Cathodoluminescence spectroscopy of monolayer hexagonal boron nitride

Shima, Kohei; Cheng, Tin S.; Mellor, Christopher J.; Beton, Peter H.; Elias, Christine; Valvin, Pierre; Gil, Bernard; Cassabois, Guillaume; Novikov, Sergei V.; Chichibu, Shigefusa F.

Abstract

Cathodoluminescence (CL) spectroscopy is a suitable technique for studying the luminescent properties of optoelectronic materials because CL has no limitation on the excitable bandgap energy and eliminates ambiguous signals due to simple light scattering and resonant Raman scattering potentially involved in the photoluminescence spectra. However, direct CL measurements of atomically thin two-dimensional materials have been difficult due to the small excitation volume that interacts with high-energy electron beams. Herein, distinct CL signals from a monolayer hexagonal BN (hBN), namely mBN, epitaxial film grown on a graphite substrate are shown by using a CL system capable of large-area and surface-sensitive excitation. Spatially resolved CL spectra at 13 K exhibited a predominant 5.5-eV emission band, which has been ascribed to originate from multilayered aggregates of hBN, markedly at thicker areas formed on the step edges of the substrate. Conversely, a faint peak at 6.04 ± 0.01 eV was routinely observed from atomically flat areas, which is assigned as being due to the recombination of phonon-assisted direct excitons of mBN. The CL results support the transition from indirect bandgap in bulk hBN to direct bandgap in mBN. The results also encourage one to elucidate emission properties of other low-dimensional materials by using the present CL configuration.

Citation

Shima, K., Cheng, T. S., Mellor, C. J., Beton, P. H., Elias, C., Valvin, P., …Chichibu, S. F. (2024). Cathodoluminescence spectroscopy of monolayer hexagonal boron nitride. Scientific Reports, 14(1), Article 169. https://doi.org/10.1038/s41598-023-50502-9

• Journal Article Type: Article
• Acceptance Date: Dec 20, 2023
• Online Publication Date: Jan 2, 2024
• Publication Date: 2024
• Deposit Date: Jan 16, 2024
• Publicly Available Date: Jan 17, 2024
• Journal: Scientific Reports
• Electronic ISSN: 2045-2322
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 14
• Issue: 1
• Article Number: 169
• DOI: https://doi.org/10.1038/s41598-023-50502-9
• Keywords: Two-dimensional materials
• Public URL: https://nottingham-repository.worktribe.com/output/29539482
• Publisher URL: https://www.nature.com/articles/s41598-023-50502-9
• Additional Information: Received: 13 July 2023; Accepted: 20 December 2023; First Online: 2 January 2024; : The authors declare no competing interests.