Fast Polarization Reversal in Polycrystalline Ferroelectric Thin Films: The Origin of Size Effects.

The origin of size effects in polycrystalline ferroelectric films of Pb(Zr_1-xTi_x)O₃ having the frequency dependence of coercive field in the form ln(ν/ν₀)∼1/E_c² is investigated. A model of a surface source emitting thin ferroelectric domains with reversed polarization is employed to explain this unusual frequency dependence of polarization switching in polycrystalline films in a wide range of frequencies. The model also predicts that the activation energy for domain nucleation increases with the source size, indicating an increase in the coercive field as minimum size sources deteriorate. The proposed mechanism for the domain nucleation in polycrystalline PZT films can explain the electrode size dependence of the limiting frequency. This dependence is related with increasing role of the athermal domain growth in strongly inhomogeneous electric field near electrode edges. [ABSTRACT FROM AUTHOR]