bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection Characteristics of Coupled-Defect-Type Photonic Crystals
Authors: Katsuyama Toshio , Hosomi Kazuhiko , Fukamachi Toshihiko , Arakawa Yasuhiko
Published: February 2005

A one-dimensional coupled-defect-type photonic crystal with an attached Au mirror has a wavelength-independent high reflectance over a wide wavelength region. Its delay time for reflected light is more than four times that for transmitted light measured with the mirror removed even though the physical path length for the reflected light is only twice that for the transmitted light. This remarkably long delay is due to the reduction of the field coupling through mirror reflection. The reflection configuration can thus simultaneously provide long delay time and wavelength-independent low loss, properties that are never obtained in a transmission configuration and that are especially advantageous in the device applications of coupled-defect-type photonic crystals.
Liquid Crystal Lens Array with Hexagonal-Hole-Patterned Electrodes
Authors: Ye Mao , Hayasaka Shin , Sato Susumu
Published: February 2005

Liquid crystal (LC) lens arrays are prepared using hexagonal-hole-patterned electrodes. Two lens array structures are studied. The LC lens arrays have a focal length that is tunable by adjusting the applied voltage. By using the electrodes with the hexagonal-hole arrays, the aperture of the lens array can be increased.
Monodomain Film Formation and Lasing in Dye-Doped Polymer Cholesteric Liquid Crystals
Authors: Ohta Takashi , Song Myoung Hoon , Tsunoda Yuko , Nagata Takaaki , Shin Ki-Chul , Araoka Fumito , Takanishi Yoichi , Ishkawa Ken , Watanabe Junji , Nishimura Suzushi , Toyooka Takehiro , Takezoe Hideo
Published: February 2005

We have succeeded in fabricating monodomain polymer cholesteric liquid crystal (PCLC) films by spin coating a polymer solution onto glass substrates with polyimide coated and rubbed unidirectionally. The thickness and helical pitch were well characterized by controlling the rotational speed of the spin coater and the chiral unit content of the polymer solution, respectively. Lasing from dye-doped PCLC films utilizing the photonic structure was confirmed.
Influence of Shallow Levels in Charge Transport Process on Enhancement of Transient Diffraction Efficiency in BaTiO3 Crystal
Authors: Sharif Sharafuddin Md. , Ogusu Kazuhiko
Published: February 2005

A unique enhancement of the transient diffraction efficiency in an undoped BaTiO3 crystal is experimentally observed. The enhancement is a strong function of the switched-off time (or dark time) of the pulsed reading beam incident to a steady-state grating, formed in advance, in the crystal. This enhancement can be maximized for an optimum dark time, which reveals the presence of two shallow levels in the charge transport process at room temperature.
Surface Temperature Measurement and Analysis of Thermal Breakdown with Ethylene-vinyl Acetate Copolymer in Room-Temperature Region
Authors: Murakami Yoshinobu , Hozumi Naohiro , Nagao Masayuki
Published: February 2005

To understand the dc breakdown characteristics of an ethylene-vinyl acetate copolymer (EVA) film at room temperature, the temperature distribution of the film surface was observed by thermograph until electric breakdown occurred. The conduction current of the EVA film was also measured and correlated with the thermograph measurements. From the conduction current, the hopping distance was estimated as 2.1 nm. The internal potential barrier was calculated as 1.1 eV. The heat generation was estimated by the equation of hopping conduction using the hopping distance and inner potential barrier. The heat dissipation was also determined from the thermal properties of the EVA film. A good agreement was obtained between the estimated heat balance and the observed temperature rise, suggesting that thermal breakdown takes place in the room-temperature region.
Dielectric and Piezoelectric Properties of BiScO3-PbTiO3 Crystals with Morphotropic Phase Boundary Composition
Authors: Zhang Shujun , Randall Clive A. , Shrout Thomas R.
Published: February 2005

The room temperature dielectric permittivity of [100] oriented 0.37BiScO3-0.63PbTiO3 (BSPT63) crystals with a morphotropic phase boundary (MPB) composition was found to be 1400, lower than that of BSPT57 crystals with rhombohedral phase (∼3000), but much higher than that of the tetragonal crystal BSPT66 (∼200). The Curie temperature of BSPT63 single crystals along [100] was found to be about 443°C, while the values were around 440°C and 445°C for [110] and [111] oriented crystals, respectively. Evidence of a ferroelectric–ferroelectric phase transformation temperature was associated with a dielectric anomaly occurring around 310–350°C for different orientations, indicating a strong curvature of the MPB. The coercive fields (E
c) were found to be 20 kV/cm for [100] oriented crystals, 24 kV/cm and 27 kV/cm for [110] and [111] directions, respectively. The piezoelectric response for [100] oriented samples (d
33 = 900 pC/N) is weaker than that in rhombohedral phase (d
33 = 1200 pC/N) but much higher than that in tetragonal phase (d
33 = 200 pC/N). The strain piezoelectric d
33 improved with the temperature increasing owing to dielectric permittivity increment, while the voltage piezoelectric g
33 is independent of temperature (g
33 ∼0.074 m2/C). Evidence of a monoclinic phase for BSPT63 crystals is inferred using the X-ray powder diffraction (XRD), and the lattice parameters were calculated to be a=4.0751 Å, b=3.9765 Å, c=3.9893 Å and β=90.166°.
Lifetime and Reliability in Pb(Mg,Nb)O3–Pb(Zr,Ti)O3 Multilayer Ceramic Actuators
Authors: Koh Jung-Hyuk , Jeong Soon-Jong , Ha Mun-Su , Song Jae-Sung
Published: February 2005

