bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Superconducting Properties of Bi-Pb-Sr-Ca-Cu-O Films (Tc=106 K) by the Dipping-Pyrolysis Process
Authors: Manabe Takaaki , Tsunoda Tatsuo , Kondo Wakichi , Shindo Yuji , Susumu Mizuta Susumu Mizuta , Toshiya Kumagai Toshiya Kumagai
Published: February 2005

Superconducting Bi-Pb-Sr-Ca-Cu-O (2223 as the major phase) films were prepared by the dipping-pyrolysis process on MgO(100) substrates using a metal naphthenate solution. From the XRD and SEM-EDX analyses, the formation of the 2223 phase with well-developed platelike grains was facilitated in the films by placing a Pb-containing BSCCO pellet on the surface of the prefired films during the heat treatment (850°C in air) and by the use of a nominal composition of Bi:Pb:Sr:Ca:Cu=1.8:0.4:2.0:2.4:3.6 in molar ratio, i.e., a Ca-and-Cu-rich composition compared to the 2223 phase. The values of T
c,zero and J
c(77 K) were 106 K and 2×103 A/cm2, respectively. The dependence of critical current densities on temperature showed that J
c was approximately proportional to (1-T/T
c)3/2, which corresponds to the results of the promixity junction tunneling (SNIS) model.
Fabrication Process and Properties of Nb-InSb-Nb Planar Junction
Authors: Hato Tsunehiro , Akaike Hiroyuki , Yoshiaki Takai Yoshiaki Takai , Hisao Hayakawa Hisao Hayakawa
Published: February 2005

A Nb-InSb-Nb planar junction with a normal layer of InSb thin film was fabricated by a new process. In this report, the details of the fabrication process and properties of the junction are discussed. The Nb-InSb-Nb junction fabricated using the new process showed a supercurrent. This means that there is no notable barrier, such as the Schottky barrier at the interface between Nb and InSb. The InSb film has a mobility of 500∼700 cm2/V·s, which is 17∼23 times larger than that of Si. This makes it possible to realize the superconductor-semiconductor-superconductor junction with a low carrier density of 1017 cm-3.
Spin Directions in Exchange-Coupled Rare-Earth Transition Metal Double Layer Films with In-Plane Magnetic Intermediate Layer
Authors: Malmhäll Roger , Niihara Toshio , Harukazu Miyamoto Harukazu Miyamoto , Masahiro Ojima Masahiro Ojima
Published: February 2005

Exchange-coupled perpendicular anisotropy rare earth-transition metal (RE-TM) double layer films with application as direct overwrite magneto-optical media have been studied employing the Hall effect. An intermediate layer was inserted between a RE-dominated TbDyFeCo layer and a TM-dominated TbFeCo layer in order to modify the exchange interaction. In the case of an in-plane magnetic anisotropy TM-dominated GdCo intermediate layer, the Gd-Co layer was inferred from the Hall effect to be almost fully magnetized in the normal direction at zero applied magnetic field and room temperature. Furthermore, an in-plane domain wall exists inside the TbDyFeCo layer at zero field when the magnetizations of the TbDyFeCo and TbFeCo layers are parallel. It was also found that the in-plane wall moves to the interface between the TbDyFeCo and GdCo layers at a temperature of about 50°C and further into the intermediate layer at higher temperatures.
Gain Switching in Coupled Quantum Wells
Authors: Doyeol Ahn Doyeol Ahn , Tae-Kyung Yoo Tae-Kyung Yoo
Published: February 2005

Optical gain switching in coupled quantum wells is studied theoretically. Our analysis is based on the multiband effective mass theory and the density matrix formalism with the intraband relaxation taken into account. Significant enhancement of the Stark effect on the gain of the coupled quantum wells is predicted. Comparison with the single quantum well shows that the gain is substantially more reduced for the coupled quantum wells at the same electric field because of enhanced charge separation in this structure. These results may allow low-voltage operation of the recently proposed field-effect quantum-well laser.
Raman Spectroscopic and X-Ray Diffraction Study of Sulfur under High Pressure
Authors: Nagata Kiyofumi , Nishio Takashi , Hironori Taguchi Hironori Taguchi , Yasuhiko Miyamoto Yasuhiko Miyamoto
Published: February 2005

Raman spectrum and X-ray powder pattern of orthorhombic sulfur have been examined at pressures up to about 10 GPa. The Raman spectrum shows reversible phase transition at 5.2 GPa, while the X-ray diffraction pattern shows no sign of phase change up to 8.3 GPa. These contradictory results are explained as follows. A high-pressure phase exists above 5.2 GPa. In this pressure region, the metastable orthorhombic phase can also exist. The argon ion laser (λ=514.5 nm) used for Raman measurement induces a structural transformation from the orthorhombic phase to the high-pressure phase. The Raman spectrum suggests that the high-pressure phase is composed of chain molecules. In addition, evidence for interference between inter- and intramolecular bondings has been observed in this phase.
Thermoluminescence and Optical Absorption of NaBr:S- Crystals
Authors: Baba Mamoru , Shibata Kiyotaka , Yutaka Kamei Yutaka Kamei , Toshio Ikeda Toshio Ikeda
Published: February 2005

Thermoluminescence and optical absorption in NaBr:S- crystals have been studied in the temperature range between 80 and 300 K. The kinetics of formation and decomposition of the so-called FH center, which consists of an F center associated with a neighboring sulfur ion, has been investigated in relation to thermoluminescence. It has been found that the thermoluminescence glow peak, which has an emission band with a peak at 815 nm (1.52 eV), appears at 230±3 K and is strongly concerned with recombination of the electron of the FH center. Such a model has been supported by observing the change in the optical absorption due to the S- centers and the FH centers.
Effect of Etching Treatment on Thermally Stimulated Current in Spherulitic Polypropylene
Authors: Kiyohiro Oka Kiyohiro Oka , Kazuo Ikezaki Kazuo Ikezaki
Published: February 2005

