Optimization of zinc sulfide thin film coating process using response surface methodology

Zinc sulfide (ZnS) thin films have been deposited on glass substrates at room temperature using chemical bath deposition method. Application of response surface methodology and central composite design for optimizing the ZnS films deposition parameters and understanding the significance and interaction of the factors affecting the film quality was discussed in this work. pH, stirring speed and deposition time were investigated as variables and band gap was selected as response in this study. The samples were characterized using X-Ray diffraction, scanning electron microscope and ultraviolet-visible spectroscopy measurements. The optimal conditions for the deposition parameters of the ZnS thin films have been found to be: pH of 10.1, stirring speed of 163 rpm and deposition time of 31 h. Under these conditions, the experimental band gap of ZnS was 3.95 eV, which is well in close agreement with value (3.97 eV) predicted by the model.