bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Strain Compensation on Crystalline Quality for InGaAs/InAlP Strained Multiple Quantum Well Structures on InP Grown by Gas-Source Molecular Beam Epitaxy
Authors: Naniwae Kouichi , Shigeo Sugou Shigeo Sugou , Takayoshi Anan Takayoshi Anan
Published: October 2002

Crystalline quality is investigated for highly compressive strained multiple quantum well (MQW) structures, with and without strain compensation. Strain compensation is created by tensile strain in the barrier layers of the InGaAs/InAlP system grown by gas-source molecular beam epitaxy on InP substrates. Detailed invesligations on the effects of strain compensation on the structural properties, optical properties and thermal stability for strained MQWs show that strain compensation produces high-quality strained MQW with very few misfit dislocations and excellent thermal stability. Strained MQWs without strain compensation have many misfit dislocations which are enhanced by thermal annealing.
Hydrogen Passivation of Carbon Acceptors in AlAs Grown by Atomic Layer Epitaxy
Authors: Haruki Yokoyama Haruki Yokoyama , Naohisa Inoue Naohisa Inoue
Published: October 2002

Hydrogen incorporation and passivation of the carbon acceptors in AlAs grown by atomic layer epitaxy are examined. It is shown that about the same amount of hydrogen as that of carbon impurities are contained in the epilayer, whereas the hole concentration is more than two orders of magnitude lower than the carbon concentration. The carbon acceptor bonds to the hydrogen and is passivated by it. Annealing, especially in nitrogen, removes the hydrogen and causes recovery of the electrical activation of carbon acceptors. The hydrogen is found to originate from the alkyl groups of trimethylaluminum (TMA), not from arsine or the carrier gas.
Heterodyne Spectroscopy Using Spectral Spread of Short Laser Pulse
Authors: Sugimoto Nobuo , Minato Atsushi , Saito Yasunori , Nomura Akio
Published: October 2002

A heterodyne absorption spectroscopy method which utilizes the spectral spread of a short laser pulse was demonstrated with laser pulses generated by an electrooptic modulator from a frequency-stabilized He–Ne laser. The spectrum of a Michelson interferometer was observed by the method in a spectral bandwidth of approximately 100 MHz.
Atomic Force Microscopy of Isotactic Polystyrene Crystals
Authors: Izumi Kunihide , Ping Gan , Toda Akihiko , Miyaji Hideki , Hashimoto Masato , Miyamoto Yoshihisa , Nakagawa Yoshitsugu
Published: October 2002

The growth of isotactic polystyrene crystals from a thin melt film is examined by atomic force microscopy. The crystals protrude from the film up to about 100 nm to form a hexagonal spiral with a hollow screw dislocation at the center; the distance between neighboring steps of the growth spiral is discussed on the basis of the critical nucleus. The entire crystal has collapsed to the substrate. An amorphous layer a few nanometers thick covers the surface of the crystal. At the crystal-liquid interface, a concave region about 2 nm deep extends ca. 400 nm.
Study of the Growth Mechanism of Nanocrystalline Si:H Films Prepared by Reactive Hydrogen Plasma Sputtering of Silicon
Authors: Sun Yong , Nishitani Ryusuke , Miyasato Tatsuro
Published: October 2002

The growth mechanism of hydrogenated nanocrystalline silicon (nc-Si:H) films prepared by reactive hydrogen
plasma sputtering of silicon has been studied by means of X-ray diffraction, Raman scattering, and infrared
absorption (FT-IR) measurements and SEM observation, and by the diagnosis of the plasma. The nc-Si:H films
obtained consist of aggregations of nanocrystalline silicon surrounded by hydrogen atoms. We have found that
growth rate and various properties of the nc-Si:H films such as grain size, hydrogen content and morphology are
associated both with the incident flux densities of hydrogen ions and the SiH
x
(x=0–4) species.
Variation of Photoluminescence Properties of Stain-Etched Si with Crystallinity of Starting Polycrystalline Si Films
Authors: Higa Katsuya , Miyasato Tanemasa Asano
Published: October 2002

We have studied the relationship between the photoluminescence property and crystallinity of stain-etched
polycrystalline Si (poly-Si) films. Poly-Si films having different crystallite size were prepared on SiO2 by electron
beam evaporation of amorphous Si with subsequent annealing in the temperature range of 600–900°C. Porous
Si layers were formed by stain etching of these poly-Si films. It has been found that the size of nanocrystallites
in the porous Si layer is independent of the crystallite size of poly-Si and appears to be almost a constant value
(about 5 nm). However, the photoluminescence peak wavelength became shorter as the crystallite size in the
poly-Si films before stain-etching was increased, and the photoluminescence intensity became stronger as the
density of crystallites in stain-etched poly-Si films was increased.
Ion Trapping by External Field of AC Electrical Quadrupole Superimposed on Static Attraction
Authors: Kanayama Toshihiko
Published: October 2002

This paper proposes a new type of ion trap, which uses the external field of two-dimensional ac quadrupole
superimposed on an attractive monopole dc field. It is demonstrated by theoretical calculation and numerical simula-
tion that the present trap accepts charged particles with a wide range of mass values without the need for adjusting the trapping parameters. This feature has been verified by trapping experiments using Xe and He ions.
Production of Fullerenes by Low Temperature Plasma Chemical Vaper Deposition under Atmospheric Pressure
Authors: Inomata Kiyoto , Aoki Nobuyuki , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

A gas phase reactor developed for generating homogenous low temperature plasma under atmospheric pressure was found to provide a new method for producing fullerenes by a plasma chemical vapor deposition (CVD) process. Into an afterglow region of atmospheric pressure Ar–He mixed gas plasma, an aromatic hydrocarbon was introduced and decomposed into black soot under appropriate reaction conditions. A benzene solution of the soot showed two clear HPLC peaks with retention times corresponding well to those of C60 and C70. The formation of C60 was further confirmed by UV spectroscopy.
First Observation of Negative Differential Resistance in Surface Tunnel Transistors
Authors: Tetsuya Uemura Tetsuya Uemura , Toshio Baba Toshio Baba
Published: October 2002

