1. Address

The Department of Natural Sciences (Fakultät für Naturwissenschaften) is located in the Adolf-Ferdinand-Weinhold-Bau (Adolf Ferdinand Weinhold Building) at Reichenhainer Strasse 70.

The postal address is:

Technische Universität Chemnitz Fakultät für Naturwissenschaften D - 09107 Chemnitz Germany

2. ECTS-Coordinator:

Dr. Eckart Fromm
Institut für Physik
Professur Nichtgleichgewichtsprozesse
Reichenhainer Str. 70, room 360 (3^nd floor)
phone: +49 (0) 371 531-3207
fax: +49 (0) 371 531-3233
email: fromm@physik.tu-chemnitz.de

3. Local EMSjS Coordinator

Prof. Dietrich R. T. Zahn
Institut für Physik
Professur Halbleiterphysik
Reichenhainer Str. 70, room 638 (6^nd floor)
phone: +49 (0) 371 531-3036
fax: +49 (0) 371 531-3060
email: zahn@physik.tu-chemnitz.de

B. Structure

The Institute of Physics, together with the Institute of Chemistry, comprise the whole of the Department of Natural Sciences at TU Chemnitz.

The Institute of Physics is both a teaching and research institute. Currently, about 100 students are enrolled in degree programs in either fundamental physics (Diplom-Studium) or physics teaching (Lehramts-Studium). However, all science and engineering students at the Technical University Chemnitz take physics courses from the Institut für Physik, so that the total student load is approximately 300.

The faculty consists of 16 professors and about 60 academic staff employees. The research programs of the 16 departmental groups (one per faculty member) are primarily in the field of condensed matter physics, and include work on fundamental as well as applied studies. The work of each group is detailed in the next section.

Cooperations with groups outside the University have a long tradition and, especially in the last few years, have been expanded widely with the goal of promoting more inter-European collaborations.

Research is only partially supported directly by the University; more and more, the department's activities are successfully attracting external funding.

C. Research Activities at the Institute of Physics

1. Surface and Interface Physics (Prof. Dr. H.-J. Hinneberg)

Our research is focused on the epitaxial growth of thin films and systems of thin films on crystalline substrates. Particular emphasis is given to understanding the geometrical and chemical structure of the resulting interfaces.
Current activities involve the processing and characterization of single crystal silicide structures and epitaxial growth of diamond films. These materials offer many new opportunities for both device application and fundamental research. Our main tools for thin film preparation are molecular beam epitaxy in ultrahigh vacuum and plasma activated chemical vapor deposition. Postgrowth treatment is by rapid thermal annealing.
The key method that our group uses for characterizing epitaxial films and interfaces is high resolution transmission electron microscopy. Other methods, used in cooperation with other groups, include Rutherford backscattering spectrometry, ion channeling, X-ray diffraction, and Raman spectroscopy. The electrical properties of both buried and surface silicide films are determined by measuring the Hall coefficient and resistivity versus temperature and magnetic field.
In addition to our research program, our group participates in a number of teaching endeavors including lectures, seminars, practical training in experimental physics for undergraduate students, and special topical lectures on the state-of-the-art of materials science and solid state physics. Also, our numerous collaborations with other research groups in Germany and abroad give our students an opportunity to meet and work with many different researchers.
The Surface and Interface Physics program is supported by the DFG.

