bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Surface Charging Effects on Etching Profile Defects
Authors: Shigemi Murakawa Shigemi Murakawa , James P. McVittie James P. McVittie
Published: October 2002

Surface charging effects on the etching profile defects during silicon (Si) and polycrystalline silicon (poly-Si) etching in non-uniform plasmas were experimentally demonstrated and their mechanisms were studied using an electrostatic ion trajectory simulator and a newly developed surface potential probe. Profile tilt and bowing were found in Si etching, while undercut and shouldering were observed in poly-Si etching. The trajectory simulation and the directly measured charging potential showed that these profile defects were induced by the potential difference between the etching materials and the charged insulating mask and were dependent on the mask patterns. The profile results agreed well with the gate oxide damage results which were also successfully explained by the surface charging.
Electrostatic Coupling of Antenna and the Shielding Effect in Inductive RF Plasmas
Authors: Sugai Hideo , Kenji Nakamura Kenji Nakamura , Keiji Suzuki Keiji Suzuki
Published: October 2002

Capacitive coupling from a current-flowing antenna to inductive rf plasma plays an important role not only in the discharge mechanism but also in the impurity release from materials around the antenna. As a result of this coupling, there appears a large negative dc voltage (V
DC) on the surface of material which insulates the antenna conductor from the plasma. The magnitude of V
DC is directly measured as a function of rf power, thickness of the insulating material, and the position along the antenna. A simple model to describe the electrostatic antenna-plasma coupling is proposed. In addition, the effect of Faraday shields on the inductively coupled rf discharge is presented.
Molecular Beam Mass Spectrometry Studies of Chemical Vapor Deposition of Diamond
Authors: Hsu Wen L. , McMaster Mark C. , Coltrin Michael E. , Dandy David S.
Published: October 2002

We have developed a novel molecular beam mass spectrometry technique that can quantitatively analyze the gas-phase composition in a chemical vapor deposition (CVD) reactor. The technique simultaneously monitors a wide variety of radical and stable species, and their concentrations can be determined with sensitivities approaching 1 ppm. Measurements performed in a diamond deposition system have provided keen insights into the important phenomena that affect the growth environment. In this paper we first discuss the primary gas sampling design issues. In the second part, details of the experimental results and their implications are described.
Silicon Molecular Beam Epitaxy on Hydrogen-Plasma-Cleaned Substrates
Authors: Hansch Walter , Hammerl Erwin , Kiunke Werner , Eisele Ignaz , Ramm Juergen , Beck Eugen
Published: October 2002

A process sequence for low-temperature in situ processing of silicon in an ultra-high vacuum (UHV) multichamber system is presented. For substrate cleaning, a hydrogen/argon discharge plasma was produced with an UHV-compatible plasma source. This low-energy plasma was used to remove, in a single step, native oxide and organic contaminations from the wafer surface at low substrate temperatures (\lesssim400° C). During the cleaning process the excitation energy of the gas atoms was determined by optical methods. The cleaning process was applied to patterned silicon substrates with micro-shadow masks. Local epitaxial growth by molecular beam epitaxy (MBE) on these substrates was used to fabricate triangular barrier diodes (TBD) to demonstrate the device quality for this cleaning procedure. The crystal quality of the grown layers and the interface was investigated by transmission electron microscopy (TEM). The electrical results for these diodes are in agreement with the grown layer sequence and the chosen dopings.
Self-Organizing Growth of Nanometer Mesa Structures on Silicon (100) Substrates
Authors: Gossner Harald , Baumgärtner Hermann , Hammerl Erwin , Wittmann Franz , Eisele Ignaz , Heinzel Thomas , Lorenz Heribert
Published: October 2002

Lateral patterning is a crucial technological step for the fabrication of complex nanostructures. It can be achieved either by etching or by a local deposition process. Most of the dry etching techniques for nanometer dimensions such as reactive ion etching (RIE) or focused ion beam (FIB) etching suffer from unintentional degradation such as crystal damage and contamination. In order to overcome these problems and to create well-defined and reproducible nanostructures we propose a self-organizing deposition process. It is based on local silicon molecular beam epitaxy (MBE) via ultrahigh-vacuum (UHV)-compatible shadow masks. By using this technique, well-defined tips and lines in the nanometer range have been fabricated. The shape of these mesa structures is basically determined by the physical growth mechanism. The sidewalls are well-defined crystallographic planes. This technique offers a convenient tool for the study of one- and zero-dimensional electronic systems.
Ultrashallow Junction Formation Using Low-Temperature Selective Si1-xGex Chemical Vapor Deposition
Authors: Honma Fumitaka , Murota Junichi , Goto Kinya , Maeda Takahiro , Yasuji Sawada Yasuji Sawada
Published: October 2002

In situ B doping and selective epitaxy on Si at 550° C in Si1-
x

Ge

x

chemical vapor deposition (CVD) have been investigated for forming high-performance ultrashallow junctions. It was found that the incorporation rate of B increased proportionally with increasing B2H6 partial pressure, and was higher for the film with a higher Ge fraction x. Using Si3N4, thermal SiO2, phosphosilicate glass (PSG) and borophosphosilicate glass (BPSG) as mask film materials, about 40-nm-, 100-nm-, 150-nm- and 150-nm-thick B-doped Si0.5Ge0.5 films, respectively, were grown selectively on Si(100). Using this low-temperature selective Si1-
x

Ge

x

CVD, a high-performance self-aligned ultrashallow junction formation has been achieved with a very low reverse current density, in the range of 10-10 A/cm2, without heat treatment.
Surface Hydrogen Effects on Ge Surface Segregation during Silicon Gas Source Molecular Beam Epitaxy
Authors: Ohtani Noboru , Mokler Scott , Xie Mao Hai , Jing Zhang Jing Zhang , Bruce A. Joyce Bruce A. Joyce
Published: October 2002

