bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Properties of Dry-Etched Si/Si1-xGex Heterostructure Wires
Authors: Tang Yin Sheng , Wilkinson Chris. D. W. , Smith David. W. , Whall Terry E. , Parker Even H. C.
Published: October 2002

This paper reports a study on the optical properties of molecular-beam-epitaxy-grown Si/Si1-
x

Ge

x

heterostructures reactive-ion-etched into nanometer-scale wires using both Raman scattering and photoluminescence measurements. The results show that except for a thin layer of disordered Si1-
x

Ge

x

alloy formed during the etching process, little damage was inflicted on the dry-etched sidewalls of the free-standing Si/Si1-
x

Ge

x

wires. With decreasing wire width, both dry-etching-induced strain relaxation and enhanced electron-hole droplet emission have been observed. The latter has been attributed to the lateral confinement of the wires which improves the nucleation of droplets. When the wire width is below about 40 nm, optical transitions due to quasi-one-dimensional confinement are clearly seen.
Intersubband Absorption in Modulation-Doped p-Type Si/Si1-xGex Quantum Wells: A Systematic Study
Authors: Fromherz Thomas , Koppensteiner Ewald , Helm Manfred , Bauer Günther , Nützel Joachim , Abstreiter Gerhard
Published: October 2002

A study of intersubband infrared (IR) absorption in modulation-doped p-type Si/SiGe quantum wells is presented for SiGe wells with widths between 26 Å and 36 Å and Ge contents in the range from 19% to 50%. Absorption lines between 725 cm-1 and 1830 cm-1 are observed. Depending on the barrier height (i.e., on the Ge content of the wells), the heavy-hole subbands excited by the IR radiation are either localized in the wells or strongly mixed with barrier-bound states and therefore delocalized. The shape of the absorption line correspondingly changes from a narrow Lorentz line to a rather broad absorption band. Using the structural parameters determined by high-resolution triple-axis X-ray diffraction, the results of a self-consistent calculation are in excellent agreement with the measured absorption spectra.
Silicon-Germanium-Carbon Alloys Extending Si Based Heterostructure Engineering
Authors: Iyer Adrian R. Powell
Published: October 2002

SiGe epitaxial growth on Si has been of interest for a number of years. In this work we consider the addition of 1 to 6% C into both Si and SiGe epitaxial material. We have used a solid, and a gas source, (acetylene), within a solid source SiGe molecular beam epitaxy system to produce a C flux. We have produced high-crystalline-quality Si1-
y

C

y

and Si1-
x
-
y

Ge

x

C

y

material using both approaches. In addition we demonstrate strain-symmetrical short-period superlattice structures grown on (100) Si with high Ge compositions ranging from 20% up to 100% Ge, at 100% Ge the Ge/Si1-
y

C

y

superlattice has an interface mismatch of 7%.
Low-Temperature Epitaxial Growth of Silicon and Silicon-Germanium Alloy by Ultrahigh-Vacuum Chemical Vapor Deposition
Authors: Jung Tz-Guei , Chang Chun-Yen , Chang Ting-Chang , Lin Horng-Chih , Wang Tom , Tsai Wen-Chung , Wang Guo-Wei Huang
Published: October 2002

Low-temperature epitaxy of silicon and silicon-germanium alloy via an ultrahigh-vacuum chemical vapor deposition system was investigated. Bistable conditions were observed for silicon epitaxial growth performed within the temperature range of 550° C to 800° C. The activation energy of the SiGe growth rate was found to decrease as the germanium composition increased. The germanium atomic molar fraction in these epitaxial layers was tightly controlled by a computer-controlled gas source switching system. Si/SiGe superlattice structures of 20-period 5 nm Si/12 nm SiGe layers were grown to demonstrate the excellent controllability of this growth technique.
Characterization of Ultrashallow P+ Profiles by Spreading Resistance Measurements
Authors: Minondo Michel , Dominique Roche Dominique Roche , Claude Jaussaud Claude Jaussaud
Published: October 2002

Very shallow p+/n junctions ( ≤0.1 µm) are required for 0.25 µm complementary metal oxide silicon (CMOS) technologies. Spreading resistance probe (SRP) analysis can quickly give an electrical resistance profile, but the real problem is the conversion of the resistance profile into a concentration profile. On the one hand, a bevel effect has been seen. It modifies the resistance profile shape near the surface region and disappears far away from the bevel edge. In our work, we try to correct for this effect making the assumption that this region gives rise to a parasitic resistance that we can subtract from the spreading resistance. On the other hand, it is necessary to make some assumptions about the variation of the electrical contact radius versus the dopant concentration, especially in the presence of high gradient profiles. We propose a semi-empirical method which allows for the correction of the concentration profiles by taking into account this radius variation without any calculation instabilities. Thus, taking into account these effects and the corresponding corrections made, we can obtain SRP profiles comparable to the secondary ion mass spectroscopy (SIMS) profiles.
Effect of Interfacial Oxide on Static and High-Frequency Performance in Poly-Emitter Bipolar Transistors Under High-Level Injection
Authors: Chyan Yih-Feng , Sze Simon Ming , Reif Chun-Yen Chang
Published: October 2002