Negative differential resistance (NDR) due to an interband tunneling has been observed at room temperature for the first time in a Surface Tunnel Transistor (STT) under forward-bias conditions. To produce clear NDR characteristics, the electron density in the channel was designed to be high enough to induce band overlap at the channel/drain junction. In order to increase the tunneling current further, a channel doped structure, in which a thin n+-GaAs layer was inserted between a p+-GaAs layer (drain) and an i-GaAs layer, was proposed. This channel doped STT exhibited a peak current density of 8 µ A/µ m, which is 280 times larger than that of the conventional STT.
Effects of Substitution by Group Ia and IIIa Elements on Superconducting Properties of YBa2Cu3Oy
Authors: Tatsumi Yukichi , Fujiwara Fumihiko Kimura
Published: October 2002

Physical properties of (Y1-
x

M

x

)Ba2Cu3O

y

and Y(Ba1-
x

M

x

)2Cu3O

y

(M=K, Rb, Cs, Sc and La) were studied. It is shown that the temperature difference ΔT between the onset and the zero of the resistivities due to the superconducting transition depends on the valence and ionic radius of substituting elements. The maximum magnetization of the hysteresis loop is analyzed by the T
4 dependence based on the two-fluid model. It is determined that the critical temperatures T
c due to these substitutions are the same or slightly higher than that of YBa2Cu3O

y

. The substitution of group IIa elements seems to be effective for pair-breaking.
New Oxide Phase Cd2(1-x)Y2xSb2O7 Pyrochlore with a Wide Band Gap and High Electrical Conductivity
Authors: Yanagawa Kazuhiko , Ohki Yoshimichi , Omata Takahisa , Hosono Hideo , Ueda Naoyuki , Kawazoe Hiroshi
Published: October 2002

It was found for the first time that the electrical conductivity of Y-substituted Cd2Sb2O7, Cd2(1-
x
)Y2
x

Sb2O7, with the pyrochlore structure, is larger than at least 3.3×100 Scm-1 and the optical band gap of the sample is wider than 3.5 eV. These values indicate that Cd2(1-
x
)Y2
x

Sb2O7 pyrochlore has a characteristic of a transparent conductor.
Effect of Light Irradiation on Sulfide-Treated GaAs with SiO2 Deposition
Authors: Ko Hyun-Chul , Kenji Uchida Kenji Uchida , Shin'ichi Nakatsuka Shin'ichi Nakatsuka
Published: October 2002

The degradation mechanism of sulfide-treated and SiO2 deposited GaAs has been studied. The sulfide treatment removes the oxide of GaAs and Ga-dangling bonds, and increases the intensity of photoluminescence. However, by the irradiation of UV light or Ar+ laser, the photoluminescence intensity is reduced substantially. X-ray Photoelectron Spectroscopy (XPS) analysis and C-V measurement show that the Ga–S bonds generated by the sulfide treatment become Ga-dangling bonds due to the light irradiation. We believe this is the reason why the photoluminescence intensity decreases, and therefore, it is necessary to avoid light irradiation after sulfide treatment and SiO2 deposition on GaAs in order to maintain the surface-passivation effect.
Large Induced Absorption Change in Porous Silicon and Its Application to Optical Logic Gates
Authors: Matsumoto Takahiro , Hasegawa Noboru , Tamaki Teruyuki , Ueda Kenji , Futagi Toshiro , Kanemitsu Hidenori Mimura
Published: October 2002

A large optically induced absorption change was observed in porous silicon. The relative intensity change of the transmitted beam is on the order of 50%. Using this phenomenon, we have demonstrated all-optical logic gates such as inverters or NOR functions. These results point to the possibility of fabricating all-optical integrated circuits on a Si substrate.
Optical and Magnetic Properties of Polyaniline Derivatives Having Ionic Groups
Authors: Kawai Tsuyoshi , Mizobuchi Hiroshi , Yamasaki Nobuo , Hisashi Araki Hisashi Araki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Copolymers of aniline and sulfonated anilines prepared by electrochemical polymerization show pH-dependent absorption spectra such as for the pure polyaniline, except for the difference in critical pH value of the chromic phenomenon. Dependences of electron spin resonance (ESR) spectra of the copolymers corresponding to the polaronic state on solution pH also suggests that protonation and deprotonation of the nitrogen atom occurs in a pH range different from that of polyaniline, and is attributed to effects of the self-doping of sulfonic acid group in the protonated form. ESR spectra of the copolymers show anomalous temperature dependence which is similar to that of antiferromagnetic material. Copolymers of aniline with sulfonated aminonaphthalenes also exhibit antiferromagnetic behavior.
Enhancement of Nitrogen Incorporation in ZnSe Grown on Misoriented GaAs Substrates by Molecular Beam Epitaxy
Authors: Nishikawa Yukie , Ishikawa Masayuki , Shinji Saito Shinji Saito , Gen-ichi Hatakoshi Gen-ichi Hatakoshi
Published: October 2002

Nitrogen incorporation and electrical activity have been investigated for ZnSe grown on GaAs substrates (100) oriented and misoriented 15° toward the [011] direction, by molecular beam epitaxy. It was found that nitrogen incorporation in the 15° misoriented case was enhanced by a factor of two compared with that on the (100) oriented substrate. Electrical activity was unity for nitrogen concentration up to 1×1018 cm-3, then was falling for both substrates. This result indicates that electrical activity is determined only by nitrogen concentration in the layer and is not affected by the substrate orientation.
Reactive Ion Beam Etching of Indium Phosphide in Electron Cyclotron Resonance Plasma Using Methane/Hydrogen/Nitrogen Mixtures
Authors: José Ramón Sendra José Ramón Sendra , José Anguita José Anguita
Published: October 2002

