bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Surface Fermi Level in Phosphidized GaAs
Authors: Sugino Takashi , Yamada Takashi , Kondo Katsuhiko , Ninomiya Hideaki , Matsuda Koichiro , Junji Shirafuji Junji Shirafuji
Published: February 2005

The location of the surface Fermi level in phosphidized GaAs has been investigated using the Kelvin probe method. The surface Fermi level changes from an energy around 0.47 eV below the conduction band edge for the as-etched surface covered with a natural oxide layer to an energy of 0.25 eV after sufficient phosphidization by phosphine (PH3)-plasma treatment. On the other hand, isothermal capacitance transient spectroscopy measurement reveals that a new electron trap with an activation energy of 0.24 eV is introduced at or near the phosphidized surface. This provides experimental evidence that the location of the surface Fermi level is closely associated with that of the electron trap induced by PH3-plasma treatment.
Dimensional Crossover Effect in Jc Characteristics of Chemical Vapor Deposition Processed YBa2Cu3O7-δ Films
Authors: Awaji Satoshi , Watanabe Kazuo , Kobayashi Norio , Hisanori Yamane Hisanori Yamane , Toshio Hirai Toshio Hirai
Published: February 2005

The critical current densities of chemical vapor deposition (CVD) processed YBa2Cu3O7-δ films were resistively measured in fields up to 13 T and in a temperature range from 4.2 to 77.3 K. For B perpendicular to the c-axis (B⊥c), an anomaly in the temperature dependence of J
c was observed at T
d≃50-60 K and the field dependence of J
c drastically changed at T
d. Since T
d was almost in agreement with the estimated dimensional crossover temperature T
co, it is suggested that the change of dimensionality influences the J
c properties.
Effect of Pt on Crystallization of Bi-Sr-Ca-Cu-O by Melt Process
Authors: Umemura Toshio , Kinouchi Shin-ichi , Egawa Kunihiko , Ayumi Nozaki Ayumi Nozaki , Shin Utsunomiya Shin Utsunomiya
Published: February 2005

We have investigated the effect of Pt on crystallization of Bi2Sr2Ca1Cu2O
y
prepared by the melt process. By observing the microstructure of specimens rapidly cooled in the process of crystallization, we found that the Pt restrained the growth of the Ca2Cu1O3 phase and even of superconducting phases. It was found that Pt formed oxides preferentially with Ca and Sr early in the crystallization process, however, such products didn't seem to grow coarsely.
High-Performance 1.5-µm Distributed Feed Back Lasers with Strained Multi-Quantum Well Structure Grown by Metalorganic Molecular Beam Epitaxy (Chemical Beam Epitaxy)
Authors: Nakao Masashi , Iga Ryuzo , Takeshi Yamada Takeshi Yamada , Hideo Sugiura Hideo Sugiura
Published: February 2005

The Metalorganic Molecular Beam Epitaxy (Chemical Beam Epitaxy) technique was used to make active layers for Distributed Feed Back (DFB) lasers. Typical characteristics of these lasers-for example a threshold current of 6 mA and a slope efficiency of 0.3 mW/mA per facet-reflect the high homogeneity and high uniformity of the grown layers. The values referred here are the best ever reported for a CBE-grown active layer.
Nonlinear Current Dependence of Potential Barrier for Flux Creep in Superconducting La-Sr-Cu-O Single Crystal
Authors: Mawatari Yasunori , Yamafuji Kaoru , Noda Tomoyuki , Nakayama Yoshimi , Kishio Koji , Kitazawa Koichi
Published: February 2005

The potential barrier for flux bundles, U, was estimated from the observed relaxation of the magnetization, M, with time, t, in a superconducting La-Sr-Cu-O single crystal. It is shown that U depends on the current density, J, and the temperature, T, as U(J, T)=U
0[(J
0/J)α-1]. The present result is different from the relationship of U\proptln (J
0/J) observed in Y-Ba-Cu-O films, and is similar to the one predicted by the collective theory. It is also pointed out that the observed increase of the effective pinning potential, U
c
*=k
B
T(-∂ln M/∂ln t)-1, with increasing T does not result from the T dependence of U
0, but is only an apparent anomaly originating from the above nonlinear U-J characteristics.
Magneto-Optical Kerr Spectra of Ultrathin Co Films
Authors: Yamaguchi Atsushi , Iwata Satoshi , Shigeru Tsunashima Shigeru Tsunashima , Susumu Uchiyama Susumu Uchiyama
Published: February 2005

Magneto-optical Kerr loops and their energy spectra have been measured for ultrathin Co films sandwiched between Au layers. Polar Kerr hysteresis loops were detected for Co layer thicknesses down to 3 Å, showing complete squareness between 5 Å and 8 Å. When the Co layer is thicker than 20 Å, the spectral shape of the Kerr rotation, as well as the Kerr ellipticity, in an energy range of 1.5∼5 eV agrees well with those calculated from bulk data. With decreasing Co thickness below 10 Å, the spectra become gradually smaller in magnitude than and different in shape from calculated ones.
Compositional Effects on In Situ YBaCuO Films Grown at Low Oxygen Pressures
Authors: Shinohara Kazuhiko , Munakata Fumio , Yamanaka Mitsugu , Matijasevic Vladimir , Rosenthal Peter , Hammond Robert , Beasley Malcolm R.
Published: February 2005

YBaCuO films were grown by reactive coevaporation at various oxygen pressures and compositions. The T
c
′s of these films were strongly affected by composition, especially by the Ba/Y ratio. The composition ratios of Ba/Y optimized for T
c>85 K were found to decrease with decreasing oxygen pressure during growth.
Anomalous Etching Residues of Sputter-Deposited Ta upon Reactive Ion Etching Using Chlorine-Based Plasmas
Authors: Nakaishi Masafumi , Yamada Masao , Kondo Kazuaki , Masaki Yamabe Masaki Yamabe , Kenji Sugishima Kenji Sugishima
Published: February 2005

