bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Control of Epitaxially Grown Sputtered PbTiO3 Thin Films
Authors: Wasa Kiyotaka , Haneda Yohko , Satoh Toshifumi , Adachi Hideaki , Hayashi Shigenori , Setsune Kentaro
Published: October 2002

Microstructures of sputtered PbTiO3 films on SrTiO3 substrates have been studied. It is known that the epitaxial PbTiO3 films include microstructures. It was found that the formation of these microstructures was strongly influenced by the off-stoichiometry of the sputtered films and substrate surface microstructures. Sputtering under the stoichiometric condition on miscut (001)SrTiO3 led to the growth of ultrathin single-crystal PbTiO3 films 10-100 nm thick with continuous structure; under the off-stoichiometric condition the sputtered films comprised microstructures with screwlike dislocation. The ultrathin films exhibited lattice distortion which modified their ferroelectric properties.
Preparation of Bismuth Titanate Thin Films by Laser Ablation
Authors: Wu Wenbiao , Fumoto Keigo , Oishi Yoshihiro , Okuyama Masanori , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Ferroelectric bismuth titanate thin films have been prepared on Si substrates at low temperature by the laser ablation method using an ArF laser. Dependences of crystallographic property of the film on substrate temperature, O2 gas pressure, laser repetition frequency and annealing temperature are presented. The preferentially c-axis-oriented films have been obtained on Si substrates at a substrate temperature of 400° C with annealing at 700° C, and on Pt substrates at a low substrate temperature of 450° C.
Low-Switching-Voltage Operation in Compact InGaAsP/InP Multi-Quantum-Well Directional Coupler with Optimized Layer Structure
Authors: Aizawa Takuya , Nagasawa Yutaka , Ravikumar K. G. , Kawanabe Kensuke , Shinzo Suzaki Shinzo Suzaki
Published: October 2002

Low switching voltage of 4 V and the compact-coupling length of 0.73 mm are achieved simultaneously in a directional coupler switch with an InGaAsP/InP multi-quantum-well waveguide. The layer structure is optimized to obtain low-switching voltage. The crosstalk of the switch is below -12 dB for both cross and bar states.
Influence of Strontium Impurities on Silicon Substrates during Thermal Processing
Authors: Yamamichi Shintaro , Muramatsu Yoshinori , Lesaicherre Pierre-Yves , Haruhiko Ono Haruhiko Ono
Published: October 2002

The influence of strontium impurities on silicon substrates was evaluated in order to introduce high dielectric constant SrTiO3 thin films into the LSI manufacturing process. Sr metal impurities were intentionally diffused into silicon during annealing at 950° C in N2 for 4 h. A 5-nm-thick SiO2 layer was formed when inserting wafers in and taking them out of the furnace, and the Sr impurity concentration was maximum beneath the SiO2/Si interface. Sr impurities cause an increase in positive charge in the SiO2 layer. However, the recombination lifetime of minority carriers in Si is not degraded by Sr impurities, even for Sr levels up to 1014 atoms/cm2. After annealing at 700° C in O2 for 2 h, no Sr was detected on the surface of a Si wafer facing a wafer covered with a SrTiO3 thin film prepared by metal organic chemical vapor deposition. Therefore, it is believed that Sr can safely be introduced into the LSI manufacturing process.
Platinum Bottom Electrodes Formed by Electron-Beam Evaporation for High-Dielectric Thin Films
Authors: Cha Seon Yong , Lee Hee Chul , Lee Won Jae , Kim Ho Gi
Published: October 2002

Platinum (Pt) bottom electrodes have been prepared on SiO2/Si substrates at various deposition temperatures by electron-beam evaporation. Subsequently, (Ba0.5Sr0.5)TiO3 (BST) films were grown under identical conditions by rf magnetron sputtering. It was found that the crystallinity of BST thin films on the Pt bottom layers was strongly dependent on that of Pt films. The surface morphology of BST films appeared to be closely related to the change in the stress of Pt films during BST deposition. In addition, the stress of Pt film has been proven to affect the electrical properties such as current-voltage characteristic and capacitance-voltage characteristic.
RuO2/TiN-Based Storage Electrodes for (Ba, Sr)TiO3 Dynamic Random Access Memory Capacitors
Authors: Takemura Koichi , Yamamichi Shintaro , Lesaicherre Pierre-Yves , Tokashiki Ken , Miyamoto Hidenobu , Ono Haruhiko , Miyasaka Yoichi , Masaji Yoshida Masaji Yoshida
Published: October 2002

Sputtered (Ba, Sr)TiO3 (BST) thin film capacitors have been fabricated with thick RuO2/TiN-based storage electrodes and poly-Si contact plugs, and the electrical properties of the storage electrodes have been studied. The electrode height was higher than 450 nm and the contact size was 0.8×0.8 µ m2. Resistance of the storage electrodes including contact plugs can be evaluated from the dispersion observed in capacitance-frequency measurements. TiN oxidation at the RuO2/TiN interface and native oxide at the TiN/Si contact contribute to the electrode resistance of RuO2/TiN electrodes. With increasing BST deposition temperature, the thickness of oxidized TiN in RuO2/TiN electrodes increases and the electrode resistance increases correspondingly. A Ru layer inserted at the RuO2/TiN interface, a T
i
N/T
i
S
i
2/S
i junction and rapid thermal annealing in N2 ambient of the TiN layer are effective ways to reduce the resistance of RuO2/TiN-based electrodes.
Characteristics of Bismuth Layered SrBi2Ta2O9 Thin-Film Capacitors and Comparison with Pb(Zr, Ti)O3
Authors: Mihara Takashi , Yoshimori Hiroyuki , Watanabe Hitoshi , Araujo Carlos A. Paz de
Published: October 2002

