表面修飾對奈米線場效電晶體之電訊號特性之影響

Abstract

近期的文獻指出在生物感測應用方面，多晶矽奈米線場效電晶體具有高靈敏度以及免標記的優點。實驗結果顯示，多晶矽奈米線場效電晶體之電訊號特性與奈米線之表面特性有絕對的相關。本研究將證實，多晶矽奈米線場效電晶體的電訊號反應會受奈米線表面上所修飾之分子官能基之pKa值，以及其疏水特性所調控，其中包含amine，methyl，carboxyl以及oxide等官能基。X射線光電子能譜 (X-ray photoelectron spectroscopy) 及液珠型態測試已用於確認奈米線表面修飾成功與否，以及分析奈米線表面修飾後的液珠角度。並且使用兩種聚合物，分別為帶有負電荷的poly(sodium 4-styrenesulfonate) 以及帶有正電荷的poly(allylamine hydrochloride) 證實奈米線表面修飾後的電荷特性。本論文中，感測條件之決定為適用於生物分子偵測以及pH量測的液體量測閘極，利用其作為奈米線表面的電壓來源以進行電訊號偵測。另外，我們發現溶液中離子濃度為調控奈米線訊號特性的重要因子，並且可藉由加入高濃度 (100 mM) 的中性鹽類，如：氯化鈉，將其影響降低。本篇研究將提供一方向，利於未來可更進一步的開發生醫應用之生物感測器時之依據。

Recent studies have been demonstrated that poly crystalline silicon nanowire field-effect transistor (poly-SiNW FET) can serve as a highly sensitive and label-free transducer for biosensing applications. Experimental result showed that the electrical characteristics of the poly-SiNW FET strongly correlate to the surface properties of the NW. Here, we demonstrate that the electrical characteristics of the poly-SiNW FETs can be modulated by the surface modification process of functional groups with various pKa values and hydrophobicity, which include amine, methyl, carboxyl and oxide. X-ray photoelectron spectroscopy (XPS) and the liquid morphology were employed to confirm and analyze the degree of the surface modification of the NW. Two polymers, poly(sodium 4-styrenesulfonate) (PSS) with negative charge and poly(allylamine hydrochloride) (PAH) with positive charge, were used to verify the surface situation of the NW. In this thesis, the sensing conditions were determined by using liquid-gating, which was found to be suitable for biodetection and pH sensing, as a gate electrode of FET configuration to tune the electrical characteristics of SiNW FETs. We found that the ion concentration in solution would be an important factor controlling the electrical properties of the NW and the effects could be minimized efficiently by adding neutral salt, sodium chloride, into the buffer solution with highly concentration (100 mM). This study should provide useful information for optimizing the performance of poly-SiNW-based biosensor for biomedical applications.