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Large-field radio interferometer at 10.65GHz have been developed to search for transient radio objects such as radio supernovae and radio bursts in stellar systems (Daishido et al. 1984). This is a spatial fast-fourier transform (FFT) type radio interferometer, being an equally-spaced, maximum redundant, two-dimensional (2D) array in an 8 × 8 configuration. Sixty-four identically-designed frontend elements are comprised of 2.4 m diameter cassegrain antennas and 200K HEMT receivers. These are steerable in elevetion and are fixed in azimuth. Although it is only partially operating, the completed system having 64 beams in the northern hemisphere is expected to provide maps having 0.1° angular resolution and a sensitivity of 50 mJy. The beams are formed by a newly-developed “Digital Lens” (complex amplitude equalizer + 2D FFT pipelined processor), with the array’s overall size being 20 × 20m.
A high performance VLBI recorder project using advanced digital technology started in 1995. TOSHIBA GBR 1000 and VLBI interface define 32 parallel, 32 MHz clock standard digital interface and support transparent recording/play-back to extremely high-speed digital bit stream. This is the formatter independent scientific recording bind the UTC to observed data. This highly reliable, low-bit-error-rate (10−16) recording system is also expected to be used in other scientific field. For the first example to examine the recorder performance in VLBI, we had been prepared 1024 Mbps sampler (256/512/1024 MSps, 2 bit, 4/2/1 ch). And here, an experimental giga-bit correlator specification for these VLBI acquisition system is introduced.
We have developed a “Relative Rates Method” to make bounding calculations regarding radionuclide migration due to uplift/erosion (“exhumation”) of a HLW repository. Results show that this method can apply to a wide range of different uplift rates and erosion rates. In addition, for the long time period, it was shown that the relative difference of uplift rate / erosion rate and potential hydraulic change arising from extreme uplift/erosion could affect radionuclide release and migration, thus uplift/erosion concerns should be fed back to site selection. Our method provides a credible and defensible basis for analysis and interpretation of possible uplift/erosion impacts for future volunteer sites.
In this paper, we first propose an improved CVD-WSix metal gate suitable for use with nMOSFETs. Work function of CVD-WSi3.9 gate estimated from C-V measurements was 4.3eV. The nMOSFET using CVD-WSi3.9 gate electrode showed that Vth variation of L/W=1 μm/10μm nMOSFETs can be suppressed to be lower than 8mV in 22chip. In CVD-WSi3.9 gate MOSFETs with gate length of 50nm, a drive current of 636μA/μm was achieved for off-state leakage current of 35nA/μm at 1.0V of power supply voltage. By using CVD-WSi3.9 gate electrode, highly reliable metal gate nMOSFETs can be realized.
The term “nanocomposite” is widely used to describe a very broad range of materials, where one of the phases has a submicrometer dimension . In the case of polymer-based nanocomposites, this typically involves the incorporation of “nano” fillers with one (platelets), two (fibers, tubes), or all three dimensions at the submicrometer scale. However, strictly speaking, simply using nanometer-scaled fillers is not sufficient for obtaining genuine/true nanocomposites: these fillers must also be well dispersed down to individual particles and give rise to intrinsically new properties, which are not present in the respective macroscopic composites or the pure components. In this chapter, we shall use a broader definition, encompassing also “nanofilled polymer composites”, where – even without complete dispersion or in the absence of any new/novel functionalities – there exist substantial concurrent enhancements of multiple properties (for example, mechanical, thermal, thermomechanical, barrier, and flammability). Further, we shall limit our discussion to one example, focusing on poly(ethylene terephthalate) (PET) with mica-type layered aluminosilicates.
The actual transverse and longitudinal displacement of PZT thick film was measured using a newly developed atomic force microscopy (AFM). The AFM is attached a feedback circuit named “torsion feedback”. The torsion and Z-height feedback circuits control an AFM cantilever to follow piezoelectric deformation of the sample. To measure transverse displacement, the cantilever contacts the edge of sample. The transverse displacement is determined from the torsion feedback signal absolutely. To measure longitudinal displacement, the cantilever contacts the center of sample. The longitudinal displacement is determined from Z-height feedback signal absolutely. A 5-μm-thick PZT film was prepared on Pt/Ti/SiO2/Si substrates. The film sample was shaped square pillar. The side electrode length (L) of square pillar shaped sample was ranged from 1000 μm to 10 μm. The relation between side electrode length and the transverse or the longitudinal displacements were investigated. With decreasing L, the transverse displacement decreased nonlinearly, and the longitudinal displacement increased nonlinearly. The finite element method (FEM) simulation suggests that the substrate clamped PZT film behaved nonlinearly. The effective -d31 and d33 were calculated from the measured displacement, and these values increase with decreasing L. The effective d33 and -d31 showed correlation, and the ratio was d33 : -d31 = 5.3 : 1 , whereas the bulk ratiois d33 : -d31 = 2.4 : 1.This result suggests that the substrate clamping effect of the transverse displacement was larger than that of the longitudinal displacement.
