Fabrication and characterization of furnace oxidized vanadium dioxide thin films

Vanadium dioxide thin films have been prepared on lightly doped silicon substrates via the electron beam evaporation of pure vanadium and subsequent furnace oxidation in an oxygen environment at 300 °C. The as-fabricated thin films exhibit a phase transition at 68 °C, a 26% change in transmittance at a near-infrared wavelength of λ = 2.5 μm, and a 17% change in transmittance at a mid-infrared wavelength of λ = 10 μm with temperature. The composition of the VO₂ has been investigated using X-ray diffraction and Raman spectroscopy. The morphology and thicknesses of the thin films have been characterized using atomic force microscopy. Fourier transform infrared spectroscopy is employed to investigate the temperature-dependent optical properties of the prepared VO₂ thin films. The dielectric constants of the insulating and metallic VO₂ are fitted to a Lorentz model and dispersion model, respectively. Furthermore the heating and cooling curves of the prepared films are presented, showing a transition range of 57 °C to 77 °C upon heating and a transition range of 37 °C to 57 °C upon cooling. Lastly, the temperature-dependent filling fraction of the prepared films is determined and a model for the optical properties of the fabricated VO₂ in phase transition is presented.