A systematic investigation into the growth of single-walled carbon nanotubes (SWNTs) on thin metallic films deposited on various substrates was performed. Aluminum-iron-molybdenum multi-layer thin films were deposited on various substrates to determine which substrates promote the growth of SWNTs over multi-walled nanotubes (MWNTs) during the decomposition of methane gas. It was determined that the substrate employed as the supporting material for the Fe thin film catalyst has a strong effect on controlling the growth of either SWNTs or MWNTs, with clear trends noticeable. The ideal substrate for SWNT growth was a spun-on alumina film, while, single crystal substrates promoted the growth of mixed SWNTs and MWNTs. All remaining substrates grew primarily MWNTs. (C) 2003 Elsevier B.V. All rights reserved.