Abstract
The cooling of hot electrons in graphene is the critical process underlying the operation of exciting new graphene-based optoelectronic and plasmonic devices, but the nature of this cooling is controversial. We extract the hot-electron cooling rate near the Fermi level by using graphene as a novel photothermal thermometer that measures the electron temperature (T(t)) as it cools dynamically. We find the photocurrent generated from graphene p–n junctions is well described by the energy dissipation rate CdT/dt = −A(T3−Tl3), where the heat capacity is C = α T and Tl is the base lattice temperature. These results are in disagreement with predictions of electron–phonon emission in a disorder-free graphene system, but in excellent quantitative agreement with recent predictions of a disorder-enhanced supercollision cooling mechanism. We find that the supercollision model provides a complete and unified picture of energy loss near the Fermi level over the wide range of electronic (15 to ∼ 3,000 K) and lattice (10–295 K) temperatures investigated.
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Acknowledgements
This research was supported by the Kavli Institute at Cornell for Nanoscale Science (KIC), AFOSR (FA 9550-10-1-0410), by the NSF through the Center for Nanoscale Systems and by the MARCO Focused Research Center on Materials, Structures, and Devices. We thank J. Song, K. McGill and J. Kevek for their helpful contributions. Device fabrication was performed at the Cornell Nanofabrication Facility/National Nanofabrication Infrastructure Network.
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The experiment was built by M.W.G. and measurements performed by M.W.G. and S-F.S. Graphene devices were fabricated by S-F.S. Theory and data analysis was performed by M.W.G. and P.L.M. All authors participated in the elaboration of the research project.
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Graham, M., Shi, SF., Ralph, D. et al. Photocurrent measurements of supercollision cooling in graphene. Nature Phys 9, 103–108 (2013). https://doi.org/10.1038/nphys2493
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DOI: https://doi.org/10.1038/nphys2493
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