bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Moving Striations in a Low-Pressure Hg–Ar Discharge: II. Study of the Mechanism for the Occurrence
Authors: Kajiwara Toshiro , Sano Masatoshi
Published: October 2002

It is considered that moving striations appearing in a low-pressure Hg–Ar ac
discharge is caused by the steep rise of electron temperature Tt near the reignition
region due to the decrease in Hg vapor pressure.
Spectral Narrowing of Atomic Resonance by Recurrent Excitation Spectroscopy: Feedback from Atom to Radiation Field via Digital-Data Processing
Authors: Mitsui Takahisa , Kinugawa Tohru , Sakurai Katsumi
Published: October 2002

We describe the theoretical analysis and experimental detail of recurrent excitation spectroscopy (RES), which contributes to precise determination of atomic resonance frequency. The basic idea of RES lies in the iterative excitation of the atomic system by radiation. During the preceding excitation, the output field emitted from the atom is recorded in the form of digital data, and the next excitation field is generated in accordance with these data. This recurrent interaction between the atomic system and the radiation field significantly reduces the spectral width of the atomic resonance, while the signal-to-noise ratio remains sufficiently high. To reflect the actual experimental situation, we present a theoretical model in the presence of background white noise, and using this model, analytical and numerical calculations are performed. We find that RES gives a better signal-to-noise ratio compared to the conventional averaging technique until spectral narrowing is terminated. The combination of RES and the digital-data processing technique has been successfully applied to the magnetic resonance of Rb atoms in the sub-MHz region, where our theoretical findings are experimentally confirmed.
Improvement of Crystalline Quality of 3-Inch InP Wafers
Authors: Gondet S. , Duffar T. , Jacob G. , Bogaert N. Van Den , Louchet F.
Published: October 2002

The process to decrease the dislocation density in 3-inch Fe-doped InP wafers is described. The
crystal growth process is a conventional liquid encapsulated Czochralsky (LEC) but thermal
shields have been added in order to decrease the thermal gradient in the growing crystal. The shape
of these shields has been optimized with the help of numerical simulations of heat transfer and
thermomechanical stresses. This process has been performed step by step with a continuous feedback
between calculations and experiments. A 50% reduction of the thermal stress has been obtained. The
effects of these improvements on the dislocation densities have been investigated by etch pits density
(EPD) and X-ray diffraction (XRD) mapping: the dislocation density has dramatically decreased
especially in the upper part of the crystal (from 70,000 to 40,000 cm-2), therefore matching the
specifications for microelectronics applications. A same improvement has been obtained for
S-doped 3-inch wafers.
Stress-Driven Formation of InGaAs Quantum Dots on GaAs with Sub-Micron Platinum Pattern
Authors: Ho Son Maeng , K. Jung S. , Don Min Byung , Kyeong Hyun Chan , Ho Choi Bum , Kyu Kim Eun , Soo Lim Yong Kim
Published: October 2002

We study the formation of self-assembled InGaAs quantum dots on GaAs substrate with a sub-micron platinum stripe pattern. Islands or quantum dots preferentially nucleate at the boundary of metal patterns. In addition, island density reduced region near the boundary of the metal pattern is found. Those results are attributed to the stress between metal stripe and GaAs surface, which produces a laterally stressed region around the metal stripe. Adatoms on this region preferentially migrate toward the edge of metal stripes with maximum stress. This result may show a possible way for the interconnection between randomly distributed self-assembled quantum dots and metal stripes.
Increased Electrical Activity of Mg-Acceptors in AlxGa1-xN/GaN Superlattices
Authors: Kumakura Kazuhide , Kobayashi Naoki
Published: October 2002

We grew uniformly Mg-doped Al
x
Ga1-x
N/GaN superlattices (SLs) by low-pressure
metalorganic vapor phase epitaxy and investigated the electrical properties of these SLs
parallel to the SL plane. Sheet hole concentration depends strongly on the SL period thickness
and Al mole fraction, and the maximum sheet concentration is 8×1012 cm-2 for Al
x
Ga1-x
N/GaN (240 Å/120 Å) SLs in the Al mole fraction range between 0.15 and 0.3, which
corresponds to the hole concentration of 3×1018 cm-3. One possible explanation for this high
sheet hole concentration is that the strain-induced piezoelectric field greatly increases the
electrical activity of the relatively deep Mg-acceptors in the SLs.
Superconducting Critical Temperature of Overdoped LnBa2Cu3Oy+Δy (Ln=La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb)
Authors: Okai Bin , Ono Akira
Published: October 2002

A series of overdoped LnBa2Cu3O
y+Δy
(Ln=La∼Yb) was synthesized
at high oxygen pressure for investigating the relationship between the superconducting
critical temperature T
c, overdoping oxygen content Δy, and Ln. T
c
of 1-2-3 compound LnBa2Cu3O
y+Δy
remains almost unchanged through various
levels of overdoping for small ionic radii of Ln. As the ionic radus of Ln increases,
T
c decreases with the level of overdoping. The decrease changes systematically
from EuBa2Cu3O
y+Δy
to LaBa2Cu3O
y+Δy
; the decrease for
LaBa2Cu3O
y+Δy
is the steepest. T
c is also reduced probably
by the mixing of Ln and Ba, as observed in NdBa2Cu3O
y+Δy
and LaBa2Cu3O
y+Δy
.
Influence of Underlayer Magnetic Properties upon Output in Metal Particulate Double-Layered Tape
Authors: Endo Katsumi , Kobayashi Hideyuki , Yoshida Osamu , Nakayama Kazuhiko , Maki Kazuo , Nakamura Yoshihisa
Published: October 2002

