken into account hereby are the field-dependence of the mobilities of the charge carriers addressed as well as the field- and temperature dependences of the injection barriers present, apart from allowing for the variation of the distribution of traps in space and depth.

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Ferroelectrics For this class of materials, typified by ���2�0� , attention is focussed on the process of ageing, i.e. the gradual change of materials properties with time, isothermal conditions and absence of external mechanical loads implied. This process manifests itself in alterations of static and, respectively, kinetic characteristics such as the clamping pressure exerted on the walls of ferroelectric domains and the asymmetry of the electrical conductivity regarding current flow parallel or antiparallel to the direction of the spontaneous polarization; phenomena, which may be explained in terms of migration of charged point defects under the influence of internal or external electric fields. Preliminary results obtained with a drift-diffusion approach suggest that the experimentally observed drastic rise of the clamping pressure with time is indeed controlled by a mechanism of this kind. The theories underlying these investigations range from microscopic to macroscopic; their realizations employ analytical as well as computational techniques.

Staff Members Head H.E. The Hon. Prof. Dr. Dr.habil. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M., O.I.A. Research Associates Prof. Dr. Vladimir I. Arkhipov, D.Sc. Dr. Yuri A. Genenko, D.Sc. Dr. Sergey V. Yampolskii

Research Projects Electrodynamics of macroscopic magnet/superconductor heterosystems (German Research Foundation (DFG), 2003-2005) Kinetic modelling of the charge transfer in organic semiconductors and ionic conductors (Collaborative Research Centre (SFB) ”Electric fatigue in functional materials”, 2003-2006, with Prof. Dr. H. v. Seggern, Darmstadt University of Technology)

Publications Arkhipov, V.I.; Emelianova, E.V.; Bässler, H.; Dopant-Assisted Charge Carrier Photogeneration in Conjugated Polymers, Chem. Phys. Lett. 372 (2003) 886-893. Arkhipov, V.I.; v. Seggern, H.; Emelianova, E.V.; Charge Injection Versus Space-Charge-Limited Current in Organic Light-Emitting Diodes, Appl. Phys. Lett. 83 (2003) 5074-5076.

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Arkhipov, V.I.; Heremans, P.; Emelianova, E.V.; Adriaenssens, G.J.; Bässler, H.; The Effect of Doping on the Energy Distribution of Localized States and Carrier Transport in Disordered Organic Semiconductors, Proc. MRS 771 (2003) L5.7.1-6. Arkhipov, V.I.; Heremans, P.; Emelianova, E.V.; Bässler, H.; Exciton Dissociation in Doped Conjugated Polymers, Proc. MRS 771 (2003) L7.15.1-6. Kadashchuk, A; Vakhnin, A; Skryshevski, Y; Arkhipov, V.I.; Emelianova, E.I.; Bässler, H.; Thermally Stimulated Luminescence in π-Conjugated Polymers Containing Fluorene and Spirobifluorene Units, Chem. Phys. 291 (2003) 243-250. Genenko, Y.A.; Rauh, H.; Enhancement of the Current in a Superconductor Strip by Means of Curved Superconducting Shields, Appl. Phys. Lett. 82 (2003) 2115-2117. Genenko, Y.A.; Rauh, H.; Snezhko, A.V., Verbesserung der Stromtragfähigkeit supraleitender Schichten durch aktive magnetische bzw. supraleitende Abschirmung, in: Tagungsband zum VDI-Statusseminar ”Supraleitung und Tieftemperaturtechnik”, Garmisch-Partenkirchen, 13.-14.2.2003, ISBN 3-93-138444-6 (CD-ROM). Milosevic, M.V.; Yampolskii, S.V.; Peeters, F.M.; The Vortex-Magnetic Dipole Interaction in the London Approximation, J. Low Temp. Phys. 130 (2003) 321-331.

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Materials Modelling The research activities of the Materials Modelling Division are directed towards the investigation of materials properties and structure formation processes. Our main tool are atomic scale computer simulations. In doing so, we are combining a variety of methods depending on time and length scales involved in the corresponding problem. Quantum mechanical calculations based on density-functional theory are used for investigations of structural and electronic properties, while large-scale molecular dynamics with analytical interatomic potentials are the main tool for studying far-from-equilibrium materials processes. Additionally, kinetic Monte-Carlo simulations and cellular automatons are the methods of choice for problems on extended time scales. Our computer equipment consists of a cluster of desktop machines and two parallel computers with 60 CPUs in total. The main research areas are: • Kinetic Monte-Carlo simulations of epitaxial thin film growth • Modelling of point defects in metal-oxides • MD-simulations of properties and formation of nanoparticles • Investigation of mechanical properties of nanocrystalline materials • Development of reactive interatomic potentials for ceramics Besides the mandatory teaching of an undergraduate course the Materials Modelling Division is currently offering a 2-semester course on atomic scale methods for materials simulations.

Staff Members Head

Dr. Karsten Albe, Juniorprofessor

Research Associates Shi-Jin Zhao, PhD Dipl.-.Ing. Michael Müller Dipl.-.Ing. Paul Erhart

Secretary

Renate Hernichel

Diploma Students Dipl.-Phys. Wolfgang Voegeli

Guest Scientist

Prof. Dr. Kai Nordlund; University of Helsinki, Finland Janne Nord, PhD; University of Helsinki, Finland

Research Projects Molecular dynamics simulations of atomic processes during interface gliding (DFG 2002-2003)

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Atomistic studies of processes far from equilibrium (DAAD, PPP Finland, 2001-2003) Atomistic computer simulations of defects and their mobility in metal-oxides (DFG-SFB 595, Project C2, 2003-2006 )

Publications J. C. Busse; C. Polop; M. Müller; K. Albe; T. Michely; Stacking-fault nucleation on Ir(111), Phys. Rev. Lett. 91 (2003), 056103-(1-4) S. G. Mayr, Y. Ashkenazy, K. Albe, and R. S. Averback, Mechanisms of Radiation-Induced Viscous Flow: Role of Point Defects, Phys. Rev. Lett. 90 (2003) 55505-(1-5) K. Albe; T. Weirich; Structure and stability of alpha- and beta-Ti2Se: Electron diffraction versus density-functional theory calculations, Acta Cryst. A 59 (2003) 18-21 J. Nord; K. Albe; P. Erhart; K. Nordlund; Modelling of compound semiconductors: Analytical bond-order potential for gallium, nitrogen and gallium nitride, J. Phys.: Condens. Mat. 15 (2003) 5649- 5662 Y. Zhong; Y. Ashkenazy; K. Albe, R.S. Averback; Ion Beam Smoothening of Metal Surfaces, J. Appl. Phys. 94 (2003) 4432-4439 W. Voegeli; K. Albe; H. Hahn; Simulation of grain growth in nanocrystalline nickel induced by ion irradiation, Nucl. Instr. Meth. B 202 (2003) 230-235 J. Nord; K. Nordlund; J. Keinonen and K. Albe; Molecular dynamics study of defect formation in GaN cascades, Nucl. Instr. Meth. B 202 (2003) 93-99 J. P. Krasnochtchekov; K. Albe; R.S. Averback; Simulations of the inert gas condensation processes, Z. Metallkunde 10 (2003) 1098-1105

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Collaborative Research Centre (SFB) “Electric Fatigue in Functional Materials”

Phase I: Jan. 2003 – Dec. 2006 www.sfb595.tu-darmstadt.de

The center of excellence (Sonderforschungsbereich) has been awarded by the Deutsche Forschungsgemeinschaft in 2002 to TU Darmstadt and is centered in the department of Materials and Earth Sciences with important contributions from the Department of Chemistry and the Department of Mechanics as well as the Mechanical Engineering Department of the University of Karlsruhe. It is comprised of a total of 17 projects and financial resources for four years of about 5.75 Mio. EURO. The center has an active guest program with guests visiting from 2 days to 3 months. For specific information, please contact either the secretary of the center, Mrs. Gila Voelzke, or the director of the center, Prof. Jürgen Rödel.

Contact: Office: SFB 595: Electric Fatigue in Functional Materials, Institute of Materials Science Petersenstr. 23 64287 Darmstadt Tel.: +49-6151-16-6362, 6315 Fax: +49-6151-16-6314 Building/Room: L201 / 258 E-mail: roedel@ceramics.tu-darmstadt.de Voelzke@ceramics.tu-darmstadt.de

Electric fatigue in functional materials encompasses a set of phenomena, which lead to the degradation of materials with an increasing number of electrical cycles. Electric cycling leads to both reversible and irreversible currents and polarisations. Ionic and electronic charge carriers interact with each other and with microstructural elements in the bulk as well as at interfaces (grain boundaries and domain walls) and interphases (electrode/electrolyte). This in turn causes local changes in the distribution of electric currents and electric potentials. As a consequence local overloads and material degradation ensues and leads to irreversible loss of material properties. This material degradation can lead finally to mechanical damage as well as to dissociation reactions. The basic phenomena of electric fatigue are not yet understood on a microscopic level. The goal of this center of excellence in the first phase is the understanding of the mechanisms leading to electrical fatigue. The second phase is designed to use this knowledge for innovative material concepts and their evaluation. New simple components are scheduled to be developed during this phase. Suitable synthesis methods need to be created and complementary characterization of materials and components is required. An understanding of the experimental results is supported by concurrent materials modelling which is geared to encompass different time and length scales from the material to the component.

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A key feature of the center is therefore the steady comparison between theory and experiment. This is utilized to find the physico-chemical origins of electrical fatigue as well as to develop strategies for new materials and improved material combinations. The materials of interest are ferroelectrics, electrical conductors (cathode materials for lithium batteries and transparent conducting oxides) and semiconducting polymers. Projects: Division A: Synthesis A1 P.I. : Professor J. Rödel Topic: Manufacturing of textured ceramics actuators with high strain A2 P.I. : Professor M. J. Hoffmann, Topic: Manufacturing and characterization of PZT-ceramics with defined defect chemistry A3 P.I. : Professor W. Jaegermann Topic: Boundary layers and thin films of ionic conductors: Electronic structure, electrochemical potentials, defect formation and degradation mechanisms A4 P.I. : Professor R. Riedel Topic: Novel functional ceramics using anionic substitution in oxidic systems A5 P.I.: Professor M. Rehahn Topic: Synthesis of semiconducting model polymers and their characterization before and after cyclic electric fatigue Division B: Characterization B1 P.I.: Dr. R.-A. Eichel / Professor K.-P. Dinse Topic: EPR-Investigations of defects in ferroelectric ceramic material B2 P.I.: Dr. Dr. A. G. Balogh / Professor H. Hahn Topic: Investigations of the defect structure and diffusion in ferroelectric materials B3 P.I.: Professor H. Fueß Topic: Structural investigations into the electric fatigue in PZT

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B4 P.I.: Dr. H. Ehrenberg / Dr. T. Buhrmester Topic: In-situ investigations of the degradation of intercalation batteries und their modelling B5 P.I.: Dr. D. Lupascu / Professor J. Rödel Topic: Model experiment for the interaction of ferroelectric domains with point defects and their agglomerates Division C: Modelling C1 P.I.: Professor P. C. Schmidt Topic: Quantum mechanical computer simulations for electron and defect structure of oxides C2 P.I.: Dr. K. Albe / Professor H. Hahn Topic: Atomistic computer simulations of defects and their mobility in metal oxides C3 P.I.: Professor D. Gross / Dr. R. Müller Topic: Microscopic investigations into defect agglomeration and its effect on the mobility of domain walls C5 P.I.: Dr. Y. Genenko / Professor H. v. Seggern Topic: Phenomenological modelling of bipolar carrier transport in organic semiconducting devices under special consideration of injection, transport and recombination phenomena Division D: Component properties D1 P.I.: Professor J. Rödel / Dr. D. C. Lupascu Topic: Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics D3 P.I.: Dr. A. Klein Topic: Function and fatigue of conducting electrodes in organic LEDs and piezoceramic actuators D4 P.I.: Dr. R. Schmechel / Professor H. v. Seggern Topic: Fatigue of organic semiconductor components

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Reports of Research Activities

Corrosion and Fatigue Behavior of the Magnesium Die-Cast Alloy AZ91 hp after Surface Treatment

C. Dindorf, C. Müller

Magnesium is of increasing importance in the automotive industry due to its lowest density among commercially used metals for increasing mileage, and thus reducing exhaust emission. To date, main use for magnesium consists of die-cast components, with the aluminum-rich AZ91 being the most prominent alloy. The components are usually used as-cast, i.e. they are only machined marginally where joined with other parts. The hcp unit cell of the magnesium matrix prohibits cold working (as a means to improve the relatively poor mechanical properties) and forging the material into its final component form after casting. Age hardening leads to an unfavorable reduction in ultimate strain. So, in order to increase fatigue properties of load-bearing components mechanical surface treatments can be employed, such as shot-peening. Shot-peening (SP) is a well established process for ferrous and many other non-ferrous alloys. By inducing compressive residual stresses and deformation into the surface layer, shot-peening results in a retardation or even prevention of crack initiation and propagation during fatigue, thus leading to an increase of the endurance limit. The effect of shot-peening was investigated regarding the corrosion and fatigue behavior of AZ91. As shot medium ferritic steel was used in the form of spheroidized cut wire, being by far the most established and least costly material used for shot-peening. With this mechanical surface treatment the endurance limit could be improved by some 40% to 100 MPa in a rotating beam bending setup. There was no evident corrosion at ambient conditions. However, if put into a 5% NaCl aqueous solution the shot-peened surface (Fig. 1b) exhibits severe corrosion compared to the as-cast state (Fig. 1a) after only three hours. Longer immersion tests of up to a week led to a massive dissolution of the whole specimen.

Fig. 1: Micrographs of specimen surfaces corroded for 3 hours in 5% NaCl solution (a) as-cast; (b) SP with ferritic shot; (c) SP with ferritic shot plus secondary peening with glass beads Fatigue properties after three-hour immersion tests of shot-peened specimens were drastically decreased relative to the as-cast state as well as shot-peened material without precorrosion. An endurance limit could not be determined for the heavily corroded specimens. EDX analysis of the shot-peened and uncorroded surface revealed a

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significant amount of residual iron from the shot-peening process. As magnesium is not only the lightest but also the least noble metal used for structural applications galvanic corrosion between the magnesium base material and the iron particles left from the ferritic shot medium leads to severe pitting on the surface. Iron concentration was undetectable for the as-cast surface. Compared to the unpeened state, polarisation curves showed a shift in the rest potential for shot-peened specimens to more noble values due to the presence of iron on the surface. For retaining the beneficial effect of shot-peening on fatigue properties while avoiding the severe galvanic corrosion, several approaches can be found in literature. For example, the detrimental iron is to be removed by a secondary peening process with an inert shot medium, e.g. glass beads. This cleansing is supposed to be sufficient to suppress any galvanic corrosion in subsequent immersion tests. In the present study, this was not the case (Fig. 1c), although EDX analysis showed a reduction in iron concentration by three fourths compared to ordinarily peened material, and SEM micrographs revealed a complete coverage of the surface with material from the glass beads. Resulting from the still unacceptable pitting, secondary peened specimens after immersion tests showed very poor fatigue properties similar to those after ordinary shot-peening and precorrosion. Another approach suggests a pickling treatment with sulphuric acid in order to chemically remove the residual iron from shot-peened surfaces. After the chemical treatment the magnesium base material was uncovered again, i.e. a 50 µm thick surface layer was removed including the detrimental iron particles. Polarisation curves indicated a complete removal of the iron as well as the die skin which is, due to a higher Al content, slightly nobler than the base material. Immersion tests of pickled specimens resulted in a mostly uniform corrosion with only very small, widely scattered specks of pitting attack. Due to the relatively mild corrosive attack fatigue properties were hardly influenced. The endurance limit of shot-peened, pickled and precorroded specimens is equal to that of shot-/secondary peened and uncorroded specimens (Fig. 2) as well as superior to that of the as-cast, unpeened material.

Fig. 2: S-N curves for three different surface treatments of AZ91; rotating beam bending setup (R = -1, 50 Hz)

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High-strength Bulk Glassy and Nanostructured Alloys with Improved Deformation Behavior

M. Calin1, G. He2, J. Eckert

1. University “Politehnica” of Bucharest, Materials Science and Engineering Faculty, Spl. Independentei 313,

Ro-77206 Bucharest, Romania 2. Light Materials Group, National Institute for Materials Science, 1-2-1 Sengen,

Tsukuba, Ibaraki 305-0047, Japan

Bulk metallic glasses and nanostructured materials with grain sizes of the order of 100 nm and below are known to be high-strength materials, with yield strength of about an order of magnitude higher than their coarse-grained crystalline counterparts. However, such materials do not deform through the classical work hardening processes as in conventional metals and alloys, thus reaching room temperature failure at small strains soon after plastic deformation commences. Due to the lack of work hardening deformation of glassy and nanostructured materials also tends to become unstable and is prone to localization such as shear banding and necking in tension. This is a severe drawback causing concerns for catastrophic failure in many load bearing applications.

Fig. 1. X-ray diffraction patterns (a) and room temperature compressive stress-strain curves (b) of as-cast Cu-based alloys.

Fig. 2. Electron microscopy micrographs: a), b) TEM images of Cu47Ti33Zr11Ni8Fe1 and Cu47Ti33Zr11Ni8Si1 rods, respectively; c) SEM image of Cu47Ti33Zr11Ni8Si1.

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To circumvent such limitations, the concept of using heterogeneous glassy/nanostructure-based materials and grain size distributions has been recently employed to develop high-strength bulk composite materials with improved room temperature ductility. For this purpose, different bulk glass-forming systems have been explored. The first example shows results obtained for Cu47Ti34Zr11Ni8 and Cu47Ti33Zr11Ni8X1 (with X = Fe, Si, Sn, Pb, Mn) bulk glass-forming alloys. Cylindrical rods of 2 mm diameter and 70 mm length were prepared by injection casting into copper molds. According to X-ray diffraction and electron microscopy (Fig. 1a, Fig. 2), only the base alloy (A = Cu47Ti34Zr11Ni8) and the Fe-containing alloy are fully glassy. The Sn-, Pb- and Mn-containing alloys exhibit a glassy-crystalline microstructure, where the crystalline phase has a bcc structure and dendritic morphology. The Si-containing alloy has a special bimodal composite structure consisting of an uniform distribution of Cu-rich nanoparticles of about 8 to 15 nm in size in a glassy matrix (Fig. 2b). Room-temperature compressive stress-strain tests (Fig. 1b) reveal that the alloys possess yield strengths of 1600 ÷ 2100 MPa, fracture strengths of 1800 ÷ 2200 MPa, Young’s moduli of 100÷109 GPa and elastic elongations of 2.0 ÷ 2.7 %, but significant plastic deformation (2.2 %) only for the Si-containing alloy. This is due to the unique nanocomposite microstructure shown in Fig. 2b. The increase of the global plasticity can be explained by the formation of multiple shear bands that make the bulk glassy alloy resistant to crack propagation.

The other example gives results obtained for Ti-based multicomponent structural composite nanomaterials, which were derived from bulk glass-forming compositions (Fig. 3). This type of material is able to achieve high strength together with high ductility (Fig. 4) by controlling the instabilities otherwise responsible for early failure. This emphasizes the possibility to manipulate such composite microstructures in favor of either strength and ductility, or a combination of both and also reveals the acquired ability to process such in situ high-strength nanostructures in bulk form through inexpensive processing routes.

Fig. 3. SEM micrographs of as-arc melted

Ti60Cu14Ni12Sn4Nb10 (a), Ti60Cu14Ni12Sn4Mo10

(b), Ti60Cu14Ni12Sn4Ta10 (c), and as-cast

Ti60Cu14Ni12Sn4Ta10 alloys (d).

Fig. 4. Room-temperature compressive true stress-strain curves of as-arc melted and as-cast Ti60Cu14Ni12Sn4(M)10 alloys.

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A Method to Determine Phase Equilibria in Multicomponent Alloys

Guoping Zhao, Markus Rettenmayr Computer simulations can reduce the time for alloy development and improve the control over production processes involving complex alloys. Accurate input data are a prerequisite for reliable simulation calculations. Simulation of solidification processes of multicomponent alloys, as e.g. used for turbine blades, often yields unsatisfactory agreement between experimental and simulated results. A major reason for this is the fact that the phase equilibria that are relevant during solidification are needed as input data into the simulation calculation, but are not available with sufficient accuracy. Several methods have been published in the literature for extrapolating phase equilibria from known lower order equilibria. However, often the extrapolated data don’t even yield qualitative agreement. Measurement of phase equilibria based on classical methods (annealing, quenching, concentration measurements at selected points in the microstructure) is tedious. In multicomponent alloys the effort is unlikely or impossible to be undertaken. In ternary alloys, typically 1500 measured data couples need to be known, in quaternary alloys the number increases to approx. 1 000 000, for each further alloying element an increase by one to two orders of magnitude is necessary. Considering that some technically important alloys consist of ten or more components (e.g. high-temperature super alloys), a faster and accurate measurement method appears to be highly desirable. A new measurement method has now been developed in the Physical Metallurgy Department. It is based on a combination of experiments and calculation and leads to a drastic reduction of the experimental effort. This is possible due to three characteristic features of the method: a) the sequence of phase equilibria that occur in a technical process is reproduced in the laboratory using directional solidification under special and well defined conditions. Data points that are not relevant in the technical process will then not be measured. b) Generating steep concentration gradients in the samples yields a high number of data points on the basis of a single experiment. c) Strong forced convection (electromagnetic stirring) ensures that the alloying elements are homogeneously distributed in the melt at all times. The varying melt concentration in the course of the solidification experiment can then be calculated instead of measured (with methods that are mostly prone to errors). Using the new method, the number of experiments for determining the phase equilibria can be reduced to three in ternary alloys, to approximately ten in quaternary alloys. The key to the process is the control of convection in the melt that leads to a defined formation of concentration gradients in the solid and that allows for the determination of the phase equilibria. In metal alloys, convection cannot easily be made visible. In the present case it can be characterized using its results, i.e. the microstructure and the concentration distribution that form during solidification. Especially the occurrence of secondary phases at well defined locations can demonstrate the successfully adjusted parameters. In Fig. 1a this is shown using the example of a binary Al-Cu alloy: after the

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primary solidification phase (α-Al (grey, lower part) an abrupt change to the secondary phases (eutectic, upper part) occurs. In an Al-Cu-Si-Mn-Fe alloy the different secondary phases begin to precipitate at defined locations with a distance of approx. 200µm (Fig. 1b).

Fig. 1a: Under strong forced convection directionally solidified Al-Cu sample (detail from end of sample), including the easily visible transition of α–Al to eutectic.

Fig. 1b: Sequence of different solidifying secondary (intermetallic) phases in a technical Al-Cu-Si-Mn-Fe-alloy.

Concentration profiles of the four alloying elements Cu, Si, Mn, and Fe in the region where primary α-Al solidifies are shown in fig. 2. The trend of the profiles of Cu and Si is in agreement with the expectation that normally an enrichment of alloying elements occurs in the course of solidification. As opposed to this, the concentration of Mn decreases in the course of solidification. This decrease would not be predicted by methods that extrapolate phase equilibria empirically. This demonstrates that measurements as e.g. with the present method are indispensable.

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Fig. 2: Concentration profiles of four alloying elements in the region of primary (α–Al) solidification in the Al-Cu-Si-Mn-Fe alloy

57

Heterogeneous Fatigue in Ferroelectrics

Y. Zhang, E. Aulbach, D. C. Lupascu, J. Rödel

The long term performance of piezoelectric actuators and ferroelectric memory cells is in large parts determined by their material reliability. In this respect, lead zirconate titanate, the system showing best initial performance within the family of ferroelectric materials, unfortunately suffers a multitude of microscopic damage mechanisms. In order to understand and ultimately circumvent material deterioration, particularly two dominant mechanisms, microcracking and electrochemical fatigue, have to be understood. A large number of studies have been performed trying to relate these two mechanisms to the macroscopic performance reduction. The motion or rearrangement of ferroelectric domains constitutes a dominant part of the material properties, similar to magnetic systems. One of the peculiarities in thin film devices, being the geometry for computer memory cells, was the observation that the reduced switching ability of domains is a very heterogeneous process. In certain parts of a device, domains would freeze, while in others their ability to invert polarity remained intact. This was mainly attributed to the interaction of these domains with the metallic electrodes in their immediate vicinity. Surprisingly, the effect also occurs in a macroscopic ceramic material. A test system permitting to measure the piezoelectric constant as a function of macroscopically applied bias fields was developed to disclose this effect. While the piezoelectric coefficient d33 itself is a small signal property, the fatigue is best monitored as changes of large signal offsets. A measurement of the dc biased piezoelectric coefficient d33(E) combines both scales and allows establishment of relations between local switching ability of domains and global offsets. The device itself measures changes in strain as a function of applied electric field. An advantage of this particular setup is that the strain measurement is performed between two metallic tips yielding a local measurement. Modifications of the switching ability of the domain system can thus be found point by point on a sample surface (Fig. 1). The displacement sensitivity is comparable to atomic force microscopy (0.1Å). Figure 2 contrasts one virgin hysteresis loop with two in different fatigue stages. Characteristically, the maxima within the loop right below the coercive electric field (Ec) disappear after fatigue. Furthermore, the

Fig. 1: A schematic of the strain measurement setup. The high voltage is maintained during ac measurement by a large capacitance in parallel.

HV

Lock-In

AC

Csource

Csample

Strain Sensor

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are highly reduced showing that a large amount of domains looses its switching ability. The offsets, which are the vertical or horizontal shift of the entire hysteresis loop, are representative of a preferred orientation of the frozen domain system in one direction. An approximately linear relation between the offset electric field (Eoffset) and the offset piezoelectric coefficient (d33,offset) is found. The explanation of the offsets resides in the non-homogeneous distribution of charged point defects throughout the sample in thickness direction yielding the preferred direction. A second heterogeneity is found laterally. Figure 3 represents these lateral changes of the coercive electric field and remnant polarization (horizontal and vertical widths of the hysteresis loops). The material fatigue is thus heterogeneous in thickness direction and laterally and thus a very local phenomenon also in bulk ceramic ferroelectrics. The detailed sources and mechanisms causing this heterogeneity are now under investigation.

Fig. 2: The hysteresis of the piezoelectric coefficient d33 as a function of applied dc electric field. Left, for a

virgin sample and right for two samples fatigued up to 4.7x106 bipolar fatigue cycles at 2 kV/mm and 50 Hz for two different spots on one sample.

Fig. 3: The lateral distribution of, left, the remnant polarization as determined from the offset in d33 and,

right, the coercive field (half width of the hysteresis in Fig. 2).

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59

Improved radiation hardness of CsBr:Eu2+ by codoping with Me*

J. Zimmermann, S. Hesse, H. von Seggern, M. Fuchs# and W. Knüpfer# # Siemens AG, Medical Solutions, Vacuum Technology, 91058 Erlangen, Germany

Digital x-ray radiography using storage phosphors is widely used nowadays. While commercially available systems are based on BaFBr:Eu2+, CsBr:Eu2+ is an interesting novel phosphor with promising properties. Not only does this material exhibit a high sensitivity for x-rays, it can also be used to fabricate high-resolution image plates since needle-like structures acting as light guides can be deposited by evaporation. After x-ray irradiation, electron/hole pairs are formed and stored in the phosphor. Electrons are trapped in Br--vacancies forming F-centers with its excitation-maximum at 680 nm. Upon

photostimulation electrons in these F-centers are released and recombine with hole centers giving rise to the so-called photo-stimulated luminescence (PSL). The main disadvantage of CsBr:Eu2+ is its low radiation hardness. The Eu2+ related PSL and fluorescence peaking at 440 nm decreases with the radiation dose. (Fig 1, dashed line). By a co-doping with Me* ions the radiation hardness could be improved as it is shown in Fig. 1 (compact line). In order to understand the physical reason for the low radiation hardness, the

photoluminescence (PL) of Eu2+ and Eu3+ with radiation dose was monitored. A sizable decrease of the Eu2+ fluorescence was observed for samples irradiated with doses up to 10 Gy. At the same time no radiation-induced oxidation of Eu2+ to Eu3+ was found, which could explain such a decrease and therewith the decrease of the PSL yield. Since Europium does not disappear from the sample, the loss in Eu2+ PL emission is believed to be due to agglomeration of Eu2+ leading finally to the well-known concentration quenching

of the Eu2+ emission. A consequence of this agglomeration is an increasing radiation-induced diffusivity of

(Eu2+-VCs)-dipoles, consisting of a Eu2+ ion and a Cs+-vacancy (VCs) for charge-compensation reasons in the monovalent CsBr. A likely reason therefore is the formation of large vacancies, which allow for an easier motion of Eu2+-

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Fig. 1 Dose dependent decrease of the PSL yield of a CsBr:Eu.

Fig. 2 Remission spectra of a CsBr:Eu2+

Fig. 3 The grey area locates the complex of M-center and (Eu2+-VCs)-dipole.

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60

ions. Such line of argumentation is supported by the x-ray induced appearance of M-centers, which were detected by remission bands occurring in the NIR regime of the spectrum. The remission thereby is proportional to the absorption. In Fig. 2 a series of measurements of the diffuse reflection (remission) is shown. Irradiating the virgin sample with a low dose leads to the formation of F-centers observed here as a remission minimum at 680 nm. At high dose additional bands occur in the NIR, which are due to so-called F’- and the above-mentioned M-center. The M-center is a complex of two anion-vacancies containing two electrons. From other investigations with non-doped CsBr such bands were reported to be extremely weak at room temperature (RT) with a relatively narrow absorption maximum at 1050nm to1070 nm.

In contrary to those findings in the present experiments M-centers were detected already at RT, however, only in Eu-doped samples with a remission minimum at 1080 nm, which is slightly shifted to higher wavelength in comparison with literature values for non-doped CsBr (Fig. 2). Due to this stabilization it is reasonable to assume, that the observed M-centers are stabilised by the (Eu2+-VCs)-dipoles as visualized in Fig. 3. It should be mentioned that in addition to the M-centers at 1080nm F’-center are found, which are responsible for the broad remission band between 800 and 2500nm. These F’-centers are anion-vacancies with two electrons occupying one anion vacancy. It was demonstrated

that long optical bleaching with white light could not eliminate the NIR-remission spectrum completely, meaning that a stable radiation defect remains. The complex of M-center and (Eu2+-VCs)-dipole naturally provides a large free space around the Eu2+ ion making agglomeration likely. Adding Me* ions to CsBr:Eu2+ the formation of F’- and M-centers is completely suppressed (see Fig. 4). On the other hand, only F-centers are generated and the material is less sensitive to irradiation (see Fig.1). Me* ions thereby substitute Cs+ sites. The explanation can be given as follows: Upon irradiation F-centers are generated most probably in the vicinity of the Me*-ions and are stabilized due to the Me*-induced distortions of the lattice (see fig. 5). No subsequent F-center motion is possible and the trapping of a second electron in the perturbed F-center is not stable or completely absent. This on the other hand explains the absence of M-centers and F’-centers. Since no M-centers are generated, no large free vacancies are formed in the vicinity of Eu2+, hence the diffusivity of Eu2+ does not increase markedly with dose, explaining the enlarged radiation hardness of the Me*-doped CsBr:Eu2+ as can be seen from Fig.1. Me*: Metal ion, not specified due to patent application

Fig. 4 Remission spectra of a Me*-codoped CsBr:Eu2+-NIP

Fig. 5 relaxation of the lattice after the removal of an Br- adjacent to Me*. Black arrows indicate the shifts.

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L=2mm

Fig. 1: Electrode configuration of the utilized O-LEFT: (a) wafer layout with 8 O-LEFT structures, (b) zoom of the layout structure of a fraction of a single O-LEFT, (c) cross section of two neighboring Au electrodes.

The organic light-emitting field-effect transistor (OLET)

Aline Hepp, Holger Heil, Wieland Weise, Marcus Ahles, Roland Schmechel, Heinz von Seggern

Since their discovery organic field effect transistors (OFETs) have been investigated extensively with regard to their application potential in low cost electronic circuits and display technology. Especially in their function as on/off switch for organic light emitting diodes (OLEDs), OFETs could establish a new generation of all organic low-prize display technology. Some years ago first success was reported in that field. However, the smallest possible integration of light source and switch would be the light emitting transistor. That device could only be realized in ambipolar operation mode (i.e. both types of charge carriers are injected), which results in carrier recombination, exciton formation and ultimately light emission. During the last years this idea was tracked intensively by many research groups all over the world, by then with no success. Recently we managed to fabricate an organic light-emitting transistor (OLET) based on vacuum deposited tetracene. That device exhibits electrical characteristics similar to a unipolar OFET and its light emission intensity can be modulated by the gate and drain voltage. Fig. 1 shows the electrode layout arranged on the substrate surface. Gold source and drain electrodes are configured as interdigitating fingers. The tetracene film is deposited on top of this structure

after a surface treatment with the silane coupling agent n-Octadecyldimethylchlorosilane (OMS), to improve tetracene film homogeneity and substrate coverage. Typical output characteristics of an OLET are displayed in Fig. 2. It exhibits the characteristics of a unipolar field-effect transistor with good saturation behavior. The electrical transfer characteristics are displayed in Fig. 3. They show no indication for ambipolar transport, neither it was possible to operate the transistor in pure n-type inversion mode. Their unusual saturation behavior is assigned to contact resistors on the source electrode, whose existence is also suggested by theoretical calculations. Field effect hole mobilities and threshold voltages, as derived from a fit to the experimental data in the linear regime

62

of the )(ID GSV -plot of the transfer characteristics are µh = 5· 10-2 cm2/(Vs) and Vth = –25 V,

respectively for VGS = -80 V.

On/off ratios in the range of 1· 106 were also determined from the transfer characteristics. Apparently, since there is no hint for ambipolar operation, the electron mobility is low and in addition the electron injection is weak. However, the significant light output at higher voltages confirms the injection of both electrons and holes. The optical characteristics of the same device as in Figs. 2 and 3 are displayed in Figs. 4 and 5. At first glance the optical response of the device is in agreement with expectations. The light emission associated to the electrical output characteristics is increasing with increasing source-drain

voltages VDS even at saturated drain currents (ID). This is attributed to an augmented electron injection, which in turn leads to a better-balanced hole-to-electron ratio and hence to stronger luminescence. Following thin film transistor theory one would expect the onset of ambipolar operation for drain voltages exceeding the gate voltage. In our devices, however, (see Fig. 4) the onset of light output, resembling the onset of electron injection,

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Fig. 4: Optical output characteristics of the tetracene O-

LEFT as recorded by a photodiode for different gate-source voltages

Fig. 5: Optical transfer characteristics of the tetracene O-LEFT as recorded by a photodiode for different drain-source voltages

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]

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DS [V]:

0 -20 -40 -60 -80

drai

n cu

rren

t ID [m

A]

gate-source voltage VGS

[V]

Fig. 3: Transfer characteristics of the tetracene O-LEFTfor different drain-source voltages.

Fig. 2: Output characteristics of the tetracene O-LEFT for different gate-source voltages.

63

starts at a common drain voltage of –20 V, even for gate voltages up to –80 V. In the present device only the intensity of the emitted light changes. It would lead to far to give an explanation for this behavior within the scope of this article. An even deeper insight into the mechanism of light emission is given by an optical image of the operating transistor, which is displayed in Fig. 6. The light is emitted only from locations close to the drain electrode and the position of light emission is independent of the applied voltage. This excludes beyond any doubt gate oxide leakage as origin for light emission. In case of leakage the emission zone should be spread over the whole transistor channel. In addition, the highest light intensity should be found near the source electrode, where the electric field through the gate insulator is maximal. Concerning the working mechanisms of the device some questions have still to be answered. A key aspect for understanding the device working principle concerns the

detailed mechanism of electron injection. Considering the energetic position of the LUMO level of tetracene at 2.4 eV, electrons have to surmount a barrier of 2.7 eV, which seems to be impossible by means of thermal energy alone. However, high electric fields may allow a tunneling through this barrier by field injection. The question at this point is still, where do these electrical fields come from, since classical transistor theory forbids electron injection. We assume that a particularity at the tetracene/gold contact facilitates electron injection. Further investigations, with photoelectron spectroscopy for example, will address this issue.

This work was financially supported by the European Union through the EU-FET-IST project ILO #IST-2001-33057.

D

S

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25 µm

D

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S

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S

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25 µm Fig 6. Picture of an operating OLET taken through an optical microscope. Source (S) and Drain (D) electrodes are arranged as shown in fig. 1.

64

Atomic resolved STM images from the formation process of a GaSe half-sheet surface termination on Si(111)

B. Jaeckel, R. Fritsche A. Klein and W. Jaegermann

Silicon is the most important material used in electronic devices. Passivation of electronic surface states, which is necessary for efficient switching devices or high efficiency solar cells, is mostly by SiO2. The saturation of the surface dangling bonds might also be useful for growth of lattice mismatched films in order to integrate optoelectronically active materials into silicon technology. Both may be achieved with a half-sheet of the layered semiconductor GaSe, which provides an electronical and chemical passivation of the Si(111) surface. In our first experiments we have prepared this surface termination by selenization of a monolayer of Ga deposited onto Si(111) at elevated substrate temperature. This procedure involves several complex rearrangements of the Si surface atoms, which we want to avoid in order to obtain a faster and better reproducible surface termination. Here we describe in-situ STM and LEED measurements carried out during the formation of the Si(111):GaSe surface termination prepared by evaporation of GaSe onto Si(111).

All samples were cleaned by flash-heating to ~1200°C, resulting in a 7x7 reconstruction of the Si(111) surface, which is shown in Fig.1a. Onto this surface GaSe was deposited at 550°C substrate temperature with a rate of 2-3 Å/min. After approximately 30s of deposition (Fig.1b) a 33x surface reconstruction was obtained, which contains only Ga, despite the exposure to both Ga and Se. Obviously only Ga binds to the surface. Further deposition of GaSe leads the formation of a 6.3x6.3 followed by a 33.633.6 x -Ga reconstruction, which are both identified by STM and LEED. The surface after three minutes of deposition is shown in Fig. 1c corresponding to the 33.633.6 x -Ga surface. First GaSe half-sheet covered areas (dark region in Fig.1c) occur after the surface is covered with more than 1/3 monolayer of Ga.

Fig. 1: Filled state (Vtip=+2V, It=0.55nA) STM- images of the intermediate states during the GaSe half-sheet formation onto Si(111) and as insets the corresponding LEED-pattern

These areas are growing continuously until the complete surface is covered by a half-sheet of GaSe (Fig2a). An atomic resolved image of this surface is displayed Fig.2b. The measured distances are in good agreement with the lattice constant of silicon in (111) orientation. Independent of doping and miss-orientation of the silicon wafers all samples pass through the intermediate surface phases. The time which is necessary to achieve a certain surface phase depends on the mis-orientation of the surface and is due to steps,

65

which restrict the diffusion-length of gallium and selenium . The structure of the resulting GaSe passivated surface is given in Fig.2c. The topmost layer is formed from selenium atoms (dark symbols) which are bound to three gallium atoms and with a double-filled electron orbital perpendicular to the surface. This orbital will be imaged with STM at positive tip-bias. The three-fold symmetry in the LEED-pattern is a result of the stacking of Se, Ga and Si which is the same as in bulk silicon. Because of the hexagonally close-packed Se layer the surface should behave like a van der Waals surface as obtained by cleavage from layered semiconductor GaSe single crystals.

Fig. 2: a) STM- image of a GaSe half-sheet terminated n-type Si(111) surface after 25min of deposition and the corresponding three-fold symmetric LEED-pattern. b) Atomically resolved STM-image of the GaSe half-sheet surface layer. c) scheme of the GaSe half-sheet termination layer of Si(111) in top and side view. The darker marked selenium atoms with filled electronic states are imaged with STM

The results show that intermediate Si:Ga surface terminations during the formation of the Si(111):GaSe half-sheet van der Waals surface termination can not be avoided by co-evaporation of Ga and Se. We explain this by the stable Si-Ga bonds which form very fast. At low Ga coverage the Ga atoms with their three single occupied orbitals form directional bonds to the single occupied dangling bonds of the Si(111) surface leading to the 33x reconstruction, where three Si surface atoms share one Ga atom. Formation of the Si(111):GaSe surface, however, requires one Ga atom per Si surface atom (Fig. 2c), which is not possible at low coverage. Selenium most likely does not adsorb strongly on the flat Si(111) terraces until the GaSe surface termination can form, which requires more than 1/3 monolayer of Ga coverage. After the selenization of terraces the steps were passivated in the last step.

66

ZnTe: A potential interlayer to form a low resistance back contact for the CdTe thin film solar cell

B. Späth, J. Fritsche, D. Kraft, A. Klein and W. Jaegermann

The CdTe thin film solar cell is a good candidate to combine a reasonable conversion efficiency with a low-cost production process. CdTe solar cells are currently produced using a layer sequence of glass/ITO/SnO2/CdS/CdTe and a metallic back contact. Negative charge flows from the CdTe to the SnO2/ITO front contact while the metallic back contact is responsible for the collection of holes. But many metals form a large schottky barrier against the flow of the holes with CdTe (Fig. 1(a)) resulting in a high contact resistance. Other metals seem to cause degradation of devices in long-term stability tests due to their high diffusion coefficients in polycrystalline CdTe. Also the attempts to create a tunnel barrier have been unsuccessful, because p-type dopants are not easily incorporated in high densities into CdTe. The full potential of CdTe solar cells will not be realized until a low resistance and stable back contact can be generated. A solution to solve this problems is to deposite a semiconductor as an interlayer, which has a nearly ideal band offset off ∆EVB 3�4�*����/�2������!���(��������#���&���������(������'������5�contact to the metal. ZnTe is a potential candidate for such an intermediate layer (Fig. 1(b)). CBVBCBVBEFEF1,49eV1,49eV2,30eVp-type CdTe

lighty dopedp-type CdTelighty doped p-type ZnTeheavily dopedMetalMetalhottky

arrier(a)(b)unnel

arrier

Fig. 1: (a) Energy diagram of a Schottky barrier between p-type CdTe and a metal. (b) With heavily p-doped ZnTe as an intermediate layer between CdTe and the metal a tunneling barrier is formed at the ZnTe/metal interface. This barrier can be easily tunnelled by the holes. In addition the valence band offset between CdTe and ZnTe is negligible. In this work nitrogen doped p-ZnTe:N films were prepared using reactive RF magnetron sputtering with Ar/N2 gas mixtures resulting in a minimum Fermi level position of EF-EVBM=0,48eV. The electronic interface properties of ZnTe with CdTe and with metals (Au and Mo) have been characterized using in-situ XPS and electrical measurements. For the CdTe/ZnTe heterojunction a valence band offset of ∆EVB=-0,08±0,05eV has been found, which is advantageous for the hole tranfer from CdTe to ZnTe (Fig. 1(b)). A chemical reaction or a formation of an interlayer compound has not been observed. The ZnTe/Au and the ZnTe/Mo interfaces show both a complex structure with formation of different interlayers. The Schottky barrier heights (ΦB,p) have been determined as 0.62±0.1eV for the Au/ZnTe contact and as 0.93±0.1eV for Mo/ZnTe (Fig. 2(a,b)). But a lower contact resistance has been found for the Mo/ZnTe contact compared to the Au/ZnTe contact as determined by using electric measurements (Fig. 2(c)).

67

ΦB=0.62 eVCBVBEFZnTeGoldCBVBZnTeMolybdenumΦB=0.93 eV(a)(b)(c)EF

Fig. 2: Comparison of the band energy diagrams of the (a) ZnTe/Au and the (b) ZnTe/Mo interfaces. A higher Schottky barrier is formed at the ZnTe/Mo interface. The current-voltage characteristics of ZnTe films with different metal contacts (Au and Mo) are shown in (c). A higher conductivity was found for the Mo contacts. The current-voltage characteristics were measured between two front surface dot contacts of equally prepared ZnTe films. HREM images of the ZnTe/Au and ZnTe/Mo interfaces are shown in Fig. 3 and 4.

Fig. 3: HREM image of the ZnTe/Au interface.

Fig. 4: HREM image of the ZnTe/Mo interface.

Gold is a noble metal, but Zn is easily dissolved in gold because of a negative enthalpy of solution. Hence, a reaction of Au with ZnTe occurs and intermediate layers of an Au:Zn alloy and AuTe2 are formed. Molybdenum is a reactive metal and does not dissolve in gold. Therefore Mo reacts heavily with the ZnTe with the formation of MoTe2 and elementary Zn. This Zn has the opportunity to dope the ZnTe at the surface by generating electronic defects in the bandgap, which are assumed to assist charge transport across the interface. However, the current transport mechanism at the ZnTe/metal interfaces is not yet understood in all detail. Its understanding is only possible by a combination of photoemission and electrical measurements. In summary, the results indicate that Mo/ZnTe/CdTe sequences are a good candidate for low resistance back contacts to CdTe thin film solar cells, which will be tested in their application in the near future.