We report on a theoretical investigation of the effect of interfacial oxide on both static and dynamic performance in polycrystalline silicon emitter bipolar transistors. The calculation is carried out up to 0.9 V, before the onset of the Kirk effect. From the model, it is found that the current gain increases and the forward transit time decreases as interfacial oxide thickness increases. Furthermore, both the current gain and the forward transit time decrease as recombination velocity increases. In addition, the intrinsic base resistance remains almost constant as interfacial oxide thickness increases, and increases as recombination velocity increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of bipolar transistors operating under high-level injection.
Effects of Seeding Layer on Perovskite Transformation, Microstructure and Transmittance of Sol-Gel-Processed Lanthanum-Modified Lead Zirconate Titanate Films
Authors: Lee Joon Sung , Kim Chang Jung , Yoon Dae Sung , Choi Chaun Gi , Kim Jae Myung , Kwangsoo No Kwangsoo No
Published: October 2002

A series of sol-gel-processed lanthanum-modified lead zirconate titanate (PLZT) thin films with La/Zr/Ti ratios of 8.5/65/35, 9/65/35, 9.5/65/35, 15.5/40/60 and 18/30/70 were prepared on indium tin oxide (ITO)-coated Corning 7059 glass substrates and heat-treated at different temperatures from 475° C to 685° C. The X-ray diffraction, microstructure, optical transmittance spectra and the polarization vs electric field curves were investigated. The P(L)ZT thin films of higher Ti/Zr ratio show lower transformation (from pyrochlore to perovskite) temperature. The PLZT(8.5–9.5/65/35) thin film with the seeding layer shows improved phase content, high optical transmittance and enhanced perovskite transformation kinetics. The grain sizes are reduced (from 5–6 µ m to 0.1–0.2 µ m) and uniform. The fracture surfaces of the films with a seeding layer consist of columnar structure of which the grains grew from the seeding layer. The optical transmittance is enhanced, and the polarization value at 400 KV/cm increases for the film with the seeding layer.
ZnS:Mn Electroluminescent Thin Films Prepared by Multisource Deposition under Controlled Sulfur Vapor Pressure
Authors: Nire Takashi , Matsuno Akira , Atsushi Miyakoshi Atsushi Miyakoshi , Koutoku Ohmi Koutoku Ohmi
Published: October 2002

ZnS:Mn thin-film electroluminescent (TFEL) devices have been prepared by using a multisource deposition (MSD) method. A new technique of sulfur vapor pressure control has been developed for the thin-film growth at a high sulfur vapor pressure. Growth kinetics of ZnS:Mn thin films on the sulfur vapor pressure have been studied. It has been found that at sulfur vapor pressure higher than 0.1 Pa, the growth rate is limited by the effective amount of the Zn flux. The ZnS:Mn film grown at the sulfur vapor pressure of 0.85 Pa shows a smooth surface and has a uniform grain size of about 200 nm. The ZnS:Mn TFEL device shows the luminance of 300 cd/m2 and the efficiency of 3.5 lm/W at 30 V above the threshold voltage of 180 V with 60 Hz drive.
A Comparison of the Effects of RF Plasma Discharge and Ion Beam Supply on the Growth of Cubic Boron Nitride Films Formed by Laser Physical Vapor Deposition
Authors: Kayo Kaneda Kayo Kaneda , Kimihiro Shibata Kimihiro Shibata
Published: October 2002

This paper presents a comparison of the effects of RF plasma discharge and ion beam supply on the growth of cubic boron nitride films formed by excimer laser physical vapor deposition (laser PVD). The film structure was analyzed by fourier transformation infrared region (FT-IR) spectroscopy and thin-film X-ray diffraction analysis. The structure of the film deposited with an RF plasma discharge provided between the substrate and target was hexagonal BN. On the other hand, that of the film deposited by irradiating the substrate directly with an ion beam was hexagonal BN (hBN) and cubic BN (cBN). It is thought that direct irradiation of the vapor generated from the target by accelerated ions increased the activation energy of the vapor, with the result that the film structure was changed. Besides irradiating the substrate directly with the ion beam resulted primarily in the etching of hBN while cBN remained.
Exchange Interaction between Magnetic Moments of Ferromagnetic Sample and Tip: Possibility of Atomic-Resolution Images of Exchange Interactions using Exchange Force Microscopy
Authors: Mukasa Kōichi , Hasegawa Hideo , Tazuke Yuichi , Sueoka Kazuhisa , Hayakawa Makoto Sasaki
Published: October 2002

The exchange interaction and force acting between magnetic moments of a ferromagnetic sample and tip are calculated using the one-dimensional electron-gas model. It is suggested from an estimate of their magnitudes that an atomic-resolution image of exchange interaction of the transition-metal sample and tip can be obtained with the use of atomic force microscopy (AFM).
Ultra-Fine Pattern Fabrication by Synchrotron Radiation X-Ray Lithography Using a Shifter-Edge Type Phase-Shifting Mask
Authors: Toshiyuki Horiuchi Toshiyuki Horiuchi , Kimiyoshi Deguchi Kimiyoshi Deguchi
Published: October 2002

This paper reports the feasibility of ultra-fine pattern fabrication using an X-ray phase-shifting mask. Using shifter-edge type phase-shifting masks, less-than-100-nm patterns can be printed without preparing thick precise X-ray absorber patterns. However, it is still important that the shifter not be too thick, because thick shifter patterns are also difficult to fabricate. Shifter thickness is decided by the refractive index n of the shifter and a small n value permits a thin shifter. However, materials with a small n value have large absorption, so the latitude in the shifter transmittance and phase-shifting angle was analyzed. It is clarified that the degradation of shifter transparency is not a serious problem, and the tolerance of phase-shifting angle is very large. It is also demonstrated that SR X-rays with a continuous spectrum can be applied. Patterns almost as fine as 50 nm have been printed.
Microwave Measurements of Moisture Content of Aggregate
Authors: Shigeru Nakayama Shigeru Nakayama
Published: October 2002

