bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase- and Wall-Locked Modes Found in a Large Reversed-Field Pinch Machine, TPE-RX
Authors: Yagi Yasuyuki , Koguchi Haruhisa , Nilsson Jenny-Ann B. , Bolzonella Tommaso , Zanca Paolo , Sekine Shigeyuki , Osakabe Takeshi , Sakakita Hajime
Published: October 2002

Phase- and wall-locked modes are found to exist in the toroidal pinch experiment called TPE-RX, a large-sized reversed-field pinch machine at the Electrotechnical Laboratory. General characteristics of the locked mode in TPE-RX are similar to those in the reversed-field pinch experiment called RFX, in spite of the difference in the vacuum vessel and the shell system. It is also found that there are certain experimental conditions under which phase-locking disappears. These experimental observations of the locked mode in TPE-RX can provide us with a general understanding of the cause of the locked mode in RFP plasmas.
Photoluminescence Studies of Hydrogen-Passivated Al0.13Ga0.87As Grown on Si Substrate by Metalorganic Chemical Vapor Deposition
Authors: Wang Gang , Ogawa Takashi , Ohtsuka Kiyosi , Zhao Guang Yuan , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

Investigations of near-band-edge transitions and hydrogen (H) plasma passivation effects
of unintentionally doped Al0.13Ga0.87As grown on a Si substrate by
metalorganic chemical vapor deposition have been performed by photoluminescence (PL) measurement.
The PL efficiency was effectively enhanced after H plasma passivation due to the passivation of
nonradiative recombination channels. In addition, the passivation of the residual impurity
carbon (C) has been confirmed by the 4.2 K PL measurement, and it was found that the passivation
effect of carbon still persists, even after 450°C post-hydrogen-plasma-passivation annealing.
Dependence of Exciton–Longitudinal-Optical-Phonon Interaction Energy on Well Width in Cd0.2Zn0.8Se/ZnSe Multiple-Quantum Wells
Authors: Zheng Ruisheng , Shigematsu Hiroshi , Fujimoto Masakatsu , Yamada Yoichi , Taguchi Tsunemasa
Published: October 2002

The dependence of exciton–longitudinal-optical (LO)-phonon interaction (Γex-ph)
on quantum-well width in Cd0.2Zn0.8Se/ZnSe multiple quantum wells has been investigated by
means of the temperature dependence of the n=1 heavy-hole exciton luminescence linewidth.
With decreasing well width, a reduction of the exciton-phonon coupling effect is induced
mainly by a decrease of the exciton-confined-LO-phonon interaction energy. It is found that
the value of Γex-ph is minimum at a well width of about 3 nm, which corresponds to the Bohr
radius of the exciton. This behavior can be interpreted in terms of a theoretical model in
which excitons are strongly interacted with half-space LO-phonons in the barrier layer and
interface optical phonons in the narrower well layer.
Analysis of Striations in a Coplanar Discharge
Authors: Guangsup Cho Guangsup Cho , Eun-Ha Choi Eun-Ha Choi , Jin-Goo Kim Jin-Goo Kim , Young-Guon Kim Young-Guon Kim , Jae-Jun Ko Jae-Jun Ko , Dai-Il Kim Dai-Il Kim , Choon-Woo Lee Choon-Woo Lee , Yoon-Ho Seo Yoon-Ho Seo , Han S. Uhm Han S. Uhm
Published: October 2002

Striations are observed only in coplanar or wedge-shaped planar AC-type discharges.
On the basis of the observation results, striations are analyzed and discovered to be related
to the ion waves generated by the self-sustained perturbations during the force-balancing
process between ion and electron wall charge clouds accumulated on the dielectric layer
over the metal electrodes.
Extraction of the Capacitance of a Metal Oxide Semiconductor Tunnel Diode (MOSTD) Biased in Accumulation
Authors: Matsumura Mieko , Hirose Yutaka
Published: October 2002

We present a method to extract the capacitance of a metal oxide semiconductor tunnel diode
(MOSTD) biased in accumulation which has been undeterminable by the conventional
capacitance–voltage method. An MOSTD is modeled by a parallel pair of a capacitor and a
resistor describing the oxide in series with another resistor associated with the substrate. All the
three equivalent circuit elements are then extractable by evaluating the impedance spectra of the
MOSTD “only” at the characteristic frequency where the magnitude of the imaginary part of the
impedance reaches the maximum. The effectiveness of the method is demonstrated with the
MOSTDs with 2.5 nm thick oxides.
Growth of Continuous and Highly (100)-Oriented β-FeSi 2 Films on Si(001) from Si/Fe Multilayers with SiO 2 Capping and Templates
Authors: Takashi Suemasu Takashi Suemasu , Noriyoshi Hiroi Noriyoshi Hiroi , Tetsuo Fujii Tetsuo Fujii , Ken'ichiro Takakura Ken'ichiro Takakura , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

We fabricated continuous and highly (100)-oriented β-FeSi2 films on Si(001) by annealing Si/Fe multilayers. An annealing temperature above 800°C was necessary to obtain high-quality β-FeSi2, but the β-FeSi2 aggregated into islands due to the annealing. Such aggregation was prevented by a SiO2 capping layer deposited on the top of the Si/Fe multilayers, but the obtained β-FeSi2 film showed a polycrystalline nature. Highly (100)-oriented continuous β-FeSi2 film was
obtained using Si/Fe multilayers on a (100)-oriented β-FeSi2
template, together with
a SiO2 capping layer.
Deposition of (111) Oriented Diamond Films on Palladium by Microwave Plasma Chemical Vapor Deposition
Authors: Ikeda Susumu , Nagano Masamitsu
Published: October 2002

