bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Microprobe with a Pair of Elliptical Mirrors
Authors: Suzuki Yoshio , Uchida Fumihiko , Hirai Yasuharu
Published: February 2005

A grazing-incidence mirror system for focusing X-rays has been developed. Two mirrors, each with an elliptical cylinder shape, are arranged in a crossed-mirror geometry (Kirkpatrick-Baez configuration) to form an X-ray source image that is demagnified by a factor of several hundred. A focused X-ray spot of 5.5 µm×4.2 µm was obtained at a wavelength of 2.0 Å using synchrotron radiation from the KEK Photon Factory 2.5 GeV storage ring and was applied to scanning X-ray microscopy.
Reactive Ion Beam Etching Using a Selective Gallium Doping Method
Authors: Nishioka Kyusaku , Morimoto Hiroaki , Mashiko Yoji , Kato Tadao
Published: February 2005

A maskless process has been realized by combining reactive ion beam etching (RIBE) with focused ion beam (FIB) technology. Si patterns of 0.3 µm with no undercutting can be obtained using RIBE with electron cyclotron resonance (ECR) plasma. A Ga compound is formed as an in situ etching mask.
Electrical Evaluation of Defects Induced in Silicon by High Energy Boron Ion Implantation
Authors: Sayama Hirokazu , Takai Mikio , Akasaka Youichi , Tsukamoto Katsuhiro , Namba Susumu
Published: February 2005

The suitable dose and annealing temperature for high energy ion implantation to form a retrograde well or a buried conductive layer for CMOS devices were investigated by studying I-V and C-V characteristics. Boron ions were implanted in Si at 400 and 700 keV with doses ranging from 1×1013 cm-2 to 3×1014 cm-2. It was found that the leakage currents induced by high energy boron implantation at 400 and 700 keV with a dose of less than 3×1013cm-2 could be suppressed at an unimplanted level by annealing at 950°C for 20 minutes.
Annealing Properties of Si-Atomic-Layer-Doped GaAs
Authors: Yamauchi Yoshiharu , Makimoto Toshiki , Horikoshi Yoshiji
Published: February 2005

Si-atomic-layer-doped GaAs layers are grown at 520°C by flow-rate modulation epitaxy using a 1-s silane pulse. Carrier profiles are measured by the capacitance-voltage method before and after annealing at 700, 800, and 900°C. The sheet carrier concentration increases with the silane mole fraction, and saturates at about 3×1012 cm-2. The samples with saturated sheet carrier concentrations exhibit a distinct plateau at the top of the carrier concentration profile after annealing, while the samples with unsaturated sheet carrier concentrations show normal Gaussian-like broadening. The peak carrier concentration at the plateau of the annealed sample is found to be sensitive to annealing temperature, indicating that the carrier concentration is controlled by some thermodynamic limitation.
GaAs(001) Epitaxial Layer on SOS Using a Specifically Designed MOCVD System
Authors: Nishimura Takashi , Kadoiwa Kaoru , Hayafuji Norio , Murotani Toshio , Ibuki Sumiaki
Published: February 2005

GaAs (001) single-domain and high-quality layers are obtained on slightly misoriented Si (001)-on-sapphire (01̄12) substrates by using a new MOCVD system specifically designed for GaAs-on-Si growth. The X-ray FWHM of 10 µm-thick GaAs is reduced from 140 arcsec to 65 arcsec by thermal cycle annealing. A crack-free 15 µm-thick GaAs layer with a dislocation density of 3×106 cm-2 is obtained by combining the thermal cycle annealing and the strained-layer superlattices.
Transition from Electron Transport to Ambipolar Transport in Photoexcited GaAs/AlAs Superlattices
Authors: Kawamoto Naoki , Nakamura Arao , Fujiwara Kenzo
Published: February 2005

We report dynamical properties of both electron transport and ambipolar transport perpendicular to the GaAs/AlAs superlattice structures using a time-resolved luminescence spectroscopy at 77 K. Changing photoexcited carrier densities, we found both types of the transport and thus estimated both mobilities in miniband states of the superlattices (L
B=0.90 nm and L
z=3.18 nm) with an enlarged well (L
z=6.36 nm). When the carrier density is lower than the residual acceptor density N
A-N
D, the electron transport is observed. At higher excitation density exceeding N
A-N
D, the ambipolar transport appears, showing a lower mobility of holes.
Improvement of InP Crystal Quality on GaAs Substrates by Thermal Cyclic Annealing
Authors: Hayafuji Norio , Kimura Tatsuya , Yoshida Naohito , Kaneno Nobuaki , Tsugami Mari , Mizuguchi Kazuo , Murotani Toshio , Ibuki Sumiaki
Published: February 2005

We have studied the effect of thermal cyclic annealing (TCA) on the crystal quality improvement of MOCVD grown InP on GaAs substrates. The crystal quality has been evaluated by the etch pit density (EPD), X-ray diffraction and photoluminescence (PL) measurement. It is found that the TCA is effective in reducing the dislocation density, and that the annealing at 700°C is essential to confine the point defects near the InP/GaAs interface. The EPD is reduced from 6×107 cm-2 to 3×107 cm-2, and the defect-related PL peak intensity is decreased below the residual level in the 5 µm-thick InP on GaAs.
LPE Growth of AlGaAs-GaAs Quantum Well Heterostructures
Authors: Mukai Seiji , Watanabe Masanobu , Itoh Hideo , Yajima Hiroyoshi , Yano Tomomi , Woo Jong-Chun
Published: February 2005

AlGaAs-GaAs single quantum wells with thicknesses d down to 6 nm are prepared by LPE at 742°C. The transmission electron microphotographs and the luminescence/photocurrent spectra of these wells indicate that the interface roughness and the transition layer thickness L of the wells are about 1.5 nm and 3 nm, respectively. Energy levels of E
1h, E
1l, and E
2h are calculated as a function of d and L, which allows us to estimate these values from luminescence or photocurrent spectra measured at room temperatures.
Systematic Raman Scattering Study on Substitutional Effects in Solid Solution Systems of Ln1+xBa2-xCu3Oy (Ln=Eu, Sm and La)
Authors: Yoshida Naoki , Nishitani Ryusuke , Sasaki Yoshiro , Nishina Yuichiro
Published: February 2005

