bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomalous Uphill Diffusion and Dose Loss of Ultra-Low-Energy Implanted Boron in Silicon during Early Stage of Annealing
Authors: Tsuji Hiroshi , Furuhashi Masayuki , Tachi Masayuki , Taniguchi Kenji
Published: February 2005

Uphill diffusion of boron implanted with 0.5 keV in silicon was investigated under nonamorphizing implant conditions. Postimplantation annealing at temperatures above 400°C induces the uphill diffusion of boron, which can be observed in an initial stage of annealing. The uphill diffusion is significantly suppressed by additional Si implantation into the boron implant region, suggesting that the uphill diffusion is mediated by the excess free self-interstitials during the annealing. Also, the uphill diffusion causes severe dose loss of implanted boron to the Si/SiO2 interface.
Polycrystalline Silicon Thin Film for Solar Cells Utilizing Aluminum Induced Crystallization Method
Authors: Ishikawa Yasuaki , Nakamura Atsushi , Uraoka Yukiharu , Fuyuki Takashi
Published: February 2005

In order to realize a polycrystalline silicon (poly-Si) thin film solar cell with low cost and high efficiency, high-quality poly-Si is indispensable. We fabricated a high-quality poly-Si film by using aluminum induced crystallization (AIC) as a method of crystallizing amorphous silicon. AIC is a method of crystallizing amorphous silicon by heat treatment below the eutectic temperature (577°C). Using AIC poly-Si film as the seeding layer and atmospheric pressure chemical vapor deposition (APCVD), continuous columnar poly-Si with large grain size was achieved. Deposition of the poly-Si thin film onto AIC poly-Si films was carried out using APCVD. Crystallinity and electronic property of the deposited films was evaluated. Comparably high Hall mobility of more than 80 cm2/Vs was successfully obtained.
Highly Selective Removal of Residual Deposited Films and Oxide Hard Masks on Polysilicon Gate Electrodes in Anhydrous HF Gases
Authors: Tuda Mutumi , Shintani Kenji , Tanimura Junji
Published: February 2005

This paper presents new vapor-phase HF processes, developed for highly selective removal of residual deposited films of etch by-products and oxide hard masks, following polysilicon gate etching. Etching of thin gate oxides in anhydrous HF gases, after exposure to an HBr/O2plasma in the gate etch process, was investigated by X-ray photoelectron spectroscopy and transmission electron microscopy. During exposure to an HBr/O2plasma, a SiBrxOylayer was formed at the near-surface region of the gate oxide. The delay or incubation time to start etching in HF gases was different between the SiBrxOyand underlying undamaged SiO2layers. Moreover, the etch rates of SiBrxOyand chemical-vapor-deposition oxides used as a mask material were much higher than that of SiO2. By utilizing these differences in incubation time and etch rate, sidewall deposition films and oxide masks on poly-Si gate electrodes were completely removed without side etching or notching of thin gate oxides.
Intensity-Invariable Raman Scattering in an Ethanol-Silica Photonic Crystal with a Varying Pseudogap
Authors: Liu Xiao-Dong , Ni Pei-Gen , Cheng Bing-Ying , Jin Chong-Jun , Zhang Dao-Zhong
Published: February 2005

We have measured the Raman scattering intensities, which are induced by a picosecond intense laser, of an ethanol-silica photonic crystal (ESPC) with a pseudogap varying with the height (up from the inner bottom of the cuvette) of the ESPC. We find that, although the center wavelength of Raman signals (RSs) generated within the ESPC is almost in the pseudogap, the total intensity of the RSs is not reduced relative to the total intensity generated at other positions. It is also found that, although the transmission of an incident beam with the wavelength of the RSs is greatly dependent on the height of the ESPC, the intensity of the RSs generated within the ESPC does not change with this height. Both anti-intuitive phenomena, we think, can be demonstrated using the different propagation mechanisms between the incidental laser and inner light sources inside a PC.
High-Spatial-Resolution Multichannel Thomson Scattering Measurements for Atmospheric Pressure Microdischarge
Authors: Kono Akihiro , Iwamoto Kazushige
Published: February 2005

High-spatial-resolution multichannel Thomson scattering measurement scheme is applied to the diagnostics of a microplasma produced between two knife-edge electrodes separated by a 100 µm microgap and driven by 2.45 GHz microwave. The method provides spatial profile of electron density, electron temperature, and gas temperature simultaneously in a single measurement, with a spatial resolution of ∼25 µm; the gas temperature is derived from the spectrum of rotational Raman scattering caused by molecules contained in the discharge gas. Measurements are carried out for discharges with air and He/N2(5%) mixture gas at atmospheric pressure and the differences in the basic plasma parameters are discussed.
Microstructure and Piezoelectric Properties of ZnO-added (Na0.5K0.5)NbO3 Ceramics
Authors: Park Seung-Ho , Ahn Cheol-Woo , Nahm Sahn , Song Jae-Sung
Published: February 2005

The orthorhombic structure of (Na0.5K0.5)NbO3 (NKN) ceramics was maintained when ZnO was added. NKN ceramics have a porous microstructure and dissolve when they are exposed to water. However, as ZnO was added, a dense microstructure was developed and deliquescence was not observed. The mechanical quality factor (Q
m) and coercive field (E
c) increased with the addition of ZnO, indicating that ZnO acted as a hardener in the NKN ceramics. The dielectric constant (ε
T
3/ε
o), piezoelectric constant (d
33) and electromechanical coupling factor (k
p) increased when a small amount of ZnO was added, which might be due to the increase in density. The good dielectric and piezoelectric properties of ε
T
3/ε
o = 500, d
33 = 121 and k
p=0.4 were obtained for the NKN ceramics with 1.0 mol% ZnO.
Zn1-xCdxO Film Growth Using Remote Plasma-Enhanced Metalorganic Chemical Vapor Deposition
Authors: Shigemori Satoshi , Nakamura Atsushi , Ishihara Junji , Aoki Toru , Temmyo Jiro
Published: February 2005

