bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltage-Controlled Emission Wavelength Switching in a Pseudomorphic Si1-xGex/Si Double Quantum Well
Authors: Yasuhara Nozomu , Fukatsu S.
Published: February 2005

Voltage-controlled emission wavelength switching (VCEWS) is demonstrated in a pseudomorphic Si1-x
Ge
x
/Si double quantum well (DQW). Under cw excitation, photoluminescence (PL) of the DQW was found to exhibit a clear switchover of emission wavelengths under longitudinal electric field, where an extinction ratio of more than 100 was obtained. In the time domain, antiphase oscillations of PL decays synchronized with the polarity switch of driving voltages were observed. The unique band line-up of pseudomorphic Si1-x
Ge
x
/Si QWs which makes loosely bound electrons susceptible to longitudinal electric fields underlies the operation of VCEWS.
Effect of Interlayer Exchange Coupling on the Curie Temperature in Ga1-xMnxAs Trilayer Structures
Authors: Yuldashev Shavkat U. , Kim Yongmin , Kim Nayoung , Im Hyunsik , Kang Tae Won , Lee Sanghoon , Sasaki Yuji , Liu Xin , Furdyna Jacek K.
Published: February 2005

We have investigated the effect of interlayer exchange coupling on the Curie temperature of ferromagnetic (FM) layers in Ga1-x
Mn
x
As(Be)/GaAs/Ga1-x
Mn
x
As trilayer structures. The FM layers in the trilayers contained the same concentration of Mn (x≈0.046), but the top ferromagnetic layer was additionally doped with Be. For this x the Curie temperature observed on a control single-layer sample of Be-doped Ga0.954Mn0.046As is lower than that of an undoped sample. However, in the case of trilayers, we observed that the Curie temperature of the Ga0.954Mn0.046As(Be) layer increased with decreasing thickness of the GaAs spacer separating the two FM layers. This increase in Curie temperature is due to the exchange coupling between the ferromagnetic layers mediated by the spin-polarized free carriers (holes) through the thin insulating spacer.
Novel Magnetic Random Access Memory Cell Consisting of Magnetic Tunnel Junction Connected in Parallel with Negative Differential Resistance Device
Authors: Uemura Tetsuya , Honma Satoshi , Marukame Takao , Yamamoto Masafumi
Published: February 2005

A novel magnetic random access memory (MRAM) cell consisting of a magnetic tunnel junction (MTJ) and negative differential resistance (NDR) device connected in parallel is described. The NDR characteristics are used to increase the effective magnetoresistance (MR) ratio of the MTJ. Circuit simulations were performed for the memory cell with a triple-barrier resonant-tunneling diode (RTD) to confirm the efficacy of the basic operation. Furthermore, a hybrid circuit built from the CoFe-based MTJ and GaAs-based interband tunnel diode was fabricated. The circuit showed that the effective MR ratio was enhanced almost tenfold from its original value of 11% to 103%.
Enhanced Optical Properties of High-Density (>1011/cm2) InAs/AlAs Quantum Dots by Hydrogen Passivation
Authors: Park Se-Ki , Tatebayashi Jun , Nakaoka Toshihiro , Sato Tomohiko , Park Young Ju , Arakawa Yasuhiko
Published: February 2005

We have achieved a large increase (by a factor of up to 3200) in photoluminescence emission from InAs/AlAs quantum dot structures using the GaAs insertion layer and by hydrogen passivation at room temperature. The hydrogen passivation can lead to the reduction in a number of nonradiative recombination centers, and thus can increase the photoluminescence efficiency. After the treatments, the linewidth and the peak position of the luminescence were negligibly changed, indicating that the samples were not damaged during the plasma treatments. In time-resolved photoluminescence measurements, the decay time of hydrogenated samples was about twice as long as those of as-grown samples due to the passivated defects in surrounding barrier materials.
Breakdown Voltage in Uniaxially Strained n-Channel SOI MOSFET
Authors: Watanabe Naoya , Kojima Takeaki , Maeda Yasuhiro , Nishisaka Mika , Asano Tanemasa
Published: February 2005

The drain breakdown voltage of n-channel silicon-on-insulator (SOI) metal oxide semiconductor field-effect transistors (MOSFETs) was found to decrease with the application of uniaxial tensile strain along the channel. The decrease in drain breakdown voltage was found to depend on the direction of the strain applied with respect to the current flow. To investigate the mechanism of this phenomenon, the influence of uniaxial tensile strain on built-in potential at the source junction and on impact ionization was investigated using an SOI lateral diode and bulk MOSFET. Uniaxial strain was induced by mechanically applying bending deformation to the chip using a cantilever structure. Built-in potential at the source junction remained unchanged. Impact ionization rate at the drain edge of MOSFET was found to increase with increasing uniaxial tensile strain. This increase in impact ionization rate is shown to be the cause of the reduced drain breakdown of SOI MOSFET in the presence of uniaxial strain.
Novel Silicon On Insulator Metal Oxide Semiconductor Field Effect Transistors with Buried Back Gate
Authors: Oh Hyuckjae , Choi Hoon , Sakaguchi Takeshi , Shim JeoungChill , Kurino Hiroyuki , Koyanagi Mitsumasa
Published: February 2005

