Mapping Modified Electronic Levels in the Moiré Patterns in MoS₂/WSe₂ Using Low-Loss EELS.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Moiré excitons in twisted 2D transition metal dichalcogenides (2D-TMDs) arise from moiré potential variations.
• While detected spectroscopically, the spatial distribution of moiré excitons in TMD heterostructures remains experimentally uncharacterized.

Purpose of the Study:

• To investigate the spatial distribution of moiré excitons in twisted MoS₂/WSe₂ heterostructures.
• To understand the influence of twist angle and stacking order on exciton behavior and optical properties.

Main Methods:

• High-resolution scanning transmission electron microscopy (STEM).
• Electron energy-loss spectroscopy (EELS).
• Analysis of MoS₂/WSe₂ heterostructures with varying twist angles.

Main Results:

• Layer interaction strength varies with twist angle, being weaker at higher angles (>5°) and stronger at lower angles.
• The optical response, including absorption peaks, is spatially dependent within the moiré supercell.
• Lower energy absorption peaks are observed in regions with AA stacking.

Conclusions:

• The study provides the first experimental mapping of moiré exciton spatial distribution in 2D-TMD heterostructures.
• Twist angle and local stacking configuration significantly influence interlayer interaction and optical properties.
• Findings offer insights for designing optoelectronic devices based on moiré superlattices.