bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Multilayer Oxide Films Prepared by RF-Magnetron Sputtering as Transparent IR-Reflector
Authors: Das Rajesh , Ray Swati
Published: July 2005

A transparent-conducting indium tin oxide (ITO)/Titanium di-oxide (TiO2) multilayer optical filter has been developed using conducting and transparent ITO and transparent insulating TiO2 films grown by RF-magnetron sputtering. The objective is to cut off the infrared portion of the solar spectrum to avoid the heating effect. The electrical resistivity of ITO film is 1.2×10-4 Ω·cm, the sheet resistance is below 8 Ω/□ and the visible optical transmission is above 85%. The refractive index of this film is 1.9. On the other hand, TiO2 is highly resistive (resistivity is of the order of 1010 Ω·cm), and has 85% visible optical transmission and very low absorption in the visible and infrared regions. The refractive index of TiO2 film is 2.6 at a substrate temperature 250°C and 2.9 at 450°C. At 450°C, the rutile titanium dioxide structure was formed which was confirmed on the basis of diffraction rings. In the multilayered ITO/TiO2 structure ITO and TiO2 layers were alternately deposited. Thicknesses of the ITO and TiO2 layers were optimized to achieve the best result. The multilayer has the same sheet resistance as that of ITO film and about 92% visible transmission with the plasma resonant frequency at 840 nm. The X-ray diffraction (XRD) pattern of the ITO/TiO2 multilayer indicates a the random orientation of crystal growth.
Effects of Annealing on Chemical Composition, Crystallinity, Optical Transmission and Electrical Conductivity of ZnO Thin Films Prepared on Glass Substrates by Chemical Bath Deposition
Authors: Kobayashi Satoshi , Oshima Kohei , Sasaki Takayuki , Tsuboi Nozomu , Kaneko Futao
Published: July 2005

The effects of annealing on the chemical composition and other properties of ZnO thin films prepared on glass substrates by chemical bath deposition are described. The atomic ratio [Zn]:[O] of the unannealed film measured by electron probe X-ray microanalysis (EPMA) is 45:55, lower than the ideal ratio 50:50. It gradually increases toward the ideal ratio with increasing annealing temperature up to 500°C. The change in the atomic ratio [Zn]:[O] is interpreted to be due to the content of remaining Zn(OH)2, whose existence in films is determined by the analysis of the O1S peak in X-ray photoelectron spectroscopy (XPS) spectra, that decreases with increasing annealing temperature. The increase in electrical conductivity is observed on annealed films. This is also interpreted to be due to the decrease in the content of remaining Zn(OH)2. Notable changes in crystallinity and optical transmission by annealing are not observed.
Silicon Carbide Etching Using Chlorine Trifluoride Gas
Authors: Habuka Hitoshi , Oda Satoko , Fukai Yasushi , Fukae Katsuya , Takeuchi Takashi , Aihara Masahiko
Published: July 2005

The etch rate, chemical reactions and etched surface of β-silicon carbide are studied in detail using chlorine trifluoride gas. The etch rate is greater than 10 µm min-1 at 723 K with a flow rate of 0.1 ℓ min-1 at atmospheric pressure in a horizontal reactor. The maximum etch rate at a substrate temperature of 773 K is 40 µm min-1 with a flow rate of 0.25 ℓ min-1. The step-like pattern that initially exists on the β-silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 µm to 1 µm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large etch rate for β-silicon carbide associated with making a rough surface smooth.
Incidence Angle Dependences of Columnar Grain Structure and Texture in Obliquely Deposited Iron Films
Authors: Okamoto Kunito , Itoh Kikuo
Published: July 2005

From the viewpoint of the crystallographic contribution to the formation of columnar grain structure we investigated the incidence angle dependences of the columnar grain structure and the texture for iron films prepared at various deposition rates R. The films were vapor-deposited at incidence angles of 15°, 30°, 45° and 65° on glass substrates heated at 473 K. The X-ray analysis using the Schulz method revealed that there exist three kinds of texture: [100], type I [111] and type II [111] textures. From the observation using replica electron microscopy and the measurement of electrical resistivity, it was found that the two characteristics of the columnar grain structure (inclination and bundling of columnar grains) depend on the kind of texture irrespective of the incidence angle. For the films with type I [111] texture, the inclination angle and the degree of bundling of columnar grains take constant values with R at a given incidence angle. For the films with [100] or type II [111] texture, on the other hand, the inclination angle and the degree of bundling change markedly with R even if the incidence angle is constant. These changes in columnar grain structure with R depending on the kind of texture can be understood by considering the appearance of the {100} crystal habit.
Photoluminescence Mechanisms in Si+-Implanted Dry SiO2 Films after Rapid Thermal Annealing at Dissociation Temperature of a-SiO2 Phase Variance
Authors: Tsai Jen-Hwan , Yu Ann-Ting
Published: July 2005

Photoluminescence (PL) mechanisms in Si+-implanted dry SiO2 films after rapid thermal annealing (RTA) at the dissociation temperature of a-SiO2 phase variance are further investigated. Two PL mechanisms are found in Si+-implanted 100-nm-thick dry SiO2 films after RTA at 1050°C in 50 mbar wet and dry nitrogen, respectively. They both increased with an increase in the fluence of silicon implantation from 4×1014 cm-2 to 4×1015 cm-2. Furthermore, the mechanism in the films after RTA at 1050°C in 50 mbar wet nitrogen tended to disappear when 50 nm of the top layer was etched from the as-implanted 4×1015 cm-2 100-nm-thick SiO2 film before RTA. However, the other mechanism in the films after isochronal RTA in dry nitrogen increased with decreasing residual film thickness to a value of 50 nm. Lastly, the mechanism in wet-N2-annealed as-implanted dry SiO2 films, increasing with an increase in water flow rate in the RTA process and being not ascribed to an oxygen-deficient structure, was attributed to a hydrogen-related structure because of the presence of Si–O–H structures even after reannealing at 850°C for <30 min, which was consistent with the non-bridging oxygen hole centers (NBOHC). The other mechanism in dry-N2-annealed as-implanted dry SiO2 films, independent of the nitrogen flow rate, attributed to oxygen- and hydrogen-deficient structures, and disappeared after heating to 600°C, was similar to that of the E'δ center.
Density Distribution Profiles of Excess Minority Carriers Injected with 904-nm-Wavelength Laser Pulse into 400-µm-Thick Silicon Wafer
Authors: Munakata Chusuke
Published: July 2005

