Nanoscale Ferroelectric Switching in Thin Films by in-situ TEM for Magnetoelectric Applications

The ferroelectric switching along the low-dimensional axis of nanoscale multiferroic BiFeO$_{3}$ thin films is studied in this work using in-situ transmission electron microscopy. With this technique, the atomic scale polarization distribution and the controlling influence of defects on growth kinetics are observed. Despite the inhomogeneous external field applied by a surface probe, nucleation sites are determined by the built-in fields formed within carrier depletion regions at the electrode interfaces. Homogenous full-film switching is often impeded by the pinning of domain growth by such features as point defect assemblies and from independent switching in the near-interface region. This inhomegeneity along the normal film axis has significant implications for the interpretation of surface probe ferroelectric switching measurements and for magnetoelectric applications which require ferroelastic switching at the interface.