2. Solid Surfaces Analysis (Prof. Dr. M. Hietschold)

Our research is focused on the submicroscopic and atomic/molecular structure of solids, especially of their surfaces and interfaces. Preparation and analysis of nanometer-scale structures is another aim of the work.
1. Electron Microscopy. We have one scanning and two transmission electron microscopes (SEM and TEM), of which one is an advanced 200 kV TEM with field emission gun and electron energy loss spectrometer. (This equipment belongs to the Electron Microscopic Laboratory of the Institute.)
2. Scanning Probe Microscopy. In our laboratory there are scanning tunneling microscopes (STM) as well as atomic force microscopes (AFM). Currently we are developing micromechanical multiple-tip scanning probe arrays (within the Sonderforschungsbereich 379) and a new instrument (SICM-SNOM) for electrochemical nanopatterning (DFG support).
3. Ultra-high Vacuum Surface Analysis. A complex surface analysis system with in-situ preparation, STM, and Low Energy Electron Diffraction (LEED) was put into operation 1995. All this equipment is used for structural investigations of organic solids and adsorbates, for preparation, modification and analysis of nanoporous silicon and nanostructures on surfaces, as well as in studies of the metal-semiconductor interfacial region. Currently, we are involved in two subprojects of the Innovationskolleg, "Methods and materials for the nanometer regime".
Close cooperations exist with the Institute of Chemistry and with the Department of Electrical Engineering and Information Technology within the Sonderforschungsbereich 379, and also with a group in theoretical physics. International exchange is ongoing with groups in the Czech Republic, Poland, Russia, Switzerland, Slovakia, the USA, and Vietnam.
Our educational activities include lectures in the undergraduate course on experimental physics as well as special topics courses on "Physics of tunneling phenomena" and "Scanning probe microscopies" for intermediate students. Several practical training units in microscopic techniques are offered. We also participate in special courses for students of electrical engineering.

3. Physics of Thin Films (Prof. Dr. P. Häussler)

The main interests of the thin film group are focused on those systems, in general alloys, that show strong interactions between the atomic, the electronic, and the dynamic structures. As a result of this interaction, the phase stability is enhanced, and electronic transport anomalies can arise. Our research is directed toward understanding

• Peierls systems
• low-dimensional systems
• quasicrystals
• amorphous metals, semiconductors, and magnets
• glassy carbon.

Our lab is equipped for in-situ preparation and characterization at temperatures between 4 K and 1100 K. Measurements of electronic-induced structural and dynamic anomalies, structurally induced pseudogaps in the electronic density of states, and transport anomalies are the experimental tools of our investigations.
Electron diffraction is used to get atomic structure data. Electronic structure is determined from photoelectron spectroscopy and measurement of transport coefficients, i.e., electrical conductivity, Hall effect, thermoelectric power, and thermal conductivity. Our interest is primarily oriented towards an understanding of basic physics, but is open to aspects of practical applicability of the observed phenomena.
Some activities, such as the investigation of the electronic structure using photoelectron spectroscopy (UPS, MXPS), are done in cooperation with the University of Basel (Switzerland). Cooperative experiments and exchanges of results are conducted with many other groups.
Our teaching activities are focused on low-temperature physics and the physics of complex systems. Our group also contributes to practical training with experiments demonstrating fundamental low-temperature properties of solid state physics.

4. Gas Discharge and Ion Physics (Prof. Dr. D. Gerlich)

Topics of interest of our group encompass the field of molecular and ion physics in elementary collision processes, as well as spectroscopy and analysis of fundamental plasma processes. We also conduct experiments in applied research in the field of surface modification by low-pressure gas discharges.
Fundamental questions about ion-molecule reactions ("state-to-state chemistry") are investigated by different techniques using ion guides and ion traps. This allows for handling very low energy ion beams and also for extended observation times for single, stored ions.
One project, funded through the Innovationskolleg, is developing new ion trap designs for the storage of microparticles. These are intended for use in investigating the dynamics of small charged aggregates (several atoms clusters microparticles) in the transition region between gas-phase and condensed-phase physics.
Several of the experiments mentioned above make use of state-of-the-art laser analytical and preparation methods. The subgroup laser preparation and analysis is working on the spectroscopy of isolated ions, ion generation through multiphoton processes, analysis of elementary reaction products, and also on the more applied field of plasma diagnostics.
The work of the subgroup low temperature - low pressure gas discharges (Prof. Dr. J. Meichsner) includes investigation of fundamental questions (plasma diagnostics using Langmuir probes and mass spectrometry), optical characterization of thin films (via ellipsometry, FTIR, UV-VIS-spectroscopy), as well as applied methods (e.g., plasma etching or polymerization).
Our primarily fundamentally oriented research also has technical applications such as the modification of textile fibers through plasma treatment or gas analysis by chemiionization.
Several international cooperations allow for fruitful exchange of results and ideas (EU Network "Structure and Reactivity of Small Molecular Ions", German-Israel Foundation, NATO scientific program). The range of student lectures given comprises fundamental, undergraduate (Atomic, Molecular Physics), as well as specialized topics (e.g. elementary collision processes, non-linear optics).

