bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Switching Speed in Acoustooptic Switches for Multiple Optical Wavelength using Gigahertz Surface Acoustic Waves
Authors: Nobuo Goto Nobuo Goto , Yasumitsu Miyazaki Yasumitsu Miyazaki
Published: October 2002

Collinear acoustooptic (AO) devices have unique wavelength-selective switching characteristics and are applicable to wavelength-division-multiplexing photonic switching systems. However, conventional AO devices require a switching time of a few µs. In this paper an improvement of the optical switching speed is discussed. In order to increase the switching rise-time to less than a few hundred ns, gigahertz surface acoustic waves (SAWs) are used to induce mode conversion with a short AO interaction length. The optical switching characteristics of the proposed device are theoretically discussed. Crosstalk between wavelength channels, which is accompanied by switching, is also discussed.
Relationship between Cavitation Threshold and Dissolved Air in Ultrasound in the MHz Range
Authors: Naito Tamotsu , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Ide Masao
Published: October 2002

Bioeffects caused by high power ultrasound in medicine must be understood. A
significant cause of bioeffects is cavitation. This paper reports on the relationship between
cavitation threshold and the amount of dissolved air for ultrasound in the MHz range used
mainly in medicine. The cavitation threshold varies according to the amount of dissolved
air in water and the frequency of ultrasound.
Transmission Conditions of Vibration Stresses to Welding Specimens of Ultrasonic Plastic Welding using Various Two-Vibration-System Equipments
Authors: Tsujino Jiromaru , Uchida Takako , Ohkusa Kunifumi , Adachi Tatsuya , Ueoka Tetsugi
Published: October 2002

Ultrasonic plastic welding is applied for welding various thermoplastic materials and is widely
used in various industrial fields. The two-vibration-system welding method and a high
frequency equipment are effective in improving the welding characteristics. A high frequency 90 kHz
system can weld plastic sheets under a 1/3 velocity amplitude as compared with that of a
low 27 kHz system, but it is difficult to weld large specimens successfully because a high
frequency vibration stress cannot be transmitted uniformly due to the stress relaxation effect by
the small vibration displacement. To improve the direct welding characteristics, three types of
two-vibration-system ultrasonic welding equipments using linear vibration loci of (1) 90 kHz
and 27 kHz longitudinal vibration systems, (2) 90 kHz longitudinal and 20 kHz torsional
vibration systems, and elliptical vibration loci of (3) 27 kHz complex vibration systems are
studied. Transmission conditions of the vibration stresses are measured by pressure sensitive
films (Prescale) which are inserted between the plastic sheets. It was shown that a high
frequency vibration stress with a small displacement amplitude may be induced uniformly in the
welding specimens by combining a low frequency vibration with large displacement amplitude.
These welding systems are effectively used to join plastic sheets successfully.
Ultrasonic Imaging Reconstructed from the Inclination Angle of a Smooth Surface
Authors: Koichi Mizutani Koichi Mizutani , Michitoshi Noguchi Michitoshi Noguchi , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

We propose a method for acoustical imaging, reconstructed from the inclination angle of a smooth surface. The detected inclination image is a differential image of the original geometry. The sensing unit consists of an ultrasonic transmitter and two ultrasonic receivers. Three transducers are kept facing an object. The inclination angle of the object surface depends on the phase difference between the two detected signals. Finally, the geometry of the object is reconstructed from the integration of the measured inclination image. Good experimental results were obtained in the reconstruction of a slightly ablated aluminum plate with an area of approximately 95×145 mm2, and a concave mirror with an area of approximately 115×115 mm2, at the frequency of 2.0 MHz. The spatial resolution corresponded to a transducer interval. This method has the advantage in that it can be used for industrial measurements and for medical diagnostics.
Tomographic Data Collection of Sonic Fields Using Laser Diffraction
Authors: Masahiro Yoshioka Masahiro Yoshioka , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

In this work, we construct an experimental setup for collecting tomographic data of sonic fields using laser diffraction. The advantage of using light is that measuring sonic fields without contact is possible. Compared with other tomographic imaging techniques of sonic fields, the structure of our setup is simple. We reconstruct the amplitude and phase images of the sonic field radiated from a piezoelectric transducer. Finally, we confirm that we can collect tomographic data which correspond to the character of the transducer.
Real-Time Three-Dimensional Velocity Vector Measurement using the Weighted Phase Gradient Method
Authors: Naotaka Nitta Naotaka Nitta , Tsuyoshi Shiina Tsuyoshi Shiina
Published: October 2002

Although the technique for measuring blood flow based on the ultrasonic
Doppler method is an important means for clinical diagnosis, it is
inappropriate for quantitative assessment of blood flow since the true
three-dimensional (3-D) velocity component cannot be obtained in many cases.
In this paper, to overcome the restriction,
a new method of 3-D velocity vector measurement is proposed. By detecting
the gradient of the weighted phase shift distribution on the receiving
aperture, the proposed method enables us to employ a smaller single aperture
compared with those used in conventional techniques, and its sensitivity is
independent of the direction of transverse flow.
Furthermore, real-time measurement can be realized since the autocorrelation
technique is utilized for the phase shift extraction as well as the present
Doppler method.
The basic performance of the method is evaluated by computer simulation.
Moreover, sector scan imaging is constructed by the proposed method and
compared with the conventional method. The obtained results validated
the feasibility and ability of the proposed method for measuring 3-D velocity.
Estimation of Elastic Constants from Surface Acoustic Wave Velocity by Inverse Analysis using the Downhill Simplex Method
Authors: Harumichi Sato Harumichi Sato , Hideo Nishino Hideo Nishino , Hideo Cho Hideo Cho , Hisato Ogiso Hisato Ogiso , Kazushi Yamanaka Kazushi Yamanaka
Published: October 2002

