Photoelectron spectra of thin alloy films:: measurements and relativistic calculations for the system c(2x2) CuMn on Cu(100)

Deposition of half a monolayer of manganese on a copper (100) surface at room temperature leads to the formation of a surface alloy with a c(2 x 2) structure. Angle-resolved photoelectron spectra of this structure were measured by ultraviolet photoelectron spectroscopy (UPS) in the regime of He I radiation. For the same geometries as in the experiments, fully relativistic calculations were performed in the framework of the one-step model of photoemission first proposed by Pendry and subsequently developed further by several authors. The layer-dependent potentials used were obtained by a tight-binding-linear muffin-tin orbitals slab calculation. In this contribution, a comparison is shown between measured and calculated spectra, as well as between the spectra of pure copper and the surface alloy on copper. The outward relaxation of the manganese atoms by 0.3 Angstrom as determined by I-V low-energy electron diffraction analysis is taken into account, but affects the spectra only slightly. The aim of this contribution is to show the influence of alloying on the UPS spectra and how well the theoretical model is able to describe such a heteroepitaxial system. (C) 1999 Elsevier Science B.V. All rights reserved.