Strain-tunable in-plane ferroelectricity and lateral tunnel junction in monolayer group-IV monochalcogenides

TL;DR

This paper investigates strain-tunable in-plane ferroelectricity in monolayer group-IV monochalcogenides and demonstrates their potential in lateral tunnel junctions with high tunneling electroresistance ratios.

Contribution

It reveals in-plane ferroelectricity in these monolayers and shows how strain enhances their ferroelectric and tunneling properties for device applications.

Findings

GeS has the best ferroelectric parameters among studied materials.

Tensile strain can improve ferroelectric properties and TER ratio.

Devices exhibit TER ratios up to 10^5, enhanced by strain.

Abstract

2D Ferroelectric materials are promising for designing low-dimensional memory devices. Here, we explore strain tunable ferroelectric properties of group-IV monochalcogenides MX (M=Ge, Sn; X=S, Se) and their potential application in lateral field tunnel junction devices. We find that these monolayers have in-plane ferroelectricity, with their ferroelectric parameters being on par with other known 2D ferroelectric materials. Amongst SnSe, SnS, GeSe, and GeS, we find that GeS has the best ferroelectric parameters for device applications, which can be improved further by applying uniaxial tensile strain. We use the calculated ferroelectric properties of these materials to study the tunneling electroresistance (TER) of a 4 nm device based on lateral ferroelectric tunnel junction. We find a substantial TER ratio $10^3-10^5$ in the devices based on these materials, which can be further improved up to a factor of 40 on the application of tensile strain.