The measurement of surface acoustic wave (SAW) velocity is used to estimate the surface properties because the velocity depends on the elastic properties near the surface.
To estimate the elastic constants, we developed a new inverse method combining the Monte Carlo method and the downhill simplex method.
The initial values are determined using many random numbers, instead of an arbitrarily chosen several sets of values, in order to reduce the risk of trapping by the local pseudo minima.
We confirm that the estimated elastic constants agree well with the reported elastic constants of Si and the experimental SAW velocity is quite well reproduced.
We estimate the elastic constants of quartz for application purposes.
Study on Photopyroelectric Signal of Optically Opaque Material Measured by Polyvinylidene Difluoride Film Sensor
Authors: Minamide Akiyuki , Shimaguchi Masayasu , Tokunaga Yoshiaki
Published: October 2002

In this paper, we propose a new one-dimensional model to analyze a
photopyroelectric signal of optically opaque materials measured by a
polyvinylidene difluoride (PVDF) film sensor. This model is considered three layers
(sample, air gap and the PVDF film) and the reflections of the thermal wave at the
interfaces of each layer. In order to check the validity of the proposed model, we
measure the inclination of the frequency dependence of the signal measured by
the PVDF film and compare it with a theoretical value. When laser light is
irradiated onto a graphite surface on the PVDF film, the measured inclinations
are -1.6 for a 9 µm PVDF film, -1.8 for a 28 µm film and -2.0 for a 110 µm film.
These inclinations were comparable with the simulated inclinations in the cases
of all the film thickness of the PVDF film considered.
Enhancement of Silicon Epitaxy by Increased Phosphorus Concentration in a Low-Energy Ion Bombardment Process
Authors: Kumami Hajime , Shindo Wataru , Ino Kazuhide , Ohmi Tadahiro
Published: October 2002

For a low-energy (<30 eV) ion bombardment process, the effect of phosphorus concentration
on low-temperature (350–400°C) silicon epitaxial growth is reported. The conditions of ion energy and ion
flux required for realizing low-temperature epitaxial growth were precisely investigated.
We found that phosphorus doping significantly enhanced silicon epitaxial growth. It
is difficult to realize high-quality film growth with lightly phosphorus-doped silicon. However,
large-mass, large-radius ion (xenon) bombardment is quite effective for improving the quality
of silicon film with lightly phosphorus-doped silicon.
In Situ Infrared Spectroscopy on the Wet Chemical Oxidation of Hydrogen-Terminated Si Surfaces
Authors: Sugita Yoshihiro , Watanabe Satoru
Published: October 2002

In situ infrared spectroscopy was used to observe the early stage of oxidation on hydrogen-terminated
Si(100) and (111) in solution. The observation confirmed that the oxidation starts with the insertion
reaction of oxygen atoms to the back bonds of the topmost silicon atoms in H2O2 solution. It was
found both that the back bond and Si–H bond were oxidized in ozonized water. The dependence of
the oxidation reaction of the Si–H bond and its back bond on surface orientation was discussed and
the evidence of island growth of the oxide film was shown.
Improved Blocking Voltage in Diode with Neutron-Transmutation-Doped Silicon by Field Oxide Annealed in N2O
Authors: Chang-Liao Kuei-Shu , Chen Chung-Hsien
Published: October 2002

The blocking voltage in diode (i.e., PN junction) using neutron-transmutation-doped
Si can be improved by a field oxide annealed in N2O. It is experimentally
determined that the reverse breakdown voltage is clearly increased although the
ideality factor and leakage current density increase slightly. The improvement of
blocking voltage may be due to the replacement of strained Si–O bonds by Si–N
bonds in the field oxide and/or the relaxation of SiO2/Si interfacial strain. The
increase of the ideality factor and leakage current for N2O-annealed devices might
be attributed to the increase of SiO2/Si interface states.
100-nm-Scale Alignment using Laser Beam Diffraction Pattern Observation Techniques and Wafer Fusion for Realizing Three-Dimensional Photonic Crystal Structure
Authors: Noritsugu Yamamoto Noritsugu Yamamoto , Susumu Noda Susumu Noda
Published: October 2002

We previously proposed a new method for realizing three-dimensional photonic crystals
in the optical wavelength region,
where two-dimensional basic structures are aligned using a laser beam diffraction pattern observation technique
and stacked by means of a wafer fusion.
In this method, it is essential to align the two-dimensional basic structures
with an accuracy of optical wavelength order at wafer fusion.
In this work, we develop an alignment system based on a laser beam diffraction pattern
observation technique and achieve alignment and wafer fusion with accuracy of less than 100 nm, for the first time.
A Proposal for Third-Harmonic Generation for Pulse Compression with Noncollinear Phase Matching
Authors: Zhang Tiejun , Yonemura Motoki
Published: October 2002

We propose a novel scheme for third-harmonic generation for pulse compression with a
noncollinear tripler. Theoretical results show that a 42 fs third-harmonic pulse at 266.7 nm could be
generated from wave mixing of a 100 fs fundamental pulse at 800 nm and a 100 fs second-harmonic
pulse at 400 nm.
Red Electroluminescence of Mn-doped CuAlS2 Powder and Single Crystal
Authors: Tanaka Katsu , Kimura Yasukazu , Okamoto Shinji , Inoue Yoji , Sato Katsuaki
Published: October 2002

In this paper, the first application of ternary compounds
of Mn-doped CuAlS2 to a new red powder electroluminescent
(PEL) phosphor has been reported. The chromaticity of the
emission is a high-purity red very close to that of the red-CRT
phosphor. The luminance–voltage (L–V), current–voltage (I–V),
and luminance–current (L–I) curves of the single crystal reveal
that the excitation of red electroluminescence (EL) is caused
by hot holes. The EL decay mechanism is found to be
dominated by Mn–Mn pair relaxation.
The DC–EL of the PEL device using Mn-doped CuAlS2 was
brighter than the AC–EL. This superior DC–EL performance is
explained by the emitting position in the phosphor-binder
layer.
Investigation of Ruthenium Electrodes for (Ba,Sr)TiO3 Thin Films
Authors: Joo Jae-Hyun , Seon Jeong-Min , Jeon Yoo-Chan , Oh Ki-Young , Roh Jae-Sung , Kim Jae-Jeong , Choi Jin-Tae
Published: October 2002

