bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetoelectric Properties in Piezoelectric and Magnetostrictive Laminate Composites
Authors: Ryu Jungho , Carazo Alfredo Vázquez , Uchino Kenji , Kim Hyoun-Ee
Published: October 2002

Magnetoelectric laminate composites of piezoelectric-magnetostrictive materials were investigated. The composites were prepared by stacking and bonding Pb(Zr, Ti)O3 (PZT) and Terfenol-D disks. Experimental results indicated that the magnetoelectric voltage coefficient, dE/dH, increased with decreasing thickness and increasing piezoelectric voltage constant (g
31) of the PZT layer. We obtained the highest magnetoelectric voltage coefficient of 4.68 V/cm·Oe at room temperature for the sample with high g33 PZT of 0.5 mm in thickness. This value is about 36 times higher than the best reported value.
Tape Casting Preparation and Pyroelectric Properties of Stacked Pb(Zr0.97Ti0.03)O3 Thick Films Doped with Nb2O5
Authors: Du Jing , Lin Shengwei , Adachi Masatoshi
Published: October 2002

Stacked Zr-rich Pb(Zr,Ti)O3 (PZT) thick films doped with different amounts of Nb2O5 have been prepared by the tape casting and stacking processes. The pyroelectric properties of the stacked thick films have been compared with those of single-layer thick films. The full-width of temperature at half maximum of pyroelectric coefficients for the stacked thick films, ΔT, was broadened to 20°C. The maximum pyroelectric coefficient in the stacked thick films was 2.4 ×10-7 C/cm2K. The thermal hysteresis of the pyroelectric coefficient could be partly eliminated by the stacked structure of thick films.
Surface and Flexoelectric Polarization in Nematic and Smectic A Phases of Liquid Crystal 4-octyloxy-4′-cyanobiphenyl
Authors: M. Blinov Lev , I. Barnik Mikhail , Hiroshi Ohoka Hiroshi Ohoka , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The temperature dependencies of surface polarization in the nematic (N) and smectic A (SmA) phases have been measured for both the planar and homeotropic orientations of 4-octyloxy-4′-cyanobiphenyl (8OCB). Polarization was determined in the field- off regime from the pyroelectric response of the cell to a short laser pulse, and the temperature increment was calculated from the in situ measurements of the light induced birefringence. The surface polarization in the N-phase for both orientations is directed from an interface into the bulk at similar magnitudes (about 0.5–0.8 pC/m) but its change at the N–SmA transition was qualitatively different for the two cases. The experimental data are consistent with the quadrupolar model of the order-electric polarization. The field-off measurement technique also allowed for the measurements of the z-component of the flexoelectric polarization of 8OCB in both the N and SmA phases using a hybrid aligned nematic cell. The sum of the flexoelectric coefficients (e
1+e
3) in both phases was shown to be positive (e
1+e
3 ≃7.4 pC/m at 40°C), which is opposite to the case of 4-pentyl-4′-cyanobiphenyl (5CB). On the molecular scale, the difference is accounted for by the different distribution of electric charges in molecular quadrupoles forming the corresponding liquid crystalline phases.
Layer Compression Modulus of Chiral Smectic Liquid Crystals Showing V-shaped Switching
Authors: Seiji Shibahara Seiji Shibahara , Jun Yamamoto Jun Yamamoto , Yoichi Takanishi Yoichi Takanishi , Ken Ishikawa Ken Ishikawa , Hideo Takezoe Hideo Takezoe
Published: October 2002

Measurements of layer compression modulus B have been performed on the chiral smectic liquid crystals showing V-shaped switching to study elastic properties. The temperature dependence of B in binary mixtures shows the usual cusp-like behavior at the untilted-tilted smectic phase transition in contrast to that in a three-component mixture showing V-shaped switching [Shibahara et al.: Phys. Rev. E 63 (2001) 051707]. Moreover, we observed the abrupt softening of B in the close vicinity of the tilted-tilted smectic phase transition (ferrielectric-antiferroelectric phase transition) for the first time.
High Resolution Electron Microscopy Observation of Different Al-oxide Layers in Magnetic Tunnel Junctions
Authors: Yu Andrew Chak Chung , Doole Ron , Petford-Long Amanda , Miyazaki Terunobu
Published: October 2002

Microstructure and morphology of Al-oxide layers in magnetic tunnel junctions (MTJs) were characterized using high resolution electron microscopy (HREM). The MTJs were fabricated using magnetron sputtering. The Al-oxide layers were prepared using four different methods; natural, thermal, and plasma oxidation techniques as well as sputtering from pure alumina. HREM results showed that sputtering conditions, surface roughness of the bottom electrode in the MTJs, and oxidation conditions for the Al-oxide are essential factors affecting the quality of the insulating layer. High sputtering power was required to deposit a relatively smooth layer of pure alumina. Al matrices were observed in Al-oxide with only 24 h natural oxidation time. It was found optimum to thermally oxidize an Al-oxide layer between 333 and 473 K for 48 h. It is more effective and useful to oxidize an Al layer at a slightly higher plasma power rather than using a longer oxidation time in plasma oxidation method.
A New Technique Keeping off the Mn Evaporant from Oxygen Atmosphere during Reactive Evaporation Process
Authors: Isai Masaaki , Shimada Takeyoshi , Matsui Takaaki , Fujiyasu Hiroshi
Published: October 2002

Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, which deteriorates it's deposition rate with increasing deposition run. It is also difficult to maintain the stoichiometry of films from run to run. This paper shows a new technique which keeps off the Mn evaporant from oxygen atmosphere during the reactive evaporation process. To achieve it a stainless steel cell has been installed in the bottom of the Mn crucible, which can successfully isolate Mn evaporant from incoming oxygen atoms. It improves the reproducibility of film composition because of stabilizing of the deposition rate.
Luminosity and Energy Resolution in e+e- Colliding Rings
Authors: Petracca Stefania , Hirata Kohji
Published: October 2002

