Effects of gamma ray irradiation on fundamental properties of perovskite thin films prepared by a sol-gel technique

Polycrystalline Fe-doped barium titanate (Fe-doped BaTiO₃) and Fe-doped calcium copper titanate (Fe-doped CaCu₃Ti₄O₁₂) thin films were deposited on quartz substrates with the annealing temperature of 800℃ by a sol-gel spin coating technique. The ⁶⁰Co source (Gammacel 220 Excell) with the exposure rate of 10 kGy/hr was used to irradiate our film in order to investigate the changes of their optical and electrical properties. The transmittance of Fe-doped BaTiO₃ film decreased by 11% after 15 kGy irradiation, while that of Fe-doped CaCu₃Ti₄O₁₂ film decreased by 4.8% after 3 kGy irradiation respectively. The refractive index of the films, as measured in the 350-750 nm wavelength range was in the 2.17-1.88 range and increased to 2.34-1.95 after gamma irradiation at 15 kGy for Fe-doped BaTiO₃ and increased from 2.24-2.00 range to 2.30-2.00 range for Fe-doped CaCu₃Ti₄O₁₂ upon the gamma irradiation with a 3 kGy dose, respectively. The extinction coefficient of both types of the films was in the order of 10⁻² and increased after gamma irradiation. The capacitance of the CaCu₃Ti₄O₁₂ film before gamma ray irradiation which increases from 1.36-1.22 pF to 1.62-1.36 pF after gamma ray irradiation with 5 kGy doses. The dielectric constant of the CaCu₃Ti₄O₁₂ film increased from 314-280 to 552-308 and loss tangent of CaCu₃Ti₄O₁₂ film increased from 0.020 - 0.013 to 0.138-030.