bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz Two-Dimensional Electrooptic Sampling Using High Speed Complementary Metal-Oxide Semiconductor Camera
Authors: Miyamaru Fumiaki , Yonera Taigiro , Tani Masahiko , Hangyo Masanori
Published: February 2005

We have developed a terahertz imaging system based on a two dimensional (2D) electro-optic sampling technique with a high-frame-rate complementary metal-oxide semiconductor (CMOS) camera. By operating the CMOS camera in a dynamic normalization and subtraction detection modes synchronized to pump laser pulses, a better signal-to-noise ratio is achieved with a high sampling rate compared to that of a system using a low-frame-rate CCD camera.
Quantum-Defect-Limited Operation of Diode-Pumped Yb:YAG Laser at Low Temperature
Authors: Shoji Takahiro , Tokita Shigeki , Kawanaka Junji , Fujita Masayuki , Izawa Yasukazu
Published: February 2005

We have demonstrated a quantum-defect-limited operation in a diode-pumped Yb:YAG oscillator at low temperature. The highest slope efficiency of 90% at the crystal temperature of 70 K was obtained, which was close to the quantum efficiency of 91.2%. An optical-to-optical efficiency and a laser gain were 74% and 8 cm-1, respectively at a low pump intensity of 2.3 kW/cm2.
350.9 nm UV Laser Diode Grown on Low-Dislocation-Density AlGaN
Authors: Iida Kazuyoshi , Kawashima Takeshi , Miyazaki Atsushi , Kasugai Hideki , Mishima Syunsuke , Honshio Akira , Miyake Yasuto , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: February 2005

We demonstrated a UV-laser diode grown on low-dislocation-density AlGaN. The combination of a low-temperature-deposited AlN interlayer technology and heteroepitaxial lateral overgrowth yielded crack-free and partially low-dislocation-density AlGaN on a grooved GaN substrate. A ridge waveguide was fabricated in the low-dislocation-density region. The lasing wavelength under pulsed current injection at room temperature was 350.9 nm, which is the shortest wavelength ever reported.
Intensity-Controllable Luminescence of Eu3+-Doped Polyimide Nanoparticles by UV Irradiation and Heat-Treatment
Authors: Ishizaka Takayuki , Kasai Hitoshi , Nakanishi Hachiro
Published: February 2005

The intensity-controllable luminescence of Eu3+-doped polyimide (PI) nanoparticles by UV irradiation and thermal treatment is reported. In this system, it was observed that the luminescence intensity of Eu3+ ions increased with increasing UV irradiation time, whereas intensity decreased with the elevation of thermal treatment temperature. It was estimated that the mechanism of the above phenomena are based on a reversible change in an energy transfer probability from PI to Eu3+ due to the UV irradiation and thermal treatment.
2.43 µm Light Emission of InGaAsSbN Quantum Well Diodes Grown on InP Substrates
Authors: Kawamura Yuichi , Nakagawa Tomokatsu , Amano Masanobu , Ouchi Kazuhiro , Inoue Naohisa
Published: February 2005

InGaAsSbN quantum well diodes operating at 2 µm wavelength region were grown by molecular beam epitaxy (MBE) on InP substrates. The emission wavelength of the electroluminescence (EL) was as long as 2.43 µm at room temperature for the quantum well diode with 1.4% nitrogen. It was found from the temperature dependence of the EL spectrum that the introduction of nitrogen induced a marked reduction of temperature dependence of the band-gap energy of the InGaAsSbN layer.
Selective Lasing of Closed Four Bounce Modes in a Layered Square Microcavity
Authors: Moon Hee-Jong , Sun Sang-Pil , An Kyungwon
Published: February 2005

We propose a selection scheme of closed four bounce modes in a layered square microcavity. We demonstrated our scheme through a lasing experiment by using a fused-silica square capillary containing a dye-doped low refractive index liquid, in which the outer size was smaller than twice the inner size of the capillary. The lasing spectrum appeared as a single periodic cluster corresponding to closed orbits having a refraction angle of 45° in the inner boundary.
Growth of Epitaxial β-FeSi2 Thin Film on Si(001) by Metal-Organic Chemical Vapor Deposition
Authors: Akiyama Kensuke , Kimura Takeshi , Suemasu Takashi , Hasegawa Fumio , Maeda Yoshihito , Funakubo Hiroshi
Published: February 2005

(100)-Oriented epitaxial β-FeSi2 films 200 nm in thickness were grown on Si(001) substrates using a 20-nm-thick template layer prepared by reactive deposition epitaxy (RDE). The films maintained a strong (100) orientation and the full width at half maximum (FWHM) of the rocking curve corresponding to the β-FeSi2
800 diffraction peak decreased from 0.96° to 0.92° with post-annealing at 1173 K in Ar atmosphere for 300 min, suggesting a slight increase in orientation perfection. The films maintained a flat surface after the post-annealing up to 300 min. No photoluminescence (PL) spectrum was observed from the as-deposited film. However, a PL of 0.806 eV was observed at 10 K for the first time from the epitaxial β-FeSi2 film with a good surface flatness, when the film was post-annealed at 1173 K for 300 min.
Ferroelectric Single Crystal Recording Media Fabricated by Polarization Controlled Wet Etching Process
Authors: Hiranaga Yoshiomi , Wagatsuma Yasuo , Cho Yasuo
Published: February 2005

Ferroelectric single crystal thin plates are promising materials for ultrahigh-density storage devices. In order to fabricate recording media with large area and high homogeneity, a polarization controlled wet etching process was developed in this paper. Differential etch rates of ferroelectrics are useful in controlling the thickness during the wet etching process. By applying DC voltage to a substrate, the etching process can be stopped when the thickness reaches the desired value. A 455-nm-thick LiTaO3 thin plate with a diameter of 3 mm was prepared using this method. Nanodomains were artificially formed by applying voltage pulses to the substrate using a metal-coated cantilever top electrode.
High-Power AlGaInP Light-Emitting Diodes with Patterned Copper Substrates by Electroplating
Authors: Horng Ray-Hua , Lee Chia-En , Kung Chung-Yuan , Huang Shao-Hua , Wuu Dong-Sing
Published: February 2005