5. Technical Physics (Prof. Dr. G. Hecht)

Our research activities are focused on the growth of thin films deposited under energetic ion bombardment. These special growth conditions can yield interesting film structures such as strongly textured or metastable crystalline phases. The deposition methods under investigation are magnetron sputtering and plasma assisted chemical vapor deposition (PACVD).
The characterization of the film-forming particle fluxes is performed mainly by using optical emission spectroscopy. Atomic force microscopy as well as measurements of electrical conductivity, mechanical film stress, mass density and microhardness are applied to determine film properties. In addition, several other methods (electron microscopy, x-ray methods, XPS, RBS...) are used in cooperation with other groups. Modeling of deposition processes represents an important part of this work. Our aim is to not only acquire knowledge of the basic mechanisms of the processes under investigation but also to make this knowledge available for the solution of practical problems.
The chair provides seminars in general physics and, jointly with the chair in Solid State Physics, a required elective in physics technologies.
International cooperation is in progress with groups at the Universities of Limoges (France) and Plzen (Czech Republic). This group participates in the Graduiertenkolleg" Thin Films and Non-crystalline Materials" and the Sonderforschungsbereich 379 "Micromechanical Sensor and Actor Arrays".

6. Solid State Physics (Prof. Dr. F. Richter)

A great deal of in situ investigation of thin film growth processes, such as cathodic arc evaporation, ion plating, and other plasma-assisted deposition methods, has been done by using quadrupole mass spectroscopy, ion energy analysis, and laser induced fluorescence. Such measurements enable one to determine the characteristics of the film-forming particle fluxes in order to develop physical models of the deposition processes. The primary goal of our work is to understand the correlations between deposition process, film structure, and film properties. Film analysis is performed in cooperation with other groups. Our own characterization methods have been developed mainly to measure the mechanical properties of thin films.
This chair conducts lectures and seminars in applied physics and solid state physics geared toward prospective teachers of physics. Together with the chair of Technical Physics we are responsible for the required elective course on physics technologies.
International research cooperations exist with groups at the Universities of Limoges (France) and Salford (United Kingdom) as well as research institutes in Australia, the Ukraine and the Czech Republic. The group is participating in the Graduiertenkolleg "Thin Films and Non-crystalline Materials" and the Sonderforschungsbereich 379 "Micromechanical Sensor and Actor Arrays".

7. Semiconductor Physics (Prof. Dr. D. R. T. Zahn)

Due to ever decreasing dimensions of semiconductor devices, interfaces are playing a more and more important role, often dominating, in determining the characteristics of electronic and opto-electronic devices. Thus, to illuminate the nature of interfaces, i.e., their geometrical, electronic, and chemical properties, and to investigate their influence on subsequent layer growth is a particularly relevant topic in both fundamental and practical realms. In addition, the controlled modification of devices, for instance, by inserting a mono-atomic interlayer of a distinct species thereby tailoring the interface properties, is another important issue. Methods of interface preparation are mostly based on molecular beam epitaxial (MBE) deposition in ultra-high vacuum (UHV).
The experimental techniques that we use include high resolution angularly resolved photoemission spectroscopy, optical spectroscopies, i.e., Raman, photoluminescence, infrared, as well as laboratory sources of synchrotron radiation and reflection anisotropy, electrical transport measurements (I-V, C-V), and deep level transient spectroscopy.
Currently we are funded by five grants (DFG, BMBF, EC) and are collaborating with 10 other research institutions in Europe. Our teaching responsibilities are focused on experimental physics, particularly solid state and semiconductor physics.