Ru/(Ba, Sr)TiO3(BST)/Ru capacitors were fabricated on TiN/Ti/Poly-Si/SiO2/Si substrate by sputtering technique. The effects of the bottom ruthenium electrode, deposited at various temperatures, on the characteristics of Ru/BST/Ru capacitor were intensively studied. Sputtered ruthenium films were grown in a columnar structure with a grain size ∼30 nm. With an increasing deposition temperature of ruthenium films, the (002) preferred orientation and grain size of ruthenium films gradually increased while the residual compressive stress in the ruthenium films was reduced. The surface of ruthenium films was oxidized to form RuO
x
on its surface during the deposition of BST films, which dramatically changed the surface morphology of ruthenium films and affected the characteristics of Ru/BST/Ru capacitor. In this work, the electrical properties of Ru/BST/Ru capacitors are explained with an emphasis on the surface morphology and residual stress of ruthenium films.
Kinetic Study of the Rotator Phase Transition in n-Alkane: Growth of the Rotator Phase
Authors: Koji Nozaki Koji Nozaki , Masamichi Hikosaka Masamichi Hikosaka
Published: October 2002

The kinetics of the growth of the rotator phase during the solid-solid phase transition from the low-temperature ordered phase in a single crystal ofn-alkane (n-pentacosane, C25H52) was investigated by means ofin situoptical microscopy. The change in morphology and the growth rate were simultaneously observed. The growth front was clear and straight at an early stage but became slightly curved with time under isothermal conditions. The growth rate of the rotator phase (V) was given byV∝exp (-const/ΔT) where ΔTis the degree of superheating. Therefore it was concluded, based on the above morphology and the growth rate, that the growth of the rotator phase is mainly controlled by two-dimensional nucleation which is a type of multinucleation.
A New Emission Spectrum of Au2 in the Gas Evaporation Technique: 761–809 nm
Authors: Okazaki Tsugio , Saito Yahachi , Kasuya Atsuo , Nishina Yuichiro
Published: October 2002

A study was conducted on the optical emission spectrum of Au2, in the range of 761 to 809 nm, at a region close to the source of evaporation of Au in low pressure helium gas (100 Torr). A new band system of Au2 dimers in the gas phase was identified. The derived spectroscopic constants on the basis of a vibrational analysis are listed as follows: νe=12845.98+0.29 cm-1, ωe'=89.58±0.37 cm-1, ωe
x
e'=0.20±0.06 cm-1, ωe''=95.80±0.31 cm-1, ωe
x
e''=0.21±0.10 cm-1.
Surface Modification and Enhancement of Luminescence due to Quantum Effects in Coated CdSe/CuSe Semiconductor Nanocrystals
Authors: Xu Ling , Huang Xinfan , Huang Hongbin , Chen Hongming , Xu Jun , Chen Kunji
Published: October 2002

We report a new and low cost method to synthesize colloidal CdSe and coated CdSe/CuSe nanocrystals in aqueous solution. The results of structural characterization and optical measurements indicated that the good size control had been achieved. The photoluminescence study confirmed the surface passivation of CdSe core with CuSe outlayer and revealed strong enhancement of band-edge luminescence due to the quantum confinement in coated CdSe/CuSe nanocrystals.
Purification of Uranium Metal using the Solid State Electrotransport Method under Ultrahigh Vacuum
Authors: Yoshinori Haga Yoshinori Haga , Tetsuo Honma Tetsuo Honma , Etsuji Yamamoto Etsuji Yamamoto , Hitoshi Ohkuni Hitoshi Ohkuni , Yoshichika Ōnuki Yoshichika Ōnuki , Mitsuo Ito Mitsuo Ito , Noriaki Kimura Noriaki Kimura
Published: October 2002

A uranium ingot was successfully purified using the solid state electrotransport (SSE) method. The concentration of impurities was dramatically reduced after the SSE treatment. In particular, magnetic transition metals such as Fe and Cu were removed almost completely. Impurities with high vapor pressure such as Mn and Zn were evaporated. The mechanism of the impurity-reduction was qualitatively explained by three effects: sweeping out by the flow of the electrical current, diffusion and evaporation. It is very important to hold the uranium ingot at a high temperature just below the melting point.
Design of Imaging Lens Systems that Use Low Dispersive Radial Gradient-Index Rod
Authors: Tsuchida Hirofumi , Nagaoka Toshiyuki , Yamamoto Kimiaki
Published: October 2002

Many effective lens design examples using gradient-index (GRIN) materials have been reported so far. However, the GRIN materials that were used in those designs
are either very difficult or impossible to produce. We show an effective design and the design techniques of imaging lens systems that utilize realizable materials.
The designed lens systems use flat-surfaced radial GRIN lens (Wood lens) with low dispersion, small Δn and small diameter.
Coupled-Mode Analysis of Bent Planar Waveguides with Finite Claddings
Authors: Mirianashvili Maria , Ono Kazuo , Hotta Masashi
Published: October 2002

Coupled-mode analysis of uniformly bent slab waveguides with finite claddings is
demonstrated. Using the method of conformal transformation, a curved waveguide structure is
translated into an equivalent straight waveguide with a modified asymmetric index profile. The
wave propagation through this structure is described by coupled-mode formalism with ideal
mode expansion. The step-index profiles as well as graded-index profiles are considered. The
numerical results of transmitted power, wave propagation along the bend and pure bend loss
are presented for TE0-mode excitation.
Low-Loss Polymeric Optical Waveguides with 45° Mirrors
Authors: Yoshimura Ryoko , Hikita Makoto , Tomaru Satoru , Imamura Saburo
Published: October 2002

