Plasma-enhanced chemical vapor deposition (PECVD) method was employed to grow the Fe-catalyzed carbon nanotubes (CNTs). The grown CNTs with a uniform diameter in the range of about 10-20 nm and the typical lengths beyond 1 mu m resulted in a very high aspect ratio. The Raman and TEM results showed that the grown CNTs contained a large amount of carbonaceous particles and crystal defects, such as Pentagon-heptagon pair defects. XPS measurement indicated that the CNTs had C-H covalent bonds. Field emission characteristics exhibited the low turn-on threshold field of 2.75 V/mu m and the maximum emission current density of 7.75 mA/cm(2) at 6.5 V/mu m. The growth mechanism of CNTs and the effects of hydrogen plasma on their structure were discussed. (c) 2005 Elsevier B.V. All rights reserved.