Impact of Post- Deposition Heat Treatment on the Morphology and Optical Properties of Zinc Oxide (ZnO) Thin Film Prepared by Spin-Coating Technique

This research work examines the structural and optical properties of ZnO thin films. Deposition were done by spin coating of solution of Zinc oxide onto pre-cleaned glass substrate at 4000 rpm for 30 sec using spin-coater under ambient condition at room temperature in order to form desired thickness of the film on the substrate. Post- deposition thermal annealing at different range of temperatures from 150°C to 600°C with steps of 50°C was carried out on the samples. The impact of thermal annealing on optical properties of the deposited thin film was investigated using UV-VIS spectrophotometer and scanning Electron Microscope for the morphology. The optical transmittance, reflectance, absorbance were recorded which was used to evaluate the optical band gap of Zinc oxide. Observation shows that band gap energy reduces as annealing temperature is increased from 150°C to 600°C. Observation made on the morphology using SEM model ASPEX 3020 showed that as the temperature increases the surface of the sample roughness increases. It was deduced that as the annealing temperature is increased the surface roughness increases. This may be due to increase in grain size with increase in annealing temperature. The band gap energy decreases as the annealing temperature increases.