bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Properties and Strain Analysis in Paraelectric ZrTiO4Thin Films Deposited by DC Magnetron Sputtering
Authors: Kim Taeseok , Oh Jeongmin , Park Byungwoo , Hong Kug Sun
Published: October 2002

The dielectric constants and dielectric losses of ZrTiO4thin films deposited by DC magnetron reactive sputtering were investigated. The paraelectric properties were measured in the 100 kHz range, and compared with an equivalent circuit model. As the deposition temperature increased (up to 600°C), the dielectric losses (tan δ) decreased (down to 0.017±0.007), while the dielectric constants (ε) were in the range of 35±7. Post annealing at 800°C in oxygen for 2 h reduced tan δ down to 0.005±0.001, higher than those of well-sintered bulk ZrTiO4. The systematic trend of tan δ as a function of deposition temperature and post annealing showed good correlations with strains in ZrTiO4thin films deduced from the broadening of X-ray diffraction peak.
Field Emission of Electrons from Graphitic Nanofibers Produced in a Hydrogen Arc Discharge
Authors: Saito Yahachi , Mizushima Ryou , Kondo Shin-ichiro , Maida Masatomo
Published: October 2002

Graphitic nanofibers (named “nanografibers”), which have a structure similar to that of multiwall carbon nanotubes but an extremely narrow (or practically absent) hollow channel, were produced by an electric arc discharge in hydrogen gas. Field emission from nanografibers was investigated using a field emission microscope with a probe hole. Nanografibers exhibited a lower onset voltage and higher current density in comparison with ordinary multiwall nanotubes prepared in helium gas. The emission characteristics are argued to originate from the morphology and structure of the nanografibers.
Two-Dimensional Modeling of Slot-Excited Surface Waves in Bounded Planar Plasmas
Authors: Abdel-Fattah Essam , Ghanashev Ivan , Sugai Hideo
Published: October 2002

The excitation of electromagnetic waves launched by a linear slot antenna in a planar bounded surface wave plasma is modeled and numerically analyzed. For simplicity, a two-dimensional (infinite along x) model is applied. The electromagnetic field distribution, the total field energy and the power reflection coefficient R are computed. All are found to depend critically on the electron density n
e, and the density dependencies qualitatively reproduce the known experimental behavior. In particular, the computed R–n
e dependencies with sharp minima at some resonance densities result in the experimentally observed [Ghanashev et al.: Jpn. J. Appl. Phys. 36 (1997) 4704] mode jumps and hysteresis loops in the power–density curves. The computational efficiency achieved through the two-dimensional formulation makes the model suitable for use as a part of a self-consistent analysis of the surface-wave plasma source operation.
Low-temperature Crystallization of Metal Organic Decomposition BaTiO3 Thin Film by Hydrothermal Annealing
Authors: Wei Zhiqiang , Xu Huaping , Yamashita Kaoru , Okuyama Masanori
Published: October 2002

BaTiO3 (BTO) thin films with perovskite structure have been prepared on Ti/Pt/Ti/SiO2/Si substrate using a combined process of conventional metal organic decomposition (MOD) process and a hydrothermal method. BTO thin films with polycrystalline structure are obtained on silicon at processing temperatures lower than 200°C. X-ray diffraction patterns show that well-developed crystallites with a pure perovskite phase have been formed. Scanning electron microscopy (SEM) and Raman spectroscopy results show that the structure of as-treated BTO thin film strongly depends on the hydrothermal treatment temperature.
Silicalite and Metallosilicate Surface Modeling and Density Functional Theory Studies of Surface Properties
Authors: Munakata Hiroaki , Miyamoto Akira
Published: October 2002

A density functional theory study of cluster models was conducted to explore the
relative stability of the cluster model for the Ti site of titano-silicalite-1, based on a
plausible reaction path. Stability of the peroxo-TS-1 species, having a Ti–O–O–Si
moiety, and peroxo-MFI-type-silicalite, having a Si–O–O–Si moiety, was examined
according to the synthetic route, that involved reaction of a TS-1 or silicalite cluster
model with hydrogen peroxide. Properties of the density of states of these peroxo-TS-1
species were analyzed.
Characteristics of the (√3×√3)R30° Superstructure of Graphite by Scanning Tunneling Microscopy
Authors: An Bai , Fukuyama Seiji , Yokogawa Kiyoshi , Yoshimura Masamichi
Published: October 2002

The bias-voltage- and the tunneling-current-dependent scanning tunneling
microscopy (STM) images of the (√3×√3)R30°
superstructure of graphite formed near defects produced by Ar+-irradiation
on highly oriented pyrolytic graphite annealed at 1373 K were investigated.
The (√3×√3)R30° superstructure of graphite is
gradually changed to a triangular structure and the area of the superstructure
becomes smaller with increasing bias voltage or decreasing tunneling current,
namely, with increasing tip-sample distance. This result indicates that the STM
image of the (√3×√3)R30° superstructure of
graphite mainly depends on the tip-sample distance. It is suggested that the
electronic superstructure induced by the defects on the surface of graphite
decays faster than the electronic structure of normal graphite in vacuum.
Extension of the ArF Excimer Lithography to Sub-0.10 µm Design Rule Devices Using Bi-layer Silylation Process
Authors: Satou Isao , Watanabe Hiroyuki , Endo Masataka , Morimoto Hiroaki
Published: October 2002