We have carried out a Raman spectroscopic study on the effect of substituting trivalent rare-earth ions (Ln=Eu, Sm and La) for Ba in LnBa2Cu3O
y
(y=6–7) into the chemical form of Ln1+x
Ba2-x
Cu3O
y
(0≤x≤0.4). The oxygen vibrational mode in the BaO plane is influenced by the substitution through significant changes in the phonon frequency and peak intensity. On the other hand, the bending mode in the CuO2 plane does not show appreciable variation with an increase in x. These results are common to the cases where Ln=Eu, Sm and Nd, but not to Ln=La, and are interpreted in terms of the oxygen defect and hole-concentration compensation.
Superconductivity in the Bi2LnxCa3-xCu2Oz (Ln=La, Pr, Nd, Sm, Eu and Gd) Systems
Authors: Sasakura Hiroyuki , Nakahigashi Kiyotaka , Minamigawa Sinnosuke , Kogachi Mineo , Nakanishi Shigemitsu , Fukuoka Nobuo , Yanase Akira
Published: February 2005

A new family of oxide superconductors of Bi2Ln
x
Ca3-x
Cu2O
z
(Ln=La, Pr, Nd, Sm, Eu and Gd) has been examined by means of the electrical resistivity and the X-ray diffraction methods. All the ceramics exhibited superconductivity, and the highest zero resistivity temperature obtained among them was about 45 K for Ln=Pr. The X-ray powder diffraction study showed that these ceramics had a similar crystal structure to that of the 2212 phase (Bi2Sr2CaCu2O
y
) and that the single phase was almost attained at the nominal composition of x=0.5 (Ln=La, Pr, Nd and Sm) and 0.6 (Ln=Eu and Gd).
Superconducting Phases with Single Tl-O Layer Structure Preparation: (Tl, Pb)Can-1Ba2CunO2n+3 (n=2, 3, 4, 5, 6)
Authors: Kusuhara Hiroyuki , Kotani Toshihiro , Takei Hiromi , Tada Kohji
Published: February 2005

Single Tl-O layer structures with two to six Cu-O layers, (Tl, Pb)Ca
n-1Ba2Cu
n
O2n+3 (n=2, 3, 4, 5, 6), are prepared, and the superconducting properties of their phases are investigated. The c-lattice constants of the observed phases obey the c-axis rule of c=6.38+3.19n for single Tl-O layer structures. With an increase in Cu-O layers, the superconducting transition temperature, determined from electrical resistivity-temperature dependency and DC susceptibility, rises, reaching a maximum value of 121 K at n=4, and then falls with a further increase of the number of Cu-O layers from four to six.
Modulated Structure of the High-Tc Superconductor Bi-Pb-Ca-Sr-Cu-O Studied by High-Resolution Electron Microscopy and Electron Diffraction
Authors: Hirotsu Yoshihiko , Tomioka Osamu , Yamamoto Naoki , Nakamura Yoshio , Nagakura Sigemaro , Iwai Yutaka , Takata Masasuke
Published: February 2005

A new type of atomic displacive modulation in the incommensurate superconducting oxide Bi-Pb-Ca-Sr-Cu-O (2223 phase) has been studied by high-resolution electron microscopy and electron diffraction. The structure is orthorhombic with cell dimensions a=0.54, b=4.2 (∼8a) and c=3.71 nm. The structural modulation has been analyzed by assuming a commensurate cell with the dimension b=8a. The intensity distribution of superstructure reflections can be well explained by taking atomic displacive longitudinal and transverse waves into account.
Ferroelasticity in La2CuO4 Single Crystals
Authors: Sawada Akikatsu , Nishihata Yasuo , Oka Kunihiko , Unoki Hiromi
Published: February 2005

Domain structures due to a tetragonal-orthorhombic phase transition at T
0≃450 K have been observed directly for the first time using a polarizing microscope. Domain walls are parallel to {100} planes in the tetragonal axial system. Domain walls have been shown to move at room temperature upon application of external compressive stress.
Superconductivity and Structure of (Tl, Pb)((Eu, La), Sr)2CuOx
Authors: Itoh Takao , Uchikawa Hiroshi
Published: February 2005

The superconductivity and structure of (Tl, Pb)((Eu, La), Sr)2CuO
x
with different Eu/La molar ratios have been investigated by means of resistivity measurements and X-ray diffractometry. Superconductivity is observed for this solidsolution system. The lattice parameters change with the Eu/La molar ratio and the stability of the superconducting phase is related to the lattice parameters.
High Tc Superconductive Film on Alumina-Ceramic Substrate by Sputter S-Guns
Authors: Onishi Shinzo , Hsieh Hshin-Ming , Elshabini-Riad Aicha
Published: February 2005

Superconducting YBa2Cu3O
x
thin films have been deposited successfully on ceramic substrates using a custom-built multimagnetron sputtering system. A niobium layer acts as the barrier layer that greatly enhances the superconducting properties. Measurements of the test results indicate an onset temperature of about 100 K, and a critical temperature T
c of 91.5 K.
Preparation of Bi-Pb-Sr-Ca-Cu-O Superconducting Fibers by the Sol-Gel Method
Authors: Zhuang Haoren , Kozuka Hiromitsu , Sakka Sumio
Published: February 2005

Bi-Sr-Ca-Cu-O superconducting fibers were prepared by the sol-get method. Gel fibers of 0.01–1 mm diameter were directly drawn from a homogeneous viscous sol which was prepared from an aqueous solution of metal acetates containing acetic acid and tartaric acid. Ceramic fibers with the high-T
c phase as the main phase were obtained by heating the gel fibers derived from the sol of molar composition of Bi:Pb:Sr:Ca:Cu=1.85:0.35:1.9:2.0:3.1 to 835°C at a slow rate of 0.33°C/min and keeping them there for 40 h. The fiber showed diamagnetism below 110 K and zero electrical resistance at 98 K.
YBCO DC SQUID of MOCVD Thin Film Bridge
Authors: Irie Akinobu , Era Masanori , Yamashita Tsutomu , Kurosawa Hideyuki , Yamane Hisanori , Hirai Toshio
Published: February 2005

