Role of Hydrogen in Suppressing Secondary Nucleation in Chemical Vapor-Deposited MoS₂

Abstract

We investigate the ability of different carrier gases to control defects and secondary nucleation in atmospheric pressure chemical vapor deposition (APCVD) growth of MoS 2 on Si/SiO 2 substrates. We observe that a reducing environment using H 2 gas is more favorable for achieving uniform two-dimensional (2D) growth. Compared to the growth in an inert environment, secondary nucleation on primary MoS 2 domains grown using H 2 as the carrier gas (H−MoS 2 ) is drastically reduced. We employ a phase-field model to understand the role of enhanced surface diffusion in H−MoS 2 , due to passivation of defects and dangling bonds, promoting compact secondary domain formation as opposed to dendritic secondary domains under an inert environment. Using X-ray photoelectron spectroscopy, we show that the Mo(VI) oxidation state (corresponding to MoO 3 ), which is prominent for MoS 2 grown under an inert atmosphere, is highly suppressed in H−MoS 2 , leading to more pristine MoS 2 . This explains the superior electrical performance of H−MoS 2 compared to those grown with other carrier gases. Our results offer a facile route to explore different growth environments to realize large-area true 2D films.

Synthesis of air-stable 1T-CrS2 thin films and their application in high-performance floating-gate memory

“…36,37 Because H 2 can reduce the secondary nucleation of CrS 2 . 42,43 The thickness of the grown CrS 2 is uniform. When H 2 and Ar are introduced, the average thickness is about 5.878 nm, while when only Ar is introduced, the average thickness is about 26.845 nm (Fig.…”

Excitonic Rydberg States in a Trilayer to Monolayer H2-Aided CVD-Grown Large-Area MoS2 Film with Excellent UV to Visible Broad Band Photodetection Applications

“…The first one is a reduction in secondary nucleation and delay in the growth process and the second one is an etching of MoS 2 layers due to H 2 . 24,25 Additionally, Figure 2d,e represents the top view FESEM images of MAr and MArH10 samples, which show the presence of islands and vertically aligned flakes on top of the MAr sample, while MArH10 exhibits a significantly smooth and clean surface. These results strongly suggest that the incorporation of H 2 during the growth process creates a reducing environment, leading to a very flat and smooth surface of the MoS 2 film.…”

“…During chemical vapor deposition (CVD) of a MoS 2 film, incorporation of H 2 in the growth environment along with the carrier gas, Ar, can serve as an effective approach to engineer the S vacancy-related defects in the MoS 2 film. Most of the previous studies where H 2 has been used along with Ar gas put focus on achieving a clean continuous monolayer of MoS 2 by mitigating secondary nucleation. , Therefore, a comprehensive observation and in-depth understanding of the complex evolution of the excitonic transitions and their Rydberg states in large-area monolayer MoS 2 are lacking, to the best of our knowledge.…”

“…Most of the previous studies where H 2 has been used along with Ar gas put focus on achieving a clean continuous monolayer of MoS 2 by mitigating secondary nucleation. 24,25 Therefore, a comprehensive observation and in-depth understanding of the complex evolution of the excitonic transitions and their Rydberg states in large-area monolayer MoS 2 are lacking, to the best of our knowledge.…”