bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Ion-Scanning Tunneling Microscope Equipped with Molecular Beam Epitaxy and Its Application to Study Semiconductor Surface Structure
Authors: Miwa Shiro , Haga Yasuhiko , Morita Etsuo , Arakawa Seiichi , Hashizume Tomihiro , Sakurai Toshio
Published: February 2005

We have developed a new combined system of a field-ion scanning tunneling microscope (FI-STM) and a molecular beam epitaxy (MBE) growth chamber equipped with six Knudsen-cells and reflection high energy electron diffraction (RHEED). This system allows us to observe compound semiconductor surfaces such as GaAs while keeping their surfaces clean. In this paper, this system was applied to GaAs(100) and Si(110) surfaces. A GaAs sample was heated up to 550°C and a GaAs thin epitaxial film was grown by MBE. 2×, 4× structures were observed by RHEED and the sample was moved to the FI-STM chamber where STM images of 2×4 reconstructed GaAs(100) surfaces were obtained. Besides the observation of GaAs, FI-STM was also applied to the Si(110) surface. We have studied the change of the Si(110) surface structures at different conditions of heating and cooling.
Lateral Supply Mechanisms in Selective Metalorganic Chemical Vapor Deposition
Authors: Ko-ichi Yamaguchi Ko-ichi Yamaguchi , Kotaro Okamoto Kotaro Okamoto
Published: February 2005

Selective epitaxial growth of GaAs was carried out by atmospheric-pressure metalorganic chemical vapor deposition, and lateral supply mechanisms of reactant species from mask areas to window areas were investigated. Since reactant species arriving on SiO2 surfaces were easily reevaporated, deviation from mass balance was observed. In the case of a SiO2 mask with width of more than 20 µm, lateral vapor-phase diffusion dominated over increment of selective epilayers because of short surface-diffusion length on SiO2 surfaces (<1 µm). It was apparent experimentally and analytically that long ridged tails of selective epilayers were formed by lateral vapor-phase diffusion. Appearance of wavelike tails at mask edges was due to surface diffusion from (111)B facets. Surface-diffusion length on (111)B surfaces was estimated at 3 µm.
Relaxation Mechanism of Thermal Stresses in the Heterostructure of GaN Grown on Sapphire by Vapor Phase Epitaxy
Authors: Hiramatsu Kazumasa , Akasaki Theeradetch Detchprohm
Published: February 2005

Thermal strains and stresses due to the thermal expansion coefficient difference in GaN(0001)/α-Al2O3(0001) layered structures are studied by varying the film thickness of GaN from 0.6 to 1200 µm. The strain in GaN is greater in films of less than a few microns thickness. It is decreased in films of thickness from several to about a hundred microns, and is almost completely relaxed in those thicker than 100 µm. The stresses and strains in the heterostructure are calculated using a model in which relaxation due to cracking in the sapphire is considered. Three relaxation mechanisms of the thermal strain are found for different film thicknesses as follows: (a) only lattice deformation (<4 µm), (b) enhancement of interface defects such as “microcracks” and/or dislocations (4-20 µm), and (c) generation of “macrocracks” in sapphire (>20 µm).
Amorphous Visible-Light Thin Film Light-Emitting Diode Having a-SiN:H as a Luminescent Layer
Authors: Boonkosum Wirote , Dusit Kruangam Dusit Kruangam , Somsak Panyakeow Somsak Panyakeow
Published: February 2005

Hydrogenated amorphous silicon nitride (a-SiN:H) has been applied for the first time as a luminescent active layer (i-layer) in an amorphous visible-light thin film light-emitting diode (TFLED). The TFLED has the structure of glass substrate/ITO/p a-SiC:H/i a-SiN:H/n a-SiC:H/Al. Visible red and yellow emissions can be observed at room temperature from the TFLEDs in which the optical energy gap of i-a-SiN:H is larger than 2.4 eV. The brightness of the red TFLED was 0.5 cd/m2, with a forward injection current density of 2000 mA/cm2 for the 0.033 cm2 cell area.
Preparation of High-Quality Microcrystalline Silicon from Fluorinated Precursors by a Layer-by-Layer Technique
Authors: Ishihara Shun-ichi , He Deyan , Masami Nakata Masami Nakata , Isamu Shimizu Isamu Shimizu
Published: February 2005

Microcrystalline silicon thin films exhibiting high crystallinity and high quality were successfully fabricated from the fluorinated precursors SiH
n
F
m
(n+m≤3) by repeating the deposition of very thin layers, 10 nm thick, and by treatment with atomic hydrogen. Hydrogen concomitant with dangling bonds is efficiently removed from the Si network at the levels of 0.45 at.% and 3.7×1016 spins/cm3, respectively. A specific texture showing a strong orientation toward (220) is observed in the X-ray diffraction (XRD) spectra. High photoconductivity and a considerable diffusion length of 400 nm for holes under the ambipolar condition verify the films' high quality and high crystallinity.
In-Plane Orientations and Grain Boundaries of YBa2Cu3O7-x Thin Films on (001)MgO Substrates Grown by Metalorganic Chemical Vapor Deposition
Authors: Suzuki Hajime , Fujiwara Yasuaki , Hirotsu Yoshihiko , Yamashita Tsutomu , Oikawa Tetsuo
Published: February 2005

