Hysteresis-free, suspended pristine carbon nanotube gas sensors

We present a novel carbon nanotube gas sensor based on a suspended and ultraclean carbon nanotube transistor. The transistor shows no apparent hysteresis under ambient conditions, thus reducing the drift of the sensor signal due to charging effects. Structural characterization with TEM shows the presence of one single-walled nanotube in the transistor channel. Exposure to 1 ppm NO₂ is shown to result in a drain current change of 115%. Together with noise measurements, a detection limit of 32 ppb NO₂ is extrapolated. The dependence of signal-to-noise ratio and the low-frequency noise on gate voltage are analyzed.