One-dimensional Tungsten Oxide&Zinc Oxide Nanowire Arrays:Synthesis And Optoelectronic Devices

Nanomaterial and Nanotechnology are the most excited and advanced research filed. One-dimensional (1D) metal oxide nanomaterial is an important class of advanced functional materials. In this paper, lare area and uniform Zinc Oxide and Tungsten Oxide Nanowire Arrays have synthesized by thermal evaporation and chemical vapor deposition method, which are the most typical metal oxide materials. This research is focuse on the one-dimensional Zinc Oxide and Tungsten Oxide nanowire arrays synthesis and application in the field of new type optoelectronic devices, such as Field-emission devices, photoelectrochemical cell, UV photodetector and Light-emitting diode. In Chapter1, current reaearch activities related to the synthesis of1D semiconductor nanostructures by various growth methods and their optoelectronic device applications are reviewed. Chapter2-5describe the synthesis method and application of zinc oxide and tungsten oxide nanomaterials. The detail information about innovation and results in this paper are list as follow:(1) Large area and uniform W18O49and W20O58nanowire arrays, there-dimensional (3D) WO3network nanostructure were synthesized by a simple thermal evaporation method. This three kinds of tungsten oxide nanostructure were detail characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. We reported the growth and field emission properties of tungsten oxide nanowire arrays on highly flexible, highly conductive, and highly robust carbon cloth substrate. Field emission with a low threshold field of～4.3MV/m, and high level emission current density12mA/cm2were observed form the tungsten oxide nanowire arrays. The emission stability was examined at an avertage emission current density of5.25m A/cm2for1hour, no observed and the fluctuation is～5%. This finding opens up great opportunities to make light-weight and rollable field emission displays.(2) Due to the uniqe and promising physical and chemical properties, tungsten oxide nanomaterial represents an important member of visible-light-driven photocatalysts.3D WO3nanostructure were grown on carbon paper by a catalyst-free reactive vapor deposition process, which exhibit a good photoelectrochemical property and visible driven photocatalytic performance. Also, double layer WO3nanowire arrays show photoelectrochemical current enhancement, due to the light trapped and absorption enhanced by the double layer structure. The highest IPCE efficiency is about73%at325nm, and total photoelectrochemical efficiency under one sun (AM1.5G) is about0.5%. Noble metal (Au, Ag, Pt, Pd) nanoparticles were coating on the surface of tungsten oxide nanostructure by self photocatalysis active. The WO3nanowire arrays photoelectrochemical property can raise by Au nanoparticles coating, with the localized surface plasmonic resonance effect.(3) Many research about zinc oxide nanostructure UV photodetectors, but the highly photocurrent and fast response time are two major contradictions in ZnO nanowire UV photodetectors. Well-crystallized ZnO nanowire arrays were grown by chemical vapor deposition method. The diameter of ZnO nanowire can tunable by control of the vacuum pressure in fabtication chamber. A simple ZnO nanowire UV photodetector was prepared by coated with a piece of ITO glass which was splited to two electrode partten. The fabricated ZnO UV photodetector shows0.14mA photocurrent and several millisecond response and reset time. In additional, WO3nanowire UV light response has also studied.(4) Tunning the band-gap of ZnO material by band-gap engineerging method is a significant reaearch filed. Wavelength tunable light-emitting diodes (LEDs) of GaxZn1-xO nanowire arrays are demonstrated by a simple modified chemical vapor deposition heteroepitaxial growth on p-GaN substrate. As gallium atom has similar electronegativity and ion radius to zinc atom, high level Ga doped GaxZn1-xO nanowire arrays have been fabricated. As x value gradually increases from0to0.66, the near-band edge emission peak of GaxZn1-xO nanowires shows a significant shift from378nm (3.28eV) to418nm (2.96eV) in room temperature photoluminescence (PL) measurement. Importantly, the electroluminescence (EL) emission of GaxZn1-xO nanowire arrays LED continuously shifts with a wider range (-100nm), from the ultraviolet (382nm) to visible (480nm) spectral region. The presented work demonstrates the possibility of band-gap engineering of low-dimensional ZnO nanowires by gallium doping and the potential application for wavelength-tunable LEDs.In summary, our research shows that tungsten oxide and zinc oxide nanowire arrays have widely application in the field of flexible electronics, photocatalyst, photoelectrochemical cell (water splitting), nanowire-based sensors and wavelength tunable LEDs.