Vibrational properties of Cu2Zn1−xCdxGeS4 solid solutions: Raman analysis and effect of thermal annealing

In this study, the Raman spectra of Cu2Zn1−xCdxGeS4 solid solutions were measured and investigated. The spectra of non-annealed samples showed the presence of three dominant bands located at around 351–359, 258, and 493 cm−1. In the case of annealed samples, Raman analysis revealed a wurtz-stannite type structure for the Cu2ZnGeS4 sample, having the most intense peak located at around 360 cm−1. For the Cu2CdGeS4 sample, the analysis allowed detection of the main peak near 358 cm−1. Additionally, a linear model to relate the change of Cd/(Zn + Cd) ratio to the Raman shift of the second intense peak was proposed.