OXYGEN-CHEMISORPTION ON ALUMINUM SINGLE-CRYSTALS - SITE DETERMINATION BY LEED STUDIES

The interaction of oxygen with aluminum single crystal surfaces at room temperature has been studied using LEED (low-energy electron diffraction). Disordered phases of aluminum oxides are rapidly formed on the (100) and (110) crystal faces. On the (111) face an ordered overlayer of oxygen atoms exhibiting (1 × 1) symmetry is developed at monolayer coverage. LEED intensity curves from this structure have been recorded for three inequivalent beams. The experimental curves are compared with theoretical ones obtained from a dynamical (multiple scattering) calculation. Theoretical intensity curves have been calculated for different possible chemisorption sites with the observed symmetry. The occurence of oxygen atoms at the 3-fold, 3-fold chemisorption sites on the (111) surface at a distance of 1.33 Å above the surface was found to give good agreement between the calculated and measured intensity curves for all the beams considered. This chemisorption site is discussed in the light of other theoretical and experimental findings for the same system. © 1979.