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FDSERS17 Novel Routes to Electromagnetic Enhancement and its Characterisation in Surface- and Tip-enhanced Raman Scattering

Abstract

Quantitative understanding of the electromagnetic component in enhanced Raman spectroscopy is often difficult to achieve on account of the complex substrate structures utilized. We therefore turn to two structurally simple systems amenable to detailed modelling. The first is tip-enhanced Raman scattering under electron scanning tunnelling microscopy control (STM-TERS) where, appealing to understanding developed in the context of photon emission from STM, it is argued that the localised surface plasmon modes driving the Raman enhancement exist in the visible and near-infrared regime only by virtue of significant modification of the tip- and sample-metal (gold here). This is due to the strong dc field-induced (~10^9 V/m) non-linear corrections to the dielectric function of gold via the third order susceptibility term in the polarization. Also, sub-5 nm spatial resolution is demonstrated in the modelling. Secondly, we suggest a novel deployment of hybrid plasmonic waveguide modes in surface enhanced Raman scattering (HPWG-SERS). This delivers strong confinement of electromagnetic energy in a ~10 nm oxide ‘gap’ between a high-index dielectric material of nanoscale width (a GaAs nanorod and a 100 nm Si slab are considered here) and a metal, yielding a monotonic variation in Raman enhancment factor as a function of wavelength with no long-wavelength cut-off, both features that contrast with STM-TERS.

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Publication details

The article was received on 10 Apr 2017, accepted on 21 Jun 2017 and first published on 21 Jun 2017


Article type: Paper
DOI: 10.1039/C7FD00128B
Citation: Faraday Discuss., 2017, Accepted Manuscript
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    FDSERS17 Novel Routes to Electromagnetic Enhancement and its Characterisation in Surface- and Tip-enhanced Raman Scattering

    P. Dawson, D. Frey, V. Kalathingal, R. Mehfuz and J. Mitra, Faraday Discuss., 2017, Accepted Manuscript , DOI: 10.1039/C7FD00128B

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