Anomalous etching of Ta which is sputter-deposited on silicon carbide (SiC) films is observed upon reactive ion etching (RIE) using a gas mixture of chlorine and chloroform. We find that α-Ta is hardly etched off by either chlorine-based plasmas or aqueous hydrofluoric acids (HF), while β-Ta is easily etched off by the same methods. The extent of α-Ta depends on the surface treatment of SiC. The difference in chemical reactivity between the α phase and β phase is discussed using photoemission spectroscopy.
Collision Cooling of Ions Stored in Quadrupole Radio-Frequency Trap
Authors: Moriwaki Yoshiki , Tachikawa Maki , Yoshiharu Maeno Yoshiharu Maeno , Tadao Shimizu Tadao Shimizu
Published: February 2005

We present a novel model for collisional energy transfer between ions and neutral molecules in the quadrupole radio-frequency trap. Calculated results quantitatively reproduce the dependence of the ion temperature T
i on the buffer gas pressure P
n, observed on Mg+ ions and several collision partners (H2, He, and CH4). It is deduced from the present model that T
i is proportional to P
n
-1/3 in the low-pressure range below 10-6 Torr, in good agreement with the experimental results.
Spatial Variation of CO2
- and SO3
- Radicals in Massive Coral as Environmental Indicator
Authors: Ikeda Sumiko , Neil David , Ikeya Motoji , Kai Ayako , Miki Toshikatsu
Published: February 2005

Electron spin resonance (ESR) signal intensities of a massive coral colony from the Great Barrier Reef are measured-along the growth direction with a microwave scanning ESR imaging system. The annual high intensity regions of CO2
- radicals are the same as the skeletal high density regions. Those of SO3
- radicals are the same as the yellow-green fluorescent bands which correlate with summer. A long-range fluctuation which has a 12-year cycle is also observed in the intensities of these two radicals. Thus, the ESR signal intensities of coral can be used as an indicator of past environmental changes.
Charge Transport and Superconducting Transitions in C60 Single Crystals and Thin Films Doped with Rubidium
Authors: Ogata Hironori , Inabe Tamotsu , Hoshi Hajime , Maruyama Yusei , Achiba Yohji , Suzuki Shinzo , Kikuchi Koichi , Ikemoto Isao
Published: February 2005

Superconductivity is confirmed in rubidium-doped C60 samples prepared from single crystals and thin films, by electrical resistivity measurements. Superconducting transition temperatures (T
c) are observed at T
c(onset)=30 K, T
c(offset)=26 K, and T
c(onset)=22 K, T
c(offset)=2.5 K, respectively. The details of the doping conditions are described.
Effect of Infrared Image Heating on Bi-Pb-Sr-Ca-Cu-O High-Tc Superconducting Films and Fibers Prepared by Pyrolysis of Organic Acid Salts
Authors: Nasu Hiroyuki , Aruga Koji , Syoyama Masashi , Jun Matsuoka Jun Matsuoka , Kanichi Kamiya Kanichi Kamiya
Published: February 2005

Infrared image heating was applied to Bi-Pb-Sr-Ca-Cu-O high-T
c superconducting films and fibers prepared by pyrolysis of organic acid salts. T
c(end) and J
c of the films were raised to 108 K and nearly 8×103 A/cm2 (at 12 K) from 103 K and about 4×103 A/cm2 (at 12 K), respectively, by infrared image heating at 845°C with the scanning speed of 2.3 mm/h. Similar effects were observed in fibers, and J
c increased by nearly 4 times. These effects seem to result from the decrease in the number of the weak links in the specimens due to partial melting.
Effect of Intermission in Layer-by-Layer Growth of Bi2Sr2Ca2Cu3O10+δ Thin Films on Nd:YAlO3(001)
Authors: Tsukada Ichiro , Kobayashi Shoji , Koyama Ichiro , Hiroshi Watanabe Hiroshi Watanabe , Kunimitsu Uchinokura Kunimitsu Uchinokura
Published: February 2005

The intermission-time dependence of crystal structures and superconductivity has been investigated for Bi2Sr2Ca2Cu3O10+δ thin films. To stimulate surface migration of Cu atoms, an intermission has been inserted just after the deposition of Cu. The effect of the intermission appears in the low-angle X-ray diffraction and the transition temperature. It is found that the intermission improves the quality of the films, but a too-long intermission is bad for their superconductivity. The film prepared with the 30-s intermission shows an untwinned structure on the Nd:YAlO3(001) substrate and has the transition temperature at 82 K.
Studies on the Low Local Temperature Rise in the Mirror Facet of a High-Power InGaAsP/GaAs Laser
Authors: Yoo Jae S. , Oh Myeong S. , Park Hea S. , Jung Seung T. , Gueorgui T. Park Gueorgui T. Park , Kyung Y. Park Kyung Y. Park
Published: February 2005

To examine the facet heating behavior, high-power InGaAsP/GaAs laser diodes were fabricated with the epitaxial layers by liquid phase epitaxy (LPE) growth onto the moving substrate. It is shown that the facet temperature rise of the InGaAsP/GaAs laser diode has been kept lower than 30°C even above 500 mW. The kinematic model in which the presence of phosphorus oxide with a high heat of formation preserves the relatively low surface recombination rate at the mirror facet of the InGaAs/GaAs laser is proposed.
Growth of Aluminum Nitride Films on Silicon by Electron-Cyclotron-Resonance-Assisted Molecular Beam Epitaxy
Authors: Miyauchi Michihiro , Yukari Ishikawa Yukari Ishikawa , Noriyoshi Shibata Noriyoshi Shibata
Published: February 2005

Aluminum nitride thin films have been prepared on silicon substrates by electron-cyclotron-resonance plasma-assisted molecular beam epitaxy (ECR-MBE). Epitaxial AlN films have been obtained by Al evaporation and 250 eV nitrogen ion irradiation on a clean Si surface at 700°C. AlN films with two kinds of crystal orientations were grown epitaxially on Si(111). The dominant one is AlN (0001)//Si(111); AlN[011̄0]//Si[112̄] and the another one is AlN(011̄0)//Si(111); AlN[0001]//Si[112̄].
Effect of Ambient on the Surface Resistance of Diamond Films during Cooling after Deposition
Authors: Mori Yusuke , Eimori Nobuhiro , Hatta Akimitsu , Toshimichi Ito Toshimichi Ito , Akio Hiraki Akio Hiraki
Published: February 2005

