bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation Behavior of High-Tc Tl-based Superconductors
Authors: Koo H. S. , Lo J. R. , Tseng T. Y. , Lin C. S.
Published: October 2002

The effects of Ca, Cu, and Ca–Cu richness on the formation
behavior and physical characteristics of high-T
c Tl-based superconductors
were investigated systematically. In addition to sintering temperature and
time, intermediate phases which proved important to the formation and
properties of nearly single-phase, triple-CuO-layers Tl2Ba2Ca2Cu3O
y

superconductors and optimal processing conditions were also investigated.
Ca and Ca–Cu richness introduced positive effects on the properties of
nearly single-phase Tl2Ba2Ca2Cu3O
y
superconductors and helps in the
formation of the appropriate intermediate phases, whereas Cu richness
produced a negative effect. The higher sintering temperatures of the
specimens accounted for the tailing of electrical resistance before the critical
zero resistance temperature was approached, and for the instability of the
superconducting phase. Lower post-annealing temperatures of the bulk
samples slightly improved the superconducting properties. The resultant
bulk Tl-based superconductors can be used as a Tl vapor source for the
formation of superconducting thin films within a closed system.
Two-Dimensional Fluid Simulation and Langmuir Probe Measurement of a Planar Inductively Coupled Oxygen Plasma
Authors: Jin Yoon Hyun , Hun Chung Tae , Cheol Seo Dong
Published: October 2002

A two-dimensional (2D) self-consistent axisymmetric fluid simulation of an inductively coupled discharge of electronegative oxygen plasma with a one-turn antenna placed on the top of the dielectric roof is presented. The model equations include continuity equations, the Poisson equation, and an electron energy balance equation. For a planar inductive discharge, the electric field component E
θ (r, z) is calculated, assuming axisymmetric geometry. Considering a deep penetration of the induced rf field, the power deposition profile is formulated and used as the electron heating term in the electron energy balance equation. The 2D distributions of charged particle densities, electric potential, electron temperature, and ionization rate are calculated and compared with experiments. The effect of neutral gas pressure on plasma characteristics is investigated. As a result, for a relatively low pressure (5 mTorr) case, the ionization rate and charged particle densities are uniform in the radial direction, and for a medium pressure (20 mTorr) case, the ionization rate and the negative ion density are sharply maximized in the axial and radial directions. The results of the simulation agree reasonably well with the results of the spatially averaged global model and experimental results.
Formation of C2 Radicals in High-Density C4F8 Plasmas Studied by Laser-Induced Fluorescence
Authors: Suzuki Chihiro , Sasaki Koichi , Kadota Kiyoshi
Published: October 2002

Spatial and temporal variations of C2 radical density in high-density C4F8 plasmas have been investigated by laser-induced fluorescence (LIF) spectroscopy. Hollow-shaped spatial distributions have been observed for the C2 density, indicating that C2 radicals are produced from fluorocarbon film on the chamber wall and are lost in the plasma column by electron impact processes. The C2 density depends largely on the seasoning condition of the vacuum chamber, which supports the surface production of C2 radicals. Bombardment of positive ions onto fluorocarbon film is necessary for such surface production. The mechanism of this surface production is not the physical sputtering of fluorocarbon film but ion-enhanced chemical reactions with fluorocarbon film. Lifetime measurements of C2 radicals have also been carried out in the afterglow. The observed decay time constants (less than 0.8 ms) are shorter for high gas pressures, indicating the loss of C2 due to gas-phase reactions.
An Open-Cavity Electron Cyclotron Resonance Plasma/Ion Source
Authors: Ning Fung-Truen , Hu Yuan , Lin Tsang-Lang
Published: October 2002

An open-cavity plasma/ion source design was presented in this study. Both the cases with
the solenoid and the ring magnet to generate the static magnetic field were studies. The
open-cavity electron cyclotron resonance (ECR) plasma/ion source design optimizes the
microwave to plasma coupling by combining the quarter wavelength transformer technique
and the resonant cavity matching technique in transverse magnetic (TM01) mode. This
design reduces the microwave reflection power typically to less than 5% of forward
microwave power and very little tuning is needed even when the plasma condition is changed.
The open-cavity plasma source design was also used in designing an ion beam source with the
plasma-floated concept. Uniform and intense ion beam can be successfully generated from
such an ion beam source. The plasma floated concept makes the system easy and safe to
operate by keeping the chamber at ground potential, not at a high voltage.
Effects of Halogen Ions on the X-Ray Characteristics of Gd2O2S:Pr Ceramic Scintillators
Authors: Nakamura Ryohei , Yamada Nobuyuki , Ishii Mitsuru
Published: October 2002

A fine powder of a Gd2O2S:Pr ceramic containing halogen ions such as F-, Cl-, Br- or I-
was synthesized and its properties as a scintillator were examined. By adding F- at a
concentration of 0.002–0.003 mole ratio, light output increased to 107% and afterglow
decreased to 4% compared with those of nonadditives. The effect of these additives was
discussed in relation to the ion radius of halogen ions. Afterglow of Gd2O2S:Pr ceramic
scintillators decreased with increasing annealing temperature. Analysis of weight loss
during heating gave a clearer understanding of this phenomenon and suggested that the
vaporization of F elements added as a sintering aid in Li2GeF6 minimizes traps in the
crystal.
Nanoscale Patterning of Au Films on Si Surfaces by Atomic Force Microscopy
Authors: Won-chul Moon Won-chul Moon , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

