缓冲层对铁电PbTiO3薄膜微结构的影响

缓冲层对铁电PbTiO₃薄膜微结构的影响

刘嘉琦^1，2，冯燕朋³，朱银莲^1*，曹 毅^1，2，刘 楠^1，2，石彤彤^1，2,唐云龙¹，马秀良^1，4

(1.沈阳材料科学国家研究中心, 中国科学院金属研究所，辽宁 沈阳 110016；2.中国科学技术大学，材料科学与工程学院，辽宁 沈阳110016；3.松山湖材料实验室，广东 东莞 523808；4.兰州理工大学材料科学与工程学院省部共建有色金属先进加工与再利用国家重点实验室，甘肃 兰州 730050)

摘  要   缓冲层作为一种调控铁电薄膜畴组态和引入新的微结构的有效手段被广泛采用。本文在大拉应变KTaO₃衬底上生长了LaNiO₃/PbTiO₃多层膜，利用透射电子显微学方法，对该薄膜体系中的缺陷结构及其与铁电畴的交互作用进行了细致地研究。结果表明，由于巨大的界面失配，LaNiO₃层中形成密集的Ruddlesden-Popper型层错，该层错经由LaNiO₃/PbTiO₃异质界面诱导PbTiO₃中形成贯穿型的层状缺陷，这种缺陷的形成对PbTiO₃内部畴结构有着一定的影响。利用电子能量损失谱，发现层状缺陷处Ti元素的价态有所降低，可能源于LaNiO₃与PbTiO₃之间的电荷传递。这一结果揭示了中间缓冲层对PbTiO₃薄膜内部微结构产生重要的影响，同时也为铁电畴的调控提供了新的途径。

关键词  钛酸铅薄膜；缓冲层；微结构；像差校正透射电子显微学

中图分类号：TG115.21⁺5.3 

文献标识码：Adoi:10.3969/j.issn.1000-6281.2020.06.008

The Effect of Structural Defects in Buffer Layer on the microstructures in Ferroelectric PbTiO₃ films

LIU Jia-qi^1,2，FENG Yan-peng³，ZHU Yin-lian¹*，CAO Yi^1,2，LIU Nan^1,2，SHI Tong-tong^1,2，TANG Yun-long¹，MA Xiu-liang^1,4

（1.Institute of Metal Research, Chinese Academy of Sciences, Shenyang Liaoning 110016; 2.University of Science and Technology of China, School of Materials Science and Engineering, Shenyang Liaoning 110016; 3.Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808; 4.School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou Gansu 730050）

Abstract   Buffer layer is widely used as an effective method to modulate domain configuration and introduce new microstructures in ferroelectric thin films. In this paper, a LaNiO₃/PbTiO₃ multilayer film was grown on the large tensile strain KTaO₃ substrate. The defect structures of the film system and the interaction between defects and ferroelectric domains were investigated by using transmission electron microscopy (TEM). The results show that dense Ruddlesden-Popper (R-P) faults are formed in the LaNiO₃ layer due to the large lattice mismatch, which induces the formation of penetrating layered defects in PbTiO₃ across the LaNiO₃/PbTiO₃ heterogeneous interface. The formation of such defects has a certain influence on the internal domain structure of PbTiO₃ layer. It was further found that the valence state of Ti ions decreased at the layered defect by using electron energy loss spectrum, which might be attributed to the charge transfer between LaNiO₃ and PbTiO₃ layers. These results reveal that the intermediate buffer layer has an important effect on the microstructure of PbTiO₃ films and provides a new way to modulate the ferroelectric domain configurations.

Keywords   PbTiO₃ film；buffer layer；microstructure；aberration-correction transmission electron microscopy

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[1] JI D, CAI S, PAUDEL T R, et al. Freestanding crystalline oxide perovskites down to the monolayer limit[J]. Nature, 2019, 570(7759): 87-90.

[2] TANG Y L, ZHU Y L, MA X L, et al.Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO₃ films[J]. Science, 2015,348(6234): 547-551.

[3] YADAV A K, NELSON C T, HSU S L, et al. Observation of polar vortices in oxide superlattices[J]. Nature, 2016,530(7589): 198-201.

[4] DAS S, TANG Y L, HONG Z, et al. Observation of room-temperature polar skyrmions[J]. Nature, 2019,568(7752): 368-372.

[5] WANG Y J, FENG Y P, ZHU Y L, et al. Polar meron lattice in strained oxide ferroelectrics[J]. Nature Materials, 2020,19(8): 881-886.

