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Cardona Queisser v. Schnering Wyder

 
 
 

	Prof. Dr. Manuel Cardona
	Phone:	+49 (0)711 6 89 - 17 10
	Fax:	+49 (0)711 6 89 - 17 12
	E-Mail:	M.Cardona@fkf.mpg.de

Cardona was one of the Founding Directors of the Institute (CV). He retired in 2000. His department was mainly concerned with optical spectroscopy of semiconductors and high-Tc superconductors in the form of bulk samples, surface layers, and low-dimensional structures like quantum wells, quantum dots and superlattices. Central to his interests is electron-phonon interaction, a topic of particular relevance to both material classes. Experimental methods used at present are Raman, hyper-Raman and Brillouin scattering off and in resonance, hot luminescence, spectroscopic ellipsometry (including synchrotron radiation as a source), optical measurements in high magnetic fields and under high pressure, photoelectron spectroscopy, scanning tunneling microscopy in ultra-high vacuum and X-ray techniques for surface and interface structure analysis. Close collaborations with the synchrotron laboratories in Hamburg (HASYLAB), Berlin (BESSY), Grenoble (ESRF) and Brookhaven (NSLS), the high pressure, technology, molecular beam epitaxy and crystal growth service groups at the MPI, the High Magnetic Field Laboratory and the Institute Laue-Langevin (ILL) in Grenoble have enabled the group to extend the variety of experimental techniques at its disposal. Surface X-ray diffraction and X-ray standing wave measurements are carried out at HASYLAB, ESRF and NSLS, while at BESSY a vacuum UV ellipsometer (5-35 eV) is operated. At NSLS a Fourier ellipsometer for the far infrared spectral range has been built and optimized for measurements of extremely small samples. At ILL neutron scattering is used to study the lattice dynamics of isotopically pure and disordered single crystals. There is also a substantial theoretical effort in computing the electronic and vibronic band structure as well as electron-phonon coupling parameters of the materials under investigation. Topics of recent activities of the group are the vibrational and electronic properties of various compound semiconductors and superlattices, in many cases with controlled isotopic composition, the structure of semiconductor surfaces in the UHV and at the electrolyte interface, as well as electronic Raman scattering processes and crystal field excitations in high-Tc superconductors. Considerable effort, partly in collaboration with the University of California at Berkeley and the Kurchatov Institute (Moscow) and Simon Frazer University (Vancouver), is spent in the growth and characterization of crystals with tailor-made stable isotope composition which are used to investigate isotope effects on a wide range of physical properties such as phonon dispersion, lattice constant, electronic band structure or thermal conductivity (see http://isihighlycited.com).

 
 

	Prof. Dr. Hans-Joachim Queisser
	Phone:	+49 (0)711 6 89 - 16 00
	Fax:	+49 (0)711 6 89 - 10 10
	E-Mail:	H.Queisser@fkf.mpg.de

Hans-Joachim Queisser, born 1931 in Berlin, was one of the Founding Directors of the Institute; he retired in 1998. Queisser is a semiconductor physicist. He studied in Berlin, Lawrence (Kansas, USA) and in Göttingen, where he received his Ph.D. in 1958 in experimental solid-state physics. In 1959, he joined Shockley´s Transitor Corporation and worked in the old apricot barn in Mountain View, California - which was the very cradle of silicon valley. His research concerned defects and perfection of silicon single crystals, device principles, p-n junctions, and solar cells. From 1966, he then investigated compound semiconductors at Bell Laboratories in Murray Hill, NJ with emphasis on optoelectronics. He became professor of physics at Frankfurt´s Goethe University in 1966. In 1969, he was asked to help establish the Stuttgart institute. Queisser maintains strong international ties; he was visitor at Stanford, UC Berkley, the National University of Singapore, the Central Research Labs of Hewlett Packard in Palo Alto, CA, Bell Labs, and Sony Corp. at Yokohama, Japan. He was president of the German Physical Society, sat 13 years on the Senate of the Max-Planck-Society and serves on many industrial boards. Home address: Knappenweg 21d, D-70569 Stuttgart, phone: +49 (0)711 681511

 
 

	Prof. Dr. Hans Georg von Schnering
	Phone:	+49 (0)711 6 89 - 15 60
	Fax:	+49 (0)711 6 89 - 10 10

Von Schnering's former department investigated cluster compounds with polyanions (elements of group 13, 14, 15) and polycations (transition elements), as well as metal complexes and special molecules. The synthesis of new compounds, crystal growth, structure determination, and determination of chemical and physical properties were central activities and served for a better understanding of structure and properties. The relationships of equilibrium conditions and kinetical processes were investigated by means of phase analysis, decomposition reactions and chemical reactions of solid state materials towards new molecular and polymeric cluster compounds. The determination of superstructures and disordered structures, investigations of valence electronic densities and dynamics of molecules in crystals as well as lattice energy considerations were important additional tools. Evaluation of Periodic Nodal Surfaces (PNS) for crystallographic symmetry groups was done with respect to a generalization of the topological pattern of crystalline matter. Physical phenomena and chemical problems concerning valence electron distributions, ionic conductivity, diffusion effects and phase transitions were also investigated in this context. The experimental work was complemented by quantum mechanical calculations (e.g. Electron Localization Function, ELF). Related software was developed applying new computer architectures. The visualization of experimental and theoretical data by 3D computer graphics was helpful to correlate and to understand even complex phenomena.

 
 

	Prof. Dr. Peter R. Wyder
	Phone:	+33 - 476 85 56 00
	Fax:	+33 - 476 85 56 10
	E-Mail:	wyder@grenoble.cnrs.fr