bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Interstitial in Electron-Irradiated Si Detected by Optical Absorption Due to Hydrogen Bound to It
Authors: Suezawa Masashi
Published: October 2002

We studied the interaction between hydrogen and point defects generated by electron
irradiation of Si by means of optical absorption measurement. Specimens were prepared from
n-type Si crystals. Those specimens were doped with hydrogen by annealing in a hydrogen
atmosphere at 1200°C followed by quenching and were subsequently irradiated with 3 MV
electrons at room temperature. We observed their optical absorption spectra at about 6 K with a
resolution of 0.25 cm-1. Many optical absorption peaks were observed in electron-irradiated
specimens. Most of those peaks disappeared at around 300°C due to isochronal annealing. On the
other hand, new optical absorption lines appeared at 2223 cm-1 and 2166 cm-1 after annealing at
high temperature, namely above 150°C. The former is known to be due to a complex of one
self-interstitial atom and 4 hydrogen atoms. We propose that the 2166 cm-1 peak is due to a complex
of one self-interstitial atom and three hydrogen atoms. These results clearly show that complexes
of self-interstitials exist after electron-irradiation of Si and they dissociate above 150°C.
X-ray Penetration Depth for Large Lattice-Mismatched Heteroepitaxial Layer by Dynamical Diffraction Theory using Computer Simulation
Authors: Yoshifumi Suzuki Yoshifumi Suzuki , Dmitri Novikov Dmitri Novikov , Gerhard Materlik Gerhard Materlik , Masaaki Yoshida Masaaki Yoshida , Yoshinori Chikaura Yoshinori Chikaura , Hideki Kii Hideki Kii
Published: October 2002

Lattice-mismatched semiconductor heteroepitaxial layers give several hundred arcseconds in full width at half maximum (FWHM) of rocking curve of diffracted intensity in double-crystal diffractometry. A depth-sensitive X-ray scattering topograph of InAs layer grown by molecular beam epitaxy (MBE) on GaAs, proposed in an earlier publication [Jpn. J. Appl. Phys. 35 (1996) L1311], is confirmed by another technique, namely, asymmetric grazing incidence diffraction topography, and numerical simulation. Contrasts from a local displacement in the strain field of the matrix are different from that from diffraction indices. The surface contrast which was observed due to a local displacement in a deep region was not visible from a local displacement in a shallower region. These results are capable of explaining the previous scattering topography results.
Submicron-Size Fabrication of Bi 2Sr 2CaCu 2Ox Thin Films by Utilizing Facet Growth
Authors: Takayuki Ishibashi Takayuki Ishibashi , Toshihiro Kawahara Toshihiro Kawahara , Hisato Kaneko Hisato Kaneko , Katsuaki Sato Katsuaki Sato
Published: October 2002

Submicron-size Bi2Sr2CaCu2O
x
(BSCCO) structures of mesa patterns with dimensions of 0.5 µm × 0.5 µm × 0.07 µm and line patterns of 0.3 µm width were fabricated on patterned SrTiO3 (001) substrates. These fine structures were obtained from the growth properties of the crystal, which favor the formation of (100), (010), (110) and (110) facets. The c-axis oriented epitaxial BSCCO thin films were prepared by the molecular beam epitaxy (MBE) method on patterned SrTiO3 (001) substrates directly written by a 30 kV Ga focused ion beam.
Magnetic Sensor Using Second Harmonic Change in Magneto-Impedance Effect
Authors: Iida Satoko , Ishii Osamu , Kambe Shiro
Published: October 2002

This study reports on a magnetic sensor composed of a Cu wire sandwiched between Co-based amorphous ribbons. The impedance of the Cu wire largely depends on the permeability of the amorphous ribbons and
changes with an external field. This phenomenon results in a change in the voltage at the fundamental frequency (V
1st) and that at the second harmonic frequency (V
2nd) at both ends of the
Cu wire. The maximum V
2nd variation rate was ∼150%/Oe which is about 15 times larger than that of V
1st. The detection of the second harmonic
voltage offers the potential for a great improvement in the magnetic field sensitivity.
An Unusual Endothermic Transition to an Optically Isotropic Phase Organized by Chiral Molecular Recognition
Authors: Yoshizawa Atsushi , Umezawa Junko , Ise Noriko , Sato Rie , Soeda Yukie , Kusumoto Tetsuo , Sato Ken-ichi , Hiyama Tamejiro , Takanishi Yoichi , Takezoe Hideo
Published: October 2002

A novel chiral liquid crystal was found to exhibit an endothermic transition upon cooling from a chiral smectic C phase to an optically isotropic phase. C-13 NMR and X-ray diffraction indicate that the isotropic phase has a layered structure in which fast isotropic reorientation of molecules or molecular assemblies occurs. We suggest that molecular aggregation via chiral recognition breaks anisotropic molecular ordering, which leads to a novel phase structure.
Photo-Enhanced Activation of Hydrogen-Passivated Magnesium in P-Type GaN Films
Authors: Yoichi Kamiura Yoichi Kamiura , Yoshifumi Yamashita Yoshifumi Yamashita , Shuji Nakamura Shuji Nakamura
Published: October 2002

We studied the effect of UV-light irradiation on annealing of as-grown Mg-doped GaN films by resistivity and Hall measurements. The annealing temperature where the resistivity reduction due to the electrical activation of hydrogen-passivated Mg occurred with the increase of hole density and the decrease of hole mobility, was reduced from 550 to 450°C by the irradiation of UV light with a peak wavelength around 350 nm. This suggests that electronic excitation reduces the thermal stability of Mg-H complexes in GaN.
Novel Bonding Technology for Hermetically Sealed Silicon Micropackage
Authors: Lee Duck-Jung , Ju Byeong-Kwon , Choi Woo-Beom , Jeong Jee-Won , Lee Yun-Hi , Jang Jin , Lee Kwang-Bae , Oh Myung-Hwan
Published: October 2002

