bluuebunny/crossref_metadata_2025 huggingface dataset:
Interface Electronic Properties between Silicon and Silicon Nitride Deposited by Direct Photochemical Vapor Deposition
Authors: Hideharu Matsuura Hideharu Matsuura , Masahiro Yoshimoto Masahiro Yoshimoto , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

Interface electronic properties of silicon nitride (SiNx)/crystalline silicon (c-Si) are studied. The interface electronic properties are improved by changing NH3/SiH4 flow ratios (F
NH3/F
SiH4) of a thin SiNx layer (≃6 nm in thickness) between c-Si and a thick SiNx layer (≃65 nm) deposited with F
NH3/F
SiH4=30, where both SiNx layers are formed by direct photochemical vapor deposition (photo-CVD). In the case of F
NH3/F
SiH4=120, the minimum interface-trap density and hysteresis obtained from the capacitance-voltage (C–V) characteristics of Al/thick SiNx/thin SiNx/c-Si diodes are 3 ×1010 cm-2 \cdotp eV-1 and 0.1 V, respectively. In the deposition of thin SiNx, the interface electronic properties are degraded by exposing SixHy or NxHy species to a c-Si surface, where these species are produced by photodecomposition of NH3/SiH4 gas mixtures. Injected carriers, which cause hysteresis of the C–V characteristics, are discussed in terms of the barrier height for tunneling and the number of interface traps.
Supercurrent-Controlled Multiple-Beam Interference of Andreev-Reflected Quasiparticle Waves
Authors: Noriyuki Hatakenaka Noriyuki Hatakenaka , Susumu Kurihara Susumu Kurihara
Published: October 2002

Multiple-beam interference of Andreev-reflected quasiparticle waves is studied. Unlike the two-beam interferometer, the multiple-beam interferometer produces sharp and large interference fringes. The interference can be controlled by the supercurrent flowing through one-dimensional superconductors.
Hole Transport in Vapor-Deposited Triphenylmethane Glasses
Authors: Borsenberger P. M. , W. T. Gruenbaum W. T. Gruenbaum , E. H. Magin E. H. Magin
Published: October 2002

Hole mobilities have been measured in a series of vapor-deposited triphenylmethane (TPM) glasses with different dipole moments. The results are described by a formalism based on disorder, due to Bässler and coworkers. The formalism is premised on the assumption that charge transport occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. A key parameter of the formalism is the energy width of the hopping site manifold. For TPM glasses, the width is between 0.093 and 0.123 eV, increasing with increasing dipole moment. The width is described by a model based on dipolar disorder. The model assumes that the total width is comprised of a dipolar component and a van der Waals component. The dipolar components are between 0.037 and 0.089 eV, increasing with increasing dipole moment. The van der Waals components are approximately 0.085 eV, and independent of the dipole moment. The van der Waals components are significantly larger than literature values reported for a wide range of triarylamine (TAA) glasses. The difference between the van der Waals components is the principal reason for the differences in mobility between TPM and TAA glasses and is attributed to differences in charge delocalization of the TPM and TAA molecules.
Investigation of Increased Photorefractive Damage Resistance in LiNbO3 by Two-Wave Mixing Measurements
Authors: Furukawa Yasunori , Sato Masayoshi , Bashaw Matthew C. , Fejer Martin M. , Iyi Nobuo , Kitamura Kenji
Published: October 2002

The increase in photorefractive damage resistance in both MgO-doped and nondoped Li-deficient LiNbO3 is studied by two wave mixing measurements. Holographic diffraction measurements demonstrated that crystals with high optical damage resistance increase photoconductivity and response time for erasing photorefractive grating. The erasure speed is linearly proportional to the MgO dopant and Li-site vacancy concentrations. The erasure time of holographic grating shows an Arrhenius dependence on temperature from which activation energy is obtained. We proposed an energy level model of the light-induced transport for LiNbO3:MgO dopants introduce donor levels 0.11 eV below the conduction band, whereas, Li-site vacancies in nondoped crystal introduce acceptor levels 0.29–0.44 eV above the valence band.
Simulation of JT-60 Discharges with an Experimentally Calibrated Theoretical Transport Model
Authors: Ji Qiang Ji Qiang , Clifford Singer Clifford Singer , Toshio Hirayama Toshio Hirayama
Published: October 2002

An experimentally calibrated theoretical transport model has been employed to study five L-mode discharges from the JT-60 tokamak. The transport model successfully reproduced electron temperature and ion temperature profile data.
Ultrasonic Relaxation in Superionic Conductor Na1+2xZr2-xMgx(PO4)3
Authors: Naoki Inoue Naoki Inoue , Yoshihiro Ogawa Yoshihiro Ogawa
Published: October 2002

We present the ultrasonic attenuation dependence on concentration x at 3 MHz as a function of temperature in Na1+2
x

Zr2-
x

Mg

x

(PO4)3. From the ultrasonic relaxation spectra, we obtained the activation energy and the relaxation strength and then compared these values to the data obtained from an electrical impedance measurement. We observed hopping conduction between two sites in the crystal.
Neuron-Type Conducting Polymers Prepared Electrochemically and Their Connection
Authors: Fujii Masaharu , Izawa Takenori , Ohnishi Hideomi , Yoshino Kiyomitsu Arii
Published: October 2002

A conducting polymer, polypyrrole, which forms a network pattern has been prepared electrochemically. The patterns have been controlled by varing the polymerization conditions. It has been found from the experiments that neuron-type conducting polymers are synthesized under the suitable conditions. Two conducting polymers with many branches have been connected. The conductivity of the path between the neuron-type conducting polymers has been changed using a third electrode. A new device is proposed, which is applicable to neural network.
Photoacoustic Spectra of CdInGaS4 with a DC Electric Field
Authors: Taro Toyoda Taro Toyoda , Kyouiti Kato Kyouiti Kato
Published: October 2002

