bluuebunny/crossref_metadata_2025 huggingface dataset:
An All-Fiber Frequency Stabilizer to a Set of Laser Diodes Based on Double Fiber Resonators
Authors: Pie-Yau Chien Pie-Yau Chien , Ci-Ling Pan Ci-Ling Pan
Published: February 2005

A relative frequency statilization technique, using double fiber resonators as the frequency discriminator, has been demonstrated. By employing the frequency-division-multiplexing technique (FDM) to the laser diodes, the frequency offset between the tested laser diodes has been stabilized to Δν/ν≤3.0×10-9.
Field Evaporation in Two-Electrode Systems
Authors: Tien T. Tsong Tien T. Tsong
Published: February 2005

Evaporation fields as positive ions and negative ions for common elements of interest in a two-electrode system are calculated based on a charge-exchange model and an image hump model. The fields required are lower at a smaller electrode separation. For alkali metals and very soft metals, formation of 1- ions requires the lowest field. For most soft metals, 1+ ions are favored. For transition metals and Si and Ge, either 2+ or 3+ charge state is favored.
Vapor Phase Homo- and Heteroepitaxies of ZnSe Films
Authors: Tetsuo Muranoi Tetsuo Muranoi
Published: February 2005

The effect of hydrogen chloride (HCl) gas on homo- and heteroepitaxies of ZnSe was investigated. As-grown (100)ZnSe/(100)GaAs and chemicaliy etched (100)GaAs were used as substrates. Thermal etching of the substrate in HCl gas flow was carried out for 5 min at various temperatures (200-400°C) prior to the film growth at 350°C. Homo- and heteroepitaxies occurred after thermal etching above 250°C and 200°C, respectively. In the case of the heteroepitaxial film, a very smooth surface was obtained and a streaky reflection high energy electron diffraction (RHEED) pattern was observed. A sharp I
x line was predominant in the photoluminescence (PL) spectrum.
Si Metal Insulator Semiconductor Tunnel Emitter Transistor (Si MIS TET)
Authors: Yoshimoto Tomomi , Matsumoto Kazuhiko , Sakamoto Kunihiro , Toshimiti Sakata Toshimiti Sakata
Published: February 2005

A Si metal-insulator-semiconductor tunnel emitter transistor which has quite a thin base layer formed by an inversion hole layer was fabricated. A common emitter current gain of 5 was obtained at room temperature. The emitter base bias at which the base current began to flow coincided well with the calculated turn on voltage at which the inversion occurred in the MIS structure. It was confirmed for the first time that the inversion hole layer really worked as the base of the transistor.
Formation of Conductive SrVO3 Films on Si Substrates
Authors: Hiroshi Ishiwara Hiroshi Ishiwara , Katsuyoshi Jyokyu Katsuyoshi Jyokyu
Published: February 2005

Formation of conductive SrVO3 films on Si substrates has been investigated in a coevaporation method of SrO
x
and VO
x
. It has been found that the conductive films are formed only when hydrogen gas is introduced near the samples during film deposition. The lowest resistivity of the films so far obtained is 1.3 mΩ·cm. It has also been found that the insulating transition layer is formed near the interface with the Si substrate.
A New SOI-Lateral Bipolar Transistor for High-Speed Operation
Authors: Sugii Toshihiro , Kojima Manabu , Fukuroda Atsushi , Tetsu Fukano Tetsu Fukano , Yoshihiro Arimoto Yoshihiro Arimoto
Published: February 2005

We proposed a new SOI-lateral bipolar transistor. The device is featured by a thin base (simulated thickness was 80 nm) and base contact which was formed just on an intrinsic base. The device has sufficient junction breakdown voltage, but a current gain of 10, due to the degraded forward-biased emitter-base junction characteristic. The current gain was improved to 30 by keeping the base region about 2 µm from the highly arsenic-implanted emitter. The device structure seems to be ideal for a future high-speed bipolar transistor.
Atmospheric Deterioration of Clean Surface of Epitaxial (001)-YBaCuO Films Studied by Low-Energy Electron Diffraction
Authors: Ohara Tomoyuki , Sakuta Ken , Makio Kamishiro Makio Kamishiro , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

The effects of gas exposure on the clean surface of the epitaxial YBaCuO thin films were closely investigated using the low-energy electron diffraction (LEED) method. The clean surface was obtained by in-vacuum annealing at 500°C. Once the clean surface was exposed to air, even at room temperature, the LEED spots disappeared or sometimes became faint. To ensure the degradation mechanism of the YBaCuO clean surface, the specimens were exposed to pure O2 and N2 gases separately and measured by LEED. As a result, it was found that O2 is very safe but N2 serves as a poisonous gas for the YBaCuO clean surface.
Infrared Radiation Detection with YBa2Cu3O7-d Microbridge
Authors: Yotsuya Tsutom , Imokawa Hirofumi , Yang Qian-Sheng
Published: February 2005

The photoresponse of YBa2Cu3O7-d
thin film with double bridges (DC-SQUID type) has been investigated under irradiation of weak laser light. The YBCO thin film of 200 nm thickness was prepared on a MgO(100) single-crystal substrate by an rf-magnetron sputtering method. It was processed to perform as a double microbridge (DC-SQUID type) patterned by ECR ion etching and then assembled as an YBCO thin-film sensor. The microbridge used here was 5 µm in width and 7.5 µm in length. The sensitivity of the sensor was determined by irradiating a modulated laser light (modulating frequency of 17 to 400 Hz, wavelength of 827 nm). The device showed both bolometric and nonbolometric behavior in the superconducting transition region. The maximum noise equivalent power (NEP) and responsivity was obtained at 76 K, and was 5×10-9 W/Hz1/2 and 19 V/W, respectively. The nonbolometric response was caused by vortex motion.
Computer-Generated Holograms for Free-Space Optical Interconnections
Authors: Shigeru Kawai Shigeru Kawai , Yuji Kohga Yuji Kohga
Published: February 2005

