Emergent ferroelectricity in subnanometer binary oxide films on silicon.

Cheema, Suraj S; Shanker, Nirmaan; Hsu, Shang-Lin; Rho, Yoonsoo; Hsu, Cheng-Hsiang; Stoica, Vladimir A; Zhang, Zhan; Freeland, John W et al. · Science · 2022

basic_science · Level V

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Abstract

The critical size limit of voltage-switchable electric dipoles has extensive implications for energy-efficient electronics, underlying the importance of ferroelectric order stabilized at reduced dimensionality. We report on the thickness-dependent antiferroelectric-to-ferroelectric phase transition in zirconium dioxide (ZrO<sub>2</sub>) thin films on silicon. The emergent ferroelectricity and hysteretic polarization switching in ultrathin ZrO<sub>2</sub>, conventionally a paraelectric material, notably persists down to a film thickness of 5 angstroms, the fluorite-structure unit-cell size. This approach to exploit three-dimensional centrosymmetric materials deposited down to the two-dimensional thickness limit, particularly within this model fluorite-structure system that possesses unconventional ferroelectric size effects, offers substantial promise for electronics, demonstrated by proof-of-principle atomic-scale nonvolatile ferroelectric memory on silicon. Additionally, it is also indicative of hidden electronic phenomena that are achievable across a wide class of simple binary materials.