Using reflection-high-energy-electron diffraction (RHEED), the temperature dependence of Ge surface segregation during silicon gas source molecular beam epitaxy (Si-GSMBE) from hydride sources was studied, and it was found that surface hydrogen, which is produced by the dissociation of Si2H6 and GeH4 on the growing surface, may act as a growth-controlling surfactant. Comparison with results from solid source growth results suggests that hydrogen significantly suppresses the Ge segregation. Segregation kinetics were examined through simulation studies and the results indicate that the addition of surface hydrogen to the system inhibits segregation due to a lowering of the Gibbs heat of segregation.
Interband Photo- and Electroluminescence from Short-Period Si/Ge Superlattices
Authors: Olajos Janos , Engvall Jesper , Grimmeiss Hermann G. , Jia Ying-Bo , Menzcigar Ulrich , Kasper Erich , Kibbel Horst , Presting Hartmut
Published: October 2002

We report on further investigations on the photoluminescence (PL) and electroluminescence (EL) properties of strained Si/Ge superlattices. The band-gap PL from strain-adjusted Si

m

Ge

n

(m=9, 6, 3; n=6, 4, 2) superlattices has been studied as a function of applied external hydrostatic pressure. The superlattices used in these measurements are of improved quality in terms of dislocation density due to a thick, step-graded Si1-
x

Ge

x

buffer layer, providing the strain symmetry. The no-phonon (NP) lines shift in all superlattices linearly to lower energies with applied hydrostatic pressure. The stress dependence was modeled using an approach based on deformation potentials and effective-mass theory. Furthermore, we report on strong EL from a novel structure consisting of only a 2-monolayer-thick Ge-layer embedded in bulk Si.
Growth of ZnSxSe1-x Crystals from ZnSe–Sb2S3–Sb2Se3 Solutions
Authors: Hiroyuki Araki Hiroyuki Araki , Hisashi Kanie Hisashi Kanie , Masatoshi Sano Masatoshi Sano
Published: October 2002

ZnS

x

Se1-
x

crystals were grown in ampoules from ZnSe–Sb2S3–Sb2Se3 solutions, cooling from 1000°C to 700°C at a rate of 9°C/h. All grown crystals had zincblende structure. The sulfur composition x was varied from 0 to 0.99 by changing the sulfur fraction [S]/([S]+[Se]) in the starting material. The value of x was larger than the sulfur fraction in the starting material. The amount of Sb in all the grown crystals was undetectable ( <0.01 at.%). The sulfur composition dependence of the lowest gap determined from a photoluminescence excitation spectrum was represented as E
0(x)=2.82+0.35x+0.63x
2 (eV) at 4.2 K. The energy of the peak position in a cathodoluminescence spectrum at room temperature was close to the energy of the lowest gap throughout the entire composition range.
Photoreflectance Study of Interface Roughness in Ge/SiGe Strained-Layer Heterostructures
Authors: Hiroyuki Yaguchi Hiroyuki Yaguchi , Kaori Tai Kaori Tai , Keizo Takemasa Keizo Takemasa , Kentaro Onabe Kentaro Onabe , Yasuhiro Shiraki Yasuhiro Shiraki , Ryoichi Ito Ryoichi Ito
Published: October 2002

Ge/SiGe strained-layer heterostructures have been investigated using photoreflectance (PR) spectroscopy. On the basis of the comparison between the experimental and calculated quantum well-related transition energies formed at the Γ point, band discontinuities at the Ge/SiGe heterojunction are determined and found to vary linearly with Ge content in the SiGe layer. Conduction band offset ratioQc(= ΔEc/(ΔEc+ΔEvHH)) at the Γ point is evaluated to be 0.68 ±0.08 . From the intrinsic linewidth of the quantum well-related transitions, roughness at the Ge/SiGe heterointerface has been characterized for the first time and is estimated to be ±1 monolayer (ML). In addition, the splittings in the PR spectra are observed in some samples at low temperatures. These splittings are due to the difference in the well width and correspond to the height (or depth) of about 10 ML.
Tailorable Doping-Spike PtSi Infrared Detectors Fabricated by Si Molecular Beam Epitaxy
Authors: Lin True-Lon , Park Jin-Suk , Gunapala Sarath D. , Eric W. Jones Eric W. Jones , Hector M. del Castillo Hector M. del Castillo
Published: October 2002

By incorporating a 1-nm-thick p+ doping spike at the PtSi/Si intertace, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors. The extended cutoff wavelengths resulted from the reduced effective potential barriers due to the combined effects of an increased electric field near the silicide/Si intertace and the Schottky image force. The p+ doping spikes were grown by molecular beam epitaxy at 450° C using elemental boron as the dopant source, with doping concentrations ranging from 5×1019 to 2×1020 cm-3. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p+ spikes. Thermionic emission dark current characteristics were observed and photoresponse in the LWIR regime was demonstrated. Furthermore, the effective potential barriers determined by the Richardson plots were used to study the electrically activated boron dopant concentrations of the thin (1-nm-thick) spikes.
Annealing Behavior of Defects in Neutron-Transmutation-Doped Floating Zone Si
Authors: Xiangti Meng Xiangti Meng
Published: October 2002

Positron annihilation measurements show that in neutron-transmutation-doped floating zone (NTD FZ) Si irradiated by two different neutron doses-6×1016and 1.2×1018cm-2, the outline of the annealing behavior of V-type defects is similar, and this defect has two obvious annealing stages; but the annealing temperature of V2-type defects is very different from each other; the concentration and annealing behavior of the radiation-induced defects and secondary V2defects are related to the neutron dose. Above 600°C some V-type defects appear again.
Room-Temperature Photoreflectance Characterization of InAlAs/InGaAs Heterojunction Bipolar Transistor Structure Including Two-Dimensional Electron Gas
Authors: Yau-Huei Chen Yau-Huei Chen , Kuo-Tung Hsu Kuo-Tung Hsu , Kuo-Liang Chen Kuo-Liang Chen , Hao-Hsiung Lin Hao-Hsiung Lin , Gwo-Jen Jan Gwo-Jen Jan
Published: October 2002

