Effect of the growth temperature on carbon nanotubes grown by thermal chemical vapor deposition method

We studied the effects of temperature on the growth of carbon nanotubes (CNTs) produced by thermal chemical vapour deposition technique. Very thin Co catalyst films with 3.5 nm thickness were deposited on SiO2/Si substrates by DC magnetron sputtering. CNT growth was performed in the flow of methane gas at growth temperatures of 825, 850, 875, 900 and 925 C. Our as-grown CNTs were characterized under scanning electron microscopy to study the morphological properties of CNTs. The topography of the as-grown CNTs at was also examined by AFM. We observed that as the growth temperature was increased from 850 C to 925 C, the average diameter of the carbon nanotubes was decreased continually from 20.4 nm to 10.5 nm. We also observed that the length of the CNTs was increasing, while radial distribution decreasing with the increasing temperature.