To investigate the influence of the magnetic material and magnetic properties of the
underlayer on double-layered tape output, we fabricated magnetic/magnetic double-coated
metal particulate (MP) tapes with two different underlayer materials: aciculate iron (Fe)
metal powder and plane barium ferrite (Ba-ferrite) powder. The aciculate Fe underlayer
does not enhance the output, however the plane Ba-ferrite underlayer does, depending on
the perpendicular orientation of the underlayer. A more high-density medium can be
obtained using a Ba-ferrite powder oriented perpendicular to the magnetic underlayer.
Influence of Guest Conformation (Rod- or Banana-like Photo-Isomers) on Flexoelectric Coefficients in Nematic Liquid Crystals
Authors: M. Blinov Lev , Mikhail Kozlovsky Mikhail Kozlovsky , Taisuke Nagata Taisuke Nagata , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A pyroelectric technique was used for direct measurements of the flexoelectric polarization P
f in hybrid aligned nematic cells filled with a guest host mixture (4-pentyl-4′-cyanobiphenyl (5CB) doped with an azo-dye). Under UV-light excitation, the mixture manifested strong photochromism due to an almost complete conversion of the rod-shaped trans-isomers of the azobenzene moiety into long-living banana-shaped cis-isomers. The temperature dependences of P
f and, consequently, the sum of the flexoelectric coefficients (e
1+e
3) were measured in situ without and with UV illumination and the kinetics of P
f was shown to follow the kinetics of trans-cis-trans isomerization. UV light induced decrease in (e
1+e
3), that is, a negative “photo-flexoelectric effect” is accounted for by a decrease in the orientational order parameter of the mixture caused by the strongly bent cis-isomers.
Dielectric Relaxation of Glass-Forming Organic Liquid in the Crossover Regime between Normal and Supercooled Liquid States
Authors: Takuya Fujima Takuya Fujima , Hiroshi Frusawa Hiroshi Frusawa , Kohzo Ito Kohzo Ito , Reinosuke Hayakawa Reinosuke Hayakawa
Published: October 2002

Focusing on the crossover regime where the system changes from a normal liquid to a supercooled one, we investigate the dielectric relaxation of a glass-forming liquid, salol. It is found that as temperature decreases, the α-process branches into two relaxation modes in the region of the crossover temperature T
*. This suggests that the supercooled liquid consists of two domains: the cooperative-rearranging domain pointed out by light scattering studies and the independently mobile one, where the relaxation time shows a temperature dependence of the Arrhenius type with the same activation energy as that of the normal liquid.
Production of Single Decagonal Quasicrystal in Al-Co-Cu System
Authors: Junqing Guo Junqing Guo , Eiji Abe Eiji Abe , Taku J. Sato Taku J. Sato , An-Pang Tsai An-Pang Tsai
Published: October 2002

An Al-Co-Cu vertical phase diagram along the 65 at% Al isopleth was constructed with the aim of growing a single decagonal quasicrystal. The decagonal quasicrystal was formed at 1000°C via a peritectic reaction between a liquid and a cubic Al55(Co, Cu)45 phase. The decagonal quasicrystal crystallized as a primary phase for alloys with Co content less than 8.5 at% over a temperature range of 650 to 1000°C. On the basis of the phase diagram, a single decagonal quasicrystal with a composition of Al66Co17Cu17 was grown from a starting alloy of Al65Co7.5Cu27.5 by the Bridgman method.
Low-Temperature Metalorganic Vapor Phase Epitaxy (MOVPE) of GaN using Tertiarybutylhydrazine
Authors: Pohl Udo W. , Knorr Kerstin , Möller Carsten , Gernert Ulrich , Richter Wolfgang , Bläsing Jürgen , Christen Jürgen , Gottfriedsen Jochen , Schumann Herbert
Published: October 2002

Tertiarybutylhydrazine was used as a novel nitrogen source for metalorganic vapor phase
epitaxy of GaN at low temperatures. Hexagonal epilayers with optically smooth and specular
surfaces were grown with trimethylgallium on basal plane sapphire as well as GaAs(111)B
substrates. On (001)-oriented GaAs, predominantly cubic GaN was grown. Incorporation of
carbon impurities was distinctly lower than in layers grown with dimethylhydrazine. The
epilayer quality is presently limited by the purity of the available tertiarybutylhydrazine.
Preparation of Iridium Films by Liquid Source Metalorganic Chemical Vapor Deposition
Authors: Dey Sandwip K. , Goswami Jaydeb , Wang Chang-Gong , Majhi Prashant
Published: October 2002

A potentially manufacturable liquid source metalorganic chemical vapor deposition
process was successfully applied to deposit Iridium films on a variety of substrates. The
depositions of Ir were carried out in the temperature range of 300–450°C from
tetrahydrofuran (THF) solution of CH3CpIrCOD
(Cp=cyclopentadienyl, COD=cyclooctadiene) in a low-pressure, hot-wall reactor. Oxygen assisted pyrolysis of the
precursor at 350°C resulted in a remarkably high Ir growth rate of 70 nm/min on IrO
x
/Si
substrate. Additionally, Ir on Si exhibited a room-temperature resistivity of 10.2 µΩ cm.
The as-deposited polycrystalline Ir films were highly reflecting, dense, and fine grained.
Ultrathin Oxide Film Formation Using Radical Oxygen in an Ultrahigh Vacuum System
Authors: Watanabe Koji , Kimura Shigeru , Tatsumi Toru
Published: October 2002

Radical oxidation at a thickness of less than 2.0 nm in an ultrahigh vacuum system
with an electron cyclotron resonance plasma has been studied. Atomic force microscopy
and grazing-incidence X-ray reflectrometry were used to evaluate the interface roughness
and oxide density, respectively. The interface roughness at a thickness of 1.8 nm,
measured by the root mean square, was 0.11 nm. The density of the radical oxide
decreased as the oxide thickness decreased, especially at less than 2.0 nm. However, the
density of the radical oxide annealed in molecular oxygen at 5×10-3 Torr and T
sub=750°C
increased without an increase in oxide thickness.
Search for Midgap Levels in 3C-SiC Grown on Si Substrates
Authors: Yamada Noboru , Kato Masashi , Ichimura Masaya , Arai Eisuke , Tokuda Yutaka
Published: October 2002

