bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Power and Long-Lifetime InGaN Multi-Quantum-Well Laser Diodes Grown on Low-Dislocation-Density GaN Substrates
Authors: Nagahama Shin-ichi , Iwasa Naruhito , Senoh Masayuki , Matsushita Toshio , Sugimoto Yasunobu , Kiyoku Hiroyuki , Kozaki Tokuya , Sano Masahiko , Matsumura Hiroaki , Umemoto Hitoshi , Chocho Kazuyuki , Mukai Takashi
Published: October 2002

Epitaxially laterally overgrown GaN on free-standing GaN was used to reduce the threading dislocations which were widely scattered over the entire surface. The threading dislocation density of the GaN layer above the window area surrounding the SiO2 mask was reduced to 5×107/cm2, and that of the GaN layer above the SiO2 mask area was reduced to 7×105/cm2. InGaN multi-quantum-well laser diodes (LDs) grown on low-dislocation-density GaN substrates were demonstrated. LDs with an output power of 30 mW exhibited an estimated lifetime of 15,000 h at a case temperature of 60°C. At a case temperature of 25°C, the current at the output power of 30 mW and at the lasing threshold current were 42 mA and 23 mA, respectively. For comparison, LDs were grown on different substrates, and the dependence of their characteristics on the substrates was examined.
Room-Temperature Photoswitching in La0.6Sr0.4MnO3 Film
Authors: XiaoJun Liu XiaoJun Liu , Akihiko Machida Akihiko Machida , Yutaka Moritomo Yutaka Moritomo , Masao Ichida Masao Ichida , Arao Nakamura Arao Nakamura
Published: October 2002

We have observed a transient transmission change (ΔT) induced by photoirradiation in La0.6Sr0.4MnO3 film at room temperature. The magnitude of ΔT is enhanced with a decrease of the probe photon energy \hbarω, suggesting a resonance feature to the “Drude-like” component. We interpreted the photoswitching effect in terms of the photoinduced suppression of the spin correlation in the half-metallic double-exchange system.
2×2 Multiwavelength Micromachined AlGaAs/GaAs Vertical Cavity Filter Array with Wavelength Control Layer
Authors: Amano Takeru , Koyama Fumio , Nishiyama Nobuhiko , Iga Kenichi
Published: October 2002

We have demonstrated a novel 2×2 multiwavelength micromachined vertical cavity filter array consisting of a pair of AlGaAs/GaAs distributed Bragg reflectors (DBR). The 2×2 multiwavelength micromachined vertical cavity filter array with a wavelength span of 12 nm was fabricated by partly etching off a GaAs wavelength control layer loaded on the top surface of a device. The resonant wavelength can be adjusted by controlling the thickness of the wavelength control layer of each filter in the 2D array.
Influence of Inertial Force on Electron Trajectories in the Surface Conduction Electron Emitter Displays
Authors: Sam Kim Young , Guon Kim Young , Il Kim Dai , Gill Kang June , Oun Kang Seung , Ha Choi Eun , Guangsup Cho Guangsup Cho
Published: October 2002

On the basis of electron trajectory calculation in surface conduction electron emitter displays, it is found that an anode current can be generated from the inertial force of electron motion along the electric field line with a small curvature over the fissure of 10 nm scale. Most electrons of the film current flow to the coplanar electrode, while the electrons from the upper surface of the cathode edge initially follow the curved electric field lines; thereafter, they accelerate to deviate from the inner electric field of the fissure and move directly toward the display surface for the anode current.
CaF2/CdF2 Double-Barrier Resonant Tunneling Diode with High Room-Temperature Peak-to-Valley Ratio
Authors: Masahiro Watanabe Masahiro Watanabe , Toshiyuki Funayama Toshiyuki Funayama , Taishi Teraji Taishi Teraji , Naoto Sakamaki Naoto Sakamaki
Published: October 2002

We have demonstrated room-temperature negative differential resistance (NDR) with a high peak-to-valley ratio (PVR) on the order of 105 using CaF2/CdF2 double-barrier resonant tunneling diode (DBRTD) structures grown on Si(111) substrates. A CdF2 quantum-well layer was grown by molecular-beam epitaxy (MBE) and CaF2 barrier layers were formed by MBE combined with the partially ionized beam technique on an n+-Si(111) substrate with 0.07° miscut, in order to reduce the pinhole density of CaF2 barrier layers. The dispersion of the peak current density and bias voltage of the NDR implies that the layer thickness fluctuation of each CaF2 barrier and CdF2 quantum-well layer is suppressed below ±1 unit layer of the (111) atomic plane for DBRTDs with an 18 µm diameter electrode. The peak and valley currents agreed reasonably with those obtained by theoretical estimation.
Coulomb Blockade and Disorder in 2D Quantum Dot Arrays
Authors: Williams Heinz-Olaf Müller , Mizuta Hiroshi
Published: October 2002

We investigate the influence of both size disorder and background charge disorder, on the Coulomb blockade voltage of two–dimensional arrays of metallic quantum dots for varying array size. Both the mean blockade voltage and its variation are considered for several array sizes with varying degrees of disorder. Design rules for devices using those arrays are derived.
New Metalorganic Chemical Vapor Deposition Process in a High Magnetic Field for YBa2Cu3O7
Authors: Ma Yanwei , Watanabe Kazuo , Awaji Satoshi , Motokawa Mitsuhiro
Published: October 2002

