bluuebunny/crossref_metadata_2025 huggingface dataset:
Sn-Sb-Se/Sb-Bi Bilayer Phase-Change Media for High-Density Write-Once Optical Recording
Authors: Nishida Tetsuya , Sugiyama Hisataka , Shinkichi Horigome Shinkichi Horigome
Published: October 2002

We have developed Sn-Sb-Se/Sb-Bi bi-layer phase-change media for high-density write-once optical disks. Crystallized marks as small as 0.5 µ m are stably recorded without initialization. These phase-change media, compared to ablative type write-once media, have high carrier-to-noise ratio, low jitter, and long life. Mark-edge recording with multi-pulse laser irradiation on the media provides a linear bit density of 0.48 µ m/ bit and track pitch of 1.2 µ m using a 690-nm-wavelength laser diode and 0.55 numerical aperture (NA) objective lens. This corresponds to 1.1 Gbit/in.2, or 14 GB formatted data capacity per both sides for a 12-inch-diameter disk with a zoned constant angular velocity (ZCAV) format.
Dynamic Measurement of Capacitance Variation of Piezoelectric Ceramics with Stress
Authors: Yasuo Cho Yasuo Cho , Yukihiro Mandai Yukihiro Mandai
Published: October 2002

In this paper, some electrostrictive constants of the polarized and non-polarized lead zirconate titanate (PZT) ceramics are measured. To measure electrostrictive constants, a new dynamic measurement method for the capacitance variation with step and alternating stress is developed. This new method enables us to obtain the electrostrictive constants in the state of fixed polarization without an aging effect. Using the measured value of the electrostrictive constant2d3333of nonpolarized PZT ceramics and the remanent polarizationP3of the fully polarized one, the piezoelectric strain constantd33is calculated. This calculated result agrees with the measured one very well
Oriented Tin-Doped Indium Oxide Films on <001> Preferred Oriented Polycrystalline ZnO Films
Authors: Yi Choong Hoon , Yasui Itaru , Yuzo Shigesato Yuzo Shigesato
Published: October 2002

<111>-oriented tin-doped indium oxide (ITO) films were deposited by rf magnetron sputtering on ZnO-coated glass substrates (ZnO/glass). The ZnO underlayers were also deposited by rf magnetron sputtering and have been known to exhibit <001> preferred orientation in a wide range of deposition conditions. The X-ray diffraction profiles of the ITO films deposited on the ZnO/glass showed predominant <111> orientation without any differently oriented crystallites, whereas the ITO films deposited on bare glass substrates (ITO/glass) under the same deposition conditions showed <100>-preferred orientation with small areas of several other orientations. A mechanism of the heteroepitaxial growth of In2O3(111)||
ZnO(001) was explained by comparing the atomic configurations of oxygen between the oxygen mostly dense-packed planes of In2O3 and ZnO parallel to In2O3(111) and ZnO(001) planes, respectively. Sn concentrations and lattice constants of the <111>-oriented films (ITO/ZnO/glass) were found to be greater than those of <100> preferred oriented films (ITO/glass) in spite of the fact that the target and deposition conditions were the same, which could be associated with the electrical properties of the films.
Free Path and Scattering Probability of Ions in a Glow Discharge Sheath
Authors: Tagami Takashi , Shuhei Tanaka Shuhei Tanaka
Published: October 2002

The transport of ions in a dc glow discharge sheath is modeled taking into account the ion energy dependence of ion-molecule collision cross section. The free path and the scattering probability of ions are obtained as a function of two parameters: the ratio of sheath thickness to ion mean free path, d
is/l
0, and the ion energy dependence of the collision cross section. The effect of ion energy on free path and scattering probability has been calculated for Ar discharge and found to be significant in typical discharge conditions. The probability of multiple scattering of ions in the sheath is formulated and calculated in 3 dimensions. The result shows that the probability of multiple scattering decreases with decreasing d
is/l
0 and increasing ion energy.
Optical and Morphological Properties of Light-Emitting Porous Silicon Prepared by Chemical Dissolution of Silicon Wafers
Authors: Amato Giampiero
Published: October 2002

Strong light emission has been observed in porous silicon layers prepared by immersing highly doped silicon wafers in a HF/HNO3/H2O etching solution. Morphological information has been obtained through porosity measurements, scanning electron microscopy (SEM), scanning tunnelling microscopy (STM) and Raman spectroscopy. The material optical properties have been investigated by photoluminescence (PL) and photoacoustic (PAS) spectroscopies. The image obtained shows that in chemically prepared porous silicon (CPS), three phases, namely, macroporous, mesoporous and microporous, exist. SiOx, c-Si, and voids are suggested to affect the optical response of the layers. Comparisons of PL spectra of CPS and electrochemically prepared PS (EPS) samples with the same and higher porosity values reveal marked similarities, suggesting that carrier confinement in nanometer-sized structures plays a key role in the light-emission process.
Effects of Light Pulse Duration on Excimer-Laser Crystallization Characteristics of Silicon Thin Films
Authors: Ryoichi Ishihara Ryoichi Ishihara , Wen-Chang Yeh Wen-Chang Yeh , Takeo Hattori Takeo Hattori , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

The waveform of an excimer-laser light pulse has been varied using two laser systems with a delayed trigger. The effects of the pulse duration on the physical properties of crystallized silicon thin films were studied. From the results that threshold energies for crystallization, amorphization and ablation increased in proportion to the square root of light pulse duration, their critical temperatures were estimated to be 1000°C, 1800°C and 2700°C, respectively. It was found that the critical temperature for µ-crystallzation is changed from about 2600°C for a thin film under short pulse duration conditions to 1800°C for a thick film under long pulse duration conditions. The long pulse is effective, but not drastic, in improving the poly-crystallized silicon film quality.
Frequency-Dependent Collector Transport Factor of Lateral Hot Electron Transistor
Authors: Gregory Khrenov Gregory Khrenov , Victor Ryzhii Victor Ryzhii
Published: October 2002