Growth orientations and structures of YBa2Cu3O7-x
(YBCO) thin films on (001) MgO substrates formed by metalorganic chemical vapor deposition (MOCVD) were investigated by means of X-ray diffraction, and plan-view and cross-sectional transmission electron microscopy (TEM). Less than half of the films are epitaxially grown (001)-oriented films, and the rest are films composed of epitaxial grains and in-plane misoriented grains with specific misorientation angles. Cross-sectional TEM revealed that the in-plane misoriented grains are grown on a flat MgO surface, while the epitaxially oriented grains are grown on MgO with surface atomic steps as large as 1 nm. The misoriented films are composed of large grains several µm in size with large-angle grain boundaries (LAGBs), and each grain contains several small grains less than 1 µm in size with slight mutual misorientations. A clear Josephson effect was observed from the films with the LAGBs. From the lattice imaging, it was found that the LAGBs tend to form lower Σ structures. A TEM microbeam analysis revealed an oxygen deficiency at the LAGBs.
Preparation and Nanoscale Characterization of Highly Stable YBa2Cu3O7-δ Thin Films
Authors: Kawasaki Masashi , Gong Jianping , Nantoh Masashi , Hasegawa Tetsuya , Kitazawa Koichi , Kumagai Masao , Hirai Kiyoto , Horiguchi Kenichi , Yoshimoto Mamoru , Koinuma Hideomi
Published: February 2005

High-quality c-axis-oriented YBa2Cu3O7-δ (YBCO) films were prepared using the laser ablation method. Films with a full width at half-maximum of the (005) X-ray diffraction peak as narrow as 0.1° and an χmin of Rutherford backscattering spectrometry as low as 3.5% were obtained by optimizing the experimental conditions. The atomic image and superconducting gap at 4.2 K were simultaneously observed for the first time on these high-quality YBCO films by scanning tunneling microscopy and scanning tunneling spectroscopy. Such observations, even after the film was stored in air for three weeks, indicates that YBCO film is sufficiently chemically and physically stable to prevent significant deterioration in superconductivity at the film surface.
Surface Morphology and Crystal Quality of In Situ Grown Epitaxial La2-xSrxCuO4 Thin Films
Authors: Teherani Féréchteh Hosseini , Keiichi Tanabe Keiichi Tanabe , Minoru Suzuki Minoru Suzuki
Published: February 2005

The surface morphology and crystal quality of epitaxial La2-x
Sr
x
CuO4 (x≈0.15) thin films grown in situ by rf-magnetron sputtering on SrTiO3(100) substrates are examined by high resolution scanning electron microscopy (HRSEM) and reflection high-energy electron diffraction (RHEED). The surface of films grown at substrate temperatures higher than 550°C, is characterized by atomically flat grains indicative of two-dimensional growth. There are precipitates between the grains due to the off-stoichiometric film composition, which appear to prevent lateral atomic migration, and cause ditches. Despite these precipitates and ditches, these grains have high crystalline quality which is revealed by a streaky ring-shaped RHEED pattern indicating a crystal coherency extending for a few hundred µm.
Electrical Responses of Ln-Ba-Cu-O (Ln=Eu, Y), Ba-K-Bi-O and Ba-Pb-Bi-O Superconducting Thin Films to Pulsed Infrared Radiation
Authors: Tanabe Keiichi , Enomoto Youichi , Hidefumi Asano Hidefumi Asano , Syugo Kubo Syugo Kubo
Published: February 2005

The electrical responses to pulsed infrared radiation (λ=1.31 µm and a typical duration=1-4 ns) of superconducting LnBa2Cu3O
y
(Ln=Eu, Y) (LnBCO), Ba1-x
K
x
BiO3 (BKBO) and BaPb1-x
Bi
x
O3 (BPBO) thin films are examined. The fall time of the voltage response for BKBO and BPBO thin films shows a significant increase at temperatures close to T
c or when the irradiation power is high enough to generate an excess quasiparticle density comparable to the pair density of these materials. The fall time for these films at lower temperatures and lower irradiation powers is 0.6-2 ns. This magnitude as well as the dependences of the fall time can be well explained on the basis of the nonequilibrium gap suppression model. LnBCO thin films, in contrast, exhibit a fall time which is almost temperature and power invariant. It is approximately proportional to the film thickness and a typical value for a 63-nm-thick film is 4 ns. This fall time is probably attributable to a bolometric response dominated by a large thermal boundary resistance at the film-substrate interface, although the possibility of the existence of a nonbolometric component in the observed responses cannot be ruled out.
Correlation between X-Ray Reflectivity and Rutherford Backscattering Spectroscopy for Density Measurement of Thin Films
Authors: Nakajima Kunio , Aoki Sadao , Sudo Shuzo , Mondo Munehiro , Kudo Hiroshi , Fujiwara Shiro , Arai Toshihiro
Published: February 2005

The film density of nickel was examined by means of X-ray reflectivity measurement and Rutherford backscattering spectroscopy (RBS). The Ni thin film was deposited by electron beam evaporation in a high-vacuum system and was annealed to change its density. The density of the as-deposited film was 7.8±0.1 g/cm3. A good correlation between the X-ray reflectivity measurement and RBS was demonstrated.
New Methods for Rotation Sensing by Using a Two-Coupler Fiber-Optic Ring Resonator
Authors: Faramarz E. Seraji Faramarz E. Seraji
Published: February 2005

This paper presents a theoretical analysis of new methods for rotation sensing by using a two-coupler type fiber-optic ring resonator. It is shown that in the proposed methods a resonance spike can be generated whose amplitude gives a direct measure of the rotation rates. The approaches are simple and have a major advantage of not using a closed-loop to control the operating points for resonance.
Lower Hybrid Resonance for Two Magnetic Field Configuration in Linear LISA Machine
Authors: Silva Cândido da Cunha Rapozo
Published: February 2005

We have observed experimentally that during lower hybrid heating, at the resonance layer, the electron parallel temperature increases, the plasma potential drops, and the energy loss and the electric field decrease, as the size of the resonance volume increases. The process of mode conversion near the lower hybrid resonance is studied through the electric field distribution, which is modified by collisional damping. The potential drop indicates the potential plug in the radial direction. The quality factor of the machine is comparable to that of a low-Q cavity resonator. The experiment was carried out in a linear mirror machine LISA (linear Spiegel apparatus), excited by a 28 MHz RF antenna, with a low-density weakly ionized plasma.
Carrier Injection Characteristics in Diamine/ZnSe Organic-Inorganic Thin-Film Heterostructures for Blue Electroluminescence
Authors: Fujita Shizuo , Yoshie Tomoyuki , Kohama Kazumasa , Yoichi Kawakami Yoichi Kawakami , Shigeo Fujita Shigeo Fujita
Published: February 2005