On numerically resolving the continuity equation for excess photocarriers, three-dimensional-type carrier distribution profiles in time and space have been obtained using a commercially available computer code. These pictures are useful for the quick understanding of the basic principle of the microwave-detected photoconductive decay method.
Formation of Palladium Silicide Films on Silicon(111)7×7 Surface at ∼150 K
Authors: Okado Hideaki , Hirono Shinsuke , Mori Hirotaro
Published: July 2005

The formation of palladium silicide on Si(111) at ∼150 K was investigated in situ by Auger electron spectroscopy, reflection high-energy electron diffraction analysis, scanning tunneling microscopy, and ex situ transmission electron microscopy. It is demonstrated that silicide was formed spontaneously by Pd deposition even at ∼150 K. The phase of the silicide was Pd2Si, and films of Pd2Si were grown epitaxially. The surface of the films was uneven. There were bumps of 1–5 nm in height and approximately 20 nm in diameter on the surface. The primarily formed silicide phase is discussed using an effective heat of formation model.
Effect of AlN Film Thickness and Top Electrode Materials on Characteristics of Thin-Film Bulk Acoustic-Wave Resonator Devices
Authors: Huang Cheng-Liang , Tay Kok-Wan , Wu Long
Published: July 2005

Highly c-axis-oriented aluminum nitride (AlN) thin films were deposited on Mo electrodes by reactive RF magnetron sputtering and their thickness effects on thin-film bulk acoustic-wave resonator (FBAR) characteristics are presented. The results obtained in this study show that thick AlN films have a strong c-axis orientation and tend to promote a small rocking curve full-width at half-maximum (FWHM), but a high grain size and a high surface roughness, hence degrading the characteristics of FBARs. The characteristics of FBARs depend not only the thickness and quality of AlN films, but also the thickness of the top electrode and the type of material used. Specifically, an increase in either AlN film or top electrode thickness increases parallel resonant quality factor (Q
P), but reduces effective electromechanical coupling coefficient (k
eff
2). However, the resonance provides a maximum k
eff
2 when AlN film thickness approaches the fundamental one-half-wavelength. The effects of the type of top-electrode material and AlN film thickness on the k
eff
2 and quality factor of the fabricated FBARs are also discussed.
Sensing Characteristics of Ruthenium Films Fabricated by Radio Frequency Sputtering
Authors: Chou Jung-Chuan , Liu Shih-I , Chen Sheng-Hong
Published: July 2005

The pH is an important parameter for analyzing the conditions in the environment, for clinical assays, and in cases of water pollution. The design of a convenient pH sensor is presented in this report. Ruthenium was investigated to fabricate a pH sensing membrane by radio frequency (R.F.) sputtering, and the reaction gas was assumed to control the sensing characteristics of the pH sensor. Additionally, the sensing membrane was deposited on a silicon substrate. This pH sensor offers many advantages, such as ease of packaging, capability of making high temperature measurements and disposability. Furthermore, this pH sensor was easily fabricated on a single chip to yield an integrated chip using semiconductor technology. According to experimental results, the ruthenium oxide membrane presented a linear pH sensitivity of 55.52 mV/pH when immersed in a standard buffer solution, the pH of which was between 1 and 12, at room temperature. The ruthenium nitride membrane presented a linear pH sensitivity of 57.05 mV/pH when immersed in a standard buffer solution, the pH of which was between 1 and 13, at room temperature. The reaction gas influenced the structure of the sensing membrane and the ruthenium nitride membrane had higher pH sensing range than the ruthenium oxide. Furthermore, the structure of the sensing film was appropriate for fabrication of the sensing chip using semiconductor processes, especially in micro-electro-mechanical systems (MEMS).
Low-Temperature-Activated Bismuth Ion-Implanted Silicon n+/p Junction
Authors: Tavakoli Shahram Ghanad , Baek Sungkweon , Hwang Hyunsang
Published: July 2005

Solid-phase epitaxially regrown n+/p junctions were investigated for sub-70 nm metal–oxide–semiconductor field-effect transistors (MOSFETs) using bismuth (Bi) ion implantation and low-temperature rapid thermal annealing. These junctions showed a small junction depth, a low sheet resistance and leakage current in low-temperature processing (700°C). The results indicated the possibility of Bi as a proper dopant for low-temperature-activated source and drain extensions that should be fabricated at a low temperature with the presence of high-k dielectric metal-electrode gate stacks in next generation MOSFETs.
Optimum Conditions for NO Reduction Using Intermittent Dielectric Barrier Discharge at Atmospheric Pressure
Authors: Kambara Shinji , Kumano Yuta , Moritomi Hiroshi , Nagao Issei , Yamamoto Kiwamu , Yukimura Ken , Maruyama Toshiro
Published: July 2005

