Plasmon excitations in coated nanocrystalline diamond spheres

Calculations based on the classic electrodynamic model are made to investigate the excitation probability for surface and volume plasmons for small diamond spheres coated with an amorphous layer. The model includes a well-defined impact parameter ρ₀ and includes coupling of interfacial modes. A detailed analysis of the multipole modes and coupling, taking into account the large damping factor of diamond, is required in order to explain why the low loss peaks due to individual plasmon modes are largely screened out for diamond. Good agreement is obtained with experimental spectra, allowing spherical particles to be identified and the nature of the amorphous layer to be identified. The theory can also be used to determine particle sizes to an accuracy of about 1 {}, both in the case of an isolated particle or a particle surrounded by a layer.