bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Behaviour of the Local Layer Structure of Antiferroelectric Liquid Crystals under a High Electric Field Measured by Time-resolved Synchrotron X-Ray Microbeam Diffraction
Authors: Takahashi Yumiko , Iida Atsuo , Takanishi Yoichi , Ogasawara Toyokazu , Ishikawa Ken , Takezoe Hideo
Published: October 2002

The local layer structure response to a triangular electric field in an antiferroelectric liquid crystal cell has been measured using synchrotron X-ray diffraction with 3 ms time resolution and a few µm spatial resolution. The initially coexisting vertical and horizontal chevron structures are irreversibly transformed to the layer structure with a rearranged molecular orientation at the surface (so-called vertical bookshelf structure). After the irreversible transformation, the rearranged layer structure shows a reversible transition between the horizontal chevron (high field, ferroelectric state) and the combination of the modified vertical and horizontal chevron (low field, antiferroelectric state) associated with the field-induced antiferroelectric-ferroelectric transition. The reversible layer structure has a smaller horizontal chevron angle (a few degrees) than that in the initial state (about 17°). The detailed microbeam diffraction revealed that the layer structure at a low electric field consists of a broad vertical chevron with a small chevron angle and a bent bookshelf in combination with a horizontal chevron, depending on the analyzing position. The stripe texture is related to the modified horizontal chevron structure.
Particle Size Distribution Measurement of Free-Falling Fine Particles in a Dusty Plasma Experiment
Authors: Kawashima Nobuki , Takeda Kazuya , Etoh Takeharu , Takehara Kousei , Kubo Haruya , Bessho Sakae
Published: October 2002

The particle size distribution in the production of a free-fall fine particle (FP) flow in a dusty plasma has been obtained experimentally by measuring the velocity distribution of falling particles at a gas pressure around 3,000 Pa. In this pressure range, from the balance of the gravitational force and the viscous force, the falling velocity is nearly proportional to the particle size. It has been confirmed that in our experimental setup, the particle velocity distribution is concentrated at a single velocity showing that the fine-particle flow is composed of particles of a single size.
Visualization of Shear Waves Radiated from Pseudocapillary Mode on Agarose Gel by Stroboscopic Photoelasticity Technique
Authors: Choi Pak-Kon , Jyounouti Etsuko , Yamamoto Ken , Takagi Kenshiro
Published: October 2002

We have demonstrated the existence of shear waves which were predicted to radiate from the pseudocapillary surface mode propagating on agarose gel. The technique of stroboscopic photoelasticity imaging was used to visualize the shear waves propagating in the bulk of the gel. The shear-wave velocity was obtained from the wavefront image, and was found to agree with that obtained from the surface-wave measurements previously reported.
Photoacoustic Spectra of Mixed TiO2 Ultrafine Powders with Rutile and Anatase Structures
Authors: Toyoda Taro , Taira Rie , Shen Qing , Ohmori Masahiro
Published: October 2002

We have measured the optical absorption of mixed TiO2 ultrafine powders with rutile and tanatase structures by photoacoustic (PA) spectroscopy, which is a powerful technique for detecting small amounts of strongly scattered materials. The values of band-gap energies, E
g, of the TiO2 ultrafine powders with different rutile contents were determined by the theory of interband transition in semiconductors. The values of E
g of rutile and anatase structures of TiO2 ultrafine powders are 3.00 eV and 3.20 eV, respectively, obtained from PA intensity and PA phase spectra, indicating the usefulness of PA spectroscopy. Mixed TiO2 ultrafine powders with rutile and anatase structures (20–140 nm diameters) were obtained by thermal oxidation of TiCl4. Rutile structure contents depend on the thermal oxidation temperature. The value of E
g of a mixed TiO2 ultrafine powder with rutile and anatase structures decreases continuously with the increase of the rutile content. This indicates that the apparent E
g can be controlled by mixing the nanometer-sized TiO2 powders with rutile and anatase structures, hence, we can control and obtain TiO2 materials with an arbitrary apparent E
g between rutile and anatase structures.
Group Velocity Measurement of Various Lamb Waves with Two-Beam Laser Interferometer
Authors: Murase Morimasa , Kawashima Koichiro , Yoshida Osamu
Published: October 2002

Multimode Lamb waves in a 1.0-mm-thick aluminum plate were excited by a line-focused Q-switched neodymium yttrium aluminum garnet (Nd:YAG) laser and the waves were received at two different positions by a laser interferometer. Using the phase spectrum method and moving average, we measured the dispersion curves of the group velocities of various modes of the Lamb waves and compared the measured results with the theoretical dispersion curves. The measured dispersion curves of the modes (S0, S1, A1, A2, and A3) of the Lamb waves agree well with the theoretical dispersion curves in the velocity range of 2000–4000 m/s and frequency x thickness range of 0.2–8.5 MHz mm. This method may be effective for material characterization of thin plates and pipes.
Estimation of Resolution and Contact Force of a Longitudinally Vibrating Touch Probe Sensor Using Lead Zirconate Titanate (PZT) Thin-Film Vibrator
Authors: Kanda Takefumi , Morita Takeshi , Kurosawa Minoru K. , Higuchi Toshiro
Published: October 2002

