bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Substrate Orientation on Arsenic Precipitation in Low-Temperature-Grown GaAs
Authors: Lee W. N. , Chen Y. F. , Huang J. H. , Guo X. J. , Kuo C. T.
Published: September 2005

Arsenic precipitation in “superlattice” structures of alternately undoped and [Si]=3 ×1018 cm-3-doped GaAs grown at 250°C on (100), (311)A, and (311)B GaAs substrates has been studied using transmission electron microscopy. It is found that upon postgrowth annealing at 800°C, As precipitates are nearly confined in the Si-doped regions, forming two-dimensional cluster arrays located approximately at the center of each Si-doped layer. The results also show that the As precipitates in the (311)B substrate are slightly denser and larger than those in the (311)A substrate and both are markedly denser and larger than those in the (100) substrate. This can be attributed to the varying excess arsenic incorporations in differently orientated substrates.
Threading Dislocations and Phase Separation in InGaAs Layers on GaAs Substrates Grown by Low-Temperature Metalorganic Vapor Phase Epitaxy
Authors: Takano Yasushi , Kobayashi Kazu , Iwahori Hideaki , Umezawa Masayoshi , Shirakata Sho , Fuke Shunro
Published: September 2005

InGaAs layers with In composition between 0.50 and 0.57 were grown on GaAs substrates with graded buffer layers at temperatures between 370 and 470°C by metalorganic vapor phase epitaxy. Periodic structure resulting from phase separation was observed in the cap layers grown at 450 and 470°C by transmission electron microscopy (TEM). Threading dislocation densities in the cap layer grown at 450°C were determined to be 6.7×107, 5.7×107, and 8.1×108 cm-2 using 1 µm graded buffer layers on an exactly oriented substrate, on a substrate misoriented toward (111)A and on that misoriented toward (111)B by plan-view TEM, respectively. The periodic structure depended on the substrate misorientation. The structure was correlated with surface morphology. The structure blocked dislocation propagation in the layers. The growth temperature was lowered below 450°C using triethylgallium instead of trimethylgallium as the Ga source. No phase separation was found for layers grown at 370 and 400°C with TEM. Threading dislocation densities in the cap layer grown at 400°C were as low as 7.1×106, 1.7×107 and 1.7×107 cm-2, for an exactly oriented substrate, a substrate misoriented toward (111)A and that misoriented toward (111)B, respectively. Low-temperature growth at around 400°C was effective in achieving homogeneous InGaAs layers with a low threading dislocation density.
Germanium Oxide Layers Used for Forward Transfer of Electrical Circuits to Foreign Plastic Substrates
Authors: Sameshima Toshiyuki , Yoshioka Kazuya , Takechi Kazushige
Published: September 2005

Germanium oxide (GeO
x
) films were used as a removing layer in order to transfer thin-film electrical circuits to foreign plastic substrates. GeO2 films were formed by sputtering with mixed gases of oxygen and argon at room temperature. They were rapidly removed at an etching rate of 1000 nm/s by a hydrochloric acid solution with a pH of 0.1 at room temperature and also removed at 700 nm/s by hot water at 70°C. Using GeO2 layers, the transfer of a hydrogenated amorphous silicon layer with Al electrodes to plastic films was demonstrated.
Metal–Oxide–Nitride–Oxide–Semiconductor Memory Device with One-Side Halo Implantation to Enable Low-Voltage Operation Using Hot-Carrier Injection
Authors: Tomiye Hideto , Nomoto Kazumasa , Koyama Kazuhide , Kobayashi Toshio
Published: September 2005

We have developed a metal–oxide–nitride–oxide–semiconductor (MONOS) memory device with one-side halo implantation, in which programming and erasing are performed by channel-hot-electron injection and hot-hole injection, respectively. This MONOS memory has a simple structure and is fabricated through the conventional complementary metal–oxide–semiconductor (CMOS) process before the specific process for the memory device. A threshold voltage shift of more than 3.0 V, obtained through a programming operation, results in a threshold voltage greater than the programming gate voltage and is sufficient to enable the 10-year lifetime of this device.
A Generalized Electrostatic Scale Length for Fully Depleted Surrounding-Gate Metal–Oxide–Semiconductor Field Effect Transistors
Authors: Chiang Te-Kuang
Published: September 2005

On the basis of the continuity of the electric flux and potential at the interface between a Si body and a gate insulator, and of the effective insulator thickness, a generalized electrostatic scale length for two-dimensional (2D) effects in fully depleted surrounding-gate (SG) metal–oxide–semiconductor field effect transistors (MOSFETs) is derived. It is found that for the same equivalent oxide thickness, a gate insulator with a higher dielectric permittivity results in stronger 2D effects caused by an increase in electrostatic scale length. Both a thin gate insulator and a thin Si body are required to realize a small electrostatic scale length to suppress short-channel effects. Compared with conventional planar MOSFETs, high-gate-permittivity SG MOSFETs theoretically can be designed such that its insulator is thicker than its Si body without increasing its electrostatic scale length. With appropriate modification of the effective insulator layer thickness, the model also indicates an increased scale length due to quantum effects.
Optical Properties of LSI Mask Using Cover Substrate
Authors: Okamoto Yoshihiko , Ogita Masami
Published: September 2005

In order to investigate the optical properties of an LSI mask that uses a cover substrate, we have designed a high-numerical aperture (NA), very low aberration reduction projection lens system. On the basis of this design, it was found that the wavefront aberration of the LSI mask that uses a cover substrate between the mask and projection lens is reduced by optimizing of the mask position and imaging position. A phase-shift mask (PSM) using a cover substrate was formed for the experiments. We measured the intensity profiles of this PSM by Zeiss aerial image measurement system (AIMS). It was found that the intensity profiles of this PSM are better than those of the conventional PSM. We have also found that an LSI mask using a cover substrate of specific thickness is able to achieve better image formation using the projection lens system.
Diminished Short Channel Effects in Nanoscale Double-Gate Silicon-on-Insulator Metal–Oxide–Semiconductor Field-Effect-Transistors due to Induced Back-Gate Step Potential
Authors: Kumar M. Jagadesh , Reddy G. Venkateshwar
Published: September 2005

In this letter we discuss how the short channel behavior in sub 100 nm channel range can be improved by inducing a step surface potential profile at the back gate of an asymmetrical double gate (DG) silicon-on-insulator (SOI) metal–oxide–semiconductor field-effect-transistor (MOSFET) in which the front gate consists of two materials with different work functions.
Enhanced Anisotropic Magnetoresistance of Ion-Beam-Deposited Ni80Fe20–NixFe1-xO Composite Films
Authors: Lin Ko-Wei , Gambino Richard J.
Published: September 2005

Composite films of Ni80Fe20–Ni
x
Fe1-x
O were prepared by a dual ion-beam deposition technique. Magnetoresistance (MR) was measured both at 77 and 298 K in a magnetic field applied in plane, parallel and perpendicular to the electrical current. Typical anisotropic magnetoresistance (AMR) was observed in as-deposited and annealed samples. The most interesting result is that for annealed samples, the shape of the MR curve is sharp and symmetric and the total MR ratio increases with oxygen content in the films, as compared with as-deposited samples. Furthermore, the total MR ratio reaches a maximum (∼ 4.5 and 14% at 298 and 77 K, respectively) in films prepared with 44% oxygen in the assist beam. This enhanced AMR is attributed to the strong anisotropic scattering at interfaces between the ferromagnetic metal and oxide phases.
Inverse Magnetoresistance Loops in Nearly Percolating Co–Ag Nanostructures and Two-Phase Model
Authors: Saito Toshiaki , Sonobe Akemi , Shimaoka Yuhji , Ugajin Tamotsu , Nakanishi Hideo
Published: September 2005

We observed unusual inverse magnetoresistance (MR) loops in the transverse configuration for nearly percolating Co–Ag granular thin films deposited by a coevaporation technique onto a room-temperature glass substrate. When the substrate was heated above about 60°C during evaporation, the inverse MR loops disappeared and converted into normal loops. On the other hand, when the sample was annealed below about 120°C after deposition onto a room-temperature substrate, the inverse MR loops remained, whereas when annealed from about 120 to 300°C, the inverse MR loops were converted into “normal+inverse”-type loops and finally into totally normal loops when annealed above about 350°C. The unusual MR loops may have originated from magnetic nanostructures in nearly percolating Co–Ag granular films. A two-phase model incorporating uniaxial anisotropy, exchange interaction and spin-dependent scattering is presented, which is able to qualitatively explain some of the observed results.
Orthogonally Twinned CrO2(110) Epitaxial Films Grown on MgO(001) Substrates Buffered by Oxidized TiN
Authors: Umada Naokazu , Yanagihara Hideto , Hatanaka Ayumu , Kita Eiji
Published: September 2005

We have succeeded in growing epitaxial CrO2(110) thin films on MgO(001) substrates with TiO2(110) buffer layers oxidizing from TiN(001) thin films. Thin TiN(001) epitaxial films grown by reactive dc-magnetron sputtering were transformed into TiO2(110) with an annealing process in low-pressure oxygen, followed by selective CrO2(110) growth on TiO2buffer layers by chemical vapor deposition. X-ray diffraction experiments and scanning electron microscopic observation revealed that the epitaxial relationship of the sample is MgO(001)[110]∥TiO2(110)[001]∥CrO2(110)[001]. Both the CrO2(110) films and TiO2(110) buffer layers are orthogonally twinned and formed with small grains of CrO2of 3–5 µm size and of TiO2of sub-µm size.
Ultrafast Single-Shot Optical Oscilloscope based on Time-to-Space Conversion due to Temporal and Spatial Walk-Off Effects in Nonlinear Mixing Crystal
Authors: Takagi Yoshihiro , Yamada Yoshifumi , Ishikawa Kiyoshi , Shimizu Seiji , Sakabe Shuji
Published: September 2005

A simple method for single-shot sub-picosecond optical pulse diagnostics has been demonstrated by imaging the time evolution of the optical mixing onto the beam cross section of the sum-frequency wave when the interrogating pulse passes over the tested pulse in the mixing crystal as a result of the combined effect of group-velocity difference and walk-off beam propagation. A high linearity of the time-to-space projection is deduced from the process solely dependent upon the spatial uniformity of the refractive indices. A snap profile of the accidental coincidence between asynchronous pulses from separate mode-locked lasers has been detected, which demonstrates the single-shot ability.
Sub-Picosecond Optical Pulse Generation with Repetition Rate of Several Tens of Gigahertz Using Electrooptic Standing-Wave Phase Grating with Periodic Domain Inversion
Authors: Shibuya Kyoji , Hisatake Shintaro , Kobayashi Tetsuro
Published: September 2005

We propose and demonstrate a novel electrooptic spatiotemporal modulator for sub-picosecond optical pulse generation with a repetition rate of several tens of gigahertz. The pulse generation is directly accomplished with an electrooptic standing-wave phase grating with periodic domain inversion that operates over 10 GHz. This device produces a phase distribution that is like a sinusoidal standing wave in the beam cross section. The output optical beam undergoes Raman–Nath diffraction with diffracted beams whose intensities vary temporally. When we extract a certain diffracted beam, we can obtain a pulse train. A near-Fourier-transform-limit pulse train with a repetition rate of twice the modulation frequency can be obtained using the zero-order undiffracted beam. In the experiment, we found that our new device operates as theoretically predicted and that we can obtain a pulse train with a pulsewidth of about 1 ps from the fabricated device at the maximum modulation power. By improving the modulation efficiency of the device or by further increasing of the modulation frequency, a sub-picosecond optical pulse train with a repetition rate of several tens of gigahertz can be generated by the new device.
Miniaturised High-Numerical Aperture Singlet Plastic Objective for Optical Recording
Authors: Hendriks B. H. W. , As M. A. J. van , Alem A. A. M. van
Published: September 2005

