bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Evaluation of Representative Figure Method for Proximity Effect Correction
Authors: Yamasaki Satoshi , Abe Takayuki , Yoshikawa Ryoichi , Itoh Masayuki , Shigemitsu Fumiaki , Tadahiro Takigawa Tadahiro Takigawa
Published: February 2005

The representative figure method has been proposed in previous papers to reduce the processing time for proximity effect correction. The Phantom, which is an application of the representative figure method to Ghost, assigns only one representative rectangle in each small area instead of the inverted original patterns, and the rectangles are exposed with a defocused beam. From the results of numerical calculation and experiment, there is little difference in correction effect between Phantom and Ghost, even if the small area size is nearly equal to the electron backscattering range. So, the small area size can be set as large as the backscattering range. It is shown that the same correction accuracy as Ghost can be obtained by Phantom. The correction exposure time can be reduced to 1/25∼1/500 that of Ghost by Phantom.
Influence of Halogen Plasma Atmosphere on SiO2 Etching Characteristics
Authors: Tokashiki Ken , Ikawa Eiji , Hashimoto Toshiki , Kikkawa Takamaro , Teraoka Yuden , Nishiyama Iwao
Published: February 2005

The influence of halogen plasma atmosphere on SiO2 dry etching characteristics has been investigated using various halogen gases (SF6, Cl2, HBr and HI). It was found that in Cl2 and HBr plasma atmospheres, when Si and SiO2 are etched simultaneously, the SiO2 etch rate increases to more than 4 times larger than the SiO2, etch rate obtained when only SiO2 is etched. It was also found that the SiO2 etch rate increases linearly in proportion to the total amount of silicon halide produced by etching Si. Low-order silicon halides such as SiX and SiX2 (X=Cl or Br) connect with oxygen atoms in solid SiO2 by Coulomb force since both silicon halide and SiO2 are electrically polarized. Silicon oxyhalide (e.g., SiOX) as an etching product of SiO2 is produced and desorbed by ion sputtermg or thermal evaporation. This is because that the Si-O bond strength in solid SiO2 (108 kcal/mol) is weaker than that in a diatomic molecule (191 kcal/mol) composed of a Si atom from silicon halide and an O atom from SiO2. Consequently, SiO2 etching progresses when silicon chloride or silicon bromide is contained in the plasma, which drastically decreases the etching selectivity of n+ poly-Si to SiO2.
Nonlinear Growth of Periodic Ripple Structures with Different Spatial Periods in Laser Etching of GaAs
Authors: Kumagai Hiroshi , Machida Hiroshi , Tanaka Koichi Toyoda
Published: February 2005

The nonlinear growth of periodic surface ripples in laser-induced etching of GaAs was investigated for different spatial periods below 200 nm. Growth gains of etched grooves were more than 5%/min at the above periods both experimentally and theoretically.
GaAs Dry Etching Using Electron Beam Induced Surface Reaction
Authors: Heiji Watanabe Heiji Watanabe , Shinji Matsui Shinji Matsui
Published: February 2005

GaAs dry etching using a showered electron beam (EB) through Cl2 gas has been studied. The etching rate of EB-assisted etching is twice that of Cl2 gas etching, and the etching yield is estimated to be 130 atoms/electron. A GaAs pattern with a 0.3 µm linewidth has been obtained by using a resist mask. It was confirmed through measuring photoluminescence that the damage induced by EB-assisted etching is nearly the same as that caused by gas etching, and less than the damage induced by reactive ion beam etching or ion beam etching. A reverse dry etching technique is demonstrated whereby a surface layer of carbon formed on the substrate resulting from EB irradiation is used as a mask for EB-assisted etching. High-selectivity is obtained between the carbon mask and GaAs. Using this technique, a 0.6 µm linewidth reverse pattern is transferred.
Crystallinity Improvement by Synchrotron Radiation Irradiation in Low-Temperature Si Epitaxial Growth Using Disilane
Authors: Utsumi Yuichi , Takahashi Jun-ichi , Housei Akazawa Housei Akazawa , Tsuneo Urisu Tsuneo Urisu
Published: February 2005

Si films were grown on Ge substrates by Synchrotron Radiation (SR)-excited crystal growth around the low substrate temperature limit for epitaxial growth. From the observation of Reflective High Energy Electron Diffraction and Raman scattering spectra, it was found that the crystallinity of the Si film was clearly improved by SR irradiation. From the temperature dependence of the growth rate, it was confirmed that SR irradiation greatly enhances the growth rate in the lower temperature region below 500°C.
Mechanism of E' Center Generation in SiO2 Film by Ion and Neutral Beam Bombardment
Authors: Yokogawa Ken'etsu , Yajima Yusuke , Mizutani Tatsumi , Shigeru Nishimatsu Shigeru Nishimatsu , Ken Ninomiya Ken Ninomiya
Published: February 2005

The radiation damage in SiO2 films thermally grown on silicon and bombarded by ion and neutral beams has been studied by electron spin resonance (ESR). It is found that the E' center generation yield is much higher for ion bombardment than for neutral bombardment in spite of the same kinds of atoms and the same incident energy. The generation yield of ion-induced E' centers depends on the incident energy and ionization energy of the parent atom. On the other hand, for neutral bombardment, it depends only on the incident energy. These results indicate that the neutral-induced E' centers are created by bond breaking due to a collision cascade. However, ion-induced E' centers are generated by both collision cascades and carriers (electrons and holes) induced in the SiO2 film by ion neutralization.
Ballistic Electron Transport on Periodic and Quasi-Periodic Triangular Lattices of Scatterers
Authors: Takahara Junnichi , Kakuta Takeshi , Yamashiro Tomoki , Takagaki Yukihiko , Shiokawa Takao , Gamo Kenji , Namba Susumu , Takaoka Sadao , Murase Kazuo
Published: February 2005

