Electronic structure and optical properties of the scintillation material wurtzite ZnS(Ag)

In order to investigate the effect of Ag doping (ZnS(Ag)) and Zn vacancy (V-Zn) on the alpha particle detection performance of wurtzite (WZ) ZnS as a scintillation cell component, the electronic structure and optical properties of ZnS, ZnS(Ag), and VZn were studied by first-principle calculation based on the density functional theory. The results show that the band gaps of ZnS, ZnS(Ag), and V-Zn are 2.17, 1.79, and 2.37 eV, respectively. Both ZnS(Ag) and VZn enhance the absorption and reflection of the low energy photons. A specific energy, about 2.9 eV, leading to decrease of detection efficiency is observed. The results indicate that Ag doping has a complex effect on the detection performance. It is beneficial to produce more visible light photons than pure WZ ZnS when exposed to the same amount of radiation, while the increase of the absorption to visible light photons weakens the detection performance. Zn vacancy has negative effect on the detection performance. If we want to improve the detection performance of WZ ZnS, Ag doping will be a good way, but we should reduce the absorption to visible light photons and control the number of Zn vacancy rigorously.