bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Gamma-Radiation on the High Tc Superconductors Er1Ba2Cu3O7-δ
Authors: El-Hamalawy Ahmed Abd El-Samie , El-Zaidia Mohamed Mohamed , Edwar Amin Ghali Edwar Amin Ghali
Published: February 2005

Er1Ba2Cu3O7-δ samples were prepared and irradiated with different doses of gamma radiation up to 60 Mrad. The effects of gamma irradiation on Er1Ba2Cu3O7-δ were characterized using electrical resistivity, X-ray diffraction, IR spectroscopy, and magnetic susceptibility. It was concluded that there is no effect on gamma irradiation up to 10 Mrad. For higher doses, the gamma irradiation is believed to cause small ion displacements of light atoms, thus decreasing the critical current density of weak links.
Nonlinear Polarization Spectroscopy with Nonpolarized Light
Authors: Gancheryonok Igor I.
Published: February 2005

A new variant of nonlinear polarization spectroscopy that is based on the use of nonpolarized pump (or) and probe beam is presented. We show that in the case of a totally depolarized strong exciting field, an initially isotropic medium acquires the properties of uniaxial absorbing crystal with optical axis along a wave normal of the pump beam. Relationship for a transverse component of the 3rd-order nonlinear susceptibility tensor is derived for arbitrary directions of interacting beams. When a probe beam is totally depolarized, a medium with light-induced anisotropy (MLIA) can be used as a light-absorbing or light-amplifying dynamic polarizer. We analyze the efficiency of such type of light controlled devices on the basis of the polarization nearness. The Mueller matrix of MLIA is calculated and some advantages of the use of partially polarized probe beam are pointed out.
Calculations of Phase Shift and Reflectivity for Phase Shifting Masks Employing Multi-Layer Films
Authors: Trieu C. Chieu Trieu C. Chieu
Published: February 2005

Calculations of phase shift and reflectivity of multi-layer phase shifting masks have been carried by a method of matrix calculus for light propagating in slabs of isotropic media. The results show that a phase noise of several degrees exists as a result of variation in material parameters due to multiple interference phenomenon in the films. The magnitude of this phase noise tends to grow for increasing refractive index of the phase shift layer. It is shown that both the phase noise and the reflectivity can be minimized with proper choice of materials. Best materials for phase shift layer should have a refractive index of 1.5 such as SiO2 or 2.0, and good etch stop layer should have low refractive index and a thickness chosen to minimize reflectivity.
Infrared Optical Constants of Anodic Alumina Films with Micropore Arrays
Authors: Nakamura Shinji , Saito Mitsunori , Huang Li-Feng , Wada Mitsunobu Miyagi
Published: February 2005

Transmission spectra were measured for anodic alumina films prepared in several acid solutions. The films anodized in a phosphoric acid solution are the most appropriate for use in the infrared range, since impurity absorptions are weak in those films. The refractive indices of the phosphoric-acid films were evaluated by the measurements of transmittance and reflectance. The refractive index decreases either by extending anodization time or by immersing a film in a sulfuric acid solution. This phenomenon is elucidated well by considering pore widening due to the dissolution of alumina. The dependence of refractive index on porosity agreed well with theoretical evaluations.
Characteristics of Y2O3:Eu/ZnS/Y2O3:Eu Red Light Emitting Electroluminescent Devices
Authors: Sowa Kunihiro , Tanabe Masami , Furukawa Seigo , Nakanishi Yoichiro , Hatanaka Yoshinori
Published: February 2005

Hot-carrier-injection-type electroluminescent (HCI-EL) devices of Y2O3:Eu/ZnS/Y2O3:Eu structure were fabricated by the electron beam deposition technique and red light emission of about 10 cd/m2 intensity was observed from Eu3+ ions. Brightness at relatively high applied voltage was proportional to the applied frequency, as has been reported, while it was decreased above several hundred Hz at relatively low applied voltage. It is considered that the resistance part of the Y2O3:Eu layer becomes dominant at relatively low applied voltage and the capacitance part becomes dominant at higher applied voltage. Red light emission from Eu3+ ions was observed for both half cycles of bipolar square wave applied to the Y2O3:Eu/ZnS/Y2O3-structure EL device, of which only one side of Y2O3 layers was doped with Eu. It is considered that light emission may occur by impact ionization of holes generated in the ZnS layer.
Two-Dimensional Epitaxial Growth of SrTiO3 Films on Carbon-Free Clean Surface of Nb-Doped SrTiO3 Substrate by Laser Molecular Beam Epitaxy
Authors: Yoshimoto Mamoru , Ohkubo Hiroyuki , Naoki Kanda Naoki Kanda , Hideomi Koinuma Hideomi Koinuma
Published: February 2005

A carbon-free clean SrTiO3(100) surface was obtained by rinsing with acetone and ethanol and subsequent oxidation under O2 flushing of 1×10-6 Torr at 650°C. A unit cell layer-by-layer growth was achieved in the laser molecular beam epitaxy growth of insulative SrTiO3 thin films on conductive Nb-doped SrTiO3 substrates thus cleaned, as verified by the observation of persisting RHEED intensity oscillation.
Study of Thin Films of Cu-In-Se-Te System Grown by Triode Sputtering
Authors: Díaz Raquel , Máximo León Máximo León , Fernando Rueda Fernando Rueda
Published: February 2005

