Atomic structure of domain and defect in layered-perovskite Bi2WO6 thin films

Layered-perovskite oxide thin films provide new opportunities to design next-generation electronic devices with their special structure and potentially excellent electrical properties. The microstructure and domain structure in epitaxial Bi2WO6 (BWO) thin films have been investigated by advanced transmission electron microscopy (TEM) combined with piezoresponse force microscopy (PFM). A slight distortion of oxygen octahedron, which accompanies the movement of the Bi2O2 fluorite-like sheet relative to the perovskite-like WO4 blocks, results in the formation of 90° domains. A kind of nanoscale defect is characterized by aberration-corrected scanning transmission electron microscopy (AC-STEM). An extra Bi-O layer is suggested to be presented at the Bi2O2 fluorite-like sheet. The present study may help to enrich the understanding of ferroelectric domain switching on the microscopic scale and the effect of defects on the ferroelectric property.