Effects of thermal annealing on the photoluminescence of zinc oxide films synthesized through the hydrothermal method

Abstract

We investigated the effects of thermal annealing on the photoluminescence emission of zinc oxide (ZnO) films. The ZnO films were synthesized through the hydrothermal growth on ZnO-seeded undoped silicon (Si) (100) substrates, followed by thermal annealing in ambient air at temperatures of 400°C, 500°C, and 600°C. Raman spectroscopy was performed to confirm the presence of ZnO on the Si substrates. Photoluminescence (PL) spectroscopy was done to analyze optical emission of the ZnO films. Results show that the as grown films have a  strong ultraviolet (UV) emission at 385 nm due to the band-to-band transition of ZnO, and a broad luminescence in the 450 nm to 600 nm visible range due to radiative transitions from defect states. The contribution of the UV and visible components to the PL emission was analyzed through peak-fitting techniques. Results show that the UV emission is dominant in the as-grown films while the visible luminescence is strongest in the annealed ZnO films.