VO2 films on flexible thin polyimide films: Fabrication and characterization of electrical and optical properties in insulator-metal transition

We report on the realization of thin polyimide films on which phase transition vanadium dioxide (VO2) films grow. Biased reactive sputtering achieved b-axis-oriented growth of VO2 films on ZnO-buffered polyimide films with a thickness of 8.5 μm. By peeling off the polyimide films from a quartz substrate, stand-alone VO2/ZnO/polyimide layered films that exhibited insulator-metal transition (IMT) with nearly three orders of resistivity change were fabricated. Dependence of IMT on a mechanical curvature was investigated for demonstrating the high flexibility. Temperature-dependent optical transmittance at 1.45 μm showed a high switching ratio for infrared light in VO2/ZnO/polyimide layered films. The proposed structure can be utilized for active metasurfaces that control terahertz waves with quite low reflection loss due to its small thickness.