bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Emitter-Base Contact Spacing on the Current Gain in Heterojunction Bipolar Transistors
Authors: Jr. William Liu
Published: February 2005

The minimum emitter-base contact spacing necessary to prevent current gain degradation is discussed for Npn heterojunction bipolar transistors designed for high-speed applications. Theoretical calculations are performed for various base doping levels, base thicknesses, and emitter widths. These results indicate that the minimum spacing for different design parameters varies between 400 Å and 1300 Å.
Effect of Fermi Level Motion on ESR and Optical Properties of CuAlS2
Authors: Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: February 2005

Optical absorption and electron spin resonance (ESR) spectra have been studied in as-grown, Cr-doped, and annealed in different atmospheres CuAlS2crystals. It has been found that the major influence on the optical and ESR properties of CuAlS2crystals, obtained by chemical vapour transport, arises from the transition ions Fe3+and Cr2+, which are present in the crystal lattice as residual impurities. Thermal treated crystals exhibit drastic changes in their absorption and ESR spectra depending on the annealing atmosphere, which is explained by the process of the Fermi level motion in the vicinity of the Fe2+/Fe3+and Cr+/Cr2+demarcation levels. The results obtained show that the valence states of Fe and Cr ions and their relative amounts in each valence state are controlled by the position of the Fermi level in the band gap of the host crystal, and are stoichiometry on dependent.
Far-Infrared Reflectance Spectra of AlxGa1-xAs/GaAs Superlattices for Various Al Mole Fractions
Authors: Fukasawa Ryoichi , Wakaki Moriaki , Shirawachi Kikuo , Ohta Seiji Nishizawa
Published: February 2005

We report far-infrared reflectance spectra of Al
x
Ga1-x
As/GaAs superlattices with various aluminium (Al) mole fractions (0.1<x<0.7). The experimental reflectance spectra agree well with the calculated ones derived using the characteristic-matrix method within the theory of thin-film optics.
Vacuum Ultraviolet Emissions from Alkali-Halide Ionic Excimer (CsF)+ by Electron Beam Excitation
Authors: Xing Da , Ken-ichi Ueda Ken-ichi Ueda , Hiroshi Takuma Hiroshi Takuma
Published: February 2005

The vacuum ultraviolet (VUV) fluorescence from an ionic alkali-halide excimer (CsF)+ was observed by electron beam excitation. A gas mixture of helium or neon with a hot vapor of cesium fluoride was excited to obtain two diffuse emission bands centered at 185 and 152 nm from the ionic excimer Cs2+F-, which is isoelectronic to the XeF excimer. The strong continuum emission centered at 185 nm was attributed to the B2Σ+→X2Σ+ bound-free band of (CsF)+, and the continuum from 145 to 155 nm was identified as the (CsF)+ D2Π→X
2Σ+ bound-free transition. The formation mechanisms of these upper states were proposed to be a two-body or a three-body collisional charge transfer of He+ or Ne+ and Penning ionization of He* with neutral ground-state CsF molecules.
High-Efficiency InGaAlP Visible Light-Emitting Diodes
Authors: Sugawara Hideto , Itaya Kazuhiko , Masayuki Ishikawa Masayuki Ishikawa , Gen-ichi Hatakoshi Gen-ichi Hatakoshi
Published: February 2005

A new structure for InGaAlP light-emitting diodes (LEDs) which include a GaAlAs current-spreading layer has been designed. Remarkable improvements in external efficiency have been achieved using this structure. The photoluminescence and electroluminescence characteristics of high-Al-content InGaAlP alloys have been investigated. A GaAs substrate with an intentional surface misorientation from the nominally (100) plane towards the [011] direction was found to have a marked effect on the improvement of emission properties. The external quantum efficiency was 1.2% at 592 nm for an In0.5(Ga0.7Al0.3)0.5P active layer LED. These LEDs have been operated for more than 1500 hours at 80°C and 50 mA.
Theory of Visible Light Emission from Scanning Tunneling Microscope
Authors: Uehara Yoichi , Kimura Yuichi , Takeuchi Sukekatsu Ushioda
Published: February 2005

The mechanism for visible light emission from the scanning tunneling microscope (STM) has been investigated theoretically by adapting a theory for light emitting tunnel junctions (LETJ). From the analysis of the calculated results and available experimental data, the following picture emerges. The tunneling current first excites localized surface plasmons (LSP) that are localized in a region of a few tens of Angstroms between the STM tip-front and the sample surface. Some of them decay into surface plasmon polaritons (SPP) that propagate along the sample surface. There are two channels of light emission: one is direct emission from LSP and the other is emission through SPP. The relative
branching ratio between these two channels depends on the experimental configuration. The effect of sample surface roughness is very small and negligible.
Electrical Resistivity and High-Field Magnetoresistance of Zr-N Film Thermometers
Authors: Yoshizawa Masahito , Ikeda Kôki , Sugawara Hitoshi , Toyota Naoki , Yotsuya Tsutom , Yoshitake Masaaki
Published: February 2005

Temperature and magnetic field dependence of the resistivity of Zr-N sputtered films have been measured. The characteristics of Zr-N film, that they can be divided into two groups by the ratio of the resistance at helium and room temperatures, have been precisely investigated. There are marked differences in both the temperature dependence of resistance and in the magnetoresistance between the two groups. The temperature dependence of magnetoresistance of the films has been discussed within the framework of Anderson localization. The origin of magnetoresistance was also discussed.
Pyroelectric Coefficient and Heat Capacity of a Ferroelectric Copolymer of Vinylidene Fluoride and Trifluoroethylene at Low Temperatures
Authors: Guo-Rong Li Guo-Rong Li , Hiroji Ohigashi Hiroji Ohigashi
Published: February 2005

