Abstract
In this work, an ultrathin 3 nm nanowire field-effect transistor (NWFET) based ammonia gas sensor is designed, and its sensitivity is analyzed at room temperature. The designed NWFET for gas sensing is observed to have a higher ratio of ION to IOFF than 109, lower DIBL and better gate controlling due to a higher surface to volume ratio. The gas-sensing performance analysis has been done for three different catalysts, iridium (Ir), ruthenium (Ru), and palladium (Pd), by gradually increasing the work function by a difference of 50 meV. The device showed higher OFF current sensitivity compared to ON current sensitivity. The power consumption and threshold voltage are observed to be least for palladium catalytic gate electrodes making palladium the most favorable catalytic for ammonia gas for the designed gas sensor.
Highlights
Various types of the gas sensor have been designed, studied, and fabricated based on different sensing mechanisms and sensing material, and many new designs and materials are being studied presently [1, 2]
Sensitivity of proposed nanowire FET gas sensor for ammonia is more in OFF state at VGS=0V than ON state as in the off state higher work function induces more minority charges in the channel [11]
Since increase in concentration of detectable gas is considered as higher change in metal work function and the sensing response for higher change in work function i.e. 200meV is maximum. It can be very clearly observed from the figure 7(a) that the nanowire field-effect transistor (NWFET) gas sensor with Palladium gate metal electrode is highly sensitivity in OFF state and least sensitivity in ON state.In Figure 7(b) and 7(c), It can be observed that proposed device shows more sensitivity response when the gate voltage is equal to or higher than the threshold voltage i.e. VGS =1.08V and VGS=1.28V for both iridium and ruthenium metal electrode respectively compared to OFF-state (VGS=0V)
Summary
Various types of the gas sensor have been designed, studied, and fabricated based on different sensing mechanisms and sensing material, and many new designs and materials are being studied presently [1, 2]. The demand for small-sized and integrated circuit compatible gas sensors has made the researcher keener towards organic and nanomaterial FET type gas sensors [3,4]. These gas sensors play a vital role in the safety of chemical industries, factories by monitoring any leakages [5]. The sensing mechanism of the designed device is based on the deposition/absorption of gas molecules to the surface of the catalytic gate electrode [9, 10]. The deposition/absorption of gas molecules on metal electrodes disturb its composition and lead to the change in work function of the metal electrode, which affects the analog parameters of transistors. We have discussed the device design and simulation model and parameters of the proposed device in section (2), followed by results and performance analysis in section (3) and conclusion in section (4)
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