bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Power InGaAlP Laser Diodes for High-Density Optical Recording
Authors: Hatakoshi Gen-ichi , Nitta Koichi , Itaya Kazuhiko , Nishikawa Yukie , Masayuki Ishikawa Masayuki Ishikawa , Masaki Okajima Masaki Okajima
Published: February 2005

Theoretical investigation has been carried out for high-power InGaAlP visible-light laser diodes. The thin active layer, essential for preventing catastrophic optical damage of the laser facet, enhances carrier overflow and causes a deterioration in temperature characteristics. Increase in the bandgap energy difference between the active layer and the cladding layer is required in order to maintain sufficient heterobarrier height. High acceptor concentration for a p-cladding layer has a great effect on the prevention of the carrier overflow and, as a result, on the improvement of the temperature characteristics. High-power transverse-mode stabilized InGaAlP lasers, operating at high temperature, were realized by employing a composition-shifted thin active layer and a highly doped p-cladding layer. High-power operation, at over 100 mW, was achieved.
Theoretical Analysis of Super-Resolution Readout of Disc Data by Semiconfocal Pickup Heads
Authors: Toshiaki Suhara Toshiaki Suhara , Hiroshi Nishihara Hiroshi Nishihara
Published: February 2005

The possibility of super-resolution readout of digital disc data by means of semiconfocal optics and apodization, i.e., improvement of resolution without increasing objective NA over conventional pickup (PU) heads, is discussed based on diffraction-theory analysis and readout simulation. After reviewing the evolution to semiconfocal pickup heads, mathematical formulae to describe the pickup performances are given. It is demonstrated that super-resolution readout, which allows miniaturization of PU heads and/or enhancement of recording density, can be realized simultaneously with focusing/tracking error detection.
A New Method of Measuring Microspot Parameters in a Magnetooptic Storage System
Authors: Yu Ruan , Cao Danhua Cao Danhua , Li Mingzhi Li Mingzhi
Published: February 2005

On the basis of frequency analysis of magnetooptic signals, a new method to measure microsized spots is described. The method not only has high measuring accuracy and the ability of real-time measurement, but it is also simple. In this paper, several mathematical models to examine measuring error are developed. By theoretical analysis, for detection frequency of 0.6 MHz and spot radius of 0.5 µm, the relative error is within 0.032%.
High-Density Magneto-Optical Disk System Using Magnetically Induced Super Resolution
Authors: Yoshimura Shunji , Fukumoto Atsushi , Masahiko Kaneko Masahiko Kaneko , Hideo Owa Hideo Owa
Published: February 2005

Magnetically induced super resolution (MSR) is a new technology developed by us. It more than doubles the readout resolution limit of a conventional optical disk system without shortening the laser wavelength or increasing the numerical aperture (N.A.) of the objective lens. We examined the characteristics of the readout signals of an MSR-by-RAD (rear aperture detection) disk and obtained a high C/N of more than 49 dB and good stability of the edge position at a mark length of 0.4 µm. We investigated the high-density MO disk system using the MSR-by-RAD disk. Owing to optimization of the writing process and waveform equalization, the system achieved a byte error rate of less than 10-4 at a bit length of 0.3 µm. This bit length corresponds to a linear density more than three times higher than that of the conventional 130-mm MO disk system of the ISO standard.
Readout Waveform Equalization in Pulse-Width-Modulated Optical Recording
Authors: Tanaka Yasuaki , Takaya Tanabe Takaya Tanabe , Ryoichi Arai Ryoichi Arai
Published: February 2005

In order to achieve a high linear density in optical recording, undesirable asymmetry in readout waveforms due to teardrop-shaped recorded marks is analyzed and suppressed by a new readout waveform equalization technique. A polygonal approximation method is used in the analysis. This considerably reduces the calculation time, compared with the conventional method, without loss in accuracy. The readout waveform equalization not only sharpens the rise/fall time, but also effectively suppresses the asymmetry by using a nonlinear component. In the case of allowance below 10% phase shift, the available linear density is improved by 1.3 times.
High-Density Overwriting on a Magneto-Optical Disk with Exchange-Coupled Triple-Layer Film
Authors: Nakaoki Ariyoshi , Tanaka Shintaro , Takashi Shimouma Takashi Shimouma , Masahiko Kaneko Masahiko Kaneko
Published: February 2005

The characteristics of high density recording on an overwritable magneto-optical disk using light intensity modulation were investigated by means of (2, 7)-RLL mark position detection. We examined the overwritable region of optimum high level, (P
H) and low level, (P
L) by varying the recording pulse width and film structure in the overwritable magneto-optical disk, in order to minimize thermal interference between closely recorded marks. A wide margin of ±30% was obtained using low power at a bit length of 0.8 µm.
High Storage Density Optical Recording with a Stable Micro Green Second Harmonic Generation Laser Consisting of Nd:YVO4 and KTP
Authors: Tatsuno Kimio , Takahashi Masahiko , Muraoka Kouji , Sugiyama Hisataka , Nakamura Junko , Tetsuo Andou Tetsuo Andou , Tsuyoshi Miyai Tsuyoshi Miyai
Published: February 2005

A stable micro second harmonic generation (SHG) laser consisting of a diode- pumped Nd:YVO4 laser doubled by KTiOPO4 achieves 3 times higher storage density than usual on an erasable optical disk.
High-Density and High-Carrier-to-Noise-Ratio Optical Disk Mastering
Authors: Nakano Toshiyuki , Taira Kozo , Masaaki Matsumaru Masaaki Matsumaru , Teruo Murakami Teruo Murakami
Published: February 2005

