Ambipolar field-effect transistor behavior of Gd@C82 metallofullerene peapods

Transport properties of ${\mathrm{C}}_{60}$ fullerene peapods and ${\mathrm{Gd@C}}_{82}$ metallofullerene peapods are investigated by using the field effect in a gated structure. The results show that ${\mathrm{C}}_{60}$ peapods exhibit unipolar p-type characteristics, whereas ${\mathrm{Gd@C}}_{82}$ peapods show ambipolar both p- and n-type characteristics. This difference in transport behavior can be explained in terms of a bandgap narrowing of the peapods. One of the important findings is that tunable electronic properties of peapods are achieved by using the different types of encapsulated fullerene molecules.