bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of a Three-Dimensional Vacuum Magnetic Sensor with a Si Tip
Authors: Uemura Koji , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

A new vacuum magnetic sensor (VMS) device suitable for three-dimensional detection of magnetic flux was fabricated. This device consists of a Si field emitter tip that generates a cross-shaped electron beam and an anode that is divided into eight symmetrically arranged sectors. The cross-shaped electron beam is rotated and displaced from an initial position by the magnetic flux in accordance with the Lorentz force interaction. The rotation angle and the translational displacement were measured from the beam current imbalance between two neighboring anode sectors. Detection sensitivities of 104%/ T and 103%/ T were obtained for magnetic flux applied parallel and perpendicular to the VMS device, respectively.
Electron-Beam-Induced Selective Thermal Decomposition of Ultrathin SiO2 Layers Used in Nanofabrication
Authors: Watanabe Heiji , Fujita Shinobu , Maruno Shigemitsu , Ken Fujita Ken Fujita , Masakazu Ichikawa Masakazu Ichikawa
Published: October 2002

We used ultrathin SiO2 layers less than 1 nm thick for nanofabrication. In this method, nanometer-scale patterning onto the oxide layers was achieved by electron-beam (EB)-irradiation and subsequent thermal heating (EB-induced selective thermal decomposition). We examined the delineation mechanism by using scanning reflection electron microscopy (SREM), and Auger electron and X-ray photoelectron spectroscopy (AES and XPS). We found that the change in the oxide layer composition caused by electron-stimulated oxygen desorption (ESD) from the oxide layers accounted for the selective thermal decomposition, by which nanometer-scale voids were densely generated.
Electron-Beam-Induced Oxidation for Single-Electron Devices
Authors: Masahiro Matsutani Masahiro Matsutani , Fujio Wakaya Fujio Wakaya , Sadao Takaoka Sadao Takaoka , Kazuo Murase Kazuo Murase , Kenji Gamo Kenji Gamo
Published: October 2002

A selective-area oxidation technique using electron beam (e-beam) irradiation with a mixture of O2 and H2O gases is studied for the fabrication of small tunnel junctions using Si and Cr. Auger electron spectroscopy clearly shows the existence of Si–O bonding at e-beam-irradiated Si surfaces. The height of SiOx is measured by atomic-force-microscope observation, and it is confirmed that the thickness of SiOx can be controlled at a nanometer scale. The line-dose dependence of the resistance of the Cr/CrOx/Cr structure was measured at room temperature and 77 K, and a step-function-like dependence was observed, which indicates that the oxidation takes place over the entire thickness of the 3-nm-thick Cr film. Nonlinear current-voltage characteristics were observed, which suggest that a thin tunneling barrier of CrOx can be realized. The selective-area oxidation technique can be applied to the fabrication of small tunneling junctions.
Co-sputtered Thin Films Consisting of Cobalt Nano-Grains Embedded in Graphite-like Carbon and Their Magnetic Properties
Authors: Delaunay Jean-Jacques , Hayashi Takayoshi , Tomita Masato , Shigeru Hirono Shigeru Hirono
Published: October 2002

The microstructure and the magnetic properties of co-sputtered cobalt-carbon thin films were analyzed. Cobalt-carbon thin films consisting of nano-crystalline cobalt grains separated by graphite-like carbon were obtained after subsequent annealing. The phase of the cobalt grains depended on the carbon concentration; a hexagonal close-packed phase and a heavily faulted close-packed phase were observed. The grain size ranged from 4 to 20 nm. The in-plane magnetic hysteresis loops measured at room temperature showed that the coercivity and the squareness were drastically changed with the carbon concentration. These changes can be related to a change in the magnetocrystalline anisotropy of the cobalt grains due to a difference in the phase and/or size effect that can be explained by the presence of superparamagnetic particles. The highest coercivity (660 oersteds) was measured in a film with a large grain size as well as a hexagonal close-packed cobalt phase. The annealing temperature was found to have an optimum value; the magnetic properties were improved upon annealing due to carbide decomposition, but at high annealing temperatures, coalescence of the grains resulted in sample degradation.
Atomic Hydrogen Induced Surface Restructuring on the Tin-Covered Si(111) Observed by Scanning Tunneling Microscopy
Authors: Masamichi Yoshimura Masamichi Yoshimura , Bai An Bai An , Kiyoshi Yokogawa Kiyoshi Yokogawa , Kazuyuki Ueda Kazuyuki Ueda
Published: October 2002

The interaction of atomic hydrogen with the Si(111)√3 ×√3R30°-Sn surface is studied by scanning tunneling microscopy (STM). At room temperature, it is difficult for hydrogen to bond to silicon atoms on the surface which are bonded covalently to Sn atoms, as compared with those bound to Ag, Al and In, which have been reported so far. After annealing at elevated temperatures, hydrogen can bond with silicon surfaces, and clustering of Sn atoms is observed. At higher annealing temperatures around 580°C, hydrogen desorbs accompanied by surface silicon atoms, which causes a transformation of the surface structure from √3 ×√3R30° to 2√3 ×2√3R30° as a result of etching. It is suggested that the difference in formation energy on the disordered Si substrate is related to the restructuring.
Phase Relations in the CuGaxIn 1-xSe 2-In Pseudobinary System
Authors: Hideto Miyake Hideto Miyake , Tetsuo Haginoya Tetsuo Haginoya , Koichi Sugiyama Koichi Sugiyama
Published: October 2002

Phase relations in the CuGaxIn1-x
Se2-In pseudobinary system have been investigated. The conditions under which In solutions are single-phase liquids and chalcopyrite crystals can be grown from the solutions were determined. The relation between the composition of the grown crystal and that of the solute in the In solutions was determined for 60 mol% In solutions.
Microstructure and Temperature Coefficient of Resistance of Platinum Films
Authors: Zhang Jialiang , Nagao Yoshimichi , Kuwano Saburo , Ito Yoshinori
Published: October 2002

