bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Hydrogen in Improvement of the Critical Temperature of Ceramic YBa2Cu3O7-x by Proton Implantation
Authors: Yokota Katsuhiro , Kura Takeshi , Katayama Saichi , Ochi Mitsukazu , Murakami Mitsuaki , Chayahara Akiyoshi , Satho Mamoru
Published: February 2005

Proton-implanted YBCO annealed in O2 atmosphere at 500°C had a critical temperature (T
c) of 93.1 K, higher than the value of 87 K for as-sintered YBCO. However, this improvement in T
c did not result from an increase in the number of O atoms bonding with Y, Ba, and Cu in the superconducting phase by the presence of H atoms.
Numerical Studies on Parameters for Stable Adiabatic Inversion by Gaussian and Square Pulses
Authors: Adachi Satoru , Niki Hideaki , Izawa Yasukazu , Yamanaka Sadao Nakai
Published: February 2005

Adiabatic inversion processes are discussed for a two-level system. It was found that the required conditions for stable inversion are Ω2/ | dΔ/dt | ≥0.5, Δsτ≥3 for Gaussian pulse and Δs/Ω≥11 for square pulse, where Ω, Δ, Δs and τ represent Rabi frequency, detuning, frequency-sweep width and optical pulse width, respectively. It was also shown that for Gaussian pulse, adiabatic conditions of Δs/Ω and Ω2/ | dΔ/dt | are related to each other, while for square pulse, both conditions are determined independently.
Influence of Recoiling Target Atoms on Kinetic Electron Emission from Molybdenum under keV Ion Bombardments
Authors: Kawata Jun , Ohya Kaoru , Mori Ichiro
Published: February 2005

Ion-induced kinetic electron emission from molybdenum in the energy range 0.7-40 keV is investigated using Monte Carlo calculations of the electron yield and the emission statistics, taking into account the electron excitations by ions and recoil atoms. The factor f
0/ε evaluated by fitting the calculations to experimental electron yields decreases at low energy, and with heavy ions (f
0: the escape probability through the surface, ε: the energy deposited to excite one electron). If the mass of the ion is larger than that of the target atom, the kinetic emission is dominated by the electron excitation by the recoils. With increasing mass of the ion, there is a complete antithesis between the emission statistics of the ion and of the recoils because of the energy transfer from the ion to the target atoms through frequent elastic collisions.
Effect of Acid Diffusion on Resolution of a Chemically Amplified Resist in X-Ray Lithography
Authors: Nakamura Jiro , Ban Hiroshi , Kimiyoshi Deguchi Kimiyoshi Deguchi , Akinobu Tanaka Akinobu Tanaka
Published: February 2005

The diffusion range of acids in a chemically amplified positive resist (EXP) was quantitatively evaluated using a contact replication method. The acid diffusion range reached a maximum depth of 0.4 µm. The acid diffusion range was diminished, as the temperature of prebaking was raised or the temperature of post-exposure baking (PEB) was reduced. The acid diffusion range also exerted a great influence on changing the replicated pattern width dependence on exposure dose. To clarify the effect of the acid diffusion on the characteristics of the resist, the distribution of the acid-catalyzed reaction in the resist and the acid diffusion range were calculated using the diffusion coefficient of the acid and the acid-catalyzed reaction rate constant determined by experiments. The calculated acid diffusion range coincided rather well with that obtained by the contact replication method.
Solubility and Diffusion Coefficient of Electrically Active Titanium in Silicon
Authors: Shigehiro Kuge Shigehiro Kuge , Hiroshi Nakashima Hiroshi Nakashima
Published: February 2005

The deep impurity levels and the solubility of titanium in silicon have been investigated by deep level transient spectroscopy (DLTS). It is found that titanium forms multilevels with an acceptor level of E
C-0.09 V, a donor level of E
C-0.27 eV and a double-donor level of E
V+0.28 eV. The solubilities as a function of reciprocal absolute temperature show a good straight line with the activation energy of 3.8 eV. The diffusion coefficient is determined in the high temperature range 1050-1150°C and in the lower range 600-800°C. The diffusion coefficient is represented by D
Ti=1.2×10-1 exp (-2.05/kT) cm2 s-1.
Theory of Optical Second-Harmonic Generation in Slab Waveguides with Dissipative Nonlinear Dielectric Cores
Authors: Tomohiro Onda Tomohiro Onda , Ryoichi Ito Ryoichi Ito
Published: February 2005

A theory of optical second-harmonic generation (SHG) in a dissipative slab waveguide is presented, where Cerenkov-radiation-type SHG and guided-mode-type SHG are treated on an equal basis. Analytical solutions of the field distribution are obtained for TE-mode second-harmonic waves generated in a slab waveguide consisting of a dissipative nonlinear-dielectric core and nondissipative linear-dielectric claddings. We then study the effects of absorption on the conversion efficiency, providing typical examples of numerical calculation for Cerenkov-radiation-type SHG.
Blue-Green Emitting SrS:Ce, Cl Thin-Film Electroluminescent Devices Prepared by Reactive Evaporation Using H2S Gas
Authors: Tohda Takao , Okajima Michio , Yamamoto Makoto , Matsuoka Tomizo
Published: February 2005

SrS:Ce, Cl phosphor films were deposited by evaporating Sr metal and CeCl3 in H2S gas. The crystallinity, luminance, and emission spectra of the films were investigated in relation to the deposition conditions. X-ray diffraction intensity from the (200) plane of the SrS films was found to increase with the substrate temperature when the H2S pressure was kept constant, and had the maximum value at the H2S pressure of 1×10-2 Pa when the substrate temperature was kept constant. The variation of luminance in relation to the H2S pressure and the substrate temperature was similar to that of the (200) diffraction intensity. The luminance of 600 cd/m2 and the maximum emission efficiency as high as 1 lm/W were obtained at 1 kHz 30 µs wide ac pulse excitation for the films deposited at 600°C and H2S pressure of 1×10-2 Pa, although the emission color was not blue but whitish green.
Temperature Dependence of Photoconductivity Spectra and Phase Lag of p-Type CuGaS2 by Polarized Light Excitation
Authors: Susaki Masami , Horinaka Hiromichi , Yamamoto Nobuyuki
Published: February 2005

