A lightly doped deep drain GaAs MESFET structure for linearamplifiers of personal handy-phone systems

An improved GaAs MESFET structure, named a buried p-layer lightly doped deep drain (BP-LD3) structure, is proposed. This structure can be fabricated by the conventional self-aligned gate and selective ion implantation technologies, and the FET characteristics show a high transconductance, a high breakdown voltage, and a low drain-source resistance. The lightly doped deep drain characterizing this structure was introduced on the basis of a two-dimensional numerical analysis including an impact ionization for a buried p-layer lightly doped drain (BP-LDD) structure which has been applied for high-speed digital ICs. The simulated results clarified that a low breakdown voltage of the BP-LDD structure originates from a high rate of carrier generation due to the impact ionization in the lightly doped drain region. The reason is that both electric field and current density become high in the region. In the new BP-LD3 structure, the electron current expands due to the deep formation of lightly doped drain, therefore impact ionization is reduced. This BP-LD3 structure was fabricated and the FET characteristics were compared with those of the conventional BP-LDD structure, and a structure which is now being studied for linear amplifiers of 1.9 GHz personal handy-phone systems. The measured breakdown voltage of 8.1 V, transconductance of 360 mS/mm, and drain-source resistance of 2.5 Ω/mm for the BP-LD3 structure indicate high potentiality for analog applications     

First-principles molecular dynamics simulation on interatomic interaction of Fe crystal with Pb and Bi atoms

The interaction mechanism between Fe crystals and Pb and Bi atoms was investigated using the first-principles molecular dynamics theory based on the density functional theory, which was the first step of an analytical approach to the simulation of steel corrosion in high temperature lead–bismuth (Pb–Bi) cooled fast breeder reactors and accelerator driven systems. The Vanderbilt ultrasoft pseudopotentials for Fe, Pb and Bi elements were calculated with the exchange and correlation corrections by the local density approximation. Crystal lattice constants calculated using the potentials agreed well with experimental ones. Using the calculated pseudopotentials, the first-principles molecular dynamics simulations were performed to investigate the interatomic interaction between Fe crystal and Pb, Bi atoms. The result shows the reasonable motions of Pb and Bi atoms near the surface of the Fe crystal and those of Fe atoms in the crystal.     

Development of a 1-week cycle menu for an Advanced Life Support System (ALSS) utilizing practical biomass production data from the Closed Ecology Experiment Facilities (CEEF)

Productivities of 29 crops in the Closed Ecology Experiment Facilities (CEEF) were measured. Rice and soybean showed higher productivities than these given by the Advanced Life Support System Modeling and Analysis Project Baseline Values and Assumption Document (BVAD), but productivities of some other crops, such as potato and sweet potato, were lower. The cultivation data were utilized to develop a 1-week cycle menu for Closed Habitation Experiment. The menu met most of the nutritional requirements. Necessary cultivation area per crew was estimated to be 255 m2. Results from this study can be used to help design the future Advanced Life Support System (ALSS) including the CEEF.     

On-Resistance Modulation of High Voltage GaN HEMT on Sapphire Substrate Under High Applied Voltage

The 620-V/1.4-A GaN high-electron mobility transistors on sapphire substrate were fabricated and the ON-resistance modulations caused by current collapse phenomena were measured under high applied voltage. Since the fabricated devices had insulating substrates, no field-plate (FP) effect was expected and the ON-resistance increases of these devices were larger than those on an n-SiC substrate even with the same source-FP structure. The dual-FP structure, which was a combination of gate FP and source FP, was effective in suppressing the ON -resistance increase due to minimization of the gate-edge electric field concentration. The ON-resistance after the applied voltage of 250 V decreased by twice that at low drain voltage by the dual-FP structure. Gallium nitride (GaN), high-electron mobility transistor (HEMT), high voltage, power semiconductor device.     

Single-Chip MPEG-2 422P@HL CODEC LSI With Multichip Configuration for Large Scale Processing Beyond HDTV Level

This paper proposes a new architecture for VASA, a single-chip MPEG-2 422P@HL CODEC LSI with multichip configuration for large scale processing beyond the HDTV level, and demonstrates its flexibility and usefulness. VASA is the world's first single-chip full-specs MPEG-2 422P@HL CODEC LSI with a multichip configuration. An LSI was successfully fabricated using the 0.13-mum eight-metal CMOS process. The architecture not only provides an MPEG-2 422P@HL CODEC but also large scale processing beyond the HDTV level for digital cinema and multiview/-angled live TV applications with a multichip configuration. The VASA implementations will lead to a new dimension in future high-quality, high-resolution digital multimedia entertainment.     

