The Raman scattering of carbon nanotubes produced in different inert gasesand their pressures by arc discharge

First- and second-order Raman spectra of carbon nanotubes produced in heliu m and argon atmospheres at a pressure ranging from 11 to 92 kPa by are disc harge have been measured and compared with each other. The position and ban dwidth of the spectral lines depend on the kind of inert gases and their pr essure. The Raman spectra of the nanotubes produced in argon gas atmosphere are much more similar to that of polycrystalline graphite than those of th e nanotubes produced in helium gas atmosphere. The position and bandwidth o f nanotube Raman peaks change with gas pressure in are discharge because di fferent diameter distribution of nanotubes is produced at different inert g as pressure. The Raman spectra of nanotubes produced at high pressure is mu ch more like that of graphite than those produced in lower pressure.