To observe defect levels near the midgap in 3C-SiC on Si (001) substrates, deep-level-transient spectroscopy (DLTS) measurement was carried out in the temperature range of 100 K to about 500 K. A DLTS peak appeared near 150 K for all samples. The spectra of some samples showed a broad signal near room temperature. Above 450 K, no peak appeared in the spectra of any sample. This indicates that electron traps with concentration >1013 cm-3 do not exist near the midgap. Isothermal constant-voltage-capacitance transient spectroscopy (CVCTS) was also carried out at temperatures above 400 K, and its results supported this conclusion.
P-Channel Metal Oxide Semiconductor Field Effect Transistors with Polycrystalline-Si1-xGex Gate Grown by Ultra-High Vacuum Chemical Vapor Deposition System
Authors: Chen Kun-Ming , Huang Hsiang-Jen , Huang Guo-Wei , Chang Chun-Yen , Chen Liang-Po
Published: October 2002

The p-channel metal oxide semiconductor field effect transistors (MOSFETs) with P+ polycrystalline silicon-germanium (poly-Si1-x
Ge
x
) gates have been successfully fabricated. The poly-Si1-x
Ge
x
gates were grown by ultra-high vacuum chemical vapor deposition (UHVCVD) system using Si2H6 and GeH4 gases. The deposition rate of poly-Si1-x
Ge
x
increases with increasing GeH4 flow rate at small flow rate, and then decreases with increasing GeH4 flow rate. This result was explained by the competition of two growth mechanisms on poly-Si1-x
Ge
x
surface. The gate oxide layer capped with a thin nitride layer was used to prevent the damage of gate oxide from UHVCVD deposition process. The fabricated MOSFETs exhibit well-behaved characteristics.
Preparation of Giant-Grain Seed Layer for Poly-Silicon Thin-Film Solar Cells
Authors: Wen-Chang Yeh Wen-Chang Yeh , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

A silicon thin-film with giant grains has been formed on a stacked substrate
having a low melting point metallic layer and a low heat capacitance layer.
Grains as large as 17 µm could be fabricated by application of a single shot
of an excimer-laser light pulse with light intensity gradient to this structure.
This technology seems attractive for the fabrication of giant-grain poly-Si thin-film solar cells.
Deoxidization of Iridium Oxide Thin Film
Authors: Yong Cha Seon , Chul Lee Hee
Published: October 2002

Deoxidization phenomenon of iridium oxide (IrO2) film, which has been used
as a diffusion barrier for ferroelectric capacitors,
is investigated changing the temperature and oxygen pressure during the post process.
The deoxidization is well understood by explaining the relationship
between the temperature and dissociation pressure according to the thermodynamics.
A simple thermodynamic calculation for the deoxidization of IrO2 gives
a guideline for successive process condition
at which the stability of IrO2 films can be maintained.
Three-Color Polymer Light-Emitting Devices Patterned by Maskless Dye Diffusion onto Prepatterned Electrode
Authors: Kazuya Tada Kazuya Tada , Mitsuyoshi Onoda Mitsuyoshi Onoda
Published: October 2002

A simple technique of maskless dye diffusion into polymer films on prepatterned electrodes is developed and three-color polymer light-emitting devices were successfully fabricated on a glass plate. In this method, prepatterned electrodes beneath precoated receiver film are utilized as heaters for activating dye molecules. Upon doping with three types of dye, 1,1,4,4-tetraphenyl-1,3-butadiene, coumarin 6 and Nile red into poly(N-vinylcarbazole) by the present diffusion method, blue, green and red emissions were obtained. It is found that the onset voltage of emission does not depend on the type of dye. The maskless dye diffusion technique can be applicable to a variety of devices such as photovoltaic devices.
Three-Dimensional Microdrilling of Glass by Multiphoton Process and Chemical Etching
Authors: Kondo Yuki , Qiu Jianrong , Mitsuyu Tsuneo , Hirao Kazuyuki , Yoko Toshinobu
Published: October 2002

We demonstrate the three-dimensional microdrilling of glass by the multiphoton process with nonresonant femtosecond laser pulses and by the subsequent chemical etching. We use photomachinable glass which is sensitive to cw UV light of a wavelength shorter than 320 nm. After the focused irradiation of nonresonant femtosecond laser pulses at 400 nm and subsequent heat treatment, crystallites of Li2O·SiO2, which are more soluble in dilute hydrofluoric acid than matrix glass, precipitate in the focused area of the laser within the glass sample. After etching the crystallites, three-dimensional holes are formed in the glass sample. We produce straight and Y-branched holes in the glass sample. This technique can be applied to the fields of microoptics, microelectronics and microchemicals.
SiO Vapor Pressure in an SiO2 Glass/Si Melt/SiO Gas Equilibrium System
Authors: Huang Xinming , Terashima Kazutaka , Hoshikawa Keigo
Published: October 2002

SiO vapor pressure concerning Czochralski (CZ) Si crystal growth has been measured successfully by an SiO2 glass/Si melt/SiO gas equilibrium system. A Si sample was sealed in a silica ampoule after being evacuated, and the ampoule was heated to a certain temperature ranging from 1450°C to 1540°C in an Ar atmosphere. SiO vapor pressure was determined from the balance of pressure between inside and outside the ampoule. The result shows that SiO vapor pressure increases with increasing temperature. It is also found that the SiO vapor pressure shifts slightly from that calculated from thermodynamic data, especially at higher temperatures.
Negative Differential Resistance of CaF 2/CdF 2 Triple-Barrier Resonant-Tunneling Diode on Si(111) Grown by Partially Ionized Beam Epitaxy
Authors: Masahiro Watanabe Masahiro Watanabe , Yuichi Aoki Yuichi Aoki , Wataru Saito Wataru Saito , Mika Tsuganezawa Mika Tsuganezawa
Published: October 2002

