Infrared optical properties of Bi2Ti2O7 thin films by spectroscopic ellipsometry

Bi2Ti2O7 thin films have been grown directly on n-type GaAs (1 0 0) by the chemical solution decomposition technique. X-ray diffraction analysis shows that the Bi2Ti2O7 thin films are polycrystalline. The optical properties of the thin films are investigated using infrared spectroscopic ellipsometry (3.0-12.5 μm). By fitting the measured ellipsometric parameter (Ψ and Δ) data with a three-phase model (air/Bi2Ti2O7/GaAs), and Lorentz-Drude dispersion relation, the optical constants and thickness of the thin films have been obtained simultaneously. The refractive index and extinction coefficient increase with increasing wavelength. The fitted plasma frequency ωp is 1.64x1014 Hz, and the electron collision frequency γ is 1.05x1014 Hz, and it states that the electron average scattering time is 0.95x10-14 s. The absorption coefficient variation with respect to increasing wavelength has been obtained