bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid Solution Range of Boron, Microhardness and Magnetic Properties of the Perovskite-Type GdRh3B Obtained by Arc-melting Synthesis
Authors: Shishido Toetsu , Yamauchi Hiroshi , Kudou Kunio , Okada Shigeru , Ye Jinhua , Yoshikawa Akira , Horiuchi Hiroyuki , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Polycrystalline samples of GdRh3B

x

were synthesized using the arc-melting method. A compound of GdRh3B

x

has a perovskite-type cubic structure (space group: Pm3m) in which the concentration of boron is distributed between x=1.000 (20 at%B) and 0.444 (10 at%B) for GdRh3B

x

. The lattice parameter a of GdRh3B

x

depends on x and varies linearly from a=0.41831(6) nm (x=1.000) to 0.4121(1) nm (x=0.444). The micro-Vickers hardness of GdRh3B

x

increases with increasing B content in the range of x=0.444∼1.000, and hardness of the GdRh3B0.444 and GdRh3B1.000 is 3.4 (±0.12) and 6.8 (±0.08) GPa, respectively. The stoichiometric compound GdRh3B has a ferromagnetic property with the Curie temperature of 14 K.
X-ray Photoelectron Study on the Adsorption of Anhydrous Hydrogen Fluoride onto Silicon Native Oxide
Authors: Yoji Saito Yoji Saito , Yutaka Nakazawa Yutaka Nakazawa
Published: October 2002

The adsorption of anhydrous hydrogen fluoride (AHF) on the surfaces of silicon native oxide was investigated by in situ X-ray photoelectron spectroscopy (XPS) in order to understand the reaction between HF and the oxide films at room temperature. A significant amount of the component is located at 670.0 eV binding energy in the observed XPS spectra, and is most likely derived from HF molecules. Moreover, the surface density of F-Si bonds slowly increases with the AHF exposure. We also attempted to accelerate the etching of the native oxide without moisture, supplying the AHF gas with remote-plasma-excited Ar, and obtained the enhanced etch rate.
Crystal Structure of CuIn3Se5 Semiconductor Studied Using Electron and X-ray Diffractions
Authors: Hanada Takeshi , Yamana Azusa , Nakamura Yoshio , Wada Osamu Nittono
Published: October 2002

The crystal structure of CuIn3Se5 is investigated by complementary use of electron and X-ray diffractions. The lattice parameters are a=5.7539(3) and c=11.519(1) Å and the space group is uniquely determined to be I42m. The crystal is not constructed of a rigid unit cell but by three kinds of local Se tetrahedrons, such as CuIn2Se4, CuIn3Se4 and In3Se4, which minimize the numbers of electron excess and deficient bonds. The average unit cell is represented by Cu0.8In0.4In2Se4, where Se and some In atoms fully occupy the 8i site with x≈1/4 and z≈1/8, and the 4d site, respectively, and Cu and the remaining In atoms partially occupy 2a and 2b sites, respectively. Since the space group I42m is not a subgroup of I42d which is the space group of CuInSe2, CuIn3Se5 is not related to CuInSe2 from the viewpoint of crystal symmetry. It is neither a vacancy ordered compound nor of a defect chalcopyrite structure.
Rotation of a Single-Phase Ultrasonic Quartz Motor by means of Contour Vibrations and Change of Rotational Directions via Frequency Changes
Authors: Takashi Aoki Takashi Aoki , Michiharu Horiuchi Michiharu Horiuchi
Published: October 2002

Rotational characteristics of an ultrasonic motor composed of a quartz rectangular parallelepiped cut perpendicular to the X, Y and Z axes were examined. Quartz crystals used in the previous studies rotated only when they were resonating electrically at fundamental resonant frequencies f
X1 corresponding to the X-axis thickness vibrations, and at satellite vibration frequencies f
S close to f
X1. It was found that the crystals presented in this paper can rotate not only at f
X (=f
X1 and f
S), but also at frequencies f
L related to the lengths of the directions of the Y and Z axes, and that the rotational directions can be changed by changing the vibration frequencies among f
X and f
L.
Preferred Orientation in Ti Films Sputter-Deposited on SiO2 Glass: The Role of Water Chemisorption on the Substrate
Authors: Ohwaki Takeshi , Yoshida Tomoyuki , Hashimoto Shoji , Hosokawa Hideki , Yasuichi Mitsushima Yasuichi Mitsushima , Yasunori Taga Yasunori Taga
Published: October 2002

Ti thin films have been grown on SiO2 glass layers at 350°C by ultrahigh vacuum magnetron sputtering with a small amount of H2O, H2 or O2 gas introduction to investigate the influence of adsorption on the crystallographic orientation of the Ti films. In situ reflection high-energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD) studies showed that a water vapor introduction at the beginning of sputter deposition promotes a highly preferred (002) orientation, whereas H2 gas or O2 gas introduction does not affect the orientation. These results indicate that the increase of water chemisorption on the substrate by H2O gas introduction and reduction of the surface free energy enhance the self-assembly of the Ti atoms toward the most stable C-axis orientation.
Superconductivity in (110) PrBa2Cu3O7-δ Thin Films Pseudomorphically Grown on (110) YBa2Cu3O7-δ Single Crystal Substrates
Authors: Usagawa Toshiyuki , Ishimaru Yoshihiro , Wen Jianguo , Utagawa Tadashi , Satoshi Koyama Satoshi Koyama , Youichi Enomoto Youichi Enomoto
Published: October 2002

We report on superconductivity in (110) oriented PrBa2Cu3O7-δ films pseudomorphically grown on (110) YBa2Cu3O7-δ (YBCO) single crystal substrates. The vertical 4-probe measurements for (110) PrBa2Cu3O7-δ/ YBa2Cu3O7-δ bilayers show clearly two superconducting transition steps associated with two different T
c's of 92.0 K of YBa2Cu3O7-δ , 89.9 K for 30 nm thick PrBa2Cu3O7-δ and 75.5 K for 220 nm thick PrBa2Cu3O7-δ. The non-substitutional “regular” Pr1+
x

