Synthesis of ZnO nanoneedles by thermal oxidation of Zn thin films

•Zn crystallite size depends on thermal deposition rate.•Nanostructures of ZnO were grown from the Zn films by thermal annealing.•The crystal size of Zn films affects the growth and quantity of ZnO nanostructures.•Obtained ZnO nanoneedles are straight and no branching was observed.•The morphology, composition and phase identification were obtained.

The nanostructured zinc oxide (ZnO) thin films were successfully synthesized by rapid thermal oxidation of zinc metallic films without introducing any catalysts or additives. The zinc thin films were deposited on glass substrates by thermal evaporation. A thin layer of Zn, deposited by magnetron sputtering, was used to enhance the adhesion of the Zn film to the glass surface. The effect of deposition methods of metallic zinc films on phase composition and structural properties of ZnO nanostructures was investigated by using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The formation of needle-shaped nanostructures of ZnO was observed. The as-grown nanoneedles had diameters in the range of 20–80 nm with lengths 20 nm–some microns. The XRD patterns of annealed samples were in agreement with those of the typical wurtzite structure ZnO and the sharp diffraction peaks indicated good crystallinity of ZnO nanoparticles. These ZnO thin films have promising potential advantages in microelectronic and optoelectronic applications.