| Summary: | 碩士 === 國立臺灣大學 === 應用物理研究所 === 104 === Gas sensors are omnipresent in our daily life owing to their tremendous values in applications spanning from health care to industrial manufacturing. Even though there exist an intensive effort, the performance of the devices still need to be improved. Particularly, the typical response time in the range of seconds and minutes is rather slow due to its intrinsic sensing mechanism related to charge transfer. In this study, we develop a graphene multiple-junctions to achieve the sensor with very high sensitivity (<10 ppm), ultra-fast sensing time (<10 ms) and stable repeatability. The sensing mechanism solely depends on the large change of the Fermi energy (EF) of graphene due to the absorbed molecules, which produces a great change of output current across the heterojunction. The charge induced by the absorbed molecules remains in the graphene layer without transferring into the underlying layer due to the well-designed band alignment among the constituent materials, which results a ultra-fast and highly sensitive performance. Furthermore, we demonstrate that with different polarity of external bias the graphene multiple-junctions sensors can be used to selectively detect different gases.
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