bluuebunny/crossref_metadata_2025 huggingface dataset:
Method for Determining Weight Coefficients for Quantum Boltzmann Machine Neuron Devices
Authors: Wu Nan-Jian , Lee Hassu , Amemiya Yoshihito , Yasunaga Hitoshi
Published: October 2002

A method for designing weight coefficients in the quantum Boltzmann machine (QBM) neuron device is proposed. The exchange interaction coefficient corresponds to the weight coefficient of the QBM neuron. A quantitative clarification of the dependence of the exchange interaction coefficient on two physical factors is given: the interval and the barrier height between the nearest-neighbor dots. It is demonstrated that the weight coefficient of the QBM neuron device can be controlled by specifying the values for these two physical factors during the design phase.
Dependence of Driving Frequency on Capacitively Coupled Plasma in CF4
Authors: Sumie Segawa Sumie Segawa , Masaru Kurihara Masaru Kurihara , Nobuhiko Nakano Nobuhiko Nakano , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

A radio-frequency CF4 plasma in reactive-ion etcher with parallel plate geometry is investigated in one dimension at a position space using the relaxation continuum model. The discharge with negative ions has the double layer similar in appearance to O2; the structure and mechanism are markedly changed as a function of driving frequency. The effect of driving frequency is numerically studied between 13.56 MHz and 200 MHz for 200 mTorr and 50 mTorr. In these studies, the plasma density is kept constant at ∼1011 cm-3, considering the charged species CF3
+, CF2
+, CF+, C+, F+, F-, and electrons. The mean energy of charged particles is also discussed.
In Situ Measurements of the Resist Etch Rate for Submicron Patterns
Authors: Kawata Hiroaki , Fukuda Hiroyoshi , Matsunaga Takashi , Yasuda Masaaki , Murata Kenji
Published: October 2002

A resist film is etched by oxygen-based plasmas, and fine grating patterns of the resist
are fabricated. During etching, a laser beam is irradiated onto the sample and the reflection
intensity from the sample is measured in order to determine the etching depth. The
reflection intensities are calculated by solving the Maxwell equations for electromagnetic
wave propagation. The dependence of the reflection intensity on the etching depth varies
greatly with the ratio of the space width to the grating period. The absolute etch rate can
be obtained by comparison between the experimental and simulated reflection intensities.
The fabricated gratings are 0.5 µm in period and the ratios of the space width to the grating
period are between 0.4 and 0.7. The reflection intensities obtained from the experiments
agree very well with those from the simulations. The etch rate decreases as the etching
depth increases, but it is almost independent of the aspect ratio of the fabricated patterns.
The etch rate decrease is not caused by an increase in the aspect ratio of the etched pattern,
but may be induced by the time variation of plasma conditions.
Diamond Deposition and Behavior of Atomic Carbon Species in a Low-Pressure Inductively Coupled Plasma
Authors: Teii Haruhiko Ito , Masayuki Ishikawa Masayuki Ishikawa , Masafumi Ito Masafumi Ito , Masaru Hori Masaru Hori , Takashi Takeo Takashi Takeo , Terumasa Kato Terumasa Kato , Toshio Goto Toshio Goto
Published: October 2002

Diamond was successfully synthesized by using
H2-rich CH4/CO/H2 and H2-rich CH4/H2
inductively coupled plasmas at a pressure of 11 Pa.
The ratio of particle size to deposition time, as a criterion
of the diamond growth rate, in
H2-rich CH4/CO/H2 mixture gas plasmas was higher than that in
H2-rich CH4/H2 mixture gas plasmas.
The deposits in H2-rich CH4/H2 and
H2-rich CH4/CO/H2
mixture gas plasmas were found to contain nondiamond phases,
as confirmed by Raman spectroscopy.
In order to investigate the mechanism involved in diamond
formation, C-atom densities in the plasmas were measured
by vacuum ultraviolet absorption spectroscopy
with a carbon hollow cathode lamp.
In addition, CH, OH and H-atom
emission intensities were measured by optical emission
spectroscopy.
As a result, it was found that
the C-atom densities increased considerably with
increasing mixture ratio of CO to CH4.
On the basis of the correlation between the quality
of deposits and the C-atom densities,
C-atoms were determined to probably contribute to the formation of
nondiamond phases in the deposits.
Ellipsometric Monitoring of First Stages of Diamond Nucleation in a Bias-Enhanced Surface-Wave-Excited Microwave Plasma
Authors: Yasuaki Hayashi Yasuaki Hayashi , Hideto Nakamura Hideto Nakamura , Masaaki Nagahiro Masaaki Nagahiro , Shigehiro Nishino Shigehiro Nishino
Published: October 2002

Changes of surface states of a substrate during diamond nucleation in a bias-enhanced microwave plasma have been monitored and analyzed by ellipsometry. In order to enable monitoring, a surface-wave-excited microwave plasma was applied, and it has been demonstrated that the generation of high-density diamond nuclei by appropriate negative-bias application and subsequent diamond growth are possible in the plasma. Evolution of the ellipsometric parameters was compared with a simulated calculation, and carbonization, incubation and nuclei growth stages have been distinguished.
Gas Phase Diagnosis of Disilane/Hydrogen RF Glow Discharge Plasma and Its Application to High Rate Growth of High Quality Amorphous Silicon
Authors: Futako Wataru , Takagi Tomoko , Nishimoto Tomonori , Kondo Michio , Shimizu Isamu , Matsuda Akihisa
Published: October 2002