We have developed a large-area (1.2 mm ×1.2 mm) chip structure for high-power AlGaInP/mirror/Cu light-emitting diodes (LEDs) to improve both the heat dissipation and substrate light-absorbing problems encountered in conventional AlGaInP/GaAs LED samples. Especially, this LED samples can be accomplished without additional dicing process. It was found that the peak-spectral wavelength of the AlGaInP LED with an electroplated copper substrate exhibited only about 3 nm shift at 400 mA, corresponding to a ∼30°C rising in the junction temperature. However, the junction temperature increased to 110°C easily for the AlGaInP/GaAs LED sample under a current injection of 400 mA. This indicates that the joule heating is less pronounced for the high-power AlGaInP/mirror/Cu LED sample where the metallic substrate provides a good heat sink.
Sample-and-Hold Imaging for Fast Scanning in Atomic Force Microscopy
Authors: Takahashi Takuji , Ono Shiano
Published: February 2005

We have proposed to use a sample-and-hold circuit for direct monitoring of cantilever deflection signals as a novel method for fast imaging in an intermittent contact mode atomic force microscopy (AFM). This method enables us to construct a quasi-topographic image from tip heights at moments when the tip taps on a sample surface. As a result, we obtained the tip height image well corresponding to the sample topography at a scanning rate above 30 Hz/line without any other customization on both a cantilever and a piezo scanner in a commercial AFM system.
Observation of Revival Structure in Femtosecond-Laser-Induced Alignment of N2with High-Order Harmonic Generation
Authors: Kaku Masanori , Masuda Keita , Miyazaki Kenzo
Published: February 2005

We report a new sensitive method using high-order harmonic generation to observe revival structure in fs-laser induced alignment of a rotational wave packet of molecules. Pump and probe fs-laser pulses with a time delay were focused collinearly into a pulsed N2gas jet, so that the pump pulse induces alignment of a ground-state rotational wave packet, and the delayed probe pulse produces harmonic radiation from the aligning molecules. The harmonic signal observed as a function of time delay has clearly demonstrated a typical time-dependent revival structure in the field-free alignment of molecules.
Physical and Reliability Characteristics of Metal-Oxide-Semiconductor Devices with HfOxNy Gate Dielectrics on Different Surface-Oriented Substrates
Authors: Cheng Chin-Lung , Chang-Liao Kuei-Shu , Wang Ping-Liang , Wang Tien-Ko
Published: February 2005

The physical and reliability characteristics of a metal-oxide-semiconductor (MOS) device with gate hafnium oxynitride (HfO
x
N
y
) deposited on (100)- and (111)-surface-oriented substrates were investigated. The X-ray photoelectron spectroscopy (XPS) results show that the oxygen 1s peak for the (111) substrate samples is lower than that for the (100) samples while the nitrogen 1s peak is higher for the former. Crystalline retardation for the HfO
x
N
y
film deposited onto the (111) substrate was characterized by X-ray diffraction (XRD) measurement. Devices with a HfO
x
N
y
film deposited on a (111) substrate exhibit better reliability characteristics, such as smaller stress-induced leakage current (SILC) and larger time to breakdown (T
bd) than those with the same film deposited on a (100) substrate.
Surfactant Effect of Sb on GaInAs Quantum Dots Grown by Molecular Beam Epitaxy
Authors: Matsuura Tetsuya , Miyamoto Tomoyuki , Kageyama Takeo , Ohta Masataka , Matsui Yasutaka , Furuhata Tatsuya , Koyama Fumio
Published: February 2005

A surfactant effect of antimony (Sb) was investigated for self-assembled GaInAs quantum dots (QDs). The introduction of Sb into the QDs cause a large blue shift of the photoluminescence (PL) wavelength with a decrease in the full width at half maximum (FWHM) and an increase in intensity in comparison with QDs without Sb. Atomic force microscope (AFM) measurement showed a marked reduction in QD density from 1.0×1010 cm-2 to 7.0×107 cm-2. This indicates that Sb suppresses the formation of QDs and that the wetting layer remains to be a quantum well (QW) structure. The PL wavelength of the GaInAsSb wetting layer was elongated by increasing the amount of Sb supply. This result indicates the expansion of the critical thickness of the growth mode change from 2D to 3D.
Calculations of Complete 4fn and 4fn-1 5d1 Energy Level Schemes of Free Trivalent Rare-Earth Ions
Authors: Ogasawara Kazuyoshi , Watanabe Shinta , Sakai Yuki , Toyoshima Hiroaki , Ishii Takugo , Brik Mikhail G. , Tanaka Isao
Published: February 2005

Calculations of complete energy level schemes for 4f

n
and 4f

n-1 5d
1 electronic configurations of free trivalent rare-earth ions have been performed. Semi-empirical Hamiltonian was used for the calculation of 4f

n
configuration while a fully relativistic first-principles many-electron method was used for the calculation including 4f

n-1 5d
1 configuration. As a result, Dieke's diagram is extended to about 200000 cm-1 in the case of 4f

n
electronic configurations and about 370000 cm-1 in the case of 4f

n-1 5d
1 electronic configurations. Calculated energy levels are plotted as a function of the atomic number.
Thermal Expansion Coefficients of Nano-Clustering Silica (NCS) Films Measured by X-Ray Reflectivity and Substrate Curvature Methods
Authors: Suzuki Takashi , Sugiura Iwao , Sato Shigeo , Nakamura Tomoji
Published: February 2005

