bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Nitrogen Inhomogeneity in LPE GaP by Spatially Resolved Photoluminescence
Authors: Nishinaga Tatau , Sasaoka Chiaki , Pak Kangsa
Published: February 2005

Nitrogen inhomogeneity in LPE GaP is studied by spatially resolved photoluminescence. It is found that the nitrogen is doped much less under the macrostep riser which is composed of high-density atomic steps. The origin of this nonuniformity is discussed and it is concluded that the equilibrium concentration of nitrogen along a step is frozen in the bulk crystal, and hence the bulk concentration shows the step velocity dependence.
Molecular Orientation and Film Morphology of Calcium Stearate Deposited on Several Substrates
Authors: Yase Kiyoshi , Inoue Takahito , Inaoka Kimio , Okada Masakazu
Published: February 2005

Calcium stearate ((C18H35O2)2Ca) was vacuum-deposited on the following substrates: KCl, mica, SiO2, deposited films of Al, Ag and Cr, surface-treated glass and amorphous carbon films. The long-chain molecules on the (001) planes of KCl and metals were arranged epitaxially to form a crossed network of rodlike crystals, whose longitudinal directions agreed with the <110> axes of substrates. On the (001) plane of mica and the (111) plane of Ag, molecules formed the random network of rectangular growth hillocks. On the polycrystallines of SiO2 and metals, surface-treated glass and carbon films, the rodlike crystals were scattered. When the temperature of the substrate was raised, molecules tended to stand normal against the substrate surfaces and formed thin films having an axial relation to the substrate crystals. deposited films,
Application of the Nucleation Theory to the Design of Bubble Jet Printers
Authors: Asai Akira
Published: February 2005

A model, based on the classical nucleation theory, has been developed to predict the nucleation process in bubble jet printers. The nucleation probability distribution curve predicted by the model agreed with an experiment which was done using a prototype bubble jet printing head. The effects of heat pulse width, heat flux, dissolved air and surface wettability on the nucleation process were investigated using the model. The results provide a new guide to the design of bubble jet printers.
A Light Pulse Source of a Few Tens of a Picosecond to Nanosecond Width with Cherenkov Radiation
Authors: Owaki Shigehiro , Tahara Yasuyuki , Okada Toichi , Kimura Yoshitake , Iida Takao , Nakahara Sumio , Sugihara Kiyoshi
Published: February 2005

It was experimentally proven that Cherenkov radiation arising from intense electron pulses passing through a dielectric material could be utilized for a light source of short pulse width. A linear accelerator at ISIR, Osaka University, which can produce intense single-bunch electron pulses, was used for a Cherenkov radiation exciter. The spectral distribution and pulse shape of the Cherenkov radiation from an air radiator with these electron pulses were investigated with a fast detection system for this purpose. The spectrum showed a peak at 200 nm and a continuous band of which intensity decreased towards the longer wavelength. The minimum pulse width of the Cherenkov radiation with the single-bunch electrons was about 40 ps, and the light peak power was about 10 kW in the spectral region of 200 to 600 nm.
Etch Pit Observation of InP
Authors: Nishikawa Hironobu , Soga Tetsuo , Jimbo Takashi , Mikuriya Nobuo , Umeno Masayoshi
Published: February 2005

The dislocations in InP are revealed by the solution of HBr+C2H5OH. This etching solution is found to be superior to HBr+H3PO4.
Eutectic Reactions and Textures of Au–Si Alloy Films on Single-Crystal Silicon
Authors: Kato Hiroshi
Published: February 2005

The texture formation of the Au–Si eutectic phase on the Si single crystal was found to depend on the cooling rate of the melted Au–Si alloy and Au film thickness deposited on Si. Transmission electron diffraction observation showed that the Au dendrite formed on Si has selective orientations of (110) and (100) on (100) Si and of (110) on (111) Si. In addition, Au films on single-crystal Si were found to eutectically melt and freeze at temperatures lower than the eutectic temperature indicated in the conventional equilibrium phase diagram. This result was obtained by observations of the eutectic reaction on Si using a differential scanning calorimeter and an optical microscope.
In Situ Conductivity, Electron Spin Resonance and Absorption Spectra Measurements in Polyaniline During Electrochemical Doping
Authors: Ohsawa Toshiyuki , Kabata Toshiyuki , Kimura Okitoshi , Onoda Mitsuyoshi , Yoshino Katsumi
Published: February 2005

In in situ measurements of ESR during electrochemical doping in polyaniline, the maximum spin density is observed at 3.25 V. ESR linewidth decreases upon doping, but after exhibiting a minimum value at 3.5 V, it increases again, tending to saturation. On the other hand, in situ conductivity measurement demonstrates the maximum value (1.6 S/cm) at around 3.5 V. Taking into consideration the complex absorption spectral change upon doping, the results are discussed in terms of polaron and bipolaron models. At higher doping levels, suppression of the interchain transfer of polaronic species due to Coulomb interaction is introduced to explain the decrease of conductivity.
An 8 mW cw Er3+-Doped Fiber Laser Pumped by 1.46 µm InGaAsP Laser Diodes
Authors: Suzuki Kazunori , Kimura Yasuo , Nakazawa Masataka
Published: February 2005

A highly efficient Er3+-doped fiber laser pumped by an InGaAsP Fabry-Perot type high-power laser diode is demonstrated. Maximum output power as high as 8 mW is obtained at 1.552 µm for a launched Er pump power of 93 mW. Its slope efficiency against the launched pump power is 14%.
Structural Properties of Silicon Oxide Films Prepared by the RF Substrate Biased ECR Plasma CVD Method
Authors: Kitagawa Masatoshi , Hirao Takashi , Ohmura Takuichi , Izumi Tomio
Published: February 2005

The influence of radio frequency (RF) bias on preparation of silicon oxide (SiO) films by the microwave electron cyclotron resonance plasma CVD method has been investigated using a SiH4, O2 and Ar gas mixture. The compositional and structural properties of films were studied by infrared (IR) absorption, refractive index (RI), Auger electron spectroscopy (AES) and electron spin resonance (ESR) measurements in correlation with RF bias power. The films deposited with the RF bias have the RI values of 1.4∼1.7, and the O/Si value of 1.6∼1.9. The IR and ESR measurements revealed that the absorption caused by O-H bonds increased and the spin density was below the limit detectable by RF bias above 200 W.
Fiber Humidity Sensor Using Fluorescent Dye-Doped Plastics
Authors: Muto Shinzo , Fukasawa Akihiko , Kamimura Mitsuharu , Shinmura Fumihide , Ito Hiroshi
Published: February 2005

