About the origin of center responsible for Cu-related blue emission band in ZnS:Cu

To choose among proposed in the literature models of the center responsible for Cu- related blue emission in ZnS:Cu (B-center), the technique of defect drift in external electric field was used. Doped with Cu zinc sulfide single crystals were investigated. After the action of direct electric field of (4–5) 102 V/cm at 300 °C blue emission was found to enhance near the cathode and to weaken near the anode. This effect was accounted for by the appearance of Cui+ ions due to dissociation of B-centers, following drift of these ions to the cathode and formation of additional B-centers in near cathode region. It was concluded that B-centers are close donor–acceptor pairs consisting of Cuzn acceptors and Cui donors. -- Highlights: • The influence of electric field on Cu-related emission in ZnS:Cu crystals was found. • This effect was ascribed to the drift of deep donor Cui in electric field. • It was concluded that blue Cu-related center was close CuZn–Cui donor–acceptor pair