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arXiv · 1901.09817

Controllable Defect Driven Symmetry Change and Domain Structure Evolution in BiFeO3 with Enhanced Tetragonality

Chao Chen·Changan Wang·Xiangbin Cai·Chao Xu·Caiwen Li·Jingtian Zhou·Zhenlin Luo·Zhen Fan·Minghui Qin·Min Zeng·Xubing Lu·Ping Yang·Guofu Zhou·Xingsen Gao·Ning Wang·Ye Zhu·Shengqiang Zhou·Deyang Chen·Jun-Ming Liu
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Abstract

Defect engineering has been a powerful tool to enable the creation of exotic phases and the discovery of intriguing phenomena in ferroelectric oxides. However, accurate control the concentration of defects remains a big challenge. In this work, ion implantation, that can provide controllable point defects, allows us the ability to produce a controlled defect-driven true super-tetragonal (T) phase with enhanced tetragonality in ferroelectric BiFeO3 thin films. This point defect engineering is found to drive the phase transition from the as-grown mixed rhombohedral-like (R) and tetragonal-like (MC) phase to true tetragonal (T) symmetry. By further increasing the injected dose of He ion, we demonstrate an enhanced tetragonality super-tetragonal (super-T) phase with the largest c/a ratio (~ 1.3) that has ever been experimentally achieved in BiFeO3. A combination of morphology change and domain evolution further confirm that the mixed R/MC phase structure transforms to the single-domain-state true tetragonal phase. Moreover, the re-emergence of R phase and in-plane stripe nanodomains after heat treatment reveal the memory effect and reversible phase transition. Our findings demonstrate the control of R-Mc-T-super T symmetry changes and the creation of true T phase BiFeO3 with enhanced tetragonality through controllable defect engineering. This work also provides a pathway to generate large tetragonality (or c/a ratio) that could be extended to other ferroelectric material systems (such as PbTiO3, BaTiO3 and HfO2) which may lead to strong polarization enhancement.

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Chao Chen, Changan Wang, Xiangbin Cai, Chao Xu, Caiwen Li, Jingtian Zhou, Zhenlin Luo, Zhen Fan, Minghui Qin, Min Zeng, Xubing Lu, Ping Yang, Guofu Zhou, Xingsen Gao, Ning Wang, Ye Zhu, Shengqiang Zhou, Deyang Chen, Jun-Ming Liu. 2019-01-28. Controllable Defect Driven Symmetry Change and Domain Structure Evolution in BiFeO3 with Enhanced Tetragonality. https://doi.org/10.1039/c9nr00932a

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