Yoshifumi Fujiyoshi

Improved high resolution image processing of bright field electron micrographs: II. Experiment

Abstract The new methods of nonlinear image processing are applied to high resolution experimental micrographs of chlorinated copper phthalocyanine taken on the Kyoto 500 kV electron microscope. With these new methods of image processing the phase and amplitude of the specimen transmission function are reconstructed from a defocus series of conventional transmission electron micrographs (bright field). Strong scattering, partial coherence and statistical noise have been included. Both of these new methods are based on the MAP (maximum a posteriori) criterion generalized to include reconstruction from multiple input images. In a companion paper (the first part of this two-part report) the theory behind these methods was presented and in this paper it is tested on actual experimental micrographs. A significant increase in resolution has been obtained with computer image processing. The point-to-point resolution obtained here with computer image processing of 500 kV electron micrographs is of the order of 1.2–1.4 A which represents a 30–50% increase in resolution.

Nonlinear high resolution image processing of conventional transmission electron micrographs: II. Experiment

Abstract A new method of nonlinear image processing is applied to high resolution experimental micrographs of chlorinated copper phthalocyanine taken on the Kyoto 500 kV electron microscope. With this new method of image processing the phase and amplitude of the specimen transmission function are reconstructed from a defocus series of conventional transmission electron micrographs. In a companion paper (the first part of this two-part report) this method was presented and tested on theoretically simulated images and in this paper it is tested on actual experimental micrographs. In each case a moderately significant increase in resolution has been obtained with computer image processing. The point to point resolution obtained here with computer image processing of 500 kV electron micrographs is of the order of 1.2–1.4 A.

Studying substrate effects on localized surface plasmons in an individual silver nanoparticle using electron energy-loss spectroscopy

In this study, electron energy-loss spectroscopy (EELS) in conjunction with scanning transmission electron microscopy (STEM) was used to investigate surface plasmons in a single silver nanoparticle (NP) on a magnesium oxide substrate, employing an incident electron trajectory parallel to the substrate surface. This parallel irradiation allowed a direct exploration of the substrate effects on localized surface plasmon (LSP) excitations as a function of the distance from the substrate. The presence of the substrate was found to lower the symmetry of the system, such that the resonance energies of LSPs were dependent on the polarization direction relative to the substrate surface. The resulting mode splitting could be detected by applying different electron trajectories, providing results similar to those previously obtained from optical studies using polarized light. However, the LSP maps obtained by STEM-EELS analysis show an asymmetric intensity distribution with the highest intensity at the top surface of the NP (that is, far from the substrate), a result that is not predicted by optical simulations. We show that modifications of the applied electric field by the substrate cause this asymmetric intensity distribution in the LSP maps.

Surface plasmon resonances in a branched silver nanorod

The properties of surface plasmon-polariton (SPP) resonance modes were investigated in a branched silver nanorod consisting of two nanorods using high energy resolution electron energy-loss spectroscopy (EELS) combined with scanning transmission electron microscopy. The experimental EELS maps of the SPP excitation showed a specific distribution depending on the resonance mode. The analytical formulas of the EELS signal and the resonance conditions for SPP resonance in the branched nanorod were derived by expanding the method reported for a one-dimensional straight resonator, and these were applied to interpret the experimental results. The SPP resonance in the branched nanorod can be attributed to Fabry-Perot type resonance that propagates in any of the three different resonance paths. It was also demonstrated that the modes of SPP resonance are changed by the position of the crossing point in the branched structure, which indicates that the combination of the lengths of the respective branches can be used to control the propagation path and the resonance energy of SPP waves in branched structures.The properties of surface plasmon-polariton (SPP) resonance modes were investigated in a branched silver nanorod consisting of two nanorods using high energy resolution electron energy-loss spectroscopy (EELS) combined with scanning transmission electron microscopy. The experimental EELS maps of the SPP excitation showed a specific distribution depending on the resonance mode. The analytical formulas of the EELS signal and the resonance conditions for SPP resonance in the branched nanorod were derived by expanding the method reported for a one-dimensional straight resonator, and these were applied to interpret the experimental results. The SPP resonance in the branched nanorod can be attributed to Fabry-Perot type resonance that propagates in any of the three different resonance paths. It was also demonstrated that the modes of SPP resonance are changed by the position of the crossing point in the branched structure, which indicates that the combination of the lengths of the respective branches can be use...