Gas phase diagnosis of disilane/hydrogen plasma was carried out using mass
spectrometry. At high growth rate (20 Å/s) conditions using pure disilane as a source
gas, the partial pressure of disilane molecules measured by mass spectrometry was more
than one order of magnitude higher than in the case when mono-silane was used as a source gas. The stability of amorphous silicon films prepared from disilane was improved by the
hydrogen dilution technique, although the disilane partial pressure in this condition was
much higher than in the case when mono-silane was used as a source gas for device
quality films. The relation between the gas phase species and the stability of the
resulting films is studied. It was found that increase in disilane related signal intensity
do not decrease film stability directly.
Particle Growth Kinetics in Silane RF Discharges
Authors: Shiratani Masaharu , Fukuzawa Tsuyoshi , Watanabe Yukio
Published: October 2002

Growth kinetics of particles above 10 nm in size in silane RF discharges has been
extensively studied and fairly well clarified. Moreover, recent developments of new
measurement methods for particles below 10 nm in size have led to a rapid advance
in understanding the growth processes of small particles. Such previous studies are
reviewed with the accent on their initial growth phase corresponding to a particle
size range below 10 nm. The notable effect of pulse modulation of the RF
discharges of suppressing particle growth is also described. Both the growth of
particles and their suppression by the modulation can be explained by a model
taking into account the production of key radicals (highly reactive neutral radicals
of SiH2 having a high production rate), particle growth reactions initiated by the
key radicals and particle diffusion in the radical production region.
Spatially Selective Formation of InAs Self-organized Quantum Dots on Patterned GaAs (100) Substrates
Authors: Zhang Ruth , Tsui Raymond , Goronkin KumarShiralagi
Published: October 2002

Self-organized InAs quantum dots are selectively formed on
patterned GaAs (100) substrate by chemical beam epitaxy. Dot formation
on top of sub-µm sized mesa stripes is a function of the stripe
top width, the stripe orientation, as well as the growth
conditions. The dot density is higher for stripes aligned in [001]
direction, and lower for stripes aligned in the [011] direction,
respectively, when compared to that obtained on a non-patterned
substrate under the same growth conditions. We attribute these effects
to dissimilar surface migration behavior of In adatoms on different
side facets of the mesa stripes. The spatial distribution of the
self-organized quantum dots (SOQDs) on top of [001] stripes becomes more uniform as the top facet width decreases, and self-alignment of the dots into well-defined rows is achieved by manipulating the growth conditions and mesa size.
Two-Dimensional Melting in a Coulomb Crystal of Dusty Plasmas
Authors: Kazuo Takahashi Kazuo Takahashi , Yasuaki Hayashi Yasuaki Hayashi , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

Two-dimensional melting was observed in a simple hexagonal Coulomb
crystal of dusty
plasmas. When gas pressure was increased, the particle arrangement of
crystalline structure changed from the ordered to the disordered phase. In the change,
translational and bond-orientational
orders of the arrangement were disturbed. On the other hand,
Monte Carlo simulation was
employed to examine the experimental results. In the Yukawa system observed in
the simulation, where
the interaction between the charged particles became weaker,
the translational order became short range at first. After that,
the bond-orientational order also
became short range. According to both experimental and simulation results,
melting transition was
induced by decreasing the Coulomb interaction between particles with
increasing pressure in the
laboratory dusty plasma. The dynamics of two-dimensional Coulomb crystals,
especially two-dimensional melting, was partly clarified in this work.
A Radio Frequency Driven DC Electron Beam Source
Authors: Shaw Denis M. , Watanabe Masahiro , Collins George J. , Sugai Hideo
Published: October 2002

A 3 cm diameter disc shaped plasma generated electron beam source,
employing ion-induced secondary electron emission from cold cathodes has
been demonstrated. An inductively coupled plasma generated in 2–20 mTorr
argon feedstock gas provides ions which impinge on the high secondary electron
emission coefficient Al2O3 cathode. A separate 13.56 MHz radio frequency bias
voltage is applied to the cathode and thereby provides the effective DC field for
both ion impingement and electron beam acceleration as described herein. A
differentially pumped retarding potential analyzer measures the electron beam
energy spectra at a location 14 cm from the cold cathode. It is found that the
maximum (negative) cathode voltage sets the maximum electron beam energy,
and the electron beam current is roughly set by the inductively coupled plasma
power, which corresponds to the ion flux to the cathode. A crude model relating
the electron beam energy spectra to the time varying cathode sheath potential
provided by the rf bias shows good agreement with measured results.
High Intensity UV Emission from Cold-Cathode Mercury-Argon Lamps
Authors: Kobayashi Shinji , Murata Takaaki , Terai Kiyohisa
Published: October 2002

A high-intensity UV light source is required in the fields of bacilli sterilization, material
processing and so on. When a continuous sinusoidal voltage waveform is applied between the
electrodes of a mercury-argon lamp, the UV emission shows saturation effect because of the
presence of a resonance line of mercury. We tried to control the plasma condition by using a
pulsed power supply. The cold-cathode mercury-argon lamp used was 180 mm long and 6.0 mm in
diameter. A square-like pulsed waveform whose frequency and duration were 70 kHz and 5 µs,
respectively, was alternately applied between the electrodes. As a result, the 254 nm UV emission
intensity was achieved, which was 30-fold that obtained by applying 30 kHz continuous sinusoidal
waveform.
Fundamental Research on Mercuryless Fluorescent Lamps I – Inner Electrode Operation with Pulsed Discharge –
Authors: Masafumi Jinno Masafumi Jinno , Hisayoshi Kurokawa Hisayoshi Kurokawa , Masaharu Aono Masaharu Aono
Published: October 2002

The characteristics of xenon-neon discharge fluorescent lamps with inner
electrodes are described in this paper.
All lamps were operated by pulsed discharge.
When the partial pressure of neon is high, the ignition voltage
and operation voltage are low because of the Penning effect.
Thus, a higher mixing ratio of neon is desirable for lower ignition
and operation voltages.
However, the luminance of phosphor increases as the mixing ratio of
xenon increases.
As the pressure of xenon increases, the second peak of phosphor
emission in afterglow increases.
These increases seem to be caused by the VUV light of xenon excimers.
Therefore, though there is the problem of ion bombardment of the cathode
under a high operation voltage, the pulsed discharge of the xenon-neon
mixture at a high xenon mixing ratio is desirable in mercuryless
fluorescent lamps because a strong radiation of xenon excimer is obtained.
Live X-Ray Topography and Crystal Growth of Silicon
Authors: Chikawa Jun-ichi
Published: October 2002

