bluuebunny/crossref_metadata_2025 huggingface dataset:
Boron Accumulation in the {311} Defect Region Induced by Self-Implantation into Silicon Substrate
Authors: Jianxin Xia Jianxin Xia , Tomoya Saito Tomoya Saito , Takenori Aoki Takenori Aoki , Yoshinari Kamakura Yoshinari Kamakura , Kenji Taniguchi Kenji Taniguchi
Published: October 2002

Boron pile-up in the {311} defect region during thermal annealing was observed for the first time. Czochralski Si wafers with a boron concentration of 2.7×1017 cm-3 were implanted with 50 keV Si+ at a dose of 5×1013 cm-2, followed by annealing at 670°C or 720°C in nitrogen ambient. During annealing, boron atoms accumulate in the region between R

p
and 2R

p
, which leads to a B-depleted region extending from 2R

p
to 0.4 µm. During lower temperature annealing, the number of boron atoms accumulated in the pile-up region reaches its maximum more slowly and has a greater peak value. After reaching its maximum, the number of boron atoms falls exponentially with a characteristic decay time of 14 h at 670°C or 3 h at 720°C. The correlation between the annealing time dependence of the boron pile-up and the evolution of interstitials contained in {311} defects suggests that the boron pile-up is due to the boron segregation to {311} defects.
Electrical Properties of La0.7Sr0.3CoO 3/Pb(Zr0.52Ti0.48)O 3/La0.7Sr0.3CoO 3 Thin Film Capacitors Formed on MgO Substrates Using the Sol-Gel Method
Authors: Sung-Min Yoon Sung-Min Yoon , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Sol-gel derived La0.7Sr0.3CoO3/Pb(Zr0.52Ti0.48)O3(PZT)/La0.7Sr0.3CoO3(LSCO)
ferroelectric capacitors were fabricated on MgO(100) substrates. In order to avoid degradation of the PZT
film during the high-temperature crystallization process of the top LSCO electrode, amorphous
phase LSCO was used in the sol-gel method. These capacitors showed good ferroelectric
hysteresis loops and no significant degradation of switchable polarization was observed after
1×109switching cycles.
Enhanced Depth Penetration in Imaging of Turbid Biological Samples by Two-Photon Fluorescence Microscopy
Authors: Daria Vincent , Nakamura Osamu , Palmes-Saloma Cynthia , Kawata Satoshi
Published: October 2002

Two-photon fluorescence microscopy provides promising applications to three-dimensional
imaging of turbid biological samples. It uses a near-infrared, mode-locked laser, which
enables deeper penetration to a turbid medium, compared to an ultraviolet (UV) excitation
source. In viewing deeper portions of the turbid sample, however, multiple scattering of the
back-propagated fluorescence emission yields a low signal-to-noise ratio (SNR). To rectify
this problem, a predetection contrast compensation, which is based on the regulation of the
excitation power, can maintain the contrast of the images taken at different depths. Variation
of the excitation power can be controlled using online histogram readout of the section
images. Results show that thin axial scans provide high SNR images taken from deep
portions of a whole-mount mouse embryo stained with a neuron specific biological marker.
Band Diagram of Metal-Insulator-Magnetic Semiconductor (La0.85Sr0.15MnO3) Structure at Room Temperature
Authors: Kudo Tomohiko , Tachiki Minoru , Kashiwai Tadahiro , Kobayashi Takeshi
Published: October 2002

We investigated electrical properties of a La0.85Sr0.15MnO3 magnetic
semiconductor through observation of photoinduced current and electron-beam-induced current (EBIC) across the Al/(100)SrTiO3/(100)La0.85Sr0.15MnO3 metal-insulator-semiconductor (MIS) structure at room temperature. The test
specimens were prepared by the Ar–F excimer laser ablation technique.
According to the current flowing direction, it was observed that the
La0.85Sr0.15MnO3 band bends downward at and near the interface. Furthermore,
from determination of the flat-band condition, the work function of
(100)La0.85Sr0.15MnO3 epitaxial film was estimated to be ∼4.8 eV.
Pressure Dependence of Photoluminescence in GaAs/Partially Ordered GaInP Interface
Authors: Kobayashi Toshihiko , Ohmae Takashi , Uchida Kazuo , Nakahara Jun-ichiro
Published: October 2002

We have measured the photoluminescence (PL) spectra of GaAs/GaInP
single quantum wells at pressures up to ∼5 GPa, and investigated the
characteristics of the 1.46 eV deep emission band. It has a very long
decay time of 200–400 ns. In addition, at normal pressure, unlike
the emission from the GaAs well, a strong blueshift of the spectral
position with excitation intensity is observed. With increasing
pressure, the deep emission shows a sublinear shift towards higher
energy, while the GaAs well exhibits a linear shift. The
pressure-dependent PL behavior at lower excitation intensity is
rather similar to those observed for partially ordered GaInP alloys.
These results suggest that the presence of ordered GaInP layers plays
an important role in the radiative recombination at 1.46 eV, and the
1.46 eV deep emission is related to the interface transitions of
electrons and holes localized at the heterointerface.
Tracking Method for Digital Optical-Disk Systems
Authors: Maeda Takeshi , Uno Motoo , Takasago Mashahiro
Published: October 2002

Servo technologies making it possible to construct a tracking
subsystem suitable for an optical disk system that stores coded data are reported
in this paper as follows. (a) two-stage actuator tracking servo (b) tracking signal
compensation (c) track-off detection and data recovery. The basic construction of
a tracking servo system for an optical disk system using write-once media is
described, but the concepts and techniques in this paper are applicable to other types of media.
Real-Time Observation of Electron-Beam Induced Mass Transport in Strained InGaAs/AlGaAs Layers on GaAs (100) and (311)B Substrates
Authors: Ogawa Tomoya , Akabori Masashi , Motohisa Junichi , Fukui Takashi
Published: October 2002

