取向铁电薄膜PMN-PT力—电和热释电性能的应变调控

发布时间：2018-06-05 00:13

本文选题：铁电薄膜 + 取向生长　；参考：《湘潭大学》2017年硕士论文

【摘要】：铁电薄膜优异的物理性能更能满足器件日益微型化的需求,被广泛应用于光电子、微电子和微机电等领域。薄膜性能的好坏影响着器件性能的优劣。不同取向生长的铁电薄膜具有不同的性能,同时薄膜与基底间的失配应变对薄膜相结构具有重要影响,因此有望通过失配应变调控不同取向铁电薄膜的力-电、热释电性能。热力学理论作为一种研究铁电薄膜的有效方法,已在(001)取向薄膜的研究中有较好的应用,但其绝大多数采用的是单畴假设,对于其它取向和多畴铁电薄膜中的应用非常少,迫切需要建立其它取向和多畴状态薄膜的热力学理论框架。(1-x)PMN-xPT块体展现出优良的机电性能,但关于其薄膜力-电、热释电性能的优化和提高的理论分析相当缺乏。为此,本论文建立了不同取向铁电薄膜的单畴和多畴热力学理论框架,以(1-x)PMN-xPT薄膜为例,计算分析了取向和应变对(1-x)PMN-xPT相结构、力-电和热释电性能的影响,并提出了应变调控优化(1-x)PMN-xPT薄膜力-电和热释电性能的方案。相关研究内容及主要结论如下:(1)从(001)取向铁电单畴块体热力学函数出发,通过对序参量进行坐标转换,并考虑薄膜所受由基底引起的失配应变,我们建立起(001)、(110)和(111)取向单畴铁电薄膜的热力学理论框架及其力-电、热释电性能计算方法。并通过不同畴组合形成多畴模型,通过考虑全局和局域畴壁处的力学、电学边界条件,我们建立起了多畴铁电薄膜的热力学理论框架及其力-电、热释电性能计算方法。(2)基于所建立的不同取向单畴铁电薄膜热力学理论框架,计算分析了不同取向单畴(1-x)PMN-xPT薄膜的应变-温度相图及其力-电、热释电性能。研究结果表明:(111)、(001)、(110)取向单畴(1-x)PMN-xPT薄膜相结构的对称性依次降低。在相变点处,不同取向单畴(1-x)PMN-xPT表现出较好的介电、压电性能,且(001)、(110)取向单畴0.7PMN-0.3PT和0.58PMN-0.42PT薄膜表现出比相同组分(111)取向(1-x)PMN-xPT薄膜更优的介电、压电性能,且(110)和(111)取向单畴(1-x)PMN-xPT薄膜表现出比(001)取向薄膜更好的热释电性能。(3)基于所建立的多畴铁电薄膜热力学理论框架,计算分析了多畴(1-x)PMN-xPT薄膜的应变-温度相图及其力-电、热释电性能。研究结果表明:多畴(1-x)PMN-xPT薄膜具有比单畴薄膜更复杂的相结构,且随着组分的增加,Te(a)/Te(c)与M(aa*)/M(ca*)相的区域依次增加。在相变点处,多畴(1-x)PMN-xPT薄膜展示出较好的介电、压电响应。多畴0.7PMN-0.3PT薄膜在较大的应变范围内不具有面外热释电系数,但其在相变点处表现出了比组分x=0.42和0.7的多畴薄膜更好的热释电性能。
[Abstract]:The excellent physical properties of ferroelectric thin films can meet the needs of miniaturization of devices, and are widely used in photoelectron, microelectronics, micro-electromechanical and other fields. The performance of the film affects the performance of the device. Different orientation ferroelectric thin films have different properties, and the mismatch strain between the films and the substrate has an important effect on the phase structure of the thin films, so it is expected to regulate the mechanical-electric and pyroelectric properties of different oriented ferroelectric thin films through mismatch strain. As an effective method for the study of ferroelectric thin films, thermodynamics theory has been well applied in the study of oriented films, but most of them are based on single-domain hypothesis, and are seldom used in other oriented and multi-domain ferroelectric thin films. There is an urgent need to establish a thermodynamic theoretical framework for other oriented and multi-domain state films. The bulk of the films shows excellent mechanical and electrical properties, but the theoretical analysis on the optimization and improvement of the mechanical and electrical properties and pyroelectric properties of the films is rather scarce. In this paper, a thermodynamic framework of single-domain and multi-domain for ferroelectric thin films with different orientations has been established. The effects of orientation and strain on the phase structure, mechano-electric and pyroelectric properties of 1-xTP-PMN-xPT thin films have been calculated and analyzed. The scheme of optimizing the mechanical-electric and pyroelectric properties of 1-x PMP-xPT thin films by strain control is also proposed. The relevant research contents and main conclusions are as follows: (1) starting from the thermodynamic function of single-domain block oriented ferroelectric, the coordinate transformation of order parameters is carried out, and the mismatch strain caused by substrate is considered. We have established the thermodynamic theoretical framework of single-domain ferroelectric thin films with single domain orientation and the calculation methods of their force-electric and pyroelectric properties. By considering the mechanical and electrical boundary conditions at the global and local domain walls, the thermodynamic theoretical framework and the force-electricity of the multidomain ferroelectric thin films are established by using different domain combinations to form a multi-domain model, and by considering the mechanical and electrical boundary conditions at the global and local domain walls, the thermodynamics of multi-domain ferroelectric thin films is established. Based on the thermodynamics theory framework of single-domain ferroelectric thin films with different orientations, the strain-temperature phase diagrams and their mechanical and pyroelectric properties of single-domain films with different orientations are calculated and analyzed. The results show that the symmetry of the phase structure of the single domain oriented single domain (1-x) PMN-xPT thin films decreases in turn. At the phase transition point, the single-domain 0.7PMN-0.3PT and 0.58PMN-0.42PT thin films with different orientations exhibit better dielectric and piezoelectric properties than those with the same composition, and the dielectric and piezoelectric properties of the films are better than those of the films with the same composition. On the basis of the thermodynamics theory framework of multidomain ferroelectric thin films, the strain-temperature phase diagram and force-electric properties of multi-domain single-domain monofilms (1-xPM-N-xPT) films are calculated and analyzed based on the thermodynamics theory of multi-domain ferroelectric thin films. Pyroelectric properties. The results show that the phase structure of the films is more complex than that of the single domain films, and the regions of the phases increase with the increase of the components. At the point of phase transition, the multi-domain 1-xPM-N-xPT thin films exhibit good dielectric and piezoelectric responses. The multidomain 0.7PMN-0.3PT films have no out-of-plane pyroelectric coefficient in a large strain range, but they exhibit better pyroelectric properties than the multidomain films with components x _ (0. 42) and 0.7 at the transition point.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2

【相似文献】