bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition of Space Charge to Wall Charge by Control Pulse after Self-Discharge in AC-Plasma Display Panel
Authors: Ko Jae-Jun , Kim Young-Guon , Kim Dae-Il , Lee Chun-Woo , Cho Guangsup , Choi Eun-Ha
Published: October 2002

The transition of space charge to wall charge after self-discharge has been experimentally tested in an AC-plasma display panel (PDP) with a versatile driving simulator (VDS) system, in which arbitrary driving waveforms and sequences can be used. When the self-discharge occurs immediately after a high voltage reset pulse is applied, a certain amount of space charge is generated in the PDP cell. By applying a suitable control pulse at this time, it is found that these space charges can be converted into sufficient wall charges for maintaining a sustain discharge without any writing pulse. Also, the saturated sustain peak current strongly depended on the control pulse condition in spite of the same sustain waveform. This means that the influence of the initial wall charge which was formed prior to the sustain period is continuously maintained throughout the sustain period.
Feasibility of Microwave Transmissivity Measurement to Obtain Density Profile of Sheet Plasmas
Authors: Akira Ejiri Akira Ejiri , Kazuo Kawahata Kazuo Kawahata
Published: October 2002

Measurement of microwave transmissivity is a very simple diagnostic method to obtain maximum density and profile information of sheet plasmas. In this method, transmissivity of the incident microwave is measured as a function of probing frequency. When a cutoff exists in the plasma, the main part of the incident wave is reflected, but a part can penetrate the plasma due to the tunnel effect. Transmissivity represents the degree of this effect, and its frequency dependence yields information on the density profile. The feasibility of this method is studied analytically using the Wentzel-Kramers-Brillouin (WKB) method, and the results are compared with those from the numerical solutions of the one-dimensional wave equation. It is shown that the method is useful when the sheet plasma is not too thick. In addition, slight homogeneity along the sheet is required to avoid the effect of refraction.
Dependence of Fluorocarbon Plasma Chemistry on the Electron Energy Distribution Function
Authors: Kokura Hikaru , Sugai Hideo
Published: October 2002

Recent diagnostics of high-density plasmas suggest a difference in the electron
energy distribution function (EEDF) between a surface wave plasma and an inductively
coupled plasma, which may be a main reason for the difference between the radical
compositions of the two types of fluorocarbon plasmas at the same electron density. In
order to account for the experimental result, a simple model is described based on a
bi-Maxwellian EEDF with a bulk-electron temperature T
b and a tail-electron
temperature T
t (>T
b). For simplicity, the conventional
C4F8 etching gas is replaced by feeding CF3, CF2 and CF radicals
into a vessel. A set of particle-balance equations is formulated with wall reactions
(radical sticking, charge neutralization) and inelastic electron collisions are taken into
account. Numerical solutions for the discharge in 2 mTorr C4F8/18 mTorr
Ar show that the plasma becomes less dissociative and CF
x
radical rich (F radical
poor) with increasing T
t and decreasing T
b. For example, the
radical density ratio of CF
x
/F at the electron density of
3×1011 cm-3 is two times larger in the bi-Maxwellian EEDF of
T
b=1.5 eV and T
t=5.0 eV than in the `single' Maxwellian EEDF
of T
b=2.75 eV.
Ultrasonic Relaxation Study in Gelatin Sols and Gels
Authors: Choi Pak-Kon , Tanimoto Ryosuke
Published: October 2002

Ultrasonic absorption was measured in gelatin sols and gels in
the frequency range of 0.2–35 MHz. Two techniques, a plano-concave
resonator method and optical beam deflection by ultrasonic waves,
were used to cover the wide frequency range. The absorption spectra
observed both in the sols and gels were well fitted to the
relaxation curves, assuming the Cole-Cole-type distribution of
relaxation times. A change in relaxation parameters upon gelation
was obtained: the relaxation frequency decreased, the relaxation
strength increased and the distribution became wider. The relaxation
mechanism is discussed in the light of the hydration equilibrium of
gelatin polymers.
Brillouin Scattering of Urea-Doped Thiourea
Authors: Yasunari Takagi Yasunari Takagi
Published: October 2002

Urea (CO(NH2)2)-doped thiourea (CS(NH2)2) crystals were
grown by the evaporation method. The values for the x concentration for [CS(NH2)2]100-x
[CO(NH2)2]
x
crystals were determined by a chemical analysis of oxygen and sulfur and checked for complementarity with dielectric constants and Brillouin shifts. The x ≤1 mol% was found for any ratio of mixed reagents. The temperature dependence of Brillouin shifts of the longitudinal acoustic phonon (C
33) in the x ≈1.1 crystal was similar to that of pure thiourea. However, the sudden jump in the incommensurate phase may indicate the escape of CO(NH2)2 as an impurity due to loose coupling.
Amplification without Inversion in the Four-level N-Type 87Rb D1-Line
Authors: Seb Moon Han , Soo Choe Yong , Ah Kim Hyun , Soo Kim Bong , Dae Kim Kyoung , Bog Kim Jung
Published: October 2002

We demonstrate amplification without inversion in the 87Rb D1-line pumped by an incoherent light. A closed N-type, four-level atomic system has been considered to obtain an insight into the origin of the gain as well as the conditions under which the system exhibits gain without population inversion in bare states. We investigate the gain as a function of the incoherent pumping rate, the coupling laser detuning, and Rabi frequency. The experimental results are in good agreement with the numerical calculations considering the velocity distribution of atoms.
Development of High-Efficiency Strip-Coupled Surface Acoustic Wave Convolver Using GaSb/InSb/AlGaAsSb/LiNbO3 Structures
Authors: Goto Hiromasa , Tsunashima Masamichi , Kanno Yasuhito , Yamagata Yo , Kuze Naohiro , Yamanouchi Kazuhiko
Published: October 2002

