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.

Scanning tunneling microscopy (STM), photoemission spectroscopy, and a variety of other experimental techniques have been used to examine both the initial stages of interface formation between various adsorbates, as well as, reconstructions occurring on the clean surfaces of Si and Ge. The initial stages of oxidation of the Si(111)-(7 x 7) and Ge(111)-c(2 x 8) surfaces were studied. Images of the same area of each surface were obtained from various exposures of oxygen. On the Si(111)-(7 x 7) surface, the results show that defect sites act as nucleation centers for the oxidation process. On the Ge(111)-c(2 x 8) surface, images of the surface for exposures of oxygen up to 1600 Langmuirs were obtained. The results show that the oxidized portions of the surface grow as islands which expand preferentially in the (112) direction. The "16 structure" and c(8 x 10) reconstructions occurring on the clean Ge(110) surfaces were examined. STM images show that the Ge(110)-"16 structure" reconstructed surface is composed of ordered facets as predicted by a low-energy-electron diffraction study. STM images of the Ge(110)-c(8 x 10) surface show that the unit cell is composed of alternating oblique sub-unit cells. Photoemission spectra of the Ge 3d core levels for both these surfaces show the presence of multiple surface-shifted components. Sb deposition on these surfaces has also been studied. Sb deposition results in the formation of a (1 x 1) or (3 x 2) ordered over-layer depending on the substrate temperature and Sb coverage. Both these surfaces have been observed with STM. Photoemission results for various coverages of Sb show that the surface-shifted components of the Ge 3d core level are suppressed by the deposition of Sb. A structural model, consistent with the data, for the (1 x 1) Sb-terminated surface is presented. Angle-resolved photoemission spectroscopy was used to measure the bulk band-dispersion relations along the high symmetry $Gamma$-$Sigma$-X directions for both Ge and Si.

The Proceedings of the 17th International Conference on the Physics of Semiconductors are contained in this volume. A record 1050 scientists from 40 countries participated in the Conference which was held in San Francisco August 6·1 0, 1984. The Conference was organized by the ICPS Committee and sponsored by the International Union of Pure and Applied Physics and other professional, government, and industrial organizations listed on the following pages. Papers representing progress in all aspects of semiconductor physics were presented. Far more abstracts (765) than could be presented in a five-day meeting were considered by the International Program Committee. A total of 350 papers, consisting of 5 plenary, 35 invited, and 310 contributed, were presented at the Conference in either oral or poster sessions. All but a few of the papers were submitted and have been included in these Proceedings. An interesting shift in subject matter, in comparison with earlier Conferences, is manifested by the large number of papers on surfaces, interfaces, and quantum wells. To facilitate the use of the Proceedings in finding closely related papers among the sometimes relatively large number of contributions within a main subject area, we chose not to arrange the papers strictly according to the Conference schedule. We have organized the book, as can be seen from the Contents, into specific subcategories and subdivisions within each major category. Plenary and invited papers have been placed together with the appropriate contributed papers.

On the nanometer scale, the local variation of the electronic density of states of aluminum based complex metallic alloys (quasicrystals and approximants) is experimentally investigated by low temperature scanning tunneling spectroscopy. We report on the correlation between the local variations of the electronic density of states and the electrical resistivity. The surface structure is investigated by scanning tunneling microscopy, low energy electron diffraction, and X-ray photoemission diffraction. Experimental results are interpreted on the basis of the respective bulk structure models.

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 is a comprehensive presentation of the current knowledge on the electronic properties and manipulation of semiconductor surfaces. This book covers several of the most important and timely topics at the forefront of scanning probe microscopy, such as atom-resolving atomic force microscopy (AFM), application of atom manipulation for fabricating nanoscale and atomic scale structures, theoretical insights into Fullerenes, and atomic manipulation for future single-electron devices.