bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Properties of a Liquid Crystal Microlens with a Symmetric Electrode Structure
Authors: Nose Toshiaki , Shin Masuda Shin Masuda , Susumu Sato Susumu Sato
Published: February 2005

A disclination line or a shifting effect of the lens center had been observed in a homogeneously aligned or a hybrid-aligned liquid crystal microlens with an asymmetric electrode structure of a hole-patterned electrode and a plane electrode. These deteriorating factors of lens properties can be eliminated by a homogeneously aligned liquid crystal microlens with hole patterned electrodes on both substrates. The lens properties are exceedingly improved and the focused light intensity becomes several times stronger than those of hitherto prepared liquid crystal microlenses.
CaYAlO4: New Low-Loss Substrate Material for Epitaxial Growth of Superconducting Thin Films
Authors: Chai K. H. Young
Published: February 2005

A twin-free substrate material, CaYAlO4, was synthesized and used for the epitaxial growth of single crystal YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for the first time. The lattice parameters of ttus new substrate are a=b=3.648 Å and c=11.89 Å. The dielectric properties, similar to those of LaAlO3, are 20(dielectric constant) and 4×10-5 (loss tangent) at 5 GHz and 77 K. Initial attempts at film growth on this substrate indicate degradation of both superconducting and microwave properties possibly due to interdiffusion.
1.54 µm Electroluminescence by Electron Impact Excitation of Er Atoms Doped in InP
Authors: Isshiki Hideo , Kobayashi Hitoshi , Yugo Shigemi , Ikoma Tadamasa Kimura
Published: February 2005

The Er-related 1.54 µm electroluminescence (EL) was observed by impact exciting Er-atoms implanted into InP in the temperature range from 77 K to 360 K. The no shift in the peak wavelength was observed against temperature change. The emission intensity was a slowly decreasing function of temperature, and its room temperature value was still about half the 77 K value. The temperature dependence of the quantum efficiency of the EL emission was discussed in comparison with that of the PL emussion.
Deep Level Transient Spectroscopy Study of Staebler-Wronski Effect in a-Si:H
Authors: Miyanishi Atsushi , Nakata Jun-ichi , Imao Shozo , Shirafuji Junji , Uichi Kubo Uichi Kubo , Yoshio Inuishi Yoshio Inuishi
Published: February 2005

Both voltage- and photoinjected DLTS study of the Staebler-Wronski effect in a-Si:H using isothermal high-speed capacitance-time (C-t) measurements (10-3∼10 s) were done to elucidate the processes of defect creation and annealing. It was found that the densities of hole traps at E
v+0.6 eV and electron traps at E
c-0.4 eV were decreased by light soaking, accompanied by a simultaneous increase of electron traps at E
c-0.9 eV and hole traps at E
v+0.8 eV due to the dangling bonds. This fact suggests that the shallower traps may relate to the weak bonds, which convert to the metastable dangling bonds by light soaking.
Nitrogen-Ion Irradiation Effect on Ba2YCu3O7 Superconductor
Authors: Shiraishi Kensuke , Hiroshi Itoh Hiroshi Itoh , Yasushi Aoki Yasushi Aoki
Published: February 2005

Single-phased Ba2YCu3O7-y
pellets were sequentially irradiated with 200 keV nitrogen ions of 0.3-6.0×1013 m-2·s-1 in a dose rate up to a dose of 2×1016 m-2 at ambient temperature. Electrical resistance was measured as a function of temperature. The superconducting transition temperature, measured with current density greater than 25 kA·m-2 was increased by the ion irradiations. The optimum dose for the enhancement of the zero-resistance temperature was about 1×1014 m-2. The transition temperature, measured with 100 kA·m-2 in current density, was increased from 86.5-87.1 K to 90.9 K by the irradiation with a dose rate of 1.3×1013 m-2·s-1 to 8.4×1013 m-2.
High-Barrier Schottky Diodes on N-Type Si(100) Due to Hydrogen Plasma
Authors: Iwakuro Hiroaki , Toru Inoue Toru Inoue , Tsukasa Kuroda Tsukasa Kuroda
Published: February 2005

Electrical characteristics of Al/Si diodes exposed to hydrogen-containing plasmas have been measured. The Schottky barrier heights increase compared with that of a control diode. The Schottky barrier height increases consistently with an increase in an applied rf power or hydrogen concentration in the plasma. Furthermore, the Si surface exposed to argon or hydrogen plasma has been observed by X-ray photoelectron spectroscopy. It is concluded that exposure of the Si surface to hydrogen plasma produced a hydrogenated amorphous layer in the Si substrate. Therefore, the increase in the Schottky barrier height is attributed to the formation of the Schottky barrier at the interface between the Al metal and the hydrogenated amorphous layer.
Observation of the Surface Recombination Current with an Ideality Factor of Unity in AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Mochizuki Kazuhiro , Masuda Hiroshi , Kawata Masahiko , Katsuhiko Mitani Katsuhiko Mitani , Chuushiro Kusano Chuushiro Kusano
Published: February 2005

The surface recombination current with an ideality factor of unity was clearly observed in AlGaAs/GaAs abrupt heterojunction bipolar transistors (HBTs) with the uniform base structure. This was derived from the difference in the base current of HBTs with and without a surface passivation layer of depleted AlGaAs. It had a linear dependence on the emitter mesa perimeter and had no component with an ideality factor of two even at a low base-emitter bias. The results were explained by a simple analysis assuming a high surface recombination velocity.
Low Thermal Budget Poly-Si Thin Film Transistors on Glass
Authors: Gang Liu Gang Liu , S. J. Fonash S. J. Fonash
Published: February 2005

