Doping of carbon nanotubes using low energy ion implantation.

Carbon nanotubes (CNTs) were implanted with thermally decomposed oxygen (O2+) and nitrogen (N2+) ions at an acceleration voltage of 20 V. With a low dose of oxygen ions, the CNT-FET exhibited p-type behaviors with substantial changes in threshold voltage and in the slope of the source-drain current (l(sd)). However, at high dosages, the device exhibited metallic behaviors. After nitrogen doping, we did not observe the effects of electron doping. Instead, nitrogen doping significantly increased l(sd) with no gating effect. Our theoretical results showed that the metallic behavior of nitrogen-doped CNTs arose from the impurity conduction band, which results from the overlapping wave function of the nitrogen impurity.