Preparation and photoluminescence of ZnO nanostructures by thermal evaporation growth without catalysts

ZnO nanostructures have been grown on p-type Si(1 0 0) and glass substrates by thermal evaporating pure zinc powder without any metal catalysts at 450 or 480 °C. The microstructures of the samples under SEM show nanowires, nanorods and feathers-like morphologies. XRD reveals a preferred orientation of the well-aligned nanorods grown on silicon substrates at 480 °C. And all kinds of grown nanostructural samples are hexagonal ZnO crystal. The growth mechanism of synthesized nanostructures is discussed. Temperature and substrate are critical experimental parameters for the formation of different morphologies of ZnO nanostructures. Room-temperature photoluminescence spectrum of the well-aligned nanorods shows a blue emission band at 420 and 444 nm. The blue luminescence is due to the electrons transition from the shallow donor levels of oxygen vacancies to the valence band.