bluuebunny/crossref_metadata_2025 huggingface dataset:
Ce4+: a New Etching Agent for Cadmium Telluride
Authors: Marín Francisco Iranzo , Debiemme-Chouvy Catherine , Vigneron Jacky , Triboulet Robert , Arnaud Etcheberry Arnaud Etcheberry
Published: October 2002

Cadmium telluride (CdTe) has been etched for the first time in a 2M H2SO4 solution in the presence of Ce4+. The etching rates have been obtained by means of step measurements. They are proportional to the Ce4+ concentration and to the dipping time and are close to etching rates obtained for III-V compounds under the same conditions. The etching rates show no decrease with time in the concentration range studied ( 10-4 M-10-1 M) even for large steps (several µ m). Etching rates up to 0.1 µ m/min have been obtained, which can be increased by a factor of about 10 by ultrasonication. The evolution of composition of the sample surface has been investigated by means of X-ray photoelectron spectroscopy (XPS) analysis. Elemental tellurium-rich, oxide-free surfaces are obtained after etching in the presence of Ce4+.
Ta/W/AlOx-Al/Ta/Nb Josephson Junctions for X-Ray Detector
Authors: Shin'ichi Morohashi Shin'ichi Morohashi
Published: October 2002

We have fabricated a Josephson junction, with an approximately symmetrical gap structure which consists of a Ta/W counter electrode, a Ta/Nb base electrode and an AlO

x

-Al barrier for operation as a superconducting X-ray detector at 0.3 K.
A Ta layer is selected due to its long lifetime of quasiparticles and high X-ray absorption efficiency. The W layer is selected as a buffer layer for a body centered cubic Ta counter electrode, and the Nb layer is chosen for a body centered cubic Ta base electrode The Al layer acts as an overlayer for fabricating the AlO

x

barrier. A fabricated junction shows a gap voltage of 1.3 mV, a sharp transition width of less than 50 µ V, and a small subgap leakage current of 1.5 µ A.
Thermal Nitridation of Si(111) Surfaces with N2 Molecules Studied by X-Ray Photoelectron Spectroscopy
Authors: Michiharu Tabe Michiharu Tabe
Published: October 2002

The initial stage of thermal nitridation of Si (111) surfaces using N2 gas has been studied by X-ray photoelectron spectroscopy. It was found, for the first time, that under N2 pressure of 1.3×10-3 Pa the nitridation rate increases with temperature from 600 to 700° C, reaches a constant value and then falls off abruptly at the critical temperature (∼880° C). Since the critical temperature coincides with that of the transformation of Si (111) from 7×7 to 1×1, we ascribe the abrupt change to significant differences in reactivity with nitrogen between 7×7 and 1×1 surfaces. This interpretation is supported by a smoother temperature dependence of nitridation on (100) 2×1 surfaces.
\mbVp × \mbB Acceleration Experiments Using Disk-Loaded Accelerator
Authors: Noboru Yugami Noboru Yugami , Hiromitsu Inoue Hiromitsu Inoue , Yasushi Nishida Yasushi Nishida
Published: October 2002

The \mbv
p ×\mbB linear electron accelerator applied to the conventional disk-loaded accelerator has been demonstrated. An energy gain of 5.4 keV for electrons is observed from an incident energy of 42 keV in a 0.5 m accelerator, when an external magnetic field of 1.1 G is applied. The energy gain is proportional to B
1.5 until the electrons are detrapped from the wave trough. The results of experiments and theories are in fairly good agreement.
Highly Sensitive Optical Method for the Characterization of SiO2 Films in Bonded Wafers
Authors: Borghesi Alessandro , Sassella Adele , Abe Takao
Published: October 2002

The thickness of very thin films (1-10 nanometers thick) and the frequency of the longitudinal optical mode of the material composing the film (related to its chemical and structural properties) are demonstrated to be measurable with high sensitivity by means of infrared transmission. The particular optical configuration proposed permits the analysis of the SiO2 film in bonded wafers. It is shown that the sensitivity of this new method increases as the films are made thinner.
Dimethylamine as a Carbon Remover in Atomic Layer Epitaxy of AlAs
Authors: Shingo Hirose Shingo Hirose , Nobuo Kano Nobuo Kano , Manabu Deura Manabu Deura , Kazuhiko Hara Kazuhiko Hara , Hiro Munekata Hiro Munekata , Hiroshi Kukimoto Hiroshi Kukimoto
Published: October 2002

We have investigated a novel method of reducing impurity incorporation in atomic layer epitaxy (ALE), by the introduction of impurity-removing gas species. The concept is experimentally tested in ALE–AlAs, in which carbon concentrations in the AlAs layers are reduced by one order of magnitude by supplying dimethylamine in between the supplies of the Al (dimethylaluminum hydride) and As (arsine) sources.
Realization of Two-Dimensional Growth and Suppression of Threading Dislocation Generation in (InP) 1(GaAs)n Quaternary Strained Short-Period Superlattices Grown on GaAs
Authors: Keiji Hayashida Keiji Hayashida , Yasufumi Takagi Yasufumi Takagi , Katsuya Samonji Katsuya Samonji , Hiroo Yonezu Hiroo Yonezu , Mikihiro Yokozeki Mikihiro Yokozeki , Naoki Ohshima Naoki Ohshima , Kangsa Pak Kangsa Pak
Published: October 2002

We investigated the growth mode and the dislocation generation process in the growth of (InP)1(GaAs)n quaternary strained short-period superlattice (SSPS) on GaAs(100) by reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM). The (InP)1(GaAs)n SSPSs with n of 2 and 3 were two-dimensionally grown even after the lattice relaxation. The generation of threading dislocations was suppressed by introducing the <011> misfit dislocations at the hetero-interface.
Enhanced Photocurrent in Organic Photoelectric Cells Based on Surface Plasmon Excitations
Authors: Wakamatsu Takashi , Saito Kazuhiro , Sakakibara Youichi , Hiroshi Yokoyama Hiroshi Yokoyama
Published: October 2002

