Optimization of SERS enhancement from nanostructured metallic substrate based on arrays of inverted rectangular pyramids and investigation of effect of lattice non-symmetry

Surface-enhanced Raman scattering (SERS) can be used to amplify Raman signals by several orders of magnitude, by utilizing Plasmon polariton (photonic and surface Plasmon mode) coupling to test molecules disposed on a textured metallo-dielectric surface. Previously the 'KlariteTM' substrate consisting of an inverted array of square pyramidal nanostructures patterned onto a Silicon substrate has been demonstrated to afford highly reproducible SERS signals. In this paper, we investigate a new rectangular lattice arrangement and investigate the effect of aspect ratio on SERS enhancement factor. Nanostructured test substrates are coated with gold by thermal evaporation, followed by a monolayer of benzenethiol or benzyl mercaptan which provides a stable test molecule for signal enhancement comparison. SERS signals are analyzed with Renishaw (MS20) Invia Raman Spectrometer at a wavelength of 785nm. The resulting SERS enhancement shows an improvement in signal level of 786% (~ 8 times) compared to standard Klarite. In addition to high enhancement we are able to maintain less than 8.8% relative standard deviation for the peak signal.

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