The design, manufacturing and testing of a miniaturised singlet plastic injection molded high-numerical aperture objective is discussed. To reduce the temperature dependence a non-periodic phase structure is incorporated in the aspherical surface of the lens. Readout experiment with this objective in an optical drive is performed.
Three-Dimensional Optical Memory in a Photoacid-Induced Recording Medium
Authors: Mizuno Takeshi , Yamasaki Kazuhiko , Misawa Hiroaki
Published: September 2005

We report a photoacid-induced write-once read-many recording medium based on poly(methyl methacrylate) for three-dimensional (3D) optical memory. Three-layered recording was achieved using only an 800 nm-femtosecond oscillator with a 82-MHz-repetition rate without structural damage. Bits of arbitrary length used in the present modulation method of Compact Disc type memory can be recorded by photo-modification in the medium. The results suggest that the medium is an attractive candidate to solve the technical problems of 3D recording, in which micro-structural integrity of medium is altered.
Dielectric Property and Electronic Structure of LaNbO4
Authors: Arai Masao , Wang Yuan Xu , Kohiki Shigemi , Matsuo Munenori , Shimooka Hirokazu , Shishido Toetsu , Oku Masaoki
Published: September 2005

Powder samples of lanthanum niobate demonstrated a dielectric anomaly at ≈500°C in both the dielectric constant and dielectric loss when the applied field frequency was 1000 kHz. They were transparent in the visible region, and exhibited a blue emission centered at 3 eV. The first-principles electronic structure computation for lanthanum niobate with both the monoclinic and tetragonal crystal structures revealed that lower conduction bands are mostly composed of Nb 4d 3z
2-1 and x
2-y
2 orbitals and their hybridization with oxygen p-orbitals is weak.
Landau Theory of Phase Transition in Ferroelectric Vinylidene Fluoride/Trifluoroethylene Copolymer Single Crystals
Authors: Ishibashi Yoshihiro , Iwata Makoto
Published: September 2005

The phase transition in ferroelectric vinylidene fluoride/triflioroethylene (P[VDF/TrFE]) copolymer single crystals is analyzed within the Landau theory. Interesting features intrinsic to the hexagonal-orthorhombic transition in P[VDF/TrFE] are clarified. It is possible that polymer materials based on P[VDF/TrFE] with a very high electromechanical coupling constant are obtainable.
Friction Reduction Using Electrically Energized Piezoelectric Buzzer
Authors: Chang Kuo-Tsai
Published: September 2005

In this paper, the characteristics of friction reduction between a moving object unit, including a moving object and a piezoelectric buzzer, and a sliding surface using ultrasonic vibration caused by a converse piezoelectric effect are investigated. The operating principle of this reduction is first expressed using a friction reduction mechanism. Then, a carbon-powder imaging method for observing the nodal patterns of vibration modes on the piezoelectric buzzer energized by AC power is presented. Moreover, an AC power supply is constructed to create a sinewave voltage at both input terminals of the piezoelectric buzzer, and a laser Doppler vibrometer system is built to measure the amplitude of the ultrasonic vibration. Furthermore, the characteristics of the vibration amplitude against the driving frequency of the piezoelectric buzzer only are measured and discussed. Finally, a test system for estimating the friction reduction effect is built to determine the minimum driving voltages at various driving frequencies for just moving the object unit.
Microwave Dielectric Properties of Ba4.2(Nd0.5,Sm0.5)9.2Ti18O54 Ceramics Doped with Al2O3 and SiO2
Authors: Lu Wenzhong , Zhu Jianhua , Kipkoech Erick R.
Published: September 2005

The effects of Al2O3 and SiO2 additives on the microwave properties of Ba6-3x
(Nd
y
,Sm1-y
)8+2x
Ti18O5 (x=0.6 and y=0.5; BNST) materials have been investigated. The microstructure of BNST doped with Al2O3 or SiO2 was analyzed using X-ray diffraction (XRD) analysis and scanning electron microscopy. XRD analysis did not reveal any second phases or modification of the BNST crystal structure. The addition of SiO2 at more than 0.2 wt % increased grain growth and shortened the densification process. The addition of small amounts of Al2O3 (≤2 wt %) increased the Qf markably and improved the TCf, while it decreased the density and dielectric constant (ε
r) of BNST. Doping 0.5 wt % Al2O3, in addition to a small amount of SiO2 (=0.2 wt %), further increased the Qf of BNST. The dielectric constant, the Qf and the TCf of the materials degrade when doped with too much SiO2. The BNST doped with 0.5 wt % Al2O3 and 0.2 wt % SiO2 exhibited dielectric properties with ε
r=74.3, Qf=8700 GHz and TCf=8.8 ppm/°C at a sintering temperature of 1320°C for 2 h.
Novel Transflective Fringe-Field Switching Mode Using Common Electrode with Box and Slit Shape
Authors: Park Jun Baek , Kim Hyang Yul , Jeong Youn Hak , Lim Dong Hoon , Kim Seo Yun , Lim Young Jin
Published: September 2005