Room-temperature negative differential resistance (NDR) of triple-barrier
cadmium di-fluoride (CdF2)/calcium di-fluoride (CaF2) heterostructure
resonant-tunneling diode (RTD) on a Si(111) substrate has been demonstrated.
CdF2/CaF2 multilayered heterostructures were grown on a Si(111) substrate
using partially ionized beam epitaxy to obtain atomically flat interfaces.
The RTD structures, which consist of triple CaF2 energy barriers and double
CdF2 quantum wells, were fabricated by electron beam (EB) lithography
and dry etching to avoid thermal and chemical damage to the CdF2 layers.
In the current-voltage characteristics of the RTD, NDR was clearly observed
even at room temperature and
the maximum peak-to-valley (P/V) ratio was about 6.
Activation Energy of Nanoscale 3C-SiC Island Growth on Si Substrate
Authors: Yong Sun Yong Sun , Tokihiro Ayabe Tokihiro Ayabe , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Activation energy has been evaluated for the nanoscale island growth
of 3C-SiC films deposited on (111) Si by hydrogen plasma sputtering
using a SiC target. The value of 5.6 kcal/mol obtained for the island
growth is lower than that reported for 3C-SiC film growth. After the
completion of nucleation, the SiC islands mainly grew in the diameter
direction of each island. The low activation energy is related to the
formation of an amorphous SiC phase during the growth of the island films.
High Temperature Characteristics of Nearly 1.2 µm GaInAs/GaAs/AlGaAs Lasers
Authors: Chen Zhibiao , Schlenker Dietmar , Miyamoto Tomoyuki , Kondo Takashi , Kawaguchi Masao , Koyama Fumio , Iga Kenichi
Published: October 2002

We have demonstrated a highly strained GaInAs/GaAs double quantum well laser operating at nearly
1.2 µm with AlGaAs cladding layers for the first time. Our previously reported high characteristic
temperature of 150 K was improved to 202 K for a 410-µm-long broad-area GaInAs/GaAs/AlGaAs laser
in the temperature range from 30°C to 70°C. The threshold current density of this laser was as low as
370 A/cm2.
Enhanced THz Radiation from Femtosecond Laser Pulse Irradiated InAs Clean Surface
Authors: Hideyuki Ohtake Hideyuki Ohtake , Shingo Ono Shingo Ono , Zhenlin Liu Zhenlin Liu , Nobuhiko Sarukura Nobuhiko Sarukura , Michiharu Ohta Michiharu Ohta , Kazuya Watanabe Kazuya Watanabe , Yoshiyasu Matsumoto Yoshiyasu Matsumoto
Published: October 2002

A significant enhancement of THz radiation from an InAs clean (100) surface is observed with irradiation of femtosecond laser pulses at 50 K. Due to the surface cleaning and cooling temperature, the THz-radiation intensity from the InAs clean (100) surface at 50 K becomes to 10 times larger than that from an uncleaned surface at room temperature.
Microphotoluminescence Intensity Images of InGaN Single Quantum Wells
Authors: Someya Takao , Arakawa Yasuhiko
Published: October 2002

Photoluminescence spectra and microphotoluminescence images were measured at
room temperature for an In0.06Ga0.94N single quantum well (SQW) and an In0.14Ga0.86N
SQW grown by atmospheric-pressure metalorganic chemical vapor deposition. The
spatial homogeneity of their optical properties was studied by means of a
photoluminescence intensity imaging technique of typical spatial resolution 150 nm It
is found that the microphotoluminescence images taken at different wavelengths show
very little difference for the In0.06Ga0.94N SQW, while some parts are complementary for
the In0.14Ga0.86N SQW. This result strongly suggests that the additional intensity
fluctuation which appears with increasing indium composition is due to phase
separation in the InGaN layers.
Spectral Phase-Locking in Ultrafast All-Optical Mach-Zehnder-Type Semiconductor Wavelength Converters
Authors: Ueno Yoshiyasu , Nakamura Shigeru , Tajima Kazuhito
Published: October 2002

We studied the spectrum-domain mechanism of the
delayed-interference signal-wavelength converter (DISC) analytically
and found that the role of the passive Mach-Zehnder interferometer in
this converter differs completely from that of conventional spectrum
filters: it converts the semiconductor-optical-amplifier-induced
cross-phase-modulated spectrum phase from out-of-phase to in-phase
(constant phase). This converter therefore efficiently generates
ultrashort nearly transform-limited pulses having a broad phase-locked
spectrum. These conclusions are consistent with the output pulse
shapes and spectra measured in experiments in which the wavelength of
2-ps 42-GHz pulses was converted from 1560 nm to 1553 nm.
Atomic Collimation with a Single Laser Pulse
Authors: Kajita Masatoshi , Morikawa Takao
Published: October 2002

In this letter we describe a new method of reducing one or two
components of atomic velocity using an optical dipole force. The optical
dipole force produces a harmonic potential transverse to the Gaussian optical
beam. If the initial atomic position is close to the center of the beam, the
transverse velocity component becomes almost zero after a quarter period of
harmonic oscillation. If the laser is switched off at this moment, a very
small transverse velocity component can be obtained. The use of a far-detuned
laser reduces the heating due to spontaneous scattering and enables
us to obtain a sub-photon recoil velocity component.
Intermixing Characteristics of Strained-InGaAs/InGaAsP Multiple Quantum Well Structure Using Impurity-Free Vacancy Diffusion
Authors: Park Jung Woo , Kim Hyun Soo , Kim Jung Soo , Oh Dae Kon , Oh Kwang Ryong , Yeo Duk Ho , Kim Sung June
Published: October 2002

The quantum well intermixing of a strained InGaAs/InGaAsP multiple quantum well using an impurity-free vacancy diffusion technique has been studied. The bandgap wavelength of quantum well was changed by the intermixing from 1.55 µm band to 1.3 µm band with a wavelength shift of 237 nm. The transformation from a multiple quantum well structure to a homogeneous alloy was observed. The strain-enhanced intermixing rate and self-interdiffusion rate were observed.
Role of Indium on Nitrogen Incorporation in GaNAs Grown by Metalorganic Molecular-Beam Epitaxy
Authors: Nobuki Morooka Nobuki Morooka , Katsuhiro Uesugi Katsuhiro Uesugi , Ikuo Suemune Ikuo Suemune
Published: October 2002

