Charge transference and conformational stress influence on the electronic properties of zigzag carbon nanowires

The structural and electronic properties of nanostructures resulting from the insertion of a linear carbon chain (LCC) into a semiconducting zigzag single-walled carbon nanotubes (SWCNTs) were studied using density functional theory. Although all isolated constituents exhibited a semiconductor behavior, semiconductor transitions to metallic character were found in the combined system. The competitive effects on the band gap due to the conformational stress and charge transfer were analyzed, both resulting in an overall metallic character. The electronic character in nanowires with (7,0) nanotube is affected by structural strain and charge transfer with a slightly higher influence of the charge transferred. Nanowires with (8,0) nanotube and bigger are mainly affected by strain, and their electronic states distribution retains the energy gap associated with isolated semiconducting nanotube with only a few empty states slightly above the Fermi level due to the charge transfer to LCC. A metallic behavior was found for all nanowires. However, a metallization dependence with nanotube diameters was found. LCC shows a metallic contribution in all cases. This study suggests that strain could produce nanostructures with a global metallic behavior which is provided by a metallic LCC plus a semiconducting nanotube for sizes as small as 6.5 A. Zigzag nanowires smaller than this last value produce strained LCC accompanied by a transition from semiconductor to metal on both subsystems.