Abstract
Surface-enhanced Raman Scattering (SERS) of rhodamine 6G (R6G) adsorbed on biharmonic metallic grating structures was studied. Biharmonic metallic gratings include two different grating components, one acting as a coupler to excite surface plasmon polaritons (SPP), and the other forming a plasmonic band gap for the propagating SPPs. In the vicinity of the band edges, localized surface plasmons are formed. These localized plasmons strongly enhance the scattering efficiency of the Raman signal emitted on the metallic grating surfaces. It was shown that reproducible Raman scattering enhancement factors of over 10(5) can be achieved by fabricating biharmonic SERS templates using soft nano-imprint technique. We have shown that the SERS activities from these templates are tunable as a function of plasmonic resonance conditions. Similar enhancement factors were also measured for directional emission of photoluminescence. At the wavelengths of the plasmonic absorption peak, directional enhancement by a factor of 30 was deduced for photoluminescence measurements.
Highlights
Raman spectroscopy is a crucial tool in the analysis of vibrational bonds which reveal the details of the molecular structure
We demonstrate that biharmonic metallic grating structures can be used as Surface Enhanced Raman Scattering (SERS) substrates
When metallic nanoparticles used as SERS substrate, maximum SERS enhancement is obtained when plasmonic resonance absorption lies between laser line and Raman emission wavelengths
Summary
Raman spectroscopy is a crucial tool in the analysis of vibrational bonds which reveal the details of the molecular structure. Typical SERS substrates, textured metallic surfaces such as spherical shapes [18] and pyramidal type voids [19, 20] allow engineering the plasmonic modes to optimize reproducible SERS enhancement. On a metal grating surface, Stokes radiation is confined into a much smaller solid angle and results in an enhancement in the measured Raman signal [21]. These types of templates show relatively low enhancement factors (104) [21] and enhanced Stokes wavelengths depend on the collection angle as well [23]. Soft nanoimprint technique is used as a replication tool allowing the fabrication of SERS templates reproducibly
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