We studied a new method of patterning a metal layer on silicon surfaces in the nanometer range. The process combines anodic oxidation patterning with atomic force microscopy, deposition of a Au thin film on a patterned substrate and chemical etching of the Si oxide that lies underneath the Au film. When the thickness of the deposited Au film is 2–5 nm, by chemical etching to remove the SiO2 pattern, the Au film bent down, sticking to the Si surface. For a Au film of 1 nm thickness, it was possible to selectively remove the Au film on the SiO2 pattern by chemical etching of the SiO2 pattern.
Performance of X-Ray Stepper for Next-Generation Lithography
Authors: Fukuda Makoto , Suzuki Masanori , Haga Tsuneyuki , Takeuchi Nobuyuki , Morita Hirofumi , Deguchi Kimiyoshi , Taguchi Takao , Aoyama Hajime , Mitsui Souichiro , Matsui Yasuji
Published: October 2002

X-ray steppers have been developed and improved to the point where
they are capable of replicating 100-nm patterns. The alignment system,
which employs an optical heterodyne system with two wavelengths, was
improved by analyzing and reducing the crosstalk and asymmetry in the
alignment optics. The overlay accuracy of the steppers with respect to
themselves is better than 20 nm, regardless of the wafer mark depth. A
magnification correction method using wafer temperature control and
chucking force is implemented on the steppers. We have achieved an overall
overlay accuracy of less than 35 nm, which includes the pattern placement
error for two masks, etching process distortion, and alignment error. This
demonstrates the capability of proximity X-ray lithography to meet the
requirements of 100-nm lithography.
In-Situ Thermomagnetic Behaviors of an FeCuNbSiB Alloy during Nanocrystallization Processes
Authors: Leu Ming-Sheng , Chin Tsung-Shune , Tung I-Chung , Lee Chein-Ming
Published: October 2002

An in-situ method was used to study thermal magnetic behaviors of
cores made of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy, by recording the
temperature dependent initial permeability (µi) in a designed thermal-cycling
annealing. The higher the isothermal annealing temperature (T
IA)
the shorter the accumulative time (t
Acc) is required to attain the highest
room temperature initial permeability (µri,RT), e.g., 61.39 ks for the T
IA at
520°C, while 70 s at 600°C. At a specific T
IA–t
Acc combination, the µi
value was found to be enhanced anomaly all the way down to room
temperature from a high annealing temperature. The composition effect, in
particular the evolution of Si content in the nanocrystal during annealing,
has also been studied and related to the observed permeability peak. The
Curie temperatures (T
c) of the nanocrystal and the residual amorphous
phase were found to dominate the µri,RT value, which was found to vary
linearly and inversely with T
c of the residual amorphous phase in the
annealed specimen. The best results obtained from the current method is
comparable with those obtained by conventional annealing via iteration,
the thermal-cycling is thus an effective, time-saving and informative
method to work out the best process-annealing schemes for a specific
composition, particularly a new one.
Stress Stability of W–Ti X-Ray Absorber in Patterning Process
Authors: Kitamura Kaeko , Yabe Hideki , Ami Shigeto , Kise Koji , Aya Sunao , Marumoto Kenji , Satoh Shin-ichi
Published: October 2002

We investigated the stress stability of the W–Ti absorber during
the patterning process. The three kinds of mask stacks used were
stable during the mask fabrication steps and after being kept in air
for six months. We also investigated the IP shift due to etching of
the quartermicron-rule device patterns. The line pattern mask
indicated larger displacement than the hole mask, however, no
remarkable anisotropic distortion was observed because the sidewall
area of those masks was not as much as in the case of 100 nm device
masks. Anisotropic distortion along the line was clearly observed in
the case of absorber etching in the 100 nm region. The maximum
displacement observed in the mask geometry was 21 nm, however, it is
expected to decrease in the case of a narrow perimeter for a low
contrast X-ray mask.
Structure Study of Si Nanocrystals Formed by Electron-Induced Reduction of SiO2 at High Temperature
Authors: Takeguchi Masaki , Furuya Kazuo , Yoshihara Kazuhiro
Published: October 2002

Si nanocrystals were formed in a SiO2 thin film by irradiation of a high-intensity
electron beam at about 900 K inside an ultrahigh vacuum field emission
transmission
electron microscope (UHV-FE-TEM). The structure of the nanocrystals was
investigated by high-resolution transmission electron microscopy (HRTEM) and
electron diffraction analysis. Relations among the lattice distances
suggest that the
structure is not a diamond structure. For the structural model, a
beta-tin structure with
elongation along the c-axis and shrinkage along the a-axes compared to
the diamond
structure is proposed.
Single-Crystalline CoSi2 Layer Formation by Focused Ion Beam Synthesis
Authors: Hausmann Stephan , Bischoff Lothar , Teichert Jochen , Voelskow Matthias , Möller Wolfhard
Published: October 2002

The effects of accumulated radiation damage which arise from the excessive current density
employed during focused ion beam implantation are described. The dwell time during beam
scanning significantly influences the focused ion beam synthesis of CoSi2 in Si. At
sufficiently low accumulated damage, single-crystalline CoSi2 layers are obtained, similarly
to conventional ion implantation. A procedure is described which enables the reduction of
radiation damage induced by a focused ion beam to the level of conventional ion
implantation. This is of importance for the formation of
single-crystalline CoSi2 layers.
Magnetic Properties of Granular Fe–Cr–O and Fe–X–Cr–O (X=Cu, Rh) Films
Authors: Morikawa Takeshi , Suzuki Motofumi , Taga Yasunori
Published: October 2002

Soft magnetic properties have been obtained in films cosputtered using dual targets of Fe and Cr2O3. The resultant Fe–Cr–O films are considered to be mainly composed of nanocrystalline Fe and an amorphous intergranular region of Cr and O. The coercivity decreases rapidly with decreasing volume fraction of Fe, resulting in good soft magnetic properties. This rapid decrease is attributed to the grain size reduction of bcc-Fe, where the so-called random anisotropy model for a single-phase nanocrystalline system is quantitatively applicable to the present granular one. The saturation magnetization 4πMs, coercivity Hc, relative permeability µ′ at 500 MHz, and ferromagnetic resonance frequency of the Fe80Cr7O13 film with average Fe grain size of 5.5 nm are 14.0 kG, 1.5 Oe, 1470, and 1.80 GHz, respectively. Furthermore, it is found that the additional elements such as Cu and Rh decrease Hc and increase the in-plane anisotropy field Hk of the Fe–Cr–O film.
Emission Characteristics of Amorphous Silicon Field Emitter Arrays Sealed in a Vacuum Package
Authors: Gamo Hidenori , Kai Teruhiko , Kanemaru Seigo , Itoh Junji
Published: October 2002