Using YBa2Cu3O7-x
(YBCO) thin films (0.5∼1.0 µm in thickness) with c axis orientation, we fabricated dc superconducting quantum interference devices (SQUIDs). YBCO films were deposited on MgO(100) single-crystal substrates by MOCVD. These films exhibit zero resistance above 80 K and critical current density of 104 to 105 A/cm2 at 77 K. The SQUIDs with microbridge are fabricated by photolithography and chemical etching techniques. The maximum voltage modulation is about 80 µV for the YBCO dc SQUID with an inductance of 70 pH, and intrinsic energy sensitivity is 740 h (h: Planck's constant) at 4.2 K. Furthermore, the SQUID was operated in flux-locked loop. The minimum flux noise in the flux-locked SQUID is 1.5×10-5 \varPhi0/√Hz in the white noise region at 4.2 K. The experiments suggest that the current-phase relationship of a micrometer-long YBCO bridge may be sinusoidal.
Electron Spin Resonance of the Oxygen Molecule in Blood
Authors: Mizushima Masataka
Published: February 2005

The oxygen molecules trapped by hemoglobins in blood are supposed to be nearly free electronically, or to have electron spin 1 each. Yet no magnetic spin resonance of blood is observed near 3.3 kG with 9.5 GHz microwave, as expected for a free spin of S=1. The spin of this molecule in a gaseous state is known to be strongly coupled to the molecular axis. For an oxyhemoglobin in which the oxygen molecule is trapped, the cylindrical symmetry around the molecular axis may be violated, generating coupling of the spin to the axes perpendicular to the molecular axis. Assuming the same compling strength of spin around the molecular axis but no coupling to other axes as in the gaseous state, and assuming completely quenched rotation, the magnetic resonance line of the oxygen molecules in oxyhemoglobin is expected to have a sharp peak at 12 kG when 9.5 GHz microwave is used. Possible magnetic spin resonance lines under similar conditions but with non-cylindrical spin field is also discussed.
Alkali-Developable Silicone-Based Negative Photoresist (SNP) for Deep UV, Electron Beam, and X-Ray Lithographies
Authors: Ban Hiroshi , Tanaka Akinobu , Kawai Yoshio , Deguchi Kimiyoshi
Published: February 2005

A new silicone-based negative photoresist (SNP) developable with alkaline aqueous solutions is prepared. SNP composed of acetylated phenylsilsesquioxane oligomer and azidopyrene is applied to deep UV, electron beam (EB), and X-ray lithographies. SNP slightly swells in alkaline developers, thus exhibiting exceptionally high resolution characteristics for a negative resist. The resistance of SNP to oxygen reactive ion etching is approximately 30 times greater than that of conventional novolac resists.
Doping of Trench Side-Walls Using an Arsenic Planar-Type Solid-Diffusion Source (S-D Source) and Analysis of Doping Uniformity by Secondary Ion Mass Spectroscopy (SIMS)
Authors: Matsuo Naoto , Okuda Seiji , Hirofuji Yuichi , Tsukamoto Kazuyoshi , Iwasaki Hiroshi , Takemoto Toyoki , Yoshioka Yoshiaki
Published: February 2005

We developed a new method of doping side-walls of sub-micron-width trenches using an arsenic planar-type solid-diffusion source at a low pressure. The sheet resistivity, which was measured on the wafer surfaces, is found to be controlled by the oxygen concentration in the tube. Arsenic was doped uniformly in the 6-inch diameter wafer with a standard deviation of 2.7%. The doping was reproducible; the standard deviation of the doping for many batches was 3.0%. A new method of evaluating uniformity of trench side-wall doping using SIMS was also developed. The doping uniformity is confirmed to be within the accuracy of the SIMS measurement.
Impurity Doping Effect on the Dislocation Density in GaAs on Si (100) Grown by Migration-Enhanced Epitaxy
Authors: Nozawa Kazuhiko , Horikoshi Yoshiji
Published: February 2005

Dislocation density in GaAs epilayers grown on Si substrates by migration-enhanced epitaxy can be reduced by heavy doping of Si without using strained-layer superlattices or repeated annealing procedures. This effect is demonstrated by TEM and EBIC observations. The EBIC topographic observations show that the dislocation density of 6-µm-thick nonoptimized samples is approximately 4×106 cm-2, which compares favorably with the value of ∼1×107 cm-2 in undoped samples. The bent dislocations are mostly arranged parallel to the steps which exist on a tilted substrate surface.
Proposal of Source Supply Efficiency Analysis for InGaAsP Grown by MOVPE
Authors: Yamamoto Eiji , Suda Kazuya , Nogiwa Seiji , Nakajima Shin-ichi , Oki Tokukoh
Published: February 2005

We propose a useful method of analyzing source supply efficiencies for InGaAsP grown by MOVPE. This study of source supply efficiencies has shown that the supply efficiency of arsenic (As) is about one tenth or less than that of indium (In) or gallium (Ga), while that of phosphorus (P) is smaller than that of As and is strongly dependent on the growth temperature. These supply efficiencies can be used to simulate In1-x
Ga
x
As
y
P1-y
alloy composition easily. To obtain a good quality of InGaAsP for a wide range of alloy compositions, we suggest as a guideline that supply efficiencies should be kept constant for any composition.
Dependence of Excitonic Emission Lines and the 1.47 eV Band on Growth Temperature and Substrate Misorientation in MOCVD-Grown CdTe Films on (100) GaAs
Authors: Taguchi Tsunemasa , Suita Muneyoshi
Published: February 2005

Epitaxial CdTe layers were grown on nominally (100)-oriented and 3°-off misoriented GaAs substrates at temperatures between 200 and 425°C by low-pressure metalorganic chemical vapour deposition (MOCVD) with the use of precracking (CH3)2Te gas. The excitonic features, at 4.2 K, exhibited a marked dependence not only on the orientation of the GaAs substrate, but also on growth temperature. A neutral-acceptor bound-exciton line with the narrow full width at half maximum of about 0.6 meV, in a layer on a misoriented substrate, is enhanced in intensity with increasing growth temperature. Remarkable spectral changes of the individual broad bands located in the vicinities of 1.47 and 1.42 eV were also found in the layers grown at temperatures between 350 and 400°C, where the 1.47 eV band with a weak LO-phonon coupling strength became predominant. We discuss the origin of the bound-exciton emission lines and the 1.47 eV band in the heteroepitaxial CdTe layers.
Observation of Direct Band Gap Properties in GenSim Strained-Layer Superlattices
Authors: Okumura Hajime , Miki Kazushi , Misawa Shunji , Sakamoto Kunihiro , Sakamoto Tsunenori , Yoshida Sadafumi
Published: February 2005

