bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly Reliable Operation of High-Power InGaAsP/InGaP/AlGaAs 0.8 µ m Separate Confinement Heterostructure Lasers
Authors: Fukunaga Toshiaki , Wada Mitsugu , Asano Hideki , Toshiro Hayakawa Toshiro Hayakawa
Published: October 2002

We report the high-power and reliable operation of InGaAsP/InGaP/AlGaAs 0.8 µ m separate confinement heterostructure single-quantum-well laser diodes. High output power of 1.8 W is achieved from an anti-reflection- and high-reflection-coated device with stripe width of 50 µ m and cavity length of 1.25 mm. This device has high characteristic temperature of 164 K and low threshold current density of 300 A/cm2. No catastrophic failure in the laser with 0.75 mm cavity length is observed during 1000 h aging test at 50° C under an automatic power control of 500 mW.
The effect of cavity length on laser characteristics is also discussed.
In Situ Observation of Surface Morphology Evolution Corresponding to Reflection High-Energy Electron Diffraction Oscillation during Molecular Beam Epitaxy of Gallium Arsenide
Authors: Homma Yoshikazu , Osaka Jiro , Inoue Naohisa
Published: October 2002

We have used scanning electron microscopy (SEM) for real-time observation of surface evolution during molecular beam epitaxy (MBE) of GaAs. Surface morphology oscillation is imaged in the initial stage of growth. The nucleation-coalescence process of 2D islands is directly compared with the reflection high-energy electron diffraction intensity oscillation. The first-layer islands coalesce almost completely to form a uniform layer, while holes and islands are observed on successive layers. The size of nucleated islands increases every layer-growth cycle, resulting in multilayer growth and coarsening of the surface.
Improvement in Junction Properties of a n-Si/poly(3-methylthiophene) Heterojunction by Post-Treatment with aq.HF
Authors: Hoshino Katsuyoshi , Ogata Takahiro , Kokado Hiroshi
Published: October 2002

Junction properties of an n-Si/poly(3-methylthiophene) (P3MeT) cell are investigated by current-voltage measurements. Efforts have been made to understand and improve the inorganic/organic interface. It was found that a great improvement in junction properties is possible by treating the cell with an aq.HF solution. Since electrical conductivity of P3MeT bulk is little affected by the HF treatment, the improvement is attributed to the enhancement in interactions between P3MeT and n-Si. The cell showed degradation upon exposure to air, but it recovered its original characteristics when it was again treated with an aq.HF solution.
Low Temperature-GaAs Current-Blocking InGaAs-AlGaAs Strained Quantum Well Lasers on P-type GaAs Substrate with Output Power over 100 mW
Authors: Sin Yong Kun , Horikawa Hideaki
Published: October 2002

Data are presented on InGaAs-AlGaAs strained quantum well lasers with a molecular beam epitaxy (MBE) grown LT-GaAs current-blocking layer on a p-type GaAs substrate. The SCH DQW structure is grown y metalorganic vapor-phase epitaxy (MOVPE) on the channeled LT-GaAs. The CW laser threshold is 50 mA at RT (uncoated) and the maximum output power of 120 mW is obtained (AR-HR coated). Far-field patterns show fundamental lateral and ransverse modes even at the output power at 100 mW.
Full widths at half-maximum of far-field patterns parallel and perpendicular to the junction plane are 14.5° and 39.5° at 100 mW, respectively.
Integration of Laser Diodes and Photodiodes in Photonic Integrated Circuit for Measurement
Authors: Hirata Takaaki , Iio Shinji , Suehiro Masayuki , Hihara Mamoru , Suhara Toshiaki , Uemukai Masahiro , Taniguchi Takehiro , Nishihara Hiroshi
Published: October 2002

Fully integrated PICs for measurement have been successfully fabricated for the first time. The device is implemented with waveguide grating components, a GRIN-SCH-SQW-DFB LD and PDs. Special care is taken to prevent direct optical coupling between integrated LDs and PDs in order to detect feeble sensing light. An interference signal is actually detected as photocurrent modulation of ∼1-nA amplitude by this integrated structure.
Diamond Epitaxial Growth by Gas-Source Molecular Beam Epitaxy with Pure Methane
Authors: Nishimori Toshihiko , Sakamoto Hitoshi , Takakuwa Yuji , Kono Shozo
Published: October 2002

Diamond epitaxial films with a thickness of 200-350 Å have been successfully grown on C(100) surfaces by gas-source molecular beam epitaxy (GSMBE) with methane without addition of hydrogen or oxygen. The activation energy was measured by a selective growth method using Ta-patterned substrates to be 15 kcal/mol. This value is close to the activation energy of H2 desorption on C(100), suggesting that the diamond epitaxial growth rate by this GSMBE is limited by hydrogen desorption.
A Novel and Highly Sensitive Gas Flow Sensor Using a Hot Spot on YBa2Cu3O7-δ Thin Films
Authors: Kikuchi Kei , Kanzaki Motoi , Neda Tokudai , Kondo Takehiko , Takata Masasuke
Published: October 2002

A novel and highly sensitive hot-wire-type flow sensor constructed of a YBa2Cu3O7-δ thin film has been fabricated. When heating voltage was applied to the sensor, a hot spot appeared and the sensor had a high sensitivity to air flow speeds of 0.04-4 m/s. Sensing characteristics have been examined for two different heating modes, constant-voltage and constant-resistance. In the constant-voltage mode, the current was proportional to the square root of the flow speed. In the constant-resistance mode, the output voltage was proportional to the fourth root of the flow speed, as is explained by the well-known King's law. In both cases, high sensitivity and good linearity were observed.
Optical Characterization of Si1-xCx/Si ( 0≤x≤0.014) Semiconductor Alloys
Authors: Lee Hosun , Kurtz S. R. , Floro J. A. , Strane J. , Seager C. H. , Lee S. R. , Jones E. D. , Nelson J. F. , Mayer T. , S. T. Picraux S. T. Picraux
Published: October 2002

