Preparation and characterization of ZnS thin films prepared by chemical bath deposition

Zinc sulfide thin films were prepared by chemical bath deposition technique using zinc sulfate (ZnSO₄·7H₂O) and thiourea SC(NH₂)₂] as sources of Zn²⁺ and S^2– ions, and ammonia (NH₃) and hydrazine hydrate (N₂H₄) as complexing agents. The structural, stoichiometric proportion, morphology and optical properties of the ZnS thin films were investigated as a function of thiourea and ammonia concentrations using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and UV-visible spectrophotometry measurements. The deposition mechanism is discussed. The results reveal that the ZnS films exhibit poor crystallinity. The ammonia concentration had an obvious effect on the surface morphology, optical properties and deposition mechanism. The S/Zn atomic ratio and optical bandgap of the ZnS thin films first increased and then decreased with increasing ammonia or thiourea concentration.