週期性奈米金屬結構對P3HT薄膜螢光的增強之研究

Abstract

本論文研究利用奈米球微影術及電子束微影系統分別製作出奈米三角形陣列和奈米光柵陣列，之後透過螢光材料的塗佈於奈米金屬結構上，欲探討奈米金屬結構之侷域表面電漿共振效應對螢光材料訊號的增強。由奈米球微影術製作的不同尺寸的奈米三角形陣列，發現到奈米金屬三角形會隨著三角形邊長減少時，其表面電漿最大共振波長會產生藍位移的現象。將相同厚度的螢光材料P3HT塗佈在直徑1微米和350奈米球做為光罩製成的奈米三角形陣列上，量測其螢光增強倍率，會發現到以直徑350奈米球製成的三角形陣列，其螢光增強倍率達3.5倍，優於以直徑1微米球製成的奈米三角形陣列的2倍。由電子束微影系統製成的奈米光柵陣列，在TM極化波垂直入射，隨著P3HT薄膜厚度增加，螢光增強效果有變大的趨勢，當激發光源為633奈米時，其螢光增強達9.2倍。另外，使用顯微拉曼光譜儀量測拉曼訊號，探討在光柵結構與P3HT薄膜之間加入25奈米的SiO２層當做緩衝層在拉曼光譜上的影響，發現到加入SiO２層後其增強因子會下降，驗證了因SiO２層會抑制螢光焠熄現象，使得螢光訊號仍強，進而使得光柵結構上的拉曼訊號強度較弱。

This thesis includes the nanosphere lithography (NSL) and E-beam lithography that develops nano-triangular arrays and paired-strips-nanoantennas arrays in subwavlength dimension. The enhancement of fluorescence signals is measured by means of coating P3HT thin film and localized surface plasmon resonances (LSPR) of metallic nanostructures. According to different sizes of nano-triangular arrays by NSL, LSPR experiences blue-shift as physical sizes of nano-triangles decrease. The nano-triangular arrays were fabricated by the nano-spheres in diameter of 1 μm and 350 nm, then embedded in same thickness of P3HT thin films. Covering P3HT organic thin film on the nano-triangular arrays made by 350 nm sphere shows the fluorescence enhancement factor is about 3.5 times higher than the nano-triangular arrays which made by 1 μm sphere. The fluorescence enhancement factor of paired-strips nanoantennas arrays would be higher as the thickness of P3HT thin film increase in TM mode. When the excitation wavelength is 633 nm, the fluorescence enhancement factor is about 9.2 times. The Raman signals are measured and compared whether the SiO2 layer as a spacing layer is existing or not. The enhancement factor would decrease when adding SiO2 layer. It can be verified that SiO2 layer would suppress fluorescence quenching phenomenon. Because the fluorescence signal is still strong, the enhancement of Raman signals on the nano-grating arrays would be weak.