One of the most promising ways of realizing metal oxide semiconductor field effect transistors (MOSFETs) with high speed and ultralow power consumption is by varying the threshold voltage of fully depleted silicon on insulator (FD-SOI) MOSFETs by changing back gate bias. We have studied FD-SOI MOSFETs with buried back gate by experiment and simulation in order to realize both high-performance and low-voltage ULSIs. It was confirmed that the back gate is very effective not only for increasing the ON current in the active mode but also for decreasing the cut-off current in the standby mode by controlling the threshold voltage.
Threshold Voltage Behavior of Body-Tied FinFET (OMEGA MOSFET) with Respect to Ion Implantation Conditions
Authors: Park Tai-su , Cho Hye Jin , Choe Jeong Dong , Park Donggun , Yoon Euijoon , Lee Jong-Ho
Published: February 2005

The body-tied finFET (called OMEGA (Ω) metal oxide semiconductor field effect transistor (MOSFET)) exhibits positive characteristics as a future complementary metal oxide semiconductor (CMOS) device. The Ω MOSFETs have unique features such as high heat dissipation to the Si substrate, no floating body effect, and low defect density, while having the key advantages of the silicon-on-insulator (SOI)-based finFET characteristics. In order to increase the threshold voltages on both the Ω NMOSFET and the Ω PMOSFET while keeping the conventional gate electrodes (n+ polysilicon and p+ polysilicon gates for NMOSFET and PMOSFET, respectively), the device characteristics of the Ω MOSFETs have been characterized with halo ion implantation doses for the Ω NMOSFET and lightly doped drain (LDD) doses for the Ω PMOSFET. It was shown that the V
TH adjustment could be partially achieved.
Electrical Characterization of Sub-micron Magnetic Tunneling Junction Cells Using Scanning Probe Microscopy
Authors: Park Seungbae , Heo Jinhee , Kim T. W. , Chung Ilsub
Published: February 2005

We attempted to measure the tunneling current behavior of magnetic tunneling junction (MTJ) cells utilizing scanning probe microscopy (SPM) interfaced with an external magnetic field generator. Magnetic field was generated by allowing current to flow through coils and controlled by current ieldfeedback circuit, thereby enabling the evaluation of tunneling current under various magnetic fields. I-V measurement was carried out in the contact mode using a conducting cantilever at a specific magnetic field. The obtained magnetoresistance (MR) ratios of MTJ cells were about 21% regardless of the variation in the size of MTJ cells, and RA ranged from 8.5 K to 12.5 K[Ωµm2]. In addition, we also attempted to observe magnetic images of MTJ cells under various magnetic fields. We believe that the novel characterization method utilizing SPM is greatly beneficial for the characterization of MTJ cells because it enables the measurement of the I-V behavior of ultrasmall cells without the need for a using an extra electrode. Thus, the novel method may be used to measure the electrical properties of ultrasmall MTJ cells, namely below 0.1 µm×0.1 µm.
High-Performance Composite-Collector InP/InGaAs Heterojunction Bipolar Transistors
Authors: Kurishima Kenji , Ida Minoru , Ishii Kiyoshi , Watanabe Noriyuki
Published: February 2005

This paper describes composite-collector InP/InGaAs heterojunction bipolar transistors that exhibit high current density and good breakdown behavior simultaneously. The collector consists of 150-nm InGaAs and 150-nm lightly n-type doped InP. Additionally, a 30-nm-thick InGaAsP layer is sandwiched between them to minimize the accumulation of transit carriers. The proposed structure makes use of the space charge in the collector to reduce the collector-current multiplication coefficient. At high current density, the space charge decreases the electric-field intensity in the narrow-band-gap InGaAs and moves the high-electric-field region into the wide-band-gap InP. The fabricated transistors exhibit flat collector I-V curves, high current density of over 4 mA/µm2, and reasonably small knee voltage. They also show a peak f
t of over 200 GHz and a peak f
max of about 350 GHz at a current density of 2 mA/µm2. The ring oscillator IC based on the emitter-coupled-logic gate provides the gate propagation delay of 3.83 ps/stage.
Thick-Dielectric Formation and MOSFET Reliability with Spin-Coating Film Transfer and Hot-Pressing Technique for Seamless Integration Technology
Authors: Sato Norio , Shimoyama Nobuhiro , Kamei Toshikazu , Kudou Kazuhisa , Yano Masaki , Ishii Hiromu , Machida Katsuyuki
Published: February 2005

The formation of thick dielectrics by the spin-coating film transfer and hot-pressing (STP) technique is proposed for the fabrication of thick multilevel interconnects. Examination of the characteristics of 20-µm-thick dielectrics on 10-µm-thick line-and-space patterns shows sufficient planarization capability with little dependence on pattern density, which enables the fabrication of a double layer of thick interconnects. To investigate the influence of hot pressing in the STP process on LSIs, the hot-carrier degradation of n-channel metal oxide semiconductor field-effect transistors (MOSFETs) was evaluated. The lifetime of transconductance g

m
of STP samples was estimated to be over ten years, which is the same as that of samples prepared by the conventional technique of spin-coating. Moreover, the lifetime showed no dependence on pressure, temperature in hot pressing and thickness of dielectrics. These results confirm that the STP technique is applicable to the fabrication of thick interconnects and does not damage the underlying MOSFETs.
Wideband Magnetooptic Probe with 10 µm-Class Spatial Resolution
Authors: Iwanami Mizuki , Hoshino Shigeki , Kishi Masato , Tsuchiya Masahiro
Published: February 2005

