From nanoparticle to nanocable: Impact of size and geometrical constraints on the optical modes of Si/SiO2 core/shell nanostructures

In the extinction spectra of Si/SiO2 core/shell nanostructures, peak features in the near UV region (3-5 eV) appear when the nanostructure geometrical configuration changes from spherical nanoparticles to cylindrical nanocables, with the peak features become more intense in the nanocables of smaller core diameter. Similar feature at similar to 4.2 eV is also observed in the spatially resolved electron energy loss spectra (SREELS) of individual nanocable, but not in the nanoparticle. The EELS simulations unravel the origin of such excitation as the monopolar interface plasmon in cylindrical nano-objects, being responsible for the observed near UV extinction modes in nanocables. (C) 2009 American Institute of Physics. [doi:10.1063/1.3237162]