Universal map of gas-dependent kinetic selectivity in carbon nanotube growth

TL;DR

This paper presents a universal kinetic model for carbon nanotube growth that explains how gas composition influences chirality-dependent growth rates, resolving previous contradictions and guiding selective synthesis.

Contribution

It introduces a comprehensive kinetic model verified by isotope labeling experiments, elucidating the role of gas-dependent kinetics in nanotube growth.

Findings

Carbon removal dominates growth at low precursor supply.

Chirality-dependent growth rates emerge with sufficient carbon and etching agents.

Kinetic maps enable rational strategies for selective nanotube growth.

Abstract

Single-walled carbon nanotubes have been a candidate for outperforming silicon in ultrascaled transistors, but the realization of nanotube-based integrated circuits requires dense arrays of purely semiconducting species. Control over kinetics and thermodynamics in tube-catalyst systems plays a key role for direct growth of such nanotube arrays, and further progress requires the comprehensive understanding of seemingly contradictory reports on the growth kinetics. Here, we propose a universal kinetic model and provide its quantitative verification by ethanol-based isotope labeling experiments. While the removal of carbon from catalysts dominates the growth kinetics under a low supply of precursors, our kinetic model and experiments demonstrate that chirality-dependent growth rates emerge when sufficient amounts of carbon and etching agents are co-supplied. As the model can be extended to create kinetic maps as a function of gas compositions, our findings resolve discrepancies in literature and offer rational strategies for chirality selective growth for practical applications.