The humidity-sensing optical fiber consists of a glass core and polymer clad doped with umbelliferon dye. Under UV light pumping. the blue fluorescence intensity from this fiber increases linearly with increasing relative humidity in the range of 20 to 80%RH. In addition. it has a fast response time and is not influenced by the presence of NH3 gas or HCl gas.
Reduction of DX Center Concentration in Al0.3Ga0.7As with In
Authors: Kobayashi Kikuo , Yamaga Mutsuo , Fujimoto Isao , Suzuki Takeo
Published: February 2005

The behavior of the DX center in Al
x
Ga1-x
As alloys slightly mixed with In grown by MBE has been investigated through deep level transient spectroscopy (DLTS). The DX center concentration in (Al0.3Ga0.7)1-y
In
y
As (y=0.05) is more than one order of magnitude lower than that without In. On the other hand, the concentration in (Al0.5Ga0.5)1-y
In
y
As (y=0.05) is higher than without In. These results are explained in terms of the change in the band structure with In content in AlGaAs alloys.
Lattice-Mismatched Growth and Transport Properties of InAlAs/InGaAs Heterostructures on GaAs Substrates
Authors: Harmand Jean Christophe , Matsuno Toshinobu , Inoue Kaoru
Published: February 2005

We report on the lattice-mismatched growth of In0.53Ga0.47As/In0.52Al0.48As modulation-doped heterostructures on GaAs substrates by molecular beam epitaxy. A buffer layer structure and its growth conditions were optimized. As a result, we obtained a sample with a mirrorlike surface which exhibits electron mobility of 10500 cm2/V·s and 48500 cm2/V·s at 300 K and 77 K, respectively. These values are comparable to those obtained in lattice-matched structures grown on InP substrates. To our knowledge, the room temperature mobility is the highest ever reported in a modulation-doped heterostructure grown on a GaAs substrate.
Oxygen Adsorption-Desorption Behavior and Superconducting Properties of High-Tc Bi(Pb)-Sr-Ca-Cu-O
Authors: Miura Norio , Suzuta Hiroki , Deshimaru Yuichi , Shimizu Youichi , Sakashita Hirofumi , Yamazoe Noboru
Published: February 2005

Temperature-programmed desorption (TPD) chromatograms revealed that a small amount of oxygen was desorbed from high-T
c Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) in the temperature range from ca. 350 to ca. 650°C prior to a steep increase of oxygen desorption in the higher temperature range. The T
c of BPSCCO was significantly lowered with the progress of oxygen desorption especially in the former temperature range, and was restored to the original level when the desorbed oxygen was recovered. With no corresponding changes in X-ray powder diffraction pattern being detected, the oxygen desorbed below ca. 650°C was concluded to have strong relevance to the superconductivity of BPSCCO.
Effect of Pressure on the Hall Effect, Electrical Resistivity and Magnetoresistance in the High-TcSuperconductor, YBa2Cu3O7-δ
Authors: Hiraoka Takeshi
Published: February 2005

The pressure effect on the Hall effect, electrical resistivity and magnetoresistance (T<Tc) has been measured in sintered YBCO. Under pressure, the Hall coefficient decreases aboveTc. The size of the negative peak of the Hall effect just belowTcalso decreases whileTcincreases. Under pressure, the magnetoresistance increases (T<86.6 K) and decreases (86.6<T<89.8 K).
Variation of Composition in a Bi(Pb)-Sr-Ca-Cu-O Grain and the Influence of Mg and Ba Doping on Its Superconductivity
Authors: Ashizawa Toranosuke , Shimoda Shuichiro , Yamana Shozo , Sumiya Keiji , Ishihara Minoru , Kuwajima Hideji
Published: February 2005

The 110 K phase (2223) and (Sr, Ca)-Cu-O phase exist in the Bi(Pb)-Sr-Ca-Cu-O ceramics. The Cu content varies in the perpendicular direction of platelike 2223 grains, but little variation is observed on the planer surface of the grains along their length. Only the 110 K phase was found in the X-ray diffraction pattern of Bi(Pb)-Sr(Ba, Mg)-Ca-Cu-O. Its electrical resistivity became zero at 110 K. By the partial substitution of Mg and Ba for Sr, the range of sintering temperatures in which we obtained a higher T
c
zero was much larger than that for Bi(Pb)-Sr-Ca-Cu-O.
Electrooptic Bistability of a Ferroelectric Liquid Crystal Device Prepared Using Charge-Transfer Complex-Doped Polyimide-Orientation Films
Authors: Nakaya Kenji , Zhang Bai Ying , Yoshida Masaaki , Isa Isao , Shindoh Shukoh , Kobayashi Shunsuke
Published: February 2005

Enhancement of bistability and response speed in a surface stabilized ferroelectric liquid crystal (SSFLC) electrooptic device was realized by doping polyimide-orientation films with a charge-transfer complex (CTC) and performing appropriate rubbing. The effects of the enhancement are thought to be attributable to the appropriate AC conductivity of CTC-doped polyimide films which are capable of neutralizing accumulated surface charges brought about by electrical polarization contributing to the spontaneous polarization of the ferroelectric liquid crystal.
Superconductive Transition at 120 K in a Tl-Bi-Sr-Ca-Cu-O System
Authors: Inoue Osamu , Adachi Seiji , Kawashima Syunichiro
Published: February 2005

