Modifications to the electronic structure of carbon nanotubes with symmetric and random vacancies

Abstract

ABSTRACT:The influence of different types of atomic vacancies on the electronic structure of carbon nanotubes (20, 0) and (12, 12) was investigated using an empirical tightbinding method. The models with vacancies randomly and symmetrically arranged in an extended unit cell were constructed. The symmetrical distribution of defects was obtained by rotating a pore, obtained by removing a hexagonal ring from a graphitic shell around the tube axis. The random defects were generated by a specially developed algorithm, which eliminates a given number of atoms from the unit cell so that the remaining carbon atoms have no more than one dangling bond. The presence of vacancies in carbon nanotube causes an enhancement of density of occupied states that is near the Fermi level and whose localization increases with the number of two-coordinated atoms at the pore boundaries. It was found that the occurrence of atomic vacancies in the carbon nanotube walls might result in the narrow-gap semiconductors and ferromagnetic materials.

Spectro-Microscopic Study of Laser-Modified Carbon Nanotubes

“…(44; 45) The structural defect and dangling bond of CNTs after laser trimming should be the important factors in the DOS reconstruction. (46) It means the eliminated amount of C 2s and C 2s/2p band and increased C 2p-π intensity is in agreement to the result of air-treated CNTs. In fact, the behavior of C 2p-π electrons of oxygen-treated CNTs is observed for a little different, because the mixing contribution between air environment and laser-induced defect play the important role in C 2p-π electrons.…”

Analysis of Randomness in Mechanical Properties of Carbon Nanotubes Through Atomistic Simulation

“…The carbon atoms might be "knocked out" by either high-energy electrons or ions, and larger holes might be introduced via oxidative purification processes 28 . The effects of vacancy defects on CNT properties have received considerable attention [28][29][30] , although the stability of these vacancies is still in doubt. The atoms missing a neighbor have higher energy and always tend to form new bonds to reduce energy.…”

HOMO–LUMO gaps for sub-graphenic and sub-buckytubic species

“…But also comparable experimental interest has developed concerning carbon nanotubes [6,7], graphenic strips [8,9] and different modest decorations to these species, while interest in traditional benzenoids has been maintained, and much extended [10][11][12]; further, for graphene, as well as large benzenoids and buckytubes, much interest has developed regarding decorations [13][14][15][16][17][18]. In the last few decades, 'chemical graph theory' has developed, with a significant fraction of the work directed [19][20][21][22] towards conjugated π -networks in the context of the tight-binding Hückel model, although only a rather modest effort was initially directed [23][24][25][26][27][28] counterbalance this have been made [29][30][31][32][33][34][35][36][37][38][39][40][41].…”

“…Conjugated-carbon nano-structures have played a central part in chemistry for well over a century, with intense interest (and three Nobel prizes) during the last couple of decades for work on conjugated (possibly metallically conducting) polymers [1,2], novel fullerene cages [3] and single-layer graphene [4,5]. But also comparable experimental interest has developed concerning carbon nanotubes [6,7], graphenic strips [8,9] and different modest decorations to these species, while interest in traditional benzenoids has been maintained, and much extended [10][11][12]; further, for graphene, as well as large benzenoids and buckytubes, much interest has developed regarding decorations [13][14][15][16][17][18]. In the last few decades, 'chemical graph theory' has developed, with a significant fraction of the work directed [19][20][21][22] towards conjugated π -networks in the context of the tight-binding Hückel model, although only a rather modest effort was initially directed [23][24][25][26][27][28] to the HOMO-LUMO gap.…”