Diameter-dependent annealing kinetics of X-ray-induced defects in single-walled carbon nanotubes

Diameter-dependent annealing effects of X-ray-induced defects in single-walled carbon nanotubes (SWNTs) were studied by Raman scattering spectroscopy. We found that X- ray-induced defects were formed in thin SWNTs at higher density than that in thick SWNTs. The X-ray-induced defects, distant pairs of interstitials and vacancies (I-V), were eliminated by thermal annealing. The recovery temperature of the X-ray-induced defects in the thin SWNTs were higher than that of the thick ones, indicating the thermal stability of the defects in thinner SWNTs are higher. In order to simulate the annealing behaviours of the X-ray-induced defects in SWNTs with diameters of ~0.9 and ~1.4 nm, we suggested the competitive reactions of diffusion of interstitials, formation of close I-V pairs and their recombination. The simulated results showed that the reaction-rate constant of elimination of close I-V pairs is dependent on tube diameter, which is presumably derived from nano-structure effects of SWNTs.