Dynamic observation of crystal imperfections has been made by live
topography to image diffraction topographs instantaneously, using an intense
X-ray source and a video camera. With the aid of synchrotron radiation, a
resolution of 6 µm was achieved using an X-ray “Saticon” camera tube having an
amorphous Se–As photoconductive layer. The property of the layer made avalanche
amplification possible, enabling live topography using a conventional X-ray
tube. Usefulness of live topography is demonstrated by in-situ observation of
crystal-melt interfaces: Dislocations exist stably at equilibrium but become
unstable with deviation from equilibrium leading to a dislocation-free state.
This result is explained as the reverse of spiral growth. A formation mechanism
of swirl microdefects is proposed on the basis of experimental results which
indicate that only vacancies are intrinsic defects in silicon.
Coulomb Blockade Effects in a Highly Doped Silicon Quantum Wire Fabricated on Novel Molecular Beam Epitaxy Grown Material
Authors: Koester Thomas , Goldschmidtboeing Frank , Hadam Birgit , Stein Josef , Altmeyer Stefan , Spangenberg Bernd , Kurz Heinrich , Neumann Robert , Brunner Karl , Abstreiter Gerd
Published: October 2002

Coulomb blockade effects are studied in highly doped molecular-beam-epitaxy grown silicon
quantum wires. The nanometer structure of the single electron tunneling transistor (SETT) is
fabricated by electron beam lithography (EBL), anisotropic reactive ion etching (RIE) and low
temperature oxide deposition. An extended Coulomb blockade is observed even at T=130 K in the
I-V characteristics, while outside the blockade region a clear Coulomb staircase is visible. The
zero-conductivity range is significantly affected by the applied gate voltage. In addition, oscillations
of the Coulomb blockade with gate potential are observed. The nature of tunnel barriers present in
this wire is discussed.
Photoacoustic Spectra of CuInSe2 Thin Films Prepared by Chemical Spray Pyrolysis
Authors: Tomoaki Terasako Tomoaki Terasako , Sho Shirakata Sho Shirakata , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

Photoacoustic (PA) spectra of CuInSe2 thin films prepared by chemical spray pyrolysis have been measured and compared with the Raman and X-ray diffraction results. Stoichiometric films having a sphalerite structure exhibit a PA band at ∼0.95 eV, which is considered to be due to the electronic transition from copper atom substituting indium site (CuIn) acceptor to indium atom substituting copper site (InCu) donor. In-rich films having the chalcopyrite structure with the In2Se3 second phase exhibit PA bands at ∼0.90 eV and ∼0.83 eV. The former PA band is considered to be due to the electronic transition from copper vacancy (VCu) acceptor to indium atom substituting selenium site (InSe) donor. The latter PA band is considered to be related to the defect complex involving InCu. For Cu-rich films, a PA signal below the absorption edge increases with increasing Cu/In ratio. This behavior is attributed to the increase in the content of the Cu-Se compound.
Mechanism of Molten KOH Etching of SiC Single Crystals: Comparative Study with Thermal Oxidation
Authors: Katsuno Masakazu , Ohtani Noboru , Takahashi Jun , Yashiro Hirokatsu , Kanaya Masatoshi
Published: October 2002

The etching mechanism of SiC single crystals by molten KOH has been investigated. The etching process is significantly affected by the etching ambience: the etching rate is greatly reduced by a nitrogen gas purge. This result clearly suggests an essential role of dissolved oxygen in the melt. SiC{0001} surfaces show a large surface polarity dependence, where the etching rate of SiC(0001)C is about four times larger than that of SiC(0001)Si. The etching rate of SiC(0001)C exhibits an Arrhenius type temperature dependence with an activation energy of 15–20 kcal/mol. The obtained activation energy and selectivity between the (0001)C and the (0001)Si surfaces are quite similar to those for thermal oxidation, which implies that the surface oxidation process occurs during molten KOH etching of SiC and is the rate-limiting step for the etching. We have conducted a comparative study of molten KOH etching with thermal oxidation in regard to the crystal orientation, polytype and carrier concentration dependence.
Electron Spin-relaxation Dynamics in GaAs/AlGaAs Quantum Wells and InGaAs/InP Quantum Wells
Authors: Tackeuchi Atsushi , Kuroda Takamasa , Nishikawa ShunichiMuto , OsamuWada OsamuWada
Published: October 2002

We have investigated the spin-relaxation process of electrons at room temperature in undoped GaAs/AlGaAs multiple-quantum wells (MQWs) and InGaAs/InP
MQWs. The spin-relaxation times are measured for different well thicknesses using time-resolved spin-dependent pump and probe absorption measurement. The spin-relaxation time, τs, for GaAs MQWs was found to depend on the electron confinement energy, E
1e,
according to τs∝E
1e
-2.2, demonstrating that the main spin-relaxation mechanism at room temperature is the D'yakonov-Perel' process. The measured spin-relaxation times of InGaAs MQWs whose band-gap is about half that of GaAs MQWs are about 5 ps and vary depending on the quantum confinement energy, E
1e, according to τs∝E
1e
-1.0. The spin-relaxation time by Elliott-Yafet process, which becomes stronger for narrower band-gap materials, is calculated for quantum wells and shown to vary according to τs∝E
1e
-1. The
spin-relaxation mechanism and possible applications using this fast
spin-relaxation process are discussed.
Flow Simulation for Chemical Mechanical Planarization
Authors: Fu Ming-Nan , Chou Fu-Chu
Published: October 2002

