SiGe-collector trench gate insulated gate bipolar transistor fabricated using multiple target sputtering

A new type of trench gate IGBT (insulated gate bipolar transistor) which uses a SiGe layer for the collector is experimentally investigated. SiGe collectors with different Ge content are deposited by multiple cathode sputtering making low temperature processing possible. The change in turn-off characteristics with Ge content is also investigated. Results indicate that the use of a SiGe collector reduces the tail current at turn-off due to the reduced injection of holes to the n⁻ drift region.     

Optimization of coded GMSK systems

In this article, block and convolutional coding for Gaussian minimum shift keying (GMSK) in additive white Gaussian noise (AWGN) channels is investigated. The performance improvement that can be obtained without an increase in bandwidth is found for block and convolutional codes with various block lengths and constraint lengths, respectively, when a simple suboptimal demodulation scheme is used. For a fixed system transmission bandwidth, the tradeoff between the percentage of bandwidth to use for coding and the percentage to use for modulation is examined and optimized for various values of bandwidth.     

Fabrication of MOSFETs in Si/CaF2/Si heteroepitaxial structures

Aluminium-gate n-channel MOSFETs have been fabricated in Si/CaF2/Si heteroepitaxial silicon-on-insulator structures. The MOSFETs were fabricated by a process including thermal oxidation in wet oxygen ambient for the formation of the gate oxide. The maximum field-effect electron mobility as high as 580 cm2/V s was obtained.     

Correlation between maximum temperature increase and peak SAR with different average schemes and masses

This paper investigates the correlation between maximum temperature increases and peak spatial-average specific absorption rates (SARs), calculated by different average schemes and masses. For evaluating the effect of mass on the correlation properly, a three-dimensional Green's function is presented. From our computational investigation, no best average mass for peak spatial-average SAR exist from the aspect of the correlation with maximum temperature increase. This is attributed to the frequency dependent penetration depth of EM waves. Maximum temperature increase in the head including the pinna is reasonably correlated with peak spatial-average SARs for most average schemes and masses considered in this paper. Maximum temperature increase in the head only (excluding the pinna) is reasonably correlated with peak 10-g SARs for the average schemes considered in this paper. The rationale for this result is explained using the Green's function. The point to be stressed here is that the slope correlating them is largely dependent on the average scheme and mass. Additionally, good agreement is observed in the slopes obtained by using two head models, which have been developed at Osaka University and Nagoya Institute of Technology. However, weak correlation is observed for the brain, which is caused by the difference of the positions where peak SAR and maximum temperature increase appear. The 95th percentile values of the slope correlating maximum temperature increases in the head or brain and peak spatial-average SAR are quantified for different average schemes and masses.     

Preparation of Alumina Fiber-Reinforced Aluminum by Squeeze Casting and Their Machinability

Alumina fiber-reinforced aluminum alloy composites were prepared by squeeze casting, and the effect of the reinforcement on the machinability of the alloy was investigated. Two kinds of short alumina fibers, which have the same fiber size but different hardness, were used. Preform in which the fibers were in a random arrangement was formed with SiO₂ binder, and then was infiltrated with the alloy melt to prepare the composite. The fiber–matrix interfacial bond via the binder is sufficient and no reaction product was detected. The cutting force of the alloy was reduced by the fiber-reinforcement. The lower the hardness of the fiber in the composite, the lower the cutting force of the composite. The roughness of the machined surface was drastically decreased by the reinforcement. Observation of the chip formed on the machined surface indicated that the fiber suppressed the formation of the built-up-edge, and this fact would lead to the reduction in the surface roughness by the reinforcement. The chips were shortened by the reinforcement. The difference in hardness of the alumina fiber hardly affected the roughness and the chip morphology. The hardness of the fiber has a strong effect to decrease the tool life.     

