Experimental evidence for dynamic modification of a growing thin film into ordered nanoclusters is presented. Co nanoclusters of approximately 50 nm diameter were assembled into one-dimensionally ordered arrays spaced 400 nm apart on Si(100) substrates during film, growth. This ordered arrangement was achieved under e-beam evaporation of Co with simultaneous two-beam laser interference irradiation of the substrate. The ordering length scale was consistent with the two-beam fringe spacing of 400 nm. In comparison, the unirradiated film shows a random distribution of Co clusters with average diameter of 17 nm. The mechanism for assembly is tentatively attributed to thermal effects arising from the spatially periodic laser interference heating of the substrate and/or film. This one step process, without the need of any pre- or postpatterning of the substrate or film, is promising as an economical and simple approach to assemble ordered nanostructured films. (c) 2005 American Vacuum Society.