In this paper, the evaluation of the sensitivity, resolution, and contact force of a touch probe sensor device for higher sensitivity and low contact force is reported. Our goal in designing our touch probe sensor was to realize high-resolution, low-contact-force, wide-scanning-area up to mm scale square, and quick-scanning surface profile measurement. The sensitivity and resolution of our touch probe sensor were 2.0×10-2mV/nm and 2.4 nm, respectively. Although this resolution depends on the noise level, the noise level of the pre-amplifier circuit was much larger than that of the vibrator. By minimizing the noise of the circuit by using low-noise-type operational amplifiers, higher resolution up to 0.2 nm can be obtained. Although the contact force was estimated to be 25 µN under a 0.3 Vp-pdriving voltage, it will be 300 nN when using a low-noise circuit.
Development of Acceleration Sensor and Acceleration Evaluation System for Super-Low-Range Frequencies
Authors: Asano Shogo , Matsumoto Hideki
Published: October 2002

This paper describes the development process for acceleration sensors used on automobiles and an acceleration evaluation system designed specifically for acceleration at super-low-range frequencies. The features of the newly developed sensor are as follows. 1) Original piezo-bimorph design based on a disc-center-fixed structure achieves pyroeffect cancelling and stabilization of sensor characteristics and enables the detection of the acceleration of 0.0009 G at the super-low-range-frequency of 0.03 Hz. 2) The addition of a self-diagnostic function utilizing the characteristics of piezoceramics enables constant monitoring of sensor failure. The frequency range of acceleration for accurate vehicle motion control is considered to be from DC to about 50 Hz. However, the measurement of acceleration in the super-low-range frequency near DC has been difficult because of mechanical and electrical noise interruption. This has delayed the development of the acceleration sensor for automotive use. We have succeeded in the development of an acceleration evaluation system for super-low-range frequencies from 0.015 Hz to 2 Hz with detection of the acceleration range from 0.0002 G (0.2 gal) to 1 G, as well as the development of a piezoelectric-type acceleration sensor for automotive use.
Strip-Type Resonators Using Second-Harmonic Thickness-Extensional Vibration
Authors: Kaida Hiroaki , Inoue Jiro
Published: October 2002

The strip-type resonator that uses 2nd-harmonic thickness-extensional (TE2-mode) vibration in a two-layered monolithic piezoelectric plate was developed for a ceramic oscillator. By using the TE2-mode vibration, piezoelectric ceramic materials that have better temperature characteristics and higher Q
m could be utilized. Furthermore, TE2-mode vibration has no problems such as spurious responses often found in the 3rd-harmonic thickness extensional (TE3-mode) vibration in a single-layered piezoelectric plate. By shaping the resonator into a strip, the resonator was miniaturized. By means of the finite element method, the displacement distribution and the relationship between resonator width and spurious responses were analyzed. From the results, it was clarified that the resonator could be miniaturized and had good frequency characteristics. Those superior characteristics were demonstrated in an experiment. It was recognized that there was no spurious response that disturbed stable oscillation and that the volume of the resonator was less than 1/10 of that of conventional trapped-energy resonators using the TE3-mode vibration in a single-layered piezoelectric plate.
Polarization Dependence of Photoinduced Birefringence in Chalcogenide Thin Film
Authors: Lee Hyun-Yong , Jang Sun-Joo , Kim Eun-Soo , Chung Hong-Bay
Published: October 2002

Polarization dependence of photoinduced birefringence has been investigated in an amorphous As–Ge–Se–S chalcogenide thin film using two 632.8 nm HeNe lasers (inducing and probing beams), which have a lower energy than the optical energy gap (E
OP) of the film, that is, an exposure to sub-band gap light (h
v < E
OP). The polarization states of the inducing beam are controlled using a pair of phase retarder and linear polarizer to obtain linearly, circularly and elliptically polarized light beams. In addition, the kinetics of photoinduced dichroism has also been studied. The amplitudes of dichroism (D) and birefringence (Δ
n) increase with increasing induction time and eventually both are saturated even if their saturation times are not the same. The scalar absorption coefficient (α) of the film before photoinduction is about 6.02×103 cm-1 at 632.8 nm, that is, it is independent of polarization, but the α after photoinduction depends strongly on the polarization of the probing beam. That is, for a 0.5-µm-thick-film induced for 25 s by a laser with a power of 5.48 mW/cm2, the difference of two polarization absorption coefficients (Δα= α⊥-α∥) for the scalar α is estimated to be about 13.8%, which corresponds to D ∼4.2%. The photoinduced birefringence also depends strongly on the polarization states of the inducing beam. For example, for 0.9-µm-thick As–Ge–Se–S film the saturation values of Δ
n are about 0.69×10-2, 0.81×10-2, and 1.33×10-2 for the circularly, elliptically, and linearly polarized beams, respectively. In particular, the saturation values of birefringence of the film are not constant for an inducing history but vary significantly.
Efficient, Inexpensive Laser Source in the Yellow for Portwine Treatment
Authors: Azzeer Abdallah M.
Published: October 2002

Lasers are becoming more and more important in clinical management of dermatoses because of their selectivity and cosmetic values. The present report is on new laser sources, based on the efficient conversion of a 532 nm laser into 562 nm and 595 nm lasers, by stimulated Raman scattering (SRS) from organic liquids.
Chip Bonding on Non-rigid and Flexible Substrates with New Stepped Processes
Authors: Park Sung Kyu , Han Jeong In , Kim Won Keun , Kwak Min Gi
Published: October 2002

Reliable interconnection of electrodes to the plastic-based display with anisotropic conductive films (ACFs), of which the conductive particles were similar in elasticity to the substrates, was accomplished. The contact resistance value was maintained even while the junction was stressed under sudden changes in temperature and pressure. It was found that the conduction failure was caused by the action of a complex mechanism on the changes of a joint structure. The major driving factor seems likely to be defects in the transparent electrodes due to the thermal strain of substrates and penetration of conductive particles. Conductive particles with elasticity similar to that of the plastic substrates did little damage to the transparent electrodes on the substrates, and low temperature and pressure under a stepped process did not bring about their deformation either. As a result, a highly reliable interconnect with a very low contact resistance was realized.
FM Detection from an Optical Chaotic Carrier
Authors: Huang Shaw-Tzuu , Hwang Tsung-Min , Juang Cheng , Juang Jonq , Lin Wen-Wei
Published: October 2002

