Two-Dimensional Ferroelastic Semiconductors in Nb₂SiTe₄ and Nb₂GeTe₄ with Promising Electronic Properties

Abstract

Two-dimensional crystals with coupling of ferroelasticity and attractive electronic properties offer unprecedent opportunities for achieving long-sought controllable devices. But so far, the reported proposals are mainly based on hypothetical structures. Here, using first-principles calculations, we identify single-layer Nb2ATe4 (A = Si, Ge), which could be exfoliated from their layered bulks, are promising candidates. Single-layer Nb2ATe4 are found to be dynamically, thermally and chemically stable. They possess excellent ferroelasticity with high reversible ferroelastic strain and moderate ferroelastic transition energy barrier, beneficial for practical applications. Meanwhile, they harbor outstanding anisotropic electronic properties, including anisotropic carrier mobility and optical properties. More importantly, the anisotropic properties of single-layer Nb2ATe4 can be efficiently controlled through ferroelastic switching. These appealing properties combined with the experimental feasibility render single-layer Nb2ATe4 extraordinary platforms for realizing controllable devices.

Intrinsic triferroicity in a two-dimensional lattice

“…Besides energy barrier, ferroelastic performance also depends on reversible ferroelastic strain, which controls the signal intensity and is defined as | 𝑎 𝑏 ⁄ − 1| × 100%. The obtained reversible ferroelastic strain for SL FeO2H is 23.5%, which is comparable with the values for 1S'-MSSe (4.7%) 22 , GeS (17.8%) 32 , InOCl (17.7%) 37 , Nb2GeTe4 (22.1%) and Nb2SiTe4 (24.4%) 38 , suggesting a strong switching signal in SL FeO2H. We therefore demonstrate the promising intrinsic ferroelastics in SL FeO2H.…”

Intrinsic Multiferroic in VNI Monolayer

“…Therefore, multiferroic order with both ferroelasticity and magnetism provides a promising approach for realizing strain-controllable magnetism in 2D materials. Remarkably, recent experiments and theoretical calculations have demonstrated the existence of 2D ferroelasticity in several metal chalcogenides, i.e., β′-In 2 Se 3 , 1T′-WTe 2 , Janus VSSe, and Nb 2 SiTe 4 . These have aroused great interest in research on the coupling between ferroelasticity and magnetism.…”

Anisotropic Infrared Response and Orientation-Dependent Strain-Tuning of the Electronic Structure in Nb2SiTe4

“…17 Field-effect transistors based on few-layer NST show relatively high carrier mobility of ~100 cm 2 V -1 s -1 . The anisotropic transport, [18][19][20][21] excellent ferroelasticity, 22 and anisotropic thermoelectric properties 23 are also theoretically predicted.…”

“…After discussing the inter-band optical transitions, we now focus on the tuning of the band structure, which shows even more intriguing scenarios. The electronic structure of NST has been predicted to be very sensitive to strain 22 and the optical transitions of NST are polarization-dependent. We thus expect the strain effects are crystallographic orientation-dependent.…”