We have fabricated a strip-coupled surface acoustic wave [SAW]
convolver using GaSb/InSb/AlGaAsSb heterostructures grown on a
LiNbO3 substrate. An InSb thin film with an AlGaAsSb buffer
layer was grown on a 128° Y-X LiNbO3 substrate by
molecular beam epitaxy; a very high electron mobility of
7000 cm2/(V·s) in 200-nm-thick InSb films was
achieved. We have fabricated a strip-coupled SAW convolver as a new
device and have achieved a very high output efficiency (F value) of
-14 dBm for modified semiconductor and electrode structures.
Effect of CO2 and Water Vapors on NOx Removal Efficiency under Conditions of DC Corona Discharge in Cylindrical Discharge Reactor
Authors: Gasparik Robert , Ihara Satoshi , Yamabe Chobei , Satoh Saburoh
Published: October 2002

Carbon dioxide (CO2) and water vapors effects on NO
x

removal efficiency was studied in the wire-cylinder discharge reactor
utilizing a DC power supply. The content of CO2 in both wet and
dry aired initial gases was 0%, 5%, 10%, 15% and 20%,
respectively. NO
x
treatment efficiency strongly depended on a DC
positive corona discharge mode, which changed with CO2
concentration regardless the water content. A glow mode of corona
discharge, established when the concentration of CO2 in the
initial gas was 0% and 5%, exhibited very low removal efficiency
(removal rate under 10% and energy yield about 1.1 NO g/kWh). In the
cases of 10%-, 15%- and 20%-content-of-CO2 input gas, the glow
corona mode was transferred into a streamer for both wet and dry
initial gases. Therefore, the removal efficiency dramatically
enhanced–the most efficient treatment was achieved when 15% of
CO2 was included in the initial gas (5.1 NO g/kWh for wet gas
and 4.8 NO g/kWh for dry gas). Water vapors played an important role
in NO2 removal via the mutual reaction forming
HNO3. Therefore, in the wet-air supplied reactor the highest
removal rates of NO
x
were as high as 48%, while in dry-air
supplied reactor only 15%.
Quantitative Measurement of Linear and Nonlinear Dielectric Characteristics Using Scanning Nonlinear Dielectric Microscopy
Authors: Yasuo Cho Yasuo Cho , Satoshi Kazuta Satoshi Kazuta , Koya Ohara Koya Ohara , Hiroyuki Odagawa Hiroyuki Odagawa
Published: October 2002

The theory for quantitative measurement of linear and nonlinear dielectric constants using scanning nonlinear dielectric microscopy is explained in this paper.
Using this theory, quantitative measurements for linear and nonlinear dielectric constants of dielectric materials were performed successfully.
Detection of Defects in Micro-Machine Elements by Using Acoustic Waves Generated by Phase Velocity Scanning of Laser Interference Fringes
Authors: Harumichi Sato Harumichi Sato , Sohei Matsumoto Sohei Matsumoto , Hisato Ogiso Hisato Ogiso , Hideo Cho Hideo Cho , Kazushi Yamanaka Kazushi Yamanaka
Published: October 2002

High aspect ratio microstructuring is a key process for fabricating microelectromechanical systems (MEMSs). Many microfabrication methods have been developed. Among them, inductively coupled plasma (ICP) source etching is especially attractive because it can fabricate high aspect ratio microstructures, at high speeds with a dry etching process. However, in such microstructures, it is difficult to nondestructively evaluate the quality of high aspect ratio etched bottoms. Therefore, we developed a technique for detecting defects in high aspect ratio microstructures on Si wafers machined by ICP source etching. Using acoustic waves generated by phase velocity scanning of laser interference fringes, we nondestructively detected 13-µm-high defects located on the bottom of narrow and deep grooves from the other side of the Si wafer, which could not be detected by means of optical techniques or a scanning electron microscope.
Nitrogen-Doping Effects on Electrical Properties of Hydrogenated Microcrystalline Silicon as Studied by Electron Paramagnetic Resonance and Conductivity
Authors: Takashi Ehara Takashi Ehara , Tetsuya Amino Tetsuya Amino , Hiroyuki Shinomiya Hiroyuki Shinomiya , Tadaaki Ikoma Tadaaki Ikoma , Kimio Akiyama Kimio Akiyama , Shozo Tero-Kubota Shozo Tero-Kubota
Published: October 2002

We have examined Raman scattering, X-ray diffraction, electron paramagnetic resonance (EPR) spectra and the conductivity of nitrogen-doped hydrogenated microcrystalline silicon. The EPR signals due to conduction electrons have been observed in the doped films, except for highly doped samples that have no microcrystalline fraction. The result indicates that the doped nitrogen atom acts as an electron donor in the microcrystalline silicon. The temperature dependence of the conductivity clarify that the activation energy depends on the doping level. The influence of the doping level on the conductivity can be interpreted in terms of the balance of the effective electron donation and the decrease of carrier mobility due to a decrease of the microcrystalline phase volume ratio. At temperatures lower than approximately 180 K, the conductivity shows little variation. This is explained using a model of the hopping conduction, in terms of defect states for all samples.
Microscopic Imaging of Circular Dichroism Using a Polarizing Undulator
Authors: Yamada Toru , Onuki Hideo , Yuri Masatada , Ishizaka Shozo
Published: October 2002

