Growth of ZnS thin films obtained by chemical spray pyrolysis: The influence of precursors

Thin films of zinc sulphide (ZnS) were prepared by spray pyrolysis using two mixed aqueous solutions: (a) dehydrated zinc acetate (10−2 M) and thiourea (4×10−2 M) in bidistillated water; (b) zinc chloride (10−2 M) and thiourea (4×10−2 M) in bidistillated water. The structure, surface morphology, chemical composition and optical properties of these films were investigated as a function of initial (Zn:S) ratio in the solution, which varied between (1:1) and (1:6) for both solutions. This parameter was optimized in order to obtain films with a good stoichiometry, crystalline quality and high transmittance. It was found that films prepared from solution A, with a (Zn:S) ratio equal to (1:4) have the largest crystal size, smoothest surface, high optical transmittance and a (Zn/S) ratio in films equal to 0.91, as determined by XPS.