[en] The plasma surface treatment, using hydrogen gas, of silicon wafers was studied as a pretreatment for silicon direct bonding. Chemical reactions of the hydrogen plasma with the surfaces were used for both surface activation and removal of surface contaminants. Exposure of the silicon wafers to the plasma formed an active oxide layer on the surface. This layer was hydrophilic. The surface roughness and morphology were examined as functions of the plasma exposure time and power. The surface became smoother with shorter plasma exposure time and lower power. In addition, the plasma surface treatment was very efficient in removing the carbon contaminants on the silicon surface. The value of the initial surface energy, as estimated by using the crack propagation method, was 506 mJ/M², which was up to about three times higher than the value for the conventional direct bonding method using wet chemical treatments

[en] Structural and optical properties of as-synthesized, Ga₂O₃-coated, and Al₂O₃-coated GaN nanowires are examined in this paper. GaN nanowires were synthesized by thermal evaporation of ball-milled GaN powders in an NH₃ atmosphere. The thermal annealing of the as-synthesized GaN nanowires in an argon atmosphere allows their surfaces to be oxidized, leading to the formation of 2 nm-thick Ga₂O₃ layers. For the oxidized GaN nanowires, the distances between the neighboring lattice planes are shortened, and an excitonic emission band is remarkably enhanced in intensity, compared with the as-synthesized GaN nanowires. In addition, the as-synthesized GaN nanowires were coated cylindrically with Al₂O₃ by atomic layer deposition technique. Our study suggests that the Al₂O₃-coating passivates some of surface states in the GaN nanowires

[en] Neutron diffraction(ND) has been utilized in this study to investigated the change of structural properties for GaN powders annealed in an NH₃ atmosphere at temperatures of 850, 950, 1050 and 1150 .deg. C for 2 hours; GaN powders annealed at 1050 .deg. C in a N₂ atmosphere for 2 hours were prepared, for comparison. Scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman scattering(RS) were performed additionally to help the interpretation of the spectra of the ND. The results of the ND experiments showed that the peaks in the ND spectra of the samples annealed in an NH₃ atmosphere became stronger and narrower as annealing temperature increased. It was observed from the ND experiments that the nitrogen-deficient phases such as Ga₂O₃ and GaO₂H were present in the sample annealed at 1050 .deg. C in a N₂ atmosphere, but that such nitrogen-deficient phases were absent in the GaN powders annealed in an NH₃ atmosphere. Our analysis of the ND data along with the SEM, XRD, and RS result revealed that the surface of the aggregates of the GaN powders annealed in a N₂ atmosphere was of N-deficient phases such as Ga₂O₃ or GaO₂H phases

[en] It is very important to observe the change in the atomic structure of melt-quenched amorphous Ge₂Sb₂Te₅ (GST) to discover the failure mechanism of phase-change random access memory (PRAM) devices during the reset process. We fabricated the phase-change devices and measured the initial resistance changes with various reset pulse amplitudes. For the observation of the atomic structure changes of GST thin films, we designed the specimens for transmission electron microscopy (TEM) and annealed them below and above the melting temperature of GST (T_m=650 C) before quenching. The annealed-and-quenched GST at 630 C has a hexagonal structure with a grain size of about 10 nm after the partial melting. The annealed-and-quenched GST at 750 C also has a hexagonal structure because of the latent heat. The observed atomic structures of GST are in accordance with the resistance changes inferred from the fabricated edge-contact type of PRAM cell. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] ZnO was added to 0.01Pb(Mg_1/2W_1/2)O₃-0.41Pb(Ni_1/3Nb_2/3)O₃-0.35 PbTiO₃-0.23PbZrO₃(0.01PMW-0.41PNN-0.35PT-0.23PZ) ceramics to reduce their sintering temperatures to below 900degC. The effects of the ZnO additive on the densification and piezoelectric properties of the PMW-PNN-PT-PZ+0.1wt% Y₂O₃+xwt% ZnO (0≤x≤2.5) ceramics were investigated. The structure of the PMW-PNN-PT-PZ ceramics was found to change from pseudocubic to tetragonal as their ZnO content was increased. The piezoelectric constant, the mechanical quality factor, and the electromechanical factor of the ceramics increased as their ZnO content increased. The optimum piezoelectric properties were found to be d₃₃=594 pC/N, k_p=57%, and Q_m=64, for PMW-PNN-PT-PZ+0.1wt% Y₂O₃+1.5wt% ZnO sintered at 900degC for 2 h. (author)