The high-frequency operation of a lateral hot-electron transistor is discussed. Analytical expressions for the induced collector current and collector transport factor are found and analyzed. It is shown that lateral geometry of the transistor results in specific features of the frequency dependence of the collector transport factor, namely, slower degradation at high frequencies in comparison with the same parameter of the hot-electron transistor with vertical structure.
The Influence of Cell Size on Lightning Surge Protection Semiconductor Devices
Authors: Satoh Hidetaka , Yoshio Shimoda Yoshio Shimoda
Published: October 2002

Transient temperature rise is analyzed for a lightning surge protective semiconductor device. When a lightning surge strikes a conventional protective device, it is found that the heat concentrates, raising the device temperature. We propose a multi-cell device that reduces the maximum temperature caused by the heat concentration, thus improving the surge handling capability of the device. We examine the influence of cell size on maximum temperature by analyzing the transient thermal characteristics. The maximum temperature is found to strongly depend on the unit cell size, so that the multi-cell device efficiently decreases the maximum temperature. Our fabricated surge protective device with 8 cells has a 30% higher surge handling capability than a conventional device for lightning surge waveforms of (10/1000) µ s.
The Effect of Ionizing Radiation Damage on the Transconductance of Short Channel Insulated Gate Field Effect Transistors
Authors: Subramanian Vivek , Bhattacharya Pradeep Kumar
Published: October 2002

This paper describes the effect of ionizing radiation on the transconductance of short channel Insulated Gate Field Effect Transistors. Devices having channel lengths ranging from 2 µ m to 0.5 µ m and a constant channel width of 10 µ m were irradiated from 3 Mrad ( SiO2) up to 8 Mrad ( SiO2) and comparisons were made to an unirradiated control set. An initial increase in transconductance was noted up to 3 Mrad ( SiO2), followed by a degradation at higher doses. At heavy irradiation levels, saturation was noted in degradation, with shorter n-channel devices showing some rebound. The mechanisms behind these variations were examined, and a qualitative model of defect generation was developed.
Determination of Composition of CdSxSe1-x Microcrystals in Semiconductor-Doped Glasses Using Raman Scattering
Authors: Miyoshi Tadaki , Nakatsuka Takanori , Naoto Matsuo Naoto Matsuo
Published: October 2002

Raman spectra of CdS

x

Se1-
x

-doped glasses are reported. The composition x is determined from the difference between CdS- and CdSe-like longitudinal optical (LO) phonon frequencies. Glass samples from different manufacturers show different compositions x of CdS

x

Se1-
x

microcrystals, even if these glasses exhibit almost the same optical transmission spectra.
Ionic-Size Effects on the Magnetism of T′-(R1-xYx)2CuO4 (R=Pr, Nd, Sm and Eu)
Authors: Shen Ruey-Chyi , Tyan Tzyy-Quen , Meen Teen-Hang , Yang Hung-Duen
Published: October 2002

X-ray diffraction and magnetic susceptibility measurements have been investigated for Gd2CuO4 and T′-(R1-
x

Y

x

)2CuO4 ( R=Pr, Nd, Sm and Eu). Lattice parameters a, b and c decrease with increasing Y concentration in (R1-
x

Y

x

)2CuO4, and the values of solubility limit are about x=0.4, 0.4, 0.4 and 0.3 for R=Pr, Nd, Sm and Eu, respectively. The magnetic anomalies that occur at T
N(Cu)∼285 K and T
m∼20 K in Gd2CuO4 are not observed in other R2CuO4 ( R=Pr, Nd, Sm and Eu), but are seen in ( Sm1-
x

Y

x

)2CuO4 with x≥0.3 and (Eu1-
x

Y

x

)2CuO4 with x≥0.05. For (Pr1-
x

Y

x

)2CuO4 and (Nd1-
x

Y

x

)2CuO4, magnetic anomalies were found at about 6.5 K and 11 K with x≥0.4 and x≥0.1, respectively. It seems that the magnitudes of anomalies in (R1-
x

Y

x

)2CuO4 are very sensitive to Y substitution and depend dramatically on the ionic radius of rare-earths. Thus, the small ionic radius of Gd has a much more important effect than its large moment on the anomalous magnetic properties of Gd2CuO4. This also provides clear evidence that the magnetic anomalies in Gd2CuO4 are due to weak ferromagnetism in the CuO2 plane resulting from the excessively small ionic radius of Gd, which induces a lattice distortion in the T′ structure.
Theoretical Design of 460 nm ZnCdSSe Laser Diodes
Authors: Wataru Imajuku Wataru Imajuku , Masashi Takahashi Masashi Takahashi , Masakazu Kobayashi Masakazu Kobayashi , Akihiko Yoshikawa Akihiko Yoshikawa
Published: October 2002

Theoretical design of ZnSSe/ZnCdSSe laser diodes emitting 460 nm at room temperature (RT) was studied by means of threshold current analysis. The threshold current density calculation was based on the laser theory established for the III-V laser diode (LD) system. The result of the threshold current density calculation indicated that the reduction of carrier overflow is an essential issue in realizing the device with a reasonable threshold current level at RT. Another indication is that 30% S content in the ZnSSe cladding layer would be a suitable target value for a practical 460 nm LD at RT, along with a multiple quantum barrier structure. The predicted threshold current density of such a LD could be as low as 450 A/cm2 at RT.
Effect of the Gas Temperature of a High-Power Chemical Oxygen-Iodine Laser on Calculated Small Signal Gain and Output Power
Authors: Fukuda Tsutomu , Yoshida Sanichiro , Ohue Hiroshi , Tomizawa Takeshi , Fujioka Tomoo , Keiichi Mito Keiichi Mito
Published: October 2002

