Characterization of ZnS Thin Films Grown Using Chemical Bath Deposition with Three Different Complexing Agents

Cadmium sulfide buffer layer was replaced with zinc sulfide thin film owing to toxicity. ZnS thin films were fabricated using chemical bath deposition. The inhibition of Zn(OH)₂ and high uniformity are important factors for the deposition of ZnS. The characteristics of ZnS thin films were analyzed by adding ethylenediamine tetra-acetate acid (EDTA) and hexamethylene tetramine (HMTA). The morphological characteristics of the ZnS buffer layer are closely related to the use of a complexing agent which controls the concentration of Zn²⁺ ions and Zn(OH)₂ in the deposition process. The addition of the complexing agent EDTA accelerated the cluster–cluster method but it exhibited lower uniformity and greater cracking phenomenon. HMTA can be effectively applied to increase the amount of Zn²⁺ ions forming ZnS. It can be easily found as Zn₂ HMTA at high temperatures. The results of the experiment with the addition of HMTA revealed that the surface of the thin film did not change with the increase in the concentration of HMTA, but the thickness of the thin film increased gradually. HMTA promoted the ion–ion method to grow the thin film uniformly, but the speed was slow. Moreover, an experiment by using mixed EDTA and HMTA as the complexing agent was performed. The best ZnS thin film with a transmittance of 83% and a denser surface was prepared using HMTA complexing agent.