68

Fig. 1: Experimental nondimensional Lissajous figure representing the sharp rheological transition from “fluid” to “solid” like behaviour

Sol – Gel Modelling Associated with the Rheology of Polymeric Precursors of Ceramic Materials

Corneliu Balan*, Ralf Riedel *Politehnica University of Bucharest, Faculty of Energetics, Hydraulics Department – REOROM

Laboratory,Splaiul, 79590 Bucharest, Romania Email: balan@hydrop.pub.ro

A general constitutive relation describing the change of viscoelastic behavior during the liquid - solid (sol - gel) transition which takes place in preceramic polymers is derived on the basis of Jeffrey’s 3-constants model with time dependent viscosities and elasticity. It is postulated that the sol - gel - transition can be analyzed analogous to the solutions of the Avrami equation used for modeling crystallization processes. Two different polymer systems used as precursor for the production of ceramic materials are investigated here: i) a mixture based on polysiloxane, alumatrane and isopropanol; ii) a non-oxidic carbodiimide gel based on the reaction of chlorosilanes with bis(trimethylsilyl) carbodiimide. Continuous measurements of the dynamic moduli versus reaction time, as well as creep tests at constant shear stress, evidenced both qualitative similarities and quantitative differences associated with the sol - gel transition of the two polymer systems. The shear rate and viscosity dependence of reaction time in creep tests, respectively the evolution of Lissajous figures associated with oscillatory experiments, are found to be consistent with the numerical simulations of the proposed constitutive relation. .

69

Structural changes during electrochemical insertion of Mg into Mo3S4

K. Nikolowski, N.N. Bramnik, Th. Buhrmester, H. Ehrenberg

From the thermodynamic point of view, magnesium is an obvious choice for use as anode material in secondary batteries. It may provide a higher energy density as traditionally used lead-acid and nickel-cadmium systems and, moreover, it is more convenient considering environmental purposes. There have been a lot of attempts to construct a working magnesium battery, but several drawbacks prevented a succesfull prototype: The first problem which had to be solved, was the development of an appropriate electrolyte-solution. The correlated second task was to find the right cathode-material. In 2000 Aurbach et al. showed a possible solution: They used Mg(AlCl2BuEt)2 in THF 0.25 M as electrolyte, which should be stable up to 2,5 V (vs. metallic Mg), and Mo3S4 as cathode material. A specific capacity of approximately 60 mAh/g was reported.

Cycle Nr.

spec

ific

cap

acit

y /

mA

h/g

charge

discharge

Fig. 1: Galvanostatic cycles (left) and specific capacity vs. cycle number (right). Nevertheless structural aspects of magnesium insertion into Mo3S4 were not investigated before. The specific capacity of constructed batteries was in the expected range and the system had a stable cyclability (fig. 1 (left) and (right)). This experiments were performed using so called Swagelok-cells, assembled in an argon filled glove box and connected to a VMP multichannel potentiostat. Besides very small capacity fading during further cycling, there is a quite big capacity loss during the first cycle. We assume that this capacity loss is due to irreversible structural changes of the cathode material during the first discharge cycle, which we studied using ex situ X-ray diffraction. The above mentioned Swagelok-cells were used to discharge batteries (eg. intercalate magensium into Mo3S4) up to the desired magnesium concentration in MgxMo3S4. An ������������x=0,1 was chosen. The ex situ diffraction data revealed, that during the first discharge cycle for x�� �������3S4 (spacegroup R-3) is found. In the region 0.2�x�� ��an additional second phase and for 0.4�x�� �� �� ������ ������ ������� � ���� ������ �������crystallize in the same spacegroup (S.G. R-3). Using the Rietveld-method the lattice constants of these three phases were determined for nine different magnesium concentrations. No changes in the lattice parameters of all phases were observed (fig. 2 (left)), but the phase ratio varied with increasing magnesium concentration (fig. 2 (right)). This can only be explained by a constant magnesium concentration for the respective phases.

70

Fig. 2: Unit cell volumes (left) and phase-ratios (right) of all three phases.

The structure of Mo3S4 consists of a three-dimensional stacking of Mo6S8-clusters. Between two of this clusters at most two of the twelve positions (two times six equivalent positions which belong to two crystallographic 18f-sites referred to as A and B) can be occupied by an intercalated ion (left). A possible conclusion is, that only site A is occupied in the first appearing phase, and that in the second phase site B is occupied too. While charging the battery again, the Phase in which magnesium ions are located in A and B sites is probably completely transformed back while an amount of the phase in which only the A sites are occupied remains, resulting in an irreversible capacity loss.

The results were confirmed by in situ X-ray diffraction experiments performed at beamline B2 at the Hamburger Synchrotronstrahlungslabor HASYLAB (Germany) using the on-site readable image plate detector OBI. This setup allows data collection for a complete diffraction-pattern in approximately 20 minutes, so that structural details in a well-defined charge/discharge-state can be analyzed. Investigations of processes occurring during further cycling are now in progress.

ab

c

d

a

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B

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71

Phase transition and Fatigue in PZT-Ceramics

L. Schmitt, I. MacLaren, H. Ehrenberg, H. Fuess H. Kungl*, M. J. Hoffmann*

* Institute for Ceramics in Mechanical Engineering, University of Karlsruhe,

D-76131 Karlsruhe, Germany

Piezoelectric perovskite-type ceramics based upon Pb(Zr1-xTix)O3 are used in a wide range of applications as bulk materials or thin solid films. The main fields of application are sensors, actuators or combined sensor-actuator systems. In this work intensive research on La3+ and Sr2+ doped ferroelectric ceramics is carried out. Investigations of the structure are done by means of X-Ray Diffractometry (XRD) and transmission electron microscopy (TEM).

The crystallography is strongly composition-dependent in the quasibinary PbZrO3-PbTiO3 phase diagram. At high temperatures a high-symmetry, primitive cubic structure is present. Below the Curie temperature, which is itself composition dependent and lies between 230°C and 500°C, results in the adoption of lower symmetry orthorhombic, rhombohedral, tetragonal or monoclinic structures, depending on the Zr4+/Ti4+ ratio. At room temperature Ti-rich compositions are tetragonal whereas the Zr-rich end is rhombohedral, both phases being ferroelectric. At an intermediate composition (Zr/Ti ������������-called morphotropic phase boundary is observed. The morphotropic phase boundary between the rhombohedral and tetragonal region is nearly temperature independent. In the vicinity of this composition both phases can occur simultaneously. Because of this coexistence, more directions of polarization are available than in the single phase compositions and the ferroelectric coefficients are peculiarly high.The transition temperatures and their dependence on composition has been investigated by X-ray diffraction. The experiments were carried out in Debye-Scherrer geometry using a STOE furnace on the B2 diffractometer at HASYLAB/DESY Hamburg. The diffractometer is equipped with an image plate detector for time efficient experiments. La3+ and Sr2+ doped PZT powder samples with compositions near the morphotropic phase boundary where examined.

Fig. 1: The temperature depen-dence of the c/a ratio of the tetragonal phase is shown. The reduction of the c/a ratio with increasing temperature is visible, indicating the increase of the cubic phase. Between 320°C and 360°C the phase transition to the cubic structure occurs. Reducing the PbTiO3 content leads to a decrease of the c/a ratio.

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4746.54645.5

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T [°C]

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Diffraction patterns of sample (Pb0.97La0.01Sr0.02)(Zr0.54Ti0.46)O3 measured from 20°C to 500°C (20°C, 80°C-400°C with an increment of 40°C, 500°C) are shown in Figure 2. Rietveld refinement revealed that this sample contains both the rhombohedral and tetragonal structures. The observed aberrations in the peak-shapes such as displacements and/or asymmetry are probably caused by real structure effects (e.g. domain structures, defects etc.). The phase transition to the cubic structure between 320°C and 360°C is shown in the inset. Further investigations are planned focussing on the effects of doping on the structural transitions and on fatigue as a result of electrical cycling.

Fig. 2: Diffraction patterns of sample (Pb0.97La0.01Sr0.02)(Zr0.54Ti0.46)O3 measured from 20°C to 500°C (20°C, 80°C-400°C with an increment of 40°C, 500°C) TEM samples were prepared by a standard procedure based on slicing, polishing, dimpling and argon-ion-milling. Cylindrical samples were cut into pieces of 0.5 mm thickness than polished to 100 µm and dimpled to ≈ 10 µm. The final argon-ion-milling produced samples with thin areas suitable for TEM investigations. These were carried out using a Philips CM20 operated at 200 kV.

Fig. 3: Bright-field image of (Pb0.97La0.01Sr0.02) (Zr0.45Ti0.55)O3 with tetragonal structure showing lamellar domain configuration with wedge-shaped domain tips. Most of the domains finish within the grain and not at the lower grain boundary. This could be to do with lattice matching at the lower grain boundary, or to do with minimising excess charge at this boundary. The area labeled with the letter A possess a different domain orientation. In the region marked by two white arrows nearly every second domain ends. The rest of the domains crossing this area show a specific 90° domain-wall contrast. The observation of wedge-shaped domains in PZT ceramics with a tetragonal composition is reported here for the first time.

500°

20°C

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Fig. 4: Bright-field image of (Pb0.97La0.01

Sr0.02)(Zr0.525Ti0.475)O3 showing a complicated domain configuration of lamellar- and wedge-shaped domains viewed along [ 111 ]. Some of these domains show bifurcation. An example of this bifurcation is pictured in the magnified cutout. For rhombohedral compositions it has been reported that the bifurcation appears at the pyroelectric phase transition between the high temperature and low temperature phase induced by the spontaneous polarisation. In the morphotropic region there is no pyroelectric phase transition. Here it may be that the occurrence of locally high strains in the core of a grain are minimised by bifurcation. A typical curved 180° domain-wall with zigzag structure which crosses the 90° domains of the lamellar domain configuration is visible at A-A. The electron-microscopic investigations revealed predominantly the existence of lamellar 90° domains.

It has been postulated that the interaction of point defects with the domain walls could lead to pinning of the walls and thus fatigue and the degradation of the ferroelectric properties. For this reason the size and form of domains in both freshly prepared and electrically fatigued PZTs will be examined by transmission electron microscopy and compared. Also the influence of A-site donor defects, which induce Pb-vacancies, on the domain size and form and the fatigue will also be investigated.

74

Analytical Characterization of Interplanetary Dust and Materials Degradation of Space Exposed Surfaces

H.M. Ortner and F.J. Stadermann*

* Laboratory for Space Sciences, Physics Dept. CB 1105, Washington University,

1 Brookings Drive, MO 63130-4899, St. Louis, U.S.A.

The analysis of cosmic particles by secondary ion mass spectrometry (SIMS) has developed into an essential tool of cosmophysics and –chemistry as well as of applied space-research. This way it is feasible to gain important information about the origin, the evolution and the structure of our solar system. On the other hand, the discrimination between terrestrial and cosmic particles was of utter importance for an estimate of damage of space exposed surfaces by the impact of such particles. This was especially important for the multitude of satellites in near-earth space, i.e. in low earth orbits, fig. 1.

Fig. 1: Draft of a satellite orbit in 500 km altitude

Particles are travelling there with velocities of around 10 km�s-1. If they hit material surfaces they evaporate due to their high impact velocity and cause the formation of a crater, which is about one order of magnitude larger than the impacting particle, fig. 2. This turned out to be a serious problem for space technology because the impact of a multitude of such particles will quickly deteriorate space exposed surfaces. The mean life time of e.g. solar panels for the generation of energy for satellites in thus seriously reduced. It is difficult to gain any information on the nature of impacting particles due to the fact that most of the particle matter is evaporating during the impact.

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Fig. 2: SEM-micrograph of an impact crater on a germanium surface caused by a cosmic dust particle. In order to clearly differentiate between ions generated from the material and such of the impacted particle in SIMS-analysis, it is advantageous to use rather exotic and highly pure substrates such as gold or germanium. The particles scattered around the impact crater are Ge-particles and not remnants of the impacted cosmic particle which evaporated completely. Only extreme traces of its matter are detectable by SIMS.

The minute amounts of particle matter which remain on the material surface in and around the impact crater can only be detected by a very sensitive method of topochemical analysis. SIMS is the topochemical method with the highest detection sensitivity and hence, it is the method of choice for such investigations. In addition, the ability of SIMS to distinguish between various isotypes of an element is the key to differentiate between terrestric and cosmic particles. Thus it was possible to find out that the most serious surface degradation observed in LEO was caused by terrestric aluminium oxide particles. The origin of such particles was a solid rocket fuel (Al-powder) which was used by one of the nations leading in space technology. It was finally feasible to ban this technology in favour of liquid fuels for rocket propulsion which do not generate Al2O3-particles. The outstanding significance of SIMS for such investigations consequently led to the development of the NanoSIMS which exhibits a dramatically improved lateral resolution in the ten-��������������� ���������������������������!��������������"�����-range for a conventional SIMS instrument). It also has a fast working multiple detection system which is important since the amount of material to be sputtered is very limited in this special application.

The significance of material degradation of space exposed surfaces – the LDF experiment The impact crater of fig. 1 demonstrates impressively how space exposed surfaces eventually deteriorate by the impact of many of such particles. This has alarmed the American National Aeronautics and Space Administration (NASA) to an extent that a respective materials degradation experiment was organized, the LDEF-experiment (Long

76

Duration Exposure Facility). The heart of this action was a large cylindrical satellite with a length of 9 m which is shown in fig. 3.

Fig. 3: View of the LDEF-Experiment in LEO (Courtesy Nasa Langley Research Center) This satellite was brought into a Low Earth Orbit in an altitude of 476 km in 1984 (see fig. 1). It contained more than 10 000 test material plates which were exposed to the rather unfriendly environment for degradation studies. These surfaces are not only hit by micrometeorites (or dust particles) of space garbage which will deteriorate the plates’ surface. The LDEF-day was only 90 min long as well as its night. In this frequency, the temperature varied from +100°C to -100!C. During sunshine a most intensive UV-radiation was also hitting the surface. This effect combined with atomic oxygen (Atox) which is also present due to the last traces of atmosphere in this altitude. The combined action of these influences resulted in interesting corrosion and erosion phenomena. The satellite was not retrieved after the planned exposure time due to the Challenger catastrophe. Only in 1990 after 34 000 earth orbits the LDEF-experiment was retrieved in the last possible moment by the Space Shuttle. It was taken into the shuttle in an altitude of only 333 km shortly before the satellite would have burned down in the upper atmosphere. However, due to its very long exposure time, corrosion and erosion phenomena were very pronounced and a lot of interesting and alarming observations were made. One of the most alarming finds was that more than 80 % of all investigated particle impact craters by SIMS turned out to be caused by terrestrial and not by cosmic particles. The highest percentage of these particles were Al2O3-particles of Russian solid state rocket fuels. This was the reason why Russia finally changed over to liquid fuel systems.

The probably most interesting conclusion of this project is the rarely so obvious observation how closely related an initially purely basic research can be to applied materials research. F.J. Stadermann had investigated 94 extraterrestric particles by SIMS in his Ph.D thesis. He had thus developed a sound procedure of how to carry out such research manipulating particles with diameters in the single micrometer range. Then it became immediately obvious how important this procedure was for the investigation of the

77

degradation of space exposed surfaces and the safe differentiation between cosmic and terrestrial particle remnants on these materials surfaces. Thus the considerable danger of a certain rocket fuel technology for the life time of satellites in LEO could be indubitably demonstrated. This consequently caused the elimination of this technology in spite of previous great political tensions caused by this discussion. A further respective consequence was the introduction of small protective shields in flight direction especially for satellites in LEO which should operate for a long time. Basic research has thus definitely influenced applied space technology. The positioning of satellites in LEO for long duration is of importance not only for military reconnaissance but also for modern communication – and positioning systems, for global catastrophe survey and many other geopolitical surveys. Without the availability of proper topochemical and analytical technology this would not have been feasible.

It is not surprising that these initial finds have ultimately led to the evolution of Interplanetary Dust to a most important scientific discipline in the Space Sciences since dust seems to be an essential component throughout Space. Consequently, material degradation by micrometeorites is one of the common phenomena space flights have to cope with. Cosmic dust constitutes an essential part of the total matter of our universe. It is also a fascinating result of this young scientific discipline that a part of the particles which come into the vicinity of our earth will eventually be trapped by the earths gravity pull. Hence, our planet is collecting cosmic dust daily in a quantity of several tons. This leads to the ultimate assumption that cosmic dust is not as exotic a material as we usually think. And every time we clean our window sills or book shelves from dust we can be sure to clean away also quite a few dust particles from Deep Space.

78

Current Distributions in a Magnetically Shielded Superconducting Filament

S.V. Yampolskii, Y.A. Genenko, H. Rauh

Strong redistribution of the current in thin superconductor strips caused by magnetic environments is a well-known effect. Although expected both in the flux-free Meissner state and in the partly flux-filled critical state, this effect is most pronounced in the former state where sharp current peaks appear at the edges of the strips; a phenomenon of purely geometrical sort due to the large aspect ratio of thin strips. By attenuating the magnetic field at the edges of the strip, suitably designed magnetic environments facilitate the reduction of such peaks, giving rise to a concomitant increase of the total loss-free current.

Substantial current enhancements in shielded strips originate from the high sensitivity of the current peaks to the particular form of the magnetic environment, and thus represent a geometrical effect intrinsic to superconductors of a planar shape. Nevertheless, a significant influence of magnetic shielding on critical currents and ac losses has been observed in three-dimensional configurations of composite cables and tapes as well. In particular, the iron-sheathed superconductor filaments of MgB2/Fe cables exhibit increased critical currents and reduced ac losses in a wide range of the strength of external magnetic fields. Cylindrical magnetic shells may, to a certain extent, protect a single filament from the applied field and from the fields due to the presence of other filaments; however, for reasons of symmetry, they cannot protect the filament from the current self-induced magnetic field as in the case of shielded strips. Indeed, a cylindrical filament already has the optimum shape in the sense that the current only creates a tangential magnetic field at the surface of the filament; but, taking the fields of the additional filaments into account, asymmetric magnetic shells should be considered too with a view of optimizing the shielding effect. This raises the fundamental point whether such environments are at all capable to strongly influence the current distributions in three-dimensional superconductors where no current peaks occur. We therefore investigate the effectiveness of magnetic shielding of a superconducting filament near a bulk magnet by calculating the distribution of the transport current in it for various filament-magnet distances and different relative permeabilities. We consider a cylindrical superconducting filament of radius R, extended infinitely in the z direction of a cartesian coordinate system x, y, z and located at a distance a from the flat surface of a bulk magnet with relative permeability µ , occupying the space ��� ≥ � + � . The filament is supposed to be in the Meissner state, carrying a total current of fixed magnitude, I. Assuming the radius of the filament is much larger than the London penetration depth, variations of the magnetic field across the surface layer of the filament may be ignored and, for mathematical convenience, this layer regarded as infinitesimally thin. Such an approach enables the magnetic field �� around the filament to be expressed through the sheet current J alone which, in cylindrical polar coordinates ����ϕ ��( ) adapted to the filament, only depends on ϕ . We seek a representation of the magnetic field in terms of the sheet current as a cylindrical current source, from which a Fredholm integral equation for the latter quantity ensues by imposing the condition of expulsion of the magnetic field in the Meissner state.

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We first show the angular variation of the sheet current for different values of the distance between the filament and the magnet, when the value of the relative permeability of the magnet is prescribed. A general trait due to current redistribution in the filament is the depression of the sheet current on the side of the filament adjacent to the surface of the magnet and an enhancement with a wide maximum on the averted side. Whereas this effect is distinctly more pronounced for the higher of the two values of the relative permeability singled out, including, at short filament-magnet distances, an almost complete suppression of the sheet current on the adjacent side, it abates when the filament-magnet distance is increased, with a tendency to reducing the sheet current anisotropy (Fig. 1).

Fig. 1: Distribution of the sheet current of the superconducting filament, J, as a function of the azimuth, ϕ , for different values of the distance between the filament and the magnet relative to the radius of the filament, α , specified in the legend, when the value of the relative permeability of the magnet, ��µ = � (upper part) and

��µ = ��� (lower part). The isotropic distribution of the sheet current in the absence of the magnet (i.e. for µ = �), represented by the unit circle (thin solid line), is shown for comparison.

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We next portray the variation of the minimum value of the sheet current at zero azimuth with the distance between the filament and the magnet relative to the radius of the filament, when the value of the relative permeability of the magnet is prescribed. A general trait due to current redistribution in the filament is the increase of the minimum value of the sheet current with the filament-magnet distance, but a decrease with the relative permeability, the effect saturating for large values of either of these quantities. In the limit of zero filament-magnet distance, the minimum value adopts a finite magnitude and finite derivative, unlike in the case of shielded strips, where divergent derivatives persist (Fig. 2).

Fig. 2: Minimum value of the sheet current of the superconducting filament, ���� , as a function of the relative permeability, µ , for different values of the distance between the filament and the magnet relative to the radius of the filament, α , specified in the legend. The minimum value of the sheet current in the absence of the magnet (i.e. for ��µ = �), adopted independently of α , is unity. In conclusion, our results demonstrate a dependence of the sheet current on the filament-magnet distance very much like for the case of magnetically shielded strips, though without current peaks typical of strips. Substantial current redistributions in the filament can already occur for low values of the relative permeability of the magnet, when the distance between the filament and the magnet is short, with evidence of saturation at moderately high values of this quantity, similar to the findings for magnetically shielded strips. We therefore expect that an asymmetric magnetic shielding configuration is indeed capable to redistribute the current in a superconducting filament effectively.