Luminosity is one of the key concepts for accelerator design. When the design target is a narrow energy peak, the (collision) energy resolution becomes more relevant. In this paper fairly accurate expressions for luminosity and energy resolution based on the Gaussian approximation of the beam distribution functions are given. All kinds of couplings are considered.
Photo-Generation of Acids and its Fluorescence Detection in a Small Area: a Near-Field Write-Once Memory
Authors: Kawai Tsuyoshi , Konishi Takahisa , Matsuda Kenji , Irie Masahiro
Published: October 2002

A polymer film containing the photo-acid generator, 1,2-naphthoquinone-2-diazido-5-sulfonic acid sodium salt (SNQD), and a fluorescence pH indicator, seminaphthofluorescein (SNAFL-1), has been used as a near-field write-once memory medium. Near-field 455 nm light from a optical fiber tip with a nano-size (∼ 100 nm) aperture produced acids in a small area and the acids were detected as the fluorescence intensity increased with the near-field 488 nm excitation light. The fluorescent spot-size was as small as 160 nm and could be read many times without destruction.
Amorphous-Si Transmission Gratings Prepared by Ga+-Focused-Ion-Beam Milling and Their Polarization Characteristics
Authors: Lee Hyun-Yong , Kim Jin-Woo , Shin Kyung , Kim Eun-Soo , Chung Hong-Bay
Published: October 2002

Amorphous-Si (a-Si) transmission gratings of ∼ 0.1 µm thickness with four-type periods (Λ= 0.4 µm and 0.6 µm for sub-wavelength and Λ=1.0 µ and 1.4 µm for above-wavelength) have been fabricated on quartz substrates using 50 keV Ga+-focused-ion-beam (FIB) milling and CF4-reactive-ion etching (RIE) methods. Some optical properties of the fabricated gratings have been investigated using a linear polarized HeNe laser beam (λ=632.8 nm). Maximum diffraction efficiencies (ηMAX), measured at an incident angle (θB) to satisfy Bragg's condition with an effective index N
eff=1.803–1.853, were very high. In particular, for gratings with Λ=0.6 µm (linewidth=0.25 µm, linespace=0.35 µm), the ηMAX at θB=17.0° is estimated to be about 96%. In addition, transmittance for two polarizations (TE and TM) was measured using a simple optical system, and the total phase difference (ΔΨTE-TM) and birefringence (Δn) were approximately calculated. The transmittance difference between TE and TM polarizations is the largest in the case of gratings with Λ=0.4 µm (approximately∼λ/2) among the gratings fabricated by us. That is, the TM/TE ratio is about 10.38, and both ΔΨTE-TM and Δn exhibit maximum values in the case of Λ=0.6 µm, which are about -76.7° and -1.35, respectively. The a-Si transmission gratings with a relatively high refractive index (∼ 2.9 at 632.8 nm) are successfully fabricated by FIB milling. In addition, we believe that this technique is one of the potential candidates for use in various optical devices and elements and, in particular, compatible with other optoelectronic devices for monolithic planar integration.
Magnetic Characteristic of Mn+ Ion Implanted GaN Epilayer
Authors: Hae Kwon Yoon Shon , Young Kim Deuk , Won Kang Xiangjun Fan
Published: October 2002

Nanoscale ferromagnets (GaMn) with the implantation of Mn+ ions have been incorporated into unintentionally doped (n-type) GaN epilayers grown on sapphire substrate by molecular beam epitaxy (MBE). Energy dispersive X-ray (EDX) spectrometry, atomic force and magnetic force microscopy (AFM and MFM) are used to characterize the GaMn precipitates which form within the GaN epilayer. MFM images reveal nanoscale ferromagnets (GaMn), and a small magnetic hysteresis loop indicates that there are ferromagnetic particles in our GaN:Mn layer involving the paramagnetic property and is measured by superconducting quantum interference device (SQUID) magnetometer.
In Situ Observation of Native Oxide Growth on a Si(100) Surface Using Grazing Incidence X-Ray Reflectivity and Fourier Transform Infrared Spectrometer
Authors: Uemura Satoshi , Fujii Masanori , Hashimoto Hideki , Nagai Naoto
Published: October 2002

It is well known that native oxide on hydrogen-terminated Si hardly grows in a drying atmosphere. We have developed an in situ observation system using grazing incidence X-ray reflectivity (GIXR) and Fourier transform infrared spectrometer (FTIR). In this study, we investigated the native oxide growth on hydrogen-terminated p-Si (100) in an actual drying atmosphere, which was prepared to 70 ppm H2O under atmospheric pressure at room temperature.
Electroluminescent Properties in Organic Light-Emitting Diode Doped with Two Guest Dyes
Authors: Mori Tatsuo , Kim Hyeong-Gweon , Mizutani Teruyoshi , Lee Duck-Chool
Published: October 2002

An organic light-emitting diode (OLED) with a squarylium dye-doped aluminium quinoline (Alq3) emission layer prepared by vapor deposition method has a pure red emission. However, since its luminance and electroluminescence (EL) efficiency is poor, the authors attended to improve the EL efficiency by doping a photosensitizer dye (a styryl dye, DCM) in an emission layer. The EL efficiency and luminance of DCM- and Sq-doped OLEDs are 2–3 times higher than those of only Sq-doped OLEDs. It was found that the excited energy is transferred from Alq3 to Sq through DCM.
Internal Friction Due to Localized Relaxation around Y-ions in Single Crystal Yttria-Stabilized Zirconia
Authors: Ohta Michihiro , Kirimoto Kenta , Nobugai Kohji , Wigmore J. Keith , Miyasato Tatsuro
Published: October 2002

