bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of InGaP/InGaAs/GaAs and InGaP/InGaAs/AlGaAs Pseudomorphic High Electron Mobility Transistors
Authors: Huang Chung-Er , Lee Chien-Ping , Huang Ron-Ting , Chang Mau-Chung Frank
Published: October 2002

We have studied the DC and RF characteristics of InGaP/InGaAs/AlGaAs and InGaP/InGaAs/GaAs pseudomorphic high electron mobility transistors (PHEMTs). The InGaP gate barrier provides adequate carrier confinement for the channel carriers and at the same time eliminates the problems associated with AlGaAs. Excellent device performance was obtained for both types of devices. No short channel effect was observed at a gate length as low as 0.3 µm. The InGaP/InGaAs/AlGaAs PHEMTs are superior in that they have higher transconductance, higher current carrying capability and better RF performance. This is attributed to the better carrier confinement at the back channel. These results demonstrate that InGaP/InGaAs/AlGaAs PHEMTs are favorable candidates for microwave applications.
Application of Anodization to Reoxidize Silicon Nitride Film
Authors: Lin Yen-Po , Hwu Jenn-Gwo
Published: October 2002

Anodic reoxidation of ultrathin Si3N4 film in deionized (DI) water followed by rapid thermal annealing (RTA) in N2 (ANO) was for the first time studied in this work. The Si3N4 film directly reoxidized in O2 by RTA (O2RTA) was used for comparison. It was found that the reoxidation process could significantly improve the characteristics of chemical-vapor-deposited (CVD) Si3N4 in terms of both the interface and bulk qualities. The ANO samples show lower leakage current, lower interface trap and bulk trap densities, and higher breakdown field than O2RTA of the same equivalent oxide thickness (EOT). The better electrical characteristics of ANO are due to more oxygen atoms incorporated into the Si3N4 films during the anodic reoxidation.
Deep Hole Traps Created by Gamma-Ray Irradiation of GaInP
Authors: Sung Wei-Jer , Liu Tong-Yuan , Yang Su-Lin , Huang Kai-Feng , Tseng Tseung-Yuen , Chou Fong-In , Wei Yuan-Yaw
Published: October 2002

Deep hole traps created by gamma-ray irradiation of Al/GaInP Schottky diodes grown by metal-organic chemical vapor deposition (MOCVD) were studied by using deep level transient spectroscopy (DLTS) technique. Two distinct deep hole traps, A and B, were observed in the irradiated GaInP samples. According to the analysis of trap concentration in various samples, the trap A is verified as a bulk defect located at 0.29 eV above the valance band. Meanwhile, the trap B is an interface state originated from the junctions of Al/Mg-doped GaInP contacts.
Anisotropy in Magnetic Hysteresis for (Cu,V)Sr2Can-1CunO2n+3 (n=3, 4) Superconductors
Authors: Yu Shan , Zhigadlo Nikolai Dmitrievich , Takayama-Muromachi Eiji
Published: October 2002

We determined anisotropies of superconducting properties of high-T
c superconductors, (Cu,V)Sr2Ca
n-1Cu
n
O2n+3 [(Cu,V)-12(n-1)n; n=3, 4]. The samples were grain aligned under a high magnetic field of 7 T. Two kinds of magnetic hysteresis data, one with the magnetic field parallel to the c-axis (ΔM
||
) and the other with the magnetic field perpendicular to the c-axis (ΔM
⊥), were measured for the aligned samples. In both phases, the anisotropy factors R=(ΔM
||
)/(ΔM
⊥) decrease to values less than unity with increasing temperature and increasing magnetic field, i.e., ΔM
||
<ΔM
⊥ for a high temperature and/or high magnetic field region. Two sets of values were calculated for critical current density and irreversibility field, corresponding to ΔM
||
and ΔM
⊥. Anisotropies of these properties are discussed in terms of vortex structures with the magnetic field parallel and perpendicular to the c-axis.
Orientation-dependent Magneto-Clapeyron Equation
Authors: Kimura Tsunehisa
Published: October 2002

Effects of an applied magnetic field on the phase transition temperature of anisotropic diamagnetic materials including crystals and liquid crystals were studied on the basis of a simple extension of the Clapeyron equation. The transition temperature was expressed as a function of the orientation of the material with respect to the applied field. Calculations for the melting points of the trans azobenzene crystal and a superdrawn polyethylene fiber showed that the shift of the melting point due to the orientation was of the order of 10-5–10-4 K. Larger shifts (∼ 10-3 K) were expected in the case of anisotropic-isotropic transitions in liquid crystal systems where their transition enthalpy is smaller by one to two orders than that for solid-liquid transitions.
Fabrication of Perovskite Manganite (La,Sr)MnO3 Thin Films by Chemical Solution Deposition and Their Low-Field Magnetoresistance Properties at Room Temperature
Authors: Tanaka Kiyotaka , Okamura Soichiro , Shiosaki Tadashi
Published: October 2002

(La,Sr)MnO3 (LSMO) thin films were fabricated on (100)SrTiO3 single crystal substrates by the chemical solution deposition (CSD) process and their properties were evaluated at room temperature. All the films sintered at the temperatures ranging from 600 to 900°C were crystallized into perovskite single-phase LSMO with random orientation. The resistivity of the films at zero magnetic field decreased with the elevation of sintering temperature and reached 19 mΩcm in the film sintered at 900°C. The saturation magnetization of the films increased with the elevation of sintering temperature and reached 410 emu/cm3 in the film sintered at 900°C. The LSMO thin films sintered above 700°C had a distinct grain structure and exhibited double peaks in magnetoresistance (MR) curves. The top values of the MR curves increased with the elevation of sintering temperature and the difference between the top value and minimum one at a magnetic field of 500 Oe was 0.57% in the film sintered at 900°C.
Study of a Holographic Grating based on Dye-Doped Polymer-Ball-Type Polymer-Dispersed Liquid Crystal Films
Authors: Fuh Andy Ying-Guey , Lee Chia-Rong , Ho Ya-Hui , Mo Ting-Shan , Liu Pin-Miao
Published: October 2002

