Room-temperature ferroelectricity in MoTe2 down to the atomic monolayer limit

Shuoguo Yuan,Chengcheng Xiao,Xin Luo,Yawei Dai,Hung Lit Chan,Jianhua Hao,Maohai Xie

doi:10.1038/s41467-019-09669-x

Abstract

Ferroelectrics allow for a wide range of intriguing applications. However, maintaining ferroelectricity has been hampered by intrinsic depolarization effects. Here, by combining first-principles calculations and experimental studies, we report on the discovery of robust room-temperature out-of-plane ferroelectricity which is realized in the thinnest monolayer MoTe2 with unexploited distorted 1T (d1T) phase. The origin of the ferroelectricity in d1T-MoTe2 results from the spontaneous symmetry breaking due to the relative atomic displacements of Mo atoms and Te atoms. Furthermore, a large ON/OFF resistance ratio is achieved in ferroelectric devices composed of MoTe2-based van der Waals heterostructure. Our work demonstrates that ferroelectricity can exist in two-dimensional layered material down to the atomic monolayer limit, which can result in new functionalities and achieve unexpected applications in atomic-scale electronic devices.

Highlights

Ferroelectrics allow for a wide range of intriguing applications
There is a critical thickness in the ferroelectrics, below which the ferroelectricity will disappear due to the increasing depolarization field in the thin films with decreasing thickness, as a result of the uncompensated charges at the interface
We construct an ultra-thin van der Waals heterostructure based ferroelectric tunneling junction (FTJ) by using the newly discovered monolayer ferroelectrics. Such a ferroelectric all-2D vdW heterostructure platform paves the way of developing thinnest ferroelectric devices, which will facilitate the miniaturization of generation memory and atomic-scale logical devices

Summary

Introduction

Ferroelectrics allow for a wide range of intriguing applications. maintaining ferroelectricity has been hampered by intrinsic depolarization effects. For the SnTe with non-layered structure, the Curie temperature (Tc) of the single-unit cell SnTe film is below roomtemperature and in-plane ferroelectricity is not suitable for many promising applications. Based on the density functional perturbation theory described in Supplementary Note 1, we calculated the non-resonant Raman spectra of the monolayer 2H and d1T-MoTe2, which accord well with the experimental observations.

Results

Conclusion