To synchronize two identical chaotic systems with different initial conditions, a drive and response system model is constructed according to Pecora and Carroll's theory. The drive and response systems become asymptotically synchronized if an FM signal is added to the drive system. The FM signal can be detected when the drive and response systems are strongly coupled.
Nano-polishing Procedure for Molecular-Scale Flattening at (001) and (00-1) Parallel Surfaces of 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate Crystal
Authors: Nanjo Hiroshi , Qian Pu , Sanada Norio , Suzuki Toshishige M. , Komatsu Kyoji , Takahashi Hidenori , Ito Hiromasa
Published: October 2002

Polishing of the parallel surfaces of an optical crystal is essentially required for smooth transmission of a laser beam. However, a procedure for polishing the (00-1) surface of a material on a molecular scale has not been reported so far. In this paper we have proposed the nano-polishing method of organic crystals by scanning the tip of an atomic force microscope with an appropriate load depending on the surface condition. It has been demonstrated that both the (001) and (00-1) planes of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal grown by a seed-standing method can be flattened on a molecular scale. Thus, we have successfully obtained molecularly parallel surfaces.
Mechanism of Negative Ion Production in a Cesium Seeded Ion Source
Authors: Morishita Takatoshi , Kashiwagi Mieko , Hanada Masaya , Okumura Yoshikazu , Watanabe Kazuhiro , Hatayama Akiyoshi , Ogasawara Masatada
Published: October 2002

The production mechanism of negative ions has been investigated experimentally in a cesium seeded volume type negative ion source. The cesium light emission intensity, Cs ion volume density, plasma parameters, H- current, and work function of the plasma grid were measured. The change in plasma parameters was small even in a high Cs ion density region(up to 1012 cm-3) which was also confirmed by zero-dimensional simulation. Upon heating the plasma grid, the work function decreased and the negative ion current increased to become three times larger than that of the low plasma grid temperature condition. This increase was in good agreement with the decrease of the work function of the plasma grid surface. Therefore, it is considered that the Cs contribution for the negative ion production is the surface effect in the negative ion source.
Effect of Ionization Potential of Hole Transport Layer on Device Characteristics of Organic Light Emitting Diode with Oxygen Plasma Treated Indium Tin Oxide
Authors: Hashimoto Yuichi , Hamagaki Manabu , Sakakibara Takeshi
Published: October 2002

We have investigated the contribution of the oxygen ions and electrons, and of the kinetic energy of these species on oxygen plasma treatment of indium tin oxide (ITO) electrode. In the case of the treatment by positive oxygen ions with kinetic energy of 50 eV, the luminance increased markedly with a lowering of the operating voltage in the organic light emitting diode (OLED). The change in the device characteristics was attributed to an effective removal of organic contaminants from the ITO surface, leading to enhanced hole injection from ITO to a hole transport layer (HTL) due to an increase in work function of the ITO. Moreover, the highest luminance and luminous efficiency were obtained in the OLED having HTL with ionization potential of 5.4 eV. These results have suggested that OLEDs fabricated using the oxygen plasma treated ITO can give the best device performance by the selection of an optimum HTL.
SiO2 Surface and SiO2/Si Interface Topography Change by Thermal Oxidation
Authors: Tokuda Norio , Murata Masahide , Hojo Daisuke , Yamabe Kikuo
Published: October 2002

Using a wide atomically flat (111) Si surface, the topography change of SiO2 surface and SiO2/Si interface by thermal oxidation was investigated for various oxidation temperatures. The initial step/terrace configuration was preserved on the SiO2 surface irrespective of oxidation temperature. On the other hand, the general step/terrace configuration of the initial Si surface was succeeded by the SiO2/Si interface at temperatures lower than 950°C, while at temperatures higher than 1050°C, the configuration was destroyed at the SiO2/Si interface with increasing oxide thickness until the steps finally disappeared. Terrace surfaces, however, were steeply microscopically roughened in the initial oxidation range irrespective of the oxidation temperature.
Growth of Si Thin Films on CeO2/Si(111) Substrate Using Electron-Beam Evaporation
Authors: Kim Chong Geol , Kim Kwan Pyo , Yang Ji Hoon , Park Chong-Yun
Published: October 2002

The growth mechanism of Si film on a CeO2(111)/Si(111) substrate has been investigated using X-ray diffraction (XRD), double crystal XRD (DCXRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). We have epitaxially grown a CeO2 film on the Si(111) surface by deposition of CeO2 at 640°C. When Si was deposited at 620°C on the CeO2(111)/Si(111) substrate using a high-vacuum e-beam evaporator, it was observed from XRD analysis that the Si film grew along the [111] direction. The TEM and AFM images showed that the top Si layer consists of large mountains and deep valleys. The XPS data showed no segregation of Ce on the Si layer surface. However, there was slight diffusion of Ce along the top layer Si grain boundary. These analysis results reveal that at the early stage of deposition, Si crystal nuclei are formed on a domain of the CeO2 film on Si(111) and grow three-dimensionally along the [111] direction, and eventually these merge into large mountains.
Transmission Electron Microscopy Study of Polycrystalline Si and Si0.69Ge0.31 Thin Films
Authors: Qin Wei , Ast Dieter G. , Kamins Theodore I.
Published: October 2002