A new low thermal budget processing approach for polycrystalline silicon thin film transistors on 7059 glass is presented. This processing incorporates three unique steps: low temperature crystallization by broad beam tungsten halogen lamps of low temperature plasma enhanced chemical vapor deposited a-Si:H, the use of high quality gate oxide magnetron sputter deposited at 400°C, and extremely short time hydrogen passivation using an electron cyclotron resonance source. These TFT's, produced with this processing on glass, were found to have mobilities in the 60 cm2/V·s range. The subthreshold slope of these devices was in the 1 V/decade range, the threshold voltage was around 5 volts and the on/off current ratio was approximately 106.
Optical Nonlinearities of Al2O3 Glasses with CdS Microcrystallites
Authors: Kawaguchi Hitoshi , Miyakawa Takayuki , Tan-no Naohiro , Kobayashi Yoshio , Kurokawa Yoichi
Published: February 2005

Fabrication of Al2O3 glasses with CdS microcrystallites by means of the sol-gel method, as well as their linear and nonlinear optical characteristics, is reported for the first time. The shift in the wavelength of the absorption edge through a quantum size effect was clearly observed for the CdS-doped Al2O3 prepared by changing the annealing temperature. A large nonlinear absorption and refractive index were obtained because a high CdS microcrystallite concentration was achieved through the sol-gel method.
In0.53Ga0.47As/InP Multiquantum Well Lasers Grown by Metalorganic Molecular Beam Epitaxy (MOMBE)
Authors: Sugiura Hideo , Noguchi Yoshio , Iga Ryuzo , Takeshi Yamada Takeshi Yamada , Hiroshi Yasaka Hiroshi Yasaka
Published: February 2005

Double-channel planar buried-heterostructure lasers with a multi-quantum well active layer are fabricated by a combination of MOMBE and liquid-phase epitaxy. The lasers exhibit room temperature cw operation at a threshold current of 30 mA and emit at a wavelength of 1.57 µm. The threshold currents of 70% of the laser chips tested are in the range of 30-35 mA. An originally designed MOMBE system with a diffusion-pumped growth chamber is also described.
Influence of Metal Impurities on Leakage Current of Si N+P Diode
Authors: Miyazaki Morimasa , Sano Masakazu , Shigeo Sumita Shigeo Sumita , Nobukatsu Fujino Nobukatsu Fujino
Published: February 2005

Dependence of the leakage current of Si N+P diodes on the surface metal (Cu, Ni or Fe) concentration after quantitative contamination was investigated, and the causes of the leakage current were studied by SIMS, TEM and optical microscopy. Cu was gettered in the N+ area, forming many large dislocations in the N+ area and inducing some dislocations in the substrate near the junction; thus, the leakage current increased remarkably. Ni was gettered in the N+ area also, but did not form large dislocations, so the leakage current did not increase. Fe was not gettered easily, and hence the leakage current increased corresponding to the Fe concentration.
Universal Passivation Effect of (NH4)2Sx Treatment on the Surface of III-V Compound Semiconductors
Authors: Oigawa Haruhiro , Fan Jia-Fa , Nannichi Yasuo , Sugahara Hirohiko , Oshima Masaharu
Published: February 2005

The effectiveness of (NH4)2S
x
treatment on the (100) surface of GaP, (Al, Ga)As, InP and InAs was studied in comparison to that on GaAs by means of Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED). It was concluded that the existence of sulfur atoms bonded to semiconductors prevents the adsorption of oxygen. This phenomenon brings about the metal-dependent Schottky barrier fabricated on the (NH4)2S
x
-treated surfaces, implying the reduction in the interface state density. The structure and effect of the (NH4)2S
x
-treated surface of III-V compounds are qualitatively the same.
Tantalum Oxide Films Formed by UV Photo-CVD Using Ozone and TaCl5
Authors: Tanimoto Satoshi , Matsui Masahiro , Aoyagi Minoru , Kamisako Koichi , Koichi Kuroiwa Koichi Kuroiwa , Yasuo Tarui Yasuo Tarui
Published: February 2005

A new UV photo-CVD is developed to fabricate thin films of high-dielectric-constant Ta2O5. The significant features of the new photo-CVD are the UV 254 nm irradiation and the use of pure O3 as an oxidant source. The as-grown films obtained at a low deposition temperature of 300°C show very low leakage current and remarkably good step coverage. UV irradiation during CVD is essential to improve the resistivity and dielectric breakdown strength of the film. This CVD method and understanding of the related mechanism may be applicable to fabrication technology of future VLSI's.
Critical Current Characteristics in Superconducting Y-Ba-Cu-O Prepared by the Melt Process
Authors: Matsushita Teruo , Otabe Edmund Soji , Ni Baorong , Kimura Keiichi , Morita Mitsuru , Tanaka Masamoto , Kimura Masao , Miyamoto Katsuyoshi , Sawano Kiyoshi
Published: February 2005

Critical current densities in superconducting Y-Ba-Cu-O specimens with different sizes of 211 particles prepared by the melt process were measured under various magnetic fields and temperatures. Discussion is given on the flux pinning properties by 211 particles and background pinning centers. At temperatures above 60 K, 211 particles are expected to be dominant pinning centers. A rapid degradation of the critical current density with elevating temperature at low temperatures below 25 K seems to be attributed to weak links in specimens.
Effect of Y Substitution for the Ca Site in the 110 K Phase of (Bi, Pb)-Sr-Ca-Cu-O Superconductors
Authors: Furukawa Hiroshi , Enomoto Hiroyuki , Kishimoto Takeshi , Shin Jae Soo , Takano Yoshiki , Mori Natsuki , Hajime Ozaki Hajime Ozaki
Published: February 2005

The effect of the substitution of the trivalent Y ions for the divalent Ca ions has been studied in the 110 K phase of Bi1.84Pb0.34Sr1.91(Ca1-x
Y
x
)2.03Cu3.06O10+y
(x=0∼0.05). We found the solubility limit of Y to the 110 K phase around x=0.015. Within the solubility limit, the c-axis seemed to decrease with increasing x. In the region of the 110 K single phase, the critical temperature T
c gradually decreased with the increase of x, corresponding to the decrease of the carrier concentration.
The 124 Phase in Y-Ba-Cu-O Films Fabricated by Metalorganic Chemical Vapor Deposition
Authors: Hayashi Harumi , Yamada Yasuji , Sugawara Kazushi , Yuh Shiohara Yuh Shiohara , Shoji Tanaka Shoji Tanaka
Published: February 2005

