Defect Healing and Enhanced Nucleation of Carbon Nanotubes by Low-Energy Ion Bombardment

Structural defects inevitably appear during the nucleation event that determines the structure and properties of single-walled carbon nanotubes. By combining ion bombardment experiments with atomistic simulations we reveal that ion bombardment in a suitable energy range allows these defects to be healed resulting in an enhanced nucleation of the carbon nanotube cap. The enhanced growth of the nanotube cap is explained by a nonthermal ion-induced graphene network restructuring mechanism.

Figure 1

(a) Observed defect healing and enhanced cap formation by ion bombardment in the energy range 15–25 eV and destruction of the network at higher energies ($>30\mathrm{eV}$). (b) Growth of the carbon network due to the ion bombardment at 15 eV, as seen in the MD simulations. The numbers in parentheses indicate the sum of the pentagons, hexagons, and heptagons; the other numbers indicate the total number of rings in the patch.

Figure 2

Evolution of the average number of rings in the carbon network as a function of the number of consecutive Ar impacts, for 4 different impact energies, averaged over 10 independent runs.

Figure 3

Experimental observations of ion bombardment on the nascent SWCNT. (a)–(d) SWCNTs grown at 0, 10, 30, and 60 s, respectively. Scale bars in (a) and (b) are 200 nm and in (c) and (d) are $1\mu \mathrm{m}$. (e) Raman spectra of 10 s growth SWCNTs with Ar ion bombardments at 0, $-20$, and $-50\mathrm{V}$ biases. The graphitic $G$ peak is most prominent at $-20\mathrm{V}$ bias. (f) Raman spectra of 30 s growth SWCNTs before and after Ar ion bombardments at 0 V bias.