81

Drift-Diffusion Model of Ageing in Ferroelectrics

N. Balke, H. Rauh, Y.A. Genenko, D.C. Lupascu Ferroelectrics underly restrictions in technological applications due to various sorts of degradation. One such phenomenon concerns ageing, i.e. the gradual change of materials properties with time t, isothermal conditions and absence of external mechanical loads implied. The experimentally observed alteration of quantities like the clamping pressure exerted on the walls of ferroelectric domains is logarithmic in an intermediate range of time and saturates at long times; behaviour arising from the loss of mobility of the walls of the domains. In perovskite ferroelectrics, a close correlation between ageing and migration of twice positively charged oxygen vacancies, termed �#O

¨ , has been assured. Regarding the material bulk, domain stabilization is believed to be due to the orientation of point-defect dipoles of negatively charged acceptor ions and �#O

¨ under the action of the spontaneous polarization. As for grain boundaries, stabilization is thought to occur by migration of �#O

¨ to these extended defects, driven by the total electric field. Here, we offer a model of ageing which addresses precisely the latter effect. Referring to a ferroelectric of perovskite type enriched with acceptor impurities in natural or doped form, let us proceed from a chemically and electrically isolated single-crystal grain, with its cubic axes oriented parallel to the axes of a cartesian system x, y, z. This grain is thought to be made up of a regular array of 180° domains of length a and spacing ����$�, their faces occupying the planes ����� = � and �� = � , their walls coinciding with strips located at = ± ��± ��� and extending infinitely in the direction of z. Each domain is supposed to exhibit a uniform spontaneous polarization ���

in the direction of x, which induces bound surface charges of opposite signs on either face of the domains, entailing a depolarization field ����

= −��

ε�

ε0 , where ��ε � stands for the bulk relative permittivity and ε0 means the

permittivity of free space. If the material has been rapidly cooled below the Curie temperature in vacuum, an initially homogeneous distribution of mobile ��#O

¨ and immobile dopant impurities of equal valency and concentration � 0 ensuring electroneutrality will exist within the domains. ��#O

¨ start to migrate to the negatively charged faces of the domains under the influence of the depolarization field, thereby building up an internal field, ���

, which opposes the depolarization field and thus impairs the resultant driving total electric field, ��� = �

�+ �

�. A diffusion flow of �#O

¨ sets in, mitigating the impact of drift, until a stationary final state is reached. Identifying the central domain bounded by the walls at � = ± � and considering, for mathematical convenience, the limit �� → ∞ , the �#O

¨ concentration �� ���( ) satisfies the continuity equation while the total electric field �� ���( ) obeys Gauss’s law. The process of charge redistribution involves two distinct quantities: the characteristic ��#O

¨ diffusion time

���� = ��

� with the vacancy diffusivity D, and the characteristic �#O¨ drift time

���µ = � µ�

� with

the vacancy mobility µ . A third key quantity, the critical �#O¨ concentration �� �

= −���� with

the vacancy charge q comes in as well. Whereas the kinetics of �#O¨ migration is, in general,

dominated by the times �� and ���µ together with the initial concentration 0 and the critical

concentration �� �, it is the latter quantity which resolves whether the depolarization field can

be fully or only partly compensated by the internal field, as ageing proceeds.

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To appraise the effect of drift diffusion on �#O¨ redistribution and field variation, the set of the

above-mentioned equations was solved numerically for two different initial �#O¨

concentrations, with physical data appropriate to BaTiO3 at room temperature, and the results were displayed graphically. We first show ‘snapshots’ of the profiles of the �#O

¨ concentration and the total electric field for a sequence of times, adopting an initial �#O

¨ concentration �� 0 < � due to a typical level of acceptor impurities in a naturally present form. After ageing has commenced, a region ahead of the positively charged face of the domain, almost totally depleted of ��#O

¨ and delineated by a pronounced step of the concentration profile, evolves which expands with time, while �#O

¨ pile up near the negatively charged face of the domain. Redistribution stops when virtually the whole domain is devoid of ��#O

¨ , which have been accumulated close to the negatively charged face of the domain. The profiles of the total electric field at the respective times decay linearly into the region free of ��#O

¨ , remaining practically constant in the residual part, except close to the negatively charged face of the domain. Since there are not enough �#O

¨ available to fully compensate the depolarization field, a finite total electric field prevails within the whole domain even in the stationary final state (Fig. 1).

Fig. 1: Normalized �O

¨ concentration � �� (upper part) and normalized total electric field � �� (lower part) as functions of the normalized coordinate � � at different values of the normalized time � �µ identified on the

curves, for the initial �O¨ concentration �0 =�×���� ��−� .

We next depict ‘snapshots’ of the profiles of the �#O

¨ concentration and the total electric field for a sequence of times, choosing an initial �#O

¨ concentration � 0 > � due to a typical level

of acceptor impurities in a lightly doped form. After ageing has begun, a region ahead of

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the positively charged face of the domain, almost totally depleted of ��#O¨ and delineated by

a pronounced step of the concentration profile, evolves which expands with time, while �#O¨

pile up near the negatively charged face of the domain. Redistribution, however, comes to a halt already when only part of the domain is devoid of �#O

¨ , which have been accumulated close to the negatively charged face of the domain. The profiles of the total electric field at the respective times decay linearly into the region free of �#O

¨ , remaining practically constant in the residual part, except close to the negatively charged face of the domain. Since there are sufficiently many �#O

¨ available to fully compensate the depolarization field, the total electric field is eventually quenched in that part of the domain where the initial �#O

¨ concentration survives (Fig. 2).

Fig. 2: Normalized �O¨ concentration � �� (upper part) and normalized total electric field � �� (lower part)

as functions of the normalized coordinate � � at different values of the normalized time � �µ identified on the

curves, for the initial �O¨ concentration �0 =�×���� ��−� .

The step-like ��#O¨ concentration profile and the almost polygonial profile of the total electric

field are caused by the effect of strong drift outweighing diffusion; a fact traceable to the different scales of the characteristic times, �� >> �µ . An analysis of the potential electric energy per unit volume of the ferroelectric domain within a pure-drift approach, applying

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the principle of virtual displacements to the walls of the central domain, when ��� → ∞ , yields the clamping pressure exerted on these walls by the migrating point defects as a function of time. Common to both cases of initial concentrations chosen above is the initially monotonic rise of the clamping pressure as time proceeds, taking on a quasi-logarithmic dependence in an intermediate range of time and turning to saturation at long times, in qualitative agreement with experimental observations (Fig. 3).

Fig. 3. Clamping pressure �� as a function of the normalized time � �µ for the initial �O

¨ concentrations (a)

�0 =�×���� ��−� and (b) �0 =�×���� ��−� . Logarithmic approximations in the respective intermediate ranges of time (dotted lines) are marked. It is instructive to compare the predictions for the clamping pressure in the stationary final state due to drift diffusion of ��#O

¨ with those based on the effect of orientation of point-defect dipoles, which purports ���

� = ����� 0 , given the spacing of uniformly aligned dipoles, d. If

a level of ��� ��×��−�

�� Ni impurities, entailing an initial ��#O¨ concentration of

���� 0 =� %& ×���� ��−� equal to the critical concentration � �

, were present, drift diffusion of

��#O¨ would bring about a clamping pressure of ����

� = �� ���'� , whereas orientation of point-defect dipoles would merely admit ����

� = �& ��('� , revealing the effect of drift diffusion relative to that of dipole alignment to be stronger by a factor of 1250! For coarse-grained BaTiO3, macroscopic coercive stresses lie between 40 and ��� �'� . We therefore believe that, notwithstanding inherent simplifications such as one-dimensional geometric and one type of migrating charge carrier limitations, the drift-diffusion model of ageing presented here does yield predictions for the clamping pressure which are both due to the most probable mechanism and in accord with experimental evidence.

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Kinetic Lattice Monte-Carlo simulations of stacking fault nucleation on Ir(111)

Michael Müller and Karsten Albe

During epitaxial growth of fcc(111) metal surfaces, an important defect is the formation of stacking-faults, i.e. the nucleation of adatom islands in hcp binding sites, which causes a deviation from the perfect ABC stacking sequence to a faulted ABAB stacking. The occurence of such stacking-faults has an significant influence on the properties of the growing film. A prominent example is the epitaxial growth of Co/Cu multilayers on Cu(111), where the formation of Co islands in stacking-fault positions leads to a destruction of the desired magnetic properties of the layer system. A detailed understanding of stacking-fault island formation can be gained from Kinetic Lattice Monte-Carlo (KLMC) simulations, which are a suitable method for simulating the diffusion controlled evolution of a metallic surface. In this study we have developed an improved KLMC code for simulating fcc(111) metal homoepitaxy that efficiently includes formation of stacking-faults and cluster diffusion. In this model, atomic positions are not restricted to perfect fcc lattice sites. Instead, a refined lattice with additional sites at all possible stacking-fault positions is used. Cluster diffusion is implemented by identifying small adatom clusters on the surface and allowing them to change between fcc and hcp stacking. The characteristic diffusion parameters for cluster diffusion had already been determined, experimentally. Additionally, a potential energy diagram for diffusion of atoms along island edges was constructed (Fig. 1).

With our KMC model, we simulated iridium island nucleation on Ir(111) in a temperature range from 125 K to 400 K. Atoms have been deposited at random sites on the surface with a deposition rate of 0.013 ML/sec as in the corresponding experiments. The simulations have been run for 10 seconds, resulting in a final coverage of 0.13 ML. Because of the small coverage, we neglected deposition on top of already existing islands. If an atom landed on top of an island, it was removed immediately and the deposition event was repeated. In order to achieve good statistics, the dimension of the surface had to be chosen large enough (from 100 nm2 for low temperatures up to 150 nm2 for the highest temperatures) to guarantee the formation of a sufficient number of islands. In Fig. 2, the temperature dependence of the stacking-fault island probability, as obtained from our KMC model and from experiment, is shown.

Fig. 1: Energy landscape for step, edge and corner diffusion.

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Fig. 2: Stacking fault probability as calculated and experimentally determined.

The agreement between experiment and simulation in both island density and stacking-fault island probability confirms that our model reproduces all processes relevant for the formation of stacking-fault islands in the system Ir/Ir(111) and that our description of cluster diffusion is adequate.

In Fig. 3, we compare the experimentally observed island shapes with those obtained from KLMC simulations. At 250 K and 375 K, dendritic islands with a triangular envelope bounded predominantly by B steps are found in full agreement with experiments. At higher temperatures, a transition from dendritic to compact islands with broad arms perpendicular to A steps can be observed. By comparing our KMC simulations with experiments, we find that the experimentally determined corner anisotropy (0.04 eV) is too small to explain the triangular shaped islands at low temperatures.

In conclusion, our simulations show that stacking-fault formation and shape of iridium islands can be fully described by means of the KLMC-method. Moreover, our results confirm that cooperative cluster motion of atoms is an important process for structure formation on surfaces.

Fig. 3: Iridium island shapes as observed in STM-experiments and obtained from KLMC simulations. (STM-

experiments by C. Busse and Th. Michely, RWTH Aachen, Germany)

87

Molecular dynamics simulation of inert gas condensation of SiC nanoclusters

Paul Erhart, Karsten Albe

Nanocrystalline silicon carbide (nc-SiC) powders of high purity and a narrow size distribution with particle sizes below 10 nm have excellent thermal, mechanical, chemical and semiconducting properties and are therefore a promising material for many advanced applications. In the past SiC nanopowders have been successfully synthesized by the chemical vapor synthesis (CVS) in the Thin Films Division of our institute. However, in order to properly adjust the particle properties a detailed understanding of the interplay between processing conditions and final particle structure is needed. Since the gas phase reactions are complex non-equilibrium processes, this is a challenging task. In this study, we have taken a first step and studied nucleation and growth of silicon carbide nanoparticles in inert gas atmospheres by means of molecular dynamics simulations based on analytical potentials. At the beginning, we have investigated how the experimental setup can be modeled in a molecular dynamics simulation. From a comparison of several different thermostating techniques, it emerged that the effect of the cooling gas cannot be mimicked by Langevin-type dynamics. Therefore, despite being computationally more expensive, additional inert gas atoms, which are coupled to a heat bath, had to be included in the simulation. Interatomic interactions were described by a computationally efficient reactive potential based on the Tersoff-Brenner bond-order scheme. New parameter sets for silicon and silicon carbide were derived and evaluated, including an extensive comparison with alternative potentials. These new potentials provide a good description of the elastic as well as structural properties and also of small molecules. In addition, they yield a reasonable description of thermal and defect properties. The results of the foregoing investigations have then been merged for the modeling of silicon carbide nanoparticle formation. Several cooling gas concentrations and precursor compositions have been compared and large differences were found with respect to the morphology and agglomeration of the particles. Clusters with an increasing degree of fractality are formed, as the cooling gas ratio is raised. Fig. 1 shows the example of two different simulations. Snapshot (a) is the result of a run with an equivalent number of cooling argon atoms and reactive species, while snapshot (b) shows a scenario where four times more cooling gas atoms are included.

a.) b,)

Fig. 1: Cluster configuration after 2 ns for precursor ratios of 1:1 (a) and 4:1 (b).

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Due to the more efficient cooling in case of the high inert gas concentration, thermalization is much very efficient. Therefore the condensing particles solidify very quickly, which prevents the formation of spherical primary particles and explains the fractal agglomerates. If the inert gas content is smaller, the condensing particles stay at higher temperatures and easily can form liquid droplets, that keep their spherical shape while cooling down. In most simulations, silicon and carbon atoms are homogeneously distributed in the final clusters. However, for the largest precursor and cooling gas ratios considered, phase separation of carbon and silicon was observed. The dimer energy has been found to affect crucially the early stages of nucleation and to influence the long time behavior as well. A detailed analysis of the fundamental reactions during the early stages of nucleation was carried out. In the initial systems SiC dimers are present, which are consumed by various processes. It turns out that reactions leading to the release of silicon monomers are more likely to occur than those, in which carbon monomers are formed. This result can be explained by the energetic preference for carbon dominated small molecules. Simple kinetic models are used to characterize the effect of the amount of cooling gas and the precursor composition on the reaction rate. With the number of silicon atoms being fixed, the consumption of the initially present dimers becomes slower, as the number of cooling gas and carbon atoms is increased. Fig 2. shows the number of small clusters forming in a time period of 60 ps as a function of time. Again, both graphs correspond to different inert gas ratios (1:1 and 4:1). The most evident feature is that for the ensemble with efficient background gas cooling the SiC dimers, which are initially present, are less quickly consumed than in the other case. Therefore a smaller number of reactive monoatomic species is present.

a.) b.)

Fig. 2: Temporal evolution of the occurence of small molecules.

Our simulations show that the formation of SiC nanoparticles from gas phase reactions can be analyzed in detail from MD trajectories. If realistic potentials are available, this method describes the most important features of the relevant processes. However, since the accessible time scale is very limited, coarse graining methods are needed, that allow for a direct connection with experiments.

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Diploma Theses

Balke, Nina; Diffusion in pyroelektrischen Kristallen, Ceramics Group, 2003 Barunovic, Robert.; Untersuchung der Eigenschaften von Gassensoren aus nanokristallinem SnO2 Pulver – Einfluss der Korngröße und der Dotierung mit Platin, Thin Films, November 2003. Bethlehem, Bernd; Magnetische Keramiken aus nanokristallinem Pulver, Thin Films, May 2003. Betz, Christoph; Morphology of vapor-deposited Pt and Pt-Rh layers, Physical Metallurgy, July 2003. Enz, Torsten; Metallische Fe-Nanopartikel, Thin Films, November 2003. Erac, Ljubomira; Strukturelle Untersuchungen an Bleizirkoniumtitanaten, Structure Research, July 2003. Erhart, Paul Harro; Atomistic Computer Simulations of Silicon and Silicon Carbide Nanoparticle Condensation: Role of Thermostats and Interatomic Potentials, Materials Modelling, June 2003. Fauchet, Claire; Mechanische Eigenschaften von Intermetall/Keramik Verbundwerkstoffen, Ceramics Group, 2003 Finckh, Richard; Materialwissenschaftliche Untersuchungen am hypothetischen Magnetfeldrezeptor der Brieftaube, Thin Films, May 2003. Fleißner, Arne; Optisch stimulierte Ströme in amorphen molekular dotierten organischen Halbleitern, Electronic Material Properties, May 2003. Gassenbauer, Yvonne: Strukturierung von WSe2 unter definierten Umgebungsbedingungen mittels Rastersondenmethoden, Surface Science, May 2003. Groß, Toni André; Der Einfluss der Synthesebedingungen auf die Struktur und die elektrochemischen Eigeschaften des Systems LixNiyCo1-y02 , Structure Research, November 2003 Halstrick, Friederike; Optimierung eines Reibbelages auf anorganischer Basis gegen eine keramische Oberfläche, Dispersive Solids, November 2003. Huhn, Pierre A.; Thermische Stabilität nanokristalliner Leichtmetallhybride für die Wasserstoffsorption im emmissionsfreien Automobil., Thin Films, November 2003. Keith, Torsten; Elektrisch neutrale Dotierungen in organischen Halbleitern, Electronic Material Properties, May 2003.

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Kiesewetter, Sven; Untersuchungen zum Einfluss von Sauerstoff auf die spektroskopischen Eigenschaften und die Stimulationseigenschaften des Röntgenspeicherstoffes BaFBr:Eu2+, Electronic Material Properties, October 2003. Kouaici, Hicham: Elektrische und optische Charakterisierung der Aktivierung von CdTe-Solarzellen, Surface Science, December 2003. Juigner, Fanny; Workpiece Fatigue Properties of the Age-Hardenable Aluminum Alloy Al-7075 after High Speed Machining, Physical Metallurgy, August 2003. Locherer, Thomas; Entwicklung einer dünnen Oxidationsschutzschicht für Ni-Basislegierungen, Dispersive Solids, TU Darmstadt, June 2003. Maurer, Florian; Synthese von InxGa1-xN durch Ammonolyse metallorganischer Vorstufen, Dispersive Solids, November 2003. Müller, Michael; Growth and Annealing processes of Metallic Thin Films and Multilayer Systems: Kinetic Lattice Monte-Carlo Simulations, Materials Modelling, May 2003. Nikolowski, Kristian, Strukturelle Untersuchungen an Magnesiumeinlagerungsmaterialien, Structure Research, November 2003. Schiefer, Hanns-Herwig Lionel; Einfluss von Bi2O3, GeO und Al Zusätzen auf das Kristallisationsverhalten von polymerbasierten SiOC-Keramiken, Dispersive Solids, TU Darmstadt, Robert Bosch GmbH, Stuttgart, May 2003. Schwanitz, Konrad; Van der Waals-Epitaxie von GaSe auf WSe2, Surface Science, December 2003. Schwarz, Björn Christian; Magnetische Wechselwirkung in Cu-W-Mo-O-Strukturen, Structure Research, November 2003 Späth, Bettina; Gesputterte ZnTe-Schichten für den Rückkontakt der CdTe-Solarzelle, Surface Science, December 2003. Taeger, Sebastian; Untersuchungen lateral inhomogener Halbleitergrenz- und Oberflächen mit elektrostatischer Kraftmikroskopie, Surface Science, May 2003. Tilger, Stefanie; Untersuchungen zu Elektreteigenschaften, Chemical Analytics, November 2003 Winkelmann, Antje; The effect of annealing upon the microstructure and properties of superhard nanocomposite coatings, Ceramics Group, 2003 Zeigmeister, Uwe; Entwicklung einer mechanischen und Oxidationsschutzschicht für keramische Substrate, Dispersive Solids, June 2003.

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PhD Theses Feger, Matthias; Präparation und Charakterisierung von Pd/γ-AIO3- und Pd/Ce0.6Zr0.4O2-Katalysatoren für die Anwendung in der Drei-Wege-Katalyse, Structure Research, July 2003 Fritsche, Jochen; Halbleitergrenzflaechen polykristalliner CdTe-Dünnschichtsolarzellen : Charakterisierung und Modifizierung elektronischer Eigenschaften, Surface Science, June 2003. Hartmann, Thomas; Preparation, characterization and physical properties of new compounds in the system Ln2O3-ReO2-1/2 Re2O7 (Ln = lanthanides or yttrium), Structure Research, July 2003 Hönack, Frank; SiCO-Keramiken mit titanhaltigen Füllstoffen, Dispersive Solids, January 2003. Kolb, Robert; Synthese und Eigenschaften keramischer Neutronenbildplatten auf der Basis von BaFBr:Eu2+ und Gd-Verbindungen, Electronic Material Properties, May 2003 von Malm, Norwin; Ladungsträgerfallen in amorphen organischen Halbleitern, Electronic Material Properties, February 2003. Marx, Peter; Mechanical Surface Coating for the Cold Forging of Steel, Physical Metallurgy, June 2003. Müller, Marcel; Magnetische und strukturelle Charakterisierung von amorphen Eisen-Scandium-Legierungen, Thin Films, July 2003 Nimz, Michael; Detection of Microstructural Alterations and Damage after Deep-Drawing, Physical Metallurgy, February 2003. Schallehn, Michael; Polymerbeschichtung und Funktionalisierung nanokristalliner Oxide in der Gasphase, Thin Films, September 2003 Schlapp, Michael; Entwicklung hocheffizienter, γ-insensitiver Detektormaterialien und Bildplatten für Neutronen, Electronic Material Properties, June 2003. Schwarz, Marcus; High Pressure Synthesis of Novel Hard Materials: Spinel-Si3N4 and Derivatives, Dispersive Solids, November 2003. Seydel, Johannes; Nanokristallines Zirkonoxid für Hochtemperatur-Brennstoffzellen, Thin Films, November 2003. Sigmund, Jochen; Wachstum und Charakterisierung von AlSb/InAs- und AlInSb/InSb-Quantentopfstrukturen mittels Molekularstrahlepitaxie, Structure Research, Dezember 2003

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Wisotzki, Elmar; Quasi-van der Waals-Epitaxie von II-VI Halbleitern auf Schichtgitter-chalkogeniden und GaSe-terminierten Si(111)-Oberflächen, Surface Science, January 2003 Wu, Qihui; Photoelectron spectroscopy of intercalation phases: Na and Li in V2O5 thin films and LiMn2O4, Surface Science, July 2003.

Habilitations Klein, Andreas; Electronic properties of thin film semiconductor interfaces, May 2003. Stahl, Branko; Magnetism at Surfaces, Interfaces and in Reduced Spatial Dimensions, January 2003.

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Institute of Applied Earth Sciences

Physical Geology and Global Cycles In the solar system, Earth is an unique rocky planet with an ocean and an atmosphere. It is inhabited by bacteria since about 4 billion years and by higher life - plants and animals - since ca. 600 million years. Organisms, air, water, and rocks are interconnected in an unending cycle of matter and energy: The Earth System. The crustal plates of Earth are driven by radioactive heat. This causes creation of new crust at mid-ocean ridges at rates of several centimetres per year. On the other side, plate margins collide, become subducted into the mantle again, or fold up vast mountain ranges like the Alps and the Himalayas, combining rocks of very different origin. During subduc-tion the basaltic crust is partially melted generating more felsic magmas which rise to form continental-type plutons and to cause lines of andesitic volcanoes such as occurring around the entire Pacific rim. This is called the endogenic cycle of rocks. At the same time Earth receives solar radiation which moves air and water in gigantic cycles around the planet. Specifically the water cycle causes the denudation of mountains by mechanical erosion and the leveling of plains by chemical weathering, the latter aided tremendously by vegetation and their CO2-input to soils. This is called the exogenic cycle of rocks. This exogenic cycle is increasingly impacted by mankind. The radiation balance of the atmosphere has been upset by the emission of carbon dioxide, methane and other tracegases, Earth is warming. Industrially produced chlorinated hydrocarbons have risen to the stratosphere, threatening the protective ozone layer. Dust from traffic, industry and agriculture produce reagents which alter the air chemistry, causing unprecedented interac-tions with the marine realm, with vegetation and even with rocks through acidification, excessive deposition of nutrients and salts. Dry and wet deposition of anthropogenic (i.e. produced by humans) particles can be measured world-wide. The population explosion caused the intensification of agriculture and the alarming loss of topsoil and cuts down on the extent of natural ecosystems at the same time. The artificial fertilization of soils causes wide-spread nitrate pollution of shallow ground waters and urbanization alters the water cycle above and below ground. Local leakage and accidents with chemicals impact soil, rivers and ground water. Civil engineering, discharges and denudation cause alterations in almost all rivers world-wide and even coastal seas show increasing eutrophication, silta-tion and ecosystem changes in the water column and in the shallow sediments. The scars left by the mining of minerals and fossil energy are visible everywhere and cause increas-ingly problems. Everywhere man has changed the rate of natural processes. He spreads ever further into the landscape, utilizing regions and building in areas which should not be used considering their natural risks. Therefore damages through natural catastrophes rise traumatically endangering the world insurance system.

