Nanodiffraction and dark-field STEM characterization of single-walled carbon nanotube ropes

The techniques of electron nanodiffraction, using a beam of diameter about 0.7 nm, and the associated dark-field scanning transmission electron microscopy (STEM) imaging using a thin annular detector, have been applied to the study of the structures and defects of bundles, or ropes, of single-walled carbon nanotubes (SWnT) formed by double laser irradiation of amorphous carbon. Series of nanodiffraction patterns obtained while the beam traverses images of SWnT ropes provide explanations for the bright bands and spots appearing in the dark-field images in terms of twists, bends and local defects of the stacking of the tubes within the ropes. In the few cases where ropes are seen to be abruptly terminated within the images, nanodiffraction patterns reveal that the rope structures become almost completely disordered as the rope end is approached.