Plasmonic coupling at a metal/semiconductor interface


Integrating plasmonic nanoparticles with semiconductor substrates introduces strong optical resonances that extend and enhance the spectrum of photocatalytic and photovoltaic activity. The effect of plasmonic resonances has been variously attributed to the field nanoconfinement, plasmon–exciton coupling, hot electron transfer, and so on, based on action spectra of enhanced photoactivity. It remains unclear, however, whether energized carriers in the substrate are generated by the transfer of plasmonically generated hot electrons from the metal, as broadly believed, or directly by dephasing of the plasmonic field at the interface. Here, we demonstrate the importance of the direct plasmonic coupling across the chemical interface for hot electron generation at a prototypical Ag nanocluster/TiO2 heterojunction by direct probing of the coherence and hot electron dynamics with two-photon photoemission spectroscopy. Energy, time and material distributions of excitations in the Ag nanocluster/TiO2 heterojunction indicate that dielectric coupling with the substrate renormalizes the plasmon resonance of the Ag nanoparticle, and its dephasing directly generates hot electrons in TiO2 on a <10 fs timescale.

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Fig. 1: The electronic and molecular structures of Ag nanoclusters on the TiO2(110)-1 × 1 surface.
Fig. 2: Plasmonic enhancement of 2PP by Ag deposition on the TiO2(110) surface.
Fig. 3: The Ag/TiO2 IFS.
Fig. 4: The sample azimuth and polarization dependence of 2PP spectra with  = 3.35 eV excitation.
Fig. 5: Interferometric time-resolved 2PP measurements of the polarization and population relaxation dynamics for Ag/TiO2 for  = 3.44 eV.


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The experimental research was supported by a grant from the NSF (CHE-1414466) and the theory by grants from the NSFC (11620101003, 21421063, 91421313), and National Key Basic Research Program of China (2016YFA0200604, 2017YFA0204904). A.A. was supported by a Fellowship from the Pittsburgh Quantum Institute. The calculations were performed at the Supercomputer Center and Environmental Molecular Sciences Laboratory at PNNL, a user facility sponsored by the DOE Office of Biological and Environmental Research, and the supercomputing centre at USTC. The authors thank A. Sirjoosingh, G. Schatz and R. Lazzari for discussion on the dielectric interactions between Ag nanoclusters and TiO2 substrate.

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S.T. performed the experiments and wrote the first draft of the manuscript. A.A. set up the experimental apparatus and assisted in the laser operation. J.R. performed the analysis of STM measurements. L.L. performed the theoretical calculations. J.Z. supervised and helped to interpret the calculations. H.P. conceived the experiment, supervised its execution, and finalized the manuscript.

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Correspondence to Jin Zhao or Hrvoje Petek.

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Tan, S., Argondizzo, A., Ren, J. et al. Plasmonic coupling at a metal/semiconductor interface. Nature Photon 11, 806–812 (2017).

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