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FESTKORPERPROBLEME XXIV ADVANCES IN SOLID STATE PHYSICS FESTKORPER PROBLEMEXXlV ADVANCESIN SOLID STATE PHYSICS Plenary Lectures of the 48th Annual Meeting of the German Physical Society (DPG) and of the Divisions "Semiconductor Physics" "Metal Physics" Low Temperature Physics" "Thermodynamics and Statistical Physics" "Thin Films" "Surface Physics" "Magnetism" "Physics of Polymers" "Molecular Physics" "' MiJnster, March 12 ... 17, 1984 Edited by P. Grosse, Aachen With 233 figures Vieweg ISSN 0430-3393 All rights reserved 9 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig 1984 No part of this publication may be reproduced, stored in a retrieval system or transmitted, mechanical, photocopying or otherwise, without prior permission of the copyright holder. Set by Vieweg, Braunschweig Printed and bound by W. Langeliiddecke, Braunschweig Cover design: Barbara Seebohm, Braunschweig ISBN 3-528-08030-2 Foreword In 1984 the Solid State Physics Division of the German Physical Society again has organized its spring meeting together with the 48th Annual Plenary Conference of the society. The conference was really a great success; .about 2500 physicists came to MOnster. In spite of the large number of participants it was possible to find many changes to communicate with colleagues. Volume XXIV of the "Festk6rper-Probleme" contains a selection of the plenary talks and invited talks of the conference. This year the talk of the winner of the Walter-Schottky-prize 1984 is not included in the volume, since the prize was awarded to G. H. D6hler, who had contributed the paper "n-i-p-i doping superlattices" to volume XXIII last year. The first two papers are dedicated to one of the most fascinating fields in modem solid state physics: Physics of microclusters (Martin), experiments and theoretical models to study the properties of crystals "ab initio" when they are growing from atoms or molecules to a large crystal. The second topic is the quantum Hall-effect (St6rmer), which was previously discussed by the Walter-Schottky-prize winner K. v. Klitzing in Vol. XXI of this series. Lower temperatures and samples of higher quality now allow experiments which show surprising effects related to fractional quantum numbers. Those effects may be explained by a collective behavior of the electron gas. The next three papers report on unconventional systems: Hydrogen in metals (Peisl), i.e. crystals in which the protons and not only the electrons play an important role, and further conducting polymers (Roth) and amorphous silicon (Fuhs). In two contributions the physics of defects in silicon is discussed (Watkins, Wagner). This complicated subject is today of large interest because of the importance of defects in silicon applied in microelectronics. Most of the articles concern physics of interfaces and surfaces. Progress in experimental technique of surface analysis and of preparation methods, as well as the activities in thin layer- and microstructure technology have increased the interest in this field: optical and tunneling spectroscopy (Abel6s, Ewert), sputter-depthproffiing (Oechsner), and light scattering (Abstreiter) to analyze surfaces and interfaces, and one paper about the surfaces of the III-V-compounds (Mtinch). The last two papers report on applied problems: one concerns high speed field effect transistors (Heime), an excellent example for the success of tailor-made V semiconductor materials by means of the application of the molecular beam epitaxy technique. The other article concerns miniature refrigerators (Heiden), very often the bottle neck for technical applications of modem solid state devices, working at low temperatures. Following the suggestions of the readers of the Festk6rperprobleme-series we include an author-index of "Festk6rperproblem