bluuebunny/crossref_metadata_2025 huggingface dataset:
Compositional Change of Silicon Carbide Surface due to Oxygen Adsorption and Heat Treatment
Authors: Minagawa Hideki , Vina Raul Oscar , Kadowaki Tohru , Mizuno Seigi , Tochihara Hiroshi , Kazunobu Hayakawa Kazunobu Hayakawa , Isamu Toyoshima Isamu Toyoshima
Published: February 2005

The compositional change of the 6H-SiC(101̄0) surface was studied under heat treatment and adsorption of oxygen. X-ray photoelectron spectroscopy (XPS) was used for the analysis of the depth composition profile and chemical binding state. After heat treatment, the carbon concentration of the surface was increased due to the surface segregation of the graphite type carbon. When the adsoption of oxygen was performed with heat treatment, the carbon concentration of the surface was increased, but the amount of segregated carbon was less than that of the sample after only heat treatment. The segregated carbon seemed to react with oxygen preferentialy and to desorb from the surface as a carbon monoxide or carbon dioxide.
Polycrystalline Diamond/Hydrogenated Amorphous Silicon P-N Heterojunction
Authors: Kiyota Hideo , Yoneda Masahiro , Izumiya Hiroshi , Okushi Hideyo , Okano Ken , Kurosu Tateki , Iida Masamori
Published: February 2005

Electrical properties of a heterojunction between a p-type polycrystalline diamond and n-type hydrogenated amorphous silicon (a-Si:H) are described for the first time. The current(I)-voltage(V) characteristics of the p-n heterojunction show good rectification, and the capacitance(C)-voltage(V) characteristics show an approximate linear C
-2-V relationship in the reverse bias condition. These results and other experimental evidence have confirmed that the rectification is caused by the depletion layer in the vicinity of the junction.
Frequency-Dependent Conductivity in Polycrystalline Chemical Vapor Deposited Diamond Films
Authors: Muto Yasuaki , Sugino Takashi , Kobashi Koji , Junji Shirafuji Junji Shirafuji
Published: February 2005

Studies have been made on frequency-dependent electrical conduction in polycrystalline diamond films prepared by plasma-enhanced chemical vapor deposition (PECVD). It is found by ac conductivity measurements that the electrical conduction in annealed diamond films is attributed to frequency-independent band conduction in a low-frequency range, f
0.8-dependent hopping conduction in a high-frequency range and thermal emission of carriers from trap levels. Activation energies of three trap levels are 0.62, 1.38 and 0.95 eV. The 0.62 and the 1.38 eV trap levels are passivated in hydrogenated diamond films.
Submicrometer-Scale Patterning of Superconducting Nb Films Using Focused Ion Beam
Authors: Akaike Hiroyuki , Fujimaki Akira , Yoshiaki Takai Yoshiaki Takai , Hisao Hayakawa Hisao Hayakawa
Published: February 2005

We have developed a novel patterning technique for superconducting Nb films with submicrometer scales, using a focused ion beam (FIB). The technique makes use of a phenomenon wherein the plasma etching rate of Nb films exposed to a Ga+ focused ion beam is much lower than that of unexposed Nb films, when they are etched by reactive ion etching (RIE) in CF4 plasma. The etching rate of films exposed to 100 keV Ga+ FIB at a dose >2×1016/cm2 was less than one-quarter of that of unexposed films. Using this technique, we have fabricated 0.1-µm-wide Nb strips with the critical current density of 1×107 A/cm2 at 4.2 K. This value is almost equal to that of bare films.
Fabrication of Ultrafine X-Ray Mask Using Precise Crystal Growth Technique
Authors: Miyamoto Yasuyuki , Kazuhito Furuya Kazuhito Furuya , Daisuke Yamazaki Daisuke Yamazaki
Published: February 2005

Fabrication of an ultrafine pitch mask for X-ray lithography by precise crystal growth is proposed. With the use of a precise crystal growth technique, a grating pattern with nanometer pitch and/or a precision of the atomic spacing can be transferred. As a preliminary experiment, masks of GaInAs/InP layered structure were grown by organometallic vapor phase epitaxy (OMVPE) and patterns were transferred by Cu-L X-ray. One-hundred-nm patterns were transferred onto resist layers.
Stark Phase Shift and Deflection in the Ultracold Atomic Interferometer
Authors: Shimizu Fujio , Shimizu Kazuko , Takuma Hiroshi
Published: February 2005

Phase shift and deflection of interference patterns induced by the static electric field are studied in an optically cooled 1s3 metastable neon interferometer with Young's double-slit configuration.
An Advantage of Pnp over Npn AlGaAs/GaAs Heterojunction Bipolar Transistors for Microwave Power Applications
Authors: William Liu William Liu , Changhong Dai Changhong Dai
Published: February 2005

This letter demonstrates that the emitter crowding effects are much more dramatic for typical Npn HBTs compared to Pnp HBTs. Hence, the design of emitter width in Pnp HBTs is much more flexible and this advantage is shown to favor Pnp HBTs for millimeter-wave power applications.
Anisotropic Irreversibility Lines for C-Axis Aligned (Bi, Pb)2Ca2Sr2Cu3O10+δ Powders
Authors: Shi J. B. , Chiou B. S. , Kuo P. L. , Ku H. C.
Published: February 2005

