bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrahigh-Vacuum Contactless Capacitance–Voltage Characterization of Hydrogen-Terminated-Free Silicon Surfaces
Authors: Yoshida Toshiyuki , Hasegawa Hideki
Published: October 2002

Hydrogen-terminated silicon (Si) surfaces were characterized using an ultrahigh-vacuum (UHV) contactless capacitance–voltage (C–V) technique which has been recently developed by our group. In addition to a U-shaped background distribution, hydrogen termination proceeds a narrow discrete surface state peak at E
V+0.65 eV whose density was sensitive to the treatment method and conditions. After optimal treatment in NH4F solution, a UHV-compatible completely passivated surface could be obtained with no appreciable discrete states. After annealing in an UHV environment above 300°C, the density of discrete surface states started to increase and eventually caused strong Fermi level pinning at E
V+0.6 eV. The most likely origin of the discrete state is the Si dangling bond not terminated by hydrogen.
Effects of Ion Beam Energy on the Formation of Cubic Boron Nitride Thin Films by Pulsed Nd:YAG Laser Deposition
Authors: Hiroharu Kawasaki Hiroharu Kawasaki , Kazuya Doi Kazuya Doi , Satoshi Hiraishi Satoshi Hiraishi , Yoshiaki Suda Yoshiaki Suda
Published: October 2002

Cubic boron nitride (cBN) thin films are synthesized on Si(100) substrates by a pulsed neodymium: yttrium-aluminum-garnet (Nd:YAG) laser deposition method using an ion beam in order to enhance the synthesis of the cBN phase.
The deposited films were characterized by a Fourier transform infrared (FT-IR) measurement method.
When a pure N2 ion beam is used, some absorption peaks for hexagonal boron nitride (hBN) are visible, but the peak for cBN cannot be observed. When argon(Ar) gas is mixed with the reactant nitrogen(N2) gas, the peak at 1050 cm-1 for cBN appears, in addition to those of hBN. When the ion-beam current and voltage is increased to 20 mA and 400 V, the absorption peak intensity for cBN increases, and that of hBN disappears. These results suggest that nitrogen and argon ion bombardment plays an important role in the formation of cBN films.
Preparation of Tungsten Nitride on Alumina by Chemical Vapor Deposition
Authors: Nagai Masatoshi , Hirano Naoya , Omi Shinzo
Published: October 2002

Tungsten nitride was synthesized on γ-alumina using a chemical vapor deposition method in a stream of WCl6, NH3, H2, and Ar at temperatures of 773 to 973 K under 70 Pa. The surface area of the W2N/Al2O3 system decreased from 178 to 140 m2 g-1 with increasing tungsten loading. The pore volume decreased with increasing deposition of W2N with a constant distribution of pore size. The X-ray diffraction analysis showed the formation of β-W2N (100) and (111) phases in the 4.9 wt% W2N/Al2O3 but not in the 1.2 and 3.3 wt% W2N/Al2O3. From the X-ray photoelectron spectroscopy analysis, the N 1s/W 4f atomic ratio increased from 1.3 to 1.6 for the 1.2 to 4.9 wt% W2N/Al2O3. W0, W2+, and W4+ were dominant for the 4.9 wt% W2N/Al2O3.
Preparation of Carbon Nanofibers by Hot-Filament-Assisted Sputtering
Authors: Onuma Yoshiharu , Matsumoto Yuji , Oo Myo Than , Segawa Nobuo , Nakao Masato , Kamimura Kiichi , Matsushima Hisao
Published: October 2002

Crystalline carbon thin films containing carbon nanofibers were obtained using a hot-filament-assisted sputtering system. Pure argon gas was employed as the sputtering gas. The filament was made from tungsten wire and heated to 2000°C. No tungsten peak was observed in the X-ray photoelectron spectroscopy (XPS) spectrum. The crystal structure of the carbon thin films was investigated by transmission electron microscope (TEM), transmission electron diffraction (TED) and field emission scanning electron microscope (FE-SEM) observations. The results revealed that the crystalline carbon films consisted of nanofibers. Parallel lines were observed in TED patterns. This indicated that the sample consisted of low-dimensional carbyne-like fibers in the graphite matrix.
Arrangement of Nanosized Ceramic Particles on Self-Assembled Monolayers
Authors: Masuda Yoshitake , Seo Won Seon , Koumoto Kunihito
Published: October 2002

