Theory of phonon-drag thermopower of extrinsic semiconducting single-wall carbon nanotubes and comparison with previous experimental data

TL;DR

This paper develops a theoretical model for phonon-drag thermopower in doped semiconducting single-wall carbon nanotubes, deriving an analytical expression and validating it against experimental data with excellent agreement.

Contribution

The paper introduces a simple analytical expression for phonon-drag thermopower in doped SWCNTs, accounting for screening effects and matching experimental results.

Findings

S^g exhibits activated behavior at low temperatures

Screening effects significantly reduce S^g magnitude

The model agrees well with experimental data from 10-200 K

Abstract

A theoretical model for the calculation of the phonon-drag thermopower, $S^{g}$, in degenerately doped semiconducting single-wall carbon nanotubes (SWCNTs) is proposed. Detailed calculations of $S^{g}$ are performed as a function of temperature, tube radius and position of the Fermi level. We derive a simple analytical expression for $S^{g}$ that can be utilized to determine the free carrier density in doped nanotubes. At low temperatures $S^{g}$ shows an activated behavior characteristic of the one-dimensional (1D) character of carriers. Screening effects are taken into account and it is found that they dramatically reduce the magnitude of $S^{g}$. Our results are compared with previous published experimental data in bulk p-doped SWCNT materials. Excellent agreement is obtained in the temperature range 10-200 K for a consistent set of parameters. This is a striking result in view of the complexity of these systems.