We have studied surface deformation due to electron-beam irradiation in strained InGaAs/AlGaAs layers grown on GaAs (100) and (311)B planes in a horizontal low-pressure metalorganic vapor phase epitaxy system at about 800°C. The surface deformation was observed in real time using a high-resolution scanning electron microscope at a magnification of 300,000. The surface deformation occurred from the inside of InGaAs/AlGaAs grown layer under the electron-beam irradiated area with the accelerating voltage of 30 kV and the scanning time ranging from 60 to 120 s. The surface deformation was not consist of amorphous-carbon contamination. The mass transport seems to be caused by the residual strain relaxation due to electron-beam irradiation.
Tailoring of Energy Levels in Strain-Induced Quantum Dots
Authors: Ahopelto Jouni , Sopanen Markku , Lipsanen Harri
Published: October 2002

High-quality strain-induced quantum dots with properties that can be tailored have been fabricated by growing small InP islands on top of an InGaAs/GaAs near-surface quantum well. The quantum dots show small inhomogeneous broadening, and peaks from the ground and excited state transitions are well resolved in the photoluminescence spectra measured from the dots. The depth of the confining potential and the energy level separation can be varied over a relatively wide range from 35 meV to 100 meV and from 7 meV to 25 meV, respectively, by changing the top barrier thickness of the near-surface quantum well and/or the size of the stressor islands.
Effect of Size Fluctuations on the Photoluminescence Spectral Linewidth of Closely Stacked InAs Self-Assembled Quantum Dot Structures
Authors: Endoh Akira , Nakata Yoshiaki , Sugiyama Yoshihiro , Takatsu Motomu , Yokoyama Naoki
Published: October 2002

We calculated the photoluminescence (PL) spectra of InAs (or
InGaAs) self-assembled quantum dots for single-layer, 2-layer stacked
and 3-layer stacked structures employing three models via the
effective mass approximation method to clarify the effect of size
fluctuations on the PL spectral linewidth. We quantitatively confirmed
that the PL spectral linewidth is determined much more by height
fluctuations than by diameter fluctuations. We examined the dependence
of the full-width at half maximum (FWHM) on the intermediate layer
thickness d for 2-layer stacked structures from d=2 nm to 6 nm
to clarify the effect of vertical coupling. The FWHM increases as d
decreases in regions where the potential barrier between the upper and
lower islands is so thin that its fluctuations are striking, while the
FWHM decreases as d decreases in regions where there is an increase
in the number of directly connected islands. We explained an
anomalously narrow PL spectrum of 31 meV for a 3-layer stacked
structure by considering extremely reduced island height fluctuations
as well as vertical coupling.
Electrical Characterization of CdS Passivation on InP
Authors: He Lili , Davis HelenDauplaise , Spaziani EricMartin , Vaccaro Kenneth. , Waters William , Lorenzo Joseph P.
Published: October 2002

InP surface passivation has been realized by a convenient chemical bath deposition (CBD) of a thin CdS layer. For comparison, samples without any treatments and/or with only a thin SiO2 layer were also prepared. Also studied was the effect of a thin layer of SiO2 deposited immediately after the CdS deposition. Schottky contacts were made on the CdS-passivated InP by electron-beam deposition of Ti/Au. Electrical characterization was conducted by current-voltage (I-V) and current-voltage-temperature (I-V-T) measurements. It was found that the electrical performance of the Schottky contacts of the CdS-passivated InP samples was improved significantly. The thickness (deposition time) of the CdS strongly affects the device electrical performance. The additional SiO2-on-CdS layer plays a key role in the process of InP surface passivation. Post-treatment in the CdS deposition process also strongly affects the surface morphology and electrical properties. Surface morphology studied by atomic force microscopy (AFM) indicates that the surface roughness increased after CdS deposition, though the degree of roughness is reverse proportional to the CdS process time. X-ray photoelectron spectroscopy (XPS) shows that the CdS layer protects the InP substrate during the oxide deposition.
Reduction of Surface Recombination in InGaAs/InP Heterostructures Using UV-Irradiation and Ozone
Authors: Driad Rachid , Lu Zheng-Hong , Scansen SylvainLaframboise , William RossMcKinnon William RossMcKinnon , Sean Patrick McAlister Sean Patrick McAlister
Published: October 2002

In this paper we report the effects of dielectric films, hydrofluoric acid (HF) chemical treatments and UV-ozone on InGaAs/InP heterostructures. To evaluate the passivation efficacy of these treatments, the heterojunction bipolar transistor (HBT) was chosen as a test vehicle, due to its sensitivity to surface recombination effects. We show that a surface treatment consisting of UV-ozone followed by HF etching allows plasma-enhanced chemical vapor deposition to be used to deposit a protective layer for InGaAs/InP HBTs without degrading the electrical characteristics. This approach leads to better stoichiometry of the semiconductor surface following the UV-ozone treatment. Compared with untreated HBTs, the UV-ozone/HF treated devices shown lower base leakage currents and consequently less low frequency noise.
Effect Of Inp Passivation On Carrier Recombination in InxGa1-xAs/GaAs Surface Quantum Wells
Authors: Lipsanen Harri , Sopanen Markku , Ahopelto Jouni , Sandmann Jörg , Feldmann Jochen
Published: October 2002

Carrier recombination in surface and near-surface In
x
Ga1-x
As/GaAs quantum wells was
studied using time-resolved and cw photoluminescence spectroscopy. Surface passivation by
an ultrathin layer (1 ML) of InP was found to yield a dramatically enhanced luminescence
intensity. A series of passivated In0.25Ga0.75As/GaAs surface quantum wells having a well
thickness of 2 to 15 nm was grown. A blue shift due to the vacuum barrier on the surface was
measured to be as high as 70 meV for a passivated 3-nm-thick In0.25Ga0.75As/GaAs surface
QW. The carrier recombination dynamics was studied for 7-nm-thick In0.10Ga0.90As/GaAs
surface and near-surface QWs. A carrier lifetime of 40 ps was obtained for an unpassivated
near-surface QW whereas lifetimes of 300 ps and 245 ps were measured for passivated near-surface and surface QWs, respectively.
Electrochemical Etching of Indium Phosphide Surfaces Studied by Voltammetry and Scanned Probe Microscopes
Authors: Kaneshiro Chinami , Sato Taketomo , HidekiHasegawa HidekiHasegawa
Published: October 2002

Using voltammetry, X-ray photoemission spectroscopy (XPS), in situ
electrochemical scanning tunneling microscopy (STM), ex situ atomic force
microscopy (AFM) and scanning electron microscope (SEM) measurements,
electrochemical etching modes for n-InP surfaces were investigated and optimized for
uniform and controlled etching in an HCl electrolyte. The voltammograms indicated the
presence of active and passive regions. The surfaces obtained in the active region were
clean and featureless with an rms roughness of 1.8 nm. On the other hand, the oxide
covered surfaces obtained in the passive region were nonuniform and porous. Etching
characteristics of the d.c. photo-anodic mode and the pulsed avalanche mode were then
investigated and compared. Both modes were found to be highly controllable and
produced uniform and clean surfaces, consuming eight holes per molecule of InP. In
particular, the pulsed avalanche etching mode realized an extremely
high etch depth controllability of 3×10-5 nm/pulse.
Design of a Low-loss Y-branch Optical Waveguide
Authors: Saito Minoru , Ono Hideki , Takahashi Hiromi
Published: October 2002

A low-loss Y-branch optical waveguide with a wide gap between two
output waveguides was designed. Its performance was simulated by the
beam propagation method. In spite of its wider gap, the excess loss was
much less than that in the case of conventional Y-branches. The wider gap is
desirable for better step coverage in buried waveguides (e.g. silica
waveguides).
Photoelastic Measurement of Strain Induced by Die-Bonding of GaAs Chip on a Copper Heatsink Plate
Authors: Tao Chu Tao Chu , Masayoshi Yamada Masayoshi Yamada
Published: October 2002

Die-bonding-induced strain in a GaAs chip bonded on a copper heatsink plate has been measured with a reflection type of infrared polariscope.
The spatial distributions of bonding-induced strain were seen to vary from sample to sample.
The maximum value of the bonding-induced strain was found to be of the order of 10-4,
which corresponded to about 1/10 of that estimated from the thermal expansion difference for the unit length between GaAs and copper when it was cooled down from the die-bonding temperature to the room temperature.
Highly Uniform Regrown In0.53Ga0.47As/AlAs/InAs Resonant Tunneling Diodes on In0.53Ga0.47As
Authors: Osaka Jiro , Maezawa Koichi , Yamamoto Haruki Yokoyama andMasafumi
Published: October 2002

The molecular beam epitaxial (MBE) regrowth of pseudomorphic In0.53Ga0.47As/AlAs/InAs resonant
tunneling diodes (RTDs) onto an InGaAs layer lattice-matched to InP substrate is successfully achieved
by elaborating native-oxide-removal conditions prior to MBE overgrowth. The quality of native-oxide
removed surface, as assessed by atomic force microscopy (AFM) and secondary ion mass spectroscopy
(SIMS), and the quality of regrown surface, as assessed by AFM, shows that the window for the
optimum native-oxide-removal temperature is very narrow: 535±10°C. The peak current standard
deviation of the RTDs regrown on the top layer of high electron mobility transistors (HEMTs) grown by
metalorganic chemical vapor deposition (MOCVD) is as low as 3% over a 2° wafer, which is almost
same as that of RTDs/HEMTs directly grown by MBE.
High Uniform Waveguide Photodiodes Fabricated on a 2-inch InP Wafer with Low Darkcurrent and High Responsivity
Authors: Funabashi Masaki , Nishikata Kazuaki , Hiraiwa Koji , Yamanaka Nobumitsu , Iwai Norihiro , Kasukawa Akihiko
Published: October 2002

We have fabricated waveguide photodiodes with high uniform characteristics on a 2-inch InP wafer introducing a novel process. The 2-inch wafer fabrication procedure was
carried out successfully by utilizing SiN
x
deposition on the back of the wafer in order to
compensate wafer warp. Almost all the measured waveguide photodiodes exhibited low
darkcurrent (average 419 pA, σ= 49 pA at 10 V reverse bias voltage) throughout the 2-inch
wafer, and high responsivity of 0.987 A/W (σ=0.011 A/W) was obtained in a consecutive
60-channel array at the input wavelength of 1.3 µm. In addition, uniformity of frequency
response was also confirmed.
Selective-Area Growth for Novel 1.3 µm Distributed Feedback Laser Diodes with Graded Grating
Authors: Takiguchi Tohru , Watanabe Hitoshi , Shibata Kimitaka , Takagi Kazuhisa , Minami Hiroyuki , Takemoto Akira , Mihashi Yutaka , Higuchi Hideo
Published: October 2002

We demonstrate a new approach to realizing graded grating, which is effective for improving
the modulation characteristics of distributed feedback (DFB) laser diodes (LDs) for analog optical
transmission, by using the selective-area-growth (SAG) technique. An ideal parabolic thickness
profile and a thickness enhancement ratio as high as 4.6 in the grating layer have been realized by
optimizing the mask shape using the simulation technique for SAG. We also successfully realized
high light-current linearity in 1.3 µm DFB-LDs with a graded grating for the first time. It has been
shown that the LDs have excellent distortion characteristics.
High Output Power Operation of a 1.3 µm Gain-Coupled Distributed Feedback Laser with Narrow Spectral Linewidth
Authors: Inaba Yuichi , Kito Masahiro , Ohya Jun , Ishino Masato , Matsui Yasushi
Published: October 2002