This study investigates the characteristics of the holographic grating formed in polymer-ball-type polymer-dispersed-liquid crystal (PBT-PDLC) films, doped with a diazo dye (G206). A dye-doped PBT-PDLC sample was fabricated, and used to write a holographic grating. Experimental results indicated that the grating had memory of the polarization of the writing beams. This polarization memory effect was inerasable if the sample was heated to the isotropic phase, and then cooled down to room temperature. Based on these observations, we believe that the memory of the grating effect does not relate to the intrinsic memory in the transmission versus applied voltage curve of PBT-PDLC films, which is thermally erasable. Rather, the effect is due to a feature of the grating, resulting from the reorientation of the liquid crystals through their interaction with the photo-induced adsorption of the doped dyes on the surface of the polymer balls.
Role of Ga3+ in SrTiO3:Pr,Ga Phosphor Studied through Its Aging Behavior under Low-Dose Electron Irradiation
Authors: Shin Sang Hoon , Jeon Duk Young , Suh Kyung Soo
Published: October 2002

We have studied the role of Ga3+ ions in SrTiO3:Pr,Ga phosphor throuth its aging behavior. At the early stage of electron irradiation with a charge dose rate of 100 µC/cm2 per second, the cathodoluminescence (CL) intensity of SrTiO3:Pr,Ga phosphor drops. On the other hand, it is found that SrTiO3:Pr,Ga phosphor shows different aging characteristics from SrTiO3:Pr as the electron irradiation proceeds. However, from a reduced beam current density irradiation with a charge dose rate of 1.2 µC/cm2 per second, it is determined that the Ga3+ ion acts as a hole-keeping center and increases the luminescence by providing a hole to the activator Pr3+ ion in the luminescence process.
Dielectric Investigation of [(SrTiO3)6(BaTiO3)6]2 Multilayer Capacitor
Authors: Yoneda Yasuhiro , Sakaue Kiyoshi , Terauchi Hikaru
Published: October 2002

Ferroelectric properties depend on the thickness of films. To observe the dielectric properties of ultrathin ferroelectric thin films, a [(SrTiO3)6(BaTiO3)6]2 multilayer thin film with a total thickness of 96 Å was investigated. X-ray diffraction confirmed that it was a well-epitaxial and highly strained film with a perovskite structure. The multilayer film exhibited ferroelectric behavior at room temperature and dielectric behavior above 250°C. However, the dielectric properties of this multilayer film were different from those of the (Ba,Sr)TiO3 bulk mixture crystals and seemed to be influenced by the size effect and ferroelectric coupling across BaTiO3 layers.
Doping Mechanisms of La, Y and Excess Oxygen in PbWO4
Authors: Li Wen-Sheng , Tang Tong B. , Huang Hong-Wei , Feng Xi-Qi
Published: October 2002

The doping mechanisms of lead tungstate doped with a rare earth (Re=La or Y) and with or without excess oxygen have been clarified on the basis of dielectric spectroscopic evidence. This tungstate has emerged as an important scintillation material for a high-energy-particle detector, and its radiation hardness may be enhanced by such doping or by oxygen annealing. We studied the dielectric relaxation induced by Re impurity, which we attribute to the defect complexes [2(RePb
3+)•–(VPb)′′]. However, the two Re differ in certain respects: La suppresses dc conductivity, yet Y increases it. This difference can be explained by our proposal that in the lattice whereas La3+ ions all substitute for Pb2+, some Y3+ occupy interstitial sites as well. We have also identified a new kind of dielectric relaxation in Re-doped crystals subjected to excessive annealing in oxygen, and attributed it to [2(RePb
3+)•–(Oi
2-)′′].
Ferroelectric and Pyroelectric Properties of Ba1-xPbxTi0.91(Hf0.5,Zr0.5)0.09O3 Thin Films
Authors: Kakemoto Hirofumi , Kakimoto Ken-ichi , Fujita Shigetaka , Masuda Yoichiro , Wada Satoshi , Tsurumi Takaaki
Published: October 2002

The Ba1-x
Pb
x
Ti0.91(Hf0.5,Zr0.5)0.09O3 (x=0, 0.03) thin films on Nb-doped SrTiO3 (100) and (111) substrates were synthesized by the pulsed laser deposition method using fourth harmonic generated light (λ=266 nm) of Nd3+:YAG laser beam. The peaks of the pyroelectric coefficient of BaTi0.91(Hf0.5,Zr0.5)0.09O3 thin film on Nb doped SrTiO3 (111) were observed at 85.6°C, 100.8°C and 103.6°C. The cross-sectional images of the this thin film on Nb doped SrTiO3 (100) substrate were observed by high resolution transmission electron microscopy. The X-ray diffraction measurements at room temperature of the Ba0.97Pb0.03Ti0.91(Hf0.5,Zr0.5)0.09O3 thin film on the Nb-doped SrTiO3(100) substrate were carried out, and it showed [100]/[001] preference orientation with satellite peaks. This thin film on the Nb-doped SrTiO3 (111) substrate exhibited ferroelectric properties.
Kinetic Study of the Rotator Phase Transition in an n-Alkane (n-C25H52) Crystal: Nucleation and Growth on Cooling
Authors: Nozaki Koji , Munekane Masanao , Hikosaka Masamichi , Yamamoto Takashi
Published: October 2002

