bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Fe and Zr Ion Implantation and High-Current Electron Beam Treatment on Chemical and Mechanical Properties of Ti–V–Al Alloy
Authors: Pogrebnjak Alexander D. , Kobzev Alexander P. , Gritsenko Boris P. , Sokolov Serghey , Bazyl Elena , Sviridenko Nikolai V. , Valyaev Alexander N. , Plotnikov Serghey V.
Published: October 2002

Using Rutherford backscattering spectroscopy, nuclear elastic resonance
analysis, atomic force microscopy, and wear resistance and microhardness tests,
the alloy Ti41–V41–Al18 was investigated after Fe ion (60 kV) and Zr (40 kV) ion
implantation and subsequent high-current electron beam (HCEB) irradiation at an
energy flow density of 6 J/cm2, called duplex treatment. Profiles show that the
maximum concentration of Fe ions was 16.5 at.% at 85 nm from the sample
surface and that of Zr ions was 0.85 at.% at 56 nm. The maximum of the Fe
concentration profile was found to shift to the larger sample depth toward the
inward after increasing the implantation dose. After double implantation, the dry
friction wear and the friction coefficient decreased. After the duplex treatment, the
thickness of the hardened layer and the wear resistance increased.
Room Temperature Bis-tolane Liquid Crystals
Authors: Wu Shin-Tson , Hsu Chain-Shu , Chuang Ya-Yuen
Published: October 2002

Several room temperature bis-tolane liquid crystals were synthesized and their physical
properties evaluated at elevated temperatures. These highly conjugated liquid crystals exhibit not
only high birefringence (Δn>0.4) but also low melting temperature. Their applications for flat
panel displays employing light scattering or Bragg reflection and for infrared spatial light
modulators are emphasized.
Optical and Crystalline Properties of Epitaxial-Lateral-Overgrown-GaN Using Tungsten Mask by Hydride Vapor Phase Epitaxy
Authors: Hiroki Sone Hiroki Sone , Shingo Nambu Shingo Nambu , Yasutoshi Kawaguchi Yasutoshi Kawaguchi , Masahito Yamaguchi Masahito Yamaguchi , Hideto Miyake Hideto Miyake , Kazumasa Hiramatsu Kazumasa Hiramatsu , Yasushi Iyechika Yasushi Iyechika , Takayoshi Maeda Takayoshi Maeda , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The epitaxial lateral overgrowth (ELO) of GaN with a stripe tungsten (W) mask pattern is performed by hydride vapor phase epitaxy (HVPE) and a buried structure of the W mask with a smooth surface is achieved for the stripe mask patterns of <1120> and <1100> direction. Optical and crystalline characteristics of the ELO-GaN are investigated by means of cathodoluminescence (CL) imaging and X-ray rocking curves (XRCs). It is found that the CL intensity at 133 K due to the near-band edge emission is stronger in the laterally overgrown region in comparison with that in the normal growth region. The φ-ω scan of XRCs reveals that the tilting of the c-axis is much smaller in the ELO-GaN grown with the W mask than that grown with an SiO2 mask.
Novel Interatomic Potential Energy Function for Si, O Mixed Systems
Authors: Takanobu Watanabe Takanobu Watanabe , Hiroki Fujiwara Hiroki Fujiwara , Hidekazu Noguchi Hidekazu Noguchi , Tadatsugu Hoshino Tadatsugu Hoshino , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

A novel interatomic potential energy function is proposed for condensed systems composed of silicon and oxygen atoms, from SiO2 to Si crystal. The potential function is an extension of the Stillinger-Weber potential, which was originally designed for pure Si systems. All parameters in the potential function were determined based on ab initio molecular orbital calculations of small clusters. Without any adjustment to empirical data, the order of stability of five silica polymorphs is correctly reproduced. This potential realizes a large-scale modeling of SiO2/Si interface structures on average workstation computers.
Long Wavelength GaInAsP/InP Laser with n-n Contacts Using AlAs/InP Hole Injecting Tunnel Junction
Authors: Sekiguchi Shigeaki , Kimura Tadayoshi , Miyamoto Tomoyuki , Koyama Fumio , Iga Kenichi
Published: October 2002

We demonstrate InP-based long-wavelength lasers with an AlAs/InP tunnel junction prepared in the upper cladding of a
standard laser structure to convert electron current supplied by the upper n-electrode to hole current. A carbon auto-doped
AlAs layer was employed as a heavy p-type layer required for the tunnel junction. The tunnel junction diode showed a small
electrical resistance under a reverse-biased condition. In addition, a negative differential resistance characteristic was
clearly observed under a forward-biased condition. The introduction of such a tunnel junction can eliminate the p-electrode
which normally exhibits a high resistivity in InP-based lasers. In the fabricated lasers with tunnel junctions, it was observed
that the tunnel junction can enhance lateral current spreading due to low resistance in the n-layer. The proposed structure
for hole sources may be useful for reducing the resistance and homogenizing the carriers in the active region of long-wavelength
vertical-cavity surface-emitting lasers (VCSEL).
Phase-Contrast X-Ray Imaging Using Both Vertically and Horizontally Expanded Synchrotron Radiation X-Rays with Asymmetric Bragg Reflection
Authors: Kagoshima Yasushi , Tsusaka Yoshiyuki , Yokoyama Kazushi , Takai Kengo , Takeda Shingo , Matsui Junji
Published: October 2002

Results of phase-contrast X-ray imaging are presented. The optical system
employed consisted of a successive arrangement of horizontal and vertical (+, -) double
crystals taking asymmetric Bragg reflection with an asymmetry factor of ∼0.2. The
original beam size was thus expanded in both directions and the field of view actually
obtained was ∼5×5 mm2. Boundary structures in samples were clearly observed with
much higher contrast than those obtained in conventional absorption-contrast imaging.
Since this method works in real time, it will provide a new X-ray imaging diagnosis
technique for in situ observation over a large area of the samples.
Photovoltaic Application of Nanomorph Silicon Thin Films Prepared by Plasma Enhanced Chemical Vapor Deposition
Authors: Sukti Hazra Sukti Hazra , Swati Ray Swati Ray
Published: October 2002

