Suspended graphene with periodic dimer nanostructure on Si cavities for surface-enhanced Raman scattering applications

Periodic gold dimer nanoantennas on a one-atomic-layer graphene sheet elevated above Si cavities were fabricated to systematically study the effects of the cavity depth on surface-enhanced Raman scattering (SERS). The periodic trend of Raman intensity as a function of the cavity depth resulting from the interference effect between the plasmonic resonance of the gold dimer and the cavity resonance of the underlying Si cavity was observed, and the electric field was greatly enhanced compared with the non-suspended system. The finite-difference time-domain method was used to simulate the interaction between the electromagnetic wave and the suspended system and to verify the observed SERS response in experiments. Our work has the advantages of combining the superior properties of graphene with suspended metallic nanostructures to result in the enhanced electric field for SERS applications.