Exciton-assisted electron tunnelling in van der Waals heterostructures

The control of elastic and inelastic electron tunnelling relies on materials with well-defined interfaces. Two-dimensional van der Waals materials are an excellent platform for such studies. Signatures of acoustic phonons and defect states have been observed in current-to-voltage measurements. These...

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Bibliographic Details
Published in:Nature materials 2023-09, Vol.22 (9), p.1094-1099
Main Authors: Wang, Lujun, Papadopoulos, Sotirios, Iyikanat, Fadil, Zhang, Jian, Huang, Jing, Taniguchi, Takashi, Watanabe, Kenji, Calame, Michel, Perrin, Mickael L., García de Abajo, F. Javier, Novotny, Lukas
Format: Article
Language:English
Subjects:
639/301/357/1018
639/925/357/995
Biomaterials
Boron
Boron nitride
Charge injection
Chemistry and Materials Science
Condensed Matter Physics
Defects
Electrical junctions
Electrical measurement
Electrodes
Electron tunneling
Electrons
Excitons
Graphene
Heterostructures
Injection
Investigations
Laboratories
Light emission
Materials Science
Nanotechnology
Optical and Electronic Materials
Optoelectronic devices
Phonons
Transition metal compounds
Tunnel junctions
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Summary:The control of elastic and inelastic electron tunnelling relies on materials with well-defined interfaces. Two-dimensional van der Waals materials are an excellent platform for such studies. Signatures of acoustic phonons and defect states have been observed in current-to-voltage measurements. These features can be explained by direct electron–phonon or electron–defect interactions. Here we use a tunnelling process that involves excitons in transition metal dichalcogenides (TMDs). We study tunnel junctions consisting of graphene and gold electrodes separated by hexagonal boron nitride with an adjacent TMD monolayer and observe prominent resonant features in current-to-voltage measurements appearing at bias voltages that correspond to TMD exciton energies. By placing the TMD outside of the tunnelling pathway, we demonstrate that this tunnelling process does not require any charge injection into the TMD. The appearance of such optical modes in electrical transport introduces additional functionality towards van der Waals material–based optoelectronic devices. The authors demonstrate exciton-assisted resonant electron tunnelling in van der Waals heterostructure tunnel junctions. Their study elucidates tunnelling mechanisms involving either indirect or direct excitons in the absence of charge injection and reveals excitonic light emission driven by inelastic electron tunnelling.
ISSN:1476-1122
1476-4660
DOI:10.1038/s41563-023-01556-7