bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective Growth of InGaAs/InP Layers by Gas Source Molecular Beam Epitaxy with Atomic Hydrogen Irradiation
Authors: Kuroda Naotaka , Sugou Shigeo , Tatsuya Sasaki Tatsuya Sasaki , Mitsuhiro Kitamura Mitsuhiro Kitamura
Published: February 2005

Selective gas source molecular beam epitaxy (gas source MBE) growth of high-quality InGaAs/InP layers on mask-patterned InP substrates is demonstrated for the first time with atomic hydrogen irradiation. A decrease in polycrystalline density of over 3 orders of magnitude is achieved for InP selective growth by atomic hydrogen irradiation. The selective growth of high-quality InGaAs/InP multiple quantum-well (MQW) structures is also demonstrated. Photoluminescence (PL) spectroscopy indicates that the peak-wavelength of she MQW structure does not depend on the mask stripe width, but significant peak-wavelength dependence on the stripe spacing width was observed.
Observation of Beam-Bunch Lengthening in the 1.3-GeV Electron Synchrotron
Authors: Hashimoto Yoshinori , Koseki Tadashi , Kudo Hirofumi , Maruyama Koichi , Masuda Hitoshi , Mutou Masayuki , Ohkuma Haruo , Shinoe Kenji
Published: February 2005

The beam-bunch lengths in the accelerating stage of the 1.3-GeV electron synchrotron were measured at the operating energies (E
0) of 0.6-0.9 GeV. Both of the obtained behaviors: the bunch-length reduction from 1.0 ns (rms width) to 0.35 ns and the position variation on the rf phase, are described well by a tracking-simulation calculation. An intensity-dependent bunch lengthening: 0.19 ns at 0.5 mA and 0.30 ns at 100 mA for a voltage pattern of the rf accelerating field at E
0=0.6 GeV, is observed. Neither the tracking calculation nor other known bunch-lengthening mechanisms can explain the data.
In Situ Observation of Atomic Layer Epitaxy of GaAs Using GaCl3 by Surface Photo-Absorption Method
Authors: Kobayashi Ryuji , Narahara Satoru , Katsumi Ishikawa Katsumi Ishikawa , Fumio Hasegawa Fumio Hasegawa
Published: February 2005

Surface photo-absorption (SPA) method was used to observe the GaAs growth process during alternate supply of GaCl3 and AsH3. The reflection intensity after the GaCl3 supply and H2 purge is different from that of the Ga atom surface formed by a desorption of arsenic from the GaAs surface. Furthermore, the spectral dependence of the SPA signal in our growth system is different from that in the triethylgallium (TEGa)-AsH3 system. These results indicate that the GaAs surface after the GaCl3 supply and H2 purge is not covered by Ga atoms. So far as growth using GaCl3 is concerned, the surface after the GaCl3 supply is inferred to be a Cl-terminated Ga surface.
Stable High-Efficiency Double-Phase-Conjugate Mirror in a Cu-Doped Potassium Sodium Strontium Barium Niobate Crystal
Authors: Gao Xin , Zheng Akira Sasaki
Published: February 2005

We report a stable high-efficiency double-phase-conjugate mirror (DPCM) in a Cu-doped potassium sodium strontium barium niobate (KNSBN:Cu) crystal. The stable high phase-conjugate transmissivity reaches 55% when using a mW-order low-power Ar+ laser at a 514 nm wavelength with two mutually incoherent incident beams. The relative stability of the phase-conjugate transmissivity of as high as 93% was obtained in 150 minutes. The incident-location and angle responses of the phase-conjugate transmissivity were observed. Unstable behaviour of the DPCM was also observed and discussed.
Encapsulation of ZrC and V4C3 in Graphite Nanoballs via Arc Burning of Metal Carbides/Graphite Composites
Authors: Saito Shunji Bandow
Published: February 2005

Ultrafine particles surrounded by graphitic carbon layers have been produced by the arc burning of a composite carbon rod containing ZrC or VC. The size of the ultrafine particles is typically in the range of 20-40 nm in diameter and the number of graphitic carbon layers surrounding a core particle ranges from about 10 to 30. The core ultrafine particles are found to be ZrC (via ZrC-graphite composite rod) and V4C3 (via VC-graphite composite rod) by selected-area electron diffraction from each composite nanoball (graphite nanoball with a core particle).
Diamond Grain Growth on Cu Substrate
Authors: Ojika Shin-ichi , Yamashita Satoshi , Ishikura Kazuhiro Kataoka
Published: February 2005

Diamond growth on Cu substrates with vapor phase deposition has been studied. Diamond was deposited on Cu substrates using an electron cyclotron resonance chemical vapor deposition apparatus. Its growth process was observed through morphological variation with time in the same field of vision, which showed that diamond grains on Cu substrates grew not only through increase of the size of grains but also through their combination, and that isolated grains at an early stage of growth migrated on the substrate as if they were attracted by each other. This manner of diamond growth is specific to cases where Cu is used as the substrate.
Measurement of Ion Temperature in Electron Cyclotron Resonance Plasma
Authors: Okuno Yoshihiro , Ohtsu Yasunori , Fujita Hiroharu , Wei Chen Wei Chen , Shoji Miyake Shoji Miyake
Published: February 2005

Ion temperatures parallel and perpendicular to an applied magnetic field are measured in electron cyclotron resonance (ECR) plasmas under a divergent or a mirror magnetic field configuration using a directional analyzer. The temperatures obtained as a function of gas pressure are found to be low (0.2∼0.5 eV) and are compared with those measured by optical emission spectroscopy of Doppler profiles. The temperatures perpendicular to the magnetic field from the two different methods agree well for both magnetic configurations. The reliability of the measurement using the directional analyzer is discussed considering the ion motions in the sheath in front of the analyzer and in the magnetic field.
High Resolution Images of Cell Surface Using a Tapping-Mode Atomic Force Microscope
Authors: Umemura Kazuo , Hideo Arakawa Hideo Arakawa , Atsushi Ikai Atsushi Ikai
Published: February 2005

