表面改質多晶矽奈米線氣體感測器之感測機制

Abstract

多晶矽奈米線電晶體有製程成本低廉、簡單的特性，並且對於環境極為敏感，用於氣體感測上有很好的效果。在特定閘極電壓下，定義感測器體的敏感度為INH3/IN2，並且用IN2當作基準點，在0.5 ppm的氨氣下所量測到的比例約為1~2，為了增進對氨氣量測的靈敏度，使用寡聚物3, 7-Bis[7-(9, 9-di-n-hexylfluoren-2-2yl)]-9, 9-di-n-hexylfluoren-2-yl] dibenzothiophene-S，塗佈於奈米線的表面做表面改質，改質過後的元件，靈敏度相較於改質前，能夠成長四倍以上，氨氣分子吸附於寡聚物表面形成的極化層是造成電性變化的主要原因，透過UPS證明其存在於介面間，而藉由XPS了解電子注入的機制，並使用同步輻射的光源，看到少量元素的載子轉移現象，透過光電子能譜術的數據指出氨氣與官能基間形成的氫鍵在介面間造成了極化層。

Polycrystalline silicon nano-wire field effect transistor (p-Si NW FET), possessing low cost and easy fabrication, was applied for ammonia gas sensor. The sensing ability is defined by INH3/IN2 at certain gate voltage, in which IN2is the baseline. The typical ratio is around 1~3 at 0.5 ppm level of ammonia gas. In order to further enhancing the ammonia sensing ability, 3, 7-Bis[7-(9, 9-di-n-hexylfluoren-2-2yl)]-9, 9-di-n-hexylfluoren-2-yl] dibenzothiophene-S, S-dioxide was applied for polycrystalline silicon surface modification. The surface modified p-Si NW FET showed 4 times enhancement compared to the unmodified p-Si NW FET. The polarity shift on the organic-inorganic interface was suspected the main reason. The charge transfer phenomena were verified by UPS and XPS with synchrotron light source (TLS). The data suggested that the hydrogen-bond formed between NH3molecule and S, S-dioxide functional group caused the polarity shift at organic layer.