bluuebunny/crossref_metadata_2025 huggingface dataset:
Physics of a Porous Solar Pond
Authors: Taga Wasaburo Unno
Published: February 2005

A solar pond is a useful system for storing solar energy only if convection is strictly prevented. The temperature difference of 50°C between the bottom and the top is obtained with a pond of 1 m depth in one week (radiative heating time), if conduction loss to the ground is neglected. It takes two and a half months (conduction time), however, for the pond to settle in a quasi-stationary state. Then, 90% of the solar energy flux can be utilized. The variation principle is generalized to prove that length scales of thermal conduction and viscous forces acting in a porous pond are reduced so much that the Rayleigh number may be lowered below the critical value for the onset of convection. Piles of coarse sheets of transparent artificial lawn or vertical strings or rods, one in each 4-mm-square area, will be sufficient to prevent convection. The conduction equation is solved, giving the daily variation of temperature as less than 1°C at the bottom and negligible at the top.
Theory of Scanning Tunneling Microscopy/Spectroscopy for Adsorbed Surfaces and Layer Crystal Surfaces
Authors: Tsukada Masaru , Schimizu Tatsuo , Watanabe Satoshi , Isshiki Nobuyuki , Katsuyoshi Kobayashi Katsuyoshi Kobayashi
Published: February 2005

A method for theoretical simulation of the sccanning tunneling microscopy (STM) image and scanning tunneling spectroscopy (STS) spectra based on the LDA (local density functional approach) is applied for some chemisorption surfaces. For the Si(111)√3×√3-Ag surface, it is demonstrated that the modified HCT model results in a honeycomb-like distribution of the bright spots in the STM image. Effects of the microscopic geometry of the tip on the STM image are discussed for this surface. A strange transparent feature of the STM image for chemisorbed molecues or outermost layers is investigated both by analytical consideration and by theoretical simulation. The unique structure of the Ag(110)-O added row model is determined by optimization calculation and its experimental STM/STS data are reproduced by first-principles calculations.
Modeling Large Surface Reconstructions on the Connection Machine
Authors: Brommer Karl D. , Larson B. E. , Needels M. , Joannopoulos J. D.
Published: February 2005

Using a massively parallel computer, we undertake an ab initio investigation of the Si(111)-(7×7) surface reconstruction. Calculation of the total energy of an ∼700 effective atom supercell at an 8 Ry plane wave cutoff allows us to determine (1) the energy difference between the (7×7) and (2×1) reconstructions, (2) the relaxed atomic geometry, (3) the scanning tunneling microscope topographs as a function of bias voltage and (4) the occupied and unoccupied electronic states.
Scanning Tunneling Microscopy of Clean Silicon Surfaces at Elevated Temperatures
Authors: Iwatsuki Hiroshi Tokumoto
Published: February 2005

In this paper, we shall review scanning tunneling microscopy on clean Si(111) and Si(001) surfaces at elevated temperatures of as high as 950?C. Various problems occurring at elevated temperatures, such as the thermal drift, the low Curie temperature of the tip-scanning elements and outgassing, are overcome by paying special caution to the design of the STM unit, the sample dimensions, and the operational methods. Several interesting phenomena appearing at elevated temperatures are presented: the appearance of the dimer rows and step edges on the Si(001) surface at temperatures up to 920?C, the dynamic behavior of the (7?7)-(1?1) phase transition on the Si(111) surface at temperatures around 860?C, the step shifting appearing on the Si(111) surface under dc electric fields (electromigration effect) around the phase transition temperature (869?C), and the surface modification of pyramids and craters created on both Si(111) and Si(001) surfaces at elevated temperatures.
Atomic-Level Studies of Diffusion on Metal Surfaces
Authors: G. L. Kellogg G. L. Kellogg
Published: February 2005

The unique attributes of the field ion microscope have enabled researchers to obtain detailed information on the diffusion of individual atoms and the nucleation of small clusters on metal surfaces. In this article I describe the experimental methods used in field ion microscope studies of these processes and discuss recent results relating to the discovery of novel diffusion modes and unexpected cluster configurations on fcc metal surfaces.
Tip-Sample Interactions in the Scanning Tunneling Microscope for Atomic-Scale Structure Fabrication
Authors: Aono Masakazu , Kobayashi Ataru , Grey Fran\ccois , Uchida Hironaga , Huang De-Huan
Published: February 2005

In a scanning tunneling microscope (STM) operated in ultra-high vacuum, if we place a well-prepared W tip above the Si(111)-7×7 surface at a separation of ∼1 nm and apply an appropriate voltage pulse to it, we can extract a single Si atom from a predetermined position routinely at room temperature. The extracted Si atoms are redeposited onto the surface with a certain probability, their positions always being at a fixed crystallographic site. The redeposited Si atoms can be displaced intentionally to other crystallographically equivalent sites. In case of the Si(001)-2×1 surface, usually two Si atoms forming a dimer are extracted together. For both surfaces, Si atoms at crystallographically different sites including step edges are extracted with different probabilities. The microscopic mechanisms of these processes are discussed.
GaAs(100) (2×4) Surface Study by Molecular Beam Epitaxy and Field-Ion-Scanning-Tunneling-Microscopy
Authors: Xu Hongwei , Tomihiro Hashizume Tomihiro Hashizume , Toshio Sakurai Toshio Sakurai
Published: February 2005

The GaAs(100) (2×4) surface was studied by molecular beam epitaxy (MBE) and field-ion-scanning-tunneling-microscopy (FI-STM). The results showed that the GaAs(100) (2×4) surface unit cell consists of two dimers and two missing dimers of As. The c(2×8) reconstruction was observed to originate by the phase shift induced by the As vacancies. We also observed the domain boundaries on the GaAs(100) (2×4) surface and they were attributed to two dimensional island growth. A structural model was proposed to explain the observed surface reconstructions.
Selectively Disorder Activated Raman Scattering in Silicon Films
Authors: Bandet Jacqueline , Frandon Jean , Mauduit Fran\ccois Fabre
Published: February 2005

