Synthesis of one-dimensional ZnO nanostructures and their field emission properties

This study fabricates one-dimensional ZnO nanostructures on a tin-doped indium oxide (ITO) glass substrate by thermal evaporation of Zn powder at 400 °C. The study finds that ZnO nanocones, ZnO nanorods and ZnO nanowires can be synthesized with a catalyst-free ITO glass, a Pt-coated ITO glass and an Au-coated ITO glass, respectively. The XRD and TEM investigations show that ZnO nanostructures possess good crystalline structures with growth direction along the c-axis of the crystal plane. Photoluminescence (PL) spectra of the ZnO nanocones and nanorods show a UV emission and a broad green emission at room temperature while the nanowires show a red-shifted UV and blue emissions. Field emission studies reveal ZnO nanorod arrays with a turn-on voltage of 3.4 V µm−1 at a current density of 10 µA cm−2 and this work finds that morphology and growth direction of the ZnO nanostructures affect the field emission property.