Observation of potassium-intercalated carbon nanotubes and their valence-band excitation spectra

Second-stage potassium-intercalated carbon nanotubes were synthesized in a specially designed ultrahigh vacuum analytical electron microscope and their valence-band excitation spectra in the region of the pi+sigma plasmon were measured by electron energy loss spectroscopy The carbon nanostructures consisted of graphene sheets. Potassium was deposited in an ultrahigh vacuum at room temperature. ks a result, a second stage of intercalated nanotubes was found to be formed close to the surface. The energy loss spectra of the intercalated nanotubes showed humps at about 16, 19, and 22 eV, in addition to those of unintercalated tubes,This suggests that intercalation modified the band structure of the interlayer bands and/or the sigma(sigma*) bands. (C) 1996 American Institute of Physics.