The device design rule has been significantly reduced, and a practical pattern
fabrication technique for sub-0.10 µm or smaller dimensions is urgently
required. The top surface imaging (TSI) process using an ArF excimer laser
(wavelength=193 nm) is a promising approach to the realization of this
demand. We have been evaluating the positive-tone silylation process as one of the TSI
processes in order to extend the limit of ArF optical lithography. We found that for the
positive tone silylation process, control of the silylation depth and profile is very
important, and the bi-layer silylation process using a thin silylation resist as a top
layer is a practical and effective process for fine pattern fabrication. In this report,
we describe the high lithographic performances of this bi-layer silylation process and
its application to sub-0.10 µm rule device manufacturing.
Hydrogen Effect on Damage Structure of Si(100) Surface Studied by in Situ Raman Spectroscopy
Authors: Hara Takanobu , Yoshida Tomoko , Tanabe Tetsuo , Ii Tatsuya
Published: October 2002

In situ Raman measurements have been performed on a Si(100) surface under irradiation by low-energy H+, D+ and He+. The intensity of the 520 cm-1 Raman peak of crystalline Si decreased almost linearly with the square root of displacement per atom (dpa), suggesting that the peak reduction originates from defect clusters but not single vacancies or interstitials. At a high dpa, the peak intensity became very low and broadened due to amorphization for all incident ions. In addition, the chemical effect of hydrogen was clearly observed, i.e., the reduction rate at low dpa was slightly enhanced by H+ and D+ irradiation as compared to that with He+, whereas H+ and D+ decelerated the amorphization as compared to He+. The initial damage enhancement is attributed to Si–H bond formation, whereas the later deceleration of the amorphization is attributed to the formation of H2 molecules recovering Si–Si bonds.
Depolarization Current by a Dipolar Defect in Semi-Insulating GaAs
Authors: Kim Hwa-Min , Kim Jong-Jae
Published: October 2002

To investigate the trap characteristic of native defects in a semi-insulating (SI) GaAs, the thermally stimulated depolarization current (TSDC) is compared with the thermally stimulated current (TSC). Beside several trap-limited current peaks, a significant TSDC peak with the activation energy of 0.40 eV is observed at 178 K. Dependence of the peak on the polarization voltage strongly suggests that this peak originates from the depolarization current from a dipolar defect in the SI GaAs.
Optical Response Spectra Calculation of Wide-Gap ZnSe Surfaces
Authors: Takashi Nakayama Takashi Nakayama , Misao Murayama Misao Murayama
Published: October 2002

Reflectance difference spectra of (110) and (001) ZnSe surfaces are calculated using the s
p
3
s
* tight-binding method. It is shown that the buckling (1 ×1) and Se-dimer (2 ×1) reconstructions well explain the observation for the (110) and (001) surfaces.
The Growth Mechanism of SiC Film on a Si(111)-(7×7) Surface by C60 Precursor Studied by Photoelectron Spectroscopy
Authors: Kazuyuki Sakamoto Kazuyuki Sakamoto , Daiyu Kondo Daiyu Kondo , Kenichi Ohno Kenichi Ohno , Akio Kimura Akio Kimura , Akito Kakizaki Akito Kakizaki , Shozo Suto Shozo Suto , Wakio Uchida Wakio Uchida , Atsuo Kasuya Atsuo Kasuya
Published: October 2002

We have investigated the growth mechanism of SiC film by the thermal
reaction of C60 molecules adsorbed on a Si(111)-(7×7) surface
using photoelectron spectroscopy.
The growth of SiC film, performed by repeating the sample annealing at 1370 K following the adsorption of C60 molecules, is confirmed by the
profile of the valence spectrum.
The bonding nature between C60 molecules and the SiC surface is
considered to have a covalent character at 300 and 670 K, and both covalent
and ionic characters at 870 K by the thermal-dependent valence and C 1s core level spectra of a 1 monolayer C60 film adsorbed on SiC.
Furthermore, we determined that the breaking of the C60 cage and the
formation of SiC occurred at 1070 K, i.e. at a temperature 100 K lower than
that on a Si(111) surface.
X-Ray Photoelectron Spectroscopic Observation on the Formation of Carbon Nitride Thin Films Produced by Low-Energy Nitrogen Ion Implantation
Authors: Shimoyama Iwao , Sekiguchi Tetsuhiro , Baba Yuji
Published: October 2002

X-ray photoelectron spectroscopy (XPS) spectra of N 1s and C 1s were measured for carbon nitride thin films prepared by low-energy nitrogen ion implantation in graphite. To assign the XPS spectra, we also measured XPS spectra for some standard materials which have s
p
2 or s
p
3 C-N bond configurations. In N 1s XPS spectra for the ion-implanted graphite, we found three clear peaks at the binding energies of E

B
=398.3, 400.3, and 402.6 eV. However, in spite of the difference in bonding systems, all the carbon nitride compounds showed similar N 1s binding energies corresponding to the second peak (E

B
=400.3 eV). Furthermore, we found a broad structure which resulted from the formation of C-N bonds at a binding energy 2 eV higher than that of the graphite peak, by removing the damage effect from the C 1s XPS spectra for the ion-implanted graphite. Based on these results, we propose an assignment of XPS spectra for the ion-implanted graphite.
Analysis of Thin Oxide Growth Mechanisms in Partial-Pressure Rapid-Thermal Oxidation of Silicon
Authors: Kotani Yasumi , Omura Yasuhisa
Published: October 2002

In this paper we analyze the growth mechanism of extremely thin silicon-oxide
layers, formed by rapid thermal oxidation under various oxygen partial pressures, on
the basis of the Deal-Grove model and the silicon-fragment model. It is determined
that the silicon-fragment model gives an acceptable interpretation of the experimental
results concerning the linear rate constant.
Characterization of Crystalline TiC Films Grown by Pulsed Nd:YAG Laser Deposition
Authors: V. Rao Yoshiaki Suda
Published: October 2002