A new type of scanning microscope for observing circular
dichroism (CD) images of samples was developed. As an illuminating
light source, a polarizing undulator which generates right- and
left-handed circularly polarized synchrotron radiations (SR)
alternately, was used in the microscope. The SR from the polarizing
undulator was focused to form a microbeam with a spot size of less
than 1 µm, by axially symmetric mirrors. The sense of rotation of
circular polarization of the undulator radiation was modulated with a
frequency of about 2 Hz. Two-dimensional CD images of a thin film of
d-10-camphorsulfonic acid, which is one of the standard samples used
for measuring a CD spectrum, were obtained by this microscope.
Quadratic-Curve Approximation of Impulse Responses to Calculate Radiated Fields from Rectangular Transducers
Authors: Hiroyuki Masuyama Hiroyuki Masuyama , Keinosuke Nagai Keinosuke Nagai , Koichi Mizutani Koichi Mizutani
Published: October 2002

A new approximation of the impulse response to
calculate speedily acoustic radiated fields from a
rectangular transducer is proposed.
The conventional approximation causes considerable error
in some cases.
The proposed method approximates the time derivative
of the response with the inclined straight lines in
the interval between its discontinuities.
This means the graph of the response itself is
approximated with quadratic curves.
We call this method the quadratic-curve approximation.
Numerical calculation indicates that the quadratic-curve
approximation reduces error with little increase in
computational load.
Carrier Concentration Dependence of Photoacoustic Spectra of Silicon by a Piezoelectric Transducer Method
Authors: Kuwahata Hiroshi , Muto Nobuo , Uehara Fumiya
Published: October 2002

Photoacoustic (PA) spectra near the energy gap (E
g) of n- and
p-type silicon (Si) were observed at various carrier concentrations
using a piezoelectric transducer method. With increasing carrier
concentration, the PA signal intensity at energies slightly higher
than E
g decreased for n-type samples and increased for p-type
samples. The decrease and the increase were considered to be due to
the increase in free electrons at the bottom of the conduction band
and to the increase in holes at the top of the valence band,
respectively. The PA spectra were not observed for either type of
sample above a carrier concentration of 1017 cm-3.
Simultaneous Transmission of Tomography Transceivers Using Multiple M-Sequence Signals
Authors: Nakamura Toshiaki , Kanaizumi Tomoyuki , Fujimori Hidetoshi , Nakano Iwao , Metzger Kurt
Published: October 2002

A tomography array which consists of five 200 Hz transceivers was deployed in the Central Equatorial Pacific in December 1998 to monitor the variability of water temperature and current in relation to El Niño. In this experiment, we intend to perform precise measurement using simultaneous transmission from five transceivers. As each transceiver receives an overlapped signal from other transceivers, multiple M-sequence signals were selected carefully and used to discriminate mutual signals among transceivers.
Analysis of Scattered Sound from Underwater Hollow Cylinders Using the Wigner Distribution Function
Authors: Kohji Futa Kohji Futa , Nobuaki Takahashi Nobuaki Takahashi , Hiroshi Ochi Hiroshi Ochi , Toshiaki Kikuchi Toshiaki Kikuchi
Published: October 2002

The scattered sound from an aluminum hollow cylinder in water is analyzed using the Wigner distribution function.
When sound is scattered by a thick-shelled cylinder, the creeping wave appears after the specular-reflected wave.
As the thickness of the cylinder shell decreases, however, the creeping wave tends to disappear and ridges parallel to the time axis come into the time-frequency plane because of the resonance in the cylinder.
While the backscattered wave exhibits a complicated distribution pattern, the wave scattered at 90 degrees is relatively monotonic.
From the computer simulation that the removal of the transverse wave propagating in the cylinder results in the emphasis of the specular reflection and the pattern becomes monotonic in the time-frequency plane, the presence of the transverse wave influences strongly the characteristics of the scattered sound from an elastic object.
Since the distribution in the plane exhibits a characteristic pattern in every case, the Wigner distribution function offers an effective means to analyze the scattered sound from an object in water.
Magnetically Enhanced Reactive Ion Etching of Lead Zirconate Titanate Thin Film by CHF3 Plasma
Authors: Lin Yin-yin , Liu Qin , Tang Ting-ao , Yao Xi , Huang Wei-ning
Published: October 2002

A metal-organic deposition (MOD) derived Pb
(Zr0.53Ti0.47)O3 thin film was patterned using
magnetically enhanced reactive ion etching (MERIE) which promised a
relatively high etching rate, large etch anisotropy and good
selectivity for lead zirconate titanate (PZT). The etched surface of
PZT thin films was investigated by X- ray photoelectron spectroscopy
(XPS). It was found that PbF2, ZrF4 and polymers containing
C, H and F were formed and remained on the etched surface while no
titanium fluoride was formed during the etching process. The major
factor that restricts the realization of a high etching rate is the
removal of PbF2. Fluoride that remained on the surface could be
removed by annealing after etching.
Analysis of Characteristics of Underwater Sound Propagation in the Ocean by a Finite Difference Time Domain Method
Authors: Iijima Fumiaki , Tsuchiya Takenobu , Endoh Nobuyuki
Published: October 2002

Many methods of calculation that are useful in deep water like the Pacific Ocean
have recently been reported for obtaining sound propagation characteristics. The
development of new method is expected for shallow water. In this paper, the finite
difference time domain (FDTD) method, which takes account of attenuation, is proposed
to calculate the propagation of sound in shallow water with a lossy seabed. The
benchmark problem proposed by the Acoustical Society of America was solved by the
FDTD method and its results were compared with other methods. The contour pattern of
the transmission loss in water and in sediment agreed well with the results of an
accurate coupled-mode calculation. A series of propagated pulse waveforms in the same
model is also calculated. It is useful for us to recognize the sound propagation not only
in water but also in sediment. The FDTD method shows the pulse waveforms with
interference between direct wave and reflected waves. These results show the validity
of the FDTD method.
Compositional Changes of SiC/Si Structure during Vacuum Annealing
Authors: Yong Sun Yong Sun , Nobuo Sonoda Nobuo Sonoda , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Compositional changes of SiC/Si structure during vacuum annealing are investigated by Auger electron spectroscopy. An amorphous SiC film is grown on the (111) Si substrate at 600°C by hydrogen plasma sputtering. The obtained SiC/Si structure is annealed in the temperature range of 650–950°C in vacuum. When the annealing temperature is lower than 800°C, no significant compositional or structural changes are observed in the SiC/Si structure. On the other hand, when the annealing temperature is higher than 800°C, crystallization of the amorphous SiC film takes place, resulting in both shrinking and subsequent stress in the SiC film. The stress leads to the crack in the film, and may enhance the gasification of Si and C atoms in the structure.
Diamond-like Carbon Films Deposited in the Plasma of Dielectric Barrier Discharge at Atmospheric Pressure
Authors: Liu Dongping , Yu Shiji , Ma Tengcai , Song Zhimin , Yang Xuefeng
Published: October 2002