[en] The phase-change temperature and crystal structures of the δ-phase SbTe alloy for Sb contents of 64 at%, 72 at%, and 76 at% have been investigated. The δ-phase SbTe alloy has a rhombohedral crystal structure, and crystallization occurs in an extremely narrow temperature range of 140-145 C compared with Sb₄₀Te₆₀. We have determined the relationship between the Sb content and the crystalline structure using X-ray diffraction and selected area electron diffraction. When the Sb content increases, the number of Sb layers stacked with Sb₂Te₃ in the unit cell increases, which results in the lowering of the activation energy for crystallization and a lower ovonic threshold voltage. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The solid solution system of 0.05Pb(Al_.0.5Nb_0.5)O₃-0.95Pb(Zr_0.52Ti_0.48)O₃ (PAN-PZT) has been studied for the piezoelectric ultrasonic motor with its high T_c. In this article, we doped the Nb₂O₅ and MnO₂ into the 0.05PAN-0.95PZT ceramics as donor and acceptor respectively and reported the doping effect on the piezoelectric properties. Apparently, Nb₂O₅ induced the 'soft' piezoelectric characteristics. However, as Nb₂O₅ also affected the sintered density, which is closely related with the piezoelectric properties, it is quite difficult to identify the role of Nb₂O₅, which might act as the donor' and/or sintering enhancer. The optimized piezoelectric properties were obtained d₃₃=430 pC/N, k_p=59%, Q_m=79, and ε₃^T/ε₀=1690, when PAN-PZT+0.7wt% Nb₂O₅ sintered at 1200degC for 1 h. When MnO₂ was doped, Mn⁴⁺ ions induced the distortion of perovskite structure and Tc shifted to lower temperature. In addition, d₃₃ and k_p decreased and Q_m dramatically increased with the addition of MnO₂. From these results, it was believed that MnO₂ mainly acted as acceptor in PAN-PZT ceramics. The optimized piezoelectric properties were obtained d₃₃=340 pC/N, k_p=61.6%, Q_m=1725, T_c=392degC, and ε₃^T/ε₀=1250, when PAN-PZT+0.7wt% Nb₂O₅ with 0.5wt% MnO₂ ceramics sintered at 1200degC for 1 h. (author)

[en] One of the candidate materials for phase-change memory, In₃Sb₁Te₂ (IST), shows multilevel phase transformations from amorphous to several crystalline materials of IST, intermediate phases such as InSb, SbTe and InTe. However, its volume can change abruptly in the multilevel phase transformation, and this change can lead to vacancy movement and atomic migration, which are related to failures and reliability issues. We propose the carbon-incorporated In₃Sb₁Te₂ (IST-C) alloy, which has higher retention ability than the IST ternary alloy. Carbon atoms delay crystallization and prevent volume change during the set/reset operation. The carbon concentration is 12.5%, and the activation energy increases from 5.1 eV to 5.4 eV. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Characteristics of piezoelectric actuator on Si membrane were investigated. Si membranes were fabricated as a function of size using bulk micromachining method. Bottom electrode Ag-Pd and piezoelectric thick films were fabricated using screen printing method, respectively. Piezoelectric thick films were sintered by rapid thermal annealing (RTA). Top electrodes Pt were deposited by DC sputtering system. We analyzed micro structure by scanning electron microscope (SEM) and investigated dynamic properties by MTI2000. Therefore, piezoelectric thick film on Si membrane had P_r of 15.7 μC cm^-2. The maximum displacement of micro actuator had 0.05 μm. We find the combination of thick film printing and MEMS process to form a Si membrane micro actuator