Two methods are applied to measure the coefficient of thermal expansion (CTE) of nano-clustering silica (NCS) films. A direct measurement of the film thickness using X-ray reflectivity yields an intrinsic CTE of 12±2 ppm/°C. From the analysis of the stress-temperature profile obtained by a substrate curvature method, the CTE of the NCS films is estimated to be approximately 9.7 ppm/°C, which almost agrees with the result of the X-ray reflectivity measurement. The advantage of each of these methods for CTE measurement of thin films is discussed.
Preparation of Platinum Thin Films by Metalorganic Chemical Vapor Deposition Using Oxygen-Assisted Decomposition of (Ethylcyclopentadienyl)trimethylplatinum
Authors: Sun Ho-Jung , Choi Eun Seok , Kweon Soon Yong , Kim Nam Kyeong , Yeom Seung Jin , Roh Jae-Sung , Sohn Hyun-Chul , Kim Jin Woong
Published: February 2005

Pt thin films were deposited by the O2-assisted decomposition of an (ethylcyclopentadienyl) trimethylplatinum [(EtCp)PtMe3] precursor, and their growth behavior was investigated by varying the amount of oxygen gas supply. An abrupt change from a very low growth rate to a significantly high growth rate was observed with an increase in O2 feeding rate, which indicated that an oxygen gas supply above a threshold was required to obtain a continuous Pt film with an acceptable growth rate. Under the deposition conditions of a substrate temperature of 340°C and an O2 flow rate of 1000 sccm, we successfully fabricated a Pt film with a smooth surface, (111)-preferred orientation, and low resistivity of 11.6 µΩ-cm on a 200-mm-diameter-wafer.
BaTi4O9 Thin Film Prepared by RF Magnetron Sputtering for Microwave Applications
Authors: Sun Ho-Jung , Jang Bo-Yun , Jung Young-Hun , Lee Suk-Jin , Nahm Sahn
Published: February 2005

We attempted to produce BaTi4O9 dielectric thin films using conventional rf magnetron sputtering combined with subsequent rapid thermal processing (RTP). By adjusting growth and RTP temperatures, a single-phase BaTi4O9 film was successfully fabricated via 550°C deposition followed by 900°C annealing. The film exhibited superior physical and dielectric properties which were comparable to bulk ceramic behaviors. It showed good surface flatness and high density corresponding to 98% of the theoretical one. Its dielectric constant and dissipation factor at 6 GHz were 37 and 0.005, respectively.
Roughening Hexagonal Surface Morphology on Laser Lift-Off (LLO) N-Face GaN with Simple Photo-Enhanced Chemical Wet Etching
Authors: Gao Yan , Fujii Tetsuo , Sharma Rajat , Fujito Kenji , Denbaars Steven P. , Nakamura Shuji , Hu Evelyn L.
Published: February 2005

A photo-enhanced chemical wet etching technique is presented to form a roughened surface morphology with hexagonal symmetry on laser lift-off (LLO) N-face GaN grown by metalorganic chemical vapor deposition (MOCVD). An aqueous solution of KOH was used as etch electrolyte. The etched surface showed cones with hexagonal pyramid structures bound by {1011} facets. A detailed analysis of the etch rates and time-evolution of the surface morphology is described as a function of KOH concentration (1.25 M to 8.8 M). The comparison between (0001) N-face and Ga-face GaN etch morphology is discussed. This roughened hexagonal surface morphology can be applied to enhance the external efficiency in GaN based light-emitting diodes (LEDs).
Ideally Ordered, High-Density Patterning of DNA on Au Disk Array Fabricated Using Anodic Porous Alumina
Authors: Matsumoto Futoshi , Nishio Kazuyuki , Miyasaka Tsutomu , Masuda Hideki
Published: February 2005

High-density patterning of DNA was performed using Au disk arrays (disk period: 500 nm, disk diameter: 125 nm) fabricated using an ideally ordered anodic porous alumina. The arrangement of patterns composed of fluorescent-dye-labeled, thiolated DNA was confirmed to correlate with the disk arrangement on the Au disk array. It was found that hybridization of fluorescent-dye-labeled target DNA with probe DNA immobilized on the Au disk array exhibits approximately 100% efficiency.
Impact of Air Filter Material on Metal Oxide Semiconductor (MOS) Device Characteristics in HF Vapor Environment
Authors: Hsiao Chih-Wen , Lou Jen-Chung , Yeh Ching-Fa , Hsieh Chih-Ming , Lin Shiuan-Jeng , Kusumi Toshio
Published: February 2005

Airborne molecular contamination (AMC) is becoming increasingly important as devices are scaled down to the nanometer generation. Optimum ultra low penetration air (ULPA) filter technology can eliminate AMC. In a cleanroom, however, the acid vapor generated from the cleaning process may degrade the ULPA filter, releasing AMC to the air and the surface of wafers, degrading the electrical characteristics of devices. This work proposes the new PTFE ULPA filter, which is resistant to acid vapor corrosion, to solve this problem. Experimental results demonstrate that the PTFE ULPA filter can effectively eliminate the AMC and provide a very clean cleanroom environment.
Self-Assembled Growth of GaSb Type II Quantum Ring Structures
Authors: Kobayashi Shigeki , Jiang Chao , Kawazu Takuya , Sakaki Hiroyuki
Published: February 2005

We demonstrate the self-assembled growth of GaSb quantum ring structures by molecular beam epitaxy. GaSb rings with the internal and external diameters of about 20 nm and 60 nm are successfully formed on GaAs by a growth procedure different from that for InAs rings reported earlier. The shape of GaSb structures can be controlled from a ring-like to an elongated disk-like geometry by changing the amount of deposited GaSb. A possible growth mechanism of GaSb rings is discussed. Photoluminescence spectra of the rings are presented and their features are discussed in terms of the type II band alignment, in which only holes are confined in the ring.
Novel Self-Switching Optical Gate Device with Internal Mode-Locked Pulses
Authors: Mukai Kohki , Kuwatsuka Haruhiko
Published: February 2005

We propose a new all-optical gate device integrating a Mach-Zehnder interferometer in the cavity of a mode-locked laser diode. The device utilizes semiconductor optical amplifiers not only as gain mediums for the mode-locked emission but also as phase shifters for optical switching with the interferometer. The gate opens and shuts with the internal mode-locked optical pulses, eliminating the need for an external optical clock pulse for the switching. Gate timing can be synchronized to input data signals when the saturable absorber with passive mode-locked setup absorbs signal pulses. This function-integrated optical device will aid in reducing the size of future high-bit-rate data processing systems.
Electron Emission from Polyvinylidenefluoride Ferroelectric Substance by Polarization Inversion
Authors: Omura Kazuaki , Morita Shinzo
Published: February 2005