Using contactless photoreflectance at 300 K we have characterized two InAlAs/InGaAs heterojunction bipolar transistor structures grown by molecular beam epitaxy. The spectra from the InAlAs and InGaAs interface can be accounted for on the basis of a triangular potential well which confined two-dimensional electron gas. A detailed lineshape fit makes it possible to evaluate the Fermi energy, and hence the two-dimensional electron gas concentration. Furthermore, other important parameters of the system, such as built-in electric fields and In composition, can be evaluated.
Temperature Dependence of Band Gap Change in InN and AlN
Authors: Qixin Guo Qixin Guo , Akira Yoshida Akira Yoshida
Published: October 2002

The optical band gap of InN and AlN single crystal films was measured through absorption spectra in the temperature range of 4.2 to 300 K. The samples were grown on (0001)α-Al2O3 substrates by metalorganic vapor phase epitaxy. The Varshni equation and the Bose-Einstein expression have been compared with the experimental results. The nitride III-V compound semiconductors have smaller temperature dependence of band gap change. In III-V compound semiconductors, the variation of the band gap change increases in the order of N, P and As.
Copper Self-Sputtering by Planar Magnetron
Authors: Asamaki Tatsuo , Ryuji Mori Ryuji Mori , Akira Takagi Akira Takagi
Published: October 2002

Aiming at filling up deep holes with metal, self-sputtering of copper is performed in a wide pressure range of 10-2 Pa to 10-4 Pa. The high target current of 7 A to 10 A for a 4-inch planar magnetron target is essential to perform the self-sputtering process wherein a very high deposition rate of about 4 µm/min at 60 mm from the target surface is obtained. The lifetime of the planar target is from 1 h to 2 h. A new type of target which has protuberances on the erosion centers is produced by trial and error, and achieved a lifetime of 4 h. Deep holes on Si wafers, 1.17 µm in depth and 0.4 µm or 0.6 µm in diameter, are examined, and verry good bottom coverage of nearly 100% is obtained.
Development of Ammonia Adsorption Filter and Its Application to LSI Manufacturing Environment
Authors: Saiki Atsushi , Oshio Ryoji , Suzuki Michio , Tanaka Akio , Itoga Toshihiko , Yamanaka Ryoko
Published: October 2002

Activated carbon treated with a hydrogen salt is found to be effective in suppressing ammonia concentration in LSI cleanrooms. The hydrogen salt which contains neither phosphor nor metals is utilized. Its adsorption capacity is about 1000 mol/m3-carbon. This corresponds to a lifetime of about two years in an ordinary cleanroom. Compared to this, untreated activated carbon adsorbs less than 10 mol/m3, so it cannot be used for more than 10 days. A chemically amplified resist, known to be susceptible to degradation from alkaline gaseous substances in cleanrooms, is shown to maintain its 0.25-µm line and space patterns under hydrogen salt treated carbon filtered air, even when the developing is delayed for 60 min after excimer laser exposure.
Observation of Aharonov-Bohm Oscillations in the Magnetoresistance of a GaAs/AlGaAs Quantum Dot
Authors: Bird Jonathan P. , Ishibashi Koji , Yoshinobu Aoyagi Yoshinobu Aoyagi , Takuo Sugano Takuo Sugano
Published: October 2002

We discuss the observation of Aharonov-Bohm oscillations in the magnetoresistance of a 1 µm GaAs/AlGaAs quantum dot. The oscillation period of 6 mT gives good agreement with the expected dimensions of the dot, implying Coulomb blockade effects to be insignificant in this case. The oscillations wash out at temperatures above 0.5 K, consistent with the expected energy spacing of the discrete states within the dot.
Model for Suppression of Dislocation Etch Pits in Vacuum-Swept Quartz Crystals
Authors: Mailadil Thomas Sebastian Mailadil Thomas Sebastian
Published: October 2002

It is well known that vacuum-swept quartz crystals do not show dislocation etch pits upon etching, whereas X-ray topographic studies show that the dislocation network remains the same. A model is presented to show that there is no preferential dissolution by the etchant at the dislocation sites in vacuum-swept crystals.
First-Order Calculations of Radiation Force for Rotating Sphere Illuminated by Circularly Polarized Gaussian Beam
Authors: Lee Soo Chang
Published: October 2002

We use the theory of scattering of a focused Hermite-Gaussian-mode beam by a rotating sphere to obtain the analytic formulas of radiation force, which include the correction terms of up to first order in angular velocities of the sphere. We also numerically investigate the effect of the first-order terms exerted on the net radiation force for spherical particles (near structural resonances) positioned on and off the propagation axis of a circularly polarized Gaussian laser beam. Numerical results show that the first-order correction for a rotating sphere levitated in the 1 W argon-ion laser beam is one or two orders of magnitude below the zeroth-order force at the highest rotational frequency of Ω≃1.5 GHz.
Temperature Dependence of Threshold Current of Transverse Single-Mode InGaAsP/InGaP Buried-Heterostructure Laser
Authors: Yoo Jae Soo , Ko Yongtae , Kim Hansaeng , Pak Georgui , Gabgyu Lim Gabgyu Lim , Taeil Kim Taeil Kim
Published: October 2002