Superconductivity and crystal structure of a Tl-Bi-Sr-Ca-Cu-O system were studied. A T
c-onset temperature of 120 K as determined by AC susceptibility measurement was achieved for the nominal composition of Tl2Bi0.5Sr2Ca3Cu4O
x
ceramics sintered at 900°C for 100 h. The superconductive phases synthesized in the Tl-Bi-Sr-Ca-Cu-O system were (Tl, Bi)Sr2CaCu2O
x
and (Tl, Bi)Sr2Ca2Cu3O
x
(“1212” and “1223” phases). Superconductivity at 120 K may be due to this “1223” phase.
Direct Preparation of Fine Powders of the 80 K Superconducting Phase in the Bi-Ca-Sr-Cu-O System by Spray Pyrolysis
Authors: Tohge Noboru , Tatsumisago Masahiro , Minami Tsutomu , Okuyama Kikuo , Arai Kouji , Kousaka Yasuo
Published: February 2005

Submicron powders of the 80 K superconducting phase in the Bi-Ca-Sr-Cu-O system have been directly prepared by the spray pyrolysis of aqueous solutions of corresponding metal nitrates, Bi:Ca:Sr:Cu=1:1:1:2. The powders obtained were spheres with uniformly distributed diameters below 1 µm. The crystalline phase of these powders was found to greatly depend on the oxygen partial pressure in the carrier gas as well as the decomposition temperature. The preparation conditions for the 80 K superconducting phase were examined.
Fabrication of Y-Ba-Cu-O Superconducting Wire by the Powder-Sol Method
Authors: Enomoto Ryo , Tamaki Masanori , Ohno Satoshi , Fuwa Mayumi , Takei Humihiko
Published: February 2005

Y-Ba-Cu-O superconducting wires have been prepared by using the powder-sol method. Wires with a typical diameter of 280 µm were made by extruding a suspension of YBCO powder with a mixture of organic metal compounds, followed by sintering at a temperature between 910°C and 940°C in flowing oxygen. The maximum current density of 2020 A/cm2 in liquid nitrogen was obtained on the wires fired at 930°C.
Preparation of Y-Ba-Cu-O Superconducting Thin Films by the Mist Microwave Plasma Decomposition Method
Authors: Koukitu Akinori , Hasegawa Yoshitsugu , Seki Hisashi , Kojima Hironao , Tanaka Isao , Kamioka Yasuharu
Published: February 2005

Superconducting thin films of the Y-Ba-Cu-O system were prepared on single crystal MgO(100) substrates by a new technique, the mist microwave plasma decomposition method. The onset and zero resistance temperatures occurred at 85 K and 78 K, respectively, for the as-grown film. The lattice constant c
0 estimated from Bragg angles of (00n) planes was 11.69 Å.
Fabrication of High-Tc Bi-Pb-Sr-Ca-Cu-O Superconducting Printed Films on Ag Tape
Authors: Hoshino Kazutomo , Takahara Hidefusa
Published: February 2005

High-T
c superconducting Bi-Pb-Sr-Ca-Cu-O films have been successfully prepared on Ag tapes by using the combination processes of screen printing, cold rolling and sintering. These highly c-axis-oriented films show a zero resistance of above 100 K. It has been found that the cold rolling process drastically improves the packing density of screen printed films as well as the critical current density J
c of the tape. The J
c of the film on the Ag tape at 77 K in a zero magnetic field is about 3100 A/cm2.
In Situ Growth of Bi-Sr-Ca-Cu-O Thin Films by Molecular Beam Epitaxy Technique with Pure Ozone
Authors: Nakayama Yoshimi , Ochimizu Hirosato , Maeda Atsutaka , Kawazu Akira , Uchinokura Kunimitsu , Tanaka Shoji
Published: February 2005

Thin films of Bi-Sr-Ca-Cu-O have been grown in situ on SrTiO3 (001) substrates using a molecular beam epitaxy technique with a pure ozone source. This allows us to grow highly oriented films at substrate temperature of 700°C without heat treatment in oxygen. One of the films showed a superconducting transition at 10.0 K.
Flux Pinning and Weak Link Structure in Ca-Doped LaBa2Cu3O7-y
Authors: Masuda Hiromu , Mizuno Fumio , Hirabayashi Izumi , Tanaka Shoji
Published: February 2005

The effect of Ca doping on the flux pinning and the weak link structure of the LaBa2Cu3O7-y
system have been studied. The magnitude and the magnetic field dependence of the critical current density were improved by Ca doping. A small amount of impurity phases of Ca-related compounds such as Ca2Cu1O3 and Ca1Cu2O3 may work as a desirable flux pinning center. Moreover, it was found that the current-temperature characteristics for Ca-doped samples showed the evidence of two kinds of superconductor phases which have different transition temperatures T
c and T
c'. The experimental result agreed well with the Ambegaokar-Baratoff theory for asymmetric Josephson junctions (S-I-S') in the temperature range of T<T
c' and with the proximity junction theory (S-N-S) in the range of T
c'<T<T
c.
InGaAsP/InP Lasers with Two Reactive-Ion-Etched Mirror Facets
Authors: Gurp G. J. van , Jacobs J. M. , Binsma J. J. M. , Tiemeijer L. F.
Published: February 2005

Reactive ion etching in chlorine, methane, argon and hydrogen was used to etch smooth vertical mirror facets on both sides of InGaAsP/InP lasers. Optical measurements and lifetests show these lasers to have the same characteristics as lasers with cleaved facets.
Proposal and Experimental Results of Disordered Crystalline Semiconductors
Authors: Sasaki Akio , Kasu Makoto , Yamamoto Teiji , Noda Susumu
Published: February 2005

A new semiconductor which exhibits unusual luminescent capability is proposed, and experimental results of photoluminescence to confirm the proposal are reported. The semiconductor can be called as a “disordered crystalline semiconductor”, since the atomic arrangement is disordered but single-crystal epitaxial growth is possible.
Novel Phases Exhibiting Tristable Switching
Authors: Chandani A.D.L. , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo , Terashima Kanetsugu , Furukawa Kenji , Kishi Akira
Published: February 2005

The phase, designated as Sm CA
*, which shows tristable switching was investigated in C8H17O–--COO–-COO*CH(CH3)C6H13 (MHPOBC) by means of thermal analyses, a miscibility test and microscope observation. The phase transition from Sm C* to Sm CA
* is not observable by AC calorimetry but small peaks comparable to the Sm A-Sm C* transition are discernible in DSC. According to the miscibility test of racemic MHPOBC with a standard compound, this new phase was found to exist between Sm C* and Sm I* and not to be miscible with Sm Bhex. Therefore, the assignment of Sm CA
* to one of the known phases is ruled out, which means that Sm CA
* is a totally new phase. The difference between the pure enantiomer and the racemate is also pointed out.
Preparation of Pb(Mg1/3Nb2/3)O3 Thin Film by Sol-Gel Method
Authors: Okuwada Kumi , Imai Motomasa , Kakuno Keiichi
Published: February 2005

