This book presents a unified view of the rapidly growing field of scanning tunneling microscopy and its many derivatives. After examining novel scanning-probe techniques and the instrumentation and methods, the book provides detailed accounts of STM applications. It examines limitations of the present-day investigations and provides insight into further trends. "I strongly recommend that Professor Bai's book be a part of any library that serves surface scientists, biochemists, biophysicists, material scientists, and students of any science or engineering field...There is no doubt that this is one of the better (most thoughtful) texts." Journal of the American Chemical Society (Review of 1/e)

Scanning tunneling microscopy (STM) and its extensions have become revolutionary tools in the fields of physics, materials science, chemistry, and biology. These new microscopies have evolved from their beginnings asresearch aids to their current use as commercial tools in the laboratory and on the factory floor. New wonders continue to unfold as STM delivers atomic scale imaging and electrical characterization of the newly emerging nanometer world. This volume in the METHODS OF EXPERIMENTAL PHYSICS Series describes the basics of scanning tunneling microscopy, provides a fundamental theoretical understanding of the technique and a thorough description of the instrumentation, and examines numerous examples and applications. Written by the pioneers of the field, this volume is an essential handbook for researchers and users of STM, as well as a valuable resource for libraries.

Since the first edition of "Scanning 'funneling Microscopy I" has been pub lished, considerable progress has been made in the application of STM to the various classes of materials treated in this volume, most notably in the field of adsorbates and molecular systems. An update of the most recent develop ments will be given in an additional Chapter 9. The editors would like to thank all the contributors who have supplied up dating material, and those who have provided us with suggestions for further improvements. We also thank Springer-Verlag for the decision to publish this second edition in paperback, thereby making this book affordable for an even wider circle of readers. Hamburg, July 1994 R. Wiesendanger Preface to the First Edition Since its invention in 1981 by G. Binnig, H. Rohrer and coworkers at the IBM Zurich Research Laboratory, scanning tunneling microscopy (STM) has devel oped into an invaluable surface analytical technique allowing the investigation of real-space surface structures at the atomic level. The conceptual simplicity of the STM technique is startling: bringing a sharp needle to within a few Angstroms of the surface of a conducting sample and using the tunneling cur rent, which flows on application of a bias voltage, to sense the atomic and elec tronic surface structure with atomic resolution! Prior to 1981 considerable scepticism existed as to the practicability of this approach.

The clean and reacted surfaces of Si(111)-(7x7), Si(100)-(2x1), Ge(111)-c(2x8), and Ge(100)-(2x1) have been studied to better understand the nature of these elemental-semiconductor surfaces. By carefully monitoring the adsorbate-induced changes in the electronic properties at the surface via spectroscopic methods such as photoemission, and by studying the resulting surface structures by scanning tunneling microscopy (STM), a quantitative description of the interaction and reaction between adsorbate and surface can be obtained. The photoemission method allows a distinction between atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between substrate and adsorbate atoms. In particular, studies of noble-metal interfaces with the (100) faces of Si and Ge demonstrate this novel combined application of photoemission and STM. The (111) faces of Si and Ge reconstruct to exhibit rather complex chemisorption geometries which are generally not well understood. For clean Si(111)-(7x7), there are three distinct surface sites giving rise to three different chemical environments. To establish the correlation between various surface-shifted components of the core levels and the surface sites, several experiments were designed and performed. The main idea behind these experiments has been to selectively replace atoms or saturate the dangling bonds of a certain surface site by adsorbate atoms, using the noble metal-semiconductor interface as the model system to test this basic approach. Results for other interface systems such as Sb, Sn and NH$sb3$ with these semiconductors are also presented for comparison. These studies indicate that the "adatoms" on the clean Si(111)-(7x7) surface are directly responsible for the metallic surface state in the valence band. Additionally these adatoms exhibit a core level shift of $-$0.77 eV relative to the bulk atoms.