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

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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.