M-shaped grating by nanoimprinting: A replicable, large-area, highly active plasmonic surface-enhanced Raman scattering substrate with nanogaps

Abstract

Plasmonic nanostructures separated by nanogaps enable strong electromagnetic-field confinement on the nanoscale for enhancing light-matter interactions, which are in great demand in many applications such as surface-enhanced Raman scattering (SERS). A simple M-shaped nanograting with narrow V-shaped grooves is proposed. Both theoretical and experimental studies reveal that the electromagnetic field on the surface of the M grating can be pronouncedly enhanced over that of a grating without such grooves, due to field localization in the nanogaps formed by the narrow V grooves. A technique based on room-temperature nanoimprinting lithography and anisotropic reactive-ion etching is developed to fabricate this device, which is cost-effective, reliable, and suitable for fabricating large-area nanostructures. As a demonstration of the potential application of this device, the M grating is used as a SERS substrate for probing Rhodamine 6G molecules. Experimentally, an average SERS enhancement factor as high as 5×108 has been achieved, which verifies the greatly enhanced light-matter interaction on the surface of the M grating over that of traditional SERS surfaces. M for Nano: An M-shaped plasmonic nanograting with nanogaps is proposed and fabricated by using room-temperature nanoimprinting and anisotropic reactive-ion etching, and enables strong field localization in the nanogaps. Surface-enhanced Raman scattering (SERS) experiments show an average SERS enhancement factor as high as 5×108 by using the M-grating substrate, which reveals its potential as a replicable, large-area, highly active SERS substrate. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.