High output power and narrow spectral linewidth operation of 1.3 µm gain-coupled
distributed feedback (DFB) lasers with InAsP buried absorptive grating is reported. In this
study, we have investigated the effect of the thickness of a separate-confinement-heterostructure
(SCH) layer on the single-mode stability and the spectral-linewidth property of 1.3 µm gain-coupled DFB lasers. As a result, we clarified that decreasing the thickness of the SCH layer led
to stable single-mode operation at high output power and the reduction of the product of the
spectral linewidth and the output power. For the fabricated gain-coupled DFB laser, a record
high output power of 230 mW and a minimum spectral linewidth of 100 kHz at an output power
of 150 mW were realized.
New Method for Reduction of Carrier Lifetime in Semiconductor Optical Amplifier Using Assist Light
Authors: Tsurusawa Munefumi , Usami Masashi , Matsushima Yuichi
Published: October 2002

We propose a novel method for reducing the absorption recovery time in a semiconductor
optical amplifier driven under a loss condition for a signal pulse that acts as a saturable
absorber. The reduction of the absorption recovery time was successfully demonstrated by
stimulated recombination due to CW additional light (assist light) whose wavelength was
longer than that of the signal. The injection current and the wavelength of the assist light for
the reduction effect were optimized experimentally. The stimulated recombination process is
ultrafast and generates little heat since the process does not involve carrier transport in the
device. This technique can be applied to ultra high repetition rate optical processing. A
minimum absorption recovery time of less than 50 ps was confirmed.
1.3-µm Surface-Normal Reflective Optical Modulators Based on the Wannier-Stark Effect in InP/InGaAsP Superlattices
Authors: Tadanaga Osamu , Kagawa Toshiaki , Itoh Yoshio , Amano Chikara , Kurokawa Yutaka Matsuoka andTakashi
Published: October 2002

Surface-normal reflective optical modulators for 1.3-µm
wavelength were investigated using the Wannier-Stark effect in
InP/InGaAsP superlattices. In a modulator with a uniform miniband
width, the extinction ratio is 3.3 dB at 28 V. In order to compensate
the electric field distribution in the modulating region, we
introduced a chirped superlattice and lowered the operating voltage
for the 3-dB extinction ratio by 5 V. In a device with an asymmetric
Fabry-Perot geometry, the extinction ratio is 11.6 dB at an applied
voltage of 14 V. The 3-dB bandwidth of this type is 5.5 GHz.
1.45 µm Intersubband Absorption in InGaAs/AlAsSb Grown by Molecular Beam Epitaxy
Authors: Mozume Teruo , Yoshida Haruhiko , Neogi Arup , Kudo Makoto
Published: October 2002

InGaAs/AlAsSb multi-quantum wells lattice matched to InP substrates have been
grown by molecular beam epitaxy, and the intersubband transitions in doped quantum
wells have been studied. By precisely controlling the As to Sb flux ratio and substrate
temperature, fairly abrupt interfaces with 1–2 monolayers of compositionary varying
layers in both heterointerfaces have been achieved as confirmed from the high-resolution
transmission electron microscopy (HRTEM) lattice images. Polarization-resolved
absorption spectra were measured either with a conventional optical absorption
measurement system or a Fourier-transform infrared spectrometer. We have observed an
intersubband transition as short as 1.45 µm (0.85 eV) in 2.0-nm-thick InGaAs/AlAsSb
quantum wells. This is the shortest quantum well intersubband transition ever reported in
any materials system.
Temperature Effects on the Structure of Polycrystalline Silicon Films by Glow-Discharge Decomposition Using SiH4/SiF4
Authors: Syed Moniruzzaman , Inokuma Takao , Hasegawa YoshihiroKurata
Published: October 2002

Polycrystalline silicon (poly-Si) films were prepared on glass substrates by the plasma- enhanced chemical vapor deposition method using SiH4/SiF4 mixtures as a function of deposition
temperature, T
d, from 150 to 400°C, and the structural properties were investigated. In addition,
the effects of addition of H2 to the SiH4/SiF4 gas were also examined. The crystallinity and grain
size of Si films with added were found to have maximum values at around T
d = 250–300°C.
However, poly-Si films without H2 addition contain numerous microvoids, and exhibit easy O
contamination, and their crystallinity monotonically increased with T
d. The change in the SiH and
SiH2 bond density with H2 addition was consistently interpreted in terms of this model. As a result,
H2 addition at low T
d was suggested to suppress O contamination and improve the crystalline
quality. By contrast, H2 addition at high T
d is likely to deteriorate crystalline quality. The results
were discussed in terms of fluorine and hydrogen chemistry.
High-Performance InAs Quantum Well based Corbino Magnetoresistive Sensors on Germanium Substrates
Authors: Behet Markus , De Boeck Jo , Mijlemans Paul , Borghs Gustaaf
Published: October 2002

High-quality InAs/Al0.2Ga0.8Sb quantum well structures were grown on
Germanium substrates by molecular beam epitaxy (MBE). Electron mobilities of
27,000 cm2/Vs for sheet concentrations of n
S=1.8×1012 cm-2 were routinely
achieved at room temperature for undoped InAs/Al0.2Ga0.8Sb quantum well
structures on Germanium substrates. We developed a simple processing
technology for the fabrication of Corbino magnetoresistive devices. Excellent
current sensitivities of 195 Ω/T and voltage sensitivities of 2.35 T-1 at a magnetic
field of 0.15 T were measured for Corbino shaped magnetoresistors on
Germanium substrate at room temperature. This sensing performance is
comparable to that obtained by identical sensors on GaAs substrate.
Growth and Characterization of High-Quality InAs0.86Sb0.05P0.09 Alloy by Liquid-Phase Epitaxy
Authors: Chen Lung-Chien , Ho Wen-Jeng , Wu Meng-Chyi
Published: October 2002

