化学法制备ZnO薄膜的微观结构研究

发布时间：2018-03-22 11:50

本文选题：ZnO薄膜　切入点：溶胶凝胶法　出处：《东北大学》2011年硕士论文　论文类型：学位论文

【摘要】：氧化锌(ZnO)是一种直接带隙宽禁带(3.37eV)Ⅱ-Ⅵ族化合物半导体材料,具有较大的激子束缚能(60meV),理论上可以在室温下实现紫外光的受激发射。因此,对ZnO的研究已成为继GaN之后宽禁带半导体研究的又一热点。由于ZnO在结构、能带、电学和光学方面的诸多优点,加之ZnO薄膜的制作方法很多,可以适应不同的应用需求,ZnO在器件应用方面具有广阔的应用范围,潜力很大,前景极好。它可以被用来制作透明电极、压敏电阻、太阳能电池窗口、表面声波器件、气体传感器、发光二极管等。在短波区域,ZnO可用于制造紫外发光器件和紫外激光器,对于提高光记录密度及光信息的存取速度起着非常重要的作用。高质量薄膜和纳米结构的制备已经成为ZnO实现应用的重要环节。液相化学方法具有价格低廉、易于实现大面积生产等优点,近年来在纳米材料合成方面逐渐引起了研究者的重视。然而,薄膜的质量提高、特殊纳米结构的可控生长和掺杂工艺一直是液相制备研究中亟待解决的问题,生长机制尚不明确,需要采用多种手段进行系统的实验研究。本文以两种化学方法即溶胶凝胶法(Sol-Gel)和化学浴沉积法(CBD)制备的ZnO薄膜作为研究对象,利用X射线衍射(XRD)、原子力显微镜(AFM)、透射电镜(TEM)和高分辨电镜(HREM)对ZnO薄膜的微观结构进行了研究,重点结合薄膜制备原理分析了两种方法制备的ZnO薄膜的生长机制。溶胶凝胶法在玻璃衬底上制备的掺铝ZnO薄膜具有六方纤锌矿结构。XRD测试结果显示,在Al掺杂量较小时,随着Al掺杂量的升高,峰位向右移动,在掺杂量为3 at%时达到最大值。但随着Al掺入量进一步增加,峰位向左移动。当掺Al量超过6 at%时,薄膜的掺杂水平逐渐恶化,致使晶格不再发生变化。AFM的观察结果表明一些ZnO薄膜的表面呈现褶皱现象,这是由于凝胶在热处理过程产生的应力变化造成的结果。不同铝掺杂量的ZnO薄膜都呈现c轴择优取向,掺杂量在3 at%时择优取向最强,随掺杂量进一步增加,择优取向度明显下降。TEM结果揭示ZnO薄膜由球状或椭球颗粒组成且呈现明显的层状生长特点。ZnO薄膜均经过5次旋涂(Spin-coating)而成,在层界面的晶粒较为粗大,形成明显的粗晶层。粗晶层之间的颗粒较小形成细晶层。相比铝掺杂量较多(4-9at%)ZnO薄膜,掺杂量较少(1—3 at%)的ZnO薄膜中粗晶层的颗粒度明显增大,具有沿着层面生长的趋势。分析结果表明,晶粒的成核、长大、粗化机制比较复杂。薄膜最终形成c轴择优取向可能是由自组装机制,自织构机制和奥斯瓦尔多熟化机制综合作用的结果。实验结果表明,随Al杂质含量的增加,ZnO晶粒得到明显的细化。分析认为,未形成掺杂的A1原子以非晶A1203的形式在ZnO晶界上形成了对晶界运动的钉扎,导致晶粒尺寸的减小。对化学浴沉积法制备ZnO薄膜的微观结构分析结果表明,薄膜是由柱状晶粒组成的多晶结构,每个柱状大晶粒均由种子层表面籽晶颗粒上外延生长而成,即籽晶的晶面取向决定了柱晶的生长取向。电镜分析结果表明,薄膜以定向粘附模式(Oriented attachment mechanism)生长。薄膜稳定性较差,经长时间电子束辐照,连续薄膜分解为颗粒结构。
[Abstract]:Zinc Oxide (ZnO) is a direct wide band gap (3.37eV) II-VI compound semiconductor, has large exciton binding energy (60meV), the theory can be achieved on the ultraviolet stimulated emission at room temperature. Therefore, the research on ZnO has become another hot spot after GaN wide band gap semiconductor research. Because ZnO can with many advantages, structure, optical and electrical aspects, and many ZnO film making method, can adapt to the needs of different applications, ZnO in device applications has broad application range, great potential and prospect. It can be used to fabricate transparent electrodes, varistors, solar window battery, surface acoustic wave devices, gas sensors, light emitting diodes. In short wave region, ZnO can be used in the manufacture of ultraviolet light emitting devices and UV laser, is very important for improving the optical recording density and optical information access speed plays The role of high quality thin films and nano structure preparation has become an important factor for the application of ZnO. The liquid phase chemical method has the advantages of low cost, easy to realize large-scale production and other advantages, in recent years in the synthesis of nano materials has attracted the attention of researchers. However, the quality of the film increased, controllable growth and doping process the special nano structure has been the preparation problems to be solved by the study, the growth mechanism is not clear, the need for systematic experimental study using a variety of means. In this paper, two kinds of chemical method sol gel method (Sol-Gel) and chemical bath deposition (CBD) ZnO films as the research