Sub-ppm NO2 detection by Al2O3 contact passivated carbon nanotube field effect transistors

We investigate carbon nanotube field effect transistors (CNFETs) with aluminum oxide (Al2O3) passivated contacts for NO2 detection. For the CNFETs, consisting of one individual pristine single walled carbon nanotube (SWNT), the measurements indicate a strong influence of adsorbed NO2 gas molecules on the exposed CNFET channel and NO2 concentrations as low as 100 ppb were detected. Applied to the contact-SWNT interfaces, Al2O3 is a suitable material to protect the metal contacts from NO2 molecules and other undesired environmental influences. We discuss the effect of the different processing steps on the CNFET characteristics and show device recovery after short heat treatment.