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

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Abstract
The oxidation of thin‐film Au‐ Al alloy, as well as pure Al, has been studied using XPS across a wide range of water vapour and air exposures (0.1 L to 1 × 1014 L). The alloys and the pure Al all undergo a similar set of oxide growth kinetics. In addition to the three stages of early growth kinetics identified for Al in previous studies, a fourth stage is identified at air exposure doses of >109 L. During this stage, the average composition of the film changes from Al2O3 to Al2O3·H2O. The Al 2p lineshapes for the oxides grown on pure Al and Au‐Al alloy are different; the origins of this appear to result, in part, from a change in the Fermi level as the oxide thickens. The Al L2,3 X‐ray absorption near‐edge structure (XANES) furthermore provides a complementary probe of the different oxide structures on alloy and Al metal. Thus, their chemical characteristics are affected also by the presence of the gold. This difference in oxide structure is detected at the interface and not through the oxide generally. Copyright © 2001 John Wiley & Sons, Ltd.