Blue electroluminescence, peaking at a wavelength
nearly corresponding to the band gap of ZnSe, is observed in
a Au/diamine(TAD)/ZnSe/GaAs/In structure,
where TAD/ZnSe layers are successively grown on a GaAs substrate
using molecular beam epitaxy/deposition.
Investigations of carrier injection characteristics
at the heterostructure revealed that
(i) electrons and holes accumulate at the TAD/ZnSe interface
under positive bias application to the Au electrode,
(ii) a strong electric field formed by the accumulated electrons
and holes, ∼107 V/cm2,
lowers the potential barriers at the TAD/ZnSe interface
for both electrons and holes,
(iii) holes injected from TAD to ZnSe recombine with electrons,
resulting in sharp blue electroluminescence in the ZnSe layer.
The similarity of these processes to those at practical
organic/organic interfaces suggests that
these kinds of tunneling injections are commonly applicable
for explanation of the operation of organic electroluminescent devices.
A New Relaxor Dielectric for High Voltage Multilayer Ceramic Capacitors with Large Capacitance
Authors: Furukawa Osamu , Hideyuki Kanai Hideyuki Kanai , Yohachi Yamashita Yohachi Yamashita
Published: February 2005

A new ceramic dielectric, based on (Pb0.65Ba0.35)(Zr0.7Ti0.3)O3 has been developed. This dielectric, fired at low temperature of 1080°C, showed a high dielectric constant of 4500, a less than 0.3% dissipation factor and flat temperature characteristics of capacitance satisfying Y5P specifications in the EIA (Electronic Industries Association) Standard. Evaluation as a multilayer ceramic capacitor (MLC) revealed an excellent capacitance dependence under a high DC field. Thus, this dielectric is one of the promising candidates for high voltage MLCs with large capacitance.
Diffusion of Point Defects in Silicon Crystals during Melt-Growth. III -Two Diffusor Model-
Authors: Habu Ryuichi , Kojima Kiyoshi , Harada Hirohumi , Tomiura Azusa
Published: February 2005

In this paper, the phenomenological diffusion equations which describe the diffusion of point defects in silicon single crystals during melt-growth and include the effect of the annihilation reaction between self interstitials and vacancies are developed. The macroscopic structure of the OSF-ring in CZ-crystals, and the swirl and D-defects in FZ-crystals, and their changes dependent on the crystal growth rate were correctly and consistently interpreted by these equations assuming that these grown-in crystal defects are generated by an agglomeration of point defects frozen into the crystals. It is shown that vacancies not only diffuse faster than self interstitials but also exist in higher concentration than self interstitials at the high temperature present in the silicon crystal during melt-growth.
Photochemical Decomposition of Triethylgallium on Si(111) Studied by Means of STM, LEED, AES and Mass Spectroscopy
Authors: Inukai Junji , Mizutani Wataru , Fukui Ken-ichi , Shimizu Hazime , Yasuhiro Iwasawa Yasuhiro Iwasawa
Published: February 2005

Adsorption and photochemical decomposition of triethylgallium [Ga(C2H5)3] on Si(111) at room temperature were investigated by means of low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), scanning tunneling microscopy (STM) and mass spectroscopy (MS). Ga(C2H5)3 was adsorbed on Si(111) until its saturation, at which point LEED and STM indicated disordered adsorption of the molecules. Irradiation of ultraviolet light onto the Ga(C2H5)3-saturated surface caused carbon incorporation contrary to the case of pyrolysis. Ethyl species were proposed to result from the photon absorption processes of the molecules.
Surface Pressure Variation in Triphenylmethane Dye Adsorbed Merocyanine Monolayers at the Air-Water Interface
Authors: Kudo Kazuhiro , Yageta Hiroshi , Shigekazu Kuniyoshi Shigekazu Kuniyoshi , Kuniaki Tanaka Kuniaki Tanaka
Published: February 2005

Surface pressure variations of merocyanine or arachidic acid monolayers formed at the air-water interface are investigated. Under the constant area condition, a marked increase of surface pressure is observed during the adsorption of triphenylmethane dyes from the subphase. The surface pressure variation is closely related to the molecular interaction and arrangement between the spreading and adsorbing materials. Experimental results and data, calculated by means of the molecular orbital method, of molecular interactions and the quantity of adsorbed molecules are compared.
Reactive Ion Etching of Sputter Deposited Tantalum with CF4, CF3Cl, and CHF3
Authors: Yue Kuo Yue Kuo
Published: February 2005

This paper discusses the reactive ion etching of tantalum with Freon gases. Factors affecting the etch rate, such as the power, pressure, and temperature, were studied over a wide range of conditions. The chlorine component enhanced the etch rate and the hydrogen component hindered the etch rate. Activation energies of the CF4 and the CHF3 processes were measured. For CF4 and CF3Cl plasmas, both the plasma phase chemistry and the surface reaction affected the etch rate. For the CHF3 plasma, the ion bombardment energy controlled the etch rate. Electron spectroscopy for chemical analysis (ESCA) results on the etched surfaces revealed: 1) the tantalum etch mechanism included two steps, i.e., the oxidation step and the product formation step; 2) residues on the CHF3 etched surface were different from those on the CF4 etched surface; 3) the difference in residues could explain the etch rate difference. Secondary ion mass spectroscopy (SIMS) analysis results showed that the CHF3 etched surface contained hydrogen and fluorohydrocarbons, which may be responsible for its low oxygen absorption.
Direct Monte Carlo Simulation of Ion-Induced Kinetic Electron Emission Statistics
Authors: Kawata Kaoru Ohya
Published: February 2005