Where is a leak point detected by "the low flow leak test" of anesthetic machines?

"The low flow leak test" is recommended for pre-anesthetic inspection of anesthetic machines. We carried out anesthesia compression tests as a standard. Even in that case, often the low flow leak test does not meet the standard. We investigated the point where there is a leak in the anesthetic machine. Observing the leak that fluctuates each time there is detachment or attachment of the canister, the primary cause of the leak is thought to be related to the canister. It is important to carry out an inspection of the canister if the low flow leak test does not meet the standard.     

Deterministic Current-Induced Perpendicular Switching in Epitaxial Co/Pt Layers without an External Field

Current-induced spin-orbit torques (SOTs) have emerged as a powerful tool to control magnetic elements and non-uniform magnetic textures such as domain walls and skyrmions. SOT-induced switching of perpendicular magnetization generally requires an external field to break the rotational symmetry of the spin-orbit effective fields responsible for the deterministic reversal. The proposed mechanisms to eliminate this requirement often rely on complex multilayer structures that necessitate laborious optimization in the material and spin transport properties, making them less attractive for applications. Herein, current-induced, external field-free switching of an epitaxial MgO/Pt/Co trilayer with an extremely large perpendicular anisotropy in excess of 3 Tesla is reported. It is found that switching occurs due to the interplay of strong SOTs, local anisotropy fluctuations, and the Dzyaloshinkii-Moriya interaction inherent to this epitaxial system. Given that these layers constitute the base stack of a magnetic tunnel junction, this switching mechanism offers the most technologically viable path toward devices such as field-free SOT-based magnetic random-access memories.     

Interface reaction between oxide glasses and Fe-Al-Si magnetic alloy

The interface reactions between oxide glasses and magnetic alloy, Fe-Al-Si (so-called Sendust), were analysed. The oxide glasses used were SiO₂-PbO, SiO₂-Na₂O, SiO₂-Li₂O and B₂O₃-Na₂O binary glasses. It was observed that the lattice constant of the alloy decreases and the saturation magnetic-flux density of the alloy increases on reaction with the glasses. It was found that the aluminium atoms in the alloy diffuse to the interface and dissolve into the glass melt as Al³⁺ ions, leading to the iron-rich composition of the alloy. On the other hand, Pb²⁺, Na⁺ and H⁺ ions in the molten glasses were reduced at the interface. Metallic lead particles about 20 m in diameter were found to be dispersed in the SiO₂-PbO melt. Reduced sodium was thought to evaporate from the SiO₂-Na₂O melt, and H₂ gas bubbles were observed at the interface between B₂O₃-Na₂O melt and the alloy. These reactions were analysed based on the standard free energy diagrams of oxidation-reduction reaction, and expressed as 3Pb _glass ²⁺ +2Al_alloy 3Pb+2Al _glass ³⁺ 3Na _glass ⁺ +Al_alloy 3Na+Al _glass ³⁺ 6H _glass ⁺ +2Al_alloy 3H₂+2Al _glass ³⁺     

Fine-particle slurry wear resistance of selected tungsten carbide thermal spray coatings

The surface degradation of tungsten carbide based thermal spray coatings when exposed to fine-particle slurry abrasion has been investigated. The coatings that were studied contain binder-phase constituents consisting of either nickel or cobalt. The coatings were deposited onto test cylinders using a detonation gun device. After applying approximately 0.15 mm thickness of thermal spray coating, the coatings were ground, then diamond polished to achieve surface roughnesses of 0.03 μm Ra or less. The coatings were exposed to a three-body abrasive wear test involving zirconia particles (less than 3 μm diameter) in a water-based slurry. Results show that preferential binder wear plays a significant role in the wear of these tungsten carbide coatings by fine abrasives. In the comparison presented here, the coating containing nickel-based binder with a dense packing of primary carbides was superior in terms of retaining its surface finish upon exposure to abrasion. The coating containing a cobalt binder showed severe surface degradation.