bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, Structure and Superconductivity of (Hg0.65V0.35)Sr2(Ca1-xNdx)Cu2Oz
Authors: Kandyel Elsayed , Kamiyama Takashi , Asano Hajime , Amer Saiid , Abou-Sekkina Morsy
Published: October 2002

Using the sealed silica-tube method, we have successfully synthesized Hg-1212 superconductors (Hg0.65V0.35)- Sr2(Ca1-
x

Nd

x

)Cu2O

z

in the range of 0.35≤x≤0.55. Rietveld refinement on the X-ray diffraction data is carried out on the basis of tetragonal space group P4/mmm. Refined occupation factors of V in the Hg site and Nd in the Ca site as well as of oxygen at (1/2, 1/2, 0) on the (Hg, V)Oδ layer give a chemical composition (Hg0.61V0.39)Sr2(Ca0.41Nd0.59)Cu2O6.78 for the as-prepared sample with the nominal composition of (Hg0.65V0.35)Sr2(Ca0.55Nd0.45)Cu2O

z

. The variation of T
c with x and T
c enhancement after O2 annealing indicate that the compounds are in the underdoped region. The highest onset T
c of 105 K is attained in the O2-annealed sample with x=0.35.
The Influence of the Rear Mask on Copying Recorded Marks for Magnetically Induced Superresolution Disks
Authors: Koyata Takahashi Koyata Takahashi , Koji Katayama Koji Katayama
Published: October 2002

Magnetically induced superresolution (MSR) disks by double masked rear aperture detection (D-RAD) sometimes show direct transition from the initialized state to the D-RAD state in the readout power curves. Peak and trough levels of read signals for these MSR disks were measured and the states of the aperture and the rear mask during the readout were clarified. When the read field is in the erase direction, the aperture opens simultaneously with the collapse of the mark in the rear mask. When the read field is in the write direction, copying a mark from the recording layer to the readout layer starts as the mark in the recording layer overlaps the rear mask and the successive wall displacement copies the mark. The MSR with the latter mechanism was found to be very effective for eliminating crosstalk.
Properties of CsLiB6O10 and KBe2BO3F2 Crystals for Second-Harmonic Generation with Ultrashort Laser Pulses
Authors: Tiejun Zhang Tiejun Zhang , Motoki Yonemura Motoki Yonemura
Published: October 2002

We discuss and evaluate properties of C
s
L
i
B6O10 (CLBO) and KB
e2BO3F2 (KBBF) crystals for second-harmonic generation with ultrashort laser pulses. Basic properties that are determined by the first- and second-order dispersions of the refractive index are discussed, and numerical calculations, including the group-velocity mismatch are carried out. We propose a novel method that compensates for the group-velocity mismatch in order to further increase the conversion efficiency under the condition in which the duration of the second-harmonic pulse is less than that of the fundamental input pulse.
Dynamics of Photoexcited Picosecond Space-Charge Fields with Hot Electron Nonlinear Transport in DC-Biased Semi-Insulating GaAs
Authors: Kazuhide Kusakabe Kazuhide Kusakabe , Yasuo Tomita Yasuo Tomita
Published: October 2002

Picosecond transient characteristics of photocarriers and space-charge fields excited by single-shot picosecond pulses at 1.064 µ m in high-dc-biased GaAs are analyzed by means of the band transport rate equations. Numerical simulations are performed and their results are compared with approximate analytic results. In particular, the effects of hot electron nonlinear transport on the dynamics of photocarriers and space-charge fields are discussed. It is found that the application of high dc electric fields results in an increase of decay rates of photocarriers and space-charge fields and induces oscillatory behaviors in their decay dynamics under certain conditions. It is also found that the space-charge field can be enhanced considerably by the hot electron nonlinear transport and its cause is attributed to an increase of the electron temperature.
Photon Recycling Effect in Semiconductor Lasers using Low Dimensional Structures
Authors: Raj Mothi Madhan , Shigehisa Arai Shigehisa Arai , Munehisa Tamura Munehisa Tamura
Published: October 2002

The photon recycling effect in quantum film, quantum wire, and quantum box has been theoretically investigated using rate equation analysis and the density-matrix method, to obtain further reduction in the threshold current. The threshold reductions due to photon recycling in quantum film, wire, and box, in the case of lattice matched Ga0.47In0.53As/InP, are 40%, 24%, and 0%, respectively, for a fixed cavity loss of lasing mode normalized by the optical confinement factor α L/ξ L=50 cm-1. The estimation also shows that photon recycling is more effective in compressively-strained (CS) Ga0.18In0.82As0.73P0.27/InP quantum structures than in lattice-matched quantum structures. In both cases, the threshold reduction due to photon recycling is larger in the quantum film structure than in quantum wire and box structures, because the deviation between the peaks of the gain and the spontaneous emission spectra is large in the quantum film structure.
Analysis of a High Density Two-Dimensional Vertical-Cavity Surface Emitting Laser Array
Authors: Takahiro Numai Takahiro Numai
Published: October 2002

A two-dimensional vertical-cavity surface emitting laser array is expected to be a key device for parallel lightwave transmission and optical interconnection systems. This paper analyzes the number of channels in a two-dimensional vertical-cavity surface emitting laser array, from the viewpoint of the electric power consumption and the light-output. Dependence of the number of channels on several parameters is examined. It was found that high slope efficiency and low electrical resistance lead to a large number of channels, and the contribution of threshold reduction is small if the threshold current is of the order of 100 µ A or less. It is also shown that if each channel is composed of plural elements, the number of channels increases.
Luminescence Properties of Rare Earth Ion-Doped Monoclinic Yttrium Sesquioxide
Authors: Okumura Miwa , Tamatani Masaaki , Ariane K. Albessard Ariane K. Albessard , Naotoshi Matsuda Naotoshi Matsuda
Published: October 2002

