H 2S adsorption and the effect of sulfur on the oxidation of Ni 3Al(111)

Abstract

We report the formation of a (2×2) sulfur adlayer by the adsorption of H 2S on Ni 3Al(111) at room temperature, followed by annealing to ∼1100 K. From Auger electron spectroscopy (AES) measurements, this pattern is consistent with a sulfur coverage ( θ S) of ≤0.25 monolayers (ML). A diffuse low-energy electron diffraction pattern with streaks, corresponding to θ S=0.3 ML, was observed after sulfur adsorption at ∼800 K, but the (2×2) order was restored upon flash annealing to ∼1100 K. AES results rule out any aluminum enrichment or sulfide formation in the surface during exposure to H 2S or thermal treatment. The presence of sulfur on the Ni 3Al(111) surface retards its oxidation at room temperature. Sulfur is found to remain at the oxide/Ni 3Al(111) interface during oxidation at ∼300 K.