Platinum thin films are prepared on alumina ceramic substrates by rf magnetron sputtering. Microstructure and morphology are found to be sensitive to the sputtering gases and substrate surface conditions. N2-sputtered films show better microstructure quality than Ar-sputtered ones for use in forming industrial platinum resistance thermometers (IPRTs). The preferred (111) orientation in both as-deposited and recrystallized Pt films are identified using X-ray diffraction analysis. Thin-film Pt resistance thermometers are fabricated by laser beam trimming. The values of temperature coefficient of resistance (TCR) for N2-sputtered films show values close to the desired IPRT specification of 3850 ppm/°C and increase proportionally to the film's thickness. The dependence of microstructure and TCR on various heat treatment conditions is also investigated.
Improvement of Sputtering Target Utilization Using Dynamic Plasma Processing
Authors: Hiroshi Harada Hiroshi Harada , Yoshito Kamatani Yoshito Kamatani , Akira Hirata Akira Hirata , Tsuyoshi Koyanagi Tsuyoshi Koyanagi
Published: October 2002

A newly proposed design of the magnetron sputtering cathode shows to vastly improve target utilization efficiency for depositing films. In order to investigate this design's primary intent to obtain widely diffused target erosion areas, the finite element method (FEM) was employed to study the magnetic field distributions on the target surface. Favorable results from the study compelled the fabrication of this magnetron sputtering cathode design. This cathode creates widely diffused erosion areas by moving the position of the intense plasma, where the target becomes deeply sputtered, on the target surface by controlling the magnetic field with solenoid coils mounted on the inside of the sputtering cathode. This sputtering cathode design proved to achieve target utilization efficiencies as high as 40% for a 1150 ×150 ×6t mm indium tin oxide (ITO) target, in addition to satisfying the properties of deposited ITO films for use in transparent electrodes.
In Situ Surface Characterization of SrTiO3 (100) Substrates for Well-defined SrTiO3 and YBa2Cu3O7-x Thin Film Growth
Authors: Nakamura Takao , Hiroshi Inada Hiroshi Inada , Michitomo Iiyama Michitomo Iiyama
Published: October 2002

The topmost atomic layer of SrTiO3 (STO) substrates was investigated using in situ low-energy ion scattering spectroscopy (LEISS) for ultra-thin YBa2Cu3O7-
x

(YBCO) film growth. The topmost layer of a STO substrate after mechanochemical polishing consisted of SrO and TiO2 planes. The topmost layer was dominantly stabilized with a TiO2 plane after the STO substrate was treated with a p
H-controlled NH4F–HF(BHF) solution. It was confirmed that the topmost layer of STO thin films deposited on STO substrates was affected by the surface structure of the STO substrates. Furthermore, the dependence of T
c of heteroepitaxial YBCO ultra-thin films on thickness was better for BHF-treated STO substrates than for other substrates.
Refractive Index Measurement of Silicon Thin Films Using Slab Optical Waveguides
Authors: Takezawa Naganori , Isamu Kato Isamu Kato , Shinji Nojima Shinji Nojima
Published: October 2002

Measurement of the real part of the refractive index (n
f
′) of silicon thin films using a slab optical waveguide (SOW) is discussed. Upon deposition of thin films on a SOW, the transmittance decreases with periodic oscillation owing to the multiple reflection. It is clarified from a simulation of a four-layer SOW that the period of oscillation is reduced when n
f
′ increases. In this paper, we discuss a method of determining the n
f
′ from correspondence of the minimum film thickness (d
0) in which the oscillation valley appears as a calculation result of transmittance for the TE0 mode to d
0 in an experiment in which the refractive index and sizes of SOW are known without considering higher modes or the TM mode. Good agreement is observed in comparison of the result of the measurement with that of the ellipsometer at a wavelength of 632.8 nm. Therefore, it can be shown that the distributions of n
f
′ of a-Si:H and SiN thin films at wavelengths from 400 to 800 nm are obtained in the same manner. In order to achieve higher accuracy of the measurement, a SOW with a larger refractive index is used.
Measurement of Magnetic Field using Ultrasonic Vibration
Authors: Iijima Tamotsu , Nakagawa Yasuhiko , Ito Hiroshi
Published: October 2002

A method of measuring a magnetic field using a vibrating coil fixed on an ultrasonic vibrator is proposed. By measuring the field of the coreless excitation coil, the validity of the mechanism of this magnetic field detection method was confirmed. As a result, the linearity of the output signal to the ultrasonic vibration, coil turns and magnetic field was confirmed. In addition it was confirmed that the resolving power of the method was over 1/10 of the geomagnetism.
X-Ray Photoelectron Spectroscopy of Si–As–Te Chalcogenide Glasses Prepared in the Earth's Gravity and in Microgravity
Authors: Wahid Shams-Kolahi Wahid Shams-Kolahi , Michihiro Kobayashi Michihiro Kobayashi , Hiromasa Hanzawa Hiromasa Hanzawa , Michio Matsumura Michio Matsumura , Hikaru Kobayashi Hikaru Kobayashi , Hiroaki Okamoto Hiroaki Okamoto , Shoichi Endo Shoichi Endo , Yuki Kobayashi Yuki Kobayashi , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

The electronic structure of Si9As14Te21 chalcogenide glasses prepared in the Earth's gravity and in microgravity are investigated by X-ray photoelectron spectroscopy (XPS). The XPS spectra of the two types of glasses are generally similar at low core energy levels, but exhibit distinct differences at higher core electron energies and energy levels close to the Fermi level. It is found that a chemical shift towards lower binding energies occurs for the Te 4d level and a chemical shift towards higher binding energies occurs for the As 3d level for both types of glasses. The chemical shifts are, however, considerably larger for the space-made glass than for its terrestrial-made counterpart. The smaller chemical shift of Te 4d and As 3d energy levels might be evidence of the existence of Te clusters in the terrestrial-made glass.
(110) YBa2Cu3O7-δ Homoepitaxy on (110) YBa2Cu3O7-δ Single Crystal Substrates
Authors: Usagawa Toshiyuki , Ishimaru Yoshihiro , Wen Jianguo , Satoshi Koyama Satoshi Koyama , Youichi Enomoto Youichi Enomoto
Published: October 2002