Nanomorph silicon (nanoa-Si) thin films have been developed from the
SiH4/H2 plasma in high plasma power regime of
plasma enhanced chemical vapor deposition (PECVD). Dark and
photoconductivity of nanoa-Si films are of the order of 10-12
S·cm-1 and 10-6 S·cm-1 respectively. The average size of
nanocrystallites, embedded in the amorphous matrix, is ∼10 nm.
Optical gap of such films is ≥1.80 eV. The photoluminescence has been
observed with a wide peak around 1.6 eV. Unlike nanocrystalline silicon,
these films are photosensitive. This nanoa-Si thin film may be a good
alternative to common wide bandgap a-SiC:H which is an active layer of the
top cell of multijunction solar cell.
Formation of Bi2212 Phase via Bi2201 Phase in Liquid-Phase Epitaxial Growth
Authors: Sock Chang Hiroyuki Enomoto , Soo Shin Jae , Hajime Ozaki Hajime Ozaki
Published: October 2002

Bi2212 single-phase films are prepared using the liquid-phase epitaxial
(LPE) method.
The dependence of the relative content of the Bi2212 phase in the as-grown
films on the growth temperature has made it clear that the Bi2212 phase can be
obtained in a narrow temperature region around 980°C.
LPE growth under the liquid-temperature gradient is examined.
It is found that the temperature gradient suppresses the growth of the Bi2212
phase.
Size Dependence of Rotation Frequency of Individual Laser Trapped Liquid Crystal Droplets
Authors: Juodkazis Saulius , Shikata Masaya , Takahashi Toshimasa , Matsuo Shigeki , Misawa Hiroaki
Published: October 2002

We report the development of an all-optical liquid-crystal (LC) switch realized by
laser manipulation of a three-dimensionally trapped micrometer-size nematic liquid-crystal
droplet. Transmission of a polarizer/LC droplet/analyzer system can be modulated at a
frequency as high as 103 Hz for micrometer sized LC droplets. An optical switching
corresponds to the rotation of the LC droplet by an angle of π/4. The dependence of rotation
frequency on LC droplet size is explained in terms of the circularly polarized light scattering
by the molecules of the LC droplet. This scattering is responsible for the transfer of angular
momentum from the light to the LC droplet.
Hydrogen-Point Defect Complexes in Electron-Irradiated C-Doped and High-Purity Si
Authors: Suezawa Masashi
Published: October 2002

To determine the species of point defects which are included in H-point defect complexes in
Si, optical absorption spectra of two kinds of electron-irradiated Si doped with H were studied.
Specimens were C-doped (carbon concentration: 1.7×1017 cm-3) and high-purity (4×1012 cm-3)
Si. They were doped with H by annealing in H2 gas followed by quenching. Then they were
irradiated with 3 MV electrons at room temperature. Their optical absorption spectra were
measured by an fourier-transform infrared absorption spectroscopy (FT-IR) spectrometer at about 6 K. The intensities of the 1987 and 1990 cm-1 peaks
in the C-doped specimen were remarkably weaker than those of the high-purity specimen. This
supports the hypothesis that the 1987 and 1990 cm-1 peaks are due to an I·2H (I; self-interstitial)
complex, not due to V·2H (V; vacancy) complex since I is known to kick out the substitutional C
to interstitial C resulting in a decrease of I concentration in C-doped Si.
Chemical Beam Etching of GaAs Using a Novel Precursor of Tertiarybutylchloride (TBCl)
Authors: Kondow Masahiko , Shi Binqiang , Tu Charles W.
Published: October 2002

We examined systematically in situ etching with a novel precursor,
tertiarybutylchloride (TBCl) in a chemical beam epitaxy system. Reflection
high-energy electron diffraction observation revealed that layer-by-layer
etching was achieved. While the etching temperature is slightly higher than
that for AsCl3 or AsBr3, it is still in the range applicable in III–V
semiconductor device fabrication. Furthermore, because TBCl is not corrosive
to stainless steel or seat materials for valves and has long-term stability
at room temperature, it is a promising alternative to AsCl3 or AsBr3 from the
viewpoint of safety to operators as well as the growth system.
Dispersion of Optical Refractive Index of Yb3+-Doped Laser Glass and Their Fitting to Lorentzian Model
Authors: Yoneda Hitoki , Yamaguchi Kazuhiko , Ueda Ken-ichi
Published: October 2002

Dispersion of optical refractive index in Yb3+-doped QX/Yb phosphate laser glass was measured
from 550 nm to 1200 nm using a spectral dispersive white-light interferometer. The absorption
spectrum was also measured and the complex optical refractive index was obtained with an
accuracy better than 10-4. The data were fitted with the Lorentzian interband model. The deviation of
the data calculated using the numerical optimization method from the experimental data was as small
as 10-5. The host and the dopant were defined separately in this model. While optical refractive
index difference between doped and undoped samples was as small as 10-4, the contributions of the
dopant to the higher order dispersion of the refractive index such as dn/dλ, dn
2/dλ2 and dn
3/dλ3
were 1.7%, 19%, and 420%, respectively. Additionally, the database with this fitting formula is
useful for different doping concentrations with a proportional change in the corresponding
coefficients. The formula with our fitting parameters will be useful in the design of QX/Yb laser
glass based laser systems.
Thermal-Electrical Breakdown of Disordered Conductor-Insulator Composites
Authors: Hirano Shingo , Kishimoto Akira
Published: October 2002

