Heavy arsenic doping of silicon grown by atmospheric pressure selective epitaxial chemical vapor deposition

Selective epitaxial Si with a high arsenic concentration of 2.2×10¹⁹ atoms/cm³ was deposited at a high growth rate of 3.3 nm/min under atmospheric pressure. It was confirmed that this method had excellent selectivity and produced films having good crystalline quality, abrupt dopant profiles at the interfaces, and smooth surfaces. The growth mechanism is discussed in terms of the relationship between the effects of arsenic surface segregation and etching by hydrogen chloride.     

Synthesis of High-Purity Zirconium Fluoride for Fluoride Glass Fibers by Chemical Vapor Deposition

A technique for synthesizing ultra-high-purity ZrF₄ using chemical vapor deposition in a ZrBr₄–HF system is developed and a purification mechanism is clarified. The Fe concentration in ZrF₄ is evaluated at less than 10 ppb based on analysis of the transmission loss spectrum of a fiber prepared using synthesized ZrF₄. Purification is achieved mainly in a sublimation process of ZrBr₄, and purification efficiency is determined by sublimation temperature and activity of impurities in ZrBr₄. The concentration of transition-metal impurities in ZrF₄, synthesized by chemical vapor deposition in the ZrBr₄–HF system, is expected to be less than 1 ppb.     

Softening phenomenon by remilling of styrene–butadiene copolymer rubber–general-purpose polystyrene resin blend

The softening phenomenon by remilling of uncured blends of various commercia styrene—butadiene copolymer rubber (styrene content, 23.5 to 48 wt-%, styrene block 0 to 18 wt-%) with general-purpose polystyrene resin was mainly studied by examining the blend ratio dependence of hardness and compression modulus (in logarithmic form), with special attention to the state of dispersion of the polymers. It was found that the blend of styrene—butadiene copolymer rubber with general-purpose polystyrene resin forms a microheterogeneous polymer blend system and that the hardness and the compression modulus change in S-shaped curves versus blend ratio. However, the degree of softening phenomenon by remilling (roll surface temperature, 70°–90°C) was found to be different for the two blend systems, i.e., random styrene—butadiene copolymer rubber and block styrene—butadiene copolymer rubber. The softening phenomenon is more pronounced in random-type rubbers; and in some block-type rubbers, no softening phenomenon was observed. The influence of the styrene content of the polymer is small. Further discussions have shown us that the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of the general-purpose polystyrene resin controls the state of dispersion of polymers thereby causing this difference in the softening phenomena among the different kinds of styrene—butadiene copolymer rubbers.     

Study on high performance ice slurry formed by cooling emulsion in ice storage (discussion on adaptability of emulsion to thermal storage material)

This study focuses on an emulsion as a new thermal storage material for ice storage. Two types of emulsions were formed using an oil–water mixture with a small amount of additive. A silicone, light and lump oils were used. The water contents of the emulsions were 70, 80 and 90%. The additive was an amino group modified silicone oil. No depression of freezing point was observed for the emulsions because of their hydrophobic properties. In order to determine the structure of the emulsions, their electrical resistances were measured. Moreover, components of the liquids separating from the emulsions were analyzed. The results indicated that one emulsion was a W/O type emulsion, while the other was an O/W type. Finally, adaptability of the two emulsions to ice storage was discussed, it was concluded that a high performance ice slurry could be formed by the W/O type emulsion.     

金属注射成形冷作工具钢的超声疲劳性能

用超声疲劳试验研究了金属注射成形(MIM)冷作工具钢和锻轧钢(JIS SKD11)的高周疲劳性能。锻轧钢试样于423K回火1h。另一方面，为了评估回火温度对疲劳性能的影响，将MIM钢试样于不同温度下进行了回火。在N=103～108疲劳寿命范围内进行了超声疲劳试验。MIM钢试样的疲劳强度和锻轧钢试样相同。MIM钢试样的疲劳强度随着回火温度升高而减低。显微组织的观察结果表明，MIM钢试样的碳化物的直径与形状比锻轧钢试样的均一。     

Formation of Tetravalent Fe Ions in LaFeO3 Perovskite Through Mechanochemical Modification by Ball Milling

Mechanochemical modification of previously synthesized LaFeO₃ perovskite‐type oxide by a high‐energy ball milling was investigated to introduce Fe⁴⁺ ions or transform some Fe³⁺ into Fe⁴⁺ in LaFeO₃. X‐ray absorption fine structure studies revealed that the formation of Fe⁴⁺ ions into LaFeO₃ perovskite has been achieved at first time by ball milling at room temperature without any additives or replacement of La³⁺ ions by some divalent cations. The structural model of Fe⁴⁺ containing LaFeO₃ could be described as with a modified perovskite having equal amounts of La and Fe vacancies, which is supported by a good correlation between the results of Fe K‐edge XANES spectra and O₂‐TPD. The synthesis of Fe⁴⁺‐containing LaFeO₃ perovskite by ball milling was able to produce the O₂ adsorption capacity of nonsubstituted perovskite‐type oxide.     