Rate equations describing the lasing kinetics of a high-power chemical oxygen-iodine laser were solved, taking into account the effect of gas temperature. The temperature rise resulting from deactivations was calculated at each computation step along the flow, with the temperature dependence of rate constants and of the heat capacitance of the total gas taken into account. It has been shown that the inclusion of the temperature effect has a significant influence on the calculated laser gain and laser output. The results of the present calculation verify the observation of surprisingly high gas temperature in the optical resonator in a previous experiment and indicate that the gas temperature of a subsonic, 1 kW-class chemical oxygen-iodine laser can easily be over 1000° C in the optical resonator unless a buffer gas is used to increase the heat capacitance.
Dielectric Properties of SrTiO3 Thin Films Grown by Ozone-Assisted Molecular Beam Epitaxy
Authors: Nakamura Takao , Tokuda Hitoki , Tanaka So , Michitomo Iiyama Michitomo Iiyama
Published: October 2002

Crystalline SrTiO3 thin films were fabricated by an ozone-assisted molecular beam epitaxy (MBE) method at a relatively low deposition temperature of around 300° C. These films had high crystallinity, smooth surface and insulating properties with increasing deposition temperature. The relative dielectric constant for a 250-nm-thick SrTiO3 film deposited at 480° C was 825 at 35 K.
This value was comparable to that of SrTiO3 films, which were deposited at over 650° C by pulsed laser deposition. This film had similar temperature and applied electric field dependence to bulk SrTiO3. The electric field-effect evaluation on SrTiO3 films in the Ag/SrTiO3/YBa2Cu3O7-
x

configuration indicated suppression of the SrTiO3/YBa2Cu3O7-
x

interface layer.
Improved High-Q Dielectric Resonator Sintered at Low Firing Temperature
Authors: You Cheng-Chyi , Huang Cheng-Liang , Wei Chung-Chuang , Jin-Wen Huang Jin-Wen Huang
Published: October 2002

The microwave properties of Ba(Co1/3Nb2/3)O3-Ba(Ni1/3Nb2/3)O3 ceramics were investigated. Ba(Co1/3Nb2/3)O3 has a low sintering temperature. However, the Q value is too low for application requirements at microwave frequencies. A new composition, Ba(Ni1/3Nb2/3)O3, which shows a positive temperature coefficient of resonant frequency was used as a compensator to improve the dielectric properties of the complex perovskite-type ceramic. Both sintering and crystallization of Ba(Co1/3Nb2/3)O3-Ba(Ni1/3Nb2/3)O3 were accelerated compared to those of Ba(Co1/3Nb2/3)O3 alone. The Q value at microwave frequencies was also improved. The dielectric ceramics with Ba(Co, Ni)1/3Nb2/3O3 system were found to be fired at a low temperature below 1400° C and to have a low temperature coefficient of resonant frequency τ
f
and high Q value. Dielectric properties of the ceramic resonator made of Ba(Co0.6Ni0.4)1/3Nb2/3O3 are a dielectric constant of 31, Q value of 10000 at 9 GHz, and temperature coefficient of resonant frequency τ
f
of -4 ppm/° C.
Spontaneous Micro-Macro Ferroelectric Domain Switching in PbZrO3-doped Pb(Ni1/3Nb2/3)O3-PbTiO3System
Authors: Yoon Man-Soon , Kim Hyun M. Jang
Published: October 2002

The possibility of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using 1-3 mol% PbZrO3-doped Pb(Ni1/3Nb2/3)O3-PbTiO3(PNN-PT) systems having tetragonal symmetry at room temperature. On cooling, the system with 60 mol% Pb(Ni1/3Nb2/3)O3underwent a spontaneous transition from a relaxor to a normal ferroelectric state. A microscopic examination demonstrated that the relaxor-normal ferroelectric transition corresponds to a micro-macro domain switching. Long-range ferroelectric domains below the transition temperature were characterized by twinlike 90° macrodomains with tetragonal symmetry. The relaxor-normal transition was further correlated with the rhombohedral-tetragonal first-order phase transition.
Effects of Porosity on Dielectric Properties of BaTiO3 Ceramics
Authors: Hsiang Hsing-I , Yen Fu-Su , Chi-Yuen Huang Chi-Yuen Huang
Published: October 2002

We investigate the porosity dependence of the ferroelectric domain density and the internal stress of fine-grained (∼1 µ m) BaTiO3 ceramics using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The ferroelectric domain density and the internal stress exerted by the neighboring grains of the fine-grained BaTiO3 were examined to elucidate the effect of porosity on the dielectric properties of BaTiO3 ceramics.
Restructuring of Polymer-Dispersed Nematic Droplets in External Electric Field
Authors: Ding Jiandong , Zhang Hongdong , Lu Jianming , Yuliang Yang Yuliang Yang
Published: October 2002

Two types of polymer dispersed liquid crystal (PDLC) films with normal and tangential anchored nematic droplets are prepared, and the restructuring of nematic droplets in external electric fields is monitored by polarized optical microscopy (POM) and small angle light scattering (SALS). The electric field effect in nematic droplets is analysed qualitatively. Some comparisons and discussion are made, and the complication of this effect is indicated.
Scaling of Ion Transport Based on Frequency and Pressure in a Parallel-Plate RF Glow Discharge
Authors: Kenji Harafuji Kenji Harafuji
Published: October 2002

