Optical Constants and Structural Properties of Epitaxial MoS₂ Monolayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition-metal dichalcogenides (TMDs) are crucial for electronics and optoelectronics.
• Current synthesis methods like mechanical exfoliation and chemical vapor deposition (CVD) have limitations in quality and uniformity.
• Epitaxy growth offers a path to continuous, crystalline, and uniform TMD films with reduced defects.

Purpose of the Study:

• To comprehensively investigate the optical and structural properties of single-layer molybdenum disulfide (MoS2) synthesized via molecular beam epitaxy (MBE).
• To compare the performance of MBE-grown MoS2 with CVD-grown MoS2 for potential photonic applications.

Main Methods:

• Synthesized single-layer MoS2 on a sapphire substrate using molecular beam epitaxy (MBE).
• Performed optical characterization using spectroscopic ellipsometry (250–1700 nm) at variable incident angles.
• Assessed structural quality via optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy.

Main Results:

• Confirmed the formation of a single-atomic layer of MoS2 with a low defect density.
• Raman and photoluminescence (PL) spectroscopy revealed superior optical properties compared to CVD-grown MoS2.
• MBE-grown MoS2 exhibited a two-times higher photoluminescence quantum yield and reduced photobleaching.

Conclusions:

• MBE is a viable technique for producing high-quality, single-layer MoS2 with excellent structural and optical properties.
• The enhanced photoluminescence quantum yield and reduced photobleaching make MBE-grown MoS2 highly promising for photonic applications.
• This study highlights MBE as a preferred method for fabricating MoS2 for advanced optoelectronic devices.