bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of Dark Current Density of AlInAs/InGaAs Metal-Semiconductor-Metal Photodetector Using Phosphine-Plasma-Treated Schottky Barrier
Authors: Daiji Hirata Daiji Hirata , Takashi Sugino Takashi Sugino , Junji Shirafuji Junji Shirafuji 
Published: October 2002

AlInAs/InGaAs metal-semiconductor-metal (MSM) photodetectors with a low dark current density are fabricated using a surface modification process with phosphine (PH3) plasma. Phosphidization of the AlInAs cap layer reduces the surface state density and allows formation of high Schottky barrier with a tunnel metal-insulator-semiconductor (MIS) structure. A dark current density as low as 0.021 pA/µm2 at 10 V is obtained.
Long Term Operation of a CW Doubly Resonant Optical Parametric Oscillator
Authors: Takeshi Ikegami Takeshi Ikegami , Sergey Slyusarev Sergey Slyusarev , Shin-ichi Ohshima Shin-ichi Ohshima , Eiichi Sakuma Eiichi Sakuma 
Published: October 2002

Long-term operation of a cw doubly resonant optical parametric oscillator was demonstrated. The minimum threshold was 9mW and the slope efficiency was 25%. Using a rigid structure cavity and a stable pump laser, it operated in a single longitudinal signal-idler mode pair for over 3 h without any mode hopping.
Microscopic Brillouin Scattering Study in TeO2: Pressure Dependence of Acoustic Modes
Authors: Muhtar Ahart Muhtar Ahart , Takehiko Yagi Takehiko Yagi , Yasunari Takagi Yasunari Takagi 
Published: October 2002

The pressure-induced ferroelastic transition of TeO2is investigated in detail using microscopic Brillouin scattering in the backward geometry as a function of pressure. Both the quasi-transverse mode (T') and the quasi-longitudinal mode (L') are measured from 1 atm. to 2 GPa (transition pressurePc=0.9 GPa), using a diamond anvil cell for various propagation directions of phonons, of which the deviations ψ from [110] are 2.3°, 4°, 7.6°, 25°, 35°, and 45°. TheT'-mode frequency for 2.3° decreases to the lowest value of ∼1.37 GHz atPc. Experimental results are generally explained on the basis of the Landau theory of the ferroelastic transition under pressure. It is concluded that the phase transition of the TeO2crystal is driven by a soft acoustic mode. However, for the mode at ψ=45° corresponding to the pure longitudinal modeC11, an elastic anomaly found in the neighborhood ofPcis larger than that for other modes.
Measurements of Absorption Coefficients in the Deep-Sea Area
Authors: Umezawa Masaaki , Tsuchiya Toshio , Kikuchi Toshiaki , Hashimoto Akio Hasegawa 
Published: October 2002

In order to design deep-sea acoustic devices, it is very important to estimate the sound absorption loss in the deep sea. It is known that there is a discrepancy between the measured absorption loss in a water tank and that in the deep sea. We have measured the sound absorption losses in the deep sea using the deep submergence vehicle “SHINKAI 6500” of the Japan Marine Science and Technology Center (JAMSTEC). Our data are close to those measured in the laboratory by Fisher. [rf:1] It appears that absorption loss decreases quadratically as a function of depth.
Evaluation of Surface Defects Using Surface Acoustic Waves Generated by Phase Velocity Scanning of Laser Interference Fringes
Authors: Harumichi Sato Harumichi Sato , Hideo Cho Hideo Cho , Hideo Nishino Hideo Nishino , Hisato Ogiso Hisato Ogiso , Kazushi Yamanaka Kazushi Yamanaka 
Published: October 2002

