Structure of multi-wall carbon nanotubes: AA ' stacked graphene helices

Abstract

The structure of multi-wall carbon nanotubes has been attributed previously to disordered stacking of the graphene planes. Evidence is presented that the nanotubes analyzed in this paper occur with stacked graphene layers in the sequence of AA', where alternate graphene planes are translated by half the hexagon width. We further present proof that the crystalline materials comprise graphene helices (similar to 5 nm in width), rather than in the form of a perfect tube. We also show that the structural model proposed here may be a common structure for multi-wall carbon nanotubes. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802881]