bluuebunny/crossref_metadata_2025 huggingface dataset:
Micron-Size Optical Waveguide for Optoelectronic Integrated Circuit
Authors: Nagata Takahiko , Tanaka Tsuyoshi , Miyake Kouji , Kurotaki Hirokazu , Shin Yokoyama Shin Yokoyama , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

Fundamental technologies for the optical interconnection in the VLSI chip have been developed by using conventional Si LSI technologies. The micron-size optical waveguide consisting of Si3N4 core and SiO2 cladding layers has been fabricated by low-pressure chemical vapor deposition (LPCVD) and atmospheric-pressure chemical vapor deposition (APCVD), respectively. The small lenses and the micron-size mirror which changes the light propagation direction from vertical to horizontal for the interlayer interconnection have also been fabricated.
Fabrication of Multiple-Electrode Chirped-Grating-Tunable Distributed-Feedback Lasers
Authors: Chen Nong , Yoshiaki Nakano Yoshiaki Nakano , Kunio Tada Kunio Tada
Published: October 2002

This paper describes fabrication and characteristics of GaAlAs/GaAs wavelength tunable distributed-feedback (DFB) semiconductor lasers with linearly chirped grating. In a two-section device, a single-mode quasi-continuous tuning range of 2.2 nm at around 868 nm has been achieved. This resulted mainly from the chirped grating structure effect rather than the free carrier plasma effect or the thermal tuning. A comparison of the two-section DFB laser with a conventional uniform grating has also been carried out.
Thermal Analysis of Laser-Emission Surface-Normal Optical Devices with a Vertical Cavity
Authors: Kajita Mikihiro , Numai Takahiro , Kurihara Kaori , Yoshikawa Takashi , Saito Hideaki , Sugimoto Yoshimasa , Sugimoto Mitsunori , Kosaka Hideo , Ichiro Ogura Ichiro Ogura , Kenichi Kasahara Kenichi Kasahara
Published: October 2002

Laser-emission surface-normal optical devices with a vertical cavity are expected to be key devices for optical interconnections. Thermal characteristics improvement is necessary for a large-scale-integrated two-dimensional array which increases the number of optical interconnections. To optimize the device structures to obtain good thermal characteristics, the temperature rise of distributed Bragg reflectors and an active layer must be known. Here, we report on the first evaluation of temperature rise in both regions, and it is found that the temperature rise is small for a compact double-mesa structure which allows a single lateral-mode oscillation. In addition, we measured the thermal crosstalk between the above compact devices, and it is found that the thermal crosstalk between one-dimensional array devices is small enough when each device operates at a few milliamperes.
Room Temperature Performance of (311) GaAs Quantum-Wire Structures
Authors: Nötzel Richard , Notomi Masaya , Kamada Hidehiro , Furuta Tomofumi , Ploog Tsutomu Yanagawa
Published: October 2002

Quantum wire structures are directly formed during the growth of GaAs/AlAs multilayer structures by molecular beam epitaxy due to the natural evolution of nanometer-scale corrugations on (311)-oriented GaAs and AlAs surfaces. The pronounced optical anisotropy clearly observable at 300 K reaches a value as high as 30% for the heavy-hole exciton resonance in 43 Å GaAs quantum-wire structures. The luminescence intensity of (311) GaAs quantum-wire structures with average GaAs layer thicknesses below 66 Å is generally higher than that of conventional (100) GaAs quantum-well structures. In 56 Å GaAs quantum-wire structures no reduction of the integrated luminescence intensity is observed up to 400 K. In the regime of unsaturated optical gain, the amplified luminescence intensity of (311) GaAs quantum-wire structures exceeds that of (100) GaAs quantum-well structures by fourfold. These findings highlight the potential of these novel low-dimensional structures for advanced semiconductor device concepts.
Silicon Cluster Terminated by Hydrogen, Fluorine and Oxygen Atoms: A Correlation with Visible Luminescence of Porous Silicon
Authors: Kumar Rajesh , Kitoh Yasuo , Shigematsu Koichi , Kunihiko Hara Kunihiko Hara
Published: October 2002

The effect of hydrogen, fluorine and oxygen surface termination atoms together with size dependence of the Si-cluster on the electronic structure are considered, using semiempirical molecular orbital calculations. The results show that the electronic structure of the Si-cluster is strongly affected by the presence of oxygen terminators which enhance the carrier localization. The transition probability between the electronic states support the high efficiency of visible luminescence. The hydrogen termination leads to a stable Si-cluster structure. Our calculations suggest that surface conditions of the Si-cluster and its size, are responsible for the visible luminescence properties of porous Si. The oxygen surface termination of the Si-ciuster is one of the requisite conditions to obtain luminescence in the red-orange region.
Electronic Structure of a Cluster Taken from High-Tc Superconductor of YBa2Cu3O7: (Cu4O2)(O4Ba)(Cu4O4)Y(Cu4O4)(O4Ba)(Cu4O2) Embedded in Ionic Cage of Point Charges
Authors: Tatewaki Hiroshi , Tanaka Kiyoshi , Noro Takeshi
Published: October 2002

We have investigated the electronic structure of a high-T
c superconductor of YBa2Cu3O7 with a cluster approximation. The adopted cluster was (Cu4O2)(O4Ba)(Cu4O4)Y(Cu4O4)(O4Ba)(Cu4O2) embedded in the appropriate ionic cage. The method of the calculations was that of ab initio self-consistent field proposed by Roothaan and Bagus. It was found that the ground state has two types of holes; one of them is localized at 2p

z

of each O(1) atom and the other at O(2) and O(3) on the CuO2 plane. The former is a very stable hole and the latter may correspond to the one that is focused on in discussion of the mechanism of superconductivity. Three lower excited states determined by the present calculation lie 1.6–1.9, 2.8 and 4.4 eV above the ground state, in agreement with the observed excitation energies of 1.7, 2.7, and 4.7 eV of crystal, where the orbitals of Ba, Y, Cu(1), and O(1) play an important role.
Photoluminescence Spectra of Tm-Doped CuAlS2 Crystals
Authors: Ohgoh Tsuyoshi , Aksenov Igor , Kudo Yuki , Sato Katsuaki
Published: October 2002

