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Direct band-gap crossover in epitaxial monolayer boron nitride
C Elias1, P Valvin1, T Pelini1
1Laboratoire Charles Coulomb, UMR5221 CNRS-Université de Montpellier, 34095, Montpellier, France.
Nature Communications
|June 16, 2019
Summary
Researchers explored hexagonal boron nitride
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Hexagonal boron nitride (h-BN) is a wide band-gap insulator.
- Its electronic and optical properties complement graphene and transition metal dichalcogenides.
- The optical properties of monolayer h-BN are not well understood, especially the direct-gap crossover.
Purpose of the Study:
- To investigate the intrinsic optical properties of monolayer hexagonal boron nitride.
- To experimentally confirm the theoretically predicted direct-gap crossover in single-layer h-BN.
Main Methods:
- High-temperature molecular beam epitaxy for scalable growth of monolayer h-BN on graphite.
- Deep-ultraviolet photoluminescence and reflectance spectroscopy.
- Atomic force microscopy for structural characterization.
Main Results:
- Successfully grew high-quality monolayer h-BN using molecular beam epitaxy.
- Revealed a direct band gap of 6.1 eV in single-layer h-BN.
- Confirmed the crossover to a direct-gap in the monolayer limit.
Conclusions:
- Monolayer hexagonal boron nitride exhibits a direct band gap of 6.1 eV.
- This finding confirms the theoretical prediction of a direct-gap crossover in the monolayer limit.
- Scalable synthesis of monolayer h-BN is achievable via high-temperature molecular beam epitaxy.
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