Control of ferroelectric polarization in BiFeO3 bilayer films through interface engineering

Abstract

Predetermining the as-grown polarization of ferroelectric thin films is essential to integrate their reliable properties into electronic devices. However, studies have so far focused mainly on the control of the polarization state of a single ferroelectric layer. Here we report a strategy for the artificial modulation of pristine polarization in BiFeO₃ bilayer films. We have fabricated multilayers of BiFeO₃/SrTiO₃/BiFeO₃ on single-crystalline SrTiO₃ (001) substrates. It is found that the out-of-plane polarization components of the BiFeO₃ bilayer can be controlled by modifying the surface terminations of SrTiO₃ interlayer and SrTiO₃ substrate. Using aberration-corrected scanning transmission electron microscopy, we directly visualize the head-to-head and tail-to-tail polarization configurations formed by the BiFeO₃ bilayers. Polar discontinuity at the ferroelectric/non-ferroelectric interface is the reason for tuning the orientation of electrical polarization. Our work provides an effective route to design fascinating ferroelectric multilayers with well-defined polarization direction.