Modification of electrical transport properties of single-walled carbon nanotubes realized by negative-ion irradiation with electron-free pure alkali-halogen plasma

Negative ions are selectively irradiated to pristine single-walled carbon nanotubes (SWNTs) with novel alkali-halogen plasma technology. Since the plasma produced consists of only positive (alkali) and negative (halide) ions, effective negative-ion irradiation can be realized without undergoing undesirable effects of electron existence. Transmission electron microscopy reveals that the inner space of SWNTs is partially filled with irradiated negative ions. Furthermore, the electrical transport measurements provide direct evidence that the p-type semiconductor behavior of SWNTs can be markedly enhanced by negative-ion irradiation.