Direct imaging of structural changes induced by ionic liquid gating leading to engineered three-dimensional meso-structures

• Published in: Nature communications Vol. 9; no. 1; pp. 3055 - 8
• Main Authors: Cui, Bin, Werner, Peter, Ma, Tianping, Zhong, Xiaoyan, Wang, Zechao, Taylor, James Mark, Zhuang, Yuechen, Parkin, Stuart S. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.08.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 140/146; 142/126; 147/137; 147/143; 147/3; 639/301/119/995; 639/766/119/544; Anisotropy; Brownmillerite; Calcium aluminum ferrite; Cylinders; Gating; Humanities and Social Sciences; Image transmission; Ionic liquids; Ions; multidisciplinary; Oxygen; Perovskites; Phase transitions; Physical properties; Road construction; Science; Science (multidisciplinary); Thickness; Thin films; Transmission electron microscopy
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-05330-1

The controlled transformation of materials, both their structure and their physical properties, is key to many devices. Ionic liquid gating can induce the transformation of thin-film materials over long distances from the gated surface. Thus, the mechanism underlying this process is of considerable interest. Here we directly image, using in situ, real-time, high-resolution transmission electron microscopy, the reversible transformation between the oxygen vacancy ordered phase brownmillerite SrCoO 2.5 and the oxygen ordered phase perovskite SrCoO 3 . We show that the phase transformation boundary moves at a velocity that is highly anisotropic, traveling at speeds ~30 times faster laterally than through the thickness of the film. Taking advantage of this anisotropy, we show that three-dimensional metallic structures such as cylinders and rings can be realized. Our results provide a roadmap to the construction of complex meso-structures from their exterior surfaces. Local and reversible oxidation is used to exploit the very different properties of oxygen and vacancy ordered oxides. Here the authors directly image and make use of anisotropic migration velocities of oxygen in SrCoO x to create 3D meso-structures of those two phases by ionic liquid gating.