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Thin films of phase pure VO 2 (M1 phase) are deposited on thermally grown oxide (Si/SiO 2) substrate by reactive pulsed laser deposition of vanadium metal target. The influence of deposition parameters is studied by varying oxygen partial pressure while keeping other parameters constant. A thin film obtained at 50 mTorr is found to be phase pure by XRD and Raman spectral studies. SEM and AFM studies show smooth morphology with a surface roughness of 3–5 nm. The quality of the thin film was further established by characterizing the 68 ° C (T S M T ) transition by 2–3 orders of jump in resistance and a 60% change in reflectivity with minimum hysteresis. This single step process of deposition would be a suitable method for fabricating devices for smart window and metamaterial applications. [ABSTRACT FROM AUTHOR]

In the present study, rapid and green microwave synthesis has been used to synthesize V2O5 and reduced graphene oxide decorated with V2O5, a hybrid nanocomposite (rGO/V2O5), using an inorganic precursor. The synthesized nanocomposite is characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and UV–visible spectroscopy. The photocatalytic activity of V2O5 and rGO/V2O5 was studied by degrading methylene blue dye in sunlight. The kinetics of the dye degradation is studied by calculating the rate constant and the half-life of the degradation process. The rGO/V2O5 nanocomposite showed low resistance, thus increasing the diffusion of electrons, which prevents electron–hole recombination and hence enhances photocatalytic activity (80% degradation efficiency) when compared with bare V2O5. [ABSTRACT FROM AUTHOR]

Structural phase transition assisted micromechanical actuation of a vanadium dioxide (VO2) coated silicon microcantilever is presented. A 300 nm polycrystalline VO2 film was deposited over the silicon surface at 520 °C using metal organic chemical vapor deposition. The formation of the M1 monoclinic phase of the as-deposited VO2 film was confirmed by X-ray diffraction studies and further verified by temperature variable Raman spectroscopy. The heated VO2 film exhibits semiconductor-to-metal transition at 74 °C, which produces a change in the electrical resistance almost of three orders in magnitude. Consequently, the VO2 film undergoes structural phase transition from the monoclinic phase (011)M1 to a tetragonal phase (110)R. This generates a compressive stress within the VO2 film resulting in large, reversible cantilever deflection. This deflection was measured with a non-contact 3D optical profilometer, which does not require any vacuum conditions. Upon heating, the VO2 coated silicon cantilever produced a large reversible tip deflection of 14 μm at 50 °C. Several heating and cooling cycles indicate steep changes in the cantilever tip deflection with negligible hysteresis. In addition, the effect of thermal stress induced cantilever deflection was estimated to be as small as 6.4%, and hence can be ignored. These results were found to be repeatable within controlled experimental conditions. [ABSTRACT FROM AUTHOR]

Thin films of vanadium dioxide (VO2) are deposited on indium tin oxide (ITO), stainless steel (SS), and glass substrates using chemical vapour deposition. X-ray diffraction and Raman spectroscopy measurements confirmed the single phase nature of the VO2, which showed a phase transition from a low conducting state at low temperature(<68 °C) to a high conducting state at high temperature (>68 °C). This was confirmed by electrical conductance and infra-red reflectance measurements. X-ray photoelectron spectroscopy was used to measure the charge states of vanadium species. The optical constants of VO2 were determined using visible and near-infra red(NIR) reflectivity and show that the VO2 film on ITO has a lowered plasma frequency compared with VO2 on glass substrates. The thin films of VO2 enable a broadband of ultra-high absorption at mid-wave infra-red frequencies due to a Fabry-Pérot (F-P) like resonance due to the dielectric properties of ITO, SS, or glass. The tunability of this absorption band via VO2 thickness and the switchability by temperature makes the system attractive for absorptive coatings with controllable emissivity. [ABSTRACT FROM AUTHOR]