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 BaTiO3 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 A, 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.