bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction of Dynamic Conoscope Observation System Using CCD Camera and Image Processor
Authors: Fujikawa Takayuki , Hiraoka Kazuyuki , Isozaki Tadaaki , Kajikawa Kotaro , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

In order to study the dynamic behavior of conoscopic images with high precision and high efficiency, we constructed a conoscope observation system using a CCD (charge coupled device) camera and an image processor. We can analyze biaxiality and apparent tilt angle by means of a homeotropic cell operated at 0.1 Hz. We discuss the result obtained in an antiferroelectric liquid crystal, 4-1-(methylheptyloxycarbonyl) phenyl 4'-octyloxy-biphenyl-4-carboxylate (MHPOBC).
Evolution of the 2-Dimensional Intensity Distribution of the Scattered Lights from Gelling Tungstic Acid
Authors: Hara Kazuhiro , Kuboyama Keiichi , Hirotaka Okabe Hirotaka Okabe , Kazumi Matsushige Kazumi Matsushige
Published: February 2005

A conventional system for light scattering measurements utilizing a laser, a TV camera and a frame memory was constructed in order to investigate the gelation process of tungstic acid. The results revealed marked changes in the 2-dimensional intensity distribution of the scattered lights at about 3600 s and 5000 s after ion exchange in the present experimental conditions ([Na2WO4]=0.76 mol/l, 296 K). By the tilting test, it was confirmed that the first characteristic time corresponded to the gelation time, around which a marked intensity increase at the position corresponding to the laser beam was observed, while at around 5000 s, the increase occurred mainly on the outskirts of the beam, probably because of the progressive densification in the network structure. Moreover, a close correlation between the scattering characteristics and the gelation process is suggested from the numerical data.
Room-Temperature Low-Threshold Surface-Stimulated Emission by Optical Pumping from Al0.1Ga0.9N/GaN Double Heterostructure
Authors: Amano Hiroshi , Watanabe Nobuaki , Koide Norikatsu , Isamu Akasaki Isamu Akasaki
Published: February 2005

The difference in the refractive index at around λ=0.37 µm between GaN and Al0.1Ga0.9N is found to be about 0.19. With use of AlGaN/GaN double heterostructures, the threshold power for surface-stimulated emission by optical pumping at room temperature has been markedly decreased to about one-twentieth that of a bulk GaN layer. The mechanism of the stimulated emission in this system is discussed.
Dielectric Properties of n-Pentyl-p-n-Cyanobiphenyl in Wide Frequency Range
Authors: Hitoshi Mada Hitoshi Mada , Akira Nishikawa Akira Nishikawa
Published: February 2005

Frequency dependence of the dielectric constant was measured for n-pentyl-p-n-cyanobiphenyl in the nematic phase. Two dielectric relaxations appear. The relaxation at high frequency is due to molecular motion; and the relaxation at low frequency is due to the ion drift, of which the relaxation time can be estimated as 8 s. Conductivity due to ion drift can also be obtained from the imaginary part of the dielectric constant to be on the order of 10-9 S/m.
Simple Rhombohedral Structure of C70 under High Pressure
Authors: Kawamura Haruki , Akahama Yuichi , Kobayashi Mototada , Hasegawa Yasumasa , Shinohara Hisanori , Sato Hiroyasu , Saito Yahachi
Published: February 2005

The pressure-induced simple rhombohedral structure in solid C70 was examined by X-ray diffraction measurement as a function of pressure. This phase was kept stable for at least several days after the release of pressure. From a model calculation, the freezing of the molecular rotation about the short axis is demonstrated in the rhombohedral phase.
Characteristics of Heterojunction Diode of C60/Tetratiafulvalane (TTF)
Authors: Yamashita Yasunori , Wataru Takashima Wataru Takashima , Keiichi Kaneto Keiichi Kaneto
Published: February 2005

The characteristics of a heterojunction diode consisting of C60/tetratiafulvalene (TTF) which are typical of a photoinduced rectifier, are reported. The device under dark conditions is almost insulative, however, upon light illumination, marked rectification is observed. The forward bias to C60 under illumination is positive against the TTF electrode. The results are discussed in terms of the photoinduced electron transfer from TTF to C60 at the junction.
Modification of Silicon Surface Using Atomic Force Microscope with Conducting Probe
Authors: Yasutake Masatoshi , Ejiri Yasunori , Hattori Takeo
Published: February 2005

It is demonstrated that nearly atomically flat Si(100) surfaces passivated with native oxides can be modified by applying a negative potential to the conducting probe of an atomic force microscope (AFM) with respect to the silicon substrate. It was verified from the detection of OKLL Auger electrons and SiLVV Auger electrons excited by the electron beam that silicon surfaces are modified by the oxidation of silicon. This oxidation is enhanced by an electric field.
Photoexcited Anisotropic Etching of Single-Crystalline Silicon
Authors: Sakaue Hiroyuki , Noboru Morimoto Noboru Morimoto , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

Anisotropic etching reaction of single-crystalline silicon (Si) was studied under illumination by a high-pressure Hg lamp employing Cl2. Etch rates of n-type Si decreased in the order of {100}, {110} and {111} planes. As the resistivity deceased and the temperature increased, the etch rate increased. With the resistivity of 0.015 Ω·cm and at 200°C, {100} and {110} planes show considerably high etch rates, while the etch rate of the {111} plane was extremely low. By utilizing the specific etch rate difference and retaining an Si oxide pattern in the same direction as <110>, a microdiaphragm with an oxide lever was fabricated.
Structural and Optical Properties of the Cu1-xAgxGaS2 System
Authors: Matsushita Hiroaki , Saburo Endo Saburo Endo , Taizo Irie Taizo Irie
Published: February 2005