In this paper we present a three-dimensional fluid dynamics simulation for chemical mechanical planarization (CMP) processes. The slurry shearing stress on the wafer surface is usually considered to be closely related to the polishing rate. To our knowledge, this is the first work that addresses the wafer-scale removal rate and nonuniformity based on flow simulation. The simulation results for the trends of wafer-scale-averaged slurry shearing stress and nonuniformity agree with those of existing removal rates and nonuniformity data. The present simulation can be used to analyze or predict the characteristics of removal rate and nonuniformity in the CMP processes that use a hard pad. The present predictions show that the nonuniformity value decreases with increasing wafer diameter for a fixed set of pad and wafer rotation speeds. This may explain why the recent CMP work for 12-inch wafer operated at a high pad rotation speed.
Exchange Interaction from Current and Voltage Probes in Galvanomagnetic Effect in Polycrystal Co Thin Film
Authors: Takashi Kimura Takashi Kimura , Fujio Wakaya Fujio Wakaya , Junichi Yanagisawa Junichi Yanagisawa , Yoshihiko Yuba Yoshihiko Yuba , Kenji Gamo Kenji Gamo
Published: October 2002

The galvanomagnetic effect in a polycrystal Co thin film was investigated by measuring magnetoresistance and Hall resistance. The observed magnetoresistance can be understood in term of the anisotropic magnetoresistance effect using the Stoner-Wohlfarth model. The observed Hall resistance cannot be explained syfficiently by the planar Hall effect using the Stoner-Wohlfarth model. In order to explain the observed Hall resistance, we took the exchange interaction from the current and voltage probes into consideration and numerically calculated the magnetoresistance and the Hall resistance. The calculated results obtained using this model are in reasonable agreement with the experimental results.
Analysis of Widely Wavelength Tunable Femtosecond Soliton Pulse Generation Using Optical Fibers
Authors: Norihiko Nishizawa Norihiko Nishizawa , Ryuji Okamura Ryuji Okamura , Toshio Goto Toshio Goto
Published: October 2002

Characteristics of wavelength-tunable femtosecond (fs) soliton pulse generation using optical fibers in a negative dispersion region are investigated both experimentally and numerically. The extended nonlinear Schrödinger equation, in which the wavelength dependence of parameters is considered, is used to analyze the characteristics of widely wavelength-tunable soliton pulses. The wavelength of the soliton pulse can be almost linearly shifted from 1.56–1.86 µm for a 220 m fiber merely by varying the fiber-input power. Ideal mono-colored fs soliton pulses of 90–300 fs are generated stably, and the generated pulses are nearly transform-limited fundamental soliton pulses. The numerical results fit the experimental ones well. The numerical analysis revealed that the wavelength of the soliton pulse can be shifted up to 2.2 µm in this system.
Absorption Spectrometry of Trace Moisture in Ammonia Gas with a 1371 nm Distributed-Feedback Diode Laser
Authors: Wu Shang-Qian , Masusaki Hiroshi , Kimishima Tetsuya , Kuze Hiroaki , Takeuchi Nobuo
Published: October 2002

We report on the sensitivity improvement of in the quantitative
measurement of trace moisture in ammonia gas. A 1371 nm lnGaAsP
distributed-feedback diode laser operating at room temperature was used as
the light source. A dual-cell optical configuration was employed in
the scheme of tunable diode laser absorption spectrometry. Using
signal and reference cells, both 92 cm in length, the interfering
effects of absorption lines of the major constituent gas (ammonia)
were canceled in a remarkable manner. Other common mode noises
including the etalon fringes associated with the wavelength scan were
also reduced. The system is capable of detecting trace moisture content of as low as 12 parts per billion. This is an
improvement of more than two orders of magnitude compared with the conventional method of single-cell detection.
Comment on “Lasing Emission from an In0.1Ga0.9N Vertical Cavity Surface Emitting Laser”
Authors: Anderson Neal G. , Loeber David A. S. , Redwing Joan M. , Tischler Michael A. , Flynn Jeffrey S.
Published: October 2002

Someya et al.. recently reported [Jpn. J. Appl. Phys. 37 (1998) L1424] optically pumped laser operation
from an InGaN-based vertical cavity surface emitting laser, which they characterize as the
“the first unambiguous observation of laser emission by a III–V nitride VCSEL.” They
claim that our previous report of lasing in a GaN-based vertical cavity laser is attributable to
phenomena other than vertical lasing. We argue against the plausibility the authors'
unsubstantiated alternative explanation for our results, which forms the basis for their
claim.
An X-Ray Photoelectron Spectroscopy Study of Elements' Chemical States in SrGa2S4:Ce Blue Electroluminescent Thin Films
Authors: Izumi Yoshitaka , Okamoto Shinji , Tanaka Katsu , Inoue Yoji
Published: October 2002

SrGa2S4:Ce blue electroluminescent thin films with a (440) single
orientation have been prepared by a multisource deposition method using a
molecular beam epitaxy (MBE) apparatus. The elements' chemical states
and the doped oxygen effects on them have been analyzed by X-ray
photoelectron spectroscopy (XPS). A small variation in the elements'
chemical state with depth indicates that the growth of the thin film is
stable. Sr ions exhibit no chemical shift due to a Sr–O bond, but Ga ions
exhibit a chemical shift due to a Ga–S bond and a larger shift due to a Ga–O bond, indicating that the oxygen ion does not substitute for a S site in which
the S ion bonds with the Sr ion. No Ce4+ ions have been detected and no
oxidation of Ce3+ ions occurs even if some of the S ligands of Ce3+ are
replaced by doped oxygen ions. The trivalent state of Ce is stable in the
SrGa2S4 crystal.
Large Transmittance Changes Near the Ultraviolet Region Observed on a Laminated Multilayer Structure of Ga2O3 and In2O3 Prepared by the Pulsed Laser Deposition Method
Authors: Aoki Takanori , Suzuki Akio , Matsushita Tatsuhiko , Kaimi Hideki , Okuda Masahiro
Published: October 2002

