Carbon nanotubes (CNTs) were grown onto the SiO2/Si substrates with Ni or Fe catalyst by chemical vapor deposition (CVD). CNTs with spiral and bamboo-like structures have been observed when Fe or Ni is used as the catalyst. Both the CNT growths with the Fe and Ni catalysts are of the tip-growth mechanism. CNTs with closed tips and open tips are obtained when using Ni as the catalyst.