The application of Raman spectroscopy as an optical non-contact method for the characterization of SiC was demonstrated. The Raman spectra provide information about the polytype and thus could give direct information about microscopic inclusions of hexagonal polytypes in 3C-SiC grown by chemical vapour deposition (CVD) after annealing at elevated temperatures. Polytype conversion sets in at a about 1700C and at higher temperatures eventually results in larger domains of 6H-SiC where twin boundaries act as barriers against a complete polytype conversion. Shallow donor states of P- and N-doped SiC were studied by using low-temperature electronic Raman spectroscopy. The various low-frequency transitions observed in N-doped SiC were attributed to the valley-orbit transitions of electrons in the 1s-ground states of donors that occupied inequivalent lattice sites. During vacuum annealing at elevated temperature graphitization of the SiC surface occurred. Raman spectroscopy was used to verify that under well controlled conditions a mono-atomic graphene layer existed. A phonon hardening of that layer, compared to free-standing grapheme, was observed and was attributed mainly to strain induced by the differing thermal expansion coefficients of graphite and SiC.

Characterization of Defects in Silicon Carbide by Raman Spectroscopy. M.Hundhausen, R.Püsche, J.Röhrl, L.Ley: Physica Status Solidi B, 2008, 245[7], 1356-68