Substrate Effect on the Plasmon Resonance of Supported Flat Silver Nanoparticles

Substrate effect on the plasmon resonance of flat Ag particles is investigated experimentally, through the comparison between a system with particles on a substrate of amorphous carbon and a system with particles embedded in amorphous carbon. We demonstrate experimentally, in agreement with the theoretical predictions of Bobbert and Vlieger, that the conventional spherical dipole approximation fails to reproduce the interaction of the oblate spheroidal particles with the substrate. On the contrary, the use of a so-called spheroidal dipole approximation yields a very good agreement with the experiment, leading only to a slight red-shift of the plasmon resonance. Moreover, we show that the shape distribution of the flat particles deposited on the substrate can be successfully extracted from an experimental spectrum within this model.