Monoclinic Y2O3 phosphors doped with Eu3+ or Pr3+ are obtained for the first time by treatments in inductively-coupled thermal plasma. This paper reports the luminescence properties of these phosphor materials. The assumption proposed earlier by the authors, that the emitting levels of Pr3+ in Gd2O3 are determined by the distance between the Pr3+ ion and the surrounding oxygen ligands, is found consistent even when the monoclinic Y2O3:Pr and other oxides are included.
Orientational Photorefractive Gratings Observed in Polymer Dispersed Liquid Crystals Doped with Fullerene
Authors: Kawatsuki Hiroshi Ono
Published: October 2002

We presented orientational photorefractive materials based on polymer dispersed liquid crystals (PDLCs) doped with fullerene ( C60) as photoconductive sensitizer and discussed the grating formation mechanism originating in the space charge field and resulting in reorientation of liquid crystal molecules. A large refractive index modulation of the order of 10-3 was obtained in the Raman-Nath region for orientational photorefractive PDLCs. A stable memory effect of the reorientation was obtained for a 40 wt/60 wt (polymer/liquid crystal) sample.
Stability of Dimethyldioctadecylammonium Bromide Monolayers on Cleaved Mica in Water and at the Air/Water Interface
Authors: Koji Abe Koji Abe , Satomi Ohnishi Satomi Ohnishi
Published: October 2002

The wettability and structure of Langmuir-Blodgett monolayers of dimethyldioctadecylammonium bromide (DMDOA) on mica are affected by partial dip in water. After 6 h of dipping, high hydrophilicity was observed at the boundary between the dipped and undipped regions. Atomic force microscopic images of this sample have shown a bare mica surface in the boundary region. The hydrophilicity is due to this exposure of the mica surface. From the fact that the three-phase (air/water/sample surface) contact line (TPL) moved slowly (≪20 µ m/s) in the boundary region during the dipping, it was concluded that the slow movement of TPL stimulates the release of DMDOA molecules. The structure of the monolayer in the boundary region is also dependent on the velocity of TPL movement. In water, we found rearrangement of the DMDOA molecules via migration on mica and/or re-adsorption.
Color Filters with Negative Birefringence for Liquid Crystal Display Use
Authors: Shao Xibin , Li BaoZhong , Wu Yuan , Yuan Jianfeng , He Tianbai , Huang Ximin
Published: October 2002

We have developed a special color film with negative birefringence, which can work as a color filter and a viewing angle extension film for liquid crystal displays (LCDs). A high-performance polyimide (PI), which can be dissolved in the usual organic solvent and shows negative birefringence after lamination, was synthesized to fabricate the film. By mixing PI with suitable proportions of green, blue or red pigment in the solvent, then laminating them onto a glass substrate, we obtained color films with good transmission spectra and suitable chromatic coordinates. The results of our experiments show that the color filters still have negative birefringence but a little lower than that of the pure PI film. and can therefore work as compensation films for normal white twist nematic liquid crystal displays (TN-LCD).
Determination of Acid Diffusion Parameters and Proximity Effect Correction for Highly Dense 0.15 µm Features on SAL-601
Authors: Ioannis Raptis Ioannis Raptis
Published: October 2002

A new method for the measurement of acid diffusion parameters in negative-tone e-beam chemically amplified resists and its application for proximity effect correction is presented. It is based on the measurement of the diameter of lithographic features (pillars) obtained from single-pixel e-beam exposures. Generally, long post exposure bake (PEB) times or low post apply bake (PAB) temperatures lead to wider features compared with short PEB times and high PAB temperatures, due to enhanced acid diffusion. The acid diffusion coefficient was found to depend exponentially on cross-linking density. Additionally, proximity effect correction parameters (triple Gaussian parameters) are easily calculated. These parameters are t
PEB dependent and in the limit (t
PEB→0) are almost equal to the corresponding values for non-amplified resists. The method has been applied to SAL-601 (Shipley), and the calculated proximity parameters were used successfully to correct the proximity effect of complicated layouts with a 0.15 µ m critical dimension.
A Study of Native Defects in Ag-doped HgCdTe by Positron Annihilation
Authors: Uedono Akira , Ozaki Kazuo , Ebe Hiroji , Moriya Tsuyoshi , Tanigawa Shoichiro , Yamamoto Kosaku , Miyamoto Yoshihiro
Published: October 2002

Native defects in undoped and Ag-doped Hg0.78Cd0.22Te were studied using positron annihilation technique. For undoped specimens, the concentration of vacancy-type defects in subsurface regions (≤500 nm) was higher than that in the bulk. This was attributed to the introduction of Hg vacancies, V
Hg, resulting from the diffusion of Hg atoms out of the specimen. Before Ag doping, the major species of vacancy-type defects in the specimens ( p-type) was identified as V
Hg, and the concentration of V
Hg was estimated to be 6×1015 cm-3. After Ag doping, the concentration of vacancy-type defects was under the detection limit of positron annihilation (≤1014 cm-3). This was attributed to an occupation of Ag atoms at Hg sites, and the resultant decrease in the concentration of V
Hg. For the Ag-doped specimens before and after thermal treatment, no large change in the concentration of vacancy-type defects was observed. Thus, the diffusion processes of Ag atoms are unlikely to involve the interaction between Ag atoms and V
Hg.
Characterization of a Twin-Free Orthorhombic YBa2Cu3Ox Crystal
Authors: Yamada Hiroshi Kutami Yasuji , Koyama Satoshi , Wen Jian Guo , Egi Toshio , Shiohara Zenbe-e Nakagawa
Published: October 2002

