Purely in-plane ferroelectricity in monolayer SnS at room temperature

TL;DR

This study demonstrates room-temperature in-plane ferroelectricity in monolayer SnS, grown via physical vapor deposition, challenging previous beliefs about layer-dependent ferroelectricity and opening new avenues for nanoelectronic applications.

Contribution

First experimental validation of in-plane ferroelectric switching in monolayer SnS at room temperature, regardless of layer odd-even effects, influenced by substrate interactions.

Findings

Monolayer SnS exhibits robust in-plane ferroelectricity at room temperature.

Ferroelectricity persists in SnS below 15 layers, independent of odd-even layer effects.

Substrate interactions may enable control over multilayer stacking and ferroelectric properties.

Abstract

2D van der Waals ferroelectric semiconductors have emerged as an attractive building block with immense potential to provide multifunctionality in nanoelectronics. Although several accomplishments have been reported in ferroelectric resistive switching for out-of-plane 2D ferroelectrics down to the monolayer, a purely in-plane ferroelectric has not been experimentally validated at the monolayer thickness. Herein, a micrometer-size monolayer SnS is grown on mica by physical vapor deposition, and in-plane ferroelectric switching is demonstrated with a two-terminal device at room temperature (RT). SnS has been commonly regarded to exhibit the odd-even effect, where the centrosymmetry breaks only in the odd-number layers to exhibit ferroelectricity. Remarkably, however, a robust RT ferroelectricity exists in SnS below a critical thickness of 15 layers with both an odd and even number of layers. The lack of the odd-even effect probably originates from the interaction with the mica substrate, suggesting the possibility of controlling the stacking sequence of multilayer SnS, going beyond the limit of ferroelectricity in the monolayer. This work will pave the way for nanoscale ferroelectric applications based on SnS as a new platform for in-plane ferroelectrics.