铁电畴纳米尺度压电变形的定量分析
发布时间：2018-08-07 21:42
【摘要】：独特的微观畴结构使得铁电材料具有优越的物理特性和广泛的应用前景,吸引着众多科研工作者的关注。压电力显微镜(PFM)作为在纳米尺度表征铁电材料的重要工具,被广泛地用于铁电畴的研究中。但电畴自身的非均匀性、PFM导电探针激发的电场高度局域性、以及探针与测试材料间复杂的长程力电相互作用,使得PFM测试定量分析还存在着很大困难,这严重阻碍了铁电材料纳米尺度力电耦合的研究,延缓了基于纳米尺度力电耦合性能电子元器件的开发。为此,本论文针对PFM技术,定量分析了铁电畴结构,包括电畴尺寸、畴壁及其厚度等因素,对铁电材料纳米尺度压电变形的影响,相应的研究内容和成果概括如下:第一,建立起了复杂铁电畴结构纳米尺度压电变形的理论框架。通过镜像电荷方法,计算模拟出了导电探针所激发的电场;考虑到复杂铁电多畴结构的极化取向及空间压电张量的非均匀分布,结合弹性本构方程,通过格林函数方法,推导出了复杂铁电畴结构纳米尺度压电位移分析的基本理论框架,为分析电畴尺寸和畴壁对纳米尺度压电变形的影响提供了基本理论框架。第二,计算分析了铁电畴壁处纳米尺度压电响应,揭示出了其特殊纳米尺度压电变形的机理。通过模拟分析发现面外非电荷畴会出现特殊的面内压电响应,而面内电荷畴则会出现特殊的面外压电响应,究其原因在于:面外非电荷畴壁处的面内压电位移来源于长程力电约束反对性的破坏,而面内电荷畴壁处的面外位移响应则源于面内压电位移的不连续。第三,分析了畴壁厚度对铁电畴纳米尺度压电变形的影响,提出了增加畴壁厚度增强纳米尺度力电耦合性能的方案。通过将畴壁视为具有一定厚度的均匀的压电介质,且其压电系数取决于其厚度和相邻电畴的压电系数,并基于此,分析并发现增大畴壁厚度能够增强90非度电荷的横向压电响应和90电荷畴的垂直压电响应,提出了基于增加畴壁厚度提高铁电材料纳米尺度力电耦合性能的新方法。第四,计算分析了电畴尺寸、倾斜畴壁及畴壁厚度对周期性铁电畴纳米尺度压电变形的影响。通过对周期性铁电畴结构的计算分析,发现畴壁的倾斜打破了铁电畴的纳米尺度压电位移响应的对称性,但并没有改变其变形起伏的周期性,且合适的电畴尺寸,才能使得周期性铁电材料同时具有优异的力电性能和较小的性能起伏。本论文的研究工作和研究成果,实现了复杂铁电畴纳米尺度压电变形的定量分析,为PFM技术的应用和发展提供了良好的理论基础和指导,也为制备优异纳米尺度压电性能的铁电材料提供了一定的实验方案。
[Abstract]:Because of its unique microcosmic domain structure, ferroelectric materials have excellent physical properties and wide application prospects, which have attracted the attention of many researchers. As an important tool to characterize ferroelectric materials at nanometer scale, (PFM) has been widely used in ferroelectric domain research. However, the heterogeneity of domain itself and the high localization of electric field excited by PFM conductive probe, as well as the complex long range electric interaction between the probe and the test material, make the quantitative analysis of PFM measurement difficult. This seriously hinders the research of nano-scale electromechanical coupling of ferroelectric materials, and delays the development of electronic components based on nano-scale electromechanical coupling. Therefore, aiming at PFM technology, this paper quantitatively analyzes the effect of ferroelectric domain structure, including domain size, domain wall and its thickness, on ferroelectric nanoscale piezoelectric deformation. The corresponding research contents and results are summarized as follows: first, A theoretical framework for nanoscale piezoelectric deformation of complex ferroelectric domain structures is established. The electric field excited by the conductive probe is simulated by the mirror charge method, considering the polarization orientation of the complex ferroelectric multi-domain structure and the non-uniform distribution of the space piezoelectric Zhang Liang, and combining with the elastic constitutive equation, the Green's function method is used. The basic theoretical framework of nano-scale piezoelectric displacement analysis for complex ferroelectric domain structures is derived, which provides a theoretical framework for analyzing the effects of domain size and domain wall on nano-scale piezoelectric deformation. Secondly, the nanoscale piezoelectric response at the ferroelectric domain wall is calculated and analyzed, and the mechanism of its special nanoscale piezoelectric deformation is revealed. Through simulation analysis, it is found that there is a special in-plane piezoelectric response in the off-plane uncharged domain and a special out-of-plane piezoelectric response in the in-plane charge domain. The reason lies in that the in-plane piezoelectric displacement at the off-plane uncharged domain wall originates from the failure of the long-course electrically constrained opposition, while the out-of-plane displacement response at the in-plane charge domain wall is due to the discontinuity of the in-plane piezoelectric displacement. Thirdly, the effect of domain wall thickness on ferroelectric domain nanoscale piezoelectric deformation is analyzed. The domain wall is regarded as a uniform piezoelectric dielectric with a certain thickness, and its piezoelectric coefficient depends on its thickness and the piezoelectric coefficient of adjacent domains. It is found that the transverse piezoelectric response of 90 degree charge and the vertical piezoelectric response of 90 charge domain can be enhanced by increasing the thickness of domain wall. A new method is proposed to improve the mechanical and electrical coupling performance of ferroelectric materials at nanometer scale based on the increase of domain wall thickness. Fourthly, the effects of domain size, inclined domain wall and the thickness of domain wall on the nanoscale piezoelectric deformation of periodic ferroelectric domains are calculated and analyzed. Through the calculation and analysis of the periodic ferroelectric domain structure, it is found that the inclination of domain wall breaks the symmetry of the nanoscale piezoelectric displacement response of the ferroelectric domain, but does not change the periodicity of its deformation and fluctuation, and the appropriate electric domain size. In order to make periodic ferroelectric materials at the same time have excellent mechanical and electrical properties and small performance fluctuations. In this paper, the quantitative analysis of complex ferroelectric domain nanoscale piezoelectric deformation is realized, which provides a good theoretical basis and guidance for the application and development of PFM technology. It also provides a certain experimental scheme for the preparation of ferroelectric materials with excellent nano-scale piezoelectric properties.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2171438
