X-ray photoelectron spectroscopy study of thin oxide lavers formed on (001)-oriented β-NiAl single crystal surfaces

Quantitative XPS data complemented by low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) results of the very first stages of oxidation of an NiAl(001) single-crystal surface are reported. The thickness, stoichiometry and alloy composition at the oxide/alloy interface and, when possible, the structure have been analysed after oxidation at room temperature and 750degreesC and under 10(-7), 10(-5) and 200 mbar of oxygen. The growth of alumina layers is essentially two-dimensional in the initial stages. Thin oxide films grown up to 50 A show an oxygen enrichment that decreases with increasing thickness. The competition between the segregation of aluminium and its consumption by oxygen in the growth kinetics of the oxide layers is evidenced by the variation of the stoichiometry of the oxide films and alloy composition at the oxide/alloy interface. Copyright (C) 2002 John Wiley Sons, Ltd.