Electron emission from polyvinylidenefluoride (PVDF) ferroelectric substance by polarization inversion was observed. To realize the electron emission, a semiconductive C-Au-S film of approximately 1 nm thickness was coated on the PVDF surface with a tooth-type electrode of evaporated Al. After polarization of the PVDF surface, a negative impulse voltage with a voltage higher than the coercive voltage was applied to the flat-type electrode on the reverse side of the PVDF surface in a vacuum. Then the emitted electron was detected by a probe in front of the tooth-type electrode. The detected charge was 6.1 ×10-12 C.
Enhancement of Upper Critical Field and Critical Temperature by Prebending Process for Practical Nb3Sn Wires
Authors: Awaji Satoshi , Oguro Hidetoshi , Nishijima Gen , Watanabe Kazuo
Published: February 2005

It is recognized that the strain in Nb3Sn conductors is a serious problem, because it suppresses superconducting properties. We have proposed that prebending treatment, which means repeated bending loads, is one of the ways to control the strain state. The upper critical field and the critical temperature were examined for the prebent Nb3Sn wires. We found that the enhancement of the upper critical field from 23.7 T to 25.2 T at 4.5 K and the enhancement of the critical temperature from 17.4 K to 17.9 K were achieved for the CuNb-reinforced Nb3Sn wire by applying the prebending strain. Since these values are similar to those of the strain-free Nb3Sn bulk, the strain state of the wires is definitely optimized by the prebending treatment.
589 nm Light Source Based on Raman Fiber Laser
Authors: Feng Yan , Huang Shenghong , Shirakawa Akira , Ueda Ken-Ichi
Published: February 2005

A fiber-based continuous-wave laser at 589 nm was demonstrated by intracavity frequency doubling of a Raman fiber laser at 1178 nm in a type-I noncritically phase matched lithium triborate crystal. The yellow laser output was limited by the emergence of higher order Stokes Raman emission and the broad linewidth of the fundamental laser at 1178 nm.
Characteristics of GaAs-Based Long-Wavelength, Highly Strained InGaAs Quantum Well Vertical-Cavity Laser
Authors: Chen I-Liang , Hsu Wei-Chou , Lu Chen-Ming , Chiou Chih-Hung , Lee Zheng-Hong , Lee Tsin-Dong
Published: February 2005

Continuous-wave (CW) operation of highly strained double quantum well InGaAs/GaAs vertical-cavity surface emitting lasers (VCSELs) emitting at 1252 nm at room temperature have been realized by metal organic chemical vapor deposition (MOCVD). Our preliminary results reveal the relation between the output performance and gain-cavity detuning of the long wavelength InGaAs VCSELs. Compared with the quaternary GaInNAs VCSEL, it is found that the InGaAs VCSEL manifests better temperature stability.
Electronic Structure of Protonic Conductor BaCe0.90Y0.10O3-δ Probed by Soft-X-Ray Spectroscopy
Authors: Higuchi Tohru , Matsumoto Hiroshige , Shimura Tetsuo , Yashiro Keiji , Kawada Tatsuya , Mizusaki Junichiro , Shin Shik , Tsukamoto Takeyo
Published: February 2005

The electronic structure of the protonic conductor Y-doped BaCeO3 (BaCe0.90Y0.10O3-δ) has been studied by photoemission spectroscopy and X-ray absorption spectroscopy. The Fermi level (E
F) of H2-annealed BaCe0.90Y0.10O3-δ shifts to the conduction band side by approximately 0.4 eV. The holes and acceptor level are observed at the top of the valence band and just above E
F, respectively. Their intensities are lower in the H2-annealed BaCe0.90Y0.10O3-δ, indicating that doped hydrogen enters hole and acceptor states. These findings indicate that the electronic structure of the protonic conductor BaCe0.90Y0.10O3-δ obeys the rigid-band model.
Lateral Graphoepitaxy of Germanium Controlled by Microstructures on SiO2 Surface
Authors: Koide Takeshi , Minemoto Takashi , Takakura Hideyuki , Hamakawa Yoshihiro , Numai Takahiro
Published: February 2005

The lateral graphoepitaxy of germanium (Ge) on a SiO2 surface was successfully demonstrated. An X-ray diffraction pattern with a (400) peak was obtained in a Ge crystal grown on microholes with four 10-nm-thick SiO2 sidewalls, which were thermally oxidized Si {111} planes. Using this Ge crystal on the microholes as a seed crystal, a Ge crystal with a (400) orientation was laterally grown on a 10-nm-thick SiO2 layer, which was a thermally oxidized flat Si (100) surface, by zone melting.
Effect of Ultrafast Optical Pulses with Different Pulse Duration on the Terahertz Radiation Spectrum of n-Type InAs
Authors: Takahashi Hiroshi , Hasselbeck Michael. P. , Quema Alex , Goto Masahiro , Ono Shingo , Sarukura Nobuhiko
Published: February 2005

Terahertz (THz) radiation from n-type InAs irradiated by ultrafast laser pulses is investigated under the existence of the magnetic field. It is found that the high-frequency component of the THz-radiation spectrum originates from the hybrid modes of the plasmons and the longitudinal optical (LO) phonons, and its intensity can be drastically enhanced by using the laser pulses with duration shorter than the oscillation period of the hybrid modes. Additionally, it is also found that the ratio of THz-radiation power from these two modes can be controlled by adjusting the pulse duration and the magnetic field strength.
Controlled Temperature Coefficient of Resonant Frequency of Al2O3-TiO2 Ceramics by Annealing Treatment
Authors: Ohishi Yoshihiro , Miyauchi Yasuharu , Ohsato Hitoshi , Kakimoto Ken-ichi
Published: February 2005

