bluuebunny/crossref_metadata_2025 huggingface dataset:
Partial Elimination of Shot Noise in Optical Delayed Heterodyne Interferometer with Incoherent Light Using Spectral Interference
Authors: Mitsui Takahisa
Published: October 2002

We succeeded in reducing the shot noise inherent in the optical delayed heterodyne interferometer with incoherent light by introducing spectral interference. Theoretically, the shot noise level of our interferometer is 1/M of the conventional delayed heterodyne interferometer, where M is the number of wavelength divisions of the spectral interference. In our simulation experiment, the shot noise was reduced 20 dB from the conventional delayed heterodyne interferometer. This technique will reduce the image-acquisition time of optical reflectometry that uses incoherent light.
Enhancement of Numerical Aperture of Liquid Crystal Microlenses Using a Stacked Electrode Structure
Authors: Honma Michinori , Nose Toshiaki , Sato Susumu
Published: October 2002

A liquid crystal (LC) microlens with a stacked electrode structure is fabricated by attaching a transparent flat electrode outside a conventional LC microlens. Numerical aperture (NA) properties in two driving methods (an addition type and a subtraction type) are discussed. NA of LC microlens in the addition-type driving method is almost the same as that of the conventional LC microlens, while in the subtraction type, NA is much larger. The enhancement of NA is explained by considering the spatial distribution of the electric field in the LC layer. The dependence on thickness of the insulating layer (t
i) of the maximum NA (NAmax) when the applied voltage is varied is also discussed. In the subtraction type, NAmax strongly depends on t
i and takes a maximum value when t
i is varied. The enhancement of NA leads to the application of LC microlens as a collimating lens of a light source with a large divergence angle such as a laser diode.
Laser Cleaning of IC Mould and Its Real-Time Monitoring
Authors: Lu Yong-Feng , Song Wen-Dong , Hong Ming-Hui , Ren Zhong-Min , Chen Qiong , Chong Tow-Chong
Published: October 2002

Laser-induced removal of organic contaminants on IC mould surfaces was studied both experimentally and theoretically. The mould surfaces before and after cleaning were observed under an optical microscope and analysed by Auger electron spectroscopy (AES). It was found that the contaminants in the irradiated area were effectively removed by pulsed laser irradiation at a laser fluence greater than the cleaning threshold of 100 mJ/cm2. The cleaning efficiency increases with increasing laser fluence and the damage threshold of the mould surfaces is about 1.05 J/cm2, which is in good agreement with the theoretical damage threshold. We also demonstrated that the acoustic wave detection in real-time can be used to both monitor the surface cleanness during the laser cleaning process and determine the cleaning threshold and cleaning efficiency.
Measurement and Calculation of Optical Band Gap of Chromium Aluminum Oxide Films
Authors: Kim Eunah , Jiang Zhong-Tao , No Kwangsoo
Published: October 2002

The optical band gap is a basic property of optical materials. The measured band gap depends not only on the material but also on its characteristics such as crystallinity and stoichiometry. The optical band gap of chromium aluminum oxide films was measured and calculated by three different methods. Firstly, we used the conventional experimental-graphical method, which is commonly used. However, this method is applicable only to an all-crystalline phase or an all-amorphous phase. The second one was an experimental-calculation method applicable to films composed of both crystalline and amorphous phases. We calculated the optical band gap between the highest occupied molecular orbital of O2p and the lowest unoccupied molecular orbital of Cr3d in Cr1.71Al0.29O3 films composed of both amorphous and crystalline phases. Also, a band gap for the d–d transition was obtained. Finally, the measured value was compared with the theoretical optical band gap calculated by the discrete variational-Xα (DV-Xα) method.
Memory Effect in an Aluminum Single-Electron Floating-Node Memory Cell
Authors: Kim Jinhee , Oh Sangchul , Yoo Kyung-Hwa , Park Jong Wan , Lee Jeong-O , Choi Jung Bum , Park Se Il , Kim Ju-Jin
Published: October 2002

We have observed a memory effect in an aluminum single-electron memory cell with a floating node. Electrons were injected to or emitted from the floating node by field emission, which was evidenced by the sudden change in the Coulomb oscillation of a single-electron transistor. With the compensating voltage applied to the back gate, the Coulomb oscillation could be completely suppressed if the gate voltage sweep direction was reversed. We found that the Coulomb-oscillation period changed with the ratio of control-gate to back-gate voltage, being fitted well to the expected formula.
Theoretical Analysis of Thermal/Electric-Field Poling Fused Silica with Multiple-Carrier Model
Authors: Liu Xueming , Sun Xiaohan , Zhang Mingde
Published: October 2002

Using the multiple-carrier model under the step-profile approximation of the charge density distribution, expressions for the width and electric field distribution in the depletion region of fused silica samples after formed by thermal/electric-field poling are derived. Theoretical results show that the peak electric field is located in the inner of the depletion region, and that the chemical formation of H+/H3O+ may take place in the negatively depleted region. The depletion region width and the second-order susceptibility, which are ∼10 µm and ∼0.35 pm/V for the normal thermal/electric-field poling in air, respectively, are proportional to the square root of the applied dc voltage, and agree well with previous experimental results.
Laser- and Electric-Field-Induced Local Refraction Index Change in a Nematic Liquid Crystal Film
Authors: Wu Jin-Jei , Chen Shu-Hsia , Fan Jen-Yu
Published: October 2002

