The study of nitrogen inclusion in carbon nanotubes obtained by catalytic laser-induced chemical vapour deposition (C-LCVD)

Nitrogen doped carbon nanotubes were grown on Fe2O3 nanoparticles deposited on silicon substrates, by laser-induced chemical vapour deposition of acetylene/ammonia mixtures. The concentration of the nitrogen has been controlled in the range 1-6 atomic% by adjusting the flow rate of ammonia, pressure and laser power. XPS and Raman spectroscopy were used to quantitatively assess the compositional and structural properties of the nitrogen-doped carbon nanotubes (NCNTs). First order Raman spectra were deconvoluted assuming five vibrational modes and the integrated peak intensity ratio ID/IG and I2D/IG of all samples are displayed. We demonstrate that the relative amount of sp2 CC carbon has the same trend as ID4/IG and the pyrrolic relative amount exhibits the same trend as I2D4/IG. The high resolution TEM images are consistent with the Raman and XPS results, revealing that the surface of the NCNTs outer walls becomes more distorted at the highest content of N while the inner walls of the nanotube preserve a high crystallinity, corresponding to the lowest ID/IG ratio.