bluuebunny/crossref_metadata_2025 huggingface dataset:
Admittance Spectroscopy of ZnO Crystals Containing Ag
Authors: Yasuo Kanai Yasuo Kanai
Published: February 2005

An experiment on admittance spectroscopy was performed on the ZnO-Ag alloy diodes, in which Ag was thought to diffuse into the ZnO crystal. It was found that Ag behaved as an acceptor in ZnO. Its energy level was 0.23 eV below the conduction band, and the electron capture cross section was about 6×10-16 cm2.
Stability of Antiferroelectricity and Causes for its Appearance in SmCα
* and SmCA
* Phases of a Chiral Smectic Liquid Crystal, MHPOBC
Authors: Takanishi Yoichi , Hiraoka Kazuyuki , Agrawal Vijay K. , Takezoe Hideo , Matsushita Atsuo Fukuda
Published: February 2005

The smectic layer thickness and the switching behavior in MHPOBC have been studied as a function of temperature; SmCα
* is a tilted phase and is antiferroelectric at least in the higher-temperature region but becomes ferrielectric with decreasing temperature. The gradual appearance of ferrielectric characteristics in SmCα
* suggests the emergence of the Devil's staircase. To explain the antiferroelectricity in SmCα
* and SmCA
*, two types of molecular interactions are proposed: one is the interaction between the spontaneous polarizations in the neighboring layers which is effective in SmCα
*, and the other is the pairing of transverse dipole moments responsible for the antiferroelectricity in SmCA
*.
Metalorganic Chemical Vapor Deposition of BaTiO3 Films on MgO(100)
Authors: Nakazawa Hidenobu , Hisanori Yamane Hisanori Yamane , Toshio Hirai Toshio Hirai
Published: February 2005

BaTiO3 thin films were prepared on MgO(100) substrates by chemical vapor deposition using barium β-diketonate {Ba(C11H19O2)2} and titanium tetraisopropoxide {Ti[OCH(CH3)2]4} as metalorganic precursors. BaTiO3 films deposited at 800-1000°C showed prominent a-axis orientation perpendicular to the substrate surface. The deposition rate of these films was 1.0-1.2 µm/h. The rocking curve of BaTiO3(200) reflection from the film deposited at 800°C indicated strong crystallographic orientation. The epitaxial relationship between the film and the substrate was found by X-ray pole figure analysis. The relative dielectric constant of a polycrystalline BaTiO3 film prepared on a Pt(100)/MgO(100) substrate at 800°C was 1040 (10 kHz, 20 V/cm).
Heteroepitaxial Growth of LiTaO3 Single-Crystal Films by RF Magnetron Sputtering
Authors: Shiosaki Yasuyoshi Saito
Published: February 2005

Lithium tantalate (LiTaO3) thin films were deposited on sapphire-C substrates by rf magnetron sputtering at various substrate temperatures. The crystallinity was examined by X-ray diffraction and reflection high-energy electron diffraction (RHEED), and the refractive indices were determined by the prism coupling m-lines technique and the interferometric transmission spectrum. Single-crystal (0001)LiTaO3 films were heteroepitaxially grown on sapphire-C substrates above 600°C, and the dispersion relation of the refractive index agreed well with that of the bulk single crystal.
X7R Multilayer Ceramic Capacitors with Nickel Electrodes
Authors: Saito Hiroshi , Chazono Hirokazu , Hiroshi Kishi Hiroshi Kishi , Nobutatsu Yamaoka Nobutatsu Yamaoka
Published: February 2005

Electrical properties and microstructures of a holmium-doped (Ba1.01Mg0.01)O1.02(Ti0.98Zr0.02)O2 system were studied. Additions of Ho2O3 had little effect in preventing the dielectrics from reducing at high temperature, but the resistivity at low temperature increased with increasing amount of Ho2O3 when treated in oxidizing atmosphere at the cooling stage. From transmission electron micrograph (TEM) observation, it was noted that the microstructure exhibited a grain core-grain shell structure. Newly developed X7R multilayer ceramic capacitors with Ni electrodes revealed highly reliable electrical properties.
Growth, Structure and Properties of La2-xSrxNiO4 (x= 0 to 0.3) Single Crystals
Authors: Wen-Jye Jang Wen-Jye Jang , Humihiko Takei Humihiko Takei
Published: February 2005

Large, homogeneous single crystals of La2-x
Sr
x
NiO4 (x=0, 0.1, 0.2, 0.3) of 7 mm in diameter and 20 mm in length have been obtained by using a lamp-image type floating-zone furnace under oxygen atmosphere. The chemical and X-ray diffraction analyses reveal the presence of excess oxygen with a presumed form of peroxide ion in the crystals of x=0 and 0.1. Small magnetic susceptibility and obvious deviation from the Curie-Weiss law are observed, whereas the diamagnetic signals from superconductivity are not detected on heating from 4 K to 300 K. The resistivity is semiconductive at room temperature and becomes insulative below 100 K.
Green Emission in CdS/CdInGaS4
Authors: Ando Shizutoshi , Endo Saburo , Nakanishi Hisayuki , Taizo Irie Taizo Irie
Published: February 2005

We deposited CdS on a CdInGaS4 single crystal for various thicknesses and measured the photoluminescence spectra. The photoluminescence spectra of the CdS/CdInGaS4 samples thus obtained with deposition periods of 20 h and 40 h showed very intense green emission peaks at 2.4 eV of the photon energy. Peak energies and shapes of the green emission in CdS/CdInGaS4 were in good agreement with those in Cd3InGaS6.
Donor Gettering of LPE (Liquid-Phase-Epitaxy) InGaAsP Layers in the Presence of Er
Authors: Wu Meng-Chyi , Chen En-Hsing , Chin Tsung-Shune , Tu Yuan-Kuang
Published: February 2005