In this paper we give the results of the trial fabrication and basic performance evaluation of the fiber-edge magnetooptic (FEMO) probe with an approximately 10-µm-thick magnetooptic (MO) crystal. It utilizes the Faraday effect during rotational magnetization in a MO crystal for magnetic field sensing. One should note that as compared to a previously reported FEMO probe, the spatial resolution was improved keeping the similar measurable bandwidth. The developed probe had a 10-µm-class spatial resolution as well as a measurable bandwidth of approximately 2.5 GHz. Furthermore, the realization of this probe made it possible to perform GHz-range magnetic near-field mappings over a fine meander circuit, which means that one can visualize fine current distributions in this frequency range. We compared the measured magnetic field maps with the simulated ones obtained using an electromagnetic field simulator for analyses of GHz-range electromagnetic field distributions. As a result, it was found that sufficiently precise near-field distributions could be measured due to the low invasiveness and superior spatial resolution of the probe.
Time-of-Flight Measurement of Lateral Carrier Mobility in Organic Thin Films
Authors: Kitamura Masatoshi , Imada Tadahiro , Kako Satoshi , Arakawa Yasuhiko
Published: February 2005

Lateral carrier transport in a copper phthalocyanine (CuPc) thin film has been investigated by the time-of-flight technique using a micro-excitation system. Drift mobility in the CuPc film has been estimated from the transient photocurrent measured for various electric field strengths. The drift mobility has been compared to the field-effect mobility of a thin-film transistor with CuPc as the channel material. The field-effect mobility was comparable to the drift mobility measured by the TOF technique.
Electric-Field-Induced Second Harmonic Generation from Vacuum-Evaporated Metallophthalocyanine Film/Metal Electrode Interface
Authors: Li Cheng-Quan , Manaka Takaaki , Iwamoto Mitsumasa
Published: February 2005

The optical second harmonic generation (SHG) was used to study the redistribution of space charges, which was caused by photoillumination, at the nanosized interface between metal electrode and phthalocyanine (Pc) film. The redistribution of space charges was observed using the SHG spectra, where the space-charge-induced electric field (SCIEF) broke the centrosymmetry of the Pc molecule and gave rise to another effective second order nonlinear polarization aside from the one induced by the second order electric quadrupole. Furthermore, an external bias was applied to the sandwiched metal-copper phthalocyanine (CuPc)-meal sample to induce the second order nonlinear polarization. The quadratic relationship between SHG intensity and the external applied bias was observed. On the basis of the four-layer model, the electric-field-induced SHG (EFISHG) process was analyzed. The theoretical results showed good agreement with the experimental data.
Conversion between Three- and Two-Dimensional Optical Waves in Attenuated Total Reflection Kretschmann Configuration with Nanostructured Langmuir-Blodgett Films
Authors: Kaneko Futao , Wakui Katsuaki , Hatakeyama Hirotsugi , Toyoshima Susumu , Shinbo Kazunari , Kato Keizo , Kawakami Takahiro , Ohdaira Yasuo , Wakamatsu Takashi
Published: February 2005

Surface plasmon (SP) emission light has been investigated for rhodamine-B (RB) dye Langmuir-Blodgett (LB) films on silver (Ag) thin film in the attenuated total reflection (ATR) Kretschmann configuration by means of reverse irradiation of a laser beam. Emission light through the prism was clearly observed for the configuration of prism/Ag/LB films corresponding to the resonant excitation conditions for SPs using the reverse irradiation. The intensities of the SP emission light increased with the thickness of the RB LB films, but nonlinear reductions of the SP emission light and photoluminescence (PL) were observed due to nonradiative energy transfer at the very small separations between the RB and Ag films. It is thought that the SPs, that is, two-dimensional optical waves, are excited by PL of the RB dyes on the Ag film and that this phenomenon is very useful for applications utilizing dye molecules on metal thin films.
Fabrication of a Photoelectrochemical Cell Using a Self-Assembled Monolayer of Tris(2,2'-bipyrisine)ruthenium(II)-Viologen Linked Thiol on Multistructured Gold Nanoparticles
Authors: Terasaki Nao , Otsuka Keisuke , Akiyama Tsuyoshi , Yamada Sunao
Published: February 2005

A novel photoelectrochemical cell consisting of a modified electrode with a self-assembled monolayer of a tris(2,2'-bipyridine)ruthenium(II)-viologen linked thiol on the surfaces of a gold-particle multistructure, an indium-tin-oxide (ITO) electrode, and an aqueous electrolyte solution containing hydroxymethylferrocene, has been fabricated. The modified electrode was constructed by the precipitation of gold nanoparticles on a planar gold electrode, and by subsequent self-assembling of the thiol compound on the surfaces of the multistructure. The spatial separation between the modified electrode and the ITO electrode was as small as ∼12 µm, which was determined from the thickness of a polyimide film used for electrical insulation. The performance of the photoelectrochemical cell was investigated. Photocurrents and photovoltages increased with increasing number of immobilized molecules.
A Novel Current Control Pad for Electromagnetic Interference Solution
Authors: Liou Wan-Rone , Tsai Chun-An , Yeh Mei-Ling , Wu Adam Y.
Published: February 2005

We demonstrate a new current control pad that can suppress the electromagnetic interference problem. The Measurement results indicate that the output buffer includes a continuously variable output current driver proportional to the optimum driving current of various output load transmission line impedances. The buffer includes a post stage, such as an electrostatic distance (ESD) potential device and an output driver transistor, via the current control stage to control the output current at various output loads. The output stage includes two paths; one path maintains the minimum current and the other supports various current ranges for design needs. By current measurements and electromagnetic interference (EMI) experiments, the linear driving current control circuit is demonstrated as an effective solution for the EMI problem.
Formation of Silicon Needle Crystal by Anodic Reaction
Authors: Harada Hiroshi , Mitarai Yuko , Nishida Atsushi , Miyakoda Masato , Mishima Jyun
Published: February 2005

