Growth, nitrogen doping and characterization of isolated single-wall carbon nanotubes using liquid precursors

Isolated single wall carbon nanotubes (SWNTs) were prepared on bare quartz and SiO2/Si substrates using a chemical vapor deposition process in which xylene was used as the carbon source. Controlled doping of isolated SWNTs with nitrogen was achieved by mixing appropriate amounts of acetonitrile with xylene. As the nitrogen concentration in the feed was increased from 0 to 33 at.%, the radial breathing mode intensity decreased dramatically while the intensity of the D-band increased gradually relative to that of the G-band. The D′-band at ∼1620 cm−1 was observed in the Raman spectrum when the nitrogen concentration reached ∼2–3 at.%.