(111)-oriented diamond films were deposited successfully on (111)-oriented
surfaces of palladium. The (111)-oriented surface of Pd was
prepared from commercially available Pd foil, by repeated cold-rolling
followed by annealing in H2. The conventional microwave plasma
chemical vapor deposition (CVD) method was employed for diamond
deposition, using CH4 diluted with H2 as the carbon source. X-ray
diffraction and Raman spectroscopy measurements revealed that a small
amount of (0001)-oriented graphite was formed together with the
(111)-oriented diamond particles. Diamond particles were probably embedded
or dissolved in Pd in some domains of the Pd substrate.
Analysis of Product Species in Capacitively Coupled C 5F 8 Plasma by Electron Attachment Mass Spectroscopy
Authors: Shinichi Imai Shinichi Imai , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

The decomposition and reaction products of C5F8 gas in a
capacitively coupled plasma have been investigated by electron attachment mass
spectroscopy (EAMS). Although only a few species are produced directly from
C5F8 molecules by dissociative electron attachment, a variety of species
appears after the discharge is ignited. The products comprise not only
fragmented species but also polymerized species with larger masses than that
of the parent molecule. It has been clarified from the energy spectra of the
F- signal that perfluoro-compounds such as CF4, C2F6 and C3F8
are produced through the decomposition of C5F8, followed by secondary
reactions in the gas phase. A tendency towards polymerization with increments
of CF2 units is also noted.
Effects of Sodium on CuIn3Se5 Thin Films
Authors: Kimura Ryuhei , Mouri Takuhei , Nakada Tokio , Niki Shigeru , Yamada Akimasa , Fons Paul , Matsuzawa Takeo , Takahashi Kiyoshi , Kunioka Akio
Published: October 2002

CuIn3Se5 films have been deposited with Na2S on Coning 7059 glass
substrates by the two-stage co-evaporation method. Stoichiometric CuIn3Se5
films with p-type conduction with the resistivities of 106 Ω·cm range were
obtained by our sodium control technique. Enhanced grain growth and
preferred (112) orientation were also clearly observed with sodium
incorporation; the same effect that has been reported for chalcopyrite
CuInSe2 thin films. The effects of sodium in these films have been
investigated by comparing the electrical and optical properties of CuIn3Se5
films with and without the Na incorporation. A correlation between the
photoluminescence spectra and the resistivity or conduction type of the
CuIn3Se5 films was found, suggesting a reduction in compensation due to the
suppression of donor-type defects by the presence of Na.
Rate Equations for the Creation of Various Metastable Dangling Bonds in a-Si:H Mediated by Floating Bonds
Authors: Tatsuo Shimizu Tatsuo Shimizu , Minoru Kumeda Minoru Kumeda
Published: October 2002

Using rate equations based on the creation and annihilation of a pair of
a dangling bond and a floating bond and their interconversion,
various metastable defect-creation processes in a-Si:H
are quantitatively analyzed for the case of
bandgap-light irradiation, electron-beam irradiation and thermal quenching
from elevated temperatures.
It is found that the calculated results can reproduce most of the observed
results.
Enhancement of Tunnel Magnetoresistance Effect on Junction with Co Cluster Layers in Coulomb Blockade Regime
Authors: Fukumoto Yoshiyuki , Kubota Hitoshi , Ando Yasuo , Miyazaki Terunobu
Published: October 2002

Tunnel magnetoresistance (TMR) effect in ferromagnet/granular/ferromagnet
(FM/GR/FM) tunnel junctions was studied, where GR=Al–O/Co/Al–O or
Al–O/Co/Al–O/Co/Al–O. The magnetoresistance (MR) ratio and the resistance of the latter junction
increased with decreasing bias voltage at low temperatures. These increases should be due to
the cotunneling effect in the Coulomb blockade regime. In contrast, the MR ratio of the
former junction exhibited a maximum of 14% near 40 mV and decreased to 10% at 1 mV.
The increase of resistance in the former junction at a lower voltage was smaller than that in
the latter junction. The difference was discussed using a simple model.
Electron Spin Relaxation in GaAs/AlGaAs Quantum Wires Analyzed by Transient Photoluminescence
Authors: Nishimura Tetsuya , Wang Xue-Lun , Ogura Mutsuo , Tackeuchi Atsushi , Wada Osamu
Published: October 2002

We report on the spin relaxation in GaAs-based quantum wires and wells studied at
50 K<T<180 K by analyzing the circularly polarized photoluminescence
transients. A 3.5-times shortening of the electron spin relaxation time is observed in
GaAs/AlGaAs quantum wires compared with that in quantum wells at 180 K. The observed results
suggest that a spin flip in the quantum wires is caused predominantly by the D'yakonov-Perel'
effect due to spin-orbit interaction. The strong quantum confinement of electrons in the reduced
dimensionality of the quantum structure leads to a larger spin splitting energy and a stronger temperature dependence of spin relaxation.
Lowering of Thickness of N-Type Microcrystalline Hydrogenated Silicon Film by Seeding Technique
Authors: K. Barua Asok , Sankar Mandal Sankar Mandal
Published: October 2002

By using a seeding technique it has been possible to
lower significantly the thickness of n-type µc-Si:H
film having acceptable dark conductivity for use
at the tunnel junction/s of multijunction a-Si solar
cells. The µc-Si:H films have been prepared by radio frequency plasma enhanced chemical vapor deposition (RFPECVD)
method (13.56 MHz) at low power and substrate
temperature suitable for the fabrication of a-Si solar
cells. The seed layer used is an ultrathin layer of
undoped µc-Si:H film which facilitates the growth of
microcrystallinity in n-µc-Si:H film. The positive
effect of seed layer in the growth of microcrystallinity
of n-µ-Si:H film has been established by the study of
dark conductivity and transmission electron microscope
(TEM) of films prepared under different deposition
conditions.
Self-Convergent Programming Scheme for Multilevel P-Channel Flash Memory
Authors: Shen Shih-Jye , Yang Ching-Song , Wang Yen-Sen , Hsu Charles Ching-Hsiang
Published: October 2002