Charging saturation and thermally stimulated currents (TSCs) were studied for positively corona-charged spherulitic and nonspherulitic polypropylene films which were etched with a mixture of H2SO4and K2Cr2O7. From the experimental results of the etching treatment effect on the TSC spectra, it is concluded that the charging saturation is caused by a decrease in the number of traps located in the amorphous part of the polymer. For spherulitic polypropylene, estimated values of trap density which is effective at room temperature were 2.5-1.1×1014[cm-3], depending on the extent of etching treatment. The densities of traps located in the crystalline parts of the nonspherulitic and spherulitic polypropylene were 0.93×1014[cm-3] and 0.76×1014[cm-3], respectively.
Effects of Excited Species in Electron Cyclotron Resonance Plasma on SiN Film Resistivity
Authors: Saito Katsuaki , Chiba Natsuyo , Fukuda Takuya , Suzuki Kazuo , Michio Ohue Michio Ohue
Published: February 2005

Optical emission spectra were measured and the relationship between resistivity of SiN films which were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) and emission intensities from species excited by electron cyclotron resonance was clarified. With increasing microwave power of lowered reacting pressure or SiH4 gas flow rate, the light intensity from excited ions increased in comparison to the intensity from excited radicals. As a result of increasing excited ion density, the SiN film was condensed and the prismatic structure observed in low-resistivity film was not absent from high-resistivity film.
Stationary Nuclear Burning of Plasmas Consisting of Lighter Than 6Li Nuclei
Authors: Kanpathipillai Murukesapillai Kanpathipillai Murukesapillai
Published: February 2005

The problem of self-sustained stationary burning of plasmas consisting of lighter than 6Li nuclei is investigated. It is found that among all the possible binary reactions between the nuclei 1H, 2H, 3H, 3He, and 4He, only 2H-2H, 2H-3H, and 2H-3He reactions are frequent and energetic enough to sustain stationary burning. The stationary burning can occur at two temperatures. Whereas the burning at the lower temperature is unstable, that at the higher temperature is asymptotically stable. It is also found that the maximum temperature at which stationary burning occurs does not depend on the absolute values of the particle and energy confinement times τ and τE, but rather on their ratio τ/τE.
Low-Temperature Synthesis of Aluminium Nitride Film by HCD-Type Ion Plating
Authors: Kishi Matsuo , Mizuaki Suzuki Mizuaki Suzuki , Kenichi Ogawa Kenichi Ogawa
Published: February 2005

Aluminium nitride (AlN) thin films were deposited on glass substrates, using aluminium and nitrogen as source materials, by hollow cathode discharge (HCD)-type ion plating. The films were evaluated using X-ray diffraction, scanning electron microscopy, infrared transmission spectroscopy and Auger electron spectroscopy, and their densities were measured. The phase of the deposits changed from Al to Al+AlN and to AlN with an increase in nitrogen flow rate. The structure of the AlN films varied from a dense structure to columnar structure with a rise in nitrogen flow rate. The film with the dense structure had a density near the theoretical value. Oxygen caused by the attack of H2O in air was detected only on the surface of films with the dense structure, but throughout the inside of the films with the columnar structure.
Stress-Free GaAs on Si by Laser Pulse Irradiation
Authors: Umeno Masayoshi , Tetsuo Soga Tetsuo Soga , Takashi Jimbo Takashi Jimbo
Published: February 2005

A novel method to relieve the stress in GaAs on a Ge-coated Si substrate using YAG (Yttrium Aluminum Garnet) laser pulse irradiation (the wavelength is 1.064 µm) is described. The stress decreases with increasing number of shots or shortening pulse width while keeping pulse energy per shot constant. The residual stress in the GaAs on Si after irradiation of 5 shots of the laser pulse (the pulse width is 2 ns and pulse energy is 0.36 J/pulse) is almost zero.
Distribution of Ignition Probability in a Heterogeneous Mixture
Authors: Kunio Terao Kunio Terao , Chihong Liao Chihong Liao
Published: February 2005

In order to investigate the regional ignitability in a heterogeneous combustible mixture, a method based on the stochastic ignition theory is developed. Applying this method to a spontaneous ignition in an n-octane spray injected into shock-heated air, a distribution of ignition probability and its variation in the spray are obtained.
A Novel Approach for Quantifying Contamination in Multiply Charged Implantation
Authors: Yoo Chue-san , Wu Chen-pao , Jen-kwang Wang Jen-kwang Wang , Mou-shiun Lin Mou-shiun Lin
Published: February 2005

A novel approach for quantifying impurity levels in doubly charged implantation is proposed and verified. It is proved to be quantitative in nature and easier to implement in a production environment than the existing Faraday cup and electrostatic methods. Application of this method is demonstrated in a phosphorous double-charged implantation. Quantitative analysis of the impurity level is also presented.
Extraction of Microwave Pulses from a Cavity Using a Y-Ba-Cu-O Superconducting Film Switch
Authors: Takahashi Kuniharu , Minami Kazuo , Kato Keizo , Yoshida Noriyuki , Takano Satoshi , Awano Mitsuru
Published: February 2005

