^aDepartment of Physics, Periyar University PG Extension Centre, Dharmapuri-

636 705, Tamilnadu, India

^bDepartment of Physics, Adhiyamaan College of Engineering, Hosur, Krishnagiri- 635109, Tamilnadu, India

The Zinc Oxide (ZnO) thin films have been deposited on glass substrate at different temperature from 300 to 500 oC by nebulizer spray pyrolysis technique. The prepared films were characterized by X-Ray diffraction (XRD), High resolution scanning electron microscope (HRSEM), Energy dispersive analysis by X-rays (EDAX), Photoluminescence (PL), UV-Vis-NIR spectrometer and impedance spectroscopy, respectively. The XRD confirms that the films are polycrystalline in nature with hexagonal wurtzite crystal structure with (002) plane as preferential orientation. The various parameters such as crystallite size, micro strain, and dislocation density were calculated from X-ray diffraction. HR-SEM images show smooth, tiny grains and dense morphology. The PL studies exhibits two emission peaks one at 389 nm corresponding to band gap excitonic emission and another located at 490 nm due to the presence of singly ionized oxygen vacancies. The UV-Vis-NIR spectrometer confirms the possibility of good transparent ZnO films with an average transmission of about ~85-95% in the visible region and optical band gap shifted from 3.37 eV to 3.2 eV with increase in temperature and which is supported by PL study. The semiconductor bahaviour and activation energy of these films have been confirmed by impedance spectroscopy measurements.