A high-resolution core-level spectroscopy investigation of the adsorption of oxygen on Al(111) at variable oxygen exposure demonstrates a low surface reactivity for an intensively cleaned surface. The threshold for oxide formation was as high as ~200L (Langmuirs), at which point the coverage of the chemisorbed oxygen exceeds half a monolayer. A simple model was presented, using which it was possible to deduce the oxygen coverage from the core-level spectra and determine the initial sticking probability. For the present data, a value of 0.018 was obtained. The changes in core-level spectra following low-temperature annealing of low-coverage O/Al(111) reflect the formation of gradually larger islands of oxygen atoms (Ostwald ripening). The island formation was consistent with a random-walk model from which the diffusion barrier could be deduced to be in the range of 0.80–0.90eV.

Adsorbate Reactivity and Thermal Mobility from Simple Modeling of High-Resolution Core-Level Spectra: Application to O/Al(111). J.Schouborg, M.K.Raarup, P.Balling: Journal of Physics - Condensed Matter, 2009, 21[26], 265003