Separate-confinement-heterostructure single-quantum-well (SCH-SQW) InGaAsP/InGaP structures were grown on a (100) GaAs substrate by liquid-phase epitaxy (LPE) and then buried-heterostructure (BH) lasers were fabricated after mesa etching. The output power of laser diodes could be cw-operated near 50 mW without any kink in the transverse single mode. The measured values of a charateristic temperature T
0 for BH InGaAsP/InGaP lasers were around 100 K for ∼500 µm cavity length. This relatively low value compared to the AlGaAs/GaAs quantum-well lasers could be better explained in terms of carrier leakage over the heterojunction barrier rather than Auger recombination which is intrinsic to quaternary semiconductor materials.
Optical Characteristics of Amorphous Silicon Nitride Thin Films Prepared by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition
Authors: Takashi Inukai Takashi Inukai , Ken'ichi Ono Ken'ichi Ono
Published: October 2002

Amorphous silicon nitride thin films were prepared by electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) at low substrate temperatures of 65–400°C, and their optical attenuation, refractive index and optical band gap were examined. The typical attenuation is as low as 0.1–0.3 dB/cm in the 0.63–1.35 µm wavelength range, but the attenuation becomes much higher in the 1.4–1.6 µm range with a peak value of 7.5 dB/cm at 1.52 µm. The attenuation values and the refractive index largely depend on the amount of hydrogen included in the films, although this does not affect the optical band gap. The peak attenuation decreases to about 0.6 dB/cm after annealing. It is thought that the peak is due to the second overtone absorption of the N–H stretching vibration.
Neutron Irradiation Induced Defects in Low Free Carrier Concentration Epitaxially Grown n-GaAs
Authors: Auret F. Danie , Goodman Stewart A. , Albertus Wilson Albertus Wilson , Gerrit Myburg Gerrit Myburg
Published: October 2002

Deep level transient spectroscopy (DLTS) of low free carrier concentration n-GaAs revealed that high energy neutron irradiation introduced five electron traps, En1–En5, in molecular beam epitaxy (MBE) grown GaAs. Only four of these defects, En1, En2, En4 and En5 could be detected in irradiated GaAs grown by organo-metallic vapor phase epitaxy (OMVPE). The En1, En2 and En4 have similar DLTS “signatures” as the E1, E2 and E3 defects created during high energy electron irradiation of GaAs. The DLTS “signatures” of En5 in the MBE and OMVPE samples are different, and this difference is attributed to the presence of a near-surface defect which is more readily detectable in the MBE GaAs.
Reflective Color Display Using Polymer-Dispersed Cholesteric Liquid Crystal
Authors: Kato Kinya , Tanaka Keiji , Shinji Tsuru Shinji Tsuru , Shigenobu Sakai Shigenobu Sakai
Published: October 2002

A reflective color display with a passive matrix has been successfully obtained using polymer-dispersed cholesteric (chiral nematic) liquid crystal (PDCLC). The PDCLC has two memory states: a selectively reflective state and a transparent one. These states are maintained for a long period without any holding techniques. These states can be changed electrically: a high-frequency electric field induces the reflective state and a low-frequency field recovers the transparent state due to the Carr-Helfrich instability. A driving scheme using dual-frequency fields was applied to a passive matrix of 8×8 to rewrite images on the matrix. This technique will lead to reflective-color display devices with high information content.
Unique Fine Microstructures of Iron Caused by Intense Shearing under Shock Compression
Authors: Dan Koji , Tamura Hideki , Sawaoka Akira B. , Mori Tsutomu , Hwang Min-der , Horie Yasuyuki
Published: October 2002

Sample assemblies consisting of an iron rod and a concentric 2024-aluminum alloy cylinder were shock-treated by impaction of an iron flyer plate. Since the shock wave velocity of the rod is slower than that of the cylinder, oblique shock waves from the cylinder interact with the plane shock waves in the iron rod and form a conical region of plane loading in the front one-third of the rod. An ellipsoidal region, due to Mach effect, might even be formed in the next one-third. Outside of the conical region, intense shearing is anticipated. Microstructures of a longitudinal cross section of the recovered rod and Vickers hardness were axis-symmetric. The ellipsoidal region could not be seen in the cross section. However, outside of the region, fine microstructures were observed. These fine structures might be formed during the intense shearing in the high-pressure ε phase of iron and subsequent reverse transition to the normal α phase.
Effects of Substrate and Bottom Electrodes on the Phase Formation of Lead Zirconate Titanate Thin Films Prepared by the Sol-Gel Method
Authors: Kim Chang Jung , Yoon Dae Sung , Lee Joon Sung , Chaun Gi Choi Chaun Gi Choi , Kwangsoo No Kwangsoo No
Published: October 2002

Lead zirconate titanate (PZT) thin films were fabricated using sol-gel spinning onto Pt/glass, Pt/Ti/glass and Pt/Ti/SiO2/Si substrates and heat-treated using rapid thermal annealing (RTA). The preferred orientation and the perovskite phase content of the PZT thin films were studied using X-ray diffraction analysis (XRD), and the polarization vs electric field (P-E) hysteresis characteristics were investigated using a standardized ferroelectric test system. All of the resulting films on platinized substrate with Ti adhesion layer were well crystallized with the perovskite phase. A preferred (111) orientation was obtained on the Pt/Ti/glass substrate. The saturation polarization of the PZT film on glass substrates was higher than that on Si substrates.
Work Function and Photothreshold of Layered Metal Dichalcogenides
Authors: Shimada Toshihiro , Ohuchi Fumio S. , Parkinson Bruce A.
Published: October 2002