A remarkable ambient effect on the resistance of CVD diamond during cooling after deposition has been observed. The diamond films that were cooled slowly down to room temperature (RT) in the 10-3 Torr range after deposition showed relatively low resistances in the range of 106∼107 Ω. On the other hand, high resistances over 1013 Ω were observed for diamond films that were cooled down to RT in an oxygen or an air ambient and at atmospheric pressure. Among these surfaces a substantial difference was observed in the electronic structure as studied by electron energy loss spectroscopy.
Effects of Substrate Eddy Current on Magnetic Anisotropy in Permalloy Underlayer for Perpendicular Media
Authors: Ishibashi Kazuo , Mallary Hiroshi Sato
Published: February 2005

A new method to prepare permalloy film on a disk substrate with an easy magnetization axis in the radial direction is described. The permalloy film is sputter-deposited under radial magnetic field from concentric circumferential eddy currents in an aluminum disk substrate. The eddy current is produced by applying an AC magnetic field perpendicular to the substrate. With a perpendicular magnetic field of 50 Hz and approximately 15 Oe, a radial magnetic field of 2 Oe was created on a 5.25′′ substrate, which was sufficiently large to align the easy axis of 1-µm-thick permalloy film in the radial direction.
Electric Trapping of Neutral Atoms
Authors: Fujio Shimizu Fujio Shimizu , Makoto Morinaga Makoto Morinaga
Published: February 2005

Two- and three-dimensional trappings of neutral atoms by an electric field are discussed. It is shown that a harmonic potential produced by the second-order Stark effect around a saddle point of the electric field intensity can be used to trap laser-cooled neutral atoms.
Numerical Solution of Electromagnetic Scattering from a Conducting Surface Coated with Magnetic Material
Authors: Chi-Sen Lin Chi-Sen Lin , M. Tahir Yaqoob M. Tahir Yaqoob
Published: February 2005

Considering a conduction current on the conducting surface and a magnetic polarization current in dielectric material, we have developed a new formulation to find the scattered field from a conducting surface coated with a dielectric layer. Two H-field intergral equations are developed by applying the boundary conditions at the conducting surface and dielectric material. These integral equations are solved by the method of moment (MOM) to find the conduction and the polarization currents from which scattered field is readily determined. With consideration of the polarization current, the effects of surface wave excitation in dielectric material are automatically included in the solution.
Proposal of Field-Effect-Type Photodetector Using Field-Screening Effect in the Absorption of Light
Authors: Kazuhiko Shimomura Kazuhiko Shimomura
Published: February 2005

A field-effect-type photodetector is proposed. The proposed device is an field-effect-transistor (FET) structure whose output current is controlled by the potential applied to the FET resulting from the field-screening effect of the photogenerated carriers in a diode overlaid on the FET.
A Novel Optoelectronic Phase-Locked Loop Based on a Square-Wave Phase-Modulated Static Fiber-Optic Gyroscope
Authors: Ci-Ling Pan Ci-Ling Pan , Pie-Yan Chien Pie-Yan Chien
Published: February 2005

We propose and demonstrate a novel optoelectronic phase-locked loop (OEPLL). The key element of the OEPLL is an electro-optic harmonic mixer consisting of a square-wave phase-modulated static fiber-optic gyroscope (FOG) with an intensity-modulated laser diode as the light source. As a first demonstration, we have phase-locked a target electronic oscillator modulating the laser diode at the 10th harmonic frequency of the reference oscillator which modulates the phase of the FOG.
Detection of Negative Ions in a Helium-Silane RF Plasma
Authors: Shiratani Masaharu , Fukuzawa Tsuyoshi , Kenji Eto Kenji Eto , Yukio Watanabe Yukio Watanabe
Published: February 2005

In order to detect negative ions in a helium-silane rf plasma, temporal evolutions of the densities of electrons and ions are observed by square-wave-amplitude modulation of an rf discharge voltage. Densities of electrons and ions are deduced using a microwave interferometer and ion saturation current of a Langmuir probe, respectively. The experiments show that negative ions are formed in the plasma even for a low concentration of 0.5% silane and their density is estimated to be about 109 cm-3 which is comparable to the electron density. The energy of electrons which form negative ions due to attachment is estimated to be below 8.9 eV, that is, below the resonance peak energy of dissociative electron attachment to SiH4.
New Pb-Based Cuprates with 1222 Structure Having No Tetravalent Ions, (Pb0.5Cu0.5)Sr2-xLn2-yLax+yCu2Oz (Ln: Gd, Dy, Ho and Er)
Authors: Sasakura Hiroyuki , Teraoka Hiroshi , Nakahigashi Kiyotaka , Yoshiara Shinnosuke Minamigawa
Published: February 2005

New Pb-based cuprates with 1222 structure have been synthesized in (Pb0.5Cu0.5)Sr2-x
Ln2-y
La
x+y
Cu2O
z
(Ln:Gd, Dy, Ho and Er) systems having no tetravalent ions such as Ce4+ and Pr4+. The composition to obtain an almost-single phase sample for each system was found to be located within a narrow limited region. After oxygen annealing at 500°C for 100 h under partial pressure of 100 atm, all the almost-single-phase samples were semiconductors, but a sample with the nominal composition of (Pb0.5Cu0.5)Sr1.45Gd1.95La0.60Cu2O
z
among them showed a diamagnetic signal starting from about 20 K.
Electrochromic Behavior of Amorphous Copperphthalocyanine Thin Films
Authors: Kohno Yasuhiko , Masui Masayoshi , Ono Kun , Tatsuaki Wada Tatsuaki Wada , Manabu Takeuchi Manabu Takeuchi
Published: February 2005

