bluuebunny/crossref_metadata_2025 huggingface dataset:
Piezoelectric Properties of SrBi4Ti4O15-Based Ceramics
Authors: Hirose Masakazu , Suzuki Toshiyuki , Oka Hitoshi , Itakura Keisuke , Miyauchi Yasuharu , Tsukada Takeo
Published: October 2002

Piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT)
based ceramics, were studied. By means of La substitution and Mn addition, the
maximum value of Q (Q
max
) between resonant frequency and anti-resonant frequency was
larger than that of SBT. These materials could be utilized in practical applications
as
substitutes for lead titanate based ceramics (PT) and lead zirconate titanate based
ceramics (PZT) which are used mainly in resonators. The reason for the higher Q
max

value was identified by microstructual analysis as being due to the absence of a defect
structure.
Dielectric and Piezoelectric Properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3 Systems
Authors: Sasaki Atsushi , Chiba Tatsuya , Mamiya Youichi , Otsuki Etsuo
Published: October 2002

The structural, dielectric and piezoelectric properties of
[Bi0.5(Na1-X
K
X
)0.5]TiO3 ceramics were studied for the compositional range, X=0–1.0. The samples were prepared by a
conventional sintering technique. From X-ray diffraction results, it was found that the
morphotropic phase boundary (MPB) between (Bi0.5Na0.5)TiO3 (rhombohedral) and
(Bi0.5K0.5)TiO3 (tetragonal) exists in the range of X=0.16–0.20. Polarization-Electric field
hysteresis loops show that the remanent polarization at X=0.20 (BNTK20) is larger than that at
X=0.0 (BNT). Peaks of electromechanical coupling factor, dielectric constant, piezoelectric
constant and elastic compliance were obtained at X=0.16–0.20 of the MPB region. Dielectric
and piezoelectric properties are enhanced in the MPB region for [Bi0.5(Na1-X
K
X
)0.5]TiO3, similar
to that observed for Pb(Zr, Ti)O3.
Lamb Wave Propagation Characteristics and Transducer Performances in Layered Substrate Composed of Piezoelectric Thin Plate and Glass Thin Plate
Authors: Kohji Toda Kohji Toda , Masaru Inoue Masaru Inoue
Published: October 2002

In a layered substrate composed of a piezoelectric ceramic thin plate
and a glass thin plate, Lamb wave propagation characteristics and
operation performances of an interdigital transducer (IDT) are
described.
The numerical analysis results of Lamb wave phase velocities in the form
of a function of the product of the frequency and the thickness of the
piezoelectric ceramic plate are in good agreement with the measured
velocities for various thickness ratios of the two plates used as layered
substrates.
The electromechanical coupling constant k
2 of the IDT on the layered
substrate reaches a peak value when the velocity of the respective Lamb
wave mode is almost equal to the phase velocity of the zeroth-order
symmetrical mode at f
d=0.
The above condition for the highest k
2 value has been experimentally
confirmed for two types of layer-structured devices: the double-layer-type
and the separation-type.
Effects of Vibration Stress and Temperature on the Characteristics of Piezoelectric Ceramics under High Vibration Amplitude Levels Measured by Electrical Transient Responses
Authors: Umeda Mikio , Nakamura Kentaro , Ueha Sadayuki
Published: October 2002

This paper presents a characteristic evaluation of piezoelectric ceramics at high vibration amplitude levels of resonance, based on the electrical transient response technique. Low-Q and high-Q materials are measured, and the effect of vibration stress is obtained without affecting temperature. It is revealed that for low-Q materials an increase of loss is caused mainly by the vibration stress, while for high-Q materials, it is caused by both the vibration stress and the temperature increase. The results show that in some high-Q materials, it is meaningless to evaluate the piezoelectric materials at low vibration level, since the characteristics change variously at high vibration levels. The force factor is changed mainly by the temperature, although its behavior is different, depending on material composition.
Temperature Characteristic Compensation of a Miniature Bi-Axial Gyro-Sensor Using a Disk-Type Resonator
Authors: Shiratori Norihiko , Hatakeyama Minoru , Okada Shigeya
Published: October 2002

One of the authors has already reported a new type of miniature bi-axial gyro-sensor with a disk-type resonator. The gyro-sensor was used to detect bi-axial
signals and therefore consisted of a quadrant-electrode-piezoelectric ceramics
(PZT) disk and a globular weight, bonded and placed, respectively, on each surface
of a metal disk. When an angular rate at right angles to the vibration was added
to the sensor, Coriolis force was applied to give a deflective motion to the globular
weight. Therefore, the sensor could detect bi-axial angular rates simultaneously.
However, in this condition, the sensor did not have good temperature
characteristics of sensitivity; the difference between the resonance frequencies of
the two modes used was changed by the ambient temperature. In order to improve
the temperature characteristics of resonance frequencies of the two modes, we
studied the frequency compensation circuit for the driving mode. Moreover, we
developed a voltage corrective circuit to achieve stable temperature
characteristics of driving voltage. When applying the two compensation methods,
the temperature characteristics of sensitivity showed changes of only -15 to 5%
over the temperature range of -10°C to 80°C. This characteristic satisfied the
general specifications for video cameras.
Presentation of a New Equivalent Circuit of a Piezoelectric Transformer under High-Power Operation
Authors: Sakurai Katsutoshi , Ohnishi Kazumasa , Tomikawa Yoshiro
Published: October 2002

In this paper, the power transmission characteristics of a piezoelectric transformer are considered. As a result, the following has been clarified: the frequency
of the maximum step-up voltage ratio coincided with the resonance
frequency, and
the frequency of maximum efficiency approximately coincided with the intermediate frequency between the resonance and anti-resonance frequencies. However, conventional equivalent circuits cannot represent these phenomena. In this paper,
we have proposed an improved equivalent circuit that was useful for presenting
the tendency of the experimental results. The specific future of this circuit is that
the series and parallel resistances that present high-power operation loss are included. The method used to derive the proposed equivalent circuit is described
and some experimental and calculated results are shown.
Preparation and Microwave Characterization of BaxSr1-xTiO3 Ceramics
Authors: Wu Long , Chen Yih-Chien , Chen Li-Jen , Chou Yi-Ping , Tsai Yuan-Tu
Published: October 2002