The temperature dependence of the static pyroelectric coefficient p and dynamic pyroelectric response voltage V
s of a highly crystallized ferroelectric copolymer of vinylidene fluoride (75 mol%) and trifluoroethylene (25 mol%) is measured in the temperature range of 10-300 K. The observed p and the heat capacity C
p derived from p/V
s both decrease with decreasing temperature, tending toward zero in the vicinity of 0 K. The temperature dependence of C
p is fitted to the capacity contributed from three- and one-dimensional acoustical modes of vibrations with Debye temperatures of 52 K and 460 K, respectively, and contributed from main optical vibrations. It is found that the one-dimensional acoustical vibrations and optical vibrations with an average frequency of about 290 cm-1 dominantly contribute to the primary pyroelectric coefficient p
1.
X-Ray Topographic Observation of a New 180° Wall and <100> Image in Pure Iron Crystal
Authors: Akira Mihara Akira Mihara
Published: February 2005

The magnetic domain structure in a (100) crystal of pure iron, of about 70 µm in thickness, was investigated using X-ray transmission topography. A visible 180° wall having strong X-ray diffraction contrast could be observed for the first time. It is considered that this new 180° wall has some Néel wall segments on the structure within the wall. Furthermore, two neighboring walls and <100> images were observed simultaneously.
Growth by Liquid-Phase Epitaxy and Characterization of Al0.28Ga0.72As0.62P0.38
Authors: Chen Chyuan-Wei , Meng-Chyi Wu Meng-Chyi Wu , Li-Kuang Kuo Li-Kuang Kuo
Published: February 2005

Al0.28Ga0.72As0.62P0.38 epitaxial layers were grown on GaAs0.61P0.39 substrates by liquid-phase epitaxy using a supercooling technique. The growth conditions and properties of the undoped AlGaAsP layers are described in detail. A fairly shiny surface and a flat AlGaAsP-GaAsP heterointerface was obtained in our study. The lattice mismatch normal to the wafer surface between the Al0.28Ga0.72As0.62P0.38 layer and GaAs0.61P0.39 substrate is ∼+0.27%. Low-electron-concentration undoped epitaxial layers can be grown from a Ga solution baked at a temperature of 900°C for 10 h or more and with a ∼6°C supersaturation temperature. We obtained the lowest electron concentrations of 1×1016 cm-3 measured by the capacitance-voltage method. By the photoluminescence measurements at various temperatures and excitation levels, the four recombination peaks observed are associated with the near-band-to-band, donor-to-valence-band, conduction-band-to-acceptor and donor-to-acceptor-pair transitions. The band gap of the Al0.28Ga0.72As0.62P0.38 is ∼2.016 eV (6150 Å). The binding energy of the donor and acceptor is 14 and 36 meV, respectively.
Compositional Dependence of the Columnar Grain Structure in Obliquely Deposited Fe1-x-Cox (x=0-1) Films
Authors: Hashimoto Takashi , Okamoto Kunito , Fujiwara Hiroshi , Itoh Kikuo , Kamiya Masao , Hara Kazuhiro
Published: February 2005

The compositional dependence of the columnar grain structure in Fe1-x
-Co
x
(x=0-1) films has been investigated. The films were vapor-deposited at an incidence angle of 65° on glass substrates kept at 473 K. The pressure during deposition was 2.7×10-2 Pa. Reflection ellipsometry detected morphology changes at compositions of 0.02, 0.5, 0.77 and 0.9. The X-ray analysis and replica electron microscopy revealed that these four compositions correspond to the crystallographic changes. With increasing x, columnar grains change texture from type I [111] (11̄0) to [100] (010) at x=0.5 and the crystal structure from bcc to hcp at x=0.9; in the x range from 0.02 to 0.77 columnar grains clearly exhibit the crystal habit. On the basis of these results the crystallographic contribution to the formation of the columnar grain structure is discussed.
Ultrasonic Flat Motor Using Coupling of Longitudinal and Flexural Vibration Modes
Authors: Iijima Tamotu , Nakagawa Yasuhiko , Ito Hiroshi
Published: February 2005

Coupling between longitudinal and flexural modes does not occur when a vibrator is symmetric. On the other hand, the elastic constant of piezoelectric ceramics can be controlled electrically, and due to this effect the coupling mode between longitudinal and flexural modes is excited in a vibrator which is symmetric dimensionally. In this paper, the mechanism of coupling between longitudinal and flexural modes and how to design the vibrator and characteristics of the motor using this coupling vibration have been investigated.
Study of Scanning Electron Microscope Irradiated Damage to Gate Oxides of Metal Oxide Semiconductor Field Effect Transistors
Authors: Nandakumar Rajendram , Pradeep Bhattacharya Pradeep Bhattacharya , Ganesh Kousik Ganesh Kousik
Published: February 2005

Damage induced on typical structures of n-channel metal oxide semiconductor field effect transistors (MOSFETs) by irradiation from a scanning electron microscope (SEM) has been studied. It is observed that up to a critical SEM beam energy of 7 keV the devices are not affected. The maximum damage to the gate insulator occurs for an energy of ∼10 keV above which the extent of damage reduces. Therefore, depending on the device structure, this sets an upper limit on the beam energies during the processing sequence at ∼7 keV. Hot electron injection method used to fill up the traps in the SEM irradiated devices showed that in short channel devices (<3 µm) all the traps do not get labelled due to loss of hot electrons into the bordering field oxide regions. Hence, the threshold voltage does not come back to its unirradiated value even after the hot electron injection procedure, thereby restricting the injection method to devices of channel lengths greater than 3 µm.
Epitaxial Growth of InN by Halogen Transport Method
Authors: Osamu Igarashi Osamu Igarashi
Published: February 2005

