Yun Shinhee, Song Kyung, Chu Kanghyun, Hwang Soo-Yoon, Kim Gi-Yeop, Seo Jeongdae, Woo Chang-Su, Choi Si-Young, Yang Chan-Ho
Department of Physics & Center for Lattice Defectronics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
Department of Materials Analysis and Evaluation, Korea Institute of Materials Science (KIMS), Changwon, 51508, Republic of Korea.
Nat Commun. 2020 Sep 29;11(1):4898. doi: 10.1038/s41467-020-18644-w.
The emergence of a domain wall property that is forbidden by symmetry in bulk can offer unforeseen opportunities for nanoscale low-dimensional functionalities in ferroic materials. Here, we report that the piezoelectric response is greatly enhanced in the ferroelastic domain walls of centrosymmetric tungsten trioxide thin films due to a large strain gradient of 10 m, which exists over a rather wide width (~20 nm) of the wall. The interrelationship between the strain gradient, electric polarity, and the electromechanical property is scrutinized by detecting of the lattice distortion using atomic scale strain analysis, and also by detecting the depolarized electric field using differential phase contrast technique. We further demonstrate that the domain walls can be manipulated and aligned in specific directions deterministically using a scanning tip, which produces a surficial strain gradient. Our findings provide the comprehensive observation of a flexopiezoelectric phenomenon that is artificially controlled by externally induced strain gradients.
在块体材料中被对称性禁止的畴壁特性的出现，可为铁电材料中的纳米级低维功能带来意想不到的机遇。在此，我们报道，在中心对称的三氧化钨薄膜的铁弹性畴壁中，压电响应因存在于畴壁相当宽的宽度（约20纳米）上的10米的大应变梯度而大大增强。通过使用原子尺度应变分析检测晶格畸变，以及使用微分相衬技术检测去极化电场，对应变梯度、电极性和机电性能之间的相互关系进行了仔细研究。我们进一步证明，使用扫描尖端可以确定性地在特定方向上操纵和排列畴壁，该扫描尖端会产生表面应变梯度。我们的研究结果提供了对由外部诱导应变梯度人工控制的挠曲压电现象的全面观察。