We report on high-quality (110) oriented YBa2Cu3O7-δ films grown on mechanically polished (110) YBa2Cu3O7-δ single crystal substrates by off-axis RF magnetron sputtering method. The homoepitaxial growth keeps the original surface flatness of substrates. Atomic Force Microscopy (AFM) measurements of the films show a surface roughness of less than 1 nm over 1×1 µm2 area range. Furthermore, cross sectional Transmission Electron Microscopy (TEM) and Reflection High Energy Electron Diffraction (RHEED) observations confirm the surface flatness of our films. The homoepitaxial films show a high T
c (zero resistivity) of 90–92 K.
Room-Temperature Epitaxial Growth of Ni-Zn Ferrite Thin Films by Pulsed Laser Deposition in High Vacuum
Authors: Takakazu Kiyomura Takakazu Kiyomura , Manabu Gomi Manabu Gomi
Published: October 2002

Thin films of Ni-Zn ferrite have been epitaxially grown in situ on basal plane sapphires at room temperature by pulsed laser deposition in high vacuum. The films deposited at oxygen pressures of 1×10-5 to 1×10-6 Torr grew with spinel-type crystal structure and (111) planar orientation. X-ray phi scan analysis showed that the [110] direction in the (Ni, Zn)Fe2O4 (111) plane is parallel to the [1100] direction in the sapphire (0001) plane. The films exhibited streaky reflection high-energy electron diffraction patterns, indicating excellent surface smoothness.
Measurement of Spontaneous Emission Factor for 850 nm Gain-Guided Vertical-Cavity Surface-Emitting Lasers
Authors: Jae-Hyun Kim Jae-Hyun Kim , Jae-Heon Shin Jae-Heon Shin , Yong-Hee Lee Yong-Hee Lee
Published: October 2002

Using a method based on the measurement of below-threshold cavity loss and optical power, we experimentally determine the spontaneous emission factor of 850 nm gain-guided vertical-cavity surface-emitting lasers. Since our method needs only below-threshold information, we can avoid complex problems concerning above-threshold effects and obtain more reliable results. It is also pointed out that the typical L-I curve-fitting method results in unreliable estimation of the spontaneous emission factor. The values of spontaneous emission factors obtained are 6.6, 4.1, and 2.4 ×10-4 for 10-, 15-, and 20-µm-diameter circular aperture VCSELs, respectively.
Electrochemical Properties of Fullerene Derivative Polymers as Electrode Materials
Authors: Shin-ichi Kawabe Shin-ichi Kawabe , Tsuyoshi Kawai Tsuyoshi Kawai , Ryu-ichi Sugimoto Ryu-ichi Sugimoto , Eriko Yagasaki Eriko Yagasaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The electrochemical characteristics of fullerene and its derivative polymers were investigated for use as electrode-active material in rechargeable batteries. These polymer electrodes showed good potential stability and high Coulombic efficiencies in charge-discharge cycles in LiClO4/PC. The charge-discharge capacity of C60O polymer was as high as 340 mAh/g.
High-Power, Long-Lifetime InGaN Multi-Quantum-Well-Structure Laser Diodes
Authors: Nakamura Shuji , Senoh Masayuki , Nagahama Shin-ichi , Iwasa Naruhito , Yamada Takao , Matsushita Toshio , Yasunobu Sugimoto Yasunobu Sugimoto , Hiroyuki Kiyoku Hiroyuki Kiyoku
Published: October 2002

The continuous-wave operation of InGaN multi-quantum-well structure laser diodes (LDs) was demonstrated at room temperature with a high output power of 50 mW, a high operating temperature of 100° C and a long lifetime of 300 hours. The characteristic temperature of the threshold current was as high as 170 K. The emission wavelength of the LDs was 416 nm.
New Stimulated Emission Channels of Pr3+ and Tm3+ Ions in Monoclinic KR(WO 4) 2 Type Crystals with Ordered Structure (R=Y and Gd)
Authors: Alexander A. Kaminskii Alexander A. Kaminskii , Ludmila Li Ludmila Li , Andre V. Butashin Andre V. Butashin , Vladimir S. Mironov Vladimir S. Mironov , Alexsei A. Pavlyuk Alexsei A. Pavlyuk , Sergei N. Bagayev Sergei N. Bagayev , Ken-ichi Ueda Ken-ichi Ueda
Published: October 2002

We report the spectroscopic and experimental data of new laser channels of Pr3+ and Tm3+ ions in monoclinic tungstates. We discovered and identified a new one-micron laser action at 1.0223 µm of 1D2 → 3F3 transition of Pr3+ ions in monoclinic KY(WO4)2 crystal at room temperature. At cryogenic temperature, two-micron lasing of Tm3+ ions at wavelength of about 1.92 and 1.93 µm were excited in two sensitized crystals, KY(WO4)2:Er3+ and KGd(WO4)2:Er3+:Yb3+, respectively.
Raman Spectra of Ordered Vacancy Compounds in the Cu-In-Se System
Authors: Shigetaka Nomura Shigetaka Nomura , Shin-ichi Ouchi Shin-ichi Ouchi , Saburo Endo Saburo Endo
Published: October 2002