Lifetime and reliability of multiplayer ceramic actuators were estimated. 5×5×5 mm3 sized multilayer ceramic actuators with 50 ceramic sheet layers embedded internal electrodes were selected in these experiments. Specially selected rectified AC bias was applied to the multilayer ceramic actuators to remove heating from charging and discharging processes. 16 sets of multilayer ceramic actuators were tested for statistical analysis. Weibull function method was employed for statistical analysis. Arrhenius model and power law model were considered to simulate experimental data. From the SEM analysis in destroyed device, crack growth of multilayer ceramic actuator was clearly observed along to the boundary between electrode and inactive region. The main reason for destruction of multilayer ceramic actuators was mechanical tensile stress come from both actuation of d
33 mode and motion of Poisson ratio.
Novel and Simple Screening Methods for Protein Crystallization by Vapor Diffusion Rate Control
Authors: Adachi Hiroaki , Niino Ai , Matsumura Hiroyoshi , Takano Kazufumi , Inoue Tsuyoshi , Mori Yusuke , Sasaki Takatomo
Published: February 2005

We investigated the effect of the vapor diffusion rate on the refinement of protein crystals. The reservoir volume, drop-to-reservoir distance, and air space were altered to change the vapor diffusion rate using a very dense insoluble liquid and specific crystallization plates. The experimental results reveal that the drop-to-reservoir distance and air space have a more significant effect on crystal growth than the reservoir volume. We propose new simple and useful methods for screening protein crystal growth conditions based on vapor diffusion rate control.
Radiation Impedance Calculation for Arbitrarily Shaped Piston
Authors: Yang Jun , Sha Kan , Gan Woon-Seng , Tian Jing
Published: February 2005

A general solution for determining self- and mutual-radiation impedances for rectangular radiators is presented in a closed form with a double integral. Using this solution, an efficient calculation method is developed for the radiation impedance of an arbitrarily shaped piston in a rigid infinite baffle. The proposed algorithm is verified by its agreement with previously published results for square pistons. Its utility is demonstrated with an example of radiation impedance of a circular piston.
Influence of UV-Curable Compositions and Rib Properties on Ink-Jet-Type Color Filter Performance
Authors: Chang Chi-Jung , Wu Feng-Mei , Chang Shinn-Jen , Hsu Mei-Wen
Published: February 2005

UV-curable jet inks were ejected into a color area separated by barrier ribs, then fixed by UV curing reaction to prepare LCD color filter (CF). The widths of the color strip and rib were 90 µm and 20 µm, respectively. Either adding oligomer or increasing the amount of monomers can improve ink curability. By increasing the monomer content instead of incorporating the oligomer, the curing reactivity was elevated without deteriorating the pigment dispersion stability, jetting directionality and drop size uniformity. The drop formation behaviors were observed by the image-capture system. The ejected drops showed straight trajectory and uniform size without error and missing dots. The chemical resistance of the barrier ribs was improved to avoid collapse caused by ink corrosion.
Porosity of Organosilicate Films in a Range of Organic Properties
Authors: Oh Teresa , Kim Kyung Sik , Lee Kwang-Man , Choi Chi Kyu
Published: February 2005

Organosilicate films divide into three properties, organic, hybrid and inorganic depending on the flow rate ratio between oxygen and bistrimethylsilylmethane precursor. The films with organic properties show decreased dielectric constant, because of pore incorporation in final materials. In this study, the porosity of organosilicate films with organic properties was investigated using the Maxwell–Garnett equation. The porosity of the films could be correlated with their IR properties, and increasing the porosity decreases the dielectric constant of the film.
Crystal Structure and Dielectric Properties of Radio Frequency Magnetron Sputtered Nanocrystalline SrTiO3 Thin Films
Authors: Wang Moo-Chin , Hsiao Fu-Yuan , Huang Hong-Hsin , Wu Nan-Chun
Published: February 2005

Nanocrystalline SrTiO3 thin films have been successfully deposited by radio frequency (RF) magnetron sputtering. The perovskite phase was obtained for the SrTiO3 thin films deposited on Pt/Ti/SiO2/Si substrates at 500°C. The SrTiO3 thin films deposited at 500°C were composed of granular crystallites with a size of approximately 35 nm and a thickness of 150 nm. The crystallite size increases with increasing film thickness. The dielectric constant of SrTiO3 thin films decreases with decreasing film thickness by changing the temperature, frequency and bias voltage.
Mass Resolution for Iron Isotopes in CR-39 Track Detector
Authors: Kodaira Satoshi , Hasebe Nobuyuki , Doke Tadayoshi , Kitagawa Atsushi , Kitamura Hisashi , Sato Shinji , Uchihori Yukio , Yasuda Nakahiro , Ogura Koichi , Tawara Hiroko
Published: February 2005

We have verified the capability of a CR-39 track detector for isotope identification using iron beam from the heavy-ion accelerator of HIMAC at NIRS. The same CR-39 stack was independently exposed to 56Fe and 55Fe ions with an energy of 460 MeV/nucleon. Mass resolutions for 56Fe and 55Fe ions were determined to be 0.28±0.12 amu and 0.28±0.11 amu in rms, respectively. A detailed analysis of the sources of the mass dispersion in the present mass identification experiment showed that significant errors were caused in the measurements of the surface position and the thickness of CR-39 sheets. By eliminating these errors as much as possible, the mass resolution is expected to be improved to ∼0.20 amu.
Measurement of Sound Fields Using Mach–Zehnder Interferometer
Authors: Nemoto Manabu , Mizutani Koichi , Ezure Tomohiro , Masuyama Hiroyuki
Published: February 2005