Photoluminescence spectra were studied for the first time in Tm-doped CuAlS2 crystals grown by the chemical vapor transport technique. Two sharp emission peaks at 1.55 eV (infrared) and 2.60 eV (blue) superposed on an orange broad emission band related to the host material were observed. The sharp emission lines were assigned to the f–f transitions in Tm3+ ions. The infrared line was found to be prominent at room temperature, the blue line at low temperatures. Both lines share the same excitation peak at 3.1 eV, which was tentatively attributed to the charge transfer transition. The temperature dependence was explained on the basis of the configurational-coordinate diagram of the luminescent center formed by the substitutional Tm3+ ion.
Effects of Pt Doping on Microstructure of YBa2Cu3Ox Superconductor Prepared by Directional Solidification
Authors: Kim Wonbaek , Shim Gunjoo , Jang Daekyu , Suh Changyoul , Shin Woosuck , No Kwangsoo
Published: October 2002

YBa2Cu3O

x

superconductor was prepared by directional solidification of Y2BaCuO5–BaCuO2–CuO–Pt powder mixture. Pt doping produced a microstructure which contained fine Y2BaCuO5 particles in textured YBa2Cu3O

x

grains. The same effect was not observed when a Pt wire was inserted in the sample instead of powders. Energy-dispersive X-ray spectroscopy (EDS) revealed that a compound containing Ba–Cu–Pt was formed around the wire as well as around the powders. The compound was identified as Ba4Pt1+
x

Cu2-
x

O9-
z

.
Contact Electrification on Thin Silicon Oxide in Vacuum
Authors: Tsuyuguchi Takeshi , Uchihashi Takayuki , Okusako Takahiro , Sugawara Yasuhiro , Morita Seizo , Yamanishi Yoshiki , Oasa Takahiko
Published: October 2002

We investigated the microscopic dissipation of contact electrified charges on a thin SiO2 film in vacuum where a thin layer of water may be adsorbed on the surface using an atomic force microscope (AFM). Charges with narrower spatial distributions were deposited in smaller amounts in vacuum than in air. Moreover, the deposited charge areas in vacuum showed no broadening with time after contact electrification. These demonstrate that the rapid surface diffusion of the charges in air may be caused by a water layer adsorbed on the insulator surfaces.
Dopant-Free Channel Transistor with Punchthrough Control Region under Source and Drain
Authors: Ohmi Mizuho Morita
Published: October 2002

A dopant-free channel metal-oxide-semiconductor field-effect transistor (MOSFET) featuring the punchthrough control region of moderate dopant concentrations under the source and the drain is proposed. This device structure is based on a new concept that the channel contains no appreciable ionized dopants at which electric field lines originating from the drain terminate whereas field lines from the drain mainly terminate at ionized dopants in the punchthrough control under the drain. The two-dimensional simulation analysis suggests that this device has good punchthrough control and consequently can be scaled down to 0.05 µm gate length. In this device, punchthrough can be suppressed by controlling the fringe effect of the pn junction formed between the drain and the punchthrough control.
Temperature-Dependent Reaction of rf Hydrogen Plasma with Silicon
Authors: Sun Yong , Nishitani Ryusuke , Miyasato Tatsuro
Published: October 2002

The reaction of rf hydrogen plasma with silicon has been studied by characterizing the reaction products as a function of silicon target temperature (80–300° C), hydrogen gas pressure (20–200 Pa) and rf power (50–400 W). It was found that the reaction rate of rf hydrogen plasma with silicon increased at temperatures below 200° C. Major products in the reaction are SiH2 and SiH3 species, and their sputtering rates depend strongly on the silicon target temperature rather than plasma density under the present sputtering conditions. The temperature dependence can be explained in terms of the chemical reaction rate of hydrogen with silicon and the surface density of adsorbed hydrogen on the silicon surface. The plasma bombardment effects on the reaction rate and the desorption rate of adsorbed hydrogen are also discussed.
Submicron Patterning Technique for YBa2Cu3Oy Films Using Focused Ion Beam Lithography
Authors: Kusunoki Masanobu , Akaike Hiroyuki , Akira Fujimaki Akira Fujimaki , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

We have developed a new technique for YBa2Cu3O

y

(YBCO) submicron structure formation. Nb films serving as etching masks are patterned into line structures with submicron dimensions, using focused ion beam lithography and a vertical etching technique of the Nb films. Then the mask patterns are accurately transferred to the YBCO film in an electron cyclotron resonance plasma etcher. Fine lines are successfully patterned down to 180 nm of the linewidth without any degradation of superconductivity, as long as a temperature rise is suppressed during plasma etching. The temperature dependence of the current-voltage characteristics can be interpreted in terms of the thermally activated vortex motion.
Fabrication of Low-Loss Microstrip Band-Pass Filter Made from Double-Sided YBa2Cu3Ox Films
Authors: Yoshitake Tsutomu , Tsuge Hisanao , Inui Tetsuji , Suzuki Shinji
Published: October 2002

A three-pole microstrip band-pass filter, with a center frequency of 9.5 GHz and bandwidth of 2%, has been fabricated using YBa2Cu3O

x

(YBCO) films deposited on both sides of (100)MgO substrates by pulsed laser ablation. A double-sided YBCO filter has a much lower passband insertion loss, 0.08 dB at 77 K and less than 0.04 dB below 60 K, compared with the 0.20 dB of a YBCO filter with a Au ground plane, and with the 1.1 dB of a conventional double-sided Au filter at 77 K. The extremely low insertion loss characteristics correspond to the element resonator unloaded quality factor (Q
u) of 6000 at 77 K and greater than 10000 below 60 K. These results demonstrate that very compact high-Q
u superconducting filters with waveguide-like performance can be achieved in planar microstrip configurations.
Effects of Conjugation of Mesogenic Core of Nematic Liquid Crystals for Polar Anchoring Energy and Surface Order Parameter on Rubbed Polyimide Films
Authors: Seo Dae-Shik , Yoshida Norihiro , Kobayashi Shunsuke , Nishikawa Michinori , Yabe Yoshikazu
Published: October 2002

