Vertically aligned carbon nanotubes (CNTs) grown by water-assisted chemical vapor deposition have revealed differences in structure and morphology depending on the deposition rate of the Al buffer layer. Rearrangement of the Fe catalyst during CNT growth is mainly influenced by the buffer layer topography, which in turn depends on the buffer layer deposition rate. A higher deposition rate makes the substrate rougher and causes the growth of more aligned, low diameter CNTs with greater height. In contrast, slow deposition results in a smooth surface, which grows misaligned, large diameter CNTs with less height. Based on the results, a CNT growth model has been proposed. (C) 2012 Elsevier B.V. All rights reserved.