A combination of conventional and high-resolution electron microscopy (HREM) was used to investigate the structure of polysilicon and poly-Si0.69Ge0.31 thin films. The polysilicon and Si0.69Ge0.31 films were grown by chemical-vapor-deposition (CVD) using SiCl2H2 at 790°C and SiCl2H2/GeH4 at 600°C, respectively. The grain morphology was columnar in all cases. Overall, the morphology of the films, on the level of conventional transmission electron microscopy (TEM), was very similar. HREM images showed that the polysilicon film contained less substructure inside grains and had fewer multiple twins and more extended twin bands than Si0.69Ge0.31. Twins with perfect five-fold symmetry were observed in Si0.69Ge0.31, but not in polysilicon. These five-fold twins are less than 18 monolayers in radius, in agreement with theory. Cross-sectional HREM images indicate that micro-twins form during the initial phase of the film growth. The atomic structure of the second-order twin boundary in Si0.69Ge0.31 was found to be identical to that reported for the second-order twin boundary in Si.
A Full Parallax Three-Dimensional Imaging System Based on a Point Light Source Array
Authors: Kim Sung-Sik , Sohn Kwang-Hoon , Savaljev Vladimir , Pen Eugene F. , Son Jung-Young , Chun Joo-Hwan
Published: October 2002

A full parallax three-dimensional imaging method based on a point light source array with a pixel cell plate is introduced. The pixel cell plate is an image display panel which is composed of pixels selected by the method from a two dimensional multiview image array to be displayed. The plate is placed in front of the light source array for the formation of the viewing zone. The pixel cell plate can also work with two-dimensional pinhole or microlens arrays to create three-dimensional images and thus provide full parallax. The pixel cell plate is consisted of a two-dimensional array of pixel cells which has the same number pixels as each image of a N×N multiview image array.
Numerical Calculation of Excimer-Laser-Induced Lateral-Crystallization of Silicon Thin-Films
Authors: Yeh Wen-Chang , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Excimer-laser-induced lateral-crystallization of Si thin-films has been characterized numerically. The effects of the Si film thickness, light intensity profile and thermal properties of the underlayer on grain growth are discussed. The tilted melt-solid interface is essential for large grain growth and the super-cooled Si region in front of the melt-solid is also important for quick start of crystal growth. It was concluded that the gradient method is suitable for large grain growth, since it can satisfy both requirements. Elongating the melt duration using a low specific heat underlayer can effectively delay the nucleation, resulting in ultra-large grain growth. The crystalline growth velocity is fastest at the Si-underlayer interface and thus preventing the heterogeneous nucleation at the interface by, such as, insertion of a low melting-point thin-film, is also effective for realizing large grain growth.
In Situ Purification of Organic Materials for Organic Light-Emitting Device Fabrication
Authors: Pardo Dino A. , Peyghambarian Nasser , Jabbour Ghassan E.
Published: October 2002

A simple, direct route to purify, as-deposited, materials for the fabrication of organic light emitting devices (OLEDs) is reported. In situ purification of 8-tris-hydroxyquinoline aluminum (Alq3) can lead to devices with electroluminescence characteristics comparable to those of devices made with materials pre-purified via traditional separation processes such as recrystallization or vacuum sublimation.
Liquid-Crystal Phase Transition Probed by Fluorescent Molecules
Authors: Toshiaki Hattori Toshiaki Hattori , Nobuhiko Hanai Nobuhiko Hanai , Hideyuki Inouye Hideyuki Inouye , Hiroki Nakatsuka Hiroki Nakatsuka
Published: October 2002

Phase transition of four liquid crystal materials have been studied by measuring the decay times of time-resolved intensity of fluorescence from two kind of dyes, malachite green and cryptocyanine, doped in these materials. It was found that the observed fluorescence lifetimes observed depend strongly on the doped molecules and that they change depending on the phase transition of the liquid-crystal materials. These results show that the fluorescence lifetime measurements are effective molecular probes for estimating the microscopic dynamics in these materials.
Deep Level Study in Heteroepitaxial 3C-SiC Grown on Si by Hexamethyldisilane
Authors: Masashi Kato Masashi Kato , Masaya Ichimura Masaya Ichimura , Eisuke Arai Eisuke Arai , Yasuichi Masuda Yasuichi Masuda , Yi Chen Yi Chen , Shigehiro Nishino Shigehiro Nishino , Yutaka Tokuda Yutaka Tokuda
Published: October 2002

Deep levels in 3C-SiC on Si grown by chemical vapor deposition using hexamethyldisilane (HMDS) were investigated by the deep level transient spectroscopy (DLTS). 3C-SiC epilayers with various thicknesses were grown by changing the growth time. Relatively thin epilayers (<1 µm) showed DLTS signals in a wide temperature range. This indicates that these epilayers have defects distributed in a wide energy range. These defects seem to originate from the 3C-SiC/Si heterointerface. On the other hand, relatively thick epilayers (>2.2 µm) showed only one DLTS peak, which corresponds to a defect having an activation energy of about 0.25 eV. This defect is a donor defect and is identical with a defect observed in 3C-SiC grown from SiH4 + C3H8.
Electrical Properties of Mg/La, Mg/Nb Co-Doped (Ba0.7Sr0.3)TiO3 Thin Films Prepared by Metallo-Organic Deposition Method
Authors: Chen San-Yuan , Wang Hong-Wen , Huang Li-Chi
Published: October 2002