Photoacoustic (PA) spectroscopy is used to study the heat generated by nonradiative processes of CdInGaS4 with an external dc electric field transverse to the light path in order to study the correlation between carrier diffusion effects and nonradiative processes in the wavelength range of 310 to 650 nm. Maxima are observed in PA spectra at 2.7 and 2.3 eV, the amplitudes of which values are proportional to the square of the applied voltage. The peak at 2.7 eV shifted toward higher energy when the modulation frequency increased. That at 2.3 eV did not shift. Therefore, there is a possibility that the peaks at 2.7 and 2.3 eV are related to the electron diffusion length and the impurity or deep levels of CdInGaS4, respectively. PA phase spectra showed minima at 2.4 eV, which shifted toward lower energy when the dc electric field strength increased.
Sol–Gel Transition in Gelatin Observed with Surface Waves
Authors: Hisashi Takahashi Hisashi Takahashi , Pak-Kon Choi Pak-Kon Choi
Published: October 2002

Surface wave velocity and absorption were measured in the frequency range 250–750 Hz in gelatin solution at around the sol–gel transition temperature. We propose a dispersion relation for surface wave propagation on gel, which takes surface tension and viscoelasticity into account. The results obtained using the dispersion relation provide the shear elasticity and viscosity in the gelation process. The shear elasticity and viscosity were interpreted within the framework of the percolation theory. The critical exponents obtained experimentallyt=1.7–2.2 ands=0.7–0.8 are in good agreement with the percolation theory.
A Low-Profile Ladder Filter for Portable Telephones Employing Length Expander Mode
Authors: Ishizaki Toshio , Asakawa Yasuteru , Furihata Tetsuya , Kato Junichi , Kawasaki Osamu
Published: October 2002

A low-profile piezoelectric ceramic ladder filter was developed. It is less than 2 mm high. Therefore it is suitable for super compact portable telephones. New rectangular bar resonators using the length expander mode were presented and a ladder filter was constructed using these new resonators. The optimization of capacitance ratio and resonator support structure in resonator design and a new piezoelectric ceramic material were discussed. In particular, the heat resistant properties of the material and the vibration transmission to the support structure were considered. These properties were improved by using the new ceramic material and a new support structure. Finally an experimental filter was constructed. It exhibited excellent characteristics which satisfied the specifications for the second IF filter of a digital cellular telephone.
Quartz Microsensors for Monitoring Thin Film Thickness
Authors: Hirofumi Kawashima Hirofumi Kawashima , Kenji Sunaga Kenji Sunaga
Published: October 2002

This paper describes a quartz microsensor for monitoring thin film thickness. A microresonator of tuning fork-type with stepped vibration bars vibrating in torsion which can be approximately regarded as “clamped-free bar” is very available for monitoring thin film thickness because it has excellent frequency temperature behavior over a wide temperature range of room temperature to high one of about 200° C. In this paper, a relationship of resonant frequency to thin film thickness of Au and Al is theoretically and experimentally clarified for the microresonator, so that the frequency deviation is proportional to the film thickness deposited on the top of the tuning arms, and the calculated values are in good agreement with the measured ones. This microresonator is, therefore, very available for monitoring thin film thickness.
Measurement of Vibration at a Surface Using an Ultrasonic Probe
Authors: Naoto Wakatsuki Naoto Wakatsuki , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

We propose a contact ultrasonic probe which can distinguish between longitudinal and transverse vibrations. In contrast to a probe which uses a convergent beam, our probe has resolution which is not limited by the wavelength, so it has high resolution even at low frequencies. It is experimentally confirmed that the probe can discriminate longitudinal and transverse vibrations and that it has resolution higher than about 4 mm which is the wavelength of a carrier wave around 1 MHz.
Focusing Method in High-Impedance Material using Transmission Line Coupler: Ultrasonic Transmission Line Coupling Method
Authors: Kiyokazu Shikano Kiyokazu Shikano , Masasumi Yoshizawa Masasumi Yoshizawa , Norio Tagawa Norio Tagawa , Tadashi Moriya Tadashi Moriya , Shin-ichi Yagi Shin-ichi Yagi
Published: October 2002

A method for focusing an ultrasonic beam within a solid material is presented. Distributed point sources formed on the surface of the solid are used. The point sources are formed using the tip of an ultrasonic transmission line. Experimental results confirm that a beam can be generated and focused to any point within a solid material.
Acoustic Imaging for Archaeological Investigations Using Wavelet Transform
Authors: Hiroyuki Hachiya Hiroyuki Hachiya , Yukinori Amao Yukinori Amao
Published: October 2002

Recently, scientific methods such as acoustical survey or ground radar, have been used in the survey of buried remnants. Archaeological cultural property is often buried at a shallow depth of about 1 to 5 m. In the configuration presented here, we receive various waves, such as the direct wave along the surface, longitudinal wave and transverse wave, at almost the same time. In this paper, we propose a processing technique using the wavelet transform to separate the desired signal. From a survey experiment at the test site, it was found that this processing technique is useful for the reconstruction of underground images for archaeological investigations.
A New Experimental Arrangement for Energy Loss Measurements
Authors: Anuradha Bhagwat Anuradha Bhagwat , Devesh Kumar Avasthi Devesh Kumar Avasthi
Published: October 2002

We have demonstrated the use of secondary ion beams and stacked detector arrangement for measuring stopping power dE/ dx of any stopping medium. The advantages of the present setup are that the energy and ion species can be changed with ease; moreover, data needed for determination of energy loss can be collected simultaneously.
Nonthermal Influence of Microwave Power on Chemical Reactions
Authors: Shibata Chokichiro , Tomohiro Kashima Tomohiro Kashima , Kimihiro Ohuchi Kimihiro Ohuchi
Published: October 2002