An instantaneous method for measuring the moisture content in aggregate such as sand is developed using a microwave open-ended coaxial cavity resonator. We measure the attenuation and frequency shift of resonant peaks of the cavity resonator, which are related to the moisture content of the sand. The standard deviations in the attenuation and frequency shift are 0.30% and 0.14% in the percentage of moisture, respectively. The frequency shift measurement is better than the attenuation measurement to calculate the moisture content.
Anharmonic Decay of High Frequency Phonons in Vitreous Silica
Authors: Hiroshi Ikari Hiroshi Ikari
Published: October 2002

Diffusive propagation profiles of heat pulses in vitreous silica have been measured at 2.3 K. The observed peak arrival times vary linearly with the propagation distance, which is different from the pure diffusion propagation observed in the presence of elastic scattering sites. Our results suggest that the high energy phonons injected into the glass propagate under the influence of elastic scattering (Rayleigh scattering) and anharmonic decay. The experimental results qualitatively agree with the theoretical study of the transport properties of high frequency phonons.
High Temperature-Elastic Moduli and Internal Dilational and Shear Frictions of Fused Quartz
Authors: Mikio Fukuhara Mikio Fukuhara , Asao Sanpei Asao Sanpei
Published: October 2002

Longitudinal and transverse wave velocities, six kinds of elastic parameters (Young, shear and bulk moduli, Lamè parameter, Poisson's ratio and acoustic wave velocity anisotropy factor) and dilational and shear internal frictions of a fused quartz have been simultaneously measured over a temperature range 298–1674 K, by an ultrasonic pulse sing-around method. These elastic moduli, Lamè parameter and Poisson's ratio increase with increasing temperature, suggesting enhancement of rigidity for mixed mode II–mode III shear by crystallization on heating. The 840 and 1110 K peaks in dilational friction might be related to phase transition of α-quartz/β-quartz and β-quartz/β2-tridymite. For shear friction, the 390 and 1360 K peaks would be attributed to β1/β2-tridymite and glass phase transitions, respectively.
Ultrasonic Behaviour of Paraffin Wax during Melting and Solidification Processes
Authors: Hiroaki Kamioka Hiroaki Kamioka
Published: October 2002

The sound velocity of paraffin wax and its attenuation were measured in the solid phase and the liquid phase near the melting point, using the pulse transmission method. An interior transducer-type cell was used for the measurement. The experiment was in the temperature range from 10°C to 80°C, and the frequency of sound waves was 1 MHz. The melting point of the specimen was 44–46°C. In the melting process, a large absorption of ultrasonic waves was observed. During the solidification process, the sound velocity and the attenuation gradually changed with elapsed time. Noticeable changes in sound velocity and attenuation occur in the solid with a microscopical quantity of liquid melt.
Phonon Hole Burning Created by Pulsed RF Electric Field in Impedance Spectrum
Authors: Fujio Tsuruoka Fujio Tsuruoka
Published: October 2002

A hole burning phenomenon was studied in the system where piezoelectric powder particles resonantly oscillate under application of rf electric field. Holes were introduced by applying pulses of a large-amplitude rf electric field to a capacitor containing the powders. The written phonon hole was detected in the frequency spectrum of the electric impedance of the capacitor. The mechanism of hole creation was analyzed from the measured complex impedance and attributed to the change of oscillation characteristics of particles.
New Method for Measuring Mechanical Vibration Loss and Dielectric Loss of Piezoelectric Transducer under High-Power Excitation
Authors: Seiji Hirose Seiji Hirose
Published: October 2002

In the Pb(Zr, Ti)O3 group ceramics, the dielectric loss becomes larger than the mechanical vibration loss under high-power excitation. In this paper, a new advanced method for measuring these losses separately and simultaneously is described. The two-step differential circuit is utilized. By adjusting the differential circuits, the dielectric loss and the damped capacitance are obtained. The resonance circuit constants under high-power excitation are obtained after adjusting the differential circuit.
Equivalent Circuit of Interdigital Transducers Based on Coupling-of-Modes Theory Considering Electrode Resistivity and Propagation Loss
Authors: Kazuhiro Hirota Kazuhiro Hirota , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

An equivalent circuit of an interdigital transducer is derived from the coupling-of-modes equations considering propagation loss and resistivity of finger electrodes. The features of the circuit are discussed, focusing on the expression of the two loss mechanisms. As an example of calculations of device characteristics using the circuit derived, the frequency responses of insertion loss of a surface acoustic wave (SAW) resonator-coupled filter are shown with electrode resistivity as a parameter.
Material Constants of LiTaO3 Determined from Surface Acoustic Wave Velocities
Authors: Kouji Taki Kouji Taki , Yasutaka Shimizu Yasutaka Shimizu
Published: October 2002

The elastic and piezoelectric constants of LiTaO3 were determined from phase velocities of the surface acoustic waves (SAWs). Velocities were measured from many ripple frequencies caused by direct electrical coupling with the SAW delay-line response, and values to 5 significant digits were the result. The material constants were calculated using Newton's iterative numerical method. The differences between theoretical and experimental values were found to decrease by one.
TT-Cut Torsional Quartz Crystal Resonators of Free-Free Bar-Type
Authors: Hirofumi Kawashima Hirofumi Kawashima , Mitsuhiro Nakazato Mitsuhiro Nakazato
Published: October 2002