Structural, electrical and optical properties and composition of thin films of Cu-In-Se-Te system grown by sputtering have been studied relating the growth conditions to film composition. The crystalline phases observed are tetragonal chalcopyrite type and a new metastable cubic phase, as determined by transmission electron diffraction (TED). The film optical absorption coefficients present two or three inflection regions corresponding to several energy gaps, two direct and one forbidden-direct gap. The energy gap values depend on composition through Cu/In and Cu/(Se+Te) ratios. The first direct gap lays in the 0.76-1.42 eV range and the forbidden direct one in the 1.46-2.23 eV range. Thermal treatments between 150-400°C have been done in still N2 atmosphere with Se and Te sources at the same temperature. This annealing does not noticeably vary the initial composition of the films.
Design of a Liquid Xenon Calorimeter for the Observation of Cosmic Gamma Ray Lines in the 1∼100 GeV Region
Authors: Doke Tadayoshi , Kasahara Katsuaki , Suson Daniel J.
Published: February 2005

A liquid xenon calorimeter has recently been designed. The main purpose is to show the capability of observing monochromatic cosmic gamma ray lines in the 1∼100 GeV region. The calorimeter has a geometric factor of ∼1 m2·sr, an energy resolution of ∼0.4% and an angular resolution of about 1 degree for GeV-region gamma rays. These characteristics will meet the conditions required for the observation of gamma ray lines produced by the pair annihilation of hypothetical SUSY heavy Majorana fermions which might exist in the galactic halo as dark matter. The calorimeter is also applicable to the search for point sources emitting gamma rays as well as the investigation of diffuse gamma rays at high energies.
Two-Circle Goniometer for Measurement of Acoustic de Haas-van Alphen Effect
Authors: Settai Rikio , Chida Minoru , Satomi Yanagida Satomi Yanagida , Terutaka Goto Terutaka Goto
Published: February 2005

A sample-orienting device with a two-circle goniometer has been developed. This permits continuous rotation of either of the two perpendicular axes in a magnetic field and provids accurate measurement of the acoustic de Haas-van Alphen effect.
Resonance of the Macromotion of Ions Trapped in a RF Trap by the Subharmonic Oscillation
Authors: Jun Yoda Jun Yoda , Kazuhiko Sugiyama Kazuhiko Sugiyama
Published: February 2005

Yb+ ions were trapped in an uncompensated rf trap with light buffer gas and then the storage time, as well as the total number of the trapped ions, was determined by the rf resonance method. When the ratio of the frequency of the trapping field to that of the macromotion of the trapped ions was an integer, the total number and the storage time were smaller and shorter, respectively, than those obtained when the ratio was a half-integer. A theoretical calculation shows that this effect, called the subharmonic oscillation, is caused by excitation of the macromotion of the trapped ions by the leaked trapping rf field, in the case in which the ion trap has an octupole besides a quadrupole potential.
Density Variation in Heat- and Pressure-Treated Egg White during Gel-to-Glass-like Transition
Authors: Kanaya Haruichi , Ishida Kenji , Hara Kazuhiro , Okabe Hirotaka , Taki Seiji , Takushi Kazumi Matsushige
Published: February 2005

Simultaneous measurements of the area (volume) and mass change were carried out in heat- and pressure-treated egg white during the process of the gel-to-glass-like state transition. The calculated density of these two specimens showed quite different time variations; the density of the heat-treated specimen remained almost constant, while that of the pressure-treated one changed considerably. Moreover, the scanning electron microscopy observations revealed that the surface structure of the pressure-treated gel is larger and more coarse than that of the heat-treated one, suggesting a close relationship between the structures of the two gels and the changes in the density during the gel-to-glass-like state transition. The differences in the microscopic structures in these two gels were also elucidated by X-ray diffraction measurements.
Heteroepitaxial Growth of GaN1-xPx (x≲0.09) on Sapphire Substrates
Authors: Osamu Igarashi Osamu Igarashi
Published: February 2005

Gallium nitride phosphide single crystals having the maximum composition of x∼0.09 were epitaxially deposited on (0001) sapphire substrates. The growth was carried out by the vapor phase reaction of the Ga-Br2-PH3-NH3-N2 system. The above maximum composition was attained at a substrate temperature of 980°C.
InAlAs/InGaAs Heterojunction Bipolar Transistors with an n-doped InGaAs Spacer
Authors: Fukano Hideki , Tomizawa Masaaki , Yoshifumi Takanashi Yoshifumi Takanashi , Masatomo Fujimoto Masatomo Fujimoto
Published: February 2005

Static and high frequency characteristics of InAlAs/InGaAs heterojunction bipolar transistors (HBTs) with a 200-Å-thick n-doped InGaAs spacer between the emitter and base are investigated. The presence of the deep notch (ΔE
n) at the emitter-base hetero-interface is confirmed from the low temperature I-V data, in which the specific humps corresponding to electrons tunneling to the quantized electron levels in the deep notch are found in the base current for the first time. Electron injection energy (E
i) into the base for the proposed HBTs is reduced by ΔE
n as compared with that for the HBTs without the n-doped spacer. Although the spacer is as thick as 200 Å, recombination current is low because the E
i still remains sufficiently high. A current gain of as high as 200 is obtained despite the higher base doping of 2×1019 cm-3. By employing the 200 Å spacer, E
i is optimized successfully for minimizing the sum of the base and collector transit times.
Modeling of Kinetic-Inductance Coplanar Striplin with NbN Thin Films
Authors: Yoshida Keiji , Hossain Mohammad Sajjad , Kisu Takanobu , Keiji Enpuku Keiji Enpuku , Kaoru Yamafuji Kaoru Yamafuji
Published: February 2005

