• electron doping;
  • ferrocene;
  • single-walled carbon nanotubes;
  • X-ray absorption spectroscopy;
  • X-ray photoemission spectroscopy

Although the possibility of using metallocenes acting as n-type dopants for metallicity mixed and separated single-walled carbon nanotubes (SWCNT) has been proven, the question of usability for real-life applications still needs to be addressed. The most important factor for their applicability is the stability of the doping outside a vacuum environment. To clarify this issue we have conducted a long-term study on purely metallic SWCNTs after being filled with ferrocene and compared it to results after prolonged exposure to air, demonstrating a decomposition of about half of the filling material leaving a lower but stable doping state. The successful conversion to double-walled carbon nanotubes by high-temperature annealing yielding p-type doped hybrid structures is evidenced additionally. These results let us conclude that SWCNTs filled with metallocenes are an ideal n, or p-type doped starting material for applied electronics based on graphitic structures.