Plasmonic nanopore structures have been expected to play a key role in next-generation nanopore devices because plasmonic-enhanced electric fields inside nanopores potentially enable the measurement of surface-enhanced Raman scattering (SERS) spectra of a single analyte passing through a nanopore. However, sufficient enhancement of the electric field inside a nanopore for SERS measurements has not been obtained. Here, we report finite-difference time-domain simulation studies of inverted cone-shaped plasmonic nanopore structures, which maximally show an ∼1000 times stronger SERS enhancement factor than that of a conventional cylindrical plasmonic nanopore structure. The enhancement was found to be achieved via nanofocusing and structural effects, causing a 1.3 and 4.7 times stronger plasmonic-enhanced electric field than that of a cylindrical structure, respectively. The present study suggests a high potential of inverted cone shapes as plasmonic nanopore structures for SERS measurement of an analyte passing through a nanopore.
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