Single-walled carbon nanotubes were grown using chemical vapor deposition with acetylene as the carbon source and cobalt as the catalyst and were analyzed ex situ, without any modification or processing, using Raman spectroscopy. The defect density exhibited an activated temperature dependence (activation energy of ∼0.8eV or ∼80kJ/mol) with fewer defects at high growth temperatures for a wide range of experimental parameters. This was consistent with a single activated mechanism, such as the catalytic healing of defects, possibly a single simple defect. Consistent with previous reports, it was observed that low growth temperatures produced smaller-diameter single-walled carbon nanotubes than did high growth temperatures. Elementary thermodynamic considerations of the strain energy in the lattice constrained the single-walled carbon nanotube diameter distribution and its temperature dependence and appeared to be consistent with the present observations. A so-called phase diagram for single-walled carbon nanotube growth was constructed and this suggested methods for controlling the diameter distribution. There was a necessary trade-off between small-diameter single-walled carbon nanotubes and single-walled carbon nanotubes with low defect densities.

Thermodynamic and Energetic Effects on the Diameter and Defect Density in Single-Walled Carbon Nanotube Synthesis. P.Vinten, P.Marshall, J.Lefebvre, P.Finnie: Journal of Physical Chemistry C, 2013, 117[7], 3527-36