The internal friction in single crystal yttria-stabilized zirconia (YSZ) doped with 9.5 mol% Y2O3 was measured for longitudinal sound waves in the frequency range from 10 Hz to 800 Hz using a vibrating reed technique. In the temperature range from 300 K to 700 K, observations of internal friction reveal two closely overlapping absorption peaks, confirming the existence of two relaxation modes in YSZ. One of the peaks is due to diffusion relaxation, which is known to be responsible for long-range transport of O-ions. The second peak shows clearly the existence of localized relaxation, which is attributed to bound oxygen vacancies within the local structure which is formed around an Y-ion due to symmetry breaking. The absorption peak caused by the localized relaxation exhibits anisotropy resulting from the asymmetric local structure, and the strength of this peak changes with temperature reflecting the number of bound oxygen vacancies.
Evaluation of Oxygen-Plasma Damage in GaAs Exposed to a Surface-Wave Plasma Source Developed for the Ashing Process
Authors: Aoki Katsuaki , Uekusa Shin-ichiro , Yamauchi Takeshi , Katsumata Hiroshi
Published: October 2002

O2 surface-wave plasma radiation of GaAs substrates and photoresist films were performed as a function of the plasma-substrate distance D and the chamber pressure P in order to obtain the optimum ashing condition for achieving lower damage, higher ashing rate (R
A) and higher uniformity than currently possible. The photoluminescence (PL) peak intensity observed from GaAs at 1.514 eV (free exciton) increased with increasing D; in particular, the PL intensity obtained from the samples with D≧112 mm and 70 Pa was stronger than that from the untreated GaAs. This result demonstrates that plasma damage can be negligible above D=112 mm even though oxides are created. On the other hand, by increasing D from 97 mm to 157 mm, R
A decreased but its uniformity improved. In the range of D≧157 mm and P=70 Pa, R
A and uniformity were saturated, while the ion energy measured in plasma decreased with increasing D, finally becoming almost 0 above D=157 mm at 70 Pa. From these results, we concluded that the optimum ashing process can be achieved at D≧157 mm and P=70 Pa, by which R
A of 3.1 µm/min and its uniformity of ±3% were obtained on an φ8 inch wafer.
Cell Placement and Neural Guidance Using a Three-Dimensional Microfluidic Array
Authors: Griscom Laurent , Degenaar Patrick , LePioufle Bruno , Tamiya Eichi , Fujita Hiroyuki
Published: October 2002

Several fabrication techniques for making three-dimensional arrays of micro-wells for biological cell patterning and single-neuron guidance are presented. Methods for making complex 3d high-aspect-ratio structures in poly-dimethylsiloxane (PDMS) membrane are explored. In this work, three-dimensional micro-molds are made directly on silicon wafers though inductively coupled plasma reactive ion etching (ICP-RIE), and also using SU-8 negative photoresist. Cell placement is achieved through an array of 50-µm square holes in a 150–100 µm thick PDMS membrane, which is placed on a glass substrate. Vertical holes in the membrane are linked by horizontal tunnels on the glass side of the membrane, for use in neural guidance or delivery of drugs or nutrients. The effectiveness of the membrane for cell placement, growth and guidance was tested using fluorescent yeast cells and PC12 neuronal cells.
Electrical Properties of Mg Doped (Ba0.5Sr0.5)TiO3 Thin Films
Authors: Hyun Yoon Ki , Chan Lee Jae , Heon Kang Jihoon Park , Moo Song Ci , Gyo Seo Yong
Published: October 2002

The microstructures and electrical characteristics of Mg doped (Ba0.5Sr0.5)TiO3 (BSTM) thin films were investigated as a function of Mg content. Also the multi-layered structure, BSTM/BST/BSTM was proposed to improve both of the leakage current and dielectric constant. With increasing Mg content, the perovskite peak intensity slightly decreased and grains became smaller. For the films above 15 mol% Mg, the secondary phase (MgTi2O5) was observed in X-ray diffraction (XRD) patterns. The dielectric constant decreased with increasing Mg content, while leakage current decreased up to 10 mol% Mg and then increased with further addition, which were explained by the effect of grain size and charge compensation. For the BSTM/BST/BSTM multi-layered films, the leakage current dramatically decreased without reduction of the dielectric constant when the thicknesses of BSTM and BST were 70 nm and 210 nm, respectively. These results confirm that a promising BST thin film capacitor can be obtained by introduction of Mg modified multi-layer structure.
Influence of Sputtering and Annealing Conditions on the Structure and Ferroelectric Properties of Pb(Zr,Ti)O3 Thin Films Prepared by RF Magnetron Sputtering
Authors: Reji Thomas Reji Thomas , Shoichi Mochizuki Shoichi Mochizuki , Toshiyuki Mihara Toshiyuki Mihara , Tadashi Ishida Tadashi Ishida
Published: October 2002

Lead zirconate titanate (PZT) thin films were prepared on Pt/Ti/Corning 7059 glass substrates by RF magnetron sputtering using a Pb(Zr0.5,Ti0.5)O3 ceramic target. X-ray diffraction studies were performed on the films to optimize the sputtering pressure, O2/(Ar+O2) mixing ratio (OMR), annealing temperature and annealing time, to prepare the films in the perovskite phase. As-deposited amorphous film goes through an intermediate pyrochlore phase before crystallizing in the perovskite phase. Perovskite phase formation started at 625°C and annealing at 650°C for 2 h was found to be necessary for complete crystallization in the single perovskite phase. Perovskite phase formation was confirmed with the existence of a perovskite rosette structure by scanning electron micrograph (SEM). Energy dispersive X-ray (EDX) compositional analysis of as-deposited films showed Pb/(Zr+Ti) ≃ 1.1; a 10% deviation from the target stoichiometry. Ferroelectric and dielectric properties of the capacitor with thin platinum films as both electrodes were investigated in detail as functions of annealing temperature and annealing time. The marked improvement in the structural and electrical properties observed in the deposited film after annealing was mainly due to the crystal growth of small crystallites. The dielectric constant and loss tangent of the films annealed at 650°C for 2 h were 580 and 0.06, respectively. The films with 1.4 µm thickness that were annealed at 650°C showed a remanent polarization (P

r
)=26 µC/cm2 and coercive field (E

c
)=51 kV/cm.
Influence of Carrier Gas Conditions on Electrical and Optical Properties of Pb(Zr, Ti)O3 Thin Films Prepared by Aerosol Deposition Method
Authors: Akedo Jun , Lebedev Maxim
Published: October 2002