We have studied the effects of the mesogenic core of nematic liquid crystals (NLCs) for polar anchoring energy and the surface order parameter on rubbed polyimide (PI) films. The order of polar anchoring energy for NLCs on rubbed PI films is 5CB>PCH5>CCH5. This order is the same for all rubbing strengths investigated. From the above results, we conclude that the polar anchoring energy strongly depends on the polarizability of the NLCs. The surface order parameter for NLCs is 5CB>PCH5>CCH5 on rubbed PI films which was imidized at 250°C. Finally, we suggest that the polar anchoring energy for NLCs on rubbed PI films is strongly related to the surface order parameter.
The Nonlinear Optical Characteristic of α-cyano-(3-methoxy-4-hydroxy-5-bromo)methylcinnamate (CMHB)
Authors: Ide Tetsuya , Inoue Yoshio , Yoshiyuki Higashigaki Yoshiyuki Higashigaki , Seiki Yano Seiki Yano
Published: October 2002

We have synthesized the nonlinear material α-cyano-(3-methoxy-4-hydroxy-5-bromo)methylcinnamate (CMHB). CMHB has been grown from solution evaporating method. CMHB belongs to the Triclinic system, and its space group is P1. The unit cell dimensions are: a=4.551 Å, b=11.085 Å, c=12.714 Å with α=101.89°, β=98.64°, γ=90.85°. The powder second harmonic generation of CMHB is 8 times higher than that of urea and the cutoff wavelength is 355 nm (in 1,4-dioxen).
Novel Optical and Electroluminescent Characteristics in Organic Superlattice Structure Utilizing Cyclopentadiene Derivative and Aromatic Diamine
Authors: Morishima Chikayoshi , Yoshida Masayoshi , Fujii Akihiko , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A superlattice structure electroluminescent diode consisting of alternating layers of organic cyclopentadiene derivative and aromatic diamine has been fabricated by organic molecular beam deposition. The electroluminescent spectrum of the diode depends on the layer thickness of cyclopentadiene derivative. The polarization anisotropy of the emission spectrum of the diode is also observed. The mechanism of emission anisotropy has been discussed in the superlattice structure.
Preliminary Measurement of H2 Pressure through Detection of Photoelectrons in Vacuum Range from 10-3 to 10-6Pa
Authors: Sekine Shigeyuki , Kiyohide Kokubun Kiyohide Kokubun , Shingo Ichimura Shingo Ichimura
Published: October 2002

H2 molecules in a vacuum chamber were nonresonantly ionized by an intense visible laser pulse, and the number of photoelectrons produced was measured as a function of H2 pressure. The signal intensity was proportional to H2 pressure in the range from 1×10-3 to 1×10-6 Pa. The present result showed experimentally that the detection of laser-induced photoelectrons can be applied for the measurement of pressure in the ultrahigh-vacuum range.
Zone-Plate X-Ray Microscope Using a Laser Plasma Source
Authors: Nakayama Shigeru , Haramura Kazuhito , Zeng Guang-Ming , Daido Hiroyuki , Nakatsuka Masahiro , Nakai Sadao , Katakura Norihiro , Nagata Hiroshi , Hiroaki Aritome Hiroaki Aritome
Published: October 2002

An imaging X-ray microscope using a laser plasma X-ray source, an objective zone plate and an ellipsoidal condenser mirror with multilayer coating is described. The 3.37 nm line emission from a carbon plasma is filtered and focused by the ellipsoidal condenser mirror and used as a light source. A magnified image (magnification: ×287) of a gold zone plate was obtained by a back-illuminated charge coupled device (CCD) whose pixel size is 22 µm×22 µm. The 0.4-µm-period pattern (outermost zones: 0.27 µm line and 0.13 µm space) is clearly resolved.
Atomic Layer Epitaxy of AlAs Using Dimethylethylamine Alane
Authors: Nagano Masahiro , Iwai Sohachi , Aoyagi Koshichi Nemoto
Published: October 2002

AlAs was grown by the atomic layer epitaxy (ALE) technique using a novel precursor, dimethylethylamine alane (DMEAA), as the aluminium source, for the first time. One-monolayer saturated growth was observed in the temperature range from 360°C to 440°C. The epilayers exhibited very smooth surface morphology. The lowest carrier concentration in the ALE layer was 3×1018 cm-3.
Removal of Adsorbed Organic Molecules with Scanning Tunneling Microscope: Formate Anions on TiO2(110) Surface
Authors: Hiroshi Onishi Hiroshi Onishi , Yasuhiro Iwasawa Yasuhiro Iwasawa
Published: October 2002

A scanning tunneling microscope (STM) operated under ultrahigh vacuum enabled us to eliminate individual formate anions ( DCOO-) adsorbed on a TiO2(110) surface. When bias voltages of +3.7 V or more were applied on the sample, the formate anions were removed under the STM tip. In contrast, much higher voltages, +5.0 V or more, were required to damage the underlying TiO2 surface. Thus we could strip off the formate anions in a desired area without damage to the substrate, to create patchworks of uncovered substrate in the monolayer of adsorbed formate anions. The threshold bias voltage for the elimination showed a small dependence on tunneling current, suggesting that the removal process is through field evaporation rather than direct excitation or thermal activation by tunneling electrons.
Effects of Electron Beam Irradiation and Subsequent Cl2Exposure on Photo-Oxidized c( 4×4) GaAs: Mechanism of In Situ EB Lithographic Patterning
Authors: Yuichi Ide Yuichi Ide , Masamichi Yamada Masamichi Yamada
Published: October 2002