The microwave dielectric properties of alumina (Al2O3) ceramics were studied. Our objective was to improve the large negative temperature coefficient of resonant frequency (τf = -60 ppm/°C) of Al2O3 ceramics by the adding rutile (TiO2) with a large positive τf (+450 ppm/°C). A near-zero τf (τf = +1.5 ppm/°C) with excellent microwave dielectric properties (Q·f = 117,000 GHz, ε
r = 12.4) was obtained in 0.9Al2O3-0.1TiO2 ceramics sintered at 1350°C for 2 h, followed by annealing at 1000°C for 2 h in air.
Magnetic and Electric Field Effects of Photoluminescence of Excitons Bound to Nitrogen Atom Pairs in GaAs
Authors: Onomitsu Koji , Okabe Takehito , Makimoto Toshiki , Saito Hisao , Ramsteiner Manfred , Zhu Hai-jun , Kawaharazuka Atsushi , Ploog Klaus , Horikoshi Yoshiji
Published: February 2005

The Magnetic and electric field effects of photoluminescence of excitons bound to nitrogen atom pairs in GaAs have been investigated for nitrogen δ-doped samples grown on (001) GaAs substrates. The excitons bound to nitrogen atom pairs produce a number of photoluminescence lines. However, these lines are much fewer than those observed in uniformly nitrogen-doped samples because of the limited spacing between two-dimensionally distributed nitrogen atoms. Among these lines, those appearing at 1.488, 1.476, and 1.428 eV are the most dominant. In this study, the characteristics of these dominant lines are investigated by an applying external field. The observed phenomena are explained by assuming that there is a continuous flow of excitons from a lower to a higher binding energy state under continuous excitation. Each photoluminescence line is found to split into two or more lines without applying an external field. The lines show a further split under a magnetic field and are finally quenched when the magnetic field is increased. The photoluminescence intensity of each line is modulated by the localization of excitons by a magnetic field and by the delocalization by an electric field.
Photoinduced Effects on Single-Charge Tunneling in a Si Two-Dimensional Multidot Field-Effect Transistor
Authors: Ikeda Hiroya , Nuryadi Ratno , Ishikawa Yasuhiko , Tabe Michiharu
Published: February 2005

We have investigated the effect of illumination on the Coulomb blockade (CB) characteristics of Si two-dimensional multidot field-effect transistors. Some of the transistors exhibit remarkable changes in their CB characteristics for single-hole tunneling as a results of illumination, i.e., the generation of a new Coulomb oscillation peak and/or a shift in gate voltage. The photoinduced phenomena can be explained by a model in which the illumination supplies an additional electron to a dot adjacent to the CB current percolation path. A Monte Carlo simulation of an equivalent circuit based on the above model can reproduce the experimental characteristics.
Low-Temperature Silicon Oxidation with Very Small Activation Energy and High-Quality Interface by Electron Cyclotron Resonance Plasma Stream Irradiation
Authors: Saito Kunio , Jin Yoshito , Ono Toshiro , Shimada Masaru
Published: February 2005

Oxidation using electron cyclotron resonance (ECR) plasma stream provides a large silicon dioxide growth rate at the initial growth stage (>6 nm/min), a very small activation energy of 0.02 eV for oxidation, and a high-quality interface with interface trap density of 3×1010 cm-2·eV-1. The plasma stream was extracted by a divergent magnetic field from the ECR region and irradiated on a single-crystalline silicon substrate with ion energies of 10–30 eV. The high-quality interface was obtained by oxidation without substrate heating and only postoxidation annealing at 400°C in hydrogen ambient.
Optical Properties of Silicon Nanoparticles by Ultrasound-Induced Solution Method
Authors: Lee Soojin , Cho Woon Jo , Chin Chong Shik , Han Il Ki , Choi Won Jun , Park Yong Ju , Song Jin Dong , Lee Jung Il
Published: February 2005

White-light-emitting silicon nanoparticles, whose surfaces were passivated with butyl, were prepared using a focused ultrasonic energy. The white light was achieved by controlling only the size distribution without adding any fluorescent ions. The white-light-emitting silicon nanoparticles had a wide size distribution of 1–5 nm and an average size of 2.7 nm, which were sufficiently small to indicate the quantum confinement effect for silicon. The photoluminescence spectrum covered a wide range of 320 nm–700 nm with a full width at half maximum of approximately 190 nm.
Self-Aligned Metal Double-Gate Low-Temperature Polycrystalline Silicon Thin-Film Transistors on Non-Alkali Glass Substrate Using Diode-Pumped Solid-State Continuous Wave Laser Lateral Crystallization
Authors: Hara Akito , Takei Michiko , Yoshino Kenichi , Takeuchi Fumiyo , Sasaki Nobuo
Published: February 2005

Self-aligned top and bottom metal double-gate (SAMDG) low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFTs) were fabricated on non-alkali glass at 550°C, using the diode-pumped solid-state continuous wave laser lateral crystallization (CLC) method. It was observed that the current drivability of SAMDG CLC poly-Si TFTs was eight or nine times larger than that of conventional top-gate excimer-laser-crystallized poly-Si TFTs, and the nominal field-effect mobility of the SAMDG CLC poly-Si TFT was larger than that of (100)-oriented single-crystal SIMOX-TFTs. In addition, a steep subthreshold value, 89 mV/dec, was observed for SAMDG CLC poly-Si TFTs. The exceptional high performance of SAMDG CLC poly-Si TFTs will allow the production of inexpensive LSI circuits on non-alkali glass substrates.
Vertical System Integration by Using Inter-Chip Vias and Solid-Liquid Interdiffusion Bonding
Authors: Klumpp Armin , Merkel Reinhard , Ramm Peter , Weber Josef , Wieland Robert
Published: February 2005