Amorphous and polycrystalline copperphthalocyanine thin films were prepared by vacuum evaporation, and their electrochromic behavior and voltamogramms were examined in a liquid electrolyte. Amorphous films prepared at the substrate temperature of -130°C underwent three color transitions (from blue to violet, then to green and to blue again) corresponding to the three peaks on the voltamogramms in the lithium perchlorate solution. In contrast, the polycrystalline thin films prepared at the substrate temperature of 180°C did not exhibit color change.
High-Resolution Electron Microscopy of Radiation Damage of YBa2Cu4Oy Superconductor Induced by 200 kV Electron Beam
Authors: Yanagisawa Yoshio Matsui
Published: February 2005

Electron-induced structural decompositions of a YBa2Cu4O
y
(124) type of high-T
c superconductor are examined with a 200-kV high-resolution transmission electron microscope (HRTEM). Partial conversions of the (CuO)2 double chains into the (CuO) single ones are induced to form a disordered structure, and precipitation of the decomposition product, CuO, is observed at the edge of the electron-irradiated crystals. Such results of 200 kV electron beam irradiations are rather similar to the thermal decomposition process, while those due to higher-energy 1-MV electrons are the knock-on atom displacements that cause amorphization [Matsui et al., Jpn. J. Appl. Phys. 30 (1991) L1375].
Effect of Crystal Pulling Rate on Formation of Crystal-Originated “Particles” on Si Wafers
Authors: Ryuta Jiro , Morita Etsuro , Tanaka Toshiro , Shimanuki Yasushi
Published: February 2005

It was recently revealed that singularities (crystal-originated “particles”) formed on Si wafers after SC1 cleaning originate from some defects in crystals and were perceived by laser particle counters. In this paper, the size distribution of crystal-originated “particles” is examined in detail by means of repeated SC1 cleanings. It is shown that, as the crystal pulling rate becomes faster, the size distribution of crystal-originated “particles” shifts toward smaller size, and the total number of origins of crystal-originated “particles” increases.
Effect of Ion Bombardment on the Properties of Hydrogenated Amorphous Silicon Prepared from Undiluted and Xenon-Diluted Silane
Authors: Dutta Joydeep , Hasezaki Kazuhiro , Mashima Satoshi , McElheny Peter J. , Suzuki Atsushi , Gautam Ganguly Gautam Ganguly , Akihisa Matsuda Akihisa Matsuda
Published: February 2005

The contribution of ion bombardment to the growth of hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapour deposition from silane and xenon-diluted silane source gases was studied by applying an external d.c. voltage to the substrate electrode. The role played by the xenon ions in the growth of the materials prepared from xenon-diluted silane source gas has been considered. It is demonstrated that the xenon ions are responsible for the growth of the materials showing stable photoconductivity behaviour under light illumination.
Dependence of Hooge Parameter of Compound Semiconductors on Temperature
Authors: Tacano Munecazu , Hisao Tanoue Hisao Tanoue , Yoshinobu Sugiyama Yoshinobu Sugiyama
Published: February 2005

Voltage noise spectrum densities of quarter-micron filaments made by GaAs, InP and heterostructures are measured in detail as a function of decreasing temperature to 10 K, and the Hooge noise parameter αH of each device is precisely determined at each temperature. Focused ion beam (FIB) implanted n-GaAs has the smallest αH of 1.0×10-8 at 60 K, decreasing from 2×10-6 at room temperature. The derived value of αH is the smallest one ever reported for compound semiconductor devices, and compares favorably with that expected from quantum 1/f noise theory. FIB-implanted n-InP has the smallest αH of about 1×10-7 at 50 K. The αH of a molecular beam epitaxially (MBE) grown In0.8Ga0.2As heterostructure depends on µpo between 1 to 10 m2/V·s, realizing 1/f noise in the cross section of optical phonon scattering.
Flux Creep in a Sinusoidal Washboard Potential in Superconductors
Authors: Teruo Matsushita Teruo Matsushita , Edmund Soji Otabe Edmund Soji Otabe
Published: February 2005

Flux creep is theoretically investigated for a model of a sinusoidal washboard potential in superconductors. An apparent pinning potential depth,U0*, defined by the relaxation rate of the shielding current density, is found to be significantly smaller than a given pinning potential depth. In particular,U0*reduces to zero at zero temperature, while the given pinning potential depth takes a finite value. The effect of the form of the potential barrier on such a significant flux creep at low temperatures is discussed.
Atomic Layer Control of SrCuOx and Layer-By-Layer Growth of Bi2Sr2Can-1CunO2n+4 (n=1 to 5) on SrTiO3 (100) by Laser Molecular-Beam-Epitaxy
Authors: Kanai Masaki , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: February 2005

The growth of SrCuO
x
thin layer and Bi2Sr2Ca
n-1Cu
n
O2n+4 on SrTiO3 (100) substrate has been studied. When Sr and Cu are supplied simultaneously to the substrates to form SrCuO
x
, either a SrO or CuO2 layer can form the surface layer depending upon the composition of the substrate surface. By the successive supply of the subunit-cell layers of Bi2Sr2Ca
n-1Cu
n
O2n+4, the structures with n=1 to 5 are formed. The reflection high energy electron diffraction pattern shows streaks all through the growth, indicating two-dimensional layer growth in all the steps controlled within the monolayer accuracy.
Preparation of Microcrystalline Silicon Carbide Films by Hydrogen-Radical-Enhanced Chemical Vapor Deposition Using Tetramethylsilane
Authors: Yasui Kanji , Akira Fujita Akira Fujita , Tadashi Akahane Tadashi Akahane
Published: February 2005