A hot-wall-type metalorganic chemical vapor deposition (MOCVD) apparatus combined with a cryocooled superconducting magnet was recently developed. This system allows the application of magnetic fields up to 11 T for the MOCVD process. After making various improvements, we succeeded in fabricating YBa2Cu3O7 (YBCO) films under optimal deposition conditions. It is found that the crystallinity of YBCO films produced on polycrystalline silver substrates by the magnetic-field-assisted CVD process is improved as compared with those without the magnetic field.
High Resolution Self-Mixing Laser-Doppler Vibrometry with a Laser-Diode-Pumped Microchip LiNdP4O12 Laser
Authors: Kenju Otsuka Kenju Otsuka , Takeki Fukazawa Takeki Fukazawa , Nobuatsu Sekita Nobuatsu Sekita , Shin-ichi Higashihara Shin-ichi Higashihara
Published: October 2002

A simple laser vibrometer system (LVS) has been built around a laser-diode-pumped microchip LiNdP4O12 (LNP) laser combined with an acousto-optic frequency shifter, using an efficient self-mixing modulation arising from the interference between a laser field and a weak field that is fed back from a rough vibrating target. The LVS provides a 50 dB carrier-to-noise ratio for 3 kHz bandwidth, even when monitoring parts that have extremely low reflectivity. Application to laser-Doppler-velocimetry (LDV) capable of discriminating the direction in which different targets are moving has been demonstrated. A remote-sensing experiment by optical fiber access to the target is described briefly.
Spatial Distribution of the High-Density Microwave Plasma and Its Effect on Crystal Silicon Film Growth
Authors: Shirai Hajime , Sakuma Yoshikazu , Yoshino Koichi , Ueyama Hiroyuki
Published: October 2002

The spatial distribution of the high-density and low-temperature microwave plasma and its effect on the fast deposition of highly crystallized microcrystalline silicon (µc-Si:H) film are demonstrated through systematic deposition and plasma diagnostics studies. The best film crystallinity is obtained under the condition in which the hot electron population and the distribution of the ion beam energy impinging on the growing surface are minimum. The intentional control of the ion beam energy is also attempted using a mesh grid electrode to suppress the ion bombardment during film growth. A low and uniform ion beam energy is effective in promoting the film crystallinity with less surface roughness and bulk inhomogeneities.
Further Frequency Upshift in DC to AC Radiation Converter by Perpendicular DC Magnetic Field
Authors: Hong Gao Hong Gao , Takeshi Higashiguchi Takeshi Higashiguchi , Noboru Yugami Noboru Yugami , Toshihiko Niiyama Toshihiko Niiyama , Shigeo Sasaki Shigeo Sasaki , Hiroaki Ito Hiroaki Ito , Yasushi Nishida Yasushi Nishida
Published: October 2002

Theory of electromagnetic wave radiation by the interaction of a relativistic ionization front with a periodic electrostatic field using a perpendicular DC magnetic field has been developed. The frequency shifts, transmission and reflection coefficients of the radiation are shown to depend on both the plasma density and the magnetic field strength. Compared with an unmagnetized case, further frequency upshift of the emitted radiation is found, although the conversion rate decreases. This mechanism can be used as a new technique for tunable electromagnetic wave radiation sources.
Liquid-Crystal Aligning Capabilities Using a New Photodimerization Method on a Poly (4′-methacryloyloxy chalcone) Surface
Authors: Seo Dae-Shik , Hwang Jeoung-Yeon
Published: October 2002

The effects of liquid-crystal (LC) alignment and electro-optical (EO) characteristics of photoaligned twisted-nematic (TN)-LC display (LCD) on a PMCh (poly (4′-methacryloyloxy chalcone)) surface using a new photodimerization method were investigated. Photopolymer layers were exposed by linearly polarized UV during heating at 100°C. Excellent voltage-transmittance (V-T) of photodimerized TN-LCD on the PMCh surface for 1 min using the new photodimerization method was observed. The voltage-holding ratio (VHR) of the photodimerized TN-LCD on the PMCh surface using the new photodimerization method is higher than that of the conventional photodimerization method. We suggest that the new photodimerization method for LC aligning is the most promising rubbing-free technique.
First-Principles Study of Titanium Dioxide: Rutile and Anatase
Authors: Masayoshi Mikami Masayoshi Mikami , Shinichiro Nakamura Shinichiro Nakamura , Osamu Kitao Osamu Kitao , Hironori Arakawa Hironori Arakawa , Xavier Gonze Xavier Gonze
Published: October 2002

The atomic and electronic structures of two phases of titanium dioxide, anatase and rutile, have been investigated by a first-principles pseudopotential method based on local density approximation in density functional theory. The calculated band structure, equilibrium lattice constants, and bulk modulus of rutile are consistent with experimental data and with other calculations. The calculated structure of anatase is also close to experimental data. The calculated bulk modulus of anatase is found to be smaller than that of rutile, presumably due to the sparsity of anatase. The band structure of anatase is given in comparison with that found in previous works. The energetics between the two phases is also discussed.
Single Electron Memory Devices Based on Plasma-Derived Silicon Nanocrystals
Authors: Dutta Amit , Hayafune Yoshinori , Oda Shunri
Published: October 2002

Single electron nonvolatile memory devices are fabricated using a narrow and short channel transistor and silicon nanocrystals as a floating gate. The silicon nanocrystals are deposited by very-high-frequency plasma processing. This deposition technique offers not only control of the dot size but also promises precise control of the tunnel oxide thickness. A single electron charging effect is observed for such devices at 77 K.
Alkyl Chain Length Dependence of Field-Effect Mobilities in Regioregular Poly(3-Alkylthiophene) Films
Authors: Y. Lim Keiichi Kaneto , Wataru Takashima Wataru Takashima , Takeshi Endo Takeshi Endo , Masahiro Rikukawa Masahiro Rikukawa
Published: October 2002

