Vapor-phase formation of single-helix carbon microcoils by using WS2 catalyst and the morphologies

Very regular single-helix carbon microcoils of outer coil diameter 1–;3 m, inner coil diameter 0.5–;2 m, and coil pitch 1–;2 m were prepared by the WS₂-catalyzed pyrolysis of acetylene in the presence of thiophene impurity. The effects of reaction temperature and thiophene gas flow rate on the growth of single-helix carbon microcoils and the morphology were examined in detail. The optimum reaction temperature was 780°C, and optimum gas flow rate of thiophene, acetylene, hydrogen and argon for obtaining regular single-helix carbon coils with a constant coil diameter were 0.2, 40, 90, and 30 sccm, respectively. The formation mechanism of the single-helix carbon microcoils is discussed.     

Linear Connected Array of Non-Adiabatic Traps

An innovative confinement concept of a linearly connected array of non-adiabatic traps is examined. A non-adiabatic trap unit consists of a cylindrical vacuum chamber with external mirror coils and a pair of inner anti-parallel coils. Positions and currents on these coils are adjusted to achieve zero magnetic fields at the center. The plasma is trapped stably in this configuration due to the “Absolute Minimum B” magnetic configuration that is created. However, like a cusp field, energy confinement of plasma in a trap unit is poor, since particles suffer random pitch-angle scattering near the central zero field region and eventually fall into the loss-cone. However, once these non-adiabatic traps are linearly connected, plasma particles escaping a unit will be effectively re-trapped within the neighboring trap due to collision-free pitch-angle scattering in the zero field region. Since the transition of a charged plasma particle from unit to a next unit is stochastic, a connected array of non-adiabatic fusion core units and similar “leak suppressor” array units with low fusion rate at both ends of the core array improves the plasma confinement sufficient to achieve reactor-grade plasmas.     

微旋管状碳纤维的微细构造和表面特性

采用ＣＶＤ法合成了结构类似于ＤＮＡ的高功能微旋管状碳纤维。考察了其微观形态、微细构造、,并研究其表面特性。微旋管状碳纤维和ＶＧＣＦ的成长机理完全不同,因此微细结构也完全不同。组成旋管的纤维从表面到芯完全被碳粒所充满,且几乎是非晶质的,该纤维的表面活性比勘察碳纤维高得多。     

Comparison of low-temperature electrical characteristics of gate-all-around nanowire FETs, Fin FETs and fully-depleted SOI FETs

Low-temperature electrical characteristics of n-type gate-all-around vertically-stacked silicon nanowire (SNW) field-effect transistors (FETs) with high-k/metal gate have been investigated and are compared to those with Fin and fully-depleted silicon-on-insulator (FD SOI) FETs. In particular, the effective electron mobilities behaviors are discussed. Nanowires with a rectangular cross section of 15 nm in width and 19 nm in height have shown a strongly degraded mobility as compared to those with Fin and FD SOI FETs. Low-temperature measurements have revealed that the mobility degradation is due to higher surface-roughness limited mobility. On the other hand, no significant difference in the interface trap densities among the kinds of FETs measured in the study have been observed from the temperature dependence in the subthreshold slope.     

A novel hetero-junction Tunnel-FET using Semiconducting silicide–Silicon contact and its scalability

A new type of silicon-based Tunneling FET (TFET) using semiconducting silicide Mg₂Si/Si hetero-junction as source-channel structure is proposed and the device simulation has been presented. With narrow bandgap of silicide and the conduction and valence band discontinuous at the hetero-junction, larger drain current and smaller subthreshold swing than those of Si homo-junction TFET can be obtained. Structural optimization study reveals that low Si channel impurity concentration and the alignment of the gate electrode edge to the hetero-junction lead to better performance of the TFET. Scaling of the gate length increases the off-state leakage current, however, the drain voltage (V_d) reduction in accordance with the gate scaling suppresses the phenomenon, keeping its high drivability.     