Physiologic stress responses to laparoscopic cholecystectomy. A comparison of the gasless and pneumoperitoneal procedures

BACKGROUND: Differences in the physiological stress response to pneumoperitoneal (PP) and gasless abdominal wall-lifting (AWL) procedures used for laparoscopic cholecystectomy have not been properly evaluated. METHODS: We compared leukocyte count, interleukin-6 (IL-6) levels, arterial blood gases, creatinine clearance, plasma renin activity, cardiothoracic ratio, and clinical outcome in 27 patients without systemic complications who underwent laparoscopic cholecystectomy, including 11 by AWL and 16 by PP. RESULTS: Transient leukocytosis and high IL-6 levels were observed at POD 1 (postoperative day) in both groups, but both values returned to baseline by POD 2. IL-6 levels correlated significantly with operation time (p < 0.01). Changes in blood gases, creatinine clearance, plasma renin activity, and cardiothoracic ratio were not different for the two groups. The clinical outcome was similar for both groups. CONCLUSIONS: Our results indicate that both PP and AWL are appropriate for patients without serious complications.     

Study on anisotropy of growth rate of ice crystal in supercooled water

The purpose of this research was to investigate the ice growth of a single crystal in three dimensions. Three-dimensional pattern of ice crystal growth in supercooled water was observed using Mach–Zehnder spectro-interferometer. Temperature was varied from −0.3 to −1.6 °C. It was found that the ice crystal began to grow as a single crystal at the tip of the capillary tube and propagated freely in supercooled water. Time variation of the shape of dendrite on a–c plane was obtained. It was found that half parabola fits the shape very closely, and the coefficient of squared term, a, of a quadratic function was calculated. The coefficient, a varied in time but at quasi steady state it was found to be depending mostly upon the degree of supercooling. Furthermore, the growth velocity in c-axis at the flat surface was calculated from the thickness measured. It was found that the velocity in c-axis is independent of the degree of supercooling but depends upon time, in other words, the thickness in c-axis.     

Mechanism of superconductivity in the polyhedral-network compound Ba8Si46

The silicon clathrates--materials composed of metal-doped Si(20) dodecahedra--were identified as the first superconductors based on pure silicon networks. The mechanism of superconductivity in these materials can be obtained by studying their phonon modes, as modified by isotope substitution, and specific-heat measurements. Here, we present experimental studies that provide strong evidence that superconductivity in Ba(8)Si(46) is explained in the framework of phonon-mediated Bardeen-Cooper-Schriefer theory. Analyses using the McMillan approximation of the Eliashberg equation indicate that the superconducting mechanism is in the medium coupling regime, but at the high-end limit. The large density of states at the Fermi level, which arises from hybridization of the Si(20) cluster and Ba orbitals, is responsible for the unexpectedly high superconducting temperature. The temperature evolution of the specific heat unambiguously shows that this is an s-wave symmetry superconductor.     

Formation of silicon dioxide layers at low temperatures (150-400 °C) by atmospheric pressure plasma oxidation of silicon

The formation of silicon dioxide (SiO₂) layers at low temperatures (150-400 °C) by atmospheric pressure plasma oxidation of Si(0 0 1) wafers have been studied using a gas mixture containing He and O₂. A 150 MHz very high frequency (VHF) power supply was used to generate high-density atomic oxygen in the atmospheric pressure plasma. Oxidation rate, structure, and thickness and refractive index profiles of the oxidized layers were investigated by ellipsometry and infrared absorption spectroscopy. Atomic force microscopy was also employed to observe atomic-scale morphologies of the layer surface and wafer Si surface, after chemical removal of the oxidized layers. It was found that stoichiometric SiO₂ layers were obtained at higher oxidation rates than conventional dry O₂ thermal oxidation and radical oxidation processes, even at a very low substrate temperature of 150 °C. Although thickness variations were observed in the plasma region, the refractive index was independent of both substrate temperature and VHF power. In addition, the SiO₂ surface and SiO₂/Si interface roughnesses were comparable to those obtained in conventional dry oxidation at high temperatures.