Optical and field emission properties in different nanostructures of ZnO

ZnO nanostructures with different morphologies e.g. nanotetrapods, nanorods, nanocombs and nanoaeroplanes has been fabricated by evaporation of pure zinc powder without catalysts in the temperature range of 400~900 °C. The structures and properties of obtained products were examined using scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, room temperature photoluminescence and field emission. Photoluminescence spectra showed an ultravoilet-green emission and strong orange-red emission peaks at room temperature. The field emission studies of the as grown nanocombs revealed that threshold field, required to draw a current density of ~1.0 μA/cm² is ~ 1.4 V/μm. An emission current density of ~9.05 μA/cm² has been drawn from nanocombs at an applied electric field of ~ 1.92 V/μm. The field enhancement factor found to be ~8050, indicating that the electron emission from nanometric dimension of the emitter. Such, ZnO nanostructures are likely to be candidates as building blocks for constructing photonic and flat panel display.