A Monte Carlo simulation is performed for the study of the statistics of kinetic secondary electron emission from a gold surface under 1-5 keV H+ ion bombardment. In this simulation, the cross section of the excitation of conduction electrons by a proton is calculated by means of the Lindhard dielectric theory, and the cascade multiplication of secondary electrons inside the solid is involved. The calculated results are consistent with experimental data and reveal the origin of the deviation from the Poisson distribution, which corresponds to the contributions from the cascade multiplication of secondary electrons (low-impact energy) and the backscattering of projectile ions (high-impact energy).
Defect Evaluation of Heavily P-Doped Si Epitaxial Films Grown at Low Temperature
Authors: Jia Ying , Oshima Takayuki , Yamada Akira , Konagai Makoto , Takahashi Kiyoshi , Tanigawa Shoichiro , Wei Long
Published: February 2005

Heavily P-doped epitaxial Si films with carrier concentration of 3×1021 cm-3 have been successfully grown by plasma chemical vapor deposition using a gas mixture of SiH4, SiF4, H2 and PH3 at a very low temperature of 250°C. From the annealing characteristics of heavily P-doped Si films, it was found that the electron concentration decreased once after annealing at 600°C but increased subsequently upon raising the annealing temperature. The possibility of the formation of a vacancy-type defect complex, typically (v-P4), a vacancy surrounded by four phosphorus atoms, was proposed to interpret this phenomenon. Furthermore, a positron annihilation experiment was employed to investigate this vacancy-type defect in Si films and good agreement was obtained between thermodynamical calculation based on the v-P4 model and the positron annihilation experiment.
Properties of Heterojunction of Si/Poly(3-methylthiophene) as a Function of Polymerization Condition
Authors: Kokado Hiroshi , Hosokawa Fumio , Katsuyoshi Hoshino Katsuyoshi Hoshino
Published: February 2005

A detailed analysis of poly(3-methylthiophene) (P3MeT) films deposited on a n-Si substrate is presented. In order to perform junction analysis, potentiometric measurements during the growth of the film, current-voltage measurements, degradation of electrical properties, FT-IR (Fourier transform infrared) measurements, and SEM (scanning electron microscope) observations are studied. New insights into the junction are obtained. The rectifying behavior is greatly improved by employing sandblasted n-Si as a substrate, compared with a nonsand-blasted n-Si substrate. Based on these results, junction formation is described as the evolution of covalent bond formation between hydroxy groups on the n-Si surface and a polymer film. The results are supported by FT-IR measurements of the sandblasted n-Si surface. A covalent bond destruction model is used to describe degradation behavior of the P3MeT/sandblasted n-Si heterojunction.
Photoluminescence Studies and Solar-Cell Application of CuInSe2 Thin Films Prepared using Selenization Techniques
Authors: Tanda Masayuki , Manaka Susumu , Yamada Akira , Takahashi Makoto Konagai
Published: February 2005

Photoluminescence measurements were carried out on CuInSe2 thin films prepared using the selenization technique with solid- or vapor-phase selenium, and the correlation between photoluminescence spectra and cell performance was studied. In our previous studies, several peaks were observed in the wavelength region below 1400 nm in the photoluminescence spectra of low-photovoltaic CuInSe2 thin films. In contrast, in the spectra of high-photovoltaic films, a strong peak was observed at 1420 nm, and there were no additional peaks below 1400 nm. From the results, it was found that there was a strong correlation between the photovoltaic effect of CuInSe2 thin films and the existence of the photoluminescence peak at 1420 nm. The origin of this peak and its behavior were investigated through the dependence of the photoluminescence spectra on the temperature and excitation intensity and the effect of air annealing.
Thermal Stability of Rapidly Annealed Ruthenium n-GaAs Schottky Contacts
Authors: Ghader Eftekhari Ghader Eftekhari
Published: February 2005

In this paper the thermal stability of ruthenium n-GaAs is reported. The annealing time was 15 s and annealing temperature was varied in the range 200-800°C. The contacts were found stable for annealing temperature up to about 750°C. For temperatures above 750°C a sharp decrease in barrier height (i.e. degradation) was observed. Also the ideality factor and reverse current showed sharp increase. This is considered as result of chemical reactions at the interface. The removal of native oxide layer and defects at the interface were used to explain the observations.
Alignment Ratio of Magnetically Aligned High-Tc Superconducting Y1Ba2Cu3O7-y and Y0.5Dy0.5Ba2Cu3O7-y Thick Films
Authors: Han Seok Kil , Young Cheol Kim Young Cheol Kim , Min Su Jang Min Su Jang
Published: February 2005

High-T
c superconducting thick films were prepared using a method of combined grain shape alignment and magnetic field alignment by orthogonal alignment forces. Superconducting films with a thickness of about 100 µm exhibiting T
c(0)=91 K were successfully obtained. We confirmed the grain alignment of thick Y1Ba2Cu3O7-y
and Y0.5Dy0.5Ba2Cu3O7-y
films by means of the X-ray diffraction method. As a result, the grain alignment is produced with an increase in the heat treatment temperature and time in a magnetic field. The alignment ratio of Y0.5Dy0.5Ba2Cu3O7-y
, which is Y1Ba2Cu3O7-y
with the Y-site doped with high-magnetic-moment and high-anisotropy rare earth, is higher than that of the Y1Ba2Cu3O7-y
.
Pinning Mechanism Studies on the Nb/Ag Superconducting Multilayer
Authors: Obi Yoshihisa , Ikebe Manabu , Fujishiro Hiroyuki , Hiroyasu Fujimori Hiroyasu Fujimori
Published: February 2005