We performed glass-to-silicon bonding and fabricated a hermetically sealed silicon wafer using silicon direct bonding followed by anodic bonding (SDAB). The hydrophilized glass and silicon wafers in solution were dried and initially bonded in atmosphere as in the silicon direct bonding (SDB) process, but annealing at high temperature was not performed. Anodic bonding was subsequently carried out for the initially bonded specimens. Then the wafer pairs bonded by the SDAB method were different from those bonded by the anodic bonding process only. The effects of the bonding process on the bonded area and tensile strength were investigated as functions of bonding temperature and voltage. Using scanning electron microscopy (SEM), the cross-sectional view of the bonded interface region was observed. In order to investigate the migration of the sodium ions in the bonding process, the concentration of the bonded glass was compared with that of standard glass. The specimen bonded using the SDAB process had higher efficiency than that using the anodic bonding process only.
Cl-Assisted Selective Area Growth of InP by Metalorganic Vapor Phase Epitaxy
Authors: Tsuchiya Tomonobu
Published: October 2002

In order to further integrate optical devices, chlorine-assisted selective area growth
by metalorganic vapor phase epitaxy was investigated. By adding hydrogen chloride (HCl)
to the conventional InP growth conditions, it was found that the spike-growth at the mask
edge was suppressed, the flatness of growth plane was preserved, and an extremely high
thickness enhancement ratio of 34 was obtained. Moreover, crystalline quality was not
damaged by adding HCl. These results suggest that further integration of optical devices is
possible by using Cl-assisted selective area growth.
Electron Spin Resonance of Ultrafine Si Particles
Authors: Dohi Minoru , Yamatani Hiroshi , Fujita Tetsuo
Published: October 2002

A previously reported EX center is a new defect observed in thermal
SiO2 layer on Si. The detailed characteristics of this defect have not been
clarified yet. The present work reports on the creation, the activation
and the passivation of the EX center by thermal treatment in ultrafine Si
particles. The electron spin resonance signal of the EX centers was
emphasized by annealing in vacuum and reduced by annealing in oxygen. The
intensity of the EX signal varied reversibly with the pressure of ambient
oxygen.
Sub-THz Emission Properties of Photoconductive Antennas Excited with Multimode Laser Diode
Authors: Osamu Morikawa Osamu Morikawa , Masayoshi Tonouchi Masayoshi Tonouchi , Masahiko Tani Masahiko Tani , Kiyomi Sakai Kiyomi Sakai , Masanori Hangyo Masanori Hangyo
Published: October 2002

The spectral profiles of the continuous wave (cw) sub-THz radiation from photoconductive devices are investigated for three antennas by exciting with a multimode laser diode (LD). The spectral profile strongly depends on the antenna structure, reflecting the antenna characteristics. The emission efficiency is compared between the cw LD and femtosecond laser excitations.
The Study of Preferred Orientation Growth of Aluminum Nitride Thin Films on Ceramic and Glass Substrates
Authors: Kao H. L. , Shih P. J. , Lai Chun-Hsi
Published: October 2002

The preferred oriented aluminum nitride (AlN) films with the c-axis parallel to the surface have been grown and demonstrated on alumina and SiO2 substrates using off-axis rf sputtering. The film orientation as well as the crystallinity was found to be strongly dependent on the total sputtering pressure. Highly oriented films with c-axis parallel to the substrates can be obtained under a total pressure of 80 mTorr containing 75% nitrogen and 25% argon and a substrate temperature of 350°C. The film orientation is beneficial for the thin film surface acoustic wave (SAW) device application. The deposition process on ceramic substrates as well as the model of growth mechanism shows the possibility of incorporating the thin film SAW devices with microwave integrated circuits.
Origin of Reducing Domain Boundaries of Si(111)-7 ×7 during Homoepitaxial Growth
Authors: Kawamura Takaaki , Hibino Hiroki , Ogino Toshio
Published: October 2002

The origin of reducing out-of-phase boundaries (OPBs) of 7×7
reconstructed domains on Si(111) surfaces during homoepitaxial growth is
analyzed. Two conditions are
necessary. One is that along a step, two or more starting points of OPBs
should exist on the upper terrace in a region bounded by two adjacent
terminating points of OPBs in the lower terrace. The other is that the step
advancement in the region must be different from site to site
so that the OPBs in the upper terrace bend to coalesce with each other.
We first simulate the creation process of OPBs and then
their reducing process using the above two conditions.
The reduction process is closely related to the initial nucleation sites of
7×7 reconstruction along a step edge and to the propagation velocity
of the 7×7 reconstructed region. The reported layer coverage
dependence on the
reduction of the average distance between the OPBs is
reproduced by the simulation.
Molecular Beam Epitaxial Growth and Structures of Al/Ag Superlattices
Authors: Toshiki Kingetsu Toshiki Kingetsu , Yasuhiro Kamada Yasuhiro Kamada , Masahiko Yamamoto Masahiko Yamamoto
Published: October 2002

We studied epitaxial growth and structures of Al/Ag superlattices prepared using molecular beam epitaxy. Samples were grown at temperatures of 20, 50, 70 and 100°C, at a growth rate of 0.1 monolayers per second, on 50-nm-thick (100) Ag buffer layers preformed on (100) MgO substrates. In situ reflection high-energy electron diffraction (RHEED) during growth and ex situ X-ray diffraction were performed to analyze the growth behavior and the structures. In all samples, (100) epitaxial growth was confirmed at early stages. Moreover, RHEED intensity oscillations were observed when Al layers were grown on Ag buffer layers. However, (111)-grown domains subsequently appeared and gradually became dominant upon prolonged growth. After sixty Al/Ag bilayer depositions, all surface areas were occupied by (111)-grown domains. Persistence of (100) epitaxial growth was strongly temperature dependent; (100) growth persisted during a few tens of bilayer depositions at 50°C, while at 20 and 70°C the growth orientation changed to (111) much faster. Other features, including the structures, are also described.
Thermal Modeling of Grooved Phase Change Optical Recording Disk
Authors: Ho Jia Jun , Chong Tow Chong , Shi Lu Ping , Liu Zhe Jie , Lee Jek Chong
Published: October 2002