The kinetics in the solid-solid phase transition of ann-alkane crystal, which is the so-called `rotator phase transition', is investigated by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and optical microscopy. Primary nucleation rate in the transition on cooling is measured by using droplet crystals, while growth rate is measured by using a single crystal, independently. The growth rate increases rapidly with the increase in the degree of supercooling compared with that on heating. A significant asymmetric behavior of the temperature dependence of the growth rate is observed between temperatures above and below the transition point. The kinetic parameters, i.e., the surface free energies between two solid phases, are estimated from a combination of the primary nucleation rate and the growth rate. It is found that the primary nucleation in the rotator phase transition ofn-alkane droplet on cooling is a homogeneous one. Furthermore, the surface free energies on cooling are slightly smaller than those on heating, and this seems to induce the asymmetric behavior of the growth rate.
Eutectic α-Fe2Si5 and ε-FeSi Formed in an Arc Furnace Showed a Three-Layer Structure
Authors: Takigawa Yasuo , Tode Mayumi , Ohmukai Masato , Kurosawa Kou , Noguchi Satoru
Published: October 2002

We melted stiochiometrically mixed (FeSi2) Fe and Si powders in a tri-arc furnace in an argon atmosphere and allowed them to cool naturally to room temperature and obtained a eutectic crystal of ε-phase embedded in α-phase of iron silicide. We determined three kinds of layers: the grain size of ε-phase was more than 100 µm, about 50 µm and less than 1 µm. Only the first layer did not contain α-phase. The interfaces between the layers were so definite that the grain size was changed abruptly between the layers. When the crystal was annealed in vacuum at 1150 K for 70 h, the last two layers were transformed to β-FeSi2 but the bottom layer containing only ε-phase was not changed by the thermal treatment.
Dependence of Composition Distribution of NiTi Sputtered Films on Ar Gas Pressure
Authors: Yamazaki Toshinari , Yoshizawa Toshio , Takada Hisatoshi , Takeda Fumio , Kikuta Toshio , Nakatani Noriyuki , Yamabuchi Tatsuo
Published: October 2002

The composition distribution of NiTi films formed by dc magnetron sputtering under various conditions was investigated and analyzed using a simulation, where the angular distribution of the sputtered atoms as well as the scattering by Ar gas were considered. The Ti concentration under a low pressure was lower than that in the target, and was higher at the substrate center than at the positions facing the erosion ring. The nonuniformity of the composition was ascribed to the difference between the angular distributions of Ni and Ti. The Ti concentration increased as the pressure increased. This occurs mainly because the deficiency in Ti atoms as an effect of the difference in the angular distributions is suppressed by the scattering. The difference in mass between Ni and Ti is also an important factor in the determination of the composition distribution.
Effect of Post-Plasma Treatment Time on the Properties of Low Dielectric Fluorinated Amorphous Carbon Films
Authors: Yang Sung-Hoon , Park Jong-Wan
Published: October 2002

The effect of plasma treatment time on the properties of fluorinated amorphous carbon (a-C:F) films was investigated. Fluorinated amorphous carbon films were prepared by using electron cyclotron resonance chemical vapor deposition (ECRCVD). The post-plasma treatment of the a-C:F films was carried out using H2 plasma with various plasma treatment times after deposition without vacuum breaking. As the plasma treatment time increased, the fluorine concentration of the film surface decreased. The refractive index and the dielectric constant remain nearly constant. The surface energy increases sharply during the first 5 s of plasma treatment. When the plasma treatment was employed, the leakage current density of a-C:F film becomes one order lower than that of the untreated film. Through this study, it was found that the plasma treatment of a-C:F films induced the surface more reactive and affected the fluorine concentration of the surface, the structure of chemical bonding and electric properties.
Optical Second Harmonic Spectroscopy of the Ge-Oxide/Ge(111) Interface
Authors: Ohashi Hiroaki , Sano Haruyuki , Mizutani Goro
Published: October 2002

We have measured reflected optical second harmonic (SH) intensity from the Ge-oxide/Ge(111) interface as a function of the incident photon energy ranging from \hbarω=1.10 to 1.65 eV. The oxide layers were formed either by oxidizing a Ge(111) substrate in pure oxygen gas at 823 K or by oxidizing a Ge(111) substrate in dry air at room temperature. We observed that SH spectra from the thermally oxidized film have resonant peaks around \hbarω=1.16 eV and 1.48 eV. We suggest that the peaks at \hbarω=1.16 eV and 1.48 eV originate from the one-photon resonance of the electronic level of the GeO2/Ge(111) interface and the two-photon resonance of the electronic level of bulk germanium, respectively.
Structural Characterization of High-Quality ZnS Epitaxial Layers Grown on GaAs Substrates by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Nakamura Seiji , Takagimoto Shinsuke , Ando Tsuyoshi , Yamada Yoichi , Taguchi Tsunemasa
Published: October 2002

