电化学沉积法制备ZnO薄膜的研究

【作者】 蒋松涛；

【导师】 吴孟强；

【作者基本信息】 电子科技大学 ， 电子信息材料与元器件， 2007， 硕士

【摘要】 ZnO是一种六角纤锌矿结构的宽禁带直接带隙半导体材料,室温下禁带宽度为3.37eV,激子束缚能高达60meV,具有高的化学稳定性以及优异的光电、压电特性等,应用领域十分广泛,是目前电子信息材料与器件领域的研究热点之一。本文首先对ZnO薄膜的功能性质、发展情况、制备技术和应用前景等进行了比较和概述,阐述了ZnO在结构、光电、气敏、压敏和压电方面的特性及应用;然后根据实验工作中对电化学沉积技术的研究实践,从基本理论、工艺设备、技术手段三个层次,简述了电化学沉积法的原理和应用;并对采用电化学沉积方法制备ZnO薄膜的机理、工艺过程及ZnO薄膜的结构与性能进行了系统的研究。本论文利用电化学沉积方法在ZnO薄膜材料制备方面开展了一系列工作,详细研究了在两种不同溶液(水溶液与非水溶液)体系中制备ZnO薄膜的工艺条件与薄膜结构与性能的关系。本研究采用标准的三电极电化学沉积系统,以ITO玻璃基片为工作电极,铂片为对电极,通过盐桥连接的Ag/AgCl电极作为参比电极。本论文首先通过对ITO玻璃基片在不同电解液中的循环伏安特性进行研究,对电化学沉积ZnO薄膜的生长过程及反应机理进行了分析,并确定了溶液的浓度比、沉积电位、温度、pH值等基本工艺参数的范围。分别在以硝酸锌为主盐的单盐水溶液体系以及以氯化锌为主盐的非水溶液(以二甲亚砜为溶剂)体系下,采用恒电位阴极沉积法在ITO玻璃基片上成功制备了有一定厚度的ZnO前躯体薄膜。通过对所制得的ZnO薄膜样品进行XRD、SEM、AFM、XPS及光学、电学性能的测试分析,探讨了不同沉积条件及退火处理对ZnO薄膜结构与性能的影响,得到了电沉积ZnO薄膜的最佳工艺参数。研究结果表明,电化学阴极沉积法制备的ZnO薄膜为六角铅锌矿结构;在水溶液体系下,Zn(NO3)2浓度为0.05～1.0mol.L-1、沉积温度为60～70℃、沉积电位为-0.8～-1.1V条件下可以获得均匀、致密结晶的ZnO薄膜,薄膜在可见光区(>400nm)均表现出了较好的光学透过性质,平均透光率超过70%,光学带隙在3.35eV左右,薄膜电阻率在1 ? ?cm左右;在非水体系下,ZnCl2浓度为0.05 mol.L-1、温度为70℃、沉积电位为-0.9V条件下得到的薄膜性能最优,达到超过80%的可见光透过率,光学带隙在3.5eV左右,电阻率为6 ? ?cm;经过退火处理能提高ZnO薄膜的致密度与结晶性,使透光率增大,电阻率升高,且Zn/O原子比更接近于1。更多还原

【Abstract】 ZnO, which has a wurtzite structure, is a wide bandgap, low dielectric constant and high chemical stability semiconductor. In recent years, zinc oxide (ZnO) has attracted intense attention due to its interesting properties, such as transparency in the visible, acoustic characteristics, high electrochemical stability, large electromechanical coupling coefficient, direct band gap and so on. At first, we overviewed functional properties, recent development and preparation techniques of ZnO thin film. Then we have systematically described elementary principle and technical equipment of electrochemical deposition method. Electrochemical deposition method is a simple and convenient method, has been extensively used in the synthesis of many different types of materials. It has several advantages such as low processing temperature, possibility of large-scale deposition, low cost, higher deposition rate, controllable film thickness and morphology. This paper was focused on the growth of ZnO films in two different solutions. The mechanism, preparation and characterization of ZnO thin films’electrodeposition were studied in detail.Experiments are performed in a conventional three electrodes electrochemical cell. The ITO-coated glass, a platinum sheet and an Ag/AgCl electrode were used as the working, counter and reference electrodes. Firstly, the mechanism of electrochemical reaction and the range of technical parameters, such as the solution concentration, pH value, deposition potential and temperature, were roughly determined from the cyclic voltammetry experiment. The effects of different electrodeposition conditions on the microstructures of ZnO thin films were investigated in detail. X-ray diffraction measurement showed that the as-grown films were of hexagonal wurtzite structure. The film morpHology was observed with a scanning electron microscope (SEM) and atomic force microscope (AFM). The XPS analysis presents a Zn/O composition close to stoichiometric. The results indicated that in aqueous solution the films obtained at 0.05M-0.1M Zn(NO3)2, -0.8V~-0.9V potential and 65-70℃were compact , homogeneous and (002) oriented, the transmission values in the visible wavelength was upto 70%. In non-aqueous solution, the best technical parameters were 0.05 mol.L-1, 70℃and -0.9V. High optical transmission values upto 80% was obtained. The microstructures of the ZnO thin films could be improved after annealing treatment.更多还原