ZnO nanostructures growth with silver catalyst—Effect of annealing

Zinc oxide (ZnO) nanostructures have been grown on both the as-deposited silver thin-film templates over silicon substrates and annealed silver thin-film templates on silicon substrates. ZnO was grown by evaporation of metallic zinc over the silver templates followed by thermal annealing in air. Sword-like ZnO nanostructures grew densely throughout the surface of the annealed silver template sample. A small number of ZnO swords embedded in a porous surface were found for the as-deposited silver template sample. It is observed that the annealing treatment of the Ag thin-film is the key factor in controlling the formation of ZnO nanostructures. XRD study shows that the nanostructures have very good crystallinity and have the hexagonal wurtzite ZnO structure. The room-temperature photoluminescence spectrum indicates that the nanostructures grown on annealed Ag template are less defective and have high optical quality. On the other hand, a very weak UV emission peak and the blue emission doublet band reveal that the ZnO sample grown on the as-deposited silver template are highly defective. The micro-Raman spectra of the ZnO nanostructures grown on both types of Ag templates show enhanced Raman scattering which is related to surface enhanced Raman scattering (SERS).