In order to determine transmission line parameters of superconducting coplanar striplines with thickness smaller than the magnetic penetration depth of the striplines, in which the influences of enlarged kinetic inductance and strongly nonuniform current distribution make it useless to apply the conventional design formula developed for normal conductors, we have conducted theoretical and experimental studies on the geometrical effects of the kinetic inductance and the microwave loss of the thin coplanar striplines. The analytical expression for the kinetic inductance of the coplanar stripline is given using the conformal mapping technique, and it is shown with the London equation and the two fluid-model that the microwave loss is directly proportional to the kinetic inductance. The comparison has been made between theory and experiment concerning the kinetic inductance and the microwave quality factor of NbN coplanar striplines with various thicknesses and widths. It is shown that the observed characteristics are well modeled by the analytical expression.
Conception of Normal Waves in Nonlinear Polarization Spectroscopy
Authors: Gancheryonok Igor I.
Published: February 2005

A theoretical study is presented of normal waves in media with nonlinear photoanisotropy (light-induced anisotropy) within the framework of the 3rd-order nonlinear susceptibility tensor. In the general case, it is shown that the normal waves are elliptically polarized. These two ellipses have the same shape and opposite directions of rotation, and their major axes are not at right angles to one another. Expressions are derived for the ellipticities and the angle of the nonorthogonality of the normal waves. Several applications of theoretical results are given to demonstrate the relevance of the conception of normal waves in nonlinear spectroscopy. We show that the media with light-induced anisotropy acquire the anisotropic properties of crystals and can be applied to a wide range of laser devices due to optically controlled parameters.
Dependence of Lattice Constant Deviation and Refractive Index on Proton Concentration in Proton-Exchanged Optical Waveguides on a Single Crystal of LiNbO3
Authors: Kenichi Ito Kenichi Ito , Kazumi Kawamoto Kazumi Kawamoto
Published: February 2005

The lattice constant deviation and refractive index change of proton-exchanged optical waveguides fabricated on a single crystal of LiNbO3 are discussed in relation to the proton concentration. The exchange rate x of Li+ with H+ has been determined by nuclear reaction analysis and the lattice constant deviation has been measured by means of the double crystal X-ray diffraction method. The value of x in the samples proton-exchanged with the benzoic acid/lithium benzoate melts is in the range of 0.55<x<0.75. After annealing in air, x decreases with increasing annealing time. The lattice constant deviation is proportional to x in the range of x<0.55, while it is almost constant in the range of x>0.55. The dependence of the refractive index change on x is very similar to that of the lattice constant deviation. Reasons for the refractive index change caused by proton exchange are discussed.
Formation of Ridges on Gd3Ga5O12 by Ion-Beam Etching and Subsequent Phosphoric Acid Treatment Utilizing Tri-Layered Etching Mask
Authors: Katoh Yujiro , Naoto Sugimoto Naoto Sugimoto , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

This paper investigates the shapes of straight ridges about 4 µm high, that are formed on [1 1 1], [1 0 0] and [1 1 0] oriented Gd3Ga5O12 (GGG) single crystal substrates by utilizing a Ta/organic layer/Si3N4 tri-layered etching mask. Following argon ion-beam etching, the substrates are soaked in phosphoric acid solution. After soaking, the ridges on a [1 1 1] substrate have perpendicular side walls because the Si3N4 film effectively protects the top surface of the ridge from acid. The stable dissolution form of a [0 0 1] direction ridge on a [1 0 0] substrate tends to have a {1 1 0} face which is inclined at 45° from the perpendicular. The side walls of a [0 0 1] direction ridge on a [1 1 0] substrate tends to be perpendicular after dissolution.
Synapse Effect of Waveguide Modulator with a Nematic Liquid Crystal Cladding for Optical Neural Computing
Authors: Chen Bao Xue , Yang Ying Bao , Li Xiang Tong , Hamanaka Hiromi , Yasufumi Iimura Yasufumi Iimura , Shunsuke Kobayashi Shunsuke Kobayashi
Published: February 2005

A new type of waveguide-like nervous mode, in which the nematic liquid crystal (NLC) layer is used as the electrically controlled active material cladding and the channel waveguides are passive, is suggested. Its synaptic weight effect is discussed theoretically with a specific numerical example, and a preliminary experiment shows the results supporting this idea.
Numerical Derivative Analysis of the Pseudodielectric Functions of ZnTe
Authors: Sadao Adachi Sadao Adachi , Kohzo Sato Kohzo Sato
Published: February 2005

The real (ε1) and imaginary (ε2) parts of the dielectric function of ZnTe have been measured by spectroscopic ellipsometry in the 1.5-5.6-eV photon-energy range at room temperature. The measured spectra reveal distinct structures at energies of the E
0, E
1, E
1+Δ1, and E
2 critical points (CPs). These data are analyzed by fitting the first-(dε/dE) or second-derivative spectrum (d2ε/dE
2) with model dielectric functions (MDF) or standard critical-point line shapes (SCP). It is found that both the MDF and SCP models successfully explain the measured derivative spectra. The MDF also shows excellent agreement with the experimental ε(ω) spectra, but the SCP does not. The CP energies determined here are: E
0=2.28 eV; E
1=3.78 eV; E
1+Δ1=4.34 eV; and E
2=5.23 eV. The E
1- and (E
1+Δ1)-exciton binding energies for ZnTe are also estimated to be ∼0.19 eV.
Clustering Poisson Process and Burst Noise
Authors: M. Athiba Azhar M. Athiba Azhar , K. Gopala K. Gopala
Published: February 2005

The theory of clustering Poisson process which generates a 1/f
α spectral pattern has been discussed first by Grüneis and later by Grüneis and Baiter. Such a model has been applied to the burst noise phenomenon observed by us in the reverse biased emitter-base junctions of Germanium transistors of type AC 128. The spectral pattern of the burst noise signal has been discussed. The present work is the first quantitative confirmation of this theory.
Microstructure of Fe-B-Si Alloy Surface Layers Produced by Laser-Quenching
Authors: Hirose Fusao , Takagi Makoto , Mori Hideshi , Kitoh Yasuo , Imura Toru
Published: February 2005

