Growth dynamics of single-wall carbon nanotubes synthesized by CO2 laser vaporization

Single-wall carbon nanotubes (SWNTs) were synthesized by the irradiation of a 20-ms CO2 laser pulse (1-kW peak power) onto a graphite-Co/Ni composite target at 25-1200 degrees C. Characterization of carbonaceous deposits using Raman scattering, scanning electron microscopy, and transmission electron microscopy showed that SWNTs were formed by laser irradiation even at room temperature. At 1100-1200 degrees C, the SWNT yield significantly increased (> 60%). A high-speed video imaging technique was used to observe the expanding vaporization plume and the emerging carbonaceous materials in an Ar atmosphere. Carbonaceous materials containing SWNTs became visible after similar to 3 ms from the initiation of laser irradiation of the target. At 1000-1200 degrees C, blackbody emission from large carbon clusters and/or particles was observed for more than 1 s after the end of the laser pulse. We suggest that the growth of the SWNTs occurs from a liquidlike carbon-metal particle via supersaturation and segregation. A continuous supply of hot carbon clusters to the particles due to the 20-ms laser pulse and the maintenance of the hot growth zone for SWNTs, performed with the help of a furnace, an thought to play a crucial role in the SWNT formation.