Scanning photoelectron microscopy was used to study the lateral distribution of a 0.5 monolayer (ML) of Au on a polycrystalline Ni surface after Au deposition at room temperature (RT) and following annealing at 620 K for different durations. The effect of the grain structure on the interfacial interactions and Au surface mobility was examined. The Ni 3p and the Au 4f photoelectron images revealed that annealing leads to lateral heterogeneity in the Au distribution. The contributions of the two processes of surface diffusion and surface alloying are considered to explain the changes in Au surface concentrations observed on different grains after deposition and annealing. (C) 2002 Elsevier Science B.V All rights reserved.