A new method of studying the laser induced temperature profiles of a multi-layered phase change optical disk is applied to the deep groove disk structure for the first time. The new model takes into consideration the thermal effects generated by both the incident and reflected light. Three-dimensional finite-element modelling and analyses of the new thermal model were carried out using commercial finite-element software MSC/PATRAN and ABAQUS. The calculated temperature differences between the new and the existing model are compared for grooves of depth 80 and 180 nm. Results showed that the reflected light gave rise to a significant temperature difference, especially in the deeper groove. Reduction of cross-erasure in adjacent tracks in a grooved phase change disk structure by using the deep groove method was also investigated. Findings showed that the reflected laser light gave rise to a significant temperature rise at the adjacent track.
Super-Resolution Effect of Semiconductor-Doped Glass
Authors: Nagase Toshihiko , Ashida Sumio , KatsutaroIchihara KatsutaroIchihara
Published: October 2002

Semiconductor-doped glass is proposed as a super-resolution layer for
future ultra-high-density optical disc systems. It was confirmed that this
material system showed very fast response and large transmittance change
by laser-beam irradiation when CdSSe-doped glass was used. The rise time
of the transmittance change was less than 10 ns and the transmittance
change reached 30%. These optical responses were obtained at a power
density of the pumped laser beam of 1 MW/cm2. This power density
corresponds to the readout power in digital versatile disk-read only
memory (DVD-ROM) and digital versatile disk-random access memory (DVD-RAM) discs. This
material system is regarded as a potential candidate for a super-resolution
readout layer that is applicable to both ROM and RAM discs.
Observation of Recording Marks in Phase-Change Media Using Scanning Electron Microscopy Channelling Contrast lmage
Authors: Luoh Tuung , Bow Jong-Shing , Peng Alex , Tsai Song-Yeu , Tseng Mei-Rurng
Published: October 2002

A technique for observing recording marks by SEM (scanning electron microscopy) channelling contrast imaging was proposed. In phase-change materials, the amorphous phases show less topographic change after the phase-change process, and we hard to be examined by SEM SEI (secondary electron image mode) imaging. Although these recording marks can be observed clearly by TEM (transmission electron microscopy), the TEM specimen preparation method is complicated. The SEM channelling contrast imaging technique provides an easier way to investigate the “distortion” of direct-overwrite amorphous marks in phase-change media.
Robust Focus and Tracking Detection for Holographic Digital Versatile Disc Optical Pickup-Head Modules
Authors: Freeman Mark O. , Shih Hsi-Fu , Wang Jinn-Kang , Yang Tzu-Ping , Hsu Lehan
Published: October 2002

This paper introduces a robust focus and tracking detection method for use
in holographic pickup heads. The method, which we call split-aperture servo
detection, provides the focus error signal and both differential phase detection
(DPD) and pushpull tracking signals but requires one less axis of alignment than
the commonly used quad detector with astigmatic focus detection. A set of
simulations designed according to Taguchi's method is presented comparing the manufacturability of holographic modules using the split-aperture approach and
the astigmatic approach. The split-aperture approach is seen to have strong
advantages. Experimental verification of a prototype digital versatile disc (DVD)
pickup is also presented.
Land/Groove Signal and Differential Push-Pull Signal Detection for Optical Disks by an Improved 3-Beam Method
Authors: Katayama Ryuichi , Meguro Shunichi , Komatsu Yuichi
Published: October 2002

In land/groove recording, it is necessary to detect both a land/groove signal
and a differential push-pull signal for stabilization of the tracking servo. The
former discriminates between land and groove during track pull-in operation,
while the latter compensates for offset of the tracking error signal due to shift of
the objective lens. This paper proposes an improved 3-beam method for detecting
both signals with the same beam configuration. A 4-segment diffraction grating is
employed, in which the grating patterns for two diagonal regions are π/2 out of
phase. A land/groove signal is obtained from sub-beam signals, while a
differential push-pull signal is obtained from the difference between the main
beam and sub-beam signals. Features of this method are the applicability to disks
with different track pitches and the robustness against disk eccentricity. A
land/groove signal was observed, and the compensation of the tracking error
signal offset with shift of the objective lens was confirmed experimentally. These
results have demonstrated the validity of this method.
Stoichiometric LiTaO3for Dynamic Holography in Near UV Wavelength Range
Authors: Furukawa Yasunori , Kitamura Kenji , Hatano KazuoNiwa , Bernasconi Pietro , Montemezzani Germano , Günter Peter
Published: October 2002

LiTaO3single crystals with near-stoichiometric composition are grown using a double crucible Czochralski method equipped with an automatic powder supply system. Their photorefractive properties are compared with those of LiTaO3crystals grown from the congruent composition melt. Two beam coupling experiments show that nearly stoichiometric LiTaO3crystals exhibit considerably higher photorefractive gain, speed and sensitivity than conventional congruent crystals. Due to the relatively large photoconductivity observed at near UV wavelengths, stoichiometric crystals are further characterized by small photogalvanic fields, making them very attractive for dynamic holography in this wavelength range.
Effects of Etching Time and Thickness on the Performance of the Microstrip Line Resonator of YBa2Cu3OxThin Films
Authors: Choi Jongwan , Hong Seungbum , Jun Byung-Hyuk , Sung Tae-Hyun , Park Yonggi , No Kwangsoo
Published: October 2002