Zn1-x
Cd
x
O films were successfully grown by remote plasma-enhanced metalorganic chemical vapor deposition (RPE-MOCVD). The content ratio of Zn1-x
Cd
x
O films was controlled by changing the molar ratio of diethyl zinc (DEZn) to dimethyl cadmium (DMCd). The wurtzite structure of Zn1-x
Cd
x
O films was obtained by increasing the Cd content up to x=0.697. The optical-band-gap energy of Zn1-x
Cd
x
O films was tuned between 1.85 eV and 3.28 eV at room temperature. The photoluminescence emission of hexagonal Zn1-x
Cd
x
O films up to x = 0.697 was observed at room temperature.
Three-Dimensional Nanofabrication with 10-nm Resolution
Authors: Yamazaki Kenji , Yamaguchi Toru , Namatsu Hideo
Published: February 2005

We have devised three-dimensional (3D) nanofabrication technology using electron-beam (EB) lithography and a sample-rotation drive. Ten-nm resolution of patterning over a 3D sample and 3D fabrication was achieved by precise control of beam focusing for patterns divided based on the depth of focus of the EB. The focus control is carried out using an offline height-measurement system we developed, which provides focusing error of less than 2 µm. The depth of focus was accurately derived using the wave optical method. We have demonstrated these techniques and the resulting resolution by making the world's smallest globe, which shows the minimum feature size of 10 nm over the world map.
In-Vivo Imaging of Cancer Implanted in Nude Mice by Two-Crystal Interferometer-Based Phase-Contrast X-Ray Computed Tomography
Authors: Takeda Tohoru , Yoneyama Akio , Wu Jin , Lwin Thet Thet , Tsuchiya Yoshinori , Hyodo Kazuyuki
Published: February 2005

Using the wave nature of X-rays, in-vitro phase-contrast X-ray imaging can clearly reveal the detailed inner structures of cancer in human and rabbit. In this study, using a newly developed imaging system with a two-crystal interferometer and the Fourier data acquisition technique, we presented, for the first time, in-vivo phase-contrast X-ray computed tomography (CT) images of cancer implanted in nude mice. The two-crystal interferometer, which helps to eliminate the distortion of the half mirror of an X-ray interferometer due to the heat from live animals, was the key device for successful in-vivo imaging. CT images obtained using the Fourier technique were available in approximately 40 min while the animal was still under anesthesia.
Properties of Defect Traps in Triple-Stack InAs/GaAs Quantum Dots and Effect of Annealing
Authors: Chen Jenn-Fang , Hsiao Ru-Shang , Shih Shen-Hung , Wang Pai-Yong , Wang Jyh-Shyang , Chi Jim Y.
Published: February 2005

The electrical and optical properties of the defect traps, with and without annealing, in InAs/GaAs quantum dots (QDs) emitting at 1.3 µm are investigated by capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS) and photoluminescence (PL). When increasing the InAs thickness to 3 ML, an abnormal temperature dependence of the C-V characteristic was observed in the triple-stack InAs/GaAs QD sample. This temperature dependence is attributed to the defect levels at 0.39 and 0.54 eV observed in DLTS. The level at 0.39 eV, found in the top GaAs barrier, is probably related to the relaxation-induced dislocations. The level at 0.54 eV is found close to the QD region. Rapid thermal annealing can reduce the concentrations of both levels. Comparing with PL result, which shows a blueshift of 140 meV and linewidth narrowing in the QD emission by annealing at 800°C, the level at 0.54 eV is speculated to be strain- or relaxation-related defects in the interface between the QDs and the barrier. Removal of this level by high-temperature RTA is important since this level lies close to the QDs and influences the optical quality of the QDs.
Near-Field Optical Recording Using a Micromachined Silicon Aperture Probe
Authors: Lee Myung Bok
Published: February 2005

Near-field optical recording using a micromachined silicon planar aperture probe was demonstrated. In contrast to conventional optical fiber probe which has been employed to near-field optical recording, the silicon probe has the advantage of mass producibility and high reliability as well as ease of optoelectronic device integration. Modification of cross-sectional profile by combining wet and dry etching resulted in the increase of light transmission efficiency of the probe by several times. By using a contact-type slider head with the aperture of 200 nm in diameter, we successfully recorded marks as small as 300 nm on a TbFeCo magneto-optical (MO) thin film as observed by magnetic force microscopy.
Electron Density Control Using Fast Gas Puffing in Reversed-field Pinch Device, TPE-RX
Authors: Sakakita Hajime , Yagi Yasuyuki , Koguchi Haruhisa , Hirano Yoichi , Shimada Toshio , Canton Alessandra M. , Innocente Paolo
Published: February 2005

Electron density is scanned using fast gas puffing in the reversed-field pinch (RFP) device, TPE-RX. The gas puffing technique extends the operating range of I
P/N from 12 to 2 ×10-14 Am (I
P and N denote the plasma current and line density, respectively). It is estimated that the poloidal beta, βP, increases as I
P/N decreases. This βP scaling with I
P/N in TPE-RX confirms a similar tendency previously obtained in other RFP plasmas. The radiation fraction increases from ∼20% in the low-density regime to ∼35% in the highest-density regime. This result indicates that the lowest I
P/N limit in RFP is similar to the density limit in tokamak plasmas.
Properties of Hydrogenated Microcrystalline Cubic Silicon Carbide Films Deposited by Hot Wire Chemical Vapor Deposition at a Low Substrate Temperature
Authors: Miyajima Shinsuke , Yamada Akira , Konagai Makoto
Published: February 2005