Photoluminescence and optical absorption measurements were carried out for Ge
n
Si
m
strained-layer superlattices grown by molecular beam epitaxy using a phase-locked epitaxy technique. A Ge4Si12 superlattice showed intense emission in the near-infrared region, and its absorption coefficient followed the (h
v-E
g)1/2 law, where h
v is the energy of incident light and E
g is the band gap energy. These results suggest that the Ge4Si12 sample has a direct band gap.
Normal-State Resistivity of the (Bi/Pb)-Ca-Sr-Cu-Oxide System
Authors: Lee Sang-Geun , Yi Kyung-Soo , Park Chong-Yun , Jang Min-Su
Published: February 2005

We measured the electrical resistivity ρ(T) of the Bi2-xPbxCa2Sr2Cu3Oy(x=0.2, 0.4, 0.6) system withTc\cong108 K in air and in the temperature range of 20 K<T<800 K. The ρ(T) shows linear temperature dependence in the rangeTc<TT2whereT2is in the range 610–680 K, depending upon the sample composition. The resistivity saturation was not observed over the temperature range we measured. From the linear behaviour of ρ(T), we estimated the order to magnitude of the electron-phonon coupling constant λ and the electron mean free pathlof high-Tcsuperconducting Bi-compounds in the high-temperature region.
Complex Susceptibility of YBa2(Cu1-xFex)3Oy
Authors: Mazaki Hiromasa , Katsuyama Shigeru , Yasuoka Hiroshi , Ueda Yutaka , Kosuge Koji
Published: February 2005

The superconducting transitions of YBa2(Cu1-x
Fe
x
)3O
y
(0≦x≦0.20) compounds were measured in terms of complex susceptibility, χ= χ' -i χ''. Two groups of samples were prepared. Group I was prepared by slow cooling from 850°C in flowing O2 gas. Group II was prepared by heating in flowing N2 gas at 800°C for 20 h, followed by slow cooling to room temperature in the same atmosphere and then by annealing in flowing O2 gas below 400°C for more than 20 h. Comparisons of the results suggest that the clustering of substituted Fe ions takes place in the Cu1-O planes of the samples in group II, and that the flux motion is restrained.
High-Resolution Transmission Electron Microscopy of Defects in YBa2Cu4O8
Authors: Yamaguchi Koji , Miyatake Takayuki , Takata Tsutomu , Gotoh Satoshi , Koshizuka Naoki , Tanaka Shoji
Published: February 2005

Microscopic structures of the high-T
c superconductor YBa2Cu4O8 (T
c=80 K) are examined by high-resolution transmission electron microscopy. Planar defects are observed as white spot lines in the micrograph of the single-phase YBa2Cu4O8 and they have a structure with an absence of one Cu-O chain in the double Cu-O chain of YBa2Cu4O8. YBa2Cu3O7 and Y2Ba4Cu7O15-like local structures exist around the planar defects.
High Pressure Oxygen Treatment and the Substitution of Sr for Ba on (Nd1/3Ba2/3)2(Ce1/3Nd2/3)2Cu3Oy Superconductor
Authors: Nobumasa Hitoshi , Shimizu Kazuharu , Kitano Yukishige , Tanaka Masataka , Kawai Tomoji
Published: February 2005

Substitution of Sr for Ba in the (Nd1/3Ba2/3)2(Ce1/3Nd2/3)2Cu3O
y
superconductor has been performed together with high pressure oxygen treatment, and the relationship among Sr content, lattice parameter, hole concentration and superconducting properties has been clarified. It has been found that there is a strong relationship between superconducting transition temperature (T
c) and c-axis length. The highest T
conset
and T
czero
of the (Nd1/3(Ba3/4Sr1/4)2/3)2(Ce1/3Nd2/3)2Cu3O
y
treated under 1300 atm oxygen pressure at 600°C for 24 hours are 59.3 K and 41.4 K, respectively. These transition temperatures are about 10 K higher than those of unsubstituted one.
Emission Spectra of Cu2, Ag2 and Au2 in Gas Evaporation
Authors: Saito Yahachi
Published: February 2005

A spectroscopic study of the light emitted from the vapor zone around the evaporation source in gas evaporation has been carried out. Spectra were photographed with a glass prism spectrograph, and electronic band spectra due to dimers were revealed for Cu, Ag and Au. The blue color of the Cu vapor zone is ascribed to the A-X and B-X band systems of Cu2, violet of Ag to the A-X band system of Ag2, and green of Au to the A-X and B-X band systems of Au2. The continuous spectra due to Rayleigh scattering by fine particles grown in the gas phase have also been observed.
Degradation of Gate Oxide Integrity by Metal Impurities
Authors: Hiramoto Kazuo , Sano Masakazu , Sadamitsu Shinsuke , Fujino Nobukatsu
Published: February 2005

The degradation of gate oxide integrity (GOI) by metal impurities on Si wafers was studied. Ni and Cu tended to precipitate at the Si surface after high-temperature annealing. When these precipitates existed before gate oxidation, they penetrated into the gate oxide film and degraded GOI. Fe tended to remain in the oxide film after oxidation and degraded GOI. The degradation was observed for annealed samples when the surface metal concentration exceeded 1.0×1012 atoms/cm2 of Ni or 5.0×1012 atoms/cm2 of Cu. It was also observed with contamination of 1.0×1013 atoms/cm2 of Fe without annealing.
Cation Self-Diffusion Mediated by Arsenic-Antisite Point Defect in GaAs and AlAs-GaAs Superlattices
Authors: Iguchi Hidehiko
Published: February 2005

