bluuebunny/crossref_metadata_2025 huggingface dataset:
A Modified EDDY Code to Simulate Erosion/Redeposition of Carbon Target in an ITER-FEAT Divertor
Authors: Kaoru Ohya Kaoru Ohya , Retsuo Kawakami Retsuo Kawakami
Published: October 2002

Modification of a Monte Carlo simulation code, Erosion and Deposition based on DYnamic model (EDDY), for plasma-surface interactions in a designed tokamak, International Thermonuclear Experimental Reactor-Fusion Energy Advanced Tokamak (ITER-FEAT), and its application for erosion and redeposition of a carbon target in the divertor are presented. The modified EDDY code allows us to treat the deposition of plasma impurities and the prompt redeposition of sputtered atoms and molecules on the target surface. At elevated temperatures, furthermore, the impurity diffusion inside the target and chemical sputtering of carbon are taken into account. In the ITER-FEAT, physical sputtering of the divertor target is very small in the scrape-off layer (SOL) region, and chemical sputtering dominates the erosion near the strike point and in the private flux region. Prompt redeposition strongly suppresses the sputtering of the target and plasma carbon impurity deposits on it. As a result, no erosion is calculated in the SOL region and a thick deposition layer is produced near the strike point. A narrow erosion zone remains only in the private flux region. Furthermore, radial distributions of each particle species released in the plasma and their redeposition profiles on the surface are discussed.
A Novel Analysis Method for Peak Broadening Due to Thin Structures in Double Crystal X-Ray Diffraction Measurements
Authors: Nakashima Kiichi
Published: October 2002

A new method for analyzing X-ray peak broadening due to thin film structures on (001) substrates in double crystal X-ray diffraction measurements is proposed. In the method, two typical features exibited by peak profiles for thin film structures are investigated. Diffrence variable ΔL is introduced as a convenient measure for analyzing the two features. It is theoretically derived that peak profiles measured using the new variable become hkl-independent if the thin film structural factors dominate the peak broadening. Measurement conditions and geometry are essentially taken into account for the derivation. Based on the theoretical results, a simple criterion is proposed to judge whether broadening of a relevant peak is due to a thin film structure or not. The method is experimentally demonstrated via application to X-ray satellite peaks of an InGaAsP/InGaAsP multi-quantum-well (MQW) sample, and it is verified that the method works well for the satellite peaks. The method is essentially applied to the analysis of unknown broad and less intense peaks (background peak), which are observed in the X-ray diffraction profiles of tensile strained InGaAsP/InGaAsP MQW. Our method clarified that the microscopic size effect dominates the profile of the unknown peak. It is concluded that the unknown peak is caused by the modulation of the composition in the tensiled well layer. The observation of the unknown peak suggests that the strain field is not uniform in either the growth or the lateral direction.
Design of a Transverse Ionization-Cooling Channel in Solenoidal Focusing Field
Authors: Hwang Il-Moon , Kim Eun-San , Yoon Moohyun
Published: October 2002

In this study, ionization cooling in solenoidal channels is investigated for a neutrino factory. Newly designed Super-FOFO cooling channels are considered and it is shown that the transverse beam emittance in the cooling channels is reduced by a factor of six. Design and simulation of the cooling channel are performed using the ICOOL program. We describe design concepts and engineering constraints for the cooling channels. The particle losses, cooling performance, bunch lengthening and growth of momentum spread in the cooling channels are examined. It is shown that the cooling channels provide cooling performance satisfying the so-called Palmer, Johnson and Keil (PJK) design parameters for a neutrino factory. Engineering feasibility for superconducting solenoids shows that the super-FOFO cooling channel has a lower value of B
J
R (magnetic field B at coils × current density J × stress R on the conductor) than several cooling channels that have been designed for a neutrino factory. The simulation result for transverse cooling is also compared with that obtained using an analytical formula. It is shown that the numerical result agrees well with that of the analytical formula.
Curved Resist Surface Fabrication by Scanning a Blue Laser Beam with Positional Dose Distribution
Authors: Horiuchi Toshiyuki , Yaguchi Hiroshi
Published: October 2002

A new fabrication method of a wing profile using lithography is proposed, and smoothly curved wing profiles are successfully fabricated in a thick resist layer of about 80 µm. The developed depth after exposure changes linearly or logarithmically to the exposure dose when a special positive novolak resist is used. The resist is scanned by a solid blue laser beam with a wavelength of 473 nm. After the scan exposure with positional dose distribution and the development, cross-sectional profiles of the resist are observed to depend on the scan dose distribution. It is clarified that the scan position interval should be narrower than the beam radius in order to obtain smooth surface profiles, and that the scan interval should be optimized considering the roughness of the required surface curve. The resist surface profiles are calculated on the assumption that the laser beam has Gaussian intensity distribution. The calculated surface profiles roughly agree with the actually printed resist patterns. By refining the scanning method and resist process, the new method will be applicable for fabricating miniature components with smoothly curved surfaces such as wings, rotor blades and propellers.
Diagnosis of Oxidation Reactions in Metalorganic Chemical Vapor Deposition of (Ba,Sr)TiO3 Films by In Situ Fourier Transform Infrared Spectroscopy
Authors: Momose Shun , Sahara Ryusuke , Nakamura Toshihiro , Tachibana Kunihide
Published: October 2002

We studied the oxidation reactions of source Ti(t-BuO)2(DPM)2 and Sr(DPM)2 molecules during metalorganic chemical vapor deposition (MOCVD) by in situ Fourier transform infrared spectroscopy (FT-IR). We used O2 and N2O gases as oxidizing agents and investigated the difference in oxidation effect between the two gases. From measurements of IR absorption spectra, we found that O2 is more reactive than N2O in the gas phase, and selectively attacks low-electron-density sites in the source molecules. We deposited strontium oxide and (Ba,Sr)TiO3 films in O2 and N2O ambients, and investigated the relationship between the qualities of deposited films and the gas-phase reactions measured by FT-IR spectroscopy. In terms of the suppression of carbon contamination and the increase in the Ti/(Ba+Sr) atomic ratio, we found that O2 is more suitable than N2O for the deposition of (Ba,Sr)TiO3 films.
Performance and Reliability Improvement of Low-Power Embedded Flash Memory with Shallow Trench Isolation Structure
Authors: Huang Heng-Sheng , Su Jason , Lee Dong-Lung , Lin Chih-Hung , Ting Wen-Chi , Hong Gary
Published: October 2002