A scanning tunneling microscope (STM) was used to observe the surface profile of an optical disk and to quantitatively evaluate the lithography conditions in the mastering process. A high-density and high-carrier-to-noise-ratio (C/N) optical disk was achieved using precise data concerned with the relations among the mastering process, the profile of the masters, and the readout signal.
Multi-Beam Optical Disk Drive for High Data Transfer Rate Systems
Authors: Katayama Ryuichi , Yoshihara Kazuhiro , Yamanaka Yutaka , Tsunekane Masaki , Kayanuma Kinji , Iwanaga Toshiaki , Okada Osamu , Yuzo Ono Yuzo Ono
Published: February 2005

A multi-beam optical disk drive, which improves the data transfer rate for magneto-optical disk systems, has been developed. The optical head employs an image rotator for tracing several tracks simultaneously. Four-channel parallel read/write operation has been achieved, and a digital video recording system with a data transfer rate of 22 Mbps has been realized. Real-time data verification at a linear velocity of 33 m/s has been demonstrated. Double track density recording, using a crosstalk canceler, has also been accomplished, and a 5.1×10-5 bit error rate has been obtained.
Large-Capacity and High-Speed Magnetic Field Modulation Recording for 3.5′′ Magneto-Optical Disk Drive
Authors: Hiramatsu Makoto , ishii kazuyoshi , Miyaoka Yasuyuki , Kimura Syunpei , Miyajima Yoshikazu , Shinichi Tachibana Shinichi Tachibana , Koyo Hasegawa Koyo Hasegawa
Published: February 2005

Recording by magnetic field modulation overwriting with a flying magnetic head and adopting a 1-7 RLL code, mark-edge recording, and ZCAV format, was attempted. A 3.5′′ magneto-optical disk drive with a large storage capacity of greater than 300 MBytes and a high data transfer rate of 2.7 MBytes/s on the outermost track was realized.
Stabilization of Focus Servo System for High-Speed Access in a 90 mm MO Disk Drive
Authors: Harutaka Sekiya Harutaka Sekiya , Shin Kagami Shin Kagami
Published: February 2005

Stability of a focus servo system was studied in a 90 mm magneto-optical (MO) disk drive that uses a separated optical system for high-speed access. The separated optical system had two major problems of focus servo system instability-one is caused by a mechanical feedback (MFB) due to mechanical resonance of a disk and the other is caused by a complex feed-back of both mechanical and optical crosstalks. The mechanisms of these problems are clarified, and high-speed access of less than 30 ms is achieved. In this paper, the mechanisms are discussed and effective solutions are presented.
Servo Signal Simulation of an MO Disk with Embossed Pits
Authors: Kobayashi Kiyoshi , Jr. Fumiaki Yamada
Published: February 2005

A two-dimensional scalar diffraction model is used to simulate servo signals in an optical disk with pre-grooves and embossed pits. Two sets of values for the optimum geometry are presented. The effect of the pit size is shown for each of the optimum sets. This paper also describes how the tracking error signal is affected by variances from the optimum values. It recommends that pit shifts from the track center and defocusing effects due to servo signal crosstalk should be avoided so as to achieve fast and reliable access, whether or not embossed pits are included.
Excitonic Excited States and Optical Spectra in Poly(p-Phenylenevinylene) Prepared by Carefully Controlled Thermal Elimination Reaction
Authors: Fukuda Takashi , Kubo Takaya , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

Optically excited excitonic states have been studied in poly(p-phenylenevinylene) films carefully prepared by the sulfonium salt method. The conspicuous vibronic structures in the reflection spectrum together with the steep absorption edge indicate that the conjugation length distribution has a smaller standard deviation than that reported by Rauscher et al. The small deviation also manifests itself in the more clearly resolved vibronic structures in the emission spectra. The photocurrent is excited only near the intrinsic absorption edge and its efficiency is very low. The resonance Raman spectrum does not show any multiphonon lines, and its relative intensity with respect to the emission intensity is considerably weak. Two strong Raman lines appear at 0.146 eV (1176 cm-1) and 0.197 eV (1586 cm-1), which are very close to the phonon energies in the vibronic spectra of emission and reflection, respectively; the transition process can be regarded as charge transfer between the phenylene and the vinylene groups.
Index-Free Full-Text Search Function Installed into Optical Disk Drive
Authors: Murai Katsumi , Azumatani Yasushi , Takagi Yuji , Fukusima Yoshihisa , Satoh Isao
Published: February 2005

An optical disk drive, equipped with additional SCSI commands for full-text search is developed. By hierarchical search architecture of parallel hardware, firmware and software, the system filters information almost at the disk-read speed. The basic search process is executed by a search engine sharing the function with a portion of the error-correcting LSI installed into the optical disk controller. The basic search performance of the developed system is 10 to 25 times faster than that of software. Also, introduction of an associative table for presearching results in performance more than 1000 times faster than that in the case in which no objective lines are found. Though our system does not have large-scale special-purpose hardware for text search, the retrieving speed of the free-text database is dramatically improved.
Application of Optical Disc System to Medical Use -Special Focus on PACS-
Authors: Miyasaka Kazuo , Goro Irie Goro Irie , Toshihiko Kudo Toshihiko Kudo
Published: February 2005

Two years of clinical experience with picture archiving and communication system (PACS) at Hokkaido University Hospital is described. Both magnetic and write-once optical discs are indispensable for medical data storage of the PACS. Data compression of medical images is routinely employed without significant degradation of image quality, to reduce data sorage space and data transferring time. Image quality of the work station and data access time are acceptable in clinical use of the PACS.
Multiple Photochemical Hole Burning in Tetraphenylporphine Derivatives Using a Focused Laser Beam
Authors: Asai Nobutoshi , Kishii Noriyuki , Shin-ichiro Tamura Shin-ichiro Tamura , Jun'etsu Seto Jun'etsu Seto
Published: February 2005

