Dual distributions for the metallic and semiconducting single-walled carbon nanotubes observed by Raman spectroscopy.

The prospective applicability of single-walled carbon nanotubes (SWNT) is highly dependent on its controlled synthesis.Effects of few macroscopic growth-conditions (such as catalyst composition, temperature of deposition etc.) reflected on thedistributions of SWNT (diameter, chiralities and semiconducting-metallic nature), are studied by Raman spectroscopicanalysis. We report the presence of two different diameter distributions for as-grown metallic and semiconducting SWNT, themetallic tubes having larger average diameters than their semiconducting counterpart. We hope that, in future, it should bepossible to selectively synthesize SWNT with pre-determined chirality, diameter and metallic/semiconducting nature.