We propose a novel operation scheme for multilevel p-channel
flash memory cell with a self-convergent programming process. By
utilizing the simultaneous Fowler-Nordheim electron tunneling out of
floating gate and channel hot electron injection into floating gate,
the threshold voltage of memory cell can be converged to a specific
value. The gate pulse level can be varied to result in different
converged threshold voltages such that multilevel can be achieved.
Owing to the nature of self-convergence, the possibility of
eliminating or reducing the verification operation in multilevel
applications increases considerably by using the proposed scheme. In
this study the reliability considerations of this programming
technique for long-term operations are also addressed.
Viewing Angle Compensators for Liquid Crystal Displays based on Layers with a Positive Birefringence
Authors: Witte P. van de , Stallinga S. , Haaren J. A. M. M. van
Published: October 2002

New compensators to enhance the viewing angle dependence of
active matrix twisted nematic displays are designed. In contrast to
the well-known discotic compensation films, these compensators are
based on layers with a positive birefringence. It is shown that by
combining layers with a positive birefringence, the optical properties
of layers with a negative birefringence can be mimicked. Expressions
are derived that relate the optical properties of the stacks of
positively birefringent layers to those of negatively birefringent
layers. Calculated conoscopic plots confirmed the correspondence. Two
compensator configurations are experimentally tested: the combination
of two positively birefringent layers with a tilted optical axis,
referred to as T×T configuration, and the combination of a positively
birefringent layer with a planar optical axis and a layer with a
tilted optical axis, referred to as the P×T configuration. In both
cases the projections of the optical axes onto the plane of the layers
are crossed with respect to each other. It is demonstrated that the
compensator based on the T×T configuration already results in a
substantial improvement of the viewing angle of the active matrix
display. The contrast values, the linearity of the grey scales, and
the color purity of the compensated display for oblique viewing angles
are all improved with respect to the non-compensated display. The
contrast as a function of viewing angle is further improved by using
compensators based on two P×T layer stacks.
Impact of Thermal Nitridation on Microscopic Stress-Induced Leakage Current in Sub-10-nm Silicon Dioxides
Authors: Ogata Tamotsu , Inoue Masao , Nakamura Tadashi , Tsuji Naoki , Kobayashi Kiyoteru , Kawase Kazuo , Kurokawa Hiroshi , Kaneoka Tatsunori , Wake Setsuo , Arima Hideaki
Published: October 2002

By statistically analyzing 28,800 cells of arrayed stacked
gate transistors, for the first time, we examine the
effectiveness of nitric oxide (NO) and nitrous oxide (N2O)
nitridation in the suppression of the microscopic
stress-induced leakage current (mSILC) observed in devices
on the order of square microns in size. We have found that
NO nitridation is more effective in suppressing the mSILC
than N2O nitridation and is very promising for the reduction
of bit failures. The difference between the SILC observed in
devices on the order of square millimeters in size and the
mSILC observed in devices on the order of square microns in
size is also discussed.
Characteristics of intermixed InGaAs/InGaAsP Multi-Quantum-Well Structure
Authors: Yeo Deok Ho , Yoon Kyung Hun , Kim Sung June
Published: October 2002

The intermixing of a InGaAs/InGaAsP multi-quantum-well (MQW) structure induced by SiO2 dielectric
cap layer deposition and heat treatment was investigated. Photoluminescence experiments reveal a large
blue shift of the effective bandgap for the intermixed quantum well. By secondary ion mass spectroscopy,
the group III and V elements of a MQW are found to interdiffuse at a similar rate after the intermixing
process. An optical waveguide was fabricated using intermixed material where a propagation loss
reduction of 450 dB was recorded at a wavelength close to the
original bandgap wavelength.
Molecular Beam Epitaxial Growth of GaN on (0001) Al2O3 Using an Ultrathin Amorphous Buffer Layer Deposited at Low Temperature
Authors: Kimura Ryuhei , Takahashi Kiyoshi
Published: October 2002

The effects of buffer layer quality and/or deposition conditions
on the molecular beam epitaxy of GaN on c-Al2O3 substrates
were investigated. In order to precisely determine the effects of a
thin buffer layer, atomically flat and monolayer-stepped
Al2O3 substrates were prepared by conventional chemical
etching with a H3PO4: H2SO4
solution. A significant improvement in
the crystalline quality of the GaN epilayer was achieved when
ultrathin amorphous buffer layers deposited at temperatures as low
as 125°C were used. It was found that low-temperature
deposition leading to an amorphous buffer layer is important for the
optimization of the subsequent GaN epitaxial layer. The thickness of
the buffer layer is critical; only a very thin amorphous layer can
be well crystallized during the thermal annealing process before
epilayer growth. It was found that GaN epilayers grown on this
buffer layer gave rise to band-edge emissions (357 nm/FWHM=19.7 meV)
without any deep emissions in low-temperature
photoluminescence and led to (0002) X-ray rocking curves with a
full-width at half maximum of about 9.8 arcmin.
Numerical Study of InGaN Pattern Formation Caused by Phase Separation
Authors: Okumura Toshiyuki , Ishida Masaya , Kamikawa Takeshi
Published: October 2002

We performed a numerical study of the two-dimensional pattern
formation of InGaN driven by a phase separation using the cell
dynamical system (CDS) approach to reveal the detailed nature of a
self-assembled InGaN dot-like structure showing characteristic
optical properties. We calculated two-dimensional pattern formations
under various conditions. First, over a wide In compositional range
(0<In<0.6), a dot-like structure appears arising from a phase
separation as well as due to the effects of strains and
defects. These results are consistent with those in the case of
experimentally observed structures reported earlier. Thus, we can
conclude that in the present study, the pattern formation by a phase
separation affects the emission mechanism of InGaN-based
semiconductor light-emitting device because of a compositional
fluctuation of In. Second, the calculated results suggest that the
pattern formations depend on the experimental parameters, such as
growth temperature, the average and local fluctuation of In
composition, the lattice mismatch of InGaN and GaN, and defects.
Hall Effect and Thermoelectric Properties of FeSix
Authors: Tani Jun-ichi , Kido Hiroyasu
Published: October 2002

