Vertically-aligned carbon nanotubes (VA-CNTs) have been attracting attention as the electrode material of polymer electrolyte fuel cell. Fe nanoparticles (FeNPs) were used as catalyst for VA-CNT growth. FeNP monolayer film was deposited on substrates by Langmuir-Blodgett (LB) technique. VA-CNTs were synthesized from FeNP LB films by thermal chemical vapor deposition (CVD) method. Number density of VA-CNTs was lowered because of thermal aggregation of FeNPs during thermal CVD. We mixed FeNPs with arachidic acids (C20) as filler molecules, and synthesized VA-CNTs from FeNPs-C20 LB films, therefore we could reduce thermal aggregation and control the number density of FeNPs. (C) 2013 Elsevier B. V. All rights reserved.