Optical Properties and Lattice Dynamics of Pure and S‐Alloyed Cu–Zn–Sn–Te Semiconductors: First‐Principles Calculations and Raman Scattering

Abstract

The electronic band structure, the optical properties, and the lattice dynamics of the quaternary Cu2ZnSnTe4 (CZTTe) semiconductor with kesterite crystallographic structure are calculated within first principles. The analysis of the phonon partial density of states shows that the highest frequency phonon mode involves mostly heavy Sn and Te atoms due to their exceptionally strong bonding. Experimental Raman spectra of Cu–Zn–Sn–Te nanocrystals, prepared by an aqueous colloidal synthesis, reveal a single characteristic line and its higher order overtones due to specific resonant conditions. In the case of Cu–Zn–Sn–(Te–S) alloy nanoparticles, other Raman features, related to Sn–S vibrations, appear in the spectra indicating a two‐mode type of transformation of their vibrational spectra. The effect of sulfur incorporation on the Te‐related frequency is opposite to the effect observed for the Se‐related frequency in CZTSSe alloys.