CROSS-SECTIONAL HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY STUDY OF THE STRUCTURES OF CARBON NANOTUBES

The structures of carbon nanotubes are investigated by cross-sectional high-resolution transmission electron microscopy. Some results for longitudinal sections are also included. No examples of perfect seamless tubes or of 'scroll-type' Archimedean spirals are found; in each case examined, papier mache-like aggregates of graphene sheets occur, each of finite extent. There is a strong tendency for the structures to relax, locally at least, towards the three-dimensional structure of graphite. Thus polygonal rather than circular or spherical geometries predominate. Some comments are offered concerning a realistic model for the structures, as well as for understanding the electronic properties of multilayer carbon nanotubules. It is proposed that our specimens grew in an atmosphere rich in single graphene sheets, rather than C-60 cages.