Scaling relations for several plasma parameters and ion energy/angular distribution have been investigated as a function of gas pressurePand driving frequencyfin a parallel-plate RF glow discharge of argon plasma under constant DC and RF voltages. A fluid glow discharge simulation shows that sheath lengthLshapproximately scales asP-1/2f-1/2, indicating that the collision probability, η=Lsh/λi(λi=ion mean free path), is proportional to √P/f. The ion flux,Fi, at the cathode shows dissimilar scaling withfandPasFi∝P0.57f1.42in spite of similar scaling of plasma densitynp∝P1.73f1.53. Monte Carlo simulation of the ion transport within the sheath region and the plasma parameter scalings suggest that the combined operation of low pressure typically less than 10 Pa and high frequency typically greater than 100 MHz provides promising conditions for anisotropic profile formation and high etching rate through independent control of ion flux and ion energy/angular distribution.
Measurement of Complex Volume Elastic Modulus of Liquid by Holography
Authors: Miyazaki Takeshi , Yamamoto Yoshitaka , Uyemura Tsuneyoshi
Published: October 2002

This paper describes a technique for measuring the complex volume elastic modulus of a transparent liquid by time-averaged holographic interferometry. The liquid in a slender transparent container whose cross section is square, is sinusoidally vibrated by a ferrite vibrator with a step horn, and the transmitted object beam, whose optical length varies sinusoidally, is holographically recorded. This technique uses the characteristics of amplitude distribution while conventional techniques use those of the vibrational behavior at one point. The dynamic elastic modulus and the loss tangent are determined from the position of the minimum amplitude and from the ratio of the minimum amplitude to the maximum neighboring one, respectively. This technique is advantageous for measuring high loss tangent.
Photothermal Vibration of Fiber Core for Vibration-Type Sensor
Authors: Inaba Seiki , Kumazaki Hironori , Hane Kazuhiro
Published: October 2002

Photothermal vibration of a quartz core of an optical fiber is described. A microcantilever rod comprised of the quartz core was fabricated by etching the clad layer from the optical fiber tip, and was vibrated photothermally using a laser diode. Frequency dependence of the vibration amplitude of the cantilever was measured for vacuum sensing. The resonance frequency decreased from 16.69 to 16.59 kHz with increase of the pressure from 100 to 102 Pa, and the resonance sharpness Q decreased from 2000 to 700 with increase of the pressure from 102 to 105 Pa.
Variable Energy Radio Frequency Quadrupole Linac by Changing the Downstream Electrode Voltage
Authors: Tetsuya Nakanishi Tetsuya Nakanishi
Published: October 2002

A method of varying the output energy of a radio frequency quadrupole (RFQ) linac is proposed. This is achieved by changing the voltage of only the downstream electrode in the cavity, which is divided by a separating plate provided between longitudinally separated electrodes. The calculated results for 31
P
1+ acceleration show that the output energy can be varied from 1.1 MeV to 1.96 MeV without greatly broadening the energy spread: the lengths of the upstream and downstream electrodes are about 1.7 m and 1.0 m, respectively. The transmission efficiency for an input current of a few mA is 87% at its maximum and higher than around 50% at all output energies. The current limit is 8 mA at 1.96 MeV. It has also been shown that the gap between the separated electrodes gives scarcely any problem to the transmission.
Self-Development Mechanism of Nitrocellulose Resist: Electron Beam Irradiation
Authors: Uchida Takashi , Kaneko Hidehiko , Yasuoka Yoshizumi , Gamo Kenji , Namba Susumu
Published: October 2002

The decomposition mechanism of a nitrocellulose film induced by irradiation of an electron beam and He+ ion beam was investigated by monitoring the changes of the infrared spectra. With irradiation of the electron beam, it was found that the electronic stopping power caused the decomposition of the nitrocellulose resist by breaking the R-O-NO2 bond. In addition, it was found that oxidation due to oxygen supplied from NO2 enhanced the decomposition, and finally, a residue was formed. This is almost the same result as obtained by heat treatment. In the case of He+ ion irradiation, the electronic stopping power caused the same decomposition process as did irradiation of the electron beam. However, the residue formed was sputtered off due to the nuclear stopping power.
High-Performance Current-Voltage Measurement System for Scanning Tunneling Spectroscopy of Deposited Molecules
Authors: Okumura Akihiko , Nakagawa Hidemoto , Miyamura Kazuo , Yohichi Gohshi Yohichi Gohshi
Published: October 2002

A tunnel current-voltage measurement system adopting analog integration of the current to improve the signal-to-noise ratio and high resolution (16-bit) analog-to-digital conversion of the integrated current was developed for scanning tunneling spectroscopy of deposited organic molecules. First-derivative images of good quality were successfully obtained with atomic-scale resolution for the first time.
Measurement of Fluorocarbon Radicals Generated from C4F8/H2 Inductively Coupled Plasma: Study on SiO2 Selective Etching Kinetics
Authors: Kubota Kazuhiro , Matsumoto Hiroyuki , Shindo Haruo , Shingubara Shoso , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

The kinetics of highly selective SiO2 etching were studied on the basis of appearance mass spectroscopy (AMS) measurement of fluorocarbon radicals generated from C4F8/H2 inductlvely coupled plasma (ICP). Results obtained by varying of H2 concentration in C4F8, total pressure and RF power implied that CF1 radical played a major role in the polymer film deposition. In particular, radical measurements carried out by varying the length of a quartz tube which was set in front of an inlet of radicals effusing into AMS revealed that CF2 radical might not contribute to the polymer deposition and that the sticking probability of CF1 radical was reduced considerably in the presence of hydrogen. It was also observed that in etching using a capillary plate as a high-aspect-ratio mask, the carbon-rich polymer film is deposited on the Si bottom surface in the presence of hydrogen at high CF1/CF2 radical density ratio. Accordingly, CF1 radicals whose surface loss is suppressed in the presence of hydrogen are likely to arrive at deep the bottom surface, forming the carbon-rich polymer by reaction of hydrogen with fluorine from CF1 radicals.
Mechanisms of the Deposition of Hydrogenated Carbon Films
Authors: Möller Wolfhard , Fukarek Wolfgang , Lange Klaus , Keudell Achim von , Jacob Wolfgang
Published: October 2002