Laser-quenching was performed to produce an amorphous alloy layer on metal blocks. Fe78B13Si9 alloy film brazed onto the surface of a stainless steel plate was melt-quenched by pulsed YAG or cw CO2 laser irradiation. Transmission electron microscope and high-resolution electron microscope observations were carried out to study the microstructure of the laser-quenched layers. In both cases, at the region very close to the free surface in the laser-quenched layer, amorphous and crystalline phases were observed. The internal area of the pulsed YAG laser-quenched layer consisted of an amorphous phase including a small amount of nanometer-size crystalline particles, while that of the cw CO2 laser-quenched layer consisted of mainly an amorphous single phase, partially including heat-affected zones in the neighborhood of the overlapped area of laser irradiation.
The Layered Composite Crystal Structure of the Ternary Sulfide, (BiS)1.07TaS2 “BiTaS3”
Authors: Gotoh Yoshito , Onoda Mitsuko , Akimoto Junji , Midori Goto Midori Goto , Yoshinao Oosawa Yoshinao Oosawa
Published: February 2005

The crystal structure of a new type of ternary sulfide with a layered composite crystal structure, (BiS)1.07TaS2 was studied by the single crystal X-ray diffraction method. The precession photograph of (BiS)1.07TaS2 revealed the composite diffraction patterns of BiS subsystem and TaS2 subsystem. The commensurate superlattice reflections of the BiS subsystem were observed together with the main diffractions of the TaS2 subsystem. The commensurate superlattice reflections of the BiS subsystem, which were not observed for other MS subsystems in (MS)
n
TaS2 (M=Pb, Sn, rare earth metals) are well indexed on the basis of the superstructure with a=5.732(4) Å, b=15.368(6) Å, c=23.135(5) Å. The structure analysis of the BiS subsystem based on the superstructure model with space group B2mm leads to a distorted NaCl-like structure with short Bi-Bi bonding (3.120(8) Å).
X-Ray Photoelectron Spectroscopic Study of Oxidation of InP
Authors: Noboru Shibata Noboru Shibata , Hideaki Ikoma Hideaki Ikoma
Published: February 2005

InP was oxidized chemically (in boiling deionized water), thermally (dry oxygen, 260°C, 30 min) and chemically under light illumination from a xenon arc lamp. The chemical compositions and their depth distributions from the surface of these oxides as well as the InP native oxide (naturally grown) were studied by angle-resolved X-ray photoelectron spectroscopy (XPS) and XPS combined with in situ Ar+ ion etching. In any oxide, indium is first oxidized to form In2O3 perhaps due to depletion of phosphorus from the InP surface induced by contact annealing, etc. InPO3 and/or InPO4 are then successively grown on an In2O3 or In2O3 rich layer. In and P atoms diffuse through the already grown In2O3 layer and react with oxidant at the surface to form InPO3 and/or InPO4. Light illumination was found to strongly enhance oxidation of InP, and substantially increase InPO3 and InPO4.
Si-Based Coatings on Iron by Low Pressure Chemical Vapor Deposition of SiH4
Authors: Liyanage Ariyawansa Nimal , Kimura Masao , Eiichi Ozawa Eiichi Ozawa , Jean Marie Friedt Jean Marie Friedt
Published: February 2005

Si-based coatings were formed on iron surfaces by low pressure chemical vapor deposition of pure SiH4 and He-diluted SiH4 under the following conditions: temperature of 350 to 850°C, gas flow rate of 0.1 to 100 sccm, gas composition of pure or He-diluted SiH4, pressure of 0.01 to 600 Torr and deposition time of 2 to 20 min. Coatings are essentially overlay type, with more than 30 at.% Si, for temperatures between 350 to 650°C regardless of other conditions. When the temperature exceeds 650°C, low gas flow rates (<10 sccm) produce diffusion type coatings with 26-29 at.% Si, whereas high gas flow rates form overlay coatings with underlying diffusion layers containing 2-5 at.% Si. Adjustment of conditions, mainly temperature and gas flow rates, allows the control of overlay or diffusion characteristics and composition gradient of coatings.
Effects of Nitrogen Pressure and RF Power on the Properties of Reactive Magnetron Sputtered Zr-N Films and an Application to a Thermistor
Authors: Yoshitake Masaaki , Tsutom Yotsuya Tsutom Yotsuya , Soichi Ogawa Soichi Ogawa
Published: February 2005

Thin Zr-N films have been prepared by reactive RF magnetron sputtering. The nitrogen partial pressure and the RF power are chosen as sputtering parameters. The relationships between film properties, such as composition, structure, optical and electrical properties, and these sputtering parameters is systematically investigated. The relationships between the nitrogen pressure and the RF power for each property of Zr-N films in the sputtering process are also discussed. It is found that the film properties can be widely changed by controlling RF power as well as nitrogen pressure. A semiconductorlike Zr-N film is obtained with sputtering in the high-nitrogen-pressure region. The conductance of the semiconductorlike Zr-N films changes with temperature, conforming to a function of exp (E/kT) in the temperature range from 200°C to 550^°C, w
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Damage Production and Reduction of Single-Crystalline TiN Films by 1.8 MeV Carbon Beam Irradiation
Authors: Saitoh Kazuo , Nakao Setsuo , Niwa Hiroaki , Ikeyama Masami , Yoshiko Miyagawa Yoshiko Miyagawa , Soji Miyagawa Soji Miyagawa
Published: February 2005

