Visibility of hexagonal boron nitride on transparent substrates

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Monolayer hexagonal boron nitride (hBN) is nearly invisible under white light due to high transmittance and low reflectance.
• This invisibility poses significant challenges in identifying, transferring, and fabricating 2D material devices.
• Efficient methods are needed to enhance the contrast of hBN for practical applications.

Purpose of the Study:

• To enhance the optical contrast of hexagonal boron nitride (hBN) on transparent substrates.
• To investigate the role of interfacial layers in contrast enhancement.
• To enable easier observation and manipulation of hBN for 2D material device fabrication.

Main Methods:

• Utilized optical microscopy for experimental observation.
• Employed simulation to analyze contrast enhancement.
• Investigated polymer-based interfacial layers on polydimethylsiloxane (PDMS) substrates.
• Analyzed contrast across different light wavelengths and RGB color components.

Main Results:

• A polymer-based interfacial layer on a PDMS substrate yielded the highest contrast for hBN.
• Contrast is higher under short-wavelength (blue) light compared to long-wavelength (red) light.
• Analysis of RGB components confirmed clear visibility of hBN in the blue channel.
• Achieved a high contrast of approximately 4.5% for hBN on the PDMS substrate.

Conclusions:

• The developed method significantly enhances the visibility of monolayer and few-layer hBN flakes.
• This technique facilitates the search, transfer, and fabrication of 2D material devices.
• The findings provide a practical solution for handling optically invisible 2D materials.