Direct observation of asymmetric domain wall motion in a ferroelectric capacitor

We report in situ transmission electron microscopy observations of the 180 degrees polarization switching process of a PbZr0.2Ti0.8O3 (PZT) capacitor. The preferential, but asymmetric, nucleation and forward growth of switched c-domains were observed at the PZT/electrode interfaces, arising due to the built-in electric field induced at each interface. The subsequent sideways growth of the switched domains was inhibited by the depolarization field due to the imperfect charge compensation at the counter-electrode and also at the boundaries with preexisting a-domains, which contributed further to the asymmetric switching behavior. It was found that the preexisting a-domains split into fine a- and c-domains constituting a 90 degrees stripe domain pattern during the 180 degrees polarization switching process, revealing that these domains also actively participated in the out-of-plane polarization switching. The real-time observations uncovered the origin of the switching asymmetry and further clarified the importance of charged domain walls and the interfaces with electrodes in the ferroelectric switching processes. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.