单晶ZnO纳米线的合成和生长机理研究

用化学气相输运(CVT)方法合成了直径在20～120nm呈单晶结构的ZnO纳米线.利用场发射扫描电 镜(FESEM)、高分辨透射电镜(HRTEM)以及选区电子衍射(SAED)等技术对ZnO纳米线的生长机理和结构进行 了系统研究,结果表明,纳米线的成核与Au Zn合金催化颗粒的饱和度有直接的关系,先饱和的颗粒上纳米线首 先成核.纳米线顶端合金颗粒组成的变化是导致纳米线生长终止的重要原因,大量纳米线的生长不是同时进行 的.本工作提供了支持纳米线气液固(V L S)生长机理的新实验证据,提出了氧化物纳米线的生长机理.

Studies on the Synthesis and Growth Mechanism of Single Crystal ZnO Nanowires

ZnO nanowires with the diameter of 50~100 nm and length up to several tens of microns were fabricated on Au coated Si or sapphire substrates by the reaction between ZnO and graphite powder through the chemical vapor transport (CVT) method. The FESEM, HRTEM and SAED results confirmed that the individual nanowire has the nature of single crystal and the crystal orientation is observed from a ZnO nanowire. New experimental evidences have been provided for the initial and final growth states to support the VLS mechanism for nanowire growth, and a growth mechanism of binary oxide nanowire proposed in the course of studying the growth process of ZnO nanowires systematically. It is considered that the Zn vapor formed by carbothermal reduction is transported to, and reacts with, the Au cluster catalysts on substrates to form Au-Zn alloy droplets. As the droplets become supersaturated by Zn vapor, the extra Zn segregates backward and reacts with the trace of oxygen in the reactor or the oxygen sources produced during the carbothermal reaction to form crystalline ZnO nanowires. The spontaneous growth of a large quantity of nanowires reduces the concentration of Zn in the alloy droplets, which may lead to the termination of nanowire growth.