A thin film of Pb(Mg1/3Nb2/3)O3 was prepared by the sol-gel method using metal alkoxides. The X-ray analysis indicated that the perovskite phase was formed by sintering at over 600°C. The orientation and the crystallization rate were greatly influenced by the type of substrate and sintering conditions.
Tomography of Microstructures by Scanning Micro-RBS Probe
Authors: Kinomura Atsushi , Takai Mikio , Matsuo Takahiro , Satou Mamoru , Namba Susumu , Chayahara Akiyoshi
Published: February 2005

Tomographic images of microstructures were nondestructively obtained by Rutherford backscattering (RBS) analysis using 1.8 MeV proton and helium ion microprobes. Multilayered Au stripes isolated by SiO2 layers and a Ge island pattern below an SiO2 capping layer were cross-sectionally imaged without cleaving the substrate or removing the upper layer. The agglomeration of the Ge island after zone-melting recrystallization (ZMR) could be detected by tomographic images.
Effects of Increasing Injection Repetition Rate of Low-Energy Injection into a Compact Storage Ring
Authors: Takada Hiroshi , Tsutsui Yasumitsu , Tomimasu Takio
Published: February 2005

The relation between the injection repetition rate and beam accumulation in an electron storage ring were studied through experiments and beam tracking calculations.
The rate is an important parameter which limits beam current storage. It was believed that the stored beam current could not be increased even if the injection repetition rate was increased over the inverse of the radiation damping time of the betatron oscillations. This is an important consideration for low-energy injection.
The experiment was performed at 90 MeV using an NIJI-I compact electron storage ring, and a beam current accumulation rate was obtained above the limit determined by the radiation damping time. It was found that beam current accumulation depended on the kick angle of the kicker magnet.
Low-Temperature Deposition of Silicon Dioxide Films by Photoinduced Decomposition of Tetraethoxysilane
Authors: Niwano Michio , Hirano Satoshi , Suemitsu Maki , Honma Koji , Miyamoto Nobuo
Published: February 2005

A new method has been proposed for depositing silicon dioxide films on semiconductors at low temperatures by using ultraviolet (UV) lights. In this method, UV light emitted from a low-pressure Hg lamp is irradiated onto spin-on material which contains tetraethoxysilane Si(OC2H5)4. The light decomposes this compound, leading to the formation of silicon dioxide films. It is found that the physical properties of silicon dioxide films deposited on silicon are similar to those of oxide films obtained by conventional deposition methods, Evidence is presented indicating that UV light irradiation plays an important role in the formation of silicon oxides.
Detection of Hypervelocity Impact of Microprojectile by Piezoelectric Ceramics
Authors: Tamura Hideki , Tohyama Motohide , Sawaoka Akira B.
Published: February 2005

A piezoelectric ceramic plate, PZT 52/48, was applied to detect the hypervelocity impact of a microprojectile. The projectiles were accelerated by a gas gun and a plasma accelerator. The output voltage signal of PZT 52/48 was evaluated with respect to the diameter and momentum of the projectile. A good linear relation was found in the momentum range up to 1×10-4 kg·m/s. It was confirmed that the PZT 52/48 plate is a suitable material for the detection of the hypervelocity impact of a microptojectile up to 4.2 km/s.
Lattice-Mismatch-Induced Deep Level in InxGa1-xAsyP1-y (0≦y≦0.41) Grown on (100) GaAs
Authors: Zhu Qin-Sheng , Hiramatsu Kazumasa , Sawaki Nobuhiko , Akasaki Isamu
Published: February 2005

The effect of lattice mismatch between a quaternary alloy layer In
x
Ga1-x
As
y
P1-y
(0≦y≦0.41) and a (100) GaAs substrate is investigated by the deep level transient spectroscopy (DLTS) technique. It is found that a new electron trap level with an activation energy of E
c-0.61 eV and a large electron capture cross section of ∼10-13 cm2 appears when the epilayer InGaAsP is lattice-mismatched to the GaAs substrate at the growth temperature. The concentration of the new trap level increases with the increase of the lattice mismatch, and the concentration becomes larger close to the heterointerface of InGaAsP/GaAs. It is suggested that this level is related to an anion vacancy and/or a complex involving an impurity which is incorporated into the heterointerface at the initial stage of growth. The capture cross section of the new level might be of an Auger type.
Silicon and Selenium Doping Effects on Band-Gap Energy and Sublattice Ordering in Ga0.5In0.5P Grown by Metalorganic Vapor Phase Epitaxy
Authors: Gomyo Akiko , Hotta Hitoshi , Hino Isao , Kawata Seiji , Kobayashi Kenichi , Suzuki Tohru
Published: February 2005

Effects of n-type dopants Si and Se on band-gap energy (E
g) and on sublattice ordering for Ga0.5In0.5P grown by metalorganic vapor phase epitaxy, under conditions in which E
g shows anomalously low E
g values if the doping is not carried out, were studied by means of photoluminescence and transmission electron microscopy. In contrast to the previously reported p-type doping case, the effects on E
g were interpreted by considering two factors: (i) impurity-doping-induced diorsdering of <1/2, 1/2, 1/2 > superlattice (SL), and (ii) Burstein shift.
Preparation of the Bi(Pb)-Sr-Ca-Cu-O Fibrous Crystals Containing the High-Tc Phase
Authors: Matsubara Ichiro , Tanigawa Hideo , Ogura Toru , Yamashita Hiroshi , Kinoshita Makoto , Kawai Tomoji
Published: February 2005

Fibrous crystals containing the high-T
c phase of the Bi(Pb)-Sr-Ca-Cu-O superconductor have been prepared by heating a melt-quenched plate in a stream of O2 gas. The fibers show a remarkable resistance drop at 105 K. The high-T
c phase is detected on a microarea X-ray diffractometer and the high-T
c crystals are found to be stacked between the low-T
c platelike crystals. The highest T
c(zero) value so far obtained is 96 K.
Anomalous Field-Induced Resistive Transition in La2-xSrxCuO4
Authors: Suzuki Minoru , Hikita Makoto
Published: February 2005