In this paper, hydrogen-radical-enhanced chemical vapor deposition (HRCVD) is presented with the purpose of depositing microcrystalline silicon carbide (µc-SiC) films at a low temperature. As a source gas, tetramethylsilane (TMS) was used. Furthermore it is explained that TMS was decomposed by hydrogen radicals generated with microwave plasma, and the excess methyl radicals were extracted from the film-growing surface. Properties of µc-SiC film have been examined with the aid of infrared (IR) absorption spectroscopy, electron-probe microanalysis (EPMA), and reflective high-energy electron diffraction (RHEED).
Liquid Encapsulated Flux Growth of ZnSe Single Crystals from Se Solvent
Authors: Unuma Hidero , Higuchi Mikio , Yamakawa Yuichi , Kodaira Kohei , Okano Yasunori , Hoshikawa Keigo , Fukuda Tsuguo , Koyama Tadashi
Published: February 2005

In order to grow ZnSe single crystals free from twins, a solution growth method from Se solvent was developed. The evaporation of Se solvent was effectively suppressed by utilizing a liquid encapsulant of molten fluorides and a gas over pressure. The liquidus curve of the Se-rich side in the Zn-Se system was established. Crystals were grown at a temperature of about 1200°C, where the solubility of ZnSe to Se solvent is high. The crystals were free from twins.
Crystallization-Induced Phason Relaxation in Icosahedral Al-Pd-Mn Alloys
Authors: Tsai An Pang , Chen Ho Sou , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: February 2005

A melt-quenched icosahedral (i-) phase with a composition such as Al74Pd17Mn9 close to but is deviated slightly from the ideal composition (Al70Pd20Mn10) of stable i-AlPdMn alloy, containing significant phason strains. It transforms to a phason-free i-phase accompanied by crystallization upon annealing at sufficiently high temperature. The composition of the i-grains approaches the ideal after the transformation. Such phason strain relaxation was not observed in the melt-quenched Al75Pd15Mn10
i-phase, for which composition considerably deviates from the ideal composition; crystallization occurs without redistribution in the composition. It was suggested that a highly stable i-phase occurs in the ground state when it has the ideal composition.
Study of the Si(111)√3×√3-Sb Structure by X-Ray Diffraction
Authors: Nakatani Shinichiro , Saito Akira , Kuwahara Yuji , Takahashi Toshio , Aono Masakazu , Seishi Kikuta Seishi Kikuta
Published: February 2005

The structure of the Si(111)√3×√3-Sb surface was investigated by the X-ray diffraction method, which is effective in determining the atomic arrangement in both lateral and normal directions. The result of the measurements on the integral and fractional order rods indicates a trimer arrangement of Sb atoms. From the data analysis using the least squares method, it is concluded that the “milk stool” model accurately estimates the structure and other models can be disregarded. Bond lengths of Sb-Sb and Sb-Si are calculated at 2.82 Å and 2.74 Å. These values agree well with the sums of the atomic radii.
Application of Copper-Decoration Method to Characterize As-Grown Czochralski-Silicon
Authors: Yamauchi Tsuyoshi , Tsumori Yasuo , Nakashizu Tsuneo , Esaka Hisao , Shigeyoshi Takao Shigeyoshi Takao , Seiji Shinoyama Seiji Shinoyama
Published: February 2005

Czochralski-silicon wafers having ring-likely distributed stacking faults (ring-SFs) were investigated by means of copper decoration. The size and density of copper precipitates were measured by X-ray transmission topography and preferential etching. In the outer region of the ring-SFs, electrical properties (recombination lifetime of minority carriers, the dielectric breakdown strength) were found to be excellent. On the other hand, in the inner region of the ring-SFs electrical properties were degraded. These phenomena may be explained by the large defects which remain in the center region of the ingot.
Proposal for Surface Tunnel Transistors
Authors: Toshio Baba Toshio Baba
Published: February 2005

A new three-terminal tunnel device, the surface tunnel transistor (STT), is proposed and its operation is demonstrated using GaAs/AlGaAs. STT consists of n+/i/p+ diode structure with an insulated gate in the i-region, which is similar to a MOSFET. However, the source and drain are oppositely doped. The most important feature of this device is that the drain must be so highly degenerated that a tunnel junction is formed with a two-dimensional (2D) electron channel under the gate. The tunneling current from source to drain is controlled by the gate bias through the concentration of accumulated 2D electrons under the gate. GaAs STTs with i-Al0.6Ga0.4As as a gate insulator are fabricated using MBE regrowth techniques on a mesa structure. This device exhibits transistor characteristics at 77 K and at room temperature, which confirms the new operation principle of STTs.
Gain Saturation of a 1.3 µm InGaAsP Traveling-Wave Amplifier in Picosecond Pulse Amplification
Authors: Liu Hai-Feng , Tohyama Masaki , Kamiya Takeshi , Kawahara Masato
Published: February 2005

Saturation energy of a 1.3 µm semiconductor laser traveling wave amplifier is found to depend both on the input pulsewidth and on the input pulse energy at picosecond regime. Shorter pulses are shown to have less saturation energy than longer pulses, which suggests the nonlinear gain give influence to the response of the amplifier. The simulated pulsewidth dependent energy gain by a set of traveling wave rate equations incorporating the nonlinear gain shows fairly good agreement with the measurements.
Photoirradiation Effect on Photoluminescence from Anodized Porous Silicons and Luminescence Mechanism
Authors: Suemune Ikuo , Nobuaki Noguchi Nobuaki Noguchi , Masamichi Yamanishi Masamichi Yamanishi
Published: February 2005

The photoirradiation effect on photoluminescence (PL) from anodized porous silicons was studied. Although PL from Si anodized in artificial light decreased with photoirradiation, PL from Si anodized in the dark was found to increase with photoirradiation in air. The main factor for the photoirradiation effect was attributed to oxidation in the surface layer by transmission infrared spectroscopy. During the temporal spectral change in the Si samples anodized in the dark, discrete PL peaks were observed. These PL peaks were excellently modeled by a quantum size effect. The observed blue shift of the PL spectra is interpreted to be due to the reduction of the microparticle size in the topmost amorphous layer with oxidation.
Scanning Electron Microscope Images of C60 Whiskers
Authors: Yositaka Yosida Yositaka Yosida
Published: February 2005