Dielectric barrier discharge at atmospheric pressure has been applied to prepare
diamond-like hydrogenated amorphous carbon films on glass and silicon substrates
from CH4–H2 mixtures. The coating with Knoop hardness up to 10 GPa can
be deposited under CH4-to-H2 ratio of 1:2 and substrate temperature of
300°C. The IR absorption analysis of the coating shows, that its hydrocarbon group
ratio [CH3/(CH2+CH)] and C–C bond type ratio
(sp3C/sp2C for CH and CH2 groups) are 20%:80% and 15:1,
respectively.
Monte-Carlo Study of Ising Model Ferromagnetic/Antiferromagnetic Spin Frustrated Superlattice
Authors: Tanaka Hidekazu , Kanki Teruo , Kawai Tomoji
Published: October 2002

Conventional Monte-Carlo calculations have been carried out to simulate an N×N×N (N=10, 16, 20) Ising superlattice consisting of alternating layers of a ferromagnet and an antiferromagnet with different exchange interaction strengths in the antiferromagnetic layer. With increasing strength of the exchange interaction in antiferromagnetic layers, the ferromagnetic Curie temperature is decreased and the susceptibility is increased in superlattices. The magnetic susceptibility of the ferromagnetic layer is at its maximum value when the magnitudes of ferromagnetic interaction and antiferromagnetic interaction are equal.
Noncollinear Second-Harmonic Generation with Compensation of Phase Mismatch by Controlling Frequency Chirp and Tilted Pulse Fronts of Femtosecond Laser Pulses
Authors: Aoyama Makoto , Zhang Tiejun , Tsukakoshi Motowo , Yamakawa Koichi
Published: October 2002

In order to achieve the efficient second-harmonic generation with femtosecond
laser pulses, we studied a noncollinear second-harmonic generation with tilted pulse
fronts and a suitableproper frequency chirp of fundamental pulses. We discussed the
compensation of a phase-mismatch by controlling thea frequency chirp of fundamental
pulses and an improvement of thea energy conversion efficiency usingwith our method.
When the energy conversion efficiency was less than 0.4% under a phase-mismatch
condition, we experimentally obtained a 30% energy conversion efficiency with a
proper frequency chirp of fundamental pulses.
Low Threshold and High Characteristic Temperature 1.3 µm Range GaInNAs Lasers Grown by Metalorganic Chemical Vapor Deposition
Authors: Sato Shunichi
Published: October 2002

Highly strained 1.3 µm range GaInNAs/GaAs double
quantum-well lasers grown by metalorganic chemical vapor deposition
are demonstrated. A high characteristic temperature of 205 K
(22–80°C) was obtained with a low threshold current density of
0.92 kA/cm2 (22°C) in a broad stripe laser. The highest
lasing operation temperature of 170°C, and continuous-wave
operation with a low threshold current of 27 mA were also obtained
in a 7.5-µm-wide ridge-stripe laser. The GaInNAs/GaAs material
system is very promising for next-generation long-wavelength
lasers.
Powerful Optically Pumped Far-Infrared Laser with Stable Output Power
Authors: Toshihiro Hori Toshihiro Hori , Masayuki Izutsu Masayuki Izutsu
Published: October 2002

This paper describes the characteristics of the output stability of a powerful optically pumped far-infrared laser and the related physical phenomena used to measure and to improve the stability characteristics. First, we mention that the frequency stability of the CO2 pump laser, measured with Doppler-free and pressure-broadened Stark Lamb dip signals, is about 250 kHzdrift per hour in the free-running mode and about 150 kHzp-p in the actively stabilized mode. Next, we show that optical resonant feedback disturbed the output stability of our far-infrared laser. Then, we show that the output stability, resonant feedback, and temperature stability are closely related and that stable output can be obtained by controlling the temperature by using high-power chillers and a long idling time. Offset-hole input couplers also reduce the feedback. As a result, FIR output is stabilized to within a few percent.
Thickness Dependence of the Time Dependent Dielectric Breakdown Characteristics of Pb(Zr, Ti)O3 Thin Film Capacitors for Memory Device Applications
Authors: Kundu T. K. , Lee Joseph Ya-min
Published: October 2002

The time dependent dielectric breakdown characteristics of lead zirconate
titanate [Pb(Zr0.53Ti0.47)O3] (PZT) thin film capacitors are studied as a
function of film thickness. The thickness of PZT films ranges from 70 nm to 470 nm.
The variation of leakage current with electric field can be described by a power law
relationship. A power law can also describe the relation between the time to dielectric
breakdown (t
BD) and the electric field. The exponent of the first power law
agrees very well with the second when the leakage current is measured using a short
delay time of 0.1 s. An extrapolation method was used to extract the t
BD
lifetime by correlating the t
BD and the leakage current. The value of
t
BD lifetime increases from 104 s to 1012 s as the film
thickness is decreased from 470 nm to 70 nm. If the leakage current is measured
using a longer delay time (>0.1 s), stress degradation of the samples is observed.
Single Phase Ba2Ti9O20 Microwave Dielectric Ceramics Prepared by Low Temperature Liquid Phase Sintering
Authors: Weng Min-Hung , Huang Cheng-Liang
Published: October 2002