The Hall effect and thermoelectric properties of sintered iron
disilicide FeSi
x
(1.9≦x≦2.4) have been
investigated. The Hall coefficient of FeSi
x
at 300 K is
positive at 1.9≦x≦2.05 and x=2.40 but negative at 2.10≦
x≦2.30. The carrier concentration at 300 K has a large
composition dependence. The Seebeck coefficient below 750 K has a
strong composition dependence, but above 750 K it has almost no
composition dependence. The mobility shows the highest value of
3.6 cm2/Vs at x=2.05 which has the lowest carrier
concentration of 3.1×1017 cm-3 in the
composition range of 2.00≦x≦2.30. It is suggested that
the amount of Si or Fe point defects in β-FeSi2 is
closely related to the transport properties of carriers.
Effects of Thermal Annealing on the Au/Ni and the Au/Ni/Si/Ni Contact Properties of p-type GaN Epilayers
Authors: Kang Tae Won , Chi Chang Sun , Park Seung Ho , Kim Tae Whan
Published: October 2002

Thermal annealing effects on Au/Ni and Au/Ni/Si/Ni layers deposited on
p-GaN epilayers by
electron beam evaporation were employed with the goal of producing ohmic
contacts with low
specific resistance. Current–voltage (I–V) measurements were carried out
to investigate the effects of
thermal annealing on Au/Ni and Au/Ni/Si/Ni contact properties of p-type
GaN epilayers, and X-ray
photoelectron spectroscopy (XPS) measurements were performed to
characterize the formation of the
alloy layer and the diffusion behavior at each interface due to thermal
treatment. The results of the I–V
curves showed that both as-deposited and annealed Au/Ni and Au/Ni/Si/Ni
contacts on p-GaN were
high quality and that the lowest specific contact resistance of
5.32×10-2 Ω·cm2 was obtained for
Au/Ni/Si/Ni annealed at 800°C for 1 min in a nitrogen atmosphere. The
results of the X-ray
diffraction and XPS measurements showed that Ni silicide layers were
formed at the Au/Ni/Si/Ni/p-GaN interfaces. These results indicate that the formation of the Ni
silicide layer due to thermal
annealing reduces the specific contact resistance of the Au/Ni/Si/Ni
contacts and that the Au/Ni/Si/Ni
contacts annealed at 800°C hold promise for potential applications in
optoelectronic devices.
Characterization of Low-Dielectric-Constant Methylsiloxane Spin-on-Glass Films
Authors: Yamada Noriko , Takahashi Toru
Published: October 2002

The structure of the methylsiloxane spin-on-glass (SOG) film obtained by coating
the SOG solution prepared from methyltriethoxysilane and
dimethyoxymethyl-3,3,3-trifluoropropylsilane, followed by curing at 450°C in
nitrogen to decompose the trifluoropropyl group, has been characterized. Outgassing
from the SOG film was small except for the organic species derived from a methyl
group which began to be desorbed above 500°C. The SOG film was found to consist
of particulates with a diameter of several nm. No pores were found in the SOG film by
atomic force microscopy (AFM) and transmission electron microscopy (TEM)
observations. Pores introduced by the thermal decomposition of a trifluoropropyl group
appear to be so small that the boundary between the pore and a siloxane network is
ambiguous. A 29Si nuclear magnetic resonance (NMR) experiment has revealed that
new Si–O–Si bonds are formed between the two Si atoms derived from
dimethyoxymethyl-3,3,3-trifluoropropylsilane after the thermal decomposition
of the trifluoropropyl group.
Effect of Chemicals and Slurry Particles on Chemical Mechamical Polishing of Polyimide
Authors: Kim Hyoung-Gyun , An Yoo-Min , Moon Doo-Kyung , Park Jin-Goo
Published: October 2002

The purpose of this study was to investigate the effect of chemicals and particles on chemical mechanical polishing (CMP) of polyimide (PI). The effect of particle size and its surface area on both the removal rates and the surface roughness was investigated as a function of the slurry content upon the addition of various chemicals. The optimal particle content was measured for silica, ceria and alumina slurries in terms of the removal rate and surface roughness. The removal rate was highest when deionized (DI)-water-based alumina slurry was used. However, the greatest surface roughness was measured when ceria slurry was used rather than alumina. Alkaline chemicals were added to the slurry to enhance the removal rates of PI during CMP. The addition of Tetramethyl Ammonium Hydroxide (TMAH) and Potassium Hydroxide (KOH) to ceria slurry but not to alumina and silica slurries increased the removal rate significantly at higher pH values. The addition of ethylenediamine and the presoaking of PI in hot DI water did not increase the removal rate in alkaline-chemical-based slurries. The addition of surfactant resulted in a decrease of the removal rate to half of that determined without the addition of surfactant.
Voltage and Frequency Dependence of Differential Capacitance in Relaxed In0.2Ga0.8As/GaAs Schottky Diodes
Authors: Chen Jenn-Fang , Chen Nie-Chuan , Wang Jiin-Shung , Wang Pai-Yong
Published: October 2002

Capacitance dispersion over frequency is investigated for
relaxed In0.2Ga0.8As/GaAs Schottky diodes. While the
high-frequency capacitance is voltage-independent, the low-frequency
capacitance is seen to decrease with reverse voltage. Based on a
Schottky barrier combined with a high-resistance layer containing
traps, a simplified equation for the differential capacitance is
derived to explain the capacitance-voltage-frequency relation. It is
found that the high-frequency capacitance corresponds to the total
thickness of the Schottky depletion and the high-resistance layer,
while the low-frequency capacitance at a small reverse voltage is the
Schottky depletion capacitance and at a large reverse voltage is the
high-frequency capacitance.
Analysis of Reciprocating Motion of a Magnet Levitating above a YBa2Cu3Ox Superconductor
Authors: Hisaya Watanabe Hisaya Watanabe , Masaharu Suga Masaharu Suga , Hajime Konishi Hajime Konishi
Published: October 2002

