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SiO maser emission from the Bulge IRAS sources has been searched by the v=1, J=1−0 and v=2, J=1—0 transitions to investigate the kinematics of the Galactic Bulge, resulting in a sample of 124 line-of-sight velocities. The rotation velocity, velocity dispersion, and velocity offset at l = 0° for the sample are found to be , and —18.2±9.7 km s−1, respectively (80% confidence interval). Furthermore we find trends for the rotation velocity and velocity dispersion to decrease with distance from the galactic plane. These trends are supported by a larger sample constructed by incorporating other available velocity data on the Bulge IRAS sources. The rotation velocity and velocity dispersion are expressed as 15.6—1.23x|b(deg)| km s−1 deg−1 and 101−3.6x |b(deg)| km s−1, respectively. The implications of the observed quantities are discussed.
Perovskite-based solar cells, typically CH3NH3PbI3, have reached power conversion efficiencies on par with single crystal silicon solar cells. Perovskite cells prepared with the most common perovskite solvent N,N-dimethylformamide (DMF) by different research groups exhibit disparate efficiencies and stability for nominally identical perovskite films. Although the differences can be related to processing conditions, a consistent physical cause for the differences has been lacking. Highly-sensitive time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals significant dimethylamine (DMA) included in perovskite films. TOF-SIMS and x-ray photoelectron spectroscopy results suggest DMA levels ranging from roughly 10–50%. Only the highest levels register as perovskite peak shifts in x-ray diffraction; lower levels are invisible. We propose that methylamine (MA) can react with DMF solvent by transamidation to produce dimethylamine (DMA), which then displaces some MA in perovskite crystals, see Fig. 1. Transamidation of DMF can be catalyzed by TiO2, Al2O3, water, or acid, but in perovskite films transamidation is inhibited by water.
The Keio Twin Research Center has conducted two longitudinal twin cohort projects and has collected three independent and anonymous twin data sets for studies of phenotypes related to psychological, socio-economic, and mental health factors. The Keio Twin Study has examined adolescent and adult cohorts, with a total of over 2,400 pairs of twins and their parents. DNA samples are available for approximately 600 of these twin pairs. The Tokyo Twin Cohort Project has followed a total of 1,600 twin pairs from infancy to early childhood. The large-scale cross-sectional twin study (CROSS) has collected data from over 4,000 twin pairs, from 3 to 26 years of age, and from two high school twin cohorts containing a total of 1,000 pairs of twins. These data sets of anonymous twin studies have mainly targeted academic performance, attitude, and social environment. The present article introduces the research designs and major findings of our center, such as genetic structures of cognitive abilities, personality traits, and academic performances, developmental effects of genes and environment on attitude, socio-cognitive ability and parenting, genes x environment interaction on attitude and conduct problem, and statistical methodological challenges and so on. We discuss the challenges in conducting twin research in Japan.
Oxygen-doped germanium crystals were used to demonstrate the interaction between implanted hydrogen or nitrogen atoms and the oxygen-related defects. The electron trap at Eo-0.26eV associated with the germanium A-center was found to be formed by electron irradiation. Another level at Eo-0.21eV also was observed on annealing at 120 °C. As for the sample implanted with hydrogen ions following electron irradiation, the trap concentration is four times as large as that for electron irradiation alone. It is probable that the germanium A-centers produced by electron irradiation capture hydrogen atoms and increase electrically active centers. After nitrogen implantation following electron irradiation, the Eo-0.26eV level almost annealed out at 140 °C and the trap at Eo-0.21eV wasn't observed. We propose that the reduction in the oxygen-related defect growth is due to the prevention of defect migration with nitrogen atoms.
Room temperature current-voltage (I-V) characteristics were studied across the thickness of the Ge nanocrystalline films, prepared by the cluster beam evaporation technique. The films thus prepared are deposited either at room temperature (Ge-RT) or at liquid nitrogen temperature (Ge-LNT). Ge-LNT nanofilm is subjected to oxidation while Ge-RT did not get oxidized. Steps were observed in the I-V characteristics of the thin Ge- LNT samples suggesting the Coulomb Blockade effect.