Characterization of a twin-free orthorhombic YBa2Cu3O

x

crystal is described in this paper. A tetragonal single crystal was grown by a crystal pulling method and the crystal was annealed in an oxygen atmosphere under a uni axial compression in order to prevent the twin formation. The resultant crystal had a twin-free structure. The onset T
c of the crystal was about 91.8 K and the J
c value was one fifth as small as that of the twinned crystal at 1 T.
Second-Harmonic Generation from Single Crystals of N-Substituted 4-Nitroanilines
Authors: Hashimoto Hideki , Okada Yoshihiro , Fujimura Hisashi , Morioka Motonobu , Sugihara Okihiro , Okamoto Naomichi , Ryoka Matsushima Ryoka Matsushima
Published: October 2002

Six N-substituted derivatives of 2-methyl-4-nitroaniline (MNA) and two N-substituted derivatives of 4-nitroaniline were synthesized and their physical and optical properties were examined in the search for nonlinear optical materials with a sufficiently large second harmonic (SH) activity and applicability to practical use. Some derivatives produced single crystals and their structures were determined by X-ray crystallography. The trends of the SH intensity of these materials could be qualitatively explained based on the b tensor (the effective molecular hyperpolarizability in the crystal). Amongst the derivatives examined in this investigation, N-benzyl-MNA showed the highest SH activity (up to twice that of MNA), thermostability and phase-matching ability.
Magnetic Properties and Crystal Structure of Composite Ba-ferrite Particles Containing α-Fe
Authors: Shin-ichi Kitahata Shin-ichi Kitahata
Published: October 2002

Composite Ba-ferrite particles containing α-Fe were prepared by reducing Co–Ti–Sn substituted Ba-ferrite platelet particles in a hydrogen gas atmosphere. The coercivity of the composite particles increased to about three times that of the starting Ba-ferrite, and a magnetic easy cone appeared when the saturation magnetization grew larger than 62 emu/g. The substitution cations, particularly the Ti ions, were shown to inhibit the transformation of the crystal structure through reduction. The enhanced coercivity observed in the composite particles was due to the decrease of both Co ions as the substitution element and iron ions at the 12k site. The magnetic easy cone seemed to be caused by the formation of paramagnetic iron ions in the particles, which interrupted the superexchange interaction between magnetic iron ions.
Optical Properties of Proton-Exchanged LiNbO3 Using Capric Acid
Authors: Shen Chi-Yen , Liou Cwo-Hwa , Ren-Chang Chu Ren-Chang Chu , Shuming Tong Wang Shuming Tong Wang
Published: October 2002

The optical properties of high-index waveguides in z-cut LiNbO3 produced by proton-exchange with capric acid were investigated. These waveguides were characterized optically and were found by the variation of index with depth to exhibit a graded index profile with a high surface index change. The change in the surface index was larger than those obtained from benzoic acid, stearic acid and octanoic acid, and smaller than that obtained from pyrophosphoric acid. The index profile could be simply modeled by the parabolic function. The diffusion rate for the proton-exchanged process was slower than those reported for benzoic acid and pyrophosphoric acid.
Acoustic Properties of the Interface of a Uniform Medium-2-2 Piezocomposite and the Field Distributions in the Composite
Authors: Qiming Zhang Qiming Zhang , Xuecang Geng Xuecang Geng
Published: October 2002

The acoustic properties of a medium-composite interface and the field distributions in a 2-2 composite are analyzed based on an approach developed recently. It is found that the effective input acoustic impedance Z
in of the composite shows marked dependence on the shear stiffness constant of the medium in contact, which is related to the non-uniform vibration distribution at the composite surface. Since for a piezoceramic polymer composite, it is the ceramic phase which performs the energy conversion between the acoustic and electric forms, the amount of acoustic energy which can enter the ceramic region is one of the most important parameters in a composite transducer design. We show that even though the effective transmission coefficient increases as the frequency is increased, the amount of acoustic energy entering the ceramic region actually decreases. From the fact that there is more than 180° phase change in the reflection wave from the medium-composite interface, it is shown that the matching layer thickness is no longer equal to the quarter wavelength, but smaller, and the theoretical predictions are confirmed experimentally.
New Liquid Precursors of Yttrium and Neodymium for Metalorganic Chemical Vapor Deposition
Authors: Tasaki Yuzo , Satoh Mamoru , Yoshizawa Shuji , Kataoka Hiroto , Hidaka Hisao
Published: October 2002

New precursors, 2,2,6,6-tetramethyl-3,5-octanedionato (TMOD) yttrium and neodymium complexes were synthesized for metalorganic chemical vapor deposition (MOCVD). The melting points of the TMOD complexes were much lower than those of the conventional dipivaloylmethanato (DPM) complexes. These complexes can be used in the liquid state where a stable deposition rate can be obtained. It was confirmed that the oxide thin films, Y2O3 and Nd2O3, could be fabricated by an MOCVD method using these complexes.
Ninety Degree Domains in RF-Sputtered BaTiO3 Thin Films on Platinum Substrates
Authors: Jang Jin Wook , Cho Woon Jo , Lee Jong Ho , Kim In Tae , Kim Young Hwan , Kim Chang Hoon , Park Jong Hyeog , Sang Sam Choi Sang Sam Choi , Taek Sang Hahn Taek Sang Hahn
Published: October 2002

