Electronic and optical properties of nitrogen-doped multiwalled carbon nanotubes

Abstract

Highly nitrogen-doped carbon nanotube (${\mathrm{CN}}_{x}\mathrm{NT}$, $x=12\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$) was synthesized by the pyrolysis of acetonitrile on Co-Mo catalysts. The electronic structures and chemical bondings of ${\mathrm{CN}}_{x}\mathrm{NT}$ were studied using various spectroscopic techniques: Raman, photoelectron and x-ray absorption spectroscopies. The ultrafast pump-probe measurements of ${\mathrm{CN}}_{x}\mathrm{NT}$ exhibited a larger third-order susceptibility ${\ensuremath{\chi}}^{(3)}$, a relaxation time of ${\ensuremath{\tau}}_{2}=1\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ 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.