Stoichiometric hydrogenated microcrystalline cubic silicon carbide (µc-3C-SiC:H) films were successfully deposited by hot wire chemical vapor deposition (HWCVD) at a substrate temperature of 280°C using monomethylsilane and hydrogen. The ratio of hydrogen to monomethylsilane (hydrogen dilution ratio) strongly affected the structural and electrical properties of µc-3C-SiC:H films. Subgap absorption measurements on the films revealed that the defect density of the films was influenced by hydrogen dilution ratio. This result indicates that hydrogen dilution ratio is one of the key parameters for obtaining µc-3C-SiC:H with low defect density.
Influence of Elastic Scattering on the Neutron-Induced Single-Event Upsets in a Static Random Access Memory
Authors: Arita Yutaka , Takai Mikio , Ogawa Izumi , Kishimoto Tadafumi
Published: February 2005

Neutron single-event upsets (SEUs) induced by elastic scattering were investigated by an experiment using 2 MeV neutron beams and by a calculation based on scattering cross-section data and angular distribution data from the evaluated nuclear data file (ENDF). The SEU rates obtained by the calculation and experiment are in fairly good agreement if the region sensitive to the SEUs (sensitive volume) is properly defined. Adopting the calculation to atmospheric neutrons, the fraction of the SEU rates induced by elastic scattering accounted for approximately 26 to 32% of the total fast-neutron-induced SEUs in the atmospheric neutron environment. Reducing well depth will effectively reduce the number of SEUs.
Preparation and Thermoelectric Properties of Misfit-Layered Sulfide [Yb1.90S2]0.62NbS2
Authors: Miyazaki Yuzuru , Ogawa Hidenori , Kajitani Tsuyoshi
Published: February 2005

We have prepared polycrystalline samples of Yb-Nb-S-based misfit-layered compound and measured their thermoelectric properties below 300 K. The compound consists of an alternate stacking of a trigonal prism (MoS2)-type [NbS2] layer and a two-layered rock-salt-type [Yb1.90S2] slab, being incommensurate parallel to the a-axis. Approximately 5% Yb deficiency is necessary to obtain single-phase samples. Metallic conductivity accompanied by a large Seebeck coefficient S has been observed down to 4.2 K for the single-phase samples. At 300 K, the sample exhibits S = 60 µV·K-1 and resistivity of ρ= 1.4 mΩ·cm, with thermal conductivity of κ= 0.80 W·K-1·m-1. The resulting figure-of-merit (Z = S
2/ρκ) becomes 3.2×10-4 K-1 at 300 K, yielding the dimensionless figure-of-merit of Z
T∼0.1.
Viewing Angle Characteristics of Transflective Display in a Homogeneously Aligned Liquid Crystal Cell Driven by Fringe-Field
Authors: Jung Tae Bong , Song Je Hoon , Seo Dae-Shik , Lee Seung Hee
Published: February 2005

We have studied the optimal cell configuration for a fringe-field driven transflective liquid crystal display that exhibits high image quality. The cell is composed of two half-plate compensation films, liquid crystal, and two parallel polarizers in the transmissive region. Viewing angle characteristics of the device mainly depends on the orientation of the polarizer axis. The measured contrast ratio in an optimized configuration is greater than 5 in polar angles of over 50° in all directions and in those over 80° in certain azimuthal cross-sectional planes.
Rapid Growth of Vertically Aligned Carbon Nanotubes
Authors: Suekane Osamu , Nagasaka Takeshi , Kiyotaki Kazuo , Nosaka Toshikazu , Nakayama Yoshikazu
Published: February 2005

100-µm-long vertically aligned multiwall carbon nanotubes were grown in 1 s. A thermal chemical vapor deposition method at 700°C was used with a catalyst of iron films and a carbon source gas of acetylene diluted with helium. This study revealed a novel rapid growth mode that appears in the beginning of chemical vapor deposition when the rate of increase in the concentration of carbon source gas is high at the substrate. This new growth mode, which precedes a normal growth mode, provides well-crystallized and straight nanotubes.
Enhancement of Critical Current Density in ErBa2Cu3Oy Thin Films by Post-Annealing
Authors: Horii Shigeru , Ichinose Ataru , Mukaida Masashi , Matsumoto Kaname , Ohazama Tohru , Yoshida Yutaka , Shimoyama Jun-ichi , Kishio Kohji
Published: February 2005

We report a remarkable increase in critical current density (J
c) by oxygen post-annealing for only a few tens of minutes in ErBa2Cu3O
y
films fabricated at two different pulsed-laser-deposition (PLD) temperatures of 720°C and 760°C. The J
c of these films were obviously enhanced to more than 1 MA·cm-2 in the annealing temperature range of 350°C–500°C in comparison with those of the as-deposited films (0.3–0.5 MA·cm-2). Even in a nonequilibrium process such as the PLD method, the homogenization of oxygen contents in films is crucial for enhancement of the films' critical current properties, which suggests that oxygen post-annealing is a practical process for improvement of critical current of PLD-REBa2Cu3O
y
coated conductors.
p-Type Doping Characteristics of GaInNAs:Be Grown by Solid Source Molecular Beam Epitaxy
Authors: Matsuura Tetsuya , Miyamoto Tomoyuki , Makino Shigeki , Ohta Masataka , Matsui Yasutaka , Koyama Fumio
Published: February 2005

We investigated the doping and electrical characteristics of p-type GaInNAs for use in a p-contact layer and in the p-distributed Bragg reflectors ( p-DBRs) of surface emitting lasers. Beryllium doping was applied to GaInNAs grown by solid source molecular beam epitaxy with the nitrogen radical. The doping efficiency for the lattice-matched GaInNAs is similar to that of the GaAs, and a slight deterioration in hole mobility indicates the alloy scattering of the GaInNAs.
The Impact of Supercritical Fluoro-Compounds on Lithography Use
Authors: Namatsu Hideo
Published: February 2005