Ba2-
x

Cu3O7-δ (x=0.0) without any interchange between Pr atoms and Ba atoms will show superconductivity by the same mechanism with other YBCO families.
Sensing Molecular Density of Monolayers from Fluoroalkyltrichlorosilane Using Atomic Force Microscope Having a Tip Modified with Fluoroalkyltrichlorosilane Molecules
Authors: Tohru Nakagawa Tohru Nakagawa
Published: October 2002

Force curves were measured on monolayers from fluoroalkyltrichlorosilane on silicon substrates using the atomic force microscope (AFM) having a tip which was chemically modified with fluoroalkyltrichlorosilane molecules. Adhesive force arose between the monolayers and the chemically modified AFM tip, and it increased with an increase in the amount of coverage of the monolayers. In contrast, the adhesive force exerted on the unmodified AFM tip was independent of the amount of coverage of the monolayers. These results indicate the AFM with a chemically modified tip can detect the molecular density of the monolayers.
Nucleation Control in the Growth of Bulk GaN by Sublimation Method
Authors: Satoshi Kurai Satoshi Kurai , Katsushi Nishino Katsushi Nishino , Shiro Sakai Shiro Sakai
Published: October 2002

Nucleation of GaN crystallites by sublimation method on sapphire (0001), scratched sapphire (0001), SiO2, Si (111), and metalorganic chemical vapor deposition(MOCVD)-GaN/sapphire (0001) was investigated. The density of the nuclei on SiO2 and Si (111) was estimated to be 6 × 103/cm2. On the other hand, a continuous film rather than discrete crystallites was obtained on both the MOCVD-GaN and the scratched sapphire. Growth nucleation control was performed by partly covering the MOCVD-GaN or scratched sapphire (0001) with SiO2. As a result, hexagonal columns about 200 µm in diameter and 200 µm high were selectively and uniformly grown at the window sites. The diameter of each hexagonal column was much larger than the width of each window. This method can be used for device processing utilizing the crystallites.
Growth and Crystallinity of Ferroelectric BaMgF4 Films on (111)-Oriented Pt Films
Authors: Aizawa Koji , Moriwaki Masashi , Ichiki Tatsuya , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Growth of well (111)-oriented Pt films on SiO2/Si(100) substrates and the crystallinity of BaMgF4 films grown on the Pt(111)/SiO2/Si(100) substrates have been investigated. It was found by X-ray diffraction analysis that well (111)-oriented Pt films with a best full-width at half maximum (FWHM) of 0.92° were grown by the radio frequency (RF) magnetron sputtering method. It was also found that (120)-oriented BaMgF4 films were grown on Pt(111)/SiO2/Si(100) substrates at temperatures of about 550°C and that the crystallinity of these BaMgF4 films improved as the FWHM of the Pt(111) diffraction peak decreased. The best FWHM obtained for a Ba MgF4 film grown on a Pt(111)/SiO2/Si(100) substrate was 0.97°, and crystallites in the BaMgF4 films grown on Pt(111)/SiO2/Si(100) substrates were larger (about 0.4 µm2) than those in the BaMgF4 films grown on Si(111) substrates.
Crystal Growth and Optical Characterization of Rare-Earth (Re) Calcium Oxyborate ReCa 4O(BO 3) 3 (Re = Y or Gd) as New Nonlinear Optical Material
Authors: Makoto Iwai Makoto Iwai , Taisuke Kobayashi Taisuke Kobayashi , Hiroyuki Furuya Hiroyuki Furuya , Yusuke Mori Yusuke Mori , Takatomo Sasaki Takatomo Sasaki
Published: October 2002

We report on the growth of GdCa4O(BO3)3 (GdCOB) and YCa4O(BO3)3 (YCOB) crystals and their characterization as new nonlinear optical materials. The crystals with good optical quality were grown by the Czochralski method. YCOB, the characteristics of which has not previously been reported to our knowledge, has a larger temperature acceptance bandwidth than that of GdCOB, and third harmonic generation of a Nd:YAG laser in this crystal was demonstrated.
New Method for the Spectral Radiance Factor Measurement of Diffuse Reflective Substrates
Authors: Shimokawa Ryuichi , Igari Ichiro Saito
Published: October 2002

We propose and demonstrate a new practical method for measuring the total/diffuse hemispherical reflectances and simultaneously reflected radiance factor of diffuse reflective substrates. This method involves the use of a collimated and focused monochromatic light beam and a specified integrating-sphere detector. The reflected radiance factor can be computed from the differential of the reflectance as a function of the polar angle.
Capacitance Anomaly in the Negative Differential Resistance Region of Resonant Tunneling Diodes
Authors: Shimizu Naofumi , Takao Waho Takao Waho , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

For In0.53Ga0.47As/AlAs resonant tunneling diodes, the peak structure in the capacitance-voltage (C-V) characteristics in the negative differential resistance (NDR) region was investigated. We experimentally reveal that the electron sheet density that is responsible for the capacitance peak is equal to half of that in the quantum well at the peak voltage. The derived electron sheet density in the quantum well at the peak current is 3.2×1011cm-2and the resulting electron lifetimes in the quantum well are 320 and 580 fs for 2.0- and 2.3-nm AlAs barriers.
High Upconversion Intensity of Er3+ in a LaF3 Thin Film on CaF2 (111) Grown by the Molecular Beam Epitaxy Method
Authors: Uda Satoshi , Adachi Kazunori , Inaba Katsuhiko , Yao Takafumi , Atsuo Kasuya Atsuo Kasuya , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Monocrystalline Er3+-doped LaF3 layers were heteroepitaxially grown on CaF2 (111) substrates with an Er3+ concentration of up to 38.7 mol% by molecular beam epitaxy. The hexagonal crystal structure of LaF3 was confirmed from the beginning of the layer formation by RHEED patterns. Green light emission at 538 nm was generated by upconversion employing near 800 nm pump wavelengths from a Ti:sapphire laser. The maximum emission intensity of green light was obtained at an Er3+ concentration of 11 mol%, which was several times higher than that obtained from an Er3+-doped CaF2 film on CaF2 (111). This is discussed in relation to the effect of the heavy mass of La on the emission mechanism.
Direct Observation of the Moving Liquid/Solid Interface during Nanosecond Pulsed Laser Annealing of Silicon
Authors: Hsieh Der Ming , Jun Yi Wang Jun Yi Wang , Andy Ying Guey Fuh Andy Ying Guey Fuh
Published: October 2002

