bluuebunny/crossref_metadata_2025 huggingface dataset:
A Highly Accurate Stress Measurement System for Producing Precise X-Ray Masks
Authors: Oda Masatoshi , Une Atsunobu , Okada Ikuo , Shinohara Shinji , Nakayama Yasuo , Hideo Yoshihara Hideo Yoshihara
Published: October 2002

A new system that measures stress in film deposited on Si wafers has been developed to produce highly accurate X-ray masks. The system consists of very rigid air sliders, an electrostatic sensor, and a soft-handling wafer chuck. With the system, wafer warp is precisely measured before and after film deposition, and the stress distribution is calculated from those measurements. Wafer warps can be measured with a repeatability of a few nanometers by this system. The stress distribution of absorber film on 2-mm-thick Si wafers can be determined with an accuracy of ±5 MPa. The stress distribution agrees well with the pattern position shifts in the membrane.
Thermal Decomposition of Dissolution Inhibitor in Chemically Amplified Resist during Prebake Process
Authors: Saito Satoshi , Kihara Naoko , Wakabayashi Hiromitsu , Makoto Nakase Makoto Nakase
Published: October 2002

The equation which represents the decomposition mechanism for two dissolution inhibitors in a chemically amplified positive resist consisting of polyvinylphenol protected with p-t-butoxycarbonylmethyl (BCM-PVP) and p-t-butoxycarbonyl (BOC-PVP) groups was investigated by isothermal thermogravimetry (TG) analysis. The reaction orders of these polymers were different and this difference was caused by the difference in the thermal deprotection reaction of the protecting group. It was shown that the decomposition of BCM-PVP is promoted as decomposition proceeds, which is expressed by the equation. This result indicates that, when BCM-PVP is used as an inhibitor in chemically amplified resists, it is important to determine the baking temperature and duration in order to prevent its decomposition.
Effect of Helium Gas Pressure on X-Ray Mask Heating during Synchrotron Radiation Exposure
Authors: Chiba Akira , Futagami Motonobu , Okada Koichi , Kato Tadao , Nobufumi Atoda Nobufumi Atoda
Published: October 2002

The temperature rise of an X-ray mask irradiated by synchrotron radiation (SR) emitted from the SORTEC storage ring has been measured in situ using the thermography technique. In order to detect IR rays in the range of 2.5-5.6 µ m wavelength, emissivities for masks with and without an absorber were measured in advance by using Fourier transform infrared spectroscopy. After measuring the temperature rise of the mask as a function of helium (He) pressure, the heat transfer coefficient was analyzed for estimating the thermal effect on the mask-wafer assembly. Using this heat transfer coefficient, the temperature rises of 20 and 0.3° C in vacuum and under atmospheric He pressure were successfully calculated at a ring current of 200 mA, respectively. The He pressure above 10 Torr in the exposure chamber is sufficient in SR lithography to minimize the temperature rises of the mask membrane and wafer.
Visualization of Molecular Orientation by Using a UV-Curable Liquid Crystal
Authors: Shin Masuda Shin Masuda , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

A novel procedure for determination of a molecular orientation state in a liquid crystal (LC) cell is demonstrated using a UV-curable LC. The molecular orientation states are visualized by means of distribution properties of light intensity observed from a cross section of the LC cell. The Freederickz transition and an inhomogeneous orientation near the edge of an electrode in the cross section of the LC cell are visualized using this procedure.
Growth of Al-In Composite Nanoparticles Prepared by Gas-Evaporation Technique and Subsequent Vapor Condensation
Authors: Takehisa Ohno Takehisa Ohno
Published: October 2002

Al-In composite nanoparticles were prepared by the condensation of In vapor onto flying Al nanoparticles which were produced in advance by a gas-evaporation technique. Their structural and morphological observations were carried out by electron microscopy. It was found that the particle is composed of an Al sphere with an In crystallite sticking to the Al surface. The growth process of the particles is discussed.
Detection of Charge Flow from Metal Surfaces in Air after Laser Pulse Excitation
Authors: Huzimura Ryoitiro , Miyanohara Mitsunori , Miyuki Furui Miyuki Furui
Published: October 2002

Negative charge flow from Al, Au, Cu and Zn targets in air at atmospheric pressure induced by irradiation with 532 nm light pulses from a Nd:YAG Q-switched laser has been detected using a simple collector facing the target. With oxidized Cu surfaces, a positive charge peak which is related to formation of Cu2O phase on the surface is observed. The positive and negative peak heights increase sublinearly with increasing laser fluence from 0.24 to 77 mJ/cm2. Possible emission mechanisms causing charge flow are discussed.
Quantitative Analysis for CH 3 Radicals in Low-Temperature Growth of 3C-SiC on Si(001) Clean Surface
Authors: Tomoaki Hatayama Tomoaki Hatayama , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

Using cracked propane (C3H8), carbonization of a Si(001) clean surface with a (2×1) structure can be realized reproducibly at as low as 750°C in gas source molecular beam epitaxy. The carbonized layer indicates single-crystalline 3C-SiC, and surface morphology is very smooth. Methyl (CH3) radicals in a cracked-C3H8 molecular beam can be detected with a mass spectrometer utilizing a threshold ionization technique. The number of CH3 radicals is estimated, and it can reach up to 3.0×1011 cm-3 with a C3H8 flow rate of 0.8 sccm and a cracker temperature of 1200°C. Based on quantitative analysis, the condensation coefficient of CH3 radicals in carbonization is discussed.
Effect of Alkanolamines on the Microstructure and Dielectric Properties of Lead Zirconium Titanium Trioxide Thin Films Prepared from Modified Metal Alkoxides
Authors: Tanaka Hirofumi , Tadanaga Kiyoharu , Tohge Noboru , Tsutomu Minami Tsutomu Minami
Published: October 2002