8. Materials Research and Liquids (Prof. Dr. J.-B. Suck)

We are interested in understanding atomic interactions in liquids, amorphous, quasicrystalline and nanocrystalline alloys, and in solid solutions, as a function of the chemical constitution, of temperature, and of the pressure. Our approach uses the combined data of inelastic and elastic neutron scattering (using sources at other institutions) and measurements of the bulk properties conducted on the same samples in Chemnitz.
When examining liquids, we look at collective excitations and auto- and inter-diffusion as probed by inelastic neutron scattering, and perform viscosity measurements using the oscillating cup method. We also examine the electromagnetic properties, such as electrical conductivity as measured by a rotating magnetic field, and magnetic susceptibility by using the Faraday method.
Currently we are especially interested in binary (supercooled) liquids near or in the miscibility gap. For example, we are looking at the influence of interfaces on the transport of droplets during solidification, also in spacelab experiments.
Our work on solid materials is concerned primarily with the production of new materials and the determination of their phase diagrams with the help of X-ray and neutron diffraction, calorimetric methods (DSC) and -in collaboration with other groups in our Institute- electron microscopy. We also investigate their atomic and spin-dynamics using neutron inelastic scattering techniques and their thermodynamic and magnetic properties by calorimetric and susceptibility measurements.
Collaborations exist with groups in Russia, France, Italy, the Netherlands, Canada, Switzerland and the USA.
Our teaching assignments concentrate on lectures and seminars in experimental physics, especially in solid state physics, materials science and the physics of liquids.

9. X-ray and Neutron Diffraction (Prof. Dr. W. Hoyer)

The main direction of our research work is the structural investigation of condensed matter by diffraction methods. X-ray diffraction and neutron diffraction are used for the investigation of

• the atomic arrangement in non-crystalline materials, especially in molten elements and alloys (total and partial structure factors and pair correlation functions),
• the atomic structure of hard coatings and other types of functional thin films (phase analysis, texture, strain and stress)
• phase transformations (separation of immiscible binary and ternary liquid alloys, supercooled melts and solidification, metastable crystalline phases).

10. Optical Spectroscopy and Molecular Physics (Prof. Dr. C. von Borczyskowski)

Our main interest is the laser spectroscopic investigation of excited electronic states with high temporal (ps to 60 fs), spectral (1 MHz), and spatial (250 nm) resolution. Of primary interest are dynamical processes in the condensed phase. Here are a few of our current research problems:

1. The influence of solvation dynamics and the optimization of charge separation in combination with energy transfer is investigated by time resolved spectroscopy of self-organized chromophores. Results are compared with molecular dynamic computer simulations.
2. By applying high resolution laser spectroscopy for the optical detection of a single spin and also combining it with near-field microscopy, single molecules are used as a nanoscopic probe in solids and on surfaces.
3. Thin films in the nanometer region are synthesized (by evaporation or sputtering) and characterized in terms of thin film optics by the group "Molecular solids and nano-composites". In cooperation with other laboratories, structure investigation by electron microscopy, SERS, and MD simulation of the film growth process are performed.
4. The temporal evolution of metal plasmas formed by laser irradiation of surfaces with respect to the electron and ion density is investigated by time resolved (100 ps) optical interferometry and modelled in two dimensions.

11. Theory of Non-Equilibrium Processes (Prof. Dr. R. Lenk)

There are many challenges for the theory of electronic transport beyond the classical formula tions that are appropriate for dilute or crystalline systems. Examples are the bulk behavior of strongly disordered or amorphous materials like glasses, melts or liquids, and man-made microstructures where quantum mechanical interference and size effects become important. Our main interest is in the diffusive dc transport outside the localization regime, however, topics such as ballistic transport are treated, too.
Typical objects of investigation are quantum films and wires, also with rough boundaries; perturbed waveguides; contacts; grain boundaries and other localized perturbations.
We have developed two independent methods:

• a general superposition method where the whole wave field is generated by a self-consistent superposition of scattered waves.
• a systematic treatment of the incoherent coupling of substructures where the final current distribution is the result of a cooperation of all the subsystems. At fixed energy, this means distribution over the different channels (in a quantum wire or film) or over the corresponding directions of flight without such size effects. At finite temperature, it means distribution over the different energies, too. A special but important case are resistive leads where the current distribution can be adapted to the specific transmission properties of an obstacle. Results are of the well-known Landauer-Büttiker type where now a given transmitter can be embedded, i.e., coupled with its surroundings, in different ways.