Er-doped InGaAsP epitaxial layers lattice-matched to InP with band gaps of 0.96 and 0.80 eV have been grown by liquid-phase epitaxy. All the Er-doped samples still exhibit n-type conduction, even though relatively large amounts of Er of up to ∼0.35 wt% were added to the growth solutions. The carrier concentrations of Er-doped InGaAsP layers are around 3∼30×1014 cm-3 and are one to two orders of magnitude lower than those of undoped layers. By 300- and 16-K photoluminescence measurements, we can observe that the full width at half-maximum of photoluminescent peaks related to the near band-to-band transition has been effectively reduced. The low carrier concentrations and narrow linewidths are better than those previously reported for layers of the same composition. We thus conclude that the dominant process occurring during the growth of InGaAsP layers in the presence of Er elements is a very efficient gettering of residual donors.
Absorption and Photoluminescence Spectra of Heavily Zn-Doped CuGaS2 Crystals
Authors: Ooe Akihiro , Tsuboi Nozomu , Iida Seishi
Published: February 2005

In heavily Zn-doped (up to 5%) CuGaS2 crystals, reductions of excitonic absorption and above-band-gap absorption were observed for optical transitions of the polarization parallel to the optic axis, probably related to a change in the exciton oscillator strength ratio of the transitions of polarizations parallel and perpendicular to the optic axis. An impurity absorption whose concentration dependence is consistent with electron transitions from ZnGa acceptors to the conduction band is reported for the first time. An emission appearing at 2.1∼2.3 eV is considered to be due to the electron transitions from a donor level of sulfur vacancies or their complexes with ZnGa to the ZnGa acceptor level, involving the effect of broadening of the latter level. The existence of isoelectronic-trap ZnCu-ZnGa pairs is suspected from time-resolved emission spectra.
Temperature Dependence of Electron Mobility in Si Inversion Layers
Authors: Masaki Kazuo , Taniguchi Kenji , Hamaguchi Chihiro , Iwase Masao
Published: February 2005

Temperature dependence of electron mobility in Si inversion layers is investigated using channel conductance measurements in the temperature range from 15 to 300 K. The electron mobility is analyzed by using the theoretical model in which two-dimensional electron gas confined in the inversion layer interacts with acoustic phonons, intervalley phonons, surface roughness, and ionized impurities. At higher temperatures above 100 K, the electron mobility is dominated by acoustic phonon scattering and intervalley phonon scattering. At temperatures below 100 K, ionized impurity scattering plays an important role in determining the mobility in the case of low electron sheet densities, whereas in the case of higher electron sheet densities, surface roughness scattering becomes important.
Variation of Transport Properties with Density of YBa2Cu3-xMxO7±y (M=Ti4+, V5+, Cr3+ or Mn4+ and x=0.0-0.1 g atom)
Authors: P. Umadevi Muralidharan P. Umadevi Muralidharan , A. D. Damodaran A. D. Damodaran
Published: February 2005

The effect of the sintered density on the transport properties like normal state resistivity, T
c (superconducting transition temperature) and absolute thermopower has been studied for doped YBCO (YBa2Cu3-x
M
x
O7±y
, where M=Ti4+, V5+, Cr3+ and Mn4+ and x=0.0-0.1 g atom). The sintered density of the sample depends on the valency of the substituent. The density increases in the order pure YBCO<Cr3+ doped YBCO<Ti4+ doped YBCO<Mn4+ doped YBCO<V5+ doped YBCO. The resistivity as well as absolute thermopower decreases with increasing density. The significance of these results for the technological applications of granular superconductors is briefly discussed.
Shot Noise in Back-Biased Step Junctions with Exponential Carrier Generation Rate
Authors: Kazuhiro Sasaki Kazuhiro Sasaki , Kazunori Sato Kazunori Sato
Published: February 2005

A theory of noise due to carrier generation in the space charge region of one-sided abrupt junctions with exponentially graded generation rate is presented. Assuming that the generation rate is expressed as C
0 exp (-x/a) and the noise spectrum as S(ω)=2q
IΓ2, we find that the noise reduction factor Γ2 lies between 0.68 and 1, depending upon the ratio of the characteristic length, a, to the width of the space charge region.
Investigation of Heat-Treating Conditions for Silver-Sheathed Bi2212 Superconducting Coils
Authors: Shibutani Kazuyuki , Egi Toshio , Hayashi Seiji , Rikuo Ogawa Rikuo Ogawa , Yoshio Kawate Yoshio Kawate
Published: February 2005

Fabrication of silver-sheathed Bi-2212 superconducting coil has been attempted by means of the partial melt growth process. Silver-sheathed Bi-2212 tapes have been cooled down slowly from the temperature range of 875-890°C to 850°C at the rate of 6°C/h. The characteristics of J
c-H, AC magnetic susceptibility and X-ray diffraction pattern have been measured, and the SEM image of the cross section has been observed. The pancake-type test coil has been fabricated using an optimized heat-treating condition. This coil generates 0.22 T in the external magnetic field of 0 T and 0.07 T in the external magnetic field of 6.64 T at 4.2 K.
Influence of Compression Processes on the Formation of H-Aggregates in Hemicyanine Monolayer on Water Surface
Authors: Kajikawa Kotaro , Shirota Koichiro , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

The influence of the compression process on the formation of H-aggregates has been studied by means of the absorption spectra of the hemicyanine monolayer on the water surface. It was found that the conventional compression by moving the barrier does not bring about the formation of the H-aggregates but that the compression by spreading the dye solution does cause the formation. Absorption spectra in several geometries reveal that most of the aggregated molecules deposited on a substrate (LB film) are aligned along the surface normal and that the molecules on water (L film) tilt from the water-surface normal.
The Gate-Bias Dependency of Breakdown Location in GaAs Metal Semiconductor Field Effect Transistors (MESFETs)
Authors: Jayne M. Ashworth Jayne M. Ashworth , Norbert Arnold Norbert Arnold
Published: February 2005