We present the first observations of `thermal-electrical breakdown' in disordered conductor-insulator
composites with a high electric field. This differs from simple electrical breakdown
governed by local heat. When a large current flows through the most conductive pathway in a
composite, the constriction of the current at the most electro-resistive point in the pathway
increases the Joule heat dissipation, and a localized thermal-electrical domain `hot spot' appears
on the composite. The thermal-electrical breakdown of the disordered conductor-insulator
composite results from the local conductivity; the hot spot starts at the most resistive point on
one of the most conductive pathways and the breakdown progresses as the hot spot evolves.
Morphology Evolution of SiO2 Films Deposited by Tetraethylorthosilicate/O3 Atmospheric-Pressure Chemical Vapor Deposition on Thermal SiO2
Authors: Tsukamoto Koji , Cheng Degang , Komiyama Hiroshi , Nishimoto Yuko , Tokumasu Noboru , Maeda Kazuo
Published: October 2002

To understand the surface dependence of chemical vapor deposition using
tetraethylorthosilicate and O3, the evolution of the morphology of 5.3-µm-thick oxide
films deposited on thermal oxide was observed by scanning electron microscopy. The
surface roughness and low etching resistance of the films was caused by different growth
rates at different surface sites. Some sites grow much faster that other sites, evolving
from island, to tree, and finally to continuous films. Because of this growth sequence, the
film has high porosity and is rough. This growth mode might be caused by site-dependent
tetraethylorthosilicate absorption rates.
Gray-Scale Atom Holography
Authors: Tetsuo Kishimoto Tetsuo Kishimoto , Jun'ichi Fujita Jun'ichi Fujita , Satoru Mitake Satoru Mitake , Fujio Shimizu Fujio Shimizu
Published: October 2002

A gray-scale photographic image of atoms has been generated by
using
a computer-designed thin-film hologram. An ultra-cold neon atomic beam
in the 1s
3 state was transmitted through a thin-film binary hologram made
of SiN4 and generated a pattern of atoms on a
micro-channel plate detector. The design
and the quality evaluation of the hologram for gray-scale pictures
are discussed theoretically. The validity of the theoretical analysis
has been tested by a hologram that
generated a simple test pattern.
Straight Quantum Wires Self-Formed by Growing GaP/InP Short-Period Superlattices on GaAs(011) Substrate
Authors: Kim Seong-Jin , Asahi Hajime , Asami Kumiko , Fudeta Mayuko , Gonda Shun-ichi
Published: October 2002

Quantum wires (QWRs) are self-formed by strain-induced composition modulation while
growing (GaP)
n
(InP)
m
short-period superlattices (SLs) on GaAs(011) substrates by gas
source MBE. Improvements in straightness, uniformity and length of these QWRs are
observed, compared with those on GaAs(100) substrates. The QWR direction is parallel to the
[011] direction and is mainly determined by the easy migration direction of group III atoms on
the surface. Multilayer quantum wires (MQWRs), self-formed while growing (GaP)
n
(InP)
m

SL/InGaP multilayers exhibit strong polarization anisotropy of as large as 71% in their
photoluminescence (PL) emission. Temperature-insensitive variation of the PL peak energy is
observed in these MQWR structures.
Influence of SiC Cover Layer of Si Substrate on Properties of Cubic SiC Films Prepared by Hydrogen Plasma Sputtering
Authors: Yong Sun Yong Sun , Tokihiro Ayabe Tokihiro Ayabe , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Cubic SiC films are grown on the (100) Si substrate with a thin SiC
cover layer at 850°C by hydrogen plasma sputtering. The influences
of the SiC cover layer on the properties of the SiC films are studied by
scanning electron microscopy observation, X-ray diffraction and infrared
absorption measurements. The obtained results demonstrate that a SiC cover
layer with a thickness of about 10 nm can eliminate the hollow voids which
form at the SiC film/Si substrate interface due to the plasma etching of
the substrate. Furthermore, the crystal quality of the SiC films depends
strongly on the crystallinity of the SiC cover layer.
Preservation of Original Single Domain Phase in the Implanted LiTaO3 Single Crystal by Using Hot Implantation
Authors: Zhang Zuhua , Rusakova Irene A. , Chu Wei-Kan
Published: October 2002

Because post-annealing of pre-amorphized LiTaO3 single crystal resulted in a regrown layer of undesired multi-domain
phase, hot implantation was studied aiming to preserve the original single domain phase. Ar ion implantation was carried out with
samples at temperatures ranging from 100°C to 377°C. The implanted layer had good crystalline quality. Unlike room temperature
implantation, which created a layer of strong optical absorption, hot implantation produced a layer as transparent as a virgin sample.
The major advantage of hot implantation is that the implanted layer remains in the original single domain phase without the help of electrical pulling.
Multiple Micro-Cavity Laser with Benzocyclobutene/Semiconductor High Reflective Mirrors Fabricated by CH 4/H 2-Reactive Ion Etching
Authors: Madhan Raj Mothi , Shunsuke Toyoshima Shunsuke Toyoshima , Shigehisa Arai Shigehisa Arai
Published: October 2002

Multiple Micro-Cavity (MMC) lasers consisting of narrow and deep grooves buried with a Benzocyclobutene (BCB) polymer, were realized by the CH4/H2-reactive ion etching (RIE) process. A threshold current of 30 mA was obtained at 200 K for the micro-cavity length ℓ
H
= 5.1 µm (groove width ℓ
L
= 183 nm,
pitch \mathnormalΛ = 5.3 µm, total cavity length L = 300 µm, stripe width W

s
= 5 µm) while also showing a stable single-wavelength operation. Room temperature operation of an MMC laser consisting of 3λ/4-BCB buried grooves (= 0.70 µm) was also obtained with a threshold current as low as 18 mA for the total cavity length of 200 µm (\mathnormalΛ = 20 µm, 10 elements,
W

s
= 5 µm), and the effective reflectivity of the MMC structure was estimated to be 94%.
Two Methods for Synthesizing the Long Period Fiber Gratings with the Inverted Erbium Gain Spectrum
Authors: Jinho Bae Jinho Bae , Joohwan Chun Joohwan Chun , Sang Bae Lee Sang Bae Lee
Published: October 2002

We propose and compare two new methods for synthesizing
piecewise-uniform long period fiber gratings. The proposed
methods, which employ the optimization algorithm based on the
lattice filter model, are used to design the equalizer
which compensates for the nonflat gain characteristics of the
erbium-doped fiber amplifiers (EDFA). We have obtained design parameters of
piecewise-uniform long period fiber gratings which fit the
inverted erbium gain spectrum of a commercially available EDFA
over the entire 1525 nm–1570 nm range. We analyze the
sensitivity of the two proposed methods with respect to the
parameter variations.
Epitaxial Growth of InAs on Single-Crystalline Mn–Zn Ferrite Substrates
Authors: Ikeda Takeshi , Fujioka Hiroshi , Hayakawa Shinjiro , Ono Kanta , Oshima Masaharu , Yoshimoto Mamoru , Maruta Hideaki , Koinuma Hideomi , Inaba Katsuhiko , Matsuo Ryuji
Published: October 2002

We have grown InAs on single-crystalline Mn–Zn ferrite substrates by
molecular beam epitaxy (MBE). In spite of a large lattice mismatch (about
30%), we succeeded in the growth of InAs epitaxial films. Reflection
high-energy electron diffraction (RHEED) and X-ray diffraction (XRD)
measurements have revealed that (111)InAs grows on (110)Mn–Zn ferrite
substrates with the in-plane alignment of [112]InAs//[001]Mn–Zn ferrite.
Electrical Properties of Excimer-Laser-Crystallized Lightly Doped Polycrystalline Silicon Films
Authors: Higashi Seiichiro , Ozaki Kentaro , Sakamoto Keiji , Kano Yoshiaki , Sameshima Toshiyuki
Published: October 2002

The electrical properties of excimer-laser-crystallized lightly phosphorus-doped
polycrystalline silicon films were investigated. The electrical conductivity of the films
increased from 6.0×10-7 to 2.3×10-1 S/cm as the laser energy density increased from 235 to
436 mJ/cm2 because the carrier concentration varied from 1.0×1011 to 1.8×1017 cm-3. In
contrast, the carrier mobility was 37.3 and 8.7 cm2/V·s at low- and high-laser-energy regimes,
respectively, and showed a minimum value of 0.24 cm2/V·s at the intermediate laser energy
density of 315 mJ/cm2. These results can be well explained by a model featuring the
localization of trap states at the grain boundary.
Vertical-Cavity Surface-Emitting Lasers with Stable Polarization Grown on (411)A-Oriented GaAs Substrates
Authors: Kaneko Yasuhisa , Mars Dan E. , Nakagawa Shigeru , Ichimura Yoshikatsu , Yamada Norihide
Published: October 2002

We demonstrate continuous-wave operation at room temperature for vertical-cavity surface-emitting
lasers (VCSELs) grown on (411)A-oriented GaAs substrates by molecular beam epitaxy. A threshold
current of 0.5 mA is obtained for selectively oxidized VCSELs with a square-shaped emitting aperture of
4×4 µm2. The polarization is well stabilized parallel to the [\overline122] direction that has the highest optical gain.
Measurement of Ionization and Attachment Coefficients in SF6 and Xenon Gas Mixtures
Authors: Xiao Deng M. , Liu Hong L. , Qin Ling
Published: October 2002

The Townsend first ionization coefficient α, electron attachment coefficient η and effective ionization
coefficient α (=α-η) in SF6 and xenon gas mixtures were measured by the steady-state Townsend method
for 22.6 \leqslantE/p \leqslant94 V·mm-1·kPa-1 and mixture ratios of 10:90, 25:75, 50:50, 75:25 and 90:10. The limiting E/p
in SF6-Xe, (E/p)lim
, which represents E/p for α/P=n/P, was derived from the pre-breakdown current growth
measurements, which varies approximately linearly with SF6 concentration in the SF6-Xe gas mixtures.
Electron Cyclotron Resonance Plasma Produced with a Closed Spheroidal Electron Cyclotron Resonance Surface in a Simple Cusp Field
Authors: Masaki Uchida Masaki Uchida , Shiho Fukumoto Shiho Fukumoto , Makoto Asakawa Makoto Asakawa , Hitoshi Tanaka Hitoshi Tanaka , Takashi Maekawa Takashi Maekawa , Yasushi Terumichi Yasushi Terumichi
Published: October 2002

With a spheroidal electron cyclotron resonance (ECR) surface completely
enclosed in a vacuum vessel in a simple cusp field,
we can produce ECR plasmas with a peak electron
density up to n

e
≃5×1011 cm-3 at a low Ar pressure of
p≃1.5×10-5 Torr by injection of 2.45 GHz microwave power of
P
in=150–400 W. The degree of
ionization reaches over 50% at this local density peak point.
Such a high degree of ionization may be due to the efficient ionization
by suprathermal tail electrons (W>30 eV), which are observed in
single probe characteristics. On the other hand, at a relatively high pressure of
p≃1.5×10-4 Torr, a flat density profile with density
nearly equal to the plasma cutoff density
(7×1010 cm-3) is obtained inside the ECR spheroid.
Quantum-Confined Stark Effect in an AlGaN/GaN/AlGaN Single Quantum Well Structure
Authors: Takahiro Deguchi Takahiro Deguchi , Kaoru Sekiguchi Kaoru Sekiguchi , Atsushi Nakamura Atsushi Nakamura , Takayuki Sota Takayuki Sota , Ryuji Matsuo Ryuji Matsuo , Shigefusa Chichibu Shigefusa Chichibu , Shuji Nakamura Shuji Nakamura
Published: October 2002

Excitonic absorption was observed in a transmittance spectrum of AlGaN/GaN/AlGaN single quantum well structure with a well width of 5 nm at room temperature. The total internal electric field strength in the well was about 0.73 MV/cm, which was estimated from the absorption peak position based on a simple calculation, neglecting excitons. The observation is clearly due to the quantum-confined Stark effect. While excitonic absorption was clearly observed even in such a high internal field, no light emission was detected under a He-Cd laser excitation at temperatures ranging from room temperature to
T = 10 K. Light emission accompanied by a blue shift of the emission peak and an increase of emission intensity was observed under higher excitation power density. The obvious conclusion in the present case is that the presence of a high internal electric field in the well is a disadvantage for light emission.
Exchange Interaction of Optically Created Electrons in Coupled Quantum Dots
Authors: Satoru Itoh Satoru Itoh , Shunichi Muto Shunichi Muto , Yoshiki Ebiko Yoshiki Ebiko , Hirotaka Sasakura Hirotaka Sasakura , Ken-ichi Shiramine Ken-ichi Shiramine
Published: October 2002

We studied the exchange interaction of electrons in coupled quantum dots using the Heitler-London approximation. We found empirical dependence of the exchange interaction of electrons on the interdot distance and electron tunneling coefficient κ. Based on the calculation, we discussed the possibility of a “transient magnetic semiconductor”.
Resonant Tunneling Diodes in Si/CaF 2 Heterostructures Grown by Molecular Beam Epitaxy
Authors: Masafumi Tsutsui Masafumi Tsutsui , Masahiro Watanabe Masahiro Watanabe , Masahiro Asada Masahiro Asada
Published: October 2002

Room-temperature negative differential resistance (NDR) was observed in
Si/CaF2 double-barrier resonant tunneling diodes fabricated
by molecular beam epitaxy with annealing. The devices consist of
Au/CaF2(amorphous)/Si(amorphous)/CaF2 (crystalline)/n+-Si(111)(substrate).
In spite of the fact that the well layer (Si) and one of the barrier layers
(CaF2) were amorphous, their interface was well distinguished in
a transmission electron microscope image, and clear NDR was obtained with
the peak-to-valley current ratio of 3.10 for a sample with a 2.8-nm-thick Si well.
The voltage at the peak current varies with the thickness of the Si well,
as predicted theoretically.
Anomalous Large Thermoelectric Power of the Si and Au Doped Ge Superlattice Thin Film
Authors: Okamoto Yoichi , Uchino Hiroko , Kawahara Toshio , Morimoto Jun
Published: October 2002

The thermoelectric properties of superlattice thin films have been studied as functions of
temperature. The superlattice thin films were prepared by the alternate deposition of Si and Ge
heavily doped with Au in ultrahigh vacuum. They have an intended artificial interval, but each
layer is in an amorphous state. An anomalously large thermoelectric power and power factor is
observed. The power factor reaches a maximum value of approximately 7 W/mK2 at
around 800 K, which is anomalously large compared to that for conventional bulk materials.
Vacancy Migration Properties of BaFCl Obtained by Molecular Dynamics Simulation
Authors: Toshio Kurobori Toshio Kurobori , Mayumi Yoshiura Mayumi Yoshiura , Min Liu Min Liu , Yukio Hirose Yukio Hirose
Published: October 2002

We have examined some characteristics of vacancy-jump motions in a
matlockite structure such as BaFCl by means of molecular dynamics
simulations. The activation energy of vacancy migration and the
mean-square displacements of individual ions have been calculated
for a bulk model containing Schottky-type defects which in BaFCl
consist of one metal ion vacancy and two halogen ion vacancies.
Furthermore, the probable mechanism for the vacancy migration
process and the anisotropy in ionic conductivity in BaFCl have
been discussed on the basis of structural considerations of the
unit cell.
Optical Properties of an InGaN Active Layer in Ultraviolet Light Emitting Diode
Authors: Takahiro Deguchi Takahiro Deguchi , Kosuke Torii Kosuke Torii , Kazuhiro Shimada Kazuhiro Shimada , Takayuki Sota Takayuki Sota , Ryuji Matsuo Ryuji Matsuo , Mutsumi Sugiyama Mutsumi Sugiyama , Akiko Setoguchi Akiko Setoguchi , Shigefusa Chichibu Shigefusa Chichibu , Shuji Nakamura Shuji Nakamura
Published: October 2002

Optical properties of a 5 nm thick InGaN active layer with In content less than a few percent in an ultraviolet light emitting diode, have been studied by employing reflectance, transmittance, and photoluminescence spectroscopy. The co-existence of the localized electronic states and the usual confined ones in the active layer has been demonstrated. A possible origin of the co-existence of those states is attributed to the non-random alloy potential fluctuation in the InGaN active layer.
Electrical and Reliability Characteristics of Ultrathin Gate Oxide Prepared by Oxidation in D 2O
Authors: Hyojune Kim Hyojune Kim , Hyunsang Hwang Hyunsang Hwang
Published: October 2002

In this letter, we present a novel gate oxidation process using D2O (deuterium oxide) as an oxidizing gas. The electrical and reliability characteristics of ultrathin gate oxide grown in D2O ambient have been investigated. Compared with a control oxide grown in H2O, a oxide grown in D2O exhibits a significant reduction of charge trapping and interface state generation. Based on a secondary ion mass spectroscopy (SIMS) analysis, we found a deuterium rich-layer at the Si/SiO2 interface. The improvement of electrical and reliability characteristics can be explained by the deuterium incorporation at the Si/SiO2 interface.
Paramorphic Growth: A New Approach in Mismatched Heteroepitaxy to Prepare Fully Relaxed Materials
Authors: Damlencourt Jean-François , Leclercq Jean-Louis , Gendry Michel , Garrigues Michel , Aberkane Nabil , Hollinger Guy
Published: October 2002

We propose paramorphic growth as a new approach for growing thick,
ideally relaxed, epitaxial layers on mismatched substrates. First, a thin seed
layer, originally grown pseudomorphically strained on a mismatched substrate
coated with a sacrificial layer, is separated by chemical etching from its
original substrate and subsequently deposited on the final substrate after being
elastically relaxed. Consequently, thick layers, lattice matched to the
cubic-relaxed seed layer, can be grown epitaxially without the introduction of
any structural defects. The validity of this approach is demonstrated by
growing fully relaxed In0.65Ga0.35As thick layers on 300×300 µm2 platforms
deposited on an InP substrate, using molecular beam epitaxy.
Effects of Gas-Flow-Rate Ratio on Electrical Characteristics and Fowler-Nordheim Stress Resistance of Si Oxynitride Grown with Helicon-Wave-Excited N2–Ar plasma
Authors: Fumihito Oka Fumihito Oka , Masayuki Tachikawa Masayuki Tachikawa , Tatsuaki Tsukuda Tatsuaki Tsukuda , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

The effects of the gas-flow-rate ratio on the electrical characteristics and the Fowler-Nordheim (FN) current stress resistance were investigated for Si oxynitride grown with helicon-wave excited (HWP) N2–Ar plasma. The flow-rate ratio of N2 [N2/(N2+Ar)] was varied from 100% (N2 only) to 60%. The X-ray photoelectron spectroscopic data (XPS) indicated that uniform Si oxynitride (probably Si2N2O) was formed through the entire film thickness when the N2 gas-flow-rate ratio was 100% (N2 only), though a small amount of Si suboxide was included. The capacitance–voltage (C–V) measurements revealed that the interface-state density was the lowest in this flow-rate ratio case, as the grown layer was postannealed at moderate temperatures (300–500°C). Fowler-Nordheim current injection was performed using the metal/Si-oxynitride/Si capacitors thus fabricated. The shift of the threshold voltage was the lowest for the sample grown without Ar mixing. It was smaller than that for the thermal Si oxide (SiO2) grown at 900°C. The results of FN current stress resistance experiments were explained in terms of the surface plasmon and avalanche breakdown models.
Effects of Postannealing on Electrical Characteristics and Fowler-Nordheim Current Stress Resistance of Si Oxynitride Grown in Helicon-Wave-Excited O2–N2–Ar Plasma
Authors: Masayuki Tachikawa Masayuki Tachikawa , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

The effects of post-thermal annealing in N2 and/or forming gas (FG) on the electrical characteristics and Fowler-Nordheim (FN) current stress resistance were investigated for Si oxynitride grown in helicon-wave excited
O2–N2–Ar plasma. The X-ray photoelectron spectroscopic data indicated growth of the Si oxynitride. The capacitance-voltage characteristics were measured to evaluate the electrical qualities of the grown Si oxynitride. The minimum interface state density D
it,min had the smallest value when the Si oxynitride sample was post-thermally annealed in FG (3% H2) at 300°C followed by annealing in N2 at 700°C. However, D
it,min was approximately 3.5 ×1011 eV-1cm-2, still higher than that for thermal Si oxide. The shift of the threshold voltage (V
th) after the stressing (±10 V, 100 min) was also the smallest for the Si oxynitride sample continuously annealed in FG (3% H2) and N2. The FG annealing does not necessarily improve the electrical characteristics and FN stress resistance. The N2 annealing after FG annealing is required to improve the electrical properties and FN reliability, in contrast with the case of Si oxide.
Self-Assembling CdSe, ZnCdSe and CdTe Quantum Dots on ZnSe(100) Epilayers
Authors: Matsumura Nobuo , Tai Eiji , Kimura Yoshihisa , Saito Takashi , Ohira Masao , Saraie Junji
Published: October 2002

CdSe quantum dots were fabricated on ZnSe(100) epilayers by the
molecular beam epitaxy (MBE) and the solid phase reaction
method. ZnCdSe quantum dots were prepared by MBE and the atomic
layer epitaxial method. CdTe quantum dots were fabricated by
alternate supply of Cd and Te beams. Nanoscale surface structures of
these self-assembling dots were observed using an atomic force
microscope. Broad emissions were observed in the photoluminescence
of these capped samples.
Polarization Properties and Frequency Stabilization of an Internal-Mirror 1523 nm He–Ne Laser under Axial Magnetic Field
Authors: Huang Tong-Long , Shy Jow-Tsong , Lin Tyson , Liu Hai-Pei
Published: October 2002

The polarization properties of an internal-mirror 1523 nm He–Ne laser under
an axial magnetic field were investigated. When the axial magnetic field was around
12 mT, the laser operated in single mode with two opposite circularly polarized
components near the center of gain profile. In addition, due to the competition between
these two opposite circularly polarized components, each mode had only one circularly
polarized component survived when the laser operated in the two-mode region. We
could stabilize the laser frequency at either the center of gain profile or the
symmetric two-mode taking advantage of the power difference between the two
circularly polarized components of the laser output, and the stability achieved was
better than 1 MHz.
Noncollinear Chirp-Compensated Second-Harmonic Generation with Subpicosecond Laser Pulses
Authors: Zhang Tiejun , Aoyama Makoto , Yamakawa Koichi
Published: October 2002

Noncollinear chirp-compensated second-harmonic generation with
subpicosecond laser pulses is discussed with regard to an optical
system that includes two dispersive elements and a nonlinear optical
crystal. Through the optimization of two dispersive elements, phase
and group-velocity matches as well as chirp compensation can be
satisfied simultaneously. Numerical results show that temporal
compression in second-harmonic pulse is achievable under the
condition that the first-order phase difference is completely
compensated.
Annealing Behavior of Layer Semiconductor p-InSe Doped with Hg
Authors: Shigetomi Shigeru , Ikari Tetsuo
Published: October 2002

Photoluminescence and Hall effect measurements are carried out to study the
annealing effect of Hg-doped InSe. The 1.237 eV emission band, which is associated
with the transition between the donor level and the acceptor level at about 0.08 eV
above the valence band, is enhanced by the increase of annealing temperature. We find
that the acceptor level due to defects or defect complexes is formed by doping of Hg
atoms and its concentration increases with increasing annealing
temperature.
Improved Time-of-Flight Technique for Measuring Carrier Mobility in Thin Films of Organic Electroluminescent Materials
Authors: Chen Baijun , Lee Chun-sing , Lee Shuit-tong , Webb Patrick , Chan Yan-cheong , Gambling William , Tian He , Zhu Weihong
Published: October 2002

Using an improved time-of-flight (TOF) technique, the drift
mobilities of electrons and holes in organic films prepared on silicon
or indium-tin-oxide (ITO)-coated glass substrates have been
determined. For the samples on silicon, the silicon was also used as a
carrier-generating layer. This substantially increased the number of
charge carriers generated and thus resulted in a higher intensity
electrical signal. Consequently, the thickness of the organic layers
can be reduced to less than 1/10 of the typical values (several
microns) required in the conventional TOF measurement. The typical
thickness of the organic layer in the present work is 400 nm. For
organic materials with a high optical absorption coefficient, samples
for the TOF measurement can be prepared by directly depositing these
materials onto ITO glass substrates with a thickness of about
1000 nm. For both types of substrate, the thickness of the organic
layer is much closer to the typical value used in organic
electroluminescent devices. The signal, and thus the accuracy, in the
present measurement were much improved over those of the conventional
TOF measurement. The logarithm of the drift mobility changed linearly
with the square root of the applied electric field.
Role of the Interface in the Temperature Dependence of the Resistivity of Conductive Composite Thin Films
Authors: Hirano Shingo , Kishimoto Akira
Published: October 2002

The role of the interface properties in the surface
resistivity–temperature (ρs–T) behavior in air and
nitrogen was
studied in conductive composite thin films consisting of epoxy resin
and electrically conductive filler. To examine the role of the
interface, we investigated the ρs–T behavior at
various heating
rates. The physicochemical changes in the properties of epoxy resin
with temperature were characterized using thermodilatometry,
thermogravimetry, dynamic mechanical spectroscopy, and Fourier
transform infrared spectroscopy. The thin films exhibited an
anomalous positive-temperature-coefficient-of-resistivity (PTCR)
transition around 130°C. However, they showed
negative-temperature-coefficient-of-resistivity (NTCR) behavior in
air, but not in nitrogen, after the PTCR transition. The thermal and
chemical analyses suggest that the number of OH functional groups in
the epoxy resin influences the occurrence of the NTCR
transition. The heating rate dependence of the ρs–T
behavior showed
that the anomalous PTCR effect in composite thin films occurs with a
rapid thermal strain rate above the glass transition temperature of
the matrix. This result suggests that composite thin films can be
used in temperature sensors that will selectively detect a rapid
environmental temperature increase. These results can be interpreted
satisfactorily by considering the interaction between the
components, which is strongly influenced by OH functional groups and
the matrix thermal strain rate. We constructed a qualitative model
of the anomalous resistivity-temperature behavior, focusing on the
microscopic interaction between the components. The results show
that the interface property plays a decisive role in controlling the
resistivity-temperature behavior in conductive thermoset-matrix
composites.
First-principles Investigation of B-site Ordering in Ba(MgxTa1-x)O3 Microwave Dielectrics with the Complex Perovskite Structure
Authors: Takahashi Takeshi , Wu Eric J. , Van Der Ven Anton , Ceder Gerbrand
Published: October 2002

The B-site cation ordering of Ba(Mg1/3Ta2/3)O3
microwave dielectrics with the complex perovskite structure has been
studied using a combination of first-principles calculations, a
cluster expansion technique, and Monte Carlo simulations. Our
calculations confirm the experimentally observed hexagonal
superstructure with space group P3m1 (D3
3d) as the
ground state. The order-disorder transition between the
low-temperature 1:2 ordered hexagonal phase (P3m1) and
high-temperature simple perovskite phase (Pm3m) is predicted to
occur at ∼3770 K. This indicates that
Ba(Mg1/3Ta2/3)O3 in equilibrium should be fully
ordered at all practical temperatures. Sintering at high temperature
for a long time or prolonging the anneal should therefore be
effective in enhancing the degree of cation order in
Ba(Mg1/3Ta2/3)O3. The charge density distribution and
one electron density of states (DOS) for the 1:2 ordered structure
indicate that Ta and O atoms possess some degree of covalency with
some overlap between the O-2p orbitals and the Ta-5d
orbitals.
Comparative Study of Anchoring Strengths for Photo- and Rubbing-Aligned Liquid Crystals on Photoisomerizable Polyimide Alignment Films
Authors: Chung Doo-Han , Takezoe Hideo , Park Byoungchoo , Jung Youngyi , Hwang Ha-keun , Lee Sooman , Han Ki-Jong , Jang Sei-Hum , Yokoyama Hiroshi
Published: October 2002

The high-electric-field technique was used to measure the
out-of-plane (polar) anchoring strength at the interface between a
nematic liquid crystal, pentylcyanobiphenyl (5CB), and a
photosensitive polyimide (PI) alignment layer possessing an azo
group in the main chain. The anchoring energy of the photoaligned
state was found to be rather strong, on the order of
0.1 mJ/m2, being at
least half of the anchoring energy on the rubbed surface of the same
azo PI. The anchoring energy exhibited a conspicuous peak near the
clearing temperature of 5CB, particularly in the photoaligned
system, indicating a significant role of molecular motion in
anchoring behavior.
Quantitative Characterization of Roughness at SiO2/Si Interfaces by Using Cross-sectional High-resolution Transmission Electron Microscopy
Authors: Ikarashi Nobuyuki , Watanabe Koji
Published: October 2002

We have developed a new method that can quantitatively characterize the
correlation length and the asperity height of the roughness at a SiO2/Si interface.
This method involves, first, <110> cross-sectional high-resolution
transmission electron microscopy (HREM) of the interfaces in very thin specimens
(≤5 nm thick). Pairs of closely spaced Si atomic columns appear in the HREM
image as black dots. The next step involves measuring the HREM image intensity
distribution along each black-dot layer parallel to the interface. Then these
intensity distributions, which are affected by interfacial roughness, are examined
layer-by-layer by Fourier analysis. Moreover, to enable detailed observation of the
interfacial roughness, we developed a specimen-preparation technique in which
CF4–O2 plasma etching is used to remove ion-milling artifacts. We
demonstrate that this examination can provide quantitative indices of the interfacial
roughness. Our method can also detect interfacial roughness that has a correlation
length of only a few nanometers.
Fabrication of Capillary Plate with Sub-Micron Holes for Investigating High-Aspect-Ratio Etching Characteristics
Authors: Kurihara Kazuaki , Sekine Makoto
Published: October 2002

We fabricated a real size capillary (RSC) plate with square
holes with sides of about 0.8 µm, using a silicon-on-insulator
wafer, for investigating the etching characteristics of
high-aspect-ratio holes. The aspect ratio of the holes was 12.3. The
RSC plate was placed on a powered electrode to measure energy
distributions of ions passing through the holes in an
octafluoro-cyclobutane plasma. We successfully measured the ion
energy distributions composed of two major peaks, of nearly the same
shape as those observed using a capillary plate with a hole diameter
of 10 µm.
Non-Paraxial Diffraction-Free Propagation of Light in a Graded-Index Planar Waveguide with Hyperbolic Secant Refractive Index Profile
Authors: Gomez-Reino Carlos , Perez María Victoria , Bao Carmen , Flores-Arias María Teresa , Vidal Silvia , Fernandez de Avila Susana
Published: October 2002

A study of non-paraxial diffraction-free propagation of light with transverse
amplitude in sech through a planar waveguide with hyperbolic secant refractive profile
is presented. Analytical solution by the stationary phase method is obtained. A
particular case is analysed.
Dual-Layer Volume Holographic Optical Elements for Three-Wavelength Optical Disk Pickup
Authors: Matsuzaki Keiichi , Shiono Teruhiro , Saimi Tetsuo
Published: October 2002

A dual-layer volume holographic optical element is proposed as a beam-splitting element for a three-wavelength (λ=0.4 µm, 0.65 µm and 0.8 µm) optical disk pickup. We fabricated it for normal incidence using photopolymer film via an inexpensive laminate process. It is demonstrated that it exhibited excellent wavelength selectivity (extinction ratio ≥∼100) with a high diffraction efficiency of 99.7%. This element could be a key device in a next-generation multi wavelength optical disk pickup.
Influence of Sheet Resistance on N2O-Grown Polyoxide
Authors: Chang Kow-Ming , Lee Tzyh-Cheang , Liu Shang-Hsuan
Published: October 2002

The influence of sheet resistance on polyoxide was explored in
this paper. Polyoxides were grown on polysilicon with different
sheet resistances (30–150 Ω/cm2). It was found that as
the sheet resistance increased from 30 Ω/cm2 to 50 Ω/cm2, the
characteristics of polyoxide was improved with higher breakdown
electric field and higher charge-to-breakdown. However, as the sheet
resistance continued to increase (>110 Ω/cm2), the
characteristics of polyoxide became worse again. This phenomenon is
explained by phosphorus concentration incorporated into
polyoxide. Phosphorus concentration helps to form a smoother
polyoxide/polysilicon interface. Thus, the characteristics of
polyoxide with high sheet resistance (>110 Ω/cm2)
was worse than that of polyoxide with low sheet resistance due to a
rough polyoxide interface. However, too much phosphorus incorporated
into polyoxide degrades the quality of polyoxide. So the
characteristics of polyoxide with low sheet resistance
(<50 Ω/cm2) became worse again. Consequently, high
quality of polyoxide should be grown on the polysilicon with middle
sheet resistance (50–110 Ω/cm2).
Integration of Chemical Vapor Deposition Aluminum and Physical Vapor Deposition Aluminum for Aluminum Plug Process of Sub-Quarter Micron Devices
Authors: Kim Won-Jun Lee , Lee Sang Yeop Han , Kim Jun Ki , Park Jin Won
Published: October 2002

A chemical vapor deposition (CVD)-physical vapor deposition
(PVD) Al plug process was successfully integrated to fabricate
device wafers with sub-quarter micron technology. Metalorganic CVD
(MOCVD) TiN stacked on ion metal plasma (IMP) Ti was used as the
underlayer of CVD Al from dimethylaluminum hydride (DMAH). Thin,
conformal CVD Al film deposited at a low temperature functioned as
an effective wetting layer for PVD Al reflow. If the CVD Al film is
too thick, a complete via fill is not achieved. After PVD Al reflow,
Al bumps were observed atop the via, which originated from the
abnormal growth of the Al grain with a non-<111>
direction. A two-step PVD Al process was applied for bump removal,
because a thin PVD Al layer deposited at low temperature with high
power acted as a seed layer for grain growth. The CVD-PVD Al plug
process exhibited via resistance and electromigration resistance
superior to those of the conventional W plug process.
Molecular Beam Epitaxial Growth of CdTe Layers on InSb(111)A and B Polar Substrates
Authors: Huerta-Ruelas J. , López-López M. , Zelaya-Angel O.
Published: October 2002

We report a study of CdTe layers grown by molecular beam epitaxy (MBE) on InSb(111)A and InSb(111)B substrates. The CdTe/InSb(111) heterostructures, prepared under different conditions, were characterizedin-situby reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES).Ex-situatomic force microscopy (AFM) and Raman spectroscopy were also applied. Our results indicate that In–Te compounds are formed at the interface. The concentrations of these compounds depend on substrate preparation, polarity of the (111) substrate, and annealing process before growth. As shown by RHEED and AFM, CdTe grows nearly two dimensionally on the (111)B surface, whereas on the A face a three dimensional growth, with polycrystalline regions, is obtained.