The importance of real space imaging and spatially-resolved spectroscopy in many of the most significant problems of surface and interface behaviour is almost self evident. To join the expertise of the tradi tional surface scientist with that of the electron microscopist has however been a slow and difficult process. In the past few years remarkable progress has been achieved, including the development of new techniques of scanning transmission and reflection imaging as well as low energy microscopy, all carried out in greatly improved vacuum conditions. Most astonishing of all has been the advent of the scanning tunneling electron microscope providing atomic resolution in a manner readily compatible with most surface science diagnostic procedures. The problem of beam damage, though often serious, is increasingly well understood so that we can assess the reliability and usefulness of the results which can now be obtained in catalysis studies and a wide range of surface science applications. These new developments and many others in more established surface techniques are all described in this book, based on lectures given at a NATO Advanced Study Institute held in Erice, Sicily, at Easter 1987. It is regretted that a few lectures on low energy electron diffraction and channeling effects could not be included. Fifteen lecturers from seven different Countries and 67 students from 23 Countries and a wide variety of backgrounds attended the school.

The Advanced Study Institute provided an opportunity for researchers in universities, industry and National and International Laboratories, from the disciplines ofmaterials science, physics, chemistry and engineering to meet together in an assessment of the impact of electron and scanning probe microscopy on advanced material research. Since these researchers have traditionally relied upon different approaches, due to their different scientific background, to advanced materials problem solving, presentations and discussion within the Institute sessions were initially devoted to developing a set ofmutually understood basic concepts, inherently related to different techniques ofcharacterization by microscopy and spectroscopy. Particular importance was placed on Electron Energy Loss Spectroscopy (EELS), Scanning Probe Microscopy (SPM), High Resolution Transmission and Scanning Electron Microscopy (HRTEM, HRSTEM) and Environmental Scanning Electron Microscopy (ESEM). It was recognized that the electronic structure derived directly from EELS analysis as well as from atomic positions in HRTEM or High Angle Annular Dark Field STEM can be used to understand the macroscopic behaviour of materials. The emphasis, however, was upon the analysis of the electronic band structure of grain boundaries, fundamental for the understanding of macroscopic quantities such as strength, cohesion, plasticity, etc.

The Advanced Study Institute provided an opportunity for researchers in universities, industry and National and International Laboratories, from the disciplines ofmaterials science, physics, chemistry and engineering to meet together in an assessment of the impact of electron and scanning probe microscopy on advanced material research. Since these researchers have traditionally relied upon different approaches, due to their different scientific background, to advanced materials problem solving, presentations and discussion within the Institute sessions were initially devoted to developing a set ofmutually understood basic concepts, inherently related to different techniques ofcharacterization by microscopy and spectroscopy. Particular importance was placed on Electron Energy Loss Spectroscopy (EELS), Scanning Probe Microscopy (SPM), High Resolution Transmission and Scanning Electron Microscopy (HRTEM, HRSTEM) and Environmental Scanning Electron Microscopy (ESEM). It was recognized that the electronic structure derived directly from EELS analysis as well as from atomic positions in HRTEM or High Angle Annular Dark Field STEM can be used to understand the macroscopic behaviour of materials. The emphasis, however, was upon the analysis of the electronic band structure of grain boundaries, fundamental for the understanding of macroscopic quantities such as strength, cohesion, plasticity, etc.