bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Analysis of Internal Moving Organs Using Super-Resolution Echography
Authors: Masuda Kohji , Ishihara Ken , Nagakura Toshiaki , Tsuda Takao , Furukawa Toshiyuki , Maeda Hajime , Sadatoshi Kumagai Sadatoshi Kumagai , Shinzo Kodama Shinzo Kodama
Published: October 2002

We have developed super-resolution echography to visualize instantaneous velocity and acceleration of internal organs from time-series echograms recorded by a high-frame-rate echograph. The algorithm for this method involves subtraction of two echograms, dividing the difference by the brightness gradient of the first echogram, and normalization of that result by the time interval between the two echograms. Velocity or acceleration is classified into some suitable colors and superimposed on the original B-mode image. Functional diagnosis of moving organs can be made by visualizing instantaneous velocity. In the case of the heart, hypokinesis can be distinguished from a normal heart by the value and the variation of colored parts representing instantaneous velocity. This can also be applied to the liver to observe pulsatile motion. By visualizing instantaneous acceleration, increase or decrease of velocity can be detected. Throb timing and the location of arrhythmia in a heart can be observed. This method has the possibility of contributing to noninvasive functional and characteristic evaluation.
Far-Infrared Spectroscopy of LiH using a Tunable Far-Infrared Spectrometer*
Authors: Matsushima Fusakazu , Odashima Hitoshi , Wang Dongbing , Shozo Tsunekawa Shozo Tsunekawa , Kojiro Takagi Kojiro Takagi
Published: October 2002

An Evenson-type tunable far-infrared spectrometer has been built to measure rotational transition frequencies of LiH up to 5 THz. R(J) transitions with J=0 to 10 (v=0) and J=1 to 10 (v=1) of 7LiH, and those with J=1 to 9 (v=0) of 6LiH have been measured. Frequency measurements with an accuracy of tens of kHz enable us to improve rotational parameters of LiH.
Growth of Pb-Phthalocyanine Thin Films on MoS2 Surfaces Studied by Means of Low-Energy Electron Transmission Spectroscopy
Authors: Ueno Nobuo , Suzuki Katsumi , Momose Masahiro , Masato Kushida Masato Kushida , Kazuyuki Sugita Kazuyuki Sugita
Published: October 2002

Low-energy electron transmission (LEET) spectroscopy was used to study the growth of Pb-phthalocyanine (PbPc) thin films on MoS2 single crystal surfaces. We observed LEET features typical of the ultrathin films which were prepared by direct molecular-beam deposition of PbPc molecules as well as by thinning thicker films by heat treatment. The dependence of the work function of the film on the film thickness gave a minimum value for the ultrathin films which exhibit LEET features different from those for thicker films. The results indicate that the ultrathin film consists of a monolayer of PbPc molecules and LEET spectroscopy is useful in observing monolayer growth of functional organic molecules. Furthermore, the effects of heat treatment and aging of the PbPc films are investigated.
Light Beating Spectroscopy of Brillouin Scattering in Solid Polymer
Authors: Hattori Koichiro , Matsuoka Tatsuro , Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: October 2002

Hyper-resolution of the optical beating technique revealed a very accurate shape of the Brillouin spectrum, which had been deformed by the insufficient resolution of Fabry-Perot technique. The curve observed in liquid CS2 near room temperature at the scattering angle 10.7° showed a Rayleigh peak whose height is about 100 times higher than the two Brillouin components. This spectrum shape, which is far from the triplet structure, is theoretically understood in terms of the Landau-Placzek ratio which predicts the ratio of the scattered power of Rayleigh to Brillouin components. This optical beating technique was, for the first time, used for a solid specimen; phonon peaks were observed in acrylic resin over a range from 90 to 460 MHz. The phonon velocities thus determined showed a strong dispersion of Δν=40 m/s above the ultrasonic velocities obtained in the MHz range by the pulse-echo method. The phonon decay time was also determined from the width of the Brillouin peaks and correlated with the ultrasonic absorption. The results of velocity and absorption consistently suggested a broad relaxation effect expanding over 4 decades of frequency centered around 1 MHz.
Brillouin Spectra and Structural Relaxation in ZnCl2–KCl Binary Melts
Authors: Zhu Hongmin , Iwabuchi Katsuyuki , Yuzuru Sato Yuzuru Sato , Tsutomu Yamamura Tsutomu Yamamura
Published: October 2002

The Brillouin scattering experiment has been carried out for molten ZnCl2-KCl binary melts over the composition range 0–45 mol% KCl. The complete profiles of Rayleigh-Brillouin spectra were obtained at scattering angle of 90°, and at temperatures ranging from 550 to 1000 K by the use of carefully purified samples. Marked change in the shape of the spectrum with variations in temperature and composition has been observed and has been concluded to be due to structural relaxation in the melts. A dispersion of sound wave propagation was observed in the melts in the hypersonic region. The spectra have been analyzed based on the viscoelastic theory on the assumption of single relaxation. The sound velocities at the limiting low and high frequencies and the relaxation time have been determined.
Photoacoustic Spectroscopy of CuxS/CdS Heterojunction
Authors: Yamagami Tetsunari , Okamoto Yoichi , Jun Morimoto Jun Morimoto , Toru Miyakawa Toru Miyakawa
Published: October 2002

The Cu

x

S/CdS heterojunction interface was studied by photoacoustic spectroscopy (PAS). By changing the modulation frequency of the incident light, the edge absorption of Cu

x

S and CdS layers clearly appeared not only in the PA intensity spectrum but also in the PA phase spectrum. The PA spectrum of the thermally annealed Cu

x

S/CdS heterojunction showed evidence of Cu diffusion into the CdS single crystal.
Determination of Material Thermal Properties Using Photoacoustic Signals Detected by a Transparent Transducer
Authors: Horita Susumu , Konishi Hideaki , Naoki Miyabo Naoki Miyabo , Tomonobu Hata Tomonobu Hata
Published: October 2002