Lead zirconium titanium trioxide (PZT) thin films were prepared by the sol-gel method using Ti and Zr alkoxides chemically modified with acetylacetone and trihydrated lead acetate dissolved in ethanol containing alkanolamines, such as monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA), as starting materials. In FE-SEM micrographs of PZT thin films with each alkanolamine, the perovskite phases of 400-600 nm in diameter and the Pb-deficient pyrochlore grains of 20-50 nm in diameter, which could not be detected by X-ray diffraction (XRD), were observed, although the XRD patterns of the films showed a single perovskite phase. The fraction and size of perovskite phases in the films using MEA are larger than those in the films using DEA or TEA.
An overcoating of PbO on these films can lead to the formation of the perovskite single phase. The PZT thin films using MEA showed better dielectric properties than the films using DEA or TEA.
Optical Properties of Poly(pentafluorophenylsilyne) Prepared by Electrochemical Polymerization
Authors: Watanabe Akira , Ito Osamu , Miwa Takao
Published: October 2002

The first polysilyne having a perfluorinated aryl group, poly(pentafluorophenylsilyne), was prepared through a combination of the Grignard reaction of bromopentafluorobenzene and tetrachlorosilane and the subsequent electrochemical polymerization using a magnesium electrode. The absorption and emission spectra of the polymer showed the characteristic of polysilyne which has a silicon network structure. The emission decay of poly (pentafluorophenylsilyne) measured by the time-resolved single photon counting technique showed non-single exponential kinetics. These optical properties were compared with those of poly(phenylsilyne).
Effect of Microwave Pulse on the Deposition Rate of Hydrogenated Amorphous Silicon in the Electron Cyclotron Resonance Plasma Deposition
Authors: Lee Ju-Hyeon , Park Sang Kook , Kim Chang Sik
Published: October 2002

Hydrogenated amorphous silicon (a-Si:H) films were deposited from Ar and silane gases by a pulsed electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. The pulse frequency of the microwave power was varied to study its effect on the deposition rate. It was found that the deposition rate of a-Si:H films is enhanced by about 40% at frequencies which are lower than 25 kHz (where the pulse width is 20 µ s) and abruptly increased up to about 89% and 97% at 27.5 kHz and 30 kHz respectively, compared to the case of the continuous wave. These results suggest that the SiH3 radical be the dominant species responsible for the deposition of a-Si:H. The lifetime of the dominant radicals is estimated as shorter than 20 µ s.
High-Crystallinity Sr1-xCuOy Films Grown by Molecular Beam Epitaxy Using a Mass-Separated Low-Energy O+ Beam
Authors: Kawaguchi Kenichi , Pindoria Govind , Kita Ryusuke , Nishiyama Madoka , Tadataka Morishita Tadataka Morishita
Published: October 2002

High-crystallinity films of the Sr1-
x

CuO

y

infinite-layer oxide were grown by molecular beam epitaxy combined with a mass-separated low-energy oxygen ion ( O+) beam as the oxygen source. The film growth was carried out under an ultralow background partial pressure of molecular oxygen, estimated to be less than 2×10-11 Torr during growth. Reflection high-energy electron diffraction patterns of the films showed well-defined Kikuchi lines. Precise measurement of the rocking curves for the films resulted in sharp peaks with a full-width at half-maximum of 0.016°.
Characterization of Stress in Porous Silicon Films Prepared by Reactive Hydrogen Plasma Sputtering Technique
Authors: Yong Sun Yong Sun , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Hydrogenated porous silicon (P-Si:H) films with columnar structure are prepared by reactive hydrogen plasma sputtering of silicon. Stress in the films is characterized by X-ray diffraction and Raman scattering measurement. Experimental results show that the stress mainly results due to a lattice expansion (Δa/a
0) of Si grains in the films. Δa/a
0 increases with decrease in Si grain size, and tends towards the limiting value of about 1.2%, both when Si grain size is below 100 Å and when a large amount of amorphous silicon hydrides are present in the films.
Scanning Tunneling Microscopy and Spectroscopy Observation of Reduced BaTiO3(100) Surface
Authors: Shimizu Tetsushi , Bando Hiroshi , Aiura Yoshihiro , Haruyama Yuichi , Oka Kunihiko , Nishihara Yoshikazu
Published: October 2002

Microscopic structure and electronic states on the BaTiO3(100) single-crystal surfaces annealed in ultrahigh vacuum were observed by scanning tunneling microscopy and spectroscopy (STM/S). The surface step edges aligned preferentially along the [001] family of axes as the annealing temperature was increased. After annealing at temperatures above 800° C, spatial ordering of Ti 3d-oxygen vacancy complexes appeared on the surface. The STS spectra showed in-gap electronic states at about 1.0 eV below Fermi energy, which agreed well with the results of ultraviolet photoelectron spectroscopy previously reported.
Novel Technique for Achieving Dual-Domain Alignment in Twisted Nematic Liquid Crystal Display and Its Application
Authors: Jamal Syed H. , Kelly Jack R. , John L. West John L. West
Published: October 2002

A simple technique for achieving dual-domain alignment in a twisted nematic liquid crystal display (TN-LCD) is proposed. By incorporating the use of linearly polarized deep UV (DUV) for liquid crystal alignment, only one rubbing and one photolithographic process are added to conventional TN fabrication. We fabricated dual-domain twisted nematic (DDTN) cells using this technique with a practical pixel resolution. This DDTN cell has very symmetrical viewing characteristics in both the vertical and horizontal viewing directions. With the use of the proper type of retardation films along with this DDTN we have been able to achieve a contrast ratio of 10:1, to almost ±40° in the vertical and beyond ±60° in the horizontal viewing directions, without any gray-scale inversion.
X-Ray Excited Current Detected with Scanning Tunneling Microscope Equipment
Authors: Tsuji Kouichi , Kichinosuke Hirokawa Kichinosuke Hirokawa
Published: October 2002

