Microscopic and Nanoscale Perspective of the Metal−Insulator Phase Transitions of VO₂: Some New Twists to an Old Tale

Abstract

The peculiarities in the electronic structure of the seemingly simple binary vanadium oxide VO2, as manifested in a pronounced metal−insulator phase transition in proximity to room temperature, have made it the subject of extensive theoretical and experimental investigations over the last several decades. We review some recent advances in theoretical treatments of strongly correlated systems along with ultrafast measurements of VO2 samples that provide unprecedented mechanistic insight into the nature of the phase transition. Scaling VO2 to nanoscale dimensions has recently been possible and has allowed well-defined VO2 nanostructures to serve as model systems for measurements of intrinsic properties without obscuration from grain boundary connectivities and domain dynamics. Geometric confinement, substrate interactions, and varying defect densities of VO2 nanostructures give rise to an electronic and structural phase diagram that is substantially altered from the bulk. We postulate that design principles deduced from fundamental understanding of phase transitions in nanostructures will allow the predictive and rational design of systems with tunable charge and spin ordering.

Spectroscopic analysis of phase constitution of high quality VO2 thin film prepared by facile sol-gel method

“…And there is no evidence for isolation of stable M2 phase for large VO 2 crystallites without apparent stresses and defects. 42 Thus it is speculate that the appearance of stable M2 phase for undoped VO 2 films is accompanied by apparent applied/external stresses or slight increase in temperature, which is different from the situation in the nanostructures that have strong surface-induced stress to stabilize M2 phase at room temperature.…”

Anisotropic electron-phonon coupling investigated by ultrafast electron crystallography: Three-temperature model

“…Despite of its simplistic atomic composition, VO 2 exhibits complex electronic and structural phase diagrams 77,78 . Like in many correlated electron materials, MIT in VO 2 is subject to intertwined control parameters (e.g.…”

Ultrafast photoinduced insulator-to-metal transitions in vanadium dioxide

“…The critical fluency is reduced when approaching the critical temperature due to a decrease in tilting angle 8 . The ultrafast switching of the optical and electrical properties have inspired a wide range of possible applications 26 .…”