We have studied electron transport properties on an artificial periodic and quasi-periodic array of scatterers. Scatterers are introduced in two-dimensional electron gas of a GaAs-AlGaAs heterojunction by employing electron beam and dry etching, or by damaging of direct focused ion beam irradiation. Novel magnetoresistance oscillations are observed at low magnetic field. It was found that the dominant features in the data arise from commensurate classical orbit.
Heat Treatment Effect on the Metal Contact of High-Tc(Pb, Bi)SrCaCuO Superconductor
Authors: Chen Y. C. , K. K. Chong K. K. Chong , T. H. Meen T. H. Meen
Published: February 2005

Better metal electrode can be obtained by heat treatment which causes deeper diffusion of metal particles into the (Pb, Bi)SrCaCuO superconductor to improve contacts between metal electrodes and the sample. However, high-Tcphase of the specimen was destroyed at 700°C and the sample showed semiconducting behaviour. Low room temperature contact resistivity was obtained about 3.21×10-4(Ω-cm2) and 2.34×10-6(Ω-cm2) at 77 K for a sample with evaporating silver electrodes and annealed at 600°C for 2 hours. Non-ohmic contacts are observed for the indium and aluminum terminals.
Proposal of Slope Estimation Method II Making Possible the Accurate Evaluation of Energy Depth of Carrier Traps from Partial Region of Thermally Stimulated Current Curves
Authors: Tanaka Mitsuhiro , Akihiro Tsuru Akihiro Tsuru , Shigeyoshi Maeta Shigeyoshi Maeta
Published: February 2005

Slope estimation method II, which enables one to utilize partial regions of thermally stimulated current curves easily, especially those without peak coordinates obtained by the partial-heating technique and so on, is proposed. This new method, which has been established from the original concept of the “fundamental element”, enables one to accurately evaluate E
t, the energy depth of carrier traps, by utilizing only two slopes freely selected from the objective single TSC curve on the newly defined Arrhenius coordinates. As the method uses differential quantities, it enables one to sensitively detect background noise from the partial TSC curves obtained experimentally, leading to evaluation of accurate E
t. The original concept of the one-to-one relation and a theory without any approximations make possible excellent characteristics with no limitations of application.
Dielectric Constants of Crystal and Amorphous Phases in Ferroelectric Polymers
Authors: Susumu Ikeda Susumu Ikeda , Masayuki Kutani Masayuki Kutani
Published: February 2005

Dielectric constants of crystal and amorphous phases in ferroelectric copolymers of vinylidene fluoride and trifluoroethylene are separated from the dielectric constant of samples including both phases by means of a two-phase model in which the depolarization field coefficient L=1/3 is assumed. Temperature dependence of the dielectric constant of the ferroelectric crystal is not much different from that of a sample with a high degree of crystallinity, which increases during heating up to a ferroelectric-paraelectric phase transition temperature. On the other hand, the dielectric constant of the amorphous phase decreases with increasing temperature after an abrupt increase at the glass transition temperature. Although the tendency to decrease is explained as a property of liquid obeying Fröhlich-Kirkwood theory, the rate of the decrease becomes steep with increasing temperature and deviates from the theory.
A Defect Model for Photoirradiated Semiconductors –Suppression of the Self-Compensation in II-VI Materials–
Authors: Ichimura Masaya , Wada Takao , Fujita Shizuo , Fujita Shigeo
Published: February 2005

A model for calculating defect concentrations in photoirradiated semiconductors is presented. When the electronic level of a defect is shallow, photoirradiation is expected to decrease its concentration. The model is applied to ZnSe. Although the self-compensation makes it difficult to grow low-resistivity p-type ZnSe under the thermal equilibrium condition, the photo-irradiation during the growth can substantially reduce the compensation ratio. According to calculation results, the hole concentration in acceptor-doped ZnSe is increased drastically by the irradiation when the excess carrier concentration exceeds 108 cm-3 at a temperature of 400°C and a Zn pressure of 10-10 atm. Thus, the irradiation can be used to control defect concentrations in semiconductors.
Gold Substrates for Scanning Tunneling Microscopy of Adsorbed Species
Authors: Inukai Junji , Mizutani Wataru , Saito Kazuhiro , Shimizu Hazime , Yasuhiro Iwasawa Yasuhiro Iwasawa
Published: February 2005

Atomically flat substrates of gold were prepared by evaporation onto cleaved mica for scanning tunneling microscopic and spectroscopic studies of adsorbates. The surface morphology was investigated with a scanning tunneling microscope (STM) and a scanning electron microscope. The STM data were analyzed through a fractallike statistical procedure. Bulk crystallography was also investigated by means of X-ray diffraction. On the gold substrate showing hydrophilic characteristics, monolayer Langmuir-Blodgett film of cadmium arachidate was deposited, and successfully imaged by STM.
X-Ray Color Movie Using the Charge-Coupled Device with a Direct X-Ray Detection Method
Authors: Tsunemi Hiroshi , Wada Mikio , Kiyoshi Hayashida Kiyoshi Hayashida , Shin'ichi Kwai Shin'ichi Kwai
Published: February 2005

We report here a high-speed direct X-ray detection system using the charge-coupled device (CCD). It can obtain digital output from the CCD at a speed of one million pixels per second. With an appropriate image size, we can obtain images at the speed of a movie. The CCD we employed has a thicker depletion region than that of the optical-use CCD. Our system can obtain energy-resolved X-ray images. We demonstrated its validity using the pinhole camera system and obtained images resolved with Fe-K and Ti-K X-rays. The image quality was determined not by the pixel size of the CCD (12×12 µm2) but by the pinhole size (200 µm in diameter) that we used. Our system is a promising focal plane detector for X-ray optics such as an X-ray microscope.
Silicon-Monohydride Termination of Silicon-111 Surface Formed by Boiling Water
Authors: Watanabe Satoru , Shigeno Mayumi , Noriaki Nakayama Noriaki Nakayama , Takashi Ito Takashi Ito
Published: February 2005

