Oxidation studies of Au-Al alloys using x-ray photoelectron spectroscopy (XPS) and x-ray absorption near-edge structure (XANES)

The oxidation of thin-film Au-Al alloy, as well as pure Al, has been studie d using XPS across a wide range of water vapour and air exposures (0.1 L to 1 X 10(14) L). The alloys and the pure Al all undergo a similar set of oxi de growth kinetics. In addition to the three stages of early growth kinetic s identified for Al in previous studies, a fourth stage is identified at ai r exposure doses of > 10(9) L. During this stage, the average composition o f the film changes from Al2O3 to Al2O3.H2O. The Al 2p lineshapes for the ox ides grown on pure Al and Au-AI alloy are different; the origins of this ap pear to result, in part, from a change in the Fermi level as the oxide thic kens. The Al L-2,L-3 X-ray absorption near-edge structure (XANES) furthermo re provides a complementary probe of the different oxide structures on allo y and Al metal. Thus, their chemical characteristics are affected also by t he presence of the gold. This difference in oxide structure is detected at the interface and not through the oxide generally. Copyright (C) 2001 John Wiley & Sons, Ltd.