Ferroelectricity in atomic-scale titanium dioxide dielectric films

Ferroelectricity at atomic-scale thickness would have important applications in next-generation electronics. Here, we report that a ferroelectric phase can be stabilized in titanium dioxide (TiO 2 ) films, a commonly known dielectric that is widely used in semiconductor technologies, by reducing thickness to <3 nanometers. Importantly, this ferroelectricity persists down to 1-nanometer thickness, approximately twice the unit-cell dimension. This thickness-dependent dielectric-to-ferroelectric phase transition demonstrates that an otherwise centrosymmetric, nonferroic fluorite-structure oxide can undergo structural inversion-symmetry breaking and exhibit voltage-switchable polarization. Atomic layer deposition–based low-temperature (<400°C) synthesis and the stability of this ferroelectricity on both silicon (Si) and amorphous surfaces [such as amorphous silicon dioxide (SiO 2 ) and amorphous carbon films] demonstrate the feasibility of integration with a large variety of materials.