We have characterized the optical properties of heteroepitexial Si1-
x

C

x

/Si (0≤x≤0.014) alloys grown on Si substrates by solid phase epitaxy using spectroscopic ellipsometry and photoluminescence. The measured dielectric function confirms that the samples are of good crystalline quality. The 14-K photoluminescence spectra of Si1-
x

C

x

/Si show several defect peaks. After hydrogen passivation, we observed a new peak near 1.15-1.17 eV which increases in energy with the incorporation of carbon. We tentatively assign this peak to the no-phonon peak of the Si1-
x

C

x

epi-layer. We discuss the alloy shift of the observed spectroscopic features in terms of the C-induced change in the Si indirect band gap.
Optimum Dark-State Voltage for Wide-Viewing-Angle Optically-Compensated-Bend-Mode Liquid-Crystal-Displays
Authors: Kuo Chen-Lung , Miyashita Tetsuya , Suzuki Makoto , Tatsuo Uchida Tatsuo Uchida
Published: October 2002

Further improvement in viewing-angle properties of our recently proposed optically-compensated-bend (OCB)-mode liquid crystal display (LCD) is reported. The intrinsic optical properties of the bend-alignment liquid-crystal cell used in this mode are analyzed and the selection of bias voltage for the black level to reduce the off-axis light leakage in the vertical viewing direction is discussed. A very wide viewing angle of more than 100 degrees in both the horizontal and vertical directions, under the conditions of contrast ratio greater than 20 and no gray-scale inversion, is confirmed theoretically and experimentally for the first time.
Effects of Post-Annealing on Oxygen Content of Indium Tin Oxide Films Fabricated by Reactive Sputtering
Authors: Honda Shinichi , Tsujimoto Akira , Watamori Michio , Kenjiro Oura Kenjiro Oura
Published: October 2002

Effects of post-annealing on the depth profile of oxygen content of indium tin oxide (ITO) films on glass substrates have been investigated. Absolute oxygen content of the films was estimated by a high-energy ion beam technique. The electrical properties and the oxygen contents, measured before and after post-annealing in vacuum, have been compared for films deposited under different conditions. Our present results implied that oxygen deficiency at the film surface, induced by post-annealing, might be responsible for the observed improvement of the electrical properties.
Measurement of Diffusion Coefficient of CF2 Radical in DC Pulsed CF4/H2 Discharge Plasma
Authors: Arai Toshihiko , Goto Miki , Takayama Daisuke , Shimizu Tetsuya , Murakami Masahiko , Horikoshi Keita , Hiroyuki Fujioka Hiroyuki Fujioka
Published: October 2002

Laser-induced fluorescence has been used to measure the CF2 radical ground-state densities after extinction of DC pulsed CF4/H2 discharge plasma. From the measurement, the CF2 radical was shown to be removed mainly by a diffusion process. Its diffusion coefficients are found to be D=430 cm2·Torr·s-1 in H2 and D=65 cm2·Torr·s-1 in CF4 at room temperature.
Temperature Fall Caused by Voltage Generation in Metal-Insulator-Metal (MIM) Structures of Polyimide Langmuir-Blodgett Films (Possible Evidence of a New Phenomenon of Energy Convertion)
Authors: Taro Hino Taro Hino
Published: October 2002

Voltage was generated in the metal-insulator-metal (MIM) structures of Al/polyimide Langmuir-Blodgett film/Au which were fabricated in 1986. Temperature fall caused by the voltage generation was ascertained by noncontact temperature measurement using a vacuum avalanche photodiode. The voltage has been generated for 6 months and is still being generated now. From the experimental results, it was found that the present MIM structures are new microscopic elements that transduce heat energy to electrical energy.
GaN/GaInN/GaN Double Heterostructure Light Emitting Diode Fabricated Using Plasma-Assisted Molecular Beam Epitaxy
Authors: Sakai Hiromitsu , Koide Takashi , Suzuki Hiroyuki , Yamaguchi Machiko , Yamasaki Shiro , Koike Masayoshi , Amano Hiroshi , Isamu Akasaki Isamu Akasaki
Published: October 2002

High-quality GaN and Ga1-
x

In

x

N (x≤0.2) have been grown by RF-plasma-assisted molecular beam epitaxy (RF-MBE) on the GaN/AlN/sapphire substrate grown by metalorganic vapor-phase epitaxy for the first time. GaN and GaInN showed intense near-band-edge photoluminescence (PL) at room temperature. A double hetero-structure (DH) of p-GaN:Mg/Ga0.8In0.2N/ n-GaN has been fabricated. The DH light emitting diode showed intense violet emission upon current injection at room temperature.
InP Layer Grown on (001) Silicon Substrate by Epitaxial Lateral Overgrowth
Authors: Tachikawa Shigeya Naritsuka , Hidehumi Mori Hidehumi Mori
Published: October 2002

An InP epitaxial layer with a dislocation-free area was obtained for the first time on (001) Si substrate by using the epitaxial lateral overgrowth (ELO) technique. Most etch pits appeared in the region over the seed area on the ELO stripe. This indicates that the SiO2 film between the lateral overgrowth layer and the substrate prevented the propagation of the dislocations from the substrate to the lateral overgrowth layer. Spatially resolved photoluminescence showed that the optical quality of an InP ELO layer grown on Si was almost the same as that of a homoepitaxially grown InP layer and that the ELO technique is also useful to relieve stress caused by both the lattice mismatch and the difference in thermal expansion coefficient.
White-noise Properties of YBa2Cu3O7-δ Grain-boundary dc Superconducting Quantum Interference Devices
Authors: Nakamura Hiroyuki , Chen Jian , Tomoya Ogawa Tomoya Ogawa , Tsutomu Yamashita Tsutomu Yamashita
Published: October 2002

