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Published October 20, 2023 | in press
Journal Article Open

Edge-Confined Excitons in Monolayer Black Phosphorus

Abstract

Quantum confinement of two-dimensional excitons in van der Waals materials via electrostatic trapping, lithographic patterning, Moiré potentials, and chemical implantation has enabled significant advances in tailoring light emission from nanostructures. While such approaches rely on complex preparation of materials, natural edges are a ubiquitous feature in layered materials and provide a different approach for investigating quantum-confined excitons. Here, we observe that certain edge sites of monolayer black phosphorus (BP) strongly localize the intrinsic quasi-one-dimensional excitons, yielding sharp spectral lines in photoluminescence, with nearly an order of magnitude line width reduction. Through structural characterization of BP edges using transmission electron microscopy and first-principles GW plus Bethe–Salpeter equation (GW-BSE) calculations of exemplary BP nanoribbons, we find that certain atomic reconstructions can strongly quantum-confine excitons resulting in distinct emission features, mediated by local strain and screening. We observe linearly polarized luminescence emission from edge reconstructions that preserve the mirror symmetry of the parent BP lattice, in agreement with calculations. Furthermore, we demonstrate efficient electrical switching of localized edge excitonic luminescence, whose sites act as excitonic transistors for emission. Localized emission from BP edges motivates exploration of nanoribbons and quantum dots as hosts for tunable narrowband light generation, with future potential to create atomic-like structures for quantum information processing applications as well as exploration of exotic phases that may reside in atomic edge structures.

Copyright and License

© 2023 American Chemical Society.

Acknowledgement

The experimental measurements were obtained under support from the U.S. Department of Energy (DOE) Basic Energy Science (BES) Physical Behavior of Materials program, under Grant DE-FG02-07ER46405. The electronic structure calculations were supported by the U.S. DOE BES Grant DE-SC0021984. H.Z. acknowledges support from the U.S. Department of Commerce, NIST under Financial Assistance Award 70NANB22H101. A.V.D. acknowledges support from the Material Genome Initiative funding allocated to NIST. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by Ministry of Education, Culture, Sports, Science and Technology (MEXT Grant JPMXP0112101001), Japan Society for the Promotion of Science (JSPS KAKENHI Grant JP20H00354), and Centers of Research Excellence in Science and Technology (CREST Grant JPMJCR15F3), Japan Science and Technology Agency (JST). This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. DOE Office of Science User Facility located at the Lawrence Berkeley National Laboratory, operated under Contract DE-AC02-05CH11231 using NERSC Award BES-ERCAP m3606 for the ground-state calculations, and from the Texas Advanced Computing Center (TACC) at The University of Texas at Austin, funded by the National Science Foundation (NSF) Award 1818253, through allocation DMR21077, for the GW-BSE calculations. F.H.d.J. and S.P. thank Prof. Da Li for kindly providing the structures from their global optimization procedure.

Contributions

S.B. and J.W. contributed equally. S.B. and J.W. conceived the project. S.B. fabricated devices and performed optical measurements and data analysis with assistance from J.W. S.P. performed first-principles calculations under the supervision of F.H.d.J. W.-C.D.Y. and H.Z. performed transmission electron microscopy and data analysis under the supervision of A.V.D. K.W. and T.T. provided hBN crystals. H.A.A. assisted in optical measurements. H.A.A. supervised the project and provided scientific input at all stages. S.B. wrote the manuscript with input from all authors.

Conflict of Interest

The authors declare no competing financial interest.

Additional Information

Disclaimer: Certain commercial equipment, instruments, software, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identifications are not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the materials or equipment identified is necessarily the best available for the purpose.

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Additional details

Created:
October 30, 2023
Modified:
October 30, 2023