Synthesis and characterisation of ZnS thin films obtained without complexing agent by the chemical bath technique

Abstract

ABSTRACT Zinc sulphide (ZnS) thin films were synthesised by chemical bath deposition technique without using complexing agent. A physicochemical study was realized on the growth solution composed of ZnCl2, KOH, and SC(NH2)2. The bath solution was at 60°C and pH values of 11.5, 12, and 12.5 were selected for growing the material. The species distribution diagrams, and solubility curves show that the growth mechanism requires the presence of zinc-hydroxide ions, and alkaline pH for growing the ZnS. The physicochemical properties of the samples improve as the pH of the solution increases. Samples deposited at pH=12.5 present a cubic structure (sphalerite) and bandgap energy of 3.72 eV, consistent with bulk-ZnS. For comparison, additional chemical baths were prepared by using NH3 as complexing agent; however, the properties of those samples result inferior. This methodology was validated by depositing ZnS films at 40°C without the complexing agent, obtaining similar results.