The fabrication of novel micro/nano-sized devices by assembling inorganic particles is anticipated for future microelectronics which will make use of their attractive functions. The surface modification of self-assembled monolayers (SAMs) was studied to prepare templates for sphere assembly. Phenyl groups of SAM were modified into silanol groups by UV irradiation through a photomask, by applying an electric current using an atomic force microscope (AFM) probe, or by contact pressure with a diamond tip. They were used as templates to arrange fine inorganic particles. In addition to the formation of ester bonds, siloxane bond formation between spheres and SAMs was also found to be effective for sphere arrangement. Low-dimensional close-packing of SiO2 spheres was achieved through the formation of siloxane bonds. The two-dimensional arrangement of functional particles on SAMs in a controlled manner through the formation of strong chemical bonds, such as ester bonds or siloxane bonds, can be applied to the microfabrication of ceramic devices.
Nanopit Formation and Manipulation of Steps on Si(001) at High Temperatures with a Scanning Tunneling Microscope
Authors: Koichi Sudoh Koichi Sudoh , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

Using a variable temperature scanning tunneling microscope (STM), we have investigated the process of nanopit formation as an intense electric field is applied to a Si(001) surface with a negatively biased STM tip at a large tip-sample distance while heating the sample at 400–500°C. We have found that nanopits are formed via layer-by-layer removal of atoms. We have demonstrated that atomic steps can be manipulated by the selective atom removal from step edges. Our results are qualitatively explained based on the field evaporation of surface Si atoms as positive ions, considering the site dependence of the binding energy and the field distribution on the surface.
Anisotropic Agglomeration of Surface-Modified Gold Nanoparticles in Solution and on Solid Surfaces
Authors: Murakoshi Kei , Nakato Yoshihiro
Published: October 2002

Anisotropic agglomeration of gold nanoparticles (diameter
ca. 6 nm) was induced in aqueous media by modifying the
particle surface with various organic thiols. The structural
anisotropy of the agglomerates in solution depended on the type of
the modifying reagents. Scanning tunneling microscopic images of the
agglomerates transferred on gold (111) surfaces show that the
agglomerates on the gold surface formed dot-interconnected lines
with a single particle width. The length of the dot-interconnected
lines was much longer on the surface than that in solution.
Evaluation of Pentafluoroethane and 1,1-Difluoroethane for a Dielectric Etch Application in an Inductively Coupled Plasma Etch Tool
Authors: Karecki Simon , Chatterjee Ritwik , Pruette Laura , Reif Rafael , Sparks Terry , Beu Laurie , Vartanian Victor
Published: October 2002

In this work, a combination of two hydrofluorocarbon compounds, pentafluoroethane (FC-125, C2HF5) and 1,1-difluoroethane (FC-152a, CF2H–CH3), was evaluated as a potential replacement for perfluorocompounds in dielectric etch applications. A high aspect ratio oxide via etch was used as the test vehicle for this study, which was conducted in a commercial inductively coupled high density plasma etch tool. Both process and emissions data were collected and compared to those provided by a process utilizing a standard perfluorinated etch chemistry (C2F6). Global warming (CF4, C2F6, CHF3) and hygroscopic gas (HF, SiF4) emissions were characterized using Fourier transform infrared (FTIR) spectroscopy. FC-125/FC-152a was found to produce significant reductions in global warming emissions, on the order of 68 to 76% relative to the reference process. Although etch stopping, caused by a high degree of polymer deposition inside the etched features, was observed, process data otherwise appeared promising for an initial study, with good resist selectivity and etch rates being achieved.
Impact of Structural Strained Layer near SiO2/Si Interface on Activation Energy of Time-Dependent Dielectric Breakdown
Authors: Harada Yoshinao , Eriguchi Koji , Niwa Masaaki , Watanabe Takanobu , Ohdomari Iwao
Published: October 2002

A structural transition region near the SiO2/Si interface has been considered to play an important role with respect to gate oxide reliability. We clarify the effects of the structural transition region on the time-dependent dielectric breakdown (TDDB) characteristics, particularly the activation energy of the oxide breakdown for ultrathin gate oxides formed by different oxidation processes, i.e., pyrogenic oxidation, rapid thermal O2 oxidation and N2O oxynitridation. Furthermore, we investigate the properties of the structural transition region, such as the density of SiO2 as measured by the grazing incidence X-ray-scattering reflectivity (GIXR) method, the Si–O–Si bond angle by Fourier-transform infrared attenuated total reflection (FTIR-ATR), the etching rate by chemical etching and X-ray photoelectron spectroscopy (XPS). Through these investigations, it is clarified that the oxide breakdown tends to occur at the Si–O–Si network with a lower bond angle (<115°) and that the strain in the structural transition region reduces the barrier to the oxide breakdown. A 1-nm-thick strained layer is found to have a strong effect on the oxide reliability and to limit oxide scaling in future ultra-large-scale integrated circuits (ULSIs).
Development of Full-Color Display Combined with Ultraviolet-Electroluminescence/Photoluminescence Multilayered Thin Films
Authors: Senda Takahiro , Cho Young-Jae , Hirakawa Takashi , Okamoto Hiroaki , Takakura Hideyuki , Hamakawa Yoshihiro
Published: October 2002