We have analyzed the reciprocating motion of a magnet levitated above a YBa2Cu3Ox superconductor using a nonlinear mechanical model with a mass, a spring, and a dashpot. We introduced velocity dependence of the pinning effect and the distribution of the pinned flux lines against the strength of the pins into the mechanical model. Improved agreement between experimental reciprocation waveforms and simulated ones was achieved. Nonlinear characteristics of reciprocating motion of the magnet above a superconductor were successfully explained with the improved dragged spring model.
Elimination of a-Axis Growth in YBa2Cu3O7-δ Films on CeO2-Buffered Al2O3
Authors: Develos Katherine D. , Mukaida Masashi , Kusunoki Masanobu , Ohshima Shigetoshi
Published: October 2002

The elimination of a-axis orientation in
YBa2Cu3O7-δ (YBCO) films grown on
CeO2-buffered Al2O3 for microwave devices was
achieved through a two-step deposition process performed at
different temperatures. The growth of a-axis-oriented YBCO film
was considered to be due to the impediment of the adatom mobility by
the surface roughness of the underlying buffer layer. For the
initial layer, the deposition was carried out at a high temperature
to increase surface mobility. Next, the deposition was performed at
a lower temperature as necessary for optimum c-axis-oriented
growth. By this method, only a c-axis-oriented film was
obtained. The characteristic surface resistance R
s(T)
values for this film were significantly lower than those with mixed
c- and a-axis orientations.
A Semiconductor Coupled-Waveguide Structure as a Dispersion Compensator
Authors: Lee Yong
Published: October 2002

An InGaAsP/InP semiconductor coupled-waveguide structure was
investigated experimentally and theoretically as a potential
dispersion compensator. In-depth numerical analysis of the
waveguide-length dependence of autocorrelation-signal widths (which
are related to pulse durations) well explains that obtained
experimentally. This strongly indicates that the observed
pulse-compression is attributed to dispersion compensation by using
significantly enhanced group-velocity-dispersion of supermodes in
the coupled-waveguide structure. Furthermore, a numerical and
experimental study revealed that a pedestal observed in the
narrowest signal is not an intrinsic problem but most likely comes
from the difference in waveguide parameters of a fabricated coupled
waveguide and a designed coupled waveguide.
Numerical Analysis of Femtosecond Time-Resolved Degenerate Four-Wave Mixing Signal including Group-Velocity Dispersion Effect
Authors: Yoshihisa Yamaoka Yoshihisa Yamaoka , Ryuji Morita Ryuji Morita , Mikio Yamashita Mikio Yamashita
Published: October 2002

We numerically analyze the group-velocity dispersion (GVD) effect of the nonlinear medium on the femtosecond time-resolved degenerate four-wave mixing (DFWM) signal with the third-order nonlinear delayed response. As a result, we find that material GVD greatly influences not only the magnitude but also the temporal profile of the DFWM signal.
Study of Electronic Structures in LaCo1-xTixO3 (x = 0, 0.05 and 0.15) Using Discrete-Variational-Xα Cluster Method
Authors: Nakatsugawa Hiroshi , Iguchi Eisuke
Published: October 2002

Electronic structures of [CoO6]9- clusters have been studied by ab initio molecular-orbital (MO) calculations using the discrete-variational (DV)-Xα cluster method in order to investigate the correlation between the change in the type of the majority carrier and electronic structures in LaCo1-x
TixO3 (x = 0, 0.05 and 0.15). The most significant features are that the e
g↑ bandwidth in the x ≠0 specimen is wide in comparison with the x = 0 specimen and the Co–O bonding MO energy levels in the x≠0 specimens are in the energy range of -3 eV to -2 eV. These calculations indicate that both the 3d electrons in donor centers of σ* bands and the O 2p ligand holes in σ* bands are responsible for the electronic conduction in the x = 0.05 and x = 0.15 specimens but the competition between the densities of 3d electrons in σ* bands and O 2p ligand holes dominates the type of the majority carrier.
Cross-Sectional Transmission Electron Microscopic Observation of Etch Hillocks and Etch Pits in LiTaO3 Single Crystal
Authors: Ueda Tomohiko , Takai Yoshizo , Shimizu Ryuichi , Yagyu Hiroyuki , Matsushima Tomoaki , Souma Makoto
Published: October 2002

Cross sections of etch hillocks and etch pits in LiTaO3 single crystal have
been observed by transmission electron microscopy. The cross-sectional samples were
prepared at their exact positions by the focused ion beam microfabrication method.
Inverted polarized domains were observed both at the top of etch hillocks and at the
bottom of etch pits, indicating that the etching figures originate in the inverted domain
formed on the surface. Furthermore, some inverted domains that were pinned by lattice
defects were also observed at the inner part of the crystal.
High Performance Transmittive Bistable Twisted Nematic Liquid Displays
Authors: Guo Jian-Xin , Kwok Hoi-Sing
Published: October 2002

Several new transmittive bistable twisted nematic liquid display
(BTN-LCD) modes are developed. Unlike previous versions, these BTN
modes do not require cross polarizers. Experiments confirmed that
these modes have high contrast ratio and reasonably high
transmittance. The dispersion characteristics of some of these modes
are comparable to ordinary waveguiding TN modes. That is, they afford
true black/white operations without any need for further color
compensation.
Formation of Iron-Nitride/Silver Nanocomposites by Ammonia-Flow Method and Nitride Phase Identification by X-Ray Absorption Near-Edge Structure
Authors: Katsuhiro Nishimaki Katsuhiro Nishimaki , Takao A. Yamamoto Takao A. Yamamoto , Takashi Nakagawa Takashi Nakagawa , Masahiro Katsura Masahiro Katsura
Published: October 2002

Magnetic nanocomposites in which iron nitride nanograins were dispersed in a silver matrix were synthesized by nitriding iron oxide nanograins buried in the matrix. The ammonia-flow method, in which the solid phase reacted with flowing ammonia, was adopted for this synthesis. Several reactions of metallic iron with NH3 were carried out under various conditions and the resultant nitride phases were observed by X-ray diffraction (XRD). Based on these results, optimum conditions for the synthesis of the nanocomposite were determined, and a nanocomposite containing only γ'-Fe4N or ε-Fe2–4N was successfully obtained. Phase identification of iron nitride in the composite was performed by X-ray absorption near-edge structure (XANES) measurement, which was found to be more suitable for the present nanocomposites than XRD.
Formation of Yttrium Aluminum Perovskite and Yttrium Aluminum Garnet by Mechanical Solid-State Reaction
Authors: Guo Xiaomei , Sakurai Kenji
Published: October 2002

Polycrystalline fine powder of yttrium aluminum perovskite (YAP)
and yttrium aluminum garnet (YAG) have been successfully synthesized
for the first time by mechanical solid-state reaction. The reaction
scheme has been studied in detail. In short, the technique uses two
reaction steps. First, a high-energy ball mill is used for the
formation of a non-equilibrium disordered phase of Y–Al–O from a
stoichiometric mixture of alumina and yttria at room
temperature. Then, subsequent heating crystallizes the powder and
obtains either YAP or YAG, depending on the initial chemical
composition. Preparing the Al2O3–YAG system is also
possible. The crystallization is completed at a maximum temperature
of 1150°C, and therefore special high-temperature equipment is
not required, unlike in conventional solid-state-reaction
procedures.
Microdomain Structure in the Disordered Zn–Mg–Ho Icosahedral Phase
Authors: Ishimasa Tsutomu , Shimizu Takayuki
Published: October 2002

Diffuse scattering related to F-type superlattice ordering was
observed in the disordered icosahedral phase formed in
Zn60Mg35Ho5 alloy annealed at 562°C. Real space
analysis of the diffuse scattering was carried out using
high-resolution electron microscopy and a Fourier filtering
method. Processed images revealed the presence of microdomains
related to weak F-type ordering. The domain diameters range between
30 and 170 Å. Each domain is separated by a boundary region, and
is related to nearby domains by an antiphase relationship. These
results indicate that the origin of the diffuse scattering is the
presence of these domains rather than statistical homogeneous
short-range ordering.
Integrated Distributed Bragg Reflector Laser with Grating Coupler for Divergent Spherical Wave Emission
Authors: Shimada Naoyuki , Uemukai Masahiro , Suhara Toshiaki , Nishihara Hiroshi , Eriksson Niklas , Larsson Anders
Published: October 2002

We propose and demonstrate an InGaAs integrated distributed Bragg reflector
laser with a grating coupler for divergent spherical wave emission from a virtual
diverging point (VDP). The small grating coupler is located close to the active
channel to realize a compact device. An external lens having a large aperture can be
used to focus the output into a small spot. Single-mode lasing up to 2.2 mW and a
VDP spot size of 4.6×4.5 µm2 (theoretical size
1.0×2.1 µm2) were obtained.
Theoretical Model and Device Performance of CuInS2 Thin Film Solar Cell
Authors: Ito Kentaro , Matsumoto Naoki , Horiuchi Tsuyoshi , Ichino Katsuhiko , Shimoyama Hiroshi , Ohashi Tsuyoshi , Hashimoto Yoshio , Hengel Imke , Beier Jutta , Klenk Reiner , Jäger-Waldau Arnulf , Lux-Steiner Martha Ch.
Published: October 2002

The capacitance vs. voltage characteristics and the current vs. voltage characteristics of the thin film solar cell consisting of a transparent
conductive oxide/CdS/CuInS2 heterostructure are analyzed in terms of the theoretical device model where a very
thin n-type CuInS2 layer exists on the
top surface of the p-type absorber layer. The CuInS2 absorber layer is prepared by sulfurization of precursors deposited on a Mo-coated soda lime
glass substrate or a Pt foil substrate. When the absorber layer is prepared on
the former the heterostructure is an abrupt junction in which the net
acceptor concentration of the absorber layer is of the order of 1016–1017 cm-3,
but when prepared on the latter it is a linearly graded junction in which the
gradient of the acceptor concentration lying in the order of 1020–1021 cm-4 is
a decreasing function of precursor thickness. The highest open circuit
voltage of 0.755 V is obtained in a solar cell that consists of the thickest absorber layer prepared on the latter and hence exhibits the lowest built-in electric field at the junction interface.
Control of Crystalline Structure and Electrical Properties of TaSiN Thin Film Formed by Reactive RF-Sputtering
Authors: Oizumi Munenori , Aoki Katsuhiro , Hashimoto Satoshi , Nemoto Satoru , Fukuda Yukio
Published: October 2002

The crystalline structure, thermal stability, and electrical
properties of TaN and TaSiN thin films formed by reactive
RF-sputtering with a broad range of N and Si composition ratios were
investigated. TaSiN with a Si/(Si+Ta) ratio less
than 25% were crystalline, whereas that with a ratio more than 25%
was amorphous, regardless of the N2 partial pressure. The
amorphous films exhibited excellent thermal stability with no
crystallization up to 900°C. Crystalline films consisted of
columnar grains with sizes ranging from 20–30 nm. Electrical
resistivity showed a strong dependence on the Si and N composition
ratios. However, amorphous films deposited at low N2 partial
pressure exhibited constant resistivity, regardless of the Si/Ta
ratio. These results clarify that the crystalline structure and
electrical resistivity of TaSiN films can be controlled by varying
the Si and N composition ratios.
The Selective Area Deposition of Diamond Films
Authors: Liu Hongwu , Gao Chunxiao , Zou Guangtian , Li Xun , Wang Chengxin , Wen Chao
Published: October 2002

