bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of a Tantalum-Based Josephson Junction for an X-Ray Detector
Authors: Morohashi Shin'ichi , Gotoh Kohtaroh , Yokoyama Naoki
Published: October 2002

We have fabricated a tantalum-based Josephson junction for an X-ray detector.
The tantalum layer was selected for the junction electrode because of its long
quasiparticle lifetime, large X-ray absorption efficiency and stability against thermal
cycling. We have developed a buffer layer to fabricate the tantalum layer with a
body-centered cubic structure. Based on careful consideration of their
superconductivity, we have selected a niobium thin layer as the buffer layer for
fabricating the tantalum base electrode, and a tungsten thin layer for the tantalum
counter electrode. Fabricated Nb/AlO
x
–Al/Ta/Nb and
Nb/Ta/W/AlO
x
–Al/Ta/Nb Josephson junctions exhibited current–voltage
characteristics with a low subgap leakage current.
Mössbauer Studies on Particle Volume Distribution of α-FeOOH in Rust Formed on Weathering Steel
Authors: Okada Takuya , Ishii Yasuyuki , Mizoguchi Tadashi , Tamura Ichiro , Kobayashi Yoshio , Takagi Yasuo , Suzuki Shigeru , Kihira Hiroshi , Itou Minoru , Usami Akira , Tanabe Kouji , Masuda Kazuhiro
Published: October 2002

Rust formed on weathering steel and that on mild steel were
studied by Mössbauer spectroscopy at various temperatures from
room temperature to 12 K. The observed spectra were decomposed into
the contribution of fine antiferromagnetic particles of
α-FeOOH (85 at.%, T
N=403 K) and that of
γ-FeOOH (15 at.%, T
N=73 K). Volume
distributions of α-FeOOH particles obtained by analyzing the
superparamagnetic relaxation effect on Mössbauer spectra show
the following distinct characteristics: While 83 vol% of
α-FeOOH particles in the rust on mild steel are larger than
7.5×10-24 m3 and the rest of them (17 vol%) are
smaller than 3.0×10-24 m3, the rust on weathering steel shows a continuous and wide volume distribution down to the
ultrafine particle region (smaller than 3.0×10-24 m3) without a missing region, and 53 vol% of
particles are smaller than 7.5×10-24 m3. It is
understood that this continuous volume distribution of
α-FeOOH particles in the rust on weathering steel is
favorable for accommodating a closely packed structure in the
protective rust layer on weathering steel.
Transmittance for a Two-Dimensional Photonic-Crystal Structure Consisting of Cylinders and Liquid Crystal
Authors: Susa Nobuhiko
Published: October 2002

The transmittance for a two-dimensional photonic-crystal
structure consisting of 8×8 cylinders filled with or surrounded by a
liquid crystal was numerically calculated using the scattering
matrix method. When the refractive index of the liquid crystal was
increased from 1.4 to 1.6, the transmittance for the
liquid-crystal-filled cylinders increased from 4.5×10-3
to 1 at a wavelength of 825 nm, and that for the cylinders
surrounded by the liquid crystal increased from 1.3×10-3
to 1 at 1060 nm (triangular lattice) and from 3.0×10-4
to 1 at 1140 nm (square lattice).
Photoluminescence Study of Resonant Tunneling Transistor with p+/n-Junction Gate
Authors: Yutaka Ohno Yutaka Ohno , Shigeru Kishimoto Shigeru Kishimoto , Koichi Maezawa Koichi Maezawa , Takashi Mizutani Takashi Mizutani
Published: October 2002

We studied photoluminescence (PL) of a resonant tunneling transistor with a p+/n-junction gate. The excitation energy was selected to be close to the band-gap energy of the GaAs collector layer 1) so as not to excite the barrier layer and quantum well directly, and 2) in order to obtain a simple luminescence spectrum. The PL signal shows strong correlation with the resonant tunneling current. The PL peak position shows a redshift with increasing collector voltage, indicating the existence of the quantum-confined Stark effect. The collector voltage dependence of the PL linewidth suggests the existence of charge accumulation in the quantum well. The accumulated electron density and the charging time were estimated. It was also shown that the PL intensity could be controlled by the gate voltage without affecting the resonant tunneling behavior of electrons.
Photoinduced Disordering Dynamics of a Cyanobiphenyl Liquid Crystal Containing Quinizarin
Authors: Morino Shin'ya , Takahashi Hiromitsu , Horie Kazuyuki
Published: October 2002

Photoinduced changes in a liquid crystal (LC) alignment were
measured for 4-octyloxy-4′-cyanobiphenyl containing
quinizarin. Kinetic analyses were carried out for both photoinduced
response and thermal relaxation of the LC alignment in the
temperature range from 50°C to 78°C. Thermal relaxation
curves of birefringence after termination of Ar+ laser
irradiation show only one component in the smectic A phase, and two
components in the nematic phase, revealing the microscopic
environment of dye molecules in LC solvents. This change does not
exactly correspond to the macroscopic phase transition from smectic
to nematic, which suggests interaction between LC mesogens and dye
molecules due to photoexcitation. An unrecoverable portion of
birefringence for thermal ordering/relaxation processes after
termination of photoirradiation was observed in the smectic phase
measured in the course of heating process.
Development of Low Temperature Ultrahigh Vacuum Atomic Force Microscope/Scanning Tunneling Microscope
Authors: Suzuki Katsuyuki , Iwatsuki Masashi , Kitamura Shin-ichi , Mooney Charles B.
Published: October 2002

