Quasi-ballistic electron transport in as-produced and annealed multiwall carbon nanotubes

TL;DR

This study demonstrates that high-temperature annealing significantly enhances the electron mean free path in CVD-grown multi-wall carbon nanotubes, enabling quasi-ballistic transport at room temperature, which is promising for nanoelectronic applications.

Contribution

It provides experimental evidence that annealing at 2700°C improves the electronic transport properties of CVD-produced MWNTs by reducing structural defects.

Findings

Annealed MWNTs exhibit EMFP of a few microns.

Annealing at 2700°C reduces structural defects.

Quasi-ballistic transport achieved at room temperature.

Abstract

The electronic properties of multi-wall carbon nanotubes (MWNTs) have attracted much attention because they could lead to nano-sized electronic devices. Using chemical vapor deposition (CVD), MWNTs are produced in large quantities at a low cost. CVD-produced MWNTs, however, generally contain a considerable amount of structural defects due to their low temperature synthesis. Since these defects act as scattering centers in electron transport and thus limit the electronic mean free path (EMFP), high-temperature annealing should lengthen the EMFP. This is based on the previous experiments in which annealing eliminated structural defects in various carbon materials including nanotubes. In this study, we investigate how high-temperature annealing affects the transport properties, especially EMFP, of CVD-grown MWNTs. To measure the EMFP of a nanotube, we submerged samples into liquid mercury (Hg) and measured the variation in conductance. We found that the EMFP is much longer in nanotubes annealed at 2700oC compared with that of as-produced ones. The annealed nanotubes show quasi-ballistic electronic transport with the EMFP reaching a few microns, even at room temperature.