Research On ZnO Nanorod Arrays For Controlling Morphology By Hydrothermal Synthesis

Zinc oxide is a semiconductor with a direct wide band gap of 3.37 eV at room temperature, its exciton binding energy is up to 60 meV, which has good value in extensive applications for fabricating nano-optoelectronics and nano-electronics devices. The nanostructures of ZnO are regarded as the most abundant one among all the nanomaterials. One dimensional (1D) ZnO nanomaterials, due to their novel physical, chemical, biological properties and the potential applications in nanodevices, become the research focus in nanotechnology. Especially the discovery of photo-induced UV laser at room temperature has been promoting greatly researches of growing high-quality oriented ZnO nanorods on the solid substrate recently. Hydrothermal synthesis method is more and more popular, due to its beneficial features as simple equipment, easy operation, low cost and more conducive to large-scale use. Therefore, this issue used hydrothermal synthesis for fabricating ZnO nanorod arrays. The samples were characterized by X-Ray Diffraction, Field Emission Scanning Electron Microscopy and Photoluminescence spectroscopy, which discussed the growth factors and growth mechanism of 1D ZnO structures and studied the optical properties of ZnO nanorods by synthesis.(1) ZnO micro/nanorods on the Si substrate were generated by hydrothermal synthesis, with Zn(NO₃)₂·6H₂O and HMT as the research system, which were through controlling conditions of the reaction. The results showed that ZnO nanorods were single crystals, which were hexagonal, good crystalline and preferred growing along the (0001) direction.(2) Not only the sizes of nanorods were adjusted, also some new morphologies were synthesized by changing growth conditions, which analyzed the growth conditions on the morphology of ZnO nanostructures. The optimization parameters of the ZnO nanorods forming completely with size uniformity whose diameter of 100nm and length of about 1μm were determined, including silicon coated with the ZnO film as the substrate, 0.05mol/L of Zn(NO3)2·6H2O and HMT in the precursor solution with 50ml of deionized water and hydrothermal synthesis at 90℃for 3h.(3) High-quality single crystal ZnO nanorod array was obtained on the Si substrate by improved hydrothermal method, whose crystal diameter of 1μm-1.5μm and length of 1.5μm-3μm. Its optimization parameters include 0.05mol/L of Zn(NO3)2·6H2O and HMT in the precursor solution with 50ml of deionized water and hydrothermal synthesis at 95℃for 3h. The test results of photoluminescence spectroscopy showed that there were two obvious peaks in ZnO nanorod photoluminescence peaks, which was UV emission peak of 391nm, another was a strong broad peak of 450nm-650nm. By annealing, the intensity of UV emission peak increased.(4) The reasons for the sizes and shapes of the nanorods were discussed by hydrothermal synthesis, and combined with SEM testing and the model of growth unit, the hydrothermal growth mechanism of ZnO was explained, which illustrated the growth factors, including the solution concentration and pH et al, made an important role on the product.