Y-Ba-Cu-O superconducting films were fabricated on MgO substrates by metalorganic chemical vapor deposition (MOCVD). The experiments were performed at susceptor temperatures between 850°C and 750°C. Efforts were focused on the formation of films containing the so-called 124 superconductor, Y1Ba2Cu4O8. The 124 phase was confirmed by X-ray diffraction to be present in the films fabricated at susceptor temperatures below 800°C. Oxygen partial pressure was found to affect the appearance of the 124 phase.
Possible Evidence for Superconducting Phenomena in Langmuir-Blodgett Heterofilms Observed at Room Temperature
Authors: Taro Hino Taro Hino
Published: February 2005

Electrical conduction of Langmuir-Blodgett (LB) heterofilms consisting of arachidic acid (Y type, nearly nonpolar) and TCNQ-derivative (Z type, polar) LB double-layer film is investigated in the temperature region between room temperature and 30 K. The temperature dependence of the conductance and the I-V characteristics are closely similar to those associated with superconducting phenomena. These results present possible evidence of the superconducting state, and they can be explained if a two-dimensional potential well with an electron gas is assumed to be generated in the LB heterofilms by the electrostatic induction.
Two-Phase Drive Self-Scanning Light-Emitting Device (SLED) Using Coupling Diodes
Authors: Ohno Seiji , Kusuda Yukihisa , Komaba Nobuyuki , Kuroda Yasunao , Ken Yamashita Ken Yamashita , Shuhei Tanaka Shuhei Tanaka
Published: February 2005

The self-scanning light-emitting device (SLED) is expected to become a new key device for two-dimensional optical information processing, because the light-emitting ON-states of the SLED are automatically transferred by input clock pulses, and the optical pulses can start the transfer action from any elements. It will be important to decrease the number of transfer clock lines in order to realize the highly packed two-dimensional integrated SLED. Therefore, we propose the two-phase drive SLED using coupling diodes and demonstrate its operation. It has a wide operating margin as well as 10 MHz as the maximum transfer frequency.
An X-Ray Phase Plate Using Bragg-Case Diffraction
Authors: Hirano Keiichi , Izumi Koichi , Ishikawa Tetsuya , Annaka Shoichi , Seishi Kikuta Seishi Kikuta
Published: February 2005

An X-ray phase plate using two-beam Bragg case diffraction is proposed. The variation of the polarization state of the transmitted (forward-diffracted) beam through the incident angle was observed. Left-handed and right-handed circular polarizations whose degree of circular polarizations were ±0.90 were experimentally produced.
Oxidation Process of Hydrogen Terminated Silicon Surface Studied by Thermal Desorption Spectroscopy
Authors: Yabumoto Norikuni , Saito Kazuyuki , Morita Mizuho , Ohmi Tadahiro
Published: February 2005

The oxidation process of hydrogen terminated silicon surface is investigated by thermal desorption spectroscopy (TDS). Oxidation proceeds by two steps, at about 500°C and 800°C, by the desorption of hydrogen and the consumption of oxygen and water. Oxygen and water are consumed simultaneously, but water consumption does not change with oxygen supply. The oxidation process changes by the presence of the native oxide.
Atomic Layer Epitaxy of AlAs Using Dimethylaluminumhydride/Trimethylaluminum Mixture as the Al Source
Authors: Ishizaki Mamoru , Kano Nobuo , Junji Yoshino Junji Yoshino , Hiroshi Kukimoto Hiroshi Kukimoto
Published: February 2005

The growth of AlAs epitaxial layers was studied by using a mixture of dimethylaluminumhydride (DMAlH)/trimethylaluminum (TMAl) and arsine in a four step gas injection sequence which involves two steps of hydrogen purge separating DMAlH/TMAl and arsine at different pulse durations of the DMAlH/TMAl flow and at temperatures ranging from 250°C to 650°C. One- and two-monolayer self-limiting growths of AlAs were achieved depending on pulse duration of DMAlH/TMAl flow and growth temperature.
Textured ZnO Thin Films for Solar Cells Grown by Metalorganic Chemical Vapor Deposition
Authors: Wenas Wilson W. , Yamada Akira , Makoto Konagai Makoto Konagai , Kiyoshi Takahashi Kiyoshi Takahashi
Published: February 2005

Textured ZnO films have been grown by metalorganic chemical vapor deposition (MOCVD) using diethylzinc (DEZ) and H2O as reactant gases. It was found that the surface morphology of films was strongly dependent on the substrate temperature. For the low substrate temperature of 150°C, the surface consists of uniformly sized tetrapodlike features. These undoped films have a high transparency in a wide wavelength range from 400 nm to 1400 nm. The low-resistivity ZnO films have also been succesfully grown using a dopant gas of B2H6 diluted with H2. A sheet resistivity as low as 10 Ω/□ was obtained.
Photoluminescence from GaAs/CaF2/Si Structure Grown by Electron-Beam Exposure (EBE) and Epitaxy Method
Authors: Uchigoshi Masahiro , Kazuo Tsutsui Kazuo Tsutsui , Seijiro Furukawa Seijiro Furukawa
Published: February 2005

The GaAs layers grown on CaF2/Si(111) structures by the electron-beam exposure and epitaxy (EBE-epitaxy) method were studied by photoluminescence (PL) measurements at the temperatures ranging from 10 K to 300 K for the first time. It is shown that the EBE-epitaxy was effective to improve the PL intensity of the GaAs layer grown on CaF2/Si structure, and this structure has a high potential for optical device applications. Furthermore, the stress of the GaAs layer grown on CaF2/Si substrate is expected to be reduced by the CaF2 layer compared with that of GaAs/Si structure.
Reduction of Dislocation Density in GaAs on Si Substrate by Si Interlayer and Initial Si Buffer Layer
Authors: Hashimoto Akihiro , Sugiyama Naoharu , Masao Tamura Masao Tamura
Published: February 2005