Filamentary crystal growth of the fullerene C60 has been achieved. Scanning electron microscope (SEM) images of filamentary crystals, so-called whiskers, revealed differences in the dimensions and the nature of surfaces depending on their growth temperatures. SEM images of the top surface of the whisker grown at 80°C revealed the following: (1) the crystal habit is an octahedron and (2) the whisker axis is parallel to the fourfold rotational symmetry axis.
Fine Structure of Porous Si with Visible Photoluminescence
Authors: Nakagawa Kiyokazu , Nishida Akio , Shimada Toshikazu , Yamaguchi Hironaru , Eguchi Kinya
Published: February 2005

Porous Si formed by anodization is studied by means of high-resolution scanning electron microscopy, optical microscopy, microphotoluminescence spectroscopy and micro-Raman spectroscopy. Surface morphologies of porous Si films are varied by changing the anodization conditions. High-resolution scanning electron microscopy measurements show that in all these films, porous Si fine structures of visible photoluminescent regions, which are confirmed with optical microscopy and micro-photoluminescence spectroscopy, are composed of particlelike structure of various sizes from several nm to several tens of nm. The peak of the Raman spectrum from the particlelike structure is shifted to lower energy and is wider than that for bulk Si, possibly due to lattice expansion around large surface fractions. Visible photoluminescence in porous Si is not due to carrier confinement in quantum wires, but is probably due to carrier confinement in this structure.
Novel Process for Visible Light Emission from Si Prepared by Ion Irradiation
Authors: Ochiai Yukinori , Ookubo Norio , Watanabe Heiji , Matsui Shinji , Mochizuki Yasunori , Ono Haruhiko , Kimura Shigeru , Toshinari Ichihashi Toshinari Ichihashi
Published: February 2005

A novel process for visible light emission from Si has been successfully developed. The sample was irradiated with argon or chlorine ions in an ECR (electron cyclotron resonance) etching apparatus. After etching, the sample was placed in HF solution for 30 minutes. Visible light emission from the sample has been confirmed at a peak wavelength of 700 nm. Various characterizations have been performed, such as SEM and TEM observations, X-ray diffraction and FTIR spectroscopy. Anodized porous silicon is also characterized for comparison.
The Formation of Nonradiative Areas for Electroluminescent Devices Using SrS:CeCl3 Phosphor Prepared by Multisource Deposition
Authors: Yoshiki Chubachi Yoshiki Chubachi , Kazushi Aoyama Kazushi Aoyama
Published: February 2005

Nonradiative areas were observed when electroluminescent (EL) devices with SrS:CeCl3 phosphor prepared by multisource deposition (MSD) using H2S gas were driven for an extended period in air atmosphere. These areas were confirmed to result from peeling off of the second insulating layer by measurement with Auger electron spectroscopy (AES) and optical microscopic observations. Infiltrated water in atmosphere into layers along hill-ocks might cause this peeling off.
Measurement of Time Lag of Electrical Breakdown in Polymethylmethacrylate under Highly Non-Uniform Field Using Nanosecond Pulse Voltage
Authors: Yamada Hiroshi , Kimura Shingo , Taniguchi Hiroshi , Fujiwara Tamiya
Published: February 2005

The waveform of prebreakdown current in polymethylmethacrylate for positive polarity has been observed using a 760 ns rectangular high-voltage pulse. A linear relation to formative time lag and gap spacing is obtained for gap lengths greater than a critical value, indicating a constant propagation velocity in this region. The velocity is deduced from the relation to be 2.2 km·s-1 at 50 kV.
Evaluation of Surface Zn Concentration in Zn Diffusion into InP
Authors: Wada Morio , Sakakibara Katsutoshi , Masahiko Higuchi Masahiko Higuchi , Yoichi Sekiguchi Yoichi Sekiguchi
Published: February 2005

The surface Zn concentration of Zn diffusion in InP was evaluated with a simple model using statistical thermodynamics, assuming that the Zn atoms in the vapor phase are isolated atoms of monoatomic gas and that the interaction between the incorporated Zn atoms in InP is negligible. The results confirmed that the surface Zn concentration obtained from diffusion experiments is well described in terms of this model. Thus, this analysis strongly supports the fact that Zn atoms are incorporated in InP not only as singly ionized acceptors, but also as singly ionized donors.
Study of the Physical Properties of High-Temperature Oxide Superconductors Based on Superfluidity Models
Authors: Masanori Sugahara Masanori Sugahara , Nobuyuki Yoshikawa Nobuyuki Yoshikawa
Published: February 2005

The state densities obtained from the differential tunnel conductance of [oxide superconductor]/[normal metal] junctions are compared with our superfluid model. Good agreement exists between the experiment and the theory in the case where the “superconducting system” consists of two kinds of superfluids: a two-dimensional system covering the CuO2 layers and a one-dimensional system parallel to the c axis.
Effect of UV Light Irradiation on the A-Axis Orientation Mechanism for Y1Ba2Cu3O7-δ Films Prepared by Laser Metalorganic Chemical Vapor Deposition
Authors: Ushida Takahisa , Higa Hiroyuki , Higashiyama Kazutoshi , Izumi Hirabayashi Izumi Hirabayashi , Shoji Tanaka Shoji Tanaka
Published: February 2005

In previous work, we reported a very effective method of controlling the orientation of YBCO film by metalorganic chemical vapor deposition (MOCVD) using ArF excimer laser irradiation on a MgO(100) substrate. The laser power density used in the previous study was 100 mJ/cm2, which was sufficient for melting the sample surface when the substrate temperature was kept at 700°C. In this work, we investigated the laser power density and repetition rate dependence of a-axis orientation of YBCO film, in order to establish whether or not melting of the surface is an indispensable factor for a-axis orientation by laser irradiation. The surface morphology depends on the laser power density and repetition rate; however, high a-axis orientation is observed even when the film surface does not appear to be melted. The a-axis orientation was obtained only with a flowing gas source with the laser irradiation. This suggests that the nuclei of a-axis orientation are formed only when the source materials are decomposed by laser irradiation on the film surface.
Visible Electroluminescence from P-Type Crystalline Silicon/Porous Silicon/N-Type Microcrystalline Silicon Carbon PN Junction Diodes
Authors: Futagi Toshiro , Matsumoto Takahiro , Katsuno Masakazu , Ohta Yasumitsu , Hidenori Mimura Hidenori Mimura , Koich Kitamura Koich Kitamura
Published: February 2005