Raman spectra have been registered and discussed, for a series of silicon films grown by low pressure chemical vapour deposition (LPCVD). The amorphous-microcrystalline phase transition of the samples has been investigated, as a function of the deposition and annealing parameters. These results have been compared to transmission electron microscopy (TEM) observations on these films. A Raman line near 500 cm-1 has been also evidenced on the low frequency side of the optical vibration mode of silicon, in the as-grown samples and in the phosphorus-doped ones; we assign this line to a selectively disorder-activated mode, due to the numerous stacking faults present in the microcrystalline films.
Application of Doping-Superlattice Collector Structure for GaAs Bipolar Transistor
Authors: Liu Wen-Chau , Sun Chung-Yih , Wei-Chou Hsu Wei-Chou Hsu , Der-Feng Guo Der-Feng Guo
Published: February 2005

In this paper, the GaAs sawtooth-doping-superlattice (SDS) collector has been respectively employed in homojunction and heterostructure transistors by molecular beam epitaxy (MBE). For both studied structures, conventional transistor behaviors and the controllable S-shaped negative-differential-resistance (NDR) performance were achieved at room temperature, simultaneously. In the normal- and inverted-mode two-terminal operations, the homojunction transistor exhibited a bi-directional switching phenomenon due to the avalanche multiplications within SDS periods or emitter-base junction depletion region. In addition, for the three-terminal operations, the common-emitter current gain of about 20 and a controllable S-shaped NDR family in larger current regime were obtained when a base current I
B was applied. In this device, the base-controlled sensitivity S
B was up to 8×10-3 V/µA. On the other hand, the heterostructure transistor was fabricated to improve the frequency response. In comparison with the prior structure, the heterostructure transistor performed similar current-voltage (I-V) characteristics, but a preferable current gain (up to 25) and base-controlled sensitivity S
B (up to 1.6×10-1 V/µA) were obtained.
A New Experimental Geometry of Elastic Recoil Detection Analysis (ERDA)
Authors: Kato Masahiko , Ikegami Hiroshi , Inoue Naoki , Hasegawa Takahi , Katayama Mitsuhiro , Aono Masakazu
Published: February 2005

Recoil process of adatoms by ion beam bombardment has been studied by computer simulation. Owing to the focusing effect, the intensity of adatom recoil depends strongly on both the angle of incidence and the angular position of the detector. When the detector is arranged in a backward direction with respect to the direction of the primary ion beam, structural information on surface hydrogen and other light elements can be obtained efficiently.
Gamma Induced Centres in Liquid Phase Epitaxial Gallium Arsenide
Authors: Alexiev Dimitri , Tansley Trevor Lionel , Butcher Kenneth Scott Alexander
Published: February 2005

Poole-Frenkel pairs in liquid phase epitaxial Gallium Arsenide induced by gamma irradiation are described. These defects are shown to be easily annealed out, with the device metallisation intact, at 200°C. Preliminary investigations indicate the usefulness of Liquid Phase Epitaxial (LPE) GaAs for high energy particle detection.
Characterization of Sb Atomic-Layer-Doped Si(100) Crystal by X-Ray Standing Wave Method
Authors: Izumi Koichi , Saito Akira , Zhang Seishi Kikuta
Published: February 2005

We applied the X-ray standing wave method to the determination of the Sb position in atomic-layer-doped Si crystal. From the fitting of the calculated with the experimental results, an extension of 0.03 and a coherent ratio of 86% were obtained.
Structure and Magnetic Properties of Electrodeposited Fe-Cu Alloy Films
Authors: Yuji Ueda Yuji Ueda , Naoya Kikuchi Naoya Kikuchi
Published: February 2005

Fe-Cu alloys have been produced over a wide composition range by means of an electrodeposition method. The composition regions of a bcc phase for 0-70 at.% Cu and a fcc phase for 73-100 at.%Cu are extended. In the bcc phase region, the average saturation magnetization at room temperature decreases with increasing Cu concentration and deviates downwards from the simple dilution law. The fcc alloy film does not show ferromagnetism. In the composition region near the 73 at.%Cu, the X-ray diffraction lines corresponding to bcc-Fe and fcc-Cu become stronger and the magnetization increases with heat treatment at 300-500°C for 1 h.
Thermally Induced Structural Modification of Nanometer-Order Mo/Si Multilayers by the Spectral Reflectance of Laser-Plasma Soft X-Rays
Authors: Azuma Hirozumi , Takeichi Akihiro , Konomi Ichiro , Yoshihide Watanabe Yoshihide Watanabe , Shoji Noda Shoji Noda
Published: February 2005

Thermally induced structural modification of a nm-order multilayer of Mo/Si was investigated by spectral reflect-ance of soft X-rays from laser-produced plasma. Dependence of reflectivity of the nm-order multilayers on the incidence angle of soft X-rays indicated that some structural changes start to occur at 300°C and that the nm-order multilayer structures shrink at 500°C because of the formation of Mo-silicide. These results were found to be consistent with the cross-sectional transmission electron microscope observations. It is clearly shown that measurement of spectral reflectance of soft X-rays from laser plasma is a powerful method for analyzing nm-order structural modifications of multilayers.
Characteristics of a New High-Sensitivity X-Ray Imaging Tube for Video Topography
Authors: Sato Fumio , Maruyama Hirotaka , Goto Katsuyuki , Fujimoto Isao , Shidara Keiichi , Kawamura Tatsurou , Hirai Tadaaki , Sakai Hideyuki , Chikawa Jun-ichi
Published: February 2005