The effects of electron beam (EB) irradiation and subsequent Cl2exposure on GaAs surface photo-oxides were investigated using X-ray photoelectron spectroscopy. Photo-oxides formed by visible-light-enhanced oxidation of c(4×4) GaAs surfaces were irradiated by an electron beam of 1.5 keV energy with doses ranging from 7.1×1016to 2.1×1018electrons/cm2. Chlorine was subsequently dosed up to 20 langmuirs using a AgCl electrochemical cell. Chlorine was not adsorbed on the photo-oxides, whereas it was readily adsorbed on EB-irradiated photo-oxides. EB irradiation induced the reduction of As5+and As3+oxides to less-oxidized As suboxides and/or elemental As, as well as partial removal of surface oxygen. An increase in the amount of Ga oxides was also observed. Chlorine exposure resulted in preferential removal of the EB-induced As suboxides and/or elemental As, as well as removal of As in the GaAs substrate and formation of Ga–Cl bonds. We attribute this to the desorption of AsCl3, and conclude that this “etching” of the surface As oxide is the key to patterning a photo-oxide mask.
Determination of the Photocarrier Lifetime in Amorphous Silicon with the Moving Photocarrier Grating Technique
Authors: Witt Christian , Uwe Haken Uwe Haken , Martin Hundhausen Martin Hundhausen
Published: October 2002

In this paper we have determined the lifetime of photogenerated
carriers in semiconductors using a technique that does not require time or
frequency resolved measurements of the photoconductivity. The lifetime is
deduced from the DC-short circuit current that is induced by a laser
interference grating of period Λ moving along the semiconductor
surface with the velocity v
gr. We observe a maximum short circuit
current density j
sc at a velocity that corresponds to a frequency
ω max=2πv
max/Λ of the moving interference
grating.
Based on a theoretical analysis of j
sc we show that ω max equals the inverse of the photocarrier lifetime τ, if the dielectric
relaxation-time τ diel is short compared to τ and if the
grating
period is chosen large compared to the ambipolar diffusion length.
Characteristics of Three-µm-Thick Silicon Solar Cells Using Bonded Silicon-on-Insulator Wafer
Authors: Takato Hidetaka , Yui Naomasa , Yutaka Hayashi Yutaka Hayashi , Toshihiro Sekigawa Toshihiro Sekigawa
Published: October 2002

Three-µm thick single-crystalline silicon solar cells were fabricated using a bonded silicon-on-insulator (SOI) wafer. The passivation effect due to the surface potential at the SOI layer/SiO2 back interface was investigated. The surface potential was changed by externally applied voltages. When the SOI layer/SiO2 back interface was in the accumulated condition, short-circuit current (I
sc) and open-circuit voltage (V
oc) were improved. Control of the surface potential is, therefore, effective in realizing high-efficiency thin silicon solar cells.
Preparation and Nonlinear Optical Properties of Ag/SiO2 Glass Composite Thin Films
Authors: Tanahashi Ichiro , Yoshida Masaru , Manabe Yoshio , Tohda Takao , Sasaki Satoshi , Tokizaki Takashi , Nakamura Arao
Published: October 2002

A multitarget sputtering method was applied to prepare Ag particles embedded in SiO2 glass thin films. In the optical absorption spectra of the films, the absorption peak due to the surface plasmon resonance of Ag particles was clearly observed at the wavelength of 390–406 nm. The full width at half-maximum of the absorption band is decreased with increasing diameter of Ag particles. The third-order nonlinear susceptibility at 400 nm was estimated to be 1.6×10-8 esu for the film with 9.0 at% of Ag by means of a degenerated four-wave mixing.
Damage Formed by Si+ Implantation in GaAs
Authors: Hara Tohru , Muraki Takeshi , Takeda Satoru , Uchitomi Naotaka , Kitaura Yoshiaki , Gao Guang-bo
Published: October 2002

Damage formed by low-dose Si+ implantation is studied. Variation of damage density with dose in Si+ implantation at 50 keV is measured at doses from 3.0×1010 to 1.0×1014 ions/cm2 by the photoacoustic displacement (PAD) technique. A close correlation has also been found between the PAD value and ion implantation dose in low-dose ion implantation. Ion implantation dose can be monitored down to 3.0×1010 ions/cm2 by this technique. This dose detection limit is much lower than that of other methods. The in-depth damage profile can also be measured by differentiating the observed PAD values with depth.
Laser-Induced Oxygen Control in Small Region of YBa2Cu3Oy Poly- and Single Crystals, Observed by Microscopic IR Reflection
Authors: Kawabata Keisuke , Tsukui Shigeki , Shono Yoshihiko , Fukuoka Nobuo , Imamura Shin'ichirou , Hayashi Yoshikazu
Published: October 2002

We have studied the oxygenation and deoxygenation induced by laser irradiation in poly- and single crystals of YBa2Cu3O

y

by microscopic IR reflection. We have observed a dramatic appearance and disappearance of the lattice-phonon modes unique to the insulator phase in accordance with the change of conductivity induced by the irradiation. By this method, we could detect the mutual conversion of the phase in an area as small as 0.1×0.1 mm2 without using electrodes, which is suitable for the study of the oxygenation and deoxygenation, particularly between y=∼6.2 to y=∼6.5. The differences in the conversion behaviors between single and polycrystals are discussed.
New Semiconductor Second-Harmonic Generator Based on Quasi-Phase-Matching for Cavity-Enhanced Fundamental Standing Wave
Authors: Hisanori Takahashi Hisanori Takahashi , Makoto Ohashi Makoto Ohashi , Takashi Kondo Takashi Kondo , Nagaatsu Ogasawara Nagaatsu Ogasawara , Yasuhiro Shiraki Yasuhiro Shiraki , Ryoichi Ito Ryoichi Ito
Published: October 2002

We propose a compact, highly efficient semiconductor second-harmonic (SH)
generator based on a new type of quasi-phase-matching (QPM) that is
achieved by modulating the optical nonlinearity at the period
of the harmonic wavelength and
by utilizing a cavity-enhanced fundamental standing wave.
The conversion efficiency of an SH generator incorporating GaP/AlP layers in a cavity
to achieve the new QPM is shown to be considerably higher than
that of a conventional QPM device.
The Eight Modes Observation in LiNbO3 Induced by 3.0 MeVHe+ Implantation
Authors: Wang Ke-Ming , Shi Bo-Rong , Zhou Zhuang , Wang Wei , Ding Pei-Jun , Wang Zhong-Lie
Published: October 2002