Surface plasmons (SP) were excited on both of the electrodes of organic photoelectric cells of Al/copper phthalocyanine/Ag structure using the attenuated total reflection method to examine the influence of excitation of SP on photoelectric effects. A marked increase in the photocurrent was caused by the excitation of SP.
Origin of the enhancement of photocurrent due to excitation of SP is discussed based on the experimental results and the calculations of the electric field inside the cell showing that the enhancement cannot be explained only by the intensity of electric field.
In-Plane Birefringence of Polyimide Films Prepared on Substrates Having Thermal Expansion Anisotropy
Authors: Ando Shinji , Sawada Takashi , Shigekuni Sasaki Shigekuni Sasaki
Published: October 2002

Polyimide films whose refractive indices in the film plane show anisotropy (in-plane birefringence, Δn) were prepared by a novel method based on the anisotropy of thermal expansion coefficients (Δα) of single crystal substrates. Polyimide molecular chains were oriented along the crystal axis having a larger thermal expansion coefficient. The Δn of polyimide films increases as the Δα and the larger thermal expansion coefficient of the substrates increase.
Cavitational Failure Phenomenon in Pb-Sn Eutectic Solders
Authors: Seong-Min Lee Seong-Min Lee
Published: October 2002

This report concerns mechanisms on the formation of r-type crack (or cavitation) associated with grain boundary sliding in Pb-Sn eutectic solders used for microelectronic applications. The experimental works indicate that cavitation takes place in a specimen deformed in a tensile test at a relatively low strain rate of 7×10-6/ s and in specimens fatigued at 0.1% to 0.2% strain range and a frequency of 1.67×10-2/ s. Based on these phenomenological observations, it is discussed that the presence of cavities requires large sliding displacements combined with a high stresses.
Surface Alteration of Amorphous Si3N4 Films by ArF Excimer Laser Irradiation
Authors: Nakamae Kazuo , Kurosawa Kou , Takigawa Yasuo , Sasaki Wataru , Izawa Yasukazu , Okuda Masahiro
Published: October 2002

ArF excimer laser induces silicon precipitation accompanied by nitrogen desorption on the surface of an amorphous Si3N4 film, when the laser fluence exceeds the critical fluence which is about 0.2 J/cm2. The amount of nitrogen desorption and the silicon precipitation of the amorphous Si3N4 film increases with increasing laser fluence. The depth of the silicon precipitation on the amorphous Si3N4 film increases exponentially with increasing laser fluence.
Electron-Energy-Loss Spectroscopy of Oxide Superconductor Bi2Sr 2CaCu 2O 8
Authors: Terauchi Masami , Tanaka Michiyoshi , Takahashi Takashi , Katayama-Yoshida Hiroshi , Mochiku Takashi , Kadowaki Kazuo
Published: October 2002

Transmission electron-energy-loss spectra of the oxide superconductor Bi2Sr2CaCu2O8 have been taken from perfect crystalline areas (100 nmφ) in an energy range of 0–60 eV at temperatures of 30 K, 100 K and 300 K. A peak at about 0.6 eV was observed at these temperatures instead of a peak at about 1 eV which was reported to be a free-carrier plasmon peak. The dielectric function derived from the loss-function indicates that the peak at about 0.6 eV can be attributed not to a collective excitation (plasmon) but to an interband transition. The electron density which contributes to the peak has been calculated to be 2 ×1019 electron/cm3. The peaks and shoulders of the spectra (the loss-function) are assigned to individual interband transitions. The temperature dependence of ε
2 has been found around 2.5 eV and 5.5 eV.
Second-Harmonic Generation in Pulsed-Laser-Deposited BaTiO3 Thin Films
Authors: Okada Tatsuo , Nakata Yoshiki , Hiroshi Kaibara Hiroshi Kaibara , Mitsuo Maeda Mitsuo Maeda
Published: October 2002

Barium titanate ( BaTiO3) thin films have been deposited on MgO substrates by pulsed-laser deposition under various deposition conditions. The films were characterized as highly oriented polycrystalline based on X-ray diffraction analysis, atomic force microscope observation and the angular dependence of the optical second-harmonic generation (SHG). The second-order nonlinear optical coefficients (d-coefficients) of one-eighth those of the bulk BaTiO3 crystal were obtained from as-grown films.
Annealing Behavior of a Light Scattering Tomography Detecting Defect near the Surface of Si Wafers
Authors: Furukawa Jun , Hisashi Furuya Hisashi Furuya
Published: October 2002

We have investigated the annealing behavior of a Light Scattering Tomography detecting Defect (LSTD) which exists in 0 to about 20 µ m beneath the surface of Si wafers. LSTDs were detected at the beam positions by the obliquely incident method of the infrared light scattering tomography (IR-LST) before and after annealing at temperatures from 1000° C to 1280° C in dry O2or N2. LSTDs still existed after annealing at temperatures below 1250° C and disappeared after annealing at 1280° C. The annealing behavior of LSTDs did not depend on the ambient, dry O2or N2, during annealing and locations of LSTDs.
Ion Scattering Spectroscopy Experiment in Collisions of He + Ions with Ta and W Targets
Authors: Arikawa Tatsuo , Osami Kishimoto Osami Kishimoto , Wataru Aoba Wataru Aoba
Published: October 2002

Quasi-resonant charge exchange processes between the vacant He 1s state and the 4f state of Ta and W target atoms were investigated. Oscillatory structures specific to the quasi-resonant charge exchange were observed in the yield curves of scattered He+ ions. From the inverse incident velocity plots of the oscillation peaks, the phase development areas, <ΔEΔR>, for both systems were evaluated in terms of the quality factor Q to discuss the “sharpness” of the quasi-resonant charge exchange process. Major components in the spectral density functions obtained by the Fourier transform of these oscillatory curves strongly suggested that the oscillations were responsible for a quantum interference between incident He+ ions and target atoms forming a collision complex during the surface collision.
Photoluminescence of Undoped GaN Grown on c-Plane Al2O3 by Electron Cyclotron Resonance Molecular Beam Epitaxy
Authors: Cho Sung Hwan , Takahiro Maruyama Takahiro Maruyama , Katsuhiro Akimoto Katsuhiro Akimoto
Published: October 2002

