Controlling Sub-nm Gaps in Plasmonic Dimers using Graphene

TL;DR

This paper demonstrates how graphene can be used as a precise, stable spacer in plasmonic dimers to achieve sub-nanometer gaps, enabling tunable and enhanced plasmonic responses.

Contribution

It introduces a method to control sub-nanometer gaps in plasmonic structures using graphene, allowing for stable, repeatable, and tunable plasmonic coupling.

Findings

Observation of plasmonic coupling via white light spectroscopy.

Disappearance of spectral doublets with increasing graphene layers.

Direct measurement of out-of-plane conductivity through plasmonic charge transfer.

Abstract

Graphene is used as the thinnest possible spacer between gold nanoparticles and a gold substrate. This creates a robust, repeatable, and stable sub-nanometre 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 infra-red, these disappear for increasing numbers of layers. These doublets arise from plasmonic charge transfer, allowing the direct optical measurement of out-of-plane conductivity in such layered systems. Gating the graphene can thus directly produce plasmon tuning.