Annealing temperature dependence of optical properties of SrTiO$_{3}$/BaTiO$_{3}$ multilayered films on indium tin oxide*

We have grown SrTiO$_{3}$/BaTiO$_{3}$ thin films with multilayered structures deposited on indium tin oxide (ITO) coated glass by a sol-gel deposition. The annealing temperatures were varied in the range of 300-650\r{ }C to study the change in optical properties of the films. The absorption edge shifts to longer wavelengths with increasing in annealing temperature. The band gap energy of the films increases in the 3.64-4.19 eV range and the grain size becomes smaller when the annealing temperature decreases. The film annealed at 650\r{ }C showed the maximum refractive index of 2.09-1.91 in the 450-750 nm wavelength range while the extinction coefficient was less than 0.05. The Urbach energy obtained from absorbance data for the multilayer films annealed at 500\r{ }C, 550\r{ }C and 600\r{ }C are 0.272 eV, 0.263 eV and 0.220 eV, respectively.