Carrier mobilities have been studied using the field effect in regioregular poly(3-alkylthiphene) (PAT, alkyl=butyl, hexyl, decyl, dodecyl and octadecyl) cast films at a field of around 104 V/cm. It was found that the carrier mobility of poly(3-butylthiophene) is 1.0×10-2 cm2/V·s, which is the largest one to date in the polythiophene family and three to four orders of magnitude larger than that of poly(3-octadecylthiophene). This result indicates that the substituted alkyl chain plays the role of a barrier to carrier migration between π-conjugated main chains, and primarily determines the mobility. The residual carrier densities are 1015 to 1016 cm-3 for all PATs and slightly lower for PATs with shorter alkyl chains. The field-effect mobilities are nearly the same as the values estimated by the time-of-flight method.
Discontinuous Crossover between Fast and Slow Kinetics at the Volume Phase Transition in Poly-N-isopropylacrylamide Gels
Authors: Takaharu Okajima Takaharu Okajima , Ichiro Harada Ichiro Harada , Kazufumi Nishio Kazufumi Nishio , Shunsuke Hirotsu Shunsuke Hirotsu
Published: October 2002

The kinetics of the volume phase transition in N-isopropylacrylamide gels has been studied as a function of crosslinker concentration. The shrinking kinetics at the transition is extremely slow in gels with a standard composition which have been used widely in various experiments. A discontinuous crossover from slow to much faster kinetics were observed in both high- and low-crosslinker-concentration regions, where the characteristic time of the shrinking process changes abruptly by two to four orders of magnitude with a minute change of the crosslinker concentration. In spite of these marked changes in the kinetics, no anomaly was observed in the degree of equilibrium swelling in these regions. A mechanism leading to sudden changes in kinetics is discussed in terms of an inhomogeneous network structure which is dependent on crosslink density.
Diamagnetic Anisotropy Derived from the Hydrogen Bond
Authors: Uyeda Chiaki , Ohtawa Kouichi , Okita Kazuyuki , Uyeda Natsu
Published: October 2002

The diamagnetic anisotropy (Δχ)DIA of ammonium dihydrogen phosphate ADP, potassium dihydrogen phosphate KDP and gypsum was obtained for the purpose of estimating the contribution of a single hydrogen bond to the (Δχ)DIA values. The field-induced harmonic oscillation method was used to measure the small anisotropies on the order of 10-10 emu/g. The (Δχ)DIA values obtained between two magnetic principal axes for CaSO4 2H2O were 1.7×10-6 emu/mol [χ1-χ2 axes], 1.2×10-6 emu/mol [χ1-χ3 axes] and 0.4×10-6 emu/mol [χ2-χ3 axes]. For KDP, the value was 1.1×10-9 emu/g [a-c axes], and for ADP it was 1.2×10-6 emu/g [a-c axes]. The measured anisotropy was assigned to the individual chemical bonds, the (Δχ)DIA values of a single hydrogen bond being estimated to be 0.7×10-6 emu/mol.
Dipping and Photo-Induced Liquid Crystal Alignments Using Silane Surfactants
Authors: Liao Ying-Jyh , Hsu Chain-Shu , Wu Shin-Tson
Published: October 2002

Dipping and photo-induced liquid crystal (LC) alignments were demonstrated
using new silanes as surface coupling agents. In the dipping method, both homogeneous
and homeotropic alignments can be achieved depending on the alkyl chain length of the
silane employed. The 110°C post curing temperature makes the dipping method
especially attractive for low temperature processing of active matrix displays. In the
UV-induced LC alignment, homogeneous cells are obtained and the LC directors are
perpendicular to the impinging UV polarization. The pretilt angle of both methods is
found to be ∼0.5°.
Etching Characteristics of α-Type Ta Film Using Cl2 Electron Cyclotron Resonance (ECR) Plasma
Authors: Takahashi Chiharu , Tsuchizawa Tai , Nishimura Hiroshi , Ono Toshiro , Oda Masatoshi
Published: October 2002

Ta film deposited by electron cyclotron resonance (ECR) sputtering (ECR-Ta) is a promising material for accurate X-ray masks. We investigated the characteristics of ECR-Ta etching with Cl2 ECR plasma in order to obtain vertical patterns. Etched ECR-Ta patterns show partial sloping along the pattern sidewall, which makes microfabrication difficult. By analyzing the crystal structure of the ECR-Ta film and estimating the ion bombardment effect of the etching process, the partial sloping can be attributed to a kind of orientation-dependent etching of ECR-Ta with a bcc cubic lattice. Vertical ECR-Ta patterns are obtained by using a Cl2–CF4 gas mixture in the overetching.
Epitaxial Growth and Electrical Characteristics of CaF2/Si/CaF2 Resonant Tunneling Diode Structures Grown on Si(111) 1°-off Substrate
Authors: Masahiro Watanabe Masahiro Watanabe , Yoshifumi Iketani Yoshifumi Iketani , Masahiro Asada Masahiro Asada
Published: October 2002

CaF2/Si/CaF2 double-barrier resonant tunneling diode (RTD) structures have been epitaxially grown on a Si(111) substrate using molecular beam epitaxy (MBE) with the partially ionized beam method. A 3.4-nm-thick Si quantum-well layer was epitaxially formed on a 1-nm-thick CaF2 barrier layer grown on the Si(111) substrate tilted 1° toward the <\overline1 \overline12> azimuth, of which the terrace width was uniformly controlled by thermal pretreatment at 1000°C for 30 min in an ultrahigh-vacuum (UHV) chamber. After the growth, thermal annealing, which results in the reduction of leakage current, was carried out at 600°C for 10 min to improve crystallinity. In the current-voltage characteristics of the RTD structures, a clear negative differential resistance has been observed under a pulsed bias condition with a peak-to-valley current ratio of 6.3 at 77 K. In the dc voltage sweep measurement, a memory effect was observed; this implies charge and discharge through the trap states in the RTD structures.
Mirror-Trapped Plasma Heated by High-Power Millimeter-Wave Radiation as an Electron-Cyclotron-Resonanse Source of Soft X-Rays
Authors: Vodopyanov Alexander V. , Golubev Sergey V. , Zorin Vladimir G. , Kryachko Andrey Yu. , Lopatin Alexey Ya. , Luchin Valeriy I. , Razin Sergey V. , Smirnov Artem N.
Published: October 2002

