Investigation of the luminescence properties of ZnO tetrapods and clusters grown on Si substrates

ZnO nanostructures are formed on Si substrates using Zn powder without catalyst. The substrate temperature was controlled from 450 to 600 °C, and the variation of structural and optical properties was investigated. From all samples both ZnO tetrapods and clusters were observed. Among them, no significant dispersion was observed from the ZnO tetrapods. However, ZnO clusters show considerable change in density and size. From the energy dispersive X-ray spectroscopy (EDX) results, atomic composition difference was observed. The clusters have considerable O-deficiencies, while tetrapods have almost stoichiometric composition. From all samples, strong luminescence, UV emission at 3.21 eV and green emission at 2.5 eV, were observed at room temperature. Cathodoluminescence measurements showed that the UV emission is closely related with tetrapods and the green emission is dominated from the clusters.