Effects of charge fluctuation and charge regulation on the phase transitions in stoichiometric VO₂.

ABSTRACT: 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 VO₂ from 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 VO₂ results 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 [Formula: see text] screening electrons. It is shown that the nature of phase transitions is linked to the lattice V³⁺/V⁵⁺ concentrations of stoichiometric VO₂ and that electronic transitions are regulated by the interplay between charge fluctuation, charge redistribution, and structural transition.

SUBMITTER: Joshi S 

PROVIDER: S-EPMC7553960 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature