Development of carbon nanotube-based gas sensors for NOx gas detection working at low temperature

Carbon nanotube (CNT)-based NOx gas sensors which can operate at room temperature were prepared on Al2O3 substrates with interdigitated Pt-electrodes using both dc sputtering method and chemical vapor deposition (CVD) method. In this method, Al buffer layer and Fe catalytic thin film were prepared on the substrate by dc sputtering method and then CNTs were grown by thermal CVD method using ethylene gas. The scanning electron microscope (SEM) images of the CNTs on the substrates indicated that the vertically aligned multi-walled CNT (MWCNT) and the randomly oriented MWCNT were grown selectively by insertion of Al buffer layer. Gas sensing property to NO and NO2 gases were measured. Resistance of the prepared CNT-based gas sensor decreased with increase of NO and NO2 gas concentration. UV light irradiation was examined to detach the adsorbed gas molecule at room temperature. In this paper, it is suggested that CNT-based gas sensors have a great possibility to apply innovative NOx gas sensor from the experimental result.