Effects of oxygen bonding on defective semiconducting and metallic single-walled carbon nanotube bundles

We report the effects of oxygen doping on the electrical properties of defective metallic and semiconducting single-walled carbon nanotube bundles. Carbon vacancies are generated by electron beam knock-out process. The carbon nanotube bundles are placed on top of suspended electrodes produced on a through-hole chip. This allows a physical correlation to be established for transmission electron microscopy inspection and electrical characterization. The dangling carbon bonds of the vacancies are very active and can easily adsorb oxygen molecules. In terms of the semiconducting bundles, oxygen bonding lowers the bandgap and the original p-type bundles thereby modifying them to become bi-polar. For the metallic bundles, a hysteretic bi-stable state in gate-voltage cycling is observed; this is attributed to the electrically controlled dipole field of the oxygen molecules.