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Surfaces and interfaces play an increasingly important role in today's solid state devices. In this book the reader is introduced, in a didactic manner, to the essential theoretical aspects of the atomic and electronic structure of surfaces and interfaces. The book does not pretend to give a complete overview of contemporary problems and methods. Instead, the authors strive to provide simple but qualitatively useful arguments that apply to a wide variety of cases. The emphasis of the book is on semiconductor surfaces and interfaces but it also includes a thorough treatment of transition metals, a general discussion of phonon dispersion curves, and examples of large computational calculations. The exercises accompanying every chapter will be of great benefit to the student.
Two-dimensional (2D) materials, in the form of a single atomic layer with a crystalline structure, are of interest for electronic applications. Such materials can be formed by a single element, e.g., by group IV or group V elements, or as a 2D surface alloy. As these materials consist of just a single atomic layer, they may have unique properties that are not present in the bulk. The (111) surfaces of the noble metals Ag and Au are important for the preparation of several 2D materials. To investigate the atomic and electronic structures, the following experimental techniques were used in this thesis: angle resolved photoelectron spectroscopy (ARPES), scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The 2D structures studied in this thesis include arsenene (an As analogue to graphene) and As/Ag(111), Sn/Au(111), and Te/Ag(111) surface alloys. Arsenene has been thoroughly investigated theoretically for many years and several interesting properties important for next generation electronic and optoelectronic devices have been described in the literature. This thesis presents the first experimental evidence of the formation of arsenene. A clean Ag(111) surface was exposed to arsenic in an ultra-high vacuum chamber at an elevated substrate temperature (250 to 350 °C ). The resulting arsenic layer was studied by LEED, STM and ARPES. Both LEED and STM data resulted in a lattice constant of the arsenic layer of 3.6 Å which is consistent with the formation of arsenene. A comparison between the experimental band structure obtained by ARPES and the theoretical band structure of arsenene based on density functional theory (DFT), further verified the formation of arsenene. The As/Ag(111) surface alloy was prepared by exposing clean Ag(111) to arsenic followed by heating to 400 °C. This resulted in an Ag2As surface alloy which formed by the replacement of every third Ag atom by an As atom in a periodic fashion. LEED showed a complex pattern of diffraction spots corresponding to a superposition of three domains of a reconstruction described by a unit cell. STM images revealed a surface with a striped atomic structure with ridges characterized by a local ?3 × ?3 structure. ARPES data showed three alloy related bands of which one can be associated with the ?3 × ?3 structure on the ridges. This band shows a split in momentum space around the point along the direction of a ?3 × ?3 surface Brillouin zone in similarity with a Ge/Ag(111) surface alloy. Sn/Au(111) surface alloys can be prepared with different periodicities. An Au2Sn phase characterized by a ?3 × ?3 periodicity and an Au3Sn phase with a 2 × 2 periodicity are formed containing 0.33 and 0.25 monolayer of Sn, respectively. The clean Au(111) surface itself, shows a complex reconstruction, the so called herringbone structure, that can be viewed as a zig-zag pattern of stripes described by a 22 × ?3 unit cell. The replacement of Au atoms by Sn results in change of the periodicity of the herringbone structure to 26 × ?3 and ? 26 × 2?3 for the Au2Sn and Au3Sn surface alloys, respectively. Furthermore, the local 1 × 1 periodicity of clean Au(111) is replaced by a ?3 × ?3 and a 2 × 2 periodicity as is clear from STM images of the respective cases. ARPES data are presented for the Au2Sn surface alloy, which reveal an electronic band structure with similarities to other striped surface alloys. In particular, the split in momentum space around the point of a ?3 × ?3 surface Brillouin zone is observed also for Au2Sn. A Te-Ag binary surface alloy can be formed by evaporating 1/3 monolayer of Te onto a clean Ag(111) surface followed by annealing. After this preparation, LEED showed sharp ?3 × ?3 diffraction spots that is evidence for a well-ordered surface layer. ARPES data revealed two distinct electronic bands that followed the ?3 × ?3 periodicity. One of these bands showed a small spin-split of the Rashba type. The experimental band structure was compared with the theoretical bands of several atomic models of Te induced structures on Ag(111). An excellent fit was obtained for a Te-Ag surface alloy with a planar honeycomb structure, with one Te and one Ag atom in the unit cell. A semiconducting electronic structure of the Te-Ag surface alloy was inferred from the ARPES data in agreement with the ?0.7 eV band gap predicted by the DFT calculations.
This textbook is intended as an introduction to surface science for graduate students. It began as a course of lectures that we gave at the University of Paris (Orsay). Its main objectives are twofold: to provide the reader with a compre hensive presentation of the basic principles and concepts of surface physics and to show the usefulness of these concepts in the real world by referring to experiments. It starts at a rather elementary level since it only requires a knowledge of solid state physics, quantum mechanics, thermodynamics and statistical physics which does not exceed the background usually taught to students early in their university courses. However, since it finally reaches an advanced level, we have tried to render it as self-contained as possible so that it remains accessible even to an unexperienced reader. Furthermore, the emphasis has been put on a pedagogical level rather than on a technical level. In this spirit, whenever possible, models which are simplified, but which contain the features that are essential to the appearance of the phenomena, have been set up and solved in a completely analytical way. The logic should be transparent enough for the reader although, most often, a more rigorous solution would need the use of a computer. To conclude, we have tried to give an account of surface physics which should be of use to the theoretician as well as to the experimentalist. The following comments can be made on the contents of this book.
