An interlayer of amorphous carbon (a-C) nanotips is used to assist the growth of carbon nanotubes (CNTs) on the Cu/Ti/Si(100) substrate by using microwave plasma-enhanced chemical vapor deposition (CVD). Without the interlayer of a-C nanotips, no CNTs are grown on Cu/Ti/Si(100) due to the very low catalytic efficiency of Cu. The a-C nanotips mainly act as the effective medium for Cu to diffuse and to assist the formation of Cu nanoparticles on the surface. The Cu nanoparticles are the catalysts for the growth of CNTs under "tip growth" mode, observed in the transmission electron microscopy experiments. The CNTs are identified to be multiwalled CNTs. The growth rate of CNTs decreases with time, and the a-C nanotips disappear with time during growth of CNTs. A growth model is proposed to explain the role of a-C nanotips on the catalytic growth of CNTs on Cu/Ti/Si(100). (c) 2006 The Electrochemical Society.