This article describes the use of supercritical fluoro-compounds for supercritical resist drying. In contrast to carbon dioxide, fluoro-compounds, which are heavier than water in liquid form, can displace the rinse water on the resist due to the difference in specific gravity. The removal of rinse water from a sample surface by replacing it with a liquid fluoro-compound, followed by the conversion of the compound to the supercritical state, enables patterns to be formed without collapse and without the use of a surfactant. Furthermore, with the help of helium, which can be released quickly from the chamber, the use of supercritical fluoro-compounds like C2HF5 and SF6 also enable the very fast supercritical resist drying of water-rinsed resists for advanced lithography.
Specific Volume of Fluorine-Doped Silica Glass with Various Fictive Temperatures
Authors: Kakiuchida Hiroshi , Saito Kazuya , Ikushima Akira J.
Published: February 2005

The specific volume of silica glass was measured as a function of fictive temperature and the concentration of fluorine dopant up to 1550°C and 7.2 mol%, respectively. It was found that the relationship between volume and fictive temperature is strongly influenced by the fluorine dopant. The rate of change in volume to change in fictive temperature, which is negative for pure silica glass, increases linearly with increasing fluorine concentration and then becomes positive at the concentration higher than 3.3 mol%. On the other hand, the relationship between fictive temperature and spatially averaged structure, observed by infrared absorption and Raman spectra, is negligibly affected by the dopant. Such a difference between behaviors in the density and in the vibrational spectra indicates the possibility that with varying fictive temperature, a structural change in the local volume around the doped fluorine is much larger than the average structural change over the whole volume in the bulk.
Narrow-Band Channel-Dropping Filter Based on Side-Polished Fiber with Long Interaction Length
Authors: Chen Nan-Kuang , Chi Sien , Tseng Shiao-Min
Published: February 2005

We demonstrate an all-fiber channel-dropping filter comprising a 2 ×2 side-polished fiber coupler with long coupling length and a narrow-band fiber Bragg grating. The side-polished fibers are fabricated on a silicon wafer acting as a polishing substrate while the alignment V-grooves are simultaneously prepared. Two polished fibers with an intracore Bragg grating between them are combined as a grating-frustrated coupler, and a low-loss channel-dropping filter was achieved with the spectral bandwidth less than 2 nm (25 dB), dropping efficiency greater than 98% and channel isolation greater than 25 dB. The filter can be manufactured through a fast and reliable fabrication process.
Recoverable Residual Image Induced by Hysteresis of Thin Film Transistors in Active Matrix Organic Light Emitting Diode Displays
Authors: Kim Byeong-Koo , Kim Ohyun , Chung Hoon-Ju , Chang Jae-Won , Ha Yong-Min
Published: February 2005

A recoverable residual image is observed and analyzed in voltage driven active matrix organic light emitting diode (AMOLED) displays of which pixel circuits consist of two thin film transistors (TFTs) and one capacitor. The cause of the residual image is proven to be the hysteresis of the driving TFT in the pixel. The hysteresis of the p-channel TFT can be explained by hole trapping and de-trapping at the interface region of the channel. The recovery time of the residual image also strongly depends on the hysteresis level. We have found that the residual image can be eliminated by reducing the hysteresis level of TFTs.
Boron Doping for p-Type β-FeSi2 Films by Sputtering Method
Authors: Liu Zhengxin , Osamura Masato , Ootsuka Teruhisa , Wang Shinan , Kuroda Ryo , Fukuzawa Yasuhiro , Suzuki Yasuhito , Mise Takahiro , Otogawa Naotaka , Nakayama Yasuhiko , Tanoue Hisao , Makita Yunosuke
Published: February 2005

High quality epitaxial β-FeSi2 thin films prepared by alternate Fe/Si multilayers stacking were doped for p-type by co-sputtering of silicon and boron, in which elemental boron chips were placed on silicon target. The starting β-FeSi2 films before doping were n-type with residual electron concentration of about 2 ×1017 cm-3 and mobility of about 200 cm2/V·s. After doping with boron, β-FeSi2 films showed the same epitaxial crystallinity with continuous structure as that of non-doped one. Doping level of p-type β-FeSi2 films with net hole concentration from 3 ×1017 to 1 ×1019 cm-3 and mobility from 100 to 20 cm2/V·s were successfully achieved. Desired net hole concentration was obtained by varying the area ratio of boron chips on silicon target.
Effect of Thickness on the Microwave Dielectric Properties of (Mg0.93Ca0.07)TiO3 Thin Films
Authors: Lee Byoung Duk , Lee Hong Ryul , Yoon Ki Hyun , Cho Yong S.
Published: February 2005

The effect of thickness on microwave dielectric properties of the (Mg0.93Ca0.07)TiO3 (MCT) thin films prepared by the metalorganic solution deposition technique were investigated. It could be obtained a well-crystallized MCT thin films annealed at lower temperature of 800°C compared with the bulk ceramics. As the thickness of MCT films increased up to 2 µm, the dielectric constants of MCT films were found to increase from 21 to 30 due to the reduction of interfacial dead layers effect with low dielectric constant at both electrodes. Also, the dielectric losses of MCT films tended to decrease to 0.0004 ±0.0001 with increasing the thickness up to 2 µm due to the reduced stresses. But, the temperature coefficients of dielectric constant (TCK) of MCT films measured at 6 GHz were about +10 ppm/°C independent of thickness.
Thermoelectric Properties of Y-Doped Polycrystalline SrTiO3
Authors: Obara Haruhiko , Yamamoto Atsushi , Lee Chul-Ho , Kobayashi Keizo , Matsumoto Akihiro , Funahashi Ryoji
Published: February 2005