Silicon wafers were melted using a Q-switched Nd:YAG laser which was incident onto the front surface of a sample. The back surface of the sample and the laser-induced liquid/solid ( l/s) interface act as the plates of a Fabry-Perot interferometer. Thus, the reflectance of an IR probe beam which is directed onto the back surface of the sample varies periodically with the moving l/s interface. From the measured time-resolved interference pattern of the reflectance, the moving velocities of the l/s interface during both melt-in and resolidification can be deduced.
Characterization and Field Emission of Sulfur-Doped Boron Nitride Synthesized by Plasma-Assisted Chemical Vapor Deposition
Authors: Sugino Takashi , Tanioka Kazuhiko , Seiji Kawasaki Seiji Kawasaki , Junji Shirafuji Junji Shirafuji
Published: October 2002

Polycrystalline boron nitride (BN) films are synthesized using BCl3 and N2 as source gases, by plasma-assisted chemical vapor deposition. BN films consist of nanocrystalline grains of 3 nm in size. The energy gap is estimated to be 6.0 eV from ultraviolet-visible optical transmission measurement. The electrical resistivity is also estimated to be 2×1011 and 4.9×102 Ω· cm for undoped and sulfur (S)-doped BN films, respectively. Electron field emission is observed from S-doped BN film deposited on the Si substrate. The emission current is detected at electric fields higher than 9 V/µ m. The emission current of 10 µ A is obtained at 21 V/µ m. This field emission characteristic is compared with that of polycrystalline diamond films treated with H2 plasma.
Surface-Polariton Fiber Polarizer: Design and Experiment
Authors: Hsu Kuang-Yu , Ma Ssu-Pin , Chen Kun-Fa , Chen Shiao-Min Tseng
Published: October 2002

We polished 633-nm single-mode fibers embedded into silicon V-grooves within a small proximity to their cores. Both designs and critical parameters of the proposed all-fiber polarizers are discussed in this Letter. Fiber polarizers comprising a buffered MgF2 dielectric and thick aluminum coating were made by us and they exhibited a high extinction ratio. Our silicon V-grooves made by microelectronic techniques had a long radius of curvature. The quality of the polished fiber surfaces was examined using an atomic force microscope. Our results are useful for phase-sensitive fiber-optic systems.
Observation of Microscopic Nonuniformity during Overetch in Polysilicon Gate Etching
Authors: Mutumi Tuda Mutumi Tuda , Kouichi Ono Kouichi Ono
Published: October 2002

Microscopic uniformity during overetch has been investigated for polysilicon gate etching in electron cyclotron resonance Cl2/O2 plasmas, using atomic force microscopy as well as scanning electron microscopy. As the O2 percentage was increased in Cl2/O2 plasmas, the aspect-ratio dependence of the poly-Si etch rate changed from a weak reactive-ion-etching (RIE) lag to a slightly inverse RIE lag; on the other hand, the aspect-ratio dependence of the SiO2 etch rate exhibited a strongly inverse RIE lag at high O2 percentages. As a result, the microscopic etch selectivity of poly-Si over SiO2 was considerably degraded with increasing aspect ratio, giving rise to gate oxides broken in large aspect-ratio features during overetch. These results are indicative of the transport of incoming oxygen atoms in microstructures limited by neutral shadowing.
Metalorganic Vapor Phase Epitaxy of Sb-Doped ZnSe
Authors: Takemura Masaaki , Hideo Goto Hideo Goto , Toshiyuki Ido Toshiyuki Ido
Published: October 2002

The Sb-doped ZnSe was grown on (100)GaAs substrate by using the Metalorganic Vapor Phase Epitaxy method in atmospheric pressure in order to obtain a p-type ZnSe film. The C-V measurement of the Sb-doped ZnSe layer suggests a p-type conduction. The maximum space charge concentration obtained was 1.5×1016 cm-3. The acceptor level of Sb, which was estimated from the photoluminescence spectrum, was found to be 69 meV.
Electroreflectance of CuInSe 2 Single Crystals
Authors: Sho Shirakata Sho Shirakata , Shigefusa Chichibu Shigefusa Chichibu , Shigehiro Isomura Shigehiro Isomura , Hisayuki Nakanishi Hisayuki Nakanishi
Published: October 2002

Electrolyte electroreflectance (ER) measurements have been carried out at room temperature (297 K) on a series of bulk single crystals of CuInSe2 prepared by the normal freezing method with various Cu/In ratios. The Cu-rich crystals exhibited sharp ER peaks and the AB-transition energy is 1.026 eV, while In-rich crystals exhibited broader ER peaks and smaller AB-transition energies (1.00–1.02 eV) than those of the Cu-rich ones. The spin-orbit splitting of the uppermost valence band is 0.236 eV. The effect of the Cu/In ratio on the ER spectra is discussed in terms of the Urbach energy determined by optical absorption measurement, and the bandgap energy of the stoichiometric CuInSe2 crystal is discussed.
Growth of NdBaCuO Superconducting Thin Films Using Mist Microwave-Plasma Chemical Vapor Deposition with Dual Sources
Authors: Takahashi Naoyuki , Takeda Naoyuki , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

