Abstract
The physics of electrons, photons and their plasmonic interactions changes greatly when one or more dimensions are reduced down to the nanometre scale1. For example, graphene shows unique electrical, optical and plasmonic properties, which are tunable through gating or chemical doping2,3,4,5. Similarly, ultrathin metal films (UTMFs) down to atomic thickness can possess new quantum optical effects6,7, peculiar dielectric properties8 and predicted strong plasmons9,10. However, truly two-dimensional plasmonics in metals has so far been elusive because of the difficulty in producing large areas of sufficiently thin continuous films. Thanks to a deposition technique that allows percolation even at 1 nm thickness, we demonstrate plasmons in few-nanometre-thick gold UTMFs, with clear evidence of new dispersion regimes and large electrical tunability. Resonance peaks at wavelengths of 1.5–5 μm are shifted by hundreds of nanometres and amplitude-modulated by tens of per cent through gating using relatively low voltages. The results suggest ways to use metals in plasmonic applications, such as electro-optic modulation, biosensing and smart windows.
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All data needed to evaluate the conclusions in the paper are present in the main text and the supplementary materials. Any relevant information related to the study is available from the corresponding author upon reasonable request.
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Acknowledgements
We acknowledge K. Kalavoor, M. Marchena and J. Osmond for their help in experiments and for discussions. We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” programme for Centers of Excellence in R&D (SEV-2015–0522), OPTO-SCREEN (TEC2016–75080-R), and grant no. MAT2017–88492-R, from FundacióPrivadaCellex, from Generalitat de Catalunya through the CERCA programme, from AGAUR 2017 SGR 1634, and from the European Union Seventh Framework Programme under grant agreement no. 609416 ICFONest. J.C.-F. also thanks MINECO for his research grant funded by means of the programme Juan de la Cierva (grant no. FPDI-2013–18078). F.J.G.A. acknowledges support from the European Research Council (Advanced Grant No. 789104-eNANO).
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F.J.G.A. and V.P. proposed the research project. V.P. coordinated the experiments and with the help of R.A.M. and D.R. designed them. R.A.M. and D.R. with the help of J.C.-F., D.S.G., R. Yongsunthon, D.E.B. and A.R. carried out the experiments and characterizations. R.Yu developed the theoretical model and performed all the simulations under supervision of F.J.G.A. D.R., V.P., F.J.G.A., R. Yu and R.A.M. wrote the manuscript. All authors contributed to the interpretation of the results and manuscript writing.
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Maniyara, R.A., Rodrigo, D., Yu, R. et al. Tunable plasmons in ultrathin metal films. Nat. Photonics 13, 328–333 (2019). https://doi.org/10.1038/s41566-019-0366-x
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DOI: https://doi.org/10.1038/s41566-019-0366-x
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