We report 90° domains in (110)-oriented polycrystalline BaTiO3 thin films. The domain and crystal structures of the thin films were investigated using transmission electron microscopy and high temperature X-ray diffraction, respectively. From X-ray diffraction, it was found that the prepared films had a (110)-preferred orientation and a tetragonal structure at room temperature. Observation in the plan-view and cross-sectional modes using transmission electron microscopy clearly indicated the presence of a 90° domain structure. In the cross-sectional mode, a 90° domain structure was observed along the film growth direction and in the plan-view mode, it was also found that a 90° domain boundary was initiated from the (111) twin boundary. The formation of a 90° domain boundary was discussed in terms of planar defects such as the (111) twin and we also proposed two kinds of stress relief mechanisms induced by 90° domain formation.
Plasma Component Filtering through a Hole Using the Sheath Generated around the Hole on Surface Modification by RF Plasma
Authors: Yori Izumi Yori Izumi , Takeo Ohte Takeo Ohte , Akira Kojima Akira Kojima
Published: October 2002

Glassy carbon (GC) surfaces were subjected to RF glow-discharged plasma treatment through a simple filter comprising of an aluminum plate with an aperture at the center. Surface properties were estimated by contact angle measurement and the atomic ratio O/C obtained from X-ray photoelectron spectroscopy (XPS). When the aperture was small enough (2r < 1 mm), the properties of the GC surface did not alter with the Ar plasma treatment. Ar ions could not pass through the hole. The surface properties under the hole were changed when 2r was 5 mm, suggesting the acceleration of the Ar ions to the GC surface as a result of the electric field in the sheath. There is a threshold value for aperture size above which the ions can pass through. On the other hand, the properties of the GC surface were changed almost uniformally after O2 plasma treatment with a small aperture size (2r < 1 mm). O2 plasma components travelled to the interior of the sample. It is considered that the radicals mainly acted because they are neutral and uninfluenced by the electric field in the sheath. Radicals in the O2 plasma moved by random walk and could reach the interior of the sample. With 2r of 5 mm, the surface under the hole was mainly changed by ion-assisted reactions.
Observation of Electric Fields at Surface and Interface of Doped GaAs/Semi-insulating GaAs Structures by Fast Fourier Transformed Photoreflectance
Authors: Nukeaw Jiti , Yasufumi Fujiwara Yasufumi Fujiwara , Yoshikazu Takeda Yoshikazu Takeda
Published: October 2002

Room-temperature photoreflectance (PR) measurements were successfully used to investigate electric fields at the surface and interface of doped GaAs/semi-insulating GaAs structures grown by molecular beam expitaxy (MBE). Fast Fourier transform (FFT) was applied to the PR spectra measured using a He–Ne laser as the pump light. The transformed spectra exhibited two well-resolved peaks, while two different Franz-Keldysh oscillation periods could not be distinguished in the original PR spectra. Using an Ar+ laser as the pump light, the FFT PR spectra showed only one peak. Because of the difference in the penetration depth of these two pump beams, the PR spectra taken with the He–Ne laser had contributions from the surface and the interface, while those taken with the Ar+ laser had only contributions from the surface. The measured electric fields at the surface and interface in GaAs with different doping levels were discussed in relation to the calculated electric fields.
Low-Threshold Self-Mode-Locked Ti:Sapphire Laser with Double Dispersion Compensators
Authors: Torizuka Kenji , Hideyuki Takada Hideyuki Takada , Kenzo Miyazaki Kenzo Miyazaki
Published: October 2002

We have developed a self-mode-locked Ti:sapphire laser that operates at a low pump power. To prevent losses in the laser cavity, we produced 12.4 fs pulses at a pump power of 1.2 W with an output coupling of 6%. We have demonstrated a new cavity configuration for low-threshold mode locking, that includes two pairs of dispersion-compensation prisms in the cavity. Using this new cavity, 32-fs pulses were generated at a pump power of only 0.7 W.
Ion-Beam-Etched Laser Facets for InP-based Lasers
Authors: Vollrath Gunther , Schlachetzki Andreas , Eckart Kuphal Eckart Kuphal , Friedrich Fiedler Friedrich Fiedler
Published: October 2002

In this paper laser facets are produced by ion beam etching (IBE) for the first time using mixtures of nitrogen and oxygen. The effects of different imperfections of etched facets on the optical reflectivity are investigated. Broad area lasers with both facets cleaved and lasers with one etched and one cleaved facet are fabricated emitting at a wavelength λ=1.55 µ m. The reflectivity of the etched facet is extracted from threshold current measurements. With known reflectivity, the increase of threshold current can be calculated for different resonator dimensions. Although the geometrical requirements for good quality etched laser facets are fulfilled, the reflectivity is still somewhat lower than for cleaved facets. Nevertheless, the expected increase of threshold current for a typical laser structure is only 1.7 mA per facet. The increase is caused by the formation of an antireflection layer, formed by backsputtering.
Diffusion of Phosphorus and Boron into Silicon at Low Temperatures by Heating with Light Irradiation
Authors: Yutaka Ishikawa Yutaka Ishikawa , Mitsuharu Maruyama Mitsuharu Maruyama
Published: October 2002

The diffusion of phosphorus and boron from a doped oxide into silicon upon heating with light irradiation was investigated at low temperatures. A tungsten halogen lamp was used as a light source. The diffusion coefficient for the 280-nm-thick doped oxide at 760° C upon light irradiation corresponded to that at 900° C upon heating in a furnace for both impurities, indicating enhanced diffusion in the former case. Arsenic diffusion was not enhanced upon heating with light irradiation. The reason for the enhanced diffusion may be that excess self-interstitials are generated at the interface between the doped oxide and silicon during light irradiation. This enhances the diffusion of impurities in silicon, which diffuse mainly by the interstitialcy mechanism.
Ozone Passivation Technique for Corrosive Gas Distribution System
Authors: Koike Kunihiko , Inoue Goichi , Takayoshi Takata Takayoshi Takata , Tatsuo Fukuda Tatsuo Fukuda
Published: October 2002