(Ba0.7Sr0.3)TiO3 (BST) thin films doped with La, Nb and Mg ions along with an Mg/La, Mg/Nb codopant were prepared on Pt/Ti/SiO2/Si substrates by the metal-organic deposition method. A decrease of grain size, dielectric constant, and leakage current with increasing doping levels was observed for all studied cases. The grain size, dielectric constant and leakage current increased with increasing annealing temperatures for specimens doped with a single dopant. However, the leakage current was reduced to a minimum for the codoped materials at the donor/acceptor compensated concentration and decreased with increasing annealing temperatures. The decreased leakage current of the codoped materials could be explained by the additional barrier height and width of the insulating layer caused by the defect dipoles around grain boundaries.
X-Ray Diffractometry and X-Ray Photoelectron Spectroscopy Investigations of Nanocrytalline Hydroxyapatite Synthesized by a Hydroxide Gel Technique
Authors: Panda Rabi Narayan , Hsieh Ming-Fa , Chung Ren-Jei , Chin Tsung-Shune
Published: October 2002

Nanocrystalline hydroxyapatite (HA), Ca10(PO4)6(OH)2, has been synthesized by a precipitate-conversion technique using hydroxide gel. Hydroxyapatite crystallizes in a hexagonal structure (space group; P63/m) having lattice parameters; a=9.407 Å and c=6.883 Å, and around 37 nm in size for the 800°C-annealed sample. Substantial crystalline characteristics are observed for the material heat-treated at 80°C. With the increase of air-annealing temperature, from 80°C to 800°C, lattice expansion along all crystallographic axes occurs indicating a structural change in the HA lattice. These results have been attributed to (1) the formation of a relative Ca2+ deficiency in HA that incorporates various chemical species in the anionic sites compared to their lower temperature air-annealed counterparts, and (2) the precipitation of CaO with increasing air-annealing temperature. The X-ray photoelectron spectroscopy studies indicate a distorted anionic structure and two electronic states for the O1 s, corroborating the observed X-ray diffraction results.
Free Volume in Polycarbonate Studied by Positron Annihilation: Effects of Free Radicals and Trapped Electrons on Positronium Formation
Authors: Chen Zhi Quan , Suzuki Takenori , Kondo Kenjiro , Uedono Akira , Ito Yasuo
Published: October 2002

Positron lifetime spectra in polycarbonate were measured as a function of temperature and time. Ortho positronium (o-Ps) lifetime remained constant with prolonged measuring time, but its intensity decreased and increased with time at room temperature and low temperatures, respectively. The temperature dependence was measured from 30 to 375 K for two samples: one was pre-irradiated by positrons at 30 K for 166 h, the other was a fresh sample. The variation of o-Ps intensity differed greatly between the two samples. We explained these results in terms of free radicals and trapped electrons. We observed a large decrease of I
3 at 100–130K and a change in the slope of τ3 at 230 K. The observations are considered to be related to the movement of the methyl group and the brittle-ductile transition, respectively, which were measured by other methods. By measuring the positron lifetime spectra between 293–493 K, the glass transition temperature was determined to be approximately 413 K.
Effect of Oxygen Partial Pressure during Firing on Electrical Properties of Sintered Body Composed of Mn1.5CoNi0.5O4
Authors: Meguro Takeshi , Abe Yoshiaki , Yokoyama Takashi , Murosawa Syogo , Komeya Katsutoshi , Tatami Junichi
Published: October 2002

The effect of P
O2
during the oxidation of a sintered body with a molar ratio of Mn:Co:Ni=3:2:1 on conversion into a cubic spinel-type oxide was investigated. Moreover, the electrical properties of the sintered body with a monophase cubic spinel structure were evaluated in atmospheres with various P
O2
values. A sintered body of monophase spinel-type oxide, Mn1.5CoNi0.5O4, was successfully obtained by heating a mixture of nitrates at 1400°C in argon, followed by cooling to 1100°C and holding at that temperature for over 168 h at P
O2
=0.40 atm, or for over 48 h in the P
O2
range from 0.55 to 1.00 atm. The electrical conductivity, σ, of the specimens oxidized at P
O2
of 0.40 to 1.00 atm increased exponentially with increasing temperature. In the region of 0.40≦P
O2
(atm)≦0.85, σ increased with increasing P
O2
. All of the specimens oxidized at P
O2
of 0.40 to 1.00 atm revealed p-type semiconductor properties, because the Seebeck coefficients were all positive. The P
O2
dependence of σ was thought to be dependent on the existence ratio of Mn3+ to Mn4+ in octahedral sites. The conduction was considered to be controlled by a small polaron hopping mechanism.
A New Type of Stacking Fault in β-SiC
Authors: Shirahata Naoto , Kijima Kazunori , Ma Xiuliang , Ikuhara Yuichi
Published: October 2002

A new type of stacking fault was found in ultrapure and ultrafine β-SiC in images obtained by high-resolution transmission electron microscopy (HR-TEM). The β-SiC particles were prepared by the plasma chemical vapor deposition (plasma-CVD) method and quenched rapidly from the gas phase. This type of stacking fault disappeared in the specimen heated at 1850°C for 10 min in Ar atmosphere. The proposed stacking fault was examined from the viewpoints of energy and synthetic condition.
Synthesis and Surface Acoustic Wave Property of Aluminum Nitride Thin Films Fabricated on Silicon and Diamond Substrates Using the Sputtering Method
Authors: Ishihara Masatou , Manabe Takaaki , Kumagai Toshiya , Nakamura Takako , Fujiwara Syuzo , Ebata Yasuo , Shikata Shin-ichi , Nakahata Hideaki , Hachigo Akihiro , Koga Yoshinori
Published: October 2002

