NUCLEAR-MAGNETIC-RESONANCE STUDIES OF SILICON-CARBIDE POLYTYPES

The Si-29 MAS NMR spectra of the 2H, 4H, 6H, and 3C polytypes of silicon carbide are presented. An attempt is made to correlate differences in the chemical shifts with local atomic environment. The results of the analysis of the spectra of pure polytypes are used as a basis for the interpretation of the spectra of mixed polytypes and a discussion of the crystallinity and impurity levels of different samples. Carbon-13 chemical shifts obtained from spectra of the same polytypes are also tabulated.