We study the Ar+ laser- and electric-field-induced local refraction index change in a planar-parallel-aligned nematic liquid crystal (NLC) film. The laser that is normally incident on the film is strong enough to induce a spatial nonuniformity of the molecular reorientation. The experimental results show that the change of the refraction index of the NLC film is always less than that calculated by the theory in current usage. This is because of the finite beam size effect which is different from the infinite plane wave assumption in the current theory. In this paper, we report some interesting phenomena which result from the finite beam size effect especially near the occurrence of the Fredericksz transition. The experimental results are compared to the theoretical calculations.
Improvement of NOx Removal Efficiency Assisted by Aqueous-Phase Reaction in Corona Discharge
Authors: Daito Shigeo , Tochikubo Fumiyoshi , Watanabe Tsuneo
Published: October 2002

The influence of water vapor and water droplets on the removal efficiency of nitrogen oxide is investigated in the pulsed positive corona discharge in atmospheric pressure air-based gas with a small amount of NO. The removal rates of both NO and NO2 are improved by feeding water vapor into the discharge reactor since NO2 is transformed into HNO3 by reaction with OH. Feeding water droplets, particularly alkaline water droplets, gives a better NO and NO2 removal efficiency than feeding water vapor. This might be explained by the rapid dissolution of the generated HNO3 into water droplets. Numerical modelling by means of a rate equation is carried out to investigate the dynamic process of gas phase and aqueous phase, and the aqueous-phase reaction in water droplets. The results suggest that gas-phase HNO3 dissolves in water droplets within short time (∼0.1 s). Therefore, the efficient transformation of NO
x
into gas-phase HNO3 is a key process in the improvement of NO
x
removal efficiency. Suppressing hydrogen ion concentration in water droplets by adding NH3 or feeding alkaline water droplets improves the dissolution rate of NO2.
Influence of Reactive Ion Etching Applied to Si Substrate on Epitaxial Si Growth and Its Removal
Authors: Hayashi Hisataka , Ohuchi Kazuya , Miyano Kiyotaka , Hokazono Akira , Mizushima Ichiro , Ohiwa Tokuhisa
Published: October 2002

The effects of post-etching treatments on Si selective epitaxial growth (SEG) have been studied. In the case of O2 downflow treatment, SEG Si had dislocations and a rough surface. It was found that this abnormal growth was caused by SiO2 formed by the post-etching treatment which could not be removed by diluted hydrogen fluoride (DHF) treatment prior to the SEG process. This SiO2 was not removed due to the existence of carbon at the Si/SiO2 interface which had been implanted by reactive ion etching (RIE). In the case of O2 plasma treatment, there was no carbon at the Si/SiO2 interface, SiO2 was completely removed by DHF, and SEG Si was grown successfully. In conclusion, a new, low-temperature Si surface removal method with precise etching depth control using O2 plasma treatment followed by DHF treatment is demonstrated to be an effective pretreatment for Si SEG.
Formation of Positive and Negative Carbon Cluster Ions in the Initial Phase of Laser Ablation in Vacuum
Authors: Kanji Shibagaki Kanji Shibagaki , Toyohisa Kawashima Toyohisa Kawashima , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

In this paper, the formation of C
n

+ and C
n

- cluster ions has been investigated. The carbon cluster ions were produced by the laser ablation of a rotating graphite target in vacuum. The study has been carried out using time-of-flight mass spectrometry. Mass spectra of positive and negative cluster ions were observed as a function of delay time between the irradiation of the laser pulse and the acceleration of ions. The mass distribution of clusters changed significantly in the initial phase (≤10 µs) after the irradiation of the laser pulse. The sizes of both positive and negative cluster ions grow with the increase in the delay time. These results indicate that clustering reactions progress even in vacuum without ambient gas. The mechanism of clustering is considered to be reactions among various carbon ions and neutral species in the laser ablation plume.
Properties of Conducting Polymer-Dye Composite and Photovoltaic Characteristics of Junction Devices
Authors: Wei Feng Wei Feng , Akihiko Fujii Akihiko Fujii , Sergey Lee Sergey Lee , Hongcai Wu Hongcai Wu , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

We have prepared new soluble conducting polymer/dye composite and photovoltaic cells with three different architectures using soluble conducting polymer (CP) as hole transport material and perylene derivatives (PV) as electron transport material. These architectures comprise single-layer (ITO/CP-PV/Al) and double-layer (ITO/CP-PV/PV/Al) as well as three-layer (ITO/CP-C60/CP-PV/PV/Al) structures. Electrical and optical properties of soluble conducting polymer composite film and current-voltage characteristics and photocurrent spectra of photovoltaic cells are discussed. The results show that the soluble conducting polymer-dye composite represents a new class of organic semiconducting material that can be used to manufacture photovoltaic cells.
Flow Pattern in a Channel during Application of Ultrasonic Vibration
Authors: Nomura Shinfuku , Sasaki Yuuichi , Murakami Koichi
Published: October 2002

In the present study, the flow pattern in a channel during application of ultrasonic vibration is investigated for the purpose of fluid control without contact. An ultrasonic transducer is fixed at the center of the bottom of a square test channel, and a standing wave field is formed in this channel. The velocity of the fluid is measured by a laser-Doppler velocimeter (LDV). By applying ultrasonic vibration to the channel flow, cavitation bubbles are generated at the sound pressure antinode in the channel when Re
d=2000. Consequently, the cavitation bubbles act on the fluid as the barrier, causing the separation of the flow, and the velocity of the fluid is reduced locally. The generation of cavitation is active at the point where the sound pressure of the standing wave formed by ultrasonic vibration is high. Moreover, the cavitation bubbles move toward to the antinode and are trapped by radiation pressure because the bubbles are of much lower density than water. Thus, the profile of fluid velocity is strongly influenced by the standing wave formed in the channel. Since the wavelength is shorter at higher frequencies, this technique can be applied to flows of various scales.
Two-Temperature Scaling for Molecular Dynamics Simulation at Constant Temperature
Authors: Fukushi Daigo , Mae Kazuki , Honda Takuya
Published: October 2002

