光辅助Ag-ZnO复合纳米材料的场发射特性研究

发布时间：2018-06-03 07:36

本文选题：场发射 + ZnO晶种膜　；参考：《中国海洋大学》2015年硕士论文

【摘要】：氧化锌(ZnO)纳米材料具有禁带宽(3.37eV),光电性质良好,化学稳定性高,在高场强下,能带易弯曲等优点,被认为是最有前途的场发射阴极材料之一。阴极材料是场发射显示器(Field Emission Display, FED)电子源的核心,因此氧化锌纳米材料的场发射性能具有相当重要的研究价值。首先,通过溶胶凝胶-水热两步法在少层晶种膜上制备ZnO纳米棒阵列。为了研究晶种膜对ZnO纳米棒生长的影响,不同层数晶种膜(2,4,6,8层)被制备,利用扫描电子显微镜、X射线衍射(XRD)、对晶种膜和晶种膜上生长的ZnO纳米棒进行表征。结果表明晶种膜层数为4时,ZnO纳米棒取向性最好,密度最大。同时用紫外荧光分光光度计测试了材料的光致发光(PL)性能,通过分析紫外发射峰和可见蓝光发射峰的峰位及其峰强比,发现4层晶种膜上生长的ZnO纳米棒具有最多的本征缺陷,其导电性最好,通过场发射测试研究,4层晶种膜上生长的ZnO纳米棒具有最低的开启电场,13.3V/μm,最大的发射电流,及最大的有效发射电流面积,其优异的场发射性能来源于材料具有较大的场增强因子、较好的导电性、较高的密度和良好的垂直取向性。其次,利用水热法制备了Ag-ZnO复合纳米材料,分别添加不同浓度的Ag+,通过XRD,扫描电子显微镜(SEM),透射电子显微镜(TEM)对复合材料进行表征,发现随着Ag+离子浓的度增加,Ag纳米颗粒的含量越来越多。通过PL光谱分析,Ag的加入使得可见光发射峰的数量增加和紫外发射峰数量减少,导致Ag-ZnO的本征缺陷增加。通过场发射性能测试,发现Ag的含量越多,场发射性能越好。根据Fowler-Nordheim (F-N)理论对,对电流曲线进行e指数拟合分析,实验曲线由不同e指数曲线组成,每一种的e指数曲线代表一种电子发射过程。结果表明Ag-ZnO纳米材料的场发射过程包括有Ag的发射和ZnO价带的发射。光辐照能够使得一部分缺陷能级上的电子吸收光子能量,发射出去,从而增强场发射电流,因此本文讨论了蓝色可见光和紫外光光辐照对ZnO纳米棒和Ag-ZnO复合纳米材料的场发射性能的影响,不同强度蓝色可见光和紫外光辐照均明显增强场发射电流。而且光照强度越强,场发射电流增强效果越明显。同样用e指数拟合分析,场发射过程分别为Ag的电子发射,价带电子发射,导带电子发射。其中导带电子发射有一部分来自吸收光子后的跃迁发射。不同波长的光辐照时,发射机理不同,鉴于ZnO独特的晶体结构特性,由于紫外光的光子能量比蓝光大,并与ZnO禁带宽度相似,更加利于增强场发射性能。
[Abstract]:Zinc oxide (ZnO) nanomaterials are considered as one of the most promising field emission cathodes due to their good optical and electrical properties and high chemical stability. Cathode material is the core of Field Emission Display, FED) electron source in field emission display, so the field emission property of ZnO nanomaterials is very important. Firstly, ZnO nanorod arrays were prepared by sol-gel hydrothermal two-step method. In order to study the effect of seed film on the growth of ZnO nanorods, ZnO nanorods grown on seed film and seed film were characterized by scanning electron microscopy (SEM). The results show that the orientation and density of ZnO nanorods are the best when the number of layers is 4. At the same time, the photoluminescence (PL) properties of the materials were tested by UV fluorescence spectrophotometer. By analyzing the peak position and peak intensity ratio of the UV emission peak and the visible blue emission peak, it was found that the ZnO nanorods grown on the four layers of crystal seed film had the most intrinsic defects. The ZnO nanorods grown on the four-layer seed film have the lowest open electric field of 13.3 V / 渭 m, the maximum emission current and the maximum effective emission current area. Its excellent field emission properties are due to its large field enhancement factor, good conductivity, high density and good vertical orientation. Secondly, Ag-ZnO composite nanomaterials were prepared by hydrothermal method. The composite materials were characterized by XRD, scanning electron microscopy (SEM) and transmission electron microscope (TEM). It is found that the content of Ag nanoparticles increases with the increase of Ag ion concentration. The number of visible emission peaks and the number of ultraviolet emission peaks are increased by the addition of Ag by PL spectroscopy, which leads to the increase of intrinsic defects of Ag-ZnO. It is found that the higher the Ag content, the better the field emission performance. According to the Fowler-Nordheim F-N) theory, the current curve is fitted with e exponent. The experimental curve is composed of different e exponent curves. Each e exponential curve represents an electron emission process. The results show that the field emission process of Ag-ZnO nanomaterials includes the emission of Ag and the emission of ZnO valence band. Light irradiation can cause electrons at some defect levels to absorb photon energy and emit it, thus increasing the field emission current. Therefore, the effect of blue visible and ultraviolet light irradiation on the field emission properties of ZnO nanorods and Ag-ZnO composite nanomaterials is discussed. And the stronger the illumination intensity, the more obvious the enhancement effect of field emission current. The field emission processes are Ag electron emission valence band electron emission and conduction band electron emission respectively. Some of the electron emission in the conduction band comes from the transition emission after the absorption of photons. Due to the unique crystal structure of ZnO, the photonic energy of ultraviolet light is larger than that of blue light, and the band gap of ZnO is similar to that of ZnO, so it is more favorable to enhance the field emission performance.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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