X-RAY PHOTOEMISSION SPECTROSCOPY STUDIES OF CERIUM THIN-FILMS ON TRANSITION-METAL FOILS - CE RE, CE/IR, AND CE/PT/

We report x-ray photoemission spectroscopy studies of the growth of ul trathin (0.1 - 5 monolayers) cerium films on polycrystalline rhenium, iridium, and platinum substrates. Our data indicate that Ce grows on R e without intermixing or compound formation, that on Pt reaction (i.e. , compound formation) as well as interdiffusion is strong, while on Ir compound formation occurs but interdiffusion is weaker than for Pt. A t low coverages the Ce has identical 3d binding energy and is trivalen t for all three substrates and there appears to be a threshold for the onset of mixed-valence behavior.