NdBaCuO superconducting thin films have been successfully prepared for the first time using mist microwave-plasma chemical vapor deposition (MPCVD) with dual sources. The deposited films showed only the (00l) peaks of NdBaCuO. The growth rate and T
c-zero (zero resistance) of the deposited films were 1.0 µ m/h and 82.6 K, respectively. It was found that NdBaCuO superconducting thin films grew in a wide range of input molar ratio of oxygen compared to the preparation of Y-system, Bi-system and Tl-system superconducting thin films by mist MPCVD.
Effect of Al-doping on the Grain Growth of ZnO
Authors: Tanahashi Masakazu , Ito Masahiro , Murao Masako , Iga Atsushi
Published: October 2002

Grain growth of ZnO in liquid phase sintering of ZnO–0.5 mol%Bi2O3 ceramics has been studied by increasing the doping amount of Al2O3 from 25 ppm to 200 ppm. Al2O3 was doped using an aluminum nitrate aqueous solution. When 50 ppm of Al2O3 was doped to ZnO ceramics, abnormal grain growth was observed, while 75 ppm Al2O3 retarded grain growth. Doping of Al2O3 to pure ZnO ceramics did not cause abnormal grain growth,but simply retarded grain growth . The ratio of diameters of these grain sizes sintered at 900° C: d (abnormal grain growth)/d(retarded grain growth) is 20–100. Mechanisms of abnormal grain growth and retardation are proposed as follows. When the doped amount of Al2O3 was 50 ppm, aluminum compound thin films which were formed around ZnO grains at a low temperature and retarded grain growth disappeared suddenly by diffusion into the ZnO grain and ZnO grains grew suddenly. When the doped amount of Al2O3 was 75 ppm and the aluminum compound film was thick enough, part of the film remained unchanged even when a considerable proportion of the aluminum diffused mainly into the ZnO to reach solubility, retarding grain growth.
Metal-Oxide-Si Capacitors Hot-Electron and Radiation Hardness Improvement by Gate Electrodes Deposited Using Amorphous Si and Gate Oxides Rapid Thermal Annealed in N2O
Authors: Kuei-Shu Chang-Liao Kuei-Shu Chang-Liao , Ling-Chih Chen Ling-Chih Chen
Published: October 2002

The hot-electron and radiation hardnesses in metal-oxide-Si (MOS) capacitors are dramatically improved by the combination of a gate electrode deposited using amorphous Si and a gate oxide rapid thermal annealed in N2O. The charge-to-breakdown performance of MOS capacitors fabricated by this technique is excellent. The numbers of hot-electron and radiation induced interface traps are significantly reduced. The hardness improvement can be explained in terms of a mechanism based on an increase in compressive stress (macroscopic strain) in the oxide and relaxation of SiO2/Si interfacial strain.
Large Phase Shifts due to the χ (2) Cascading Nonlinearity in Large Walk-off and Loss Regimes in Semiconductors and Other Dispersive Materials
Authors: Ueno Yoshiyasu , Stegeman George I. , Kazuhito Tajima Kazuhito Tajima
Published: October 2002

The nonlinear phase shift associated with χ(2) cascading was studied for ultrashort pulses in regimes with large temporal walk-offs between the fundamental and the χ(2)-generated second-harmonic (SH) pulses, a situation typical of semiconductors. Despite the small overlap between the fundamental and SH pulses after they walk-off each other, a nonlinear phase shift was numerically observed to occur at a rate comparable to that before they walk-off. A π/2 phase shift was demonstrated even in a waveguide 15 times longer than the walk-off length.
Excimer-Laser-Produced Amorphous-Silicon Vertical Thin-Film Transistors
Authors: Akihiko Saitoh Akihiko Saitoh , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

A new method has been proposed for fabricating short-channel amorphous-silicon vertical thin-film transistors (TFTs). The channel is formed at the side wall of the gate electrode, but the source and drain are formed on the flat glass and the gate electrode regions, respectively. Due to the desirable shadowing effects of the side wall, the channel remains in an amorphous state, but the source and drain are crystallized selectively by excimer-laser irradiation. The 1.5 µm-long TFTs had field-effect mobility as high as 0.7 cm2/(V·s) and no current crowding effects.
Silicon Thin Film with Columnar Structure Formed by RF Diode Sputtering
Authors: Unagami Takashi , Lousa Arturo , Messier Russel
Published: October 2002

The morphology of amorphous silicon (a-Si) thin films prepared by rf diode sputtering was examined. The self-bias potential drops sharply with deceasing argon gas pressure below 30 mTorr and strongly influences the morphology of the sputtered a-Si films. In particular, a film deposited at a pressure of 20 mTorr has a very highly oriented columnar structure and each column has a dome-shaped top. The experimental results show that the self-bias potential is an important determinant of sputtered a-Si film microstructure.
Theoretical Analysis of the Threshold Current Density in GaN/AlGaN Strained Quantum Well Lasers with a Modulation-Doped Structure
Authors: Niwa Atsuko , Tsukuru Ohtoshi Tsukuru Ohtoshi , Takao Kuroda Takao Kuroda
Published: October 2002

The dependence of the threshold current density on the doping type and dopant concentration in GaN/AlGaN modulation-doped (MD) strained quantum well (QW) lasers is theoretically investigated. This investigation is based on a detailed band structure calculation using the tight-binding method. It is found that the threshold current density of GaN/AlGaN n-type MD-QW lasers can be reduced to 1/2–1/3 that of undoped lasers due to the reduced transparent injected carrier density. The threshold current in p-type MD lasers, however, increases because of decreased carrier lifetime. These results show that n-type MD-QW lasers are more suitable for short-wavelength lasers based on III–V nitrides.
Ferroelectric Switching Behavior in Thin Films of Polyurea-5
Authors: Tajitsu Yoshiro , Ishida Mineyuki , Ishida Kazufumi , Ohigashi Hiroji , Date Munehiro , Fukada Eiichi
Published: October 2002