Emission characteristics of amorphous silicon field emitter arrays (a-Si
FEAs) in a vacuum package sealed with TO-5 have been measured and
evaluated. The TO-5 header mounted with a FEA, was inserted through a
hole in a glass plate and was hermetically sealed to the glass plate using epoxy
resin as a sealant. In the same a-Si FEA device, lower emission currents have
been observed in the vacuum package, as compared with those measured in an
ultra-high vacuum (UHV) chamber. On the other hand, an a-Si FEA
monolithically integrated with a thin-film transistor (TFT) has exhibited almost
the same emission characteristics both in the vacuum package and in the UHV
chamber at the region of saturated emission currents due to the TFT function.
A highly stable emission current of approximately 0.1 µA and with fluctuations
of less than 2% has been achieved in the vacuum package at the TFT gate and
the extraction voltages of 14 V and 150 V, respectively.
Coulomb Interaction Effect Correction in Electron-Beam Block Exposure Lithography
Authors: Kimitoshi Takahashi Kimitoshi Takahashi , Yasuo Manabe Yasuo Manabe , Hiromi Hoshino Hiromi Hoshino , Yasuo Nara Yasuo Nara , Yasuhide Machida Yasuhide Machida
Published: October 2002

A new proximity effect correction technique for variably shaped
beam and block exposure tools capable of correcting pattern size
variations due to the Coulomb interaction effect is proposed. The
Coulomb interaction affects the forward scattering term of a
double-Gaussian energy intensity distribution. The double-Gaussian
energy intensity distribution function is modified so that the forward
scattering term has an electron-beam current dependency. The
relationship between the electron-beam current and electron-beam blur
is determined by a knife-edge electron-beam profile
measurement. Experiments show that the relationship between the
electron-beam blur and the current can be roughly approximated by a
linear function of the electron-beam current below 1.5 µA. This
relationship is applied to the double-Gaussian-based proximity effect
correction program. Successful correction is demonstrated for 0.13 µm L/S test patterns.
A Novel Nanoscale Metal Transistor Fabricated by Conventional Photolithography
Authors: Kiyoshi Fukushima Kiyoshi Fukushima , Ryouta Sasajima Ryouta Sasajima , Kouji Fujimaru Kouji Fujimaru , Hideki Matsumura Hideki Matsumura
Published: October 2002

A novel nanoscale transistor, the metal/insulator tunnel
transistor (MITT), which consists of a metal source/drain and an
insulator channel, is fabricated by conventional photolithography, and
its operation is experimentally verified. In the MITT, an insulator
channel is sandwiched between the metal source and drain, and upon
this insulator channel a gate insulator and a gate electrode are
prepared. The Fowler-Nordheim (F-N) tunneling currents which flow
through the metal/insulator tunnel junction are controlled by changing
the gate voltage, through variation of the tunnel barrier thickness. In this
paper, it is demonstrated that the MITT can be fabricated by much
simpler processes than MOSFET and that the MITT can be operated by
optimizing the MITT structure at room temperature. The results indicate the
feasibility of using MITT as the
future switching device in ultralarge-scale integrated circuits
(ULSI).
Fabrication of Photonic Crystals Consisting of Si Nanopillars by Plasma Etching Using Self-Formed Masks
Authors: Tada Tetsuya , Poborchii Vladimir V. , Kanayama Toshihiko
Published: October 2002

We fabricated two dimensional photonic crystals (a square and a triangular lattice) with a photonic band gap (PBG) in the visible light range by periodically arranging Si nanopillars with a period of 270 nm. The pillar diameter and height are 50 nm and 1 µm, respectively. The fabrication process uses iron clusters as nuclei for self-formation of etching masks during electron cyclotron plasma etching with SF6gas at -135°C to obtain high-aspect-ratio Si nanopillars. The iron clusters are arranged by electron beam lithography. The reflection spectra of the square lattice photonic crystal have a peak around 570 nm for transverse magnetic polarization light while that for transverse electric polarization have a peak around 550 nm. This is consistent with our theoretical calculation that the photonic crystal has a PBG at these wavelengths.
Patterning and Functionalizing Self-Assembled Monolayers
Authors: Wataru Mizutani Wataru Mizutani
Published: October 2002

For fabricating nanometer-scale devices,
functionalized molecular components must be positioned
with a molecular resolution and their orientation must also be controlled.
Self-assembly techniques were investigated, and various methods were
developed for patterning and functionalizing self-assembled monolayers (SAMs)
which cover solid surfaces spontaneously with well-ordered and oriented molecules.
For patterning SAMs, we studied the phase separation of binary component monolayers,
molecular extraction, and growth control on patterned substrates.
We are developing techniques for characterizing the
functions of molecules in SAMs; for example, we detected a local change in
electric conduction and barrier height depending on the molecular species.
Preventing Coma Aberration by Annular Apodizer for Optical Disk Tilting
Authors: Ando Hideo
Published: October 2002

This research was carried out to determine the optimum parameters for
an optical apodizer, applicable to a pick-up head for higher recording density
optical disks. The coma aberration generated by tilting a disk increases the
side-lobe intensity of the beam waist spot, and the increased side-lobe portion
of the beam waist spot mainly deteriorates crosstalk from an adjacent track.
Calculations were made to estimate coma aberration, in which the author
adopted the annular radius of the apodizer and the side-lobe intensity
of the beam waist spot as parameters. The result, which was confirmed
experimentally, is that an annular apodizer whose radius is half the pupil
radius effectively prevents coma aberration.
A Theory of Morphotropic Phase Boundary in Solid-Solution Systems of Perovskite-Type Oxide Ferroelectrics
Authors: Ishibashi Yoshihiro , Iwata Makoto
Published: October 2002

