Influence of mobile ions on nanotube based FET devices

Carbon nanotube field-effect transistors often exhibit a hysteresis effect in the gate-voltage dependence. We report devices fabricated with small hysteresis, and demonstrate a method to introduce this effect controllably by coating nanotube devices with charged polymers. In addition, the hysteresis is sensitive to humidity on sub-second time scales, showing promise as a humidity sensor. The polymer charge is related to the threshold shift observed, proving that the induced hysteresis results from ionic motion.