The thermoelectric properties of Y-doped polycrystalline SrTiO3 (Sr1-x
Y
x
TiO3) are measured from 10 K to 900 K. The Y component is doped up to the solubility limit of Sr1-x
Y
x
TiO3, x=0.1. The Y-doped polycrystalline samples show a low resistivity, ∼1 ×10-5 Ω·m and a large absolute value of the Seebeck coefficient, ∼150 µV/K, at room temperature. Consequently, they have a high power factor, 1.2 ×10-3 W/mK2, defined as PF=S
2/ρ, where S is the Seebeck coefficient and ρ is the resistivity. Furthermore, we observe a decrease in the thermal conductivity of SrTiO3 due to phonon scattering by the Y dopant.
Solvent Vapor Posttreatment of Polymer Films in Polymer Light-Emitting Diodes
Authors: Liu Chen , Zou Xuecheng , Yin Sheng
Published: February 2005

A promising approach called solvent vapor posttreatment, which can control the interchain interactions of polymer films in polymer light-emitting diodes (PLEDs), is reported in this paper. This method leaves the degree of interchain interactions in polymer films in a state similar to that if the films were spin-cast directly from that solvent. When the treatment time is selected appropriately, the film morphology of the surface film is changed without a change in the bulk film. Therefore the heterostructure is formed, which improves the electroluminescence performance of PLEDs.
Plasma Oscillations in Terahertz Photomixing High-Electron-Mobility Transistor Structure on p+-Substrate
Authors: Satou Akira , Vyurkov Vladimir , Khmyrova Irina
Published: February 2005

The excitation of plasma oscillations in a channel of a high-electron-mobility transistor (HEMT) induced by optical illumination for terahertz (THz) generation requires a back contact to collect photogenerated holes. In particular, it could be a heavily doped p+-substrate. The effect of such a substrate on plasma oscillations in the channel is considered. Both possible reasons for oscillation damping, hole collisions and heavy hole–light hole transitions, are taken into account. We show that for properly designed structures, the influence of the p+-substrate on plasma oscillations can be negligible.
Effect of Temperature Differences on Adatom Diffusion and Growth of Nano-Islands on Si(100) Surfaces
Authors: Toyoshima Saori , Kawamura Takaaki
Published: February 2005

In the fabrication of nano-islands on a surface without any supply of atoms from the outside, the effect of temperature differences on the surface is studied using a kinetic Monte Carlo simulation. By locating a low-temperature region on a Si(100)-2×1 surface at 800 K, morphological variations on the surface are investigated. When the temperature is less than 730 K, an island forms in the region. If the nucleus of growth is placed in the region in advance, the critical temperature for growth is lowered. The growth condition of islands may be explained by analyzing the hopping rates of atoms on the surface.
An Anomalous Peak on Intermediate Frequency Response of Superconductor-Isolator-Superconductor Mixers and Its Effect on Mixing Performance
Authors: Shan Wenlei , Wang Mingjye , Shi Shengcai , Irimajiri Yoshihisa , Noguchi Takeshi
Published: February 2005

In this paper, we mainly investigate the origin and impact of an anomalous peak observed on the intermediate frequency (IF) response of some 600 GHz Nb superconductor-isolator-superconductor (SIS) mixers. The dependences of the IF peak on temperature and magnetic field are studied to verify its Josephson-junction-like behavior. The cross sections of two SIS junction samples are analyzed by transmission electron microscopy to locate this parasitic Josephson weak link. Five different junction samples are measured to determine the impact of the Josephson weak link on the mixer performance. Finally, an equivalent circuit model is proposed to explain its behavior.
Determination of Polar Anchoring Strength at Vertical Alignment Nematic Liquid Crystal-Wall Interface Using Thin Hybrid Alignment Nematic Cell
Authors: Hung La Trong , Oka Shinichirou , Kimura Munehiro , Akahane Tadashi
Published: February 2005

A method of determining the polar anchoring strength W
d of a vertical alignment nematic liquid crystal-wall interface is proposed. W
d is evaluated from the measurements of the optical retardation of a thin hybrid alignment nematic cell as a function of the wavelength of the incident light and cell rotating angles. As an example, the anchoring strength W
d = 2.5 ×10-4 [J/m2] is measured at the interface between the nematic mixture ZLI-2293 and the polyimide vertical alignment film PI-1.
Very Compact Arrayed-Waveguide-Grating Demultiplexer Using Si Photonic Wire Waveguides
Authors: Fukazawa Tatsuhiko , Ohno Fumiaki , Baba Toshihiko
Published: February 2005

We demonstrated an arrayed-waveguide-grating (AWG) demultiplexer using Si photonic wire waveguides, for the first time. We designed and fabricated an AWG of 110 ×93 µm2 size on a silicon-on-insulator substrate. The demultiplexing function was observed in the wavelength range of 1.50–1.57 µm with a channel spacing of ∼6 nm and a free spectral range of > 90 nm. A narrower channel spacing of 1 nm is possible in an area of ∼(500 µm)2, using an optimization of arrayed waveguides and slab waveguides.
Optical Properties of Novel GaN 3D Structures Grown by Metal-Organic Chemical Vapor Deposition (MOCVD)
Authors: Sacilotti Marco , Imhoff Luc , Dumas Colette , Viste Pierre , Vial Jean-Claude , Baldeck Patrice , Colombier Isabelle , Donatini Fabrice
Published: February 2005

Optical properties of novel micrometer-size Ga and GaN three-dimensional structures obtained by the metal-organic chemical vapour deposition (MOCVD) technique are presented in this letter. These structures are obtained as metallic three dimensions (3D) micrometer-size objects on an appropriate substrate by metalorganic (TMGa) pyrolisis and then GaN transformed on annealing under NH3 atmosphere at 650–750°C. These 3D GaN structures are analysed by optical means, using two-photon excitation (800 nm) and by UV Hg lamp fluorescent spectroscopy techniques, adapted to two-optical-microscopes apparatus. Very intense and blue/yellow light emission is observed from these 3D structures under 800 nm two-photon laser excitation and under UV Hg lamp excitation.
10.5 km Fiber-Optic Quantum Key Distribution at 1550 nm with a Key Rate of 45 kHz
Authors: Yoshizawa Akio , Kaji Ryosaku , Tsuchida Hidemi
Published: February 2005

