Begrenzung effect in Si3N4 encapsulated plasmonic Sn nanoparticles

Previous studies of metal nanoparticle plasmonic properties yielded various nontrivial effects beyond the simple dipole response to light, such as the higher-order plasmon modes and dark and bright localized surface plasmons. Another intriguing plasmonic effect is the reduction of bulk plasmon (BP) resonances strength due to the Begrenzung effect, a phenomenon of the BP resonance modifications at the surface, which has been experimentally observed before and mathematically derived. In this work the LSP and BP resonances of tin nanoparticles were studied with electron energy loss spectroscopy (EELS) up to 45 eV. The effect of the Begrenzung effect on the plasmon resonances is here determined by reduced experimental EELS signals on Si3N4 encapsulated tin nanoparticles, which is explained by a detailed analysis of simulations. These simulations reveal an ubiquitous manifestation of the Begrenzung effect at multiple energies. The disentanglement of the multiple plasmon resonances in the SiNx covered tin nanoparticles give evidence of a rich plasmon occurrence which has been comprehensively mapped, that could lead to precise tailoring of plasmon properties up to extreme ultraviolet energies.