Surface enhanced Raman scattering from crystal violet molecules adsorbed on Ag thin films was studied employing the attenuated total reflection configuration. Systematic variations of the enhanced Raman intensity with time were observed on the samples in which the crystal violet molecules were accumulated into aggregated clusters. The intensity first progressively increases to reach a maximum value, stays at the maximum for certain periods of time, then gradually decreases to a plateau, and stabilizes. The intensity variation period is different from one sample to the others, and it can take as long as several weeks before the intensity stabilizes. On the other hand, no intensity variation was observed on the samples in which the crystal violet molecules were less stacking and uniformly distributed over the film surface. We attribute the observed variation of the enhanced Raman intensity to the redistribution of the. crystal violet molecules adsorbed on the films.
