Jan Mertens †, Anna L. Eiden †‡, Daniel O. Sigle †, Fumin Huang †, Antonio Lombardo ‡, Zhipei Sun ‡, Ravi S. Sundaram ‡, Alan Colli §, Christos Tserkezis ,II Javier Aizpurua, II Silvia Milana ‡, Andrea C. Ferrari ‡, and Jeremy J. Baumberg *†
† NanoPhotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, United Kingdom; ‡ Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom; § Nokia Research Center, Broers Building, Cambridge CB3 0FA, United Kingdom; II Materials Physics Center CSIC-UPV/EHU and DIPC, Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián, Spain
Nano Lett., 2013, 13 (11), pp 5033–5038
Graphene is used as the thinnest possible spacer between gold nanoparticles and a gold substrate. This creates a robust, repeatable, and stable subnanometer gap for massive plasmonic field enhancements. White light spectroscopy of single 80 nm gold nanoparticles reveals plasmonic coupling between the particle and its image within the gold substrate. While for a single graphene layer, spectral doublets from coupled dimer modes are observed shifted into the near-infrared, these disappear for increasing numbers of layers. These doublets arise from charger-transfer-sensitive gap plasmons, allowing optical measurement to access out-of-plane conductivity in such layered systems. Gating the graphene can thus directly produce plasmon tuning.