C-axis oriented aluminum nitride (AlN) thin films with a thickness of 1 µm were prepared by reactive DC magnetron sputtering on polycrystalline diamond substrates at a substrate temperature of 623 K. The average surface roughness (R
a) of the AlN thin films was less than 2 nm obtained by locating the diamond substrates at a position of 100 mm from the aluminum target. The full width at half maximum (FWHM) of the rocking curve for the AlN(002) peak determined by X-ray diffraction analysis was about 0.2°. The surface acoustic wave (SAW) structures were completed by the deposition of aluminum electrodes on the as-deposited AlN surfaces. The SAW characteristics of an interdigital transducer (IDT)/AlN/diamond structure were investigated. The phase velocity and coupling coefficient were 10,120 m/s and 0.3%, respectively.
Electrical Properties of Ni–Cr–N Thin Films Deposited by Multitarget Reactive Sputtering
Authors: Sato Yuichi , Watanabe Masaya , Sato Susumu
Published: October 2002

Ni–Cr thin films of various compositions are deposited by multitarget reactive sputtering with nitrogen gas introduction, and the electrical properties of the films are investigated. An increase in the lattice parameter is observed when nitrogen contents are less than 25%, and nitrides are formed in the deposited films when nitrogen contents reach much higher values. The resistivity of the deposited films at room temperature increases with increasing nitrogen content, and their temperature coefficient of resistance (TCR) changes from approximately +100 to -100 ppm/°C through nearly equal to zero. Gage factors of the films are about 2 and are independent of the nitrogen content.
Contactless Method for Electrical Characterization of Silicon-on-Insulator Materials
Authors: Tsugunori Okumura Tsugunori Okumura , Kazuyoshi Eguchi Kazuyoshi Eguchi , Aimin En Aimin En , Michihiko Suhara Michihiko Suhara
Published: October 2002

The Kelvin-probe method, in combination with surface photovoltage (SPV) measurements, is applied to the nondestructive electrical characterization of silicon-on-insulator (SOI) materials. It is shown that a simple sandwich-type electrode configuration can be used for the contactless characterization of the SOI layer, when the capacitance between the vibrating electrode and the SOI surface is much smaller than the buried-oxide (BOX) and depletion-layer series capacitances. The light-intensity dependence of the SPV gives data equivalent to common cuurent–voltage (I–V) characteristics of diodes. Thus, we call the proposed method the contactless
I–V
method. Lastly, we demonstrate that UV illumination is effective for applying the contactless
I–V
method to ultrathin SOI layers such as fully depleted SOI material.
Amorphization in the Ni–Nb System upon Ion-Beam-Assisted Deposition
Authors: Zhao Bin , Zeng Fei , Pan Feng
Published: October 2002

The amorphization of Ni–Nb multilayered alloy films was studied by Ar+ ion-beam-assisted deposition (IBAD). The Ar+ ion energies were from 2 to 8 keV. Some amorphous alloys were obtained in the experiment and the nominal composition range favoring amorphization was determined to be 20–80 at.% Ni. A new hcp phase was formed in the Ni80Nb20 films by IBAD with 8 keV Ar+ ion energy. The Nb-rich solid solution with fcc structure was also obtained in some samples. The evolution of phase structure is interpreted by kinetics of the far from equilibrium process.
Kink-Solitons in Quantum-Dot Cellular Automata
Authors: Nakagawa Satoshi , Eto Mikio , Kawamura Kiyoshi
Published: October 2002

We examine the propagation of electric polarization in quantum-dot cellular automata (QCA) as a kink-soliton. We solve the time-dependent Schrödinger equation numerically by the Hartree approximation and also by the exact method. By the Hartree approximation, we find that the shape of the kink-soliton can be fitted very well to a function of hyperbolic tangent, which coincides with the solution of the nonlinear wave equation obtained in the continuum limit. At the junction between different kinds of QCA, the soliton is perfectly transmitted or reflected, like a classical particle. The exact calculations yield different behaviors of kink-solitons at the junction; partly transmitted and partly reflected, similar to a quantum wave packet.
Nonlinear Terahertz Gain Estimated from Multiphoton-Assisted Tunneling in Resonant Tunneling Diodes
Authors: Asada Masahiro , Sashinaka Nobuo
Published: October 2002

The power-dependent terahertz (THz) gain due to subband transitions between adjacent quantum wells is estimated from the current change of triple-barrier resonant tunneling diodes (RTDs) under THz irradiation. To induce high THz voltage across the RTDs, patch antennas with low conduction loss are integrated. Due to high THz voltages induced, photon-assisted tunneling by the multiphoton process is observed. Components of tunneling currents with photon emission and absorption are extracted from the observed results, and the gain coefficient in the multiphoton process is estimated. It is shown that the gain coefficient is almost constant for incident power in the low incident power region in which one- or two-photon processes are dominant, and starts to rapidly decrease when the incident power exceeds this region. Reasonable agreement with theoretical calculation is obtained.
Graphite-Nanofiber Field Emitter for Relativistic-Electron-Beam Sources for Pumping KrF Lasers
Authors: Okuda Isao , Takahashi Eiichi , Owadano Yoshiro
Published: October 2002

The relativistic-electron-beam (e-beam) generation initiated by field emission from a graphite-nanofiber cathode is reported. The completion time of the plasma-sheath formation over the cathode surface is discussed in terms of observed diode perveances. A short plasma-sheath formation time of 25 ns is obtained at a macroscopic electric field of 85 kV/cm. This type of emitter can be used for e-beam sources for pumping KrF lasers.
Plasma Instability and Nonlinear Terahertz Oscillations in Resonant-Tunneling Structures
Authors: Ryzhii Victor , Shur Michael
Published: October 2002