We demonstrated a new simultaneous determination technique for the thermal diffusivity and the thermal conductivity of a material using photoacoustic (PA) signals detected by a transparent transducer. The samples were illuminated by a pump beam directly or through the transducer, and these two kinds of PA signals were analyzed. It was shown theoretically that we cannot ignore the two effects of small optical absorption of the transducer and the thermal resistance between the sample and the transducer upon detection of PA signals from the viewpoint of quantitative evaluation. The thermal resistance was provided by a small air gap layer. The thermal properties of Si, InP and Ta were determined by this technique and these measured values were in good agreement with those in the literature.
Analysis of Scholte Wave between Seawater and Marine Sediment
Authors: Kimura Masao , Dunlop John I. , Jessup Bryan L. , Le Linda
Published: October 2002

In this study,in situexperiments of Scholte waves between seawater and marine sediment are conducted in Jervis Bay and Hunters Bay, Australia, and velocity dispersion characteristics are obtained using the multiple filter method.
Polarimetric Optical Fiber Hydrophone Using Birefringence of LiNbO3
Authors: Koiwa Hideyo , Takahashi Sumio , Okajima Katsunori , Nagata Toshiaki Kikuchi
Published: October 2002

A polarimetric optical fiber hydrophone using a LiNbO3 element and a single-mode optical fiber was constructed. As a light source a He–Ne laser was used. The principle is based on the change in birefringence of LiNbO3 by sound pressure. The linear relationship between the output voltage and sound pressure has been obtained for sound pressure levels from 144 to 179 dB re 1 µPa. As the change of birefringence caused by sound pressure is small, the linearity is expected to extend further to high-sound-pressure levels.
Reabsorption of Visible Luminescence in Porous Si
Authors: Murayama Kazuro , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

It is found that the photoluminescence spectrum of a porous Si sample changes from one peak to two peaks with decreasing temperatures to less than 131 K. The spectrum change could be interpreted in terms of the reabsorption of the luminescence by absorption centers stable at low temperatures in porous Si. This suggests that some of the anomalous temperature dependences of the luminescence intensity can be explained by the reabsorption.
Doping Properties of Zinc in InAlGaAs Grown by Low-Pressure Metal-Organic Vapor-Phase Epitaxy
Authors: Tsuji Masayoshi , Kikuo Makita Kikuo Makita , Kenko Taguchi Kenko Taguchi
Published: October 2002

The electrical and optical properties of Zn-doped InAlGaAs layers grown by low-pressure metal-organic vapor-phase epitaxy are studied with different Al contents. Hole concentration of InAlGaAs decreases with increasing Al content, which is due to the relationship between the Al content and the Zn acceptor binding energy derived from the low-temperature 2K photoluminescence spectra. The deterioration of Zn-doped InAlAs layers is observed in layers grown with a lower V/III gas-phase ratio, which is the result of an oxygen-related deep level.
Changes in Collector and Base Currents for AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Iizuka Norio , Tohru Sugiyama Tohru Sugiyama , Masao Obara Masao Obara
Published: October 2002

The changes in the collector and base currents after a 5-min operation with a collector current density of more than 2.5×104 A/cm2 has been investigated for AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with a Be doped base layer. Their dependence on the V/III flux ratio during molecular beam epitaxy (MBE) growth and on ion implantation conditions for emitter isolation were examined. A larger change in the collector current was observed for HBTs which were grown under a lower V/III ratio or fabricated under a heavier implantation condition. A change in the base current has also been found even when the change in the collector current was small. The change has been attributed to a decrease in the non-radiative recombination rate. A high V/III flux ratio growth and a low damage implantation are needed to suppress the changes.
Homogeneous Nucleation of Misfit Dislocations in Strained Layers
Authors: Lee Hyo-Hoon Park
Published: October 2002

The mechanism of strain relaxation by homogeneous nucleation of misfit dislocations from the interface in strained layers has been investigated. Transmission electron microscopy examination in a coherently strained GaInAsP/GaInP heterostructure demonstrated that the critical thickness of the strained layer for the nucleation of 90° 1/6<112> partial dislocations from a tensile interface is much shallower than that of 60° 1/2<110> perfect dislocations from a compressive interface. A critical thickness model for the interface nucleation of these dislocations is developed as a modification of the classical surface nucleation model.
Positive- and Negative-Image Processings Based on Photoinduced Anisotropy in Methylred-doped Polyvinyl Alcohol Film
Authors: Takeda Tomoaki , Hirofumi Fujiwara Hirofumi Fujiwara , Kazuo Nakagawa Kazuo Nakagawa
Published: October 2002

Positive- or negative-contrast image processing and partially inverted-contrast image processing were demonstrated with the use of methylred-doped polyvinyl alcohol (MR/PVA) film. The mechanism for spatial light modulation is based on photoinduced anisotropy of anisotropic methylred-dye molecules doped in a transparent polyvinyl alcohol film. This dye-doped film exhibits large optical anisotropy at relatively small powers of argon-ion laser, and continuous-tone image processings can be performed. With MR/PVA film of 40 µm thickness and a writing beam of 100 mW/cm2 at 488 nm, the phase difference due to photo-induced anisotropy (corresponding to the birefringence) of 115° at 530 nm was obtained. The spatial resolution of the MR/PVA film was more than 30 lines/mm.
Ionization Energy Levels of Divalent Cations and Transition Metal Cations in Y3Fe5O12 Single Crystals
Authors: Furukawa Yasunori , Masayoshi Sato Masayoshi Sato , Steven A. Markgraf Steven A. Markgraf
Published: October 2002