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All these processes and changes and their consequences are topics of Environmental Geology. Understanding global change and accepting the responsibility of mankind for this planet and its resources for future generations are prerequisites for the planning of a sustainable development. The division of Physical Geology and Geological Cycles at the Institute for Applied Geo-sciences addresses several questions important to environmental geology both in the pre-sent and in the geological past. These can be summarized as follows: • Paleoclimatology (through the study of varved sediments in the Dead Sea Basin/

Jordan and in Lake Van/Turkey and through the study of speleothems) • Carbonate geochemistry through time (through the study of alkaline crater lakes,

stromatolites and through modeling of early ocean conditions also for other planets and moons of the solar system)

• Karst and cave development (through the studies of cave development in limestone, gypsum and lava and through the study of cave deposits and their paleontological content and geochemical composition)

• Biogeochemistry of rivers (through the study of the biogeochemistry of rivers such as the Ebro and Rhine or in Patagonia).

Currently two German research funded projects are pursued, the reports of which follow below.

Staff Members Head

Prof. Dr. Stephan Kempe

Research Associates Dr. Doris Döppes Dr. Wilfried Rosendahl

Technical Personnel

Ingrid Hirsmüller

Jürgen Krumm

Secretaries (Partial)

Kirsten Herrmann Edith Paulitz

Monika Schweikhard

Diploma Students

Sven Beier Vera Mügge Stefanie Müller Matthias López Correa

Doctoral Students Jun Q. Yu Piet Nordhoff (zusammen mit Prof. Hansen, Göttingen)

Guest Scientists

Prof. Dr. Jozef Kazmierczak, Polish Acad. Sciences

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Research Projects Kempe & Rosendahl: Speleothemes and Pleistocene climate in Central Europe (DFG) Rosendahl: Absolute chronology of tufa dams in the Seeburg Valley/Swabian Alb (City of Bad Urach) Döppes, Kempe & Rosendahl: Cave contents in the Unicorn Cave and Pleistocene climate (Society Unicornu Fossile)

Publications Burger, J.; Rosendahl, W.; Loreille, O.; Hemmer, H.; Eriksson, T.; Götherström, A.; Hiller, J.; Collins, M. J.; Wess, T.; Alt, K. W.; Molecular phylogeny of the extinct cave lion Panthera leo spelaea, Molecular Phylogenetics and Evolution (2003) 9pp. Kazmierczak, J.; & Kempe, S.; Calcium build-up in the Precambrian Sea: A major promoter in the evolution of eukaryotic life. – in: J. Seckbach (ed.): Origins, Evolution and Biodiversity of Microbial Life, Kluwer (2003). Kazmierczak, J.; & Kempe, S.; Modern terrestrial analogues for the carbonate globules in Martian meteorite ALH84001, Naturwissenschaften 90 (2003) 167-172. Kazmierczak, J.; Kempe, S.; Altermann, W.; Microbial Origin of Precambrian Carbonates: Lessons from modern analogues. - in: Eriksson, P.; Altermann, W.; Nelson, D.; Mueller, W.; Catuneanu, O. (eds.): “The Precambrian Earth: Tempos and Events”, Elsevier (2003). Kempe, S.; Kazmierczak, J.; Modern Soda Lakes: Model Environments for an Early Alkaline Ocean. – in: Müller, T.; Müller, H. (eds.): Modelling in Natural Sciences; Design, Validation and Case Studies, Springer Verlag, Berlin, Heidelberg (2003) 309-322. Kempe, S.; Bauer, I.; Henschel, H.-V.; The Pa‘auhau Civil Defence Cave on Mauna Kea, Hawai‘i, a lava tube modified by water erosion, J. of Cave and Karst Studies 65 (2003) 76-85. Kempe, S.; Werner, M.S.; The Kuka‘iau Cave, Mauna Kea, Hawai‘i, created by water erosion, a new Hawaiian cave type, J. of Cave and Karst Studies 65 (2003) 53-67. Kempe, S.; Reinboth, F.; Die Baummannshöhle, Harz; Befahrung der historischen Teile 3. Mai, 2003; eine Zeitreise ins Jahr 1763, geführt von Johann Friedrich Zückert, der Arzeygelahrtheit Doctor, Exkursionsführer, Arbeitsgemeinschaft für Karstkunde e.V. Elbingerode (2003) 41pp. Kempe, S.; Der hypokryotische Ozean auf Europa, Deut. Ges. Meereskunde, Mitt. (2003) 14-16. Kempe, S.; Die alten Inschriften der Adelsberger Grotte /Postojnska Jama, Die Höhle 54 (2003) 36-44.

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Kempe, S.; Biogeochemistry of the Rhine basin. – in: Dikau, R.; Dix A.; Hennrich, K. (eds.): Land use and climatic impacts on the Rhine river system during the period of agriculture (2003). López Correa, M.; & Rosendahl, W.; Aus heißen Quellen - wie der Böttinger Marmor entstand.- in: Rosendahl, W.; López Correa, M.; Gruner, C.; Müller, T. (Hrsg.): Der Böttinger Marmor. Bunter Fels aus heißen Quellen. Staatsanzeiger Verlag, Stuttgart (2003) 4-15. Rosendahl, W.; Wie wir wurden, was wir sind - eine kurze Stammesgeschichte des Menschen.- in: Wieczorek, A.; Rosendahl, W. (Hrsg.): MenschenZeit - Geschichten vom Aufbruch der frühen Menschen, Verlag Pilipp von Zabern, Mainz (2003) 11-27. Rosendahl, W.; Der Mann von Rhünda - ein neuer Eiszeitjäger aus Hessen, Archäologische und Paläontologische Denkmalpflege des Landesamtes für Denkmalpflege Hessen (Hrsg.), Hessen-Archäologie, Stuttgart (2003) 22-24. Rosendahl, W.; Darga, R.; The "Neue Laubenstein-Bärenhöhle", Chiemgau/Bavarian Alps - the first alpine cave bear cave in Germany, Atti Mus. Civ. Stor. Nat., Trieste 49 (2003) 93-99. Rosendahl, W.; López Correa, M.; Gruner, C.; Müller, T. (Hrsg.), Der Böttinger Marmor. Bunter Fels aus heißen Quellen, Staatsanzeiger Verlag, Stuttgart (2003) 56pp. Rosendahl, W.; López Correa, M.; Granatäpfel, Rüsselkäfer und Bulldogg-Fledermäuse - Pflanzen und Tiere am Böttinger Kraterrand. - in: Rosendahl, W.; López Correa, M.; Gruner, C.; Müller, T. (Hrsg.): Der Böttinger Marmor. Bunter Fels aus heißen Quellen. Staatsanzeiger Verlag, Stuttgart (2003) 16-23. Rosendahl, W.; Maureille, B.; Trinkaus, E.; Rediscovery of the Badegoule 5 human skeletal remains (Badegoule, Le Lardin-Saint-Lazare, Dordogne, France), Paléo 15 (2003) 10 pp. Rosendahl, W.; Rosendahl, G.; Die Neandertaler - zum Leben und Wesen der ältesten Chiemgauer. - in: Binsteiner, M.; Darga, R. (Hrsg.): Steinzeit im Chiemgau, Verlag Dr. F. Pfeil, München (2003) 31-36. Rosendahl, W.; Rosendahl, G.; Kraft, H.P.; Wieczorek, A.; Der Aufbruch der frühen Menschen, Spektrum der Wissenschaft, Heidelberg 3/03 (2003) 90-92. Wieczorek, A.; Rosendahl, W. (Hrsg.); MenschenZeit - Geschichten vom Aufbruch der frühen Menschen. Verlag Pilipp von Zabern, Mainz (2003) 130 pp.

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Hydrogeology Hydrogeology is dealing with groundwater under natural conditions as well as under the influence of man, e.g. sealing of terrains, contaminated sites or agriculture. Equally important parts are the hydraulics, balance and quality and protection of groundwater. Hydrogeologists are working in the field, in the laboratory and with EDV. With this the hydrogeology delivers essential contributions to evaluation and management of water resources. There are important connections to the fields of engineering geology, sedimentology, environmental science and civil engineering, as well as to the conservation of nature.

Staff Members Head

Prof. Dr. Götz Ebhardt

Research Associates

PD Dr. Peter Harres Dipl.-Geol. Meike Beier

Dipl.-Geol. Katy Unger

Technical Personnel

Rainer Brannolte

Secretaries

Ingrid Merz Annemarie Schmidt-Witte

PhD Students

Dipl.-Geol. Meike Beier Dipl.-Geol. Katy Unger

Dipl.-Geol. Uwe Werner Dipl.-Geol. Guido Vero

Diploma Students

-

Research Projects Balance of water and substances in urban areas - example of the city of Darmstadt - (Hessisches Landesamt für Umwelt u. Geologie 2000-2003) Groundwater quantity and quality in the alluvial deposits of the lower Rio Gallego (Ebro/Spain): Influences of infiltration of river water and irrigation Quantification of groundwater flow originating from the Odenwald and the Sprendlinger Horst into the Hessian Ried and the Lower Main Plain (in cooperation with Hessisches Landesamt für Umwelt u. Geologie)

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Engineering Geology

Sedimentary Engineering Geology uses geoscientific methods for the solution of tasks in planning and execution of building measures. This contains investigations for the attitude of sediments and rocks as building ground or building material and for geological processes influencing these characteristics. Engineering geology is consequently a link between geosciences and engineering sciences. For the engineering geology, problems in technical environmental conservation are of increasing importance. The departement of engineering geology is equipped with modern, computer controlled test appliances and carries out investigations of soils and rocks, corresponding to valid standards. The equipment contains triaxial- and box shear-testing machines, Permeameter, swell- and shrink-testing machines, compression-permeability-machines and a strength test apparatus of the company CONTROLLS. For the determination of strength- and deformation-characteristics of rocks, a modern, computerbased testing system of the company FORM+TEST Riedlingen was installed. Researchfields are the determination of soil physical characteristics of loose soils, stress-strain-behaviour of soils and rocks, swelling analysis of the „Messel oil shale“, slope stabilities in the „Martelltal“ and the special geotechnical characteristics of rubble-recycling-materials and slags from waste incineration facilities. These works are often carried out in partnership with the industry.

Staff Members Head

Prof. Dr. Herward Molek

Research Associates

Dr.-Ing. Thomas Nix Dr.-Ing. Harald Vogel

Dipl.-Ing. Jasper Steuernagel Dipl.-Ing. Claudia Kraft

Technical Personnel

Horst Gareis Achim Schöler

Gabriela Schubert

Secretaries

Kirsten Herrmann Edith Paulitz

Monika Schweikhard

Diploma Students

Sven-Oliver Schmitt Reka Cufal

Markus de Jesus Oliveira Jochen Hofmann

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Special courses Engineering Geolo-gy for Departement of Civil Engineering and Surveying

Susanne Ackermann Dirk Sticher Branimir Javorovic Donatello Mare

Research Projects Engineering geological and geomechanical analysis for the fracture origin of sinkholes in karst areas Geotechnical characteristics of rubble-recycling-materials and tests of slags from waste incineration facilities for the use of these components as dike-building-materials (Dt. Bundesstiftung Umwelt, Industry 2002-2004)

Long-term stability of slopes in the UNESCO-world heritage Messel pit

Publications Molek, H.; Engineering-geological and geomechanical analysis for the fracture origin of sinkholes in the realm of a high velocity railway line, 9the Multidisc. Confence on Sinkholes and the Engineering and Environmental Impacts of Karst Huntsville/USA 2003, 8 p. Nix, T., Feist-Burkhardt, S., New methods applied to the microstructure analysis of messel oil shale: confocal laser scanning microscopy (CLSM) and environmental electron microscopy (ESEM), Geological Magazine 140 (4) (2003): 469-478 Vogel, H.; Molek, H.; Geotechnische Funktionssicherheit von Flussdeichen - Leitfaden zur Bewertung, Ber. 14. Tagung für Ingenieurgeologie Kiel 2003, S. 273-278 Harms, F.-J.; Nix, T.; Felder, M.; Neue Darstellungen zur Geologie des Ölschiefer-Vorkommens Grube Messel, Natur und Museum Frankfurt/M. 133 (2003) S. 140-148

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Applied Sedimentology Sedimentary rocks cover about 75% of the earth’s surface and host the most important oil and water resources in the world. Sedimentological research and teaching at the Darmstadt University of Technology focus on applied aspects with specific emphasis on hydrogeological, engineering and environmental issues. However, also research related to oil exploration is carried out with a speciality in palynology and reservoir characterization. To predict groundwater movement, pollutant transport or foundations of buildings in sedimentary rocks a detailed knowledge about the hydraulic, geochemical or geotechnical properties is needed which often vary about several magnitudes. This kind of subsurface heterogeneity can be related to distinct sedimentological patterns of various depositional systems. In addition, changes of depositional systems with time can be explained by specific controlling parameters e.g. changes in sea level, climate, sediment supply and are nowadays described by the concept of sequence stratigraphy. The research in applied sedimentology also includes modelling of erosion and sediment transport and its implication for the management of rivers and reservoirs with the help of GIS. In 2002, a georadar equipment has been established as a specific method for near-surface investigations. First results in the exploration of soils, rocks, and river dikes could be achieved on various test sites in SW Germany (see also research reports).

Staff Members

Head Prof. Dr. Matthias Hinderer

Research Associates Dr. Jens Hornung Dr. Thomas Schiedek

Technical Personnel Erich Wettengl

Secretaries Ingrid Merz Annemarie Schmidt-Witte

Dipl.-Geol. Inge Neeb

Dipl.-Geogr. Holger Schäuble

Dipl.-Geogr. Jörg Lämmermann

PhD Students

Dipl.-Geol. Frank Owenier

Dipl.-Geol. Katrin Ruckwied

Dipl.-Geol. Crisanto Silva

Robert Bienkowski Nils Lenhard Anne Schnitzspahn Diploma Students

Michael Kauer Marco Kollbacher Marek Naser

Research Projects

Reservoir-characterisation and sedimentary geology in general:

• Vulcanoclastics as whitnesses of plate-reorganisation in the middle Miocene of Mexico.

• The geology of raw materials, sequence stratigraphy and palynology in the “Muschelkalk” of south Germany and Hungary.

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Quarternary sedimentary geology and surface processes:

• Sediment budget and sequence stratigraphy of Pliocene and Quaternary unconsolidated deposits of the Rheingletscher area, Swiss midlands and the Upper Rhein Graben (DFG since 2002)

• Computer-aided global analysis of modern denudation rates in small to medium-sized drainage basins (river loads, reservoir siltation, lake sedimentation) (DFG since 2001)

Hydrogeology, engeneering-geology:

• Characterisation of periglacial debris layers with ground penetrating radar in terms of sedimentology and hydrogeology.

• Structural clarification of river dikes at Main and Rhine (SW-Germany) using ground penetrating radar (together with Engineering Geology, Regierungspräsidium).

• Pathways of diffuse deposited persistant pollutants in a heterogeneous subsurface.

• Analysis and prediction of reservoir-filling patterns using GIS

• Water-rock interaction in the geothermal field Los Humeros, Central Mexico.

Publications

Schlunegger, F. & Hinderer, M. (2003): Pleistocene/Holocene climate change, re-establishment of fluvial drainage network and increase in relief in the Swiss Alps. – Terra Nova 15: 88-95. Blackwell.

Hinderer, M. (2003): Large to medium-scale sediment budget models – The Alpenrhein as a case study. In: Lang, A., Hennrich, K. & R. Dikau: Long Term Hillslope and Fluvial System Modelling - Concepts and Case Studies from the Rhine River Catchments. Lecture Notes in Earth Sciences, 101, Heidelberg.

Hinderer, M. & Einsele, G. (2002): Rifts as denudation-accumulation systems: concept, models and examples. - In: Renaut, R.W. & Ashley, G.M. (Hrsg.), Sedimentation in Continental Rifts, SEPM Spec. Publ. 73, Tulsa, Oklahoma, USA.

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Georesources and Geohazards The Georessources and Geohazards Group has been established at Darmstadt University of Technology in 2001. It teaches phenomena and risk management of geohazards (earthquakes, volcanic eruptions, subrosion etc.) and georesources (groundwater, mineral resources, soils), the geology of raw materials, photogeology, and techniques of geographical information systems (GIS). Main interests are in the complex relationships of a specific geologic architecture with possible land use forms. In this context GIS- based risk assessment and decision methodologies are used and developed which may support sustainable use of land and resources and allow estimates of geohazards in different land use scenarios.

Staff Members Head Prof. Dr. Andreas Hoppe Research Associates Dr. Oswald Marinoni Dipl.-Geol. Stefan Lang Dipl.-Ing. Christian Lerch Technical Personnel Dipl.-Kartogr. (FH) Ulrike Simons Holger Scheibner Secretaries Kirsten Herrmann, Monika Schweikhard PhD Students Lic. geogr. Teresa Lamelas Gracia

Research Projects Research concentrates on areas in the peripheries of urban centres with conflicting interests of land use (e.g. winning of groundwater vs. extraction of raw material vs. agriculture vs. nature protection etc.): The Cenozoic terrestrial subsidence basin (Hanau-Seligenstadt Basin) between the Odenwald and Spessart Mts. serve as a model for suburban / agro industrial areas. There, the geologic evolution is reconstructed since autumn 2001 with a sequence stratigraphic approach by Stefan Lang using some 500 drill cores from the archives of the Hessian and Bavarian Geological Surveys. Regionalisation and evaluation of its georesources and geohazards supported by a geographical information system is compiled by Christian Lerch. 3D-visualization is supported by Gocad-software. In May 2003, a seismic survey on the River Main between Hanau and Aschaffenburg with a ship and equipment from the Marine Section of the Senckenberg Institute at Wilhelmshaven supported the investigations as well as two cores near the River Main drilled by the Geological Survey of Hesse which will allow a more precise correlation of seismic data and other drill cores. A second project, sponsored by the German Research Council (DFG), started in summer 2003 with the PhD student Teresa Lamelas Gracia. It will describe and evaluate georesources and geohazards in the surroundings of Zaragoza (Aragón Province,

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northern Spain) and cooperate with partners at the University of Zaragoza and the Darmstadt University of Technology. This area is currently under debate because of a plan of the Spanish government to deviate high amounts of Ebro River waters to the south-eastern parts of the country where it should support the agro industrial complexes. Further investigations areas are planned for Brazil. Contacts to potential partners in Brazil have been established in spring 2003 during visiting and lecturing stays of Andreas Hoppe and Oswald Marinoni at the Universities of Belo Horizonte (PUC, UFMG), Brasília (UnB), Rio Claro (UNESP) and Salvador da Bahia (UFBa).

Publications (with addendum for 2001 and 2002) Chaves, M.L.S.C., Karfunkel,J., Hoppe, A. & Hoover, D.B.: Diamonds from the Espinhaço Range (Minas Gerais, Brazil) and their redistribution through the geologic record.- J. S.Amer. Earth Sci. 14: 277-289, Amsterdam (2001). Hoppe, A., Karfunkel, J. & Noce, C.M.: Sítio Inhaúma, MG – Camadas aragoníticas pré-cambrianas. – in Carlos Schobbenhaus et al., eds: Sítios geológicos e paleontológicos do Brasil, 175-180, Brasília (Dep. Nac. Prod. Min. – CPRM – SIGEP) [ISBN 85-85258-03-9] (2002). Karfunkel, J., Noce, C.M. & Hoppe, A.: Serra da Água Fria e Vizinhanças, MG – Vestígios de glaciação neoproterozóica. – in Carlos Schobbenhaus et al., eds: Sítios geológicos e paleontológicos do Brasil, 165-173, Brasília (Dep. Nac. Prod. Min. – CPRM – SIGEP) [ISBN 85-85258-03-9], www.unb.br/ig/sigep/sitio023/sitio023.htm (2002). Lang, S. & Hoppe, A.: Fluvial base level cycles in Plio-Pleistocene of the Hanau-Seligenstadt Depression (Hesse, Germany) deduced from lithologic well data. – Terra Nostra 2003/3 (Abstr. 18. Meet. Sedimentol. & 1. Reg. Meet. SEPM Central Europ. Sect.; Wilhelmshaven 10-14 June 2003): 122, Berlin (2003). Lerch, C.: Nachhaltige Rohstoffgewinnung in Ballungsgebieten. – Technik & Mensch – VDI BV Frankfurt-Darmstadt 3: 3-4, Monsheim (2003). Lerch, C., Marinoni, O., Lang, S. & Hoppe, A.: Geology and land use: sustainability in the surroundings of urban areas (southern Hesse, Germany). – Proc. 4. Europ. Congr. Reg. Geoscient. Cartogr. Inform. Syst.: 109-110, Bologna (17.-20. 2003). Marinoni, O.: Modelling geographical distributions of geological layers with a coupled ordinary-indicator kriging technique. – Proc. 4. Europ. Congr. Reg. Geoscient. Cartogr. Inform. Syst.: 494-495, Bologna (17.-20. 2003). Marinoni, O.: Improving geological models using a combined ordinary-indicator-kriging approach. - Engineering geology 69: 37-45 (2003). Przyrowski, R., Hoppe, A. & Schäfer, A.: Northern Upper Rhine Graben Plio-Pleistocene seismic stratigraphy. - Abstr.-Vol. (ed. by P. Dèzes) 4th Eucor-Urgent Int. Symp. „Assessing Natural Hazards in a Densely Populated Area“, 34, Basel (2003).

