中国物理B ›› 2024, Vol. 33 ›› Issue (9): 96805-096805.doi: 10.1088/1674-1056/ad62e0

所属专题: SPECIAL TOPIC — Stephen J. Pennycook: A research life in atomic-resolution STEM and EELS

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Multiphase cooperation for multilevel strain accommodation in a single-crystalline BiFeO3 thin film

Wooseon Choi1,†, Bumsu Park2,†, Jaejin Hwang3,†, Gyeongtak Han4, Sang-Hyeok Yang1, Hyeon Jun Lee5, Sung Su Lee6, Ji Young Jo6, Albina Y. Borisevich7, Hu Young Jeong8, Sang Ho Oh9,‡, Jaekwang Lee3,§, and Young-Min Kim1,¶   

  1. 1 Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea;
    2 Samsung Electronics, Hwaseong 18448, Republic of Korea;
    3 Department of Physics, Pusan National University, Busan 46241, Republic of Korea;
    4 LG Energy Solution, Daejeon 34122, Republic of Korea;
    5 Department of Materials Science and Engineering, Kangwon National University, Republic of Korea;
    6 School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea;
    7 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, TN 37831, USA;
    8 Graduate School of Semiconductor Materials and Devices Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea;
    9 Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju 58330, Republic of Korea
  • 收稿日期:2024-04-22 修回日期:2024-07-10 接受日期:2024-07-15 发布日期:2024-08-30
  • 通讯作者: Sang Ho Oh, Jaekwang Lee, Young-Min Kim E-mail:shoh@kentech.ac.kr;jaekwangl@pusan.ac.kr;youngmk@skku.edu
  • 基金资助:
    Project supported by Samsung Research Fundings & Incubation Center of Samsung Electronics (Grant No. SRFCMA1702-01). Y.-M.K acknowledges partial support from the National Research Foundation of Korea (NRF) (Grant No. 2023R1A2C2002403) funded by the Korean government in Korea.

Multiphase cooperation for multilevel strain accommodation in a single-crystalline BiFeO3 thin film

Wooseon Choi1,†, Bumsu Park2,†, Jaejin Hwang3,†, Gyeongtak Han4, Sang-Hyeok Yang1, Hyeon Jun Lee5, Sung Su Lee6, Ji Young Jo6, Albina Y. Borisevich7, Hu Young Jeong8, Sang Ho Oh9,‡, Jaekwang Lee3,§, and Young-Min Kim1,¶   

  1. 1 Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea;
    2 Samsung Electronics, Hwaseong 18448, Republic of Korea;
    3 Department of Physics, Pusan National University, Busan 46241, Republic of Korea;
    4 LG Energy Solution, Daejeon 34122, Republic of Korea;
    5 Department of Materials Science and Engineering, Kangwon National University, Republic of Korea;
    6 School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea;
    7 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, TN 37831, USA;
    8 Graduate School of Semiconductor Materials and Devices Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea;
    9 Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju 58330, Republic of Korea
  • Received:2024-04-22 Revised:2024-07-10 Accepted:2024-07-15 Published:2024-08-30
  • Contact: Sang Ho Oh, Jaekwang Lee, Young-Min Kim E-mail:shoh@kentech.ac.kr;jaekwangl@pusan.ac.kr;youngmk@skku.edu
  • Supported by:
    Project supported by Samsung Research Fundings & Incubation Center of Samsung Electronics (Grant No. SRFCMA1702-01). Y.-M.K acknowledges partial support from the National Research Foundation of Korea (NRF) (Grant No. 2023R1A2C2002403) funded by the Korean government in Korea.

摘要: The functionalities and diverse metastable phases of multiferroic BiFeO$_{3}$ (BFO) thin films depend on the misfit strain. Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known, it is unclear whether a single-crystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs. Thus, understanding the strain relaxation behavior is key to elucidating the lattice strain-property relationship. In this study, a correlative strain analysis based on dark-field inline electron holography (DIH) and quantitative scanning transmission electron microscopy (STEM) was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film. The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief, forming irregularly strained nanodomains. The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale. The globally integrated strain for each nanodomain was estimated to be close to $-1.5%$, irrespective of the nanoscale strain states, which was consistent with the fully strained BFO film on the SrTiO$_{3}$ substrate. Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation. This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films, such as BFO, with various low-symmetry polymorphs.

关键词: BiFeO$_{3}$, scanning transmission electron microscopy, electron holography, multiferroic material, strain mapping

Abstract: The functionalities and diverse metastable phases of multiferroic BiFeO$_{3}$ (BFO) thin films depend on the misfit strain. Although mixed phase-induced strain relaxation in multiphase BFO thin films is well known, it is unclear whether a single-crystalline BFO thin film can accommodate misfit strain without the involvement of its polymorphs. Thus, understanding the strain relaxation behavior is key to elucidating the lattice strain-property relationship. In this study, a correlative strain analysis based on dark-field inline electron holography (DIH) and quantitative scanning transmission electron microscopy (STEM) was performed to reveal the structural mechanism for strain accommodation of a single-crystalline BFO thin film. The nanoscale DIH strain analysis results indicated a random combination of multiple strain states that acted as a primary strain relief, forming irregularly strained nanodomains. The STEM-based bond length measurement of the corresponding strained nanodomains revealed a unique strain accommodation behavior achieved by a statistical combination of multiple modes of distorted structures on the unit-cell scale. The globally integrated strain for each nanodomain was estimated to be close to $-1.5%$, irrespective of the nanoscale strain states, which was consistent with the fully strained BFO film on the SrTiO$_{3}$ substrate. Density functional theory calculations suggested that strain accommodation by the combination of metastable phases was energetically favored compared to single-phase-mediated relaxation. This discovery allows a comprehensive understanding of strain accommodation behavior in ferroelectric oxide films, such as BFO, with various low-symmetry polymorphs.

Key words: BiFeO$_{3}$, scanning transmission electron microscopy, electron holography, multiferroic material, strain mapping

中图分类号:  (Scanning transmission electron microscopy (STEM))

  • 68.37.Ma
61.05.jp (Electron holography) 77.55.Nv (Multiferroic/magnetoelectric films) 68.55.-a (Thin film structure and morphology)