Electronic and optical properties of nitrogen-doped multiwalled carbon nanotubes

Highly nitrogen-doped carbon nanotube (CNxNT, x=12 at. %) was synthesized by the pyrolysis of acetonitrile on Co-Mo catalysts. The electronic structures and chemical bondings of CNxNT were studied using various spectroscopic techniques: Raman, photoelectron and x-ray absorption spectroscopies. The ultrafast pump-probe measurements of CNxNT exhibited a larger third-order susceptibility chi((3)), a relaxation time of tau(2)=1 ps and improved saturable absorption, as compared with undoped multiple-walled carbon nanotubes, which indicate that N-doping can improve all-optical switching properties of carbon nanotubes.