The Study Of High Performance Surface-enhanced Raman Scattering Substrates Developed By Focus Ion Beam Nanofabrication

Material testing has become one of the most concerned topics in recent years.Raman Scattering is a powerful tool for trace detections and biochemical applicationsbecause of its ultrasensitivity, low-cost, and real-time. Howere in a long time after theRaman scattering was discovered, the applications in bio-sensing had been limited byits inherent much weak signal until1977, the researchers found that Raman Scatteringsignal can be largely enhanced by roughened noble metal surface. Therefore the mostcritical aspect of SERS is the research of efficient SERS-active substrates.The traditional way to fabricating SERS substrates includes electrochemicalmethod, chemical synthesis method and template method. Nevertheless, fabrication ofSERS substrates with both high sensitivity and high stableness still remains difficult.The main underlying enhancement mechanism was attributed to the Localized SurfacePlasmon Resonance (LSPR) occurring when the nanostructure is much smaller thanthe excitation wavelength. Recently, focused ion beam direct writing (FIBDW)technology has been an increasingly important nano-fabrication technique, and couldbe used in the SERS substrate’s development.This thesis mainly describes the research of SERS substrates. On the one hand,we found a suitable structure for the specific wavelength through FDTD software andthen fabricated SERS substrates by FIB Nanofabrication. In our experiments, wefound that thin gold film which is coated on the Si substrate or quartz glass is soft, soit is difficult to obtain nanostructures with less spacing. Owning to this, we report anovel method with high flexibility and efficiency for developing SERS substrates bypatterning nanostructures on Si substrates using Focused Ion Beam Direct Writing(FIBDW) technology following with precise thermal evaporation of gold film on thesubstrate. By optimizing the processing parameters and the gold film thickness, weobtained high enhancement SERS substrates. Besides, we successfully fabricatedthree dimensional nanostructures by electron beam induced deposition technology. Itis found that the SERS substrate shows high sensitivity, stability and repeatability,such as the spacing of nanostructures can be down to10nm and the enhancementfactor can reach107.