Relaxation dynamics of ionic liquid-VO2 interfaces and influence in electric double-layer transistors

Oxide semiconductor systems are often electrostatically doped with ionic liquids as gate insulators towards modulating carrier density and inducing phase transitions, while simultaneously serving as a means to probe their electronic phase diagram. The electronic and electrochemical properties of ionic liquid/correlated oxide interfaces are, therefore, important in interpreting such field-effect phenomena. Here, we use DEME-TFSI and VO2 as a model system to investigate the interface properties, slow relaxations, as well as field-effect in electric double layer transistor geometry. The stability of these interfaces is probed by combination of current-voltage measurements, x-ray photoelectron spectroscopy, impedance spectroscopy, and constant current charging. Three-terminal field effect transistor-type devices fabricated by photolithography are used to investigate kinetics of channel resistance modulations under varying gate bias polarity. Bias regions for reversible modulation of channel conductance have been determined. A time-dependent transconductance effect and as large as 20x increase in conductance are observed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704689]