Spatially Controlled Fabrication of Surface-Enhanced Raman Scattering Hot Spots through Photoinduced Dewetting of SilverThin Films

Abstract

A well-designed narrow gap between noble metal nanostructures plays aprominent role in surface-enhanced Raman scattering (SERS) to concentrate electromagneticfields at the local point, called a"hot spot". However, SERS-active substrate fabricationremains a substantial hurdle due to the high process cost and the difficulty of engineeringefficient plasmonic hot spots at the target area. In this study, we demonstrate a simplephotolithographic method for generating ultrasensitive SERS hot spots at desired positions.The solid-state dewetting of a Ag thinfilm (thickness of similar to 10 nm) using a continuous-wavelaser (similar to 1 MW/cm2) generates a closely packed assembly of hemispherical Ag nanoislands.Some of these nanoislands provide substantial plasmonic-field enhancement that is sufficientfor single-molecule detection and plasmon-catalyzed chemical reaction. Such hot spotstructures can be patterned on the substrate with a spatial resolution of better than 1 mu m. Inintegrated analytical devices, the patterned SERS hot spots can be used as position-specificchemical-sensing elements.