Anisotropic irreversibility lines due to thermal fluctuation for quasi-two-dimensional high-T
c superconductors were observed in c-axis-aligned powders of the (Bi, Pb)2Ca2Sr2Cu3O10+δ Bi(2223) compound with T
c=108 K. The anisotropic ratio H
r(⊥c)/H
r(//c) decreases sharply from 13.6 at 100 K to low values of 3.2 at 80 K and 3.1 at 70 K. The simple 3D-like power law H
r=a·(1-T/T
c)
n
was observed only in the low field region (≤200 G) with n=2.19 for H⊥c and 2.99 for H//c. In the higher field region up to 4 kG, the temperature dependence of H
r(T) lines changes into a 2D-like exponential function H
r=b·exp
(-T/T
0) due to the breakdown of the interlayer and/or intralayer coupling of the conduction channel which consists of three Cu-O planes, with T
0=14.2 K for H⊥c and 13.7 K for H//c. The magnetic susceptibility ratio χc/χab for this highly anisotropic superconductor in a low applied field of 8 G increases sharply from 9.8 at 5 K to 17.9 near T
c.
Lattice Dynamic Study of Semiconducting Bi2Sr2Y(Cu1-xSnx)2Oyby119Sn-Mössbauer Spectroscopy
Authors: Ishii Hiromi , Nishida Tetsuaki , Katada Motomi , Aomine Takafumi
Published: February 2005

The119Sn-Mössbauer spectra of semiconducting Bi2Sr2Y(Cu1-xSnx)2Oyceramic consist of singlet peaks (δ: 0.02-0.09 mm·s-1, Γ: 1.09-1.20 mm·s-1) in the temperature range 298 K-7 K. The absorption area (A) increases almost linearly with decreasing temperature, indicating the “normal” Sn-site vibration expressed by the “combined Debye and Einstein model”. A comparison of the theoretical curve to the lnA-vs-Tand δ-vs-Tplots yields the Debye and Einstein temperatures of 370 and 200 K, respectively. These results suggest that the Sn4+is present in the BiO4planars, constituting Bi(Sn)O5pyramids.
Scanning Tunneling Microscope Study of the Structural Transformation of the Si(111)7×7 Surface to the Na-Induced 3×1 Surface
Authors: Jeon Dong-Ryul , Hashizume Tomihiro , Wang Xiangdong , Bai Chunli , Kumi Motai Kumi Motai , Toshio Sakurai Toshio Sakurai
Published: February 2005

The structure of the Na-induced Si(111) 3×1 surface has been studied using a field-ion-scanning-tunneling-microscope. The STM images showed that the entire Si surface was uniformly covered with a single layer of atomically resolved Na 3×1 structure. Upon annealing, the Na layer peeled off gradually, revealing the underlying Si substrate, which exhibited various intermediate reconstructions such as 2×2, 5×5, and 9×9 before the 7×7 structure was restored at 800°C. Our observations suggest that the top layer of the Si substrate converts to the bulk terminated 1×1 structure upon Na deposition and annealing.
Electron Spin Resonance and Optical Absorption of Ti3+and V3+in CuAlS2
Authors: Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: February 2005

Electron spin resonance (ESR) and optical absorption spectra have been studied in Ti- and V-doped CuAlS2crystals, grown by the chemical vapour transport technique. Identification of the ESR centers as being due to Ti3+and V3+has been confirmed by the observation of hyperfine structures arising from hyperfine interaction with four second-shell27Al nuclei (titanium-case) and with the nuclear magnetic moment of51V (vanadium case). The results obtained show that both Ti and V in CuAlS2are trivalent, with Ti3+ions substituting for Al3+-sites and V3+ions substituting for Cu+-sites.
Surface Resistance of Bi2Sr2Ca1Cu2Oy Strip Lines Made from Green Sheet
Authors: Ohshima Shigetoshi , Okuyama Katsuro , Sawaya Kunio , Noguchi Keisuke
Published: February 2005

The surface resistance, R
s, of Bi2Sr2Ca1Cu2O
y
(2212) strip lines prepared by the doctor blade method was measured by the strip-line resonance method. The highest T
c
R=0
of these strip lines measured by the conventional dc method was about 80 K. The R
s values were very sensitive to the surface and grain morphology of the films. It was verified through scanning electron microscope (SEM) observation and X-ray analysis that the R
s values of strip lines consisting of crystal grains whose c axes were oriented normal to substrate were smaller than those of strip lines with nonoriented grains. The values were about 6-22 mΩ at 70 K in the frequency range of 0.6-2.5 GHz. The R
s values were proportional to f
1.0, in contradiction to the f
2 dependence expected from the two-fluid model.
Poling Dynamics and Negligible Relaxation in Aromatic Polyurea Studied by In Situ Observation of Second-Harmonic Generation
Authors: Nagamori Hisatoshi , Kajikawa Kotaro , Takezoe Hideo , Fukuda Atsuo , Ukishima Sadayuki , Iijima Masayuki , Takahashi Yoshikazu , Fukada Eiichi
Published: February 2005

The poling process has been observed by means of second-harmonic generation in aromatic polyurea prepared by vapor deposition polymerization. Polymerization from the as-grown oligomer and crystallization proceed simultaneously with an electric-field-induced alignment of the urea group at about 130°C. Consequently, the poled structure is thermally quite stable even at 200°C and shows negligible relaxation at room temperature.
Photoreflectance Studies of Ga0.5In0.5P/GaAs Heterostructures Grown by Metalorganic Chemical Vapor Deposition Technique
Authors: Hwang Jenn-Shyong , Hang Zhijiang , Tyan Shin-Long , Ding Sheng-Wei , Tung Jen-Hsiung , Chen Chin-Yuan , Lee Biing-Jye , Hsu Jung-Tsung
Published: February 2005

Photoreflectance was used to study lattice-matched Ga0.5In0.5P/GaAs heterostructures grown using metalorganic chemical vapor deposition. The built-in electric field in the GaAs region at the Ga0.5In0.5P/GaAs interface was evaluated using the observed Franz-Keldysh oscillations. The fundamental energy gaps, E
o and E
o+Δo, of Ga0.5In0.5P were also determined. In addition, we found that as the doping concentration of the Ga0.5In0.5P increased, the broadening parameters of the band gap also increased.
Drastic Decrease in Viscosity of Molten LiNbO3 under Non-Oxygen Atmosphere
Authors: Koji Shigematsu Koji Shigematsu , Shigeyuki Kimura Shigeyuki Kimura
Published: February 2005

