Synthesis of hybrid nano-structured ZnO crystal by nanoparticle-assisted pulsed laser deposition and their application

本项目的目的是为利用纳米粒子辅助脉冲激光沉积法合成的纳米结构ZnO晶体开发电光器件奠定基础。本文的研究课题和成果总结如下：我们已经成功地在预退火的c-cut蓝宝石衬底和a-cut蓝宝石衬底上合成了垂直排列和水平排列的ZnO纳米线。研究发现，通过改变激光辐照强度和激光烧蚀的重复频率，可以控制纳米线的表面密度。研究证实了垂直排列ZnO纳米线具有场发射能力，并利用垂直排列ZnO纳米线制备了可见光发射器件。为了观察单根ZnO纳米线的光致发光，研究了一种处理ZnO纳米线的方法。在乙醇中超声波去除生长基质上的纳米线，并通过介电泳力将单个纳米线收集到一对微电极上。3)激光在ZnO纳米线中的作用，当在355nm处用ns脉冲激发单根ZnO纳米线时，观察到激光在纳米线中的微腔效应作用。得到了每根纳米线的阈值激励功率为13.6 mW。

The aim of this project is to establish the basis for the development of electro-optic devices using nano-structured ZnO crystals which are synthesized by a newly-developed nanoparticle- assisted pulsed-laser deposition method. The subjects and the achievements are summarized as follows.1) Controlled growth of ZnO nanowires We have succeeded in synthesizing vertically-aligned and horizontally- aligned ZnO nanowires using pre-annealed c-cut sapphire and a-cut sapphire substrates, respectively. It was found that the surface density of the nanowires can be controlled by changing the laser fluence and repetition rate for laser ablation.2) Field emission from nanowires It was confirmed that the vertically-aligned ZnO nanowires have a capability of field emission and a visible light emitting device are fabricated using a vertically-aligned ZnO nanowire field emitter.2) Handling of nanowires In order to observe the photoluminescence from a single ZnO nanowire, a handling technique for ZnO nanowires was developed. The nanowires were removed from the growth substrate by ultra-sonication in ethanol and single nanowire was collected onto a pair of microelectrodes by dielectrophoresis force.3) Laser action in single ZnO nanowire When single nanowire was excited by ns-pulse at 355 nm, laser action with a help of micro-cavity effect in the nanowire was observed. A threshold excitation power of 13.6 mW per single nanowire was obtained.