We report results on the 77 K photoluminescence (PL) of undoped GaN epilayers grown on c-plane sapphire substrate by electron cyclotron resonance molecular beam epitaxy (ECR-MBE). It was found that the PL properties of undoped GaN epilayers are strongly affected by the growth conditions such as nitrogen pressure, growth temperature and ECR plasma power. The intensities of the donor-to-acceptor (D-A) pair emission peak at about 3.2 eV and of the deep-level emission peak at around 2.3 eV change with the variation of these three growth conditions. Assuming that the D-A peak and deep-level emission peak are related to native defects and carbon impurities, respectively, the systematic change of the PL spectra with growth conditions can be reasonably interpreted. At the optimum growth conditions, the PL spectra at 77 K are dominated by excitonic peak at 3.47 eV and the intensity of deep-level emission peak is one order of magnitude less than that of the excitonic peak. However, since the region regarded as optimum is relatively narrow, it is important to control the growth conditions precisely.
X-Ray Photoelectron Spectroscopy (XPS) Analysis of Oxide Formation on Silicon with High-Purity Ozone
Authors: Akira Kurokawa Akira Kurokawa , Shingo Ichimura Shingo Ichimura
Published: October 2002

Initial oxide formation on a Si(111) surface with high-purity ozone (more than 80% ozone concentration at the sample position) is investigated by X-ray photoelectron spectroscopy (XPS). The suboxide formed by oxidation is characterized from Si2p
spectra. From the comparison of the suboxides formed with ozone and oxygen exposures, it is clear that ozone forms less suboxide than oxygen. Ozone oxidizes a monohydride Si surface, which oxygen does not oxidize appreciably.
Measuring Surface Shape from Specular Reflection Image Sequence –Quantitative Evaluation of Surface Defects of Plastic Moldings–
Authors: Miike Hidetoshi , Koga Kazutoshi , Yamada Takehito , Kawamura Tatsuji , Kitou Masaaki , Takikawa Naohisa
Published: October 2002

A sensitive method for surface shape perception based on image sequence processing is developed. Utilizing a moving slit light source, defects on a plane plastic injection molding are visualized as deformation of the slit image through specular reflection. By considering the geometric configuration of the light source, a plastic test piece and a video camera, the distributions of surface inclination and surface undulation are evaluated quantitatively.
Effects of Damping Resistance on the Modulation Voltage of Large-Inductance High-Tc Superconducting Quantum Interference Devices
Authors: Suzuki Daisuke , Matsuda Shinya Kuriki
Published: October 2002

We have studied the effect of damping resistance which is added in parallel to the inductance of high-T
c dc superconducting quantum interference devices (SQUIDs). The SQUIDs were fabricated from YBa2Cu3O7-δ (YBCO) films on (001) SrTiO3 bicrystal substrate. It was observed that the reduced modulation voltage in large-inductance SQUIDs was improved by the damping resistance, while the modulation of the critical current was unchanged. A resonance structure existing in the I-V characteristic seemed to limit the effect of the damping resistance.
Determination of Molecular Constnts of the X3Σg
- State of O2
Authors: Shimauchi Midori , Miura Tokiwa , Hiroshi Takuma Hiroshi Takuma
Published: October 2002

From the absorption lines assigned to the B-X, 2-7 band of O2 in the KrF laser spectrum, new molecular constants of v=7(X) are obtained. The term values, T

v
, for v=0-3 recently determined by Raman spectroscopy are modified to render them consistent with those obtained by UV spectroscopy for v=11-18, 4 and 7. This modification, based on the theoretical energy formulas of fine structure levels of 3Σ, is numerically justified by the new T
7 value and also by the set of spectroscopic constants of X
3Σ
g

- obtained.
Chemical-Vapor Deposition Techniques of Al for Direct Growth on Oxidized Si and High-Speed Growth
Authors: Matsumiya Yasuo , Kitahara Kuninori , Ohtsuka Nobuyuki , Kazuo Nakajima Kazuo Nakajima
Published: October 2002

This paper reports two novel Al-chemical vapor deposition (CVD) techniques for direct growth on SiO2 and high-speed growth. Blanket growth on SiO2 was achieved by using dimethylethylamine alane (DMEAA) as a precursor. Growth at 220° C following seeding at 300° C yields relatively smooth surfaces and resistivities of 3.3 µΩ· cm. Selective filling of via holes and nonselective blanket growth were continuously performed by changing precursors from dimethylaluminum hydride (DMAH) to DMEAA during growth. High-speed growth was achieved by adopting the liquid-transport method. A growth rate of 0.7 µ m/min was obtained for DMAH with growth selectivity being maintained.
Discharging Current Transient Spectroscopy for Evaluating Traps in Insulators
Authors: Matsuura Hideharu , Yoshimoto Masahiro , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

A novel method [discharging current transient spectroscopy (DCTS)] is developed for evaluating traps in insulators, and is then applied to silicon nitride ( SiNx) films prepared by direct photo-chemical vapor deposition. A single-level trap on the order of 1016cm-3with an emission rate (ep) of around 0.3 s-1and energetically distributed traps on the order of 1017cm-3·eV-1withep<0.1 s-1are obtained at room temperature.
Preparation of La-Modified Lead Titanate Thin Films by Rf-Magnetron Sputtering Method and Their Pyroelectric Properties
Authors: Kamada Takeshi , Komaki Kazuki , Hayashi Shigenori , Kitagawa Masatoshi , Takayama Ryoichi , Deguchi Takashi , Takashi Hirao Takashi Hirao
Published: October 2002