Two types of low-loss polymeric optical waveguide with 45° mirrors, which
accomplish 90° out-of-plane optical deflection into or from their substrate, were fabricated by
cutting the waveguides with a 90° V-shaped or a 45° wedge-shaped diamond blade. The excess
losses caused by the mirrors were less than 0.3 dB at 0.83 µm, which showed that the mirror
surfaces were very smooth.
Erbium Doping in Silicon by Thermal Indiffusion
Authors: Wong Emile Man Wah , Liu Hongwei , Man Shi Qing , Pun Edwin Yue Bun , Chung Po Sheun
Published: October 2002

A rare-earth ion, namely erbium, was doped into silicon (Si) using thermal
indiffusion. Codoping using ytterbium oxide (Yb2O3) and germanium (Ge) to increase
photoluminescence (PL) intensity was also demonstrated, and the effect of different Yb/Er
ratios on Si was studied. Room temperature PL intensity relative to Er-diffused sample
was found to increase by ∼30 times using Yb/Er (27/1) codopant. When a SiGe/Yb/Er
layer was used, room temperature PL intensity was further increased to more than 60 times.
Sensitivity Coefficients of Pirani Gauge for Various Atoms and Molecules
Authors: Kusakabe Toshio , Horiuchi Tadahiko , Nakai Yohta , Tawara Hiroyuki
Published: October 2002

The sensitivity coefficients of a Pirani gauge in a constant voltage with bridge imbalance monitoring have been determined for various atoms and molecules. Except for light particles such as He atoms, H2 and D2 molecules, the observed coefficients show a strong correlation with the reduced thermal conductivities of free gas particles.
Differential Conductance Imaging of Si and Ge Islands Deposited on Si(001) by Scanning Tunneling Microscopy
Authors: Yoshinori Suganuma Yoshinori Suganuma , Masahiko Tomitori Masahiko Tomitori
Published: October 2002

The current modulation imaging techniques based on scanning
tunneling microscopy (STM) were applied to Si and Ge islands grown on a
Si(001) surface to reveal the atomic and electronic structures of
their surfaces. These techniques are advantageous for acquiring both
the images of
topography and electronic states with a good signal/noise in a short time
over
the sample surface. The topographic effect over the step of the islands
was demonstrated as an artifact that appears in the images of the
electronic states.
Ballistic Transport in Artificial Nano-Circuits
Authors: Shousuke Nakanishi Shousuke Nakanishi , Ryo Tamura Ryo Tamura , Masaru Tsukada Masaru Tsukada
Published: October 2002

Some remarkable features of the two-terminal
transmission probability T(E) of artificial nano-circuits are clarified.
These include a switching effect of T(E)
caused by applying a magnetic field to the system,
as well as large induced loop currents in the internal ring parts.
The electric current passing through the nano-circuits is calculated
by the Landauer-Büttiker formalism
using the Green's function method and
the tight-binding scattering matrix method.
The two-terminal conductance vanishes when
the interference of the electron wave
makes the value of T(E) zero,
or when the energy of the incident electron corresponds
to the degenerate energy levels of the circuit
satisfying a certain condition of the wavefunctions.
It is also found that a large loop current in the nano-circuit is
induced by a small source-drain current for a particular energy region.
Data Processing in the Extraction of Properties from Force Curves for Mapping
Authors: Sugisaki Katsumi , Nakano Katsushi , Sugimura Hiroyuki , Kandaka Noriaki , Nakagiri Nobuyuki
Published: October 2002

Properties extracted from force curves obtained by atomic force
microscopy (AFM) conducted at various locations on a sample can be
mapped to determine their distribution over the sample surface, that is,
force curve mapping. Since a huge amount of force curve data must be
handled in such mapping, automatic force curve analysis is required. We
have developed an algorithm which makes use of a differentiated force
curve having peaks at the snap-in and snap-out points of the original force
curve and negative values when the AFM tip is in contact with the sample
surface. This algorithm was applied to various samples.
Characterization of Double-Buffer Layers and Its Application for the Metalorganic Vapor Phase Epitaxial Growth of GaN
Authors: Uchida Kenji , Nishida Ken , Kondo Masataka , Munekata Hiroo
Published: October 2002

Preparation of newly-developed GaN double-buffer layers (DBLs) and their influence on
crystalline quality of GaN epilayers grown by metalorganic vapor phase epitaxy
(MOVPE) are described. The DBLs are the buffer layer structures which consist of two
10-nm-thick GaN layers deposited successively at different temperatures T
1 and T
2. We
have found that the initial deposition temperature T
1 must be higher than the latter
deposition temperature T
2 to form a smooth DBL, which in turn results in the preparation
of high-quality epilayers. Residual strain and threading dislocation in the epilayers can
also be effectively reduced by using such a DBLs. The estimated biaxial compressive
stress in the 0.8-µm GaN epilayers grown on the DBLs is 0.08–0.09 GPa, while that
grown on the single-buffer layer (SBL) is 0.15 GPa.
Effect of Additive Gases on Dimension Control during Cl 2-Based Polysilicon Gate Etching
Authors: Lee Ho-Seok , Jun Bum-Jin , Lee Dong-Duk , Baik Ki-Ho , Seol Yeo-Song
Published: October 2002

