Composition dependence of dielectric function in ferroelectric BaCo_xTi_(1_x)O_3 films grown on quartz substrates by transmittance spectra

摘要

Near-infrared-ultraviolet optical properties of BaCo_x/Ti_(1-x)O_3 (BCT) (x from 1.0% to 10%) films have been investigated by the transmittance spectra. The dispersion functions in the photon energy range of 1.24-6.2 eV have been extracted by fitting the experimental data with Adachi's model. It was found that the oscillator and dispersion energies linearly increase with the Co composition and the maximum optical transition occurs near the energy range of 4.3-5.0 eV for the BCT materials. The absorption coefficient at the visible region linearly increases with the composition due to grain boundaries and disorder induced band tail into the forbidden gap.