We have used a commercial scanning tunneling microscope to detect the electrons emitted from the sample's surface under the X-ray irradiation condition for the first time. The tip current is detected only under the X-ray irradiation condition and is amplified in air. Thus, we believe that the origin of this current is the electrons emitted from the film surface due to the photoelectric effect, and the current which is amplified by ionization of the molecules in air by the emitted electrons is detected. The dependences of the detected signal on sample voltage, intensity of X-rays and tip sample distance were investigated.
Novel Transparent and Electroconductive Amorphous Semiconductor: Amorphous AgSbO3 Film
Authors: Yasukawa Masahiro , Hosono Hideo , Ueda Naoyuki , Kawazoe Hiroshi
Published: October 2002

Amorphous AgSbO3 films prepared by RF sputtering under O2 gas plasma and by subsequent postannealing at 500° C in O2 gas flow were found to be novel transparent and electroconductive amorphous semiconductors. The optical band gap of the films was ∼2.3 eV. The electrical conductivity was ∼10-1 Ω-1· cm-1 at room temperature and its temperature dependence showed thermal activation-type behavior with an activation energy of ∼0.23 eV. Hall measurements indicated n-type conduction. Concentration of carrier electrons and the Hall mobility at room temperature of the sample were ∼3×1017 cm-3 and ∼7 cm2·V-1·s-1, respectively. The value of the mobility was close to that of the polycrystalline films ( ∼8 cm2·V-1·s-1).
Effective Grinding Procedure for Sm2Fe17Nx Powder with High-Performance Permanent Magnetic Characteristics
Authors: Machida Ken-ichi , Shiomi Atsushi , Izumi Hirokazu , Adachi Gin-ya
Published: October 2002

Finely and uniformly ground powder samples (mean particle size <3 µ m) of Sm2Fe17N

x

(x= approx. 3.0) which were obtained by ball milling in hexane solution containing a surface-active agent for 1-3 days, provided high remanence (B
r) and coercivity ( i
H
c) values: B
r=1.2-1.3 T and i
H
c=0.9-1.1 MA· m-1 (11-14 kOe), although their mean particle size (<3 µ m) was still larger than that of the calculated one for the single magnetic domain (∼0.3 µ m). These excellent magnetic characteristics were attributed to size uniformity, surface smoothness, and less strain induced in the finely ground powder particles.
Effects of High Polymer Concentration for Alignment of Liquid Crystal on Rubbed Polyimide Surfaces Containing Trifluoromethyl Moieties
Authors: Seo Dae-Shik , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

The effects of high polymer concentration for alignment of liquid crystal (LC) on rubbed polyimide (PI) surfaces containing trifluoromethyl moieties have been successfully evaluated by measuring the pretilt angle, surface ordering, and polar anchoring strength. The pretilt angle of 5CB is increased by combination of steric interaction between the LCs and the substrate surfaces on rubbed special PI and low surface energy due to rich fluorine atoms on surfaces was demonstrated. The surface order parameter of 5CB for high polymer concentration is small compared to low polymer concentration. We suggest that the surface order parameter is decreased by low surface energy caused by rich fluorine atoms. The polar anchoring strength of 5CB near the clearing temperature for high polymer concentration is very weak compared to low polymer concentration. Finally, we suggest that the pretilt angle, surface ordering, and polar anchoring strength in 5CB strongly depend on character of polymer on surfaces.
Identification of Formation of Conically Converging Shock Waves in an Alumina-Sphere-Dispersed Copper Rod
Authors: Kidokoro Hideki , Tamura Hideki , Burkhard Günther , Tanabe Yasuhiro , Akira B. Sawaoka Akira B. Sawaoka
Published: October 2002

Shock compression of a concentric assembly of an inner rod and an outer cylinder which has a higher shock velocity than the rod led to generation of a Mach disk in the rod due to interference of conically converging shock waves. A sintered copper rod containing small alumina spheres was used as the inner rod. Shock wave configuration including Mach disk formation in the rod was identified through the observation of deformation of the alumina spheres.
ESR and Optical Studies of CuInS2 Single Crystals
Authors: Nishikawa Nobuyuki , Aksenov Igor , Shinzato Takeshi , Sakamoto Takao , Katsuaki Sato Katsuaki Sato
Published: October 2002

Infrared (IR) absorption and ESR spectra of iron and chromium impurities were studied in CuInS2 crystals. Both iron in its divalent and trivalent valence states and chromium in its divalent state were observed. The charged states of these ions showed a drastic change in accordance with the Fermi level movement in the band gap introduced by vacuum- and sulfur vapor-annealing. The g-values of these divalent ions determined from ESR (g
ł=2.20 in Fe2+ and =1.935 in Cr2+) were in good agreement with those estimated theoretically using approximate values of crystal-field parameters (D
q∼350 cm-1 in Fe2+ and D
q∼570 cm-1 in Cr2+) deduced from optical absorption spectra.
Model for Lasing Oscillation due to Bi-Excitons and Localized Bi-Excitons in Wide-Gap Semiconductor Quantum Wells
Authors: Mitsuru Sugawara Mitsuru Sugawara
Published: October 2002

