Influence of different pH regulators and pH values on optical properties of ZnS nanocrystalline thin films

ZnS thin films were prepared under different pH regulators and pH values by the chemical bath deposition method (CBD). Deposition mechanism was discussed and optical properties of ZnS thin films were measured by n k d- film analysis system. Results show the addition of pH regulators is beneficial to decrease the precipitation of the solution. The decrease of the precipitation of the solution could increase the deposition rate of the film. When there is addition of NH₃ and the controlled pH value is 10.9 in the solution, the deposition rate of the film is largest, which is agreement with the discussed condition that when there is no pH regulator and the pH value is dropped to 10.9 in the solution. Band edge of the transmission of all films shifts greatly to short wavelength and tends to be similar. Band gap values of all the films are larger than 4.00eV. Grain size of all the thin films is almost 5nm and the films have the pronounced quantum size effect. It shows that it is easy for ZnS to form a lot of nucleation points on the substrate, but difficult to grow up because of the existence of intermolecular hydrogen bond effect in the solution.