Ba
x
Sr1-x
TiO3 ceramics have been synthesized by a conventional
solid-state reaction for x=0.2, 0.4, 0.6, 0.8. The phase constitution
was examined by X-ray diffraction. The microwave dielectric properties
of Ba
x
Sr1-x
TiO3, such as the real part of the relative dielectric
constant and loss factor, were measured by the postresonator method on
the TE011 resonant mode for the different compositions. The real part
of the relative dielectric constant varies from 200 to 900, with a
loss factor from 10-3 to 10-2 at a resonant frequency of approximated 2 GHz.
Microwave Dielectric Properties of Ba4(Nd28/3-yRy)Ti18O54 (R = Eu, Dy, Ho, Er and Yb) Solid Solutions
Authors: Hitoshi Ohsato Hitoshi Ohsato , Junichi Sugino Junichi Sugino , Atsushi Komura Atsushi Komura , Susumu Nishigaki Susumu Nishigaki , Takashi Okuda Takashi Okuda
Published: October 2002

We have investigated the formation and the microwave dielectric properties of the
Ba4(Nd28/3-y
 R
y)Ti18O54 (R = Eu, Dy, Ho, Er and Yb) solid solutions in which R ions are substituted for Nd ions in Ba6-3x
Nd8+2x
Ti18O54 solid solutions with x=2/3.
Based on the change of the volume of the unit cell, it was inferred that Eu, Dy, Ho and Er ions substituted into rhombic A1-sites, but Yb ions did smaller sites such as B-sites and C-sites after substituting A1-sites.
The quality factor (Q·f) improved as the ionic radius of substituted
R ions increased. In the Eu series, the best Q·f value of 10405 GHz was obtained.
The temperature coefficients of the reasonant frequency (τ
f
) in the Dy, Ho and Er series were improved by more than 50%, but the dielectric constant (ε

r
) showed only a nominal change of about 3–4 in the vicinity of 80.
Generation of Forward Phase-Conjugate Beam by Cu:KNSBN-Cat Type Self-Pumped Phase-Conjugator
Authors: Doi Masato , Sasaki Akira , Iwata Futoshi , Zheng Yujin
Published: October 2002

A forward phase-conjugate beam was generated using a copper-doped
(K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 (Cu:KNSBN) crystal with Cat type self-pumped phase-conjugator incident geometry. This Cat self-pumped phase-conjugator was formed
simply with a small incident beam diameter of 0.4 mm at an incidence angle of 30°. In
this configuration, the forward phase-conjugate beam could be generated at the same
time with the self-pumped phase-conjugate beam. Furthermore, it was possible to
generate the forward phase-conjugate beam while maintaining the high reflectivity of
the self-pumped phase-conjugate beam. A forward phase-conjugate reflectivity of 0.9%
was achieved at a self-pumped phase-conjugate reflectivity of 12%.
Pockels Effects of Polyurea-5 Film Prepared by Vapor-Deposition Polymerization
Authors: Tajitsu Yoshiro , Date Munehiro , Fukada Eiichi
Published: October 2002

In order to investigate the ferroelectric properties of
polyurea-5 prepared by vapor-deposition polymerization in comparison
with those of polyvinylidene fluoride (PVDF) and copolymers of
vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)), the
residual polarization P
r, the piezoelectric constant e
31 and the
Pockels effects were measured. As a result, the P
r values of
polyurea-5, PVDF, and P(VDF/TrFE) were obtained as 20 mC/m2, 60 mC/m2
and 100 mC/m2, respectively. On the other hand, polyurea-5, PVDF and
P(VDF/TrFE) showed e
31 of 5 mC/m2, 60 mC/m2 and 100 mC/m2, respectively. We obtained P
r∼e
31 in the case of P(VDF/TrFE) and PVDF. In the case
of P(VDF/TrFE) and PVDF, P
r∼e
31 has been reported by many researchers.
However, in the case of polyurea-5, P
r>e
31 was obtained. The e
31 of
polyurea-5 is about 1/20 that of P(VDF/TrFE). Also, to measure the
Pockels effects of polyurea-5 films, a laser beam was introduced
parallel and perpendicular to the thickness of the polyurea-5 film
which was poled at room temperature. As a result, the Pockels
coefficient of the polyurea-5 film was obatined to be 0.09 pm/V, which
was approximately 1/4 that of PVDF or P(VDF/TrFE) films; however, this
value is fairly large for polymers.
Monostabilization of Surface-Stabilized Ferroelectric Liquid Crystal Using Polymer Stabilization
Authors: Kobayashi Hirokazu Furue
Published: October 2002

Surface-stabilized ferroelectric liquid crystals (SSFLCs) fabricated by adopting polymer stabilization in terms of the UV photocure of doped photocurable monoacrylates with mesogenic side chains at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a monopolar electric field, exhibit monostable electrooptical characteristics with grayscale capability without threshold. We suggest a model for explaining the monostability of this polymer-stabilized SSFLC by investigating theoretically the free energy of the SSFLC before and after the photocure.
Theory of Morphotropic Phase Boundary in Solid Solution Systems of Perovskite-Type Oxide Ferroelectrics: p-e Hysteresis Loop
Authors: Iwata Makoto , Ishibashi Yoshihiro
Published: October 2002

The p-e hysteresis loop near the morphotropic phase boundary in the
perovskite-type oxide solid solution system is discussed on the basis of a Landau-type free energy function. It was found that the coercive field in the p-e
hysteresis loop decreases upon approaching the morphotropic phase boundary and
vanishes at the morphotropic phase boundary, because of the instability in the
direction perpendicular to the polarization.
Blue Luminescence from Photochemically Etched Silicon
Authors: Yamamoto Naokatsu , Takai Hiroshi
Published: October 2002