Work functions and photothreshold values of various layered metal dichalcogenides ( ZrSe2, HfSe2, NbSe2, 1T-TaS2, 2H-TaS2, MoS2, MoSe2, α-MoTe2, SnS2, SnSe2) have been measured by a photoemission technique. The measured photothreshold values, except for Sn compounds, are compared with the calculated values based on various band models. The agreement between the observed and calculated values is satisfactory for most of the materials.
Effect of Added Ethanol in Atmospheric-Pressure Chemical Vapor Deposition Reaction Using Tetraethoxysilane and Ozone
Authors: Masahiko Maeda Masahiko Maeda , Koichi Ikeda Koichi Ikeda
Published: October 2002

Ethanol added in tetraethoxysilane (TEOS)-ozone ( O3) atmospheric-pressure chemical vapor deposition (APCVD) reaction is found to affect both deposition rate and step coverage characteristics. The added ethanol decreases the effective ozone concentration in the gas phase; that is, it acts as an ozone scavenger. In the region of flow-shaped step coverage, both the deposition rate and step coverage were enhanced simultaneously. These results suggest that the added ethanol also contributes to the formation of reaction intermediates which affect the flow-shaped step coverage. In addition, it is considered that reaction between these intermediates and ozone molecules is necessary for flow-shaped step coverage.
A Modulating Aperture by Domain Wall Displacements in Magneto-Optical Materials
Authors: Fritz Haberl Fritz Haberl , Johann Hochreiter Johann Hochreiter , Martin Gaugitsch Martin Gaugitsch , Hans Hauser Hans Hauser
Published: October 2002

Two laser beams are focused onto a thin permalloy film. By changing the direction of the magnetization of the permalloy film the magneto-optic Kerr-effect is exploited either to rotate the plane of polarization or to modulate the amplitude of the reflected light. The domain wall behaviour is determined by the applied field and demagnetizing fields in order to compensate the inner field. Acting as a modulation aperture, the displacements can be controlled accurately by the amplitude or the frequency of the applied field. In a first step, the film is characterized for our application by measuring the velocity of the domain wall displacements by two focused beams with known distances. By measuring the delay between the modulation of the reflected beams it is possible to accurately determine the beam separation under the condition of reproducible wall movements. Therefore, a moving domain wall acts like a high-speed modulator. The method could be used for many applications, for instance refraction measurements by dispersion of the refractive index in the atmosphere or rapid quality control of magnetic materials.
Comparison of Slow-Neutron Intensities in Pulsed Spallation Neutron Sources with Various Proton Energies 0.8–3 GeV
Authors: Kiyanagi Yoshiaki , Watanabe Noboru , Arai Masatoshi
Published: October 2002

The choice of the proton energy for an intense pulsed spallation neutron source is one of the most important topics in recent years. A high proton energy, but with a modest beam current, is more acceptable from an accelerator point of view. We calculated the slow-neutron intensities from a reference target-moderator-reflector assembly for various proton energies over the range 0.8–3 GeV. The result shows that the slow-neutron intensity per unit proton beam power slightly decreases with proton energy: even at 3 GeV the intensity is about 80% of the 0.8 GeV case. A higher proton energy is also acceptable from a neutronic point of view.
InGaAs Epilayers of High In Composition Grown on GaAs Substrates by Molecular Beam Epitaxy
Authors: Okamoto Kotaro , Ryoji Hananoki Ryoji Hananoki , Koji Sakiyama Koji Sakiyama
Published: October 2002

Thick (2 µ m) InxGa1-xAs epilayers of high In composition have been grown on (100) GaAs substrates, and the quality and the growth mode of the epilayers have been investigated by reflection high-energy electron diffraction, double-crystal X-ray diffraction and scanning (reflection) electron microscopy. In the range ofx>0.8, three-dimensional islands are formed at the initial stage of the growth, and during island growth, strain due to the lattice mismatch is almost completely released through the generation of dislocations. When the average size of the islands exceeds about 50 nm, coalescence occurs among the islands each of which is almost free from strain. Therefore, after the occurrence of island coalescence, the epilayers can grow without suffering misfit strain, and highly dislocated layers are confined within a narrow region neighboring the interface.
Silicide-Formation-Induced Defects in Si Substrates in Ti/Si and Ni/Si Systems by a Monoenergetic Positron Beam
Authors: Long Wei Long Wei , Shoichiro Tanigawa Shoichiro Tanigawa
Published: October 2002

The formation of silicides via the thin-film deposition of transition metals Ti and Ni onto Si substrates using a monoenergetic positron beam has been investigated. From the depth dependence of positron annihilation characteristics, the diffusion length of positrons was determined on the basis of a one-dimensional diffusion model. In the case of the Ti/Si system, the formation of the silicides did not induce shortening of the diffusion length of positrons in the Si substrate. On the contrary, the diffusion length of positrons in the resulting silicides was very short, indicating the presence of a great number of positron traps in silicides. The diffusion of Si atoms as a dominant diffusion species during TiSi2 formation could not be recognized in the present experiment. On the other hand, in the case of the Ni/Si system, the silicidation induced a very short diffusion length of positrons in the Si substrate. On the contrary, the diffusion length in the resulting silicide is long, to an extent comparable with that for defect-free metals. The diffusion of Si during NiSi2 formation was observed in the present experiment.
Alignment of Surface-Stabilized Ferroelectric Liquid Crystal by the Self-Assembled Monolayers of Amphiphilic Diacetylene Derivatives
Authors: Tanaka Toshihiko , Honda Yoshiaki , Tani Takeshi , Terahara Atsushi , Tabe Yuka , Sugi Michio
Published: October 2002

Surface-stabilized ferroelectric liquid crystal was aligned by the self-assembled monolayers (SAMs) of amphiphilic diacetylene derivatives formed on an indium tin oxide/glass substrate to maintain bistability when ferro-electric liquid crystal with high spontaneous polarization was used. The SAMs were disposed uniaxially either after rubbing them or passing them through a meniscus at a three-phase contact between a substrate, air, and n-hexane before exposing them to ultra-violet (UV) light. Infrared transmission spectra, contact angles against water and time of flight secondary ion mass spectra have revealed that the modified surface was a sparse monolayer of the diacetylenes, and that they were polymerized by UV light.
Investigation of Internal Loss and Power Transmission Characteristic of Width Shear Vibration Piezoelectric Transformer
Authors: Masanori Ueda Masanori Ueda , Noboru Wakatsuki Noboru Wakatsuki
Published: October 2002

