Controlled introduction of defects into aligned multi-walled carbon nanotubes was achieved by time-dependent plasma etching. The subsequent morphological changes in multi-walled carbon nanotubes were fingerprinted using Raman and X-ray photo-electron spectroscopy, via which introduction of defects by functionalization was confirmed. It was found that the introduction of defects along the nanotube body affected all of the Raman vibrational modes. A systematic analysis of the relationship between D, D′, D* and G modes indicated that no single peak could be used as an accurate standard for the estimation of defects in nanotubes.

Spectral Fingerprinting of Structural Defects in Plasma-Treated Carbon Nanotubes. N.Chakrapani, S.Curran, B.Wei, P.M.Ajayan, A.Carrillo, R.S.Kane: Journal of Materials Research, 2003, 18[10], 2515-21