Competing Atomic and Molecular Mechanisms of Thermal Oxidation of Si vesus SiC

Thermal oxidation is a universal process in solids and is of practical importance in semiconductor technology. The oxidation of Si and SiC provide a unique opportunity for studying the oxidation mechanism because the products are the same oxide SiO$_{2}$. The oxidation of Si follows a linear-parabolic law with molecular oxygen identified as the oxidant. The oxidation of SiC obeys the same linear-parabolic law as Si but with different rates and temperature dependences. Using results from first-principle calculations, we first show that an atomic oxygen mechanism can account for the oxidation of Si-face SiC. We then discuss implications of the results and identify the determining factors in the competition between atomic and molecular mechanism. This work is supported by NSF GOALI grant DMR-0907385.