It is shown that the formation of a Si needle crystal is possible by the anodic reaction of p-type 23 Ω·cm Si. The height of the needle increased to 25 and 34 µm with the increases of anodic current density and anodic time, respectively. The width of the needle depended on the resistivity of Si and was 2.1 and 0.54 µm for 23 and 10 Ω·cm, respectively.
Enhancement of Data Retention Time in Dynamic Random Access Memory through Optimization of Sidewall Oxidation Precleaning (0.13 µm Tech 512 Mb)
Authors: Chai Yong Y. , Yoon Kwang Y.
Published: February 2005

In this paper, we propose a dynamic random access memory (DRAM) data retention time enhancement method that minimizes silicon loss and undercut at the shallow trench isolation (STI) sidewall by reducing the standard cleaning 1 (SC1) time. SC1 time optimization mitigates the parasitic electric field in the STI's top corner, which reduces the inverse narrow width effect resulting in the reduction of channel doping density without increasing the subthreshold leakage of cell Transistor. Moreover, it minimizes the electric field in the depletion area from the cell junction to the P-well, thereby increasing yield or data retention time.
Array of Superconducting Quantum Interference Devices with Multiturn Input Coil
Authors: Morooka Toshimitsu , Myoren Hiroaki , Takada Susumu , Chinone Kazuo
Published: February 2005

Arrays of dc-superconducting quantum interference devices (dc-SQUIDs) were investigated, in which each dc-SQUID element has a multiturn input coil. The dependence of flux noise on the number of turns of the input coil was studied for current amplifiers. SQUID arrays were fabricated by a Nb/AlO
x
/Nb Josephson tunnel junction fabrication process. Results show that the flux noise of the SQUID array amplifier does not depend on the turn number of the input coil. A SQUID array amplifier consisting of 128 dc-SQUID elements was fabricated, in which each element had a 7-turn input coil and a mutual inductance between the input coil and the SQUID loop of 460 pH. This amplifier showed an ultrahigh current resolution of 1 pA/Hz0.5 and a maximum input current of 11 µA for signals of 50 kHz, which is sufficient bandwidth for X-ray detection applications. These values correspond to a large dynamic range of 87 dB. The flux-voltage characteristics of this SQUID array, however, showed asymmetric behavior, which originated from electronic resonance in stray capacitance and the mutual inductance between the SQUID loop and the multiturn input coil.
Design and Evaluation of a Solid Immersion Mirror Using a Dielectric Layer Stack for Near-Field Optical Recording
Authors: Konno Kenji , Okitsu Masahiro , Ogura Kazuyuki , Hatano Hiroshi
Published: February 2005

A new solid immersion mirror (SIM) with high optical efficiency utilizing angular dependence of a dielectric layer stack for near-field optical recording is proposed. The new SIM with a dielectric layer stack was designed, fabricated, and evaluated. The SIM had both convex and aspherical surfaces with a dielectric multilayer stack on one surface and an aluminum reflection coating on the other. The front and rear surface error rms values of the fabricated SIM were 43 mλ (λ=405 nm) and 90 mλ, respectively. The rms error of the wavefront aberration of the SIM was 150 mλ.
Acoustic Scattering by a Poroelastic Sphere Near a Flat Boundary
Authors: Hasheminejad Seyyed M. , Badsar Seyyed A.
Published: February 2005

An analysis of sound scattering by a fluid-saturated porous-elastic sphere immersed near the rigid (compliant) boundary of an acoustic halfspace is outlined. The novel features of the Biot dynamic model of poroelasticity along with the translational addition theorem for spherical wave functions are employed to develop a closed-form solution in the form of infinite series. The analytical results are illustrated with a numerical example in which a water-saturated porous sphere, submerged near a rigid wall, is insonified by a plane wave at oblique wave incidence. The numerical results reveal the considerable effects of surface permeability condition, porosity (tortuosity), frame stiffness, incident wave frequency, and proximity to the rigid interface on basic acoustic field quantities. The proposed model can be of practical use in a wide range of applications such as underwater acoustics, colloidal system characterization and microparticle structure identification.
Transmission Ellipsometry of 4-Octyl-4'-Cyanobiphenyl Liquid-Crystalline Free-Standing Films
Authors: Matsuhashi Nobuaki , Okumoto Yoshitaka , Kimura Munehiro , Akahane Tadashi
Published: February 2005

The incidence angle dependence of the phase difference for 100 4-octyl-4'-cyanobiphenyl (8CB) liquid-crystalline free-standing films (FSFs) of thickness ranging from 2 to 9 layers was measured with high resolution by transmission ellipsometry using a photoelastic modulator (PEM). Dispersion was very small, and measurement results with high reproducibility were obtained.
Plasma Copolymerization of C6F6/C5F8 for Application of Low-Dielectric-Constant Fluorinated Amorphous Carbon Films and Its Gas-Phase Diagnostics Using In Situ Fourier Transform Infrared Spectroscopy
Authors: Shirafuji Tatsuru , Tsuchino Akio , Nakamura Toshihiro , Tachibana Kunihide
Published: February 2005

