NOx Gas Detection Characteristics in FET-type Multi-walled Carbon Nanotube-based Gas Sensors for Various Electrode Spacings

In this study, we fabricated a p-channel FET-type $NO_x$ gas sensor by using multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes (CNTs) have good electronic, chemical-stability, and sensitivity characteristics. In particular, gas sensors require characteristics such as high speed, selectivity, and sensitivity. The fabricated sensor was used to detect $NO_x$ gas for different values of the gate-source voltage ($V_{gs}$) and the electrode spacings (30, 60, 90, and $120{\mu}m$). The gas sensor that absorbed $NO_x$ gas molecules showed a decrease in resistance. The sensitivity of the gas sensor was increased by increasing the electrode spacing. Additionally, while changing the Vgs and the temperature inside the chamber for the MWCNT gas sensor, we obtained the sensitivity and the normalized response for detecting $NO_x$ gas. We also obtained the adsorption energy ($U_a$) by using Arrhenius plots based on the reduction of resistance due to voltage variations. The adsorption energy was found to increase with increasing applied voltage.