In order to maintain the reliability of structural materials such as ceramics, it is important to nondestructively detect surface defects that reduce the strength of materials. Therefore, we have developed the phase velocity scanning (PVS) method. The PVS method does not involve the use of coupler (noncontact) and has excellent directivity. We report that the sensitivity for detecting surface acoustic waves (SAW) was improved using a video signal. The video signal S/N ratio, which is defined as the ratio of generated SAW to background noise, is 46.5 dB. Back propagation waves were not detected within the limit of the S/N ratio. Utilizing this excellent directivity we succeeded in B-mode imaging to detect indentation cracks (Knoop indentation cracks). Scattered waves were detected on the indentations of above 100 gf but could not be detected for those of below 50 gf. This result implies that this method can be used to evaluate the critical load of initiating median cracks which is difficult using conventional methods.
Analysis of Acoustic Field in Liquid Radiated by Dispersive Surface Acoustic Wave Transducer
Authors: Nobuhiro Tasaki Nobuhiro Tasaki , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai 
Published: October 2002

We obtained images of the acoustic field radiated from a dispersive surface acoustic wave (SAW) device by numerical calculation and by experiment in order to control the field by varying the frequency. First, a numerical calculation using Smith's equivalent circuit taking loss into account was carried out. Then we produced a transducer using a dispersive SAW device driven in liquid. We made an experiment using the transducer and visualized the radiated acoustic field by the Schlieren method to confirm the validity of the calculation method. The transducer can be used to scan radiating positions over a distance of 9 mm for driving frequencies in the range of 1.5–2.5 MHz. The numerical results agree well with the experimental ones.
Study of Quasi-Two-Dimensional Hole Gas in Si/SixGe1-x/Si Quantum Wells
Authors: Sanghoon Cheon Sanghoon Cheon , Seungchang Lee Seungchang Lee , Songcheol Hong Songcheol Hong , Kyeonghwa Yoo Kyeonghwa Yoo 
Published: October 2002

Quasi-two-dimensional hole gas in strained Si/SixGe1-x
/Si quantum well structure is investigated both theoretically and experimentally. The hole effective mass and the charge distribution in the structure are obtained from the self-consistent solution of the Schr\ddotodinger-Poisson equations. The calculation results show the dependence of the averaged mass on the measurement temperature and the averaged mass of 0.20 m
0 at T = 4 K. High quality Si/Si0.8Ge0.2/Si p-type modulation-doped quantum well is grown by molecular beam epitaxy and the electrical properties measured. Hall mobility as high as ∼10,400 cm2/V·s with a sheet carrier concentration of ∼1.1 ×1012 cm-2 and an effective mass of ∼0.30 m
0 is obtained at T = 4 K.
Lower-Temperature Growth of Hydrogenated Amorphous Silicon Films from Inductively Coupled Silane Plasma
Authors: Masashi Goto Masashi Goto , Hirotaka Toyoda Hirotaka Toyoda , Masatoshi Kitagawa Masatoshi Kitagawa , Takashi Hirao Takashi Hirao , Hideo Sugai Hideo Sugai 
Published: October 2002

A high-density (1011 cm-3) inductively coupled plasma at low pressure (0.1 Pa) of SiH4 enables the growth of hydrogenated amorphous silicon films of high photoconductivity (10-5 S/cm) at substrate temperatures ( <100 °C) considerably lower than that with a conventional capacitive rf plasma. Such low-pressure high-power discharges were achieved by inserting a loop antenna into a plasma with magnetic multipole confinement. Thus, this type of rf reactor appears to be promising to realize high-speed deposition of large-area a-Si:H films at room temperature.
Generation of Ultrashort (∼ 65 fs) Pulses from 1.55 µ m Gain-Switched Distributed Feedback (DFB) Laser with Soliton Compression by Dispersion Arrangements
Authors: Masanao Miyamoto Masanao Miyamoto , Masahiro Tsuchiya Masahiro Tsuchiya , Hai-Feng Liu Hai-Feng Liu , Takeshi Kamiya Takeshi Kamiya 
Published: October 2002