We have fabricated p-type crystalline silicon/porous silicon/microcrystalline silicon carbon pn junction diodes and demonstrated current-induced visible light emission. We observed two kinds of electroluminescence; one was a weak white emission at a forward current of about 90 mA, and the other was a strong orange-red one at a forward current from about 200 to 619 mA.
Picosecond Luminescence Decay in Porous Silicon
Authors: Matsumoto Takahiro , Daimon Masahiro , Toshiro Futagi Toshiro Futagi , Hidenori Mimura Hidenori Mimura
Published: February 2005

Picosecond luminescence decay is observed for the first time in porous Si. This decay consists of two exponential decay components that become large with decreasing emission energy. Besides the picosecond luminescence decay, nanosecond luminescence decay was also observed. This shows nonexponential decay behavior with dominant components between 100 ns and 1 µs. This also becomes large with decreasing emission energy. Based on our results, the luminescence in porous Si seems to originate partially from the amorphous phase.
In Situ Electron Microscopy of Crystal Growth of Isotactic Polystyrene from the Melt
Authors: Izumi Kunihide , Ping Gan , Toda Akihiko , Miyamoto Hideki Miyaji
Published: February 2005

In situ observation of the growth of isotactic polystyrene has been carried out under a transmission electron microscope. Bundles of lamellar crystals first emerge from the melt, and then a planar crystal parallel to (001) grows out from one end of each bundle. The planar crystal assumes the shape of a hexagon faceted with {110} planes surrounding the bundle at the center. The thickness of the melt surrounding the crystal is smaller than that of the outer area.
Fabrication and Characteristics of Schottky Gated Field Effect Transistors Utilizing Poly(1,4-naphthalene vinylene) and Poly(p-phenylene vinylene)
Authors: Ohmori Yutaka , Muro Keiro , Onoda Mitsuyoshi , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Fabrication and characteristics of Schottky gated poly(1,4-naphthalene vinylene) and poly(p-phenylene vinylene) field-effect transistors (FETs) have been reported for the first time. The FET has been realized utilizing the polymer film formed on a Schottky gated electrode deposited upon a glass substrate. From FET characteristics, the carrier concentrations and carrier mobilities are evaluated for poly(1,4-naphthalene vinylene) and poly(p-phenylene vinylene). Electrical properties are discussed on the basis of the FET characteristics for the nominally undoped samples.
Fast Recovery from Excitonic Absorption Bleaching in Type-II GaAs/AlGaAs/AlAs Tunneling Biquantum Well
Authors: Tackeuchi Atsushi , Inata Tsuguo , Sugiyama Yoshihiro , Nakata Yoshiaki , Satoshi Nakamura Satoshi Nakamura , Shunichi Muto Shunichi Muto
Published: February 2005

We propose the type-II tunneling biquantum-well (TBQ) structure which consists of a series of GaAs wells, AlGaAs barriers and AlAs layers. The type-II TBQ has no significant optical absorption except for the GaAs wells and shows fast recovery from excitonic absorption bleaching. In this structure, photoexcited electrons in the GaAs wells escape by tunneling through the AlGaAs barriers toward X states in the AlAs layers. The recovery time of excitonic absorption bleaching in the GaAs wells was reduced to 8 ps as the AlGaAs barrier thickness was decreased to 1.1 nm.
Thick Bi2Sr2CaCu2Ox Films without Substrates Prepared by Dip-Suspension in Melts
Authors: Yomo Takashi , Yoshiaki Tanaka Yoshiaki Tanaka , Ryozi Suganuma Ryozi Suganuma
Published: February 2005

Thick Bi2Sr2CaCu2O
x
(2212) films (about 100∼300 µm thick) without substrates were newly prepared by dipping Pt-loops in melts, followed by solidifying melt-suspensions (dip-suspension method). These films show the 2212 phase after annealing at about 1113 K for 1 h. The X-ray powder diffraction data of these annealed films were compared with those of thick films with substrates made by melt-crystallization on polycrystalline MgO. The grain alignments near film surfaces without substrates were slightly more random than those with substrates.
Lasing Properties and Lasing Mechanism in a ZnSe/ZnSSe Multiple Quantum Well Heterostructure
Authors: Fujii Yoshihisa , Suemune Ikuo , Kuroda Yasuhide , Masahiro Fujimoto Masahiro Fujimoto , Masamichi Yamanishi Masamichi Yamanishi
Published: February 2005

Lasing properties in a ZnSe/ZnSSe multiple quantum well heterostructure were studied quantitatively at room temperature with photopumping. The internal optical absorption loss was measured in II-VI heterostructure for the first time and it remained at the low value of 9 cm-1. The internal quantum efficiency of about 40% and the differential quantum efficiency of 28% were estimated. The lasing peaks were red shifted by about 50 meV in comparison to photoluminescence peaks measured with low excitation, and the energy separation was almost independent of the temperature. The lasing mechanism was studied by measuring the temperature and excitation-level dependencies of the emission spectra.
Observations of SiC Mirror Damage Induced by an Argon Excimer Laser
Authors: Ohmukai Masato , Naito Hiroyoshi , Okuda Masahiro , Kurosawa Kou , Sasaki Wataru , Takigawa Yasuo , Matsushita Tatsuhiko , Tsunawaki Yoshiaki
Published: February 2005