The breakdown behaviour of refractory metal self-aligned GaAs metal semiconductor field effect transistors (MESFETs) has been studied by two-dimensional simulation using a drift-diffusion transport model and emission microscopy. Exact quantitative simulation of the device characteristics has been achieved for a device with a four fold implant scheme. The location of breakdown, as defined as the area of high avalanche generation rate, has been found to have a specific gate bias dependence: For open channel bias condition (V
gs=0 V) impact ionization is initiated at the n+ to channel implant interface, under subthreshold conditions however at the gate contact edges. The shift of the location as well as the MESFET specific gate bias dependence of drain breakdown could be explained by careful examination of the electric fields and the currents (holes and electrons) involved. These results have been experimentally verified by the light emission of the devices which were measured by high resolution emission microscopy.
A Superlow-Noise AlGaAs/InGaAs/GaAs Doped Channel Heterojunction Field-Effect Transistor (DC-HFET) with 0.15-µm Gate Length
Authors: Sawada Minoru , Nagami Kimihiki , Nishida Masao , Kaizaki Yasuhiro , Daijiro Inoue Daijiro Inoue , Yasoo Harada Yasoo Harada
Published: February 2005

A doped channel heterojunction field-effect transistor (DC-HFET) has been developed using an AlGaAs/InGaAs/GaAs pseudomorphic system which has an electron confinement effect superior to that of an AlGaAs/GaAs system. An excellent minimum noise figure (N
F
min) of 0.65 dB and associated gain (Ga) of 11.3 dB were realized at 12 GHz (drain current (I
ds)=18 mA, drain voltage (V
ds)=2 V). The NF had weak dependences on the I
ds and frequency, as in the case of high electron mobility transistors (HEMTs). The transconductance (g
m) at I
ds=10 mA was 385 mS/mm and maximum g
m reached 570 mS/mm (I
ds=50 mA).
In0.5Ga0.5As/InAlAs Modulation-doped Field Effect Transistors on GaAs Substrates Grown by Low-Temperature Molecular Beam Epitaxy
Authors: Masato Hiroyuki , Toshinobu Matsuno Toshinobu Matsuno , Kaoru Inoue Kaoru Inoue
Published: February 2005

We report on the lattice-mismatched growth and electrical properties of In0.5Ga0.5As/InAlAs modulation-doped heterostructures on GaAs substrates by molecular beam epitaxy using a wide-gap InAlAs graded buffer layer and low-temperature Molecular Beam Epitaxial growth at about 350°C. A drastic reduction in residual carrier accumulation has been achieved, and a high electron mobility at room temperature of 11100 cm2/V·s was obtained with an electron concentration of 3×1012/cm2. It was found that the cause of residual carrier accumulation is related to the growth interruption or temperature rise after the growth of the graded buffer layer. The fabricated Modulation-doped Field Effect Transistors showed low output conductance, good pinch-off characteristics and no kink effect. The higher transconductance of 270 mS/mm was also obtained.
Low Temperature Magnetoresistance of a Quasi-Ballistic Narrow Wire Confined by Split Metal Gates
Authors: Ochiai Yuichi , Onishi Taizo , Bird Jonathan Paul , Kawabe Mitsuo , Ishibashi Koji , Aoyagi Yoshinobu , Namba Susumu
Published: February 2005

We have studied a size effect related to boundary scattering in two different types of quasi-ballistic, narrow wire system. Lateral confinement of a two dimensional electron gas, confined at the interface of a GaAs/AlGaAs heterojunction, was achieved alternatively through the use of a dry etch or by means of a pair of split metal gates. Clear differences in the magnitude of the size effect are observed between these two systems, which we explain in terms of the relative degree of specular and diffusive boundary scattering in the wires.
Blue Electroluminescence from ZnSe p-n Junction Light-Emitting Diodes
Authors: Ohkawa Kazuhiro , Akira Ueno Akira Ueno , Tsuneo Mitsuyu Tsuneo Mitsuyu
Published: February 2005

Pure blue-light emission has been obtained from homoepitaxial ZnSe p-n junction light-emitting diodes (LEDs). Homoepitaxy is made on ZnSe substrates dry-etched by a BCl3 plasma. High-quality p-n junctions consists; of N-doped p-type ZnSe formed by active-nitrogen doping and Cl-doped n-type ZnSe using ZnCl2 as a dopant source. Current-voltage characteristics of the LEDs exhibited good rectification properties. The peak energy of blue electroluminescence from the LEDs was 2.67 eV with a narrow full width at half-maximum of 49 meV.
Transverse Mode Characteristics of a DBR-Surface Emitting Laser with Buried Heterostructure
Authors: Ogura Mutsuo , Fujii Seiji , Okada Takumi , Mori Masato , Mori Katsumi , Asaka Tatsuya , Iwano Hideaki
Published: February 2005

Distributed Bragg reflector (DBR)-surface emitting lasers (SELs) with buried heterostructure (BH) are fabricated with the combination of metal-organic chemical vapor deposition (MOCVD), electron cyclotron resonance (ECR) dry-etching and liquid phase epitaxial (LPE) regrowth techniques. Low threshold and stable fundamental lateral-mode characteristics are realized by the optimum design of the cavity diameter and refractive indices. Other important characteristics such as polarization characteristics, series resistance and thermal resistance are also discussed.
Quantum Mechanical Transmission and Reflection of Quasi-Particles at Arbitrary Potential Barriers in the Superconducting Base Transistor
Authors: Yamamoto Tetsuya , Suzuki Hiroshi , Usuki Tatsuro , Yorinobu Yoshisato Yorinobu Yoshisato , Shoichi Nakano Shoichi Nakano
Published: February 2005

We propose a systematic method for calculating the quasi-particle transmission, T, and reflection, R, probabilities at the arbitrary potential barrier, by using multistep potential approximation. T and R were calculated from first principles using the Bogoliubov equations of motion. For the N/I/S emitter-base tunneling junction and base-collector heterojunction in the superconducting base transistor, T and R were computed as functions of quasi-particle energy, potential barrier height and width. In the case of the YBCO/n-InGaAs base-collector heterojunction with a Schottky barrier height of 70 meV, it was found that T was greater than 0.5. This suggests that a combination of YBCO and n-InGaAs is suitable for use in the base-collector heterojunction of a superconducting base transistor. We also show I-V curves for the N/I/S tunneling junction.
Measurement of Disintegration Rates of 60Co Volume Sources by the Sum-Peak Method
Authors: Takao Kawano Takao Kawano , Hiroshi Ebihara Hiroshi Ebihara
Published: February 2005