We report the successful generation of optical pulses (∼ 65 fs) from a 1.55 µm gain-switched distributed feedback semiconductor laser with fiber optic compression techniques by a novel dispersion arrangement. These pulses are the shortest ever generated starting from a semiconductor laser diode and are promising for practical applications in ultrafast photonic systems.
Improved Morphology and Surface Resistance of EuBa 2Cu 3O 7-δ Thin Films on MgO Substrates Obtained by Intermittent Magnetron Sputter Deposition
Authors: Koji Tsuru Koji Tsuru , Shin-ichi Karimoto Shin-ichi Karimoto , Shugo Kubo Shugo Kubo , Minoru Suzuki Minoru Suzuki 
Published: October 2002

We demonstrate that the surface morphology of off-center magnetron sputtered EuBa2Cu3O7-δ (EBCO) thin films on MgO (100) substrates is improved significantly by using the intermittent deposition method. This method comprises three steps. First, an initial EBCO layer, 2 to 10 unit cell layers thick, is grown at 630–660°C under a low oxygen partial pressure of 0.1 Pa. Then the initial layer is in situ annealed for 30 min under the same conditions used for the deposition. Finally, another EBCO layer is grown on top of the first layer. An EBCO thin film grown in this way has an extremely smooth surface and the surface resistance at 50 GHz is 3 mΩ or less at 77 K, which compares with the best value ever reported.
High-Tc Superconductor-Insulator-Superconductor Heterostructures with Highly Resistive Insulator Layers
Authors: T. Frey T. Frey , J. Mannhart J. Mannhart , J. G. Bednorz J. G. Bednorz , E. J. Williams E. J. Williams 
Published: October 2002

Trilayers in which a dielectric or ferroelectric film such as SrTiO3, BaTiO3 or Ba

x

Sr1-
x

TiO3 separates two layers of a high-T
c superconductor are required for many device applications of high-T
c materials. To clarify the mechanism limiting the insulation properties of the insulating layer, the microstructure of such samples was analyzed using transmission electron microscopy. These studies suggest that diffusion along threading dislocations or along grain boundaries in the insulating layer lowers its resistivity. Substitution of the insulating monolayer with a bilayer increases the resistivity from ≃1011 to 3×1013 Ω· cm (at 2×105 V/cm, below 100 K). To our knowledge, this is by far the highest resistivity achieved in such heterostructures.
Nanolithography Using Fullerene Films as an Electron Beam Resist
Authors: Tetsuya Tada Tetsuya Tada , Toshihiko Kanayama Toshihiko Kanayama 
Published: October 2002

Electron beam (e-beam) irradiation has been found to reduce the dissolution rate of evaporated C60 films in organic solvents such as monochlorobenzene, which shows that this material acts as a negative e-beam resist with a sensitivity of 1×10-2 C/cm2. It has higher dry-etch durability than conventional novolac resists. Its applicability to nanofabrication has been demonstrated by fabricating Si pillars of 20–30 nm diameter using electron cyclotron resonance microwave plasma etching and dot patterns defined in the C60 film as etching masks.
InGaN-Based Multi-Quantum-Well-Structure Laser Diodes
Authors: Nakamura Shuji , Senoh Masayuki , Nagahama Shin-ichi , Iwasa Naruhito , Yamada Takao , Matsushita Toshio , Hiroyuki Kiyoku Hiroyuki Kiyoku , Yasunobu Sugimoto Yasunobu Sugimoto 
Published: October 2002

InGaN multi-quantum-well (MQW) structure laser diodes (LDs) fabricated from III-V nitride materials were grown by metalorganic chemical vapor deposition on sapphire substrates. The mirror facet for a laser cavity was formed by etching of III-V nitride films without cleaving. As an active layer, the InGaN MQW structure was used. The InGaN MQW LDs produced 215 mW at a forward current of 2.3 A, with a sharp peak of light output at 417 nm that had a full width at half-maximum of 1.6 nm under the pulsed current injection at room temperature. The laser threshold current density was 4 kA/cm2. The emission wavelength is the shortest one ever generated by a semiconductor laser diode.
High-Conversion-Efficiency Solar Cell Using Fluorescence of Rare-Earth Ions
Authors: Ryouhei Nakata Ryouhei Nakata , Naoaki Hashimoto Naoaki Hashimoto , Katsuyasu Kawano Katsuyasu Kawano 
Published: October 2002