Aqueous HF etching of the silicon surface removes surface oxide, leaving a silicon surface terminated inhomogeneously by silicon mono-, di-, and trihydrides. We studied the effect of the immersion in water following the HF etching, on the surface hydride structure on Si(111), by measuring Si-H stretching vibration using infrared absorption spectroscopy. Immersion in boiling water (100°C) for 600 s produces a surface homogeneously terminated with silicon monohydride normal to the surface and free of oxidation. We concluded that water can remove silicon dihydride and trihydride and leave a silicon surface terminated with monohydride. The homogeneous surface has a low defect density of less than 0.5%.
Enlargement of Poly-Si Film Grain Size by Excimer Laser Annealing and Its Application to High-Performance Poly-Si Thin Film Transistor
Authors: Kuriyama Hiroyuki , Kiyama Seiichi , Noguchi Shigeru , Kuwahara Takashi , Ishida Satoshi , Nohda Tomoyuki , Sano Keiichi , Iwata Hiroshi , Kawata Hiroshi , Osumi Masato , Tsuda Shinya , Nakano Shoichi , Kuwano Yukinori
Published: February 2005

By both numerical simulation and experimental investigation, we found it possible to enlarge the grain size (∼3000 Å) of polycrystalline silicon (poly-Si) films by excimer laser annealing, using a new method to control the solidification process of molten Si - low-temperature (≦400°C) substrate heating during laser annealing. Poly-Si thin-film transistors (TFTs) fabricated by this new excimer laser annealing method showed a high field-effect mobility of 230 cm2/V·s, and good uniformity of field-effect mobility (±10%) within the effective laser irradiation area.
Observation of Luminescence from a Highly Concentrated Nd Center in GaP by Direct Optical Excitation and Comparison with Nd Centers Excited Under Host Excitation
Authors: Taniguchi Moriyuki , Hiroshi Nakagome Hiroshi Nakagome , Kenichiro Takahei Kenichiro Takahei
Published: February 2005

We report the studies of direct excitation on Nd-doped GaP samples grown by metalorganic chemical vapor deposition. It is found that extremely sharp photoluminescence excitation lines, with full width at half maximum of less than 0.02 nm at 4 K, can be observed when the excitation photon energy is in resonance with the Nd internal 4f-shell transition energy. We used direct excitation spectra to estimate the concentration of each individual Nd luminescence center, and found that the majority of the Nd ions form one particular kind of noncubic center which cannot be effectively excited through energy transfer from the host crystal. Such a phenomenon is likely to be the reason why the efficiencies of the rare-earth-doped III-V compounds are low. It also suggests that if we can fully utilize all the available rare-earth ions, a much higher efficiency can be achieved.
A New Optical Neuron Device for All-Optical Neural Networks
Authors: Akiyama Koji , Takimoto Akio , Miyauchi Michihiro , Kuratomi Yasunori , Junko Asayama Junko Asayama , Hisahito Ogawa Hisahito Ogawa
Published: February 2005

A new optical neuron device has been developed. The device can perform both summation and thresholding operations in optics, and consists of a PIN a-Si:H photoreceptor, aluminum neuron electrodes and a ferroelectric liquid crystal light modulator. The a-Si:H photoreceptor shows characteristics of an ideal quantum efficiency (η∼1) and a good linearity (γ∼1). The optical neuron device exhibits a response time of ∼30 µs for incident light power of 9 µW and a contrast ratio of 300:1. Using this neuron device, a lenslet array and a memory mask, an all-optical neural network has been constructed. The network demonstrates an associative memory function on purely optical parallel processing without any help from electric computation.
Novel Temperature Dependences of Helical Pitch in Ferroelectric and Antiferroelectric Chiral Smectic Liquid Crystals
Authors: Li Ji , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

A variety of temperature dependences of helical pitch were found in ferroelectric SmC* and antiferroelectric SmCA
* chiral smectic liquid crystals with large spontaneous polarization. In the vicinity of the transition temperatures of the materials showing the second-order SmA-SmC* or SmA-SmCA
* phase transition, the pitch gradually increases with decreasing temperature over several degrees. In the materials which show the first-order phase transition from SmA to SmC* or to SmCA
*, the maximum pitch suddenly appears at the transition. It was also confirmed in all of the materials used that the helix undergoes a discontinuous change in the pitch length and its handedness at the SmC*-SmCA
* phase transition. The molecular orientational structure of the ferrielectric phase is also discussed on the basis of the temperature dependence of the pitch of (S)-MHPOBC.
X-ray Photoelectron Spectroscopy Study in Bi2Sr2Ca1-xNdxCu2O8+d
Authors: Yamanaka Hidetoshi , Enomoto Hiroyuki , Shin Jae Soo , Kishimoto Takeshi , Takano Yoshiki , Mori Natsuki , Hajime Ozaki Hajime Ozaki
Published: February 2005

X-ray photoelectron spectroscopy (XPS) measurements were performed in Bi2Sr2Ca1-x
Nd
x
Cu2O8+d
(0≤x≤1) in order to investigate the change in the electronic states through the decrease of the holes in this system. The negative chemical shifts of the Cu 2p main peaks were observed, while their satellites did not shift but decreased in areas. These behaviors indicated that the holes at both Cu and O sites decrease with increasing Nd concentration x.
Single-Crystalline Epitaxial ZnS Waveguides for Phase Matched Second Harmonic Generation Devices
Authors: Saitoh Tohru , Toshiya Yokogawa Toshiya Yokogawa , Tadashi Narusawa Tadashi Narusawa
Published: February 2005

