Compositional, structural, and optical study of nanocrystalline ZnS thin films prepared by a new chemical bath deposition route

Zinc sulphide nanocrystalline thin films are prepared by a new chemical bath deposition route on glass and quartz substrates using a weak acidic bath, in which nitrilotriacetic acid acts as a complexing agent and thioacetamide acts as a source of sulphide ions. The thickness of films varied from a few nm to 500 nm. The chemical composition of films was determined by energy dispersive X-ray analyzer and Fourier transform infrared spectroscopy. The films are very close to ZnS stoichiometry and no organic compounds, or Zn(OH)2, or ZnO species were observed as impurities in them. X-ray diffraction indicates that the films have cubic zincblende structure. SEM images showed that the films consisted of small uniform grains (about 40 nm in size) and were free of pinholes. The effect of film thickness on optical properties, band gap energy and the size of nanocrystals were studied by UV–vis spectrophotometer measurements. The films of about 170 nm thickness have high transmittance of about 75% in the visible region.