Titanium carbide (TiC) thin films have been grown on Si (100) substrates using a pulsed neodymium: yttrium-aluminum-garnet (Nd:YAG) laser deposition method. X-ray diffraction (XRD) pattern of the TiC film shows that substrate temperature is one of the most important parameters in the fabrication of crystalline TiC film. Crystalline TiC films can be prepared at substrate temperatures above 500°C. Field emission scanning electron microscope (FE-SEM) indicates that the surface of the film is very smooth and pinhole-free.
Growth Interruption Effect on the Formation of CdSe/ZnSe Quantum Dots
Authors: Ohishi Masakazu , Saito Hiroshi , Yoneta Minoru , Ichikawa Takaaki , Fujimoto Tomohiro
Published: October 2002

CdSe dot generation and dot development on a ZnSe(100) surface
are investigated by insitu observation of specular spot intensity
(I
sp) in a reflection high energy electron diffraction (RHEED)
pattern during CdSe growth, using the alternate molecular beam
supplying method. From the temporal I
sp observation, it is confirmed
that CdSe dots are generated immediately after the 1-ML CdSe is
formed on 2-ML CdSe wetting layer on ZnSe(100). We also confirmed
that the dot growth by Ostwald ripening continues during Cd-beam
irradiation, and that the dots sublimate when they are exposed to
vacuum at a growth temperature of 250°C. The beam interruption
(or growth interruption) strongly affects on the PL peak energy.
Structural Properties of P-Type Microcrystalline Silicon as a Window Layer of Solar Cells
Authors: Sasaki Toshiaki , Fujikake Shinji , Ichikawa Yukimi
Published: October 2002

Microcrystalline silicon (µc-Si) material has been used widely for amorphous silicon-based solar cells as a window layer and a tunnel junction layer. In such applications the layers are very thin, thus, the film properties of the initial growth stage of the µc-Si layer strongly affect the performance of solar cells. We studied the structural properties of the p-type µc-Si layer used for the window layer of p-i-n solar cells and the relationship between them and the photovoltaic performance. To observe the structural properties, measurements such as Raman scattering spectra, scanning electron microscopy and transmission electron microscopy were carried out with samples having a p-i-n cell structure. The results show that the µc-Si layer structure strongly depends on the substrate temperature, and that the photovoltaic performance of the solar cell also varies with the substrate temperature of the µc-Si layer deposition. The effect of the structural properties of the µc-Si layer on the device performance was discussed on the basis of these studies.
Magnetic Properties of β-FeSi2 Semiconductor
Authors: Tagaya Kimihito , Hayashi Yoshikazu , Maeda Yoshihito , Umezawa Kenji , Miyake Kiyoshi
Published: October 2002

High-quality crystals of β-FeSi2 are ion-beam synthesized on the surface of a floating-zone(FZ)-grown Si wafer, and superconducting quantum interference device (SQUID) and ESR measurements are performed. β-FeSi2 semiconductors exhibit paramagnetic properties, and the Weiss temperature is positive near room temperature. The magnetic susceptibility changes anomalously with temperature.
Observation of Self-Phase-Matched Lossless Radiative Modes in Dielectric Spheres
Authors: Yi Soung-soo , Stafsudd Oscar M.
Published: October 2002

A theoretical investigation of plane-wave electromagnetic scattering in active dielectric spheres predicted the existence of resonances that occur at discrete wavelengths. These resonances may be understood from a phase-matched leaky mode, in which the gain in the dielectric exactly compensates for the radiative loss of a mode. This results in a radiative mode that does not decay in time. Therefore, it is described as a lossless radiative mode. Experiments have been performed to verify the existence of these resonances. Self-phase-matched resonances from pumped active dielectric spheres have been observed. Optical pumping was used to provide the gain, and the threshold of each resonant mode was found to be a function of the dye concentration and the radius of the dielectric sphere.
Theory of Photorefractive Grating Formation in the Presence of the Bulk Photovoltaic Effect
Authors: Okamura Hideki
Published: October 2002

A simple analytical expression for the evolution of photorefractive grating was derived for photovoltaic materials. The theory is based on the band transport model under the quasi-cw approximation, and a small light modulation was assumed. The resultant expression is consistent with the existing theory and is applicable to all the time regions of the evolution of the grating. It accounts for the major characteristics of the photorefractive effect observed in Fe:LiNbO3 including the apparently anomalous large phase shift of the grating, the shift of the grating during erasure, and the quasi-equivalence of the bulk photovoltaic effect to an external field. We also conducted numerical simulations based on the coupled wave theory. The result is consistent with the experiment reported elsewhere, except for the large beam coupling that was experimentally observed. This can, however, be ascribed to an origin external to the grating formation.
Dependence of the Photoacoustic Signal Intensity on Modulation Frequency for CdInGaS4 Crystals under a Transmission Detection Configuration
Authors: Shen Qing , Toyoda Taro
Published: October 2002

Dependence of the photoacoustic (PA) signals on the modulation
frequency was
measured for CdInGaS4 crystals in the reflection and transmission
detection configurations
(RDC and TDC). The PA signals originate from both the thermal
diffusion and
photo-excited carrier diffusion processes under TDC. The two processes
can be separated
by changing the modulation frequency of the excited light. The
experimental results show
the possibility of characterizing the thermal and electronic
properties of CdInGaS4 crystals by
the PA technique in TDC.
Scaling Dependence of a Low Temperature Operated Copper Vapor Laser
Authors: Ohzu Akira , Kato Masaaki , Maruyama Yoichiro
Published: October 2002

An experimental study focused on the radial scaling of HyBrID (Hydrogen Bromide In Discharge) copper vapor lasers has been carried out by using laser tubes (length 1.2 m) of inner diameter 40, 60 and 80 mm. The detailed parametric dependence on laser output power with each of the bore tubes is compared under the same operating conditions. 90 W of output power was obtained with both a 40 and 60 mm bore tube. By increasing the tube temperature, similar high output power can be produced with a 80 mm bore tube. Enlarging the tube bore results in a reduction of extractable average output power. It has been found that the output characteristics strongly depend on the tube temperature. Control of the tube temperature is crucially important for efficiently producing high output power. A discussion is presented in which the lasing performance under the differing tube conditions is compared.
Effects of Interfacial States on Electrical Properties of SrBi2Ta2O9 Thin Films
Authors: Choi Gwang-Pyo , Park Jeong-Ho , Lee Chi-Heon , Kim Il-doo , Kim Ho-Gi
Published: October 2002