We present a model for lasing oscillation due to bi-excitons and localized bi-excitons in wide-gap II–VI semiconductor quantum wells. We introduce the condition for population inversion in bi-exciton–exciton optical transition, and show the importance of studying the thermodynamic equilibrium between bi-exciton and exciton states. The Saha equation shows that bi-excitons decompose into two free excitons at fairly low temperatures due to the small binding energy (10 to 30 meV) in II–VI quantum wells, making the population inversion possible only at low temperatures. We point out that bi-excitons localized at certain potential minima in the quantum-well plane will achieve the population inversion even at room temperature if the local potential is deep enough to prevent thermal activation (about 100 meV). By simple theoretical calculation, we show that the localized bi-exciton–exciton optical transition will produce sufficient optical gain for lasing oscillation and has potential application in low-threshold-current blue-light emitting lasers.
Preparation of CuInSe2 Thin Films by Chemical Spray Pyrolysis
Authors: Shirakata Sho , Murakami Tomonori , Kariya Tetsuya , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

CuInSe2 thin films have been prepared by chemical spray pyrolysis (CSP) on glass substrate from the ethanol aqueous solution containing CuCl2, InCl3 and N,N-dimethylselenourea. Properlies of the CuInSe2 films (electrical, structural, optical absorption and morphological properties) have been systematically studied in terms of substrate temperature (T
s), pH and the ion ratio (Cu/In) of the spray solution. Good chalcopyrite CuInSe2 films with large grains have been grown using the neutralized spray solution (pH=4) at the growth temperature of 360° C. On the other hand, low values of T
s, pH and Cu/In led to the production of sphalerite films.
Electrooptic Performance of Electroclinic Liquid Crystals and Their Mixtures
Authors: Crawford Gregory P. , Naciri Jawad , Ranganathan Shashidhar Ranganathan Shashidhar , Banahalli R. Ratna Banahalli R. Ratna
Published: October 2002

The electrooptic properties of two novel electroclinic liquid crystal homologs and their mixtures exhibiting the chiral smectic-A phase with no underlying (low temperature) tilted phase are reported. The field-dependence of the induced tilt angle and of the electroclinic response time of the mixtures are intermediate between those of the pure compounds. A feature of the result is that the mixtures exhibit properties that are attractive from the point-of-view of applications–a broad (65°C) range of the chiral smectic-A, large values of the induced-tilt angle and electroclinic coefficients, and, fast electroclinic response times.
Pulsed Plasma Processing for Reduction of Profile Distortion Induced by Charge Buildup in Electron Cyclotron Resonance Plasma
Authors: Fujiwara Nobuo , Takahiro Maruyama Takahiro Maruyama , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

The distortion of etched profiles was investigated in pulse-modulated Cl2 and HCl plasmas using optical emission spectroscopy. Notch depth reduction was observed in both gases with repeated pulsing of the plasma. This reduction strongly depends on the off-time length. According to optical emission analysis, attenuation in the off-period was quite different in Cl2 and HCl plasmas; it was 2 times faster in HCl plasma. This is explained by higher ambipolar diffusion of protons existing in HCl plasma. The damping process of plasma greatly influences the notch characteristics. In the case of HCl plasma, no aspect-ratio dependence of notching was observed. This indicates that accumulated charges on every pattern area were neutralized by exposure to repeated pulses of plasma.
New Interpretation of the Effect of Hydrogen Dilution of Silane on Glow-Discharged Hydrogenated Amorphous Silicon for Stable Solar Cells
Authors: Okamoto Shingo , Yoshihiro Hishikawa Yoshihiro Hishikawa , Shinya Tsuda Shinya Tsuda
Published: October 2002

The effect of hydrogen dilution on glow-discharged hydrogenated amorphous silicon (a-Si:H) is investigated at substrate temperatures of 100–200° C. The dependence of the properties of a-Si:H on the hydrogen dilution ratio γ (γ=[ H2 gas flow rate]/[ SiH4 gas flow rate]) can be explained in terms of two different effects: i.e., decrease of the film deposition rate at a low γ and implantation of hydrogen atoms into a-Si:H during and after film deposition at a high γ. The latter effect, which is similar to that of hydrogen plasma post-treatment, increases the hydrogen content (C
H) and optical gap (E
opt) of a-Si:H with no significant deterioration in photoconductivity or SiH2/SiH ratio estimated from infrared absorption. It is found that the electric conductivity and defect density of a-Si:H, both in the annealed state and light-soaked state, have a better correlation with the hydrogen content with SiH2 bond configurations (C
SiH2
) than with C
H or E
opt. A conversion efficiency of 8.8% is achieved after light soaking (1.25 sun, AM-1.5, 48° C, open load, 310 h) for a single-junction a-Si:H solar cell using an a-Si:H i-layer with reduced C
SiH2
.
Position-Dependent Instability of Lithium-Drifted Silicon Detector
Authors: Miyachi Takashi , Ohkawa Shoichi , Matsuzawa Hidemi , Otogawa Takao , Kobayashi Norihiro , Onabe Hideaki
Published: October 2002

The variation in detector sensitivity was studied using 1150 nm light and scanning-electron microscope images. The charge-collection efficiency induced by photons is clearly position-dependent at low voltage. We propose that such variation is caused by vacancies.
Simultaneous Measurements of Liquid Properties Using Multichannel Shear Horizontal Surface Acoustic Wave Microsensor
Authors: Jun Kondoh Jun Kondoh , Kazuki Saito Kazuki Saito , Showko Shiokawa Showko Shiokawa , Hideyuki Suzuki Hideyuki Suzuki
Published: October 2002

Surface acoustic waves (SAW) with a shear horizontal polarized displacement (SH-SAW) can be used to determine mechanical and electrical properties of an adjacent liquid. We propose a new multichannel SH-SAW microsensor for liquid characterization. The SH-SAW microsensor, which is fabricated on 36° rotated Y-cut X-propagating LiTaO3, consists of three SAW delay lines. The propagating surfaces of two of the delay lines are metallized and electrically shorted, and the other one has a free surface which is an electrically active area. The viscosity, conductivity and permittivity of liquid are obtained simultaneously using the multichannel SH-SAW microsensor.
Characteristics of a Discretely Weighted Conical Transducer for Generation of Limited Diffraction Beams
Authors: Takashi Koike Takashi Koike , Ken Yamada Ken Yamada , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