We have developed the series of thin-film bismuth layer structured ferroelectric (BLSF) materials such as SrBi2Ta2O9, SrBi2Nb2O9, SrBi4Ti4O15 and their solid solutions using metallo-organic-decomposition (MOD) spin-on coating techniques. We found that SrBi2Ta2O9 is one of the best potential candidate materials for ferroelectric nonvolatile memories. The SrBi2Ta2O9 thin-film capacitor had the remanent polarization (P
r+-P
r-) of 20 µ C/cm2, coercive field of 35 kV/cm and dielectric constant of 250. SrBi2Ta2O9 thin film on platinum electrode has fatigue-free characteristics for up to 2×1011 cycles without requiring any complicated electrode system such as conductive oxide. Moreover, SrBi2Ta2O9 thin film has many advantages, e.g., high signal/noise ratio of 8 at 1.2 V, low-voltage operation at as low as 1 V, long data-retention, little surface effect, superior imprint properties and low leakage current. We considered that these advantages are due to (1) less space charge and (2) the inherent domain motion.
Analysis of the Resistance Degradation of SrTiO3 and BaxSr(1-x)TiO3 Thin Films
Authors: Numata Ken , Fukuda Yukio , Aoki Katsuhiro , Akitoshi Nishimura Akitoshi Nishimura
Published: October 2002

For bulk SrTiO3 (ST), it is known that the leakage current increases abruptly at a certain time under a constant bias (resistance degradation). We investigated the resistance degradation of ST and Ba

x

Sr(1-
x
)TiO3 (BST) thin films because it will be a reliability problem when these thin films are applied to DRAM cell capacitors or on-chip capacitors. The 1000-Å-thick ST or BST was sputter-deposited in situ on an electron-beam-evaporated Pt bottom electrode. The I-t and I-V characteristics were measured for these films with thermally evaporated Au top electrodes. For positive bias on the top electrode, the films showed resistance degradation similar to that of bulk single-crystal ST.
However no degradation was found for negative bias. The I-V characteristics showed that only the electric field enhancement at the bottom interface does not account for this polarity dependence of the resistance degradation. A possible explanation is intrinsic inhomogeneous distribution of oxygen vacancies in the films.
Bulk Photovoltaic Effect for the Linearly Polarized Light in Pb(Zn1/3Nb2/3)O3Single Crystals
Authors: Chu Sheng-Yuan , Mulvihill Maureen L. , Ye Zhou , Kenji Uchino Kenji Uchino
Published: October 2002

The bulk photovoltaic effect in non-centrosymmetric crystals is caused by asymmetric generation, recombination or scattering of excited nonequilibrium electronic carriers. In this paper, the photovoltaic effect has been investigated in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3single crystals using linearly polarized light. Angular dependence of photovoltaic voltage and current on the polarization direction of light was observed in the crystal. A phenomenological model was proposed to fit the experimental results from which the photovoltaic coefficients were calculated.
Multilayer Piezoelectric Ceramic Vibrator with Internal Electrodes
Authors: Fuda Yoshiaki , Ono Hiroshi , Shiotani Futoshi , Katsunori Kumasaka Katsunori Kumasaka
Published: October 2002

Multilayer piezoelectric vibrators made from high mechanical quality factor (Q
m) PbZrTiO3 ceramic material with internal electrodes have been investigated for application to ultrasonic devices. The existence of internal electrodes activates the ceramic sintering reaction and as a result, cofiring of the the multilayer vibrator at a lower temperature becomes possible. Multilayer vibrators with 2-9 layers of internal electrodes were fabricated, and evaluated. The values of Q
m>1500 and k
31=0.36 can be obtained. It was found that high-power ultrasonic devices driven by low voltages.
Stepped-Cantilever Piezoelectric Actuator Using Anisotropic Composite Material
Authors: Kusakabe Chiharu , Tomikawa Yoshiro , Kurose Tomoki , Ohnishi Kazumasa
Published: October 2002

This paper deals with a vibrational analysis of a stepped-cantilever piezoelectric actuator for the purpose of magnifying its end displacement. The piezoelectric actuator used here is a bimorphic type. As a basic bar of the bimorphic cantilever, we have investigated three kinds of carbon-fiber-reinforced plastic (CFRP) bars. Vibrational analysis has been performed using an electrical circuit analogy of the mechanical vibration system. As a result of simulation and experiment, it was proven that the end displacement could be increased by selecting an appropriate form of stepping.
Effect of Firing Temperature on Composition and Phase in Pb(Co1/3Nb2/3)O3-PbTiO3-PbZrO3 Ceramics
Authors: Ogawa Toshio , Ono Masayuki , Masahiro Fujiwara Masahiro Fujiwara
Published: October 2002

We studied the firing temperature dependence of ceramic bulk density, composition and crystal phase in Pb(Co1/3Nb2/3)O3-PbTiO3-PbZrO3 ceramics to clarify the origin of their semiconducting properties. The low resistivity and large dielectric loss of the ceramics were due to B-site vacancies resulting from Co vaporization during firing. An addition of CoO to the stoichiometric ceramic compositions inhibited the vaporization and the production of a pyrochlore phase in the perovskite phase. The A-site vacancies were produced by adding excess Co at higher firing temperatures, whereby the vacancies resulted from the change in Co valence with increasing firing temperature. The dependence of resistivity and dielectric loss in the ceramics on firing temperature was well explained by the compensation between the B-site vacancies and the change in valence of Co (Co2+→Co3+).
Stability of PbZrO3-PbTiO3-Pb(Mn1/3Sb2/3)O3Piezoelectric Ceramics under Vibration-Level Change
Authors: Sadayuki Takahashi Sadayuki Takahashi , Yasuhiro Sasaki Yasuhiro Sasaki , Seiji Hirose Seiji Hirose , Kenji Uchino Kenji Uchino
Published: October 2002