We succeeded in obtaining high-resolution images of a cell surface using a tapping-mode atomic force microscope (tapping-mode AFM) in air. The resulting images resolved many particles of 40-80 nm in radius and distinguished regions where the particles formed clusters from other regions. Such images could not be obtained using a contact-mode atomic force microscope (contact-mode AFM) operated under the same conditions. The result demonstrates the possibility of cell surface research using the tapping-mode AFM with molecular resolution.
Electroluminescence from Lateral P-N Junctions Grown on (111)A GaAs Patterned Substrates
Authors: Inai Makoto , Yamamoto Teiji , Toshihiko Takebe Toshihiko Takebe , Toshihide Watanabe Toshihide Watanabe
Published: February 2005

Lateral p-n junctions were grown on (111)A GaAs patterned substrates by a plane selective doping method and electroluminescence (EL) properties of the lateral p-n junctions were investigated. EL was observed along the <011> line, and the line formed a triangular pattern on the substrate. The emission spectrum had a sharp peak at 870 nm at room temperature. Even though these p-n junctions were not optimized for LED structures, the emission intensity of EL was higher than that from p-n junctions of conventional structure. These characteristics are advantages of lateral p-n junctlons grown on (111)A GaAs patterned substrates. These are the first observations of EL from (111)A GaAs lateral p-n junctions.
All-Optical Switch with Switch-Off Time Unrestricted by Carrier Lifetime
Authors: Kazuhito Tajima Kazuhito Tajima
Published: February 2005

We propose a symmetric Mach-Zehnder-type all-optical switch which is based on the nonlinear refractive index change induced in semiconductors. Unlike most all-optical switches, the switch-off time, as well as the switch-on time, of this novel device is not limited by the usually slow carrier lifetime, allowing a very fast switching speed. Its switching characteristics are theoretically examined under various conditions. It is shown that the device offers a nearly square modulation characteristic that is suitable for most switching applications.
ZnSe-Based Diode Lasers with Stripe-Geometry Fabricated by Ion Bombardment
Authors: Yoshii Shigeo , Hayashi Shigeo , Tsujimura Ayumu , Ohkawa Kazuhiro , Mitsuyu Tsuneo , Takeishi Hidemi , Takahashi Yasuhito , Narusawa Tadashi
Published: February 2005

Current confinement of ZnSe-based diode lasers on p-GaAs substrates has been achieved by ion bombardment. Nitrogen ions were used for the bombardment to produce a high-resistivity region in n-Zn(S)Se cladding layer. The threshold current was reduced by one-third with the introduction of this current-blocking region. The devices showed laser action up to 150 K under pulsed current injection.
Improvement of Thermal Stability and Critical Current of Superconducting Nb Multi-Layer Wiring
Authors: Tsukada Keiji , Jun Kawai Jun Kawai , Hisashi Kado Hisashi Kado
Published: February 2005

A spiral coil of double-Nb layers is fabricated to investigate the thermal degradation mechanism of Nb multi-layer wiring. The superconductivity of the coil with a sputtered SiO2 insulation layer easily deteriorates as a result of surface oxidation where the step coverage is incomplete. Higher critical current and thermal stability are obtained by a combination of planarization using spin-coated SiO2 for the insulation between Nb wiring, surface nitridation of Nb, and taper etching of the contact hole. The critical current of the coil with a spin-coated SiO2 film is about twice that of a coil with sputtered SiO2; even though it was baked at 300°C for 30 min for each layer.
Photoinduced Current across Polyimide Langmuir-Blodgett Films in the Absence of an External Electric Field
Authors: Mitsumasa Iwamoto Mitsumasa Iwamoto , Atsushi Fukuda Atsushi Fukuda
Published: February 2005

We fabricated Au/PI/Al junctions using polyimide (PI) Langmuir-Blodgett (LB) films and then examined the photoinduced current across PI LB films in the absence of an external electric field. The generation of transient photoinduced current was explained with respect to the space-charge field formed in as-deposited PI LB films and the change in the space charge field with photoirradiation.
Schottky Characteristics of Subhalf-Micron Gate GaAs Metal-Semiconductor Field-Effect Transistor
Authors: Tamotsu Kimura Tamotsu Kimura , Tomoyuki Ohshima Tomoyuki Ohshima
Published: February 2005

This paper describes Schottky characteristics of the subhalf-micron W-Al gate GaAs metal-semiconductor field-effect transistor (MESFET), which is fabricated using the phase-shifting mask technology. We observed that Schottky characteristics depend on the gate length and gate direction especially in the subhalf-micron range. This phenomena is caused by the piezoelectric effect; however, the degree of the barrier height shift is small compared to that of the threshold voltage, and this can be explained by the depth profile of the induced charges under the gate of subhalf micron.
New-Type Photocathode for Polarized Electron Source with Distributed Bragg Reflector
Authors: Saka Takashi , Kato Toshihiro , Nakanishi Tsutomu , Tsubata Mitsuru , Kishino Katsumi , Horinaka Hiromichi , Kamiya Yoshihiro , Okumi Shoji , Takahashi Chikako , Tanimoto Yasunori , Tawada Masafumi , Togawa Kazuaki , Aoyagi Hideki , Nakamura Shinsuke
Published: February 2005

In order to increase the quantum efficiency of the strained GaAs photocathode for a highly polarized electron source, we designed a new type of photocathode with a distributed Bragg reflector (DBR). A Fabry-Perot cavity is formed by the DBR and the GaAs surface. A large enhancement of quantum efficiency was observed at the laser wavelength which satisfied the condition for the resonant absorption of incident laser light. Based on this experiment, it appears promising to make a photocathode which has the quantum efficiency of more than ∼1% together with electron spin polarization higher than 80%.
High-Resolution Isochromat Inverse Photoemission Spectroscopy
Authors: Suga Shigemasa , Matsushita Tomohiro , Shigeoka Hiroaki , Namatame Akio Kimura
Published: February 2005

