Roles of laser light and heat in formation of single-wall carbon nanotubes by pulsed laser ablation of CxNiyCoy targets at high temperature

Laser ablations were performed on CxNiyCoy targets (x, y = 98.8, 0.6 or 91, 4.5) using a Nd:YAG pulsed laser. Influences of the laser-beam intensity and atmospheric temperature on the structures of target surfaces and carbonaceous deposits were compared. These influences were found to be similar except for the following; the diameter did not change enormously when the laser-beam intensity was varied, while it decreased and its distribution range was widened as the atmospheric temperature decreased. The quantity of carbon expelled from the target was determined mainly by the laser-beam intensity, and the quantity of Ni and Co removed from the target was affected by both the laser-beam intensity and the atmospheric temperature. These results indicate that the atmospheric temperature controls the chemical reaction of carbon by which single-wall carbon nanotubes are formed, while the laser-beam intensity controls the process by which carbon, Ni, and Co are expelled from the target.