Room-Temperature Ferroelectricity in Ultra-Thin p-Type BiCuSeO Films

Atomically thin 2D layered ferroelectric semiconductors, where polarization switching transpires within the channel material itself, are pivotal to advancing the next generation of high-performance electronics. Nevertheless, the challenge remains in either the controllable synthesis of films or the manipulation of associated ferroelectricity. Here, 2D p-type BiCuSeO (BCSO) films with a thickness down to ≈3 nm are successfully synthesized using molecular beam epitaxy. The room-temperature (RT) out-of-plane ferroelectricity is confirmed by piezoelectric force microscopy, showing robust ferroelectric switching capability. Insights derived from density functional theory, coupled with the ferroelectric dipole map in cross-sectional scanning transmission electron microscopy images, suggest that the polar displacement of [CuSe] layers under electric fields primarily contributes to ferroelectricity in the BCSO film. Furthermore, the switching behavior of the BCSO-based ferroelectric tunnel junction has been clarified, exhibiting distinct ON and OFF states. Our results illustrate that such an ultrathin RT ferroelectric semiconductor could serve as a versatile material for future multifunctional electronic devices.