The paper reviews the elementary processes during the plasma-enhanced chemical vapour deposition of hydrogenated carbon films from methane, with special emphasis on the surface processes which determine the growth rate and film structure. Corresponding model calculations are critically discussed in comparison to experimental findings.   Whereas a simplified plasma modeling can be performed with some reliability, only very limited information is available on the the surface physical and chemical mechanisms determining the growth rate as well as the stoichiometry and the structure of the deposited films. Proposed surface models involving widely different processes yield similar results and are thus indiscernible in comparison to results from deposition experiments. Nevertheless, reasonable fits to growth data can be obtained using a combined plasma-surface model.   For the formation of film structure, recent ellipsometric data indicate that hydrogen chemistry might play a decisive role in addition to or rather than ion collisional effects.
Novel Method for Defect Detection in Al Stripes by Means of Laser Beam Heating and Detection of Changes in Electrical Resistance
Authors: Nikawa Kiyoshi , Matsumoto Chika , Inoue Shoji
Published: October 2002

We have successfully detected defects (voids and Si nodules) in Al stripes using an optical beam induced current (OBIC) system in which defects, even those beneath a metal surface, were detectable as the difference in changes in resistance, produced by laser beam heating, between defective and defect-free areas. Our method, which we refer to as optical beam induced resistance change (OBIRCH), is nondestructive since the temperature increase caused by laser irradiation is on the order of 1° C and the density of the base current applied to the stripes is on the order of 106 A/cm2 or less. The results of scanning ion microscopy (SIM) (conducted after areas identified by OBIRCH as being defective had been successively cross-sectioned with a focused ion beam [FIB]) indicated that the minimum void size detectable by OBIRCH was on the order of 10-3 µ m3, and we are able to show that OBIRCH has many advantages over conventional void detection methods.
Relative Errors of Free-Carrier Density at Different Temperatures Calculated from Approximations for the Fermi-Dirac Integral
Authors: Yue Yun , Liou Juin J. , Adelmo Ortiz-Conde Adelmo Ortiz-Conde
Published: October 2002

We present the relative errors of the free-carrier concentration in a semiconductor at all temperatures associated with three different approximations for the Fermi-Dirac integral of the order of 1/2. The results suggest that the errors peak at around 200 K and decrease outside this temperature range for all three doping concentrations considered (1018, 1019, and 1020cm-3).
The Analysis of Chemical State of Obliquely Evaporated Co-Ni-O Film by Auger Electron Spectroscopy
Authors: Kawano Mariko , Yano Akira , Tetsuo Mizumura Tetsuo Mizumura
Published: October 2002

Obliquely evaporated Co-O and Co-Ni-O films show different coercivity dependences on saturation magnetization. To clarify the origin of this difference, we introduced numerical analysis in Auger electron spectroscopy and analyzed the chemical state (metal or oxide) of the Co-Ni-O magnetic layer. In the Co-Ni-O magnetic layer, cobalt was oxidized preferentially compared to nickel. Therefore the compositional ratio of metallic Co to Ni in the magnetic layer was assumed to be different from that of source material. This preferential oxidation of cobalt was considered to be the cause of the difference in coercivi ty dependences on saturation magnetization between Co-O and Co-Ni-O.
A Travelling-Wave Velocity-Matched Wideband Laser Beam Modulator
Authors: Endo Michiyuki , Ghosh Gorachand , Kawakami Tomoteru , Iwasaki Takashi
Published: October 2002

A wideband optical modulator is designed by use of a laser beam and an electro-optic crystal. The reflections at the junctions of a travelling-wave velocity-matched bulk type modulator have been taken into consideration to formulate the modulation index. The frequency response characteristic features of the theoretical curve and the experimental points are rather similar up to 12 GHz.
X-Ray and Optical Investigations of the Dislocation Domains in Ferroelectric Liquid Crystals
Authors: Beresnev L. A. , Schumacher E. , Pikin S. A. , Fan Z. , Ostrovsky B. I. , Hiller S. , Onokhov A. P. , W. Haase W. Haase
Published: October 2002

In ferroelectric liquid crystals with high enough spontaneous polarization P
s≥50 nC· cm-2 the formation of special periodic structure takes place after switching off the moderate value of the electric field. There are dislocation walls which separate the regions of inclined smectic layers with the opposite signs of inclination angle δ for neighbour regions (domains). We have found that 1) angle δ is proportional to the value of the spontaneous polarization, 2) the period D of the dislocaton walls is inversely proportional to P
2
s, 3) during the electric field treatment the periodicity of domains and the tilt angle δ of the inclination of smectic layers can differ essentially in the bulk of FLC layer and near the electrode surfaces. Complicated character of SSFLC switching can be related with the interference of bulk and surface dislocation walls. The role of the charged dislocation walls in the phenomenon of volume bistability is also discussed.
Characterizations of Liquid Crystal Alignment on Poly-Diisopropyl Fumarate Langmuir-Blodgett Films
Authors: Chizaki Makoto , Abe Hiroyuki , Iwa Hiroyuki , Tomokiyo Ryou , Shigehara Kiyotaka , Amaya Naoyuki , Kaiya Norihiro , Iimura Yasufumi , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

