Abstract

Using the Discrete-Dipole-Approximation (DDA) the influence of the substrate on the dipole and multipolar plasmon resonances in spherical and sphere-like silver nanoparticles has been studied in depth. The effects of the contact area, the substrate material, the substrate thickness, the surrounding environment and the particle size on the plasmon resonance bands have been examined.
We studied in particular the validity of extending the so-called “universal scaling law”, derived for a pair of particles in previous works, to a linear chain of any size consisting of silver nanospheres. Details of the variation of the dipole plasmon resonance parameters with component particle size, interparticle separation and host medium, under parallel and perpendicular polarization directions of the incident light, have been studied in a systematic way. In a two-dimensional array of silver nanospheres, the interparticle separation dependency of the maximum absorption cross-section is presented. The variation of the absorption efficiency has been also investigated as a function of the component particle size and the surrounding medium. The effect of the host medium on the absorption cross-section has been found to be dependent on the component particle size. The sensitivity of the longitudinal dipole plasmon resonance wavelength to the refractive index of the host medium and the component sphere radius has been also expressed as a function of the interparticle separation.
Finally, the effect of the direct neighboring particles on the optical responses has been studied for various ensemble configurations, which can be arranged in two-dimensional or three-dimensional arrays.