In this paper, we propose a method of noncontact measurement of sound fields, radiating from an ultrasonic transducer, using a Mach–Zehnder interferometer. The deviation of refractive index, which depends on sound pressure, was transformed into the intensity of the interference light using the interferometer, in which a light beam passes through the measured object. Projection data used in the computerized tomography (CT) method along the optical axis was obtained by single linear scanning in the range of ±40 mm and was electronically quadrature-detected as the complex amplitude. The 36 projections were acquired by the rotation of the sound fields in the range of 0≤θ≤π (rad) with an interval of π/36 rad. Finally, the complex sound fields were reconstructed in the region of 48×48 mm2 by the CT method. The plane of reconstruction was 5 mm apart from the plane of the transducer. The ultrasonic transducer used in the experiment was driven at a frequency of 1.416 MHz and had a diameter of 8.0 mm. The experimental results were approximately in agreement with the numerical results.
Microstructures of Self-Assembled PbTiO3 Nanoislands Prepared by Metalorganic Chemical Vapor Deposition
Authors: Nonomura Hajime , Fujisawa Hironori , Shimizu Masaru , Niu Hirohiko , Honda Koichiro
Published: February 2005

Self-assembled PbTiO3 nanoislands were prepared on Pt(110)/SrTiO3(110) and Pt(100)/SrTiO3(100) by metalorganic chemical vapor deposition (MOCVD), and their microstructures were investigated. On Pt(110)/SrTiO3(110), the shapes of (101)-PbTiO3 islands changed from square to rectangular ones elongated along the <010> direction as deposition time increased. Transmission electron microscopy (TEM) and selected-area electron diffraction results showed that (101)-PbTiO3 nanoislands with deposition times of 10–300 s had a tetragonal structure. TEM observations also revealed that the nucleation of PbTiO3 islands started at the platinum terrace ledge. Piezoresponse force microscopy observations verified that the (101)-PbTiO3 nanoislands deposited for 10–300 s had ferroelectricity. When Pt/SrTiO3(100) was used as a substrate, square-shaped PbTiO3 nanoislands exhibiting ferroelectricity were also obtained.
Electro-Optical Properties and Structures of (Pb, La)(Zr, Ti)O3 and PbTiO3 Films Prepared Using Aerosol Deposition Method
Authors: Nakada Masafumi , Ohashi Keishi , Akedo Jun
Published: February 2005

The electro-optical (EO) properties, film structures and far-infrared spectra were measured for lanthanum-modified lead zirconate titanate [PLZT, Pb0.91La0.09(Zr0.65Ti0.35)O3] and lead titanate [PT, PbTiO3] films, prepared by the aerosol deposition (AD) method. The EO response appeared for AD films annealed at over 500°C, and increased as the annealing temperature increased. Downward shifts of the diffraction peaks, compared with diffraction peak positions of the corresponding to powders, were observed for as-deposited PLZT films in X-ray diffraction patterns of θ-2θ scans. The (200) peaks shifted to higher angles with increasing X-ray incidence angle to the film surface, indicating that the peak shifts were caused by lattice distortion induced by in-plane compressive stress. The (200) peaks shifted to the powder position when annealed at 600°C, which means that the annealing can relax the residual stress. Far-infrared spectroscopy measurements of reflectivity and transmittance were carried out on the PLZT and the PT powders and films, and the IR spectra of PT films were analyzed using the classical damped harmonic oscillator models to determine the oscillation parameters. We observed LO mode degradation and the broadening of the dielectric function peaks on the AD films. The frequencies of the E (1TO) soft-phonon mode of the annealed PT films were shown to have downward shifts of over 20 cm-1, compared with those of bulk ceramics and single crystals, suggesting that the AD may have induced a microscopic lattice degradation in the PT films, which may be responsible for the small EO response.
Improvement in Homogeneity and Ferroelectric Property of Mist Deposition Derived Pb(Zr,Ti)O3 Thin Films by Substrate Surface Treatment
Authors: Kawasaki Susumu , Motoyama Shin-ichi , Tatsuta Toshiaki , Tsuji Osamu , Okamura Soichiro , Shiosaki Tadashi
Published: February 2005

Pt/TiO2/SiO2/Si substrate UV surface treatment was carried out with O3 or N2/O2 atmosphere before film deposition to improve the homogeneity of mist deposition (MD)-derived Pb(Zr, Ti)O3 (PZT) films. The effect of the surface treatment was determined by measuring the contact angle of the distilled water on Pt substrates. The largest improvement in wettability was achieved in the N2/O2 atmosphere at the O2 partial pressure of approximately 10%. The macroscopic homogeneity of PZT films deposited onto the surface-treated Pt substrates was dramatically improved with a decrease in the contact angle. Although the contact angle of 0° was achieved by over 5 min UV treatment in any atmosphere, the P–E hysteresis properties and J–E characteristics were further improved with treatment time, even after the contact angle of 0° was reached. The improvement in electrical properties corresponded closely to the improvement in microscopic surface roughness. The PZT film deposited onto UV/N2-treated Pt substrates for 30 min showed the two fold remanent polarization (2P
r) of 52 µC/cm2, while the PZT film on the 5-min-treated substrate showed 44 µC/cm2.
Crystal Orientation Dependence on Electrical Properties of Pb(Zr,Ti)O3 Thick Films Grown on Si Substrates by Metalorganic Chemical Vapor Deposition
Authors: Okamoto Shoji , Yokoyama Shintaro , Honda Yoshihisa , Asano Gouji , Funakubo Hiroshi
Published: February 2005

(111)c- and (100)c-oriented SrRuO3 films were successfully grown on (111)Pt/TiO2/SiO2/(100)Si and (100)LaNiO3/(111)Pt/TiO2/SiO2/(100)Si substrates, respectively, by RF-magnetron sputtering method. On these (111)c- and (100)c-oriented SuRuO3 films, (111)- and (001)/(100)-oriented fiber-textured Pb(Zr0.35Ti0.65)O3 films with 2.0 µm in thickness were grown by metalorganic chemical vapor deposition (MOCVD). Well-saturated polarization-electric field (P-E) hysteresis loops were observed for both films. The remanent polarization (P
r) values of (111)- and (001)/(100)-oriented 2.0 µm-thick Pb(Zr,Ti)O3 (PZT) films were almost the same at approximately 45 µC/cm2 at 200 kV/cm, while the coercive field (E
c) values of these films were slight different at 61 kV/cm and 71 kV/cm, respectively. Moreover, the field-induced strains measured by scanning probe microscopy were also almost the same at approximately 0.2% up to 100 kV/cm. These data show the crystal orientation independence of the remanent polarization and field-induced strain of Pb(Zr0.35Ti0.65)O3 films.
Fabrication of KNbO3 Epitaxial Thin Films on Sapphire Substrates by Pulsed Laser Deposition
Authors: Higuchi Takamitsu , Aoyama Taku , Iwashita Setsuya , Kijima Takeshi , Shimoda Tatsuya
Published: February 2005

