Selectively resonant Raman spectra of folded phonon modes in SiC

The excitation energy dependence of the Raman intensities of folded longitudinal phonon modes in various SiC polytypes was measured in near resonant conditions. Selective enhancement of the folded longitudinal phonon modes relative to the non-folded longitudinal phonon mode was observed. We used a bond-Raman-polarizability model to analyze this selective enhancement effect. In this model, bond-Raman-polarizabilities of three bond arrangement are supposed to have different excitation energy dependence. By using this model, the excitation energy dependence of the relative intensities of the folded longitudinal phonon modes is successfully interpreted.