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Geomaterials Science Geomaterials science investigates composition, microstructure, properties, behaviour and formation conditions of minerals, rocks, melts and fluids. This demands an extensive characterisation of geomaterials and experiments on their behaviour with respect to pressure, temperature, deformation and chemical environment. Of special importance is the factor time, i.e., the question how fast the reactions and processes occur. The time scale covers the range from microseconds to the geologic time scale up to millions of years. Geomaterials science is the materials science of geosciences. The research program of the Division Geomaterials Science of the Institute of Applied Geosciences is dedicated to the crystal chemistry of the constituents of rocks and materials. We are studying the real structure, phase transformations and deformational behaviour of crystals, predominantly by methods of transmission electron microscopy. Research topics of the last 10 years were: microstructure and properties of high tech ceramics; weathering and corrosion of natural building materials; cooling history of volcanic rocks deduced from the microstructure; microstructure and mineral reactions of metamorphic rocks; formation conditions, thermic and deformational history of meteorites; electronic states and coordination number of crystalline and amorphous phases, especially the quantitative determination of the ratio Fe2+/Fe3+ .

Staff Members Head Prof. Dr. Wolfgang Friedrich Müller Research associates Priv.-Doz. Dr. Peter van Aken Dr. Stefan Lauterbach Technical Personnel Josef Kolb, Gerlinde Seifert Secretary Christa M. Reinhard PhD Students Dipl.-Geol. Eric Barnert

Research Projects Intergrowths between amphiboles, talc and chlorite in a metamorphosed ultramafic rock of the KTB pilot hole, Bavaria (DFG) Shock effects in andalusite TEM study on eclogites from the Tauern window of the lower schist cover and the eclogite zone (DFG)

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Chain periodicity faults in omphacite as slip system (DFG) Crystal chemistry and microstructures of Fe2SiO4 – Fe3O4 spinelloids (DFG) Synthesis and Characterization of Mixed-Valence Barium Titanates

Oxygen Vacancies in Perovskite and Related Structures: Implications for the Lower Mantle Oxidation state of iron in hydrous mantle phases: Implications for subduction and mantle oxygen fugacity An interface clusters mixture model for the structure of amorphous silicon monoxide Strong magnetic linear dichroism in Fe L23 and O K electron energy-loss near-edge spectra of antiferromagnetic hematite α-Fe2O3 Publications Brenker,F.E.; Müller, W.F.; Brey, G.P.; Variation of antiphase domain size in omphacite: A thermo-chronometrical tool revisited, Am. Mineral. 88 (2003) 1300-1311. Höche, T.; Olhe, P.; Keding, R.; Rüssel, C.; van Aken, P.A.; Schneider, R.; Kleebe, H.-J.; Wang, X.; Jacobson, A.J.; Stemmer, S.; Synthesis and Characterisation of Mixed-Valence Barium Titanates. Philosophical Magazine 83 (2003), 165-178. Hohl, A.; Wieder, T.; van Aken, P.A.; Weirich, T.E.; Denninger, G.; Vidal, M.; Oswald, S.; Deneke, C.; Mayer, J.; Fueß, H.; An interface clusters mixture model for the structure of amorphous silicon monoxide (SiO), Journal of Non-Crystalline Solids 320 (2003) 255–280. Müller, W.F.; Schmädicke, E.; Okrusch, M.; Schüssler, U.; Intergrowths between anthophyllite, gedrite, calcic amphibole, cummingtonite, talc and chlorite in a metamorphosed ultramafic rock of the KTB pilot hole, Bavaria, Eur. J. Mineral. 15 (2003) 295-307. van Aken, P.A.; Lauterbach, S.; Strong magnetic linear dichroism in Fe L23 and O K electron energy-loss near-edge spectra of antiferromagnetic hematite α-Fe2O3, Physics Chem. Minerals 30 (2003) 469-477. Weinbruch, S.; Styrsa V.; Müller, W.F.; Exsolution and coarsening in iron-free clinopyroxene during isothermal annealing, Geochim. Cosmochim. Acta, 67 (2003) 5071-5082.

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Technical Petrology The scientific and educational field of this relatively young branch within the applied geosciences is based on fundamental knowledge in magmatic, metamorphic (greenschist facies to ultra-metamorphism) and low-temperature petrology (studies in diagenesis and sub-greenschist facies metamorphism) but also in sediment petrography. The principal effort is concentrated on the characterization and classification of magmatic, sedimentary and metamorphic rocks. On these fundamentals it is possible to evaluate the mechanical, chemical and physical properties of rocks and the determination for their technical use in engineering geology, in environmental sciences, and in material sciences. The determination of the genetic history and evolution of rocks through time and space gives, e.g., information for ore and hydrocarbon exploration and the basics on the study of rock and ore deposits for prospection and exploitation interests. To understand mineralization, re-crystallisation and petrogenesis of rocks an important effort is focussed on tectono-thermal research, tectonophysics and structural geology (from the kilometre to nanometre scale). Many natural processes are catalytically controlled by deformation. A better understanding of these processes can be recorded from deformation versus crystallisation and deformation versus metamorphism/ heating studies in the field and by experimental simulations. Therefore technical petrology is strongly field oriented and linked to mineralogy, structural geology and also to geochemistry. Technical petrology in our department will be centred on low-temperature petrology with strong relations to applied mineralogy and sedimentology, two other fields of principal interest at the TU Darmstadt.

Technical petrology covers a broad field of studies: - on diagenesis with application in bore hole and geothermal exploration, on clay and carbonaceous materials related with problems in tunnel constructions, - on applied organic and clay petrology (exploration of hydrocarbons), - on rock-water interactions of fluids, contaminated fluids and weathering depending on petrologic variations, - on maceral analysis of coals, - on sorption properties of carbonaceous and clay materials, - on the determination of nano- and microstructures of mixed-layering (rock swelling capacity) and graphitisation structures (refractory quality), - on the improvement of forward numerical geothermal, and maturity, and basin-analysis models (studies on hydrocarbon and fluid migration), - on kinetic models to describe illite aggradations, and smectite-illite reaction progress, and the coalification of macerals, - or on the synthesis of graphite structures and organic matter maturity related to technical aspects, - on recognizing of soot and carbon black in filtering installations or the thermal resistance of organic particles among other applications. It is important to understand the chemical and physical parameters of natural systems to be able to recognize the differences caused by anthropogenic changes.

In the low-temperature range, neoformation of mesoscopic and macroscopic phases is very rare and the minerals to be studied have a very small grain-size. Also stable thermodynamic conditions are scarce and metastable phases and chemical disequilibria condition are very common. Therefore a broad analytical spectrum must be applied. In general microscopy and basically XRD studies have to be combined with DTA, TGA, isotopic geochemistry, and gas chromatography. Due to the small size, also fluid inclusion studies, AEM, TEM, HRTEM, Raman spectroscopy, EELS and XAS give important hints to

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low temperature petrologic researches. These techniques have to be used in the same way in a natural or synthetic system. The main research interests of the study group of R. Ferreiro Mählmann (head of the group since August 2002) are concentrated in the petrologic and petrographic study of tectono-metamorphic orogenic terrains (Alps, Vosges, Carpathians, Andes, New Caledonia). More specifically research is concentrated on diagenesis and low-temperature metamorphism, dealing primarily with pelites and rocks rich in organic matter. Of special interest is the application of different analytical techniques in the study of the metamorphism of organic matter. Here the principal interest is focussed on the study of vitrinite, bituminite and secondary macerals, important constituents of coals and the main source for oil and gas formation and economic reservoirs. In low-grade metamorphic studies mineral-disequilibrium is a frequent factor and is documented through the irregularity of the alteration processes of mineral and organic matter reactions. The research is focussed on the application of field-petrology and mineralogical laboratory methods to problems related to equilibrium and disequilibrium conditions between different organic and inorganic parameters. To find a general solution for these kinds of problems field data are combined with empirical deductions and with the results of temperature-time-pressure experiments. The results are used to establish kinetically based models that offer a better constraint of temperatures. Used kinetic models are introduced in commercial forward-modelling packages to get numerical approaches. These models allow the answer to several complex tectono-metamorphic questions (e.g. amount of tectonic load, erosion and exhumation, deformation-metamorphism relations, heat flow history, paleo-geothermal gradients, basin reconstruction, orogenic history). They also provide information related to coal, oil and gas formation, hydrocarbon migration, the potential of hydrocarbon formation, the metamorphic and meteoric fluid flow mechanics and to hydrothermal path-ways in the studied rocks. The research of the study group of D. Scheuvens and E. Stein (now at University Gießen) focuses on the deformation and metamorphism of crystalline rocks. We try to combine structural, petrological and geochronological data to reconstruct P-T-deformation-time paths of metamorphic and plutonic rocks in order to unravel the orogenic evolution in parts of mountain belts. Our data result both from field and laboratory work with emphasis on micro-structural observations. The main project of D. Scheuvens is located in the Campo crystalline complex (southern part of the central Alps). The major aim of the project is to discriminate between pre-Alpine and eo-Alpine tectono-metamorphic events to get a better understanding of the orogenic processes that were active during Cretaceous stacking and exhumation in this part of the Alpine belt. The current project of E. Stein investigates the interplay of plutonism, deformation and metamorphism in the eastern part of the `zone axiale´ of the Montagne Noire (southern France), a classical geological region to study the burial and exhumation of rocks. A further small project of D. Scheuvens and E. Stein mainly deals with the structural evolution of the eastern part of the Frankenstein intrusives (northern Odenwald) and its contact aureole from high-grade to brittle conditions.

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One event during 2003 have to be mentioned in addition: Organization as co-convener with Peter Arkai (Univ. Budapest) and Kenneth Livi (Johns Hopkins Univ.) in Nice (EGS-AGU-EUG Joint Assembly 2003) of the session “Processes at low temperatures: advances in studies of disequilibrium systems”. The meeting was such a mass of poor quality and expensive that we decided to finish our collaboration with EUG. 2003 was basically a year used to reorganize the laboratories and rock collections and to prepare the new lectures in the scientific and educational field of technical petrology, created in 2002 succeeding the branch of structural geology and petrology. During the following years, the focus of the teaching program will shift towards technical subjects without having to neglect classical petrology and petrography (the basics until something can be applied).

Staff Members Head Prof. Dr. Rafael Ferreiro Mählmann Research associates Dr. Dirk Scheuvens Dipl.-Min. Reinhold Apfelbach Technical Personnel Josef Kolb Secretary Natali Vakalopoulos Zambrano Diploma Students Johannes Schoenherr

Research Projects Laboratory study of vitrinite maturation rate as a function of temperature, time, starting material, aqueous fluid pressure, and oxygen fugacity (PRFACS, cooperation with University Stanford, USA), finished in 2003.

Very low grade metamorphism studies in Chile, New Caledonia, and Romania (SNF, CEEC/NIS, August Collin Fond, cooperation with University Basel, CH; University Genève, CH; Geological Survey of Romania, RO and University of Chile, Santiago de Chile, CL), finished in 2003. Petrostructural and P-T-t-d evolution of the austroalpine Campo crystalline Complex - northern Italy (DFG, cooperation with University Vienna, A and GFZ Potsdam, D). The pattern of diagenesis and metamorphism. Mapping in the Eastern and Central Alps (cooperation with University Frankfurt a. M., D).

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Map of the Alpine metamorphism in the Alps. CMGM subcommission of metamorphic maps.

Geochronology and tectono-thermal history of the Penninic-Austroalpine boundary (Arosa Zone) in Eastern Switzerland; a multi-methodical comparison of methods (SNF, Willkomm Fond, cooperation with University Bern, CH and Departement für Zivilschutz, Bern, CH).

Experimental study on the temperature, pressure, water activity and oxygen fugacity dependence of organic matter, specifically bituminite reflectance (USGS, cooperation with University Stanford, USA).

Raman-spectroscopic, C-isotopic and microscopic studies of carbonaceous material in a metamorphic profile from diagenesis to amphibolite facies (SNF, August Collin Fond, cooperation with University Basel, CH and C.R.E.G.U. Nancy, F).

Deformation, fluid flow and mineral reactions along the Glarus overthrust and along the extensional Turba Mylonite Zone, eastern Swiss Alps, Switzerland. Effects of tectonic shear strain on phyllosilicates and organic matter (SNF, OTKA Hungary, August Collin Fond cooperation with University Basel, CH; University Genève, CH; University Budapest, HU; Johns Hopkins University Baltimore, USA).

Bituminite parameters to determine thermal metamorphism (cooperation with University of Chile, Santiago de Chile, CL; Institutul Geologic al Romaniei, Bucharest, RO; University Complutense, Madrid, E; Stanford University, USA; University Gießen, D and ETH Zürich, CH).

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Environmental Mineralogy Environmental mineralogy focuses its research on the characterization of individual aerosol particles by electron beam techniques (high-resolution scanning electron micro-scopy, transmission electron microscopy, environmental scanning electron microscopy). We study individual aerosol particles in order to derive the physical and chemical properties (e.g. complex refractive index, deliquescence behavior) of the atmospheric aerosol. These data are of great importance for modeling the global radiation balance and its change due to human activities. We are also interested in studying the particulate matter exposure at working places and in urban environments. As aerosol particles may have adverse effects on human health, the knowledge of the particle size distribution and the chemical and mineralogical composition of the particles is of prime importance in order to derive the exact mechanisms of the health effects. Our research is carried out in cooperation with the following national and international partners: Max Planck Institute for Chemistry (Department of Biogeochemistry) in Mainz, Institute for Atmospheric Physics (University of Mainz), Forschungszentrum Karlsruhe (Institut für Meteorologie und Klimaforschung), Institute for Tropospheric Research in Leipzig, Paul Scherrer Institut (Laboratory of Atmospheric Chemistry) in Villigen (Switzerland), National Institute of Occupational Health in Oslo (Norway), and McDonnell Center for the Space Sciences in St. Louis (USA). Other fields of research include kinetics of mineral reactions and cosmochemistry.

Staff Members Head

Prof. Dr. Stephan Weinbruch

Research Associates Dr. Martin Ebert

Technical Personnel

Thomas Dirsch

Secretary

Petra Gebert

PhD Students

Dipl.-Min. Marion Inerle-Hof Dipl.-Geol. Gabi Melisa Dipl.-Geoökol. Barbara Vester Dipl.-Ing. Annette Worringen

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Research Projects Environmental scanning electron microscopical studies of the hygroscopic behaviour of individual aerosol particles. Exposure to aerosol particles in urban areas (Graduiertenkolleg “Spurenanalytik von Elementspezies: Methodenentwicklungen und Anwendungen, Universität Mainz). Source apportionment of rural and urban aerosols. Optical properties of complex aerosol particles derived from transmission electron microscopy (MPI für Chemie, Abteilung Biogeochemie, Mainz). Environmental scanning electron microscopical studies of ice-forming nuclei. Characterization of working place aerosols (National Institute of Occupational Health, Oslo, Norway) Characterization of atmospheric aerosols by Nano-SIMS (McDonnell Center for the Space Sciences in St. Louis (USA). Publications Wentzel M., Gorzawski H., Naumann K.-H., Saathoff H., and Weinbruch S.; Transmission electron microscopical and aerosol dynamical characterization of soot aerosols., J. Aerosol Sci. 34, (2003) 1347-1370. Rohr U., Ortner H.M., and Weinbruch S.; Topochemical speciation of intercalated palladium in graphite by valance band X-ray spectrometry in the electron microprobe., Analytical Chemistry, 75, (2003) 6576-6585. Weinbruch S., Styrsa V., and Müller W.F.: Exsolution and coarsening in iron-free clinopyroxene during isothermal annealing., Geochim. Cosmochim. Acta, 67, (2003) 5071-5082.

Graham B., Guyon P., Maenhaut W., Taylor P. E., Ebert M., Matthias-Maser S., Mayol-Bracero O. L., Godoi R. H. M., Artaxo P., Meixner F.X., Lima Moura M. A., Eça D'Almeida Rocha C. H. , Van Grieken R., Glovsky M. M., Flagan R. C., Andreae M. O.; Composition and diurnal variability of the natural Amazonian aerosol, J. Geophys.Res 108, (2003) (D24) 4765, doi:10.1029/2003JD004049.

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Institute of Geography Human Geography Urban Geography and Regional Research Among topics investigated by Urban Geography are factors affecting the functional types of cities and settlements (historical and present), internal spatial structure (e.g. functions and developement of the Central Business District, social problem areas), urban systems and networks, localisation and hierarchy of commercial centers, regional expansion (suburbanization) and spheres of influence. In our Institute the regional focuses of studies are the Rhine-Main-area, France and South-Africa.

Staff Members Head Prof. Dr. Heinz-Dieter May Research Associates Dipl.-Geogr. Dirk Basmer Tatjana Blau M.A. Stephanie Gutberlet M.A. Tamara Lindstaedt M.A. Technical Personal Dipl.-Geogr. Dirk Basmer Secretary Renate Ziegler-Krutz PhD Student Michael Kolmer M.A.

Research Projects Retail trade development, city marketing and regional marketing in South Hessen Urban development in France: New towns and technopoles Effects of military conversion on urban and socio-geographic structures Tourism in the Western Cape Province (South Africa), development and geographical effects

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Publications Demhardt, I. J.; Vom Apartheidstaat zur Regenbogennation: Tourismusentwicklung in der Republik Südafrika, in: Christoph Becker / Hans Hopfinger / Albrecht Steinecke (Hrsg.): Geographie der Freizeit und des Tourismus: Bilanz und Ausblick, München / Wien, (2003) 666-678. Demhardt, I. J.; German Contributions to the Cartography of South West and East Africa from Mid 19th Century to World War I, in: Proceedings of the 21st International Cartographic Conference, Durban, (2003) 893-907. Demhardt, I. J.; Wine and Tourism at the „Fairest Cape“: Post-Apartheid Trends in the Western Cape Province and Stellenbosch (South Africa), in: Journal of Travel & Tourism Marketing, Volume 14, Numbers 3/4 (2003), 113-130.

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Reports of Research Activities

Modern terrestrial analogues for the carbonate globules in Martian meteorite ALH84001

Jozef Kazmierczak, Stephan Kempe Modern carbonate globules, located in cracks of submerged volcanic rocks and in calcareous pinnacles in alkaline (sodic) Lake Van, Turkey, appear to be analogues for the ~ 3.9 billion year old carbonate globules in Martian meteorite ALH84001. These terrestrial globules have similar diameters and are chemically and mineralogically zoned. Furthermore, they display surface and etching structures similar to those described from ALH84001 that were interpreted as fossilized microbial forms. These terrestrial carbonates formed at low temperatures where Ca-rich ground waters enter the lake. Chemical, mineralogical, microbiological, and biomolecular methods were used in an attempt to decipher the process responsible for the genesis of these structures. Although the exact mode of formation of Lake Van carbonates remains an enigma, their similarity to the Martian globules indicates that the ALH84001 carbonates may have formed in similar setting on ancient Mars. The evidence of fossil microbial life in Martian meteorite ALH84001, first presented over six years ago by NASA (MacKay et al. 1996) includes: (i) carbonate globules containing ultra small ovoids and sausage-like bodies interpreted as remains of bacteria-like organisms, (ii) magnetite crystals interpreted as possible products of magnetotactic bacteria, and (iii) polycyclic aromatic hydrocarbons (PAHs) interpreted as indigenous organic biomarkers. Yet the origin of magnetite and PAHs remains inconclusive (Gibson et al. 2001; Thomas-Keprta et al. 2002). The origin of the carbonate globules and the putative bacterial structures has been the subject of intense debate (e.g., McSween and Harvey 1998; Treiman 1998, 1999; Treiman et al. 2002). We describe carbonate globules from the largest alkaline water body on Earth, Lake Van, Turkey (Kempe et al. 1991). Following conclusions can be drawn from our observations: (1) The Van carbonate globules are similar in size and shape to the ALH84001 carbonate globules (e.g., Mittlefehldt 1994; McKay et al. 1996). (2) The Van globules display chemical zonation similar to that displayed in the ALH84001 globules, underscored by Mn-Fe enrichment of their recrystallized central parts and Mg-enrichment of their rims. (3) The Van globules display bacteriomorphic surface features similar in size and shape to those described from the ALH84001 carbonate globule surfaces. The formation process(es) responsible for these features may be biogenic, abiogenic, or both. Our report demonstrates also that: (i) structures closely resembling the ALH84001 carbonates do really exist on Earth in a soda lake environment; (ii) similarly as in ALH84001 the carbonate globules occur in cracks of volcanic rocks; (iii) the difficulties we faced in interpreting the origin of the studied modern Lake Van carbonate globules may be taken as a warning signal to all trying to interpret the origin of the carbonates from ALH 84001 that the task is not easy and cannot be solved by the analytical approach thus far applied; (iv) the discovery of Lake Van globules, so closely resembling those of ALH84001, suggests that Martian lakes may also had been alkaline and it supports researchers advocating former lacustrine basins as landing sites for Mars missions.

