Preparation And Phase Transition Properties Of VO₂ Thin Films By Reactive Magnetron Sputtering

VO₂ is a typical thermochromic compound,whose phase transition temperature is 68℃. With the phase transition,its resistivity,magnetic susceptibility and optical transmissivity can produce reversible mutations.So the VO₂ thin films have extra high application value at smart windows,photoelectric switch,laser protection,optical storage and other fields.In this study,the target was simple substance vanadium.Vanadium oxide thin films were prepared by reactive magnetron sputtering through controlling the oxygen partial pressure and the annealing process accurately.The crystal phase structures of different films were characterized by XRD.Their surface micro-topography was studied by SEM and AFM.XPS ascertained the valence state of the V and stoichiometry of V and O atomicity.Raman spectroscopy analyzed the binding mode of V and O atoms.These testing and analysis show that 2%Pa oxygen partial pressure and 400℃annealing 2.5h are better process parameters for preparing VO₂ thin films.At these conditions,the films exhibit good crystalline states.The films have three VO₂ characteristic diffraction peaks:(100),(010),(001),and the vanadium form with V⁴⁺ mainly,n_o:n_v=2.044.Resistance-temperature measurements of fresh VO₂ thin films show that its phase transition temperature is 66.2℃,the thermal hysteresis width is 9℃,resistance reversible mutations reach three orders of magnitude.Then VO₂ thin films phase transition stability preliminary study were performed.The fresh VO₂ thin films what phase transition occur continuously five times,its phase transition temperature is 66.7℃,the thermal hysteresis width is 12℃,resistance reversible mutations still reach three orders of magnitude.A month later,the phase transition temperature is 68.5℃,the thermal hysteresis width is 20℃,resistance reversible mutations reduce to two orders of magnitude.The films' temperature coefficient of resistance(TCR) was calculated through resistance-temperature curve.The result of TCR exceeds-2×10^-2K^-1.So VO₂ thin films have good phase transition stability,meet practical requirements.