Molecular screening effects on exciton-carrier interactions in suspend carbon nanotubes

TL;DR

This study investigates how molecular adsorption influences exciton and trion interactions in suspended carbon nanotubes, revealing screening effects that alter photoluminescence properties and electronic bandgap.

Contribution

It provides quantitative analysis of molecular screening effects on exciton-trion interactions and demonstrates changes in electronic properties due to molecular adsorption.

Findings

Molecular adsorption reduces the electronic bandgap.

Screening effects alter the voltage dependence of photoluminescence.

Charge neutrality points shift after molecular adsorption.

Abstract

Photoluminescence spectroscopy measurements are performed on suspended carbon nanotubes in a field-effect configuration, and the gate voltage dependence of photoluminescence spectra are compared for the pristine and the molecularly adsorbed states of the nanotubes. We quantify the molecular screening effect on the trion binding energies by determining the energy separation between the bright exciton and the trion emission energies for the two states. The voltage dependence shows narrower voltage regions of constant photoluminescence intensity for the adsorbed states, consistent with a reduction in the electronic bandgap due to screening effects. The charge neutrality points are found to shift after molecular adsorption, which suggests changes in the nanotube chemical potential or the contact metal work function.