Temperature dependence of thermal conductivity of VO2 thin films across metal insulator transition
Thermal conductivity of a 300 nm thick VO2 thin film and its temperature dependence across the metal insulator phase transition (TMIT) were studied using a pulsed light heating thermoreflectance technique. The VO2 and Mo/VO2/Mo films with a VO2 thickness 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 VO2 films were deposited by reactive rf magnetron sputtering using a V2O3 target and an Ar O2 mixture gas at 645 K. The VO2 films consisted of single phase VO2 as confirmed by X ray diffraction and electron beam diffraction. With increased temperature, the electrical resistivity of the VO2 film decreased abruptly from 6.3 x 10 1 to 5.3 x 10 4 O cm across the TMIT of around 325 340 K. The thermal conductivity of the VO2 film increased from 3.6 to 5.4 W m 1 K 1 across the TMIT. This discontinuity and temperature dependence of thermal conductivity can be explained by the phonon heat conduction and the Wiedemann Franz law.