Effect of annealing temperature on the structural and optical properties of zinc oxide (ZnO) thin films prepared by spin coating process

ZnO thin films were deposited onto the glass substrates by spin coating method. Zinc acetate dihydrate, 2-methoxyethanol and monoethanolamine (MEA) were used as starting materials for the thin film preparation. Films were obtained by spin coating at 4000 rpm for 30 sec at room temperature and were annealed at different temperatures ranging from 200°C to 400°C. The effect of annealing temperature on the structural and optical properties of the ZnO thin films was investigated. Surface morphology of thin films was studied using atomic force microscope (AFM). The optical absorbance and transmittance measurements were recorded by using a single beam spectrophotometer in the wavelength range 300 nm to 900 nm. Evaluated optical band gap value agrees approximately with that of bulk ZnO. It is observed that band gap decreases as the annealing temperature is increased from 200°C to 400°C.