12. Relaxational, Radiative, and Tunneling Processes (Prof. Dr. R. Pässler)

We are interested above all in theoretical descriptions of radiative and nonradiative relaxation processes of excited charge carriers in semiconductors that are accompanied by processes of emission or absorption of many phonons. Characteristic cases of a predominance of non-radiative multiphonon processes over other known relaxation mechanisms have been demonstrated in our publications, in particular, for a series of repulsive traps.
The aim of our present investigations is a selfconsistent theoretical interpretation of larger sets of correlated optical and electrical data for semiconductor systems with deep traps. The corresponding configuration coordinate diagrams are determined by numerical fittings of thermally activated photoionization cross-section bands. Detailed investigations and interpretations of the relaxation properties of deep substitutional impurities in silicon are being conducted with experimental groups (particularly of the University of Lund, Sweden). With our novel numerical deconvolution procedures we are capable of determining simultaneously the actual temperature dependencies of zero-phonon binding energies, the Franck-Condon shifts and the associated effective phonon energies as well as the electronic parts of photoionization cross sections for cases of neutral and charged centers.
We have developed a novel analytical framework that is capable of a much more detailed and accurate representation of the qualitatively different contributions of acoustical and optical modes to the total gap shrinkage effect in semiconductors. Detailed numerical analyses of experimental gap shrinkage data taken from literature are being conducted. Forthcoming experimental and theoretical investigations in this field are performed in collaboration with colleagues from the University of Regensburg.
Our main contribution to the Department's teaching program is lectures and seminars on statistical mechanics, thermodynamics, and classical mechanics. Special lectures are given on the fundamentals of radiative and nonradiative multiphonon processes.

13. Theory of Disordered Systems (Prof. Dr. M. Schreiber)

Electronic and structural properties of various materials, e.g. amorphous semiconductors, metals, superconductors, conjugated polymers are calculated, aiming in particular at the relaxation dynamics and transport phenomena. We employ simple models and try to solve them exactly in order to reach a fundamental understanding of the characteristics of disordered systems. Typical tools are the multifractal analysis and the theory of random matrices. On the other hand we use molecular dynamics and Monte-Carlo methods to treat problems in materials science on a quantum mechanical basis. In this way we consider e.g. superhard materials and high-Tc superconductors, which are of technological significance. Thus, our interdisciplinary research comprises semiconductor physics, chemical physics, and statistical physics.
Most of the research requires large scale numerical efforts. Several pentium PCs and workstations are used for developing and testing programs, which are then run on various parallelizing or vectorizing supercomputers at different sites in Germany.
Cooperation and joint projects exist with different institutions in Germany and abroad, especially in Japan, USA, England, Estonia, Austria and Switzerland. We are supported by the EU and by the DFG in several "Schwerpunktprogramme".
In Chemnitz our group participates in the "Graduiertenkolleg", the "Innovationskolleg", and a "Sonderforschungsbereich".
Teaching of regular courses on theoretical physics for diplom students and teachers is supplemented by various topical lectures. Programs for PhD students, workshops and conferences are organized every year.

14. Atomic structure and electronic structure of non-crystalline materials (Prof. Dr. H. Solbrig)

Current understanding of the quantum-mechanical mechanisms which stabilize non-crystalline materials is far from complete. Such mechanisms act on very different length scales—from interatomic distances up to several hundreds atomic diameters. Due to the recent progress in computer performance the cooperation of these mechanisms can now be investigated theoretically. We are primarily concerned with the theory of electron-ion interrelations in metallic systems such as amorphous and liquid metals and quasicrystals. We want to know how the arrangement of the ions in space and the valence electrons as quantum particles are tuned to each other and which consequences arise from this for properties such as electronic conductivity.
By means of computers we generate structure models, i.e. the real-space positions of the atoms in a small piece of the material to be investigated. The structure models are then analyzed with respect to structure properties which are accessible by diffraction experiments. From such material models we calculate the electronic density of states and other electronic properties (conductivity, optical spectra). We use multiple-scattering methods so that the results can be interpreted in terms of repeated scatterings and interference of the scattered waves. This provides insights which are complementary to those which are obtained upon employing orbital-based approaches.
We contribute lectures and exercises for various parts of both the standard university courses on theoretical physics for students majoring in physics and physics education. Practical exercises are offered to advanced students in which the application of numerical techniques in materials sciences is demonstrated. A compulsory lecture series on liquid and amorphous metals is conducted jointly with experimental physicists. In addition, optional lectures are offered on topics such as astrophysics and relativity.