NO in N2 gas was removed by injecting ammonia radicals, which were externally generated by flowing NH3 gas diluted with Ar gas through a dielectric barrier discharge (DBD) with a one-cycle sinusoidal-wave power source. The discharge was intermittently formed between coaxial cylindrical electrodes at an applied peak-to-peak voltage of 2–15 kV. The generated radicals were introduced in a reaction chamber and reacted with NO. In order to find optimum parameters for NO reduction and energy efficiency, the reaction temperature in the mixing zone, the voltage applied to the gap of the electrodes for DBD generation and its repetition rate, the NO gas concentration, and the ammonia concentration and flow rate were varied. A maximum energy efficiency of 140 g/kWh at a NO reduction of over 99% is obtained at a voltage slightly higher than the discharge firing voltage and a repetition rate of 5 kHz, which corresponds to a duty cycle of 5%. Thus it is found that the use of the intermittent power source is an advantage for obtaining a high energy efficiency of NO reduction.
Boron Emission Rate from Si/SiO2 Interface Traps to Bulk Silicon for Dose Loss Modeling
Authors: Tsuji Hiroshi , Furuhashi Masayuki , Tachi Masayuki , Taniguchi Kenji
Published: July 2005

The evolution of the boron dose loss for a 0.5 keV 5×1012 cm-2 B implant during thermal annealing is measured at temperatures of 820, 870, and 920°C in nitrogen ambient. The amount of boron dose loss decreases with increasing annealing time, which is expressed with an exponential function. The activation energy for the decay time constant is found to be 2.64 eV. The boron emission rate from Si/SiO2 interface traps to bulk silicon is derived as a function of annealing temperature.
Fast Ion Bunch Generation by Ultraintense Laser Pulse on Plasma Foil Target
Authors: Okada Toshio , Mikado Yuichi , Kitada Tuneyuki , Sugie Michio , Andreev Alexander A.
Published: July 2005

Particle-in-cell (PIC) simulations of fast particles produced by a short laser pulse with a duration of 40 fs and an intensity of 1020 W/cm2 interacting with a foil target are performed. The dependence of the energy of the generated fast ions on the target geometry is examined. The absorbed laser energy is transferred to fast electrons, which interact with the foil and are partially ejected from the foil surfaces. These electrons produce an electric field that causes an ion beam to be emitted from the rear surface of the foil. Three different kinds of target are considered. The optimum target plasma conditions for the maximum ion acceleration are determined.
Radial Ordering of Fine Particles in Plasma under Microgravity Condition
Authors: Hayashi Yasuaki
Published: July 2005

Microgravity experiments on fine-particle plasma were carried out and the ordering and behavior of fine particles were analyzed under the microgravity condition as well as under a change in gravitational conditions. Fine particles aligned in radial directions were observed under microgravity, although they were aligned in the vertical direction under the gravity condition. It has been suggested by comparison with the result obtained under microgravity that under the gravity the mutual influence between positive ion flow and negative fine particles results in the vertical alignment of fine particles and in the vertical flow of ions toward fine particles along with the deformation of plasma.
Characteristics of Silicon Carbide Etching Using Magnetized Inductively Coupled Plasma
Authors: Lee Hyo Young , Kim Dong Woo , Sung Yeon Jun , Yeom Geun Young
Published: July 2005

In this study, SiC etching was carried out using fluorine-based magnetized inductively coupled plasmas. The SiC etch rates and etch selectivities of SiC to Cu and Ni were investigated for the purpose of obtaining high etch rates in the application of SiC etching to various optical devices and micro-electromechanical systems (MEMS). Among SF6, CF4 and NF3, SF6 showed the highest SiC etch rates and etch selectivities to Cu and Ni, due to its highest F atomic density and to the formation of nonvolatile fluoride on Cu and Ni. Cu generally showed higher etch selectivity than Ni, possibly due to the easier formation of fluoride in this case. The application of a weak axial magnetic field ranging from 0 to 80 G showed maximum SiC etch rates at 40 G, possibly due to the formation of a resonance mode. When a field of 40 G was applied, the SiC etch rate was increased approximately two times and, in this condition, the F atomic density and ion densities in the plasma were also at a maximum. The highest SiC etch rate obtained in our experiment was 2020 nm/min with an inductive power of 1400 W, a bias voltage of -600 V, a pressure of 10 mTorr of SF6, and a magnetic field of 40 G. The etch selectivity to Ni obtained in this condition was about 40.
Characterization of Low-Temperature Stress Hump in Relation to Phase Formation Sequence of Nickel Silicide
Authors: Hong Jeong Eui , Byun Jeong Soo , Kim Sun Il , Ahn Byung Tae
Published: July 2005

The stress hump phenomenon observed at a low temperature of approximately 140°C during in situ stress-temperature measurement of sputtered Ni thin film on a (001) Si substrate has been investigated. We found that the stress hump was not related to the formation of NiSi2, but originated from the thickening of an amorphous Ni–Si intermixing layer in the temperature range of 100–140°C followed by the formation of the Ni2Si phase at temperatures above 140°C.
Mg II 448.1 nm Spectral Line Stark Broadening Parameters
Authors: Djeniže Stevan , Srećković Aleksandar , Bukvić Srdjan
Published: July 2005

The Stark width (W) and shift (d) of the singly ionized magnesium (Mg II) 448.1 nm spectral line in 3d
2
D
5/2–4f
2
F
7/2
0 transition have been measured at a 16 900 K electron temperature and 1.35×1023 m-3 electron density in nitrogen plasma generated in an optically thin linear, low-pressure, pulsed arc discharge. They represent the first experimental results obtained at an electron temperature higher than 12 000 K. Magnesium atoms, as impurities in the driving gas, have been introduced by erosion from the pure magnesium bands fixed on the discharge electrodes providing conditions free of self-absorption. Our W and d have been compared to existing experimental and theoretical data. A good agreement was found between the results calculated by semiclassical perturbation formalism and our data, particulary in the case of the Stark shift.
Frequency-Domain Measurement of Cavity Ring-Down Spectroscopy
Authors: Xiaoming Gao , Sasada Hiroyuki , Anzai Kenji , Yoshida Naohiro
Published: July 2005

We have recorded the transmission spectrum of an optical cavity absorption cell filled with methane gas using a tunable continuous-wave light source in the mid-infrared region. To determine the absorption strength of the gas, we have measured the linewidth of the cavity fringe. This method corresponds to frequency-domain measurements of cavity ring-down spectroscopy (CRDS) because the linewidth is the Fourier transform of the photon lifetime from which the absorption strength is derived in CRDS. The absorption strengths determined from the present linewidth measurements indicate excellent agreements with both those derived from the transmittance measurements and those calculated from line parameters listed in the HITRAN 2004 database.
Electroluminescence Enhancement in Dry-Processed Organic-Inorganic Layered Perovskite Films
Authors: Matsushima Toshinori , Fujita Katsuhiko , Tsutsui Tetsuo
Published: July 2005

Organic-inorganic layered perovskite, (C6H5C2H4NH3)2PbI4, was grown on silica substrates or indium tin oxide (ITO) substrates by vacuum vapor deposition. High-quality layered perovskite films, which showed sharp and intense exciton peaks, were obtained when substrate surfaces were covered with either an octadecyltrichlorosilane (OTS) monolayer or a vacuum-deposited copper phthalocyanine (CuPc) layer. Light-emitting devices (LEDs) with structures of ITO/OTS/layered perovskite/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/2,4-pentanedionato lithium (Li acac)/Al, ITO/CuPc/layered perovskite/BCP/Li acac/Al, and ITO/layered perovskite/BCP/Li acac/Al were fabricated. Sharp electroluminescence (EL) peaks from excitons stabilized in a quantum well structure were observed in each LED at 105 K. The LED with the CuPc layer exhibited the highest EL intensity and efficiency among the three LEDs. This EL enhancement is ascribed to the improvement in film properties and a decrease in the height of the hole injection barrier induced by growing the layered perovskite film on a CuPc layer.
A Double-Layered Line-Focusing PVDF Transducer and V(z) Measurement of Surface Acoustic Wave
Authors: Lee Yung-Chun , Chu Chi-Chen
Published: July 2005

In this paper, we present a new ultrasound transducer and its measurement system for surface acoustic waves. The transducer has double-layered PVDF films; one acts as the transmitter of ultrasound while the other acts as the receiver. By forming the PVDF films into a concave cylindrical shape, a line-focusing transducer is formed and can be used for the V(z) measurement of surface acoustic waves and wave velocity measurements. The most important advantage of using the doubled-layered PVDF transducer is that the transmitting/receiving electronics can be greatly simplified. Furthermore, the operating frequency bandwidth can be extended significantly. In this work, the capability and accuracy of the transducer and its measurement system are demonstrated with both isotropic and anisotropic samples. Potential applications and further improvements are also addressed.
Numerical Simulation of Distributed Cavity Phase Shift in Atomic Fountain Frequency Standard
Authors: Yanagimachi Shinya , Fukuyama Yasuhiro , Ikegami Takeshi , Kurosu Takayuki
Published: July 2005

The spatial phase variations in feeding a microwave cavity with asymmetrical amplitudes and phases were calculated using the finite element method (FEM) that was applied to the three-dimensional (3D) model of the microwave cavity developed at the National Metrology Institute of Japan (NMIJ)/AIST. The distributed cavity phase shift (DCPS) in an atomic fountain frequency standard was calculated for atomic interaction with the position-dependent amplitudes and phases inside the cavity. The tolerances of asymmetry in the phases and amplitudes of microwaves were determined in order to achieve an uncertainty of 5×10-16 with respect to the DCPS.
Antimony Treatment Effect on Cd1-xMnxTe Growth on GaAs by Metal-Organic Vapor Phase Epitaxy
Authors: Goto Hideo , Sawada Satomi , Tahashi Masahiro , Ido Toshiyuki
Published: July 2005

A heteroepitaxial film of Cd1-x
Mn
x
Te has been grown on a (100)GaAs substrate by metal-organic vapor phase epitaxy. It is shown that a high quality Cd1-x
Mn
x
Te film can be grown on the GaAs substrate by pretreating the GaAs substrate with triethyl antimony at 650°C. The best full width at half maximum of the X-ray diffraction peak of the Cd1-x
Mn
x
Te film (x=0.12) obtained was 650 arc sec. The effects of the triethyl antimony on the film quality of Cd1-x
Mn
x
Te are discussed.
X-Ray Responsivities of Direct-Scintillator-Deposited Charge-Coupled Device
Authors: Miyata Emi , Miki Masami , Tawa Noriaki , Miyaguchi Kazuhisa
Published: July 2005

We report a new photon-counting detector for 0.1–100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and a scintillator. The scintillator is directly deposited on the backside of the X-ray CCD. Low energy X-rays below 10 keV can be directly detected by the CCD. The majority of hard X-rays above 10 keV passes through the CCD but can be absorbed in the scintillator, generating visible photons there. Since CCDs have moderate detection efficiency for visible light, visible light can be absorbed by the same CCD. We developed a method of direct deposition of CsI(Tl) forming a needlelike structure on the CCD and succeeded in fabricating the CsI(Tl) deposited CCD (SD-CCD). We investigated the spectral capabilities of our device with 109Cd and 241Am. We found that the lateral spread of visible light emitted from needlelike CsI(Tl) was so large that the pulse height of pixels was not significant compared with the noise level. We then operated the SD-CCD in the on-chip binning mode and investigated its spectral capabilities. The energy resolution of the SD-CCD was 52±1% and 42±2% at 22.1 and 59.5 keV, respectively.
Properties of Magnetic Nanoparticles for Magnetic Immunoassays Utilizing a Superconducting Quantum Interference Device
Authors: Enpuku Keiji , Inoue Katsuhiro , Soejima Kazuyuki
Published: July 2005