Reduction of the dislocation density in GaAs on Si by the use of a Si interlayer and an initial Si buffer layer is reported. The Si interlayer of 2∼3 monolayers thick was inserted into the GaAs epitaxial layer on a Si substrate by low-temperature Si deposition. Molten KOH etching and cross-sectional transmission electron microscope (XTEM) observations showed a reduction of the dislocation density by 10-2∼10-3 times at the top surface by the Si interlayer insertion compared to that of conventional growth. An additional reduction of the dislocation density by the initial Si buffer layer grown at 680°C coupled with the interlayer was observed.
Low-Temperature Formation of the PtSi Layer by Codeposition of Pt and Si in a Molecular Beam Epitaxy System
Authors: Fujii Kunihiro , Kanaya Hiroyuki , Kumagai Yoshinao , Yamaka Fumio Hasegawa
Published: February 2005

Pt and Si were codeposited on Si(100) substrates to form polycrystalline PtSi layers in a molecular beam epitaxy (MBE) system. Properties of codeposited Pt silicide layers depended on the substrate temperature and the ratio of evaporated Pt and Si. The film codeposited at the substrate temperature of 200°C with the stoichiometric ratio (Pt/Si=1/1) had a similar crystallized grain structure (oriented to [110]) and the same resistivity (∼35 µΩ·cm) as those of the PtSi layer formed by the thermal reaction at 500°C. The film codeposited at a lower temperature (80°C, Pt/Si=1/1) or under a Si-rich condition (Pt/Si=3/4, 200°C) showed a smaller grain size and a higher resistivity.
Observation of Superconductivity in Nb2O5 Doped YBa2Cu3O7-δ Compound by Rapid Quenching
Authors: Paulose K. V. , J. Koshy J. Koshy , A. D. Damodaran A. D. Damodaran
Published: February 2005

Superconductivity in YBCO compound depends on its oxygen stoichiometry and to keep the oxygen stoichiometry at the desired level, slow cooling of samples in oxygen atmosphere was reported to be essential. In our present work it is found that the widely accepted procedure of slow cooling at a rate of 1°C/min or annealing at 600°C for several hours after high temperature sintering is not essential to obtain high temperature superconductivity if the YBCO samples are doped with small amount of Nb2O5. Superconductivity could still be obtained by directly quenching the doped specimen in oxygen from sintering temperature. Tetragonal to orthorhombic transformation takes place in seconds in doped samples indicates that the rate of absorption of oxygen has tremendously increased by the Nb2O5 addition.
Study of the Reaction of Ba2YCu3Oy with Air at Room Temperature
Authors: Ono Akira , Satoshi Takenouchi Satoshi Takenouchi , Yoshio Ishizawa Yoshio Ishizawa
Published: February 2005

The copper oxide Ba2YCu3O
y
(BYCO) reacted with moisture at room temperature when the compound with y=6.45-6.50 was annealed at low temperatures. Water molecules were considered to be incorporated into the vacant sites of BYCO. This reaction was strongly influenced by the synthesis temperature of BYCO, annealing temperature and oxygen numbers of annealed specimens. It is proposed that this reaction is responsible for the 2a superstructure of the annealed BYCO.
Phase Control of Superconducting Bi-Sr-Ca-Cu-O Thin Films Prepared by Laser Ablation Method
Authors: Egami Yoshihiro , Tabata Hitoshi , Kinugasa Masanori , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: February 2005

Three phases of Bi2Sr2Ca
n-1Cu
n
O2n+4 superconductors, i.e., Bi2Sr2Cu1O6(2201), Bi2Sr2Ca1Cu2O8(2212) and Bi2Sr2Ca2Cu3O10(2223), have been controlled by a laser ablation method. The 2201, 2212 and 2223 phases are selectively formed by controlling the substrate temperature, the starting composition of targets and the ambient pressure. The oxygen partial pressure plays an important role in these three parameters. Under a pressure higher than 6×10-2 Torr, the 2201 phase is dominantly formed in the wide range of substrate temperature and composition. Under a lower oxygen partial pressure (from 3×10-3 to 6×10-2 Torr), on the other hand, the control of the three phases, 2201, 2212 and 2223, is possible for as-deposited films only by changing the target compositions. For the 2212 thin film, Cu-rich samples show good superconducting behavior, while particles are observed on the film surface. The surface morphology of the thin film becomes better for the Cu-poor and Bi-rich samples.
Cross-Sectional Observation of Fe3O4-γFe2O3 Intermediate Thin Films
Authors: Sato Masaru , Tatsuru Namikawa Tatsuru Namikawa , Yohtaro Yamazaki Yohtaro Yamazaki
Published: February 2005

Fe3O4-γFe2O3 intermediate films were investigated in terms of the microstructures which appeared in the crosssections of the films. The samples were prepared at the oxidation stage where the coercivity of the films rapidly increased. It was found that, in the intermediate films, there were two layers parallel with the surface of the substrates. This structure is newly recognized in this system using a high-resolution transmission electron micro-scope. Furthermore, it was found that Fe3O4 and γFe2O3 phases coexist in the intermediate films, and that there was a considerable difference in the structure of grain boundaries between those two phases.
Assignment of New Facets Developing on {111} Surfaces of Vapor-Deposited Diamond Crystals
Authors: Keiji Hirabayashi Keiji Hirabayashi , Noriko Iwasaki Kurihara Noriko Iwasaki Kurihara
Published: February 2005

The morphology of diamond particles synthesized by hot-filament chemical vapor deposition have been studied for assignment of the new and flat surfaces developing on rough {111} surfaces of a cubo-octahedron with the increase of crystal size. The new surfaces are assigned to {100} according to the interplanar angle with {100} surfaces of a cubo-octahedron, its smoothness, and the maintenance of the original cubo-octahedron shape with the increase of size, which have been observed by a scanning electron microscope.
Transparency Improvement of Potassium Titanyl Phosphate (KTP) Crystals by Annealing under Oxygen Atmosphere
Authors: Terashima Kazutaka , Michiko Takena Michiko Takena , Masaru Kawachi Masaru Kawachi
Published: February 2005

