Raman intensity profiles of zone-folded modes in SiC: Identification of stacking sequence of 10H-SiC

Abstract

Raman intensity profiles are measured for 10H-SiC crystals, for which various zone-folded phonon modes are observed. Raman intensity profiles are calculated based on a bond polarizability model assuming several stacking sequences for the 10H polytype using a linear chain model. Among several candidates for the stacking sequences, the 3322 stacking structure provides the best-fit profile for experimental spectral profiles. The hexagonality value of 0.4 predicted from the stacking sequence of this polytype is consistent with that derived from the frequency splitting between the experimental A1 and E-type transverse optical modes. This fact is consistent with an empirical rule that the value of the reduced wavevector for the strongest folded transverse acoustic and optical modes are equal to the hexagonality of the polytype. In the present analysis of the Raman intensity profiles, the calculated intensity profiles for specified folded transverse optical modes are found to be relatively strong and strikingly dependent on force-field parameters in α-SiC that consists of the mixture of the cubic and hexagonal stacking structures. These force-field parameters can reproduce well the experimental Raman intensity profiles of various SiC polytypes including 10H-SiC.