BaTiO_(3)纳米单晶薄膜在外加电场作用下畴结构演化的相场研究  

Phase Field Study on Domain Structure Evolution of BaTiO_(3)Nano Single Crystal Thin Films under Applied Electric Field

作　　者：李昊晴 苏煜[1] LI Haoqing;SU Yu(School of Aerospace Engineering,Beijing Institute of Technology,Beijing 100081,China)

机构地区：[1]北京理工大学宇航学院,北京100081

出　　处：《人工晶体学报》2024年第7期1136-1149,共14页Journal of Synthetic Crystals

基　　金：国家重点研发计划(2023YFF0616800);国家自然科学基金(12172046)。

摘　　要：铁电薄膜的工作电场加载频率及基底失配应变可影响微观畴结构形态和材料宏观铁电性能。本文利用相场模拟方法分别研究了在-0.1%、-0.7%的失配应变下,0.1~100 kHz频率范围内BaTiO_(3)纳米单晶薄膜的铁电性能变化规律。研究发现,随着外加电场频率的增大,薄膜电滞回线由四方形向椭圆形转变,标准蝶形曲线向腰果形曲线发生改变。在50 kHz以下的低频段,矫顽场随频率增加而快速升高,但剩余极化强度变化幅度不大;而在50 kHz以上的高频段,矫顽场随频率增加略有升高,剩余极化强度则呈下降趋势。在低频段下铁电性能的频率依赖性受失配应变的影响较大,而在高频段下则对失配应变不敏感。同时发现,压缩失配应变可导致剩余极化及矫顽场显著升高,而拉伸应变的效果相反。分析表明,BaTiO_(3)纳米单晶薄膜铁电性能的频率依赖性源自内部微结构演化速度与外电场施加速率的相互竞争。本研究可为铁电功能薄膜材料的实验设计提供理论基础,为其在高频电子器件中的应用提供有力支撑。The frequency of the applied electric field and the epitaxial strain can affect the microstructure and the overall properties of ferroelectric thin films.In this study,the ferroelectric characteristics of BaTiO_(3)nano single crystal thin films were investigated via phase field simulation under the epitaxial strain of-0.1%and-0.7%,respectively,in the frequency range of 0.1~100 kHz.It is found that,with the increase in frequency,the square-shaped hysteresis loop gradually changes to an elliptic loop and the butterfly loop changes to a kidney-shaped loop.When the applied frequency is below 50 kHz,the coercive field increases rapidly with the increase in frequency,but the change in remnant polarization is not significant.When the frequency is over 50 kHz,the coercive field only increases slightly,and the remnant polarization exhibits a downward trend.It is observed that the frequency dependence of ferroelectric properties is more significantly affected by the epitaxial strain while the frequency is low.The frequency dependence is not very sensitive to the epitaxial strain while the frequency is high.Meanwhile,the compressive epitaxial strain causes significant rise in both the remnant polarization and coercive field,and the tensile epitaxial strain leads to opposite effects.By analysis,it is found that the underlying mechanism of the frequency-dependent hysteresis is due to the competition between the speed of microstructure evolution and the frequency of the applied electric field.The findings of this study serve as theoretical basis for the experiment and design of ferroelectric functional thin films,and they provide knowledge-based support for the application of high-frequency electronic devices.

关 键 词：铁电薄膜 相场方法 钛酸钡纳米单晶薄膜 金兹堡-朗道方程 频率效应 失配应变 

分 类 号：O482.4[理学—固体物理] TB383.2[理学—物理]