The initial oxidation of the 4H-SiC (0001) surface with C-related point defects: Insight by first-principles calculations

The initial oxidation of 4H-SiC (0001) surfaces with C-related point defects (SurfCD) is studied by using first -principles coupled with thermodynamics calculations to gain deeper insights into the effects of C-related point defects on the formation of SiO2 and SiO2/SiC interface. Three types of SurfCD, including a surface with C interstitial defect (SurfCi), a surface with antisite defect (SurfCsi) and a surface with C vacancy (SurfVc) are considered. The initial oxidation of SurfCD commences on the chemisorption of oxygen atoms at the bridge sites between the Si atoms adjacent to the C-related point defects. As the oxygen coverage increased, the effects of C-related point defects on the adsorption sites and energies of oxygen atoms, the diffusion of oxygen atoms and the interfacial lattice strain are elucidated. The thermodynamic diagrams of O/4H-SiC structures are performed to investigate the stability of surface during the actual oxidation conditions for SurfCi, SurfCsi and SurfVc. Ther-modynamically stable intermediate structures are observed on these surfaces during the initial formation of SiO2, the 1 ML structures are the most stable; the Si dangling bonds, Si-O-C structure and C-clusters are observed in the 1 ML structures. Moreover, the evolution mechanisms and electronic properties of the defects are further investigated.