We propose here computer-generated holograms (CGHs) suitable for use in optical interconnections and computing. They are constructed by using a new method in which aberrations are low and adjustments are made to equalize their diffracted light beam intensities. Multi-facet holograms of nine sub-holograms are produced by using an electron-beam. Diffracted light beams from the produced holograms are focused nearly down to their diffraction limits. Uniformity in the beam intensities is more than ten times that of non-adjusted holograms.
Ferroelectric Behavior of Vinylfluoride-Trifluoroethylene Copolymer
Authors: Maeda Kazuhiko , Shigeru Tasaka Shigeru Tasaka , Norihiro Inagaki Norihiro Inagaki
Published: February 2005

Dielectric and thermal properties of the copolymer of vinylfluoride and trifluoroethylene were investigated in a temperature range of -100°C to 250°C. This copolymer with form I crystal has a high melting point, compared to those of the homopolymers, and shows a maximum dielectric constant at 143°C, which is below the melting point. The dielectric behavior suggests that this crystalline copolymer may be ferroelectric. The microstructural analysis by 19F-NMR indicated a certain fraction of alternating sequence.
Crystalline InSe Films Prepared by RF-Sputtering Technique
Authors: Ikari Shigeru Shigetomi
Published: February 2005

The X-ray diffraction, optical absorption and Raman spectra of rf-sputtered InSe films are measured as a function of annealing temperature. The films annealed at 400°C have a crystalline structure and the c-axis in the rhombohedral phase is oriented perpendicular to the substrate plane. The optical properties in crystalline films follow the same mechanism as that of the InSe single crystal.
Production of Diatomic and Triatomic Molecular Negative Ions of Gold and Copper by Sputtering
Authors: Wada Motoi , Sasao Hiroshi Tsuda
Published: February 2005

Monoatomic, diatomic and triatomic negative ions of Au and Cu produced on a surface of the sputtering target of a self-extraction negative ion source were measured. The bias potential applied to the target was varied from 100 to 500 V with respect to a Cs-introduced Ar plasma. The ratios of the polyatomic negative ions to the monoatomic negative ions increased in accordance with the increasing energy of the incident ions, and decreased as the amount of Cs in the discharge was increased. The atomic negative ion fraction can be maintained at a value higher than 90% by controlling these parameters.
Self-Limiting Growth in Atomic Layer Epitaxy of ZnTe
Authors: Takemura Yasushi , Nakanishi Hideki , Makoto Konagai Makoto Konagai , Kiyoshi Takahashi Kiyoshi Takahashi
Published: February 2005

ZnTe films were grown on GaAs substrates by atomic layer epitaxy using the molecular beam epitaxy technique. We investigated the growth rate per cycle as a function of beam intensities of Zn and Te at the substrate temperature of 250°C and obtained the self-limiting growth of 0.5 monolayer per cycle, independent of Zn or Te beam intensity in the selected ranges.
Planarized Be δ-Doped Heterostructure Bipolar Transistor Fabricated Using Doping Selective Contact and Selective Hole Epitaxy
Authors: Kuo T. Y. , Cunningham J. E. , Goossen K. W. , Ourmazd A. , Jan W. , C. G. Fonstad C. G. Fonstad , F. Ren F. Ren
Published: February 2005

We report a heterostructure bipolar transistor (HBT) in which the base is δ-doped with Be to a concentration of 1×1014 cm-2 and the Be is spatially confined to within 15 Å. To fabricate the HBT without inducing Be redistribution and avoid critical emitter mesa etching, we have developed a new low-temperature base-contacting procedure (T
max=420°C) which requires no base-emitter etching. A 50 µm diameter δ-HBT shows a current gain of 20. Upon reducing the size of the emitter to 3×8 µm, the current gain of the δ-HBT increases to 30. This, we belive, is due to our new processing technique which eliminates the critical base-emitter etch and hence reduces surface recombination. In addition, we grew and fabricated HBT's in holes that have been pre-etched into the substrates. High quality material has been achieved in the holes.
Preparation of Superconducting Ba2YCu3O7-y Films by the Dipping-Pyrolysis Process at 700° and 750°C
Authors: Kumagai Toshiya , Manabe Takaaki , Wakichi Kondo Wakichi Kondo , Susumu Mizuta Susumu Mizuta
Published: February 2005

Superconducting Ba2YCu3O7-y
(BYCO) films were prepared by the dipping-pyrolysis process using metal acetylacetonates as starting materials through heat treatments below 800°C under controlled low oxygen partial pressures (p(O2)'s) followed by O2 annealing. Values of T
c,zero(r)'s were greatly dependent on the temperature and p(O2) of heat treatment; they were 64 K and 85 K with the heat treatments at 700° and 750°C, respectively, under an initial p(O2) of 2×10-4 atm for 2-µm-thick BYCO films. Moreover, silver precoating was effective for improving the superconducting and surface properties of the films heat-treated at 700°C.
Photoluminescence of Ti Doped 6H-SiC Grown by Vapor Phase Epitaxy
Authors: Kimoto Tsunenobu , Nishino Hironori , Ueda Tetsuzo , Yamashita Atsushi , Woo Sik Yoo Woo Sik Yoo , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Sharp luminescence peaks near the bandgap have been observed in 6H-SiC epitaxial films doped with Ti. The intensity of the Ti-related peak increases with the increase of Ti concentration in the films. The peak energy of the zero-phonon line (2.864 eV) is independent of both excitation intensity and temperature. Above results reveal that the luminescence lines are attributed to exciton recombination bound to Ti atoms and its phonon replicas.
Preparation and Characterization of Vanadyl-Phthalocyanine Ultrathin Films Grown on KBr and KCl by Molecular Beam Epitaxy
Authors: Tada Hirokazu , Koichiro Saiki Koichiro Saiki , Atsushi Koma Atsushi Koma
Published: February 2005

