Oxygen induced surface segregation of Cu on the Au 0.7Cu 0.3(100) surface

Abstract

The oxygen induced surface segregation of Cu on the Au 0.7Cu 0.3(100) surface was investigated by means of LEED and AES techniques. The dissociative adsorption of O 2 did not take place on this clean surface for a long time exposure at least up to 10 4 L, and so the oxygen was forcibly introduced onto the surface through a pre-deposition of few a layers of Cu and its successive oxidation. The oxygen coverage was controlled by a heat treatment, which leads the system to a thermal equilibrium state. For the clean surface, the segregation of Au was clearly observed and the surface concentration of Au was estimated to be about 86%, greater than the bulk concentration of 70%. At low coverages below 0.16 ML, no remarkable oxygen induced segregation of Cu was observed. But, above 0.2 ML, the surface concentration of Cu was proportional to the oxygen coverage. The (2 × 4) LEED pattern was observed in a wide range of oxygen coverage. The maximum intensity of the (2 × 4) was observed at about 0.45 ML.