Low-dielectric-constant fluorinated amorphous carbon films have been prepared from a C6F6 and C5F8 gas mixture by an inductively coupled plasma-enhanced chemical vapor deposition method. The films from 100% C5F8 have volatile nature, and they are vaporized by heating to 400°C. On the other hand, the films prepared with 100% C6F6 have higher thermal stability. After the thermal treatment of the composite films, the dielectric constant of the films is reduced to 1.6, although the residual thickness of the films is not 100%. This result suggests that the tissue from C5F8 is vaporized by thermal treatment and voids are formed in the films. Void concentration in the films is estimated to be 40–60%. The structural change due to the thermal treatment stops after 5–10 min, and no marked structural changes are observed after further thermal treatment at 400°C. The higher thermal stability of the films prepared with C6F6 has been attributed to the incorporation of the aromatic ring structure in the films. The gas-phase diagnostics of the deposition processes and the structural analysis of the films have suggested that C6F6 is highly polymerizable and its ring structure can be incorporated in the films.
Applicability of Laser Imaging System Using a Near Infrared Laser to Measure Density Fluctuations in High-Temperature Plasmas
Authors: Matsuo Keiji , Kado Shinichiro , Uchida Nana , Kawakubo Masafumi , Iguchi Harukazu , Okamura Shoichi , Matsuoka Keisuke
Published: February 2005

A new type of laser imaging method using a near infrared laser rather than a CO2 one (10.6 µm) is developed and its applicability to the density fluctuation measurement in high-temperature plasmas is evaluated. A near-infrared yttrium aluminum garnet (YAG) laser system is installed on the Compact Helical System (CHS) at the National Institute for Fusion Science (NIFS). The applicability of this laser imaging method to a middle sized toroidal device is tested. The minimum detectable signal level of 6.9×1011 cm-2 for the density fluctuation has been obtained, which is required for practical use.
13C NMR Relaxation Study of Segmental Motion of Poly(L-histidine) in Aqueous Solution
Authors: Uchino Shinichi , Hiraoki Toshifumi , Tsutsumi Akihiro
Published: February 2005

To study the segmental motion of poly (L-histidine) (PLH) in aqueous solution, the 13C spin-lattice relaxation time (T
1) was measured at six resonance frequencies (ωC/2π) ranging from 15 to 100 MHz at temperatures from 10 to 80°C. For backbone Cα, plots of log
(T
1/ωC) against log
(ωC) gave the well-superposed master curve, showing that the time-temperature reduction rule is realized. The shift factor obeyed the Arrhenius-type temperature dependence with the activation energy of 25.0 kJmol-1. Using this activation energy for the temperature dependence of the correlation time, the master curve was well reproduced by the Dejean–Lauprêtre–Monnerie (DLM) model. One of the parameters relating to the segmental motion was τ0/τ1=15, where τ0 and τ1 are the correlation times for the isolated single and correlated pair conformational transitions, respectively. It was found that the spectral density function J(ωC) has the exponent to the correlation time τ1 as ωC
J(ωC)∼(ωCτ1)0.71 in the region of ωCτ1≪1.
Comparison of Superconducting Transition Characteristics of Two Iridium/Gold Bilayer Transition Edge Sensor Devices
Authors: Kunieda Yuichi , Fukuda Daiji , Ohno Masashi , Takahashi Hiroyuki , Nakazawa Masaharu , Inou Tadashi , Ataka Manabu
Published: February 2005

We are developing a high-energy-resolution X-ray microcalorimeter for X-ray fluorescent spectrometry using a superconducting transition edge sensor (TES) that consists of a bilayer of iridium and gold (Ir/Au). In this paper, we have studied the superconducting transition characteristics of two different bilayer structures. Type 1 is a simple stacked bilayer where a square-pattern film of iridium is covered with an identical pattern of gold. Type 2 is based on the Type 1 Ir/Au film, however, it has Au side banks. The resistance-temperature characteristics of these films are investigated by a four-wired resistance measurement method. As a result, the transition curve of Type 2 obeyed the Ginzburg–Landau (GL) theory; however, the transition curve of Type 1 was entirely different from that of Type 2. The reason there was a difference in these transition curves of the two devices is discussed in terms of the difference in the electric current distribution inside TESs. Even if we assume a uniform bilayer film and a uniform proximity effect over the entire film, the current density inside the device affects the characteristics of the transition curves.
Investigation of SiCs+, GeCs+ and SiCs2
+ Secondary Ion Emission from Si1-xGex
Authors: Mikami Akira
Published: February 2005

The entire composition range of Si1-x
Ge
x
was examined to investigate the generation mechanisms of SiCs+, GeCs+ and SiCs2
+ ions in secondary ion mass spectrometry. The generation efficiency of Cs+ secondary ion varied strongly with the sputtering yield along with the composition, while the generation efficiency ratio of SiCs+ or GeCs+ to Cs+ was almost constant for the composition. The combination probabilities of Cs+ and neutral Si or Ge are also constant independent of the composition. Therefore, the composition of Si1-x
Ge
x
can be derived using a single Si1-x
Ge
x
whose composition is known or using pure Si and pure Ge as the standard samples. The intensity of Cs2
+ exhibited a peak around x=0.5. The peak may denote that half of the Cs atoms are ionized. SiCs2
+ is not only generated by a combination of Cs2
+ and neutral Si because the generation efficiency ratio of SiCs2
+ to Cs2
+ varies with the composition.
Joule Heating of Field EmitterTip Fabricated on Glass Substrate
Authors: Higa Katsuya , Asano Tanemasa
Published: February 2005

The increase in temperature during the operation of an array of Si field emitters fabricated on a glass substrate was investigated. A field emitter having a very high aspect ratio was prepared by the anodization of silicon. The results show that significant Joule heating due to emission current flow takes place at the emitter tip during electron emission, resulting in changes in field emission characteristics and the melting of the apex of the silicon tip when emitters are fabricated on a glass substrate.
Generation Mechanism of Heat Flows near the Stack as a Prime Mover in a Thermoacoustic Cooling System
Authors: Sakamoto Shin-ichi , Tsujimoto Toshiyuki , Watanabe Yoshiaki
Published: February 2005

