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研究了sol-gel法制备Bi_4Ti_3O_(12)铁电薄膜和该薄膜的电学性质、光学性质,以及Bi_4Ti_3O_(12)晶体的热力学唯象理论。主要内容如下:①以正丁醇钛和硝酸铋为原料,合成了稳定均匀的Bi-Ti溶胶和凝胶。研究了乙醇胺的催化作用机理和前驱体溶液的水解、聚合反应机理。发现乙醇胺与Bi~(3+)离子的络合反应阻止Bi离子的水解。研究了干凝胶的晶化过程,发现干凝胶在晶化过程中有三个中间相存在。②分别在Pt/Ti/Si、Si、Y-ZrO_2、SrTiO_3(100)和石英玻璃基片上生长出c轴取向的Bi_4Ti_3O_(12)薄膜。薄膜的取向程度受到衬底表面结构和Bi_4Ti_3O_(12)晶体的晶面能的制约。前驱体溶液的酸碱度对薄膜的结晶性有较大影响。③研究了Bi_4Ti_3O_(12)/n-Si薄膜的C—V特性,从理论上分别推导出理想的和有载流子注入的MFS结构的C—V曲线的回滞方向。④研究了c轴取向Bi_4Ti_3O_(12)纳米薄膜的光学吸收性能和量子尺寸效应引起的光能隙漂移现象。薄膜的能隙宽度强烈依赖于薄膜的晶粒大小。⑤用Landau-Ginsburg-Devonshire形式系统地研究了在应力条件下Bi_4Ti_3O_(12)的铁电性质、介电性质和压电性质,以及在应力诱导下的Bi_4Ti_3O_(12)居里温度的漂移现象。
The electrical properties, optical properties and thermodynamic phenomenology of Bi_4Ti_3O_ (12) ferroelectric thin films prepared by sol-gel method were studied. The main contents are as follows: ①Ti-butoxide and bismuth nitrate were used as raw materials to synthesize a stable and uniform Bi-Ti sol and gel. The catalytic mechanism of ethanolamine and the mechanism of hydrolysis and polymerization of the precursor solution were studied. It was found that the complexation of ethanolamine with Bi ~ (3+) ions prevented the hydrolysis of Bi ions. The crystallization process of xerogel was studied and it was found that there are three intermediate phases in xerogel during the crystallization process. ② c-axis oriented Bi_4Ti_3O_ (12) thin films were grown on Pt / Ti / Si, Si, Y-ZrO_2, SrTiO_3 (100) and quartz glass substrates, respectively. The degree of orientation of the film is governed by the surface structure of the substrate and the plane energy of the Bi_4Ti_3O_ (12) crystal. The pH of the precursor solution has a greater impact on the crystallinity of the film. (3) The C-V characteristics of Bi_4Ti_3O_ (12) / n-Si thin films were studied and the hysteresis direction of C-V curves of ideal and carrier-injected MFS structures were deduced theoretically. (4) The optical energy gap shift caused by the optical absorption and quantum size effect of c-axis oriented Bi 4 Ti 3 O 12 thin films was investigated. The energy gap width of the film strongly depends on the grain size of the film. ⑤ Ferroelectric properties, dielectric properties and piezoelectric properties of Bi_4Ti_3O_ (12) under the stress conditions and the Curie temperature of Bi_4Ti_3O_ (12) under stress-induced stress are studied systematically by Landau-Ginsburg-Devonshire model.