Vibration-level characteristics of electromechanical properties in the pseudo-ternary solid solution system PbZrO3-PbTiO3-Pb(Mn1/3Sb2/3)O3ceramics were studied using a constant current control method. Stability under a vibration-level change was determined from the measurements of Young's modulusY0Eand mechanical dissipation factorQm-1. Durability degree for a high vibration-level excitation was estimated by a heat generation phenomenon. The durability was found to be dependent on the stability. As the stability increased, the durability also increased. The durability degree for a high vibration-level excitation was improved in the pseudo-ternary solid solution system PbZrO3-PbTiO3-Pb(Mn1/3Sb2/3)O3ceramics over the binary solid solution system PbZrO3-PbTiO3ceramics.
Dielectric Dispersion of the Complex Perovskite Oxide Ba(Fe1/2Nb1/2)O3 at Low Frequencies
Authors: Masaru Yokosuka Masaru Yokosuka
Published: October 2002

Ceramic specimens of the complex perovskite oxide Ba(Fe1/2Nb1/2)O3 were fabricated by conventional solid state sintering. Dielectric constants were measured as a function of temperature as well as of frequency. As a result, dielectric constants showed an unusual temperature dependence. Moreover, a large dielectric dispersion was observed below 1 MHz, and it was represented by the Cole-Cole circular arc law. The present dielectric dispersion was interpreted on the basis of the interfacial polarization at the grain boundary region.
Dielectric Property of Flux-Grown PbTiO3 Single Crystal
Authors: Kakuta Kouji , Tsurumi Takaaki , Osamu Fukunaga Osamu Fukunaga
Published: October 2002

Single crystals of pure PbTiO3 were grown by a flux method using the PbO-TiO2-B2O3 mixture as a flux solution. A mechanical detwining treatment was carried out by applying pressure to the platelet edges of the crystals in order to eliminate 90° domains in the crystal. The temperature and frequency dependences of the dielectric permittivity of the crystals were measured and analyzed. It was found that the dielectric properties of PbTiO3 single crystals were explained as a superposition of the effects of dielectric relaxation, electric conduction and simple dielectricity. By analyzing frequency dependence of dielectric permittivity using an equivalent circuit, the relative dielectric permittivity tensors ε
11/ε
0 and ε
33/ε
0 of PbTiO3 at room temperature were determined to be 130 and 90, respectively.
Dielectric and Piezoelectric Properties of Pb(Yb1/2Nb1/2)O3-PbTiO3 Solid Solution System
Authors: Yamamoto Takashi , Satoru Ohashi Satoru Ohashi
Published: October 2002

Solid solutions of (1- x)Pb(Yb1/2Nb1/2)O3-( x)PbTiO3
x=0 to 0.8 were investigated from the viewpoint of dielectric and piezoelectric properties. With increasing PbTiO3 content (x), phases at room temperature continuously changed from antiferroelectric (x=0), ferroelectric (x=0.1 to 0.15), relaxor (x=0.2 to 0.49), and again to ferroelectric (x>0.49), where crystal structures of all these phases were perovskite. Sintering temperature was lowered to around 950° C in the relaxor phase (x=0.2 to 0.49). Piezoelectric constants exhibited a maximum at x=0.49 to 0.50 near the morphotropic phase boundary (x=0.49). In the sample with x=0.50, Curie point was 349° C, and remanent polarization and coercive field were 32.8 µ C/cm2 and 2.75 kV/mm, respectively. Also, electromechanical coupling factors for planar (k
p) and thickness (k
t) modes were 0.527 and 0.436, respectively.
Relaxor Dielectric Materials for Multilayer Ceramic Capacitor in High-Temperature Applications
Authors: Yamashita Yohachi , Kanai Hideyuki , Furukawa Osamu , Hasegawa Kouichi , Mukaeda Satoshi , Handa Kiyoji
Published: October 2002

A relaxor ceramic dielectric based on the (Pb, Ba)[(Zn1/3Nb2/3)(Mg1/3Nb2/3)Ti]O3 system has been developed for multilayer ceramic capacitors (MLC) in high-temperature applications. This dielectric material is designed to exhibit a capacitance peak value at around 60° C, which is a typical temperature inside a switching mode power supply (SMPS). An MLC fabricated using this new dielectric and fired at 1050° C has a relative dielectric constant of 9000 and a CR product ( capacitance×resistance) of 8000 Ω F at room temperature. However, at 60° C the relative dielectric constant is 14000 and the CR product is 4000 Ω F. The change in capacitance with temperature is less than -30% from 0 to 125° C. This makes the new MLC a promising candidate for use as a filter capacitor in high-frequency SMPS.
Preparation of Perovskite Oriented PbZrxTi1-xO3 Films with Suppressed Vapor Phase Reactions by a Digital Chemical Vapor Deposition Method
Authors: Hirai Tadahiko , Teramoto Kazuhiro , Goto Takaaki , Tarui Yasuo
Published: October 2002

We show that vapor phase reactions of precursors during the deposition of PbTiO3 and PbZr

x

Ti1-
x

O3 (PZT) films contribute to the film formation, and that the vapor phase reactions are reduced in the digital chemical vapor deposition (CVD) method. From the results of experimental deposition of PbO
x
, ZrO
x
, and TiO
x
films using three oxidant gas introduction modes, we can infer that the vapor phase generation of PbO
x
, ZrO
x
, and TiO
x
makes a large contribution to the formation of these films when the precursors and oxidant gas are mixed in the vapor phase. On the other hand, in our digital CVD method alternating oxidant gas supply mode, the PbO
x
, ZrO
x
and TiO
x
films were formed predominantly through surface reactions and reducing vapor phase reactions. We also successfully applied the digital CVD method to the deposition of oriented PbZr

x

Ti1-
x

O3 film on a MgO(100) substrate at the susceptor temperature 530° C. It should be possible to extend this technique to atomic layer epitaxy (ALE) of PbZr

x

Ti1-
x

O3 films.
Microwave Dielectric Properties of the Ba6-3x(Sm 1-y,\mbRy) 8+2xTi 18O 54 (\mbR=Nd and La) Solid Solutions with Zero Temperature Coefficient of the Resonant Frequency
Authors: Hitoshi Ohsato Hitoshi Ohsato , Hiromichi Kato Hiromichi Kato , Makoto Mizuta Makoto Mizuta , Susumu Nishigaki Susumu Nishigaki , Takashi Okuda Takashi Okuda
Published: October 2002

