Plasmonic nanocavities fabricated by directed self-assembly lithography and nanotransfer printing and used as surface-enhanced Raman scattering substrates

Abstract

In this study, plasmonic nanocavity arrays were fabricated as surface-enhanced Raman scattering (SERS) substrates through directed self-assembly (DSA) of block copolymer and nanotransfer printing (NTP). NTP is a simple and efficient process of replicating plasmonic nanofeatures from a silicon template. The template was fabricated with the combination of nanoimprint and DSA lithographies and can be reused repeatedly. Utilizing DSA lithography allows us to cost-effectively produce nanofeatures. Gold nanocavities with 10 nm gap size, 30 nm height, and 40 nm period were fabricated. Gold nanoslits with the same dimensions were also fabricated for comparison. The field enhancement properties of both structures were investigated numerically and experimentally. The localized field enhancement in the nanocavity was considerably stronger than that in the nanoslit. The SERS sensing result greatly agreed with the simulation result. The nanocavity substrate enhanced the SERS signals six times higher than the nanoslit substrate. This approach is a promising candidate for SERS substrate fabrication, thus eliminating the trade-off between throughput and reproducibility.