異質結構之高性能石墨烯氣體偵測器

Abstract

氣體偵測器應用範圍廣泛，主要在於檢測可燃、有毒及爆炸性氣體，所以通常用於住宅環境、工業建築之安全檢測。傳統的氣體檢測方法依賴於電荷載子傳輸的物理性質變化，這樣的感測時間是非常緩慢的，且感測時間通常是在好幾秒以內的範圍。為了克服這個缺點，在本研究裡我們製造出石墨烯/氧化鋅/P型矽基版的異質結構氣體偵測器。這個新的複合結構可以表現出高靈敏性、快速感測時間以及穩定的重複性，感測機制完全取決於石墨烯的費米能階變化，由於被吸收的氣體分子施予石墨烯電荷載子的傳輸，其橫跨於異質結構的輸出電流改變。工作原理藉由氣體分子施予電荷載子於石墨烯層且不往下層傳輸，導致能帶彎曲改變造成大幅度之電流變化。此外，在本研究中我們也證明不同偏壓下可量測不同氣體，因此本研究有助於發展高性能石墨烯之氣體偵測器。

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.