Thin polyurea-5 films were prepared by vapor-deposition polymerization of 1,5-diaminopentane and 1,5- diisocyanatepentane. In order to investigate the ferroelectric properties of polyurea-5, we measured switching behavior. Switching phenomena were observed for the polymer thin films at room temperature. It was found that the switching time depends on the applied electric field E, and that the amount of reversed polarization is nearly independent of E. The results clearly revealed characteristics of ferroelectric switching phenomena. As a result, we obtained a residual polarization of about 20 mC/m2 at room temperature. We found also that the switching time is long, and that the shape of switching curves is broad, compared to those of typical ferroelectric polymers, vinylidene fluoride and trifluoroethylene copolymers.
Characterization of Thin Bonded Silicon-on-Insulator Structures by the Microwave Photoconductivity Decay Method
Authors: Ichimura Masaya , Makino Takanori , Asakura Hideki , Usami Akira , Morita Etsuro , Eisuke Arai Eisuke Arai
Published: October 2002

Thin silicon-on-insulator (SOI) layers of 0.5–2 µ m thickness are characterized by the microwave photoconductivity decay (µ-PCD) method with an N2 laser as the excitation source. The penetration depth of the N2 laser light is less than 0.1 µ m, and thus the excess carriers are excited only in the SOI layers. The measured recombination lifetime is sensitive to SOI thickness and interface properties, and thus the µ-PCD method can be used for characterization of the interface and observation of thickness variation. The surface (interface) recombination is considered as the dominant recombination mechanism.
Characterization of Domain-Inverted Layers in LiTaO 3 by Line-Focus-Beam Acoustic Microscopy
Authors: Jun-ichi Kushibiki Jun-ichi Kushibiki , Masahito Miyashita Masahito Miyashita
Published: October 2002

A characterization procedure of domain-inverted layers employed in LiTaO3 optoelectronic devices by line-focus-beam acoustic microscopy is explored. A special specimen of -Z-cut LiTaO3 with a domain-inverted layer of about 1.8 µm thickness, processed under the fabrication conditions for quasi-phase-matching second-harmonic-generation devices, was prepared for measurements of the leaky surface acoustic wave (LSAW) velocities in the frequency range 100 to 300 MHz. Intrinsic decreases in LSAW velocity were obtained with the rate of 0.127 m/s/MHz, which were in excellent agreement with the theoretical results. These resulted from formation of a domain-inverted layer on the -Z surface. Slight variations in domain-inverted depth on the specimen, caused by variation in process temperature, were also detected, with the measurement resolution of 0.01 µm at 225 MHz.
Control of Crystal Orientation for BaBiO3 Thin Film on SrTiO3(100) Substrate Using BaO Buffer Layer
Authors: Takehiko Makita Takehiko Makita , Hitoshi Abe Hitoshi Abe
Published: October 2002

We have fabricated BaBiO3 thin films on a SrTiO3(100) substrate by molecular beam epitaxy method using a BaO buffer layer. The crystal orientation of BaBiO3 using the BaO buffer layer was mainly the (100) direction, while that of BaBiO3 without the BaO buffer layer was the (100) and (110). Atomic force microscope images showed that the facet of the BaBiO3 thin film using BaO grew along the <100> direction of the SrTiO3(100) substrate whereas that of BaBiO3 without BaO grew along the <110> direction.
An Experimental Pattern Recognition System Using Bidirectional Optical Bus Lines
Authors: Doi Takeshi , Uehara Akihito , Takahashi Yoshiyuki , Yokoyama Shin , Iwata Atsushi , Hirose Masataka
Published: October 2002

In the parallel processing system for matching input patterns with a vast number of reference patterns, bidirectional bus lines are required for data distribution and inter-unit communications. This paper describes an experimental pattern recognition system using bidirectional optical bus lines integrated using an Si LSI technique. A waveguide that can distribute an optical signal to all receiving branches from any transmission branch was designed, based on a finite-difference time-domain analysis. A complementary metal oxide semiconductor (CMOS) test chip for the pattern matching processing unit with amplifiers for a photodetector and drivers for a light emitting diode was also designed. This system selects the reference pattern most similar to an input pattern by using the waveguide. The basic operations of fabricated CMOS test chips were confirmed and the optical power branch ratios of the bidirectional optical waveguide were measured. In consideration of the measurement results, an improved optical waveguide for dividing optical power uniformly to branches is proposed.
Diffusion Barrier Mechanism of Extremely Thin Tungsten Silicon Nitride Film Formed by ECR Plasma Nitridation
Authors: Hirata Akihiko , Machida Katsuyuki , Maeyama Satoshi , Watanabe Yoshio , Kyuragi Hakaru
Published: October 2002

The diffusion barrier mechanism of tungsten silicon nitride (WSiN) film formed by ECR plasma nitridation is investigated. For this purpose, we examined film thickness, nitrogen content, surface composition, and local atomic ordering of this WSiN and correlated these characteristics with its barrier capability. It is revealed that WSiN shows good barrier capability when RF bias is applied to the substrate during nitridation even though it is less than 6-nm thick. Applying RF bias increases the nitrogen content in WSiN. Moreover, Si atoms are preferentially sputtered and the local atomic ordering in WSiN is lowered because the effect of ion bombardment is remarkably pronounced. It is supposed that these film characteristics contribute to the suppression of phosphorus diffusion through interstitial sites. As a result, WSiN functions as an excellent barrier layer even though it is extremely thin.
Electroluminescence Measurement of n+Self-Aligned Gate GaAs MESFETs
Authors: Niwa Hiroyuki , Ohno Yutaka , Kishimoto Shigeru , Mizutani Takashi , Yamazaki Hajime , Taniguchi Toru
Published: October 2002

