Growth mechanisms of inner-shell tubes in double-wall carbon nanotubes

The growth process of inner-shell tubes from C₆₀ peapods and ferrocene (FeCp₂) filled single-wall carbon nanotubes was studied with Raman spectroscopy and X-ray diffraction (XRD). In the peapod case, it is shown that the Raman signal of the fullerenes decays about a factor five faster than the XRD peak of the 1D fullerene chain. The growth of the inner-shell tubes coincides well with the 1D chain decay. In the FeCp₂ case, the inner tubes grow already at 600 °C in about one hour. Additionally, even for the same starting material, the inner-outer tube pair distribution is different than for C₆₀ based inner tubes.