Dielectric enhancement and Maxwell–Wagner effects in ferroelectric superlattice structures

Abstract

In an attempt to reproduce the functional properties associated with relaxor electroceramics, pulsed laser deposition has been used to fabricate thin-film capacitor structures in which the dielectric layer is composed of a superlattice of Ba0.8Sr0.2TiO3 and Ba0.2Sr0.8TiO3. The properties of the capacitors were investigated as a function of superlattice periodicity. The dielectric constant was significantly enhanced at stacking periodicities of a few unit cells, consistent with relaxor behavior. However, enhancement in dielectric constant was generally associated with high dielectric loss. Analysis of the imaginary permittivity as a function of frequency shows that fine-scale superlattices conform to Maxwell–Wagner behavior. This suggests that the observed enhancement of the real part of the dielectric constant is an artifact produced by carrier migration to interfaces within the dielectric. A comparison of this data with that already published on dielectric superlattices suggests that previous claims of an enhancement in dielectric constant may also be attributed to the Maxwell–Wagner effect.