ZnO纳米材料的制备、表征及性能研究

i目 录中文摘要 .IAbstract .III第一章 绪论 .11.1 纳米材料的概念及其特性 .11.2 ZnO 结构的特点与性质 .41.3 ZnO 纳米结构的典型形貌 .81.4 ZnO 纳米材料的制备及研究概况 .131.5 ZnO 纳米材料的性能及应用 .151.6 选题依据和研究内容 .16第二章 实验设备与测试表征方法 .192.1 实验设备介绍 .192.2 实验中所需要的主要材料和试剂 .212.3 衬底的处理 .212.4 样品的测试与表征 .21第三章 四角状 ZnO 纳米结构的制备及机理研究 .253.1 四角状 ZnO 纳米结构的制备 .253.2 四角状 ZnO 纳米结构的表征 .263.3 四角状 ZnO 纳米结构的生长机理 .30ii3.4 本章小结 .32第四章 多角状 ZnO 纳米晶须的制备及机理研究 .334.1 多角状 ZnO 纳米晶须的制备 .334.2 多角状 ZnO 纳米晶须的表征 .344.3 多角状 ZnO 纳米晶须的生长机理 .394.4 本章小结 .42第五章 花束状 ZnO 纳米棒的制备及机理研究 .435.1 花束状 ZnO 纳米棒的制备 .435.2 花束状 ZnO 纳米棒的表征 .435.3 花束状 ZnO 纳米棒的生长机理 .485.4 本章小结 .50第六章 全文总结及对今后研究工作的建议 .51参考文献 .53硕士期间发表的论文 .59致 谢 .61IZnO 纳米材料的制备、表征及性能研究中文摘要近年来，由于宽禁带半导体材料在短波长发光器件、光探测器和大功率电子器件方面的广阔应用前景而备受关注，发展十分迅速,成为研究的热点。ZnO 是一种非常重要的多功能 n 型 IIVI 直接宽禁带化合物半导体材料。室温下，其禁带宽度为 3.37 eV，而且具有很大的激子束缚能和很好的热稳定性。ZnO 作为一种应用广泛的半导体，其独特的铁电、热电、催化和光催化特性以及在太阳能电池、气敏传感器、紫外光电二极管、透明电极及光电器件方面的重要应用，使其成为各国研究的热点。研究者已经利用化学气相沉积法、化学溶液沉积法、脉冲激光沉积法、电化学法、水热法、喷雾热解法、热蒸发法等制备出包括纳米线、纳米棒、纳米晶须、纳米带、纳米管和纳米花等多种形貌的 ZnO 纳米结构。本文采用脉冲激光沉积和热蒸发法制备了 ZnO 多种纳米结构。用 X 射线衍射(XRD)、傅里叶红外吸收谱(FTIR)、扫描电子显微镜(SEM) 、透射电子显微镜(TEM)、高分辨透射电镜 (HRTEM)和光致发光谱(PL)等测试手段详细的分析了ZnO 纳米材料的结构、组分、形貌和光致发光特性。并初步提出了核的大小影响ZnO 纳米结构的形貌的观点,并对 ZnO 纳米结构的生长机理进行了研究。所取得的主要研究结果如下：1. 利用脉冲激光沉积(PLD)技术预先在蓝宝石(001)衬底上制备了ZnO薄膜，在Si(111)衬底上制备了Zn薄膜。制备的ZnO和Zn薄膜将会在后面ZnO纳米结构的生长过程中起到不同的作用。ZnO薄膜为ZnO四角纳米结构的生长提供了生长点，Zn薄膜则能够有效地促进ZnO晶核的形成从而有效地促进 ZnO纳米结构的生长。2. 利用非催化的热蒸发的方法在沉积了ZnO薄膜的蓝宝石 (001)衬底上制备了四角ZnO 纳米结构，在镀Zn薄膜的Si(111)衬底上制备了多角状的ZnO纳米晶须和花束状ZnO 纳米棒。用X射线衍射(XRD)、傅里叶红外吸收谱(FTIR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)、选取电子衍射(SAED)和光致发光谱(PL)等测试手段对ZnO纳米结构进行了分析。3. ZnO纳米结构光学特性的研究。在室温下，用波长为325 nm的Xe灯作为激II发光源激发样品发光。多种ZnO纳米结构都只有一个紫外发光峰和一个绿光发光峰。对于紫外发光峰对应于六方纤锌矿ZnO纳米结构的近带边发射,通常认为近带边发光归因于激子辐射复合发光。而对于绿光发光峰，通常被认为是由于深能级或缺陷态复合发光。一般认为绿光发光源于单个电离的氧空位与价带空穴之间的辐射复合跃迁所致。因此，我们认为在实验中的绿光发光峰是因为制备的ZnO纳米结构中存在氧空穴所致。4. 通过对ZnO纳米结构的生长过程的分析，我们讨论了各种ZnO纳米结构的生长机理。研究了在衬底上镀不同薄膜对ZnO纳米结构形貌的影响。并提出了核的大小影响ZnO纳米结构形貌的观点。关键词：ZnO纳米结构；脉冲激光沉积；热蒸发；光致发光分类号：TN304.21IIIFabrication, Characterization and Properties of ZnO NanostructuresAbstractIn recent years, the wide band gap semiconductor has attracted a lot of interests and advanced rapidly, mainly due to their promising applications in short-wave light emitting devices，photodetectors and high power electronic devices. Zinc oxide (ZnO), is one of the most important multifunctional n-type IIVI compound semiconductors, with a direct wide bandgap (3.37 eV), high exciton binding energy (60 meV) at room temperature and superior thermal stability. As a widely used semiconductor material, ZnO have gained itself substantial interest from all over the world due to its unique piezoelectric, pyroelectric, catalytic and photocatalytic properties, and its potential applications in preparing solar cells, gas sensors, UV photodiodes, transparent electrodes and optoelectric devices. ZnO nanostructures with various shapes, such as, nanowires, nanorods, nanowhiskers, nanobelts, nanotubes, nanoflowers have been successfully synthesized by different methods including chemical vapor deposition (CVD), chemical solution deposition method, pulsed laser deposition (PLD), electrochemical deposition, hydrothermal synthesis, spray pyrolysis technique and thermal evaporation.In this paper, various ZnO nanostructures are synthesized by PLD and thermal evaporation. The morphology, structure and compositions of the ZnO nanostructures were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electronic microscope (SEM), transmission electronic microscope (TEM), high-resolution transmission electronic