A new approach for 3D system integration, called Inter Chip Via-Solid Liquid Interdiffusion (ICV-SLID) is introduced. This is a new chip-to-wafer stacking technology which combines the advantages of the Inter Chip Via (ICV) process and the solid-liquid-interdiffusion technique (SLID) of copper and tin. The fully modular ICV-SLID concept allows the formation of multiple device stacks. A test chip was designed and the total process sequence of the ICV-SLID technology for the realization of a three-layer chip-to-wafer stack was demonstrated. The proposed wafer-level 3D integration concept has the potential for low cost fabrication of multi-layer high-performance 3D-SoCs and is well suited as a replacement for embedded technologies based on monolithic integration.
Material Design of Transparent, Half-Metallic and Room-Temperature Ferromagnets in I2-VI Semiconductors with 4d Transition Metal Element
Authors: Seike Masayoshi , Sato Kazunori , Yanase Akira , Katayama-Yoshida Hiroshi
Published: February 2005

A new class of 4d transition-metal-doped anti-CaF2 I2-VI diluted magnetic semiconductors (DMSs) is presented based on first-principles calculations. We have systematically investigated the stability of the ferromagnetic state in K2O-, K2S-, K2Se-, K2Te-, Li2S-, Na2S- and Rb2S-based DMSs. Anti-CaF2 I2-VI compounds have a large lattice spacing due to their large ionic radius of cations and many of them are wide-bandgap semiconductors. From the total energy differences between the ferromagnetic state and the spin-glass state, ferromagnetic solutions are derived and it is found that Zr-, Tc- and Ru-doped K2O, Zr-, Nb-, Tc- and Ru-doped K2S, and Zr-, Nb-, and Ru-doped K2Se, K2Te, and Rb2S are good candidates for transparent, half-metallic and room-temperature ferromagnetic DMSs with a large magnetoptical effect.
A Quaternary Magnetic Alloy Semiconductor (Ga,In,Mn)N
Authors: Kondo Tsuyoshi , Hayafuji Jun-ji , Oiwa Akira , Munekata Hiro
Published: February 2005

The physical properties of the III-N-based quaternary magnetic alloy semiconductor (Ga,In,Mn)N prepared by RF-plasma-assisted molecular beam epitaxy are reported. Epilayers are either highly resistive or n-type, and exhibit paramagnetic behavior. Magnetic circular dichroism (MCD) spectra show the presence of spin-polarized band-to-band transition (3–3.5 eV), the Mn2+
d-d
* intra-ionic transition (∼2.3 eV), and the transition associated with rather deep Mn acceptor level (∼1.7 eV). Green-emission band (∼2.3 eV) is observed in photoluminescence experiments for In-containing samples. Near-band-edge emission (∼3.4 eV) is also obtained from multiple-quantum-well structures. n-type samples show negative magnetoresistance at RT, from which strong s,p-d spin exchange interaction is inferred.
Liquid-Crystal Blazed grating with Spatially Distributed Four-Level Twisted Nematic Domains
Authors: Honma Michinori , Nose Toshiaki
Published: February 2005

A liquid crystal (LC) cell with multiple twisted nematic domains is fabricated by rubbing alignment films along different directions and is applied to an LC four-level blazed grating. It is theoretically derived that the four-level stepwise phase profile is achieved under optimum LC molecular orientation conditions. The LC four-level blazed grating is obtained by microrubbing using a tiny stylus with a curvature radius of 25 µm. The electrically controllable diffraction efficiency and unique polarization-splitting properties are revealed; namely, the diffraction efficiency can reach approximately 0.8 and the polarization directions of ±1st-order diffractions are orthogonal to each other.
Synthesis of Carbon Nanofibers by Ion beam Irradiation of an Aromatic Compound
Authors: Kimura Takahide , Koizumi Hitoshi , Kinoshita Hiroshi , Takahashi Heishichiro , Ichikawa Tsuneki
Published: February 2005

Cabon nanofibers (CNFs) were synthesized at room temperature without a catalyst by the ion beam irradiation of an aromatic compound: CNFs with a length of 1–10 µm and a diameter of approximately 100 nm were generated by the irradiation of decacyclene with 200 keV He+ or N+ ions. The number density and length of the CNFs depend on the fluence and species of the ions. Observations by transmission electron microscopy indicate that the CNFs were amorphous.
Composite-Channel Metamorphic High Electron Mobility Transistor for Low-Noise and High-Linearity Applications
Authors: Chang Edward Yi , Lin Yueh-Chin , Chen Guan-Ji , Lee Huang-Ming , Huang Guo-Wei , Biswas D. , Chang Chun-Yen
Published: February 2005

A metamorphic high-electron-mobility transistor (MHEMT) with In0.55Ga0.45As/In0.67Ga0.33As/In0.55Ga0.45As composite channel layers was developed for low-noise and high-linearity applications. The use of a composite channel results in high electron mobility and good confinement of electrons in the channel region which are the desired characteristics of low-noise and high-linearity devices. The noise figure of the 0.25 ×160 µm2 devices is 0.23 dB with 15.06 dB associated gain, and the output third-order intercept point (IP3) is 18.67 dBm at 6 GHz. The device shows great potential for high-linearity and low-noise applications at high frequencies.
A Low Threshold Current Density InAs/AlGaSb Superlattice Quantum Cascade Laser Operating at 14 µm
Authors: Ohtani Keita , Fujita Kazuue , Ohno Hideo
Published: February 2005

We report a low threshold current density InAs/AlGaSb superlattice quantum cascade laser operating at 14 µm. In order to reduce the threshold current density, InAs/AlGaSb superlattice structures providing large oscillator strength and fast carrier depopulation are used for the active layers. Observed threshold current density at 80 K is 0.92 kA/cm2, which is about 5 times lower than that of the first InAs/AlSb quantum cascade laser reported earlier. This is among lowest threshold current density of quantum cascade lasers operating in the mid-infrared spectrum region.
Improved Charge-Trapping Nonvolatile Memory with Dy-doped HfO2 as Charge-Trapping Layer and Al2O3 as Blocking Layer
Authors: Choi Sangmoo , Cho Myungjun , Samantaray Chandan B. , Jeon Sanghun , Kim Chungwoo , Hwang Hyunsang
Published: February 2005