An experiment was performed to obtain a high-conversion-efficiency solar cell by shifting UV-region sunlight to the visible region, in which the optical absorption and emission properties of rare-earth Eu activator ions were exploited. A thin disc of CaF2:Eu single crystal was used as an alternative to the antireflection (AR) film in a solar cell. The effectiveness of rare-earth ions was examined. Their relative efficiencies were found to be higher at Eu concentrations from 0.001 to 2 mol%, with a maximum value of 1.5 at 0.05 mol%, than those of nondoped crystal when subjected to low illuminance by a Xe-lamp-based solar simulator. For the purpose of putting the crystal to practical use as an AR film, rare-earth ions were implanted into CaF2 crystal at a dose of 1014–1015 ions/cm2 and an energy of up to 140 keV.
Estimation of Dislocation Concentration in Plastically Deformed Al–Li Based Alloy by Positron Annihilation
Authors: Mamdouh Abdelrahman Mamdouh Abdelrahman 
Published: October 2002

Measurements of positron annihilation mean lifetime τ have been performed on eight different specimens of Al–Li based alloy plastically deformed at room temperature up to 40% thickness reduction. This measurement shows clearly positron trapping by dislocations. The positron lifetime τ exhibits a saturation for deformations larger than (15%) thickness reduction. The fitted lifetime varies from (183 ±2 ps) for annealed sample to (205 ±2 ps) for the dislocation saturated value. Using a trapping model, the data yield the values of µ= 3.83×10-8 cm3 s-1 for the specific trapping rate and σ= 3.58×10-15 cm2 for the trapping cross section, some what lower than those for plastically deformed Al single crystals. The value obtained for Δτ, the increase in lifetime of positrons trapped at dislocations in plastically deformed Al–Li based alloy sample over annihilation in the annealed sample, is 22 ps. This is about 40% of the lifetime increase for the case of positrons trapped at dislocations in plastically deformed Al single crystals. Dislocation densities at different thickness reduction have been estimated.
Oxynitridation of Silicon Using Helicon-Wave Excited and Inductively-Coupled Nitrogen Plasma
Authors: Yoshinaga Okamoto Yoshinaga Okamoto , Shinjiro Kimura Shinjiro Kimura , Hideaki Ikoma Hideaki Ikoma 
Published: October 2002

Si was oxynitrized (and/or nitrized) in both helicon-wave-excited and inductively-coupled N2 or N2+Ar mixed plasma. Fairly good capacitance-voltage (C–V) characteristics were obtained after post-thermal annealing at 400°–500°C for 30 min in nitrogen ambient. X-ray photoelectron spectroscopic (XPS) measurements showed that chemically stoichiometric Si oxynitride, Si2 N2 O, was uniformly formed throughout the whole film thickness at a flow-rate ratio of N2 of 80% in a N2 + Ar mixed plasma (N2:Ar = 8:2). On the other hand, SiO2 was formed at the outer surface while Si2 N2O was formed in the middle portion of the film and near the interface between the grown film and Si, when the flow-rate ratio of N2 was less than about 80%. The growth rate and the degree of “nitridation" were maximum at flow-rate ratio of N2 of 80%. The leakage current in the film was found to be mainly the Fowler-Nordheim-type tunneling current.
Diamond Growth by Dual Hollow Cathode Arc Chemical Vapor Deposition
Authors: Gou-Tsau Liang Gou-Tsau Liang , Franklin Chau-Nan Hong Franklin Chau-Nan Hong 
Published: October 2002

