Micrometer x-ray diffraction study ofVO2films: Separation between metal-insulator transition and structural phase transition

Abstract

In order to clarify whether ${\text{VO}}_{2}$ is a Mott insulator or a Peierls insulator, the metal-insulator transition (MIT) and the structural phase transition (SPT) are simultaneously monitored for ${\text{VO}}_{2}$ films by current-voltage curve and diffraction measurements using a synchrotron micro-x-ray beam. In the regime showing a metallic conductivity below the SPT temperature (approximately $70\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$), only the diffraction planes of the monoclinic structure are observed, while planes of the tetragonal structure are absent. This observation reveals the presence of a monoclinic and metal phase between the MIT and the SPT as a characteristic of a Mott insulator.