A new type of high-sensitivity X-ray imaging tube having an amorphous selenium photoconductive layer with a thickness of 8 µm has been fabricated. Signal charges induced by X-ray photons can be avalanche-multiplied in the photoconductive layer under a large electric field. The sensitivity of the tube reaches the level of individual X-ray photon detection. For the detection of such a small number of X-ray photons, a new kind of noise is generated due to the fluctuation of absorption depth in the photoconductive layer under the operation conditions of avalanche multiplication. Signal-to-noise ratio can be improved by the accumulation of signal charges in the photocon-ductive layer. An example of real-time X-ray topography by weak X-rays using this experimental tube is demonstrated.
Study of Measuring the Velocity of Erythrocytes in Tissue by the Dynamic Light Scattering Method
Authors: Kashima Susumu , Sohda Akihiko , Hiroki Takeuchi Hiroki Takeuchi , Toshihiko Ohsawa Toshihiko Ohsawa
Published: February 2005

Measurement of the velocity of erythrocytes in small vessels in tissue is one of the important factors used for examining tissue condition and blood circulation in a living body. Theoretical analysis has been carried out to measure the velocity, based on the dynamic light scattering method. We obtained a theoretical model that, the mean frequency of the power spectrum of scattered laser light from a tissue could be expressed as a function of the velocity, the angular scattering characteristic of an erythrocyte and the mean number of collisions between photons and erythrocytes. The theoretical model was verified by experimental results using a tissue blood flow model system. The velocity and the number density of erythrocytes in a tissue can be measured simultaneously using the method, and thus we can obtain the mass flow of erythrocytes.
Measurement of Elastic Moduli by Rectangular Parallelepiped Resonance Method II
Authors: Masahiro Inohara Masahiro Inohara , Tetsuro Suzuki Tetsuro Suzuki
Published: February 2005

The rectangular parallelepiped resonance method can be a very powerful method if universal procedure to obtain elastic moduli from measured resonance frequencies is established. The procedure proposed in this paper has the possibility to determine all elastic moduli of crystals with symmetry down to orthorhombic symmetry. However, we have only confirmed that the method gives correct elastic moduli of specimen with cubic symmetry without previous information. Although we need a great many of measured resonance frequencies from the lowest frequency to very high frequencies to determine all independent elastic moduli of specimen having lower symmetry than cubic symmetry, we can determine the shear moduli (C
44, C
55, C
66) from much fewer of measured resonance frequencies.
Nonlinear Equivalent Circuit Model Analysis of Acoustic Devices and Propagation of Surface Acoustic Wave
Authors: Cho Yasuo , Junji Wakita Junji Wakita , Nozomu Miyagawa Nozomu Miyagawa
Published: February 2005

The generation of acoustic phase conjugate waves is demonstrated using our previously reported nonlinear equivalent circuit of thin bar with length-extensional vibration. Next, a new nonlinear equivalent circuit for propagating nonlinear surface acoustic wave (SAW) is proposed. Using this new circuit, it is shown that the metallic grating wave guide of SAW is equivalent to the nonlinear lattice in which the SAW soliton propagates. Finally, the experimental study about this waveguide is successfully performed.
Emphasis of Second Harmonic Component Generated at Focal Region for Nonlinearly Distorted Sound Detected by a Large Planar Receiver
Authors: Shigemi Saito Shigemi Saito , Mitsuhiko Murata Mitsuhiko Murata
Published: February 2005

Fundamental and nonlinearly generated second harmonic components averaged on an infinite plane set perpendicular to the axis of focused sound are investigated by means of perturbation analysis of the Khokhlov-Zabo-lotskaya-Kuznetsov equation and an experiment with a 1.9 MHz focused Gaussian beam. The averaged second
harmonic component P
2 advances in its phase φ by π/2 radians relative to the averaged fundamental component during its propagation across the focal region. By means of the phase variance φD from the phase in front of the focal region, ||
P
2||
sin φD can be used for emphasizing the second harmonic portion generated at the focal region.
High-Speed Measurement of B/A for Liquidlike Media by Time-of-Flight Method
Authors: Endoh Nobuyuki , Kibukawa Hiroshi , Kojima Kenji , Takeshi Itoh Takeshi Itoh , Ken-ichi Kurakami Ken-ichi Kurakami
Published: February 2005

Acoustical nonlinearity parameter B/A measurement is reported for soft tissues, because the B/A values of soft tissues have great potential for tissue characterization. The interference method previously reported required about two minutes to obtain the B/A value. High-speed measurement is required to obtain the B/A change, because B/A values at adiabatic and isothermal conditions relate physical factors of soft tissues. Use of the time-of-flight (TOF) method has been reported to obtain B/A values at about 60 times atmospheric pressure. However, since physical characteristics in soft tissues usually change under such circumstances, the tissue characterization requires B/A values obtained at near-normal pressures. In this paper, we describe an improvement of the high-speed measurement method for liquidlike media under the pressurized condition of 3 times atmospheric pressure. We studied change in B/A as a function of time in a pressure chamber.
Ultrasonic Transducer with Stacked Porous Piezoelectric Ceramics
Authors: Mizumura Koichi , Yoshiaki Kurihara Yoshiaki Kurihara , Hiroshi Ohashi Hiroshi Ohashi
Published: February 2005

