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

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 A_1g 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.