Direct observation of near-field induced resonant electron tunneling in a sub-nanometer plasmonic gap

Abstract

Localized surface plasmon resonance (LSPR) excitation of nanostructures and charge transfer in plasmonic nanocavities plays a central role in nanoscale optoelectronics and in applications for plasmonic devices. However, the direct observation of near-filed induced charge transfer has remained as a challenging experiment. Here we present LSPR-assisted resonant electron tunneling from an Ag or Au tip to the image potential states of a Ag(111) surface using scanning tunneling microscopy (STM). The LSPR-assisted tunneling process results in an incident photon-energy dependent red-shift of the field emission resonances (FERs) in the gap. Using the precise control of the gap distance in the STM junction we demonstrate tuning of the relative contribution from the LSPR-assisted and the normal STM electron tunneling processes. Furthermore, the FER intensity mapping of local defects on the surface allows assigning unambiguously the respective FER levels with and without laser excitation.

arXiv comment17 pages, 4 figures, Author's website: http://www.fhi-berlin.mpg.de/pc/kumagai/

References in corpus (5)

• Orbital-selective single molecule excitation and spectroscopy based on plasmon-exciton coupling
• Narrow-line single-molecule transducer between electronic circuits and surface plasmons
• Nonlinear Optical Rectennas
• Two-photon Induced Hot Electron Transfer to a Single Molecule in a Scanning Tunneling Microscope
• Light Emission from Ag(111) driven by Inelastic Tunneling in the Field Emission Regime

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• Phase-sensitive tip-enhanced sum frequency generation spectroscopy using temporally asymmetric pulse for detecting weak vibrational signals
• Ultrafast optically induced tunneling in narrow metallic gaps from the time dependent density functional perspective