By means of an in-situ Rutherford-backscattering-spectrometry (RBS) channeling technique, we have investigated creation and reduction of irradiation damage in single-crystalline TiN films induced by 1.8 MeV carbon beam. Both the effects of ion channeling and of beam heating on variation of damage level are shown briefly by successive irradiations on the order of 1017 C+/cm2 under different conditions. It is shown that the <100> aligned irradiation with a high-intensity beam repairs almost completely the damage produced by random irradiation where the sample is heated to about 450^°C
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Photoemission Profiles in Parallel-Plate RF Discharge in SF6 Gas
Authors: Ishikawa Itsuo , Tatsuyuki Amamiya Tatsuyuki Amamiya , Shinji Suganomata Shinji Suganomata
Published: February 2005

A small amount of N2 gas was added to SF6 as a probe gas in SF6 discharge. Spatiotemporal emission profiles at the N2 337.1-nm line in 1 MHz discharge at pressures of around 0.3 Torr show a moving luminous peak from the negative glow region toward the electrode, whose polarity changes from negative to positive in each cycle of an applied voltage. The emission at the N2
+ 391.4-nm line, on the other hand, does not show such a profile. The moving luminous peak is considered to reveal a contracting part of the cathode sheath.
Magnetic Field Switching of Cylindrical Magnetron Sputtering Rates for Coating Glass Fibers and Rods
Authors: Yu Zengqi , Li Lumin , Shi Binxing , Collins George , Meyer Jack , Harbison Barry , Aggarwal Ishwar
Published: February 2005

Abrupt switching of the sputtering rate in a cylindrical magnetron via changes in the longitudinal magnetic field has been investigated. The hollow cylindrical magnetron, equipped with an internal array of cylindrical-shaped coaxial anode grids, was employed to achieve a controllable modulation of the sputtering deposition rate via external variation of the longitudinal magnetic field though a critical field value. The rapid change of sputtering rate versus magnetic field allows for abrupt control of the sputter deposition rate of films on cylindrical rod or fiber substrate placed within the coaxial geometry.
Process Study of Silicon Carbide Coatings Deposited on Steel by Plasma-Assisted Chemical Vapor Deposition from Tetramethylsilane-Argon Gas System
Authors: Zhang Wei , Marc Lelogeais Marc Lelogeais , Michel Ducarroir Michel Ducarroir
Published: February 2005

Silicon carbide coatings were prepared in an RF plasma-assisted chemical vapor deposition (CVD) device from the tetramethylsilane-argon gas system. The present paper is devoted to investigation of the plasma process and determination of the deposition rate with the experimental parameters. By employing the general convective diffusion equation, we obtain a simple analytical expression of the deposition rate. Calculated results are compared with experimental data. The agreement between calculated and measured results as functions of total pressure, total flow rate, reactant composition, and plasma geometry is fairly good. The kinetic parameters selected are found to have a reasonable order of magnitude in comparison to those of other studies.
Dependence of Young-Fringes Contrast on Generated Speckle Diameter
Authors: Nakagawa Kiyoshi , Toshiyuki Takatsuji Toshiyuki Takatsuji , Takumi Minemoto Takumi Minemoto
Published: February 2005

The dependence of Young-fringes contrast on both formation condition of specklegrams and readout condition of specklegrams has been investigated theoretically and experimentally. The ratio N of a periodic distance of the Young
fringes to the average diameter of speckles forming the fringes determines the Young-fringes contrast. It is desired that the ratio N becomes larger than 1.1 in order to obtain fully developed Young fringes with a high contrast.
Probable Errors in the Internal Reflection Method for Optical Constant Measurements
Authors: Shin-ichi Kondo Shin-ichi Kondo
Published: February 2005

The internal reflection method (IRM), recently developed for optical constant measurements of deposited films, was investigated in terms of probable errors. The optimum angle of incidence for IRM was shown to lie in the range of 60°-75°. With these incident angles, IRM using a fused-silica prism demonstrated the effect of reducing the probable errors to a few tenths of those in the ordinary free surface reflection method.
Edge Recording on Direct Overwrite Exchange-Coupled Multilayer Media
Authors: FUkami Tatsuya , Nakaki Yoshiyuki , Tokunaga Takashi , Yuji Kawano Yuji Kawano , Kazuhiko Tsutsumi Kazuhiko Tsutsumi
Published: February 2005

The possibility of edge recording on direct overwrite exchange-coupled multilayer media was evaluated. It has been established that overwrite media are not inferior to conventional magnetooptical (MO) media in edge recording because overwrite methods which use light power modulation have an advantage of reduced standard deviation of edge jitter even if the residual signal level is high. In this paper, direct overwrite exchange-coupled quadrilayer media were examined to prove this advantage.
Numerical Analysis of Leakage Field Modulation for a Novel Direct Overwrite Medium
Authors: Kikitsu Akira , Ashida Sumio , Yumi Mizusawa Yumi Mizusawa , Katsutarou Ichihara Katsutarou Ichihara
Published: February 2005

The numerical calculation of the leakage field in a novel laser-power modulation direct overwrite medium has been carried out. The medium had four functional layers: initializing layer, biasing layer, thermal isolating layer and storage layer. The leakage field applied to the storage layer was changed by the laser power. The degree of leakage field change and overwritable domain width, where the direction of an effective field applied to the storage layer could be modulated, were obtained as the figures of merit for overwriting performance. Si-N and Zr-O films were chosen as the thermal isolating layer in order to change the thermal response in the storage layer and the biasing layer. It has been found that the medium with a Si-N thermal isolating layer is suitable for overwriting and that leakage field modulation over 120 Oe was available within a domain width of 0.7 µm.
Detection and Printability of Shifter Defects in Phase-Shifting Masks II. Defocus Characteristics
Authors: Watanabe Hisashi , Sugiura Emiko , Imoriya Tadashi , Yoshihiro Todokoro Yoshihiro Todokoro , Morio Inoue Morio Inoue
Published: February 2005