We have observed a drastic change in magnetic-field-induced resistive transition behavior in La2-x
Sr
x
CuO4 as x increases from 0.1 to 0.3. For x≤0.15, applying a field induces development of a tail in the resistive transition curve, while for x=0.3, it merely causes parallel shift of the curve to lower temperatures, which is common to conventional type II superconductors. By analyzing field-dependent fluctuation conductivity, it is shown that this change in resistive transition is accompanied by a dramatic increase in coherence length in the CuO plane when x approaches 0.3.
Superconductivity in a Tl-Sr-Y-Cu-O System
Authors: Inoue Osamu , Adachi Seiji , Kawashima Syunichiro
Published: February 2005

Superconductivity and crystal structure for nominal compositions of Tl1.2Sr3-z
Y
z
Cu2.35O
x
(z=0, 0.15, 0.3, 0.5, 0.7, 1.0) ceramics were studied. Superconductive transitions were observed for z≦0.5. The maximum onset temperature was 95 K, but the zero-resistance temperature was below 40 K. The superconductivity near 90 K may have been caused by the so-called “1212” phase. It is considered that the Ca site of TlSr2CaCu2O
x
was substituted by Sr and Y in this superconductor.
Crystal Growth and Superconductivity of Tl-Ca-Ba-Cu-O System
Authors: Kotani Toshihiro , Kaneko Tetsuyuki , Takei Hiromi , Tada Koji
Published: February 2005

Single crystals of oxides in the Tl-Ca-Ba-Cu-O system with the general formula Tl2Ca
n-1Ba2Cu
n
O
x
(n=1, 2, 3, 4) have been successfully grown by the flux method. All crystals were of the platelet form ranging from 0.6 to 5 mm2. The transition temperatures of as-grown crystals, determined by DC SQUID magnetometer, were 84 K, 110 K, and 118 K for n=1, 2, and 3, respectively, but slightly lower for 115 K, where n=4. The results of the differential thermal analysis (DTA), X-ray diffraction measurement and energy dispersive X-ray microanalysis (EDX) will be also reported.
Fusible Poly(3-alkylselenophene) and Its Properties
Authors: Yoshino Katsumi , Onoda Mitsuyoshi , Manda Yasuhisa , Sawada Keiji , Sugimoto Ryu-ichi , Inoue Shigehito
Published: February 2005

The electrical conductivity of poly(3-alkylselenophene) is low and exhibits the range of an insulator. The band gap of poly(3-alkylselenophene) is evaluated at around 2.4 eV, which is larger than that of poly(3-alkylthiophene). The results are interpreted in terms of the decrease of the coplanary of selenophene rings due to a steric hindrance between the alkyl group and the large Se atom. Poly(3-alkylselenophene) is found to be soluble in several solvents. However, the color of the solution does not change drastically with temperature. Poly(3-dodecylselenophene) is found to be fusible at around 250°C, which is higher than the corresponding temperature for poly(3-dodecylthiophene) with the same alkyl chain length.
Gamma-Irradiation Effect on High-Tc Superconductor YBa2Cu3O7-x
Authors: Kutsukake Takao , Somei Hiromichi , Ohki Yoshimichi , Nagasawa Kaya , Kaneko Fumitaka
Published: February 2005

The effect of γ-irradiation on YBa2Cu3O7-x
was studied. It is concluded that there is virtually no change upon γ-irradiation up to 1000 MR (≃8 MGy), except for in the superconducting volume fraction.
Ion Irradiation Effects on Critical Current of Superconducting Bi-Sr-Ca-Cu-O Films
Authors: Takamura Saburo , Hoshiya Taiji , Agura Takeo , Kobiyama Mamoru
Published: February 2005

The critical currents under applied magnetic field are measured by the resistive method in polycrystalline Bi-Sr-Ca-Cu-O films after He ion irradiation at room temperature. The critical current decreases by irradiation and is inversely proportional to the resistance in the normal state after irradiation. The critical current is recovered appreciably by annealing at 400°C after irradiation.
Effect of Substrate Temperature and Composition on the Crystalline State of Ba2YCu3O7-δ Magnetron-Sputtered Thin Films
Authors: Shirakawa Yukihiko , Kobayashi Makoto
Published: February 2005

The effect of substrate temperature and composition on the crystalline state of Ba2YCu3O7-δ thin films prepared by magnetron sputtering are investigated. The as-sputtered films deposited above 560°C have a c-axis orientation perpendicular to the substrate. Their superconducting transition temperature are above 80 K at the thickness of 4000 Å and 48 K at the thickness of 100 Å. The preferred orientation and superconducting properties are strongly affected by the amount of deviation from the stoichiometric composition.
Domain Wall Motion in Magnetic Thin-Film Heads Driven by High-Frequency Current
Authors: Saka Chiaki , Shiiki Kazuo , Yuitoo Isamu
Published: February 2005

A domain wall motion is analyzed by calculating the time derivative of a Kerr signal waveform in the thin-film head. The Kerr signal is measured in a small 18×15-µm area with a 1 MHz coil current. It is found that the 180° wall moves a few microns in the direction of the magnetic field. In the observed area, one end of the wall moves before the other end. In the range of absolute currents of more than the critical value, wall motion does not follow the current change. Though the average velocity of the motion is about 4 m/s for a half cycle, the actual velocity is about 10 m/s.
Proposal on Reducing the Damping Constant in Semiconductor Lasers by Using Quantum Well Structures
Authors: Uomi Kazuhisa , Chinone Naoki
Published: February 2005

We propose that quantum well structures are effective for decreasing the nonlinear damping constant, K factor (\varGamma=K
f
r
2, \varGamma: damping factor, f
r: relaxation oscillation frequency) in semiconductor lasers. Theoretically calculated results indicate that by using quantum well structures with low threshold gain the K factor can be reduced by about 50% and the frequency limited by the nonlinear damping is a maximum of 50 GHz.
Low-Phase-Aberration Output of 830 nm AlGaAs Offset-Coupled Laser Arrays
Authors: Shinozaki Keisuke , Furukawa Ryozo , Fukunaga Toshiaki , Watanabe Nozomu
Published: February 2005