To clarify the effect of microwave irradiation on acceleration of chemical reactions other than heating, Arrhenius' plots were taken for the disintegration reaction of sodium hydrogen carbonate water solution. Then to observe the influence of microwave field on the reaction, gas-generating velocities with different irradiated microwave powers were measured under a constant temperature condition. As a result, it was recognized that the microwave field acts to decrease the activation energy of the reaction. Next, pulsed and CW microwave powers, both having the same mean power, were applied to the solution and the pulsed microwave field was observed to accelerate disintegration more than CW. Although the molecular mechanism is not clear, a decrease of the activation energy seems to accelerate the reaction.
Measurement of Micrometer Order Displacement Using Phase-Shift Type Ultrasonic Correlation System in MHz Range
Authors: Kazuhiko Imano Kazuhiko Imano , Hiroshi Inoue Hiroshi Inoue
Published: October 2002

The ultrasonic correlation system was improved to detect a displacement which is much smaller than the wave length of sound, by shifting the phase of the reference wave with respect to the acoustic signal. To investigate the range resolution of the new system, micrometer order displacement was measured using MHz-range ultrasonic waves. Results obtained using the new system show good agreement with the values set by the precision micrometer stage. Range resolution better than λ/300 (1 µ m) has been achieved. As an application of the system, the surface topography was also investigated using a 5 MHz focused ultrasonic transducer in the 2-dimensional scanning mode. Surface displacement smaller than λ/10 was successfully imaged.
Nonlinear Piezoelectricity of PZT Ceramics and Acoustic Phase Conjugate Waves
Authors: Yamamoto Ken , Kokubo Akira , Ohno Masahiro , Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: October 2002

We succeeded in generating acoustic phase conjugate waves with nonlinear PZT ( Pb(Zr

x

Ti1-
x

)O3) ceramics. The efficiency of the phase conjugator, which is defined as the amplitude ratio of the phase conjugate wave to the incident wave, is found to be proportional to the variation in sound velocity under an applied electric field. We measured the sound velocity in PZT ceramics with different compositions by varying the applied electric field. The results correlated well with the observed efficiency. The PZT ceramics are generally more capable than LiNbO3 crystal of generating phase conjugate waves. We confirmed the time-reversal property of the phase conjugate waves by visualizing its propagation with the stroboscopic schlieren technique.
Pressure Dependence of Ferroelectric Properties in PbZrO3-PbTiO3 Solid State System under Hydrostatic Stress
Authors: Takashi Yamamoto Takashi Yamamoto , Yuzo Makino Yuzo Makino
Published: October 2002

Pressure dependence of ferroelectric properties in PbZrO3-PbTiO3 solid state system (PZT) were calculated under hydrostatic stress and compared with experimental results. When the ratio of electrostrictive coefficients in PZT, Q
11/Q
12 was exactly equal to -2.000, the ferroelectric properties were not affected by the application of hydrostatic pressure; i.e. isotropic compressive stress. At ratios other than Q
11/Q
12=-2.000, the Curie points were decreased with increasing hydrostatic pressure, in particular near the morphotropic phase boundary (MPB). The piezoelectric charge and voltage coefficients, d
ij and g
ij, increased and decreased, respectively, near the MPB with increasing hydrostatic pressure, due to the pressure dependence of the dielectric constant and spontaneous polarization.
Analysis of the Near-Field Transient Radiation Considering the Velocity Amplitude on the Transducer Face
Authors: Lawu Tjundewo , Tabei Makoto , Mitsuhiro Ueda Mitsuhiro Ueda
Published: October 2002

The velocity amplitude on the transducer face was estimated using the near-field transient radiation on the axis of the circular transducer obtained experimentally. The velocity amplitude can be obtained by deconvolving the pressure waveform with the electrical characteristics of the transducer and then integrating the result. Using the estimated velocity amplitude, the pressure waveforms were numerically calculated and compared with those obtained experimentally.
Trial Construction of a Noncontact Ultrasonic Motor with an Ultrasonically Levitated Rotor
Authors: Tohgo Yamazaki Tohgo Yamazaki , Junhui Hu Junhui Hu , Kentaro Nakamura Kentaro Nakamura , Sadayuki Ueha Sadayuki Ueha
Published: October 2002

We propose a new ultrasonic motor, in which the rotor is levitated and driven to rotate at very high speed by the ultrasonic field radiated from the stator into the air gap between the rotor and the stator. The noncontact bearing-less structure of this motor makes it possible to exceed the revolution speed limit of conventional contact ultrasonic motors, and develop a new application of ultrasonic motors. Two motors with different resonance frequencies are fabricated, and their characteristics are investigated experimentally.
Magnetotransport and Magnetic Properties of Mechanically Alloyed CoxCu100-x
Authors: Ueda Yuji , Shoji Ikeda Shoji Ikeda , Susumu Chikazawa Susumu Chikazawa
Published: October 2002

Co–Cu binary alloys, whose Co concentrations range from 10 to 30 at.%, are produced by mechanical alloying. The structure, magnetoresistance (MR), and magnetism have been investigated for the as-milled and annealed alloys. After milling for 50 h, a supersaturated solid solution of fcc-CoCu is formed at Co concentrations of 10 to 30 at.%. The Co

x

Cu100-
x

(x = 10 – 30) alloys annealed at 700° C for 1 h separate into two phases of fcc-Co and fcc-Cu. The maximum MR ratio, under 15 kOe at room temperature, is 6.4% for the sample with x = 20 annealed at 450° C for 1 h. The samples annealed at temperatures less than 450° C exhibit high MR ratio at x = 25. The magnetism of the sample with x = 20, which shows a maximum MR ratio, exhibits superparamagnetic behavior, but a slight ferromagnetic behavior have also been observed. Co–Cu alloys produced by mechanical alloying have a wide distribution of Co particle size with blocking temperature from low temperature to room temperature.
Optical Confinement in Thin Film Si Solar Cells by Diffuse Reflective Substrate
Authors: Shimokawa Ryuichi , Kenichi Ishii Kenichi Ishii , Tetsuo Takahashi Tetsuo Takahashi
Published: October 2002

