Relative Raman intensities of the folded modes in SiC polytypes

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Abstract
A theoretical model, based on the bond-polarizability concept, is presented for the calculation of the Raman scattering intensities for crystals. The bonds in a unit cell are classified into groups in which the individual bond Raman polarizabilities are equivalent. The Raman polarizability of the crystals is expressed as the sum of the product of the bond Raman polarizability and the relative displacement of the end atoms linked by the bond. The theory is applied to the SiC polytypes. The calculated Raman intensity profiles reproduce qualitatively the observed Raman spectra of the folded modes which arise from TA- and TO-phonon branches along the c direction.