Monte Carlo simulation of initial Al(111) oxidation

A Monte Carlo method is used to simulate the early oxidation stage on AI(III). The model is based on a lattice-gas approach. Three principally different cases are compared: (i) O-2 dissociation producing hot atoms on the surface (based on the work by Brune et al. [J. Chem. Phys. 99 (1993) 2128]), (ii) abstractive dissociation (special case of (i)), and "normal" dissociation with no hot atoms. Other ingredients in the model, which are varied are surface mobility, attractive forces between the oxygen atoms, site exchange between O and Al atoms to form an oxide, oxygen diffusion by random walk through the oxide and oxide formation at the oxide/Al interface. Simulation results for adsorption at room temperature and adsorption at room temperature followed by annealing at high temperature are compared with the STM investigations by Brune et al. The model predictions of the surface configuration of the oxygen adatoms in the low coverage regime are in best agreement with the STM observations when assuming hot dimer dissociation. The influence of the relative rates of the oxygen deposition rate and conversion rate to oxide formation on the overall oxidation process has also been analysed. (C) 2001 Elsevier Science B.V. All rights reserved.