The design of programming/erasing (P/E) coupling ratios of advanced low-power embedded flash cells (working as an on/off switch) with a shallow trench isolation (STI) structure has been discussed to meet future performance requirement. The reason that the stress-induced reliability degradation (SIRD) problem becomes more severe when the STI structure is used in a low-power flash cell has also been clearly explained. In this paper, we suggest a drain (or source) side erase method for both lower-voltage operation and quick data writing. This device must be operated at a suitable bias condition to achieve the best reliability. For further improvement in the control and uniformity of the reliability performance, a modified STI module and modified cell drain side engineering are proposed and verified on a 256 K NOR-type embedded low-power flash test vehicle.
Low-Temperature Crystallization of Sol-Gel Derived Pb(Zr0.4,Ti0.6)O3 Thin Films
Authors: Maki Kazunari , Soyama Nobuyuki , Nagamine Kaoru , Mori Satoru , Ogi Katsumi
Published: October 2002

We have studied the crystallization of sol-gel derived Pb(Zr0.4Ti0.6)O3 [PZT(40/60)] thin films at 435 down to 420°C. The PZT(40/60) films were prepared at these temperatures on Pt/SiO2/Si substrates by a combination of diol-based solutions and modified film preparation processes. Various properties of the PZT(40/60) films such as microstructures, crystal orientation, ferroelectric properties, relative permittivity, and leakage current density were evaluated. It was found that PZT(40/60) films could be crystallized at 435 to 420°C by the diol-based solutions and the modified film preparation processes. The PZT(40/60) films had microstructures with perovskite-single-phase fine columnar grains and good electric characteristics such as remanent polarization (P
r) of 12 to 15 µC/cm2, relative permittivity (ε
r) of 780, and breakdown voltage of more than 10 V.
Estimation of Hydrothermally Deposited Lead Zirconate Titanate (PZT) Thin-Film
Authors: Kanda Takefumi , Kobayashi Yutaka , Kurosawa Minoru K. , Yasui Hidehiko , Higuchi Toshiro
Published: October 2002

The mechanical output of piezoelectric vibrators, particularly actuators, is determined by the limit of the vibration velocity. To obtain large vibration velocity, it is important to deposit a thick piezoelectric film. We have succeeded in depositing thick lead zirconate titanate (PZT) films by the hydrothermal method. The thicknesses of the films were 2 µm, 9.8 µm, 20 µm and 30 µm when the reaction times were 2, 5, 10, and 15, respectively. We have also estimated Young's modulus of the PZT films from the resonance frequency of the bimorph vibrators. From the measurement results, Young's modulus of the PZT film was 1.3×1010 N/m2. This value corresponded to only 16% of that of bulk PZT. The piezoelectric constants of hydrothermally deposited PZT film were inferior to those of bulk PZT. To obtain much larger constants, it is necessary to obtain larger Young's modulus.
Ferroelectric Bi4Ti3O12 Films on Si(100) with An Ultrathin Buffer Layer of Silicon Oxynitride: A Comparative Study Using X-Ray Photoelectron Spectroscopy
Authors: Rokuta Eiji , Hotta Yasushi , Choi Jae-hyoung , Tabata Hitoshi , Kobayashi Hikaru , Kawai Tomoji
Published: October 2002

Using pulsed-laser deposition, ferroelectric Bi4Ti3O12 (BiT) films were grown on Si(100) with and without an ultrathin buffer layer of silicon oxynitride (SiON), and the interface states were investigated using X-ray photoelectron spectroscopy. For both as-grown specimens, the additional oxidation of the interface Si was observed, and their thicknesses were almost identical. Due to the postannealing at 700°C in an oxygen ambient, on the other hand, a large difference in the Si oxidation was observed between the two specimens. The BiT films on Si(100) without the SiON buffer layer failed in preventing the significant development of the interfacial Si oxidation. On the contrary, it was clarified that the 1.3-nm-thick SiON buffer layers suppressed the additional oxidation to less than 3.5 nm.
Cation Distribution and Structural Instability in Bi4-xLaxTi3O12
Authors: Osada Minoru , Tada Masaru , Kakihana Masato , Watanabe Takayuki , Funakubo Hiroshi
Published: October 2002

Raman spectra of Bi4-x
La
x
Ti3O12 have been investigated. For an increasing degree of La doping, we find a substantial hardening of the vibration involving Bi atoms at the perovskite A site, whereas the Bi mode at the Bi2O2 layer is negligibly changed. From a comparison with a simple mass consideration, we identify a precise cation distribution, which indicates a pronounced site selectivity of La ions for the A site for x<∼ 1. At room temperature, the lowest mode at 28 cm-1 shows a significant softening with La doping. This behavior resembles the temperature dependence in the nondoped material (at constant composition). A remarkable correlation is found between the soft-mode frequency and T
C for Bi4-x
La
x
Ti3O12. We suggest that this correlation, as well as the soft-mode frequency for substituted materials, offers useful guidelines for designing materials in a controlled manner.
Preparation and Properties of SrBi2Ta2O9 Ferroelectric Thin Films Using Excimer UV Irradiation and Seed Layer
Authors: Hayashi Takashi , Togawa Daichi
Published: October 2002

