界面影响BFO铁电薄膜极化翻转行为的原位电学研究

                                                                 界面影响BFO铁电薄膜极化翻转行为的原位电学研究
                                                                        陈潇忻，刘中然，李  柱，李吉学，田  鹤*
                                          （浙江大学电子显微镜中心，硅材料国家重点实验室，材料科学与工程学院，浙江 杭州 310027）
摘  要   铁电薄膜在高密度存储器等微型功能器件具有巨大的应用前景，在外场下研究铁电薄膜极化翻转机制具有重要意义。本文用原位透射电镜技术对BFO薄膜电容器的铁电极化翻转动态行为及界面因素进行了研究。原位结果观察到“面内层状”与典型“成核生长”两种铁电极化翻转模式；HAADF高分辨与高斯拟合分析结果表明界面几何构型的影响作用，界面几何曲率的不同导致局部电荷密度不同，并进一步影响局部内建电场和成核势垒，使得铁电极化翻转呈现不同的行为模式。本研究为调控铁电成核与翻转方式以及器件界面设计提供了新的见解和参考。
关键词   铁电薄膜；极化翻转；原位透射电镜；BFO
中图分类号：TB34；O766+.1；O766+.4；TG115.21+5.3   
文献标识码：A  doi:10.3969/j.issn.1000-6281.2024.06.001
 
                  In-situ TEM study of interface effect on polarization switching mechanism in BFO ferroelectric thin film
                                     CHEN Xiaoxin，LIU Zhongran，LI Zhu，LI Jixue，TIAN He*
(Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou Zhejiang 310027，China)
Abstract   Ferroelectric thin films have promising applications in micro-functional devices such as high-density memory. Studying the polarization switching behavior of ferroelectric thin films under an external field is of great significance. In this paper, the dynamic behavior of ferroelectric polarization reversal and interface factors of BFO thin film capacitor were investigated using in-situ TEM. The In-situ results revealed two types of ferroelectric polarization switching modes: "in-plane layer-like" and typical "nucleation growth". The results from HAADF high-resolution and Gaussian fitting analysis demonstrated that the geometric configuration of the interface played a crucial role. Variations in the geometric curvature of the interface led to different degrees of local charge aggregation, which in turn affected the local built-in electric field and nucleation barrier, resulting in distinct ferroelectric polarization reversal behaviors. This study provides new insights and references for the regulation of ferroelectric nucleation and switching mode, as well as interface design in devices.
Keywords   ferroelectric thin film; polarization switching; In-situ TEM; BFO

[1]  ELISEEV E A, MOROZOVSKA A N, et al. Domain wall conduction in multiaxial ferroelectrics[J]. Physical Review B, 2012, 85(4): 45312-45312.
[2] YANG S Y, SEIDEL J, BYRNES S J, et al. Above-bandgap voltages from ferroelectric photovoltaic devices[J]. Nature Nanotechnology, 2010, 5(2): 143 -147.
[3] HE Q, YANG S Y, YANG C H, et al. Domain wall magnetism in multiferroic BiFeO3[J]. American Physical Society, 2010, S1. 084.
[4] SCHAAB J, SKJARVO S H, KROHNS S, et al. Electrical half-wave rectification at ferroelectric domain walls[J]. Nature Nanotechnology, 2018, 13(11): 1028-1034.
[5] SLUKA T, TAGANTSEV A K, BEDNYAKOV P, et al. Free-electron gas at charged domain walls in insulating BaTiO3[J]. Nature Communications, 2013, 4: 1808-1814.
[6] LI L, BRITSON J, JOKISAARI J R, et al. Giant resistive switching via control of ferroelectric charged domain walls[J]. Advanced Materials, 2016, 28(31): 6574-6580.
[7] NELSON C T, GAO P, JOKISAARI J R, et al. Domain dynamics during ferroelectric switching[J]. Science, 2011, 334(6058): 968-971.
[8] LI L, ZHANG Y, XIE L, et al. Atomic-scale mechanisms of defect-induced retention failure in ferroelectrics[J]. Nano Letters, 2017, 17(6): 3556-3562.
[9] GAO P, BRITSON J, JOKISAARI J R, et al. Atomic-scale mechanisms of ferroelastic domain-wall-mediated ferroelectric switching[J]. Nature Communications, 2013, 4(1): 1-9.
[10] ZHANG Y, TAN Y, SANDO D, et al. Controlled nucleation and stabilization of ferroelectric domain wall patterns in epitaxial (110) bismuth ferrite heterostructures[J]. Advanced Functional Materials, 2020, 30(48): 2003571.
[11] 冯燕朋, 唐云龙, 朱银莲, 等.  (110)取向BiFeO3薄膜界面诱导结构特性研究[J].电子显微学报, 2020, 39 (6): 680-686.
[12] 石彤彤, 耿皖荣, 朱银莲, 等. 多铁性BiFeO3薄膜中复杂畴组态的亚埃尺度研究[J].电子显微学报, 2021, 40 (5): 522-528.
[13] AOYAGI K, KIGUCHI T, EHARA Y, et al. Diffraction contrast analysis of 90° and 180° ferroelectric domain structures of PbTiO3 thin films[J]. Science & Technology of Advanced Materials, 2011, 12(3): 034403.
[14] ASADA T, KOYAMA Y. Ferroelectric domain structures around the morphotropic phase boundary of the piezoelectric material PbZr1−xTixO3[J]. Physical Review B, 2007, 75(21): 214111.
[15] BALKE N, GAJEK M, TAGANTSEV A K, et al. Direct observation of capacitor switching using planar electrodes[J]. Advanced Materials for Optics and Electronics, 2010, 20(20): 3466-3475.
[16] GAO P, NELSON C T, JOKISAARI J R, et al. Revealing the role of defects in ferroelectric switching with atomic resolution[J]. Nature Communications, 2011, 2(1): 1-6.
[17] JIA C L, MI S B, URBAN K, et al. Atomic-scale study of electric dipoles near charged and uncharged domain walls in ferroelectric films[J]. Nature Materials, 2008, 7(1): 57-61.
[18] MA J, MA J, ZHANG Q, et al. Controllable conductive readout in self-assembled, topologically confined ferroelectric domain walls[J].  Nature Nanotechnology, 2018, 13(10): 947-952.
[19] GANPULE C S, ROYTBURD A L, NAGARAJAN V, et al. Polarization relaxation kinetics and 180° domain wall dynamics in ferroelectric thin films[J]. Physical Review B, 2001, 65(1): 014101.
[20] 吕笑梅, 黄凤珍, 朱劲松. 铁电材料中的电畴: 形成，结构，动性及相关性能[J]. 物理学报, 2020, 69(12): 33-50.
[21] GAO P, NELSON C T, JOKISAARI J R, et al. Direct observations of retention failure in ferroelectric memories[J]. Advanced Materials, 2012, 24(8): 1106-1110.
[22] KIM Y M, MOROZOVSKA A, ELISEEV E, et al. Direct observation of ferroelectric field effect and vacancy-controlled screening at the BiFeO3/LaxSr(1-x)MnO3 interface[J].  Nature Materials, 2014, 13(11): 1019-1025.
[23] LI L, CHENG X, BLUM T, et al. Observation of strong polarization enhancement in ferroelectric tunnel junctions[J]. Nano Letters, 2019, 19(10): 6812-6818.
[24] CHU Y H, ZHAO T, CRUZ M P, et al. Ferroelectric size effects in multiferroic BiFeO3 thin films[J]. Applied Physics Letters, 2007, 90(25):1481.