PATHWAYS FOR INITIAL WATER-INDUCED OXIDATION OF SI(100)

First-principles molecular orbital methods and gradient-corrected dens ity functional calculations on silicon clusters are used to study poss ible pathways for the initial oxidation of Si (100)-2X1. In these reac tions, the adsorbed hydroxyl oxygen inserts into the dimer Si-Si bond to form a suboxide (=Si-O-Si=) surface structure. The reaction typical ly follows a two-step pathway involving an intermediate energy minimum . In the case of an ideal surface with full water coverage, the reacti on is exothermic by 1.3 eV and the overall reaction barrier is estimat ed at 2.4 eV. However, an alternative pathway involving a dangling bon d site lowers the activation barrier to 2.1 eV. The implications for t he oxidation reaction rates are discussed as well as possible alternat ive pathways. (C) 1998 American Institute of Physics.