A novel second harmonic generation (SHG) device using single-crystalline epitaxial ZnS waveguide was proposed. First, theoretical analyses were carried out. A possibility of mode-coupled phase matching was confirmed by calculating the mode dispersion curves. Optical crystalline orientation of the waveguide was theoretically determined. We found that the maximum conversion efficiency can be obtained when the crystalline orientation of the waveguide surface is (001) and the propagating direction is <110>. The output power was estimated as 4.9 mW (λ=0.42 µm) at the phase matched condition, assuming that the fundamental power is 100 mW and the waveguide length is 5 mm. Second, a ZnS waveguide having an optimized crystalline orientation was fabricated. The SHG in the waveguide was confirmed using YLF laser as a fundamental wave.
Construction of a Point-Focusing Small-Angle X-Ray Scattering Diffractometer for the Study of Fluctuations in Solutions
Authors: Hayashi Hisashi , Tohji Kazuyuki , Udagawa Yasuo
Published: February 2005

A point-focusing diffractometer for the measurement of the small-angle X-ray scattering (SAXS) from molecular solutions has been constructed. This diffractometer consists of a double bent LiF monochromator whose focal length is 700 mm for Cu Kα radiation, a sample cell with 0.1 mm-thick mica windows, a bath circulator coupled with a cell holder, and a PSPC system. With this diffractometer, small-angle resolution of better than 0.42° is achieved. To evaluate the performance of the diffractometer, the SAXS on several pure liquids and aqueous solutions was measured. The results show that this diffractometer produces incident beams intense enough to measure SAXS on the solutions, making the collimation effect negligible simultaneously.
Photo-Induced Transferred Charge in Rare-Earth-Doped Alkaline-Earth Sulfide Electroluminescent Thin Films
Authors: Tanaka Shosaku , Yoshiyama Hideki , Nakamura Kazuyoshi , Wada Shunji , Haruyuki Morita Haruyuki Morita , Hiroshi Kobayashi Hiroshi Kobayashi
Published: February 2005

The spectral response of the photo-induced transferred charge in Eu2+- or Ce3+-doped CaS and SrS thin-film electroluminescent (EL) devices has been studied. It is found that excitation spectra of the photo-induced transferred charge agree with those of photoluminescence. This result implies that the Eu2+ or Ce3+ luminescent centers are ionized by electric field when the centers are excited to the (4f)
n-1(5d) excited state. The dynamics of the EL emission are controlled by field-dependent ionization of the luminescent centers and by field-dependent trapping at the ionized centers, rather than by impact excitation of the luminescent centers.
NaNO3 Effects on the Superconducting Properties of YBa2Cu3Oy
Authors: Lee Eun Hong , Jeong Ju Young , Hyo Ill Song Hyo Ill Song , Seok-Yeol Yoon Seok-Yeol Yoon
Published: February 2005

Y-based superconductors were prepared by sintering the mixtures of calcined YBa2Cu3O
y
powder and NaNO3. NaNO3 has been found to have high oxygen potential in a YBa2Cu3O
y
superconductor. With this potential, the critical temperature of YBa2Cu3O
y
+4.5 wt.% NaNO3 sintered in air was almost the same as that of a pure YBa2Cu3O
y
sintered in oxygen. NaNO3 or its decomposition products seemed to induce liquid phase sintering to result in larger grains and denser structure. With these structural changes, the critical current density was found to increase with NaNO3.
Biaxial Alignment of High-Tc Superconductor Polycrystals (III): Demonstration in a Bi-2212(Yb) Thick Film
Authors: Zhang Bao-Shan , Chen Feng , Hidalgo Rafael , Wang Sheng-Qi , Zhang Xin-Yu , Zhang Jian-Zhong , Markiewicz Robert S. , Lu Bill C. Giessen
Published: February 2005

To produce polycrystalline superconductor ceramics with potentially higher critical currents by eliminating grain boundary weak links caused by grain orientation misfit, we use a method combining grain shape alignment and magnetic field alignment by orthogonal alignment forces. Continuing this work, we report here X-ray diffraction data demonstrating the first preparation of an ∼80µm thick Bi2Sr2Ca0.7Yb0.3Cu2O
x
film having substantial biaxial grain alignment; a very high degree of c-axis alignment is combined with >30% preferential <100> axis alignment within the a-b plane (relative to a random <100> axis distribution in that plane). While films with this composition are not good superconductors, they demonstrate the feasibility of the method.
Spontaneous Appearance of Toroidal Field in Field Reversed Configuration Plasma
Authors: Shiokawa Akira , Okada Shigefumi , Yoshifumi Ito Yoshifumi Ito , Seiichi Goto Seiichi Goto
Published: February 2005

The field reversed configuration (FRC) plasma had been thought to have poloidal field only, but in this experiment, toroidal field was observed. We report magnetic probe measurements on our FIX machine, and the existence of toroidal field in the FRC plasma during its translation. The magnitude of the toroidal field is 100∼150 G at the peak, and the direction of the toroidal field is counterclockwise looking toward the θ-pinch region, irrespective of the direction of the external axial field. The obtained toroidal field has a direction opposite to the toroidal field in FRX-C/LSM.
Structure Characterization and Electrochemical Properties of Glucose Sensor
Authors: Kitabayashi Hiroyoshi , Kiyoshi Yaseod Kiyoshi Yaseod , Masakazu Okada Masakazu Okada
Published: February 2005

An enzyme-immobilized film as a biosensor is prepared by combining physical vapor deposition with an electrostatic interaction. The films of 11-aminoundecanoic acid (11-AUA) and 12-aminododecanoic acid (12-ADA) formed on KCl have two different molecular orientations arranged laterally and normally to the substrate surface, respectively. A constant amount of glucose oxidase solution is dropped on the films to form the enzyme-immobilized films. It is found that the normally oriented film of 12-ADA has higher sensitivity as a glucose sensor than do the others.
Diffusion Barrier Effect of Ultra-Thin Photo-Nitrided a-Si:H Overlayer on SnO2/Glass Substrate
Authors: Kawabata Keishi , Shiratsuki Yoshiyuki , Hayashi Tsukasa , Yamada Keichi , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: February 2005