Microstrip transmission lines in the form of an open-ended half-wavelength resonator were fabricated by depositing YBa2Cu3Oxthin films on MgO substrates using the pulsed laser deposition method. All YBa2Cu3Oxthin films hadc-axis orientation. The effects of etching time and thickness on the performance of the microstrip line resonator were investigated. As the etching time increased, the loaded quality factor decreased and the surface resistance increased due to the undercut and the increase in roughness of the etched surface. The quality factor and the surface resistance showed a strong dependence on the film thickness. The superconducting properties and the microwave characteristics correlated well with the microstructure.
Photorefractive Oscillation in a Thin Plate of Ce-doped BaTiO3 Crystal
Authors: Mu Xiaodong , Xu Xinguang , Lu Jianren , Shao Zongshu , Luo Haosu , Qi Zhenyi
Published: October 2002

A photorefractive oscillator in a c-cut Ce-doped BaTiO3 plate is demonstrated.
The output characters of this oscillator show that the contradirectional two-wave mixing
(CTWM) is an important interaction as well as forward two-wave mixing (FTWM).
According to the experimental results, the oscillation conditions of this oscillator and a
new method to determine the photorefractive index are presented.
Spatially Resolved Gain Measurements of a Slab Type RF Excited CO2 Laser
Authors: Matsuoka Naoya , Kutsukake Taro , Nanri ShigeruYamaguchi , Fujioka Tomoo
Published: October 2002

Spatially resolved small signal gain in a slab type radio frequency (RF) discharge
excited CO2 laser medium was analyzed in order to observe the effect of the plasma
sheath region near the slab electrodes. Choosing four lines of 10.6 µm transition such
as P(14), P(20), P(26) and P(30), we measured each gain with a resolution of 0.1 mm
using a digital beam profiling system based on a two-dimensional pyro-electric infrared
detector array. As a result, the gain was found to have a peak value of 0.4%/cm at the
center of the gap between the electrodes, which was reduced to approximately half in
the sheath region. Gas temperature (rotation temperature of CO2) was calculated to be
400 K at the center and it increased to 600 K in the sheath region.
Changes in Chemical Bondings by Li Deintercalation in LiMO2 (M=Cr, V, Co and Ni)
Authors: Koyama Yukinori , Kim Yang-Soo , Adachi IsaoTanaka
Published: October 2002

First principles molecular orbital calculations for LiMO2 and MO2 have been carried out using
the discrete variational Xα cluster method. Li in LiMO2 is nearly completely ionized. Strong
covalent interaction between M and O is noted. The removal of Li significantly increases the
interaction between M and O. This results in the “oxidation” associated with the de-intercalation not of M but of O. The formal redox notation for the de-intercalation, i.e.,
M(IV)/M(III), is thus far from reality. The difference in the de-intercalation capability among
four LiMO2 compounds is ascribed to the difference in the magnitude of electrostatic
repulsion between the oxygen layers in MO2.
Diffusion Size Effect in the Shubnikov-de Haas Oscillation of Antimony
Authors: Satoh Naoki
Published: October 2002

Transverse magnetoresistance of pure antimony was measured at 1.2 K
in magnetic fields up to 9 T in order to investigate the sample size
dependence of the Shubnikov-de Haas (SdH) effect as well as the
nonoscillatory magnetoresistance. It was found that the nonoscillatory part
of the magnetoresistance ρ
x
x
decreased in magnitude with decreasing sample
size. Also, a marked sample size dependence of the SdH oscillation amplitude
was observed. The electron-hole recombination time τeh was obtained by two
different ways, that is, it was calculated from the result of the sample size
dependence of the nonoscillatory part ρ
x
x
and from that of the SdH
oscillation amplitude. The obtained values of τeh were
3.3×10-10 s from
nonoscillatory part of ρ
x
x
, and 2.5×10-10 s from the SdH oscillation
amplitude. Those values were in good agreement with each other and were
two orders of magnitude smaller than that of bismuth, 1.5×
10-8 s.
Analyses of High Frequency Capacitance–Voltage Characteristics of Metal-Ferroelectrics-Insulator-Silicon Structure
Authors: Takeshi Kanashima Takeshi Kanashima , Masanori Okuyama Masanori Okuyama
Published: October 2002

Capacitance–voltage (C–V) characteristics of the
metal-ferroelectrics-insulator-silicon (MFIS) structure have been
calculated by the conventional metal-oxide-silicon (MOS) analysis
method. The potential profile is obtained by using the Poisson
equation of D–E hysteresis, and its capacitance is estimated as
combination of SiO2-Si capacitance and ferroelectric film
capacitance obtained from dielectric constant corresponding to the
internal field. PbZrxTi1-x
O3 (PZT) and
SrBi2Ta2O9 (SBT) ferroelectrics, SiO2, MgO, SrTiO3
(STO) and CeO2 insulators, and silicon semiconductor, were used
as independent parameters for the analyses. The dependence of MFIS
C–V characteristics on ferroelectric properties, film thickness
and impurity concentration of the semiconductor is calculated. Film
thicknesses of ferroelectrics and insulators affect the memory
window width markedly, and have to be optimized in order to obtain a
large memory window width. On the other hand, MFIS C–V
characteristics and memory window width are not influenced by P
r
because the effective P
r is small in the MFIS structure.
Shortening of Detection Time for Observation of Hot Electron Spatial Distribution by Scanning Hot Electron Microscopy
Authors: Nobutaka Kikegawa Nobutaka Kikegawa , Bingyang Zhang Bingyang Zhang , Yoshihiro Ikeda Yoshihiro Ikeda , Norio Sakai Norio Sakai , Kazuhito Furuya Kazuhito Furuya , Masahiro Asada Masahiro Asada , Masahiro Watanabe Masahiro Watanabe , Wataru Saito Wataru Saito
Published: October 2002