Low-temperature processing of SrBi2Ta2O9 (SBT) thin films on Pt(200 nm)/Ti(50 nm)/SiO2/Si substrates was investigated by the sol-gel method. The excimer UV irradiation onto as-deposited SBT thin films at 200–300°C in O2 atmosphere and the use of a Sr–Ta–O seed layer were very effective in lowering the crystallization temperature for SBT thin films to 500°C. The SBT thin films prepared by an excimer UV process and subsequent rapid thermal annealing process with the seed layer showed a homogeneous and smooth surface microstructure with fine grains of approximately 50 nm in size. The 600°C-annealed SBT thin films of approximately 200 nm thickness with the seed layer exhibited a Pr of 2.3 µC/cm2 and a Ec of 43 kV/cm.
Theoretical Stability of Polarization in Metal/Ferroelectric/Insulator/Semiconductor and Related Structures
Authors: Watanabe Yukio , Masuda Akihiro
Published: October 2002

The stability of spontaneous polarization in metal/ferroelectric/insulator/semiconductor and related structures is theoretically studied by considering semiconductivity, i.e., the effect of the finite band-gap width. The theory is based on thermodynamics reported previously by us and is extended in order to also examine the surface relaxation of the spontaneous polarization and the quantum confinement effect and to rigorously treat the electron statistics, the work function of the metal electrode and the multidomain. Basic concepts related to these issues are concisely summarized. The results explain the experimental observations well, at least qualitatively, and resolve the pessimistic predictions drawn from conventional theories.
Studies on the Solid Solution of Mn in BaTiO3
Authors: Kirianov Andrei , Ozaki Nobutaka , Ohsato Hitoshi , Kohzu Noriyuki , Kishi Hiroshi
Published: October 2002

BaTi1-x
Mn
x
O3 solid solutions with 0≤x≤0.04 were synthesized in reducing atmosphere (P
O2<10-9 Pa) and in air at 1350°C for 2 h. The effect of Mn ions with different valences on the crystal structure of BaTiO3 was studied by the room-temperature Raman scattering, electron spin resonance (ESR) and X-ray powder diffraction analyses. The crystal structure of the solid solution was analyzed to determine the change of its lattice parameters. It was found that in a reducing atmosphere, Mn2+ ions promoted the tetragonal-to-cubic transformation, as both a contraction of c-axis and an extension of a-axis were observed with an increase in Mn content. In contrast, Mn ions in the air-synthesized samples promoted the tetragonal-to-hexagonal transformation. The formation of the hexagonal phase was accompanied by a strong extension of the c-axis of the tetragonal phase from 4.032 Å to 4.042 Å. This was attributed to Jahn-Teller distortions caused by Mn3+ ions.
Surface Passivation Using P2S5/(NH4)2Sx and Hydrogen Fluoride Solutions on Ag/n-InAs and Ag/n-InSb Schottky Diodes
Authors: Jeng Ming-Jer , Wang Hung-Tsung , Chang Liann-Be , Lin Ray-Ming
Published: October 2002

A method for surface passivation using both phosphorus sulphide/ammonia sulphide [P2S5/(NH4)2S
x
] and hydrogen fluoride (HF) solutions has shown great effectiveness for the reduction of InAs and InSb substrate surface oxides. In comparison with samples treated by P2S5/(NH4)2S
x
or HF solutions alone, the surface layer produced by the new passivation treatment has a high stability against oxidation even after an 18 h baking treatment at a temperature of 300°C in N2 ambient. In addition, the barrier heights of Ag/n-InAs and Ag/n-InSb Schottky diodes can still reach as high as 0.37 and 0.19 eV, respectively, even though the Ag/n-InAs and Ag/n-InSb diodes were baked for 18 h at 300°C.
dc-Electrical Degradation of the BT-Based Material for Multilayer Ceramic Capacitor with Ni internal Electrode: Impedance Analysis and Microstructure
Authors: Chazono Hirokazu , Kishi Hiroshi
Published: October 2002

The impedance of a BaTiO3 (BT)-based multilayer ceramic capacitor with a nickel internal electrode (Ni-MLCC) was investigated by measuring the frequency domain at various temperatures. All the obtained impedance data could be successfully fitted to a 4-RC section electrical equivalent network. The 4-RC section electrical equivalent network was successfully correlated to the microstructure: the core, the shell, the grain boundary, and the ceramic/internal electrode interface regions. Based on this electrical equivalent network, the electrical properties including the Curie-Weiss law, the current-voltage characteristics, and dc electrical degradation, were well explained. A model for the degradation behavior for BT-based Ni-MLCC with thin active layer thickness was proposed.
Degree of Crystallization and Contamination Effect on Ferroelectric Ceramic Powder Produced by Fine Grinding
Authors: Munekata Mutsuo , Kamata Osamu , Shirasaka Toshikazu , Higuchi Toshirou
Published: October 2002

Fine grinding of ferroelectric materials is indispensable and elemental in order to produce electronic components of small size and high-performance ceramics. The deterioration of the electrical properties occurs due to contamination during conventional fine grinding. In addition, the crystallinity (degree of crystallization) of ground fine particles is low, and in mass-production there was the problem of the deformation of the dimensions caused by the sintering process. In our experiment, by using the wet cycloid mill, it was possible to control the amorphizability (lattice distortion) and fine particles with high crystallinity and good electrical properties could be obtained.
Growth and Characterization of Potassium Niobate (KNbO3) Crystal from An Aqueous Solution
Authors: Komatsu Ryuichi , Adachi Kensuke , Ikeda Ko
Published: October 2002

Ferroelectric orthorhombic potassium niobate (KNbO3) crystal is successfully grown from an aqueous solution dissolving K2NbO3F as a nutrient. Although the size of each crystal is about 10 µm or less, properties of the formed KNbO3 crystals have been examined. The possibility of using this method in the future to grow KNbO3 crystals or thin films has also been investigated in order to apply KNbO3 to acoustic devices.
The Dielectric Properties and Phase Transition of (1-x)Pb(Yb1/2Ta1/2)O3-xPb(Yb1/2Nb1/2)O3
Authors: Kim Hyun-Jung , Lee Jae Ho , Choo Woong Kil
Published: October 2002