We propose a new method to measure the vacuum ultraviolet inverse photoemission spectrum in an isochromat mode with high resolution. In this new method, two filters (F1 and F2) with slightly different cutoff energies hν1 and hν2 (hν1<hν2) are used as the window for measurement. The transmittance of the two filters is assumed to be equivalent except for the region of hν1∼hν2. The spectrum measured by F1 is properly normalized and subtracted from the spectrum obtained by F2. The resulting difference spectrum provides the inverse photoemission spectrum measured with high resolution defined by hν2-hν1, which can be better than 0.2 eV.
Synthesis of Nanocrystalline Silver Particles in Glass and Their Recovery
Authors: Biswanath Roy Biswanath Roy , Dipankar Chakravorty Dipankar Chakravorty
Published: February 2005

Silver particles having diameters in the range 7.1 to 12.4 nm have been synthesized within an oxide glass medium and then recovered by a simple chemical etching technique. These nanosized particles after compaction exhibit electrical resistivity behavior which is characterized by a phonon softening effect. The optical absorption of these nanosized particles embedded in potassium bromide follow tbe prediction of the effective medium theory.
Interferometric Observation of the Interfacial Concentration Gradient Layers Around a Lysozyme Crystal
Authors: Komatsu Hiroshi , Satoru Miyashita Satoru Miyashita , Yoshihisa Suzuki Yoshihisa Suzuki
Published: February 2005

A Michelson interferometer of the reflection type was successfully used, for the first time, to observe the surface microtopography and the interfacial concentration gradient layers around protein crystals, which were either growing or dissolving in the solution. The significance of this technique was mentioned for the analysis of the growth kinetics of crystals from solution.
Studies of Third-Order Nonlinear Optical Properties of Polyazine and Its Oligomers
Authors: Nalwa Hari Singh , Hamada Tomoyuki , Atsushi Kakuta Atsushi Kakuta , Akio Mukoh Akio Mukoh
Published: February 2005

The third-order nonlinear optical properties of a polyazine and its oligomers are reported for the first time. Third-harmonic generation measurements revealed a nonresonant third-order nonlinear optical susceptibility χ(3)(-3ω; ω, ω, ω) of 1.53×10-12 esu for a pentamer and 8.0×10-12 esu for propylmethylpolyazine at 1.5 µm. Dipole polarizability (α) and second hyperpolarizability (γ) of oligomer model compounds were also calculated by employing the ab initio coupled-perturbed Hartee-Fock (CPHF) theory. Both polarizabilities and χ(3)(-3ω; ω, ω, ω) increase significantly as the length of π-electron delocalization increases in the polyazine backbone.
Measurement of Strain in Locally Oxidized Silicon using Convergent-Beam Electron Diffraction
Authors: Kimoto Koji , Usami Katsuhisa , Sakata Hiroshi , Tanaka Michiyoshi
Published: February 2005

Possibility has been studied for analysis using convergent-beam electron diffraction (CBED) of strain in large-scale integrated circuits (LSIs). In the present study, a strain of 1×10-4 can be detected, which is sufficient to analyze strain in LSIs. This technique is applied to the measurement of strain in locally oxidized silicon (LOCOS). The silicon substrate is found to have a maximum compressive strain of 4×10-4 at a point 1.5 µm from the SiO2 edge. Although the influence of specimen thinning preparation on stress is not negligible, the stress distribution was found to suffer from a uniform shift of tensile stress by about 30 MPa.
Visible Photoluminescence from Si Microcrystalline Particles*
Authors: Toshihiko Kawaguchi Toshihiko Kawaguchi , Shin Miyazima Shin Miyazima
Published: February 2005

Visible photoluminescence from oxidized Si microcrystalline particles was observed under excitation of an He-Cd laser at room temperature. The particles had been prepared by mean of the SiH4 gas breakdown method with a Nd3+-YAG pulse laser. The particles formed a single-crystalline structure of Si. The photoluminescence spectrum obtained from these particles showed maximum intensity at a wavelength of 730 nm. This wavelength did not change with particle size. These Si particles exhibited visible photoluminescence when oxidized.
Reproducibility of Phonon Structures in the Tunneling Conductance of Bi2-xPbxSr2Ca2Cu3O10-y
Authors: Ohuchi Masahiko , Daisuke Shimada Daisuke Shimada , Nobuo Tsuda Nobuo Tsuda
Published: February 2005

Phonon structures appeared in the tunneling conductance of a Bi2-x
Pb
x
Sr2Ca2Cu3O10-y
-GaAs junction. They are similar to the previous structures obtained for SnO2 junctions. There is no large structure other than that of the phonon in a single phonon frequency range. Above that range, tiny peaks appeared up to 180 meV, which may be anharmonic phonon structures. From the phonon positions, 2Δ is determined to be 60±4 meV and from the temperature of disappearance, T
c is estimated to be 95±6 K. Thus, 2Δ/k
B
T
c is 7.3±1.0.
Bi2Sr2CuOx Thin Films with (011) Vicinal Surfaces Fabricated on Vicinal LaSrGaO4(110) by Molecular Beam Epitaxy
Authors: Ishibashi Takayuki , Fujita Tomoya , Song Kang-Ho , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Bi2Sr2CuO
x
(2201) thin films with (011) vicinal surfaces have been prepared by molecular beam epitaxy (MBE) on vicinal LaSrGaO4(110) substrates with tilt angles of 4° and 6° toward [001]. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) patterns have indicated that the films have two kinds of domains. The epitaxial relationship between these domains and LaSrGaO4 substrates has been investigated and found that the b-axis of each domain was misoriented approximately ±12° from [110] LaSrGaO4 and the a-axis aligned along [11̄0] LaSrGaO4. The growth of the +12°-misoriented domains was achieved on 6°-tilted LaSrGaO4(110) at 690°C.
Photoluminescence Spectra of Carbon Clusters Embedded in SiO2
Authors: Hayashi Shinji , Masahide Kataoka Masahide Kataoka , Keiichi Yamamoto Keiichi Yamamoto
Published: February 2005

