LAUSR

Abstract The ZnO nanoparticles synthesized by a simple solution based chemical bath deposition method were characterized using different experimental techniques. Photoluminescence (PL) studies were performed in ambient as well as in vacuum conditions. The emission spectra exhibit two bands corresponding to UV emission at 380 nm and a wide visible luminescence centered at 571 nm due to surface defects in ambient conditions. Under vacuum condition, the spectra show a reduction in the intensity of the wide visible luminescence and an enhancement in the UV emission. These nanoparticles were annealed at high temperatures in air. The wide visible luminescence remains at the same intensity in both ambient and in vacuum condition for the annealed samples indicating that some of the surface adsorbed defects are removed due to annealing. Fourier Transform Infrared Spectroscopy (FTIR) and Electron Spin Resonance (ESR) results reveal the presence of [OH - ] related groups on the surface of the samples. An analysis of the O1s peak in ZnO using X-ray Photoelectron Spectroscopy (XPS) measurement confirms the presence of intrinsic defects such as oxygen related vacancies and adsorbed oxygen species in the sample. Our investigation shows that the green emission observed in ZnO samples is primarily due to oxygen vacancies.