Effect of mixture ratios and nitrogen carrier gas flow rates on the morphology of carbon nanotube structures grown by CVD

We report on the growth of carbon nanotubes (CNTs) by thermal Chemical Vapor Deposition (CVD) and investigate the effects of nitrogen carrier gas flow rates and mixture ratios on the morphology of CNTs on a silicon substrate by vaporizing the camphor/ferrocene mixture at 750 C in a nitrogen atmosphere. Carbon layers obtained after each CVD growth run of 15 min are characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Growth of CNTs is found to occur on silicon substrates. The SEM micrographs helped better understand the nanotube growth morphology while Raman Spectroscopy was used to detect the presence of nanotubes and also identify their nature vizely semiconducting or metallic, single-walled or multi-walled. Raman Spectra was also useful to estimate the quality of the samples as a ratio of nanotube to non-nanotube content. The length and diameters of the aligned CNTs were found to depend on the pyrolysis temperatures, mixture ratio, and the nitrogen carrier gas flow rates.