Macroscopic Thermal Rectification Device Using Vanadium Dioxide Thin Film

thermal rectifier is a device in which heat flows in the forward direction but very little can flow in the opposite direction. Because the heat current can be controlled, the device is promising for future practical applications. In this study, the experiments were performed to investigate temperature-gated thermal rectification using macroscopic vanadium dioxide (VO_2) thin films deposited on an asymmetric substrate. The VO_2 phase transition, occurred near 340 K, changed both the electrical and thermal properties. Therefore, we used these properties to investigate the thermal rectification. The VO_2 thin films were prepared on cover glass substrates by RF sputtering with a VO_2 disk target at 500 ^∘C . The morphology of the thin films was investigated. Silver paste and a copper band were used to connect the films with a heater and temperature controller. We observed thermal rectification in the temperature range of T = 310 K–370 K in several film samples obtained with different degrees of asymmetry, deposition times, and post-annealing times. It is found that 60^∘ triangular-shaped samples have a rectification coefficient of 1.14, and the rectification coefficient is increased with the increasing of the angle. In addition, the two rectangular-shaped samples have the coefficient of 1.06, which could also be enhanced by increasing the ratio of width.