It was shown that a diagram of the Raman intensity ratio of the G to D peaks and the G peak width could reveal two damaging stages of multi-walled carbon nanotube films. In a transition period, additional peaks appeared in the X-ray absorption spectra, thereby indicating some significant change in the electronic structure. Also, a remarkable increase occurred in the diameter of the multi-walled carbon nanotubes in the latter stage, suggesting the formation of dislocation dipoles which may relate to the change in the properties of field-emission devicesDefect Evolution in Multiwalled Carbon Nanotube Films Irradiated by Ar Ions. S.I.Honda, S.Nanba, Y.Hasegawa, Y.Nosho, A.Tsukagoshi, M.Niibe, M.Terasawa, R.Hirase, H.Izumi, H.Yoshioka, K.Y.Lee, K.Niwase, E.Taguchi, M.Oura: Japanese Journal of Applied Physics, 2012, 51[11], 110202