摘要
Two-dimensional materials with ferroelectric properties break the size effect of conventional ferroelectric materials and unlock unprecedented potentials of ferroelectric-related application at small length scales.Using first-principles calculations,a sliding-induced ferroelectric-to-antiferroelectric behavior in bilayer group-IV monochalcogenides(MX,with M=Ge,Sn and X=S,Se)is discovered.Upon this mechanism,the top layer exhibits a reversible intralayer ferroelectric switching,leading to a reversible transition between the ferroelectric and antiferroelectric states in the bilayer MXs.Further results show that the interlayer van der Waals interaction,which is usually considered to be weak,can actually generate an in-plane lattice distortion and thus cause the breaking/forming of intralayer covalent bonds in the top layer,leading to the observed anomalous phenomenon.This unique property has advantages for energy harvesting over existing piezoelectric and triboelectric nanogenerators.The interlayer sliding-induced big polarization change(40μC cm^(−2))and ultrahigh polarization changing rate generate an open-circuit voltage two orders of magnitude higher than that of MoS_(2)-based nanogenerators.The theoretical prediction of power output for this bilayer MXs at a moderate sliding speed 1 m s^(−1)is four orders of magnitude higher than the MoS_(2)nanogenerator,indicating great potentials in energy harvesting applications.
基金
The authors gratefully acknowledge the support of NSFC(Grant Nos.11974269,51728203)
the support by 111 project 2.0(Grant No.BP0618008)
J.D.also thanks the support of the National Key R&D Program of China(Grant No.2018YFB1900104)
J.Z.L.acknowledges the support from ARC discovery projects(DP180101744)and HPC from National Computational Infrastructure from Australia
This work is also supported by State Key Laboratory for Mechanical Behavior of Materials.
