Reaction mechanisms of oxygen at SiO2/Si(1Â 0Â 0) interface

First-principles total-energy calculations are performed to clarify the reaction mechanisms of O atoms and O2 molecules at SiO2/Si(1 0 0) interface. The calculated energies reveal that the incorporation of O2 molecules into the substrate dominates the interfacial reaction of the oxidant. The low energy barrier for O2 incorporation (0.2 eV) corresponds to the hybridization of oxygen-2p orbitals of O2 and the valence band states of the Si substrate, while that for O atom incorporation corresponds to the O-O bond dissociation and the formation of Si-O-Si bonds. The cooperative reaction of each O atom in the O2 molecule with each Si atom at the interface leads to the low energy barrier.