Photoconductivity spectra and phase lag of the photocurrent for the modulated excitation light are studied between 80 and 340 K on undoped p-type CuGaS2. For the low-resistivity samples, both the intrinsic peak and the extrinsic peak via shallow donor are clearly observed in the polarization-dependent spectra, indicating the selection rule of the uppermost valence bands. For the high-resistivity samples, however, the polarization-dependent behavior of the spectra is greatly reduced due to the mergence of the broadened shallow donor band into the conduction bandtails. On the other hand, a broad peak via deep donor is observed for both types of samples, where almost trap-free hole current with a small phase lag is dominant below 250 K. Above 250 K, there appears a rapid increase in the phase lag, showing the enhancement of the thermal release of trapped holes on a shallow acceptor state.
Magnetic and Electrical Properties of Nonequilibrium Fe-W Alloys Produced by Sputter Deposition
Authors: Sumiyama Kenji , Masashi Hirata Masashi Hirata , Wataru Teshima Wataru Teshima
Published: February 2005

X-ray diffraction, magnetization and electrical resistivity have been measured for Fe1-x
W
x
alloys sputter deposited on water-cooled and liquid-nitrogen-cooled substrates. A single bcc phase appears for 0<x<0.2 and 0.7<x<1.0, while an amorphous phase for 0.2<x<0.6, being independent of the substrate temperature. The bcc phase is ferromagnetic for x<0.8, while the amorphous phase is paramagnetic even at 4.2 K. The magnetic moments of Fe atoms in the Fe-rich bcc alloys are larger than that of pure Fe. The residual resistivity of the amorphous alloys is larger than that of the bcc alloys, being smaller than 1.5 µΩm, and the temperature coefficient of resistivity is slightly positive for the whole concentration.
Study of Surface Reaction Probability of CFx Radicals by Trench Deposition Method
Authors: Yabe Hideki , Akimasa Yuuki Akimasa Yuuki , Yasuji Matsui Yasuji Matsui
Published: February 2005

The surface reaction probabilities of CF
x
radicals are determined with a trench deposition method for C:H:F films deposited by the discharge in a CF4/H2 mixture. It is found that the overall sticking probability of CF
x
is β=0.1-0.2 and 0.2 for substrates placed on the reactor wall and on the earth electrode, respectively. The respective roles of the sticky and less-sticky radicals (probably CF and CF2, respectively) are derived by making use of the film profiles, and their sticking probabilities are found to be about 1.0 and 0.05, respectively. Moreover, it is shown that the method is applicable to estimate the contribution of the ion-enhanced deposition, e.g., 50-60% of the film thickness for the present condition of the gas flow ratio of CF4/H2=19/16 at the rf discharge pressure of 0.4 Torr.
RHEED Investigation of the Au(001)-p(2×2)-As Structure Induced by the Deposition-Concurrent Surface Segregation of As
Authors: Ken-ichi Sano Ken-ichi Sano , Tsugio Miyagawa Tsugio Miyagawa
Published: February 2005

We observed the p(2×2) structure on the surface of Au(001) during the epitaxial growth of Fe/Au multilayers on GaAs(001). This structure disappeared after removal of the segregated As atoms by sputter etching for a short period, and transformed to a hexagonal structure of the 5×1 type, the well-known surface reconstruction of the clean Au(001) surface. When the deposition of Au was conducted on sputter-etched clean surfaces of Fe(001), the surface structure was of the 5×1 type instead of p(2×2). These results show that the p(2×2) structure is induced by the surface segregation of As on Au surfaces during the deposition. The p(2×2) structure transformed to 1×1 after depositing less than 0.4 ML of Fe atoms. The correlation between the process of the deposition-concurrent surface segregation and the observed surface structure is discussed.
Variation of the Recombination Coefficient of Atomic Oxygen on Pyrex Glass with Applied RF Power
Authors: Wickramanayaka Sunil , Hosokawa Naokithi , Yoshinori Hatanaka Yoshinori Hatanaka
Published: February 2005

The wall recombination coefficient (γ) of atomic oxygen on a pyrex surface and O(1D) concentration in the downstream flow were measured in a radio-frequency (13.56 MHz) oxygen discharge in the applied power region of 200 W-2500 W. The NO2
* continuum intensity was used to monitor the atomic oxygen. The γ varies from 1.1×10-4 to 6.1×10-5, having a minimum value of 5.1×10-5 at 700 W, at which point the glow discharge plasma changes to an arclike plasma. The mechanism of the transition of glow discharge plasma to arclike plasma and possible reasons for the inconstant γ are discussed in light of electron density, O(1D) concentration in the downstream flow, and the gas temperature.
Electron-Impact Dissociation of Methane into CH3 and CH2 Radicals I. Relative Cross Sections
Authors: Nakano Tohru , Hirotaka Toyoda Hirotaka Toyoda , Hideo Sugai Hideo Sugai
Published: February 2005

The abundances of primary neutral radicals CH3 and CH2 resulting from electron-impact dissociation of methane have been measured. This was accomplished with threshold-ionization mass spectrometry in a differentially pumped dual-electron-beam device. The relative partial cross sections for dissociation into CH3 and CH2 are reported for electron energies between 10 and 100 eV. A maximum cross section is found at 20-30 eV for both CH3 and CH2 radicals. At higher energies, the cross section decreases rather sharply, in particular for dissociation into the CH2 radical.
Fundamentals of Nondestructive Measurement of Biaxial Stress in Steel Utilizing Magnetoelastic Effect under Low Magnetic Field
Authors: Kenji Kashiwaya Kenji Kashiwaya
Published: February 2005

The relationship between magnetization and principal stress under a triaxial stress field is deduced theoretically from an equilibrium condition between magnetoelastic and magnetization energies calculated on polycrystalline iron. The relationship is expressed by a formula in which the intensity of magnetization parallel to the principal axis of the stress tensor decreases in proportion to the difference between the largest principal stress and the magnetizing-directional principal stress. A biaxial stress is developed in a cruciform testpiece made of mild steel, and then magnetizations in the direction of principal stress parallel and normal to the surface of the testpiece are measured using U- and C-shaped magnetic sensors, respectively. The measured results are revised considering the spread of magnetic flux. The experimental results fundamentally agree with theoretical predictions. The quantitative discrepancies are discussed.
Pattern Transfer Characteristics of Transparent Phase Shifting Mask
Authors: Watanabe Hisashi , Sugiura Emiko , Yoshihiro Todokoro Yoshihiro Todokoro , Morio Inoue Morio Inoue
Published: February 2005

Phase shifting technologies achieve significant improvement in both resolution and depth of focus (DOF). We have proposed a “transparent-type” phase shifting mask which has a simple structure (no Cr layer) that considerably improves the resolution limit of optical lithography.1) In this paper, we describe in detail pattern transfer characteristics of the transparent phase shifting mask with i-line steppers. The effects of numerical aperture (NA) and coherence factor (σ) on the resolution capability and DOF were investigated using simulations and experiments. Patterns are printed using i-line steppers with a numerical aperture (NA) of 0.45 and 0.65. A pattern of 0.23 µm lines and spaces is resolved with a 0.45 NA i-line stepper. DOF for 0.25-µm features is found to be in the 1.5-µm range. Well-resolved 0.18-µm lines and spaces are obtained with a 0.65-NA i-line stepper. Transparent phase shifting mask technologies extend the resolution limit of i-line lithography to the resist features below 0.2 µm.
Dynamic Characteristics of Optical Bistability and Limiting in Polymer Dispersed Liquid Crystal
Authors: Tagawa Akira , Ozaki Masanori , Munezawa Takuro , Nomura Yasuo , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Hybrid optical bistability and limiting using electro-optical effect in the polymer dispersed liquid crystal (PDLC) with electrical linear feedback have been studied. Optical limiting and bistability are realized for the case of negative and positive feedbacks, respectively. Dynamic properties of switching between optical bistable states by the incident light pulse are also studied. The switching can be realized by superimposing the light pulse of a very short duration (several hundred µs) on the incident light.
Fabrication of 0.25-µm Patterns on a Membrane Substrate-Based X-Ray Absorber
Authors: Fujino Takeshi , Hashimoto Motoko , Yoshioka Nobuyuki , Moriizumi Koichi , Satou Tetsuo , Hiroaki Morimoto Hiroaki Morimoto , Yaichiro Watakabe Yaichiro Watakabe
Published: February 2005

X-ray mask fabrication techniques, which are used in X-ray lithography for 0.25-µm devices, are studied in this paper. Initially, the process latitude for both the single- and trilayer processes is discussed according to the simulation results. The bottom layer thickness in the trilayer process was optimized to reduce the influence of backscattered electrons, and a proximity effect correction was introduced for the 0.25-µm pattern fabrication. In order to suppress membrane heating, a reverse-side polyvinyl alcohol (PVA) coating method was developed. The temperature was monitored with a special thermometer, and the effectiveness of the PVA coating was examined.
X-Ray Mask Technology Utilizing an Optical Stepper
Authors: Oizumi Hiroaki , Soga Takashi , Ogawa Taro , Masayoshi Saitoh Masayoshi Saitoh , Kozo Mochiji Kozo Mochiji
Published: February 2005

An X-ray mask with half of a 64-Mbit dRAM chip whose minimum feature size was 0.3 µm wide was developed using a W absorber on a SiN membrane. To precisely control the W film stress, Ar+ ions were implanted into the W film prepared by chemical vapor deposition (CVD). To evaluate mask-to-mask overlay accuracy except that due to electron-beam-writing error, pattern placement measurement marks were delineated by optical exposure. It was found that the overlay accuracy between two masks with different pattern densities could be 0.08 µm (3σ) which is very nearly the limit of measurement accuracy.
Dynamic Oscillation Modes Caused by a Pulsed X-Ray Exposure in an X-Ray Mask Membrane
Authors: Akira Chiba Akira Chiba , Koichi Okada Koichi Okada
Published: February 2005

The dynamic behavior with three oscillation modes caused by pulsed X-ray exposure in an SiN X-ray mask membrane has been predicted by simulation using the weighted residual method. The displacement caused by thermal distortion cannot take place during pulsed X-ray exposure with a 10-ns pulse duration in the three dynamic response modes: damped oscillation, critical damping, and overdamping. The damped oscillation mode with an overshooting effect is caused by an elastic wave effect after a 1-µs time lapse. According to the pulse duration effect, the dynamic behavior is divided into three regions: quasi-static, transient, and saturated regions. For the quasi-static region, the elastic wave effect and three oscillation modes can be neglected. Differences in the dynamic behavior occur in the transient region. In the saturated region, the displacement cannot take place during the pulsed X-ray exposure, due to the elastic wave effect.
Dissolution Inhibition of Phenolic Resins by Diazonaphthoquinone: Effect of Polymer Structure
Authors: Hattori Takashi , Ueno Takumi , Shiraishi Hiroshi , Nobuaki Hayashi Nobuaki Hayashi , Takao Iwayanagi Takao Iwayanagi
Published: February 2005

