Formation of Organic Color Centers in Air-Suspended Carbon Nanotubes Using Vapor-Phase Reaction

TL;DR

This study demonstrates a vapor-phase method to create organic color centers in air-suspended carbon nanotubes, enabling room-temperature single-photon emission with diameter-dependent properties and longer emission lifetimes.

Contribution

It introduces a vapor-phase functionalization technique for air-suspended nanotubes, advancing the fabrication of quantum light sources with controlled defect densities and emission characteristics.

Findings

Color centers exhibit diameter-dependent emission intensity.

Longer emission lifetime compared to E11 excitons.

Theoretical model explains reactivity based on tube strain.

Abstract

Organic color centers in single-walled carbon nanotubes have demonstrated exceptional ability to generate single photons at room temperature in the telecom range. Combining the color centers with pristine air-suspended tubes would be desirable for improved performance, but all current synthetic methods occur in solution which makes them incompatible. Here we demonstrate formation of color centers in air-suspended nanotubes using vapor-phase reaction. Functionalization is directly verified on the same nanotubes by photoluminescence spectroscopy, with unambiguous statistics from more than a few thousand individual nanotubes. The color centers show a strong diameter-dependent emission intensity, which can be explained with a theoretical model for chemical reactivity taking into account strain along the tube curvature. We are also able to estimate the defect density by comparing the experiments with simulations based on a one-dimensional diffusion equation, whereas the analysis of diameter dependent peak energies gives insight to the nature of the dopant states. Time-resolved measurements show a longer lifetime for color center emission compared to E$_{11}$ exciton states. Our results highlight the influence of the tube structure on vapor-phase reactivity and emission properties, providing guidelines for development of high-performance near-infrared quantum light sources.