Luminescence of ZnIn₂S₄ and ZnIn₂S₄:Cu Single Crystals

Abstract

Single crystals of ZnIn 2 S 4 and Znin 2 S 4 :Cu were grown by the method of the chemical transport reactions, The space group for the crystal structure was determined to be the rhombohedral C 3 v b ( R 3 m ) group. It was found that both ZnIn 2 S 4 and ZnIn 2 S 4 :Cu crystals show fairly bright red luminescence. The characteristics of the luminescence and photoconductivity were measured in detail. The origin of the luminescence centers was discussed with the assistance of knowledge on ZnS type phospbors. The center for the red Iuminescence in ZnIn 2 S 4 :Cu may be the same type of center as that for the copper-green luminescence in ZnS, the luminescence transition being, therefore, probably that of free electron to the acceptorlike level of copper at zinc site. As for the red luminescence in the undoped crystal, it is suggested that the crystal involves two kinds of centers, i.e. the red luminescence center due to copper contained as impurity and the self-activated center due to iodine, which has been used as transporter, acting as coactivator.