The viscosity of undoped and MgO-doped LiNbO3 was measured by the oscillation damping method under non-oxygen atmosphere. The obtained viscosity values of undoped LiNbO3 were not much different from those of MgO-doped LiNbO3, but considerably smaller (1/2-1/4) than the previously reported values, which were measured in air. This drastic decrease was attributed to non-oxygen atmosphere. It was pointed out that the uniform dispersion of the
dopant and the uniform liquid structure were easily realized under non-oxygen atmosphere.
Preparation of (111)-Oriented β-Ta2O5 Thin Films by Chemical Vapor Deposition Using Metalorganic Precursors
Authors: Tominaga Koji , Muhammet Rusul , Kobayashi Ichizo , Masaru Okada Masaru Okada
Published: February 2005

Tantalum pentaoxide thin films with orthorhombic structure have been grown on quartz and Si(100) substrates at 600∼700°C under reduced pressure of 5 Torr by metalorganic chemical vapor deposition. Ta(OC2H5)5 and Ta(DPM)4Cl were used as the source materials, and were compared with each other with respect to deposition behavior, crystal structure and orientation of Ta2O5 films. When the Ta(DPM)4Cl precursor was used, fine (111)-oriented Ta2O5 films were obtained on quartz and Si(100) substrates in a temperature range of 625∼675°C.
Low Dislocation Density GaAs on Vicinal Si(100) Grown by Molecular Beam Epitaxy with Atomic Hydrogen Irradiation
Authors: Shimomura Hirofumi , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

This work describes a novel technique for reducing the dislocation density of GaAs grown on Si(100). Atomic hydrogen has been irradiated for both the surface cleaning stage of the substrate prior to and during the growth by the conventional molecular beam epitaxy (MBE). Effects of atomic hydrogen irradiation at the Si surface cleaning stage shows that not only clean single domain surfaces can be obtained below 700°C, which is much lower than the normal surface preparation temperature, but also results in a drastic reduction of the dislocation density in the GaAs films. The epitaxial films grown at different substrate temperatures have exhibited different values of dislocation densities as determined by etch pit density (EPD) measurements, and the average density of as low as 7×104 cm-2 has been obtained for GaAs films grown at low-temperature of 330°C.
Improved Surface Crystallinity of MgO Crystal Substrate through Annealing in Oxygen Atmosphere
Authors: Awaji Takahiro , Sakuta Ken , Yoshiyuki Sakaguchi Yoshiyuki Sakaguchi , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

The oxygen annealing (OA) effects on MgO substrates commercially available were closely investigated. The smeared low-energy electron diffraction spot pattern and transmissionlike spot pattern of reflection high-energy electron diffraction were dramatically changed to those of almost ideal MgO crystals through OA at 1000°C. After OA, the spotty cathodeluminescence (CL) pattern disappeared almost completely, and the peak wave-length of CL spectra shifted from blue (∼400 nm) to red (∼715 nm). The 5-nm-thick epitaxial YBaCuO films grown on (100)MgO substrates with OA exhibited good superconductivity. Otherwise, superconductivity was not evident. However, the macroscopic subgrain structure seen in the X-ray topographs showed no meaningful changes between before and after OA.
Mirrorless Microcavity Spontaneously Formed in Ferroelectric Liquid Crystals
Authors: Kajikawa Kotaro , Isozaki Tadaaki , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

We have observed second-harmonic generation (SHG) from ferroelectric liquid crystals (FLC) as a function of helicoidal pitch. Not only the transmitted but also the reflected SH intensities markedly increase when the wavelength of the SH light coincides with the optical pitch of the helicoid. This fact implies the existence of cavity action by FLC: the helicoidal structure confines the SH light generated inside.
Downstream Gas Temperature Variation of Glow and Plasmoidal Oxygen Radio Frequency Discharges
Authors: Wickramanayaka Sunil , Hatanaka Yoshinori , Hitoshi Jimba Hitoshi Jimba , Naokichi Hosokawa Naokichi Hosokawa
Published: February 2005

The downstream gas temperature variation of radio frequency (13.56 MHz) electrodeless discharges is measured as a function of power, gas flow rate and pressure. The gas temperature is seen to increase linearly with power but shows a drastic drop at the point where glow discharge plasma shifts to the plasmoid state. The drop in temperature is assumed to be due to the dissipation of energy which leaves the localized plasmoid. The variation of gas temperature is found to follow a relationship similar to that of the gas residence time in the discharge region with changing flow rate and pressure.
Sub-100-nm-Scale Patterning Using a Low-Energy Electron Beam
Authors: Kiyoshi Ishii Kiyoshi Ishii , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

This study explores the feasibility of nanometer-scale patterning using a low-energy electron beam. Improved resolution results from low-energy electron beam generation by a retarding field optical column with a Zr/W Schottky electron (SE) source. The beam is focused to 17 nm with a current of 100 pA at an energy of 2 keV. The 2-keV electron beam is used to expose a 50-nm-thick poly(methylmethacrylate) (PMMA) resist on a Si substrate. A 95-nm line-and-space pattern can be produced by carefully controlling the exposure dose.
Ultra-Dry Oxidation for Improving the Time-Dependent Dielectric Breakdown Lifetime of Ultra-Thin Silicon Oxide Films
Authors: Hiroshi Yamada Hiroshi Yamada , Michiharu Tabe Michiharu Tabe
Published: February 2005