Compositional dependence of the structural and optical properties of the Cu1-x
Ag
x
GaS2 system has been studied. Whereas the compositional dependence of the lattice constant “a” was linear, those for the lattice constant “c” and the optical band gap showed upward bowing. The phase diagram of this system was also studied by means of differential thermal analysis (DTA), and solid solubility throughout this whole system was found. The transition point is a chalcopyrite-to-zincblende transition at x < 0.5. It was found that the emission spectra for this system have two peaks, the energies of which depend on the composition x.
Molecular Beam Epitaxy of GaAs/AlAs on Mesa Stripes along the [001] Direction for Quantum-Wire Fabrication
Authors: López Máximo , Tomonori Ishikawa Tomonori Ishikawa , Yasuhiko Nomura Yasuhiko Nomura
Published: February 2005

We report on the growth of GaAs/AlAs layers by molecular beam epitaxy on GaAs (100) substrates patterned with mesa stripes oriented along the [001] direction. The GaAs growth led to the formation of {110} facets which were smoother than the facets formed on [01̄1]- and [01̄1̄]-oriented mesa stripes. It was also found that the GaAs growth rate on the {110} facets is extremely low. We fabricated quantum wire-like structures by narrowing the width of the mesa-top (100) facet, which is limited by the (11̄0) and (110) facets, to the nanometer scale, and then growing an AlAs/GaAs quantum well. The resulting structure was as narrow as ∼30 nm with a thickness of ∼30 nm at its center.
GaAs/AlGaAs Single Quantum Well Optical Switch Fabricated on Si Substrate
Authors: Yuasa Takayuki , Nagashima Yoshikazu , Murase Tutomu , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

We report a single-mode waveguide-type optical switch with a double hetero (DH)-structure fabricated on a Si substrate by Metalorganic Chemical Vapor Deposition (MOCVD). This switch utilizes the quantum confined Stark effect (QCSE). The sample consists of an Al0.3Ga0.7As cladding layers and Al0.25Ga0.75As guiding layer with an 8.3-nm-wide GaAs single quantum well (SQW). To measure the light absorption under reverse bias, the photocurrent method was applied out using a cw Ti:sapphire laser. We measured about a 10 nm shift of the absorption edge at -8 V. This switch exhibits a 33.1 dB/mm extinction ratio at 867 nm wavelength under -8 V bias.
Metalorganic Chemical Vapor Deposition of Aluminum-Copper Alloy Films
Authors: Katagiri Tomoharu , Kondoh Eiichi , Takeyasu Nobuyuki , Nakano Tadashi , Hiroshi Yamamoto Hiroshi Yamamoto , Tomohiro Ohta Tomohiro Ohta
Published: February 2005

Al-(0.7-1.4 wt%) Cu alloy films for LSI interconnects were formed, for the first time, by a metalorganic chemical vapor deposition method, using dimethylaluminumhydride ((CH3)2AlH) and cyclopentadienylcoppertriethylphosphine ((C5H5)CuP(C2H5)3) as precursors. The depth profile of Auger electron spectroscopy showed that the deposited films had a uniform Cu distribution. The transmission electron microscopy (TEM) and electron diffraction analyses confirmed the presence of CuAl2 precipitates in the films.
Novel Face-Centered Icosahedral Phase in Al-Mg-Li System
Authors: Niikura Akio , Tsai An Pang , Inoue Akihisa , Yamamoto Tsuyoshi Masumoto
Published: February 2005

A new class of the icosahedral phase is found for the first time in a melt-quenched Al50Mg25Li25 alloy. The icosahedral phase reveals a face-centered icosahedral lattice analogous to the structure of icosahedral AlCuFe.
TiO2 Thin Films Formed by Electron Cyclotron Resonance Plasma Oxidation of Ti Thin Films
Authors: Yoshio Abe Yoshio Abe , Takuya Fukuda Takuya Fukuda
Published: February 2005

TiO2 thin films with a relative-dielectric constant of 20 were fabricated by electron cyclotron resonance (ECR) plasma oxidation of Ti thin films without substrate heating. The relative-dielectric constant was found to be constant for film thicknesses from 3.5 to 26 nm, and the maximum capacitance of 37 fF/µm2 was obtained for the thickness of 3.5 nm.
Polycrystalline CuInSe2 Thin Films for Solar Cells by Three-Source Magnetron Sputtering
Authors: Nakada Tokio , Kazuo Migita Kazuo Migita , Akio Kunioka Akio Kunioka
Published: February 2005

Polycrystalline CuInSe2 films were deposited in a wide range of Cu/In ratios by three-source magnetron sputtering technique onto soda-lime glass and Mo-coated glass substrates at elevated substrate temperatures. Good run-to-run reproducibility was achieved in our sputtering system using melt-grown polycrystalline selenium target. In-excess films which are desirable for solar cells were obtained in the temperature range of 400 to 500°C. These films showed a preferential (112) orientation of the chalcopyrite structure and possessed an excellent adhesion property to the substrates. Preliminary solar cells with ZnO:Al/CdS/CuInSe2 structure resulted in a conversion efficiency of 6.3% under AM 1.5 illumination.
Effective Photoresponse in C60-Doped Conducting Polymer due to Forbidden Transition in C60
Authors: Morita Shigenori , Kiyomatsu Shinji , Fukuda Masahiko , Zakhidov Anvar A. , Yoshino Katsumi , Kikuchi Koichi , Achiba Yohji
Published: February 2005

The enhancement of photoconductivity in conducting polymers upon C60 doping has been observed at the photon energies corresponding to photo-excitation in both conducting polymer and C60. In particular, the marked enhancement at 1.8 eV is attributed to the hu-t1u forbidden transition in C60. This anomalous effect is interpreted by taking the electronic energy states of both conducting polymers and C60 into consideration.
Novel Technique of Infrared Reflection Absorption Spectroscopy for Si Surface Study
Authors: Yamada Hisayoshi Ohshima
Published: February 2005

