title: Adsorbate reactivity and thermal mobility from simple modeling of high-resolution core-level spectra: application to O/Al(111).
abstract: 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 is as high as ∼200 L (langmuirs), at which point the coverage of the chemisorbed oxygen exceeds half a monolayer. A simple model is presented, using which it is possible to deduce the oxygen coverage from the core-level spectra and determine the initial sticking probability. For our data a value of 0.018 ± 0.004 is 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 is consistent with a random-walk model from which the diffusion barrier can be deduced to be in the range of 0.80-0.90 eV.
authors.affiliation: Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors.forename: Jakob
authors.initials: J
authors.lastname: Schouborg
authors.forename: Merete K
authors.initials: MK
authors.lastname: Raarup
authors.forename: Peter
authors.initials: P
authors.lastname: Balling