InN was epitaxially grown on (0001) α-Al2O3 substrates by the halogen transport method. Surface treatment of the substrate by a H2+Br2 gas (passed over In) just before the growth was essential for obtaining the epitaxial layers of InN. Arrays of extra spots were observed in the reflection electron-diffraction patterns of thin InN films. The extra spot arrays could be explained from the viewpoint that the crystal film was composed of twins. In these twin structures, the twinning planes were (7̄ 12 5̄ 0) and (1̄ 1̄ 20 9̄ 0). These extra spots ultimately disappeared with prolonged growth time. This result shows that as the growth proceeds, crystallites having a predominant orientation overwhelm other crystallites.
Current-Voltage Characteristics of a-Si:H Film Photodiodes Prepared by Mercury-Sensitized Photochemical Vapor Deposition
Authors: Takako Niiyama Takako Niiyama , Hidetoshi Nozaki Hidetoshi Nozaki
Published: February 2005

The current-voltage characteristics of a-Si:H Schottky diodes were studied. The authors adopted a structure comprising Pt Schottky diodes to clarify the relationship between the characteristics of a-Si:H films and a-Si:H diodes. The current-voltage characteristics were closely related to the trap state density in the band gap. The thermionic-emission model was found to be suitable for the transport mechanism in this study. The space charge limited current is suggested as the dominant carrier transport mechanism when a strong forward bias is applied.
Determination of Flat-Band Voltages for Fully Depleted Silicon-on-Insulator (SOI) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET's)
Authors: Lyu Jong-Son , Lee Kee-Soo Nam
Published: February 2005

A method to determine the flat-band voltage, V
FB, in silicon-on-insulator (SOI) metal-oxide semiconductor (MOS) structures has been proposed. It is based on the measurement of the back channel threshold voltages of SOI MOS field-effect transistors (MOSFET's) as a function of the front gate bias. This method is very useful for fully depleted SOI MOSFET's with a low channel dopant concentration. Mean values of V
FB's obtained from this method were -0.79 V for n+ polysilicon gate SOI n-MOSFET's with a gate oxide of 205 Å and an acceptor concentration of 4×1015 cm-3, and -0.12 V for n+ polysilicon gate SOI p-MOSFET's with a gate oxide of 205 Å and a donor concentration of 5×1015 cm-3. The accuracy in the determination of V
FB is mainly dependent on precise evaluations of the front gate oxide thickness, the surface silicon thickness, and the channel dopant concentration.
Transmission Self-Electro-Optic Effect Devices Based on Wannier-Stark Localization in a GaAs/AlAs Superlattice
Authors: Kawashima Kenji , Fujiwara Kenzo , Teiji Yamamoto Teiji Yamamoto , Kikuo Kobayashi Kikuo Kobayashi
Published: February 2005

We have studied optical switching of transmission-type self-electro-optic effect devices (SEEDs) based on Wannier-Stark localization (WSL) in a GaAs/AlAs superlattice (SL). Switching properties of both resister-biased and symmetric SEED are investigated as a function of operation wavelength. Clear optical bistability between two stable transmission states is obtained in the S-SEED configuration using the WSL. The detailed results of optical switching experiments are presented and explained in terms of a blue-shift mechanism of the optical absorption edge and an additional absorption mechanism due to spatially indirect Stark-ladder transitions in the SL. The SEED operation with a high transmission state is also demonstrated, and the advantages of the WSL are discussed for application to vertical transmission photonic switches.
Resistive Transition of Ag-Sheathed Bi-Sr-Ca-Cu-O Tapes
Authors: Akihiko Endo Akihiko Endo , Shunichi Nishikida Shunichi Nishikida
Published: February 2005

The effect of magnetic field on the electric resistivity transition of Ag-sheathed (Bi, Pb)2Sr2Ca2Cu3O
y
tapes in magnetic fields was studied. The transition can be described by the flux creep model, in which the activation energy depends on the temperature, magnetic field and current density. The results show that the activation energy is proportional to the square root of the intensity of the magnetic field (\proptH
-1/2). It is also clarifled that the critical current densitles are controlled by a flux creep mechanism rather than a flux flow model above 40 K.
Junction Characteristics of an Au/Ba1-xKxBiO3/Niobium-Doped SrTiO3 Structure
Authors: Suzuki Hiroshi , Iyori Masahiro , Yamamoto Tetsuya , Suzuki Seiji , Takahashi Kazuhiko , Tatsuro Usuki Tatsuro Usuki , Yorinobu Yoshisato Yorinobu Yoshisato
Published: February 2005

Au/Ba1-x
K
x
BiO3 and Ba1-x
K
x
BiO3/niobium-doped SrTiO3, two types of junctions which correspond to the emitter base and base collector in superconducting base transistors, respectively, have been fabricated and studied. The highest T
c end point (T
c0) of 28 K was obtained of thin film Ba1-x
K
x
BiO3 by rf-sputtering method. The Au/Ba1-x
K
x
BiO3 tunnel spectrum showed a clear gap structure and was very close to the ideal Bardeen Cooper Schrieffer theory's (BCS) form with Δ(0)=3.19 meV. The Ba1-x
K
x
BiO3/SrTiO3(Nb) junction with heavy niobium doping (0.1 wt%) showed tunnellike I-V characteristics. The dI/dV spectrum for a high-T
c superconductor/semiconductor junction displayed the energy gap structure of a superconductor.
Theoretical Analysis of Wavelength Tuning and Power Variation for Complementary Twin-Active-Guide Lasers
Authors: Yamamoto Eiji , Suda Kazuya , Hamada Madoka , Seiji Nogiwa Seiji Nogiwa , Tokukoh Oki Tokukoh Oki
Published: February 2005

