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(Color online) (a) Valence EELS of crystalline Si and stoichiometric (b) and of Si rich silicon oxide, before and after annealing. The dominant bulk plasmon peak shifts from (corresponding to and Si, respectively) as the sample is annealed. The rectangle corresponds to the energy window used in energy filtered TEM. Spectra were normalized to their plasmon maxima.
(a) Conventional elastic scattering image and (b) energy filtered image at . Bright areas on the lower image correspond to elemental Si. The conventional elastic scattering image shows a low density of nanoparticles (circles), while the plasmon loss image shows a significantly higher density, most of which are amorphous or misaligned crystalline particles that were invisible to conventional microscopy. (Measurements were done without an objective aperture.)
(Color) Tomographic reconstruction from a series of plasmon loss images recorded at different sample tilts on the Tecnai F20. Nanoparticles are visualized by isosurface rendering at fixed threshold (blue shapes), while the actual reconstructed plasmon loss signal at is visualized by volume rendering (white “fog”). Complex, nonspherical morphologies are dominant.
(Color) (a) Zero tilt plasmon loss image, (b) top view, and (c) side view of the reconstructed nanoparticle. Projection (a) shows features that would probably be identified as two separate spherical particles. However, 3D reconstruction [(b) and (c)] reveals this to be a single particle with a “horseshoe” morphology. [The particle is visualized by surface rendering in (b) and by surface and volume rendering in (c). The edge of the square grid is .]
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