A microwave pulse source utilizing a Y-Ba-Cu-O (YBCO) superconducting film switch was studied. A YBCO thin film with T
c as high as 86 K was fabricated by a laser ablation technique. It was installed in a cylindrical TE111 mode cavity made of copper with a resonant frequency of 2.84 GHz. The cavity was evacuated and immersed in liquid nitrogen. The switching from superconducting to normal states in the YBCO film was made using a 1.06-µm pulsed Q-switched Nd:YAG laser with a half-time-width of 10 ns. Microwave pulses were extracted from the cavity by the YBCO film switch with a rise time of 30 ns. A microwave pulse peak power of about 3.4 µW was obtained for the 0.2 µm film at 79 K and at an incident laser energy of 3.6 mJ. The peak power gain of the output pulse was calculated theoretically. The experimental results were found to agree with the calculated ones qualitatively.
On the Closed Loop Control of a PZT to Stabilise a Mach-Zehnder Interferometer
Authors: S. Dilwali S. Dilwali , G. Soundra Pandian G. Soundra Pandian
Published: February 2005

When stabilising a fiber optic Mach-Zehnder interferometer using a PZT, the maximum possible closed-loop bandwidth is limited by the resonance frequency of the PZT. A PZT control circuit using a current source drive is proposed that gives an improved control bandwidth when compared with a voltage source drive. Equations are given to select the parameters of the system to get an optimum second order response, along with experimental results.
Hole Compensation Mechanism of P-Type GaN Films
Authors: Nakamura Shuji , Iwasa Naruhito , Masayuki Senoh Masayuki Senoh , Takashi Mukai Takashi Mukai
Published: February 2005

Low-resistivity p-type GaN films, which were obtained by N2-ambient thermal annealing or low-energy electron-beam irradiation (LEEBI) treatment, showed a resistivity as high as 1×106 Ω·cm after NH3-ambient thermal annealing at temperatures above 600°C. In the case of N2-ambient thermal annealing at temperatures between room temperature and 1000°C, the low-resistivity p-type GaN films showed no change in resistivity, which was almost constant between 2 Ω·cm and 8 Ω·cm. These results indicate that atomic hydrogen produced by NH3 dissociation at temperatures above 400°C is related to the hole compensation mechanism. A hydrogenation process whereby acceptor-H neutral complexes are formed in p-type GaN films was proposed. The formation of acceptor-H neutral complexes causes hole compensation, and deep-level and weak blue emissions in photoluminescence.
Characterization of Ultrahigh-Speed Pseudomorphic InGaAs/AlGaAs Inverted High Electron Mobility Transistors
Authors: Fujishiro Hiroki Inomata , Hiromi Tsuji Hiromi Tsuji , Seiji Nishi Seiji Nishi
Published: February 2005

A detailed characterization of ultrahigh-speed pseudomorphic InGaAs/AlGaAs inverted high electron mobility transistors (pseudomorphic I-HEMT's) is reported. Charge control analysis indicates that the pseudomorphic I-HEMT accomplishes improved transconductance (g
m) and reduced short channel effects due to higher concentration and excellent confinement of two-dimensional electron gas (2DEG) in the InGaAs channel. The 0.2 µm gate pseudomorphic I-HEMT's reported here exhibit superior DC and RF performances, i.e., maximum transconductance (g
m
max) of 565 mS/mm, cutoff frequency (f
T) of 110 GHz and propagation delay times (τpd's) of 6.6 ps/gate at R.T. and 4.9 ps/gate at 120 K. Delay time analysis reveals the reduction of both the electron transit time (τtransit) and the channel charging time (τchannel) in the pseudomorphic I-HEMT, which are significant factors in the ultrahigh-speed performance. Higher electron saturation velocity (υs:2.1×107 cm/s) and improved g
m are considered to contribute to the reduction in τtransit and τchannel.
In Situ X-Ray Chemical Analysis of Y1Ba2Cu3O7-x Films by Reflection-High-Energy-Electron-Diffraction Total-Reflection-Angle X-Ray Spectroscopy
Authors: Kamei Masayuki , Aoki Yuji , Toshio Usui Toshio Usui , Tadataka Morishita Tadataka Morishita
Published: February 2005

Both the surface crystalline structure and chemical composition of Y-Ba-Cu-O film were examined in situ using reflection-high-energy-electron-diffraction and total-reflection-angle X-ray spectroscopy (RHEED-TRAXS). The chemical composition determined by TRAXS agreed well with that determined by inductively coupled plasma spectroscopy. The compositional deviation from Y1Ba2Cu3O7-x
affected the surface crystalline structure of films, as was detected by RHEED and confirmed by scanning electron microscopy. RHEED-TRAXS is a powerful tool for in situ examination of the crystal growth of Y-Ba-Cu-O films.
Influence of Growth Temperature on the Magnetic and Optical Properties of Liquid-Phase-Epitaxial(LPE)-Grown Lanthanum- and Gallium-Substituted Yttrium Iron Garnet ((La, Ga):YIG) Films and Their Application to Waveguides
Authors: Sugimoto Naoto , Tate Akiyuki , Shinji Mino Shinji Mino , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

We measure the growth temperature dependence of the magnetic and optical properties of lanthanum- and gallium-substituted yttrium iron garnet films deposited on gadolinium gallium garnet substrates by the liquid-phase-epitaxial-growth method for use as integrated optical waveguides. The magnetization of the film can be saturated in the film plane by a weak external-magnetic field (<45 Oe). The refractive index is controlled in a range of 2.192 to 2.204 by the growth temperature, which ranges from 893 to 835°C. Rib waveguides with low propagation loss (2.3 dB/cm at 1.55 µm wavelength evaluated by measuring the contrast in Fabry-Perot cavity resonance signals) are also fabricated.
ZnS:Mn Electroluminescent Films Prepared by Hot Wall Technique
Authors: Takeuchi Yoji , Okuno Yasuki , Nakamura Takatou , Ishino Kenei , Akihiro Ishida Akihiro Ishida , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: February 2005