Properties of magnetic nanoparticles are studied for application to magnetic immunoassays utilizing a superconducting quantum interference device (SQUID). In this application, a magnetic marker is made of magnetic nanoparticles, and the binding reaction between an antigen and its antibody is detected by measuring the magnetic field from the marker. Magnetization of an assembly of the particles is simulated when the effects of the thermal noise and the distribution of the particle size are taken into account. Magnetic signals from the assembly of the particles are clarified for three detection methods, i.e., susceptibility, relaxation and remanence. From the comparison with experimental results, it was shown that the demagnetization effect also significantly influences the magnetic signal from the particles. When these effects are taken into account, the simulation results agree semi-quantitatively with the experimental ones.
Dependence of Dynamic Aperture on Betatron Tune at 2.5 GeV Pohang Light Source Storage Ring
Authors: Kim Eun-San
Published: July 2005

The Pohang Light Source (PLS) storage ring is a synchrotron light source that has been operated using a 2.5 GeV full energy injection from a linac since October 2002. It is necessary to search for betatron tunes that can realize large dynamic apertures in a 2.5 GeV full energy injection. Accordingly, we investigated dependence of dynamic aperture on the betatron tune to obtain large dynamic apertures in the storage ring by a simulation method. We examined dynamic apertures by a tune survey within a specified tune space with and without machine errors. It is also shown how large are the dynamic apertures in the storage ring recovered are after the correction of a closed orbit distortion. The operating tune is examined from the viewpoint of dynamic apertures obtained by a tune survey.
Development of Four-Probe Microscopy for Electric Conductivity Measurement
Authors: Ishikawa Makoto , Yoshimura Masamichi , Ueda Kazuyuki
Published: July 2005

A four-probe microscope consisting of independently driven actuators has been developed in a scanning electron microscope chamber. By using an automatic probe approaching system, the resistivity of a Si(111) wafer is measured by the four-point probe method with the probe spacing changed from 18 µm to 500 µm. The measured voltage vs probe spacing curve is highly reproducible and is qualitatively in good agreement with the expected behavior, taking into account the correction factor for a non-semi-infinite medium.
Transient Response Analysis of Piezoelectric Vibrator Driven by Impulse Force
Authors: Chang Kuo-Tsai
Published: July 2005

In this paper, the investigation of a voltage transient response and its characteristics for a piezoelectric vibrator driven by an external impulse force is reported. An equivalent circuit with an impulse force is used to first derive a theoretical transient response and its characteristics. Then, a driving and measuring system is constructed to determine the transient responses and their characteristics at various impulse forces. Moreover, relationships between the transient response and the impulse force are measured and discussed.
Study of the Magnetic Field Effect on Commercial Thermistors using a Water Triple Point
Authors: Nara Koichi
Published: July 2005

The effect of a magnetic field on commercial thermistors was precisely studied in detail using the water triple point. A thermistor with a code of 44004 manufactured by YSI Inc. was found to show a small correction. Its orientation effect and sensor dependence was found also to be small. The correction ΔT (mK) against magnetic field B(T) was found to be 0.069(B/T)2 (mK). The uncertainty of the correction function is estimated to be as small as 2 mK up to 15 T.
Relationship Between Type of Bow Holding and Propagation of Performed Sound in Small Concert Hall in Violin Performances
Authors: Matsutani Akihiro
Published: July 2005

The propagation of violin sound performed by eight amateur players was compared in the front and rear seats of a small concert hall. It was found that the propagation of the performed sound in the hall is different according to the type of bow holding of the players and the difference of the instrument. The relationship between the player and the instrument influences the listeners' impressions in the concert hall. It is important to perform a sound that is adjusted to the characteristics of the concert hall to minimize the decrease in the sound level in the rear seats of the hall.
Analysis of Shear Horizontal Surface Acoustic Wave Sensors with the Coupling of Modes Theory
Authors: Shen Chi-Yen , Hsu Cheng-Liang , Hsu Kuo-Chien , Jeng Jin-Shing
Published: July 2005

This study has investigated a method for accurate analysis and design of shear horizontal surface acoustic wave (SH-SAW) sensors. The coupling of modes (COM) theory was used to develop an analytical model to satisfy Barkhausen's criteria for oscillation and avoid mode hopping. The theoretical simulation was highly consistent with the experimental results. The SH-SAW sensor presented here exhibited excellent reversibility, sensitivity, and repeatability when ammonia was at the ppb level.
Preparation of ZnS–CdS Alloy Quantum Dots by Chemical Synthetic Methods and Size-Selective Photoetching Effects on Size Distribution
Authors: Kim DaeGwi , Nabeshima Akihiko , Nakayama Masaaki
Published: July 2005

We have prepared ZnS–CdS alloy (Zn1-x
Cd
x
S) quantum dots (QDs) using chemical synthetic methods and investigated size-selective photoetching effects on the size distribution. The preparation of Zn1-x
Cd
x
S QDs with an alloy composition from x=0 to x=1 is successful using either of the following two methods: a reverse-micelle method using AOT/heptane micellar solutions, and a standard colloidal method in aqueous polyvinyl pyrrolidone solution. Reduction of the size distribution of the colloidal alloy QD to ∼5% was achieved by a size-selective photoetching process. The present results indicate the potential of preparing Zn1-x
Cd
x
S QDs with a narrow size distribution.
Template Assisted Fabrication of Tin Nanospheres by Thermal Expansion and Rapid Solidification Process
Authors: Chen Chien-Chon , Kuo Chin-Guo , Chao Chuen-Guang
Published: July 2005