In order to minimize the pattern transfer difference (PTD) between a
dense cell pattern and isolated pattern, we investigated the effects of
additive gases (O2, HBr, and N2) and bias power in Cl2-based polysilicon
gate etching. When the flow rate of N2 was increased, a larger PTD was
due to a marked increase in the critical dimension bias in the isolated
pattern. The PTD was also influenced to a large extent by the bias power.
When the bias power was increased, there occurred a linear increase of
the PTD in Cl2/N2 plasma, which also exhibited a striking dependence on
the bias power in Cl2/HBr plasma; however, in Cl2/O2 plasma, the PTD
showed no notable the dependence on bias power. From these data, it is
proposed that the PTD between the two may be due to the ion scattering
and polymer build-up difference.
Amorphous Silicon Carbide/Crystalline Silicon Heterojunction Solar Cells: A Comprehensive Study of the Photocarrier Collection
Authors: Cleef Maarten W. M. van , Rubinelli Francisco A. , Rizzoli Rita , Pinghini Roberto , Schropp Ruud E. I. , Weg Werner F. van der
Published: October 2002

We have studied the current–voltage (I–V) characteristics of p+ a-SiC:H/n c-Si heterojunction solar cells at
different conditions. Under standard test conditions (300 K, 100 mW/cm2, AM1.5) these cells
show normal I–V characteristics with a high fill factor (FF = 0.73) and a relatively high
efficiency for their simple structure (η≈13%). However, below room temperature and at
illumination levels above 10 mW/cm2 they exhibit an S-shaped I–V curve and a low fill factor.
Simulation studies revealed that this effect is caused by the valence band discontinuity at the
amorphous/crystalline interface which hinders at low temperatures the collection of
photogenerated holes at the front contact. At low temperatures a high hole accumulation at
the interface combined with extra trapping of holes inside the p+ a-SiC:H layer causes a shift
of the depletion region, from the c-Si into the p+ a-SiC:H. This leads to an enhanced
recombination inside the c-Si depletion region causing a significant current loss (S-shape).
Tunnelling through the valence band spike can reduce these effects. For lower doped p a-SiC:H layers (E
act>0.4 eV) this S-shape can even occur at room temperature.
Low-Pulse-Energy Excimer-Laser-Induced Damage in Thermally Oxidized Si(100) Substrates
Authors: Ozaki Yoshiharu
Published: October 2002

Thermally oxidized Si (100) substrates were irradiated with excimer laser pulses with a low energy density, and the minority-carrier recombination lifetime and interface state density were measured. Irradiation with an ArF (λ=193 nm) excimer laser shortened the lifetime and raised the interface state density. These effects depend on the fluence, but not the energy density, of the pulses. Irradiation with KrCl (λ=222 nm), KrF (λ=248 nm), and XeCl (λ=308 nm) excimer lasers did not affect the lifetime.
Damping Characteristics of a Magnet Oscillating above a YBCO Superconductor
Authors: Muneo Futamura Muneo Futamura , Takeshi Maeda Takeshi Maeda , Hajime Konishi Hajime Konishi
Published: October 2002

We measured and analyzed damping oscillation of a permanent magnet above a YBa2Cu3Ox superconductor.
A mechanical model composed of a mass, a spring, and a dashpot was used to analyze the damping oscillation of the magnet.
By introducing the dragged spring model for the pinning effect, we obtained good agreement between the analytical and experimental results.
Dynamic Grating Filtering in Photorefractive Crystals by Using Vibration
Authors: Donn S. C. , Huang K. C. , Sun Ching-Cherng
Published: October 2002

We propose a simple theory to analyze the effect of application of a high frequency
vibration signal to a photorefractive crystal on the dynamic index grating. The theory
shows that the grating visibility is zero when the vibration amplitude is an integral
multiple of the grating space. By using this principle, we can apply a vibration signal
to a crystal and construct a low-pass filter on the index grating in spatial domain.
Studies of Deep Levels in HgCdTe Grown on CdZnTe and Si Substrates
Authors: Yoshino Junya , Morimoto Jun , Wada Hideo
Published: October 2002

The influence of different substrates on the deep levels in Hg1-x
Cd
x
Te was investigated by
spectral analysis of deep-level transient spectroscopy (SADLTS). In this study, CdZnTe, which
had almost the same lattice constant and thermal expansion coefficient as Hg1-x
Cd
x
Te, and Si,
which had a larger lattice constant and thermal expansion coefficient than Hg1-x
Cd
x
Te, were used as
the substrates. The results of SADLTS show that there are six levels between 27 meV and 56 meV
as activation energies in Hg1-x
Cd
x
Te grown on the Si substrate, while there are six levels between
10 meV and 44 meV as activation energies in Hg1-x
Cd
x
Te grown on the CdZnTe substrate. It was
confirmed that the Hg1-x
Cd
x
Te grown on the Si substrate had deeper levels than Hg1-x
Cd
x
Te grown
on the CdZnTe substrate.
Characterization of Laser-Induced Self-Phase Modulation in Host-Guest Liquid Crystals
Authors: Ono Hiroshi , Harato Yoshiro
Published: October 2002

A self-phase modulation that originated in photothermal effects in host-guest
liquid crystals (HGLCs) with three kinds of nematic-isotropic transition temperatures
(T
NI) was characterized by investigating both the experimental diffraction beam
pattern and theoretical one. The experimental diffraction patterns were in good
agreement with the calculated results using Kirchhoff's diffraction integral in the case
of the Gaussian-type phase distribution. The diffraction patterns depended on the
polarization direction of the incident He–Ne laser and the results were explained by the
strong anisotropy of HGLCs. Higher photosensitivity caused by the large temperature
dispersion of refractive index was obtained in low T
NI of HGLCs than in high T
NI
of HGLCs.
Novel Liquid Crystal Grating with a Relief Structure by a Simple UV Irradiation Process
Authors: Wen-Tao He Wen-Tao He , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

A novel method of fabricating a liquid crystal grating is proposed. The liquid crystal grating, which has a periodic groove structure, can be fabricated by a simple single-step process with UV irradiation through a grating photomask using a mixture of liquid crystal and prepolymer materials. Phase separation in the UV curing process leads to completely separated layers of liquid crystal and polymer sections with the surface-relief grating structure. The grating structure of the cured polymer layer is investigated by using a polarizing microscope and a scanning electron microscope (SEM). Voltage control property of the diffraction efficiency is also investigated and the applicability of this liquid crystal grating to an electrical switchable diffraction device is discussed.
New Methods for Measurement of Neutron Energy Spectrum with CR-39 Nuclear Track Detectors
Authors: Wang Wang , Yulan Yulan , Guo Guo , Shilun Shilun , Li Li , Li Li , Tu Tu , Caiqing Caiqing
Published: October 2002