The recording properties of photochemical hole burning (PHB) in tetraphenylporphine (TPP) derivatives with a focused laser beam were studied. We demonstrated the possibility of more than 200-multiplicity recording in the frequency domain in tetrakis(pentafluorophenyl)porphine (TFP) in a 10-µm-diameter laser spot at 4 K. The effect of the laser irradiation time on the depth was also investigated using tetrakis(4-methoxyphenyl)porphine (TMP). Although the hole depth decreased with decreasing laser irradiation time down to the ms order due to the bottleneck effect (because of long triplet lifetime), a detectable hole is formed with irradiation by a 8 ms pulse using TMP.
Holographic Recording in Cerium Doped Strontium Barium Niobate a-Axis Single Crystal Fibers
Authors: Sugiyama Yasuyuki , Yagi Shôgo , Yokohama Itaru , Iwao Hatakeyama Iwao Hatakeyama
Published: February 2005

We have grown cerium doped strontium barium niobate (Ce:SBN60) single-crystal fibers, 250 µm-1 mm in diameter, along the a-axis by the laser heated pedestal growth method. The properties of holographic recording in the fiber are investigated. This fiber is expected to have high writing sensitivity due to its large relevant figure of merit and relatively wide grating spacing. The diffraction efficiency reaches more than 40% at 50 ms for a transmitted object beam with an exposure power of 75.2×2 µW. The angular sensitivity is 1.5 mrad at an incident angle of 21°. We also demonstrate image recording in the fiber.
Stimulated Electronic Transition Concept for an Erasable Optical Memory
Authors: Albin Sacharia , Satira James D. , Shull David L. Livingston
Published: February 2005

A new concept for an erasable optical memory is demonstrated using stimulated electronic transition (SET). Large bandgap semiconductors are suitable materials for the SET medium. We have investigated the properties of MgS:Eu, Sm and SrS:Eu, Sm as possible media for the SET process. Quantum storage is achieved in the form of charges in deep levels in the medium and stimulated radiative recombination is used as the reading process. Unlike magneto-optic (M-O) and phase change (PC) processes, optical writing, reading and erasing are achieved without localized heating. The SET process will have an inherently faster data transfer rate and a higher storage density, and the medium will be more durable than the M-O and PC media. A possible application of the SET process in neural networks is also discussed.
Effect of Annealing Method on Vacancy-Type Defects in Si-Implanted GaAs Studied by a Slow Positron Beam
Authors: Shikata Shin-ichi , Fujii Satoshi , Wei Long , Tanigawa Shoichiro
Published: February 2005

The effect of annealing encapsulants on the activation of Si implanted into GaAs was studied by slow positron beam annihilation. For encapsulants, two kinds of silicon nitrides and silicon dioxide were used and capless annealing under arsine ambient was performed for reference purposes. From the measurements of the Doppler-broadened profiles of the positron annihilation as a function of the incident positron energy, gallium vacancy concentrations were estimated. It was found that silicon dioxide cap annealing includes a high concentration of gallium vacancies, which is approximately 2.5 times larger than that for silicon nitride annealing and four times that for capless annealing. With the electrical measurement, the out-diffusion of Ga into the cap insulator film was found to have no enhancing effect on electrical activation.
X-Ray Standing Wave Analysis of Al/GaAs/Si(111)
Authors: Kawamura Tomoaki , Oshima Masaharu , Fukuda Yukio , Ohmachi Yoshiro , Izumi Koichi , Ishikawa Tetsuya , Kikuta Seishi , Wei Zhang Xiao
Published: February 2005

The Al/GaAs interface formed on Si(111) is investigated by means of the X-ray standing wave technique. Different fluorescence profiles of Ga and As Kα are observed from a Al/GaAs/Si(111) sample. Comparing the results of Al/GaAs/Si(111) with GaAs/Si(111), most of the Ga atoms are found to change their positions randomly by evaporating Al metal on the GaAs films even at room temperature. On the contrary, most of the As atoms continue to maintain original positions in the diamond structure. This can be explained by interchanging the sites of Ga and Al atoms, and forming (Al, Ga)As layers. The results suggest that interdiffusion and interchange between Al and GaAs layers should not be neglected even at room temperature.
Stress Effect on Current-Induced Degradation of Be-Doped AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Mochizuki Kazuhiro , Isomae Seiichi , Masuda Hiroshi , Tomonori Tanoue Tomonori Tanoue , Chuushiro Kusano Chuushiro Kusano
Published: February 2005

The effect of stress on the current-induced degradation of current-voltage characteristics in AlGaAs/GaAs heterojunction bipolar transistors with Be-doped base layers is investigated. Transistors with different orientations of the emitter mesa and different thicknesses of the passivation film are bias tested at room temperature. The results are compared with the stress distributions along the emitter-base junction obtained from a two-dimensional calculation using the boundary element method. It is found that the degradation is caused by the diffusion of Be under high-current density operations and that the flux of Be diffusing from the base layer to the emitter layer is strongly related to the stress distributions around the periphery of the emitter-base junction.
Monte Carlo Simulation of Response Time for Velocity Modulation Transistors
Authors: Maezawa Koichi , Takashi Mizutani Takashi Mizutani , Masaaki Tomizawa Masaaki Tomizawa
Published: February 2005

We have studied the response time for velocity modulation transistors (VMTs) using particle Monte Carlo simulation. The intrinsic VMT model with zero gate-source spacing was used to avoid the change in total number of electrons due to the difference in source resistances between the two channels. The results show that the response time for VMTs is about half that for ordinary high electron mobility transistors (HEMTs). The remaining factor limiting the response time is the electron redistribution in the channel, which is shown to be caused by the difference in velocity-electric field characteristics in the two channels. A “virtual” VMT model with a single channel, where the impurity concentration is changed abruptly at a certain moment, has also been studied to clarify the effect of electron redistribution.
Harmonic Susceptibilities of a Single-Crystal YBa2Cu3Oy Bulk Superconductor
Authors: Yamamoto Kazunuki , Mazaki Hiromasa , Yasuoka Hiroshi , Terashima Takahito , Bando Yoshichika
Published: February 2005