The origin of the appearance of the morphotropic phase boundary in
perovskite-type oxide solid solution systems is clarified on the basis of a Landau-type free-energy function expressed in terms of polarization and strain components.
The dielectric susceptibilities and piezoelectric constants are shown to increase in
the vicinity of the morphotropic phase boundary.
Influence of Long-Range Lateral Ordering in Structures with Quantum Dots on the Spatial Distribution of Diffracted X-Ray Radiation
Authors: Faleev Nikolai , Pavlov Konstantin , Tabuchi Masao , YoshikazuTakeda YoshikazuTakeda
Published: October 2002

Perfectly crystalline (InAs–GaAs) multilayer periodic structures on (001) GaAs, which contain InAs
quantum dots (QDs), have been studied by high-resolution X-ray diffraction. It has been shown
that the existence of such scattering objects as QDs strongly influences X-ray diffraction, changing
the spatial distribution of scattered radiation. Additional long-range ordering in layers containing
QDs results in unusual and significant elongation of superlattice and substrate reflections in the q
x direction. A novel qualitative model of scattering layers consisting of perfect InAs and GaAs
coherent clusters has been developed.
Highly Sensitive Cavity-Enhanced Sub-Doppler Spectroscopy of a Molecular Overtone Band with a 1.66 µm Tunable Diode Laser
Authors: Ishibashi Chikako , Sasada Hiroyuki
Published: October 2002

Sensitive sub-Doppler resolution molecular spectroscopy developed
by Hall and co-workers [J. Opt. Soc. Am. B 15 (1998) 6] has been applied to
the 1.66 µm region using a widely tunable external-cavity diode laser. We
have recorded saturated absorption spectra of the 2ν3 vibrational overtone
band of methane with a sensitivity of 9.5×10-11 cm-1 at a time constant of
1.25 s and a spectral linewidth of 320 kHz (full width at half maximun; FWHM) over the tunable range of 1.63 to 1.68 µm.
Growth of Low Etch Pit Density Homogeneous 2′′ InP Crystals Using a Newly Developed Thermal Baffle
Authors: Hirano Ryuichi
Published: October 2002

Low Etch pit density 2′′ InP crystals were grown by the liquid-encapsulated Czochralski (LEC)
method using a newly developed thermal baffle. The average EPD of Sn-doped InP crystals
was reduced to less than 3000 cm-2. The minimum average EPD was about 200 cm-2. Visible
facets were observed and the crystal was somewhat rectangular. No lineage-type defects were
observed even in the last portion of the crystal. Dislocation-free (DF) (EPD≦500 cm-2)
S-doped InP crystals were also obtained with lower S concentration using the newly developed
baffle. The minimum S concentration for growing the DF crystal was 1.7×1018 cm-3.
New Scanning Photoluminescence Technique for Quantitative Mapping the Surface Recombination Velocity in InP and Related Materials
Authors: Krawczyk Stanislas , Bejar Moez , Khoukh Abdelaziz , Blanchet Robert , Sermage Bernard , Cui Delong , Pavlidis Dimitris
Published: October 2002

This paper introduces a new approach, based on room temperature (RT) scanning
photoluminescence (SPL) measurements, for non-destructive quantitative mapping of the
surface or interface recombination velocity in compound semiconductor structures. The
developed technique is validated and applied here to spatially resolved evaluation of the surface
recombination velocity of InP substrates and InGaAs(C)/InP heterostructures.
Self-Induced Spiking Oscillations and Associated Instabilities in a Laser-Diode-Pumped Three-Mode Nd:YVO 4 Laser
Authors: Kenju Otsuka Kenju Otsuka , Hiroaki Utsu Hiroaki Utsu , Ryoji Kawai Ryoji Kawai , Kazuyoshi Ohki Kazuyoshi Ohki , Yusuke Asakawa Yusuke Asakawa , Siao-Lung Hwong Siao-Lung Hwong , Jing-Yuan Ko Jing-Yuan Ko , Jyh-Long Chern Jyh-Long Chern
Published: October 2002

Self-induced Q-switching-type spiking oscillations and associated
instabilities have been observed in a free-running laser-diode-pumped
microchip Nd:YVO4 laser operating in three-mode regimes, and dynamical
characterizations of spiking pulsations have been demonstrated. Observed
instabilities have been reproduced by numerical simulations of the model
equations including intensity-dependent cross-gain coupling in three-mode
lasers.
A Very Simple Method of Flattening Si(111) Surface at an Atomic Level Using Oxygen-Free Water
Authors: Fukidome Hirokazu , Matsumura Michio
Published: October 2002

Si(111) surfaces were found to be very easily flattened at an
atomic level by immersing the wafers in water, from which
dissolved oxygen was removed by the addition of sulfite ion as
chemical deoxygenator, at room temperature. After the
treatment with this oxygen-free water, the Si(111) surfaces
slightly misoriented in the <112> direction showed straight and
parallel steps and wide terraces under atomic force microscopy
observation. When wafers slightly misoriented in the opposite
direction were treated in the same manner, the steps showed a
characteristic zigzag pattern with an angle of 60°. The steps
that appeared on both surfaces were attributable to monohydride
steps generated on the edge of flat terraces.
Detection of Magnetic Nanoparticles with Superconducting Quantum Interference Device (SQUID) Magnetometer and Application to Immunoassays
Authors: Enpuku Keiji , Minotani Tadashi , Gima Takemitsu , Kuroki Yukinori , Itoh Yuzuru , Yamashita Makiko , Katakura Yoshinori , Kuhara Satoru
Published: October 2002