This paper describes a TT-cut torsional quartz crystal resonator of free-free bar type. An object of this paper is to clarify the frequency temperature behavior, series resistance and a quality factor for TT-cut torsional quartz crystal resonators of free-free bar-type. The analysis results are then compared with the measured data. The principal results indicate that the calculated values of frequency temperature behavior for resonators of free-free bar-type agree comparatively well with the measured ones. Similar to the torsional resonators of tuning fork-type, a torsional quartz crystal resonator of free-free bar-type is also found to have an absolute value of the second order temperature coefficient β smaller than half a value of that for a flexural mode quartz crystal resonator.
Thin-Film Bulk Acoustic Resonators Employing ZnO/Pyrex-Glass Composite Diaphragm Structure
Authors: Yoshiki Makishima Yoshiki Makishima , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

This paper discusses the application of ZnO/Pyrex-glass composite diaphragm structure to thin-film bulk acoustic resonators (FBARs). Analysis of ZnO/Pyrex-glass composite diaphragm structure showed for thickness-longitudinal vibration that zero temperature coefficient of frequency with relatively large electromechanical coupling constant of about 20% is realised for the second- and third-order resonances as well as for the fundamental resonance. An FBAR employing the ZnO/Pyrex-glass composite diaphragm structure was fabricated, and Q values of 970 and 858 were obtained, respectively, for the fundamental and second-order resonances at 298.7 MHz and 497.5 MHz.
Quartz Temperature Sensors of Torsional Vibration Formed from Doubly Rotated Plates
Authors: Kawashima Hirofumi , Nakazato Mitsuhiro , Shimizu Yasutaka
Published: October 2002

This paper describes quartz temperature sensors using the torsional vibration mode and formed from doubly rotated plates. An objective of this paper is to clarify theoretically and experimentally their frequency temperature behavior. Another objective is to realize a miniaturized quartz temperature sensor with easy processing, low frequency, small series resistance R
1 and sufficient temperature sensitivity. The analysis results for frequency temperature behavior are then compared with the measured data. The theoretical and experimental results are in good agreement. In addition, a miniaturized quartz temperature sensor that is easily formed by an etching process is found to be successfully obtained with a frequency of 413 kHz, series resistance R
1 of 4.2 k Ω and temperature sensitivity of 23.7 ppm/°C in the calculation and 25.4 ppm/°C in the experiments.
Effect of Ultrasound in Soybean Protein Extraction
Authors: Fukase Hirokazu , Ohdaira Etsuzo , Nobuyoshi Masuzawa Nobuyoshi Masuzawa , Masao Ide Masao Ide
Published: October 2002

Application of ultrasound for accelerating the extraction of nutriments in food processing has been attempted. However, conditions of exposure to ultrasound were not clear in previous studies. This paper reports on the relationship between the ultrasonic pressure and the amount of extracted protein from soybeans. Experiments were conducted using a beaker, in which the ultrasonic fields were precisely measured. Soybean flakes suspended in water were put in the beaker and placed in a water tank. The amount of extracted protein in water upon ultrasonic exposure was calculated by the Kjeldahl method. It was found that the amount of extracted protein increased in proportion to ultrasonic pressure up to the total amount of soybean protein soluble in water. Furthermore, this paper describes the denaturation of the protein produced by the ultrasonic cavitation.
Construction of a Vernier Tandem (3+3)-Pass Brillouin Spectrometer and Its Application to Surface Acoustic Wave Study in Metallic Multilayer Films
Authors: Akira Yoshihara Akira Yoshihara
Published: October 2002

In order to study the elastic and magnetic properties of metallic multilayers by Brillouin scattering, we have constructed a (3+3)-pass vernier tandem Fabry-Perot interferometer. We have also developed master/slave and time-sharing techniques and electronics to stabilize the interferometer during a long spectrum accumulation period of over several hours. In this report, we describe the details of the tandem spectrometer and the control techniques. As an application of the tandem spectrometer, we have studied sound velocity of Rayleigh surface waves existing in Ag/Cu multilayers as a function of the multilayer period. We have observed considerable softening of more than 20% of the surface velocity as the multilayer period decreases from 150 Å to 7 Å.
A Two-Dimensional Array Probe Using an Insulating Layer and a Signal Line on the Vibrator
Authors: Hashimoto Shinichi , Shiroh Saitoh Shiroh Saitoh , Mamoru Izumi Mamoru Izumi
Published: October 2002

A two-dimensional array probe using a newly developed method for drawing out signal lines is proposed. In this probe, an insulating layer and a conductive layer with about 10 µm total thickness are deposited on one electrode of a vibrator. The insulating layer has a through-hole to connect the electrode to the conductive layer. The conductive layer is patterned to inner signal lines that are terminated at both edges on the side of the vibrator. An outer signal line is drawn from each signal line terminal of the vibrator by wire bonding. The specifications of the fabricated two-dimensional array probe are 5 MHz, 30×5 elements and two acoustic matching layers. The pulse-echo characteristic and directional response of an element were evaluated, and a -6 dB bandwidth of 64% and -20 dB pulse-echo directional response of 10° were obtained. This measured bandwidth was not drastically reduced as compared with that of a conventional probe, and the measured directional response became slightly narrower as compared with the calculated result.
Effect of Controlled Sound Pressure Field on Fragmentation in Piezoelectric Extracorporeal Shock Wave Lithotripsy
Authors: Yanagida Yuji , Iwama Nobuyuki , Hideki Kosaku Hideki Kosaku , Kiyoshi Okazaki Kiyoshi Okazaki
Published: October 2002