A new design for a dual hollow cathode arc chemical vapor deposition system is used to grow diamond films. The inner hollow cathode is the primary thermionic emission source. The outer hollow cathode magnified the discharge current. Contrary to the single hollow cathode chemical vapor deposition, the dual hollow cathode chemical vapor deposition can deposit diamond films free of cathode contaminants, and therefore, enhance the film quality. With the aid of electron bombardment of the substrate, the dual cathode design can grow diamond films of good crystalline quality, and with a high growth rate, 2.3 µ/h, even at a high CH4 concentration such as 10% and at a low pressure of 15 Torr.
Observation of Vicinal Si(111)7×7 Surface by Energy-Filtered Reflection High-Energy Electron Diffraction
Authors: Yoshimi Horio Yoshimi Horio , Yasuyuki Hashimoto Yasuyuki Hashimoto 
Published: October 2002

Extra spots near the specular spot have clearly been observed for a vicinal Si(111)7×7 surface by zero-loss energy-filtered reflection high-energy electron diffraction (EF-RHEED) at [112] incidence with 10 kV electron beam. The extra spots are distributed in a line across the specular spot. From the geometrical consideration of these extra spots, the mean terrace length parallel to the [112] direction was reasonably estimated based on a regularly arranged step surface with single step height. Glancing angle dependences of the extra spots were also simulated, and good agreement with the experimental results was obtained.
Electroluminescence from an InGaAs-Based High Electron Mobility Transistor Designed for High-Speed Operation
Authors: Naoteru Shigekawa Naoteru Shigekawa , Takatomo Enoki Takatomo Enoki , Tomofumi Furuta Tomofumi Furuta 
Published: October 2002

The electroluminescence (EL) of an InGaAs-based high electron mobility transistor (HEMT) designed for high-speed operation was first investigated by cleaving the device and measuring the EL coming from the exposed side of the channel. The gate length and the gate-source separation of the HEMT were 0.1 and 0.55 µm, respectively. We observed the EL attributed to the recombination of the majority electrons and the ionization-induced holes in the InGaAs channel for a drain-source voltage larger than 1.3 V. This means that the EL is useful for evaluating the impact ionization in such devices. Furthermore we proposed an expression relating the EL intensity to the concentration of the holes at the source edge, and investigated the gate-source voltage (V
GS) dependence of the concentration. We found that their concentration reveals a peak at V
GS=-0.4 V.
Development of an Ion and Electron Dual Focused Beam Apparatus for Three-Dimensional Microanalysis
Authors: Tetsuo Sakamoto Tetsuo Sakamoto , Zhaohui Cheng Zhaohui Cheng , Masanori Takahashi Masanori Takahashi , Masanori Owari Masanori Owari , Yoshimasa Nihei Yoshimasa Nihei 
Published: October 2002

We are developing a novel three-dimensional (3D) microanalysis method by means of successive cross-sectional Auger mapping. In this method, a 3D elemental map will be obtained by repetition of the cross-sectioning of a sample using a gallium focused ion beam (Ga FIB) and Auger mapping of the cross section using an electron beam (EB). On the basis of this concept, an ion and electron dual focused beam apparatus was developed by combining a Ga FIB and a mass spectrometer with a scanning Auger microprobe. In this paper, we describe the concept and instrumentation of the dual focused beam apparatus. Two types of preliminary experiments; i) successive cross-sectioning of a microparticle (6.8 µmφ) and ii) successive cross-sectional sample current imaging of a bonding wire of an IC, demonstrated the capability to create flat analytical surfaces favorable for the 3D analysis with arbitrary shape and heterogeneity.
Brillouin Scattering in B2O3–Li2O–LiCl Glass
Authors: Yamada Jun-ichi , Shirakawa Yoshiyuki , Iida Takamichi , Matsukawa Mami , Ohtori Norikazu , Umesaki Norimasa 
Published: October 2002