Ba6-3x
(Sm1-y
,R

y
)8+2x
Ti18O54 (R = Nd and La; x = 0.6, 0.0 ≤y ≤1.0) solid solutions in which Nd or La ions are substituted for Sm ions were studied from the point of microwave dielectric materials. In both Sm-Nd and Sm-La series, formation of solid solutions was found, which was deduced from linear change of the lattice parameters. We found high-quality resonator materials in the both series which show high ε
r of 84, Q· f products of 9000 GHz, and temperature coefficient of resonance frequency τ f=0 ppm/\CC. The compositions of those materials in the Sm-Nd and the Sm-La series were determined to be y = 0.2 and 0.1, respectively. A relationship between dielectric constant and volume of octahedron is also stated.
Dielectric Relaxation Modes in the Phases of Antiferroelectric Liquid Crystals
Authors: Hiroyuki Uehara Hiroyuki Uehara , Yoshihiro Hanakai Yoshihiro Hanakai , Jun Hatano Jun Hatano , Shin'ichi Saito Shin'ichi Saito , Katsuyuki Murashiro Katsuyuki Murashiro
Published: October 2002

Complex dielectric constant of an antiferroelectric liquid crystal family represented by 4-(1-methylheptyloxycarbonyl) 3-fluorophenyl 4'-dodecylbiphenyl-4-carboxylate was measured in the frequency range between 10-2 Hz and 107 Hz. The experimental results were analyzed using a generalized Cole-Cole expression, and seven dielectric relaxation modes were confirmed to exist. Possible models of collective molecular motions are proposed for mode assignments on the basis of the experimental results of temperature dependence of the modes, together with those of cell gap and bias field dependences.
Strained SrTiO3/BaTiO3 Superlattices Formed by Laser Ablation Technique and Their High Dielectric Properties
Authors: Tabata Hitoshi , Tanaka Hidekazu , Kawai Tomoji , Okuyama Masanori
Published: October 2002

Artificial dielectric superlattices of SrTiO3/BaTiO3 (STO/BTO) have been formed by a pulsed laser ablation technique with in situ monitoring of reflection high-energy electron diffraction (RHEED) oscillation. The superlattices with a stacking periodicity of a few unit cells show higher dielectric constant than that of (Sr0.5Ba0.5)TiO3 films with change of temperature or applied frequency. The tetragonal structures of the superlattices are maintained at temperatures of more than 200° C owing to a large stress at the interfaces between STO and BTO layers.
Electrical Characteristics of Metal/Cerium Dioxide/Silicon Structures
Authors: Tatsuo Nakazawa Tatsuo Nakazawa , Tomoyasu Inoue Tomoyasu Inoue , Masataka Satoh Masataka Satoh , Yasuhiro Yamamoto Yasuhiro Yamamoto
Published: October 2002

Electrical characteristics of a Au/CeO2/Si structure have been measured by means of capacitance-voltage (C–V) and conductance-voltage (G–V) methods. Single crystalline and polycrystalline CeO2 films are grown on silicon substrates using electron-beam evaporation. MOS characteristics of the samples are classified by the crystallinity of the CeO2 films rather than by the orientation or conduction type of the Si substrate. Polycrystalline CeO2 film samples show a fine structure around the flat-band voltage in the C–V curves and injection-type hysteresis. It is clarified that the characteristics of the single crystalline CeO2 film sample are free from such undesirable properties caused by negative charge and carrier injection. Dielectric constant ε
r of the CeO2 films is estimated to be around 20, which is close to the bulk value (∼26).
Energy Eigenvalues and Quantized Conductance Values of Electrons in Si Quantum Wires on \mb{100\mb} Plane
Authors: Seiji Horiguchi Seiji Horiguchi , Yasuyuki Nakajima Yasuyuki Nakajima , Yasuo Takahashi Yasuo Takahashi , Michiharu Tabe Michiharu Tabe
Published: October 2002

A method to obtain the eigenstates of electrons in Si wires with arbitrary cross-sectional shapes and wire directions on the {100} plane is presented within the effective mass approximation, taking into account the six anisotropic valleys near the X points in bulk Si. In general, six equivalent valleys in bulk Si change to three pairs of doubly degenerate valleys in wires, and each pair has a quantized conductance value of 4e2/h(eis elementary charge andhis the Planck constant). In <110>-oriented wires, two of the three pairs become fourfold degenerate and the quantized conductance value of these states becomes 8e2/h. Calculated energy levels for quantized motion perpendicular to the wire direction in wires with rectangular, triangular and trapezoidal cross sections show that the order of the energy levels in different degenerated pairs of valleys depends strongly on both the cross-sectional shape and the wire direction. It is also shown that calculated conductance as a function of gate voltage agrees with an experimental result semiquantitatively.
Refractive Index Dispersion in Ternary Germanate Glasses
Authors: Sakaguchi Shigeki , Todoroki Shinichi , Rigout Nathalie
Published: October 2002

The refractive index dispersion in germanate oxyfluoride glasses of GeO2-P2O5-MF2 (M=Ca, Zn), which are developed for optical fiber application, is investigated in the 0.4-4 µ m wavelength range by the minimum deviation method. The prepared glasses have a GeO2 content varying from 80 to 30 mol%. The dispersion curves for these glasses tend to shift to shorter wavelengths as the GeO2 content is decreased. Material dispersions are also derived from the refractive index measurements and the zero-material dispersion wavelengths (λ0) are found in the vicinity of 1.5 µ m. On the basis of the empirical relationship between λ0 and the minimum loss wavelength (λ0), the λ min values are located at around 1.8 µ m. A minimum loss of as low as 0.08 dB/km is expected for the present germanate glasses.
Raman Scattering of Se-Doped Gallium Nitride Films
Authors: Kuo Hung-Red , Feng Ming-Shiann , Guo Jeng-Dah , Ming-Chih Lee Ming-Chih Lee
Published: October 2002