We have investigated a charge-trapping nonvolatile memory (NVM) device with high-k dielectrics as a charge-trapping layer (HfO2 and Dy-doped HfO2) and a blocking layer (Al2O3). Compared with a conventional SiO2/Si3N4/SiO2 stack, both SiO2/HfO2/Al2O3 and SiO2/Dy-doped HfO2/Al2O3 stacks show significantly improved program and erase (P/E) speed. The improvement in P/E speed characteristics can be explained by the larger band offset of HfO2 and the increased thickness of the blocking oxide, which are the main advantages of high-k materials. Moreover, for a SiO2/Dy-doped HfO2/Al2O3 stack with an optimum Dy concentration, the enhanced retention characteristics were observed at a measurement temperature below 150°C due to the deep energy level of the charge trap.
Photochemical Fixation of Individual Polymer Nanoparticles on Glass Substrates in Solution at Room Temperature
Authors: Ito Syoji , Yoshikawa Hiroyuki , Masuhara Hiroshi
Published: February 2005

A new method for fixing single polymer nanoparticles onto a substrate was developed by local photopolymerization. A nanoparticle, dispersed in ethylene glycol containing monomer, crosslinker, and radical photoinitiator, was moved to the surface of a glass substrate using a focused near-infrared laser beam. Local photopolymerization around the nanoparticle was induced by additional irradiation of an ultraviolet pulsed laser beam, resulting in the generation of an acrylamide gel containing the nanoparticle on the substrate. The nanoparticles become fixed and remained after washing. The morphology of the formed polymerized gel was evaluated by atomic force microscope (AFM) observation.
Analysis of the Frequency-Dependent Electromeniscus Phenomenon from the Viewpoint of Canonical Theory
Authors: Matsuura Hiroshi , Tanikawa Tamio , Kokaji Shigeru
Published: February 2005

We investigated the transition of liquid geometry as a function of the frequency of the sinusoidal electric potential applied to the surface of a liquid. The application of an electric potential of low frequency generated a hemispherical liquid geometry, and the hemisphere narrowed as the frequency was increased, forming an electromeniscus. This electromeniscus was applied in erecting a carbon nanotube (CNT) on the substrate. In this paper, we analyze the dynamic mechanisms of the electromeniscus phenomenon. The application of canonical theory explains the mass-reduction mechanism of the oscillating liquid.
1.3–1.5-µm-Wavelength GaAs/InAs Superlattice Quantum-Dot Light-Emitting Diodes Grown on InP (411)A Substrates
Authors: Mori Jun , Nakano Tomonori , Shimada Takashi , Hasegawa Shigehiko , Asahi Hajime
Published: February 2005

High-lateral-density multilayer quantum-dot (MQD) structures are self-formed by growing (GaAs)2(InAs)2 short-period superlattices (SLs) sandwiched with InP layers on InP (411)A substrates by gas source molecular-beam epitaxy. Light-emitting diodes (LEDs) with this MQD layer as an active layer are fabricated and strong electroluminescence (EL) emission is observed. EL peak wavelengths from 1.3 µm to 1.5 µm are obtained by changing the SL period. EL peak intensity increases linearly with increasing driving current up to 100 mA (320 A/cm2). When increasing the LED temperature from 80 K to 300 K, EL peak intensity decreases very slowly by only a factor of 0.1.
High-Efficiency Oxide Heterojunction Solar Cells Using Cu2O Sheets
Authors: Minami Tadatsugu , Tanaka Hideki , Shimakawa Takahiro , Miyata Toshihiro , Sato Hirotoshi
Published: February 2005

An inexpensive oxide heterojunction solar cell, consisting of a transparent conducting ZnO thin film deposited on a Cu2O sheet prepared by oxidizing copper at a high temperature, has been demonstrated. High-energy conversion efficiencies over 1% were obtained in Al-doped ZnO (AZO)/Cu2O devices fabricated using AZO thin films prepared by pulsed laser deposition (PLD) or r.f. magnetron sputtering. An open-circuit voltage of 0.41 V, a short-circuit current density of 7.13 mA/cm2, a fill factor of 0.42 and an energy conversion efficiency of 1.21% were obtained in a PLD-AZO/Cu2O device under AM2 solar illumination. The high efficiency of AZO/Cu2O devices is attributed to Cu2O sheets with excellent crystallinity and the low damage resulting from AZO depositions at low temperature.
Diamond Powders Less Than 100 nm in Diameter as Effective Solid Lubricants in Vacuum
Authors: Gubarevich Anna Valeryevna , Usuba Shu , Kakudate Yozo , Tanaka Akihiro , Odawara Osamu
Published: February 2005

The frictional behavior of detonation nanodiamond and single-crystal fine diamond powders were studied to determine the effect of particle diameter on their lubricative and abrasive characteristics. In vacuum, nanodiamond with an average aggregate size of 75 nm and mechanically crushed single-crystal diamond powders with an average diameter of 50 nm formed a uniform lubricating layer while sliding against a SiC ball and showed very low friction coefficients of 0.03 and less than 0.01, respectively, under moderate conditions of 0.5 N applied load and 3.5 mm/s sliding speed. A clear tendency was observed for both the friction coefficient and specific wear rates to decrease with decreasing particle/aggregate size.
Self-Assembly of Si Nanoparticles: Emergence of Two-Dimensional Si Nanoparticle Lattices
Authors: Sato Seiichi , Yao Hiroshi , Kimura Keisaku
Published: February 2005

Monolayers consisting of two-dimensional (2D) Si nanoparticle lattices were synthesized using a self-assembly process of Si nanoparticles at an octanol/aqueous solution interface. The component nanoparticles were prepared in an aqueous solution by dissolving Si sub-oxide powder that contained Si nanocrystals. The Si nanocrystals, which were dispersed in the aqueous solution, were transferred into an octanol phase and assembled at the octanol/aqueous solution interface. The average diameter of the component nanocrystals in the 2D lattices varied from 7 to 11 nm in different lattices, which suggests that the lattices incorporate nanoparticles of the same size and expel those of different sizes during lattice growth.
New Class of Diluted Ferromagnetic Semiconductors based on CaO without Transition Metal Elements
Authors: Kenmochi Kazuhide , Seike Masayoshi , Sato Kazunori , Yanase Akira , Katayama-Yoshida Hiroshi
Published: February 2005

