Optical Properties of Supported Metallic Nanoparticles: Towards Quantitative Modeling

The French partner aims at understanding the vapor deposition growth and morphological behavior of metallic nanometer-size islands on oxide supports. Motivated by industrial applications, two main research directions of are developed: - the understand ing of wetting at metal/oxide interfaces; - the problem of gas adsorption and oxidation in the framework of heterogeneous catalysis. However, in situ studies of the growth process itself or gas exposure are rather challenging since non-invasive and real time methods are required. Instead of using time consuming near field imaging technique, this team has developed of a know-how of optical characterization through the excitation of plasmon resonances inside the nanoparticles. With Surface Differ ential Reflectivity Spectroscopy (SDRS), the relative change of the sample reflectivity is recorded in the UV-visible range as function of time, and even with sub-monolayer sensitivity. By a comparison with in situ small angle X-ray scattering, the group demonstrated the optical techniques have the potential of giving good precision for the overall morphology if spectra are analyzed with suitable models. The idea is to go beyond the limitations of the previously developed GranFilm software and to revive a previous collaboration on the theory of optical properties of granular layers in the light of new experimental developments in the Paris group. The Norwegian partner brings the needed background in electromagnetic simulations and the French group the ex perimental questioning. Two original directions involving theoretical development and numerical implementations are foreseen during this project: - calculating the optical response of core-shell particles, - handling theoretically the size distrib ution found in the real samples. The final goal is to have a freely available numerical simulation tool that could suit to the experimental needs in terms of calculation of optical Fresnel coefficients.