We have fabricated Langmuir-Blodgett (LB) films of a poly-diisopropyl fumarate (PDiPF) for nematic liquid crystal alignment and have characterized their alignment capability using a nematic liquid crystal of pentyl-cyano biphenyl (5CB). We prove that the PDiPF-LB films can be obtained by simple processes compared with polyimide-LB films. We present deposition conditions of the PDiPF-LB films, and the relationship between optical axes of the PDiPF-LB films and the alignment direction of 5CB on the films.
Electrical Transport Properties of Al-Cu-Os Icosahedral Quasicrystal
Authors: Yuko Honda Yuko Honda , Keiichi Edagawa Keiichi Edagawa , Shin Takeuchi Shin Takeuchi , An-Pang Tsai An-Pang Tsai , Akihisa Inoue Akihisa Inoue
Published: October 2002

The conductivity at 4.2 K in the Al65Cu20Os15 icosahedral phase (i-phase) is about 10 Ω-1cm-1, which is much lower than those of Al–Cu–Fe and Al–Cu–Ru i-phases reported previously. However, the overall temperature dependence of the conductivity and the magnetoconductivity behave very similarly to one another among the three i-phases. Their behaviors in a low-temperature region can be described by the electron-electron interaction and the weak localization theories.
Nickel Oxide Electrochromic Thin Films Prepared by Reactive DC Magnetron Sputtering
Authors: Yoshimura Kazuki , Miki Takeshi , Sakae Tanemura Sakae Tanemura
Published: October 2002

Nickel oxide electrochromic thin films were prepared by reactive DC magnetron sputtering. The as-deposited optical property and electrochromic behavior strongly depended on the target operation mode and the substrate temperature. The sample sputtered with low oxygen flow rate, high power and substrate temperature of 200-300° C showed a wide transmittance modulation range, and the deposition rate was as high as 30 nm/min. Its integrated luminous transmittance could be controlled from 6.6 to 82.3%. X-ray diffraction measurements of this sample in a colored state and bleached state suggested that the boundary and surface of NiO microcrystallites played an important role in the electrochromic reaction of sputtered nickel oxide films.
Microstructures and Electrical Properties of (Pb, La)TiO3 Thin Films Grown on the Pt Electrodes with a Percolating Network Structure
Authors: Lee Don-Hee , Lee Jeong Soo , Cho Sung Moon , Nam Hyo Jin , Lee Jue Haeng , Choi Jun Rim , Kim Kwang-Young , Kim Sung-Tae , Okuyama Masanori
Published: October 2002

We have investigated the microstructures and electrical properties of Pb0.95La0.05TiO3 (PLT) thin films deposited on the (100)-oriented Pt/(100)MgO substrates by rf magnetron sputtering and have fabricated a thin film infrared sensor. The (100)-oriented Pt film is formed via a coalescence of Pt islands and the Pt layer goes through a transition from nonconducting islands to a conductive percolating network as the Pt deposition time increases. The highly c-axis oriented PLT thin film has been successfully grown on the Pt bottom electrode with a network structure. The PLT thin film on the interconnected percolating Pt network exhibits a well saturated ferroelectric hysteresis loop with the remanent polarization of 1.6 µ C/cm2 and the coercive field of 70 kV/cm. The responsivity and detectivity of the thin film infrared sensor are 700 V/W and 6×108 cm√ Hz/W at 10 Hz, respectively, without any poling treatment.
Ultra Thin Film Growth of Pd by Radical Enhanced Vapor Deposition
Authors: Fujimoto Toshiyuki , Isao Kojima Isao Kojima
Published: October 2002

The vapor deposition of Pd on graphite was carried out in an oxygen radical atmosphere, and resulting surfaces were analyzed by an Auger electron microprobe and a scanning tunneling microscope. In contrast with deposition under oxygen atmosphere or under vacuum, coexistence of the oxygen radical during deposition enabled the Pd to form an ultra thin film whose thickness was 0.6 nm.
Usefulness of Magnetic Neutral Loop Discharge Plasma in Plasma Processing
Authors: Tsuboi Hideo , Itoh Masahiro , Tanabe Masafumi , Hayashi Toshio , Taijiro Uchida Taijiro Uchida
Published: October 2002

Usefulness in plasma processing is demonstrated for a plasma produced in a closed magnetic neutral loop, which consists of zero magnetic field points connected continuously. A preliminary experiment was carried out to show the advantage of magnetic neutral loop discharge (NLD) plasma in sputter etching processing of SiO2/Si wafer in the lower Ar gas pressure range. The experiment shows that a high-density plasma was obtained for Ar gas lower than 0.1 Pa and the sputter etching rate is 3 times higher than that for the usual inductively coupled plasma (ICP). In a large-loop case, the sputter etching profile obtained has a peak at a radius along the azimuthal direction. This implies that a uniform etching profile could be realized by controlling the radius of the neutral loop during process operation. The NLD plasma current induced with an rf primary one-turn antenna coil reaches up to one-third of that of the primary.
Synthesis of Diamond Using RF Magnetron Methanol Plasma Chemical Vapor Deposition Assisted by Hydrogen Radical Injection
Authors: Ikeda Masanobu , Hori Masaru , Goto Toshio , Inayoshi Muneto , Yamada Koji , Hiramatsu Mineo , Nawata Masahito
Published: October 2002

A new plasma chemical vapor deposition (P-CVD) system was developed for synthesis of diamond. This system consisted of a parallel-plate radio frequency (RF) (13.56 MHz) plasma reactor, with a radical source using a microwave (2.45 GHz) discharge plasma and substrate heating using a cw-CO2 laser. In this system, hydrogen (H) radicals were generated in the microwave H2 plasma and preferentially injected near the substrate in the parallel-plate RF magnetron methanol ( CH3OH) plasma region. By scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, it was found that diamond was successfully synthesized using this system. The effects of H radical on the diamond formation were also investigated from the results of optical emission measurements in the RF plasma region, thin-film deposition and etching of the nondiamond phases by varying amounts of H radical injection.
New Research Fields in Ultrasonic Blood Flow Measurement
Authors: Kageyoshi Katakura Kageyoshi Katakura
Published: October 2002