We present a theoretical analysis, based on the gain levering effect, of wavelength tuning and power variation for complementary twin-active-guide (CTAG) lasers. The wavelength tuning range is strongly dependent not only on a combination of active layer structures but also on drive condition. Furthermore, slope efficiency in output power vs driver current characteristics is controlled by a bias current into one side of the twin-active layer. These simulations agree with the characteristics of fabricated devices measured under pulsed operations.
Substrate Dependence of Laser-Induced Damage Threshold of Scandium Oxide High-Reflector Coatings for UV Pulsed Laser
Authors: Tamura Shigeharu , Kimura Saburo , Sato Yoshiyuki , Yoshida Hidetsugu , Yoshida Kunio
Published: February 2005

The substrate dependence of the laser damage threshold of high-reflector (HR) coatings (Sc2O3/MgF2 HRs and Sc2O3/SiO2 HRs) for a 355-nm pulsed laser was examined. A correlation between the thermal expansion coefficient of the substrates and the damage thresholds was observed: HRs on substrates with larger thermal expansion coefficient (BK-7, sapphire) had higher threshold than those on substrates with a smaller coefficient (fused silica).
Cathodoluminescent Properties and Energy Transfer in Red Calcium Sulfide Phosphors (CaS:Eu, Mn)
Authors: Ruelle Nathalie , Fouassier Mai Pham-Thi
Published: February 2005

Red and orange calcium sulfide phosphors (CaS:Eu and CaS:Mn) were prepared by the flux method. Eu2+ and Mn2+ show strong concentration quenching at 0.1 and 0.8% respectively. Use of the potassium polysulfide flux leads to efficient phosphors; their efficiency reaches 60 and 100% of Y2O2S:Eu, respectively. Calcium sulfide codoped with Eu and Mn shows a strong increase of Eu2+ in addition to Mn2+ emission. The colour obtained varies between red and orange depending on the concentration rates of Mn and Eu. A luminous efficiency of about 86% was reached for CaS:Eu(0.08%), Mn(0.3%). The decay characteristics of Mn2+ in CaS:Mn, Eu show that the fast part depends on the Eu2+ content. On the other hand, the Eu2+ decay became slower in the presence of Mn2+. These observations support the resonant mechanism of the energy transfer from Mn2+ to Eu2+.
X-Ray Spectroscopic Studies of CaF2, CaO and CaS
Authors: Chikara Sugiura Chikara Sugiura
Published: February 2005

The Kα emission and Kβ emission spectra in the fluorescence of Ca2+in CaF2, CaO and CaS are measured with a two-crystal vacuum spectrometer. Chemical shifts are observed for the Ca2+Kα1,2, Kβ1,3and Kβ5emission peaks. The measured Kβ5emission bands are presented along with the ultraviolet photoelectron spectrum of the F-2p valence band of CaF2, the X-ray photoelectron spectrum of the O2-2p valence band of CaO, the S2-Kβ emission spectrum of CaS and the Ca2+K absorption spectra of these compounds, reported previously. By using these spectra, the first small peak at the Ca2+K absorption threshold of each compound is identified as being due to a core exciton, the energy level of which is formed below the bottom of the conduction band. The binding energies of the excitons are estimated to be 3.6 (±0.4), 2.5 (±0.5) and 0.6 (±0.5) eV for CaF2, CaO and CaS, respectively.
Steady-State Tokamak Operation by Use of Magnetic Monopoles
Authors: Kazumichi Narihara Kazumichi Narihara
Published: February 2005

Steady-state tokamak operation based on a magnetic monopole circuit is considered. Circulation of a chain of iron cubes which trap magnetic monopoles generates the needed loop voltage. The monopole circuit is enclosed by a series of compensation coils in which the magnetic field is feedback-controlled so that the force on the circuit balances the mechanical friction. The driving power is supplied through the current sources of poloidal, ohmic and compensation coils. The current drive efficiency is the same as that of the ohmic current drive.
Kinetics of Chemical Reactions in Hydrocarbon-Hydrogen Plasmas for Diamond Deposition
Authors: Bou Pierre , Jean Claude Boettner Jean Claude Boettner , Lionel Vandenbulcke Lionel Vandenbulcke
Published: February 2005

A previous paper has outlined the basis of a kinetic model applied to the growth of diamond layers using microwave plasmas. The present work deals with the influence on the gas phase composition of the discharge, of some externally controlled parameters such as the methane concentration in hydrogen-methane mixtures, the gas temperature, the nature of the inlet hydrocarbon gas (CH4 or C2H2), and the total flow rate. The importance of the relative concentrations of hydrocarbon neutrals and H atoms at the substrate interface has already been pointed out qualitatively; here, it is proposed that the calculated species concentrations in the discharge can be linked to the nature and deposition rates of the carbon layers. In order to do this, sticking coefficients have been assigned to different neutrals and the influence on the initial plasma composition of this “deposition loss rate” for these species has been taken into account. The relative importance of various species to diamond growth is thus deduced.
Dynamic In-Plane Motion of an X-Ray Mask Membrane Induced by Synchrotron Radiation Irradiation
Authors: Akira Chiba Akira Chiba
Published: February 2005

In-plane motion of thermal distortion in an X-ray mask membrane has been investigated numerically by using a one-dimensional dynamic model. The difference between continuous multiple scanning (CMS) exposure and intermittent multiple scanning (IMS) exposure methods was compared in terms of thermal distortion behavior. Since a residual temperature field is formed by the CMS exposure method, a distorted membrane is not restored to the original state for every scan. For the IMS exposure method, a distorted membrane can be restored to the original state for every scan. Thermal stresses, not dependent on the scanning speed of the CMS exposure method, decrease with increasing scanning speed of the IMS exposure method.
Preparation of PbTiO3 Films Utilizing Self-Control Mechanism of Stoichiometric Composition in Dual-Beam Vacuum Evaporation Method
Authors: Satoshi Ueno Satoshi Ueno , Hiroshi Ishiwara Hiroshi Ishiwara
Published: February 2005

