多晶矽奈米線氨氣感測平台開發與感測機制探討

Abstract

非侵入性氨氣感測器在慢性肝病以及腎衰竭的早期診斷上具有相當大的潛力，藉由疾病的早期診斷，不但能降低醫療的成本同時也能改善病的人生活品質，使病人免受慢性病的折磨，為了達到這個目標，我們必須開發一個超高靈敏度的非侵入式氨氣感測器。目前已被證實，低成本的多晶矽奈米線場效電晶體具有較高的體積表面積比，所以比其他感測器擁有更高的靈敏度，適合用於開發為非侵入式氨氣感測器。在本篇研究中，我們建立一個最佳化的多晶矽奈米線氨氣感測平台，利用此平台我們可以偵測到0.25 ppm的氨氣,這個感測能力已經能依據口中呼出的氨氣濃度來分辨健康的人(0.278 ppm)和患有慢性肝病的人(0.745 ppm)。不過對於多晶矽奈米線場效電晶體的氨氣感測機制目前尚未明白，需要被透徹的了解，所以我們使用單晶矽奈米線場效電晶體和不同表面修飾的多晶矽奈米線場效電晶體來進一步探討其感測機制。從實驗結果中得知，氣體的電荷偶極效應和多晶矽奈米線的晶界都與氨氣感測的機制有相關，其中以氣體的電荷偶極效應扮演主要的角色，至於更深入感測原理我們會在未來的研究中加以釐清。在本篇研究中，我們開發了一個新穎性的氨氣感測平台，同時對於多晶矽奈米線場效電晶體的氨氣感測機制也做了初步的探討。在未來，我們期望多晶矽奈米線場效電晶體氨氣感測氣能實際應用在生醫感測和臨床疾病檢測上。

Non-invasive ammonia sensor has potential for early stage detection of liver cirrhosis and renal failure to reduce medical diagnostic costs and improve the quality of life of patient suffering from chronic diseases. An ultra-sensitive device that plays a critical role in non-invasive ammonia sensing is to be developed. Due to its higher surface-to-volume ratio, a low cost polycrystalline silicon nanowire field-effect transistor (Poly-Si NWFET) device was demonstrated to exhibit higher sensitivity than other sensors toward ammonia sensing. In this research, a poly-Si NWFET based gas sensing platform was established for label-free detection of ammonia. Significant variation in electrical response was observed in the presence 0.25 to over 1 ppm of ammonia gas, which range is the critical ammonia concentrations that can be used to distinguish between healthy person (0.278 ppm) and cirrhotic patient (0.745 ppm) in their breath. We further investigated the ammonia gas sensing mechanism by using single-crystalline NWFET and nanowire surface modified poly-Si NWFET device. The results indicated that the electrical responses of poly-Si NWFET induced by ammonia gas may be heavily dependent on both the surface properties and grain boundaries of the polycrystalline nanowire. We proposed that gas charge-dipole effect may play a major role in gas sensing with poly-Si NWFET. The detailed ammonia-sensing mechanism will be explored in the future. In conclusion, a novel ammonia gas sensing platform was developed and its ammonia sensing mechanism has been preliminary explored. It can be expected that poly-Si NWFET based ammonia sensors could be promising for medical application and clinical diagnosis in the future.