KNbO3 epitaxial thin films were fabricated on sapphire r-plane substrates with an MgO buffer layer by pulsed laser deposition. X-ray diffraction measurements revealed that both MgO and KNbO3 were epitaxially grown on the Al2O3 (1-102) substrate with an orientation relationship as KNbO3 (100)pc/MgO (100)/Al2O3 (1-102) (out-of-plane) and KNbO3 [010]pc//MgO [010]//Al2O3 [11-20] (in-plane), although both MgO and KNbO3 were tilted 6–9° with respect to the substrate surface. Raman scattering measurements revealed that the KNbO3 film was composed of the orthorhombic ferroelectric phase, and that the (010)ortho (Y) domain, in which the polarization axis was parallel to the substrate surface, was dominant. The present study enables the production of KNbO3 epitaxial thin-film wafers, which correspond to Y-cut KNbO3 single crystals with a large electromechanical coupling coefficient (k
2=0.53), for surface acoustic wave propagation.
Evaluation of Bit Error Rate for Ferroelectric Data Storage
Authors: Hiranaga Yoshiomi , Cho Yasuo
Published: February 2005

Bit data was recorded on a LiTaO3 single-crystal medium using a data storage system which was based on scanning nonlinear dielectric microscopy, and bit error rate was evaluated. The recording medium with a highly homogeneous thickness of 119 nm was prepared employing both polarization controlled wet etching and dry etching techniques. A 256×256 data bit array was recorded at an areal density of 258 Gbit/inch2. The bit error rate was determined to be 1.2×10-3 by visual inspection. An automated analysis method was subsequently discussed in detail.
Relationship between Microstructural Evolution and Electrical Properties in Ba(Ti, Zr)O3-Based Materials for Ni-MLCC
Authors: Mizuno Youichi , Morita Koichiro , Hagiwara Tomoya , Kishi Hiroshi , Ohnuma Kenji , Ohsato Hitoshi
Published: February 2005

The influence of the microstructural evolution induced by increasing firing temperature on the change in dielectric properties induced by re-oxidation treatment in the Ba(Ti, Zr)O3(BTZ)-Ho-Mn system was investigated. The microstructural observation of as-fired disk samples revealed gradual grain growth with firing temperature. From the temperature characteristic (TC) measurement, the shift to higher temperatures of dielectric maximum (T
max) due to re-oxidation treatment became larger with grain growth although the chemical compositions were quite the same. It was found that grain growth accelerated the valence change of Mn by re-oxidation treatment and the substitution of dopants in a grain in this system. Microstructural evolutions, such as compositional distribution and the concentration of additives in a grain, had an influence on the changes in dielectric properties induced by re-oxidation treatment.
Pressure Dependence of Piezoelectric Properties of Pb(Zn1/3Nb2/3)O3-PbTiO3 Binary System Single Crystal near a Morphotropic Phase Boundary
Authors: Yasuda Naohiko , Itoh Yuuki , Ohwa Hidehiro , Matushita Mituyoshi , Yamashita Yohachi , Iwata Makoto , Ishibashi Yoshihiro
Published: February 2005

The piezoelectric properties of a Pb[(Zn1/3Nb2/3)0.91]Ti0.09O3 binary system single crystal oriented along the [001] direction in the rhombohedral phase was investigated under pressures up to 500 MPa at 25°C. With increasing hydrostatic pressure, the change of the resonance and antiresonance frequency characteristic curves of the impedance and phase from sharp to broad ones was observed. The resonance frequency f
r increased, while the antiresonance frequency f
a remained almost constant. The electromechanical coupling coefficient in the k31 mode decreased markedly with pressure, and the value of the k
31 mode decreased by 18% at 500 MPa. The electromechanical coupling coefficient in the k
33 mode decreased slightly with pressure. The value of the k
33 mode decreased slightly by only 3% at 500 MPa. The large decrease in the k
31 value with pressure exhibited a marked contrast with the slight decrease in the k
33 value with pressure. The changes in the values of the elastic compliances s
11
E and s
33
E with pressure were observed to be large from the changes in f
r and f
a with pressure. s
11
E and s
33
E at 400 MPa were estimated to be 7.23 and 13.95×10-11 m2/N, respectively. The large k
31 in the k
31 mode is considered to be due to the mechanical softness of the PZN-PT(91/9) single crystal. On the other hand, the slight decrease in k
33 with pressure is thought, on the basis of the engineered domain concept, to be due to the stable domain configuration responsible for the longitudinal k
33 mode.
Effect of Poling Field on Piezoelectric Properties of KNbO3 Crystal Grown by Vertical Bridgman Method
Authors: Kudo Kenichi , Kakiuchi Kenji , Endo Naoyuki , Bamba Noriko , Hoshikawa Keigo , Fukami Tatsuo
Published: February 2005