Manganese-doped zinc sulfide electroluminescent (EL) films were prepared for the first time by a hot wall technique with Mn planar doping. Undoped and Mn-doped ZnS films on glass substrates exhibit preferred cubic (111) orientation at the substrate temperature of 280°C. The Δ2θ value (full width at half-maximum) of the 111 reflection of the ZnS:Mn film in an X-ray diffraction pattern was found to be improved with an increase in Mn concentration and film thickness. By means of secondary ion mass spectroscopy (SIMS) and electron spin resonance (ESR) analyses, it was confirmed that this doping technique was very efficient in obtaining a homogeneous Mn2+ distribution which yielded highly luminescent EL devices. For an optimum device with double insulators of stacked Ta2O5/Al2O3 layers, the maximum luminance and efficiency at 1 kHz sinusoidal excitation were 3200 cd/m2 and 1.3 lm/W, respectively.
Edge Effect on the Determination of Capture Rate of Minority Carriers from Transient Capacitance Measurement
Authors: Tomokage Hajime , Hidefumi Kamibayashi Hidefumi Kamibayashi , Tokuo Miyamoto Tokuo Miyamoto
Published: February 2005

The depletion edge region must be taken into account in the determination of the capture rate of minority carriers from a transient capacitance after the application of an injection pulse to a reverse-biased pn junction. A simple expression to evaluate the edge effect is proposed, with which the capture rate of minority carriers can be determined if the capture rate of majority carriers is known. Measurements are performed on an Au-doped Si p+n diode to determine the hole capture rate of the Au acceptor level.
Mg-Doped Lithium Niobate: Some Comments on Stoichiometry, Structure and Properties
Authors: Anthony Roy West Anthony Roy West
Published: February 2005

The change in properties with composition of Mg-doped LiNbO3 crystals at ∼10% MgO, reported by Hu et al. [Jpn. J. Appl. Phys. 30 (1991) 1412] may be reinterpreted in terms of a different change in solid solution mechanism to the one proposed by Hu et al. For Mg contents greater than ∼10%, phase diagram studies indicate that any crystals would be constrained to have compositions close to or on the stoichiometric join of constant overall cation content, with substitution mechanism 3Li++Nb5+\rightleftharpoons4Mg2+ rather than to have A site vacancies as suggested by Hu et al. The Curie temperature, T
c, varies with composition. In addition to the well-established decrease in T
c associated with cation vacancy creation, a second mechanism must also operate to reduce T
c, probably associated with substitution of Mg onto B(Nb) sites.
Low-Temperature Synthesis of Diamond Films in Thermoassisted RF Plasma Chemical Vapor Deposition
Authors: Watanabe Ichiro , Takashi Matsushita Takashi Matsushita , Koujyu Sasahara Koujyu Sasahara
Published: February 2005

The synthesis of diamond films using radio-frequency (13.56 MHz) glow discharge plasma chemical vapor deposition (CVD) is investigated. A variety of films are prepared from a mixture of ethyl alcohol and hydrogen, and they are evaluated using Raman spectroscopy. Diamond films grow when external heating is used in combination with the radio-frequency glow discharge. The films grow at temperatures between 350 and 800°C. In this temperature range, film of reasonable quality is obtained at 550∼600°C. The diamond grows even at the low temperature of 350°C although it contains a few nondiamond carbons. These temperatures are considerably lower than those generally regarded as the optimal regime for diamond growth.
Observation of Surface Corrugation of Highly Oriented Pyrolytic Graphite by Scanning Tunneling Microscope in Air
Authors: Iri Takeo , Hiroaki Shiba Hiroaki Shiba , Hiroyuki Nishikawa Hiroyuki Nishikawa
Published: February 2005

The apparent surface corrugation of highly oriented pyrolytic graphite (HOPG) was investigated with a scanning tunneling microscope (STM) in air using mechanically polished PtIr tips. It was found that the tunneling resistance was the most dominant parameter governing the observed atomic corrugation. The tunneling resistance was defined by the ratio of bias voltage to tunneling current required for STM measurements. The maximum corrugation of about 0.3 nm was attained at the tunneling resistance around 107Ω. The dependence of the corrugation upon tunneling resistance is qualitatively explained taking into account the variation of tip function, by means of both the elastic deformation of the sample surface and the separation change of the tip and surface.
Investigation of the Transient Glow Discharge in Nitrogen
Authors: Fujiwara Tamiya , Yamada Hiroshi , Hiroshi Taniguchi Hiroshi Taniguchi , Keiichiro Sugita Keiichiro Sugita
Published: February 2005

With the development of the pseudospark device, glow discharge with high power has recently become of interest. In this study, the voltage across a gap, the discharge current and the glow duration have been measured during transient glow discharge in the pressure range of 40-130 Torr in nitrogen. The results show that there exists a large difference between a previous investigation by Chalmers (1971) and the present study in the quantity of energy dissipated in the gap during the transient glow. However, in regard to the volume density of energy dissipated in the cathode fall, the values obtained by Chalmers and the present authors almost agree. From this result it is considered that the energy density is more essential than the energy quantity with respect to the transition of discharge from a transient glow to an arc.
ECR Plasma CVD in Different Magnetic Field Configurations
Authors: Murata Masayoshi , Uchida Satoshi , Kishimoto Kengo , Tanaka Masayoshi , Akio Komori Akio Komori , Yoshinobu Kawai Yoshinobu Kawai
Published: February 2005

An electron cyclotron resonance (ECR) plasma is produced with a slotted Lisitano coil, and the axial distribution of the plasma parameters is measured in detail for different magnetic field configurations. It is found that the plasma density in uniform magnetic fields axially decreases more slowly than that in divergent magnetic fields. Furthermore, carbon films are formed by ECR plasma chemical vapor deposition (CVD), and the deposition rate obtained in the uniform magnetic fields is found to be larger than that obtained in the divergent magnetic fields.
Linear Response Theory for Velocity Distribution Measurement of Sputtered Neutral Particles by Means of Multiphoton Resonance Ionization Spectroscopy
Authors: Masahiko Inoue Masahiko Inoue
Published: February 2005