The critical currents of the Nb/Ag multilayer, a proximity-effect-coupled artificial layered superconductor, have been measured. The behavior of the flux pinning force is compared with that of the Nb/Al2O3 multilayer, a previously studied Josephson-coupled layered superconductor. Several qualitative and quantitative differences in the pinning characteristics of the two systems are pointed out.
Transient, Quasi-Static and Translation without Precession: A Hybrid of Bloch-Néel Quasi-Static Wall in Motion
Authors: Huei Li Huang Huei Li Huang , Shoan Chung Chen Shoan Chung Chen
Published: February 2005

Domain wall motion under the influences of weak in-plane fields applied along arbitrary directions in an infinite medium with uniaxial anisotropy has been considered. Typically, the azimuthal angle of the magnetization vector along with the domain wall central plane exhibits transient, stationary and oscillatory behavior. The azimuthal angle displays a terrace-like structure at the critical field when subject to a weak perturbation field along the domain wall normal direction. As a result, the domain wall cants out its magnetization vector out of the wall plane and stays in that configuration as it continues to translate onward like a hybrid of Bloch-Néel wall in a quasi-static manner without precession. The in-plane field along the wall normal has limited effect on the domain wall upper bound velocity, while the field parallel to the domain wall can substantially increase it. At a higher drive field, the magnetization (φ) precesses nonuniformly with time and results in nonuniform, anharmonic oscillatory behavior for domain wall motion. Also, as domain wall picks up its velocity, it contracts to reduce its surface demagnetization energy and at the same time interchanges between Bloch type and Néel type in an oscillatory manner.
High Sensitivity Readout of 2D a-Si Image Sensors
Authors: Fujieda Ichiro , Street Robert A. , Weisfield Richard L. , Nelson Steve , Nylén Per , Perez-mendez Victor , Cho Gyuseong
Published: February 2005

A highly sensitive charge-sensitive amplifier IC was used to read out large-area two-dimensional arrays of amorphous silicon (a-Si) p-i-n photodiodes addressed by a-Si thin film transistors (TFTs). At the highest sensitivity mode, the random noise of the sensor was equivalent to an input charge of 1500 electrons rms. Feedthrough charge injection associated with TFT switching had to be avoided at the expense of the signal charge. Image lag caused by charge trapping in a-Si was suppressed by limiting the input light intensity. A simple model was developed for the noise contribution from a pixel and compared with measurements.
Effect of Additions on Conduction Properties of ZnO Varistors
Authors: Shen Chi-Yen , Wu Long , Chen Ying-Chung
Published: February 2005

In this paper, several substitutive and defect reactions have been analyzed to describe the conduction properties in ZnO varistors. The composition of ZnO varistors with added Co and Mn ions of high valence, i.e., Co3+ and Mn4+, was deduced to result in higher donor concentration, trap density, barrier height and leakage current, but a lower nonlinearity coefficient in comparison with that of ZnO varistors with added Co and Mn ions of low valence, i.e., Co2+ and Mn2+. The capacitance-voltage (C-V) and current-voltage (I-V) measurements were employed in the experiment, respectively. Theoretical inference was found to be consistent with the experimental results of electrical characteristics.
High-Temperature MBE Growth of Si-Direct Current Heating Effects on (111) and (001) Vicinal Surfaces
Authors: Stoyanov Stoyan S. , Masakazu Ichikawa Masakazu Ichikawa , Takahisa Doi Takahisa Doi
Published: February 2005

The molecular beam epitaxial (MBE) growth model is extended to account for the electromigration of Si adatoms on both (001) and (111) Si surfaces. Step bunching is predicted to occur at the (111) surface when the heating current has step-down direction. Electromigration-induced formation of a major reconstruction domain at (001) Si is not expected when the growth process is controlled by step kinetics. When the process is controlled by surface transport, the vicinal surface is predicted to be dominated by either the 1×2 or 2×1 domain depending on the direction of the current. Microprobe reflection high-energy electron diffraction (µ-RHEED) observations of MBE growth of the (001) Si surface at temperatures of 750-900°C reveal preferential growth of the SA steps when the heating dc has a step-up direction. This is in contrast with the reported preferential growth of SB steps at lower temperatures (400-600°C). The difference in the surface reconstruction is interpreted to indicate a transition from step-kinetics-controlled growth (at 400-600°C) to surface-diffusion-controlled growth (at 750-900°C).
Phenomenological Studies in Laser Cladding. Part I. Time-Resolved Measurements of the Absorptivity of Metal Powder
Authors: Kizaki Yoshimi , Azuma Hirozumi , Yamazaki Satoshi , Takagi Hisashi Sugimoto
Published: February 2005

Time-resolved measurements were introduced to study the dynamic behavior of the absorptivity of metal powder under CO2 laser irradiation conditions. The absorptivity of metal powder was more than 90% under short-term laser irradiation (6-20 ms), but it was below 30% under relatively long-term laser irradiation (50-1000 ms). The experimental results propose that the dynamic change of the absorptivity is caused by time-dependent aggregation of powder particles induced by laser irradiation.
Plastic Deformation of Al-Pd-Mn Icosahedral Quasicrystal
Authors: Shin Takeuchi Shin Takeuchi , Tatsuo Hashimoto Tatsuo Hashimoto
Published: February 2005

Compression experiments have been performed for coarse-grained Al72Pd20Mn8 icosahedral quasicrystals at high temperatures. Above 950 K, specimens became deformed due to localized slip, exhibiting pronounced yield drop. Analysis of the stress-relaxation curve at the lower yield point has shown that the internal stress accounts for about half of the lower yield stress. From the strain-rate sensitivity and the temperature dependence of the effective stress, the activation volume and the activation enthalpy of plastic deformation have been analyzed. The obtained results have been interpreted in terms of dislocation glide in quasicrystals.
Effects of Oxygen Addition on Growth of Diamond Film by Arc Discharge Plasma Jet Chemical Vapor Deposition
Authors: Naoto Ohtake Naoto Ohtake , Masanori Yoshikawa Masanori Yoshikawa
Published: February 2005