Cation self-diffusion in GaAs and AlAs-GaAs superlattices is discussed in terms of activation enthalpy through a review of experimental results. It is argued that cation diffusion should be mediated by As-antisite point defects with use of As-antisite-rich materials and/or As-rich diffusion sources. It is suggested that As-antisite-mediated cation diffusion should yield the characteristic value of the activation enthalpy of ∼2.5 eV under intrinsic conditions. Experiments of interdiffusion from the literature in superlattices show the Fermi-level dependence of activation enthalpy. These lead to the conclusion that the As-antisite defect is responsible for p-type impurity-enhanced cation self-diffusion.
A New Emission Band Related to EL2 in GaAs
Authors: Mori Yuzo , Yoshimura Yoshimasa , Kamoda Hiroki , Ohkura Hiroshi , Chiba Yoshinori
Published: February 2005

A new emission band peaking at 1.0 eV in semi-insulating and n-type GaAs has been observed at 70 K in the anti-Stokes and Stokes regions upon excitations with 1.34 µm and 1.06 µm laser lights, respectively. The intensity of the band is correlated to that of the 0.63 eV photoluminescence band associated with the EL2 deep level when it is varied by photoquenching, sample change, and excitation intensity. The peak energy is close to the energy of intracenter transition of EL2 and the energy between EL20 and the L-valley of GaAs. An excitation mechanism through a metastable state is tentatively proposed to explain the 73 meV anti-Stokes shift at 70 K.
Growth of III-VI Compound Semiconductors by Metalorganic Molecular Beam Epitaxy
Authors: Teraguchi Nobuaki , Kato Fuji , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

Growth of III-VI compound semiconductors (Ga2S3, Ga2Se3 and Ga2Te3) has been tried for the first time by metalorganic molecular beam epitaxy (MOMBE). The growth rate decreases with increasing substrate temperature, and single crystal Ga2Te3 films were obtained on (100) InP substrates. In Ga2Te3 growth, the lattice mismatch between Ga2Te3 and the substrate is critical in obtaining good epitaxial films.
Preparation of Superconducting Bi-Sr-Ca-Cu-O Films by the Organometallic Route Using Plasma Oxidation
Authors: Kobayashi Toshio , Uchikawa Fusaoki , Nomura Kenji , Masumi Tatsuo
Published: February 2005

In the process of preparing superconducting films from organometallic compounds, plasma oxidation has been attempted on an organometallic compound film as a method of decomposing organic components included in the starting materials. Organic components were removed by plasma oxidation more smoothly than by the conventional thermal decomposition method. Plasma oxidation encouraged the growth of microcrystals in the resulting compound. A smooth 0.2 µm film of Bi2Sr2Ca1Cu2O
x
without any cracks was obtained. The film showed the superconducting transition temperature T
ce=78 K.
Growth of the 2223 Phase in Leaded Bi-Sr-Ca-Cu Oxide under Reduced Oxygen Partial Pressure
Authors: Aota Katsumi , Hattori Hisao , Hatano Takeshi , Nakamura Keikichi , Ogawa Keiichi
Published: February 2005

The growth process of 2223 phase in a leaded Bi-Sr-Ca-Cu oxide system has been investigated under various oxygen partial pressures using differential thermal analysis, combined with XRD of the quenched specimen. It is shown that under a slow heating rate, the DTA curves exhibit two or three endothermic peaks between 820 to 900°C, and the peak positions are lowered with reduction in the O2 partial pressure. The 2223 phase is found to grow most efficiently in the partial melting state sandwiched between the two endothermic peaks, and the temperature range between the two peaks becomes maximum around 0.1-atm O2 partial pressure.
Josephson Effect in Wide Superconducting Bridges Made by Epitaxial Ba2YCu3Ox Thin Films on YSZ/Si(100)
Authors: Myoren Hiroaki , Nishiyama Yukio , Miyamoto Naokazu , Osaka Yukio , Hamasaki Toshihiko
Published: February 2005

Using the silicon substrates patterned with the trench, the superconducting microbridge junction has been fabricated in as-grown Ba2YCu3O
x
thin films by rf magnetron sputtering. The microbridge junctions with constrictions as small as submicron dimensions were obtained. These microbridge junctions behaved as Josephson junctions and microwave-induced steps were observed. The observed characteristics seem to be consistent with those expected for a homogeneous wide superconducting bridge (constriction size≫coherence length).
Basic Properties, Linewidth Enhancement Factor and Spectral Linewidth of SQW Laser Diodes Emitting in the 780 nm Region
Authors: Yamada Noriyuki , Hirata Takaaki , Maeda Minoru , Hosomatsu Haruo
Published: February 2005

GRIN-SCH-SQW laser diodes with quite a narrow well width of 3 nm were successfully fabricated by MOVPE. Oscillation wavelength and dispersion of linewidth enhancement factor α were found to be greatly dependent on cavity length i.e. threshold level. α measured at oscillation wavelength was 2.1 in the 300 µm-long laser, and 3.7 in the 1000 µm-long laser. This dependence was roughly explained by taking account of bandgap shrinkage and broadening of the gain spectrum. The narrowest spectral linewidth obtained was 1.5 MHz at an output power of 8.7 mW with a linewidth-power product of 5.7 MHz·mW in the 1000 µm-long laser.
A High-Efficiency, High-Repetition-Rate KrF(B→X) Excimer Lamp Excited by Microwave Discharge
Authors: Kumagai Hiroshi , Obara Minoru
Published: February 2005

KrF(B→X) fluorescence pulses of 5-9-µs pulse duration with 55-kHz operation frequency were produced from a microwave-discharge-pumped KrF mixture. A high average KrF fluorescence power of 43 W was obtained with an intrinsic efficiency of 12.5% when the average microwave power of 341 W was deposited into the 25-Torr mixture of 2%F2/1%Kr/48.5%He/48.5%Ne. We also obtained a peak KrF fluorescence power of 215 W with a power efficiency of 15.9%.
Effects of Oxygen Doping on the Electrical and Optical Properties of Sputtered ZnS:TbOF Electroluminescent Thin Films
Authors: Ohnishi Hideomi , Okamoto Kenji
Published: February 2005

