Polarized Raman scattering analysis of Cu2ZnSnSe4 and Cu2ZnGeSe4 single crystals

The polarized Raman spectra of the Cu2ZnSnSe4 and Cu2ZnGeSe4 single crystals were measured for various in-plane rotation angles on the basal (1 1 2) crystal facet. The position of up to 15 (for Cu2ZnSnSe4) and 16 (for Cu2ZnGeSe4) Raman peaks was determined in the spectral region 50–300 cm−1. From the analysis of the experimental dependence of the intensity of the Raman peaks with the rotation angle, a symmetry assignment for most of the detected modes and an estimation of numerical values of Raman tensor elements were derived. The kesterite type structure of Cu2ZnSnSe4 and Cu2ZnGeSe4 single crystals was established by the quantity of the observed nonpolar A and polar B (TO+LO) symmetry modes.