Light-emitting layers are formed by the photochemical etching of Si in
HF with H2O2 as an oxidant under the irradiation of a He–Ne laser (633 nm, 18.4 W/cm2). Photoluminescence (PL) using a He–Cd laser (325 nm) from the etched layer has a peak wavelength at 640 nm and a wide full-width at half maximum
(FWHM) of approximately 0.3 eV. The peak position and the wide FWHM
from the etched layer are considered to be similar to those from
porous silicon. The PL peak wavelength can be varied from 700 nm to 640 nm by increasing the etching
time, so that red or yellow luminescence can be observed in daylight. The
etched layer formed with H2O2 emits blue photoluminescence at 440 nm after being dipped in an ethanol for 17 h, and the blue light emission can be seen in air. The visible luminescence of the photochemically etched layers can be explained by the well-known quantum size effect of nanocrystalline Si.
Ultraviolet InGaN and GaN Single-Quantum-Well-Structure Light-Emitting Diodes Grown on Epitaxially Laterally Overgrown GaN Substrates
Authors: Mukai Takashi , Nakamura Shuji
Published: October 2002

Ultraviolet (UV) InGaN and GaN single-quantum-well-structure light-emitting diodes (LEDs) were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. When the emission wavelength of UV InGaN LEDs was shorter than 380 nm, the external quantum efficiency (EQE) of the LED on ELOG was much higher than that on sapphire only under high-current operation. At low-current operation, both LEDs had the same EQE. When the active layer was GaN, EQE of the LED on sapphire was much lower than that on ELOG even under low-and high-current operations, due to the lack of localized energy states formed by alloy composition fluctuations. When the emission wavelengths were in the blue and green regions, EQE was almost the same between LEDs on both ELOG and sapphire due to a large number of deep localized energy states formed by large alloy composition fluctuations. The localized energy states are responsible for the high efficiency of InGaN-based LEDs in spite of a large number of dislocations.
Dependence of Contact Resistance on Substrate Doping and Impact of Mixed Ion Implantation
Authors: Kwang Park Yeon-Cheol Heo , Gook Park Jeong-Ho Lee , Duk Lee Jong
Published: October 2002

The dependence of contact resistance (R
C), especially metal contact on p+-Si, has been investigated with several processes such as the etching of contact hole and the doping of junction region. In order to obtain highly reliable contact characteristics in deep submicron devices, it is found that the oxide etching process with high selectivity to silicon and the high surface doping concentration in contact open area are required. The R
C can be reduced about 50% by adopting high selectivity etching process. High surface concentration made by BF2 and B mixed implantation shows 20% reduction of R
C, while plug implantation can improve R
C by 50%. Optimized doping profile combined with high etch selectivity is indispensable for low R
C, because substrate loss is unavoidable. These results are also confirmed by process simulation using the measured parameters such as the contact depth by TEM and the doping profile by SIMS.
The Effects of Cu Diffusion in Cu/TiN/SiO2/Si Capacitors
Authors: Mi-Young Kwak Mi-Young Kwak , Dong-Hyuk Shin Dong-Hyuk Shin , Tae-Won Kang Tae-Won Kang , Ki-Nam Kim Ki-Nam Kim
Published: October 2002

The effects of Cu diffusion in Cu/TiN/SiO2/Si structures have been evaluated by capacitance–voltage (C–V) measurements. The capacitors were annealed at temperatures between 500°C and 900°C for 1h and were stressed at 250°C for 1 h with positive or negative electric fields of 0.4–1.0 MV/cm. High frequency C–V characteristics of the annealed capacitors were measured before and after bias temperature stress treatment. The device failure due to Cu diffusing into Si substrate was not observed to occur by annealing of up to 700°C for 1 h.
Contact and Space-Charge Effects in Quantum Well Infrared Photodetectors
Authors: Victor Ryzhii Victor Ryzhii , H. C. Liu H. C. Liu
Published: October 2002

We present the results of a new self-consistent analytical model for the calculation of the dark current and the electric-field and space-charge distributions in quantum well infrared photodetectors (QWIPs). This model takes into account thermionic emission from the QWs, tunneling injection of electrons from the emitter contact, transport of the excited and injected electrons across an active region of a QWIP and their capture into the QWs. It is shown that the electric-field and space-charge distributions in the QW structure are nonuniform in general. The character of their nonuniformity is determined by the relationships between the structural parameters, parameters of elementary processes, and bias voltage.
Role of O2 in Aluminum Etching with BCl3/Cl2/O2 Plasma in High Density Plasma Reactor
Authors: Baek Kye Hyun , Park Changwook , Lee Won Gyu
Published: October 2002

Role of O2 in aluminum etching process using BCl3/Cl2/O2 plasma was investigated in inductively coupled plasma (ICP) etching system. Optical emission spectroscopy (OES) of BCl3/Cl2/O2 plasmas shows that reaction between oxygen and boron chloride occurs in the presence of O2. This reaction seems to result in increase of aluminum etchant chlorine radicals and generation of B
x
O
y
species. Increase of chlorine radicals may play role to enhance aluminum etch rate at relatively low O2
concentration (≤6%). As the concentration of O2 increased, local etch stop of aluminum was observed along the aluminum grain boundary at 9% O2 and it was extended to cause etch stop on all exposed surface at 15% O2. Two possible causes of etch stop (i.e. deposition of reaction byproduct B
x
O
y
species and surface oxidation of aluminum) were postulated and examined. Investigation of these possibilities shows that the major cause of etch retardation, in the presence of O2, is surface oxidation of aluminum rather than the formation of inhibitor layer via the deposition of B
x
O
y

species.
Single-Electron Memory Fabricated from Doped Silicon-on-Insulator Film
Authors: Toshitsugu Sakamoto Toshitsugu Sakamoto , Hisao Kawaura Hisao Kawaura , Toshio Baba Toshio Baba
Published: October 2002