High-quality La-modified lead titanate (PLT) films were grown on MgO substrates by an rf-magnetron sputtering method. In this method, intermittent deposition was realized by periodical repetition of deposition and nondeposition processes with rotation of the substrate holder. The difference between intermittent and continuous methods was examined in terms of the crystal structure and the pyroelectric properties of the films. Intermittent deposition was found to enhance the horizontal grain growth of the films. Excellent PLT films with a high pyroelectric coefficient of 5.0×10-8 C/cm2·K and low dielectric constant of 185 were reproducibly obtained by this method.
Design and Fabrication of a Multi Loop Superconducting Quantum Interference Device, the Clover-Leaf Superconducting Quantum Interference Device
Authors: Matsuda Naoki , Uehara Gen , Kazami Kunio , Takada Youichi , Kado Hisashi
Published: October 2002

Reducing the number of loops in a Drung-type superconducting quantum interference device (SQUID) from eight to four minimally reduces the voltage swing. A four-loop SQUID, called a clover-leaf SQUID (CLS), has been designed in order to reduce the area of the SQUID chip. The CLSs are fabricated by the Nb/Al/AlO

x

/Nb tunnel junction process. They occupy a 4.5-mm-square area on the substrate and have high field-to-flux sensitivity (S=0.63 nT/Φ0). Typical magnetic field resolution is 4.0 fT/Hz0.5 at the white-noise level. The measured biomagnetic fields of this SQUID confirm that its performance level is acceptable.
Selective Area Epitaxial Growth of GaAs Using Metal Gallium and Trisdimethylaminoarsine
Authors: Jelen Christopher , Goto Shigeo , Nomura Yasuhiko , Morishita Yoshitaka , Yoshifumi Katayama Yoshifumi Katayama
Published: October 2002

The selective area growth (SAG) of GaAs by gas-source molecular beam epitaxy (GSMBE) using metal gallium and trisdimethylaminoarsine (TDMAAs) has been investigated. GaAs growth was carried out at various substrate temperatures and TDMAAs beam equivalent pressures (BEP) on (001) GaAs substrates patterned with SiO2, and a phase diagram for the selective and non-selective growth is presented. SAG was found to occur at elevated growth temperatures or high TDMAAs flow rates. The growth rate decreased with increasing TDMAAs BEP, and eventually etching of GaAs by TDMAAs was observed.
Numerical Simulation of Static and Dynamic Characteristics of Dual-Gate Metal Oxide Semiconductor Thyristor
Authors: Iwamuro Noriyuki , Yasukazu Seki Yasukazu Seki
Published: October 2002

Static and dynamic characteristics of a newly proposed vertical metal oxide semiconductor (MOS)-gated thyristor structure called the dual-gate MOS thyristor (DGMOT) are reported for the first time. The feature of this device is that IGBT mode turn-off is achieved due to a novel integration of a lateral n-metal oxide semiconductor field effect transistor (MOSFET) with the thyristor structure while the thyristor mode operation is achieved in the on state. It is possible to obtain a lower on-state voltage drop in the DGMOT while preserving its fast turn-off speed. It has been numerically demonstrated using 600 V forward blocking devices that the on-state voltage drop of 1.04 V and the turn-off time of 0.40 µ s are achieved. This result suggests that the DGMOT could be a superior alternative to the power bipolar junction transistor and may expand the application fields of the MOS-gated devices to the low-frequency operation circuit.
Demonstration of Temperature Dependent-Damping of a Vibrating System by Superconducting YBa2Cu3O 7-x
Authors: Terentiev Alexander N. , John P. Harrison John P. Harrison
Published: October 2002

A major problem associated with superconducting magnetic bearings is the damping of vibration. A demonstration is given of the use of a dissipation peak due to flux line movement in YBa2Cu3O7-
x

to provide temperature-dependent damping of vibration of a mechanical oscillator. Scaling of the present results shows that it is possible to decrease the resonance Q of a 1 kg oscillator to 10 with just 0.02 kg of melt-processed YBa2Cu3O7-
x

. The proposed superconducting damper is distinct from the levitation superconductor in the magnetic bearing.
Low Temperature Fabrication of Diamond Films with Nanocrystal Seeding
Authors: Yara Takuya , Makita Hiroshi , Hatta Akimitsu , Ito Toshimichi , Akio Hiraki Akio Hiraki
Published: October 2002

Well-faceted diamond films have heen fabricated at 200° C on the silicon substrate by the magnetoactive microwave plasma chemical vapor deposition (CVD) method. The substrate was seeded with nanocrystal diamond about 5 nm in diameter synthesized by the explosion process. The nanocrystal seeding brought about the improvement in quality of the fabricated films and the decrease in the time required for diamond nucleation. It took about 5 h to seed the scratched Si substrate at temperatures below 300° C.
Third Harmonic Generation from Quantum-State PbS Embedded in Langmuir-Blodgett Film Matrix
Authors: Moriguchi Isamu , Hanai Kouhei , Teraoka Yasutake , Kagawa Shuichi , Yamada Sunao , Matsuo Taku
Published: October 2002

PbS-bearing Langmuir-Blodgett (LB) films were synthesized by alternating the processes of sulfidation by the exposure to H2S gas and intercalation of Pb2+ ions. These processes allowed the in situ formation and growth of the nano-sized (quantum-state) PbS in the hydrophilic interlayers of the stearate LB film. The third-order nonlinear optical susceptibility, χ(3), of the quantum-state PbS embedded in the LB matrix was evaluated for the first time by third harmonic generation. The PbS/LB films showed the χ(3) values of the order of 10-12 esu, and the in situ growth of the quatum-state PbS resulted in the enhacement of χ(3).
On the Reaction Scheme for Ti/TiN Chemical Vapor Deposition (CVD) Process Using TiCl4
Authors: Mochizuki Yuji , Okamoto Yasuharu , Ishitani Akihiko , Hirose Kazuyuki , Toshikazu Takada Toshikazu Takada
Published: October 2002