The role of indium on the growth surfaces of GaNAs was studied with metalorganic molecular-beam epitaxy. GaNAs was grown with and without triethylindium (TEIn) supply. High-resolution X-ray diffraction measurements reveal an increase in nitrogen incorporation in GaNAs with TEIn supply and negligible indium incorporation. This indicates that indium plays the role of a surfactant on the growth surface and enhances nitrogen incorporation in GaNAs.
Photoconductive Anisotropy in Smectic Liquid Crystalline Photoconductor, 2-(4′-Octylphenyl)-6-dodecyloxynaphthalene
Authors: Funahashi Masahiro , Hanna Jun-ichi
Published: October 2002

Photoconductive anisotropy of a liquid crystalline photoconductor, 2-(4′-octylphenyl)-6-dodecyloxynaphthalene (8-PNP-O12) exhibiting smectic B (SmB) and
smectic A (SmA) phases, was studied by steady-state and transient photocurrent
measurements for homogeneous and homeotropic alignment cells. In the steady-state
photocurrent measurement under UV light illumination, the photoconductive
anisotropic ratio, i.e., a photocurrent ratio for the homogeneous cell to the homeotropic
one, was 10 in the SmB phase and 5 in the SmA phase, in contrast to no difference in
the isotropic phase. In the transient photocurrent measurements, very small
photocurrents at a detection limit were observed in the homeotropic cells irrespective
of the mesophases, while rapid nondispersive transient photocurrents were obtained in
the homogeneous cells.
Low Threshold GaInAsP/InP Distributed Feedback Lasers with Periodic Wire Active Regions Fabricated by CH 4/H 2 Reactive Ion Etching
Authors: Nobuhiro Nunoya Nobuhiro Nunoya , Madoka Nakamura Madoka Nakamura , Hideo Yasumoto Hideo Yasumoto , Shigeo Tamura Shigeo Tamura , Shigehisa Arai Shigehisa Arai
Published: October 2002

Low damage GaInAsP/InP narrow wire structures with vertical mesa shape were realized by CH4/H2-reactive ion etching followed by a slight wet chemical etching and an embedding growth by organo-metallic vapor phase epitaxy.
By using this fabrication process, a threshold current density as low as 330 A/cm2 (66 A/cm2/well, @L=860 µm) was obtained for 1.55 µm wavelength five-quantum-well distributed feedback (DFB) laser consisting of periodic wire active regions. To our knowledge this is the lowest value reported for 1.55 µm GaInAsP/InP DFB lasers fabricated by the dry etching process.
Effects of Substrate Materials on Growth of Carbon Nanotubes by Chemical Vapor Deposition Using Metal-Phthalocyanines
Authors: Hisashi Araki Hisashi Araki , Hirotake Kajii Hirotake Kajii , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The growth of carbon nanotubes by chemical vapor deposition of metal-phthalocyanine at 700°C was examined using various substrate materials. Intense growth was observed only at the micro-defects of Ni, Fe and stainless steel foils and only at uneven sites, such as scratches and edges of Ta and W foils. Partial growth was recognized only on the rough surface of porous Si. Nanotubes grew densely on the oxidized surface of an Al plate, similar to the case of growth on a quartz plate. High-density growth was inferred to be induced at sites with lower wetting for metal vapor.
Improved Efficiency of CuInS2-Based Solar Cells without Potassium Cyanide Process
Authors: Watanabe Takayuki , Matsui Masahiro
Published: October 2002

A high open-circuit voltage (V
oc) exceeding 0.80 V was obtained by adding Ga to Na-incorporated CuInS2 thin films. Cu(In, Ga)S2 films were fabricated by sulfurization of Na-containing Cu-In-Ga precursors in H2S atmosphere. The inclining Ga profile resulted in a graded band gap. Therefore, the enhancements of cell performance by Ga addition were not only increase in Voc but also that in short-circuit current density (J
sc). We achieved an efficiency of 11.2% with V
oc=0.802 V, J
sc=20.9 mA/cm2 and FF=0.667. This is the highest efficiency reported for CuInS2 solar cells fabricated without the potassium cyanide (KCN) process.
Recharging Instability and Periodic Domain Structures in Multiple Quantum Well Infrared Photodetectors
Authors: Maxim Ryzhii Maxim Ryzhii , Victor Ryzhii Victor Ryzhii , Robert Suris Robert Suris , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

Using ensemble Monte Carlo particle modeling we demonstrate
that monotonic electric-field distributions
in multiple quantum well infrared photodetectors (QWIPs)
can be unstable. This instability can lead to oscillatory electric-field and charge
domains with a period equal to twice the QW structure period.
This effect is due to the heating of the electron gas in
continuum states resulting in a nonlocal dependence of the capture
rate on the electric field.
Improvement of Decay Properties of a Liquid Crystal Microlens with a Divided Electrode Structure
Authors: Mao Ye Mao Ye , Michinori Honma Michinori Honma , Susumu Sato Susumu Sato
Published: October 2002

Two methods to create a horizontal electric field were proposed for improvement of the turn-off operation of a liquid crystal microlens with a divided electrode structure. Using these methods, a decrease in decay or recovery time of the microlens from more than ten seconds to only several milliseconds was realized.
Capacitance Dispersion in n-LT-i-p GaAs Structures with the Low-Temperature Layers Grown at Different Temperatures
Authors: Chen Jenn-Fang , Chen Nie-Chuan , Wang Pai-Yong , Wang Jiin-Shung , Weng Chi-Ming
Published: October 2002

The electrical properties of annealed low-temperature GaAs are studied
by investigating the frequency-dependent capacitance of n-LT-i-p structures
with the low-temperature (LT) layers grown at different temperatures. Relative
to the sample grown at 610°C, the samples grown at 200, 300 and 400°C
show significant capacitance dispersions over frequency which is explained
by the emission of carriers from traps. Based on a proposed band diagram
where a dominating trap at 0.66–0.74 eV exists in the LT layers, the
high-frequency dispersion is shown to be affected by resistance-capacitance (RC)
time constant effects. From the mid-frequency capacitance versus voltage
characteristics, the concentrations of the occupied traps are estimated to be
≈1017 cm-3 for samples grown at 200, 300 and 400°C, which are found to be
consistent with those obtained from analyzing the current-voltage
characteristics of n+-LT-n+ structures.
Wide Viewing Angle and Fast Response Time Characteristics of Nematic Liquid Crystal Using Novel Vertical-Alignment-1/4π Cell Mode on Homeotropic Alignment Layer
Authors: Seo Dae-Shik , Lee Jeong-Ho
Published: October 2002

