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

In this paper, vanadium dioxide thin films were successfully deposited at room temperature by high power impulse magnetron sputtering (HiPIMS) using two different magnetron configuration: (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 VO2(M) phase. The 120 nm films were first characterized at room temperature by X-ray diffraction (XRD). Then, the thermochromic behavior of the VO2 films was investigated by electrical and optical characterizations. The effect of annealing temperature on thermochromic properties of VO2 was studied showing that high quality VO2(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 VO2 at lower temperature as well as the potential of this technology for the deposition of VO2(M) films onto temperature-sensitive substrates