A semi-grand canonical kinetic Monte Carlo study of single-walled carbon nanotube growth

Georg Daniel Förster,Esko Kauppinen,Hua Jiang,Thomas D Swinburne,Christophe Bichara

doi:10.1063/5.0030943

Abstract

Single-walled carbon nanotubes exist in a variety of different geometries, so-called chiralities, which define their electronic properties. Chiral selectivity has been reported in catalytic chemical vapor deposition synthesis experiments, but the underlying mechanisms remain poorly understood. In this contribution, we establish a simple model for the prediction of the growth rates of carbon nanotubes of different chiralities as a function of energies characterizing the carbon nanotube–catalyst interface and of parameters of the synthesis. The model is sampled efficiently using kinetic Monte Carlo simulations in the semi-grand canonical ensemble, uncovering the interplay of the external experimental conditions and the configuration and energetics of the interface with the catalyst. In particular, the distribution of chiral angle dependent growth rates follows non-monotonic trends as a function of interface energies. We analyze this behavior and use it to identify conditions that lead to high selectivity for a variety of chiral angles.

Highlights

Single-Walled Carbon Nanotubes (SWNTs) are crystalline structures that can be seen as rolled up graphene sheets with a remarkably large aspect ratio, reaching up to tens of centimeters in length and a few nanometers in diameter
Chiral selectivity has been reported in catalytic chemical vapor deposition synthesis experiments, but the underlying mechanisms remain poorly understood
Since their first observation and characterization,1 tremendous research efforts went into the development of efficient synthesis techniques, the most prominent being the catalytic chemical vapor deposition (CVD), in which a carbon-rich gaseous feedstock (e.g., CO, CH4, and ethanol) is being decomposed at a high temperature, on the surface of a catalyst, often a transition metal, to nucleate and grow a tube

Summary

Introduction

Single-Walled Carbon Nanotubes (SWNTs) are crystalline structures that can be seen as rolled up graphene sheets with a remarkably large aspect ratio, reaching up to tens of centimeters in length and a few nanometers in diameter. Since their first observation and characterization, tremendous research efforts went into the development of efficient synthesis techniques, the most prominent being the catalytic chemical vapor deposition (CVD), in which a carbon-rich gaseous feedstock (e.g., CO, CH4, and ethanol) is being decomposed at a high temperature, on the surface of a catalyst, often a transition metal, to nucleate and grow a tube.. This is not always the case in the present instance, and the fact that perfect SWNTs with a defined structure can be grown up to a centimeter length implies a negligible concentration of topologically active defects in this size range

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