We proposed discretely weighted conical transducers as a simple and practical method of generating Bessel-type limited diffraction beams. In this paper we present the design and fabrication of a discretely weighted conical transducer and examine its capability of generating narrow-beam ultrasound. The transducer has eight annular electrodes, to which position-dependent discrete voltages are applied to create approximately the desired velocity distribution of vibration. It is shown experimentally that an almost uniform -6 dB beamwidth of 6–9 wavelengths is obtained in the axial range of z=10 mm to 200 mm using a transducer 25 mm in diameter operating at 3.6 MHz.
Design of a Cylindrical Ultrasonic Micromotor to Obtain Mechanical Output
Authors: Takeshi Morita Takeshi Morita , Minoru Kurosawa Minoru Kurosawa , Toshiro Higuchi Toshiro Higuchi
Published: October 2002

A cylindrical ultrasonic micromotor has been demonstrated and the operating principle has been confirmed. The stator transducer in this motor was 2.4 mm in diameter, 10 mm long and 0.25 mm thick. One advantage of the ultrasonic micromotor is the possibility of high torque. However, the previous motor was only used to rotate the tiny screw which was used as a rotor. We presents a method of improving the efficiency of this ultrasonic micromotor and the results obtained.
Efficiency Improvement of an Ultrasonic Motor Driven with Rectangular Waveform
Authors: Takaaki Ishii Takaaki Ishii , Tsuyoshi Shinkoda Tsuyoshi Shinkoda , Sadayuki Ueha Sadayuki Ueha , Kentaro Nakamura Kentaro Nakamura , Minoru Kurosawa Minoru Kurosawa
Published: October 2002

Ultrasonic motors have many advantages such as high torque, silent drive, quick response and no magnetic field generation, but their efficiency is not high enough compared with that of the electromagnetic motor. In order to improve the efficiency of the ultrasonic motor, we propose a novel design of the motor by shaping the torsional vibration velocity. That the shaped vibration velocity improved the efficiency of the motor was confirmed by numerical calculation and experimental results. In this experiment, a hybrid transducer type ultrasonic motor was used and the efficiency was improved from 34% to 42%.
Vibration Modes and Resonant Frequencies of a New Tuning Fork with 4 Vibrating Arms
Authors: Atoji Nobuhisa , Murakami Masayoshi , Sugawara Sumio , Kudo Subaru
Published: October 2002

A new tuning fork of the plane structure with 4 vibrating arms
is proposed here. First, the mode of vibration and the resonant
frequency were clarified by finite element analysis and experimental
investigation. As a result, it became clear that there
are modes of vibration suitable for application to a vibratory
gyroscope. The influence of the support on these modes is fairly
small in comparison with a conventional tuning fork. The operation
as a vibratory gyroscope was confirmed experimentally.
Since the tuning fork has 4 vibrating arms, the drive and detection
can each be carried out using one pair of arms. The
influence of acceleration on the output voltage is small because
differential detection is realized electrically by using a pair
of arms. Also, the electrode arrangement is simplified. It was
clarified that the new tuning fork operates as a high-performance
vibratory gyroscope with the above advantages.
Grain-Oriented Ceramics in Bismuth Layer-Structure Compounds for Capacitor Material
Authors: Shoji Kazuo , Sakata Yasuo Uehara
Published: October 2002

The systematic investigation of the composition of high-permittivity bismuth layer-structure oxides and the examination
of the grain-oriented ceramics were carried out. Through
investigation of the composition of high-permittivity
materials, it was clarified that the dielectric constant ε
s of
more than 1000 can be attained using Pb4Bi4Ti7O24 compound.
Moreover, it was confirmed that favorable characteristics for
use as dielectric ceramics for high-voltage capacitors
(stability of ε
s on DC bias, high resistivity, etc.) can be
attained using this compound. The examination of the
characteristics of grain-oriented Pb4Bi4Ti7O24 ceramics
clarified that the dielectric breakdown strength and the
stability of ε
s on DC bias can be improved in the direction
perpendicular to the polarization axis. As a result,
grain-oriented ceramics are considered to be appropriate for
use as capacitor materials.
Effect of Trans-Cis Isomerization of a Chiral Azo-Dye on Dye-Induced Ferroelectricity in an Achiral Liquid Crystal
Authors: M. Blinov Lev , V. Kozlovsky Mikhail , Keizo Nakayama Keizo Nakayama , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A chiral azo-dye showing reversible trans-cis isomerization upon UV light irradiation was used as a dopant to induce ferroelectric properties in an achiral smectic C liquid crystal matrix. The kinetics of the isomerization in the smectic matrix was studied optically. The influence of the isomerization process on the ferroelectric properties of the mixture was investigated by observation of the ferroelectric switching in the smectic C phase and electroclinic response in the smectic A phase. The experimental results show that the banana-shaped cis isomers are less efficient in inducing the spontaneous polarization than their rodlike trans counterparts.
Measurements of Molecular Densities in Low Pressure Discharge Plasmas Using Laser Raman Scattering
Authors: Song Yi Bing , Hirakawa Yuichiro , Uchino Kiichiro , Muraoka Katsunori , Sakoda Tadanori , Yanagishita Koji , Nakamura Shizuo
Published: October 2002