We have investigated novel single gap transflective fringe-field switching (FFS) mode using different shape of common electrode in transmissive and reflective part. The common electrode of transmissive part is box type like conventional FFS mode. In reflective part, using slit type of common electrode, operating voltage matches with that of transmissive part without the loss of liquid crystal efficiency resulting from decrease of rubbing angle.
Energy Dissipation at Ultrasonically Oscillating Superhydrophobic Surface in Various Liquids
Authors: Fujita Mitsuhiro , Muramatsu Hiroshi , Fujihira Masamichi
Published: September 2005

A film with a superhydrophobic rough surface was prepared on an AT-cut quartz crystal resonator (QCR). Using the QCR with the film, we measured energy dissipation at the ultrasonically oscillating superhydrophobic surface in various liquids such as water, ethanol and water–glycerol mixtures. The QCR was successfully used to determine the mode of contact of the rough surface with each liquid, i.e., either Wenzel or Cassie contact. Furthermore, it was found that the interfacial friction strongly depended on the contact mode. The interfacial friction was reduced byca.50% when the contact mode was the Cassie type.
Electrical Properties of a Thin Anodized Capacitor Made of Y-Doped Al Alloy Film
Authors: Onozuka Tomotake , Sasaki Hayato , Mikuni Naohiro , Shinkai Satoko , Sasaki Katsutaka , Yamane Misao , Abe Yoshio
Published: September 2005

We have prepared an Al–Y anodized capacitor using sputter-deposited Al–Y alloy film with 5 at. % Y atoms, and evaluated the capacitor properties and the leakage current properties before and after heat treatment. In addition, the characterization of Al–Y anodized films was examined by X-ray diffraction, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy analyses. As a result, it is revealed that the thermal stability of an Al–Y anodized capacitor is superior to that of a pure Al anodized capacitor because of its excellent passive nature, and the loss properties can be improved by increasing the heat treatment temperature in air because of the reduction of the equivalent series resistance. Furthermore, it is clarified that the cause of the short-circuited state observed at 550°C is the formation of a narrow capillary-like conduction path of metallic Al atoms as a result of the interdiffusion of Al.
Production of Plasma Jet Based on High-Current Pseudo-Spark Discharge
Authors: Kamada Takaharu , Fujiwara Tamiya , Itagaki Minoru , Ishikawa Toshiaki , Watanabe Masayuki
Published: September 2005

A plasma jet based on a high-current pseudo-spark discharge has been developed. A pseudo-spark discharge (PSD) is a high-current glow-like discharge, which is formed on the left side of the minimum of the Paschen curve. Although the discharge current exceeds several tens of kiloamperes, the discharge retains the glow mode because of the hollow cathode effect. The PSD is formed with a large number of arc channels, which are usually narrow. Consequently, the PSD has a large cross section. In this study, the PSD anode has a hole with a larger diameter than that of the cathode in order to generate a plasma jet. The plasma is effectively accelerated by the electromagnetic force due to the modified shape of electrodes. The electron temperature and density of the plasma jet were measured by a double probe technique. At the discharge current of 10 kA, the temperature of the plasma jet reached approximately 1.9 eV and the density was of the order of 1014 cm-3 at the distance of 72 mm from the anode.
Measurements of Gas Temperature in High-Density Helicon-Wave H2 Plasmas by Diode Laser Absorption Spectroscopy
Authors: Aramaki Mitsutoshi , Okumura Yuji , Goto Motoshi , Muto Sadatsugu , Morita Shigeru , Sasaki Koichi
Published: September 2005

The gas temperatures in high-density H2 plasmas excited by helicon-wave discharges were measured by absorption spectroscopy using a diode laser as the light source. The gas temperature was evaluated from the Doppler broadening of the absorption line profile at Hα. The gas temperature increased with rf power from 0.05 to 0.18 eV at a gas pressure of 50 mTorr. The temporal variations of the gas temperature after the initiation of discharge and the termination of the rf power were investigated. The power consumed by heating the gas was evaluated using the temperature and the time constant of the temporal variation.
Lost Hole-Blocking Property of Blue-Emitting Alq by Inserting Detached Layer
Authors: Mori Tatsuo , Itoh Takaaki , Iwama Yuki , Mizutani Teruyoshi
Published: September 2005

The authors found an interesting and strange phenomenon that is inexplicable using a simple energy diagram. Blue-emitting Alq (BAlq), a hole-blocking material, exhibits an excellent hole-blocking property in an organic light-emitting diode (LED) consisting of naphthyl-substituted diamime derivative (NPD) and BAlq. Nevertheless, its hole-blocking property is lost by inserting Alq3 between BAlq and a cathode. This fact suggests that an indirect interaction is imparted to the NPD/BAlq interface from a detached (not neighboring) layer. In addition, difference electroluminescence (EL) spectrum analysis is very effective in the discussion of EL mechanism.
Light Transmission in Carbon Nanotube Array: Fano-Resonance Analysis
Authors: Cho Hojin , Jung Hyun Young , Park Q-Han , Suh Jung Sang , Jhe Wonho
Published: September 2005

The Fano's equation (FE) describes electron transition from the ground state to the excited state. We show that FE is valuable for describing the far-field transmission of light in optical systems. FE is also effective in estimating the transmission behaviors at various resonance conditions, which are investigated in transmission experiments by using two kinds of comparative samples: periodical hexagonal arrays of Al2O3 with and without multiwall carbon nanotubes. Our experimental results show that FE complements Maxwell's equations even in the waveguide problem and provides a clear and simple analysis.
Design of Reflecting Mirrors for Electron Cyclotron Wave Launching System in GAMMA 10
Authors: Tatematsu Yoshinori , Nozaki Kiyoshi , Saito Teruo , Ikegami Hirokazu , Sekine Takayuki , Nagai Daichi , Kubo Shin , Shimozuma Takashi , Imai Tsuyoshi , Cho Teruji
Published: September 2005