Microwave dielectric ceramics of Ba2Ti9O20 were prepared by
adding PbO–B2O3–SiO2 (PBS) as a liquid phase sintering aid. With the
addition of 5 wt% PBS, dense and single-phase Ba2Ti9O20 dielectric
resonators could be fabricated at a sintering temperature below 1200°C. The
microwave dielectric properties of PBS–Ba2Ti9O20 ceramics were
found to depend upon the density, the amount of liquid phase and the sintering
temperature. Although glass addition results in a decrease of the dielectric properties,
the sintered PBS–Ba2Ti9O20 ceramics still exhibit much better
dielectric properties than that of pure Ba2Ti9O20 ceramics at low
sintering temperatures.
Fabrication of Periodic Domain-Inversion in X-cut LiTaO3 by Heat Treatment Technique in an Electric Field
Authors: Onoe Atsushi , Chikuma Kiyofumi
Published: October 2002

In this paper, we report a new fabrication technique, which makes it possible to obtain a deep and uniform periodic domain-inverted structure in X-cut LiTaO3. The structure is fabricated on an X-cut LiTaO3 crystal, in which a periodical proton-exchange region has been previously formed, by heat treatment under an added external electrostatic field. It is found that a uniform period of 10.8 µm can be obtained by this method. The generation mechanism of domain-inversion is also examined. It is observed that an electric field is essentially effective not only in the proton-exchange region where the temperature is above the Curie temperature (T
c) but also in the neighboring region where the coercive field is lowered by proton-diffusion. Our result also shows that the stronger the strength of an applied electric field, the deeper the depth of domain-inversion grows.
Observation of Clean and Oxygen-Adsorbed Pt(113) Surfaces by Scanning Tunneling Microscopy
Authors: Yamanaka Toshiro , Xue Qi Kun , Kimura Kazushi , Matsushima Tatsuo , Hasegawa Yukio , Sakurai Toshio
Published: October 2002

Clean and oxygen-adsorbed platinum (113) surfaces were studied
at room temperature by scanning tunneling microscopy (STM). It was
found that a clean surface was reconstructed into a (1×2)
missing row structure. Significant facetting was observed at the
initial stage of annealing at 1150 K; however, wider (113) terraces
were obtained after annealing for a longer time. After adsorption of
atomic oxygen, the protruding atomic rows running in the
[110] direction were separated by many dark nodes. The
intervals of the nodes ranged from 6 to 9 Å, which corresponded
to two or three times the atomic distance along the rows, suggesting
that oxygen atoms were adsorbed at these intervals.
Characterization of Calcium-Modified Lead Titanate Thin Films Derived from a Diol-Based Sol–Gel Process
Authors: Wang Chih-Ming , Huang Yao-Te , Chen Ying-Chung , Lee Maw-Shung , Kao Ming-Cheng
Published: October 2002

Polycrystalline thin films of Ca-modified lead titanate (PCT) were deposited on
Pt/SiO2/Si substrates using a diol-based sol–gel process. Calcium
acetylacetonate hydrate was adopted as a starting material instead of the calcium
acetate or calcium nitrate tetrahydrate used conventionally. By changing the Ca content
(5–35 mol%) and heating temperature (500–800°C), the influences of various
processing parameters on the characteristics of thin films were studied. With the
increase of the Ca content, the relative dielectric constant (ε
r)
of PCT thin film increased from 43 to 70 at the heating temperature of 700°C.
It was found that the coercive field (E
c) and the remanent polarization
(P
r) decreased, but the pyroelectric coefficient (γ) increased with
an increase of Ca content. The results reveal that PCT thin film with a Ca content of
25 mol% exhibits the largest figures of merit for the voltage responsivity and the
specific detectivity at a heating temperature of 700°C.
Anisotropic Etching of Si and WSiN Using ECR Plasma of SF6–CF4 Gas Mixture
Authors: Takahashi Chiharu , Jin Yoshito , Nishimura Kazumi , Matsuo Seitaro
Published: October 2002

The characteristics of Si etching with electron cyclotron resonance (ECR) plasma
of SF6–CF4 are studied in order to improve anisotropy in dry etching using
fluoride gases. Si undercutting is decreased by increasing the amount of CF4. Si
patterns with vertical sidewalls are obtained with an etch rate of 40 nm/min. Oxygen
addition to SF6–CF4 increases Si/SiO2 etching selectivity to more than
10, but does not cause any undercutting. It is concluded that carbon (C) that decomposes
from CF4 protects the pattern sidewall from undercutting by fluorine radicals.
These results are applied to the anisotropic etching of WSiN as the gate material for
GaAs metal-semiconductor field effect transistors (MESFETs). WSiN patterns are more
vertical when the chamber inner wall exposed to SF6–CF4 ECR plasma is
stainless steel rather than quartz. This is attributed to the reduction of the amount of
CO, which possibly forms volatile tungsten-carbonyl [W(CO)6] and, along with
fluorine radicals, causes undercutting. It is confirmed that the stainless steel inner
wall does not cause serious wafer contamination by metallic elements when WSiN
patterns are almost vertically etched.
Atomic Force Microscopy of Single-Walled Carbon Nanotubes Using Carbon Nanotube Tip
Authors: Choi Nami , Uchihashi Takayuki , Nishijima Hidehiro , Ishida Takao , Mizutani Wataru , Akita Seiji , Nakayama Yoshikazu , Ishikawa Mitsuru , Tokumoto Hiroshi
Published: October 2002

