Synthesis of Large-Area WS2 monolayers with Exceptional Photoluminescence

TL;DR

This paper reports a method to synthesize large-area monolayer WS2 with enhanced photoluminescence by introducing hydrogen into the growth environment, significantly improving optical quality and coverage.

Contribution

The study demonstrates that adding hydrogen to the carrier gas during WS2 synthesis dramatically improves film quality and size, enabling practical applications.

Findings

Hydrogen addition increases WS2 film coverage to mm² scale.

Photoluminescence emission linewidths are below 40 meV in optimized films.

Emission intensities are nearly ten times higher with hydrogen.

Abstract

Monolayer WS2 offers great promise for use in optical devices due to its direct bandgap and high photoluminescence intensity. While fundamental investigations can be performed on exfoliated material, large-area and high quality materials are essential for implementation of technological applications. In this work, we synthesize monolayer WS2 under various controlled conditions and characterize the films using photoluminescence, Raman and x-ray photoelectron spectroscopies. We demonstrate that the introduction of hydrogen to the argon carrier gas dramatically improves the optical quality and increases the growth area of WS2, resulting in films exhibiting mm2 coverage. The addition of hydrogen more effectively reduces the WO3 precursor and protects against oxidative etching of the synthesized monolayers. The stoichiometric WS2 monolayers synthesized using Ar+H2 carrier gas exhibit superior optical characteristics, with photoluminescence emission full width half maximum values below 40 meV and emission intensities nearly an order of magnitude higher than films synthesized in a pure Ar environment.