Ferroelectricity and piezoelectricity in monolayers and nanoplatelets of SnS

TL;DR

This paper uses first-principles calculations to demonstrate that monolayers and nanoplatelets of SnS with odd numbers of layers exhibit ferroelectricity, revealing potential for high-temperature ferroelectric applications.

Contribution

It provides the first theoretical evidence that odd-layer SnS nanoobjects are ferroelectric and explains the polarization mechanism related to lone pair ordering.

Findings

Odd-layer SnS nanoobjects are ferroelectric.

Polarization arises from uncompensated polarization in antiferroelectric bulk SnS.

The ferroelectric mechanism involves short-range lone pair ordering.

Abstract

The ground-state structure of monolayers and nanoplatelets of SnS with a thickness from two to five monolayers is calculated from first principles. It is shown that nanoobjects with only odd number of monolayers are ferroelectric. The ferroelectric, piezoelectric, and elastic properties of these polar structures are calculated. The appearance of polarization in these nanoobjects is explained by an uncompensated polarization that exists in an antiferroelectric structure of bulk SnS. The mechanism of ferroelectricity, in which the ferroelectric distortion is associated with short-range ordering of lone pairs, can be regarded as a way of creating ferroelectrics with high Curie temperature.