Correlation between transparency and electrical resistivity for Y3Fe5O12 single crystals doped with various divalent and transition metal cations is examined. Regardless of the dopant, when the electrical resistivity becomes greater than 105 Ω ·cm the transparency at 1.5 µm drastically increases. The activation energy for various dopants is determined from the temperature dependence of the electrical resistivity. The activation energy differs for each dopant, and the value gives the ionization level for carriers in the forbidden band gap.
Deep Impurity Centers in CdS Single Crystals Studied by Spectral Analysis of Deep Level Transient Spectroscopy
Authors: Yoshino Junya , Tanaka Kazuyoshi , Okamoto Yoichi , Jun Morimoto Jun Morimoto , Toru Miyakawa Toru Miyakawa
Published: October 2002

Deep impurity centers in CdS single crystals were studied by using spectral analysis of deep level transient spectroscopy (SADLTS) to obtain the emission rate spectrum. We found one deep level below the conduction band with the activation energy and the capture cross section distributed around their central values E
0=0.31 eV and σ0=4.0×10-16 cm2 over widths ΔE=0.013 eV and Δσ=9.3×10-17 cm2, respectively.
ZrAl3 Intermetallic Compound Thin Film as a Diffusion Barrier between Al and Au Layers
Authors: Jin-Kuo Ho Jin-Kuo Ho , Kwang-Lung Lin Kwang-Lung Lin
Published: October 2002

A layer of intermetallic compound ZrAl3 of 100 nm thickness functioning as a diffusion barrier between Al and Au thin films was investigated. The performance of the barrier was characterized by in situ monitoring of electrical resistance during heating under vacuum. The value of sheet resistance remained constant up to about 340° C; then it increased gradually to a maximum at about 550° C. The increase of resistance reflected the occurrence of interactions between thin films. With the aid of Auger electron spectroscopy depth profile and X-ray diffraction analyses, it was found that the degradation of the ZrAl3 barrier layer was mainly attributed to the diffusion of Al through ZrAl3 grain boundaries, reacting with Au to form Au5Al2 initially on the surface at 300° C. As temperature was increased further, AuAl2 was found at the Au/ZrAl3 interface.
Step Structure Transformation Induced by DC on Vicinal Si(111)
Authors: Akiko Natori Akiko Natori
Published: October 2002

The step structure transformation between a regular step and a bunching structure on Si(111) induced by DC is studied by means of the extended BCF (Burton Cabrela Frank) theory, in which surface electromigration of Si adatoms is considered. The stability condition of a regular step under DC supply is clarified, in addition to that under AC supply. In the unstable condition, the step bunch grows from a small fluctuation of a regular step. The dynamics of the step structure transformation under DC are investigated by solving the kinetic equations on step positions at typical temperatures, and the associated bunching mechanisms are proposed based on the competition among the drift, evaporation and backward diffusion fluxes.
Ge Epitaxial Overlayers on Si(001) Studied by Surface-Sensitive X-Ray Absorption Fine Structure: Evidence for Strain-Induced Surface Rearrangement
Authors: Oyanagi Hiroyuki , Sakamoto Kunihiro , Ryu Shioda Ryu Shioda , Tsunenori Sakamoto Tsunenori Sakamoto
Published: October 2002

The structure of Ge epitaxial overlayers on well-oriented Si(001) ( Ge

n

/Si(001), n<7) has been studied by the surface-sensitive X-ray absorption fine structure (XAFS) technique in situ after layer-by-layer growth by molecular beam epitaxy (MBE). It is found that surface rearrangements unique to the number of Ge layers take place. For 1 monolayer (ML) Ge on Si(001), elongated Ge dimers with a local structure characteristic of s
2
p
3 configuration are observed, suggesting that surface strain induces a substrate-to-adatom charge transfer. For 2 ML Ge, ∼1/2 of Ge atoms in the second layer are replaced with Si atoms in the third layer, relieving elastic strain in the second layer caused by a large atomic size mismatch ( ∼10%) between the adatom and substrate atom. A possible model structure with the Ge0.5Si0.5 double layer interface is proposed. The results suggest that surface strain induces a site-specific atomic migration channel between the adjacent layers, serving as a driving force of interface mixing associated with the growth of Ge on Si or Si on Ge.
Ion-Assisted Crystal Growth by Post Irradiation as Applied to Nitride Formation
Authors: Min Kyung-youl , Tarutani Masayoshi , Masahiko Inoue Masahiko Inoue , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

A (100)-oriented TiN film was successfully prepared by means of the post irradiation of the 5 keV N2
+ ion beam onto the predeposited titanium film ∼500 Å thick on a Si(001) substrate at room temperature. The crystal growth of TiN film was monitored by reflection high energy electron diffraction (RHEED) during the experiment in ultrahigh vacuum (UHV). The TiN film was also studied by reflection electron microscopy (REM) and cross-sectional transmission electron microscopy (XTEM). Results have clearly shown that the color and crystallographic orientation of the TiN film are substantially controlled by the ion dose; the TiN film showed polycrystallinity at a low ion dose, whereas the TiN(100)-oriented face grew mainly with high ion dose, ∼1×1017 ions ·cm-2. The color of the film also changes as ion dose increased; in particular, a golden color became conspicuous between ∼3×1016 ions · cm-2 and ∼5×1016 ions·cm-2.
Cross Section Measurements for Electron-Impact Dissociation of CHF3into Neutral and Ionic Radicals
Authors: Goto Masashi , Nakamura Keiji , Hirotaka Toyoda Hirotaka Toyoda , Hideo Sugai Hideo Sugai
Published: October 2002

