Sensing Mechanisms of Carbon Nanotube Based NH3 Gas Detectors

Abstract

In this chapter, we discussed in details the sensing mechanisms of CNT based NH3 detection. By selective Si3N4 passivation, We clearly show that the SB modulation at the CNT/metal contacts dominates the sensing performance at room temperature, and the sensor exhibits high sensitivity and good tunability under appropriate gate voltages. At higher temperatures, say 150oC or above, NH3 molecules start to adsorb on the CNT wall and the charge transfer process from the adsorbed NH3 molecules to the CNTs contributes to the sensing signal. As the mechanisms are identified, the next step is how to improve the sensing performance, and more chanllegingly, how to differentiate between different gas species. One promising way could be functionalizaton method (Feng, et al., 2005, Qi, et al., 2003). For example, using metal catalysts in the form of nanoparticles to decorate CNT, which promotes the interaction with speicific gas speicies. With a combination of several metal nanoparticle, the sensing performance to various gas molecules could be compared and contrasted.