Changes in the surface composition of AgPd, AuPd and CuPd alloys under ion bombardment

Abstract

In sputtering composite materials it is found in general that the surface composition is changed due to preferential sputtering. The surface composition of the single-phase alloy systems AgPd, AuPd, and CuPd has been studied under 2 keV argon ion bombardment using Auger Electron Spectroscopy (AES). Ten alloys with different composition of each system were analyzed. To observe changes in the surface composition due to ion bombardment, reference data for the bulk composition were obtained by scribing and fracturing the samples in the UHV-system prior to AES analysis. For all three systems an enrichment in Pd at the surface was found due to sputtering. This indicates that the mass ratio of the components which varies from 1.6 for CuPd over 1.0 for AgPd to 0.5 for AuPd has no significant influence on the surface composition due to ion bombardment. Comparing measured sputtering yields for Au, Ag, Cu and Pd it is found that Pd has the lowest sputtering yield. These measurements together with previous results for different single-phase alloy systems indicate that the surface becomes always enriched in the alloy component which has the lower sputtering yield for the pure element. Deviations occur only for large mass ratios of the components.