四點探針有機薄膜電晶體之氣體感測研究

Abstract

在論文中，我們建立一個可定量控制氣體濃度的感測系統，並利用具四點探針結構的有機薄膜電晶體進行氨氣感測的研究。當氨氣與有機薄膜電晶體反應時，電晶體的汲極電流會被減少、臨界電壓會往負值增加、但次臨界擺幅幾乎不受氨氣的影響而改變。而由四點探針結構的量測顯示，電晶體的薄膜電阻與接觸電阻均隨氨氣濃度的提高而增加。而利用薄膜電阻所推算出來的本質載子遷移率也會因氨氣濃度的提高而隨之減少。最後則將探討載子遷移率降低、臨界電壓往負值增加、及幾乎不受氨氣影響的次臨界擺幅，並根據電晶體特性改變的結果，提出可能的反應機制。

In this thesis, we tried to construct a gas sensing system, in which we can control the gas concentration quantitatively; moreover we also utilized the gated-four-probes organic thin film transistor to investigate the NH3 gas-sensing experiment. When the NH3 gas was interacted with OTFT, it was found that the OTFT drain current will be reduced and the threshold voltage will be enlarged toward a negative value. However, the subthreshold swing was not changed significantly by the NH3 gas. From the analysis of gated-4-probes OTFT, both the film resistance and the contact resistance were increased with the raise of NH3 concentration. Additionally, the intrinsic field-effect mobility, which was estimated from the film resistance, was also reduced with the raise of NH3 concentration. Finally, the reduction of the mobility, the increase of the threshold voltage, and the almost unchanged subthreshold swing were discussed. A probable mechanism deduced from the change of the OTFT was also summarized and proposed in this study.