The effect of the pH value on the growth and properties of chemical-bath-deposited ZnS thin films

Zinc sulfide thin films were prepared by chemical bath deposition from different host solutions. The variation in the optical and electrical properties of these films with the pH value of the reaction mixture was investigated in detail. The films showed a high transmission (>80%) and a wide band gap of 3.93 eV. The resistivity of the films was found to decrease with the increase in pH of the reaction mixture and was ≈104 Ω cm for pH 10.6. The refractive index, extinction coefficient and the dielectric constants of the chemical-bath-deposited ZnS films were measured. The films prepared from the zinc nitrate solution have been found to possess a higher band gap, better transparency and surface morphology compared to the films grown from zinc chloride solution.