High-quality InAs0.86Sb0.05P0.09 epitaxial layers lattice-matched to InAs substrates
were grown by liquid-phase epitaxy employing a supercooling technique. The epitaxial
layers exhibit a shiny and mirror-like surface morphology and a flat interface. The
energy gap of InAs0.86Sb0.05P0.09 epitaxial layers is 0.4 eV estimated by Fourier-transform infrared reflectance. The InAs0.86Sb0.05P0.09 diodes have an ideality factor of
1.1 and a breakdown voltage of 3.5 V. The background electron concentration,
measured by capacitance-voltage measurements, is 1.1×1016 cm-3 for the undoped
InAsSbP layers.
Thermal Stability of Amorphous-like WNx/W Bilayered Diffusion Barrier for Chemical Vapor Deposited-Tungsten/p+-Si Contact System
Authors: Chang Kow-Ming , Deng I-Chung , Yeh Ta-Hsun , Lain Kuen-Der , Fu Chao-Ming
Published: October 2002

The barrier characteristics of tungsten nitride/tungsten (WN
x
/W) bilayer formed by an
in situ nitridation on a thin chemical vapor deposited amorphous-like tungsten (CVD a-W)
film in CVD-W/Si contact system have been investigated. The thickness of WN
x
layer after
a 5 min of N2 plasma exposure at 300°C approximated 50 nm and the atomic ratio of W to
N in WN
x
layer was 2:1. In the CVD-W/a-WN
x
/a-W/Si multilayered sample, no discernible
tungsten silicide was detected by X-ray diffractometer (XRD) at W/Si interface after
annealing at 750°C. Meanwhile, with the Rutherford backscattering spectroscopy (RBS)
analysis and the measurement of p+n junction leakage current, the CVD-W/a-WN
x
/a-W/Si
multilayer maintained the integrity of interface and the CVD-W/a-WN
x
/a-W/p+n diode kept
the reverse leakage current density less than 9×10-9 A/cm2 while the post annealing was
carried out at 700°C for 30 min. As the experimental results, the effectiveness of
amorphous-like WN
x
/W bilayered diffusion barrier is attributed to stuff grain boundary
with N atoms as well as to eliminate the rapid diffusion paths by using CVD a-W material.
Polymer-like Organic Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition Using the Para-xylene Precursor as Low Dielectric Constant Interlayer Dielectrics for Multilevel Metallization
Authors: Chun Quan Yong , Jongryang Joo Jongryang Joo , Donggeun Jung Donggeun Jung
Published: October 2002

Polymer-like organic thin films were deposited by plasma enhanced chemical vapor
deposition (PECVD) using the para-xylene precursor. The effect of the plasma power on the
dielectric constant and thermal stability was significant. As the plasma power was increased
from 5 W to 60 W, the relative dielectric constant increased from 2.70 to 3.21. The film
deposited at a higher plasma power showed higher thermal stability. The film deposited
at 60 W was stable up to 450°C. All the deposited films were insulating under an
applied field of ≤1 MV/cm.
Exchange Interactions for R–Co–B (R=Rare-Earth) Compounds
Authors: Maruyama Fumio
Published: October 2002

To compare the strength of the exchange interactions between R and Co spins and between Co spins for R–Co–B compounds, we calculated the molecular field coefficients, n
RCo and n
CoCo, for R
n+1Co3n+5B2n
with n=1(RCo4B), n=2(R3Co11B4), n=3(R2Co7B3) and R2Co14B using the experimental Curie temperature. The calculated n
RCo values decrease with increasing atomic number of R and Co concentration. The calculated n
CoCo values increase with increasing Co concentration.
Structural and Magnetic Characterization of Evaporated Fe/Zr Multilayers
Authors: Pan Feng , Zhang Ming , Liu Xin-tao , Zhang Zi-shu
Published: October 2002

Fe/Zr multilayers were prepared by alternate vapor deposition of pure Zr and Fe at a rate of 0.1–0.2 nm s-1 in a high-vacuum electron-gun evaporation system. The thickness of the constituent metals was varied from 1 nm to 12 nm controlled by an in situ quartz microbalance. The evaporated Fe/Zr films were investigated by transmission electron microscopy for structural properties, Rutherford backscattering and X-ray diffraction for thickness and periodicity, and vibrating-sample magnetometer for magnetic characterization. Experimental results showed that a rapid transformation from the polycrystalline to amorphous state in the iron layers occurred with decreasing Fe layer thickness in the Fe/Zr multilayers. The transformation was influenced by the Fe and Zr layer thicknesses and their thickness ratio in the films. The magnetization of the multilayers decreased significantly with decreasing Fe layer thickness, accompanying the amorphous Fe phase formation. The amorphous Fe in Fe/Zr multilayers still exhibited ferromagnetic behavior, and the observed average magnetization was 0.41 µB for Fe(1.0 nm)/Zr(9.0 nm) multilayers in a magnetic field of 10 kOe. The possible mechanisms responsible for these phenomena are also discussed.
Theory of Morphotropic Phase Boundary in Solid-Solution Systems of Perovskite-Type Oxide Ferroelectrics: Elastic Properties
Authors: Ishibashi Yoshihiro , Iwata Makoto
Published: October 2002

Elastic stiffness constants in a perovskite-type oxide solid-solution system are
discussed on the basis of the Landau-type free energy function expressed in terms of
polarization and strain components. It is found that some of the elastic stiffness
constants become extremely small in the vicinity of the morphotropic phase
boundary.
In-Plane Operation of Alignment-Controlled Holographic Polymer-Dispersed Liquid Crystal
Authors: Kato Kinya , Hisaki Tomoko , Date Munekazu
Published: October 2002

