The Preparation and Characterization of 1-D Orderly ZnO Nanorod Arrarys
LIU Ran,ZHANG Ting*,ZHAO Su-ling,XU Zheng,ZHANG Fu-jun,YUAN Guang-cai,XU Xu-rong
Institute of Optoelectronics Technology, Beijing Jiaotong University, Key Laboratory of Luminescence and Optical Information (Beijing Jiaotong University), Ministry of Education, Beijing 100044，China
Abstract：Improving on the sealing and high pressure conditions of traditional hydrothermal method, vertical ZnO nanorod arrays were synthesized on indium tin oxide substrate by employing Zn(NO3)2·6H2O, (CH2)4N6 as the starting materials in the presence of polyethylenimine(PEI) at ambient pressure and low temperature (92°). Between the substrate and the nanorods, a layer of ZnO flim was prepared as buffer layer and seed layer. The ZnO film was gained by spin-coating zinc acetate solution on indium tin oxide substrate, then annealed at 350 ℃ for 20 min, which can make zinc acetate decompose into zinc oxide. The zinc acetate spin-coating and decomposition procedure was carried out twice to ensure a complete and uniform coverage of ZnO seeds. The second layer was annealed at 500 ℃ for 30 min. Different spin-coating speeds were adopted, one was 2 500 r·min-1,and the other was 5 000 r·min-1. XRD result indicated that the seed layer with 5 000 r·min-1 has better alignment than the layer with 2 500 r·min-1. The aligned seeds with 5 000 r·min-1 show only a (002) reflection, indicating their complete c-axis texturing, whereas the spin-coated seeds give a powder pattern because they rest at all angles on the substrate. SEM result shows that the layer is made up of grains with an the average size of about 30 nm. Well-aligned ZnO nanorod arrays were synthesized by putting the substrate with ZnO seeds into the precursor solutions vertically for one hour. The nanorod arrays were taken out and rinsed with clean ethanol and pure-water for several times, blown dry with a stream of nitrogen, then annealed at 400 ℃ for 30 min in order to wipe off the organic solvent. At room-temperature, the SEM and XRD were measured. SEM results indicate that the crystal structure of most of ZnO nanorods is hexagonal wurtzite crystallographic phase structure, mainly vertical to the substrate. ZnO nanorods have good crystallization, the diameter of the rods is around 40 nm, and the length is above micrometer. The XRD results showed the nanorod arrays have (002) and (004) angles, and the (002) is quite strong. Absorption spectra of the nanorod arrays shows ZnO essence absorption and strong ultraviolet absorption, indicating that ZnO has good quality. Optical properties were studied, and the excitation spectra of the nonorod arrays showed a strong and narrow peak at 387 nm with FWHM smaller than 30 nm and a weak blue peak.
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