Structural properties of ZnS epitaxial layers grown on GaAs (001) substrates by low-pressure metalorganic chemical vapor deposition have been studied by high-resolution X-ray diffraction, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The full width at half maximum (FWHM) of the ZnS (004) diffraction curves decreased with increasing layer thickness and the value determined for an 8-µm-thick ZnS layer was as narrow as 30 arcsec. The decrease in FWHM indicated the improvement of the crystalline uniformity of the ZnS epitaxial layer. Cross-sectional TEM measurement enabled us to observe a large number of stacking faults and microtwins in the vicinity of the interface between ZnS and GaAs. In addition, the decrease in the stacking-fault density with increasing layer thickness was observed, and the stacking-fault density for a 6-µm-thick ZnS surface was estimated to be about 5×107 cm-2. On the other hand, a large number of rhombus-shaped holes were observed on the ZnS surface. An increase in the size and a decrease in the density of these holes were observed with increasing layer thickness. Hence, the root-mean-square value of ZnS surface roughness increased with increasing layer thickness. Cross-sectional AFM measurement indicated that the rhombus-shaped holes on the ZnS surface had a reverse-pyramidal shape formed by four symmetric {113} facets.
Improvement of Electrical Property of Sol–Gel-Derived Lead Zirconate Titanate Thin Films by Multiple Rapid Thermal Annealing
Authors: Wang Xusheng , Ishiwara Hiroshi
Published: October 2002

Ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films were fabricated by sol–gel and multiple rapid thermal annealing (MRTA) techniques on Pt/Ti/SiO2/Si(100) substrates. The perovskite-phase PZT thin films were formed and grown preferentially along the (111) direction. Higher degree of orientation, higher content of perovskite phase and smaller grain size were obtained in the PZT thin films prepared by MRTA compared with that by normal RTA. The typical values of remnant polarization and leakage current density derived by MRTA were about 14.5 µC/cm2 and 9.1×10-8 A/cm2, which were lower than those derived by conventional RTA by about 17% and 100%, respectively.
Quantitative Analysis of Hydrogen in Amorphous Films of Hydrogenated Carbon Nitride
Authors: Ohkawara Yoshiaki , Ohshio Shigeo , Suzuki Tsuneo , Ito Haruhiko , Yatsui Kiyoshi , Saitoh Hidetoshi
Published: October 2002

The amorphous phase of hydrogenated carbon nitride, a-CN
x
:H (0 ≦x ≦1), films may have clusters consisting of a mixture of sp
2- and sp
3-hybridized materials with cluster sizes of 0.2–2 nm. The hydrogen termination limits the size of the carbon and carbon nitride clusters. It also influences the mechanical properties of the sample. In this experiment, the relationship between the hydrogen content and the mechanical properties of carbon and related materials was investigated using elastic recoil detection analysis (ERDA), nanoindentation techniques and Raman spectroscopy. The samples were classified into three categories of hardness: mechanically soft a-CN
x
:H (hardness: 1–8 GPa), mechanically hard a-CN
x
:H (8–30 GPa) and hard hydrogenated amorphous carbon (a-C:H) (more than 30 GPa). The hydrogen contents of the sample were 10–50 at.%, 5–40 at.%, and less than 3 at.% for soft a-CN
x
:H, hard a-CN
x
:H and hard a-C:H, respectively.
Field Emission Property of Al:ZnO Whiskers Modified by Amorphous Carbon and Related Films
Authors: Ohkawara Yoshiaki , Naijo Takanori , Washio Tsukasa , Ohshio Shigeo , Ito Haruhiko , Saitoh Hidetoshi
Published: October 2002

A new type of ceramic field emitter was designed using the chemical vapor deposition process. There are two major features of the materials used to construct the emitter: an electrically conductive Al:ZnO whisker with an extremely sharp tip and amorphous carbon and related coating materials with a relatively low electron affinity at the tip region. Some aggregations of whiskers were synthesized as a function of the radius of curvature at the whisker tip. In addition, four types of amorphous coatings were provided for this experiment: C:H, CN
x
:H with C–H and N–H terminations, CN
x
:H with N–H termination and CN
x
films. The field emission property was influenced not only by the radius of curvature at the tip but also by the termination structure of the amorphous carbon and related films.
Effects of Substrate Pretreatments and Catalyst Applications on Si–C–N Films and Nanotube Formations
Authors: Chang Hui Lin , Kuo Cheng Tzu
Published: October 2002

The Si–C–N films were synthesized on Si substrates by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, H2 and N2 as the source gases. Metal coating on Si columns were placed around the specimen and acted as catalyst and additional source of Si. Some of the Si substrates were mechanically polished or chemically etched with HF–KIO3–H2O solutions to obtain different surface roughness before film depositions. Effects of the substrate pretreatment and the action of catalysts on surface morphologies, compositions, band structure, field emission of the films were examined. Nanotubes or nanowires structures were found for films deposited on no-treatment substrate using Fe, Co and Pt catalysts. However, chemical etching substrate can enhance formation of crystals and film nucleation with or without the addition of catalyst. This was the first work to demonstrate the possibility of fabricating the Si–C–N nanotubes through use of the catalysts and by controlling the deposition conditions by MPCVD. Under the present deposition conditions and by using Fe catalyst, the lowest turn-on voltage of the films can be as low as 1.3 V/µm, while the corresponding emission current density at field strength of 20 V/µm can go beyond 2000 µA/cm2.
Carrier Injection/Transport Characteristics of Photochromic Diarylethene Film
Authors: Taniguchi Akira , Tsujioka Tsuyoshi , Hamada Yuji , Shibata Kenichi , Fuyuki Takashi
Published: October 2002

Photochromic diarylethenes with electric carrier (hole) controlling ability for nondestructive readout were investigated. The ionization potential of the photostationary colored diarylethene films was around 5.7–5.8 eV, irrespective of differences in their molecular structures. Good hole injection/transport characteristics were observed for the colored films of diarylethenes with triphenylamine groups.
Analysis of 235U Fission by Selective Channel Scission Model
Authors: Ohta Masayuki , Matsunaka Masayuki , Takahashi Akito
Published: October 2002

