Anion-induced robust ferroelectricity in sulfurized pseudo-rhombohedral epitaxial BiFeO thin films polarization rotation

• Published in: Materials horizons 2023-10, Vol.1 (1), p.4389-4397
• Main Authors: Xi, Guoqiang, Pan, Zhao, Fang, Yue-Wen, Tu, Jie, Li, Hangren, Yang, Qianqian, Liu, Chen, Luo, Huajie, Ding, Jiaqi, Xu, Shuai, Deng, Shiqing, Wang, Qingxiao, Zheng, Dongxing, Long, Youwen, Jin, Kuijuan, Zhang, Xixiang, Tian, Jianjun, Zhang, Linxing
• Format: Article
• ISSN: 2051-6347; 2051-6355
• DOI: 10.1039/d3mh00716b

Polarization rotation caused by various strains, such as substrate and/or chemical strain, is essential to control the electronic structure and properties of ferroelectric materials. This study proposes anion-induced polarization rotation with chemical strain, which effectively improves ferroelectricity. A method for the sulfurization of BiFeO 3 thin films by introducing sulfur anions is presented. The sulfurized films exhibited substantial enhancement in room-temperature ferroelectric polarization through polarization rotation and distortion, with a 170% increase in the remnant polarization from 58 to 100.7 μC cm −2 . According to first-principles calculations and the results of X-ray absorption spectroscopy and high-angle annular dark-field scanning transmission electron microscopy, this enhancement arose from the introduction of S atoms driving the re-distribution of the lone-pair electrons of Bi, resulting in the rotation of the polarization state from the [001] direction to the [110] or [111] one. The presented method of anion-driven polarization rotation might enable the improvement of the properties of oxide materials. A feasible anion engineering strategy by introducing sulfur anions in BiFeO 3 epitaxial thin films, resulting in a driven polarization rotation for robust ferroelectricity.