Optical confinement in thin film crystalline Si solar cells on diffuse reflective substrates has been experimentally and theoretically investigated. First, optical properties of thin film cells and reflective substrates are quantitatively characterized using the photometry technique. Furthermore, optical confinement models for practical thin film cells on reflective substrates deviating from the Lambertian law are presented, and inspected by comparing computed and experimental optical-property results of realized 4.2 µ m thin film cells. It is thus found that optical confinement is mainly determined by both reflectivity and optical diffusivity of the reflective substrates and degraded by the medium buffer-layer. Finally, we present scenarios for future technological realization of high absorption efficiency.
Microscopic Approach to Shock Waves in Crystal Solids. II Rankine-Hugoniot Relations
Authors: Masaru Sugiyama Masaru Sugiyama , Toshiyuki Isogai Toshiyuki Isogai
Published: October 2002

By using the statistical-mechanical basic equations for shock wave phenomena in crystal lattices at finite temperatures, the Rankine-Hugoniot relations are derived from a microscopic point of view and their physical implications are discussed. Numerical analysis on the basis of the equations is also performed to elucidate microscopic modes, and the validity of the assumptions adopted in the derivation of the Rankine-Hugoniot relations is examined.
Directional Single-Electron-Tunneling Junction
Authors: Masamichi Akazawa Masamichi Akazawa , Yoshihito Amemiya Yoshihito Amemiya
Published: October 2002

This paper proposes a directional single-electron-tunneling (SET) junction that allows electron tunneling in only one direction. It is shown that this device will provide various SET circuits with novel functions in simple construction. Theoretical analysis indicates that a metal–insulator–insulator–metal (M–I–I–M) SET junction could achieve excellent directionality with a large forward/reverse conductance ratio of the order of hundreds of thousands. As one of the circuit applications, a multiple-valued memory cell using directional SET junctions is proposed and its writing and storage operation is simulated.
Quantitative Evaluation of Vertical Cracks by the Photothermal Beam Deflection Method
Authors: Takuji Nakanishi Takuji Nakanishi , Atsushi Yarai Atsushi Yarai
Published: October 2002

Artificially made narrow vertical cracks of various widths were detected and quantitatively evaluated using a photothermal beam deflection method (mirage detection method). In order to evaluate the influence of thermal characteristics, two test sample materials whose thermal conductivities largely differed from each other were chosen. Experimental investigations clarified that the vertical “signal amplitude depth” is proportionally related to crack widths when the crack widths are of almost the same order as the pumping beam spot size of the material.
Scanning Tunneling Microscope Studies on Recovery Processes of Sputter-Induced Surface Defects on Si(111)-7×7
Authors: Kazuya Yoneyama Kazuya Yoneyama , Keiichi Ogawa Keiichi Ogawa
Published: October 2002

Vacant regions have been introduced onto the Si(111)-7×7 surface by 1 keV Ar ion bombardment and studied by scanning tunneling microscopy. The vacant regions are defect regions where adatoms have been removed by Ar ion impact. When annealed at temperatures from 500°C to 730°C, the vacant regions recover the initial 7×7 structure via the new metastable 7×7 structure found in the present study. Both rate-controlling steps are described by single activation free energies with dominant -TΔS and minor ΔE terms. The activation entropies ΔS/(eV K-1) are found to be - 1.9 ×10-3 for the metastable 7×7 formation and -2.6×10-3 for the stable 7×7 formation.
Atomic Force Microscopy Images of Liquid-Phase-Adsorbed Pyridine Molecules on Stilbite(010)
Authors: Masaharu Komiyama Masaharu Komiyama , Minming Gu Minming Gu
Published: October 2002

For the first time molecular images of liquid-phase-adsorbed aromatics on a zeolite surface were obtained. Pyridine molecules adsorbed on a cleaved stilbite(010) surface from an aqueous solution were imaged by contact-mode atomic force microscopy. Adsorbed pyridine appears to form a 2-dimensional quasi-solid phase on the surface. The adsorbed layer exhibits an approximately hexagonal symmetry, with a unit cell dimension of 5.1 ±0.3 Å. Molecular orientation within the adsorbed layer is also discussed.
Analysis of Wafer Bonding by Infrared Transmission
Authors: Dieter Bollmann Dieter Bollmann , Christof Landesberger Christof Landesberger , Peter Ramm Peter Ramm , Karl Haberger Karl Haberger
Published: October 2002

In solid state technology, two silicon wafers can be combined by wafer bonding. Small particles between the two surfaces may cause voids. For quality control, the voids can be detected by transmission of infrared light, provided by a Nd:YAG laser at a wavelength of 1.064 µm, where silicon is transparent. The defects are made visible via a CCD-camera on the monitor of a computer and appear as interference rings. This paper describes a method to enhance the visibility of the defect relative to other superimposed patterns e.g. from metallization. The voids are deformed elastically by applicating an external air pressure inside an inspection chamber. Insufficient bonded wafers, caused by particles as small as 1/2 µm, can be detected by routine in order to enhance the yield.
Rapid Thermal Annealing Behavior of MoSi2/p-Si Schottky Contacts Formed at Various Deposition Rates
Authors: Ghader Eftekhari Ghader Eftekhari
Published: October 2002