Thin films (d=120–150 nm) with a laminated structure of Ga2O3 and In2O3 have been deposited using the split target constructed of Ga2O3 and In2O3 by a pulsed laser deposition technique with an ArF laser. The transmittance change between the as-deposited and the annealed states for the film with the trace ratio of Ga:In=3:1 (the weight percent ratio of Ga:In=5.5:1) was 65 % at the wavelength of 350 nm.
Studies on DC Conductivity and Magnetic Susceptibility of Polyaniline Doped with Different Acids
Authors: Elamin Abdulkader M. , Kai LunYao Kai LunYao
Published: October 2002

We report a comparative study among four kinds of polyaniline
(PANI) synthesized with four different kinds of acids, under the same
conditions for synthesis; PANI-HCl, PANI-H2SO4,
PANI-H3PO4 and PANI-C4H6O6. We measured the
temperature dependence of the dc conductivity σdc(T)
and the magnetic susceptibility χtot(T). The
room-temperature conductivity of HCl and H2SO4-polyaniline
was 5–8 times higher than that of H3PO4 and
C4H6O6-polyaniline, in which the values of 18.1, 16.8,
3.8 and 1.85 S/cm were found, respectively. The best fit for our dc
conductivity data was obtained using the quasi-one-dimensional
variable-range hopping (Q1D VRH) model between nearest
neighbors. Polyaniline reported in this paper leads to a high magnetic
susceptibility χtot (at T=295 K) of
10-4 emu/mol.2rings. This is one or two orders of magnitude
higher than those reported earlier for polyaniline. Data on
σdc(T) and χtot(T) are also discussed.
Influence of Grain boundary Layers on the Dielectric Relaxation of Nb-Doped SrTiO3
Authors: Kim Seong-Ho , Seon Ho-won , Park Jae-Gwan , Park Jae-Hwan , Kim Yoonho
Published: October 2002

The dielectric relaxation of Nb-doped SrTiO3 in the temperature range of 500–900 K was investigated to understand the effect of space charge in grain boundary layers. The dielectric relaxation phenomena were observed for all specimens, regardless of the doping content of Nb. The permittivity maximum temperature (T
εm
) shifted and the permittivity peak height varied with the doped content of Nb. In order to study the effect of space charge in the grain boundary on the dielectric relaxation, Bi ions were diffused along the grain boundary of a 0.6 mol% Nb-doped SrTiO3 specimen. It was found that the dielectric relaxation behavior changes with the diffusion of Bi. These relaxations can be explained in terms of the space charge, which is varied by defects, in grain boundary layers.
Fabrication of Nanopit Arrays on Si(111)
Authors: Won-chul Moon Won-chul Moon , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

The fabrication of nanopit arrays on n-type Si(111) substrates by
anodic oxidation with atomic force microscope (AFM) followed by chemical
etching is presented. Possible applications for nanopit arrays include
controlled nucleation sites in crystal growth and metal embedding for
quantum devices. In this study, we investigate the anodic oxidation and
chemical etching processes in order to optimize the conditions for the
fabrication of dots and pits of the desired shape and size. The dependence
of the process on bias voltage, pulse length, and humidity is reported.
Generalized Relation Theory of Torque Balance Method for Azimuthal Anchoring Measurements
Authors: Zhou Ying , He Zhan , Sato Susumu
Published: October 2002

The theory of the torque balance method for azimuthal anchoring energy
measurements is investigated in detail under a general case of anchoring strength
relationships between two substrates and a generalized relationship equation is deduced.
As an example, azimuthal anchoring energies of several polyimide (PI) materials in
magnetically aligned twisted-nematic (TN) cells are determined and the experimental
results are discussed.
Raman Spectroscopy Studies of the Influence of Substrate Temperature and Ion Beam Energy on CNx Thin Films Deposited by Nitrogen-Ion-Assisted Pulsed Laser Deposition
Authors: Ren Z. M. , Lu Y. F. , Ho D. H. K. , Chong T. C. , Cheong B. A. , Pang S. I. , Wang J. P. , Li K.
Published: October 2002

Carbon nitride thin films were deposited by nitrogen-ion-assisted pulsed laser
ablation of graphite. A KrF excimer laser with pulse duration of 23 ns and wavelength
of 248 nm was used as the laser source for the ablation. Raman spectroscopy
measurements were used to characterise the deposited thin films. The influences of
substrate temperature and nitrogen ion beam energy on the electronic properties of the
deposited thin films were studied. The suitable parameters of substrate temperature
and ion energy were suggested given our deposition conditions and setup in order to
obtain large graphite-like crystallite structures or to realize a high content of amorphous
CN
x
. X-ray photoelectron spectroscopy (XPS) was also adopted to assist the
characterisation and evaluation of the deposited CN
x
thin films.
Design and Experimental Characteristics of n-Si/CaF2/Au Hot Electron Emitter for Use in Scanning Hot Electron Microscopy
Authors: Zhang Bingyang , Ikeda KazuhitoFuruya , Kikegawa Nobutaka
Published: October 2002

For scanning hot electron microscopy experiments, n-Si/CaF2/Au hot electron emitters
were designed and fabricated to characterize the emission properties. A self-consistent
method was used in analyzing the hot electron energy and the tunneling current density
while considering the quantum mechanical effects in the space-charge region. By comparison
of the theoretical calculations with the experimental results for current density, the tunneling
electron effective mass of CaF2 is estimated to be about 0.3m
0. This material structure can
provide an electron current density of more than 10 A/cm2 at the hot electron energies of 2.9 eV or 3.7 eV by selecting the thickness of CaF2 to be 3 nm or 4 nm, respectively, for the
electron density of 8×1019 cm-3, or at 3.2 eV or
3.4 eV by selecting the electron density of 1019 cm-3 or
2×1018 cm-3, respectively, for the insulator
thickness of 3 nm.
Thin Film Detection Employing Frequency Shift in Sheath Current Oscillation
Authors: Urayama Takuya , Niimi Hirofumi , Fujii Syuitsu , Horiike Yasuhiro , Shindo andHaruo
Published: October 2002

