Multi-walled carbon nanotubes, dispersed on graphite substrates, were irradiated with 30keV Ar+ ions to a dose of 5 x 1011/cm2. The irradiated nanotubes were investigated using scanning tunneling microscopy and spectroscopy under ambient conditions. Atomic-resolution scanning tunneling microscopic images revealed individual nanotube defects which appeared as hillocks, 0.1 to 0.2nm in height, due to the locally changed electronic structure. The results were in agreement with previous theoretical predictions. Electron density patterns (superstructures) were observed near to the defect sites, which originated from the interference of incident waves and waves scattered by defects. The period of these superstructures was larger than the period determined by the atomic structure. After annealing at 450C in a nitrogen atmosphere, the irradiated multi-walled carbon nanotubes were investigated again. The effect of heat treatment upon the irradiation-induced nanotube-defects was observed in both scanning tunneling microscopic images and in recorded scanning tunneling spectra.

Scanning Tunneling Microscopy Investigation of Atomic-Scale Carbon Nanotube Defects Produced by Ar+ Ion Irradiation. Z.Osváth, G.Vértesy, L.Tapasztó, F.Wéber, Z.E.Horváth, J.Gyulai, L.P.Biró: Materials Science and Engineering C, 2006, 26[5-7], 1194-7