Determining plasmonic hot-carrier energy distributions via single-molecule transport measurements

• Published in: Science (American Association for the Advancement of Science) 2020-07, Vol.369 (6502), p.423-426
• Main Authors: Reddy, Harsha, Wang, Kun, Kudyshev, Zhaxylyk, Zhu, Linxiao, Yan, Shen, Vezzoli, Andrea, Higgins, Simon J., Gavini, Vikram, Boltasseva, Alexandra, Reddy, Pramod, Shalaev, Vladimir M., Meyhofer, Edgar
• Format: Article
• Language: English
• Subjects: Carrier transport; Decay; Energy; Energy harvesting; Landau damping; Nanostructure; Photochemistry; Photometers; Plasmonics; Plasmons; Polaritons; Solar energy
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abb3457

Hot carriers are expected to arise in plasmonic nanostructures because of the nonradiative decay of surface plasmons. However, identifying and determining just how “hot” these carriers actually are has been challenging. Reddy et al. devised a technique that looks at the carrier transport through a single molecular junction, which effectively acts as an energy filter, and show that it can be used to determine the distribution of hot carriers in a plasmonic nanostructure (see the Perspective by Martín-Moreno). These hot carriers could be harnessed to enhance the performance of technologies, including plasmon-driven photochemistry, solar energy–harvesting devices, and efficient photodetectors. Science , this issue p. 423 ; see also p. 375 Single-molecule transport measurements are used to quantify the hot-carrier distributions in plasmonic nanostructures. Hot carriers in plasmonic nanostructures, generated via plasmon decay, play key roles in applications such as photocatalysis and in photodetectors that circumvent bandgap limitations. However, direct experimental quantification of steady-state energy distributions of hot carriers in nanostructures has so far been lacking. We present transport measurements from single-molecule junctions, created by trapping suitably chosen single molecules between an ultrathin gold film supporting surface plasmon polaritons and a scanning probe tip, that can provide quantification of plasmonic hot-carrier distributions. Our results show that Landau damping is the dominant physical mechanism of hot-carrier generation in nanoscale systems with strong confinement. The technique developed in this work will enable quantification of plasmonic hot-carrier distributions in nanophotonic and plasmonic devices.