Sensors for sub-ppm NO2 gas detection based on carbon nanotube thin films

TLDR

Carbon nanotube films grown by plasma‑enhanced CVD on Si₃N₄/Si substrates have been studied as resistive sensors for detecting NO₂. A thermal cycling process that repeatedly heats and cools the CNT films was used to tune their resistance and improve NO₂ response. The sensors showed a decrease in resistance upon NO₂ exposure, with peak sensitivity at ~165 °C, achieving detection limits of 10 ppb, rapid response, and strong selectivity.

Abstract

Carbon nanotubes (CNTs) deposited by plasma-enhanced chemical vapor deposition on Si3N4/Si substrates have been investigated as resistive gas sensors for NO2. Upon exposure to NO2, the electrical resistance of the CNTs was found to decrease. The maximum variation of resistance to NO2 was found at an operating temperature of around 165 °C. The sensor exhibited high sensitivity to NO2 gas at concentrations as low as 10 ppb, fast response time, and good selectivity. A thermal treatment method, based on repeated heating and cooling of the films, adjusted the resistance of the sensor film and optimized the sensor response to NO2.