Effects of oxygen addition on growth and crystallinity of diamond films are discussed. The etch rate of graphite by Ar-O2 plasma jet is 130 times larger than that by Ar-H2 plasma jet. Nucleation density of diamonds decreases with oxygen addition. The growth rate of diamond decreases with increase in the amount of added oxygen. Surface unevenness and porosity also decrease with increase in the amount of added oxygen, and it was found that the optimum oxygen concentration is about 33%. A diamond film of 1.2 mm thickness was fabricated under these conditions in 20 h. Surface unevenness of the diamond film was reduced to about 100 µm. The growth rates of the {111} planes and {100} planes become isotropic with 33% oxygen content. Therefore the diamond film surface is only slightly uneven and the film shows good crystallinity.
Unique Electrical and Magnetic Properties of Pyrolyzed Poly(hydrazocarbonyl-1,4-phenylenecarbonyl) Film
Authors: Roh Young Bae , Araki Hisashi , Yoshino Katsumi , Hojyo Shiro , Takase Masaaki , Suzuki Takashi
Published: February 2005

Graphitelike films with high conductivity exceeding 1.6×104 S/cm have been newly prepared by pyrolysis of poly(hydrazocarbonyl-1,4-phenylenecarbonyl) films (PHP) at 2800°C. Pyrolyzing processes have been examined by means of X-ray diffraction, thermoelectric power (TEP), and electron spin resonance (ESR) measurements. The rapid increase of conductivity similiar to that of soft carbon and the three-dimensional ordering of crystallites occurred in the heat treatment temperature (HTT) range of 1700-2000°C. The unusual ESR characteristics observed in the range of low HTT (≤1000°C) may be caused by oxygen radicals evolving in the molecular structure of pyrolyzed PHP films.
Multi-chamber Ultrahigh Vacuum Scanning Tunneling Microscope System for Investigating Processed GaAs Surfaces and Observation of Argon-Ion-Bombarded GaAs Surfaces
Authors: Ichiro Tanaka Ichiro Tanaka , Shunsuke Ohkouchi Shunsuke Ohkouchi
Published: February 2005

A multi-chamber ultrahigh vacuum scanning tunneling microscopy (UHV-STM) system has been constructed for investigations of processed GaAs surfaces. This system comprises five UHV chambers connected by UHV tunnels. A specially designed STM unit which can be used with a 23-mm-diameter molybdenum block, is installed in an STM-chamber for surface observations. A molecular beam epitaxy (MBE) chamber for epitaxial growth of GaAs layers and a process-chamber for argon ion-bombardment are included in the five chambers. First, the surface of the MBE-grown layer on a GaAs (001) wafer was observed with STM. The sample was then transferred to the process-chamber and bombarded with argon ions. Many defects, which seemed to be caused by the ion-bombardment, were found in an STM image taken with the ion-bombarded sample.
A New Concept of Isotope Separation Using Ion Cyclotron Resonance in a Magnetic Field Having a Radial Component
Authors: Katakura Hisao , Miura Kenji , Inoue Masao
Published: February 2005

A new method of isotope separation is proposed.
Isotopes are ionized in a magnetic field in a solenoid
and are confined axially in an electrostatic potential well.
Ions moving in a cyclotron orbit undergo a force which is perpendicular
to both the radial magnetic field component and the velocity.
Because axial oscillation takes place over the region
where the component changes its direction,
two isotopes can be separated in opposite directions
by accelerating one of the isotopes at one extreme of the oscillation
and the other at the other extreme.
The axial motion of ions is assumed to be in phase (phase-locked).
To experimentally confirm the effect of the radial component on ion motion,
we moved the center of oscillation along the axis of the solenoid
from its center to a position where both the axial and radial components
vary with the coordinates, and we excited the cyclotron motion of ions.
From the measured shift in the signal frequency of the accelerated ions,
we could estimate the amount of displacement of the center of
the cyclotron orbit as a function of the velocity of the accelerated ions.
The condition for separation is studied by solving
the equation for ion motion
with two different magnetic field distributions.
Computer simulation of the ion trajectory
is carried out to demonstrate the feasibility of the method.
Current Status of Piezoelectric Substrate and Propagation Characteristics for SAW Devices
Authors: Yasutaka Shimizu Yasutaka Shimizu
Published: February 2005

This paper describes the current status of surface acoustic wave (SAW) materials and devices which are being manufactured or are under study in Japanese industries. This information are obtained from 31 companies to which the author sent a questionnaire. SAW propagation characteristics such as Rayleigh wave and leaky wave are also briefly summarized.
High-Frequency Measurement of Surface Elasticity of a Soluble Monolayer at Water Surface Using Ripplon Light Scattering Method
Authors: Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: February 2005

Surface elasticity and surface viscosity of a soluble monolayer on the surface of octanoic acid solution were measured in the frequency range from 40 kHz to 1 MHz using the wide-band ripplon light scattering method. The surface elasticity was found to be independent of frequency in the frequency range measured and the value agreed well with those obtained using other techniques at low frequencies. The results show that the surface layer of octanoic acid molecules behaves effectively as an insoluble layer at ripplon frequencies.
Statistical-Mechanical Study of Ultrasonic Waves in a Crystal Lattice
Authors: Sugiyama Masaru , Hajime Kikkawa Hajime Kikkawa , Kouji Mizuno Kouji Mizuno
Published: February 2005