Molecular dynamics simulations for a binary system are carried out using a temperature scaling procedure under isothermal conditions to keep the temperature constant. However, the temperatures of each atomic species are diverse in the cases of component atoms with significantly different masses. The causes of the deviation of atomic temperatures in the ordinary scaling method with one thermostat are examined. The deviations appear when the mass ratio of light atoms to heavy is below 0.4. We apply the two-temperature control method using different heat baths for individual species to render the temperatures of the two different species the same, although this generally breaks the momentum conservation law as reported by Nosé [Mol. Phys. 57 (1986) 187 and Prog. Theor. Phys. Suppl. (1991) No. 103, 1]. It is found that the deviation from the conservation law of the system is not very large and the method is useful except under extraordinary conditions.
Analysis of Unstable Two-Phase Region in Wurtzite Group III Nitride Ternary Alloy Using Modified Valence Force Field Model
Authors: Takayama Toru , Yuri Masaaki , Itoh Kunio , Baba Takaaki , Jr. James S. Harris
Published: October 2002

The Group III-nitride ternary system is studied with respect to an unstable two-phase region in the phase field. The unstable two-phase region is analyzed using a strictly regular solution model. The interaction parameter used in the analysis is obtained from a strain energy calculation using the valence force field model, modified for both wurtzite and zinc-blende structures to avoid overestimation of the strain energy. The structural deviation from an ideal wurtzite structure in InN, GaN, and AlN is also taken into account in our model. According to the calculated results of the interaction parameters, the critical temperature for wurtzite InGaN, InAlN, and GaAlN are found to be 1967 K, 3399 K, and 181 K, respectively. This suggests that, at a typical growth temperature of 800–1000°C a wide unstable two-phase region exists in both InGaN and InAlN. In order to show the validity of our calculation results, we compare the calculated results and the experimental results using the calculation of the interaction parameter for the InGaAs system. The calculated results agree well with the experimental results.
Determination of Donor Densities and Donor Levels in 3C-SiC Grown from Si2(CH3)6 Using Hall-Effect Measurements
Authors: Masuda Hideharu Matsuura , Chen Yi , Nishino Shigehiro
Published: October 2002

Without any assumption of the number of types of impurities, the densities and energy levels of donors in undoped 3C-SiC grown from Si2(CH3)6 are precisely determined by the simple graphical method proposed here, using the temperature dependence of the majority-carrier concentration obtained by Hall-effect measurements. We detect at least three types of donors whose energy levels (ΔE
D) are 7–14 meV, 46–54 meV and 97–120 meV as measured from the conduction band, although it was reported that ΔE
D for nitrogen atoms decreased with an increase in the donor density from ∼50 meV to ∼15 meV. In addition to the ∼15 meV donor that was reported in undoped 3C-SiC grown from a mixture of SiH4 and C3H8, at least two donor levels are detected in undoped epilayers grown from Si2(CH3)6. From the viewpoints of donor density and compensation ratio, the quality of undoped 3C-SiC grown from Si2(CH3)6 is better than that of undoped 3C-SiC grown from a mixture of SiH4 and C3H8.
Electronic Structure and Chemical Bondings of MgCr2-xO4
Authors: Moriwake Hiroki , Tanaka Isao , Oba Fumiyasu , Adachi Hirohiko
Published: October 2002

Cr-vacancies are known to be abundant in MgCr2O4 which have been
thought to contribute to p-type conduction. In order to understand the electronic
mechanism behind the formation of Cr-vacancies and spatial distribution of holes
associated with the Cr-vacancy, first principles molecular orbital calculations of
MgCr2O4 and its isostructural compound, MgAl2O4, have been
systematically performed using model clusters. The holes are found to be almost
confined to an Al-vacancy in MgAl2O4. The spatial distribution of holes is
wider in the case of a Cr vacancy in MgCr2O4. However, the major part of the
hole-charge is localized on the neighboring oxygen ions, not on Cr-ions. Covalent
bonding between Cr and O is markedly reinforced by the formation of Cr-vacancies in
MgCr2O4. At the same time, the decrement of the ionic bonding is much
smaller also in MgCr2O4. These two factors are expected to play important
roles for the relative stability of Cr-vacancies in MgCr2O4 as compared with
MgAl2O4.
Ultrafast Optical Switching in a Silver Nanoparticle System
Authors: Inouye Hideyuki , Tanaka Koichiro , Tanahashi Ichiro , Hattori Toshiaki , Nakatsuka Hiroki
Published: October 2002

An ultrafast response of a silver nanoparticle system, as fast as 360 fs, was observed in a femtosecond optical-Kerr-shutter experiment. The ultrafast response is attributed to a self-diffraction of a pump pulse due to transient grating. We estimated χ(3) of the silver nanoparticle system to be 1.5 × 10-7 esu in the femtosecond region.
Influence of Annealing on the Optical Properties of PbWO4 Single Crystals Grown by the Bridgman Method
Authors: Senguttuvan Nachimuthu , Ishii Mitsuru , Tanji Kiyokazu , Kittaka Takeshi , Usuki Yoshiyuki , Kobayashi Masaaki , Nikl Martin
Published: October 2002

