A new type of electron beam-induced reactions is reported. Focused electron beams, the probe size of which is about 0.8 nm, were irradiated on carbon and Si substrates with an introduction of an aluminum trichloride or a gold trichloride gas in the chamber. Nanometer-sized carbon and Si rods were formed using carbon and Si substrates, respectively, by moving the beam position at a certain speed. As no aluminum, gold or chlorine was found in the rods, it is considered that chloride gases behaved as a sort of catalysis. (C) 2004 Elsevier B.V. All rights reserved.