The structure and optical properties of the nanocrystalline ZnS films prepared by sulfurizing the as-deposited ZnO films

The nanocrystalline ZnS films are successfully produced by sulfidation of the as-deposited ZnO films of various sputtering time in the H2S-H2-N2 mixture. At the deposition time ≤ 30 min, after 2 h sulfidation at 500 °C, the as-deposited ZnO films can be converted totally to the hexagonal ZnS films with a strongly (0 0 2) preferred orientation. However, the ZnS films converted from the 10-min deposited ZnO films have a poor crystallinity because of the great influence of the substrates on the properties of the films with the very small thickness. The good crystallinity, the high optical transparency of about 80% in the visible region and the band-gap energy of 3.68 eV are obtained for the ZnS films formed by sulfurizing the 30-min deposited ZnO films. In addition, it is found that the ZnS films produced by sulfurizing the as-deposited ZnO films almost have the same good crystallinity as those prepared by sulfurizing the annealed ZnO films, a reason for which is due to the strongly (0 0 2) preferred orientation during the growth of the ZnS films. This indicates that the ZnS films formed by sulfidation of the as-deposited ZnO films are suitable for use in the thin film solar cells.