Tin (Sn) nanospheres with diameters ranging from 100 to 300 nm were fabricated by thermal expansion and rapid solidification process. The Sn melt was injected into an anodic aluminum oxide (AAO) template to form Sn nanowires. The Sn nanowire and AAO composite was then heated to the Sn melting temperature (∼232°C) and quenched to low temperature (8°C). The Sn melt exhibits high surface tension and AAO has nanoscale roughness on its surface. These two properties caused Sn nanospheres to form easily on the AAO surface when the partial Sn melt expanded out from AAO channels and rapidly solidified on the AAO surface.
Effects of Ion Bombardment on Carbon Nanotube Formation in Strongly Magnetized Glow-Discharge Plasmas
Authors: Kaneko Toshiro , Matsuoka Hiroki , Hatakeyama Rikizo , Tohji Kazuyuki
Published: July 2005

The effects of ion bombardment on the formation of multi-walled carbon nanotubes (MWNTs) are investigated by controlling radio-frequency (rf) glow-discharge plasmas in strong magnetic fields. When a magnetic field is weak (0.03 T), the MWNTs growing directly on an rf electrode are deformed by the bombardment of the high-energy ions generated by a large sheath electric field in front of the rf electrode. On the other hand, when a strong magnetic field (2 T) is applied, the MWNTs are observed to be well aligned and not to be deformed even under the condition that the rf electrode is negatively biased. These results can be explained by the fact that the ion bombardment energy is reduced despite the existence of the large sheath electric field, which is caused by the magnetization of the ions in the strong magnetic field.
Analyses of Early Stages of Vertically Aligned Carbon Nanotube Growth by Plasma-Enhanced Chemical Vapor Deposition
Authors: Hayashi Yasuaki , Watanabe Yousuke , Ueda Keisuke , Nishino Shigehiro
Published: July 2005

The pretreatment and early stages of aligned carbon nanotube (CNT) growth by hot-filament-assisted plasmas-enhanced chemical vapor deposition have been analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy, and in situ ellipsometry. It was found that the effect of pretreatment on the aligned growth is due to the formation of finer catalyst particles through sputtering by ions accelerated in a sheath electric field. It was also found that the optimum growth temperature affects the aligned growth of CNTs. Poorly aligned growth at the higher temperatures is due to the insufficient formation of finer catalyst particles under the competition with coalescence. To align the growth of CNTs, fine catalyst particles smaller than a certain size are required.
Growth of mm-Long Carbon Nanotubes by Grid-Inserted Plasma-Enhanced Chemical Vapor Deposition
Authors: Kishimoto Shigeru , Kojima Yoshihiro , Ohno Yutaka , Sugai Toshiki , Shinohara Hisanori , Mizutani Takashi
Published: July 2005

Vertically aligned long multi-walled carbon nanotubes (MWNTs) have been successfully grown by grid-inserted plasma-enhanced chemical vapor deposition (PECVD). A thin Fe (1 nm)/Ti (1 nm) double-layer catalyst was effective in growing the long MWNTs. The length of the MWNTs increased to 1 mm for the growth time of 120 min without growth termination. A thick Fe catalyst or thick Ti underlayer resulted in a low growth rate. Transmission electron microscopy, energy-dispersive X-ray analysis and thermo-gravimetric analysis (TGA) measurements suggest that the MWNTs were grown in a root growth mode. Moreover, the TGA measurements suggest that MWNTs of high quality/purity were successfully grown by grid-inserted PECVD with a double-layer catalyst.
Microwave Plasma-Enhanced Chemical Vapor Deposition of Carbon Nanostructures Using Biological Molecules
Authors: Yoshimura Masamichi , Tanaka Kei , Ueda Kazuyuki
Published: July 2005

Biological molecules are used as catalysts for the growth of carbon nanostructures by microwave plasma-enhanced chemical vapor deposition. Large and small carbon nanotubes are formed perpendicular to the silicon substrate. The dependence of the initial coverage of ferritin molecules on the surface as well as the bias voltage dependence on the structures grown are investigated. The ferritin molecules tend to diffuse and coalesce at high temperatures and high bias voltages, which gives rise to the large carbon nanotubes with a few tens of nanometers in diameter. The density of the small nanotubes increases with decreasing bias voltage.
Change of Interlayer Exchange Coupling in Fe/Y Multilayers by Hydrogenation
Authors: Endo Yasushi , Takama Daisuke , Yamamoto Masahiko , Suenobu Tomoyoshi , Fukuzumi Shunichi
Published: July 2005

We have investigated the change of interlayer exchange coupling in Fe (3.0 nm)/Y (t nm) multilayers upon increasing the thickness of the spacer layer by hydrogenation. The coupling behavior changes from an antiferromagnetic (AFM) state to a non-coupled (NC) state, both before and after hydrogenation. The maximum value of coupling strength (J
1) is found to become much lower after hydrogenation than before hydrogenation. The range of the spacer layer thickness for maintaining AFM coupling is found to be extended from 1.4 nm to 1.8 nm by hydrogenation. Both the difference in the AFM coupling strength and the extension of the spacer layer thickness of AFM coupling should be attributed to the change from a Y layer to a yttrium–hydride (Y–H) layer by hydrogenation.
Position-Controlled Growth of Single-Walled Carbon Nanotubes by Laser-Irradiated Chemical Vapor Deposition
Authors: Fujiwara Yasuyuki , Maehashi Kenzo , Ohno Yasuhide , Inoue Koichi , Matsumoto Kazuhiko
Published: July 2005

