Surface morphological and photoelectrochemical studies of ZnS thin films developed from single source precursors by aerosol assisted chemical vapour deposition

Abstract

Zinc sulphide (ZnS) thin films have been deposited on fluorine-doped tin oxide-coated conducting glass substrates at 375, 425 and 475°C temperatures from single source adduct precursors [Zn(S2CNCy2)2(py)] (1) [where, Cy=cyclohexyl, py=pyridine] and [Zn{S2CN(CH2Ph)(Me)}2(py)] (2) [where, Ph=Phenyl, Me=Methyl] using aerosol assisted chemical vapour deposition (AACVD). The precursor complexes have been characterized by microanalysis, infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray single crystal and thermogravimetric analysis. Thermal analysis showed that both precursors (1) and (2) undergo thermal decomposition at 375°C to produce ZnS residues. The deposited ZnS films have been characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. Scanning electron microscopic studies indicated that the surface morphology of ZnS films strongly depends on the nature of the precursor and the deposition temperature, regardless of marginal variation in thermal stability of the precursors. Direct band gap energies of 3.36 and 3.40eV have been estimated from the ultraviolet–visible spectroscopy for the ZnS films fabricated from precursors (1) and (2), respectively. The current–voltage characteristics recorded under air mass 1.5 illumination confirmed that the deposited ZnS thin films are photoactive under anodic bias conditions. Furthermore, the photoelectrochemical (PEC) results indicate that these synthesised single source precursors are suitable for obtaining ZnS thin films by AACVD method. The ZnS thin film electrode prepared in this study are very promising for solar energy conversion and optoelectronic applications. The PEC properties of ZnS electrodes prepared from (2) are superior to that of the ZnS electrode prepared from precursor (1).