A system is developed to magnetically measure biological antigen-antibody reactions
with a superconducting quantum interference device (SQUID) magnetometer. In this system,
antibodies are labeled with magnetic nanoparticles of γ-Fe2O3, and the
antigen-antibody reactions are measured by detecting the magnetic field from the magnetic
nanoparticles. A setup of the system is described, and the sensitivity of the system is
studied in terms of detectable weight of nanoparticles. Magnetic particles as small as 600 pg
can be detected at present. An experiment is also conducted to measure antigen-antibody
reaction with the present system. It is shown that the sensitivity of the present system is
better than that of the conventional optical method. A one order of magnitude improvement
of sensitivity will be realized by the sophistication of the present system.
Mechanism of DC Offset Voltage Generation in Hybrid-Aligned Nematic Liquid Crystal Displays
Authors: Tanaka Yasuharu , Goto Yoko , Iimura Yasufumi
Published: October 2002

In order to study the mechanism of DC offset voltage generation in a hybrid-aligned nematic liquid crystal display (HAN-LCD), we theoretically and experimentally studied the electrooptic characteristics of a HAN sample. The results showed that decreasing the thickness of a LC alignment film strongly reduces the generation of a DC offset voltage. We also pointed out that a flexoelectric effect appearing in a HAN sample contributes significantly to the generation of a DC offset voltage.
Control of Nucleation Site and Growth Orientation of Bulk GaN Crystals
Authors: Yano Masaichi , Okamoto Mitsuo , Yap Yoke Khin , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo
Published: October 2002

The melt growth of bulk GaN crystals is hindered by high nitrogen pressure (∼45000 atm) at melting point. Recently, bulk GaN crystals were grown at a pressure of ∼100 atm by means of Na flux. However, the flux growth method failed to control the nucleation site and growth orientation of GaN. In this work, oriented GaN crystals were obtained by means of a seeded Na flux method with the addition of oriented AlN(0001) film to the growth ambient. The nucleation of bulk GaN was spatially confined to the top surface of the AlN film and grown with the GaN[0001] axis parallel to the AlN[0001] axis. In contrast, no bulk GaN was observed on the SiC(0001) surface which was also lattice matched with the GaN. Both X-ray diffraction (XRD) and cathodoluminescence confirm the high quality of the as-grown GaN.
Self-Organized Formation of Hexagonal Hollow Arrays in Anodic GaAs
Authors: Yoshitaka Morishita Yoshitaka Morishita , Shingo Kawai Shingo Kawai , Jun Sunagawa Jun Sunagawa
Published: October 2002

The dependence of the structural properties on the anodization conditions was investigated to gain insights into the formation conditions of ordered hollow arrays on GaAs surfaces. The microscopic surface features were observed by a secondary electron microscope. Honeycomb hollows were formed on the substrate surfaces anodized with an appropriate bias voltage between the substrate and the platinum electrode under the illumination of W lamp. Ordered hexagonal hollows with the average diameter and standard distribution of 200 and 19 nm were obtained for the sample prepared by the anodization with the bias voltage of 12 V under the illumination of W lamp in an NH4OH solution (29 wt%) at 0°C.
Correlation between Dislocation Density and the Macroscopic Properties of GaN Grown by Metalorganic Vapor Phase Epitaxy
Authors: Watanabe Atsushi , Takahashi Hirokazu , Tanaka Toshiyuki , Ota Hiroyuki , Chikuma Kiyofumi , Amano Hiroshi , Kashima Takayuki , Nakamura Ryo , Akasaki Isamu
Published: October 2002

The correlation between the dislocation density and the electrical and optical properties of
lightly Si-doped GaN films grown by metalorganic vapor phase epitaxy was investigated.
Photo-electro-chemical (PEC) etching, developed by Youtsey et al.. [Appl. Phys. Lett. 73
(1998) 797], was applied to determine the dislocation density. We modified the PEC
etching technique by introducing an additional pulsed sequence. Clear correlation was
observed between the dislocation density and the Hall mobility and room-temperature
photoluminescence intensity. The influence of the reactor pressure on the dislocation
density is also discussed.
The White Light Supercontinuum Is Indeed an Ultrafast White Light Laser
Authors: Chin See Leang , Petit Stéphane , Borne Frédéric , Miyazaki Kenzo
Published: October 2002

We identify the white light supercontinuum generated by femtosecond Ti-sapphire laser
pulses as an ultrafast white light laser because the relative coherence lengths of all the
wavelength components of the supercontinuum are essentially the same as that of the laser
pulse when compared to an incoherent white light source.
Crystal Orientation Fluctuation of Epitaxial-Lateral-Overgrown GaN with W Mask and SiO2 Mask Observed by Transmission Electron Diffraction and X-Ray Rocking Curves
Authors: Honda Yoshiaki , Iyechika Yasushi , Maeda Takayoshi , Miyake Hideto , Hiramatsu Kazumasa , Sone Hiroki , Sawaki Nobuhiko
Published: October 2002

Fluctuation of the crystal orientation of epitaxial-lateral-overgrown (ELO) GaN with a tungsten (W) mask is compared to that with a SiO2 mask by means of selected-area transmission electron diffraction (TED) and X-ray rocking curves (XRCs). XRCs of (0004) reflection exhibited three peaks for ELO-GaN on a SiO2 mask, and were confirmed to originate from domains of different c-axis orientation by TED. On the other hand, fluctuation of the c-axis was not observed for ELO-GaN with a W mask. These results indicate that the crystalline quality of ELO-GaN with a W mask is better than that with a SiO2 mask.
Fabrication of Micro-Aperture Surface Emitting Laser for Near Field Optical Data Storage
Authors: Shinada Satoshi , Koyama Fumio , Nishiyama Nobuhiko , Arai Masakazu , Goto Kenya , Iga Kenichi
Published: October 2002

