Selective synthesis of large-area monolayer tin sulfide from simple substances

TL;DR

This paper presents a simple method to selectively synthesize large-area monolayer tin sulfide (SnS) crystals using controlled sulfur vapor and high-temperature etching, enabling potential device applications.

Contribution

It introduces a novel, straightforward approach for growing high-quality monolayer SnS crystals with controlled properties from bulk material.

Findings

Monolayer SnS can be grown up to tens of micrometers in size.

Selective p-type SnS synthesis achieved by sulfur vapor control.

High-temperature etching in nitrogen produces large-area monolayer SnS.

Abstract

Both tin monosulfide (SnS) and tin disulfide (SnS2) are thermodynamically stable layered materials with potential for spin-valleytronic devices and photodetectors. Notably, monolayer SnS, owing to its low symmetry, exhibits interesting properties such as ferroelectricity, shift-current, and a persistent spin helix state in the monolayer limit. However, creating atomic-thickness crystals of SnS is challenging owing to the enhanced interlayer interactions caused by lone pair electrons, unlike to SnS2. Here, we demonstrate that p-type SnS can be selectively grown by simply varying the sulfur vapor concentration relative to tin using single-element precursors. We show that monolayer SnS crystals, up to several tens of micrometers in lateral scale, can be easily and safely obtained by high-temperature etching of bulk SnS in a pure nitrogen gas atmosphere. These findings pave the way for device applications based on high-quality tin sulfide.