We demonstrate large area periodic arrays of elevated gold ellipse pairs with precisely controlled gaps for use as stable and controllable surface enhanced Raman scattering (SERS) substrates. We systematically investigated the role of changing gap distance, ellipse aspect ratio, and post height for optimizing the SERS enhancement factor. Localized and long range plasmonic effects are responsible for the significantly enhanced Raman signal; by controlling the geometry of a SERS substrate, here the size and aspect ratio of the ellipse nanoantennae, the plasmon resonance can be readily tuned in a broad wavelength range. This tunabilty provides a method for designing the response of SERS substrates at different excitation wavelengths. Plasmon effects exhibited by the elevated gold ellipse dimer substrates are also confirmed through finite difference time domain (FDTD) simulations. A plasmon resonance red shift from the visible to near infrared with an increase of the ellipse aspect ratio is observed, allowing systematic optimization of the resulting SERS signal intensity. Optimized elevated ellipse-dimer substrates with 10 nm gaps characterized with 785 nm excitation exhibit uniform SERS enhancement factors on the order of 10<sup>8 </sup>for adsorbed <i>p</i>-mercaptoaniline molecules.

Periodic arrays of gold ellipse dimer nanoantennae with 10-nm gaps as highly active and tunable SERS substrates

251st National Meeting (2016)

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