A new mode of operation for an alignment-controlled holographic polymer-dispersed liquid crystal (HPDLC) device has been confirmed experimentally. In this mode, called in-plane operation, an electric field is applied parallel to the substrates. In the alignment-controlled HPDLC device, the polymer layers are formed periodically with aligned LC layers. We confirmed the fundamental operation of this in-plane mode experimentally. The polarization dependence of the reflected light proves that the LC molecules in the LC layers move in-plane. The in-plane operation makes the alignment-controlled HPDLC device polarization free.
Strain Affected Properties of Icosahedral Al–Pd–Mn Single Ingot
Authors: Yokoyama Yoshihiko , Yamada Yoshihiro , Fukaura Kenzo , Sunada Hisakichi , Note Ryunosuke , Inoue Akihisa , Sugiyama Kazumasa , Hiraga Kenji
Published: October 2002

Some physical properties of the Al–Pd–Mn icosahedral quasicrystal are drastically
changed by inhomogeneous strain distribution, as exemplified for the electrical
resistivity and the Vickers hardness. In order to reveal the intrinsic properties of the
Al–Pd–Mn icosahedral alloy, the study on the relation between the strain and the
properties was investigated. By the full anneal treatment (1000 K, 50 h), the
anisotropies of the electrical resistivity and the Vickers hardness are found to
annihilate significantly with decreasing anisotropic strain distribution. And the
intrinsic properties are estimated by the extrapolation from the relation between the
strain and the physical property to the no strain state.
X-Ray Absorption Near Edge Structure and X-Ray Diffraction Studies of New Cubic CsVTeO5 and CsVTeO6 Compounds
Authors: Young-Sik Hong Young-Sik Hong , Jacques Darriet Jacques Darriet , Joo-Byoung Yoon Joo-Byoung Yoon , Jin-Ho Choy Jin-Ho Choy
Published: October 2002

The compounds CsVTeO5 and CsVTeO6 have
been synthesized by solid-state reactions in an oxygen flow.
CsVTeO6 was decomposed to CsVTeO5 at 550°C,
and this CsVTeO5 was re-transformed into CsVTeO6
under high oxygen pressure. The local structure around vanadium
and its valence state have been studied by X-ray absorption near
edge structure spectroscopy at the vanadium K-edge.
CsVTeO6 shows a weak peak at the pre-edge region, which
indicates that the vanadium is stabilized in an octahedral site as
expected in normal AB2O6 pyrochlore. On the other
hand, a strong pre-edge peak appeared in CsVTeO5 as in
CsVO3 and V2O5, which confirms that the local
symmetry around the vanadium atom is highly distorted without an
inversion center. The Rietveld refinement shows that CsVTeO5 has the cubic symmetry (space group Fd3m) with a = 10.4842(2) Å, which is similar to the high-temperature
polymorphic CsTiAsO5 phase with highly distorted
octahedral symmetry around the titanium atom.
Change in the Oxidation State of the Adsorbed Oxygen Equilibrated at 25°C on ZnO Surface during Room Temperature Annealing after Rapid Quenching
Authors: Fujitsu Satoru , Koumoto Kunihito , Yanagida Hiroaki , Watanabe Yuichi , Kawazoe Hiroshi
Published: October 2002

The porous ZnO quenched from 500°C in air showed very low electrical resistance with non-ohmic current–voltage
behavior. This characteristic was resulted from the surface energy barrier formed by negatively charged chemisorbed oxygen.
The resistance and the non-ohmic exponent of the quenched specimen gradually decreased by holding the specimen at room
temperature. Electron spin resonance measurements showed a change in the oxidation state of chemisorbed oxygen from its
high temperature type, O2-, into low temperature types, O2
- and O- while being kept at room temperature. From this viewpoint,
it was judged that the decrease in the resistance and the non-ohmic exponent resulted from the release of the trapped electron
by this change in the oxidation state. The resistance and the non-ohmic exponent of the sample doped with CoO were higher
than those of the undoped sample, and their decrease for the CoO-doped sample while being kept at room temperature was
slower than those for the undoped sample. The rate of change in the oxidation state was also slower in the CoO doped sample.
Secondary Electron Detection for Multiple-Channel Scanning Electron Microscope: Computer Simulation
Authors: Nakasuji Mamoru , Shimizu Hiroyasu
Published: October 2002

A new scanning electron microscope (SEM) which
consists of multiple beam probes, a secondary electron (SE)
selector, multiple channel SE detectors and monitors is studied.
For this system the throughput is improved channel-number that
of the conventional SEM. The SE selector consists of a
hemispherical shell with multiple holes and a positive potential.
Because of a diverging lens effect due to the potential formed
inside the spherical shell, the SEs emitted from different
positions go to different holes. Around the holes there is a
converging lens effect, and the SEs are collected into the holes
and detected by the SE detectors behind the holes. All the SEs
for which the emission angle is smaller than 80°, the initial
energy is smaller than 2 eV and which have an emitting position
variation in the range width smaller than 0.5 mm are collected by
the SE detector.
A Study of Mechanical Stability Issues in Multilevel Air-Dielectric Interconnect Schemes for ULSIs
Authors: Anand Minakshisundaran B. , Yamada Masaki , HidekiShibata HidekiShibata
Published: October 2002