The y-cut LiNbO3 was implanted by 3.0 MeV He+ to a dose of 2×1016 ions/cm2 at liquid nitrogen temperature. The eight black and bright modes from He implanted LiNbO3 waveguide were observed before and after rapid annealing. The refractive index profile is obtained by means of a non-stationary mode index calculation. The comparison of refractive index profile with damage profile is given. The result shows that the peak position of the refractive index profile is found to be in good agreement with the peak position of damage profile induced by 3.0 MeV He+ implanted in LiNbO3 based on transport of ions in matter (TRIM'92).
Preparation and Characterization of Low-Dielectric Glass Composite with Aluminum Borate
Authors: Hwang Jau-Ho Jean
Published: October 2002

The effect of aluminum borate ( Al18B4O33) on crystallization and thermal expansion of Pyrex borosilicate glass has been studied. X-ray diffraction (XRD) results show that with 40 vol% aluminum borate, the precipitation of cristobalite in the Pyrex borosilicate glass is completely inhibited. This result is further evidenced by the linear thermal expansion measurement in which, in contrast to the system without aluminum borate, the thermal expansion coefficient remains unchanged with sintering time and is close to that of silicon, 3×10-6 K-1. Moreover, the composite with 40 vol% aluminum borate has a dielectric constant of 5.2 and a dielectric loss of 0.8% at 1 MHz.
Anisotropic Molecular Orientation of Poly(o-trimethylsilyl)-Phenylacetylene Film Swollen under High Magnetic Field
Authors: Itadani Toshiaki , Saito Koichi , Akiya Takeo , Nagata Shiro , Niino Hiroyuki , Yabe Akira , Fukuda Kenzo
Published: October 2002

Poly(o-trimethylsllyl)-phenylacetylene (PTP) film, which was swollen in acetone under a high magnetic field of 15 T, showed birefringence and dichroism. Comparing the IR dichroism of magnetic-field-treated film with that of mechanically stretched film, it was found that the polymer long chain was aligned perpendicularly to the magnetic field. This alignment originated from the magnetic anisotropy of crystalline structures in PTP film.
Effects of Salts and Metal Oxides on Electrochemical and Optical Properties of Streptococcus mutans
Authors: Kawai Tsuyoshi , Nagame Seigo , Kambara Masaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The effects of calcium salts and metal oxide powders on electrochemical, optical and biological properties of Streptococcus mutans have been studied as a novel method to determine the strain. Electrochemical signals of Streptococcus mutans show remarkable decrease in the presence of saturated calcium salts such as CaHPO4, Ca3(PO4)2, and Ca5(PO4)3OH depending on the strains of Streptococcus mutans: Ingbritt, NCTC-10449, or GS-5. The number of viable cells also decreases upon addition of these powders. The effects of metal oxides such as ZnO and BaTiO3 on the electrochemical characteristics and photoluminescence of Streptococcus mutans have also been studied.
Chemical Treatment Effects on Si Surfaces in SC2 Solutions Studied by Spectroscopic Ellipsometry
Authors: Kobayashi Kazuyuki , Takahiro Susuki Takahiro Susuki , Sadao Adachi Sadao Adachi
Published: October 2002

Si surfaces chemically treated in HCl:H2O2:H2O=X:1:6 [X=1 (SC2) and 0] at 80°C have been studied using spectroscopic ellipsometry (SE). The SE data clearly indicate that both theX=1 and 0 solutions result in surface chemical oxidation. The chemical oxidation occurs immediately upon immersion of the samples in the solutions. The thickness of chemical oxide shows a saturated value of ∼9.5±1 (X=1) and ∼11.5±1 Å (X=0) against immersion timet.
A Novel Quantum Cellular Automata Logic with Loop Structures
Authors: Tetsufumi Tanamoto Tetsufumi Tanamoto , Riichi Katoh Riichi Katoh , Yujiro Naruse Yujiro Naruse
Published: October 2002

The effects of additional cells on the circuit operation of
quantum cellular automata (QCA) logic, proposed by Lent et al.,
are numerically studied using the extended Hubbard model self-consistently.
We investigate the differences in logic circuit operation between Lent's inverter
and our original 4-cell one characterized by a loop structure in the cases of
4 and 5 quantum dot cells (QDC).
We find that the 4-cell inverter with loop structure
composed of 4-QDC exhibits favorable characteristics in QCA logic operation.
Heisenberg-Picture Operators for Two-Photon Jaynes-Cummings Model
Authors: Hiroshi Iwasawa Hiroshi Iwasawa , Kuniaki Matsuo Kuniaki Matsuo
Published: October 2002

The dynamics of the degenerate two-photon Jaynes-Cummings model in Heisenberg picture is investigated. By solving the Heisenberg equations, the exact solutions of the photon annihilation operator a( t), the atomic dipole moment operator σ-( t), and the population difference operator σ

z

( t) are obtained. We demonstrate that the correlation functions for the photon annihilation and dipole moment operators can be directly evaluated from these exact solutions. The solutions of the time-evolution operators are shown to be quite useful in the calculation of two-time correlation functions. Furthermore, some results of the dynamical behavior of the average values for the photon number , the in-phase field component <X
1(t)>, and the population difference <σ
z
(t)> are demonstrated by computer simulations.
One-Shot Excimer Laser Laminar Annealing of SrTiO3 Thin Films in Solidus Phase
Authors: Taga Masahiro , Hitoshi Miyake Hitoshi Miyake , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

By virtue of high optical absorptance and low thermal conductivity of SrTiO3, and short duration of the laser pulse, one-shot ArF excimer laser irradiation exerted an efficient annealing effect on the top SrTiO3 thin layer in the SrTiO3/YBa2Cu3O

y

/MgO heterostructure without causing interfacial deterioration. Namely, our new method is characterized by laminar annealing of nanosecond duration. Actually, by one-shot laser irradiation, the permittivity of the top SrTiO3 film (110 nm thick) was improved from 52ε
0 (as grown) to 220ε
0. Annealing strongly depended on the laser energy but not on the pulse number. When the laser energy was increased up to 150 mJ/cm2, at which the top surface of the underlying YBa2Cu3O

y

reached its molten phase, the SrTiO3 permittivity degraded markedlly.
Ultrasoft X-Ray Emission Spectroscopic Analysis for Effects of Vacuum Ultraviolet Rare Gas Excimer Laser Irradiation on Silicon Nitride Films
Authors: Kurmaev Ernst Z. , Shamin Sergei N. , Dolgih Vitalij E. , Kurosawa Kou , Nakamae Kazuo , Takigawa Yasuo , Kameyama Akihiro , Yokotani Atsushi , Sasaki Wataru
Published: October 2002

