Time period for the growth of single-wall carbon nanotubes in the laser ablation process: evidence from gas dynamic studies and time resolved imaging

Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni-Co-graphite composite targets at 1200 degreesC under argon gas. The effe cts of the temperature gradient near the target and the gas how rate on the diameter distribution of SWNTs were studied in order to understand their g rowth dynamics. Raman spectroscopy was used to analyze the diameter distrib ution of SWNTs. The flow rate was found to affect the relative yields of SW NTs having different diameters when the temperature gradient around the tar get was large. Scattering images from the ablated species at different flow rates, recorded by a high-speed video camera, indicated that 10 ms after t he ablation the velocities of backward moving species increased with increa sing flow rate. These findings are used to estimate the time required for d etermining the diameter distribution and the growth of SWNTs. (C) 2000 Else vier Science B.V. All rights reserved.