The authors report electric transport properties of resonance tunneling field-effect transistors fabricated using C60-filled metallic double-walled carbon nanotubes. The devices exhibit strong resonance tunneling characteristics and the distinct negative differential resistance with high peak-to-valley current ratio about 1300 is observed at room temperature. In particular, at high bias voltages, the tunneling current is completely dominated by the Coulomb oscillation peaks with uniform conductance at room temperature, reflecting a strong single-electron tunneling effect.

Electrical transport properties of double-walled carbon nanotubes (DWNTs) are modulated by encapsulating the azafullerene C 59 N which is synthesized via a plasma ion-irradiation method. The encapsulation of C 59 N molecules inside DWNTs has been confirmed by both transmission electron microscopy and Raman spectroscopy. The pristine DWNTs with outer diameter 4 -5 nm are found to exhibit an ambipolar semiconducting behavior due to their small band gap. It is found that C 60 fullerene encapsulated DWNTs exhibit a unipolar p-type semiconducting behavior. By comparison, C 59 N encapsulated DWNTs display an n-type semiconducting behavior. Our findings demonstrate that C 59 N operates as an electron donor compared with the acceptor behavior of C 60 , which is further clarified by photoelectron emission spectroscopy.