Lin Jun Liang, Sun Yuanwei, He Ri, Li Yanxi, Zhong Zhicheng, Gao Peng, Zhao Xiang, Zhang Zhidong, Wang Zhan Jie
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
Shenyang National Laboratory for Materials Science, Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), Shenyang 110016, China.
Nano Lett. 2022 Sep 14;22(17):7104-7111. doi: 10.1021/acs.nanolett.2c02175. Epub 2022 Aug 19.
Artificial superlattices have demonstrated many unique phenomena not found in bulk materials. For this investigation, SrTiO/SrRuO paraelectric/metallic superlattices with various stacking periods were synthesized via pulsed laser deposition. A robust room-temperature ferroelectric polarization (∼46 μC/cm) was found in the superlattices with 2 unit cell (u.c.) thick SrRuO layers, despite the fact that neither SrTiO nor SrRuO is inherently ferroelectric. Results obtained from atomically resolved elemental mapping and X-ray photoelectron spectroscopy verified that oxygen vacancies accumulated at the SrTiO/SrRuO interfaces, causing lattice distortions and increased tetragonality (/). The observed ferroelectric responses can be mainly attributed to the broken spatial inversion symmetry induced by the ordered distribution of oxygen vacancies at the SrTiO/SrRuO interfaces, coupled with the triggering of external electric field. The resulting polarization mechanism induced by oxygen vacancies suggests viable ways for improving the electrical properties of ferroelectric materials, with the goal of expanding the functionality of a range of electronic devices.
人工超晶格已展现出许多在块状材料中未发现的独特现象。在本研究中，通过脉冲激光沉积合成了具有不同堆叠周期的SrTiO/SrRuO铁电/金属超晶格。在具有2个晶胞（u.c.）厚SrRuO层的超晶格中发现了强大的室温铁电极化（约46 μC/cm），尽管SrTiO和SrRuO本身都不是铁电体。从原子分辨元素映射和X射线光电子能谱获得的结果证实，氧空位在SrTiO/SrRuO界面处积累，导致晶格畸变并增加四方性（/）。观察到的铁电响应主要可归因于SrTiO/SrRuO界面处氧空位的有序分布引起的空间反演对称性破坏，以及外部电场的触发。由氧空位诱导的极化机制为改善铁电材料的电学性能提供了可行的方法，目标是扩展一系列电子器件的功能。
