Practical Guide to Surface Science and Spectroscopy

Modern surface science probably began sometime in the late 50's and early 60's, when ultrahigh vacuum technology became widely accessible. Ultrahigh vacuum provides the necessary environment to prepare and maintain well-defined surfaces long enough for experimental studies. Soon afterwards, many electron-based spectroscopy techniques were developed, providing information on composition, structure and electronic properties of surfaces. Since a material interacts with the outside world through its surfaces, it is easy to see the significance of surface science in today's wide range of scientific and engineering disciplines, including catalysis, corrosion, thin-film growth, alloy design, micro/nano-electromechanical systems, tribology, semiconductor and magnetic storage devices. As a practical guide, this text provides sufficient background and details for someone to get up to speed on a given topic in surface spectroscopy or phenomenon within a reasonable amount of time. In order to get the most of this book, it is important that the readers are familiar with topics such as kinetic theory of ideal gases, basic quantum mechanics, elementary band theory (including Fermi-Dirac statistics) and semiconductors at the level of Kittel's Introduction to Solid State Physics.

Chapter 1 presents the fundamentals of ultrahigh vacuum and electron spectroscopy techniques. The concept of statistical noise is included in this discussion. This chapter provides important foundation materials for the next five chapters. In spite of the many changes introduced by the use of computers in the past 20 years, the basic approach to electron spectroscopy remains the same today.

Chapters 2 through 6 present the principles and practice of several commonly used surface science techniques: Auger electron spectroscopy, photoelectron spectroscopy, low-energy electron diffraction, electron-energy-loss spectroscopy, low-energy ion scattering, secondary ion mass spectrometry and scanning probe microscopy. Here is where my personal preference in emphasis and level of detail comes into play. For example, while many-electron effects are discussed in photoelectron spectroscopy, I do not mention shake-up features explicitly. In the chapter on scanning probe microscopy, discussions devoted to variants of scanning tunneling microscopy (e.g., atomic force microscopy, magnetic domain imaging etc) are quite limited. The latter subject continues to advance rapidly, and there is plenty of up-to-date literature that can readily be explored by interested readers.

The focus of Chapter 7 is interfacial segregation. Here, I follow John Cahn's rigorous treatment of Gibbs adsorption, rather than the traditional "dividing interface" approach. Cahn's treatment is elegant, and it removes many misconceptions in surface thermodynamics. For example, the commonly held notion that the lower surface energy component should segregate to the surface is proved to be incorrect. Chapter 8 begins with a "standard" treatment of surface states and discusses how surface states affect electronic properties of metal and semiconductor surfaces. Both the Schottky (with no surface states) and surface-state models are used to describe metal-semiconductor interfaces. Finally, Chapter 9 presents a survey of gas-surface interactions, introducing concepts of adsorption, desorption, catalytic selectivity, promoters, poisons, etc. The chapter ends with several case studies to illustrate examples of gas-surface interactions. The choice of these case studies is more a reflection of my personal interest, rather than the absolute significance of the phenomena illustrated.

It is quite a humbling experience to write a book and to be sure that the information is accurate and up-to-date. Over the years, many friends, colleagues and former students made suggestions and corrections to the original lecture notes. Nevertheless, the errors and omissions are all mine. The materials in the CD were developed using Multimedia Toolbook. While the software has been extensively tested, there is always one more bug. I can only hope that the bug does not bite.

Happy exploring!