Piezoelectric transformers proposed by Rosen [ Proc. Electronic Components Symp. (1957) p. 205] have been studied for high-voltage step-up applications. A piezoelectric transformer using a LiNbO3 plate proposed recently by Nakamura et al. [ Proc. Japan Acoustic Society (1990) p. 687 [in Japanese]] has low loss and a simple structure. The plate of a conventional piezoelectric transformer was supported only at the point of the node of the vibration. Rigid support is required for high-power applications. To apply a piezoelectric transformer to a power circuit, we studied internal loss of transmitting power and how to support the piezoelectric plate. Based on the studies, we proposed a piezoelectric transformer which uses energy trapping of width shear vibration in a LiNbO3 plate. This paper describes the investigation of the spurious mode, internal loss and power transmission characteristic. Efficiency of 95% or more can be obtained above a load rasistance range of about 20 Ω and under about 1000 Ω.
1.9 GHz Low-Loss Surface Acoustic Wave Filter: Lift-Off Method and 3 mm Square Small Size Package
Authors: Mishima Naoyuki , Kuroda Yasushi , Reiko Kobayashi Reiko Kobayashi , Toshiyuki Takagi Toshiyuki Takagi
Published: October 2002

A novel 1.9 GHz low-loss surface acoustic wave (SAW) filter for personal handy phone systems has been produced. The 0.5 µm line and space electrode of SAW filter on the LiTaO3 substrate was fabricated by the lift-off process using negative photoresist. A deep UV light source was used in the photo exposure process. Electrodes with 0.2 µ m gap could be easily formed by the lift-off process. This SAW filter chip was mounted in the new small size (3.0 mm square) leadless ceramic package. Because the parasitic inductance and capacitance of this package are smaller than the usual 4.8 mm×5.2 mm package, a 1.9 GHz filter with small insertion loss of 1.7 dB was obtained. The suppression level of this filter at 4.5 GHz was greater than 30 dB.
A Study of Quartz Tuning Fork Resonators in the Overtone Mode with Unwanted Temperature Characteristics
Authors: Eishi Momosaki Eishi Momosaki , Takeo Kaneko Takeo Kaneko
Published: October 2002

Quartz crystal resonators with frequencies of hundreds of kilo-hertz are frequently used in paging instruments. Quartz tuning fork resonators in the overtone mode are suitable for such applications. However, quartz tuning fork resonators in the overtone mode have been studied in less detail than those in the fundamental mode. It is necessary for the quartz tuning fork resonators in the overtone mode to be carefully designed from the point of view of total vibrational system-design including the supporting leads and capsules. In this paper, we clarify the unwanted temperature characteristics which is a result of total vibrational system design.
Equivalent Circuit Analysis of Piezoelectric Bending Vibrators
Authors: Aoyagi Ryohji , Tanaka Haruo
Published: October 2002

Two types of piezoelectric bending vibrators are analyzed by using the equivalent circuit of the bending motion of the multilayerd piezoelectric bar, which was derived by the authors, starting from Hamilton's principle. The electrical admittances and resonant frequencies of the vibrators are calculated and are compared with the experimental results.
Control of Nonlinear Piezoelectricity and Its Application to Efficiency Improvement of Surface Acoustic Wave Elastic Convolver
Authors: Cho Yasuo , Kadota Shin-ichi Haitsuka
Published: October 2002

The newly discovered effect concerning the enhancement of nonlinear piezoelectricity of lead zirconate titanate (PZT) ceramics by applying a bias electric field to the substrate has enabled more than 20 dB efficiency improvement in a surface acoustic wave (SAW) elastic convolver. Next, a novel biasing method for stabilizing the time variation of convolution output signal with static field and for obtaining a more efficient convolver is proposed. Finally, the temperature dependence of the PZT convolver is also investigated. These results suggest the possibility of fabricating a SAW elastic convolver of which efficiency is higher than that of a SAW monolithic convolver.
Self-Oscillated Ultrasonic Stepping Motor with Function of Angular Displacement Self-Correction: Nonaxisymmetric ((2,1))-Mode Thin Disk Motor
Authors: Xiaoduo Chen Xiaoduo Chen , Manabu Aoyagi Manabu Aoyagi , Chiharu Kusakabe Chiharu Kusakabe , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

This paper deals with experimental investigation of a self-oscillated open-loop driving motor using a slitted rotor and a nonaxisymmetric ((2,1)) vibration mode thin annular disk which has four projection teeth on its inner circumference. This motor is suitable for application to watches because it can be constructed in a thin configuration and the slitted rotor enables the self-correction of angular displacement. In the experiment, two types of self-oscillation circuits were investigated for suitable driving. The results were that the self-oscillated driving motor could be achieved by using an operational amplifier and some inverter IC elements. That is, the self-correction function of the angular displacement of a stepping motor was confirmed in the case of the nonaxisymmetric-mode disk motor.
Method of Probe Measurement in N2/SiH4 Microwave Plasma
Authors: Kato Isamu , Tadashi Sakamoto Tadashi Sakamoto , Tsuyoshi Shimoda Tsuyoshi Shimoda
Published: October 2002