One drawback of phase-shifting lithography lies in the high printability of shifter defects. A transparent object on masks (shifter defects) produces lead or lag of the optical phase, which causes an unique printability with respect to focus level. We investigated the printability of shifter defects on phase-shifting masks in out-of-focus conditions. Two types of shifter defects related to the phase angle were investigated: (a) a phase error which is a shifter layer having an incorrect thickness and (b) a phase angle defect which is a defect having a phase angle other than 180°. Phase error causes asymmetrical pattern profiles. It was found that the illumination coherence factor (σ) has a strong influence on the allowance of the shifter thickness (phase error). The effect of phase angle defects located in a large clear area and in small features was investigated. The phase angle defects have an optimum focal plane other than the best focal plane. A defect with a low phase shift located in fine patterns has high printability. In order to establish a mask fabrication process for production-worthy phase-shifting masks, further investigation in the detection of low phase angle shifter defects is necessary.
Experimental Examination of an Overwrite Method Utilizing Leakage Field Modulation by the Laser Power Level
Authors: Ichihara Katsutaro , Ashida Sumio , Akira Kikitsu Akira Kikitsu , Yumi Mizusawa Yumi Mizusawa
Published: February 2005

A recently proposed novel single beam overwrite method was examined in order to prove the overwrite concept. The storage layer, the thermal control layer, the biasing layer, and the initializing layer were stacked on a glass substrate and were examined by a magneto-optical read/write tester. It was clear that the leakage field from the biasing layer was modulated by the laser power level and that an overwritable operating region was obtained by this leakage field modulation. The operating margin increased by increasing the linear velocity of the disk. An overwrite CNR of 35 dB was obtained in velocities above 8 m/s with a 20% completely erasing power margin.
Effect of Anodic Bonding Temperature on Mechanical Distortion of SiC X-Ray Mask Substrate
Authors: Shoki Tsutomu , Yoh-ichi Yamaguchi Yoh-ichi Yamaguchi , Hiroyuki Nagasawa Hiroyuki Nagasawa
Published: February 2005

Distortion of SiC X-ray mask substrate during anodic bonding has been found to occur due to the difference in the thermal expansions of SD glass frame and Si wafer deposited with SiC, and the distortion characteristics can be explained by the bi-metal effect. The reduction in the difference in the expansion is required to obtain lower substrate distortion, and has been realized by using the SD-2 glass, which has the most accurate matching of the expansion to Si, and by lowering the bonding temperature. Any other parameters than the bonding temperature, such as the applied voltage and the bonding time, have been found not to cause the distortion. Homogeneously concave mask substrate bonded at 230°C, using 4-mm-thick SD-2 glass frame and 1-mm-thick wafer, has the flatness values of 2.18 µm and 0.26 µm for the wafer and the membrane area, respectively.
X-Ray Phase-Shifting Mask for 0.1-µm Pattern Replication under a Large Proximity Gap Condition
Authors: Somemura Yoh , Deguchi Kimiyoshi , Kazunori Miyoshi Kazunori Miyoshi , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

The effects of Fresnel diffraction on the patterning characteristics in synchrotron radiation lithography are greatly influenced by X-ray phase shift in the absorber, especially when a low-contrast X-ray mask is used. We show that the resolution in sub-quarter-micron region can be markedly improved without reducing the proximity gap by utilizing the phase-shifting effects in the absorber. By controlling the absorber thickness within a suitable range (1.5≤mask contrast≤4.0, -30°≥phase shift φ≥-120°), fine patterns as small as 0.1 µm can be replicated with a large exposure latitude at a large proximity gap of 30 µm. Based on these results, we propose a novel X-ray phase-shifting mask with shallowly etched patterns (L in width) at the absorber edge as a phase shifter. This mask can be fabricated by a simple self-alignment process and also offers the possibility of 0.1-µm pattern replication at the 30-µm proximity gap by using 0.02≤L≤0.1 µm.
A Scanning Tunneling Microscope Based Microcolumn System
Authors: Chang T. H. P. , Muray L. P. , Staufer U. , D. P. Kern D. P. Kern
Published: February 2005

A novel concept based on scanning tunneling microscope (STM) aligned field emission (SAFE) with microfabricated lenses to form an exceptionally high brightness electron source and miniaturized electron probe forming system has been explored. Electron optical studies have shown that such miniaturized columns can have performance surpassing conventional columns at the same potential. Processes for fabricating microlenses from silicon membrane using electron beam lithography and reactive ion etching (RIE), and a special W<111> field emission tip preparation and annealing procedure have been developed. Prototype 1 kV microcolumns based on this concept measuring 2.5 mm have been successfully fabricated and demonstrated to be fully operational. Scanning electron microscope images in the transmission mode have been achieved. The expected performance of such microcolumns coupled with the very significant reduction in physical column size can open new possibilities in many applications which include microscopy, lithography, metrology, testing, storage, etc. It can be shown that by the use of an array of these miniaturized columns, high throughput sub-100 nm lithography can be achieved.
Tilt-Target Magnetron Sputter for Deposition of Magnetooptical Disk
Authors: Chao Shiuh , Hsiao Tsai-Chu , Huang Der-Ray , Tzuan-Ren Jeng Tzuan-Ren Jeng
Published: February 2005