Phase-locked lasers with refractive-index waveguides have been developed. The elemental stripes of the laser are evanescently and offset coupled. A fundamental supermode operation in the 2/3-element laser arrays is achieved. The phase aberration is less than λ/14 (λ=830 nm). The output power of the laser array increases almost linearly up to 200 mW with an external differential slope efficiency of 0.75 W/A.
Fusible Conducting Poly(9-alkylfluorene) and Poly(9,9-dialkylfluorene) and Their Characteristics
Authors: Fukuda Masahiko , Sawada Keiji , Yoshino Katsumi
Published: February 2005

Conducting poly(9-alkylfluorene) and poly(9,9-dialkylfluorene) with long alkyl chains have been prepared and found to be fusible at relatively low temperature. Unlike in poly(3-alkylthiophene), electrical conductivity and band gap energy do not change remarkably at the solid-liquid phase transition. These polymers also demonstrate drastic changes of optical and electrical properties upon doping.
Chemical Bonds at and Near the SiO2/Si Interface
Authors: Hattori Takeo , Igarashi Takayuki , Ohi Makoto , Yamagishi Hiroaki
Published: February 2005

The concept of local electronegativity defined by Lucovsky1) was modified and applied to the study of the chemical bonds at and near the SiO2/Si interface. Even for a flat interface and no Si-Si bond in the oxide film, chemical bonds different from those in the bulk are found to exist not only at the interface, but also near the interface. The local electronegativities of silicon and oxygen atoms change their magnitudes within 1 nm of the interface.
GaAs Atomic Layer Epitaxy Using the KrF Excimer Laser
Authors: Kawakyu Yoshito , Ishikawa Hironori , Sasaki Masahiro , Mashita Masao
Published: February 2005

Complete self-limiting monolayer growth was achieved successfully in GaAs atomic layer epitaxy (ALE) using a KrF excimer laser. In thermal growth without laser irradiation, monolayer growth was achieved only for an extremely narrow temperature range around 500°C. With laser irradiation, monolayer growth was achieved for a relatively wide temperature range from 470°C to 530°C. The expanded temperature range for ALE under laser irradiation suggests an enhanced decomposition of Ga-containing adsorbates due to the photochemical effect, but not the thermal effect.
Organometallic Chemical Vapor Deposition of ZrF4-Based Fluoride Glasses
Authors: Fujiura Kazuo , Ohishi Yasutake , Takahashi Shiro
Published: February 2005

By organometallic chemical vapor deposition (OMCVD), fluoride glasses in a ZrF4-BaF2 binary system are successfully synthesized. β-Diketone chelates of Zr and Ba as starting materials can be volatilized and completely fluorinated with HF gas into ZrF4-BaF2 compounds. 65 mol%ZrF4-35 mol%BaF2 powder synthesized by OMCVD is identified as homogeneous glass by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). By this method, ZrF4 is also obtained in an amorphous state. The OMCVD is available for preparation of fluoride glass, which is promising for optical fiber.
Scanning Tunneling Microscopy of Anisotropic Monatomic Steps on a Vicinal Si(001)-2×1 Surface
Authors: Miki Kazushi , Tokumoto Hiroshi , Sakamoto Tsunenori , Kajimura Koji
Published: February 2005

Using scanning tunneling microscopy (STM), we investigated the surface step structure of Si(001) with a misorientation of 0.3° towards [110]. The STM images show uniform (2×1)+(1×2) terraces (double domain structure) separated by monatomic height steps. Alternate terraces show straight and kinked step edges. This anisotropic feature of step edges is attributed to both a large difference in formation energy between the two types of steps and an anisotropic diffusion of surface adatoms.
Atom Beam-Irradiation Effects on Selective Epitaxial Growth of GaAs by Metalorganic Chemical Vapor Deposition
Authors: Yamaguchi Ko-ichi , Okamoto Kotaro
Published: February 2005

By exposure to an atom beam, polycrystal deposition on mask films (W and SiO2) was suppressed in the selective epitaxial growth of GaAs by metalorganic chemical vapor deposition (MOCVD) under atmospheric pressure. While surface migration was enhanced on W surfaces, reevaporation was enhanced on SiO2 surfaces by atom beam irradiation. By optimizing growth conditions, selective epitaxial growth was realized without polycrystal deposition on stripe-shaped masks where the maximum width of the stripe was 40 µm for W masks and 150 µm for SiO2 masks.
Amorphous ZnO Thin Film Nonlinear Resistor
Authors: Ibuki Sumiaki
Published: February 2005

Thin films which were evaporated from materials with mixed ZnO:Bi ceramics and ZnSe sintered powders on ITO glass substrates at 250∼450°C, exhibit good nonlinear current-voltage characteristics. This nonlinearity is considered to result from the reduction and oxidation of ZnSe during the evaporation process, and a randomly mixed system composed of mainly ZnO and residuals of Se and ZnSe is formed.
Drain Current DLTS Study of an AlGaAs/GaAs MISFET
Authors: Shimizu Naofumi , Mizutani Takashi
Published: February 2005

The deep levels in the AlGaAs/GaAs heterostructure MISFETs were investigated by means of a current DLTS technique. From the analysis of DLTS spectra, two kinds of electron traps, the activation energies of which were 0.15±0.04 eV and 0.26±0.08 eV, were found. The DLTS signal amplitude for the MISFETs normalized by the steady-state drain current was smaller by a factor of 7∼70 than that for HEMTs which were measured as a reference, suggesting the advantages of the MISFETs which employ undoped AlGaAs as a gate insulator.
Effects of Ion Irradiation on the Critical Current Density of Ba2YCu3O7-δ Thin Films
Authors: Masegi Tamaki , Terai Takayuki , Takahashi Yoichi , Enomoto Youichi , Kubo Shugo
Published: February 2005