The magnetic response of a single-crystal YBa2Cu3O
y
bulk specimen in a weak magnetic field was measured in terms of harmonic susceptibilities χ
n
=χ
n

′-iχ
n

′′ (n=1, 2, 3). From the fundamental susceptibility χ1 measured in an ac field parallel and perpendicular to the c axis, we found an apparent anisotropic nature of the sample. χ2 and χ3 were analyzed within the framework of the Kim-Anderson model for critical current density. Comparison of the observed and calculated χ
n
suggests that generation of the higher-harmonic susceptibilities arises from the supercurrent according to the critical-state (Kim-Anderson) model, although the absolute values of calculated χ
n
are several times larger than the observed ones. Details of the experiment are presented together with the analyses of the data.
Analysis of Effective Interaction Length for Crossing Beams in a Para-Hydrogen Raman Laser
Authors: Tsunemi Akira , Tashiro Keigo Nagasaka
Published: February 2005

The amplification by stimulated rotational Raman scattering in para-hydrogen was studied for the pump and Stokes beams which crossed each other with a small angle. The dependence of amplification gain on crossing angles was explained using a plane wave model with three dimensional overlaps.
Nonlinear Dielectric Relaxation Spectra of Polyvinyl Acetate
Authors: Takeo Furukawa Takeo Furukawa , Kiyokazu Matsumoto Kiyokazu Matsumoto
Published: February 2005

The frequency spectra of the linear and third nonlinear permittivities, ε1
* and ε3
*, have been measured for polyvinyl acetate (PVAc) at temperatures above T
g. The Debye relaxation of ε1
* associated with the micro-Brownian motion of noncrystalline segments is found to be accompanied by the complex frequency dependence of ε3
* due to combined contributions from the intrinsic nonlinear dielectricity and the electrostriction. Additional measurements for the elastic compliance s
* allow subtraction of the latter contribution (\propts
*ε1
*2) to yield the intrinsic nonlinear dielectric relaxation spectra in the form of Δε3/(1+iωτ3)3 in accordance with phenomenological prediction. The evaluated relaxation strengths, Δε1 and Δε3, lead to estimates of equivalent Langevin dipoles consisting of eleven monomers and a saturation polarization of 20 mC/m2.
Models of Molecular Orientation in Surface-Stabilized Ferroelectric Liquid Crystals with High-Pretilt Aligning Film
Authors: Itoh Nobuyuki , Koden Mitsuhiro , Shuji Miyoshi Shuji Miyoshi , Tomio Wada Tomio Wada
Published: February 2005

Surface-stabilized ferroelectric liquid crystals (SSFLC) with high-pretilt (about 15°) aligning film showed three types of states (C1U, C1T and C2) with different optical properties. The transmitted light of these states was calculated using the 4×4 matrix method, and the optical memory angle and transmission spectra were compared with the experimental observations. The experimental characteristics of these states were consistent with the calculated results, indicating the validity of the proposed molecular orientational models of these states. In addition, we simulated the effect of the pretilt angle of the aligning film on the optical properties of the SSFLC device.
Vanadium-Related Deep Levels in n-Silicon Detected by Junction Capacitance Waveform Analysis
Authors: Kawahara Hisatsugu , Okamoto Yoichi , Tahira Kenichiro , Morimoto Jun , Nakashima Toru Miyakawa
Published: February 2005

Multiexponential (ME-) and spectral analysis (SA-) Deep Level Transient Spectroscopy (DLTS) are made on vanadium-related deep levels in n-silicon. We resolved three traps with large amplitude and three more traps with comparatively small amplitude, VA (ΔE=0.08 eV, σ=3.2×10-18 cm2), VB (ΔE=0.28 eV, σ=2.6×10-14 cm2) and VC (ΔE=0.24 eV, σ=8.4×10-18 cm2). These vanadium-related levels do not have appreciable broadening of the emission rate spectrum.
Stark Modulation Spectra of ICl Rovibronic Transition B3Π0
+←X1Σ+ and Permanent Electric Dipole Moments of B3Π0
+ State
Authors: Watanabe Akiyoshi , Takei Taka-aki , Yoshito Amako Yoshito Amako
Published: February 2005

Stark modulation spectra of the ICl rovibronic transitions B
3Π0
+(υ′=1, 2)←X
1Σ+(υ′′=0) and B
3Π0
+(υ′=3)←X
1Σ+(υ′′=1) were observed and analyzed. From the analysis of the Stark shifts for the M
′=±2←M
′=±2 component of the P(3) lines, the permanent electric dipole moments in the B
3Π0
+(υ′=1, 2, 3) states were determined with their signs relative to that in the X
1Σ+ state.
Laser Cooling and Trapping of Alkaline Earth Atoms
Authors: Takayuki Kurosu Takayuki Kurosu , Fujio Shimizu Fujio Shimizu
Published: February 2005

Characteristics of laser trapping of Ca and Sr are experimentally studied and discussed. The lifetime of the trap is found to be limited by accumulation of the population in the 3P2 state, not by the decay 1P1→1D2. This result allows us to generate a continuous free-falling flow of ultra-cold ground state atoms which is useful for ultra-high resolution spectroscopy. Effects of an optical pumping laser which recycles the 1D2 population in Sr are investigated.
Effects of Fresnel Diffraction on Resolution and Linewidth Control in Synchrotron Radiation Lithography
Authors: Yoh Somemura Yoh Somemura , Kimiyoshi Deguchi Kimiyoshi Deguchi
Published: February 2005