In order to understand the basic mechanisms working in the dissolution of phenolic resin/diazonaphthoquinone (DNQ) positive photoresists, several polyhydroxystyrene derivatives have been studied in terms of their dissolution capabilities. The influence of the structure and the molecular weight distributions of phenolic resins on the inhibition effect were examined. In phenolic resins which have alkyl groups ortho to the hydroxy group a strong dissolution inhibition effect is found. As for the molecular weight distribution, the mixtures of a higher-molecular-weight polymer with lower dissolution rate and a lower-molecular-weight polymer with higher dissolution rate give strong dissolution inhibition by DNQ.
Evaluation of Hydrogenation on Semiconductor Surfaces Treated with Hydrogen-Plasma Beam Excited by Electron Cyclotron Resonance
Authors: Koui Tomoaki , Suemune Ikuo , Kishimoto Akihiro , Kazuhiko Hamaoka Kazuhiko Hamaoka , Masamichi YAmanishi Masamichi YAmanishi
Published: February 2005

Hydrogen (H) plasma excited by electron cyclotron resonance (ECR) offers a powerful technique for cleaning semiconductor surfaces at low temperature and for realizing atomically flat surfaces. This paper evaluates the neutralization of impurities near semiconductor surfaces during the H-plasma cleaning process, which is known as the hydrogenation effect. It was found that hydrogenation in the present ECR cleaning process is quite different from that in the usual radio-frequency plasma. It was found that hydrogenation with the H-plasma excited with ECR is dependent on the angle of incidence of the plasma beam and is also dependent on the presence of the surface oxide and on the related surface flatness in the atomic level.
Ionized Cluster Beam Deposition Source for Aluminum and Aluminum Oxide Formation
Authors: Ito Hiroki , Kajita Naoyuki , Shigeru Yamaji Shigeru Yamaji , Yoshibumi Minowa Yoshibumi Minowa
Published: February 2005

Low-energy ion bombardment during film growth can significantly modify film properties. The advantages of using the ionized cluster beam (ICB) deposition techniques include reduced damage and high deposition rates at low temperature. The long-lived ICB source without the electron extractor is designed for an in-house experiment of aluminum deposition. In the initial experiment for aluminum metallization, low resistivity and highiy preferrentially oriented Al films were obtained at acceleration voltages from 0.5 to 1.0 kV and at room temperature. This ICB source provides uniform ion current profiles within ±10% at deposition rates up to 0.1 µm/min over a 254 mm-diam substrate. It has been operated for more than 300 µm-thick Al film deposition without any maintenance.
Focused Ion Beam Induced Deposition in the High Current Density Region
Authors: Takahashi Yoshio , Yuuichi Madokoro Yuuichi Madokoro , Tohru Ishitani Tohru Ishitani
Published: February 2005

Focused ion beam induced deposition (FIB·ID) in a high current density region is investigated. High current density experiments are done with current densities of 1.3 A/cm2 and 8.6 A/cm2. A 30 kV Ga+ beam is line-scanned at various scanning speeds over a SiO2 substrate in a W(CO)6 gas environment. To analyze these results, a conventional model is improved by taking into consideration FIB scanning and impurity effects. The FIB·ID is simulated in a wide current density region using the improved model. It is found that shortening the dwell time is more effective than increasing the precursor gas flux for the high current density FIB·ID.
Alignment Technique for Thin-Film-Transistor Liquid-Crystal Displays
Authors: Shimada Shinji , Nomura Takao , Takahashi Eiichi , Adachi Masahiro , Toda Kiyoshi , Mitsuo Ishii Mitsuo Ishii , Katsunobu Awane Katsunobu Awane
Published: February 2005

In high-definition thin-film-transistor liquid-crystal displays (TFT-LCDs), it is important to establish the stability of liquid-crystal molecule alignment. In this paper, we describe the relation between pretilt angle and reverse tilt disclination in the high-definition TFT-LCD at 60°C. We conclude that a pretilt angle of more than 3° is required to prevent the occurrence of the reverse tilt disclination. Next, we consider this result, using a brief computer simulation on the electric field distribution in the TFT-LCD. Then, we describe the temperature dependence of the pretilt angle. We conclude that we can control the magnitude of pretilt angle by changing liquid crystal, polyimide material and process conditions, but the pretilt angle decreases at the same rate as the temperature becomes higher, without dependence on these parameters.
Properties of Silicon-Oxygen Alloy Films Prepared from SiH4+CO2 Gas Mixture
Authors: Haga Koichi , Murakami Akishige , Yamamoto Kenji , Watanabe Masafumi Kumano
Published: February 2005

Measurement of electrical properties, etch rates in HF (49%) and HF-HNO3 (49% HF:63% HNO3=1:20) solutions and X-ray photoemission spectra are reported for amorphous silicon-oxygen alloy films (a-SiO
x
:H) prepared by r. f. glow discharge decomposition of a SiH4-CO2 gas mixture. Activated band conduction is observed in the temperature range of 324-424 K. Though the addition of oxygen causes a decrease in the conductivity, the activation energy for conduction remains at a constant value of around 1.0 eV in the films with oxygen content x from 0.17 to 0.5. The broadening toward the high binding energy of the Si-2p core level in X-ray photoemission spectra with oxygen content is explained by the effects of oxygen atoms incorporated into the films.
Photoluminescence Properties of Cu+ Centers in MgS, CaS, SrS and BrS
Authors: Nobuhiko Yamashita Nobuhiko Yamashita
Published: February 2005

The detailed emission and excitation spectra and the temperature dependence of the excitation efficiency are obtained for MgS:Cu+, CaS:Cu+, SrS:Cu+ and BaS:Cu+ at various temperatures between 16 and 293 K. In the excitation spectra of all the powder phosphors, two bands assigned to the intraionic transitions in the Cu+ ion are observed. The luminescence mechanism is explained by the isolated Cu+ ion model. The temperature dependence of the excitation efficiency suggests that the Cu+ ion in CaS, SrS and BaS occupies an off-center position of the sulfur octahedron.
Method of the Selenization of Liquid Cu-In Alloy for the Synthesis of CuInSe2
Authors: Nomura Shigetaka , Takizawa Takeo , Kudo Takayoshi , Yasushi Nagata Yasushi Nagata , Toshiyuki Mounai Toshiyuki Mounai
Published: February 2005