It is demonstrated that Fourier-transform infrared reflection absorption spectroscopy with a novel arrangement is a powerful technique to study the nature of Si surfaces. The technique was applied to the observation of the Si-H bond absorption (2083 cm-1) on HF- or NH4F-treated Si(111) surfaces and the Si-O-Si bond absorption (1000-1300 cm-1) of oxides on the Si surface formed by native oxidation in air. Both absorptions were clearly observed.
Time-Dependent Variation of Composition of SC1 Solution
Authors: Takahashi Isao , Kobayashi Hideyuki , Ryuta Jiro , Mikio Kishimoto Mikio Kishimoto , Takayuki Shingyouji Takayuki Shingyouji
Published: February 2005

We investigated the time-dependent variation of composition of NH4OH/H2O2/H2O mixture, the standard cleaning 1 (SC1) solution in the RCA cleaning process. The NH4OH concentration decreased with time and that of H2O2 was almost constant. It was clarified that the decrease rate of NH4OH concentration depended on the temperature and H2O2 concentration in the SC1 solution. As the temperature was raised, the decrease rate accelerated. Conversely, as H2O2 concentration was raised, the rate decelerated. It is concluded that the hydrogen bond between NH3 and H2O2 prevents NH3 evaporation.
Measurement of Organic Matter on Si Wafer by Thermal Desorption Spectroscopy
Authors: Okada Chizuko , Takahashi Isao , Kobayashi Hiroyuki , Jiro Ryuta Jiro Ryuta , Takayuki Shingyouji Takayuki Shingyouji
Published: February 2005

Organic matter on a Si surface was investigated using thermal desorption spectroscopy (TDS). It was clarified that acetone, ethanol and toluene contaminants on a bare Si surface can be detected by the TDS system, ESCO EMD-WA1000K, and these organic contaminants have different desorption temperatures and fragment patterns. Therefore organic contaminants on Si wafers were thought to be separated by desorption temperature, and characterized from the fragment pattern at that desorption temperature. Here, the desorption temperature is thought to be proportional to the activation energy for desorption. Thus bonding strength between organic contaminants and the Si surface is qualitatively estimated from the desorption temperature.
Barrier Heights of Schottky Junctions on n-InP Treated with Phosphine Plasma
Authors: Sugino Takashi , Sakamoto Yoshifumi , Sumiguchi Tatsuo , Kuninori Nomoto Kuninori Nomoto , Junji Shirafuji Junji Shirafuji
Published: February 2005

Surface treatment of n-InP by phosphine (PH3) plasma is carried out to modify the surface properties. It is observed from Kelvin probe measurements that the surface Fermi level shifts near the conduction band edge after PH3 plasma treatment, while the surface Fermi level is located around 0.4 eV below the conduction band edge for a surface wet-etched before PH3 plasma treatment. A funneling metal-insulator-semiconductor (MIS) Schottky structure is formed on PH3-plasma-treated InP to evaluate the treated surface. The Schottky barrier height evaluated from the Richardson plot is found to depend strongly on the metal work function. This suggests that the surface state density pinning the surface Fermi level is profoundly reduced due to PH3 plasma treatment.
Near-UV Electroluminescence from a ZnCdSSe/ZnSSe Metal-Insulator- Semiconductor Diode on GaP Grown by Molecular Beam Epitaxy
Authors: Ichino Kunio , Onishi Toshikazu , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

A near-UV light-emitting diode based on metal-insulator-semiconductor structure using a ZnCdSSe/ZNSSe single quantum well system on a GaP substrate is demonstrated. The device emits intense near-UV light at a wavelength of 391 nm from the ZnCdSSe quantum well with current injection at 77 K.
Fabrication of Tunnel Junctions with YBCO/Insulator/YBCO Layered Structure Using (013)-Oriented Films as Base Layer
Authors: Matsui Toshiyuki , Suzuki Takeshi , Ohi Akihiko , Hiroshi Kimura Hiroshi Kimura , Kazuo Mukae Kazuo Mukae
Published: February 2005

Tunnel junctions with a Y-Ba-Cu-O (YBCO)/SrTiO3 (STO)/YBCO layered structure were fabricated using (013)-oriented YBCO ((013)YBCO) as a base layer, for the first time. We observed obvious gap structures at around 22 mV and around 10 mV, corresponding to twice the gap voltages parallel and perpendicular to CuO2 plane in the junctions, respectively. According to AFM images of the base (013)YBCO layer, the (013)YBCO surface was not atomically flat. These results suggest that the dominant structures of the (013)YBCO surface were formed not by (013)-planes, but by both (010)- and (001)-planes.
Magnetic Properties of Nonsuperconducting Pb2Sr2RCu3O8+y (R=Y, Pr, Gd and Tb)
Authors: Liaw Ken-Whie , Meen Teen-Hang , Chen Ying-Chung , Lee Wun-Hsin , Yang Hung-Duen
Published: February 2005

X-ray diffraction patterns reveal that all samples contain the single Pb2Sr2YCu3O8+y
phase. The results of electrical-resistivity measurements show that Pb2Sr2RCu3O8+y
(R=Y, Pr, Gd and Tb) are not superconducting at temperatures above 10 K. The paramagnetic effective moments µeff and the magnetic transition temperatures T
N derived from the magnetic susceptibility data are 3.11µB, 7.94µB and 10.04µB, and 8.5 K, 3 K and 5.5 K for R=Pr-, Gd- and Tb-containing compounds, respectively. The similarities and differences in terms of electrical and magnetic properties of these compounds compared with those of the corresponding RBa2Cu3O7-δ are briefly discussed.
Study of Memory Alignment of Nematic Liquid Crystals on Polyvinyl Alcohol Coatings
Authors: Vetter Peter , Yoshinori Ohmura Yoshinori Ohmura , Tatsuo Uchida Tatsuo Uchida
Published: February 2005

Polymer layers can cause memory alignment of nematic liquid crystals. We describe an experimental method to characterize this effect. We studied the temperature dependence of the memory alignment on polyvinyl alcohol coatings. We also investigated the influence of the time span during which the memory alignment is generated. We propose an adsorption-desorption mechanism by which we can explain our observations in a reasonable way.
A Proposal on and Verification of Surface Alignment of Liquid Crystals Aligned by Frictional Rubbing
Authors: Hitoshi Mada Hitoshi Mada , Toshihiko Sonoda Toshihiko Sonoda
Published: February 2005

