Dynamic response of polydomain ferroelectric barium titanate epitaxial thin films and its field dependence

The nature of ferroelectric domain dynamics in polydomain epitaxial barium titanate thin film was investigated using the linear electro-optic effect. The dynamic response was studied as a function of bias field under pulsed excitation. Upon removal of the bias pulse a millisecond long transient response was observed that is attributed to 90°domain reversal. The dynamic response and its field dependence are described by the Kohlrausch-Williams-Watts stretched exponential function in time with an average relaxation time 〈τ〉. This average time for polarization reversal is a function of applied electric field E and is given by 〈τ〉 = τ0 exp (α/E), where τ0 is the prefactor and α is the activation field. The measured activation fields depended on bias. Activation fields of 2.0 and 0.7 V/μm measured under high and low bias conditions are comparable to those observed for bulk barium titanate.