It has been clarified that probe current decreases linearly with increasing deposition time of a SiN film on a probe. From this result, a probe current-voltage characteristic without any deposition of the SiN film can be extrapolated from some probe current-voltage characteristics of different deposition times of the SiN film. It has been clarified that the 450 Å SiN film deposited on the probe can be removed by ion bombardment with -200 V applied to the probe for 220 s in the pure N2 plasma (T
e\fallingdotseq13,000 K, n
e\fallingdotseq5.0×109 cm-3). By repeating these two methods, it is clear that repeated ordinary probe measurement is possible in the N2/SiH4 plasma. By using this method, the spatial distributions of electron temperature and electron density are measured in the N2/SiH4 plasma in the deposition chamber of a double-tubed coaxial-line type microwave plasma chemical vapor deposition (MPCVD) system.
Doppler-Free Optogalvanic Spectroscopy of Ca+and Ca
Authors: Ohmukai Ryuzo , Watanabe Masayoshi , Imajo Hidetsuka , Kazuhiro Hayasaka Kazuhiro Hayasaka , Shinji Urabe Shinji Urabe
Published: October 2002

The high-resolution Doppler-free optogalvanic spectra of Ca+and Ca were observed using a commercial hollow-cathode lamp and a single-mode cw ring Ti:sapphire laser or a dye laser. The measured full width at half-intensity-maximum (FWHM) of the Ca+Doppler-free component was 167 MHz, which is sufficient for calibrating the wavelength for the laser cooling of Ca+ions. The amount of collision broadening in the Ca+spectrum was much greater than that in the Ca spectrum.
Effects of External Modulation Signals on the Tracking of Resonance and Antiresonance of Piezoelectric Resonators II. Two Types of Sinusoidal Modulation
Authors: Shigeo Hayashi Shigeo Hayashi
Published: October 2002

Computer control has been introduced to the tracking system based on a phase-locked loop. The system is examined with respect to stability against external modulation signals of the form a
0
s
i
n 2πf
0
t. Two modes of modulation have been adopted: (i) sudden application of the signal at t=0 and (ii) adiabatic alteration of a
0. The critical amplitudes a
c above which phase lock is lost are measured for f
0 below 300 Hz. Above the critical frequency, f
c≈ 155 Hz the hysteretic amplitudes a
H and a
L are also measured in the adiabatic mode. Computer simulations are in good agreement with the experimental results except for f
0>f
c in the sudden modulation. It is suggested that f
c is closely related to a characteristic time t
c for the lock acquisition process with no modulation signals.
Strain Imaging of Lead-Zirconate-Titanate Thin Film by Tunneling Acoustic Microscopy
Authors: Takata Keiji Takata Keiji , Kushida Keiko Kushida Keiko , Torii Kazuyoshi Torii Kazuyoshi , Miki Hiroshi Miki Hiroshi
Published: October 2002

This paper presents a new method for imaging of the piezoelectric property of piezoelectric films with high resolution using tunneling acoustic microscopy. This method is based on detecting fine strains generated by the tip voltage. Such strain is detected either through the surface displacement of the piezoelectric film or through a vibration generated in the film. This method enables us to measure and image the piezoelectric constants, polarization directions, and coercive electric fields of piezoelectric materials.
Measurement of Acoustic Properties of Magnetic Fluid and Its Application to Nondestructive Evaluation
Authors: Kazuhiko Imano Kazuhiko Imano , Hiroshi Inoue Hiroshi Inoue
Published: October 2002

The ultrasonic velocity in a magnetic fluid (MF) on a base of water is measured under different temperatures, frequencies and magnetic fields. Two Kinds of ultrasonic correlation systems are employed. The maximum velocity is observed at 38°C without distinction of frequency. In the frequency range of 4∼10 MHz, a weak frequency dependence of ultrasonic velocity of 1∼2 m/s is observed. Dependence of external magnetic field in the magnetic field strength of 0∼±0.2 T is on the order of 10-4. An experiment with a magnetic fluid as an acoustic coupling medium is performed to demonstrate its usefulness in ultrasonic nondestructive evaluation (UNDE).
Evaluation of Piezoelectric Ceramic Substrates for Ultrasonic Bulk Wave Filters and Resonators Using Pulse Interference Method
Authors: Kitamura Takeshi , Kadota Michio , Kasanami Toru , Kushibiki Jun-ichi , Chubachi Noriyoshi
Published: October 2002

In recent years, market demand has creared a need for high reproducibility in the frequency characteristics of piezoelectric ceramic filters and resonators that use the thickness extension mode. In order to increase this reproducibility, it is necessary mainly to improve accuracy in controlling the substrate thickness, and to reduce variations in elastic properties of substrate materials prior to the completion of products. The pulse interference method using longitudinal waves has been applied to the evaluation of piezoelectric ceramic substrates. A good correlation has been obtained between the interference frequencies, measured with this method, of substrates immediately after polishing and the frequency characteristics of completed products. It has been shown that this method is extremely useful for improving productivity of ultrasonic bulk-wave filters and resonators whose frequency characteristics directly depend upon the longitudinal wave velocities of substrate materials and their thicknesses.
Characteristics of Planar Optical Device Using Acoustooptic Effect
Authors: Yukinori Hatayama Yukinori Hatayama , Yasumitsu Miyazaki Yasumitsu Miyazaki , Nobuo Goto Nobuo Goto
Published: October 2002

A planar acoustooptic (AO) device composed of two adjacent channel waveguides is proposed and analyzed. The planar AO device is suitable for integrating the devices in the horizontal direction, as compared with vertically coupled AO devices. This planar AO device is useful in optical integrated circuits such as integrated N×N matrix switches. We discuss the coupling process and the efficiency characteristics of the proposed planar AO devices. The required surface acoustic wave (SAW) frequency is 100 MHz at the waveguide separation distance of 0.5 µm.
Study of Glass Transition of Propanol by Photoacoustic Method
Authors: Yatsu Akio , Seiji Kojima Seiji Kojima , Tetsuro Suzuki Tetsuro Suzuki
Published: October 2002

