【作者】 王晓明；

【导师】 谢二庆；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2008， 硕士

【摘要】 场致电子发射在平板显示器以及其它真空电子器件中具有巨大的应用前景。多年来科学家们一直在寻求具有良好发射性能的材料,这种材料应该具有低的开启电场、高的发射电流密度及良好的电流稳定性。碳基材料如金刚石、类金刚石（DLC）、碳纳米管（CNTs）等都具有良好的场发射性能,尤其是CNTs具有非常低的开启电压和非常高的发射电流密度。但碳基材料发射电流的不稳定成为限制其应用的主要问题,因而人们开始研究宽带隙氧化物半导体材料,尤其是具有一维纳米结构的纤维状材料。此类材料不仅具有与CNTs相类似的低开启电场、高发射电流密度等特点,而且具有良好的化学与热稳定性,能够稳定的发射电流。氧化锌（ZnO）作为一种重要的Ⅱ-Ⅵ族氧化物宽带隙半导体材料,具有良好的化学稳定性和热稳定性,在短波光电器件和场发射显示器方面有着潜在的应用前景。一维纳米结构的ZnO材料具有许多特殊的性能,特别是具有优异的场发射特性。对ZnO一维纳米结构的制备、性能、生长机理及应用进行系统的研究不论在基础研究还是实际应用方面都具有重要的意义。本文利用电纺丝方法制备了ZnO一维纳米纤维,并研究了其场发射特性,主要内容如下:1.以聚乙烯醇（PVA M_w=89,000～98,000）和醋酸锌作为前驱溶液配制溶胶-凝胶,采用静电纺丝技术,制备了一维ZnO纳米纤维,系统地研究了材料制备过程中各种因素对纤维形貌、尺寸、结构以及均匀度等特性的影响,发现醋酸锌的质量、PVA的浓度、溶剂的含量以及退火温度是影响纤维特性的主要因素。2.采用扫描电子显微镜（SEM）、X射线衍射（XRD）、拉曼光谱（Raman）、场致电子发射（FE）等分析手段对样品进行了表征与测试。结果表明,经过对各种浓度配比的PVA/Zn（CH₃COO）₂·2H₂O杂化纤维进行热处理,得到了纯净的单组分的ZnO纳米纤维或纳米结构,纤维分布均匀,直径为50-200nm,并且均为纤锌矿相。3.对不同条件下制备的纳米ZnO材料进行场发射测试,结果表明:纤维结构的样品,其开启电场在5.1-12.3 V/μm之间,最大发射电流密度可达3000μA/cm²以上,且发射电流稳定;表面形貌不均匀或非纤维结构的样品,其发射电流相对较小,为400-800μA/cm²,且在高场下发射电流很不稳定。研究结果表明,直径较小的ZnO一维纳米纤维的场发射性质良好,因此这种ZnO纳米材料有望在平板显示器中获得应用。更多还原

【Abstract】 Field electron emission has more tremendous prospect in flat panel displays and other electronic devices. In the past few years, scientists have been looking for suitable materials with low turn-on field, high emission current density and good current stability all the time. Some carbon-based materials such as diamond, diamond-like carbon （DLC） and carbon nanotubes （CNTs） have good field emission properties especially CNTs due to its very low turn-on field and high emission current density. However, the emission current of carbon-based materials were not so stable that this kind of materials were limited in the large scale application. It has been given more attention that the wide band oxide semiconductors especially the fibrous materials with one-dimensional nanostructure. This kind of materials has not only the characteristics of low turn-on field and high emission but also have good chemical stability ensuring the emission current stable and uniform.Zinc oxide （ZnO） is an important II-VI wide bnad oxide semiconductor, with good thermal and chemical stability, which has potential applications in short-wave opto-electronic devices and field emission displays. ZnO materials with one-dimensional nanostructure have a lot of special properties especially excellent field emission property. Investigation on fabrication, properties, growth mechanisms and applications of ZnO one-dimensional nanostructures plays an important role in both fundamental research and practical applications.In the thesis, ZnO one-dimensional nanofibres were prepared by electrospinning and field emission properties were researched. The main content was summarized as follows:1. ZnO nanofibres were fabricated by sol-gel process and electrospinning technique, using polyvinyl alcohol （PVA M_w=89,000～98,000） and Znic acetate as precursor. Kinds of factors which affected the morphology, size, structure and uniformity of fibres were discussed systematically, showing that the mass of znic acetate, the concentration of PVA, the weight of solvent and annealing temperature were the major factors affecting the characteristics.2. The products were characterized by scanning electron microscope （SEM）, x-ray diffraction （XRD）, raman spectrum （Raman） and field emission （FE）. The results show that pure single component of ZnO nanofibres with homogeneous diameters of 50-200nm or nanostructures were obtained after calcination of various concentration ratio of PVA/Zn（CH₃COO）₂·H₂O hybrid fibres and all the products were wurtzite phase.3. The test result of field emission properties of different ZnO products show that the turn-on field of nanofibres was between 5.1V/μm and 12.3V/μm with the maximum emission current density above 3000μA/cm² while the emission current density of the uneven morphology was lower and unstable at high electric field. Results indicated that the field emission properties of ZnO one-dimensional nanofibres with smaller diameters were so good that this kind of ZnO nanomaterials may have wide applications in plan field emission display.更多还原