Reactive ion beam etching of indium phosphide in electron cyclotron resonance plasma using methane/hydrogen/nitrogen mixtures has been performed. This etch chemistry provides a clean process with no polymer deposition. With etching at an ion acceleration voltage of 300 V, mirrorlike etched surfaces are obtained with donor passivation of about 10%. The electrical damage zone is restricted to a depth of 20 nm. Chemical etching limited by sputter-induced desorption of etch products of low volatility is proposed as the etch mechanism.
Influence of Substrate Misorientation on Carbon Incorporation in GaAs by Metal Organic Chemical Vapor Deposition
Authors: Ito Hiroshi , Watanabe Noriyuki , Takumi Nittono Takumi Nittono , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

The influence of substrate misorientation on carbon incorporation in GaAs is systematically investigated. The hole concentration in samples grown at 600° C is found to have a strong orientation dependence and decreases when the substrate is tilted from (100) toward the [011] direction. This behavior is explained by a model based on the atomic bonding geometries. On the other hand, hole concentration does not have an obvious dependence on substrate misorientation angle nor misorientation direction when the growth temperature is lower than 550° C. These tendencies are interpreted as the result of suppressed surface migration of C sources due to the stable adsorption nature of group IV elements.
Improved Crystalline Quality of Molecular Beam Epitaxy Grown GaAs-on-Si Epilayer through the Use of Low-Temperature GaAs Intermediate Layer
Authors: Phua Cheng Chiang , Tow Chong Chong Tow Chong Chong , Wai Shing Lau Wai Shing Lau
Published: October 2002

Improvements in crystalline quality of GaAs epilayers on Si have been achieved through the use of low-temperature (LT) GaAs intermediate layer grown at 230° C. The use of this LT-GaAs intermediate layer between the GaAs nucleation layer and the GaAs overlayer has improved the photoluminescence (PL) peak intensity by about five times, and reduced the GaAs (004) X-ray diffraction full width at half maximum (FWHM) by 59 arcsecs. The PL results were subsequently confirmed by cathodoluminescence images.
Vacancy-Type Defect Clusters in Diamond Grown from Molten Graphite at High Pressures
Authors: Oshima Ryuichiro , Motohiro Togaya Motohiro Togaya , Kenji Hattori Kenji Hattori
Published: October 2002

Substructures of a synthetic diamond grown from the melt of superheated graphite at a high pressure of 18 GPa have been examined by transmission electron microscopy. Vacancy-type dislocation loops are observed, which are in contrast to interstitial-type dislocation loops in natural diamonds previously reported. Cavities are also formed. The results suggest that quenched-in vacancies are condensed during rapid cooling from high temperatures to room temperature under high pressures.
Nanoscale Pattern Formation with the Scanning Tunneling Microscope on Polymer Thin Films
Authors: Tang Sau Lan , Alistair J. McGhie Alistair J. McGhie , Andris Suna Andris Suna
Published: October 2002

Nanometer-scale structures can be routinely fabricated with voltage pulses applied through the sharp tip of the scanning tunneling microscope (STM) on thin (<2000 Å) films of hydroxypropylcellulose. Structures were 20–30 Å in diameter in ambient atmosphere, and ∼200 Å in diameter in ultrahigh vacuum. Thermally induced structures can also be created with a modest power input (0.1–3 V tip bias voltages, 6 nA current, 10's of seconds duration for a ∼100 Å thick film). The structure formation mechanism appeared to include thermal effects from the current and its implications will be discussed.
Change in Velocity in Silicon Melt of the Czochralski (CZ) Process in a Vertical Magnetic Field
Authors: Yi Kyung-Woo , Watanabe Masahito , Eguchi Minoru , Koichi Kakimoto Koichi Kakimoto , Taketoshi Hibiya Taketoshi Hibiya
Published: October 2002

The influence of a magnetic field on the velociry of molten silicon has been characterized both theoretically and experimentally. The velocity decrease observed by X-ray radiography in the magnetic field is in good agreement with the results obtained by numerical modelling. It is found that the rate of decrease in velocity in a vertical magnetic field is well presented using the magnetic number rather than the Hartmann number. Accordingly, the analytical expression using the square of the magnetic number, M, well describes the velociry changes as v/v
0=(1+M
2/4)1/2-M/2, for experimental as well as numerically calculated data.
A Metastable Alpha-Particle Irradiation Induced Defect in n-GaAs
Authors: Auret F. Danie , Rudolph M. Erasmus Rudolph M. Erasmus , Stewart A. Goodman Stewart A. Goodman
Published: October 2002

We report the introduction and characterization of a metastable alpha-particle irradiation induced defect, Eα8, in n-GaAs by deep level transient spectroscopy (DLTS) using Schottky barrier diodes. The Eα8 defect, with an energy level 0.18 eV below the conduction band, as determined by low-field DLTS measurements, could be reversibly transformed (removed and re-introduced) by employing zero and reverse bias anneals, respectively, in the 100–140 K temperature range. The transformation kinetics of Eα8 displayed first order behaviour and was found to be charge state dependant.
A Novel Amorphous Silicon Doping Superlattice Device with a Controllable Gate
Authors: Liu Ching-Ru , Fang Yean-Kuen , Kuin-Hui Chen Kuin-Hui Chen , Jun-Dar Hwang Jun-Dar Hwang
Published: October 2002

A novel amorphous silicon doping superlattice structure with controllable switching performance has been developed successfully. The structure can be operated as two-terminal or three-terminal device. In two-terminal operation, the potential redistribution owing to avalanche multiplication effect induces the occurence of S-shaped switching behavior. The switching behaviors of the device are varied by applying a control bias to the third electrode.
Sharp Optical Emission from CuInSe2 Thin Films Grown by Molecular Beam Epitaxy
Authors: Niki Shigeru , Makita Yunosuke , Yamada Akimasa , Obara Akira , Misawa Syunji , Igarashi Osamu , Aoki Kazuhiro , Kutsuwada Noboru
Published: October 2002