Raman spectra of Se-doped gallium nitride films have been measured for the first time with good resolution and a wide range of excitation wavelengths. The signals from both buffer layer and epilayer are identified unambiguously. We have observed not only the resonant scattering related to the transition below the band gap but also the phonon-plasmon coupling due to the doping effect. The carrier concentration obtained from lineshape fitting is consistent with that from Hall measurements. By comparing the Raman shifts with those of other nitrides and gallium compounds, we found that most of them are almost linearly proportional to the square root of reciprocal masses. The bonding strengths are thus inferred from the slopes.
Crystallization and Properties of a Low k Glass Composite
Authors: Jean Jau-Ho , Chang Ruey-Ling , Chia-Ruey Chang Chia-Ruey Chang
Published: October 2002

The effect of gallium oxide on crystallization, thermal expansion and dielectric behaviors of a binary glass composite which contains a low-softening Pyrex borosilicate glass and a high-softening high silica glass has been studied. It is found that on sintering, cristobalite precipitates out of the initial amorphous binary glass mixture; however, the addition of gallium oxide prevents this. The above result is further supported by microstructural observation, thermal expansion and dielectric constant measurements.
Experimental Evaluation of Surface Tension Criteria for Alignment Behavior of Liquid Crystals on Solid Surfaces
Authors: Nakano Fumio , Isogai Masato , Hisao Yokokura Hisao Yokokura
Published: October 2002

Experimental verification has been carried out the surface tension difference criteria for liquid crystal alignment on solid surfaces. Organic polymer films, with surface tension values controlled from 16.0 to 44.8 mN/m (which includes the surface tension of liquid crystal ZLI-1132) were examined. On films thick enough to avoid undesirable topological effects ( >80 nm), the surface tension value at which the surface changed from a homogeneous to a homeotropic alignment was 31.2 mN/m, which is very close to the 31±0.5 mN/m value of ZLI-1132.
In Situ Spectroscopic Examination of Plasma Emission during Excimer Laser Deposition of Pb0.95La0.05(Zr0.7Ti0.3)0.9875O3 Thin Films
Authors: Hsiu-Fung Cheng Hsiu-Fung Cheng
Published: October 2002

The optical emission spectra radiated from the laser-induced PLZT plume under various levels of laser fluence and oxygen pressure were systematically examined. The plasma temperature of Ti species corresponding to each spectrum was estimated using the Boltzmann plot technique. No emission belonging to diatomic species was observed. For the Pb species, only the spectral lines from excited neutral atoms were observed. For the Ti and Zr species spectral lines from both excited neutral atoms and singly ionized ions were obtained. The intensity of the spectral lines increased with the laser fluence when the oxygen pressure (P
O2) was kept constant. The plasma temperature of the Ti species varied insignificantly with the laser fluence under P
O2=0.1 mbar. On the other hand, the spectral intensity markedly decreased and the plasma temperature significantly increased when P
O2 level was reduced to below 0.01 mbar. The plasma temperature changed only moderately, when P
O2 increased from 0.1 mbar to 1 mbar. The crystallinity of thus obtained PLZT films varied with the oxygen pressure.
On the Electrostatic Potential Profile Determined from Ion Endloss Spectrum
Authors: Isao Katanuma Isao Katanuma , Kameo Ishii Kameo Ishii , Yasuhito Kiwamoto Yasuhito Kiwamoto , Toshiki Takahashi Toshiki Takahashi , Tetsuya Goto Tetsuya Goto , Yoshinori Tatematsu Yoshinori Tatematsu , Teruo Saito Teruo Saito , Kiyoshi Yatsu Kiyoshi Yatsu , Teruo Tamano Teruo Tamano
Published: October 2002

The electrostatic potential profile in the outer region of a tandem mirror is calculated by analyzing the ion endloss data which were obtained experimentally. The potential profiles depend on the boundary condition of the position where the potential is zero on the axis. Comparing the calculation with experimental data it is found that the point of maximum potential (plug) does not exist at the outer mirror throat.
Analysis of the Light Emission Originating from Dissociative Recombination Process in Argon Afterglows
Authors: Okada Tomio , Sugawara Minoru
Published: October 2002

The spectrum of emitted light of the afterglow in the range of 400 to 850 nm has been measured in the argon afterglow at 665 Pa. Every Ar*line observed has been attributed to transitions from 4p→4s, 4p′→4s, 4p′→4s′and 5p→4s. We have observed experimentally that transitions from 5p levels reveal quite different behavior from those from 4p and 4p′levels. The light intensity from the 5p→4s transitions decayed to a minimum value within 10 µ s after the termination of the discharge and thereafter increased quickly to a maximum in 23 to 28 µ s followed by a slow decay. The light from the 4p→4s, 4p′→4s and 4p′→4s′transitions exhibited a sharp decay in about 20 µ s, which was followed by a slow decay. We have analyzed the temporal decay of the emitted light and also attributed the rapid increase of the light intensity due to the increase of the coefficient of the dissociative recombination which may be caused by the rapid decay of electron temperature in the early afterglow.
Anisotropic Properties of Ice/Water Interface: A Molecular Dynamics Study
Authors: Nada Hiroki , Yoshinori Furukawa Yoshinori Furukawa
Published: October 2002

Ice/water interface structures were studied using a molecular dynamics method. The simulations were carried out for both ice {0001}/water and ice {101̄0}/water interfaces. The results strongly suggest that each interface has a diffuse structure and that the physical properties of the interfacial region differ from each other between the interfaces. The anisotropy in the structures and dynamic properties of ice/water interfaces, that is, the difference in the structures and dynamic properties between the interfaces were observed for the first time in this molecular dynamics simulation.
Silicon Wafer Half-Mirror in Far Infrared
Authors: Michio Sasanuma Michio Sasanuma , Yutaka Takeshita Yutaka Takeshita
Published: October 2002

