Characterization of oxidized Ni3Al(110) and interaction of the oxide film with water vapor

X-ray photoelectron spectroscopy was used to characterize the oxidation of Ni3Al(1 1 0) and interaction of the oxide film at ambient temperature with increasing pressures of water vapor (10(-6)-5 Torr). The Ni3Al(I 10) substrate was oxidized in 10(-6) Torr O-2 at 800 K followed by annealing to 1100 K. The Ni(2p), AI(2p) and 0(1s) spectra were monitored to investigate the changes in spectral features and binding energy due to oxidation. The data indicate that the oxide film, upon annealing in UHV, is composed of NiO, Al2O3 and an intermediate phase denoted here as AlOx. Upon exposure of the oxide film at ambient temperature to increasing water vapor pressure, a shift in both the 0(1s) and Al(2p)(oxide) peak maxima to lower binding energies is observed. In contrast, exposure of Al2O3/Al(poly) to water vapor under the same conditions results in a high binding energy shoulder in the O(Is) spectra (indicating hydroxylation). Spectral decomposition provides further insight into the difference in reactivity between the two oxide films. The corresponding trends of the O(1s)/Ni-0(2P(3/2)) and Al(2p)/Ni-0(2P(3/2)) spectral intensity ratios suggest conformal changes of the oxide film on Ni3Al(I 10). (C) 2002 Elsevier Science B.V. All rights reserved.