Temperature dependence of Raman scattering in the Cu2ZnSnSe4 thin films on a Ta foil substrate

Abstract

The temperature dependence (in range from 24 to 290 K) of Raman spectroscopy of the Cu2ZnSnSe4 (CZTSe) films with Zn-rich (series A) and Zn-poor (series B) composition obtained on a Ta foil is investigated. Analisys and approximation by the Lorentz function of the CZTSe Raman spectra suggests that the CZTSe most intense Raman peak consists of two modes (at 192/189 and 194/195 cm−1), which are slightly shifted from each other. In addition, the Raman peaks around 192 and 189 cm−1 lead to asymmetric broadening of dominant peaks at 194 and 195 cm−1 in Raman spectra of the CZTSe films series A and B, respectively. In the case of the Sn-rich CZTSe films, we attribute of Raman peak around 189 cm−1 to SnSe2 compound. However in the case of the Snpoor CZTSe films, the observable shift is too high to assign confidently the 192 cm−1 band to a SnSe2 compound, which was not detected by XRD analysis. We suppose that this mode is attributed to disordered kesterite structure. The temperature dependence Raman spectra for both series of the CZTSe films shows that a change temperature from 290 to 24 K leads to position shift and narrowing of the CZTSe Raman A-modes. The calculated temperature coefficients and anharmonic constants in Klemens model approximations for temperature dependence of shift position and FWHM of the CZTSe A-modes shown that four-phonon process has dominant contribution in damping process and as a consequence in Raman spectrum changes for two series of the CZTSe films.