Local structural determination of N at SiO2/SiC(0001¯) interfaces by photoelectron diffraction

Nitridation effectively reduces the density of defects and improves the performance of SiC metal-oxide-semiconductor field-effect transistors. Photoelectron spectroscopy and diffraction can characterize the amorphous SiO2/SiC(0001¯) interface with nitridation treatment by oxidation in a N2O-containing atmosphere. The N 1s spectra indicate that N covers about 1/3 of the monolayer, and the N atoms are bonded to the Si atoms. Forward focusing peaks (FFPs) appear in the photoelectron diffraction patterns in the direction of the surrounding atoms around the excited atom. The similarity between the sixfold symmetric N 1s FFP pattern and the C 1s pattern strongly suggests that the majority of N atoms are located at C sites in the topmost layer of the 4H-SiC substrate where N bonds to three Si atoms. The local strains of the atomic arrangement around the N atoms are quantitatively evaluated by analyzing the FFP patterns corresponding to the third-nearest neighbor Si atoms.