Electronic structure and atomic positions of metallic surface alloys

Abstract

Photoemission spectra collected over a large solid angle give information about the form and energies of spectral features, which are related to the underlying electronic structure of the sample. Spectra measured as a function of exit angle reflect the phenomenon of photoelectron diffraction, which is related to the underlying crystallographic structure of the sample. We report applications of these techniques by our group to the study of a number of systems involving ultra-thin metallic layers on surfaces, which can be true surface alloys, whose properties are often very different from those in the bulk. The surface systems we chose manifest surfactant behavior, catalytic activity and intercomponent effects. Our electronic structure results were derived from photoemission and X-ray excited Auger spectroscopies: interpretation of these data requires inclusion of the phenomena of relaxation and screening. Our crystallographic results were derived from photoelectron diffraction in combination with LEED: derivation of the results requires comparison with multiple scattering theoretical simulations and involves considerable computational effort. We have studied In, Sn and Sb on Pd(1 1 1) and Ni(1 1 1), Cu on Pd(1 1 1) and Pd on Cu(1 1 1), Sb on Ag(1 1 1) and Pd and Mg oxides on Ag(1 1 1)—we present representative results of these studies.