Soft X-ray line emission of pulse electron-cyclotron-resonance (ECR) discharge in Argon sustained by a powerful beam of millimeter waves in a mirror magnetic trap was investigated. An X-ray spectrum in the range of 6–17 nm has been obtained, and the absolute spectral intensity of radiation in this range has been determined. It was shown that such a discharge is an effective source of soft X-ray radiation with an approximately 10% conversion efficiency of microwaves into X-rays and a spectral power maximum of 7.3 kW/nm at a wavelength of 9 nm.
Fabrication of Bulk Ceramics by High-Power Millimeter-Wave Radiation
Authors: Makino Yukio , Ueno Toshiyuki , Matsumoto Takeshi , Miyake Shoji
Published: October 2002

High-power 28 GHz millimeter-wave radiation was applied to the fabrication of bulk AlN, Si3N4 and Al2O3. Millimeter-wave radiation enables the rapid sintering of these ceramics at a temperature from 50°C to 300°C lower than that of the conventional method. The rapid sintering is attributed to the enhancement of atomic migration due to the “nonthermal effect” of the millimeter wave. It is indicated that millimeter wave radiation can be used for the efficient fabrication of bulk ceramics.
The Relationship between the Hardness and the Point-Defect-Concentration in Neutron-Irradiated MgO·3.0Al2O3 Single Crystals
Authors: Suematsu Hisayuki , Yatsui Kiyoshi , Yano Toyohiko
Published: October 2002

MgO·3.0Al2O3 single crystalline samples were irradiated by fast neutrons under various conditions and the hardness of the irradiated and unirradiated samples was measured using a Vickers hardness tester. The hardness of an as-irradiated sample increased by 23%. After isochronal annealing, the hardness gradually decreased and nearly recovered to that of the unirradiated sample above 600°C, and fully recovered after annealing at 900°C. The volume of the sample also increased after the irradiation and changed in a similar manner to the hardness by annealing. A relationship between the hardness and the concentration of point defects is proposed and the experimental results agree with the proposed relationship. This implies that the point defects pin down the dislocations generated by the indentation and increase the hardness of neutron irradiated MgO·3.0Al2O3 samples.
Influences of Shock Waves on High-Pressure, Pulsed Glow Discharge due to Excimer Laser Excitation
Authors: Imada Go , Yamanoi Hiroshi , Suzuki Masataro , Masuda Wataru , Yatsui Kiyoshi
Published: October 2002

The high-pressure, pulsed glow discharge has been studied to gain a further understanding of the excitation discharge on application of excimer lasers. The influence of shock waves on the discharge has been investigated disregarding other factors which may affect the discharge instabilities, such as gas density depletion, discharge products, residual ions, halogen gas, and electrode heating. A shock wave of 1.2 in Mach number is produced by a shock tube with a gas mixture of helium and argon. It is found that if the shock wave, propagating across the discharge direction, does not reach the middle of the discharge region, glow discharge occurs only in front of the shock wave. Even if the shock wave passes through the middle of the discharge region, the glow discharge occurs only in front of the shock wave. However, an arc-like filament through the shock front is also produced. If the shock wave passes through the discharge region, the glow discharge can be produced again behind the shock front, however, a surface discharge is also produced between the main electrode and the pre-ionization pin electrode.
Application of Diamond-like Carbon Film to Phase-change Optical Recording Discs
Authors: Chang Jen-Fung , Hwang Wen-Chi , Guo Chiou-Ting , Ueng Herng-Yih , Young Tai-Fa , Sun Kuo-Hsuan , Hwang Jenn-Shyong
Published: October 2002

The recent development of new optical recording media is oriented toward high-density optical systems, in which data storage protection becomes very critical. Amorphous carbon films deposited by plasma-enhanced chemical vapor deposition are very smooth and possess high mass density, low friction coefficient, and very large values of hardness and elastic modulus. In this study, diamond-like carbon (DLC) film coatings on phase-change recording media are characterized using an atomic force microscope (AFM), UV-visible spectrometer and disc testers. The influence of mechanical, optical and structural properties of DLC films on the surface and spectral properties and electrical signals of discs with various DLC film thicknesses are investigated. The results of our studies indicate that DLC films indeed provide a suitable coating for protecting data stored on phase-change optical discs.
Subpixel Spatial Resolution of the X-Ray Charge-Coupled Device Based on the Charge Cloud Shape
Authors: Hiraga Junko , Tsunemi Hiroshi , Miyata Emi
Published: October 2002

When an X-ray photon lands into a pixel (event pixel), the primary charge is mainly collected into the event pixel. If the X-ray landing position is sufficiently close to the pixel boundary, the primary charge spills over to the adjacent pixel forming split events. We can easily understand that there are three parameters coupled together; the X-ray landing position inside the pixel, the X-ray event pattern and the primary charge cloud shape. We can determine any one of them from the other two parameters. Since we know the charge cloud shape using the multi-pitch mesh experiment, we can calculate the X-ray landing position with subpixel resolution using the event pattern. We applied our method to Ti–K X-rays for the charge-coupled device with 12 µm square pixel. Once the primary charge splits into the adjacent pixel, we can determine the X-ray landing position with subpixel resolution. Using three- or four-pixel split events, we can determine the X-ray landing position with an accuracy of less than 1 µm. For a two-pixel split event, we obtained a similar position accuracy in the split direction with no improvement in the direction perpendicular to it. We will discuss the type of charge-coupled device (CCD) which can achieve the subpixel resolution for the entire area of the CCD.
Direct Observation of Effective Temperature of Ta Atom in Layer Compound TaS2 by Neutron Resonance Absorption Spectrometer
Authors: Tokuda Koji , Kamiyama Takashi , Kiyanagi Yoshiaki , Moreh Raymond , Ikeda Susumu
Published: October 2002

