Terahertz Properties of a VO2 Thin Film near Metal-Insulator Transition Region

Abstract

Vanadium dioxide (VO2) has been attracting great interests as a first-order metal-insulator transition (MIT) material. Even though VO2 has been studied extensively more than 50 years, physical principles of MIT process of VO2 is still not clear and many theoretical debates are going on. Especially at THz frequency, temperature dependences of dielectric constant from many papers show big differences. In this work, we present THz properties of a VO2 thin film grown on a sapphire substrate across the metal-insulator transition measured by high precision THz-TDS. Our experimental data show giant real part of permittivity near the metal-insulator transition temperature. This dielectric anomaly is shown for the first time with THz-TDS. Bruggeman (BR) effective medium theory (EMT) successfully explains our giant permittivity while Maxwell-Garnett (MG) EMT fails. Our results provide precise THz complex permittivity and insight for THz application devices using VO2 thin film.