Profile-tailoring mirrors have been designed using a newly developed electromagnetic code for a high-power plug electron heating system in the GAMMA 10 tandem mirror. An axisymmetric Gaussian-like radiation profile on the resonance surface was realized with the designed mirrors; this profile is confirmed by a low-power measurement in the atmosphere. With the new heating system, a new record of 2.1 kV for the ion-confining potential has been attained.
Electron Energy Spectrometer for Laser-Driven Energetic Electron Generation
Authors: Li Zhong , Nakamura Shu , Fukumi Atsushi , Hayashi Yukio , Orimo Satoshi , Nishiuchi Mamiko , Sagisaka Akito , Mori Michiaki , Shirai Toshiyuki , Iwashita Yoshihisa , Noda Akira , Daido Hiroyuki
Published: September 2005

An electron energy spectrometer for studying the energy spectrum of electrons emitted from solid foils irradiated by a femtosecond intense laser pulse and its calibration with a β source is described. The intensity distribution of the magnetic field induced by a dipole magnet and the time decay of the photostimulated luminescence of an imaging plate were determined. Both the energy scale and the electron intensity conversion ratio of the electron energy spectrometer were calibrated with a 90Sr–90Y β source. The energy spectrum of hot electrons emitted from a 3-µm-thick Tantalum foil target irradiated by laser pulses with a pulse duration of 50 fs and a peak intensity of 2×1018 W/cm2 was determined with the calibrated electron energy spectrometer.
Magnetic Levitation of Plastic Chips: Applications for Magnetic Susceptibility Measurement and Magnetic Separation
Authors: Tanimoto Yoshifumi , Fujiwara Masao , Sueda Manabu , Inoue Katsuya , Akita Motoko
Published: September 2005

Magnetic levitation of polyethylene, polycarbonate, polypropylene, polystyrene, poly(methyl methacrylate) and polyamide was carried out using a compact superconducting magnet (vertical bore, 1500 T2 m-1). First, their diamagnetic susceptibilities were calculated from the product of the magnetic field and the field gradient necessary for levitation. Second, polypropylene, polyamide, and poly(ethylene terephthalate) chips were separated by magnetic levitation. Magnetic levitation is shown to be a convenient and useful technique for both diamagnetic susceptibility measurements and magnetic separations of diamagnetic substances.
Enhancement of Dye Fluorescence by Gold Nanoparticles: Analysis of Particle Size Dependence
Authors: Nakamura Toshihiro , Hayashi Shinji
Published: September 2005

Rose Bengal was spun on spherical gold nanoparticles immobilized on a quartz plate by a silane coupling agent. The enhancement of the dye fluorescence was studied by changing the diameter of the gold nanoparticles from 20 to 250 nm. A maximum enhancement of dye fluorescence was observed at a size of 100 nm. We found good agreement between the experimental result and the theoretical calculation. From the theoretical analysis it is suggested that the maximum enhancement is obtained when the incident light and fluorescence light are in optimum resonance with the surface plasmons in the gold nanoparticles. These results demonstrate that the control of particle size is extremely important to obtain an optimum enhancement of dye fluorescence caused by metal particles.
Dispersibility of Amphibious Montmorillonite
Authors: Yeh Meng-Heng , Hwang Weng-Sing , Kuo Wuei-Jueng
Published: September 2005

The objective of this study is to develop a suitable method to convert hydrophilic montmorillonite into amphibious montmorillonite by replacing the sodium ions normally found in clay with poly(oxyethylene) (POE)-amide chlorite cations. Amphibious montmorillonite has a high d-spacing and good dispersion characteristics in many different types of solutions, including those having an intermediate hydrophilic lipophilic balance (HLB) value. Four different modifying cations are tested and X-ray diffraction analysis is performed to measure the resulting changes in the d-spacing of the MMT. Scanning electron microscopy is employed to investigate the morphology of the modified clays. A laser-doppler particle analyzer is used to measure the particle size of the clays in various solutions. Dobrat's method is applied to calculate the dispersibility of each clay and Stoke's law is used to evaluate the settling rate. The results indicate that the d-spacing of the POE-amide chlorite cation modified montmorillonite increases from 1.28 to 3.51 nm. The amphibious montmorillonite demonstrates good dispersion characteristics in eight commonly employed coating solutions with intermediate HLB values.
Preparation and Mechanical Properties of Polychloroprene–Montmorillonite Composites
Authors: Yeh Meng-Heng , Hwang Weng-Sing , Chang Yu-Chia
Published: September 2005

The principal objective of the present study is to improve the mechanical properties of polychloroprene through the addition of montmorillonite (MMT). Three modifying cations are tested. The polychloroprene–MMT composite is characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In general, the results indicate that the addition of MMT enhances the mechanical properties of polychloroprene. Furthermore, the mechanical properties of the composite are dependent not only on the particular MMT modifier, but also on the mixing process employed.
Electrical Resistivity of Carbon Micro Coil Measured by a Multi-Probe Unit Installed in a Scanning Electron Microscope
Authors: Kajihara Yukio , Hihara Takehiko , Sumiyama Kenji , Motojima Seiji
Published: September 2005

We have done four-terminal resistance measurement of a carbon micro-coil (CMC) using a multi-probe unit installed in a scanning electron microscope (SEM). With minimizing a charging effect of specimens for SEM observation, we have kept sufficient electrical insulation between the sample and the substrate. CMC shows an ohmic conduction and has a resistivity value of about 1.5×10-4 Ω m at room temperature. This resistivity measurement method will be applicable to other micro-scale samples.
ΔE×E Silicon Telescope of Energetic Heavy Ions Trapped in Radiation Belts
Authors: Matsumoto Haruhisa , Koshiishi Hideki , Goka Tateo , Fujii Masayuki , Hareyama Makoto , Kajiwara Nobuhiro , Kodaira Satoshi , Sakurai Kunitomo , Hasebe Nobuyuki
Published: September 2005