In the present work, the evaporation rate of PbWO4 (PWO, powdered crystal) and PbO (powder) in the temperature range of 700 to 1200°C was measured by thermogravimetric analysis. The log
V vs T
-1 plot was determined to be linear and the temperature dependence of the evaporation rate of PWO was found to be the same as that of PbO in the solid state. This shows that the crystals grown by the Czochralski method are Pb-deficient as a result of self-annealing. The optical transmittance and the excitation-emission spectra of the as-grown and annealed PWO crystals grown by the Bridgman method were also measured. Annealing was performed in the temperature range of 500 to 1000°C (isochronal) for 1 h. The surface emission of the annealed samples exhibited a particularly strong peak at 485 nm whose intensity decreased with increasing annealing temperature. The transmittance was found to exhibit a small but consistent increase with increasing annealing temperature at about 350 nm.
Multicolor Switching Properties in Fluorescent Liquid Crystal Displays
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Junya Kishida Junya Kishida , Susumu Sato Susumu Sato
Published: October 2002

Multicolor fluorescent liquid crystal displays (LCDs) are proposed. The twisted nematic (TN) cell containing a dichroic fluorescent dye is utilized as a UV shutter, a polarization switch and an active emitter. We describe two fluorescent LCD modes of different stacking order of the fluorescent TN cell, alternative fluorescent layer and a sheet polarizer. The fluorescence color can continuously be changed by applying a voltage across the TN cell and color variations between green and blue, red and green, and red and blue are demonstrated in both modes. The brightness is considerably improved by applying the polarized light emitting phenomenon from the LC cell to the fluorescent LCD, which makes the use of nonpolarized excitation UV light possible.
Ellipsometric Study of Silicate Treatment of Aluminum Offset Printing Plates
Authors: Kawabata Shuichi , Sugai Toshio , Futami Kazuo
Published: October 2002

The silicate treatment of aluminum offset printing plates has been studied by ellipsometry. Aluminum is very reactive with oxygen and the aluminum surface is easily oxidized in the atmosphere. The presence of the oxide layer on the aluminum surface brings about some ambiguities in the analysis of the ellipsometric data of the overlaid film. Few researchers have estimated the thickness of a siliceous film on aluminum plates as far as we know. However their estimations are very vague, ranging from one monolayer (∼0.3 nm) to 1 µm.1,2) We carried out a series of experiments to determine the thickness of a siliceous film on an aluminum surface by means of ellipsometry. The thicknesses of the siliceous films on the aluminum film surface were successfully estimated by applying Bruggeman's effective medium approximation to the composite layer of the aluminum and the aluminum oxide. In our experiments, the thicknesses of the composite layer and the siliceous film were estimated to be in the range from 1.3 nm to 1.6 nm and about 0.7 nm, respectively.
Optical Properties of Ag(AlxGa1-x)S2 Epitaxial Layers Grown on GaAs(100) by Multisource Evaporation
Authors: Tsuboi Nozomu , Matsuda Shigeru , Kurasawa Masaki , Kobayashi Satoshi , Kaneko Futao
Published: October 2002

Reflectance anomaly and photoluminescence emission spectra of Ag(Al
x
Ga1-x
)S2 epitaxial layers, which were grown in the range of x<0.3 on GaAs (100) substrate by the multisource evaporation method, were observed in the exciton region. According to analyses of the reflectance anomaly spectra, assuming the single Lorentzian oscillator model for the free exciton, it was found that the oscillator energy and the damping constant of the model increased with an increase of x. Because the oscillator energy and the damping constant coincided with the peak energy and the spectral full-width at half maximum of the emission respectively, the emission was identified as free exciton emission, indicating the good optical quality of the layers. Taking account of the lattice strain effect, the composition dependence of the A1-mode Raman scattering frequency of the layers coincided with that of the bulk crystals.
Determination of Director Distributions in Liquid Crystal Polymer-Films by Means of Generalized Anisotropic Ellipsometry
Authors: Benecke Carsten , Seiberle Hubert , Schadt Martin
Published: October 2002

We report on how to achieve and measure director tilt angle
distributions θ(z) in cross-linked nematic
liquid crystal polymer (LCP) films by means of generalized anisotropic
ellipsometry. LCP-alignment
is made by linearly photopolymerized (LPP)-photo-alignment of LCP
films on single substrates. For
the first time arbitrary tilt angle distributions are achieved and
experimentally verified. It is shown
that not only the birefringence Δn of novel LCP-materials, which
exhibit values up to Δn=0.4, but also
the tilt distribution θ(z) of the LC director can be
varied. θ(z) is
shown to be tunable between substrate
surface and LCP/air interface over the entire range
90°≥θ≥0°. The
control of the tilt distribution in
thin LCP-films on single substrates is essential for many
applications, for instance in LPP/LCP wide-view films designed to
increase the field of view of liquid crystal
displays (LCDs).
Comparative Study of Photoluminescence Dynamics of Tris(8-hydroxyquinoline) Aluminum-Based Organic Multilayer Structures with Different Types of Energy Lineups
Authors: Fujita Shizuo , Nakazawa Tadahiro , Asano Mitsuru , Fujita Shigeo
Published: October 2002

Photoluminescence (PL) dynamics of aluminumquinoline (Alq3; tris(8-hydroxyquinoline) aluminum)-based organic multilayer structures, i.e., Alq3/oxadiazole (t-BuPBD; (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole), Alq3/cyclopentadiene (PPCP; 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene), and Alq3/diamine (TPD; N,N′-diphenyl-N,N′-bis-(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine), which possess different types of energy lineups (equivalent to types I and II of inorganic semiconductor multilayer structures) of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels, were investigated and compared. The fast energy transfer followed by strong PL in Alq3 was proved for Alq3/PBD which is of type-I energy lineup, while the tendency of separation of excitons, i.e., electrons and holes generated in the excited molecules, was demonstrated for Alq3/PPCP and Alq3/TPD which are of type II. These results indicate that the energy lineup with respect to HOMO and LUMO energy levels can be a guideline for luminescence dynamics in organic multilayer structures.
Amorphous Refractory Compound Film Material for X-Ray Mask Absorbers
Authors: Iba Yoshihisa , Kumasaka Fumiaki , Iizuka Takashi , Yamabe Masaki
Published: October 2002

