He Ri, Lin Jun Liang, Liu Qing, Liao Zhaoliang, Shui Lingling, Wang Zhan Jie, Zhong Zhicheng, Li Run-Wei
Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China.
ACS Appl Mater Interfaces. 2020 Oct 7;12(40):45602-45610. doi: 10.1021/acsami.0c13314. Epub 2020 Sep 25.
Introducing point defects in complex metal oxides is a very effective route to engineer crystal symmetry and therefore control physical properties. However, the inversion symmetry breaking, which is vital for many tantalizing properties, such as ferroelectricity and chiral spin structure, is usually hard to be induced in the bulk crystal by point defects. By designing the oxygen vacancy formation energy profile and migration path across the oxide heterostructure, our first-principles density functional theory (DFT) calculations demonstrate that the point defects can effectively break the inversion symmetry and hence create novel ferroelectricity in superlattices consisting of otherwise nonferroelectric materials SrTiO and SrRuO. This induced ferroelectricity can be significantly enhanced by reducing the SrTiO thickness. Inspired by theory calculation, SrTiO/SrRuO superlattices were experimentally fabricated and are found to exhibit surprising strong ferroelectric properties. Our finding paves a simple and effective pathway to engineer the inversion symmetry and thus properties by point defect control in oxide heterostructures.
在复杂金属氧化物中引入点缺陷是设计晶体对称性从而控制物理性质的一种非常有效的途径。然而，对于许多诱人的性质（如铁电性和手性自旋结构）至关重要的反演对称性破缺，通常很难通过点缺陷在体晶体中诱导产生。通过设计氧空位形成能分布和穿过氧化物异质结构的迁移路径，我们的第一性原理密度泛函理论（DFT）计算表明，点缺陷可以有效地打破反演对称性，从而在由原本非铁电材料SrTiO和SrRuO组成的超晶格中产生新型铁电性。通过减小SrTiO的厚度，可以显著增强这种诱导铁电性。受理论计算的启发，实验制备了SrTiO/SrRuO超晶格，发现其表现出令人惊讶的强铁电性质。我们的发现为通过氧化物异质结构中的点缺陷控制来设计反演对称性从而调控性质开辟了一条简单有效的途径。
