Cas and pressure effects on the production of single-walled carbon nanotubes by laser ablation

We report the production of single-walled carbon nanotubes (SiWNTs) under a rgon, nitrogen and helium atmospheres in the pressure range of 50 to 500 To rr using a continuous wave 10.6-mu m CO2-laser. Both argon and nitrogen can be equally used as buffer gas to synthesize SWNTs in high yield between 20 0 and 400 Torr. Below 200 Torr the amount of SWNTs in the soot is drastical ly decreased and the material is dominated by amorphous carbon. Negligible amounts of SWNTs were formed using helium. These gas and pressure effects a re assigned to changes on the local temperature environment. (C) 2000 Elsev ier Science Ltd. All rights reserved.