The wide viewing angle and fast response time characteristics of negative dielectric
anisotropy nematic liquid crystal (NLC) using a novel vertical-alignment (VA)-1/4π
cell mode on a homeotropic alignment layer were investigated. Good voltage-transmittance curves and low driving voltage using the novel VA-1/4π cell mode
without a negative compensation film were obtained. The iso-viewing angle
characteristics of NLC using the novel VA-1/4π cell mode without a negative
compensation film can be achieved. The fast response time of 24.4 ms in NLC was
successfully measured. The iso-viewing angle, fast response time, and low driving
voltage characteristics using the novel VA-1/4π cell mode can be achieved.
Anisotropic Molecular Orientation of Poly [4, 4'-oxydiphenylene- 1, 2, 3, 4-cyclobutanetetracarboximide] Films Irradiated by Linearly Polarized UV Light
Authors: Kenji Sakamoto Kenji Sakamoto , Kiyoaki Usami Kiyoaki Usami , Takeshi Araya Takeshi Araya , Sukekatsu Ushioda Sukekatsu Ushioda
Published: October 2002

We have investigated the anisotropic molecular orientation of poly [4,
4'-oxydiphenylene-1, 2, 3, 4-cyclobutanetetracarboximide] (CBDA-ODA)
films induced by irradiation with linearly polarized ultraviolet light
(LPUVL). The molecular orientation was monitored by measuring the
polarized infrared (IR) absorption spectra of a 10-nm-thick film. The
anisotropy of the molecular orientation exceeded that of a rubbed film
with the same film thickness. From the LPUVL exposure dependence of
IR absorption we found that preferential cleavage occurs to the
cyclobutane ring in the polyimide backbone structure oriented parallel to
the polarization direction of LPUVL. Then the orientation of the cleaved
polyimide molecule is randomized. We conclude that the large
anisotropy of the LPUVL-exposed film is caused by the anisotropic
cleavage of the cyclobutane rings and the orientational randomization of
the cleaved polyimide molecules.
Surface Vibration with a Double Period in Piezoelectric Ceramic on Stainless Steel
Authors: Seto Takatoshi
Published: October 2002

We studied a mechanical drive where a piezoelectric ceramic (lead
zircoate titanate) was deflected on a stainless-steel plate by
electric voltage application. The surface of the submicron-sized drive of the piezoelectric
was observed using an atomic force microscope. We found that for an
alternating current voltage at a frequency of 20 Hz, surface vibration of
the piezoelectric occurred at 10 Hz. The unique force conversion leading to
the doubling of the period of vibration was considered based on the
time dependence of the friction.
Regulated Epitaxy of YBa2Cu3O7-δ by Atomic Control of Step Arrays on Vicinal SrTiO3(100) Substrates
Authors: Nie Jia-Cai , Takashima Hiroshi , Terada Norio , Shoji Akira , Koyanagi Masao
Published: October 2002

We have investigated the surface morphologies of vicinal SrTiO3 substrates and
YBa2Cu3O7-δ (YBCO) thin films by atomic force microscopy (AFM). Extremely
regular step arrays had been successfully developed vicinal SrTiO3 with 5.7°
misorientation. AFM reveals a great improvement of the surface microstructures of
YBCO thin films grown on such terraced vicinal substrates, exhibiting a regular step-flow growth mode and almost precipitate-free surfaces of practical device sizes. By a
high growth rate and low growth temperature, the step bunching and therefore the
total roughness have been substantially suppressed.
Production Considerations for Europium-152 Teletherapy Sources Including Design of a Source Capsule with Intrinsic Beam-Hardening Capability
Authors: Adelman Stuart Lee
Published: October 2002

Production parameters are presented for europium-152 which suggest that teletherapy sources can be
manufactured by 60 days of irradiation at modest fluxes; e.g.,
6×1013 neutrons·cm-2·s-1. Comparisons with
cobalt-60–where irradiations lasting 1 to 3 years at fluxes from 1014 to
1015 neutrons·cm-2·s-1 are standard
practice–show that raw-isotope costs for europium-152 are below cobalt-60 by nearly two orders of
magnitude. Analysis shows that europium-152, whose limiting specific activity is much less than that of
cobalt-60, can yet be contained in quantities which deliver 1 Gy·min-1·m in comparable capsules, and
designs are proposed which incorporate depleted uranium filtration. Isotopic purity of europium-152 is
likely to be 97.5%–adequate for teletherapy.
Microscopic Investigation of Al0.43Ga0.57N on Sapphire
Authors: Kashima Takayuki , Nakamura Ryo , Iwaya Motoaki , Katoh Hisaki , Yamaguchi Shigeo , Amano Hiroshi , Akasaki Isamu
Published: October 2002

The microscopic structure of Al0.43Ga0.57N films grown on four types of structures on sapphire substrates
was investigated by transmission electron microscopy. Al0.43Ga0.57N grown on a low-temperature-deposited AlN
buffer layer is predominantly composed of small grains of about 50 to 250 nm in diameter. The crystalline quality
of Al0.43Ga0.57N grown on a high-temperature grown GaN layer is much improved. However, it generates a crack
network due to the difference of the lattice constant of Al0.43Ga0.57N and that of GaN. Critical thickness for crack
generation is as thin as 50 nm or less. The low-temperature-deposited AlN interlayer prevents crack generation
in the thick Al0.43Ga0.57N layer, while simultaneously improving the crystalline quality significantly, acting as a
dislocation filter, especially for dislocations having screw components.
A Simple and Material Independent Method for the Determination of Anchoring Properties of Rubbed Polyimide Surfaces
Authors: Acharya Bharat R. , Kim Jae-Hoon , Kumar Satyendra
Published: October 2002

