ABSTRACT
Cd4GeS6 and Cd4GeS6:Co2+ single crystals were grown using the chemical transporting reaction method to investigate their optical absorption. The anomalous temperature dependence of the optical energy gaps accorded well with the anomalous temperature dependence of the unit cell volume of these single crystals. Impurity optical absorptions of the Cd4GeS6:Co2+ single crystal attributed to the electronic transition between energy levels of the Co2+ ion were observed.
