Temperature-dependent multiangle FTIR NIR-MIR ellipsometry of thermochromic VO2 and V1−xWxO2 films

VO2 and W-doped VO2 thin films were prepared by Radio Frequency (RF) reactive magnetron sputtering using V-metal target. The amount of W doping was quantified by Rutherford Backscattering Spectrometry (RBS). The optical constants of VO2 and V1−xWxO2 films were inferred above and below the transition temperature by temperature-dependent multiangle ellipsometry in the Near InfraRed (NIR) spectral range and by temperature-dependent multiangle Fourier Transform InfraRed ellipsometry (FTIR) in the Near InfraRed-Middle InfraRed (NIR-MIR) spectral range up to 20,000 nm. The effect of the doping concentration on their optical constants was studied. A validation of the results was obtained comparing the optical constants determined by point-by-point fitting with those determined by the Lorentz-Drude model and the empirical Lorentz-Cauchy dispersion formula.