A low temperature ultrahigh vacuum atomic force microscope (UHV-AFM) has been developed, which allows the sample to be cooled from room temperature to lower than 28 K during observation and can be attached to the conventional UHV-AFM. Atom resolved non-contact atomic force microscopy (NC-AFM) images of the Si(100) surface were obtained at 120 K and 50 K using the produced low temperature UHV-AFM/STM, and the Si(100) dimer structure was successfully observed for the first time by NC-AFM. It was found that the Si(100)-c(4×2) structure mainly covered the area at 120 K, but the p(2×2) structure area increased at 50 K.
Evaluation of an Electric Field over Sample Surfaces by Electron Standing Waves in a Vacuum Gap of Scanning Tunneling Microscopy
Authors: Yoshinori Suganuma Yoshinori Suganuma , Masahiko Tomitori Masahiko Tomitori
Published: October 2002

Electric field intensities over sample surfaces have been evaluated
from peak intervals of differential conductance oscillation due to electron
standing waves, which are excited in a vacuum gap of scanning tunneling microscopy.
By comparing the intervals measured for different samples of Au(111),
Si(111), Si(001) and Ge(001) with tips of similar radius, we have
demonstrated that the electric field intensities are different on these
surfaces. This study provides a new method to evaluate the electric field
near surface regions on a nanometer scale.
Dimensional Effects on the Drain Current of N- and P-Channel Polycrystalline Silicon Thin Film Transistors
Authors: Shih Po-Sheng , Zan Hsiao-Wen , Chang Ting-Chang , Huang Tiao-Yuan , Chang Chun-Yen
Published: October 2002

N-channel and p-channel polysilicon thin film transistors
(poly-Si TFTs) with different geometries were fabricated and
characterized to study the interactive effects of active channel
area on drain current. We find that for both non-passivated and
passivated p-TFTs, since no avalanche multiplication is involved,
the drain current is increased with reduced active channel area due
to the reduction of grain-boundary trap density. In contrast, a
somewhat unexpected trap dependence of the kink effect is observed
in n-TFTs. Consequently, the dependence of active channel area on
drain current differs between non-passivated n-TFTs with large trap
density and passivated n-TFTs with small trap density.
Low-Resistance Ohmic Contacts to AlGaN/GaN Heterostructure Using Si/Ti/Al/Cu/Au Multilayer Metal Scheme
Authors: Youn Chang-Joo , Kang Kwang-Yong
Published: October 2002

A Si/Ti/Al/Cu/Au metallization scheme has been developed to achieve a low specific contact resistivity to a n-AlGaN/GaN heterostructure. A specific contact resistivity as low as 3.8 ×10-5 Ωcm2 was obtained after annealing at 800°C for 30 s. The interfacial reaction between the Si/Ti/Al/Cu/Au layers and the AlGaN was investigated by secondary-ion mass spectroscopy and transmission electron microscopy. An Al–Ti–Si–N intermetallic phase layer was observed at the interface. The ohmic contact formation is found to be related to Si diffusion and the formation of the Al–Ti–Si–N intermetallic phase layer.
Crystallinity of Large YBa2Cu3Oy Single Crystals Grown by the Solute Rich Liquid-Crystal Pulling Method
Authors: Kuroda Kiyoshi , Kamiyama Takashi , Oikawa Ken-ichi , Yamada Yasuji , Koshizuka Naoki , Koyama Satoshi , Namikawa Yasuo , Yamaguchi Yasuo , Torii Shuki , Asano Hajime
Published: October 2002

The solute rich liquid-crystal pulling method, a modified
Czochralski-pulling technique, can be used to grow very large single
crystals, larger than 1 cm along each axis. In order to examine the
crystallinity of the YBa2Cu3O
y
single crystals grown by
this technique, neutron diffraction was applied for six crystals
subjected to various annealing conditions. The typical mosaicity was
smaller than 1° along the c-axis and 2° in the
a
b-plane. Some crystals were of high quality, with a mosaicity of
less than 0.2° for every direction. The oxygen inhomogeneity
present in the as-grown samples was eliminated by prolonged-duration
oxygen annealing. Furthermore, we succeeded in observing the
orthorhombic II and III (ortho-II and III) phases, and determined the
correlation lengths along the a-axis as ξa=16 Å
and ξa=19 Å for y≈6.60 (ortho-II) and
y≈6.70 (ortho-III), respectively.
Study on Preparation Conditions of Single-Oriented (002) Zr Thin Films on n-(001) Si
Authors: Hideto Yanagisawa Hideto Yanagisawa , Katsutaka Sasaki Katsutaka Sasaki , Hidekazu Miyake Hidekazu Miyake , Yoshio Abe Yoshio Abe
Published: October 2002

We have investigated the preparation conditions of single-oriented (002) Zr film on n-(001) Si by varying the sputtering parameters during deposition using an ultrahigh-vacuum dc magnetron sputtering system. The crystallinity and preferential orientational plane of Zr film on Si were examined by X-ray diffraction analysis, and the chemical nature at the Zr/Si interface was evaluated by X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses. We found that the Zr film with the single-oriented (002) plane grew on (001) Si under the conditions of sputtering power above 50 W and substrate temperature range of 350–400°C. For this reason, it is speculated that a thin interdiffusion layer, which consists of elementary atoms (Zr and Si) and Zr silicide, formed at the Si interface plays the role of a buffer layer to relax the misfit between Zr and Si.
Mixed Ge-Si Dimer Formation in Ge/Si(100) and Si/Ge(100) Growth
Authors: Ko Young-Jo , Park Kang-Ho , Ha Jeong Sook , Yun Wan Soo
Published: October 2002