Hybridized hydrogen production system with Fe—I. Photochemical reaction in concentrated phosphoric acid

An attempt was made to carry out the following photochemical reaction, 2Fe²⁺ + I^?₃ + light → 2Fe^3? + 3I^? in concentrated phosphoric acid in order to obtain hydrogen iodide as a gaseous product. By means of the above photochemical, and two other consecutive chemical reactions, water is decomposed into hydrogen and oxygen. Compared to the water-splitting system with dilute sulfuric acid, this system has an advantage of easy separation of hydrogen iodide from the reaction mixture. Experiments are made with various conditions of phosphoric acid, temperature, light intensity and concentrations of iodine.     

Fundamental welding R&D results for manufacturing vacuum vessel of JT-60SA

The real vacuum vessel (VV) manufacturing of JT-60SA has started since November 2009 at Toshiba. Prior to starting manufacturing, fundamental welding R&Ds had been performed by three stages. In the first stage, primary tests for screening welding method were performed. In the second stage, the trial welding for 1 m-long straight and curved double shell samples were conducted. The dependences of welding quality and distortion on the welding conditions, such as arc voltage and current, setting accuracy, welding sequence, and the shape of grooves were studied. In addition, welding condition with low heat input was explored. In the last stage, fabrication sequence was confirmed and established by the trial manufacturing of the 20° upper half mock-up [1]. This paper presents the R&D results obtained in the first and second stages.     

Surface modification of poly(ethylene terephthalate) by plasma polymerization of poly(ethylene glycol)

Poly(ethylene glycol) (PEG) was ‘polymerized’ onto poly(ethylene terephthalate) (PET) surface by radio frequency (RF) plasma polymerization of PEG (average molecular weight 200 Da) at a monomer vapour partial pressure of 10 Pa. Thin films strongly adherent onto PET could be produced by this method. The modified surface was characterized by infra red (IR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), cross-cut test, contact angle measurements and static platelet adhesion studies. The modified surface, believed to be extensively cross-linked, however showed all the chemical characteristics of PEG. The surface was found to be highly hydrophilic as evidenced by an interfacial free energy of about 0.7 dynes/cm. AFM studies showed that the surface of the modified PET became smooth by the plasma polymerized deposition. Static platelet adhesion studies using platelet rich plasma (PRP) showed considerably reduced adhesion of platelets onto the modified surface by SEM. Plasma ‘polymerization’ of a polymer such as PEG onto substrates may be a novel and interesting strategy to prepare PEG-like surfaces on a variety of substrates since the technique allows the formation of thin, pin-hole free, strongly adherent films on a variety of substrates.     

Suppurative lesions without prominent epithelioid cell response in abscess-forming granulomatous lymphadenitis

To clarify the clinicopathological significance of the suppurative lesions without an epithelioid granulomatous response (SLs without Ep) in lymph nodes and their relationship to abscess-forming granulomatous lymphadenitis (AGL) and cat scratch disease (CSD), 10 cases were assessed clinicopathologically and immunohistologically. SLs without Ep were located in the subcapsular sinus, paracortical area and medullary cords, but not in the germinal centers. The microabscesses were surrounded by collections of monocytoid B-lymphocytes (MBLs), histiocytes without epithelioid features, neutrophils, small lymphocytes and small numbers of plasma cells. The majority of the MBLs seen in the SLs without Ep were of the large cell type. The histological triad of toxoplasmic lymphadenitis, i.e., reactive follicular hyperplasia, small clusters of epithelioid cells and aggregates of MBLs, were also seen in all cases. Some of the clinical and pathological findings in our 10 cases were characteristic of CSD, i.e., (1) cat exposure before the lymphadenopathy was in four of the 10 cases, (2) occurrence in autumn and winter months in all cases, (3) typical suppurative granulomas surrounded by palisaded epithelioid cells were in four of the 10 cases, and (4) Warthin-Starry silver stain-positive bacteria were detected in seven of the 10 cases. The results of our study suggest that SLs without Ep are an early stage of CSD.