Optical properties of beta-In2S3 and beta-In2S3 : Co2+ single crystals

beta -In2S3 and beta -In2S3:Co2+ single crystals were grown by the chemical transport reaction method using In2S3, S, and ZnS as starting materials an d (ZnCl2 + I-2) as a transport agent. The single crystals crystallized into a tetragonal structure. The indirect optical energy band gaps of the singl e crystals at 298 K were found to be 2.240 eV and 1.814 eV for beta -In2S3 and beta -In2S3:Co2+, respectively. The direct optical energy band gaps wer e found to be 2.639 eV and 2.175 eV for beta -In2S3 and beta -In2S3:Co2+, r espectively. Impurity optical absorption peaks were observed for the beta - In2S3:Co2+ single crystal. These impurity absorption peaks were assigned, b ased on the crystal field theory, to the electron transitions between the e nergy levels of the Co2+ ion sited in T alpha symmetry.