Electrical properties of SrBi2Ta2O9 thin-film capacitors with Pt electrodes were characterized immediately and 24 h after top electrode annealing. The leakage current density decreased abruptly 24 h after annealing, whereas it was very high, over 10-4 A/cm2 at 3 V, immediately after annealing. The dielectric dispersion was observed immediately after annealing and became weaker with increasing stabilization time (the sustaining time in air after annealing is finished). It was found that the interface resistance increased and the quantity of metallic Bi at the interface decreased with increasing stabilization time. This suggests that conducting phases may be transformed in to resistive phases due to the interaction of Bi and O atoms. It was also observed that the imprint of SBT capacitors was strongly dependent upon the initial poled state. The imprint property was improved as stabilization proceeded and this may be due to the relative reduction of electronic carriers participating in the trapping/detrapping.
Amorphous Carbon Fibrilliform Nanomaterials Prepared by Chemical Vapor Deposition
Authors: Takikawa Hirofumi , Yatsuki Miki , Miyano Ryuichi , Nagayama Makoto , Sakakibara Tateki , Itoh Shigeo , Ando Yoshinori
Published: October 2002

Carbon nanomaterials were prepared by chemical vapor deposition (CVD) and hot-filament CVD (HF-CVD) methods. The substrates were silicon <100 > and copper plates on which catalytic metal or metal-oxide thin films were coated by means of the cathodic arc deposition technique. Ethylene gas was used as a precursor. HF-CVD with a filament temperature of 1,000°C yielded a larger amount of carbon deposit at a lower furnace temperature of 600°C. High-resolution microscopic observation revealed a variety of amorphous carbon nanomaterials, such as frost columns, coral beads, microcoils, nanocoils, and amorphous nanotubes.
Forward and Inverse Solutions for the Scattering of Longitudinal Waves Normally Impinging upon Multilayered Chiral Media
Authors: Sung Chia-Chi , Chang Yuh-Ming , Ro Ruyen
Published: October 2002

A matrix method is employed in this paper for the solution of wave propagation problems in multilayered chiral/achiral slabs bound by two semi-infinite achiral media. Reflection and transmission characteristics of the multilayered chiral slab for longitudinally elastic waves with normal incidence are thoroughly discussed. In addition, by using realistic refractive indices, the desired scattering characteristics are inversely obtained by accurately tailoring the constitutive parameters of the multilayered chiral materials. The obtained results will benefit the design of broadband acoustic impedance transformers and acoustic filters for arbitrarily desired transmittance characteristics.
Effect of Binder Content on Shrinkage Behavior of a Multilayered Ceramic Substrate
Authors: Chen Lih-Shan , Fu Shen-Li , Huang Wen-Kwei
Published: October 2002

Among the many variables governing the shrinkage of ceramic substrate, packing density is the most important. The effect of binder content on the shrinkage behavior of a free and constrained sintering glass-ceramic multilayered substrate is investigated. For lower packing density, the packing of ceramics within the glass-ceramic green sheets was looser and a higher sintering shrinkage was obtained. A good agreement between the calculated and experimental vertical shrinkage is obtained for constrained sintering glass-ceramic substrates using the proposed analytical procedure.
Spectroscopical Measurements of Ablation Plasma Generated by an Excimer Laser from Functionally Graded Materials
Authors: Uchida Yoshihisa , Yamada Jun , Uchida Yoshiyuki
Published: October 2002

Functionally graded materials (FGMs) are drawing attention in the fields of industrial applications. For industrial applications, FGMs require reprocessing, such as cutting and drilling. It is generally difficult to reprocess FGMs. Therefore, excimer laser processing that enables microprocessing has been made available. When the FGM is exposed to a laser beam, ablation plasma is generated. The mechanism of generating the ablation plasma, which differs for each material, influences the accuracy of production, but this has not been investigated sufficiently. The purpose of this study is to analyze the mechanism of ablation plasma generation and to achieve precise microprocessing and surface treatment methods for FGMs by controlling the plasma generation. This paper reports on the characteristics of the electron temperature in ablation plasma. The laser used in this experiment was an ultraviolet pulse excimer laser with a wavelength of 308 nm, a maximum pulse energy of 500 mJ and a pulse duration of 30 ns. The electron temperature dependence of the ablation plasma plumes on the ceramic-metal content of FGMs is observed.
Investigation of Microdeflection Liquid Crystal Display Modes
Authors: Ishimaru Masashi , Okada Hiroyuki , Onnagawa Hiroyoshi
Published: October 2002

Microdeflection liquid crystal display modes have been investigated.
Zigzag-shaped electrodes, which are patterned on each side of the substrate, face each
other. Each microdomain deflects extraordinary rays in the molecular direction by using
an obliquely applied electric field. The contrast ratio was 462:1 for parallel nicols
under He–Ne laser illumination.
Control of Crystal Orientation of Ferroelectric SrBi2Ta2O9 Thin Films with Multi-Seeding Layers
Authors: Osaka Tetsuya , Yoshie Tomohisa , Hoshika Takeshi , Koiwa Ichiro , Sawada Yoshihiro , Hashimoto Akira
Published: October 2002