Transparent Pb(Zr, Ti)O3 (PZT) thin films with over 1 µm thickness were deposited by the aerosol deposition method (ADM). The transparency of the PZT thin film deposited at room temperature strongly depended on the kinds of carrier gases and the particle flow velocity. The color of the film became black if He gas was used as a carrier gas, and became transparent using N2, O2 or air gases, which were difficult to electrically discharge during the impacting of particles. The transmittance values in the 0.5–0.8 µm wavelength region of as-deposited 2-µm-thick PZT thin films on indium tin oxide (ITO) substrate were 70–80%. After annealing at 600°C, the remanent polarizations and the coercive fields of PZT thin films were 36 µC/cm2 and 89 kV/cm, respectively. With increasing carrier gas velocity, the remanent polarization decreased and the coercive field increased.
Preparation of Pb(Zr0.52TiO0.48)O3 Thin Films at Low-Temperature of Less than 400°C by Hydrothermal Treatment Following Sol-Gel Deposition
Authors: Wei Zhiqiang , Yamashita Kaoru , Okuyama Masanori
Published: October 2002

Sol-gel Pb(Zr0.52TiO0.48)O3 (PZT) thin films have been successfully crystallized at the low temperature of 160°C by hydrothermal treatment in various kinds of hydroxide (KOH, Pb(OH)2 and Sr(OH)2) solutions on Pt/Ti/SiO2/Si substrates with prebaking at 300°C. Hydrothermally treated PZT films in KOH+Pb(OH)2 solution show good crystallinity with pure perovskite phase and are oriented to (111). The films show granulated structure with grain size of about 100 nm. The sample after post-baking at 400°C shows good hysteresis loop with P
r=26.3 µm/cm2 and E
c=40.1 kV/cm. The leakage current density of the thin film after postbaking is about 5.78×10-8 A/cm2 at ±66 kV/cm (±2 V).
Microstructure and Electrical Properties of (Pb, La)(Zr, Ti)O3 Films Crystallized from Amorphous State by Two-Step Postdeposition Annealing
Authors: Kobune Masafumi , Matsuura Osamu , Matsuzaki Tomoaki , Sawada Tatsuya , Fujisawa Hironori , Shimizu Masaru , Niu Hirohiko , Honda Koichiro
Published: October 2002

Dense amorphous lead lanthanum zirconate titanate (PLZT) films with composition (Pb0.925La0.075)(Zr0.4Ti0.6)0.981O3 were deposited on Pt/MgO(100) substrates by rf-magnetron sputtering without heating the substrates and were subsequently crystallized by two-step postdeposition annealing and postdeposition annealing after chemical-oxidation treatment using ultrasonic-wave vibrations. The optimum soaking temperature of the crystal growth process in the two-step annealing process to crystallize as-deposited PLZT films was determined to be 750°C based on the measurements of the crystallinity and the degree of c-axis orientation. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) observations revealed that the distinct grain growth and sufficient crystallization for PLZT films were yielded by postannealing after chemical-oxidation treatment. PLZT films fabricated by postannealing after chemical-oxidation treatment had symmetric, slim and rectangular hysteresis loop shapes with the remanent polarization 2P
r\fallingdotseq51 µC/cm2 and the coercive field 2E
c\fallingdotseq73 kV/cm. Based on the results of AFM observations and electrical properties, the present process with postdeposition annealing after chemical-oxidation treatment shows great promise as a practical process for crystallizing ferroelectric thin films from the amorphous state.
Effects of Bottom Electrodes (Pt and IrO2) on Physical and Electrical Properties of Bi4-xLaxTi3O12 (BLT) Thin Film
Authors: Yang Woo Seok , Kim Nam Kyeong , Yeom Seung Jin , Kweon Soon Yong , Choi Eun Seok , Roh Jae Sung
Published: October 2002

Bi3.35La0.85Ti3O12 (BLT) thin (90 nm) films were prepared on Pt (200 nm) and IrO2 (200 nm) electrodes by metalorganic decomposition (MOD) method, and crystallized by rapid thermal annealing (RTA) and the subsequent furnace annealing. BLT films were c-axis oriented on both electrodes irrespective of RTA temperature (600 and 700°C). However, the degree of c-axis orientation was much higher on IrO2 than on Pt, and significantly reduced only on Pt with decreasing RTA temperature. This result was related to the different stress of BLT film which is negligible on Pt, but 500 MPa (tensile) on IrO2 in the RTA temperature range of 600–700°C. The crystalline orientation of BLT film directly affected switching polarization (P
*-P
∧) which had much smaller value of 5 µC/cm2 on IrO2 than 12 µC/cm2 on Pt, and was increased to 16 µC/cm2 only on Pt with the decrease of RTA temperature. On the other hand, leakage characteristics were not changed with bottom electrode materials.
Comparison of Microstructure and Ferroelectric Properties of Alkoxy-Derived MBi4Ti4O15 (M: Ca or Sr) Thin Films
Authors: Kato Kazumi , Suzuki Kazuyuki , Nishizawa Kaori , Miki Takeshi
Published: October 2002