Air-dielectric interconnect schemes are under active consideration for use in high performance LSIs because they
can improve speed significantly. However, mechanical stability is the biggest engineering issue in these schemes. In
this paper, an investigation of mechanical stability issues is presented. It is found that the deflection of the wires due to
their own weight is unlikely to be a problem. For a typical long wire
cross-section of 2 µm×2 µm, wires of length
slightly more than 1mm can be allowed without appreciable sag. On the other hand, it is found that the initial tensile
stress in the metal wires produces significant bending stresses at the bottom of the via plugs. The dependence of the
bending stress on various geometrical parameters is studied in detail. It is found that bending stresses of more than
1 GPa can result even for a very low initial tensile stress in the
wire of 20 MPa.
Transmission Electron Microscope Observations of Si/Si Interface Bonded at Room Temperature by Ar Beam Surface Activation
Authors: Takagi Hideki , Maeda Ryutaro , hosoda Naoe , Suga Tadatomo
Published: October 2002

Silicon wafers are strongly bonded at room temperature by Ar beam surface etching in
ultrahigh vacuum. The bonding interface is investigated using a transmission electron
microscope (TEM). Residual strain originating from surface roughness exists in the interface
region. It is observed only in specimens bonded at room temperature, because it relaxes even
by low-temperature annealing at 400°C. An amorphous-like intermediate layer is observed in
high-resolution images of the interface. The layer is quite unstable and different from the
oxide layer which is often observed at the Si/Si interface prepared by the conventional
hydrophilic wafer bonding method. Both annealing and electron beam irradiation during TEM
observation cause recrystallization of the layer. The layer contains Ar, but the O concentration
is less than the detection limit of analytical TEM. The layer thickness changes according to
the kinetic energy of Ar beam. These points demonstrate that Ar atom implantation during the
surface etching introduces surface damage, forming the amorphous-like layer.
Structures of Boron Nitride Nanotubes with Single-Layer and Multilayers Produced by Arc Discharge
Authors: Saito Yahachi , Maida Masatomo , Matsumoto Takehisa
Published: October 2002

Nanoscale materials created from boron nitride (BN) by arc discharge between ZrB2 electrodes in an N2 atmosphere have been investigated by electron microscopy. BN nanotubes were formed together with Zr-compound nanoparticles encapsulated in BN cages. Most of the tubes were multilayered and had diameters from 3 to 40 nm and lengths on the order of 100 nm. Single-layer tubes with diameters of 2 to 5 nm were also formed as a minority. Concerning the helical structures of BN tubes, a variety of chiral angles, including the zigzag and the armchair types, were observed. The morphology of the tube tips suggests the presence of pentagons and heptagons which are energetically less favorable compared with squares (four-membered rings).
Analysis of Beam Wave Scattering by Recording Marks on Phase-Change Optical Disk Using Boundary Element Method with Finite Element Method
Authors: Yasumitsu Miyazaki Yasumitsu Miyazaki , Keiji Tanaka Keiji Tanaka , Ryuichi Chiba Ryuichi Chiba
Published: October 2002

Two-dimensional numerical solutions for electromagnetic fields are
presented for scattering by grooves and recording marks on rewritable
phase-change optical disks with multilayered structure.
The boundary element method (BEM) combined with the finite element method (FEM) can be applied to the scattering analysis of various groove forms and
recording marks for different conditions of the incident beam.
Recording marks are represented by an area with an altered refractive index in
the multilayered structure.
Near and scattered far field characteristics from grooves having trapezoidal
cross section are studied for different polarizations of incident beam waves.
Characteristics of read-out signals are also calculated as functions of groove
height and film thickness of the multilayer. As a result of numerical
analysis, the groove height required to obtain maximum tracking sensitivity
and the optimum film thickness of multilayers are found.
It is important to optimize the groove height for the cancellation of
crosstalk.
Simulation Study of Phase-Change Optical Recording Disks
Authors: Chou Lih-Hsin , Jen Chun-Ping , Chieng Ching-Chang
Published: October 2002

Effects of phase change in the recording layer due to temperature changes and the material
parameters used in the simulated transient temperature distributions were examined. The initial
structure of the recording layer was the key parameter for simulated temperature distributions in both
the erasing and writing processes. Latent heat due to the phase change had little effect on the
transient temperature distributions, however, the temperature-dependent heat capacity had significant
effects and resulted in a transient temperature distribution level lower than that using a constant
room-temperature capacity value. From the simulated transient temperature profile, cooling rate,
dependence of phase-changed spot size on the laser power and laser pulse duration, as well as the
phase-change characteristics in the phase-change optical disk, could be obtained. By applying
proper material parameters, the disk with a hydrogenated amorphous carbon film as the top dielectric
layer with a disk structure of PC/ZnS–SiO2(111 nm)/GeSbTe(20 nm)/α–C:H (63 nm)/Al(70 nm) showed
less temperature variation between the center and the edge of the irradiated spot than that of a disk
with a conventional disk structure of PC/ZnS–SiO2(144 nm)/GeSbTe(20 nm)/ZnS–SiO2(21 nm)/Al(70 nm).
Less temperature variation may give rise to a written spot with more uniform microstructures.
Optical Properties of Au–SiO2 Composite Films –a Possible Candidate as an Element in Phase-Change Optical Media–
Authors: Ashida Sumio , Kikitsu Akira , Nagase Toshihiko , Nakamura Naomasa , Ichihara Katsutaro
Published: October 2002

The thin films used for phase-change recording media need to be
chosen in consideration of both optical and thermal properties. Metal-dielectric composite films are one of the candidates for such films; they may
allow adjustment of the light absorption and heat flow inside the recording
medium. The properties of Au–SiO2 composite films are examined by
comparing experimental results with theoretical predictions obtained using
the Maxwell-Garnett theory. It is found that the optical constant for a
sputter-deposited Au–SiO2 composite film cannot be accurately predicted by
the theory for wavelengths longer than 500 nm if an assumed value of the
optical constant of the bulk metal is used. However, much more accurate
predictions are performed if the optical constant of the metal particles is
used. It is shown that appropriate values for the optical constant of the
metal particles are the ones calculated by the inverse application of the
Maxwell Garnett theory.
Comparison of Cross-Talks between Phase Encoding and Amplitude Encoding in Phase Change Rewritable Optical Discs
Authors: Baoxi Xu , Chong Chong Tow , Wang Wilson
Published: October 2002