The sum-peak method has been applied to the determination of the disintegration rates of 60Co volume sources (1.05×104 Bq, 1.05×103 Bq and 1.05×102 Bq, in 100-ml polyethylene bottles) by using a NaI(Tl) detector of a diameter of 50 mm and a height of 50 mm.
The experimental results showed that decreasing the disintegration rates resulted in enlarged underestimation in comparison with the true disintegration rates. It was presumed that the underestimations of the disintegration rates determined by the sum-peak method resulted from the overestimations of the areas under the sum peaks caused by the overlap of the area under the Compton scattering of the γ-ray (2614 keV) emitted from a naturally occurring radionuclide 208Tl under the sum peaks.
Spectroscopic Study on Plasma-Enhanced Chemical Vapor Deposition of YBa2Cu3Ox Superconducting Thin Films
Authors: Sugii Nobuyuki , Imagawa Kazushige , Sakae Saito Sakae Saito , Keiichi Kanehori Keiichi Kanehori
Published: February 2005

The effect of plasma enhancement on the chemical vapor deposition of YBa2Cu3O
x
thin films is investigated using optical emission spectroscopy. Emission due to π* excitation of organometallic complexes is observed at 316 nm. On the other hand, emission due to oxygen atoms or ions is not observed. High oxygen pressure and coexistence of Ar gas are thought to be the reason for this result. The intensity of emission due to organometallic complexes increases as the microwave power increases. Since the crystallinity of the grown films is improved with increasing microwave power, excitation of organometallic complexes is thought to have an effect on enhancing crystallization.
Raman Scattering in ZnSxSe1-x Alloys
Authors: Hayashi Kouji , Nobuhiko Sawaki Nobuhiko Sawaki , Isamu Akasaki Isamu Akasaki
Published: February 2005

Raman scattering at room temperature is reported in ZnS
x
Se1-x
alloys for the range of 0≦x≦1. The optical phonon energies are varied as a function of x and subjected to asymmetric broadening. The asymmetric broadening of the spectra is explained by a “spatial correlation” model assuming spherical compositional clusters of which distribution is described by the Gaussian correlation function. The results demonstrate that Raman spectroscopy is a powerful tool to study the microscopic structure of the substitutional disorder.
Magnetooptical Characterization of Clb-Type Heusler Compounds, Pt1-x/2Mn1+xSb1-x/2(x=-0.1 and 0, 0.1)
Authors: Takanashi Kōki , Sato Katsuaki , Watanabe Jun , Sato Yumiko , Hiroyasu Fujimori Hiroyasu Fujimori
Published: February 2005

Diagonal (εxx) and off-diagonal (εxy) elements of the dielectric tensor for a polished surface of a bulk sample of stoichiometric PtMnSb were obtained from the measured spectra of reflectance (R), magnetooptical Kerr rotation (θK) and ellipticity (ηK). The enhancement of θKby annealing was found to be due mainly to the decrease in the imaginary part of εxx. The magnetooptical absorption spectrum was in good agreement with that estimated from the joint density of states calculated by van der Heideet al. The spectra of εxxand εxyxwere also obtained for nonstoichiometric Pt1-x/2Mn1+xSb1-x/2(x=-0.1 and 0.1). It was suggested that the band structure was changed by the existence of excess Mn atoms.
Pressure Effect of the Lattice Parameters for Mn2Sb and MnMGe (M=Al, Ga)
Authors: Kanomata Takeshi , Kawashima Takashi , Kaneko Takejiro , Takahashi Hiroki , Mōri Nobuo
Published: February 2005

High-pressure powder X-ray diffraction experiments have been performed for Mn2Sb, MnAlGe and MnGaGe up to a pressure of 7.7 GPa at 300 K. Mn2Sb exhibits a discontinuous change in the lattice parameters a and c at about 3.5 GPa with increasing pressure. For MnAlGe and MnGaGe, the lattice parameters decrease linearly with increasing pressure.
Linear and Nonlinear Optical Properties of a Comb-Like Polymer
Authors: Chen Yongming , Rahman Matior , Takahashi Toru , Mandal Braja , Lee Junyoung , Tripathy Jayant Kumar
Published: February 2005

Linear and nonlinear optical properties of a comb-like polymer, viz. copolymer of methylmethacrylate (MMA) and 4-[4-(-methylacryloxy) octyloxy 2-methylphenyliminomethyl] cyanobenzene, are described. The second order nonlinear optical coefficient and the short and long term decay constants of second harmonic generation (SHG) intensity of the poled polymeric films are obtained from SHG measurements. The stability of the second order nonlinear optical properties is monitored by studying the time behavior of SHG. The Waveguiding loss was found to be 1 dB/cm.
UV-Laser-Excited Micro-Raman Spectroscopy of Organic Materials
Authors: Urabe Hisako , Takeda Shigeto , Simizu Ryosuke , Tsukakoshi Motowo , Kasuya Takahiro
Published: February 2005

Preliminary results on the Raman spectra of organic materials obtained using a newly assembled UV-laser-excited Raman-microprobe system are reported. Fluorescence-free spectra are obtained for the materials, which show tremendous fluorescence when excited by visible laser light. Signal enhancement due to a preresonant effect is also observed.
Amorphous Silicon-Carbon Alloy Prepared by the CMP (Controlled Plasma Magnetron) Method
Authors: Nishikuni Masato , Ninomiya Kunimoto , Okamoto Singo , Takahama Tsuyoshi , Tsuda Shinya , Ohnishi Michitoshi , Shoichi Nakano Shoichi Nakano , Yukinori Kuwano Yukinori Kuwano
Published: February 2005

Hydrogenated amorphous silicon-carbon (a-SiC) films were fabricated using a novel plasma CVD method, called the CPM (Controlled Plasma Magnetron) method. The films obtained had a large Si-C bond density and a low Si-H bond density. The absorption coefficient at the photon energy level of 2.5 to 3.5 eV for these films was one order of magnitude lower than that for conventional a-SiC films. Furthermore, the dark conductivity of boron-doped films increased to more than 10-4 (Ω·cm)-1, which is the highest value achieved for a-SiC with a carbon content of 55%.
Vp×B Acceleration of Electrons by Phased Gaussian Laser Beams
Authors: Ryo Sugihara Ryo Sugihara
Published: February 2005

