| Zinc oxide (ZnO) is an importantⅡ-Ⅳcompound semiconductor with a wide direct band gap of 3.3eV at room temperature and a large excitation binding enery of 60meV. ZnO films have many realized and potential applications in many fields, such as surface acoustic wave devices, transparent electrodes, ultraviolet photodetectors, light emitting diodes, piezoelectric devices, gas sensors and planar optical waveguides, etc, due to their excellent optical and piezoelectric properties. In recent years, with widespread developing in short wavelength luminescent devices, ZnO films have received a great attention as a direct wild-gap semiconductor, and it will be another hostspot following GaN in the research of photo-electronic fields.In the present work, high qulity ZnO films were deposited on quart glass (SiO2) substrate by radio frequency (rf) magnetron sputtering, and the structural, surface appearance, element, film thickness, optical and waveguide properties were investigated by using many analyzing approaches. The specific contents of the dissertation are as follows:At first, we investigated the effect of working pressure on the structural and optical properties of ZnO films. By means of XRD diffraction spectra, the structural and crystal quality of ZnO films were analyzed, it was found that ZnO films deposited under the condition of lower working pressure were high c-axis preferred orientation and when the working pressure became lower,the crystal quality of films was enhanced at first, damaged laterr.When the working pressure is 0.5 Pa, the crystsl quality of films deposited is best.The surface appearance and the effect of working pressure on the roughness of thin film surface were investigated by atom force microscopy (AFM). The result showed that the arithmetic average roughness (2.579nm) and the mean square roots(3.245nm) of the films are minimum and the crystal quality of the films is best,as the working pressure is 0.5 Pa, the result of AFM is agreed with X-ray. The composition of thin film and the relation between working pressure and the deposition rate were analyzed by Rutherford backscattering (RBS). The rate of Zn and O element in ZnO films is about of 1:0.96 calculated by their Counts from RBS, which is almost of same with the target material. The ZnO/SiO2 optical waveguide structures were fabricated successfully, and the effective refractive index of TE and TM mode for some samples were measured by prism coupling method at a wavelength of 633nm, and so the indexes refractive of the films were calculated by using the effective index refractive. It was found from the measured results that the indexes refractive of the films are less than of the bulk materials and under the condition of lower sputtering pressure, the indexes refractive of ZnO films is more closer to bulk crystal Refractive index.Secondly, we investigated the effect of sputtering power on the structural and optical properties of ZnO films. By means of XRD diffraction spectra, the structural and crystal quality of ZnO films were analyzed, it was found that ZnO films deposited under the condition of biger sputtering power (100W,120W,150W) were high c-axis preferred orientation and Higer sputtering power is benefit to enhance the quality of ZnO films. The surface appearance and the effect of sputtering power on the roughness of thin film surface were investigated by atom force microscopy (AFM). It was found that increasing sputtering power is conducive to increasing grain size, improving the crystal quality and decreaseing the roughness of that thin film surface. When the sputtering powers are 120W and 150W, the ZnO/SiO2 optical waveguide structures were fabricated successfully. The properties of ZnO/SiO2 optical waveguide have been evaluated by using prism coupler method, and the effective refractive index of TE and TM mode for some samples have been measured by using prism at a wavelength of 633nm, and so the indexes refractive of the films were calculated by using the effective index refractive. It was found from the measured results that the indexes refractive of the films are less than that of the bulk materials, and under the condition of biger sputtering power, the indexes refractive of ZnO films is closer to Crystal Refractive index.Thirdly, we investigated the effect of temperature of substrate on the structural and optical properties of ZnO films. By means of XRD diffraction spectra, the structural and crystal quality of ZnO films were analyzed. The result showed that the temperature of substrate exerted important influence on the crystal quality of films. Higher temperature of substrate was investigated to be benefit to form a high quality ZnO film with high c-axis preferred orientation. When the temperature of substrate was heated to 300℃, the intensity of diffraction peak of ZnO films with (002) is weakest and the lattice constant of c axis is 0.0352(?) littler than standerd attice constant of bulk materials, however, the c axis lattice constants of ZnO films deposited in the other temperatures are biger than standerd attice constant, the result indicated that,when the temperature of substrate was 300℃, the growth mode of ZnO films was changed. The surface appearance and the effect of temperature of substrate on the roughness of thin film surface were investigated by atom force microscopy (AFM). The properties of ZnO/SiO2 optical waveguide have been evaluated by using prism coupler method, and the effective refractive index of TE and TM mode for some samples have been measured at a wavelength of 633nm, and so the indexes refractive of the films were calculated by using the effective index refractive. It was found from the measured results that the indexes refractive of the films deposited under different temperature of substrate are less than of the bulk materials. The UV-visible spectrophotometer analysis indicates that average optical transmittance of ZnO films deposited under different temperature of substrate is more than 80% to visible light, band gap of the films is from 3.32 to 3.35eV, which is closer to that of the bulk materials.Finally, we investigated the effect of sputtering time on the structural and optical properties of ZnO films. By means of XRD diffraction spectra, the structural and crystal quality of ZnO films were analyzed. The result showed that the longer of time of sputtering the better of the crystal quality of films. The surface appearance and the effect of deposition time on the roughness of thin film surface were investigated by atom force microscopy (AFM). The properties of ZnO/SiO2 optical waveguide have been evaluated by using prism coupler method, and the effective refractive index of TE and TM mode for some samples have been measured at a wavelength of 633nm, and so the indexes refractive of the films were calculated by using the effective index refractive. It was found from the measured results that the indexes refractive of the films are less than of the bulk materials, and the indexes refractive of ZnO films deposited under longer deposition time is more closer to Crystal Refractive index. |
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