Chirality correlation in double-wall carbon nanotubes as studied by electron diffraction

Structural correlation between two adjacent graphitic layers in double-wall carbon nanotubes (DWNTs) was systematically examined by using electron diffraction. Chiral angles and tube diameters were carefully measured, and the chiral indices of individual DWNTs were accurately determined. As a result, it was found that the interlayer distances of DWNTs were widely distributed in the range between 0.34 and 0.380.3em0exnm. Chiralities of the inner and outer tubes tended to be distributed at higher chiral angles, approaching 30^∘, for the tubes with diameter D<~30.3em0exnm. On the other hand, for the tubes with D>~30.3em0exnm, the chiral angles were widely distributed, covering the chiral map entirely. Therefore, we consider that tubes with small diameters have a tendency to form armchair type. Correlation of chiralities between the inner and outer tubes was found to be random.