Electrostatic plasmon resonances of metal nanospheres in layered geometries

Electrostatic plasmon resonances of metal nanospheres situated in a stratified medium are analyzed theoretically utilizing a Green's function surface integral equation method. An efficient scheme for direct calculation of both particle plasmon eigenfrequencies and absorption cross sections is presented. By means of symmetry considerations we reduce the three-dimensional analysis to a single integral along the polar angle of the nanosphere and we show how all effects of the stratified surrounding can be built into the Green's function. We exemplify our approach by calculating the plasmon eigenfrequencies and absorption cross sections of silver nanospheres above a silicon surface and within a thin silicon film. The analysis of such configurations is important for plasmon enhanced solar cells.