A system of phased multi-laser beams can construct an effective slow wave which traps and accelerates electrons if an external magnetic field is applied so as to obey the V
p×B acceleration principle. The shape of an individual laser beam is chosen to be Gaussian in one dimension, and the wave field is assumed to be linearly polarized. The beam divergence accompanied by the Gaussian beam is also taken into account. A necessary condition for the electron trapping is obtained. Acceleration of the electron satisfying the condition is continuous and subsequently, arbitrarily large energy is theoretically possible.
Effects of Deuterium on Low-Temperature Si Epitaxy by Photo-Chemical Vapor Deposition
Authors: Jia Ying , Yamada Akira , Makoto Konagai Makoto Konagai , Kiyoshi Takahashi Kiyoshi Takahashi
Published: February 2005

Epitaxial Si films have been successfully grown by the photochemical vapor deposition process using the mixture of SiH4, SiH2F2 and D2 gases at temperatures from 200 to 475°C. Using H2 as diluting gas, the epitaxial Si films were obtained at temperatures from 200 to 350°C. However, the upper limit of the growth temperature was raised about 100°C (from 350 to 475°C) by substituting D2 for H2 as the diluting gas. Surface morphology and crystallinity were also improved with D2. Furthermore, we carried out heavy phosphorous doping with D2 and obtained a film with an electron concentration of 1×1021 cm-3.
Ohmic Contacts of AuGeNi and Ag/AuGeNi to n-GaSb with Various Sintering Temperatures
Authors: Su Yan Kuin , Fuh Shyang Juang Fuh Shyang Juang , Kuang Jou Gan Kuang Jou Gan
Published: February 2005

The ohmic contact properties of Ag/AuGeNi/n-GaSb and AuGeNi/n-GaSb systems were investigated in this paper by measuring the barrier height and specific contact resistance with various sintering temperatures. The lowest specific contact resistance was about 8×10-3-8×10-4 Ω·cm2 for the Ag/AuGeNi/n-GaSb contact system when the sintering temperature was 400°C for 2 min. This is better than that of the AuGeNi/n-GaSb contact system. Rutherford backscattering spectroscopy (RBS) was also used to study the interface between Ag/AuGeNi and GaSb during heat treatment. The Au peak in RBS spectra disappeared and the spectra became smooth when the ohmic contact was formed.
Low-Temperature Deposition of Y-Ba-Cu-O Superconducting Films by Thermal Chemical Vapor Deposition
Authors: Yamane Hisanori , Hasei Masaharu , Kurosawa Hideyuki , Toshio Hirai Toshio Hirai
Published: February 2005

Y-Ba-Cu-O superconducting films having a zero-resistance temperature of 84-85 K were prepared at 650°C on SrTiO3(100) single-crystal substrates without postannealing by thermal chemical vapor deposition using β-diketone metal chelates as sources and O2 with low partial pressure as a reactant gas. The films mainly consisted of YBa2Cu3O
x
with a-axis and c-axis orientations normal to the film planes.
Post Growth Fabrication of GaAs/AlGaAs Reflection Modulators via Impurity Free Disordering
Authors: Ghisoni Marco , Parry Gareth , Pate Malcolm , Hill Geoff , Roberts John
Published: February 2005

Disordering of GaAs/AlGaAs multiple quantum well asymmetric Fabry-Perot modulators (AFPM) was carried out using impurity free vacancy diffusion (IFVD), involving the deposition of a SiO2 cap followed by rapid thermal annealing at 930°C. Blue shifts of up to 52 meV, while maintaining clearly resolved heavy and light hole excitons, were achieved. This enabled the production of both normally-off (contrast >10 dB for -5 V bias) and normally-on (reflection change >30% for -8V) AFPM's from the same wafer, thus displaying how IFVD can be used to tailor the optoelectronic properties after growth.
Influence of the Optical Purity on the Smectic Layer Thickness and the Transition Order in Enantiomeric Mixtures of an Antiferroelectric Liquid Crystal
Authors: Ikeda Asako , Takanishi Yoichi , Takezoe Hideo , Fukuda Atsuo , Inui Shiroh , Kawano Shin , Saito Masaki , Iwane Hiroshi
Published: February 2005

The transition behavior in the (R)- and (S)-mixtures of 4-(1-trifluoromethylheptyloxycarbonyl)phenyl 4-(5-dodecyl-oxypyrimidin-2-yl)benzoate (TFMHPDOPB) has been studied by X-ray diffraction. Two important findings were made. In all the mixtures, the transition is of the first order irrespective of the spontaneous polarization and the transition sequences; SmA-SmC*
A (pure enantiomers), SmA-SmC* (R:S=3:1) and SmA-SmC (racemate). The layer thickness depends on the optical purity even in the SmA phase, although the overall profiles of the temperature dependence are almost the same in all the mixtures.
Thermal Stability of Au-Sn/Near Noble Metal Barrier Metallization Systems
Authors: Osamu Wada Osamu Wada , Tsugio Kumai Tsugio Kumai
Published: February 2005

We studied the reaction barrier characteriatics and thermal stability of evaporated Pd, Pt and Rh films when used with Au-Sn (30 wt% Sn). Sn in Au-Sn diffused preferentially into a barrier metal uniformly for all three metals. The diffusion coefficient was sufficiently small for Pt and Rh. Rh showed the samllest diffusion coefficient between 200°C and 400°C with the highest activation energy, 1.95 eV, below the melting point of Au-Sn (280°C). This result demonstrates the usefulness of Pt, and especially Rh, in highly stable metallization systems applicable to flip-chip integration.
Atomic Layer Growth of Bi-Sr-Ca-Cu-O by Molecular Beam Epitaxy Using Ozone under UV Irradiation
Authors: Yokoyama Shin , Ishibashi Takayuki , Masaaki Yamagami Masaaki Yamagami , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Bi-Sr-Ca-Cu-O thin film with a zero-resistance critical temperature of 58 K has been grown by the molecular beam epitaxy technique in an ozone and oxygen mixture ambient under irradiation of ultraviolet light without postheat treatment. In situ reflection high-energy electron diffraction measurement during the layer-by-layer growth reveals that the reconstruction takes place just after completing the deposition of a single unit layer (a half-unit cell).
Coexistence of Bolometric and Nonbolometric Optical Responses in High-Tc LnBa2Cu3Oy(Ln=Y, Eu) Thin Films
Authors: Tanabe Keiichi , Kubo Syugo , Enomoto Youichi , Hidefumi Asano Hidefumi Asano , Akihiko Yamaji Akihiko Yamaji
Published: February 2005

