A high-quality round-shaped monolayer MoS2 domain and its transformation

Abstract

MoS₂ is widely used in many fields including spin-valleytronics, logic transistors, light emitting devices, clean energy and biology. However, controllable synthesis of two-dimensional MoS₂ sheets remains a great challenge. We report the formation of round-shaped monolayer MoS₂ domains with a tunable size and the shape transformation from triangle to round. A qualitative interpretation of the formation mechanism is presented and the process can be controlled by either a thermodynamic or a kinetic growth regime depending on the growth rate. The round-shaped MoS₂ domains show a high electron mobility of 1.39 cm² V⁻¹ s⁻¹, comparable to the mechanically exfoliated counterparts. Our study reveals the dominant factors that influence the synthesis of MoS₂ and improves our understanding of the nucleation and growth mechanisms of MoS₂, towards fine control over the synthesis of MoS₂ and other TMDs.