Ultrathin films of vanadyl-phthalocyanine (VOPc) have been grown heteroepitaxially on cleaved (001) faces of KBr and KCl by molecular beam epitaxy (MBE). Their structures were investigated in situ by reflection high energy electron diffraction (RHEED). VOPc molecules form a single domain square lattice (3√2/2×3√2/2-R45°) on a KBr substrate, whereas two equivalent square lattices (√5×√5-R±26.6°) on a KCl substrate. The molecular distances between neighboring molecules have been found to be-about 14 Å in both cases.
A High Density High Performance Cell for 4M Bit Full Feature Electrically Erasable / Programmable Read-Only Memory
Authors: Arima Hideaki , Ajika Natuo , Ohi Makoto , Takayuki Matsukawa Takayuki Matsukawa , Natsuro Tsubouchi Natsuro Tsubouchi
Published: February 2005

A new electrically erasable / programmable read-only memory (EEPROM) cell structure is proposed, which achieves a high capacitive coupling ratio of more than 0.8 in a small cell size of 11.25 µm2 using 0.6 µm lithography. This new cell has sufficient cell threshold windows which extend to more than 5 volts and a programmed cell current of more than 30 µA at a program voltage of 14 volts. The cell endurance is more than 105 erase/write cycles. Using this cell structure, a 4-mega-bit full-feature EEPROM of high performance and high reliability can be acquired.
Electronic Structure of (BEDT-TTF)2X Salts Studied by Scanning Tunneling Spectroscopy
Authors: Mori Yoshihisa , Maruyama Yusei , Mori Hatsumi , Saito Gunzi
Published: February 2005

Two-dimensional arrangements of molecular images by Scanning Tunneling Microscopy are observed for some (BEDT-TTF)2X salt crystals, and moreover Scanning Tunneling Spectroscopy has clearly revealed the two-dimensional electronic structure of such crystals.
Effect of Nitrogen Uptake on the Curie Temperature of Intermetallic Compounds R2Fe17 and R2Fe17C0.5
Authors: Hiroshi Nagata Hiroshi Nagata , Hironobu Fujii Hironobu Fujii
Published: February 2005

We studied the effect of nitrogen uptake on the Curie temperature T
c and the lattice constants a and c in the R
2Fe17 and R2Fe17C0.5 systems. Both the lattice constants increase by about 1.3 to 3% without changing crystal structures after full uptake of nitrogen, indicating that the nitrogen atoms occupy interstitial sites. The T
c increases by 230 K to 480 K upon nitriding, and the R dependence becomes markedly weak compared to that of the host R2Fe17 compound series. The results obtained suggest that the rise of T
c strongly correlates with the rate of increase of lattice constant a due to nitrogen introduction.
Current Density Dependence for Dark-Line Defect Growth Velocity in Strained InGaAs / AlGaAs Quantum Well Laser Diodes
Authors: Fukagai Kazuo , Ishikawa Shin , Yuasa Kenji Endo
Published: February 2005

Dark-line defects (DLDs) of threading dislocation origin in strained InGaAs/AlGaAs quantum well laser diodes were observed by the electron-beam induced current technique. Current density dependence for the DLD growth velocity was compared quantitatively with that for unstrained GaAs/AlGaAs quantum well laser diodes for the first time. The <110>DLD growth velocity in InGaAs QW laser diodes is estimated to be about 1/100 of that for the <100>DLD growth in the GaAs QW laser diodes, showing linear dependence on injected current densities.
Electronic Structure of Al-Li-Cu Quasicrystal: Photoemission and Inverse Photoemission Studies of Icosahedral and Crystalline Phases
Authors: Matsubara Hideki , Ogawa Susumu , Kinoshita Toyohiko , Kishi Kazuhiko , Takeuchi Shin , Kimura Kaoru , Suga Shigemasa
Published: February 2005

Photoemission and inverse photoemission measurements are reported for icosahedral and crystalline phases of Al-Li-Cu with similar compositions. In the photoemission spectra, Al and Li core states of the icosahedral quasicrystal are shifted to larger binding energies from those of the crystalline phase by 0.4 eV, in contrast to negligible shift of Cu states. A gaplike feature of the density of states is observed in the inverse photoemission spectra of the quasicrystal just above the Fermi level. Comparison between the theoretical calculation and the experimental results of the crystalline phase is discussed.
A New Reactor for Metalorganic Chemical Vapor Deposition Equipped with an Internal Rotary Flow Selector
Authors: Wada Naoki , Sakai Shiro , Ueta Yoshihiro , Koshiba Shohei , Uematsu Kunimasa , Higashiyama Kenji , Shintani Yoshihiro , Yuasa Takayuki , Umeno Masayoshi
Published: February 2005

A reactor for metalorganic chemical vapor deposition is newly developed. The reactor has an internal flow selector by which two out of four continuously flowing gases are selected. The gas switching is performed just by rotating the flow selector without turning the valves on and off, eliminating the valve lifetime problem. The reduced effective reactor volume enables rapid gas switching at a relatively fast growth rate. GaAs/AlAs quantum wells are grown to check the gas switching ability. The cross-sectional transmission electron microscopy (TEM) image clearly shows 30-, 50- and 100 Å-thick quantum well structures, as expected.
Ar Ion Laser-Assisted Metalorganic Molecular Beam Epitaxy of InGaAs
Authors: Iga Ryuzo , Hideo Sugiura Hideo Sugiura , Takeshi Yamada Takeshi Yamada
Published: February 2005

Selective growth of InGaAs by Ar-ion-laser-assisted metalorganic molecular beam epitaxy is studied. Laser irradiation enhances the InGaAs growth rate at substrate temperatures below 500°C, but suppresses it above 530°C. It is found that the variation in the InGaAs growth rate due to laser irradiation is attributed to the variation in the GaAs growth rate in the InGaAs film. The cross-sectional profile of the area where the growth rate suppression occurs is concave with steep sidewalls and a flat bottom, while that of the area where the growth rate enhancement occurs is Gaussian-like.
Effect of Discharge Current on the Microstructure of Diamond Films Deposited on Aluminum Substrate at Low Substrate Temperature by DC Plasma CVD
Authors: Nakao Setsuo , Noda Mikio , Hirohumi Watatani Hirohumi Watatani , Shigeo Maruno Shigeo Maruno
Published: February 2005