CaBi4Ti4O15 (CBTi144) and SrBi4Ti4O15 (SBTi144) thin films were prepared on Pt-passivated silicon substrate using complex metal alkoxide solutions. The CBTi144 thin films crystallized to a single phase of perovskite at 650°C via a mixture of perovskite and pyrochlore phases. The 650°C-annealed CBTi144 thin films consisted of uniform and isotropic grains and had a closely packed columnar structure. In contrast, the SBTi144 thin films crystallized to the perovskite phase at relatively lower temperature and consisted of smaller and non-uniform grains. The dielectric constants and loss factors of the 650°C-annealed CBTi144 and SBTi144 thin films were 300 and 0.03, and 330 and 0.04, respectively, at 100 kHz. The remanent polarizations and coercive electric fields were 6.0 µC/cm2 and 79 kV/cm, and 2.9 µC/cm2 and 55 kV/cm, respectively, at 9 V. The dielectric and ferroelectric properties depended on both the cation size in the A site and the microstructure.
Properties of Lead Zirconate Titanate Ceramics Determined Using Microwave and Hot-Press Hybrid Sintering Process
Authors: Takahashi Hirofumi , Kato Kazuaki , Qiu Jinhao , Tani Junji , Nagata Kunihiro
Published: October 2002

Piezoelectric materials play an important role in smart material and structural systems, and high-performance piezoelectric actuators with larger force and displacement output are in demand. It was shown in our previous work that the hybrid sintering process using a 28 GHz microwave technique and hot pressing offers advantages over conventional technologies reference. It was also confirmed that the maximum achieved value of piezoelectric constant d
31 of the specimens of the hybrid-sintering process is approximately 360×10-12 m/V, which is about 38% larger than 260×10-12 m/V, the d
31 of the conventionally sintered specimens. In this study, the material properties, including electromechanical coupling factor, Young's modulus, frequency constant, Curie temperature and dielectric constant, of the specimens fabricated with the microwave sintering process were further investigated for different sintering temperatures. The Curie point T

c
decreases, but the dielectric constant ε

r
at T

c
increases with the grain size of specimens for all sintering methods. The influence of grain size on T

c
and ε

r
can be attributed to the residual stress induced by the lattice mismatch between the cubic phase and the tetragonal-rhombohedral mixed phase.
Morphotropic Phase Boundary and Electrical Properties of Bisumuth Sodium Titanate–Potassium Niobate Solid-Solution Ceramics
Authors: Ishii Hideki , Nagata Hajime , Takenaka Tadashi
Published: October 2002

A morphotropic phase boundary (MPB) between (Bi1/2Na1/2)TiO3 (rhombohedral system) and KNbO3 (orthorhombic system) was determined by using X-ray diffraction and dielectric measurements. A solid solution, (1-x)(Bi1/2Na1/2)TiO3–xKNbO3 [BNTK-100x], shows a rhombohedral symmetry and orthorhombic symmetry at a composition of around 0≦x≦0.95 and 0.96≦x≦1.00, respectively. The dielectric constant, ε
s, at Curie temperature, T
c, was the largest value in the BNTK-96 system. From these results, the MPB of the BNTK system seems to exist in BNTK-96. The BNTK ceramics were confirmed to be ferroelectric by observing their hysteresis loops. Resistivities, ρ, of BNTK-100x (0.94≦x≦0.98) are 109–1012 Ω·cm. An electromechanical coupling factor, k
33, of BNTK-96 is 0.16 which is an unsaturated value.
Crystal Growth and Dielectric Properties of Solid Solutions of Pb(Yb1/2Nb1/2)O3–PbTiO3 with a High Curie Temperature near a Morphotropic Phase Boundary
Authors: Yasuda Naohiko , Ohwa Hidehiro , Kume Motoyuki , Hosono Yasuharu , Yamashita Yohachi , Ishino Shinnichirou , Terauchi Hikaru , Iwata Makoto , Ishibashi Yoshihiro
Published: October 2002

The Pb(Yb1/2Nb1/2)O3–PbTiO3 (PYN–PT) binary system single crystal near the morphotropic phase boundary (MPB) composition with (100) planes of 1–2 mm length on one side was successfully grown by the flux method using PbO–PbF2–B2O3 flux. The PYN–PT (47/53) single crystal was found, by simultaneous microdifferential thermal analysis and thermogravimetric analysis, to show a peritectic melting point at 1205°C with a decomposition of the perovskite crystals into a pyrochlore phase and a liquidus point at 1253°C. The structure of the PYN–PT (47/53) single crystal was determined by X-ray diffraction study to be tetragonal with a=4.05±0.01 A and c=4.14±0.01 A at room temperature. The PYN–PT single crystal shows the maximum value of the relative permittivity ε
r of 16000 at 1 kHz at a Curie temperature T
c of 404°C, which is as high as that in the Pb(Zr, Ti)O3 system near the MPB and the value of the remanent polarization P
r of about 26 µC/cm2 at 140°C.
Poling Treatment and Piezoelectric Properties of Potassium Niobate Ferroelectric Single Crystals
Authors: Wada Satoshi , Seike Akira , Tsurumi Takaaki
Published: October 2002

Piezoelectric properties of potassium niobate (KNbO3) single crystals were investigated as a function of crystallographic orientations, i.e., [110]
c
of polar direction and [001]
c
of nonpolar direction. Prior to the piezoelectric measurements, the optimum conditions for a conventional poling method were investigated, and it was found that the optimum conditions for a conventional poling method were as follows, i.e., (a) high temperature above 100°C, (b) long soaking time over 1 h, (c) slow heating and cooling rates below 1°C/min, and (d) lower poling current below 1 µA. However, fully poled KNbO3 crystals were not obtained using the conventional poling method. Thus, to achieve fully poled KNbO3 single crystals, a new 2-step poling method was proposed. This method is composed of 2 poling stages, i.e., the 1st step for non-180° domain switchings at higher temperatures under a low DC bias field, and the 2nd step for 180° domain switchings at lower temperatures under a high DC bias field. Using the 2-step poling method, KNbO3 crystals were successfully poled, and then, their piezoelectric properties of k
31 modes were measured using a resonance method. The [110]
c
poled KNbO3 crystals exhibited electromechanical coupling factor k
31 of 28.9% and piezoelectric constant d
31 of 18.4 pC/N while the [001]
c
poled KNbO3 crystals exhibited k
31 of 31.2% and d
31 of 51.7 pC/N. The piezoelectric constant d
31 along nonpolar [001]
c
direction was 2.8 times higher than that along polar [110]
c
direction.
Finite Element Method Simulation of a New One-Chip-Style Quartz Crystal Motion Sensor with Two Functions of Gyro and Acceleration Detection
Authors: Koitabashi Tatsuo , Kudo Seiichi , Okada Shigeya , Tomikawa Yoshiro
Published: October 2002

