Effects of substrate and electric fields on charges in nanotubes

In this paper, we study how the distribution of net charges in carbon nanotubes can be influenced by substrate and external electric fields, using theoretical calculations based on an extension of the atomic charge-dipole model. We find that the charge enhancement becomes less significant when the tube gets closer to substrate or when the dielectric constant of substrate increases. It is demonstrated that net charges can be shifted to one side of tube by longitudinal electric fields and the polarity of charges can be locally changed, while transversal fields give much less influence on the charge enhancement. These properties could be generalized for other metallic or semiconducting nano/microwires and tubes.