Stacked porons Pb(Zr, Ti)O3 (P-PZT) disks are applied to an ultrasonic transducer of 50 kHz to lower the resonance impedance in the thickness mode vibration. The stacked disk structure is composed of four adhered P-PZT disks. Each of them has a resonance frequency of 200 kHz in the thickness mode. The transducer with stacked P-PZT disks, evaluated in water, features the low resonance resistance of 336 Ω, low Q value of 5.3, transmitting sensitivity of 153.8 dB for 1 µPa/V and a receiving sensitivity of -180.2 dB for 1 V/µPa.
Vibrational Analysis of Tuning Fork Gyroscope with Orthogonal Vibration Arms
Authors: Kudo Subaru , Konno Masashi , Yoshida Sumio Sugawara
Published: February 2005

In this paper we describe the tuning fork gyroscope with orthogonal vibration arms used as a yaw rate sensor. The vibrational displacements of the gyroscope are analyzed using the finite element method, and a new structure for a gyroscope which can be supported at a vibrationless point is presented. It is expected that this gyroscope will be applicable as a yaw rate sensor with a high quality factor and high stability.
Composite Diaphragm Ultrasonic Transducers Employing Air-Gap Structure
Authors: Shiokawa Jun-ichi , Makishima Yoshiki , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: February 2005

This paper aims at discussing the possibility of applying an air-gap structure to the development of composite diaphragm ultrasonic transducer arrays. Analysis suggests that low-loss, wide-bandwidth transducers could be realised using Pyrex-glass/ZnO/Pyrex-glass composite diaphragms fabricated on an air-gap. It is also shown that the transducer performance is considerably improved with another polyimide matching layer. A transducer consisting of a Pyrex-glass/ZnO/Pyrex-glass composite diaphragm on an air-gap was experimentally fabricated, and its basic performance was shown.
Propagation Characteristics of Surface Acoustic Waves in ZnO/LiNbO3 Structures
Authors: Kiyoshi Nakamura Kiyoshi Nakamura , Toshiaki Hanaoka Toshiaki Hanaoka
Published: February 2005

In this paper, we report that the propagation characteristics of surface acoustic waves (SAWs) in a structure consisting of a piezoelectric layer on a piezoelectric substrate depend on the relationship between the polarities of the two piezoelectric media. The theoretical analysis of the characteristics of the Rayleigh wave in ZnO/128°-rotated Y-cut LiNbO3 structures shows that there is a large difference in values of electromechanical coupling factor K in the two cases where the ZnO layer is deposited on the positive surface and the negative surface of LiNbO3, and that the value of K
2 can be as high as 13.3%. The mode coupling phenomenon between the Rayleigh and Love waves is also discussed.
Characteristics of Zinc Oxide Films on Glass Substrates Deposited by RF-Mode Electron Cyclotron Resonance Sputtering System
Authors: Kadota Michio , Minakata Toru Kasanami
Published: February 2005

There are two types of electron cyclotron resonance (ECR) sputtering systems, DC-mode and RF-mode. In this paper, the properties of zinc oxide (ZnO) film deposited by an RF-mode ECR sputtering system capable of long-term stable deposition are investigated. It is confirmed for the first time that this system is capable of depositing a ZnO film having a sidewall structure without columnar or fibrous grains on an interdigital transducer (IDT)/glass substrate. The ZnO films so deposited were capable of driving the 1.1 GHz fundamental mode in a Rayleigh surface acoustic wave (SAW) without the large propagation loss at high frequencies of conventional ZnO films. Furthermore, ZnO films deposited by this system exhibited 1.7 dB lower insertion loss and a closer agreement between effective electromechanical coupling factors (k
eff) and the corresponding values calculated with the finite element method (FEM) in comparison with the films deposited by the DC-mode ECR sputtering system.
Lamb Wave Propagation Characteristics on Water-Loaded LiNbO3 Thin Plates
Authors: Akihiro Sawaguchi Akihiro Sawaguchi , Kohji Toda Kohji Toda
Published: February 2005

Propagation characteristics of leaky Lamb waves propagating along a water-solid interface of a rotated Y-cut X-propagation LiNbO3 thin plate are numerically analyzed. Velocity dispersion characteristics, mode conversion efficiency, electromechanical coupling constant of an interdigital transducer and transducer efficiency in the Z-cut plate are described as a function of frequency times substrate thickness. The zeroth-order symmetrical mode has a high coupling constant of over 20% for rotation angles from 0° to 15°. The experimental results obtained from the center frequencies of the leaky Lamb wave devices are in good agreement with results from numerical analysis. The analyzed propagation characteristics and transducer performance are useful in constructing a leaky Lamb wave device with a water-solid interface.
A Longitudinal-Flexural Complex-Mode Ultrasonic High-Power Transducer System with One-Dimensional Construction
Authors: Watanabe Yuji , Yoneo Tsuda Yoneo Tsuda , Eiji Mori Eiji Mori
Published: February 2005

A newly designed longitudinal-flexural complex-mode transducer system is described. The one-dimensional composition of the transducer system is brought about by placing two sets of piezoelectric ceramics in a straight bar. This bar vibrates with longitudinal-mode vibration and flexural-mode vibration at the same resonant frequency. Therefore, the transducer can take the place of the conventionally used longitudinal-mode transducer when a complex mode is required. This paper describes the design procedure of the transducer system.
Characteristics of Bending Parts of Metal Plates Using Ultrasonic Bending Systems with a Vibration Punch and a Vibration Die
Authors: Tsujino Jiromaru , Ueoka Tetsugi , Takiguchi Kazuhiro , Hajime Satoh Hajime Satoh , Kazumitsu Takahashi Kazumitsu Takahashi
Published: February 2005