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Fig. 1 Submerged (water depth 16 m) calcareous pinnacles from Lake Van (A, D) fed by Ca-rich groundwater springs contain calcareous (aragonitic or aragonitic/calcitic) globules (B, E, H) composed of ultra small bodies (F, I). These structures closely resemble carbonate globules (C) from the Martian meteorite ALH84001 containing nanostructures (G, J) interpreted as putative fossil bacteria. B: Transmitted light micrograph of aragonitic globules showing concentric brownish zones enriched in highly fluorescent organic substance. E, F: SEM images (at 25 kV, sputtered with 10-15 nm Pt coating) of handpicked globules. H: SEM image (at 25 kV, sputtered with 10-15 nm C coating) of a linear group of sectioned and slightly etched globules. I: Highly magnified SEM image (25kV) of one of the sectioned globules shown in (H). C, G: NASA source – for imaging details see: McKay et al. 1996; Treiman 1999; Gibson 2001; J: after M. M. Grady, Natural History Museum (London)

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Lava Caves of Jordan

S. Kempe, A. Al-Malabeh*, H.-V. Henschel

* Hashemite University, Department of Earth and Environmental Sciences, P.O. Box 150459, Zarka 13115, Jordan;

The central section of Jordan is covered by young alkali olivine basaltic lava flows, the Harrat Al-Jabban volcanics, part of the large intercontinental Harrat As Scham volcanic field. The origin of these lavas may be connected to the existence of a continental intraplate hot spot plume. Its eruptive site should appear to move southward as the Arabian Plate moves northward due to the opening of the Red Sea. The top most and therefore youngest flows, are ca. 400 000 years old (Tarawneh et al., 2000). In these lavas we explored, surveyed and studied in September 2003 two lava tunnels (Abu Al-Kursi and Beer Al-Hamam) and two other lava caves (Table 1). Table 1: Data of Jordan lava caves (locations WGS 84). Name of Cave Latitude Longitude Stations Length Stations Depth Direction Type Abu Al-Kursi W 32°15.401' 36°39.442' 2 to 18 77.1 m 2 to 18 8.1 m N-S Lava Tunnel Abu Al-Kursi E 32°15.401' 36°39.442' 20 to 34 153.7 m 1 to 34 12.2 m W-E Lava Tunnel Azzam Cave 32°17.104' 36°36.594' 13 to 25 44.1 m 1 to 25 4.2 m NWN-SES Pressure Ridge Beer Al-Hamam 32°07.91' 36°49.42' 32 to 23 445.0 m 1 to 23 17.2 m NW-SE Lava Tunnel Dahdal Cave 32°17.344' 36°35.718' 5 to 12 28.9 m 1 t0 12 0.0 m SW-NE Pressure Ridge

The two smaller caves are most probably pressure ridge caves formed by the buckling-up of the upper layers of the still hot and plastic pahoehoe flows flowing down from near-by Al-Qu’ays Volcano. Abu Al-Kursi (Figs. 1, 2, 3) and Beer Al-Hamam (Fig. 4, 5) on the other hand are large lava tunnels, up to 15 m wide and 8 m high, which served to transport lava subterraneously over large distances, i.e. possibly over several tens of kilometres. They are now accessible through ceiling collapses, which allow studying the structure of the roofs. These consist of uninterrupted sets of lava sheets which show that the tunnels did not form by over-crusting lava channels but by repeated under-flowing and inflating of initial lava deltas. In this way the lava flows build forward only at the tip, while the rest of the flow is stationary apart from the lava flowing in the tunnel inside. These processes have been studied in Hawaii (e.g., Kempe, 2002) and can now be used to interpret the findings in Jordan. The discovery of these tunnels shows that the basaltic lava must have been very hot upon eruption, and that they were piped through the tunnels over large distances, thus allowing flow over terrain at slopes of around or less than 2°, comparable to the distal slopes of Hawaiian volcanoes. In fact there should have been many of these tunnels in parallel in these youngest flows. Due to the large age of the flows, it came somewhat as a surprise that the tunnels are still accessible. Dahdal Cave, Abu Al-Kursi and Beer Al-Hamam contain thick deposits of sediments, which -in case of two latter caves- are also the cause of their terminations. Beer Al-Hamam is entered by a wadi during torrential rains, which washes sediment from the surface into the tunnel. The lower part of the cave ponds during rains and it fills with a large reservoir of water. In the upper part of the cave the sediment surface shows signs of fast flowing water. The sediments have been sampled at a profile. They are mostly silts with some fine sand and they contain large concentrations of ammonium nitrate in the upper centimetres, derived from pigeon droppings. In both sections of Abu Al-Kursi, the

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sediment the smooth sediment floor is smooth, covered with a thin layer of fines, laid down by occasional floods that pond at the end of the caves. No sign of flowing water is seen. All caves are known locally. Azzam Cave has been used as a sheep pen until recently. Its entrance seems to be dug out as suggested by a sediment pile nearby containing pot shards. Abu Al-Kursi is visited by adventurous explorers from time to time as is evident from black droppings caused by the use of plastic irrigation pipes as makeshift torches. Beer Al-Hamam must have been visited in the past because we found stone cairns inside but its visit involves climbing down into a 5 m deep overhanging pit. Dahdal Cave was also visited in the past, since it contains a stone wall. These visits may date to prehistoric times though. Plenty of flint stone tools (neolithic?) are found in the surrounding of Dahdal Cave and in two digs in the entrance of Abu Al-Kursi. Dahdal Cave and both sections of Abu-Al-Kursi contain camel bones and may have been used by hyenas as dens in the past (Fig. 3). Shallow circular pits are found throughout Abu Al-Kursi, they do not seem to be anthropogenic since the dug out material is missing. Possibly these are hyena or wolf sleeping pits. A wolf or jackal mandible was collected in the cave.

Fig. 1: Survey of the lava tunnel Abu Al-Kursi in Jordan

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Fig. 2: View of Eastern Hall of Abu Al-Kursi.

Fig. 3: Camel bones, possibly a former hyena den (note bones with missing ends).

Fig. 4: Entrance to Beer Al-Hamam, a collapse hole in the roof of the lava tunnel

Fig. 5: An upslope view of the lower part of Beer Al Hamam (note sediment floor with channel).

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The Holocene Travertine Dam and its Lake Deposits from Seeburg / Southwest Germany

Wilfried Rosendahl, Matthias López Correa

Seeburg is located at the northern margin of the Swabian Alb, approximately 35 km south-east of Stuttgart. The village is situated at the junction of the Fischburg-Valley with the upper Erms-Valley. Fischburg-Valley is drained by the Fischbach (Fish creek), which originates from two small creeks in the upper valley section. The Erms emerges from a strong karst spring (400 l/s), in the narrow Trailfingen gorge, about 1 km south of Seeburg. Large amounts of dissolved carbonate originate from a karstic aquifer in Upper Jurassic limestones and were reprecipitated as travertine at the confluence of both streams. Quick travertine dam growth blocked-off the Fish creek and produced a lake, which extended progressively upstream. During its largest extent the lake had a maximum length of 1 km (EISENSTUCK 1949). Historical documents report a maximum water depth of 10 m to 12 m. In 1616 a tunnel was built to regulate the watertable and to facilitate wood transport in the Erms-Valley below. This 525 m long artificial passage penetrates the travertine dam 14 m below its highest point and gives some insight to the internal dam structure. Abandoned quarries within the village provide interesting outcrops. According to general assumptions, the travertine barrier should have a thickness of 20 m and evolved under favourable climatic conditions during the mid-Holocene in the Atlantic period. An exposure of a 2 m thick sequence of lake deposits in 2000, on a construction site, sparked the authors’ interest to study travertine emplacement and lake evolution more intensively. Precise timing of the dam and lake genesis, in combination with a climatic framework, was the first goal of our renewed research activities. Peat, laminated clays and silts, as well as carbonate sands and marls, where exposed in a 36 m long core from the lake basin. This drill hole in the lake bottom close to the village revealed the entire sediment sequence behind the natural dam. Bedrock floor (Upper Jurassic limestones) of the valley was met at -28.00 m below the recent Fish creek level. Subrounded to rounded limestone pebbles between -28.00 m and -26.50 m are followed by fine gravels from -26.50 m to -24.00 m. These sediments indicate an undisturbed flow of the Fish creek, predating travertine dam emplacement. Alternating layers of clay, marls, accompanied by organic deposits, indicate unequivocal lake conditions between -24.00 m and -1.50 m. Fluvially redeposited material and recent soils make up the surficial layers. The horizons -23.80 m (SEEBK1), -19.90 m (SEEBK2) and -2.00 m (SEEBK6) were dated with the 14C-AMS method on wood and peat samples. SEEBK1 (peat) yielded an age of 10 250 a cal BP, while SEEBK2 (peat) dated at 7 870 a cal BP and SEEBK6 (wood) in historical times at 1740 AD. These new results show that travertine deposition commenced with the beginning of the Boreal. Dam thickness had reached 4 m by the end of the early-Atlantic period (SEEBK2). The subsequent 16 m post-date the early-Atlantic (SEEBK2), probably spanning the entire Atlantic period (SEEKT2) and most likely also younger Holocene intervals. Lake deposits in the core indicate a termination of dam growth at -5.00 m below the recent valley bottom. This position is currently being dated. The horizon at -2.00 m dated at 1740 AD, a time period, when the valley was already affected by human regulation of the watertable. Two additional ages, using conventional radiocarbon dating, were received from the travertine dam at -3.00 m below (SEEKT2) and 12.00 m above (SEEKT1) the Fish creek level. SEEKT1 (travertine) yielded a 14C-age of 9 500 a cal BP for the highest carbonate deposits, while sample SEEKT2 (travertine) centered over 6 230 a cal BP. SEEKT2 is in

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good congruence with stratigraphical relations and chronological data of lake deposits in the core. It is likely that SEEKT1 was affected by the hardwater effect, resulting in a too old age. In addition to chronological information, these new studies show that travertine dam thickness must be considerably more than assumed before. Highest and youngest travertine deposits occur below the church in the centre of the village, 12 m above the recent fish creek. Core data indicate 24 m thick lake deposits below the Fish creek level. Resulting dam thickness must be close to 36 m. New drill holes from dam and lake deposits, in combination with geophysical investigations will provide further insights. Tab. 1: Radiocarbon ages from the Seeburg travertine dam and its lake deposits.

sample radiocarbon age 14C-method material depth (below Fish creek)

Position

SEEBK1 10 250 a cal. BP AMS peat - 23.80 m lake deposits SEEBK2 7 870 a cal. BP AMS peat - 19.90 m lake deposits SEEBK6 1740 AD AMS wood - 2.00 m lake deposits

SEEKT1 9.500 a cal BP conventional travertine + 12.00 m travertine dam SEEKT2 6.230 a cal BP conventional travertine - 3.00 m travertine dam

Fig.1: Chematic landscape graphic of the Fischburg-Valley with important landmarks.

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Engineering-geological and geomechanical analysis for the fracture origin of sinkholes in the realm of a high velocity railway line

Herward Molek

In many countries, specific subterranean karst phenomena are caused by cavern development in carbonate, gypsum and chloride beds, covered by sediments and rocks. Apart from the early realization of an endangered situation within the scope of site investigations, especially a proof for the possibility of karst cavities openings and the formation of sinkholes at the earth´s surface is important. By an example of analytic geomechanical modelling, the formation of sinkholes, caused by deep sulfate karst, shall be calculated. To answer the question, if sinkholes may form at the earth´s surface after the collapse of cavities in a known depth, two realistic geomechanical models are used for the fracture process: formation of a fracture arch and formation of a progressive failure. Regarding the calculations results, it is to state that already small cavities in a depth of 30 m may break though to the earth´s surface. Accordingly, constructional reinforcements had to be included in the planning. ENGINEERING-GEOLOGICAL SITUATION The investigation site is situated near the “Fränkischen Linie“ – a regional tectonical fault zone – which separates the Saxon-Thuringian block from the South German block. From the engineering geological point of view, the sinkholes are of great importance. They are arranged like a pearl string and predominantly bound to this prominent tectonic faultzone. Due to the heavy tectonic destruction of the sedimentary rocks, favourable conditions for the dissolution of the subjacent karst-rocks exist. GEOMECHANICAL MODEL The calculation for model A grasps the fracture mechanism as the development of a fracture arch. The geometry of the cavity varies from 2a (cavity-width) = 3,0 m and 2b (cavity-height) = 1,5 m to 2a = 40 m and 2 b = 30 m (Fig. 1). Model B (Fig. 1) grasps the fracture mechanism by two breaks to the earth´s surface:

• The first case for a break through (1) assumes, that the horizontal beds are strongly jointed and the progressive break through to the earth´s surface takes place along the vertical discontinuities.

• The second case for a break through (2) assumes the vertical jointing of the beds as well, but in contrast to the break through model (1) a fracture arch may evolve in the hard oolitic limestones.

The geometric cavity-parameters vary from 2a (cavity-width) = 3,0 m and 2b (cavity-height) = 1,5 m to 2a = 50 m and 2b = 25 m.

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model A model B 2a: width of cavity 2b: height of cavity Hi : thickness of the layers above the cavity

Fig. 1: Analytical model for the formation of a fracture arch (model A) and analytical model for the formation of a progressive failure along vertical tectonic faults or joints (model B).

Tab. 1: Engineering-geological models for the risk of sinkhole-formation P- Progressive failure PT- Progressive failure along the tectonical vertical faults or joints G- arch genesis

Parameter of rock masses Model A Model B

i Hi Si �Bri Break through

(1) Break through

(2) Layer

[–] [m] [–] [°] Fi [–]

form upwards

trend

Fi [–]

form upwards

trend

Fi [–]

form upwards

trend cohesive soil 6 1 1.04 27 1 P 1 P 1 P

limestone 5 3.85 1.08 40 5 G - PT - PT oolitic

limestone 1 4 0.15 1.15 45 8 G - PT 2/5 G

marly limestone

3 6.50 1.04 36 2 G - PT - PT

oolitic limestone 2

2 0.90 1.08 45 8 G - PT 2/5 G

marly limestone

1 17.60 1.04 36 2 G - PT - PT

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CONCLUSIONS The calculations demonstrated, that, near the tectonical faultzone of the Fränkischen Linie, Model B has to be considered for practice-orientation, because it comprehends the frequent occurrence of vertical joints. Regarding the results of the analytical calculations for Model B, break through (2) gives the best representation of the actual geological situation. It seems obvious, that relatively small cavities of 3 m width and 1,5 m height in a depth of 30 m may be responsible for a break through to the earth´s surface. These relatively small cavities, which cause sinkhole diameters of 6 m on the earth´s surface, represent the most common cause of damage. Larger sinkholes with a diameter about 50 m on the earth´s surface are imaginable. Certainly the geometric parameters for the equivalent karst cavity, a width of 50 m and a height of 25 m, are implausible. Because of the discontinuous fracture propagation, with interruptions between the cavities roof and the earth´s surface, further occasional sinkhole formation is expected.

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Concluding discussion of engineering geological investigations on the long-term stability of slopes in the unesco-world-heritage messel pit

Thomas Nix, Herward Molek

The oil shale-deposits of the Messel pit have become famous through the discovery of superbly preserved vertebrate fossils of Eocene age and the controversial proposal about the after-use of the former open mine pit. Since 1995, when the Messel pit was placed on the UNESCO list of world heritage sites, especially the long-term safety of the artificial slopes is relevant for its future utilisation. The Messel pit is situated about 20 km south of Frankfurt am Main, Hesse, Germany, near the cities of Darmstadt, Dieburg and Langen. Sediments of the Eocene Messel Formation accumulated inside a maar-lake, separated from the surrounding Palaeozoic rocks by marginal faults, originated by the initially collapsing diatreme-structure. The deposits are subdivided lithostratigraphically from top to bottom into three units: • Upper Messel-Formation (clay, silt, sand with brown coal), • Middle Messel-Formation (Messel oil shale), • Lower Messel-Formation (clays, sandstones, breccias) From 1885 to 1971 the oil shale of the Middle Messel-Formation was excavated by open-cast mining and crude oil was extracted in an associated plant until 1961. Slope failures already caused damages and losses of lives during the many years of open cast mining. Currently all artificial slopes are considered as unstable. Because the Messel pit is operated as an opencast pit according to §52 of the federal mining law, the provincial government has taken over the responsibility for the site including possible health and safety issues. Therefore a geotechnical long-term monitoring of the slopes according to DIN 1054-100 is performed since 1993. As mentioned before, extensive slope deformations or sliding processes are presently pointed out for all of the artificial slopes. Different mechanisms of movement combined with different states, styles and distributions of activity appear: 1. Spacious active, suspended or dormant, combined rotational and translational

sliding failures on existent discontinuities inside the tertiary sediments, 2. Limited active, suspended or dormant, retrogressing, combined rotational and

translational rock slides on discontinuities inside the Palaeozoic rocks of the south-eastern and eastern rim,

3. Deformations in man-made replenishments within and beyond the mining area, leading back to the failure of the underlying tertiary sediments or deformations of underlying displaced masses,

4. Creeping movements of the displaced masses of 1. and 2. (resp. of the momentary inactive displaced masses of 1. and 2.).

Mass movements of the Eocene sediments are limited by the marginal faults (detachment planes) of the Messel oil shale-deposit. Near the deposits border-area the deep-seated main sliding surfaces are predominantly located at the transition zone between the Lower Messel-Formation and the oil shale of the Middle Messel-Formation. Towards the deposits centre where the dip of beds parallels the slope angle, these shear zones overlap to the oil shale of the Middle Messel-Formation, using its fine lamination as a sliding plane. Slope failures in the tertiary Messel-sediments are attributed to the complex concurrence of permanent factors such as development of stress respectively state of stress, characteristic material properties and joint system, provoking in combination the increase of shear stress, the contribution to low strength and the reduction of material strength.

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Unloading of the overcompacted sediments due to erosion and surface mining induced relaxation and development of lamination-parallel zones of weakness on which just the residual strength became operative and on which the slopes primarily failed.

Fig. 1: Threshold level for mobilisation of landslides for monthly precipitation (1983-2001) in winter half year. For normal status, measurement and monitoring indicates long-ranging small deformations for all landslides in the northern, eastern and south-western slope.

Fig. 2: Schematic description of interacting forces in a planar sliding plane within the black shale by a) gravitation and pore water pressure, b) gravitation and hydraulic pressure parallel to the slope and c) fissure water pressure.

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Exceeding intense rainfalls may episodically trigger these slides to temporarily accelerated sliding. Considering monthly- and 72h-sum-intervalls of precipitation, qualitative stimulus thresholds of NMonat, crit > 105 mm (Fig. 1) and N72h, crit > 35 mm were defined, whose exceedance accelerates deformations. The rapid infiltration of rainfall causes a temporary rise in pore-water pressures (Fig. 2a), hydraulic pressures (Fig. 2b), hydrostatic fissure-water pressures (Fig. 2c) and an increasing softening of the shear zone material. These influences are generally supposed to be the primary mechanisms by which the slides are reactivated. The slope stability analysis demonstrated that according to DIN 1054-100 the required safety factors of η = 1,3 for loading case 2 (exceptional situation) and η = 1,4 for loading case 1 (normal situation) are not ensured for any of the reactivated, suspended or dormant landslides. The required long-term safety of the artificial slopes is likewise not guaranteed. Small deformations will endure and episodic, temporary accelerations will occur every three to five years up to the achievement of stable slope-conditions. The identifiable risks for object and consequential damages resulting from slope instability are not tolerable. Taking into consideration a cost benefit analysis it seems adequate to reduce these risks by permanent control- and monitoring measurements according to the monitoring procedures of DIN 1054-100. Therefore a modified configuration for control- and monitoring measurements is introduced. Additionally, low priced local structural engineering measures leading to an increase of safety enhancement of vulnerable subareas are presented and recommended.

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Sedimentological-hydrogeological characterization of periglacial soil layers with ground penetrating radar in the Seebach

region, northern Black Forest, Germany

M. Hinderer, M. Kauer, T. Schiedek, J. Hornung, F. Owenier

Periglacial soil layers are very common in the Central European highlands. Because of their high permeability they take action as an important part in discharge and retardation of pollutants. Regarding the genetically implied strongly heterogenous structure of the periglacial layers a quantitative prognosis of preferential flow and pollutant-behaviour is difficult. The ground penetrating radar is an easy usable, not-invasive method to overcome this problem. The reflection patterns of emitted electromagnetic waves show an high resoluted view of the heterogeneity of the shallow subsurface. The interpretation of the radargram has to consider the sedimentological structures (texture, stratification) as well as the water saturation. This was done by a calibration of the radar patterns with outcrops, drillings and geological mapping. Repeated measurements in different weather conditions show the influence of the pore saturation. These key parameters can be translated to hydraulic or retardation relevant parameters and can be used for hydraulic and transport modelling. Measurements took place since the summer of 2003 in the hydraulic and hydrochemical intensivly explored test area in the Black Forest (Bunter Sandstone, Seebach-region, 15 km SE of Baden-Baden, south-western Germany). Four 500-1000 m long slope sections were measured from the ridge to the floor of the valley with the ground penetrating radar and processed with the program Reflexw (version 3.0).All measurements were done using 100 and 200 MHz-antennas with the system SIR-2000 from GSSI (Geophysical Survey Systems Inc.). The following types of radar facies could be discriminated:

1. Up to 5 meter continuously, almost strongly concave curved reflectors of high amplitude. Interpretation: quarternary layers of fine debris with fluvial channels in alluvial valley positions (Fig. 1a).

2. Until 10 meters continuing reflectors with high amplitude. Interpretation: Surface of the outcropping Bunter Sandstone (Fig. 1b).

3. Parabolic, interrupted reflection patterns with medium and low amplitudes. Interpretation: periglacial block debris layers in the ridge area with rupture edges and removing gaps (Fig. 1c).

Weather-dependant measurements in dry and wet weather conditions show changes of all types of radar facies. Higher moisture/saturation of the subsurface causes weaker reflexions, lower wave velocity, higher vertical resolution, but lower depth of invasion. The specific changes of the reflection patterns show discrete impermeable zones and preferential flow due to leakages.

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Fig.1 a-c: Interpreted radargraphs (file 411) of one section in the Seebach region. a: Quarternary debris layers of the Seebach valley, high amplitudes with about 5 meter long reflexions, wavy, fluvial structures b: Surface of the outcropping Bunter Sandstone, high amplitudes, more than 10 meter continuing reflexions, often interrupted c: Intermediate zone of soil layers, low amplitudes, short reflexions, with “hummocky clinoforms“.

b)

c)

a)

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Sustainable use of georesources in the surroundings of urban areas

Christian Lerch, Oswald Marinoni, Stefan Lang and Andreas Hoppe

In the peripherals of large cities the use of natural resources often competes with the needs of urban development and environment protection. This conflict can be solved by an assessment of different forms of land use with regard to aspects of sustainability. Sustainable use of raw material or soil has to be based on a proper knowledge of the underground. Within the scope of the project a geological model is established in order to develop resource maps. Using these maps and maps of the current land use, planning maps are built. Resource planning maps can be one aspect of a multicriterial decision which should lead to a more sustainable land use (Fig. 1).

Fig.1: Correlation between geological model, resource planning maps and multicriterial land use decision

The project area is the Hanau-Seligenstadt Basin, a Cenozoic graben between Odenwald and Spessart Mountains southeast of Frankfurt/Main, which is oriented parallel to the Upper Rhine Graben. From a study of more than 150 well profiles the architecture of the fluvial Pliocene and Pleistocene sediments is gathered with a sequence stratigraphic approach. Stratigraphic base level cycles effect successions from coarse stacked channel sediments to fine grained overbank sediments related to either an increase of accommodation volume or a decrease of sediment supply. These sequences are presumed as approximately isochronous and thus used for a stratigraphic division of the basin. Two Plio-/Peistocene base level cycles were observed. Further analysis of additional 350 wells may change this picture.

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The geological information and the deduced data are stored in a database and can be processed using different methods to get filtered information for individual resources. The lithologic well data and the base level cycle boundaries are computed to a 3D data array using Earthdecision GOCAD. It represents the spatial distribution of an attribute (e.g. grain size) in the underground. Thus deposits of sand and gravel can be located easily (Fig. 2). Data of hydrological well logs are used to model the groundwater surface. Its combination with the lithological dataset allows estimates of availability as well as of vulnerability of groundwater. Soil data and the spatial lithological data are used to classify subsoil quality areas. These resource maps will be compared with current and planned land use, then.