Optical properties of CuInSe2 (CIS) films grown on (001) GaAs by molecular beam epitaxy (MBE) have been investigated by means of low temperature photoluminescence (PL) spectroscopy. Distinct emission lines including a bandedge emission were observed reproducibly from Cu-rich films, indicating high crystalline quality. Such well-defined PL spectra have made possible the extensive characterization of radiative recombination processes through the intrinsic defects in this material; some of the emission lines were attributed to phonon replicas with a phonon energy of 28–29 meV for the first time. PL spectra were found to be very sensitive to the MBE growth parameters such as substrate temperature, suggesting dominant defects in CIS epitaxial films can be controlled by varying the growth conditions.
Single-Wall Carbon Nanotubes Growing Radially from Ni Fine Particles Formed by Arc Evaporation
Authors: Saito Yahachi , Okuda Mitsumasa , Fujimoto Naoya , Yoshikawa Tadanobu , Tomita Masato , Hayashi Takayoshi
Published: October 2002

DC arc evaporation of nickel-graphite composite in helium atmosphere produces single-wall (SW) nanotubes. Electron microscopy examination of carbonaceous soot synthesized by this method revealed that the SW tubes grew radially from ultrafine nickel particles, and that they were found exclusively in soot material formed on the surface of a sluglike deposit grown on the end of a cathode.
Measurements of Parameters of Two-Electron-Temperature Plasma Produced by Electron Cyclotron Resonance
Authors: Tsuboi Hideo , Horio Shigeo , Kajitani Yukinori , Masahiro Itoh Masahiro Itoh , Toshio Hayashi Toshio Hayashi
Published: October 2002

Langmuir probe measurements were carried out for two-electron-temperature plasmas (T
eb and T
et; bi-Maxwellian) produced by electron cyclotron resonance (ECR). The tail electron temperatures were observed not only in the ECR region but also in the downstream region. The tail temperatures (T
et; 9.6∼24.0 eV) in the downstream region were higher than those ( 7.6∼12.3 eV) in the ECR region, whereas the tail densities (N
et; ∼109 cm-3) in the downstream region were one order of magnitude lower than those ( ∼1010 cm-3) in the ECR region.
Relationship between Carrier Diffusion Length and Light-Induced Defects in Hydrogenated Amorphous Silicon
Authors: Sakata Isao , Mitsuyuki Yamanaka Mitsuyuki Yamanaka , Toshihiro Sekigawa Toshihiro Sekigawa
Published: October 2002

It has been shown, by taking account of the variation of experimental conditions of steady-state photocarrier grating (SSPG) measurements with long exposure to light, that light-induced Si dangling bond states control hole diffusion lengths under illumination in plasma-deposited hydrogenated amorphous silicon (a-Si:H) with defect density less than 1016 cm-3. This conclusion is simple but different from previous reports where SSPG data were treated incorrectly. On the other hand, the effects of defect states on diffusion lengths are small in chemical-vapor-deposited a-Si:H treated with hydrogen plasma.
Fabrication of Josephson Junctions by Focused Electron Beam Irradiation
Authors: Suzuki Masanobu , Kawahara Nobuaki , Imura Hiroki Hoshizaki
Published: October 2002

The YBa2Cu3O

x

(YBCO) films patterned to a bridge shape were locally irradiated by a focused electron beam of 4 nm diameter in a transmission electron microscope. Electron beam irradiation allowed controlled reduction of the critical currents and raised the normal state resistance of the films. Irradiated films exhibited Shapiro steps when exposed to microwave irradiation. It was found that irradiated films functioned as Josephson junctions.
Epitaxial Growth of Bi2Sr2Cu1-xTixOy Thin Films on SrTiO3 (100) and Bi2Sr2CaCu2O8 Single Crystals for Construction of Tunneling Barrier
Authors: Choopun Supab , Matsumoto Takuya , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

The growth of high-resistivity Bi2Sr2Cu1-
x

Ti

x

O

y

(x=0, 0.1, 0.2, 0.3) thin films on SrTiO3 (100) substrates has been performed using the laser molecular beam epitaxy method. The aim is to obtain a tunneling barrier with a barrier higher than that of Bi2Sr2CuO6 (2201) film. The growth process has been observed in situ by reflection high-energy electron diffraction, and the films are characterized by the X-ray diffraction method. The growth of Bi2Sr2Cu0.8Ti0.2O

y

film on the superconducting Bi2Sr2CaCu2O8 single crystal has also been examined for the tunneling barrier. This has a higher barrier than the titanium-free 2201 film in the Au/barrier/Bi2Sr2CaCu2O8 tunneling junctions.
Application of Focused Ion Beam Techniques to the Fabrication of Lateral-Type Thin-Film Edge Field Emitters
Authors: Yasuhito Gotoh Yasuhito Gotoh , Kazunori Inoue Kazunori Inoue , Toshiya Ohtake Toshiya Ohtake , Hideaki Ueda Hideaki Ueda , Yasuyuki Hishida Yasuyuki Hishida , Hiroshi Tsuji Hiroshi Tsuji , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

Focused ion beam (FIB) techniques were applied to the fabrication of lateral-type thin-film edge field emitters (FE's). In the present paper, two different processes to fabricate lateral-type thin-film edge FE's have been demonstrated. One technique utilizes the FIB as an etching tool. The FIB with a diameter of 1 µm was used to cut a thin nickel film with a thickness of 150 nm deposited on a silicon substrate which had been thermally oxidized, in order to produce an emitter-collector gap. As a result, a diode structure with the gap of about 2 µm could be obtained. In the other technique, a tungsten oxide thin film was exposed with the FIB to form the electrodes, followed by development in sodium hydroxide solution and reduction in hydrogen ambient. The FIB with a diameter of 5 µm was used to expose the tungsten oxide, a negative resist against ion beam irradiation, with a thickness of 40 nm. A diode structure with the gap of also about 2 µm could be obtained. Current-voltage characteristics of these devices were measured and field emission currents were observed. Ejection of the electrons from the latter FE into vacuum was confirmed with luminescence of zinc sulfide phosphor.
Novel Amorphous-Silicon-Based Light Converter
Authors: Fang Yeau-Keuen , Lee Kuen-Hsien , Kuo Yaw-Jou Yang
Published: October 2002

