Thermally activated switching kinetics in second-order phase transition ferroelectrics

The understanding of electric polarization dynamics is a complex problem of critical importance for both fundamental studies of ferroelectric materials and their applications to nonvolatile memories. In this paper we focus on second-order phase transition ferroelectrics, as defined in Landau-Devonshire framework, which display a particular free-energy profile as a function of the ordering parameter, that has two energy minima separated by an energy barrier. Assuming a domain nucleation polarization reversal mechanism, this particular energy dependence allowed us to introduce an electric polarization reversal model based on the nonequilibrium statistics of the domain nucleation process. Using the Pauli master equation we have determined the time-dependent occupation probabilities of the polarization states of the nucleation sites, which can be used to generate analytical expressions for the temporal dependence of the reversed polarization, transient switching current, and the switching time. In addition, we have derived an analytic expression for the time and thermal dependence of the coercive field and we discuss the depolarization field effects on the polarization reversal dynamics in thin-film ferroelectric structures.