object, using the X ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) on the microstructure of ZnO thin films were studied, based on the principle analysis of thin films prepared by two methods The growth mechanism of ZnO films. The sol-gel method on glass substrates of Al doped ZnO thin films prepared by six with wurtzite structure.XRD test results show that when the concentration of Al is low, with the increase of Al doping amount, the peak position moves to the right, the doping amount is reached the maximum value of 3 at%. With the amount of Al further increases, the peak position moves to the left. When the doping amount of Al is more than 6 at%, the doping level of the films gradually deteriorated, resulting in the observed lattice will no longer change.AFM showed that the surface of ZnO films showed some wrinkles, this is because the gel in heat treatment of the stress caused by the change of the ZnO thin films with different doping concentration of aluminum is c axis preferred orientation, the doping amount of 3 at% in the preferred orientation of the strongest, with the doping content increases further, the degree of orientation decreased significantly.TEM results reveal that ZnO films by spherical or ellipsoidal particles and present Ming The growth characteristics of.ZnO thin film layered were significant after 5 times of spin coating (Spin-coating) formed in the grain interface layer is relatively thick, the formation of coarse grain layer obviously. The small particles of coarse grain layer formed between the fine grain layer. Compared to more aluminum (4-9at%) doped ZnO thin films, doping small amount (1 - 3 at%) coarse grain layer of ZnO thin film in particle size increased significantly, along with the level of growth trend. The analysis results show that the nucleus into the grain growth, the coarsening mechanism is complex. The final film forming orientation C may be caused by the self-assembly mechanism, since the comprehensive effect of texture mechanism and Osvaldo ripening mechanism results. The experimental results show that with the increase of Al content of impurities, ZnO grains are obviously refined. The analysis thinks, has not formed the doped A1 atoms in amorphous A1203 in the form of ZnO is formed on the grain boundary pinning of grain boundary motion, resulting in the decrease of the grain size of. The microstructure analysis of bath deposition of ZnO thin films prepared by the results show that the films are polycrystalline structure composed of columnar grains, each column of large grain size by the epitaxial growth of crystal particles on the surface layer of the seed seed and seed crystal orientation, which determines the orientation growth of columnar crystal. Electron microscopy analysis showed that in the film, directional adhesion model (Oriented attachment mechanism). The growth of film stability is poor, the long time of electron beam irradiation, continuous film is decomposed into a granular structure.

【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TQ132.41;TB383.2

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