A novel amorphous-silicon-based light converter has been developed. The device consists of an amorphous-silicon pin diode as the input-light sensing unit and a GaAsP light-emitting diode (LED) as the light-emitting unit. With appropriate selection of the i-a-Si:H layer thickness, the device can convert UV and visible light into red light. The key features of the device are low cost and simplicity of the preparation process. In this letter, the design, operation, fabrication, and measurements of the device have been described in detail.
A New Method to Align Smectic Liquid Crystals by Photo-Polymerization
Authors: Sukhmal C. Jain Sukhmal C. Jain , Heinz-S. Kitzerow Heinz-S. Kitzerow
Published: October 2002

A novel technique to produce planar and homeotropic alignment of smectic liquid crystals is presented. The technique is based on producing an anisotropic polymer network in the bulk by photo-polymerizing a mixture of photoresist material and liquid crystal by linearly polarized UV-light. Both uniform planar alignment and homeotropic alignment can be obtained depending on the curing conditions. In the case of planar alignment, the orientation of liquid crystal molecules is governed by the direction of the polarization vector of the UV-light, thus making it possible to produce a defined azimuthal orientation of the liquid crystal director. This technique obviates the need to give any previous treatment to the bounding substrates.
Direct Observation of Species Liberated from GaAs Native Oxides during Atomic Hydrogen Cleaning
Authors: Masamichi Yamada Masamichi Yamada , Yuichi Ide Yuichi Ide
Published: October 2002

A real-time mass spectroscopic observation of liberated species was carried out to investigate the mechanism of atomic-hydrogen-( H•)-induced deoxidation of GaAs native oxides. Atomic hydrogen treatment at 410°C caused, initially, the liberation of molecular arsenic ( As2/As4), resulting in the removal of As oxides, which was then followed by the liberation of Ga2O, leading to complete deoxidation. These results indicate that the deoxidation proceeds through two stages. The main chemical reactions are As2O

x

+2 x H•→ x H2O+ As2/(1/2As4) in the first stage and Ga2O3+ 4H•→2H2O+ Ga2O in the second stage.
A Theory for Three-Dimensional Measurement of Nonuniform Electric Field Using Kerr Effect
Authors: Uto Sadahito , Nagata Yasuhiro , Kimihiro Takechi Kimihiro Takechi , Kiyomitsu Arii Kiyomitsu Arii
Published: October 2002

An optical method using the Kerr effect is useful to measure electric fields in dielectric liquids without disturbance. The computed tomography (CT) method has been applied to the measurement of two-dimensional field distributions by us. However, three-dimensional electric field distributions, in which field vectors are not always perpendicular to the transmitted light, have not been measured as yet. A three-dimensional field vector can be reduced to a two-dimensional one. This leads to the application of the CT method to the measurement of a more general distribution. This paper reports on a theory and a simulation of nonuniform three-dimensional electric field measurements.
Compatibility of Differential Scanning Calorimetry and ac Calorimetry
Authors: Ichiro Hatta Ichiro Hatta
Published: October 2002

In the simultaneous measurement of heat capacity by differential scanning calorimetry and ac calorimetry using the same apparatus with ac temperature modulation superposed on a linear temperature ramp, the principle of measurement by ac calorimetry is not sufficiently understood yet. This paper gives an explanation, especially from the viewpoint of ac calorimetry. The experimental conditions required for the simultaneous measurement are considered.
Detection of Defects in Irradiated Silicon Oxide by X-Ray Photo-Electron Spectrum Difference
Authors: Masakazu Nakabayashi Masakazu Nakabayashi , Takao Yamaguchi Takao Yamaguchi
Published: October 2002

This letter shows that binding energy for Si2
p
photoelectrons in oxide with defects induced by X-ray irradiation decreases. Moreover, binding energy in wet thermal oxide grown at 820°C also decreases with decreasing oxide thickness.
Electric Properties of Metal/Diamond Interfaces Utilizing Hydrogen-Terminated Surfaces of Homoepitaxial Diamonds
Authors: Makoto Aoki Makoto Aoki , Hiroshi Kawarada Hiroshi Kawarada
Published: October 2002

As-grown homoepitaxial diamond surfaces fabricated by chemical vapor deposition are terminated by hydrogen, and are expected to have a low density of surface states. On such diamond surfaces, high-quality Schottky contacts have been obtained utilizing metals with low electronegativities, such as Al or Pb. The ideality factors of those point contacts to diamond are less than 1.1, which is the nearest value to unity ever reported in diamonds. Quantitative measurements of Schottky barrier heights at various metal contacts have also been performed. A strong correlation between the barrier heights and the metal electronegativities is observed. Even an ohmic property is obtained when metals with higher electronegativities were used. The effect of Fermi level pinning is reduced at the interfaces between metals and hydrogen-terminated diamonds.
Ridge Structures Formed on Nd3Ga5O12 and Sm3Ga5O12 Single Crystal Substrates
Authors: Katoh Yujiro , Naoto Sugimoto Naoto Sugimoto , Akiyuki Tate Akiyuki Tate
Published: October 2002