A method of the selenization of a Cu-In alloy for the synthesis of CuInSe2 is presented. This method can avoid binary compounds formed in the reaction processes which have been one of the main problems of the stoichiometry control. A single phase of CuInSe2 is obtained with the selenization temperature above the melting point of CuInSe2. Below this optimum selenization temperature, Cu7Se4 and In2Se are found as additional phases, which is consistent with the formation mechanism of CuInSe2 in the normal melting method.
Organic Dyes/Co Hybrid Double Layered Film
Authors: Kitaguchi Tooru , Katayama Toshikazu , Suzuki Yoshishige , Koshizuka Nagayoshi Tsukane
Published: February 2005

A new enhancement method of Kerr rotation angle (θK) is developed in a hybrid double layered film consisting of a magnetic layer and a dye layer. A strong enhancement is observed near the electron transition wavelength of an organic dye. The wavelength and the value of θK enhancement do not depend on the thickness of the dye film at all. A magneto-optical disk using the structure is very interesting because the electron transition wavelength of an organic dye can be designed easily.
Memory Effects in Nematic Liquid Crystals by a Surface Molecular Reorientation
Authors: Nose Toshiaki , Shin Masuda Shin Masuda , Susumu Sato Susumu Sato
Published: February 2005

A liquid crystal cell with an asymmetric electrode structure is prepared by using a slit-patterned or a hole-patterned electrode and an unpatterned counterelectrode. Only the surface of the latter substrate is treated by rubbing. When the liquid crystal cell is once heated up to an isotropic phase and then cooled down to a nematic phase with a sufficiently high electric field, a memory effect of the molecular orientation along a lateral component of a nonuniform electric field, which is produced by the patterned electrode structure, is observed after removing the electric field. This memory state can be erased by heating the cell up to the isotropic phase and it can be reproduced repeatedly. These phenomena are discussed in terms of the molecular orientation effects on the surface of an alignment layer without rubbing treatment.
Dielectric Character Due to the Percolative Growth of Clusters in a Metal-Ceramics Mixture
Authors: Katsukuni Yoshida Katsukuni Yoshida
Published: February 2005

The dielectric property was measured to observe growth of metallic clusters in Nb-Al2O3 sintered mixtures with Nb volume fraction f ranging from 0 to 0.15. As Nb clusters grow large, the effective dielectric constant ε* (or capacitance) increases to diverge, reflecting the occurrence of the percolation transition at around f=0.15. The power law was found to hold for ε* with a critical exponent of 0.6.
Oxidation of Si(100) Surfaces with Bi and Ag Overlayers in Ozone Atmosphere
Authors: Yamada Tomoyuki , Mitsuhiko Ogihara Mitsuhiko Ogihara , Hitoshi Abe Hitoshi Abe
Published: February 2005

Desorption of Bi and Ag deposited on Si(100) surfaces has been studied by Auger electron spectroscopy for heat treatment in distilled ozone atmospheres. Bi was desorbed from the Si surface at a substrate temperature T
s of 350∼450°C and Ag was desorbed at T
s of 500∼570°C. The reflection high-energy electron diffraction (RHEED) patterns for Ag overlayers suggested that three-dimensional Ag(100) layers are formed on Si(100).
Growth of Ce-Substituted Yttrium Iron Garnet Films by MoO3-K2MoO4-Y2O3 Flux and Their Faraday Rotation Spectra
Authors: Tamanoi Ken , Nomoto Takenari , Shinagawa Kiminari , Toshiaki Saito Toshiaki Saito , Tachiro Tsushima Tachiro Tsushima
Published: February 2005

Ce-substituted YIG films are grown using a liquid-phase epitaxy method from MoO3-K2MoO4-Y2O3 pseudoternary flux. The growth rate is found to be less than that in PbO-based flux by 1/100. The films with more Ce3+ ions are grown from melts where CeVO4 is used as a starting cerium material. Ce doping of less than 0.05 (at./f.u.) is attained. Faraday rotation characteristics of the Ce-substituted YIG are observed in the grown films.
Intrinsic Gettering of Iron Impurities in Silicon Wafers
Authors: Aoki Masaki , Akito Hara Akito Hara , Akira Ohsawa Akira Ohsawa
Published: February 2005

We present a new experimental approach to using intrinsic gettering to remove Fe impurities. We annealed samples, followed by quenching, and measured the Fe concentration near the surface using deep-level transient spectroscopy. The supersaturation of Fe impurities is necessary for the intrinsic gettering of Fe. However, for a higher supersaturation, Fe impurities precipitate faster than gettering. The optimum degree of supersaturation is one order of magnitude. Gettering is limited by the reaction of Fe with the oxygen precipitates in the defect region, rather than by Fe diffusion to the defect region.
Photoluminescence of Si1-xGex/Si Quantum Well Structures
Authors: Terashima Koichi , Tajima Michio , Ikarashi Nobuyuki , Taeko Niino Taeko Niino , Toru Tatsumi Toru Tatsumi
Published: February 2005

Photoluminescence (PL) spectra of Si1-x
Ge
x
/Si multiple quantum wells (MQW) grown by molecular beam epitaxy (MBE) have been investigated. Strong emission bands appear for all the as-grown samples. The PL intensity is increased by a factor of 5-10 after the annealing at 600-700°C. The annealing at 800°C results in the disappearance of the strong emission bands. The dependence of the PL intensity on the excitation power density indicates that some recombination center is involved in the strong emission. Annealing effects of the PL spectra can be explained as the behavior of this recombination center under the heat treatments. Transmission electron microscopy (TEM) observations show that the quality of the quantum well structures is related to the observed PL characteristics. The intense PL may be due to the two-dimensional carrier confinement.
In Situ Observation of Electromigration in Cu Film Using Scanning µ-Reflection High-Energy Electron Diffraction Microscope
Authors: Masu Kazuya , Hiura Yohei , Tsubouchi Kazuo , Ohmi Tadahiro , Nobuo Mikoshiba Nobuo Mikoshiba
Published: February 2005