The scanning hot electron microscope (SHEM) is a tool to observe non-thermal- equilibrium electrons under the surface of a solid, and it enables us to study the hot electron diffraction pattern caused by a small structure in the propagation layer. To observe the hot electron spatial distribution by SHEM, the detection time must be shortened. The reduction of the noise current including vibrational noise is investigated comprehensively. By the reduction of noise, in particular, that of nonstationary noise with digital measurements, the hot electron current was detected in 30 s, 1/20 of the measurement time reported previously.
Epitaxial Growth of AlN Thin Films on Sapphire by Pulsed Laser Deposition and Effect of N2 Ambient on Crystallinity
Authors: Okamoto Mitsuo , Mori Yusuke , Sasaki Takatomo
Published: October 2002

High-quality epitaxial AlN films were grown on (0001) sapphire substrates using pulsed laser deposition from sintered AlN
targets in a nitrogen ambient. The X-ray rocking curves of the AlN(0002) peak became narrower with decreasing ambient pressure
and yielded a full-width at half maximum of 0.078°. The N/Al composition ratio increases with N2 pressure. The Al/N
composition ratio can be varied by changing the ambient N2 pressure.
Secondary Electron Emission Yield from Uranium Surface due to Uranium Ion Bombardment
Authors: Tamura Koji , Okazaki Tetsuji , Adachi Hajime , Ohba Hironori , Shibata Takemasa
Published: October 2002

We have measured the secondary electron emission yield from a uranium
surface bombarded by uranium ions from a laser ion source at impact
energies of 300–3000 eV. The uranium surface was prepared by the
deposition of uranium atoms, and the uranium ion beam was generated from
a laser ion source. Secondary electrons were not emitted under a threshold
energy of about 1000 eV. Above this threshold energy, the secondary electron
emission yield increased linearly with the impact energy, and became 0.12 at
the impact energy of 3000 eV.
Two-Dimensional Self-Consistent Simulation of a DC Magnetron Discharge
Authors: Shidoji Eiji , Ohtake Hiroto , Nakano Nobuhiko , Makabe Toshiaki
Published: October 2002

A two-dimensional simulation of dc magnetron discharge is performed by a hybrid
of fluid and particle models. In this hybrid model, ions and bulk electrons are treated by
the fluid model and fast electrons are treated by the particle model. The numerical
results indicate that the number density of the fast electrons has little effect on the
electric field distribution in dc magnetron discharge at 30 mTorr since the ratio of fast
electrons to bulk electrons is quite low. The transport of fast electrons is, however, quite
important for dc discharge because the spatial distribution of the net ionization rate is
subject to the spatial behavior of the fast electrons.
Properties of Ferroelectric Memory FET Using Sr2(Ta, Nb)2O7 Thin Film
Authors: Yoshikazu Fujimori Yoshikazu Fujimori , Takashi Nakamura Takashi Nakamura , Akira Kamisawa Akira Kamisawa
Published: October 2002

Compounds of the Sr2Nb2O7 (SNO) family are suitable for use
as ferroelectric materials for ferroelectric memory field effect transistors
(FETs),
because these substances have a low dielectric constant,
low coercive field
and high heat resistance.
C–V and I
D–V
G hysteresis curves
which depend on ferroelectric polarization were obtained.
These capacitors were applied to
floating gate ferroelectric random access memory (FFRAM) cells.
The degradation in the ferroelectricity of STN capacitors
was not observed
during the fabrication of FFRAM cells.
We succeeded in operating FFRAM cells at a lower voltage
than that required for PZT.
Data retention characteristics of metal ferroelectric metal insulator semiconductor
(MFMIS) structures with STN films
were first measured to be up to 2 weeks.
Data retention is close related to be
the leakage current of the ferroelectric.
The MFMIS FET has the potential to retain data for 10 years.
Copper Damascene Interconnection with Tungsten Silicon Nitride Diffusion Barrier Formed by Electron Cyclotron Resonance Plasma Nitridation
Authors: Hirata Akihiko , Machida Katsuyuki , Kyuragi NobuyoshiAwaya , Maeda Masahiko
Published: October 2002

This paper describes the application of tungsten silicon nitride (WSiN) formed by electron
cyclotron nitridation (ECR) plasma nitridation as a diffusion barrier for copper (Cu)
damascene interconnection. WSiN(6 nm)/WSi
x
(14 nm) multi-layer prevents Cu
diffusion well when WSiN is formed with RF bias application to the substrate. The RF
power increases the nitrogen concentration of the WSiN and enhances its amorphousness,
which lead to the improved barrier capability. WSiN can be formed inside the trench,
and the WSiN on the trench side walls prevents Cu diffusion. The use of this extremely
thin barrier metal suppresses the increase of interconnection resistivity.
Transmission Electron Microscopic Studies of TiSi2 Microstructures and the C49-C54 Phase Transformation in Narrow Lines
Authors: Okihara Masao , Tai Kaori , Harada MakikoKageyama , Hirashita Norio , Onoda Hiroshi
Published: October 2002

