Phase-field simulations of surface charge-induced polarization switching

Understanding and controlling surface charge-induced polarization switching have attracted interest of researchers extensively, and the rich physical interactions between ionic and atomic displacements play a significant role in polarization reversal. In this work, we investigated the mechanism of surface charge-induced polarization switching in PbZr_0.2Ti_0.8O₃ and BiFeO₃ thin films by phase-field simulations. We observed ferroelectric polarization reversal by applying positive/negative charge on the top of a thin film, because the double well of free energy becomes asymmetric by applying surface charge. It is found that the nucleation of switching always starts from the surface and gradually expands into the whole film. In BiFeO₃ thin films, the formation of an anti-vortex domain provides topological protection for hindering surface charge-induced polarization switching. The present study, therefore, contributes to a better understanding of charge-induced polarization switching and provides guidance for the experimental design of reversible electronic devices by selecting the appropriate polarity region.