The techniques for measurement of neutron energy spectrum with CR-39 detectors have been recently developed, which are based
on measurements of the mixed restricted energy loss (REL) (i.e., part of energy loss where energy carried by δ-ray electrons is less
than the ω0-ceiling on the energy of delta rays) distribution of the recoil nuclei of C and O inside CR-39 induced by fast neutrons.
One of the methods for obtaining the neutron energy spectrum from the REL distribution of the recoil nuclei of C and O inside CR-39 is to determine the true ratio of C/O in each channel of REL distribution, which can be carried out using the computer program
written by us. The other method is similar to the Monte Carlo simulations, which can be done by obtaining a calculated REL
distribution of the recoil nuclei of C and O through the angular distributions of the scattering neutrons in the center of the mass
system under an assumed neutron energy spectrum. For the sake of checking the correctness and the accuracy of these methods,
measurements of monoenergetic neutrons (E
n=13.3 MeV) have been carried out by these methods. The feasibility of measuring the
neutron energy spectrum with CR-39 with these techniques has been shown.
Atomic Beam Diode-Laser Spectroscopy
Authors: Takashi Wakui Takashi Wakui , Wei-Guo Jin Wei-Guo Jin , Kenji Hasegawa Kenji Hasegawa , Haruko Uematsu Haruko Uematsu , Tatsuya Minowa Tatsuya Minowa , Hidetsugu Katsuragawa Hidetsugu Katsuragawa , Masanori Wakasugi Masanori Wakasugi
Published: October 2002

Combined with a collimated atomic beam source, diode laser
without external cavity has been used as a spectroscopic light
source to study atomic hyperfine structures and isotope shifts of
Ba i.
Spectroscopic measurements of the 6s
2
1
S
0 – 6s6p
3
P
1
transition of Ba i have been carried out.
All hyperfine peaks of 135,137Ba have been clearly seen
and resolution of 50 MHz has been attained.
Hyperfine constants A and B of the 3
P
1 state of
135,137Ba have been determined.
Isotope shifts of stable Ba isotopes have also been measured.
From the measured isotope shifts, the 6s electron density at the
nucleus has been deduced to be 76.4(53) a.u. and
discussed in terms of the Hartree-Fock approximation.
Effect of Surface Roughness on Room-Temperature Wafer Bonding by Ar Beam Surface Activation
Authors: Takagi Hideki , Maeda Ryutaro , Chung Teak Ryong , Hosoda Naoe , Suga Tadatomo
Published: October 2002

Using Ar beam etching in vacuum, strong bonding of Si wafers is attained at room
temperature. With appropriate etching time, the bonding occurs spontaneously without any
load to force two wafers together. However, surface roughness of the wafers increases during
Ar beam etching. Because surface roughness has a strong influence on wafer bonding, long
etching time degrades the bonding strength. Using atomic force microscope, we measured
surface roughness enhancement caused by Ar beam etching, and investigated the relationship
between surface roughness and bonding properties such as strength and interfacial voids. The
results agree well with theoretical predictions using elastic theory and energy gain by bond
formation. A guideline for successful room-temperature bonding is proposed from these results.
Theoretical Investigations of Adsorption Behavior on GaAs(001) Surfaces
Authors: Ito Tomonori , Shiraishi Kenji
Published: October 2002

Adsorption behavior on GaAs(001)-(2×4)β2 and -c(4×4) surfaces is systematically investigated by the calculation of migration potentials for Ga
adatoms and Monte Carlo simulation. In the calculation procedure, we use
an energy formalism based on the empirical interatomic potentials and the
electron counting model in order to incorporate the strain and electronic
energy contributions. The calculated migration potentials for Ga adatoms
imply that Ga adatoms preferentially reside in missing dimer sites on both
(2×4)β2 and c(4×4) surfaces. On the (2×4)β2 surface, lattice sites in the missing dimer row near As-dimer kinks and B-type step edges are stable for
Ga adatoms, whereas no preferential adsorption site is found near A-type
step edges. Opposite qualitative trends are found in the migration
potentials near step edges on the c(4×4) surface. The calculated results are consistent with experimental results and are discussed in terms of atomic
configurations and the number of electrons remaining in Ga dangling bonds.
Based on the energy formalism, an electron counting Monte Carlo (ECMC)
simulation was performed to investigate the adsorption or desorption
sequences on GaAs(001)-(2×4)β2 and -c(4×4) surfaces in MBE growth. The results imply that Ga adatoms impinging on the GaAs(001) surfaces play an
important role in the incorporation or desorption of As to restore the
electron counting model.
Properties of Regioregular Poly(3-alkylthiophene) Schottky Diodes
Authors: Musa Ismail , Eccleston William
Published: October 2002

An investigation into the effect of carrier trapping in polymer Schottky diodes is presented.
The diodes have been fabricated using regioregular poly(3-octylthiophene) as the
semiconductor and aluminium and indium doped tin-oxide as the rectifying and ohmic
contacts respectively. The diodes show rectification ratios up to 3–4 orders of magnitude.
Evidence for image-force lowering of the Schottky barrier is observed. The frequency
dependence of the capacitance, conductance and dielectric loss is analysed, from which
detailed information on the metal/semiconductor interface and the doping level is obtained.
An equivalent circuit is proposed.
Optimization of Program Threshold Window from Understanding of Novel Fast Charge Loss in Nonvolatile Memory
Authors: Shen Shih-Jye , Hsu Charles Ching-Hsiang , Liang Mong-Song
Published: October 2002