We have studied white (high-frequency)-noise properties of YBa2Cu3O7-δ grain-boundary dc superconducting quantum interference devices (SQUIDs). Bias voltage (V) dependence of the white-noise voltage spectral density (S
v) was measured for dc-SQUIDs and junctions. As a result, S
v at low bias voltage can be explained by the thermal noise theory of tunnel junctions. Furthermore, the energy resolution of 1.96×10-32 J/Hz is obtained at 43 K in the white-noise region. The measured energy resolution of the dc-SQUIDs is in good agreement with the theoretical results. According to the above results, YBa2Cu3O7-δ dc-SQUIDs with a quantum noise limit might be realized at 4.2 K.
Effect of Impurity Doping on Density Anomalies in Molten Silicon
Authors: Kawanishi Soroku , Sasaki Hitoshi , Kazutaka Terashima Kazutaka Terashima , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

The density of molten silicon doped with 0.1 at% boron or 0.1 at% gallium was measured over a temperature range from the melting point to 1650° C by using an improved Archimedean method with modified dipping procedure to study the influence of impurity doping on density anomaly. Density anomaly with the thermal volume expansion coefficient of about 8.0×10-4 K-1 has been observed from 1420° C to 1435° C for the pure molten silicon, together with the drasric decrease in density, regarded as the stage prior to solidification, from the melring temperature to 1420° C.
This anomaly was also observed in 0.1 at% boron-doped silicon melt, but completely suppressed in 0.1 at% gallium-doped melt. No change was observed, however, in the thermal volume expansion coefficient, which remained about 0.6×10-4 K-1, regardless of the addition of such impurities over 1435° C.
Concentration dependence of density anomalies was also investigated using the molten silicon doped with 0.1-1.0 at% gallium, showing no sign of the anomalous temperature coefficient.
Effect of Biaxial Strain on Cubic and Hexagonal GaN Analyzed by Tight-Binding Method
Authors: Masaaki Nido Masaaki Nido
Published: October 2002

The effect of tensile and compressive biaxial strain on the valence band structures around the valence band edge, for both cubic and hexagonal GaN, were analyzed using a tight-binding method, which took the spin-orbit interaction into account. Biaxial strain was induced in the (001) and (0001) plane for cubic and hexagonal GaN, respectively. The strain induced change in the band structures was qualitatively the same for two types of GaN, however, it was remarkably different compared with GaAs, due to the very small split-off energy in GaN. The advantages of tensile strained GaN semiconductor lasers were discussed.
Superconductivity in Cr-1212 Cuprates Sr2-xBaxYCu2.8Cr0.2Oz
Authors: Akira Ono Akira Ono
Published: October 2002

The Cr-1212 cuprates Sr2-
x

Ba

x

YCu2.8Cr0.2O7 (x≤0.75) were annealed at high oxygen pressures. Although the Ba-free sample was not superconductive, the others exhibited bulk superconductivity after annealing. The critical oxygen content needed for the appearance of superconductivity for the x=0.5 cuprate is close to 7.22 or 7.28 and depends on annealing temperature. The higher value is due to the higher Cr valence. Even if unusually high Cr valence of 6+ is assumed, the average formal Cu valence required for the appearance of superconductivity is high. The Cr-1212 phase (x≤0.5) is a special material in this respect.
Pulse Response of Electroluminescence in Poly(3-alkylthiophene) Mixed with Fluorescent Dye
Authors: Masayoshi Yoshida Masayoshi Yoshida , Akihiko Fujii Akihiko Fujii , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Pulse response of electroluminescent (EL) diode utilizing poly(3-alkylthiophene) mixed with fluorescent dye has been investigated. By mixing fluorescent dye with poly(3-alkylthiophene), the response time of EL emission became slow compared with that of undoped poly(3-alkylthiophene). The mechanism of the EL response in the fluorescent-dye-doped poly(3-alkylthiophene) is discussed in terms of hopping transport of electrons through 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole molecules.
Temperature Dependence of X-Ray Topographic Images Taken around Indentations of Si Single Crystals
Authors: Kawamura Masato Yoshioka
Published: October 2002

This paper describes how X-ray topographic images taken around indentations are affected by temperature. Vickers indentations were made on the (111) surface of Si single crystals. In the low-temperature range (0-400° C), the images resemble the number “8” and show a twofold symmetry. On the other hand, they show a threefold symmetry, similarly to a nest of triangles, in the elevated temperature range (higher than 500° C). The difference in the topographic images reflects the difference in the mechanisms of deformation by indentations. It was concluded that the change of the images with temperature rise was attributed to the relative increase in plastic deformation in a microscopic sense rather than elastic deformation.
Effect of Ambient Gas Pressure on the Preferred Orientation of Barium Titanate Thin Films Prepared by Pulsed Laser Deposition
Authors: Kim Dong-Young , Lee Soon-Gul , Park Yong-Ki , Soon Ja Park Soon Ja Park
Published: October 2002

Barium titanate thin films were deposited by pulsed laser deposition. The effect of ambient gas pressure on the preferred orientations of the films was systematically investigated. Irrespective of the substrate used, the preferred orientation of films deposited without oxygen flow (10-5 Torr) was the (100) equivalent planes which are electrically neutral. The orientation varied with increasing ambient gas pressure. The variation in the film orientations also depended on the type of substrate. An explanation of the cause of variation in the film orientation with the deposition pressure was attempted in relation to the ionic species near the substrate during deposition.
Influence of As/Al and Sb/Al Gas Flow Ratios on Growth of AlAs1-xSbx Alloys
Authors: Wei-Kuo Chen Wei-Kuo Chen , Jehn Ou Jehn Ou
Published: October 2002

