Terahertz conductivity of the metal-insulator transition in a nanogranular VO2 film.

Terahertz time-domain spectroscopy is used to measure the complex terahertz conductivity of a nanogranular vanadium dioxide (VO2) thin film as a function of temperature through the metal-insulator transition. The Drude-Smith model provides a good fit to the observed terahertz conductivity, revealing a metallic state that forms via switching of individual nanograins and strong carrier confinement within the nanograins due to scattering off grain boundaries. Furthermore, the directly applied Drude-Smith model provides a more accurate description of the measured terahertz conductivity in this material than either Bruggeman or Maxwell-Garnett effective medium theories. [ABSTRACT FROM AUTHOR]