Surface compositional modifications during O⁺₂ bombardment of binary alloys

Surface compositional modifications of binary alloys during 15-keV O +2 bombardment under 45°incidence were studied using Auger electron spectroscopy under ultrahigh vacuum conditions. For A1-Ni, Cr-Ni, Fe-Ni, and Pd-Ni alloys, the reactive preferential sputtering by O +2 causes a surface enrichment of the alloy component which has the smaller metal-oxygen bond energy per metal atom. For Cu-Ni and Ag-Pd alloys, where oxidation by the O+2 beam was slight, the surface compositions after O+2 bombardment were qualitatively similar to those caused by nonreactive preferential sputtering with Ar+.