Temperature variations in a thermoacoustic cooling system consisting of a loop-tube were investigated. The heat flows were discussed using observation results of the temperature variations in the tube. The regenerator, stack 1, was employed as a prime mover and stack 2 as a heat pump. At the cooling point, on the stack 2, the temperature decrease of 22°C was confirmed. Heat flows did not appear in the location far from the stack 1 except near the stack 2. On the other hand, heat flows induced by the sound energy flow and acoustic streaming, appeared near the stack 1. The sound energy flow was caused by the thermoacoustic effect. The directions of the sound energy flow and heat flow were opposite, according to the energy conservation law. In the loop-tube, the strong nonlinearity was observed in the generated sound, and the acoustic streaming was induced.
Surface Acoustic Wave Sensors
Authors: Shiokawa Showko , Kondoh Jun
Published: February 2005

Acoustic wave sensors are highly sensitive in detecting the properties of solid or fluid materials in contact with their surfaces, including the surface mass change, liquid density, liquid viscosity and electrical conductivity. In this paper, primarily, the commonly used acoustic wave sensors are reviewed and their mass sensitivities are compared. The fundamentals of the sensing system using the shear horizontal surface acoustic wave (SH-SAW) sensor on a 36° rotated Y-cut X-propagating LiTaO3 are described. Since the high sensitivity of the electrical perturbation is a significant advantage of the SH-SAW sensor, its applications based on acoustoelectric interaction are also presented.
Two Model Equations for Describing Nonlinear Sound Beams
Authors: Kamakura Tomoo
Published: February 2005

This short article is an introductory review and guidance on nonlinear acoustics, the study of which dates back to the 18th century. First, interpretation is made for the meaning and research field of nonlinear acoustics. Second, two typical model equations are presented describing finite-amplitude sound beams radiated in a viscous fluid from unfocused and focused powerful sources with finite apertures. The three basic characteristics of a wave, diffraction, dissipation, and nonlinearity are combined successfully in the model equations. Third, an innovative application referred to as a parametric acoustic array is shortly reviewed. Numerical demonstration shows specifically the sharp directivity of the parametric array.
Nanosecond Switching of Nanoscale Ferroelectric Domains in Congruent Single-Crystal LiTaO3Using Scanning Nonlinear Dielectric Microscopy
Authors: Fujimoto Kenjiro , Cho Yasuo
Published: February 2005

The domain switching characteristics of a congruent LiTaO3(CLT) single crystal are investigated mainly with respect to switching speed. It is found that fast nanosecond domain switching can be achieved by reducing the sample thickness, even for CLT, which has been thought to be unsuitable for high-speed switching. As an example, the authors successfully obtain a polarization inverted domain dot with a radius of 7.9 nm in a 60-nm-thick CLT plate by application of a 4 ns, 10 V pulse. These results demonstrate that the speed of polarization reversal is closely related to the thickness of the medium.
Effect of Ultrasonic Frequency on Lactic Acid Fermentation Promotion by Ultrasonic Irradiation
Authors: Shimada Tadayuki , Ohdaira Etsuzo , Masuzawa Nobuyoshi
Published: February 2005

The authors have been researching the promotion of lactic acid fermentation by ultrasonic irradiation. In the past research, it was proven that ultrasonic irradiation is effective in the process of fermentation, and the production of yoghurt and kefir was promoted. In this study, the effect of the ultrasonic frequency in this fermentation process was examined. In the frequency range of this study, it was found that the action of fermentation promotion was exponentially proportionate to the irradiated ultrasonic frequency.
Promotion of Sedimentation of Dispersed Fine Particles Using Underwater Ultrasonic Wave
Authors: Miura Hikaru
Published: February 2005

A method that uses underwater ultrasonic waves to promote sedimentation of fine particles dispersed in suspension, such as pigments, has been experimentally studied. Relationships among factors such as concentration of suspension before ultrasonic irradiation (0.1–1%), sound pressure (0–100 kPa) and irradiation time (0–180 s), and promotion of sedimentation of dispersed fine particles upon irradiation of ultrasonic waves were experimentally examined using abrasive particles (silicon carbide) with average particle sizes of 4–10 µm.
Current Waveforms of Electric Discharge in Air under High-Intensity Acoustic Standing Wave Field
Authors: Nakane Tomoo , Miyajima Takeshi , Otsuka Tetsuro
Published: February 2005

An electric discharge phenomenon in a high-intensity ultrasound field is influenced by a vibration from a medium in a boundary layer of an electrode. Static pressure is also a component that affects the discharge phenomenon. An intermittent spark discharge unit was set in a high-intensity standing wave field at 164 dB SPL and waveforms of electric discharge were measured. It was found that a prebreakdown current wave existed in a pilot plant; this is one of the important factors for describing the mechanism of the discharge in a high-intensity standing wave field.
Fabrication of a Near-Field Optical Fiber Probe Based on Electroless Nickel Plating under Ultrasonic Irradiation
Authors: Mononobe Shuji , Saito Yuichi , Ohtsu Motoichi , Honma Hideo
Published: February 2005

We present a method of fabricating a near-field optical probe with a nickel film whose thickness gradually decreases to a few tens of nanometers toward the apex. This method involves etching an optical fiber and electroless nickel plating with ultrasonic agitation. Using 1 MHz ceramic transducers, we have reproducibly fabricated the probe with a tip diameter of less than 40 nm. This reproducibility is high compared to those for Langevin-type transducers.
An Ultrasonic Suction Pump with No Physically Moving Parts
Authors: Yun Cheol-Ho , Hasegawa Takeshi , Nakamura Kentaro , Ueha Sadayuki
Published: February 2005

