Monte Carlo simulation of initial Al(111) oxidation

A Monte Carlo method is used to simulate the early oxidation stage on AI(II I). The model is based on a lattice-gas approach. Three principally differe nt cases are compared: (i) O-2 dissociation producing hot atoms on the surf ace (based on the work by Brune et al. [J. Chem. Phys. 99 (1993) 2128]), (i i) abstractive dissociation (special case of (i)), and "normal" dissociatio n with no hot atoms. Other ingredients in the model, which are varied are s urface mobility, attractive forces between the oxygen atoms, site exchange between O and Al atoms to form an oxide, oxygen diffusion by random walk th rough the oxide and oxide formation at the oxide/Al interface. Simulation r esults for adsorption at room temperature and adsorption at room temperatur e followed by annealing at high temperature are compared with the STM inves tigations by Brune et al. The model predictions of the surface configuratio n of the oxygen adatoms in the low coverage regime are in best agreement wi th 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.