Absolute cross sections for electron-impact dissociation of CHF3from the threshold to 200 eV are presented for formation of the neutral radicals CF3, CHF2, CF2, CHF and CF. This measurement was accomplished by appearance mass spectrometry in a dual electron beam device. The threshold energies for neutral dissociation into CF3, CHF2and CF were measured to be 11.0, 13.0 and 19.5 eV, respectively. The surface loss probability of each radical and the electron-impact nitrogen dissociation were measured to calibrate the relative dissociation cross sections of CHF3. The branching ratio for dissociation at 150 eV is CF3:CF2:CF:CHF2:CHF=27:5:10:2:1. In addition to the neutral dissociation, the cross section for dissociative ionization of CHF3was extensively measured for formation of CF3+, CHF2+, CF2+, CHF+, CF+, CH+and F+.
Effect of III/V-Compound Epitaxy on Si Metal-Oxide-Semiconductor Circuits
Authors: Andreas Lubnow Andreas Lubnow , Guang-Ping Tang Guang-Ping Tang , Hergo-Heinrich Wehmann Hergo-Heinrich Wehmann , Erwin Peiner Erwin Peiner , Andreas Schlachetzki Andreas Schlachetzki
Published: October 2002

Several approaches to the heteroepitaxial growth of InP on (100)Si employing an electrochemically etched Si mesa, SiO2 masks, and a maskless procedure were investigated with the objective of achieving area-selective InP integration into Si metal-oxide-semiconductor (Si-MOS) technology. Maskless InP/Si device layer growth by metal-organic vapour-phase epitaxy with good selectivity on a structured InP buffer layer, surrounded by oxide, was achieved. Undesired InP depositions were removed with an SiO2 emulsion, spun on prior to InP growth. To study the effects on the Si-based electronics, p-metal-oxide-semiconductor field-effect tansistors (MOSFETs) were exposed to the various stages of the heteroepitaxial InP growth process. We have studied the influence of hydride atmospheres and thermal anneals on their electrical performance. A standard InP-on-(100)Si growth procedure was found to be acceptable for the MOS components, as demonstrated by a Schmitt-trigger laser-diode driver circuit.
General Formula for the Deformation of a Plate due to Surface Sress
Authors: Kazuo Kitahara Kazuo Kitahara
Published: October 2002

We derive a formula for the deformation of a plate due to an arbitrary distributuion of surface stress caused by adsorbtion of atoms on the surface. This is a generalization of Stoney's formula.
Characterization and Control of Native Oxide on Silicon
Authors: Morita Mizuho , Ohmi Tadahiro
Published: October 2002

Characterization and control methods of native oxide growth on silicon (Si) surfaces at room temperature and during temperature ramp-up are described. The X-ray photoelectron spectroscopy (XPS) data have sufficient resolution to discern the stepwise increase in the amount of native oxide on hydrofluoric acid (HF)-cleaned Si surfaces exposed to air at room temperature. The native oxide growth on HF-cleaned Si surfaces can be controlled by lowering oxygen or water concentration in the ambient of the process at room temperature and by passivating the Si surface for semiconductor processes at temperatures higher than 300° C. In situ control methods of native oxide growth result in low-resistance tungsten (W)/n+-Si contacts and very thin oxide films with high electrical insulating performance.
Magnetotransport in One-Dimensional Lateral Surface Superlattice Fabricated by Low-Energy Argon Ion Irradiation
Authors: Takahara Junichi , Yoshimatsu Seiji , Gamo Kenji , Namba Susumu , Takaoka Sadao , Murase Kazuo
Published: October 2002

One-dimensional lateral surface superlattice has been fabricated into the high-mobility heterostructure by low-energy ion irradiation and the magnetotransport properties are investigated. At weak magnetic field, Weiss oscillations are observed and this indicates that weak modulation potential is introduced in two-dimensional electron gas by low-energy ion irradiation. Moreover, Hall resistance oscillations are observed as theoretically predicted. A positive magnetoresistance observed around zero magnetic field is investigated in detail and is compared quantitatively with the theory of magnetic breakdown. At a high magnetic field where the cyclotron radius is much smaller than the superlattice period, anisotropic magnetoresistance with respect to the direction of current flow is observed.
Theoretical and Experimental Study of High-Energy Implanted Collectors for Bipolar Transistors in Bipolar-Complementary Metal Oxide Semiconductor Transistor Technology
Authors: Marty Arlette , Ashburn Alain Nouailhat
Published: October 2002

This work is a theoretical and experimental study of the properties of retrograde collector profiles for bipolar transistors produced using high-energy ion implantation. One-dimensional device simulations are carried out, and show that compared with a uniform profile, the retrograde profile allows transistor operation at higher current levels without incurring an unacceptable increase in the base-collector capacitance. Two-dimensional process and device simulations are also carried out to analyze the two-dimensional electrical behavior of the retrograde collector. At low collector-emitter bias, quasi saturation is observed due to the vertical drop in potential, which is associated with a lateral drop in the potential in the collector resistance, and must be minimized. At high collector-emitter bias, the injection regime, resulting from the Kirk effect, occurs. Experimental bipolar transistors are designed and fabricated based on these simulation results. The proposed self-aligned design minimizes both the extrinsic base-collector junction capacitance and the series collector resistance. A measured transit frequency (f
T) of 7.8 GHz is obtained, which is ample for many analog and digital VLSI circuits which require operating frequencies up to a few gigahertz.
Nuclear Magnetic Resonance of 7Li in Li2B4O7 Single Crystal and Glass
Authors: Matsuo Toru , Shibasaki Masayuki , Katsumata Tooru , Onoda Yoshito
Published: October 2002