To investigate the influence of Fresnel diffraction on resolution and linewidth control in synchrotron radiation (SR) lithography, a detailed analysis is performed that takes X-ray phase shift in the absorber into account. The phase shift for 0.65-µm-thick Ta absorber is estimated to be -180°. It becomes clear that the phase shift plays a important role in limiting pattern resolution and linewidth control, especially for replicating fine (<0.3 µm) patterns. The conditions for replicating 0.2-µm lines-and-spaces resist patterns under practical conditions-i.e., with a mask contrast of 7 and a proximity gap of around 30 µm-are described. Designing a Ta absorber that is slightly narrower (<0.05 µm) than 0.2 µm is a great advantage for replicating 0.2-µm patterns because the dose-margin for replicating the patterns faithfully is improved.
Ionic Thermocurrent Measurements in Single Crystals, Pellets and Polycrystalline Samples of AsO2
--Doped KI
Authors: Jai Prakash Jai Prakash
Published: February 2005

Ionic thermocurrent (ITC) measurements in single crystals, pellets and polycrystalline samples of AsO2
--doped KI have been recorded. ITC peaks due to isolated and associated centres have been observed in single crystals and polycrystalline samples. In pellets, observed ITC peaks are assigned to associated centres. An attempt has also been made to correlate these peaks.
Microwave Amplification by Plasma Osaka Tube with Hot Cathode
Authors: Miyawaki Sawami , Ueda Hiroyuki , Iida Yukio , Morita Masanobu
Published: February 2005

Experimental results of microwave amplification by means of an Osaka tube (an improved version of the Barkhausen-kurz oscillator) with plasma in an operating space are described. The maximum gain is obtained at the upper hybrid frequency of the plasma for the case of ionic collector current, while the maximum gain is at the frequency corresponding to cyclotron motion in the Osaka tube for electronic collector current.
1H Nuclear Magnetic Resonance Study of Hydrogenated Amorphous Silicon Deposited from a Xe-diluted Silane Plasma
Authors: Hayashi Shigenobu , Hayamizu Kikuko , Mashima Satoshi , Suzuki Atsushi , Mcelheny Peter J. , Yamasaki Satoshi , Matsuda Akihisa
Published: February 2005

We have studied hydrogen distributions in hydrogenated amorphous silicon films deposited from a Xe-diluted silane plasma (a-Si:H(Xe)) by means of 1H nuclear magnetic resonance (NMR). The hydrogen content of these films increases with the deposition power, while the ratio of the narrow (Hn) to the broad (Hb) components in the 1H NMR spectra is almost constant. We have also measured 1H NMR spectra of the films annealed at progressively higher temperatures up to 500°C; these spectra demonstrate that both the Hn and Hb hydrogens begin to evolve at lower temperatures for the films deposited from plasmas with a higher power density. We have proposed structural models to explain the hydrogen distributions in the a-Si:H(Xe) films.
Mechanism of Ultraviolet Irradiation Effect on Si-SiO2Interface in Silicon Wafers
Authors: Ken-ichi Katayama Ken-ichi Katayama , Fumio Shimura Fumio Shimura
Published: February 2005

The effect of ultraviolet (UV) irradiation on the effective minority-carrier recombination lifetime (τeff) in silicon wafers was studied by a noncontact laser/microwave photoconductance (LM-PC) technique. The τeffgreatly increased in samples with native oxide after the irradiation, which can be attributed to an increase in the surface recombination lifetime (τs) due to the change in the surface carrier recombination velocity (S). The dominant factor for the τschange can be negative charges created by the photo-induced electrons in the surface area. The band bending near the Si-SiO2interface, which is caused by the electric field generated by negative charges, plays a dominant role in changingS.
Electroluminescence from Strained SiGe/Si Quantum Well Structures Grown by Solid Source Si Molecular Beam Epitaxy
Authors: Fukatsu Susumu , Usami Noritaka , Chinzei Tsuneo , Shiraki Yasuhiro , Nishida Akio , Nakagawa Kiyokazu
Published: February 2005

Electroluminescence (EL) is reported for Si0.8Ge0.2/Si quantum well (QW) structures grown by “solid source” Si molecular beam epitaxy for the first time. The spectral profile was dominated by SiGe quantum well emissions, no-phonon (NP) transitions due to symmetry-breaking SiGe alloy disordering and its transverse optical (TO) phonon replica. EL was observed from 27 up to 120 K. The integrated intensity was found to linearly increase with increasing injection current. Hole depopulation out of the quantized state was responsible for EL spectral variation at higher temperatures.
Magnetic Susceptibility and X-Ray Diffraction Studies on the Growth and Disappearance Processes of the Superconducting Phase in C60Kx
Authors: Kobayashi Mototada , Akahama Yuichi , Kawamura Haruki , Shinohara Hisanori , Sato Hiroyasu , Saito Yahachi
Published: February 2005

The growth and disappearance processes of the superconducting phase in C60K
x
have been studied by X-ray diffraction and AC magnetic susceptibility measurements as a function of reaction time at reaction temperatures of 250 and 300°C. At 250°C reaction, phase sequence of x=3, 4 and 6 was observed, while the x=4 phase was hardly observed at 300°C reaction. The onset T
c was constant at 18 K throughout the processes. The transition arose from the x=3 phase. A trial to control this phase by using a two-zone method and the origin of the transition observed near 9 K were also discussed.
Ferroelectric Polarization Reversal in Polyureas with Odd Number of CH2 Groups
Authors: Tasaka Shigeru , Toshikatu Shouko Toshikatu Shouko , Norihiro Inagaki Norihiro Inagaki
Published: February 2005

Ferroelectric polarization reversal was found in polyureas with an odd number of CH2 groups: polyheptamethyleneurea, polynonamethyleneurea and copoly(heptametylene/nonamethylene urea) (polyurea 79). Remanent polarization as high as 440 mC/m2 and coercive field of 28 MV/m were observed in quenched polyurea 79 at 90°C. The irreversible dielectric anomaly in a temperature region of crystal transition was shown in the quenched samples. Polyureas with an odd number of CH2 groups are ferroelectrics.
Mechanism of the Increase of Highly Charged Ion Intensity by use of an Electrode in the First-Stage Chamber of the RIKEN 10 GHz Electron Cyclotron Resonance Ion Source
Authors: Nakagawa Takahide , Kageyama Tadashi , Kase Masayuki , Akira Goto Akira Goto , Yasushige Yano Yasushige Yano
Published: February 2005

