Quantifying Doping Levels in Carbon Nanotubes by Optical Spectroscopy

Controlling doping is essential for the 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 entirely absent. Here, we describe efforts toward a quantitative characterization of doping in redox- or electrochemically doped semiconducting single-wall carbon nanotubes (s-SWNTs) using vis-NIR absorption spectroscopy. We discuss how carrier densities up to about 0.5 nm(-1) can be quantified with a sensitivity of roughly 1 charge per 10(4) carbon atoms assuming inhomogeneous or homogeneous carrier distributions.