Negative Differential Conductance and Hot Phonons in Suspended Nanotube Molecular Wires

TL;DR

This paper investigates the electron transport and thermal properties of suspended metallic carbon nanotubes, revealing negative differential conductance due to hot phonons and using this to measure their thermal conductivity at high temperatures.

Contribution

It provides the first analysis of self-heating effects in suspended nanotubes to probe their thermal conductivity and phonon scattering mechanisms.

Findings

Suspended nanotubes show negative differential conductance at low electric fields.

Thermal conductivity of individual nanotubes is approximately 3600 W/m·K at 300 K.

Thermal conductivity decreases with temperature following a 1/T dependence.

Abstract

Freely suspended metallic single-wall carbon nanotubes (SWNTs) exhibit reduced current carrying ability compared to those lying on substrates, and striking negative differential conductance (NDC) at low electric fields. Theoretical analysis reveals significant self-heating effects including electron scattering by hot non-equilibrium optical phonons. Electron transport characteristics under strong self-heating are exploited for the first time to probe the thermal conductivity of individual SWNTs (~ 3600 Wm-1K-1 at T=300 K) up to ~700 K, and reveal a 1/T dependence expected for Umklapp phonon scattering at high temperatures.