Until now, it has not been clarified why the fission product of 235U induced by thermal neutrons shows two peaks. It is possible to explain this problem by the present idea of channel-dependent fission barrier introduced by the selective channel scission (SCS) model. Fission of 235U induced by thermal neutrons was analyzed theoretically by the SCS model. Using the SCS model the fission barrier of each scission channel is calculated. If the excited energy of the nucleus is more than some of the channel-dependent fission barriers, those channels can be opened to achieve fission. It is understood that the distribution of fission barriers results in two peaks for 236U. Hence, the distribution of fission products from thermal neutron fission of 235U also gives two peaks. It is known that fission products are almost stable isotopes at the peaks. If the nucleus can be excited at a lower energy level than that by thermal neutrons, cleaner fission of 235U is possible.
A Theory of Polarization Reversals in Ferroelectrics near the Morphotropic Phase Boundary of Perovskite-Type Oxides
Authors: Iwata Makoto , Orihara Hiroshi , Ishibashi Yoshihiro
Published: October 2002

A theory of polarization reversals near the morphotropic phase boundary in perovskite-type oxides was developed on the basis of the Landau-Khalatnikov equation of motion. It was found that for a weak electric field, the polarization reversal takes place through a rotation of polarization, and it becomes faster upon approaching the morphotropic phase boundary. It was clarified that a saddle point in the free energy as a function of polarization plays an important role in this type of polarization reversal.
NO Gas Sensor Based on Surface Photovoltage System Fabricated by Self-Ordered Hexagonal Mesoporous Silicate Film
Authors: Zhou Hao-Shen , Yamada Takeo , Asai Keisuke , Honma Itaru , Uchida Hidekazu , Katsube Teruaki
Published: October 2002

The first reported NO gas sensor based on a surface photovoltage (SPV) semiconductor device system is fabricated with a metal/SiO2(self-ordered hexagonal mesoporous)/Si3N4/SiO2/Si structure (MIS). A size controlled silicate mesoporous film is successfully synthesized by spin coating on a Si3N4/SiO2/Si silicon wafer using poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (Pluronic P123=EO20PO70EO20) triblock copolymers as a template. The characteristics of the mesoporous films were investigated by X-ray diffraction (XRD) and transmission electron microscope (TEM). The sensing properties of the self-ordered hexagonal mesoporous SPV system have been investigated by repeated exposure to NO gas and air. The changes in the average value and phase of the AC photocurrent (Iph) have been observed after exposure of the films to 100 ppm NO gas. The response of the alternative photocurrent results from the physical adsorption and chemical interaction between detected NO gases and the self-ordered hexagonal mesoporous film.
Discharge Property of Resin Particles Refined by Silica Particles
Authors: Makabe Akira , Narita Miyuki , Makino Kazutaka , Hamada Fumio
Published: October 2002

The discharge property in the solid state has been utilized for ceramics processing and printer technology. The charge of particles has to be controlled in these fields because it affects the particle filling process in ceramics processing and the print quality of a printer. Fine silica particles are used to refine ceramics or resin particles for optimization of flowability, the discharge ability and the wettability. However, it is difficult to understand these properties, because critical factors “affecting” for these properties have not been elucidated yet. For example, the discharge property has not been examined in connection with the surface chemical structure of particles. In this study, we report the electron accepting or electron donating ability of chemicals and find that the discharge property is significantly influenced by that ability. Work function values are measured for polystyrene resin particles covered by different kinds of silica particles. In addition, we suggest a simple evaluation method for solid discharge through the measuring of pH in solution form. The relationships among the discharge, pH and work function values are examined. As a result, we arrive at some results to elucidate these phenomena.
Capacitance X-Ray Absorption Fine Structure Method using Dopant Photoionization: X-Ray Absorption Spectroscopy of ∼nm Thickness Channel in Semiconductor Devices
Authors: Masashi Ishii Masashi Ishii
Published: October 2002

A capacitance X-ray absorption fine structure (capacitance XAFS) method which implements the X-ray induced photoionization of the dopant is proposed for the local structure analysis of electrically active regions in semiconductor devices. In a semiconductor device, the X-ray absorption spectrum of a channel results from capacitance changes due to inner-shell absorption in a ∼nm thickness region below the depletion layer in spite of the high transmittance inherent in hard X-rays. The absorption signal of the proposed capacitance XAFS measurement using a Schottky barrier gate is shown to reproduce the depth modulation of the X-ray intensity. This experimental finding can be explained by the Schottky barrier theory considering the photoionization of the dopant in the ∼nm thickness channel. Accordingly, this method enables a channel to be observed with ∼nm depth resolution.
Effect of Crystal Orientation on Dielectric Properties of Lead Zirconium Titanate Thin Films Prepared by Reactive RF-Sputtering
Authors: Kalpat Sriram , Du X. , Abothu Issac R. , Akiba Akira , Goto Hiroshi , Uchino Kenji
Published: October 2002

Theoretical calculations based on phenomenology of ferroelectrics have been previously reported for lead zirconium titanate (PZT) system. This paper offers an experimental comparison of the crystal orientation dependence of dielectric properties for PZT thin films grown using reactive RF-sputtering. Highly oriented PZT thin films with a rhombohedral composition have been grown in different orientations using selective rapid thermal annealing cycles. The PZT(100) oriented films showed larger dielectric constant and loss compared to PZT(111) films. The PZT(100) films possessed sharp square-like hysteresis loops indicating a instantaneous switching of domains at the coercive field whereas the PZT(111) films showed smooth hysteresis loops as expected from our phenomenological calculations.
Emittance Measurement of Axisymmetric High-Current Electron Beam Confined by a Longitudinal Magnetic Field
Authors: Yasushi Hayashi Yasushi Hayashi , Akitoshi Okino Akitoshi Okino , Eiki Hotta Eiki Hotta
Published: October 2002