Elastic waves with audio or ultrasonic frequencies propagating in a crystal lattice at a finite temperature are studied from the viewpoint of nonequilibrium statistical mechanics. In order to demonstrate the essential principle of the present approach, a simple system, that is, a one-dimensional anharmonic lattice is studied in detail. The dispersion relation for the wave and the relationship between random thermal motion in a crystal lattice and collective motion of an elastic wave are obtained. Singular behaviour of ultrasonic waves in a crystal near its melting point is also discussed.
Electrical Impedance and Elastic Property in Na2Zr1.5Mg0.5(PO4)3-Al2O3 Composite
Authors: Inoue Naoki , Matsumoto Yasuhiro , Yoshihiro Ogawa Yoshihiro Ogawa , Takahi Hasegawa Takahi Hasegawa
Published: February 2005

The electrical impedance of Na2Zr1.5Mg0.5(PO4)3-Al2O3 composite has been studied as a function of frequency ranging from 120 Hz-20 MHz at temperatures ranging from 30-253°C. In the complex impedance representation, we observed either one or two semicircles strongly dependent on Al2O3 concentration, and a transition from two semicircles to one semicircle at 10 mol% Al2O3. Ultrasonic velocity showed an anomaly at 10 mol% Al2O3. Due to the dependence of both electrical impedance and elastic data on Al2O3 concentration, we observed the bulk conduction and grain boundary diffusion of the sodium ion in Na2Zr1.5Mg0.5(PO4)3.
Raman Scattering Study of Boson Peak of Glass
Authors: Seiji Kojima Seiji Kojima
Published: February 2005

The low frequency Raman response was studied in the liquid-glass transition of propylene glycol. The boson peak continuously appears from a Rayleigh wing at about 60 K above T
g on cooling. The depolarization ratio is nearly constant from 5 cm-1 to 200 cm-1, and is temperature independent between 90 K and 300 K. Both the lineshape and the depolarization ratio of the spectra were fitted by the exponential correlation function of the structural disorder.
Velocity of Sound in and Elastic Properties of Cs2O-B2O3 Glasses
Authors: Kodama Masao , Noboru Nakashima Noboru Nakashima , Toru Matsushita Toru Matsushita
Published: February 2005

Ultrasonic velocity in caesium borate glasses has been measured as a function of the composition at a frequency of 10 MHz and a temperature of 298 K, and was found to exhibit a maximum, a minimum and another maximum in succession as the caesium oxide content increased. Elastic properties of these glasses expressed in terms of the shear modulus are discussed with respect to the three kinds of structural units present in the glass network.
Space-Periodic Modulation Model of Piezoelectric Polarization Due to Photorefractive Internal Field for Generation of Nonlinear Vibration
Authors: Michio Ohki Michio Ohki , Tadashi Shiosaki Tadashi Shiosaki
Published: February 2005

Strong nonlinear behavior was observed in a LiNbO3:Fe piezoelectric resonator with a photorefractive space-periodic grating. The mechanism of the phenomena is considered in terms of a one-dimensional model in which space-periodic electric charges are related to each other. Two vibrational modes of charges, an in-phase vibration and an antiphase one, are considered in this model. The antiphase vibration can be caused by space-periodic modulation of piezoelectric polarization due to a photorefractive internal field. Only the antiphase vibration contributes to the nonlinear phenomena. Transfer of the energy between the two modes is important for understanding the phenomena.
Role of Higher-Order Elastic Moduli in Large Elastic Finite Deformation
Authors: Tetsuro Suzuki Tetsuro Suzuki , Ken'ichi Osuka Ken'ichi Osuka
Published: February 2005

It is proposed here that the change in free energy of crystals associated with large elastic finite deformation can be estimated using higher-order elastic moduli up to a limited order. Numerical estimation of the change in free energy is performed for two examples of finite elastic deformation, with use of the data for higher-order elastic moduli of β-brass obtained by Swartz. One example is Bain deformation, which converts a bcc lattice into an fcc lattice or vice versa. The other is shear deformation along the (100) atomic plane.
Self-Defocusing Effect in a Focused Acoustic Beam in Superfluid 4He
Authors: Sasaki Yasuo , Kishi Hidenobu , Kobayashi Ippei , Okuda Koichi Karaki
Published: February 2005

Nonlinear propagation of the focused acoustic beam in superfluid 4He was experimentally investigated. We measured the amplitude of an, acoustic wave propagating through superfluid 4He as a function of input power and reflector-to-lens distance under pressure range of 17-24 atm using a reflection mode acoustic microscope. In the high-pressure region, a new type of nonlinear behavior was observed in which the effective focal length becomes larger with increasing input power (self-defocusing effect). Discussion is presented regarding the origin of this nonlinear behavior.
Measurement Method of Spatial Distribution of Nonlinearity Parameter B/A Using Nonlinear Interaction of Two Sound Waves
Authors: Akihito Kato Akihito Kato , Yoshiaki Watanabe Yoshiaki Watanabe
Published: February 2005

A measurement method of the spatial distribution of the nonlinearity parameter B/A is presented. The nonlinear interaction of two waves propagating in the same or opposite directions is discussed, and the process for obtaining the absolute spatial distribution of B/A is precisely deduced. Experiments are carried out for the simple spatial distribution model of B/A. The observed results support the present method, and estimations for the spatial distribution of B/A are obtained. The spatial resolution of measurement is discussed and some features appearing in the observed results, which are related with the present method, are mentioned.
Fabrication and Characteristics of a Submillimeter Detector Element Formed on a CdTe Single-Crystal Wafer as a Multichannel Detector Array Applicable to Diagnostic Imaging with Energy Information
Authors: Tsutsui Hiroshi , Ohtsuchi Tetsuro , Koichi Ohmori Koichi Ohmori , Sueki Baba Sueki Baba
Published: February 2005

