Frequency- and electric-field-dependent conductivity of single-walled carbon nanotube networks of varying density

TL;DR

This study investigates how the electrical conductivity of single-walled carbon nanotube networks varies with frequency and electric field, revealing relationships between network density, contact length scale, and transport properties.

Contribution

It provides a comprehensive analysis of frequency and electric field-dependent conductivity in SWCNT networks, introducing empirical relations and insights into contact length scales.

Findings

AC conductivity increases with frequency above an onset frequency $$

The contact length scale $L_{E}$ decreases with increasing film thickness

Onset frequency $$ correlates with the length scale $L_{E}$

Abstract

We present measurements of the frequency and electric field dependent conductivity of single walled carbon nanotube(SWCNT) networks of various densities. The ac conductivity as a function of frequency is consistent with the extended pair approximation model and increases with frequency above an onset frequency $\omega_0$ which varies over seven decades with a range of film thickness from sub-monolayer to 200 nm. The nonlinear electric field-dependent DC conductivity shows strong dependence on film thickness as well. Measurement of the electric field dependence of the resistance R(E) allows for the determination of a length scale $L_{E}$ possibly characterizing the distance between tube contacts, which is found to systematically decrease with increasing film thickness. The onset frequency $\omega_0$ of ac conductivity and the length scale $L_{E}$ of SWCNT networks are found to be correlated, and a physically reasonable empirical formula relating them has been proposed. Such studies will help the understanding of transport properties and benefit the applications of this material system.