The electrical and luminescent properties of green-color ZnS:TbOF thin-film electroluminescent devices have been investigated. It is shown that appropriate oxygen doping is an important factor in the improvement of the luminance. The high luminance achieved by oxygen doping is due not only to the efficiency improvement based on the formation of TbOF complex center but also to the increased amount of transported charges flowing through the active layers.
Antiferroelectric Chiral Smectic C Materials Having a 2-Alkyl Alkanoyl Group in the Chiral Part
Authors: Nishiyama Isa , Yoshizawa Atsushi , Fukumasa Mitsuo , Hirai Toshihiro
Published: February 2005

Novel antiferroelectric chiral smectic C (SmCA
*) materials are presented. Four homologous compounds having a 2-alkyl alkanoyl group in the chiral part are investigated. Three of them have SmCA
* and show very short helical pitch in SmC*. In contrast, the other one has no SmCA
* and exhibits rather long pitch in SmC*. This result suggests that the length of the pitch relates closely to occurrence of SmCA
*. The introduction of an ethyl group into the chiral carbon instead of a methyl group increases the stability of SmCA
* in contrast with decreasing that of SmA and SmC*. All four compounds show the third state even in SmC* by application of an AC field. Microscope observation indicates that the third state in SmC* is different from that in SmCA
*.
Silicon Dioxide Thin Films Prepared by Chemical Vapor Deposition from Silicon Tetraacetate
Authors: Maruyama Toshiro , Shionoya Jun
Published: February 2005

Silicon dioxide thin films were prepared by a low-temperature chemical vapor deposition method. The raw material was silicon tetraacetate which is nontoxic and easy to handle. At a reaction temperature above 150°C, the thin films were obtained with a high deposition rate. The reaction temperature and the deposition rate are comparable to the corresponding values in the chemical vapor depositions of SiO2 from hydride and alkoxide. In addition, the deposition can be carried out in air. Silicon tetraacetate appears to offer a viable alternative to silicon hydride and alkoxide for low-temperature SiO2 production.
Site of Ultrasonic Signal Generation from a Junction of a Transistor-Chip by Excitation of the Chopped Electron Beam
Authors: Takenoshita Hiroshi , Kobayashi Mutsuo
Published: February 2005

An npn Si transistor-chip specimen was angle-lapped so that the junction between the base(B) and collector(C) was exposed to the microscopic field. Bias voltage was applied between the C and emitter electrodes, and the B was kept open. Photographs of the SEM and electron-acoustic microscopy were compared with the X-Y recorder charts. When compared under several bias conditions, the site of EAM signal generation stayed almost unchanged in spite of the variation of bias voltage. On the other hand, the site of electron-beam-induced current signal generation spread in response to the variation of bias condition.
An X-Ray Diffraction Method for Characterization of Several Lattice-Matched Heteroepitaxial Films
Authors: Itoh Nobuo , Wakahara Akihiro , Sato Tomohiko , Pak Kangsa , Yoshida Akira , Yonezu Hiroo
Published: February 2005

It has been considered that when the structure amplitude |F| for a quasi-forbidden reflection of a lattice-matched heteroepitaxial film is considerably larger than that of the substrate or the other layer, for example, for the 200 reflection of InGaP/GaAs, only the film can be observed and characterized. To show the validity of this method, the respective layers in an InGaAs/InP/(100)GaAs structure have been characterized; the upper InGaAs layer, the inner InP layer and the GaAs substrate have been observed using the 311A reflection with a very small glancing angle (∼0.5°), the 200 reflection of the quasi-forbidden reflection and the 400 reflection, respectively.
Heavily P-Doped (>1021 cm-3) Silicon Films Grown by Photochemical Vapor Deposition at a Very Low Temperature of 250°C
Authors: Yamada Akira , Jia Ying , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

Heavily phosphorus-doped epitaxial silicon films have been successfully grown by a novel photochemical vapor deposition process at a very low temperature of 250°C. The epitaxial layers were deposited from SiH4-SiH2F2-PH3 gases diluted with H2 on single-crystal silicon substrates. The highest electron concentration of 2.3×1021 cm-3 was obtained at a doping quantity (PH3/SiH4) of 4.2%. From the dependence of resistivity on the sample temperatures, it was found that the obtained samples were “metallic”.
Dry Oxidation Study on CVD-SiO2/Thermal-SiO2/Si Structure
Authors: Kuroda Shigeki , Nishi Kenji , Ueda Jun
Published: February 2005

Silicon dioxide growth in dry oxygen has been investigated on a CVD-SiO2/thermal-SiO2/Si multilayer structure at 900°C and 1000°C. Borophosphosilicate glass (BPSG), phosphosilicate glass (PSG) and nondoped silica glass (NSG) have been used as the CVD-SiO2 layers. The growth rate of thermal SiO2 under a CVD layer increases in the order of NSG, PSG and BPSG. The oxide grown under the BPSG layer is even thicker than thermal-SiO2/Si without a CVD layer. A new enhanced oxidation model, which takes into account the liquidlike nature of BPSG and PSG during oxidation, is proposed to explain the experimental results.
Optically Coupled Three-Dimensional Common Memory with Novel Data Transfer Method
Authors: Takata Hirokazu , Mori Hiroki , Iba Junichiro , Koyanagi Mitsumasa
Published: February 2005

An optically coupled three-dimensional common memory has been proposed to perform real-time parallel data processing at the hardware level. In this memory, high-speed block data transfer is carried out by optical coupling among memory layers with LEDs and photoconductors. In order to increase the packing density of this memory, the scalability of the LED and photoconductor is evaluated. In addition, it is shown that a high packing density and a large memory capacity comparable to the conventional SRAM can be achieved by a newly proposed sense-amplifier-coupling data transfer method.
Effect of W Film Stress on W-Gate MOS Characteristics
Authors: Matsuhashi Hideaki , Nishikawa Satosi , Ohno Seigo
Published: February 2005

The fixed oxide charge density (N
f) of W-gate MOS capacitors has been investigated as a function of both annealing temperature and stress of the W film. It is found that N
f greatly increases upon 1000°C annealing when the total stress, which is defined as the product of the W film stress before 1000°C annealing and thickness of the W film, is more than 1.4×105 dyne/cm (compressive). The interface state density (D
it) also increases with increase in N
f. For the samples whose N
f is large, etch pits are revealed on the Si surface by Secco etching. There is a linear correlation between the etch pit density and the N
f value. It is supposed that the increases of N
f and D
it are due to Si defects formed at the SiO2/Si interface by the large stress of the W film.
SiO2/Si Interfaces Studied by STM
Authors: Niwa Masaaki , Iwasaki Hiroshi
Published: February 2005

