Single-wall carbon nanotubes synthesis by means of UV laser vaporization: Effects of the furnace temperature and the laser intensity processing parameters

Carbon single-wall nanotubes (SWNTs) have been successfully synthesized by means of KrF laser vaporization of a Co-Ni-doped graphite pellet in a flowing argon atmosphere. The effects of two key processing parameters, namely the furnace temperature (in the 25-1150 degreesC range) and the laser intensity (in the 0.8-4.4 x 10(8) W/cm(2) range), on the yield and the structural characteristics of the carbon SWNTs were investigated. By characterizing the obtained deposits by means of transmission electron microscopy and micro-Raman spectroscopy techniques, we were able to identify a threshold temperature as low as similar to550 degreesC, below which no carbon SWNTs can be grown. The increase of the furnace temperature from 550 to 1150 degreesC was found to lead not only to a significant increase in the SWNTs yield but also to the formation of larger SWNTs bundles. Raman analysis have also revealed that the diameter distribution peak shifts from similar to1.05 to similar to1.22 nm as the temperature is raised from 550 to 1150 degreesC. At the highest furnace temperature of 1150 degreesC, we also found that a minimum laser intensity of about 1.6 x 10(8) W/cm(2) is required to grow carbon SWNTs by means of the KrF laser. Higher laser intensities have resulted in a higher yield of SWNTs with relatively thicker bundles. Moreover, the increase of the laser intensity was found to promote the growth of 1.22 nm-diameter nanotubes to the detriment of thinner carbon nanotubes (1.05 and 1.13 nm-diameters).