Temperature-induced metal-insulator transition (MIT) in vanadium dioxide (VO2) has been under intense research interest for decades both theoretically and experimentally. Due to the complex nature of electron correlations, the underlying physics behind the MIT in VO2 has yet to be fully grasped. In this work, we utilize the fine resolution of the scattering-type scanning near-field optical microscope to investigate the MIT in an epitaxial VO2 thin film on the (100)R TiO2 substrate with mid-infrared light. Bidirectional tweed-like metal-insulator phase coexistence patterns are observed and understood under the Landau free energy paradigm. More interestingly, delayed metallic nucleation is observed near the surface cracks due to local strain relief. This research proposes ideas in investigating the temperature-pressure phase diagram and tuning the interplay between local strain and MIT in oxide thin films.
Bibliographical noteFunding Information:
This work was supported by the RISE2 node of NASA’s Solar System Exploration Research Virtual Institute under NASA Cooperative Agreement No. 80NSSC19MO2015. X.Z.C., M.K.L., and D.N.B. acknowledge support from the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage (C2QA) under Contract No. DE-SC0012704. S.K. acknowledges support from the National Science, Research and Innovation Fund (NSRF) via the Program Management Unit for Human Resources & Institutional Development, Research and Innovation (Grant No. B05F640051). T.V.S. and H.T.K. acknowledge support from the Institute of Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Korean government (MSIT) via Grant No. 2017-0-00830.
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