Optical properties of silicon wafer are examined. Its low absorptance to IR light and stability in air, make it suitable for use as a half-mirror for light in the far IR.
Interference of Nuclear Bragg Scattered X-Rays in X-Ray Interferometer with Large Optical Path Difference
Authors: Izumi Koichi , Mitsui Takaya , Seto Makoto , Yoda Yoshitaka , Ishikawa Tetsuya , Zhang Xiao Wei , Ando Masami , Seishi Kikuta Seishi Kikuta
Published: October 2002

Interferometry of the nuclear Bragg scattered X-rays from 57Fe2O3 (777) with the optical path difference of 2.4 mm was reported. In order to carry out this measurement, a new X-ray interferometer of the wavefront-dividing type was designed and fabricated. The interference pattern was observed using this X-ray interferometer, since the temporal coherence length of the nuclear resonantly scattered X-rays is much longer than the optical path difference. From the visibility of the interference pattern, the vertical size of the X-ray source was estimated to be 50 µ m.
Low-Energy Electron Diffraction and Scanning Tunneling Microscopy Study on the Reconstruction of the Vanadium (111) Surface
Authors: Nakayama Koji , Sato Tomoshige , Usami Seiji , Iwatsuki Masashi
Published: October 2002

In a previous paper, we proposed a model of a reconstructed vanadium single-crystal (111) surface on the basis of our low-energy electron diffraction (LEED) observations of the clean surface formed in the (√ 3×√ 3) R30° structure [Surf. Sci. 288 (1993) 355.]. In this paper we report the observation of the reconstructed V(111) surface in real space by use of a ultrahigh vacuum (UHV)-scanning tunneling microscopy (STM) (JSTM-4500VT) with which it is possible to precisely control the temperature of a sample even at high temperatures up to 1500 K.
A main cleaning procedure was to anneal the sample for 20 h at over 1300 K in UHV and to flash it at 1500 K many times immediately prior to the STM measurement. It was possible to interpret the observed STM images reasonably using our previously proposed model for the reconstructed surface. In the STM images, however, we observed unexpected step structures on the (111) surface that could not be found in the LEED measurement. We have proposed a model of this step structure on a V(111) face based on the above model of the reconstructed surface.
Emitter Edge-Thinning Effect on InGaAs/InP Double-Heterostructure-Emitter Bipolar Transistor
Authors: Wu Yu-Huei , Su Jan-Shing , Hsu Wei-Chou , Lin Wei , Liu Wen-Chau , Kao Ming-Jer , Rong-Tay Hsu Rong-Tay Hsu
Published: October 2002

An emitter edge-thinning design is used for a lattice-matched InGaAs/InP double-heterostructure-emitter bipolar transistor (DHEBT) grown by low-pressure metalorganic chemical vapor deposition (MOCVD). Using the emitter edge-thinning technique, the surface recombination current is reduced and the current gain is improved. This structure reveals a typical current gain as high as 120 at a collector current density of 241 A/cm2, along with an offset voltage as low as 45 mV.
Furthermore, the problem of surface recombination current is also discussed in terms of the emitter size effect on current gain. The Gummel plots are shown to explain the influence of the emitter edge-thinning process on the base current ideality factor.
Microcrystallinity of Undoped Amorphous Silicon Films and Its Effects on the Transfer Characteristics of Thin-Film Transistors
Authors: Liang Chia-Wen , Chiang Wen-Chuan , Ming-Shiann Feng Ming-Shiann Feng
Published: October 2002

The microcrystallinity of hydrogenated amorphous silicon films deposited by the conventional radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) method and its dependence on chamber pressure are discussed. In a wide range of pressure at which the microcrystalline film can be formed, a critical pressure (500 mT) is found. Films deposited at this critical pressure possess the highest crystalline volume fraction and the smallest grain size. An ion-bombardment-assisted model is proposed to explain the experimental results. Concerning the applications of microcrystalline films to thin-film transistors (TFTs), the subthreshold swing and the field effect mobility are studied, both of which are found to be smaller than those of the hydrogenated amorphous silicon (a-Si:H) TFTs.
Polycrystalline Cu(InGa)Se2 Thin-Film Solar Cells with ZnSe Buffer Layers
Authors: Ohtake Yasutoshi , Kushiya Katsumi , Ichikawa Mitsuru , Yamada Akira , Makoto Konagai Makoto Konagai
Published: October 2002

A ZnSe buffer layer has been applied as an attractive alternative to a CdS buffer layer in the development of polycrystalline Cu(InGa)Se2 (CIGS) thin-film solar cells, thus eliminating entirely the use of cadmium by employing the ZnO/ZnSe/CIGS structure. Moreover, we propose the use of a new deposition method for ZnSe buffer layers, the atomic-layer deposition (ALD) method. This method is basically the same as an “atomic-layer epitaxy” method but is applied to polycrystalline materials. Currently the best efficiency of CIGS thin-film solar cells with an about 10-nm-thick ZnSe buffer layer is 11.6%. Applying irradiation with a solar simulator under one-sun (AM-1.5, 100 mW/cm2) conditions, the efficiency of these cells was improved from about 5% to over 11% due to increased open-circuit voltage and fill factor with no change in short-circuit current density even after six-hour irradiation.
Analysis on Electrostatic Tip-Sample Interaction in Aqueous Solution under Potentiostatic Condition
Authors: Hieda Hiroyuki , Ishino Takashi , Tanaka Kuniyoshi , Nobuhiro Gemma Nobuhiro Gemma
Published: October 2002

