Preparation Of Different ZnO Nanostructures Materials And Related Photoluminescence Property

As a new semiconductor material with a wide and direct band gap and a large excition binding energy (60meV), ZnO has versatile electric, optical, and chemical properties depending on its structure, scale, dimensionality and configuration.[0] Consequently, ZnO nanostructured materials show great promising applications in opto-electric devices, sensors et al.In this paper, various morphologies of ZnO nanostructured materials are prepared by polymer template and hydrothermal method respectively. The results of the present study are listed as follows:(1) Micrometer-sized uniform spherical ZnO ultrafine powder was prepared by polymer polyvinyl alcohol (PVA) template method. Polar polymer polyvinyl alcohol with long chain is used as grids localization and lattice reagent to control nucleation and crystal growth. The results of SEM and XRD indicate that the concentration of the PVA solution, sintering temperature is the main factors for the preparation. The ultraviolet emission peak located at 385nm which originates from the interband transition of electrons has been observed.(2) One-dimensional ZnO nanorods with diameters in 15～50nm aligned in radial cluster were firstly synthesized by PVA as soft-template. The growth of ZnO nanorods is controlled by changing annealing temperature. It is shown that ZnO nanorods tend to be uniform and the crystallization is gradually improved with the temperature increasing from 400 to 700oC. The growth mechanism is discussed. Preferential growth of ZnO crystals is helpful for growing along radial direction anisotropically of ZnO. At the same time, development of the same crystal facets and the various crystal facets relative growth rate of ZnO are also influnced, which lead to the formation of nanorods in radial clusters. The photoluminescence spectra show a strong ultra violet emission and relatively weak defect emissions. The sharp strong emission peak at 354nm owing to the inter-band transition indicates the extraordinary photoluminescence property of ZnO nanorods.(3) ZnO micro- and nano-rods have been synthesized onto glass substrates through aqueous growth method with the thermal decomposition of an aqueous solution of Zn (NO3)2·4H2O and methenamine (HMT). The growth mechanism shows that cyrstal morphologies result from ZnO in solution surrounding, which strongly depends the processing parameters. The photoluminescent spectra of samples show that there is an ultraviolet emission with peak at 386nm when the excitation wavelength at 325nm.(4) By using the ZnO crystal seed, the dense-arrayed and regular oriented ZnO nanorods were obtained by hydrothermal method. The results of XRD confirm that the nanorods are preferentially oriented in c-axis. It is found that the revolving speed to preparation of seed layer and the concentration have significant influence on the formation of ZnO nanorods arrays. Optical characterazition shows that the ZnO nanorods arrays exhibit strong blue and green emission.