Selective gas sensing with MoS2 thin film transistors

We demonstrate, for the first time, selective gas sensing using MoS
2
bilayer Thin Film Transistors (TFTs). The TFTs were fabricated using exfoliation from bulk crystals and transferring onto Si/SiO
2
substrates. For control purposes, we used the same TFTs but with the surface covered by a 10 nm Al
2
O
3
layer. The extracted field effect mobility varied from 0.1 to 7 cm
²
/V-s in different samples and was only a very weakly dependent on temperature in the range from room temperature to 220 °C. The room temperature on-to-off ratio was ∼ 10
⁴
and decreased to 10
³
at 220 °C. Under the exposure to ethanol, acetonitrile, toluene, chloroform, and methanol vapors, the TFT current in uncovered samples changed with the increase amount strongly dependent on the kind of gas. The covered TFTs exhibited no change. We also report on 1/f noise measurement under the gas exposure and show that, just like for graphene transistors, the change in the noise spectra is also dependent on the kind of the sensed gas and could be used as component of the gas signature. The MoS
2
devices demonstrate a much larger sensitivity than similar graphene devices.