Sulfiding effects on ZnS thin films obtained by evaporation technique

ZnS thin films were grown on a glass substrate using physical vapor deposition techniques at room temperature. Subsequently, the thin films were annealed in three different atmospheres: vacuum, nitrogen-sulfur and vacuum-sulfur. In order to sulfurize the thermal treatment atmosphere within CSS equipment, a graphite box was designed that maintained sulfur in its steam phase while all of the intervals of temperatures were tested. In addition, during the annealing pure ultra-high nitrogen gas was used. It was found that heat treatment is indispensable in nitrogen-sulfur and vacuum-sulfur atmospheres in order to increase the polycrystallinity and stoichiometry of ZnS thin films. The polycrystalline nature and pure phase were determined by XRD technique. The EDS results showed that the films annealed in a sulfur atmosphere were close to stoichiometry and that direct band gap varied from 3.68 to 3.84 eV. The most effective atmosphere was nitrogen-sulfur, showing enhancement in the optical, structural, and morphological properties.