Excitation of the supported metal particle surface plasmon with external electron beam

Abstract

Classical energy loss theory is used to study the surface plasmon excitations of a supported spherical particle under the non-retardation approximation. The predicted results for the case in which the metal sphere (Al) is half-embedded in dielectric support (AlF 3) are in good agreement with the experimental results. Theeffects of the surface oxide layer and of the particle size on the electron energy loss spectrum shape are presented. It is shown that the dipole approximation is not valid in the study of the supported particle structure. The applicabilities of both the results predicted by coherent-state theory and the results of the classical energy loss theory given in this paper for the study of the supported particle are discussed. It is suggested that use of the coherent-state theory for calculating the excitation probabilities of the surface plasmons is in reasonable agreement with the EELS experiment on the supported particle system for thin supports. The classical theoretical results used in this paper are applicable only for the relatively thick supports. The agreement of the experimental EELS results with either of these two theoretical predictions depends on the relative coupling strength of the particle with the support.