We have studied the effects of the SiO2/Si interface parallel to an electron beam on transmission electron energy-loss spectra of a SiO2 area for poly-Si/SiO2/Si samples. The dependence of the energy-loss spectra on the distance from the interface to the probe position and on the distance between two interfaces was investigated. Spectra obtained from the center of the thick (150 nm) SiO2 layer had no peak in the energy region of 4–10 eV. However, a peak at about 7 eV was observed in the spectra obtained at a position of 7.5 nm from the SiO2/Si interface for the same specimen. This peak was assigned to a SiO2/Si interface plasmon excitation. For the thin (15 nm) oxide poly-Si/SiO2/Si sample, on the other hand, the peak appeared at 8.7 eV. Furthermore, this peak shifts to higher energies as the oxide thickness decreases. This peak was assigned to an excitation of a symmetric interference plasmon mode in two close planar SiO2/Si interfaces.
Spatiotemporal structures formed in ionization waves are experimentally investigated in this study. A system involving ionization waves in a discharge tube has a few degrees of freedom in time and space. In our experiment, neon plasma is produced in a glass tube by a glow discharge between electrodes after the tube is evacuated to form a high vacuum. Spatiotemporal signals for the analysis are sampled as fluctuations in the light intensity by using a line-scan camera and photodiodes. The largest Lyapunov exponents are calculated from the time-series data sampled from the line-scan camera and photodiodes. Reconnection in the spatiotemporal structure is observed, which is caused by Eckhaus instability. Topological defects in the spatiotemporal structure are observed, which result in the appearance of spatiotemporal chaos; this leads to an order structure when an electric pulse is applied to the system as an external force or when coupled oscillators are synchronized.
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