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Direct Observation of the M2 Phase with its Mott Transition in a VO2 Film
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- Authors
- Hoon Kim, Tetiana V. Slusar, Dirk Wulferding, Ilkyu Yang, Jin-Cheol Cho, Minkyung Lee, Hee Cheul Choi, Yoon Hee Jeong, Hyun-Tak Kim, Jeehoon Kim
- Issue Date
- 2016-12
- Citation
- Applied Physics Letters, v.109, no.23, pp.1-5
- ISSN
- 0003-6951
- Publisher
- American Institute of Physics (AIP)
- Language
- English
- Type
- Journal Article
- Abstract
- In VO2, the explicit origin of the insulator-to-metal transition is still disputable between Peierls and Mott insulators. Along with the controversy, its second monoclinic (M2) phase has received considerable attention due to the presence of electron correlation in undimerized vanadium ions. However, the origin of the M2 phase is still obscure. Here, we study a granular VO2 film using conductive atomic force microscopy and Raman scattering. Upon the structural transition from monoclinic to rutile, we observe directly an intermediate state showing the coexistence of monoclinic M1 and M2 phases. The conductivity near the grain boundary in this regime is six times larger than that of the grain core, producing a donut-like landscape. Our results reveal an intra-grain percolation process, indicating that VO2 with the M2 phase is a Mott insulator.
- KSP Keywords
- Atomic force microscope(AFM), Direct observation, Electron correlations, Grain core, Intermediate states, M2 phase, Mott insulator, Mott transition, Near the grain boundary, Raman scattering(SERS), conductive atomic force microscopy