The  effect  of  annealing  on  the  optical  properties  of  (Al 2O3)  thin  films  prepared  by  chemical  spray  pyrolysis 

       The recent study deal with the structural and optical properties of Al 2O3 thin films prepared by the chemical spray pyrolysis technique at glass substrate(450°C) and studying the effect of annealing at different temperatures (500,550,600) °C on the optical properties.The results of X-ray diffraction showed that the prepared films are polycrystalline, the study of optical properties included the record of transmittance spectrum of the films with the wavelengths range from (300-900)nm, and then measuring the forbidden energy gap of electronic transitions where it was found that the values of the forbidden energy gap of both allowed and forbidden transitions are (3.4)eV and (2.5)eV successively and it was (1.6)eV for the allowed indirect transition. When annealing the Al 2O3 thin films, the values of the forbidden energy gap of the allowed and forbidden of direct transitions are (2.7)eV and (3.6)eV and it is (1.9)eV for the allowed indirect transition. Also, absorption coefficient , reflectance and optical constants such as extinction coefficient, refractive index, dielectric constants with it's two parts real and imaginary and optical conductivity as a function of photon energy have been studied, the study showed that the annealing caused an increase in energy gap values,reflectance, transmittance, refractive index and real part of dielectric constant, and a decrease in the values of absorptance, absorption coefficient, extinction coefficient, imaginary part of dielectric constant and the optical conductivity.