Heavy Ion Telescope (HIT) is an instrument onboard the Japanese satellite “TSUBASA”, which was launched in February 2002 for the observation of heavy ions in radiation belts. The HIT instrument, based on the ΔE×E particle identification method, consists of two position-sensitive silicon detectors and 16 PIN-type Si detectors with 420 µm in thickness. The geometric factor varies from 12 to 18 cm2 sr being dependent on the energy of ions. This instrument was designed to measure the fluxes of heavy ions from He to Fe nuclei in the energy range from 18 to 179 MeV/n, though dependent on the nuclear species to be measured. The nuclear charge separation in this instrument was highly sophisticated as 0.06 charge units for nuclei such as C and O, for instances, in observing energetic ions from He to Fe. Furthermore, isotopic separation was sufficient for the observations of nuclei such as He, Ne, Mg and Si. The observation of energetic ions in radiation belts was successfully achieved during both quiet and disturbed periods of solar activity. The detector system and observational results of ions in the radiation belts are described as the performance of the HIT instrument in space.
Current Injection Laser Oscillation in TlInGaAs/GaAs Double Quantum Well Diodes with InGaP Cladding Layers
Authors: Fujiwara Atsushi , Mukai Toshikazu , Matsumoto Takeshi , Hasegawa Shigehiko , Asahi Hajime
Published: September 2005

TlInGaAsN/AlGaAs heterostructures were proposed for use in the fabrication of temperature-stable lasing wavelength and threshold current laser diodes. As a first step, we grew TlInGaAs/GaAs quantum well (QW) structures on GaAs(100) substrates and demonstrated an electroluminescence (EL) emission of up to 300 K. Compared with InGaAs/GaAs QWs, we confirmed that the temperature variation of the EL peak energy was decreased by the addition of Tl into InGaAs. We also demonstrated the pulsed current injection laser oscillation in the TlInGaAs/GaAs double QW laser diodes with InGaP cladding layers up to 176 K.
Terahertz Wave Enhanced Transmission through a Single Subwavelength Aperture with Periodic Surface Structures
Authors: Ishihara Kunihiko , Hatakoshi Gen-ichi , Ikari Tomofumi , Minamide Hiroaki , Ito Hiromasa , Ohashi Keishi
Published: September 2005

We demonstrate resonantly enhanced transmission of terahertz (THz) wave radiation (λ∼200 µm) through a bull's eye structure (a single subwavelength aperture surrounded by concentric periodic grooves in a metal plate). The phenomenon is caused by the resonant excitation of surface waves, which are known as surface plasmon polaritons in the optical region, generated by the concentric periodic grooves. Strongly enhanced transmission of THz-wave radiation is observed through the single subwavelength circular aperture (diameterd= 100 µm). We also show that introducing the Bragg reflector to the bull's eye structure results in the further increase of the enhanced transmission.
Characterization of Silica-Nanoparticle-Dispersed Photopolymer Films that include Poly(methyl methacrylate) as Host Binder Material
Authors: Takahashi Hiroshi , Yamauchi Junya , Tomita Yasuo
Published: September 2005

Transmission volume holograms recorded in methacrylate photopolymer films doped with silica nanoparticles and transparent plastics are studied. It is found that poly(methyl methacrylate) (PMMA), which is a well-known host material for plastic dye lasers, works as an efficient host binder material and that a refractive index modulation of 0.005 is possible with PMMA of 50 vol %. It is also shown that silica nanoparticles at a concentration as high as 30 vol % can be uniformly dispersed in a monomer–PMMA mixture to form a volume holographic grating with a refractive index modulation of 0.005.
Experimental Study on Safe Performance of Nozzle-Type Electrostatic Neutralizer
Authors: Choi Kwang Seok , Yamaguma Mizuki , Kodama Tsutomu , Suzuki Teruo , Mogami Tomofumi
Published: September 2005

The safe performance of a nozzle-type electrostatic neutralizer was examined experimentally in inflammable gas (ethylene)–air mixtures. A 100 MΩ-coupled electrode produced ion pairs safely for reducing static charges from polymer materials, and incendiary discharges were suppressed by the resistor and voltage supplied to the electrode. The performance of the neutralizer (flange-type) driven with an AC (50 Hz) or DC high-voltage power source was also evaluated with a full-size pneumatic powder-transport system. It was confirmed that the nozzle-type neutralizer is markedly effective for reducing electrostatic charges from polymer materials; however, several disadvantages were also noted.
Simultaneously Suppressing Bandwidth and Divergence for a High-Power Laser-Diode Array with an External-Cavity Technique
Authors: Gao Xin , Ohashi Hiroyuki , Okamoto Hiroshi , Takasaka Masaomi , Saitoh Masayuki , Shinoda Kazunori
Published: September 2005

We report an external-cavity technique to simultaneously suppress the bandwidth and the divergence for a high-power laser-diode array, which features a stripe mirror and a volume Bragg grating. Using this technique, we have effectively suppressed the bandwidth from 1.81 to 0.91 nm and the divergence (1/e
2) from 7.5° to 2.3° with an output peak power of 9.3 W.
Lasing of Poly(3-alkylthiophene) in Microcapillary Geometry
Authors: Yoshida Yuichi , Nishimura Tetsuharu , Fujii Akihiko , Ozaki Masanori , Yoshino Katsumi
Published: September 2005