The possibility of using Raman scattering as a method of molecular density measurements in low pressure discharge plasmas has been investigated. Firstly, the detection limit of Raman signal was examined in low pressure air. It was shown that the Raman scattering from nitrogen molecules was detectable down to 0.06 Pa (particle density of 1.4×1019 m-3) when a photon counting detection system was used. The method was then applied to detect methane and its reaction products in an electron cyclotron resonance plasma operated at a pressure of 50 Pa. Densities of CH4, C2H2, C2H6 and H2 were absolutely determined using the calibrated data of the optical system. Also, it was clearly demonstrated that the gas composition in the discharge was dependent on gas flow rate. These experimental results showed the usefulness of the method for quantitative measurements of molecular densities in processing plasmas.
Optical Gain Calculation for Strained Quantum Well Lasers by the Fourier Expansion Method
Authors: Seoung-Hwan Park Seoung-Hwan Park , Doyeol Ahn Doyeol Ahn
Published: October 2002

In this paper, we extend the Fourier expansion method to calculate the optical gain of strained quantum well (QW) lasers within the 6×6 Luttinger-Kohn Hamiltonian. The optical matrix elements, in a Fourier expansion framework, can be derived in a simple form by averaging around the axis normal to the well plane. As a numerical example, we calculate the band structure and the optical gain of InxGa1-x
As/InGaAsP/InP QW lasers. We also study the effect of the spin-orbit split-off band coupling on the optical gain. It is shown that the calculated results are in reasonable agreement with those obtained by the conventional finite difference method.
Chromium Fluoride Attenuated Phase-Shifting Mask for Argon Fluoride Excimer Laser Lithography
Authors: Jun Ushioda Jun Ushioda , Yuko Seki Yuko Seki , Katsumi Maeda Katsumi Maeda , Takeshi Ohfuji Takeshi Ohfuji , Hiroyoshi Tanabe Hiroyoshi Tanabe
Published: October 2002

Chromium fluoride (CrF) film was chosen as the phase shifter for attenuated phase-shifting masks because of its high transmittance at 193 nm. The refractive index n and absorption coefficient k was derived by using the reflectance-transmittance (RT) method. Using argon fluoride (ArF) excimer laser exposure equipment and a chemically amplified positive resist, fine hole patterns were resolved. Depth of focus (DOFs) with 0.24 µm were extended to 30%. The resolution limit was 0.20 µm, while it was 0.22 µm with a conventional mask.
Large-Area Optical Proximity Correction with a Combination of Rule-Based and Simulation-Based Methods
Authors: Sachiko Miyama Sachiko Miyama , Kazuko Yamamoto Kazuko Yamamoto , Kiyomi Koyama Kiyomi Koyama
Published: October 2002

We have developed a practical one-dimensional (1D) optical proximity correction (OPC) system based on a combination method. Our OPC system integrates a rule-based and a simulation-based method so that correction time can be reduced to a minimum, while maintaining sufficient accuracy for the correction. The correction accuracy depends on a simulator implemented in the system. By incorporating the 1D context within the range of the proximity effect into the rule table, higher accuracy in the OPC is obtained as compared with conventional methods which involve looking up tables based on duty ratio, or distance to the nearest neighbor. We applied this system to the linewidth correction of 0.3-µm rule logic gates, and obtained width specifications within ±10% and DOF ±0.4 µm. Since correction is basically carried out at the speed of a rule-based correction, our OPC method is applicable to large area layouts. The correction time for a layout of 116 mm2 was only 64.2 min. The results of OPC for real devices such as SRAMs and DRAMs are also given, demonstrating the feasibility of large-area 1D OPC.
Recent Progress in Electron-Beam Cell Projection Technology
Authors: Yamashita Hiroshi , Nozue Hiroshi , Nomura Eiichi , Itoh Katsuyuki , Ema Takahiro , Hirasawa Satomi , Kojima Katuyoshi , Takao Tamura Takao Tamura , Ken Nakajima Ken Nakajima
Published: October 2002

NEC's recent progress in the development of electron-beam (EB) cell projection technology is reviewed. To make it practical, not only the development of a high-performance EB direct writing system but also the establishment of its peripheral technologies in the micro-fabrication process are pursued. In order to obtain high lithographic performance in the EB cell projection lithography system HL-800D (Hitachi), the fundamental effects in EB lithography such as the Coulomb interaction effects, the proximity effect and electron scattering by cell projection aperture (EB mask), have been studied. In addition, high-resolution and high-sensitivity resists have been developed. The Coulomb interaction effects are found to be the most critical issue in cell projection lithography because it affects resolution, linewidth accuracy and throughput. For high resolution, the beam current was reduced to suppress the Coulomb interaction. As a result, a resolution of 0.15 µ m, which is sufficient for fabricating a 1G DRAM, was obtained using the high-resolution resist. To achieve high-linewidth accuracy of less than ±5% for 0.2 µ m lines-and-lines (L/S), optimization of the EB mask structure and the development of a proximity effect correction method which includes the Coulomb interaction effect correction were carried out. Inspection technology for devices of 0.2 µ m or less was also investigated in order to accurately measure linewidth, and to detect defects, particularly those caused by shot stitching error. Finally, the cell projection technology has been applied to the device fabrication of a 1G DRAM, and was demonstrated to be feasible for the development of futuristic advanced devices.
Critical-Temperature Optimization in Sr2YCu3Oz and Sr2TmCu3Oz
Authors: Akira Ono Akira Ono
Published: October 2002

Superconducting cuprates Sr2YCu3O

z

and Sr2TmCu3O

z

are synthesized under various conditions to optimize their superconducting properties. The maximum value of the superconducting transition temperature (T
c) is 70 K for Sr2YCu3O

z

and 62 K for Sr2TmCu3O

z

; which are realized after firing for more than 9 h when carbon-free starting samples are used for high-pressure synthesis. The enhancement of T
c is attributable to an increase in oxygen pressure.
Tilting of Liquid Crystal through Interaction with Methyl Orange Molecules Oriented by Circularly Polarized Light
Authors: Lim Tong Kun , Choi Sang Un , Sang Don Lee Sang Don Lee , Young Il Park Young Il Park
Published: October 2002