Effects of ion irradiation on the critical current density of high-T
c superconducting Ba2YCu3O7-δ thin films have been studied. For the film subjected to a fluence of 5.02×1011 ions/cm2 of 514 keV O+, the critical current density determined from I-V characteristics was enhanced by about 10% from 53 to 75 K. The temperature dependence of the critical current density was not affected by ion irradiation. Irradiation effects on the critical temperature of these films have also been investigated.
Preparation of the High-Tc Superconductor Pb2Sr2Y0.5Ca0.5Cu3O8+δ with Zero Resistance at 75 K
Authors: Masuzawa Masahiro , Noji Takashi , Koike Yoji , Saito Yoshitami
Published: February 2005

Good quality samples of the high-T
c superconductor Pb2Sr2Y0.5Ca0.5Cu3O8+δ have been prepared by solid-state reaction under low oxygen pressure and adequate post-annealing in flowing nitrogen gas. The best sample shows metallic temperature dependence of the resistivity above T
c, an onset of the superconducting transition at 83 K and zero resistance at 75 K. The adequate post-annealing, which is considered to decrease crystalline disorder, is effective in attaining good superconducting quality.
Influence of Carbon on Critical Temperatures of Superconducting Y-Ba-Cu-O
Authors: Itoh Mineo , Ishigaki Hiroyuki , Demizu Kei
Published: February 2005

High T
c copper oxide superconductors, such as Y-Ba-Cu-O, commonly have a high chemical activity during sintering. Y-Ba-Cu-O superconductors are influenced by impurities in air, which cause degradation of the superconducting properties, critical current density (J
c) and temperature of zero resistance (T
c
zero). XPS analysis of low J
c and T
c
zero materials shows a presence of carbon in a higher amount compared to high J
c and T
c
zero materials. This paper shows that J
c and T
c
zero are very susceptible to impure gases in air.
Reappearance of ESR in the Bi(Pb)-Sr-Ca-Cu-O System in the Superconducting State
Authors: Hayashi Yoshikazu , Sako Sanshiro , Fukui Minoru , Fujita Tetsuo , Sasakura Hiroyuki , Minamigawa Shinnosuke , Nakahigashi Kiyotaka
Published: February 2005

The electron spin resonance of Cu2+ ions in the high-T
c phase of the Bi(Pb)-Sr-Ca-Cu-O system has been confirmed to appear above T
c. Two components of ESR, namely, the relatively sharp anisotropic and the very broad isotropic ones, are observed in accordance with a previous result. Both of these spectra apparently disappear at the transition temperature T
c. However, the anisotropic spectrum reappears at a temperature well below T
c. The result is discussed in relation to the layered structure of the high-T
c superconductor with three sheets of a CuO2 plane.
Transport Properties of New High-Tc Superconductors Ln2-x+yCexBa2-yCu3O10-δ (Ln=Nd, Eu)
Authors: Tamegai Tsuyoshi , Iye Yasuhiro , Ogata Masahisa , Obara Kazuhiko , Akimitsu Jun
Published: February 2005

Transport properties were investigated for the new high-T
c superconductors Ln2-x+y
Ce
x
Ba2-y
Cu3O10-δ (Ln=Nd, Eu) with T
c in the 30 K range. Hall coefficients for these compounds are positive, indicating a hole conduction and are slightly temperature dependent with a broad maximum around 120 K. Average hole number per copper ion in the Cu-O planes estimated from the Hall coefficient just above T
c is 0.09, which is considerably lower than that of 0.23 in YBa2Cu3O7-y
. This may be the reason why T
c in Ln2-x+y
Ce
x
Ba2-y
Cu3O10-δ is as low as 30 K. If we adopt midpoints of the resistive transition as T
c in the magnetic field, the upper critical field at absolute zero for the europium compound is estimated as 22 Tesla.
Angular Dependence of the Upper Critical Field of La1.85Sr0.15CuO4 Single-Crystal Thin Films
Authors: Suzuki Minoru
Published: February 2005

Resistive transition curves of a La1.85Sr0.15CuO4 single-crystal thin film have been measured for various magnetic fields and angles between the CuO plane and the field. Using the mean-field approach to determine T
c(H), the upper critical field H
c2 and its angular dependence are estimated. For the magnetic fields parallel and perpendicular to the CuO plane, values for dH
c2
///dT=-11.8T/K and dH
c2
⊥/dT=-1.0T/K are obtained, resulting in an anisotropy factor of 12. The angular dependence of dH
c2/dT is explained well by the effective mass model. The Ginzburg-Landau coherence lengths are 32 Å in the CuO plane and 2.7 Å in the c-axis direction.
Critical Current Densities in Superconducting Y-Ba-Cu-O Prepared by the Quench-and-Melt Growth Technique
Authors: Matsushita Teruo , Ni Baorong , Murakami Masato , Morita Mitsuru , Miyamoto Katsuyoshi , Saga Makoto , Matsuda Shoichi , Tanino Mitsuru
Published: February 2005

The critical current characteristic of a Y-Ba-Cu-O specimen prepared by the quench-and-melt growth (QMG) technique was investigated by the ac-inductive method. It was found that there were two kinds of currents. The bulk critical current density is 1.0×108 A/m2 at 77 K and 0.12 T. This value is comparable to a previous estimate from dc-magnetization measurements. The local current density amounts to 3.2×1010 A/m2 under the same conditions. Appearance of two kinds of currents seems to be caused by nonsuperconducting second-phase layers formed along the direction of grain growth, which disturb uniform current.
Planar Defects in the New Superconducting Oxide (Eu1-xCex)2(Ba1-yEuy)2Cu3Oz Observed by High-Resolution Transmission Electron Microscopy
Authors: Matsui Yoshio , Horiuchi Shigeo , Sawa Hiroshi , Obara Kazuhiko , Akimitsu Jun
Published: February 2005

Planar defects in the 2-2-3 type of new superconducting oxide, R2B2Cu3O
z
[R is (Eu1-x
Ce
x
), (Ba1-y
Eu
y
); x and y are about 0.33 and z is about 8.54], recently discovered by Sawa et al. (to be published in J. Phys. Soc. Jpn.) are examined by high-resolution transmission electron microscopy. The planar defects are derived by the local replacements of R2O2-layers by R-layers to form defect stabs of 1.2 nm thickness, having local structure similar to that of RBa2Cu3O
y
.
Preparation of High-Tc Bi-Sr-Ca-Cu-O Films on MgO Substrates by the Method of Solvent Evaporation Epitaxy (SEE)
Authors: Takeya Hiroyuki , Takei Humihiko
Published: February 2005