A measurement system for the velocity distribution of sputtered neutral particles by means of multiphoton resonance ionization spectroscopy (MPRIS) combined with the time-of-flight (TOF) technique was formulated using the simple linear response theory in matrix form. The relationship between each parameter for the measurement and the observed TOF spectrum could be indicated visibly in the present form. It was demonstrated that the optimum condition for the velocity distribution measurement can be derived easily with the present method. It was also demonstrated that the velocity distribution measured is seriously affected by the pulse shape of the primary ion beam.
The Novel Preparation of P-N Junction Mesa Diodes by Silicon-Wafer Direct Bonding (SDB)
Authors: Hwangleu Ching-Fa Yeh
Published: February 2005

The key processes of silicon-wafer direct bonding (SDB), including hydrophilic surface formation and optimal two-step heat treatment, have been developed However, H2SO4/H2O2 solution being a strong oxidized acid solution, native oxide is found to have grown on the wafer surface as soon as a wafer is treated in this solution. In the case of a wafer further treated in diluted HF solution after hydrophilic surface formation, it is shown that the wafer surface can not only be cleaned of its native oxide but also remains hydrophilic, and can provide excellent voidless bonding. The N+/P and N/P combination junction mesa diodes fabricated on the wafers prepared by these novel SDB technologies are examined. The ideality factor n of the N/P mesa diode is 2.4∼2.8 for the voltage range 0.2∼0.3 V; hence, the lowering of the ideality factor n is evidently achieved. As for the N+/P mesa diode, the ideality factor n shows a value of 1.10∼1.30 for the voltage range 0.2∼0.6 V; the low value of n is attributed to an autodoping phenomenon which has caused the junction interface to form in the P-silicon bulk. However, the fact that the sustaining voltage of the N/P mesa diode showed a value greater than 520 V reveals the effectiveness of our novel SDB processes.
Characterization of Sidewall Damage Induced by Reactive Ion-Beam Etching
Authors: Matsutani Akihiro , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

The sidewall damage induced by reactive ion-beam etching (RIBE) with Cl2 has been studied. The sidewall damage depth was estimated from the ion-beam-angle dependence, and the photoluminescence (PL) emitted from the etched sidewall of a GaInAsP/InP DH wafer was directly measured. The sidewall damage depth of an InP substrate was estimated as less than a few hundred angstroms at an extraction voltage of 400 V. The PL intensity from the sidewall of a GaInAsP/InP DH wafer decreased considerably after RIBE, compared with that of a cleaved facet. The deteriorated PL intensity was recovered remarkably through passivation with (NH4)2S
x
.
Limitation in the Cone of Light through GRIN Lenses: Stops, Pupils and Vignetting
Authors: Gomez-Reino C. , E. Acosta E. Acosta , M. V. Perez M. V. Perez
Published: February 2005

This work deals with the limitation in the extents of the light beams through GRIN lenses by analyzing the stops, pupils and vignetting. The obtained results will be applied to the particular case of Selfoc lenses.
Focusing Characteristics of Convex-Shaped Distributed-Index Microlens
Authors: Sasaki Asako , Toshihiko Baba Toshihiko Baba , Kenichi Iga Kenichi Iga
Published: February 2005

We have investigated the structure and performance of novel convex-shaped distributed-index microlenses. The surface curvature of its convex shape and the index distribution formed in the ion exchange process were measured precisely. Based on the measured structural parameters, focusing characteristics were evaluated by the ray tracing simulation. It was confirmed that 93% of its large numerical aperture (∼0.5) is attributed to the convex shape. The focusing characteristics show that laser light is directly focused to a 10 µmφ circular spot with 4 dB coupling loss, which is compatible with single-mode fibers.
Tunable Filters with Extended Tunability
Authors: Hideaki Okayama Hideaki Okayama , Masato Kawahara Masato Kawahara
Published: February 2005

Filters with extended tunability using waveguide devices are proposed. The first and second types of filters are combinations of a filter with a wide tuning range and a filter with narrow passbands. The first type is composed of cascaded filters and the second type is the filter with a wide tuning range embedded in a resonator. The last type of filter uses the Vernier effect which has seldom been applied to nonresonant-type devices. The tunability of these filters can overcome the limitation set by the electrooptic property of the material. The performance of the fabricated multibranch Mach-Zehnder interferometric filter, which is the key component for implementing the proposed filter configuration, is demonstrated.
Optical Surface Mount Technology
Authors: Uchida Teiji , Akazawa Yoshinori Masuda
Published: February 2005

Optical surface mount technology (O-SMT) is proposed on the analogy of surface mount technology widely employed in current electronics, in order to meet growing serious problems in manufacturing processes for practical optoelectronic systems.
Analysis of Light-Induced Degradation in Amorphous Silicon Alloy Solar Cells and Its Application to Accelerated Test Method
Authors: Nakata Yukihiko , Yokota Akitoshi , Sannomiya Hitoshi , Moriuchi Sohta , Inoue Yasumi , Nomoto Katsuhiko , Manabu Itoh Manabu Itoh , Takateru Tsuji Takateru Tsuji
Published: February 2005