AlAs1-
x

Sb

x

epilayers were grown on InP (100) substrates using the metalorganic chemical vapor epitaxial growth technique. Experimental results demonstrate that the solid concentration of AlAsSb is more naturally expressed as a function of the input As/Al partial pressure ratio, and not of the V/III ratio or the Sb mole fraction in group V used during the growth. In fact, the AlAs solid concentration and the input partial pressure ratio of As to Al are proportional to each other. According to the phase diagram described above, the controllability of the solid concentration of AlAsSb could be improved.
Physics and Control of Conduction Type in CuInS2with Defect Chalcopyrite Structure
Authors: Yamamoto Tetsuya , Katayama-Yoshida Hiroshi
Published: October 2002

We have studied the influence of intrinsic defects, cation vacancies (VCu, VIn) and anti-site defects (InCu, CuIn), on the bandstructure of nonstoichiometric CuInS2based upon theab-initioelectronic band-structure calculations using the augmented spherical wave (ASW) method. We have found that an energy shift of the center of gravity of S 3pband is a key parameter for controlling change in the type of conductivity. Inp-type crystals (VCu, CuIn, and VIn), we have clarified an increase in the strength of the interaction between Cu 3dstates and S 3pstates caused by a weight shift of the S 3pband towards higher energies in contrast to that inn-type (InCu).
Coumarin-4-Doped Sol-Gel Coating Film as Optical pH Sensor
Authors: Takahashi Yoshihiro , Shimada Ryuichi , Maeda Akinori , Kojima Kenzo , Ota Hiroshi
Published: October 2002

Coumarin 4, a pH indicator, was entrapped in a silica matrix coated as a thin film onto a silica substrate by the sol-gel technique. The absorbance and fluorescence changes of the immobilized indicator were examined in the pH sensing range. The increase in absorption and fluorescence intensities as the acid form of the immobilized coumarin 4 is converted to its basic form, is dependent on pH.
The dynamic range and the response time of this probe were pH 3-9 and less than 10 s, respectively.
Electronic NO 2 Sensor Using Merocyanine-Doped Langmuir Blodgett Films
Authors: Masayuki Morisawa Masayuki Morisawa , Shunya Morita Shunya Morita , Shinya Sakamoto Shinya Sakamoto , Shinzo Muto Shinzo Muto , Hiroshi Ito Hiroshi Ito
Published: October 2002

The NO2 sensor using merocyanine-doped Langmuir-Blodgett (LB) films, the mechanism of which is based on a change in surface conductivity due to the attachment of electrophilic gas molecules, was investigated. Its sensitivity depended on the number of LB layers. The sensor with 5 layers was most sensitive and had a very fast response time of less than 5 s, good reproducibility and maximum sensitivity in the low NO2 concentration range of 0 to 10 ppm.
Light Pulses Emitted at Microfractures Formed by Friction between Two Solid Materials
Authors: Yamashita Tadaoki , Imasato Katsusaburou , Nagashima Naoyuki Haraguchi
Published: October 2002

Short-duration light pulses have been observed to be emitted at the moment of microfracture (pit size of 10-20 µm) when two solids are rubbed against each other. When a fused silica sample is scratched by a diamond grain, the observed light pulses have a rise time of less than 10 ns and pulse width of 10-20 ns. A continuous spectrum at 500-800 nm is observed, suggesting 3000° C material part. At 300-400 nm, intense line spectra are observed, which suggests the existence of gaseous *O2 molecules desorbed from SiO2. When the solid fractures, the fractured part heats up to a very high temperature almost instantaneously, and cools down within 10-20 ns.
Enhanced Critical Current in Tl-Ba-Ca-Cu-O Superconductors Prepared by Diffusion Process with Fluorine Addition
Authors: Kikuchi Akihiro , Kinoshita Takashi , Nishikawa Naohiro , Komiya Seiki , Kyoji Tachikawa Kyoji Tachikawa
Published: October 2002

In the Tl-Ba-Ca-Cu-O (TBCCO) diffusion composites, critical current (I
c) at 77 K is significantly improved by fluorine (F) addition to the coating layer. The F addition decreases the degradation of I
c under magnetic field at 77 K, and shifts the irreversibility lines to higher temperatures. The X-ray diffraction study reveals that F addition promotes the phase transformation from 2223 to 1223. Meanwhile, annealing in flowing O2 at 550° C-600° C also increases I
c at 77 K.
O2 annealing seems to improve the weak links between superconducting grains. The largest transport critical current density (J
c) of the specimen with F addition and O2 annealing exceeds 10000 A/cm2 at 77 K.
In the present TBCCO diffusion composites with F addition, the effect of phase transformation on I
c performance has been clearly observed.
Thermal Expansion and Surface Elasticity in Langmuir Films of Myristic Acid
Authors: Sakamoto Takaaki Tokui , Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: October 2002

Ripplon light scattering experiments were conducted on the surface of water on which a molecular monolayer of myristic acid was spread in the coexistence state of liquidlike condensed phase and gas phase. The condensed phase was distinguished from the gas phase by the observed surface elasticity, ε\cong 10 mN/m. The temperature dependence of its total area gave the linear thermal expansion coefficient of the film to be 0.23×10-2 K-1 at 20-25° C, which is in good agreement with the value estimated from the static pressure-area isotherms. The surface elasticity showed a monotonous decrease towards 0 as the temperature increased to 40° C, implying a possibility of the critical phenomenon.
Contrast of Atomic-Resolution Images from a Noncontact Ultrahigh-Vacuum Atomic Force Microscope
Authors: Ohta Masahiro , Ueyama Hitoshi , Morita Yasuhiro Sugawara
Published: October 2002

