Single walled carbon nanotubes (SWNTs) are an interesting material with many possible applications including nanoelectronics, flexible electronics and sensors. One of current challenges in application of SWNTs is the fact that their synthesis procedures yield SWNTs with a distribution of chiralities, radii, and properties, instead of a homogenous material. It is also not currently possible to selectively fabricate specific distributions for different applications. In an effort for understand and control SWNT growth, we explored a range of growth conditions in the chemical vapor deposition (CVD) growth of SWNTs, including the use of liquid carbon sources instead of gaseous carbon sources. Some of the condition variables explored were carbon source composition, carbon source concentration, growth temperature, and carrier gas composition. Using a combination of Raman spectroscopy and SEM imaging, we demonstrate a clear dependence of changes in the distribution of SWNTs on that growth conditions varied. Of particular interest was the ratio of semiconducting SWNTs to metallic SWNTs, which was determined by correlating Raman spectroscopy data with device measurements. Distribution changes were seen using a range of carbon source molecules and can be used to tune as required for different applications. The greatest single chirality enrichment was seen at high temperatures using 2-butanol as the carbon source, while the greatest range of chiralities was seen with ethanol as the carbon source. Correlating the SWNT distribution changes with the growth conditions varied also yields insight into the growth mechanism of CVD grown SWNTs. This insight and a better understanding of the SWNT growth mechanism will lead to a further realization of SWNT application potentials.
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