Introduction of charged domain walls into BiFeO3 thin films using a pit-patterned SrTiO3 (001) substrate

Abstract

This work demonstrated the artificial introduction of charged domain walls (CDWs) into a ferroelectric BiFeO3 (BFO) thin film by domain structure control using a pit-patterned SrTiO3 (STO) (001) surface. The pattern consisted of 1 × 1 μm square holes with sloped sides, fabricated on the STO (001) surface by electron beam lithography and Ar+ ion etching. Scanning electron and atomic force microscopy analyses demonstrated that the pit slopes had angles of 6.1°–7.6°, which were sufficient to limit the in-plane growth direction of the BFO at step edges on the STO surface, and thus control the domain structure. Lateral and vertical piezoresponse scanning force and transmission electron microscopy confirmed the artificial introduction of CDWs in the pit and showed that the sign of the CDWs could be reversed via ferroelectric polarization switching. This domain control technique based on a pit pattern provides a simple approach to the integration of ferroelectric DWs into functional devices.