Adsorption and surface diffusion of oxygen on 3C and 2H-SiC polytypes: Numerical studies

Silicon carbide oxidation is an important technological issue either in semiconductor or in thermostructural composite applications. Since this phenomenon starts with oxygen adsorption and surface diffusion, these first steps have been investigated by theoretical chemistry methods, in order to provide some insights. Density Functional Theory (DFT) calculations have been performed for the determination of binding energies of single oxygen atoms on different surface sites (Si-terminated and C-terminated) of cubic (3C) and hexagonal (2H) polytypes of SiC. Atomic movements of adsorbed oxygen have been tracked; diffusion paths and energy barriers have been found. The influence of the oxygen coverage ratio has also been investigated, showing a synergetic effect between oxygen adatoms. Finally, the differences between 3C and the more reactive 2H polytypes are also discussed.