Simple and Reliable Patterning of Plasmonic Nanostructures by Spontaneous Adhesion Lithography

Nanoscale gaps in noble metal films can locate surface plasmons. Molecules positioned within such metallic nanogaps significantly enhance light-matter interactions, increasing absorption, emission, and, most notably,... [ view full abstract ]

Nanoscale gaps in noble metal films can locate surface plasmons. Molecules positioned within such metallic nanogaps significantly enhance light-matter interactions, increasing absorption, emission, and, most notably, surface-enhanced Raman scattering (SERS). However, the reliable and reproducible fabrication of ultranarrow gaps (< 20 nm) for real applications is still challenging. Here, we show a method to fabricate simply and reliably sub-20-nm metallic gap arrays with aspect ratios in excess of 100,000. This method exploits the ability of selected self-assembled monolayers to attach conformally to a pre-patterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method can be carried out under ambient conditions via a simple mechanically induced process that involves no intricate alignment procedures and high-cost instruments. With this method, we fabricated densely packed gold nanostructures of varying geometries separated by ultrasmall gaps. Optical and SERS measurements on the patterned structures show that this technique has promising applications in the fabrication of tunable plasmonic nanostructures with nanogaps.