The material properties of two ultra low-k organic polymers are characterized for copper interconnect integration. The k-values are 2.2-2.3 for both. Compared to OSG materials of similar k-values, these polymers have lower porosity and smaller pore size, achieved using selfassembled chemistry. Both materials demonstrate excellent resistance to plasma damage: no water uptake was detected after exposure to selected etching plasmas. This characteristic, combined with the small pore size and low porosity, results in the successful integration of the organic low-ks in 80 nm spacing with no significant increase in the integrated k-values.
It is found that higher open porosity in polymer A is accompanied by higher leakage current, which is not however linked to lower dielectric breakdown lifetimes.
Two methods are employed in the gas evaporation technique to form Ge nanocrystals with the Si-passivated surface. One uses one boat with a SiGe alloy as a source, and the other uses two boats each with Si and Ge. As a result of characterization by the x-ray diffraction (XRD) measurement, Raman scattering and x-ray photoelectron spectroscopy (XPS), it is found that Ge nanocrystals with the Si-passivated surface were formed by coevaporation of Si and Ge from two boats, while SiGe alloy nanocrystals were formed by evaporation of the Si-Ge alloy source from one boat.
The high-Tc YBCO superconducting films have been prepared using a cw CO2 laser evaporation from a single bulk target. The adjustment of the target composition, especially the yttrium concentration, was found to be a key factor to achieve a desired film composition. After post-annealing at 930°C, the films deposited on YSZ substrate exhibited a zero resistance temperature of 85K. The deposition rate of the films was about lOOA/sec.
Anisotropic etching of n+ poly-Si is achieved using a hot Cl2 molecular beam and a sidewall protection technique. A hot molecular beam is produced by a free jet expansion of a gas heated in a furnace. A nitrogen radical beam is used to prevent the sidewall etching. The etch rate of n+ poly-Si is 4.3 nm/min at the anisotropic etching condition.
Titania thin films grown by reactive bias sputtering were characterized. In order to investigate the role of energetic ion on the growth of crystalline phases of TiO2 thin films, we applied substrate biases during deposition. The structural properties were analyzed using X-ray diffractometry (XRD), and related to the optical properties of the films. The atomic composition was determined using Rutherford backscattening spectrometry (RBS).
Negative substrate bias, Vb, showed a significant influence on the phase formed composition and microstructure: Vb in the range of 15 and 60 V enhanced the growth of crystalline phases and the rutile dominated the phase composition. However, the quantity of rutile decreased when Vb was raised to 100 V. The excess of oxygen was shown in the films by RBS.
Control of epitaxial relationship of CaF2 films grown on Si(111) substrates was considered to be important to improve surface morphology and crystallini ty of GaAs films on CaF2/Si(111) structures. We successfully grew CaF2 films with the “type-A” epitaxial relationship on Si(111) substrates, that is, the crystallographic orientation of the CaF2 films were aligned in the same direction as that of the Si(111) substrates. These “type-A” CaF2 films were grown by a two step growth method. It was found that surface morphology of GaAs films on the CaF2/Si(111) structures was drastically improved by growth of the “type-A” CaF2 films.
A study was conducted on the preparation of Al2 O3 -coated metal substrates for high density electronic assembly. Al2 O3 films of 3∼15μm thickness were deposited on metal substrates, such as aluminum, stainless steels and the like, at a deposition rate of 0.2∼5μm/min. They were examined in terms of chemical composition, microstructure, density, hardness, breakdown voltage, thermal conductivity and so on. It was found that the dense and stoichiometric films could be achieved by adjusting the process parameters, in particular, substrate temperature, deposition rate and distance between target and substrate. The results obtained led to the conclusion that this new Al2O3-coated metal substrate could be effective for high density electronic assembly.
