Modulating flow near substrate surface to grow clean and large-area monolayer MoS₂

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Chemical vapor deposition (CVD) is crucial for synthesizing 2D materials like transition metal dichalcogenides (TMDs).
• Controlling precursor flow near the substrate is a sensitive parameter affecting 2D material growth.
• Current CVD methods often yield small MoS2 monolayer domains.

Purpose of the Study:

• To investigate how subtle changes in carrier gas flow near the substrate impact MoS2 monolayer quality and coverage.
• To develop methods for synthesizing large-area, high-quality MoS2 monolayers using CVD.
• To demonstrate controlled growth of patterned MoS2 monolayers.

Main Methods:

• Fine-tuning carrier gas flow under extreme conditions during CVD.
• Utilizing substrate surface blockades to modify local precursor flow.
• Employing computational simulations to understand flow dynamics near blockades.
• Conducting electrical and optical measurements to assess sample quality.

Main Results:

• Achieved centimeter-long continuous MoS2 monolayers, significantly larger than typical microscale domains.
• Synthesized MoS2 monolayers under conditions typically favoring bulk material formation.
• Demonstrated patterned growth of continuous MoS2 monolayers guided by flow simulations.
• Confirmed high quality of as-grown MoS2 monolayers through detailed characterization.

Conclusions:

• Substrate-vicinity precursor flow tuning is a powerful strategy for optimizing CVD growth of 2D materials.
• This approach allows for the synthesis of clean, large-area, and patterned MoS2 monolayers.
• The findings offer a versatile method for obtaining high-quality 2D materials even with non-optimal CVD parameters.