ROOM-TEMPERATURE GROWTH OF THIN PD FILMS ON AL(110) SURFACES

High-energy ion backscattering spectroscopy (HEIS) and X-ray photoemis sion spectroscopy (XPS) have been used to study the growth of thin Pd layers on Al(110) surfaces at room temperature. The results are not co nsistent with the layered growth model presented previously for this s ystem, but suggest instead that an AlPd alloy forms at the interface. Measured Al and Pd surface peak areas for MeV He+ ions incident normal to the surface show that the Pd atoms intermix with and displace Al s ubstrate atoms. The interface mixing was observed to continue up to ab out 10 ML of Pd coverage, at which point the intermixing stops. XPS me asurements of the Pd 3d photopeaks show a chemical shift that is consi stent with the formation of an Al-Pd-like compound at the interface an d the growth of Pd metal thereafter. (C) 1997 Elsevier Science B.V.