We propose a method for emittance measurement of an axisymmetric high-current electron beam confined by a longitudinal magnetic field. In this method, the beam current is measured by a multi-layer Faraday cup to obtain the radial beam current profile using Abel inversion. Based on the theory of a beam in a uniform focusing channel, the transverse electron temperature is uniquely defined by the shape of the current density profile. Therefore, measuring the current density profile enables the determination of the beam emittance. Because the method does not require to use slits, the measurement has been markedly simplified. The method has been adopted to a test beam. The emittance is found to be 20.2π mm·mrad, which basically agrees with that obtained by a slit-slit method.
Advanced Micro-Lithography Process for i-line Lithography
Authors: Ishibashi Takeo , Toyoshima Toshiyuki , Kanda Takashi , Yasuda Naoki , Katayama Keiichi , Tanaka Mikihiro , Tanaka Hatsuyuki
Published: October 2002

In our previous paper [Jpn. J. Appl. Phys. 40 (2001) 419], we reported the development of an advanced micro-lithographic process for producing 0.1 µm contact holes by KrF excimer laser (248 nm) lithography. This chemical shrinkage technology, called resolution enhancement lithography assisted by chemical shrink (RELACS), utilizes the cross-linking reaction catalyzed by the acid component remaining in a predefined resist pattern. We report herein the results of the application of RELACS to i-line (365 nm) lithography. The properties of RELACS for i-line lithography were very different from those for KrF lithography. This is due to the difference in chemical mechanism between i-line and KrF resists. The characteristics of the application of RELACS to i-line lithography were studied by conducting basic experiments on the addition of a photo-acid generator (PAG) to an i-line resist and investigating the property of the cross-linking reactions involved in the pre-doping of various acids to RELACS film. Finally, we optimized RELACS materials to match i-line resist and realized the fabrication of contact holes less than 0.2 µm diameter by i-line lithography.
Nanoprojection-Shaped Silicon Field Emitter as Relativistic-Electron-Beam Source for Pumping KrF Lasers
Authors: Okuda Isao , Takahashi Eiichi , Owadano Yoshiro
Published: October 2002

The relativistic-electron-beam (e-beam) generation initiated by field emission from etched-silicon wafers with nanometer-scale needle-like projections on the surfaces (5–15 nm tip radius, 6 µm height, and 106–109/cm2 surface concentration) is reported. The time required for cathode-plasma formation is evaluated based on observed diode perveances. The application of the silicon emitters as e-beam sources for pumping KrF lasers is discussed.
Slit Structure as a Countermeasure for the Thermal Deformation of a Metal Mask
Authors: Yamazaki Toshinari , Yoshizawa Toshio , Yamabuchi Tatsuo , Hirobayashi Shigeki , Kikuta Toshio , Nakatani Noriyuki , Mizuguchi Takashi
Published: October 2002

A metal mask used for the pattern formation of sputtered films is sometimes deformed during film deposition, because its temperature increases during deposition. In this study, a slit structure as a countermeasure for the deformation is proposed. The mask investigated is made of 0.3-mm-thick stainless steel and is composed of a frame with many beams running inside the frame. The slits in the structure absorb the thermal expansion of the beams, which results in the relaxation of thermal stress in the beams. The relaxation of the stress is analyzed using the finite element method as well as the theory of beam bending. It was experimentally confirmed that a mask furnished with well-designed slits was not deformed.
Property of Lead Zirconate Titanate Actuator Manufactured with Microwave Sintering Process
Authors: Takahashi Hirofumi , Kato Kazuaki , Qiu Jinhao , Tani Junji
Published: October 2002

In this study, the application of a 28 GHz microwave sintering process was attempted for the sintering of lead zirconate titanate (PZT) materials and sintering conditions were thoroughly investigated. Microwave sintering offers advantages over conventional technologies, such as repression of grain growth due to rapid heating, and improvement of microstructure due to internal heating. As a result, the sintering time of PZT materials using a 28 GHz microwave was reduced to 1/10 of the time needed for the conventional process, with improvement of material properties such as the electromechanical coupling factor and dielectric constant. Moreover, the performance of actuators fabricated by the microwave sintering process was evaluated in a vibration test and compared with the performance of actuators fabricated using conventional technology; the performance superiority was confirmed.
X-Ray Analysis of the Layer Structure in the Chiral Smectic Phase Showing V-shaped Switching
Authors: Takanishi Yoichi , Ogasawara Toyokazu , Ishikawa Ken , Takezoe Hideo , Takahashi Yumiko , Iida Atsuo
Published: October 2002

The layer structure of the chiral smectic phase showing V-shaped switching was investigated using the X-ray diffraction method. In thin planar cells of a three-component mixture in which V-shaped switching was first reported, the chevron layer structure was confirmed. The layer structure almost kept chevron even in the application of an electric field, and additional small diffraction peaks suggesting the existence of a substructure during V-shaped switching were observed. Preliminary time-resolved results are also reported.
Tunnel-type Giant Magnetoresisitance in Co–Al–Ta–O Insulated Granular System
Authors: Yonemura Mitsuharu , Naga Shoichi , Kamei Kazuhito
Published: October 2002