The effect of discharge current (I
d) on the diamond structure has been investigated. The films deposited on Al substrate at a low substrate temperature (T
s) of about 200°C by DC plasma CVD are composed of ball-like grains containing microcrystalline diamond crystals with a hydrogenated amorphous component. When I
d increases, the growth rate of the grains and the size of the diamond crystals increase, and the amorphous component decreases. These results show that the increase of I
d enhances the diamond structure formation, in addition to the T
s factor's well known effect on the formation of a definite diamond film.
Growth of Short-Period ZnSe-ZnSxSe1-x Strained-Layer Superlattices by Metalorganic Molecular Beam Epitaxy
Authors: Wu Yi-hong , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

We report on metalorganic molecular beam epitaxial (MOMBE) growth of short-period ZnSe-ZnS
x
Se1-x
strained-layer superlattices (SLSs), in which special attention has been paid to in situ monitorring of the growth by reflection high-energy electron diffraction (RHEED). GaAs (001) wafer, which was employed as the substrate, was pretreated with (NH4)2S
x
solution; this pretreatment was found to be favorable for layer-by-layer growth of the constituent layers. The superlattice structures obtained here were characterized by X-ray diffraction and photoluminescence measurements, suggesting formation of well-defined SLSs in spite of the short periods in the structures.
Sintering-Induced Impurity Phase in La1.8Sr0.2CuO4-δ
Authors: Serafini Daniel , Alberto Caneiro Alberto Caneiro , Jose Pablo Abriata Jose Pablo Abriata
Published: February 2005

Microstructural changes induced by prolonged heat treatment of La1.8Sr0.2CuO4-δ are reported. Experimental evidence of the formation of an impurity phase during sintering of La1.8Sr0.2CuO4-δ is presented.
Effect of Temperature and Oxygen Pressure on Preparation of Bi2Sr2CaCu2Ox Thin Films by Metalorganic Deposition
Authors: Yaegashi Seiji , Murakami Hirohiko , Nishino Junya , Yuh Shiohara Yuh Shiohara , Shoji Tanaka Shoji Tanaka
Published: February 2005

Bi2Sr2CaCu2O
x
superconducting thin films have been prepared by metalorganic deposition (MOD) under various oxygen pressures. The pressure-temperature (P-T) phase diagram of Bi2Sr2CaCu2O
x
was determined under oxygen pressures from 0.02 to 0.2 atm. A film which was fired at 785°C in 0.06 atm oxygen with the thickness of about 0.1 µm showed a critical current density (J
c) of 2×104 A/cm2 at 30 K. The relationship between J
c and firing conditions is discussed.
Distinct Duplex Oxide Scale of Surface-Oxidized Co-Cr Film Observed by Auger Electron Spectroscopy
Authors: Kitakami Osamu , Ogawa Yoichi , Hideo Daimon Hideo Daimon , Tsuyoshi Maro Tsuyoshi Maro
Published: February 2005

The structure of a surface-oxidized Co-Cr film for perpendicular magnetic recording media is investigated by Auger electron spectroscopy. It is found that an oxidized Co-Cr film has a distinct duplex oxide scale on its surface when oxidation is carried out at relatively high temperature (∼400°C). From the outermost surface of the film, a CoO-dominant oxide scale and Cr2O3-dominant oxide scale are formed on the Co-Cr alloy film in order.
Second-Harmonic Generation from an Interfacial Layer between Orientation Films and Liquid Crystal Layers of Nematic Liquid Crystal Cell
Authors: Mochizuki Akihiro , Sotoyama Wataru , Tatsuura Satoshi , Ishitsuka Takeshi , Kobayashi Katsusada Motoyoshi
Published: February 2005

A second-harmonic generation (SHG) has been observed in a nematic liquid crystal cell containing highly polarized liquid crystal and orientation films with high polarization. No SHG is observed when a nonpolar liquid crystal is used regardless of the polarities of the orientation films used. The observed SHG is thought to originate from the ferroelectriclike layer, which comprises decomposed polar liquid crystals, at the interface between the orientation film and the liquid crystal layer.
Diamagnetization in the Vortex State of Bi(Pb)-Sr-Ca-Cu-O: Magnetic Field Measurement at the Surface by Nuclear Magnetic Resonance
Authors: Maniwa Yutaka , Sato Hiroshi , Mituhashi Taku , Mizoguchi Kenji , Ikuyo Shiozaki Ikuyo Shiozaki , Kiyoshi Kume Kiyoshi Kume
Published: February 2005

Diamagnetization M of high-T
c oxide superconductor Pb-doped Bi-Sr-Ca-Cu-O powder in the vortex state has been studied by nuclear magnetic resonance (NMR) of the surface material coated on the sample. It was found that there is no apparent anomaly in the temperature dependence of M extracted from NMR in field cooling below 1.1 T, in contrast with the result obtained by superconducting quantum interference device (SQUID) magnetometer which shows an unusually steep increase in M(T) at low temperatures. An origin of the different results produced by the two methods is discussed.
Anomalies in the Electrical Resistivity of Tl-Sr-V-O System: Search for Superconductivity
Authors: Adhikary K. , Gulnar A. , Kamat R. V. , Vaidya V. N. , Prasad Ram , Soni N. C. , Tomy C. V. , Malik S. K.
Published: February 2005

High temperature oxide superconductors without copper are of interest from the view point of understanding the mechanism of superconductivity in oxide systems. Consequent to a report by Matsuda e
t
a
l.1) of observation of superconductivity at 30 K and metastable superconductivity at 130 K in Tl-Sr-V-O system, we have synthesized several strontium vanadates of the nominal composition M
n
SrVO
x
with M=Tl, Bi, Pb, Y and K (n=0.2 to 1.0 for Tl and 0.25 for the rest), and studied their resistivity behavior. Samples were prepared following the recipe given by Matsuda et al. We have not been able to observe superconductivity in any of these systems between the temperature range of 12 to 300 K. However, some resistivity anomalies are observed in Tl containing vanadates synthesized under different heat treatment schedules.
Electron-Irradiation Enhancement of the Critical Magnetization Current in the Bi1.4Pb0.6Sr2Ca2Cu3O10 Superconductor
Authors: Shiraishi Kensuke , Kazumata Yukio , Kato Takahiko
Published: February 2005

