Impurity optical absorption of Co2+-doped BaGa2S4, BaGa2Se4, BaIn2S4, and BaIn2Se4 single crystals Original Research Article

BaGa2S4:Co2+, BaGa2Se4:Co2+, BaIn2S4:Co2+, and BaIn2Se4:Co2+ single crystals were grown by the chemical transport reaction method. Impurity optical absorption peaks were observed in the single crystals in the wavelength regions of 680–880 and 1200–2000 nm. Analyzing the impurity optical absorption peaks within the framework of the crystal field theory, it was identified that the cobalt-dopant exists as Co2+ in the single crystals and the impurity optical absorption peaks are due to the Co2+ sited in the pseudo-Td symmetry point.