The electronic structure change after plasma exposure in representative materials used in electronic devicescrystalline Si substrate and Si 3 N 4 filmis investigated by a first-principles approach. We prepared the starting structures of Si, α-, and β-Si 3 N 4 with various key species (Ar, Br, Cl, N, and O) in processing plasmas. We investigated the electron charge density distribution and density of state (DOS) with the interstitial species after optimizing the prepared initial structures. Model predictions showed that the interstitial species create the DOSs, and that the energy-band edge extends to the midgap. The creation of the DOSs was clearly found in the β-Si 3 N 4 structure model, while no obvious creation was obtained in the α-Si 3 N 4 structure. This creation of the DOSs is consistent with the current-voltage (I-V) characteristics of the damaged Si 3 N 4 films presumably consisting of αor β-Si 3 N 4 local structure. The distortion of the I-V curves was considered to be attributed to the creation of the DOSs, which play a role as carrier trapping/detrapping sites.

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In this study, NaI transparent ceramics were synthesized by the spark plasma sintering (SPS) method, and optical and scintillation properties were investigated. To evaluate the potential of the transparent ceramics, a NaI single crystal was also prepared by the vertical Bridgman-Stockbarger method. The diffuse transmittance of the transparent ceramic fabricated at 470 °C was equivalent to that of the single crystal. All the samples showed scintillation peaking at 320 nm due to self-trapped exciton (STE). In addition, scintillation peaks ascribed from lattice defects were detected at 450 nm for the transparent ceramics and 540 nm for the single crystal. The scintillation decay time constants of the transparent ceramic fabricated at 440 °C were 5.7, 18, and 189 ns. The light yield of the transparent ceramic turned out to be 910 photons/MeV and was two-thirds of the single crystal.

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Arboreal small mammals nesting in tree hollows usually line nests with materials such as leaves and shredded bark. Pteromys volans orii (Siberian flying squirrel), an endemic subspecies to Hokkaido, Japan, uses shredded bark. Since their nest materials have a very consistent shape, we suspect the squirrels use much effort to collect and shred the bark. To save effort, they may reuse nest materials made by other individuals. To test this, we mixed artificial nest materials (coloured cotton strings) into nest materials and observed the transfer of strings among nests. Of 39 nest boxes seeded with coloured cotton strings, number of strings decreased in 25 boxes (64.10%). Strings from 12 boxes were moved to other boxes. In addition, we found that P. volans orii possibly reused nest materials prepared by other individuals. Both nests and nest materials may be important re-useable resources for P. volans orii.