| Ferroelectric materials have been utilized in a broad range of electronic, optical, and electromechanical applications and hold the promise for the design of future high-density nonvolatile memories and multifunctional nanodevices. The applications of ferroelectric materials stem from the functional structures of domains and domain walls and the ability to switch them by applying an electric field. A fundamental understanding of the microscopic mechanism underlying the domain formation and the domain switching, therefore, is critical for design of practical ferroelectric devices. In this work, a systematic study of atomic-scale polarization structures and microscopic domain-switching processes in ferroelectric BiFeO3 thin films is performed by using atomic-resolution scanning transmission electron microscopy (STEM) and in situ transmission electron microscopy (TEM). The presented results, including structures and switching of strongly charged domain walls (sCDWs) and complex phenomena induced by nanoscale impurity defects, shed light on the interplay between ferroelectric polarization and bound charge, strain, or defect-induced local perturbations. This study opens up the possibility for developing novel ferroelectric nanodevices by control of sCDWs or through defect engineering. |