We succeeded in observing individual single-walled carbon nanotubes (SWNTs) using an atomic force microscope (AFM) in the tapping mode by paying attention to the preparation of both samples and AFM tips. To disentangle the bundles of SWNTs, we added a small amount of amine into N,N-dimethylformamide. To achieve a high resolution in tapping-mode AFM imaging, we used carbon nanotube (CNT) tips whose radii could be reduced. We were able to image individual SWNTs using CNT tips with widths that were half of those imaged using conventional silicon tips. With this improved resolution, we could clearly resolve the two SWNTs lying parallel on a mica substrate.
Mechanical Properties of Membrane Surface of Cultured Astrocyte Revealed by Atomic Force Microscopy
Authors: Hatsuki Shiga Hatsuki Shiga , Yukako Yamane Yukako Yamane , Etsuro Ito Etsuro Ito , Kazuhiro Abe Kazuhiro Abe , Kazushige Kawabata Kazushige Kawabata , Hisashi Haga Hisashi Haga
Published: October 2002

In order to examine the mechanical properties of the membrane surface of
astrocytes, we observed living astrocytes by atomic force microscopy (AFM)
both in contact mode and force-mapping mode.
Ridge-like structures reflecting actin filaments were observed in the
topographic images in contact mode, but not in force-mapping mode, using a
zero-loading force.
When we measured the elasticity of astrocytes, we observed that the cell membrane
above the nucleus was soft and the cell membrane above the cytosol was stiff.
In particular, the parts reflecting actin filaments were very stiff.
This effect of actin filaments on the elasticity of astrocytes was confirmed
by the loss of actin filaments after application of actin-polymerization inhibitor.
Kelvin Probe Force Microscopy on InAs Thin Films on (110) GaAs Substrates
Authors: Takuji Takahashi Takuji Takahashi , Takashi Kawamukai Takashi Kawamukai , Shiano Ono Shiano Ono , Takeshi Noda Takeshi Noda , Hiroyuki Sakaki Hiroyuki Sakaki
Published: October 2002

Surface potential distributions on InAs thin films grown on (110) GaAs substrates
were studied by Kelvin probe force microscopy.
The topography showed that their surfaces were covered by many terraces.
The surface Fermi levels (E

F
S
) were evaluated from the potential images,
and E

F
S
near the terrace edge was higher than that on the terrace top,
while both of them were above the conduction band edge of bulk InAs.
These results indicate that the electrons are more concentrated near the terrace edge.
The film thickness dependence of E

F
S
was also studied,
but the quantum confinement effects in the InAs thin films were not confirmed experimentally.
Scanning Tunneling Microscopy and Barrier-Height Study of K-Adsorbed Si(111) 7×7
Authors: Shu Kurokawa Shu Kurokawa , Jun Yoshikawa Jun Yoshikawa , Akira Sakai Akira Sakai
Published: October 2002

We have carried out scanning tunneling microscopy and barrier-height (STM-BH) imaging of a K-adsorbed Si(111) 7×7 surface. At small coverages, most K atoms that adsorb at room temperature are observed in the form of K clusters. Contrary to the previous scanning tunneling microscopy (STM) observation by Hashizume et al. [J. Vac. Sci. & Technol. B 9 (1991) 745], isolated K adatoms are rarely found, perhaps because of their high mobility on Si(111) 7×7 at room temperature. In barrier-height (BH) imaging, a significant reduction of -2 ∼-3 eV is observed in the local BH at K sites. The K-induced reduction of BH is larger in the filled state than in the empty state. This polarity dependence of the BH reduction is discussed in terms of the band structure effect in BH.
Mg/Si(100) Reconstructions Studied by Scanning Tunneling Microscopy
Authors: A. Saranin Osamu Kubo , V. Zotov Andrey , Toru Harada Toru Harada , Tadashi Kobayashi Tadashi Kobayashi , Nobumitsu Yamaoka Nobumitsu Yamaoka , Jeong-Tak Ryu Jeong-Tak Ryu , Mitsuhiro Katayama Mitsuhiro Katayama , Kenjiro Oura Kenjiro Oura
Published: October 2002

Using scanning tunneling microscopy (STM),
the behavior of Mg submonolayers on a Si(100)2×1 surface
has been studied during deposition at room temperature (RT) and upon
annealing at 250°C and 400°C. RT-deposited Mg forms
meandering chains of features that run roughly perpendicular to the
substrate Si dimer rows and, at saturation, tend to form the arrays of
the 2×2 reconstruction.
Annealing at 250°C transforms the chains to
random groups of Mg clusters. Subsequent annealing at 400°C
induces Si redistribution at the surface and results in the
formation of straight chains of features that are again aligned perpendicular
to the Si dimer rows. These high-temperature (HT) features are plausibly composed
of 1 Si atom and 1–2 Mg atoms. The spacing of the HT features within
the chain is 2a (a=3.84 Å) and stacking of the chains produces
the domains of 2×2, 2×3 and other 2×n reconstructions.
At saturation, almost the entire surface is occupied by the 2×2
reconstruction. At higher Mg coverages, the growth of a silicide occurs
both at RT deposition and upon annealing.
Simultaneous Imaging of Tunneling Current Variation by Noncontact Atomic Force Microscopy in Ultrahigh Vacuum
Authors: Toyoko Arai Toyoko Arai , Masahiko Tomitori Masahiko Tomitori
Published: October 2002

The tunneling current between a sample surface and a tip on an oscillating
cantilever is simultaneously sampled with noncontact atomic force microscopy
(nc-AFM) images while changing the applied bias voltage. The tunneling
current can be detected with the tip on an oscillating AFM cantilever,
although it is reduced to less than 10% of the value at the closest
separation,
depending on the amplitude. The tunneling current and the chemical attractive
force are large through the surface states at the same energy level on both the
tip and the sample surface, the energy levels of which can be tuned by changing
the bias voltage. By tuning them, the atomic contrast in a nc-AFM image is
enhanced.
On the other hand, by detuning them, the atomic contrast is weakened or can be
inverted owing to the contribution of a short-range repulsive force.
Noncontact-Mode Atomic Force Microscopy Observation of α-Al2O3(0001) Surface
Authors: Sasahara Akira , Uetsuka Hiroshi , Onishi Hiroshi
Published: October 2002

