Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666&hthinsp;°C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 &mgr;m in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. ©1998 American Institute of Physics.