Transmission electron microscopy was used to study phase transformation of TiSi2 from
C49 to C54 phases. By the pre-amorphization implantation (PAI) treatment, the
metastable C49 grain size is reduced and shows heavily defective structures. In
particular, circular distributed defects surrounding a less-defective region are frequently
observed for the C49 matrix. These regions are found to have mosaic structures while
maintaining specific orientation. The results indicate two-dimensional growth of C49
from the less-defective region to the circular defective region. Furthermore,
heterogeneous nucleation of C54 is often observed at the defective regions. This
suggests local stress associated with this two-dimensional growth which enhances the
heterogeneous nucleation of C54. On the contrary, strong epitaxial relationships
between C49 grains and Si substrate are observed with high concentration in non-PAI
samples. Since these C49 grains aligned on the substrate are considered to be stable
even at relatively high temperatures, C54 nucleation sites are assumed to markedly
decrease in narrow lines.
Double Probe Characteristics of a Non-Maxwellian Plasma
Authors: Sato Masumi
Published: October 2002

The validity of the floating double probe method is investigated theoretically for plasmas of
non-Maxwellian electron energy distribution function (EEDF) using the bi-Maxwellian
distribution. A numerical procedure for depicting a double probe curve from single probe
curves is presented and the electron temperature diagnostic is examined based on the equivalent
resistance method. It is pointed out that there is a possibility of offering misleading results for
the electron temperature when using the double probe method to non-Maxwellian EEDF
plasmas, depending on the shape of the EEDF and the plasma parameters.
An Optomechanical Pressure Sensor Using Multimode Interference Couplers
Authors: Hah Dooyoung , Yoon Euisik , SongcheolHong SongcheolHong
Published: October 2002

A new optomechanical pressure sensor using multimode interference (MMI) couplers and a thin p+-Si membrane
is presented. We simulate the device characteristics by the normal mode theory considering deflection and strain
of the membrane. The optical waveguide is made of a single-mode, strip-loaded SiO2-SiN
x
-SiO2 system. Device
size can be reduced to 0.5×13 mm2 by using a MMI coupler, and the total thickness of the membrane is 5.9 µm.
The measured sensitivity is 11.98 ppm/Pa in a range of 50 kPa, which is larger than that of conventional
capacitive sensors.
Transmission X-Ray Microscopy with 50 nm Resolution Installed at Ritsumeikan Synchrotron Radiation Center
Authors: P. Kern Atsuhiko Hirai , Yasuyuki Nakayama Yasuyuki Nakayama , Hiroshi Kihara Hiroshi Kihara
Published: October 2002

A transmission X-ray microscope having two zone plates has been developed at BL-12, Ritsumeikan Synchrotron Radiation Center (Rits SR Center). By incorporating a new type of condenser zone plate (diameter 9 mm, zone number 41,890, outermost zone width 53.7 nm) in the microscope, 50 nm resolution has been obtained from both knife edge test and star test pattern at a wavelength of 3.2 nm, and for diatoms, the 0.1 µm inner structures have been clearly resolved.
Temperature Phase-Matching Properties for Harmonic Generation in GaSe
Authors: Eiko Takaoka Eiko Takaoka , Kiyoshi Kato Kiyoshi Kato
Published: October 2002

The high accuracy Sellmeier equations of GaSe were constructed from
the phase-matching conditions for harmonic generation of a CO2 laser and published refractive indices. The high accuracy
thermo-optic dispersion formula is also presented.
Holographic Optical Element with High Assembly Tolerance for the Optical Module of Digital Versatile Disc Pickup-Heads
Authors: Shih Hsi-Fu , Ju Jau-Jiu , Yau Hon-Fai , Freeman Mark O.
Published: October 2002

The astigmatic focus detection method and differential phase detection
(DPD) tracking method are now widely used in a digital versatile disk (DVD)
pickup head. The DPD tracking method requires the returning spot to remain
centered in a quad detector and therefore makes the optical alignment very
critical. In this paper, a novel holographic optical element (HOE) pattern design
to relax the alignment tolerance and achieve a stable DPD tracking servo
property is described. Simulations show that the servo signals are insensitive to
photo-detector (PD) misalignment when compared to that of a conventional
HOE design.
Cr Impurity Effect on Antiphase Boundary in FeAl Alloy
Authors: Senying Liu , Leiro Jarkko Albert
Published: October 2002

In the FeAl alloy, the electronic structures of (110) and
(121) antiphase boundaries (APBs) and the effect of Cr on them are
calculated using the recursion method. The density of states, the interaction
energy between the atoms, and the energy of APBs are presented.
On the basis of these results, the effects of Cr and APB on the physical
properties of the FeAl alloy are discussed.
The 1/f Noise Associated with Electromigration in AlSiCu Thin Films
Authors: Cheng Yu , Gong Jeng , Liou Der-Ming , Yee Hoshin
Published: October 2002

Noise measurements were performed on electromigration-damaged single-layer AlSiCu films, that show no resistance change and on multilayer AlSiCu/TiW films that show obvious resistance increase before the samples open. The experimental results showed that single-layer AlSiCu films have 1/f noise only, and no 1/f
2 noise is observed during the entire stress period. Moreover, the 1/f noise increases drastically shortly before the samples open. For multilayer samples, 1/f
2 noise was observed during the stress period, and increased with the stress current density. This result implies that the theory of resistance-drift-induced 1/f
2 noise is valid in electromigration-damaged metal thin films.
Electrical and Structural Properties of Tin-Doped Indium Oxide Films Deposited by DC Sputtering at Room Temperature
Authors: Song Pung Keun , Shigesato Yuzo , Kamei Masayuki , Yasui Itaru
Published: October 2002

Tin-doped indium oxide (ITO) films were deposited on soda-lime glass plates without
substrate heating by dc magnetron sputtering. Crystallinity and electrical properties of the
films were investigated by X-ray diffraction and Hall-effect measurements, which showed
clear dependence on target–substrate distance (T–S) and on total gas pressure (P
tot) during
deposition. Degradation in crystallinity was observed at relatively high or low P
tot, where the
upper or lower P
tot level for depositing films with high crystallinity was increased with
decreasing T–S. Based on a hard sphere collision model, the crystallinity of the films was
considered to be strongly affected both by the kinetic energy of sputtered In (or Sn) particles
and by the bombardment of high energy particles arriving at the growing film surface. The
former could enhance the crystallinity, whereas the latter degraded both the crystallinity and
conductivity. Such degradation in electrical properties was mainly due to a decrease in carrier
density.
Ultrasonic Wave Propagation in Particle Compounded Gels
Authors: Ueba Shizuko , Matsukawa Mami , TakahikoOtani TakahikoOtani
Published: October 2002