Metallic tin diffusion into p-type hydrogenated amorphous silicon (a-Si:H) deposited on a flat or textured SnO2/glass substrate has been dramatically reduced by introducing a photo-nitrided a-Si:H (5-Å-thick) diffusion barrier between photochemical vapor deposition (photo-CVD) a-Si:H and SnO2, and the diffusion depth is about 30 Å from the a-Si:H/SnO2 interface. It is also shown that the optical transmittance is significantly improved by employing a 5-Å-thick photo-nitrided barrier layer.
Bistable Optical Thin CdS Film Devices: All-Optical and Optoelectronic Features
Authors: Bruno Ullrich Bruno Ullrich , Choukri Bouchenaki Choukri Bouchenaki
Published: February 2005

We have performed experiments on thin (6 µm) spray-deposited CdS films. All-optical and optoelectronic (hybrid) bistabilities were observed at 210 K. We have been successful for the first time in demonstrating that it is possible to reach, in thin CdS films, the same contrasted bistable loops in both transmission and photocurrent. The origin of the bistability is explained by the measured dependence of transmission on temperature. A generalized model based mainly on Urbach's rule is presented for calculating the temperature dependence of transmission. A good agreement between theory and measurement is obtained.
A Double-Layer Electrically Controlled Birefringence Liquid-Crystal Display with a Wide-Viewing-Angle Cone
Authors: Itoh Yasuhisa , Seki Hidehiro , Uchida Tatsuo , Masuda Yoichiro
Published: February 2005

Electrically controlled birefringence (ECB) mode displays using liquid crystal with negative dielectric anisotropy are promising for highly multiplexed dot-matrix liquid-crystal displays. This mode, however, has the problem of a narrow viewing angle because it is based on the birefringence of the liquid-crystal molecule. To solve this problem, a double-layer electrically controlled birefringence (D-ECB) liquid-crystal display is proposed. In this device, each layer compensates the variation of retardation as a function of viewing angle. As a result, the liquid-crystal display with a wide-viewing-angle cone under the application of voltage was realized.
Ion-Assisted Deposition of Aluminum Nitride on the Fluorozirconate Glass Surface
Authors: Dai Yisheng , Kawaguchi Toshiyasu , Osuka Takuo , Tada Masashi , Suzuki Koichi , Suzuki Susumu , Akio Masui Akio Masui
Published: February 2005

Aluminum nitride films were grown on the surface of the fluorozirconate glass by an ion-assisted deposition (IAD) method. The films did not affect the infrared transmission of the glass. The Al-N bonding in the films was confirmed by the IR absorption band centered around 650 cm-1. The absorption decreased with assist ion beam current, which is attributed to the reduction of film thickness by the sputtering effect and agrees well in trend with the changes in visible transmission and thickness. The glass surface with the films exhibits good resistance to himidity.
Bi2Sr2Ca1Cu2O8/Bi2Sr2Cu1O6 Superconducting Superlattices: Modulation of the Number of CuO2 Plane between Bi2O2 Layers
Authors: Horiuchi Ken , Kawai Tomoji , Masaki Kanai Masaki Kanai , Shichio Kawai Shichio Kawai
Published: February 2005

Superlattices with a combination of a superconductor and semiconductor have been formed by the periodic stacking of Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 layers. The observed X-ray diffraction patterns of the superlattices are consistent with those calculated from the ideal superstructures. The resistivity-temperature curve of the superlattices containing three unit layers (45 Å) of Bi2Sr2CaCu2O8 exhibits the same superconducting behavior as that of a Bi2Sr2CaCu2O8 film, indicating the Bi-Sr-Ca-Cu-O system has a strong two-dimensional nature.
Large Second-Order Optical Nonlinearity of New Organic Materials of Bis(benzylidene)cycloalkanone Derivatives
Authors: Jun Kawamata Jun Kawamata , Kuon Inoue Kuon Inoue
Published: February 2005

Several bis(benzylidene)cycloalkanone derivatives have been synthesized. From reflection measurement in powder form, it is found that some of them show intense phase-matchable second harmonic generation (SHG). In particular, the SHG in 2,5-bis(4-methylbenzylidene)cyclopentanone is found to be 30 times as intense as that of urea. The cutoff wavelengths are below 430 nm. It is also shown that these compounds are not only highly stable, but also have a very high damage threshold against laser illumination.
Strong Dependence of Hydrogen Passivation on Donor Concentration and on Donor Depth Profile in Silicon
Authors: Murakami Kouichi , Shigeru Fujita Shigeru Fujita , Kohzoh Masuda Kohzoh Masuda
Published: February 2005

We find from an electron spin resonance (ESR) study that the efficiency of hydrogen passivation of phosphorus donors in silicon decreases from 35 to 0 percent as the donor concentration increases. The measurement of the depth profile of deuterium by secondary ion mass spectrometry (SIMS) shows that deuterium concentration becomes smaller at a P peak region with donor concentrations higher than a critical value (∼1×1019/cm3). These results indicate that hydrogen becomes inactive for H-P complex formation in heavily donor-doped, metallic silicon.
The Effect of an Electrode in the First Stage of RIKEN Electron Cyclotron Resonance Ion Source (ECRIS)
Authors: Takahide Nakagawa Takahide Nakagawa , Tadashi Kageyama Tadashi Kageyama
Published: February 2005

The beam intensity of argon ions was measured when an electrode was used in the first stage of a RIKEN Electron Cyclotron Resonance Ion Source (ECRIS). The enhancement of higher charge state performance was observed when we used the electrode. The beam intensity is strongly dependent on the bias voltage of the electrode. We also observed that larger current of higher-charge-state ions can be obtained when we used the electrode after coating the chamber wall with Al2O3.
Optical Second Harmonic Generation from Poled Thin Films of Aromatic Polyurea Prepared by Vapor Deposition Polymerization
Authors: Kajikawa Kotaro , Nagamori Hisatoshi , Takezoe Hideo , Fukuda Atsuo , Ukishima Sadayuki , Takahashi Yoshikazu , Iijima Masayuki , Fukada Eiichi
Published: February 2005

