Chemical solution-immersion deposition of BiFeO3 films reduced to nanometer thickness with stabilized polarization

Abstract

Bismuth ferrite (BiFeO3, BFO), a representative ferroelectric material exhibiting multiferroic characteristics at ambient temperature and demonstrating reversible polarization under external electric fields, has attracted significant attention in the development of prototype ferroelectric devices utilizing its films. Moreover, nanometer-thick, ultra-thin BFO films with stabilized polarization facilitate device miniaturization and low-power consumption. Herein, we report the fabrication of high-quality BFO films with enhanced crystallinity in a rhombohedral structure through the cost-effective chemical solution-immersion deposition method, which maintains compatibility with existing semiconductor technologies. Notably, piezoresponse force microscopy and Kelvin probe force microscopy characterizations demonstrate stabilized polarization with a low decay exponent of 0.014. The out-of-plane ferroelectric polarization can still be reversed at ambient temperature, even when the film thickness is reduced to approximately 3 unit cells. This research presents an effective approach for fabricating ultra-thin ferroelectric films, particularly suitable for future non-volatile memory devices.