Attenuation and sound velocity in particle compounded agar were
measured by an ultrasonic wave transmission technique at frequencies
ranging from 1 MHz to 8 MHz. The observed values were discussed using
Urick's theory for viscous suspensions. The measured values of
attenuation and sound velocity were in good agreement with the
calculated values using Urick's theory up to a particle concentration
of 10%. This means that Urick's theory can be applied not only to
suspensions, but also to particle compounded gels. Furthermore, from
the investigation of the experimental results obtained using this
theory, it was clarified that the attenuation depends on the particle
density. In particular, it should be noted that n depends on the
particle diameter (the attenuation α can be expressed with the
equation α= α0
f
n, where α0 and n are constants and f is
frequency). All measured and calculated results suggested that the
acoustic properties in these kinds of particle compounded gels could be
estimated theoretically.
Numerical Consideration of the Relationship between Nonlinear Response and Shell Parameter of Microbubble with Coated Membrane Shell
Authors: Shinichi Takeuchi Shinichi Takeuchi , Kawan Soetanto Kawan Soetanto
Published: October 2002

The nonlinear response of the microbubble ultrasound contrast
agent with a coated membrane shell is studied in this paper for
development of a harmonic imaging system, which is used to detect the
harmonic components included in the waves scattered from microbubbles.
The effect of the shell parameters, dominating the mechanical
characteristics of the coating membrane, on the nonlinear response is
considered numerically in this study. It is shown that a greater shell
elasticity parameter S

p
causes an increase in the resonant
frequency of a microbubble. However, a greater shell friction parameter
S

f
causes only a slight decrease in the resonant frequency. It is also
shown that an increase in the shell elasticity and friction parameters
S

p
and S

f
causes a decrease in the harmonic component
excitation efficiency.
Reconstruction of Wide-Bandwidth Scattering Responses from Narrow-Bandwidth Ultrasound Echo in Air
Authors: Toyokatsu Miyashita Toyokatsu Miyashita , Takahiro Itaya Takahiro Itaya , Takuya Matsumoto Takuya Matsumoto
Published: October 2002

We present an experimental evaluation of high-resolution acoustic impulse
responses of structured objects in air, obtained by a new signal processing
technique.
Typical acoustic transducers in air have a high Q of 20 and a narrow
passband of 40 kHz around the resonance frequency of 200 kHz.
First we simply deconvolved an echo signal from an object with the
transfer function of the measuring system with the aid of a flat reflector.
After an adequate extraction of the deconvolved spectrum in the passband,
we extrapolated it to a wide-band spectrum from 0 Hz to 3 MHz
by a factor of 75, applying a linear prediction using an autoregressive
(AR) model and Levinson's recursive formula.
Resolution of the reconstructed impulse responses of structured objects
in air is equal to a sampling spacing Δx = 24 µm
which corresponds to a sampling frequency of 7.14 MHz,
and the range accuracy is within 5Δx.
Wide-Angle Parabolic Equation Solution of Ocean Acoustic Propagation with Lossy Penetrable Bottom
Authors: Hada Masuya , Fujii Taro , Tsuchiya Takenobu , Anada Tetsuo , Endoh Nobuyuki
Published: October 2002

Accurate and efficient analysis methods of underwater sound
propagation are essential for the development of ocean acoustic
tomography. In this paper, the outlines of the derivation of two
recently developed finite-difference parabolic equation methods
based on the higher-order Pade approximations are given to predict
the sound propagation in ocean acoustics. In order to show the
validity and usefulness of these approaches, numerical examples are
presented for the shallow water models considering the attenuation
of sound field in ocean-bottom sediment.
In Vivo Measurement of Small Velocity Signals and Change in Thickness of the Heart Walls
Authors: Kanai Hiroshi , Koiwa Yoshiro , Saito Yoshiko , Susukida Ikuko , MotonaoTanaka MotonaoTanaka
Published: October 2002

We have previously developed a new method for accurately tracking
the movement of the heart wall based on both the phase and magnitude
of the demodulated signals to determine the instantaneous position of
an object. By this method, velocity signals of the heart wall with
small amplitudes less than several micrometers on the motion
resulting from a heartbeat can be accurately detected. Moreover, the
method has been applied to multiple points preset in the heart wall
along an ultrasonic beam so that the spatial distributions of the
local change in thickness during one cardiac cycle is determined. In
this paper, the method is applied to the free wall of the right
ventricle (RV), the interventricular septum (IVS), and the posterior
wall of the left ventricle (LV). From the relationships among the
results for these parts of the heart, new findings which characterize
the velocity signals and the change in thickness in each cardiac
period are described. This method offers potential for quantitative
myocardial diagnosis.
Fundamental Study of Echo from Inside a Bone
Authors: Irie Takasuke , Ohdaira Etsuzo , Ide Masao , Itoh Kouichi , Nagai Hiroshi
Published: October 2002

In the present study, we investigate the attenuation of ultrasound in bone, using a reflex method
to detect the echo and obtain an image of the tissue inside the bone by ultrasound. In the
experiment, we developed a standard reflector, and measured the magnitude of reflected waves
before and after inserting a bone sample between the transducer and the standard reflector. From
the results of the experiment, we could determine the attenuation level of ultrasound in the tissue
inside the bone and the dynamic range required for obtaining an image. The possibility of echo
detection and obtaining an image was suggested.
Electronic Structures and Optical Properties of ZnO, SnO2 and In2O3
Authors: Yiming Mi Yiming Mi , Hidefumi Odaka Hidefumi Odaka , Shuichi Iwata Shuichi Iwata
Published: October 2002

