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Solid films of C60 deposited on CaF2 under ultra-high vacuum show luminescence in the 700-1100nm spectral range at 20K. A 1400 cm-1 progression in the ag soccerball inflation mode is observed. The low-temperature absorption spectrum exhibits similar fine structure. The characterization of vibronic splittings in the ground and emitting state and the transition intensity mechanism are discussed.

We have derived ternary phase diagrams of the type M-Si-O, where M=Sc, Y and La under the conditions of 298K and 1 atm oxygen partial pressure. These phase diagrams provide a direct view of the thermodynamics that governs stabilities of phases containing these elements in contact with each other, and should be useful for integrating Y- and La-based oxide superconductors with Si.

Contents: Epitaxial Growth and Electro-Optical Properties of Metal GaAs superlattices, Electrical Resistivity, Magnetic Susceptibility and Thermoelectric Power of PtGa(2), Electronic structure study of the Pt-Ga intermetallic thin films on GaAs (100) using X-ray photoemission spectroscopy, RHEED Studies of Epitaxial Growth of CoGa on GaAs by MBE-Determination of epitaxial phases and orientations, Internal Photoemission in CoGa/GaAs Schottky Barriers, Possible Injection of Electrons into the L Valley, Chemistry of Metal/ Compound-Semiconductor Interfaces, Phase Stability Versus The Lattice Mismatch of (100)Co1-xGa(x) Thin Films on (100)GaAs, Electrical resistivity of ultrathin, epitaxial CoGa on GaAs, and Growth and Annealing of Co(1-x)Ga(x) Thin Films on GaAs (100).

We present the first quantitative experimental study of the morphology of amorphous solid surfaces formed by non-equilibrium processes and compare the results with theories developed to explain the formation of such surfaces.

Investigated are broadening and skewing of scanning tunneling microscope topographs caused by tip size and symmetry. Model images were generated numerically by convoluting a gaussian response function for the tip with an idealized graphite image. Atomic-scale features were retained even for a 9.4 A FWHM tip function, which demonstrated that single-atom tips are not required to obtain atomic resolution topographs. Model tips with an elliptical radial cross section produced many of the familiar skewed images of graphite. Such response functions could also be used to remove the skew from an experimental topograph, and thus provide an approximation for the shape of the physical tip. Keywords: Topographs, Numerical imaging, Response functions.

The electrical resistivity (p), magnetic susceptibility (X) and thermoelectric power (S) of PtGa2 were measured as a function of temperature (T) . This compound is metallic at high temperatures, as shown from the room- temperature resistivity value and the linear dependence of the S vs. T curve at temperatures above the Debye temperature. It undergoes a superconducting phase transition with a critical temperature (Tc) at zero magnetic field of 2.13K. The density of states (DOS) at the Fermi energy (EF) at high temperatures obtained from X and S data are 22% and 15% higher, respectively, than the value obtained previously from a semi-empirical band-structure calculation. (JES)

The scanning tunneling microscope (STM) has been used to investigate graphite surfaces roughened by 5 ke V Ar+ion bombardment. The (0001) surfaces of several samples were etched with the same total ion dose but with different sputter rates for each surface. STM images taken after sputtering show that the roughness of the sputtered surfaces depended on the sputter rate and that the surface topography of each sample appeared self-similar over a large range of length scales. These experimental observations agree with predictions of the recently proposed Shadow Model. The two dimensional height-height correlation function is utilized as a means of quantitative analysis for STM topographs of sputtered surfaces. (JES)

Films of cuprous chloride (CuCl), a zinc-blende semiconductor lattice-matched to Si, were deposited by molecular beam epitaxy onto a room- temperature Si(111)-7x7 substrate and studied with surface-sensitive spectroscopies. Low-energy electron diffraction revealed an ordered 1x1 pattern at several monolayers coverage and Auger electron spectroscopy yielded an approximate Cu to Cl surface stoichiometry of one-to-one for as-deposited films. Ion scattering experiments indicated that the initial stage of CuCl growth involved Cl-Si bonding. Annealing the films initiated chemical reactions, which resulted in the loss of Cl and the formation of a Cu silicide. (jes)

Single-phase films of Pt-Ga intermetallic compounds with different stoichiometric compositions were grown using molecular beam epitaxy (MBE) and investigated with X-ray photoemission spectroscopy (XPS). The qualitative aspects of the peak shifts and shapes are consistent with those of other compounds that have been previously investigated. Semi-quantitative analyses show that the valence bands are dominated by Pt-Ga hybridization, rather than by Pt d-d interactions, and that the final state effects dominate initial state charge transfer in determining the binding energies (BE) of the Pt core level peaks. (JES)

Ternary phase diagrams for systems of the type M-Si-O, where M = Mg, Ca, Sr, and Ba, have been derived. These phase diagrams can be used to understand experimental results reported in the literature for thin film chemical reactions of SrO on Si and provide guides in designing stable structures that involve different materials in intimate contact. These particular phase diagrams are especially relevant for investigating the chemical stability of interfaces between SiO2 and the oxide superconductors. (JES)

The intention of the editors was to bring together an interdisciplinary and international group of researchers working on various aspects of semiconductor heterostructures so that we could all learn from each other. In particular, we hoped to forge new links between those who study chemical interactions at heterostructure interfaces and those who are concerned with the effects of interfacial defects on the electrical and optical properties of semiconductor structures. The fact that there must be some relationship between chemical reactivity and defect formation has long been recognized, but as yet there is no detailed understanding of the actual mechanisms involved. Scientists studying either the causes or the effects of interfacial defects must appreciate all the issues and work closely with each other. Only through such collaboration can the formation of semiconductor interfaces be truly understood and, eventually, their properties controlled. If this Symposium and the resulting book have stimulated only a few such interactions, then we feel that our efforts have been successful. (TTL)

The objective of this research program is to investigate the metal systems that are thermodynamically stable on Gallium arsenide. Moreover, for novel device applications, the metal films should be epitaxial on GaAs, and that means the lattice mismatch between metal and GaAs should be as small as possible. From this stable metal contacts, we can then explore new properties and physics of the metal/GaAs heterojunction. Furthermore, new metal quantum well and superlattice devices can be fabricated, and a new generation of detectors and devices with improved performance will emerge. The theoretical calculation of the metal quantum well (QW) photodetector has shown that the device can be served as a long wavelength (infrared) detector with an absorption efficiency one order of magnitude higher than a semiconductor QW device (e.g., AlGaAs/GaAs/AlGaAs. This enhancement is due to the higher oscillation strength of the metal intersubband transition.