The alignment of liquid crystals on a treated surface has been qualitatively explained by introducing the concept of a hot spot. The coherent length of liquid crystals and the density of hot spot are important factors governing the stability of alignment. This proposal of hot spot was verified experimentally. A method to obtain good alignment is also proposed.
Formation of Carbon Nanotubes by Evaporation of Carbon Rod Containing Scandium Oxide
Authors: Ohkohchi Masato , Ando Yoshinori , Bandow Shunji , Saito Yahachi
Published: February 2005

Carbon nanotubes and nanoparticles formed by dc arc-discharge evaporation of a carbon composite rod containing scandium oxide were studied by high-resolution scanning electron microscopy (SEM). Nanotubes obtained from the composite rod were more abundant than those obtained from pure carbon rod. Many fibrous nanotubes were gathered together and bunched to form long bundles. Moreover, a number of nanoparticles whose size was nearly the same as the diameter of nanotubes were attached to the surface of each tube in the bundle. It was found that scandium had the effect of promoting the growth of nanotubes.
Continuous GaAs Film Growth on Epitaxial Si Surface in Initial Stage of GaAs/Si Heteroepitaxy
Authors: Tachikawa Masami , Mori Hidefumi , Mitsuru Sugo Mitsuru Sugo , Yoshio Itoh Yoshio Itoh
Published: February 2005

Improvements in the initial stage of GaAs growth on the epitaxial silicon surface without high-temperature Si surface treatment and in the GaAs-Si interface have been observed for the first time by transmission electron microscopy (TEM). Plan-view and cross-sectional TEM images show that initial GaAs layers (10-nm-thick GaAs layer grown at 400°C) on Si continuously cover the whole Si surface. We also observed dislocations in 100-nm-thick GaAs layers grown at 650°C after 400°C growth. The number of dislocations was considerably less than that in conventional thermally treated mechanochemically polished Si samples. These observations show that the epitaxial Si surface has the effect of improving the initial stage of GaAs growth on Si as well as the GaAs-Si interface.
Preparation of MgIn2O4-X Thin Films on Glass Substrate by RF Sputtering
Authors: Un'no Hiroshi , Hikuma Naoko , Omata Takahisa , Ueda Naoyuki , Hashimoto Takuya , Kawazoe Hiroshi
Published: February 2005

MgIn2O4-X
thin films were deposited onto a silica glass plate by the RF sputtering method. The highest conductivity observed for the film post-annealed under H2 flow was 2.3×102 S/cm, with a carrier concentration of 6.3×1020 cm-3 and a mobility of 2.2 cm2·V-1·s-1. No distinct optical absorption band was observed in the visible region.
The Absolute Coverage of K on the Si(111)-3×1-K Surface
Authors: Hashizume Tomihiro , Katayama Mitsuhiro , Jeon Dong-Ryul , Aono Masakazu , Toshio Sakurai Toshio Sakurai
Published: February 2005

The absolute coverage of K on the Si(111)-3×1-K surface which was prepared by deposition of K on the 420°C Si substrate was determined, by using coaxial impact-collision ion scattering spectroscopy, to be 0.29±0.03ML. This result rules out the possibility that the 3×1-K phase is formed by K impurity stabilization claimed by several groups. Another important implication of this result is that K atoms of the 3×1 overlayer are not imaged bright in the STM.
In Situ Observation of Halogen-Transport Atomic Layer Epitaxy of GaAs in Inert Carrier Gas System
Authors: Takahashi Naoyuki , Yagi Minoru , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: February 2005

Atomic layer epitaxy (ALE) using GaCl source in an inert carrier gas system is investigated by means of two in situ monitoring methods: gravimetric method and surface photo-absorption (SPA) method. It is shown that the growth of a monomolecular layer unit occurs in the inert carrier gas system as well as in the H2 carrier gas system. In the SPA measurement, the reflected light intensity during GaCl supply and subsequent inert gas or H2 purge is stronger in the inert carrier gas system than that in the H2 carrier gas system. Based on these results, reaction mechanisms are proposed for the two systems.
Nonresonant Multiphoton Ionization of H2, CO and CO2 by Second Harmonics of Picosecond YAG Laser
Authors: Sekine Shigeyuki , Kokubun Kiyohide , Shingo Ichimura Shingo Ichimura , Hazime Shimizu Hazime Shimizu
Published: February 2005

A nonresonant multiphoton ionization method has been applied for pressure measurement in ultrahigh vacuum. Second harmonics of a commercial picosecond YAG laser was used for ionization of gases in order to reduce noise caused by scattered laser light. Saturation of ionization was observed for H2, CO and CO2 gases at incident laser power density of about 1013 W·cm-2.
Photoreflectance and Photoluminescence Studies of CuAlxGa1-xSe2 Alloys
Authors: Shirakata Sho , Chichibu Shigefusa , Sudo Ryo , Ogawa Akihiro , Matsumoto Satoru , Shigehiro Isomura Shigehiro Isomura
Published: February 2005

Photoreflectance (PR) and photoluminescence (PL) measurements have been carried out at 77 K on single crystals of CuAl
x
Ga1-x
Se2 alloys grown by the chemical vapor transport method. Energies of excitons associated with uppermost valence bands have been determined as a function of composition based on the analysis of PR spectra. Spin-orbit and crystal field splittings have been obtained. PL spectra exhibited an exciton-related line, a peak due to free-to-acceptor transition and a deep level emission band. These PL lines and peaks are discussed in terms of the compositional dependence of the exciton energy.
Observation of Hydrogen-Terminated Silicon (111) Surface by Ultrahigh-Vacuum Atomic Force Microscopy
Authors: Kageshima Masami , Yamada Hirofumi , Morita Yukinori , Tokumoto Hiroshi , Nakayama Kan , Akira Kawazu Akira Kawazu
Published: February 2005

