Electrical transport and low-frequency noise in MoS2 field-effect transistors under controlled gas atmospheres

Two-dimensional semiconductors, and particularly MoS2, are promising active materials for room-temperature gas sensing devices because their channel conductance is strongly modulated by surface adsorption. Here we report a systematic study of the electrical transport properties of back-gated MoS2 field-effect transistors (FETs) under controlled atmosphere and pressure. Transferred MoS2 devices show stable n-type operation with a pronounced dependence of conductance, threshold voltage and hysteresis on ambient conditions, consistent with adsorption/desorption and trap dynamics at the MoS2/SiO2 interface. To further clarify the microscopic kinetics underlying these macroscopic electrical variations, we performed low-frequency noise (LFN) measurements. This combined transport–noise approach provides access to microscopic fluctuation mechanisms that cannot be distinguished from conventional DC characterization alone. The spectra exhibit a 1/f γ background and Lorentzian components whose characteristic frequencies are in the tens-of-hertz range (≈40–60 Hz) and at ∼2.0 kHz. The slow component shows thermally activated behavior with Ea ≈ 0.19 eV, consistent with physisorption-controlled dynamics, while the faster component is compatible with contact-related fluctuations. Measurements on CVD-grown MoS2 FETs reproduce the same slow fluctuations, supporting the generality of the adsorption-driven process. Overall, this work establishes a solid transport baseline for MoS2 FETs in controlled atmospheres and demonstrates that LFN spectroscopy provides a powerful tool to disentangle surface-adsorption kinetics from contact and interface effects.