Dielectric enhancement and Maxwell-Wagner effects in ferroelectric superlattice structures

In an attempt to reproduce the functional properties associated with relaxo r electroceramics, pulsed laser deposition has been used to fabricate thin- film capacitor structures in which the dielectric layer is composed of a su perlattice of Ba0.8Sr0.2TiO3 and Ba0.2Sr0.8TiO3. The properties of the capa citors were investigated as a function of superlattice periodicity. The die lectric constant was significantly enhanced at stacking periodicities of a few unit cells, consistent with relaxor behavior. However, enhancement in d ielectric constant was generally associated with high dielectric loss. Anal ysis of the imaginary permittivity as a function of frequency shows that fi ne-scale superlattices conform to Maxwell-Wagner behavior. This suggests th at the observed enhancement of the real part of the dielectric constant is an artifact produced by carrier migration to interfaces within the dielectr ic. A comparison of this data with that already published on dielectric sup erlattices suggests that previous claims of an enhancement in dielectric co nstant may also be attributed to the Maxwell-Wagner effect. (C) 2000 Americ an Institute of Physics. [S0003-6951(00)01136-0].