Single crystals of KNbO3 were grown by the vertical Bridgman method. The crystals were cut into 6×3×0.5 mm3 plates, and dielectric constants and resonance characteristics were observed as a function of the electric field strength used in the poling treatment. For the [001]pc-poled crystal, which stands for [001] direction in pseudocubic crystal lattice, the dielectric constant increased once with increasing amount of poling field and then decreased again with higher fields. For [101]pc-poled crystal, both a reduction in dielectric constant and a higher phase angle shift in the resonant region were observed when the electric field exceeded 85 V/mm. The series of observations can be consistently interpreted using the domain structures estimated from the anisotropic dielectric constant. The vibrators having their longitudinal directions along the a
pc and b
pc axes showed quite different piezoelectric responses, revealing that the polarization vector lies only in the [101]pc and [101]pc directions.
Piezoelectric Microactuators for Use in Magnetic Disk Drives
Authors: Kurihara Kazuaki , Hida Masaharu , Umemiya Shigeyoshi , Koganezawa Shingi
Published: February 2005

A head-slider drive dual-stage microactuator system for use in magnetic disk drives was developed. This microactuator system has a symmetrical structure and operation, and utilizes simple rectangular multilayered piezoelectric actuator devices. A prototype model with a pico slider and head suspension was tested and demonstrated. It exhibited a 0.8 µm displacement at a dc applied voltage of 30 V and a fundamental resonant frequency of over 20 kHz.
A K-Band Distributed Analog Phase Shifter Using Etched Ba0.6Sr0.4TiO3 Thin Films
Authors: Ryu Han-cheol , Moon Seung Eon , Lee Su-jae , Kwak Min-hwan , Kim Young-tae , Kang Kwang-young
Published: February 2005

This work presents the design, fabrication and microwave performance of distributed analog phase shifter (DAPS) fabricated on etched Ba0.6Sr0.4TiO3 (BST) thin films for K-band applications. Single phase Ba0.6Sr0.4TiO3 thin films for interdigitated capacitors (IDC) were deposited by the pulsed laser deposition (PLD) on (001) MgO substrates. The DAPS design consists of periodically loading high impedance coplanar waveguide (CPW) with tunable BST IDC, and the phase shift of the loaded line can be controlled by varying the applied bias voltage to the BST thin films. BST thin films except IDC areas were etched, which means that BST layers locally exist beneath IDC and are removed from the CPW by photolithography and RF-ion milling, to reduce the insertion loss of DAPS and to eliminate the alteration of unloaded CPW properties according to an applied dc bias voltage. The DAPS can be accurately and easily modeled using a combination of full-wave electromagnetic and microwave circuit analysis. Experimental results are shown to agree very well with the simulated ones at the frequencies of interest. The fabricated DAPS showed that the return loss was better than -13 dB through the whole K-band frequency range. The measured differential phase shift based on BST thin films was 179° and the insertion loss is -5.6 dB–-2.1 dB with increasing the bias voltage from 0 to 200 V at 20 GHz.
Dielectric and Magnetic Properties of a Titanium Oxide and Carbonyl Iron Composite Material and Application as a Microwave Absorber
Authors: An Young Joon , Miura Takashi , Okino Hirotake , Yamamoto Takashi , Ueda Shunkichi , Deguchi Takeshi
Published: February 2005

A microwave absorber for use in an electronic toll collection (ETC) device, having a central frequency of 5.8 GHz, is fabricated using a composite of dielectric (titanium oxide, TiO2) and magnetic (carbonyl iron, Fe(CO)5) materials. The reflection loss in free space, using a circularly polarized wave, was -20 dB or more around a central frequency of 5.8 GHz at incident angles of up to 60°, which satisfy the necessary conditions for ETC use.
Enthalpy of Formation of Various Phases and Formation Energy of Point Defects in Perovskite-Type NaNbO3 by First-Principles Calculation
Authors: Shigemi Akio , Wada Takahiro
Published: February 2005

In order to clarify the thermodynamic relations of various phases in NaNbO3, the enthalpies of formation for the cubic (Pm3m), tetragonal (P4/mbm), orthorhombic (Ccmm, Pnmm, Pbma) and rhombohedral (R3c) phases in NaNbO3 were calculated using a plane-wave pseudopotential method. The NaNbO3 phase with a lower symmetry has a smaller enthalpy of formation. The enthalpy of formation for the rhombohedral (R3c) phase is the smallest. Moreover, in order to quantitatively evaluate the formation energies of point defects in NaNbO3, first-principles pseudopotential calculations using plane-wave basis functions were performed. Relaxation of first- and second-neighbor atoms around a vacancy was considered in a 40-atom supercell. The formation energies of point defects were calculated as a function of the atomic chemical potentials of constituent elements. The formation energy of Na vacancy was the lowest under the oxidation limit of NaNbO3 and that of O vacancy was the lowest under the reduction atmosphere. The formation energy of Nb vacancy was the highest under both oxygen-rich and -poor conditions. This result agrees with the empirical rule that the B site defect in the perovskite-type oxide does not exist.
Design of Optimum the Insulator Gate Bipolar Transistor using Response Surface Method with Cluster Analysis
Authors: Wang Chi-Ling , Lai Ming-Hung , Huang Sy-Ruen , Yeh Chao-Yu
Published: February 2005

In this paper, a statistical methodology that can be used for the optimization of the Insulator Gate Bipolar Transistor (IGBT) devices is proposed. This is achieved by integrating the response surface method (RSM) with cluster analysis, weighted composite method and genetic algorithm (GA). The device characteristic of IGBT was simulated based upon the fabrication simulator, ATHENA, and the device simulator, ATLAS. This methodology, yielded another way to investigate the IGBT device and to make a decision in the tradeoff between the breakdown voltage and the on-resistance. In this methodology, we also show how to use cluster analysis to determine the dominant factors that are not visible in the screening of all experiments.
Degradation of Gate Oxide Reliability due to Plasma-Deposited Silicon Nitride
Authors: Ogino Masaaki , Sugahara Yoshiyuki , Kuribayashi Hitoshi , Yamabe Kikuo
Published: February 2005