Characteristics of ultrasonic vibration bending of pure aluminum and anticorrosive aluminum plates of 2.0 to 3.0 mm thickness are studied using a 19 kHz longitudinal vibration punch and a 27 kHz vibration die. With ultrasonic vibration, the springback angle decreases to zero under sufficient vibration amplitude, bending angle increases and marked improvement of bending surface condition is obtained. Hardness of the specimen and elongation of the bending surface decrease, and roughness of the bending surface is decreased by vibration. Radius of curvature of the bending part increased to about double that without vibration.
Observation of Acoustic Emission Signals from a Ceramic Coating Layer on Polyethylene Terephthalate Film
Authors: Noritaka Nakaso Noritaka Nakaso , Hiroyuki Yasujima Hiroyuki Yasujima
Published: February 2005

We observed 100-MHz-band acoustic emission (AE) signals from a 2-µm-thick ceramic coating layer on a 12-µm-thick polyethylene terephthalate (PET) film using a point focus beam (PFB) transducer. The S/N was about 11 dB. The power spectra of the signals showed peaks at 36 MHz and 70 MHz, which are attributed to the AE energy propagating along the specimen as Lamb waves.
Chemical Isotropic Etching of Single-Crystal Silicon for Acoustic Lens of Scanning Acoustic Microscope
Authors: Hashimoto Hisayoshi , Tanaka Shinji , Sato Kazuo , Ishikawa Isao , Kato Sigeo , Chubachi Noriyoshi
Published: February 2005

An acoustic lens for a scanning acoustic microscope (SAM) was newly fabricated by means of chemical isotropic etching of a silicon wafer. This novel lens fabrication process has been developed to obtain surfaces with good sphericity and smoothness, which are essential requirements for acoustic lenses. Acoustic lenses are conventionally fabricated by using grinding methods. A variety of wafers, etchants and etching conditions were investigated; the (100) wafer was the most preferable for fabrication of a symmetrical lens profile, and the optimum etchant was found to be a mixture of hydrofluoric, nitric and acetic acids with a ratio of 2:3:3 at a temperature of 50°C. A silicon acoustic lens with a radius of 140 µm designed for use at 600 MHz and a resolving power of 1.8 µm was successfully fabricated.
Photoluminescence Study of Heavily Te-doped GaAs Grown by Liquid-Phase Epitaxy
Authors: Chen Chyuan-Wei , Wu Meng-Chyi , Lu Shoei-Chyuan , Chang Chung-Chi
Published: February 2005

Systematic studies of photoluminescence (PL) are used to characterize the heavily Te-doped GaAs layers with electron concentrations of 9.4×1018-2.3×1019 cm-3. For the undoped layer with an electron concentration of 1×1015 cm-3, the near-band-to-band transition is found to dominate the low-temperature PL spectra. While at concentrations above 1018 cm-3, both the band filling as well as band tailing due to the carrier scattering with the ionized donor impurities and band shrinkage due to the exchange interaction between free carriers are considered to account for the observed luminescence behavior. The dependence of spectral shape and broadening on the doping level, excitation power and temperature has been investigated in detail. At concentrations above 1×1019 cm-3, the low-temperature PL spectra is mainly dominated by the low energy, band-edge artifact peak B at 1.488 eV which passes through the substrate, reflects off the back surface, and is emitted from the epitaxial surface. The low-energy transition becomes stronger with doping due to the increase in the band shrinkage.
Strain Evaluation at Si/SiO2 Interface Using the Electroreflectance Method
Authors: Morifuji Masato , Yongwattanasoontorn Pornchai , Taniguchi Kenji , Ozawa Chihiro Hamaguchi
Published: February 2005

An electroreflectance (ER) method is proposed as a new technique to measure
strain at the Si/SiO2 interface.
Measured ER spectra from the Si/SiO2 interface show shifts in photon
energy corresponding to the magnitude of surface strain of Si.
The surface strain is evaluated from band structures of strained Si calculated
from an empirical pseudopotential method.
Theoretical ER spectra of strained Si derived from the energy bands show
good agreement with the experimental results.
The surface strains of the Si subjected to various processing conditions
are evaluated by comparing the shifts of the experimental spectra to those
of the calculated ones.
Dielectric Studies on Binary Mixtures of Tri-n-butyl Phosphate (TBP) and Long-Chain Primary Alcohols (Modifiers)
Authors: Swain Sarat Kumar Dash
Published: February 2005

Dielectric constant (ε) of Tri-n-butyl phosphate (TBP), in binary mixtures with five long-chain primary alcohols viz; 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol has been measured at ν=455 kHz and at temperature 302 K. The data is used to evaluate mutual correlation factor g
ab, excess molar polarization ΔP and excess free energy of mixing ΔF
ab by using Winkelmann-Quitzsch eqn. for binary mixtures to assess the suitability of the alcohols as modifiers. The trend of variation of these parameters exhibit marked dependence on chain-length of the alcohols indicating 1-heptanol to be an efficient modifier.
Three-Dimensional Dielectric Dispersion Equation for Zn-Ta-Ta System in Ba(Zn1/3Ta2/3)O3 Crystal
Authors: Hiroshi Tamura Hiroshi Tamura
Published: February 2005

This paper describes the procedure for deriving a three-dimensional dielectric dispersion equation. As a crystal model, the Ba(Zn, Ta)O3 complex perovskite structure is chosen and three ions, one zinc and two tantalum, are used in the derivation of the dispersion equation. The dynamical matrix for the system Zn-Ta-Ta is derived first. From the eigenvalues and the eigenvectors of this matrix, the resonant frequencies and the forms of the normal modes for this system are determined. With use of the eigenvectors for infrared-active modes, the equation of motion under an applied field is derived for each ion. The dielectric dispersion equation is given from the equation of motion for each infrared-active mode.
Application of Atomic Force Microscopy to the Study of Size Fluctuation in E-Beam Patterned Quantum Wire Structures
Authors: Notomi Masaya , Masashi Nakao Masashi Nakao , Toshiaki Tamamura Toshiaki Tamamura
Published: February 2005

