【作者】 刘文成；

【导师】 蔡伟；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2008， 博士

【摘要】 本文采用碳热还原和雾化辅助的热蒸发法制备了具有独特结构的准一维ZnO纳米材料,研究了碳热还原法制备条件对ZnO形貌的影响规律,阐明了其影响机理。采用雾化辅助的热蒸发法实现了准一维ZnO纳米材料的掺杂。采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、X射线光电子能谱和激光拉曼谱等系统研究了准一维ZnO的形貌、物相和表面化学结构,揭示了纳米车轮等特殊准一维ZnO纳米材料的生长机制。系统研究了准一维ZnO纳米材料的光学、电输运以及气敏特性,阐明了Pb和Sn掺杂对气敏性能的影响规律和机制。采用碳热还原热蒸发法,通过控制温度、载气流量、压强、原料配比和总质量等参数,获得了多种ZnO纳米结构,其中包括纳米线、纳米带、纳米梳、纳米锥、纳米空心球、纳米塔、纳米旗、纳米花、纳米花环和鱼骨状纳米梳等。在不加催化剂的条件下,制备出自催化生长的ZnO纳米阵列。采用雾化辅助的热蒸发法获得了ZnO纳米车轮,其生长机制是VS机制结合极性面控制机制共同作用:氧化锌纳米带存在Zn²⁺和O^2-终结的表面,梳齿易在Zn²⁺终结面生长;随着梳脊长度的增加,一些梳脊横端面较小的纳米梳容易因为极性面产生的静电力而发生弯曲,最终形成纳米车轮。采用雾化辅助的热蒸发法,通过向雾化溶液中加入特定成分的掺杂溶质,分别实现了Sn、In和Pb等元素的掺杂,并获得一些特殊形貌的纳米结构,如Sn掺杂诱发生长出超长纳米梳;In掺杂诱发生长出纳米环;Pb掺杂则获得了纳米管。研究表明,纯ZnO纳米材料光致发光谱有很强的紫外发光和较弱的可见发光,Sn、In和Pb等掺杂后,紫外发光变弱而可见光增强,紫外光向低能方向有少量偏移,偏移量分别为45、22和16meV。I-V特性的测试表明沉积在Al电极表面的准一维ZnO纳米材料与Al电极形成肖脱基接触。由于半导体隧道效应,随着测试温度的升高,其电阻呈下降趋势,当温度超过200℃时,表面氧的物理吸附转为化学吸附,电阻下降趋势变缓。研究发现,Pb和Sn掺杂的ZnO纳米材料,促进了ZnO纳米材料表面氧吸附,显著提高对氧气和乙醇的灵敏度。当温度低于300℃时,未掺杂ZnO纳米材料对50ppm乙醇的灵敏度最大值为11,Sn和Pb掺杂后,灵敏度最大值分别提高到62和102。更多还原

【Abstract】 The carbothermal reduction method and the spray pyrolysis assisted thermal evaporation method were developed in this work to synthesize quasi-one-dimensional （Q1D） ZnO nanomaterials. The modification of ZnO morphologies as well as the mechanisms with the varying parameters of the carbotheraml reduction method has been clarified. Additional elements were successfully doped into the Q1D ZnO nanomaterials via the spray pyrolysis assisted thermal evaporation method. The morphologies, crystal structures and the surface chemical constructions of the Q1D ZnO nanomaterials were carefully characterized by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS） and Raman spectroscopy. The growth mechnanisms of the Q1D ZnO nanomaterials such as nanowheels have been revealed. The physical properties, including photoluminescence, electrical transportation and gas sensing property, were measured with respect to the effects and the mechanism of Pb and Sn addition.Various ZnO nanomaterials were synthesized by controlling the parameters of the carbothermal reduction method, such as temperature, flow rate, pressure, atomic ratio of initial materials and total mass. Several unique nanostructures, including nano-wires, rods, belts, combs, cones, hollow bulbs, towers, flags, flowers, wreathes and fish-bone-like combs were obtained in this work. Meanwhile, ZnO nanowires arrays were successfully fabricated without any catalyst.ZnO nanowheels have been obtained by the spray pyrolysis assisted thermal evaporation method and it can be formed as a result of the compititive cooperation of the vapor-solid （VS） and polar-surface-dominated （PSD） mechanisms. It is suggested that two sides of a nanobelt are dominated by Zn²⁺ and O^2- ions, respectively. The teeth preferential growth is along [0001] direction of the Zn-terminated （0001） polar surfaces. With the growth of the ridge, it began to bend with a small cross section where the electrostatic force generated due to the polarity surface, as a result of that nanowheel can be formed. The Sn-, In- and Pb doped ZnO nanostructures were obtained by means of adding a certain solute into the spray solution, respectively. Additionally, some unique nanostructures can be induced with additional elements. For example, ultra-long teeth nanocombs were achieved in Sn-ZnO, nanorings in In-ZnO and nanotubes in Pb-ZnO.The photoluminescence of pure ZnO nanostructures shows a strong ultra-violet emission but a relatively weak visible emission at room temperature. However, with Sn, In and Pb addition, the peak intensity of ultra-violet emission may be lessened with a slight blue-shift of 45, 22 and 16 meV, respectively.I-V characterization of the Al electrodes with Q1D ZnO nanomaterials deposition is supposed to be Schottky contact. In terms of the tunneling effect of semiconductor, the resistance decrease with the increasing temperature and slows down when the temperature is over 200℃due to the conversion from an oxygen physical into an oxygenchemical absorption.The oxygen absorption to ZnO nanomaterials surface are increased in the condition of Pb and Sn doping. Therefore, the sensitivities to oxygen and ethanol can be substantially improved. The largest sensitivity of the undoped ZnO nanomaterials with 50 ppm ethanol is of 11, approximately, as the measurement temperature is below 300℃, while that of Sn-ZnO and Pb-ZnO nanomaterials are increased to 62 and 102, repectively.更多还原