Time-dependent dielectric breakdown lifetime of 5-nm-thick silicon oxide films oxidized in an ultra-dry oxygen gas of less than 1-ppm moisture concentration was investigated. The lifetime for the ultra-dry films was larger than that for the conventional films oxidized in more than 100-ppm humidity. In particular, a pronounced improvement can be confirmed in the case when a silicon substrate is an anode. Since stress-induced positive charges, which affect the lifetime, are mainly generated near the anode-side oxide interfaces, the oxide-silicon interface conditions are probably improved by the ultra-dry oxidation.
Site Dependence of Soft Errors Induced by Single-Ion Hitting in 64 kbit Static Random Access Memory (SRAM)
Authors: Noritake Katsunori , Matsukawa Takashi , Koh Meishoku , Hara Ken-ichi , Makoto Goto Makoto Goto , Iwao Ohdomari Iwao Ohdomari
Published: February 2005

With the use of a single α particle of 3 MeV from a collimated micron-size ion beam, soft errors have been induced incidentally in 64 kbit SRAMs. Mapping of the soft error sites has revealed that the drain regions of “off”-state transistors are most susceptible to the single-ion hitting.
C-13 NMR and X-Ray Investigations of Phase Transitions in an Antiferroelectric Liquid Crystal
Authors: Yoshizawa Atsushi , Nishiyama Isa , Kikuzaki Hiroshi , Noriko Ise Noriko Ise
Published: February 2005

We have investigated molecular motion and ordering in the smectic phases of a nonoriented antiferroelectric liquid crystal by means of C-13 NMR and powder X-ray diffraction. The marked line broadenings for core carbons observed by C-13 NMR indicate the existence of the characteristic molecular motion for the molecular core in the antiferroelectric chiral smectic C (SmC*
A) phase. In the smectic phases appearing during the cooling and heating processes, local and overall molecular motions of each molecule observed by C-13 NMR are discussed in comparison with long-range order inside the layer observed by X-ray diffraction.
Dispersion of the Third-Order Nonlinear Optical Susceptibility in C60 Calculated with a Tight-Binding Model
Authors: Kikuo Harigaya Kikuo Harigaya , Shuji Abe Shuji Abe
Published: February 2005

The frequency dependence of third harmonic generation (THG) in C60 is calculated, making use of a tight-binding model for π-electrons. The magnitudes of the THG, about 10-12 esu, near zero frequency, agree with those in experiments for the low-energy region. We can also explain the order of the magnitude, 10-11 esu, around the three-photon resonance peak due to the lowest allowed excitation, recently measured by Meth et al. At higher energies, we predict a large enhancement of the THG at 3ω∼6 eV as a result of double resonance enhancement.
Atomic Scale Flatness of Chemically Cleaned Silicon Surfaces Studied by Infrared Attenuated-Total-Reflection Spectroscopy
Authors: Sawara Kenichi , Yasaka Tatsuhiro , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

Hydrogen-terminated Si(111) and Si(100) surfaces obtained by aqueous HF or pH-modified (pH=5.3) buffered-HF (BHF) treatments have been characterized by a Fourier transform infrared (FT-IR) attenuated-total-reflection (ATR) technique. The BHF treatment provides better surface flatness than the HF treatment. Pure water rinse is effective for improving the Si(111) surface flatness, while this is not the case for Si(100) because the pure water acts as an alkaline etchant and promotes the formation of (111) microfacets or microdefects on the (100) surface.
Characteristics of Impurity-Doped GaSe Radiation Detectors
Authors: Yamazaki Toshinari , Hideo Nakatani Hideo Nakatani , Nagayasu Ikeda Nagayasu Ikeda
Published: February 2005

The properties of GaSe radiation detectors doped with Si, Ge and Sn were investigated. It was found that doping with these impurities substantially decreased the leakage current and that most detectors doped with the impurities at about 0.005 to 0.1 at.% showed fairly good energy resolutions from 4 to 15% for 241Am 5.5 MeV alpha particles, while most pure GaSe detectors did not function because of their excessively large leakage current.
Interchange Stability Criteria for Anisotropic Central-Cell Plasmas in the Tandem Mirror GAMMA 10
Authors: Hojo Hitoshi , Inutake Masaaki , Ichimura Makoto , Watanabe Ryota Katsumata
Published: February 2005

Flute interchange stability of anisotropic central-cell plasmas in the tandem mirror GAMMA 10 is studied numerically. The stability criteria on the beta value is obtained as a function of axial localization length of the pressure in both central and anchor cells. The temperature anisotropy of the plasma is also discussed.
Transpiration Experiment of AgGaS2
Authors: Endo Shiroyuki , Yasutoshi Noda Yasutoshi Noda , Yoshitaka Furukawa Yoshitaka Furukawa
Published: February 2005

A transpiration experiment has been carried out for AgGaS2 using HBr as the reactant. The main reaction was proposed as follows: AgGaS2(s)+4HBr(g)=AgBr(s)+GaBr3(g)+2H2S(g). From the weight change of AgGaS2, the heat of formation of AgGaS2 was estimated to be -370 kJ·mol-1.
Temperature Correlation in Hyperbolic Heat Conduction with Random Heat-Generation Source
Authors: Kanji Etori Kanji Etori
Published: February 2005

An autocorrelation function of temperature derived from the hyperbolic heat-conduction equation is discussed using a Gaussian random process with an internal heat-generation source. As a result, the effect of relaxation time, related to finite high-speed propagation of a temperature wave in a solid, is analytically estimated and compared with the conventional parabolic heat conduction.
Anomalous Directivity of a Piezoelectric Polymer Film Hydrophone
Authors: Nakamura Yasuhiro , Takeshi Kawabata Takeshi Kawabata , Takahiko Otani Takahiko Otani
Published: February 2005

An irregular phenomenon that arises in the directivity characteristics of a hydrophone utilizing a piezoelectric polymer film as an active element is studied. At the radial resonant frequency of a Rayleigh-type surface wave induced on the hydrophone's backing material, a sharp null in the directivity characteristics is observed, as if the hydrophone apparently has a narrow directivity pattern. This irregularity is shown to be caused by the interference between an incident wave and a Rayleigh-type surface wave induced on the backing material.
Calculation of Acoustic Near Field from Bessel Beam Transducers with Annular Transducer Array
Authors: Nagai Keinosuke , Hiromasa Monma Hiromasa Monma , Koichi Mizutani Koichi Mizutani
Published: February 2005

