The Chemical Physics Of Solid Surfaces

of available information. Even more importantly, some authors who have contributed substantially to an area may have been overlooked. For this I apologize. I have, however, not attempted to trace techniques or observa tions historically, so there is no implication (unless specified) that the authors referred to were or were not the originators of a given method or observation. I would like to acknowledge discussions with co-workers at SFU for input relative to their specialties, to acknowledge the help of students who have pointed out errors and difficulties in the earlier presentation, and to acknowledge the infinite patience of my wife Phyllis while I spent my sabbatical and more in libraries and punching computers. S. Roy Morrison 0 1 Contents Notation XV 1. Introduction 1 1. 1. Surface States and Surface Sites . 1 1. 1. 1. The Chemical versus Electronic Representation of the Surface. 1 1. 1. 2. The Surface State on the Band Diagram 4 1. 1. 3. The Fermi Energy in the Surface State Model. 6 1. 1. 4. Need for Both Surface Site and Surface State Models 6 1. 2. Bonding of Foreign Species to the Solid Surface 7 1. 2. 1. Types of Interaction. 7 1. 2. 2. The Chemical Bond . 10 1. 2. 3. Acid and Basic Surface Sites on Solids . 13 1. 2. 4. Adsorbate Bonding on Various Solid Types. 16 1. 2. 5. Movement of Surface Atoms: Relaxation, Reconstruction, and Relocation .

The Chemical Physics of Solid Surfaces, Volume 6: Coadsorption, Promoters, and Poisons focuses on the processes, reactions, and approaches involved in coadsorption and the functions of promoters and poisons in synthesis and reactions. The selection first offers information on adsorbate-adsorbate interactions on metal surfaces and interaction between alkali metal adsorbates and adsorbed molecules. Discussions focus on coadsorption of alkali metals and other molecules; model experiments of catalyst promotion; effective medium theory; direct and indirect hybridization effects; and elastic interaction between adsorbates. The publication then ponders on coadsorption of carbon monoxide and hydrogen on metal surfaces and adsorption on bimetallic surfaces. The manuscript examines the chemical properties of alloy single crystal surfaces and promotion in ammonia synthesis. Topics include substrate dependence of nitrogen adsorption and ammonia synthesis; effects of promotion on nitrogen dissociation and ammonia synthesis; and theoretical modeling. The text then elaborates on promotion in the Fischer-Tropsch hydrocarbon synthesis, promoters and poisons in the water-gas shift reaction, and strong metal-support interactions. The selection is a recommended reference for physicists and readers interested in coadsorption, promoters, and poisons.

* At the present stage of development of surface science, there has seemed to be a need for a book-length review spanning the disciplines of surface physics and surface chemistry-a review to summarize and show the con nection between the observations from each discipline. The various results and theories, derived on the one hand from studies of the physical, electronic, and optical properties of surfaces and on the other hand from studies of the chemical activity of surfaces, supplement each other in the search for a realistic model of the surface. The improved understanding possible with such an interdisciplinary approach has been confirmed by recent develop ments which cannot be classified as either surface chemistry or surface physics. Specifically, recent new experimental techniques and quantum mechanical models have provided a much more accurate picture of the nature of the electronic energy levels (bonding orbitals) present at a solid surface. With this more accurate picture we are now able to reconcile the various chemical and physical models that appeared in the early literature on surfaces. The objective of this work has therefore been to describe the results and current models of surface science spanning a broad gray area between surface physics and surface chemistry with some overlap into each of these disciplines. Relevant aspects of surface chemistry are discussed; we cover chemical interactions where bonding and electronic properties dominate, but stop short of specialized topics such as surfactants or liquid/liquid interfaces.

At the International Summer Institute in Surface Science (ISISS), which is held bienially on the Campus of the University of Wisconsin-Milwaukee, invited speakers present tutorial review lectures during the course of one week. The majority of the presentations deal with the gas-solid interface, but now and then relevant reviews concerning liquid-solid or solid-solid interfaces are included. The goal of ISISS was outlined in the first ISISS publication: "We recognize that the International Summer Institute in Surface Science should foster mutual understanding and interaction among theorists and experimentalists in the various areas of surface science. Progress can be achieved only when we occasionally peek over the fence into neighboring areas, not so much to amuse ourselves that the grass is greener on the other side as to learn from their progress and, perhaps equally fruitfully, from their limitations and setbacks. In addition, it is an important task in any field of science to assess, take count of what is done and, what is more important, to point in future directions. " Since the foundation of ISISS in 1973, the invited speakers - internation ally recognized experts in their area of specialization - have been asked to write review articles too. We wanted in this way to ensure that the largest possible group of scientists could benefit from the special review concept.

Surface Properties of Electronic Materials is the fifth volume of the series, The Chemical Physics of Solid Surfaces and Heterogeneous Catalysis. This volume indicates the present state of some basic properties of semiconductor surfaces. Chapter one summarizes the general problems in electronic materials and the areas affected by the surface science methods. The next two chapters illustrate the existing perception of the electronic and structural properties of elemental and compound semiconductor surfaces. This volume also deals with the properties of adsorption of semiconductors relating to both relevant gas phase species and metals. Chapters four to six of this volume explore compound semiconductors and elemental semiconductors. The remaining chapters of this volume explore the adsorption of metals on elemental semiconductors; aspects of growth kinetics and dynamics involved in molecular beam epitaxy; molecular beam epitaxy of silicon; insulators; and metastable phases. The last chapter covers the surface chemistry of dry etching processes.