Light-induced degradation in amorphous silicon alloy single-junction solar cells has been studied systematically. The dependence of the light-induced degradation in the conversion efficiency and the other photovoltaic parameters on light intensity and bias voltage has been clarified quantitatively. It has been shown that the light-induced degradation characteristics of the photovoltaic parameters can be described by a single function of certain normalized parameters of the exposure condition. Theoretical background for the experimental results has been clarified by applying a defect creation model modified to the a-Si alloy solar cells. Moreover, using the above single function, we have proposed a new accelerated test method by indoor measurement under the solar simulator instead of outdoor testing under natural sunlight. The validity of the accelerated test method has been confirmed experimentally.
Fabrication of a Biological Visual Perception System Using a Microlens Array in a Hybrid Pattern Recognition System
Authors: Kamemaru Shun-ichi , Yamaguchi Shigeru , Yano Jun-ichi
Published: February 2005

The authors have proposed a concept and a system based on a biological perception system using optical components and a microcomputer. In this paper, we describe a breakthrough in the solution of the problem of the interconnection between the optical and digital processing parts. The breakthrough has been derived from the technique of separation of the peak signal from noise. Reduction of reflection noise, the effective aperture size of the microlens and the recognition algorithm are also discussed for the complete recognition system. Experimental results show good feasibility of the proposed system.
Optical Learning Neural Network Using Selfoc Microlens Array
Authors: Hayasaki Yoshio , Tohyama Ichiro , Yatagai Toyohiko , Mori Masahiko , Ishihara Satoshi
Published: February 2005

An optical network system with learning capabilities and a 2-D architecture is proposed. The 2-D architecture is implemented by a multiple imaging system of Selfoc microlens arrays, which enables us to develop a compact optical neural network system. Synaptic weights of neurons are memorized in a Pockels readout optical modulator, and the system obtains the learning capabilities. Experimental verification of multiple imaging and learning is presented. In the experiments, the neural network system stores the three patterns by an orthogonal learning method. The performance of the optical neural network system is estimated in terms of a point spread function of the Selfoc microlens.
Dependence of Electronic Properties of Hydrogenated Amorphous Ge on Deposition Condition
Authors: Nakashita Toshio , Inoue Akira , Hagiwara Shingo , Uehara Fumiya , Kohno Kenji
Published: February 2005

Hydrogenated amorphous Ge(a-Ge:H) thin films are prepared by the capacitive-coupled plasma chemical vapor deposition method using GeH4 as a reactive gas. The deposition temperature and radio frequency (rf) power density are changed from 100°C to 260°C and from 0.2 W/cm2 to 2 W/cm2, respectively. The dependence of the optical and electronic properties including the infrared absorption, photo- and dark conductivities on both the deposition temperature and rf power density are examined. For a substrate temperature of 175°C, the photo- and dark conductivities exhibit maxima and the bimolecular recombination process in the photoconduction becomes dominant compared to the monomolecular recombination process. It is also found that the value of the energy gap is proportional to the hydrogen content in the region below 2 at.%. When the rf power density is increased from 0.2 to 2.0 W/cm2 under the constant substrate temperature of 160°C, the films are improved although the hydrogen content is unchanged.
Low Temperature Fourier Transform Infrared Spectroscopic Studies of Hydrogenated Amorphous Silicon Nitride Films
Authors: Man Mohan Pradhan Man Mohan Pradhan , Manju Arora Manju Arora
Published: February 2005

Low-temperature IR absorptance measurements on thin films of hydrogenated amorphous silicon nitride have revealed the existence of different groups such as NH, SiH and SiH2. Although NH stretching vibration is not observed in the IR transmission-absorption measurements at ambient temperature in such thin films, it becomes quite intense in the temperature range of 230 K to 100 K, and its absorptance slowly reduces on further lowering of temperature. Absorptance-temperature curves revealed that the SiH wagging mode and SiH2 bending mode undergo a large variation in absorptance on lowering of the temperature. Low-temperature Fourier transform infrared (FTIR) spectroscopic studies have been found to be very useful for characterisation of the hydrogenated amorphous silicon nitride films.
Changes of Superconductivity and Crystal Structure on Ba2YCu3O7-x Thin Film by 2.5 MeV Ni2+ Ion Irradiation
Authors: Terai Takayuki , Kusagaya Kazuyuki , Furuta Tai , Takahashi Yoichi , Kubo Shugo , Enomoto Youichi
Published: February 2005

Effects of 2.5 MeV Ni2+ ion irradiation on thin films of high-T
c oxide superconductor Ba2YCu3O7-x
were investigated in the fluence range 1.0×109 cm-2<φt<3.0×1014 cm-2. An increase of transport J
c due to irradiation was observed below 1.0×1010 cm-2 in φt, while above this fluence, both T
c and J
c decreased. In X-ray diffraction (XRD) measurement, decrease in intensity and increase in the full width at half maximum (FWHM) value of peaks and in the c-axis lattice constant were observed above 1.0×1013 cm-2 in φt.
Observation of Ring-Distributed Microdefects in Czochralski-Grown Silicon Wafers with a Scanning Photon Microscope and Its Diagnostic Application to Device Processing
Authors: Shimizu Hirofumi , Munakata Chusuke , Honma Noriaki , Aoki Shigeru , Yuji Kosaka Yuji Kosaka
Published: February 2005

A scanning photon microscope (SPM) based on ac surface photovoltage imaging is applied to observe oxygen-related microdefects which are distributed in a ring in oxidized Czochralski-grown silicon wafers, and morphological and microstructural characteristics of the microdefects are then analyzed. The overall distribution of the ring-shaped region revealed by the SPM correspond well to that observed with X-ray topography. The SPM is able to differentiate deteriorated regions as different image contrasts, where stacking faults or oxide precipitates accompanying punched-out dislocation loops exist.
Photoemission Studies of Polyimide Surfaces
Authors: Yasuko Yamada Maruo Yasuko Yamada Maruo , Tohru Maruno Tohru Maruno
Published: February 2005

