【作者】 丁卫华；

【导师】 翁文剑；

【作者基本信息】 浙江大学 ， 材料学， 2003， 硕士

【摘要】 ZnO属于六方晶系6 mm点群，晶体在c轴垂直面上的电性和弹性都是对称的，因而c轴择优取向的多晶薄膜能够具有单晶那样的压电性和光电性质，而具有平整均匀的表面形貌则是ZnO薄膜作为一种集成功能薄膜应用性能的保证。此外，氧化锌作为压电薄膜则应该具有较高的电阻率，而氧化锌在集成光学上的应用则要求有着较高的透过率和折射率。 本论文对氧化锌晶体结构，氧化锌薄膜的压电和光电特性，作为薄膜外延生长缓冲层和集成光学上的应用及前景进行了综述，同时对氧化锌薄膜的制备方法以及溶胶凝胶法制备薄膜的特点进行了介绍。 本论文研究了在载波片和Si(001)上溶胶凝胶旋涂法的制备工艺对薄膜的结晶、取向状况以及薄膜形貌的影响，探讨了溶胶凝胶旋涂法制备的氧化锌薄膜的形成过程，同时引入两步热处理方法来优化薄膜的结构。 运用XRD、SEM、TEM以及AFM等对所得的样品进行了分析和研究，结果表明：采用不同的旋涂工艺得到不同的薄膜厚度，而采用每次涂膜形成氧化物膜后再进下一次涂膜的方式能更好的保持ZnO薄膜的c轴择优取向生长。由于在ZnO薄膜中掺入Li和Mg能有效提高薄膜结晶过程中的扩散，因此，掺Li和Mg氧化锌薄膜有更好的结晶度和表面形貌平整度。此外，结合高温和低温热处理方法优点的两步热处理法得到的B型薄膜同时具有较好的C轴择优取向性和更为平整均匀的表面形貌。另外，在硅基板上也制备出了良好的C轴择优取向性的掺杂氧化锌薄膜。 同时运用高阻仪、紫外可见光谱、棱镜耦合仪等对掺Li和Mg的氧化锌薄膜光电性能以及能带结构进行了研究，可以得出以下结论：合适量的掺Li和Mg有利于提高氧化锌薄膜的电阻率，其最大值可达11.18×10~7Ωcm，完全满足氧化锌薄膜作为一种压电薄膜的应用。Mg离子的半径大于Li离子，所以它的掺入能提高薄膜的相对密度，从而提高其折射率。随着Li掺杂浓度的增大光学能隙继续增大，这是因为掺杂的Li改变了锌在导带下的次能级，使之由浅变深，在Li/Zn摩尔比为0.2时其光学能隙开始降低 浙江大会硕十甘位伯式 （3三 7eV），这是因为过多的 L i使得简并导带的形成导致禁带变冬到厂致，这表明h的掺 入能改变氧化锌的禁带宽度。此外合适量的 Li：ZflO和（Li，Mg）：Zflofk膜在可见光区的 平均透射率在80％以上，而过多的掺入由于带入了 ＊的缘故，使得其透过率下降。因 此，本研究中获得的掺 Li和 Mg的 ZnO薄膜的各方面性能指标能够满足作为集成光电薄 膜应用的要求。 本论文通过对Li：ZnO以及（Mg人中ZnO t4膜的分析研究，深入地探讨了旋涂方式、热 处理温度、掺杂浓度和热处理方式等对ZnO ＠膜结晶取向的影响以及电学和光学性能的 影响关系等，对Z；。O＠膜在集成压电以及光电等方面的进一步研究和发展有重要理论和 实践指导意义。更多还原

【Abstract】 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.更多还原