Preparation and phase transition characterization of VO 2 thin film on single crystal Si (100) substrate by sol–gel process

Vanadium dioxide (VO 2 ) thin films were fabricated on single crystal Si (100) substrates by sol–gel method, including a process of annealing a vanadium pentoxide (V 2 O 5 ) gel precursor at different temperatures. The crystalline structure and morphology of the films were investigated by XRD, FE-SEM and AFM, indicating that the films underwent the grain growth, agglomeration and grain refinement process with increased annealing temperatures. The film annealed at 500 °C exhibits the formation of VO 2 phase with a strong (011) preferred orientation and high crystallinity, the surface of the film is uniform and compact with a grain size of about 120 nm. Meanwhile, the film exhibits excellent phase transition properties, with a decrease of transmittance from 35.5 to 2.5% at λ = 25 μm and more than 3 orders of resistivity magnitude variation bellow and above the phase transition temperature. The phase transition temperature is evaluated at 60.4 °C in the heating transition and 55.8 °C in the cooling transition. Furthermore, the phase transition property of the VO 2 film appears to be able to remain stable over repetitive cycles 100 times.