Single-crystalline α-Al2O3(0001) surfaces were investigated by low-energy electron diffraction (LEED), X-ray photoelectron
spectroscopy (XPS) and noncontact-mode atomic force microscopy
(NC-AFM). When the α-Al2O3(0001) surface was annealed in air at 1273 K, terraces of ∼80 nm width and steps of ∼0.2 nm height appeared. NC-AFM topography revealed, however, that the terraces
were not atomically flat. Several previously reported methods for
preparing (1×1) α-Al2O3(0001) surfaces were examined. However, the cleaning procedures used in these methods were not sufficient to
prepare atomically flat (1×1) α-Al2O3(0001) surfaces; the surfaces thus prepared exhibited a topography which was much more ragged than that of an as-received surface.
Scanning Tunneling Spectroscopy Study of TiO2(110) Surface
Authors: Sakai Yoshiyuki , Ehara Shaw
Published: October 2002

The electronic states of a (110) surface of a single crystal TiO2 sample were studied in real space with atomic resolution by scanning tunneling spectroscopy.
We found that the inversion of the dominant tunneling current site occurs in the positive sample voltage region above 1.9 V. According to the discrete-variational
(DV)-Xα calculations of the surface electronic states, atomic alignments observed in the scanning tunneling microscopy image at a higher tunneling bias voltage are of six-fold coordinated titanium ion rows while those at a lower voltage are of five-fold coordinated Ti rows. A broad peak was observed in the empty state region of a differential conductance spectrum, which is considered to originate from the intrinsic surface states of TiO2(110).
A New, Low-Thermal-Budget Planarization Scheme for Pre-Metal Dielectric Using Electron-Beam Cured Hydrogen Silsesquioxane in Device
Authors: Lee Hae-Jeong , Goo Juseon , Kim Seong-Ho , Hong Jin-Gi , Lee Hyeon-Deok , Kang Ho-Kyu , Lee Sang-In , Lee Moon Yong
Published: October 2002

Employing an electron-beam (E-beam) cured hydrogen silsesquioxane (HSQ) based inorganic spin-on-glass as a pre-metal dielectric (PMD) material, we developed a simple planarization process with low thermal budget and good planarity in stacked capacitor dynamic random access memory (STC DRAM) device. We observe the basic E-beam cured HSQ film characteristics such as Fourier-transform infrared absorption spectra (FTIR), wet etch rate, film shrinkage, refractive index (RI), X-ray photoelectron spectroscopy (XPS), and electron spin resonance spectroscopy (ESR) in non-patterned wafer. No degradation of device characteristics such as Vth change, hot carrier hardness, and gate oxide quality has been observed. This process resulted in lower leakage current and higher capacitance for Ta2O5 capacitor as well as better planarization performance compared with the conventional undoped silicate glass (USG) etch back process. These results show that E-beam curing process as a low thermal budget PMD scheme would be a promising process for high capacitor dielectric materials.
Effect of In(4×1) Reconstruction Induced Interface Modification on the Growth Behavior of InSb on Si(111) Substrate
Authors: Rao B. V. , Gruznev Dimitri , Tambo Toyokazu , Tatsuyama Chiei
Published: October 2002

We studied the molecular-beam epitaxial growth processes of InSb on Si(111)-(7×7) and Si(111)-In(4×1) [denoted as In(4×1)] surface phases over a temperature range of 170–400°C. The In(4×1) surface phase strongly influences the growth processes depending on the growth temperature. The In(4×1) reconstruction slightly improves the epitaxial quality of the film at 210°C. However, at 300°C, films grown on In(4×1) surface phase are highly disordered, whereas direct growth produced good quality films. Results from the two-step growth procedure also indicated a similar modification of the growth behavior by the In(4×1) reconstruction. This temperature-dependent effect is in contrast to the one we reported earlier for InSb growth on the Si(001)-In(4×3) surface phase. We studied the interface formation by depositing 1 monolayer Sb on the In(4×1) surface phase at various deposition temperatures and propose a model for the observed growth behavior.
Analysis of Optical Force and Optical Potential Well for Trapping Particles near a Light-Illuminated Slit Using a Finite-Difference Time-Domain Method
Authors: Choi Wan Hae , Jo Jae Heung , Chang Soo
Published: October 2002

We analyze numerically the optical force and the optical potential well for trapping a circular-cylinder type object in a near zone of a light-illuminated metal slit. Our analysis is based on the finite-difference formulas of the optical force and the optical potential energy to be developed, a finite-difference solution of Maxwell's curl equations, and an absorbing boundary condition to define the problem in a finite region. We show that trapping forces induced by the field gradient produced in the vicinity of a slit can provide a two-dimensional potential well for trapping nanometric particles against a gravitational force. The results may be used to predict the properties of gradient-force traps in a more complicated system.
Semiclassical Approach in the Analysis of Ring Laser: I. Derivation of Rate Equations Including Backscattering and Interference
Authors: Yoshiyuki Shimosako Yoshiyuki Shimosako , Takahiro Numai Takahiro Numai
Published: October 2002

