ZnO粉体的水热合成及其形貌变化

【作者】 赵伟；

【导师】 周剑平；

【作者基本信息】 陕西师范大学 ， 凝聚态物理， 2010， 硕士

【摘要】 ZnO作为一种直接禁带半导体材料,具有压电,光电和掺杂过渡族元素后表现出的磁性。由于其禁带宽度为3.37eV和激子结合能为60eV,作为氮化镓的良好的代替品,有望成为新一代的发光材料。在发光二极管,和激光器上有很大的应用前景,成为这几年的研究热点。在当前很多制备ZnO的方法中水热法作为一种工艺简单,廉价的方法被广泛的用于制备ZnO粉体。但用水热法制备ZnO的实验中影响实验结果的因素多,实验的规律性差。对于水热法实验生成的具有花状结构的ZnO生成机理的研究报告并不是很多。对于ZnO的稀磁性能的研究,用Co掺杂ZnO的系统研究也鲜有报告。本文用水热法制备ZnO,针对以上所讲的三个方面,主要的研究内容和结果如下：第一：在不同的反应条件下进行实验,研究不同反应条件对生成的ZnO形貌的影响,分别改变温度,时间,反应的pH值,和在实验中加入不同的添加物。反应得到的结论是：随着时间的增大生成的ZnO颗粒越来越大,结晶度越完整。而在温度逐渐升高的时候,ZnO是由颗粒状的小晶体到棒状的ZnO晶体再到具有三维结构的ZnO纳米花结构的一个变化过程。pH值对于ZnO形貌的影响是随着pH值的增大颗粒尺寸明显减小。花状结构出现在pH为9和9.5时。不同的添加物对形貌也有很大的影响。第二：花状结构ZnO的生长过程和生成机理的初步的研究,并对其发光性能做了探讨。生成的过程是以ZnO棒表面的缺损处为节点,形成二维的十字状结构,继而再以十字交叉点为节点,生成三维的ZnO结构。ZnO的PL光谱分析结果表明随着pH的增大,400nm附近的本征发光峰相对强度逐渐变弱,由深能级缺陷引起的600nm附近发光峰相对强度逐渐变大,并且出现大范围的蓝移现象。对退火前后ZnO的PL谱的研究表明,退火能有效的减少ZnO中的缺陷浓度。第三：用过度族元素Co掺杂制备ZnO的稀磁半导体。表明在普通的水热法中,Co在ZnO体系中的最大掺杂浓度为5%,同时还研究了不同的水热环境对Co掺杂浓度的影响,研究结果表明随着pH值的增大,Co在ZnO中的掺杂浓度会稍有提高。Co掺杂使得ZnO的各向异性减弱,出现的较短ZnO纳米棒。通过磁滞回线的测试,得到了Co掺杂ZnO在室温下具有铁磁性。更多还原

【Abstract】 ZnO is a direct band gap semiconductor with piezoelectric and photoelectric properties. Because of its band gap of 3.37 eV and the exaction binding energy of 60 meV, it will be a good substitute for GaN and expected to be a new generation of light-emitting material. In the light-emitting diodes and lasers, ZnO has a great prospect and become a research focus in recent years.Hydrothermal method, as a simple and cheap route, is widely used to prepare ZnO powders. And the preparing process of ZnO powders is affected by many factors, thus leading to a bad law. The mechanism of flower-like structure ZnO is seldom reported. And the effect of Co doping on the diluted magnetic properties of ZnO prepared by hydrothermal method is also rarely reported. This research focus on the preparation of ZnO powders with the hydrothermal method and the discuss the formation, and the main contents and results are as follows:First:The impact of different reaction conditions, i.e., the temperature, time, reaction pH, and different additives on the morphology of ZnO was investigated. We conclude that the particle size and crystallization increase with the reaction time. However, with temperature gradually increasing, the formation of ZnO crystal changes from a granular shape to a rod shape and then to a three-dimensional nano-structure. The particle size of ZnO decreases obviously with the pH value. The flower-like structure appears in the pH value of 9-9.5. The additives also a effect the morphology of ZnO powders.Second:ZnO flower-like structure formation of the growth process was studied preliminarily, and their luminescent properties was also researched. The process generated by the surface defect ZnO rods for the nodes to form a two-dimensional cross-like structure, and then again to cross the intersection for the node, generate three-dimensional structure of ZnO. The density of intrinsic emission peak around 400nm was inhibited, and the deep level defect emission peak around 600 nm was increased and shown a big range of blue shift with a higher pH value. The study on PL spectrum of ZnO powders before and after annealing shown that annealing can reduce the concentration of defects in ZnO effectively.Third:Diluted magnetic semiconductor of ZnO was prepared by doping the transition elements Co. The samples were prepared by ordinary hydrothermal method, and the results indicated that the maximed doping concentration is 5% in the ZnO system. The impact of different hydrothermal environments on Co doping concentration was also studied. The result showsed that the doping concentration of Co was increasing with a higher pH value and anisotropy of ZnO was weakened by the doping of Co. Ferromagnetic properties of Co-doped ZnO were obtained at room temperature by the test of hysteresis loop.更多还原