Plasma-Induced Phase Change in Vanadium Dioxide

We report here, a plasma-driven metal-insulator transition (MIT) in thin thermo chromic vanadium dioxide (VO
2
) films. VO
2
is a Peierls- Mott insulator that undergoes a change from an insulating to a metallic state at ~68 °C, accompanied by a structural transition from monoclinic to rutile phase
¹
. In our VO
2
low-temperature plasma devices, the observed transition occurs as a result of the strong electric field in the cathode sheath of the pulsed gas-phase plasma. Prior studies by Ko et al. at Harvard
²
, demonstrated a non-plasma-based electric field-assisted phase transition with fields of~ 1 0
⁷
V/m, and calculations by Hormoz et al. in estimating the critical field required for transition via a Poole-Frenkel mechanism supported these results
³
, The magnitude of this required field is identical to those in the cathode fall region of some plasma devices regularly fabricated at the University of Illinois for various applications, including a plasma transistor where the intense sheath field is capable of reverse-biasing the collector-base junction
⁴
, The magnetron-sputtered VO
2
films utilized for this work ranged in thickness from 50 nm to 150 nm and had an area of 1 x 1 cm2. Optical and electrical investigation across the transition would be presented in this novel method of MIT-triggering in the correlated oxide.