A negatively biased electrode is set in the first-stage chamber of the RIKEN 10 GHz ECR (electron cyclotron resonance) ion source. By use of this electrode, the output intensities of highly charged ions have been markedly increased. We studied the mechanism of this phenomenon, investigating the dependence of highly charged ion intensity upon the electrode bias voltage and current as well as the gas pressure of the first-stage chamber.
In Situ Focused Ion Beam (FIB) Observation of Al Electromigration
Authors: Masa-Ichi Kumikawa Masa-Ichi Kumikawa , Hirotaka Komoda Hirotaka Komoda
Published: February 2005

A new method for obtaining real-time monitoring of stressed interconnects has been discovered. This technique uses the focused ion beam (FIB) system. Under a stress of 3 MA/cm2 at 473 K, voids grown at a triple point occurred in Al-1.0%Si interconnects, and hillocks formed, as is seen during in situ observation of the aluminum microstructure. Since this study is theoretical, additional observation and study of the electromigration phenomenon using in situ monitoring is recommended.
Anisotropy and Lateral Homogeneity of InP-Mass Transport
Authors: Hansen Karsten , Peiner Erwin , Andreas Schlachetzki Andreas Schlachetzki , Herbert Burkhard Herbert Burkhard
Published: February 2005

InP-mass transport performed in a conventional liquid-phase epitaxial (LPE) system using (111)B-InP protection wafers was investigated by scanning-electron microscopy and wavelength-selective transmission-infrared (IR) microscopy. Refilling of undercut-etched mesa stripes of a length of 2 mm was found to be laterally homogeneous within ±6% when the process temperature was 721°C. In the <100> direction, an enhanced growth rate compared to that in the <110> direction was found. This anisotropy tended to disappear when the distance from the wafer to the protection wafer was reduced.
Band Discontinuity at AlxGa1-xP/GaP Heterointerfaces Studied by Capacitance Measurements
Authors: Morii Akio , Okagawa Hiroaki , Hara Kazuhiko , Junji Yoshino Junji Yoshino , Hiroshi Kukimoto Hiroshi Kukimoto
Published: February 2005

The band discontinuity at Al
x
Ga1-x
P/GaP heterointerfaces for varying Al content has been studied by capacitance-voltage measurements and self-consistent numerical analysis of the apparent carrier concentration profile by taking account of the true heterointerface position and donor deionization. By extrapolating the results for the Al
x
Ga1-x
P/GaP system, it is shown that the band lineup of the AlP/GaP heterojunction is of type II with a conduction-band discontinuity of 0.23 eV. Discussion is presented of comparison with the previously reported values.
Lower Critical Fields in Bi-2212 and Bi-2223 Superconductors
Authors: Tagaya Kimihito , Senda Kunihiro , Yosida Taturu , Nobuo Fukuoka Nobuo Fukuoka , Hiroyuki Sasakura Hiroyuki Sasakura
Published: February 2005

Low-field microwave magnetoabsorptions were observed for Bi-2212 and Bi-2223 specimens, and the lower critical fields were investigated. The principal values of H
c1 were determined over a temperature range from 4 to 60 K. Their temperature variations may be related to the low dimensional character of superconductivity.
Effectiveness of Iron Clusters as Pinning Centers in the YBa2(Cu1-xFex)3Oy System
Authors: Katsuyama Shigeru , Majima Kazuhiko , Kosuge Hiroshi Nagai
Published: February 2005

The magnetic hysteresis curve of YBa2(Cu1-x
Fe
x
)3O
y
(0≦x≦0.08) prepared by means of two kinds of heat treatment was measured by superconducting quantum interference device (SQUID) magnetometer. YBa2(Cu1-x
Fe
x
)3O
y
samples were slowly cooled from 890°C in air, and then some were heated at 800°C in N2 gas. All products, including those heated in N2 gas, were annealed at below 400°C in O2 gas. The difference ΔM in the hysteretic magnetization between the increasing and decreasing magnetic fields of the samples treated in N2 gas shows the maximum value at x=0.02. This indicates that the clustered Fe atoms formed in the Cu1-O planes act as effective pinning centers for flux lines.
Directional-Coupled Optical Switch between Stacked Waveguide Layers Using Electro-Optic Polymer
Authors: Sotoyama Wataru , Tatsuura Satoshi , Katsusada Motoyoshi Katsusada Motoyoshi , Tetsuzo Yoshimura Tetsuzo Yoshimura
Published: February 2005

A vertical optical switch consisting of an electro-optic polymer is described. Two-layer stacked slab waveguides were fabricated with para-nitroaniline-bonded epoxy polymer as the core layer and polyvinylalcohol as the cladding layer. After poling treatment, a He-Ne laser beam was coupled to the waveguides, and guided-wave switching was observed between the two waveguide layers with application of voltage to the electrodes.
Microstructure of Visible Light Emitting Porous Silicon
Authors: Nishida Akio , Nakagawa Kiyokazu , Hiroshi Kakibayashi Hiroshi Kakibayashi , Toshikazu Shimada Toshikazu Shimada
Published: February 2005

The relationship between the microstructure and photoluminescence of porous Si is investigated. High-resolution scanning electron microscopy shows that porous Si has a small-particle structure, with particle sizes ranging from several nm to several tens of nm. Transmission electron microscopy shows that these particles are composed of single-crystal Si spheres covered with an oxide layer. Porous Si with larger particles emits light with longer wavelengths. This suggests that the effective photoluminescence of porous Si is due to three-dimensional carrier confinement in quantum boxes.
Heteroepitaxial Growth of InAs on Misoriented GaAs(111)B Substrates by Molecular Beam Epitaxy
Authors: Takano Yasushi , Ikei Takashi , Hachiya Yoshiaki , Kishimoto Yasunori , Kangsa Pak Kangsa Pak , Hiroo Yonezu Hiroo Yonezu
Published: February 2005

