Negative direct recoil spectroscopy study of the initial oxidation of Al(111)

The submonolayer oxygen-covered Al(111) surface has been studied by Negative Direct Recoil Spectroscopy (DRS) with the aim of detecting or dismissing the presence of subsurface oxygen atoms. Experiments were performed at room temperature and with a coverage of 75% of saturation as measured by DRS. Four possible subsurface adsorption sites have been checked selectively and results compared with those from computer simulations. No subsurface oxygen was found in any of these sites down to the detection limit of DRS, which has been determined to be as small as 2.5% here. This is much less than that previously found by MEIS. On the basis of our results, the decrease of the work function, while the surface approaches the monolayer coverage (result reported by several groups in the past), cannot be attributed to the penetration of oxygen atoms below the surface. (C) 1998 Elsevier Science B.V. All rights reserved.