Using a force microscopy, we investigated electrostatic tip-sample interaction in aqueous solutions. A force between a gold-coated microsphere tip and an oxidized silicon sample was measured with their surface potentials being controlled independently by bipotentiostat. The variations in the force characteristics were observed with the respective changes in the tip potential and the sample potential. The observed force characteristics were found to agree with the theory of electrical double layer interaction under constant potential assumption.
Excimer-Laser Annealing Technology for Hydrogenated Amorphous-Silicon Devices
Authors: Kim Chang-Dong , Ishihara Ryoichi , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Dehydrogenation characteristics have been investigated in detail for excimer-laser annealing of hydrogenated amorphous silicon (a-Si:H) films. Only the XeF excimer-laser light has a negligibly small photonic-dissociation rate of the Si-H bonds, and thus hydrogen atoms remain in the annealed film, resulting in highly conductive poly-Si film. The XeF excimer-laser annealing has been confirmed to be useful for fabricating high-performance a-Si:H thin-film transistors.
Effect of Gamma Irradiation on Superconductivity of Pb-Doped Bi2Sr2CaCu2OyCrystals
Authors: Liangbin Wang , Wenbin Wu , Jingsheng Zhu , Xianming Liu , Yunlan Huang , Guien Zhou , Xiao-Guang Li , Yuheng Zhang
Published: October 2002

Bi2.4-xPbxSr2CaCu2Oycrystals withx=0.05, 0.1 and 0.2 were irradiated with60Co γ-rays of 0.6 MR/h up to a dose of 64.8 MR at room temperature. For all the irradiated samples withx=0.05, 0.1, the superconducting transition temperatureTcincreased after γ-ray irradiation, while theTcof irradiated samples withx=0.2 increased at lower doses, and then decreased at 64.8 MR. X-ray photomission spectroscopy results reveal that higher oxidation states of Bi and Cu occurred in the sample irradiated with 64.8 MR. The dependence ofTcon γ-ray irradiation dose can be explained in terms of the change of valence state of Bi and Cu.
Preparation of a Nd–Fe–B Bond Magnet using High Frequency Magnetic Fields
Authors: Guido Eilers Guido Eilers , Masaaki Doi Masaaki Doi , Masaaki Matsui Masaaki Matsui
Published: October 2002

In this study we suggest a new method to prepare an anisotropic bond magnet. In order to achieve an anisotropic magnet we take advantage of the magnetic anisotropy of the tetragonal Nd2Fe14B crystals. A dispersion of a melt spun Nd–Fe–B magnet powder with epoxy resin was hardened in a high frequency (HF) magnetic field (ν= 230 kHz) to align the easy magnetization axis (c-axis in Nd2Fe14B) with the external field. Magnetization measurements and an X-ray analysis showed that an alignment of the powder due to the treatment in a HF magnetic field was achieved. A Mößbauer analysis confirmed the alignment.
Switching of Single Hexagonal Particles with Nonuniform Magnetic Properties
Authors: Uesaka Yasutaro , Nakatani Yoshinobu , Hayashi Nobuo
Published: October 2002

Switching fields of hexagonal particles with nonuniform magnetic properties are investigated using computer simulation. The switching field of a hexagonal particle with a low anisotropy energy constant (K
u) region at a corner of all three thickness layers is lower than that of the uniform particle when the field is applied almost perpen-dicular to the hexagonal plane. However, when the field is applied almost parallel to the hexagonal plane, the switching field of the nonuniform hexagonal particle is similar to that of the uniform particle. A hexagonal particle with a low K
u region at the center also switches in a lower field than the uniform particle does when the field is applied perpendicular to the hexagonal plane. The switching field of a hexagonal particle with low K
u region in the surface layer is almost the same as that of a uniform particle.
Impurity Evaluations of SiO2 Films Formed on LiNbO3 Substrates
Authors: Nagata Hirotoshi , Takahashi Hiroki , Takai Hiroshi , Kougo Tamotsu
Published: October 2002

SiO2 films deposited by sputtering (SP) and vacuum evaporation (VE) techniques are commonly used as buffer layers in LiNbO3-based devices. The impurity levels in such films are measured as 1017 to 1022 atoms/cm3 for H, Li and Nb ions, which might affect the electrical properties of the devices. The major differences between the SP and VE films are in the density and the hydrogen contents, which possibly influence the I/V characteristics of the films and leads to different dc drift phenomena of LiNbO3 optical modulators made of such layers.
High-Efficiency Operation of a Tm3+, Ho3+ Co-Doped Alumino-Zirco-Fluoride Glass Fiber Laser Near Room Temperature
Authors: Doshida Minoru , Minoru Obara Minoru Obara
Published: October 2002

High-efficiency operation at two micrometers for a very short (less than 30 mm long) Tm3+, Ho3+ co-doped AZF glass fiber laser pumped by a Ti:sapphire laser has been demonstrated near room temperature. A cw output power of up to 150 mW with a slope efficiency of 37% was achieved using a 24.5-mm-long, Tm3+, Ho3+ co-doped AZF glass fiber at 15° C.
Impurity Levels of Alkaline Metals in Zincselenide Single Crystals Examined by Photoluminescence
Authors: Kenji Yoshino Kenji Yoshino , Yasushi Matsushima Yasushi Matsushima , Makoto Hiramatsu Makoto Hiramatsu
Published: October 2002

Zincselenide (ZnSe) single crystals doped with alkaline metals (Li, Na, K, Rb and Cs) were grown by sublimation method. In order to obtain the impurity levels of alkaline metals in ZnSe, we measured the temperature as well as excitation intensity dependences of the photoluminescence spectra. To further verify our results, we also measured the selective photoluminecence spectra of the aforementioned doped ZnSe. The values of the acceptor binding energy (E
A) of Li, Na, K, Rb and Cs were 118 ±2, 98 ±2, 94 ±2, 89 ±2 and 74 ±2 meV, respectively. The acceptor binding energy level is found to increase as the atomic number of the dopant decreases.
A Sharp Photocurrent Enhancement in Photoelectrochemical Cells with a Photocathode Sensitized by Dye Films of Rhodamine-C18 and Methylviolet-C18 Prepared by Langmuir-Blodgett Techniques
Authors: Fernando Annesly Nandana , Kitagawa Akio , Suzuki Masakuni , Takahashi Kohshin , Komura Teruhisa
Published: October 2002

