REALIZATION OF PLASMONIC 2D & 3D NANOSTRUCTURES FOR SURFACE ENHANCED RAMAN SCATTERING DETECTION.

Abstract

Surface enhanced Raman spectroscopy (SERS) has been widely investigated as an effective technique for low-concentration bio-chemical molecules detection. In order to fabricate SERS substrates with high enhancement factors and signal uniformities, various approaches are applied. Laser micro/nano-processing provides effective methods to fabricate SERS substrates in a large area. In this thesis, 2D and 3D plasmonic nanostructures are designed and fabricated by laser means. Firstly, a rapid two-step approach to fabricate 2D SERS substrates in ambient air is developed. Nanoparticles are synthesized via the nucleation of laser induced plasma species and air molecules. With Ag film coating, these nanoparticles function as hotspots for SERS detection. To further improve the sensitivity, 3D well-ordered SiNWs are investigated. Laser interference lithography and metal assisted chemical etching are used to fabricate various aspect ratios of SiNWs. Ag nanoparticles are decorated on the substrates via redox reaction. An optimized aspect ratio for the SiNW array is studied. The well-ordered SiNWs demonstrate better SERS signal intensity and uniformity than the randomly arranged SiNWs.