Influence of thiourea on the synthesis and characterization of chemically deposited nano structured zinc sulphide thin films

Nanocrystalline ZnS thin films incorporated onto glass substrates by chemical bath deposition method were investigated by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV-Visible Spectroscopy (UV-Vis), Photoluminescence (PL), and Raman Spectroscopy (FT-R) studies. The influence of thiourea on the structural and optical properties of ZnS films was discussed in detail. The X-ray diffraction patterns confirmed the rhombohedral structure of ZnS thin films. AFM measurements indicated the nano carpet-like surface morphology variation in film with influence of thiourea. The optical absorption studies in the wavelength range of 200-800 nm showed that the band gap energy of ZnS has decreased from 3.69-3.36 eV, as thiourea varied from 0.2-0.8 M. The PL spectra divulged a shift near band edge emission around 360 nm, when thiourea concentration was increased. The Stokes shift calculations from PL emission spectra supported the relative intensities estimated from PL energy band spectra and showed a dependable repeatability for different molar concentrations. The Zn-S complexes were identified in the Raman spectra and the Raman spectral shift for 0.6 M composition of thiourea, which was found to be appreciable for ZnS thin films. The characterization studies clearly exposed the effect of thiourea onto the chemically deposited ZnS thin films.