A 3.5-inch magnetooptical disk is made by tilting the TbFeCo target in a DC circular magnetron sputtering process. The composition of the recording layer is controlled by using the Tb-rich deposition area. The optimal tilt angle of our target for uniform radial composition distribution on the disk is found to be about 15°. A model was proposed to explain the observed Tb, Fe and Co content variation with the tilt angle of the target. The dynamic read/write test also showed that good carrier to noise ratio (CNR) was obtained at this angle. A new deposition process for magnetooptical (M-O) disk based on the tilt target method is proposed; it has the merits of enabling simultaneous deposition of multiple disks. The CNR of the disk made at 15° tilt angle is 53 dB.
Novel Electron Beam Direct Writing Technique for the Hole Pattern of Quarter-Micron Devices
Authors: Fujino Takeshi , Ishii Atsushi , Kawai Kenji , Matsuba Motoko , Nakao Shuji , Yaichiro Watakabe Yaichiro Watakabe , Yoichi Akasaka Yoichi Akasaka
Published: February 2005

The electron beam (EB) direct writing technique for the hole pattern of quarter-micron devices was developed. The resist structure used in this technique was EB resist (0.5 µm)/“buffered tungsten (W) layer” (0.05 µm)/SiO2/Si substrate. The “buffered W layer” was dry-etched using an EB resist mask, then SiO2 was dry-etched using the “buffered W layer” as the dry-etching mask. The alignment mark structure was TiN (0.035 µm)/“alignment W layer” (0.085 µm)/Al (0.4 µm) multilayered metallization which was used for metal wiring beneath the SiO2 layer. The thicknesses of the “alignment W layer” and “buffered W layer” have a strong influence on alignment mark detection and were optimized using computer simulation. Due to this structure and process sequence, high resolution was attained without using a trilayer resist process. In addition to this resist structure, proximity effect correction with data undersizing was applied in order to fabricate patterns as designed.
Multi-Coil System for Electron Cyclotron Resonance Plasma Generation
Authors: Nakamura Tsuyoshi , Samukawa Seiji , Ishida Toshinori , Ishitani Akihiko , Yutaka Kawase Yutaka Kawase
Published: February 2005

The authors have developed a new multi-coil system for electron cyclotron resonace (ECR) plasma generation. The features of this multi-coil system are precise magnetic field control and the capability of achieving compatibiliry with low magnetic field gradient and high magnetic field uniformity. A low gradient and high uniformity of magnetic field in the ECR region contribute to highly dense and highly uniform plasma generation. Therefore, etching characteristic improvement is expected. As compared with the conventional two-coil system, the present multi-coil system achieved improvement of magnetic field uniformity of more than 60% at a low magnetic field gradient less than 20 G/cm, ion current density of more than 25%, and ion current density uniformity of about 75% in Ar plasma.
Domain Formation and Erasure in Co/Pt Multilayer Recording Thin Films
Authors: Xue Tsing , Mark D. Schultz Mark D. Schultz , Mark H. Kryder Mark H. Kryder
Published: February 2005

The domain dynamics in Co/Pt multilayers were experimentally investigated with a 10 ns exposure time magneto-optic microscope system. The images obtained reveal that during domain formation a ring shaped magnetization structure is temporarily created which is often larger than the final domain size. The width and intensity of this ring varies with applied field. This is believed to be due to a wide region of in-plane magnetization which occurs where the film temperature is only slightly below the Curie temperature. Observations of erasure show that erasure occurs in less than 50 ns, but requires a large reversed field to be successful.
Contact Fill by Ionized Cluster Beam
Authors: Ito Hiroki , Kajita Naoyuki , Hisao Yoshida Hisao Yoshida , Teruo Ina Teruo Ina
Published: February 2005

Ionized cluster beam (ICB) deposition of TiN barrier metal for ultra large scale integration (ULSI) applications has been developed. The bottom coverage of reactive-ICB was 54% and 24% for 4.0 and 6.7 aspect ratio contacts (2.0 µm in depth and 0.5 µm amd 0.3 µm in diameter). Therefore the ICB has high potential to fill sub-half-micron contact holes with high aspect ratios. The resistivity of Ti and TiN deposited by ICB and reactive-ICB is found to be 50 µQ cm and 180 µQ cm, respectively, at a substrate temperature of 300°C. The ICB can also provide low contact resistance and good adhesion by low energy ion bombardment during film growth. The beam simulation explains the bottom coverage of ICB as well as conventional sputtering. Using the larger number of atoms in a cluster, the bottom coverage becomes almost 100% due to the long mean free path of the deposited cluster in gas and its heavy mass.
Effects of Contact-Hole-Etching Damage on Aluminum Chemical Vapor Deposition
Authors: Tani Kouichi , Tetsuo Yamaji Tetsuo Yamaji , Satoshi Nishikawa Satoshi Nishikawa
Published: February 2005

The effects of contact-hole-etching damage on aluminum (Al) chemical vapor deposition (CVD) have been investigated. When Si wafers were etched by reactive ion etching (RIE) under the conditions of contact hole etching, two kinds of damage were observed on the etched surface; i.e., an amorphized layer at a depth of 30 Å and a contaminated (carbon, oxygen, and fluorine) layer at a depth of 100 Å. Aluminum deposited on the as-etched wafer had granular structure and the grains were not connected with each other, which indicates that the growth of Al is suppressed by the damages. The effect of these damages was be removed by annealing at 1050°C or etching at a depth of 30 Å (slight etching). In both cases, the amorphized layer was disappeared by recrystallization or was removed by etching, but the contaminated layer still remained. Therefore, it is concluded that the nucleation of Al is suppressed by the amorphized layer, but not by the contaminated layer. When this slight etching is made after contact hole etching, perfect contact hole filling with Al can be achieved by selective CVD.
Investigation of Hydrogen Plasma Etched Si Surfaces
Authors: Ishii Masahiko , Nakashima Kenji , Ichiro Tajima Ichiro Tajima , Minoru Yamamoto Minoru Yamamoto
Published: February 2005