The Bi1.4Pb0.6Sr2Ca2Cu3O10 ceramic was irradiated with 1 MeV electrons of 1.1-27.5×1011 cm-2·s-1 dose rate to a dose of 1.0×1015 cm-2 at ambient temperature, and the magnetization measurements were carried out at 5, 20 and 50 K in magnetic fields up to 5 T. Whereas the magnetization current density at 5 and 20 K was increased by the irradiation, the current density measured at 50 K was decreased in low magnetic fields. The enhancement of 17-25% in the current density at 5 K, which was dependent on dose rate, changed slightly with an increase in strength of the magnetic field.
Highly Reliable Transverse-Mode Stabilized InGaAlP Visible Light Laser Diodes at High-Power Operation
Authors: Itaya Kazuhiko , Ishikawa Masayuki , Nitta Koichi , Masaki Okajima Masaki Okajima , Gen-ichi Hatakoshi Gen-ichi Hatakoshi
Published: February 2005

The aging characteristics of transverse-mode stabilized InGaAlP laser diodes at high-power operation above 10 mW have been investigated. A rapid degradation mode related to the inner optical density of the laser was observed. This degradation mode could be effectively suppressed by reducing the inner optical density, adopting an asymmetric facet coating, and with a thinner active layer. Highly reliable operation at a high-power level above 10 mW for more than 1000 hours has been realized.
An Electrochemical Model of Neural Network Formation with Conducting Polymer by Electrochemical Polymerization
Authors: Kawai Tsuyoshi , Motobayashi Hitoshi , Takao Kuwabara Takao Kuwabara , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

One of the simplest models of neural network-formation by electrochemical process is demonstrated utilizing electrochemical polymerization of pyrrole in an agar gel, with which conducting network is formed by applying voltage pulses.
Impurity Diffusion Barrier Effect of Ultra-Thin Plasma-Nitrided a-Si:H Overlayer on SnO2/Glass Substrate
Authors: Hayashi Tsukasa , Kawabata Keishi , Yamada Keiichi , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: February 2005

Tin diffusion into p-type a-Si1-x
C
x
:H (x=0.28) deposited on an SnO2/glass substrate has been significantly reduced by employing an ultra-thin plasma-nitrided a-Si3N4:H barrier layer inserted between a-Si1-x
C
x
:H and SnO2. It is shown that the a-Si3N4:H layer is very uniform to prevent Sn diffusion and that reduced Sn atoms form chemical bonds with Si, C and N in the a-Si1-x
C
x
:H/a-Si3N4:H/SnO2 interfaces. The reduced Sn atoms bonded to Si, C, or N tend to increase the density of states in the a-Si1-x
C
x
:H valence band tail near the Fermi level.
Preparation of Superconducting Bi2Sr2CaCu2Ox Ceramics by Low-Temperature Heat Treatment
Authors: Won-Hyuk Lee Won-Hyuk Lee , Yoshihiro Abe Yoshihiro Abe
Published: February 2005

Superconducting ceramic rods (T
c≈80 K) of Bi2Sr2CaCu2O
x
were successfully prepared by heat treatment in air at 700°C for 20-50 h; the temperature of 700°C is believed to be the lowest temperature reported so far. The precursor rod specimens were made by vacuum casting the stoichiometric melts into silica tubes; the as-cast rods are spontaneously devitrified during cooling and are composed of crystalline phases of Bi2Sr2CuO
x
(2201 phase) and small amounts of Cu2O and unidentified crystalline phases.
Microstructure and Microwave Properties of Tl2Ba2CaCu2O8 Thin Films on CaNdAlO4(001)
Authors: Young K. H. , Arney D. , E. J. Smith E. J. Smith , D. Strother D. Strother
Published: February 2005

High-quality epitaxial Tl2Ba2CaCu2O8 superconducting thin films have been grown on CaNdAlO4 (001) substrates by a two step process. Analysis results from secondary ion mass spectroscopy and X-ray energy dispersive spectroscopy of a film annealed at 850°C indicated non-uniform Nd and Ca interdiffusion from the substrate into the film. A second film, annealed at 800°C, exhibited better superconducting properties with a T
c of 100.7 K, transition width of 2.5 K, and J
c of 3.5×105 A/cm2 at 77 K. Microwave measurement at 77 K of a 2.3 GHz microstrip resonator made from the 800°C annealed film on a CaNdAlO4 substrate exhibited a low power Q of 2,100.
CuCl Microcrystallite-Doped SiO2 Glass Thin Films Prepared by RF Sputtering
Authors: Tsunetomo Keiji , Shimizu Ryuichiro , Kawabuchi Akira , Hayuyuki Kitayama Hayuyuki Kitayama , Yukio Osaka Yukio Osaka
Published: February 2005

CuCl microcrystallites were successfully doped into SiO2 glass thin films by means of the magnetron rf-sputtering technique. A transmission electron microscopy (TEM) measurement showed that the microcrystallites had a spherical configuration. The average size of the microcrystallites was less than 5 nm and it was affected by the preparation condition and postdeposition annealing time. Optical absorption peaks corresponding to Z3 and Z1,2 exciton were observed. These absorption lines shifted to a higher-energy side with decreasing microcrystallite size. This phenomenon seems to relate to the quantum size effect.
Room Temperature Stark-Ladder Transitions in GaAs/AlAs Superlattices with Different Miniband Widths
Authors: Kawashima Kenji , Fujiwara Kenzo , Yamamoto Teiji , Mitsuhiro Sigeta Mitsuhiro Sigeta , Kikuo Kobayashi Kikuo Kobayashi
Published: February 2005