The results of measurements of Si-L2,3 X-ray emission spectra of Si3N4 films deposited on GaAs substrates after irradiation by Kr2 and Ar2 excimer lasers are presented. By using the excitation of X-ray emission spectra with focused electron beam, local precipitation of crystalline silicon is found.
Comparatively Large Second-Order Hyperpolarizability of Aromatic Sulfonate Anion with Short Cutoff Wavelength
Authors: Duan Xuan-Ming , Okada Shuji , Oikawa Hidetoshi , Matsuda Hiro , Hachiro Nakanishi Hachiro Nakanishi
Published: October 2002

The second-order hyperpolarizabilities (β) of ionic species of sodium p-toluenesulfonate ( pTSNa) and its corresponding neutral derivative methyl p-toluenesulfonate ( p TSMe) in methanol were evaluated to be 2.2×10-29 and 1.2×10-29 esu, respectively, using the hyper Rayleigh scattering method at 1064 nm. Since ionic p TSNa has short cutoff wavelength of 280 nm as well as comparatively large |β| value, i.e., about twice that of neutral p TSMe and about two-thirds that of p-nitroaniline, aromatic sulfonate ions are concluded to be worth investigating as potential chromophores for second-order nonlinear optics.
Oscillations in Magnetoresistance in Epitaxial (100) and (111) NiFe/Cu Multilayers
Authors: Kawawake Yasuhiro , Sakakima Hiroshi , Yousuke Irie Yousuke Irie , Mitsuo Satomi Mitsuo Satomi
Published: October 2002

Multilayers (MLs) of NiFe/Cu with (100) and (111) orientation were epitaxially grown on Si(100)/Cu and Si(111)/Ag/Cu substrates, respectively. The RKKY-like oscillations of magnetoresistance ratios were observed in the epitaxial NiFe/Cu MLs with the Cu spacer layer thickness (t
Cu). The (100)-oriented NiFe/Cu MLs showed maxima at t
Cu=0.9, 1.6, 2.0 and 2.5 nm, while the (111)-oriented MLs showed maxima at t
Cu=0.9 and 1.9 nm.
Metal-Insulator-Metal Tunneling Light-Emission Junction in Surface Acoustic Wave Field
Authors: Min Cai Yi , Sun Cheng Xiu Sun Cheng Xiu , Gao Zhong Lin Gao Zhong Lin
Published: October 2002

In the study of metal-insulator-metal (MIM) light-emitting tunneling junctions (LETJs), we adopt surface acoustic waves (SAW) in order to induce light emission instead of surface roughness and set our MIM LETJs in the field of SAW. As a result, the LETJs' efficiency and stability have been increased appreciably.
  In this paper, we introduce the LETJs' basic structure and technology, and discuss its emission spectrum and I-V characteristic curve. Above all, we observe the negative resistance phenomenon (NRP) in its I-V curve.
Critical Layer Thickness of n-In0.52Al0.48As/In0.8Ga0.2As/In0.52Al0.48As Pseudomorphic Heterostructures Studied by Photoluminescence
Authors: Ueno Yoshiki , Taguchi Takashi , Matsugatani Kazuoki , Takeuchi Yukihiro , Sugiyama Yoshinobu , Tacano Munecazu , Tadashi Hattori Tadashi Hattori
Published: October 2002

Photoluminescence (PL) analysis on n-In0.52Al0.48As/In0.8Ga0.2As/In0.52Al0.48As/InP pseudomorphic heterostructures grown by molecular beam epitaxy has been carried out to investigate the critical layer thickness. Crystal quality degradation is followed by the relaxation of the lattice-mismatched layer. The critical layer thickness for this material system that is measured by PL is found to agree with the value from the energy balance model.
Smectic Layer Rotation in Antiferroelectric Liquid Crystal
Authors: Ozaki Masanori , Moritake Hiroshi , Keizo Nakayama Keizo Nakayama , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Smectic layer rotation in the antiferroelectric liquid crystal upon application of asymmetric pulses of electric field has been observed. Application of the electric field with sawtooth waveform of more than 103 cycles induces rotation of the direction of the smectic layer normal by more than 60° away from the initial alignment axis even in the sample without surface treatment for a unidirectional alignment. This rotation is reversible, and the layer rotates in the opposite direction upon application of pulses of electric field with opposite polarity. This anomalous layer rotation has been tentatively interpreted to originate from the essential difference in F →A
F and A
F →F transition mechanisms.
Area Density Control of Quantum-Size InGaAs/Ga(Al)As Dots by Metalorganic Chemical Vapor Deposition
Authors: Oshinowo John , Nishioka Masao , Satomi Ishida Satomi Ishida , Yasuhiko Arakawa Yasuhiko Arakawa
Published: October 2002

We have investigated the accumulation of InGaAs dots ( ∼15 nm) on GaAs and AlGaAs surfaces, by metalorganic chemical vapor deposition (MOCVD). Scanning electron micrography (SEM) shows highly uniform dots formed by the Stranski-Krastanow growth mode. The average area InGaAs dot density can be controlled from 108 cm-2 up to more than 1011 cm-2 by substrate off-angle orientation, deposition thickness, and growth temperature. The results indicate high area dot density for low surface diffusion.
Comparative Study on Effect of Boronization and Titanium Gettering in Compact Helical System Heliotron/Torsatron Device
Authors: Yamada Hiroshi , Morita Shigeru , Matsuoka Keisuke , Nishimura Kiyohiko , Okamura Shoichi , Sagara Akio , Ida Katsumi , Inoue Noriyuki , Noda Nobuaki , Sakakibara Satoru , Jihua Xu Jihua Xu , Ichihiro Yamada Ichihiro Yamada
Published: October 2002