We have studied the influence of iron impurity, and the effects of annealing on KTiOPO4 single crystals. It was found that in high-power second harmonic generation, the iron concentration should be minimized. Annealing at 800°C caused the optical absorption edge to shift 5-10 nm towards shorter wavelengths, and for undoped crystals, the optical transmittance was also increased. Annealing in atmospheres of increasing oxygen concentration increased the transparency. A high recovery capability against X-ray irradiation damage was also obtained after annealing. The measured full width at half-maximum of the X-ray diffraction (800) peak was apparently decreased in annealed crystals.
Kinetics of Metal Ion Liberation by Acid Treatment in Fatty Acid Salt Langmuir-Blodgett Films
Authors: Saito Mitsuyoshi , Ikegami Keiichi , Tabe Yuka , Saito Kazuhiro , Shin-ichi Kuroda Shin-ichi Kuroda , Michio Sugi Michio Sugi
Published: February 2005

The liberation process of metal ions in fatty acid salt LB films soaked in a dilute hydrochloric acid has been studied using X-ray diffraction and IR measurements. The reaction kinetics was found to be described as a pseudomonomolecular reaction. It is suggested that the metal ions, after being liberated from the carboxylate sites, are removed from the film system into the solution.
Simple Model for Gate-Voltage Dependent Parasitic Resistancein Short Channel Lightly Doped Drain Metal Oxide Semiconductor Field Effect Transistors
Authors: Lee Jung-Il , Lee Myung-Bok , Lee Sang Young , Yoon Kwang Nham Kang
Published: February 2005

The parasitic resistance of the lightly doped drain (LDD) is modeled as parallel combination of the resistance of an accumulation layer formed at the surface of the LDD, and that of the bulk LDD. In saturation regime, velocity saturation in both the channel and the LDD is taken into account and the resulting resistance shows a quasi-linear behavior with respect to the gate voltage.
Dislocation Generation of III-V Semiconductors by the Biaxial Stress in GaAs/SiO2, InP/SiO2 and III-V/Si Structure
Authors: Masami Tachikawa Masami Tachikawa , Hidefumi Mori Hidefumi Mori
Published: February 2005

Dislocation generation of III-V compound semiconductor crystals caused by the biaxial stress in SiO2 film on GaAs and InP wafers has been observed. The biaxial stress of around 108 dyn/cm2 generates dislocations of around 107 cm-2 above 450°C, which is the ordinary thin-film crystal growth temperature. The temperature dependence of critical stress for dislocation formation agreed with that reported for the upper yield stress of bulk III-V crystals. This shows that dislocation generation of III-V semiconductors basically occurs when the biaxial stress exceeds the upper yield stress of the materials. Comparing this experiment and the III-V/Si heteroepitaxy structure, it is suggested that the dislocation generation of III-V/Si in the cooling stage is also caused by thermal mismatch. Great thermal mismatches of GaAs and Si materials produce thermal stress sufficient for dislocation generation.
Growth and Optical Properties of Novel Wide-Band-Gap Strained-Layer Single Quantum Wells: Zn1-yCdySe/ZnSxSe1-x
Authors: Wu Yi-hong , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

We report the growth and optical properties of a new strained-layer wide-band-gap single-quantum well (SQW): Zn1-y
Cd
y
Se/ZnS
x
Se1-x
. A SQW structure with four ZnCdSe wells of 1, 4, 8 and 12 monolayers (ML5) was grown on a GaAs substrate by metalorganic molecular beam epitaxy (MOMBE). The corresponding full widths at half-maximum (FWHMs) of 4.2 K photoluminescence peaks are 15.8, 18.2, 18.4 and 15.0 meV, respectively. These values are considerably small in spite of the high strain in well layers (about 2%), which are attributed to the well-defined structures of the SQW as confirmed by reflection high-energy electron diffraction (RHEED) in situ observation.
Electrical Characteristics and Reliability of Pt/Ti/Pt/Au Ohmic Contacts to p-Type GaAs
Authors: Okada Hiroyuki , Shin-ichi Shikata Shin-ichi Shikata , Hideki Hayashi Hideki Hayashi
Published: February 2005

The ohmic contacts to p-type GaAs formed by GaAs/Pt/Ti/Pt/Au systems were investigated. The specific contact resistance below 8×10-7 Ω·cm2 was achieved when the interface Pt between GaAs and Ti/Pt/Au was thicker than 50 Å, which is about one-fourth of the conventional Ti/Pt/Au contact. The activation energies of the initial degradation of the Pt/Ti/Pt/Au electrodes correspond to the reaction of GaAs and Pt to form PtAs2. However, even after the initial degradation, Pt/Ti/Pt/Au with the thin Pt interface layer still shows lower contact resistivity. These systems are promising for practical p-tye ohmic contacts for AlGaAs/GaAs heterojunction bipolar transistors.
Applications of Transition-Emitter Superlattice to Bipolar Transistors
Authors: Wen-Chau Liu Wen-Chau Liu , Wen-Shiung Lour Wen-Shiung Lour
Published: February 2005

A novel bipolar transistor with a superlatticed transition emitter has been fabricated and demonstrated at room temperature. The use of the i-Al0.5Ga0.5As/n+-GaAs superlattice allows electrons to transport and prevents holes from injecting, which improves the emitter injection efficiency. Since the AlGaAs layers in the superlattice are undoped, the problems of DX centers and persistent photoconductivity (PPC) effect can be reduced signficantly. Furthermore, from the experimental results, the potential spike at the emitter-base interface is so small that it can be neglected. An extremely small collector offset voltage of 55 mV and the common-emitter current gain of about 65 have been simultaneously obtained at room temperature in the nonoptimized device. Consequently, the proposed device indeed exhibits good potential for digital circuit applications.
Negative-Differential-Resistance (NDR) Superlattice-Emitter Transistor
Authors: Wen-Shiung Lour Wen-Shiung Lour , Wen-Chau Liu Wen-Chau Liu
Published: February 2005

