Resolving the Landauer paradox in ferroelectric switching by high-field charge injection

The critical dimension for reverse domain nucleation in the ferroelectric polarization switching of Pb(Zr0.4Ti0.6)O-3 (PZT) thin film was estimated experimentally from a coercive voltage estimation in Pt/Al2O3/PZT/Ir ferroelectric thin-film capacitors with various Al2O3 thicknesses and switching currents. The critical nuclei dimension for reverse domain formation in a 300-nm-thick PZT was only 4.5 +/- 0.4 nm, which is in agreement with theoretical predictions of the critical nucleus size. Almost all the coercive voltage was applied to the nucleation layer thickness during ferroelectric switching. The classical Merz's exponential law for the domain velocity description and Laudauer's paradox of an implausibly large nucleation energy barrier were understood in terms of the charge-injection limited domain motion described by thermionic field emission at the Pt/Al2O3 interface or Fowler-Nordheim tunneling at the Pt/PZT interface.