Transport in carbon nanotube field-effect transistors tuned using low energy electron beam exposure

We have studied the effect of low energy (30 keV) electron beam exposure on carbon nanotube field-effect transistors, using an electron beam lithography system to provide spatially controlled dosage. We show that reversible tuning of the transport behavior is possible when a backgate potential is applied during exposure. n-type behavior can be obtained by electron beam exposure of a device with positive gate bias, while ambipolar behavior can be obtained via negative gate bias. The observed transport behavior is relatively stable in time. We propose possible mechanisms for the observed phenomena and suggest directions for further research.