A schematic reaction mechanism is proposed to explain the Ti/TiN chemical vapor deposition (CVD) process using the TiCl4molecule as the source species. The scheme can be considered as two successive steps: (I) TiCl4molecules are adsorbed onto surface reactive sites through concerted electron delocalizations, (II) ambient reducing agents such as H2or NH3reactively eliminate Cl atoms from Ti atoms in the form of HCl. Preliminary molecular orbital (MO) calculations indicate that step (I) is an energetically easy process. Conversely, step (II) is expected to be the rate-determining process with a considerable activation energy. As a whole, the characteristics of resultant CVD films (e.g., the conformality) are probably controlled not by the TiCl4-adsorption step (I) but by the Cl elimination step (II).
Decay Kinetics for Isotropic Radicals in Carbonates
Authors: Debuyst René , Dejehet Fernand , Samira Idrissi Samira Idrissi
Published: October 2002

Electron spin resonance (ESR) signals of isotropic CO3
- and CO2
- radicals are frequently encountered in irradiated carbonates. These centers are thought to be surrounded by water molecules. Until now, their thermal annealing curves were generally described in terms of several simultaneous first order-reaction kinetics. A reinvestigation of some recent data allows us to conclude that, at sufficiently low temperatures, a second-order equal concentration dispersive kinetics suffices to reproduce satisfactorily the decays. When the annealing temperature approaches that of the water departure, this mechanism becomes inadequate. Mixed first-and second-order classical reaction and 1.5-order reaction kinetics have then been tentatively used.
Spin-Valve Memory Elements Using [{Co-Pt/Cu/Ni-Fe-Co}/Cu] Multilayers
Authors: Irie Yousuke , Sakakima Hiroshi , Satomi Mitsuo , Yasuhiro Kawawake Yasuhiro Kawawake
Published: October 2002

A new type of magnetoresistive memory using spin-valve multilayers composed of semi-hard magnetic layers and soft magnetic layers separated with nonmagnetic layers was developed. The fabricated memory element was composed of a word line of Au film and a magnetoresistive sense line of [{CoPt/Cu/NiFeCo}/Cu]

N

multilayers. This spin-valve memory has nonvolatile and nondestructive readout properties.
Photoelectron Spectroscopy of EuBa2Cu3O7-y Thin Film Surfaces Treated by an Electron Cyclotron Resonance Oxygen Ion Beam
Authors: Asano Hidefumi , Suzuki Minoru , Kiyokura Takanori , Maeda Fumihiko , Menz Andreas , Watanabe Yoshio , Masaharu Oshima Masaharu Oshima
Published: October 2002

Surface modification of EuBa2Cu3O7-
y

(EBCO) thin films induced by an electron cyclotron resonance (ECR) oxygen ion beam treatment has been studied using X-ray and synchrotron-radiation photoelectron spectroscopy (XPS and SRPES). The in situ characterization has been performed during the course of 50 eV ECR oxygen treatment for 30 min. Time-dependent analysis shows that the contaminant carbon layer on the surface region can be removed at the initial stage of the treatment (<2 min), and that the copper valence of the surfaces can be recovered to Cu2+ after 30 min treatment. It is found that room-temperature treatment using ECR oxygen can alter the contaminated, oxygen-depleted surface to a clean, well-oxygenated surface. The present results suggest that ECR treatment which can modify the surfaces in a well-defined manner would be a feasible technique for surface cleaning of high-temperature superconductors.
Electroabsorption of Photoconductive Azo Pigments
Authors: Umeda Minoru , Yokoyama Masaaki
Published: October 2002

Photoexcited states of fluorenone bisazo and triphenylamine trisazo pigments, both generating photocarriers extrinsically with the hole-transport-type arylamine molecules through the photoinduced electron transfer with high efficiency, were investigated by means of electromodulated absorption spectra. As a result, it was found that the former pigment forms a Frenkel exciton and the latter pigment a charge-transfer (CT) exciton. The different types of excitons well explained the photosensitivity of photoreceptors based on these two azo pigments.
Preparation and Magnetooptical Properties of Cd 1-xMnxTe Microcrystal-Doped SiO2 Glass Thin Films
Authors: Nasu Hiroyuki , Hayashi Masayuki , Matsuoka Jun , Kamiya Kanichi , Tanaka Katsuhisa , Hirao Kazuyuki
Published: October 2002

Semimagnetic semiconductor Cd1-
x

Mn

x

Te microcrystals were successfully embedded in SiO2 glass thin films by rf-sputtering. x could be increased to 0.8 without changing CdTe-type crystal structure. The optical absorption edge of the microcrystals in the films shifted to the higher-energy side compared to that for the bulk crystal, indicating the presence of the quantum size effect. Faraday-rotation was observed from the films, and their Verdet constant was comparable to those of commercial paramagnetic Faraday-rotation glasses although the volume fraction of the microcrystals was as small as 4%. The estimated Verdet constant of Cd0.2Mn0.8Te microcrystals itself was 10 times that of the corresponding bulk single crystal.
CFX (X=1-3) Radical Measurements in ECR Etching Plasma Employing C4F8 Gas by Infrared Diode Laser Absorption Spectroscopy
Authors: Miyata Koji , Takahashi Kunimasa , Kishimoto Shigeru , Hori Masaru , Toshio Goto Toshio Goto
Published: October 2002

CF, CF2 and CF3 radical densities were investigated in electron cyclotron resonance (ECR) plasma employing C4F8 (octafluoro-cyclobutane) and C4F8/H2 gases using infrared diode laser absorption spectroscopy.
  It was found that CF2 radical density in ECR C4F8 plasma was on the order of 1013 cm-3 at microwave power below 300 W and pressure of 0.4 Pa, which was quite high compared to CF and CF3 radical densities. With addition of H2 to C4F8 plasma, CF radical density increased markedly and the CF radical became dominant along with the CF2 radical. The mechanisms of these behaviors of radicals are discussed on the basis of these experimental results.
Micropattern of Inorganic Film Prepared by UV-Irradiation and Heat Treatment of Polyalkylsilyne Film
Authors: Watanabe Akira , Nagai Yoshinori , Minoru Matsuda Minoru Matsuda
Published: October 2002