Optimum conditions for preparing PbTiO3 films on Si and SrTiO3 substrates are investigated in the dual-beam vacuum evaporation method using PbO and TiO2. It has been found that tetragonal PbTiO3 films are formed on Si substrates at temperatures ranging from 550°C to 600°C, and that the stoichiometric composition of the films is easily obtained at 600°C by supplying excess PbO molecules to the substrate. It has also been found that PbTiO3 films grow epitaxially on SrTiO3 substrates at temperatures around 550°C.
Effects of Mn Ions on the Piezoelectric Property of (Pb, La)(Zr, Ti)O3
Authors: Izaki Toru , Haneda Hajime , Watanabe Akio , Uchida Yoshishige , Tanaka Junzo , Shirasaki Shin-ichi
Published: February 2005

The effects of sintering temperature and manganese concentration on microstructure and electromechanical property were studied in [Pb0.9La0.1][Zr0.5Ti0.5]O3 piezoelectric ceramics with the substitution of the B-site by manganese by means of scanning electron microscope (SEM) and electron spin resonance (ESR). Grain growth is enhanced by increasing temperature but suppressed by manganese substitution. There was no relationship between Qm (inverse of mechanical vibration loss) and the grain size. Some part of manganese is considered to be reduced to Mn2+ ions during sintering. Qm is considered to be affected by the reduction of manganese ions because it was proportional to Mn2+ concentration, not to total manganese content.
Durability of Piezoelectric Ceramics for an Actuator
Authors: Sakai Takenobu , Mamoru Ishikiriyama Mamoru Ishikiriyama , Ryuji Shimazaki Ryuji Shimazaki
Published: February 2005

Change of piezoelectric properties with the number of loading cycles was measured under various driving conditions, i.e., temperature, preset pressure and driving voltage. Although ε33
T/ε0 changed very little, K
p decreased markedly. K
p decrease is affected by driving condition factors, i.e., minus voltage, preset pressure and temperature, in that order. By optimal arrangement of these factors, K
p decrease could be reduced considerably. K
p decrease is mainly due to 90° switching of the domain. Improvement of mechanical strength for the piezoelectric material is effective both for the suppression of microcrack occurrence and for prevention of K
p decrease. We found that microcrack occurrence caused domain switching. We suggest a deterioration mechanism for piezoelectric ceramics.
Piezoelectric-Ceramic Cylinder Vibratory Gyroscope
Authors: Abe Hiroshi , Tetsuo Yoshida Tetsuo Yoshida , Kikuo Turuga Kikuo Turuga
Published: February 2005

This paper presents a piezoelectric-ceramic vibratory gyroscope with a new structure. The vibrator of this vibratory gyroscope consists of a piezoelectric-ceramic circular cylinder and no adhesion process is necessary. On its outer cylindrical surface, six elongated electrodes are formed in parallel with each other along the central axis. These electrodes are used both for poling treatment and AC excitation as well as detection. Adjustment of resonant frequencies between each of the three terminals by trimming helps eliminate any compensations of circuit constants, so that simple circuitry can be obtained. Because of its small size and simple structure, this vibratory gyroscope is expected to be used in the shake sensor for cameras and hand-held video cameras.
Epitaxially Grown Al Electrodes for High-Power Surface Acoustic Wave Devices
Authors: Sakurai Atsushi , Kimura Koji , Hideharu Ieki Hideharu Ieki , Toru Kasanami Toru Kasanami
Published: February 2005

A deposition process of epitaxial Al film on a quartz substrate was studied to obtain Al electrodes of surface acoustic wave (SAW) devices having high resistance to stress migration. A vapor deposition system was used under relatively moderate deposition conditions: (1) pressure range of 10-5 Pa; (2) deposition temperature of 150°C; (3) deposition rate in the range of 120∼240 nm/min. The growth mode of epitaxial Al film differed from that of polycrystalline Al film on quartz.
Liquid Viscosity Measurement Using SH Wave Propagation Characteristics on Piezoelectric Ceramic Thin Plate
Authors: Akihiro Sawaguchi Akihiro Sawaguchi , Kohji Toda Kohji Toda
Published: February 2005

Liquid viscosity measurement using shear horizontal (SH) wave propagation characteristics on a piezoelectric ceramic thin plate is described. The mode conversion loss associated with the compressional component U3 is zero, because the SH wave on the piezoelectric ceramic substrate poled along the horizontal axis has only the horizontal component U2, The IDT has a much larger electromechanical coupling factor for the S0 mode SH wave than that of the SH surface acoustic wave (SAW). The metal-coated condition of the liquid-loaded surface is essential for detecting the liquid viscosity. There exists a linear relationship between the fractional phase velocity change of the S0 mode and the square root of the liquid viscosity. The measured results on liquid viscosity using the S0 mode SH wave devices, for some concentrations of glycerol-water solutions, are in good agreement with the theoretical prediction.
Dynamic Characteristics of BaTiO3 Ceramic Semiconductors with a Multilayer Structure
Authors: Tashiro Shinjiro , Junichi Arakawa Junichi Arakawa , Hideji Igarashi Hideji Igarashi
Published: February 2005

Transient changes of temperature and current were numerically analyzed in BaTiO3 semiconductors with a multilayer structure to which a constant electric field was applied. The numerical analysis required the radiation coefficient of the multilayer sample and the temperature dependence of resistivity of the material as input data. Temperature distribution of the sample was modeled to be uniform since the material possesses positive temperature coefficients of resistivity in the temperature range above the Curie point. The results of the numerical analysis agreed qualitatively with experimental results in the transient response, although the numerical analysis yielded some disagreements with experimental results when the applied electric field was low. The disagreements between analytical and experimental results are discussed with a focus on temperature distribution in samples.
Complex Impedance Analysis of Nb-Doped (Ba0.6Sr0.4)TiO3 PTC (Positive Temperature Coefficient) Thermistors
Authors: Takao Toshishige Yamamoto
Published: February 2005

