The surface composition of Pt10Ni90(100), Pt25Ni75(111) and Pt50Ni50(110) single crystal alloys has been determined by ion scattering spectroscopy (ISS) and ultraviolet photoelectron spectroscopy (UPS). Pt enrichment of the topmost layer due to preferential sputtering occurs independently of the surface orientation. Annealing the sputtered alloys results in face specific surface compositions: Pt enrichment for the (111) surface, Ni enrichment for the (110) surface and a composition close to the bulk value for the (100) surface. Exposure of the sputtered surfaces to oxygen induces segregation of Ni. Adsorbate induced segregation is correlated with segregation due to annealing. The determination of workfunctions by UPS results support the ISS results on surface composition. The experimental results on surface segregation are discussed with respect to thermodynamic calculations.
Corresponding author: P. Varga (varga).