Straight ridge patterns are formed in the [1̄ 1̄2] and [1̄10] directions on (111) Nd3Ga5O12 (NGG) and Sm3Ga5O12 (SGG) single crystal substrates, and in the [001] and [11̄0] directions on a (110) NGG substrate by argon ion-beam etching and subsequent soaking in a hot phosphoric acid solution. The ridge shapes are observed with a scanning electron microscope (SEM). The crystal faces, which appear on the ridge side walls, are examined. The anisotropic etching in the phosphoric acid solution strongly depends on the ridge direction as well as on the substrate orientation. The indices are similar to those observed for Gd3Ga5O12 (GGG).
Orientation of MgO Thin Films on Si(100) and GaAs(100) Prepared by Electron-Beam Evaporation
Authors: Masuda Atsushi , Nashimoto Keiichi
Published: October 2002

MgO thin films were prepared on Si(100) and GaAs(100) by electron-beam evaporation. MgO thin films with (100) orientation were obtained at 610°C with the deposition rate of 0.5 Å/s, and those with (111) orientation were obtained below 440°C with deposition rate higher than 8 Å/s, on Si substrates. (100) oriented MgO thin films, however, grew on Si at 440°C upon decreasing the deposition rate to 0.3 Å/s. MgO thin films with (100) orientation having cube-on-cube epitaxy were obtained on GaAs substrates at the temperature as low as 280°C even at the deposition rate of 1.4 Å/s.
Low-Frequency Waves during GAMMA 10 End-Plate Biasing Using Microwave Reflectometry
Authors: Tokuzawa Tokihiko , Mase Atsushi , Itakura Akiyosi , Inutake Masaaki , Kameo Ishii Kameo Ishii , Teruo Tamano Teruo Tamano
Published: October 2002

The effect of the ambipolar potential on the stability of low-frequency waves has been studied by applying a bias voltage to the end plates of a tandem mirror. Reflectometers, as well as the microwave scattering method, are used for measurements of thek-ω spectrum and radial profile of density fluctuations. Two types of instabilities, a rotationally driven flutelike mode and a drift-wave mode, are observed during the existence of confining potentials. It is shown that end-plate biasing in a tandem mirror plasma is useful for shaping the radial potential profiles to control the fluctuations.
Cation Source Dependence of Ga0.5In0.5P Growth Rate by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Wu Janne-Wha , Chang Chun-Yen , Lin Kun-Chuan , Chan Shih-Hsiung , Chen Horng-Dar , Chen Po-An , Chang Edward Yi , Mei-Shong Kuo Mei-Shong Kuo
Published: October 2002

The Ga0.5In0.5P epilayer was grown by low-pressure metalorganic chemical vapor deposition. Trimethylgallium and triethylgallium were used as the gallium sources, while trimethylindium and ethyldimethylindium were used as the indium sources. The use of triethylgallium incorporated with trimethylindium enhanced the growth rate of Ga0.5In0.5P as compared to incorporation with ethyldimethylindium. While the use of trimethylgallium incorporated with ethyldimethylindium enhanced the growth rate of Ga0.5In0.5P significantly, as compared to incorporation with trimethylindium.
Preparation of (Tl, Pb)–Sr–Ca–Cu–O Superconducting Thin Films by the Mist Microwave-Plasma Chemical Vapor Deposition Method
Authors: Takahashi Naoyuki , Koukitu Akinori , Kamioka Hisashi Seki
Published: October 2002

Superconducting thin films of (Tl, Pb)–Sr–Ca–Cu–O were prepared on single-crystal MgO(100) substrates by the mist microwave-plasma chemical vapor deposition method. The X-ray diffraction patterns showed that the prepared films consisted of the 1223 and 1212 phases with c-axis orientation perpendicular to the substrates. The dependence of the critical temperature of films on the input molar ratio of oxygen was investigated. The maximum critical temperature (100 K) of as-deposited films was obtained at the input molar ratio of oxygen about of 0.3.
Dependence of Magnetoresistance and Antiferromagnetic Coupling on Preparation Conditions in Epitaxial (100)Co/Cu Superlattices
Authors: Kingetsu Toshiki , Yoshizaki Fukio
Published: October 2002

Epitaxial (100)Co/Cu superlattices were grown by dc magnetron sputtering with various Ar pressures to investigate the dependence of magnetoresistance (MR) and antiferromagnetic (AFM) coupling on preparation conditions. The MR ratio and AFM coupling were found to be larger for a sample prepared with higher Ar pressure, where X-ray and reflection high-energy electron diffractions indicate that the Co/Cu interfaces are rougher. These results are the reverse of previously reported ones in terms of the correlation between MR ratio and interface roughness. A cause of this discrepancy may be a difference in the scale of roughness.
Oriented Growth of Cu(110) on YSi2-x(11̄00)/Si(100) and Diffusion Behavior in Copper Silicide Formation
Authors: Nomura Kouichi , Noya Atsushi , Katsutaka Sasaki Katsutaka Sasaki , Kouji Sunaga Kouji Sunaga
Published: October 2002

The growth and diffusion characterization of Cu films on the YSi2-
x

(11̄00)/Si(100) substrate are studied. On the YSi2-
x

(11̄00) layer prepared using a thin template layer, highly oriented Cu(110) film growth is observed, and Cu diffusion through the YSi2-
x

layer and the subsequent Cu3Si formation occur at temperatures as low as 200° C. On the contrary, the growth of Cu with normal orientation is evident on the YSi2-
x

layer with poor epitaxial quality, and the out-diffusion of Si forms a Cu3Si layer on the YSi2-
x

layer. The film growth on YSi2-
x

layers is discussed on the basis of the lattice match between superlattice cells of Cu and YSi2-
x

, and the diffusion behavior is interpreted in terms of relaxation of the affinity of Cu for Si.
Scattering of Pulsed Trimethylgallium Beam from Clean and Oxidized GaAs Surfaces
Authors: Masahiro Sasaki Masahiro Sasaki , Seikoh Yoshida Seikoh Yoshida
Published: October 2002