The electrical responses to infrared radiation of high-T
c LnBa2Cu3O
y
(Ln=Y, Eu) thin films with various crystal orientations and a wide range of critical current densities are studied using modulated laser light (λ=1.3 µm). All films show clear nonobolometric responses with an order of magnitude comparable to that of bolometric responses at temperatures below T
c. The strong correlation between the responsivity of the nonbolometric response and the Cooper pair density among various oxide superconductors confirms that the nonbolometric response is due to nonequilibrium gap suppression. The cutoff frequency for a bolometric response of higher than 1 MHz and the observed film temperature rise mostly agree with values estimated assuming a microbolometer thermally linked to the substrate.
DC Superconducting Quantum Interference Device Utilizing the High Tc Step-Edge Junction
Authors: Enpuku Keiji , Udomoto Junichi , Kisu Takanobu , Erami Akihisa , Yuichi Kuromizu Yuichi Kuromizu , Keiji Yoshida Keiji Yoshida
Published: February 2005

An artificial step-edge junction for developing the high T
c weak links is presented. The step-edge junction is fabricated by using the step edge of the double layer of the epitaxial YBaCuO films. The dc superconducting quantum interference device (SQUID) made of the junction shows a clear voltage-vs-flux (V-Φ) relation up to T=81.3 K. The voltage modulation depth ΔV of the V-Φ relation is ΔV=1.6 µV at T=77 K. A preliminary experiment shows that the magnetic-flux noise of the SQUID at T=77 K is, at most, Φ
n
=4.4×10-4Φ0/√Hz at f=10 Hz. These results show the promising properties of the step-edge junction for the weak link of high T
c superconductors.
Heteroepitaxial Growth of CeO2(001) Films on Si(001) Substrates by Pulsed Laser Deposition in Ultrahigh Vacuum
Authors: Nagata Hirotoshi , Tsukahara Tadashi , Gonda Satoshi , Mamoru Yoshimoto Mamoru Yoshimoto , Hideomi Koinuma Hideomi Koinuma
Published: February 2005

Pulsed laser deposition in ultrahigh vacuum (UHV) was applied to the epitaxial growth of CeO2 film on Si(001). Although the direct deposition of CeO2(001) on Si(001) was unsuccessful, the desired epitaxy was achieved by inserting the growth of a SrTiO3 layer. The formation of a CeO2(001)//SrTiO3(001)//Si(001) layered structure was verified by reflection high-energy electron diffraction analysis of the growing surface at a temperature between 650 and 700°C in UHV. In addition to lattice matching, chemical interaction at the growing surface had a decisive effect on the epitaxy and orientation of growing ceramic lattices.
Electron Energy Loss Spectrum Near Carbon K-Edge in Solid C60
Authors: Saito Yahachi , Shinohara Hisanori , Akinori Ohshita Akinori Ohshita
Published: February 2005

The carbon K-edge excitation spectra of solid C60 have been obtained using electron energy-loss spectroscopy. In the near-edge region, in addition to the π* and σ* resonance bands well known for graphite and amorphous carbon, a shoulder is found at 289 eV, suggesting the presence of a peak in the density of unoccupied π* states. Another feature discernible to the solid C60 is the width of the σ* resonance band; it is about 15 eV, which is an intermediate value between those for graphite and amorphous carbon.
High-Luminance Green Zn2SiO4:Mn Thin-Film Electroluminescent Devices Using an Insulating BaTiO3 Ceramic Sheet
Authors: Minami Tadatsugu , Miyata Toshihiro , Shinzo Takata Shinzo Takata , Ichiro Fukuda Ichiro Fukuda
Published: February 2005

High-luminance green emission has been achieved from an electroluminescent (EL) device consisting of a Zn2SiO4:Mn thin-film phosphor and a thick BaTiO3 ceramic insulator. The EL characteristics are strongly dependent on the preparation conditions of the Zn2SiO4:Mn thin film deposited by rf magnetron sputtering. The high-luminance green emission, which results from the 4G-6S transition in the Mn2+ ion, is obtained in a device using a Zn2SiO4:Mn thin film postannealed at 1000°C. A luminance of 3400 cd/m2 and a maximum luminous efficiency of 0.15 lm/W were obtained in the device driven with a sinusoidal-wave voltage of 430 V at 5 kHz.
Electron Focusing in a Widely Tapered Cross Junction
Authors: Sakamoto Toshitsugu , Takagaki Yukihiko , Takaoka Sadao , Gamo Kenji , Murase Kazuo , Namba Susumu
Published: February 2005

Magnetic electron focusing in a two-dimensional electron gas within a widely tapered cross junction is observed. The cross junction consists of a square-shaped open space and four narrow probes attached to the corners. The periodicity of peaks in the Hall and bend resistances is in good agreement with the focusing field for an electron injected at 90° to the boundary connecting the injection and collection probes. Numerical simulation, taking electrons as classical billiard balls, explains most of the experimental features.
Hydrogen-Etching Effect of Substrate on Deposition of Diamond Films by DC Plasma Chemical Vapor Deposition
Authors: Nakao Setsuo , Noda Mikio , Hirohumi Watatani Hirohumi Watatani , Shigeo Maruno Shigeo Maruno
Published: February 2005

The effect of hydrogen plasma etching (HPE) of a Si substrate on the morphology and the quality of the diamond films deposited by DC plasma chemical vapor deposition in CH4-H2 mixture gas have been studied. It has been found that the HPE treatment before diamond deposition results in the modification of the substrate surface through the removal of the Si oxide layer and the formation of an uneven surface, and enhances the nucleation and growth of diamond. The amorphous component contained within the deposited films decreases through the use of the etched substrate, especially when the CH4 concentration is higher than 3%.
Heteroepitaxial Growth of BaTiO3 Thin Films on SrTiO3 Substrates under Hydrothermal Conditions
Authors: Kajiyoshi Koji , Nobuo Ishizawa Nobuo Ishizawa , Masahiro Yoshimura Masahiro Yoshimura
Published: February 2005