We studied the electroluminescence (EL) for n+self-aligned gate GaAs metal-semiconductor field-effect transistors (MESFETs) at room temperature. It has been found that the spatial distribution of the EL intensity is dependent on the luminescence energy. The EL peak with bandgap energy is observed at a region between the source and the gate metals, while the EL with an energy higher than the band gap energy is observed on the drain-side edge of the gate. By studying the correlation between the integrated EL intensity and the drain/gate current, it is concluded that the electron-hole recombination is a dominant luminescence mechanism for both the high and low energy regions for the present n+self-aligned gate GaAs MESFETs.
Photoluminescence Due to Degenerate Electron-Hole System in Silicon-on-Insulator Wafers under Ultraviolet Light Excitation
Authors: Shigeo Ibuka Shigeo Ibuka , Michio Tajima Michio Tajima , Mina Saito Mina Saito , Jaroslaw Jablonski Jaroslaw Jablonski , Masatoshi Warashina Masatoshi Warashina , Keigo Nagasaka Keigo Nagasaka
Published: October 2002

Photoluminescence (PL) spectroscopy has been used for characterization of silicon-on-insulator (SOI) wafers with SOI thickness of 75 nm fabricated by separation by implanted oxygen (SIMOX) technique. While PL signals from the substrate were dominant under conventional visible light excitation, a characteristic broad line was observed under ultraviolet (UV) light excitation throughout our temperature range between 4.2 to 70 K. The spectral distribution of the characteristic line agreed with calculated shape using convolution of the occupied electron and hole densities of states. This agreement can be regarded as strong evidence for formation of degenerate electron-hole systems, electron-hole liquid and electron-hole plasma, in the SOI layer. The detection of luminescence due to these systems allows us to suggest that relief of crystalline damage in the SOI layer induced by oxygen implantation and improvement of quality of interfaces between the SOI layer and oxide layers are efficiently achieved in the present low dose SIMOX process with an internal thermal oxidation.
Absorption Coefficient Measurements of MgZnCdSe II-VI Compounds on InP Substrates and Quantum Confined Stark Effect in ZnCdSe/MgZnCdSe Multiple Quantum Wells
Authors: Hattori Hiroshi , Nomura Ichirou , Nagano Takeshi , Shimbo Hiroyuki , Haraguchi Masaru , Morita Toshihiro , Kikuchi Akihiko , Kishino Katsumi
Published: October 2002

Selective removal of the InP substrates of MgZnCdSe II-VI compound samples by chemical etching using HCl:H3PO4 solutions was investigated for the first time. Using a selective removal technology, the absorption coefficients of the MgZnCdSe layers were estimated from the optical transmission measurements at room temperature. Furthermore, the bandgap energies of MgZnCdSe were obtained as a function of the Mg composition by fitting the theoretical absorption coefficients to the experimental values. In addition, for ZnCdSe/MgZnCdSe multiple quantum well (MQW) samples, absorption coefficient variations due to the quantum confined Stark effect (QCSE) were observed near the absorption edge of the MQW by applying an electric field.
Fabrication of Nanometer-Scale Vertical Metal-Insulator-Metal Tunnel Junctions Using a Silicon-on-Insulator Substrate
Authors: Haraichi Satoshi , Wada Toshimi , Gorwadkar Sucheta M. , Ishii Kenichi
Published: October 2002

We have developed a vertical metal-insulator-metal (MIM) junctions fabrication process using a silicon on insulator (SOI) substrate. The diameter of the contact-hole of the top SiO2 layer tends to saturate with an increase in exposed dose, and a mask with a contact-hole of a minimum diameter of about 15 nm was successfully fabricated. An aluminum vertical array of two MIM junctions exhibited the typical current-voltage (I-V) characteristics of tunnel junctions at room temperature. However, they showed a large dispersion of conductance and a large leakage current after repeated I-V measurements of 30–50 times, probably because of the granular structure of the deposited Al films. A chromium vertical array of two MIM junctions exhibited the linear I-V characteristics of a metal wire at room temperature just after fabrication. They exhibited the typical I-V characteristics of tunnel junctions after 300°C annealing, probably because of the structural transition of chromium oxide films from the low-resistance CrO2 to the high-resistance Cr2O3.
Fabrication of a Tris(8-hydroxyquinoline) Aluminum (Alq3)/Poly(N-vinylcarbazole) (PVK) Superlattice Structure and Its Use for Electroluminescent Device
Authors: Chen Baijun , Liu Shiyong
Published: October 2002

Superlattices consisting of alternating layers of organic/polymeric materials have been fabricated from tris(8-hydroxyquinoline)aluminum (Alq3) and poly(N-vinylcarbazole) (PVK) by multisource-type high-vacuum organic molecular deposition. The characteristics of superlattice structures are determined by the small-angle X-ray diffraction, optical absorption and photoluminescence. Electroluminescent devices (ELDs) with a superlattice structures have also been fabricated and the emission characteristics are discussed.
Characterization of Dopant Interdiffusion and Power Reduction on TiSi2 Local Wiring Technology in Sub-Half-Micron Complementary Metal Oxide Semiconductor
Authors: Ida Jiro , Ohtomo Atsushi
Published: October 2002

The TiSi2 local wiring technology has been newly characterized from the viewpoints of dopant interdiffusion and power reduction. It was found that only the p+/n junction degrades when TiSi2 local wiring connects the n+ layer and p+ layer. The results of electrical measurements using a set of new test patterns suggest the reason to be that boron does not diffuse from TiSi2 to Si due to the high efficiency of TiB formation. More than a 20% reduction in power dissipation at a low-power supply voltage of 1 V was obtained, which demonstrates that the scheme is promising for low-power sub-half-micron complementary metal oxide semiconductor.
Effect of Annealing Method to Crystalize on Sr0.9Bi2.3Ta2O9+α Thin Film Properties Formed from Alkoxide Solution
Authors: Koiwa Ichiro , Tani Kouichi , Mita Juro , Iwabuchi Toshiyuki
Published: October 2002

