Reflection High Energy Electron Diffraction And Reflection Electron Imaging Of Surfaces

This volume contains the papers presented at the NATO Advanced Research Workshop in "Reflection High Energy Electron Diffraction and Reflection Electron Imaging of Surfaces" held at the Koningshof conference center, Veldhoven, the Netherlands, June 15-19, 1987. The main topics of the workshop, Reflection High Energy Electron Diffraction (RHEED) and Reflection Electron Microscopy (REM), have a common basis in the diffraction processes which high energy electrons undergo when they interact with solid surfaces at grazing angles. However, while REM is a new technique developed on the basis of recent advances in transmission electron microscopy, RHEED is an old method in surface crystallography going back to the discovery of electron diffraction in 1927 by Davisson and Germer. Until the development of ultra high vacuum techniques in the 1960's made instruments using slow electrons more accessable, RHEED was the dominating electron diffraction technique. Since then and until recently the method of Low Energy Electron Diffraction (LEED) largely surpassed RHEED in popularity in surface studies. The two methods are closely related of course, each with its own specific advantages. The grazing angle geometry of RHEED has now become a very useful feature because this makes it ideally suited for combination with the thin growth technique of Molecular Beam Epitaxy (MBE). This combination allows in-situ studies of freshly grown and even growing surfaces, opening up new areas of research of both fundamental and technological importance.

Publisher Description

This book is a comprehensive review of the theories, techniques and applications of reflection electron microscopy (REM), reflection high-energy electron diffraction (RHEED) and reflection electron energy-loss spectroscopy (REELS). The book is divided into three parts: diffraction, imaging and spectroscopy. The text is written to combine basic techniques with special applications, theories with experiments, and the basic physics with materials science, so that a full picture of RHEED and REM emerges. An entirely self-contained study, the book contains much invaluable reference material, including FORTRAN source codes for calculating crystal structures data and electron energy-loss spectra in different scattering geometries. This and many other features makes the book an important and timely addition to the materials science literature for researchers and graduate students in physics and materials science.

This book provides a comprehensive introduction to high energy electron diffraction and elastic and inelastic scattering of high energy electrons, with particular emphasis on applications to modern electron microscopy. Starting from a survey of fundamental phenomena, the authors introduce the most important concepts underlying modern understanding of high energy electron diffraction. Dynamical diffraction in transmission (THEED) and reflection (RHEED) geometries is treated using a general matrix theory, where computer programs and worked examples are provided to illustrate the concepts and to familiarize the reader with practical applications. Diffuse and inelastic scattering and coherence effects are treated comprehensively both as a perturbation of elastic scattering and within the general multiple scattering quantum mechanical framework of the density matrix method. Among the highlights are the treatment of resonance diffraction of electrons, HOLZ diffraction, the formation of Kikuchi bands and lines and ring patterns, and application of diffraction to monitoring of growing surfaces. Useful practical data are summarised in tables including those of electron scattering factors for all the neutral atoms and many ions, and the temperature dependent Debye-Waller factors given for over 100 elemental crystals and compounds.

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.

This book, written by a pioneer in surface physics and thin film research and the inventor of Low Energy Electron Microscopy (LEEM), Spin-Polarized Low Energy Electron Microscopy (SPLEEM) and Spectroscopic Photo Emission and Low Energy Electron Microscopy (SPELEEM), covers these and other techniques for the imaging of surfaces with low energy (slow) electrons. These techniques also include Photoemission Electron Microscopy (PEEM), X-ray Photoemission Electron Microscopy (XPEEM), and their combination with microdiffraction and microspectroscopy, all of which use cathode lenses and slow electrons. Of particular interest are the fundamentals and applications of LEEM, PEEM, and XPEEM because of their widespread use. Numerous illustrations illuminate the fundamental aspects of the electron optics, the experimental setup, and particularly the application results with these instruments. Surface Microscopy with Low Energy Electrons will give the reader a unified picture of the imaging, diffraction, and spectroscopy methods that are possible using low energy electron microscopes.

This volume contains the papers presented at the NATO Advanced Research Workshop on "Kinetics of Ordering and Growth at Surfaces", held in Acquafredda di Maratea, Italy, September 18-22, 1989. The workshop's goal was to bring together theorists and experimentalists from two related fields, surface science and thin-film growth, to highlight their common interests and overcome a lack of communication between these two communities. Typically surface scientists are only concerned with the microscopic (atomic) description of solids within one monolayer of the surface. Thin-film growers are usually considered more empirical in their approach, concerned primarily with the "quality of their product", and have not necessarily found it useful to incorporate surface science understanding into their art. This workshop aimed to counter at least in some measure these stereotypes. Its focus was on generating dialogue on the fundamental structural and kinetic processes that lead to the initial stages of film growth, from both the surface science and crystal growth perspectives. To achieve this, alternate days emphasized the view of surface science and thin-film growth, with considerable time for discussion, a format that appeared to succeed well. The success of the workshop is in large measure due to the efforts of the organizing committee, L. C. Feldman, P. K. Larsen, J. A. Venables, and J. Villain, whose advice on the constitution of the program was invaluable.