Heteroepitaxial growth of BaTiO3 films on SrTiO3 single-crystal substrates was studied in Ba(OH)2 solution under hydrothermal conditions above 450°C. The epitaxial relation, BaTiO3 (hkl)//SrTiO3 (hkl), was confirmed for the films on (100), (110), (111) and (210) faces of the SrTiO3 crystals. Morphology of the grown surfaces faceted by {100} faces was directly affected by the indices of the substrate surface as a result of the epitaxial relation. In particular, monolithic films having a smooth surface were formed on SrTiO3 (100) substrates.
Silver Addition and Zirconium Substitution in the YBa2Cu3O7-xPrepared by Organic Acid Salt Thermal Decomposition Process
Authors: Asaka Takashi , Okazawa Yoshiyuki , Yasuaki Shiomi Yasuaki Shiomi , Kyoji Tachikawa Kyoji Tachikawa
Published: February 2005

The high-TcYBa2Cu3O7-x(123) superconductor has been synthesized through a decomposition of organic acid salts.Tc's of 92 K have been obtained after a relatively short sintering in the 123 specimen. Effects of silver addition and zirconium substitution on superconducting properties and structures were studied. The Ag addition and the Zr substitution appreciably enhances theJcof sintered 123 specimen. The Ag addition decreases the optimum sintering temperature by about 50°C. The Zr substitution is found to significantly change the morphology of 123 grains.
Novel Particulate Media with Coercivity up to 2150 Oe Based on Non-Acicular γ-Fe2O3 Modified with Co/Mn/Zn
Authors: M. C. Deng M. C. Deng , Tsung-Shune Chin Tsung-Shune Chin
Published: February 2005

A series of non-acicular particulate media with coercivity of up to 2150 Oe, residual magnetization of up to 50 emu/g and squareness ratio of up to 0.72 has been developed based on γ-Fe2O3, modified with Mn, Co and Zn. They were prepared by coprecipitation of Fe, Mn, Co, and Zn ions from an aqueous solution, using an organic alkali, such as triethylamine, to adjust the pH, followed by suitable annealings. The fine particle size of around 50 nm, strong magnetocrystalline anisotropy and annealed directional ordering are possible causes of high coercivity. These media are potential candidates for high density recording.
Influence of H2O on the SiO2 Growth by Parallel-Resonant RF Plasma Oxidation
Authors: Kitagawa Akio , Takeuchi Masaki , Yoshitake Shibata Yoshitake Shibata , Masakuni Suzuki Masakuni Suzuki
Published: February 2005

The influence of water vapour on the SiO2 growth rate in plasma oxidation is investigated. The oxygen plasma was generated by the rf power of 130 W in a parallel resonant condition, and the water concentration in the plasma was controlled by mixing a small amount of water vapour with dry oxygen gas through a bubbler device. It is found that the water vapour in oxygen plasma considerably enhances the SiO2 growth rate. The refractive index of the SiO2 film is not affected by the hydrogen partial pressure in the plasma.
Oxidation of GaAs Surface by Oxygen Plasma and Its Application as an Antireflection Layer
Authors: Wen-An Loong Wen-An Loong , Hong-Long Chang Hong-Long Chang
Published: February 2005

The optical reflectivity of a GaAs wafer is found to decrease from about 45% down to about 5% for both the g-line and i-line by oxidation in low-power oxygen plasma at 300°C for 4 hours. The oxide layer on the GaAs top surface used as an in situ antireflection layer for optical microlithography is demonstrated to be effective.
Laser Cooling and Trapping of Li
Authors: Lin Zhong , Shimizu Kazuko , Zhan Mingsheng , Shimizu Fujio , Hiroshi Takuma Hiroshi Takuma
Published: February 2005

Neutral 7Li and 6Li atoms are laser cooled and trapped using the 22P3/2(F=3)↔22S1/2(F=2) and 22P3/2(F=5/2)↔22S1/2(F=3/2) transitions, respectively. The Zeeman tuning is employed in the deceleration stage. Using a magneto-optical trap with a tetrahedral laser-beam configuration the atomic density of 3×109 atoms/cm3 is obtained for 7Li and a half of that for 6Li. The measured temperature of the trapped 7Li atoms is 350±40 µK when the detuning is 8 MHz to the red.
Dependence of Electron Cyclotron Resonance Plasma Characteristics on Magnetic Field Profiles
Authors: Nakamura Seiji Samukawa
Published: February 2005

Ion energy distribution is influenced by the magnetic field profiles in electron cyclotron resonance (ECR) plasma. When a 875 G equi-magnetic field is nonuniform, the microwave absorption concentrates at the ECR position which is located near the microwave window. Then, the mean ion energy distribution on the substrate holder becomes much broader due to the ion acceleration by the plasma potential difference. In addition, the ion energy distribution depends on the uniformity of the magnetic field gradient at the ECR position. The microwave is absorbed efficiently around the small gradient ECR position. Therefore, a uniform magnetic field gradient at the ECR position causes a uniform and sharp ion energy distribution.
Microstructure and Microwave Properties of Tl2Ba2CaCu2O8 Thin Films on NdGaO3
Authors: Young K. H. , Negrete G. V. , M. M. Eddy M. M. Eddy , E. J. Smith E. J. Smith
Published: February 2005

High-quality epitaxial Tl2Ba2CaCu2O8 superconducting thin films have been grown on NdGaO3(001) by a two step process. One film, annealed at 850°C, shows interdiffusion of Ga by secondary ion mass spectroscopy, resulting in an incomplete AC susceptibility transition at 80 K. For films annealed at lower temperature, excellent crystallinity and transport properties were obtained. Ground plane substitution of the film in a 5 GHz microstrip resonator indicated worse microwave performance than similar films on LaAlO3(001) substrates. The 2.3 GHz resonator made from the film on NdGaO3 gave significantly worse quality factor (Q) values (1850) than those made on LaAlO3.
Low-Energy Electron Energy Loss Spectroscopy on Bi2Sr2Can-1CunO2n+4+x (n=1, 2)
Authors: Ando Atsushi , Saiki Koichiro , Koma Atsushi , Eisaki Hiroshi , Uchida Shin-ichi
Published: February 2005