Topologies of SiO2/Si(100) interfaces grown by several oxidation conditions were successfully observed using a scanning tunneling microscope (STM) in air with a wider area than ever reported. Hydrogen terminated Si surfaces were prepared by means of HF dipping and were checked by XPS and AES. The interfaces showed ripplelike corrugations that consisted of steps caused by the misorientation of the silicon single crystal. The large step height was produced by wet oxidation. Morphologies of the interfaces measured by STM were consistent with the observation by TEM.
TEM Observation of Defects Induced by Ni Contamination on a Si(100) Surface
Authors: Sadamitsu Shinsuke , Sano Masakazu , Hourai Masataka , Sumita Shigeo , Fujino Nobukatsu , Shiraiwa Toshio
Published: February 2005

The behavior of Si(100) surface defects induced by intentional Ni contamination was studied by means of etch-pit observation and transmission electron microscopy. After annealing at 1150°C for 1 hour in N2 atmosphere, shallow pits (SP) were observed only on the surface of the wafer. These SP were thought to be attributable to NiSi2-type silicides formed on the surface by the selected area diffraction pattern. During the additionl thermal oxidation, oxidation-induced stacking faults (OSF) were always formed at each of the large SP but not always at small ones.
Electrical Properties of Bi2Sr2Ca1-xYxCu2Oy at High Temperatures
Authors: Munakata Fumio , Shinohara Kazuhiko , Yamanaka Mitsugu
Published: February 2005

Temperature dependence of the resistivity of Bi2Sr2Ca1-x
Y
x
Cu2O
y
compounds was measured in air and N2. The temperature dependence of the resistivity in this system showed behavior similar to that in Eu1+x
Ba2-x
Cu3O
y
except for Bi2Sr2Y1Cu2O
y
. The results of Bi2Sr2Y1Cu2O
y
indicate that the hole is stable in the region where Cu1+ and Cu2+ exist. The high stability of holes suggests the possibility that the role of copper and oxygen in the electrical conduction of high-T
c oxide superconductors is separate.
Preparation and Crystallization Process of the High-Tc Superconducting Phase (Tc(end)>100 K) in Bi, Pb-Sr-Ca-Cu-O Glass-Ceramics
Authors: Ibara Yoshikazu , Nasu Hiroyuki , Imura Takeshi , Osaka Yukio
Published: February 2005

A high-T
c superconducting phase (T
c(end)>100 K) in Bi, Pb-Sr-Ca-Cu-O glass-ceramics was prepared by conventional melt-quenching and annealing techniques. No crystalline phase could be detected in the as-quenched specimens, but annealing for crystallization was necessary to observe the superconducting transition. This report investigates the appropriate amount of PbO in the starting materials for observing the high-T
c phase and crystallization process. The highest T
c(onset) and T
c(end) were 120 K and 102 K, respectively.
A. C. Susceptibility of the Superconducting Bi-(Pb)-Sr-Ca-Cu-O System
Authors: Sumiyama Akihiko , Endo Hozumi , Tsuchiya Jun , Kijima Naoto , Mizuno Masaaki , Oguri Yasuo
Published: February 2005

The ac magnetic susceptibility of the Bi-(Pb)-Sr-Ca-Cu-O system in which the high-T
c phase (T
c>100 K) is the chief constituent has been measured. The diamagnetism attributed to the Josephson-like weak coupling is sensitive to the synthetic conditions and the grain contact structure. The magnetic susceptibility of BiSrCa3Cu4O
x
sintered for different periods has revealed that the Josephson-like coupling property is degraded as the volume fractions of the low-T
c phase (T
c∼75 K) and the insulating phases are decreased and the high-T
c phase is formed.
Low-Temperature Electron Microscopy of a Bi2(Sr, Ca)3Cu2Ox Superconductor
Authors: Horiuchi Shigeo , Shoda Kaoru , Iwatsuki Masashi , Harada Yoshiyasu , Matsui Yoshio
Published: February 2005

A superconducting crystal Bi2(Sr, Ca)3Cu2O
x
with T
c at 80 K has been examined by low-temperature electron microscopy, in which the specimen is cooled at a temperature lower than 10 K. High-resolution electron micrographs and electron diffractograms obtained at the low temperature are almost the same as those obtained at room temperature, suggesting that the crystal structure with the modulation along the b axis is not substantially changed on the transition to the superconducting state.
Space-Group Determination of a New Superconductor (Nd0.66Sr0.205Ce0.135)2CuO4-δ Using Convergent-Beam Electron Diffraction
Authors: Tsuda Kenji , Tanaka Michiyoshi , Sakanoue Jun , Sawa Hiroshi , Suzuki Seiichiro , Akimitsu Jun
Published: February 2005

The space group of a superconductor (Nb0.66Sr0.205Ce0.135)2CuO4-δ was determined to be P4/nmm by convergent-beam electron diffraction.
Structural Features and Superconducting Properties of As-Grown Y-Ba-Cu-O Films
Authors: Sagoi Masayuki , Terashima Yoshiaki , Kubo Koh-ichi , Mizutani Yoshihisa , Miura Tadao , Yoshida Jiro , Mizushima Koh-ichi
Published: February 2005

The structural features of superconducting Y-Ba-Cu-O films prepared by reactive sputtering have been discussed in relation to the preparation conditions. Conductivity anisotropy and the anomalous diamagnetic response observed for the films have also been discussed.
Preparation and Properties of a Layered Copper Oxide Bi2-xPbxSr2Y1-uCauCu2Oy
Authors: Ono Akira
Published: February 2005

A search for a new superconducting material was made in the Bi-Pb-Sr-Y-Ca-Cu oxide system. A single phase of BiPbSr2YCu2O
y
was prepared, but it was a semiconducting material showing no superstructure in the powder X-ray diffraction patter. Phase stability, lattice constants and properties of electrical resistivity were studied for specimens in the examined system.
Controlling Plastic Relaxation Using Graded Superlattice Buffer Layers
Authors: Villaflor Antonio Basanes , Kimata Morihiko
Published: February 2005