The dielectric properties and phase transition behaviors of (1-x)Pb(Yb1/2Ta1/2)O3-xPb(Yb1/2Nb1/2)O3 (PYT1-x
PYNx) solid solution have been investigated. The primary transition that occurs at 310°C of PYT is not affected by substitution of Ta5+ by Nb5+. The secondary phase transition of PYT which happens to be relaxor-like in character is critically affected by Nb5+ substitution. Although the profiles of X-ray diffraction of the solid solution are not noticeably changed by Nb5+ substitution, its selected area electron diffraction reveals that the superlattice diffraction spots become incommensurate due to Nb5+ substitution. This incommensuration coincides with disappearance of the secondary phase transition on Nb5+ substitution.
Hole Confinement to CuO2 Layers in High-Tc Cuprate Superconductors due to Crystal Potential
Authors: Ishizuka Kazuo , Wang Shaoqing , Uchida Masaya , Horiuchi Shigeo
Published: October 2002

The distribution of positive holes in high-T
c cuprate superconductors is discussed in terms of the electrostatic potential in crystals. The maps of the crystal potential are drawn for Tl2Ba2Ca
n-1Cu
n
O2n+4 (n=1–4) homologous series of high-T
c superconductors. Close to the CuO2 layer, there are always negative regions, which extend over the entire crystal. Moreover, the potential distribution at a plane of an apical oxygen becomes positive almost everywhere. It is thus realized that a supercurrent carried by holes will be confined within the conduction layer between the planes of apical-oxygen. Furthermore, the potential of the TlO layer, which is considered as a charge reservoir, is far positive. According to the potential gradient, electrons will move out from the CuO2 (conduction) layer to the TlO layer, while holes will move in the opposite direction.
Dielectric and Piezoelectric Properties of (A0.5Bi0.5)TiO3–ANbO3 (A=Na, K) Systems
Authors: Wada Takahiro , Toyoike Kouji , Imanaka Yousuke , Matsuo Yoshihiro
Published: October 2002

The microstructural, dielectric and piezoelectric properties of the (Na0.5Bi0.5)TiO3–NaNbO3 and (K0.5Bi0.5)TiO3–KNbO3 systems were studied in order to find new lead-free piezoelectric ceramic materials. In the (1-X) (K0.5Bi0.5)TiO3–(X) KNbO3 system, it was confirmed from the measurements of the electromechanical coupling factor, K
p, that piezoelectricity occurred within the wide compositional range between X=0 and 0.35. The sample with X=0.075 showed a maximum K
p of 15.1%. However, the expected morphotropic phase boundaries were not found in the (Na0.5Bi0.5)TiO3 or (K0.5Bi0.5)TiO3 rich side of the solid solution systems.
Effects of Electrode Materials on Natural Unidirectionality of Langasite
Authors: Wang Shou-Qi , Kimura Ryouhei , Yamaguchi Kunio , Harada Jiro , Uda Satoshi , Hasegawa Koji
Published: October 2002

In this study, we carried out experimental research on the directivity of surface acoustic wave (SAW) filters with Al, W and Ta electrodes formed on langasite single-crystal wafers, in order to find electrode materials that make the natural unidirectionality disappear. The results proved that by using W and Ta, the natural unidirectionality disappears at the normalized thickness (h/λ) of 0.033–0.037. This suggests a potential application of these metals as electrode materials for langasite-based SAW filters so that the design process of the single-phase unidirectional transducer (SPUDT) filter can be simplified by using tools for conventional SPUDT filters.
Temperature Dependence of Piezoelectric Properties of Grain-Oriented CaBi4Ti4O15 Ceramics
Authors: Ogawa Hirozumi , Kimura Masahiko , Ando Akira , Sakabe Yukio
Published: October 2002

Piezoelectric properties of grain-oriented bismuth layer structured compound CaBi4Ti4O15 ceramics and their temperature dependencies were studied. The grain-oriented CaBi4Ti4O15 ceramics were fabricated by the templated grain growth method. The highly preferentially (00l) oriented CaBi4Ti4O15 ceramics were obtained and their Lotgering (00l) orientation degree was almost 100%. The electromechanical coupling coefficient of the longitudinal vibration mode (k
33) was approximately three times as large as that of the nonoriented specimen, and the temperature coefficient of resonant frequency (|f

r
-T
C|) was the same as that of the nonoriented specimen. The 24 vibration mode is separated from the 15 vibration mode in the thickness shear vibration of the grain-oriented ceramics. The electromechanical coupling coefficient k
15 of the grain-oriented specimen was twice as large as k
15 of the nonoriented ceramics, while, k
24 was one-third that of k
15 of the nonoriented specimen. The |f

r
-T
C| of the 15 vibration mode of the grain-oriented specimen was half that of the 15 vibration mode in the nonoriented ceramics, and that of the 24 vibration mode of the oriented specimen was much larger than that of the 15 vibration mode in the nonoriented ceramics.
Sr1-xCaxBi2Ta2O9 Piezoelectric Ceramics with High Mechanical Quality Factor
Authors: Shibata Kazuo , Shoji Kazuo , Sakata Koichiro
Published: October 2002

The dielectric, ferroelectric and piezoelectric characteristics of Sr1-x
Ca
x
Bi2Ta2O9 (x=0–1) ceramics were examined. The samples were prepared by a conventional ceramic technique at 1260°C to 1340°C for 2 h. The Curie temperature of samples gradually rose from 324°C to 896°C when x was increased. The coercive field E
c of the sample with x=0.75 was approximately 16 MV/m, and the value of E
c was about 3 times that of x=0. In the x=0.75, the maximum value of the mechanical quality factor Q
m was obtained, approximately 11000.
Thermal Coupling Effect on the AC Thermal Signal and DC Characteristics of High-Temperature Superconducting Bolometers
Authors: Hong Meng-Tsong , Chen Ying-Chung , Ou Min-Nan , Wu Mei-Fang , Chow Timothy-Chi , Chou Hsiung
Published: October 2002

