Origin of ultrafast growth of monolayer WSe2 via chemical vapor deposition

Shuai Chen,Gang Zhang,Viacheslav Sorkin,Bharathi M Srinivasan,Ramanarayan Hariharaputran,Yong-Wei Zhang,Junfeng Gao

doi:10.1038/s41524-019-0167-2

Abstract

The ultrafast growth of large-area, high-quality WSe2 domains with a compact triangular morphology has recently been achieved on a gold substrate via chemical vapor deposition. However, the underlying mechanism responsible for ultrafast growth remains elusive. Here, we first analyze growth processes and identify two possible pathways that might achieve ultrafast growth: Path 1, fast edge attachment and ultrafast edge diffusion; Path 2, fast kink nucleation and ultrafast kink propagation. We perform kinetic Monte Carlo simulations and first-principles calculations to assess the viability of these two paths, finding that Path 1 is not viable due to the high edge diffusion barrier calculated from first-principles calculations. Remarkably, Path 2 reproduces all the experimental growth features (domain morphology, domain orientation, and growth rate), and the associated energetic data are consistent with first-principles calculations. The present work unveils the underlying mechanism for the ultrafast growth of WSe2, and may provide a new route for the ultrafast growth of other two-dimensional materials.

Highlights

Two-dimensional (2D) materials, such as graphene, boronitrene, phosphorene, transition metal dichalcogenides (TMDs), have attracted a great deal of attention due to their fascinating lattice structures and electronic properties.[1,2,3,4] WSe2, a member in the TMD family, is a semiconducting material with a sizable band gap, high charge mobility, high on–off ratio, and tunable electronic and optical properties.[5,6,7] For example, bulk WSe2 is a p-type semiconductor with an indirect band gap of ∼1.2 eV, while monolayer WSe2 exhibits a direct band gap of ∼1.65 eV.[8]
Path 1: fast attachment and ultrafast edge diffusion be the underlying mechanism for the ultrafast growth of highquality triangular WSe2 domain observed experimentally.[10]
By performing growth process analysis, kinetic Monte Carlo (kMC) simulations and firstprinciples calculations, we investigated the underlying mechanism for the ultrafast growth of regular triangular WSe2 monolayer with compact edges on Au(111) via chemical vapor deposition (CVD)

Summary

Introduction

Two-dimensional (2D) materials, such as graphene, boronitrene, phosphorene, transition metal dichalcogenides (TMDs), have attracted a great deal of attention due to their fascinating lattice structures and electronic properties.[1,2,3,4] WSe2, a member in the TMD family, is a semiconducting material with a sizable band gap, high charge mobility, high on–off ratio, and tunable electronic and optical properties.[5,6,7] For example, bulk WSe2 is a p-type semiconductor with an indirect band gap of ∼1.2 eV, while monolayer WSe2 exhibits a direct band gap of ∼1.65 eV.[8]. The carrier mobility in WSe2 recently obtained by epitaxy growth is up to 143 cm2/(V s),[10] which is remarkably higher than that in other TMDs.[11,12,13]

Objectives

Methods

Results

Conclusion