Manipulation of fullerene-induced impurity states in carbon peapods

Electronic structures of several semiconducting and metallic carbon peapods have been studied using density functional theory. We have systematically investigated the effects of two key factors, the tube diameter and the type of the encaged metal atom inside C-60, on the energy level and the electron occupation number of C-60-induced impurity states in semiconducting peapods. The manipulation of these impurity states controls the type of the majority carrier (p or n) and the carrier density of a semiconducting peapod. In addition, the possibility of superconductivity of potassium-doped peapods has been discussed.