Properties Of Semiconducting ZnS Thin Films Prepared By A Controlled Method

In the dissertation, ZnS thin films were produced by sulfidation of ZnO, Zn, orZn/S/Zn films, which were deposited by sputtering and evaporation. These films werecharacterized by XRD, SEM and UV-VIS spectrophotometer. Effects of sulfidationcondition on the structural and optical properties of the sulfurized films were studied.Hexagonal ZnS thin films were grown by a sulfidation (above300℃) processfollowing air-annealing of the as-deposited ZnO films. These thin films exhibited a(002)-plane preferred orientation. Under the optimum sulfidation temperature and time(500℃and2h), the resultant ZnS films had a high crystallinity, homogeneousdistribution in the composition and grain size, and good transparency (80%). Properlyenhancing in-air-annealing temperature can improve the crystallinity of ZnS films. Thephotoluminescence spectra of ZnS films and their emission origin were also discussed.ZnO thin films were annealed in sulfur-vapor (500℃) and converted into ZnS.However, the required time was up to18h. The ZnS thin films have a (002)-planepreferred orientation. The low optical transmittance and broadening of absorption edgewere found for the thin films, due to the residual and excessive sulfur existing in thefilms. The sulfurized thin flms had markedly greater grains (about1μm) than theas-deposited flms, due to recrystallization of ZnS in sulfur vapor. The Zn films insulfur-vapor (500℃) was transformed into ZnS, with the required time of only1h.Besides, their optical transparency was improved by gradient sulfidation.The Zn/S/Zn three-layer structure, after annealing in Ar atmosphere, formed cubicZnS thin films. The optical transmittance for ZnS thin films was as high as80%, whichwas comparable to the transmittance for ZnS films prepared by sulfidation of sputterdeposited ZnO in H2S gas. Moreover, the former is an environmental friendly method.