In order to explore new application fields of a helicon-wave discharge, we have investigated the production of helicon-wave plasmas in very low magnetic fields (0-10 mT) and the resultant nanocarbon creation using methane and/or hydrogen. The reactive plasmas are effectively produced by the helicon wave around 3 mT independently of gas species in the wide range of pressures (0.1 -10 Pa), where hydrocarbons and atomic hydrogens are generated. Using the helicon-wave reactive plasma as a precursor source for plasma-enhanced chemical vapor deposition, well-aligned carbon nanotubes and nanowalls are found to be formed even in a very low gas pressure of 0.7 Pa. (c) 2005 Elsevier B.V. All rights reserved.