This chapter presents a review on the recent progress in transmission electron microscopy (TEM) studies of ferroelectric DWs in one of the most widely studied ferroelectric systems — BiFeO3 thin films. This system has been chosen representative for a much wider range of ferroelectric perovskites with functional DWs, due to its strong spontaneous polarization, coexistence of ferroelectricity, ferroelasticity and antiferromagnetism, and numerous functionalities at the DWs. Here, the chapter first briefly introduces the instrumentation, experimental procedures, imaging mechanisms, and analytical methods of the state-of-the-art TEM-based techniques. The application of these techniques to the study of DW structures and switching behaviors is demonstrated, with particular emphasis on the critical roles of interfaces and defects, and interplay between different types of DWs. The phenomena and mechanism discovered in the model system of BiFeO3 are also applicable to many other ferroelectric materials with similar DW structures. The results not only advance the fundamental understanding of static and dynamic properties of ferroelectric DWs, but also form the basis for designing of practical ferroelectric-DW-based devices.
Controlled manipulation of conductive ferroelectric domain walls and nanoscale domains in BiFeO3 thin films