microscope (HRTEM) and photoluminescence (PL) , respectively. We have put forward the viewpoint of the the morphological differences might be a consequence of the different sizes of the nucleus.The the possible growth mechanism of the ZnO nanostructures is also discussed in brief. All the results are as follows:1. First, the ZnO films and Zn films were deposited on sapphire (001) and Si(111) substrates by pulsed laser deposition(PLD), respectively. This ZnO and Zn films will IVplayed a different role in the growth process of the ZnO nanostructures. The pre-deposited ZnO films by PLD on the substrates can provide growing sites for the tetrapod-like ZnO nanostructures. The pre-deposited Zn films by PLD on the substrate can promote the formation of the ZnO nuclei and also promote the growth of the ZnO nanostructures effectively.2. Tetrapod-like ZnO nanostructures, multipod ZnO whiskers and flower-like ZnO nanorods were grown on ZnO-coated sapphire (001) substrates and Zn-coated Si(111) substrates by catalyst-free thermal evaporation method. The as synthesized ZnO nanostructures were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), area electron diffraction (SAED) and photoluminescence (PL) , separately.3. Optical properties of the ZnO nanostructures. For the optical property, the measurement of PL spectrum was performed with a Xe lamp as the excitation source (wavelength was 325 nm) at room temperature. There are also have two peaks: a ultraviolet (UV) peak and a green emission peak. The UV peak correspond to the near-band-adge emission, which usually ascribed to the near-band-edge exciton transition. The green emission peak is referred to as a deep-level or trap-state emission. The deep level emission in ZnO may be attributed to the singly ionized oxygen vacancy in the ZnO nanostructures and the results from the recombination of electrons at the conduction band with holes trapped in oxygen-related defects. Thus, the green emission would be a result of the existence of the oxygen vacancies in the ZnO nanostructures. So, we can conclude that there are a number of oxygen vacancies in ZnO nanostructures in our experiment.4. We discussed the growth mechanism of each kind of ZnO nanostructures by analyzing the growth process of the ZnO nanostructures. We studied the influence of the morphology of the ZnO nanostructures. We investigated the influences of different films on the different substrate on the surface morphology of the ZnO nanostructures. The results indicate that the differences morphological of the nanostructures might be a consequence of the different sizes of the nucleus. We also propose the viewpoint that the differences morphological of the nanostructures might be a consequence of the different sizes of the nucleus.VKeywords: zinc oxide nanostructures; pulsed laser deposition; thermal evaporation; photoluminescenceClassification: TN304.211第一章 绪论早在 1959 年美国著名的物理学家、诺贝尔奖获得者 R.P. Feyneman1 首先提出了纳米技术基本概念的设想，他在演讲中提到:“如果有朝一日人们能把百科全书存储在一个针尖大小的空间内，并能移动原子，那么这将给科学带来什么?”。这正是对于纳米科技的预言，是人类纳米科技最早的梦想，这也被科学界认为是纳米技术萌芽的标志。纳米概念的提出为人类的科学研究展开了一幅全新的画卷，随着纳米科技的研究和发展，纳米材料制备技术已日渐成熟，使得纳米材料已经广泛应用于人类的生活中。纳米材料研究已成为材料科学研究的一个热点，其相应发展起来的纳米技术被公认为是 21 世纪最具有前途的科研领域。1.1 纳米材料的概念及其特性1.1.1 纳米材料的概念纳米材料 2又称为纳米结构材料(Nanostructured Materials), 是指在三维空间中至少有一维处在纳米尺度(1-100 nm)范围，或由它们作为基本单元构成的材料，包括了纳米块体材料和纳米复合材料。纳米材料是整个纳米技术领域的一个重要组成部分，它涉及了纳米材料的结构、性能、应用以及纳米材料的制备和检测等各个纳米研究领域。纳米材料是纳米技术应用的基础，其分类如图1-1所示。这几部分既相互独立又相互联系，在任何领域的发展都将会带动其它相关领域的发展。其中纳米材料学是纳米领域最富有活力和研究内涵极其丰富的一个学科分支。纳米材料按其维数来分，可分为四类 3：(