It was found that the photocurrent quantum efficiency of photoelectrochemical cells with p-CuSCN photo-cathode sensitized with double dye layers such as Rhodamine- C18 and Methylviolet- C18 is greatly enhanced (∼15%), when the double dye system is prepared using Langmuir-Blodgett (LB) technique. An ordered arrangement of dye molecules in LB films provides a suitable condition to transfer photogenerated holes and electrons between two dye layers, so that photogenerated holes upon excitation can transfer effectively into the valence band of p-CuSCN.
Molecular Motions of Non-Crystalline BEK
Authors: Shirouzu Shigenori , Ishii Tatsuo , Iga Toru , Hayashi Mikiya , Shinji Chino Shinji Chino
Published: October 2002

Relaxation behaviors of BEK, a new engineering plastic with high heat resistance (T
g: 181° C, T
m: 364° C), were investigated. Dielectric relaxation peaks were observed at -83° C and 51° C in 9.8 Hz, and their activation energies were 7 kcal/mol and 19 kcal/mol, respectively. The relaxation peaks were also observed in mechanical measurements. The `chemical structure-relaxation behavior' relationship in BEK and its related polymers suggests that the origins of the high temperature relaxation peak of BEK are crankshaft type chain motions while those of the low-temperature relaxation peak are wigglings of benzonitrile or phenyl groups.
Ferroelectric Hysteresis Behavior and Structural Property of Even-Numbered Nylon Film
Authors: Itoh Takashi , Tanaka Toshihiko , Hashimoto Masato , Takashi Konishi Takashi Konishi
Published: October 2002

Nylon 6 film quenched from the molten state into liquid nitrogen exhibits an electric displacement vs electric field hysteresis loop at room temperature with the remanent polarization of 26 mC/m2, as well as an exothermic anomaly around 340 K in the specific heat due to the heating process, which is attributed to the independent dipole rotation in the nematic-type unstable structure with loose molecular packing and imperfect hydrogen bonding.
Electrical Properties of CuPc Films Prepared by Plasma-Activated Evaporation in N2 and NOx Environments
Authors: Choi Chang-Gu , Lee Soonchil , Won-Jong Lee Won-Jong Lee
Published: October 2002

CuPc films with good mechanical and chemical resistance were prepared by the plasma-activated evaporation method and the electrical properties of the films were measured in pure N2 and in 100 ppm NO

x

environments. In N2 environment, the dc conductivity of the film depends on the temperature as e
-E/k
T
while the ac conductivity is independent of temperature and proportional to ω
n
with the exponent n∼0.95. Adsorption of NO

x

gas affects mainly the dc conductivity by forming acceptor states to generate holes, but negligibly affects the ac conductivity. The increment of dc conductivity is related to the amount of adsorbed NO

x

gas molecules, which depends on the temperature and the film morphology. The impedance of CuPc thin film can be reasonably expressed as that of an equivalent circuit consisting of two resistor-capacitor pairs in series corresponding to the grain and the grain boundary. As the exposure time in NO

x

environment increases, the resistances of both grain and grain boundary decrease, while the capacitances do not vary with the exposure time.
Blue Light Emission from Silica Films Prepared by Plasma-Enhanced Chemical Vapor Deposition Using Triethoxysilane
Authors: Nakamura Tomoyoshi , Shida Azusa , Matsui Kazunori
Published: October 2002

Film preparation was carried out by plasma-enhanced chemical vapor deposition using triethoxysilane (TES)/O2, TES/N2, and TES/Ar systems. Films deposited at 50° C showed IR bands due to silica networks and organic groups such as Si-H, Si-OEt and C=O. For the TES/O2 system, the intensities of the signals due to organic groups decreased with an increase in substrate temperature, resulting in conventional silica spectra above 200° C. The organic groups still remained at 200° C for films prepared from TES/N2, and Si-H groups were observed even at 350° C. The films exhibited blue photoluminescence at room temperature. Relative intensity of the photoluminescence was related to IR absorption intensity of the Si-H groups, suggesting that O-Si-H complexes or defects induced by Si-H may be the cause of photoluminescence.
Time History of the Resistance and Inductance in a Pulsed Electric Discharge
Authors: Persephonis Peter , Giannetas Vasilis , Ioannou Athanasios , Parthenios John , Charalambos Georgiades Charalambos Georgiades
Published: October 2002

The time behavior of the electric characteristic resistance and inductance in a pulsed gas discharge is revealed through a procedure which exploits only the voltage waveform. This can be achieved combining step by step the waveform with the differential equation governing the performance of the system. This method is described analytically in the text. Its application showed that the resistance drops sheerly in the first few ns from a very high value while the inductance presents a peak in the “formation phase” of the discharge (first 40 ns). These are due to the reaction of the system to the oncoming sudden variation.
Molecular Design of Dissolution Inhibitor in Chemical Amplification Resist System by Molecular Orbital Method: Transparency and Reactivities with “Protons”
Authors: Nobutoki Hideharu , Kumada Teruhiko , Hiroshi Koezuka Hiroshi Koezuka
Published: October 2002

The molecular orbital (MO) method has been applied to study the transparency of any dissolution inhibitors in the deep-UV region and the reactivities of those molecules with protons derived from a photoacid generator in a chemical amplification resist system for excimer laser lithography. The results indicate that 1,3-bis(tert-butoxycarbonyloxy) benzene is the best dissolution inhibitor with respect to both the transparency and the reactivities among the five dissolution inhibitors studied, because it has small absorption peaks in the wavelength range longer than 215 nm and easily decomposes into the oxycarbonyloxyl compound and the tert-butyl group upon proton attack. The validity of the MO approach is confirmed by the experimental results.