The spin lattice relaxation rates and the absorption line shapes of 7Li in both Li2B4O7 single-crystal and glass samples were measured from room temperature up to 900 K. At lower temperatures the dominant contribution to the relaxation rate was the spin-phonon interaction in both samples. For the single crystal the relaxation caused by the diffusion of Li ions became significant above 760 K, and the narrowing of the absorption line started at about 650 K. For glass the narrowing of the line started at room temperature and the effect of the diffusion of Li ions on the relaxation rate was dominant above 400 K. From these results the correlation time τ c of the fluctuating field at Li sites in the crystal and glass of Li2B4O7 was obtained.
Experimental Study on a Second-Harmonic Intensity Modulator with Quasi-Phase-Matched Optical Waveguides
Authors: Ito Kenchi , Sten Helmfrid Sten Helmfrid , Kimio Tatsuno Kimio Tatsuno
Published: October 2002

A second-harmonic intensity modulator with quasi-phase-matched optical waveguide is fabricated and demonstrated. The domain-inverted structure and proton-exchanged optical waveguides are fabricated on a Z-cut LiTaO3 substrate. Traveling-wave type Al electrodes are fabricated on the SiO2 buffer layer. Second-harmonic radiation can be modulated by giving phase mismatch to the second-harmonic generator by using the electro-optic effect. The conversion efficiency of the device is 0.4%/Wcm2 and the switching voltage is 180 V, when the duty ratio of the quasi-phase-matched grating is 0.4. Modulation is achieved up to about 1 MHz.
Step Edge Structures on Si(112) and (113) Surfaces Treated in NH4F Solution
Authors: Ken Fujita Ken Fujita , Norio Hirashita Norio Hirashita
Published: October 2002

Step edge structures on H-terminated Si (112) and (113) surfaces have been investigated with infrared absorption spectroscopy. NH4F acid is used to prepare almost straight bilayer step edges on the surfaces. It has been found that the step edges with the dihydride fluctuate within the width of one row of Si–H oscillators. The reason for the fluctuation is attributed to the etching of Si atoms of straight step edges during NH4F treatment. The assignment of C mode absorption has been refined based on our experimental result. Therein, the surface orientation dependence of the absorption spectra is quantitatively investigated by taking account of the effect of step fluctuation. The ratio of actually fluctuating step edges to original step edges is estimated.
Twinning Structure and Growth Hillock on Diamond (001) Epitaxial Film
Authors: Tsuno Takashi , Takahiro Imai Takahiro Imai , Naoji Fujimori Naoji Fujimori
Published: October 2002

Surface observation was carried out for diamond homoepitaxial films grown on (001) substrates. Nonepitaxial crystallites and growth hillocks were observed on the films. The majority of the nonepitaxial crystallites were found to be {111} penetration twins, which were considered to originate from the twin nucleation on {111} facet on substrates or epitaxial films. The penetration twins in the configuration of 4-fold symmetry were also observed and they are attributed to the twin nucleation in etch pits on the surface. On the top of the pyramidlike growth hillock, the twinning structure with a pair of parallel {111} twinning planes was observed. The twinning structure is accompanied by a reentrant corner on the surface and induced the enhancement of growth rate, resulting in the formation of growth hillocks.
Comments on “The Effects of Gaseous Helium and Nitrogen on Thermopower Measurements: A Note of Concern for the Discrepancy of the Results Observed in High Temperature Superconductors”
Authors: Antonio B. Villaflor Antonio B. Villaflor , Luis H. de Luna Luis H. de Luna
Published: October 2002

Lumped thermal circuit analysis is employed to show that the pressure dependence of the thermopower reported in the above paper is due to the finite thermal conductance between the separate heated points where the differential temperature and thermoelectric potential were measured. A system which allows equivalent measurements at a single heated point is proposed leading to a pressure independent thermopower without requiring high vacuum.
Distribution of [111]-Tilt Grain Boundaries in Evaporated Fullerene Film
Authors: Yutaka Takahashi Yutaka Takahashi
Published: October 2002

A thin film of C60was deposited on heated glass by a vacuum evaporation technique and observed by transmission electron microscope. Because grains were highly oriented to [111]-directions for the glass surface, there were many [111]-tilt boundaries in the film. Misorientation of the grain boundaries was not randomly distributed but preferred and unstable orientations were found.
Photodegradation of Polysilanes Studied by Far-Infrared Spectroscopy
Authors: Watanabe Akira , Ito Osamu , Matsuda Minoru , Suezawa Masashi , Sumino Koji
Published: October 2002

The photodegradation of polysilanes was investigated by far-infrared spectroscopy. The band intensity of asymmetric and symmetric Si–Si stretching vibration of poly(methylphenylsilylene) was decreased by UV-irradiation. The formation of the Si-branching structure in the UV-irradiated poly(methylphenylsilylene) was suggested. Poly(phenylsilyne) showed stability of the Si rings during the photodegradation.
Contact Ionization Ion Sources for Ion Cyclotron Resonance Separation
Authors: Tatsuya Suzuki Tatsuya Suzuki , Kazuko Takahashi Kazuko Takahashi , Masao Nomura Masao Nomura , Yasuhiko Fujii Yasuhiko Fujii , Makoto Okamoto Makoto Okamoto
Published: October 2002

Contact or surface ionization of lithium halides has been studied using a mass spectrometer in order to develop an effective ion source for plasma isotope separation. Among the lithium halides, LiI has been found the most effective to produce Li+ions. To increase the work function of the metal surface, oxide surfaces have been investigated, and tantalum oxides have shown effective ionization in a relatively lower temperature region.
Density Measurement of O Atoms in Helicon Wave Oxygen Discharge by Two-Photon Laser-Induced Fluorescence
Authors: Kadota Kiyoshi , Konno Yuji , Aoto Koji , Sato Tatsuo Shoji
Published: October 2002