A method to determine liquid crystal (LC) anchoring properties, that exploits the
changes induced in a rubbed polyimide (PI) film upon exposure to linearly polarized ultra-violet light, has been devised. The width of the Gaussian PI chain distribution
is determined from the measured rotation of the PI film's index ellipsoid, the long axis
of which is also the LC easy axis, as a function of exposure time. A quasi-microscopic
surface free energy is used to model the anchoring properties. This approach provides a
simple LC material independent method for determining the LC anchoring properties.
Fluorinated Carbon Films with Low Dielectric Constant Made from Novel Fluorocarbon Source Materials by RF Plasma Enhanced Chemical Vapor Deposition
Authors: Cristian Petrica Lungu Cristian Petrica Lungu , Ana Mihaela Lungu Ana Mihaela Lungu , Masamichi Akazawa Masamichi Akazawa , Yosuke Sakai Yosuke Sakai , Hirotake Sugawara Hirotake Sugawara , Masayoshi Tabata Masayoshi Tabata
Published: October 2002

An attempt to fabricate fluorinated carbon (fluoropolymer) films
by rf (13.56 MHz) plasma enhanced chemical vapor deposition
was made using novel fluorocarbon source materials of
C7F16, (C3F7)3N/(C4F9)3N
and C8F18/C8F16O.
The deposited films were transparent and displayed
excellent electrical properties as interlayer dielectrics
for LSI using deep-submicron technology,
namely, a dielectric constant as low as 2.0
and a dielectric strength higher than 2 MV/cm.
The refractive index of these films was 1.38.
Development of an X-Ray Interferometer for High-Resolution Phase-Contrast X-Ray Imaging
Authors: Hirano Keiichi , Momose Atsushi
Published: October 2002

An X-ray interferometer for high-resolution phase-contrast X-ray
imaging was developed by thinning the central part of the analyzer
crystal of a triple Laue-case (LLL) X-ray interferometer. The
interferometer was tested at beamline 47XU at the SPring-8, and the
improvement of the resolution of interference patterns was
successfully observed for a plastic sphere of 1 mm diameter.
Behavior of Electron Traps in Phosphidized GaAs by Nitrogen Plasma Treatment
Authors: Sugino Takashi , Nozu Satoshi , Matsuda Koichiro
Published: October 2002

GaAs is treated with remote PH3 and N2 plasmas. Electron traps induced by plasma treatments are investigated by isothermal capacitance transient spectroscopy measurements. PH3 plasma process generates the TP trap (E
C-0.26 eV), while N2 plasma process produces the TN trap (E
C-0.66 eV). It is found that the TP trap is changed to the TPN3 trap with an energy level as shallow as 0.16 eV below the conduction band edge and a capture cross section as small as 1.8×10-21 cm2 by treating with N2 plasma subsequently after PH3 plasma treatment.
Formation Mechanism of Metal-Oxides on Plasma-Exposed WSix/poly Si Gate Stacks
Authors: Liu Ziyuan , Kawashima Yoshiya , Komatsu Atsushi , Hamada Takehiko , Kawano Hideo , Shiotani Keiji
Published: October 2002

The formation mechanism of WO
x
(x=2, 3), which breaks down the insulating SiO2 layer covering of WSi
x
/poly Si gate
electrodes, has been investigated. Plasma exposure was found to introduce oxygen into the surface of WSi
x
films and caused the
WO
x
formation during the subsequent thermal oxidation. It was revealed that the oxidation product on plasma-exposed WSi
x

films depends on the grain orientation and no WO
x
was formed on c-axis oriented grains. This observation was
substantiated by growing WSi
x
films with preferred c-orientation and no evidence of WO
x
was found.
Heavily Boron-Doped Silicon Single Crystal Growth: Boron Segregation
Authors: Taishi Toshinori , Huang Xinming , Kubota Masayoshi , Kajigaya Tomio , Fukami Tatsuo , Hoshikawa Keigo
Published: October 2002

Heavily boron-doped silicon single crystals have been grown successfully by the
Czochralski (CZ) method. The limit of boron concentration in the silicon melt for
dislocation-free silicon crystal growth and segregation with heavy boron doping
were investigated. It was found that a dislocation-free silicon crystal could be
obtained even when the initial boron concentration in the silicon melt was up to
3.8×1020 atoms/cm3 with a solidified fraction of about 0.5. The lowest resistivity
of the dislocation-free B-doped silicon crystal was about 0.7 m Ω·cm. It is
confirmed that the equilibrium segregation coefficient of boron decreases from 0.8
with heavy boron doping.
Effects of Atomic Hydrogen on the Growth of GaN by RF-Molecular Beam Epitaxy
Authors: Hashiguchi Yoshihiro Okamoto , Okada Yoshitaka , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

We have studied the effects of atomic hydrogen (H) irradiation under near-optimal
GaN growth conditions.
Atomic H irradiation during GaN growth suppresses three-dimensional growth and
promotes two-dimensional growth under a slightly nitrogen-rich growth condition.
This may suggest an increase in Ga surface diffusion length.
The photoluminescence intensity of sample with atomic H irradiation (with H) grown
under an optimal condition was approximately four times as high as that of sample
without atomic H irradiation (without H), and full-widths at half maximum (FWHM)
was reduced by 13% for with H.
In addition, roughness was reduced by 42% for with H.
Thus atomic H irradiation of GaN grown under the optimal condition is effective
in improving the crystal quality of GaN.
We have also studied the change in surface reconstruction by changing the amount of atomic
H and substrate temperature.
The origin of the observed (5 × 5) reconstruction pattern is related to H adsorption on Ga atoms.
Timing Jitter Reduction of a Passively Q-Switched Laser
Authors: Huang Sheng-Lung , Tsui Tsung-Yuan , Wang Chien-Hung , Kao Fu-Jen
Published: October 2002

The timing jitter of passively Q-switched Nd:Y3Al5O12/Cr4+:Y3Al5O12 (Nd:YAG/Cr4+:YAG) laser
is studied both numerically and experimentally. It is found that spontaneous noise in the microwatt
range can significantly affect the repetition rate of high-power Q-switched lasers, and creates large
pulse-to-pulse timing jitter. External modulation on the Cr4+:YAG saturable absorber by a laser diode is
proposed to alleviate this jitter problem. Reduction in timing jitter by a factor of 2.5 is demonstrated.
High Deposition Rate of Polycrystalline Silicon Thin Films Prepared by Hot Wire Cell Method
Authors: Mitsuru Ichikawa Mitsuru Ichikawa , Jun Takeshita Jun Takeshita , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai
Published: October 2002