A neutron resonance absorption spectrometer, DOG, has been installed at KENS, High Energy Accelerator Research Organization Neutron Source, which enables us to investigate the motions of a particular element by analyzing the line width of resonance absorption spectrum. We measured the temperature dependence of the effective temperature of Ta motion in TaS2 as well as in Ta metal using DOG. The effective temperatures extracted from the observed absorption spectrum agree well with the calculated values from the phonon density of states of Ta metal over a wide temperature range of 10 to 300 K. We also succeeded in measuring both the angular dependence and the temperature dependence of effective temperatures of Ta in a layer compound TaS2. Based on the temperature dependence of the effective temperature, the partial phonon density of states of Ta in TaS2 was discussed.
Signal Simulation of 25 Gbytes Read-Only Optical Disk System using a High Numerical Aperture Objective Lens
Authors: Yanagisawa Takuma , Nomoto Takayuki , Ohsawa Seiichi , Yokogawa Fumihiko
Published: October 2002

We have already developed and reported the high-definition digital-versatile-disk read-only-memory system of capacity 15 Gbytes using a blue laser and new signal processing technique. On the other hand, a high numerical-aperture system has been reported of numerical-aperture 0.85 and cover layer thickness 0.1 mm. In this paper, we examined the increase in capacity on application of our signal processing technique to the high numerical-aperture system using computer simulation. As a result, we found that a 25 Gbytes read-only-memory disk system had sufficient system margins on applying the limit equalizer and the adaptive tangential equalizer. Furthermore, if the crosstalk canceler is applied, we may achieve a system of capacity larger than 25 Gbytes.
Feasibility of High-Data-Rate Media with Ge–Sb–Te Phase-Change Material
Authors: Ishii Norihiko , Shimidzu Naoki , Tokumaru Haruki , Okuda Haruo , Hirotsune Akemi , Ushiyama Junko , Terao Motoyasu , Maeda Takeshi
Published: October 2002

We experimentally studied an optical disk with a large capacity and high data-transfer rate that can record high-definition television signals. A high rotation speed was used to achieve the high data-transfer rate. Using Ge–Sb–Te phase change material, a carrier-to-noise ratio of about 50 dB was achieved at a linear velocity of 15–30 m/s with a 0.4-µm-long mark. High-speed crystallization was necessary to erase recording marks. Therefore, by appropriately designing layers that assist nucleation, we obtained a DC erase ratio of 29 dB with a 0.4-µm mark and 1-mW power margin for over-25-dB erase ratio at a linear velocity of 18 m/s. Furthermore, the 0.4-µm mark-space repetition jitter was less than 7% even after 1000 cycles. A data transfer rate of 60 Mbps was obtained by optimizing the write strategy using a multi-pulse with an optical system equivalent to that of current digital versatile disk (DVD).
Effect of ZnS Adhesion Layer on Overwrite Cyclability of Phase Change Optical Recording Media
Authors: Ebina Atsushi , Hirasaka Masao , Isemoto Jun , Takase Aya , Fujinawa Go , Sugiyama Ikuto
Published: October 2002

A high-performance phase change optical recording disk, which has a five-layered structure, was proposed. This disk has a ZnS adhesion layer between a GeSbTe recording layer and a ZnS–SiO2 second dielectric layer. A 2×105 overwrite cyclability was achieved with the original five-layered phase change optical recording disk. The cross-sectional transmission electron microscope observation and the in-plane X-ray diffraction measurement indicate that both the five-layered disk and the four-layered disk have almost the same crystalline structure. The contact angle measurements, however, indicate that the ZnS adhesion layer improves the adhesive force between the GeSbTe recording layer and the ZnS–SiO2 second dielectric layer. It is considered that the high overwrite cyclability results from this improvement of the adhesive force. Moreover, the electron probe microanalysis results indicate that the ZnS layer acts as a protective layer against the Ge diffusion from the GeSbTe recording layer.
Mask Films for Thermally Induced Superresolution Readout in Rewritable Phase-Change Optical Disks
Authors: Lu Yung-Hsin , Dimitrov Dimiter , Liu Jia-Reuy , Hsieh Tsung-Eong , Shieh Han-Ping David
Published: October 2002

Tellurium was studied as a mask film in a thermally induced superresolution rewritable optical disk for detecting below-diffraction-limit marks. Mark trains of 0.15 µm could be retrieved with 9 dB in carrier-to-noise (CNR) using an optical system with the laser wavelength of 780 nm and an objective lens of 0.55 numerical aperture. Readout cyclability was examined and methods to further improve readout cyclability were proposed.
Spatial Property of Formed Patterns Depending on Focus Condition in a Two-Dimensional Optoelectronic Feedback System
Authors: Yoshio Hayasaki Yoshio Hayasaki , Yuuki Tamura Yuuki Tamura , Hirotsugu Yamamoto Hirotsugu Yamamoto , Nobuo Nishida Nobuo Nishida
Published: October 2002