In this study, a new one-chip-style quartz crystal motion sensor which detects one-axis angular velocity and one-axis acceleration is proposed. Some characteristics of the sensor are simulated by the finite element method, along with some simulations of vibrational characteristics. This sensor is aimed to be used as a small wristwatch-type instrumentation unit to monitor some motions of the human body. The dimensions of the prototype sensor are 16 mm in length, 6 mm in width and 0.3 mm in thickness. The sensor consists of two parts with different functions; one part is a flatly supported vibratory gyrosensor using a quartz crystal trident-type tuning fork resonator and the other is a frequency-changeable type acceleration sensor. The results of simulations show, that the gyrosensor part has a good linearity of sensitivity, although it is also sensitive to an angular velocity which could not be detected fundamentally. It also has a good linearity of sensitivity for detection of acceleration.
First-Principle Studies on Elastic Properties and Spontaneous Polarizations of PbTiO3
Authors: Nishida Kunio , Kasai Shigeharu , Tanaka Katsuhiko , Sakabe Yukio , Ishii Fumiyuki , Oguchi Tamio
Published: October 2002

The elastic properties of the tetragonal phase of PbTiO3 were investigated using the full-potential linearized argumented plane wave (FLAPW) method. The geometric optimization calculations were performed against the lattice deformations. It is shown that the elastic properties including the sublattice relaxations can be well described by the simple Hook's law. The value of the spontaneous polarization using Berry's phase approach based on the optimized geometry fairly reproduced the experimental value.
Quantized Resonant-Tunneling Phenomena of AlGaAs/GaAs/InGaAs Heterojunction Bipolar Transistors
Authors: Tsai Jung-Hui
Published: October 2002

The quantized resonant-tunneling behaviors of heterojunction bipolar transistors (HBTs) with an n-AlGaAs/n-GaAs/n
--InGaAs heterostructure emitter and an ultra thin p
+-GaAs base layer are demonstrated by theoretical and experimental analysis. In these devices, a thin n
--InGaAs pseudomorphic quantum well (QW) in the emitter region is formed between the n-GaAs emitter and the ultra thin p
+-GaAs base layer. By solving the Poisson equation, the design of the n-GaAs emitter layer is discussed. A transfer-matrix method is developed to describe the quantum mechanism of miniband structures, in which electrons tunnel resonantly from the depleted emitter side to the collector side through the InGaAs QW and ultra thin p
+-GaAs base layers., A device with high current gain, low offset voltage, and a pronounced N-shaped negative-differential-resistance (NDR) phenomenon at room temperature is observed experimentally.
Growth of 3C-SiC Layers on Si Substrates with a Novel Stress Relaxation Structure
Authors: Irokawa Yoshihiro , Kodama Masahito , Kachi Tetsu
Published: October 2002

Silicon (Si) substrates having cavities immediately beneath the surface layer were used as a stress relaxation structure in 3C-SiC heteroepitaxial growth on Si substrates. Single crystalline 3C-SiC layers were grown on these Si substrates by means of low pressure chemical vapor deposition (LPCVD). The layers' quality was characterized by micro-Raman spectroscopy and current–voltage (I–V) characteristics. These results revealed that this structure improved the crystal quality in the 3C-SiC layers.
Energy Transfer Processes in Yb3+- and Tm3+-Ion-Doped Oxide and Fluoride Crystals
Authors: Mita Yoh , Togashi Masahiro , Umetsu Yousuke , Yamamoto Hajime
Published: October 2002

Energy transfer characteristics from Yb3+ to Tm3+ ions have been investigated on five different oxide lattices as well as four fluoride lattices for the purpose of characterizing the host materials and of obtaining optimizing procedures for laser and display devices. It has been shown that the energy transfer coefficients of the oxide crystals are distinctly larger and more strongly dependent upon the donor concentration than those of the fluoride lattices. Microscopic interaction parameters have been determined for the oxide as well as the fluoride lattices by comparing the experimental results with the results of computer simulation, assuming dipole–dipole (d–d) interaction between relevant ions. It has also been shown that d–d interaction parameters in the oxide host materials have significantly different values for different materials.
Effect of Reducing Atmosphere on Electrical Properties of Sol–Gel-Derived Pb(Zr,Ti)O3 Ferroelectric Films on Textured LaNiO3 Electrode
Authors: Chao Gwo-Chin , Wu Jenn-Ming
Published: October 2002

Reducing-atmosphere treatment at 400°C for 10 min was performed on sol–gel-derived Pb(Zr,Ti)O3 (PZT) thin films, which were spin-coated on a LaNiO3/Pt/Ti/SiO2/Si substrate and annealed. The reducing atmosphere does not produce any significant change of the preferred orientation perovskite structure of these ferroelectric thin films. However, the relative dielectric constant and the remanent polarization of the PZT films decrease significantly with the reducing-atmosphere treatment. In addition, the endurance of electrical signal cycling is also decreased by the reducing atmosphere treatment. On the other hand, the leakage currents of the reducing-atmosphere-treated PZT films are decreased by about one order of magnitude.
Synthesis of Conductive LaNiO3 Thin Films by Chemical Solution Deposition
Authors: Ueno Kengo , Sakamoto Wataru , Yogo Toshinobu , Hirano Shin-ichi
Published: October 2002