We propose a new class of diluted magnetic semiconductors based on CaO without transition metal elements. The electronic structure and the magnetic properties of B-, C- or N-doped CaO are calculated by using the Korringa-Kohn-Rostoker method within the local spin density approximation. The substitutional and magnetic disorder is taken into account by the coherent potential approximation. It is found that B, C and N impurities show finite local magnetic moments in CaO at the oxygen-substitutional site. Moreover, these C- and N-doped CaO show the room-temperature ferromagnetism with half-metallic density of states.
Metalorganic Vapor Phase Epitaxy of InAs Layers on GaAs Substrates Using Low-Temperature Growth of InGaAs Graded Buffer Layers
Authors: Takano Yasushi , Umezawa Masayoshi , Shirakata Sho , Fuke Shunro
Published: February 2005

InAs layers were grown on GaAs substrates by metalorganic vapor phase epitaxy using InGaAs graded buffer layers and two-step growth. Layer quality was investigated by transmission electron microscopy. The threading dislocation density in InAs grown with the graded buffer layer was determined to be 1.6 ×107 cm-2. That value was one order of magnitude lower than that of InAs layers grown by two-step growth. Graded buffer layer growth is more effective for InAs layers on GaAs substrates with low threading dislocation density than two-step growth.
Optical Damage Resistance of Near-Stoichiometric LiNbO3 Crystal Doped with Sc
Authors: Nakamura Masaru , Takekawa Shunji , Liu Yuowen , Kitamura Kenji
Published: February 2005

Near-stoichiometric LiNbO3 (SLN) crystals doped with Sc (Sc:SLN) were grown from Li-rich solutions through a top-seeded solution growth (TSSG) method using resistance heating equipment. The optical damage resistance of the Sc:SLN crystals was investigated at a wavelength of 532 nm. The Sc:SLN crystals doped with more than 0.4 mol% Sc doping concentration showed no optical damage. The OH absorption peak for the Sc:SLN crystals shifted from 2.88 µm to 2.85 µm at 0.4 mol% Sc. This critical Sc doping concentration in the SLN crystal was one-fifth that in a congruent melt composition LN (CLN) crystal which required at least 2 mol% Sc (1 mol% Sc2O3) to suppress optical damage. The 0.4 mol% Sc doping required to suppress optical damage in the SLN crystal was also low compared to the 1 mol% Mg doping required for the same purpose. Hence, the Sc:SLN crystal is a more promising material with respect to resisting optical damage when applied to, for example, electrooptic devices.
Vertical and Smooth Microfabrication of InP Using Simple High-Density Plasma System with SmCo Ring Magnet
Authors: Matsutani Akihiro , Ohtsuki Hideo , Ohashi Ken , Yokoyama Tomonori , Yamakage Hirokazu , Koyama Fumio
Published: February 2005

We demonstrated the formation of high-density plasma using a SmCo ring magnet and its application to the vertical and smooth etching of InP. It is found that the high-density plasma using the magnet is well confined inside the magnetic fields. The ion density of the plasma using the magnet is much higher than that of the plasma without the magnet at the same input RF power. The etching profile and the roughness of the etched bottom surface are improved using the high-density plasma. The proposed dry etching technique using the high-density plasma formed with a magnet will become an effective technique for the microfabrication of semiconductors or other materials.
Enhancement of the Ferromagnetic Transition Temperature in Self-Assembled (Ga1-xMnx)As Quantum Wires
Authors: Jeon Hee Chang , Chung Kwang Jae , Chung Kwang Jo , Kang Tae Won , Kim Tae Whan
Published: February 2005

Self-assembled (Ga1-x
Mn
x
)As diluted magnetic semiconductor quantum wires (QWRs) were grown on GaAs (100) substrates by molecular beam epitaxy with a goal of producing (Ga1-x
Mn
x
)As QWRs with a high ferromagnetic transition temperature (T
c). Scanning electron microscopy and X-ray diffraction measurements showed that the grown (Ga0.84Mn0.16)As QWRs were straight crystals. Magnetic force microscopy images showed that the grown QWRs were symmetric single-domain particles. The magnetization curve as a function of magnetic field at 5 K indicated that the (Ga0.84Mn0.16)As QWRs were ferromagnetic, and the magnetization curve as a function of temperature showed that T
c was as high as 350 K. The marked increase in T
c originated from the enhancement in quantum confinement effect resulting from the reduction in structural dimension. These results have opened a new frontier for investigations of fundamental spintronic science.
Photoresponse Nonlinearity of a Uni-Traveling-Carrier Photodiode and Its Application to Optoelectronic Millimeter-Wave Mixing in 60 GHz Band
Authors: Fushimi Hiroshi , Furuta Tomofumu , Ishibashi Tadao , Ito Hiroshi
Published: February 2005

Nonlinear photoresponse observed in the pulsed operation of an InP/InGaAs uni-traveling-carrier photodiode (UTC-PD) is analyzed in terms of the dynamic capacitance associated with charge storage in the absorption layer. To model such an effect, a variable carrier traveling delay time which changes with operation voltage and current is introduced. Optoelectronic millimeter-wave mixing for 59.4-GHz and 600-MHz-modulated 1.55 µm optical signals was examined, and found to efficiently generate a 60 GHz up-converted signal. The characteristics are semiquantitatively explained by the dynamic capacitance model.
Single Gap Transflective Liquid Crystal Display with Dual Orientation of Liquid Crystal
Authors: Lim Young Jin , Song Je Hoon , Kim Yong Bae , Lee Seung Hee
Published: February 2005

We propose a single-cell-gap transflective liquid crystal display (LCD) with dual orientation of LC at an initial state. Owing to hybrid alignment in the reflective region, the effective cell retardation value becomes half of that in the transmissive region where the LCs are homogenously aligned. Consequently, a transflective display driven by a vertical or fringe electric field with a single cell gap and high image quality is realized.