Effect of annealing temperature on the optical properties of ZnO nanoparticles

In this work, ZnO films were prepared by drop casting technique. The films were deposited on quartz substrates under different annealing time (15,30,45 and 60 min.) at a constant temperature (800 °C). The optical properties were achieved by measuring the absorbance and transmittance spectra in the wavelength range (200-900) nm. It was found that the absorbance decreases while transmission increases as the annealing time increases, while the reflectance decreases as the annealing time increases. The optical measurements indicate the kind of transition which was a direct allowed with an average band gap energies lie between 3.3 eV and 3.54 eV with the change of annealing time.