Si(111) surface terminated with hydrogen by NH4F treatment was observed with an ultrahigh-vacuum atomic force microscope (UHV-AFM). Monoatomic steps, triangular etch pits and contamination islands were imaged. Atomically resolved images were also obtained and the periodicity in these images is in good agreement with the Si(111):H-1×1 (monohydride) structure. The corrugation amplitude is 0.10-0.12 nm, which is much larger than any STM result. This value is in fairly good agreement with the value expected in the contact hard sphere model.
Widely Tunable Operation of Ti:Sapphire Lasers under Optimum Coupling Condition
Authors: Funayama Masahiro , Mukaihara Katsuji , Morita Hiroyuki , Okada Tatsuo , Tomonaga Nariyuki , Izumi Jun , Noda Yoshitoshi , Mitsuo Maeda Mitsuo Maeda
Published: February 2005

Widely tunable operation of Ti:sapphire lasers under the optimum coupling condition was investigated. The rate equation analysis on the pulsed Ti:sapphire laser shows that the tunable range can be extended by increasing the cavity-Q value and the pump laser fluence, and this was demonstrated with a Nd:YAG laser-pumped Ti:sapphire laser. If a coupling mirror has a wavelength-dependent reflectivity which increases in shorter and longer wavelengths of the tunable region, the entire spectral region can be tuned under the optimum coupling condition. A dielectric-coated coupling mirror with such wavelength dependence was developed, and a pulsed Ti:sapphire laser was operated under the nearly optimum condition over its tunable range of 690-960 nm without exchanging the mirror. The conversion efficiency was 30% at the maximum point.
Upgrade of RIKEN 10 GHz Electron Cyclotron Resonance Ion Source Using Plasma Cathode Method
Authors: Nakagawa Takahide , Kageyama Tadashi , Kase Masayuki , Akira Goto Akira Goto , Yasushige Yano Yasushige Yano
Published: February 2005

Beam intensities of highly charged nitrogen, neon, argon and krypton ions from the RIKEN 10 GHz electron cyclotron resonance ion source were measured by applying the so-called plasma cathode method to its first-stage structure. This modification has allowed fairly large enhancement of their output intensities as compared with those obtained with the negatively biased electrode previously reported. In addition, characteristics of stability and lifetime have been greatly improved. Optimum gas pressures in the first and second stages have been lowered by nearly a factor of four. In this method gas mixing is not very effective in further increasing the beam intensities of highly charged light ions, except for krypton ions.
Carbon Nanotubes at As-Grown Top Surface of Columnar Carbon Deposit
Authors: Yoshinori Ando Yoshinori Ando
Published: February 2005

Carbon nanotubes are usually found inside the carbon deposit, which grows on the cathode of dc carbon-arc
rod, as fibers or whiskers with co-existing carbon nanoparticles. Curled and intertwined carbon nanotubes having random orientation were also found on the top surface of the columnar carbon deposit, which has a sootlike color. The growth of carbon nanotubes at the top surface of the columnar deposit suggests that carbon nanotubes are formed on the top surface and restored as a columnar deposit.
Quantitative Image Analysis in Brewster Angle Microscopy: Molecular Tilt of a Stearic Acid Monolayer on Water
Authors: Hosoi Kazukuni , Ishikawa Tomohiro , Akihiro Tomioka Akihiro Tomioka , Kenjiro Miyano Kenjiro Miyano
Published: February 2005

A stearic acid monolayer on water has been observed with a Brewster angle microscope. The pressure dependence of the alkyl chain tilt angle has been deduced from the quantitative analysis of microscopic images.
Holography Machine HORN-1 for Computer-Aided Retrieval of Virtual Three-Dimensional Image
Authors: Yabe Takashi , Tomoyoshi Ito Tomoyoshi Ito , Masashi Okazaki Masashi Okazaki
Published: February 2005

We propose a method to efficiently retrieve the original 3-D (three-dimensional) objects by computers as a virtual image from a hologram. The present method is based on the correlation between the hologram of a point source and the hologram of objects. We have succeeded in the retrieval of objects with the wavelength resolution in any direction. This resolution is not possible with conventional holography. HORN-1 (HOlographic ReconstructioN) is a machine specially prepared for this purpose and enables us to accomplish this work within a short period of time. The machine has achieved a speed of 500 MFLOPS with one circuit.
Preliminary Pressure Measurement in the Range of 10-9 Pa Using a Picosecond Pulsed Laser
Authors: Kokubun Kiyohide , Sekine Sigeyuki , Shingo Ichimura Shingo Ichimura , Hazime Shimizu Hazime Shimizu
Published: February 2005

Results of the preliminary pressure measurement using a picosecond pulsed YAG laser are presented. By this method, pressures in the range of 10-9 Pa were measured for H2 gas. Advantages of this method and the problem of noise are discussed compared with the method using an excimer laser.
In Situ Spectrum Observation of Ga Deposition Process during GaAs Metal-Organic Chemical Vapor Deposition Using Surface Photo-Absorption
Authors: Yamauchi Yoshiharu , Kunihiko Uwai Kunihiko Uwai , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

In situ spectrum measurement by surface photo-absorption (SPA) is applied to study the Ga deposition process on (001) GaAs in metal-organic chemical vapor deposition (MOCVD). The change in SPA spectra is measured in the wavelength range from 300 nm to 800 nm, when triethylgallium is supplied on As-stabilized surface. The change at 470 nm is caused by the disappearance of the uppermost As dimer of c(4×4) surface followed by the appearance of a(2×4) As dimer domain or the formation of Ga-As back bonds. A broad spectrum from 500 nm to 800 nm is observed after one-monolayer Ga deposition, implying a correlation with Ga droplet formation. The calculated spectrum supports this broad spectrum being due to the photo-absorption by free Ga atoms on Ga-stabilized surface or metallic Ga atoms included in droplets.
In Situ Hydrogenation of Amorphous Silicon Prepared by Thermal Decomposition of Disilane
Authors: Yamanaka Mitsuyuki , Yutaka Hayashi Yutaka Hayashi , Isao Sakata Isao Sakata
Published: February 2005