The influence of deposition rate and rapid thermal annealing on the electrical properties of MoSi2/p-Si contacts were examined. It was experimentally determined that contacts formed at deposition rate of 0.6 nm/s have a better quality compared with the contacts formed at other deposition rates. Also, these contacts showed a better thermal stability than the contacts formed at other deposition rates. The formation of surface charges associated with defects and different grain sizes and their variation with deposition rate and annealing temperature and possible intermixing of elements at the interface were used to explain the observations.
Deterioration of the Frequency-Conversion Efficiency of a LiTaO3 Waveguide Device with Nonlinear Quasi-Phase-Matched Second-Harmonic Generation
Authors: Yamamoto Yukihiro , Yamaguchi Satoshi , Yamada Noriko , Matsumoto Takahiro , Kondo Yukiko
Published: October 2002

A quasi-phase-matched second-harmonic generation in a periodic-lens sequence waveguide on -z-face LiTaO3 (lithium tantalate) crystal was observed. The fabricated waveguide is a segmented domain-inverted waveguide. Second-harmonic generation was not observed after three months after fabrication. We conclude that the phenomenon stems from the rediffusion of protons which were used to fabricate the domain-inverted region of the waveguide.
The Effect of Dopant Concentration on the Mobility of a Triphenylmethane Doped Polymer
Authors: Magin E. H. , W. T. Gruenbaum W. T. Gruenbaum , P. M. Borsenberger P. M. Borsenberger
Published: October 2002

Hole mobilities have been measured in poly(styrene) (PS) doped with bis(4-N,N-diethylamino-2-methylphenyl) (4-4-methoxyphenyl)methane (TPM). TPM is a weakly polar donor molecule with a dipole moment of 2.1 D. The results are described by a formalism based on disorder. The formalism is based on the assumption that charge transport occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. The parameters of the formalism are σ, the energy width of the hopping site manifold, Σ the degree of positional disorder, µ0 a prefactor mobility, and ρ0 a wavefunction decay constant. The energy widths are between 0.105 and 0.113 eV, increasing with increasing TPM concentration. The concentration dependence of the widths is described by an argument based on dipolar disorder. Values of Σ are between 2.4 and 3.8, increasing with increasing dilution. The prefactor mobilities are between 1.6×10-5 and 7.4×10-2 cm2/ Vs and can be described by a wavefunction decay constant of 1.2 Å.
Liquid Crystalline Behaviors of Conducting Polyacetylene Derivative with Mesogenic Substituent and Its Mixture with Ferroelectric Liquid Crystal
Authors: Katsumi Yoshino Katsumi Yoshino , Kentaro Kobayashi Kentaro Kobayashi , Katsunori Myojin Katsunori Myojin , Masanori Ozaki Masanori Ozaki , Kazuo Akagi Kazuo Akagi , Hiromasa Goto Hiromasa Goto , Hideki Shirakawa Hideki Shirakawa
Published: October 2002

Liquid crystalline behavior has been studied in a polyacetylene derivative substituted with long side chains containing phenylcyclohexyl mesogenic units such as poly [5-( p-( trans-4'- n-octylcyclohexyl)phenoxy)-1-pentyne] (PPCH803A). A texture typical of smectic liquid crystal has been observed using an optical microscope. The smectic layer structure has also been confirmed by X-ray diffraction. Anisotropy of the optical absorption spectrum of the smectic phase, which is consistent with the results of the X-ray diffraction measurements, has been observed. The band gap of PPCH803A in the liquid crystalline phase has been evaluated as 2.9 eV, which is smaller than that in the isotropic liquid phase. The dielectric constant of PPCH803A changes stepwise at the phase transition temperatures. A mixture of PPCH803A with a ferroelectric liquid crystal of low molecular weight exhibits a large dielectric constant and unique ferroelectric behavior.
Crystal and Electrical Characterizations of Oriented Yttria-Stabilized Zirconia Buffer Layer for the Metal/Ferroelectric/Insulator/Semiconductor Field-Effect Transistor
Authors: Hirai Tadahiko , Teramoto Kazuhiro , Nagashima Kazuhito , Koike Hiroshi , Matsuno Shinya , Tanimoto Satoshi , Yasuo Tarui Yasuo Tarui
Published: October 2002

Using reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and X-ray pole figure measurements, we evaluated the crystallinities of yttria-stabilized zirconia (YSZ) thin films as an intermediate layer for metal/ferroelectric/insulator/semiconductor-structure field-effect transistors (MFIS-FETs). A highly oriented YSZ film was grown on a Si(100) substrate by the vacuum evaporation method. The [100] axes of the YSZ crystals were aligned parallel to [100] axes of Si crystals in the plane. In addition, electrical characterizations of the highly oriented YSZ thin films on Si(100) were evaluated from current–voltage ( I–V ) and capacitance–voltage ( C–V ) measurements. The I–V measurement indicated a breakdown field of about 3 MV/cm (at I=1 nA/cm2). The C–V measurement results suggest that mobile ions were present in the YSZ films. Oriented perovskite PbTiO3 films were deposited on YSZ crystal and YSZ/Si(100) substrates by the digital chemical vapor deposition (CVD) method. These PbTiO3 films included many PbTiO3 grains with their [100] axes parallel to the [100] or [110] axis of YSZ crystals in the plane of the PbTiO3/YSZ interface.
Surface Electronic Properties and Atomic Images of the As-prepared Nd1Ba2Cu3Oy Single Crystals
Authors: Ting Wu , Egi Toshio , Itti Rittaporn , Kuroda Kiyoshi , Naoki Koshizuka Naoki Koshizuka , Shoji Tanaka Shoji Tanaka
Published: October 2002