We proposed that the stress of the side walls of an absorber pattern causes the pattern distortion of an X-ray mask. The surfaces of the pattern side walls have a high compressive stress layer because they are easily oxidized in air after absorber pattern etching. This stress becomes a serious problem in proportion to the high degree of pattern integration. To lower the surface oxide layer stress of the film, we developed a TaGe nitride (TaGeN) absorber. The oxide layer stress of TaGeN films becomes lower with increasing the N2 content in the sputtering gas, and the stress value of Ta0.35Ge0.20N0.45 can be decreased to 1/17 that of TaGe. We fabricated a TaGeN X-ray mask and practically demonstrated that the TaGeN absorber was effective for high image placement accuracy to an X-ray mask having high dense patterns with a 0.1 µm pattern size.
Evaluation of Overlay Accuracy for 100-nm Ground Rule in Proximity X-Ray Lithography
Authors: Aoyama Hajime , Fukuda Makoto , Mitsui Souichirou , Taguchi Takao , Suzuki Masanori , Haga Tsuneyuki , Morita Hirofumi , Matsui Yasuji
Published: October 2002

An evaluation was made of the overall overlay accuracy of proximity X-ray lithography (PXL), which includes mask placement error, the alignment error of the stepper, and deformation arising from wafer processing. The relative placement accuracy of X-ray masks between first and second layers was below 22 nm (3σ) for both the x- and y-directions. Exposure was carried out using an optical heterodyne alignment system and magnification correction, and an overlay accuracy below 30 nm (mean ±3σ) was obtained. The overlay error was broken down into various components to estimate the error budget. The analysis revealed the alignment error of the X-ray stepper to be about 25 nm, and the common in-plane deformation to be about 11 nm. The common in-plane deformation was almost the same as the relative mask placement accuracy without scale error. The accuracy obtained in this study clearly demonstrates the suitability of PXL for the fabrication of 100-nm ground rule devices. Moreover, the analysis indicates that it is also applicable to the 70-nm technology node.
Computational Fresnel Images of Magnetic Nanoparticles
Authors: Aoyama Naoto , Yamamoto Kazuo , Tanji Takayoshi , Hibino Michio
Published: October 2002

Lorentz microscopy is applied to observe the magnetic structures of Fe fine particles in granular films. Observed particles, 20–60 nm in diameter, are prepared by precipitation in an Fe–Mo amorphous thin film. In order to understand accurately the observed Lorentz micrographs, image contrast is simulated mimetically. Some analyses for single-magnetic-domain particles are shown in comparison with experimental data. The minimum size of the observable Fe particle is thought to be about 10 nm in diameter.
High-Density Nanoetchpit-Array Fabrication on Si Surface Using Ultrathin SiO2 Mask
Authors: Meishoku Koh Meishoku Koh , Souichi Sawara Souichi Sawara , Tomomi Goto Tomomi Goto , Yoshinori Ando Yoshinori Ando , Takahiro Shinada Takahiro Shinada , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

Nanoetchpit arrays (NEPAs) with a density of 1.56 T(1012)pit/in2 were artificially fabricated on Si surfaces. The key to the success of high-density-NEPA fabrication is through utilization of ultrathin SiO2 layer as an Si etching mask and N2H4 (hydrazine) solution as an Si etchant. The NEPAs were fabricated in only three steps: (1) focused electron-beam (EB) irradiation onto SiO2 mask, (2) SiO2 mask development using an HF-based solution, and (3) Si etching using hydrazine. The enhanced etching phenomenon of EB-exposed SiO2 in an HF-based solution was applied to pattern the SiO2 mask. Thin SiO2 layers with a thickness of 8 nm at the initial stage (4 nm after the development) were used as Si etching mask to suppress both spreading of the EB-exposed region by the forward scattering of the electrons and lateral extension of the SiO2 etching region during the development. Si substrates were etched through 4-nm-thick SiO2 mask by dipping in a hydrazine solution with an extremely high etching selectivity for Si/SiO2. By using this simple process, 8-nm-diameter NEPAs with a 20 nm pitch were successfully arranged on Si surfaces.
Effects of Gas-Phase Thermal Decompositions of Chemical Vapor Deposition Source Molecules on the Deposition of (Ba, Sr)TiO3 Films: A Study by In Situ Fourier Transform Infared Spectroscopy
Authors: Shun Momose Shun Momose , Toshihiro Nakamura Toshihiro Nakamura , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

We studied the thermal decompositions of Ti(t-BuO)2(DPM)2, Sr(DPM)2 and Ba(DPM)2 under actual chemical vapor deposition (CVD) conditions by in situ Fourier transform infrared spectroscopy (FT-IR). From the temperature dependence of the IR absorbance, we investigated the thermal stability of the chemical bonds in the source molecules. The obtained FT-IR data were correlated with the characteristics of the deposited BST films. Although Sr(DPM)2 and Ba(DPM)2 molecules decompose completely in the gas phase before Sr and Ba atoms are incorporated in the film, the deposition of Ti atoms does not require the complete decomposition of Ti(t-BuO)2(DPM)2 molecules in the gas phase. In this study, we discuss the effects of these thermal decompositions on the deposition mechanism of (Ba,Sr)TiO3 films.
Ferroelectric Properties of Al-doped Lead Titanate Zirconate Thin Films Prepared by Chemical Solution Deposition Process
Authors: Iijima Takashi , He Gang , Wang Zheng , Tsuboi Hideki , Hiyama Kunio , Okada Masuhiro
Published: October 2002