We investigated a memory device that uses a single-electron transistor as the read-out component and a Si floating dot as the memory node. The device was fabricated from highly-doped silicon-on-insulator (SOI) film by using electron-beam lithography and a high-resolution resist (calixarene). We observed the charging and discharging of the floating dot and determined that the memory operation was not affected by the background charge, which is crucial for single-electron devices.
Structural and Electrical Recovery of YBa2Cu3Ox that Absorbed Water by Heat Treatment
Authors: Edo Shoichi , Takama Toshihiko
Published: October 2002

The YBa2Cu3O6.4 superconductor transforms to a
normal conductor with a long lattice spacing of about 13 Å by
annealing at around 200°C in water vapor. Heating the normal
conductor to a higher temperature led to the recovery of its structure
and superconductivity. The recovery process was investigated by means
of powder X-ray diffraction, ac magnetic susceptibility,
thermogravimetry and differential scanning calorimetry
measurements. The heat flow with an endothermic peak at 260°C
and the weight loss during heating revealed that the recovery is
caused by desorption of water.
Non-c-axis-Oriented EuBa2Cu3O7-δ Thin Films Grown on Al2O3(11̄02) Substrates with CeO2 Buffer Layers
Authors: Hironori Wakana Hironori Wakana , Atsushi Yokosawa Atsushi Yokosawa , Osamu Michikami Osamu Michikami
Published: October 2002

EuBa2Cu3O7-δ (EBCO) thin films with different growth orientations were prepared on Al2O3(11̄02) substrates with CeO2 buffer layers by dc magnetron sputtering. The EBCO thin films were deposited immediately after off-axis rf magnetron sputtering of CeO2(001) films. The effects of substrate temperature and oxygen concent on epitaxial orientation of EBCO thin films were examined. With the increase in oxygen concentration, the surface roughness of an EBCO thin film increased. An appropriate oxygen concentration existed. It was clarified that the orientation of an EBCO thin film depended on CeO2 film thickness. The (100)- and (110)-oriented EBCO thin films were obtained on CeO2 buffer layers 30–90 Å thick and more than 700 Å thick, respectively. The (100)- and (110)-oriented EBCO films had in-plane epitaxial orientation relationships of Al2O3[11̄20] ∥CeO2[100] ∥EBCO[013] and Al2O3[112̄0] ∥CeO2[100] ∥EBCO[11̄0], respectively. The (100)-oriented EBCO films deposited on 50-Å-thick CeO2 (001) buffer layers had T
ce's of 72.0 K, and (110)-oriented EBCO films deposited on 750-Å-thick CeO2(001) buffer layers had T
ce's of 70.0 K. The T
ce decreased with increasing CeO2 buffer layer thickness above 800 Å. The a-axis-oriented EBCO thin films exhibited T
ce's of about 85.4 K on the 50-Å-thick CeO2 buffer layers prepared by a self-template method.
Rapid Preparation of High-Tc Superconductors of the Bi-2212 Phase Using a Domestic Microwave Oven
Authors: Masatsune Kato Masatsune Kato , Kenji Sakakibara Kenji Sakakibara , Yoji Koike Yoji Koike
Published: October 2002

Single-phase samples of high-T
c superconductors of the Bi-2212 phase have been prepared using a domestic microwave oven. It is to be important for the preparation to control the temperature of the sample environment and to repeat the microwave-radiation process with intermediate grinding, because the Bi-2212 phase is stable only in a narrow temperature range and requires a long heat-treatment time for formation. The partial substitution of Pb for Bi is also to be effective for the formation of the Bi-2212 phase.
Weakly Index Guided Buried-Stripe Type 980 nm Laser Diodes Grown by a Combination of Gas Source Molecular Beam Epitaxy and Metalorganic Vapor Phase Epitaxy with an AlGaAs/InGaP/GaAs Double Etch Stop Structure
Authors: Horie Hideyoshi , Nagao Satoru , Shimoyama Kenji , Fujimori Toshinari
Published: October 2002

In order to fabricate weakly index guided buried-stripe type 980 nm laser diodes (LDs)
precisely and reproducibly, we have developed a novel double etch stop (DES) structure
which consists of AlGaAs/InGaP/GaAs layers. By employing the DES structure, an
effective refractive index step (Δn
eff) of 3.6×10-3 and a waveguide bottom width (W
b) of
2.2 µm were realized to maintain a stable transverse mode. The LDs were fabricated by
a combination of gas-source molecular beam epitaxy (GS-MBE) and metalorganic vapor
phase epitaxy (MOVPE) on a 2-inch wafer and showed uniformly high performance,
especially in the region within a 15.5 mm radius from the center. A high kink level of
315±15 mW was achieved. Considering wafer uniformity, we estimated that Δn
eff and
W
b should be controlled to about 3.6×10-3±
3.5×10-4 and 2.22±0.06 µm, respectively,
under the condition of a vertical optical confinement factor
\varGamma\fallingdotseq1.16%/well. We have
also confirmed the high quality of the entire process, including the DES method, by
employing a reliability test at 200 mW light output power up to
2500 h.
Effect of Surface Termination on the Electronic States in Nanocrystalline Porous Silicon
Authors: Matsumoto Takahiro , Arata Goh , Nair Selvakumar V. , Masumoto Yasuaki
Published: October 2002

We report comparative studies of hydrogen-(H-PS) and deuterium-terminated porous Si (D-PS) nanostructures fabricated by electrochemical anodization with photochemical etching treatment. Experimental results show that the photochemical etching treatment can cause a blueshift of both the absorption and the photoluminescence of PS. However, D-PS shows a higher emission energy than H-PS in spite of the nanometer structure and the band gap energy being the same for both PS samples. These results can be understood by considering both the band gap upshift due to the quantum size effect and the energy reduction due to the coupling of the confined carriers to the surface vibration of terminated atoms on nanocrystals. Based on a tight-binding calculation, we argue that the difference of the emission energy can be understood in terms of the trapping of conduction electrons at the surface Si-H or Si-D bonds.
The Microwave Dielectric Properties and the Microstructures of Bi(Nb, Ta)O4 Ceramics
Authors: Huang Cheng-Liang , Weng Min-Hung
Published: October 2002