Recent work in ultrasonic blood flow measurement technology is reviewed. Two fundamental limitations in this field and possible methods for overcoming them are introduced. Application of ultrasonic measurement to local evaluation of arterial wall distensibility is also discussed.
Static and Dynamical Properties of SH Phonons Related to Resonant Transmission through Double-Barrier Structure
Authors: Seiji Mizuno Seiji Mizuno , Shin-ichiro Tamura Shin-ichiro Tamura
Published: October 2002

We study both the static and dynamical properties of SH phonons related to the transmission spectrum in an AlAs/GaAs/AlAs triple-layer structure acting as an elastic double barrier to phonons. Specifically, the frequency range where the resonant transmission occurs for oblique phonon incidence is studied in detail. We derive analytical expressions for the transmission rate and asymptotic phase time for phonons. These formulas are applied to the estimation of the time delays for phonon packets traveling through the system of interest and are found to be useful for designing a mode-selective phonon resonator in the THz-frequency range.
Propagation Characteristics of Plate-Mode Waves on Wedge-Shaped Substrate
Authors: Naoto Wakatsuki Naoto Wakatsuki , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

Propagation characteristics of plate-mode waves in a wedge-shaped. piezoelectric ceramic plate are described based on numerical and experimental results. Distributions of phase velocity, group velocity and mechanical displacement are given as functions of the product of frequency F and substrate thickness D. In the experiment, the transition that the Rayleigh-mode wave disperses into 0th-order antisymmetrical and symmetrical modes as it propagates on the wedged substrate is studied. The process in which the two wave modes are reflected from the front end of the substrate and then degenerate again into the Rayleigh-mode wave is also observed and analyzed.
A Study of Unfavorable Vibration Characteristics of Rectangular AT-Cut Quartz Resonators with Cylindrical Capsules
Authors: Momosaki Eishi , Michiaki Takagi Michiaki Takagi
Published: October 2002

Rectangular AT-cut quartz resonators with cylindrical capsules meet the requirement for downsizing of the dimensions in quartz crystal resonators. But it was found that unfavorable vibration characteristics occurred when they were used at high drive levels. We analyzed the vibration data and clarified that the causes were due to the different types of vibrational couplings of the X-dimension dependent spurious modes. Considerations for optimal design were determined as a result.
Discrete Green Function Theory for Multi-Electrode Interdigital Transducers
Authors: Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

The paper describes the extended discrete Green function theory for the analysis of multi-electrode interdigital transducers having electrodes of unequal pitch and/or width. Such a configuration is effectively used to develop unidirectional transducers. First, the field distribution on double- and triple-electrode gratings is calculated by generalisation of Aoki and Ingebrigtsen's method. Then, the discrete Green function is derived by representing the total field as a sum of contributions from various grating modes. Finally, the impulse response model for transducers having various electrode configurations is derived from the discrete Green function.
Finite-Element Analysis of Periodic Surface Acoustic Waveguides
Authors: Koji Hasegawa Koji Hasegawa , Masanori Koshiba Masanori Koshiba
Published: October 2002

A numerical approach based on the three-dimensional finite-element method is developed for the analysis of periodic surface acoustic waveguides. Only a region corresponding to one period of the waveguide is discretized using three-dimensional elements of hexahedral form with 20 nodal points, and cutoff frequencies of a stop band and standing-wave distributions at these frequencies are calculated. These data are used for determining the self- and mode-coupling coefficients of coupled-mode equations with which the reflection characteristics of finite periodic surface acoustic waveguides are easily estimated. In this method, all the effects of piezoelectric perturbation, mechanical perturbation, energy storage due to nonradiated bulk waves, and three-dimensional field distributions are automatically taken into account. Using this method, aluminum strip gratings on an Al/45° X-Z Li2B4O7 or 128° Y-X LiNbO3 substrate are analyzed, and the effects of strip width in the aperture direction on the reflection characteristics are investigated.
Design and Evaluation of Li2B4O7 Surface Acoustic Wave Filter
Authors: Otsuka Kazuhiro , Funami Masayuki , Ito Motoki , Katsuda Hirohiko , Tacano Munecazu , Adachi Masatoshi , Kawabata Akira
Published: October 2002

A 250 MHz Li2B4O7 surface acoustic wave (SAW) filter was successfully designed using a newly developed program for double-mode SAW (DMS) filters. The elastic, piezoelectric and dielectric constants of Li2B4O7 grown by the resistance-furnace heating Czochralski method were measured precisely to determine the accurete phase velocity and the electromechanical coupling coefficient of SAW.
The mode coupling coefficients were determined as a function of the electrode thickness as well. These coefficients were introduced in the simulation program, and the SAW filter was designed. The DMS filter fabricated in this study had almost the same characteristics as those expected from the design.
Improved Power Durability of Surface Acoustic Wave Filters for an Antenna Duplexers
Authors: Nishihara Tokihiro , Uchishiba Hidema , Ikata Osamu , Yoshio Satoh Yoshio Satoh
Published: October 2002

For portable telephone applications, we improved the power durability of ladder-type filters composed of one-port surface acoustic wave (SAW) resonators. In these ladder-type filters, the chip temperature was raised and power durability was weak around both cut-off frequencies in transmission characteristics. Power durability tests of a duplexer composed of ladder-type filters showed that the receiver filter (Rx) in which the power was leaked from the transmitter one (Tx) was weaker than the Tx. We therefore studied Rx in this work. In filter design, reducing the resonator resistance to suppress the rise in chip temperature improved power durability. The lifetime of electrode material was improved to up to 10,000 times longer than that of an Al-Cu single-layer film by use of a 3-layered film of Al-Cu/Cu/Al-Cu.
Proposal of Cryogenic Plasmas in Liquid Helium II
Authors: Minami Kazuo , Watanabe Souichi , Qin Wenhong , Tomimoto Fumihiro , Kuwabara Shigeyuki , Amin Md. Ruhul , Kato Keizo , Satow Takashi
Published: October 2002

