The effect on the optical modes of quaternary chalcogenides upon metal and chalcogen substitution

Abstract

Raman-scattering spectra of polycrystalline Cu2ZnSnSe4, Ag2ZnSnSe4, and Cu2CdSnTe4 were investigated in order to investigate the vibrational modes upon substitution on the metal and chalcogen sites. The non-symmetric modes shift dramatically with metal substitution in the kesterite materials, with Ag2ZnSnSe4 modes shifting by 50 cm-1 in comparison with that of Cu2ZnSnSe4. Tellurium substitution results in a lower frequency of the symmetric modes. Structural data are employed to elucidate our results. These results are intended to provide further insight into these materials as they continue to be of interest for potential thermoelectric and photovoltaic applications.