We have observed second-harmonic generation (SHG) in poled thin films prepared by the vacuum evaporation technique for the first time. We have shown the high potential of poled aromatic polyurea prepared by vapor deposition polymerization as SHG devices: (1) fairly high nonlinear susceptibility, i.e., χ
z
z
z

(2)=8.0×10-9 esu (3.4 pm/V) and χ
z
x
x

(2)=2.2×10-9 esu (0.92 pm/V): (2) wide transparent range down to 400 nm: (3) well controllable film thickness: (4) high T
g and negligible relaxation; and (5) the possibility of a variety of main-chain structures.
Laser Deposition of AlN Thin Films on InP and GaAs
Authors: Pijush Bhattacharya Pijush Bhattacharya , Dwarka N. Bose Dwarka N. Bose
Published: February 2005

Aluminium nitride thin films (∼1000 Å) were deposited by pulsed laser (ruby, 30 ns) evaporation on compound semiconductors GaAs and InP for fabrication of metal-insulator-semiconductor (MIS) diodes. The deposition was carried out with a laser energy density of 2.5 J·cm-2 at a rate of 10-11 Å/pulse at ∼10-6 Torr, the substrate temperature being 300 K. Low-angle X-ray diffraction showed the films to have a wurtzite structure. The resistivity of the films was 5×1012 Ω-cm with a breakdown field of 1-2×106 V-cm. The dielectric constant of the films was in the range of 7.5-7.8. A lower value of interface state density was obtained on InP (∼1.8×1011 cm-2·eV-1) rather than on GaAs (∼8×1011 cm-2·eV-1). These results are compared with earlier studies of laser-deposited BN films on InP.
Thermal Desorption of Galliumchloride Adsorbed on GaAs (100)
Authors: Sasaoka Chiaki , Yoshitake Kato Yoshitake Kato , Akira Usui Akira Usui
Published: February 2005

Adsorption and desorption of galliumchloride (GaCl) on GaAs surfaces are investigated to understand the self-limiting process in the chloride atomic layer epitaxy (ALE). Adsorption energy of GaCl on GaAs (100) surfaces is determined by temperature programmed desorption (TPD). As stabilized 2×4 surfaces and Ga stabilized 4×6 reconstructed surfaces are exposed to a GaCl molecular beam which is produced by a newly designed GaCl cell. GaCl desorption is observed on both 2×4 and 4×6 surfaces, while the desorption of GaCl
x
(x=2, 3), AsCl
x
(x=1∼3) and Cl2 are not detected. The adsorption energy of GaCl, E
ad, is calculated to be 38 kcal/mol for the 2×4 surface and 32 kcal/mol for the 4×6 surface. The adsorbed species in chloride ALE process is also discussed with reference to the surface residence time of GaCl.
High-Resolution Electron Energy-Loss Spectra of Solid C60
Authors: Kuzuo Ryuichi , Terauchi Masami , Tanaka Michiyoshi , Saito Yahachi , Shinohara Hisanori
Published: February 2005

High-resolution electron energy-loss spectra were obtained from solid C60. Two bulk plasmon peaks were observed at 6.4 eV and 25.5 eV. Eleven fine features due to single electron excitations were observed as shoulders of the two plasmon peaks at 2.1, 2.8, 3.7, 5.1, 6.1, 7.5, 9.5, 10.7, 15, 18 and 20 eV. The `Einsatz' point at 1.4 eV in the imaginary part ε2 of the dielectric function, which was obtained by Kramers-Kronig analysis of the spectra, may be due to the interband transition (band gap) between the highest occupied electronic state and the lowest unoccupied state.
Large Dielectric Dispersion in Ordered Perovskite Pb(Yb1/2Nb1/2)O3
Authors: Naohiko Yasuda Naohiko Yasuda , Hiroshi Inagaki Hiroshi Inagaki
Published: February 2005

A large dielectric dispersion in ordered perovskite Pb(Yb1/2Nb1/2)O3 has been observed over a wide temperature range of -140 to 190°C in the frequency range of 1 kHz to 4 MHz.
Microstructure of Rapidly Quenched Bismuth Iron Oxide Systems with Ferromagnetic Character
Authors: Tanaka Katsuhisa , Hirao Kazuyuki , Mori Naohiro Soga
Published: February 2005

Mössbauer measurements and high-resolution electron microscopy have been carried out on rapidly quenched 10CaO·30Bi2O3·60Fe2O3 and Bi3Fe5O12 which exhibit ferromagnetic character at room temperature. The intensity of the peaks due to internal fields in Mössbauer spectra are very weak at room temperature and increases with a decrease of temperature, indicating that the specimens are superparamagnetic. The electron micrograph clearly shows that the specimens contain microcrystals of 5 to 10 nm. The ferromagnetic character of the present oxides is brought about by the ferrimagnetic microcrystals precipitated.
Influence of Wall Material on Charge-Exchange Neutral Emission from High-Temperature Hydrogen Plasma
Authors: Nishimura Kenji , Kaoru Ohya Kaoru Ohya , Ichiro Mori Ichiro Mori
Published: February 2005

The wall effect on the energy spectra of charge-exchange neutrals emitted from a high-temperature plasma is investigated using Monte Carlo calculations of transports of the neutrals, not only in the plasma but also in the wall. The results show that, in high- (low-) density plasma, the high- (low-) energy component of the spectra increases with backscattering from the wall surface. This variation is enhanced with the use of heavy materials for the wall. Furthermore, the ionization loss of the neutrals in the wall and the sputtering of the wall are discussed.
Memory Device Using a Conducting Polymer and Solid Polymer Electrolyte
Authors: Kaneto Keiichi , Tanemasa Asano Tanemasa Asano , Wataru Takashima Wataru Takashima
Published: February 2005