This paper describes acoustic fields radiated from Bessel beam transducers with an annular ring array. We calculate the fields without the para-axial approximation such as the Fresnel one, in order to elucidate the near fields from the transducers. We find that field intensities from some transducers abruptly increase and decrease in the near region. This makes the transducers inappropriate for imaging applications. Annular transducer elements of width less than 1 wavelength prove to be effective in avoiding the abrupt changes.
Surface Acoustic Wave Binary Phase Shift Keying System for Time-Division Multiple Access
Authors: Ikeda Toshio , Yoshiaki Shinoda Yoshiaki Shinoda , Kohji Toda Kohji Toda
Published: February 2005

An ultrasonic technique for constructing a binary phase shift keying (BPSK) communication system for time-division multiple access is described, which utilizes two surface acoustic wave (SAW) devices with three interdigital transducers (IDTs). One of the SAW devices operates as a phase shifter in the modulation system, and the other as a phase comparator with a synchronous reference signal for the demodulation. A practical TDMA system utilizing SAW devices with the center frequency of 50 MHz is effective for 23 channels of audio signal transmission.
Insertion Loss and Acoustic Reflection Expressed by Scattering Matrices with Energy-Dissipation for Surface Acoustic Unidirectional Interdigital-Transducers
Authors: Shiba Takashi , Yamada Yoshihiro , Oda Jun Yamada
Published: February 2005

Insertion loss and acoustic reflection for surface acoustic wave (SAW) unidirectional-interdigital transducers are expressed by scattering matrices with energy dissipation in a general form. In the case where circuit energy dissipation could be represented as a lumped resistance (or a conductance), loss and reflection of the transducers can be calculated. Furthermore, the dissipation matrix elements expressed by electrical reflection are proposed. These results are verified by experiments.
Measurement of Velocity of Surface Acoustic Waves on Proton-Exchanged Lithium Tantalate Using Comb Filters
Authors: Hirabayashi Makoto , Takeshi Yamasaki Takeshi Yamasaki , Yasutoshi Komatsu Yasutoshi Komatsu
Published: February 2005

The phase and group velocities of surface waves onz-cut proton-exchanged lithium tantalate were measured. Lithium ions were exchanged for hydrogen ions in heated pyrophosphoric acid. The insertion loss of the filters, which were formed directly on the exchanged layers, was nearly equal to the loss on unexchanged lithium tantalate. The reduction of the phase velocity was proportional to the thickness of the exchanged layers. The reduction was 3.8% forx-propagating surface waves when the layer thickness normalized by the surface wavelength was 0.082. The reduction of the group velocity was 6.4%, which was nearly equal to the reported value ofz-cut lithium niobate.
New Biosensor Using Shear Horizontal Surface Acoustic Wave Device
Authors: Kondoh Jun , Matsui Yoshikazu , Shiokawa Showko
Published: February 2005

This paper describes a new biosensor to detect an enzyme reaction in liquid using surface acoustic wave (SAW) devices fabricated on 36°-rotated Y-cut, X-propagating LiTaO3. The sensing wave on the substrate is a predominantly shear-horizontal-mode SAW (SH-SAW) and is affected by a strong acoustoelectric interaction between the piezoelectric potential and electrical properties of the materials in the adjacent liquid. As an example of an electrical property, pH change associated with an enzyme reaction leads to measurable perturbation in the wave-propagation characteristic. Taking advantage of this phenomenon we realized a SAW biosensor which consists of an immobilized urease membrane on the surface. Also, highly sensitive detection for the urea solution was obtained in our preliminary experiments.
Welding Characteristics of Ultrasonic Wire Bonding Using High-Frequency Vibration Systems
Authors: Tsujino Jiromaru , Mori Takahiro , Takashi Onozato Takashi Onozato , Koichi Hasegawa Koichi Hasegawa
Published: February 2005

Welding characteristics of ultrasonic wire bonding using 60 kHz and 90 kHz complex vibration as well as 120 kHz linear vibration welding systems are studied. The locus shapes of the complex vibration welding tip are controlled from linear to elliptical or circular. Aluminum wire specimens of 0.1 mm diameter are welded successfully using the welding equipment. The required vibration amplitudes of these complex vibration systems are about one-half to one-third and required weld time is shorter than those for a conventional system of linear vibration. The required vibration velocity of a higher-frequency system is smaller than that of a lower-frequency system.
Experimental Image Quality Estimation of Ultrasonic Diffraction Tomography
Authors: Akira Yamada Akira Yamada , Kazuo Kurahashi Kazuo Kurahashi
Published: February 2005

Validity of ultrasonic diffraction tomography is experimentally investigated with the incorporation of error reduction techniques. Scattering measurement and reconstruction calculations are carried out using weak scattering gelatin cylinders and the strong scattering acrylic rods as the test objects. As a result, it is verified that images can be obtained with high fidelity within the tolerances of practical situations.
Three-Dimensional Imaging by Synthetic Aperture Focusing Technique Using a Large Aperture Plane Ultrasonic Transducer
Authors: Tsuneo Kikuchi Tsuneo Kikuchi , Sojun Sato Sojun Sato
Published: February 2005

This paper describes a new method for obtaining three-dimensional (3-D) images of point scatterers using a large aperture plane ultrasonic transducer (LAPUT). The surface of the LAPUT was tilted towards its rotation axis. Scattered signals from point scatterers are received and recorded at each rotation angle. The images of the point scatterers can be reconstructed three-dimensionally by synthesizing these signals. This method is expected to provide 3-D images more easily than the conventional methods. The theoretical analysis and the images obtained by both simulations and experiments are described.
Improved Growth Kinetic Model for Metalorganic Molecular Beam Epitaxy Using Triethylgallium
Authors: Asahi Hajime , Kaneko Tadaaki , Yasutoshi Okuno Yasutoshi Okuno , Shun-ichi Gonda Shun-ichi Gonda
Published: February 2005

