THE MODIFICATION OF ALLOYS BY LOW-ENERGY ION-ASSISTED DEPOSITION

Thin film alloys of Al/Pt were produced by sputtering a binary target, comprising a piece of Al mounted adjacent to a piece of Pt, using a broad-beam Kaufman ion source. By suitable geometrical positioning of the target with respect to the substrate, different compositions of Al/Pt thin films were produced. The effect of irradiation by an additional 200 eV Ar ion beam during film deposition on the composition of the resulting alloy has been investigated. It was found that, for given deposition conditions, the films became richer in Pt as the ion-assisting current density increased. A simple model shows that this effect can be explained by preferential sputtering of Al from the alloy, although other irradiation-induced effects could contribute further to this Pt enrichment. TEM measurements indicate that the grain size of these films also increases with ion-assisting current density and AFM results show that the surface of the alloys becomes much smoother.