A feasibility study to realize a minimal-sized X-ray detector element applicable to a multichannel array for diagnostic imaging with energy information is attempted. A thirty-two-channel radiation detector is fabricated by arranging thirty-two detector elements, each having an effective detection volume of 1×0.25×0.3 mm3 with a pitch of 0.25 mm, on a CdTe single-crystal wafer measuring 1(width)×8(length)×0.3(thickness) mm3. Thirty-two divided electrodes are arranged on its surface, and a common electrode is provided on its rear surface. A radiation spectrum measurement conducted at room temperature for one of the elements with 241Am γ-ray (59.54 keV) shows an energy resolution of 12% full width at half maximum (FWHM). Furthermore, by providing radiation shielding grids between electrodes, a reduction of K-shell characteristic X-ray escape from 40% to 30%, as well as a resultant reduction in channel crosstalk against the total counts, is accomplished.
Effects of Acoustic Interaction between Transducers in Water on Active Sound Power Reduction
Authors: Sugimoto Shigeo , Akio Hasegawa Akio Hasegawa , Toshiaki Kikuchi Toshiaki Kikuchi
Published: February 2005

The effect of mutual radiation impedance on active power reduction is investigated both theoretically and experimentally. The mutual radiation impedance is computed for circular piston transducers and its effect on active power reduction is discussed for several arrangements of transducers. Some arrangements can provide significant power attenuation in the 30 dB range. The active and reactive intensities for a test array radiator consisting of five PZT Langevin transducers are measured in water, and notable effects of the mutual radiation impedance on active power reduction are demonstrated.
Analysis of the Thickness Edge Mode in Piezoelectric Plates and Its Application to Resonators
Authors: Watanabe Hiroshi , Saito Hironobu , Shimizu Hiroshi
Published: February 2005

The thickness edge mode in a piezoelectric ceramic plate poled in the thickness direction is theoretically analyzed, and calculated results for the characteristics of the mode, i.e., the displacement-vector and electric potential distributions, are presented for the case of Pb(Zr, Ti)O3 ceramics. In application of the results, miniaturized edge-mode piezoelectric resonators are developed for use in the frequency range above 1 MHz.
Low-Loss Piezoelectric Transformer Using Energy Trapping of Width Vibration
Authors: Wakatsuki Noboru , Masanori Ueda Masanori Ueda , Masuji Satoh Masuji Satoh
Published: February 2005

Piezoelectric transformers proposed by Rosen have been studied for high-voltage step-up applications. A piezoelectric transformer using LiNbO3 proposed recently by Nakamura and Adachi has low loss and a simple structure. The plate of a conventional piezoelectric transformer was supported only at the node of vibration. Rigid support and loss suppression are required for high-power and high-voltage applications. To apply a piezo-electric transformer to a power circuit, we studied methods for supporting the piezoelectric plate and reducing loss. Based on these studies, we proposed a piezoelectric transformer using energy trapping of the width-shear vibration in a LiNbO3 plate.
Transduction Characteristics of a Surface Acoustic Wave Unidirectional Interdigital Transducer with Liquid Loading
Authors: Masao Takeuchi Masao Takeuchi , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: February 2005

A conventional bidirectional interdigital transducer (IDT) has recently been used in applications such as acoustic imaging, sensors and ultrasonic micromotors. However, no thorough analysis of the electroacoustic transduction characteristics of an IDT taking account of substrate surface loading due to liquid or gas has been carried out until now. Also, no attempt has been made to apply a unidirectional interdigital transducer (UDT) in these uses. In this paper, the operation of the UDT with liquid loading on a substrate surface is theoretically analyzed on the basis of the coupled mode and perturbation theories. The floating-electrode-type UDT for surface acoustic wave (SAW) placed on the interface between a 128° YX LiNbO3 substrate and water shows a directivity of about 6 dB for the longitudinal wave radiating into water.
Piezoelectric-Ceramic Biaxial Accelerometer
Authors: Yasunori Ohtsuki Yasunori Ohtsuki , Tetsuo Yoshida Tetsuo Yoshida
Published: February 2005

A new type of biaxial accelerometer using a piezoelectric ceramic cylinder with a plural of strip electrodes has been developed. The sensitivities of the X and Y axes of this accelerometer are about 14.6 pC/G, and the crosstalk of the two axes is below 0.7 pC/G. Frequency characteristics spread from 10 to 1000 Hz (±1 dB). This accelerometer can detect accelerations in two directions acting at one point. Because it uses only one detecting element, the difference in sensitivity between these two axes is very small. This accelerometer will be applicable to the air bag system of auto-mobiles.
Characteristics of a Bidirectional Rotary Ultrasonic Motor Using Obliquely Polarized Piezoelectric Transducers
Authors: Ishii Takaaki , Ueha Kazumasa Ohnishi
Published: February 2005

Obliquely polarized piezoelectric ceramic transducers are newly employed to an ultrasonic motor. Since the direction of polarization is neither parallel nor perpendicular to the applied electric field, the longitudinal and the torsional vibrations are excited simultaneously. In addition, the direction of rotation can be switched by changing the driving frequency. Thus, this motor rotates in both clockwise and counterclockwise directions in spite of a single-phase input signal. The principle and the characteristics of the ultrasonic motor are described.
Waveform of Driving Pulse Train to Prevent Metallic Sound of Ultrasonic Motors
Authors: Kusakabe Chiharu , Tomikawa Yoshiro , Takano Takehiro , Aoyagi Manabu
Published: February 2005

This paper describes the relationship between the shape of the pulse train and the transient vibration of an ultrasonic motor to prevent the growth of sound when the motor is driven in a stepping manner. Considering the two resonance modes of the motor, the equivalent electrical circuit is derived to analyze the transient vibration. Simulation with three kinds of pulse trains proved that the modification of the driving pulse train is effective for preventing the growth of metallic sound generated when the motor is intermittently driven.