Ab initio study of F- and Cl-functionalized single wall carbon nanotubes

Abstract

First-principles calculations were carried out to study the functionalization of single wallcarbon nanotubes by the chemical absorption of F and Cl atoms. Our results confirmedthat the band gap of semiconductor zigzag carbon nanotubes is reduced on addition of F orCl atoms on the walls of the nanotubes. For metallic armchair nanotubes, the doublydegenerate states crossing the Fermi level were separated by the introduction of F or Clatoms. An additional energy level emerged near the Fermi level, due to coupling betweenthe carbon nanotube and the F or Cl atom. For zigzag nanotubes, charge transfers of0.27e from the tube tothe Cl atom and of 0.41e to the F atom took place, while for armchair nanotubes, thecharge transfers from the nanotube to Cl and F are 0.25 and0.42e, respectively. The Cl–C and F–C bond lengths were found to be 2.09 and 1.49 Å,respectively. The systems show semiconducting behaviour when charged with one electronper halogen atom, but remain metallic under hole injection, regardless of the chirality ofthe carbon nanotubes.