Interpretation of electron diffraction from carbon nanotube bundles presenting precise helicity

The structure of bundles of carbon nanotubes produced by catalytic chemical vapor deposition has been studied by electron diffraction. The experimental results were analyzed with the kinematical theory of diffraction. An interpretation of the diffraction patterns demonstrates unambiguously that some bundles are made of double-walled carbon nanotubes, and not single-walled nanotubes as previously reported in Phys. Rev. B 64, 125425 (2001). In this previous work, we have focused our attention on bundles presenting one or two helicities. The interpretation of our diffraction data based on the assumption of double-walled nanotubes is shown to fit remarkably with experiment. In the present paper, the detailed analysis of an electron diffraction pattern from a small bundle exhibiting two helicities is made and we deduced the most probable wrapping indices of the two tubes constituting the double-walled nanotubes.