Synthesis, Characterization And Photoluminescence Property Of ZnO Quasi-one-dimensional Nanostructures

Zinc oxide nanomaterial is a new type direct wide band gap semiconductor material, which has important applications in optical-electron devices. In this paper, tetrapodlike and aligned nano-ZnO have been synthesized by thermal evaporation method. XRD (X-ray diffraction), HRTEM (high-resolution transmission electron microscopy) and SAD (select area electron diffraction) were employed to characterize the structure features of the products. SEM (scanning electron microscope) was used to characterize the morphology of our products. The optical properties have also been investigated by the photoluminescence.Tetrapodlike nano-ZnO has been synthesized without catalyst. XRD shows the tetrapods are pure hexagonal wurtzite crystal structure. The crystal plane space is 0.16 nm that corresponds tothe (11 2|- 0) faces. The SAD verifies this result. The growth direction of these branches of thetetrapodlike nano-ZnO is parallel to the [11 2|- 0] direction. The morphology of ZnO nanostructures is affected strongly by the argon flow rates. As the flow rate increases, nano-ZnO morphology changes from an initial mixture of tetrapod, nanowire, nanosheet, and nanodendritic to a uniform tetrapodlike morphology. The growth mechanism of the nano-ZnO was explained by the VS mechanism. The photoluminescence (PL) spectra show that the emission intensity changes evidently with the change of argon flow rate in the tube. The UV emission in the PL spectra become weaker and the blue emission become stronger, namely the ratio of the blue emission to the UV emission become bigger with the increasing of the argon flow rate. It is suggested that the oxygen vacancy is responsible for strong blue emission. The supposition is confirmed by the results that the blue light emission peaks disappear after the products are oxidized annealing in air at 700℃ and the blue light emission peaks appear again after the oxidized products are deoxidized annealing in H₂ at 700℃. Our experimental results provide the proofs that blue light emission of nano-ZnO originates from oxygen vacancy.Aligned cone-shaped nano-ZnO is synthesized with Zn as catalyst. XRD reveals the crystal structure of the product is the typical wurtzite crystal structures. The growth process of the aligned nano-ZnO follows the VS mechanism. The PL spectrum includes a near-band-edge emission peak in the ultraviolet region at 380nm and a defect-related deep-level emission peak in...