Ground-state O atoms in oxygen plasma have been detected by means of two-photon laser-induced fluorescence at 226 nm. A calibration method for obtaining the absolute O atom density was established, using O atoms produced by photodissociation of molecular oxygen with 226 nm photons. The O atom density in helicon wave oxygen discharge was determined, and a typical value was 1.3×1019m-3at a gas pressure of 50 mTorr and electron density of 5.2×1016m-3. Spatial and temporal variations of the O atom density have been successfully measured.
Mass Spectrometry of Discharge Products at 13.56 MHz in SF6Gas
Authors: Nagaseki Kazuya , Kobayashi Hidehiko , Ishikawa Itsuo , Nishimura Eiichi , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Discharge products in SF6RF plasma were measured by means of direct sampling using a quadrupole mass spectrometer. In the plasma, the neutral dissociative species SF2and SF4are present. The positive ion SF3+is predominant, and SF5+, SF2+, SF+and F+are also present. The concentration of each neutral and ion product depends on RF power, gas flow rate and area of the silicon wafer set on the grounded electrode. When SF, SF2, SF+and SF2+increase to certain amounts, S2F+, SF2+and S+can be observed.
InN Thin-Film Growth Using N2, NH3 and N2–He RF Plasmas
Authors: Sato Yuichi , Sei Kakinuma Sei Kakinuma , Susumu Sato Susumu Sato
Published: October 2002

InN thin films are prepared by reactive evaporation and the applicability of various rf plasmas such as N2, NH3 and N2–He mixtures is investigated. Many indium droplets appear in the films when NH3 plasma is used. On the other hand, the number of droplets is greatly decreased and c-axis-oriented InN films are obtained by addition of N2 to NH3 plasma or by using pure N2 plasma. In case of films prepared using N2–He plasma, although the c-axis-oriented InN films are obtained, some damage appears in the films. In addition to these differences originating from the kind of gas used, the surface morphology and the crystallinity of the prepared films deteriorate as the gas pressure increases. These are improved by lowering the reaction ratio between indium and nitrogen in the vapor phase.
Tungsten Chemical Vapor Deposition on Silicon and Silicon Dioxide with Plasma Excited Hydrogen
Authors: Yoji Saito Yoji Saito , Teruo Takagi Teruo Takagi
Published: October 2002

Nonselective chemical vapor deposition of tungsten films on silicon and silicon dioxide substrates by remote-plasma excited argon and hydrogen gaseous mixtures at substrate temperatures below 350° C was achieved. The growth rate shows an almost linear relationship with the hydrogen partial pressure above 0.6 Torr, but depends slightly on the argon partial pressure. The hydrogen partial pressure also influences the resistivity of the deposited films. The sufficient supply of the excited hydrogen improves growth rate and film properties.
High-Speed Etching of Indium-Tin-Oxide Thin Films Using an Inductively Coupled Plasma
Authors: Nakamura Keiji , Imura Tomonori , Sugai Hideo , Ohkubo Michiko , Ichihara Katsutaro
Published: October 2002

The dry etching of indium-tin-oxide (ITO) films using a high-density inductively coupled rf plasma is described. Various etching characteristics are examined for an etching gas of CH4/H2 mixture. A very high etching rate of ITO films of over 200 nm/min was obtained at 100% CH4, while the high etching rate of ∼100 nm/min was achieved even at 100% H2 with the moderate dc self-bias voltage of 300 V. The etch selectivity of ITO to SiO2 and Si3N4 was over ∼10. The dependences of etching rate on substrate temperature and self-bias dc voltage suggest that the high-flux ion bombardment given by the inductive rf plasma enhances the etching of ITO films. On the other hand, the crystallinity of ITO has a nominal effect on the etching characteristics of ITO films.
Selective Etching of Hydrogenated Amorphous Silicon by Hydrogen Plasma
Authors: Otobe Masanori , Kimura Masao , Oda Shunri
Published: October 2002

The selective etching of hydrogenated amorphous silicon (a-Si:H) with respect to crystalline Si (c-Si) by hydrogen plasma is investigated. We have revealed that a-Si:H is etched ten times faster than c-Si. With lower etching temperature, etching selectivity and etching rate of a-Si:H and c-Si increase. Under the high-pressure condition, the etch rate becomes low because the bright region of a very-high-frequency plasma moves away from the grounded electrode. The etching rate of a-Si:H is not sensitive to the structure of the a-Si:H deposited at 70–300° C. The surface morphologies of etched a-Si:H and c-Si are rougher for higher etching temperature. The mechanism of selectivity in etching is discussed.
Improvement in the Uniformity of Resistivity in a Magnetron-Sputtered Indium Tin Oxide Film by Controlling the Plasma Flux Distribution
Authors: Katsutaro Ichihara Katsutaro Ichihara , Michiko Okubo Michiko Okubo
Published: October 2002

The uniformity of resistivity in a magnetron sputtered indium tin oxide (ITO) film has been improved by controlling plasma distribution near the substrate. Plasma distribution was controlled by setting the auxiliary electro magnet around the target. Langmuir probe measurement showed that the plasma density and energy near the substrate were largely changed by the auxiliary magnetic field. ITO film was prepared on a glass substrate which was fixed above the target. The uniformity of film resistivity was improved when the plasma was converged under insufficient oxygen condition. It was also improved when the plasma was diverged under excess oxygen condition. The spatial change of the film resistivity was reduced to within ±10% over an 18 cm length along the short axis of the target, while it was above ±45% when the plasma was not controlled. Furthermore, the mean resistivity over the substrate surface was decreased to about three fourths by plasma control.
Selective Tungsten Chemical Vapor Deposition with High Deposition Rate for ULSI Application
Authors: Suzuki Hiroshi , Maeda Yuuji , Morita Kenji , Morita Mizuho , Ohmi Tadahiro
Published: October 2002

