Hisao Kuriyaki

Synthesis of Ca-substituted pressure using CuI

Abstract Ca-substituted Y124 superconductors Y 1− x Ca x Ba 2 Cu 4 O 8 ( x = 0.05, 0.1) were synthesized at ambient oxygen pressure by a solid-state reaction method which used CuI instead of the conventional CuO. Experimental results showed a promoting effect of copper iodide on the formation of the 124 phase at normal oxygen pressure. T c determined from the Meissner effect was 88 K for x = 0.05 and 90 K for x = 0.1. For the same Ca-substitution rates T c(zero-resistance) of 80.5 K and 82.0 K was obtained respectively.

Photo-rechargeable battery using new layer compound CuFeTe/sub 2/

Summary form only given. Photoelectrochemical(PEC) system using a junction of semiconductor electrode and electrolyte can convert photoenergy to electrochemical(EC) energy. If electrode can in-situ storage EC energy, it has two functions ; energy conversion and storage in a single material. Many studies have been made to realize this type of photo-rechargeable battery. However, no remarkable results have yet been reported, because it is difficult to research useful materials. Ternary transition metal dichalcogenide CuFeTe/sub 2/(CFT) synthesized firstly by us is a layered material having Van der Waals gap and p-type semiconductive property. We have previously observed that Li atoms intercalate into this compound, then at present we try its usefulness as an active elecrode in the photo-rechargeable battery. Experiments were carried out on CFT|LiCl0/sub 4/(acetonitrile) | Pt system under illumination of Xe lamp(500W) and photo-charging effect was observed. For 30 minutes illumination, photonic-charged energy density is estimated to be 0.562 Wh/kg from dark-discharging current.

Electrical Anisotropy of Layered Compound ZrSe2 and HfSe2

The electrical resistivity and the Hall coefficient of the layered compound ZrSe 2 and HfSe 2 grown by iodine vapour transport method have been measured. High anisotropy in electrical resistivities has been found for these compounds. The Hallmobility exhibits a temperature dependence of the form µ∝ T -1.6 in ZrSe 2 as well as in HfSe 2 . It is well explained in terms of homo-polar-mode optical scattering.

Design and measurements of test element group wafer thinned to 10 /spl mu/m for 3D system in package

We designed and measured test element group wafers thinned to 10 /spl mu/m for 3D system in package. The n-well p-Si diodes in 10 /spl mu/m thick wafer showed increasing of the reverse saturation current in comparison to the currents in 20 /spl mu/m, 30 /spl mu/m or 640 /spl mu/m thick wafer. While the pMOSFETs and nMOSFETs in 10 /spl mu/m thick wafer showed no degradation of mobility, sub-threshold swing and threshold voltage. Defects might be induced by mechanical stress during wafer back grinding process near wafer back side, within a few micron-meters from the wafer back surface.

A “mechanical aligning” method for preparing high-Jc YBa2Cu3Ox superconductors

High-Jc YBa2Cu3Ox ceramic samples were prepared by a mechanical aligning method which involved of large crystal growing and vibration aligning. In these samples, the crystal grains were found to be highly oriented and closely packed. Accordingly, the maximum critical current density was found to be 4200 A/cm2 at the liquid nitrogen temperature.

Synthesis and characterization of BaVS/sub 3/ single crystals grown in melted Te

Abstract Single crystals of BaVS 3 were synthesized by a new technique; grown in melted tellurium. The crystals were obtained in the form of large needle with typical dimensions of about 10mm in length and 1mm in width. The electrical resistivity gradually decreased with decreasing temperature from 300K to 130K, which clearly showed a metallic behavior, but steepy increased at 70K. It was firstly found out that a change of the gradient in the temperature dependent resistivity occurred at 250K. This is caused by a structural transformation, demonstrating the crystals grown by our technique with high-quality.

Uniformity of an Electroless Plated Ni on a Pad Connected to Different Size Pads or a Pn Junction for Under Bump Metallurgy in a Flip-Chip Assembly

We investigated electroless Ni uniformity on Al metal pads connected to different size pads or a pn junction for under bump metallurgy in flip-chip assemblies. In an electrically isolated pad, Ni thickness decreased as the pad size decreased. Because of nonlinear diffusion of Pb2+ stabilizer in the plating solution, fewer electrons were supplied to the smaller pad than to the larger pad by an anodic oxidation reaction on the pad surface. In pads smaller than 50 mum square, the Ni thickness increased when connected to a 100 mum square pad. This increase might be caused by electrons flowing from the 100 mum square pad to the smaller pad to produce an equipotential for the connected pads. In addition, the Ni thickness was increased by electrical connection to an n-type Si in the presence of fluorescent light illumination for a pn junction area larger than 100 mum2. For a pad connected to a p-type Si, however, Ni thickness decreased in comparison to that of an electrically-isolated pad, regardless of the light illumination or pn junction area. The change of Ni height on pads connected to the pn junction is attributable to photoelectrons injected into the n-type Si, or to electron-hole recombination in the p-type Si. These results indicate that the pads should be of the same size within a chip for better Ni uniformity. Moreover, blocking light during Ni electroless plating can eliminate Ni thickness differences due to an n-type Si connection.

Influence of Crystallinity on the Electrical Property of KFe(S1-xSex)2

The electrical properties of KFe(S1-x Sex )2 (0≤x≤0.89) were studied on crystals annealed for a long period. The resistivity ρ along the c-axis shows high values: 1.6×104 Ωcm for x=0 and 8.6×101 Ωcm for x=0.89 at 290 K. The nonmetallic temperature-dependent resistivity is approximated by ρ∝exp [(T0/T)1/2], where T0 is a constant. Both the susceptibility and the Seebeck coefficient show metallic behavior. Observations using a transmission electron microscope indicate that the specimens consist of many grains. It is concluded that these compounds are essentially metallic. The high resistivity and the nonmetallic temperature dependence are ascribed to the imperfections in the crystal.

Microstructures and dissociated dislocations in YBa2Cu3O7−x prepared by a “grain-coating” technique

Abstract Microstructures of YBCO prepared by a “grain-coating” technique were observed through transmission electron microscopy. The coating material of Ag or Bi 2 O 3 is detected by EDS analysis only at grain boundaries and not inside grains in which abundant dislocations are found. Most of the dislocations are dissociated into partial dislocations with stacking faults. Two types of stacking fault are observed: One has a large width and is terminated by straight or smooth partial dislocations, the other is terminated by curved dislocations of which the separation is alternately large and small. The stacking fault vector is found to be 1 6 [0 3 1] , being consistent with an extra CuO layer in the 123 matrix. The coating material improves the weak-link at grain boundaries and increases the J c , while plenty of dislocations associated with stacking faults act as effective pinning centers and contribute to increasing the J c in a high magnetic field.

Resistivity Response to Oxygen of Transition Metal Dichalcogenide TiS2

The resistivity responses of layered compound TiS2 to oxygen and nitrogen gases were measured around room temperature. The resistivity showed a selective and reversible response to oxygen. This may be due to the fact that oxygen intercalates into van der Waals gaps in the layered structure of TiS2. The resistivity showed an increment of 1% oxygen partial pressure in 10 min at 50°C. From the comparison with a commercial oxygen gas sensor, it was shown to operate at a lower temperature with the response time as short as the commercial one.