Surface-diffusion-limited growth of atomically thin WS2 crystals from core-shell nuclei

TL;DR

This study investigates the surface-diffusion-limited growth mechanism of atomically thin WS2 crystals via chemical vapor deposition, revealing how core-shell nuclei influence monolayer formation and providing insights into controlled synthesis.

Contribution

It offers a detailed understanding of the growth process of monolayer WS2, highlighting the role of core-shell nuclei and surface diffusion in crystal development.

Findings

Growth begins with WO3-WS2 core-shell nanoparticles as nucleation sites.

Lateral monolayer WS2 growth occurs through surface diffusion of adatoms.

The study elucidates the growth mechanism for large-area monolayer WS2.

Abstract

Atomically thin transition metal dichalcogenides (TMDs) have recently attracted great attention since the unique and fascinating physical properties have been found in various TMDs, implying potential applications in next-generation devices. The progress towards developing new functional and high-performance devices based on TMDs, however, is limited by the difficulty of producing large-area monolayer TMDs due to a lack of knowledge of the growth processes of monolayer TMDs. In this work, we have investigated the growth processes of monolayer WS2 crystals using a thermal chemical vapor deposition method, in which the growth conditions were adjusted in a systematic manner. It was found that, after forming WO3-WS2 core-shell nanoparticles as nucleation sites on a substrate, the growth of three-dimensional WS2 islands proceeds by ripening and crystallization processes. Lateral growth of monolayer WS2 crystals subsequently occurs by surface diffusion process of adatoms. Our results provide understanding of the growth processes of monolayer WS2 by using chemical vapor deposition methods.