We have studied room temperature Stark-ladder transitions in GaAs/AlAs superlattices with different miniband widths. Measured dependence of field-induced energy shifts of the Stark-ladder transitions on superlattice period agrees with theory. We have also shown dependence of quantum coherence on superlattice parameters, and observed the highest quantum coherence of 11 periods in the wide-miniband superlattice. These results give clear evidence that Wannier-Stark localization occurs over a wide range of miniband widths, and that is responsible for a negative differential conductivity mechanism.
Enhancement for Synthesis of Bi-Pb-Sr-Ca-Cu-O Superconductor by the Spray Drying and Subsequent Calcination with Rapid Heating
Authors: Awano Masanobu , Kani Keiko , Yasumasa Takao Yasumasa Takao , Hiroyoshi Takagi Hiroyoshi Takagi
Published: February 2005

The synthetic processing of a Bi-Pb-Sr-Ca-Cu-O superconductor by the spray drying and subsequent calcination was examined. The nitrate solution of the superconductor was spray dried and then promptly, the spray-dried powder was decomposed at the temperature in the stable range of the high T
c phase for relatively short time (1-2 hours). Other homogeneous starting materials could not react to the high T
c phase in such a short time. The results suggest that the optimum condition at which to synthesize the high T
c phase is not only homogeneity, but also the condition of the precursor and reaction method.
Properties of Tl2Ba2Ca1Cu2Ox Thin Films Prepared on Polycrystalline Yttria-Stabilized Zirconia Substrate with a Tc of 106 K and a Jc of 1.7×104 A/cm2 by Dual-Magnetron Sputtering and Post Annealing
Authors: Saito Yukio , Nabatame Toshihide , Kobrin Paul , Cheung Jeffery
Published: February 2005

Tl2Ba2Ca1Cu2O
x
(Tl-2212) superconducting films have been fabricated on flexible polycrystalline yttria-stabilized zirconia (YSZ) substrates by dual-magnetron sputtering of metal Tl and Ba2Ca1Cu2 alloy followed by annealing in Tl vapor. X-ray diffraction showed only the Tl-2212 phase with c-axis orientation. A t
c of 106 K and a J
c of 1.7×104A/cm2 at 77 K in zero magnetic field were measured.
New High-Pressure Phases of Carbon
Authors: Takano Kaoru J. , Hiroshi Harashima Hiroshi Harashima , Masao Wakatsuki Masao Wakatsuki
Published: February 2005

Reversible phase transformations with volume contractions were found at 18 GPa and 22 GPa when graphite was compressed at room temperature. Volume contraction was detected in a diamond anvil cell by observing a plateau in the curve of generated pressure versus the cell load. The phase realized at 18 GPa is thought to work as an intermediate phase in the transformation from graphite to hexagonal diamond. A structure of this phase, though not yet identified, is also discussed.
Heavily Carbon-Doped P-Type InGaAs Grown by Metalorganic Molecular Beam Epitaxy
Authors: Akatsuka Takeshi , Miyake Ryuji , Nozaki Shinji , Yamada Takumi , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

A proofreader's error was made in the last page (p. L539). Because the error covers a wide area (column 2, line 1-19), the corrected whole paper is publishied as follows:
Preparation of YBa2Cu3Oy Superconducting Thin Films on Metallic Substrates by Excimer Laser Ablation
Authors: Saitoh Junichi , Fukutomi Masao , Komori Kazunori , Tanaka Yoshiaki , Asano Toshihisa , Takahara Hiroshi Maeda
Published: February 2005

Superconducting thin films of YBa2Cu3O
y
on a metallic substrate are prepared in situ by a pulsed laser ablation technique. The growth quality of the superconducting YBa2Cu3O
y
films has been compared on YSZ/Hastelloy substrates with or without a Pt underlayer. The zero-resistance temperature, T
co, of 90.0 K and a transport critical current density, J
c, greater than 4.0×104A/cm2 at zero field and 77.4 K were achieved when a YSZ/Pt/Hastelloy substrate was used. The insertion of a thin Pt layer at the boundary between YSZ and Hastelloy stabilized the YSZ buffer layer, resulting in the subsequent growth of a well-crystalline YBa2Cu3O
y
film.
Laser-Scanning Micromanipulation and Spatial Patterning of Fine Particles
Authors: Sasaki Keiji , Koshioka Masanori , Misawa Hiroaki , Noboru Kitamura Noboru Kitamura , Hiroshi Masuhara Hiroshi Masuhara
Published: February 2005

Laser-scanning micromanipulation and spatial patterning of polystyrene latex or titanium dioxide particles in solution were demonstrated for the first time. A trapping laser beam was repetitionary scanned at 13∼50 Hz by computer-controlled galvano mirrors to align micrometer-order particles along the pattern produced by the scanning laser beam. Characteristic features of the present technique are discussed.
Effect of Current on Collective Motion of Flux Lines in a Bulk Y1Ba2Cu3O7-δ Superconductor
Authors: Yang Z. J. , Bratsberg H. , Johansen T. H. , Skjeltorp G. Helgesen
Published: February 2005

When a permanent magnet, placed above a high temperature superconductor (HTSC), is moved by an external force, the flux lines in the HTSC will follow the magnet and perform a collective motion due to the interaction between the flux lines and the magnet. Here, the collective motion of flux lines in an Y1Ba2Cu3O7-δ (Y123) HTSC is studied by a mechanical pendulum method for various transport currents I through the sample. The magnet is set in low frequency (typically 1 Hz) oscillations with a mechanical pendulum, and the current I is flowing perpendicular to the direction of the magnet motion.
The experiments show that the shift of the stiffness (corresponding the shift of the frequency squared) exhibits a cross-over phenomenon: from independence to power law-like dependence for increasing currents. The results are compared with the theories of collective flux creep in HTSCs.
Chemical Approach to the Superconductivity with High Tc. A Model of Pair Formation in Hole-Doped Cupurates
Authors: Hiroshi Kawazoe Hiroshi Kawazoe
Published: February 2005