We demonstrate that the self-excitation of plasma oscillations in a resonant-tunneling transistor structure results in the generation of transient current at frequencies in the terahertz range. The amplitudes and the frequencies of different modes of the generated oscillations can be tuned by the voltage.
Effects of Mn Dopant on the Leakage Current Properties in SrTiO3 Thin Films
Authors: Morito Kentaro , Suzuki Toshimasa , Fujimoto Masayuki
Published: October 2002

With increasing Mn dopant concentration, polycrystalline Sr(Ti1-x
Mn
x
)O
y
(x=0, 0.002, 0.01, and 0.05) thin films grown on Pt electrodes show a notable improvement in leakage characteristics in the high electrical field region, due to Mn dopant substitution on Ti sites as a low-valency acceptor. The addition of Mn also induces a distinct transition of the conduction mechanism, which can be clearly classified into two models; one is a Schottky-emission current mode limited by interface through thermionic electron emission, appearing at low Mn dopant concentrations up to x=0.01, and the other is a space-charge-limited current mode strongly dependent upon the inherent conductivity in thin-film materials, observed only in highly doped thin films with an Mn concentration of x=0.05. This mode transition is attributable to the improvement in the insulating property of Sr(Ti1-x
Mn
x
)O
y
thin films, possibily through the oxygen-vacancy compensation of Mn acceptor dopant.
Neutron, Electrical, and Magnetic Investigations of the PrFeO3–PbTiO3 System
Authors: Kim Jeong Seog , Cheon Chae-il , Shim Hae-Seop , Jang Pyong Woo
Published: October 2002

The solid solutions of the (1-x)PrFeO3–xPbTiO3 system were explored for the purpose of finding ferroelectromagnetism. Neutron diffraction data were collected at room temperature to 700°C and refined by the Rietveld method for magnetic and crystal structure analyses. Dielectric permittivity (ε
r) and loss tangent were measured by a low-frequency impedance analyzer for varying frequency. The hysteresis curves of the polarization-electric field and magnetization-magnetic field were measured at room temperature. At room temperature, the crystal structure symmetry of the solid solutions change from orthorhombic to tetragonal i.e., Pbnm, I4 cm, and P4 mm with increasing PbTiO3 content. The solid solution at x=0.8 undergoes structural transition from tetragonal to cubic phase with increasing temperature in a series of I4 cm, I4/mcm (P4/mmm), and Pm3m. The solid solution composition of 0.4≤x≤0.6 exhibited ferromagnetism and the compositions of x≥0.4 were ferroelectric.
High-Power Characteristics of Multilayer Piezoelectric Ceramic Transducers
Authors: Sasaki Yasuhiro , Umeda Mikio , Takahashi Sadayuki , Yamamoto Mitsuru , Ochi Atsushi , Inoue Takeshi
Published: October 2002

In this report, the behavior of the mechanical quality factor Q

m
for multilayer piezoelectric transducers which operate at a low to high vibratory velocity is described. It has long been known that the Q

m
of multilayer piezoelectric devices, such as transformers and actuators, decreases when the number of ceramic layers in the devices is increased. In such devices, the output power converges to a saturated value with heat generation much lower than that which the value of Q

m
measured at low vibration velocity would suggest. This fact implies that the Q

m
strongly depends not only on the number of ceramic layers, but also on vibratory velocity and temperature. It appears that high-power and vibratory velocity characteristics of the Q

m
for multilayer piezoelectric transducers have not been studied sufficiently. Taking the temperature factor into consideration, we used the electrical transient response method and equivalent circuit analysis to investigate the vibratory velocity characteristics of the Q

m
for multilayer piezoelectric transducers.
Construction of a Low-Frequency Flat-Type Piezoelectric Vibratory Gyroscope
Authors: Aizawa Hiroyuki , Sugawara Sumio , Terada Jiro
Published: October 2002

A new low-frequency flat-type piezoelectric vibratory gyroscope structure is proposed here, and is analyzed by the finite-element method. In-plane modes are used for driving and detecting in this structure. The vibratory gyroscope is composed of two tuning forks with an additional mass and the central arm that combines these forks flatly. Moreover, another mass is added to the center of the central arm that changes only the resonant frequency of the detecting mode. Therefore, the difference in the resonant frequencies of both modes can be adjusted by changing the dimensions of the mass. The structure is hardly affected by a support because the displacements at the support part become very small. Using the metal structure with the piezoelectric ceramics for driving and detecting, it was clarified that the vibratory gyroscope operates as an angular rate sensor.
Microwave Dielectric Properties of BanLa4Ti3+nO12+3n Homologous Series
Authors: Okawa Takashi , Kiuchi Katsumasa , Okabe Hiroki , Ohsato Hitoshi
Published: October 2002

We have investigated the phase structure and microwave dielectric properties of the Ba
n
La4Ti3+n
O12+3n
homologous series. In BaLa4Ti4O15 with n=1 composition, we obtained high Q characteristics at the dielectric constant ε
r=46, the temperature coefficient of the resonant frequency τ
f
=-11 ppm/°C and Q·f=46000 GHz. In the BaO–La2O3–TiO2 system, Ba
n
La4Ti3+n
O12+3n
compounds exist on the tie line BaTiO3–La4Ti3O12 near the tungstenbronze-type like Ba6-3x
R8+2x
Ti18O54 (R=rare earth) solid solutions. There are three kinds of compounds: n=1, BaLa4Ti4O15; n=2, Ba2La4Ti5O18; and n=4, Ba4La4Ti7O24. These compounds have a layered hexagonal perovskite-like structure, which has a common substructure in the crystal structure. We have investigated the phase compositions and microwave dielectric properties of Ba
n
La4Ti3+n
O12+3n
. With an increase of n, the dielectric constant, ε
r, increases and the quality factor, Q·f, decreases.
Domain Structures in K3Li2-xNb5+xO15+2x Single-Crystal Fibers Produced by the Laser-Heated Pedestal Growth Technique
Authors: Matsukura Makoto , Takeyama Takashi , Karaki Tomoaki , Adachi Masatoshi
Published: October 2002

