Fabrication of SiNW arrays by laser means and its applications in SERS detections

Abstract

Silicon nanowire (SiNW) arrays are fabricated by laser interference lithography (LIL) and metal assisted chemical etching. The LIL produces well-ordered surface nanostructures and the following metal assisted chemical etching configures the patterns into high-aspect-ratio three dimensional (3D) nanostructures. The SiNWs exhibit strong antireflection properties. The surface reflection decreases with the height of SiNWs. With Ag thin film coating, such black Si surfaces are applied as surface enhanced Raman scattering (SERS) substrates to measure the 4-methylbenzenethiol molecules adsorbed on the sample surface. The change of SERS signal intensity with the height of SiNWs is investigated. Higher SiNWs exhibit stronger SERS signals due to the large surface area. Meanwhile, Ag nanoparticles (NPs') decoration on SiNWs via either thermal annealing or redox reaction has been demonstrated for the SERS detection in comparison to Ag film coating. Ag NPs' decoration by redox reaction greatly improves the SERS signal intensity due to the generation of high density hotspots. However, the thermal annealing method weakens the SERS signals due to oxidation of Ag NPs.