A Bi-Ta multi-seeding layer system is proposed to improve the ferroelectric properties of SrBi2Ta2O9 (SBT) thin films prepared by a sol-gel method for applications to nonvolatile memories. For seeding layers composed of different ratios of Bi to Ta, three different structures were observed after heat treatment at 800°C: γ-Bi2O3, Bi3TaO7 and Bi1.4Ta2O6.75. γ-Bi2O3 with a sillenite structure exhibited a plate-like surface morphology. Bi3TaO7 with a fluorite structure exhibited a flat surface morphology. Bi1.4Ta2O6.75 with a pyrochlore structure exhibited a rough surface morphology. Because a flat surface morphology with a fluorite structure is desirable for a seeding layer, the Bi–Ta seeding layers, with a Bi to Ta ratio equal to 3 to 1, were used as multi-seeding layers. When the seeding layers were sandwiched between SBT thin films, multi-seeding layers provided, after heat treatment at 800°C, a higher degree of crystal orientation in the a- or b-axis direction than a simple SBT thin film without seeding layers. Orientation in the a- or b-axis direction is desirable for SBT thin films to obtain improved ferroelectric properties, especially high remanent polarization values. The SBT thin film with Bi–Ta multi-seeding layers was found to have higher saturation characteristics than that without seeding layers, which suggests that the former type of SBT thin film has a good potential for low-voltage operation. The multi-seeding method is thus effective for improving ferroelectric properties of SBT thin films for nonvolatile memories.
Preparation of Layer-Structured CaBi2Ta2O9 Ferroelectric Thin Films through a Triple Alkoxide Route
Authors: Kato Kazumi , Suzuki Kazuyuki , Nishizawa Kaori , Miki Takeshi
Published: October 2002

A triple alkoxide solution for CaBi2Ta2O9 (CBT) thin films was prepared. CBT thin films were deposited on Pt-passivated silicon and Pt-passivated quartz glass substrates. The thin films on Pt-passivated silicon crystallized to form the perovskite structure at low temperatures and showed preferred orientation along the c-axis. The thin films did not show ferroelectric P–E hysteresis loops. In contrast, the 750°C-annealed thin film on Pt-passivated quartz glass showed random orientation and exhibited excellent P–E hysteresis loops. The remanent polarization (P
r) and the coercive electric field (E
c) at 13 V were 6.9 µC/cm2 and 170 kV/cm, respectively.
Selective-Area Repoling of Single-Crystalline LiTaO3 and Its Characterization
Authors: Yagyu Hiroyuki , Matsushima Tomoaki
Published: October 2002

Selective-area repoling (SARP) of single-crystalline LiTaO3 has been investigated. SARP is impossible at room temperature, whereas single-domain inversion can occur. At high temperatures, SARP is completed under the applied field of 12 kV/mm at 190°C, which is almost the same condition as that required for single-domain inversion. By fitting the SARP current to the Avrami theory, it is deduced that a sidewise growth mechanism is dominant in the process. A few kinds of metal in the electrode and surface contamination can diffuse into LiTaO3 during SARP and thus affect the charge density and convergence time, i.e., the progress of SARP. Transmission electron microscopy has revealed the domain structure, the lattice defect and the single-domain capping layers that have positive surface charge on both the front and back. Inverted microdomains formed in the capping layer do not easily grow and coalesce into single domains and remain after the SARP process.
Effect of Microstructure on Reliability of Ca(TiZr)O3-Based Multilayer Ceramic Capacitors
Authors: Motoki Tomoo , Naito Masahiro , Sano Harunobu , Konoike Takehiro , Tomono Kunisaburo
Published: October 2002

We examined the reliability of Ca(TiZr)O3 (CTZ)-based Ni-electrode multilayer ceramic capacitors (MLCs) prepared by two different processes with particular interest in the microstructure. One process was to calcine the mixture of CaCO3 and TiO2 to prepare CaTiO3 (CT) powder and the mixture of CaCO3 and ZrO2 to prepare CaZrO3 (CZ) powder, and then mix these calcined powders and sinter them to synthesize the CTZ-based ceramics. The other was to calcine the mixture of CaCO3, TiO2 and ZrO2 powders together to prepare CTZ powder and then sinter them. These two processes of CTZ ceramic preparation resulted in a different crystallinity and distribution of the elements. We found that these factors influenced the reliability of CTZ-based MLCs.
Temperature Dependence of Piezoelectric Properties of a High Curie Temperature Pb(In1/2Nb1/2)O3-PbTiO3 Binary System Single Crystal near a Morphotropic Phase Boundary
Authors: Yasuda Naohiko , Ohwa Hidehiro , Hasegawa Daisuke , Hayashi Koji , Hosono Yasuharu , Yamashita Yohachi , Iwata Makoto , Ishibashi Yoshihiro
Published: October 2002

The temperature dependence of the dielectric and piezoelectric properties of a 0.72Pb(In1/2Nb1/2)O3-0.28PbTiO3 binary system single crystal oriented along the [001] axis near a morphotropic phase boundary was investigated in poled and unpoled states. With poling, the permittivity ε
r and the dielectric loss tangent tan
δ decrease from 2650 and 0.05 before poling to 800 and 0.01 after poling, respectively. The change in both the ε
r and the tan
δ at the ferroelectric rhombohedral-to-tetragonal phase transition temperature T
fr with temperature are significantly reduced with poling. The electromechanical coupling coefficient in the rectangular bar mode, k
33
′=77%, for phase-array ultrasonic transducers was obtained using the rhombohedral 0.72Pb(In1/2Nb1/2)O3-0.28PbTiO3 single crystal oriented along the [001] axis. With increasing temperature, the value of k
33
′ decreases slightly in the rhombohedral phase, shows a slight anomaly around T
fr, and then remains almost constant in the tetragonal phase. Even at 200°C, the k
33
′ value decreases by only 5%. The piezoelectric constant d
33 was 700 p
C/N at room temperature.
Preparation of Pb(Zr0.53Ti0.47)O3 Thick Films by an Interfacial Polymerization Method on Silicon Substrates and Their Electric and Piezoelectric Properties
Authors: Tsurumi Takaaki , Ozawa Shuichi , Abe Goro , Ohashi Naoki , Wada Satoshi , Yamane Masayuki
Published: October 2002

