Sub-critical field domain reversal in epitaxial ferroelectric films.

Domain nucleation in epitaxial (001)-oriented Pb(Zr_0.2TiO_0.8)O₃ ultrathin ferroelectric films under a sub-critical field regime is investigated by means of piezoresponse force microscopy (PFM). Analytical fits to the domain radius and velocity as a function of time indicate that 180 domain nucleation and growth under a biased PFM tip exhibit a thermally activated, creep behavior. It is also found that an electric field of less than half of the local coercive (or critical) field E_c^loc detected by PFM can create stable domains under prolonged bias application. Under these sub-critical bias conditions, it is the temporal evolution of the local electric-field profile due to the slow drift of screening charges or defects (e.g., ionic vacancies) that dictates domain nucleation and growth. [ABSTRACT FROM AUTHOR]