Controlling Morphology and Excitonic Disorder in Monolayer WSe₂ Grown by Salt-Assisted CVD Methods

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Synthesis

Background:

• Chemical synthesis offers superior control over 2D crystal properties compared to top-down methods.
• Precise manipulation of 2D crystal structures is crucial for advanced optoelectronic, photovoltaic, and quantum devices.
• Controlling edge structure in 2D crystals via gas-phase synthesis remains a significant challenge.

Purpose of the Study:

• To demonstrate a novel method for tuning the edge structure of 2D tungsten diselenide (WSe2) monolayers.
• To establish a direct link between synthetic parameters, material morphology, and optical properties.
• To provide a comprehensive understanding of the factors influencing synthetic 2D materials.

Main Methods:

• Utilized a salt-assisted low-pressure chemical vapor deposition (CVD) technique.
• Controlled tungsten (W) metal flux during WSe2 monolayer growth by adjusting the WO3 to NaCl mass ratio.
• Analyzed material morphology and optical properties to correlate synthetic parameters with structural outcomes.

Main Results:

• Successfully tuned the W metal flux, enabling direct control over the edge structure of 2D WSe2.
• Demonstrated that the degree of structural disorder in WSe2 is a function of W metal flux.
• Observed that edge disorder couples to excitonic disorder, resulting in broadened and spatially varying emission profiles.

Conclusions:

• The developed salt-assisted CVD method provides precise control over WSe2 edge structure and optical properties.
• Understanding the relationship between synthetic parameters and material properties is key to advancing 2D material applications.
• This work highlights opportunities and intrinsic limits in the synthesis of advanced 2D materials.