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

Abstract

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. Thermodynamically 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.