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论文类型： 期刊论文

发表时间： 2013-02-27

发表刊物： PHYSICAL REVIEW B

收录刊物： SCIE、Scopus

卷号： 87

期号： 8

ISSN号： 1098-0121

摘要： The initial oxidation of 4H-SiC is investigated under realistic temperature and pressure conditions in order to better understand the mechanism of defect creation at the SiO2/SiC interface. The oxidation reaction commences on a clean 4H-SiC (0001) surface with chemisorption of the on-surface oxygen atoms at high-symmetry coordinated sites. Our calculations show that oxygen adsorption on the 4H-SiC (0001) surface occurs preferentially at the bridge site when the coverage is low of 1/9 monolayer (ML). As oxygen coverage increases to 3/4 ML, the first oxygen atom is incorporated into the subsurface region that actuates the formation of a surface oxide on the SiC surface. Above 1 ML, oxidation mechanisms in the subsurface layer are explored by taking into account oxygen incorporation and substitutions. To determine the stability of these O/SiC structures for real oxidation conditions, a surface phase diagram of 4H-SiC initial oxidation is constructed over a coverage range of 1/9-2 ML. With the increase of oxygen chemical potential, the 1/9-, 1/4-, 3/2-, and 2-ML configurations become thermodynamically favorable. Moreover, a C-2 dimer defect is observed in the 2-ML configuration. This can be extended to the SiO2/SiC interface as a thin SiO2 layer and may provide a possible mechanism for the creation of a C-cluster defect in the interface. DOI: 10.1103/PhysRevB.87.085320