The spatial properties of a pattern generated in an optoelectronic system composed of an electronically addressable spatial light modulator, a detector array, and two-dimensional optical feedback are experimentally investigated. The square-root dependence of the fundamental spatial frequency on the positive and negative deviations from the in-focus condition of the optical feedback is demonstrated under conditions of the inversion property of the spatial light modulator. The optoelectronic system has a serial process, but its spatial properties are almost equivalent to the spatial properties of an all-optical system based on an optically addressed spatial light modulator. Patterns generated by variation of the frame rate of the optoelectronic system are also demonstrated.
25 Gbyte Read-Only Memory Disk by Injection-Compression Molding Process
Authors: Imai Tetsuya , Shida Noriyoshi , Higuchi Takanobu , Suga Keiji , Iida Tetsuya , Yokogawa Fumihiko
Published: October 2002

We studied the feasibility of fabricating a disk replica at a recording capacity of 25 Gbytes by a conventional injection molding process. This work is the first attempt at fabricating a disk replica using a stamper recorded by an electron beam recorder. The bottom jitter value of the injection-molded disk was 9.3% when using a conventional equalizer and 6.5% when using an additional limit equalizer. These values were highly similar to those of the photo-polymer (2P) disk. The residual error on the axial tracking of the injection-molded disks was smaller than that of the 2P disk, and the residual error on the radial tracking was almost the same as that of the 2P disk.
Wobble Addressing Method for Land and Groove Structured Optical Storage
Authors: Ko Jungwan , Yoon Du-Seop , Lee Kyung-Geun , Park In-Sik , Otsuka Tatsuhiro , Shin Dong-Ho , Miyamae Akira , Yamada Hideaki
Published: October 2002

In this paper, two wobble addressing methods for land and groove structured optical discs are proposed. These methods use only modulated wobble signals for addressing, while excluding the need for an embossed prepit. As a consequence, the overhead associated with the proposed methods is less than that of the conventional addressing method for rewritable digital versatile discs. In addition, the proposed methods enable the use of a one-beam mastering machine for making discs. This is possible because a signal from a land track is optically added to two signals from adjacent groove tracks, which are produced by a single laser beam for each signal, while maintaining its phase relationship for signal decoding. The advantages of the proposed methods have been demonstrated through computer simulation as well as through evaluation of test discs.
Influence of Injection Molding Process on the Local Fluctuations of Magneto-Optical Signals
Authors: Umezawa Tomokazu , Horiguchi Toru , Tomie Takashi
Published: October 2002

The local fluctuations of magneto-optical (MO) signals were investigated in the vicinity of the preformat pits of polycarbonate (PC) substrates fabricated under different injection molding conditions and also using stampers which had different shapes of grooves and preformat pits. A strong correlation was observed between the substrate birefringence and the fluctuation of the MO signal. The rate-of-change of the fluctuations, as the phase shift of the optical head was varied, was attributed to the shapes of preformat pits and grooves. The fluctuation of the MO signal could be controlled by varying the injection molding conditions and the shapes of preformat pits and grooves.
An Implementation of Limited Multi-Level (LML) Optical Recording
Authors: Langereis Geert , Coene Wim , Spruijt Louis
Published: October 2002

Multi-level pits and lands are mastered compatible with the compact disc (CD) format in a sub-channel on top of the original Runlength-Limited (RLL) channel, which remains unaffected. By introducing multi-level effects only in long pit and land runlengths of the main RLL channel, two additional Limited Multi-Level (LML) channels are created. Via the restriction of the multi-level modulation to relatively long runlengths, it is realized that the jitter in the original channel is not affected and that separate (independent) slicers for all pit multi-level effects and for the land multi-level effects can be used. An additional achievement is that a slicer is devised for retrieving the LML-bits which is optimized for maintaining a maximum capacity in the multi-level channel. The LML system is evaluated using both simulations and experiments on read-only discs.
Soft Decision Decoding for Holographic Memories with Intrapage Intensity Variations
Authors: Min Byun Seungjune Jeon , Byoungho Lee Byoungho Lee
Published: October 2002

A holographic memory system using a two-dimensional array of code sequences and soft decision decoding is implemented. The random error correction and burst error correction capability of this system is shown. We can obtain lower bit error rates using soft decision Viterbi decoding rather than using hard decision decoding or simple thresholding. Different threshold levels for each data pixel position are determined by considering intrapage intensity variations. With these threshold levels, much lower bit error rates are obtained. The experimental results are presented.
Plastic Ball Grid Array Reflow Using a Fast-Modulated CW Laser
Authors: Liu Daming , Lu Yong-Feng , Yuan Yuan , Chen Tao , Prematilleke Lalith
Published: October 2002

Plastic ball grid array reflow using a fast-modulated CW laser is studied. A CW/Q-switched Nd:YAG laser is modified to work in the fast-modulated CW mode. Sn–Pb eutectic solder balls with a diameter of 760 µm and Au–Ni–Cu solder pads are used in the study. By varying the laser power and the laser-on time, respectively, the solderable parameter region of laser reflow for the solder balls and the solder pads is obtained. Shear strength tests are also performed to find out the optimal reflow parameters. The measured shear strength is higher than 1500 gf, with the maximum value over 1900 gf. An energy equilibrium model is proposed to compare the solderable region predicted theoretically with the experimental results and to estimate the average temperatures of solder joint under the given experimental conditions.
Low-Background Laser Plasma Induced by Nd-YAG Laser at Low Pressures
Authors: Kurniawan Hendrik , Suyanto Herry , Kagawa Kiichiro , Maruyama Tadashi , Tjia May On
Published: October 2002