Single-walled carbon nanotubes (SWNTs) were synthesized by chemical vapor deposition using Ar-ion laser irradiation as a source of heat. The circular area corresponding to the position of the laser spot in the growing process was characterized by Raman scattering spectroscopy and scanning electron microscopy. The results revealed that SWNTs can be synthesized at exactly controlled positions and localized regions. The regions of SWNT growth strongly depended on the power of the laser; therefore, only suitable power from laser irradiation could synthesize SWNTs over an entire circular area. By making a partial improvement to the apparatus, the optical instrument and the laser power, we finally synthesized SWNTs in an extremely localized area of approximately 5 µm in diameter.
Growth Control of Carbon Nanotube using Various Applied Electric Fields for Electronic Device Applications
Authors: Maeda Masatoshi , Hyon Chan-Kyeong , Kamimura Takafumi , Kojima Atsuhiko , Sakamoto Kazue , Matsumoto Kazuhiko
Published: July 2005

The control of the growth direction of a carbon nanotube was accomplished by applying an electric field during the growth of the carbon nanotube. The effects of two types of applied bias, one is a constant DC bias, and the other is a ramp bias, on the control of the growth direction were examined. By maintaining a constant DC bias we could control the growth direction of the carbon nanotube, however, the bridging ratio between the two electrodes was as small as 35%. We suppose that this low bridging ratio may be caused by the etching effect of hydrogen. When a ramp bias was applied, bridging ratio tended to increase with the slope of ramp bias. Under optimal conditions, the bridging ratio reached a value as high as 95%.
Fabrication of a Single-Electron Inverter in Single-Wall Carbon Nanotubes
Authors: Tsuya Daiju , Suzuki Masaki , Aoyagi Yoshinobu , Ishibashi Koji
Published: July 2005

A single-electron inverter has been fabricated in single-wall carbon nanotubes (SWNTs) by connecting two single-electron transistors (SETs) in series. Each SET was fabricated in different SWNTs only by depositing metallic contacts on them. For one SET, SWNTs appeared to be single and semiconducting, while they appeared to form a bundle for the other SET. The inverter performance was obtained at 1.5 K with a full voltage swing and a gain of ∼0.6, although the SETs were not fabricated from the simple individual metallic nanotubes.
Photoresponse of Carbon Nanotube Field-Effect Transistors
Authors: Ohno Yutaka , Kishimoto Shigeru , Mizutani Takashi
Published: July 2005

Photoresponse of carbon nanotube field-effect transistors (FETs) is investigated using microscopic measurements. The nanotube FETs, with an isolated single-walled carbon nanotube (SWNT) for the channel, were fabricated by means of the position-controlled nanotube growth technique. An increase in the off-state current and the threshold-voltage shift of the FET were caused by laser illumination. The increase in the off-state current is attributed to photocurrent due to carriers excited in the SWNT channel. The excitation spectrum of the photocurrent had a peak corresponding to optical absorption by the third interband gap of the van Hove singularity of the semiconducting SWNT with a diameter of ∼2 nm. The photocurrent increased in proportion to incident laser power with a dynamic range over four orders of magnitude. The external quantum efficiency was 2×10-7. An inverter action to optical-signal input was observed near the threshold voltage of the FET. The responsivity was as high as 2×10-3 A/W for a single SWNT channel. This high responsivity is explained by the field-effect amplification phenomenon.
Measurements of Electronic Transport Properties of Single-Walled Carbon Nanotubes Encapsulating Alkali-Metals and C60 Fullerenes via Plasma Ion Irradiation
Authors: Izumida Takeshi , Jeong Goo-Hwan , Neo Yoichiro , Hirata Takamichi , Hatakeyama Rikizo , Mimura Hidenori , Omote Kenji , Kasama Yasuhiko
Published: July 2005

We report on the measurements of the electronic transport properties of Cs-encapsulated single-walled carbon nanotubes (SWNTs), Li-encapsulated SWNTs, and C60-encapsulated SWNTs synthesized by plasma ion irradiation method. After fabricating field-effect transistor (FET) configurations using pristine and plasma-ion-irradiated SWNTs, the electronic transport properties of these devices are investigated in vacuum at room temperature. As a result, C60-encapsulated SWNTs give rise to a p-type semiconducting property as pristine SWNTs do. On the other hand, it is clearly observed that Cs-encapsulated SWNTs exhibit n-type transport behavior. Moreover, Li-encapsulated SWNTs show an ambipolar transport property with both n-type and p-type characteristics. Thus, the electronic properties of SWNTs are found to be successfully controlled by plasma ion irradiation.
Carbon Nanotube-Poly(vinylalcohol) Nanocomposite Film Devices: Applications for Femtosecond Fiber Laser Mode Lockers and Optical Amplifier Noise Suppressors
Authors: Sakakibara Youichi , Rozhin Aleksey G. , Kataura Hiromichi , Achiba Yohji , Tokumoto Madoka
Published: July 2005