In order to study the mechanism of selective-area growth in metalorganic molecular beam epitaxy (MOMBE), we examined the difference in the scattering of a pulsed trimethylgallium (TMG) beam from a clean (epitaxially prepared) GaAs surface and an oxidized GaAs surface, which is effective as a mask for selective-area epitaxy. Although a long surface residence ( 896 µs at 546 K) was necessary to interpret the time-of-flight (TOF) spectrum of TMG scattered from a clean GaAs surface, the TOF spectra of TMG scattered from an oxidized surface were well reproduced only by a translationally drifting Maxwellian velocity distribution (without a surface residence). We consider that the difference in the surface residence time during scattering causes the decomposition selectivity of a metalorganic source on clean and oxidized surfaces, which is the essence of selective-area growth. We also observed that the energy exchange between the mask surface and incident TMG molecules during scattering is small when the mask is effective for selective-area growth.
Laser-Irradiation Induced a-Axis Orientation in c-Axis-Oriented YBa2Cu3Ox Films Prepared by Pulsed Laser Ablation
Authors: Minamikawa Toshiharu , Suzuki Tenmin , Segawa Kazuhito , Akiharu Morimoto Akiharu Morimoto , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Superconducting YBa2Cu3O

x

films on MgO(100) substrates were prepared by pulsed laser ablation with pulsed laser irradiation on the growing film surface. The irradiation effects on the crystal structure were studied for various substrate temperatures and irradiation fluences. These experiments revealed that a poorly crystallized film was successfully converted to a well-crystallized film with a-axis orientation after irradiation at a low substrate temperature. At a high substrate temperature, the a-axis-oriented crystallites were introduced into c-axis-oriented films upon irradiation, without degradation of the crystallinity, suggesting the possibility that these crystallites play the role of pinning centers in high-T
c superconducting films.
An Optical Adaptive Device and Its Application to a Competitive Learning Circuit
Authors: Tsuji Kiyotaka , Yonezu Hiroo , Hosono Kohji , Shibao Kazuhiro , Ohshima Naoki , Kangsa Pak Kangsa Pak
Published: October 2002

A mechanism suppressing the divergence of synaptic weights should be added to the network performing unsupervised learning algorithms with the Hebbian rule. In order to realize competitive learning in hardware, a synaptic connection circuit keeping a sum of synaptic weights constant was fabricated with the complementary field effect transistor (CMOS) floating gate process. The synaptic weights of each neuron were varied by applying the optical correction signals. The sum of synaptic weights was kept constant and the weights were memorized in a nonvolatile manner. A primitive competitive learning circuit was constructed with the synaptic connection circuits and a winner-take-all (WTA) circuit. The self-organization of the competitive circuit was confirmed experimentally and by means of simulations. The limitation of operating range and the feasibility of large-scale integration were discussed.
AlGaAs/GaAs Heterojunction Bipolar Transistors with Reduced Base-Collector Capacitance Fabricated Using Selective Metalorganic Chemical Vapor Deposition
Authors: Son Jeong-Hwan , Kim Chang-Tae , Hong Song-Cheol , Young-Se Kwon Young-Se Kwon
Published: October 2002

Selectively grown AlGaAs/GaAs heterojunction bipolar transistor (HBT) with a reduced base-collector capacitance is proposed and fabricated using selective metalorganic chemical vapor deposition (MOCVD) technique. The proposed HBT features a triangular void over SiO2 stripe. The extrinsic base-collector capacitance is significantly reduced due to the isolation of the extrinsic collector region from the collector metal contact by the void. The DC current-voltage characteristics of the selectively grown HBT are similar to those of the conventional one. However, the microwave performance is improved due to the reduced base-collector capacitance in the selectively grown HBT. For the device with two 3×10 µ m2 emitter fingers, the selectively grown HBT has a maximum oscillation frequency 1.4 times higher than that of the conventional device, and the current gain cutoff frequency f
T of 43 GHz and the maximum oscillation frequency f
max of 20.5 GHz are obtained.
Martensitic Transformation in Fe-29 wt%Ni Alloy Ultrafine Particles
Authors: Yunhong Chen , Guichang Deng , Huaixian Lu , Jinhui Wang , Gang Li
Published: October 2002

The ultrafine-particle samples of Fe-29 wt% Ni alloy with different average particle sizes (12 to 100 nm) are prepared by the evaporation condensation method in N2atmosphere. They exhibit a mixture of martensite α′(bcc) and austenite γ (fcc) phases. Each individual particle is a single crystal (bcc or fcc). The volume fraction of martensite increases markedly with the decrease of the average particle size. During heating, as the average particle size decreases, the temperature (AsandAf) for α′→γ reverse martensitic transformation decreases, and the range (As-Af) of reverse transformation temperature becomes narrower, whereas during cooling (down to 77 K), we have not observed γ→α′martensitic transformation. The stabilization of austenite and the growth mechanism of martensite and austenite are preliminarily discussed in this paper.
High-Reflectivity InGaP/GaAs Multilayer Reflector Grown by MOCVD for Highly Reliable 0.98-µm Vertical-Cavity Surface-Emitting Lasers
Authors: Shinoda Kazunori , Hiramoto Kiyohisa , Uomi Kazuhisa , Tomonobu Tsuchiya Tomonobu Tsuchiya
Published: October 2002

We report an InGaP/GaAs multilayer grown by low-pressure MOCVD for highly reliable 0.98-µ m InGaAs vertical-cavity surface-emitting lasers. High reflectivity of over 99% is obtained for the 45-period multilayer. The stability of the layer thickness over the entire multilayer is discussed from the viewpoint of the asymmetrical reflectivity spectrum. Our results indicate that the layer thickness slightly decreases during epitaxial growth.
650 nm AlGaInP Visible Light Laser Diode with Dry-Etched Mesa Stripe
Authors: Yoshikawa Takashi , Sugimoto Yoshimasa , Hotta Hitoshi , Tada Kentaro , Kobayashi Kenichi , Miyasaka Fumito , Kiyoshi Asakawa Kiyoshi Asakawa
Published: October 2002

