Silver nanoparticle layers were fabricated using spin coating and rapid thermal processing of poly(vinyl)-N-pyrrolidone/Ag nanoparticle composite thin films on glass. Fast thermal degradation of the polymeric matrix at 420 °C results in spontaneous aggregation of Ag nanoparticles, accompanied by strong enhancement and a shift toward longer wavelengths of the absorption peak due to surface plasmon resonance (SPR). Longer annealing times lead initially to fragmentation of the aggregates, and then to partial coalescence of the nanoparticles with a corresponding shift of SPR towards shorter wavelengths. We investigated the dependence of the shape, size, and absorbance spectra of these aggregates on the spin speed and the conditions of thermal processing. © 2005 American Institute of Physics.