We fabricated a micro-aperture vertical cavity surface emitting laser (VCSEL) for use in near
field optical data storage. A composite mirror of Au and a 11-pair semiconductor distributed
Bragg reflector (DBR) provides a reflectivity of more than 99%. Fabricated VCSEL devices
exhibited sub-mA low threshold operation. A micro-aperture with a diameter below 400 nm was
introduced in Au film using focused ion beam etching. A localized near field at a 400 nm aperture
was observed and the output power from the aperture was estimated to be 10 µW.
Li-Doped Nickel Oxide as a Thermoelectric Material
Authors: Woosuck Shin Woosuck Shin , Norimitsu Murayama Norimitsu Murayama
Published: October 2002

Thermoelectric properties of ceramic samples of NiO doped with Li are studied in the
temperature range of 450–1280 K, with different Li contents. The substitution of Li for Ni
atoms in a cubic NiO lattice results in a high thermoelectric power factor over a wide
temperature range. Furthermore, Li substitution decreased the thermal conductivity
resulting in an increase in the thermoelectric figure of merit,
Z = 0.75 ×10-4 K-1 over 1000 K, suggesting that NiO is a promising oxide-base material for high-temperature thermoelectric devices.
Missing Ag Atom on Si(111)√3×√3–Ag Surface Observed by Noncontact Atomic Force Microscopy
Authors: Morita Seizo , Sugawara Yasuhiro , Orisaka Shigeki , Uchihashi Takayuki
Published: October 2002

We investigated missing bright spots, i.e., atomic point defects, on a
Si(111)√3×√3–Ag
sample surface by the noncontact atomic force microscopy (NC-AFM) as
a function of the tip-sample surface distance. Then, we compared the
experimental results with the proposed NC-AFM imaging mechanisms based on
the honeycomb-chained trimer (HCT) model. As a result, we confirmed that the
observed missing bright spots were generated by only one missing Ag atom in the
topmost layer which constitutes an Ag trimer. This is conclusive evidence that
only one Ag atom contributes to more than one bright spot in the NC-AFM image.
We also found that the position of the missing Ag atom varied.
Application of Orthogonal Wavelet Decomposition to Plasma Fluctuation Study
Authors: G. Bruskin Leonid , Atsushi Mase Atsushi Mase , Yasuyuki Yagi Yasuyuki Yagi , Teruo Tamano Teruo Tamano
Published: October 2002

Multi-scale analysis of plasma fluctuations in fusion devices is performed using wavelet decomposition over the orthogonal
compactly supported basis of wavelets. The discrete wavelet analysis allowed us to monitor separately the turbulence
properties in different frequency bands during the RF heating on the tandem mirror GAMMA 10 and discrete event on the
reversed-field pinch TPE-1RM20 fusion devices. Orthogonal discrete wavelet transform can be considered to be complementary
to Fourier and continuous wavelet transforms, better suited for the study of wide-spectrum transitional events.
Dislocation-Free Czochralski Silicon Crystal Growth without the Dislocation-Elimination-Necking Process
Authors: Hoshikawa Keigo , Huang Xinming , Taishi Toshinori , Kajigaya Tomio , Iino Takayuki
Published: October 2002

Dislocation-free silicon crystals have been grown successfully from heavily-boron-doped silicon melts by the Czochralski method without the dislocation-elimination-necking process (Dash neck). A dislocation-free silicon seed of <001> orientation with
a boron concentration of about 4×1019 atoms/cm3 was used to grow a silicon crystal with
the same boron concentration. No dislocation was generated in the seed during the
dipping process, and no misfit dislocation occurred in the grown crystal. These results
show that shoulder and body growth can be started immediately after the seeding
process.
CuAu-Type Ordering Self-Formed by Growing GaP/InP Short-Period Superlattices on GaAs (011) Substrate
Authors: Kim Seong-Jin , Asahi Hajime , Asami Kumiko , Gonda Shun-ichi
Published: October 2002

(GaP)
n
(InP)
n
short-period superlattices (SLs) grown on a GaAs
(011) substrate by gas-source molecular beam epitaxy (MBE) are
studied by transmission electron microscopy (TEM). The satellite
spots which indicate the formation of a GaP/InP monolayer
superlattice in the [100] direction (CuAu-type ordering) are clearly
observed, for the first time, in the (011) transmission electron
diffraction (TED) pattern. The (011) plan-view TEM image shows
composition modulation along the [100] direction and the
self-formation of a straight wire structure with a length of over 1 µm in the [011] direction.
Barrier Height Enhancement of Ni/n-Type InP Schottky Contact Using a Thin Praseodymium Interlayer
Authors: Jeng Ming-Jer , Wang Hung-Thung , Chang Liann-Be , Cheng Yi-Chang , Lee Cheng-Min , Lin Ray-Ming
Published: October 2002

A praseodymium interlayer with a thickness of 100 Å at Ni/InP Schottky contacts is
shown to enhance the barrier height and reduce the reverse-bias current density. It is
demonstrated that even though the contact was baked for 8 h at a temperature of 300°C, its
barrier height and reverse-bias current density could still be maintained at about 1.05 eV
and 1.86×10-10 A/cm2 at -3 V, respectively. It is believed that praseodymium has high
reactivity with oxygen to form praseodymium oxide with a wide band gap and a strong
chemical bond. Similar to metal-insulator-semiconductor diodes, praseodymium can
effectively increase the Schottky barrier height and reduce the reverse leakage current.
Wavelength Tunable Polarization Mode Converter Utilizing Strain-Optic Effects in Ti:LiNbO 3
Authors: Sik Jung Hong , F. Taylor Ohanses Eknoyan
Published: October 2002

