High resolution XPS studies of thin film gold-aluminum alloy structures

The surface oxidation behavior at room temperature of two thin films of the alloys Al2Au and Au2Al was investigated using X-ray photoelectron spectros copy (XPS). Relatively large chemical shifts of both Au4f and Al2p photoele ctron lines with the alloy composition assist the identification of additio nal alloy phases. The spectral resolution has been improved by the use of t he Maximum Entropy Method which removes the external contributions to the p hotoelectron linewidth. In the case of Au2Al, as much as 80% of the surface phase is transformed into two new alloy phases. This is equivalent to a tr ansformed layer thickness of 10 nm. For the Al2Au, oxidation also results i n a partial phase transition to a gold-enriched alloy, but the transition r egion extends only to an estimated depth of 2 nm. (C) 1999 Elsevier Science B.V. All rights reserved.