Synthesis and Characterization of Vertically Aligned Carbon Nanotubes by Chemical Vapor Deposition (CVD)

In this study, the effect of Co catalyst thickness, growth time, Al- blocking layer and carrier gas (Ar) on growth of CNTs upon Si substrate using ethanol as carbon source by chemical vapor deposition (CVD) was investigated; the thickness of Co film and growth time were varied from 1 to 10 nm and 10 to 120 min respectively. Structural information of CNTs, morphology and size distribution of catalysts were studied by scanning electron microscopy (SEM) and Raman spectroscopy. It was found that grain size of Co nano-particles and density and alignment of CNTs depend on thickness of Co film. Vertically aligned CNTs have been grown on 1 and 5 nm Co films and by increasing Co thickness to 7 and 10 nm, spaghetti like structure of CNTs is observed. By increasing the growth time from 10 to 100 min, the density of spaghetti structure is increased, and results of this study show that Co poisoning and CNT burning occur for growth times more than 100 min. In absence of Al layer no CNT growth was observed and without carrier gas during ethanol feed into CVD chamber, low density of CNTs with spaghetti-like structure was seen.