Thermally induced structural and compositional modification of the Cu/Si(111)-7×7 interface

We have investigated the morphology, local composition, and surface stoichiometry of the annealed Cu/Si(111)-7×7 interface using scanning electron microscopy, scanning Auger microscopy, characteristic x-ray emission spectroscopy, and angle-resolved Auger emission. It is found that annealing of intermixed Cu/Si phases with copper thickness between 5 and 20 Å at temperatures of ∼600 °C causes most of the Cu to evaporate. The Si which had been in the intermixed phase recrystallizes in the form of submicron-sized islands. The Cu which does not evaporate forms a very stable Cu3Si-like skin which uniformly covers the surface. This morphology is very different from what has been reported for Ag/Si (Ag island formation) or Au/Si (micron-sized Au islands with silicide skin) and can be related to the kinetics of Cu desorption and the initial intermixed phase.