An improved growth kinetic model for the MOMBE (metalorganic molecular beam epitaxy) of GaAs and GaSb using TEGa (triethylgallium) is proposed. This model can reproduce simultaneously the experimental curves of the growth rate variation with substrate temperature and group V flux and the desorption rate variation of TEGa and DEGa with substrate temperature, particularly the low-temperature decomposition of TEGa to DEGa. It is found that the decomposition reaction of MEGa to Ga is a rate-limiting process, and that the difference in the growth characteristics between GaAs and GaSb is caused by the difference in the suppression effect of excess group V atoms on the decomposition process of DEGa due to the difference in the desorption parameters of As and Sb. It is also found that the decrease of the growth rate at high temperatures is caused by a rapid increase of the rate constant for the desorption of DEGa and that the nonlinear variation of growth rate with TEGa flux in the intermediate temperature region is caused by the second-order recombination process of MEGa with Et radicals.
Spectroscopic Study on N2O-Plasma Oxidation of Hydrogenated Amorphous Silicon and Behavior of Nitrogen
Authors: Masuda Atsushi , Fukushi Iwao , Yonezawa Yasuto , Minamikawa Toshiharu , Morimoto Akiharu , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: February 2005

A novel oxidation process in hydrogenated amorphous silicon (a-Si:H) utilizing nitrous oxide (N2O) plasma was established and studied in detail. The interfacial neutral defect density for the sample prepared in this process at 300°C is greatly reduced compared with that obtained using O2 plasma. The distribution and behavior of N incorporated in this oxide was examined in detail by means of X-ray photoelectron spectroscopy (XPS). As a result, the accumulation of N near the SiO2/a-Si:H interface was confirmed. At low oxidation temperature, the N bonded to O exists near the oxide surface. The reasons for the reduction of the interfacial neutral defect density and for the accumulation of N near the interface are also shown. It is also clarified that this process utilizes the advantages of both the effect of atomic O and the accumulation of N near the interface.
The Characterization of Al2O3 Prepared by Anodic Oxidation
Authors: Yeh Ching-Fa , Juing-Yi Cheng Juing-Yi Cheng , Jau-Hone Lu Jau-Hone Lu
Published: February 2005

Aluminum is a good candidate of low resistivity metal as a gate electrode metal and a gate bus-line metal in amorphous silicon thin-film transistor of liquid crystal display. But it easily brings about hillocks and whiskers during the heat process, and causes defects. Al2O3 formed on aluminum layer is expected to work as a protective layer against hillock formation. The formation of Al2O3 is developed by anodic oxidation method. The electrical characteristics of Al2O3 layers formed at constant DC anodic bias or constant DC current density were investigated. The optimal growth condition of Al2O3 has been developed. In addition, the double-layer of Al2O3/SiN is also shown to be sufficiently protective against hillock formation.
High-Resolution Transmission Electron Microscopy of AlAs/GaAs Interfacial Structure in the <110> Projection
Authors: Ikarashi Nobuyuki , Tanaka Masaaki , Baba Toshio , Sakaki Hiroyuki , Koichi Ishida Koichi Ishida
Published: February 2005

We have established an imaging condition of <110> high-resolution transmission electron microscopy (HREM) for edge-on observations of AlAs/GaAs interfacial step structures. It is shown that <110> HREM images of GaAs and AlAs show a remarkable contrast around a specimen thickness equivalent to the GaAs extinction distance due to a large difference in {111} amplitudes between GaAs and AlAs. A specimen preparation technique in which chemical etching was used to remove ion milling artifacts was also developed to accomplish this observation. Using this HREM method, we have made observations of AlAs/GaAs interfaces grown by molecular beam epitaxy, giving information about the straightness of the interfacial step edges and the distribution of step intervals. These results show a marked difference in the interfacial step structure between steps parallel to [11̄0] and steps parallel to [110].
Chemical States of Bromine Atoms on SiO2 Surface after HBr Reactive Ion Etching: Analysis of Thin Oxide
Authors: Koshino Keiji , Matsuo Jiro , Moritaka Nakamura Moritaka Nakamura
Published: February 2005

Low-energy ion scattering spectroscopy (ISS) and X-ray photoelectron spectroscopy (XPS) have been used to determine the nature of Br atoms on very thin thermal silicon dioxide (approximately 5 nm) after HBr reactive ion etching (RIE). The result of ISS clarified that the etched surface was covered with 1 monolayer Br. The Br atoms on the etched SiO2 surface were found, from the result of XPS analysis, to have two chemical adsorption states. The experiment of atomic Br exposure showed that one adsorption state was on the as-grown SiO2 surface and the other state was at the damaged sites induced by ion bombardment.
Photodissociation of Trimethylindium and Trimethylgallium on GaAs at 193 nm Studied by Angle-Resolved Photoelectron Spectroscopy
Authors: Shogen Satoshi , Ohashi Masafumi , Hashimoto Satoshi , Yutaka Matsumi Yutaka Matsumi , Masahiro Kawasaki Masahiro Kawasaki
Published: February 2005

The chemisorption and photodecomposition of trimethylindium (TMIn) and trimethylgallium (TMGa) on a GaAs(100) surface have been studied by means of angle-resolved X-ray and ultraviolet photoelectron spectroscopy. Increase in the substrate temperature from 150 to 300 K causes the In-C bond cleavage of the adsorbed TMIn to generate methyl radicals that react with Ga species in the substrate to form Ga-C bonds. The 193 nm irradiation of TMIn adsorbed on GaAs at 150 K induces the In-C bond cleavage. The carbon species desorb from the substrate. Irradiation at 351 nm causes no change in the X-ray photoelectron spectra of the adsorbed species. These results imply that photodissociation is not due to photoabsorption of the GaAs substrate but that of the adsorbed species on the substrate. Photoirradiation of 488 nm on TMIn adsorbed on GaAs at 150 K induces pyrolytic cleavage of the In-C bond.
Sources of Disk Noise on a Co/Pt Disk
Authors: Maesaka Akihiro , Kazuhiro Bessho Kazuhiro Bessho , Shun'ichi Hashimoto Shun'ichi Hashimoto
Published: February 2005