Composite films of carbon and SiO2 were prepared by a rf cosputtering technique and their photoluminescence and absorption spectra were measured. A strong and broad photoluminescence peak located around 2.2 eV (visible to the naked eye) was observed for the samples with relatively low carbon concentrations. The blue shift of the photoluminescence peak observed with decreasing carbon concentration and the increased absorption in the UV region strongly suggest that carbon clusters comparable to or smaller than C60 formed in the SiO2 matrices are responsible for the strong photoluminescence.
Generation of High-Current Photoelectrons Using a Subpicosecond Ultraviolet Laser
Authors: Kawamura Yoshiyuki , Jeong Young Uk , Akiyama Yasuhiro , Kubodera Shoichi , Katsumi Midorikawa Katsumi Midorikawa , Koichi Toyoda Koichi Toyoda
Published: February 2005

Laser-induced photoelecrons produced using an ultrashort pulse laser and a metal cathode have been accelerated to relativistic energy. The pulse duration and the wavelength of the laser are 0.5 ps and 248 nm, respectively. The acceleration voltage is 0.61 MV. The current density at the cathode surface was estimated to be about 1 kA/cm2, which is about one hundred of times higher than the theoretically calculated value of the space-charge-limited current density given by the Langmuir equation. Theoretical analysis of the space-charge-limited current density for an ultrashort electron bunch was performed.
Thin Gallium Oxide Film Deposited in Vacuum for In Situ Process Use
Authors: Ozasa Kazunari , Ye Tianchun , Aoyagi Yoshinobu
Published: February 2005

Gallium oxide deposition was carried out on GaAs with the alternating supply of source gases, TEGa and H2O2. Strong temperature dependence of growth rate per cycle was observed together with some structural change in the films. A critical thickness of 20 nm for the thermal desorption of gallium oxide, above which the film thickness was not changed by the thermal treatment at 600°C for 90 min, was observed for the first time. With implications for in situ process use, deposition characteristics of GaAs on these gallium oxides were investigated by chemical beam epitaxy (CBE), and the results indicated that oxide structure greatly affects selectivity.
Estimation of Metal-Deposited Field Emitters for the Micro Vacuum Tube
Authors: Ishikawa Junzo , Tsuji Hiroshi , Inoue Kazunori , Nagao Masayoshi , Sasaki Takahiro , Takashi Kaneko Takashi Kaneko , Yasuhito Gotoh Yasuhito Gotoh
Published: February 2005

The material dependence on the emission characterisitics of metal-deposited field emitters has been investigated in order to determine the cathode material suitable for vacuum microelectronics devices. It is shown that the relationships between the intercepts and the slopes of the experimental F-N plots give the apparent differences of the materials even though the radii of the apices are not equal among the emitters. We derive the modified F-N equation from the experimental values and the semi-empirical assumption as a linear variation of the work function with electrical field due to an adsorption effect. From this equation we calculate the emitting area, the radius of the emitter apex and the work function.
Frequency Spectrum of Fluctuations Near a Rational Surface in a Toroidal Heliac
Authors: Zama Tatsuya , Kitajima Sumio , Takayama Masakazu , Takeuchi Nobunao , Hiroshige Watanabe Hiroshige Watanabe
Published: February 2005

Density and space potential fluctuations have been studied in electron cyclotron resonance heating (ECRH) plasma of a helical axis stellarator TU Heliac using Langmuir probe techniques. These fluctuations are coherent and global, which can be explained by a drift instability model in cylindrical geometry. A particular fluctuation mode vanishes inside a rational surface. The ratio of this mode, n/m, corresponds to the rotational transform ι/ of this rational surface, (m, n: poloidal, toroidal fluctuation modes, respectively). This phenomenon near the rational surface can also be explained by a drift instability theory.
Marked Enhancement of Photoconductivity and Quenching of Luminescence in Poly(2,5-dialkoxy-p-phenylene vinylene) upon C60 Doping
Authors: Yoshino Katsumi , Yin Xiao Hong , Muro Keiro , Kiyomatsu Shinji , Morita Shigenori , Zakhidov Anver A. , Noguchi Takanobu , Ohnishi Toshihiro
Published: February 2005

The absorption spectrum and electrical conductivity of poly(2,5-dioctyloxy-p-phenylene vinylene) (OO-PPV) are hardly influenced by doping of a small amount of C60, suggesting that C60 is not an effective dopant for OO-PPV. On the other hand, photoluminescence has been markedly quenched and photoconductivity has been enhanced by several orders of magnitude upon introduction of several mol% of C60, suggesting photo-induced charge transfer between OO-PPV and C60. These results are discussed in terms of relative electronic energy states of OO-PPV and C60. The photoexcited exciton-polaron (Ex-P) is speculated to migrate along 50∼100 monomer units of the polymer main chain in its lifetime and dissociate when encountered with C60.
Electronic Structures of Porous Si Studied by Core-Level Absorption and Photoemission Spectroscopy
Authors: Inoue Koichi , Kenzo Maehashi Kenzo Maehashi , Hisao Nakashima Hisao Nakashima
Published: February 2005

For the investigation of the electronic structures of porous Si, 2p core-level absorption and photoemission spectra are measured with synchrotron radiation. The core-level absorption spectra indicate that the conduction band of porous Si shifts toward higher energy as compared with that of bulk Si. This shift correlates well with the photoluminescence blueshift. From photoemission spectra of porous Si in the Si 2p core-level regions, oxidized states on the porous surface are examined.
In-Depth Profile of Electrical Property of InAs Epitaxial Layer Grown on Semi-Insulating GaAs by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Iwamura Yasuo , Hiroyuki Shigeta Hiroyuki Shigeta , Naozo Watanabe Naozo Watanabe
Published: February 2005