Frequency-dependent complex impedances were measured in Nb-doped (Ba0.6Sr0.4)TiO3 PTC (positive temperature coefficient) ceramics. The complex impedance data were analyzed in Cole-Cole-type equivalent circuits by the computer fitting method in order to determine individual resistance and capacitance values of the bulk grain and grain boundary. The PTC effect was found to have originated from the temperature-sensitive behavior of the grain boundary resistance. The temperature dependences of dielectric constants of both the bulk grain and grain boundary calculated on the basis of the two-layer model agreed closely to those predicted by Heywang's model. The width and potential height of the grain boundary layer were estimated to be 0.26 µm and 0.1 eV, respectively, in the temperature range below -20°C. The estimated donor density of 6×1018 cm-3 was much lower than calculated from the amount of Nb2O5 added.4
JIS YB Lead Complex Perovskite Ferroelectric Material
Authors: Fumio Uchikoba Fumio Uchikoba , Kentaro Sawamura Kentaro Sawamura
Published: February 2005

Excess WO3 and higher sintering temperature were used for decreasing the temperature dependence of the dielectric constant in Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 ternary systems. Under some conditions, materials with both JIS YB specifications (dielectric constant change less than 10% over the temperature range from -25 to 85°C) and high dielectric constant, 5000-7400, were obtained. In the materials, core-shell-like distributions of B-site components were observed. These core-shell structures consist of W-rich regions and Ti, Nb-rich regions. In the compositions containing 2% WO3, sintered at 1150°C, core-shell-like domain structures are observed. The fringe pattern corresponded to the Ti, Nb-rich region, and superlattice electron diffraction spots indicating B-site ordering were observed in the W-rich region. In addition, the amounts of WO3 varied the appearance of the core-shell structure.
Junction Properties and Gap States of ZnO Thin Film Prepared by Sol-Gel Process
Authors: Okamura Takeshi , Seki Yoji , Nagakari Shoken , Hideyo Okushi Hideyo Okushi
Published: February 2005

N-type ZnO thin films with a crack- and columnar-free structure were successfully prepared on p-type Si substrates by the sol-gel process. The current-voltage (I-V) characteristics of the heterojunction of n-ZnO/p-Si show a rectification, and the capacitance-voltage (C-V) characteristics show an approximately linear C
-2-V relationship in the reverse bias condition. In the ZnO thin film, two gap states located at 0.054 eV and 0.12 eV below the conduction band were measured by isothermal capacitance transient spectroscopy (ICTS).
Polar Optic Phonon Scattering Limited-Mobility in Narrow Quantum Wells
Authors: Biswa Ranjan Nag Biswa Ranjan Nag , Sanghamitra Mukhopadhyay Sanghamitra Mukhopadhyay
Published: February 2005

Polar optic phonon scattering and mobility limited by such scattering are discussed for quantum wells with widths ranging between 10 nm and 2 nm. Numerical results are given for the InP/Ga0.47In0.53As/InP system for both the bulk-mode and the confined-mode models. Mobilities are found to be close to those given by the infinite-barrier, parabolic-band, bulk-mode model even when all the refinements of bulk-mode theory are taken into account or the analysis is made by using the confined-mode theory.
Growth and Crystallographic Analysis of YBa2Cu3Ox Thin Films on NdGaO3 Substrates
Authors: Masashi Mukaida Masashi Mukaida , Shintaro Miyazawa Shintaro Miyazawa
Published: February 2005

The growth and crystallographic analysis of a-axis-oriented YBa2Cu3O
x
(abbreviated to YBCO) grains in c-axis-oriented films on NdGaO3 substrates is described. a-axis-oriented grains grow at high substrate temperatures and high oxygen pressures. Reflection high energy electron diffraction (RHEED) patterns and φ-scan (in-plane rotation) X-ray measurements reveal that the grains exhibit a twofold symmetry indicating independent b- and c-axis orientations in the surface plane. The in-plane orientation of a-axis-oriented grains is thought to be responsible for the rectangular surface lattice of (110) NdGaO3 substrate.
Magnetic Field Influence on Er3Ni Specific Heat
Authors: Tokai Yoichi , Takahashi Akiko , Sahashi Masashi , Hashimoto Takasu , Yayama Hideki , Tomokiyo Akihisa
Published: February 2005

Er3Ni specific heat in 0, 1, 3, and 4.3 T magnetic fields was measured. The specific heat curves for 0 T and 1 T have a single peak due to magnetic phase transition, but those for 3 T and 4.3 T have no peak. Er3Ni specific heat decreases with increasing magnetic field around its ordering temperature, but increases in the higher-temperature region. Using the measured specific heat data, regenerator efficiency and cooling power were calculated to estimate the specific heat reduction influence due to a magnetic field on the Er3Ni regenerator performance. The results show that efficiency and cooling power in the practical leaking magnetic field are almost the same as those in 0 T.
Aspect Ratio of the Ba-Ferrite Platelets in Recording Media
Authors: Kohmoto Osamu , Jr. Chester Alexander , Kubo Osamu , Cates James C.
Published: February 2005

Ferromagnetic resonance (FMR) in particulate media for perpendicular recording has been studied by considering the shape anisotropy of the platelets and the volumetric packing factor. By the obtained FMR equation, the aspect ratio of 3.5 was derived from the angular dependence of the resonance fields in 34 GHz FMR measurements. The ratio is consistent with the value obtained by transmission electron microscopy.
Phase Retrieval Using a Lorentzian Filter
Authors: Nobuharu Nakajima Nobuharu Nakajima
Published: February 2005