AlSb layers thicker than the critical thickness for the onset of plastic relaxation were successfully grown on (001) GaSb substrates by molecular beam epitaxy. This was achieved using graded superlattice buffer layers (gSL-BL). The accommodation of misfit strain using this buffer is discussed, and the X-ray diffraction characteristics of the buffer are presented. The diffraction pattern is shown to modulates into two sets of satellite peaks.
Photoacoustic EXAFS of Solid Phase
Authors: Masujima Tsutomu , Shiwaku Hideaki , Yoshida Hisanobu , Kataoka Mikio , Reichling Michael , Imai Hideo , Kawata Hiroshi , Iida Atsuo , Koyama Atsushi , Ando Masami
Published: February 2005

Fine structures observed in X-ray photoacoustic spectra of various solids were compared with those in the absorption spectra. For a precise comparison, the photoacoustic spectra were corrected for energy-depending X-ray absorption of gas existing in the optical path. Finally corrected photoacoustic spectra showed a leveled or decreasing trend with increasing photon energy. Good correspondence between the X-ray photoacoustic spectra and the absorption spectra further confirmed that the fine structures in the photoacoustic spectra are identical with the extended X-ray absorption fine structures (EXAFS).
Reduction of the Barrier Height of Silicide/p-Si1-xGex Contact for Application in an Infrared Image Sensor
Authors: Kanaya Hiroyuki , Hasegawa Fumio , Yamaka Eiso , Moriyama Takashi , Nakajima Masakatsu
Published: February 2005

Silicide/p-Si1-x
Ge
x
Schottky contacts were studied for using in an infrared (IR) image sensor. Si1-x
Ge
x
layers were grown on p-type (100) Si substrates by using molecular beam epitaxy (MBE). Schottky barrier heights of PtSi(Ge) or PdSi(Ge)/p-Si1-x
Ge
x
contacts decreased as the Ge content increased. When the Si1-x
Ge
x
layer was strained, the barrier height was smaller than when relaxed for the same value of x. These results suggest the possibility of a long wavelength (8–12 µm) IR image sensor using a silicide/p-Si1-x
Ge
x
Schottky contact for the strained layer monolithically grown on a p-Si CCD substrate.
Broadening Mechanism of Resistive Transition under Magnetic Field in Single Crystalline (La1-xSrx)2CuO4
Authors: Kitazawa Koichi , Kambe Shinsaku , Naito Michio , Tanaka Isao , Kojima Hironao
Published: February 2005

The resistive transitions near the superconducting critical temperature were measured under magnetic field up to 5 T on a FZ-grown high-quality single crystal (La0.93Sr0.07)2CuO4 (T
c=37.5 K) The crystal was sufficiently large along the c-axis that the dc four-probe method could be applied along this axis as well as along the usual a-b plane. It was found that the width of the temperature region over which the resistive transition is broadened depends only on the relative orientation between the magnetic field and the crystalline c-axis, but not on that between the field and the current. It indicates that the mechanisms based on the fluxoid motion, such as the flux creep model, the Kosterlitz-Thouless transition model and the superconducting glassy state model, are unlikely to explain the broadening of the resistive transition under magnetic fields in (La1-x
Sr
x
)2CuO4.
Anisotropic Diamagnetism of 110 K Bi-Pb-Sr-Ca-Cu-O
Authors: Ishida Takekazu , Sakuma Takashi , Sasaki Toku , Kawada Yuzo
Published: February 2005

The 110 K Bi compounds have been prepared by means of a Pb-doping technique. The 110 K phase was obtained in an almost single-phase form. The ac susceptibility of the pellet can be interpreted in terms of bulk and coupling contributions. The powdered specimen was molded in a Stycast 1266 under a 8.9 T magnetic field to align the sense of the c axis. We found that the ac susceptibility was very anisotropic with respect to the c axis.
Transport and Magnetic Properties of Nd-Ce-Cu Oxides
Authors: Uji Shinya , Aoki Haruyoshi , Matsumoto Takehiko
Published: February 2005

Transport and magnetic properties of the T'-phase Nd2-x
Ce
x
CuO4 system have been studied to investigate the occurrence of superconductivity by electron doping. The lattice constants and susceptibility of the system are reasonably interpreted in terms of all the Ce ions being tetravalent. The resistivity decreases by more than three orders of magnitude with Ce doping up to x=0.2. The measurements of thermopower confirm that the resistivity decrease arises from the increase of electron carriers supplied by the Ce4+ ions. Anomalous resistivity decreases are observed below 11 K, suggesting the occurrence of superconductivity in this system.
Resistivity Zero of Quenched Bi2Sr2CaCu2Ox at Above 90 K
Authors: Ishida Takekazu
Published: February 2005

It has been verified that Bi2Sr2CaCu2O
x
does not remain as an 80-K superconductor upon quenching. The resistivity zero of the low-T
c Bi compound exceeds 90 K. We emphasize that Bi2Sr2CaCu2O
x
is equivalent to YBa2Cu3O7-δ as far as T
c is concerned. The characteristic combination of two CuO2 layers may be responsible for the specification of T
c.
Superconducting Properties of Bi-Pb-Sr-Ca-Cu-O Ceramics Prepared by the Melt-Quenching Method
Authors: Sato Ryuji , Komatsu Takayuki , Matushita Kazumasa , Yamashita Tsutomu
Published: February 2005

We prepared superconducting Bi0.8Pb0.2SrCaCu
x
O
y
ceramics by the melt-quenching method, and examined the effects of the materials (alumina and platinum) of the crucible and the concentration of Cu element on the superconducting properties. It was found that the Al element, which was introduced from an alumina crucible, and an excess amount of Cu element, which was estimated as a deviation from the nominal composition of the high-T
c phase, caused a degradation in the superconducting properties. The annealed (840°C, 250 h) sample of Bi0.8Pb0.2SrCaCu1.5O
y
exhibited superconductivity with a T
c(zero) of 104 K and a critical current density (77 K, zero magnetic field) of 250 A/cm2.