Surface and volume plasmons in metallic nanospheres in a semiclassical RPA-type approach: Near-field coupling of surface plasmons with the semiconductor substrate

Abstract

The random-phase-approximation semiclassical scheme for description of plasmon excitations in large metallic nanospheres, with radius range 10-60 nm, is formulated in an all-analytical version. The spectrum of plasmons is determined including both surface and volume type excitations and their mutual connections. The various channels for damping of surface plasmons are evaluated and the relevant resonance shifts are compared with the experimental data for metallic nanoparticles of different size located in dielectric medium or on the semiconductor substrate. The strong enhancement of energy transfer from the surface plasmon oscillations to the substrate semiconductor is explained in the regime of a near-field coupling in agreement with recent experimental observations for metallically nanomodified photo-diode systems.

Mechanism of plasmon-mediated enhancement of photovoltaic efficiency

“…Using the above notation one can rewrite the electron part of the Hamiltonian (1), H e , in the following form [15]:…”

“…The matrix element of near-field dipole interaction for the transition of a semiconductor electron from the state in the valence to the conduction band, assumed as Ψ i(f ) (r, t) = (2π) −3/2 exp ik · r − iE i(f ) (k)t/h (i-initial, f -final, respectively) can be calculated by application of the Fermi golden rule, which leads to a probability of transition per time unit [15],…”

“…The advantage of this description [15,16] consists in full-analytic formulation allowing for application to more complicated physical situations, as e.g., plasmons interaction with surrounding medium, in order to describe plasmonic enhancement of photo-voltaic effect in the case of metallic particles deposited on the photo-active layer of the semiconductor, or for description of transport of plasmon-polaritons, with wide potential applications for subdiffraction nano-photonics [21]. It is indicated that the properties of plasmon oscillations in large nanospheres (i.e., with radii in the range of 10 − 60 nm) are governed by strong radiation-induced energy losses, not analysed previously for such sized metallic particles, despite wide plasmon descriptions e.g., within fully classical Mie-type approach to large metallic particles [22,23,24] and microscopic Kohn-Sham-type analyses of small and ultra-small metallic clusters [11,12,18].…”

“…The main factor for plasmon oscillations in large nanospheres was identified [15,16,17] as radiation phenomena, which for radius larger than 10 nm dominate plasmon damping as growing with the radius a as a 3 . The pronounced cross-over in the vicinity of 10 nm (for Au, Ag and Cu) has been predicted [16]-for smaller nanospheres, the scattering damping (including boundaries and so-called Landau damping [18]) is important, while for larger spheres, the radiation losses are overwhelming.…”

“…In the present paper we develop the RPA (random phase approximation) semiclassical theory of plasmons, formulated [15] for large metallic nanospheres in analogy to RPA theory of plasmons in bulk metal [19,20] (Pines-Bohm theory). The advantage of this description [15,16] consists in full-analytic formulation allowing for application to more complicated physical situations, as e.g., plasmons interaction with surrounding medium, in order to describe plasmonic enhancement of photo-voltaic effect in the case of metallic particles deposited on the photo-active layer of the semiconductor, or for description of transport of plasmon-polaritons, with wide potential applications for subdiffraction nano-photonics [21].…”