A series of systematic investigations have been carried out on a new type of full-color display devices combining ultraviolet (UV) thin film electroluminescence (EL) with red, green and blue (RGB) visible-light phosphors. The device structure is composed of phosphor/Indium Tin Oxide (ITO)/a-SiN
x
/ZnF2:Gd/a-SiN
x
/Al/glass. UV emission from a ZnF2:Gd active layer is employed as an excitation source for the phosphors. For the UV-EL/photoluminecsence (PL) hybrid device using blue light-emitting phosphors, a maximum luminance of 10 cd/m2 and a maximum efficiency of 0.015 lm/W has been achieved while the luminance of red and green light-emitting devices were 50 and 30 cd/m2, respectively, under an applied voltage of 250 V0-p (5 kHz sinusoidal voltage). Technical data on the fabrication of the thin film UV-EL device together with RGB visible-light PL layers are presented. Research and development efforts on the optimum design and optoelectronic performance and related characterizations are also described and discussed. It is believed that there will be a tremendous demand for the developed device which has a much higher picture element resolution and the possibility of a higher brightness as compared with recently introduced plasma display panels (PDPs).
Use of Multiple Pairs of Gain and Saturable Absorber Regions for Semiconductor Optical-Pulse Compressor
Authors: Shimizu Mitsuaki , Suzuki Yoshihiro , Mukai Seiji , Hasama Toshifumi
Published: October 2002

We propose a compact semiconductor optical-pulse compressor using multiple
pairs of gain and saturable absorber regions. We performed numerical analysis of the
operating characteristics using traveling-wave rate equations, and determined that
picosecond optical pulses such as Q-switched or gain-switched pulses could be compressed efficiently. We also confirmed that this technique was effective for
compressing the 40–100-ps-wide optical pulse generated by commonly-used lasers, such
as self-pulsating lasers. In addition, the effect of gain saturation was investigated, and
found to be one of the important factors to determine the compressing
characteristics.
Amorphous GaN Grown by Room Temperature Molecular Beam Epitaxy
Authors: I. Westwood Martin Kuball
Published: October 2002

Amorphous GaN films were grown at room temperature by molecular beam epitaxy on the oxide layer of GaAs(001) substrates. Their properties were investigated by transmission electron microscopy/diffraction and micro-Raman spectroscopy. A broad Raman peak at 650 cm-1 identifies the amorphous GaN. The results suggest that the local short-range bonding structure in amorphous GaN is different from crystalline GaN supporting theoretical predictions [Stumm and Drabold: Phys. Rev. Lett. 79 (1997) 677] that amorphous GaN is attractive for device applications.
A 25-nm-long Channel Metal-Gate p-Type Schottky Source/Drain Metal-Oxide-Semiconductor Field Effect Transistor on Separation-by-Implanted-Oxygen Substrate
Authors: Atsushi Itoh Atsushi Itoh , Masayuki Saitoh Masayuki Saitoh , Masahiro Asada Masahiro Asada
Published: October 2002

A 25-nm-long channel metal-gate PtSi Schottky source/drain metal-oxide-semiconductor field effect transistor (MOSFET) fabricated on a separation-by-implanted-oxygen (SIMOX) substrate was demonstrated. The drain current and transconductance were 293 µA/µm and 431 mS/mm, respectively.
Scale Transformation Method in Self-Consistent Solution of Schrödinger and Poisson Equations
Authors: Ma Yutao , Liu Litian , Yu Zhiping , Li Zhijian
Published: October 2002

A new scale transformation method is used in the solving of the Schrödinger equation. With this new method, the uniform grids used in the discretization in the conventional method are changed into nonuniform grids. Consequently, for some cases, the computing quantity is greatly reduced while maitaining the required accuracy. The calculation of the quantized inversion layer in metal-oxide-semiconductor (MOS) structure is used to demonstrate the efficiency of the new method.
Formation of Micropeak Array on a Silicon Wafer
Authors: Teiichirou Chiba Teiichirou Chiba , Ryuusuke Komura Ryuusuke Komura , Akira Mori Akira Mori
Published: October 2002

