ZnO纳米线的合成与生长机理

采用化学气相沉积系统制备ZnO纳米线,以覆盖一层约5nm厚的Ag薄膜的单晶Si(001)为衬底,纳米线的生长遵循气-液-固(VLS)机理。对得到的样品采用X射线衍射(XRD)和扫描电镜(SEM)进行晶体结构和形貌的表征。XRD结果表明衬底温度在600~700℃时生长的ZnO纳米线具有六方结构和统一的取向。通过扫描电子显微镜分析,比较了生长温度对纳米线直径和长度的影响。实验表明我们可以通过催化剂和温度来实现ZnO纳米线生长的可控。与传统的VLS生长方式不同的是在我们制备的ZnO纳米线顶端并没有看到催化剂颗粒,表明纳米线的生长方式是底部生长,我们对其生长机理进行了研究。

Synthesis and Growth Mechanism of ZnO Nanowires

ZnO is a wide band gap semiconductor (3.37 eV) with higher excitation banding energy of 60 meV. ZnO one-dimensional materials have stimulated much attention due to the promising potentials in extensive applications, ranging form surface acoustic wave filters, optoelectronic devices, and light-emitting diodes. Many techniques have been used to grow ZnO nanowires, such as pulsed laser deposition, metal-organic chemical vapor deposition and template against anodic alumina membrane. Among the various techniques VLS (vapor-liquid-solid) method is favored for the simplicity and high quality products. This method often uses some of catalysts such as Au, Cu, Sn or other additives assist are often used in this method to control the growth process. There were reports about the syntheses of 1D ZnO nanowires arrays via a VLS process. However there is still the difficult problems about the controllable growth of the ZnOnanowires. We obtained ZnOnanowires through VLS method and researched controllability and growth mechanism of ZnO nanowires. ZnO powders were used as source material and the experiment was performed in a horizontal tube furnace. ZnO powders were spread in an alumina boat and place at the center of the furnace tube with temperature of 1350℃. Si(100) substrate covered with Ag catalysts was put down stream with the temperature of 400~800℃ for 30 min. Ar gas (40 sccm: standard cubic centimeter mass) was used as the carrier gas. The prepared nanowires were investigated by X-ray diffraction. The morphology and size distribution of the nanowires were characterized using SEM. Clearly the ZnO nanowires grown at substrate temperature ringing 600~700℃ are highly crystallized and exhibit a typical wurtzite structure. SEM showed that temperature of substrate has important influence on diameter and length of the ZnO nanowires. It was controllable that we can realize the ZnO nanowires growth through the catalyst and temperature. We have not seen that catalyst particle is on the top of ZnO nanowires, it is different from traditional VLS mechanism. The growth mechanism of ZnO nanowires was proposed.