The properties of metal alloy (CoPt and inconel) and semiconductor (GaAs and InP) nanoclusters formed via femtosecond laser pulses were investigated. Ablation of the target materials was carried out both in vacuum (10(-4) Pa) and at set pressures in a number of background gases. The results of this work indicate that short laser pulses (low picoseconds/femtoseconds) alone are not enough to guarantee the production of films with stoichiometries matching those of the target materials. The production of stoichiometric alloy films depends on the similarity of the vapor pressures of the target constituents, while the production of stoichiometric compound films requires ablation in the presence of a background gas and compound constituents of comparable mass. (C) 2004 Elsevier B.V. All rights reserved.