We report on the energetics of the mixed Ge-Si dimer
formation and adatom diffusion into subsurface layers for various
dimer structures on Si(100) and Ge(100) surfaces through
first-principles total-energy calculations. On both Si and
Ge(100) surfaces, the mixed dimer formation is found to be more
favorable than the pure Si-Si and Ge-Ge dimer formation. For Ge
atoms on Si(100), the diffusion into the subsurface layers is not
energetically favorable and thus, the mixed Ge-Si dimer is stable
against the subsurface diffusion. For Si atoms on Ge(100), the
diffusion of Si into the subsurface layer, which segregates Ge
atoms onto the surface, is found to be more favorable than
remaining as part of mixed Ge-Si dimers.
Energetics of InAs Thin Films and Islands on the GaAs(001) Substrate
Authors: Ligen Wang Ligen Wang , Peter Kratzer Peter Kratzer , Matthias Scheffler Matthias Scheffler
Published: October 2002

We perform ab initio calculations to obtain the
formation energy of thin InAs films grown on the GaAs(001) substrate.
For the island surface morphology,
a hybrid method combining
ab initio calculations and elasticity theory is employed.
Our results show that two-dimensional growth is favored
for the first monolayer in a wide range of chemical potentials.
Additional deposited material may transform the surface morphology
into the three-dimensional island growth mode. The driving force behind
this surface morphology change is relieving the elastic energy in the films.
Cs Adsorption on ZrC(111): Photoemission Spectroscopy Study
Authors: Kenichi Ozawa Kenichi Ozawa , Takashi Yoshii Takashi Yoshii , Tetsu Noda Tetsu Noda , Kazuyuki Edamoto Kazuyuki Edamoto , Shinichiro Tanaka Shinichiro Tanaka , Shigeki Otani Shigeki Otani
Published: October 2002

Room-temperature adsorption of Cs on ZrC(111) surface has been studied by core-level photoemission spectroscopy. The work function of the substrate surface decreases monotonically with Cs adsorption and approaches the Cs metal value without showing a clear work function minimum. Cs 4d core-level lineshape analysis reveals that the loss peaks due to overlayer plasmon excitation are already formed in the initial stages of adsorption. These results suggest that the adsorbed Cs atoms are in a metallic state which is brought about by the formation of Cs islands at low coverages and that adsorption proceeds via growth of these islands.
Adsorption of Atomic Hydrogen on Ag-Covered 6H-SiC(0001) Surface
Authors: Fujino Toshiaki , Fuse Takashi , Ryu Jeong-Tak , Inudzuka Katsuhiko , Yamazaki Yujin , Katayama Mitsuhiro , Oura Kenjiro
Published: October 2002

We have investigated atomic hydrogen (H) adsorption on an Ag-covered 6H-SiC(0001) surface, using coaxial impact-collision ion-scattering spectroscopy (CAICISS) and time-of-flight elastic recoil detection analysis (TOF-ERDA). It has been revealed that the two-dimensional (2D) layer of Ag on the 6H-SiC(0001) surface is changed to three-dimensional (3D) islands by the adsorption of H on the surface. The 3D Ag islands have an Ag(111) crystalline structure. When this surface is annealed at 550°C, the 3D Ag islands do not revert to a 2D layer but desorb from the surface together with H.
Micropatterning of Chemical-Vapor-Deposited Diamond Films in Electron Beam Lithography
Authors: Kiyohara Shuji , Ayano Kenjiro , Abe Takahisa , Mori Katsumi
Published: October 2002

The micropatterning of chemical-vapor-deposited (CVD) diamond
films using electron beam lithography technology has been
investigated. The use of metal naphthenates as mask resist materials
is proposed, because of their resistance to oxygen plasma in order
to form an oxide film on the surface. The exposure characteristics
of metal naphthenates, as well as the etching characteristics of CVD
diamond and metal naphthenate films processed with electron
cyclotron resonance (ECR) oxygen plasma were
investigated. Furthermore, the crystal structure of CVD diamond
micropatterns fabricated by this process was evaluated using Raman
spectroscopy. We found that the metal naphthenates exhibited
negative exposure characteristics upon electron beam
irradiation. The sensitivity and the gamma value were 2.4×10-3 C/cm2 and 1.6, respectively. A maximum etching selectivity of 10 was
obtained under etching conditions of a microwave power of 300 W and
oxygen gas flow rate of 3 sccm. Line micropatterns 1 µm and 0.5 µm in width with a height of approximately 1 µm were fabricated with an
etching time of 1 h. The crystal structure of the CVD diamond films
after etching and the line micropatterns fabricated by this process
remained constant; Raman spectra indicated only the presence of a
diamond (sp3 bonding) peak at 1333 cm-1.
Estimation of Epitaxial Temperature Using X-Ray Diffraction for Si Films Grown on (100) Si by Molecular Beam Epitaxy
Authors: Kazuhiro Nakamura Kazuhiro Nakamura , Hirofumi Shimizu Hirofumi Shimizu , Jun Kodera Jun Kodera , Katsuhiro Yokota Katsuhiro Yokota
Published: October 2002

Silicon films were grown at low temperatures (≤350°C)
by solid-source molecular beam epitaxy (MBE). The films were characterized using reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and atomic force microscopy (AFM). A single-crystalline silicon homoepitaxial layer
was obtained at the substrate temperature of 350°C. The thickness of the layer was about 0.4 µm and the growth rate was about 1 Å/s. The crystallinity of the silicon films was discussed by comparing the results of RHEED and XRD measurements. The method for estimating the epitaxial temperature using X-ray diffraction is discussed. At a temperature between 200°C and 250°C, the silicon film changed from a small-grain amorphouslike polycrystalline film
to a larger-grain mosaiclike polycrystalline film. Single-crystalline silicon was homoepitaxially grown on (100) Si at a critical temperature which existed between 300°C and 350°C.
Nanofabrication on Hydrogen-Terminated Diamond Surfaces by Atomic Force Microscope Probe-Induced Oxidation
Authors: Tachiki Minoru , Fukuda Tohru , Sugata Kenta , Seo Hokuto , Umezawa Hitoshi , Kawarada Hiroshi
Published: October 2002