Sr0.9Bi2.3Ta2O9+α (SBT) thin films were formed from a mixed alkoxide solution and were heat-treated by various annealing methods. The SBT thin film heat-treated with the standard temperature rising at a rate of 10°C/min (standard thermal annealing: STA) showed higher squareness (effective remanent polarization/effective saturation polarization) and effective remanent polarization values than those of the film heat-treated with a rapid temperature rise at a rate of 125°C/s (rapid thermal annealing: RTA). This difference was large in the region of low applied voltage. The low values of the SBT film with RTA treatment were caused by lower crystal continuity in the direction of film thickness than that of the SBT film with STA treatment. The SBT film with RTA treatment showed a higher leakage current density for the entire applied voltage region than that of the film with STA treatment. The higher leakage current density was caused by fine nonstoichiometric (Bi-rich) particles which exist at grain boundaries of large grains. Therefore, it was concluded that the high squareness ratio and low leakage current density are obtained in SBT film which has only one grain in the film thickness direction and does not have nonstoichiometry fine particles around grain boundaries.
Thermal and Optical Properties of Metal Azo Dyes for Digital Video Disc-Recordable Discs
Authors: Suzuki Yuki , Horie Michikazu , Okamoto Yuuko , Kurose Yutaka , Maeda Shuichi
Published: October 2002

The effects of the optical and thermal properties of metal azo dyes on the recording
characteristics of digital video disc-recordable (DVD-R) discs have been studied. A
sharp threshold for thermal decomposition of the dye assures a clear mark edge and
low jitter for the minimum mark length of 0.4–0.44 µm. A steep absorption edge at the
635 nm side is also critical to high reflectivity and for fabricating clear mark edges.
Following these guidelines, excellent 0.4 µm shortest mark length recording
characteristics are achieved with original metal azo dye.
Transport Properties of SbTeSe Phase-Change Media
Authors: Wu Chih Yuan , Yao Yeong Der , Huang Der Ray
Published: October 2002

The low-temperature electrical resistivities ρ, magnetic
susceptibility χ and structure of Sb2Te3-x
Sex compounds (x=
0, 0.6, 0.9, 1.2, 3) have been investigated. In all the samples, the ρ
behavior with temperature T is metallic except in the case of the sample
with x = 3. We extract the electron-phonon coupling constant λ by
comparing our experimental results with the Boltzmann transport theory. The
high residual electrical resistivity is explained as being due to the
low-conduction electron density. All the compounds exhibit diamagnetic
behavior, however, the magnetic susceptibility χ(T) exhibits
paramagnetic behavior with T.
Real Time Measurements of Phase Change Dynamics
Authors: Trappe Cyril , Béchevet Bernard , Facsko Stefan , Kurz Heinrich
Published: October 2002

We present reflectivity measurements allowing the quantitative determination of crystallization times from 103 s down to 10-8 s. For the slow speeds the crystallization of a written mark at constant temperatures is monitored. For the fast speeds time resolved measurements are employed. The presented experimental methods show a high potential to yield information on stoichiometry induced variation of the crystallization speed and on the physical mechanism of phase change processes.
Super-Resolution Optical Readout System with Partial Response Maximum Likelihood Detection
Authors: Tanabe Takaya , Dobashi Hisanobu
Published: October 2002

A readout system that uses super-resolution optics and a partial response maximum likelihood (PRML) detection, which improves readout sensitivity and achieves high-density recording, has been developed.
In this system, a shading band is placed in the collection path to shade the center part of the reflected beam across the track direction at the aperture plane, resulting in good optical transfer function (OTF)
in the high-frequency region. The readout signal from the photo-detector is equalized for the partial responses channel using only a transversal filter and applying Viterbi detection. Experiments using a
magneto-optical disk drive having a class I partial response (PR(1, 1)) and a run-length limited code (RLL(1, 7)) were performed to demonstrate the good readout sensitivity of this method. The results show that this compact system achieves 30% higher recording density than a conventional system.
Photostimulable Luminescence Glasses as a Novel Material for Optical Memory
Authors: Hirao Kazuyuki , Qiu Jianrong , Shimizugawa Yutaka
Published: October 2002

We report on photostimulated luminescence in sodium borate glasses doped with Eu2+ (Ce3+)
and Sm3+. When X-ray or 266 nm UV laser irradiated glasses were excited by a He–Ne laser (633 nm),
photostimulated luminescence at 470 nm for Eu2+-doped glass and at 360 nm for Ce3+-doped
glass due to the 5d-4f transition of Eu2+ and Ce3+ was observed. X-ray absorption spectra of
glasses, X-ray irradiated for various durations and photostimulated excitation spectra were measured.
On comparing with the mechanism of photostimulated luminescence in BaFBr:Eu2+, the
luminescence is proposed to have resulted from the photostimulated recombination of holes and
electrons at traps, which leave the electrons in a long-lived excited state. These glasses can be used as
materials for read once and write many optical memories, which is considered to be important for the
protection of certain types of software.
Pattern-Dependent Charging and the Role of Electron Tunneling
Authors: P. Giapis Konstantinos , S. Hwang Gyeong
Published: October 2002

We review the prevailing causes of and remedies for profile distortion (notching) resulting from pattern-dependent charging during etching in high density plasmas.
A new mechanism for notch reduction, based on electron tunneling through thin gate oxides,
is explained through detailed modeling and simulations of charging and profile evolution
in polysilicon gate definition. Tunneling currents from the substrate decrease
surface charging potentials–responsible for ion deflection–at the
bottom of high aspect ratio trenches. The exponential dependence of electron tunneling
on the oxide electric field predicts an abrupt transition from severe notching to
virtually no notching as the gate oxide thickness is decreased, which has been seen
in experiments.
Mechanism of Charging Reduction in Pulsed Plasma Etching
Authors: S. Hwang Gyeong , P. Giapis Konstantinos
Published: October 2002