Surface-sensitive analysis using X-ray photoelectron spectroscopy (XPS) has been performed to characterize surfaces of several polyimides and a related imide. Molecular orbital calculations were carried out to estimate the chemical shifts and characterize the surface chemical states. On polyimide and imide surfaces, both the photoelectron intensity decrease of the carbonyl group and the shake-up phenomenon were detected. It is proposed that (1) the photoelectron intensity decrease of the carbonyl group on the polyimide film surfaces is caused by the shake-up phenomenon, and not by carbonyl deficiencies on the surfaces, and that (2) the intensity decrease of the carbonyl group on the imide film surface is caused by the combination of shake-up phenomenon and carbonyl deficiences on the surfaces.
Damage in ZnO Film Preparation by Planar Magnetron Sputtering System with Obliquely Facing Targets of Zn
Authors: Tominaga Kikuo , Sueyoshi Yasuhiko , Masaki Shirai Masaki Shirai , Hiroshi Imai Hiroshi Imai
Published: February 2005

ZnO films were prepared by a sputtering system having two obliquely facing Zn targets. It was found that the influence of film bombardment by energetic particles such as O- and O was observed at lower gas pressures. To prepare highly c-axis-oriented ZnO films, the inclination angle of the two targets should be limited to angles such that direct film bombardment by the energetic particles becomes small.
Hologram-Shifting Method for High-Speed Electron Hologram Reconstruction
Authors: Ru Qingxin , Hirayama Tsukasa , Junji Endo Junji Endo , Akira Tonomura Akira Tonomura
Published: February 2005

A simple digital method for high-speed or real-time reconstruction of electron holograms is described. The method is based on the so-called hologram shifting which causes a phase-shifting effect. Consequently the phase-shifting formula, which requires only some simple calculations, can in priciple be utilized to reconstruct electron holograms in real time.
Preparation and Characterization of CuInSe2 Thin Films by Molecular-Beam Deposition Method
Authors: Nishitani Mikihiko , Negami Takayuki , Masaharu Terauchi Masaharu Terauchi , Takashi Hirao Takashi Hirao
Published: February 2005

Polycrystalline CuInSe2 films were prepared by coevaporation of the elements under an ultrahigh vacuum by a molecular-beam deposition method. The composition of the film was controlled by changing the In molecular-beam flux intensity while the other elements remained at a constant value. It is shown, at the substrate temperature of 500°C, that there is a critical In molecular-beam flux intensity for the fabrication of stoichiometric films. At the In molecular-beam intensities higher than the critical value, single-phase CuInSe2 films with nearly constant compositions are obtained as a result of the removal effects of excess In. It is shown that the present coevaporation process is suitable for the fabrication of stoichiometric or slightly In-rich composition films. Furthermore, the structural and electrical properties of the films were investigated and discussed in relation to film composition.
Selective Deposition and Bond Strain Relaxation in Silicon PECVD Using Time Modulated Silane Flow
Authors: Parsons Gregory N. , John J. Boland John J. Boland , James C. Tsang James C. Tsang
Published: February 2005

The use of time modulated gas flows in plasma enhanced chemical vapor deposition (PECVD) gives an additional degree of flexibility to the growth process to control film nucleation and modify the properties of the deposited films. Specifically, we show that time modulated flow of silane into a hydrogen plasma allows for substrate selective nucleation and enhanced crystallinity of microcrystalline silicon films. We have used Raman spectroscopy, infrared absorption spectroscopy and scanning tunneling microscopy (STM) to investigate reactions between atomic hydrogen and the growth surface that result in crystallite formation and selective deposition. We show that exposing the growth surface to atomic hydrogen results in: 1) breaking of highly strained surface bonds; and 2) etching of silicon from the surface. We find that substrate dependent nucleation, and the different etch rates of the different nucleii, lead to selective deposition. However, we show that etching is not sufficient to account for microcrystallite formation, and that bond strain relaxation by atomic hydrogen promotes motion of adatoms on the surface and leads to the nucleation of crystalline silicon. The selective deposition technique has been applied to the formation of thin film transistor devices, and these results are also presented.
Low-Temperature Growth of SiO2 Thin Film by Photo-Induced Chemical Vapor Deposition Using Synchrotron Radiation
Authors: Matsui Yuichi , Nagayoshi Ryoichi , Nakamura Masakazu , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

SiO2 thin films have been grown on Si and MgF2 wafers at low temperatures in the range of room temperature (R.T.)-200°C by photo-induced chemical vapor deposition (photo-CVD) using synchrotron radiation (SR). The thin films grow selectively on the irradiated area. Deposition rate at R.T. is about 8-13 nm/min, and depends on the electron beam current of SR. The thin films deposited even at R.T. have few impure Si-H and Si-OH bonds, because source gases are decomposed and react effectively, in the vapor phase and on the substrate surface by the SR light. The minimum fixedoxide-charge density is 1.6×1011 cm-2 in SiO2 film of thickness 92 nm deposited at R.T. This density is low in comparison with those of films deposited at low temperature by the other CVD methods.
Novel Static Magnetron Triode Reactive Ion Etching
Authors: Masaaki Sato Masaaki Sato , Yoshinobu Arita Yoshinobu Arita
Published: February 2005

Static magnetron triode reactive ion etching (SMTRIE) has been developed as a new method that achieves high-rate and high-uniformity etching with low metal oxide semiconductor (MOS) damage. An overview of the method is provided together with an application to Al-Cu etching. Four axisymmetric coils produce radial magnetic flux near and parallel to the etching cathode, and cylindrical magnetic flux parallel to the surrounding side cathode. This field creates a magnetron-type discharge near both cathodes, thus producing high plasma density that is both axisymmetrically and radially uniform. Al-Cu etching results demonstrate the excellent uniformity of SMTRIE. In addition, no gate damage was observed even at high power or under relatively poor uniformity. SMTRIE is one of the most promising etching methods for application to deep submicron geometries where precise and low-damage etching are indispensable.
Mechanism of High Selectivity and Impurity Effects in HBr RIE: In-Situ Surface Analysis
Authors: Nakamura Moritaka , Matsuo Keiji Koshino
Published: February 2005

