Oxide Scale Sublimation Chemical Vapor Deposition for Controllable Growth of Monolayer MoS₂ Crystals

Abstract

A newly developed oxide scale sublimation chemical vapor deposition (OSSCVD) technique for 2D MoS₂ growth is reported. Gaseous MoO₃ , which is supplied separately from H₂ S, can be generated in situ by flowing O₂ over Mo metal with oxidation and sublimation processes. In this method, particularly, controllably and abruptly modulating the supply of MoO₃ is achievable by precisely tuning O₂ flow. Having appropriate conditions, where the generation rate of MoO₃ on the Mo metal surface is not larger than its sublimation rate, is critical to enable stable growth. Otherwise, MoS₂ deposition can be caused by accumulated MoO₃ on the metal surface, regardless of oxygen supply. Proof-of-concept experiments with varied process parameters are conducted, confirming OSSCVD enables MoS₂ growth with significantly improved flexibility, controllability, and reproducibility relative to conventional powder-source CVD. By utilizing alkali-aluminosilicate glass, Dragontrail, as catalytic substrate, single-crystalline MoS₂ triangular domains as large as 25 µm are obtained, followed by a fully covered monolayer on Dragontrail in 25 min. Substrate pretreatment by H₂ S yields enlarged domain size and reduced domain density, owning to the extracted alkali metals from Dragontrail into the growth zone. The study opens new avenues for the controllable growth of high-quality MoS₂ and other transition metal dichalcogenides.