Direct Observation of Nanoscale Native Oxide on 6H-SiC Surface and Its Effect on the Surface Band Bending

The RCA-cleaned 6H-SiC surface has a 1 nm native oxide layer, which was directly observed by high-resolution transmission electron microscopy and confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The surface band bending caused by the native oxide layer was studied by synchrotron radiation photoelectron spectroscopy. The binding energy of Si 2p core level for the Ni/oxygen-free SiC interface showed almost zero shift (<0.07 eV). However, it red-shifted about 0.34 eV for the Ni/native-oxide/SiC interface, it indicated that negative charged interface states induced in the Ni/native-oxide interface resulted in the upward bending of the interface energy band.