Temperature-induced change from p to n conduction in metallofullerene nanotube peapods

Metallofullerene nanotube peapods were prepared by introducing Dy@C₈₂ into the interior space of single-walled carbon nanotubes. Transport measurements show that the Dy@C₈₂ molecules function as electron donors and transfer charge to the carbon nanotube host. The amount of charge transferred varies with the temperature. At room temperature, the doped nanotube shows p-type behavior as seen from the response to a back gate. As the temperature decreases, the conductance becomes n type and at T<215 K metallic behavior is observed, indicating the degenerate state by doping. Below about 75 K, single-electron charging phenomena dominate the transport and show irregular Coulomb blockade oscillation, implying that the insertion of Dy@C₈₂ splits the tube into a series of several quantum dots.