Surfaces of SiC films deposited on graphite substrates are observed by means of X-ray photoelectron and Raman scattering spectroscopies after the films are used as a cavity reflector of an argon excimer laser. X-ray photoelectron spectra show that silicon precipitates due to laser irradiation, and further Raman scattering spectra indicate that the silicon is in its amorphous state.
Growth-Rate Self-Limitation Mechanism in InP Atomic Layer Epitaxy Studied by Surface Photo-Absorption
Authors: Yasuyuki Kobayashi Yasuyuki Kobayashi , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

The pyrolysis of trimethylindium (TMI) and phosphine (PH3) on an (001) InP surface is studied by surface photo-absorption. In the same manner as the pyrolysis of trimethylgallium on GaAs, self-limitation is observed in the change in reflectivity when TMI is supplied to a P-stabilized surface at 350°C. This result indicates that the surface is saturated by TMI adsorption to form a CH3-terminated In surface. H2 purging after TMI adsorption increases the reflectivity further to the level of a metal surface with an In monolayer, indicating that CH3 groups desorb during purging. This paper also finds the pyrolysis of PH3 on a CH3-terminated In surface is much slower than on In metal surface. The growth rate is self-limited to less than one monolayer per cycle in InP atomic layer epitaxy because the surface is not completely transformed to a P surface during PH3 supply, as PH3 pyrolysis is slow on a CH3-terminated In surface. The growth rate approaches one monolayer per cycle when PH3 is supplied to an In metal surface produced by CH3 desorption.
Control of Organic-Crystal Orientation in Glass Capillary by Modified Bridgman-Stockbarger Method
Authors: Murayama Hitoshi , Muta Kenichi , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

The control of organic-crystal orientation in glass capillaries was successfully achieved using the modified Bridgman-Stockbarger furnace designed so that the pulling direction of the capillary makes a finite angle θ with respect to the temperature gradient. It was confirmed in 2-methyl-4-nitroaniline (MNA) using a polarizing optical microscope that the resultant optical X-axis makes an angle of θ with the fiber axis. The range of the controllable angle covers at least from 20° to 40°. The mechanism of crystal growth with a desirable axis orientation is also discussed.
Oxidation Site of Polycrystalline Silicon Surface Studied Using Scanning Force/Tunneling Microscope (AFM/STM) in Air
Authors: Sugawara Yasuhiro , Fukano Yoshinobu , Nakano Akihiko , Ida Tohru , Seizo Morita Seizo Morita
Published: February 2005

The oxidation site of the polysilicon surface was studied using a scanning force/tunneling microscope in air. In the case of a polysilicon surface without an oxidation annealing process, the tunneling conductance at the grain boundary decreased faster than that far from the grain boundary. As a result, we confirmed that the area at the grain boundary was preferentially oxidized. On the other hand, in the case of a polysilicon surface with oxidation annealing process, we confirmed that the preferential oxidation of the grain boundary was suppressed.
High-Resolution Observation of Ge Decorated on Thin Films of Long Chain Compounds
Authors: Yase Kiyoshi , Inaoka Kimio , Masakazu Okada Masakazu Okada
Published: February 2005

The germanium decoration method is found to be useful for characterizing the molecular orientations in thin films of long chain compounds of calcium stearate. When Ge was deposited on the (001) planes of thin crystals, it tended to form starlike clusters with a diameter of 10 nm, while, on the (110) planes, Ge formed continuous films with striations of 5 nm. The fine structure and the growth mechanism of deposited Ge are revealed by high-resolution transmission electron microscopic observation.
Low-Temperature Chemical Vapor Deposition of Silicon Nitride Using A New Source Gas (Hydrogen Azide)
Authors: Ishihara Ryouichi , Kanoh Hiroshi , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Silicon nitride films were deposited at temperatures as low as 350°C by chemical vapor deposition using a new source gas, hydrogen azide (HN3). Silicon nitride film deposited at 425°C was nitrogen-rich and showed hydrogen content of about 28 atomic%. The breakdown field strength was as high as 8.7 MV/cm and the resistivity was as high as 1015 Ω·cm. Amorphous silicon thin-film transistors equipped with this film as the gate dielectric showed good transistor characteristics.
Photoluminescence and Photoreflectance Study of Electronic Structure in Pseudomorphic n-AlGaAs/InGaAs/GaAs
Authors: Kanata Takashi , Nakayama Hiroshi , Nishino Taneo , Sakaguchi Harunori
Published: February 2005

The electronic structure of n-Al0.28Ga0.72As/In0.23Ga0.77As/GaAs has been investigated by photoluminescence (PL) and photoreflectance (PR) spectroscopies. Transitions associated with the n=1 and 2 electron subbands in the In0.23Ga0.77As single quantum well were observed. Two-dimensional carrier density was evaluated in terms of the quantum confined Franz-Keldysh (FK) effect of the transition between the lowest states of electrons and heavy holes. Because of penetrations of the confined electron density into the neighboring layers, PR spectra of GaAs show FK oscillation.
Single-Electron Tunneling in Coupled Quantum Dots
Authors: Katsumoto Shingo , Sano Naokatsu , Shun-ichi Kobayashi Shun-ichi Kobayashi
Published: February 2005

Conductance oscillations against gate voltages due to single-electron tunneling (SET) were observed in quantum dots connected by quantum point contacts in series. The oscillations were smeared out by increasing the biasing voltages.
Preparation of YBa2Cu3O7-δ Superconductor Coating on Austenitic Steel by Electrophoretic Deposition Method-Study on Buffering Layers
Authors: Minami Naotaka , Nobuyuki Koura Nobuyuki Koura , Hiromasa Shoji Hiromasa Shoji
Published: February 2005

A preparation method of a superconducting oxides, YBa2Cu3O7-δ, coating on austenitic stainless steel by electrophoretic deposition at high voltages has been investigated in order to increase the J
c value. Without a buffering layer, Ni, Cr, and Fe atoms diffused from the substrate to the superconductor phase. It was found that ZrO2 and Ag layers coated on the substrate as the buffering layer restrain the diffusion of the metals. Consequently, high density YBa2Cu3O7-δ superconductor coating could be obtained at high voltage depositions, therefore, it indicated that high J
c samples can be prepared by this method.