In a high-temperature superconducting (HTSC) bolometer, the irradiated thermal energy is absorbed by the film and finally drained to the heat sink. The intensity of the thermal signal depends on the level of the AC irradiation energy accumulated. It is usually expected that the magnitude of AC thermal signal is enhanced by weakening the thermal coupling of the bolometer to the heat sink. However, in this study, we found that the AC thermal signal, ΔT/W
D, was not enhanced but was depressed by weakening the thermal coupling of the setup. This could be attributed to the nature of the low dissipation ability in the weak thermal coupling configuration which accumulated a higher level of DC Joule heat and gave rise to a huge temperature gradient between the film and the heat sink. As a result, the heat dissipation was sped up and the AC thermal signal, ΔT/W
D, was depressed. Even though the AC thermal signal was lower in the weak thermal coupling configuration than in the strong one, the optimum operation condition, where maximum ΔT/W
D was exhibited, was located in the lower bias current region. This has the advantage of enabling the weak thermal coupling configuration to be operated in a lower-power consumption region.
Waveforms of the Vibration Velocity and the Current of a Piezoelectric Transducer in the Transient State
Authors: Umeda Mikio , Nakamura Kentaro , Takahashi Sadayuki , Ueha Sadayuki
Published: October 2002

In this paper the relationship between the vibration velocity waveform and the current waveform of a piezoelectric transducer in the transient state is presented. Using the AC burst voltage source, the waveforms of the vibration velocity and the current at high vibration amplitude levels are observed and the relationship between them is investigated. The effects of the burst driving conditions on the results of the transient measurement are discussed based on the electrical transient responses. It has been shown that the results are not affected by the electrical driving conditions. The beat in the burst driving state is also investigated using these results.
PbNb2O6 Ceramics with Tungsten Bronze Structure for Low Qm Piezoelectric Material
Authors: Soejima Junichiro , Nagata Kunihiro
Published: October 2002

A broadband ultrasonic transducer was made from [(Pb
x
,Ba1-x
)1-3y/2La
y
]Nb2O6 which was prepared by substituting Ba and La for Pb in PbNb2O6. Analysis of the piezoelectric performance as a function of ceramic composition revealed that samples with x=0.40–0.80 and y=0–0.10 have the maximum electromechanical coupling factor (k

t
). The k

t
of this sample was 0.45, and the k

p
was 0.32. Since k

p
was relatively high with respect to k

t
, a high-order radial mode appeared in the vicinity of the thickness mode resonance frequency. Slots were cut into both sides of the disk to reduce this phenomenon. The slotted disk had a reduced radial vibration mode, and the k

p
decreased to 0.06. The k

t
increased to 0.61, and the mechanical quality factor (Q
m) was 20. This ceramic can be used as an efficient broadband transducer.
Characteristics of Superconducting Nb Layer Fabricated Using High-Vacuum Electron Beam Evaporation
Authors: Morohashi Shin'ichi , Takeda Norihisa , Tsujimura Shogo , Kawanishi Masanori , Harada Keita , Maekawa Shoji , Nakayama Noriaki , Noguchi Takashi
Published: October 2002

We have fabricated a niobium (Nb) layer for a Josephson junction by means of a high-vacuum electron beam (EB) evaporation technique. The high-vacuum EB-evaporated Nb layer is deposited under the base pressure of 4×10-9 Pa and the deposition rate of 1.2 nm/min. In spite of the extremely low deposition rate, Nb layers of over 50 nm thickness have the transition temperature of 9.3 K and the ratio of residual resistivity of more than 3. The surface roughness and the grain size of the high-vacuum EB-evaporated Nb layer are studied using atomic force microscopy and X-ray diffraction analysis. The stress in the high-vacuum EB-evaporated Nb layers is examined by measuring the change in the radius of curvature of the substrate before and after Nb layer deposition, and the X-ray diffraction patterns of the Nb layers. The high-vacuum EB-evaporated Nb layer exhibits a weak tensile stress.
Influence of M (M=Zn and Ni) Substitution for Cu on Microwave Dielectric Characteristics of Yb2Ba(Cu1-xMx)O5 Solid Solutions
Authors: Kan Akinori , Ogawa Hirotaka , Ohsato Hitoshi , Sugishita Junji
Published: October 2002

The effects of M (M=Zn and Ni) substitution for Cu on the microwave dielectric properties and the crystal structure of Yb2Ba(Cu1-x

M

x
)O5 solid solutions were investigated. Yb2Ba(Cu1-x
Ni
x
)O5 (x=0 to 1) solid solutions are a single phase, whereas the limit of Yb2Ba(Cu1-x
Zn
x
)O5 solid solutions is x=0.75. The formation of the solid solutions is caused by the difference of ionic radii between Yb3+ and M
2+ ions. The ε

r
values of Yb2Ba(Cu1-x
Zn
x
)O5 (x=0 to 0.75) solid solutions vary from 7.9 to 14.9, depending on the composition x. This variation is interpreted as an increase in the volume of the Yb2O11 polyhedron induced by an expansion of the bottom plane with M substitution for Cu. Moreover, the Q·f values of the solid solutions are extremely improved by M substitution for Cu, and the maximum Q·f values with Zn and Ni substitutions for Cu are 52815 and 50042 GHz, respectively.
Newly Developed Polymer-Stabilized Ferroelectric Liquid Crystals: Microsized Bistable Domains and Monostable V-Shaped Switching
Authors: Hirokazu Furue Hirokazu Furue , Hiroshi Yokoyama Hiroshi Yokoyama , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