For an end point detection of etching in ULSI fabrication
processes, the behavior of the sheath oscillating current was
theoretically and experimentally investigated under the radio
frequency bias application. The oscillation of the displacement
current in sheath was numerically calculated employing the fluid
equations of plasma, and its frequency spectrum was analyzed in
computational Fast Fourier Transformation. The results showed that the
shift occurred mainly at lower regime than the center frequency under
the condition of an relatively small bias voltage change. This
behavior of the frequency shift was also confirmed by a simple
experiment. A new method is proposed for detection technique of thin
insulation film on substrate in process employing the frequency shift
of this kind.
Construction and Performance of “Inverse Monochromator” as Wavelength Variable Notch Filter for Raman Spectroscopy
Authors: Yonggu Shim Yonggu Shim , Hiroaki Kimura Hiroaki Kimura , Nobuyuki Yamamoto Nobuyuki Yamamoto
Published: October 2002

A monochromator called “Inverse monochromator” has been designed and constructed, and its performance as a wavelength variable notch filter has been examined. Two single monochromators of small size are put in back to back configuration to make a monochromator with zero-dispersion. The 0.7-mm-diameter vertical rod at the center of the intermediate aperture is used to reject a narrow wavelength band selected with the wavelength scale knob. The rejection factor is measured to be 2.5×10-3 for central wavelength and quasi white light, being about 90 nm wavelength bandwidth, is obtained from the intermediate aperture with 12 mm width. The newly designed monochromator acts as wavelength variable notch filter and can be effectively used in Raman spectroscopy with optional excitation wavelength.
Scanning Transmission Electron Microscopy (STEM) Study of InAs/GaAs Quantum Dots
Authors: Murray Ray , Malik Surama , Childs PhilipSiverns , Roberts Christine , Joyce Bruce , Davock Helen
Published: October 2002

Scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX) have been used to investigate the size and composition of InAs/GaAs quantum dot (QDs). It is shown that the QD exist within the wetting layer and not on it. In QD bilayers where the dots are uncorrelated along the growth direction a comparison of the indium EDX signals from the wetting layer (WL) and a dot allow us to estimate the compositions of these regions as In0.07Ga0.93As and In0.31Ga0.69As respectively. We have used the STEM technique to investigate the effects of annealing QDs in order to modify the emission energy. EDX measurements show that the dots increase in size by a factor of 2 for the longest anneals and there is a concomitant decrease in the indium concentration resulting in blue shifts up to 300 meV and a narrowing of the linewidth to ∼12 meV.
Growth and Characterization of Hot-Wall Epitaxial InGaN Films Using Mixed (Ga+In) Source
Authors: Chu Shucheng , Saisho Tetsuhiro , Fujimura Kazuo , Sakakibara Shingo , Tanoue Fumiyasu , Ishino Kenei , Ishida Akihiro , Harima Hiroshi , Oka Yasuo , Takahiro Katsumi , Chen Yefan , Yao Takafumi , Fujiyasu Hiroshi
Published: October 2002

A simple mixed-source (metallic gallium and indium) method has been used successfully in a hot-wall epitaxial system to
grow high-quality InGaN films on sapphire with GaN buffer layers. The InGaN films exhibit sharp and strong near-band-edge-emissions, ranging from violet (384 nm) to blue (448 nm), with photoluminescence (PL) peak widths ranging from 12–33 nm at room temperature. The influence of the mixed-source In/Ga ratio on the In incorporation and crystal quality is
investigated, and it is found that a relatively low In/Ga ratio, 1/4–1/5 in the source or 2–3 in the vapor is desirable for
improving the crystal quality and enhancing In incorporation. The PL spectra are obtained from 10 K to 300 K and the
activation energy, deduced from the thermal quenching of the PL intensity, is about 30.5 meV, suggesting a rather small
compositional fluctuation. PL peaks also exhibit anomalous redshifts (10–70 K) and blue shifts (80–140 K).
Spin State Analysis of Epitaxial Mn Compound Films Using High Resolution X-Ray Fluorescence
Authors: Yamaguchi Akihisa , Hayakawa Shinjiro , Ono Kanta , Fujioka Hiroshi , Oshima Masaharu
Published: October 2002

We have determined the spin states of Mn compounds by using Mn Kα1 peak widths and
relative Mn Kβ′ peak intensities of high-resolution X-ray fluorescence (HRXRF) spectra. The
number of unpaired 3d electrons for molecular beam epitaxy (MBE)-grown MnAs films was
calculated to be 2.8, which is in good agreement with that determined from the experimental value
of magnetic moments. We think this technique is very promising for microbeam analysis and in situ
analysis of spin states during crystal growth.
Preparation and Femtosecond Third-Order Nonlinear Optical Properties of Cu/SiO2 Composite Thin Films
Authors: Tanahashi Ichiro , Inouye Hideyuki , Tanaka Koichiro , Mito Akihiro
Published: October 2002

A multitarget sputtering method was applied to embed Cu particles in SiO2 glass thin films
(Cu/SiO2 films) with a high concentration of Cu particles (18 at.%). In the optical-absorption
spectra of the as-deposited Cu/SiO2 films, the absorption peak due to the surface plasmon
resonance of Cu particles was observed around 580 nm. The imaginary part of the third-order
nonlinear susceptibility, | Im [χ(3)]|, exhibited a peak at the absorption peak, and the
maximum value was estimated to be 1.8×10-10 esu in the femtosecond time region. The
nonlinear response time derived from the recovery time of the nonlinear absorption of the film
was estimated to be 1.4 ps at the absorption peak of the surface
plasmon.
A Novel 1.3-µm High T0 AlGaInAs/InP Strained-Compensated Multi-Quantum Well Complex-Coupled Distributed Feedback Laser Diode
Authors: Chen Bo , Wang Wei , Wang Xiao-Jie , Zhang Jin-Yuan , Fan Zhou
Published: October 2002

