| Zinc oxide (ZnO) is a wide band gap (3.4eV) semiconductor with the hexagonal crystal structure (wurtzite type). ZnO thin films with the c-axis orientation perpendicular to the substrate show excellent piezo-electrical properties and are widely used in piezo-electrical filed. And the dense anjd uniform surface of the films is required when ZnO thin films are used as integrated functional films.In the thesis, the relations between the structures and properties, the applications and prospects of ZnO thin films were reviewed with regard to the fields of piezo-electrical materials, opticai-electrical materials, buffer layers and integrated optical materials. Various preparation methods of ZnO thin films were described.In this work, ZnO thin films were prepared by sol-gel method on the glass substrate in order to study the influence of the preparation techniques on the crystallization, orientation and morphology of the films. We adopted a two-step heat treatment technique to optimize the micrcjstructure of the films, and subsequently discussed the forming process of the ZnO thin films. Two coating approaches were adopted, one was to do next coating after 550癈 heat-treatment (called A coating technique); the other was to do next coating after 100癈 drying, the films coated by several times were heated at 550癈(calIed B coating technique).XRD, SEM, TEM and AFM were used to characterize the crystallization behavior, orientation and surface morphology of the ZnO thin films. It is revealed that the films prepared through A coating technique can get better c-axis orientation than those through B coating technique for a relatively thick films. Li, Mg and both of them were doped into ZnO films, which could improve the crystallization, orientation and morphology. An AFM image of sample LZA-B21 thin film is indicative of the grain growth in the direction perpendicular to the substrate surface. Moreover, the two-step heat treatment method was utilized in the preparation of the films, the films prepared by the first coating with 550 癈 heat-treatment and the second coating with of with 500 癈 heat-treatment (B type films) were highly c-axis oriented with smooth, dense and uniform surface morphology. Highly c-axis oriented ZnO thin films were also grown on Si (001) substrate by the present technique.inElectrometer resistance meter, ultraviolate-visable spectrophotometer, spectroscopic ellipsometer were used to measure the electrical and optical properties. The results for the electrical properties of the thin films are revealed that the doping of Li and Mg could increase the electrical resistivity of the films, the highest electrical resistivity value was 11.18X 107Qcm, which can meet the demands of piezo-electrical devices. Compared with Li doing, Mg doping could increase the film refractive index because of its bigger grain. Moreover, the optical band gap was widened with the increase of Li/Zn moral ratio, but it decreased to 3.37eV when Li/Zn moral ratio came to 0.2, and the optical band gap was independent of Mg/Zn molar ratios. The transmittance of ZnO thin films with suitable doping molar ratio is above 80% in the UV-visible range.The films obtained in this work show to have a high c-axis orientation, smooth and smooth morphology, high electrical resisitivity and high transparency, which can meet the requirements for piezo-electrical devices. This research will also be greatly helpful for understanding the orientation of sol-gel derived films, and for optimizing the preparing conditions.
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