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

Abstract

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.

Hysteresis reduction and measurement range enhancement of carbon nanotube based NO2 gas sensors by pulsed gate voltages

“…6,8,16 . The fabrication of the CNFET devices starts from a highly doped silicon substrate, which acts as a back gate in the final device, covered with a 200 nm thick thermally grown dry silicon oxide.…”

Ultra-low power operation of self-heated, suspended carbon nanotube gas sensors

“…26 Studies have suggested that NO 2 adsorption on the metal may change its work function, thereby contributing to the NO 2 sensor response. 27 By passivating the metal regions we ensure that the sensor response originates from the nanotube itself.…”

Carbon nanotube gas sensor array for multiplex analyte discrimination

“…11b) exhibits clear inflexion points at the gas introduction and stop while channel passivated devices exhibit barely none. These observations support that NO 2 sensing occurs by interaction with the CNT channel [59]. The twice weaker response observed for channel passivated devices is ascribed to the CNT surface uncovered close to the metal-CNT contact (as can be seen in Fig.…”

“…The absence of response of fully passivated devices during the whole gas sequence evidences the correct impermeability of the passivation layer to the gases tested [59]. Fig.…”