2.5 and 5 mol% Al were doped to lead titanate zirconate (PZT) thin films using a chemical solution deposition process, and ferroelectric properties of Al-doped PZT thin films were compared with those of nondoped PZT film. Doped Al seems to be substituted at the Zr/Ti site (B site) since the c/a ratio decreased with increasing Al content. The shape of a P–E hysteresis curve of the thin films did not show remarkable differences between nondoped and Al-doped PZT. Values of P

s
, P

r
and E

c
of the 2.5 mol% Al-doped PZT thin films were about 43 µC/cm2, 19 µC/cm2 and 58 kV/cm, respectively. On the other hand, the leakage current of the thin films showed a tendency to decrease with increasing Al content. The fatigue properties of the Al-doped PZT thin film showed a slight improvement, because the reduction rate of the fatigue was smaller than that of a nondoped PZT thin film.
Charge Properties of Bi-Rich Strontium Bismuth Tantalate Thin Films
Authors: Tanaka Masahiro , Hironaka Katsuyuki , Onodera Akira
Published: October 2002

The thermal behavior of charge properties and the polarization-retention of a Sr0.8Bi2.2Ta2O9 thin film were investigated in a range from room temperature to 558 K. The anomaly caused by the thermally stimulated space charge was observed. The anomaly started at about 425 K and showed a peak at about 525 K. However, the thermal behavior of the charge properties of the film in this temperature range is explained as being in a ferroelectric phase according to the Landau theory.
Effect of Molecular Mass of B-site Ions on Electromechanical Coupling Factors of Lead-Based Perovskite Piezoelectric Materials
Authors: Yamashita Yohachi , Hosono Yasuharu , Harada Kouichi , Ichinose Noboru
Published: October 2002

The effects of the molecular mass of B-site ions of Pb(B′B′′)O3–PbTiO3 (B′=Mg, Zn, Ni, Sc, In and Yb; B′′=Nb and Ta) and Pb(B, Ti)O3 (B=Zr, Hf and Sn) piezoelectric materials on the electromechanical coupling factors were investigated. The relationship between the electromechanical coupling factor k

p
near a morphotropic phase boundary (MPB) and the molecular mass of B-site ions is systematically discussed. The reason why k

p
of Pb(Zr, Ti)O3 (PZT) is larger than that of Pb(Hf, Ti)O3 (PHT) or Pb(Sn, Ti)O3 (PST) is explained in terms of the molecular mass difference between A-site and B-site ions of Pb(B, Ti)O3. It may be concluded that a combination of the B-site ions which have a lower molecular mass in MPB composition, play an important role in realizing large electromechanical coupling factors in lead-based perovskites. From this viewpoint, MPB compositions of Pb[(Sc1/2Nb1/2)0.58Ti0.42]O3 (PSNT 58/42), which has the largest molecular mass difference between A-site and B-site (Amass-Bmass=147.1) ions may be the best combinations of all Pb(B′B′′)O3–PbTiO3 and Pb(B, Ti)O3 systems so far reported. However, if Pb[(Al1/2Nb1/2)1-x
Ti
x
]O3 and Pb[(Ga1/2Nb1/2)1-x
Ti
x
]O3 systems can be synthesized into pure perovskite structures near the MPB, a better piezoelectric performance than PZT 53/47 or PSNT 58/42 is expected.
Electronic States of Perovskite-Type Oxides and Ferroelectricity
Authors: Hiromu Miyazawa Hiromu Miyazawa , Eiji Natori Eiji Natori , Satoru Miyashita Satoru Miyashita , Tatsuya Shimoda Tatsuya Shimoda , Fumiyuki Ishii Fumiyuki Ishii , Tamio Oguchi Tamio Oguchi
Published: October 2002

A relation between B-site transition metal and ferroelectricity is investigated in A
BO3 perovskite-type oxides. We focus on intensity of the covalent bonds between the B-site atom and the oxygen octahedron and evaluate Harrison's covalency parameter α. The density functional theory within the local density approximation is adopted to obtain the valence electron energy levels of free atoms from which the covalency α is calculated. Strong correlation between the covalency α and the Curie temperature (T
C) is found. As the covalency α increases, T
C of ferroelectricity arises. It is also noted that the hybridization between Pb 6p and O 2p is crucial for the high ferroelectricity of PbTiO3.
Raman Scattering in (1-x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 Mixed Crystal System
Authors: Iwata Makoto , Hoshino Hidetaka , Orihara Hiroshi , Ohwa Hidehiro , Yasuda Naohiko , Ishibashi Yoshihiro
Published: October 2002

The temperature-concentration phase diagram in the (1-x) Pb(Zn1/3Nb2/3)O3–x PbTiO3 mixed crystal system was obtained from dielectric measurements, and the temperature dependences of the Raman spectra in the entire concentration range were measured. The lattice vibration and nano-scale clusters in the mixed crystal system were discussed on the basis of observed Raman spectra.
Low-Temperature Deposition of SrRuO3 Thin Film Prepared by Metalorganic Chemical Vapor Deposition
Authors: Okuda Norikazu , Saito Keisuke , Funakubo Hiroshi
Published: October 2002

SrRuO3 thin films were prepared on (100) LaAlO3 substrates by
metalorganic chemical vapor deposition (MOCVD) at various deposition temperatures
from 550°C to 750°C. The composition of the film can be controlled by
monitoring the composition of the input source gas. Below 600°C, the degree of
a-axis orientation of the film gradually decreased with decreasing deposition
temperature. However, the resistivity of the film was almost the same for that
reported for the single crystal and was independent of the deposition temperature when
the Ru/(Ru+Sr) ratio of the film was 0.5. The film had almost the same
value for the film thickness from 30 to 250 nm deposited at 750°C. Moreover, it
increased with the Ru/(Ru+Sr) ratio below 0.45.
InAs Planar Diode Fabricated by Zn Diffusion
Authors: Iwamura Yasuo , Watanabe Naozo
Published: October 2002