We have demonstrated the lasing of poly(3-alkylthiophene) thin films in microcapillaries. The microcavities in the microcapillaries have excellent advantages over conventional microrings. The inner emission layer is covered and protected from the outside environment only by enclosing glass tube. A high-quality polymer thin film could be obtained by spontaneous capillary action at the inside surface of the microcapillary. We also compared the microcapillary with conventional microring structures by spectral analysis using a Fourier transform.
Ta-doped Anatase TiO2 Epitaxial Film as Transparent Conducting Oxide
Authors: Hitosugi Taro , Furubayashi Yutaka , Ueda Atsuki , Itabashi Kinnosuke , Inaba Kazuhisa , Hirose Yasushi , Kinoda Go , Yamamoto Yukio , Shimada Toshihiro , Hasegawa Tetsuya
Published: September 2005

We present electrical transport and optical properties of Ta-doped TiO2 epitaxial thin films with varying Ta concentration grown by the pulsed laser deposition method. The Ti0.95Ta0.05O2 film exhibited a resistivity of 2.5×10-4 Ω cm at room temperature, and an internal transmittance of 95% in the visible light region. These values are comparable to those of a widely used transparent conducting oxide (TCO), indium tin oxide. Furthermore, this new material falls into a new category of TCOs that utilizes d electrons.
Multiwavelength Er-Doped Fiber Ring Laser Incorporating Highly Nonlinear Fiber
Authors: Yamashita Shinji , Inoue Yukihiro
Published: September 2005

We demonstrate a multiwavelength Er-doped fiber ring laser using a fiber Fabry–Perot interferometer as the comb filter. By simply incorporating a highly nonlinear fiber (HNLF), multiwavelength lasing over a wavelength range of 40 nm is achieved at room temperature. We found that the self-phase modulation (SPM) and the four-wave mixing (FWM) in the HNLF enables the multiwavelength lasing.
Alignment Method of Polymer Waveguide and Optical Component using Fluorescence
Authors: Hasegawa Masaki
Published: September 2005

We have developed a new method of aligning the optical axes of a polymer waveguide (PWG) and the optical components without monitoring the intensity of light passing through them. A light path can be seen as a fluorescent image from PWG material excited by an incident light without adding any fluorescent dyes. By observing the intensity and shape of such a light path, the optical axes of the input optical components and PWG can be adjusted without monitoring the output power passing through them. This alignment method can be applied to the assembly of a complicated optical system that consists of PWGs and optical components, such as mirrors and microlenses.
InAs Quantum Dot Lasers with Extremely Low Threshold Current Density (7 A/cm2/Layer)
Authors: Shimizu Hitoshi , Saravanan Shanmugam , Yoshida Junji , Ibe Sayoko , Yokouchi Noriyuki
Published: September 2005

This paper describes the successful stacking of multilayered InAs quantum dots (QD) on a GaAs substrate up to 12 layers. The laser oscillated from the ground state under the condition of mirror loss at less than 7–8 cm-1. The extremely low threshold current density per QD-layer of 7 A/cm2/layer was obtained with a lasing wavelength of 1.21 µm at room temperature, which is the lowest value for any known semiconductor laser.
InAsSbN Quantum Well Laser Diodes Operating at 2-µm-Wavelength Region Grown on InP Substrates
Authors: Kawamura Yuichi , Nakagawa Tomokatsu , Inoue Naohisa
Published: September 2005

InAsSbN quantum well laser diodes operating at a 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 2.51 µm at room temperature. In addition, laser operation at 2.31 µm was obtained at 190 K without postgrowth thermal annealing, where the threshold current density was 4.1 KA/cm2 and the T
0 value estimated for the temperature range from 50 to 190 K was 60 K.
Polymer-Coated Silicon Micromirror Array for Integrated Optical Pickup Application
Authors: Lee Myung Bok , Kim Hae Sung , Sohn Jin Seung
Published: September 2005

Fabrication of a micromirror array for the development of an integrated optical pickup using a blue laser diode is demonstrated. The micromirror array can be obtained by combining silicon wet etching and polymer UV embossing. Conventional wet etching of a Si(100) wafer that is cut with a 9.7° tilt toward the <110> direction can produce 45° mirrors; however, the surface roughness is not sufficiently low for the application to optical pickup. To overcome this, we compensated the surface roughness by the addition of polymer UV embossing with a precise glass master mold onto the wet-etched Si surface. The surface roughness of polymer-coated mirror was lower by one-eighth compared to the etched-Si mirror, satisfying the specifications of a mirror for the optical pickup.
Uniform Vertical Alignment of Liquid Crystal That Has a Large Negative Dielectric Anisotropy
Authors: Chen Cheng , Anderson James E. , Bos Philip J.
Published: September 2005

We report that when a material that has a longitudinal dipole, (and therefore a positive dielectric anisotropy), is added to liquid crystalline materials that have a large negative dielectric anisotropy, that greatly improved vertical alignment is achieved. Specifically the addition of 5CB, with a weight percentage ranging from 2% to higher than 10%, to a commercial high negative Δε material, is found to change the alignment of the mixture from homogeneous to vertical. We also provide an explanation of the contradiction of this result with previous predictions that materials with a negative dielectric anisotropy should favor vertical alignment, while positive materials should favor homogeneous alignment.
Eddy Current Testing Utilizing Cooled Normal Pickup Coil and Superconducting Quantum Interference Device Picovoltmeter
Authors: Yang Tong Qing , Yao Kenichiro , Yamasaki Daisuke , Enpuku Keiji
Published: September 2005

