Designing two-dimensional ferroelectric materials from phosphorus-analogue structures

Two-dimensional (2D) ferroelectric (FE) materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices. Herein, we screen out 39 new 2D ferroelectric materials, MX (M: Group III-V elements; X: Group V-VII elements), in three phosphorus-analogue phases including black phosphorene-like α-phase, blue phosphorus-like β-phase, and GeSe-like γ-phase using high-throughput calculations. Seven materials (α-SbP, γ-AsP, etc.) exhibit FE switching barriers lower than 0.3 eV/f.u., ferroelectric polarization larger than 2 × 10⁻¹⁰ C/m, and high thermodynamic stability with energy above hull smaller than 0.2 eV/atom. We find that the larger the electronegativity difference between M and X, the larger the ferroelectric polarization. Moreover, larger electronegativity differences result in lower in-plane piezoelectric stress tensor (e₁₁) for MX consisting of Group IV and VI elements and larger e₁₁ for those consisting of Group V elements. Further calculations predict a giant tunneling electroresistance in ferroelectric tunnel junction α-Sb(Sn)P/α-SbP/α-Sb(Te)P (1.26 × 10⁴%) and large piezoelectric strain coefficient in α-SnTe (396 pm/V), providing great opportunities to the design of non-volatile resistive memories, and high-performance piezoelectric devices.