On the Origin of Preferential Growth of Semiconducting Single-Walled Carbon Nanotubes

TL;DR

This study links the preferential growth of small diameter semiconducting single-walled carbon nanotubes to thermodynamic stability differences revealed by density functional theory, explaining their higher abundance in low-temperature plasma-assisted synthesis.

Contribution

It demonstrates a thermodynamic basis for the preferential growth of semiconducting nanotubes, supported by experimental correlation and theoretical calculations.

Findings

Small diameter nanotubes are predominantly semiconducting.

Density functional theory shows semiconducting nanotubes have lower energies.

Thermodynamic stabilization scales with 1/d^2 for small diameters.

Abstract

A correlation is observed between the diameter (d) distribution of single walled carbon nanotubes and the percentages of metallic and semiconducting tubes in materials synthesized at low temperature (600 C) by plasma-assisted chemical vapor deposition. Small diameter nanotubes (average d~1.1 nm) show semiconducting-tube percentage much higher than expected for random chirality distribution. Density functional theory calculations reveal discernable differences in the cohesive energies and heat of formation energies for similar-diameter metallic, quasi-metallic and semiconducting nanotubes. Semiconducting nanotubes exhibit the lowest energies and the stabilization effect scales with ~1/d2. This is a likely thermodynamic factor in preferential growth of small diameter semiconducting nanotubes.