Characterization of ZnO Thin Film and Its Applications on Communication Devices and Liquid Sensors
| Autor: | Walter Water, 水瑞鐏 |
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| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 Poly-crystal ZnO films with c-axis (002) orientation have been successfully grown on the silicon and quartz substrate by RF magnetron sputtering technique. The deposited films were characterized as a function of deposition temperature, argon-oxygen gas flow ratio, and RF power. Crystalline structures, stress and surface roughness characteristics of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurement. The preferred c-axis orientation of ZnO films can be grown at low RF power and low substrate temperature condition. Postdeposition annealing ZnO films in vacuum circumstance were found to relieve stress, improve rough surface and increase resistivity one order. ZnO film has better piezoelectric characteristics after postdeposition annealing process, and then a delay-line resonator was fabricated and showed a large return loss of 42dB at the center frequency about 2GHz after annealing for 400°C one hour in vacuum. An experimental study of Love wave devices based on ZnO/90° rotated ST-cut quartz by different thickness of ZnO films is also presented. Phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency have been studied as a function of layer thickness. The maximum electromechanical coupling coefficient is obtained for 1.8mm ZnO film and near zero temperature coefficient of frequency is obtained for 2.6mm ZnO film for a wavelength of 40mm, respectively. In order to fabricate sensors with higher sensitivity, the effect of substrate temperature on the sensitivity of viscosity and conductivity were investigated. The Love wave sensor has higher sensitivity for ZnO films sputtered on unheated substrate than that of on heated substrate. The maximum sensitivity up to -18.77’10-8m2skg-1 of ZnO film with thickness of 1.8mm for a wavelength of 40mm is much larger than SiO2/Quartz structure. The required characteristics of ZnO film for resonator filter and sensor applications are contrariwise. Preferred deposition condition was found to have good film quality for resonator filter and sensor applications, respectively. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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