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

Wooseon Choi, Bumsu Park, Jaejin Hwang, Gyeongtak Han, Sang Hyeok Yang, Hyeon Jun Lee, Sung Su Lee, Ji Young Jo, Albina Y. Borisevich, Hu Young Jeong, Sang Ho Oh, Jaekwang Lee, Young Min Kim

Research output: Contribution to journalArticlepeer-review

Abstract

The functionalities and diverse metastable phases of multiferroic BiFeO3 (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 SrTiO3 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.

Original languageEnglish
Article number096805
JournalChinese Physics B
Volume33
Issue number9
DOIs
StatePublished - Sep 1 2024

Funding

Project supported by Samsung Research Fundings & Incubation Center of Samsung Electronics (Grant No. SRFC-MA1702-01). Y.-M.K acknowledges partial support from the National Research Foundation of Korea (NRF) (Grant No. 2023R1A2C2002403) funded by the Korean government in Korea. A. Borisevich acknowledges support from FaCT, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, Collaboratives Research Division.

FundersFunder number
Basic Energy Sciences
Collaboratives Research Division
U.S. Department of Energy
Office of Science
Find A Cure Today Breast Cancer Foundation
SamsungSRFC-MA1702-01
National Research Foundation of Korea2023R1A2C2002403

    Keywords

    • BiFeO
    • electron holography
    • multiferroic material
    • scanning transmission electron microscopy
    • strain mapping

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