Design and fabrication of the nano-periodic metallic structure and study of its optical property

• Main Authors: Sheng-En Chen, 陳聖恩
• Other Authors: Shu-Sheng Lee
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/22787961230402476228

碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 100 === Surface plasmons resonance(SPR) and surface enhanced Raman scattering(SERS) are very important technologies for analysis of biological molecules. The testing and analysis theories of them are different. The SPR is the dynamic analysis for intermolecular binding, and the SERS is the detection for the molecular structure. The Raman scattering light intensity is quite weak, so how to enhance the exciting electric field becomes an important issue. The localized surface plasmons(LSP) will be produced by the metal annular aperture structure, and thus this kind of structure is also a good pattern for designing substrate of SERS. Therefore, the finite difference time domain method (FDTD) method has been adopted to do the simulation in this research. The property of the reflective light of different dimension metal nano-annular aperture structures incident by the normally polarized X-axis plane wave was obtained. The structural parameters such as the diameters of the outside and inside the annular aperture structure, vertical and horizontal distance between them, and the coating metal films thickness were the factors during the simulation process. The dimension of the metallic nano-annular aperture structure which can produce the largest electric field concentration was decided first. Then, the thickness of the metallic films were changed and the better thickness for inducing SPR effect was decided. The electron beam evaporator was used to coat gold (Au) thin films on the SF2 glass substrate with the 50nm and 60nm thickness respectively. The 2 nm or 5 nm thick chromium(Cr) thin film was coated between the gold film and the glass. The nano-annular aperture structures fabricated by the focus ion beam which etched the gold film surface of the substrated. The substrate with the metallic nano-annular aperture structures can induced the SPR phenomena with the 633 nm wavelength incident light by Opto-BioMorphin, OB Morph. The transmitted spectrum showed that wavelength of the resonant transmission light was from 550 nm to 610 nm. Finally, the Thiopheno molecules as the sample and the maximum signal intensity of the reflective light was detected while the inner diameter was 200 nm and the outer diameter was 400 nm of the nano-annular aperture structures on the 5 nm thick Cr film and 50 nm thick Au film of the substrate; however, the Raman scattering effect was not so obvious to tell the sample. The structures still needed further modification to have the better Raman scattering effect.