The ferroelectric domain structures in the <110 > oriented K3Li2-x
Nb5+x
O15+2x
(KLN) single-crystal fibers have been found to have a bi-domain configuration from the results of the piezoelectric, and scanning nonlinear dielectric microscopy (SNDM) measurements. It is found that the directions of spontaneous polarization faced each other across the domain boundary, as opposed to the case in LiNbO3 fibers. A new mechanism based on the stress during the growth is proposed to explain the domain structures of the KLN fibers.
Preparation of Ge1-yCy Alloys by C Implantation into Ge Crystal and Their Raman Spectra
Authors: Kanzawa Yoshihiko , Katayama Koji , Nozawa Katsuya , Saitoh Tohru , Kubo Minoru
Published: October 2002

We attempted to prepare Ge1-y
C
y
alloys by implantation of C atoms into Ge crystals and post-annealing. For samples annealed at temperatures higher than 450°C, X-ray diffraction (XRD) spectra indicated that the Ge1-y
C
y
alloys were successfully prepared. The highest substitutional C content was about 1 at.%. The optimum annealing temperature to incorporate C atoms into the substitutional sites was 450–500°C. We also investigated the dependence of the Raman intensity of the Ge–C local mode on the substitutional C content. The intensity of the Ge–C local mode was found to increase in proportion to the substitutional C content. Furthermore, the relationship between Ge–C peak intensity and substitutional C content was relatively in good agreement with that theoretically predicted.
Confinement Effect of Primary Plasma on Glass Sample Induced by Irradiation of Nd-YAG Laser at Low Pressure
Authors: Hedwig Rinda , Kurniawan Hendrik , Kagawa Kiichiro
Published: October 2002

The characteristics of the laser plasma which was induced by focusing a Q-sw Nd:YAG laser pulse repeatedly at a fixed position on a glass sample were examined under the reduced pressure of approximately 2 Torr. It was observed that at the initial irradiation the secondary plasma could not be generated when the pulse energy was set below around 30 mJ, while the primary plasma was produced distinctly. However, after several shots of irradiation the secondary plasma was suddenly generated and this generation continued with an almost constant emission intensity. This fact can be interpreted on the basis of the confinement effect due to the wall of the crater produced by the pre-irradiation, which is solely responsible for the generation of the shock wave. This fact provides strong support for the shock wave model previously proposed by us to explain the mechanism of secondary plasma formation.
Absorption Spectrum and Optical Parameters of Nd-Doped Gadolinium Aluminium Tetraborate Crystals
Authors: Jiang Huai-Dong , Wang Ji-Yang , Hu Xiao-Bo , Li Shi-Tong , Teng Bing , Zhang Cheng-Qian
Published: October 2002

Nd-doped gadolinium aluminium tetraborate Nd
x
Gd1-x
Al3(BO3)4 (NGAB) crystals have been grown by flux method, with large sizes and good optical quality as well as different Nd3+ ion densities of 0 to 10 at.% in the lattice structure. These crystals belong to the trigonal system with point group 32, conforming space group R32. The unit cell constants are a=0.9305(8) and c=0.7248(1) nm, V=0.5436 nm3 for a Nd3+ content of 10 at.%. When Judd–Ofelt (JO) theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites is applied to NGAB, it results in a good fit on absorption of the crystal. The three intensity parameters Ω
t
are fitted as 1.559×10-20, 1.751×10-20 and 2.395×10-20 cm2 at t=2, 4 and 6 respectively, with a root-mean square deviation of 9.35×10-22 cm2. The spectral parameters of NGAB crystal have indicated that it is a promising candidate of self-frequency doubling crystals.
Surface Modification of Low Dielectric Fluorinated Amorphous Carbon Films by Nitrogen Plasma Treatment
Authors: Yang Sung-Hoon , Kim Heondo , Park Jong-Wan
Published: October 2002

The effects of nitrogen post-plasma treatment on the properties of fluorinated amorphous carbon (a-C:F) films were investigated. In this study, the a-C:F films were prepared by an electron cyclotron resonance chemical vapor deposition (ECRCVD) system (ASTeX AX4505) using a gas mixture of fluorocarbon (C2F6) and hydrocarbon (CH4). The post-plasma treatment was carried out for various strengths and durations after deposition without breaking the vacuum seal. As the power and time of the treatments increased, the fluorine concentration of the film surface decreased, yet the surface energy increased sharply. The dielectric constant and the refractive index of a-C:F films remain nearly constant regardless of the plasma treatment power. From this study, it was found that the plasma treatment of a-C:F films produces a more reactive surface and affected the fluorine concentration of the surface, the structure of chemical bonding and the electric properties.
Transient Properties of a Liquid-Crystal Microlens
Authors: Ye Mao , Sato Susumu
Published: October 2002

The dynamical behaviors of the reorientation of the directors in a liquid-crystal microlens and of the phase retardation of an incident light beam are analyzed numerically. Director behaviors such as tilt and twist deformations are explained physically, and the simulation agrees with the experimental observations. The evolution of the phase profile over time is observed experimentally by placing the cell between two crossed polarizers and recording the change of the interference pattern with time. The evolution of the pattern over time also agrees with our prediction.