Imaging of Interlayer Coupling in van der Waals Heterostructures Using a Bright-Field Optical Microscope

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Van der Waals heterostructures, built from stacked atomic layers, are promising for next-generation flexible electronic devices.
• Device performance hinges on layer thickness and interlayer electronic coupling, affecting charge and energy transfer.
• Interlayer coupling depends on layer orientation and interface cleanliness.

Purpose of the Study:

• To demonstrate an efficient method for monitoring interlayer coupling in transition metal dichalcogenide heterostructures.
• To utilize photoluminescence imaging for characterizing van der Waals heterostructures.
• To track changes in interlayer coupling and exciton emergence after thermal annealing and with varying twist angles.

Main Methods:

• Photoluminescence imaging in a bright-field optical microscope.
• Analysis of color and brightness in images to identify layer thickness (mono- and few-layer).
• Monitoring changes in interlayer coupling and interlayer excitons in heterobilayers.

Main Results:

• An efficient photoluminescence imaging technique for monitoring interlayer coupling was demonstrated.
• The method successfully identified mono- and few-layer crystals.
• Changes in interlayer coupling and the emergence of interlayer excitons were tracked after thermal annealing and as a function of twist angle.

Conclusions:

• Photoluminescence imaging provides a powerful tool for characterizing van der Waals heterostructures.
• The technique's sensitivity to material and crystal thickness enables diverse applications.
• This method is valuable for analyzing heterostructures assembled through various methods, including mechanical/chemical exfoliation and crystal growth.