An electrically erasable memory device is fabricated using a conducting polymer and solid polymer electrolyte. The conductivity of the memory channel consisting of the conducting polymer is controlled by electrochemical doping through the counter (writing) electrode. The channel conductivity was varied by the number of writing or erasing pulses by 3-4 orders of magnitude.
Effect of Reduction on Superconductivity and Electronic State of Nd-Ce-Cu-O System
Authors: Yokoyama Yuko , Katayama Toshikazu , Oyanagi Hiroyuki , Hasumi Yuichi , Yoshikazu Nishihara Yoshikazu Nishihara
Published: February 2005

The effect of reduction on the superconductivity and electronic state of Nd2-x
Ce
x
CuO4-δ has been investigated by measurements of the magnetization and X-ray absorption near-edge structure of the Cu K-edge for specimens annealed at various oxygen pressures and temperatures. The superconducting onset temperature and diamagnetization increase with decreasing oxygen partial pressure of annealing. We find that the electron density estimated from the edge shift of the Cu K-edge absorption increases with the increase in the degree of reduction and that the magnitude of superconductive diamagnetization becomes constant above a certain degree of reduction. It is concluded that the electron density beyond a certain critical value is necessary for the occurrence of the superconductivity in this system.
Low Density of Gap States in a-Si:H Deposited by Vacuum UV Direct Photochemical Vapor Deposition Method
Authors: Shirafuji Tatsuru , Yoshimoto Masahiro , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

a-Si:H films are deposited by direct photochemical vapor deposition using a vacuum ultraviolet light (147 nm) emitted from a microwave-excited Xe resonance lamp. The hydrogen concentration is estimated to be less than 9 at.% for deposition temperatures ranging from 200 to 300°C. The hydrogen bonding configuration is mainly Si-H. Defect densities estimated from below-gap absorption coefficients reach 2.2×1015 cm-3. Mobility-gap E
µ measured using an internal photoemission method is about 1.80 eV, which is 0.05 eV larger than its optical gap E
opt of 1.75 eV. The difference between E
µ and E
opt is smaller than that of conventional GD films, which suggests that localized state densities at the band edges are lower.
Deposition of TiO2 Films by Reactive Sputtering in Magnetic Field
Authors: Akira Shibata Akira Shibata
Published: February 2005

When TiO2 films are deposited on a Si substrate, the magnetic screening of the substrate is proposed to reduce the deep-level trap by Ti atom bombardment. The substrate is placed in the field of a permanent magnet. It is found that the films deposited with the magnet do not form any deep level in the substrate, and exhibit better optical property and crystalline structure than those deposited without the magnet.
Improved Electron Mobility of Two-Dimensional Electron Gas Formed Area-Selectively in GaAs/AlGaAs Heterostructure by Focused Si Ion Beam Implantation and MBE Overgrowth
Authors: Kawano Akihiro , Arimoto Hiroshi , Kitada Hideki , Akira Endoh Akira Endoh , Toshio Fujii Toshio Fujii
Published: February 2005

We studied the effects of annealing and the Si implantation dose on the electrical properties of two-dimensional electron gases formed area-selectively in GaAs/Al
x
Ga1-x
As (x=0.3) heterostructures by focused Si ion beam implantation into AlGaAs and GaAs MBE overgrowth. The implanted Si was electrically activated by rapid thermal annealing (RTA: 1000°C, 6 s). We found that pre-annealing at 600°C for 30 minutes prior to the RTA suppresses Si outdiffusion into the GaAs channel layer, and that lower implantation doses produce higher electron mobilities. We also found that low energy implantation and pre-annealing at 600°C for one hour before MBE overgrowth improve electron mobility. We obtained an electron mobility of 32000 cm2/V·s at 77 K with a Si dose of 2×1012 cm-2.
Detection of Oxygen Deficient Regions in YBa2Cu3Ox Superconductors by Polarized Optical Microscopy
Authors: Murakami Masato , Yoshida Masashi , Fujimoto Hiroyuki , Gotoh Satoshi , Naoki Koshizuka Naoki Koshizuka , Shoji Tanaka Shoji Tanaka
Published: February 2005

We have found that oxygen deficient regions in YBa2Cu3O
x
superconductors exhibit different colors from that of the matrix under polarized light. When oxygen annealing was insufficient, large melt-grown YBaCuO crystals occasionally contained narrow bands exhibiting different colors where the twin structure was absent. Upon annealing in oxygen atmosphere, these banded regions disappeared, indicating that these regions are oxygen deficient. Raman spectroscopy measurements also confirmed that such regions are oxygen deficient.
Observation of Magnetic and Nuclear Phase Shifts of Neutrons by Interferometry
Authors: Nakatani Shinichiro , Hasegawa Yuji , Tomimitsu Hiroshi , Kikuta Toshio Takahashi
Published: February 2005

The variation of intensities of O-(transmitted) and H-(diffracted) neutron beams from a perfect crystal neutron interferometer of LLL type was measured, using both non-magnetic and ferromagnetic materials as phase shifters. The visibilities of the intensity oscillation curves of O- and H-beams changed as a function of the rotation angle of the ferromagnetic plate owing to the magnetic double refraction of neutrons. The agreement between experimental results and calculated ones was well.
GaAs/AlGaAs Lensed Light Emitting Diode by the Meltback and Regrowth in Liquid Phase Epitaxy
Authors: Hahm Sung-Ho , Gyu-Seog Cho Gyu-Seog Cho , Young-Se Kwon Young-Se Kwon
Published: February 2005

