Stability of oxygen adsorption sites and ultrathin aluminum oxide films on Al(1 1 1)

First-principles density-functional calculations are used to study oxygen adsorption and incorporation, and properties of (two O-layer) Al2O3 film in different sites at the Al(1 1 1) surface. For a monolayer (ML) of O chemisorbed in the on-surface hcp hollows the most stable O-(1×1) subsurface structure is found in tetrahedral sites below the topmost Al atomic plane. A ML of subsurface oxygen atoms induces a very large (37%) increase in the mean interplanar distance of the topmost Al layers. The stability of the structures formed by the incorporated O atoms is almost independent of the type of the on-surface O-layer. It is suggested that the sizeable work-function change appearing for some of the structures allows to discriminate between different kinds of oxygen incorporation. The stability of the ultrathin Al2O3 film on the Al(1 1 1) surface is very little dependent on the geometry of the oxygen ML at the film/substrate interface.