Gate-controlled sensing of ammonia by single-layer MoS2 field-effect transistor

Abstract

Two-dimensional transition metal dichalcogenides (TMDC) and MoS2 in particular are promising materials as sensitive layers for gas sensing due to room operation temperature, high sensitivity, low dimensions, vast methods of selectivity alteration, etc. MoS2 response to toxic gases exposure depends on applied electric field that expands capabilities of resistive detection techniques, therefore, requires in-depth study. We fabricated a back-gated MoS2 based field-effect transistor (MoS2-FET) with standard photolithography technique on Si/SiO2 substrate. AFM microscopy confirmed the single layer nature of MoS2 flakes by cross-section featuring a thickness of 0.7 nm. Raman spectroscopy revealed A1g and E1 2g modes position at 403.5 cm-1 and 382 cm-1 respectively. The mobility in the absence of passivation was about 10-1 cm2 V−1s−1. MoS2-FET exhibits room-temperature NH3 sensing with resistive response to 200 ppm exposure of about ~60%, signal-to-noise ratio about 8, and response/recovery time about 100 s.