A method for changing a sound pressure field by electronic driving control of individual piezoceramic elements is studied so that extracorporeal shock wave lithotripsy may become a more effective and safer therapeutic method. First, we examine this method with respect to the field of a shock wave. At 1 kV driving voltage, the focal zone can be changed from 2.2 mm×7.1 mm to 2.8 mm×34.0 mm, and the peak pressure can be decreased to 64% of the original value. The change of fragmentation ability in this method is shown by measuring the number of shots required to break a model stone. The fragmentation is the most intense at a point 10 mm in front of the focal point, and the fragmentation ability remains as effective even if peak pressure is decreased. This method can decrease the peak pressure while maintaining the fragmentation effect.
Measurement of Shock Wave Pressure Distribution of Extracorporeal Shock Wave Lithotripter Using Pressure-Sensitive Paper: Practical Usefulness and Limitations
Authors: Oyanagi Masamichi , Kudo Nobuki , Yanagida Yuji , Nobuyuki Iwama Nobuyuki Iwama , Kiyoshi Okazaki Kiyoshi Okazaki
Published: October 2002

A new method for evaluating shock wave pressure distribution of extracorporeal shock wave lithotripters, using pressure-sensitive paper has been developed. It is a simple method to visualize the shock wave pressure distribution and has a better spatial resolution than the hydrophone. The pressure-sensitive paper can be used to visually detect whether the focal point is on the correct position, and to detect changes of pressure distribution. Additionally, the relationship between lithotripter power and integrated density as a new evaluating value shows linearity. Therefore, this method is useful for quality assurance of lithotripters at hospitals.
Application of Generalized Near-Field Acoustical Holography to Scattering Problems
Authors: Saijyou Kenji , Yoshikawa Mitsuhiro Ueda
Published: October 2002

Generalized near-field acoustical holography (GENAH) is applied to scattering problems, making use of its wavelength-limitation-free characteristic in the reconstruction process. GENAH signal processing is directly adapted for the reconstruction of the scattered field, while a method to extract the scattered-pressure hologram is independently proposed to create scattering GENAH. The measurement of the near field of a scatterer yields the superimposed incident and scattered fields. Their decomposition is carried out by subtracting the incident-pressure hologram from the superimposed-pressure hologram in K space. The validity of this decomposition method was demonstrated by comparing the experimental and theoretical results of finite submerged shells. Reconstruction of shell-surface vibration induced by scattering displayed a reasonable result.
Generation of Electron-Acoustic Signals and Distribution of Potential in Transistor Chip under Applied of Bias
Authors: Hiroshi Takenoshita Hiroshi Takenoshita
Published: October 2002

An observation area was first selected using scanning electron microscopy (SEM)-mode images. Switching to an electron-acoustic microscopy (EAM)-mode, the area selected from SEM images was then studied with EAM images using electron-acoustic signals. We carried out nondestructive internal observation at the fixed area of an Si transistor chip put into operation by application of bias voltage (V
b) in situ by EAM. The results showed that (a) the distribution of potential caused by V
b application in the chip could be determined nondestructively from the change in the contrast of EAM images and (b) the internal structure of devices in operation could be observed nondestructively by EAM.
Study of Models on the Generation and Propagation of Photoacoustic Signals in a Drilled Hole in Epoxy Resin
Authors: Tokunaga Yoshiaki , Minamide Akiyuki , Nakada Keimei Tamura
Published: October 2002

This paper describes improved models derived from an experiment in generation and propagation of photoacoustic signals in a drilled hole of an epoxy resin with different backing materials, a white polypropylene and a black one. The major difference between the improved and the old models is as follows. The photoacoustic signal at the top edge of the hole was generated not only due to absorbed incident light, but also due to absorbed and scattered light at the top edge of the hole. In addition, we show the propagation paths of the PA signals generated at the top edge of the hole.
High Signal-to-Noise Ratio and High Resolution Detection Techniques for Photopyroelectric Thermal Wave Imaging Reconstruction
Authors: Yarai Atsushi , Kazuo Sakamoto Kazuo Sakamoto , Takuji Nakanishi Takuji Nakanishi
Published: October 2002

This paper describes high signal-to-noise ratio and high resolution detection techniques for photopryoelectric thermal wave imaging equipment. A high signal-to-noise ratio technique is mainly achieved by realizing a very low-noise first stage pre-amplifier and its assembling technique and by the use of very low noise second stage amplifier. High resolution detection is achieved by using a metal probe tip with a very small diameter. This equipment could be achieved mainly due to the high signal-to-noise technique and the finite element method (FEM) analysis. A high-fidelity tomographic image reconstructed by these techniques is also shown.
Thermal Wave Tomography with Ray-Optic Reconstruction
Authors: Takaue Ryoichi , Hirata Kazuhiro , Koga Shotaro , Morio Matsunaga Morio Matsunaga , Kunisuke Hosokawa Kunisuke Hosokawa
Published: October 2002

Thermal wave tomographic imaging of an aluminum sample with a new photopyroelectric detector is reported. The new detector can detect the local ac temperature field when it comes into contact with the back surface of a sample. Compared to the capacitively coupled detector, this detector is easier to handle and has increased sensitivity to the photopyroelectric signal. The effects of the laser beam modulation frequency and subsurface defects in the sample on the tomographic image have also been studied. It is revealed that the resolution of the tomograph increases with increasing modulation frequency and decreasing metal-tip diameter of the detector.
Analysis and Design of Magnetooptic Guided Wave Devices in Cerium-Doped Garnet Thin Films
Authors: Shin'ichiro Kikuchi Shin'ichiro Kikuchi , Yasumitsu Miyazaki Yasumitsu Miyazaki
Published: October 2002

