Photoassisted chemical deposition of nano crystalline ZnS thin films from aqueous alkaline bath

摘要

Photoassisted chemical deposition technique (PCD) was utilized to fabricate nanocrystalline zinc sulfide (ZnS) thin films from an aqueous alkaline solution bath. The solution comprised of zinc nitrate, hydrazine hydrate, ammonium nitrate, ammonia solution and thiourea. Samples were prepared on glass substrates by multiple dips on optimization. The as-deposited films were highly adherent and homogeneous. All the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV spectrophotometry. Compositional studies were carried out by EDAX. The crystallanity was observed to be poor and the phases were mixed. SEM images showed uniformly distributed spherical nano grains for as-grown films. Optical studies showed gradual increase in transmittance in the visible region. The band gap of the asprepared films was found to be 3.85eV. The morphological and optical variation of the films with temperature was also studied by annealing the samples at 2000C for 2 hours. The transmittance was found to be improved on annealing. Further we have investigated the variation in the morphology of the PCD films on different substrate like seeded soda lime glass prepared by succesive ionic layer adsoption and reaction (SILAR) method. It was seen that the growth of the as-prepared films were augmented in the presence of seed. We have compared the properties of these films with that of the as-grown films by chemical bath deposition (CBD) without the assistance of UV-irradiation.