The frequency dependence of photoacoustic signals was measured to investigate the enthalpy relaxation of the glass transition of n-propanol. The dielectric relaxation was also measured for comparison. It was found that the enthalpy relaxation obeys the Vogel-Tammann-Fulcher law (VTF law), and the parameters of the VTF law in enthalpy relaxation are different from those of dielectric relaxation. The distribution of enthalpy relaxation time is broader than that of the dielectric one.
High-Frequency and High-Gain Amplification of Photothermal Beam Deflection Angle Using Cylindrical Reflection Mirror
Authors: Yarai Atsushi , Fukunaga Yoichiro , Kazuo Sakamoto Kazuo Sakamoto , Takuji Nakanishi Takuji Nakanishi
Published: October 2002

A new technique for amplification of photothermal beam deflection angle was developed. This technique, based on a very simple operation principle, uses a cylindrical reflection mirror for a new deflection amplifier. This paper presents experimental data and the results of theoretical analysis. Mirage signal amplification of more than 35 times was achieved. Additionally, mirage signals obtained with this new deflection-angle amplifier did not significantly decrease even in the high modulation frequency range.
Vacancy-Type Defects in Be-Implanted InP
Authors: Long Wei Long Wei , Shoichiro Tanigawa Shoichiro Tanigawa , Akira Uedono Akira Uedono , Kazumi Wada Kazumi Wada , Hideo Nakanishi Hideo Nakanishi
Published: October 2002

Vacancy-type defects generated by the ion implantation of 60 keV Be+ions in InP have been investigated by a slow positron beam technique. The vacancy-type defects increase with the implantation dose. The calculated total capture of positron was found to be linear to the implantation dose. The depth profiles of vacancy-type defects were found to be nearly the same as the stopping profiles of implanted ions.
Detection of Intermediates in Thermal Chemical Vapor Deposition Process Using Tetraethoxysilane
Authors: Satake Tetsuya , Sorita Tetsuji , Fujioka Hirofumi , Hiroshi Adachi Hiroshi Adachi , Hiroyuki Nakajima Hiroyuki Nakajima
Published: October 2002

The thermal decomposition process of tetraethoxysilane (TEOS) in the gas phase has been studied using a gas-chromatograph mass spectrometer (GC-MS) connected to an electric furnace. TEOS decomposed over 500°C to give a TEOS dimer and trimer. It has been confirmed that formation of TEOS oligomers occurs in the gas phase. Ethylene, acetaldehyde and ethanol were also detected, which are low-molecular-weight products formed by thermal decomposition of TEOS. Ethylene was the principal product among the low-molecular-weight products. This indicates that triethoxysilanol is an intermediate in the formation of TEOS oligomers.
Passivation of Shallow and Deep Levels by Hydrogen Plasma Exposure in AlGaAs Grown by Molecular Beam Epitaxy
Authors: Bosacchi Antonio , Franchi Secondo , Gombia Enos , Mosca Roberto , Bignazzi Alberto , Grilli Emanuele , Guzzi Mario , Zamboni Riccardo
Published: October 2002

We report on the effects of exposure to a hydrogen plasma (hydrogenation) and of thermal annealing (dehydrogenation) on shallow and deep levels in direct-gap AlGaAs:Si grown by molecular beam epitaxy. Photoluminescence (PL) experiments show that hydrogenation results in the passivation of shallow levels, thus confirming the data of capacitance-voltage measurements, while deep-level transient spectroscopy shows that ME5, ME6 and DX centers are passivated by hydrogenation. Dehydrogenation at 420°C results in an almost complete recovery of the free electron concentration, and restores, to a significant extent, only the DX center. The study of samples grown at different temperatures shows that the significant increase of the PL efficiency after hydrogenation and its decrease after dehydrogenation are consistent with the passivation of the ME5 and ME6 levels and with their partial reactivation, respectively.
Kinetic Study of Metallic Silver Photoinduced Surface Deposition Phenomenon
Authors: Takeshi Kawaguchi Takeshi Kawaguchi , Shigeo Maruno Shigeo Maruno
Published: October 2002

The kinetics of photoinduced surface deposition (PSD) of metallic silver have been studied through observation of growth of the photodeposited Ag particles. The amount of metallic Ag segregated by PSD increases in proportion to exposure time at the early stage and subsequently to the square root of exposure time. The kinetics can be explained by the change in the rate-determining step from the photoelectronic process to diffusion process of Ag+ ions in glass.
Coercivity of Melt-Spun Nd–Fe–B–Ti Alloys with Large Volume Fraction of Free-Iron Dispersoid
Authors: Yao June-Min , Chin Tsung-Shune , Chu Cheng-Hao Lin
Published: October 2002

Nanocrystalline free-iron dispersoid was precipitated in the melt-spun and heat-treated Nd12Fe82Ti

x

B6-
x

(A-alloys), and Nd10Fe84Ti

y

B6-
y

(C-alloys), (x, y = 0 to 5). Annealing at a temperature between 600 and 800° C for 3.6 ks, though introduces large volume fraction of free iron dispersoid, bestows high coercivity in the range of 3.5 to 8.8 kOe, at a Ti level of 1 to 3 at.%, depending on annealing temperatures. Remanence enhancement was observed in C-alloys with a calculated volume fraction of around 10% free-iron dispersoid. The domain-wall-pinning mechanism of an A-alloy can not be well-fitted by a Gaunt's plot of temperature dependence of coercivity. Transmission electron microscopy reveals a nanocrystalline structure consisting of at least two phases of the Nd2Fe14B phase with a grain size of 30 to 100 nm, and the free-iron dispersoid of 5 to 50 nm. Exchange hardening mechanism is found to be responsible for the high coercivity of these alloys.