Synthesis of large size ZnO microrods by a simple way of thermal evaporation

Abstract Large size needle-like ZnO microrods with diameters around 100 μm and length of up to 2.5 mm have been achieved by a simple method of thermal evaporation of ZnO powder discs in the open air. Metallic catalysts and vacuum condition are not necessary. Both the micro-sized and nano-sized ZnO rods were grown vertically at different sites of the substrate. The as-synthesized microrods and nanorods are pure ZnO without any other element, and both of them consist of single crystalline cores with hexagonal cross sections. As determined by the electron diffraction and high-resolution TEM image, the growth direction of ZnO micro/nanorods is [0001] and most of them are free from defects and dislocations. The formation mechanisms for the microrods and nanorods in different sizes have been preliminary presented. The technique developed in this work makes it possible to fabricate the large size ZnO microrods.