Micrometer-scale monolayer SnS growth by physical vapor deposition

TL;DR

This paper investigates the growth mechanism of monolayer SnS via PVD, revealing substrate modification and surface diffusion effects that enable monolayer formation despite expectations of multilayer growth.

Contribution

It uncovers how substrate surface modification and precursor diffusion facilitate monolayer SnS growth, challenging prior assumptions about multilayer formation.

Findings

Substrate surface is modified by sulfur from impurities, aiding monolayer growth.

Enhanced surface diffusion of SnS precursors promotes lateral monolayer formation.

Impurities in feed powder influence growth mechanism and surface interactions.

Abstract

Recently, monolayer SnS, a two-dimensional group IV monochalcogenide, was grown on a mica substrate at the micrometer-size scale by the simple physical vapor deposition (PVD), resulting in the successful demonstration of its in-plane room temperature ferroelectricity. However, the reason behind the monolayer growth remains unclear because it had been considered that the SnS growth inevitably results in a multilayer thickness due to the strong interlayer interaction arising from lone pair electrons. Here, we investigate the PVD growth of monolayer SnS from two different feed powders, highly purified SnS and commercial phase-impure SnS. Contrary to expectations, it is suggested that the mica substrate surface is modified by sulfur evaporated from the Sn2S3 contaminant in the as-purchased powder and the lateral growth of monolayer SnS is facilitated due to the enhanced surface diffusion of SnS precursor molecules, unlike the growth from the highly purified powder. This insight provides a guide to identify further controllable growth conditions.