Optimizing cathodoluminescence microscopy of buried interfaces through nanoscale heterostructure design

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Mapping buried interfaces with nanoscale resolution is vital for embedded active components.
• Cathodoluminescence (CL) microscopy is a powerful tool for visualizing such interfaces.

Purpose of the Study:

• To demonstrate and optimize cathodoluminescence microscopy for visualizing buried interfaces in transition metal dichalcogenide (TMD) heterostructures.
• To investigate the impact of hexagonal boron nitride (hBN) encapsulation layers on CL signal brightness and spatial resolution.

Main Methods:

• Fabrication of TMD monolayers encapsulated by varying thicknesses of hBN.
• Cathodoluminescence microscopy for nanoscale imaging and spectral analysis.
• Analysis of the trade-off between emission brightness and spatial resolution as a function of encapsulation thickness.

Main Results:

• CL microscopy effectively visualizes buried interfaces in TMD/hBN heterostructures.
• Encapsulation layer thickness tunes spatial resolution and emission brightness, with an optimal trade-off around 100 nm total encapsulation.
• An isotropic exciton diffusion length of >200 nm in hBN was determined, limiting spatial resolution.
• Spectrally distinct signals can overcome exciton diffusion limits for imaging nanoscale inhomogeneities.

Conclusions:

• Heterostructure design, specifically hBN encapsulation, allows for optimization of CL microscopy for buried interface analysis.
• Exciton diffusion in the encapsulating layer is a key factor limiting spatial resolution.
• Advanced CL techniques can surpass intrinsic resolution limits for detailed nanoscale imaging.