Quantifying Doping Levels in Carbon Nanotubes by Optical Spectroscopy

TL;DR

This paper presents a method to quantitatively measure doping levels in semiconducting carbon nanotubes using VIS-NIR absorption spectroscopy, enabling precise assessment of charge carrier densities.

Contribution

It introduces a quantitative approach to determine doping levels in carbon nanotubes via optical spectroscopy, improving upon qualitative methods.

Findings

Carrier densities up to 0.5 nm^{-1} can be quantified.

Sensitivity of roughly one charge per 10^4 carbon atoms.

Applicable to both homogeneous and inhomogeneous carrier distributions.

Abstract

Controlling doping is essential for a successful integration of semiconductor materials into device technologies. However, the assessment of doping levels and the distribution of charge carriers in carbon nanotubes or other nanoscale semiconductor materials is often either limited to a qualitative attribution of being 'high' or 'low' or it is entirely absent. Here, we describe efforts toward a quantitative characterization of doping in redox- or electrochemically doped semiconducting carbon nanotubes (s-SWNTs) using VIS-NIR absorption spectroscopy. We discuss how carrier densities up to about 0.5 $\rm nm^{-1}$ can be quantified with a sensitivity of roughly one charge per $10^4$ carbon atoms assuming in-homogeneous or homogeneous carrier distributions.