Reversible Manipulation of Polar Topologies in Oxide Ferroelectrics via Electric Fields

Polar topologies show great potentials in memories and other nano-micro devices. To integrate with silicon conducting circuits, it is vital to understand the dynamic evolution and the transformation of different domain configurations under external stimulus. Here in situ transmission electron microscopy is performed and the electrically controlled creation and annihilation of large-scale polar flux-closure array from typical c/a domains in PbTiO₃/SrTiO₃ bilayers is directly observed. It is found that the transformation is reversible after removal of external electric fields. Increasing external electric fields on (PbTiO₃/SrTiO₃)₅ multilayered films, it is further found that the flux-closure domains are nucleated and propagated via the steps of first the formation of new c domains and then connection with neighboring c domains. The transition from a/c domains to flux-closure arrays under electric fields is collaborated with evaluating energy variations by phase-field simulations in which the electrostatic energy plays an important role. These results demonstrate the polar topologies can be reversibly manipulated by external stimuli, which sheds light on further understanding the dynamics behavior of polar topologies and helps for future nanoelectric applications.