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Preparations, Properties and Devices of One Dimensional ZnO Nanostructure

Author: YangZao
Tutor: LiuQuanHui
School: Hunan University
Course: Materials Physics and Chemistry
Keywords: ZnO one dimensional nanomaterials preparation method optical property ethanol sensor
CLC: TB383.1
Type: PhD thesis
Year: 2008
Downloads: 788
Quote: 3
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Abstract

Quasi-one-dimensional (1D) nanomaterials, including nanowires (rods), nanoneedles, nanobelts, nanotubes/nanocables, etc, are attracting considerable attention recently. Among these materials, functional oxide semiconductor nanostructures can be used as fundamental ingredients of intellgent systems, because their physical and chemical properties can be tuned through adjusting cation valence state and anion deficiency. In this dissertation, we focus on one dimensional ZnO nanomaterial. A new method of synthesizing ZnO nanorods and ZnO nanoparticles is researched. We discuss the growth factor, the growth mechanism of ZnO nanostructure and study optical property of ZnO nanorods. The optical property of different ZnO nanostructure is discussed. High-quality single-crystalline ZnO nanorod close-packed arrays are successfully fabricated in a substrate-free manner by improving new method. The growth mechanism of ZnO nanorod close-packed arrays is proposed. We report the fabrication and characterization of ethanol sensors with extremely high sensitivity using ZnO nanorod closed-packed arrays as the sensing materials. The ethanol sensing mechanism about it are studyed. N-shape ZnO nanorods are fabricated by the same method. We study growth mechanism and ethanol sensing of N-shape ZnO nanorods. The main contents and conclusions are summarized as:1. We synthesize ZnO nanorods of 25-100 nm in diameter and lengths from 0.2 to 1μm in length. The aspect ratio is 10-40. The results show ZnO nanorods possess a single crystal hexagonal structure. There is few or no structure defect. The growth direction of ZnO nanorods is [0001]. The fabrication of single crystal ZnO nanorod provides a simple inexpensive way for developing its latent application, manufacturing all kinds of nanoelectronic device and the photoelectronic device. It also provide a possibility method for studying the Graetzel solar cell’s electronic transmission mechanism and improving photoelectric transformation efficiency. This new route may be extended to the controllable formation of a wide variety of one-dimensional semiconductor nanomaterial.2. We study affected growth factor of ZnO structure. When other conditions are invariable, The length decreases but the diameter increases with addition of the mass of citric acid at the same temperature;With the rising of the calcining heat, the shape of ZnO changes from rod to granule for a given amount of citric acid and the granules have the obvious reunion. With extension of calcine time, the diameter of ZnO nanorod increases but the length decreases.3. We synthesize ZnO nanorods bythe frontal method. We study optical property of ZnO nanorod by IR,PL,UV-vis. We find that ZnO nanorods have very good crystal quality and the excellent optical property. We discover that the different appearance of ZnO have certain influence on ZnO optical property by studying optical property of ZnO nanorods and ZnO particles.4. ZnO nanorod close-packed arrays are successfully fabricated in a substrate-free manner by improving new method. Each nanorod of ZnO nanorod close-packed arrays grows along the [0001] direction and is single crystalline with an average diameter of 50 nm, and an average length of 0.5μm. The aspect ratio is 10.The ZnO nanorod close-packed arrays show a strong exciton absorption peak at 372 nm in UV–visible absorption spectra, exhibiting a blue-shift relative to the bulk exciton absorption (387 nm). Finally, a new growth mechanism is proposed for the substrate-free preparation of ZnO nanorod close-packed arrays.5. We report the fabrication and characterization of ethanol sensors with extremely high sensitivity using ZnO nanorod closed-packed arrays as the sensing materials. The sensitivity of the sensors is about 10 to 1 ppm ethanol.The high sensitivity is explained in terms of closed-packed surface-depletion and full face contact model. Our results demonstrate that ZnO nanorod closed-packed arrays are very promising materials for fabricating gas sensors.6. N-shaped ZnO nanorods were first synthesized by glacial acetic acid assisted annealing process. These nanorods grow from a thin platelet base and are parallel to each other to form n-shaped ZnO nanorods. The widthes of thin platelet bases range from 50 to 130nm. The diameters of the nanorods are 25～60nm and their lengths are 0.2～0.6um. Sensors realized from n-shaped ZnO nanorods were very sensitive to ethanol gases. The sensitivity was as high as 3.5 at 1 ppm ethanol exposure. These experimental results strongly suggested that n-shaped ZnO nanorods could be an excellent candidate for applications in gas sensors at the industry level.

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