To enhance the carbon nanofilaments (CNFs) formation density, SF6 was incorporated in the source gases (C2H2/H-2) during the initial deposition stage. The source gases and SF6 were manipulated as the cyclic on/off modulation of C2H2/H-2/SF6 flow in a thermal chemical vapor deposition system. The characteristics of the CNFs formation on the substrate were investigated according to the different cyclic modulation processes and the substrate temperatures. By the incorporation of SF6 in the cyclic process CNFs could be formed at the substrate temperature as low as 350 degrees C. Among the different processes, mutual alternating cyclic modulation process of C2H2 and SF6 could most highly enhance the CNFs formation density. The cause for the enhancement in the characteristics of as-grown CNFs by the incorporation of SF6 was discussed in association with the slightly enhanced etching ability by the incorporation of SF6. (C) 2010 Elsevier B.V. All rights reserved.