Abstract
Abstract An ideal surface-enhanced Raman scattering (SERS) nanostructure for sensing and imaging applications should provide a high signal enhancement and can be obtained by easy fabrication process with large hot spot numbers/areas. In this paper, we present a simple, precise, and high-throughput technique for producing double-nanoshelled Au nanoparticles (DNS Au NPs) arrays with well-controlled nanogap of several nanometers by employing ALD HfO2 as the dielectric layer. This DNS Au NPs structure provides respectable SERS by inducing stronger plasmon electric field from the tunable nanogap structure ranging between 10 and 1 nm and large hot-spot areas as a nanoring instead of a spot. The SERS enhancement is inversely proportional to the thickness of HfO2 and a maximum of 20 folds enhancement is found at 1nm nanogap. Moreover, we also employed Ag as second layer instead of Au forming DNS Ag NPs structures, and it significant improved the SERS performance more than an order to the DNS Au NPs.