We report, for the first time, a quantitative study on the size fluctuation in e-beam patterned quantum wire structures using atomic force microscopy. By numerically treating the high resolution three-dimensional data obtained with an atomic force microscope, we determine the average wire width and evaluate standard deviations of wire widths. Using these data, we investigate the intra and interwire fluctuations separately. Results show that intrawire fluctuation is greatly reduced by reverse-mesa etching but that the interwire fluctuation remains. This shows that atomic force microscopy is a very powerful tool for the investigation of semiconductor multi-dimensional quantum confined structures.
Observation of Atomic Defects on LiF(100) Surface with Ultrahigh Vacuum Atomic Force Microscope (UHV AFM)
Authors: Ohta Masahiro , Konishi Takefumi , Sugawara Yasuhiro , Morita Seizo , Suzuki Mineharu , Enomoto Yuji
Published: February 2005

We have constructed an atomic force microscope (AFM) operating under an ultrahigh vacuum (UHV). We have imaged the cleaved (100) surface of LiF ionic crystal to clarify the AFM's performance. As a result, for the first time, we have obtained atomically resolved AFM images of atomic defects penetrating the surface. This result seems to suggest that the cleaved LiF (100) surface was imaged under the condition of monoatomic or small cluster tip-sample interaction.
Radical Kinetics in a Fluorocarbon Etching Plasma
Authors: Yukinobu Hikosaka Yukinobu Hikosaka , Hideo Sugai Hideo Sugai
Published: February 2005

Neutral free radicals, CF3 and CF2, in a radio-frequency CF4/H2 discharge were detected using appearance mass spectrometry. The spatial density distributions of these radicals were obtained with the mixing ratio of H2/CF4 as a key parameter. Adding a 10% H2 gas to CF4 enhanced the CF2 density by a factor of 50 and flattened the spatial profile. By the injection of the H2 gas abruptly into the CF4 discharge, the temporal transition to the CF4/H2 discharge was investigated. When the percentage of H2≥5%, a strange time variation is found for the CF3 radical: its density sharply rises by a factor of 10 and slowly falls to a value close to the initial one. The slow time response was attributed to the H2-induced polymer deposition. The surface loss probability of CF2 and CF3 was measured in various conditions which suggested the importance of surface chemistry of radicals.
A Phenomenlogical Study of Particulates in Plasma Tools and Processes
Authors: Gary S. Selwyn Gary S. Selwyn
Published: February 2005

Particle contamination in a variety of plasma processes and tools has been studied using a real-time, in-situ detection technique, rastered laser light scattering. In agreement with previous studies, particles were suspended in the plasma. The distribution of particles, however, is highly ordered and predictable, in contrast to the randomness which typifies particulate behavior in uncharged environments, such as cleanrooms. The importance of electrostatic particle trapping is seen, as a means of understanding this ordered distribution of particles, for predictive performance of process tools in manufacturing, and for contamination control in processing tools. The implications of these results on future plasma processing is briefly discussed.
Photoluminescence of Eu2+ and Eu3+ Centers in CaS:Eu,Na Phosphors
Authors: Yamashita Nobuhiko , Fukumoto Shigeru , Ibuki Sumiaki , Ohnishi Hideomi
Published: February 2005

Photoluminescence and excitation spectra, luminescence decay curves, and time-resolved photoluminescence spectra are observed for CaS:Eu,Na powder phosphors at various temperatures between 10 and 297 K. The detailed spectra of the Eu3+ center in CaS are observed for the first time. The emission lines due to the Eu3+ center are classified into two groups originating from centers A and B. The A center is attributed to the isolated Eu3+ center, whereas the B center, to the paired Eu3+-Eu2+ center.
Magneto-optical Disk for Magnetic Field Modulation Recording Method with Multi-Pulsed Laser Irradiation
Authors: Kawasaki Satoshi , Ishizuka Kenichi , Shinichi Katsuda Shinichi Katsuda , Mitoshi Sohmuta Mitoshi Sohmuta
Published: February 2005

The authors report magnetic field modulation (MFM) recording characteristics for magneto-optical (MO) disks, whose magnetic sensitivity was improved through sputter-etching treatment of the SiN layer beneath the magnetic layer. The sputter-etching treatment increased weak-field recording noise, as well as reproduced signal amplitude. Jitter caused by such noise can be reduced by the introduction of a new MFM recording method with multi-pulsed laser irradiation. This paper discusses the mechanism for the improvement of such MFM recording characteristics on the sputter-etched MO disks.
Polarization Characteristics of Alumina Films Anodized at Low Temperature
Authors: Huang Li-Feng , Mitsunori Saito Mitsunori Saito , Mitsunobu Miyagi Mitsunobu Miyagi
Published: February 2005

A prominent polarization function appears in anodic alumina films when oxidation is carried out at low temperature around 0°C. The alumina film that is anodized at 25 V and 0°C exhibits the extinction ratio of >30 dB/mm at the wavelengths of 0.6-1.6 µm. The polarization function seems to originate from unoxidized aluminum, which increases upon lowering of the anodization temperature. Using the polarization function, we fabricated a polarizer consisting of laminated alumina films.
Initial Boronization of JT-60U Tokamak Using Decaborane
Authors: Saidoh Masahiro , Ogiwara Norio , Shimada Michiya , Arai Takashi , Hiratsuka Hajime , Koike Tsuneyuki , Shimizu Masatsugu , Ninomiya Hiromasa , Nakamura Hiroo , Jimbou Ryutarou , Yagyu Jyunichi , Sugie Tatsuo , Sakasai Akira , Asakura Nobuyuki , Yamage Masashi , Sugai Hideo , Jackson Gary L.
Published: February 2005