Previously we presented a method for retrieving the phase of the Fourier transform of an object from Fourier intensity data obtained with and without an exponential filter in the object plane. In the case of phase retrieval in remote sensing, however, it is difficult to carry out the direct operation of filtering at the object plane. An alternative phase retrieval method using a Lorentzian filter is proposed, by which the Fourier phase can be retrieved from intensity data obtained with and without the Lorentzian filter in the Fourier-transform plane of the object. Optical systems for applying the method to one- and two-dimensional cases are also described. The performance of the phase retrieval method is shown in computer simulation studies of the reconstructions of a one-dimensional real object and a two-dimensional phase object.
Blurring and Broadening of Reflection Spectra Due to Structural and Alignment Changes of Conjugated Chains Caused by Isomerization and Stretching in Trans-Polyacetylene
Authors: Kubo Takaya , Watanabe Toshio , Nishioka Takahiro , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

An optimized thermal isomerization condition has been established to produce trans-(CH)
x
films which show the reflection spectra with well-resolved vibronic structure peaking at the lowest subband. The conjugation lengths with about 100 and 150 double-bond (C=C) units are estimated to be responsible for the 1.56 eV peak of as-grown (CH)
x
and the 1.51 eV peak of trans-(CH)
x
, respectively. The 0.05 eV peak shift accounts for the extension of the trans-part by 50% of the initial length. The effect of mechanical stretching for alignment on the reflection spectra has also been studied by paying particular attention to the conjugation-length distribution. The reflection spectra obtained using light polarized parallel and perpendicularly to the stretching direction indicate that the shorter chains align more easily than the longer ones; the observed perpendicular reflection does not arise from the reflection with light polarized perpendicularly to the (CH)
x
chains but from the reflection with light polarized parallel to the longer ones which remain unaligned. It appears the real dimensionality of trans-(CH)
x
must be reconsidered by taking account of the distribution of conjugated chain lengths.
Nonlinear Dielectric Relaxation Spectra Calculated with a Free Rotation Model of the Dipole Moment
Authors: Yasuyuki Kimura Yasuyuki Kimura , Reinosuke Hayakawa Reinosuke Hayakawa
Published: February 2005

Nonlinear dielectric relaxation spectroscopy has recently been utilized to investigate the details of electrical dynamics in a variety of substances. The nonlinear spectra obtained have usually been analyzed in terms of a phenomenological nonlinear response theory proposed by Nakada. In this paper, to check the validity of the phenomenological theory, the dielectric relaxation spectra of first and third orders are calculated from the molecular theory based on a free rotation model of the dipole moment. The after-effect function of exponential decay type assumed in the phenomenological theory is not applicable to the free rotation model. The validity of phenomenological expressions for nonlinear spectra as approximate or semiempirical formulas is discussed in detail.
Charge Carriers Responsible for Thermoluminescent Recombination Process in Heavily Irradiated NaCl
Authors: Katsuyuki Inabe Katsuyuki Inabe , Nozomu Takeuchi Nozomu Takeuchi
Published: February 2005

The thermal annealing behavior of optical absorption bands reveals that two bands peaking at 2.10 and at 5.90 eV correspond to the thermoluminescence (TL) glow (525 K peak) of heavily irradiated NaCl. On the basis of the emitted photon energy compared with the energy levels of the relevant electron and hole centers, the TL is considered to be caused by the recombination of the thermally released holes with the F centers dissociated from the Na clusters.
Deposition System for SEM “In Situ” Observation of Growing Crystals and the Preliminary Study of Zn Vapor Deposition
Authors: Gonda Takehiko , Teranishi Toyoyuki , Hirahara Toukou , Tanaka Yasuaki , Yumoto Hisami , Gotoh Yoshihiko
Published: February 2005

An apparatus for “in situ” observation of growing crystals in scanning electron microscope (SEM) was constructed. The design of the apparatus and the preliminary study of the growth of Zn crystals were described.
Reflection High-Energy Electron Diffraction Study of the Growth of Ge on the Ge(111) Surface
Authors: Fukutani Katsuyuki , Hiroshi Daimon Hiroshi Daimon , Shozo Ino Shozo Ino
Published: February 2005

Intensity oscillations, spot profiles and rocking curves of the (00) rod in reflection high-energy electron diffraction (RHEED) during the growth of Ge on the Ge(111) surface are investigated under various conditions. Two types of RHEED intensity oscillations with a period of one monolayer have been observed at specific conditions. One type of oscillation observed at a substrate temperature of 180°C is ascribed to the overlapping of the specular reflection and the 333 bulk reflection. The other type of monolayer oscillation observed at a low substrate temperature for a low glancing angle suggests the monolayer mode growth. Rocking curves of the (00) rod have been measured at various stages of growth, which demonstrate the periodic change of the intensity distribution of the rod during growth.
Synthesis of β-SiC Layer in Silicon by Carbon Ion `Hot' Implantation
Authors: Deguchi Masahiro , Kitabatake Makoto , Hirao Takashi , Arai Naoki , Izumi Tomio
Published: February 2005

A β-SiC layer was prepared by the carbon ion implantation technique into silicon substrates heated up to 450°C with annealing treatment. The carbon ion was implanted at an energy of 30 keV and dose in the range of 1-5×1017 ions/cm2. β-SiC grains, whose size was 100-500 Å, were observed in the implanted layer after annealing at 1200°C, by cross-sectional transmission electron microscopy. The dependence of substrate temperature, carbon ion dose, and annealing temperature on SiC formation was investigated by infrared absorption, electron spin resonance, and Auger electron spectroscopies. `Hot' implantation, which is a method of heating the substrate during carbon ion implantation, was effective for enhancing the formation of Si-C bonds.
Formation and Properties of Cubic Boron Nitride Films on Tungsten Carbide by Plasma Chemical Vapor Deposition
Authors: Okamoato Masaki , Yoshiharu Utsumi Yoshiharu Utsumi , Yukio Osaka Yukio Osaka
Published: February 2005