A new ultrasonic suction pump is described in this paper. The pump uses the suction force of a rigid cylinder tube vibrating at an ultrasonic frequency and has no physically moving parts. The pump consists of a longitudinal bolt-clamped Langevin transducer (BLT) combined with a stepped horn working at a resonance frequency of 24 kHz. A glass tube with the length of the half-wavelength-resonance is glued at the tip of the horn. To enhance pump performance, we introduced a reflection plate and a thin rod installed to the end of the glass tube with a small gap. Maximum pressures of 7.2 kPa and 23.5 kPa were recorded using the reflection plate and the thin rod, respectively. In this study, we experimentally investigate the characteristics of the pump and the operating physics. The maximum pressure is a function of the vibration velocity of the end surface of the glass tube and of the gap.
Ultrasonic Study of Positive-Temperature-Coefficient Ceramics
Authors: Kashiwagura Nobuo , Yoshida Osamu , Kobayashi Masakazu , Nakata Kentaro , Mizuno Shinji , Kamioka Hiroaki
Published: February 2005

Shear and compressional wave velocities in (Ba0.996Y0.004)TiO3 semiconductive ceramics were accurately measured by the pulse transmission method over the temperature range between 20°C and 210°C. The temperature dependence of the ultrasonic wave velocities exhibits a marked feature at the characteristic temperatures of transition in resistivity. The elastic moduli were calculated using ultrasonic data.
Ultrasound Emisson Characteristics of a Thermally Induced Sound Emitter Employing a Nanocrystalline Silicon Layer
Authors: Kihara Takashi , Harada Toshihiro , Hirota Jun , Koshida Nobuyoshi
Published: February 2005

Due to a strong quantum confinement effect, the thermal conductivity and heat capacity per unit volume of a nanocrystalline silicon (nc-Si) layer prepared by electrochemical anodization are extremely low when compared to those of single crystal silicon (c-Si). These large differences in the thermal properties between nc-Si and c-Si make it possible to produce an efficient ultrasound emitter device based on thermo-acoustic conversion without any mechanical vibration. In this paper, the fundamental ultrasound characteristics of a fabricated thermally induced nc-Si ultrasound emitter are explained with regard to an application as an ultrasound speaker. Ultrasound generated at the same frequency as the input signal exhibits a flat frequency response over a wide range and is non-directional. This behavior is totally different from that of conventional airborne ultrasound devices such as piezoceramic transducers.
Analysis of Acoustic Fields from Acoustic Convex Lens
Authors: Song In-Jin , Kim Jung-Ho , Kim Moo-Joon , Ha Kang-Lyeol , Chubachi Noriyoshi
Published: February 2005

In order to give a wide beam width characteristic to a vibrating element, acoustic convex lenses were fabricated and the diverged acoustic field was investigated experimentally. To design the acoustic lenses, an acoustic field estimation method was proposed by using an angular spectrum method. It was confirmed that the estimation of the diverged acoustic field is possible using the suggested method and the acoustic convex lens can achieve the wide beam width characteristics of the vibrator.
Submicrometer-Order Displacement Measurements Using an Air-Coupled Ultrasonic Transducer at Frequencies of 40 and 400 kHz
Authors: Sasaki Katsuhiro , Nishihira Morimasa , Imano Kazuhiko
Published: February 2005

Noncontact air-coupled ultrasonic systems for measuring micrometer- or submicrometer-order displacements are newly constructed at frequencies of 40 and 400 kHz. The phase detection accuracy of the displacement measurements under several thousandths of ultrasonic wavelengths λ is markedly improved by the introduction of phase differences between the reference waves and the transmitting wave signal. To verify our system, the displacement of the reflector, which is translated by a high-precision mechanical stage, is measured using a single piezoelectric ceramic transducer in the reflection mode. Resolutions of displacement of better than 1 µm or 0.1 µm (λ/8500) using ultrasonic waves of 40 or 400 kHz in air, respectively, are achieved.
Estimation of Wall Reduction of Plate Using the Fundamental Symmetric Mode Lamb Wave
Authors: Cho Hideo , Nakazawa Hiroo , Takemoto Mikio
Published: February 2005

Final aim of this study is to estimate the corrosion-induced wall reduction of the bottom plate in storage tanks from the outside of the tank. We excited strong S0-mode Lamb waves by impacting the center of the edge plane of a plate, and monitored both the amplitude and arrival time of the S0-mode reflected from artificial slits by a low frequency receiver mounted at the edge plane. The amplitude of reflected S0-mode Lamb waves increased proportionally with slit depth. Locations of defects, calculated from the arrival time of reflected S0-mode Lamb waves, were estimated as the locations of actual slits with an error below 2%.
Application of a Double-Layered Piezoelectric Transducer in the Generation of Short Ultrasonic Pulses
Authors: Fukuda Makoto , Nishihira Morimasa , Imano Kazuhiko
Published: February 2005

A double-layered piezoelectric disk-type transducer (DLPT) without a backing and/or an intermediate layer is newly constructed and analyzed to generate short ultrasonic pulses. One of the disks is excited for the purpose of transmission and the other is used for canceling the ringing of the pulse. The driving conditions of the system, including the DLPT and the peripheral electronic component for generating the short ultrasonic pulse, are optimized by analysis using the cascade connection of a transmission line model. Experiments using the active ringing cancellation method with DLPT in water are also demonstrated. The analysis and experimental results were mostly in agreement with each other. A short ultrasonic pulse having a pulse width of 1.5 wavelengths is achieved.
Estimation of the Travel Time Using the New Measurement Technique for Long-range Transmission
Authors: Wang Yong , Hachiya Hiroyuki , Nakamura Toshiaki , Fujimori Hidetoshi
Published: February 2005

