Intrinsic diameter dependent degradation of single-wall carbon nanotubes from ion irradiation

The structural response of single-wall carbon nanotube (SWCNT) thin-films to ion irradiation has been systematically studied with increasing fluence between 5 × 1012 and 1 × 1015 (150 keV 11B+)/cm2 as a function of SWCNT diameter distribution. SEM analysis reveals that the SWCNT morphology remains intact after radiation exposure. The optical absorbance intensity decreases with increasing fluence, and near complete suppression is observed at approximately 2.5 × 1014 (11B+)/cm2, resulting in an equivalent reduction in signal intensity for resonant Raman spectroscopy. Changes observed in the optical response with increasing fluence demonstrate that defective SWCNTs behave similarly to other strongly doped or physically shortened SWCNTs. The Raman D/G′ increases with fluence for all samples, yet the magnitude of increase is strongly dependent on the SWCNT diameter distribution. The diameter dependence stems from differences in the SWCNT mass per unit length, which is incorporated into an inter-vacancy length (Lv) model that describes the radiation-induced changes. Ultimately, all SWCNT data converge to show an equivalent change in D/G′ at a corresponding Lv, even though the fluence required to achieve a particular Lv varies with SWCNT diameter. Thus, the radiation-induced changes in SWCNTs are intrinsically linked to their diameter, representing a fundamental property unique to this class of nanomaterials.