Indium arsenide layers of various thicknesses were grown on semi-insulating GaAs by low-pressure metalorganic chemical vapor deposition (MOCVD) using trimethylindium (TMIn) and tertiarybutylarsine (TBAs) as precursors. On the assumption that properties of the underlying grown layer do not change during growth of the upper layer, the in-depth profile of the electrical property of the epitaxial layer was obtained by the differential Hall effect. It was proved that the uppermost layer, 1.8 µm from the interface, has an electron mobility of 61300 cm2/V·s and a carrier concentration of 2.1×1016 cm-3 (the average mobility of 29800 cm2/V·s and average carrier concentration of 1.8×1016 cm-3) at 80 K.
Metal-Organic Vapor Phase Epitaxy Growth and Optical Study of GaAs/GaAs1-xPx Strained-Barrier Single Quntum Well Structures
Authors: Zhang Xiong , Onabe Kentaro , Yamaguchi Hiroyuki , Ito Yasuhiro Shiraki
Published: February 2005

GaAs/GaAs1-x
P
x
(x=0.15, 0.20, 0.22) single quantum wells which involve tensile-strained GaAs1-x
P
x
barrier layers have been grown on GaAs substrates by metal-organic vapor phase epitaxy (MOVPE) and characterized by double-crystal X-ray diffration, photoluminescence (PL), and Fourier-transform reflectance spectroscopy (FT-RS). Despite the relatively large relaxation ratio of the strain (sometimes as high as 7.5%), these structures exihibit smooth surface morphology ass well as intense and narrow excitonic emissions. The composition-dependent energy band offset ratios for the GaAs/GaAs1-x
P
x
strained-barrier single quantum well structures have also been determined.
A Theoretical Investigation of the Metastability of Al on a (100) Zinc Blende Substrate
Authors: Tomonori Ito Tomonori Ito
Published: February 2005

The structural metastability of Al thin films on a (100) zinc blende substrate is discussed using cohesive energy calculations for bulk form and thin layers with both the pseudopotential perturbation approach and universal empirical potentials. In bulk form, face centered cubic (FCC) Al is more stable than body centered cubic (BCC) Al by 103 meV/atom. The total crystal energy, as a function of the (100) substrate lattice parameter, also indicates that FCC-Al is more stable structure over the lattice parameter range of semiconductor substrates with a zinc blende structure. In the epitaxial state, the stability of (110) FCC-Al equivalent to body centered tetragonal (BCT)-Al is found to be a competing phase. The planar energy difference between BCT- and FCC-Al is very small and is estimated to be 20 meV/atom at the interface between thin films and a substrate.
A New Method to Determine the Oxygen Content of YBa2Cu3O7-δ: Open-Circuit Voltage Measurement
Authors: Choy Jin-Ho , Kang Seong-Gu , Park Dong-Hoon Kim
Published: February 2005

A new electrochemical method to determine the oxygen content of YBa2Cu3O7-δ (0.08≤δ≤0.5) has been developed by correlating the open-circuit voltage (OCV) with δ. In the superconducting domain, the observed OCV value increases linearly as the oxygen vacancy decreases with the following equation: δ=-0.0018 E

i
=0 (mV)+1.04; r=0.99. Since no change in oxygen content is found before and after the electrochemical measurements, we propose that this is a prompt and new nondestructive analytical way compared to any other methods previously reported.
Metalorganic Vapor Phase Epitaxy of ZnSe Using Tertiarybutylselenol as Selenium Source Precursor
Authors: Nishimura Kohsuke , Yasuyuki Nagao Yasuyuki Nagao , Kazuo Sakai Kazuo Sakai
Published: February 2005

Metalorganic vapor phase epitaxy of ZnSe on a GaAs substrate was carried out using a novel organic selenium source, tertiarybutylselenol (t-BuSeH), for the first time. A constant and high growth rate was attainable in the growth temperature range of 280-500°C using t-BuSeH. The low-temperature reaction between diethylzinc and t-BuSeH was virtually eliminated, therefore growth uniformity and reproducibility were satisfactory. The grown ZnSe layers were evaluated to be of high quality by photoluminescence and X-ray diffraction measurement.
Observation of InP Surfaces after (NH4)2Sx Treatment by a Scanning Tunneling Microscope
Authors: Kurihara Kazuhiro , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: February 2005

InP surfaces after (NH4)2S
x
treatment were observed by a scanning tunneling microscope (STM) in air. The stabilized image of the flat surface was observed on the sample after (NH4)2S
x
treatment for 30 s. The rms roughness was measured as 0.08 nm. When no surface treatment was applied, the surface was very rough when observed in the constant current mode. Since the STM image of the same sample with Au/Pd coating showed a flat surface and the current-voltage characteristics at the convex and concave portions were different, fluctuation of electron states on the InP surface is concluded to be the cause of the observed roughness. This result shows that a stable InP surface can be obtained by (NH4)2S
x
treatment.
Model Calculations for Giant Magnetoresistance in Metallic Superlattices
Authors: Nakanishi Hiroshi , Ayao Okiji Ayao Okiji , Hideaki Kasai Hideaki Kasai
Published: February 2005

The effects of three factors on the magnetoresistance in superlattices composed of magnetic and nonmagnetic slabs are studied within the framework of the coherent potential approximation: (i) the number of interfacial layers, in which magnetic and nonmagnetic ions are randomly distributed adjacent to interfaces between slabs, (ii) average distribution number and (iii) the relative position of electron energy levels of these ions. It is shown that the absolute value of the resistance is mainly determined by factors (i) and (ii), and that its magnetic-field-dependent part, on the other hand, is mainly determined by factor (iii).
Study of Si Etch Rate in Various Composition of SC1 Solution
Authors: Kobayashi Hiroyuki , Ryuta Jiro , Shimanuki Takayuki Shingyouji
Published: February 2005