We have observed void and hillock formation at the grain boundary and inside the grain in the Cu line due to electromigration (EM), by means of in situ nondestructive imaging of micrograins using a scanning µ-reflection high-energy electron diffraction (µ-RHEED) microscope. Accelerated electromigration testing was performed at a dc current density of 5×106 A/cm2 and at 250°C in the scanning µ-RHEED microscope. The triple point of grain boundaries was confirmed to weaken the EM endurance. Furthermore, we conjectured that high EM endurance inside the grain could be achieved with the current flow along the <011> direction for fcc metal such as Cu.
High-Mobility and High-Stability a-Si:H Thin Film Transistors with Smooth SiNx/a-Si Interface
Authors: Uchida Hiroyuki , Takechi Kazushige , Shinichi Nishida Shinichi Nishida , Setsuo Kaneko Setsuo Kaneko
Published: February 2005

Through use of an atomic force microscope (AFM), surface morphologies for SiN
x
and a-Si:H films were investigated. By controlling deposition conditions, very smooth films have been obtained. The thin film transistor (TFT) with smooth a-Si:H on smooth SiN
x
has both high mobility (1.0 cm2·V-1·s-1) and high stability at the same time. This high-performance TFT will make an important impact in application to high-pixel-density liquid crystal displays (LCDs), such as for use in workstations and high-definition television (HDTV).
GaAs Interfaces with Octadecyl Thiol Self-Assembled Monolayer: Structural and Electrical Properties
Authors: Nakagawa O. S. , Ashok S. , Sheen C. W. , Märtensson J. , Allara D. L.
Published: February 2005

A passivation layer on chemically etched (100) GaAs surface was synthesized with octadecyl thiol, CH3(CH2)17SH, and its structural and electrical properties were investigated. The layer is a self-assembled monolayer (SAM) in all-trans-planar-zig-zag conformation and is the first conformationally ordered SAM on any semiconductor surface. The barrier height of GaAs Schottky diodes can be modified by the octadecyl thiol SAM passivation without sacrificing good diode characteristics. Octadecyl and other alkane thiol SAM's enable introduction of a nano-scale, controlled structure on a GaAs surface and prove useful in an assessing the GaAs surface electrical properties.
GaAs Pseudo-Heterojunction Bipolar Transistor with a Heavily Carbon-Doped Base
Authors: Nozaki Shinji , Saito Koki , Shirakashi Junichi , Qi Ming , Yamada Takumi , Tokumitsu Eisuke , Konagai Makoto , Matsumoto Kiyoshi Takahashi
Published: February 2005

A GaAs pseudo-heterojunction bipolar transistor with a heavily carbon-doped base grown by metalorganic molecular beam epitaxy was fabricated, and the highest dc current gain of 1.7 was obtained, which evidences band-gap narrowing in the base. However, hole injection from the base to the emitter still cannot be ignored, and the use of a heavily carbon-doped InGaAs base is proposed to improve transistor characteristics.
Carbon-Doped-Base AlGaAs/GaAs HBTs Grown by Gas-Source Molecular Beam Epitaxy Using Only Gaseous Sources
Authors: Takahashi Tsuyoshi , Yamaguchi Yasuhiro , Sandhu Adarsh , Ando Hideyasu , Toshio Fujii Toshio Fujii , Naoki Yokoyama Naoki Yokoyama
Published: February 2005

We report the fabrication and electrical characteristics of carbon-doped-base AlGaAs/GaAs heterojunction bipolar transistors (HBTs) grown by gas-source molecular beam epitaxy (GSMBE) using only gaseous sources. The base of HBTs is compositionally uniform and doped with carbon to a carrier concentration of 4×1019 cm-3. A current gain of 45 was obtained at a collector current density of 4×104 A/cm2. These HBTs were electrically stable under current stress, as confirmed by current gain and Gummel plots.
Reliable High-Power Operation of InGaAlP Visible Light Laser Diodes with Strained Active Layer
Authors: Nitta Koichi , Itaya Kazuhiko , Nishikawa Yukie , Ishikawa Masayuki , Masaki Okajima Masaki Okajima , Gen-ichi Hatakoshi Gen-ichi Hatakoshi
Published: February 2005

Reliable high-power operation of transverse-mode stabilized InGaAlP laser diodes has been achieved with a selectively buried ridge waveguide (SBR) structure and a very thin (150 Å) In0.62Ga0.38P active layer. A strained In0.62Ga0.38P layer was employed in order to improve the temperature characteristics during high-power operation. An over 100 mW maximum output power was obtained. Operation current density was found to have a large effect on the device reliability. Lasers with a long cavity operate in a low current density, resulting in an increase in device lifetime. In the 600 µm long SBR lasers, stable continuous wave (CW) operation exceeding 1000 hours has been achieved with a 30 mW output at 50°C.
BiSrCaCuO/BiSrCuO S/N Heterostructure Grown by Halide Chemical Vapor Deposition
Authors: Ihara Masaru , Nakao Hiroshi , Hideki Yamawaki Hideki Yamawaki , Takafumi Kimura Takafumi Kimura
Published: February 2005