Boronization with decaborane which is solid at room temperature has been successfully applied to the Compact Helical System (CHS) experiment. The effect of boronization on neutral-beam-injection (NBI)-heated plasma has been compared with the optimized case of titanium gettering. The concentration of oxygen has been reduced by a factor of 2 with boronization. Metal impurities can also be completely suppressed. Plasma performance has been improved in the high-density region with \barn
e> 5×1019 m-3. The effective lifetime covers at least 200 NBI discharges while the favorable condition with titanium gettering has an effective lifetime of only 20∼30 discharges.
Estimation of the Mobility-Lifetime Products in Amorphous Silicon in the Presence of Dispersive Transport
Authors: Jiang-Huai Zhou Jiang-Huai Zhou
Published: October 2002

Applying the intuitive multiple trapping theory, we have calculated the time-of-flight (TOF) charge-collection µτ
product, (µτ)
c
c
, under the condition of dispersive transport and find that (µτ)
c
c
=(1/α-α)µ0τ
f
d
≈µ0τ
f
d
, where α is a
temperature-dependent constant, µ0 is the free-carrier mobility, and τ fd is the TOF charge-collection free-carrier deep-trapping time. The steady-state photoconductivity µτ product, (µτ)
s
s
, is argued to be (µτ)
s
s
=µ0τ
f
r
where τ
f
r
is the steady-state free-carrier recombination lifetime. As a result, (µτ)
s
s
/(µτ)
c
c
≈τ
f
r
/τ
f
d
. Our calculation shows that the presence of dispersive transport does not affect the ratio of (µτ)
s
s
and (µτ)
c
c
, and that the difference between (µτ)
s
s
and (µτ)
c
c
is due almost entirely to a difference between the free-carrier recombination lifetime in the steady state and the free-carrier deep-trapping time in the TOF charge-collection experiment. The origin of the difference between (µτ)
s
s
and (µτ)
c
c
is discussed.
Compound-Source Molecular Beam Epitaxy for ZnCdSe/ZnSSe/ZnMgSSe Laser Structure
Authors: Ohkawa Kazuhiro , Yoshii Shigeo , Takeishi Hidemi , Tsujimura Ayumu , Hayashi Shigeo , Takeshi Karasawa Takeshi Karasawa , Tsuneo Mitsuyu Tsuneo Mitsuyu
Published: October 2002

We have developed compound-source molecular beam epitaxy (CSMBE) for ZnSe-based laser diodes. The CSMBE technique employs compound sources instead of elemental sources, and can reduces the number of growth parameters. Continuous-wave operation at room temperature of ZnCdSe/ZnSSe/ZnMgSSe laser diodes grown by CSMBE has been demonstrated. The threshold current was 68 mA for a gain-guided device 5 µm wide and 750 µm long.
High-Density Recording Using Phase-Change Optical Disk
Authors: Morimoto Isao , Nishimura Kazuhiro , Suzuki Toshio , Takeguchi Keigo
Published: October 2002

High-track-density recording has been investigated using a phase-change optical disk. Crosstalk was measured as a function of track pitch. Crosstalk of less than -26 dB was obtained at the track pitch of 1.0 µm using a red laser diode, an objective lens of large numerical aperture and a thin substrate. Amorphous marks were observed by transmission electron microscopy, and it was found that the width of amorphous marks remains on the order of the groove width even at high recording power, though the length increases with the increase of the recording power.
Straight Step Edge Formation on an InAs(001) Vicinal Surface by the Transition of Surface Reconstruction
Authors: Shunsuke Ohkouchi Shunsuke Ohkouchi , Nobuyuki Ikoma Nobuyuki Ikoma
Published: October 2002

Step structures of InAs (001) vicinal surfaces tilted by 1° towards the [11̄0] direction were investigated using scanning tunneling microscopy. A transition from an As-stabilized ( 2×4) to an In-stabilized ( 4×2) reconstruction caused a change in the step structure of the vicinal surfaces from ragged to straight along the [110] direction with the incorporation of step bunching. The straight shape of the step structure seems to be caused by desorption of arsenic atoms along the [110] direction.
Mechanism of CF Polymer Film Deposition through High-Aspect-Ratio SiO2 Holes
Authors: Ono Tetsuo , Hamasaki Ryoji , Tatsumi Mizutani Tatsumi Mizutani
Published: October 2002

The deposition of polymer films through SiO2 microholes was studied by using a multichannel capillary array (MCA). CHF3 plasma polymer films were deposited on Si substrates through an MCA (hole diameter 10 µm, aspect ratio 40) made of lead glass, and X-ray photoelectron spectroscopy was used to analyze the films. The deposition rate under MCA was higher than those of flat surfaces. Pb from the MCA material was detected in the film deposited through the MCA, and CF polymers deposited through the MCA were more carbon rich than those deposited outside the MCA. These results suggest that polymers reach the bottom of the hole by being etched from and redeposited on the sidewall.
Refrigeration Character of New-Type Peltier Refrigerator Using High-Tc (Bi, Pb)2Sr2Ca2Cu3Oy Superconductor
Authors: Takahiro Nakano Takahiro Nakano , Takasu Hashimoto Takasu Hashimoto
Published: October 2002

We have investigated the refrigeration characters of the Peltier refrigerators using the high-T
c (Bi, Pb)2Sr2Ca2Cu3O
y
superconductor (Bi-2223) as a thermoelectrically passive material at low temperatures. For the Peltier refrigerator using the Bi89Sb11 and the Bi-2223, the maximum temperature drop of 7.1 K has been obtained when the temperature of the hot junction is 78 K. For the Peltier refrigerator using the Bi85Sb15 and the Bi-2223, the operating temperature dependence of the refrigeration character has been measured; furthermore the possibility of refrigeration has been demonstrated at temperatures above the superconducting transition temperature (T
c=110 K) of the Bi-2223.
Observation of Threading Dislocation Generation Process in Highly Lattice-Mismatched Heteroepitaxy
Authors: Kawai Takahiro , Yonezu Hiroo , Saito Daishiro , Mikihiro Yokozeki Mikihiro Yokozeki , Kangsa Pak Kangsa Pak
Published: October 2002