We fabricated single-wall carbon nanotube (SWNT)/poly(vinylalcohol) (PVA) nanocomposite freestanding films and examined their application in devices in which the saturable absorption of SWNTs at near-infrared optical telecommunication wavelengths can be utilized. In a passively mode-locked fiber laser, we integrated a 30-µm-thick SWNT/PVA film into a fiber connection adaptor with the film sandwiched by a pair of fiber ferrules. A ring fiber laser with a SWNT/PVA saturable absorber was operated very easily in the mode-locked short-pulse mode with a pulse width of about 500 fs. Reproducible stable device performance was confirmed. In examining noise suppression for optical amplifiers, mixed light of semiconductor amplified spontaneous emission (ASE) source and 370 fs laser pulses was passed through a 100-µm-thick SWNT/PVA film. The transmission loss of the femtosecond pulse light was smaller than that of the ASE light. This proved that the SWNT/PVA film has the ability to suppress ASE noise.
Electrical Properties of Connected Multiwall Carbon Nanotubes
Authors: Hamada Yoshihiro , Negishi Hideki , Akita Seiji , Nakayama Yoshikazu
Published: July 2005

We have investigated the carrier transport properties of multiwall carbon nanotubes (MWNTs) by scanning probe microscopy. Kelvin force microscopy revealed that the potential profile was almost flat along the axis of an MWNT with a current flow of ∼10 µA. Furthermore, current-mode imaging with an applied voltage of 10 mV along an MWNT protruding from an electrode the current to be almost constant at ∼20 nA despite variations in the distance from the electrode to the probe. We also found small corrugations with a period of ∼25 nm on the current profile, which originate from the standing wave of the carrier in the MWNT protruding from the electrode. These results strongly suggest that the carrier transport in the MWNT is ballistic even at room temperature.
Digital Designs of Broadband Visible Antireflection Coating for Wide Angular Incidence
Authors: Liou Yeuh-Yeong , Liu Yu-Tsung
Published: July 2005

A design algorithm based on a modified minimizing search technique is applied to design a visible antireflection coating for a wide angular incidence with an angle up to 30° from the normal. The design approach consisting of tuning and minimizing operations is effective in refining the antireflective performance and simplifying the design structure of the desired solution. It is shown that the maximum wide angular visible spectral reflectance of minimizing search antireflection coating designs for a three-material 60-layer system is reduced to less than 0.490% with 15–21-layered structures, and the average visible spectral reflectance for each incident angle is reduced to below 0.137%.
Mechanical Properties of Sharpened Carbon Nanotube Tips
Authors: Akita Seiji , Ohashi Masakaki , Nakayama Yoshikazu
Published: July 2005

We investigate the mechanical properties of sharpened nanotube tips for use in scanning probe microscopy in terms of tip bending under a force acting on the side of the tip. The sharpened nanotube probe fabricated by means of a modified electrical breakdown process effectively acts as a probe with high lateral resolution not only in the topographic measurement but also in the potential distribution measurement. Based on molecular mechanics calculations for a sharpened triple-walled nanotube probe, although the interlayer van-der-Waals interaction weakens the probe stiffness expected on the basis of the continuum model, the stiffness of the tapered nanotube is confirmed to be 10 times higher than that for a single-walled nanotube with the same tip radius and the same length.
Comparison of Field Emissions from Side Wall and Tip of an Individual Carbon Nanotube
Authors: Konishi Yasumoto , Hokushin Shogo , Tanaka Hiroyoshi , Pan Lujun , Akita Seiji , Nakayama Yoshikazu
Published: July 2005

Electrons are generally emitted from the tip of a carbon nanotube (CNT) when the CNT stands on a substrate, but it is not clear where electrons are emitted when a CNT is bent or lies down on a substrate. We have investigated the field emission properties of the side wall of a multi-walled carbon nanotube (MWNT) compared with that of the tip of a MWNT. We also calculated electric field intensities at the side wall and the tip of a MWNT using the finite element method. The turn-on voltage is 150 V for the tip and 570 V for the side wall of the MWNT, which is consistent with calculations indicating that the intensity of the electric field concentrated on the tip of a CNT is 2.8 times larger than that on the side wall of a CNT shaped like a loop. This suggests that the field emission is predominantly from the tips of CNTs in a field emitter. However, the emission current from the side wall is larger than that from the tip of MWNTs.
Direct Observation of Field Emission Sites in a Single Multiwalled Carbon Nanotube by Lorenz Microscopy
Authors: Fujieda Tadashi , Hidaka Kishio , Hayashibara Mituo , Kamino Takeo , Ose Yoichi , Abe Hidekazu , Shimizu Tetuo , Tokumoto Hiroshi
Published: July 2005

Emission sites were observed as bright spots near the tip end of a multiwalled carbon nanotube (MWNT) by means of Lorenz microscopy. The bright spots appeared above electric fields as electrons were emitted. A marked fluctuation was observed in the emission current above 20–30 µA, which was closely related to structural changes at the tip of the MWNT. The layers of the MWNT were peeled off during field emission and they functioned as the second emission sites for the concentration of electric field.
Novel Fabrication Process for HfO2 Thin Film for Gate Dielectric
Authors: Nagasato Yoshitaka , Ueno Tomo
Published: July 2005

A novel process for fabricating a high-k dielectric/Si structure is proposed. The structure is fabricated by ultrahigh vacuum (UHV) sputtering of Hf metal followed by postannealing in atmospheric oxygen ambient. In the fabrication of structures by this method, an interfacial layer such as SiO2 is scarcely formed because the Si surface is already covered with Hf metal from UHV sputtering, before heating in oxygen ambient. Also a postoxidation condition is set up so that the metal Hf, but not the substrate Si, is oxidized completely. Consequently, the HfO2/Si structure was fabricated with an interfacial layer thickness of as low as 0.2 nm. In addition, thermal stability of the HfO2 film fabricated by this method was maintained up to 800°C for 30 min, which is a standard thermal budget for the impurity activation process. These experimental facts show that this novel process is effective for fabricating the high-k dielectric/Si stacked structure with ultrasmall equivalent oxide thickness (EOT) for the next-generation metal-oxide-semiconductor field effect transistor (MOSFET).