Etching of Si wafer surface in an NH4OH:H2O2:H2O mixture (SC1 solution) is studied in regard to the effect of the composition of the solution. It is clarified that, when H2O2 concentration is constant, the etch rate increases linearly with OH- ion concentration and reaches a saturation etch rate. This saturation etch rate is inversely proportional to H2O2 concentration. Microroughness of Si surface after SC1 treatment is also investigated. It is also found that microroughness is independent of NH4OH concentration when the etch rate is kept constant.
C60 Grown on the Cu(111)1×1 Surface
Authors: Motai Kumi , Hashizume Tomihiro , Shinohara Hisanori , Saito Yahachi , Pickering Howard W. , Yuichiro Nishina Yuichiro Nishina , Toshio Sakurai Toshio Sakurai
Published: February 2005

C60 molecules adsorbed on the Cu(111)1×1 surface have been investigated by the field ion-scanning tunneling microscope (FI-STM). C60 molecules initially segregate to the terrace edges and grow, with increasing coverages, into a monolayer film with the close-packing fcc(111) configuration which results in a 4×4 overlayer phase. Highly featured STM images of C60 adsorbate have been observed and interpreted for the first time based on the local density of the states of C60 adsorbed on the surface. Based on various STM images as a function of the bias voltage, four possible C60 adsorption geometries are determined.
AIN as a Dry-Etch Durable Resist for Electron and Ion Beam Lithography
Authors: Tetsuya Tada Tetsuya Tada , Toshihiko Kanayama Toshihiko Kanayama
Published: February 2005

Irradiation with an electron or ion beam has been found to reduce the etching rate of rf-sputtered AIN in alkaline or acidic solutions, which shows that this material acts as a negative-type electron and ion beam resist. It has a good resolution and high dry-etch durability. The performance of this resist was demonstrated by defining a 30-50 nm pattern with a high aspect ratio (>10) in a Si substrate. Although the sensitivity is much lower than that of conventional polymer resists, we believe this material is well suited for experimental fabrication of nanostructures.
Fundamental Characteristics of Hydrophilic Polymer (Polyether Block Amide) as a Humidity Sensor
Authors: Yatsuzuka Kyoko , Yoshio Higashiyama Yoshio Higashiyama , Kazutoshi Asano Kazutoshi Asano
Published: February 2005

Polyether block amide (PEBA), which is a hydrophilic polymer, was examined as a polymeric resistive humidity sensor. The PEBA has extremely high water absorbability and a high melting point, and is chemically stable. Humidity-sensitive thin polymer films for sensors were prepared by spreading a phenol solution of PEBA on alumina substrates with gold comb electrodes by means of a spinning method. The humidity-impedance characteristics of sensors show no hysteresis, good reproducibility and stability in long-term use. The time responses of the sensors are slow for humidification and very quick for desiccation compared with conventional sensors.
Nanometer Recording on Graphite and Si Substrate Using an Atomic Force Microscope in Air
Authors: Hosaka Sumio , Hajime Koyanagi Hajime Koyanagi , Atsushi Kikukawa Atsushi Kikukawa
Published: February 2005

Nanometer recording has been demonstrated with tens nanometer diameter pits and gold mounds formed on graphite and Si substrate using an atomic force microscope at atmospheric pressure. The probe is prepared by means of coating thin gold film on an SiO2 birdbeak-type cantilever probe, fabricated by a Si microprocess. Applications of voltage pulses between the probe and the graphite make about 10-nm diameter pits and Au mounds. Furthermore, about 50-nm to 30-nm diameter Au mound formations on Si wafer covered with natural silicon oxide are also demonstrated. The results indicate that the technique has potentials to achieve Tera-bit/in2 highly packed storage in air, and directly to write nanometer sized patterns on an insulating thin film.
Preparation of Epitaxial SrCuOX Thin Films with an Infinite-Layer Structure
Authors: Terashima Yoshiaki , Sato Rie , Takeno Shiro , Shin-ichi Nakamura Shin-ichi Nakamura , Tadao Miura Tadao Miura
Published: February 2005

The authors successfully prepared epitaxially-grown SrCuO
X
films with an infinite-layer structure by stacking atomic layers of SrO
X
and CuO
X
alternately, using a shutter-controlled sputtering method. High-resolution electron microscopy (HREM) observation indicated that the films had an infinite-layer structure and were epitaxially grown. It was considered that in order to prepare epitaxial SrCuO
X
films with an infinite-layer structure, the CuO
X
layers had to be CuO, not Cu2O or Cu.
Comparison of Transport Properties between Tl-(1223) and Tl-(2223) Phases of Tl-Ba-Ca-Cu-O Systems
Authors: Nabatame Toshihide , Saito Yukio , Aihara Katsuzo , Tomoichi Kamo Tomoichi Kamo , Shin-Pei Matsuda Shin-Pei Matsuda
Published: February 2005

Thin films of the (1223) phase (Tl-(1223), single Tl-O layer) and the (2223) phase (Tl-(2223), double Tl-O layers) of the Tl-Ba-Ca-Cu-O system were prepared using the laser ablation method. Both films had a high transport critical current density (J
c) of 1.5×105 A/cm2 at 77 K in zero magnetic field. When the magnetic field was applied parallel to the a-b plane (a-b plane//B), transport properties in both films at different temperatures were similar. On the other hand, in fields perpendicular to the a-b plane (a-b plane ⊥B), J
c of the Tl-(1223) thin film was higher than that of the Tl-(2223) thin film at 40, 60 and 77 K. The irreversible magnetic fields (B

c2
* values) obtained from the resistivity change in the magnetic fields were 8.0 and 2.0 T at T/T
c=0.6 for the Tl-(1223) and Tl-(2223) thin films, respectively. These results suggested that the thickness of the Tl-O layer, which is non superconductive, determines transport properties for fields applied perpendicular to the a-b plane.
Photo- and Electron-Beam-Induced Currents from Epitaxial YBa2Cu3Oy Metal-Insulator-Superconductor (MIS) Structure in the Normal State
Authors: Iwabuchi Mamoru , Tatsuhiko Fujii Tatsuhiko Fujii , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