Contrast variations of atomic-resolution images were investigated on an InP(110) surface using an ultrahigh-vacuum atomic force microscope (UHV-AFM) in the noncontact mode. The contrast of the atomic-scale AFM image suddenly changed during scanning, which seems to be due to the positional change of the atoms on the tip apex. We observed atomic-scale point defects. These phenomena seem to occur only in monoatomic tip-sample interaction. We also observed an atomic-scale dark area which seems to be due to the convolution of the atomically flat tip and point defects.
Dynamics of Trapped Ions in the Presence of Laser Cooling and Radio-Frequency Heating
Authors: Yoshiharu Maeno Yoshiharu Maeno , Maki Tachikawa Maki Tachikawa , Yoshiki Moriwaki Yoshiki Moriwaki , Tadao Shimizu Tadao Shimizu
Published: October 2002

We establish a theoretical model which quantitatively describes the dynamics of laser cooled ions confined in a radio-frequency (rf) trap. In our model the laser cooling efficiency and the rate of collisional radio-frequency (rf) heating are explicitly formulated. Considering the balance between these two effects, the ion temperature is determined at each trap parameter. This model precisely reproduces the laser-induced-fluorescence (LIF) line profile observed for 24 Mg+ ions.
Formation of Fine Particles of Zinc Sulfide from Thiourea Complexes by Spray Pyrolysis
Authors: Tohge Noboru , Tamaki Shinkichi , Okuyama Kikuo
Published: October 2002

Fine particles of ZnS were able to be prepared by ultrasonic spray pyrolysis of an aqueous solution containing Zn(NO3)2 and SC(NH2)2 in appropriate molar ratios, the carrier gas being N2. The particles obtained were spherical with smooth surfaces ranging from 0.5 to 1.3 µ m in diameter. Their crystalline phase was hexagonal when deposited at around 800° C; the particles obtained at low temperatures such as 400° C were amorphous, whereas the pyrolysis at 900° C produced ZnS particles including a zinc oxide phase.
Characteristics of Field-Induction-Drain (FID) Amorphous-Silicon Thin-Film Transistors
Authors: Tanaka Keiji , Kinya Kato Kinya Kato
Published: October 2002

The field-induction-drain (FID) structure is adopted to amorphous silicon (a-Si) thin-film transistors (TFTs). An OFF current of 1.5×10-16 A/µ m (V
DRAIN=10 V, V
GATE=-20 V) and an ON/OFF current ratio of 109 are achieved by the FID a-Si TFT.
Measurement of the OFF current characteristics proves that the OFF current of the FID TFT is dominated by generation-recombination current, not by field-emission current. The FID structure is very promising for reducing anomalous leakage current and obtaining high ON/OFF current ratio.
ESR Characterization of CuAlSe2 Single Crystals
Authors: Nishikawa Nobuyuki , Kai Tetsuya , Aksenov Igor , Sato Katsuaki
Published: October 2002

High-quality single crystals of CuAlSe2 were grown by the chemical vapor transport technique starting from a polycrystalline CuAlSe2 powder prepared by heating constituent elements above their melting points. The defect states of the crystals were characterized using photoinduced ESR technique at 120 K.
An isotropic ESR signal “A” due to a hole trapped by an acceptor was found at the g value of 2.032. The activation energy obtained from the temperature-quenching curve of the A-signal was 40 meV±10 meV. This value was consistent with the level position determined from the difference between the band gap and the peak position of the excitation spectrum of the A-signal. The signal was tentatively assigned to a hole trapped by the Cu vacancy.
Interfacial Degradation of Insulator/YBa2Cu3Oy Heterostructure due to Mutual Diffusion of Constituent Atoms
Authors: Takeshi Ashida Takeshi Ashida , Shingo Tomohisa Shingo Tomohisa , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

The interfacial degradation of the insulator (SrTiO3, BaTiO3, PbTiO3, and BaO etc.)/YBa2Cu3Oy heterostructures during excimer-laser deposition and subsequent annealing has been investigated. The secondary-ion mass spectroscopy (SIMS) measurement revealed, though very crudely, the mutual diffusion of constituent atoms. More precise data have been obtained quantitatively by measuring the change of the zero-resistance temperatures T
c0's (Kosterlitz-Thoules transition) of ultrathin YBa2Cu3Oy before and after deposition of the insulating layers and annealing. The interfacial degradation developed with time t as t
∼0.4, reflecting the thermal diffusion of constituents. The degradation also depended on the partnering insulating layer, i.e., it was minimized by BaTiO3 and PbTiO3 (lower-melting-point insulators).
Electron Spin Resonance Isochrone Dating of Fracture Age: Grain-Size Dependence of Dose Rates for Fault Gouge
Authors: Ikeya Motoji , Tani Atsushi , Chihiro Yamanaka Chihiro Yamanaka
Published: October 2002

A new isochrone method of electron spin resonance (ESR) dating has been proposed utilizing the different average dose rates of external radiation for different grain sizes due to the range of external α- and β-rays. The equivalent doses (E
D s) obtained by the additive dose method were plotted as a function of the external dose rate (D
ex) corrected for the grain sizes. The slope gives an ESR isochrone age since the fracture (T
fra) or the surface formation; the coordinate abscissa gives the internal dose (D
in
T
for) where D
in is the internal dose rate and T
for is the age of the mineral formation. The method has been applied to quartz ( SiO2) grains in geological fault gouge at outcrops of the Rokko Fault giving T
fra=102,000 years and T
for of nearly zero for grains less than 100 µ m.
Impact Ionization in 0.1 µ m Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Kurata Hajime , Nara Yasuo , Toshihiro Sugii Toshihiro Sugii
Published: October 2002

The impact ionization rate in a silicon metal-oxide-semiconductor field-effect transistor (MOSFET) is universally plotted on a simple straight line when l
n(I
sub/I
d) is plotted versus 1/(V
ds-V
dsat). V
dsat is the drain saturation voltage. However, we found a deviation from this universal relationship for different gate voltages applied to the MOSFETs fabricated by 0.15 µ m technology. We show that the deviation is due to the gate-voltage dependence of the saturation electric field E
sat, which results from the degradation of the effective surface mobility µ eff. The new method for finding a universal relationship is proposed.
A Missing Link is Found: a Novel Homologous Series of Superconducting Pb-Based Cuprates
Authors: Yamauchi Hisao , Tamura Toshiyuki , Wu Xiao-Jing , Adachi Seiji , Shoji Tanaka Shoji Tanaka
Published: October 2002

