高折射率奈米粒子與金膜產生強偶極耦合的暗場成像

Abstract

異質材料組成的奈米結構對於遠場散射與近場增益上有特殊的耦合效應,例如：高折射率奈米粒子與高反射率基板的系統。在此將矽奈米粒子沉積在鍍有金薄膜的基板上，並且使用顯微鏡進行暗場散射訊號與近場增益的分析，發現在近紅外光的散射訊號有明顯的增強且寬頻的訊號，在近場也有很強的增益。由於顯微鏡暗場量測架構屬於斜向入射，因此造成矽奈米粒子模態位移。尤其在p-polarized光激發下，能在近紅外光波段產生散射訊號的增強。研究結果說明，此奈米結構有助於螢光增強頻譜、拉曼增強頻譜等等。

We investigate the coupling of dipole resonances induced in a hetero-material system composed of a high-refractive-index nanoparticle and a highly reflective substrate. A broad scattering signal and strong electric near-field enhancement in the near-infrared region are generated by a hybrid Si nanoparticle on a gold-film system under oblique illumination. Dark-field microscopy investigations of the scattering signal measurement reveal the resonance shifts of the dipole mode of silicon nanoparticles on gold films. Further, the scattering signal is enhanced for p-polarized illumination in the near-infrared region. The results indicate that the coupling of Si nanoparticles on a gold-film system facilitates a possible application for both surface-enhanced fluorescence and surface-enhanced Raman scattering with low light-into-heat conversion.