For the application of selective tungsten chemical vapor deposition (CVD) on ULSI device fabrication, two serious problems still remain: loss of selectivity and damage on devices. Selective tungsten deposition with the high rate of 1 µm/min has been achieved by a new CVD system having a cold susceptor, where the high selectivity has been well maintained continuously. We have also found that the tungsten-Si contacts with good performance of low contact resistance and no device damage can be formed by controlling the initial growth of tungsten.
ZnS Thin Films Prepared by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Li Jiin Wen , Yan Kuin Su Yan Kuin Su , Meiso Yokoyama Meiso Yokoyama
Published: October 2002

In this paper, the deposited properties of ZnS thin films prepared by the low-pressure metalorganic chemical vapor deposition (MOCVD) technique utilizing dimethyl-zinc (DMZn) and H2S as the source materials have been reported. The effects of the growth conditions on the growth rate of the films have been measured and the growth mechanism has been discussed. High-quality ZnS thin films with strong preferred orientation can be grown. The Δ2θ value of the zinc blende (111) plane diffraction peak can be reduced below 0.175°. The atomic ratio of S/Zn and lattice constant are 0.96 and 5.418 Å, respectively.
Characteristics of Hall Accelerator with He, H2, CH4, O2 and Ar Gases
Authors: Okada Morihiro , Toku Hisayuki , Yasushi Yamamoto Yasushi Yamamoto , Kiyoshi Yoshikawa Kiyoshi Yoshikawa
Published: October 2002

Discharge characteristics and extracted ion beam energy distributions of a Hall-accelerator-type ion source for low-voltage continuous operation (HALOC) with He, H2, CH4, Ar and O2 gases have been studied, and discussed in terms of gas species, electron scattering cross section (total cross section) of ions, electron mean free time, cycloidal length, and the neutralization of ions in the extracted beam.
A Low Parasitic Capacitance Scheme by Thermally Stable Titanium Silicide Technology for High Speed Complementary-Metal-Oxide-Semiconductor
Authors: Yoshida Takehito , Ogawa Shinichi , Akio Miyajima Akio Miyajima , Kousaku Yano Kousaku Yano
Published: October 2002

This paper presents a dopant drive-out process from elevated source/drain (S/D) structures with titanium silicide local interconnects, which reduces not only the S/D areas but also junction capacitance in advanced complementary-metal-oxide-semiconductor (CMOS) fabrication. A low-oxygen-content process with an optimized boron (B) doping realizes a thermally stable titanium silicide with reduced Ti–B compound formation. Electrical measurements of the metal-oxide-semiconductor field effect transistors (MOSFETs) show good I-V characteristics and high endurance to short-channel effects. Furthermore, the MOSFETs have hot-carrier and bias-temperature aging properties similar to those of controlled devices. Consequently, it has been clarified that the delay time per stage of the MOSFETs with the local interconnects can be reduced with decreasing junction capacitance.
High-Reliability Lithography Performed by Ultrasonic and Surfactant-Added Developing System
Authors: Iwamoto Toshiyuki , Shimada Hisayuki , Shimomura Shigeki , Onodera Masanobu , Ohmi Tadahiro
Published: October 2002

Formation of high-precision fine resist patterns has been achieved by an effective removal of dissolved resist polymers, that is, the reaction products of the development process. Also, it has been found that the reaction products give rise to the degradation of the resist contrast, resist sensitivity, and process margins. In order to remove the reaction products, two techniques have been employed, namely physical method of development with agitation (ultrasonic waves or with a stirrer) and chemical method of adding surfactant to the developer. By combining physical and chemical methods, the dissolved polymers have been effectively removed, thus allowing the resist to reveal its inherent patterning pertormance.
Characteristic High-Field Dependence of Magnetoresistance in Fe/Ag Granular Thin Films Fabricated by Sputtering and Annealing
Authors: Makhlouf Salah A. , Kenji Sumiyama Kenji Sumiyama , Kenji Suzuki Kenji Suzuki
Published: October 2002

Magnetoresistance (MR) have been measured at 4.2 K in magnetic fields up to 140 kOe for Fe/Ag granular films produced by sputtering and heat treatment. In a Ag-rich specimen, the MR ratio is larger than 25% even in the as-deposited state, whereas it is suppressed with increasing Fe content. The MR ratio becomes about 55% in the 14 at.%Fe specimen annealed at 573 K for 10 min. Based upon the giant MR (GMR) models of granular materials, these results indicate the importance of Fe particle size and Fe/Ag interface roughness in achieving GMR.
Faraday Force Magnetometer for High-Sensitivity Magnetization Measurements at Very Low Temperatures and High Fields
Authors: Sakakibara Toshiro , Mitamura Hiroyuki , Takashi Tayama Takashi Tayama , Hiroshi Amitsuka Hiroshi Amitsuka
Published: October 2002

A Faraday force magnetometer has been developed for static magnetization measurements at very low temperatures down to 100 mK and in fields up to 9 T. The magnetic force acting on a specimen located in the adiabatic vacuum chamber of a dilution refrigerator is detected by a newly designed load-sensing variable capacitor. Use of a superconducting magnet with gradient coils enables accurate measurement of magnetic moment with a resolution of better than 1×10-7A·m2( 1×10-4emu). An application to magnetization measurements on the heavy-electron antiferromagnet CeB6is presented.
Theory for Phase Transition of Phospholipid Multilayer Systems at Low Water Content
Authors: Yoshiroh Kaminoh Fumiaki Kanô , Issaku Ueda Issaku Ueda
Published: October 2002