Roughness of Si surfaces irradiated with a hydrogen electron cyclotron resonance plasma at several substrate temperatures was investigated using scanning electron microscopy and reflection high-energy electron diffraction (RHEED). When the substrate temperature is below 100°C, the surface remains smooth after irradiation for 10 min. However, at the higher temperatures, conelike projections are formed on the surface. By RHEED analysis, the facet orientation of the projections changes from (511) to (211) with growth of the roughness. These facet surfaces are composed of microsteps with {111} risers. The temperature dependence of the Si etch rate was also measured, so that the etch rate decreased with increase of the substrate temperature. IR spectroscopy and elastic recoil detection analysis were used to identify hydrogen penetration into the Si bulk. The temperature dependence of both the etch rate and the roughness formation will be discussed on the basis of the reduction of hydrogen atoms contributing to the etch reaction.
Two-Step Doping Using Excimer Laser in Boron Doping of Silicon
Authors: Akane Toshimitsu , Takahiro Nii Takahiro Nii , Satoru Matumoto Satoru Matumoto
Published: February 2005

A two-step doping method consisting of the deposition of dopant films and the incorporation of dopant atoms using excimer laser has been studied in boron doping of silicon. These processes are carried out in the same chamber successively. Sheet resistance can be varied widely by changing both the number and the energy density of the depositing laser pulses. In this method, dopants diffuse in the melted silicon from a fixed total dopant source with a simple Gaussian distribution when the number of melting pulses is small. The diffusion coefficient of B in liquid Si is determined experimentally.
Sub-Half-Micron Silicon Pattern Generation by Electron Beam Direct Writing on Polysilane Films
Authors: Okamoto Katsuhiko , Shin Hidetoshi , Shiba Kazutoshi , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: February 2005

Polysilane thin films have been grown by the glow discharge of SiH4 at a substrate temperature of -90°C or -110°C. The bonded hydrogen in the film is effused by electron beam (EB) irradiation, resulting in three-dimensional Si network formation. The unirradiated part of the polysilane is easily oxidized in air at room temperature, while the EB-irradiated region is hardly oxidized. This enables us to fabricate the fine silicon pattern with a width of about 0.1 µm embedded in SiO2. Such a fine silicon line obtained by EB direct writing can be crystallized by 800°C annealing in an N2 atmosphere for 2 h.
Synchrotron Radiation Damage Mechanism of X-Ray Mask Membranes Irradiated in Helium Environment
Authors: Arakawa Tomiyuki , Okuyama Hiroshi , Okada Koichi , Nagasawa Hiroyuki , Syoki Tsutomu , Yamaguchi Yoh-ichi
Published: February 2005

The mechanism of X-ray mask membrane displacement induced by synchrotron radiation (SR) has been discussed. Silicon nitride (SiN) and silicon carbide (SiC) membranes were irradiated by SR in a 1 atm helium ambient. SR-induced displacement for both membranes was 25-97 nm (σ). Oxygen concentration in both SiN and SiC was below 0.01 in O/Si atomic ratio. Although an increase in dangling bond density of SiN was observed, no remarkable increase in spin density was detected in SiC. Moreover, the most important finding was that thin oxides were grown on the membrane surface after SR irradiation. From these results, it is considered that the oxide growth on SiC membrane surfaces, and both the oxide growth and the increase of dangling bond density in SiN play an important role in the SR-induced displacement for the X-ray mask membranes.
Repair of Phase-Shift Masks Using Low Energy Focused Ion Beams
Authors: Hsiaowen Lee Hsiaowen Lee , R. Fabian W. Pease R. Fabian W. Pease
Published: February 2005

Focused Ga+ ions in the energy range of 25 keV to 50 keV are commonly used to remove opaque defects in chromium-on-quartz photolithographic masks. The resulting implantation of the quartz causes staining and it is necessary to etch away the stained quartz. In a phase-shifting mask, this gives rise to unacceptable phase shifts. We have investigated the use of low energy focused ions and find that not only is the depth of staining significantly reduced but the loss of transmissivity (without etching) can be reduced to a negligible level (more than 90% transmissivity) for 500 eV Ga+ ions. With well-designed ion optics such ions can be focused into a 0.3 µm diameter for 1 nA current.
High-Mobility Quantum Wires Fabricated by Ga Focused Ion Beam Shallow Implantation
Authors: Itoh Masayuki , Tadashi Saku Tadashi Saku , Seigo Tarucha Seigo Tarucha
Published: February 2005

High-mobility quantum wires are fabricated using shallow implantation of a low energy focused Ga ion beam into a modulation doped Al
x
Ga1-x
As/GaAs heterostructure. Lowering the implant energy keeps the implanted ions away from the two-dimensional electron gas and reduces crystallographic damage. The electron mobility is 5.0×105 cm2/V·s for the wires 10 µm long with an effective width of 0.152 µm, which is much higher than that for previous wires. The effective wire width is independently derived from two measurements: (1) four-terminal conductance at zero-magnetic field and (2) the magnetic depopulation effect in the Shubnikov-de Haas oscillation. As the implantation dose decreases, the electron mobility increases with an effective width of more than 2.1-µm, while it is nearly constant for narrower wires. This suggests the existence of unintentionally implanted neutral Ga atoms and/or stray Ga ions.