A micropattern of inorganic thin film was formed by heat treatment of a polyalkylsilyne film at 300° C after UV irradiation with photomask. The Si-Si chain of spin-coated polyalkylsilyne film was photooxidized by UV irradiation with photomask in air. The XPS spectra showed that the Si-O-Si chain of the UV-irradiated part changed into SiO2 upon heat treatment in vacuo. On the other hand, the heat treatment changed the masked part into an a-Si-like structure with low optical band gap. The micrograph demonstrated lines of the irradiated area and spaces of the masked area.
Dynamic Electrooptic Effect Induced by Chromophore Motion in Poling Process
Authors: Shinji Aramaki Shinji Aramaki
Published: October 2002

Electrooptic and dielectric properties of a side-chain methacrylate polymer were studied as a function of frequency and temperature. Similar behaviors for the two dispersions were observed, which was attributed to the orientational motion of dipoles. The dispersion formula for the orientational electrooptic birefringence was derived, based on a rotational diffusion equation.
XeF Excimer-Laser Activation of Ion-Implanted Dopants in Hydrogenated Amorphous-Silicon Films
Authors: Kim Chang-Dong , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

XeF excimer-laser annealing was found to be very effective for activating ion-implanted dopants in hydrogenated amorphous-silicon (a-Si:H) films at room temperature, because of the low photon energy of the XeF excimer-laser light. The XeF excimer-laser-annealed a-Si:H films showed conductivity as high as 5×10-3 S/cm with the phosphorus atom dosage of 1×10-6 cm-2 without post-hydrogenation. With XeF excimer-laser annealing and ion implantation, the threshold voltage of a-Si:H thin-film transistors could be changed by more than 20 V without deterioration of on-characteristics.
In Situ Observations of GaAs Initial Growth on Si Substrates Studied Using an Ultrahigh-Vacuum Transmission-Electron Microscope/Molecular-Beam Epitaxy System
Authors: Yodo Tokuo , Tamura Masao , Tomita Masahiro , Wazawa Masahiro
Published: October 2002

An ultrahigh vacuum transmission-electron microscope equipped with a molecular-beam epitaxy chamber (UHV-TEM/MBE) has been constructed in order to observe the in situ heteroepitaxial growth stages of GaAs/Si. Preliminary in situ TEM observations of the initial growth stages of single-crystalline GaAs on vicinal (100) Si (thickness, 20-50 Å) were carried out using this UHV-TEM/MBE system under optimized growth conditions. The assignment of dislocations, stacking faults and/or twins, and the relation with the critical-size of islands were examined based on moire images in individual islands (size, 40-1000 Å) for the first time.
Coloration of Fluorophosphate Glasses Containing Fluorescein Molecules by Heat Treatment or Gamma Ray Irradiation
Authors: Nishida Tetsuaki , Sasaki Shigeo , Toma Tetsuya , Yonezo Maeda Yonezo Maeda
Published: October 2002

The 70SnF2·30P2O5 glasses containing 25-500 ppm of fluorescein exhibit change in color from light yellow to reddish orange (absorption maximum, λ=500 nm) when heated at 240° C for 120-180 min. The fluorophosphate glasses also change the color from light yellow to reddish brown (λ=480 nm) when irradiated with 60Co γ-rays of 5×104 Gy. The P-F stretching mode observed in the Fourier transformed infrared (FT-IR) spectra showed an increase in peak intensity along with the coloration, suggesting a cleavage of the weak chemical bond between fluoride ions ( F-) and fluorescein molecules. The coloration is ascribed to change of the molecular structure of fluorescein from non-crystalline to crystalline type. ESR spectra of γ-ray irradiated 70SnF2·30P2O5 glasses showed a poorly resolved doublet, which was ascribed to a hole-trapped PO3F- center produced by electron scattering: PO3F2-→PO3F-+e-.
Method to Determine the Effective Group Refractive Index of an Optical Waveguide Using a Steplike Optical Frequency Sweep Generator
Authors: Yoshizawa Akio , Ogura Mutsuo , Masahiko Mori Masahiko Mori
Published: October 2002

The effective group refractive index of an optical waveguide is measured by a steplike optical frequency sweep generator, in which a confocal Fabry-Perot cavity is employed as a frequency discriminator to determine the spacing between the steps. In the measurement, a DBR laser changes the carrier frequency stepwise with a 2 GHz frequency spacing. The accuracy is improved to be approximately 0.1%.
Band-Gap Renormalization and Excitonic Effects in Tunneling in Asymmetric Double Quantum Wells
Authors: Tackeuchi Atsushi , Heberle Albert P. , Rühle Wolfgang W. , Köhler Klaus , Muto Shunichi
Published: October 2002

Tunneling in asymmetric double quantum wells is studied using time-resolved photoluminescence. The photoluminescence lineshape and peak position of the narrow quantum well are strongly influenced by band-gap renormalization caused by the tunneling carriers. Tunneling is quenched in a field regime of ±10 kV/cm around the ground-state resonance due to excitonic effects.
Potential Sputtering of Protons from a Surface under Slow Highly Charged Ion Bombardment
Authors: Kakutani Nobukazu , Azuma Toshiyuki , Yamazaki Yasunori , Komaki Ken-ichiro , Kenro Kuroki Kenro Kuroki
Published: October 2002

Sputtering phenomena have been experimentally studied for slow highly charged ions ( 0.5-4.8 keV Arq+(q=4-16)). It is found that (1) the yield of proton sputtering from hydrogen-containing C60strongly increases with the charge state of the incident ion, (2) the energy spectra of sputtered protons consist of two components which are identified as potential sputtering and conventional kinetic sputtering, and (3) the peak energy and width of the potential sputtering component depend very weakly on the incident energy and the incident charge, which is consistent with the prediction of the classical-over-the barrier model.
In Situ Studies on X-Ray Diffraction and Resistance of Graphitelike Film during the First Redox Cycle and the Effect of 12 Crown 4
Authors: Roh Young Bae , Kawai Tsuyoshi , Araki Hisashi , Yoshino Katsumi , Takase Masaaki , Suzuki Takashi
Published: October 2002