Optical devices using magnetostatic surface waves (MSSWs) have important applications in optical signal processing and optical computing. In this paper we propose the analysis and design of an optical mode conversion device that features improved properties. The device consists of cerium-doped thin and thick garnet films. The design features 100% mode conversion over an interaction length of about 5 mm for an applied microwave power density of a few mW/mm. The characteristics of optical wavelength filtering under a fixed biasing magnetic field are also investigated. The results can be used to construct an optical demultiplexer with wavelength separation as narrow as 2 nm in the wavelength band of 1.3 µm. The MSSW center frequency assumed in the calculation is f
c= 3.1504 GHz.
Adjustable Acoustic Knife Edge for Anisotropic and Dark-Field Acoustic Imaging
Authors: Oleg Kolosov Oleg Kolosov , Kazushi Yamanaka Kazushi Yamanaka
Published: October 2002

A new effective method for acoustic anisotropy and dark-field imaging in reflection ultrasonic focusing devices is proposed. Part of the spherical acoustic wave propagating to and coming from the object is stopped by an ultrasonically opaque acoustic knife edge (AKE) set at the aperture plane of the focusing lens or transducer. This AKE provides the focusing device with directional sensitivity and the capacity for dark-field imaging. Sensitivity of the AKE system to the elastic anisotropy of the leaky surface acoustic wave (LSAW) velocity was demonstrated using an X-cut LiNbO3 crystal. Dark-field imaging of cracks in Si3N4 ceramics and the structure of carbon fiber-reinforced plastic (FRP) was performed. This method can be easily applied to commercially available focusing systems and allows optimization of the setup for the microscopic study of various objects.
Active Sound Power Reduction Based on Mutual Radiation Impedance Effect between Transducers in Water
Authors: Sugimoto Sigeo , Akio Hasegawa Akio Hasegawa , Toshiaki Kikuchi Toshiaki Kikuchi
Published: October 2002

The output sound power of a primary transducer (corresponding to a noise source) in water can be reduced by arranging an array of controllable secondary transducers. The mutual radiation impedance method is used to evaluate the total output power from the primary and secondary transducers. The output power is calculated from a quadratic function of the velocity of the active area of the secondary transducer. For various arrangements of the primary and secondary transducers, the quadratic equations are derived in terms of the velocity of the active area of the secondary transducer. If the two transducers are spaced less than one half-wavelength apart in water and are 180° out of phase, the best reduction in total output power can be achieved at the optimum velocity of the active area of the secondary transducer.
Asymptotic Analyses of Sound Fixing and Ranging Wave Propagation in Acoustic Channel of Deep Ocean
Authors: Ohshima Kouji , Kazushi Fukuda Kazushi Fukuda , Toyohiko Ishihara Toyohiko Ishihara
Published: October 2002

In this paper, we propose the asymptotic representations for calculating the sound fields in the sound fixing and ranging (SOFAR) channel of a deep ocean. We present an acoustical ray representation obtained directly from the ray tracing technique for calculation of the sound fields in the illuminated region in the SOFAR channel. We also present the diffracted ray representation and the hybrid ray-mode representation to calculate, respectively, the sound fields in the refraction shadow and the boundary layer. Numerical comparisons with the reference solution obtained from the normal-mode theory have confirmed the accuracy and utility of the asymptotic representations for the sound fields. We have clarified that the various asymptotic representations can provide an effective means for predicting sound fields and for understanding the physical phenomena of sound propagation in the SOFAR channel.
Third-Order Piezoresistance Coefficients in p-Type Si
Authors: Yamichi Ohmura Yamichi Ohmura
Published: October 2002

By tensor property and crystallographic symmetry considerations, it has been shown that there are 20 independent nonzero components of the third-order piezoresistance (TOPR) coefficients (π3) for cubic semiconductors which crystallize in diamond ( O
h
) or zincblende ( T
d
) structures. Piezoresistances for p-type Si obtained from conductivities calculated for sixfold degenerate valence bands with and without stress are highly nonlinear so that they are more suitably expressed with up to the fifth-order (π5) stress terms than merely with up to the π3 term for the odd-order stress terms. For several current and uniaxial stress directions, TOPRs are given in terms of 20 components of TOPR coefficients, and calculated π3's which are obtained using up to the third-order stress term correspond in the order of magnitude with experimental ones.
Reduction Mechanism of Threading Dislocation Density in GaAs Epilayer Grown on Si Substrate by High-Temperature Annealing
Authors: Takagi Yasufumi , Yonezu Hiroo , Yoshiaki Hachiya Yoshiaki Hachiya , Kangsa Pak Kangsa Pak
Published: October 2002

The effects of high-temperature annealing were investigated by transmission electron microscopy (TEM) and secondary ions mass spectroscopy (SIMS) on reduction of threading dislocation density in GaAs epilayers grown on Si substrates. It was found that the dislocation density in the annealed GaAs epilayers grown on Si was remarkably reduced. This phenomenon could be attributed to an increase in the velocity of dislocation glide motion including climb motion caused by reaction with vacancies at high temperature. In addition, specific long dislocations running parallel to the GaAs–Si hetero-interface were observed. The specific dislocations were distributed around the diffusion front of Si atoms in the GaAs epilayer. These results led to a model for reduction of threading dislocation density by high-temperature annealing.
Calculation of Characteristic X-rays in Diagnostic X-ray Spectrum
Authors: Nobuyuki Nakamori Nobuyuki Nakamori , Kaname Yamano Kaname Yamano , Masayoshi Yamada Masayoshi Yamada , Hitoshi Kanamori Hitoshi Kanamori
Published: October 2002