Novel possibilities to create cryogenic plasma states in liquid helium II below 2.16 K at 1 atm are proposed. Below 0.4 K, a mixture of positive and negative ions in the superfluid can be collision-free in the sense that the momentum relaxation collision frequencies between ions and neutral atoms, impurity atoms and excitons such as phonons, rotons and vortices are less than the plasma frequencies. In particular, positive ions in the plasmas are analogous to free electrons in conventional gaseous discharges at low pressures, although the plasma parameters are quite different from each other. A possible cryogenic plasma is proposed to be produced as a transient state. Preliminary experiments for ion mixture left after pulsed discharges in liquid helium II are demonstrated.
High Power Travelling-Wave Type Ultrasonic Motor
Authors: Kawai Yasuaki , Asai Kiyokazu , Naito Shin-ichi , Fukui Takashi , Adachi Yoshihiro , Handa Noboru , Ikeda Koichi , Tsuda Kazuhiko
Published: October 2002

We have performed an experiment aimed at developing a high power ultrasonic motor based on a thin, lightweight, travelling-wave type design. This paper presents a detailed analysis of experimental results. Three prototype motors of the improved type were fabricated, having outer diameters of 50, 70 and 90 mm. Compared to a motor employing a piezoelectric element of the same outer diameter and the same resistive resin material as conventional types of motors, approximately twice as high maximum torque and four times as high maximum output power have been obtained with the prototype motors. It has also been confirmed that these motors have sufficient durability to withstand high-loads.
Basic Investigation on Reflection Mode Ultrasonic Attenuation Tomography
Authors: Kazuhiko Hamamoto Kazuhiko Hamamoto , Budi Andreas Budi Andreas , Tsuyoshi Shiina Tsuyoshi Shiina , Masayasu Ito Masayasu Ito
Published: October 2002

Quantitative evaluation of tissue character by medical ultrasound is called \lq\lqtissue characterization", and it is one of the most important themes for medical ultrasonics. \lq\lqUltrasonic computed tomography (CT)" is expected to enable reconstruction of a quantitative image, which can show new diagnostic information such as the slope of the attenuation coefficient. Transmission mode CT and diffraction tomography, however, are affected by bone and unknown ultrasonic characters. In this paper, a new method of reconstructing an exact and quantitative distribution of the slope of the attenuation coefficient is proposed. This method uses reflected pulse waves in order to avoid the influence of bone. Moreover, this method is independent of unknown sound velocities, transmittances, reflectances and white noise. Simulation results show that it is possible to reconstruct a quantitative image of a region including bone from noisy data, by this method.
Photoacoustic Spectroscopy of Polyaniline Films
Authors: Toyoda Taro , Hiroki Nakamura Hiroki Nakamura
Published: October 2002

Photoacoustic spectra as well as optical absorption spectra were measured to study the heat generation by nonradiative processes in electrodeposited polyaniline films in the wavelength range of 310 to 800 nm. The shapes of both spectra depend on the pH for polymerization of electrodeposited polyaniline films. The shapes of infrared spectra also show the pH dependence. Photoacoustic spectra show that the changes of signal intensity are different from those of optical absorption spectra, suggesting the character of lattice relaxation of a low-dimensional system.
Improvement of Electronic Transport Characteristics of Amorphous Silicon by Hydrogen Dilution of Silane
Authors: Mireshghi Ali , Lee Hyoung-Koo , Hong Wan-Shick , Drewery John S. , Jing Tao , Kaplan Selig N. , Victor Perez-Mendez Victor Perez-Mendez
Published: October 2002

We have investigated the electrical and material properties of intrinsic amorphous silicon deposited with hydrogen dilution of silane. The hydrogenated material was used as intrinsic layers of n-i-p diodes, which showed interesting electrical characteristics. From time of flight (TOF) measurement for our best samples produced at hydrogen to silane ratio of 15, we obtained mobility (µ) values about 3-4 times larger than our standard amorphous silicon (a-Si:H). Approximately a factor of 2 improvement was observed for µτ values. The N
D
* values of the hydrogen diluted a-Si:H were measured for the first time and show lower ionized dangling bond density than the normal a-Si:H material. At a hydrogen to silane gas flow ratio of 20, some microcrystalline formation was observed in the deposited material. We propose a simple macroscopic model to assess the effect of microcrystals and grain boundaries on the electronic properties of mixed amorphous and microcrystalline material.
Trap Centers in Germanium-Implanted and in As-Grown 6H-SiC
Authors: Uddin Ashraf , Tsutomu Uemoto Tsutomu Uemoto
Published: October 2002

We have investigated the trap centers in germanium (Ge)-ion-implanted SiC(6H-SiC:Ge) and in as-grown SiC(AG:6H-SiC) samples using photoluminescence (PL) and deep-level transient spectroscopy (DLTS). Three carbon-vacancy related luminescence peaks were observed in 6H-SiC:Ge in PL measurements. Six electron trap centers were observed both in 6H-SiC:Ge and in AG:6H-SiC by DLTS. These trap-center-related peaks disappeared from both 6H-SiC:Ge and AG:6H-SiC after surface oxidation and subsequent removal of the oxide layers. Germanium atoms related to donor-type deep level at 1.2 eV below the conduction band edge is observed in 6H-SiC:Ge by DLTS. The six common trap centers are related to native defects. The deep-level activation energy, concentration and capture cross section are estimated.