Changes in the chemical state and concentration of iron in carbon nanotubes obtained by the CVD method and exposed to pulsed ion irradiation

Data on the distribution of iron in nitrogen-containing multiwall carbon nanotubes (N-MWCNTs) and changes in its chemical state and concentration under different parameters of irradiation by a pulsed ion beam are obtained by methods of transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersion analysis. It is shown that the irradiation of N-MWCNTs with an energy density of 0.5 J/cm$^2$ lead to the formation, on their lateral surfaces, of structures with a size of 2–10 nm, consisting of metallic iron encapsulated in a carbon shell. An increase in the energy density to 1–1.5 J/cm$^2$ leads to a substantial removal of iron clusters from the tips of carbon nanotubes and a reduction in the amount of iron in the bulk of the N-MWCNT layer.