We investigated the sources of disk noise on Co/Pt disks, focusing on ferromagnetic exchange coupling between grains, and found that strong exchange coupling results in low disk noise because of the suppression of fluctuation of magnetic-moments between grains. The dispersion in the (111) orientation of grains is also related to noise. The degree of surface smoothness of the SiN underlayer influences the degree of (111) orientation in Co/Pt, and the smoother surface produced by sputtering using Xe gas yielded lower disk noise. Furthermore, sputter etching of SiN decreased the noise, by contributing to stronger magnetic coupling and better (111) orientation, to a level of disk noise comparable to that of a TbFeCo disk.
Investigation of Operative Slip System in β-Sn Single Crystal and the Relation between the Crystal Orientation and the Slip Systems
Authors: Aytaş Bahattin Düzgün
Published: February 2005

The β-Sn single crystals used in this study were melted and grown by the modified Bridgman technique under a vacuum of 10-3 Torr, and oriented by the back-reflection Laue method. By applying the tensile test to the crystals whose orientations were determined, operative slip systems were found, and the relation between the crystals orientation and the slip systems was investigated. Where the crystal orientation was deviated from [110] direction, the slip systems were also changed and hence it was seen that slip modes depend on the direction of applied stress.
Molecular Orbital Theory of Field Evaporation
Authors: Sawamura Makoto , Tsukada Masaru , Aono Masakazu
Published: February 2005

We present a theory based on nonempirical molecular orbital calculations for field evaporation. To investigate desorption under a high electric field, a cluster model is constructed for a silicon surface with a hydrogen atom absorbed on top of it. The peripheral dangling bonds of the silicon surface are terminated by hydrogen atoms. We obtained the potential energy surfaces for an absorbed hydrogen atom on a silicon surface under both positive and negative biases. In case the field strength is 20.0 V/nm, the activation energy decreases to 0.6 eV under a negative bias and to 1.5 eV under a positive bias, while it is 11.7 eV for the nonbiased surface. Electron population analysis reveals that the desorbed particles are a proton under a positive bias and a negative hydrogen ion under a negative bias. We employed unrestricted Hartree-Fock calculations with an STO-3G basis set.
Theoretical Study on Total-Reflection-Angle Effect of Fluorescent X-Rays Emitted from Atoms Deposited on Surfaces
Authors: Yoshio Suzuki Yoshio Suzuki , Shuji Hasegawa Shuji Hasegawa
Published: February 2005

Theoretical analysis is performed for the angular distribution of fluorescent X-rays in a total-reflection-angle X-ray spectroscopy (TRAXS) experiment. The angular dependence of fluorescent X-ray intensity is caused by the interference effect between the direct beam and that reflected by the substrate surface. The calculation results agree with the experimental results reported by Hasegawa et al. [Jpn. J. Appl. Phys. 24 (1985) L387].
Two-Dimensional Direct Quenching Measurement of OH in a Cross Section of a Bunsen Flame
Authors: Hirano Akira , Florence Ricoul Florence Ricoul , Masahide Tsujishita Masahide Tsujishita
Published: February 2005

In flame analysis, the laser-induced fluorescence (LIF) method is becoming popular for detecting intermediate species and measuring temperature. However, when a typical tunable laser with a pulse duration of around 10 ns is used, the pressure of the target to be measured is often too high to obtain a fluorescent signal having a linear relationship to molecular concentration, due to collisional quenching by which relaxation without fluorescence occurs. In a reactive field such as a flame, especially when two-dimensional measurement is desired, the problem of quenching is more serious because the quenching time constant differs at each measuring point. Accordingly, an effective two-dimensional quenching measurement method is desirable. For this purpose, we attemped to determine the quenching time constant distribution, using an image intensifier and a XeCl excimer-laser-pumped dye laser with a doubling crystal, which is the typical and widely used tunable laser, at the pressure at which the LIF signal is significantly affected by collisional quenching. In this way, we succeeded in determining the quenching time-constant distribution in the cross section of a premixed Bunsen flame at 1/2 atmospheric pressure. In addition, this experiment is the first measurement of two-dimensional fluorescence decay time on the order of a few nanoseconds.
Magnetization Contrast Enhancement of Recorded Magnetic Storage Media in Scanning Lorentz Electron Microscopy
Authors: Yoshio Takahashi Yoshio Takahashi , Yusuke Yajima Yusuke Yajima
Published: February 2005

An imaging technique suitable for observing bit patterns on longitudinal media using a scanning Lorentz electron microscope has been investigated. In regularly recorded media, the effect of magnetization on the image contrast tends to be reduced by stray magnetic field. It is shown, however, that the magnetization contribution to the contrast can be enhanced compared to the stray field contribution when the sample is tilted in a specific direction. A numerical estimate shows that 60° tilting about an axis along the track direction should give a net contrast which is four times greater than with no tilting. This contrast enhancement upon tilting the sample has been confirmed through the observation of recorded CoPt media.
Electrical Insulation Properties of Carbon-Controlled Semi-Insulating GaAs
Authors: Otoki Yoohei , Watanabe Masatoshi , Takahashi Susumu , Okubo Shoji Kuma
Published: February 2005

