期刊
APPLIED PHYSICS LETTERS
卷 109, 期 23, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.4971848
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资金
- Institute for Basic Science (IBS) [IBS-R014-D1]
- Electronics and Telecommunications Research Institute (ETRI)
- Center for Topological Matter at POSTECH [2011-0030786]
- National Research Foundation of Korea [2011-0030046] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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. Published by AIP Publishing.
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