Out-of-plane ferroelectricity with a high transition temperature in ultrathin films is important for the exploration of new domain physics and scaling down of memory devices. However, depolarizing electrostatic fields and interfacial chemical bonds can destroy this long-range polar order at two-dimensional (2D) limit. Here we report the experimental discovery of the locking between out-of-plane dipoles and in-plane lattice asymmetry in atomically thin In2Se3 crystals, a new stabilization mechanism leading to our observation of intrinsic 2D out-of-plane ferroelectricity. Through second harmonic generation spectroscopy and piezoresponse force microscopy, we found switching of out-of-plane electric polarization requires a flip of nonlinear optical polarization that corresponds to the inversion of in-plane lattice orientation. The polar order shows a very high transition temperature (∼700 K) without the assistance of extrinsic screening. This finding of intrinsic 2D ferroelectricity resulting from dipole locking opens up possibilities to explore 2D multiferroic physics and develop ultrahigh density memory devices.
Bibliographical noteKAUST Repository Item: Exported on 2021-04-06
Acknowledged KAUST grant number(s): OSR-2016-CRG5-2996
Acknowledgements: The support from National Science Foundation (EFMA-1542741) and the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No.OSR-2016-CRG5-2996. W.F., Y.H., and P.H. were supported by the National Natural Science Foundation of China (NSFC, No.61390502 and No.61505033). A.D. acknowledges support from the National Science Foundation under Grant No.DMR-1708615. L.W.M. acknowledges support from the Army Research Office under Grant No.W911NF-14-1-0104. Y.H. and D.A.M. were supported by the Cornell Center for Materials Research with funding from the NSF MRSEC program (DMR-1719875).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
ASJC Scopus subject areas
- Physics and Astronomy(all)