Hopping Conduction in Disordered Carbon Nanotubes

TL;DR

This study investigates electrical transport in disordered carbon nanotubes, revealing hopping conduction as the dominant mechanism, influenced by disorder, with implications for understanding charge transport in nanoscale materials.

Contribution

The paper provides experimental evidence of Coulomb-gap variable range hopping in disordered nanotubes and extracts key disorder-dependent parameters, advancing understanding of conduction mechanisms.

Findings

Hopping conduction follows an exp[-(T0/T)^{1/2}] dependence.

Field dependence of conductance also follows a similar exponential form.

Weak positive magnetoresistance observed at low temperatures.

Abstract

We report electrical transport measurements on individual disordered carbon nanotubes, grown catalytically in a nanoporous anodic aluminum oxide template. In both as-grown and annealed types of nanotubes, the low-field conductance shows as exp[-(T_{0}/T)^{1/2}] dependence on temperature T, suggesting that hopping conduction is the dominant transport mechanism, albeit with different disorder-related coefficients T_{0}. The field dependence of low-temperature conductance behaves an exp[-(xi_{0}/xi)^{1/2}] with high electric field xi at sufficiently low T. Finally, both annealed and unannealed nanotubes exhibit weak positive magnetoresistance at low T = 1.7 K. Comparison with theory indicates that our data are best explained by Coulomb-gap variable range hopping conduction and permits the extraction of disorder-dependent localization length and dielectric constant.