Tilting of the director of liquid crystal sandwiched between two cell walls was achieved through interaction with obliquely oriented methyl orange (MO) molecules in the polyvinyl alcohol (PVA) film coated onto the cell. Slantwise orientation of those MO molecules in the PVA film with respect to the cell surface was achieved by pumping them obliquely with circularly polarized light. The long axis of the MO molecules was found to be oriented along the direction of propagation of the pumped light due to the photoinduced isomerization and relaxation mechanism of the MO molecules. When the MO molecules were tilted 52° with respect to the cell wall, the director of liquid crystal molecules was found to be tilted 3° with respect to the cell surface plane.
Magnetically Excited Plasma Oxidation of InP: Effects of Ar Mixing and Substrate Heating
Authors: Shingo Sato Shingo Sato , Akihiro Funyu Akihiro Funyu , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Oxide films of InP with good electrical characteristics and of sufficient thickness were obtained using magnetically excited plasma oxidation with Ar + O2 mixed gas as an oxidant or with substrate heating to 200°C. These oxides were grown in helicon-wave-excited plasma. Both Ar mixing and substrate heating strongly enhanced the growth rate of the oxide film. However, the capacitance-voltage ( C-V) characteristics of these oxides were not always good. The oxides grown in inductively coupled plasma, on the other hand, showed excellent C-V characteristics.
A Theoretical Investigation of Migration Potentials of Ga Adatoms near Kink and Step Edges on GaAs(001)- (2×4) Surface
Authors: Shiraishi Tomonori Ito
Published: October 2002

Migration potentials of Ga adatoms near kink and step edges are qualitatively investigated using empirical interatomic potential and an energy term. The energy term, as a function of the number of electrons remaining in the Ga dangling bond, is extracted from ab initio pseudopotential calculations. The calculated results imply that the lattice sites in the missing dimer row are favorable for Ga adatoms on the GaAs(001)-(2×4)β2 surface, since the formation of Ga dimers reduces the number of electrons remaining in Ga dangling bonds. Lattice sites in the missing dimer row near a kink and B-type step edge are stable for a Ga adatom, whereas no preferential adsorption site is found near an A-type step edge. This is simply because a Ga adatom in the missing dimer row near a kink and B-type step edge is weakly stretched by an As atom and As-dimer on the plane one layer below as opposed to being strongly stretched by two As-dimers near an A-type step edge.
Preparation of La0.84Sr0.16CrO3 Powders by pH-Controlled Glycine-Nitrate Process
Authors: Shin Hyeung-Chul , Lee Kang-Ryeol , Park Sung , Jung Choong-Hwan , Kim Sun-Jae
Published: October 2002

The variations in the crystallinity and particle size of La0.84Sr0.16CrO3 powders synthesized using precursor solutions with various pHs in the glycine-nitrate process were investigated. Increasing the pH of the precursor solution promotes the formation of a complex between the Sr nitrate and the COOH group of the glycine. Powders with a higher crystallinity and finer particle size were obtained with increasing the pH of the precursor solution. It is thought that higher crystallinity and finer particle size of the powders synthesized using precursor solutions with high pH are due to homogeneous combustion resulting from the increased degree of complex formation of the Sr nitrate with the carboxylic acid group of the glycine.
Prerequisite for Photoluminescence D Line Spectra of Heat-Treated Carbon-Lean Czochralski Silicon Crystals
Authors: Cho Ki Hyun , Lee Jeong Yong , Suh Eun Kyung , Kim Ki Wan
Published: October 2002

We present a systematic experimental investigation on the prerequisite for D line luminescence at the photon energies of 0.81 and 0.87 eV in heat-treated carbon-lean Czochralski (CZ) silicon crystals. For examination of the influence of a transition metal on photoluminescence D lines, carbon-lean CZ silicon wafers annealed using simulated MOS thermal cycles were deliberately contaminated with Cu. The results show that the presence of specific extended defects, i.e., planar-type defects bounded by {111} planes and composed of 60°-type dislocations and stacking faults in this experiment, is a prerequisite for the generation of D1 and D2 lines in heat-treated carbon-lean CZ silicon crystals, and that the diffusion of Cu into the heat-treated samples reduces the D2 line intensity significantly whereas it enhances D1 line luminescence up to a certain level of Cu contamination.
Proton-Exchanged LiNbO3 Optical Waveguides Using Toluic Acid
Authors: Shen Chi-Yen , Chu Ren-Chang , Cwo-Hwa Liou Cwo-Hwa Liou , Shuming Tong Wang Shuming Tong Wang
Published: October 2002

Proton-exchanged optical planar waveguides have been fabricated in z-cut LiNbO3 using new proton sources: m-toluic acid and p-toluic acid. These waveguides were characterized optically and were found to exhibit a graded index profile with a high surface index change, being 0.14 and 0.1337 for m-toluic and p-toluic acid, respectively. The changes in the surface index of both acids were larger than those produced by benzoic acid, stearic acid and octanoic acid, and smaller than that produced by pyrophosphoric acid. The index profile could be approximated by the parabolic function. The diffusion rates for the proton-exchanged process using both m-toluic acid and p-toluic acid were slower than that reported for benzoic acid.
Improvement of Open Circuit Voltage of SnO 2–nSi Solar Cells
Authors: Azuma Shimizu Azuma Shimizu , Shigeru Shinoda Shigeru Shinoda , Sanae Sugita Sanae Sugita , Kohki Hiroshima Kohki Hiroshima , Koji Yano Koji Yano , Masanobu Kasuga Masanobu Kasuga
Published: October 2002

