Liquid-phase alkali-doping of individual carbon nanotube field-effect transistors observed in real-time

The carbon nanotube (CNT) is known to be very sensitive to changes in its surrounding environment. Our study is on the effects of mild, liquid-phase alkali-doping on electronic transport in individual CNTs. We find clear and consistent reversal from p- to n-type behavior, with all seven investigated CNT field-effect transistors (FETs) retaining a similar ON/OFF ratio and subthreshold slope. We have also measured the realtime electronic response during liquid-phase doping, and demonstrate detection of alkali cations with a signal response that ranges over more than three orders of magnitude. The doping is fully reversible upon exposure to oxygen, and the doping cycle is repeatable. We also confirm an earlier finding that the redox chemistry involved can facilitate thermodynamically stable solutions of CNTs, and its potential for multi-purpose use in nanotechnology processing may be appealing for large-scale fabrication.