Transmission electron microscopy was used to investigate  in situ  the structure of laser-ablated single-wall C nanotubes which had been deposited onto Ni grids. It was found that most of the nanotubes formed highly curved bundles, which split or joined to form various structures. Individually grown nanotubes were found to contain more defects.

Y.Zhang, S.Iijima: Philosophical Magazine Letters, 1998, 78[2], 139-44