The effects of plasma-enhanced chemical vapor deposition (PE-CVD) silicon nitride (p-SiN) passivation films on time dependent dielectric breakdown (TDDB) of gate oxide were studied. It was found that degradation of TDDB characteristics with p-SiN films was suppressed by the change in p-SiN deposition conditions. The correlation between trapped electron density and TDDB characteristics varied, depending on the p-SiN films. The degradation of TDDB characteristics was also enhanced with phosphosilicate glass (PSG) under the p-SiN passivation film.
Growth of Droplet-Free AlGaN Buffer Layer with +c Polarity by Molecular Beam Epitaxy
Authors: Takigawa Shinichi , Furuta Kei , Shen Saburo Shimizu** , Kitamura Toshio , Okumura Hajime
Published: February 2005

AlGaN growth on a (0001) sapphire substrate was investigated to realize a droplet-free buffer layer with the +c polarity by molecular beam epitaxy (MBE). By applying an aluminum flux intensity smaller than that of the effective nitrogen radical species for growth, a droplet-free AlGaN surface was achieved even under group-III-rich growth conditions. We found that lattice polarity depends on flux intensity ratio during the growth. The AlGaN buffer layer process is a promising method to achieve both the +c polarity and droplet-free growth of III-nitride films by MBE, which is essential for the improved performance of III-nitride semiconductor devices.
Vapor Pressure of Hf and Si Precursors for HfxSi1-xO2 Deposition Evaluated by a Saturated Gas Technique
Authors: Machida Hideaki , Kada Takeshi , Ishikawa Masato , Ogura Atsushi , Ohshita Yoshio
Published: February 2005

The vapor pressure of the precursor is an important parameter, which is correlated with supply amount and deposition rate during chemical vapor deposition (CVD). Tetrakis(ethylmethyl)hafnium, tetrakis(diethylamido)hafnium, tetraethoxysilane, tetraisocyanatosilane and tri(diethylamino)silane are promising precursors for CVD. Hf
x
Si1-x
O2 films deposited using these precursors have been studied for applications in high-k gate insulators. The vapor pressure values are required for estimating adequate deposition conditions. Therefore, Clausius–Clapeyron equations for the precursors were systematically determined using a saturated gas technique.
NMR Measurements with a Hybrid Magnet
Authors: Hashi Kenjiro , Shimizu Tadashi , Goto Atsushi , Iijima Takahiro , Ohki Shinobu
Published: February 2005

Field profile and stability of the hybrid magnet installed in the National Institute for Materials Science (NIMS) were measured by NMR at 30 T in order to check its ability for solid-state NMR measurements. The field profile shows that the field homogeneity is 186 ppm in the region of ±5 mm from the field center. Time dependence of the magnetic field of 30 T shows the presence of fluctuations with a total amplitude of about 30 G (100 ppm). The fluctuations with frequencies of 50 Hz and its second harmonic are attributed to a power supply.
Large Temperature Coefficient of Resistance in La0.7Ca0.3MnO3 Thin Films Obtained by Metal Organic Deposition Process
Authors: Daoudi Kais , Tsuchiya Tetsuo , Mizuta Susumu , Yamaguchi Iwao , Manabe Takaaki , Kumagai Toshiya
Published: February 2005

La0.7Ca0.3MnO3 (LCMO) thin films with perovskite structure were successfully grown by metal-organic deposition (MOD) on LaAlO3 (001) substrates. The epitaxial growth of the films was confirmed by X-ray diffraction (θ-2θ scans and pole-figure analysis). The temperature coefficient of resistance (TCR) was calculated from the temperature dependence of the resistance measurements. The effects of annealing temperature and film thickness on the resistance and TCR were investigated. The LCMO thin films present a high resistivity-peak temperature of approximately 264 K. The LCMO thin films obtained by MOD show a maximum TCR of ∼27.5%/K, and can be considered as good candidates for bolometric applications.
Temporal Compression by Stimulated Brillouin Scattering of Q-switched Pulse with Fused Quartz Glass
Authors: Yoshida Hidetsugu , Fujita Hisanori , Nakatsuka Masahiro , Fujinoki Akira
Published: February 2005

An 8 ns Nd:YAG laser pulse has been temporally compressed to a 1 ns or less phase conjugation pulse in a fused quartz glass at three wavelengths. Maximum reflectivity of SBS was 40–45% without damage. The brightness of the compressed pulse was about fourfold higher than that of the incident pulse. Damage-free operation using fused quartz glass as a better phase conjugation material could lead to the construction of a more compact, laser-diode-pumped, and all-solid-state laser system.
High-Quality Organic 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate (DAST) Crystals for THz Wave Generation
Authors: Adachi Hiroaki , Taniuchi Tetsuo , Yoshimura Masashi , Brahadeeswaran Srinivasan , Higo Teruaki , Takagi Masayuki , Mori Yusuke , Sasaki Takatomo , Nakanishi Hachiro
Published: February 2005

Using the Slope Nucleation Method (SNM) and highly purified materials along with an optimized growth program, we produced high-quality organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystals. The growth method greatly improved crystallinity. The difference frequency mixing, based on the KTiOPO4 (KTP)-optical parametric oscillator (OPO), generated a coherent, tunable, THz wave in the range of 2 to 30 THz using DAST crystals. These superior DAST crystals also extended the THz generation time. We achieved a constant THz energy output for over 10 h, whereas conventional DAST crystals had reduced the THz wave output in less than 1 hour. We anticipate increased use of DAST crystals for THz generation because of superior performance.
Water-Vapor Decomposition Using Zirconium-Nickel Alloy
Authors: Kawano Takao
Published: February 2005

