Adsorption and migration of carbon adatoms on zigzag carbon nanotubes

Using density-functional tight-binding and ab initio methods we study the adsorption and migration of carbon adatoms on surfaces of single-walled zigzag carbon nanotubes. We demonstrate that the adatoms form strong covalent bonds with the nanotubes and that the migration is strongly anisotropic. The adatom adsorption energy and migration barrier depend on the nanotube diameter and chirality. The migration barriers, being in the range of 0.6-1 eV, are in a good agreement with the experimental values (about 0.8 eV) reported in the literature. (C) 2003 Elsevier Ltd. All rights reserved.