Metallic monoclinic phase in VO2 induced by electrochemical gating: In situ Raman study

Gupta, Satyendra Nath and Pal, Anand and Muthu, DVS and Kumar, Anil PS and Sood, AK (2016) Metallic monoclinic phase in VO2 induced by electrochemical gating: In situ Raman study. In: EPL, 115 (1).

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Abstract

We report in situ Raman scattering studies of electrochemically top gated VO2 thin film to address metal-insulator transition (MIT) under gating. The room temperature monoclinic insulating phase goes to metallic state at a gate voltage of 2.6V. However, the number of Raman modes do not change with electrolyte gating showing that the metallic phase is still monoclinic. The high-frequency Raman mode A(g)(7) near 616 cm(-1) ascribed to V-O vibration of bond length 2.06 angstrom in VO6 octahedra hardens with increasing gate voltage and the B-g(3) mode near 654 cm-1 softens. This shows that the distortion of the VO6 octahedra in the monoclinic phase decreases with gating. The time-dependent Raman data at fixed gate voltages of 1 V (for 50 minutes, showing enhancement of conductivity by a factor of 50) and 2 V (for 130 minutes, showing further increase in conductivity by a factor of 5) show similar changes in high-frequency Raman modes A(g)(7) and B-g(3) as observed in gating. This slow change in conductance together with Raman frequency changes show that the governing mechanism for metalization is more likely due to the diffusion-controlled oxygen vacancy formation due to the applied electric field. Copyright (C) EPLA, 2016

Item Type:	Journal Article
Publication:	EPL
Additional Information:	Copy right for this article belongs to the EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 6 RUE DES FRERES LUMIERE, MULHOUSE, 68200, FRANCE
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	03 Dec 2016 05:16
Last Modified:	03 Dec 2016 05:16
URI:	http://eprints.iisc.ac.in/id/eprint/55236

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