Electro-optically wavelength tunable polarization mode converters have been produced in LiNbO3 substrate using strain-induced polarization mode coupling. Polarization conversion in excess of 82% was achieved at a wavelength of 701.39 nm for both transverse electric (TE) and transverse magnetic (TM) input polarizations. The maximum conversion efficiency is highly wavelength selective with a spectral width of 1.45 nm in a 3.2 mm long device. Electro-optic tuning of the center wavelength with a linear tuning rate of 0.029 nm/V was demonstrated.
Improvement of Fluorescence Characteristics of Er3+-Doped Fluoride Glass by Ce3+ Codoping
Authors: Meng Zhicong , Yoshimura Tomoshi , Nakata Yoshiki , Vasa Nilesh J. , Okada Tatsuo
Published: October 2002

The fluorescence characteristics of Ce3+:Er3+ codoped
fluoride glass are reported. It is observed that the decay rate of
the 4I11/2 state of Er3+ increased by increasing the
Ce3+ concentration. Further, the branching ratio for the
transition from the 4I11/2 state to the 4I13/2
state of Er3+ increased from 0.20 to 0.95 by codoping
6.0 mol% Ce3+ into Er3+-doped ZBLAN-H fluoride glass. As
a result, the 1.55 µm fluorescence quantum yield has been
significantly improved.
Charge Density Waves in Quasi-One-Dimensional Compound InxNb3Te4 (0≤x≤1.0): Electron Diffraction Observations
Authors: Ohtani Tsukio , Yokota Yasuhiro , Sawada Hiroaki
Published: October 2002

Electron diffraction measurements revealed that the quasi-one-dimensional compound
In
x
Nb3Te4 (x=0.40, 0.60, 0.90, 1.0) exhibits charge density wave (CDW) modulation below
∼150 K. The CDW wave vectors were q=±(1/3a
*+1/3b
*)+z
c
*, where z is 0.433, 0.440,
0.453, and 0.462 for x=0.40, 0.60, 0.90, and 1.0, respectively. The increase in z with
increasing x was interpreted as arising from the increase in Fermi energy due to In intercalation.
Artificial SrTiO3/SrO Superlattices by Pulsed Laser Deposition
Authors: Iwazaki Yoshiki , Suzuki Toshimasa , Sekiguchi Shoichi , Fujimoto Masayuki
Published: October 2002

Artificial SrTiO3/SrO superlattice thin films epitaxially grown on SrTiO3
substrates were fabricated by pulsed laser deposition. The artificial superlattices were
designed and fabricated by introducing a Ruddlesden-Popper (RP) layer periodically.
The intensity of reflection high-energy electron diffraction (RHEED) patterns during the
growth of the superlattices increased at the deposition of SrTiO3 layers and decreased at
the deposition of the SrO monolayer, alternately. The gradual intensity decrease of
RHEED reflection during SrO layer deposition is attributable to the island growth of
SrO. The different type of RP layers normal to the film surface, observed in a high-temperature deposited superlattice, may originate from the higher diffusion condition
and island growth of SrO.
Studies of Ir–Ta–O as High Temperature Stable Electrode Material and Its Application for Ferroelectric SrBi2Ta2O9 Thin Film Deposition
Authors: Zhang Fengyan , Maa Jer-shen , Hsu Sheng Teng , Ohnishi Shigeo , Zhen Wendong
Published: October 2002

An Ir–Ta–O/Ta/Si structure with Ir–Ta–O as electrode and Ta as diffusion barrier layer
on silicon substrate has been fabricated. The Ir–Ta–O film was deposited by reactive
sputtering using separate Ir and Ta targets in oxygen ambient. Annealing results
performed from 500–1000°C in oxygen ambient showed that the Ir–Ta–O film exhibited
extraordinary high temperature stability. This film showed good conductivity and
integrity even after 5 min annealing at 1000°C. No destructive peeling and hillock
formation were observed. By using this film as bottom electrode for depositing
ferroelectric SrBi2Ta2O9 thin film at 800°C, good ferroelectric properties were achieved.
Surface Microroughness Observed during Wet Etching of Silicon Dioxide with High Electric Field Stress
Authors: Yamabe Kikuo , Kai Liao , Murata Masahide
Published: October 2002

Surface microroughness during stepwise wet etching of silicon dioxide with high
electric field stress was observed by atomic force microscopy (AFM). It was found
that the rms (root mean square) value of the above oxide surface increased with
increasing electric field stress. This indicates that the internal damage in silicon
dioxide caused by the high electric field stress is distributed two-dimensionally
and the degradation does not progress uniformly. The depth profile of the rms value
was also obtained during stepwise etching of the silicon dioxide, which may reflect
the depth profile of the internal damage in the silicon dioxide caused by the high
electric field stress.
Effect of Underlayers on the Morphology and Orientation of Aluminum Films Prepared by Chemical Vapor Deposition Using Dimethylaluminumhydride
Authors: Sugiyama Masakazu , Iino Tomohisa , Itoh Hitoshi , Aoyama Jyun-ichi , Komiyama Hiroshi , Shimogaki Yukihiro
Published: October 2002

In order to understand the surface roughening mechanism during the chemical vapor deposition of aluminum (Al-CVD), the authors investigated the effect of underlayers on the nucleation, coalescence and surface roughening of Al film using in situ surface reflectivity measurement. The maximum reflectivity corresponded to the Al nuclei coalescence for the TiN and Cu underlayers, while the reflectivity decreased almost continuously for the Si, Ta and TaN. Surface observation of the initial growth revealed that a high Al nucleation density is necessary for fabrication of smooth Al films. Crystallographic orientation of Al film was observed at the characteristic points of the reflectivity behavior. Film orientation showed different trends for the TiN and Cu underlayers, corresponding to the difference in the reflectivity behavior. The existence of second nucleation of Al on continuous Al films is suggested to be the cause of surface roughening.
Surface Morphology and Dielectric Properties of Stoichiometric and Off-Stoichiometric SrTiO3 Thin Films Grown by Molecular Beam Epitaxy
Authors: Ota Hiroyuki , Migita Shinji , Xiong Si-Bei , Fujino Hidetoshi , Kasai Yuji , Sakai Shigeki
Published: October 2002

