FORMATION OF A SURFACE ALLOY BY ANNEALING OF PT CU(111)/

The dissolution of Pt/Cu(111) and the kinetic blocking of the dissolut ion process which results in the formation of a surface alloy have bee n studied. We use AES, PES, XPD, and LEED to characterise the non-clas sical dissolution behaviour. Chemical shifts on the Pt4f7/2 and the Cu 3p core levels are measured during dissolution. The top layer of the s urface alloy is Cu3Pt for an annealing temperature of 315-degrees-C. F or the higher annealing temperature of 350-degrees-C the Pt concentrat ion is smaller. The alloy composition is therefore temperature depende nt and the formation of a relatively stable alloy in local equilibrium over the surface layers is determined by the segregation and ordering behaviour. The chemical ordering of the surface alloy and its electro nic structure remains to be verified.