Monocrystalline cubic SiC (β -SiC) thin films with lower defect densities have been epitaxially grown by chemical vapor deposition on off-axis Si (100) substrates with off-directions different from the conventional 〈011〉. Stacking faults of β -SiC films are investigated by the electrolytic etching and SEM observation. The effects of off-direction deviated from 〈011〉 are examined for the first time. The off-angle is fixed at 2 degrees. We find a reduction in defect density with increasing deviation angle θ, of off-direction from  toward [011[ (θ = 0 - 45°). The defect density becomes one order of magnitude smaller than that of on-axis (100) substrates. A typical value of the stacking fault density is approximately 6 × 106 cm−2 on the substrate with θ = 30° (film thickness: 24μ m).
We have discovered new transparent conducting oxides (TCOs), anatase Ti1-xMxO2 (M=Nb,Ta), in thin film form. Both films with 0.03 ≤ × ≤ 0.06 showed resistivity of 2−3 × 10−4 Ωcm and internal transmittance of ∼95% in the visible light region (40 nm in thickness), at room temperature. These values are comparable to those of typical TCOs, such as In2−xSnxO3 (ITO).
The intercalation of fluorine into graphite introduces defects into the highly crystalline pristine fibers. These defectsare studied using temperature-dependent resistivity and magnetoresistance measurements. A logarithmic increase in resistivity at low temperature is observed, whereas the high temperature behavior is metallic. At weak magnetic fields and low temperatures, a negative magnetoresistance is observed, which becomes positive at high fields. These effects are explainedusing the two theories of weak localization and hole-hole interaction. In the light of TEM pictures of the microstructure of the fluorinated fibers, the origin of the defects in the intercalated fibers is discussed.
New type pseudoelasticity in Fe3Al with the D03 structure was examined using the single crystals. The pseudoelasticity occurred due to a reversible motion of 1/4<111> superpartials dragging the nearest-neighbor anti-phase boundaries. The chemical composition and microstructure of Fe3Al alloys strongly influenced the shape recovery ratio and Fe-23.0at%Al alloy with fine domain structure was the most favorable for the appearance of the pseudoelasticity. The recovery ratio of Fe-23.0at%Al exceeded 80 % in the wide temperature range from -50 to 200 oC.
TBA and TBP are attractive candidates for group V sources for MOVPE growth from the viewpoint of safety. We studied how the composition of InGaAsP crystals depends on growth conditions, and investigated its electrical and optical properties. The relationship between group V sources and crystals indicates that TBA and TBP decompose into AsH and PH. Since there is no carbon in AsH and PH, carbon contamination in the crystals is expected to be small. Carrier concentrations ranged from 5×1014 cm−3 to 1.5×1015 cm−3. Photoluminescence spectra at 4.2K showed strong band-edge emission with no acceptor-related emission. Based on the electrical and optical properties of the crystals, we conclude that high-quality InGaAsP crystals can be grown using TBA and TBP.
Relationship between the degree of imide-ring-condensation and the absorbed quantity of sodium ion was studied in a polyimide film of 100nm thick immersed in an alcoholic solvent containing sodium ion in order to elucidate a mechanism of incorporation of ionic species. Absorption and depth-profile of sodium ion in a film were quantitatively determined by chemical analysis and secondary ion mass spectroscopy. Concentration of sodium ion in a thin film by two orders of magnitude was observed, and distribution of sodium ion in a thin film was found to be uniform, which cannot be accounted for by any kinds of previous models based on diffusion, permeation, or solvation. Instead, chemical ion-exchange model is proposed and is found to satisfactorily explain the experimental results.
