Electrical properties of single-walled carbon nanotubes (SWCNTs) filled with Fe are studied by fabricating them as the channels of field-effect transistor devices. The synthesis of Fe-filled SWCNTs is realized by using ferrocene as the starting material. Our results reveal that ferrocene-filled SWCNTs show the interesting ambipolar behavior. In contrast, Fe-filled SWCNTs can exhibit high performance unipolar n-type semiconducting characteristics, suggesting the possibility of creating ferromagnetic semiconducting SWCNTs. Moreover, Coulomb blockade oscillations are significantly observed on Fe-filled SWCNTs, which indicates that they exhibit excellent single-electron transistor characteristics at low temperatures.

Electronic transport properties of Cs-encapsulated double-walled carbon nanotubes (DWNTs) synthesized via a plasma irradiation method are investigated by fabricating them as field-effect transistor devices. The authors’ results indicate that Cs-encapsulated DWNTs exhibit a high performance n-type characteristic in contrast to ambipolar behavior of pristine DWNTs. Coulomb blockade oscillations are observed on the Cs-encapsulated DWNTs at low temperatures. In addition, it is found that the semiconducting characteristics of the as-synthesized Cs-encapsulated DWNTs can possibly be controllable by adjusting applied negative dc bias voltages during the plasma synthesis process.