We have investigated how the morphology of transition metals prepared by radio-frequency magnetron sputtering influences on the vertically aligned carbon nanotube growth during thermal chemical vapor deposition (CVD). By changing the catalyst morphology systematically with sputtering temperature, pressure, and time, we were able to control the density, diameter, and length of the aligned carbon nanotubes at a given thermal CVD growth condition. We found that the sputtering temperature and pressure determine the grain size and density of the transition metals that control the diameter, length, and density of carbon nanotubes. Formation mechanism of nucleation seeds for carbon nanotubes in terms of these variables is further discussed. (C) 2004 Elsevier B.V. All rights reserved.