Potassium intercalated bundles of single-wall carbon nanotubes: electronic structure and optical properties

We present electron energy-loss spectroscopic measurements of potassium intercalated bundles of single-wall carbon nanotubes. The loss function at low momentum transfer can be simulated within a simple Drude–Lorentz model, indicating that all of the nanotubes were driven metallic by intercalation. From the value of the unscreened plasma energy (1.85 eV) and the damping (0.4 eV), a lower limit for the optically derived conductivity of the fully intercalated material of 1200 S cm −1 is found. This indicates an effective mass 3.5 times greater than that in the analogous graphite intercalation compound.