Thin hydrogenated amorphous silicon (a-Si:H) layers with thicknesses of 90-600 Å grown by thermal decomposition of disilane were treated with rf hydrogen plasma just after deposition at the same temperature (430-440°C). During this process (referred to as in situ hydrogenation), atomic hydrogen passivates defects, and the effective thickness of this passivated layer is estimated to be 220 Å. Atomic hydrogen also induces structural relaxation of the Si network even in a-Si:H deposited at high temperature (>400°C) while the change of bonded hydrogen content is rather small in in situ hydrogenation.
Voltage Versus Flux Relation of High Tc DC Superconducting Quantum Interference Device with Different Inductances
Authors: Keiji Enpuku Keiji Enpuku
Published: February 2005

The voltage versus flux (V-Φ) relation of dc superconducting quantum interference devices
(SQUIDs) in the presence of thermal noise at T=77 K is studied. A theoretical expression for the modulation voltage ΔV in the V-Φ relation is presented as a function of SQUID inductance. The theoretical expression is compared with experimental results of ΔV reported recently for high T
c SQUIDs with different inductances. It is shown that experimental results agree quantitatively with theoretical ones. It is also shown that imperfection of Josephson junctions degrades the modulation voltage more significantly when the inductance increases. The dependence of the modulation voltage on the inductance clarified in the paper is useful for developing a magnetic sensor using the SQUID.
Epitaxial Growth of Co/Cr Bilayer Films on MgO Single Crystal Substrates
Authors: Atsushi Nakamura Atsushi Nakamura , Masaaki Futamoto Masaaki Futamoto
Published: February 2005

Co/Cr bilayer films have been epitaxially grown on MgO (100) and (110) substrates. The Cr (100) and the Co (112̄0) planes are parallel to the MgO (100) substrate plane. The Co layer has a bicrystalline structure which consists of two types of domains with their c-axes lying in-plane and perpendicular to each other. The Cr (211) and the Co (11̄00) planes are parallel to the MgO (110) substrate plane, and a single-crystalline Co layer is obtained with an in-plane c-axis consisting of slightly misoriented subgrains. Both films show azimuthal magnetic anisotropy in the film plane.
Laser Pulse Excitation on Optical Absorption Band in NaCl Single Crystal after Intense Electron Irradiation
Authors: Inabe Katsuyuki , Masaaki Adachi Masaaki Adachi , Nozomu Takeuchi Nozomu Takeuchi
Published: February 2005

Transient observation under excitation with laser pulses is carried out on the optical absorption band in electron-irradiated NaCl using a monochromator coupled with a charge-coupled device (CCD) linear sensor. The free electron effect of the 2.10 eV band is confirmed from the result that no saturation effect of the band is observed even with high-power (320 GW/m2) excitation, in contrast to the saturation effect of the band of localized electron centers in NaCl.
Simultaneous Time-Resolved Measurements of Weight and Small-Angle X-Ray Scattering of Heat- and Pressure-Treated Egg White during Gel-to-Glasslike Transition
Authors: Kanaya Haruichi , Hara Kazuhiro , Takushi Eisei , Matsushige Kazumi
Published: February 2005

Time-resolved measurements of weight and the small-angle X-ray scattering (SAXS) profiles of heat- and pressure-treated egg white during the gel-to-glasslike transition were performed simultaneously. Although the weight decreased with time in both types of egg whites, the Guinier radii calculated from the SAXS profiles showed quite different tendencies; in the heat-treated gel, it decreased considerably with time, but that of the pressure-treated one remained almost constant. These results indicate that the denaturation procedure considerably influences the gel structure and their semimicroscopic properties during the transition.
Hydrogen Plasma Durability of Chemically Treated SnO2 Thin Films
Authors: Kawabata Keishi , Hirose Takeshi Tanaka
Published: February 2005

The chemical stability of SnO2 surfaces against hydrogen plasma exposure has been studied by treating a SnO2/glass system either in steam at a substrate temperature of 200 and 400°C or in ethyl alcohol at 200 and 400°C, or by fluorinating the surface at 400°C in an NF3+O2 gas mixture. Also, an electroplated Zn layer on SnO2 has been oxidized at 400°C. X-ray photoelectron spectroscopy of such surfaces has revealed that the reduction reaction of the SnO2 surface exposed to hydrogen plasma is dramatically suppressed by the steam treatment at 400°C.
Temperature-Programmed Scattering (TPS) Study on Reactivity Difference of GaAs and GaAs Oxide Surfaces
Authors: Sasaki Masahiro , Seikoh Yoshida Seikoh Yoshida , Chikashi Yamada Chikashi Yamada
Published: February 2005

The reactivity of GaAs and GaAs oxide surfaces to trimethylgallium (TMG) was studied by temperature-programmed scattering (TPS) through the energy accommodation coefficient (EAC). The substrate temperature was increased at a constant rate while the scattered TMG was being measured under a constant flux of TMG supplied to the substrate by a cryo-shrouded quadrupole mass spectrometer. Since the detection efficiency of the spectrometer is inversely proportional to the translational velocity of scattered TMG, the observed intensity variation represents the change in translational velocity of reflected TMG during the temperature increase. The variation of the signal intensities was least-squares analyzed to yield the EAC, which is a measure of the surface reactivity. The thus-obtained reactivity of photo-oxidized GaAs to TMG is smaller than that of dark-oxidized GaAs, which is even smaller than that of a bare GaAs surface. This difference in the reactivity is discussed in relation to the mechanism of selective area growth of GaAs using GaAs oxide as a mask.
Optical Energy Gap Measurement of Plasma Chemical Vapor Deposition Very Thin Films Using Evanescent Wave
Authors: Naganori Takezawa Naganori Takezawa , Isamu Kato Isamu Kato
Published: February 2005

