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Hot-electron emission processes in waveguide-integrated graphene

Abstract

Photoemission plays a central role in a wide range of fields, from electronic structure measurements to free-electron laser sources. In metallic emitters, single-photon1, multiphoton2,3,4,5 or strong-field emission6,7,8,9,10 processes are the primary photoemission mechanisms. Here, using a sub-work-function 3.06 eV continuous-wave laser, photoemission from waveguide-integrated monolayer graphene is observed to occur at peak power densities >5 orders of magnitude lower than reported multiphoton and strong-field emission6,11,12. The behaviour is explained by the emission of hot electrons in graphene. In monolayer graphene, the need for photoelectrons to be transported to an emitting surface is eliminated, dramatically enhancing the probability of emission before thermalization. These results indicate that integrated-photonics-driven hot-electron emission provides a rich new area of exploration for both electron emission and integrated photonics.

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Fig. 1: Device schematics and emission processes.
Fig. 2: Waveguide-integrated graphene device.
Fig. 3: Electron emission characterization.
Fig. 4: Hot-electron scattering, electron emission and optical absorption simulation.
Fig. 5: Comparison with literature.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

The ensemble Monte Carlo Boltzmann Transport Equation Solver source codes are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported by AFOSR grant no. FA9550-16-1-0306 and the Molecular Foundry at Lawrence Berkeley National Laboratory, a user facility supported by the Office of Science, Office of Basic Energy Sciences of the US Department of Energy (DOE) under contract no. DEAC02-05CH11231. R.A acknowledges a USC Provost Graduate Fellowship.

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F.R. and R.K. designed the experiments. F.R. carried out the sample fabrication and measurements. Q.L. carried out graphene growth. R.A. and R.K carried out the electronic simulations. F.R. carried out the optical simulations. All authors contributed to analysing the data. F.R., R.A., H.U.C. and R.K. wrote the paper while all authors provided feedback.

Corresponding author

Correspondence to Rehan Kapadia.

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The authors declare no competing interests.

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Supplementary Information

Supplementary details, Figs. 1–11 and refs. 1–17.

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Rezaeifar, F., Ahsan, R., Lin, Q. et al. Hot-electron emission processes in waveguide-integrated graphene. Nat. Photonics 13, 843–848 (2019). https://doi.org/10.1038/s41566-019-0524-1

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