PhD ceremony Mr. O. Zinchenko: Computer simulation study of light scattering from nanoporous gold formed by chemical dealloying

PhD ceremony: Mr. O. Zinchenko, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Computer simulation study of light scattering from nanoporous gold formed by chemical dealloying

Promotor(s): prof. H.A. de Raedt

Faculty: Mathematics and Natural Sciences

The first part of this thesis focusses on the Metropolis Monte Carlo simulations of chemical dealloying of metal alloys, providing insight in porous network formation during chemical dealloying.

As a model system, the gold-silver alloy immersed in nitric acid was considered. The dealloying process was simulated in two stages: equilibration and dealloying. By changing the interaction parameters during the equilibration and dealloying stages, it was discovered that only a narrow range of these parameters yields acceptable, physically realistic nanoporous gold structures. The gold fraction in gold-silver alloy turns out to be an essential parameter for the dealloying process.

The second part of this thesis studies the light scattering properties of nano- porous gold using the finite-difference time-domain simulation technique applied to the structures obtained by Metropolis Monte Carlo simulations. The dependence of the porosity, the roughness of the entrance surface, the feature size of a nanoporous gold film and the polarization of the incident wave on the transmission and reflection spectra was investigated. A common characteristic of all simulation results is that in the short wavelength regime the spectra are fairly robust with respect to all these changes while in the long wavelength regime there are some qualitative changes. Un- fortunately, the latter cannot be explained in a simple terms, probably due to the fact that propagation of an electromagnetic wave through a complex structure such as nanoporous gold is very complicated process.