A new Pb-based superconductor containing the Pb-1223 phase has been successfully synthesized by means of a high-pressure technique. Bulk superconductivity has been detected at temperatures below 115 K.
This means that a new superconducting homologous series, Pb-12(n-1)n, exists. To date, there exist homologous series of superconducting layered cuprates for each of the M-(Ba, Sr)-Ca-Cu-O systems where M stands for an element with the atomic number between 80(Hg) and 83(Bi) except 82(Pb)–a missing link. This missing link has been found.
A Samarium-Iron Nitride Magnet Fabricated by Shock-Compaction Technique
Authors: Oda Hideaki , Kondo Ken-ichi , Uchida Hirohisa , Matsumura Yoshihito , Tachibana Shingo , Kawanabe Takashi
Published: October 2002

A samarium-iron nitride Sm2Fe17N3 powder was shock-consolidated by using a propellant gun with metal-plate impactor system. Disk-like magnets were consolidated under each experimental condition. At an optimum condition in this study, apparent density of shock-compacted Sm2Fe17N

x

magnets was 97% of solid density, and X-ray diffraction patterns of these magnets showed no appearance of the decomposition of rhombohedral Sm2Fe17N

x

structure. The highest value of the maximum energy product obtained so far was 10.5 MG·Oe. Microstructural analyses suggested the possibility of improving magnetic properties of the magnets.
Application of Amorphous Flake to Electromagnetic Interference (EMI) Noise Filter
Authors: Ishii Osamu , Senda Masakatsu , Takei Koji , Mori Toshinori
Published: October 2002

This paper describes the application of a Co-based amorphous alloy flake to a common-mode noise filter. Saturation magnetization and relative permeabllity are measured to be 7000 G and 1150, respectively. The amorphous flake exhibits high loss characteristics; the resistance of a 0.0065 cm3 amorphous flake increases from 0.14 Ω at 1 MHz to 2.2 Ω at 1 GHz as the frequency is increased. It is confirmed that a filter of 1/7 the volume of a conventional filter (ferrite core) exhibits the same noise attenuation in the 10 MHz∼1 GHz frequency range.
Temperature Dependence of the Photorefractive Effect in Proton-Exchanged Optical Waveguides Formed on Lithium Tantalate Crystals
Authors: Kondo Yukiko , Yoichi Fujii Yoichi Fujii
Published: October 2002

Temperature dependence of the photorefractive effect in proton-exchanged waveguides formed on lithium tantalate crystal is investigated. The index change induced by the photorefraction is reduced by the annealing process. Resistance to the photorefractive effect is greatly improved when the samples are heated at temperatures as high as 80° C. In the low-intensity region, the dark conductivity seems to be dominant in the photorefractive effect.
Increase of Leakage Current and Trap Density Caused by Bias Stress in Silicon Nitride Prepared by Photo-Chemical Vapor Deposition
Authors: Matsuura Hideharu , Yoshimoto Masahiro , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

Leakage current at low electric fields in silicon nitride ( SiN
x
) prepared by photo-chemical vapor deposition is increased by bias stress. Discharging current transient spectroscopy (DCTS) for determining the density and energy distribution of traps in insulators is applied to the study of the change of traps by bias stress. After holes of 2.6×10-2 C/cm2 are injected into SiN
x
, the densities of single-level traps ( ∼0.80 eV) and energetically distributed traps located between 0.83 eV and 0.90 eV above the top of the valence band in SiN
x
increase, which could result in the increase of leakage current.
Quantum Well Infrared Photodetector with Optical Output
Authors: Ershov Victor Ryzhii , Maxim Ryzhii Maxim Ryzhii , Irina Khmyrova Irina Khmyrova
Published: October 2002

A quantum well infrared photodetector which converts long-wavelength infrared radiation into short-wavelength infrared (or visible) radiation is considered. The quantum well infrared photodetector utilizes an intraband absorbtion of radiation in a quantum well in the emitter and interband emission in either classical or quantum well in the collector. It is shown that the efficiency of energy conversion of short-wavelength radiation into long-wavelength radiation can be about unity.
Trapping and Low-Energy Extraction of Photodissociated Ions of SF6
Authors: Yamamoto Seiji , Mochiji Kozo , Mikami Naohiko
Published: October 2002

This paper describes a technique for spatially confining mass-selected ions and extracting them to a solid surface at low kinetic energy. This technique combines rf ion trapping with multiphoton ionization by a KrF excimer laser. SF5+ions photodissociated from SF6were separated from other ionic species and stored in the cylindrical ion trap cell for at least 100 ms. The stored ions were extracted onto the surface with low kinetic energies around 10 eV. This technique should be useful for studying surface reactions with mass-selected, state-specified, and very-low-kinetic-energy ions and for developing etching processes that can be used to control the surface structure of semiconductors on an atomic scale.
Characterization of Chemically Vapor Deposited Silicon Nitride Films from Disilane and Ammonia
Authors: Henda Redhouane , Laanab Larbi , Scheid Emmanuel , Fourmeaux Robert
Published: October 2002

