The composition of NiCu surface alloys, prepared by decomposition of nickel carbonyl on a Cu(100) surface, has been studied before as well as after annealing using MeV Rutherford Backscattering Spectroscopy.
NiCu films with a thickness of 2 nm and of 10 nm, respectively, having a sharp interface with the copper substrate, were grown. The nickel fraction is found to be 65% and 93% respectively. The outermost monolayer is slightly enriched in copper. During annealing interdiffusion between the film and the interface occurs and the enrichment of the surface increases. In case of the 10 nm film the observed diffusion rate is much higher than is expected on the basis of diffusion coefficients published in the literature. This is ascribed to the presence of defects and/or grain boundaries in the grown surface alloy.