Epilayers of InAs without twins were grown on 0.5°-misoriented GaAs(111)B substrates by molecular beam epitaxy. For a 2-µm-thick InAs epilayer, the full width at half-maximum of the X-ray rocking curve as low as 200 arcsec was obtained by using two-step growth in spite of 7% lattice mismatch. During InAs growth, the reflection high-energy electron diffraction pattern remained streaked without showing extra spots. This behavior was different from that observed in the InAs growth on GaAs(100), where spotty patterns were observed in the initial growth stage.
The Effect of Temperature on I-V Characteristics of a-Si:H Photodiode
Authors: Kuan-Lun Chang Kuan-Lun Chang , Ching-Fa Yeh Ching-Fa Yeh
Published: February 2005

A 16-bit/mm, high-resolution, Schottky a-Si:H photodiode linear sensor array was fabricated, and the effect of temperature on its I-V characteristics was studied. Annealing the a-Si:H photodiodes at 200°C in air for 30 minutes lowered the dark current and improved the I
p/I
d. Under reverse bias, the dark current increased with temperature and doubled for every 8.89°C rise, while the photocurrent showed few effects below 100°C.
Properties of Step-Edge Microbridge Josephson Junction Mixer Fabricated by YBaCuO Thin Film
Authors: Fukumoto Yoshito , Kajikawa Hiroshi , Rikuo Ogawa Rikuo Ogawa , Yoshio Kawate Yoshio Kawate
Published: February 2005

The conversion efficiency and minimum detection power of a step-edge microbridge Josephson junction mixer (SEJJ mixer) were evaluated for both fundamental mixing and harmonic mixing. The SEJJ was fabricated by a YBaCuO thin film and all of the circuits inside the mixer were made from microstrip line circuits in order to reduce the microwave propagation losses. The conversion efficiencies (η) were -31 dB, -46 dB and -53 dB for fundamental mixing, second harmonic mixing and third harmonic mixing, respectively. The dependence of η on the harmonic number (N) was expressed as η\proptN
-4.6 for N≦3. The minimum detection power (MDP) of -60 dBm (1.0 nW) was obtained in fundamental mixing, with a linear dynamic range of more than 40 dB.
In Situ Monitoring of Optical Reflectance Oscillation in Layer-by-Layer Chemical Vapor Deposition of Oxide Superconductor Films
Authors: Zama Hideaki , Kenji Sakai Kenji Sakai , Shunri Oda Shunri Oda
Published: February 2005

We have applied in situ optical diagnostics for the first time in layer-by-layer chemical vapor deposition (CVD) of oxide superconductor films. A cw diode laser of 780 nm emission is used for the light source of the optical experimental system. We have observed the variation of the optical reflection from the growing surface during the layer-by-layer CVD of YBaCuO and related oxides. This method can be used as a diagnostic tool to monitor (i) the crystal growth with an atomic-scale accuracy similar to RHEED oscillation and (ii) the surface reactions of the decomposition of precursors, the oxidization of metals, and so forth.
Optoelectronic Synchronization of Distributed Microwave Oscillators Using Semiconductor Laser Diodes
Authors: Wu Hsiao-Hua , Chen-Shiung Chang Chen-Shiung Chang , Ci-Ling Pan Ci-Ling Pan
Published: February 2005

We report a laser-diode-based system for optoelectronic synchronization of two distributed microwave oscillators at 10-GHz. The relative phase between the 10-GHz signals can be continuously tuned over a complete cycle by an optical delay line. Phase-locking of the two oscillators with a frequency offset of 10 kHz is also demonstrated. This method can be used to synchronize millimeter-wave oscillators for distributed architectures via fiber-optic links in the future.
Electron Impact H-H and D-D Fusions in Molecules Embedded in Al I. Experimental Results
Authors: Kohji Kamada Kohji Kamada
Published: February 2005

Both H-H and D-D fusion reactions, detected via high energy particle emission on CR-39, are shown to occur when 200 and 400 keV electrons are bombarded onto H+ or D+ ion implanted Al thin crystals. Roughly 1-2×103 particle emissions, including both hydrogen and helium isotopes, in whole space were observed in each case. Collisions between recoilled D atoms due to the high energy electron impact give only 10-12 to 10-26 times smaller fusion rates than the experimental results. The present observations suggest the presence of a new kind of fusion reaction which occurs with negligible kinetic energy of the reacting nuclei.
Analysis on Electric Field Effect in Al/SrTiO3/YBa2Cu3Oy Structure
Authors: Matsui Ken-ichi , Awaji Takahiro , Hirano Takashi , Fujii Tatsuhiko , Ken Sakuta Ken Sakuta , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

Planar-type Al/(100)SrTiO3/(001)YBa2Cu3O
y
metal-insulator-superconductor field-effect transistors (MISFETs) were investigated experimentally and theoretically. The applied gate field induces the change of the carrier concentration in YBa2Cu3O
y
channel (or conducting layer thickness), which in turn modulates the critical current J
c through the flux-creep model and flux-flow resistivity ρt through the Bardeen-Stephen model. Theoretical results explained, to a certain extent, the observed field effect in the MISFET semiquantitatively.
Giant Magnetoresistance in FeNiCo/Cu Multilayers
Authors: Jimbo Mutsuko , Kanda Tatsuya , Goto Shoji , Shigeru Tsunashima Shigeru Tsunashima , Susumu Uchiyama Susumu Uchiyama
Published: February 2005

