Defects in arc-discharge-produced single-walled carbon nanotubes

High-yield single-wall carbon nanotubes (SWCNTs) have been produced in large quantity using a Y-Ni alloy composite graphite rod as anode in a dc arc discharge. Termination of the tubes was found to be the most common defect in the arc-discharge-produced SWCNTs. A comparison is made with samples produced by laser ablation. High-resolution transmission electron microscopy was used to investigate the cap structure of the terminated SWCNTs and their relatives. The cap shapes of most SWCNTs with high aspect ratios are hemispherical, while those of highly defective squat SWCNTs are polyhedral. Inclusion of carbon materials in the SWCNTs was also observed. The results provided the basic information for understanding the growth mechanism of SWCNTs.