We fabricated new polymer-stabilized ferroelectric liquid crystal displays (PS-FLCDs) by UV photocure of doped monoacrylates with a mesogenic side chain at a temperature where the LC medium is in the SmC* phase under the application of a bipolar square-pulsed AC electric field. Then, we investgated the effect of polymer density on the molecular alignment structure of the PS-FLC by observation of the microscopic textures and measurement of the electrooptical characteristics. The PS-FLC with low concentration of polymer (4 wt%) exhibits bistable electrooptical characteristics accompanied with microsized domain switching. On the other hand, the PS-FLC with high concentration of polymer (10 wt%) exhibits monostable V-shaped electrooptical performance without a threshold.
Dielectric Relaxation Behavior of Ferroelectric Phase in Antiferroelectric Liquid Crystals
Authors: Sakamoto Mihoko , Tatemori Syuichi , Ito Megumi , Uehara Hiroyuki , Hatano Jun
Published: October 2002

The ferroelectric phase in optically pure samples and racemized ones of an antiferroelectric liquid crystal were studied by a dielectric dispersion experiment. In the optically pure samples, in addition to the Goldstone mode, a new relaxation mode was found, which is related to a molecular motion within the plane parallel to the cell surface. A model based on a field-induced conformation change of molecules was proposed for the ferrielectric-like behavior of SmCβ*.
Influence of Liquid-Crystal Directors in an Electric Field on Elastic Wave Propagating in Liquid-Crystal Cell
Authors: Masaru Inoue Masaru Inoue , Katsumi Yoshino Katsumi Yoshino , Hiroshi Moritake Hiroshi Moritake , Kohji Toda Kohji Toda
Published: October 2002

Propagation characteristics of a shear-horizontal (SH) wave in a trilayer structure composed of a liquid-crystal layer sandwiched between two glass plates are examined by numerical analysis and experimental investigation from the viewpoint of the anisotropy of the viscosity. Electric field dependences of the viscosities of two kinds of nematic liquid crystals with positive and negative dielectric anisotropies are related to the SH wave phase velocity. The orientation of the liquid-crystal director is a key factor for affecting the viscosity change. The present technique is promising for evaluating the anisotropy of the viscosity of liquid crystal.
Electronic Structure of Bi4Ti3O12 Thin Film by Soft-X-Ray Emission Spectroscopy
Authors: Higuchi Tohru , Tanaka Masashi , Kudoh Kazuhide , Takeuchi Tomoyuki , Harada Yoshihisa , Shin Shik , Tsukamoto Takeyo
Published: October 2002

The electronic structure of a ferroelectric Bi4Ti3O12 (BIT) thin film was investigated by soft-X-ray emission spectroscopy (SXES). In the valence band energy region, Ti 3d and O 2p partial density of states were observed in O 1s and Ti 2p SXES spectra. The energy position of the Ti 3d state overlapped with that of the O 2p state. This finding indicates that the O 2p state strongly hybridizes with the Ti 3d state in the valence band.
Raman Scattering in (1-x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 Mixed Crystal System II
Authors: Iwata Makoto , Tomisato Nobuaki , Orihara Hiroshi , Arai Norio , Tanaka Nobuo , Ohwa Hidehiro , Yasuda Naohiko , Ishibashi Yoshihiro
Published: October 2002

The temperature-concentration dependences of the Raman spectra in the high-temperature region above the Burns temperature and the electron diffraction at room temperature were investigated in the (1-x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 mixed crystal system. It was found that in the concentration range below x=0.8, the Raman active modes exist in the cubic phase and the intensities of the Raman lines in the cubic phase decrease with increasing temperature. A finite region where the Raman active modes are observed in the cubic phase was determined in the temperature-concentration phase diagram. On the other hand, no (1/2, 1/2, 1/2) superlattice diffraction was observed in the mixed crystal with the content above x=0.2. The present result indicates that the Raman active modes in the high-temperature phase cannot be explained by the zone folding for the superstructure with the Fm3m symmetry.
Dynamical Properties of Relaxor Ferroelectric Lead Scandium Tantalate Probed by Micro-Brillouin Scattering
Authors: Ko Fuming Jiang , Lushnikov Sergey , Kojima Seiji
Published: October 2002

We report the Brillouin scattering of a disordered Pb(Sc1/2Ta1/2)O3 crystal with degree of order S=0.29. In z(x,x+y)=Z scattering geometry, the broad minimum of longitudinal acoustic mode (LA) shifts and the broad maximum of LA width were observed around 245 K corresponing to the maximum temperature T
m of low frequency dielectric constant. Relaxation times were determined by assuming a complex elastic constant from LA modes, and they were attributed for the first time to the fluctuations of polar microregions. In addition, central peaks with marked temperature dependences were observed below 400 K showing a sharp anomaly at 293 K. Concerning specific heat, no anomaly was found for the as-grown crystal, while two broad anomalies around 293 and 270 K for PST (S=0.31), and only one marked anomaly at 293 K for PST (S=0.85) were observed in the cooling process, respectively. A two-phase transition model (Fm3m-R3m, Z=2; Pm3m-R3m, Z=1) was proposed to explain the experimental results.
Domain Orientation Imaging of PbTiO3 Single Crystals by Vertical and Lateral Piezoresponse Force Microscopy
Authors: Hirotake Okino Hirotake Okino , Teruhiko Ida Teruhiko Ida , Hiroshi Ebihara Hiroshi Ebihara , Hirofumi Yamada Hirofumi Yamada , Kazumi Matsushige Kazumi Matsushige , Takashi Yamamoto Takashi Yamamoto
Published: October 2002

Four kinds of domain structures (180° c-c, 180° a-a, 90° a-a and 90° a-c domains) on grown surfaces of PbTiO3 single crystals were imaged successfully using vertical and lateral piezoresponse force microscopy (PFM). Domain orientations (i.e., polarization vector distributions) at the surface of each domain structure are presented. These domain images are compared with simultaneously observed surface topographic images decorated by an acid etching treatment.
Ion-Beam-Assisted Nanocrystal Formation in Silicon Implanted with High Doses of Pb+ and Bi+ Ions
Authors: Kalitzova Maria , Zollo Giuseppe , Yankov Rossen , Angelov Christo , Simov Stephan , Pizzuto Cesare , Faure Joel , Kilian Lilian , Bonhomme Pierre , Manno Daniela , Voelskow Matthias , Vitali Gianfranco
Published: October 2002

