Abstract
The behavior of C atoms during the thermal oxidation of a SiC surface has been a subject of controversy. In this study, we oxidize a SiC surface by atmospheric-pressure plasma treatment near room temperature. We find that more C atoms are included in the SiO2 film after plasma oxidation than after conventional thermal oxidation in O2 ambient at 1000°C, which is probably caused by the difference in oxidation temperature. We demonstrate that plasma oxidation followed by HF etching results in clusters of C atoms remaining at the SiO2/SiC interface. We speculate from X-ray photoelectron spectroscopy results that the C clusters are mixtures of C-C, CH2 and C-O. These C clusters allow us to obtain graphene with few pits because they are an additional C source for forming a homogeneous buffer layer over a SiC surface at elevated temperatures in ultrahigh vacuum.