We examined the experimental data of Fewellet al.[Handbook of Computed Tomography X-Ray Spectra(HHS Publication, Rockville, 1981) No. 81–8162], which exhibited the variation of the characteristic radiation yield with the beam angle, but did not confirm any model proposed by previous workers to explain its variation. We developed a new method of calculating the intensity of \hyphenationbrems-strah-lung the characteristic radiation for the X-ray tube used in medical diagnosis. Our method was based on the photoelectric interactions of the bremsstrahlung photons with the target material, where the bremsstrahlung spectra used were calculated taking into account the electron energy distributions in a target material described in our previous paper. Our method did not include any adjustment parameters to fit with experimental data. Our calculated results are in good agreement with the experimental results of Fewellet al.In particular, the dependence of the intensity of the characteristic radiation on the beam angle, calculated using our method, agreed with the experiment results of Fewellet al., while the methods proposed by previous workers led to the reverse dependence.
X-Ray Photoelectron Spectroscopy and X-Ray Absorption Near Edge Structure Study of Structural Change of Perhydropolysilazane to Silicon Nitride by Heat Treatment
Authors: Yokoyama Yasuharu , Horiuchi Kazunaga , Ohta Tsugio Maeshima
Published: October 2002

We studied the structural change of perhydropolysilazane to silicon nitride during the process of heat treatment by means of in situ X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS), together with Fourier transformed infra-red (FT-IR) and temperature programmed desorption (TPD) spectroscopies. It was revealed that nucleophilic attack on silicon atoms in the polymer began to proceed above 200° C, by nitrogen atoms in the polymer itself and also in atmospheric ammonia. From 400° C to 600° C, dehydrogenation also occurred and produced dangling bonds which were attacked by ammonia molecules to form the network of SiN4 tetrahedra. Although oxidation by residual moisture was observed to some extent at 600° C, further heat treatment in ammonia formed Si–N bonds via replacement of oxygen atoms by nitrogen atoms to complete the formation of Si3N4-like structure.
Low-Temperature Selective Epitaxial Growth of GaAs Using Triethylgallium and Amino-As in Metalorganic Molecular Beam Epitaxy
Authors: Tadachika Hidaka Tadachika Hidaka , Ikuo Suemune Ikuo Suemune
Published: October 2002

Selective-area growth of GaAs was achieved at low temperatures up to 400° C by metalorganic molecular beam epitaxy using triethylgallium (TEG) and an amino-As, tris-dimethylamino arsenic (TDMAAs). We found that growth processes near the edges of selectively grown area were highly dependent on the shapes of mask edges. The mechanism of selective-area growth was studied by quadrupole mass spectrometry. The catalytic cracking of both TEG and TDMAAs on GaAs surfaces and absence of such on SiO

x

mask surfaces led to growth selectivity. Simultaneous supply of As4 and TEG on SiO

x

surfaces was found to enhance the decomposition of TEG dramatically, which resulted in the deposition of polycrystalline GaAs on SiO

x

surfaces.
Growth and Characterization of K3Li2-xNb5+xO15+2x Micro Single Crystals Formed by the µ-Pulling Down Method for Blue SHG Applications
Authors: Yoon Dae-Ho , Makiko Hashimoto Makiko Hashimoto , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Potassium lithium niobate ( K3Li2-
X

Nb5+
X

O15+2
X

: KLN) crystals are difficult to grow by conventional crystal growth methods because of the distinct change of composition. Using the micro pulling down ( µ-PD) method, crack-free and homogeneous KLN crystals with a length of 150 mm and diameters of 150, 300 and 500 µm have been grown successfully. The crystals show good structural quality, single-domain structure and an excellent second harmonic generation property. The red irradiation of a Ti: sapphire laser and semiconductor laser diode was converted by µ-PD crystals to blue laser light with half wavelength.
Stroboscopic Observation in Antiferroelectric Liquid Crystals under Application of Very Short Reverse Pulse Voltage
Authors: Okada Hiroyuki , Watanabe Manabu , Hiroyoshi Onnagawa Hiroyoshi Onnagawa , Kazuo Miyashita Kazuo Miyashita
Published: October 2002

The stroboscopic observation of antiferroelectric liquid crystal molecules under very short reverse pulse voltage which is effective in improving the electrooptic responses from ferroelectric state to antiferroelectric state has been investigated. Stroboscopic micrographs under low reverse pulse voltage show an anomalous transmittance behavior, and transmittance step-back phenomena, wherein transmittance declines once and then rises again just after removal of reverse pulse voltage application, are clarified.
Electrical Conduction by Percolation Process in Insulating Polymer Containing Small Amount of Conducting Polymer
Authors: Yin Xiao Hong , Yoshino Katsumi , Yamamoto Hideo , Watanuki Toshiro , Isa Isao , Nakagawa Shinichi , Adachi Mikio
Published: October 2002

Electrical conductivity is studied in two component composites, one of which is insulating polymer (nylon6, nylon66) in fibers coated with conducting polypyrrole and the other, polyethylene in spheres without coating. Conductivity is enhanced by more than 15 orders of magnitude when the concentration of polypyrrole-coated insulating polymer exceeds 2–5 vol%, which corresponds to an effective polypyrrole concentration of 0.01–0.03 vol%. This insulator-metal transition-like characteristic can be explained by a percolation model. Thermoelectric power is proportional to absolute temperature and is independent of the concentration of polypyrrole-coated insulating fibers above the percolation threshold, which support the percolation model. The percolation threshold depends on the shape of the coated fibers of the insulating polymer but does not depend on the type of coated insulating polymer. The percolation threshold increases with decreasing length of polypyrrole-coated insulating fibers.
Plasma Cleaning and Etching Using Quartz Bell Jar with SnO2 Transparent Thin-Film Heater in CHF3–SiO2 Mocrowave Etching System
Authors: Seiichi Watanabe Seiichi Watanabe
Published: October 2002