Oriented thin films of the high-T
c superconductor, Bi2Sr2CaCu2O
x
, were prepared on a MgO (001) substrate by means of a KCl solvent evaporation technique. The film consisted of three phases: a major phase as Bi2Sr2CaCu2O
x
, a minor phase as Bi2Sr2CuO
x
and a trace phase as Bi2Sr2Ca2Cu3O
x
, whose ratio depended on the growth conditions. The films showed superconducting transitions in the as-grown state above 81 K and no residuai resistivity was observed below this temperature. The epitaxiai relationship between the film and the substrate is also mentioned.
Preparation of Y-Ba-Cu-O Thin Films by the CVD Method in a Vacuum-Evaporation-Type Reactor
Authors: Inoue Masumi , Takase Eiji , Takai Yoshiaki , Hayakawa Hisao
Published: February 2005

Y-Ba-Cu-O thin films were prepared on MgO(100) substrates by the CVD method using a vacuum-evaporation-type apparatus of compact size. Effects of the substrate temperature on the composition, electrical properties and crystallinity of the films were investigated. The composition ratio Ba/Y was virtually unaffected by the substrate temperature, while the ratio Cu/Y slightly decreased with increasing substrate temperature. The superconducting transition temperature and crystallinity were improved by increasing the substrate temperature. The film prepared at 740°C showed transition temperatures T
con=89 K and T
czero=57 K.
Raman Scattering Characterization of Strain in GaAs Heteroepitaxial Films Grown on Sapphire and Silicon-on-Sapphire Substrates
Authors: Humphreys T. P. , Posthill J. B. , Das K. , Sukow C. A. , Nemanichi R. J. , Parikh N. R. , Majeed A.
Published: February 2005

We report results pertaining to the measurement of strain by Raman spectroscopy in GaAs epitaxial films grown by molecular beam epitaxy on sapphire and silicon-on-sapphire substrates. Comparative studies indicate that the GaAs layers deposited directly on sapphire substrates show no measurable strain, and only a small residual tensile strain is observed in the films grown on silicon-on-sapphire substrates. The magnitude of the strain in the GaAs/silicon-on-sapphire heterostructures is reduced by over a factor of 4.5 as compared to that observed in the GaAs films deposited directly on single-crystal silicon (100) substrates under the same growth conditions.
Phase Transitions and Switching Behavior in a Fluorine-Containing Ferroelectric Liquid Crystal
Authors: Yamada Yuichiro , Mori Kahoru , Yamamoto Norio , Hayashi Hitoshi , Nakamura Koji , Yamawaki Masao , Orihara Hiroshi , Ishibashi Yoshihiro
Published: February 2005

Phase transitions and switching behavior in a fluorine containing ferroelectric liquid crystal, whose optical purity was controlled by mixing (R) and (S) enantiomorphs, were studied. Only for the pure (R) or (S) enantiomorphs, the phase transition from the SmA to the third state SmCA
*, occurred directly. For the mixtures of (R) and (S) enantiomorphs, the phase transition occurred from the SmA to the SmCA
* via the SmC*. In these mixtures, with decreasing temperature in SmC*, internal disclination loops changed from “boat type” to “stripe type”.
Thermally Stimulated Depolarization Current Study of Molecular Motions in Polychlorotrifluoroethylene
Authors: Shimizu Hiroshi , Nakayama Kazuo
Published: February 2005

Thermally stimulated depolarization current (TSDC) spectra of polychlorotrifluoroethylene with relatively low crystallinity were measured in the range of 85 to 400 K. Three TSDC peaks were observed at 362.5 K, 275 K, and 197.5 K, corresponding to β, γa and γc relaxation processes, respectively. Each relaxation process was analyzed from elementary TSDC spectra obtained by the thermal sampling technique. In these relaxation processes, it was found that the distribution of relaxation times was interpreted as a distribution in activation energies and the temperature dependence of relaxation times was ruled by the compensation law.
Phason Strains and Periodicity in Al-Ru-Cu Icosahedral Quasicrystals
Authors: Hiraga Kenji , Lee Kap Ho , Hirabayashi Makoto , Tsai An-Pang , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

Phason strains in a stable AN-Ru-Cu quasicrystal prepared by a conventional melting method were examined by electron diffraction and high-resolution electron microscopy. The phason strains are frozen in an as-cast AN-Ru-Cu alloy, and then are relaxed and virtually disappear by annealing at a high temperature of 1118 K which is about 50 K below the melting point of the alloy. The frozen phason strains, which are homogeneous at a µm scale having a long-range correlation, show a tendency to produce a periodicity along one axial direction.
Surface Conductance of Metal Surfaces in Air Studied with a Force Microscope
Authors: Morita Seizo , Ishizaka Tatsuya , Sugawara Yasuhiro , Okada Takao , Mishima Syuzo , Imai Syozo , Mikoshiba Nobuo
Published: February 2005

With a force microscope, the surface conductances of various metals in air were investigated by measuring both the contact force and the current between the metal surface and the W lever simultaneously. When the Ag surface approached the W lever, current began to flow only in the strong repulsive-force range in contrast to the Au surface, so that the Ag surface seemed to be oxidized slightly. In the case of the Ti surface, current was not observed even in the strong repulsive-force range, so that the Ti surface seemed to be oxidized thick enough to sustain this strong repulsive force.
Formation of CH Radical by Surface Bombardment in a Methane/Argon DC Discharge
Authors: Yamashita Yuhji , Toyoda Hirotaka , Sugai Hideo
Published: February 2005

Space-resolved optical emission spectroscopy was applied to investigate the deposition process of amorphous hydrogenated carbon (a-C:H) in a dc glow discharge. The CH(A2
Δ→ X2Π) emission was strongly enhanced and localized near the cathode surface in a CH4/Ar discharge. The time evolution of the CH emission along with the deposition or etching of a-C:H films revealed the CH radical formation by two surface processes: (i) fragmentation of energetic hydrocarbon particles at their impact on the cathode, and (ii) sputtering of the already deposited a-C:H film.