We report on the doping dependence of so-called peapods where C60 is encapsulated inside single-wall carbon nanotubes (SWCNT's) using Raman spectroscopy as probe. The charge transfer in intercalated C60 peapods is analyzed as a function of doping with FeCl3 (p type) and potassium (n type). A competition between a charge transfer to the SWCNT pods and to the C60 peas is observed. At low intercalation levels, the charge transfer is predominantly to the SWCNT pods. The Fermi level shifts beyond the second van Hove singularity of the semiconducting tubes and below the first singularity of the metallic tubes, respectively. The doping of the valence band for FeCl3 intercalation (p doping) and of the conduction band for K intercalation (n type) is symmetric. At high levels of potassium intercalation, the Fermi level shifts beyond the third singularity of the semiconducting tubes and the C60 molecules are charged as well finally yielding a C606- state that forms a one-dimensional metallic single-bonded C60 polymer. For intermediate charging levels of the C60 molecules, no line phases are observed in contrast to the fullerides. Rather, a quasicontinuous charge transfer is observed. This provides a unique procedure to establish a continuous charge transfer to C60 by intercalation.
|Number of pages||7|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Mar 1 2003|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics