bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatially-Controllable Quantum Well Intermixing with Stripe-Size Dependence in AlGaAs Heterostructures
Authors: Son Nak-Jin , Han Haewook , Kwon O-Dae
Published: October 2002

Quantum well intermixing based on impurity-free vacancy disordering in Al0.07Ga0.93As /Al
x
Ga1-x
As graded-index (x=0.23–0.5) heterostructures has been performed on a single wafer with various mesa structures by a one-step annealing. From photoluminescence and laser characteristics, it has been demonstrated that the extent of quantum well intermixing can be spatially controlled by simply varying the mesa widths. It has been found that the bandgap shift induced by the intermixing increases as the mesa width decreases.
Simulation of Temporal Waveform Control of Laser Pulse by Frequency Chirping
Authors: Kato Yoshinori , Yoshida Hidetsugu , Fujita Hisanori , Nakai Sadao
Published: October 2002

Arbitrary temporal waveform control can be achieved by means of amplifier gain control
with a chirped laser pulse. In order to simulate precise waveforms of laser pulses, we
developed a multilevel simulation code with transitions between each manifold. Using the
developed code, we examined the generation of required temporal waveforms for laser fusion
experiment. The maximum amount of chirping decreased considerably at low input intensity
and large amplifier gain. In the case of the calculation for a specialized laser system (Gekko
XII), a tailored pulse shape can be generated with less than 4 nm chirp, using the current
modulation technique. Comparing the amplified pulses with chirping to those without chirping,
peak intensity and energy up to peak were 2.34 and 1.41 times higher, while total energy was
0.528 times lower. It was indicated that frequency chirping is one of the most promising
methods for generating the tailored pulses for future laser fusion experiments.
Growth and Optical Properties of Ce-Substituted Fibrous YIG Single Crystals
Authors: Sekijima Takenori , Funakoshi Takaaki , Katabe Kosuke , Tahara Keiichiro , Fujii Takashi , Wakino Kikuo , Okada Masakatsu
Published: October 2002

Ce-substituted fibrous YIG (Y3-X
Ce
X
Fe5O12; Ce:YIG) single crystals were successfully grown by a floating zone method using YAG laser heating. We observed that Ce:YIG crystals show uniform distribution of Ce in the YIG crystal and an excellent magnetooptical property in the near-infrared region up to the Ce substitution of X=0.3. However, the solubility limit of Ce into the YIG crystal was confirmed to be approximately 0.3 in our growth method, by the composition analysis, lattice constant and Faraday rotation measurements. Ce-substituted YIG with X=0.3 shows a large Faraday rotation and small optical absorption coefficient in the wavelength region of 1.51–1.57 µm and is expected to be applicable to the optical isolator.
Atomic and Electronic States of Ag in Sputter-Deposited Ge–Ag Alloys Studied by Photoemission Spectroscopy and Cluster Calculation
Authors: Suzuki Atsuko , Tanaka Kazuhide
Published: October 2002

The ultraviolet photoemission spectra of the Ag-4d band in sputter-deposited Ge100-x
Ag
x

(0≦x≦39.6) alloys change characteristically with Ag concentration. For 0≦x≦5.6, where
X-ray diffraction shows that Ag atoms are dissolved in an amorphous Ge matrix, a single narrow
Ag-4d peak is observed between Ge-4s and -4p bands. For 5.6<x≦16.9, where aggregation of
Ag atoms is suggested to occur, the Ag-4d peak undergoes broadening with a few fine structures.
The spectrum at the Fermi edge also manifests a semiconductorlike to metallic profile change
with increasing Ag concentration. Electronic structure calculations by the DV-Xα method on
Ge–Ag alloy clusters with a diamond structure provide density-of-states curves which are
consistent with several features of these UPS spectra.
Electric Properties of Coplanar High- TCSuperconducting Field-Effect Devices
Authors: Suzuki Shigeru , Tobisaka Hiroshi , Oda Shunri
Published: October 2002

We have investigated coplanar superconducting field-effect devices, which consist of a YBa2Cu3OXthin film for the center channel and two side-gate electrodes, and a SrTiO3substrate as a gate insulator. Because of its simple structure, this device requires only a few steps in the fabrication process. We first simulated the electric-field distribution of the device by numerical calculation. The result indicated that significant current modulation was expected under 10 V gate voltage in this device. Based on the calculation, we fabricated the devices and measured their electric property, which showed 2%ICmodulation. Modulation showed a saturation characteristic, which resulted from the electric field dependence of dielectric constant of SrTiO3at low temperatures. This is the first observation of a superconducting field-effect device with a coplanar structure.
Elastic Anomaly and Glass Transition in Dehydrated Egg White Gel
Authors: Atsushi Nakamura Atsushi Nakamura , Kazuhiro Hara Kazuhiro Hara , Akihiro Matsumoto Akihiro Matsumoto , Nobuyasu Hiramatsu Nobuyasu Hiramatsu
Published: October 2002

Evolution of the complex elastic stiffness of dehydrated heat-treated egg white gel
(DHTEWG) was measured with increasing temperature,
from -30 to +170°C, at the rate of 8°C/min.
In the measurement, the real component of the complex elastic stiffness decreased markedly
and the imaginary component showed a broad peak around the temperature
where a thermal anomaly had been observed (T
g; 50°C);
furthermore, the elastic loss tangent showed a sharp peak at higher temperatures.
Because these characteristics are usually observed in noncrystalline polymers
around the glass transition temperature, the occurrence of glass transition
in DHTEWG around T
g was confirmed.
Characteristics of Directly-Coupled High-Tc Superconducting Quantum Interference Device Magnetometers for Multichannel Applications
Authors: Kwon Hyukchan , Kim In-Seon , Lee Yong-Ho , Kim Jin-Mok , Park Yong Ki , Park Jong-Chul
Published: October 2002

We have characterized directly-coupled dc superconducting quantum interference device (SQUID) magnetometers for multichannel applications. YBa2Cu3O7-δ single layers were deposited on 1 cm×1 cm SrTiO3 bicrystal substrates by laser ablation and patterned by Ar ion milling. From the comparison of the experimental data with the theoretical predictions, we have shown that the degradation of the modulation voltage is caused by the thermal noise flux and thermal noise rounding in the I–V curve. In addition, the SQUID noise at low frequencies could be explained well by critical current fluctuations of the Josephson junctions with a value of S

I
0
/I
0
2≈(1–4)×10-8/Hz. We have achieved a magnetic field noise of 170 fT/√ Hz at 1 Hz. We demonstrated the use of our magnetometers to obtain realtime traces of a magnetocardiogram inside a magnetically shielded room.
Electron Spin Resonance, Electron-Nuclear Double Resonance and General Triple Resonance Studies on the Contributions to Line Broadening of CO2
- in A-type Carbonated Apatites and Biocarbonates
Authors: Schramm Delson U. , Rossi Alexandre M. , Bemski George
Published: October 2002

Electron spin resonance (ESR), electron-nuclear double resonance (ENDOR) and general triple resonance were combined to study linewidth differences observed in the ESR spectra of CO2
- species in calcium carbonate and carbonated apatite. In the latter compound, the motion and a distribution of g-factors (g-strain) are dominant contributions to the observed linewidth. The linewidth temperature behavior follows previous models for CO2
- rotating in calcite. In apatite, these radicals rotate more freely and movement is not restricted to g

x
x
-g

z
z
plane. In carbonates theoretical fit of the linewidth at 9.5 and 34.0 GHz shows the existence of two orthorhombic spectra with slightly different g values and linewidths, which contribute to the observed linewidth difference between narrow and broad line species. Superhyperfine interactions with protons of water molecules, located probably near the second and the third nearest neighbor lattice sites, are responsible for minor contributions to line broadening of CO2
- spectrum.
Nonlinear Gain for a Subnoise-level Signal in a Digital Spectrum Analyzer
Authors: Shigemi Inagaki Shigemi Inagaki , Eizi Ezura Eizi Ezura , Masaaki Kobayashi Masaaki Kobayashi , Kimio Morimoto Kimio Morimoto
Published: October 2002

In order to observe a subnoise-level signal, that is, a low-level signal
with a comparable or smaller amplitude of intruding noise,
an averaging over a multiple number of samplings is inevitable.
Under these conditions,
if an analog-to-digital converter (ADC) is used,
the response of the converter deviates from a step function.
For a signal range of about 50 dB,
we compare the measured response of the spectrum analyzer
with the simulated response of an ADC
for a Gaussian noise distribution.
This effect explains the disagreement
between the expected and measured value
of the blackbody radiation in a cavity reported in
Jpn. J. Appl. Phys. 36 (1997) 2399.
Preparation and Dielectric Property of BaTiO3–SrTiO3 Artificially Modulated Structures
Authors: Tsurumi Takaaki , Miyasou Takamitsu , Ishibashi Yurika , Ohashi Naoki
Published: October 2002

In order to elucidate the origin of the asymmetry observed in
the D-E or C-V hysteresis loops of BaTiO3 (BTO)–SrTiO3 (STO)
epitaxial films, “artificially modulated structures” (AMSs),
where the chemical composition was continuously changed along
the direction of film thickness, were prepared and their dielectric
properties were measured. A fully automatic molecular beam
epitaxy system was developed to fabricate AMSs. Two kinds of
AMS, (BTO←STO) and (STO←BTO) where Ba/Sr ratios were
changed from the film/substrate interface to the film surface in
the reverse direction, were prepared on Nb-doped STO single
crystals. The simulation of XRD profiles indicated that a
relaxation of the crystal lattice occurred along the a-axis in the
two AMSs, and the degree of the relaxation was more significant
in (BTO←STO)AMS. It was observed that the asymmetry of the
C-V hysteresis loop was changed by the modulation of chemical
composition, and that the origin of the asymmetry was attributed
to the lattice relaxation rather than the asymmetry of the stress
field.
Size Effect of the Dielectric Properties in Bismuth-Based Layer- Structured Ferroelectric Films
Authors: Hamada Masakazu , Tabata Hitoshi , Kawai Tomoji
Published: October 2002

Bismuth-based-layer-structured ferroelectric films have been formed epitaxially on Nb-doped
SrTiO3 substrates by pulsed laser deposition (PLD). These films show an
atomically smooth surface with a wide terrace of 100 nm–200 nm, as observed by atomic
force microscopy (AFM) which is ideal for measuring such properties. Crystal growth
apparently changes from the step-flow mode to the island-state mode according to the
number of perovskite layers sandwiched by bismuth oxide layers. Additionally, the
dielectric constant of the three film types, that is Bi2VO5.5 (n=1), Bi3TiNbO9 (n=2), and
Bi4Ti3O12 (n=3) decreases proportionally with decreasing film thickness. It is considered
that the size effect plays an important role in determining dielectric properties. Bismuth-layered
ferroelectric films, with their atomically flat surfaces and accurate electrical
properties, are an ideal material for applications in semiconductor devices.
Preferred Orientation, Phase Formation and the Electrical Properties of Pulsed Laser Deposited SrBi2Ta2O9 Thin Films
Authors: Fujimura Norifumi , Thomas Darin T. , Streiffer Stephen K. , Kingon Angus I.
Published: October 2002

Systematic studies on the preferred orientation, phase formation and the
electrical properties of pulsed laser deposited SrBi2Ta2O9 (SBT) have been performed.
At a substrate temperature of 600°C, the film on SiO2 was not crystallized. Above 650°C,
very strong diffraction from a non-ferroelectric, (111)-oriented fluorite phase was
obtained. Its crystallinity increased with increasing Bi content in the target. The fluorite
phase was also observed in the film on Pt deposited below 600°C, which together with
the pyrochlore phase resulted in the formation of an interfacial reaction product, Bi2Pt.
Above 650°C, the films tend to grow as the perovskite SBT phase with a c-axis
orientation which is not the polarization axis. In contrast, the formation of the fluorite
and pyrochlore phases can be suppressed on Ir electrodes.
Influence of the Microstructure Evolution on Electrical Properties of Multilayer Capacitor with Ni Electrode
Authors: Mizuno Youichi , Okino Yoshikazu , Kohzu Noriyuki , Chazono Hirokazu , Kishi Hiroshi
Published: October 2002

The influence of the microstructure evolution on electrical properties as a parameter of the
firing temperature was studied for materials in the BaTiO3(BT)–MgO–Ln2O3 (Ln=Ho and Dy)
system. The sintering behavior and the formation of the core-shell structure were dependent on
the kind of doped rare earth elements. The stability of the core-shell structure and electrical
properties of Dy doped specimens against the firing temperature were much lower than those of
the Ho doped specimens. Especially, the Dy doped disk specimens fired at more than
1320°C, in which the core-shell grains were destroyed as judged by the differential scanning
calorimetry (DSC) measurement and the transmission electron microscopy (TEM) observation,
exhibited characteristic electrical properties. The electrical properties of the Ho doped
multilayer capacitor (MLC) specimen were superior to those of the Dy doped one. It was found
that the microstructure had a definite influence on the electrical properties, such as the
temperature dependence of the dielectric constant and the capacitance aging behavior under an
unloaded field.
Core/Shell Structure in Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3
Authors: Mishima Tsuneo , Kamigaki Kousei , Nambu Shinji
Published: October 2002

Low-temperature hot-pressed Pb(Mg1/3Nb2/3)O3(PMN)–PbTiO3(PT) materials
exhibited a small temperature dependence of dielectric constants. The microstructure
was studied by means of a transmission electron microscope (TEM). It was found that
a core/shell structure with a pure PMN core and a PMN-PT shell was formed in the
majority of grains. The small temperature dependence of dielectric constants was
attributed to the existence of the core/shell structure. It was also found that the
core/shell structure was formed at the early stage of hot-pressing and that diffusion of Ti
was suppressed under pressure once the material became dense.
Effects of Stoichiometry and A-site Substitution on the Electrical Properties of Ferroelectric YMnO3
Authors: Shimura Tamaki , Fujimura Norifumi , Yamamori Shigeki , Yoshimura Takeshi , Ito Taichiro
Published: October 2002

We proposed the use of RMnO3 (R: rare-earth elements) for metal-ferroelectric-insulator-semiconductor
field-effect transistor (MFIS-FET) type ferroelectric random access
memories (Ferroelectric RAMs). To decrease the leakage current in this material, the effects
of nonstoichiometry and A-site substitution were studied. Current-voltage characteristics
revealed that the carriers in the RMnO3 originate in excess oxygen and show Frenkel-Poole-type
emission. Significant grain growth was observed in the Mn-rich composition. In
particular, Mn-rich YbMnO3 shows the lowest leakage current and the best frequency
dependence of dielectric permittivity.
Nonlinear Piezoelectric Effect in Ferroelectric Ceramics
Authors: Takahashi Sadayuki , Yamamoto Mitsuru , Sasaki Yasuhiro
Published: October 2002

Ferroelectric ceramic is often subjected to both high electric and high stress in piezoelectric
power devices, causing nonlinear piezoelectric response. In this work, nonlinear behavior of
the ferroelectric ceramic, Pb(Mn1/3Sb2/3)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3, electrically excited at
resonant mode was studied. It was found that an induced vibration stress has a greater effect
on the nonlinearity than an electric field. Mechanical loss factor Q
m
-1, Young's modulus c
E and
piezoelectric d
31 constant are shown to be a function of the square of the vibration stress above
the stress threshold. It was also found that the nonlinear proportional constant for the stress
becomes smaller in the order of Q
m
-1, d
31 and c
E, and that the softer in piezoelectricity the
material is, the larger the nonlinear proportional constant becomes.
Electromechanical Fatigue of Lead Zirconate Titanate Ceramics
Authors: Makino Hiroaki , Kamiya Nobuo
Published: October 2002

Mechanical fatigue of lead zirconate titanate ceramics when both an ac electric field
and mechanical stress were applied to the specimen was investigated. Fatigue strengths under an ac
electric field degraded compared with the fatigue strengths under short-circuit conditions while the
slope of the S-N curve was the same as that under the short-circuit condition. The reason for the
degradation of fatigue strength under an ac electric field is considered to be the microscopic internal
stress caused by the electric-field-induced strain. Degradation of fatigue strengths under an ac
electric field became larger when the electric field became bipolar even though the amplitude of the
field was the same. The reason for the dependence of fatigue strength under an ac electric field on
the applied field polarity is considered that the internal stress became large when the ac electric field
became bipolar.
Measurement of the Sound Velocity in Liquids Using a Leaky Lamb Wave Transducer Composed of a Layer-Structured Substrate
Authors: Motegi Kenji , Toda Kohji
Published: October 2002

A leaky Lamb wave transducer composed of a thin piezoelectric ceramic plate
and a thin glass plate is described for the purpose of measuring the sound
velocities in liquids. The propagation characteristics of leaky Lamb waves are
numerically analyzed first and the operational characteristics of the transducer
are experimentally demonstrated by measuring the frequency dependence of the
admittance and the radiation angle of the longitudinal wave into the liquid.
The sound velocities in the saline solution of different concentrations are
estimated by sweeping the operation frequency. This transducer has an operation
mode with a wide frequency range in which three propagation modes of leaky Lamb
waves are involved, which is favorable for this application.
Application of Gas Jet Deposition Method to Piezoelectric Thick Film Miniature Actuator
Authors: Schroth Andreas , Maeda Ryutaro , Akedo Jun , Ichiki Masaaki
Published: October 2002

Currently the development of piezoelectiric miniature actuators is a subject of interest
in the industrial field of mobile electronic devices. Although the deposition of PZT(Pb(Zr.52,
Ti.48)O3) in the thickness range of 10 to 100 µm is a key technology for the realization
of miniature actuators, thick films of PZT have rarely been prepared by
other deposition methods for glued PZT structures. It is also difficult to obtain a
thickness of less than 50 µm. This is the reason why we have designed and fabricated a
two-dimensional miniature scanner actuated with a relatively thick piezoelectric layer
by a recently introduced gas deposition method of ultra fine particles with a subsonic
gas jet stream. A piezoelectric PZT layer, of thickness 30 microns is deposited onto a
stainless steel substrate and patterned by the simple lift off method, to fabricate a
bimorph type actuator beam. Mirror scanning is performed by four independent
actuator beams. The device can be scanned along two axes by two independent
resonant frequencies. Deflection of the fabricated scanning mirror is measured by laser
interferometer and compared with the simulation results obtained by FEM (finite
element method). Scanning of the laser light is also demonstrated by the fabricated
device.
Fundamental Studies on Scanning Electron-Beam Dielectric Microscopy
Authors: Yasuo Cho Yasuo Cho , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

Fundamental studies on scanning electron-beam dielectric microscopy are elucidated. This microscopy is used for determining the temperature coefficient distribution of dielectric materials using an electron-beam as a heat source instead of a light source of a photothermal dielectric microscope. This microscopy, with the abilities of in situ observations of SEM images and material compositions, has an intrinsic resolution better than that of photothermal dielectric microscopy. To demonstrate the usefulness of this technique, the two-dimensional image of a two-phase composite ceramic composed of TiO2 and Bi2Ti4O11 is measured.
Banded Structure and Domain Arrangements in PbTiO3 Single Crystals
Authors: Chou Chen-Chia , Chen Cheng-Sao
Published: October 2002

In the present work we report the ferroelectric domain arrangements and characteristics of banded structures observed in flux-grown PbTiO3 single crystals.
Investigations of etched crystals indicate that most of the specimens show banded structures which may correspond to surface relief characteristics of as-grown crystals. Banded structures, which are different
from domain structures, possess structural characteristics similar to those of martensite variants in various alloys and ceramics. The stresses produced during transformation were relieved by the formation of
the banded structures and the 90° domain structures, suggesting that the band structures and 90° domains are the products of self-accommodation in as-grown PbTiO3 crystals during the cubic/tetragonal
(C/T) transformation. Image characteristics imply that banded-structure-induced domain intersections may store high strain energy in lead titanate crystals and therefore hinder polarization switching of the crystals.
Atomic Force Microscope Observation of 90° Domain Structure in the Crystallized Grains from Amorphous PbTiO3
Authors: Su Jang Masaaki Takashige
Published: October 2002

We used an atomic force microscope(AFM) to study the surface morphology of the crystallized samples of PbTiO3 from the amorphous state prepared by rapid quenching. The specific structure on the surface was detected. We discussed a possible relationship between such a structure and the 90° domain structure of the crystalline PbTiO3.
Raman Scattering Studies of Pb(ZrxTi1-x)O3 and Pb1-3y/2Ndy(ZrxTi1-x)O3 Ceramics with UV and Visible Laser Lights
Authors: Johannes Frantti Johannes Frantti , Vilho Lantto Vilho Lantto , Masato Kakihana Masato Kakihana
Published: October 2002

Raman scattering studies of lead zirconate titanate (Pb(ZrxTi1-x
)O3, PZT, 0.10≤x≤0.70), Nd-modified lead titanate (Pb1-3y/2NdyTiO3, PNT, 0.02≤y≤0.10) and Nd-modified lead zirconate titanate (Pb1-3y/2Ndy(Zr0.53Ti0.47)O3, PNZT, 0≤y≤0.04) bulk ceramics using uv and visible laser lights (wavelengths 363.79 nm and 514.532 nm, respectively) were carried out at room temperature. In the case of uv light, Raman spectra revealed three or four high-frequency modes above 1000 cm-1 in all the samples and a weak mode at around 970 cm-1 in PNT samples. These modes do not correspond to the first-order modes from the ideal crystal symmetries (C
4v

1, C
3v

1, C
3v

6) which were the only phases revealed by the X-ray diffraction measurements. The intensities of these modes were strongest in the trigonal phase region and decreased with decreasing Zr content. The frequency of the mode at around 1170 cm-1 in PZT ceramics showed anomalous behaviour at the phase transitions between the tetragonal and high-temperature trigonal phases and between the high- and low-temperature trigonal phases. These modes probably correspond to an electronic process in the Pb3+ hole traps.
Pulse Compression with a Noncollinear Type I Frequency Doubling Crystal
Authors: Zhang Tiejun , Yonemura Motoki
Published: October 2002

We propose a new scheme to generate a compressed second-harmonic pulse with a noncollinear type I frequency doubling crystal. Theoretical calculations predict that a 25 fs second-harmonic pulse could be generated from a 100 fs fundamental pulse with the proposed scheme.
Slow Carrier Relaxation among Sublevels in Annealed Self-Formed InGaAs/GaAs Quantum Dots
Authors: Mukai Kohki , Sugawara Mitsuru
Published: October 2002

Slow carrier relaxation among discrete sublevels in self-formed InGaAs/GaAs quantum dots was studied by means of photoluminescence (PL) and time-resolved photoluminescence spectroscopy before and after annealing. The PL intensity of the ground level drastically decreased after annealing at above 600°C, while that of the second level was not much influenced, suggesting a delicate balance between carrier relaxation and recombination among sublevels. We propose a model to describe the decay process of the number of carriers in an uncoupled dot ensemble, and determine the carrier relaxation lifetimes (≈10-10 s) and the recombination lifetimes (≈10-9 s) of sublevels in annealed samples by time-resolved measurements. Simulation with the measured lifetimes adequately explained the change of PL spectra after annealing.
Preparation of Position-Controlled Crystal-Silicon Island Arrays by Means of Excimer-Laser Annealing
Authors: Chang-Ho Oh Chang-Ho Oh , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Two-dimensionally aligned and ultralarge Si grains were grown on a glassy substrate by phase-modulated excimer-laser annealing, for the first time. Grains as large as 7 µm were grown at predetermined positions at 500°C, and were expected to be aligned with less than 30 µm pitch. Serious effects of the laser beam divergence, which is influenced by the optical system, are pointed out.
Threading Dislocations in Multilayer Structure of InAs Self-Assembled Quantum Dots
Authors: Ken-ichi Shiramine Ken-ichi Shiramine , Yasunobu Horisaki Yasunobu Horisaki , Dai Suzuki Dai Suzuki , Satoru Itoh Satoru Itoh , Yoshiki Ebiko Yoshiki Ebiko , Shunichi Muto Shunichi Muto , Yoshiaki Nakata Yoshiaki Nakata , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

A multilayer structure consisting of 20 layers of InAs self-assembled quantum dots was grown by molecular beam epitaxy and observed by transmission electron microscopy. The positions of quantum dots in a quantum-dot layer were not correlated with those in the lower quantum-dot layer because of the thick (70 nm) GaAs spacer layer. Threading dislocations were observed, which originated from large strain-relaxed (incoherent) InAs islands in a quantum-dot layer. The dislocations were 30° dislocations in the [112] and [112] directions, and were generated by a misfit between large InAs islands and a GaAs overlayer.
A Fully Integrated Aluminum Dual Damascene Process Using a New Double Stopper Structure
Authors: Anand Minakshisundaran B. , Nakamura Naofumi , Wada Jun-ichi , Oikawa Yasushi , Katata Tomio , Shiba Katsuyasu , Shibata Hideki
Published: October 2002

A fully integrated aluminum dual damascene process is presented. The process incorporates a double silicon
nitride etch stopper structure to achieve better etching control. Use of silicon nitride etch stoppers usually results in
increased wire capacitance. However, the new process presented here succeeds in significantly reducing the impact of the silicon nitride stopper layers on wire capacitance by arranging for the stopper layers to be away from the wire
corners. The integration of this process with a previously reported aluminum reflow process to obtain an integrated
aluminum dual damascene process is described and the results obtained are discussed.
Noise Current Induced by Switching of a Dielectric Isolated Lateral Insulated Gate Bipolar Transistor on Silicon-on-Insulator
Authors: Sumida Hitoshi , Hirabayashi Atsuo
Published: October 2002

When a dielectric isolated lateral insulated gate bipolar transistor (DI-LIGBT) on
silicon-on-insulator (SOI) is turned on or off, a displacement current occurs in the
surrounding area separated by dielectric isolation, referred to as a noise current in
this note. We have determined this noise current during switching of the DI-LIGBT
experimentally, and have investigated the dependence of its behavior on the cell
pattern of the DI-LIGBT. The high noise current can be observed at the turn-on
transient of the device, and its peak depends strongly on the cell pattern of the
device structure.
Effects of Grain Boundaries on Temperature Dependence of Microwave Surface Resistance of YBa2Cu3O7-x Thin Films
Authors: Tunyiswa Mazwi Ben , Nakajima Kensuke , Chen Jian , Kim Sang-Jae , Wang Huabing , Yamashita Tsutomu
Published: October 2002

This paper investigates the temperature dependence of microwave surface resistance (R
S) of
YBa2Cu3O7-x
(YBCO) thin films with different microstructures at 10 GHz, using a coplanar resonator
technique. YBCO thin films with different grain sizes were obtained as a result of changing the
quenching procedure after film deposition by dc sputtering. The value of R
S was found to vary with
varying surface morphology and can be explained by the coupled grain model (CGM) when a
temperature-dependent grain boundary resistance (R) is used. The temperature (T) dependence of R
is given by R=R
0+C(T/T
C)2
T, where T
C is the superconducting critical temperature, and R
0 and C
are the fitting parameters, depending on the properties of each sample.
Ferroelectric Properties of SrBi2Ta2O9 Thin Films Deposited on Various Bottom Electrodes by a Modified Radio-Frequency Magnetron Sputtering Technique
Authors: Yang Cheol-Hoon , Shin Woong-Chul , Choi Eun-Suck , Hwang Jun-Sik , Yoon Soon-Gil , Choi Won-Youl , Kim Ho-Gi
Published: October 2002

Ferroelectric layered-oxide SrBi2Ta2O9 thin films were successfully deposited on metalorganic
chemical vapor deposited (MOCVD) Pt/Ta/SiO2/Si (MPTSS), MOCVD-RuO2/Si (MRS), and Pt/Ti/SiO2/Si (PTSS) substrates using a sintered Sr1.2Bi2.4Ta2.0O9 ceramic and Bi metal targets by modified rf magnetron sputtering. The 190 nm thick Sr1.0Bi2.7Ta2.0O9 films deposited on PTSS substrates
have a remanent polarization (P
r) of 4.3 µC/cm2 and a coercive field (E
c) of 36.6 kV/cm at an
applied voltage of 5 V. The SBT films deposited on PTSS showed a fatigue-free characteristic
up to 1.0×1010 cycles under a 5 V bipolar pulse and a leakage current density of 8.0×10-9 A/cm2 at 150 kV/cm.
Fabrication of Lens Rasters Using a Laser Beam Scanning Method
Authors: Jeon Hyung-Wook , Lee Hyuk-Soo , Son Jung-Young , Smirnov Vadim V. , Choi Yong-Jin , Chun You-Seek
Published: October 2002

A cylindrical lens raster array is drawn on a dichromatic gelatine layer by
hardening with a scanning laser beam. The thicknesses of the gelatine layer used for
the array range from 40 to 80 µm. The laser beam intensity profile is modified by a
mask with a specific transparency function to fabricate the desired lens profile. This
method is used to produce lens rasters which can be used as 3-dimensional image
projection screens and anamorphosers.
Thermal Properties of InAs0.86Sb0.05P0.09 Homostructure Diodes
Authors: Chen Lung-Chien , Wu Meng-Chyi , Ho Wen-Jeng
Published: October 2002

High-quality InAs0.86Sb0.05P0.09 layers having a lattice near-match with the InAs
substrate were grown by liquid-phase epitaxy (LPE) employing a supercooling technique,
and the p-n junction diodes were fabricated using Zn-diffused techniques. In this work,
we investigated the current–voltage (I–V) relationship with temperature from 30°C to 160°C.
The dark current of the diode at 30°C had values of 31.8 µA (0.4 A/cm2) at -0.25 V and 143 µA
(1.8 A/cm2) at -2 V. The dark current in the InAs0.86Sb0.05P0.09 diode in the temperature
range of 30 to 80°C varies as exp
(-E
g/n
k
T) with n=1.7–1.8, however when the temperature
exceeds 100°C, the ideality factor n decreases to 1.1 and 1.2 at -0.25 and -2 V, respectively.
Soft Modes Responsible for α-β and β-γ Phase Transitions of KIO3 Crystals
Authors: Muhtar Ahart Muhtar Ahart , Seiji Kojima Seiji Kojima , Masayoshi Takagi Masayoshi Takagi , Masaki Maeda Masaki Maeda , Ikuo Suzuki Ikuo Suzuki
Published: October 2002

The α-β and β-γ phase transitions of KIO3 crystals have been studied by Raman scattering. The two lowest optical modes of 32 cm-1 and 38 cm-1 at -180°C show remarkable softening towards the β-γ transition temperature of 72°C. The third lowest mode of 63 cm-1 at -180°C also softens markedly towards the α-β transition temperature of 212°C. This mode shows a kink near the β-γ phase transition and a strong polarization dependence. These three soft modes strongly suggest that these two phase transitions have a displacive nature.
Surface Kinetics of CFx Radicals and Fluorine Atoms in the Afterglow of High-Density C4F8 Plasmas
Authors: Suzuki Chihiro , Sasaki Koichi , Kadota Kiyoshi
Published: October 2002

Temporal variations of absolute densities of CF, CF2 and atomic fluorine (F) were measured
in the afterglow of high-density C4F8 plasmas generated by helicon-wave discharges.
Laser-induced fluorescence (LIF) spectroscopy was adopted for CF and CF2 radicals,
while vacuum ultraviolet (VUV) absorption spectroscopy was employed for the F atom.
CF and F densities gradually decreased for 20–80 ms after the extinction of the rf power,
while CF2 density steadily increased during the same period.
This slow increase in CF2 density can be explained by surface kinetics of the radicals.
In the afterglow of discharges with a high degree of dissociation,
the increase in CF2 density is approximately equal to CF density at the beginning of the afterglow.
The mechanism for the surface production of CF2 in the afterglow is discussed
based on the close relationships between the temporal variations of CF and CF2 densities.
Electron Energy-Loss Spectroscopy Study of the Metal-Insulator Transition in V2O3
Authors: Hiroyuki Abe Hiroyuki Abe , Masami Terauchi Masami Terauchi , Michiyoshi Tanaka Michiyoshi Tanaka , Shik Shin Shik Shin
Published: October 2002

Electron energy-loss spectra of V2O3 of the paramagnetic metallic (PM) and antiferromagnetic insulating (AFI) phases have been measured by a high-resolution transmission electron energy-loss spectroscopy (EELS) technique. An excitation at about 1 eV was previously observed in both the PM and AFI phases by an optical measurement and assigned to the excitation of a free-carrier plasmon. A sharp peak has, however, been observed at 1.1 eV in our EELS spectra of the PM phase but not in those of the AFI phase. We assigned the peak to an interband plasmon due to d-d transitions by inspecting the dielectric function derived from the EELS spectra. The peak of the O 1s EELS spectra due to the O 1s → V 3d(t
2g
) transition increased in energy by 0.4 eV but decreased in intensity at the transition from the PM phase to the AFI phase. The increase of the energy is due to a splitting of the V 3d(t
2g
) band, which is partly filled at the PM phase, into the fully occupied and unoccupied bands and a shift of the unoccupied band to an energy higher than the Fermi level in the PM phase. The decrease of intensity is considered to be due to the decrease of the transition probability of the O 1s → V 3d(t
2g
) transition, which is attributed to the decrease of the hybridization of the V 3d with O 2p orbitals at the transition from the PM phase to the AFI phase.
Control of Microscratches in Chemical-Mechanical Polishing Process for Shallow Trench Isolation
Authors: Park Heungsoo , Kim Kwang-Bok , Hong Chang-Ki , Chung U-In , Lee Moon-Yong
Published: October 2002

A method of controlling microscratches on silicon oxide surfaces induced
by chemical-mechanical polishing (CMP) process for the planarization of
shallow trench isolation is discussed. The frequency of microscratches
during polishing shows its high dependency on the characteristics of CMP
consumables such as slurry and pad. A diluted slurry solution, pH-controlled
with a potassium hydroxide (KOH) solution of pH 13, produces
best results in reducing microscratches on silicon oxide surfaces during
polishing. In conclusion, careful preparation of the CMP consumables is
required to reduce microscratches on silicon oxide during polishing.
Incidence of Final States-Density for Impact Ionization on the Electron Ionization Rate
Authors: Rmou Abdelaziz , Luquet Henri , Perotin Michèle , Skouri El Mostafa
Published: October 2002

The anisotropy of electron impact ionization rate as related to the band structure is experimentally established. At present, theoretical studies often attribute its dependence to the overlap integrals variations, alloy disorder effect or impact ionization process involving a second conduction band. We present a different numerical calculation of electron impact ionization probability in Ga1-x
Al
x
Sb avalanche photodiodes (0≤x≤0.08). The ionization probability is calculated directly from the numerical evaluation of the matrix element including the full details of the first conduction band. It is found that the dependence of the electron ionization probability on the final states-density for impact ionization is very crucial compared with variations in overlap integrals or alloy disorder effect.
Low-Temperature Plasma Etching of Copper Films Using Ultraviolet Irradiation
Authors: Choi Kang-Sik , Han Chul-Hi
Published: October 2002

Inductively coupled plasma etching of copper under ultraviolet (UV) irradiation is proposed. We achieved an etch rate of about 300 nm/min at room temperature using Cl2/N2 (or Cl2/Ar) gas mixture. UV light irradiation lowers the activation energy of copper etching from 1.6 eV to 0.12 eV and enhances CuCl desorption, which makes it possible to etch copper at low temperatures. The etch rate increases almost linearly with increasing UV light intensity, and then saturates at high UV intensity. It is concluded that the etching process is not a simple thermal process, but a kind of photodesorption of CuCl due to ultraviolet irradiation. This etching method will bring us closer to high-resolution copper metallization.
Numerical Evaluation for the High-Frequency Response of Josephson Junctions Having Finite Capacitance
Authors: Yoshinao Mizugaki Yoshinao Mizugaki , Jian Chen Jian Chen , Kensuke Nakajima Kensuke Nakajima , Tsutomu Yamashita Tsutomu Yamashita
Published: October 2002

The high-frequency response of a Josephson junction is numerically
investigated. The resistively shunted junction (RSJ) model
and the resistively and capacitively shunted junction (RCSJ) model
are employed. Simulation results for the Shapiro steps are
different between the two models. The difference with respect to the RF current
is explained by employing a simple resistor and capacitor model.
Fabrication, Writing, and Reading of 10 Gbits/in2 Longitudinal Quantized Magnetic Disks with a Switching Field over 1000 Oe
Authors: Kong Linshu , Zhuang Lei , Li Mingtao , Cui Bo , Chou Stephen Y.
Published: October 2002

Quantized magnetic disks (QMDs) with a density of 10 Gbits/in2 were fabricated
using nanoimprint lithography and a lift-off process. Each bit in the QMD
consists of a patterned single domain Co bar with a length of 200 nm, a width of
60 nm, and a bar spacing of 130 nm. Magnetic force microscope (MFM) was used to
write and read the QMD. In 2.5 µm×2.5µm MFM window, error-free MFM writing
has been achieved, even though there is no feedback control of the writing tip
position and the Co bars switching field was as high as 1020 Oe.
Giant Magnetoresistanc of Dual Spin-Valves Using Antiferromagnetic α-Fe2O3 as a Pinning Layer
Authors: Sugita Yasunari , Kawawake Yasuhiro , Satomi Mitsuo , Sakakima Hiroshi
Published: October 2002

We report the large magnetoresitance (MR) ratio of a dual spin-valve structure in
α-Fe2O3(50 nm)/Co/Cu/Co/Cu/Co/α-Fe2O3(50 nm) films using the insulating
antiferromagnetic α-Fe2O3 as a pinning layer. The MR ratio of a dual spin-valve is
obtained as 27.8%, the highest value ever reported. This large MR ratio may indicate
that the specular reflection of the conduction electrons occurs at the metal/insulator
(Co/α-Fe2O3) interfaces.
Difference in the Electronic Structure of SrBi2Ta2O9 and SrBi2Nb2O9
Authors: Kaoru Miura Kaoru Miura , Masahiro Tanaka Masahiro Tanaka
Published: October 2002

We calculated the electronic structures of SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) using the discrete variational Xα method. We conclude that the difference in the remanent polarization between SBT and SBN is due to the difference in the displacement between tantalum ions and niobium ions rather than the difference in the displacement of the other ions and the difference in ionic charges.
Influence of Interfacial Oxide on Self-Alignment Silicide Process
Authors: Huang Jen-Yun , Wu Shinn-Tyan
Published: October 2002

The microstructure of titanium silicide is affected by the presence of an interfacial oxide (SiO
x
) layer on silicon prior to sputtering deposition of titanium film. The microstructure is investigated by transmission electron microscopic (TEM) and scanning electron microscopic (SEM), the texture is determined from X-ray pole figures and resistivity is determined by four-point probe measurement. It is discovered that the silicide film becomes discontinuous if the oxide layer (SiO
x
) is thicker than 3.4 nm and the film is highly resistive. If the oxide layer is thinner than 1.7 nm, the resistivity is not affected because the interfacial oxygen atoms are presumably snowplowed to the surface. The grains of discontinuous silicide exhibit a weak epitaxial relationship with Si(001).
Time-Dependent Deformation Behavior of Amorphous Nitrogen-containing Carbon Films
Authors: Daisuke Tanaka Daisuke Tanaka , Shigeo Ohshio Shigeo Ohshio , Hidetoshi Saitoh Hidetoshi Saitoh
Published: October 2002

An indentation creep test has been performed to investigate the nanostructure
changes in nitrogen-containing carbon films showing a relatively
high hardness value.
The time-dependent indentation depth of the hard films indicates
a monatomic increase at the initial stage of the creep procedure
and thereafter, remains constant.
Using the results of the slope of the time-displacement relation
at the initial stage of the creep procedure,
the strain rate sensitivity exponent m is obtained.
Several experiments were conducted under various applied forces,
ranging from 20 to 600 mN, to confirm the differences in the viscous flow
characteristics of samples with various nitrogen contents.
The results revealed that viscous flow of the sample began only
when the applied force was increased beyond a critical value.
The critical loading force rapidly dropped with increasing
extent of nitrogen-carbon bonding in the film.
Monte Carlo Simulation of Hydrogen Diffusivity in Aluminum with Anisotropic Grain Boundaries
Authors: Ichimura Minoru , Sasajima Y.
Published: October 2002

The hydrogen diffusivity in polycrystalline aluminum is simulated by the Monte Carlo method based on the random walk theory. We have previously performed a simulation of hydrogen diffusivity in aluminum with isotropic grain boundaries, known as the grain boundary cross (GBC) effect. In this study, a similar diffusivity simulation of a sample with anisotropic grain boundaries is performed. The anisotropy of grains corresponds well with the columnar grains in the real specimens for which the diffusivity peak was measured. For samples with anisotropic grain-shapes, the hydrogen diffusivity is enhanced along the longer side of grain boundaries for larger grains, and is increasingly suppressed by trapping at grain boundary junctions for smaller grains. This results in a complicated or disordered peak at some intermediate grain sizes. This is termed the grain boundary anisotropic (GBA) effect. An examination of these simulation results supports and confirms the anisotropic qualities of the GBC effect previously determined experimentally by us.
Patterned Alignment of Liquid Crystal on Photopolymer by Single-Exposure Photocuring Process
Authors: Kumar Rajesh Kumar Rajesh , Rumiko Yamaguchi Rumiko Yamaguchi , Akira Sato Akira Sato , Susumu Sato Susumu Sato
Published: October 2002

We have promoted the complex patterned orientation of liquid crystal on polyvinyl cinnamate (PVCi) substrates by a single-exposure technique using the photocuring process. The process involves the polymerization of the polymer simultaneously by optical and thermal means. The information restored in the form of homogeneous or homeotropic orientation of the liquid crystal is nonerasable and permanent.
Local Tunneling Barrier Height Image of the Si(111)-(7×7) Surface
Authors: Sasaki Masahiro , Komai Masaaki , Ozawa Ryo , Yamamoto Shigehiko
Published: October 2002

The local tunneling barrier height (LBH) image of Si(111)-(7×7) surface
is compared with the corresponding scanning tunneling microscope
(STM) image. At a negative sample bias voltage, while the faulted half
adatoms in the 7×7 unit cell in the STM image are observed to be 0.24 Å
higher than the unfaulted half adatoms, there exists no difference in the
LBH image contrast between faulted and unfaulted halves. At a positive
sample bias voltage, we observe no difference between the faulted and
unfaulted halves both in the STM and LBH images. The results suggest
that there exists an unexpected mechanism which determines the STM and
LBH images.
Structural Characterization of Codeposition Growth β-FeSi2 Film
Authors: Lin Chenglu , Wang Lianwei , Chen Xiangdong , Chen L. F. , Wang L. M.
Published: October 2002

Epitaxial β-FeSi2 film on Si(111) was prepared by codeposition of iron and silicon onto a β-FeSi2 template at 400°C and subsequent annealing at 700°C for 2 h. The template was prepared by reactive deposition epitaxy on Si(111). X-ray diffraction (XRD) pattern shows only β-FeSi2(202) or (220) peak which is in correspondence with the epitaxial β-FeSi2(101) or (110) on Si(111). Cross-sectional transmission electron microscopy (XTEM) and high resolution TEM (HRTEM) observation show that the β-FeSi2/Si interface was quite flat near atomic level. Conversion electron Msbauer spectrum proves that the film grows in one or more epitaxial equivalent orientations rather than in a polycrystalline manner.
Competing Surface Oxidation Reactions During Diamond Synthesis in Low Pressure Flames
Authors: Kim J. S. , Cappelli M. A.
Published: October 2002

Carbon oxidation reactions affecting diamond growth in
low pressure premixed flames are addressed. Modifications
are made to the relatively simple yet robust Harris growth
mechanism [S. J. Harris: Appl. Phys. Lett. 56 (1990) 2298],
to better capture anomalous behavior seen in past
experimental studies of films deposited from low pressure
acetylene-oxygen (C2H2–O2), ethylene-oxygen (C2H4–O2), and
methane-oxygen (CH4–O2) flames. With surface reactions
involving oxygen, detailed simulations are shown to better
predict the observed growth rates, generally to within a
factor of two for C2H2–O2 and C2H4–O2 flames. More
importantly, the simulations with oxidation reactions
capture the sharp onset of growth as reactant mixture
compositions are varied towards rich flame conditions. The
model is less successful at capturing the growth rates seen
in CH4–O2 flames. The diamond synthesized in CH4–O2 is seen
to be more defective, with a seemingly greater fraction of
sp
2 bonds, the presence of which are not accounted for in
the simple growth mechanism employed in this study.
Polarization Properties of Vertical-Cavity Surface-Emitting Lasers with Various Patterns in Tilted Pillar Structures
Authors: Park Min Soo , Ahn Byung Tae , Chu Hye Yong , Yoo Byueng-Su , Park Hyo-Hoon
Published: October 2002

We have studied the polarization properties of vertical-cavity surface-emitting lasers
with various patterns in tilted pillar structures. Laser pillars with circular, square, diamond
and rectangular patterns were formed by reactive ion beam etching. Tilted pillars were
obtained by tilting the [110] or [110] direction of the (001) GaAs substrate. The sizes of
pillars varied from 10 µm to 20 µm and their tilt angle varied from 15° to 30° toward
[110] or [110] with respect to [001]. The vertical asymmetry of the tilted pillar strongly
affected the polarization selectivity of vertical-cavity surface-emitting lasers with the tilted
pillar, rather than the anisotropy of an overlapped region in the planar direction.