The hot wire (HW) cell method has been newly developed and successfully applied to grow polycrystalline silicon films at low temperatures with a relatively high growth rate of 0.9–1.1 nm/s.
In the HW cell method, mono silane (SiH4) is decomposed by reacting with a heated tungsten wire placed near the substrate.
It is found that polycrystalline silicon films can be obtained at substrate temperatures of 175–400°C without hydrogen dilution when the deposition pressure is 0.1 Torr.
Low Energy Electron Stimulated Etching of Thin Si-Oxide Layer in Nanometer Scale Using Scanning Tunneling Microscope
Authors: Nan Li Nan Li , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

With a low-energy electron stimulated reaction on Si oxide nanofabrication of thin Si-oxide layers on Si surfaces has been carried out using scanning tunneling microscope (STM). By dosing a very localized low-energy electron beam from the STM tip followed by thermal desorption, nanometer-scale windows of 50 nm on average can be cut through the Si oxide layers with a minimum size of ∼25 nm. With this method, line- and ring-window patterns were successfully formed on the Si oxide layer. E-beam exposure dependence of the window size was observed on the fabricated line windows, which indicates high controllability of the nanofabrication procedure.
Photoalignment of Nematic Liquid Crystal by Polystyrene Exposed to Linearly Polarized Deep UV Light
Authors: Masaki Hasegawa Masaki Hasegawa
Published: October 2002

We studied the photoalignment of a nematic liquid crystal (LC) by polystyrene exposed to linearly polarized deep UV light (LPDUV). The polystyrene aligned the LC parallel to its irradiated polarization axis. The retardation of the polystyrene and the order parameter of the dye used as the dopant in nematic LC increased slowly with the LPDUV dosage. The slow optical axis of the LPDUV-exposed polystyrene was perpendicular to the LPDUV axis.
Metalorganic Chemical Vapor Deposition of Epitaxial SrBi2Ta2O9 Thin Films and Their Crystal Structure
Authors: Ishikawa Katsuyuki , Nukaga Norimasa , Funakubo Hiroshi
Published: October 2002

Epitaxial SrBi2Ta2O9 (SBT) thin films were grown by metalorganic chemical vapor deposition using Bi(CH3)3–Sr[Ta(O·C2H5)6]2–O2 sources.
The SBT phase with the c-axis oriented normal to the substrate and the fluorite phase with its a-axis oriented normal to the substrate could be
deposited onto (100)SrTiO3 and (100)yttria-stabilized zirconia (YSZ) substrates at 640 and 750°C, respectively. On the other hand, the films deposited onto
(100)LaAlO3 substrates consisted of the a-axis oriented fluorite phase together with the c-axis oriented SBT phase when the deposition temperature
was greater than 640°C. These epitaxial relationships appear to be related to the crystal structure and lattice mismatch between the film and substrate.
Field Emission from an Ion-Beam-Modified Polyimide Film
Authors: Akiyoshi Baba Akiyoshi Baba , Katsuya Higa Katsuya Higa , Tanemasa Asano Tanemasa Asano
Published: October 2002

We demonstrate the field emission of electrons from an ion-beam-modified polyimide material.
A 25-µm-thick polyimide sheet is used as the starting material.
The electrical resistivity of this polyimide film is found to abruptly decrease after Ar ion irradiation at doses higher than 5×1015 cm-2.
To prepare a field emitter array, a pyramid-like structure is fabricated directly on the polyimide sheet using oxygen-plasma etching, and Ar ions are subsequently irradiated.
An emission current of the order of µA is observed at relatively low electric fields for the irradiated samples, while no emission is detected from unirradiated samples.
An emission current stability of 1.9±0.3 µA is observed.
The current-voltage characteristics of the polyimide field emitters are compared with those of a field emitter made from a photoresist.
Detection Mechanism of Spontaneous Polarization in Ferroelectric Thin Films Using Electrostatic Force Microscopy
Authors: Lee Kyongmi , Shin Hyunjung , Moon Won-Kyu , Jeon Jong Up , Pak Y. Eugene
Published: October 2002

Mechanism on the detection of spontaneous polarization in a Pb(Zr0.5Ti0.5)O3
(PZT) film using contact mode of electrostatic force microscopy (EFM) is
investigated. Theoretical calculations are performed on deflections induced by
electrostatic force (u
ω
e) between the tip and the sample and electromechanical
vibrations (u
ω
p) of the ferroelectric materials, respectively. From the calculation,
u
ω
e and u
ω
p are 3.73×10-9 and 1.77×10-13 m. Enhanced mode of EFM shows the
complete cancellation of the EFM image induced by the electrostatic force
between the tip and the film through controlling dc voltage. Hence, electrostatic
force effect is a main contributor on the detection mechanism of spontaneous
polarization using EFM in contact mode.
Intense-Heavy-Ion-Beam Transport through an Insulator Beam Guide
Authors: Takashi Kikuchi Takashi Kikuchi , Shigeo Kawata Shigeo Kawata , Shigeru Kato Shigeru Kato , Susumu Hanamori Susumu Hanamori , Masaru Yazawa Masaru Yazawa
Published: October 2002

In this study, we investigate an intense-heavy-ion-beam transport through an insulator beam guide by numerical simulation. In our previous papers [Jpn. J. Appl. Phys. 35 (1996) L1127, Jpn. J. Appl. Phys. 37 (1998) L471], we proposed a new system for electron and proton beam transport using an insulator beam guide. We apply this system to a singly charged cesium (Cs+) ion beam transport. An intense Cs+ ion beam generates a plasma on the insulator surface. Electrons are extracted from the plasma, and the beam charge is effectively neutralized by the electrons. Electron extraction is self-regulated by the net space charge of the beam. Consequently, an intense Cs+ ion beam can be efficiently transported by the proposed system.