Synthesis and characterization of large-sized monolayer MoS2 nanoflakes by sulfurization of exfoliated MoO3 powder

Zusong Zhu,Dequan Zhu,Shengbao Zhan,Jiancun You,Guisheng Jiang,Jun Wen,Lihua Zhang

doi:10.1063/5.0076711

Abstract

We demonstrate a novel approach based on sulfurization of MoO3 powder pre-exfoliated on the SiO2/Si substrate to synthesize high crystalline quality and large-sized monolayer MoS2 films uniformly covering the whole substrate. The surface morphology, thickness, crystalline quality, and luminescence mechanism of the MoS2 films were characterized by the optical microscopy, Raman spectroscopy, and photoluminescence spectroscopy. The results reveal that MoS2 films directly synthesized on the bare SiO2/Si substrate by our method have high surface coverage superior over those of one-step chemical vapor deposition (CVD) method and exhibit uniform monolayer with larger lateral length up to ∼120 µm compared to those of the traditional two-step CVD method. Our proposed growth strategy opens up new pathways for CVD synthesis of high crystalline quality and large-sized uniform monolayer MoS2 films and can also be utilized for synthesizing other two-dimensional materials.

Highlights

Over the past decade, several methods have been developed to successfully synthesize monolayer or fewer layered MoS2 materials
In the past few years, researchers have devoted much effort to synthesize monolayer single-crystal MoS2 with large domain size and discovered the correlations between the Chemical vapor deposition (CVD) growth parameters and the morphology and property of MoS2.5–11 The common method is that the gaseous MoO3 and S precursor evaporated from solid sources are simultaneously transported to the reaction zone and react to form MoS2 directly on the surface of the target substrate
We report a novel two-step CVD approach, sulfurization of pre-exfoliated MoO3 powder on the SiO2/Si substrate, to synthesize large edge size high crystalline quality and high thickness uniformity monolayer MoS2 nanoflakes

Summary

INTRODUCTION

Several methods have been developed to successfully synthesize monolayer or fewer layered MoS2 materials. Tang et al reported a vertical CVD design with gaseous precursors (MoCl5) to grow a uniform density and high quality monolayer MoS2 over the whole substrate with the average domain size of 9.7 μm.. Using a comparably small amount of precursors is a popular method to reduce the nucleation density and provide space for the growth of large MoS2 domains. Based on this consideration, the pre-deposited molybdenum-base precursor films (mainly, metal molybdenum or MoO3) were usually used to decrease the nucleation density. We report a novel two-step CVD approach, sulfurization of pre-exfoliated MoO3 powder on the SiO2/Si substrate, to synthesize large edge size high crystalline quality and high thickness uniformity monolayer MoS2 nanoflakes. We investigate the surface morphology, and Raman and photoluminescence spectroscopy properties of the as-grown MoS2 nanoflakes

EXPERIMENTAL SECTION

Optical characterization

Characterization of thickness uniformity

Luminescence mechanism

CONCLUSIONS