Determination of energy and spatial distribution of oxide border traps in In0.53Ga0.47As MOS capacitors from capacitance–voltage characteristics measured at various temperatures

In this work, we have systematically studied the frequency dispersion of the capacitance–voltage (C–V) characteristics of In_0.53Ga_0.47As metal–oxide-semiconductor (MOS) capacitors in accumulation region at various temperatures based on a distributed border traps model. An empirical method to evaluate the frequency and temperature dependent response of the border traps distributed along the depth from the interface into the oxide is established. While the frequency dependent response results from the dependence of the time constant of the border traps on their depths, the temperature dependent response is ascribed to the thermal activated capture cross-section of the border traps due to the phonon-related inelastic capturing process. Consequently, it is revealed that the frequency dispersion behaviors of the accumulation capacitance at different temperatures actually reflect the spatial distribution of the border traps. On this basis, we propose a methodology to extract the border trap distribution in energy and space with emphasis on analyzing the C–V characteristics measured from low to high temperatures in sequence.     

Dc power system for mutual coupled large scale superconducting coils

The large helical device (LHD) is a fusion experimental facility which has a large scale mutually coupled superconducting coil system and it is now under operation at the National Institute for Fusion Science (NIFS). This paper shows the design and the operation results of the dc power systems to drive these coils. First, the outline of the LHD and the power supplies are described. Next, a control system and the current controller for the power supplies are introduced. Finally, some experimental results are introduced.     

Expression of putative fatty acid transporter genes are regulated by peroxisome proliferator-activated receptor alpha and gamma activators in a tissue- and inducer-specific manner

Regulation of gene expression of three putative long-chain fatty acid transport proteins, fatty acid translocase (FAT), mitochondrial aspartate aminotransferase (mAspAT), and fatty acid transport protein (FATP), by drugs that activate peroxisome proliferator-activated receptor (PPAR) alpha and gamma were studied using normal and obese mice and rat hepatoma cells. FAT mRNA was induced in liver and intestine of normal mice and in hepatoma cells to various extents only by PPARalpha-activating drugs. FATP mRNA was similarly induced in liver, but to a lesser extent in intestine. The induction time course in the liver was slower for FAT and FATP mRNA than that of an mRNA encoding a peroxisomal enzyme. An obligatory role of PPARalpha in hepatic FAT and FATP induction was demonstrated, since an increase in these mRNAs was not observed in PPARalpha-null mice. Levels of mAspAT mRNA were higher in liver and intestine of mice treated with peroxisome proliferators, while levels in hepatoma cells were similar regardless of treatment. In white adipose tissue of KKAy obese mice, thiazolidinedione PPARgamma activators (pioglitazone and troglitazone) induced FAT and FATP more efficiently than the PPARalpha activator, clofibrate. This effect was absent in brown adipose tissue. Under the same conditions, levels of mAspAT mRNA did not change significantly in these tissues. In conclusion, tissue-specific expression of FAT and FATP genes involves both PPARalpha and -gamma. Our data suggest that among the three putative long-chain fatty acid transporters, FAT and FATP appear to have physiological roles. Thus, peroxisome proliferators not only influence the metabolism of intracellular fatty acids but also cellular uptake, which is likely to be an important regulatory step in lipid homeostasis.     

Electrical characteristics of MOSFETs with La2O3/Y2O3 gate stack

A metal oxide semiconductor field effect transistor (MOSFET) with ultra-thin La₂O₃/Y₂O₃ high-k gate dielectric was fabricated. The effects of thermal treatment process on both physical and electrical characteristics of the La₂O₃/Y₂O₃ stack were studied using XPS and electrical measurements. It was observed that the effective mobility of the fabricated MOSFETs with La₂O₃/Y₂O₃ gate stack was not degraded with increasing the annealing temperatures up to 600 °C. X-ray photoelectron spectroscopy (XPS) analysis also revealed that the formation of SiO₂ and silicate layer at the interface was suppressed in La₂O₃/Y₂O₃ stack compare to that of in La₂O₃ single layer. Obtained results suggesting that La₂O₃/Y₂O₃ gate stack is one of the promising candidates for high-k gate insulator to be used in the future metal oxide field effect transistors.     

Chemical vapour deposition of TiB2 protective layers on a brass plate

A brass plate was coated with TiB₂ layers from a gas mixture of TiCl₄, BCl₃, H₂ and argon. The lowest deposition temperature was very low, 530° C, which is 70° C lower than for a copper plate and 150 to 250° C lower than for other substrates. The corrosion resistivities of the brass plate against 12 N HCl, 16 N HNO₃, 36 N H₂SO₄ and sea water, as well as the abrasion resistivity against whirled sea sand, were improved outstandingly by coating with the TiB₂ layers.