Morphology and Properties of Tetraleg ZnO Nanostructures Fabricated by Zn-Powder Evaporation without Catalysts at Lower
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Morphology and Properties of Tetraleg ZnO Nanostructures Fabricated by Zn-Powder Evaporation without Catalysts at Lower Temperature Yue Zhang1, Yunhua Huang, Jian He, Ying Dai, Sen Wang and Cheng Zhou Department of Materials Physics, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China ABSTRACT By simply controlling temperature and atmosphere, tetraleg ZnO nanostructures with different morphologies and sizes have been fabricated respectively through pure zinc powder evaporation without catalysts at temperature of 600~800 oC. The growth mechanisms of the nanostructures were proposed and discussed. Photoluminescence spectra showed a UV and green emission peaks at room temperature. Field emission measurements revealed that the turn-on field is very low and the emission current density is relative to the morphology and size. Such ZnO nanostructures are likely to be candidates as building blocks for constructing photonic and field emission crystals. INTRODUCTION Due to their promising potentials in extensive applications, one of the present research of one-dimensional (1D) nanomaterials is to investigate their properties arising from quantum confinement, such as electronic quantum transport and enhanced radiative recombination of carriers, which can be used for next generation of computational devices and nanoscale lasers, respectively. The other aspect focuses on the geometric effects, for example, their high flexibility and hardness resulting from the defect-free lattice can be used to reinforce other materials, and the high aspect ratio makes them genuine candidates of election field emission (FE) because the tip geometry and the apex structure are essential to the FE properties[1-6]. As an oxide, ZnO exhibits high melting point and is quite stable under harsh environments. Therefore, ZnO-based 1D nanostructures are candidates as nanoscale lasers crystals and appropriate alternative to CNT for field-emission devices[7]. By now, in addition to tetraleg nanorods, other ZnO nanostructures such as nanowires, nanobelts, nanotubes, nanopropellers, nanosprings and nanorings[6,8-12] have also been synthesized successfully. Photoluminescence (PL) and FE properties of several types of ZnO have been investigated[7,13]. But in all the ZnO structures, tetraleg ZnO (T-ZnO) nanorods are very interesting, as a result of their diversified morphologies, variant properties and easy synthesis. In this paper, we report several kinds of T-ZnO nanorods, which were fabricated by a simple method. Such structures were synthesized onto silicon substrates by metal zinc powder evaporation and deposition without a catalyst at lower temperature. The growth mechanisms of the nanorods were briefly discussed, and the PL spectra have been measured. On the other hand, FE property was investigated in detail.
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EXPERIMENTAL PROCEDURE Tetraleg ZnO nanostructures were fabricated by the following procedure. The silicon substrate was placed face down on an alumina ceramics boat loaded with metal zinc powder (99
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