Tunnel metal-insulator-semiconductor (MIS) SnO2–nSi solar cells were made by oxidizing (100) and (111) Si substrates at various oxidation temperatures and times, and by spray-depositing SnO2 to the surface. Open-circuit voltage V
oc decreases with increasing oxidation temperature, and the cells made on (100) Si have higher V
oc than those on (111) Si which were made under the same oxidation conditions. V
oc is related to the n-factor and effective barrier height. The n-factor increases linearly with increase of the density of surface states D
ss, while the effective barrier height decreases slowly with increase of D
ss. For the improvement of V
oc, it is effective to increase D
ss. Experimental results support the theoretical prediction. When the oxidation temperature decreases, D
ss increases, which results in an increase of the n-factor and V
oc. The (100) solar cell has a higher V
oc than the (111) cell because it has a higher D
ss.
Faraday Effect of ZrF4–BaF2–LnF3 Glasses (Ln=La, Ce, Pr, Tb and Dy)
Authors: Qiu Jianrong , Kawamoto Yoji , Hirao Kazuyuki
Published: October 2002

The wavelength dispersions in the Faraday effect of 60ZrF4·30BaF2·10LnF3 glasses (Ln=La, Ce, Pr, Tb and Dy) are examined. Glass containing LaF3 has a positive Verdet constant in the wavelength region from 350 to 850 nm, and the magnitude of the Verdet constants decreases with increasing wavelength. In contrast, the Verdet constants of glasses containing other rare-earth ions are negative, and the absolute magnitude of the Verdet constants decreases with increasing wavelength. The effective transition wavelengths of glasses containing paramagnetic rare-earth ions have been calculated using the Van Vleck and Hebb theory. Factors determining the Verdet constants of these glasses are discussed.
Electron Scattering by Mn Impurities in Si Detected by Cyclotron Resonance Measurement
Authors: Sekika Yamamoto Sekika Yamamoto , Tyuzi Ohyama Tyuzi Ohyama
Published: October 2002

In this paper, we report on investigation of the low-temperature transport properties of silicon doped with transition metals, using the cyclotron resonance technique. For clarification of the states of metal impurities in silicon, secondary ion mass spectroscopy (SIMS), deep level transient spectroscopy (DLTS), and electron spin resonance (ESR), photoluminescence (PL) and Hall measurements were also performed. It was shown that of the various transition metals used, only manganese significantly affects the probability of electron scattering. The inverse relaxation time obtained from the cyclotron resonance linewidth varies with the square root of temperature. This temperature dependence cannot be explained by the typical scattering theories such as neutral shallow impurity scattering and ionized impurity scattering. We used high-resistivity silicon to display the contribution of transition metals effectively. Transition metals were doped by thermal diffusion at 1100°C after being evaporated onto the silicon surface. ESR measurements revealed the existence of interstitial manganese, while Hall measurements revealed a rather high density of Mn clusters. Following room temperature annealing, the intensity of the ESR signal for interstitial manganese rapidly decreased due to clustering, while the density of Mn clusters and the inverse relaxation time did not change significantly. Thus, the electron scattering was mainly caused by manganese clusters efficiently produced in the pure silicon host.
Spatially Controlled Formation of an Atomically Flat Si(001) Surface by Annealing with a Direct Current in an Ultrahigh Vacuum
Authors: Ando Atsushi , Sakamoto Kunihiro , Miki Kazushi , Kazuhiko Matsumoto Kazuhiko Matsumoto , Tsunenori Sakamoto Tsunenori Sakamoto
Published: October 2002

We propose a new technique for the spatially controlled formation of an atomically flat large Si(001) surface obtained by annealing with a direct current in an ultrahigh vacuum. This technique uses barrier structures to depress step movement for spatial control and enables the fabrication of a large atomic-step-free Si(001) surface at the desired position after annealing. We have also demonstrated spatially controlled formation using artificial step bands as barrier structures. Single atomic round Si(001) planes of about 4 µ m in diameter were obtained by annealing the 6 µ m square patterned substrate at 1000° C for 2 h.
A Percolation Approach to Dielectric Breakdown Statistics
Authors: Tetsufumi Tanamoto Tetsufumi Tanamoto , Akira Toriumi Akira Toriumi
Published: October 2002

The stochastic breakdown model proposed by Niemeyer et al. has been improved by taking the time evolution into account in the two-dimensional lattice system. A Markov process has been assumed in the breakdown process and `time' has been defined reflecting the distribution of broken bonds in the cluster. The change of breakdown patterns with time predicts various aspects of breakdown phenomena. We have shown that the final breakdown path does not always form a straight line. We have proposed one of the possible origins for the polarity problem and shown that the polarity difference is understood by the relative position of the damaged layer to the starting point of breakdown.
Improving the Transient Response of a Si Metal-Semiconductor-Metal Photodetector with an Additional i-a-SiGe:H Film
Authors: Laih Li-Hong , Wang Jyh-Cheng , Chen Yen-Ann , Tsay Wen-Chin , Jen Tean-Sen , Chen Jyh-Shin , Jyh-Wong Hong Jyh-Wong Hong
Published: October 2002

An annealed intrinsic hydrogenated amorphous silicon germanium (i-a-SiGe:H) barrier layer deposited on a Si wafer ([111], 4 k Ω-cm) was employed to fabricate a planar interdigitated metal-semiconductor-metal photodetector (MSM-PD). At a bias of 15 V, and an incident light wavelength of 850 nm, this Si-based MSM-PD with an annealed 70 nm i-a-SiGe:H film had a responsivity of about 0.32 A/W, and a dark current density of around 400 fA/µ m2. Also, the temporal response of this device had a rise time of 21 ps, a fall-time of 236 ps and a full-width at half-maximum (FWHM) of 51 ps.