The generation process of threading dislocations in highly lattice-mismatched heteroepitaxy was investigated by transmission electron microscopy (TEM). In the growth of InAs epilayers on GaAs substrate, the misfit strain was partially accommodated by the formation of coherent three-dimensional islands before the generation of misfit dislocations. However, the misfit dislocation was eventually introduced in each grown three-dimensional island in order to relieve the misfit strain. It was clearly shown that the misfit dislocations propagate towards the growth direction; i.e., threading dislocations originated from the grown islands.
Poly(vinyl alcohol)/Liquid Crystal Composite Films with Low Driving Voltage
Authors: Hiroshi Ono Hiroshi Ono , Nobuhiro Kawatsuki Nobuhiro Kawatsuki
Published: October 2002

A poly(vinyl alcohol) (PVA)/liquid crystal (LC) composite film with a low driving voltage of 6 V
r
m
s
, a low hysteresis of less than 0.2 V
r
m
s
, and a fast response time of 11 ms at the operating voltage of 6 V
r
m
s
was formed from the emulsion composed of a mixture of water with methanol (WM-mixture), PVA, LC, and a photocrosslinkable mixture of nonaoxyethylenediacrylate (9EG-A) with perfluorooctylethylacrylate (FA-108). It was found in the composite film that the liquid crystal droplets, surrounded by a thin layer of the photocured polymer, were deformed as well as disordered, which enhanced light scattering.
Extrinsic Photocarrier Generation at Fluorenone Bisazo Pigment/α-Phenylstilbene Derivative Interface
Authors: Minoru Umeda Minoru Umeda , Tatsuya Niimi Tatsuya Niimi
Published: October 2002

We have investigated the molecular interface between an azo pigment and an α-phenylstilbene derivative where photocarriers are extrinsically produced from a microscopic viewpoint. From the measurement of the azo-pigment photoluminescence quenching by the α-phenylstilbene derivative, only the molecules that contact with the azo-pigment particles are known to promote generation of the photocarriers. The electron-transfer reaction at the interface for photocarrier generation is proven to occur adiabatically.
Superconductivity in Artificially Layered Ba–Ca–Cu–O Thin Films
Authors: Li Xiaomin , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

Thin films of Ba–Ca–Cu–O have been grown by successive deposition of BaCuO2 and CaCuO2 layers with different numbers of each layer. The samples of (BaCuO2)3+(CaCuO2)1 show a zero resistance at 30–38 K with the onset of 70–80 K. The diamagnetic transition is also observed below 26–30 K. X-ray diffraction analysis shows the c-axis orientation of the films with a lattice constant of c=15.38 Å. This value is nearly equal to the sum of three times BaCuO2's c-axis length plus the CaCuO2's c-axis length based on the infinite layer structure of BaCuO2 and CaCuO2. By means of an artificial layer-by-layer growth process, a new superconducting system of layered Ba–Ca–Cu–O structure is formed.
A Piezoelectric Quartz Microactuator for a Large Pseudo-Static Displacement
Authors: Toshiyoshi Hiroshi , Kobayashi Dai , Hiroyuki Fujita Hiroyuki Fujita , Toshitsugu Ueda Toshitsugu Ueda
Published: October 2002

A piezoelectric quartz microactuator based on a new driving mechanism is reported. The actuator is fabricated by anisotropic etching of a Z-cut quartz substrate and operatred by means of piezoelectricity. The uniqueness of the actuator is that large static displacement is generated under AC volutage at the mechanical resonant frequency (8.5 kHz). Therefore, we call it a pseudo-static displacement actuator. The pseudo-static displacement is relatively large (40 µm), considering the size of the actuator (5 mm across). Furthermore, it is 20 time larger than the displacement in true DC volage operation.
Preparation of Chemically Adsorbed Functional Monolayers Containing Poly(ethylene oxide) Chains on Glass Surface and Their Surface Resistivities
Authors: Yasuo Takebe Yasuo Takebe , Yasuhiko Shirota Yasuhiko Shirota
Published: October 2002

For the purpose of developing transparent and ultrathin antistatic films, chemically adsorbed monolayers containing poly(ethylene oxide) chains have been prepared on a glass surface by the reaction of a chemically adsorbed chlorosilane derivative with poly(ethylene glycol)s having different average molecular weights. The surface resistivities of the monolayers were found to be about two orders of magnitude lower than that of clean glass at a humidity of 40%.
Electrochemical Characteristics of Stable Polyacetylene Derivatives: Poly(o-trimethylsilylphenylacetylene)
Authors: Yoshino Katsumi , Takahashi Hiroyuki , Morita Shigenori , Sugimoto Tsuyoshi Kawai
Published: October 2002

Activation phenomena have been observed in the cyclic voltammogram of the film of poly(o-trimethylsilylphenylacetylene) (PTMSiPA) prepared by the solution casting method. Upon electrochemical doping in PTMSiPA the absorption peak in the visible range due to the interband transition is suppressed and a new broad peak appears in the infrared range. Corresponding to this spectral change, the film changes from red to colorless. Spin density evaluated by ESR decreases with electrochemical doping and becomes negligibly small. These doping characteristics have been interpreted in terms of the soliton model just as for the case of nonsubstituted polyacetylene, and the electronic energy scheme of this polymer has been evaluated. A relatively large diffusion coefficient ( 9.2×10-8 cm2/s) of anion dopant ( BF4
-) was obtained in this film. It was also found to exhibit high Coulombic efficiency in the charge-discharge characteristics as a secondary battery.
Nonlinear Optical Properties of Poled Polymer of Phenoxy Resin Containing α-Cyano Unsaturated Carboxylate
Authors: Sugihara Okihiro , Nakayama Hideki , Okamoto Naomichi , Sakakibara Taro , Taketani Yutaka
Published: October 2002

A new nonlinear optical polymer of phenoxy resin containing 2-cyano-5-(4-methoxyphenyl)-2,4-pentadienoate as a pendant group is synthesized. A high concentration (84%) of chromophores with a relatively high value of hyperpolarizability ( 50×10-30 esu) is obtained. The corona-poled polymer film shows hypochromic shift (Φ=0.084) and birefringence (Δn(ω)=0.9% and Δn(2ω)=1.6%). A second-order nonlinear coefficient of d
33=22 pm/V is achieved. The value decreases to 70% after 10 h but remains stable thereafter.