A 1.3-µm AlGaInAs/InP buried heterostructure (BH) stripe
distributed feedback laser with a novel AlInAs/InP complex-coupled
grating grown by low-pressure metalorganic chemical vapor deposition
(LP-MOCVD) is proposed and demonstrated. A high characteristic
temperature (T
0=90 K between 20–80°C) and
temperature-insensitive slope efficiency (0.25 dB drop from 20 to
80°C) in 1.3 µm AlGaInAs/InP DFB lasers was obtained by
introducing Al(Ga)InAs graded-index separate-confinement
heterostructure (GRINSCH) layers and a strained-compensated (SC)
multi-quantum well (MQW).
Lasing of a Microsphere in Dye Solution
Authors: Fujiwara Hideki , Sasaki Keiji
Published: October 2002

Lasing of micrometer-sized, nonluminescent, spherical particles
dispersed in an aqueous solution of rhodamine B was demonstrated. The
microspherical resonance field is composed of an evanescent field
surrounding the sphere as well as a propagation component within the
particle, so that the dye solution just outside of the spherical
surface can function as a gain medium within an optical cavity.
Periodical ripple structures were observed in the emission spectra,
which agreed well with the Mie scattering theory. The lasing
threshold was determined to be 7 mW for a 28 µm glass microsphere in
10-2 mol/l rhodamine B solution. The decrease
in the lasing emission intensity caused by photodegradation can be
suppressed by thermal diffusion of the dye molecules in the liquid
solution.
Outward-Inward Mode Coupled Unstable Resonator
Authors: Sunako Katsuhiko , Fujioka Tomoo
Published: October 2002

A new type of unstable resonator is proposed, in which the
inward mode is coupled with the outward mode through the reflection
from a flat mirror located at the outlet of the confocal unstable
resonator, and the output is taken from the aperture at the center of
the concave mirror. The calculation based on the Fresnel-Kirchhoff
integral showed the applicability of the new resonator to high-power
and high-quality laser.
Dielectric Properties of Al2O3-Doped Barium Strontium Titanate for Application in Phased Array Antennas
Authors: Wu Long , Chen Yih-Chien , Chou Yi-Ping , Tsai Yuan-Tu , Chu Sheng-Yuan
Published: October 2002

Effects of Al2O3 doping on the dielectric properties of barium strontium titanate for application in phased array antennas have been studied. The grain size of the specimen is maximum for barium strontium titanate doped with 1 wt% Al2O3. The density and the real part of the relative dielectric constant decreases with increasing Al2O3 content. The loss factor is minimum for barium strontium titanate doped with 2 wt% Al2O3 content. The real part of the dielectric constant and the loss factor with frequency of all the specimens is stable in the measurement frequency range from 1 MHz to 40 MHz. The real part of the dielectric constant of the specimens decreases with increasing applied DC field. The loss factor of the specimens is influenced much less by the DC field than the real part of the dielectric constant. The tunability is about 24% for barium strontium titanate doped with 1 wt% Al2O3 content.
Control of Grain Structure of Sputtering Lead-Zirconate-Titanate Thin Film Using Amorphous Lead-Titanate Buffer Layer
Authors: Sakoda Tomoyuki , Aoki Katsuhiro , Fukuda Yukio
Published: October 2002

Crystalline lead-zirconate-titanate (PZT) films of perovskite
structure with fine grains were successfully obtained on Ir substrates
using an amorphous lead-titanate (a-PTO) buffer layer. The grain size
of PZT ranged from 100 to 150 nm. The results of the temperature
dependence of the X-ray diffraction patterns of PZT films prepared on
a-PTO buffer layer revealed that PZT films with a single perovskite
phase were obtained at 500°C. In addition, 250-nm-thick PZT
films fabricated with a-PTO buffer layer and crystallized at
600°C showed excellent ferroelectric properties. The
2P
r values of Ir/PZT/Ir capacitors with a-PTO buffer layer
satisfactorily saturated at the applied voltage of 3.5 V. No
degradation in the polarization density was observed for switching
cycles up to 1×109.
Change of Distribution of Free Volume in a Polymer Caused by Crystallization
Authors: Kakizaki Maeko , Hideshima Teruo
Published: October 2002

The marked effect of crystallization on the shape of loss-permittivity-versus-frequency
curve of poly(aryl ether ketone ketone) reported by [Ezquerra et al..: Phys. Rev. B 50 (1994)
6023] is explained by a simple theory assuming a distribution of free volume which has been successfully used to explain the temperature dependence of the shape of loss-permittivity-versus-frequency curve in various polymers. From this result the relation between the distribution of free volume and the degree of crystallinity is clarified.
Dielectric Properties of Hydrogen Silsesquioxane Films Degraded by Heat and Plasma Treatment
Authors: Chung Sung-Woong , Shin Joo-Han , Park Nae-Hak , Park Jin Won
Published: October 2002