Two characteristic X-ray diffraction peaks originated from electrolyte decomposition in graphitelike pyrolytic polymer prepared by pyrolysis at 2800° C. These peaks were clearly observed, with in situ X-ray diffraction measurements using a beryllium window, during the first discharge but they did not appear during the subsequent charge and discharge cycles. Upon addition of crown ether (12 crown 4) into the electrochemical cells, the two diffraction peaks attributed to the excessive electrolyte decomposition during discharge due to the cointercalation of solvent and lithium ions disappeared completely. The reversibilities of change in resistance and structure of graphitelike material (cathode) and also the capacity of the cell have been greatly improved.
Systematic Measurement of Critical Current Density for Narrow Y B a2C u3OyLines
Authors: Kusunoki Masanobu , Andoh Hiroya , Fujimaki Akira , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

Critical current densities (Jc's) of submicron YBa2Cu3Oy(YBCO) lines were studied. Increase inJcwith reduction of line width (w) was observed reproducibly, when temperature rise of the substrate is suppressed during plasma etching of YBCO. Intermittent etching and liquid-nitrogen cooling were very effective in obtaining sufficient cooling. Temperature dependence of current-voltage characteristics was interpreted in terms of thermally activated vortex motion. This result indicated the existence of a potential barrier to vortex motion. In particular, the surface barrier played an important role in determiningJcin the submicron lines. Furthermore, the dependence ofJconwwas strongly dependent on the current concentration to the edges due to Meissner effect.
Extended Broad-band Emission in Vacuum Ultraviolet by Multi-Rare-Gas Silent Discharges
Authors: Kubodera Shoichi , Honda Masanori , Kitahara Mitsuo , Kawanaka Junji , Sasaki Wataru , Kou Kurosawa Kou Kurosawa
Published: October 2002

We have demonstrated extended broad-band fluorescence emission in vacuum ultraviolet (VUV) by using silent discharges of rare gas mixtures. Two new VUV continua with considerably broad emission bandwidths have been observed, which have emission bandwidths of ∼30 nm [full width at half maximum] at center wavelength of 145 nm for an argon/krypton mixture and of 163 nm for a krypton/xenon mixture. A frequency-integrated average VUV emission power for a krypton/xenon continuum is 2.5 W, corresponding to a power conversion efficiency of 9.6%.
Classical Edge Magnetoplasmons in GaAs/AlGaAs Two-Dimensional Hole System
Authors: Masayoshi Tonouchi Masayoshi Tonouchi , Philip Hawker Philip Hawker , Mohammed Henini Mohammed Henini , Victor W. Rampton Victor W. Rampton
Published: October 2002

We have clearly observed classical edge magnetoplasmons (classical EMPs) in a two-dimensional hole system (2DHS) for the first time. The classical EMPs are excited in a GaAs/AlGaAs heterostructure by radio-frequency electric field excitation (≤1 GHz) in a high magnetic field B (≤5 T). The resonant frequency changes in almost inverse proportion to B, and its response is similar to that of EMPs in a two-dimensional electron system (2DES). However, the EMP excitation mechanism in the 2DHS seems to differ from that in the 2DES.
Migration of Metals on Graphite in Scanning Tunneling Microscopy
Authors: Masanori Ohto Masanori Ohto , Satoru Yamaguchi Satoru Yamaguchi , Keiji Tanaka Keiji Tanaka
Published: October 2002

Metals such as Au deposited on graphite substrates are found to migrate very easily when biased in scanning tunneling microscopes. Depending upon the film thickness and the tip voltage, a hillock surrounded by grooves or a hole surrounded by hillocks with a height of ∼±10 nm and a lateral dimension of ∼100 nm are formed. The mechanism of these surface-modification phenomena is discussed in light of electro- and thermomigration.
Self-Assembled Alkanethiol Monolayer on Patterned Gold Fabricated by Scanning Probe Anodization-Based Nanolithography
Authors: Sugimura Hiroyuki , Nakagiri Nobuyuki
Published: October 2002

Nanolithography based on scanning probe anodization was applied to fabricate Au structures on a silicon (Si) surface. A hydrogen-terminated Si (Si-H) substrate was first patterned by scanning probe anodization, and then treated in a gold (Au) electroless plating bath. The Au plating proceeded selectively on the Si-H surface where it was not anodized, while the anodized surface areas remained free from plating. Consequently, Au lines narrower than 100 nm were fabricated between the anodic oxide lines. A self-assembled monolayer (SAM) of n-hexadecyl mercaptan was formed onto the surface of these Au nanostructures. It was confirmed by Auger electron spectroscopy that the SAM formation was localized on the Au surface.
Cold Electron Emission from Electroluminescent Porous Silicon Diodes
Authors: Koshida Nobuyoshi , Ozaki Tsuyoshi , Sheng Xia , Hideki Koyama Hideki Koyama
Published: October 2002

It is demonstrated that electroluminescent porous silicon (PS) diodes operate as surface-emitting cold cathodes. The PS diode is composed of a semitransparent thin Au film, PS layer, n-type Si substrate and ohmic contact. When a sufficient positive bias voltage is applied to the Au contact in vacuum, the diode uniformly emits electrons as well as visible light. This cold emission is explained by the model that electrons are injected from the substrate, drifted by the field within the PS layer, and ejected as hot electrons through the thin Au film. This mode gives important insight for understanding the electroluminescence mechanism of PS, and shows the potential of PS devices not only for optoelectronic applications, but also for vacuum microelectronic ones.
Rubbing-Induced Molecular Orientation and Polarized Electroluminescence in Conjugated Polymer
Authors: Hamaguchi Maki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A preferred molecular orientation in a conjugated polymer, poly(2,5-dinonyloxy-1,4-phenylenevinylene) (NO-PPV), can be obtained by a unidirectional rubbing treatment of its thin solid film. Polarized electroluminescence with dichroic ratio of 1.6 as well as anisotropic optical absorption and photoluminescence have been observed for the rubbed NO-PPV film. An analysis of orientation distribution in the rubbed NO-PPV film suggested that radiative decay occurs in both oriented and unoriented layers. Surface geometry measurements suggested that plastic deformation of the polymer along the rubbing direction was the cause of the preferred orientation even in the conjugated polymer with rigid main chain structure.
InAs Island Formation Aligned along the Steps on a GaAs(001) Vicinal Surface
Authors: Ikoma Nobuyuki , Shunsuke Ohkouchi Shunsuke Ohkouchi
Published: October 2002