15. Theoretical Physics, Computational Physics (Prof. Dr. K. H. Hoffmann)

Our research interests are within the fields of non-equilibrium thermodynamics, statistical physics and computational physics.
In particular, we study the Dynamics and Structure of Complex Systems in which the systems have many local minima and barriers in the energy function. Common examples of such systems are spin glasses, polymers, neuron networks, and molecular glasses. Due to the special structure of the phase space, the time to reach thermal equilibrium increases with decreasing temperature. So there are a number of experiments to be done where the system has not yet reached equilibrium. A prominent example are the aging experiments on spin glasses.
Another research problem we are dealing with is the Optimization of Thermodynamic Processes. Here we consider irreversible thermodynamic processes which maximize a process parameter such as work or entropy production. Then we ask, for instance, what is the influence of additional constraints such as a given finite process time on the performance of the process. We also try to obtain bounds (more restrictive than those coming from equilibrium physics like the Carnot efficiency) for the process variable of interest.
Closely connected to these fields are stochastic optimization procedures which we use to determine optimal structures for complex systems as well as optimal processes.
We pursue our research activities in close collaboration with groups from Denmark, the USA and other European countries. Our work is supported by the DFG and the EU.

Our teaching activities include:

• the required course in "theoretical physics"
• a course on computational physics
• a course on "energy and energy transformation"
• contributions to the computer science program
• a computer lab
• other courses in theoretical physics

16. Teaching of Science (Prof. Dr. R. Göbel)

Research Goals

• objective learning difficulties in physics, investigation of differences in technical and colloquial language and the problems caused thereby for pupils learning physics (analytical aspect), conception of cognition and appropriation processes to reduce difficulties in learning (synthetic aspect)
• activating cognition activity of pupils, identification of invariable patterns of knowledge- appropriation processes in physics and of approaches to a didactical and methodical arrangement of typical situations of cognition; stimulating pupils by including their collected everyday and practical life experience
• increase the level of experimentation by pupils, analysis of the experimenting process especially with regards to registration, evaluation, and assessment of measured data; evaluation and reformulation of pupil instructions for laboratory experiments to stimulate more independent exploration and scientific thinking
• development of didactical and methodical aids for teachers and pupils, compiling workbooks, books for teachers, and reference books.

• course of instruction on "Teaching physics" and "Teaching chemistry" for preparation to teach at primary and secondary schools and vocational schools:
  • didactic lectures and seminars to teach general and special teaching physics and chemistry
  • practical training "Physics experiments for school children" and "Chemistry experiments for school children"
  • practical experience at schools
  • special didactic block practical training
  • support of scientific research (mainly of students teaching at primary schools)
  • in-service training, further instruction of teachers.

D. Course of Study. Five years to DiplomphysikerIn (Dipl. Phys.)

The best time for students to participate in an exchange program is during their third or fourth year. The length of stay should be one or two semesters.
The physics curriculum for Master's Degree (Diplom) students follows German federal standards. The first four semesters (88 semester weeks, or 1320 h) comprise the "Grundstudium" and conclude with the "Vordiplom" examination. The next six semesters are the "Hauptstudium" (72 semester weeks, or 1080 h), with two semesters dedicated to original research for the thesis. Submission of a thesis and subsequent "Diplom" examination are required for matriculation.
In the Grundstudium, mathematics and the fundamentals of all areas of physics are covered in course work to give students an overview of the entire discipline. Experimental skills are taught in lab courses taken all four semesters. Students may choose to minor in Computer Science or Chemistry, and take the fundamentals courses in those subjects.
During the Hauptstudium, students become familiar with current research. They are required to choose at least one area of specialty in physics and must take courses in another subject of interest, either a second physics field or one in another science, engineering, or (unique to TU Chemnitz) economics.
A special laboratory course, which brings students into contact with the state-of-the-art of their special topic or a related area, is taken prior to starting thesis work.
Work on an original thesis is performed under the supervision and with the assistance of a professorial chair and his or her doctoral students and academic staff. By the end of the two-semester period, Diplom students should be able to perform independent scientific work.
After the final Diplom examination, students may choose to enroll in a doctoral degree (Dr. rer. nat.) program. At Chemnitz, funding for doctoral students is available through the Graduiertenkolleg, stipends from the State of Saxony, and other foundations.
Additional information about enrollment and courses are contained in the brochure "Studying Physics" ("Physik: Informationen zum Studium") that can be obtained by contacting the department.