Aligned carbon nanofibers (ACNFs) were grown on silicon substrates coated with NiFe catalyst films by negative bias-enhanced hot filament chemical vapor deposition (CVD). The growth and structure of the aligned carbon nanofibers were investigated by scanning electron microscopy (SEM). The results indicate that the aligned carbon nanofibers could be synthesized after the glow discharge appears when the negative bias is higher than a certain value, while they are bent if the glow discharge does not appear. Furthermore, the diameters of the aligned carbon nanofibers are reduced and their lengths are increased with increasing the negative bias. It is shown that the glow discharge resulting from the negative bias plays an important role in the growth of aligned carbon nanofibers. Here, the effects of the glow discharge on the growth and structure of the aligned carbon nanofibers are discussed. (C) 2004 Elsevier B.V. All rights reserved.