This paper describes and discusses intensively the charge loss characteristics in the stacked-gate
memory device with interpoly oxide-nitride-oxide (ONO) dielectric at elevated temperatures. There
exist two distinct phases in the charge loss characteristics. The dominant mechanism in the first phase
can be described as the charge transport in the nitride layer. The second phase is dominated by
effective thermionic emission effect from the stacked gate system. A linearly proportional
relationship is also observed between normalized charge loss in the first phase and initial threshold
voltage shift. Due to the fast charge loss rate, the charge loss in the first phase governs the threshold
instability of the stacked-gate device. A method to determine the programming window for better
threshold voltage stability based on charge loss in first phase is proposed.
Influence of Microroughness of Si and Native Oxide on Adsorption of Organic Carbon in Water
Authors: Matsuo Naoto , Kawamoto Naoya , Miyoshi Tadaki
Published: October 2002

The relationship between adsorption of organic carbon present in water and Si surface roughness
is examined. The mean roughnesses, R
a, of Si(100) surface after etching in HF solution is the
same as that of Si(111) surface. There is no difference between the roughness of the native oxide
formed during rinse in ultrapure water and that of the native oxide/Si interface for Si(111). The
roughness shows a constant value over all rinse times. These studied observations indicate that the
microroughness of the Si surface does not serve as the dominant adsorption site for organic
carbon. It is also shown that the field-enhanced oxidation at the beginning of the growth of the
native oxide film is important to discuss the dominant adsorption site.
Preliminary Experiment for Polymer Waveguide-Type Optical Isolator: A Pulsed Optical Isolator Operation in Poly(l-Menthylmethacrylate/Benzylmethacrylate) Copolymer Slab Waveguide
Authors: Shinzo Muto Shinzo Muto , Kiyoshi Ishiyama Kiyoshi Ishiyama , Eisuke Nihei Eisuke Nihei , Yasuhiro Koike Yasuhiro Koike
Published: October 2002

A copolymer of l-menthylmethacrylate (MtMA) and benzylmethacrylate (BzMA), poly(MtMA/BzMA) was synthesized to construct a polymer slab waveguide-type optical isolator operating in the blue wavelength region. This isolator is based on the simultaneously occuring reciprocal and nonreciprocal TE–TM mode conversions in a three-layered slab waveguide which consists of the poly(MtMA/BzMA) copolymer core on a fused quartz substrate. When a high magnetic field of about 18 kOe was applied to a device with a core thickness of 4.5 µm and a 5 cm propagation length, a pulsed optical isolator operation with an isolation ratio of approximately 15 dB was obtained at a wavelength of 441.6 nm, for the first time.
Growth and Structure of Spherulites in Polymer-Dispersed Liquid Crystals Fabricated by Photopolymerization-Induced Phase Separation
Authors: Karasawa Takeshi , Taketomi Yoshinao
Published: October 2002

Spherulites appear during the formation of a polymer-dispersed
liquid crystal (PDLC) under certain fabrication conditions. High UV
irradiance results in a sample dominated by liquid crystal droplets while
low UV irradiation results in the growth of spherulites, possibly because
the latter condition creates fewer droplets, which is preferable for
spherulitic growth. Spherulites that are nucleated adjacent to each other
maintain their circular shape during growth until they make contact with
each other, and then form a straight line boundary while maintaining
radial growth. Direct observation of the inner aspect of PDLCs by means of
Nomarsky differential interference microscopy and scanning electron
microscopy (SEM) has revealed that the three-dimensional structure of a
spherulite is plate like and that the boundary line seen in polarization
microscopy contains no structure within the resin matrix, indicating that
the body of a spherulite consists mainly of liquid crystal. A model of
merging spherulites is proposed in this paper.
Super-Flat Interfaces in Pseudomorphic InxGa1-xAs/Al0.28Ga0.72As Quantum Wells with High In Content (x = 0.15) Grown on (411)A GaAs Substrates by Molecular Beam Epitaxy
Authors: Masanobu Ohashi Masanobu Ohashi , Tatsuya Saeki Tatsuya Saeki , Takahiro Kitada Takahiro Kitada , Satoshi Shimomura Satoshi Shimomura , Yasunori Okamoto Yasunori Okamoto , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

Pseudomorphic In
x
Ga1-x
As/Al0.28Ga0.72As
(x = 0.085–0.15) quantum wells (QWs) with well widths of
1.2, 2.4, 3.6, 4.8, 7.2 and 12 nm have been grown
on (411)A and (100) GaAs substrates at a temperature
(T
s) of 520°C by molecular beam epitaxy (MBE).
The interface flatness of the QWs was
characterized by photoluminescence (PL) at 4.2 K.
PL linewidths of the narrow
(411)A QWs (L
w = 2.4 nm) with x = 0.085 and 0.15 were 7.3 meV which is
approximately 30–40% smaller than those of the (100) QWs, indicating that
extremely flat interfaces over a macroscopic area
[(411)A super-flat interfaces] have been realized in the pseudomorphic
In
x
Ga1-x
As/Al0.28Ga0.72As QWs (up to x = 0.15)
grown on the (411)A GaAs substrates, similar to lattice-matched
GaAs/Al
x
Ga1-x
As
QWs grown on (411)A GaAs substrate previously reported.
Highly Oriented Nb-Doped Lead Titanate Thin Films by Reactive Sputtering: Fabrication and Structure Analyses
Authors: Matsushige Ricardo Cury Ibrahim
Published: October 2002

