This thesis addresses scanning tunneling microscopy (STM) studies of metal defects in GaAs(110). Single-atom defects are useful for their potential applications in developing nano-scale miniaturized or new types of optical, magnetic, and electronic devices, as well as expanding our understanding of atomic-scale interactions. STM is used to measure physical and electronic properties of surface and near-surface materials with atomic resolution, but affects the properties of defects being studied.

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.

Scanning Tunneling Microscopy I provides a unique introduction to a novel and fascinating technique that produces beautiful images of nature on an atomic scale. It is the first of three volumes that together offer a comprehensive treatment of scanning tunneling microscopy, its diverse applications, and its theoretical treatment. In this volume the reader will find a detailed description of the technique itself and of its applications to metals, semiconductors, layered materials, adsorbed molecules and superconductors. In addition to the many representative results reviewed, extensive references to original work will help to make accessible the vast body of knowledge already accumulated in this field.

This research program is aimed at studying the atomic structure of semiconductor surfaces using scanning tunneling microscopy (STM). Extensive work has been carried out on the behavior of both indium and gallium on the (111) and the (100) surfaces of silicon. The STM images provide new structural information on all of the metal-induced surface reconstructions observed in these systems. The STM has been particularly applicable to the study of multi-phase surfaces, localized defects, local metal segregation, all of which arise during the growth of a metal on a semiconductor, and can play an important role in the properties of the surface. Information on such spatially localized features (Sub-100 A) is inaccessible by other means. Some preliminary studies of the InP (110) surface have been done. It is anticipated that the the primary thrust of the research will shift to compound semiconductor surfaces during the coming year. Keywords: Atomic structure; Semiconductor surfaces; Silicon; Indium; Gallium; Scanning tunneling microscopy. (JHD).

This volume will be devoted to the technical aspects of electrical and electromechanical SPM probes and SPM imaging on the limits of resolution, thus providing technical introduction into the field. This volume will also address the fundamental physical phenomena underpinning the imaging mechanism of SPMs.