[Abstract]:Because of its unique microcosmic domain structure, ferroelectric materials have excellent physical properties and wide application prospects, which have attracted the attention of many researchers. As an important tool to characterize ferroelectric materials at nanometer scale, (PFM) has been widely used in ferroelectric domain research. However, the heterogeneity of domain itself and the high localization of electric field excited by PFM conductive probe, as well as the complex long range electric interaction between the probe and the test material, make the quantitative analysis of PFM measurement difficult. This seriously hinders the research of nano-scale electromechanical coupling of ferroelectric materials, and delays the development of electronic components based on nano-scale electromechanical coupling. Therefore, aiming at PFM technology, this paper quantitatively analyzes the effect of ferroelectric domain structure, including domain size, domain wall and its thickness, on ferroelectric nanoscale piezoelectric deformation. The corresponding research contents and results are summarized as follows: first, A theoretical framework for nanoscale piezoelectric deformation of complex ferroelectric domain structures is established. The electric field excited by the conductive probe is simulated by the mirror charge method, considering the polarization orientation of the complex ferroelectric multi-domain structure and the non-uniform distribution of the space piezoelectric Zhang Liang, and combining with the elastic constitutive equation, the Green's function method is used. The basic theoretical framework of nano-scale piezoelectric displacement analysis for complex ferroelectric domain structures is derived, which provides a theoretical framework for analyzing the effects of domain size and domain wall on nano-scale piezoelectric deformation. Secondly, the nanoscale piezoelectric response at the ferroelectric domain wall is calculated and analyzed, and the mechanism of its special nanoscale piezoelectric deformation is revealed. Through simulation analysis, it is found that there is a special in-plane piezoelectric response in the off-plane uncharged domain and a special out-of-plane piezoelectric response in the in-plane charge domain. The reason lies in that the in-plane piezoelectric displacement at the off-plane uncharged domain wall originates from the failure of the long-course electrically constrained opposition, while the out-of-plane displacement response at the in-plane charge domain wall is due to the discontinuity of the in-plane piezoelectric displacement. Thirdly, the effect of domain wall thickness on ferroelectric domain nanoscale piezoelectric deformation is analyzed. The domain wall is regarded as a uniform piezoelectric dielectric with a certain thickness, and its piezoelectric coefficient depends on its thickness and the piezoelectric coefficient of adjacent domains. It is found that the transverse piezoelectric response of 90 degree charge and the vertical piezoelectric response of 90 charge domain can be enhanced by increasing the thickness of domain wall. A new method is proposed to improve the mechanical and electrical coupling performance of ferroelectric materials at nanometer scale based on the increase of domain wall thickness. Fourthly, the effects of domain size, inclined domain wall and the thickness of domain wall on the nanoscale piezoelectric deformation of periodic ferroelectric domains are calculated and analyzed. Through the calculation and analysis of the periodic ferroelectric domain structure, it is found that the inclination of domain wall breaks the symmetry of the nanoscale piezoelectric displacement response of the ferroelectric domain, but does not change the periodicity of its deformation and fluctuation, and the appropriate electric domain size. In order to make periodic ferroelectric materials at the same time have excellent mechanical and electrical properties and small performance fluctuations. In this paper, the quantitative analysis of complex ferroelectric domain nanoscale piezoelectric deformation is realized, which provides a good theoretical basis and guidance for the application and development of PFM technology. It also provides a certain experimental scheme for the preparation of ferroelectric materials with excellent nano-scale piezoelectric properties.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
【参考文献】
相关期刊论文 前1条
1 章士瀛;21世纪电子元件的发展趋势[J];电子元件与材料;1999年01期
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