Pb(Zr0.53Ti0.47)O3 (PZT) films of 10 to 50 µm in thickness were prepared by a new sol-gel process using an interfacial polymerization technique. The interfacial polymerization process is that an alkoxide precursor solution is poured on the surface of water in a container to form a gel film at the interface between the two immiscible liquids. The precursor solution was prepared by adding PZT alkoxide solution, PZT powders coated with Pb5Ge3O11 (PG), and a surfactant into hexane solvent. After the polymerization at the interface, the gel films were gently placed on a silicon substrate by draining the water in the container. The gel films containing PZT powders were sintered at 950°C for 10 min to obtain crystallized PZT films. The remanent polarization of a PZT thick film was 33.1 µC/cm2. The piezoelectric d
33 constant measured with a Mach-Zehnder interferometer was 225 pm/V and was independent of frequency from 0.2 to 3 kHz. A process to create patterns of PZT thick films was developed. The resonance frequencies of four square patterns of 2×2 mm2 in size were consistent, which indicated that the interfacial polymerization process enables the fabrication of uniform thick films in a large area.
Microwave Dielectric Properties and Crystal Structure of Y2(Ba1-xSrx)(Cu1-yZny)O5 Solid Solutions Synthesized by a Solid-State Reaction Method
Authors: Kan Akinori , Ogawa Hirotaka , Ohsato Hitoshi , Ishihara Soichi
Published: October 2002

The microwave dielectric properties of Y2Ba0.7Sr0.3(Cu1-y
Zn
y
)O5 (y=0 to 1) solid solutions have been discussed on the basis of the crystal structure refined by the Rietveld method. The variations in the lattice parameters depend on the changes in the atomic distances in an MO5 (M=Cu and/or Zn) pyramid with Zn substitution for Cu. In addition, it is recognized that these variations in the MO5 pyramid also exert on the variations in the atomic distances of an AO11 (A=Ba and/or Sr) polyhedron. The quality factor (Q·f) of the microwave dielectric properties obtained in this study shows a maximum in the sample of Y2Ba0.7Sr0.3(Cu0.15Zn0.85)O5 solid solution, increasing with the increase of Zn content in the solid solutions, and the value is 23643 GHz. Thus, it was suggested that the Q·f values are closely related to the variation in atomic distances of both AO11 polyhedra and MO5 pyramids.
Polarization Reversal in Ferroelectric Fluoro-Polymers
Authors: Konno Atsushi , Shiga Kazuyoshi , Suzuki Hideshige , Koda Tomonori , Ikeda Susumu
Published: October 2002

This paper deals with polarization reversal in single crystalline films of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene. The activation electric field is about 0.9 GV/m, which is relatively large compared with that for other samples. The process of polarization reversal in the single crystalline films becomes very sharp, and the sharpness is discussed on the basis of the nucleation and growth theory.
Two Levels of Ni/n-GaAs Schottky Barrier Heights Formed on a Wafer by Controlling pH of Pretreatment Chemicals: Effect of Oxygen Adsorption
Authors: Tsuzuku Tatsutoshi , Sugimura Tomoyuki , Kasai Yuuki , Inokuma Takao , Iiyama Kouichi , Takamiya Saburo
Published: October 2002

Schottky barrier heights of Ni/n-GaAs junctions were controlled by changing the pH of pretreatment chemicals. An effective barrier height of 0.8 eV was obtained by treatment with dilute HCl liquid (pH = l), and 0.6 eV by treatment with dilute NH4OH liquid (pH = 13). Surface analysis by an x-ray photoelectron spectroscopy indicated the existence of about twice the density of oxygen at the surface of the HCl-treated wafer as compared with that pretreated by the NH4OH liquid. The former shows nearly linear C
-2–V characteristics, while the latter shows larger but less frequency dependent capacitances. Two levels of Ni/n-GaAs Schottky barriers were formed on a wafer by successive pretreatments and selective Ni evaporations.
Scanning Tunneling Microscopy and Atomic Force Microscopy Studies of Laser Irradiation of Amorphous WO3 Thin Films
Authors: Qiu Hong , Lu Yong-Feng
Published: October 2002

The effect of irradiating amorphous WO3-x
thin films by an excimer laser and a Nd-YAG (yttrium-aluminum-garnet) laser on the evolution of electronic states was investigated by scanning tunneling spectroscopy (STS) and X-ray photoelectron spectroscopy (XPS). The original films prepared by pulsed-laser deposition (PLD) were first irradiated by a KrF excimer laser at 248 nm in air. The surface was reduced to a quasi-metallic one with oxygen deficiency and the number of W 5d occupied states was increased. A number of surface states appeared on the films. When the films were subsequently irradiated by the Nd-YAG laser at 1.06 µm in air, the number of W 5d occupied states was reduced due to oxygen restoration. The number of surface states was also greatly reduced. A water layer on the surface, which played a key role in photolysis, was monitored by STS by trapping charges in the Schottky barrier. Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) images of the films at three states: original, surface reduced, and surface restored, were compared in terms of average profile roughness and height. Thermal effects (thermochromism) dominated in the Nd-YAG laser irradiation, resulting in a maximum average roughness in the AFM images, whereas photon effects (photochromism) dominated in excimer laser irradiation, which led to the highest conductance. Slight nanocrystallization occurred in the laser-irradiated films.
Microwave Dielectric Properties of (Pb, Ca)(Mg, Nb, Sn)O3 Ceramics
Authors: Choi Ji-Won , Ha Jong-Yoon , Kang Chong-Yun , Yoon Seok-Jin , Kim Hyun-Jai , Yoon Ki Hyun
Published: October 2002

