First-principles calculations for initial oxidation processes of SiC surfaces: Effect of crystalline surface orientations

The initial oxidation processes on both the C-face and Si-face SiC surfaces are investigated by performing electronic-structure calculations within the density functional theory. We find the characteristic features of stable structures and adsorption-desorption behavior depending on the surface orientation of SiC. The desorption of C atoms as CO molecules on the C-face occasionally occurs in addition to the adsorption of O atoms even for the surfaces with low oxygen coverage, whereas the adsorption of O atoms preferentially occurs on the Si-face. These calculated results indicate that the incorporation of O atoms along with the desorption of C atoms is predominant even during the initial oxidation processes on the C-face of SiC. Moreover, on the C-face, three-coordinated O atoms can be formed at the topmost layer of the SiC surface, resulting in the formation of SiO2-like layers whose characteristics are different from those on the Si-face. These findings suggest that the differences in carbon-desorption behavior and resultant structural difference of SiO2 layers between the C-face and the Si-face are possible origins of the orientation dependence of oxidation rate observed in SiC oxidation. (c) 2015 The Japan Society of Applied Physics