We propose the use of an evanescent field of waveguided light transmitted along a portion of an optical fiber with the cladding removed (a cladless optical fiber) to obtain the optical energy gap (E
o) of a semiconductor. Through our study of this new method of measurement, it is clarified that E
o of hydrogenated amorphous silicon (a-Si:H) semiconductor can be determined using a longer fabricated film which is thinner than ordinarily used. While ordinary methods of measurement require a film thickness on the order of 1 µm, this new method of measurement requires a film thickness on the order of 4 nm, with the cladless part of 50 mm in length.
Scanning Electron Microscope Observations of As+-Ion-Implanted Region
Authors: Takahashi Yasuhito , Yabuuchi Yasufumi , Inazato Sachiko , Ogura Kazumichi , Ono Akishige
Published: February 2005

Lateral and depth profiles of the ion-implanted region were first observed using cleaved cross-sectional scanning electron microscope. The amorphous region induced by ion bombardment appears dark relative to the crystalline region. It is found that the secondary electrons, as well as the backscattered ones, are influenced by the so-called channeling effect.
A Method for Calibrating Pressure by Applying the Pressure-Temperature Phase Diagram of Tin
Authors: Yasuo Fujinaga Yasuo Fujinaga
Published: February 2005

The pressure in a solid medium is determined by means of isobaric measurement of the electrical resistance of tin as a function of temperature. The transition temperatures at the phase boundaries I (A4)→III (bct) and III→L (liquid) are used for evaluation of the pressure value by applying the pressure-temperature phase diagram of tin. It is shown that the pressure value is located approximately on the calibration curve obtained using the conventional calibration method in solid media with bismuth and barium as the pressure calibration materials.
Self Organized Grain Growth Larger than 1 µm through Pulsed-Laser-Induced Melting of Silicon Films
Authors: Toshiyuki Sameshima Toshiyuki Sameshima
Published: February 2005

Large-grain growth (>1 µm) was observed through pulsed-laser-induced melting of silicon films. When silicon islands with a width of 10 µm and a thickness of 70 nm formed on a quartz substrate were melted completely by irradiation of a XeCl excimer laser with an energy of 360 mJ/cm2, the shape of the film was changed into a globular shape. The width shrank to 2.4 µm and the film thickness increased to 270 nm near the edge. Large grains with a size of 1.2 µm were grown and grains were lined two deep in the globular islands. The large-grain growth occurs along a temperature gradient in the lateral direction, which is caused during the change of the film shape.
YBa2Cu3O7 Growth on Metal Substrates with SrTiO3 Buffer Layer by Metal-Organic Chemical Vapor Deposition
Authors: Umemura Toshio , Matsuno Shigeru , Kinouchi Shin-ichi , Egawa Kunihiko , Miyashita Shoji , Nakabayashi Fusaoki Uchikawa
Published: February 2005

We prepared oxide superconducting YBa2Cu3O7-x
thin films on Hastelloy substrates with a SrTiO3 buffer layer by metal-organic chemical vapor deposition (MOCVD) using a single source of tetrahydrofuran solution. To clarify the cause of poor superconducting properties, the cross section of YBa2Cu3O7-x
/SrTiO3/Hastelloy was examined by TEM. The YBa2Cu3O7-x
and SrTiO3 layers grew perpendicular to the Hastelloy surface, which was columnar. The orientation of the YBa2Cu3O7-x
layer seems to depend on that of the SrTiO3 layer. As a result, it is considered that the deposition of a good single-crystalline buffer layer on Hastelloy is the most important factor for obtaining excellent YBa2Cu3O7-x
films.
Observation of Single-Electron Charging Effect in BiSrCaCuO Granular Thin Films
Authors: Han Xiaoyi , Shinohara Masayuki , Nobuyuki Yoshikawa Nobuyuki Yoshikawa , Masanori Sugahara Masanori Sugahara
Published: February 2005

The electrical field effect of highly resistive BiSrCaCuO granular thin films was studied. In order to form a uniform granular structure, BiSrCaCuO thin films where deposited on SrTiO3(110) substrates. When the films have relatively high room-temperature sheet resistance, the insulating transition at low temperatures and the charging effect are observed, which may be due to the single-electron tunneling effect in the array of small intergrain junctions.
Mechanical Alloying Process of a Mixture of α-Fe and γ′-Fe4N Powders
Authors: Koyano Tamotsu , Takizawa Toru , Toshiharu Fukunaga Toshiharu Fukunaga , Uichiro Mizutani Uichiro Mizutani
Published: February 2005

Bcc-like metastable powder of iron nitride can be synthesized by mechanical alloying of a mixture of elemental Fe and γ′-Fe4N powders. Its heat of formation deduced from differential scanning calorimetry is about +6.5 kJ/mol at a composition of 11 at%N. Both this value and its magnetization at room temperature are in good agreement with those of the bcc-like powder produced by ball milling of elemental Fe powder in NH3 gas atmosphere.
Stimulated Emission Processes in Zn1-xCdxSe/ZnSe Multiquantum Wells
Authors: Jen Jen Y. , Tsutsumi Takeharu , Souma Izuru , Fujiyasu Yasuo Oka
Published: February 2005

A stimulated emission effect has been studied in Zn1-x
Cd
x
Se/ZnSe (x=0.3) multiquantum wells (MQWs) with the well width of 7 to 70 Å. The luminescence spectrum of the quantum well (QW) exciton at 4.2 K is shifted from the absorption spectrum by 10-12 meV to the lower-energy side. The deviation of the peak energy of the luminescence shows that the excitons in the MQW are inhomogeneously broadened by the monolayer fluctuation of the QW width. Stimulated emission is observed in the low-energy shoulder of the exciton luminescence band, which shifts to lower energies with increasing excitation intensity. The gain process is explained by the exciton-exciton scattering in the MQWs.
Separation of Two Subsystems in Nd13Fe46B41 Composite Crystal Utilizing Synchrotron Radiation
Authors: Ohba Takuya , Hara Toru , Sasaki Satoshi , Takata Masaki , Komura Yukitomo
Published: February 2005