High-speed single-photon detectors are crucial for efficiently performing quantum key distribution. We demonstrate fiber-optic quantum key distribution at 1550 nm using single-photon detectors operating at 10 MHz. Discharge pulse counting is adopted for single-photon detection in order to suppress after-pulse generation. Furthermore, by setting a dead time in single-photon detection, we discard after-pulses to reduce the number of bit errors in the quantum key distribution. Using discharge pulse counting and after-pulse discarding in the quantum key distribution, we can achieve a key rate of 45 kHz with a bit-error rate of 2%. The fiber length is 10.5 km.
Al2O3 Insulated-Gate Structure for AlGaN/GaN Heterostructure Field Effect Transistors Having Thin AlGaN Barrier Layers
Authors: Hashizume Tamotsu , Anantathanasarn Sanguan , Negoro Noboru , Sano Eiichi , Hasegawa Hideki , Kumakura Kazuhide , Makimoto Toshiki
Published: February 2005

An Al2O3 insulated-gate (IG) structure was utilized for controlling the surface potential and suppressing the gate leakage in Al0.2Ga0.8N/GaN heterostructure field effect transistors (HFETs) having thin AlGaN barrier layers (less than 10 nm). In comparison with the Schottky-gate devices, the Al2O3 IG device showed successful gate control of drain current up to V
GS = +4 V without leakage problems. The threshold voltage in the Al2O3 IG HFET was about -0.3 V, resulting in the quasi-normally-off mode operation.
Evaluation of Fast Neutron Induced Single Event Upset in a Static Random Access Memory and Simulation by Monte Carlo N-Particle Code (MCNPX)
Authors: Arita Yutaka , Takai Mikio , Ogawa Izumi , Kishimoto Tadafumi , Nagai Yasuki , Hatanaka Kichiji , Matsuoka Nobuyuki
Published: February 2005

Neutron-induced single-event upsets (SEUs) in a 0.4 µm 4 Mbit CMOS SRAM (complimentary metal oxide semiconductor static random access memory) were investigated using high-energy neutron beams and Monte Carlo simulation by MCNPX (Monte Carlo N-Particle Code). The Monte Carlo simulation, based on the assumption that the primary cause of SEUs is alpha particles generated by nuclear fission, agreed with the experimental results within the accuracy of ±29% in the case of small cell charges (<10 fC). When the devices were exposed to fast neutrons in the front-surface direction, the SEU rates increased by a factor of 1.1 to 2 in comparison with the case of back-surface irradiation. According to the Monte Carlo simulation, the difference between the alpha particle production cross section of the carbon atom in package materials and that of the silicon atom caused this phenomenon.
Very High Selective Etching of GaAs/Al0.2Ga0.8As for Gate Recess Process to Pseudomorphic High Electron Mobility Transistors (PHEMT) Applications Using Citric Buffer Solution
Authors: Liao Chin-I , Sze Po-Wen , Houng Mau-Phon , Wang Yeong-Her
Published: February 2005

Highly selective wet etching of GaAs on Al0.2Ga0.8As can be realized using citric buffer (citric acid/H2O2/H2O) solutions. The selectivity can be up to 256, which is distinct from the previous non-selectivity inference, due to consulting the role of H2O2 in this etching system. The etch stop mechanism is demonstrated by X-ray photoelectron spectroscopy (XPS) and indicates the formation of dense oxide Al2O3 on Al0.2Ga0.8As to stop etching. The applications to pseudomorphic high electron mobility transistors (PHEMT) gate recess processes, no obvious drain current decrease can be perceived even after 8 min overetching. The etched surface is very smooth with the roughness of only 1.97 Å. The devices also show excellent etched uniformity with a small threshold voltage deviation of 28 mV and good electrical performance, which is useful to the heterostructure device fabrications.
Unprecedented Imaging Capability Hard X-ray Detector Employing Scintillator-Deposited Charge-Coupled Device
Authors: Miyata Emi , Tawa Noriaki , Koizumi Gensuke , Miki Masami , Miyaguchi Kazuhisa
Published: February 2005

We report on a new photon-counting detector possessing an unprecedented spatial resolution, a moderate spectral resolution and a high background-rejection capability for 0.1–100 keV X-rays. The detector consists of an X-ray charge-coupled device (CCD) and a scintillator. We coupled the scintillator to the surface of the back-illuminated (BI) CCD. Hard X-rays absorbed in the scintillator create hundreds or thousands of visible lights whose number is proportional to the incident X-ray energy. Since the quantum efficiencies of BI CCDs for visible lights are high, the charge collection efficiency for visible lights emitted from the scintillator becomes high. We investigate the spatial resolution of our device by measuring the contrast transfer function for 17.4 keV X-rays and find almost unity up to 10 line pairs per mm in the photon-counting mode. We thus perform a demonstrative experiment with a sharp edge and determine the spatial resolution to be (10±3) µm which is twofold that of the CCD pixel size.
Growth of ZnSe Epilayer on Si Using Ge/GexSi1-x Buffer Structure
Authors: Yang Tsung-Hsi , Yang Chu Shou , Luo Guangli , Chou Wu Ching , Yang Tsung-Yeh , Chang Edward Yi , Chang Chun-Yen
Published: February 2005