An experimental study has been carried out on the dynamical process taking place in the secondary plasma generated by a Q-sw Nd-YAG laser (26 mJ, 1,064 nm, 8 ns) on a variety of metal samples at a reduced pressure of 0.5 Torr. It was found that light emission of plasma produced at such a low pressure was ascribable to collisions of ultrafast atoms with surrounding gas molecules, instead of the shock wave excitation mechanism proposed earlier for plasma generated at pressures around a few Torr or higher. This plasma exhibited excellent characteristics for spectrochemical applications because of its extremely low background emission. Using air as a surrounding gas, the background emission at 0.5 Torr was reduced by 10-fold compared to that at 1 Torr. It was also demonstrated that replacing air with helium as a surrounding gas further reduced the background emission by more than 10-fold. Temperature measurement performed by means of the Boltzmann two-line method showed that the average temperature of plasma generated below 1 Torr had the tendency to increase with decreasing pressure, contrary to the trend observed at higher pressures. It was also found that the propagation length of the emission front varied with time at constant velocity, which is significantly different from that predicted by the shock-wave model.
Self-Assembled GaN Quantum Dots Grown by Plasma-Assisted Molecular Beam Epitaxy
Authors: Daudin Bruno , Feuillet Guy , Mariette Henri , Mula Guido , Pelekanos Nikolaos , Molva Engin , Rouvière Jean-Luc , Adelmann Christoph , Martinez-Guerrero Esteban , Barjon Julien , Chabuel Francis , Bataillou Benoit , Simon Julia
Published: October 2002

It is shown that under specific growth conditions the strain relaxation of GaN deposited on AlN obeys the Stranski-Krastanov mechanism. As a consequence, it is demonstrated that, for both cubic and hexagonal phases, the growth of self-organized three-dimensional islands can be achieved. These islands behave as quantum dots, exhibiting optical properties dominated by localization effects.
Physical Origins of Fine Structure in the Resonant Tunneling through Laterally Confined 1D-0D-1D Structures
Authors: Dan Csontos Dan Csontos , Hongqi Xu Hongqi Xu
Published: October 2002

Experimental studies of electron transport through gated vertical resonant tunneling structures have been seen to display complicated features in the measured I–V characteristics. The interpretation of the data has been difficult due to the lack of detailed knowledge of the lateral confining potential profile in different parts of the device as well as the associated tunneling properties. In this work we theoretically investigate the electron transport through laterally confined double-barrier resonant tunneling structures connected via narrow emitters and collectors to two-dimensional electron reservoirs. In particular we investigate the effects of variation of the lateral confining potential in different parts of the device. The calculated I–V spectra display complicated fine features which can be explained by the complex interplay between the density of states in the dot and the density of states in the narrow emitter and collector as the lateral confining potential is varied. The calculations may provide physical insight to the complicated features seen in the experiments.
Spontaneous Charge Polarization Wave Related to Single Electron Tunneling in a Junction Cell Array with Nonuniform Parameters
Authors: Haruyama Junji , Fukuda Shigenobu
Published: October 2002

We predict the appearance of a spontaneous polarization wave (SPW) of charges related to single electron tunneling in capacitor-coupled nanotunnel junction arrays, using a classical Monte Carlo simulation. When two one-dimensional (1D) nanojunction arrays including non-uniform tunnel resistances are strongly capacitor-coupled, excess electrons are accumulated in the islands, connected to the largest tunnel resistance, of one array and, hence, holes are accumulated to compensate them in the island of the other array. This leads to a SPW, synchronized with the Coulomb staircase. It is shown that the SPW is observable even at very high frequencies without a decrease of SPW amplitude, by reducing the tunnel resistances. This SPW will be useful in cell array devices utilizing single electron tunneling.
Beating of the Shubnikov-de Haas Oscillations in GaAs/AlGaAs Quantum-Dot Arrays
Authors: Ochiai Yuichi , Aoki Nobuyuki , Lin Li-Hung , Andresen Anthony , Prasad Chetan , Ge Fuding , Bird Jonathan P. , Ferry David K. , Risaki Tomomitu , Ishibashi Kohji , Aoyagi Yoshinobu , Sugano Takuo
Published: October 2002

The Shubnikov-de Haas oscillations measured in split-gate quantum-dot arrays are found to exhibit a marked beating behavior, which we attribute to a carrier density variation between the quantum-point-contact leads and the component dots of the array. A simple analysis supports these arguments, revealing that the carrier density in the quantum point contacts vanishes as the array is pinched off. The beating may be suppressed by increasing the measurement current, a behavior which we attribute to the injection of energetic electrons in the source into initially unoccupied Landau levels in the quantum point contacts.
Single Electron Transistor Fabricated on Heavily Doped Silicon-on-Insulator Substrate
Authors: Antti Manninen Antti Manninen , Jari Kauranen Jari Kauranen , Jukka Pekola Jukka Pekola , Alexander Savin Alexander Savin , Martin Kamp Martin Kamp , Monika Emmerling Monika Emmerling , Alfred Forchel Alfred Forchel , Mika Prunnila Mika Prunnila , Jouni Ahopelto Jouni Ahopelto
Published: October 2002

Experiments on side-gated silicon single electron transistors (SET) fabricated on a heavily doped thin silicon-on-insulator substrate are reported. Some of the devices showed single-island-like and some multi-island-like behaviour, but the properties of individual samples changed with time. Single-electron gate modulation was observable up to T=100 K, at least. A slow response of SET current to a large change in gate voltage was observed, but the process speeded up under illumination.
Dynamic Behavior of Kink-Solitons at Junctions in Quantum-Dot Cellular Automata
Authors: Satoshi Nakagawa Satoshi Nakagawa , Mikio Eto Mikio Eto , Kiyoshi Kawamura Kiyoshi Kawamura
Published: October 2002