Fig. 2: Assumption of Quaternary base, faults and distribution of gravel (dark grey) in the Hanau-Seligenstadt Basin (arrow shows to north).

Land use decisions are complex tasks and require the consideration of various aspects and criteria. Among these, not only geoscientific but also economic, ecologic and social considerations play an important role whereby each of these aspects brings additional criteria into the decision process. To be able to manage such complex constellations multicriteria decision aid methods can be used. The geological evaluation plays a special role within land use decision processes. Since geological land use interactions usually have much longer time scales than the land use - or exploitation phases, a geologic hazard evaluation must belong to the first steps of a land use evaluation process. To promote more sustainable approaches optimised databases and a geographic information system (GIS) are therefore needed which store

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not only the geologic inventory but also include information on possible geohazards and geopotentials. To answer questions like: “Where is the most favorable location alternative from the geological point of view?” decision support methodologies are used. Among the great variety of approaches, the PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations) outranking approach is a very favorable one since it offers a high degree of transparency. Among several variants of this methodology (PROMETHEE I to VI), POMETHEE II offers the possibility to establish a hierarchical ranking of all alternatives under consideration. Its basic principle is based on a pair wise comparison of alternatives along each recognized criterion where one tries to quantify the preference of one alternative over the other in terms of so called preference values. In further aggregations these preference values are then used to establish a ranking of the available alternatives. GIS integrated software modules are currently developed to combine decision support methodology with the powerful spatial analysis and visualization capabilities of a GIS.

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Modelling geographical distributions of geological layers with a coupled ordinary-indicator kriging technique

Oswald Marinoni

The generation of geological models always goes along with the geologists wish to keep the models as accurate as possible. On the one hand, the developed models have to depict the geometry of the underground, on the other hand they are expected to characterise further properties of the in-situ rock or soil masses like permeability or mechanical parameters. The past has shown that a geologists experience and „feeling“ play an inevitable role in the creation of valuable models but it has also been recognized that the geological model uncertainty is hard to quantify when statistical methods are being left aside or not used to their full extent. With respect to a statistically consistent model, it is not sufficient to describe the statistics of soil or rock properties only, a statistical modelling of the underground geometry is also required. One way to statistically model the underground geometry is the use of geostatistical interpolation techniques generally known as kriging. However, the most commonly used ordinary kriging techniques produce strongly smoothed model results that lead to an inaccurate regionalisation of geological layers. To avoid smoothing, geostatistical simulation techniques are an adequate tool but these techniques give an idea about local variability and are therefore not used for exact local predictions. A methodology has been developed by the help of which smoothing effects around zero value zones can be significantly reduced. The improvements in the geometrical modelling of the geology are depicted in Figure 1.

The simulation-free approach implies the use of a combined application of ordinary- and indicator kriging techniques. The approach takes advantage of the exact local estimation provided by ordinary kriging and uses the binary indicator method to establish a probability of occurrence criterion that is used to model a geographic distribution more accurately. The methodology is well suited for large scale models that are especially needed in urban areas.

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500 m

Corrected

zero thicknesses

Smoothed

Groundmoraine

Sand

Sand

Groundmoraine

S N

S N

smoothed thicknesses

Groundmoraine

Sand

Sand

Fig. 1: Smoothed and corrected geological model (example from Pleistocene sediments). Note that in the area of smoothed thicknesses borehole investigations encountered zero thicknesses of groundmoraine material. Note also the modelled zero thicknesses after the correction.

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Transmission electron microscopic study of the complex intergrowths between amphiboles and layer silicates in a metamorphic rock

from the KTB pilot hole, Bavaria

W.F. Müller, E. Schmädicke *, M. Okrusch **, U. Schüssler ** * Mineralogisches Institut, Universität Erlangen, Schlossgarten 5, D-91054 Erlangen

** Mineralogisches Institut der Universität Würzburg, Am Hubland, D-97074 Würzburg

A metamorphosed ultramafic rock, penetrated by the KTB (Kontinentales Tiefbohr-Programm) pilot hole at a depth of 1382.36 m, contains the assemblage Ca-amphibole – anthophyllite – chlorite – talc, formed at about 630°C/10 kbar under conditions of the high-P amphibolite facies. The results of the study were the following: 1. For the first time, a complex lamellar intergrowth of the amphiboles anthophyllite, cummingtonite, Ca-amphibole and the layer silicate talc was detected by TEM methods. The spatial sequence of phases in a range of 10 to 15 µm, perpendicular to the lamellae, is talc → anthophyllite → anthophyllite/ cummingtonite intercalations → anthophyllite → Ca-amphibole. All the amphiboles have the directions b* and a* in common; anthophyllite and the monoclinic amphiboles are intergrown along (100), anthophyllite and talc with (100)Ath//(001)Tlc. Cummingtonite was only recorded in lamellae of up to 1 µm width. In general, cummingtonite displays the space group C2/m. Only one lamella was detected which may have the space group P21/m. 2. Two types of planar faults were recorded in the Mg-Fe amphiboles investigated with TEM: anthophyllites display chain multiplicity faults (CMFs) //(010), anthophyllite and cummingtonite chain arrangement faults (CAFs) //(100). 3. Anthophyllites relatively rich in Al exsolve platelets or lamellae of gedrite with composition planes of the type {hk0}. Orientations close to {230} and {110} have been recorded, so far not described in the literature. In the same anthophyllite grain, homogeneous and heterogeneous nucleation has been observed; the latter one occurred on CMFs //(010). 4. Ca-amphibole displays lamellar exsolution of cummingtonite //(100). Some grains show numerous dislocations. In one case, a cellular structure was observed. 5. Intergrowths of anthophyllite and chlorite with the orientation relationship a*Ath // c*Chl and b*Ath // b*Chl have been recorded. Since the microstructures observed in the ultramafic rock are the result of the petrological conditions, we will try to connect our TEM observations with the metamorphic and deformational history. As indicated by rare eclogitic relics, the amphibolite-metagabbro succession, penetrated by the KTB pilot hole, experienced a high-pressure with maximum P-T conditions of about 15 kbar/750°C (O’Brien et al., 1992). For a metagabbro sample recovered at a depth of 1268 m, not far from the ultramafic rock investigated, these authors calculated about 13 kbar and 580-650°C. On uplift and cooling, the succession underwent a partial overprint leading to assemblages of the high-P granulite facies at about 670-720°C and 10-12 kbar. Subsequently, a pervasive amphibolite-facies metamorphism took place at still high pressures of 8-11.5 kbar and a poorly defined temperature range of 575-675°C (O’Brien et al., 1992). In the ultramafic rocks associated with the metagabbros, the assemblage Ca-amphibole-anthophyllite(-cummingtonite)-chlorite-talc was presumably formed during the amphibolite-facies event (Matthes et al., 1995). No mineral relics unambiguously testifying to the eclogite and granulite stages have been observed in the ultramafics. Textural evidence

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recorded by the optical microscope and the TEM suggests a stable coexistence of Ca-amphibole, anthophyllite, chlorite and talc. This is corroborated by a petrogenetic grid, calculated for the system CaO-MgO-FeO-Al2O3-SiO2-H2O (CMFASH), in which this paragenesis covers a wide stability field. A pseudosection in the CMFASH system, calculated for the average bulk-rock composition closely conforming to that of the sample investigated displays a distinctly reduced stability field of this assemblage. This, in combination with conventional geothermometry, leads to peak metamorphic conditions of 630±50°C and 10±1 kbar, corresponding to the high-P amphibolite facies and well in accord with the estimates of O’Brien et al. (1992). The stable coexistence of Ca-amphibole, anthophyllite, chlorite and talc, observed in petrographic thin section and supported by the calculated phase diagram, was confimed by TEM on a submicroscopic scale. The interfaces encountered testify to textural equilibrium. Cummingtonite was detected only in lamellar intergrowths with anthophyllite, but never in mutual contact with Ca-amphibole, talc and chlorite. This fact, together with a bulging grain boundary of anthophyllite into cummingtonite indicates that cummingtonite is not part of this stable assemblage.

Fig. 1: Intergrowth of anthophyllite (A) and chlorite (Chl) with the orientation relationship a*Ath // c*Chl and b*Ath // b*Chl. TEM bright field image (left) and electron diffraction pattern.

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Characterization of Iron Valence State and Magnetic Linear Dichroism in Minerals by Electron Energy-Loss Spectroscopy

P.A. van Aken, S. Lauterbach Determination of iron valence states is crucial in the characterisation of geological materials, and has been a long-standing objective in analytical mineralogy. The high spatial resolution available on a transmission electron microscope (TEM) combined with the benefits of electron energy-loss spectroscopy (EELS) allows detailed analysis of multivalent element ratios on the scale of nanometres. Such data permits to determine redox states for mineral crystallisation and to interprete geological evolution of mineral reactions. Estimation of p-T conditions of igneous and metamorphic rocks via geothermobarometers that involve for example Fe2+-Mg2+ exchange in coexisting minerals and determination of oxygen fugacity can be significantly affected by neglecting Fe3+ or using incorrect values. Hence, the precise knowledge of the ferrous/ferric ratio in iron-bearing minerals is indispensable for the under-standing of the exact crystal chemistry of constituent minerals. Energy-loss near-edge structures (ELNES) of the Fe L23 core-loss edges display valence-specific multiplet structures, which can be used as oxidation state fingerprints. The Fe valence state influences the L23 ELNES in two distinct ways. Firstly, the shape and, hence, the intensity distribution of the L23 ELNES can be altered. Although electronic excitations from 2p to 3d and 4s symmetry orbitals are allowed by the selection rule of dipole transition, the probability of transition to the s orbitals is much lower, and, hence, the Fe L23 ELNES is dominated by excitations to 3d orbitals. After the excitation of a 2p core electron, the atomic state changes from the 2p63dn ground state to a 2p53dn+1 final state resulting in two sharp and intense features known as white lines, which are due to a strong interaction between the remaining core hole and the excited electron. The L3 and L2 lines are due to quasi-atomic transitions of 2p3/2 to 3d3/23d5/2 and 2p1/2 to 3d3/2, respectively, and their intensities are related to the unoccupied states in the 3d bands. Secondly, a chemical shift of the edge onset is observed due to shifts in the binding energies of the electronic energy levels which are caused by changes in the effective charge. Systematic investigations on the Fe L23 ELNES of mono and mixed valence Fe-bearing natural minerals and synthetic solid solutions of garnets (almandine-skiagite and andradite-skiagite), pyroxenes (hedenbergite-acmite) (Fig. 1), and spinels (magnetite-hercynite) are presented where the presence of multiple valence states is distinguished by a splitting of the Fe L3 edge (Fig. 1). We demonstrate the feasibility of ferrous/ferric ratio quantification in minerals by analysing the Fe L23 ELNES as a function of the ferric iron concentration. The simplest method uses a modified integral intensity ratio of the Fe L23 white lines where two 2 eV-wide integration windows centring around both the Fe L3-maximum for Fe3+ and the Fe L2-maximum for Fe2+ are employed. This refined routine compared to the previously published quantification method of the ferrous/ferric ratio in minerals leads to an improved universal curve with acceptable absolute errors of about ±0.03 to ±0.04 for Fe3+/�Fe ratios. We report strong magnetic linear dichroism (MLD) at the Fe L23 (Fig. 2) of the antiferromagnetic compound hematite αFe2O3 in high-resolution orientation- and temperature-dependent electron

137

energy-loss spectroscopy (EELS). Large intensity differences of corresponding spectral features are observed when the Fe L23 and O K edges are measured with momentum transfer either parallel or perpendicular to the magnetization. The resultant difference spectra for the Fe L23 edges are consistent with the MLD observed in x-ray absorption spectroscopy. The consequences of the observed MLD at the Fe L23 edges on the deter-mination of Fe3+/)Fe in hematite using different independent quantification methods are discussed. For the first time, we have observed MLD at the O K edge of hematite. The magnetic origin of this O K edge MLD is proved by temperature-dependent investigations across the Morin transition temperature TM = 263 K, at which the Fe electron spins, i.e. the magnetic moments, rotate by 90°. The O K edge MLD is interpreted in terms of superexchange between the spins of the Fe 3d and O 2p electrons through overlapping Fe 3d and O 2p orbitals. The experiments were performed in a transmission electron micro-scope, yielding information about the anisotropic electronic structure at nanoscale spatial resolution when operated with a focussed electron probe. This opens the way to measure micromagnetism in thin films and multilayers with chemical specifity.

Fig. 1: Fe L3 edges from the pyroxene solid solutions hedenbergite-acmite (ac-hd). The spectra have been normalised to the integral Fe L3 white-line intensity, and some of the spectra have been shifted vertically for clarity. The Fe L3 white-line maxima are located at 707.8 eV and 709.5 eV for Fe2+ (hd100) and Fe3+ (ac100), respectively. The Fe3+/ΣFe ratios are data from literature.

Fig. 2: Fe L23 edges of α-Fe2O3 measured with the incident beam direction ik

�

parallel to the c�

axis. At room temperature, ik

�

is parallel to the magnetization M�

, ( ) °=∠ 0, Mki

��

( ), and below the Morin transition temperature, ik

�

is perpendicular to M�

, ( ) °=∠ 90, Mki

��

(———). The difference between both spectra is plotted on the same scale. Transitions from 2p into t2g and eg levels are indicated.

138

Low-temperature, high-pressure metamorphic evolution of pelitic rocks in northern New Caledonia

Sebastién Potel 1, 2, Rafael Ferreiro Mählmann 1, 3, Willem B. Stern 1, Josef Mullis 1 & Martin Frey 1, (†)

1 Mineralogisch-Petrographisches Institut, Universität Basel, Bernoullistrasse 30, CH-4056 Basel,

Switzerland 2 Institut für Geowissenschaften, Senckenbergstrasse 3, D-35490 Giessen, Germany 3 Material- und Geowissenschaften, Technische Petrologie, Schnittspahnstrasse 9, D-64287 Darmstadt,

Germany (†) Martin Frey died in an accident in the Swiss Alps on September 10, 2000. Our work is dedicated to him,

an excellent researcher and a friendly colleague.

This study presents a contribution to understanding thermal history in a low-temperature/high-pressure (LT-HP) metamorphic terrane, with particular emphasis on the relationship between organic maturity and clay mineral reaction progress. A Late Eocene LT-HP metamorphic belt characterizes Northern New Caledonia; the P-T gradient increases from southwest to northeast. Metapelites in the pumpellyite-prehnite and blueschists zones contain lawsonite, Mg-carpholite, Fe-stilpnomelane and Fe-glaucophane. Thermodynamic calculations indicate a progression of metamorphic conditions from less than 3 kbar and 250 °C in kaolinite-bearing rock in the southwest, up to 15 kbar and 410 °C in magnesio-carpholite bearing sample in the northeast. The Kübler index (KI) ranges from high diagenetic to epizonal values, and complete transformation of K-white mica polytypes from 1Md to 2M1 is reached at the transition between the low and high anchizone. Calculated temperatures and measured vitrinite reflectance (VR) values at the transition between high diagenetic zone-anchizone and anchizone-epizone boundaries indicate temperatures of 230 ± 10 and 295 ± 10 °C and coal ranks between 2.9 ± 0.2 and 4.8 ± 0.7 %Rmax respectively. The earliest formed fluid inclusions are stretched (in the southwest) or decrepitated (in the northeast) requiring a nearly isothermal uplift path with a possibly slight increase of maximum burial temperature and/or heat flow. This path allows an increase of the maturation of organic matter and the re-equilibration of KI to the same time-invariant metamorphic level (equilibrium close to steady state conditions). Therefore, the evolutions of the KI and VR are consistent with those generally observed in low-temperature and low-pressure metamorphic belts. Due to the multi-method study, it can be demonstrated that the evolution of organic matter and KI depend strongly on the pressure-temperature path evolution through time. In addition, it is shown that the illite-muscovite b cell dimension is a robust method to determine maximum pressure reached in low temperature domains with a polyphase metamorphic history, nevertheless a high temperature-low pressure exhumation event follows low temperature-high pressure metamorphic conditions during subduction.

139

Metamorphic evolution of a low-grade high –temperature low-pressure metamorphic core complex (Danubian Window)

in the South Carpathians Magda Ciulavu 1,2,*, Rafael Ferreiro Mählmann 1,3, Antoneta Seghedi 2, Stefan M. Schmid 4

& Martin Frey 1†

1 Mineralogisch-Petrographisches Institut, Universität Basel, Bernoullistrasse 30, CH-4056 Basel, 2 Institutul Geologic al Romaniei, 1 Caransebes Street, RO 78 344 Bucharest 32, 3 Technische Petrologie, TU Darmstadt, Schnittspahnstraße 9, D 64287 Darmstadt, 4 Geologisch-Paläontologisches Institut, Universität Basel, Bernoullistrasse 32, CH-4056 Basel, * Canadian Natural Resources Ltd., Calgary, Alberta, † we are very sorry for Martin Frey´s premature disapiarence in a mountain accident in September 2000 The Danubian window, characterized by high temperature-low pressure (HT-LP) metamorphic conditions, is evidently of great interest for methodological studies, because HT-LP conditions under low grade metamorphic conditions received little attention so far. The general increase in metamorphic grade from southwest to northeast in the Danubian window is indicated by mineral paragenesis studies, as well as by illite crystallinity (IC) measurements and organic matter reflectance (OMR). For the first time this study distinguishes between metamorphic conditions related to Cretaceous nappe stacking, and those related to Tertiary exhumation along the Getic detachment. The occurrence of the prehnite-pumpellyite facies in the Severin-Cosustea units shows that in the south-eastern area, Cretaceous metamorphism did not exceed 300 °C. The highest pressure is constrained by the upper stability limit of prehnite to be at around 4.0 kbar. The Danubian units situated within the diagenesis zone were not below 200 °C, due to epidote formation. The IC data, indicating values near the diagenesis zone/anchizone limit, confirm these higher temperatures. Assuming temperatures between >200 and <300 °C, pressures between 2.1 and 2.8 kbar were calculated by using kinetic maturity models. Pre-detachment peak pressure conditions of 4.0 ± 1.0 kbar are found in areas not altered by a subsequent syn-detachment metamorphic overprint. Highest temperatures in chloritoid and epidote-hornblende bearing mylonites have been inferred for samples from the northern border of the Danubian window (between >300 and <400 °C). Along a syn- to post-detachment retrograde pressure path, post-dating chloritoid formation, the occurrence of clinozoisite + chlorite + quartz suggests temperatures >300 °C in the northwest, while the association andalusite + quartz and biotite + chlorite indicates temperatures between 370 and 400 °C at <3.5 kbar in the northeast. In the Severin units at the northern border, IC, mineral chemistry and mineral parageneses all indicate an identical early metamorphic evolution, but lower syn-detachment pressures (3.0 kbar) and temperatures conditions (300 to 350 °C). It is demonstrated that the slope of the regression lines between IC and OMR data gives valuable qualitative information about the relative magnitudes of P and T: the slope of the regression line for the Danubian window samples indicates LT-MP to LT-LP conditions during nappe stacking and HT-LP conditions during the formation of the Getic detachment. HT-LP conditions, can easily be explained by isothermal decompression during the (Getic) detachment event, the elevation of the geotherm being caused by crustal thinning and rapid exhumation of the Danubian units. Probably, also a higher heat-flux prevailed at the end of the Getic detachment, at a time when the retrograde chloritoid decomposition reactions took place, documenting late-stage HT greenschist facies metamorphism.

140

Diploma Theses Ackermann, Susanne; Modellierung der hydraulischen Eigenschaften von Flussdeichen aus Sekundärrohstoffen; Engineering Geology, 2003 Aissaoui-Vallée, Faiza; Karstmorphologische Untersuchungen in ausgewählten Bereichen der südlichen Frankenalb unter ingenieurgeologischen Aspekten, Geology, May 2003 Anthes, Silvia; Geologische Kartierung der Flasergranitoid Zone im Raum Kolmach-Lindenfels und die geologische Untersuchung zweier Bohrkerne am Ostrand des Frankenstein-Plutons, Geology, January 2003 Bienkowski, Robert; Genese hochsaurer Fluide im Geothermalfeld von Los Humeros, Zentral-Mexiko, Geology, November 2003 Cufal, Reka; Geologische Kartierung im Martelltal südöstlich von Gand unter besonderer Berücksichtigung rutschungsgefährdeter Bereiche- Bereich A; Engineering Geology, January 2003 De Jesus Oliveira, Markus; Untersuchung der hydraulischen Verhältnisse bei der Durchströmung von Flussdeichen mit Hilfe maßstabsgerechter Modellversuche; Engineering Geology, March 2003 Hofmann, Jochen; Ermittlung der auslösenden Faktoren von Murgängen im Hinteren Martelltal, Südtirol; Engineering Geology, April 2003 Javorovic, Branimir; Quellung des Rupeltones in ungestörter und gestörter Lagerung; Engineering Geology, July 2003 Krause, Joachim; U/Pb-Datierungen von Zirkonen und Monaziten des Vialais Granits und seiner Rahmengesteine in der Montagne Noire, Südfrankreich, Geology, January 2003 Mügge, Vera; Geopfadskonzept für den Marteller-Höhenweg im Martelltal / Vinschgau-Italien, 2003. Müller, Stefanie; Geomorphologische Untersuchungen zur spätglazialen und holozänen Gletscherentwicklung im Hinteren Martelltal, Südtirol (Italien), 2003. Memeti, Valbone; Polyphase Struktur- und Metamorphosenentwicklung in den „schistes x“ am E-Rand der Montagne Noire, Südfrankreich, Geology, January 2003 Schmitt, Sven-Oliver; Geologische Kartierung im Martelltal südöstlich von Gand unter besonderer Berücksichtigung rutschungsgefährdeter Bereiche- Bereich B; Engineering Geology, January 2003 Sticher, Dirk; Verdichtbarkeit von Müllverbrennungsschlacken; Engineering Geology, 2003

141

Magister Theses Fürst, Beate; Neue Formen von Einzelhandelszentren im Verdichtungsraum. Strukturen und Funktionen erläutert am Beispiel Dreieich-Sprendlingen, Human Geography, July 2003 Patalen, Violetta; Die Entwicklung und Planung der High-Tech-Industrie im westlichen Teil des Landkreises Offenbach unter besonderer Berücksichtigung von Heusenstamm, Dreieich und Langen, Human Geography, January 2003 Schmitt, Susanne; Stadtimage als Aspekt des Stadtmarketings – Mannheim und Wiesbaden im Vergleich, Human Geography, November 2003

PhD Theses Nix, Thomas; Untersuchung der ingenieurgeologischen Verhältnisse der Grube Messel (Darmstadt) im Hinblick auf die Langzeitstabilität der Grubenböschungen. Engineering Geology, June 2003