Recently, high quality single crystals of Nd1Ba2Cu3O

y

(Nd123) high temperature superconductors (HTSC) have been successfully fabricated in our laboratory. In this paper, parts of the results of surface characterization of Nd123 single crystals employing an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) are reported. Atomic images are shown. The surface natural termination layer is unambiguously determined. It is demonstrated that the surfaces of the as-prepared single crystals of Nd123 HTSC are stable and clean in air. The effect of surface defect structures on the surface electronic properties is also investigated.
Surface Steps Observed in a Dry Annealed z-Cut LiNbO3 Substrate
Authors: Hirotoshi Nagata Hirotoshi Nagata , Kaori Shima Kaori Shima
Published: October 2002

Surface reformation is observed in an OH-reduced z-cut LiNbO3 single-crystal substrate after annealing at 1000° C in a dry oxygen atmosphere. Atomic force microscopic observation reveals a step-like texture with step height of 0.7 nm height, corresponding to half of the z-axial length of LiNbO3.
Calibration of the Stark-Broadening Parameters of Two	He I Lines with Forbidden Components
Authors: Pérez C. , Rosa I. de la , Aparicio J. A. , S. Mar S. Mar , M. A. Gigosos M. A. Gigosos
Published: October 2002

Measurements of the Stark-broadening parameters of two \HeI lines with forbidden components, have been done in a pulsed arc plasma. Electron density, ranging from 1.50×1022 to 1.45×1023 m-3, is obtained by the interferometry of two wavelengths. Plasma temperature, determinated by Boltzmann plots of several \HeIlines, lies in the interval 16 000–25 000 K. A set of four geometrical profile parameters are obtained and compared with previous experimental and theoretical results. The empirical formulae proposed in this paper can be used in plasma diagnostics.
Recovery of SEM Image by In-Situ Cleaning of Contaminated Objective Aperture
Authors: Yuichirou Yamazaki Kenji Ohtoshi , Motosuke Miyoshi Motosuke Miyoshi
Published: October 2002

We studied the effect of in-situ cleaning of a contaminated scanning electron microscope (SEM) objective aperture, applying the down-flow ashing process with a O2+CF4 gas mixture. Model experiments, using resists instead of contamination layers, were carried out and empirical equations which describe the dependence of etching rates on experimental parameters were obtained. A conversion factor between resist and contamination layer etching rates was experimentally obtained, and the conditions required for in-situ cleaning were determined. By applying in-situ cleaning, the SEM images, which had deteriorated after two weeks of operation, were recovered to nearly the same level of quality as those obtained using a new aperture.
Stable Solution Method for Viscoelastic Oxidation Including Stress-Dependent Viscosity
Authors: Tetsuya Uchida Tetsuya Uchida , Masato Fujinaga Masato Fujinaga , Norihiko Kotani Norihiko Kotani , Satoru Kawazu Satoru Kawazu , Hirokazu Miyoshi Hirokazu Miyoshi
Published: October 2002

A new computer program that simulates viscoelastic oxidation of silicon has been developed. Since in this program a tangential procedure is used for time stepping, numerical stability has been improved, and the instability problem that arises from the incorporation of stress dependence into oxide viscosity has been resolved. Thus, oxidation-induced stresses calculated by our program using stress-dependent viscosity have reasonable magnitude over the entire device area. Moreover, in our program, volume expansion due to oxidation of silicon was treated as a dilational strain, as opposed to its treatment as a forced displacement of oxide/silicon interface or a uniaxial strain perpendicular to the interface in most previous programs. Due to this difference, our program can simulate the generation of intrinsic stress below viscous flow temperature (ca. 960°C), and as a result, stress distribution calculated by our program changes drastically at the viscous flow temperature.
Microwave Properties of Y1Ba2Cu3O7-x Step-Edge Josephson Junction Series Arrays
Authors: Yoshikawa Shuichi , Yamaguchi Keiichi , Hayashi Kunihiko , Katsumi Suzuki Katsumi Suzuki , Youichi Enomoto Youichi Enomoto
Published: October 2002

Effects on microwave detection of a series-connected Josephson junction array are examined. The series-connected 10 step-edge Josephson junctions (10-SEJJs) are fabricated by Y1Ba2Cu3O7-
x

thin films on MgO substrates. Their responsivities as microwave broad-band detectors are evaluated by constructing microstrip circuits for measuring transmission and return power. 948 V/W is obtained at 17 K. This value is several times greater than 139 V/W of a single SEJJ at 17 K. Additionally, the return power from 10-SEJJs is less than that from the single SEJJ, as the bias current or the temperature increases. The small return power is attributed to the increase in the normal resistance of the SEJJ.
Mössbauer Study of (Fe 1-xCox)7Se 8
Authors: Kim Eng Chan , Kim Sin Giu Kang
Published: October 2002

(x=0.02, 0.05, 0.08) has been studied with Mössbauer spectroscopy and X-ray diffraction. The crystal structure is found to be a triclinic superstructure of the NiAs structure while Fe7 Se8 has a hexagonal structure. Abrupt change of quadrupole shifts near 124 K suggests that the spin-rotation transition proceeds abruptly, in contrast with the gradual transition reported for Fe7 Se8 with a triclinic superstructure. Isomer shifts indicate a ferrous character for the iron ions at all four sites. Both Néel and Debye temperatures are found to decrease with increasing cobalt concentration.
Application of Zn-Compound Buffer Layer for Polycrystalline CuInSe2-Based Thin-Film Solar Cells
Authors: Kushiya Katsumi , Nii Tetsuro , Sugiyama Ichiro , Sato Yasuhiko , Yoshitugu Inamori Yoshitugu Inamori , Hiroshi Takeshita Hiroshi Takeshita
Published: October 2002

