Ashida Yuichi, Ishibe Takafumi, Yang Jinfeng, Naruse Nobuyasu, Nakamura Yoshiaki
Graduate School of Engineering and Science, Osaka University, Toyonaka, Japan.
The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Japan.
Sci Technol Adv Mater. 2022 Dec 23;24(1):1-9. doi: 10.1080/14686996.2022.2150525. eCollection 2023.
Vanadium dioxide (VO) material, known for changing physical properties due to metal-insulator transition (MIT) near room temperature, has been reported to undergo a phase change depending on the strain. This fact can be a significant problem for nanoscale devices in VO, where the strain field covers a large area fraction, spatially non-uniform, and the amount of strain can vary during the MIT process. Direct measurement of the strain field distribution during MIT is expected to establish a methodology for material phase identification. We have demonstrated the effectiveness of geometric phase analysis (GPA), high-resolution transmission electron microscopy techniques, and transmission electron diffraction (TED). The GPA images show that the nanoregions of interest are under tensile strain conditions of less than 0.4% as well as a compressive strain of about 0.7% (Rutile phase VO[100] direction), indicating that the origin of the newly emerged TED spots in MIT contains a triclinic phase. This study provides a substantial understanding of the strain-temperature phase diagram and strain engineering strategies for effective phase management of nanoscale VO.
二氧化钒（VO）材料因在室温附近由于金属-绝缘体转变（MIT）而改变物理性质而闻名，据报道其会根据应变发生相变。对于VO中的纳米级器件而言，这一事实可能是一个重大问题，因为在VO中应变场覆盖的面积比例很大，在空间上不均匀，并且在MIT过程中应变的量可能会发生变化。在MIT过程中直接测量应变场分布有望建立一种材料相识别方法。我们已经证明了几何相位分析（GPA）、高分辨率透射电子显微镜技术和透射电子衍射（TED）的有效性。GPA图像显示，感兴趣的纳米区域处于小于0.4%的拉伸应变条件以及约0.7%的压缩应变（金红石相VO[100]方向）下，这表明在MIT中新出现的TED斑点的起源包含三斜相。这项研究为应变-温度相图以及纳米级VO有效相管理的应变工程策略提供了实质性的理解。