The microwave dielectric properties and the microstructures of
(1-x)BiNbO4-x
BiTaO4 ceramics (x=0, 0.15, 0.2, 0.4, and
0.6) doped with 0.5 wt% CuO are investigated. Ta is substituted for
Nb in order to adjust the temperature coefficient of the resonant
frequency (τf) and improve the quality factor (Q). All
BiNb(1-x)Ta
x
O4 compositions can be sintered to achieve
a 96% theoretical density below 960°C. The sintering
temperatures of BiNb(1-x)Ta
x
O4 increase with increasing
of x values. The dielectric constants (ε
r) of
all compositions saturate at 44–45 in spite of the Ta
content. Q×f values of 13000–22000 (GHz) are obtained for all
compositions when the sintering temperatures are in the range of
920–940°C. By increasing the amount of the
doped Ta, the temperature coefficient of the resonant frequency
τf can be adjusted from a positive value of
+15 ppm/°C to a negative value of
-30 ppm/°C. The
BiNb(1-x)Ta
x
O4 ceramics can be applied to multilayer
microwave devices with low sintering temperatures.
Dielectric and Pyroelectric Properties of Alkoxy-Derived KTa0.35Nb0.65O3 Thin Film
Authors: Suzuki Kazuyuki , Sakamoto Wataru , Yogo Toshinobu , Hirano Shin-ichi
Published: October 2002

Perovskite KTa0.35Nb0.65O3 thin films were synthesized from an alkoxy-derived precursor by the chemical solution deposition method. Highly (100) oriented KTa0.35Nb0.65O3 thin films were successfully synthesized on MgO(100) and Pt(100)/MgO(100) substrates. X-ray pole figure measurements showed that KTa0.35Nb0.65O3 films had excellent in-plane and out-of-plane relations to MgO(100) and Pt(100)/MgO(100) surfaces. The KTa0.35Nb0.65O3 film showed the Curie temperature at about 100°C with a diffused transition. Typical polarization-electric field (P–E) hysteresis loops were observed for KTa0.35Nb0.65O3 films on Pt(100)/MgO(100) substrates. The remanent polarization (P
r) of the KTa0.35Nb0.65O3 film gradually decreased with increasing temperature. The pyroelectric coefficient after poling was about 1.2×10-8 C/(cm2K) at room temperature.
Characterization of Self-Phase Modulation in Liquid Crystals on Dye-Doped Polymer Films
Authors: Ono Hiroshi , Saito Isao
Published: October 2002

Photothermal effects in nematic liquid crystals (NLCs) on dye-doped polymer film, which caused self-phase modulation, were investigated using Kirchhoff's diffraction integral including higher-order optical phase modulation. The self-phase modulation was also analyzed by numerically solving a heat-conduction equation. The photothermal effects, including dependence on the pump beam intensity, were successfully described with good accuracy by the heat-conduction analysis.
Ultraviolet-light Induced Liquid-Crystal Alignment on Polyimide Films
Authors: Gong Shaoqin , Kanicki Jerzy , Ma Lan , Zhong John Z. Z.
Published: October 2002

Bond-breaking and oxidation occur during broadband ultraviolet
light (UV light) illumination of the polyimide film in the air
according to spectroscopic analysis. Surface tension and polarity are
increased based on the measurements of contact angles. The
liquid-crystal (LC) pretilt angles of the rubbed polyimide films are
reduced by both unpolarized and polarized UV light illumination. Both
the LC alignment and pretilt angle are generated on unrubbed polyimide
films through the photoalignment process. The mechanism of
photoalignment of LC is discussed.
Magnetic-Field-Induced Freedericksz Transition of a Homeotropical Alignment Liquid Crystal Doped with Double-Azo
Authors: Xiang Xiang , Ying Ying , Lin Lin , Ziyang Ziyang , Li Li , Tao Tao , Liang Liang , Xuxia Xuxia , Zhang Zhang , Jieli Jieli , Huang Huang , Jin-wang Jin-wang , Ji Ji , Liang-nian Liang-nian
Published: October 2002

The Freedericksz transition induced by a perpendicular static magnetic field of a homeotropical alignment nematic liquid crystal doped with a small amount of double-azo has been studied. It was observed that the doped 5CB markedly decreases the critical magnetic field, compared to that in the case for pure 5CB. We regard that in the guest-host system, the guest double-azo has a much larger diamagnetic susceptibility anisotropy and will drag the 5CB molecule to reorientate under a weaker magnetic field.
New Vapor Phase Growth Method of FeN Thin Films Using a Chloride Source
Authors: Takahashi Naoyuki , Toda Yoshihiro , Nakamura Takato , Fujii Toshitaka
Published: October 2002

A new method using FeCl3 and NH3 sources has been demonstrated for the vapor phase growth of FeN on a glass substrate. The X-ray diffractogram showed a typical ε-Fe3N with a hexagonal structure pattern. The growth rate increased with increasing growth temperature. The maximum growth rate was about 10 µm/h at 700°C. The saturation magnetization and coercive forces of ε-Fe3N deposited at 700°C were 112.2 emu/g and 32.0 Oe, respectively.
Influence of Driving Frequency on the System Parameters in Surface Discharge of AC Plasma Display Panels
Authors: Choi Eun-Ha , Cho Tae-Seung , Cho Dae-Sik , Choi Myung-Chul , Kim Jin-Goo , Lim Jae-Yong , Jung Yun , Ahn Jung-Chull , Kim Tae-Young , Kim Seong-Soo , Chong Min-Woo , Choi Seong-Hyuk , Kim Young-Guon , Ko Jae-Jun , Kim Dae-Il , Lee Chun-Woo , Seo Yun-Ho , Cho Gaungsup , Uhm Han-Sup
Published: October 2002