The giant magnetoresistance effect of Fe16Ni66Co18/Cu multilayers prepared by the RF magnetron sputtering method is reported. A magnetoresistance ratio as large as 35% is obtained at 300 K, and it oscillates as a function of Cu layer thickness. The oscillation period is about 1 nm, which is similar to the case of Co/Cu multilayers. The maximum interlayer coupling strength for the first peak is about 0.05 erg/cm2. For the second peak the coupling is as weak as 0.003 erg/cm2 with a magnetoresistance ratio of 13%.
Visible Photoluminescence from Porous Silicon
Authors: Murayama Kazuro , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

The photoluminescence properties of porous Si have been systematically investigated by detailed measurements of the excitation and emission spectra. The strong visible light emission is explained by a model in which the radiative recombination of electron-hole pairs created in the silicon nanostructure occurs through the luminescence centers with strong phonon coupling. A wide band gap energy of the porous Si layer compared to that of bulk Si can explain the excitation spectra of the luminescence.
Growth Mechanism of Microcrystalline Silicon Prepared by Alternating Deposition of Amorphous Silicon and Hydrogen Radical Annealing
Authors: Masanori Otobe Masanori Otobe , Shunri Oda Shunri Oda
Published: February 2005

The growth mechanism of microcrystalline silicon (µc-Si) prepared by hydrogen radical annealing has been investigated. Alternating deposition of amorphous silicon (a-Si) (thickness of about 4 nm) and sufficient hydrogen radical annealing, results in µc-Si as large as 50 nm. The size of µc-Si can be controlled to less than 10 nm by inserting a-Si layers between crystallized layers to block the diffusion of hydrogen radicals. These results imply that the growth of µc-Si by this method is caused by hydrogen radicals diffused through a-Si, and that µc-Si grows epitaxially from µc-Si formed in the previous cycle.
Characterization of CuAlS2 Films Grown by Molecular Beam Epitaxy
Authors: Yoshio Morita Yoshio Morita , Tadashi Narusawa Tadashi Narusawa
Published: February 2005

Undoped and As-doped CuAlS2 films have been grown on GaAs(100) substrates by molecular beam epitaxy, and their optical and electrical properties have been characterized. X-ray diffraction patterns show that the films grow epitaxially with the c-axis perpendicular to the substrate surface. Both undoped and As-doped CuAlS2 films have exhibited a near-band-edge emission around 3.4 eV with accompanying deep-level-related emissions at 77 K. An As-doped CuAlS2 film exhibits p-type conductivity with the lowest resistivity of 1 Ω·cm and the carrier concentration of 5×1017 cm-3.
Mechanical Properties of Bi-Based Superconducting Whiskers
Authors: Matsubara Ichiro , Hashimoto Yoshihiro , Atago Kunio , Yamashita Hiroshi , Kawai Makoto Kinoshita
Published: February 2005

Mechanical properties of Bi2Sr2CaCu2O
x
whiskers which are composed of several plate-like single crystals stacked in a layered structure have been examined. Tensile strength, which is assumed to be an intrinsic strength of the compound, has been measured by pulling the whiskers in the direction of a-axis corresponding to the whisker axis. The maximum tensile strength and elastic modulus determined from the stress-strain curve are 940 MPa and 92 GPa, respectively.
Effects of Effective-Mass Hamiltonian Forms on Valence Band Structures of Quantum Wells
Authors: Shunji Nojima Shunji Nojima
Published: February 2005

Calculations have been made of the valence band structures of two typical quantum well films, GaAs/Al0.3Ga0.7As and In0.53Ga0.47As/InP, using two kinds of effective-mass Hamiltonian forms (characterized by β=0 and β=-1). While the two methods produce no significant difference for GaAs/Al0.3Ga0.7As, a great difference is revealed for In0.53Ga0.47As/InP. The method using β=0 appears to be a better choice for the latter system.
Optical Absorption Spectra in CuAlS2Doped with Vanadium
Authors: Aksenov Igor , Yuki Kudo Yuki Kudo , Katsuaki Sato Katsuaki Sato
Published: February 2005

Optical absorption spectra were measured at room temperature in undoped and V-doped single crystals of CuAlS2grown by the chemical vapour transport technique. Intense absorption bands characteristic of vanadium have been observed. These bands were attributed to the d-d type transitions between 3d-originated orbitals of V3+ion as well as to the charge-transfer type transitions from the valence band of the host crystal to the 3d-shell orbitals of V3+ion.
Growth and Thermodynamic Analysis of Atomic Layer Epitaxy of ZnSxSe1-x
Authors: Koukitu Akinori , Ikeda Hitoshi , Takayuki Miyazawa Takayuki Miyazawa , Hisashi Seki Hisashi Seki
Published: February 2005

ZnS
x
Se1-x
epitaxial layers have been grown by atomic layer epitaxy (ALE) for the first time, using elemental Zn, H2S and H2Se as source materials at atmospheric pressure. The high-crystalline-quality layer is obtained at a sulfur content of about 6%, where the epitaxial layer is closely lattice-matched to the GaAs substrate. The vapor-solid distribution relationship for the group VI elements is experimentally obtained. A thermodynamic model is developed for the ALE growth of ZnS
x
Se1-x
alloys. It is shown that the solid composition grown by atmospheric-pressure ALE is thermodynamically controlled.
Zn1-XCdXSe (X=0.2-0.3) Single-Quantum-Well Laser Diodes without GaAs Buffer Layers
Authors: Hayashi Shigeo , Tsujimura Ayumu , Yoshii Shigeo , Kazuhiro Ohkawa Kazuhiro Ohkawa , Tsuneo Mitsuyu Tsuneo Mitsuyu
Published: February 2005

Laser diode action has been observed from a ZnSe-based single-quantum-well structure grown on GaAs substrates without GaAs buffer layers. The lasers emit coherent light under pulsed current injection at 77 K in a wide wavelength range from 490 nm to 520 nm depending on the quantum well composition ratio. In spite of uncoated facets, the lowest threshold current density of the lasers was as low as 160 A/cm2. The output power from the lasers exceeded 100 mW per facet.