Numerical simulations of charging and etching in time-modulated high-density
plasmas suggest a new mechanism for the reduction of pattern-dependent charging,
which is based on low energy positive ions. During the power-off period and before
the sheath collapses, the electron temperature and plasma potential decrease rapidly,
resulting in low energy ions which can be deflected by smaller local electric fields.
The flux of deflected ions to the upper mask sidewalls increases enabling neutralization
of the negative charge accumulated there due to the electron shading effect.
Current balance at the trench bottom surface is achieved at lower charging potentials,
which lead to significantly reduced notching and gate oxide degradation.
Pulsing period and duty ratio are examined
as parameters to control the performance of pulsed plasmas.
Effects of Charge Build-up of Underlying Layer by High Aspect Ratio Etching
Authors: Yonekura Kazumasa , Kiritani Masahide , Sakamori Shigenori , Yokoi Takahiro , Fujiwara Nobuo , Miyatake Hiroshi
Published: October 2002

The effects of the “electron shading” charge build-up at the
bottom of holes are investigated using fluorocarbon gas plasma. The
etch rates of the electrically conductive films such as phosphorus-doped
polysilicon at the bottom of the holes change depending on
whether the films are patterned or not. This is caused by the
decrease of the low-energy ions which reach the bottom of the holes
due to positive charging of the underlying layers. Furthermore, the
potential at the bottom of the contact holes is investigated using
metal-nitride-oxide-silicon (MNOS) capacitors. The positive charging
due to the electron shading effect is measured. In order to reduce
the electron shading charge build-up, the pulse-modulated plasma is
investigated. The selectivity to the underlying layer increases upon
using pulse-modulated plasma.
Trace Rare Gases Optical Emission Spectroscopy for Determination of Electron Temperatures and Species Concentrations in Chlorine-Containing Plasmas
Authors: Donnelly Vincent M. , Malyshev Mikhail V. , Kornblit Avi , Ciampa Nicolas A. , Colonell Jennifer I. , Lee John T. C.
Published: October 2002

Trace rare gas optical emission spectroscopy has been used to obtain electron temperatures (Te) and percent dissociation of Cl2in chlorine-containing, high-density inductively (transformer) coupled plasmas. In this method, a small amount of an equal mixture of the rare gases is added to the plasma and emission spectra that include lines from the rare gases are recorded. Modeling of the dependence of the rare gas emission intensities onTeallowsTeto be derived from the best match between the observed and computed intensities.Tein Cl2plasmas increases from 1.7 eV at 20 mTorr to 3.4 eV at 0.5 mTorr. These values are 1.3 to 1.8 times lower than those recorded with a Langmuir probe. This discrepancy is due at least in part to artifacts associated with using a single Langmuir probe in a reactor with semiinsulating walls. Absolute percent dissociations of Cl2were determined by monitoring the intensity of an emission band of Cl2, normalized to emission from Ar and Xe. Cl2percent dissociation increased with power and decreased with pressure. At 1.0 mTorr, Cl2is about 85% dissociated at a power density of 0.1 W/cm3and 95% dissociated at 0.3 W/cm3in a Cl2plasma. Addition of BCl3to Cl2increases the dissociation of Cl2.
Detection of Submicron Particles in Water Using Fabry-Perot Interferometer
Authors: Takanashi Satohiko , Ishikawa Mumeharu , Ohbayashi Koji
Published: October 2002

A new system to detect nano-size particles suspended in water has
been realized using a Fabry-Perot interferometer to reduce background
scattering due to water. Measurements have been carried out on samples of
polystyrene latex spheres suspended in water, revealing the capability of this
system to detect particles of up to 0.042 µm diameter.
A Structural Study of Ag-Rich Ag–As–S Glasses
Authors: Kawaguchi Takeshi
Published: October 2002

Thermal behavior, density, infrared absorption and X-ray photoelectron spectroscopy of Ag
x
As60-x
S40 bulk glasses (35 ≤x ≤47.5) have been investigated to obtain structural information on glasses that exhibit photoinduced surface deposition (PSD) of Ag. The compositional trends in the range of 40 ≤x ≤47.5, where the PSD effect is observed, were very different from those in the range of 35 ≤x ≤40. The trends in the range of 40 ≤x ≤47.5 can be explained by assuming the existence of excess Ag+ ions in the glasses. The excess Ag+ ions, which contribute to the PSD, may lie between isolated AsS3 pyramids and bind loosely with surrounding S atoms.
Estimation of the Scatterer Distribution of the Cirrhotic Liver using Ultrasonic Image
Authors: Tadashi Yamaguchi Tadashi Yamaguchi , Hiroyuki Hachiya Hiroyuki Hachiya
Published: October 2002

In the B-mode image of the liver obtained by an ultrasonic imaging system, the speckled pattern changes with the progression of the disease such as liver cirrhosis.
In this paper we present the statistical characteristics of the echo envelope of the liver, and the technique to extract information of the scatterer
distribution from the normal and cirrhotic liver images using constant false alarm rate (CFAR) processing.
We analyze the relationship between the extracted scatterer distribution and the
stage of liver cirrhosis.
The ratio of the area in which the amplitude of the processing signal is more than the threshold to the entire processed image area is related quantitatively to the stage of liver cirrhosis.
It is found that the proposed technique is valid for the quantitative
diagnosis of liver cirrhosis.
Improvement of Underground Image (II): Underground Imaging Using Shear Waves
Authors: Tsuneyoshi Sugimoto Tsuneyoshi Sugimoto , Hiroki Saitou Hiroki Saitou , Motoyoshi Okujima Motoyoshi Okujima
Published: October 2002

An underground imaging method using shear waves was proposed and some improvements were made in the resolution. In spite of these improvements, there was a problem that an underground image spreads horizontally. This problem was solved by adopting the envelope display method.
Further improvements were achieved by taking into account the influence of the surface wave and sound attenuation.