A passivation technique using highly concentrated ozone has been developed for electropolished stainless steel tubings that supply corrosive gases. The strong oxidizing ability of ozone enables the inner surface to form an anticorrosive passivation film with thickness up to 60 Å under room temperature and atmospheric pressure conditions. The ozone passivation film has excellent resistance to pitting corrosion. An improvement of corrosion resistance of the ozone-passivated surface was proven by the evaluation of the concentration of dissolved metals and particle generation after exposure to ClF3. Moreover, we discuss the mechanism of ozone passivation reaction on the stainless steel surface.
Sub-Quarter Micron Logic-Gate-Pattern Fabrication Using Halftone Phase-Shifting Masks
Authors: Akihiro Otaka Akihiro Otaka , Yoshio Kawai Yoshio Kawai
Published: October 2002

A new technique for enhancing the resolution of isolated line patterns is proposed. It is based on the balance in the intensity and the phase between the 0th-order rays and the rays diffracted from a line pattern. We deduce this technique from a condition of a high-contrast image by using the complex amplitude. We show that this technique can be achieved with an optimized halftone phase-shifting mask and optimized off-axis illumination. The optimum transmittance of the mask is 30% for a 0.4-λ/ NA line pattern and the optimum illumination for isolated lines in the x and y direction is quadrupole-shaped illumination whose centers are (±0.4, ±0.4). We tested this method in KrF lithography with an 8% halftone phase-shifting mask and found that a complex 0.20-µ m gate pattern can be fabricated with a large depth of focus of 1.2 µ m.
Extending Spatial-Phase-Locked Electron-Beam Lithography to Two Dimensions
Authors: Goodberlet James G. , Ferrera Juan , Farhoud Maya , Vanessa Z. Chan Vanessa Z. Chan , Henry I. Smith Henry I. Smith
Published: October 2002

The global-fiducial grid mode of spatial-phase-locked electron-beam lithography in two dimensions is investigated. A phase-locking scheme for two-dimensions is proposed and analyzed. An expression for the minimum locking dose is derived. The use of a scintillating grid is proposed, and results from optical detection of a scintillating fiducial grating are reported.
Photothermal Response Characteristics of Host-Guest Liquid Crystals
Authors: Kawatsuki Hiroshi Ono
Published: October 2002

Photo-response properties in host-guest liquid crystals were investigated using a crystal rotation method combined with a pump and probe technique. The crystal rotation signals were in good agreement with the calculation results obtained using the Jones matrix analysis. Considering these experimental results and the relation between the polarization of the pump beam and the signal intensity, it is concluded that the photo-response properties can be explained by a change in the refractive index owing to temperature variation caused by laser light absorption. The refractive index change in host-guest liquid crystals sensitized at a He–Ne laser wavelength (632.8 nm) due to irradiation with a 20 mW of the pump beam (beam diameter was 740 µm) was estimated to about -0.004. The refractive index change was roughly proportional to the pump beam intensity. The change was reversible and the typical photothermal response time was less than 500 ms.
Fast Atom Beam Etching of Glass Materials with Contact and Non-Contact Masks
Authors: Toma Yasushi , Hatakeyama Masahiro , Ichiki Katsunori , Huang Hailing , Yamauchi Kazuo , Kenji Watanabe Kenji Watanabe , Takao Kato Takao Kato
Published: October 2002

Fast atom beam (FAB) etching of multicomponent glass and silica glass was performed using a contact mask (electron beam resist) and two non-contact masks (typically 5-µ m-diameter particles and a copper mesh with a 5 µ m line width and 20 µ m line spacing). FAB etching of a multi component glass substrate with the micro-particle mask successfully fabricated a precisely projected, 1.0-µ m-high outline pattern on the substrate. FAB etching of a silica glass substrate with the copper-mesh mask, which was separated from the substrate by about 100 µ m, successfully produced a projected, 34-nm-high outline pattern on the substrate. A combination of electron beam lithography with FAB etching on silica glass successfully fabricated nano-scale ultrafine patterns whose aspect ratio was higher than 7 (50 nm line width and 360 nm height). In all three fabrications, the side walls and etched surfaces were very smooth and were perpendicular to each other.
Fabrication of Flat End Mirror Etched by Focused Ion Beam for GaN-Based Blue-Green Laser Diode
Authors: Ito Tsuyoshi , Ishikawa Hiroyasu , Egawa Takashi , Jimbo Takashi , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

Heteroepitaxial GaN film was deposited on sapphire by metalorganic chemical vapor deposition. An end mirror for the GaN-based blue-green laser diode was prepared using focused ion beam (FIB) etching. The tilt angle normal to the GaN layer was shown to be less than 1° by scanning ion microscopy. The root mean square surface roughness was 11 Å as observed by atomic force microscopy. The data indicates that FIB is a powerful technique for the fabrication of GaN-based blue-green laser diodes.
Microanalysis of Impurity Contamination in Masklessly Etched Area Using Focused Ion Beam
Authors: Park Yang-Keun , Takai Mikio , Nagai Takaaki , Kishimoto Takehisa , Lehrer Christoph , Frey Lothar , Ryssel Heiner
Published: October 2002

Localized contamination during 30 keV Ga+ focused ion beam (FIB) processing with and without iodine gas has been investigated using micro-Rutherford backscattering spectrometry (RBS) and RBS mapping images by a microprobe with 300 keV Be2+ with a beam spot size of 80 nm. Etching rates with and without iodine gas were compared with those by simulation. Residual Ga atoms of an order of 1016 ions/cm2 were found to be distributed at and nearby the bottom of the etched area due to implantation and redeposition from the Ga FIB. It was also confirmed that the gas assisted etching technique was more effective to reduce the contamination of etched areas.
Calculation of Molecular Orientational Order and Maxwell Displacement Current of Biaxial Molecules at the Air-liquid Interface
Authors: Chen-Xu Wu Chen-Xu Wu , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: October 2002

