Growth and characterization of nitrogen-doped single-walled carbon nanotubes by water-plasma chemical vapour deposition

Nitrogen-doped single-walled carbon nanotubes (N-SWNTs) are directly grown on SiO₂/Si substrates at 450°C with methane and ammonia gases by water-plasma chemical vapour deposition. The strongest radial breathing mode peak in Raman spectra of the grown N-SWNTs, probed with a 633 nm laser excitation, was assigned to (7, 5) semiconducting nanotubes with a diameter of 0.83 nm. As the doped nitrogen content increases, the D-band to G-band ratio in Raman spectra, indicating the imperfection of nanotubes, gradually increases and saturates at around 4%. X-ray photoelectron spectroscopy shows that nitrogen atoms are doped with a pyridine-like configuration in the N-SWNTs.