Electric field dependence of Raman-active modes in single-wall carbon nanotube thin films

TL;DR

This study investigates how an external electric field affects Raman-active modes in single-wall carbon nanotube thin films, revealing mode shifts, intensity changes, and implications for nanotube electronic properties.

Contribution

It provides a detailed analysis of electric field effects on Raman modes in SWNT films and introduces a model explaining the observed phenomena.

Findings

Electric field causes downshifts in D and G Raman modes.

Radial breathing mode intensities vary with electric field depending on nanotube type.

Results support the presence of Kohn anomalies in metallic graphitic materials.

Abstract

We report on electrical Raman measurements in transparent and conducting single-wall carbon nanotube (SWNT) thin films. Application of external electric field results in downshifts of the D and G modes and in reduction of their intensity. The intensities of the radial breathing modes increase with electric field in metallic SWNTs, while decreasing in semiconducting SWNTs. A model explaining the phenomenon in terms of both direct and indirect (Joule heating) effects of the field is proposed. Our work rules out the elimination of large amounts of metallic SWNTs in thin film transistors using high field pulses. Our results support the existence of Kohn anomalies in the Raman-active optical branches of metallic graphitic materials [Phys. Rev. Lett. 93 (2004) 185503].