Refractive index of BaTiO₃ and SrTiO₃ films

Experimental data on the wavelength dependence of the refractive index in the wavelength range 0.3-1.0 μm is presented for thin films of BaTiO 3 and SrTiO3. The films of thickness 1-4 μm were prepared by sputter deposition at substrate temperatures of 300 to 600 K, resulting in amorphous films at the lower temperatures and " microcrystalline" films at the higher. Both thin-film phases have a lower index at a given wavelength than the corresponding crystalline value (e.g., at λ=5000 Å, n=2.00, 2.07, and 2.51 for amorphous, microcrystalline, and crystalline BaTiO3, respectively). The dispersion of the refractive index in the thin films follows a single-oscillator model with a higher oscillator energy and smaller oscillator strength than in the crystalline phase.