Kinetics of polarization reversal in ferroelectric films: role of domain nucleation and domain wall motion

Understanding of polarization reversal mechanisms in ferroelectric films is essential for evaluation and prediction of the properties of ferroelectric devices including nonvolatile memories. The widely accepted approach based on the domain wall motion kinetics describes correctly switching in single crystals but does not work properly for thin ferroelectric films used for memory applications. Recently an alternative approach based the on statistics of nucleation of the reversed polarization domain has been proposed. The switching model based on this approach provides an adequate description of the polarization reversal in thin films as a function of time and voltage at room temperature. The present paper examines the validity of this concept at different voltages and temperatures and discusses the competing switching mechanisms. In particular, it is shown that at very low temperatures a crossover between nucleation-limited switching kinetics and switching kinetics of domain wall motion typical for single crystal occurs in PZT ferroelectric films. The practical application of the polarization reversal models for evaluation of the switching behavior of ferroelectric capacitors is discussed.