Effect of multiple dipping of SILAR deposited ZnO thin films by physico-chemical process

Undoped zinc oxide (ZnO) thin films were deposited on microscopic glass substrates by a chemical technique known as ‘Successive Ionic Layer Adsorption and Reaction’. The technique involves multiple dipping of the substrates in an aqueous solution of sodium zincate kept at room temperature and deionized water kept near boiling point. The effect of multiple dipping is one of the important factors that determine the quality of film. Thin films of various thicknesses have been obtained by varying the number of dipping, while all other deposition parameters such as pH of the solution, molarity, reaction temperature, reaction time and annealing temperature were kept constant. The structural, surface morphology and optical properties of the ZnO thin films have been studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–Vis-spectrophotometer. XRD and SEM studies reveal that the grain size increases with the increase in number of dipping of the glass substrate. Optical spectra were recorded using UV–Vis spectrophotometer. The optical band gap of ZnO thin film was found to decrease with increase in the number of dipping.