The influence of the driving frequency on the wall charge and voltage is experimentally investigated for the surface discharge of AC plasma display panels. A square pulse with a rising time of 150 ns and a duty ratio of 40% was used in the experiment. It is found that the capacitance C
0 of the surface discharge in a gas-filled region is almost constant and is 0.3 pF/cell, whereas the capacitance C
g in the dielectric region is significantly decreased from 7.5 pF/cell to 0.8 pF/cell, as the driving frequency is increased from 10 kHz to 200 kHz. It is also found that both the wall charge and the wall voltage decrease from 34.5 pC/cell to 15.6 pC/cell and from 104.4 V to 76.5 V, respectively, as the driving frequency increases from 10 kHz to 200 kHz.
Effects of N2 Addition on Aluminum Alloy Etching in Inductively Coupled Plasma Source
Authors: Kim Kil Ho , Baek Kye Hyun , Shin Kang Sup , Park Changwook , Lee Won Gyu
Published: October 2002

Addition of N2 to the plasma activated with Cl2,
BCl3, or their mixtures in an inductively coupled plasma source
induces drastic changes in the plasma state. These N2-related
changes in the plasma state sometimes result in abnormal phenomena in
aluminum alloy etching, like the wave-like fringes on the sidewalls of
patterned metal lines. Optical emission spectroscopy revealed that
admixing small amounts of N2 to the plasma activated with
Cl2, BCl3, or their mixtures generally expedites
dissociation processes to increase the density of Cl* radicals
within it. On the other hand, N2 addition also accelerates the
formation of passivation polymers via carbon species sputtered from
patterned photo-resists. The polymers adhere to the sidewalls of
patterned metal lines and protect them against the lateral attacks of
deflected etchants such as Cl* radicals. Our studies tell
that the relative abundance of Cl* radicals within the plasma
over the passivation polymers, which is controlled by the amount of
N2 addition, seems to be a critical factor in determining the
occurrence of the wave-like fringes on the sidewalls of patterned
metal lines.
Development of Phase-lock System between Two Single-Mode Lasers for Optical-Optical Double Resonance Spectroscopy
Authors: Kumagai Motohiro , Kanamori Hideto , Matsushita Michio , Kato Tatsuhisa
Published: October 2002

The difference frequency between two single-mode CW lasers was stabilized to a microwave (MW) frequency reference by using an optical phase-lock loop (PLL). The long-term frequency jittering of the beat spectrum was much suppressed by this method. The difference frequency was able to be continuously scanned from 0.1 to 18 GHz by changing the microwave reference frequency. It was also possible to scan the two lasers synchronously keeping the difference frequency constant. This stable and flexible light source would be an ideal light source for optical-optical double resonance (OODR) spectroscopy and resonance laser Raman experiments. For the demonstration, this new system was applied to an OODR experiment using a Rubidium atom. The hyperfine structures in the D2line were observed in the sub-Doppler condition.
Direct Measurement of Fluid Mechanical Properties in Micro Space: Liquid Crystal Orientation under Shear
Authors: Soga Iwao , Dhinojwala Ali , Granick Steve
Published: October 2002

The shear-induced molecular orientation of a nematic liquid
crystal, 5CB (4-pentyl-4′-cyanobiphenyl) was studied in a
newly-developed apparatus in which the liquid crystal was confined
between optical windows at a film thickness that is continuously
variable. The molecular orientation was measured in situ
during shear in the presence and absence of DC electrical bias between
the two surfaces. In this preliminary study we present findings for a
spacing of 10 µm, which is comparable to the spacing of
actual liquid crystal display technology. Fourier transform infrared
time resolved spectroscopy (FTIR-TRS) synchronized with the shear
motion provided the molecular orientation as a function of time during
the shear cycle. Only a slight orientation along the shear direction
was found in the isotropic state but, in the homeotropic state, the
molecular orientations in response to shear reflected a competition
process between orientation in orthogonal directions. Shear promoted
orientation parallel to the confining plates, and a DC bias voltage
promoted orientation perpendicular to the confining plates.
High-resolution Observation of SrTiO3 Interface by Convergent Beam Illumination
Authors: Masanori Mitome Masanori Mitome , Yoshio Bando Yoshio Bando , Akio Watanabe Akio Watanabe , Keiji Kurashima Keiji Kurashima , Yoshizo Kitami Yoshizo Kitami
Published: October 2002

The convergent beam illumination method has previously been proposed in order to determine the atomic arrangement in surface or interface structures on the sub-nanometer order. This method reduces interference fringes that appear at the surface or interface, and the fine structure can be analyzed. In this paper, the atomic arrangement near a SrTiO3 interface is determined from a transmission electron microscope image taken with convergent beam illumination. A cycloidal undulated structure can be found at the interface that is caused from misorientation of two crystals on each side of the interface. This structure cannot be found from images taken under conventional conditions, and therefore, it shows that the convergent beam illumination method is useful for analyzing the local structures.
Second-Order Zeeman Frequency Shift in the Optically Pumped Cesium Beam Frequency Standard with a Dual Servo System
Authors: Yang Sung Hoon , Baek Kwang Jae , Kwon Taeg Yong , Kim Young Bum , Lee Ho Seong
Published: October 2002

The second-order Zeeman effect produces the largest frequency shift among several causes to alter the reference frequency in the optically pumped cesium beam frequency standard. We introduce a novel way to reduce the uncertainties due to the Zeeman effect by adopting a dual servo system, one for stabilizing the current for static magnetic field and the other for normal clock operation. As a result, the combined uncertainty of the second-order Zeeman frequency shift is reduced to 3.2 ×10-15, which is smaller by one order of magnitude than that without the servo system.
Molecular Beam Epitaxial Growth of InAs Quantum Dots Directly on Silicon
Authors: Lars Hansen Lars Hansen , Frank Bensing Frank Bensing , Andreas Waag Andreas Waag
Published: October 2002

