INVESTIGATION OF PT25NI75(111) - PREFERENTIAL SPUTTERING AND SURFACE SEGREGATION

The surface composition of Pt25Ni75(111) has been determined by ion sc attering spectroscopy and Auger electron spectroscopy. The surface lay ers are found to be enriched in Pt due to preferential sputtering. The rmal treatment induces further segregation of Pt at the topmost atomic layer. From the different sampling depths of ISS and AES composition profiles are deduced, which show a strong dependence on the temperatur e during thermal treatment. At an annealing temperature of 770 K the t hermally induced Pt segregation is determined by the composition of th e sputter induced altered layer being enriched in Pt. However, at an a nnealing temperature of 970 K the sputter induced altered layer has di sappeared and the Pt segregation at the topmost atomic layer is determ ined by the bulk composition.