水热法制备ZnO:Cd纳米棒及其应用研究

发布时间：2018-04-24 08:24

  本文选题：水热法 + ZnO:Cd纳米棒　； 参考：《重庆师范大学》2015年硕士论文

【摘要】：ZnO是一种重要的新型半导体金属氧化物材料,具有压电、光电特性和高的电荷迁移率等特点,被广泛应用于发光二极管、压敏器件等领域,在气敏传感器和发光器件方面也有广泛的应用。近年来许多专家学者,通过掺杂其它元素来改善ZnO气敏性能和发光特性,Cd和Zn同属第二副族,物理化学性质相似,容易实现Cd替代ZnO中Zn,形成替位掺杂,从而使得ZnO的结构、性质发生改变。Cd掺杂以后使得ZnO的晶粒尺寸减小,带隙变窄。这对于研究ZnO气敏特性和发光特性具有重要意义。本文主要以六水硝酸锌(Zn(NO3)2·6H2O)为Zn源,四水硝酸镉(Cd(NO3)2·4H2O)为Cd源,采用低温水热法成功合成了ZnO和ZnO:Cd纳米棒(其中Cd/Zn的摩尔比分别为0.01、0.02、0.03、0.04)。通过X射线衍射仪、场发射扫描电子显微镜和激光共聚焦拉曼光谱仪分别对样品的晶体结构、表面形貌和晶体内部应力进行了表征。将制备的样品均匀旋涂在切割好的玻璃衬底上制成薄膜样品,利用双光束紫外/可见/近红外分光光度计对其进行透射方面的分析,通过简单计算进而确定其光学带隙宽度。利用荧光/磷光发光分光光度计对ZnO及ZnO:Cd纳米棒光致发光特性进行研究。探究结果表明:纯的ZnO和不同掺杂浓度的ZnO:Cd纳米棒晶体结构均呈六角纤锌矿,Cd的掺杂使得晶体粒子尺寸减小,ZnO薄膜的光学带隙宽度变窄,由分析可得带隙减小原因有以下两个方面:一是在晶体内部存在张应力。二是在ZnO的带隙中形成了其它的杂质能级。当Cd掺杂量为2%时,我们可以看到样品存在位于2.67e V的蓝光发光峰,而这个峰在其它样品中并没有发现。通过分析研究我们得出此蓝光光致发光峰是由于电子从导带底到Zn空位(VZn)之间发生跃迁产生的。从光致发光峰中我们同样可以看出由于Cd掺杂增强了ZnO位于2.90e V附近紫光光致发光峰的强度。利用气敏测试装置对其氢敏进行研究得出:在150℃下,不同掺杂浓度的ZnO:Cd及纯ZnO薄膜,当氢气浓度为500ppm时,掺杂浓度为2%时薄膜的灵敏度最高。对掺杂浓度为2%的ZnO:Cd薄膜进行了不同温度下测试得出,当温度达到80℃时,对1000ppm氢气的灵敏度已经达到了2.34。随着温度的继续增长,灵敏度出现了先增长后减小的趋势。当温度在220℃时灵敏度已经达到了最大值6.13,响应恢复时间也比较少。在220℃下对氢气进行了超灵敏实验得出,Cd掺杂浓度2%的ZnO:Cd薄膜传感器件对氢气的最小灵敏度为50ppm。在低温80℃下和220℃下薄膜型气敏传感器都具有良好的可重复性。当样品在空气中暴露5个月后,掺杂浓度为2%的ZnO:Cd纳米棒比纯ZnO的结构更稳定。本文研究可以得出ZnO:Cd纳米棒对于发展蓝紫发光器件以及开发低温和超灵敏氢敏器件具有重要的研究意义。
[Abstract]:ZnO is an important new type of semiconductor metal oxide material with the characteristics of piezoelectric, optoelectronic and high charge mobility. It is widely used in light emitting diodes, varistors and other fields. Gas sensors and luminescent devices are also widely used. In recent years, many experts and scholars, by doping other elements to improve the gas sensitivity and luminescence characteristics of ZnO CD and Zn belong to the second secondary family, physical and chemical properties are similar, it is easy to realize CD instead of ZnO, forming substitution doping, thus making the structure of ZnO. The crystal size of ZnO decreases and the band gap becomes narrower after doping with CD. It is of great significance to study the gas sensing and luminescence characteristics of ZnO. In this paper, ZnO and ZnO:Cd nanorods were successfully synthesized by low temperature hydrothermal method with zinc nitrate hexahydrate as Zn source and cadmium nitrate tetrahydrate as CD source. The crystal structure, surface morphology and internal stress of the samples were characterized by X-ray diffractometer, field emission scanning electron microscope and laser confocal Raman spectroscopy, respectively. The prepared samples were evenly spin-coated on the cut glass substrates to make thin film samples. The transmission of the films was analyzed by double beam ultraviolet / visible / near infrared spectrophotometer. The optical band gap width was determined by simple calculation. The photoluminescence characteristics of ZnO and ZnO:Cd nanorods were studied by fluorescence / phosphorescence spectrophotometer. The results show that the crystal structure of pure ZnO and ZnO:Cd nanorods with different doping concentrations are hexagonal wurtzite doping, which makes the crystal particle size decrease and the optical band gap width narrow. The reasons for the decrease of band gap are as follows: one is the existence of tensile stress in the crystal. Second, other impurity energy levels are formed in the band gap of ZnO. When the CD doping amount is 2, we can see that there is a blue luminescence peak at 2.67e V, but this peak is not found in other samples. It is found that the blue photoluminescence peak is due to the transition of electrons from the bottom of the conduction band to the Zn vacancy. It can also be seen from the photoluminescence peak that the intensity of the purple photoluminescence peak of ZnO near 2.90e V is enhanced by CD doping. The hydrogen sensitivity of ZnO:Cd and pure ZnO films with different doping concentration at 150 鈩，

本文编号：1795884