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The Synthesis and Application of Different ZnO Nanostructures with Macroscale in Appearance

Author: ZhangNing
Tutor: ZhuZiQiang；YuKe
School: East China Normal University
Course: Microelectronics and Solid State Electronics
Keywords: Zinc oxide Nanostructures macro Sensor Schottky barrier diode Laser
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 103
Quote: 0
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Abstract

ZnO is a direct wide band gap semiconductor (room temperature band gap of 3.37eV, the exciton binding energy of 60meV), has a huge potential in the electronics and light emitting devices. ZnO nanostructures exhibit material is significantly different chemical and physical properties, and is currently one of the hot spots of nanomaterials. Inspired by macroscopic carbon nanotubes, described in this paper are prepared the various macroscopic scale morphology of ZnO nanostructures and their optical sensors and laser exploratory research and application. The main conclusions of the paper are as follows: 1. Using conventional thermal evaporation method in the case of metal-catalyzed the ZnO nanostructures macro of. This crystal growth thermal evaporation method not only preparation process is simple, low cost, and with good reproducibility. In addition to the synthesis of ultra-long ZnO nano comb test, but also prepared for the first time out of the ultra-long ZnO nanorod, nanobelt, the diameter and thickness of only a few hundred nanometers in length reached mm even centimeter; the fractal we prepared ZnO macro-structure, from a large number of nanorod self-assembly generation, has a great surface than on the international has not reported this unique structure. One hand, the macro ZnO nanostructures having the characteristics of the nano-materials, on the other hand having a macroscopic morphology of avoiding the use of complex micro-operations (such as the use of atomic force microscopy, scanning electron microscopy) the disadvantage of poor controllability, it easy to combine traditional craft applications in optoelectronic devices. In addition, we take advantage of the energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy of these different morphologies macro morphology of ZnO nanomaterials, structure and composition of research and analysis of the growth mechanism of ZnO with different morphologies macro. We found that Cu and CuO to change between the macroscopic size plays an important role in the growth process of the ZnO nanomaterials by nano-sized. 2 based on fractal ZnO macro-structure having a great surface, the ratio of this characteristic, we made the resistive type gas sensor and a humidity sensor. By the same concentration of different gases (hydrogen, ammonia, hydrogen sulfide, and nitrogen dioxide gas) test, and found that the gas sensor is very sensitive reaction of hydrogen sulfide gas: its resistance changes. And from theoretically analyzed the reasons for having such a good sensitivity in the sensor. In addition, we found when tested fractal ZnO the feathery macro structure of the humidity sensor, the humidity sensitivity of the sensor for different changes in humidity, showing a better linearity. In the high humidity, the linear trend presents slight fluctuations, we discuss the reasons for this saturation of high humidity. Exist between the metal semiconductor Schottky contact this theory, we take advantage of the large size diameter long single ZnO nanorod successfully made the Schottky diode and metallic silver. Through the diode current - voltage (Ⅰ - Ⅴ) and found the process to solve the problem of the past of ZnO nanobelts and nanowires diameter metal electrode when there is a bad contact Schottky diode. The test results show that the diode having a good rectifying characteristic. In addition, we were in different temperature and the concentration of NH _{diode current-voltage curves of such ZnO were tested in the atmosphere of 3} and found that the diode only has good thermal stability, but also on the different concentrations of ammonia The gas has a higher sensitivity. Finally, we discuss the mechanism of ultra-long ZnO nanorod metal contact rectifying phenomenon. Based on ZnO materials have unique optical and electrical properties, we make use of ZnO ultra-long nano made of a new type of laser. In the long ZnO nano with surface hydrogen plasma treatment, low-voltage DC excitation, we first discovered by the excitation light phenomenon. Although the ZnO powder and heterojunction electrically stimulated luminescence is not uncommon, but this phenomenon emitting laser by the n-type ZnO single crystal after hydrogen plasma treatment in the international yet reported. By testing found that the excitation spectrum mainly in the UV region and the blue region. Wherein the ultraviolet region of the laser light may be coherent laser feedback caused by random. Is worth noting that the three laser lines in the blue region is very unique and rare, and all three also showed some regularity. We also found that the laser in a hydrogen atmosphere, the generation of secondary and multiple light emitting. Finally, by studying the current-voltage curve before and after the luminous, a simple analysis of the mechanism of this laser light that hydrogen plays an important role in the process of the Blu-ray emission of the ZnO lasers.

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