On the basis of the electrodynamic interaction of biaxial molecules (with their larger permanent dipoles perpendicular to the molecular axes) with a liquid surface, we calculate the molecular orientational order and the Maxwell displacement current (MDC) of biaxial molecules with a thermostatistical approach in the range of molecular area of immeasurably low surface pressure. It is shown that MDC generated by orientational change of the permanent dipoles along long molecular axes dominates the compression process shortly after the onset of the transition at A
0 from the planar surface alignment phase to the polar one, despite their smaller dipole moments than those perpendicular to the long molecular axes. This agrees with the fact that the MDC should change with the dipole moment along the long molecular axis. The results also reveal the thermodynamic motions of the dipoles parallel and perpendicular to the long molecular axis during the compression process.
Effects of Substrate Materials on Properties of Superconducting Bi 2Sr 2CaCu 2O 8 Epitaxial Thin Films
Authors: Shin-ichi Karimoto Shin-ichi Karimoto , Shugo Kubo Shugo Kubo , Koji Tsuru Koji Tsuru , Minoru Suzuki Minoru Suzuki
Published: October 2002

We have studied the effects of substrate materials on the surface morphology, crystal quality and electrical properties of Bi2Sr2CaCu2O8 superconducting epitaxial thin films grown on MgO (100), SrTiO3 (100), NdGaO3 (001), LaSrGaO4 (001), LaAlO3 (001) and YAlO3 (001). Films grown on substrates with a large lattice mismatch have a lower T
c and include a number of outgrowth grains. By contrast, films grown on substrates with a small lattice mismatch have a very smooth surface with almost no outgrowth grains or precipitates and have a higher T
c. These results are interpreted in terms of the internal stress caused by the lattice mismatch between the film and substrate.
Influence of the Magnetic Field Gradient on the Extraction of Slow Sodium Atoms outside the Solenoid in the Zeeman Slower
Authors: Kondo Yoshiteru , Saito Mitsuyo , Yamashita Masafumi , Toshiharu Tako Toshiharu Tako , Atsuo Morinaga Atsuo Morinaga
Published: October 2002

In order to produce an intense steady flux of slow sodium atoms outside the solenoid in a Zeeman slower, the relation between the extraction velocity of the atoms and the magnetic field gradient at the exit of the Zeeman solenoid was examined. When the magnetic field gradient was 0.5 T/m, slow atoms with a velocity of 160 m/s were extracted outside the solenoid with a slowing laser detuning of 250 MHz. On the other hand, when the magnetic field gradient was higher, i.e., 1.4 T/m, slow atoms with a velocity of 30 m/s were extracted with a slowing laser detuning of 550 MHz. The magnetic-field adiabatic following condition is discussed by comparing the experimental results with those of a Monte Carlo simulation.
New Method of Time Series Analysis and Its Application to Wolf's Sunspot Number Data. II: Periodicities of The Daily Sunspot Numbers
Authors: Terachi Saburou , Ohtomo Norio , Tanaka Yukio , Tokiwano Kazuo , Kaneko Noboru
Published: October 2002

The daily sunspot numbers data from 1979 October 1 to 1993 December 31 were analyzed using a new method of time series analysis proposed by the authors, and the long- and short-term periodicities were investigated. A three-dimensional (3D) spectral array of the normalized power spectral densities (PSD's) obtained by the segment time series analysis revealed the temporal behavior of the 27- and 155-d periodicities in the solar activity minimum. In the normalized 3D spectral array, the solar rotation cycle of 27-d accompanied by its multiplets was confirmed to migrate gradually from the low frequency region toward the high frequency region in the solar activity minimum as the solar activity increases, while the 155-d periodicity exists in the solar activity maximum only. Moreover, the behavior of the daily sunspot numbers variation was conjectured to be deterministic chaos, based on the exponential characteristics of the PSD's and the subharmonic relations of the spectral lines.
Unusual Voltage-Holding Ratio Characteristics Using In-Plane Switching of Nematic Liquid Crystals
Authors: Oh-e Masahito , Umeda  , Ohta Masuyuki , Sukekazu Aratani Sukekazu Aratani , Katsumi Kondo Katsumi Kondo
Published: October 2002

Unusual characteristics of the voltage-holding ratio were found when using in-plane switching of homogeneously oriented nematic liquid crystals. Even when employing liquid crystals with much lower resistivity than is applicable to the conventional active matrix driving technique, voltage-holding ratio characteristics were higher than those in conventional electric fields applied along the direction perpendicular to the substrate plane. The unusual holding ratio characteristics were attributed to the electric field direction being approximately parallel to the substrate plane.
IrO2/Pb(ZrxTi1-x)O3(PZT)/Pt Ferroelectric Thin-Film Capacitors Resistant to Hydrogen-Annealing Damage
Authors: Kushida-Abdelghafar Keiko , Miki Hiroshi , Fumiko Yano Fumiko Yano , Yoshihisa Fujisaki Yoshihisa Fujisaki
Published: October 2002

The PZT polarization hysteresis characteristics in a Pt/PZT/Pt ferroelectric capacitor are degraded by annealing in a hydrogen-containing atmosphere due to the catalytic effect of the top Pt electrode. This can be avoided by using an IrO2/PZT/Pt capacitor structure as we proposed. During hydrogen annealing of the as-grown capacitor, the top IrO2 electrode is deoxidized, degrading the capacitor characteristics. However, the polarization hysteresis characteristics are preserved after hydrogen annealing at 300° C if the IrO2/PZT/Pt capacitor is pre-annealed in oxygen at 600° C.
Magnetoresistance Effect in Layered-Perovskite La2-2xCa1+2xMn2O7 Thin Films
Authors: Asano Hidefumi , Jun Hayakawa Jun Hayakawa , Masaaki Matsui Masaaki Matsui
Published: October 2002

