The Effects of Substrate Phonon Mode Scattering on Transport in Carbon Nanotubes

TL;DR

This paper investigates how substrate surface polar phonon scattering significantly reduces the mobility of carbon nanotube transistors, with predictions on how various factors influence this effect.

Contribution

It reveals the substantial impact of substrate phonon scattering on CNTFET mobility and predicts experimental signatures related to tube diameter, density, temperature, and separation.

Findings

Mobility at room temperature can be reduced by nearly an order of magnitude due to substrate phonons.

The effect depends strongly on tube diameter and CNT-substrate separation.

Predicted experimental signatures include variations in mobility with density, temperature, and other parameters.

Abstract

Carbon nanotubes (CNTs) have large intrinsic carrier mobility due to weak acoustic phonon scattering. However, unlike two-dimensional metal-oxide-semiconductor field effect transistors (MOSFETs), substrate surface polar phonon (SPP) scattering has a dramatic effect on the CNTFET mobility, due to the reduced vertical dimensions of the latter. We find that for the Van der Waals distance between CNT and an SiO$_2$ substrate, the low-field mobility at room temperature is reduced by almost an order of magnitude depending on the tube diameter. We predict additional experimental signatures of the SPP mechanism in dependence of the mobility on density, temperature, tube diameter, and CNT - substrate separation.