Elangovan Hemaprabha, Barzilay Maya, Huang Jiawei, Liu Shi, Cohen Shai, Ivry Yachin
Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
Solid State Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
ACS Nano. 2021 Aug 24;15(8):13380-13388. doi: 10.1021/acsnano.1c03623. Epub 2021 Aug 6.
Nanoscale devices that utilize oxygen vacancies in two-dimensional metal-oxide structures garner much attention due to conductive, magnetic, and even superconductive functionalities they exhibit. Ferroelectric domain walls have been a prominent recent example because they serve as a hub for topological defects and hence are attractive for next-generation data technologies. However, owing to the light weight of oxygen atoms and localized effects of their vacancies, the atomic-scale electrical and mechanical influence of individual oxygen vacancies has remained elusive. Here, stable individual oxygen vacancies were engineered at domain walls of seminal titanate perovskite ferroics. The atomic-scale electric-field, charge, dipole-moment, and strain distribution around these vacancies were characterized by combining advanced transmission electron microscopy and first-principle methodologies. The engineered vacancies were used to form quasi-linear quadrupole topological defects. Significant intraband states were found in the unit cell of the engineered vacancies, proposing a meaningful domain-wall conductivity for miniaturized data-storage applications. Reduction of the Ti ion as well as enhanced charging and electric-field concentration were demonstrated near the vacancy. A 3-5% tensile strain was observed at the immediate surrounding unit cells of the vacancies. Engineering individual oxygen vacancies and topological solitons thus offers a platform for predetermining both atomic-scale and global functional properties of device miniaturization in metal oxides.
利用二维金属氧化物结构中的氧空位的纳米级器件因其所展现出的导电、磁性甚至超导功能而备受关注。铁电畴壁就是一个突出的近期例子，因为它们是拓扑缺陷的汇聚点，因此对下一代数据技术具有吸引力。然而，由于氧原子的轻质量及其空位的局域效应，单个氧空位在原子尺度上的电学和力学影响仍然难以捉摸。在此，在典型的钛酸钙钛矿铁电体的畴壁处设计出了稳定的单个氧空位。通过结合先进的透射电子显微镜和第一性原理方法，对这些空位周围的原子尺度电场、电荷、偶极矩和应变分布进行了表征。设计出的空位被用于形成准线性四极拓扑缺陷。在设计出的空位的晶胞中发现了显著的带内态，这为小型化数据存储应用提出了有意义的畴壁电导率。在空位附近证实了钛离子的还原以及增强的电荷和电场集中。在空位紧邻的周围晶胞处观察到了3 - 5%的拉伸应变。因此，设计单个氧空位和拓扑孤子为预先确定金属氧化物中器件小型化的原子尺度和整体功能特性提供了一个平台。