Thin-film S/N heterostructures of superconducting BiSrCaCuO and metallic BiSrCuO with good surface morphology, crystallinity, and superconducting properties were formed on (100) MgO substrates by halide chemical vapor deposition (CVD). Critical temperatures (T
c at zero resistance) and critical current densities (J
c) of the BiSrCaCuO films on MgO substrate were T
c=75 to 80 K and J
c=1×106 A/cm2 at 60 K. Resistivity of the metallic BiSrCuO films was 0.7 to 1.5×10-3 Ω·cm from 10 to 300 K. High-resolution transmission electron microscopy (HRTEM) images showed the interface between the BiSrCaCuO and BiSrCuO films to be atomically abrupt. The critical temperature of S/N multilayer samples was about 75 K.
Measurement of H- Density in a Magnetized Plasma
Authors: Wada Motoi , Takeshima Shigeki , Sasao Hiroshi Tsuda
Published: February 2005

The ratio of the density of negative hydrogen ions (H-) to the density of electrons in a weakly (about 50 G) magnetized plasma was measured using a photodetachment technique. In a plasma near the extraction electrode, the measured ratio was close to unity. Because of the high concentration of H-, the maximum ratio of the extracted H- current to the total extraction current was more than 10%. The ratio of the H- density to the electron density was measured by changing the strength of the magnetic field. It showed a good correlation to the ratio of the H- current to the extraction current when the alteration of the H- extraction characteristics due to the magnetic field was taken into account. A similar correlation between the H- density and the H- current was found when the H2 pressure was changed.
Experimental and Simulation Study of an Auxiliary Circuit to Improve Gain of the Quantum Flux Parametron
Authors: Hioe Willy , Hosoya Mutsumi , Goto Eiichi , Miyamoto Reiji Suda
Published: February 2005

The gain of parametron-type devices like the Quantum Flux Parametron (QFP) is reduced by non-uniformity which causes an apparent input bias. A method to improve gain by circuit design is considered. A booster, a dc-activated QFP attached to the output of a clock-activated QFP, improves gain by doubling total output current without significantly increasing minimum input current. The booster's operation is analyzed theoretically from its quasi-static behavior and compared to results obtained from low-speed experiments on fabricated test circuits and computer simulations at high-clock rates.
Ion Current Density and Ion Energy Distributions at the Electron Cyclotron Resonance Position in the Electron Cyclotron Resonance Plasma
Authors: Samukawa Seiji , Nakagawa Yukito , Ikeda Kei
Published: February 2005

Extremely highly selective phosphorus-doped polycrystalline silicon etching is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. To characterize these etching results, the ion current density and the ion energy distribution in a ECR plasma are measured. Microwave power is absorbed completely at the ECR position. Therefore, the ECR position has maximum ion current density in an ECR plasma. Moreover, the mean ion energy and the width of ion energy distribution has minimum values at the ECR position. The ECR position in the ECR plasma can satisfy a high ion current density and a low ion energy at the same time. These characteristics correspond to the etching results.
Epitaxial ZnS MπS Blue Light Emitting Diode Fabricated on n+-GaAs by Low-Pressure Metalorganic Vapor Phase Epitaxy
Authors: Shigeki Yamaga Shigeki Yamaga
Published: February 2005

Au/π-ZnS/n+-ZnS (metal-π-semiconductor) light-emitting diodes have been fabricated on n+-GaAs substrates by metalorganic vapor phase epitaxy. Blue electroluminescence (EL) was observed at room temperature when the positive and negative bias voltage were applied to the Au contact. It has been found under the forward bias (Au:+) that EL is emitted near the interface between the n+-ZnS and GaAs substrate, while a fairly bright blue EL is observed near the Au contact under the reverse bias (Au:-). It has been shown that these emissions are caused by impact ionization of accelerated electrons in high a field.
Crack Propagation and Mechanical Fracture in GaAs-on-Si
Authors: Hayafuji Norio , Kizuki Hirotaka , Miyashita Motoharu , Kadoiwa Kaoru , Nishimura Takashi , Ogasawara Nobuyoshi , Kumabe Hisao , Tada Toshio Murotani
Published: February 2005

This paper describes the study of crack propagation and mechanical fracture in GaAs-on-Si, which are closely related with the residual stress. The crack propagation is often observed as the GaAs thickness exceeds about 3 µm, and the upper limit of the number of cracks increases linearly as the GaAs thickness increases. The cracks propagate from the surface defects, where stress ten times larger than the original residual thermal stress in GaAs-on-Si exists. The mechanical fracture strength (ζ) of the GaAs-on-Si wafer decreases as the GaAs thickness increases, and becomes equal to that of the bulk GaAs at the thickness of about 3 µm due to the concentrated stress near the cracks. The back coating of SiO2 is effective for stress relaxation, and the preliminary result of about 3×108 dyn/cm2 of stress relaxation is obtained.
Epitaxial Growth of SrxTiOy and Fabrication of EuBa2Cu3O7-δ/SrxTiOy/Pb Tunnel Junctions
Authors: Osamu Michikami Osamu Michikami , Masayoshi Asahi Masayoshi Asahi
Published: February 2005

Thin films deposited from a SrTiO3 (STO) target using rf magnetron sputtering were examined. The Sr1.6TiO
y
films with perovskitelike structure grew epitaxially at substrate temperatures above 500°C. The trilayered films of EuBa2Cu3O7(EBCO)/STO/EBCO were deposited eptaxially on STO(110) substrates, but partial polycrystal growth in the EBCO film of the third layer was observed. In view of this result, EBCO(110)/STO(110)/Pb tunnel junctions were produced on STO(110) substrates. The I-V characteristics of junctions with an R
nn of 10 Ω showed a gap opening at a bias voltage of about 10 mV, a clear gap structure at 2.5 mV and R
j/R
nn=12.4 below 2.5 mV. The low-energy gap below 2.5 mV was caused by the deterioration of the EBCO base electrodes due to the junction fabrication process. The large R
j/R
nn suggests that an STO epitaxial ultrathin film can be a good low-leakage barrier. On the other hand, lower resistance junctions showed the development of a supercurrent at zero bias.
Superconductivity in Pb2+ Doped Dy-Ba-CuO System
Authors: Murty S. Narayana , Umakantham K. , Murty A. Bhanumathi
Published: February 2005