We have investigated the tunnel-type giant magnetoresistance (TMR), the related magnetic and electric properties and the microstructure of Co–Al–Ta–O granular thin films which were prepared by the reactive sputter-deposition technique with oxygen and argon. The TMR attained a maximum value of 12.5% at room temperature under a magnetic field of 1 T for Co40Al13Ta3O44 films. The MR ratio is the largest in a granular system similar to Co–Al–O. During the sputtering, O2 gas flow was introduced at 2.2 sccm into the chamber filled with Ar at a total pressure higher than 1×10-4 Torr. The specific electric resistance of the film that showed the maximum TMR is 1.46×105 µΩ·cm. Ta forms an oxide compound similar to Ta2O5 in the insulator matrix. The effect of Ta addition on the TMR appears at around 2.8 at.%. The MR ratio increases with an increase of the fraction of fcc-Co, accompanying the decrease of the Co–O fraction and the decrease in ferromagnetic interaction between Co particles. The specimen that shows large TMR consists of nanometer-sized Co particles which are completely isolated by amorphous Al2O3 and Ta2O5 intergranular layers. The standard free energy of oxidation of Co, Al and Ta may play an important role in the formation of the microstructure of Co–Al–Ta–O granular films and in TMR improvement.
Lattice Thermal Conduction across Disordered Interfaces
Authors: Nishio Yoshimasa , Teraki Junichi , Hirano Tohru
Published: October 2002

Lattice thermal conduction across the disordered interfaces in multilayered materials has been studied. The model consists of an array of slabs of scattering centers (mass defects) embedded in a host material. The layered distribution of the mass defects can be characterized by the structure factor in the scattering probability due to the slabs. We assume that the physical arrangement of the scattering centers within a slab is quenched disorder and is approximately described by the structure factor of a homogeneous liquid interacting via hard sphere pair potentials. By varying the packing fraction of the scattering centers from low density to high density, the calculated thermal conductivity exhibits the minimum which reflects the local structural organization of the scattering centers. The relation to thermoelectric energy conversion has also been discussed.
Stable Patterns of Vortices in Rotating Superfluid Helium
Authors: Nam Sang-Tack
Published: October 2002

We obtain stable configurations of many vortices in superfluid helium in a rotating spherical vessel and a drop using the Onsager-Feynman model and the method of free energy minimization, and compare the equilibrium configurations of vortices in a rotating spherical vessel with known ones in a rotating cylindrical vessel. As a result of the comparison, the critical angular velocity of the rotating spherical vessel is shown to be larger than that of the rotating cylindrical vessel for the same vortex numbers in the stable vortex configuration.
The Loss Kinetics of Substitutional Carbon in Si1-xCx Regrown by Solid Phase Epitaxy
Authors: Kim Yong Jeong , Kim Tae-Joon , Kim Tae-Kyung , Park Byungwoo , Song Jong Han
Published: October 2002

Epitaxial layers of Si1-x
C
x
(x=0.016) were synthesized using ion implantation and solid phase epitaxy (SPE), and the loss kinetics of substitutional carbon was investigated. As annealing temperature and time increase, more carbon atoms were found to diffuse from substitutional to interstitial sites. The activation energy for the loss of substitutional carbon into interstitial sites was obtained over the temperature range, 700–1040°C, using both high-resolution X-ray diffraction (HR-XRD) and Fourier transform infrared spectroscopy (FTIR). Both methods yielded similar activation energies (∼3 eV) for the loss kinetics. In addition, SPE layers regrown by rapid thermal annealing (RTA) were shown to have better crystalline quality than those regrown by furnace annealing.
Molecular Orientation and Aggregation of Titanyl Phthalocyanine Molecules on Graphite Substrates: Effects of Surface Topography of the Substrate
Authors: Kera Satoshi , Okudaira Koji K. , Harada Yoshiya , Ueno Nobuo
Published: October 2002

Penning ionization electron spectroscopy (PIES) was used to investigate the effects of crystallographic inperfection of the substrate surface on organic ultrathin-film growth. For titanyl phthalocyanine (OTiPc) evaporated on graphite, it was found that the molecular orientation and aggregation in the film depend significantly on the type of graphite substrate. On a highly oriented pyrolytic graphite (HOPG), OTiPc film prepared by 1-monolayer-equivalence (MLE) deposition consists of islands of double layers, while on Grafoil, the molecules do not aggregate as on the HOPG, and form a monolayer. This large difference originated from the surface topography of the two graphite substrates.
Characteristics of Electron Pump Circuits Using Silicon Multiple Tunnel Junctions
Authors: Altebaeumer Thomas , Ahmed Haroon
Published: October 2002

Electron pumps based on multiple tunnel junctions have been realized in silicon using highly doped nanowires in silicon-on-insulator material. The electron pump characteristics show a clear transfer of the pattern of Coulomb blockade oscillations to one of a pumping action. Furthermore, the pump current tends to scale linearly with the frequency. The results can be explained by a pumping mechanism in asymmetric multiple tunnel junctions. These devices allow sufficient control of electron packets which are potentially useful as basic building blocks of silicon-based binary-decision-diagram logic circuits.
Towards the Origin of the Shear Force in Near-Field Microscopy
Authors: Schüttler Martin , Leuschner Mirko , Lippitz Markus , Rühle Wolfgang W. , Giessen Harald
Published: October 2002

