金奈米結構披覆多孔矽用於表面增強拉曼散射基板

拉曼散射為光子和化學分子間的非彈性散射現象。表面增強拉曼散射這項技術強化了分子微弱的拉曼訊號，故成為靈敏的分子鑑定工具，常應用在化學及生物醫學領域。實驗中製備不同表面形貌的多孔矽和一般的單晶矽作為二維金奈米結構的SERS活性基板，包括改變金薄膜厚度、使用雷射誘導法長金在多孔矽上。本實驗以R6G為探測分子進行SERS效應之研究。本論文中以電化學蝕刻技術來製備多孔矽，因電化學蝕刻保有濕式蝕刻的優點，且設備成本低、蝕孔異向性高等優點，我們以鐵氟龍、O-ring、白金片作為正負電極組裝成蝕刻設備，藉調整蝕刻時間、蝕刻電流、蝕刻液等方法來製備不同結構的多孔矽層。厚度為7 nm時的金奈米半連續膜結構有著最豐富的熱點，得到平均EFs為7.6 × 103 的增強效果，為單晶矽奈米金薄膜中最佳的R6G分子SERS訊號。而在相同奈米金薄膜厚度下，基板改為多孔矽時，因原始表面結構極為粗糙，粗糙度上升增加奈米金薄膜表面積及熱點形成的機會，使得整體SERS訊號提升了十餘倍，在7 nm時EFs達5.36 × 105。使用雷射誘導法使金奈米粒子平均附著在多孔矽基板上，得到最佳的EFs為4.62 × 103。

關鍵字

多孔矽；金奈米粒子；表面增強拉曼散射

並列摘要

Raman scattering is the inelastic scattering of photons and chemical molecules. Surface-enhanced Raman scattering (SERS) greatly enhances the normally weak Raman signal and thus becomes a sensitive technique for identification of analyte molecules in chemical or biological analysis. In this study, a number of SERS active substrates with two-dimensional gold nanostructures were prepared including single crystal and different surface morphology of porous silicon. We change the gold film thickness and use of Laser-Induced growth of gold nanoparticles on porous silicon. Rhodamine 6G (R6G) was used as the target molecule to evaluate the SERS effect. We fabricate porous silicon on silicon wafer using electrochemical etching, in which electrochemical etching is the most common method to fabricate directional pores due to its low-cost and etching anisotropy. We use Teflon , o-ring, platinum as anode and cathode to assemble the etching device to form a thick silicon layer with different porous structure by adjusting the etching time, etching current, etching solvent. The strongest SERS signal was obtained from the 7 nm thick film with an average enhancement factors (EFs) of 7.6 × 103. It’s believed that the semicontinuous gold film of the 7 nm on single crystal provides abundant hot spots and gives the strongest SERS signal. In the same nanometer gold film thickness , substrate was change to porous silicon, because the original surface structure is extremely rough, roughness increase the chance of rising gold nano-film surface area and the formation of hot spots ,gives 10 times improvement and on the 7 nm thick gold film the EFs reaches around 5.36 × 105. An average best EFs of 4.62 × 103 has been obtained by Laser-Induced growth of gold nanoparticles on porous silicon.