Alternating thin films of the anionic squarylium (SQ) dye and poly(dially1dimethylammonium chloride) (PDDA) were formed by the sequential deposition of SQ and PDDA from aqueous solution onto a glass substrate. UV-vis absorbance measurements reveal that the bilayer deposition process was linear and highly reproducible from layer to layer. (c) 2005 Elsevier Ltd. All rights reserved.