Vibrational studies of copper thiogallate solid solutions

Vibrational spectra of Ga2S3–Cu2S solid solutions have been studied at room temperature. Raman scattering and far-infrared spectra of the zinc-blende structure were carried out in the compositional range 0.10≤n≤0.25. All the spectra can be interpreted using a localized model considering the decoupled, weakly deformed GaS4 tetrahedral units. The presence of copper atoms in the structure is detected by a hardening of the Ga–S bonds and a modification of the tetrahedral network. Vibrational modes of the three crystalline forms of the semiconducting ternary compound CuGaS2 have also been investigated. The results show that the mode frequencies are very sensitive to a small variation in the compound stoichiometry.