where ( ) is the frequency dependence of permittivity, DC is permittivity of ITO at the direct current (DC) conditions, is the conductivity, 0 is the permittivity of vacuum, ∞ is the permittivity at high frequency, P is the plasma frequency, Γ is the damping constant. Wolf et. al analyzed ITO films using Drude model and found the parameters for the sputtered films to be following ∞ = 4.4, P = 3.36 × 10 16 rad/s, Γ = 1.05 × 10 14 1/s . The 3D conductivity model can be used for materials which have low losses. A simple formula for conductivity at direct current (DC) condition can be derived to define model from DC measurements of refractive index and conductivity. However, if material has a frequency(wavelength) dependence of electrical conductivity, it is obvious that a different model has to be applied for simulations. If free electric charges can follow at the AC frequency, the 3D conductive model becomes a suitable approximation. However, another model is required if response of charges to a high frequency is not instantaneous. The Drude model is promising for modeling the free electron behaviour in noble metals. It was successfully adapted for plasmonic metals Au, Ag, Cu. The relationship between parameters of the 3D conductivity and Drude-plasma can be combined as: