Reactive molecular dynamic simulations of early stage of wet oxidation of Si (001) surface

We have investigated the initial stage of oxidation of Si (001) surface by water (H₂O) molecules using reactive molecular dynamics (MD) simulation at 300 K and 1200 K without any external constraint on the water molecules. Previously, reported water reaction behaviors on silicon surface by ab initio calculations or experimental observations were reproduced by the present MD simulation. The present simulation further revealed that the hydrogen atom in H₂O is more attractive than oxygen atom in O₂ to bond with Si, such that it accelerates the dissociation process of H ₂O. It was also observed that the oxidation reaction was enhanced with increased number of the supplied water molecules. It was suggested that the repulsion between water molecules and their fragments facilitates the dissociation of both water molecules and hydroxyl decomposition on the Si surface. Therefore, the wet oxidation behavior appeared to have more temperature dependence even in the early stage of oxidation.