Detailed electrical and photoemission studies were carried out to probe the chemical nature of the insulating ground state of VO2, whose properties have been an issue for accurate prediction by common theoretical probes. The effects of a systematic modulation of oxygen over-stoichiometry of VO2from 1.86 to 2.44 on the band structure and insulator–metal transitions are presented for the first time. Results offer a different perspective on the temperature- and doping-induced IMT process. They suggest that charge fluctuation in the metallic phase of intrinsic VO2results in the formation of e−and h+pairs that lead to delocalized polaronic V3+and V5+cation states. The metal-to-insulator transition is linked to the cooperative effects of changes in the V–O bond length, localization of V3+electrons at V5+sites, which results in the formation of V4+–V4+dimers, and removal of
Many correlated systems feature an insulator-to-metal transition that can be triggered by an electric field. Although it is known that metallization takes place through filament formation, the details of how this process initiates and evolves remain elusive. We use in-operando optical reflectivity to capture the growth dynamics of the metallic phase with space and time resolution. We demonstrate that filament formation is triggered by nucleation at hotspots, with a subsequent expansion over several decades in time. By comparing three case studies (VO2, V3O5, and V2O3), we identify the resistivity change across the transition as the crucial parameter governing this process. Our results provide a spatiotemporal characterization of volatile resistive switching in Mott insulators, which is important for emerging technologies, such as optoelectronics and neuromorphic computing.
more » « less- NSF-PAR ID:
- 10288480
- Publisher / Repository:
- American Association for the Advancement of Science (AAAS)
- Date Published:
- Journal Name:
- Science
- Volume:
- 373
- Issue:
- 6557
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- p. 907-911
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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