Ferromagnetic thin films of La2-2
x

Ca1+2
x

Mn2O7 (x=0.3) with a tetragonal Sr3Ti2O7-type layered perovskite structure have been deposited on MgO and SrTiO3 (001) substrates by magnetron sputtering. The epitaxial thin films in this study have the a-axis normal orientation with 90° domains having the a/c boundaries in the film plane. These thin films exhibit highly enhanced magnetoresistance (MR) effects (MR ratio Δρ/ρ0 of -93% at µ0
H=1 T) compared with those reported for thin films of cubic ferromagnetic perovskite with isotropic Mn–O networks. These MR behavior can be explained by taking account of the two-dimensionality and anisotropy of the Mn–O networks in the ferromagnetic layered perovskites.
The Carrier Injection Type Thin-Film Light-Emitting Diode with Hydrogenated Amorphous Carbon Active Layer
Authors: Woo Yeong Cho Woo Yeong Cho , Koeng Su Lim Koeng Su Lim
Published: October 2002

A hydrogenated amorphous-carbon (a-C:H) active-layer carrier-injection type thin-film light-emitting diode (TFLED) with a very low threshold voltage of 3.5 V was fabricated for the first time using a photochemical vapor deposition method. Compared to an intrinsic hydrogenated amorphous silicon carbide active layer TFLED, its electroluminescence (EL) spectrum peak shifted from 720 nm to 600 nm without hydrogenation of the intrinsic film or interface (p/i or i/n) band grading. This blue shift is caused by the band gap widening from 2.4 eV for a-SiC:H to 3.2 eV for a-C:H. The current transport mechanism of the TFLED could be explained by the ohmic current near the subthreshold voltage region and the Fowler-Nordheim tunneling current over the threshold voltage.
Preparation and Luminescence of Crystallized Ba1-XSrXMoO4 Solid-Solution Films by an Electrochemical Method at Room Temperature
Authors: Yoshimura Masahiro , Ohmura Mitsuhiro , Cho Woo-Seok , Masatomo Yashima Masatomo Yashima , Masato Kakihana Masato Kakihana
Published: October 2002

A complete series of well-crystallized solid-solution Ba1-
X

Sr

X

MoO4 films has been prepared on molybdenum substrates in an electrolytic solution containing Ba2+ and Sr2+ ions by an electrochemical method at room temperature (25° C). The SrMoO4 film showed only green emission at liquid-nitrogen temperature, strongly suggesting that it consisted of well-crystallized defect-free crystals. However, the other films did not luminesce at this temperature but showed green emission at liquid-helium temperature.
Electrogenerated Chemiluminescence from Poly(3-hexylthiophene)
Authors: Hamaguchi Maki , Hidetaka Nambu Hidetaka Nambu , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electrogenerated chemiluminescence (ECL) from a π-conjugated polymer, poly(3-hexylthiophene) (PAT6), is reported. The pulse electrolysis of a film of PAT6 in an acetonitrile solution of tetrabutylammonium tetrafluoroborate yields a red emission. The ECL spectrum is almost the same as that of photoluminescence of PAT6, indicating that the radiative annihilation of electrochemically formed charged excited states takes place. The mechanism of ECL is discussed in terms of the dynamics of the charged excited species.
Stability of Field Emission Current from Boron-Doped Diamond Thin Films Terminated with Hydrogen and Oxygen
Authors: Masayoshi Nagao Masayoshi Nagao , Toshiyuki Kondo Toshiyuki Kondo , Yasuhito Gotoh Yasuhito Gotoh , Hiroshi Tsuji Hiroshi Tsuji , Junzo Ishikawa Junzo Ishikawa , Koichi Miyata Koichi Miyata , Koji Kobashi Koji Kobashi
Published: October 2002

The stability of field emission current from B-doped diamond thin films terminated with hydrogen and oxygen was measured to investigate the influence of the surface treatment and the dopant concentration on the emission stability. The diamond films were prepared by microwave plasma chemical vapor deposition. The O-termination was performed by acid cleaning in boiling chromic acid and boiling aqua regia. The H-termination was performed by exposing the above sample to hydrogen plasma. The dependence of the emission stability on the B2H6gas (dopant gas) concentration and the surface treatment was investigated. As a result, little dependence on the B concentration was observed, but dependence on the surface treatment was significant. The field emission of the H-terminated diamond thin films was confirmed to be more stable than the O-terminated films.
Comparison of the Fluorine Atom Density Measured by Actinometry and Vacuum Ultraviolet Absorption Spectroscopy
Authors: Yozo Kawai Yozo Kawai , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

The validity of actinometry for measurement of fluorine atom density was examined by comparing the results with those obtained by vacuum ultraviolet absorption spectroscopy. The experiments were carried out in high-density CF4 and C4F8 plasmas excited by helicon-wave discharges. As a result, the error in the relative F atom density measured by actinometry was within a factor of ∼2 for the same working gas. On the other hand, the value of K in the actinometry relation n
F = K
n
Ar (I
F/I
Ar) was considerably different between the CF4 and C4F8 plasmas. Hence evaluation of the absolute F atom density by actinometry is generally difficult, except for rough order-estimation by substituting K ≃2.
Formation of Metastable Phases in the Zr–Al System by Electron Beam Deposition
Authors: Miura Susumu , Matsuzaki Kunio , Inoue Akihisa , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