The epitaxial growth of ZnSe layers on Si substrates utilizing a Ge/Ge0.95Si0.05/Ge0.9Si0.1 buffer structure is demonstrated. In this study, we examine the structure, optical characteristics and atomic interdiffusion of the ZnSe epilayer grown on Si. In a sample with a 2° off-cut Si substrate, the outdiffusion of Ge into the ZnSe epilayer is suppressed. The low-temperature PL measurements indicate that the sample with a 2° off-cut Si substrate improves its optical characteristic effectively. The X-ray diffraction analysis and transmission electron microscopy (TEM) results indicate that the use of a 2° off-cut Ge/Ge0.95Si0.05/Ge0.9Si0.1/Si substrate markedly improves the crystallinity of and reduced the number of threading dislocations in ZnSe grown on Si.
X-Rays Beam Condensation by Confinement in a Thin Crystal
Authors: Fukamachi Tomoe , Negishi Riichiro , Yoshizawa Masami , Sakamaki Toshio , Kawamura Takaaki
Published: February 2005

We have observed condensation of X-rays emitted from an edge of a thin Ge parallel crystal, using X-rays from synchrotron radiation. When highly parallel X-rays with the energy near an absorption edge of an atom or a nucleus are incident on a thin crystal in the Bragg case, a part of X-rays is confined in the crystal and do not come out either from the top or the bottom surface. The density of confined beam increases as the width of the incident beam is increased. The confined beam can come out from an edge of a thin crystal with higher density than the incident beam.
Growth of Diamond from Si-Containing Amorphous Carbon Film Using Synchrotron Radiation
Authors: Kimura Yuki , Kido Osamu , Oomoto Masayuki , Ogawa Koji , Namba Hidetoshi , Kaito Chihiro
Published: February 2005

Si-doped amorphous carbon film prepared by the simultaneous vacuum evaporation of carbon and silicon has been irradiated by a synchrotron radiation (SR) beam. The preferential growth of diamond crystals was found by transmission electron microscope observation conducted after SR irradiation. It was also found that the solid-solution phase of carbon and silicon with the diamond structure was produced in the as-deposited film and at the initial stage of the crystallization. The solid-solution crystal remained in the stable phase up to 6 nm in size. The catalytic effect of Si was prominent in the growth of diamond.
Identification of Emissive Interface-Related Defects in Polyfluorene-Based Light Emitting Devices
Authors: Gamerith Stefan , Nothofer Heinz-Georg , Scherf Ullrich , Emil J. W. List* Emil J. W. List*
Published: February 2005

We report on a distinct defect related emission band between 2.45 and 2.6 eV in blue light emitting polyfluorene type polymer light emitting devices. The origin of this novel feature at 2.45–2.6 eV which becomes apparent in addition to the well investigated emission band from bulk keto defects at 2.3 eV is spatially located close to the cathode of the device. It is identified as being related to chemical defects in the polymer, formed by a chemical reaction of the polymer in the presence of the deposited cathode metals Al or Ca.
Hot Ion Beam Generation from Rare-Gas Cryogenic Targets
Authors: Rajyaguru Chirag , Higashiguchi Takeshi , Maezono Yoshinari , Katto Masahito , Yokotani Atsushi , Kurosawa Kou , Sasaki Wataru , Kubodera Shoichi
Published: February 2005

Energetic ions having a maximum velocity of the order of 107 cm/s were detected in the interaction of a frequency-doubled Q-switched Nd:YAG laser with rare-gas cryogenic targets at the laser intensity of 1 ×1012 W/cm2. It was observed that the angular distribution of ions strongly peaked in the target normal direction confined to a narrow range of angle following ∼cos
pθ ( p=3–5). Scaling of the ion current and their velocity as a function of an incident laser energy were investigated. To analyze the effect of energetic particles from a plasma, a silicon substrate was used as a particle target. Its surface morphology revealed that micron-size solid fragments from the target dominantly affected the silicon surface.
Successful Growth of InxGa1-xAs (x>0.18) Single Bulk Crystal Directly on GaAs Seed Crystal with Preferential Orientation
Authors: Azuma Yukinaga , Nishijima Yoshito , Nakajima Kazuo , Usami Noritaka , Fujiwara Kozo , Ujihara Toru
Published: February 2005

We attempted to utilize a GaAs single crystal with preferential orientation as a seed to obtain an InGaAs single bulk crystal. The preferential orientation of the InGaAs bulk crystal was determined as [110] in a preliminary experiment to utilize multiple seed crystals with random orientations. By subsequent zone growth of InGaAs on GaAs(110), an In
x
Ga1-x
As (x>0.18) single bulk crystal with a diameter of 15 mm and a length of 13 mm was successfully obtained on the seed without a compositionally graded InGaAs layer. The large lattice mismatch between GaAs and InGaAs was likely to be accommodated by an array of thin columnar grains at the interface.
Electrochemical Detection of Free Chlorine Using Anodic Current
Authors: Kodera Fumihiro , Kishioka Shin-ya , Umeda Minoru , Yamada Akifumi
Published: February 2005

We have developed a new analysis method for high free-chlorine concentration using anodic current. The measurement was carried out using linear sweep voltammetry with a platinum disk electrode. An oxidation wave that was concentration dependent at about 1100 mV vs Ag/AgCl was observed, and a good linear relationship in the concentration range of 0.1–12.0 mmol·dm-3 (Cl) was obtained between the oxidation peak current and concentration. This method seemed to be very useful for the analysis of high free-chlorine concentration.
Band Lineup at the Interface between Boron-Doped P-Type Hydrogenated Amorphous Silicon and Crystalline Silicon Studied by Internal Photoemission
Authors: Sakata Isao , Yamanaka Mitsuyuki , Shimokawa Ryuichi
Published: February 2005

We have measured for the first time the band lineup at the interface between boron-doped p-type hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) by internal photoemission and have found that the band discontinuity mainly exists on conduction-band (CB) side in this type of heterojuctions. This band lineup is related with the low back-surface recombination velocity observed in n+(c-Si) - p(c-Si) - p+(a-Si:H) solar cells.
Properties of (111) Diamond Homoepitaxial Layer and Its Application to Field-Effect Transistor
Authors: Kasu Makoto , Kubovic Michal , Aleksov Aleksandar , Teofilov Nikolai , Sauer Rolf , Kohn Erhard , Makimoto Toshiki
Published: February 2005

