Coupled dynamics of electrons and phonons in metallic nanotubes: current saturation from hot phonons generation

TL;DR

This paper models the coupled electron-phonon dynamics in metallic nanotubes, revealing how hot phonons influence current saturation and suggesting performance improvements through phonon thermalization control.

Contribution

It introduces a self-consistent solution of coupled Boltzmann equations for electrons and phonons in metallic SWNTs, accurately predicting IV curves and hot phonon effects.

Findings

Good agreement with experimental IV curves

Hot phonons reach effective temperatures of thousands of Kelvin

Resistivity depends on optical phonon thermalization time

Abstract

We show that the self-consistent dynamics of both phonons and electrons is the necessary ingredient for the reliable description of the hot phonons generation during electron transport in metallic single-wall carbon nanotubes (SWNTs). We solve the coupled Boltzmann transport equations to determine in a consistent way the current vs. voltage (IV) curve and the phonon occupation in metallic SWNTs which are lying on a substrate. We find a good agreement with measured IV curves and we determine an optical phonon occupation which corresponds to an effective temperature of several thousands K (hot phonons), for the voltages typically used in experiments. We show that the high-bias resistivity strongly depends on the optical phonon thermalization time. This implies that a drastic improvement of metallic nanotubes performances can be achieved by increasing the coupling of the optical phonons with a thermalization source.