In order to meet the requirement for the development of a more environment-friendly device structure for polycrystalline CuInSe2-based thin-film solar cells, Zn compound buffer layers for use as an alternative to CdS buffer layers have been fabricated by a chemical-bath deposition (CBD) method which is believed to be cost-effective and applicable to large-area deposition. CIS-based thin-film solar cells with a Zn(O, OH)

x

buffer layer showed a relatively low efficiency of about 10% because of the difficulty in the reduction of the amount of OH- ions in the buffer layer. By adding a sulfur source to the CBD solution as a new approach to reduce the amount of OH- ions, a dramatic decrease in the content of hydroxide in the buffer layer and the formation of a better heterointerface between the CIS-based thin-film absorber and the ZnO window layer were achieved simultaneously for the first time. The application of Zn(O, S, OH)

x

as a buffer layer to CIS-based thin-film solar cells led to the higher efficiency of 12.8% on the active area of 3.2 cm2. Zn(O, S, OH)

x

fabricated by a CBD method was demonstrated to be a promising alternative to CdS and a more environment-friendly buffer layer, although further investigation is required to understand the mechanisms of the irradiation effect.
Optimization of Silicon-Based 2-Terminal Tandem Solar Cells with GaAs1-xPx and InGa1-xPx as Top Cell Material
Authors: Yuji Komatsu Yuji Komatsu , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

A new structure of Si-based 2-terminal tandem solar cells was numerically analyzed. The structure was optimized to obtain high efficiency considering realistic material parameters. Gallium arsenide phosphide (GaAs_1-xP_x) and indium gallium phosphide (In_1-xGa_xP) were proposed as top cell materials. The conversion efficiency of the cell was calculated by simulating its voltage–current performances under the operating conditions. An efficiency of 33.1% can be expected for a GaAs_0.73P_0.27/Si cell and 34.4% for an In_0.57Ga_0.43P/Si cell. In_1-xGa_xP was shown to be more promising as a top cell material because it has a larger absorption coefficient than aAs_1-xP_x.
Novel Method of Measuring Surface Torsional Anchoring Strength of Nematic Liquid Crystals
Authors: Tadashi Akahane Tadashi Akahane , Hideki Kaneko Hideki Kaneko , Munehiro Kimura Munehiro Kimura
Published: October 2002

A simple and accurate method of measuring the surface torsional anchoring strength of nematic liquid crystals is proposed. This method is based on the simultaneous determination of the actual twist angle and the cell gap (optical retardation) of a twisted nematic cell in which the easy axes of the upper and lower substrates are at a particular angle ( e.g., 90°). The TN cell is placed between two polarizers. The TN cell and the analyzer are mounted on rotatable stages. The measurement procedure consists of the following steps. (1) Using monochromatic light, we minimize the amount of light transmitted by rotating both the TN cell and the analyzer (we denote these minimizing angles of the analyzer and the TN cell from the polarizer as Ψ p
(1) and Ψ0
(1), respectively. (2) We set the TN cell at a particular angle from Ψ0
(1), and minimize the amount of light transmitted by rotating only the analyzer (we denote this minimizing angle of the analyzer as Ψ p
(2)). From the values of Ψ p
(1) and Ψ p
(2), we can determine both the actual twist angle and the optical retardation using the analytical expression for optical transmissivity based on the Jones matrix method. We discuss the accuracy of this method. Experimental examples are also shown.
Influence of Poling Field on Polymerization in Polyurea Thin Films for Second-Harmonic Generation Prepared by Vapor Deposition Polymerization
Authors: Segi Takeshi , Suzuoki Yasuo , Tabata Akimori , Takagi Teruyoshi Mizutani
Published: October 2002

Using 4,4′-diphenylmethane diisocyanate and 1,4-diamino-2-nitrobenzene (DNB), an aromatic polyurea thin film (PU(DNB)) was fabricated by vapor deposition polymerization. In PU(DNB), although the enhanced optical nonlinearity due to the introduction of the NO2 groups was achieved, a drastic decay of second-harmonic intensity was observed immediately after the poling field was turned off at 200° C. The structural analysis revealed that the polymerization proceeded during heat treatment, but not during the poling process. This was attributed to the reduction of the reactivity of DNB monomers under the poling field due to possible interaction between the NO2 group (electron acceptor) and the NH2 group (electron donor) through the π-electron system.
Wavelength-Multiplexed Holographic Recording in Cerium Doped Strontium Barium Niobate by Using Tunable Laser Diode
Authors: Tatsuya Kume Tatsuya Kume , Koutarou Nonaka Koutarou Nonaka , Manabu Yamamoto Manabu Yamamoto
Published: October 2002

Seven multiplexed two-dimensional images are recorded and reconstructed by wavelength-multiplexed holographic recording in a cerium (Ce) doped strontium barium niobate (SBN) single crystal by using a tunable laser diode. Analytical formulas for calculating diffraction efficiency are derived by using modified coupled wave equations. Wavelength and angle selectivities of the holograms, which indicate the crosstalk between the multiplexed holograms, agree well with theoretical selectivities derived from the analysis. The theoretical and experimental results suggest that 300 to 400 holograms can be multiplexed.
Dynamic Simulation of Erosion and Deposition of a Tungsten Surface Due to High-Fluence Bombardment of Carbon Ions in Plasmas
Authors: Kaoru Ohya Kaoru Ohya , Jun Kawata Jun Kawata , Akio Harada Akio Harada
Published: October 2002