InAs quantum dots (QD) embedded in a silicon matrix show a photoluminescence line at a wavelength of about 1.3 µm [Semicond. Sci. Technol. 13 (1998) 1262]. This wavelength range is very interesting for the integration of classical silicon technology with optical fiber applications for chip-to-chip or intra-chip communication. To get InAs QDs of reproducible size and shape the growth conditions for the formation of quantum dots have to be optimized. Here, we report on detailed investigations on the molecular beam epitaxial growth of InAs QDs on silicon and their embedding in a silicon matrix. A variety of surface analytical techniques have been used, including in-situ electron diffraction (RHEED), in-situ photoelectron spectroscopy (XPS) and ex-situ atomic force microscopy (AFM).
Analysis of Short-Channel Schottky Source/Drain Metal-Oxide-Semiconductor Field-Effect Transistor on Silicon-on-Insulator Substrate and Demonstration of Sub-50-nm n-type Devices with Metal Gate
Authors: Wataru Saitoh Wataru Saitoh , Atsushi Itoh Atsushi Itoh , Shigeharu Yamagami Shigeharu Yamagami , Masahiro Asada Masahiro Asada
Published: October 2002

The Schottky source/drain metal-oxide-semiconductor field-effect transistor (MOSFET) has potential for scaling to the nanometer regime, because low electrode resistances with very shallow extension can be realized using metal source/drain. In this study, very short channel n- and p-type Schottky source/drain MOSFETs with silicon-on-insulator (SOI) structure were analyzed theoretically, and n-type devices were demonstrated experimentally. It was shown theoretically that a drivability of the Schottky source/drain MOSFET comparable to that of conventional MOSFETs can be realized with a low Schottky barrier height. The short-channel effect can be suppressed even with a 15-nm-long channel at t
OX = 1 nm and t
SOI = 3 nm. The room-temperature operation of sub-50-nm n-type ErSi2 Schottky source/drain MOSFETs on a separation by implanted oxygen (SIMOX) substrate was demonstrated.
Close Correlation between Enthalpy of Mixing and Internal Strain Energy in III–V Compound Alloys
Authors: Oyama Katsushi , Uda Hiroshi , Ikegami Seiji , Sonomura Hajimu
Published: October 2002

The correlation of enthalpy of mixing and internal strain energy calculated by the
elastic sphere model has been studied for III–V ternary alloy semiconductors of the
AB0.5C0.5 type. A plot of the enthalpy of mixing and the internal strain energy on a
plane for 18 different alloy systems shows nearly linear correlation. This result
strongly supports the conclusion drawn in our previous paper that the immiscibility
domains, in which the alloys are not formed completely, for III–V alloys can be
predicted simply from the isoenergy chart obtained by the elastic sphere model.
Investigation on the P-Type Activation Mechanism in Mg-doped GaN Films Grown by Metalorganic Chemical Vapor Deposition
Authors: Youn Doo-Hyeb , Lachab Mohamed , Hao Maosheng , Sugahara Tomoya , Takenaka Hironori , Naoi Yoshiki , Sakai Shiro
Published: October 2002

An investigation on the p-type activation in Mg-doped GaN epilayers has been carried out in relation to the defect structure. The samples were grown by the metalorganic chemical vapor deposition method. Sapphire with (0001) orientation (C-face) was used as the substrate. After growth, the samples were heat-treated under flowing N2, at temperatures ranging from 600 to 850°C. The p-type activation arises from the dissociation of electrically inactive Mg–H complexes and the neutralization of the dissociated H+ during the annealing process. The annealing temperature dependence of hole concentration and hole mobility was studied. The p-type activation process resulted in a different maximum hole concentration and an optimum annealing temperature. Subsequent microstructural characterization of our samples revealed that the dislocations play a key role in p-type conductivity and may explain the difference observed in the electrical properties. Indeed, the analyses of transmission electron microscopy (TEM) images and X-ray diffraction (XRD) data show that Mg-doped GaN exhibits a different X-ray rocking curve full width at half maximum (FWHM) and dislocation density. Furthermore, it was found that the higher the dislocation density, the higher the hole concentration. Therefore, we suggest that dislocations could act as a migration path or a neutralizing source for dissociated hydrogen impurities.
Drastic Improvement in Surface Flatness Properties by Using GaAs (111)A Substrates in Molecular Beam Epitaxy
Authors: Yamaguchi Hiroshi , Homma Yoshikazu , Kanisawa Kiyoshi , Hirayama Yoshiro
Published: October 2002

We have studied the surface flatness properties of (111)A planes in both homoepitaxial growth of GaAs on GaAs and highly-mismatched heteroepitaxial growth of InAs and InSb on GaAs by molecular beam epitaxy. The homo-epitaxially grown GaAs (111)A surface has atomically flat terraces as wide as about 1 µm, which make it possible to clearly image the layer-by-layer growth processes of GaAs byin-situscanning electron microscopy, in contrast with conventionally used (001) surfaces where the high density of steps prevents clear imaging. The surface flatness improvement using (111)A substrates is much more drastic in highly-mismatched heteroepitaxy. The three-dimensional islanding governed by the Stranski-Krastanov mechanism is strongly suppressed for the growth of both InAs and InSb on GaAs substrates. The lateral and vertical electron transport properties of Ga(Al)As/InAs/GaAs heterostructures are studied, verifying the improved electric properties by using the (111)A substrates. The application for novel hot-electron transistors is clearly demonstrated.
Temperature Dependence of Transmission Characteristics of Multilayer Film Narrow Bandpass Filters
Authors: Sakaguchi Shigeki
Published: October 2002

