Temperature-dependent inner tube growth and electronic structure of nickelocene-filled single-walled carbon nanotubes

We have filled single-walled carbon nanotubes (SWCNTs) with nickelocene and transformed them to double-walled carbon nanotubes by annealing in vacuum. We study the temperature-dependent inner tube growth by means of Raman spectroscopy and investigate the SWCNTs’ electronic structure by X-ray photoelectron spectroscopy. It is found that larger diameter inner tubes grow at higher temperatures than smaller diameter tubes. Both electron and hole doping of SWCNTs are achieved as the encapsulated nickelocene molecules are reacted at temperatures in the range from 250 up to 1200° C.