Chemical models of the positive hole and hole pair in the p-type and copper-based superconductors with high T
c were proposed. Formation of the hole pair was expressed in a chemical reaction formula, O1
-+O1
- → (O2,1)2-, where O1
- means that O2- constituting a crystalline lattice is changed into O- on capturing a positive hole, and the suffix 1 denotes that the species exists in the crystalline lattice. A peroxide ion is considered to be a model structure of the hole pair. The hole, O1
-, was treated as a five-electron system in discussing the mechanism of formation of the hole pair.
Substrate Bias and Pressure Effect on Formation of YBaCuO Thin Films in RF Magnetron Sputtering System
Authors: Nakagawa Akira , Masayuki Sugiura Masayuki Sugiura , Yoichi Okabe Yoichi Okabe
Published: February 2005

Effect of substrate bias on formation of YBaCuO films at various pressures by the rf magnetron sputtering method is studied. It is found that the best films are obtained at the optimum bias voltage with regard to the end point of the critical temperature. The optimum substrate bias lowers the energy of ions which damage YBaCuO films. Furthermore, this optimum bias approaches 0 V when the total pressure becomes higher, where the energy of ions is small.
Multiple-Tip Effect on Scanning Tunneling Microscope Images of Deoxyribonucleic Acid
Authors: Hu J. , Gu M. , Wang Z. , Yao X. , Xu Y. , Zhang L. , Huang Z. , J. Zhu J. Zhu , M. Li M. Li
Published: February 2005

A theoretical model has been developted to correct the multiple-tip effect, which occurs very often to scanning tunneling microscope (STM) images derived from specimens of considerable roughness. Based on this model, computer simulations showed satisfactory results in the treatment of STM images of deoxyribonucleic acid (DNA). Also, the finite surface structure of an STM tip can be determined by the approach. Discussions were given on the multiple-tip effects happened to some STM biological applications.
Low-Temperature Oxidation of Silicon in Dry O2 Ambient by UV-Irradiation
Authors: Ishikawa Yutaka , Tsuyoshi Shibamoto Tsuyoshi Shibamoto , Ichiro Nakamichi Ichiro Nakamichi
Published: February 2005

The mechanism of thermal oxidation of silicon in dry O2 ambient with UV-irradiation has been discussed. The dependence of SiO2 thickness on oxidation time follows the model proposed by Cabrera and Mott for relatively short oxidation time. Such dependence follows the model by Deal and Grove for longer time. The main oxidizing species is ozone (O3) or some other reactive species generated from O3 at lower temperatures and this gradually changes to O2 with an increase in temperature. The SiO2 film formed at 500°C for 1 h by the present technique has a similar quality to that of SiO2 formed at high temperatures in dry O2 ambient, as evaluated from Fourier Transform-Infrared (FT-IR), Auger Electron Spectroscopy (AES) and Capacitance-Voltage (C-V) characteristics.
A Semiempirical Monte Carlo Approach to Secondary Electron Emission from a Hydrogen-Implanted Carbon Surface
Authors: Nishimura Kenji , Kaoru Ohya Kaoru Ohya , Ichiro Mori Ichiro Mori
Published: February 2005

For a plasma-surface interaction, the influence of an implantation of hydrogen atoms on the secondary electron emission from a carbon surface bombarded by low-energy (<2 keV) electrons is investigated using a single scattering Monte Carlo simulation of transport of a primary electron and a semiempirical model of secondary electron emission. In the simulation, the mean escape depth, which is dependent on the hydrogen concentration in carbon, is used and the average energies deposited to excite an electron from carbon and hydrogen atoms are separately treated. The simulated secondary electron yield increases with increasing hydrogen concentration, i.e., the H/C ratio. This increase in H/C ratio of 0.5 agrees with that of a graphite limiter exposed to a hydrogen plasma in the JET Tokamak at low energy (<1 keV). Furthermore, the enhancement of the incident-angle dependence observed by exposure to the plasma is explained by the present simulation for the first time.
Maskless Patterning of Ferrite Film by Selected Area Film Growth in Aqueous Solution by “Laser-Enhanced Ferrite Plating”
Authors: Hori Seiichiro , Itoh Tomoyuki , Abe Masanori , Tamaura Yutaka
Published: February 2005

By irradiating substrate with Ar-laser (λ=514.5 nm) beams, Fe3O4 films were deposited in an aqueous solution at a rate as high as ∼660 nm/min. By synchronously moving the substrate during the plating process, we successfully drew letters of ferrite film patterned on a glass substrate by selected area growth without using any masks. This technique is useful for fabricating fine-patterned ferrite film devices (e.g., microwave circulators and isolators) using as a substrate such non-heat-resistant materials as GaAs ICs.
Correlation between Front Speed and Initial Explosion Energy of the Blast Wave Induced by a TEA CO2 Laser
Authors: Kurniawan Hendrick , Kobayashi Takao , Nakajima Sadao , Kagawa Kiichiro
Published: February 2005

A TEA (Transversely Excited Atomospheric-pressure) CO2 laser beam has been focused on several metals such as Zn, Pb, Ag and Sn-Pb compounds at reduced ambient gas pressure. It is shown that the radius of the expanding luminous front of the laser induced secondary plasma is proportional to one-fifth power of the intensity of the primary plasma. The radius of the luminous front is equal for different metals. From these results, it is concluded that the primary plasma is the source of a blast wave and the secondary plasma is excited by it.
Fabrication and Evaluation of X-Ray Multilayer Mirrors Prepared by Laser-Induced Chemical Vapor Deposition
Authors: Shin-Ogi Masataka , Seki Shoji , Ishino Yukinobu , Hiroshi Nagata Hiroshi Nagata , Yoshihiko Suzuki Yoshihiko Suzuki
Published: February 2005

This study demonstrates a new preparation process for fabricating X-ray multilayer mirrors. Tungsten/carbon multilayer mirrors were prepared using laser-induced chemical vapor deposition (laser-CVD). The structure and properties of the mirror were examined using X-ray diffraction, synchrotron radiation and transmission electron microscopy (TEM) measurements. The reflectivity at a grazing angle of 14.5 degrees was observed to be 4.1% at a wavelength of 5 nm. The reflectivity was lower than the ideal reflectivity. The reduction in the reflectivity was caused by the lower-density film (tungsten layer), interface roughness and diffuse interfaces. Furthermore, after annealing at room temperature for two months, the increment of the period of this mirror was about 33%. This was due to the oxidation of tungsten films in W/C (tungsten/carbon multilayer mirror).
Growth and Characterization of InGaP Yellow-Green Light-Emitting Diodes by Liquid-Phase Epitaxy
Authors: Chen Chyuan-Wei , Meng-Chyi Wu Meng-Chyi Wu , Shoei-Chyuan Lu Shoei-Chyuan Lu
Published: February 2005