CW operation of 650 nm GaInP/AlGaInP index waveguide-type visible-light laser diodes (LDs) with dry-etched mesa stripes fabricated by Cl2 reactive ion beam etching was achieved for the first time. Its threshold current of 47 mA and slope efficiency of 0.40 W/A are almost the same as those of wet-etched LDs fabricated from the same wafer (L=500 µ m). Cross-sectional scanning electron microscopy image of the buried mesa stripe shows that dry-etched LD has a symmetric mesa shape, promising a small focusing spot size and a stable mode operation, whereas the wet-etched mesa is asymmetric because of the use of a 6°-misoriented substrate for this wavelength operation. The aging test operated with a light output power of 3 mW at 50° C reveals that these LDs have an operating time of over 3000 h, indicating they have sufficient lifetime for conventional uses.
Photonic Devices Based on Crystalline Organic Semiconductors for Optoelectronic Integrated Circuits
Authors: Ammermann Dirk , Rompf Christoph , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Crystalline organic thin films are deposited under ultrahigh vacuum conditions at substrate temperatures from 77 K to 300 K.
Due to the weak van der Waals bonding forces between the organic molecules, lattice matching is not required for layer growth. Structures can be prepared both on dielectric or amorphous substrates and on top of completely processed III-V or Si wafers. In this paper, we discuss the fabrication and performance of organic semiconductor electroluminescent devices, waveguides, and photodetectors.
Spectral Fluctuations in the Stokes Output Pulse Pumped with a High-Pressure CO2 Laser
Authors: Suzuki Mitsutoshi , Miyamoto Yasuaki , Yoshihiro Shimazaki Yoshihiro Shimazaki
Published: October 2002

Analytical solution of the broadband Stokes field, whose linewidth is 2 GHz full width at half-maximum (FWHM), in four-wave mixing based upon stimulated Raman scattering is obtained using the fully quantum mechanical approach developed by Raymer et al. [Phys. Rev. A 32 (1985) 332]. Shot-to-shot variations of the Stokes energy initiated by quantum noise are calculated and the probability distribution function of the pulse energy is shown to be of negative-exponential shape in a no-pump-depletion region. Output Stokes field is expanded into the coherent modes, and it is shown that the most significantly excited mode of the Stokes field contains more than 99% of the Stokes pulse energy. Shot-to-shot fluctuations of the mean frequency of the narrow-band Stokes field, whose linewidth is 100 MHz (FWHM), is 200 MHz; however, that of the broad-band Stokes field reaches 1 GHz.
Optical Gain Using Three-band Model Taking into Account the Excitonic Effects
Authors: Takeshi Uenoyama Takeshi Uenoyama
Published: October 2002

Excitonic effects of optical gain in quantum wells have been studied theoretically in a three-band model. Taking into account an additional localized level in the energy gap, the optical gain in terms of the population inversion between the localized state and one of the band-edge subband states is observed with the very small carrier concentration. Simultaneously, the excitonic absorption is observed due to the band-edge electron-hole interaction. The former optical gain is extremely enhanced by the latter excitonic effect through the coupling between the two transitions. This enhanced optical gain might show a possibility of fabricating very low threshold current laser diodes.
Possibility of InP-Based 2-Dimensional Photonic Crystal: An Approach by the Anodization Method
Authors: Toshihiko Baba Toshihiko Baba , Miyuki Koma Miyuki Koma
Published: October 2002

We have investigated the possibility of InP-based 2-dimensional (2D) photonic crystal experimentally and theoretically. To fabricate such crystal, we aimed at utilizing triangular rods and holes automatically formed at the surface of (111)A InP substrate by an anodization method. Favorable characteristics are that the rods and holes orient perpendicular to the surface and have submicron width and high aspect ratio. In addition, observed photoluminescence spectra indicated negligibly slow surface recombination at the anodized surface. From the calculation of band diagram, the photonic gap was found for uniform triangular rods. Thus low-damage 2D photonic crystal which controls light emission and propagation in the 2D plane can be realized by controlling the size uniformity and position of rods using the patterned oxide mask.
GaAs Oxide Removal Using Hydrogen Plasma Studied by Surface Second-Harmonic Generation
Authors: Kimura Takahiro , Chikashi Yamada Chikashi Yamada
Published: October 2002

Surface-reflection second-harmonic generation (SHG) was applied to observe the surface-oxide removal of GaAs(001) using a pulsed hydrogen plasma. Real-time observations were carried out to monitor a specific polarization component of SHG.
The p-polarized SH intensity under p-polarized excitation increased in the [01̄1] azimuth of incidence and decreased in the [011] azimuth of incidence during hydrogen plasma irradiation while the other component, the p-polarized SH intensity under s-polarized excitation did not change. The input polarization-angle dependence was examined before and after the oxide removal. The variation in the SH intensity during the hydrogen plasma treatment was found to be mainly due to variation in the surface-susceptibility tensor elements. Among these, an “isotropic” tensor element, ∂
z
z
z
(or ∂ξξz
=∂ηηz
), changes most significantly.
Magnetoresistance Effects in Ni-Fe-Co/Cu/Co-Pt Trilayers
Authors: Hoshino Katsumi , Nakatani Ryoichi , Hoshiya Hiroyuki , Sugita Yutaka , Tsunashima Shigeru
Published: October 2002

Magnetoresistance effects in Ni-Fe-Co/Cu/Co-Pt trilayers have been investigated with various thicknesses of each layer. The Co-Pt layers exhibited high coercivities when deposited directly on Si substrates to a thickness of more than 3.2 nm. An antiparallel alignment of the magnetizations in the Ni-Fe-Co and the Co-Pt layers with each other occurred under low magnetic fields because the Co-Pt layer had a higher coercivity than the Ni-Fe-Co layer; thus the trilayers have magnetoresistance ratios higher than 4.0% for Cu layer thicknesses between 1.5 nm and 3.0 nm. The thermal stability of these trilayers was also investigated. These trilayers maintained high magnetoresistance ratios after annealing up to 300° C.