The microwave dielectric properties of (Pb0.4Ca0.6){(Mg1/3Nb2/3)1-x
Sn
x
}O3 (0≤x≤0.1) ceramics have been investigated. The (Pb0.4Ca0.6)(Mg1/3Nb2/3)O3 ceramic was tetragonal complex perovskite single phase material and single phase specimens having tetragonal complex perovskite could also be obtained in case of substituting by tin(Sn). The partial substitution of [Mg1/3Nb2/3]4+ by Sn4+ at B-site of the perovskite structure significantly improves the loss quality factor (Q) and slightly decreases dielectric constant (ε
r) and temperature coefficient of resonant frequency (τf). The temperature coefficient of resonant frequency of 0 ppm/°C was realized at x=0.01. The Q·f
o value and ε
r for this composition were found to be 7130 GHz and 64.7 respectively.
Polarization States of Ferroelectric Liquid-Crystal in a Twisted Structure
Authors: Kim Young Jin , Zhuang Zhizhong , Patel Jay S.
Published: October 2002

The twisted ferroelectric liquid-crystal structure is investigated using a smectic liquid-crystal that has a low tilt angle of about 25° in the smectic C* phase and has a smectic A phase. The twisted ferroelectric alignment is achieved in a cell that has non-parallel rubbed boundary conditions. Using a polarimeter the structure is investigated by using polarized light. The change of the polarization of the light, as the sample is rotated in the absence and in the presence of an applied field, is compared with the expected behavior based on a theoretical model. By measuring and by calculating Stokes parameters, we are able to demonstrate an agreement between the theory and the experiment, and verify that the twisted structure is produced in this material. This twisted structure shows analog switching in a low field regime.
Gate-Length Dependence of Negative Differential Resistance in InGaAs/InAlAs Quantum Well Field-Effect Transistor
Authors: Kim Seong-Jin , Sugaya Takeyoshi , Ogura Mutsuo , Sugiyama Yoshinobu
Published: October 2002

We have investigated the gate-length dependence of negative differential resistance (NDR) in an InGaAs/InAlAs quantum well field-effect transistor (QW-FET) by varying the gate length from 50 nm to 0.8 µm. A pronounced N-shaped NDR is clearly observed in these QW-FETs. The gate leakage current is detectable only by the onset of NDR. We believe that the NDR should be attributed to the real space transfer of channel electrons into the barrier layer with low mobility underneath the gate by gate field-assisted tunneling (RSTT). Both peak-to-valley current ratio (PVR) and onset voltage (V
NDR) are found to be strongly dependent on the gate length. The NDR characteristics in terms of PVR and V
NDR are improved dramatically by reducing the gate length, and originate from the velocity overshoot due to the suppression of scattering probability.
Submicron Nonvolatile Memory Cell Based on Reversible Phase Transition in Chalcogenide Glasses
Authors: Nakayama Kazuya , Kojima Kazuhiko , Hayakawa Fumihito , Imai Yutaka , Kitagawa Akio , Suzuki Masakuni
Published: October 2002

Electrically rewritable nonvolatile memories using chalcogenide semiconductors were studied. The memory cell size was changed from 0.3 to 1.5 µmφ using a focused ion beam. This material can be used for nonvolatile random access memory. Reversible phase transition between the amorphous and crystalline states, which is accompanied by a considerable change in electrical resistivity, is exploited to store bits of information. The currents for write/erase were decreased with reducing memory cell size. In the memory cell of 0.6 µmφ, more than 104 repetition cycles of the phase transition were attained by the electric pulses. The voltages for the crystallization and amorphization processes were 2 V and 2.2 V, respectively.
Photodarkening and Photobrightening in Glasses Doped with CdS and CdSxSe1-x Nanocrystals
Authors: Miyoshi Tadaki , Hirano Akito , Suenaga Tomomi , Nagata Junya , Nagai Tetsuro , Matsuo Naoto
Published: October 2002

The photobrightening of photodarkened CdS- and CdSxSe1-x
-doped glasses has been investigated with luminescence experiments. Photobrightening depends on the wavelength of laser light, and is observed in all samples investigated, when the wavelength of laser light is longer than that of the absorption edge. Photobrightening is explained by considering the reexcitation of trapped electrons in glass.
Embedding and Immobilizing Protein Molecules into Two-Dimensional Protein Arrays for Single-Molecule Imaging by Tapping Mode Atomic Force Microscopy
Authors: Furuno Taiji
Published: October 2002

Soluble proteins, ferritin and catalase, were imaged as single molecules by tapping mode atomic force microscopy (AFM) in water. They were isolated and immobilized in two-dimensional (2D) arrays of smaller proteins: ferritin was embedded in 2D arrays of catalase, and catalase was embedded in streptavidin arrays. In the preparation of each sample, two kinds of proteins were dissolved simultaneously in a buffer solution, and were bound to a surface film of polypeptide spread at the air/buffer interface. The protein-bound film was transferred onto a hydrophobic surface of silicon wafer. The isolated molecules of ferritin and catalase protruded halfway from the surface of 2D arrays of majority constituents. The lateral dimensions of these molecules were of convolution with the cantilever tip with the end radius of ∼3 nm. The characteristic shape or size of ferritin and catalase has been well captured as single molecules. This paper demonstrates that embedding protein molecules into protein arrays is a useful means for immobilizing proteins for single-molecule imaging by AFM.
Surface Modification of Si3N4-Coated Silicon Plate for Investigation of Living Cells
Authors: Hirata Isao , Iwata Hiroo , Md. Ismail Abu Bakar , Iwasaki Hiroshi , Yukimasa Tetsuo , Sugihara Hirokazu
Published: October 2002

