[en] The electronic structure change after plasma exposure in representative materials used in electronic devices — crystalline Si substrate and Si₃N₄ film — is investigated by a first-principles approach. We prepared the starting structures of Si, α-, and β-Si₃N₄ 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-Si₃N₄ structure model, while no obvious creation was obtained in the α-Si₃N₄ structure. This creation of the DOSs is consistent with the current-voltage (I–V) characteristics of the damaged Si₃N₄ films presumably consisting of α- or β-Si₃N₄ 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. (author)

[en] In this study, NaI transparent ceramics were synthesized by the spark plasma sintering method, also 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 ℃ was equivalent to that of the single crystal. All the samples showed scintillation peaking at 320 nm due to self-trapped exciton. 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 ℃ were 5.7, 18, and 189 ns. The light yield of the transparent ceramic turned out to be 910 photons MeV⁻¹ and was two-thirds of the single crystal. (author)

[en] We have developed a dilatometric measuring system for thermal expansion and magnetostriction, those are more singular than specific heat in approaching to a quantum critical point. With decreasing temperature, thermal expansion becomes small in proportional to the square of temperature, thus, high sensitivity and reproducibility are necessary for the dilatometric measurements in millikelvin temperatures. Our dilatometer composed of the sample and the reference capacitor provides the extremely high resolution of ΔL/L ∼ 10"−"1"0 using the ratio-transformer-based capacitance bridge. The dilatometer was installed on the "3He-"4He dilution refrigerator with the 9 T superconducting magnet, and temperature was measured by the "3He melting curve thermometer. We have measured thermal expansion and magnetostriction of the typical heavy fermion compound CeRu_2Si_2 along a-axis at temperature down to 10 mK in magnetic fields up to 9 T