A study was made of the effects of Ar+, He+ and C+ ion bombardment on multi-walled carbon nanotubes at room and elevated temperatures using transmission electron microscopy and Raman spectroscopy. Based upon transmission electron microscopy data, a universal damage scale was introduced for the visual analysis and characterization of irradiated nanotubes. It was shown  for the first time that the amount of irradiation-induced damage in nanotubes was larger than the value predicted for bulk materials using the simple binary collision approximation, which could be associated with higher defect production due to electronic stopping in these nanoscale systems. The Raman spectra of the irradiated samples were in qualitative agreement with the transmission electron microscopy data and indicated the presence of irradiation-induced defects. However, it was difficult to obtain quantitative information on defect concentration due to a non-uniform distribution of defects in the nanotube films and in part due to the presence of other carbon nanosystems in the samples, such as graphitic crystallites and carbon onions.

Characterization of Ion-Irradiation-Induced Defects in Multi-Walled Carbon Nanotubes. O.Lehtinen, T.Nikitin, A.V.Krasheninnikov, L.Sun, F.Banhart, L.Khriachtchev, J.Keinonen: New Journal of Physics, 2011, 13, 073004