[6] LI S, ZHU Y L, TANG Y L, et al. Thickness-dependent a₁/a₂ domain evolution in ferroelectric PbTiO₃ films[J]. Acta Materialia, 2017,131: 123-130.

[7] FENG Y, TANG Y, MA D, et al. Thickness-dependent evolution of piezoresponses and stripe 90 degrees domains in (101)-oriented ferroelectric PbTiO₃ thin films[J]. ACS Applied Materials & Interfaces, 2018,10(29): 24627-24637.

[8] TANG Y L, ZHU Y L, LIU Y, et al. Giant linear strain gradient with extremely low elastic energy in a perovskite nanostructure array[J]. Nature Communications, 2017, 8: 15994.

[9] ZOU M J, TANG Y L, ZHU Y L, et al. Anisotropic strain: A critical role in domain evolution in (111)-oriented ferroelectric films[J]. Acta Materialia, 2019, 166: 503-511.

[10] ZHANG L, ZHENG D, FAN L, et al. Controllable ferromagnetism in super-tetragonal PbTiO₃ through strain engineering[J]. Nano Letters, 2020, 20(2): 881-886.

[11] HUANG Y L, NIKONOV D, ADDIEGO C, et al. Manipulating magnetoelectric energy landscape in multiferroics[J]. Nature Communications, 2020,11(1): 2836.

[12] MISHRA R, KIM Y M, SALAFRANCA J, et al. Oxygen-vacancy-induced polar behavior in (LaFeO₃)₂/(SrFeO₃) superlattices[J]. Nano Letters, 2014,14(5): 2694-2701.

[13] LEE D, JEON B C, BAEK S H, et al. Active control of ferroelectric switching using defect-dipole engineering[J]. Advanced Materials, 2012,24(48): 6490-6495.

[14] DAMODARAN A R, BRECKENFELD E, CHEN Z, et al. Enhancement of ferroelectric Curie temperature in BaTiO₃ films via strain-induced defect dipole alignment[J]. Advanced Materials, 2014，26(36): 6341-6347.

[15] KIM H, ZHANG J Y, RAGHAVAN S, et al. Direct observation of Sr vacancies in SrTiO₃ by quantitative scanning transmission electron microscopy[J]. Physical Review X, 2016，6(4): 041063.

[16] TANG Y L, ZHU Y L, MA X L. On the benefit of aberration-corrected HAADF-STEM for strain determination and its application to tailoring ferroelectric domain patterns[J]. Ultramicroscopy, 2016,160: 57-63.

[17]   许明慧，曹立朋，王伟鹏，等. 电子束辐照下SrCrO₃的结构稳定性研究[J]. 电子显微学报，2018，37(3): 226-231.

[18]   KUROIWA Y, AOYAGI S, SAWADA A, et al. Evidence for Pb-O covalency in tetragonal PbTiO₃[J]. Physical Review Letters, 2001,87(21): 217601.

[19]   MARTIN S, MICHELE R, FLORA P, et al. Polarity compensation mechanisms on the perovskite surface KTaO₃(001)[J]. Science，2018，359(6375): 572-575.

[20] GARCIA-MUNOZ J L, RODRIGUEZ C J, LACORRE P, et al. Neutron-diffraction study of RNiO₃ (R=La, Pr, Nd, Sm):electronically induced structural changes across the metal-insulator transition[J]. Physical Review B, 1992，46(8): 4414-4425.

[21]   邹敏杰, 唐云龙, 冯燕朋, 等. 铁电薄膜中180°荷电畴壁的亚埃尺度结构特性[J]. 电子显微学报，2018，37(5): 468-473.

[22]   冯燕朋, 朱银莲, 唐云龙, 等.  PbTiO₃/SrTiO₃(001)复杂畴组态和缺陷的研究[J]. 电子显微学报, 2018，37(6): 556-562.

[23] SUZUKI T, NISHI Y, FUJIMOTO M. Ruddlesden-Popper planar faults and nanotwins in heteroepitaxial nonstoichiometric barium titanate thin films[J]. Journal of the American Ceramic Society, 2000,83(12): 3185-3195

[24] NAKHMANSON S. Revealing latent structural instabilities in perovskite ferroelectrics by layering and epitaxial strain: a first-principles study of Ruddlesden-Popper superlattices[J]. Physical Review B, 2008,78(6): 064107

[25] DU K, ZHANG M, DAI C, et al. Manipulating topological transformations of polar structures through real-time observation of the dynamic polarization evolution [J]. Nature Communications, 2019,10: 4864.