Water-vapor decomposition using zirconium-nickel alloy was investigated. The fastest decomposition of water vapor and the generation of hydrogen were observed at about one hour after the start of the decomposition process. Subsequently, the reaction whereby more than 90% of the water vapor in a gas was decomposed was maintained for about seventy hours. The X-ray diffraction spectra of the zirconium-nickel alloy before starting the experiment and after the decomposition experiment was completed were examined and the chemical reaction equation of water-vapor decomposition was proposed. The equation was confirmed by experimentally investigating the increase in the weight of the alloy and the ratio of the volume of water vapor decomposed to that of hydrogen generated. It can be concluded that zirconium-nickel alloy can easily decompose water vapor and can be used to extract hydrogen in the form of hydrogen molecules.
Barrier Thickness Dependence of Electrical Properties and DC Device Characteristics of AlGaN/GaN Heterostructure Field-Effect Transistors Grown by Plasma-Assisted Molecular-Beam Epitaxy
Authors: Higashiwaki Masataka , Matsui Toshiaki
Published: February 2005

We report on the barrier thickness dependence of the electrical properties and DC device characteristics of Al0.4Ga0.6N/GaN heterostructure field-effect transistors (HFETs). The HFET structures with 8–25-nm-thick AlGaN barrier layers were grown on sapphire substrates by plasma-assisted molecular-beam epitaxy. All of the fabricated HFET devices with a gate length of 1 µm showed a good DC performance and an excellent pinch-off characteristic. The extrinsic transconductance of the HFET devices increased from 185 to 360 mS/mm with decreasing AlGaN barrier thickness from 25 to 8 nm, while the maximum drain current for a gate bias of +1.0 V decreased from 1.1 to 0.68 A/mm.
Ion-Induced Secondary Electron Emission Coefficient (γ) from MgO Protective Layer with Microscopic Surface Structures in Alternating Current Plasma Display Panels
Authors: Oh Jun Seok , Choi Eun Ha
Published: February 2005

We have investigated the influence of microscopic surface structures of the MgO protective layer on the ion-induced secondary electron emission coefficient in alternating-current plasma display panels (AC-PDPs). The microscopic surface structures of the MgO protective layer have been formed by using a mesh mask with an electron beam evaporation method. The ion-induced secondary electron emission coefficient γ of the MgO protective layer with mesh-patterned microscopic surface structures has been measured by the γ-FIB (focused ion beam) system. It is found that the MgO protective layer with microscopic surface structures has a higher γ than those without any surface structures.
Single-Shot Creation of Nanometer-Sized Silicon Tadpoles by Ultrahigh-Intensity Laser
Authors: Azuma Hirozumi , Daido Hiroyuki , Kamiya Nobuo , Ito Tadashi , Mori Michiaki , Ogura Kouichi , Sagisaka Akito , Orimo Satoshi , Takeuchi Akihiro , Suzuki Noritomo , Hayashi Yukio , Hazama Hisanao , Matukado Koji , Fukumi Atsushi
Published: February 2005

The single-shot creation of tadpolelike silicon nanoparticles constructed with multi-crystalline heads and amorphous tails by a high brightness fs-pulse laser was demonstrated. This is also the first demonstration of the creation of a nanosized connection of multicrystalline silicon with amorphous silicon. This result should expand the creation of new materials by a laser ablation using a high-intensity fs laser, and the created silicon nanoparticles can be applied to scientific and industrial fields.
Construction of X-ray Dark-Field Imaging with a View Size of 80 mm Square and First Visualization of Human Articular Cartilage of Femoral Head under a Nearly Clinical Condition
Authors: Ando Masami , Sugiyama Hiroshi , Kunisada Toshiyuki , Shimao Daisuke , Takeda Ken , Hashizume Hiroyuki , Inoue Hajime
Published: February 2005

Field size of 80 mm ×80 mm for X-ray dark-field (DFI) imaging at 35 keV using a 2.16-mm-thick 440 Laue diffraction analyzer has been achieved. Under this condition, only refracted X-rays from sample can transmit through this filter to form DFI while the beam that has not changed its direction is repelled to the diffraction direction. Its spatial resolution is 10 microns or better. An excised human femoral head in a water-filled vinyl bag simulating a clinical condition shows a high-contrast and high-spatial-resolution articular cartilage that has not been visualized by X-ray technique
Metallic LaTiO3/ SrTiO3Superlattice Films on the SrTiO3(100) Surface
Authors: Shibuya Keisuke , Ohnishi Tsuyoshi , Kawasaki Masashi , Koinuma Hideomi , Mikk Lippmaa Mikk Lippmaa
Published: February 2005

Metallic epitaxial LaTiO3/SrTiO3superlattice films were fabricated on SrTiO3(100) substrates. The superlattice structure maintained compressive epitaxial strain on LaTiO3and stabilized the perovskite LaTiO3crystal phase, which is not thermodynamically stable in thick films on SrTiO3. The superlattice films had very smooth surfaces and grew coherently on the substrates. The lowest resistivity was obtained in a (LaTiO3)2/(SrTiO3)3superlattice film, reaching 200 µΩ·cm at 300 K. These superlattice films can be applied as epitaxial electrodes in n-type SrTiO3epitaxial hetero-devices such as field-effect transistors.
Single-photon Interference over 150 km Transmission Using Silica-based Integrated-optic Interferometers for Quantum Cryptography
Authors: Kimura Tadamasa , Nambu Yoshihiro , Hatanaka Takaaki , Tomita Akihisa , Kosaka Hideo , Nakamura Kazuo
Published: February 2005

We have demonstrated single-photon interference over 150 km using time-division interferometers for quantum cryptography, which were composed of two integrated-optic asymmetric Mach-Zehnder interferometers, and balanced gated-mode photon detectors. The observed fringe visibility was more than 80% after 150 km transmission.
Improved Performance of Electrophosphorescent Organic Light-emitting Diode by Graded Doped Emissive Layer
Authors: Lei Gangtie , Wang Liduo , Qiu Yong
Published: February 2005

