Carbon nanotubes (CNTs) have been grown by catalytical chemical vapor deposition (CCVD) with a thin iron layer as the catalyst. High surface tension metal, tantalum (Ta), and low surface tension, SiO2, have been deposited as the supporting layers before depositing the catalysts. SEM, TEM, STEM and EELS have been used to examine the morphology, structure, and chemical profile of iron nanoparticles and CNTs. The results have shown that the catalyst nanoparticle morphologies were distinctly different on two supports. In particular, Fe nanoparticles on SiO2 were found to follow a Vollmer-Weber (VW) growth mode and a Stranski-Krastanov (SK) growth mode on Ta. It was also found that CNT growth varied significantly on two supports in terms of morphology, growth rate and growth mode. Dense CNTs were grown on Ta with fast growth rates (> 1µm/min) and vertical alignment for the iron thicknesses of 1.5-9 nm. In contrast, CNTs grown on SiO2 exhibited a slow growth rate (< 100 nm/min) with all deposited iron thicknesses, indicating a severe catalyst poisoning. The results suggested that the catalyst morphology in combination with the presence of an iron wetting layer contributed to the enhanced CCVD growth of CNTs on Ta.