A novel AlGaAs/GaAs superlattice-emitter transistor (SET) has been fabricated and investigated at low temperature. The proposed SET device exhibits significant double negative-differential-resistance (NDR) behavior with a high peak-to-valley current ratio due to tunneling through the ground band and the first excited band in the superlattice. In the transistor operation, a common-emitter current gain of over 60 and a collector offset voltage smaller than 0.2 V at 77 K have been obtained. Due to its excellent properties, especially when using GaAs-based material, the proposed SET can be used as a functional device which provides good potential for frequency multipliers and multiple-valued logic circuit applications.
DC Superconducting Quantum Interference Device of YBa2Cu3O7-x Step-Edge Junctions
Authors: Yoshii Mitsuyoshi , Kita Jun-ichi , Osamu Nakatsu Osamu Nakatsu , Yasuharu Yamada Yasuharu Yamada
Published: February 2005

DC superconducting quantum interference devices (DC-SQUIDs) are made of YBa2Cu3O7-x
(YBCO) thin films by conventional photolithography and argon ion milling. The YBCO thin films are prepared on magnesia substrates with step edges by the rf magnetron sputtering method. The step-edge junctions for the SQUIDs exhibit clear DC and AC Josephson effects. The SQUIDs respond well to change of magnetic flux and have a white flux noise at 51.4 K of 8.1×10-5 Φ0/Hz1/2 at 1 Hz, 5.8×10-5 Φ0/Hz1/2 at 10 Hz and a noise increase at a low-frequency range of less than 10 Hz.
4×4 Surface-Emitting 1.55 µm InGaAsP/InP Laser Arrays with Microcoated Reflectors Fabricated by Reactive Ion Etching
Authors: Hideho Saito Hideho Saito , Yasuhiro Kondo Yasuhiro Kondo
Published: February 2005

4×4 surface-emitting 1.55 µm InGaAsP/InP laser arrays with microcoated reflectors are fabricated. These surface-emitting laser arrays can be operated in the CW condition at 20°C and driven independently. The average CW threshold current of these lasers is about 55 mA and the average maximum output power is about 4 mW at 20°C. Using this 4×4 surface-emitting laser array, simple letters can be rendered by brightened dots. The laser wafer has a buried-heterostructure (BH) fabricated by all MOCVD (Metal Organic Vapor Deposition) and dry etching. The etched vertical laser facets and the inclined reflectors are fabricated simultaneously by inclined RIE using Cl2 gas, a TiO2 mask, and a 50 degree stainless steel sample holder. A microcoating process for the inclined reflectors and the back laser facets that achieves high reflectivity has also been developed.
Auger Electron Spectroscopy Study on the Stability of the Interface between Deposited Cu9Al4 Intermetallic Compound Film and Si
Authors: Noya Atsushi , Sasaki Katsutaka , Shirou Ohtaka Shirou Ohtaka , Nobuyuki Sasao Nobuyuki Sasao
Published: February 2005

The interaction of deposited Cu9Al4 intermetallic compound film with a silicon substrate is studied by Auger electron spectroscopy. Although the incorporation of silicon into the Cu9Al4 film with low concentration level is observed, the interface is stable up to the annealing temperature of 700°C without forming aluminum spikes or a copper silicide layer. It is revealed that Cu9Al4 film is a useful material to realize a stable interface when employed as a metallization material for silicon devices.
Investigation of A3B5-Crystal Polar Face Structure
Authors: Chaplanov Victor , Galkin Igor , Aleksey Nefedov Aleksey Nefedov , Sergey Yakimov Sergey Yakimov
Published: February 2005

The X-ray diffraction investigation of A3B5 single crystals with a natural oxide film at their surface was carried out in an angular region sufficiently large to achieve spatial resolution of the order of several spacings. A model of the structure distortion has been proposed. The model parameter values, i.e., the distorted layer thickness L and the mean contraction Δd/d of the interplanar distance in this layer, have been presented. One can note that the specimens have a perfect crystal-oxide interface after the standard surface treatment technique. Its thickness is of the order of 1 nm.
An Atomic Model of Electron-Irradiation-Induced Defects on {113} in Si
Authors: Seiji Takeda Seiji Takeda
Published: February 2005

An atomic model of defects on {113} in Si has been derived experimentally from high-resolution electron micrographs. A simulated image of the proposed model agrees well with experiment. The model is constructed by two kinds of structural units. One is incorporated by self interstitial atoms to form tiny rods of the hexagonal Si. The atomic arrangement of this unit was proposed by Bourret (1987) and Tan et al. (1981). Another structural unit is characterized by eight-membered-atom rings. These two kinds of the units are arranged on a {113} plane without any dangling bond and any kink of a defect plane.
Compositional Latching in GaAs1-xPx/GaAs Metalorganic Vapor Phase Epitaxy
Authors: Miura Yoshinao , Onabe Kentaro , Zhang Xiong , Nitta Yoshiki , Fukatsu Susumu , Shiraki Yasuhiro , Ito Ryoichi
Published: February 2005

MOVPE growth studies of GaAs1-x
P
x
(x=0.05-0.40) on GaAs substrates, combined with X-ray diffraction analysis and secondary-ion mass spectroscopy, have demonstrated a “compositional latching” effect in thin layer growth, where the incorporation of P from vapor to solid is suppressed due to lattice strain on the growing surface. A tentative growth model based on strain-dependent incorporation probabilities for P and As has been proposed. The grown surface feature is strongly dependent on the degree of relaxation of the lattice strain.
ESR in Low-Tc Bi-(Pb)-Sr-Ca-Cu-O Single Crystal at Room Temperature
Authors: Shiozaki Hiroko Maruyama
Published: February 2005

ESR in the low-T
c superconductor phase of Bi-(Pb)-Sr-Ca-Cu-O single crystal at room temperature was measured, and clear uniaxial anisotropy was observed with g
// of 2.265 and g
⊥ of 2.066. A hyperfine structure was also seen in the spectra, and its dependence on the magnetic field orientation gave the maximum value of A
⊥ at <110>. Signals have been expected to come from Cu2+ ions in CuO2 planes.
High-Frequency Transmission through Bi-Sr-Ca-Cu-O Double-Sided Microstripline on an MgO Substrate
Authors: Tanaka Atsushi , Jason Crain Jason Crain , Koichi Niwa Koichi Niwa
Published: February 2005