Boron nitride (BN) films could be deposited on tungsten carbide (WC) using the plasma chemical vapor deposition (CVD) technique. The deposited films are characterized by infrared reflectance polarization spectroscopy, transmission electron microscopy (TEM) and transmission electron diffraction (TED). The BN films directly deposited on WC were a mixture of cubic and hexagonal phases. However, the predominant films in the cubic phase were only formed with use of a thin buffer layer of boron (B) films. The grain size was estimated to be about 100 Å from images of TEM and TED patterns.
Water-Enhanced Debonding of Room-Temperature Bonded Silicon Wafers for Surface Protection Applications
Authors: Tong Qin-Yi , Roman Gafiteanu Roman Gafiteanu , Ulrich Gösele Ulrich Gösele
Published: February 2005

Reversible bonding of silicon wafers can be used to protect mirror polished silicon surface against organic contamination and particles. The present paper will report on debonding experiments of room-temperature bonded wafer pairs. It is found the water can significantly enhance the equilibrium crack length created by a blade inserted between two bonded wafers. A simple analytical model of this phenomenon is proposed which takes into account the interfacial energy between silicon and water. Combined with the “one-wafer bent” concept, it is anticipated that room-temperature reversibly bonded wafers with diameters up to 8 inches can be easily separated by using this technique. Water-enhanced debonding appears to be suitable for industrial applications due to its compatibility with main stream integrated circuit technology.
Coprecipitation of Binary and Ternary Systems: Ba-Cu, La-Ba-Cu as Carbonates and Y-Ba-Cu as Carbonates and Oxalates
Authors: Meetali Dasgupta Meetali Dasgupta , Sharad G. Dixit Sharad G. Dixit
Published: February 2005

Coprecipitation of binary Ba-Cu and ternary La-Ba-Cu and Y-Ba-Cu as carbonates has been investigated experimentally as a function of pH, concentration and temperature. Quantitative precipitation can be achieved at high pH values using a higher temperature and higher molar concentration of the salts in the solution. The results have been qualitatively explained in terms of the precipitation criteria based on conditional solubility product and side reaction coefficients.
Photo-Deposition of Hydrogenated Amorphous Silicon on Downstream Substrates Using an Upstream Windowless Hydrogen Lamp
Authors: Shaw Denis M. , Sheng Terry , Yu Zengqi , Adachi George J. Collins
Published: February 2005

An upstream 19 cm diameter disc-shaped hydrogen plasma has been used to deposit hydrogenated amorphous silicon films on 7.5 cm diameter wafers placed 10 cm downstream with 10 percent thickness variation. The disk plasma may offer an alternative to radio frequency excitation and this study is the first in that direction. The films have an optical band gap of 1.75 eV and an optimum photosensitivity of 2×105. The total hydrogen content was 20 at.%. There is one SiH bond for every 20 Si-H bonds. A 42 cm diameter hydrogen disk plasma has also been constructed and characterized as regards uniformity of optical emission.
Simulation of Shapiro Steps in a Josephson Junction Based on the Microscopic Theory of the Tunnel Junction
Authors: Imai Syozo , Shinagawa Mitsuru , Morita Seizo , Yosihisa Takeuti Yosihisa Takeuti , Nobuo Mikoshiba Nobuo Mikoshiba
Published: February 2005

Shapiro steps in a Josephson tunnel junction were investigated by the simulation based on the microscopic theory of the tunnel junction. A nonzero pair-breaking parameter, δ=0.1, was assumed to make the computation tractable. The dependence of the step width of the zeroth- and the first-order Shapiro steps on the rf power was calculated for the frequency range, 0.2f
g≦f≦1.5f
g, where f
g is the energy gap frequency. The steps are unstable at low frequencies, f\lesssim0.7f
g, and for large values of the junction capacitance. They become stable for larger frequencies. The steps are stable, on the whole, for small capacitance. The frequency dependence of the first maximum of the first-order Shapiro step, I
1
MAX, was obtained. It shows the Riedel peak, with even larger height than the prediction of the theory assuming a constant voltage source for a small capacitance.
Four States of Surface-Stabilized Ferroelectric Liquid Crystal with Parallel Rubbing
Authors: Koden Mitsuhiro , Katsuse Hirofumi , Tagawa Akira , Tamai Kazuhiko , Itoh Nobuyuki , Shuji Miyoshi Shuji Miyoshi , Tomio Wada Tomio Wada
Published: February 2005

The orientational states of surface-stabilized ferroelectric liquid crystals with parallel rubbing were investigated by changing the pretilt angle of the aligning film. Four states, C1-uniform (C1U), C1-twisted (C1T), C2-uniform (C2U), and C2-twisted (C2T) states, were observed. The C1U and C2U states showed extinction positions, whereas the C1T and C2T states did not. The memory angle of the C1U state was larger than that of the C2U state for the respective cells. The molecular orientational model of these states is discussed with regard to the experimental results.
Homoepitaxial Chemical Vapor Deposition of 6H-SiC at Low Temperatures on {011̄4} Substrates
Authors: Yamashita Atsushi , Yoo Woo Sik , Tsunenobu Kimoto Tsunenobu Kimoto , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Homoepitaxial chemical vapor deposition of 6H-SiC at low temperatures on {011̄4} substrates has been investigated. The crystal growth was carried out using a SiH4-C3H8-H2 system in the temperature range of 1000∼1500°C. Crystallinity of grown layers was characterized by means of reflection high-energy electron diffraction and etch-pit observation. The influences of surface polarity and growth conditions on crystallinity of grown layers were investigated. Significant effects of C/Si ratio on the growth were observed. Homoepitaxial growth of 6H-SiC was realized on (01̄14̄)C-face substrates at temperatures as low as 1100°C, which is 700°C lower than that on {0001} basal planes.