Few-layered α-MoTe2 Schottky junction for a high sensitivity chemical-vapour sensor

摘要

For the first time, we connect in series two α-MoTe _(2) -based Schottky diodes (SDs) to form a back-to-back diode using the micromechanical exfoliation method. The α-MoTe _(2) SD exhibits an excellent ON/OFF current ratio of ～10 ~(3) and low-voltage operation at 5 V. Although various studies of α-MoTe _(2) field-effect transistors (FETs), phototransistors, and p–n diodes have been reported, there are no reported theoretical or experimental studies of α-MoTe _(2) for chemical sensing. Here, we experimentally assess the SD and a FET for gas sensing with exposure to different concentrations of NO _(2) and NH _(3) . Interestingly, the α-MoTe _(2) SD showed a faster response and recovery time to NH _(3) and NO _(2) than the α-MoTe _(2) FET owing to its Schottky junction, which is favorable for detecting the Schottky-barrier height change due to gas exposure. The SD showed a fast response of 15 s when exposed to 70-ppb NO _(2) and ～1 s when exposed to 70 ppb NH _(3) with a relative resistance change of 13% and 101%, respectively, and this was attributed to its physisorption process. In addition, our results are confirmed by density functional theory. The α-MoTe _(2) -based SD is shown to be promising as an electrical rectifier or as a gas sensor owing to its simple and inexpensive electrical circuitry and excellent performance, including its low voltage, high ON/OFF current ratio and good sensitivity to toxic gases at room temperature. Further, it may be suitable for diverse uses, such as chemical and biosensing applications.