We report a blue electrophosphorescent organic light-emitting diode (PHOLED) with performance improved by designing a graded doped emissive layer. The graded doped emissive layer is formed by doping a guest material, bis[(4,6-difluorophenyl)-pyridinato-N, C2'] (picolinato) Ir(III) (FIrpic), in the host material, N, N'-dicarbazolyl-1, 4-dimethene-benzene (DCB), with a gradient increase in concentration. The graded doped emissive layer PHOLED shows a peak power efficiency of 15.4 cd/A and a maximum brightness of 35000 cd/m2, a sharp increase compared to the conventional PHOLED which has a peak power efficiency of 8.7 cd/A and a maximum brightness of 17000 cd/m2. It is also noted that the efficiency of the graded doped device dropped slowly at high current density. We attribute this improvement mainly to the fact that the concentration distribution of guest material is in accord with that of electrons in the devices and the carrier recombination zone is adjusted away from the electrodes.
Annealing Behavior of Interstitial Nitrogen Pair in Czochralski Silicon Observed by Infrared Absorption Method
Authors: Tanahashi Katsuto , Yamada-Kaneta Hiroshi , Inoue Naohisa
Published: February 2005

Annealing behaviors of interstitial nitrogen pairs (N-N pairs) in Czochralski (CZ) silicon are investigated by infrared absorption measurement. The annealing processes at 1000°C and 1100°C decrease the intensity of the infrared absorption peak at 963 cm-1, which is caused by the N-N pairs. The 963 cm-1 peak disappears during the annealing processes at 1000°C and 1100°C for 90 min and 30 min, respectively. It is proposed that the N-N pairs aggregate on grown-in void defects and/or grown-in oxide precipitates during annealing.
Synthesis of Wave Plates Using Multilayered Subwavelength Structure
Authors: Yu Wanji , Satoh Kazuo , Kikuta Hisao , Konishi Tsuyoshi , Yotsuya Tsutom
Published: February 2005

The form-birefringence effect exhibited in the multilayered subwavelength structure (SWS) has been applied for the realization of wave plates. The SWS was obtained by coating a thin film of a material with a high refractive index onto a base SWS fabricated on a substrate with low refractive index. The multilayer SWS fabricated by this coating process exhibits strong form birefringence compared with that of the base SWS. This fact results in less depth required to realize wave plates than that with only the base SWS. In this study, a quarter-wave plate for the operating wavelength of a He-Ne laser (λ= 632.8 nm) was designed and fabricated using the above described multilayered SWS. The experimental results demonstrated that the fabricated device is effective as a quarter-wave plate and gives transmission efficiencies near 90% for both transverse electric (TE) and transverse magnetic (TM) waves.
Ultra-Small Photonic-Crystal-Waveguide-Based Y-Splitters Useful in the Near-Infrared Wavelength Region
Authors: Inoue Kuon , Sugimoto Yoshimasa , Ikeda Naoki , Tanaka Yu , Asakawa Kiyoshi , Sasaki Hidekazu , Ishida Koji
Published: February 2005

We report on the successful development of an ultra-small photonic-crystal(PC)-waveguide-based 120° Y-splitter operating at 1310 nm, which consists of mutually intersecting single-line-defects in the Γ-K direction with an additional air-hole in the middle of the intersection, based on the air-bridge-type GaAs PC of an array of air-holes. The transmittance spectra observed by using a halogen-lamp-based spectrometer newly developed for thin PC-waveguide samples, reveal that a total transmittance of 85% at two output ports is achieved with a band-width as broad as 50 nm. This result indicates that the present Y-splitter should be useful as a key component in future ultraminiature planar optical circuits.
In Situ Study of Iron Catalysts for Carbon Nanotube Growth Using X-Ray Diffraction Analysis
Authors: Nishimura Kenji , Okazaki Nobuharu , Pan Lujun , Nakayama Yoshikazu
Published: February 2005

We have investigated how an iron catalyst changes during the growth of vertically aligned carbon nanotubes by in situ measurement of X-ray diffraction. It is found that heating the catalyst film to a growth temperature of 700°C in He atmosphere induces its oxidation beyond 100°C due to adsorbed moisture and changes the film to particles at approximately 600°C. At 700°C, the catalyst particles consist mainly of iron oxide with a cubic system. By feeding C2H2, the catalyst starts to be deoxidized and then absorbs carbon atoms to form Fe-C and Fe3C. The growth mechanism of nanotubes is discussed in terms of the crystalline phase and orientation of the catalyst.
Growth of Thick GaN Films with High Growth Rate Using Sublimation Method under High Pressure
Authors: Imade Mamoru , Kobayashi Satoru , Kawamura Fumio , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo
Published: February 2005

We found that the growth rate of GaN is much higher using the sublimation method under high pressure than under normal pressure. It seems that the high thermal decomposition temperature under high pressure suppresses the decomposition of the growing GaN film. A growth rate of 130 µm/h was achieved by optimizing the growth temperature and the ambient pressure. This growth rate is as high as that achieved through hydride vapor phase epitaxy (HVPE). The GaN crystals were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD).
Waveband Switching in a Fiber Ring Laser Incorporating a Polarization-Independent Interleaving Filter Based on a Polarization-Diversity Loop Structure
Authors: Lee Yong Wook , Jung Jaehoon , Lee Byoungho
Published: February 2005

In this paper we demonstrate an interleaved waveband switching in a fiber ring laser incorporating a semiconductor optical amplifier as a gain medium and a polarization-independent interleaving filter based on a polarization-diversity loop structure as a wavelength-selective element. The interleaver consists of a polarization beam splitter, high birefringence fibers, and half-wave plates. By employing the interleaver, multiwavelength switching operation of up to 19 laser lines with the signal to noise ratio over 30 dB and 0.8 nm wavelength spacing, whose switching displacement was 0.4 nm, has been successfully demonstrated at room temperature.