A decaborane-based boronization system has been installed in the JT-60U tokamak in order to reduce the influx of impurities during plasma discharges. Boronization has been performed under a glow discharge using a helium-decaborane gas mixture. The properties of the boron films deposited through boronization and the effects of boronization on the tokamak discharges were investigated. It was found that the deposition of a boron layer with high purity was achieved with few impurities other than hydrogen through boronization, and that the present boronization deposited toroidally nonuniform boron film. It was also found that the decaborane-based boronization resulted in good plasma performance similar to that of conventional boronization.
Study of X-Ray Reflectivity from Si Film/Interface Layer/Si Substrate and Application to Low-Temperature Epitaxially Grown Si/Si Substrate
Authors: Usami Katsuhisa , Norio Kobayashi Norio Kobayashi , Akihiro Miyauchi Akihiro Miyauchi
Published: February 2005

An approximate equation for X-ray reflectivity from a Si film/interface layer/Si substrate with a smooth surface was derived analytically. The oscillation amplitude, corresponding to the Si film thickness, is modulated with a sine function due to the presence of the interface layer. The thickness and X-ray refractive index of the interface layer can be evaluated from the period of the sine function and the maximum value of the oscillation amplitude, respectively, when the reflectivity is expressed on a logarithmic scale. This method was applied to analysis of a defective Si film epitaxially grown on Si substrate. The oscillation structure was observed in the X-ray reflectivity and its amplitude was modulated with a sinelike function. This meant that there was a layered structure near the interface between the epitaxially grown Si film and Si substrate. The average thickness and density of the layer were evaluated from the reflectivity and were determined to be about 1.4 nm and 2.09 g/cm3, respectively.
Photoluminescence Properties of Sn-Related Donor State in AlxGa1-xAs
Authors: Kang Junyong , Iida Seishi , Huang Qisheng , Fukuda Tsuguo
Published: February 2005

We have investigated the near-gap recombinations in Sn-doped Al
x
Ga1-x
As by photoluminescence. By analyzing the variations of spectral lineshapes under various excitation intensities, only one type of recombination was assigned to associate with the Sn-related donor state, which was different from the hydrogenlike shallow donor states and the DX centers. Phonon replicas were observed to accompany the recombination in the samples with high AlAs mole fractions of direct gaps, as well as in those of indirect gaps. The Franck-Condon shift and the phonon energy of the recombination were found to increase with increasing AlAs mole fraction. This behavior was explained in terms of a variation of local lattice distortion around an ionized Sn-related donor and a weighted average of two local vibrational mode frequencies of the Sn-related donor.
Comparison of Measurement Techniques for Gate Shortening in Sub-Micrometer Metal Oxide Semiconductor Field Effect Transistors
Authors: Bhattacharya Pradeep , Mohammad Bari Mohammad Bari , Krishnaraj Rao Krishnaraj Rao
Published: February 2005

In this paper, various methods of evaluating the electrical channel length change (or gate shortening) as a result of applied gate voltage in sub-micrometer metal oxide semiconductor field effect transistors (MOSFETs) are investigated and the method best suited for such short channel length devices is reported. Studies were performed on n-channel transistors (n-MOSFETs) fabricated using X-ray and optical lithography and having channel lengths in the range of 0.4 to 4 µm and 1.5 to 10 µm respectively. The effective channel lengths were extracted from the current-voltage (I-V) measurements. The measurements were made for different low and high sets of gate voltages. In comparing various methods it was found that the method due to Terada and Muta, and Chern et al. gave accurate results consistently for short channel MOSFETs, whereas the Whitfield method gave accurate results only for larger channel length MOSFETs. The accuracy of the Whitfield method is sensitive to applied gate voltage during I-V measurements. The Peng and Afromowitz method is unsuitable for finding the effective channel length of sub-micrometer MOSFETs especially if the MOSFETs have high values of external resistance.
Kβ X-Ray Emission and K X-Ray Absorption Spectra of Sulfur in Sulfate Compounds
Authors: Chikara Sugiura Chikara Sugiura
Published: February 2005

With a two-crystal vacuum spectrometer, the sulfur Kβ emission spectra in fluorescence are measured for a series of alkali, alkaline-earth and hydrated 3d transition-metal salts with the SO4
2- ion. In addition, the sulfur K absorption spectra in a series of hydrated 3d transition-metal sulfates are measured with a bent-quartz-crystal vacuum spectrograph. The measured Kβ emission and K absorption spectra are presented along with the sulfur K absorption spectra of alkali and alkaline-earth sulfates reported previously. It is shown that the Kβ emission and K absorption spectra of sulfur in alkali and alkaline-earth sulfates are influenced by the cations, while those of hydrated 3d transition-metal sulfates are little affected by the metal ions. The sulfur Kβ emission spectra and the sulfur K absorption spectra are interpreted in terms of the molecular orbitals of the SO4
2- ion.
Resistivity of Ultrafine Iron Particles in a Glass Matrix
Authors: Saibal Roy Saibal Roy , Dipankar Chakravorty Dipankar Chakravorty
Published: February 2005

Bulk samples containing nanometer-sized iron particles in a silica glass matrix have been prepared by hot pressing sol-gel derived precursor powders subjected to reduction treatment. All samples exhibit metallic behaviour. The resistivity variation as a function of temperature in the range of 80 to 340 K shows a phonon softening effect in these ultrafine particles.
Epitaxial Growth of TiO2 Rutile Thin Films on Sapphire Substrates by a Reactive Ionized Cluster Beam Method
Authors: Fukushima Kazunori , Takaoka Gikan H. , Yamada Isao
Published: February 2005

