Temperature dependence of thermal conductivity of VO₂ thin films across metal-insulator transition

Thermal conductivity of a 300-nm-thick VO₂thin film and its temperature dependence across the metal-insulator phase transition (T_MIT) were studied using a pulsed light heating thermoreflectance technique. The VO₂and Mo/VO₂/Mo films with a VO₂thickness of 300 nm were prepared on quartz glass substrates: the former was used for the characterization of electrical properties, and the latter was used for the thermal conductivity measurement. The VO₂films were deposited by reactive rf magnetron sputtering using a V₂O₃target and an Ar-O₂mixture gas at 645K. The VO₂films consisted of single phase VO₂as confirmed by X-ray diffraction and electron beam diffraction. With increased temperature, the electrical resistivity of the VO₂film decreased abruptly from 6.3 × 10_-1to 5.3 × 10_-4Ωcm across the T_MITof around 325-340K. The thermal conductivity of the VO₂film increased from 3.6 to 5.4W m_-1K_-1across the T_MIT. This discontinuity and temperature dependence of thermal conductivity can be explained by the phonon heat conduction and the Wiedemann-Franz law.