Seminar- Doping of nanoscale semiconductors: insights and lessons from the spectroscopy of carbon nanotubes

Event Date
Monday, 18 March 2019 - 12:00pm
Speaker/host external
Professor Tobias Hertel
, Julius-Maximilians University Würzburg
Imperial College London

Venue: Room G01, Royal School of Mines

Abstract: Doping of nanoscale semiconductors is often critical for providing electronic or photonic device functionality. However, for many materials the commonly used charge transfer techniques often lack the sophistication or the required understanding to become technologically viable. Here, we discuss recent insights into the doping of semiconducting carbon nanotubes (s-SWNTs) using a variety of spectroscopic probes and doping schemes. We will report on femtosecond time-resolved pump-probe-, VIS-, NIR-, FTIR-, EPR- and single particle fluorescence- spectroscopies of redox and electrochemically doped nanotubes. The insights gathered from these investigations allow a quantitative determination of doping levels in carbon nanotubes by monitoring easily accessible spectroscopic signatures such as exciton-band position, shape or oscillator strength. Similarly, the experiments also reveal information on the distribution or localization of charge carriers. Our findings identify fundamental challenges with providing surplus carriers for use in device technologies due to notoriously weak screening, strong electronic correlations and the resulting sensitivity to external perturbations in low-dimensional, atomically thin semiconductors.