Hydrogen silsesquioxane (HSQ)-type spin-on-glass (SOG) is a very attractive candidate material for intermetal dielectric (IMD) in the semiconductor industry. The low dielectric
property of HSQ materials helps to minimize interconnection delay. However, it was found that
the chemical structure of HSQ film is damaged and hydrogen inside the film is displaced when
treated by a thermal process or plasma-enhanced tetraethyl orthosilicate (PETEOS) capping
oxide deposition. As these steps are essential in the integration process of IMD materials, the
thermal and chemical stability of HSQ was evaluated. We investigated the dielectric properties
of the HSQ/PETEOS bilayer as a function of the deposition sequence and thermal treatment
using C–V measurement, refractive index measurement, and Fourier transform infrared (FTIR)
spectra. The three polarization components (electronic, ionic, and orientation) of HSQ were
identified by a Kramers-Kronig transformation of the IR absorbance. It was found that the
polarization induced by the orientation of the permanent dipoles, which is related to the adsorbed
water, was the most effective component in affecting the dielectric constant of the damaged
HSQ. Also, the PETEOS capping layer was shown to play a role in protecting thermally
damaged HSQ against moisture absorption.
Controllable Nanopit Formation on Si(001) with a Scanning Tunneling Microscope
Authors: Naotada Ueda Naotada Ueda , Koichi Sudoh Koichi Sudoh , Nan Li Nan Li , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

The possibility of controlling the field-induced nanoscale-pit formation on the Si(001) surface by using an ultrahigh-vacuum scanning tunneling microscope has been demonstrated. Quadrilateral nanoscale-pits can be formed at high temperatures of 500–600°C by strong electric fields between the sample and the scanning tip through layer by layer removal of Si atoms from the silicon surface. The depth of nanopits increases linearly with the duration of applying electric fields. An array of uniformly shaped nanopits can be fabricated, indicating the controllability of this nanofabrication technique.
Structures and Electronic Properties of SinC5-n Clusters in Electric Fields
Authors: Kazuyuki Watanabe Kazuyuki Watanabe , Mio Shindo Mio Shindo , Kazuhiro Tada Kazuhiro Tada , Kazuaki Kobayashi Kazuaki Kobayashi
Published: October 2002

We obtained the structures of silicon-carbon clusters SinC5-n
and Si5C5 by first-principles supercell calculations using the local density approximation and the pseudopotential plane wave method. The ground-state atomic geometries of SinC5-n
agreed well with previous studies by ab initio Hartree-Fock calculations. The ground-state structure of Si5C5 is a distorted monocyclic geometry resembling a stable C10 structure. We calculated the electric polarizability tensors of SinC5-n
clusters by applying a low electric field. We found an abrupt drop in the average polarizability when n increases from 2 to 3, reflecting the structural change from one to two dimensions. We manipulated Si2C3 and Si3C2 clusters theoretically with a high electric field. Linear (Si2C3) and plane (Si3C2) clusters bend in the direction of the field. Field-induced distortion is interpreted using the electronegativity of Si and C atoms. The present simulation enabled us to emphasize the electronegativity of atoms in mixed clusters as a crucial factor in controlling and designing the structures of clusters using high electric fields.
Preparation of Lead Titanate Ultrathin Film Using Langmuir-Blodgett Film as Precursor
Authors: Sugai Hiroshi , Iijima Takashi , Masumoto Hiroshi
Published: October 2002

The Langmuir-Blodgett (LB) method is investigated as a process for the
fabrication of ultrathin films of oxides such as lead titanate. LB film was fabricated by
depositing a monolayer prepared from a fatty acid such as stearic acid (C17H35COOH)
and a subphase containing lead chloride (PbCl2) and titanium potassium oxalate
(K2TiO (C2O4)2). For converting from an LB film containing lead and titanium to an
inorganic film, ultraviolet/ozone (UVO) treatment was applied. Subsequent thermal
annealing resulted in a dense oxide ultrathin film. The crystallographic orientation of
lead titanate thin films was controlled by conditions of precursor preparation such as
the molecular ratio of lead and titanium, pH value and/or temperature in the subphase
and the surface pressure. An X-ray diffraction pattern of the thin film indicating a
well-defined perovskite structure was observed. Moreover, the results demonstrated
the potential application of LB deposition for controlling the crystallographic
orientation of lead titanate ultrathin films, particularly in the (111) or (101)(110)
planes.
Preparation of PbTiO3 Thin Film by Mist Source Plasma Enhanced Chemical Vapor Deposition (CVD) Using Heptane Solvent
Authors: Wakiya Naoki , Nagata Shingo , Higuchi Masashi , Shinozaki Kazuo , Mizutani Nobuyasu
Published: October 2002

Heptane has been proposed as a new solvent for liquid source chemical vapor deposition
(LSCVD) and liquid source mist chemical vapor deposition (LSMCVD) instead of
tetrahydrofuran (THF). The range of the explosive limit of heptane is much narrower than that of
THF, and heptane does not have self-explosive characteristics unlike THF. The boiling point of
heptane is higher than that of THF, therefore, selective vaporization of the solvent can be avoided.
The preparation of PbTiO3 thin films was attempted using a liquid source in which Pb(DPM)2 and
Ti(O-i-Pr)4 were dissolved in heptane. The substituent exchange reaction was not perceived in
heptane. Moreover, fine mists of the solution could be generated using an ultrasonic nebulizer.
These facts indicate that heptane is an excellent solvent. The solution was applied to the plasma-enhanced LSMCVD apparatus and PbTiO3 thin films having stoichiometric composition and
smooth and flat microstructures were prepared on Pt/Ti/SiO2/Si substrates. The dielectric and
ferroelectric properties of PbTiO3 thin films agree well with those reported in literature.
Surface Electrical Potential of Spontaneously Poled La-Modified PbTiO3 Thin Film by Kelvin Force Microscopy
Authors: Yamamoto Takashi , Sakamoto Junichi , Matuzaki Eiji , Takayama Ryoichi
Published: October 2002

Both surface electrical potential and surface structure of
spontaneously poled Pb0.85La0.15Ti0.963O3 (PLT) c-axis-oriented
film on (100)Pt-coated (100)MgO single-crystal substrate were
simultaneously measured by Kelvin force microscope in air. The
surface electrical potential clearly revealed the polarity of the
polarization on the film surface, i.e., the film surface had either
positive or negative electrical potential. However, the surface
electrical potential was strongly affected by floating charged
particles.