Defect formation and annealing kinetics in ion irradiated carbon nanotube buckypapers

We studied the frequency shifts in G, D and D∗ Raman modes in freestanding multiwall carbon nanotube buckypapers. Upon ion irradiation by 140 keV He+ or 3 MeV H+ ions, the intensity ratio of D–G modes linearly increases with fluence before amorphization. The ratio is used to quantitatively measure the level of disorder in the buckypaper. The study shows that, upon post-irradiation annealing, defect removal requires little energy addition in lightly damaged buckypaper, which is evidenced by an activation energy of 0.36 eV. Once amorphized, defect removal becomes very difficult. The D–G intensity ratio has no reduction in heavily damage sample after annealing up to 850 °C.