Photoluminescence property of ZnO–SiO₂ composites synthesized by sol–gel method

The room temperature photoluminescence property of ZnO particles embedded in sol–gel silica was investigated. Three ZnO emissions at about 3.25 eV (ultraviolet (UV)), 2.8 eV (blue), and 2.45 eV (green) were observed. The blue and green emissions were ascribed to interstitial zinc and oxygen vacancy defects in ZnO. At heating temperatures above 900°C, the interaction of ZnO with SiO₂ gave rise to Zn₂SiO₄, which enhanced the green emission markedly by limiting the oxidation process of oxygen vacancy. Heating in low oxygen pressure was found to enhance the UV emission substantially. The effects of heating temperature and ambient on blue and green emissions were also discussed.