An InAs planar diode with an optical window in the upper electrode was fabricated by the selective diffusion of Zn. Diethylzinc (DEZn) was used as a precursor for Zn and the diffusion process was carried out in a metalorganic chemical vapor deposition (MOCVD) system containing tertiary butylarsine (tBAs) as an As precursor to suppress the thermal decomposition of InAs. Typical diffusion conditions were: temperature 530°C, time 30 min, pressure of DEZn and tBAs 1.0 Pa and 75 Pa, respectively, and ambient pressure 40 kPa. Electrical characteristics of the diode were excellent: the ideality factor was as small as 1.05 for forward-biased current–voltage characteristics at 200 K and the reverse current was less than 10-8 A at 80 K. The peak photosensitivity at 175 K was 0.28 A/W around 3.2 µm in wavelength without antireflection coating. When the diode was driven at 150 mA at 80 K, two mid-infrared emission peaks were observed at 3.04 µm and 3.25 µm.
Characterization of Sc–O/W(100) Surface as Schottky Emitter: Work Function Change for Activation Processing
Authors: Kawano Takashi , Takai Yoshizo , Shimizu Ryuichi
Published: October 2002

To elucidate the electron emissivity of the Sc–O/W(100) Schottky emitter,
the Sc–O/W(100) surface, prepared by scandium deposition onto the W(100) surface
followed by oxygen exposure and heating at an operating temperature of
∼1400 K, was studied by ion scattering spectroscopy (ISS), Auger electron
spectroscopy (AES) and measurement of the relative work function change. The results
have revealed that heating of the oxygen adsorbed Sc/W(100) surface leads to the
diffusion of the oxygen atoms into the substrate to locate very probably beneath the
topmost scandium atoms. This relocation of the oxygen atoms forms an electric double
layer, resulting in a significant decrease of the work function. The topmost surface
composition of the Sc–O/W(100) system observed by ISS did not change during cooling
the sample from ∼1400 K to room temperature under the present conditions.
The results of the present work strongly suggest that the surface properties of the
Sc–O/W(100) system are very similar to those of the Zr–O/W(100) system at the
operating temperature.
Two-Dimensional Stress Distributions in Disk and Ring High-Tc Superconductors
Authors: Tsuchimoto Masanori , Takashima Hideyoshi
Published: October 2002

Stresses in a bulk high-T
c superconductor (HTS) are numerically evaluated when the bulk HTS is fully magnetized by field cooling. The stress distributions for disk and ring models are obtained through numerical analyses with the finite-difference method. Differences between one- and two-dimensional solutions are examined using the Bean model in terms of the maximum tension stress and shear stress.
Determination of Third-Order Optical Nonlinearity Dispersion of 1-Methyl-1′-Octadecyl-2,2′-Cyanine Perchlorate Langmuir-Blodgett Films Using Electroabsorption Spectroscopy
Authors: Hidetoshi Murakami Hidetoshi Murakami , Ryuji Morita Ryuji Morita , Takashi Watanabe Takashi Watanabe , Keisuke Asai Keisuke Asai , Itaru Honma Itaru Honma , Haoshen Zhou Haoshen Zhou , Mikio Yamashita Mikio Yamashita , Kenkichi Ishigure Kenkichi Ishigure , Hidemi Shigekawa Hidemi Shigekawa
Published: October 2002

The absorption and electroabsorption (EA) spectra of 1-methyl-1′-octadecyl-2,2′-cyanine perchlorate (S120) Langmuir-Blodgett films were measured. From these results, dispersion of the third-order nonlinear optical susceptibility χ(3)(-ω; 0,0,ω) in the range of 1.8 to 2.7 eV was determined. In addition, the linear-polarizability difference Δα and the permanent dipole-moment difference Δµ between excited and ground states were evaluated. Upon comparison with the results of measurement of the S120 monomer film, it was found that the third-order nonlinear optical susceptibility of the S120 LB film is strongly enhanced by a factor of 1000. It was concluded that this strong enhancement is attributed to the fact that S120 molecules with a short methyne chain that tightly binds two quinoline rings form a rigid J-aggregate with a one-dimensional structure that hardly twists, so as to yield a sharp absorption band with a large transition moment. Finally, we evaluated the average aggregation number of the S120 LB film to be 3–4.
A Liquid Crystal Display Having a Rubbing-Free Photo-Aligned Monomolecular Layer as an Alignment Film
Authors: Ohtake Kazufumi Ogawa Tadashi , Nomura Takaiki
Published: October 2002

Twisted nematic (TN) type liquid crystal displays (LCDs) using a rubbing-free photo-aligned monomolecular layer as a liquid crystal (LC) alignment film have been developed for the first time. The photo-aligned monomolecular layer was formed by a chemical adsorption (CA) technique using a new chlorosilane-type surfactant. The new chlorosilane-type surfactant synthesized has a long straight hydrocarbon chain, a chalconyl group at the molecular end and a trichlorosilyl group at the other end. The surfactant reacted with the surfaces of a thin film transistor (TFT) array and a color filter by dehydrochlorination in a moisture-free organic solvent. The photo-aligned monomolecular layer was constructed with molecules which were cross-linked or polymerized at the chalconyl group and anchored to the surfaces via siloxane (–SiO–) covalent bonds. The molecules were aligned and cross-linked or polymerized by irradiation of polarized deep UV light. In this LCD, the liquid crystal molecules were aligned at the molecular level along the molecular alignment direction of the photo-aligned monomolecular layer. High durability was realized, because the monomolecular layer was anchored to the surfaces via covalent bonds and cross-linked (or polymerized). Low cost will also be realized, because as the monomolecular layer is aligned by means of non-contact rubbing-free technique, the yield of defect-free displays will be high.
Selective Disordering of InGaAs Strained Quantum Well by Rapid Thermal Annealing with SiO2 Caps of Different Thicknesses for Photonic Integration
Authors: Shimada Naoyuki , Fukumoto Yutaka , Uemukai Masahiro , Suhara Toshiaki , Nishihara Hiroshi , Larsson Anders
Published: October 2002