Field-assisted local oxidation on a hydrogen-terminated (001)
diamond surface was performed using an atomic force microscope
(AFM). Anodic oxidation by a surface water meniscus layer is
suggested to account for this oxidation process. Through the
oxygenated area, Fowler-Nordheim (F-N) tunneling current was
observed. The difference in electron affinity between the
hydrogen-terminated surface and the oxygenated area was confirmed by
scanning electron microscopic (SEM) observations.
Effects of Hydrogen Diluted silane plasma on Amorphous Silicon Solar Cells
Authors: Isomura Masao , Kondo Michio , Matsuda Akihisa
Published: October 2002

We systematically studied amorphous silicon (a-Si:H) films and solar cells which were fabricated by H2-diluted SiH4 plasma. The H2 dilution improves the quality of poor materials resulting from non optimized pure SiH4 conditions however this improvement can also be achieved by reducing the RF power under pure SiH4 conditions. The H2 dilution is not always necessary for the optimization of a-Si:H. Higher diluted plasma reduces the optical absorption coefficient of a-Si:H, resulting in a lower short circuit current (I
sc), and the H2-dilution conditions could not give higher conversion efficiency (Eff) than the optimized pure SiH4 condition. The H2-diluted plasma at a relatively low pressure (0.2 Torr) causes a lower open circuit voltage (V
oc) in spite of wider optical gaps and lower I
sc than values estimated from the optical absorption coefficient, probably due to the damage of underlying layers by H ions or radicals. These plasma damages are suppressed by increasing the pressure up to ∼1.0 Torr.
Effect of Oxygen on the Activation of Mg Acceptor in GaN Epilayers Grown by Metalorganic Chemical Vapor Deposition
Authors: Chung Sung Hoon , Lachab Mohamed , Wang Tao , Lacroix Yves , Basak Durga , Fareed Qhalid , Kawakami Yoshihisa , Nishino Katsushi , Sakai Shiro
Published: October 2002

The effect of oxygen mixed in nitrogen on p-type activation in Mg-doped GaN epilayers grown by metalorganic chemical vapor deposition (MOCVD) was investigated. The samples annealed in N2/O2 (1%) ambient exhibited the best electrical properties with respect to hole concentration. SIMS data suggested that oxygen reacted with hydrogen present in the Mg-doped GaN samples during the thermal annealing process, thereby enhancing the activation of Mg acceptors.
An In-house-Built Thermally Stimulated Current Measurement Setup: Strontium Titanate as a Test System
Authors: Lakshminarayanan Bala , Akbar Sheikh , Wang Ching , Alim Mohammad
Published: October 2002

A semiautomated thermally stimulated current (TSC) measurement setup was developed in-house, which is capable of measuring low currents (<10-15 A) in a wide temperature range. This setup was used to study defects (bulk traps) in strontium titanate ceramics and single crystals. Strontium titanate was chosen as a test system because of the availability of data in the literature. Analysis of the TSC curves using various methods revealed traps with activation energies of approximately 0.64 eV and 0.80 eV, which can be attributed to acceptor impurities in single crystal and undoped SrTiO3, respectively. In polycrystalline SrTiO3 doped with 0.5, 1.0 and 1.5 mole% Nb2O5, traps with activation energy of ∼0.95 eV were found. These traps are believed to arise from Nb2O5 dissolved in the SrTiO3 matrix, as confirmed by scanning electron microscope with energy dispersive X-ray spectrometry (SEM/EDX) and electrical conductivity measurements.
Mn-Modified Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramics: Improved Mechanical Quality Factors for High-Power Transducer Applications
Authors: Chen Yun-Han , Hirose Seiji , Viehland Dwight , Takahashi Sadayuki , Uchino Kenji
Published: October 2002

Piezoelectric ceramics are potential high-power electroacoustic sources, and have been studied for many years. However, when these devices are driven under high-level vibration, the electromechanical characteristics depart significantly from the conventional linear piezoelectric relationships due to the loss and nonlinear behavior in terms of elastic and dielectric properties. In this paper, we present results concerning the development of modified Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) ceramics with improved mechanical quality factors for high-power application. We have focused efforts on base PMN–PT compositions close to the morphotropic phase boundary. Evidence will be presented which indicates that the improved mechanical quality factor results from the introduction of “hard” characteristics into PMN–PT by the substituents. Investigations of the nonlinearity of the electromechanical properties on the vibrational amplitude were performed using a constant displacement method. The degradation of the mechanical quality factor with increasing drive amplitude also presents thermal stability problems for the usage of these materials in high-power transducer applications.
Two-Dimensional Optical Analysis of Small Pixels in Reflective Silicon Microdisplay
Authors: Huang Ho-Chi , Huang Dan-Ding , Chen Jun
Published: October 2002

We present a two-dimensional optical analysis of small pixels in
reflective liquid-crystal-on-silicon microdisplay. The optical
analysis is divided into two parts. In the first part, the
two-dimensional (2D) director configuration of the liquid crystal
display (LCD) in rectangular mesh was calculated by simultaneously
solving the 2D Poisson and continuum theory equations. In the second
part, generalized Jones matrix was used to simulate for optical
reflectance through the LCD with the 2D director configuration
obtained from the first part. This optical modeling was applied to
analyze optical reflectance of small pixels in reflective mixed-mode
twisted nematic and birefrigence (MTB) cells on silicon substrate.
Both the simulated and experimental data of the MTB cells under frame
and column inversions were presented. It was found that the frame
inversion could give rise to a higher contrast ratio than the column
inversion at the same driving voltage. It was also found that the
optical reflectance decreased as the pixel size decreased due to the
lateral electric field between the small pixels.
Phase-Modulation Optical Spatial Filters Applicable to Inspection Systems for Patterned Silicon Wafers
Authors: Naoko Yamamoto Naoko Yamamoto , Mitsuhiro Iwata Mitsuhiro Iwata , Ryoji Minakata Ryoji Minakata
Published: October 2002

