Direct band-gap crossover in epitaxial monolayer boron nitride
Description
Hexagonal boron nitride is a large band-gap insulating material which complements the electronic and optical properties of graphene and the transition metal dichalcogenides. However, the intrinsic optical properties of monolayer boron nitride remain largely unexplored. In particular, the theoretically expected crossover to a direct-gap in the limit of the single monolayer is presently not
con rmed experimentally. Here, in contrast to the technique of exfoliating few-layer 2D hexagonal boron nitride, we exploit the scalable approach of high-temperature molecular beam epitaxy to grow high-quality monolayer boron nitride on graphite substrates. We combine deep-ultraviolet photoluminescence and reflectance spectroscopy with atomic force microscopy to reveal the presence
of a direct gap of energy 6.1 eV in the single atomic layers, thus conforming a crossover to direct gap in the monolayer limit. The giant exciton binding energy in monolayer boron nitride requires selective optical pumping through resonant excitation of phonons. These results on large area monolayer boron nitride demonstrate its potential within the family of van der Waals crystals for photonic and light-matter applications in the deep ultraviolet.
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Subjects
- Boron nitride
- Atomic force microscopy
- Molecular beam epitaxy
- boron nitride, direct gap semiconductor, ultra-violet, monolayer
- Physical sciences::Physics
- Q Science::QC Physics::QC350 Optics. Light, including spectroscopy
Divisions
- University of Nottingham, UK Campus::Faculty of Science::School of Physics and Astronomy
Deposit date
2019-06-28Data type
Scanning Probe Microscopy Images, Raman spectra, photoluminescence and reflectance spectraContributors
- Cassabois, Guillaume
- Gil, Bernard
- Summerfield, Alex
- Novikov, Sergei
- Mellor, Chris
- Eaves, Laurence
- Foxon, C. Thomas
- Cheng, Tin S.
- Elias, C.
- Valvin, P.
- Pelini, T.
Funders
- Engineering & Physical Sciences Research Council
- Leverhulme Trust
- Government of the Russian Federation
- GaNeX (ANR- 11-LABX-0014)
Data collection method
Asylum Cypher Atomic Force Microscope, custom built ultra-violet photoluminescence equipmentResource languages
- en