The order-disorder transition in phospholipid membranes at low water content is analyzed. Phospholipid bilayers are the main component of cell membranes and undergo thermotropic order-disorder phase transition. When the water content in the lipid suspension is decreased to below a critical level, the transition temperature rises as the water content decreases. The membrane-water mixture is treated as an integral system. The system is defined as an array of alternating lipid bilayers and strongly bound water layers, and the stacked bilayer is either in a solid-gel or liquid-crystalline state. At the middle of the transition, the number of clusters is increased whereas the size of the cluster is decreased, indicating an increase in fluctuation. Bilayers behave cooperatively by forming clusters, and the cooperativity depends strongly on the interaction between the bilayer and interfacial water. By assuming inhomogeneity of the water content at each interface, the theory demonstrates multiplicity of the transition peaks at low water content.
Crystallographic and Electrical Properties of Epitaxial BaTiO3 Film Grown on Conductive and Insulating Perovskite Oxides
Authors: Watanabe Yukio , Matsumoto Yasuaki , Kunitomo Haruo , Mitsuru Tanamura Mitsuru Tanamura , Erina Nishimoto Erina Nishimoto
Published: October 2002

BaTiO3 films of various thicknesses were grown on doped and undoped SrTiO3(100) substrates and on (La, Sr)2CuO4 films by a pulse laser deposition method. Both BaTiO3 and (La, Sr)2CuO4 films were smooth and free of particulates. X-ray diffractometry showed that all materials were three-dimensionally aligned with the cube-on-cube epitaxial relationship, and that the films obtained on SrTiO3(100) were of a c-axis-oriented tetragonal phase contrary to previous studies using metal bottom electrodes. As the film thickness decreased, the tetragonality of these films increased and the dielectric constant along the c-axis decreased rapidly, despite reduction of disorder at the interface by use of perovskite electrodes. The 2000-Å-thick BaTiO3 grown on (La, Sr)2CuO4 film had the remnant polarization of about 1.5 µ C/cm2. The results were discussed using a surface layer model.
Film Degradation in AlN Preparation by Facing Target System
Authors: Tominaga Kikuo , Kusaka Kazuya , Chong Mufei , Takao Hanabusa Takao Hanabusa , Yoshihiro Shintani Yoshihiro Shintani
Published: October 2002

In AlN films prepared by the facing target system, a decrease in degree of c-axis orientation, film coloring and film cracking or peeling from the substrate were observed. This film degradation is thought to be related to insulative films in general. In order to clarify how these phenomena are induced, we prepared samples under various sputtering conditions; i.e., by changing target holders, placing a ground mesh in front of the substrate and using a positively biased electrode. It is confirmed that plasma exposure severely influences c-axis orientation of AlN films. To decrease this influence, it is important that electrons flow adequately into the anode.
Fatigue and Refreshment of (Pb, La)TiO3 Thin Films by Multiple Cathode Sputtering
Authors: Maiwa Hiroshi , Ichinose Noboru , Kiyoshi Okazaki Kiyoshi Okazaki
Published: October 2002

The ferroelectric fatigue and refreshment of (Pb, La)TiO3 thin films by multiple cathode rf-magnetron sputtering were investigated. The remanent polarization of the fatigued (Pb, La)TiO3 thin films increased after the application of the DC bias voltage of -20 V for 104 s. By heat treatment of the fatigued films at 400° C for 1 h, the coercive field decreased, and squareness of the loop was improved. These behaviors were discussed from the viewpoint of the behavior of defect dipoles.
A New Recessed Channel Metal-Oxide-Semiconductor Field-Effect Transistor with Selectively Halo-Doped Channel and Deep Graded Source/Drain
Authors: Lee Woo-Hyeong , Young-June Park Young-June Park , Jong Duk Lee Jong Duk Lee
Published: October 2002

To improve the performance and reliability of deep submicron metal-oxide-semiconductor (MOS) devices, we propose a gate-recessed metal-oxide-semiconductor field-effect transistor (GR-MOSFET) which has a selectively halo-doped recessed channel and a deep graded source/drain formed without counter-doping. The GR-MOS structure eliminates the tradeoff between drain-induced barrier lowering (DIBL) and hot carrier effect which are most important in deep submicron device design. It also reduces the V
T lowering effect and lateral electric field at the drain. The fabricated 0.25 µm GR-MOSFET with a 10 nm gate oxide has exhibited 15% higher transconductance, more than 20% increased saturation current at V
D=V
G=3 V, 1 V higher B
V
DSS and 6 times less substrate current compared with a LDD-MOSFET of same device dimension.
Dielectric Properties of Ca-Based Complex Perovskite at Microwave Frequencies
Authors: Hiroshi Kagata Hiroshi Kagata , Junichi Kato Junichi Kato
Published: October 2002

We have investigated microwave dielectric properties and crystal structures of Ca(B3+
1/2B1/2
′5+)O3 (B: Al, Cr, Mn, Fe; B′: Nb, Ta) and Ca(B2+
1/3B2/3
′5+)O3 (B: Mg, Ca, Co, Ni, Cu, Zn; B′: Nb, Ta) perovskite ceramics. Compared with well-known Ba-based perovskite dielectrics, the Ca-based complex perovskite dielectrics had lower relative permittivities (ε

r
), lower Q values, and larger negative temperature coefficients of resonant frequencies (τ
f
). Ca(Mg1/3Ta2/3)O3 had the highest Q value (Q
f=78000 GHz) in this investigation. All Ca(B1/2B1/2
′)O3 had perovskite structures similar to CaTiO3 with a unit cell including four simple perovskite cells. Ca(B1/3B2/3
′)O3 with a small B ion such as Ni had the same structure Ca(B1/2B1/2
′)O3. Ca(B1/3B2/3
′)O3, however, had perovskite structures with larger unit cells than CaTiO3 when B ions had larger ionic radii.