Epitaxial growth and electronic structure of Au films of fcc (111) metals studied by electron reflection spectroscopy

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Abstract
The reflection coefficient for low-energy electrons on clean fcc (111) metal surfaces shows details determined by the electronic potential in the first few surface layers. This is used to monitor the epitaxial growth of Au overlay films on Pd, Ag, and Ni substrates. On Pd, the lattice constant of the initial Au layers contracts to conform to the Pd but after about three layers assumes the value for bulk Au. Observed shifts of the Au peaks are consistent with predictions of band theory. For Ag and Ni substrates the first few Au layers grow with the bulk lattice constant. The decrease of substrate peak intensity with thickness is consistent with layer-by-layer growth for all three substrate metals. On Pd, thicker Au films show quantum size-effect oscillations at low energies, implying film-thickness uniformity on an atomic scale. These results are compared with those of other techniques. We conclude that electron reflection is a sensitive and relatively simple way of monitoring the growth stages of epitaxial layers.