WSe₂ Monolayers Grown by Molecular Beam Epitaxy on hBN

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Transition metal dichalcogenides (TMDs) like WSe2 are crucial for next-generation electronics and optoelectronics.
• Achieving high-quality, large-area WSe2 monolayers with controlled orientation remains a challenge.
• Existing methods, such as mechanical exfoliation, often yield limited sample sizes and reproducibility.

Purpose of the Study:

• To develop a scalable and reproducible method for growing high-quality WSe2 monolayers.
• To optimize growth conditions for enhanced photoluminescence and domain formation.
• To demonstrate the superiority of epitaxially grown WSe2 over exfoliated WSe2 for device applications.

Main Methods:

• Utilized a three-step molecular beam epitaxy (MBE) process on hexagonal boron nitride (hBN) substrates.
• Employed atomic force microscopy (AFM) to analyze domain orientation and film morphology.
• Verified monolayer characteristics using optical spectroscopy and high-resolution transmission electron microscopy (HRTEM).

Main Results:

• Achieved optically uniform WSe2 monolayers with maximized photoluminescence efficiency.
• Demonstrated controlled formation of hexagonal WSe2 domains on hBN.
• Exciton complex behavior in MBE-grown WSe2 was found to be analogous to exfoliated samples.

Conclusions:

• The developed MBE process provides a superior alternative to mechanical exfoliation for WSe2 monolayer fabrication.
• Epitaxially grown WSe2 exhibits excellent optical quality, uniformity, and reproducibility.
• This advancement facilitates the development of large-scale functional devices based on TMD monolayers.