In research on ring lasers, backscattering has been analyzed by adding phenomenological coupling terms into rate equations. However, it has been difficult to quantitatively estimate a relation between lock-in phenomena and reflection due to backscattering. Also, the phase relation between a traveling wave and its backscattered wave has not been clarified. To overcome these problems, rate equations for ring lasers have been derived here. Spatial distribution functions for electric fields and polarizations are expressed as a superposition of a traveling wave and its backscattered wave with amplitude reflectivity R as a parameter. Also, the Doppler effect and linear mode pulling are included. Consequently, it is found that interference terms, which were neglected in previous works, play an important role in the rate equations in addition to saturation terms for R > 0.03. The phase relation between the traveling wave and its backscattered wave is also revealed.
Read-Out Signal Simulation of an Optical Disk Having an Oxide Super-Resolution Film
Authors: Ariyoshi Tetsuo , Shimano Takeshi , Shintani Toshimichi , Terao Motoyasu
Published: October 2002

The read-out signal simulation of an optical disk having a cobalt-oxide super-resolution film was performed to find the optimum condition for a higher recording density of the super-resolution disk. A simple model of the complex refractive index change in a super-resolution film due to its temperature was applied, which can explain experimental data. It was found that this type of super-resolution disk must increase its reflectivity as the incident laser-beam intensity rises. To confirm this experimentally, a new super-resolution disk with an added Ge–N layer was prepared, and its read-out signals were measured, which agreed well with the calculated results.
Numerical Analyses for Efficient Photoionization by Nonmonochromatic Fields
Authors: Shuichi Hasegawa Shuichi Hasegawa , Atsuyuki Suzuki Atsuyuki Suzuki
Published: October 2002

Numerical analyses on excitation and ionization probabilities of atoms with hyperfine structures were performed in order to compare two different excitation methods, adiabatic excitation and broadband excitation. The lifetime of the intermediate states was considered in order to investigate the effect of the absorption line broadening. The dependences of the two excitation methods on the lifetime were found to be quite different. The ionization probability by the adiabatic excitation is higher than that by the broadband excitation for identical excitation laser intensity.
Characteristics of a SrS:Ce Thin-Film Electroluminescent Device Prepared by Post-Annealing in H2S
Authors: Morishita Takashi , Matsuyama Hiroyoshi , Matsui Masahiro , Wakihara Masataka
Published: October 2002

Strontium sulfide doped with cerium (SrS:Ce) thin-film electroluminescent (TFEL) devices annealed in the presence of H2S are investigated. X-ray diffraction patterns of SrS phosphor layers show a preferential (220) orientation, and cerium accumulated in the lower portion of the phosphor in samples annealed in H2S. The relative concentrations of S and Sr (S/Sr ratios) of the phosphors before annealing are thought to be responsible for the EL characteristics. Annealing in H2S had a significant effect on the crystallinity of phosphors with low S/Sr ratios before annealing.
A Generalized Hysteresis Model of Antiferroelectric Liquid Crystals
Authors: Nakagawa Masahiro
Published: October 2002

In this paper, we shall put forward a generalized irreversible rotation model which takes account of the long-range couplings between the adjacent dipoles in each layer to explain the experimentally observable hysteresis curves in ferro-, antiferro- and ferrielectric phases with the corresponding wave numbers of the ferroelectric orderings along the layer normal. It is found that the long-range interaction between the dipoles critically affects on the dynamic response under an alternating electric field. In the present model, it may be possible to explain the experimentally found subphases of the antiferroelectric materials in a unified framework. That is, the dynamic response of the possible phases between the ferroelectric (SmC*) phase (the upper temperature) and the antiferroelectric (SmCA
*) phase (the lower temperature) will be substantially explained by a unified irreversible model under an alternating electric field. In addition, the hysteresis curve with the devil's staircase, as seen in the field-induced phase transitions, is found to be critically affected by the coupling strength between the spontaneous polarizations in each layer. We shall also show that the present model may be considered as a candidate to explain the thresholdless, hysteresis-free, the V-shaped switching as has been experimentally found.
Multinuclear NMR Study on the Sol–Gel Transition of Aqueous κ- and λ-carrageenan Solutions: Selective Site Binding of Group I Cations
Authors: Masahiko Annaka Masahiko Annaka , Kiriko Suzuki Kiriko Suzuki , Ryoko Takahashi Ryoko Takahashi , Takayuki Nakahira Takayuki Nakahira , Masayuki Tokita Masayuki Tokita , Hiroaki Utsumi Hiroaki Utsumi , Hiroko Seki Hiroko Seki
Published: October 2002

Multinuclear NMR study was carried out to study the interaction between group I cations (Na+, K+, Rb+ and Cs+) and κ- and λ-carrageenans. κ- and λ-carrageenans showed a marked difference in their physical properties, particularly in their gel-forming ability. Unlike aqueous λ-carrageenan solution, the gelation of κ- carrageenan produces highly selective binding sites for alkali metal ions, in which Rb+, K+ and Cs+ ions bind more strongly than Na+. The alkali metal NMR suggests the occurrence of selective site binding of ions to form the cross-linking domains in κ-carrageenan.
Nucleation and Growth of Ge at Pb/Si(111) Surfaces: Reaction-Limited Aggregation
Authors: Hwang Ing-Shouh , Chang Tien-Chih , Tsong Tien T.
Published: October 2002

The nucleation and growth of two-dimensional (2D) Ge islands at
Pb-layer-covered Si(111) surfaces is studied using scanning tunneling microscopy
(STM). Ge adatoms are highly mobile on the Pb layer. There is a threshold deposition
coverage for nucleation of Ge islands to occur. Above it, the observed island density
increases rapidly but the average island size decreases rapidly first and then increases
slowly again. Our results indicate that the nucleation and growth processes are
hindered by high energy barriers required for Ge clusters to exchange with the Pb
atoms. A compact-to-fractal island shape transition is observed as the deposition flux
is lowered, as the temperature is raised, or at a low Ge coverage, which contradicts
previous theoretical predictions and experimental findings. Our results may shed much
needed light on the fundamental mechanism in surfactant-mediated epitaxy (SME).