Surface-enhanced Raman scattering nanodomes fabricated by nanoreplica molding

We demonstrate a surface-enhanced Raman scattering substrate consisting of a closely spaced metal nanodome array fabricated on flexible plastic film. We used a low cost, large area replica molding process to produce a 2-dimensional periodic array of cylinders that is subsequently overcoated with SiO₂ and silver thin films to form dome-shaped structures. Finite element modeling was used to investigate the electromagnetic field distribution of the nanodome array structure and the effect of the nanodome separation distance on the electromagnetic field enhancement. The SERS enhancement from the nanodome array substrates was experimentally verified using rhodamine 6G as the analyte. With a separation distance of 17 nm achieved between adjacent domes using a process that is precisely controlled during thin film deposition, a reproducible SERS enhancement factor of 1.37x10⁸ was demonstrated. The nanoreplica molding process presented in this work allows for simple, low cost, high-throughput fabrication of uniform nanoscale SERS substrates over large surface areas without the requirement for high resolution lithography or defect-free deposition of spherical microparticle monolayer templates.