Effects of Deposition Time and Temperature on the Optical properties of Chemically Deposited ZnO thin film

Abstract

Zinc Oxide thin film was successfully deposited using chemical bath deposition method. The optical and morphological measurements were reported using ultra-violet visible spectrophotometer and Scanning Electron Microscope respectively. The elemental composition was investigated using Energy Dispersive X-ray and the result showed peaks corresponding to the two main elements (Zinc and Oxygen) only, signifying the purity of the deposited films. The optical property was observed to depend on the deposition times and temperature. The films’ percentage transmittance was observed to reduce with increasing deposition time, with the film sample deposited for 30 min exhibiting the highest percentage transmittance of 82.7% among the samples deposited for the same temperature. Reduction in the deposition temperature to 60 ^oC increased the films’ transmittance to the highest value of 84.8%. The direct band gap energy values increased from 3.47 to 3.51 eV when the deposition time was increased from 30 to 60 min and reduced to 3.46 eV when the deposition temperature was reduced from 70^oC to 60^oC. Urbach energy was deduced from its exponential relationship with photon energy and the result showed that the value increase with increasing deposition time but decreased with deposition temperature. These results from this study revealed that ZnO thin film possessed the required properties suitable for its application as transmission conducting oxide in solar cells.