In this paper we discuss ion-beam-assisted nanocrystal nucleation in amorphized silicon (a-Si) layers produced by high-dose implantation of Pb+ and Bi+. (100)-oriented Si wafers were implanted at room temperature (RT) with 50 keV Pb+ and Bi+ ions at doses ranging from 5×1013 to 1×1018 cm-2 and a constant ion current density of 10 µA cm-2. The resulting structures were studied by conventional transmission electron microscopy (CTEM), high resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectroscopy (RBS) in combination with computer simulations. The dynamics of the ion-beam-induced crystallization of new phases and precipitates evolution in the implanted layer were studied as a function of implant dose. It is established that the front of the new phase crystallization (cubic Pb and hexagonal Bi nanocrystals) starts approximately at the peaks of the implanted species profiles; the crystallography of the nucleated nanocrystal is examined as a function of the dose.
Ashing Properties in a Surface-Wave Mode Plasma with a High-Permittivity Alumina Window
Authors: Shinagawa Keisuke , Shindo Haruo , Kusaba Kouta , Koromogawa Takashi , Yamamoto Jin , Furukawa Masakazu
Published: October 2002

Ashing properties in a surface-wave mode at 133 Pa and 1 kW with an alumina disk-plate window are investigated by comparison of those in a volume mode with a quartz disk-plate window. In the surface-wave mode, plasma is confined to the alumina window surface area and ashing in a downstream area is carried out mainly by atomic oxygen. The ashing activation energy of 0.42 eV in the surface-wave mode ashing is comparable to 0.5 eV with an ashing condition by atomic oxygen at the ground state [O(3P)](the so-called downstream state). These results indicate that the plasma in the surface-wave mode can realize a downstream ashing condition. On the other hand, ashing with a quartz window was done by plasma, where the activation energy is influenced by built-in high-frequency magnetic field. Moreover, the ashing rate distribution in the surface-wave mode characterized with the alumina window is more uniform than that in the volume mode with the quartz window.
Magnetoresistance of La0.7Sr0.3MnO3 Thin Films Grown on Polycrystalline MgO Substrates
Authors: Satoh Issei , Kobayashi Takeshi
Published: October 2002

In this study, the intergrain magnetoresistance (IMR) of La0.7Sr0.3MnO3 (LSMO) thin films at 77 K and the IMR's deposition temperature (T
d) dependence were examined. All LSMO films were grown on the polycrystalline MgO substrate (40–60 µm grain size) by the Ar–F excimer laser ablation (pulsed laser deposition) method. The T
d's ranged from 450 to 600°C. Due to a large lattice mismatch between LSMO and MgO, LSMO film grows in the shape of column with a (110) axis. On the substrate grain boundary, LSMO forms a tilted nanocolumn boundary, which produces a large IMR effect. There exists an optimum T
d (∼500°C) which provides the LSMO film with the largest IMR. Below and above this temperature, IMR decreases monotonically with decreasing and increasing of T
d. This is due to an antithetical T
d dependence of the boundary definition against the column crystallinity.
Growth of 3C-SiC on Si Substrate with Ge1-0.63C0.63 Buffer Layer
Authors: Yong Sun Yong Sun , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

We report the strain buffer effects of the Ge1-0.63C0.63 layer on the growth of the 3C-SiC film on the Si(001) substrate. The introduction of the Ge1-0.63C0.63 buffer layer with a suitable thickness results in crystal growth of the 3C-SiC film on the Si substrate. The crystal growth of the 3C-SiC film is related to a crystallization process of the Ge1-0.63C0.63 buffer layer during the film growth.
Raman Investigation of the Localized Vibrational Mode of Carbon in Strain-Relaxed Si1-xGex:C
Authors: Morita Ken , M. Itoh Kohei , Hoffmann Lone , Nielsen Brian B. , Harima Hiroshi , Mizoguchi Kohji
Published: October 2002

The localized vibrational mode (LVM) of carbon in strain-relaxed Si1-x
Gex:C samples with x=0, 0.05, 0.35, and 0.5 have been investigated by Raman spectroscopy at room- and liquid-nitrogen-temperatures. The position of the Raman peaks due to LVM of carbon shifts linearly to lower frequencies with increasing x from 0 to 0.5. The LVM frequencies of carbon obtained by Raman measurement agree very well with those determined by Hoffmann et al. in infrared (IR) absorption recently.
Spatial Coherence of Supercontinuum Emitted from Multiple Filaments
Authors: Watanabe Wataru , Itoh Kazuyoshi
Published: October 2002

We experimentally show that the supercontinuum beams emitted from multiple filaments by focusing femtosecond laser pulses into a liquid or a crystal are mutually coherent. The time-resolved Schlieren method reveals that the positional correlation of different filaments in an artificial array of a supercontinuum is high.
Acceleration of Crystallization Speed by Sn Addition to Ge–Sb–Te Phase-Change Recording Material
Authors: Kojima Rie , Yamada Noboru
Published: October 2002

We have demonstrated that a quaternary Ge–Sn–Sb–Te phase-change recording material obtained by adding Sn to Ge–Sb–Te has a higher crystallization speed than Ge–Sb–Te, and gives a larger erase ratio than Ge–Sb–Te when film thickness is decreased. Static evaluations have shown that a 6-nm-thick quaternary material was crystallized by laser irradiation of 50 ns. Measurements carried out under the conditions of a wavelength of 405 nm, a linear speed of 8.6 m/s and a mark length of 0.294 µm showed that the erase ratio of over 30 dB was obtained with the new composition for a 6-nm-thick layer. A carrier-to-noise ratio (CNR) exceeding 50 dB was also obtained. We think that these effects of Sn addition which give rise to complete crystallization are brought about by abundant nucleation in the amorphous phase even in thin layers. It was confirmed by X-ray diffraction analyses that the new Ge–Sn–Sb–Te material has a single-phase-NaCl-type structure, like the conventional compositions of Ge–Sb–Te.
Sensitivity of the Photo-Crosslinkable Polyimide for Liquid Crystal Alignment
Authors: Lee Wen-Chin , Hsu Chain-Shu , Wu Shin-Tson
Published: October 2002

