Adsorbate reactivity and thermal mobility from simple modeling of high-resolution core-level spectra: application to O/Al(111)

• Published in: Journal of physics. Condensed matter Vol. 21; no. 26; pp. 265003 - 265003 (7)
• Main Authors: Schouborg, Jakob, Raarup, Merete K, Balling, Peter
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.07.2009; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Electron energy loss spectra; Exact sciences and technology; Impact phenomena (including electron spectra and sputtering); Physics; Ultrathin films; Chemisorption; Oxygen; Annealing; Aluminium; Coverage rate; Core levels; Electron energy loss spectra; Random walk model; Adsorption; Ostwald ripening; Diffusion barriers; Modelling
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/21/26/265003

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.