Brillouin scattering measurement has been carried out in B2O3–Li2O–LiCl glass. The observed Brillouin frequency shift increases with
the addition of a modifier element (both Li2O and LiCl). However, if the
ratio of B2O3 to the modifier is a constant, Brillouin frequency shift
decreases with increasing LiCl concentration. In order to obtain
additional information on the local structure, Raman scattering and
density measurements have been performed. Raman spectra have been
observed as a distinct peak near 780 cm-1 which shows the formation of
tetrahedrally coordinated boron. By increasing LiCl concentration, the
Raman band near 780 cm-1 decreases, but the band near 806 cm-1
increases. This illustrates the breathing motion of oxygen in a boroxol
ring. This result indicates that LiCl mainly modifies the B2O3 network
without forming tetrahedrally coordinated boron.
By comparing the glass transition temperature (T
g) obtained from
the temperature dependence of the Brillouin frequency shift with that
from the results of differential scanning calorimetry (DSC) measurement,
it is observed that both the values of T
g almost agree. The concentration
dependence of T
g is discussed in terms of viscosity.
Integrated Hologram Pickup with an Optical Waveguide Device for Magnetooptical Disk Players
Authors: Yoshida Yoshio , Minami Koji , Yoshimoto Akihito , Yamamoto Hiroyuki , Kurata Yukio 
Published: October 2002

An integrated magnetooptical (MO) pickup is developed with an optical
waveguide device that can detect the MO signal. In this pickup, the optical waveguide
device is mounted in a package with a laser diode and a photodiode for servo signal
detection, so all optical functions are integrated into a unit except a light converging
function. The optical waveguide device is constructed with a prism coupler, a thin-film
bi-prism and four PIN photodiodes, on a 1 mm×2 mm Si substrate. The optical
utilization efficiency and the extinction ratio of the device are more than 50% and 1 : 10,
respectively. The carrier-to-noise ratio of the signal reproduced with this pickup
reaches up to 45 dB.
Electronic Structures and Chemical Bonding of TiX2(X=S, Se, and Te)
Authors: Kim Yang-Soo , Mizuno Masataka , Tanaka Isao , Adachi Hirohiko 
Published: October 2002

A systematic study of the electronic structures and chemical bonding of the titanium dichalcogenide TiX2(X=S, Se, and Te) layered structures is performed by a first-principles molecular orbital calculation using the discrete-variational (DV)-Xα cluster method. The intra- and interlayer chemical bonding properties are also investigated using the bond overlap population. Valence band structures obtained by the calculation are in good agreement with experimental results obtained by X-ray photoemission spectroscopy. Each peak in the density of states (DOS) is identified from the viewpoint of chemical bonding. There is a considerably strong covalent bonding between Ti and chalcogen atoms in TiX2. The covalency of chemical bonding is shown to increase and the ionicity to decrease in the series of TiS2–TiSe2–TiTe2. Both in intra- and interlayer chalcogen-chalcogen bonding and intralayer Ti–Ti bonding are much weaker than Ti-chalcogen intralayer bonding. However, interlayer interaction is found to be not purely of the van der Waals type.
Development of an Ultrashort-Pulse Reflectometer for Density Profile Measurements on GAMMA 10
Authors: Jr. Shigeyuki Kubota 
Published: October 2002

An ultrashort-pulse reflectometer is under development for electron density profile and fluctuation measurements on the GAMMA 10 tandem mirror. At the heart of the system is an impulse generator which creates an 8 V, 65 ps full-width half-maximum pulse. Data was taken at the midplane of the GAMMA 10 central cell. The incident wave was launched with ordinary-mode polarization and frequency components of the reflected wave in the range 8–10 GHz were detected. The observed values of the time-of-flight are in rough agreement with those obtained from calculations using the Abel-inverted profile obtained from a 70 GHz microwave interferometer. These results suggest that the present system can be expanded to yield a reliable diagnostic for electron density profile measurements.