Interactions at the Ni3Al(111)−S−Al2O3 Interface at Elevated Temperatures: Ordering of Al2O3 on an S-Modified Substrate

Abstract

Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM) have been used to investigate the growth, morphology, and thermal stability of the oxide prepared on a (2 × 2)-S-covered Ni3Al(111) surface. The results demonstrate that although sulfur significantly alters the oxidation rate and oxide morphology on the Ni3Al(111) substrate at room temperature, it does not inhibit the formation of the ordered γ‘-Al2O3 at elevated temperatures. The oxide formed on the S-modified Ni3Al(111) surface at room temperature is stable up to at least 1100 K. Sulfur remains at the oxide−Ni3Al(111) interface during oxygen exposure at ∼300 K. During annealing, however, sulfur is removed from the oxide−alloy interface. Annealing from 300 to 1100 K results in the segregation of aluminum to the oxide−alloy interface, as evidenced by an enhancement in the Al(1396)/Ni(848) atomic ratio, and the appearance of a metallic aluminum peak in the Auger spectra.