Evolution of electric field assisted dissolution of nanoparticles investigated by spectroscopic ellipsometry

The evolution of electric field assisted dissolution (EFAD) of nanoparticles process is studied by means of spectroscopic ellipsometry. Multilayer structures with embedded Ag islands flms are prepared by electron beam evaporation and subjected to EFAD process using different voltages and treatment times. Modelling of ellipsometric data evidences the dissolution process by the progressive quenching of the localized surface plasmon resonance of nanoparticles. Further quantitative information is revealed by the analysis of the effective dielectric function of Ag islands films in terms of the spectral density function. The amount of dissolved metal appears to follow a non-linear dependence with the applied voltage. Ag islands become elongated in the film plane as dissolution takes place. In the case of multiple Ag islands films, the process takes place in a sequential way, starting from the film closest to the glass substrate. Accumulation of Ag in a near-surface glass region is revealed by the presence of a refractive index gradient. Overall, the study demonstrates the usefulness of ellipsometry for providing novel insights into the EFAD process.