Electronic transport through defective semiconducting carbon nanotubes

TL;DR

This study analyzes how defects affect electronic transport in semiconducting carbon nanotubes using quantum transport calculations, revealing localization effects, dependence on diameter, and distinctions based on bandgap classifications.

Contribution

It provides a detailed analysis of defect-induced localization and transport properties in various semiconducting CNTs, including the effects of defect type, diameter, and bandgap classification.

Findings

Localization length depends linearly on CNT diameter.

Transport properties vary with defect density and type.

Distinction in behavior based on (m-n) mod 3 classification.

Abstract

We investigate the electronic transport properties of semiconducting ($m$,$n$) carbon nanotubes (CNTs) on the mesoscopic length scale with arbitrarily distributed realistic defects. The study is done by performing quantum transport calculations based on recursive Green's function techniques and an underlying density-functional-based tight-binding model for the description of the electronic structure. Zigzag CNTs as well as chiral CNTs of different diameter are considered. Different defects are exemplarily represented by monovacancies and divacancies. We show the energy-dependent transmission and the temperature-dependent conductance as a function of the number of defects. In the limit of many defetcs, the transport is described by strong localization. Corresponding localization lengths are calculated (energy dependent and temperature dependent) and systematically compared for a large number of CNTs. It is shown, that a distinction by $(m-n)\,\mathrm{mod}\,3$ has to be drawn in order to classify CNTs with different bandgaps. Besides this, the localization length for a given defect probability per unit cell depends linearly on the CNT diameter, but not on the CNT chirality. Finally, elastic mean free paths in the diffusive regime are computed for the limit of few defects, yielding qualitatively same statements.