The InSb(100) surface was grown using the techniques of molecular-beam expitaxy. The surface was found to undergo several surface reconstructions, including a c(4\ifmmode\times\else\texttimes\fi{}4), a c(8\ifmmode\times\else\texttimes\fi{}2), an asymmetric (1\ifmmode\times\else\texttimes\fi{}3), a symmetric (1\ifmmode\times\else\texttimes\fi{}3), and a (1\ifmmode\times\else\texttimes\fi{}1). High-resolution photoemission spectra of the In and Sb 4d core levels clearly exhibited surface-shifted components for some of these reconstructed surfaces. Analyses of the In and Sb core-level photoemission intensities as well as of the surface to bulk intensity ratios for the c(4\ifmmode\times\else\texttimes\fi{}4) and c(8\ifmmode\times\else\texttimes\fi{}2) structures were carried out. The c(4\ifmmode\times\else\texttimes\fi{}4) surface was found to be terminated with 1--(3/4 monolayers of Sb, while (3/4 monolayer of In was found to be the termination of the c(8\ifmmode\times\else\texttimes\fi{}2) surface. Structural models are proposed for the c(8\ifmmode\times\else\texttimes\fi{}2) and c(4\ifmmode\times\else\texttimes\fi{}4) based upon these coverages and upon existing models of the similar GaAs(100) structures.

We present a model to explain the resonances in the photoemission cross section of a surface state as a function of photon energy. The model is based on an extension of the direct-transition model for bulk states, and should be applicable to a surface state with a long decay length. Energy broadening of the final states and momentum broadening of the initial surface state are included in the consideration. Resonances in the surface-state photoemission cross section are expected to occur for photon energies corresponding to direct transitions from the surface state to final Bloch states. The cross section of a surface state in Ag(111) was measured over the photon energy range of 36--65 eV, and a resonance at 54 eV was observed. The data were compared with the theoretical results. The data for a similar surface state in Cu(111), studied previously by Louie et al. (Phys. Rev. Lett. 44, 549 (1980)) were reanalyzed in terms of the present model. The results for these two systems, Ag(111) and Cu(111), will be compared.

The Ge(111) surface was observed to be metallic under compressive strain, while normally it is semiconducting in the fully annealed state. The compressive strain was produced by the lattice mismatch between Ge and Si for epitaxial Ge films on Si(111). When the strain is relieved, the metallic surface becomes semiconducting.

The clean CdTe(100) surface prepared by sputtering and annealing was studied with high-energy electron diffraction (HEED) and photoemission. HEED showed the surface to be a one-domain, (2\ifmmode\times\else\texttimes\fi{}1) reconstruction. Photoemission spectra showed two surface-shifted components for the Cd 4d core level, with an intensity ratio of about 1:3, accounting for nearly an entire atomic layer. No surface-induced shifts for the Te 4d core level were detected. A model is proposed for the surface structure in which the surface layer is free of Te, and Cd atoms form dimers resulting in a (2\ifmmode\times\else\texttimes\fi{}1) reconstruction; in addition, about (1/4) of the surface area is covered by excess loosely attached Cd atoms. Ag was evaporated on the surface at room temperature and found to grow three dimensionally in the [111] direction. The Ag was found to interact only weakly with the substrate, although the Cd atoms originally loosely bound on top of the surface were found to float on the evaporated Ag islands. A small coverage-dependent surface photovoltage, induced by the synchrotron radiation used for photoemission, was observed; with this effect taken into account, band bending was monitored, the final Fermi-level position being near 0.96 eV above the valence-band maximum. This corresponds to a Schottky-barrier height of about 0.60 eV for the n-type sample used in this experiment. The mechanism for generation of the surface photovoltage will be discussed.