A thermally controllable quartz bell jar with a SnO2 transparent thin-film heater was developed. The heating effect of the quartz bell jar on plasma cleaning and etching was investigated in a CHF3–SiO2 microwave etching system. By means of quartz bell jar heating, plasma polymer deposition on the inside wall of the quartz bell jar was decreased, the plasma-cleaning time was shortened and the SiO2/poly-Si selectivity was increased. In the reaction chamber, etching and plasma polymerization take place on the reaction chamber wall as well as on the wafer. The concentration distribution of radicals and ions in the plasma is dependent on these reactions. Accordingly, control of the reaction chamber wall temperature is important both to improve the etching characteristics and to prevent time fluctuation of the etching characteristics.
First-Principles Theory of Electronic States under Strong Field and Current and Its Application to Scanning Tunneling Microscopy
Authors: Kenji Hirose Kenji Hirose , Masaru Tsukada Masaru Tsukada
Published: October 2002

A method of the first-principles calculation of the electronic states under strong field and current is proposed, which is effective for bielectrode systems with atomic structure. A microscopic distribution of the field and current is calculated in a self-consistent way with the electron distribution in the surface region. The method is applied to the scanning tunneling microscope system around the contact region. The channel for the ballistic electron emission is opened in the tunnel barrier due to the proximity of the tip and surface, and is enlarged by the applied bias voltage. The force acting on the top surface atom by the tip is calculated, and the mechanism of atom extraction is clarified qualitatively.
Structural Correlation among Different Phases in the Initial Stage of Epitaxial Growth of Au on Si(111)
Authors: Tomohide Takami Tomohide Takami , Daiji Fukushi Daiji Fukushi , Tomonobu Nakayama Tomonobu Nakayama , Masayuki Uda Masayuki Uda , Masakazu Aono Masakazu Aono
Published: October 2002

Structures created on the Si(111) substrate in the presence of Au atoms corresponding to coverages (θ; Au) of ∼0.7–1.4 monolayers (ML) are discussed on the basis of the observed scanning tunneling microscopy images. At small θ; Au's ( ∼0.7–1.0 ML), a √3×√3 phase and a less-ordered phase coexist, the fractional area of the latter being increased with increasing θ; Au, and at larger θ; Au's (\stackrel>∼ 1.1 ML), a 6×6 phase appears as a single phase, in agreement with previous reports. It is shown that the less-ordered phase coexisting with the √3×√3 phase already has a close relation to the 6×6 phase in structure. The most fundamental structure of the 6×6 phase is seen at a large θ; Au of ∼1.4 ML, in which a layer of Au atoms sits on the Si(111) substrate incommensurately. As θ; Au decreases, some Au atoms appears to be removed with a periodicity of 6×6. The Au coverage of the √3×√3 phase seems to be ∼2/3 ML.
Initial Stage of Oxygen Adsorption onto a Si(111)–7×7 Surface Studied by Scanning Tunneling Microscopy
Authors: Hasegawa Tsuyoshi , Makiko Kohno Makiko Kohno , Shigeyuki Hosoki Shigeyuki Hosoki
Published: October 2002

The initial stage of oxygen adsorption onto a Si(111)-7×7 surface has been studied at room temperature by scanning tunneling microscopy. The surface was exposed to oxygen under a partial pressure of 1×10-9 Torr. Initial exposure led to bright and dark features at adatom sites. This dark feature, which was previously reported as a main channel for oxidation, only appeared in the faulted half of the dimer adatom stacking-fault (DAS) structure. The images suggest that the adsorption onto the un-faulted half starts after the faulted half are occupied with oxygen atoms. This clearly indicates that oxygen adsorption occurs at adatom sites with higher energy states.
Lattice Matching of α-Cyclodextrin Commensurate with Molybdenum Disulfide Studied by Scanning Tunneling Microscopy
Authors: Miyake Koji , Aiso Yoshiaki , Komiyama Makoto , Harada Akira , Kamachi Mikiharu , Hidemi Shigekawa Hidemi Shigekawa
Published: October 2002

Lattice matching between α- cyclodextrin (α- CyD) and molybdenum disulfide ( MoS2) was investigated by scanning tunneling microscopy (STM) using the CyD molecular necklace and molecular tube as specimens. Stable sites for α- CyD on the MoS2 substrate observed by STM were in good agreement with the model we proposed.
An Integrated Atomic Force Microscopy/Scanning Tunneling Spectroscopy Microscope and Its Application for p-n Junction Observations
Authors: Kenji Yamazaki Kenji Yamazaki , Shigeru Nakajima Shigeru Nakajima
Published: October 2002

We have developed an integrated atomic force microscopy (AFM)/scanning tunneling spectroscopy (STS) microscope that can simultaneously obtain, for the same area, a topographic image and current imaging tunneling spectroscopy (CITS) images derived from current-voltage ( I-V) characteristics on insulator-mixed surfaces. The I-V characteristics and CITS images of p-n junctions are stable and clearly show the differences between p--n and n+
-regions, and thus these regions can easily be distinguished. The characteristics can be explained by theoretical energy-band analysis. Sinde the current decreases with time after HF cleaning, the current changes are also probably related to changes in native oxide thickness Studies of impurity concentration distribution and oxide growth on silicon surfaces are found to be possible by integrated AFM/STS microscopy.