We examine the propagation of electric polarization in quantum-dot cellular automata (QCA) as a kink-soliton. Focusing on its behavior at a junction between different kinds of QCA, we solve the time-dependent Schrödinger equation numerically using the Hartree approximation and an exact method. Using the Hartree approximation, the soliton is perfectly transmitted or reflected, like a classical particle. This property agrees with the numerical solution of the nonlinear wave equation obtained in the continuum limit. The exact calculation method yields different behavior patterns for the solitons at the junction, partly transmitted and partly reflected, similar to a quantum wave packet.
Photoluminescence Dynamics of CdS Nanocrystals Fabricated by Sequential Ion Implantation
Authors: W. White Daisuke Matsuura , D. Budai John , Alkiviathes Meldrum Alkiviathes Meldrum
Published: October 2002

We have studied photoluminescence (PL) dynamics of CdS nanocrystals fabricated by sequential Cd+ and S+ ion implantation into Al2O3 matrices. The PL spectrum and PL decay dynamics of CdS nanocrystals are sensitive to the measurement temperature. This is because excitons trapped at shallow localized states are thermally excited to the high-energy state at high temperatures. Two PL bands appear near the absorption edge at elevated temperatures near 100 K. From time-resolved PL spectra and the PL decay dynamics, it is concluded that the observed PL bands near the absorption edge are due to free excitons and excitons trapped at shallow localized states. The PL mechanism in CdS nanocrystals is discussed.
Laser-Induced Activation of p-Type GaN with the Second Harmonics of a Nd:YAG Laser
Authors: Cheng Yung-Chen , Liao Chi-Chih , Feng Shih-Wei , Yang Chih-Chung , Lin Yen-Sheng , Ma Kung-Jeng , Chou Chang-Cheng , Lee Chia-Ming , Chyi Jen-Inn
Published: October 2002

Magnesium-doped p-type GaN has been activated by irradiation with photons of 532 nm wavelength from the second harmonic of a Q-switched neodymium-doped ytterbium aluminum garnet (Nd:YAG) laser. With appropriate laser fluence levels and irradiation pulse numbers, such a laser-induced activation process resulted in a hole concentration about the same as that obtained through the conventional thermal activation technique. Temperature measurement revealed that the laser-induced process is very unlikely to be thermal. It was speculated that the process might involve the photon-induced breaking of the H–Mg bonds.
Nitrogen Incorporation Mechanism and Dependence of Site-Competition Epitaxy on the Total Gas Flow Rate for 6H-SiC Epitaxial Layers Grown by Chemical Vapor Deposition
Authors: Aigo Takashi , Kanaya Masatoshi , Katsuno Masakazu , Yashiro Hirokatsu , Ohtani Noboru
Published: October 2002

The doping mechanism of nitrogen and the dependence of site-competition epitaxy on the flow rate of H2 carrier gas were studied for 6H-SiC epitaxial layers grown by chemical vapor deposition. The indication was that nitrogen, decomposed into a mono-atomic form (N) in the gas phase, participated in the doping process. The nitrogen decomposition and the reaction at SiC surfaces played an important role in the doping. Site-competition epitaxy for (0001)Si faces was not observed for the high flow rate of the H2 carrier gas because the nitrogen decomposition and the incorporation of the decomposed nitrogen into the epitaxial layers were suppressed by the high gas flow rate. As for (0001)C faces, neither site-competition epitaxy nor its dependence on the flow rate of the H2 carrier gas was observed. Based on the result on site-competition epitaxy, the high flow rate of the H2 carrier gas was applied to epitaxial growth on (0001)C faces in order to reduce the residual donor concentration and that as low as 1.5×1015 cm-3 was obtained for nondoped layers.
Nature of Surface and Bulk Defect Induced by Low Dose Oxygen Implantation in Separation by Implanted Oxygen Wafers
Authors: Park Jea-Gun , Kim Suk-Goo , Lee Gon-Sub , Shim Tae-Hun
Published: October 2002

Two new metrologies have been proposed to characterize unknown surface and bulk defects in separation by implanted oxygen (SIMOX) wafers. They included the following: i) laser scattering particle counter plus coordinated atomic force microscope (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. Three types of surface defects were found and described as follows: i) a hole with a locally thinned top silicon layer (Park Defect A), ii) a hole formed locally without either a silicon or a buried oxide layer (Park Defect B), and iii) a hole formed with both a locally thinned top silicon and a buried oxide layer (Park Defect C). In addition, a bulk defect was found to occur as locally distributed square-shaped pits accompanied by the disappearance of the buried oxide layer (isolation defect). All surface and bulk defects in SIMOX wafers originate from oxide particle generation by electrostatic discharge and mechanical abrasion between the wafer and the pin of the wafer holder during oxygen ion implantation.
The Effect of Chlorine on Silicon Oxidation: Simulation based on the Interfacial Silicon Emission Model
Authors: Uematsu Masashi , Kageshima Hiroyuki , Shiraishi Kenji
Published: October 2002

Silicon oxidation in dry oxygen containing small amounts (1–3%) of chlorine gas is simulated based on the interfacial silicon emission model. We assume that the presence of chlorine (Cl) reduces the interfacial silicon emission, which governs the oxidation rate at the interface. The simulation is done by reducing the rate of Si-atom emission in the presence of Cl. In addition, the equilibrium concentration of oxygen in the oxide is increased in proportion to Cl concentration to fit the experimental oxide thickness.
Lattice Parameter Deviation of InP Single Crystals Grown by the Horizontal Bridgman Method under Controlled Phosphorus Vapor Pressure
Authors: Shimizu Atsushi , Nishizawa Jun-ichi , Oyama Yutaka , Suto Ken
Published: October 2002

InP crystals were grown by the horizontal Bridgman method under controlled ambient phosphorus vapor pressure. The lattice parameter was measured by X-ray diffraction analysis. The lattice parameter of the InP crystals increased with increasing phosphorus vapor pressure. The relationship between the lattice parameter and composition indicates that the In-rich composition is attributed to the P-vacancies. This corresponds to the photoluminescence spectra of P-vacancy-related emission.