| Abstract
| - The initial stages of the uptake of molecular oxygen on V(100) single-crystal surfaces were characterized bytemperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and ion scatteringspectroscopy (ISS). As in previous reports on this system, a small amount of oxygen contamination wasalways detected on the surface, but that could be minimized by avoiding severe annealing after sputtering ofthe surface and appears to not affect the chemistry of the surface in any significant way, at least in terms ofmethanol conversion. Oxygen adsorption is dissociative even at liquid nitrogen temperatures. At lowtemperatures, saturation is reached at a coverage of approximately 1.0 ML, but above 170 K further uptakecan occur, leading to the formation of a thin V2O3 + VO2 mixed oxide film. Thick oxide films, with thicknessesof the order of nanometers, could only be generated above 320 K and by using high oxygen doses. In general,the temperature at which the adsorption is carried out proved to play an important role in determining thesurface stoichiometry and film thickness of the resulting surface oxides. Diffusion of oxygen into the bulkstarts at approximately 500 K and displays an estimated activation energy of 132 kJ/mol.
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