Mass transfer in polycrystalline ytterbium monosilicate under oxygen potential gradients at high temperatures

Mass transfer in polycrystalline Yb₂SiO₅ wafers with precise composition control was evaluated and analyzed by oxygen permeation experiments at high temperatures using an oxygen tracer. Oxygen permeation proceeded due to mutual grain boundary diffusion of oxide ions and Yb ions without synergistic effects such as acceleration or suppression. The oxygen shielding properties of Yb₂SiO₅ were compared with those of the other line compounds such as Yb₂Si₂O₇ and Al₂O₃ based on the determined mass transfer parameters. It was found that the more preferentially an oxide ion diffuses in the grain boundary compared to the interior of the grain, the greater the effect of suppressing the movement of the oxide ion by applying an oxygen potential gradient becomes.     

Tunneling Conductance Dependence of the Tunneling Spectra in Bi2Sr2CaCu2O8

We have measured the tunneling spectra in Bi₂Sr₂CaCu₂O₈ with a scanning tunneling microscope(STM) at various tip-sample distances by changing the tunneling conductance in a controlled manner. When the tunneling conductance is increased from 1×10^–9 to 1×10^–5 S, the spectra do not show changes in particular. However, the gap value decreases steeply and the asymmetric back ground density of states turns inverted V-shaped one above 6×10^–4 S. The changes in the tunneling spectra at the high tunneling conductances are explained by the enhancement of the local carrier density induced by the pressure that the STM tip applied to the sample.     

Oxidation of doped europium in BaMgAl10O17 by annealing studied by x‐ray‐absorption fine‐structure measurements

Abstract— We studied the influence of annealing in air on doped europium in BaMgAl₁₀O₁₇ by performing x‐ray absorption fine‐structure measurements. We determined the oxidation of doped divalent europium by annealing in air at over 500°C. The interatomic distance between the europium and the surrounding oxygen atoms was compressed by oxidation. It also appears that the oxidation process of europium is determined by the diffusion of oxygen into BaMgAl₁₀O₁₇.     

A 300-MHz 25-/spl mu/A/Mb-leakage on-chip SRAM module featuring process-variation immunity and low-leakage-active mode for mobile-phone application processor

An on-chip 1-Mb SRAM suitable for embedding in the application processor used in mobile cellular phones was developed. This SRAM supports three operating modes - high-speed active mode, low-leakage low-speed active mode, and standby mode - and uses a subdivisional power-line control (SPC) scheme. The combination of three operating modes and the SPC scheme realizes low-power operation under actual usage conditions. It operates at 300 MHz, with leakage of 25 /spl mu/A/Mb in standby mode, and 50 /spl mu/A/Mb at the low-leakage active mode. This SRAM also uses a self-bias write scheme that decreases of minimum operating voltage by about 100 mV.     

Electrical characterization of homoepitaxial diamond p–n junction

Electrical properties of homoepitaxial diamond p–n⁺ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 10⁵ at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density N_i of the p–n⁺ junction is not uniform and N_i at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce N_i at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n⁺ interface and incorporating during the growth of p-type layer, which makes to reduce N_i at the vicinity of the p–n⁺ interface.     

Applications of computer and numerical analysis techniques in welding research

In recent years, computer technology has made remarkable progress and a computer has become an indispensable tool for both engineers and scientists. In this article, utilization of computers in welding research is briefly summarized. Their use in numerical analysis is particularly discussed and applied to physical phenomena in molten pool, hydrogen diffusion and residual stresses due to welding. A comparison is made between theoretical and experimental results.