We have studied a method to realize an optical spatial filter applicable to inspection systems for patterned silicon wafers by means of a phase-modulation filter. A simulated-annealing method can be used to design a one-dimensional binary phase spatial filter which effectively levels a periodic pattern corresponding to memory cells and so on. The optimum cost function is the maximum optical amplitude on the observation plane of the inspection system. The suitable binary phase ranges from 0.7π to 1.3π. Furthermore, leveling of a nonperiodic pattern corresponding to particles or defects can be avoided when the cells of the spatial filter which make no contribution to the leveling of the periodic pattern are set to have the same phase as that of the cell at the lowest spatial frequency. As a result, the nonperiodic patterns can be emphasized more than periodic patterns. To verify the applicability of the simulation, we fabricated the designed optical spatial filter on a quartz substrate by photolithography and reactive ion etching, and measured its characteristics. As a result, we have confirmed that the fabricated optical spatial filter has the same effect as that of the designed one.
Kinetic Study of the Metalorganic Chemical Vapor Deposition of PbTiO3 Films from Pb(C2H5)4/Ti(i-OC3H7)4/O2 Reaction System
Authors: Hong Lu Sheng , Wei Chung Chieh
Published: October 2002

Lead titanate (PbTiO3) films are prepared from mixtures of tetraethyl lead [Pb(C2H5)4], titanium tetraisopropoxide [Ti(i-OC3H7)4] and oxygen at temperatures ranging from 823 to 873 K by the low-pressure chemical vapor deposition (LPCVD) method. The kinetics of the film growth process has been studied, including investigating the growth rate dependency at various substrate temperatures and the concentrations of Pb(C2H5)4, Ti(i-OC3H7)4, and O2, respectively. A reaction model applying the Eley-Rideal mechanism is proposed to explain the experimental film growth rate dependency. The model involves (i) a strong surface adsorption species, Pb(C2H5)4, chemisorbing on the substrate surface to react with a dissociatively adsorbed oxygen to form PbO, (ii) a less adsorptive species, Ti(i-OC3H7)4, directly coming from the gas phase to react with the surface adsorbed species to form PbTiO3 films. The proposed reaction model fits the growth rate data quite well.
Digital Signal Processor Implementation of Active Noise Control Systems for Broadband Noise Cancellation in Engine Exhaust Systems
Authors: Wu Jian-Da , Bai Mingsian R.
Published: October 2002

This paper describes the principle and application of broadband active noise control (ANC) for engine exhaust systems using a spatially feedforward structure. The algorithm of the proposed controller is obtained from previous work by Roure (1985), Munjal and Eriksson (1988), Hong and Bernstein (1998), and there exist some conclusions for this structure. The self-adaptive broadband controller is discussed and implemented on a digital signal processor (DSP), using finite impulse response (FIR) and infinite impulse response (IIR) filters. Experiments were carried out to evaluate the proposed system for reducing the noise under different engine operating conditions. The experimental results indicate that the ANC system is effective in reducing the broadband noise for engine exhaust systems using the spatially feedforward structure.
Effects of Superconducting Wiggler on the Electron Beam of the Pohang Light Source
Authors: Jinhyuk Choi Jinhyuk Choi , Eungsoo Park Eungsoo Park , Mungyung Kim Mungyung Kim , Moohyun Yoon Moohyun Yoon
Published: October 2002

A 7.5 T superconducting wiggler is expected to be installed in the storage ring of Pohang Accelerator Laboratory. In contrast to conventional multiperiod insertion devices, approximate analytic methods using the average values will not work for this single period, high-field wiggler. We divide the wiggler into very thin slices and add up the contributions from all the sections. The linear effects, radiation effects, and dynamic aperture reduction are examined and we also propose a matching mechanism.
An orthogonal Relation for Electromagnetic Fields in Two-Dimensional Multilayered Dispersive Dielectric Medium Including Evanescent Fields
Authors: Jingbo Li Jingbo Li , Masahiro Agu Masahiro Agu
Published: October 2002

A new method is developed to derive an orthogonal relation for electromagnetic fields in two-dimensional multilayered dispersive dielectric media. The orthogonal relation holds between the fields with two different wave vectors, where evanescent fields appear when the total reflection condition is satisfied at the boundary between different media. By means of the derived orthogonal relations, we show that the mode expansion of the total field energy, including evanescent waves, reduces to the sum of the energies of independent harmonic oscillators.
Micro-structure Transformation of Silicon: A Newly Developed Transformation Technology for Patterning Silicon Surfaces using the Surface Migration of Silicon Atoms by Hydrogen Annealing
Authors: Sato Tsutomu , Mitsutake Kunihiro , Mizushima Ichiro , Tsunashima Yoshitaka
Published: October 2002

The micro-structure transformation of silicon (MSTS), which is a transformation technology for patterning silicon surfaces by hydrogen annealing, is presented for the first time. The transformation was controlled by the parameters of annealing pressure as well as annealing time and temperature. Voids of sub-micrometer regime size can be intentionally formed in the silicon substrates by making use of transformation. Electrical characteristics, such as the reliability of the thin dielectrics formed in the deep trenches, were improved with the aid of the MSTS process, due to the flattening of the inside surface of the trenches and the rounding of the corners. The mechanism of the transformation by MSTS was studied by means of molecular dynamics, which clearly shows the migration of silicon atoms on the surface. MSTS is a promising technology for the fabrication of future integrated circuits in silicon.
Lateral Solid-Phase Recrystallization from the Crystal Seed Selectively Formed by Excimer Laser Annealing in Ge-Ion-Implanted Amorphous Silicon Films
Authors: Seo Jin-Wook , Akiyama Satoru , Aya Yoichiro , Nohda Tomoyuki , Hamada Hiroki , Kajiyama Kenji , Kanaya Masatoshi , Kuwano Hiroshi
Published: October 2002