Ocean acoustic tomography (OAT) is a powerful approach for observation of mesoscale ocean fluctuations. The precise estimation of travel time is required for ocean current measurement. We previously proposed the measurement of travel time using phase information. In this paper, we present the theoretical analysis of phase deviation using the Rice distribution. We then propose a new measurement technique of travel time termed as the complex vector method. We also demonstrate the ability of this method by computer simulation and received signals from OAT experiment in 1999. The preliminary results are promising. We conclude that the proposed estimated method is useful in long-range ocean transmission.
Relative Position Estimation of Moving Distributed Sources Using the Extended Kalman Filter
Authors: Yoon Jong-Rak , Park Kyu-Chil , Ro Yong-Ju
Published: February 2005

The relative positions of moving distributed sources are estimated by the Doppler frequency shift estimate of each source using the extended Kalman filter (EKF). Each source is assumed to radiate a different frequency with a different spatial position. The Doppler frequency shift of each source along the Closest Point of Approach (CPA) is unique with respect to time and frequency and this is mapped with respect to each source position. Since the Doppler frequency shift should be estimated with a high time resolution and a high frequency resolution particularly for a moving source with a relatively fast time-varying amplitude, the EKF frequency-amplitude estimator is proposed to fulfill this goal. The performance of the technique is examined by an illustrative numerical example and is verified by an experiment using loudspeaker sources on the roof of a car.
Frequency Equations of an Ultrasonic Vibrator for the Elastic Sensor Using a Contact Impedance Method
Authors: Aoyagi Ryoji , Yoshida Tetsuo
Published: February 2005

When an ultrasonic vibrator is forced to come into contact with a static load, it is known that the resonance frequency and quality factor of the vibrator are influenced by the reaction of the object. On the basic of this phenomenon, a study to measure the physical constants, such as the elastic modulus of materials, is under way. However no report concerning the accurate analysis of the relationship between the said change and the physical constants has been available. In this paper, we present the analytical result of the relationship equations. The resonance frequency is increased in the case that the body in contact is sufficiently hard, whereas it is decreased in the case that the body is soft. Frequency equations expressing both the phenomena referred to above were obtained in a unified manner. Furthermore, the appropriateness of the said equations was confirmed by experiments. It is concluded from the studied that the analytical results are in agreement with the experimental results.
Analysis of High-Lateral-Resolution Imaging Using Thin Quartz Fibers as Transmission Lines
Authors: Hashimoto Yoshikazu , Takamura Yoshihiro , Yagi Shin-ichi , Moriya Tadashi
Published: February 2005

As a quantitative imaging tool for ultrasonic endoscopy with high lateral resolution, we proposed a new measurement method for tissue acoustic impedance utilizing the adjacent near-field at one end of a quartz fiber. In this note, the fine prospect for matching layer design at a fiber end with a diameter less than wavelength of ultrasound transmitted into a tissue medium is reported. Real-time simulations by the three dimensional finite element method ensure that the shear wave propagation is dominant in the matching layer, and the reflection coefficient obtained from echoes at the matching frequency is very sensitive for the evaluation of tissue acoustic impedance.
High-Performance Polycrystalline Silicon Thin-Film Transistors Fabricated by High-Temperature Process with Excimer Laser Annealing
Authors: Jiroku Hiroaki , Miyasaka Mitsutoshi , Inoue Satoshi , Tsunekawa Yoshifumi , Shimoda Tatsuya
Published: February 2005

Polycrystalline silicon (p-Si) thin-film transistors (TFTs) were fabricated using a high-temperature process that included solid-phase crystallization (SPC) and dry thermal oxidation with excimer laser annealing (ELA). X-ray diffraction and transmission electron microscopy analyses showed that the ELA process improved the quality of p-Si films markedly. The p-Si TFTs exhibited a higher performance than the SPC and a-Si+ELA p-Si TFTs. The field-effect mobility for n-type self-aligned TFTs was 251 cm2·V-1·s-1. The longitudinal junction diffusion length of the p-Si TFTs was shorter than that of the SPC p-Si TFTs. This is favorable for fine design rules. This fabrication process is consistent with the high-temperature-processed p-Si TFT development trend towards using large substrates, low temperatures, and fine design rules.
Modeling of Focused Carbon Nanotube Array Emitters for Field-Emission Displays
Authors: Nicolaescu Dan , Filip Lucian Dragos , Kanemaru Seigo , Itoh Junji
Published: February 2005

Vertically aligned carbon nanotubes (CNTs) grown in patterned areas are used as electron sources in field emission displays (FEDs), but detrimental electron beam spreading may occur in a vacuum space. In this paper, a novel emitter structure with two coaxial electrodes and vertically aligned CNTs is proposed and analyzed using three-dimensional (3D) computation of the electric field. One of the gate electrodes plays a role in electron extraction and the other one in electron beam focusing. Unlike the case of double-gated Spindt emitters, the focusing gate electrode is placed near the plane of the CNT tips while the extraction electrode is placed at some distance from it. An improved electric field uniformity within the CNT array and focusing of the electron beam are thus achieved. Electron beam confinement characteristics and field emission properties are calculated as functions of device geometry and its functional parameters.