During the last decade, surface research has clearly shifted its interest from the macroscopic to the microscopic scale; a wealth of novel experimental techniques and theoretical methods have been applied and developed successfully. The Topics volume at hand gives an account of this tendency. For the understanding of surface phenomena and their exploitation in tech nical applications, the theoretical and experimental analysis at the microscopic level is of particular interest. In heterogeneous catalysis, for example, a chemical reaction takes place at the interface of two phases, and the process occurring at the surface is composed of a sequence of individual microscopic steps. These individual steps include adsorption, desorption, surface diffusion, and reaction on the surface. These elementary steps are greatly influenced by the structure and the dynamics of the surface region. Especially the catalytic activity may strongly depend on the structure of the catalyst's surface. The necessity of per forming surface investigations on a microscopic scale is also reflected clearly in research work relating to metal-semiconductor interfaces which determine es sentially the properties of electronic device materials. The experimental probe on the atomic scale, coupled with parallel theoretical calculations, showed that the electronic properties of a metal-semiconductor interface strongly depend on the crystallographic structure of the semiconductor; in particular, it is im portant to know in this context the modification of the atomic arrangement in the surface region caused by the termination of the crystal by the surface.

This volume is based on lectures and contributed papers presented at the Eighth Course of the International School of Materials Science and Tech nology that was held in Erice, Sicily, Italy at the Ettore Majorana Centre for Scientific Culture during the period 1-13 July 1985. The subject of the course was "Electromagnetic Surface Excitations". Forty lectures were given by eleven distinguished scientists and engineers from France, Italy, the United Kingdom, and the United States. In addition to the lectur ers, approximately fifty participants representing eleven different countries throughout the world t. ook part in the course. Short contributed papers were presented by seventeen participants on the results of their own re search. The subject of the Course is of great importance for both pure science and for practical applications such as telecommunications. A technolog ical revolution is occurring in which the transmission of information by means of electrical currents travelling in copper wires is being replaced by transmission by means of light travelling in objects known as optical wave guides. The manipulation and processing of the light signals prior and subsequent to transmission through the wave guide has resulted in a technology often referred to as integrated optics. Important to the opera tion of integrated optics devices is the behavior of electromagnetic waves near surfaces and interfaces. One of the goals of the course was to further the dialogue between engineers and physicists in common areas of interest related to the propagation of electromagnetic waves along surfaces.

This volume contains almost all of the 79 papers presented at the Fourth International Conference on Vibrations at Surfaces. The proceedings reflect the significant advances that have been made in the field of surface vibrations since the previous conference on the topic held in 1982. The presented papers showed a tendency of development in new directions, particularly in relation to dynamical effects occurring in atom and molecule-surface interactions. These proceedings cover the field of surface vibrational spectroscopy in such a way as to make the book an asset to those involved in both experimental and theoretical work in this field.

Physics at Surfaces is a unique graduate-level introduction to the physics and chemical physics of solid surfaces, and atoms and molecules that interact with solid surfaces. A subject of keen scientific inquiry since the last century, surface physics emerged as an independent discipline only in the late 1960s as a result of the development of ultra-high vacuum technology and high speed digital computers. With these tools, reliable experimental measurements and theoretical calculations could at last be compared. Progress in the last decade has been truly striking. This volume provides a synthesis of the entire field of surface physics from the perspective of a modern condensed matter physicist with a healthy interest in chemical physics. The exposition intertwines experiment and theory whenever possible, although there is little detailed discussion of technique. This much-needed text will be invaluable to graduate students and researchers in condensed matter physics, physical chemistry and materials science working in, or taking graduate courses in, surface science.

This volume contains review articles which were written by the invited speak ers of the seventh International Summer Institute in Surface Science (ISISS), held at the University of Wisconsin - Milwaukee in July 1985. The form of ISISS is a set of tutorial review lectures presented over a one-week period by internationally recognized experts on various aspects of surface science. Each speaker is asked, in addition, to write a review article on his lecture topic. No single volume in the series Chemistry and Physics of Solid Surfaces can possibly cover the entire field of modern surface science. However, the series as a whole is intended to provide experts and students alike with a comprehensive set of reviews and literature references, particularly empha sizing the gas-solid interface. The collected articles from previous Summer Institutes have been published under the following titles: Surface Science: Recent Progress and Perspectives, Crit. Rev. Solid State Sci. 4, 125-559 (1974) Chemistry and Physics of Solid Surfaces, Vols. I, II, and III (CRC Press, Boca Raton, FL 1976, 1979 and 1982), Vols. IV and V, Springer Ser. Chern. Phys., Vols. 20 and 35, (Springer, Berlin, Heidelberg 1982 and 1984). The field of catalysis, which has provided the major impetus for the de velopment of modern surface science, lost two of its pioneers during 1984 and 1985: Professors G.-M. Schwab (1899-1984) and p.k. Emmett (1900-1985).

During the past fifteen years there has been a dramatic increase in the number of different surfaces whose structures have been determined experimentally. For example, whereas in 1979 there were only 25 recorded adsorption structures, to date there are more than 250. This volume is therefore a timely review of the state-of-the-art in this dynamic field.Chapter one contains a compilation of the structural data base on surfaces within a series of tables that allows direct comparison of structural parameters for related systems. Experimental structural trends amongst both clean surfaces and adsorbate systems are highlighted and discussed.The next chapter outlines the successes of local density functional theory in predicting the relaxations and reconstructions of clean metal and semiconductor surfaces, and the behaviour of adsorbates such as hydrogen, oxygen and alkali elements on metal surfaces, thereby explaining some of the experimental trends observed within the database. These ab initio density functional calculations are of ground state properties at the absolute zero of temperature. Chapter three provides an introduction to finite temperature effects in a pedagogical review of current statistical mechanical treatments of phase transitions at surfaces, many of which display the prominent role of fluctuations or non-mean field behaviour. The final chapter discusses the relationship of the reactivity of a surface to its morphology and composition, which is particularly relevant to a fundamental understanding of catalysis.

In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, coherent and self-contained guide to the rapidly growing field of surface phonons was needed.

Semiconductors can exhibit electrical instabilities like current runaway, threshold switching, current filamentation, or oscillations, when they are driven far from thermodynamic equilibrium. This book presents a coherent theoretical des- cription of such cooperative phenomena induced by generation and recombination processes of charge carriers in semicon- ductors.