TiO2 thin films were grown on sapphire substrates at 500°C by means of reactive ionized cluster beam (RICB) deposition. The TiO2 thin films grown on sapphire (0001) and (112̄0) substrates were single-crystalline and had the rutile structure. The epitaxial orientation relationships between the rutile films and the sapphire substrates were found to be (1) rutile (200)//Al2O3(0001) and (2) rutile (101)//Al2O3(112̄0). On (11̄02) sapphire substrates, the films showed both the anatase (101) and rutile (101) structures. The concept of near-coincidence lattice sites was applied to show that the lattice misfit at the interface between these rutile and sapphire planes was small (less than a few percent).
Effect of Incident Direction of ArF Laser to Graphite Substrates on the Formation of Photo-Chemical Vapor Deposition SiC Film
Authors: Suzuki Hiroshi , Hiroshi Araki Hiroshi Araki , Tetsuji Noda Tetsuji Noda
Published: February 2005

The effect of the ArF incident beam direction to graphite substrates on the structure of photo-chemical vapor deposition (photo-CVD) SiC films at 294-714 K was examined using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Microcrystalline β-SiC film was obtained using the perpendicular beam even at room temperature, whereas only amorphous SiC was formed using the parallel beam. Crystalline SiC formation was considered to be due to the direct excitation of the graphite substrate followed by the surface migration of reactant radicals.
Inductive Effect of Magnetic Field on Crystal Growth in Amorphous-Ni-P Alloy
Authors: Yamamoto Motokazu , Watanabe Nobuyoshi , Zhao Yi , Ge Bingheng
Published: February 2005

Amorphous-Ni-P alloy crystallizes when heated, and it has been found that the growth of crystals is induced by applying a magnetic field. Crystals which thus grow are Ni5P4 containing Ni. Ni crystal nuclei are believed to be generated by the magnetic field in the initial stage of growth, and Ni5P4 crystals grow around them.
Transmissivities of Radiation Beams and Particle Beams in Binary Mixed Materials
Authors: Ryusuke Tsuji Ryusuke Tsuji
Published: February 2005

The dependence of radiation and particle beam transmissivity on grain size in binary (A and B) mixed materials is studied by means of a statistical method. The beam transmissivity at a distance L from the source is approximated as exp [-p
L/λA] exp [-(1-p)L/λB] exp [α2
p(1-p)L
d/2] in one dimension, where λA and λB are the mean free paths of beam particles in materials A and B, respectively, p is the volumetric ratio of material A in the mixed region, d is the grain size, and l
a
l
p
h
a=λA
-1-λB
-1. This approximation is valid if the condition abs [(p-1/2)-αp(1-p)d]<1/2 holds. In the case that d>α-1(1-p)-1, λA>0 and λB=∞, the beam transmissivity is approximated as (1-p)L/d.
Cathode Fall Characteristics of Fluorescent Lamps under High-Frequency Operation
Authors: Yoshio Watanabe Yoshio Watanabe , Seiichi Murayama Seiichi Murayama
Published: February 2005

The cathode fall voltage in a fluorescent lamp is investigated under operation frequencies of DC, 50 Hz and 43 kHz. The cathode fall voltage is measured by a probe technique, from the discharge voltage at a short electrode distance. The obtained effective values of the cathode fall voltage are about 11 V, 10 V and 6 V for DC, 50 Hz and 43 kHz, respectively. The reason why the cathode fall voltage is low under 43 kHz operation, in which the electrode heating loss is smallest, is explained as follows. Ion space charges in front of the electrode always exist under high-frequency operation. Thus, the discharge current is always concentrated at the cathode-spot position. Therefore, the cathode-spot position is efficiently heated even with small heating power.
Simplified AC Photovoltaic Measurement of Minority Carrier Lifetime in Czochralski-Grown Silicon Wafers Having Ring-Distributed Stacking Faults
Authors: Honma Noriaki , Shimizu Hirofumi , Chusuke Munakata Chusuke Munakata
Published: February 2005

A simplified ac photovoltaic method is proposed for rapid measurement of minority carrier lifetime. It is used for lifetime distribution measurement in a Czochralski-grown silicon wafer having ring-distributed stacking faults. A ring-distributed short-lifetime region was observed which corresponded to the stacking fault ring detected by X-ray topography. In addition, a ring-shaped region where the lifetime is longer than 100 µs was observed for the first time outside the short-lifetime region. This long-lifetime region could not be detected by X-ray topography.
Dependence of the Grown-in Defect Distribution on Growth Rates in Czochralski Silicon
Authors: Sadamitsu Shinsuke , Umeno Shigeru , Koike Yasuo , Hourai Masataka , Shigeo Sumita Shigeo Sumita , Tatsuhiko Shigematsu Tatsuhiko Shigematsu
Published: February 2005

As-grown defects in 6-inch-diameter Czochralski-silicon crystals grown under different crystal growth rate conditions (0.4, 0.7, 1.1 mm/min) were studied by means of preferential etching and IR light-scattering tomography (LST). Grown-in defect images were classified into four types as follows: (a) flow patterns (wedge-shaped etch pits), (b) IR-defect images observed by LST, (c) ringlike distributed small pits, and (d) large pits. It was found by secondary ion mass spectrometry that IR defects are oxygen precipitates. Large pit defects were identified by transmission electron microscopy as large dislocation loops with a length of about 30 µm. At growth rates from 0.7 mm/min to 1.1 mm/min, flow pattern defects and IR defects coexist inside a ringlike distributed oxidation-induced stacking fault (ring-OSF) region. However, at growth rates less than 0.7 mm/min, large pit defects were observed in the region outside the ring. Characteristic ringlike distributed small pit defects were observed on the outer periphery of the ring region. Flow pattern defects were annihilated during annealing at 1100°C, while IR defects were stable at 1250°C.