We present the first report of observation of photoinduced and electron-beam-induced short-circuit currents across the Al/(100)SrTiO3/(001)YBa2Cu3O
y
metal-insulator-superconductor (MIS) structure in the normal state. Observed current flow is an indication of downward band bending of the YBa2Cu3O
y
surface layer at the MIS interface, in accordance with the prediction by Hirano et al. based on its large work-function value (Jpn. J. Appl. Phys. 31 (1992) L1345). The electron-beam-induced current (EBIC) image revealed structural defects at the interface. From this image, diffusion length in the (001)YBa2Cu3O
y
layer was roughly estimated as 0.1∼0.2 µm.
Dependence of Magnetic Properties of Co/Pt Multilayers on Deposition Temperature of Pt Buffer Layers
Authors: Shiomi Shigeru , Nishimura Tomotaka , Tadashi Kobayashi Tadashi Kobayashi , Morio Masuda Morio Masuda
Published: February 2005

A 15-nm-thick Pt buffer layer was deposited on a glass slide at temperature T
s(Ptbuf) ranging from 30 to 300°C by e-gun evaporation. Following the cooling in vacuum to ambient temperature, Co and Pt layers have been alternately deposited on it. Very large perpendicular anisotropy and coercivity have been obtained at T
s(Ptbuf) higher than 200°C. The (111) preferred orientation of the Co/Pt multilayer as well as the Pt buffer layer became more pronounced with elevating T
s(Ptbuf), to which the enhancement of perpendicular anisotropy with elevating T
s(Ptbuf) might be ascribable.
Preparation of Substituted Y3Fe5O12 Single-Mode Buried Waveguides on a [1 0 0] Oriented Gd3Ga5O12 Substrate
Authors: Katoh Yujiro , Sugimoto Naoto , Akiyuki Tate Akiyuki Tate , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

A [1 0 0] oriented Gd3Ga5O12 (GGG) substrate is used to prepare a [0 1̄ 1] direction buried channel waveguides of flux grown substituted Y3Fe5O12 (YIG) films. Substituted YIG films are employed as a core as well as claddings. Ion-beam etching is used to form core ridges. Smooth side walls of core ridges are obtained after the soaking in hot phosphoric acid due to the good symmetry of garnet crystal. A well confined circular single-mode near-field intensity pattern is observed at λ=1.55 µm for waveguides less than 7 µm wide. Although the deviation is large, one of the waveguides exhibits a low propagation loss of less than 1 dB/cm which is comparable to the propagation loss of the film.
Microscopic Study of an Artificial Grain Boundary Josephson Junction in a BiSrCaCuO Thin Film Formed on a SrTiO3(110) Substrate Using a MgO Buffer Layer
Authors: Tanimura Junji , Takami Tetsuya , Kuroda Ken'ichi , Wada Osamu , Kataoka Masayuki , Kojima Kazuyoshi , Tetsuo Ogama Tetsuo Ogama
Published: February 2005

An artificial grain boundary Josephson junction in a BiSrCaCuO thin film was fabricated on an off-oriented SrTiO3(110) substrate using a MgO buffer layer, and was investigated using a transmission electron microscope (TEM). The MgO buffer layer was oriented with a (110) plane parallel to the (110) plane of the 5° off-oriented SrTiO3 substrate. The BiSrCaCuO film was grown with the c-axis normal to the (110) plane of the MgO buffer layer, while it had an (11n) orientation on the SrTiO3(110) substrate. Consequently, an artificial grain boundary was formed in the BiSrCaCuO film at the edge of the MgO buffer layer, and it was clearly observed with cross-sectional TEM.
Damage Formed on Silicon Surface by Helicon Wave Plasma Etching
Authors: Hara Tohru , Kawaguchi Kazu , Hayashi Jun , Nogami Hiroshi , Tsukada Tsutomu
Published: February 2005

The damage formed on a silicon surface by exposure to helicon wave oxygen plasma is studied. Oxygen plasma is formed by the typical conditions employed for photoresist patterning. The damage density formed on a silicon surface decreased from 1.9×1016 to 9.3×1015/cm2 with an increase of helicon wave power from 500 to 2000 W. This decrease is mainly due to the increase of plasma density and to a decrease of self-bias voltage with the power increase. It must be noted that this phenomenon is much different from the damage changes in magnetic enhanced reactive ion etching (MERIE). However, the damage density increases with a bias power increase. These results show that much lower damage etching can be achieved by helicon wave plasma etching if higher helicon wave powers and lower bias powers are supplied.
Spontaneous Emission Enhancement in Pillar-Type Microcavities
Authors: Tezuka Tsutomu , Nunoue Shin-ya , Haruhiko Yoshida Haruhiko Yoshida , Takao Noda Takao Noda
Published: February 2005

A reduction in photoluminescence decay time of pillar-type microcavities was observed with decreasing the detuning between the resonance wavelength of the cavities and the luminescence peak wavelength of the active layers. The radiative recombination time was extracted from the measured photoluminescence decay time by a diffusion equation analysis. The obtained spontaneous emission enhancement factor was between 1.6 and 1.8. This is the first observation of a spontaneous emission enhancement in three-dimensionally confined semiconductor microcavities.
Laser-Induced-Fluorescence Detection of SiH2 Radicals in a Radio-Frequency Silane Plasma
Authors: Kono Akihiro , Koike Naoki , Okuda Kenichi , Toshio Goto Toshio Goto
Published: February 2005

Silylene radicals (SiH2) in a 40-W 40-mTorr RF (13.56 MHz) SiH4/Ar plasma were detected by use of a laser-induced-fluorescence (LIF) technique. The observed SiH2 density increased with increasing Ar partial pressure. The absolute SiH2 density, estimated from the comparison of the LIF intensity with the intensity of Rayleigh scattering caused by N2 molecules, is in the range of 109-1010 cm-3.
Optical and Rheological Properties of Poly(3-alkylthiophene) Solution
Authors: Yoshino Katsumi , Morita Shigenori , Xiao Hong Yin Xiao Hong Yin , Tsuyoshi Kawai Tsuyoshi Kawai
Published: February 2005

