Reactive molecular dynamics simulation of early stage of dry oxidation of Si (100) surface

Abstract

Initial stage of oxidation of Si (100) surface by O2 molecules was investigated in atomic scale by molecular dynamics (MD) simulation at 300 K and 1200 K without external constraint on the oxygen molecules. A reactive force field was used for the simulation to handle charge variation as well as breaking and forming of the chemical bonds associated with the oxidation reaction. Results of the present simulation are in good agreement with previous first principle calculations and experimental observations: the oxygen molecules spontaneously dissociated on the Si (100) surface and reacted with Si first layer without energy barrier. The simulation also exhibited that the reacted oxygen preferentially located in the back bonds of the surface dimer. Consecutive oxidation simulation with 300 O2 molecules showed that the diffusion of oxygen atom into the subsurface of clean Si surface can occur during very short time of the present oxidation simulation. The present MD simulation also revealed that the oxidation at 300 K results in more stoichiometric oxide layer than that at 1200 K.