Raman spectra of ordered vacancy compounds (OVC) of CuIn2Se3.5and CuIn3Se5have been measured at room temperature. Similar nonpolarized Raman spectra are obtained for CuIn2Se3.5and CuIn3Se5. However, polarized Raman spectra are not available for CuIn3Se5because of its unfavorable crystallinity. A signal at 154  cm-1is assigned to be Γ1mode ofD2dsymmetry, originating from the vibration of selenium atoms in thex-y(a-axes) plane. This signal corresponds to the signal at 178  cm-1for CuInSe2of chalcopyrite-type in the Cu-In-Se system. The lowering of Γ1mode frequency for the defect structure is attributed to looser-bound selenium atoms on account of vacancies in the cation sites. Signals assigned as Γ3mode are unexpectedly observed in the geometries allowing the longitudinal optical (LO) modes of Γ4and Γ5symmetries. The respective mode peaks are found to be more dispersive in frequency for CuIn2Se3.5than for CuInSe2.
High Electron Mobilities in Surfactant-Grown Germanium on Silicon Substrates
Authors: Reinking Dirk , Kammler Martin , Hoegen Michael Horn-von , Karl R. Hofmann Karl R. Hofmann
Published: October 2002

We present the first investigation of the electrical properties of relaxed Ge layers grown on Si(111) substrates by surfactant-mediated epitaxy with Sb. Electron Hall mobilities and carrier concentrations of 1 µ m thick epitaxial Ge layers grown on p-type Si-substrates at temperatures between 640° C and 720° C were determined at 300 K and 77 K. The highest electron mobilities, 3100 cm2/Vs and 12300 cm2/Vs, at 300 K and 77 K, were observed in the 720° C sample. At 300 K an electron concentration of only 1.1×1016 cm-3 was measured suggesting a substantially lower incorporation of the surfactant Sb compared to earlier publications. The low Sb doping was independently supported by secondary ion mass spectroscopy (SIMS).
Electroluminescence from Deuterium Terminated Porous Silicon
Authors: Matsumoto Takahiro , Masumoto Yasuaki , Nakagawa Takashi , Hashimoto Masahiro , Ueno Koki , Koshida Nobuyoshi
Published: October 2002

We report the optical and electrical properties of deuterium terminated porous Si. It is found that the replacement of hydrogen with deuterium reduces the degradation not only of photoluminescence but also of electroluminescence. The luminescence degradation was analyzed using a rate equation model for photoinduced oxidation.
High Frequency Responses of YBa2Cu3O7-y Josephson Junctions on Si Substrates Fabricated by Focused Electron Beam Irradiation
Authors: Kim Sang-Jae , Myoren Hiroaki , Chen Jian , Nakajima Kensuke , Esashi Tsutomu Yamashita
Published: October 2002

YBa2Cu3O7-
y

(YBCO) Josephson junctions on silicon (Si) substrates were fabricated by focused electron beam (FEB) irradiation. The junctions exhibit an operation temperature ( T) dependence of current ( I)-voltage ( V) curves in the same manner as an SNS junction. As the temperature decreases, the junctions exhibit weak microwave-induced steps with flux flow-like I-V curves. At 25 K where the resistively shunted junction (RSJ)-like I-V curve appears, the junction exhibited the microwave-induced Shapiro steps up to 4 mV in d
V/d
I-V curves. This suggests that the junction can respond up to about 2 THz.
Growth of GaN on GaAs(111)B by Metalorganic Hydrogen Chloride VPE Using Double Buffer Layer
Authors: Takahashi Naoyuki , Matsuki Shiroshi , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

GaN epitaxial layers were grown by metalorganic hydrogen chloride vapor phase epitaxy (MOH-VPE) using double GaN buffer layers on GaAs substrate. In this method, the first GaN buffer layer was deposited on GaAs(111)B substrate at 550° C, and after annealing at 850° C for 10 min, the second buffer layer was deposited at 500° C. Then the GaN epitaxial layer was grown at 850° C. The X-ray full width at half maximum (FWHM) value of the obtained hexagonal GaN was smaller than that of a GaN epitaxial layer with a single buffer layer. The room temperature photoluminescence spectra exhibited a strong peak at approximately 361.5 nm.
Characteristics of Nb/Al/AlOx/Al/AlOx/Nb Junctions Based on the Proximity Effect
Authors: Sugiyama Hideyuki , Yanada Akiko , Ota Michiaki , Akira Fujimaki Akira Fujimaki , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

We present the results of a systematic study of Nb/Al/AlO

x

/Al/AlO

x

/Nb junctions having a structure in which an Al/AlO

x

film is added into a Nb/Al/AlO

x

/Nb junction, in this letter. A Josephson current flows across the junctions because the second Al layer has superconductivity due to the proximity effect. The critical current density J
c and quasiparticle characteristics strongly depend on the mean thickness of a second Al film and the transparency of the AlO

x

barriers. The junctions have relatively large conductance due to the proximity effect. This conductance results in a small hysteresis on its current-voltage curve compared to that of the Nb/Al/AlO

x

/Nb junction at the same J
c. Furthermore, the spread of the critical current for the 64 junctions connected in series is ±1.2%. This shows that the junctions have uniform enough characteristics to be used in integrated circuits.
Change in the Low-Lying Raman Scattering Spectrum in the Glass Transition of Dehydrated Polyacrylamide Gel
Authors: Kazuhiro Hara Kazuhiro Hara , Atsushi Nakamura Atsushi Nakamura , Nobuyasu Hiramatsu Nobuyasu Hiramatsu
Published: October 2002

The low-lying Raman scattering spectra were observed in the glass transition of a dehydrated polyacrylamide (PAAm) gel after examination of the transition by the differential scanning calorimeter (DSC) measurement. With increasing temperatures, a marked decrease in the scattering intensity of the Boson peak was observed. However, the peak could be still distinguished at temperatures much higher than the glass transition temperature. This feature could be due to the cross-linking of the polymer chains in the gel.
(110) Substrates for ZnSe on GaAs Heteroepitaxy
Authors: Narusawa Tadashi , Nishiyama Fumitaka , Zhu Ziqiang , Yao Takahumi
Published: October 2002