Metallic conductive LaNiO3 thin films have been prepared by the chemical solution deposition method. A homogeneous and stable LaNiO3 precursor solution was prepared by controlling the reaction of metal organics. Dehydration of the starting material Ni(acac)2·2H2O was a key factor in preparing a proper LaNiO3 precursor solution, because the hydrolysis of La(OiPr)3 has to be suppressed through the removal of hydrated water. The precursor films were prepared from the solution by dip-coating and spin-coating. 110-oriented LaNiO3 thin films were synthesized from the LaNiO3 precursor solution on fused silica substrates at 700°C. LaNiO3 film prepared by spin-coating had a better surface smoothness than that prepared by dip-coating. The resistivities of 100-nm-thick LaNiO3 films prepared by dip-coating and spin-coating were 3.8×10-5 Ω m and 2.9×10-5 Ω m, respectively, at room temperature.
Undergate-type Triode Carbon Nanotube Field Emission Display with a Microchannel Plate
Authors: Jin SeGi Yu , Yi Whikun , Kang Jeongho , Jeong Taewon , Choi Yongsoo , Lee Jeonghee , Heo Jungna , Lee Nae Sung , Yoo Ji-Beom , Kim Jong Min
Published: October 2002

The characteristics of a field emission display (FED), which is based on an undergate-type triode carbon nanotube (CNT), have been examined by incorporating an electron-multiplying microchannel plate (MCP) between the anode and cathode plates of a FED. The MCP was fabricated by electroless plating and the sol–gel process on punched alumina. By applying appropriate voltages between the two faces of an MCP within a FED, the current at the anode plate of a FED was found to be enhanced more than three to five times, leading to higher brightness. The focusing of field emitted electrons was also improved by adjusting the bottom voltage of the MCP, which resulted in a clear image. Therefore, the incorporation of the MCP improved the performance of an undergate-type CNT FED, which can now be considered as one of the key candidates for flat panel displays.
J Dependence of the Isotope Shift in the Gd I 4f76s26p9P Term
Authors: Jin Wei-Guo , Wakui Takashi , Endo Toshiaki , Uematsu Haruko , Minowa Tatsuya , Katsuragawa Hidetsugu
Published: October 2002

High-resolution laser spectroscopy in Gd I has been performed using a tunable diode laser. Isotope shifts of the even-mass isotopes have been measured for two transitions from the 4f
75d6s
2
9
D
4 and 9
D
5 levels to the 4f
76s
26p
9
P
3 and 9
P
4 levels in Gd I. The J dependence of the isotope shift, related to the crossed-second-order (CSO) effect, has been obtained for the 4f
76s
26p
9
P
3 and 9
P
4 levels. The CSO parameter z
6p
of the 4f
76s
26p configuration has been estimated for the first time.
Influence of NaCl Concentration on the Gas–Liquid Interface Deformation of Water in Magnetic Fields
Authors: Lee Seung-Hwan , Takeda Minoru , Nishigaki Kazu
Published: October 2002

To clarify the deformation characteristics of a seawater surface in magnetic field, the gas–liquid interface deformation of water and NaCl aqueous solution at room temperature was investigated. In this research, a uniform magnetic field (UMF) and a gradient magnetic field (GMF) were used. The deformation of water was rarely observed in UMF of 0 to 10 T, but it was clearly observed in GMF. The deformation of water and NaCl aqueous solution in GMF decreased in proportion to the increase of NaCl concentration. The decrease was mainly affected by the increase of density in the aqueous solution as the NaCl concentration increased. In addition, it is considered that the deformation of NaCl aqueous solution depends not only on the magnetic force but also on the osmotic pressure of the concentration gradient.
Compensation Model for n-type GaN
Authors: Yi Gyu-Chul , Park Won Il
Published: October 2002

The defect structure for unintentionally doped and deliberately Se-doped, n-type GaN was investigated. For impurity doping, Se was incorporated into GaN films during vapor phase epitaxial growth. Both nominally undoped and Se-doped, n-type GaN films were highly compensated as determined by the Hall effect measurements and photoluminescence spectroscopy. It was also found that the compensation by acceptors increases with increasing Se doping concentration. Based upon these experiments and the theoretical calculations, a defect compensation model for n-type GaN was developed.
Comparison Study of Metal Induced Lateral Crystallized and Solid-Phase Crystallized Polycrystalline Silicon Thin Film Transistors with Different Channel Thickness
Authors: Jin Zhonghe
Published: October 2002

N- and P-type polycrystalline silicon thin film transistors are fabricated with channel thickness of 30 nm and 100 nm by metal induced lateral crystallization (MILC) and conventional solid-phase crystallization (SPC) of amorphous silicon. Significant improvement is obtained for the MILC devices by ultrathin channel layer. But for SPC devices, improvement is not as significant. The possible reasons are proposed and discussed.
Photocreated Defects in Very Thin Hydrogenated Amorphous Silicon Films
Authors: Shimizu Tatsuo , Shimada Masaki , Kumeda Minoru
Published: October 2002

ESR measurements were carried out for a 10-nm-thick a-Si:H film. The results show that the high-density defects in the near-surface layer can be treated in the same manner as the bulk defects in the case of light soaking, if both the penetration depth of the light and the dependence of the defect creation rate on the defect density are taken into account.
Improvement in Field Trapping Capability of (Nd,Eu,Gd) Ba2Cu3Oy with Ag2O Addition
Authors: Muralidhar Miryala , Jirsa Milos , Sakai Naomichi , Murakami Masato
Published: October 2002

We prepared (Nd,Eu,Gd) Ba2Cu3O7-δ (NEG-123) pellets of 22 mm diameter and 9 mm thickness with 10 mole% NEG-211, 0.5 mole% Pt, and various amounts of Ag2O ranging from 0 to 50 wt% using the oxygen-controlled melt-growth (OCMG) process. The irreversibility field increased with Ag2O content up to 20 wt%, and even with 50 wt% the magnetization loop was open at 77 K and 7 T. In the sample with 20 wt% Ag2O, a large critical current density of 10 kA cm-2 was recorded even at 7 T and 77 K for fields applied parallel to the c-axis. The trapped field in the NEG-123 bulk was measured using a Hall probe at 77 K after field-cooling in 5 T. A single-peak profile observed in the sample with silver addition proved that silver dispersion is effective in improving mechanical properties without deterioration of electromagnetic properties.
Crack-free and c-Axis In-plane Aligned Superconducting Y0.7Ca0.3Ba2Cu3O7-δ Films for Terahertz Radiating Josephson Plasma Devices
Authors: Sarin Kumar A. K. , Kawasaki Masashi , Koinuma Hideomi
Published: October 2002

