The effect of Ti layer on the growth of aligned carbon nanotubes on Si using Pd, Ni, or Co as catalysts by microwave-heated chemical vapor deposition was systematically studied. For all growths, a thin Ti layer of 16 or 22 nm, a thin catalyst layer of 6-30 nm, a growth time of 15-45 min, and a growth temperature of 590 or 690 degrees C were varying deposition parameters. It was found that the growths with Ni or Co as the catalyst on Ti-coated Si could always produce well-aligned carbon nanotubes. However, a carbonaceouslike film was found to exist on the top of nanotubes in most Ni-catalyzed carbon nanotube films. In contrast, carbon nanotubes grown from Pd catalyst were generally not aligned. Furthermore, the nanotubes grown from Pd at 590 degrees C are crooked or twist, and very short. (c) 2005 American Vacuum Society.