Dielectric properties of (Ba0.5Sr0.5)TiO3 thin films

The dielectric properties of (Ba0.5Sr0.5)TiO3 (BST) thin films with high el ectrical resistivity were investigated. BST films are deposited on Pt/TiO2/ SiO2/Si substrates by a metal-organic deposition (MOD) method. The dielectr ic permittivity and ac conductivity of the films are measured in the freque ncy range 102-105 Hz. The dielectric permittivity epsilon (r) decreases sli ghtly with frequency f, following the relationship epsilon (r) = a + bf(n-1 ) (a, b and n are constants, n < 1). The ac conductivity <sigma>(f) increas es with frequency as sigma>(*) over bar * (f) similar to f(n). These result s indicate that the phonon-assisted jumps of electrons between localized st ates play an important role in the dielectric properties of BST thin films. The dielectric permittivity and ac conductivity of the BST thin films incr ease with grain size, and decrease with increasing temperature. A prelimina ry explanation is given. (C) 2000 Elsevier Science S.A. All rights reserved .