1 research outputs found
Electrochemically Induced Transformations of Vanadium Dioxide Nanocrystals
Vanadium dioxide (VO<sub>2</sub>)
undergoes significant optical, electronic, and structural changes
as it transforms between the low-temperature monoclinic and high-temperature
rutile phases. Recently, alternative stimuli have been utilized to
trigger insulator-to-metal transformations in VO<sub>2</sub>, including
electrochemical gating. Here, we prepare and electrochemically reduce
mesoporous films of VO<sub>2</sub> nanocrystals, prepared from colloidally
synthesized V<sub>2</sub>O<sub>3</sub> nanocrystals that have been
oxidatively annealed, in a three-electrode electrochemical cell. We
observe a reversible transition between infrared transparent insulating
phases and a darkened metallic phase by in situ visible–near-infrared
spectroelectrochemistry and correlate these observations with structural
and electronic changes monitored by X-ray absorption spectroscopy,
X-ray diffraction, Raman spectroscopy, and conductivity measurements.
An unexpected reversible transition from conductive, reduced monoclinic
VO<sub>2</sub> to an infrared-transparent insulating phase upon progressive
electrochemical reduction is observed. This insulator–metal–insulator
transition has not been reported in previous studies of electrochemically
gated epitaxial VO<sub>2</sub> films and is attributed to improved
oxygen vacancy formation kinetics and diffusion due to the mesoporous
nanocrystal film structure