Initial stages of oxidation of the Pt3Ti(111) and (100) single crystal surfaces

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Abstract
The process of segregation of titanium oxides onto the surface of Pt3Ti upon the exposure to oxygen at different pressures and temperatures was studied by LEED and AES. Oriented [111] and [100] monocrystals as well as polycrystals were synthesized for study. Qualitatively similar behavior was observed with all three types of surfaces, with three stages of oxidation observed on each surface. A layer of stoichiometry close to TiO segregated onto the surface in the initial stage of oxidation, depleting the subsurface region of the alloy in Ti. The TiO formed a compact, epitaxial monolayer which completely blocked the metallic surface for chemisorption by carbon monoxide. Further oxidation caused formation of a multilayer of TiO1.2, an oxide with an orthorhombic structure derived from TiO by removing Ti atoms to form an ordered vacancy lattice. Finally, oxidation at the relatively extreme conditions of atmosphere pressure at high (>1000 K) temperature caused formation of thick TiO2 (rutile) overlayers.

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