Superconducting Dy0.35Ba0.65Pb0.1Cu0.9O3-δ compounds have been prepared and identified as single phase. The crystal structure was determined to be an orthorhombic derivative of the perovskite. Electrical resistivity is measured as a function of temperature. Superconducting transition was observed at 80 K.
Magnetic Texture Determination of RE-Fe-B Sintered Magnets (RE=Pr and Nd)
Authors: Jahn Ludwig , Hirosawa Satoshi , Volker Christoph Volker Christoph , Klaus Elk Klaus Elk
Published: February 2005

Magnetic measurements on series of RE-Fe-B hard magnets with systematic variation of alignment in the easy as well as in the hard directions have been carried out under low fields of up to 1.6 T after magnetic field cooling. The experimental results have been compared with theoretical calculations of remenence, magnetization and susceptibility. The calculations include the anisotropy constants K
1 and K
2 and a suitably chosen one-parametric distribution function of the easy axes of the form (2n+1) cos2n
α. The distribution parameter n and the saturation magnetization I
s

′ of the polycrystal are determined.
Determination of the Type of Ferroelectric Domain Nucleated around the Dislocation by the Mechanism of Domain Wall Nucleation
Authors: S. G. Ingle S. G. Ingle , J. G. Dupare J. G. Dupare
Published: February 2005

According to the elastic theory of dislocations, the stresses in the region surrounding the core of the dislocation can be relieved if we give a small hypothetical displacement, called the relieving displacement, to the atoms in this region. This concept has been developed to show that nucleation of a suitable domain region is favoured around a dislocation, while the actual nucleation takes place under the influence of the suitably applied external dc electric field. There are several equivalent directions possible for the polar axis, and the relieving displacement can decide which one of these is to be preferred for the domain region to be nucleated around the dislocation. The approach is illustrated with reference to the case of KNbO3 where the mechanism of domain formation is that of domain wall nucleation. It is shown that the effect of having a suitable domain around the dislocation is to reduce the strain energy of the dislocation. The domain width has been calculated, and it is found to be agreeing with the earlier observed experimental values.
Anomalous Current-Voltage Characteristics in Al/Lead Phthalocyanine/Au Structure
Authors: Kinya Kumazawa Kinya Kumazawa , Mitsugu Yamanaka Mitsugu Yamanaka
Published: February 2005

We prepared lead phthalocyanine (PbPc) films by conventional vacuum evaporation, and observed inversion of the rectifying property of the Al/PbPc/Au structure in air and vacuum for the first time. The inversion of the rectifying property is a unique behavior of the Al/PbPc/Au junction using the amorphous PbPc film.
Heat Treatment Effects of ZnO:Al Thin Films Prepared by Facing-Target-Type Sputtering Method
Authors: Konishi Ryōsuke , Kazuhiro Noda Kazuhiro Noda , Hiroshi Sasakura Hiroshi Sasakura
Published: February 2005

ZnO:Al films were deposited by a facing-target-type method on a glass substrate, which is held at 300°C. The minimum resistivity was obtained with an Al concentration of 1.3%. The decrease of resistivity after the heat treatment of ZnO:Al (1.3%; calculated from area ratio of target) film seems to be mainly attributed to the increase of Hall mobility. The improvement of Hall mobility is not due to the improvement of crystallinity, but it may be due to the decrease of oxygen impurities at interstitial sites.
Force Microscopy Using Common-Path Optical-Heterodyne Interferometer
Authors: Kikuta Hisao , Asai Shigeki , Hiroyuki Yasukochi Hiroyuki Yasukochi , Koichi Iwata Koichi Iwata
Published: February 2005

This paper proposes a common-path optical-heterodyne interferometer for developing a very stable force microscope. The deflections of the force-sensing cantilever are detected by the optical heterodyne method which reduces low-frequency noise. The optical system is a common-path interferometer using a Wollaston prism, which reduces the effects of mechanical vibrations and perturbation of the optical path length. In this paper, we proposed the optical system, constructed a system and measured the surface profile of optical disk grooves.
Causes and Prevention of Temperature-Dependent Bubbles in Silicon Wafer Bonding
Authors: Mitani Kiyoshi , Lehmann Volker , Stengl Reinhard , Feijoo Diego , Ulrich M. Gösele Ulrich M. Gösele , Hisham Z. Massoud Hisham Z. Massoud
Published: February 2005

Unbonded areas or bubbles generated at the interface of bonded silicon wafers in the temperature range of 200-800°C have been investigated. Experiments described in this paper demonstrate that the desorption of hydrocarbon contamination at the silicon wafer surfaces appears to be a necessary condition for the formation of these bubbles. SIMS data also indicate the existence of hydrocarbons at the bonding interface. It is speculated that hydrocarbon gas such as CH4 is required for bubble nucleation and that either CH4 or H2 itself or a mixture of both gases is contained in these bubbles. Finally, methods to prevent the formation of these bubbles are presented.
Fabrication and Operational Stability of Inverted Floating Gate E2PROM (Electrically Erasable Programable Read Only Memory)
Authors: Lee Jin-Yeong Kang
Published: February 2005

The inverted floating gate E2PROM was designed and fabricated. In this device, the floating gate is located above the control gate, and the control gate is located between the floating gate and channel. This structure improves the operation stability since it suppresses interpolysilicon oxide current during programming and prohibits channel leakage current during erasing. As a result, the inverted floating gate device exhibits good programming/erasing characteristics and endurance with a threshold voltage shift of less than 0.3 V after 106 programming-erasing cycles, and it also shows higher operational voltage margins and wider programming-erasing windows than the conventional one under practical operating conditions.