In this letter we present definitive evidence that the ZnSe epitaxial layer grows far better on GaAs(110) than on conventional GaAs(100) substrates. This evidence was derived from channeling measurements of 2 MeV He ions along major crystalline directions; the ZnSe on GaAs(100) system exhibited a large interface disorder peak in channeling backscattering spectra, whereas the ZnSe on GaAs(110) system gave smooth and featureless spectra. We deduce the quantitative interface disorder from the result of the measurements, and discuss a possible correlation between the interface structure and the charge neutralization problem of this heteroepitaxial system.
Ferroelectric Properties in Banana-Shaped Achiral Liquid Crystalline Molecular Systems
Authors: Sekine Tomoko , Takanishi Yoichi , Niori Teruki , Takezoe Junji Watanabe
Published: October 2002

We investigated the ferroelectric behavior in novel ferroelectric liquid crystals consisting of banana-shaped achiral molecules. Under the application of a triangular-wave electric field, we observed a single peak corresponding to the switching current in the higher-order smectic ( SmX2) phase as well as the smectic A
b
( SmA
b
) phase, where ferroelectricity had been already reported. This result proves that the spontaneous polarization is switchable with a single hysteresis loop in SmX2 as well as in SmA
b
. We also discussed the dielectric behavior in both the phases.
Fabrication of Epitaxial Diamond Thin Film on Iridium
Authors: Ohtsuka Kazuki , Fukuda Hideo , Suzuki Kazuhiro , Atsuhito Sawabe Atsuhito Sawabe
Published: October 2002

We have successfully grown smooth diamond thin films epitaxially on (001) iridium surfaces through a direct-current plasma chemical vapor deposition process with two steps: ion irradiation pretreatment and diamond growth. The epitaxial areas of diamond thin films with a mean thickness of about 1.5 µ m seem to act as optical mirrors. The average roughness (Ra) of the thin film, as measured by atomic force microscopy, is about 1 nm. Confocal Raman spectroscopy was used to investigate the depth profile of the thin film. Raman bands due to nondiamond carbon components were nominal at the diamond/iridium interface or at other depths.
Fragment Mass and Break Point Distributions in Dynamic Fragmentation of a Rod
Authors: Toshihiko Kadono Toshihiko Kadono
Published: October 2002

The dynamic fragmentation of a rod is investigated by conducting experiments and a computer simulation. A “lateral impact experiment” in which a hypervelocity nylon projectile collides at the top of the plaster rods is carried out. The fragment mass distribution and the alignment of the fragments are investigated. The cumulative number distribution of the fragment mass can be expressed by an exponential distribution while the distribution of the break points is different from the random one. Thus, the fragmentation in the lateral impact experiments cannot be described by Poisson statistics. The results of a simple one-dimensional model for elastic fracture resemble those observed in lateral impact experiments.
Two-Dimensional Hydrogen Analysis by Time-of-Flight-Type Electron-Stimulated Desorption Spectroscopy
Authors: Ueda Kazuyuki , Ken'ichi Ishikawa Ken'ichi Ishikawa , Masamichi Yoshimura Masamichi Yoshimura
Published: October 2002

Two-dimensional hydrogen images of a solid surface are obtained using scanning electron-stimulated desorption (ESD) spectroscopy. The diameter of the scanning electron probe is 3 µ m, and the scanned area is 387×387 µ m2 in 64×64 pixels. Here, we present experimental results of hydrogen images obtained for a silicon oxide layer and grid mesh using time-of-flight-type ESD spectroscopy.
Application of an X-Ray Transmission Phase Plate to Measurements of X-Ray Magnetic Circular Dichroism
Authors: Keiichi Hirano Keiichi Hirano , Hiroshi Maruyama Hiroshi Maruyama
Published: October 2002

An X-ray transmission phase plate made of a diamond crystal was combined with a fixed-exit double-crystal monochromator for X-ray magnetic circular dichroism (XMCD) experiments. Synchrotron radiation from bending magnets was monochromated by the monochromator and transformed to circular polarization by the phase plate for XMCD measurement of a disordered Fe–Pt alloy at the Pt L3-edge (E
0=11.565 keV). The measured XMCD spectrum agreed well with a previous result obtained with an elliptical multipole wiggler on the BL-NE1 at the Accumulation Ring of the National Laboratory for High Energy Physics (KEK).
Fabrication of Sub-Micron Tungsten Carbide (WCx)/Amorphous Carbon (a-C) Stacked Junction By Beam-Induced Reaction Processes
Authors: Miura Naruhisa , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai
Published: October 2002

Deposition of a carbon microfilm was performed by an electron-beam-induced deposition technique using scanning electron microscopy, and its electrical as well as optical properties were characterized. Peaks originated from a diamond-like carbon (DLC) were observed by Raman scattering spectroscopy and it was indicated that the deposited film consisted of amorphous carbon (a-C). Its electrical characteristics were studied using metal-insulator-metal diodes. The I-V curve of the diode showed nonlinear characteristics, and a dielectric constant was estimated at about 5. Furthermore, a tungsten carbide (WCx) film was grown by an ion-beam-induced deposition technique, and it was used in a WCx/a-C/WCx stacked junction of submicron size. It could be estimated from the dependence of the thermionic emission current on temperatures that an intrinsic barrier height in this WCx/a-C system was approximately 0.19 eV.
Rapid Preparation of YBa 2Cu 3O7-x with T c ∼ 90 K Using a Domestic Microwave Oven
Authors: Masatsune Kato Masatsune Kato , Kenji Sakakibara Kenji Sakakibara , Yoji Koike Yoji Koike
Published: October 2002