A new recrystallization method improving the electrical properties of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) and reducing the fluctuation of the electrical characteristics among them is proposed. It can be realized by the amorphization of poly-Si films through Ge-ion implantation, the crystallization of the drain region, which functions as a crystal seed in the subsequent process, through excimer laser annealing (ELA), and lateral solid-phase recrystallization (LSPR) from the drain to the source along the channel through furnace annealing. In this study, basic experiments are performed to determine the optimum condition of ELA for the formation of the crystal seed with good crystallinty and to investigate the aspect of LSPR growth from the seed.
Predicted Performance of Superconductor-Insulator-Superconductor Mixers with Inhomogeneous Distributed Junction Arrays
Authors: Takeda Masanori , Noguchi Takashi , Shi Sheng-Cai
Published: October 2002

The mixing properties of a new type of distributed superconductor-insulator-superconductor (SIS) junction array, which consists of different dimensions of junctions and spacings between every two junctions, have been theoretically investigated using the quantum theory of mixing. A set of dimensions of junctions and spacings between every two junctions of the distributed junction array have been determined so as to minimize the reflection coefficient of an S-parameter, S
11, at the input port in the array using microwave computer-aided design, assuming that each SIS junction is represented by a parallel combination of linear normal-state resistance and geometrical capacitance. When the array is composed of well optimized set of dimensions of junctions and spacings between every two junctions, it is demonstrated that excellent mixing properties are attained over a broad-band in spite of the low critical current density of an SIS junction. It is also found that the degradation of mixing properties, which is always observed at certain frequencies in a conventional array with the equal dimensions of junctions and spacings, can be considerably suppressed in the array with a well optimized set of dimensions and spacings of junctions.
Design and Evaluation of Noise Suppressing Tonpilz Hydrophone Structures
Authors: Im Jong-in , Roh Yongrae
Published: October 2002

This paper describes the design and evaluation of a noise
suppressing hydrophone that is robust to external noise without
sacrificing its performance as a receiver. To increase robustness of
the receiver to the external noise, first, effects of location of the
external noise on its performance are analyzed with the finite element
method (FEM). Based on the results, geometrical variations are
implemented on the structure with additional air pockets and damping
layers that work as acoustic shields or scatterers of the noise, and
fourteen trial models are developed for the noise suppressing
hydrophone structures. Also acoustic impedance and damping
coefficients of the material inside the acoustic walls are varied and
the effects of the material property on the hydrophone response to the
external noise are analyzed. The results show that the effect of the
external noise is most significant when it is applied to near the
mid-side surface of the hydrophone housing. The external noise is
isolated most efficiently when two thin damping layers combined with
five air pockets are inserted to the circumference of the hydrophone
housing. The damping coefficients are not so influential in
de-coupling the structural vibration from the sensing element. The
optimum acoustic impedance of the damping layer is estimated to be
smaller than 1 Mrayl or larger than 4 Mrayl. These properties can not
be readily obtained from conventional polymers alone, and hence
development of new composite materials, i.e. ceramic-polymer
composite or metal-ceramic composites, is required for realization
of effective damping layers. Overall, of the fourteen structural
variations of the hydrophone, the best one shows about 87% reduction
in the response of the original structure to external noise.
Microdischarge Optical Emission Spectroscopy as a Novel Diagnostic Tool for Metalorganic Chemical Vapor Deposition of (Ba,Sr)TiO3 Films
Authors: Shun Momose Shun Momose , Toshihiro Nakamura Toshihiro Nakamura , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

Microdischarge optical emission spectroscopy (µD-OES) was developed as a diagnostic tool for analyzing chemical reactions in metalorganic chemical vapor deposition of (Ba,Sr)TiO3 films. The degree of thermal decomposition of the CVD source molecules was obtained from the observed emission spectra of the small plasma excited at the OES sensor head. According to the observation of SrII and BaII emission lines, Sr(DPM)2 and Ba(DPM)2 decompose at the gas temperatures of 270°C and 280°C, respectively. The temperature dependence of the observed emission intensity showed a behavior similar to that of the deposition rate. The oxidation of the CVD source molecules in the gas phase was also investigated by observing the change in the emission spectra due to the addition of oxygen gas. We also measured the spatial distribution of the source molecules by radially moving the OES sensor head, and compared it with the uniformity of the film thickness.
Laboratory Extreme-Ultraviolet Faraday-Rotation Apparatus Using Multilayer Polarizers
Authors: Hu Weibing , Hatano Tadashi , Watanabe Makoto
Published: October 2002

A laboratory apparatus for Faraday-rotation measurement in the extreme ultraviolet (EUV)
region (50–70 eV) has been developed, using Al/YB6 multilayers as both polarizers and
analyzers. The light source was a laser-produced plasma. A magnetic field was generated by
Sm–Co permanent magnets. The Faraday-rotation angle of 2.7° (absolute value) for a 21-nm-thick Ni film at 65.3 eV could be easily measured, coinciding well with the result using
synchrotron radiation.
A Novel He Atom Scattering Technique Complementary to Temperature Programmed Desorption
Authors: Yagyu Shinjiro , Kino Yasunobu , Yamamoto Shigehiko
Published: October 2002