Electronic structures of the high-T
c superconductor Bi2Sr2Ca
n-1Cu
n
O2n+4+x
(n=1, 2) have been investigated by low-energy electron energy loss spectroscopy (LEELS) in the valence and shallow core electron excitation region. The LEELS spectra are almost independent of the incident electron energy, that is, of probing depth, indicating rather extended electronic states of those materials. It has been also discovered that the existence of Ca layer does not affect the overall spectra so much except in the Ca 3p core electron excitation region.
Crystal Structure and Tc of YBa2Cu3Oy (y>7)
Authors: Okai Bin , Ohta Masatsune
Published: February 2005

At a high oxygen pressure of 6 GPa, YBa2Cu3O
y
was heat-treated. With an increasing supply of oxygen, the crystal structure of the processed specimens gradually changed from orthorhombic (y=7) to tetragonal (y=7.7), whereas the onset of superconducting transition temperature consistently remained at 92 K for all of the specimens. The distribution of charges among the copper-oxygen chains and the CuO2 sheets in YBa2Cu3O
y
(y>7) are discussed.
The Effect of Surface Oxides on the Creation of Point Defects in GaAs Studied by Slow Positron Beam
Authors: Lee Jong-Lam , Wei Long , Tanigawa Shoichiro , Haruhiro Oigawa Haruhiro Oigawa , Yasuo Nannichi Yasuo Nannichi
Published: February 2005

The depth distributions of the positron annihilation in as-etched GaAs before and after the air exposure were characterized by a slow positron beams. The characteristic value of S parameter at near-surface region is decreased after the air exposure of the etched-GaAs, which indicates that the thin oxide layer is formed on the fresh surface of the etched GaAs during the air exposure. It is found that the mean diffusion length of positrons is not changed after the as-etched GaAs was exposed to air atmosphere. This implies that the trapping centers for a positron are not created below the surface by the chemisorption of oxygen atoms.
High Output Power (>20 W) and High Quantum Efficiency in a Photopumped ZnSe/ZnSSe Blue Laser Operating at Room Temperature
Authors: Nakanishi Koichiro , Suemune Ikuo , Fujii Yoshihisa , Yamanishi Yasuhide Kuroda
Published: February 2005

High output power of 24 W was observed from a photopumped ZnSe/ZnSSe blue laser operating at room temperature. A differential quantum efficiency greater than 25% was estimated in the lasing region of the photopumped wafer. The improved lasing property is attributed mainly to the improved waveguiding structure verified from the far-field measurement. The other is the introduction of a ZnSe/ZnSSe superlattice buffer which improved the crystalline property of the active layer grown above. The lowest threshold power was 50∼70 kW/cm2 for a cavity length of 220 µm under pulsed operation.
Epitaxial Growth of SrTiO3 Films on Si(100) Substrates Using a Focused Electron Beam Evaporation Method
Authors: Hiroyuki Mori Hiroyuki Mori , Hiroshi Ishiwara Hiroshi Ishiwara
Published: February 2005

A novel epitaxial growth method of SrTiO3 films on Si(100) substrates is presented in which, in order to reduce the surface oxide layers of the substrates, thin Sr layers are deposited prior to deposition of SrTiO3 films. It has been shown that the film composition becomes nearly stoichiometric when single-crystalline SrTiO3 sources are evaporated by a focused electron beam and that SrTiO3 films grow epitaxially on Si(100) substrates under the optimum conditions of the Sr layer thickness, deposition temperature, and annealing temperature.
Optical Modulation and Measurement of Kerr Constant Using Polymer Waveguide Doped with Organic Nonlinear Materials
Authors: Muto Shinzo , Koichi Miyagawa Koichi Miyagawa , Takashi Nagata Takashi Nagata
Published: February 2005

Optical modulators consisting of polymer thin-film waveguides doped with organic nonlinear materials such as 2-methyl-4-nitroaniline and trans-β-carotene were simply and inexpensively constructed. The basic modulation property of these devices was demonstrated experimentally. The measured Kerr constants of these polymer thin films depended on the dopant concentration and had a value on the order of 10-13 m/V2.
Etching of GaAs by Atomic Hydrogen Generated by a Tungsten Filament
Authors: Kobayashi Ryuji , Kunihiro Fujii Kunihiro Fujii , Fumio Hasegawa Fumio Hasegawa
Published: February 2005

It was found that GaAs was etched effectively by atomic hydrogen generated by a tungsten (W) filament. The experiment was performed in a pure H2 gas or H2 and He gas mixture at atmospheric pressure. The W-filament was heated up to 2000°C. The GaAs was etched with a smooth surface in pure H2 gas and the etching rate was as high as 15 µm/h at a substrate temperature of 850°C, though the etching rate was low and the surface was rough with Ga droplets in He gas. These results suggest that Ga is removed from the GaAs surface as a hydride such as GaH3.
Wide-Wavelength GaInAs PIN Photodiodes Using a Lattice-Mismatched Light-Absorbing Layer and a Thin InP Cap Layer
Authors: Wada Morio , Sakakibara Katsutoshi , Higuchi Masahiko , Yoichi Sekiguchi Yoichi Sekiguchi , Hideto Iwaoka Hideto Iwaoka
Published: February 2005

We have fabricated PIN photodiodes (PDs) with a thick lattice-mismatched GaInAs absorbing layer and a thin InP cap layer by metal-organic vapor phase epitaxy (MOVPE). The lattice mismatch and the X-ray FWHM of 2.3-µm GaInAs were 0.5% and 138 arcsec, respectively. These PDs exhibited a very low temperature-dependent response from 1.0 to 1.70 µm with quantum efficiencies as high as 45% at 0.78 µm, 86% at 1.3 µm, 85% at 1.55 µm and 70% at 1.75 µm. A reverse leakage current of 30 nA at -2 V bias was measured, and a -3 dB cutoff frequency of 2.5 GHz was obtained for the 110 µm-dia. PDs.