High-T
c superconducting samples of YBa2Cu3O7-x
with T
c ∼90 K have been prepared in a short time of 25 min, using a domestic microwave oven operated at 2.45 GHz and 200 W, without any post-heat treatment. Post-heat treatment is not necessary due to improvement of the sample environment during the microwave process. That is, a pellet of mixed powders of raw materials is surrounded by mixed powders of raw materials and subsequently wrapped in glass wool, in order to suppress rapid dissipation of heat from the surface of the pellet. This leads to successful preparation of homogeneous and oxygenated samples of YBa2Cu3O7-x
.
A Cleaning Model for Removal of Particles due to Laser-Induced Thermal Expansion of Substrate Surface
Authors: Lu Yong-Feng , Song Wen-Dong , Ye Kai-Dong , Lee Yuan-Ping , Daniel S. H. Chan Daniel S. H. Chan , Teck-Seng Low Teck-Seng Low
Published: October 2002

Taking Van der Waals force and cleaning force due to fast thermal expansion of substrate surface induced by pulsed laser irradiation into account, a cleaning model was established for removal of tiny particles from substrate surfaces. The cleaning condition and cleaning threshold can be obtained from this model. Theoretical predictions have been verified by the experimental results for removing quartz particles from silicon substrate. For laser-induced removal of quartz particles from silicon substrate surfaces, the cleaning threshold is about 135 mJ/cm2. Cleaning efficiency increases with increasing laser fluence, and large particles can be removed more easily than small ones.
Effects of Niobium Substitution for Titanium on Electrical Properties in Single Crystals of Lead Bismuth Titanate
Authors: Miyayama In-Sook Yi
Published: October 2002

Single crystals of Nb-doped lead bismuth titanate, PbBi4(Ti0.99Nb0.01)4O15, were synthesized by the vertical gradient freeze method, and electrical properties of the crystals were investigated by measuring DC conductivity, dielectric permittivity, and the D-E hysteresis loop. The p-type conductivity decreased upon Nb doping by as much as one to two orders of magnitude in the direction parallel to the bismuth layer. The dielectric permittivities decreased at Curie temperature (T
c) but increased about threefold at room temperature upon Nb doping. From the D-E hysteresis curves, the absence of spontaneous polarization in the direction perpendicular to the bismuth layer was confirmed in undoped and Nb-doped single crystals. The coercive field decreased in the direction parallel to the bismuth layer upon Nb doping at room temperature. It was found that Nb doping has effects to give a lower conductivity, favorable to high-temperature poling for polycrystals, and to improve ferroelectricity and dielectric permittivity at room temperature.
Dielectric Anomalous Peak of Relaxor Ferroelectrics under Small DC Bias
Authors: Zhang Yong , Gui Hong , Longtu Li Longtu Li , Zhilun Gui Zhilun Gui
Published: October 2002

The DC bias field dependence of the dielectric response of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3- Nb2/3)O3–PbTiO3 ceramics has been investigated. The bias characteristics of the real and imaginary parts of the dielectric permittivity show a temperature-dependent anomalous peak at a small bias level. The dielectric constant ε
*(ω, T)=ε
′(ω, T)+ iε
′′(ω, T) of relaxor ferroelectrics is calculated by considering the dynamics of the freezing process using the Monte Carlo method. The simulation agrees very well with the experimental results. A model has been suggested to explain the dependence of dielectric response on the electric field.
Comparison of Carbon, Aluminum, Silicon and Copper Films Deposited by High Peak Intensity Laser Ablation
Authors: Sato Shunichi , Toshio Yoneyama Toshio Yoneyama , Takeo Horaguchi Takeo Horaguchi
Published: October 2002

Thin films were deposited by laser ablation of carbon, alumimum, silicon and copper, using a high peak power Ti:sapphire laser. Each film was deposited on a silicon substrate at room temperature at a peak intensity of 3×1014 W/cm2. A smooth film was obtained by laser ablation of carbon and the other films were composed of many particles of 100 nm in diameter on average. The film deposited by laser ablation of silicon was twice as thick as the others. The results of X-ray photoelectron spectroscopy showed that all the films contained carbon. Furthermore, it was shown that the films deposited by laser ablation of aluminum and silicon contained oxygen as aluminum and silicon oxides, respectively.
Super-Wide Electron Cyclotron Resonance Plasma Source Excited by an Independent Double-Slot Antenna
Authors: Yoshiki Hiroyuki , Amadatsu Shigeki , Itadani Koji , Saijo Tatsuya
Published: October 2002

In this paper we describe an improved super-wide electron cyclotron resonance (ECR) plasma source which consists of permanent magnets, a solenoid coil and an independently excited double-slot antenna. Each slot antenna is prepared in the side wall of the rectangular waveguide positioned so that the two slot antennas are parallel and shifted by the distance of λ g/4 (λ g: waveguide wavelength) from each other. An 800-mm-wide (one-dimensional distributed) plasma of oxygen gas is produced, and an ion current density uniformity within ±5% over 770 mm in length can be obtained.
Organic Distributions on the Surfaces of Alumina Green Tape
Authors: Jau-Ho Jean Jau-Ho Jean , Ruey-Ling Chang Ruey-Ling Chang
Published: October 2002

Distributions of organic additives including poly(vinyl butyral) (PVB) and dibutyl phthalate (DBP) on the surfaces of alumina green tape have been investigated. More PVB and DBP were observed on the bottom surface (Mylar side) than on the top surface (air side) of the green tape. Microstructural observations revealed more porous powder packing on the bottom surface than on the top surface. The above results are explained based upon competitive wetting behavior of organic vehicle/alumina powder and organic vehicle/Mylar film.
Effects of Implanted Materials on Impurity-Induced Layer Disordering in Strained Ga0.8In0.2As/GaxIn1-xAsyP1-y/Ga0.51In0.49P/GaAs Quantum Well Structure
Authors: Jang Dong Hoon , Lee Jung Kee , Park Kyung Hyun , Cho Ho Sung , Seong Tae-Yeon , Chul Soon Park Chul Soon Park , Kwang-Eui Pyun Kwang-Eui Pyun
Published: October 2002

