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Molecular Foundry

HIGHLIGHTSOptimizing Cathodoluminescence Spectroscopy Through Nanoscale Heterostructure Design
March 3, 2022

Scientific Achievement

a) Top: sketch of the cross-sectional side view of a TMD monolayer encapsulated in hBN. Bottom: sketch plot of the intensity of the CL signal as a function of the e-beam position across the TMD edge b) This cartoon highlights the random path of an incident electron as a consequence of multiple electron scattering events; one of these events can generate an e-h pair that diffuses beyond the electron interaction volume and can excite the TMD, even though the e-beam does not directly interact.

A team of Foundry staff and users harnessed sample design to optimize spatial resolution and brightness in cathodoluminescence (CL) microscopy for visualization of nanoscale buried interfaces.

Significance and Impact

This provides a comprehensive method to optimize encapsulated TMDs for CL imaging that will enable the study of buried structures in beam-sensitive materials like quantum dot superlattices or biological samples.

Research Details

  • The team focused on monolayer 2D semiconductor transition metal dichalcogenide (TMD) MoSe2 encapsulated in a hexagonal boron nitride (hBN) layer and determined the exciton diffusion in the hBN to be >200nm (first report).
  • They optimized both spatial resolution and brightness of TMD emission by tuning the hBN thickness below 100 nm.
  • Hyperspectral CL maps resolved spectrally distinct nanoscale features below diffusion-limited spatial resolution.
L. Francaviglia, J. Zipfel, J. Carlström, S. Sridhar, F. Riminucci, E. Wong, D. Blach, E. S. Barnard, K. Watanabe, T. Taniguchi, A. Weber-Bargioni, D. F. Ogletree, S. Aloni and A. Raja, Nanoscale, 2022, DOI: 10.1039/D1NR08082B.

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