Abstract

The surface-enhanced Raman scattering (SERS) technique refers to the phenomenon of the Raman signal being enhanced by a factor of 10⁴–10⁶ from the probed molecules on the metallic nanostructure because of the locally enhanced electromagnetic field resulting from the excitation of the localized surface plasmon resonance. A large electromagnetic field can be produced and confined in the gap region of a nanostructure such as bowtie-shaped [1] or dimer antenna [2]. Nanostructures suspended over Si substrate through Si posts could yield up to 2 orders of magnitude additional SERS enhancement response compared to the flat substrate [3]. In this study, ordered Au dimer nanostructure array defined by electron beam lithography was attached on the suspended graphene over Si rectangular cavity with varying cavity depth which was fabricated by micro-electro-mechanical system method. The SERS signals were evaluated for different sizes of dimer, gaps between circle, and Si cavity depths. Finite-difference time-domain (FDTD) method was used to compare the simulated electric field enhancements with experimental measurements.

© 2016 Japan Society of Applied Physics, Optical Society of America