We have investigated a novel method utilizing the He atom
scattering (HAS) technique which is most sensitive to surface
adsorbates, and is complementary to temperature programmed desorption
(TPD). The principle of this novel method is discussed. The novel
technique is demonstrated by monitoring the coverage of desorbing
species from a Pt(111) surface irradiated with hyperthermal ethane
molecules. The new technique will provide us with information on the
binding energy and concentration of adsorbed species at very low
coverage which cannot be obtained with the conventional TPD process.
Low-Temperature Growth of Si Oxide with Good Electrical Qualities Using Helicon-Wave-Excited O2–Ar Plasma and Forming Gas Annealing
Authors: Tatsuaki Tsukuda Tatsuaki Tsukuda , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

P-type Si(100) substrate was oxidized using helicon-wave-excited O2–Ar plasma at low temperatures. Post–thermal annealings were performed after oxidation in forming gases (FGs) containing 3% and 5% H2. The capacitance–voltage (C–V) characteristics were significantly improved by post-thermal annealing at 500°C in FG containing 3% H2, and a minimum interface state density of 1.5 ×1010 eV-1cm-2 was obtained, which was comparable to those at device-grade thermal-Si–oxide/Si interfaces. The interface-state densities was about ∼1011 eV-1cm-2 for the oxide samples post-thermally annealed in O2 ambient. The Fowler–Nordheim (FN) tunneling current is the dominant leakage current mechanism similar to that of thermal Si oxide. However, the barrier height was somewhat smaller than that of the thermal oxide. FN current stress experiments were carried out to simulate the hot-carrier injection endurance of the grown oxide film with both electrical polarities of the stress voltages. The shift of the threshold voltage was the smallest for the oxide sample post-thermally annealed in FG containing 3% H2. The results of the FN stressing could be well interpreted by the surface plasmon and avalanche breakdown models.
Decision-Directed Correction for Bloom in Optical Recording Channels
Authors: Gopalaswamy Srinivasan , Kee Ng See , Farhang-Boroujeny B.
Published: October 2002

A threshold adaptation scheme is proposed in a non-Viterbi
simple detector for d=2 minimum run-length-constraint coded
optical recording schemes, to increase robustness to bloom. The
detector has a simple structure comprising of a threshold detector,
post processing error correction, and decision directed threshold
adaptation. The equalization target is a free symmetric 7-tap target
and the detection exploits the d=2 constraint in the input
sequence. The detector is evaluated for digital versatile disk (DVD)
specifications and compared with other threshold-based detectors as
well as Viterbi detectors following targets of length up to
5. Performance improvement of over 1.5 dB is observed with the
proposed feature for bloom larger than 15% of the channel bit period.
An Experimental Model of Sled System in an Optical Disk Drive
Authors: Meng Hock Jinsong Han , Li Wenhua , Chong Chong Tow , Kok Leong Kenji Shintani , Raymond Rayaraj Raymond Rayaraj
Published: October 2002

Comprehensive experiments and analysis were conducted on SONY CD-ROM drives to derive a model of the sled system, with an emphasis on dynamic analysis of sled friction. Our study featured a novel method of friction analysis, in which all the measurements were conducted in transient period and all the calculations were transferred from the time domain to the velocity domain, and a new concept of elastic effect in sled systems, which gave a reasonable explanation of the oscillatory phenomenon in sled movement. The simulation results based on the derived model agreed well with the experimental data and repeated comparisons revealed the model's reliability. This confirmed the model's practicability in developing high-performance sled servos and track jump controllers.
Flat Intensity Lens with High Optical Efficiency and Small Spot Size for Use in Optical Disc
Authors: Tawa Fumihiro , Hasegawa Shin-ya , Futamata Akio , Uchiyama Takashi
Published: October 2002

The optical system in recordable optical discs must realize both, a smaller spot size for
high data capacity, and an increased optical power for a high data transfer rate. We have
devised a simple optical element that converts the Gaussian intensity distribution into a flat
intensity distribution by refraction without optical power loss or
aberrations.
Terminal Attractor Optical Associative Memory for Pattern Recognition
Authors: Lin Xin , Mori Masahiko , Ohtsubo Junji , Watanabe Masanobu
Published: October 2002

Optical associative memory with terminal attractor (TA) is
proposed for pattern
recognition. With numerical simulations, the optimal control parameter
in the TA model
associative memory is determined. The optimal control parameter is
also used in an
optical experiment. The capacity of TA model associative memory is
also investigated
based on the consistency between the stored pattern and the obtained
equilibrium state
in statistical thermodynamics. The results of numerical simulations
indicate that the
memory rate of the TA associative memory is greater than 0.35. We also
compare TA
model with the conventional Hopfield model, and show that the TA model
can
eliminate spurious states in the Hopfield model and increase recalling
ability and
memory capacity.
Magneto-Optical Disk for Blue Lasers
Authors: Sabi Yuichi , Kawase Kimitaka , Yamaguchi Kazunori , Ando Nobuhiko , Maeda Yasuaki , Harada Tsutomu , Kanno Masaki
Published: October 2002

We propose a new disk structure for conventional TbFeCo disks, which is suitable for blue
laser light sources, i.e., an additional thin metal layer adjacent to the TbFeCo layer. The metal
layer effectively improved a thermal characteristic of the medium, which resulted in a high
carrier level even in a relatively high readout power. Using the improved medium, high-density
recording was demonstrated in a 407 nm laser and 0.60 numerical aperture (NA) lens
system. Despite the decay of the Kerr effect and photocurrent compared to those in an MD
DATA2 red system, the new medium achieved an acceptable jitter level at a density of only
about 11% lower than that expected from the MTF scaling. This effect
was also found to be effective for a red laser with an NA 0.85 lens.
Optical Disk System Using a High-Numerical Aperture Single Objective Lens and a Blue LD
Authors: Itonaga Makoto , Chaen Shuichiro , Nakano Eiji , Nakamura Hideki , Ito Fumihiko , Iwata Kazumi , Kondo Tetsuya , Nakagawa Eiji , Kojima Takeo , Nishizawa Akira , Miyazaki Ken
Published: October 2002

