Synchrotron radiation x-ray absorption fine-structure and raman scattering studies on 6H-SiC materials

Abstract

The synchrotron radiation (SR) X-ray absorption fine-structure spectroscopy (XAFS) technology was employed on Si Kedge absorption spectra for bulk 6H-SiC with different doping concentration. Their Fourier transform spectra were analyzed, which have shown a parabolic linear distribution of bond lengths. Through combined Raman and XAFS studies, the coincidental results could be obtained. In the Raman spectroscopy, the LO mode intensity becomes weaker and broader as the doping concentration increases. This indicates that the crystallinity is damaged by the heavy doping concentration. The Raman curves have been fitted by theoretical formulas and the accurate information of the intensity, peak position, and FWHM in each TO and LO modes have been obtained. By the EXAFS and the fitting program, the bond length of Si-C in 6H-SiC decreases as the doping concentration increases. It is believed to be caused by the nitrogen atoms substituting for carbon atoms in the SiC lattice. But further research work is needed to identify this. The little change in Si-Si bond length indicates the influence of doping is still under local structure, near the absorbed atoms.