Zr–Al binary alloy films with a thickness of about 2 µm prepared by electron beam deposition were found to exist in an amorphous phase in the composition range of 15 to 60 at% Al, although no amorphous phase has been reported in rapidly solidified Zr–Al alloys. The deviation of the Al content from the range causes the formation of mixed hcp-Zr+metastable bcc-Zr phases in the range of 5 to 15 Al at% and L12-type Al3Zr phases in the range of 60 to 85 at% Al. The hardness of the amorphous Zr–Al films increases from 5.98 to 9.18 GPa as the Al content increases from 20 to 58 at%.
Asymmetric Coulomb Staircase in a Capacitive Single Electron Transistor with an Asymmetric Bilayer Tunnel Barrier
Authors: Hiroshi Nakashima Hiroshi Nakashima , Kiyohiko Uozumi Kiyohiko Uozumi
Published: October 2002

Numerical calculations of electrical properties in a capacitive single electron transistor with an asymmetric bilayer tunnel barrier are presented. Our analysis is based on the semiclassical tunnelling model, but the particle tunnel rates through each junction are determined by directly calculating a golden rule equation. The asymmetric Coulomb staircase in the current vs drain voltage characteristics of the system is demonstrated. The current vs gate voltage characteristics of the system are also reported.
Dielectric Properties of AB2O6 Compounds at Microwave Frequencies (A=Ca, Mg, Mn, Co, Ni, Zn, and B=Nb, Ta)
Authors: Lee Hyo-Jong , Kim In-Tae , Kug Sun Hong Kug Sun Hong
Published: October 2002

The microwave dielectric properties of AB2O6 compounds, where A=Ca, Mg, Mn, Co, Ni, or Zn, and B=Nb or Ta, were investigated. All samples were prepared using the mixed oxide method. In particular, AB2O6 compounds with Mg2+ and Zn2+ revealed very good dielectric properties with respect to dielectric resonator applications. However, their temperature coefficient of resonant frequencies should be modified. It was found that the electronegativity of AB2O6 compounds is relevant to their dielectric constant. The temperature coefficient of resonant frequency was discussed in terms of volume contraction.
The Fraction of Sp3 Bonding in Carbon Thin Film Prepared Using Pulsed Laser Deposition
Authors: Yamamoto Kazuhiro , Koga Yoshinori , Kokai Shuzo Fujiwara
Published: October 2002

The fraction of s
p
3 bonding in carbon thin film prepared using pulsed laser deposition with a KrF excimer laser is investigated. The carbon film deposited at the laser fluence of 0.2 J/cm2 has a graphitic structure. It is suggested that the neutral species of C3 is effective in the formation of this structure. The C+ ion increases with a laser fluence higher than 0.9 J/cm2 and the s
p
3 bonding fraction in carbon film increases. The s
p
3 fraction in the film also increases with a negative bias to the substrate. The impact of energetic C+ species to the substrate is attributed to the formation of s
p
3 bonding.
Spin-Dependent Tunneling between a Soft Ferromagnetic Layer and Hard Magnetic Nanosize Particles
Authors: Inomata Koichiro , Ogiwara Hideo , Saito Yoshiaki , Yusu Keiichiro , Ichihara Katsutaro
Published: October 2002

Spin-dependent tunneling has been investigated for ferromagnetic tunnel junctions with a new structure, which consists of a hard ferromagnetic insulating granular thin film sandwiched between two soft ferromagnetic layers, or soft ferromagnetic and non-ferromagnetic layers. The granular film, consisting of ferromagnetic Co80Pt20 nanosize particles embedded in a SiO2 matrix with 13 nm thickness, has a high coercive force. The film was prepared by co-sputtering of Co80Pt20 and SiO2 targets on a glass substrate with a Cr or a Co80Pt20/Fe underlayer as a bottom electrode. A ferromagnetic Co9Fe layer as a top electrode was deposited over the granular film to form cross pattern junctions of 0.01 mm2 junction area through a metal mask. The tunneling magnetoresistance up to 4.5% at RT was observed for a Co9Fe/Co80Pt20–SiO2/Co80Pt20/Fe junction at a low field.
Simulated Computed Tomography for the Reconstruction of Vacancies Using an Atomic Force Microscope Image
Authors: Ryuji Nishi Ryuji Nishi , Takayuki Ohta Takayuki Ohta , Yasuhiro Sugawara Yasuhiro Sugawara , Seizo Morita Seizo Morita , Takao Okada Takao Okada
Published: October 2002

We numerically demonstrate the possibility that vacancies as a typical kind of point defect inside a sample can be reconstructed from the force gradient distribution measured with the atomic force microscope using computed tomography (AFM-CT). By the calculation with the Lenard-Jones potential, it is predicted that the vacancy, even in the third layer, can be observed in the experimental force gradient. We show that the depth of the vacancy can be determined by tomography using only the attractive section of the force gradient distribution.
Brillouin Scattering Measurement of Optothermally Excited Phonon
Authors: Hideaki Tanaka Hideaki Tanaka , Koichiro Hattori Koichiro Hattori , Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: October 2002

UHF-band ultrasonic waves were successfully generated in liquid using an infrared semiconductor laser. The output power was modulated with sinusoidal driving current. The laser illuminates a thin metal film formed on a flat surface of a sapphire rod immersed in a sample liquid, causing periodical thermal expansion of the metal film, which effectively emits ultrasonic waves into the liquid. The absence of electrical or mechanical resonance in the process of ultrasonic generation provides us with an ideal flatness in the frequency response of ultrasonic excitation over the range of 30–120 MHz. Ultrasonic propagation in the liquid was observed using the optical beating Brillouin scattering technique over 100 MHz and very flat frequency response of the laser-ultrasonic transducer was confirmed. The intensity of the excited ultrasonic wave is about 104 times larger than that of the spontaneous phonon, markedly increasing the sensitivity of the Brillouin scattering measurement.