| Surface enhanced Raman scattering (SERS) relies on hot spots to identify the chemical fingerprints. The hot spots have extremely strong electric field and are usually generated by localized surface plasmon resonance (LSPR). The electrical field coupling of LSPR in the gap of metal nanoparticle dimmer can result in a field enhancement up to 108. Although single-molecule SERS detection could be realized with strong coupled LSPR field, the signals were often accompanied with low reproducibility and poor stability.Firstly, The author describes the enhancing units of metal-nanoparticles-based SERS systems and summarized the reasons leading to SERS irreproducibility in both 2-dimension or 3-dimension substrate. Ordered silicon nanowires array (SiNWs) covered by Ag nanoparticles (AgNPs) here was selected as a faulty solution and the author describes the fabrication of ordered SiNWs array with tunable sizes by Nanosphere Lithography and Metal-assisted Chemical Etching. Then the author analyzes the electric field distribution in nanowires array of different materials motivated under 633 nm laser by optical wave guide theory and Finite Difference Time Domain (FDTD) simulation. Following this, the author demonstrates the SiO2/Si core-shell nanowires (SiO2/SiNWs) array coated by AgNPs as a solution and verified it by experiment.The thesis is composed of following chapters.1:The author reviewes the SERS systems based on metal nanoparticles (MNPs) and summarized their common features. After analyzing the reasons for the low SERS reproducibility, he further introduced ordered arrays of silicon covered with silver nanoparticle as a faulty solution. Fabrication methods of Nanoshpere Lithography and Metal-assisted Chemical Etching are described to make ordered hexagonal-packed vertical SiNW arrays, and characterization tools of morphology and optical properties are introduced.2:Surface electrical wave distribution on different nanowire was got by FDTD simulation and optical waveguide theory. This is come from the guided mode which supported by nanowire of specific size under 633nm laser. The guided mode redistribute the electric field energy around the surface of nanawire and would make great contribution to the even Raman signal. Following this, the author demonstrates the SiO2/Si core-shell nanowires (SiO2/SiNWs) array coated by AgNPs as a solution.3:The author fabricated SiO2/SiNWs of 150nm in diameter, 1μm in length and a period of 300nm as a SERS system and compared it with another two classical substrate. After multiplex SERS mapping, it has been proved that this substrate is of higher reproducibility and signal resolution. |
