Abstract
Various vertically aligned carbon nanotubes (VACNT) are prepared to utilize iron seed catalysts of selected layer thicknesses at controlled chemical vapor deposition growth conditions. The growth processes are improved by optimizing the argon-to-hydrogen and hydrogen-to-hydrocarbon ratios and water vapor flow rates. The effects of gas flow ratios, water vapor flow rates, and growth time on VACNT growth rates and aspect ratios are determined. The analytical studies include Raman spectroscopy to assess the characteristic bands of carbon nanotubes, as well as scanning electron microscopy to evaluate the array structures of carbon nanotubes. Findings show that VACNT with 422 x 10(3) aspect ratios can be achieved with Ar/H-2 of similar to 15 and H-2/C2H4 of similar to 2 at 10-20 sccm of water vapor.