Structure, composition and optical properties of ZnS thin films prepared by spray pyrolysis

Thin films of zinc sulfide (ZnS) are prepared by spray pyrolysis using mixed aqueous solutions of ZnCl2 and thiourea. The structure, surface morphology, chemical composition and optical properties of these films are investigated as a function of substrate temperatures Ts, deposition times td and solution spray rate s. These parameters are optimized in order to obtain films with a good crystalline quality and high transmittance. It is found that the films prepared at substrate temperature of 500°C, deposition time of 35 min (about 1 μm thick) and solution spray rate of 5 ml min−1 have good adherence to the glass substrates and exhibit a mixture of hexagonal (α) and cubic (β) phases, with a preferential orientation along the (1 1 1 )β direction. The X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA) show that the optimized films contained very little oxygen and is nearly stoichiometric. These films also show an optical transmittance more than 70% in the visible range.