Noguchi Yuji, Matsuo Hiroki, Kitanaka Yuuki, Miyayama Masaru
Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-856, Japan.
Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8563, Japan.
Sci Rep. 2019 Mar 12;9(1):4225. doi: 10.1038/s41598-019-40717-0.
Controlling and manipulating defects in materials provides an extra degree of freedom not only for enhancing physical properties but also for introducing additional functionalities. In ferroelectric oxides, an accumulation of point defects at specific boundaries often deteriorates a polarization-switching capability, but on the one hand, delivers interface-driven phenomena. At present, it remains challenging to control oxygen vacancies at will to achieve a desirable defect structure. Here, we report a practical route to designing oxygen-vacancy distributions by exploiting the interaction with transition-metal dopants. Our thin-film experiments combined with ab-initio theoretical calculations for BiFeO demonstrate that isovalent dopants such as Mn with a partly or fully electron-occupied e state can trap oxygen vacancies, leading to a robust polarization switching. Our approach to controlling oxygen vacancy distributions by harnessing the vacancy-trapping capability of isovalent transition-metal cations will realize the full potential of switchable polarization in ferroelectric perovskite oxides.
控制和操纵材料中的缺陷不仅为增强物理性能提供了额外的自由度，还为引入额外功能提供了额外的自由度。在铁电氧化物中，特定边界处点缺陷的积累通常会降低极化切换能力，但另一方面，会产生界面驱动现象。目前，随意控制氧空位以实现理想的缺陷结构仍然具有挑战性。在此，我们报告了一种通过利用与过渡金属掺杂剂的相互作用来设计氧空位分布的实用途径。我们的薄膜实验与针对BiFeO的从头算理论计算相结合表明，具有部分或完全电子占据e态的等价位掺杂剂（如Mn）可以捕获氧空位，从而实现强大的极化切换。我们利用等价位过渡金属阳离子的空位捕获能力来控制氧空位分布的方法将实现铁电钙钛矿氧化物中可切换极化的全部潜力。
