Ballistic Transport in Metallic Nanotubes With Reliable Pd Ohmic Contacts

TL;DR

This study demonstrates that palladium contacts enable highly reproducible ohmic contacts to metallic nanotubes, facilitating detailed analysis of ballistic transport and revealing mean free paths up to several microns.

Contribution

It introduces Pd as a reliable contact material for metallic nanotubes, improving reproducibility and enabling precise measurement of ballistic transport properties.

Findings

Pd contacts are more reliable than Ti for ballistic nanotube devices.

Mean free path for defect scattering can reach up to 4 microns.

Acoustic phonon scattering mean free path is about 500 nm at room temperature.

Abstract

Contacting metallic single-walled carbon nanotubes by palladium (Pd) affords highly reproducible ohmic contacts and allows for detailed elucidation of ballistic transport in metallic nanotubes. The Pd ohmic contacts are more reliable than titanium (Ti) previously used for ballistic nanotube devices. In contrast, Pt contacts appear to give non-ohmic contacts to metallic nanotubes. For both ohmic and non-ohmic contacts, the length of the nanotube under the metal contact area is electrically turned off. Transport occurs from metal to nanotube at the edges of the contacts. Measurements with large numbers of Pd contacted nanotube samples reveal that the mean free path for defect scattering in SWNTs grown by chemical vapor deposition can be up to 4 microns. The mean free paths for acoustic phonon scattering are on the order of 500 nm at room temperature and >> 4 microns at low temperatures.