Microstriplines having both a Bi-Sr-Ca-Cu-O line and groundplane have been reproducibly fabricated on MgO substrates by RF magnetron sputtering. The samples, characterized by X-ray diffraction (XRD) and DC resistivity measurements, were found to be highly oriented, nearly single 110 K phase material. Their microwave transmission properties have been investigated at frequencies up to 20 GHz and the high-frequency loss of the superconducting microstrips were compared with that observed for geometrically equivalent gold lines at room temperature and 77 K. It is found that the transmission loss in these samples at 77 K is less than that of the gold microstrips for frequencies below approximately 2 GHz.
Flux Density Distribution in YBa2Cu3Ox Thin Films Determined by Use of the Faraday Effect in Iron Garnet Films
Authors: Yokoyama Yuko , Hasumi Yuichi , Obara Haruhiko , Suzuki Yoshishige , Katayama Toshikazu , Gotoh Satoshi , Koshizuka Naoki
Published: February 2005

The flux penetration and trapping behavior in superconducting YBa2Cu3O
X
films have been observed quantitatively by means of the magnetooptical Faraday effect in iron garnet films with perpendicular magnetization. The mazelike domain pattern of the iron garnet film placed on the superconducting film is affected by the flux in the superconducting film and is observed using a polarizing microscope. Bi- and Ga-substituted YIG films grown by the liquid-phase epitaxy (LPE) method provide suitable characteristics at low temperature for this technique. Flux density profiles are obtained quantitatively for the disk-shaped YBa2Cu3O
X
film. The critical current density is also determined from the profiles.
YBa2Cu3O7-x Thin Film Prepared by Laser Ablation
Authors: Nagaishi Tatsuoki , Itozaki Hideo , Tanaka Saburo , Matsuura Takashi , Ota Nobuhiro , Naoji Fujimori Naoji Fujimori , Shuji Yazu Shuji Yazu
Published: February 2005

High critical current density YBa2Cu3O7-x
thin films on (100)SrTiO3 were successfully prepared by laser ablation. The zero resistance transition temperature (T
c(R=0)) was 90.5 K and the critical current density (J
c) at 77.3 K was 8.0×106 A/cm2 under a zero magnetic field. J
c degraded to 1.7×104 A/cm2 in a magnetic field of 8 T parallel to the c-axis of the film, and to 4.0×105 A/cm2 in a magnetic field of 8 T perpendicular to the c-axis of the film. The characteristics of the film, mis-oriented crystallites and stacking faults, were revealed by transmission electron microscopy (TEM).
Microscopic Study on (11n)-Oriented BiSrCaCuO Films by Cross-Sectional Transmission Electron Microscopy
Authors: Wada Osamu , Tanimura Junji , Kuroda Ken'ichi , Kataoka Masayuki , Kojima Kazuyoshi , Hamanaka Koichi , Tetsuo Ogama Tetsuo Ogama
Published: February 2005

Microstructures of superconducting BiSrCaCuO films with (11n) orientation grown on SrTiO3(110) substrates by sputtering were first observed by cross-sectional transmission electron microscopy (TEM). Two kinds of films, which have 2212 and 2223 compositions, were studied here. Both films have two preferred orientations with the c-axes almost parallel to the [100] and [010] directions of the SrTiO3 substrate. High-resolution TEM observation of 2223-composition film showed that there is a transient region consisting of a few atomic layers at the interface.
The Form Change of Metal Thin Film as Measured by the Refracted X-Ray Fluorescence (RXF) Method
Authors: Yuji C. Sasaki Yuji C. Sasaki
Published: February 2005

The refracted X-ray fluorescence (RXF) method can measure the form change of evaporated Mn thin film. The Mn thin film was changed from rough island thin film to flat island thin film by evaporated Au atoms. In this letter, we report that the RXF method is effective as a method of studying surfaces and interfaces.
Temperature Dependences of 13C-NMR Spectra and Conductivities with Metal-Free Phthalocyanines Dispersed in Bisphenol-A-Polycarbonate
Authors: Hirohashi Toshio Enokida
Published: February 2005

Temperature dependences of conductivities of the thin films with α-, β-, τ- and X-forms metal-free phthalocyanines (H2Pcs) dispersed in bisphenol-A-polycarbonate and solid-state cross-polarization magic-angle-spinning (CP/MAS) 13C-NMR of H2Pcs were measured. The activation energies at higher (T>300 K) and lower (T<200 K) temperature region could be calculated in the range of 140 and 373 K. 13C-NMR spectra of the H2Pcs indicated the apparent differences, furthermore, individual spectra were changed at the function of temperature due to the influences by the N-H tautomerism in the H2Pc molecules.
Large-Area Doping for Poly-Si Thin Film Transistors Using Bucket Ion Source with an RF Plasma Cathode
Authors: Kawachi Genshiro , Aoyama Takashi , Suzuki Takaya , Ohno Yasunori , Mimura Akio , Mochizuki Yasuhiro
Published: February 2005

In order to realize stable processing of large-area ion doping, a filament-less bucket ion source with an rf plasma cathode (RFC) was studied and applied to the fabrication of poly crystalline Si thin film transistors (poly-Si TFTs). By using Ar as a discharge gas, the RFC can be utilized for the bucket ion source instead of a hot filament cathode (HFC). The throughput, uniformity of the sheet resistance and the characteristics of the fabricated TFTs were equivalent to those of a hot filament cathode type ion source. This technique seems applicable to the doping process of poly-Si TFTs.
Modeling of Mechanism of Leakage in a Shallow p+/n Junction Formed by Preamorphization
Authors: Tanaka Akira , Tetsuo Yamaji Tetsuo Yamaji , Satoshi Nishikawa Satoshi Nishikawa
Published: February 2005