Electrical insulation properties of liquid encapsulated Czochralski (LEC) GaAs crystals doped with carbon in concentrations ranging from 5×1015 cm-3 to 2.0×1016 cm-3 were investigated. The leakage current decreased with increase of carbon concentration and the turn-on voltage at which current starts to increase abruptly became as high as 75 V, corresponding to the average electric field of 150 kV/cm. At low voltage, the leakage current was determined by the resistivity which depended on the carbon concentration. The turn-on voltage was not temperature-dependent in the case of high carbon concentration and can be explained by the theory of trap-filled voltage up to 50 V. This improvement of the insulation can be achieved not only by carbon doping but also by proper ingot annealing by which native defects other than EL2 are diminished and the microscopic distribution of the electrical properties is made uniform.
Microwave Surface Resistance of Plasma-Sprayed YBaCuO Thick Films on Large-Area Metallic Substrates
Authors: Ezura Eizi , Asano Kiyomitsu , Hayano Hitoshi , Hosoyama Kenji , Inagaki Shigemi , Isagawa Shigeru , Kabasawa Makoto , Kojima Yuji , Kosuge Shigeyoshi , Mitsunobu Shinji , Momose Takashi , Nakada Kiyokazu , Nakanishi Hiroshi , Shimbo Yukio , Shishido Toshio , Tachikawa Kyoji , Yoshihara Takeshi Takahashi
Published: February 2005

The microwave surface resistance of YBaCuO thick films was measured using a demountable copper cavity operated at 3 GHz in the TE011 mode over a temperature range from 4.2 K to 300 K. The films were deposited onto end plates and cylinder walls of silver substrates or nickel-buffered copper substrates by a low-pressure plasma-spraying technique combined with a melt-reaction method. The area of the end plate was 177 cm2 and that of the cylinder wall was 396 cm2. The surface resistance was obtained from the Q values measured before and after substituting either the end plate or the cylinder wall for one covered with the film. The ratio of the surface resistance of the film to that of the copper was lower than 0.08 at 5.2 K and 0.65 at 77.3 K for the end plate and was 0.15 at 5.1 K and 1.91 at 77.3 K for the cylinder wall.
Influence of Self-Reorientation Effect on Isothermal and DC Demagnetization Remanence Curves
Authors: Tsuyoshi Maro Tsuyoshi Maro , Osamu Kitakami Osamu Kitakami
Published: February 2005

We have calculated two types of remanence curves (I
r: isothermal remanence curve and I
d: DC demagnetization curve) using a phenomenological model based on the mean field theory and the normal distribution function as the switching field. In this paper, the reorientation effect of magnetic moments due to the internal field in the absence of the external field is taken into account. The model shows that this effect plays an influential role in I
r and I
d curves for magnetic materials with large negative interaction coefficients.
Electronic Energy Levels of Luminescence Centers in Silver Halide Crystals
Authors: Sanemi Sonoike Sanemi Sonoike
Published: February 2005

Infrared quenching of luminescence peaks has been studied in impurity-doped silver halide crystals. The values of the trap depth of the luminescence centers are estimated tentatively from the excitation spectra for infrared quenching. An energy level scheme is proposed for several luminescence centers in the band gap. A model of color centers is also proposed, taking into account the experimental results reported previously. It is revealed that these centers are deeper than expected for electrons or holes in silver halides.
Stabilization of Superoxide and CO3
- Radicals through Crystalliation of CaCO3
Authors: Kazuhide Meguro Kazuhide Meguro , Motoji Ikeya Motoji Ikeya
Published: February 2005

Unstable superoxide radicals (g
a=2.010, g
b=2.064, g
c=2.049, and g
d=2.006) and CO3
- hole centers (g

x
=2.017, g

y
=2.011, and g

z
=2.002) were stabilized in CaCO3 when the inorganic material was crystallized from radical solution. The radicals surrounded by the lattice give strong electron spin resonance (ESR) signals at room temperature. The signal intensities of superoxide and CO3
- radicals generated in H2O2 solution and doped in CaCO3 are much stronger than those obtained by adsorption. The color of radical-doped CaCO3 is different from that of the radical-adsorbed one. On heating the samples, the spectrum and the color of the radical-doped CaCO3 powder changed. The effects of impurities on the spectrum of radical-doped inorganic materials are studied. Some doping experiments have been conducted using other inorganic materials.
Hot-Pressed BN-AlN Ceramic Composites with High Thermal Conductivity. Part III
Authors: Takao Kanai Takao Kanai , Kei Tanemoto Kei Tanemoto
Published: February 2005

Hexagonal boron nitride-aluminum nitride (50-50 wt%) ceramic composites were synthesized by means of uniaxial hot pressing with variation in the starting materials of boron nitride. The bulk density and the anisotropy of thermal conductivity, thermal expansion coefficient and Vickers hardness, decrease with decreasing particle size of boron nitride. It is concluded that the densification of the composites is dominated by the sintering of aluminum nitride and boron nitride impedes the sintering of aluminum nitride.
Photoluminescence of Si-Rich SiO2 Films: Si Clusters as Luminescent Centers
Authors: Hayashi Shinji , Nagareda Takeshi , Yoshihiko Kanzawa Yoshihiko Kanzawa , Keiichi Yamamoto Keiichi Yamamoto
Published: February 2005

Si-rich SiO2 films have been prepared by a rf cosputtering method and their photoluminescence, as well as infrared absorption and Raman spectra, has been measured for the as-deposited and annealed films. Photoluminescence spectra very similar to those of porous Si were observed for the sample with a relatively low Si content. Redshift of the luminescence peak was observed upon annealing. Results of infrared and Raman measurements strongly suggest that Si clusters are embedded in the as-deposited sample, and that their size increases upon annealing. The photoluminescence is thus thought to arise from the Si clusters, in which the gap between the highest-occupied and lowest-unoccupied molecular orbitals decreases as the size increases, causing the redshift of the photoluminescence peak. A sample containing well-grown Si microcrystals was also prepared by increasing the Si content. No detectable photoluminescence signal was observed for this sample.