The brominated surface layer of SiO2 was studied after HBr reactive ion etching (RIE) with in-situ X-ray photoelectron spectroscopy (XPS). Bromine was observed, but neither the Si-Si nor the Si-Br
x
bond was spectrally detected. Most of the bromine on the SiO2 surface desorbed after atmospheric exposure. Oxygen was depleted by both HBr RIE and rare gas sputtering, and the XPS peak was broadened by sputtering. Carbon addition enhanced the oxygen depletion and the peak broadening. Results indicate that the conventional “chemical sputtering” does not occur in the HBr RIE of SiO2, but rather oxygen extraction by ion bombardment or preferential sputtering initiates the etching reaction. After the extraction, bromine reacts with silicon within the same collision cascade, and prevents the Si-O recombination, which is observed as the peak broadening. Carbon enhances the oxygen extraction.
Silicidation Reaction and Stress in Ti/Si
Authors: Chen Shih-Chang , Tamura Hiroyuki , Hara Tohru , Kinoshita Kei , Inoue Ken , Endo Nobuyuki , Nakamura Shigeaki
Published: February 2005

In situ stress measurement in titanium silicide (TiSi2) during silicidation is performed at temperatures ranging from 30 to 900°C. In a 900 Å-thick Ti layer, the stress changes from tensile to compressive at 500°C and reaches a maximum of 6.8×108 Pa at 650°C. The stress decreases abruptly at 700°C. This clearly indicates that the silicidation reaction has been accomplished under higher stress conditions in the conventional silicidation process. The abrupt stress change appearing at 600∼650°C is due to the diffusion of Si from the Si substrate into the Ti layer in the silicidation reaction. This stress, however, decreases rapidly with grain growth of C54 TiSi2. However, lower stress with weak temperature dependence is obtained in the silicidation of a thin Ti layer. Lower-stress silicidation can be achieved when a thin Ti layer is silicided at higher temperatures, above 650∼700°C, or a thick (900 Å thick) layer at 700°C.
Study on Chlorine Adsorbed Silicon Surface Using Soft-X-Ray Photoemission Spectroscopy
Authors: Matsuo Jiro , Karahashi Kazuhiro , Akira Sato Akira Sato , Shinpei Hijiya Shinpei Hijiya
Published: February 2005

In a study of the surface reaction of molecular and atomic chlorine on Si(100) and Si(111) using X-ray photoemission spectroscopy and molecular beam scattering, we have found only SiCl in the chlorinated layer formed by the molecular chlorine exposure, with no change in this bonding configuration after annealing. Most desorption products were SiCl2. SiCl desorbed above 900°C, probably due to the recombinative desorption of SiCl+Cl→SiCl2. SiCl desorbed directly from the surface without any reaction. Heavily chlorinated species, such as SiCl2, SiCl3 and SiCl4, were observed on Si(100) and Si(111) surfaces exposed to atomic chlorine. These heavily chlorinated species quickly desorbed from the surface after annealing at 300°C. No heavily chlorinated species were observed on the silicon surface exposed to molecular chlorine. The chlorinated layer on Si(111) was thinner than that on Si(100), explaining the appearance of the <111> facet reported in photo-enhanced etching.
Tilt Deformation of Metalorganic Chemical Vapor Deposition Grown GaP on Si Substrate
Authors: Suzuki Takayuki , Mori Masatoshi , Jiang Z. K. , Soga Tetsuo , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

The behavior of the stress and the deformation of a GaP layer grown on misoriented (001)Si was investigated for the thickness and the growth temperature. The compressive stress in the GaP layer decreased with increasing thickness up to 0.5 µm and then changed into the tensile stress. However, there was poor dependence of the tensile stress in a 1 µm-thick GaP layer on growth temperature. The tilt deformation of the GaP layer strongly depended on the growth temperature. It was found that the deformation strongly depended on the misfit strain in the GaP layer for a Si substrate at the growth temperature rather than the thermal strain, and that the tilt was under the influence of the atomic step on a Si substrate.
Dopant Segregation in Earth- and Space-Grown InP Crystals
Authors: Danilewsky Andreas Nikolaus , Okamoto Yusuke , Nishinaga Klaus Werner Benz
Published: February 2005

Macro- and microsegregation of sulphur in InP crystals grown from In solution by the travelling heater method under microgravity and normal gravity are analyzed using spatially resolved photoluminescence. Whereas the macrosegregation in earth- as well as space-grown crystals is explained by conventional steady-state models based on the theory of Burton, Prim and Slichter (BPS), the microsegregation can only be understood in terms of the non-steady-state step exchange model.
Generation of Strongly Ionized Aluminum Plasma in a Low-Temperature Tokamak Discharge
Authors: Kenji Hiramatsu Kenji Hiramatsu , Shuichi Takamura Shuichi Takamura
Published: February 2005

A new technique to produce a strongly ionized plasma from aluminum metal is achieved by use of the plasma-assisted arc in a tokamak discharge with low temperature (\lesssim10 eV), high electron density (\gtrsim1012cm-3), and low gas pressure (10-5∼10-4Torr). On arcing, the spectral lines of AlI, AlII and AlIII have been observed. Using the comparison spectroscopic method with no need of absolute measurement of spectral line intensity, we obtained the result that doubly ionized aluminum ions are dominant, and the density is estimated to be about 1011cm-3. The aluminum plasma thus produced is useful and has potential for plasma processing, such as thin-film formation of AlN.