A model of the leakage induced by preamorphization is developed, assuming that the depth profile of excess interstitials making up dislocation loops is equal to the profile before annealing and that it is approximated by Gaussian distribution. It has been confirmed that this model well reproduces experimental data. Furthermore, Ge+ preamorphization was compared with Si+ in detail. An advantage of Ge+ preamorphization over Si+ has been confirmed in a wider range of conditions than in our previous report. A 0.08-µm-deep p+/n junction whose leakage current is less than 1×10-8A/cm2 is fabricated with a 40-nm-thick amorphous layer formed by Ge+ implantation.
Organometallic Vapor-Phase Epitaxial Growth and Characterization of GaAs/Zn(S, Se) Multilayered Structures
Authors: Fujita Shigeo , Murawala Prakash A. , Maruo Seiji , Tsuji Osamu , Fujita Shizuo
Published: February 2005

We report growth conditions of lattice-matched dissimilar semiconductor multilayered structures of GaAs/Zn(S, Se) systems by organometallic vapor-phase epitaxy (OMVPE). Since the optimum growth temperature for GaAs is much higher than that of Zn(S, Se), we performed low-temperature growth (470°C) of GaAs by photo-assisted OMVPE. A smooth growth surface of GaAs on Zn(S, Se) was achieved by lattice-matching, sufficient preflow of triethylarsenic (TEAs) and a Zn-stabilized surface before starting the growth of GaAs; hence we succeeded in the fabrication of a ZnSSe/GaAs/ZnSSe double hetero (DH) structure and a superlattice. Thermal annealing of the DH structure showed no appreciable Zn diffusion into GaAs up to 650°C but showed thermal stability at the interface up to 550°C.
In Situ Ultraviolet Laser Treatment during Plasma Deposition for the Improvement of Film Qualities in Hydrogenated Amorphous Silicon
Authors: Suzuki Atsushi , Toyoshima Yasutake , Peter J. Mcelheny Peter J. Mcelheny , Akihisa Matsuda Akihisa Matsuda
Published: February 2005

Hydrogenated amorphous silicon (a-Si:H) films were prepared with ultraviolet laser irradiation to modify the growing surface during the plasma-enhanced chemical vapor deposition. Using this treatment, the photoconductivity was improved by three to four orders of magnitude in films deposited at substrate temperatures below 100°C. Additionally, the optical band gap remained unchanged with the in-situ laser treatment. Consequently, high quality a-Si:H films, characterized by high photoconductivity and wide optical gap, were obtained at low substrate temperatures.
Low-Temperature Annealing Effect on Bi-Sr-Ca-Cu-O Thin Films Prepared by Layer-by-Layer Deposition
Authors: Tsukamoto Akira , Imagawa Kazushige , Hiratani Masahiko , Keiichi Kanehori Keiichi Kanehori , Kazumasa Takagi Kazumasa Takagi
Published: February 2005

Thin films of Bi-Sr-Ca-Cu-O superconductors are prepared by layer-by-layer deposition using automatically controlled shutters. The films are deposited by microwave-discharged plasma assisted reactive evaporation. The thin films of the 2201 phase, 2212 phase, and 2223 phase are obtained in accordance with respective shuttering sequences. As-grown films do not show superconductivity, because of excess oxygen content. Superconducting thin films of the 2212 phase with zero resistance at 40 K are obtained by low-temperature annealing at 550°C in an oxygen partial pressure of 0.1 atm.
Carbon K-Shell X-Ray Absorption Near-Edge Structure of Solid C60
Authors: Shinohara Hisanori , Sato Hiroyasu , Saito Yahachi , Tohji Kazuyuki , Udagawa Yasuo
Published: February 2005

Absorption measurements above the carbon K-edge of solid C60 have been reported for the first time, which utilize 100-1,000 eV synchrotron radiation. The C60 cluster contains a significant fraction of sp2 hybridized carbon bonds as revealed by the presence of a prominent π* resonance in the XANES (X-ray Absorption Near-Edge Structure) spectrum. The π* band in C60 is characterized by the two humps at 285 and 288 eV, suggesting the presence of a “cage-strained” π-bond network. Furthermore, the band width and the spectral feature of the σ* resonance imply that the long-range order is less distinct than in graphite or diamond.
Synthesis of Amorphous Powders of Ni-Si and Co-Si Alloys by Mechanical Alloying
Authors: Miura Keisuke Omuro
Published: February 2005

Amorphous powders of the Ni-Si and Co-Si alloys are synthesized by mechanical alloying (MA) from crystalline elemental powders using a high energy ball mill. The alloying and amorphization process is examined by X-ray diffraction, differential scanning calorimetry (DSC), and scanning electron microscopy. For the Ni-Si alloy, it is confirmed that the crystallization temperature of the MA powder, measured by DSC, is in good agreement with that of the powder sample prepared by mechanical grinding from the cast alloy ingot products of the same composition.
Correlations between Self-Interstitials and Vacancies during Thermal Oxidation in Silicon
Authors: Takahisa Okino Takahisa Okino
Published: February 2005

It is generally accepted that there are four relations between self-interstitials and vacancies during thermal oxidation in silicon; local equilibrium between self-interstitials and vacancies, oxidation-enhanced and -retarded diffusions (OED and ORD) and oxidation stacking faults (OSF). From a mathematical point of view on these relations, a method for their analysis was established. The results of this study clearly indicate some OED, ORD and OSF to be governed by only an interstitialcy or vacancy mechanism. A method for obtaining analytical solutions is also discussed.
Room-Temperature Observation of Excitonic Absorption in GaxIn1-xAs/InP (0.2≤x≤0.47) Quantum Wells Grown by Chemical Beam Epitaxy
Authors: Yokouchi Noriyuki , Uchida Toshikazu , Uchida Takashi , Miyamoto Tomoyuki , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

Ga
x
In1-x
As/InP (0.2≤x≤0.47) lattice-matched and strained quantum wells having 10 wells were grown by chemical beam epitaxy (CBE). The absorption properties were investigated and excitonic absorption peaks were clearly observed at room temperature. The wavelengths of excitonic peaks were in good agreement with a theoretical estimation obtained by using effective mass approximation including heavy and light hole energy split at the Γ point.