An optical disk system using a blue laser diode and a single
objective lens that has a numerical aperture of 0.7, is proposed. A
sufficiently low jitter value was obtained with a read-only disk
having 17-Gbyte capacity. The paper also includes discussion on the
influence of the laser noise and RF modulation method on the
playback signal.
Near-Field Optical Recording by Reflection-Mode Near-Field Scanning Optical Microscope: Submicron-Sized Marks and Their Thermodynamic Stability
Authors: Kim Myong R. , Jhe June-Hyoung Park
Published: October 2002

About 150 nm sized marks were recorded and readout was
performed using a reflection-mode near-field scanning optical
microscope (NSOM) in the 4-layered phase-change optical disk
structure. Full-width at half-maximum (FWHM) values of the linewidth
of the marks recorded at different writing speeds decreased with
increasing writing speed. The thermodynamic stability of the
submicron-sized marks and its implications are discussed on basis of
the surface energy and its effect on the temperature of phase
transformation, including crystallization and melting.
Pretilt Angles of Vertically Aligned Nematic Liquid Crystal (NLC) with the Application of Copolymers Possessing Chalconyl and Cholesteryl Moieties
Authors: Hwang Jeoung-Yeon , Seo Dae-Shik , Son Jong Ho , Suh Dong Hack
Published: October 2002

We performed the synthesis of a new copoly (M4Ch-ChMA), copoly ((4-methacryloyloxy) chalcone-cholestery methacrylate), with chalconyl and cholesteryl moiety characteristics for photoalignment materials. Good thermal stabilities of the synthesized copolymers are confirmed by thermogravimetric analysis (TGA) measurement. The pretilt angles of the nematic liquid crystal (NLC) are reduced as UV exposure time is increased on the copolymer surfaces. A pretilt angle of 81° in NLC was observed with UV exposure of 3 min on the copolymer-3 surface. The NLCs pretilt angle is attributed to increased chalcone with increasing the UV exposure time.
High Mobility Thin Film Transistors Fabricated on a Plastic Substrate at a Processing Temperature of 110°C
Authors: Gosain Dharam Pal , Noguchi Takashi , Usui Setsuo
Published: October 2002

We present results from excimer laser processed poly-silicon
thin film transistors fabricated on a plastic substrate. Except for
the temperature rise during excimer laser irradiation for
crystallization, the highest processing temperature that the
substrate was subjected to was 110°C. Transistor field-effect
mobility of 250 cm2/V·s and sub-threshold swing of
0.16 V/decade were measured in these devices. These are the best
characteristics reported to date for a thin film transistor (TFT) on
a plastic substrate. The performance is attributed to our optimized
laser crystallization process of helium sputtered Si films,
laser-assisted low-temperature doping processes, and transient
annealing.
Interface-Treated Josephson Junctions in Trilayer Structures
Authors: Maruyama Michitaka , Yoshida Kazuhiro , Furutani Toshiki , Inagaki Yukitoshi , Horibe Masahiro , Inoue Masumi , Fujimaki Akira , Hayakawa Hisao
Published: October 2002

We have demonstrated interface-treated Josephson junctions without deposited
barriers in a trilayer structure. In the junctions, barriers were formed through an
etching process and an annealing process for base YBa2Cu3O7-x
(YBCO)
films. The junctions showed resistively-shunted-junction-type characteristics over
the entire temperature range below 70 K. A magnetic field modulation of more than
80% was observed throughout the operating temperature range. The obtained
I
c
R
n product was 2.1 mV at 4.2 K. The 1σ spreads in
the junction parameters of 10% or better were observed for eight out of nine junctions
in a chip.
Reduction of Fluctuation in Semiconductor Conductivity by One-by-One Ion Implantation of Dopant Atoms
Authors: Takahiro Shinada Takahiro Shinada , Atsuki Ishikawa Atsuki Ishikawa , Chie Hinoshita Chie Hinoshita , Meishoku Koh Meishoku Koh , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

The inherent fluctuation of electrical properties in a fine semiconductor region has been successfully reduced for the first time by implanting a small number of dopant atoms by means of single ion implantation (SII) which enables us to implant dopant ions one by one into a fine semiconductor region until the necessary number is reached. Trimming of the conductance of a fine resistor which corresponds to an active region in semiconductor devices has been tried by using the SII. Firstly the conductance increase per one dopant atom in a sub-µm scale Si resistor was measured to be 18 nS/atom. Secondly very fine test resistors with a size of sub-µm were made by conventional device fabrication technology and the statistical distribution of conductance in the test devices was obtained. Then the number of single ions necessary to trim the conductance value to a certain value in the higher side of the initial distribution was implanted to each test resistor. The initial conductance fluctuation of 63% has been reduced to only 13%.
A New Self-Fabrication of Large-Scale Deoxyribonucleic Acid Network on Mica Surfaces
Authors: Kanno Takashi , Tanaka Hiroyuki , Miyoshi Norio , Kawai Tomoji
Published: October 2002

We have successfully fabricated large-scale deoxyribonucleic acid (DNA)
networks on mica surfaces using a simple and easy fabrication method for the first
time. Sample drops of poly(dA-dT)·poly(dA-dT) which is a synthetic linear DNA
were spotted on freshly cleaved mica and blown off with air. At low DNA
concentrations, clusters of DNA molecules were separated from each other. However at
high concentrations, substrates were covered with a two-dimensional DNA network
measuring more than 12 mm laterally. The DNA network discovered in our study seems
highly practical due to its simple and easy fabrication method and its length.
We believe this DNA network has the potential to serve as a biomaterial for medical,
engineering and environmental applications.