The structure and density of amorphous S1O2 films grown by chemical vapor deposition (CVD) or thermal oxidation are studied by Fourier-transform infrared (FT-IR) absorption, neutron diffraction, and Rutherford backscattering (RBS) measurements. CVD oxides, formed in an atmospheric-pressure CVD reactor with a SiH4-O2 gas mixture at 400 °C, are compared with thermal oxides, grown at 980 °C in H2-O2 atmosphere. The average Si-O-Si bond angle deduced from the stretching frequency of FT-IR is found to be smaller in CVD oxides than in thermal oxides, and the density revealed by RBS measurements is found to be a little lower in CVD oxides than in thermal oxides. These differences are explained by the medium-range structural disorder revealed by FT-IR measurements as well as by neutron diffraction measurements. The medium-range structural disorder in CVD oxides is responsible for large silanol content in the oxides and is the origin in difference between CVD and thermal oxides.
The basic concept underlying the alloy design and microstructural control method utilised in developing a new type of β(B2)+ γ (A1) two-phase ductile shape memory alloy in the Ni-Al base systems is briefly reviewed. The characteristic features of the shape memory effect (SME) in the Ni-Al-Fe and Ni-Al-Fe-Mn alloys are reported with particular reference to the transformation and deformation temperatures, the volume fractions of the γ phase, the morphology of the β + γ structure and the effect of cycling. Training by cycling treatment has a significant effect on the degree of shape recovery and pseudo-elasticity in the β + γ two-phase alloys. These duplex β + γ alloys also exhibit a combination of relatively high damping capacity and high yield strength. It is emphasized that these alloys could be expected to fill the need for a new group of shape memory alloys which operate at elevated temperatures over 100°C.
Applying laser ablation technique, we have synthesized two types of SiO2 films that include nanometer-sized Si particles. One is synthesized by alternative deposition of Si nanoparticles layers and SiO2 layers. The synthesized film exhibits red photoluminescence (PL) with a peak energy below 1.5 eV. The other is synthesized by annealing at 1000°C of SiOx films, which are formed by laser ablation in diluted O2 gas. We find that there is a narrow range of composition for efficient red PL. Based on the experimental results, we tentatively discuss a possible model for the origin of the red PL.
We have investigated influences of Ti sources on properties of (Ba,Sr)TiO3 [BST] films prepared on Pt/SiO2/Si substrates by liquid source chemical vapor deposition (liquid source CVD): TiO(DPM)2 [titanyl bis (dipivaloylmethanato), TiO(C11 H19O2)2], Ti(O-i-Pr)2 (DPM)2 [bis (isopropoxy) bis (dipivaloylmethanato) titanium, Ti(o-i-C3H7)2(C11H19O2)2], and TTIP [titanium tetraisopropoxide, Ti(O-i-C3H7)4]. Improved electrical properties and step coverage were obtained using TiO(DPM)2 at a substrate temperature TS=420'C and a reactor pressure P=1.5Torr as follows: a dielectric constant ε=210, equivalent SiO2 thickness teq=0.51nm, leakage current density JL=6.6×10∼−8A/cm2 at +1.1V, dielectric loss tan δ=0.007, and coverage of 0.8. However, hillocks appeared on the BST film surface under these conditions, while the film surfaces were relatively smooth using TTIP. The density of these hillocks appeared to be related to the BST(110) peak intensity of the X-ray diffraction pattern.
Availability of tensilely strained GaInP/AIGaInP quantum well, which is essential to laser diodes operating at 635–650nm, is investigated by combining conventional and time-resolved photoluminescence measurements. It is found that optical characteristics are improved by introducing tensile strain into barrier layers in addition to well layers, while samples with unstrained or compressively strained barrier layers reveal inferior characteristics. Experimantal data indicate that these optical characteristics are not determined by interfacial stress, but by the energy band discontinuity between well and barrier layer.