Zn-doped InGaP/Te-doped ZnGaP on n-type GaAsP substrate homostructural light-emitting diodes has been reproducibly fabricated by liquid-phase epitaxy using a supercooling technique. The growth and characterization of Te- and Zn-doped InGaP layers are described. The strongest photoluminescence peak intensity occurs at 1×1018 and 6×1017 cm-3 for electron and hole concentrations, respectively. Diodes fabricated from the p-n homostructure are characterized by current-voltage measurement, electroluminescence, light output power, and external quantum efficiency. A forward-bias turn-on voltage of 1.5 V with an ideality factor of 2.02 and a breakdown voltage as high as 20 V are obtained from the current-voltage measurements. The emission peak wavelength and the full width at half-maximum of electroluminescence are around 5840 Å and 66-55 meV at 20 mA, respectively. The light output power of the uncoated diodes is about 35 µW at a dc current of 100 mA, and an external quantum efficiency of ∼0.02% is observed. The EL spectra are compared to the PL spectra of the Zn-doped InGaP layer at 300 and 50 K.
Carrier Concentration Dependence on Tc in Bi2Sr2-xRExCaCu2O8+δ (RE=Nd and Ce)
Authors: Koyama Kuniyuki , Tahata Norikazu , Noguchi Seiichiro
Published: February 2005

Structure, resistivity and susceptibility have been measured in the Bi2Sr2-x
RE
x
CaCu2O8+δ (RE=Nd and Ce) system. The samples with 0≤x≤1 (RE=Nd) and 0≤x≤0.25 (RE=Ce) have almost single phases of the Bi2Sr2CaCu2O8+δ structure. The x-dependence on T
c in the Ce-substituted system is almost twice as strong as that in the Nd-substituted one. The valences of Nd and Ce ions in the samples were determined from susceptibility measurement as trivalent and tetravalent, respectively. The hole concentration was determined from the Hall effect measurement. The results confirm that the hole concentration in the Ce-substituted system becomes twice as strong as that in the Nd-substituted one, as expected from the universal relationship between the T
c and the hole concentration in the Bi2Sr2CaCu2O8+δ system.
Electronic Structure of the Organic Superconductor κ-(BEDT-TTF)2Cu(NCS)2 Studied by Angle-Resolved Photoemission Spectroscopy
Authors: Yoshimura Masamichi , Shigekawa Hidemi , Mori Takehiko , Kageshima Masami , Kato Hiroo , Sakisaka Yasuo , Saito Gunzi , Akira Kawazu Akira Kawazu
Published: February 2005

In the photoemission spectra of the κ-(BEDT-TTF)2Cu(NCS)2 surface, two characteristic structures were observed at the binding energies of ∼-7.5 eV and ∼-11.5 eV, which were attributed to the π- and σ-bonding states, respectively, in comparison with the results of the molecular orbital (MO) calculations. Polarization dependence appearing in the spectra was comprehensively interpreted by the electronic structures calculated for those states, which is in good agreement with the results previously obtained using a scanning tunneling microscope.
Stabilization of Radicals by Doping from Aqueous Solutions into Crystals of Hydroxyapatite
Authors: Kazuhide Meguro Kazuhide Meguro , Motoji Ikeya Motoji Ikeya
Published: February 2005

Unstable superoxide, ·O2
-, and semiquinone can be stabilized when hydroxyapatite Ca10(PO4)6(OH)2 is crystallized from aqueous solutions containing these radicals. The inorganic microcrystals surround the radicals and stabilize them for nearly a year at room temperature. Radicals adsorbed on the surface of apatite showed spectra different from those obtained by doping. Semiquinone radicals in apatite were almost stable up to about 600°C. Effects of additional Fe3+ and F- impurities on the electron spin resonance (ESR) spectrum of superoxide-doped apatite were studied to determine the site of the radicals in the lattice. Superoxide may be substituted at the OH- site.
Electro-Optic Functional Waveguide Using New Polymer p-NAn-PVA for Integrated Photonic Devices
Authors: Ura Shogo , Ohyama Ryuji , Toshiaki Suhara Toshiaki Suhara , Hiroshi Nishihara Hiroshi Nishihara
Published: February 2005

A thin film waveguide consisting of newly-developed polymer p-NAn-PVA was fabricated and characterized. The thin film was formed by spin-coating and poled by applying an electric field. The electro-optic (EO) coefficient r
33 was measured to be 14 pm/V, which is as large as half of the r
33 of LiNbO3. As an application of this waveguide, a waveguide EO grating switch was proposed and demonstrated. The switching operation was confirmed preliminarily.
Polarization Control of Surface Emitting Lasers by Anisotropic Biaxial Strain
Authors: Mukaihara Toshikazu , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

In order to control the polarization direction of surface emitting lasers, we have introduced biaxial tension in the active layer. By making an elliptical etch well, we introduce the anisotropic strain in the active region. We experimentally demonstrated polarization stabilization along the major axis of the elliptically holed region.
Hot-Pressed BN-AlN Ceramic Composites with High Thermal Conductivity-Part II
Authors: Kanai Takao , Akiro Ando Akiro Ando , Kei Tanemoto Kei Tanemoto
Published: February 2005

Hexagonal boron nitride-aluminum nitride (75-25, 50-50, 40-60, 30-70, 20-80 wt%) ceramic composites are synthesized by uniaxial hotpressing. Their thermal and mechanical properties are evaluated. The anisotropy of thermal conductivity and thermal expansion coefficient decreases and the mechanical strength increases with increasing aluminum nitride content. Hexagonal boron nitride gives large anisotropies of these properties of the composites even for aluminum-nitride-rich compositions.