The cross-talk characteristics in the case of phase encoding and
amplitude encoding are studied for phase change rewritable optical
media for different track pitches and different mark lengths on
adjacent tracks. The results show that the cross-talk ratio in the
case of phase encoding is larger and that the depth tolerance of the
groove is smaller than those in the case of amplitude
encoding. Although the use of phase encoding can result in an increase
of the linear recording density, in the case of track density, the
increase is far less than that reached using amplitude encoding.
Effects of Aperture Wall on the Readout Signal of Erasable Thermal Phase Change Super Resolution (EPSR) Disks
Authors: Liu Jia-Reuy , Lu Yeong-Shinn , Tien Chung-Hao , Tang Nai-Yuan , Shieh Han-Ping David
Published: October 2002

A “below-diffraction-limited” aperture within the readout spot for high-density recording can be
achieved on erasable thermal phase change super resolution (EPSR) disks. Compared to the large
aperture wall formed by the DC detection method, the small aperture wall formed by pulse readout can
not only increase the signal amplitude, but also suppress readout noise when detecting the EPSR disks.
The small aperture wall width generated by pulse readout in the EPSR disk resulted in an 8 dB higher
in carrier-to-noise (CNR) than that by DC readout in the conventional single-recording-layer phase
change disk when reading the below-diffraction-limited marks of 0.4 µm.
Rewritable Dual-Layer Phase-Change Optical Disk
Authors: Nagata Ken'ichi , Yamada Noboru , Nishiuchi Kenichi , Furukawa Shigeaki , Akahira Nobuo
Published: October 2002

This paper describes the development of a rewritable phase-change
optical disk with a dual-layer structure. To obtain equivalent signal
amplitude and recording sensitivity from the medium located on the beam
incident side (the first medium) and the medium beneath (the second medium),
we developed a high transmittance first medium featuring a very thin
recording film (7 nm) and no reflection layer, and a high recording
sensitivity and high reflectivity second medium with a semi-transparent
front layer and a reflection layer. We confirmed a jitter of approximately
10% for both media at a recording density corresponding to 8.5 GB on a 120 mm disk. The laser power required to record on the first medium was 12 mW, and the second medium, 13 mW. It was also confirmed that the new
rewritable dual-layer phase-change optical disk possesses the potential
for operation with a blue laser.
Initial Magnetization Curve and Magnetic Domain Pattern of Co/Pt Multilayered Thin Film
Authors: Wu Te-ho , Qiu Zu-yin , Lai Wen-bin , Huang Jung-chun , Wu Jong-ching
Published: October 2002

This study inquires into the relationships between the initial magnetization curve
and the magnetic domain pattern in the demagnetized states for multilayered Co/Pt
thin film samples. The magnetic domain pattern for the sample demagnetized by an
in-plane magnetic field and for the sample demagnetized by a perpendicular magnetic
field were found to be quite different even though both states have zero magnetization.
The former state has denser and finer domains than the latter. The initial
magnetization for the fine domains increases with an increase in magnetic field, while
for the coarse domains, the initial magnetization remains at zero for magnetic field
below coercivity H
c, then rises sharply to saturated magnetization when magnetic
field is nearly equal to H
c. Moreover, the magnetic domain pattern for the sample
demagnetized by an in-plane magnetic field can be use to estimate the domain wall
energy as long as the domain size is known
Transient Reflectivity Measurement in Phase Transformation of Phase Change Rewritable Discs
Authors: Yongjun Wu , Ting Zhou , Chong Chong Tow
Published: October 2002

An optical device for measuring transient reflectivity, induced by nanosecond laser pulses, of phase change (PC) rewritable discs has been developed. The transient reflectivity reveals the phase transformation process in PC recording layers which have been sputtered onto the polycarbonate substrate of the disc. Two specially designed diaphragms were used to increase the signal-to-noise ratio. The device optical system and operation are described. Some experimental results are presented.
Strain-Rate and Temperature Dependence of Plastic Deformation in White Tin Single Crystals
Authors: Nagasaka Muneo
Published: October 2002

Tensile tests at high and intermediate temperatures [200 K (0.4 T
m)–500 K (0.99 T
m), where T
m is the melting temperature] have been performed on single
crystals of high-purity white tin with low dislocation density and with the tensile
axis along the [100] direction. It is found that the stress-strain curves at
temperatures below 300 K show two yield points. The first yield point
phenomenon appears when a sudden multiplication of mobile dislocations occurs due to the deformation. The second yield point phenomenon appears when the
dislocations forming the cell structure become mobile and the cell structure
disappears. The activation energy of the second upper and lower yield stresses has
the transition temperature, about 480 K (0.95 T
m). Above the transition
temperature the activation energy was found to be almost equal to the lattice diffusion energy. Below the transition temperature the activation energy is about
half of the lattice diffusion activation energy and has a value expected for
dislocation pipe diffusion.
Complex Refractive Indices of GeSbTe-Alloy Thin Films: Effect of Nitrogen Doping and Wavelength Dependence
Authors: Kim Sang Y. , Kim Sang J. , Seo Hun , Kim Myong R.
Published: October 2002

The effects of nitrogen doping on the complex refractive indices of Ge2Sb2Te5 phase-change optical recording materials and their wavelength dependence were examined. With an increase in nitrogen concentration, the extinction coefficients decreased monotonically. The calculated reflectance spectra at normal incidence showed a good quantitative agreement with the measured values. The observed optical properties were correlated with the characteristic features of the microstructure, including grain size refinement, internal residual stresses, and changes in the bonding state.