By selectively seeding, polycrystalline diamond films have been patterned on mirror-polished Si substrate using hot-filament chemical vapor deposition. Results show high selectivity and high quality in patterned diamond films deposited at 0.05% CH4/H2 concentration and at the growth rate of 2.6 µm/h. The selective area deposition (SAD) method is easy to be applied to a large and a different substrate.
Effective Lifetimes of Diffusing Metastable Particles Affected by Reflection in a Cylindrical Cavity
Authors: Susumu Suzuki Susumu Suzuki , Haruo Itoh Haruo Itoh , Nobuaki Ikuta Nobuaki Ikuta , Hisashi Sekizawa Hisashi Sekizawa
Published: October 2002

The behavior of the effective lifetimes of metastable particles is investigated by solving the diffusion equation taking the reflection phenomenon of the metastable particles at the boundaries into account. The analysis of the one-dimensional diffusion equation for the metastable particles proposed by us is extended to the diffusion in three-dimensional space. The variation of the spatiotemporal density distribution of the metastable particles in the cylindrical cavity, and the behavior of the effective lifetimes of the metastable particles are systematically reported.
Numerical Study of the Effects of Frequency in Inductively Coupled Plasma Using Particle-in-Cell/Monte Carlo Simulation
Authors: Jin-Sung Oh Jin-Sung Oh , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

The effects of induction frequency on inductively coupled plasma (ICP) have been investigated in a collision-dominated region in Ar under a constant dissipated power using the particle-in-cell/Monte Carlo (PIC/MC) simulation. The plasma density, potential, electron energy distribution and mean electron energy are discussed as a function of the applied frequencies of 6.78 MHz, 13.56 MHz, 27.12 MHz and 100 MHz at pressure of 100 mTorr and 300 mTorr.
Effect of Basic Additives on Acid-Catalyzed Electron-Beam Negative Resist Using Intramolecular Dehydration of Phenylcarbinol
Authors: Migitaka Sonoko , Yamamoto Jiro , Uchino Shou-ichi , Hashimoto Michiaki , Murai Fumio , Shiraishi Hiroshi
Published: October 2002

The effect of basic additives on a negative electron-beam resist
utilizing acid-catalyzed intramolecular dehydration of
1,3,5-tris(2-(2-hydroxypropyl))benzene (Triol) was
investigated. Quinoline was selected as the most effective additive
to suppress acid-diffusion among investigated ones. Though the
addition of quinoline decreased the Triol resist sensitivity, it
enhanced the contrast and critical-dimension (CD) deviation
stability to post-exposure-baking temperature variation. Optimized
resist system achieved the CD deviation stability: 1.5 nm/°C
and 100-nm line and space patterns with a dose of
6.2 µC/cm2 @ 50 kV. Influence of the additive on the
Triol resist insolubilization mechanism was discussed.
Nondestructive Detection of Flaw in Carbon-Fiber-Reinforced Plastics Using High-Tc Superconducting Quantum Interference Device
Authors: Kasai Naoko , Suzuki Daisuke , Hatsukade Yoshimi , Koyanagi Masao
Published: October 2002

The nondestructive detection of small cracks and deep-lying
flaws in structures is important for safety
inspection. Carbon-fiber-reinforced plastics (CFRP) are complex
materials for use in aircrafts and structures. We investigated the
possibility of detecting flaws in CFRP using a nondestructive
evaluation system using high-T
c superconducting quantum
interference device (SQUID). A SQUID system for the nondestructive
evaluation was developed using a SQUID magnetometer and a SQUID
gradiometer fabricated based on a YBa2Cu3O7-δ
thin film. Holes, the diameters of which were equal to or larger
than 0.4 mm, were made in CFRP plates and all holes except the
smallest one were detected by a current-injection method using this
system. The results show that the location and the diameter of the
holes can be estimated from the distribution of the magnetic flux
density, B

z
, measured by the magnetometer or the distribution
of the first-order gradient of B

z
, dB

z
/dx, measured by
the gradiometer. The effect of texture of the carbon fiber in CFRP
on the magnetic signal strength was discussed.
Continuum X-Ray Generation from W Film on Cu Substrate
Authors: Obori Kenichi , Yurugi Toshikazu , Ding Ze-jun , Nagatomi Takaharu , Fujii Kentarou , Kimura Yoshihide , Shimizu Ryuichi
Published: October 2002

The dependence of the continuum X-ray generation from a W film
on the primary energy (15 to 30 keV) and film thickness (0.1 to
0.7 µm) have been investigated by experiment and Monte Carlo
(MC) simulation in order to develop a high-power rotor-type
X-ray source of high efficiency. The continuum X-ray spectra
obtained by MC simulation show excellent agreement with the
experimental data, confirming the fact that the present MC
simulation is applicable for a systematic study to optimize the
construction of an X-ray source. The dependence of the continuum
X-ray generation on the thickness of the W film has revealed that
the continuum X-ray spectra from the W film of thickness
∼0.7 µm are almost similar to those of the bulk W in the
investigated range of primary energies. This indicates that the
thickness of the W film of ∼0.5 µm is sufficient for the
rotor-type X-ray source, although a commercial-type source is of the
order of hundreds µm with the primary energy of ∼50 keV.
Plasma Diagnostics in Inductively Coupled Plasma Etching Using Cl2/Xe
Authors: Matsutani Akihiro , Ohtsuki Hideo , Koyama Fumio , Iga Kenichi
Published: October 2002

We investigated the plasma characteristics in an inductively
coupled plasma (ICP) etching process using Cl2/Xe by means of a
quadrupole mass spectrometer equipped with an ion energy
analyzer. It was found that the ion energy of Cl+ increased with
decreasing etching pressure, and the quantity of Cl+ increased with
decreasing Cl2 flow rate. Ions including etching products such as
Si+, Cl+, Xe+ and SiCl
x

