Electronic structure of potassium-doped carbon nanotubes

Abstract

We present a density functional study of zigzag carbon nanotubes containing potassium atoms inside. We find that the effect of potassium doping is not simple charge transfer. The nearly free electron state of nanotube couples with the $\mathrm{K}\hspace{0.5em}4s$ orbital. The state comes downward as the tube is thicker and crosses the Fermi level when the diameter is as large as $0.8–1\mathrm{nm}$. It is distributed near the center of the tube and extends to the tube direction, which suggests high conductivity via this state.