AlGaAs micro-lens was fabricated for light emitting diode (LED) applications using the liquid phase epitaxy (LPE) meltback technique. The lenses can be used to enhance the optical power of AlGaAs/GaAs LED's. The meltback technique using the LPE provides simple fabrication procedures which is not easily achieved in the conventional lensed
structure.
Determination of the Dominant Nonradiative Recombination Parameters in Heavily Si-Doped GaAs/AlGaAs Multiple Quantum Well Structures
Authors: Patel Suryakant , Kamata Norihiko , Eiji Kanoh Eiji Kanoh , Koji Yamada Koji Yamada
Published: February 2005

The trap density, electron and hole capture rates of the dominant nonradiative recombination center in heavily Si-doped ([Si]=1.6×1019 cm-3) GaAs/Al0.22Ga0.78As multiple quantum well structures were determined by examining the excitation power dependence of time-resolved photoluminescence characteristics. Sufficient power excitation allowed us to observe the increase of the band emission lifetime due to the trap-filling effect. A theoretical analysis based on the deep-level statistics agreed fairly well with the experiment, which revealed the recombination mechanism in such a heavily doped condition for the first time.
In Situ Optical Observation of Surface Kinetics during GaAs Metalorganic Chemical Vapor Deposition
Authors: Yamauchi Yoshiharu , Naoki Kobayashi Naoki Kobayashi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: February 2005

GaAs growth process is investigated by in situ optical methods during metalorganic chemical vapor deposition. Formation and annihilation of Ga droplets are observed on GaAs surface, using surface photo-absorption and scattered light observations. When triethylgallium is supplied in excess of one Ga atomic layer coverage to the As-stabilized surface, the scattered light is observed after the saturation of reflectivity due to surface photo-absorption, indicating Ga droplet formation on the surface. AsH3 supply to the surface with Ga droplets results in the annihilation of these droplets followed by the formation of the As-stabilized surface. These are observed, respectively, from the decay of scattered light intensity and subsequent decay of reflectivity of the surface photo-absorption.
Photoelectron Emission Study of Hydrogenated Amorphous Carbon Films Prepared by RF Plasma Chemical Vapor Deposition
Authors: Nakayama Masatoshi , Ueda Kunihiro , Shibahara Masanori , Maruyama Kazunori , Kamata Kiichiro
Published: February 2005

The ultraviolet (UV) threshold energy for photoelectron emission of the carbon films synthesized by the RF plasma chemical vapor deposition (CVD) method with additional dc bias negative to the substrate was measured with an atmospheric UV photoelectron analyzer. The additional dc negative bias decreased the UV threshold energy and the amount of CH2and CH3groups (hydrogen content) of the carbon films, and increased the Vickers hardness and refractive index. The applied negative bias is considered to promote the formation of a network structure like that of diamond.
Effect of Coating on the Plasma Chamber Wall in RIKEN Electron Cyclotron Resonance Ion Source
Authors: Takahide Nakagawa Takahide Nakagawa
Published: February 2005

The beam intensities of carbon, nitrogen, and argon ions from the RIKEN ECR (electron cyclotron resonance) ion source were measured before and after producing aluminum and magnesium ions. Aluminum and magnesium ions were produced by radially inserting a ceramic rod (Al2O3, MgO) into the plasma in the second stage of the ECR ion source. It has been observed that the beam intensities of higher-charge-state ions are enhanced after producing aluminum and magnesium ions. This is supposed to be due to the effect of the coating of aluminum and magnesium oxide on the plasma chamber wall.
Detection of Strain in InP/InGaP Superlattices by Dark-Field Electron Microscopy and Nano-Diffraction Technique
Authors: Tanaka Nobuo , Kakibayashi Kazuhiro Mihama
Published: February 2005

Lattice bending around the interfaces of strained InP/InGaP/InP superlattices was analyzed by using thickness fringes in the dark-field electron microscopy and nanometer-area electron diffraction patterns. The present paper is complementary to a previous paper about strain detection by using thickness fringes in the bright-field electron microscopy (Jpn. J. Appl. Phys. 30 (1991) L52). By using the two methods, lattice bending around the interfaces of the superlattices with a lattice misfit of 1% was quantitatively evaluated in a three-dimensional form. Comparison between the methods and the usual lattice-imaging method in high-resolution electron microscopy(HREM) is discussed.
Achieving High Current Gain and Low Emitter Resistance with the SiCx:F Widegap Emitter
Authors: Sugii Toshihiro , Tatsuya Yamazaki Tatsuya Yamazaki , Takashi Ito Takashi Ito
Published: February 2005

We investigated the relationship between current gain and emitter resistance of the heterojunction bipolar transistor using an SiC
x
terminated by fluorine atoms (SiC
x
:F) widegap emitter and achieved high current gain and low emitter resistance. The emitter resistance of about 40 Ω·µm2 and no relationship between current gain and emitter resistance indicate the absence of the interfacial oxide effect on the electrical characteristics. The compatibility of high current gain and low emitter resistance will lead to higher cut-off frequency due to decreased emitter charge storage.
Effect of Ion Doping Process on Thin-Film Transistor Characteristics Using a Bucket-Type Ion Source and XeCl Excimer Laser Annealing
Authors: Aoyama Takashi , Kawachi Genshiro , Mochizuki Yasuhiro , Suzuki Takaya
Published: February 2005

The effect of the ion doping process on polysilicon thin-film transistor (TFT) characteristics was investigated using a bucket-type ion source and XeCl excimer laser annealing. Generally, as the acceleration voltage (V
a) of phosphorous ions, the doping time (t
d) and the laser energy (E
a) for impurity activation increased, the field effect mobility (µ) was increased and the leakage current (I
off) was decreased. The conditions of V
a from 1.5 to 2.0 kV, t
d from 10 s to 5 min, and E
a from 150 to 260 mJ/cm2 were found to enable TFT performance with µ of more than 20 cm2/Vs, threshold voltage of less than 5 V, and I
off of less than 5×10-11 A.