High quality thermochromic VO2 thin films deposited at room temperature by balanced and unbalanced HiPIMS

Abstract

In this paper, vanadium dioxide thin films were successfully deposited at room temperature by high power impulse magnetron sputtering (HiPIMS) using two different magnetron configurations: (i) a conventional balanced magnetron and (ii) an unbalanced magnetron. In the case of the unbalanced magnetron, the magnetic field is extended towards the substrate and the energetic ions in the plasma actively participate in film growth allowing to improve film crystallinity. The as-deposited thin films were annealed under Ar flow for 1 h to obtain thermochromic VO 2 (M) phase. The 120 nm films were first characterized at room temperature by X-ray diffraction (XRD). Then, the thermochromic behavior of the VO 2 films was investigated by electrical and optical characterizations. The effect of annealing temperature on thermochromic properties of VO 2 was studied showing that high quality VO 2 (M) film can be obtained at 300 °C using unbalanced HiPIMS. A very efficient change in transmittance exceeding 70% is observed in the IR spectral region. This investigation demonstrates the capability of using unbalanced HiPIMS to achieve high optical performances for VO 2 at lower temperature as well as the potential of this technology for the deposition of VO 2 (M) films onto temperature-sensitive substrates. • Fabrication of dense and stoichiometric crystalline VO 2 (M) thin films by HiPIMS. • Remarkable thermochromic behavior investigated by mid-infrared transmittance (2–25 μm) and resistivity measurements. • Thermal images using long-wavelength thermal camera (7.5–13 μm). • Use of unbalanced magnetron for annealing temperature reduction down to 300 °C.