We study the temporal growth pattern of surface fluctuations on a series of spinodally unstable polymer films where the instability can be adjusted with the film thickness,ho.For the most unstable film studied(whose (H_0 - h_(sp))/h_(sp) = 0.988;h_(sp)is the thickness where the second derivative of the interfacial potential of the film equals zero),the growth rate function of the surface modes as a function of the wavevector fits well to the mean-field theory.When the film thickness is increased such that (H_0 - h_(sp))/h_(sp)<= 0.977,the mean-field theory demonstrates marked disagreement with experiment,notwithstanding the provision of the known corrections from nonlinear effects and thermal noise.We show that the deviations arise from large-amplitude fluctuations induced by homogeneous nucleation,which are not considered in the conventional treatments.
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