Amorphous silicon nitride films a:SiN

x

were prepared by low pressure chemical vapor deposition (LPCVD) from disilane ( Si2H6) and ammonia ( NH3). Most of the depositions were performed at 600° C with various NH3/Si2H6 gas ratios ranging from 4 to 50. Different deposits with composition (x= N/Si) ranging from silicon-rich to stoichiometric silicon nitride were characterized by means of infrared spectroscopy (FTIR), ellipsometry, electron energy loss spectroscopy (EELS), and their structure analysed by transmission electron microscopy (TEM). Transmission infrared measurements showed low hydrogen content (<4.7%) in all the deposited films. Changes in atomic ratio (x= N/Si) and density of the films were correlated with their refractive index and discussed.
Simple Direct Monitoring of SiH3Radical and Particulates in a Silane Plasma with Ultraviolet Transmission Spectroscopy
Authors: Toyoda Hirotaka , Goto Masashi , Kitagawa Masatoshi , Hirao Takashi , Hideo Sugai Hideo Sugai
Published: October 2002

The silyl radical ( SiH3) in a H2/SiH4rf plasma is successfully detected by an easy and inexpensive method, i.e., high-sensitivity ultraviolet transmission spectroscopy (UVTS). The diffusive absorption band of the SiH3radical is observed in the 205-240 nm region. The relative SiH3density is measured as a function of RF power from 20 to 100 mW/ cm2by UVTS. The UV transmittance is very sensitive to particulates in the plasma, thus enabling both particulates and SiH3radicals to be monitored simultaneously.
Carbon Doping in AlGaAs Using Trimethylarsine by Metalorganic Chemical Vapor Deposition with a High-Speed Rotating Susceptor
Authors: Watanabe Noriyuki , Ito Hiroshi , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

We have investigated for the first time carbon (C) doping in AlGaAs using trimethylarsine (TMAs) as an arsenic source by metalorganic chemical vapor deposition with a high-speed rotating susceptor. Hole concentration decreases with increasing growth temperature and V/III ratio, and increases with increasing Al composition. These dependencies of the hole concentration on the growth conditions and the Al composition in AlGaAs are explained by a model which assumes that the thermal decomposition of precursor molecules in the gas phase is considerably suppressed.
Color-Variable Electroluminescent Diode with Single Quantum Well Structure Utilizing 8-Hydroxyquinoline Aluminum and Aromatic Diamine
Authors: Fujii Akihiko , Yoshida Masayoshi , Ohmori Yutaka , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A color-variable electroluminescent diode has been realized utilizing a 1-nm-thick dye molecule layer with single-quantum-well (SQW) structure. The electroluminescent (EL) spectrum changes with increasing applied voltage from 8 V to 20 V.
The result is discussed in terms of the shift of the recombination region toward the ITO electrode, depending on applied voltage.
Computer Simulation of Fatigue in Ferroelectric Thin Films by a Modified Diffusion Limited Aggregation Model with Drift
Authors: Li Xingjiao , Liu Jianshe , Lu Dexin , Zhao Jianhong , Huang Longbo , Jiangde Xuan Jiangde Xuan
Published: October 2002

Two-dimensional computer simulation of fatigue in ferroelectric thin films has been carried out by using a modified diffusion limited aggregation model with drift. The simulation shows that the fatigue process follows a power-law at early time regime and speeds up dramatically at later time regime. It has been revealed that both the fatigue endurance value and the average value of fractal dimension of the fatigued units pattern increase as the drift strength increases.
Effect of Electron Beam Irradiation on Si Surface Cleaning in Ultrahigh-Vacuum System
Authors: Hiroshi Miura Hiroshi Miura , Kouichi Ohtaka Kouichi Ohtaka , Daisuke Shindo Daisuke Shindo
Published: October 2002

Effect of electron beam irradiation (15 kV) on Si surface cleaning prior to epitaxial growth in an ultrahigh-vacuum system was investigated. A CaF2 film was epitaxially grown on the Si surface, and the interface was observed by high-voltage electron microscopy. Amorphous layers, which were observed in the interface prepared with conventional thermal treatment at 750°C, became much smaller with electron beam irradiation after the thermal treatment. Based on the electron microscope observation, the effect of electron beam irradiation on Si surface cleaning was briefly discussed.
Electron Tunneling through Chemical Oxide of Silicon
Authors: Saito Kenji , Matsuda Masanori , Yasutake Masatoshi , Takeo Hattori Takeo Hattori
Published: October 2002

Carrier transport between gold and n+-Si through chemical oxides of Si was measured for the first time using an atomic force microscope with a conducting probe. It was found from the theoretical calculation of carrier transport in 0.7-nm-thick chemical oxide formed in a mixed solution of H2SO4and H2O2that the carrier transport can be explained as a direct tunneling of electrons through chemical oxide.
Estimation of Surface Tension of Molten Silicon Using a Dynamic Hanging Drop
Authors: Chung Sang-Ik , Izunome Koji , Yokotani Atsushi , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

A new method to determine the surface tension of high-temperature liquids was developed using the rotation of a hanging drop. The measurement of surface tension of silicon melt was performed by observing the oscillation of a silicon droplet hanging from a SiC-coated carbon rod. The oscillation of the liquid drop was induced by a sudden high rotation speed above 570 rpm. The surface tension of molten silicon was estimated as 0.819 N/m at the melting point of 1415° C and its temperature coefficient was -0.308×10-3 N/mK. We concluded that the dynamic hanging drop method could be used to measure the surface tension of high-temperature liquids.
Strain Analysis in Fine Al Interconnections by X-Ray Diffraction Spectrometry Using Micro X-Ray Beam
Authors: Yamamoto Naoki , Sakata Shinji
Published: October 2002

An energy dispersive diffraction X-ray spectrometer with a sub-micron X-ray beam is developed to analyze crystalline structures in micro-regions of ULSIs. It is used to analyze strain in fine Al interconnections. The strain (ε) in lines with Al single-layer structures showed a dependence on the line width (W)=ε
-0.8 at W below 1.5 µ m. The origin of these strains is mainly intrinsic stress in Al films and thermal stress caused by differences in the coefficients of thermal expansion between Al and Si. Introducing barrier metals reduces the dependence of strain in an Al layer on the line width.
Tunable Single Frequency Erbium Doped Fiber Ring Lasers Using Fiber Grating Etalons
Authors: Komukai Tetsuro , Masataka Nakazawa Masataka Nakazawa
Published: October 2002