Area-selective disordering of an InGaAs strained quantum well was performed by rapid thermal annealing with thick and thin SiO2 caps. The lasing wavelength difference as large as 23 nm was obtained between Fabry-Perot lasers in 300 nm and 30 nm capped areas. We present fabrication of lasers integrated with disordered passive waveguides and demonstrate significant reduction of the passive waveguide loss from roughly 40 cm-1 to 3 cm-1.
Orientational Dependence of Electro-optic Properties of SrBi2Ta2O9 Ferroelectric Thin Films
Authors: Moon Seung Eon , Back Se Bum , Kwun Sook-Il , Lee Yoon Sang , Noh Tae Won , Song Tae Kwon , Yoon Jong-Gul
Published: October 2002

A-/b- and c-axis oriented SrBi2Ta2O9 thin films were grown on the MgO(110) and MgO(100) substrates, respectively, by rf magnetron sputtering deposition method. Optical anisotropy was shown in the infrared reflectance spectra for the SrBi2Ta2O9 thin films. Quadratic electro-optic effects were observed only in the a-/b-axis oriented films. The effective quadratic electro-optic coefficient was about 3.8 ×10-17 m2/V2.
Photoalignment of Liquid Crystals on Photo-Cross-Linkable Polymer Films with Anthracene at the End of the Side Group
Authors: Kawatsuki Nobuhiro , Arita Tadahiro , Kawakami Yuya , Yamamoto Tohei
Published: October 2002

Three kinds of photo-cross-linkable polymethacrylate films with an anthracenemethoxybiphenyl side group or an anthracenemethyl side group were irradiated by a linearly polarized (LP) UV light, and the resultant films were applied to the alignment layer for liquid crystals (LC). The photoinduced optical anisotropy of the film was negative and similar among the polymers. Uniform LC alignment could not be obtained on the polymer without the biphenyl group, but the LC aligned homogeneously on the polymers with a biphenyl group. When the absorptive direction of the anthracene group was parallel to the long axis of the biphenyl group, the alignment direction was parallel to the electric vector (E) of the LP-UV light at the beginning of the irradiation and it changed to perpendicular with increase in the exposure dose. In contrast, when the absorptive direction of the anthracene group was not parallel to the long axis of the biphenyl group, the LC alignment direction was perpendicular toE. These types of alignment behavior suggest that the LC alignment direction is controlled by the direction of the biphenyl group in the photo-cross-linked side group.
Effect of Nonstoichiometry on Microstructure of Epitaxially Grown BaTiO3 Thin Films
Authors: Suzuki Toshimasa , Nishi Yuji , Fujimoto Masayuki
Published: October 2002

The microstructural features over a wide range of cation nonstoichiometry in barium titanate thin films grown on (100) SrTiO3 substrates by pulsed laser deposition were investigated by X-ray diffraction and transmission electron microscopy. Well-crystallized perovskite barium titanate was heteroepitaxially grown even with 20% excess titanium, but the film contained column-like amorphous secondary phases and some planar defects. In the case of 50% excess titanium, the film consisted of columnar nanocrystallites epitaxially grown on the substrate and a surrounding titanium-rich amorphous matrix. The incorporation of 50% excess barium, on the other hand, significantly degraded film crystallinity due to the formation of nanometer-scale amorphous phases.
In Situ Measurement of Composition in High-Temperature Solutions by X-Ray Fluorescence Spectrometry
Authors: Toru Ujihara Toru Ujihara , Gen Sazaki Gen Sazaki , Satoru Miyashita Satoru Miyashita , Noritaka Usami Noritaka Usami , Kazuo Nakajima Kazuo Nakajima
Published: October 2002

We proposed an in situ technique based on X-ray fluorescence spectrometry to measure the composition of a high-temperature solution in a crucible. The sample holder for this technique was composed of carbon, which is transparent to X-rays. Using the present technique, equilibrium compositions of zinc in a gallium solution were measured. The results agreed well with the liquidus curve of the Ga–Zn phase diagram, and thus the validity of this technique was proved.
Synthesis of New Ba Complex as Metalorganic Source for Metalorganic Chemical Vapor Deposition and Optimization of Its Molecule Structure
Authors: Zama Hideaki , Morishita Tadataka
Published: October 2002

New Ba(DPM)2-amine (DPM=dipivaloylmethane) adduct compounds were attempted to be synthesized from Ba(DPM)2 and amines. Complexes obtained were evaluated based on decreases of their weight with increasing temperature by thermogravimetry. The simple vaporizing phenomenon, showing a one-step weight-reduction curve, was observed only in the case of using tetraethylenepentamine and pentaethylenehexamine (pentaen) as adduct molecules, which have a simple chain structure and five to six primary and secondary amine radicals. From the viewpoint of applicability to film growth, they have the best structure based on a survey in this study using sixteen amine molecules with distinctive structures. When we used Ba(DPM)2-pentaen as a metalorganic source for a metalorganic chemical vapor deposition method at a vaporizing temperature of 140°C, the Ba supply rate remained stable within a standard deviation of 1.6% for over 300 h.