The composite crystal, Nd13Fe46B41, was examined utilizing synchrotron radiation. Diffraction profiles along the c
* axis were measured at the wavelength of Nd and Fe absorption edges. It was clarified that two subsystems, Nd and Fe subsystems, contribute differently, and that the modulation periods of Nd and Fe are slightly different. The widths of peaks from Nd and Fe reveal that the fundamental period of the Nd subsystem fluctuates much more than that of the Fe subsystem.
Diamond-Like Carbon Films Prepared by Photochemical Vapour Deposition
Authors: Ray Swati , Abdul Rafik Middya Abdul Rafik Middya , Asok Kumar Barua Asok Kumar Barua
Published: February 2005

Diamond-like carbon films have been successfully grown at comparatively low substrate temperature (250°C) on single-crystal silicon substrates by the photochemical vapour deposition technique. Raman spectroscopy and scanning electron microscopy studies have shown the formation of diamond particles embedded in the diamond-like carbon film. However, some amount of graphitic carbon is present in the material. The presence of sp3 as well as sp2 hybridised carbon atoms is also confirmed by infrared vibrational spectroscopy. Extremely high transparency (>90%) for 500 Å film from the near-infrared to visible regions is an indication of the high optical gap of the film.
X-Ray Photoelectron Spectroscopy Using a Focused-Laser-Produced Plasma X-Ray Beam
Authors: Aoki Sadao , Ohchi Tadayuki , Sudo Shuuzou , Nakajima Kunio , Onuki Tetsuji , Sugisaki Katsumi
Published: February 2005

The observation of X-ray photoelectrons induced by laser-produced plasma X-rays has been made for the very first time. Aluminum plasma X-rays were monochromatized to 5.25 nm (236 eV) using a multilayer mirror and focused to 50 µm×70 µm by the Wolter type-I mirror. Au(4f) and SiO2(2p) photoelectrons were observed with the hemispherical electrostatic electron energy analyzer. The multichannel detector has been used to detect the pulse photoelectrons of the required energy bands individually.
Depth Profile Measurement of Activated Boron-Concentration in Diamond Thin Films Utilizing Schottky Diode C-V Curves
Authors: Kobayashi Takeshi , Hou Gen Riang , Tetsuro Maki Tetsuro Maki , Shozo Shikama Shozo Shikama
Published: February 2005

The depth profiles of activated boron concentration N
B in the Al/p+-diamond Schottky diodes were systematically investigated from the junction capacitance-voltage (C-V) curves. The observed 1/C
2 vs V plot did not fall on straight lines, indicating a nonuniform depth profile of N
B. Using these C-V curves, activated boron concentration N
B profiles were obtained. From the outermost surface to 50∼300-nm-deep layers (depending upon the original doping amount), N
B decreased by two∼three orders of magnitude from its original value. This kind of abrupt profile developed only in regions in contact with Al.
Cross Sectional Shape Dependence of Quantum Wire Band Structures and Optical Matrix Elements
Authors: Tanaka Takuji , Yamauchi Tadaaki , Schulman Joel N. , Yasuhiko Arakawa Yasuhiko Arakawa
Published: February 2005

The tight binding method is used to analyze the band structures and the optical matrix elements of GaAs/Al
x
Ga1-x
As quantum wires which have triangular and square cross sections, focusing on a comparison of the polarization dependences. The results show that, in the triangular-shaped quantum wire, the decreased symmetry enhances the non-parabolicity in the E-k dispersion curve, which results in a decrease of the magnitude of important optical transitions as compared with those of the square-shaped quantum wire. This property of the triangular-shaped quantum wire leads to a significant difference in the polarization dependence of the optical transitions between the two types of quantum wires. These results demonstrate the importance of considering the influence of the cross sectional shape in the design of quantum wire devices, especially when comparing high and low symmetry cross sections.
High-Pressure Synthesis of New Superconducting Compound CuSr2(Y, Ce)2Cu2Oz
Authors: Akira Ono Akira Ono
Published: February 2005

A new Cu-1222 compound, CuSr2(Y, Ce)2Cu2O
z
, is prepared under ∼2 GPa of oxygen. It crystallizes in a tetragonal structure. Samples containing a significant amount of the Cu-1222 phase exhibit superconducting diamagnetic signals below ∼50 K. Synthesis conditions of the Cu-1222 phase are studied using various kinds of starting samples. It is concluded that the Cu-1222 phase is stable under high oxygen pressures, while another phase, (Cu, Ce)Sr2(Y, Ce)2Cu2O
z
is metastable at ∼2 GPa of oxygen.
Low-Temperature GaAs Metalorganic Chemical Vapor Deposition Using Dimethylamine Gallane and Arsine
Authors: Yoshiharu Yamauchi Yoshiharu Yamauchi , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

Dimethylamine gallane (DMAG) is used for low-temperature GaAs metalorganic chemical vapor deposition (MOCVD) because it has a much lower decomposition onset temperature than trialkyl Ga sources. We grow GaAs layers using the simultaneous supply mode (conventional MOCVD) and an alternate supply mode (flow-rate modulation epitaxy-FME) for DMAG and arsine, and compare their electrical and optical properties. Mirror-like surfaces are obtained at substrate temperatures above 250°C, and low-temperature photoluminescence spectra show different excitonic features for both supply modes. For the simultaneous supply mode, an increase in arsine partial pressure during growth shifts the bound exciton peak to a longer wavelength due to the increase of the defect-related exciton peak. For the FME mode however, no peak shift is observed with increasing arsine partial pressure, indicating that defect incorporation is well suppressed in FME.
Morphology-Dependent Multiorder Raman Spectra from a Liquid Glycerol Droplet by Low-Power He-Ne Laser Pumping
Authors: Taniguchi Hiroshi , Tomisawa Humihiro , Nagashima Ryuji
Published: February 2005

Multiorder Raman spectra (MRS) from a single liquid-droplet of glycerol are observed, according to morphology-dependent resonances (MDRs) by cw He-Ne laser-pumping with a low-power output. A technique of making liquid spheres and fundamental characteristics of the MRS concerning the MDRs due to a continuous variation of droplet sizes are presented.