Physical analysis of remained oxidation byproducts as the origins of lattice distortion at the surface of 4H-SiC by Fourier-transform infrared spectroscopy

The physical analysis of oxidation byproducts as a form of oxygen-related structure remained in distorted 4H-SiC surface region was conducted by Fourier-transform infrared spectroscopy with attenuated total reflection mode. The infrared absorption peaks were observed at the wavenumbers of 838, 1295, and 1540 cm−1, which are respectively attributable to Si-O bending, C-O stretching, and conjugated C=O asymmetric stretching vibration. We found these peak intensities showed good correlation with the anomalously large surface distortion of SiC induced by thermal oxidation and reduced by Ar annealing, which we have reported previously. They increased by surface distortion introduction and vice versa. These results suggest that the surface lattice distortion introduction is attributed to the formation of oxygen-related structures at the 4H-SiC surface, while the decomposition and removal of those structures from the surface region is a possible mechanism of lattice relaxation.