Spectroscopic signatures of edge states in hexagonal boron nitride
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Wu Zhou1,4(
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We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at different edge structures in monolayer and bilayer hexagonal boron nitride (h-BN). We find that edges with bonding unsaturated sp2 boron atoms have a unique spectroscopic signature with a prominent pre-peak at ~ 190.2 eV in the B K-edge fine structure. First-principles calculations reveal that the observed pre-peak arises from excitations to the in-plane lowest-energy empty sp2 boron dangling bonds at the B-terminated edge. This spectroscopic signature can serve as a fingerprint to explore new edge structures in h-BN.
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Spectroscopic signatures of edge states in hexagonal boron nitride
), Wu Zhou1,4(
),
Abstract
We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at different edge structures in monolayer and bilayer hexagonal boron nitride (h-BN). We find that edges with bonding unsaturated sp2 boron atoms have a unique spectroscopic signature with a prominent pre-peak at ~ 190.2 eV in the B K-edge fine structure. First-principles calculations reveal that the observed pre-peak arises from excitations to the in-plane lowest-energy empty sp2 boron dangling bonds at the B-terminated edge. This spectroscopic signature can serve as a fingerprint to explore new edge structures in h-BN.
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Acknowledgements
This research performed in the CAS Key Laboratory of Vacuum Sciences in University of Chinese Academy of Sciences is financially supported by the National Key R&D Program of China (No. 2018YFA0305800), the National Natural Science Foundation of China (Nos. 51622211 and 51872284), the CAS Key Research Program of Frontier Sciences, the CAS Pioneer Hundred Talents Program, and Beijing Nova Program (No. Z181100006218023). The electron microscopy work was supported in part by Oak Ridge National Laboratory's Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. Work at Vanderbilt University was supported by U.S. Department of Energy grant DE-FG02-09ER46554 and by the McMinn Endowment.
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