Atomically resolved STM images of carbon nanotube defects produced by Ar~+ irradiation

摘要

Multiwall carbon nanotubes (MWCNTs) dispersed on graphite on highly oriented pyrolytic graphite (HOPG) substrate were irradiated with Ar~+ ions of 30 keV. The irradiated samples were investigated by scanning tunneling microscopy (STM) and spectroscopy (STS) in air. The irradiation-induced defects appear as hillocklike protrusions on the nanotube walls, similar to the hillocks observed earlier on ion irradiated HOPG. The results are in agreement with recent predictions, which attribute the STM features produced by ion irradiation to local modifications of the electronic structure. "3~(1/2) X 3~(1/2)R" type superstructures are also observed near some of the defects. After annealing at 450℃ in nitrogen atmosphere, the irradiated MWCNTs were investigated again by STM. The effect of heat treatment on the irradiation-induced nanotube defects is also discussed.