Growth mechanisms of single-wall carbon nanotubes in a chemical vapor deposition (CVD) process on Fe/Mo-Al catalyst

Abstract

The formation mechanisms involved in the growth of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition (CVD) was studied. Transmission electron microscopy (TEM) was used to analyze the encapsulated metal catalyst particles found within the tubes, and the dimensions and location of these particles was determined. SWNTs were found to have encapsulated particles in the end of tubes, with large length to diameter ratios. As a result of these observations, we concluded that SWNTs are formed via an open-ended, base-growth mechanism (VLS mechanism). Additionally, we have demonstrated the formation of two kinds of bundles of SWNTs (Parallel bundles and as-rope bundles). SWNTs grown with thermal CVD on Fe/Mo-Al catalyst did not contain similar elongated particles or particles along the middle of the tubes, indicating that these new growth mechanisms are only applicable in the case of tubes grown via vapor phase CVD growth methods.