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

Abstract

For the first time, we connect in series two -MoTe2-based Schottky diodes (SDs) to form a back-to-back diode using the micromechanical exfoliation method. The -MoTe2 SD exhibits an excellent ON/OFF current ratio of approximate to 10(3) and low-voltage operation at 5 V. Although various studies of -MoTe2 field-effect transistors (FETs), phototransistors, and p-n diodes have been reported, there are no reported theoretical or experimental studies of -MoTe2 for chemical sensing. Here, we experimentally assess the SD and a FET for gas sensing with exposure to different concentrations of NO2 and NH3. Interestingly, the -MoTe2 SD showed a faster response and recovery time to NH3 and NO2 than the -MoTe2 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 NO2 and approximate to 1 s when exposed to 70 ppb NH3 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 -MoTe2-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.