The erosion-deposition process of a tungsten surface bombarded by Maxwellian carbon ions is investigated using a Monte Carlo simulation model which combines dynamic composition change in the surface layer with transport of sputtered particles in a scrape-off layer plasma. During ion bombardment at ion temperatures of 50–70 eV, a transition from erosion to deposition is observed without transport in the plasma. With transport, however, only carbon deposition occurs due to redeposition of sputtered carbon atoms.
Measurements of the Off-Angle of Crystal Surface and the Refractive Index of Crystal for X-rays by the X-ray Two-Incidence Surface Method
Authors: Takehiro Maehama Takehiro Maehama , Chushin Afuso Chushin Afuso
Published: October 2002

A new convenient diffraction measurement technique is proposed, which enables us to measure exactly the off-angle β of a crystal surface and the refractive index for X-rays n. When X-rays which are Bragg-reflected by the first crystal enter the second crystal (sample) through the surface and the side at the same time, both X-rays propagate in the crystal in slightly different directions because of the refraction effect. Therefore, the rocking curve which is measured by rotating the second crystal around the axis perpendicular to the incident plane has double peaks. From the angle between the two peaks, β and n of the crystal can be estimated. The applicability of the proposed method to GaAs (100) surfaces with β=0, 2 and 3° is demonstrated.
Formation of an X-Ray microbeam Using a Schwarzschild X-Ray Objective
Authors: Iketaki Yoshinori , Horikawa Yoshiaki , Shouichirou Mochimaru Shouichirou Mochimaru , Koumei Nagai Koumei Nagai
Published: October 2002

A soft X-ray microbeam was formed using a Schwarzschild X-ray objective designed to have transmittance at a wavelength of 14 nm. The widths of the X-ray beam on and off the focal plane were measured using a knife-edge method, and it was found that the size of the X-ray microbeam was 70 nm on the focal plane. We obtained X-ray transmission images of a silicon etching pattern and demonstrated that an image at a spatial resolution of better than 100 nm was obtained using the microbeam. We also discuss practical applicability of the microbeam.
Evaluating Polarization in Dielectrics with Continuously Distributed Dipole Relaxation Time by Discharge Current Transient Spectroscopy
Authors: Hideharu Matsuura Hideharu Matsuura
Published: October 2002

The application of discharge current transient spectroscopy (DCTS) to the evaluation of the steady-state polarization P
s(τ) in dielectrics with continuously distributed dipole relaxation time (τ) is discussed. The method proposed in Jpn. J. Appl. Phys. 35 (1996) 2216 can be used to evaluate P
s(τ) only in dielectrics with discrete τ. Using the method discussed here, P
s(τ) corresponding to the transient discharge current, which obeys a power law with respect to discharge time, can easily be evaluated.
Pressure Effects on Electrical and Optical Properties of Si–As–Te Chalcogenide Glasses Fabricated in the Gravity Environment and in a Microgravity Environment
Authors: Wahid Shams-Kolahi Wahid Shams-Kolahi , Michihiro Kobayashi Michihiro Kobayashi , Hiromasa Hanzawa Hiromasa Hanzawa , Hiroaki Okamoto Hiroaki Okamoto , Shoichi Endo Shoichi Endo , Yuki Kobayashi Yuki Kobayashi , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Pressure-induced changes in the electrical resistivity and optical-absorption spectrum have been studied for two kinds of Si9As14Te21 ternary chalcogenide amorphous semiconductor samples fabricated in a microgravity environment and under the gravity environment of the earth. Band gap narrowing occurs for both materials as is found commonly in chalcogenide glasses, whereas the change is less pronounced for the space-made material than for the terrestrial-made material. A significant difference is found in the pressure-induced change of the optical Urbach energy, that is, it increases for the space-made material but decreases for the terrestrial-made material in the low-pressure regime. These observations are accounted for upon assuming that the origin of the electronic states at the top of the valence band differs for these two materials although the material composition is identical.
Yield Measurement of Secondary Electrons Emitted from Silicon Dioxide Film in Negative-Ion Bombardment
Authors: Yoshitaka Toyota Yoshitaka Toyota , Hiroshi Tsuji Hiroshi Tsuji , Yasuhito Gotoh Yasuhito Gotoh , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

The yield of secondary electrons emitted from insulating materials subjected to negative-ion bombardment was studied. In general, such measurements for insulating materials are difficult because surface charging due to ion implantation makes the apparent yield unity. We used silicon dioxide (SiO2) film and a small ion current for the yield measurements. As a result, charge compensation due to the leakage current minimized the surface charging and the true yield was obtained. The experimental results showed that secondary electrons emitted due to negative-ion bombardment consist of electrons due to both kinetic emission and detachment from negative ions. In addition, it was found that the yield depends on the ion species. It was concluded that the same tendencies as those for negative-ion-implanted conductive materials are observed.
Preparation of SrTiO3 Films on 8-Inch Wafers by Chemical Vapor Deposition
Authors: Arai Tomoko Tsuyama , Inaishi Yoshiaki , Sawado Yoshinori , Ichizo Kobayashi Ichizo Kobayashi , Junichi Hidaka Junichi Hidaka
Published: October 2002

SrTiO3 films were grown on 8-inch-diameter Si substrates by
chemical vapor deposition [CVD] using bis(dipivaloylmethanato)
strontium [ Sr(DPM)2], titanium tetraisopropoxide [ Ti(OiPr)4] and O2.
We have developed an oil-circulating showerhead-type nozzle to prevent
condensation and decomposition of source materials. Conditions of
supplying Sr(DPM)2 were investigated with respect to cylinder pressure
and the charge in the cylinder, using a simple vapor transport system.
The deposition rate of SrTiO3 films on 8-inch wafers was improved to
2 nm/min by increasing the charge in the source cylinder and decreasing
the cylinder pressure. A thickness uniformity of 3.4% and a composition
uniformity of 4.6% were obtained by complete mixing of gases. A step
coverage of 85% was obtained using Sr(DPM)2, titanyl
bis(dipivaloylmethanato) [ TiO(DPM)2] and N2O.