The effect of interdiffusion on the growth mode of copper on Al{111}

Abstract

The growth mode of thin Cu films on Al{111} has been studied using Auger electron spectroscopy and low energy electron diffraction. Careful examination of the LVV Auger peak of Al clearly indicates the occurrence of mixing of the Cu/Al interface at substrate temperatures as low as 120 K. We have utilised the Al LVV Auger peak to follow the degree of interdiffusion as a function of deposition time. Auger signal versus deposition time (AS− t) plots, which are often used to monitor growth mode, are shown to behave in an almost identical fashion to that expected for layer-by-layer (Frank-van der Merwe) growth despite the observed interdiffusion. The original large lattice mismatch (∼11%) between film and substrate initially prevents epitaxial growth of copper. However, at coverages ≳ 2.5 equivalent monolayers, copper is seen to grow in an incommensurate epitaxial fashion due to the relaxed lattice strain in the diffused interface region.