The shear force from a gold or a graphite sample acting on an approaching near-field optical probe is studied in detail. The adiabatic and dissipative contributions to the force are clearly distinguished by monitoring the amplitude as well as the phase of the tip vibration when the tip approaches the surfaces. We also take into account that not only the damping and the resonance frequency but also the mass of the system changes when the tip approaches the surface. The relative strength of the contributions to the force varies differently but characteristically with the distance of the two samples, starting at a much larger distance in the case of graphite. The adiabatic contribution is larger in the case of the gold sample. Measurements at various temperatures are performed using the gold sample, showing a dependence of the shear force on the varying conditions.
Analysis of Exploding Plasma Behavior in a Dipole Magnetic Field
Authors: Takanobu Muranaka Takanobu Muranaka , Hideyuki Uchimura Hideyuki Uchimura , Hideki Nakashima Hideki Nakashima , Yuri P. Zakharov Yuri P. Zakharov , Sergey A. Nikitin Sergey A. Nikitin , Arnold G. Ponomarenko Arnold G. Ponomarenko
Published: October 2002

Numerical analyses on plasma behaviors in a dipole magnetic field are performed using a three-dimensional (3D) hybrid code. Results are compared with the experimental data and magnetohydrodynamics (MHD) analysis. Dependence of plasma expansion on initial plasma energy and location are discussed by temporal evolutions of plasma position and magnetic field strength. An overall good agreement in the expansion behavior of plasmas among these results is found. The asymmetrical shape of the expanding plasma in the cross-field direction is also noticed, and the reason for this is discussed. For future engineering applications, these results will be useful in designing an optimal configuration of the magnetic thrust chamber for laser fusion rockets, and for studying the effective explosive methods for protecting the earth from collisions by asteroids or comets.
Polarities of Electromagnetic-Wave Modes in a Magnetoplasma-Filled Cylindrical Waveguide
Authors: Ding Zhenfeng , Liu Xufeng , Ma Tengcai
Published: October 2002

Polarities of several ultra-low-electromagnetic-wave modes propagating in a magnetoplasma-filled cylindrical waveguide under typical conditions are studied. Analytical and numerical results show that the polarity of a wave mode determined using a conventional propagation factor is reasonable only in some limited parameter regions, and thus must be analyzed using rotational direction of the resultant transverse components of an electromagnetic-wave electric field along the force line of an external magnetic field. EHp modes appearing in the range of ωpe>ω are physical dominant right-hand polarized modes.
Quantum Chemical Study on Decomposition and Polymer Deposition in Perfluorocarbon Plasmas: Molecular Orbital Calculations of Excited States of Perfluorocarbons
Authors: Nakamura Toshihiro , Motomura Hideki , Tachibana Kunihide
Published: October 2002

Electronic excited states of various perfluorocarbons were investigated using an ab initio molecular orbital calculation. The chemical reactions via the excited states were also predicted from the antibonding characteristics of the molecular orbitals concerned and the first-order derivative of the potential surface of the excited state. In marked contrast to saturated perfluorocarbons, unsaturated perfluorocarbons can be easily excited to the lowest triplet state with a π–π* transition, generating biradicals and subsequently leading to polymerization. In addition to the conventionally used perfluorocarbons, the possibility of two-double-bonded, one-triple-bonded and aromatic perfluorocarbons for application to plasma processing was examined on the basis of quantum chemistry. The use of these novel types of fluorocarbon is predicted to be promising for chemical vapor deposition (CVD) of low dielectric constant interlayer films and etching with high selectivity of SiO2 to Si and Si3N4 because of the excellent potential shown by them to yield a high polymerization and deposition rate.
Photovoltaic Characteristics of Phthalocyanine-Polysilane Composite Films
Authors: Haga Yutaka , Harada Yuto
Published: October 2002

Poly[p-(methylphenylsilanylene)anthrylene] (PMPSA) which introduced anthracene into the Si–Si backbone structure of poly(methylphenylsilanylene) (PMPS) was synthesized. Schottky barrier photovoltaic cells consisting of semitransparent aluminum and phthalocyanine (H2Pc) dispersed in PMPSA were fabricated (H2Pc-PMPSA). The effects of a binder polymer and annealing of PMPSA on the photovoltaic characteristics were investigated. Since the conductivity of H2Pc-PMPSA composite films increases by the introduction of anthracene and the annealing, the photovoltaic property of H2Pc-PMPSA improves markedly. It is found that the power conversion efficiency becomes a maximum for H2Pc-PMPSA with a copolymerization ratio (1:1) at the annealing temperature of 160°C for 2 h. The photovoltaic parameters have the following values: the power conversion efficiency η is 4.42%, the fill factor F.F. is 0.30, the open circuit voltage V
oc is 0.84 V and the short circuit photocurrent J
sc is 0.71 µA/cm2. Furthermore, the carrier transport mechanisms of H2Pc-PMPSA composite films are discussed.
Effect of Lithium Perchlorate Doping and Prebiasing on Electrical Conduction of Molecularly Doped Poly (N-vinylcarbazole) Light Emitting Diode
Authors: Itoh Eiji , Yamashita Takanori , Miyairi Keiichi
Published: October 2002

The effect of lithium perchlorate (LiClO4) doping on the electrical properties of light emitting diodes prepared by spin coating from the mixtures of Alq3 and Coumarin 6 and poly (N-vinylcarbazole) was investigated in this study. We compared the current density–voltage (I–V) and the luminance–voltage (L–V) characteristics of the devices with and without LiClO4. It was found that the charge injection and the efficiency of the luminance were enhanced by doping a small amount of LiClO4. We also investigated the effect of prebiasing on the current flows and the time response of current flows (I–t curves) during the prebiasing. The current flow in the film with LiClO4 decreased in the first several 10 s, and then gradually increased and reached a constant value, whereas the current flow in the film without LiClO4 decreased monotonously during the prebiasing. The charge injection was improved by the prebiasing, and it was ascribed to the field enhancement effect due to the accumulation of ionic charges at the electrode/film interface.