Theoretical study of the initial oxidation processes on the Si(0 0 1) surface

The initial oxidation processes on the Si(0 0 1) surface are theoretically investigated by using molecular dynamics (MD) simulations based on the first-principles (FP)/molecular mechanical (MM) hybrid method. Combinations of several representative positions and directions of the incident oxygen molecule are employed as the initial configuration of the oxygen molecule. The backbond oxidation process in the first layer, which had been known to be barrierless reaction, is seen for most of the cases and its mechanism is clarified by the kinetic energy analysis. The steering motion of the oxygen molecule before dissociation is found in several cases. The backbond oxidation process in the second layer is seen for the cases in which the oxygen molecule is initially located at the site between two neighboring dimer rows. The second layer backbond oxidation reproduced in our simulations is considered to correspond to earlier stages of the second layer backbond oxidation.