Two methods were developed for enhancing the photosensitivity of the cinnamates-contained polyimide (PICA). One is to increase the content of cinnamate side chain in PICA main chain and another is to blend some photosensitizer into PICA films. Our experimental results show that increasing the rate of photo-dimerization decreases the alignment ability of the PICA films. Using the molecular simulation method, we successfully describe the photoalignment mechanism of the PICA films. It is also found that photo-induced LC alignment ability of the PICA film could be enhanced through choosing a proper coating solvent.
Electroluminescent Properties of a Bis(2-methyl-8-quinolinato) Aluminum Hydroxide Complex
Authors: So Shukong , Lee Kaman , Choi Waikit , Leung Louis , Lo Wingyee
Published: October 2002

Organic electroluminescence (EL) devices were fabricated using a bis(2-methyl-8-quinolinato) aluminum hydroxide complex [Al(Mq)2OH] as the light-emitting material. The device exhibits bright blue EL at a peak wavelength of 485 nm. A maximum luminance of about 14,000 cd/m2 can be achieved at a driving current density of 480 mA/cm2. The efficiency of the device is about 4.6 cd/A. Possible mechanisms of EL blue shift of Al(Mq)2OH with respect to Alq3 are discussed.
Photoabsorption of Synthetic Silica Glass under ArF Excimer Laser Irradiation
Authors: Shimbo Masaru , Nakajima Toshio , Tsuji Naoki , Kakuno Tsutomu , Obara Takashi
Published: October 2002

In-situ measurement of the transmittance change at 220 nm in synthetic silica glass under the ArF excimer laser irradiation showed three phenomenological stages: 1) initial coloring stage, 2) saturation stage where the coloring reaction equilibrates to the discoloring reaction and 3) heavy dosing stage where a rapid increase in photoabsorption occurs after an increase in the number of laser shots. The coloring rate at the initial stage depends only on the sum of the exposed laser power regardless of laser energy density, frequency and OH concentration. The concentration of OH in the glass reduces the photoabsorption at the saturation stage by increasing the extent of discoloring reaction while it scarcely influences on the number of shots at which the rapid photoabsorption occurs in the heavy-dose region.
Novel Polarized-Light Emitting Polymer Systems: II. Use of Form Birefringent Polarization-Selective Mirrors
Authors: Bastiaansen Natalie Stutzmann , Paul Smith Paul Smith
Published: October 2002

In reflectivity measurements on submicron-embossed polystyrene films, we found that form-birefringent polymer gratings can be described by generalized Fresnel equations for a biaxially anisotropic film in an optically isotropic medium. Thus, polarized-light emitting illumination systems may be envisioned that basically consist of an optically isotropic substrate, into which light is coupled from an external light source, and a second layer, which comprises a form-birefringent, submicron relief structure on the bottom surface that acts as polarization-selective mirror and a light out-coupling structure on the top surface. Such a design should simplify device manufacturing considerably as the main parts of the systems could be produced by injection molding using inexpensive bulk polymers.
Temperature Dependent Polarized-Piezoreflectance Study of Near Direct Band Edge Interband Transitions of AlInP2
Authors: Wen-Chun Yeh Wen-Chun Yeh , Chi-Jen Lin Chi-Jen Lin , Ying-Sheng Huang Ying-Sheng Huang , Chih-Song Chang Chih-Song Chang , Kwong-Kau Tiong Kwong-Kau Tiong
Published: October 2002

We report a detailed temperature dependent study of polarized piezoreflectance (PzR) for two AlInP2 epilayers that exhibit different degree of ordering in the range between 23 and 500 K. The polarized PzR measurements showed anisotropic character along the [110] and [110] directions for the partially ordered sample. The PzR spectra were fitted using the first-derivative of a Lorentzian line shape functional form. The direct band-, crystal field splitting- and spin-orbit splitting to conduction band transition energies which are denoted as E
g, E
g+ΔE
12 and E
g+ΔE
13 respectively, at various temperatures were accurately determined. The temperature dependence of these near direct band-edge critical points transition energies were analyzed by the Varshni expression and an expression containing the Bose-Einstein occupation factor for phonons. The parameters that describe the temperature variation of transition energies were evaluated and discussed.
Phase Constitutions and Microwave Dielectric Properties of Zn3Nb2O8–TiO2
Authors: Kim Dong-Wan , Kim Jin-Ho , Kim Jeong-Ryeol , Hong Kug-Sun
Published: October 2002

The phase constitutions and microwave dielectric properties of (1-x)Zn3Nb2O8–xTiO2 were investigated using X-ray powder diffraction and a network analyzer, respectively. Four mixture regions were studied with increasing TiO2 content (x): (1) Zn3Nb2O8, ZnNb2O6, and Zn2TiO4, (0<x≤0.5) (2) ZnNb2O6 and Zn2TiO4, (0.5<x<0.65) (3) Zn2TiO4, ZnTiNb2O8, and TiO2 (0.65≤x≤0.75), (4) Zn2TiO4 and TiO2 (0.75<x<1). This structural evolution with composition was ascribed to the interrelations between Zn3Nb2O8 and TiO2. It was demonstrated that the microwave dielectric properties correlated to crystal structure rather than chemical composition. In the mixture region of Zn2TiO4, ZnTiNb2O8, and Zn2TiO4, the amount of TiO2 and ZnTiNb2O8 considerably increased and decreased, respectively, with increasing TiO2 content (x). This resulted in the increase of relative dielectric constant (ε
r) and temperature coefficient of resonant frequency (τf). At x=0.725, Q×f is 5190 GHz, ε
r and τf are 36 and 4 ppm/°C, respectively.