The (111)-oriented chemical-vapor-deposited diamond homoepitaxial layers with low defect density exhibited well-resolved free-exciton transitions in cathodoluminescence at 13 K and a sharp peak at 1332 cm-1 (linewidth: 1.9 cm-1) in Raman scattering. Furthermore, using these (111) layers, we fabricated metal-semiconductor field-effect transistors (FETs). FETs with an 11-µm-long gate exhibited a maximum drain current of 24 mA/mm and maximum transconductance of 14 mS/mm. These values are of the same order as those for the (001) orientation.
Cross-Sectional Analysis on Hardness and Sp3 Bond Fraction of Diamond-Like Carbon Film Prepared by Mass-Separated Ion Beam Deposition
Authors: Yamamoto Kazuhiro
Published: February 2005

Carbon films were prepared on Si(100) wafers by mass-separated ion beam deposition (MSIBD). Cross-sectional analysis of the film hardness and structure was performed. The hardness has the maximum value of 80 GPa at the surface region, and decreases to 60 GPa gradually on approaching the bottom region of the film from the surface. There is a good correlation between the film hardness and the sp3 bond fraction. The maximum value of the sp3 bond fraction of 89% is obtained at the film surface region, and the fraction decreases to 67% at the bottom region of the film.
Synthesis of AlxGa1-xN Alloy by Solid-Phase Reaction under High Pressure
Authors: Saitoh Hiroyuki , Utsumi Wataru , Kaneko Hiroshi , Aoki Katsutoshi
Published: February 2005

Bulk specimens of Al
x
Ga1-x
N alloys covering a composition range of 0≤x≤1 were synthesized by a solid-phase reaction under high pressure. In situ X-ray diffraction profiles were measured to observe the alloying process, which began at around 800°C under 6.0 GPa. SEM observation and X-ray analysis of the recovered specimen indicated a uniform distribution of Al and Ga and continuous variations of the lattice constants against the composition, which implies that a solid solution of AlN and GaN is formed regardless of atomic composition.
β-Adrenergic-responsive activation of extracellular signal-regulated protein kinases in salivary cells: role of epidermal growth factor receptor and cAMP
Authors: Yeh Chih-Ko , Ghosh Paramita M. , Dang Howard , Liu Qun , Lin Alan L. , Zhang Bin-Xian , Katz Michael S.
Published: February 2005

The β-adrenergic receptor agonist isoproterenol exerts growth-promoting effects on salivary glands. In this study, activation of ERKs, members of the mitogen-activated protein kinase family, by isoproterenol was examined in a human salivary gland cell line (HSY). Immunoblot analysis indicated that isoproterenol (10−5 M) induced transient activation of ERK1/2 (4.4-fold relative to basal at 10 min) similar to that caused by EGF (6.7 fold). Isoproterenol, like EGF, also induced phosphorylation of the EGF receptor. However, inhibition of EGF receptor phosphorylation by the tyrphostin AG-1478 only partially attenuated isoproterenol-induced ERK phosphorylation, whereas EGF-responsive ERK activation was completely blocked. The Gi inhibitor pertussis toxin also caused partial inhibition of isoproterenol-stimulated ERK activation. The cAMP analog 8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate (CPT-cAMP) and the cAMP-elevating agents IBMX and cholera toxin produced transient ERK1/2 activation, similar to the effect of isoproterenol, in HSY cells. The stimulatory effects of isoproterenol and cAMP on ERK phosphorylation were not reduced by the PKA inhibitor H-89, whereas the Src family inhibitor 4-amino-5-(4-chlorophenyl)-7-( t-butyl)pyrazolo[3,4- d]pyrimidase (PP2) and transfection of a dominant-negative Src construct diminished isoproterenol-induced ERK activation. Isoproterenol induced marked overexpression of the cell growth-related adhesion molecule CD44, and this effect of isoproterenol was abolished by the ERK pathway inhibitor PD-98059. In summary, we show a dual mechanism of isoproterenol-induced ERK phosphorylation in HSY cells—one pathway mediated by EGF receptor transactivation and the other by an EGF receptor-independent pathway possibly mediated by cAMP. Our results also suggest that isoproterenol-induced growth of salivary tissue may involve ERK-mediated CD44 expression.
Tissue culture of sockeye salmon intestine: functional response of Na+-K+-ATPase to cortisol
Authors: Veillette Philip A. , Young Graham
Published: February 2005

A method to culture tissue explants of the intestine from freshwater-adapted sockeye salmon ( Oncorhynchus nerka) was developed to assess possible direct effects of cortisol on Na+-K+-ATPase activity. As judged by several criteria, explants from pyloric ceca and the posterior region of the intestine remained viable during short-term (6-day) culture, although Na+-K+-ATPase activity declined and basolateral components of the enterocytes were observed to be partially degraded. Addition of cortisol to the culture medium maintained Na+-K+-ATPase activity (over 2–12 days) above that of control explants and, in some cases, was similar to levels before culture. The response to cortisol was dose dependent (0.001–10 μg/ml). Within the physiological range, the response was specific for cortisol and showed the following hierarchy: dexamethasone ≥ cortisol > 11-deoxycortisol > cortisone. Insulin maintained Na+-K+-ATPase activity over controls in explants of ceca but not posterior intestine. To compare in vivo and in vitro responses, slow-release implants of cortisol (50 μg/g) were administered to salmon for 7 days. This treatment elevated plasma cortisol levels and stimulated Na+-K+-ATPase activity in both intestinal regions. The results demonstrate that the teleost intestine is a direct target of cortisol, this corticosteroid protects in vitro functionality of Na+-K+-ATPase, and explants retain cortisol responsiveness during short-term culture.