Ferroelectricity down to at least 2 nm in multiferroic BiFeO3 epitaxial thin films

We report here on the preservation of ferroelectricity down to 2 nm in BiFeO3 ultrathin films. The electric polarization can be switched reversibly and is stable over several days. Our findings bring insight on the fundamental problem of ferroelectricity at low thickness and confirm the potential of BiFeO3 as a lead-free ferroelectric and multiferroic material for nanoscale devices.