The impurity-induced layer disordering in B- or Si-implanted Ga0.8In0.2As/Ga

x

In1-
x

As

y

P1-
y

/Ga0.51In0.49P /GaAs quantum well structure has been studied. The wavelength shift of the photoluminescence peak and the degree of intermixing can be determined by the type and energy of implanted ions with followed annealing at the temperature of 900° C. A photoluminescence peak shift of 70 meV was obtained by 120 keV Si-implantation and annealing at 900° C. The diffused interface was also studied by cross sectional transmission electron microscopy.
Atomically Flat GaAs(001) Surfaces Obtained by High-Temperature Treatment with Atomic Hydrogen Irradiation
Authors: Yamaguchi Kengou , Qin Zhixin , Nagano Hajime , Kobayashi Masakazu , Takahashi Akihiko Yoshikawa
Published: October 2002

An atomically flat GaAs(001) surface can be obtained by a two-step atomic hydrogen (atomic-H) irradiation technique. This method includes low-temperature cleaning and high-temperature smoothening of the GaAs substrate surface. The reflection high energy electron diffraction (RHEED) and AFM study showed that a wide terrace with a 1 monolayer step height was observed when a GaAs(001) surface was cleaned at 400 °C and smoothened at 540 °C with atomic-H irradiation. The irradiation of atomic-H during the high temperature process maintained a certain surface stoichiometry, and resulted in an atomically flat substrate surface. This technique is useful for heterovalent epitaxy systems involving a single chamber growth system.
Pinning Effect on Punched-Out Dislocations in Silicon Wafers Investigated Using Indentation Method
Authors: Akatsuka Masanori , Sueoka Koji , Katahama Hisashi , Morimoto Nobuyuki , Adachi Naoshi
Published: October 2002

The mechanical strength of silicon wafers was investigated using the indentation method.
Sizes of rosette patterns L, generated during annealing at 900° C for 30 min, were measured
for as-grown floating zone (FZ) and Czochralski (CZ) silicon wafers. It was found that (1) the
rosette size L of FZ wafers was larger than that of CZ wafers and (2) L decreases in proportion
to the -2/3 power of interstitial oxygen concentration ([Oi]) for CZ wafers
([ Oi]=3.7–15.5×1017 atoms/cm3). From the experimental results, it was concluded that the wafers, in
which [Oi] was larger than approximately 2×1017 atoms/cm3, had the ability to pin on
dislocation movements. The pinning effect on dislocations by oxide precipitates or stacking
faults was also investigated using the indentation method. It was found that precipitates, of
which the density was approximately 1×109 /cm3 and the average size was lower than
approximately 500 nm, did not affect the rosette sizes L. On the other hand, stacking faults, of
which the density was approximately 1×107 /cm3 and the average size was approximately
50 µ m, have shown the pinning effect.
Argon Assisted Plasma Chemical Vapour Deposition of Amorphous Silicon Carbide Films
Authors: Chaudhuri Partha Chaudhuri Partha , Das Ujjwal Kumar Das Ujjwal Kumar
Published: October 2002

The sharp variation of carbon incorporation has been reported in amorphous silicon carbide thin films deposited by plasma chemical vapour deposition (CVD) from a mixture of silane, methane, argon and hydrogen by controlling the hydrogen percentage in the mixture of argon and hydrogen used as the diluent gases while other deposition parameters are kept constant. A model based on the reaction kinetics in the plasma has been proposed which successfully explains the sharp changes in the film properties dependent on the carbon content in the film.
Rotator Phase Transition through an Intermediate State in Odd n-Alkanes: In Situ Optical Observation Study
Authors: Koji Nozaki Koji Nozaki , Takashi Yamamoto Takashi Yamamoto , Tetsuhiko Hara Tetsuhiko Hara , Masamichi Hikosaka Masamichi Hikosaka
Published: October 2002

The rotator phase transitions in odd n-alkanes, n-C21H44 and n-C25H52, were investigated by optical microscopy. On cooling an n-C25H52 single crystal, a new transient intermediate state was observed within 1/30 s between the rotator phase (RV) and the low-temperature phase (IV). The rotator phase transition in n-C25H52 proceeds through two successive structural changes: uprighting of molecules and ordering of side packing. The two-stage changes on cooling were found to be peculiar to the transition accompanied by the molecular tilting motion, such as the RV→IV transition in n-C25H52. In contrast, in n-C21H44, the intermediate state was not observed.
The Free Energy of Condensed Matter under Stress
Authors: David J. Bottomley David J. Bottomley
Published: October 2002

The currently accepted form of the free energy of condensed matter under stress, derived using the Helmholtz free energy, is disproved. Recognizing that the Gibbs free energy is the correct function of state, a new formula for the free energy density E which is linear–rather than quadratic–in the strain is derived. For isotropic and cubic media, the formula is E=-(c
11+2c
12)ε where the c

i
j
are elastic stiffness constants and ε is the strain. The formula is in accordance with published data.
Ion Energy Analysis through rf-Electrode
Authors: Naoki Mizutani Naoki Mizutani , Toshio Hayashi Toshio Hayashi
Published: October 2002

Energy measurements of ions which impinge on an rf-electrode in plasma were taken using two modes, a dc-mode and an rf-mode. We calculated the ion energy distributions which were obtained using these modes and found that, for the dc-mode, the energy distribution broadened, and the center of the distribution varied, depending on the mass number of the ion. The distribution had extra peaks in addition to the normal saddle-shaped peaks. The features of the calculated distribution agreed well with the experimental results. The rf-mode was necessary to obtain the correct ion energy at the rf-electrode.
Negative Resistance of AlGaAs Diodes Co-doped with Si and Mn
Authors: Gho Seok-Jung , Park Seoung-Hwan , Lim H. , Choe Byung-Doo , Lee Chang Woo , Kim Min Kyung Ko
Published: October 2002

