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-likeα-phase,blue phosphorus-likeβ-phase,and GeSe-likeγ-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 junctionα-Sb(Sn)P/α-SbP/α-Sb(Te)P(1.26×104%)and large piezoelectric strain coefficient inα-SnTe(396 pm/V),providing great opportunities to the design of non-volatile resistive memories,and high-performance piezoelectric devices.