Single wavelength operation was demonstrated in an erbium doped fiber ring laser consisting of an optical circulator and a Fabry-Perot etalon formed by two identical fiber gratings. Simultaneous operation at two wavelengths has been achieved in a ring laser which incorporates two Fabry-Perot etalons.
Read/Write Characteristics of MnBi Magneto-Optical Disk Fabricated on Photo-Polymer Substrate
Authors: Nakada Masafumi , Mitsuya Okada Mitsuya Okada
Published: October 2002

A quadrilayer MnBi magneto-optical disk on a photo-polymer (2P) substrate has been fabricated by a low-temperature growth method. Magneto-optical properties and read/write characteristics for the 2P MnBi disk are confirmed to be comparable to those of a glass MnBi disk annealed at 380° C. The carrier to noise (C/N) ratio for the 2P MnBi disk is 20 dB lower than that of a conventional TbFeCo disk because of its high disk noise. While the Kerr rotation angle at the flat area of the MnBi disk is three times that for a TbFeCo disk, the carrier level is about 1 dB lower. Controlling the Bi layer morphology in the groove area will be the most important factor in achieving future improvement of the C/N ratio for MnBi magneto-optical disks.
Electrically Pumped CdZnSe/ZnSe Blue-Green Vertical-Cavity Surface-Emitting Lasers
Authors: Yokogawa Toshiya , Yoshii Shigeo , Tsujimura Ayumu , Sasai Yoichi , Merz James
Published: October 2002

We demonstrate an electrically pumped CdZnSe/ZnSe blue-green vertical-cavity surface-emitting laser (VCSEL) with a SiO2/TiO2 dielectric multilayer mirror. Electrically pumped lasing was achieved at 77 K with a threshold current of 3 mA (pulsed). A low far-field radiation angle of 7° was observed above the threshold in a 10-µ m-diameter device, which indicates the spatial coherence expected for lasing.
Novel Proton-Gated Optical Transistor Devices
Authors: Zen Yang Hwang , Chong Mou Wang Chong Mou Wang
Published: October 2002

An optical rectifier device is fabricated with thin-film 2-pyridylcarboxylic acids. The initially inactive redox centers, pyridyl nitrogens, become activated under 260 nm illumination. This photoelectrochemical behavior is ascribed to the photoinduced proton transfer reactions, via which the pyridyl nitrogens behave as stronger bases than their counterpart ground states, and trigger a substantial cathodic current to flow. The drain current is gate-potential (V
G) and drain-voltage (V
D) dependent; the optimized current collection is ca 50% at V
G=-0.62 V vs SCE and V
D=+0.6 V vs the emitter. The signal rectification efficiency reaches 0.012 with 2-pyridylacetic acid under 260 nm illumination.
SrS:Ce Thin Films on Different Insulating under Layers
Authors: Tanoue Huan Yang , Hibino Satoshi , Sakakibara Shingo , Yokoi Katuyuki , Tadahiko Hotta Tadahiko Hotta
Published: October 2002

SrS:Ce thin films were prepared on several kinds of insulating underlayers, Ta2O5, SiO2, Si3N4 and their composite films, by hot wall deposition. The crystallinity of the SrS:Ce films was found to depend strongly upon the underlayers, although no crystal structures were confirmed for the underlayers. The SrS:Ce films grown directly on Ta2O5 layers gave the best crystallinity, and better luminance levels were also obtained for their electroluminescent devices, due to both the large dielectric constant of Ta2O5 and good crystallinity of the SrS:Ce films.
Photo-Induced Alignment and Patterning of Hybrid Liquid Crystalline Polymer Films on Single Substrates
Authors: Schadt Martin , Seiberle Hubert , Schuster Andreas , Stephen M. Kelly Stephen M. Kelly
Published: October 2002

By means of photo alignment and simultaneous cross-linking of linearly photopolymerizable (LPP)-polymers we have succeeded in generating uniaxial planar alignment in adjacent liquid crystal polymer (LCP)-films deposited on single LPP-substrates. It became thus possible to design optically anisotropic and photopatternable hybrid layers of LPP- and LCP-films on single substrates. Hybrid photopolymer configurations were made and are shown to render high resolution optical phase retarder images feasible. The new technology opens-up the possibility to generate and photopattern polarization interference color filters and color compensators integrated directly on liquid crystal display substrates. Moreover, the technology is the basis for new copy proof optical devices.
Structural Study of Chemical-Vapor-Deposited Diamond Surface by High-Resolution Electron Microscopy
Authors: Nan Jiang Nan Jiang , Akimitsu Hatta Akimitsu Hatta , Jaihyung Won Jaihyung Won , Yusuke Mori Yusuke Mori , Toshimichi Ito Toshimichi Ito , Takatomo Sasaki Takatomo Sasaki , Akio Hiraki Akio Hiraki
Published: October 2002

A structural study of the chemical-vapor-deposited (CVD) diamond surface using high-resolution electron microscopy (HREM) is presented. The CVD diamond used for HREM study was directly deposited onto molybdenum grids by a microwave plasma-assisted chemical vapor deposition method. The HREM images reveal a thin amorphous layer of which average thickness is about 0.8–1.2 nm on the as-grown diamond surface, whereas the average thickness of the surface amorphous layer is decreased to less than 0.4–0.5 nm for the samples annealed in air following deposition. When the samples annealed in air were exposed to hydrogen plasma for 10 min, a distinct damaged layer on the diamond surface was observed. HREM study demonstrates that such a damaged layer consists of amorphous solid and small diamond bumps, and its thickness is about 1.5–2 nm. It is also found that hydrogen plasma has a much higher etching speed in the rough regions, edges and protuberances than that in the smooth regions on the diamond surface.