InAs island formation on a GaAs(001) substrate misoriented by 1° toward the [110] direction was investigated by scanning tunneling microscopy. On a 2.0ML InAs-deposited GaAs surface, three-dimensional islands were observed; some of the islands were aligned along the [11̄0] direction. That is, the islands were selectively formed at steps running relatively straight along the [11̄0] direction on the GaAs surface. These results show the possibility of controlling the arrangement of InAs islands on a surface by controlling the step structure on the surface, which induces selective island formation at the steps.
Accurate Evaluation of Silicon Planar Doping in InAlAs for InAlAs/InGaAs Modulation Doped Structure Grown by Metal Organic Chemical Vapor Deposition
Authors: Ito Hiroshi , Kurishima Kenji , Enoki Takatomo , Tomizawa Masaaki , Yasunobu Ishii Yasunobu Ishii
Published: October 2002

A method for accurately evaluating the sheet carrier concentration in the Si planar-doped InAlAs is presented. Using a five planar-doped layer structure in intentionally doped n-InAlAs, the influence of depletion layers on the sheet carrier concentration is effectively suppressed. The Si activation rate in InAlAs is found to be considerably higher than in previously reported results. A comparison between the experiments and calculations of the total sheet carrier concentration in an InAlAs/InGaAs modulation doped structure reveals that the influence of residual carriers in InAlAs layer should be considered in the layer structure design.
Reaction Engineering Modeling of Low-Pressure Metalorganic Chemical Vapor Deposition of Nb2O5 Thin Film
Authors: Jung Sang-Chul , Imaishi Nobuyuki , Park Heung-Chul
Published: October 2002

Thin films of niobium oxide (V) were prepared by low-pressure metalorganic chemical vapor deposition (LPMOCVD) from bis-dipivaloylmethanate niobium trichloride in a horizontal tube hot-wall reactor. The dependence of growth rate, crystal orientation, morphology and chemical composition on operating conditions were studied experimentally. The profile of the thin film grown on microscale trenches and the macroscopic growth rate distribution in the reactor were studied by micro/macro-numerical simulations.
\bfiIn Situ IR Spectroscopic Study of the Reaction of Dimethylaluminum Hydride with Photochemically Deposited Amorphous Silicon
Authors: Toshimasa Wadayama Toshimasa Wadayama , Yoshihisa Maiwa Yoshihisa Maiwa , Hironobu Shibata Hironobu Shibata , Aritada Hatta Aritada Hatta
Published: October 2002

The reaction of dimethylaluminum hydride (DMAH) with photochemically deposited hydrogenated amorphous silicon (a-Si:H) has been studied in situ with polarization modulation IR spectroscopy. Below 473 K, the absorption bands due to SiH3 species incorporated in the a-Si:H completely disappear upon exposure to DMAH under UV illumination while those due to SiH2 species remain nearly unchanged. The intensity reduction of the SiH2 absorption bands is observed above 473 K. These spectral changes are observed only in early stages of DMAH exposure. These results suggest that DMAH reacts with SiH3 species present on the topmost surface of the a-Si:H film.
Thermal Stability in Al/Ti/GaAs Schottky Barrier
Authors: Hara Tohru , Zhu Jian Yao , Mochizuki Akira , Asai Syuji , Higashisaka Asamitsu , Kohzu Hideaki
Published: October 2002

Interfacial reaction occurs at the Al/Ti interface in the Al/Ti/GaAs Schottky barrier at low temperatures. Therefore, the barrier layer is required between Al and Ti layers to manufacture thermally stable Al/Ti/GaAs Schottky gates in metal semiconductor field effect transistors (MESFET's). In this study, a double layer of Ti2Ga3 and TiAs is formed by interfacial reaction at the Ti (30 nm thick)/GaAs interface at 450° C. In the double layer, Ti2Ga3 is employed as the barrier layer for Al and the TiAs layer as the Schottky electrode with high barrier height. Interfacial reaction does not occur at the Al/Ti2Ga3 interface with annealing at 450° C and a thermally stable Al/Ti2Ga3/TiAs/GaAs Schottky gate can be obtained by employing the Ti2Ga3 barrier layer formed by this interfacial reaction. Moreover, barrier height can be increased by 0.12 eV in the TiAs/GaAs Schottky gate from that of the Ti/GaAs gate. We describe the barrier effect of the Ti2Ga3 layer for Al.
Dose Dependence of Recrystallization Behavior in Germanium-Ion-Implanted Polycrystalline Silicon Films
Authors: Myeon-Koo Kang Myeon-Koo Kang , Takayuki Matsui Takayuki Matsui , Hiroshi Kuwano Hiroshi Kuwano
Published: October 2002

Recrystallization behavior in polycrystalline silicon (poly-Si) films amorphized by germanium ion (Ge+) implantation on a SiO2 layer is investigated. The nucleation rate decreases as the Ge+ dose increases, which is strongly related to the increase in the disordered states in as-implanted amorphous Si films. The growth rate first increases and then decreases as the Ge+ dose increases, which can be explained by the strain effect induced by Ge atoms. The grain size of recrystallized poly-Si films increases as the Ge+ dose increases. The optimum implantation dose to achieve good crystallinity is found to be 1×1015 ions/cm2.