This report describes the temperature dependence of the
transmission center wavelength in narrow bandpass filters made of cavity
type multilayer films. The center wavelength shift is represented in
relation to the properties of the film and substrate materials and the layer
stacking structure. Approximate expressions are presented for estimating
the wavelength shift by using a form such as the average of the optical path
length increment ratio. It is possible to eliminate the temperature
dependence by selecting a substrate with a suitable thermal expansion
coefficient, whose value can be estimated by a simple expression.
Optical Properties of Ge40Sb10Te50Bx (x = 0–2) Films
Authors: Lee Chain-Ming , Chin Tsung-Shune , Huang Yi-Yuan , Tung I-Chung , Jeng Tzen-Ren , Chiang Dong-Yao , Huang Der-Ray
Published: October 2002

Phase-change optical recording media of the base composition
Ge40Sb10Te50 with or without boron doping
(0.3–1.1 at.%) were prepared by rf sputtering on Si(100) substrate
at a film thickness 100 nm. Crystalline state was obtained by
subsequent annealing at 300°C for 10 min. The structure
study of crystallized films showed that lattice parameter of the fcc
Ge40Sb10Te50 phase increases slightly with B
doping. Crystallization temperature increases manifestly with minor B
addition (10°C at 0.3 at.% B, and 25°C at 1.1 at.% B).
The reflectivity contrast between the crystalline and amorphous states
of the undoped Ge40Sb10Te50 film ranges from 29%
at the wavelength 350 nm to
38% at 800 nm. With an optimal 0.3 at.% B
doping, the reflectivity contrast exceeds
40% throughout the whole visible wavelength
range. The distinct changes in refractive
index and extinction coefficient of the
Ge40Sb10Te50B
x
films due to
crystallization is elucidated and found to
be advantageous in obtaining high
reflectivity contrast.
Effects of Structural Disorder on the Transport Properties of B2-phase Fe0.52Al0.48 Alloy Films
Authors: Yull Rhee Joo , V. Kudryavtsev Yuri , Ki-Won Kim Ki-Won Kim , Young-Pak Lee Young-Pak Lee
Published: October 2002

The influence of the order-disorder structural transition on the transport properties of Fe-rich B2-phase Fe0.52Al0.48 alloy films has been investigated. The disordered alloy film was obtained by vapor-quenching deposition onto glass substrates cooled by liquid nitrogen. The electric resistance of the ordered and disordered Fe0.52Al0.48 alloy films have been measured in the 5–300 K temperature range in the presence and absence of a magnetic field of 0.5 T. The influence of the order-disorder structural transition on the location of the resistance minimum at low temperature was analyzed within the framework of the “variable-range-hopping conductivity” approach.
Observation of a Dominant EL2-like Mid-Gap Trap in In0.12Ga0.88As/GaAs Superlattice Grown at Low Temperature by Molecular Beam Epitaxy
Authors: Chen Jenn-Fang , Wang Pie-Yong , Wang Jiin-Shung , Wong Hong-Zheng
Published: October 2002

Admittance spectroscopy is used to study a low-temperature (LT)-grown relaxed In0.12Ga0.88As/GaAs p-i-n superlattice. The capacitance-frequency spectra show two step-like trapping effects which are explained by the existence of two traps (E
a=0.73 eV, σ= 4.6 ×10-11 cm2 and E
a=0.75 eV, σ=3.7×10-15 cm2) in the LT-grown superlattice region. These two traps are the dominating defects observed in deep-level transient spectroscopy with one being a majority trap and the other being a minority trap. The emission parameters and photo-capacitance quenching effect for the 0.75 eV trap agree with those known for EL2 defects, suggesting that the EL2 defect is strongly enhanced in InGaAs/GaAs by LT growth.
Investigation of Antiferroelectric Liquid Crystalline Free-Standing Films by Transmission Ellipsometry
Authors: Haruyoshi Kobayashi Haruyoshi Kobayashi , Nobuaki Matsuhashi Nobuaki Matsuhashi , Yoshitaka Okumoto Yoshitaka Okumoto , Tadashi Akahane Tadashi Akahane
Published: October 2002

Thin free-standing films (FSFs) of an antiferroelectric liquid crystal (AFLC) were investigated by transmission ellipsometry. The phase difference between p-polarized and s-polarized light was measured as a function of the temperature and the incidence angle of the light beam. It was found that the structure of an FSF with two layers is anticlinic (SmC*
A) throughout the temperature range investigated whereas the bulk sample shows several phases, from SmC*
A to SmA phases. The four layer FSF showed only one phase transition (from SmC*
A to SmA) in this temperature range. Even for such a thin film as one with five layers, a subphase or subphases between SmC*
A and SmA were found.
The Dependence of Properties of Alumina–Zirconia–Graphite Refractories on Particle Size Distribution by Furnas Model
Authors: Yu Shan-Pu , Wang Moo-Chin , Hon Min-Hsiung
Published: October 2002

The alumina–zirconia–graphite (AZG) refractories were obtained through baking techniques using fused Al2O3, partially stabilized ZrO2 and flake graphite as the starting materials with Al, Si, and SiC powders as additives. Furnas model are used to describe the particle size distribution for coarse Al2O3 (500–1000 µm)/medium Al2O3 (61–125 µm)/fine Al2O3 (<44 µm) in which the contents of coarse, medium and fine Al2O3 powders are variable on the basis of constancy of other fine particles in the matrix. Bulk density of AZG refractories determined by Furnas model is about 3.0 g/cm3. The lowest apparent porosity (5.1%) was obtained at a weight ratio for coarse Al2O3/medium Al2O3 of 2.14. The reheat linear change fraction is 0.1–0.2% for all samples, indicating that this material has acceptable volume stability. The number of air exposure cycles for the thermal shock resistance (R
st) were 11–16, and the relation of R
st with apparent porosity (P
o) is correlated by R
st = 1.12 P
o + 5.91. The relation of erosion fraction (E
r) with P
o is expressed as E
r = 0.30 P
o - 0.27. Therefore, the R
st increased and the E
r decreased while the P
o increased in this AZG system.