S.-G. Park, D.-H. Kim
Korea Institute of Materials Science,
Keywords: plasmons, Raman scattering, fluorescence, nanostructures
Summary:Plasmonic metal nanoparticles (NPs) and nanostructures induce localized surface-plasmon resonance (LSPR). This LSPR phenomenon has been used for label-free biosensors and plasmon-enhanced spectroscopic sensors. Since a SERS enhancement factor exponentially increases as the distance between plasmonic nanostructures decreases, it is very crucial to make plasmonic nanostructures with ultra-high density of small nanogaps for ultra-sensitive SERS sensors. In this work, we report 3D multilayered plasmonic nanostructures with highly enhanced eletromagnetic enhancements due to formation of high density of spherical Au NPs on the 3D dielectric-metal nanopillar array. Since the surface energy(14 mJ/m2) of the 1 nm thick dielectric layer is significantly lower than the surface energy(1210 mJ/m2) of Au, the surface migration of the Au adsorbed atoms incident on the dielectric layer is activated during Au evaporation process. With 1 nm thick conformal dielectric interlayer with low surface energy, the top Au NPs possess spherical shapes, thereby increasing density of Au NPs even in the 100 nm deposition thickness and enhancing plasmonic coupling efficiency among the plasmonic nanomaterials. It is found that when the Au NPs present on the side parts of the Au nanorods, the Au NPs may induce the plasmonic coupling stronger than that located on the top part of the Au nanorods. We finally demonstrated that 3D multilayered plasmonic substrate showed ultra-sensitive SERS properties with a SERS enhancement factor of 10^9 and very low light loss (less than 0.1%) characteristics in the entire visible region. It is concluded that understanding and controlling metal growth modes on the underlying nanostructured surface is critical to make high density of plasmonic nanostructures and thereby enhancing light–matter interactions.