This is a revised edition of the 1999 text on the electronic structure and properties of solids, similar in spirit to the well-known 1980 text Electronic Structure and the Properties of Solids. The revisions include an added chapter on glasses, and rewritten sections on spin-orbit coupling, magnetic alloys, and actinides. The text covers covalent semiconductors, ionic insulators, simple metals, and transition-metal and f-shell-metal systems. It focuses on the most important aspects of each system, making what approximations are necessary in order to proceed analytically and obtain formulae for the properties. Such back-of-the-envelope formulae, which display the dependence of any property on the parameters of the system, are characteristic of Harrison's approach to electronic structure, as is his simple presentation and his provision of all the needed parameters.In spite of the diversity of systems and materials, the approach is systematic and coherent, combining the tight-binding (or atomic) picture with the pseudopotential (or free-electron) picture. This provides parameters ? the empty-core radii as well as the covalent energies ? and conceptual bases for estimating the various properties of all these systems. Extensive tables of parameters and properties are included.The book has been written as a text, with problems at the end of each chapter, and others can readily be generated by asking for estimates of different properties, or different materials, than those treated in the text. In fact, the ease of generating interesting problems reflects the extraordinary utility and simplicity of the methods introduced. Developments since the 1980 publication have made the theory simpler and much more accurate, besides allowing much wider application.
At present, there is an increasing interest in the prediction of properties of classical and new materials such as substitutional alloys, their surfaces, and metallic or semiconductor multilayers. A detailed understanding based on a thus of the utmost importance for fu microscopic, parameter-free approach is ture developments in solid state physics and materials science. The interrela tion between electronic and structural properties at surfaces plays a key role for a microscopic understanding of phenomena as diverse as catalysis, corrosion, chemisorption and crystal growth. Remarkable progress has been made in the past 10-15 years in the understand ing of behavior of ideal crystals and their surfaces by relating their properties to the underlying electronic structure as determined from the first principles. Similar studies of complex systems like imperfect surfaces, interfaces, and mul tilayered structures seem to be accessible by now. Conventional band-structure methods, however, are of limited use because they require an excessive number of atoms per elementary cell, and are not able to account fully for e.g. substitu tional disorder and the true semiinfinite geometry of surfaces. Such problems can be solved more appropriately by Green function techniques and multiple scattering formalism.
Understanding the electronic structure of solids is a basic part of theoretical investigation in physics. Application of investigative techniques requires the solid under investigation to be "periodic." However, this is not always the case. This volume addresses three classes of "non-periodic" solids currently undergoing the most study: alloys, surfaces and clusters. Understanding the electronic structure of these systems is fundamental not only for the basic science, but also constitutes a very important step in various technological aspects, such as tuning their stabilities, chemical and catalytic reactivities and magnetism. Expert practitioners give an up-to-date account of the field with enough detailed background so that even a newcomer can follow the development. The theoretical framework is discussed in addition to the present status of knowledge in the field. Electronic Structure of Alloys, Surfaces and Clusters also includes an extensive bibliography which provides a comprehensive reading list of work on the topic.
In recent years the availability of techniques and the asking of basic and technological questions has led to an international explosion of activity in the study of solid surfaces. Originally published in Reports in Progress in Physics, Electronic Properties of Surfaces reflects the modern knowledge in this field, presenting critical appraisals of progress in surface science. The book should be particularly valuable for researchers new to this field.
Imagine that a young physicist would approach a granting agen cy and propose to contribute to heterogeneous catalysis by studying the heat conductivity of gases in contact with a hot filament. How would he be received now? How would he have been treated sixty years ago ? Yet, more than sixty years ago, Irving Langmuir, through his study of heat transfer from a tungsten filament, uncovered most of the fundamental ideas which are used to-day by the scientific com munity in pure and applied heterogeneous catalysis. Through his work with what were for the first time "clean" metal surfaces, Langmuir formulated during a period of a little over ten years un til the early thirties, the concepts of chemisorption, monolayer, adsorption sites, adsorption isotherm, sticking probability, cata lytic mechanisms by way of the interaction between chemisorbed spe cies, behavior of non-uniform surfaces and repulsion between adsor bed dipoles. It is fair to say that many of these ideas constituting the first revolution in surface chemistry have since been refined through thousands of investigations. Countless papers have been pu blished on the subject of the Langmuir adsorption isotherm, the Langmuir catalytic kinetics and the Langmuir site-exclusion adsorp tion kinetics. The refinements have been significant. ThE original concepts in their primitive or amended form are used everyday by catalytic chemists and chemical engineers allover the world in their treatment of experimental data, design of reactors or inven tion of new processes.