Electronic structures and optical properties of ZnO, SnO2 and In2O3 are investigated by using a first-principles calculation method based on the density functional theory. The dielectric functions dominated by electron interband transitions are analyzed in terms of the calculated electronic band structures and charge density distributions are analyzed to clarify the chemical bonding and electrical conduction characteristics. The calculated results elucidate the similarities and disparities among these materials and also provide a guideline for manufacturing optoelectronic devices with as large a transparent region as possible.
The Raman and Infrared Spectra Depend on Oxidation in Nanometer Silicon Powder
Authors: Zuo Zuo , Jian Jian , Jia Jia , Junhui Junhui , Xu Xu , Cunyi Cunyi
Published: October 2002

Nanometer silicon powder of 10 nm scale have been prepared by
laser induced chemical vapor deposition. The Raman and infrared (IR)
spectra of the nanometer silicon powder annealed at different
temperature have been measured. The observed shifts in the Raman
spectra are ascribed to the reduction of the silicon crystallite size
by the oxidation of the surface in annealing process.
Several- and Many-Electron Artificial-Atoms at Filling Factors between 2 and 1
Authors: Austing Guy , Tokura Yasuhiro , Honda Takashi , Tarucha Seigo , Danoesastro Martin , Janssen Jorg , Oosterkamp Tjerk , Kouwenhoven Leo
Published: October 2002

We introduce new phenomena that can be studied in an artificial-atom
vertical single electron transistor. As we move from the few-electron regime to the
several-electron regime, and then the many-electron regime, features in the
conductance peaks related to magnetic field induced spin polarization evolve. This
allows us to probe the spin-flip region bounded by the last single-particle crossing
at low field, and the eventual formation of a maximum density droplet at high field.
Cross-Sectional Transmission Electron Microscope Observation of Small Structures Made by Field-Induced Scanning Tunneling Microscope Fabrication
Authors: Aoki Nobuyuki , Ochiai Yuichi , Hong Chulun , Kikutani Tomoyuki , Hori Hidenobu , Yamada Syoji
Published: October 2002

We observed cross-sectional transmission electron microscope images of small structures on a
GaAs substrate made by the scanning tunneling microscope (STM) field-induced fabrication
method. A cross-sectional image of a GaAs dot, fabricated by applying a voltage pulse to a W tip,
was 400 nm wide and had a highly symmetric double ditch structure. The inside of the dot
consisted of GaAs polycrystal and the boundary was clearly limited by specific crystal planes. If
the fabrication mechanism is considered to be field-induced evaporation in the STM regime, the
anisotropy would have arisen due to a difference in work function between each plane. We also
observed a Ni dot fabricated using a Ni-coated tip. The dot was a spherical with about a 110 nm
diameter and it consisted of Ni polycrystal. Using the tip, we could obtain only one or two Ni dots,
suggesting it behaves like a solid source rather than a liquid ion
source.
Development of a Hybrid Scanning Near-field Optical/Tunneling Microscope (SNOM/STM) System
Authors: Ken Nakajima Ken Nakajima , Ruggero Micheletto Ruggero Micheletto , Keita Mitsui Keita Mitsui , Takashi Isoshima Takashi Isoshima , Masahiko Hara Masahiko Hara , Tatsuo Wada Tatsuo Wada , Hiroyuki Sasabe Hiroyuki Sasabe , Wolfgang Knoll Wolfgang Knoll
Published: October 2002

Scanning near-field optical microscope (SNOM) is hybridized with a scanning tunneling
microscope (STM) to investigate nanoscopic optical phenomena in both the near-field region
and its proximity. The system is realized by introducing a doubly metal-coated optical fiber
tip with an extremely small aperture (<100 nm), where the metal is coated on the aperture
to obtain a half-transparent conducting tip after the fabrication of an
“aperture probe.” A simultaneous SNOM/STM observation is performed for an Au (111)
surface, where the evanescent field at the tip vicinity through the aperture is scattered
by the local structures of the sample and the far-field component of the scattered light is
collected as an optical signal. The distance control is carried out under the constant-current
condition in order to separate the optical properties from surface topography.
An optical resolution of λ/ 100 and identical channel transport for both electrons and photons
are achieved. The intensity changes, as a function of the gap distance, are also measured in the
far-field and the near-field regions and the proximity.
Effects of Rapid Thermal Annealing on Cobalt Silicided p+ poly-Si Gates Fabricated by BF2
+ Implantation into Bilayered CoSi/a-Si Films
Authors: Lai Wen-Koi , Liu Han-Wen , Juang Miin-Horng , Cheng Huang-Chung
Published: October 2002

The cobalt polycide gate formed by implanting BF2
+ ions into the bilayered CoSi/a-Si films and the subsequent rapid thermal anneal has been studied. The resulting gate
oxide integrity is characterized with respect to various silicide thicknesses and
implantation energies. Significant degradation in gate oxide integrity and flat-band
voltage shift were found with increasing silicide thickness and annealing temperature,
especially for the thicker CoSi2 films, which is attributable to severe boron penetration.
Although a thinner silicide can achieve excellent gate dielectric reliability, it will lead to
poor high-temperature thermal stability. Moreover, shallower implantation depth and
lower annealing temperature, which sustain less boron penetration, would cause the
poly-Si gate depletion effects. Therefore, appropriate conditions, which comprise the
CoSi2 thickness, the implantation energy, and the annealing temperature, should be
employed to optimize the device performance while retaining the thin dielectric reliability.