Phase changeable vanadium dioxide (VO₂) thin films grown from vanadium pentoxide (V₂O₅) using femtosecond pulsed laser deposition

There are significant challenges accompanied by fabricating a pure crystalline VO₂ (M1) thin film with an abrupt metal to insulator phase change properties. Most fabrication methods yield an amorphous VO₂ thin film that requires a post-annealing process to be converted into crystalline VO₂ (M1). Hence, the thickness of VO₂ (M1) films produced is very limited. In this work, we report the growth of pure VO₂ (M1) crystalline thin films onto a sapphire substrate in an oxygen atmosphere by the femtosecond pulsed laser deposition technique and using vanadium pentoxide (V₂O₅) as an ablation target. The thin films were deposited at substrate temperatures of 25 °C, 400 °C, and 600 °C, which reveal the crystallized structures of VO₂ (M1) without post-annealing. The thin film deposited at a substrate temperature of 600 °C exhibits a sharp and an abrupt metal-to-insulator transition (MIT) at a temperature of 66.0 ± 2.5 °C with nearly four orders of magnitude of the resistivity change (3.5 decades) and a narrow MIT hysteresis width of 3.9 °C. Furthermore, the influence of the substrate temperature, nanoparticle or grain size, and film thickness on the MIT parameters such as sharpness of the transition temperature, hysteresis width, and amplitude are discussed for potential applications of tunable antennas, terahertz planar antennas, and RF-microwave switches.