Abstract
We theoretically investigate the influence of defect-induced long-range deformations in carbon nanotubes on their electronic transport properties. To this end we perform numerical ab-initio calculations using a density-functional-based tight-binding model for various tubes with vacancies. The geometry optimization leads to a change of the atomic positions. There is a strong reconstruction of the atoms near the defect (called ‘distortion’) and there is an additional long-range deformation. The impact of both structural features on the conductance is systematically investigated. We compare short and long CNTs of different kinds with and without long-range deformation. We find for the very thin (9, 0)-CNT that the long-range deformation additionally affects the transmission spectrum and the conductance compared to the short-range lattice distortion. The conductance of the larger (11, 0)-or the (14, 0)-CNT is overall less affected implying that the influence of the long-range deformation decreases with increasing tube diameter. Furthermore, the effect can be either positive or negative depending on the CNT type and the defect type. Our results indicate that the long-range deformation must be included in order to reliably describe the electronic structure of defective, small-diameter zigzag tubes.
Highlights
Carbon nanotubes (CNTs) offer a large variety of properties from metallic types to semiconducting types depending on their structure parameters [1,2,3]
In the following we focus on the long-range deformation in CNTs caused by defects
We focus on the following vacancies: monovacancies (MV), divancancies which are aligned diagonally (DV1), and divacancies which are aligned in parallel (DV2) to the tube axes
Summary
Carbon nanotubes (CNTs) offer a large variety of properties from metallic types to semiconducting types depending on their structure parameters [1,2,3]. It is well known that introducing vacancies in a perfect crystal will inhibit the electronic transport Such vacancies will always be accompanied by a defect-induced short-range reconstruction of the lattice, which is named ‘distortion’ in the following. For nano-scale systems, defects may induce a weak long-range reconstruction which influence the electronic structure [5]. In the following, this is named ‘deformation’. In the following study we investigate the influence of the long-range deformation on the electronic transport properties of carbon nanotubes with vacancies. The conductance is computed based on the quantum transport theory described below
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