+ were observed in the
etching plasma. It is
suggested from the results of this experiment that the etching
profile can be controlled by the in situ monitoring of the
quantity
of Cl+ ions.
An Increase of More Than 30% in the Electrooptic Coefficients of Fe-Doped and Ce-Doped Stoichiometric LiNbO3 Crystals
Authors: Kondo Yukiko , Fukuda Takeshi , Yamashita Yuri , Yokoyama Koichi , Arita Kanji , Watanabe Masato , Furukawa Yasunori , Kitamura Kenji , Nakajima Hirochika
Published: October 2002

The composition dependences of the electrooptic coefficients in LiNbO3 crystals and the
influence of doping with Ce-ions and Fe-ions were measured precisely and investigated in
detail for the first time. The electrooptic coefficient r
33 increases with an increase in the
Li/Nb ratio. The r
33 in stoichiometric LiNbO3 crystal was 1.14 times as large as that in
conventional congruent LiNbO3 crystal whose electrooptic coefficient is 32.6 pm/V. The
electrooptic coefficient r
33 is also increased by doping with some ions. An increase of more
than 30% in electrooptic coefficients (from those in nondoped congruent LiNbO3) can be
obtained by doping with Ce- or Fe-ions.
The lattice constants are also measured. The lattice constant along the c-axis decreases
with an increase in the Li/Nb ratio, or by doping with Ce- or Fe-ions, and in this way the
crystal structure changes into a less symmetric structure. This may be the reason why the
electrooptic coefficient increases with an increase in the Li/Nb ratio or by doping with Ce- or
Fe-ions.
Monolithically Integrated Master Oscillator Power Amplifier with Grating Coupler for Collimated Output Beam
Authors: Uemukai Masahiro , Miyata Michitaro , Shimada Naoyuki , Suhara Toshiaki , Nishihara Hiroshi , Eriksson Niklas , Modh Peter , Larsson Anders
Published: October 2002

A monolithically integrated master oscillator power amplifier with a grating
outcoupler for emitting a collimated beam is demonstrated. In order to improve the
device performance, theoretical simulation is performed based on the beam
propagation method, and both compensation for wavefront distortion produced in the
amplifier and optimization of the radiation decay factor are incorporated in a new
design of the grating outcoupler. The device was fabricated by a simple process
without regrowth. Stable single-mode lasing up to 183 mW output power at a
wavelength of 985 nm was obtained under CW operation. As a result of optimization
to minimize the divergence angle of the output beam, a well-collimated beam, with a
nearly circular profile and divergence angles smaller than
0.28°×0.38°, was
maintained in high-power operation.
Fundamental Study of Parallel Moduling Scheme Based on a Micro-Optical Bench and Collimating Planar Microlenses
Authors: Aoki Yasuhiko , Mizuno Rogerio Jun , Shimada Yuji , Iga Kenichi
Published: October 2002

We have conducted a feasibility study of a parallel moduling scheme based on a collimating guide using planar microlenses. This
optical subsystem consists of a stacked planar optical circuit and a
micro-optical bench (MOB) for alignment. We measured the coupling
loss of microlens collimation and determined that single-mode
fiber-to-fiber coupling of approximately 2 dB is possible. We also
investigated the optical crosstalk of the collimating optical system
using planar microlenses (PMLs), and the crosstalk of less than
-70 dB was achieved. As an initial subsystem experiment using
vertical cavity surface emitting lasers (VCSELs), we fabricated a
VCSEL array (λ=850 nm, I
th=1.8 mA at room
temperature, CW) and bonded it on a Si MOB.
Analyses of Thermally Stimulated Current Curves with No Peaks
Authors: Yoshimi Kamitani Yoshimi Kamitani , Shigeyoshi Maeta Shigeyoshi Maeta
Published: October 2002

A theory that enables one to accurately estimate three parameters, namely, an energetic depth of carrier trap site E
t, an escape frequency factor ν and a charge carrier density n
t, from thermally stimulated current (TSC) curves with no peaks is proposed. Generally, these three parameters could not be evaluated from any TSC datum without peak coordinates. Such TSC data are usually measured experimentally in order to separate signals from each other in various composite cases. Our proposed theory makes it possible to evaluate several sets of three parameters. The proposal is a method to compensate the charges lost in experiments. Three types of charge compensation processes are reported in detail. The accuracy of evaluation of each of the three parameters is very good and the E
t values of three significant figures could be obtained by numerical analyses.
Effects of Discharge Frequency in Plasma Etching and Ultrahigh-Frequency Plasma Source for High-Performance Etching for Ultralarge-Scale Integrated Circuits
Authors: Samukawa Seiji , Donnelly Vincent M. , Malyshev Mikhail V.
Published: October 2002

A low-temperature, uniform, high-density plasma is produced by applying
ultrahigh-frequency (UHF) power through a spokewise antenna. The plasma is uniform
within ±5% over a diameter of 30 cm. No magnetic field is needed to maintain
the high-density plasma. Consequently, the plasma source is fairly simple and
lightweight. This plasma creates a high electron density and a low degree of
dissociation of the feed gas at the same time because the electron energy distribution
function is not Maxwellian (bi-Maxwellian distributions). The plasma characteristics
are highly suitable for the precise etching of Al and gate electrodes. Additionally, by
the combination of bi-Maxwellian electron energy distribution in the UHF plasma and
new fluorocarbon gas chemistries (C2F4, CF3I), selective radical
generations of CF2 and CF3 could be realized for high-aspect contact hole
patterning of SiO2. A high ion density and a high-energy tail in the electron energy
distribution can also be maintained over a wide range of pressure
(from 3 to 20 mTorr), whereas in conventional inductively coupled plasma
(ICP: 13.56 MHz), the ion density and number of high-energy electrons are drastically
reduced when the gas pressure is increased. This indicates that the ionization in the
UHF plasma does not depend significantly on gas pressures between 3 and 20 mTorr
because the discharge frequency is higher than the frequency of electron collisions in
the plasma. As a result, the UHF plasma provides a process window for
high-performance etching that is wider than the one provided by an ICP.