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."

The development of surface physics and surface chemistry as a science is closely related to the technical development of a number of methods involving electrons either as an excitation source or as an emitted particle carrying characteristic information. Many of these various kinds of electron spectroscopies have become commercially available and have made their way into industrial laboratories. Others are still in an early stage, but may become of increasing importance in the future. In this book an assessment of the various merits and possible drawbacks of the most frequently used electron spectroscopies is attempted. Emphasis is put on prac tical examples and experimental design rather than on theoretical considerations. The book addresses itself to the reader who wishes to know which electron spectroscopy or which combination of different electron spectroscopies he may choose for the particular problems under investigation. After a brief introduction the practical design of electron spectrometers and their figures of merit important for the different applications are discussed in Chapter 2. Chapter 3 deals with electron excited electron spectroscopies which are used for the elemental analysis of surfaces. Structure analysis by electron diffrac tion is described in Chapter 4 with special emphasis on the use of electron diffrac tion for the investigation of surface imperfections. For the application of electron diffraction to surface crystallography in general, the reader is referred to Volume 4 of "Topics in Applied Physics.""