First-principles molecular orbital methods and gradient-corrected density functional calculations of Si clusters were used to study possible pathways for the initial oxidation of (100)-(2 x 1). In these reactions, the adsorbed hydroxyl O was inserted into the dimer Si-Si bond to form a sub-oxide, =Si-O-Si=, surface structure. The reaction typically followed a 2-step path involving an intermediate energy minimum. In the case of an ideal surface with full water coverage, the reaction was exothermic by 1.3eV and the overall reaction barrier was about 2.4eV. However, an alternative path which involved a dangling-bond site lowered the activation barrier to 2.1eV.

Pathways for initial water-induced oxidation of Si(100) B.B.Stefanov, K.Raghavachari: Applied Physics Letters, 1998, 73[6], 824-6