We report on a detailed study of the filling factor and electronic structure of the trimetal nitride fullerene ${\mathrm{Dy}}_3\mathrm{N}@{\mathrm{C}}_{80}\left(\mathrm{I}\right)$ filled single-wall carbon nanotubes (SWCNTs), the so-called endohedral peapods $\left({\mathrm{Dy}}_3\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs}\right)$, using photoemission spectroscopy as a probe. The photoemission response close to the Fermi energy exhibits the manifestation of one-dimensional electronic structures, i.e., van Hove singularities and a power-law (Tomonaga-Luttinger liquid) behavior. Within the experimental accuracy the spectral shapes are the same as those of the pristine SWCNTs reference sample. From a comparison between the valence-band spectra of the peapods and the SWCNT measured with $400\mathrm{eV}$ photon energy, we determine the bulk filling of ${\mathrm{Dy}}_3\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs}$ to be $74\pm 10\%$. In addition, from a detailed analysis of the resonant photoemission across the Dy $4d\text{−}4f$ edge, we show that the effective Dy valency of ${\mathrm{Dy}}_3\mathrm{N}@{\mathrm{C}}_{80}@\mathrm{SWCNTs}$ is about 3.0 which is slightly larger than for ${\mathrm{Dy}}_3\mathrm{N}@{\mathrm{C}}_{80}$.

• Received 17 November 2005

DOI:https://doi.org/10.1103/PhysRevB.73.205411