The co-doping effects of Mn on AlGaAs:Si diodes grown by a single-step liquid phase epitaxy (LPE) technique are investigated. Their current-voltage (I-V) characteristics are studied as a function of Mn and Al compositions. It is found that the breakdown voltage and the voltage drop increase with the concentrations of Mn and Al. These results are well explained by the increase of the thickness of the P°-region and the decrease of free hole concentration in its region.
All-Optical Switch Derived from the Negative Nonlinear Absorption Effect in Erbium-Doped Fibers
Authors: Yoshinobu Maeda Yoshinobu Maeda , Masatoshi Migitaka Masatoshi Migitaka
Published: October 2002

An all-optical switch which has a negative amplification of the optical signal was demonstrated in an erbium-doped fiber. The dependence of the negative nonlinear absorption effect on the modulation degree of the incident laser was investigated and we obtained the negative amplification degree of -3 for a fiber length of 6 m at room temperature. It has been confirmed that the mechanism of the effect can be explained by calculating the rate equations based on an analytical model for a five-level system of the Er3+ ion. It is suggested that the effect was due to stimulated emission from the 4
S
3/2 level to the 4
I
13/2 level.
Ta62Te38Twelvefold Quasicrystal Synthesized by Non-Equilibrium Solid State Reactions
Authors: Uchida Masaya , Horiuchi Shigeo
Published: October 2002

We have synthesized Ta-rich substances in the Ta–Te system by non-equilibrium solid state reactions between Ta and TaTe2. A twelvefold quasicrystal has been identified in the region with a composition of Ta62Te38by means of scanning as well as transmission electron microscopy.
Controlling Fluorine Concentration of Fluorinated Amorphous Carbon Thin Films for Low Dielectric Constant Interlayer Dielectrics
Authors: Kazuhiko Endo Kazuhiko Endo , Toru Tatsumi Toru Tatsumi
Published: October 2002

Control of the fluorine to carbon (F/C) ratio of fluorinated amorphous carbon (a-C:F) thin films by changing the deposition pressure is investigated. Decreasing the deposition pressure increases the dissociation of the source fluorocarbon material in the plasma, causing a decrease in the F/C ratio of the deposited film. There is a tradeoff relationship between the dielectric constant and the thermal stability. Both the thermal stability and the dielectric constant of the a-C:F films are increased as the F/C ratio is decreased. Thus, the tradeoff relationship between them can be optimized by the pressure during deposition.
An Interpretation of the Correlation Between the Intensity of Scanning Tunneling Microscopy (STM) Induced Light Emission and the Topographic Height for the Metal Particles
Authors: Ryusuke Nishitani Ryusuke Nishitani , Tsuyoshi Umeno Tsuyoshi Umeno , Atsuo Kasuya Atsuo Kasuya
Published: October 2002

The correlation between the intensity of Scanning Tunneling Microscopy(STM) induced light emission and the topographic height for metal particles is described. The topographic height dependence of the STM induced light emission from the STM induced dipole on the gold particles is calculated. The light emission is considered as the radiation from tunneling induced dipole, and the intensity is calculated as a function of the orientation of the dipole moment which depends on the position of the STM tip over the particles. The light intensity is nearly proportional to the topographic height of the particles. This result explains the linear correlation of the contrast between the photon intensity map and the STM topographic image.
InGaN/GaN/AlGaN-Based Laser Diodes with Modulation-Doped Strained-Layer Superlattices
Authors: Nakamura Shuji , Senoh Masayuki , Nagahama Shin-ichi , Iwasa Naruhito , Yamada Takao , Matsushita Toshio , Kiyoku Hiroyuki , Sugimoto Yasunobu , Kozaki Tokuya , Umemoto Hitoshi , Masahiko Sano Masahiko Sano , Kazuyuki Chocho Kazuyuki Chocho
Published: October 2002

InGaN multi-quantum-well-structure laser diodes with Al0.14Ga0.86N/GaN modulation doped strained-layer superlattice cladding layers grown on an epitaxially laterally overgrown GaN substrate were demonstrated to have an estimated lifetime of more than 10000 h under continuous-wave operation at 20° C. Under operation at a high temperature of 50° C, the lifetime was longer than 1000 h. With the operating current increasing to above the threshold, a self-pulsation with a high frequency of 3.5 GHz was observed. The carrier lifetime was estimated to be 1.8 ns from the pulsed modulation of the LDs.
Continuous Wave Diode Laser Induced Two-Photon Fluorescence Excitation of Three Calcium Indicators
Authors: Zhang Zhanxiang , Sonek Gregory. J. , Wei Xunbin , Berns Michael W. , Tromberg Bruce J.
Published: October 2002

Continuous wave (CW) diode laser induced two-photon fluorescence spectra have been measured for calcium indicators of Indo-1, Oregon-green, and Fluo-3. The near 2.0 log-log power-dependence of fluorescence intensity versus incident laser power indicates that the fluorescence from these three calcium indicators was excited by two-photon absorption process of 809-nm laser light. Calcium-dependent emission spectra of Indo-1 and Oregon-green for two-photon excitation under wavelength of 809-nm have also been measured.
YMnO3 Thin Films Prepared from Solutions for Non Volatile Memory Devices
Authors: Fujimura Norifumi , Tanaka Hirofumi , Kitahata Hiroya , Tadanaga Kiyoharu , Yoshimura Takeshi , Taichiro Ito Taichiro Ito , Tsutomu Minami Tsutomu Minami
Published: October 2002

We demonstrated for the first time that hexagonal YMnO3 films were fabricated from solutions which were effective for lowering the formation temperature. Two different processes, a thermal decomposition method and a reflux method, were studied. In the thermal decomposition method, the solution containing Y(OAc)3·4H2O and Mn(OAc)2·4H2O dissolved in ethanol containing diethanolamine was used for coating. Firing temperatures over 900° C were needed to obtain the YMnO3 single phase film using the thermal decomposition process. In the reflux method, the precursor solution prepared from 2-ethoxyethanol as a solvent was refluxed at 125° C and the solution obtained was used for coating. The reflux process drastically lowered the firing temperatures to 700° C, and this process also improved the microstructure. Effects of reflux on the crystallization process and dielectric properties have been demonstrated.