Electrical measurements of dielectric nonlinearities in ferroelectric bilayer thin films

Abstract

Frequency dependence of the dielectric response is studied for ferroelectric bilayer thin-film capacitors under a cyclic bias voltage. The approach used in this work enables probing strong dielectric nonlinearities at millisecond and microsecond time scales during polarization switching in thin films. The frequency-dependent changes that are observed in the relative dielectric permittivity of PbZr0.8Ti0.2O3/PbZr0.6Ti0.4O3 and PbZr0.6Ti0.4O3/PbZr0.2Ti0.8O3 epitaxial bilayers without applying the cyclic bias are small in the kHz-to-MHz frequency range. When the bias is applied, a strong frequency dependence of the relative dielectric permittivity is observed during polarization switching. For instance, the permittivity of the PbZr0.6Ti0.4O3/PbZr0.2Ti0.8O3 bilayer changes from εr≈300 at 100 kHz to εr≈1600 at 2 kHz. The observed frequency dependence of the permittivity can be described by [1+TT+Tcln(1ωt0)]2 that has been proposed for dynamic response in systems involving pinning at two-dimensional domain walls.