Highly oriented lead titanate thin films have been deposited on bare (100)MgO substrates and on (100)Pt/(100)MgO substrates by reactive sputtering. By adding metallic niobium chips to the target, Nb-doped PbTiO3 films could be obtained as well. The variation in the orientation of PbTiO3 films due to the deposition conditions is described in detail. Due to the highly oriented nature of the films, two types of X-ray diffraction methods were used to evaluate the effect of Nb doping on the tetragonality ratio c/a: one was the conventional θ–2θ Bragg-Brentano X-ray diffraction method (XRD), the other was the in-plane energy-dispersive total reflection X-ray diffraction method (ED-TXRD), which could provide the lattice vectors perpendicular (c axis) and parallel (a axis) to the substrate, respectively. Furthermore, the epitaxy of the deposited PbTiO3 films in relation to the (100)-cut MgO single crystal substrate could be confirmed using ED-TXRD.
Linear Concentrated Electric Field in Inhomogeneous Media
Authors: Hideyuki Sugioka Hideyuki Sugioka , Akira Asai Akira Asai
Published: October 2002

To understand breakdowns in inhomogeneous media,
distributions of the electric potential in a model system of thin films
have been calculated.
The calculations show that
the linear concentrated region of the electric field
is likely to
appear as the randomness of the system increases,
and appears most frequently
near the percolation threshold p
c.
For general inhomogeneous media,
it is presumed that
the concentrated region
appears at p
c
and can trigger breakdowns.
Comparative Studies on Sensitivity and Stability of Fiber-optic Oxygen Sensor Using Several Cladding Polymers
Authors: Masayuki Morisawa Masayuki Morisawa , Gargi Vishnoi Gargi Vishnoi , Toshiki Hosaka Toshiki Hosaka , Shinzo Muto Shinzo Muto
Published: October 2002

An attempt has been made to improve the sensitivity and stability of the polymer optical fiber (POF) sensor for continuous monitoring of gaseous oxygen. It utilizes the quenching phenomenon of cladding fluorescence. Three polymers namely, poly(cyclohexyl methacrylate) (PCMA), poly(l-menthyl methacrylate) (PMtMA) and poly(4-methyl-1-pentene), which have a relatively large oxygen permeability, were used as cladding layer doped with a sensitive dye such as a 9,10-diphenyl anthracene (DPA), on the polymer cores with 1 mm diameter. When these sensor heads were pumped using a D2-lamp, the response at the fluorescence of λ=431 nm was found to be very fast and reversible in all the cases, for oxygen concentrations ranging from 0.5% to 100%. However, the differences in fluorescence quenching rate, stability and response time were observed to be dependent upon the polymer used. In particular, the PCMA sample showed good long-term stability. These comparative studies of POF oxygen sensors seem to be useful for developing practical devices.
Reduction of Point Defects and Formation of Abrupt Hetero-Interfaces in Low-Temperature Molecular Beam Epitaxy of GaAs and GaP under Atomic Hydrogen Irradiation
Authors: Mikihiro Yokozeki Mikihiro Yokozeki , Hiroo Yonezu Hiroo Yonezu , Takuto Tsuji Takuto Tsuji , Kazuya Aizawa Kazuya Aizawa , Naoki Ohshima Naoki Ohshima
Published: October 2002

The removal effect of excess As and P atoms adsorbed on GaAs (100) and GaP
(100) surfaces by atomic hydrogen (H) irradiation was investigated by
reflection high-energy electron diffraction and X-ray photoelectron
spectroscopy.
It was found that the excess As and P atoms were effectively removed
by atomic H irradiation at a low temperature of 350°C.
Then, we attempted to obtain a high-quality GaAs epitaxial layer
and an ordered (GaAs)1(GaP)3 strained short-period superlattice (SSPS)
with abrupt GaAs/GaP hetero-interfaces in the low-temperature growth
under atomic H irradiation. The quality of the GaAs epitaxial layer
and the abruptness of the GaAs/GaP hetero-interfaces in the (GaAs)1(GaP)3
SSPS were evaluated by photoluminescence, deep-level transient spectroscopy
and transmission electron microscopy. As a result, it was clarified
that the density of point defects in the GaAs epitaxial layer was reduced
and an abrupt GaAs/GaP hetero-interface of the (GaAs)1(GaP)3 SSPS was
formed in the low-temperature growth under atomic H irradiation.
Infrared Radiation Detector with YBa2Cu3OX Thin Film
Authors: Kakehi Yoshiharu , Yotsuya Tsutom , Kusaka Tadaoki , Suzuki Yoshihiko , Ogawa Souichi , Imokawa Hirofumi
Published: October 2002

We investigated an infrared (IR) radiation detector using a c-axis oriented YBa2Cu3O
X

thin film with a microbridge structure. The photoresponse was measured under IR radiation
and was found to depend on the bias current. A bolometric response was observed under
relatively low bias current, which was inversely proportional to the square root of the
modulation frequency of IR irradiation. The frequency dependence can be explained by a heat
diffusion process that is similar to that of a microbolometer. With increasing bias current, a
nonbolometric response was observed just above the superconducting transition temperature
(T
c). This was caused by the enhancement of additional flux creep induced by modulated IR
light, which was equivalent to an increase in resistance. The maximum responsivity and noise
equivalent power (NEP) were 1.7×104 V/W and 2.1×10-14 W/Hz1/2, respectively.
The Exchange-Coupled Field in NiO/Ni Double Layer on Silica Substrates
Authors: Ihara Nobutaka , Akao Shingo , Akimoto Satoru , Narushima Shin , Saito Toshiaki , Shinagawa Kiminari , Tsushima Tachiro
Published: October 2002

The effect of silica substrate on the exchange-coupled field H
ex in NiO/Ni films was
examined. Ni film was vacuum-evaporated on a silica substrate, and then it was oxidized
thermally in oxygen to form a NiO/Ni double-layered film. In comparison with our previous
results of NiO/Ni film on MgO, H
ex for silica and MgO substrate showed almost the same
behavior. When the substrate temperature was varied during the evaporation of Ni, it was
found that the crystal orientation of Ni in the NiO/Ni double-layered film changes, and H
ex is
almost independent of the Ni crystal orientation.