Optical properties of β-In2S3and β-In2S3:Co2+single crystals

β-In 2 S 3 and β-In 2 S 3 :Co 2+ single crystals were grown by the chemical transport reaction method using In 2 S 3 , S, and ZnS as starting materials and (ZnCl 2 + I 2 ) as a transport agent. The single crystals crystallized into a tetragonal structure. The indirect optical energy band gaps of the single crystals at 298 K were found to be 2.240 eV and 1.814 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. The direct optical energy band gaps were found to be 2.639 eV and 2.175 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. Impurity optical absorption peaks were observed for the β-In 2 S 3 :Co 2+ single crystal. These impurity absorption peaks were assigned, based on the crystal field theory, to the electron transitions between the energy levels of the Co 2+ ion sited in T d symmetry.