Dielectric relaxation in amorphous thin films of SrTiO3 at elevated temperatures

Abstract

Temperature and frequency dispersion of dielectric permittivity was investigated on thin amorphous films of SrTiO3 prepared by a sputtering method using neutralized argon-ion beams. The amorphous SrTiO3 films deposited on glass substrates exhibited a marked dielectric relaxation at temperatures 500–800 K in a frequency range 0.1–50 kHz. This behavior was explained based on a dipolar relaxation of the Cole–Cole type with the static dielectric constant ε′s≂380, the constant at high frequency ε′∞≂35, and the distribution parameter of the relaxation time β≂0.8. The analysis of the temperature dependence of relaxation time gave the activation energy for the relaxation of about 1.08 eV and the characteristic relaxation time of the order of 10−12 s. In the temperature range where strong relaxation occurred, a semiconductor-type conduction having the activation energy of about 0.84 eV became dominant. A correlation between the mechanisms of the dielectric relaxation and the thermally activated motions of ionized defects in the amorphous structure is discussed.