Sputtering of two alloy systems by polyatomic ions: Ag-Au and Cu-Zn

High-purity, polycrystalline targets of Ag, Au, Cu and Zn, and alloys of Ag-Au and Cu-Zn, were sputtered with monomer and trimer ions of arsenic at an energy of 45 keV per atom. Sputtered material was collected on high-purity aluminum foils during the approach to steady state of the implant (low dose) and beyond (high dose). From an analysis of these collectors with Rutherford backscattering spectroscopy (RBS) the sputtering yields and angular distributions of atoms sputtered were measured. Analysis of the optical photon emission from the sputtered neutral atoms allowed a determination of the steady fluence and surface fractions for some of the targets. The measured sputtering yields of Ag and Au agreed with measurements made by Thompson and Johar, demonstrating non-linear sputtering under polyatomic ion bombardment. Similar measurements were made with the Cu and Zn targets. The collectors exposed to alloy sputtering were studied for evidence of preferential sputtering enhancement above and beyond linear (mass-related) effects, which might be attributed to an onset of thermal processes as the density of a collision cascade is increased. The alloy targets were also analyzed for evidence of surface segregation and changes in bulk composition beneath the implanted layer. (orig.)