SrTiO3 thin films are epitaxially grown on Nb-doped
SrTiO3 substrates by atomic-layer-controlled molecular beam
epitaxy. It is found that the morphology and the dielectric properties
of the films strongly depend on the cation composition. Atomic force
microscopy images show that particle-free surfaces are obtained in
stoichiometric SrTiO3 and 15% Ti-rich films. For the
stoichiometric film, in particular, atomically flat surfaces with
steps and terraces are observed. The dielectric constant of the
stoichiometric thin film at 25 K reaches a maximum of 1850 at the
bias voltage of -1.2 V. The dielectric constant rapidly
decreases to about 25% of the maximum value by the application of
-1.2±5.3 V, indicating excellent tunability of the dielectric
constant by the dc voltage. The saturated polarization is more than
10 µC/cm2.
30-nm-Gate InP-Based Lattice-Matched High Electron Mobility Transistors with 350 GHz Cutoff Frequency
Authors: Tetsuya Suemitsu Tetsuya Suemitsu , Tetsuyoshi Ishii Tetsuyoshi Ishii , Haruki Yokoyama Haruki Yokoyama , Takatomo Enoki Takatomo Enoki , Yasunobu Ishii Yasunobu Ishii , Toshiaki Tamamura Toshiaki Tamamura
Published: October 2002

The device characteristics and fabrication of 30-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates are reported. The gate length of 30 nm is achieved for a T-shaped gate geometry, which is necessary to minimize gate resistance for short-gate HEMTs, by using fullerene-incorporated nanocomposite resist in the electron beam direct writing of the bottom of the gate. In addition, the two-step-recess gate technology is used to minimize the extension of effective gate length. The devices provide excellent RF characteristics; a record cutoff frequency of 350 GHz is achieved.
Piezoelectric Stark-like Ladder in GaN/GaInN/GaN Heterostructures
Authors: Christian Wetzel Christian Wetzel , Tetsuya Takeuchi Tetsuya Takeuchi , Hiroshi Amano Hiroshi Amano , Isamu Akasaki Isamu Akasaki
Published: October 2002

The electronic bandstructure of strained Ga1-x
InxN wells between barriers of GaN
is found to exhibit an unusual Stark-ladder controlled mainly by the piezoelectric dipole
across the strained layer. In luminescence and reflection spectroscopy
four distinct steps including a strong redshift with respect to the thin film band gap are identified.
Huge piezoelectric fields F ≤1 MV/cm are derived directly
from Franz-Keldysh oscillations and interband transitions between carriers originating on opposite sides of the well.
For the largest strain and electric field, a Stark-like ladder is identified.
This provides important details for the interpretation of the electronic band structure in group-III nitride heterostructures.
Solution Using a Codoping Method to Unipolarity for the Fabrication of p-Type ZnO
Authors: Yamamoto Tetsuya , Katayama-Yoshida Hiroshi
Published: October 2002

We have investigated the electronic structures ofn- orp-type doped ZnO based onab initioelectronic band structure calculations. We findunipolarityin ZnO;n-type doping using Al, Ga or In species decreases the Madelung energy whilep-type doping using N species increases the Madelung energy, in addition to causing substantial localization of the N states. Codoping using reactive codopants, Al, Ga or In, enhances the incorporation of N acceptors inp-type codoped ZnO. We find the delocalized states of N forp-type ZnO codoped with N and Al (Ga).
Alternative Buffer Architectures for High Critical Current Density YBCO Superconducting Deposits on Rolling Assisted Biaxially-Textured Substrates
Authors: Dominic F. Lee Dominic F. Lee , Mariappan Paranthaman Mariappan Paranthaman , John E. Mathis John E. Mathis , Amit Goyal Amit Goyal , Donald M. Kroeger Donald M. Kroeger , Eliot D. Specht Eliot D. Specht , Robert K. Williams Robert K. Williams , Frederick A. List Frederick A. List , Patrick M. Martin Patrick M. Martin , Chan Park Chan Park , David P. Norton David P. Norton , David K. Christen David K. Christen
Published: October 2002

Although high critical current density (J

c
) YBCO can be deposited on rolling
assisted
biaxially-textured substrates (RABiTS) with the YSZ/CeO2/Ni architecture, improvement
in uniformity is needed due to the presence of two-component YBCO epitaxy and cracking in
the CeO2 buffer. We have determined that Yb2O3 is an excellent buffer
material that provides a single-component YBCO epitaxy. In addition, crack-free epitaxial
Y2O3 can be consistently deposited onto textured Ni substrates. High quality YBCO
films have been deposited, and J

c
as high as 1.8 ×106 A/cm2 at 77 K
has been
obtained on this Yb2O3/Y2O3/Ni alternative RABiTS architecture.
Ellipsometric Study of Self-Assembled InAs/GaAs Quantum Dots
Authors: Hosun Lee Hosun Lee , Euze Seong Euze Seong , Seong-Min Kim Seong-Min Kim , Maeng-Ho Son Maeng-Ho Son , Byung-Don Min Byung-Don Min , Yong Kim Yong Kim , Eun-Kyu Kim Eun-Kyu Kim
Published: October 2002

We measured the pseudo-dielectric function
of self-assembled InAs/GaAs quantum dots at
room temperature using spectroscopic ellipsometry.
We observed a strong excitonic peak at 0.9 eV, which was attributed to
quantum dot transitions. We also observed a plateau from 1.2 eV to 1.4 eV, which
arose from steplike joint density of states originating from an InAs wetting layer.
Our room
temperature data are very similar to the 1.8 K photoluminescence excitation spectra of
InAs/GaAs quantum dots reported in the literature. The higher energy dielectric response of the
quantum dots
enabled us to estimate the morphology of the quantum dots using
effective medium analysis. These results were compared to atomic force microscopy measurement
results.
Effective medium
analysis showed that a GaAs cap layer was preferentially grown on the InAs wetting layer rather
than on InAs islands.