Growth and oxidation of Fe films on polycrystalline Ag catalysts

X-ray photoelectron spectroscopy (XPS) studies of the growth and oxidation of Fe films on a polycrystalline Ag catalyst are the subject of this paper. Fe films of high purity were prepared by deposition of Fe at 300 K. Quanti tative evaluation of the observed XPS data and comparison with growth model s point to a layer-by-layer growth mechanism. The films are not stable agai nst annealing. At temperatures > 550 K diffusion of Ag into the Fe overlaye r is observed. The adsorption of oxygen on the Fe/Ag substrate leads to the formation of various iron oxides, depending on the experimental conditions such as layer thickness, oxygen exposure, temperature. No significant inte raction of the adsorbed oxygen with the Ag substrate is observed. (C) 1999 Elsevier Science B.V. All rights reserved.