Contrary to the case of the solution of poly(3-alkylthiophene) in chloroform, the solution of poly(3-alkylthiophene) in anisole exhibits anomalous voltage-dependent viscosity. That is, in the temperature range of 10-40°C, the viscosity increases with increasing applied voltage but that at temperature as high as about 60°C decreases with increasing applied voltage, with a tendency to saturation. The absorption spectrum of poly(3-alkylthiophene) in anisole also exhibits a redshift of about 70 nm above the critical temperature. These anomalies are discussed in terms of the change in conformation of poly(3-alkylthiophene) in solvents.
X-Ray Spectroscopic Studies of Photo-Structural Changes in Glassy Se100-xTex
Authors: Srivastava Sanjay Kumar , Agnihotri Arun Kumar , Kumar Ashok , Sanjay Swarup Sanjay Swarup , Amar Nath Nigam Amar Nath Nigam
Published: February 2005

Recently it has been reported that reversible and irreversible photo-structural changes occur in amorphous chalcogenide glasses. The present paper reports an X-ray spectroscopic study of Se100-x
Te
x
(x=5 to 30) alloys before and after the light exposure. The results indicate that no change in Se K-edge occurs upto x=5 at%. However, at higher concentration of Te (x>5 at%), Se K-edge shifts towards higher energy side with respect to Se K-edge in unexposed sample. A high energy shift of the K-absorption edge of Se in the present case may, therefore, be related to photocrystallization due to light exposure. The results also indicate that the photocrystallization is highly composition dependent in Se100-x
Te
x
glassy system.
Effect of Deuterium Anneal on SiO2/Si(100) Interface Traps and Electron Spin Resonance Signals of Ultrathin SiO2 Films
Authors: Fukuda Hisashi , Ueno Tomo , Kawarada Hiroshi , Ohdomari Iwao
Published: February 2005

Anneal kinetics of the SiO2/Si(100) interface defects of 5-nm-thick SiO2 films have been investigated through comparison of the electron spin resonance (ESR) center with the interface trap density D

i
t
. The ESR signal showed two distinct defects (so-called Pb0 and Pb1) at the SiO2/Si(100) interface: These Pb0 and Pb1 defects are annihilated by a low-temperature (500°C) deuterium (D2) anneal. By contrast, the D2 anneal at 900°C causes an increase in the number of the defects after a decrease at the initial stage (< 10 s). We conclude that there are annihilation and dissociation processes causing the Pb0 and Pb1 defects, dependent on the D2 anneal time and temperature.
Study of Ag Addition to YBa2Cu3O7-x Films Prepared using Electrophoretic Deposition
Authors: Fujimoto Manabu , Nojima Hideo , Shintaku Hidetaka , Taniguchi Hiroshi , Masaya Nagata Masaya Nagata , Masayoshi Koba Masayoshi Koba
Published: February 2005

Ag addition to YBa2Cu3O7-x
superconducting films prepared using electrophoretic deposition on Cu substrates was investigated. The electrical characteristics of the films, such as zero-resistance temperature (T
c), critical current density (J
c), and resistivity at room temperature (ρ) were greatly improved by Ag doping. The T
c of 94 K was attained with the electrophoretic Ag-doped film on Cu substrate. By doping with Ag, the grain growth was enhanced but no shift in YBa2Cu3O7-x
peaks was observed in X-ray diffraction patterns. From the electron probe microanalysis of the sample cross section, the doped Ag was found to exist in the region devoid of YBa2Cu3O7-x
grains.
Laser Emission from Dye-Doped Small Spheres by Ultraviolet N2 Laser Pumping
Authors: Taniguchi Hiroshi , Yamada Hiroshi , Fujiwara Tamiya , Tanosaki Shinji , Ito Hiroto , Morozumi Hidemi , Baba Mamoru
Published: February 2005

A small spherical dye laser containing rhodamine 6G pumped by a compact TEA UV-N2 laser is reported. Small spheres of good quality are observed under the microscope. The lasing characteristics of the spherical dye laser are different from the usual bulk dye laser, with respect to the direction of the laser beam. The former is oriented in all directions while the latter is unidirectional. The waveform and spectral characteristics from the dye-doped small spheres show lasing in the whispering-gallery modes.
Li-Doping Effect on Bi-Sr-Ca-Cu-O Superconductor Prepared by Arc Melting Method
Authors: Tetsuo Soumura Tetsuo Soumura , Kazuhisa Tsutsui Kazuhisa Tsutsui
Published: February 2005

Bi2Sr2Ca1(Cu1-x
-Li
x
)2O
y
superconductors were prepared by the arc melting method and were studied in relation to the Li-doping effect on the superconductivity. The partial substitution of Li for Cu is effective in lowering the formation temperature of the 2212-phase. A rise in the critical temperature from 81 K to 90 K was realized with the addition of Li. However, Li doping in excess causes deterioration in the superconductive quality due to the formation and growth of Li-Sr compounds. The optimum Li substitution ratio is from 10% to 20% for Cu, and the relevant annealing temperature is around 770°C.
Electroluminescence in ZnS1-xTex:CeF3 Thin-Film Devices Prepared in Oxygen Atmosphere
Authors: Sang Ho Sohn Sang Ho Sohn , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

The effects of oxygen codoping on ZnS1-x
Te
x
:CeF3 thin-film electro-luminescent devices are reported. ZnS1-x
Te
x
:CeF3 (x=0 and 1.25×10-3) films are prepared at substrate temperatures of 200°C and 300°C in vacuum and in oxygen remarkably. X-ray diffraction studies showed that the film orientation of the (111) plane and film uniformity are markedly improved when the films are prepared at 300°C in oxygen atmosphere. The emissive peak position and intensity of ZnS1-x
Te
x
:CeF3 devices change with substrate temperature and annealing, depending on the background atmosphere during film deposition. Oxygen codoping at a higher substrate temperature leads to an enhancement of luminance.