An eddy current probe utilizing a cooled normal pickup coil and a high-Tcsuperconducting quantum interference device (SQUID) picovoltmeter was developed. The pickup coil could be moved in an unshielded environment, during which the signal voltage across the pickup coil was transferred to the SQUID picovoltmeter, which was fixed in a cylindrical magnetic shield. By moving the pickup coil, we successfully detected a small crack on the back surface of a Cu plate in the unshielded environment. The dependences of the detected signal on the excitation frequency and thickness of the Cu plate were clarified. The frequency dependence could be used to estimate the depth of the crack from the surface of the Cu plate.
Observation of Intense Bursts of Terahertz Synchrotron Radiation at UVSOR-II
Authors: Takashima Yoshifumi , Katoh Masahiro , Hosaka Masahito , Mochihashi Akira , Kimura Shin-ichi , Takahashi Toshiharu
Published: September 2005

We have detected very intense bursts of terahertz synchrotron radiation at the UVSOR-II electron storage ring operated in single bunch mode. The bursts were observed in the wavelength range from 0.2 to 3.0 mm by using a liquid-helium-cooled InSb hot-electron bolometer. The typical duration and interval of the bursts were about 200 µs and 10–15 ms, respectively. Each burst shows the quasi-periodic structure of about 30 µs. The peak intensity of the bursts was about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength was much shorter than the electron bunch length.
Intermolecular Interaction by Apical Oxygen in Titanyl Phthalocyanine
Authors: Harada Yoshihisa , Tokushima Takashi , Takata Yasutaka , Kamakura Nozomu , Takeuchi Tomoyuki , Kobayashi Keisuke , Shirota Yasuhiko , Shin Shik
Published: September 2005

Local charge distribution around the titanium atom of amorphous and α-crystalline TiOPc films was investigated using Ti 2 p X-ray absorption and emission spectroscopy. The X-ray emission spectra show two characteristic features that correspond to charge transfer states that result from in-plane Ti–N and apical Ti–O hybridizations. In the amorphous phase, the Ti–O charge transfer state has both localized and delocalized properties, whereas in the α-crystalline phase it has only the delocalized property. These different properties evidence the role of the oxygen atom in forming a network with a neighboring molecule and in balancing the total dipole moment in the α-crystalline phase.
Enhancement of Blue Emission from Mg-Doped GaN Using Remote Plasma Containing Atomic Hydrogen
Authors: Kamiura Yoichi , Kaneshiro Masahiro , Tamura Jin , Ishiyama Takeshi , Yamashita Yoshifumi , Mitani Tomotsugu , Mukai Takashi
Published: September 2005

We have found for the first time that blue emission from Mg-doped GaN was greatly enhanced by remote plasma treatment (RPT) with plasma containing atomic hydrogen, in particular, water vapor plasma, at low temperatures of 300–400°C. The highest enhancing factor was twenty, achieved by water vapor RPT at 400°C for 30 min. The enhanced blue emission was stable up to 500°C, similarly to blue emission from as-grown samples, suggesting the same origin and mechanism. We have confirmed that the emission mechanism is donor–acceptor pair (DAP) recombination, and have concluded that RPT produces a hydrogen-related donor level at E
c-0.37 eV involved in the DAP emission.
Research on Operating Degradation of Pentacene Thin-Film Transistors
Authors: Hu Yan , Dong Guifang , Liang Yan , Wang Liduo , Qiu Yong
Published: September 2005

The degradation mechanism of pentacene thin-film transistors under operating mode in contrast to static mode was researched. More rapid degradation was found under operating mode than under static mode. After a systematic analysis, it was concluded that the reasons lie in the change of the interface between the insulator layer and the semiconductor layer, the doping of mobile impurities in the conductive channel, the degradation of the gate insulator, and the heat induced in the operating process.
Synthesis of Crooked Gold Nanocrystals by Electrochemical Technique
Authors: Huang Chien-Jung , Chiu Pin-Hsiang , Chen Ming-Da , Meen Teen-Hang
Published: September 2005

In this article, we demonstrate the synthesis of crooked gold nanocrystals (CGNCs) by an electrochemical technique using micelle templates formed by two surfactants with different amounts of isopropanol solvent, the primary surfactant being hexadecyltrimethylammonium bromide (C16TABr) and the cosurfactant being tetradodecylammonium bromide (TC12ABr). To investigate the influence of isopropanol solvent on the CGNCs, the amount of isopropanol was varied in the range from 50 to 300 µL. It was found that the aspect ratios (γ) of CGNCs were in the range from 1.06 to 1.46, and the UV–vis optical absorption measurement revealed a pronounced redshift of the surface plasmon band from 532 to 560 nm. The CGNCs were composed of many large gold grains with small gold nuclei, and it was determined that several grains are present within each of the CGNCs using a dark-field transmission electron microscopy (TEM) image. It is suggested that the CGNCs have a polycrystalline structure. The CGNCs have been determined to be pure gold with a face-centered cubic (fcc) structure by electron diffraction (ED) analysis.
Milliwatt Power Blue InGaN/GaN Light-Emitting Diodes on Semipolar GaN Templates
Authors: Chakraborty Arpan , Baker Troy J. , Haskell Benjamin A. , Wu Feng , Speck James S. , Denbaars> Steven P. , Nakamura Shuji , Mishra Umesh K.
Published: September 2005

Growth of semipolar Group-III nitrides based devices offers a means of reducing the deleterious effects of the polarization-induced electric fields present in the polar quantum wells. We report on the fabrication of blue InGaN/GaN multiple-quantum well light-emitting diodes (LEDs) on semipolar (10-1-1) and (10-1-3) oriented GaN templates. A maximum on-wafer continuous wave output power of 190 µW was measured at 20 mA for 300×300 µm2 devices, and output power as high as 1.53 mW was measured at 250 mA. Drive-current independent electroluminescence peak at 439 nm was observed for the LEDs grown on both the planes. The current–voltage characteristics of these LEDs showed rectifying behavior with a forward voltage of 3–4 V at 20 mA.