External excitation of the Josephson plasma in YBa2Cu3O7-δ by injecting current is expected to result in the emission of light in the terahertz (THz) region. In order to fabricate such THz light emitting devices, one has to grow underdoped (T
C=60 K), c-axis in-plane aligned YBa2Cu3O7-δ films free from cracks. However, the large thermal expansion coefficient of this compound along the c-axis due to the oxygen incorporation makes it difficult to avoid cracking. Here we report that substitution of Y by Ca made it possible to obtain crack-free, 60 K phase Y0.7Ca0.3Ba2Cu3O7-δ films with a larger oxygen deficiency (δ) than YBa2Cu3O7-δ. This experiment is designed so as to compensate the reduction of hole concentration due to the large oxygen deficiency with the hole doping by Ca substitution.
Superconductivity and Structure of Bi2Sr2Ca1-xPrxCu2Oy System
Authors: Salamati Hadi
Published: October 2002

The effect of Pr substitution on the superconductivity and structure of the Bi2Sr2Ca1-x
Pr
x
Cu2O
y
system is investigated. The onset superconductivity transition temperature, T
c(on), first increased and reached its maximum value of 87 K at x=0.2 and then decreased until it became zero at about x\cong0.7. At a higher doping level a metal–insulator transition is observed. The microstructure of the system has been analyzed by scanning electron microscope and X-ray diffraction. These analyses show that the ratio of (2212) to (2201) phase is improved up to x=0.2 and then reduced at higher concentrations.
Effects of Stray Fields in Flat-End and Pointed-End NiFe/Cu/NiFe/NiO Wires
Authors: Kimura Takashi , Wakaya Fujio , Gamo Kenji
Published: October 2002

The effects of the stray fields induced by pinned layers in two-types of 1-µm-wide NiFe/Cu/NiFe/NiO wires were investigated using the giant magnetoresistance effect and exchange anisotropy. One wire had flat ends and the other had pointed ends. It was found that the switching field of the free layer in the flat-end wire was smaller than that in the pointed-end wire because of the larger demagnetizing and stray fields and that the stray field in the pointed-end wire can be negligible. The stray field estimated from the experimental result in the flat-end wire was consistently explained by the magnetic charges at the wire end in the pinned layer
InGaAs/InGaAsP Quantum Well Laser at 2.04 µm for Diode Spectroscopy of Carbon Dioxide Isotope
Authors: Ubukata Akinori , Dong Jie , Suzuki Katsumasa , Matsumoto Koh
Published: October 2002

We demonstrate the utility of a compressively strained InGaAs/InGaAsP laser emitting at 2.05 µm for diode spectroscopy of carbon dioxide isotope (13CO2). By applying a highly compressive strain to and using thick wells in the active layer, the extension of the laser emission wavelength beyond 2.0 µm is achieved. The threshold current is as low as 6 mA at 283 K, and a wavelength-tuning rate of 0.016 nm/mA is obtained. A linear maximum power per facet of as high as 6 mW is obtained at 283 K. The side mode suppression ratio (SMSR) is 34 dB. The applicability of the diode spectroscopy system for the measurement of 13CO2 is also demonstrated. The detection limit of 13CO2 is estimated to be less than 2 ppm for the present experimental setup.
Numerical Modeling and Experimental Confirmation of an Efficient Phosphosilicate-Fiber Raman Laser
Authors: Ahmed Feroz , Prabhu Mahendra , Taniguchi Atsushi , Kim Nam Seong , Ueda Ken-ichi , Kishi Naoto
Published: October 2002

A model for a fiber Raman laser has been numerically solved including all the interactions between forward and backward travelling waves. The predicted numerical results are experimentally confirmed using a fiber Raman laser with P2O5-doped fiber. The maximum output power of 3.1 W at 1483.5 nm with a slope efficiency of 46% is experimentally obtained using a 300 m P2O5-doped fiber. Numerical results suggest that an output power of as much as 4 W with a slope efficiency of 57% can be achieved if the Raman cavity is optimized for the same input pump power.
Preparation and Characterization of Pb(Zr,Ti)O3 Films Deposited on Pt/RuO2 Hybrid Electrode for Ferroelectric Random Access Memory Devices
Authors: Lee Hee-Chul , Lee Won-Jong
Published: October 2002

Polycrystalline Pb(Zr,Ti)O3 (PZT) films were fabricated at a low temperature of 450°C by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. Stoichiometric PZT films with the pure perovskite phase could be obtained over a wider range of deposition conditions on Pt/RuO2 hybrid electrodes than on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 hybrid electrodes showed low leakage current and superior polarization characteristics compared with those on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 were not as fatigue-free as those on RuO2 but had higher resistance to fatigue than those on Pt. The introduction of a PbTiO3 buffer layer prior to PZT film deposition on Pt/RuO2 improved the fatigue characteristics by suppressing the formation of nonstoichiometric interfacial layers. Good leakage current property (J: 5.8 ×10-7 A/cm2 at 200 kV/cm) and fatigue characteristic (P
* - P
∧: 9% drop after 4 ×109 fatigue cycles) could be obtained for the 110-nm-thick PZT film using Pt/RuO2 hybrid top and bottom electrodes. This electrode structure is thought to be promising for use as a capacitor of high-density ferroelectric random access memory (FRAM) devices. The fatigue model that can explain the fatigue characteristics of PECVD-PZT capacitors with various hybrid electrode configurations is also suggested.