We report a simple new method to improve the cell adhesion ability on the Si3N4 surface. Light-addressable potentiometric sensors (LAPS) have become a powerful tool for studying the biological action of cells. The Si3N4 surface of a LAPS structure was coated with poly-L-ornithine and laminin to improve its cell adhesion ability. The thickness of the coated layer was very thin, about 4 nm, as determined by atomic force microscopy measurement and thus this treatment surface is suitable for biological sensing applications such as the detection of cell activities.
Electronic Properties of Added Rows on TiO2(110) Surface Observed by Scanning Tunneling Spectroscopy
Authors: Sakai Yoshiyuki , Ehara Shaw
Published: October 2002

The electronic properties of added rows on TiO2(110) surface have been studied in real space with atomic resolution by scanning tunneling spectroscopy. It is found that no vacant Ti 3d state is observed near the Fermi level in the tunneling spectra, and accordingly the tunneling conductance is lowest at the added row sites. On the other hand, a peak of vacant states appears at 1.2 eV above the Fermi level in the spectra obtained at a hill by which an added row is terminated.
A Method for the Measurement of Acoustic Impedance and Speed of Sound in a Small Region of Bone using a Fused Quartz Rod as a Transmission Line
Authors: Hatakeyama Rokuro , Yoshizawa Masazumi , Moriya Tadashi
Published: October 2002

Precise correction for γ-ray attenuation in skull bone has been a significant problem in obtaining quantitative single photon emission computed tomography (SPECT) images. The correction for γ-ray attenuation is approximately proportional to the density and thickness of the bone under investigation. If the acoustic impedance and the speed of sound in bone are measurable using ultrasonic techniques, then the density and thickness of the bone sample can be calculated. Whole bone usually consists of three layers, and each layer has a different ultrasonic character. Thus, the speed of sound must be measured in a small section of each layer in order to determine the overall density of whole bone. It is important to measure the attenuation constant in order to determine the appropriate level for the ultrasonic input signal. We have developed a method for measuring the acoustic impedance, speed of sound, and attenuation constant in a small region of a bone sample using a fused quartz rod as a transmission line. In the present study, we obtained the following results: impedance of compact bone; 5.30(±0.40)×106 kg/(m2s), speed of sound; 3780±250 m/s, and attenuation constant; 2.70±0.50 Np/m. These results were used to obtain the densities of compact bone, spongy bone and bone marrow in a bovine bone sample and as well as the density of pig skull bone, which were found to be 1.40±0.30 g/cm3, 1.19±0.50 g/cm3, 0.90±0.30 g/cm3 and 1.26±0.30 g/cm3, respectively. Using a thin solid transmission line, the proposed method makes it possible to determine the density of a small region of a bone sample. It is expected that the proposed method, which is based on ultrasonic measurement, will be useful for application in brain SPECT.
Measurements of IR Spectra and Thermophysical Properties of Tetragonal Zirconia by Thermal Radiation Calorimetry
Authors: Tanaka Hirokazu , Sawai Shinya , Morimoto Kohsuke , Hisano Kumao
Published: October 2002

Normal emission spectra from a clear surface of tetragonal zirconia ceramic stabilized by 5.3 wt% yttria are measured in the frequency range of 200–4500 cm-1. The values of the hemispherical total emissivity are derived from a spectral analysis based on virtual mode equations and Kramers-Krönig relations. With these values, thermal conductivity data are obtained from measurements of temperature gradients in the sample at temperatures between 400 K and 850 K. Heat capacity measurements are carried out by quasi-static thermal radiation calorimetry. The present results are consistent with data in the literature obtained by other methods. Based on the comparison of the spectral reflectivity with the emission spectrum, it is suggested that the effects of radiation heat transfer in the ceramic sample may be compensated for by the scattering process of grain boundaries.
Thermal Diffusivity Measurement of Chemical-Vapor-Deposited Diamond by an AC Calorimetric Method
Authors: Takahashi Fumiaki , Fujii Kazuhiko , Hamada Yukihiro , Hatta Ichiro
Published: October 2002

An ac calorimetric method has been extensively applied to the thermal diffusivity measurement of a variety of materials from polymer to diamond. In a sample with high thermal diffusivity, the reflection of ac temperature waves at the edge of the sample affects the thermal diffusivity measurement. In addition, in a short sample, it becomes very significant. In this paper, we propose a new method to derive the thermal diffusivity in such a sample from the decay and the phase shift of ac temperature waves. We applied the present method to the thermal diffusivity measurement of chemical-vapor-deposited (CVD) diamond plates. As a result, it was found that the obtained thermal diffusivity for the diamond sample with finite length agrees with that of the plate-like sample with infinite length.
Slow Decay of Excess Carrier Concentration in Bonded Silicon-on-Insulator Wafers
Authors: Hirano Masashi , Ichimura Masaya , Arai Eisuke
Published: October 2002

We measured the temperature dependence of photoconductivity in bonded silicon on insulator (SOI). The decay of excess carrier concentration has a very slow component with a time constant larger than 1 ms at low temperatures. This slow component was not found in bulk Si. When the SOI samples were illuminated with steady light, the slow component was diminished. This indicates that the slow component is due to traps at or near SiO2/Si interfaces.
Production of Oxide-Passivated Nanosized Co Particles Dispersed in a Two-Dimensional Plane
Authors: Sako Sanshiro , Ohshima Kazunari
Published: October 2002

The initial island structure in the film grown by vacuum deposition is useful for the sample preparation of nanosized particles. The Co particles produced by this method had a narrow size distribution, and the stable Co cores were surrounded with thin CoO shells in air. These ferromagnetic particles are dispersed in a two-dimensional plane and have single magnetic domains; thus they have an interesting form for the study of the magnetic interaction among particles. The effects of vacuum pressure and deposition time for oxidation were investigated in samples produced with a constant amount of evaporation.