The effects of atomic hydrogen (H) on formation of In(Ga)As quantum dots (QDs) by self-organizing process have been investigated. The low size fluctuation and uniform-shaped QDs are obtained at growth temperature above 450°C. The average size of InGaAs QDs are decreased from 40 nm to 20 nm by atomic H irradiation. The InGaAs QDs are formed uniformly on growth surface in with-H condition while preferentially formed and distributed along the step edges in without-H case. The photoluminescence (PL) peak intensities and full width at half maximum (FWHM) are also improved by atomic H irradiation. The waiting time before GaAs cap layer deposition is a important factor on the optical properties of QDs.
We have studied intersubband transitions in InAs/AlSb quantum wells experimentally and theoretically. Experimentally, we performed polarization-resolved infrared absorption spectroscopy to measure intersubband absorption peak frequencies and linewidths as functions of temperature (from 4 K to room temperature) and quantum well width (from a few nm to 10 nm). To understand experimental results, we performed a self-consistent 8-band k·p band-structure calculation including spatial charge separation. Based on the calculated band structure, we developed a set of density matrix equations to compute TE and TM optical transitions self-consistently, including both interband and intersubband channels. This density matrix formalism is also ideal for the inclusion of various many-body effects, which are known to be important for intersubband transitions. Detailed comparison between experimental data and theoretical simulations is presented.
A short discussion about growth kinetics of Si and Si1-xGex, epitaxial layers in a reduced pressure CVD reactor using both dichlorosilane and silane is presented. Through careful observations of the growth of very thin Si layers on SiGe, an anomaly in the Si growth ratewas detected such that the thinner the Si layer, the higher the Si growth rate on SiGe. Due to the difficult nature of very thin film characterization, several analysis techniques were used. A possible explanation based on TEM observations is put forward.
This paper is overviewed the recent progress on GaN HEMTs. High power, high frequency and high efficiency performance are reported. In addition, the results about long-term reliabilities and good manufacturability demonstrate that GaN HEMTs are ready for mass production.
Electrode materials consisting of Cu, Ti and Ni were formed on Bi-doped n-type Mg2Si by means of a monobloc plasma-activated sintering (PAS) technique. Due to the difference in thermal expansion coefficients between Ti and Mg2Si, rather high residual thermal stresses gave rise to the introduction of cracks, which were mainly located in the Mg2Si layer, when Ti was used as the electrode material. In the case of the Cu electrodes, monobloc sintering could not be performed in a reproducible manner because Cu melts abruptly and effuses at around 973K, which is 100 K lower than the sintering temperature that is required for Mg2Si of good crystalline quality. When compared with the results for Cu and Ti, the monobloc PAS process for Ni was both stable and reproducible. The room-temperature I-V characteristics of Ni electrodes were considered to be adequate for practical applications, with durable Mg2Si-electrode junction properties being realized at a practical operating temperature of 600 K with ΔT = 500 K. The highest open circuit voltage (VOC) observed was 41 mV at ΔT = 500 K (between 873 K and 373 K) for Ni electrodes fabricated using the monobloc PAS process. The voltage (V) and current (I) values with a 10 Ohm load were ∼ 48 mV and ∼ 2 mA at ΔT = 500 K.
Low temperature (150 °C) deposition of doped and undoped polycrystalline Si (poly-Si) as well as SiNX films on polyethylene terephthalate (PET) films has been achieved with practical deposition rates by using pulsed-plasma CVD under near-atmospheric pressure. The precursor is SiH4 diluted in H2 for poly-Si while N2 has been additionally used for SiNx. No inert gases such as He was used. A short-pulse based power system has been employed to maintain a stable discharge in the near-atmospheric pressures. With this technique, deposition of poly-Si thin film with virtually no incubation layer is possible, which in the case of P-doped poly-Si shows a Hall mobility (μH) of 1.5 cm2/V·s.
Growth of a Co/Cu/Co multilayer is investigated by molecular-dynamics simulation. The interactions between Co and Cu atoms are calculated in terms of the generic-embedded atom method potential. It is confirmed that two-dimensional island growth of Cu atoms on the Co substrate occurs in the simulations. The roughnesses of the surface and the interface are evaluated by means of the standard deviations of the heights of the surface and interface atoms. Intermixing atoms between the layers are also counted. We conclude that there exists an optimum combination of the incident energies of deposited Cu and Co atoms which minimizes both the roughness and intermixing of the interface.