Marking on a silicon wafer with a small dot matrix has been performed using a diode-pumped second-harmonic generation (SHG) laser of yttrium aluminum garnet (YAG), liquid-crystal-display (LCD) mask, and projection optics. The image was obtained after laser irradiation through a patterned mask on the LCD. The each dot is a square with sides of 3.6 µm, the pitch of each dot is 4.5 µm and the height (not the depth) of each dot is approximately 0.5 µm. The height of the dot strongly depends on the laser energy density. The dot topography is unique, with a central peak and peripheral depression. We have named this topography “micropeak.” Regarding the shape of the micropeak, significant differences are observed from that of the textured Sombrero bump with a central peak. These differences are believed to result from the material of the substrate, i.e., silicon. We present a hypothesis of the micropeak formation mechanism: The density of silicon in the liquid state is greater than that in the solid state, which is a physical property. In the congealing process of molten silicon, a unique liquid-gas interface is formed, which first moves downward, and then upward, resulting in the micropeak.
Differential Temperature Controller for Stable Temperature Control of a Nonlinear Optical Crystal at Approximately 200°C
Authors: Ikegami Takeshi
Published: October 2002

A differential temperature controller is described, which can control the temperature of a nonlinear optical crystal at approximately 200°C, with a temperature stability better than 1 mK. To demonstrate its performance, the temperature of a monolithic, continuous-wave optical parametric oscillator (OPO) was stabilized and an output intensity fluctuation of 3.5% rms was achieved even under free-running operation.
Formation of pn Homojunction in Cu(InGa)Se2 Thin Film Solar Cells by Zn Doping
Authors: Takeshi Sugiyama Takeshi Sugiyama , Sutichai Chaisitsak Sutichai Chaisitsak , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai , Yuriy Kudriavtsev Yuriy Kudriavtsev , Antonio Godines Antonio Godines , Antonio Villegas Antonio Villegas , Rene Asomoza Rene Asomoza
Published: October 2002

In this study, a pn homojunction was intentionally fabricated in the Cu(InGa)Se2 (CIGS) layer by Zn doping. For Zn doping of the CIGS layer, Zn was evaporated after CIGS formation, and a potential improvement in cell performance was confirmed by this technique. Furthermore, Zn diffusion into the CIGS film was investigated by secondary ion mass spectroscopy (SIMS). A conductivity-type conversion from p-type to n-type was studied by the measurement of the cross-sectional electron beam-induced current (junction EBIC: JEBIC) and the spectral response of solar cells. A conversion efficiency of 11.5% has been achieved using the Zn-doped CIGS layer without a buffer layer and by the formation of a pn homojunction in the CIGS absorber.
Dielectric and Pyroelectric Properties of (Ba,Sr,Ca)TiO3 Ceramics for Uncooled Infrared Detectors
Authors: Sung-Soo Lim Sung-Soo Lim , Myung-Soo Han Myung-Soo Han , Suk-Ryong Hahn Suk-Ryong Hahn , Sung-Gap Lee Sung-Gap Lee
Published: October 2002

(Ba0.6Sr0.3Ca0.1)TiO3 (BSCT) powders, which were prepared by the sol–gel method using a solution of Ba, Sr and Ca acetate and Ti isopropoxide, were spray-dried under the optimum conditions of a 10000 rpm atomizer speed and 1.5 wt% polyvinyl alcohol (PVA) addition. BSCT ceramics, undoped and doped with MnCO3 (0.1 mol%) and Y2O3 (0–0.9 mol%), were fabricated by the cold isostatic press method, and then the structural and electrical properties as a function of the Y2O3-dopant amount were studied. The specimen, doped with more than 0.5 mol% Y2O3, showed small and uniform grains of 1–3 µm in diameter. The Curie temperature and the maximum dielectric constant decreased with increasing Y2O3 content and the dielectric loss of the specimen, doped with 0.5 mol% Y2O3, showed a minimum value of 0.009 at the Curie temperature. The pyroelectric coefficient decreased as the dopant of Y2O3 increased and the doped specimen of 0.3 mol% Y2O3 showed a good value of 354 ×10-9 C/cm2K under a 4 kV/cm DC bias field. The figure of merit F.M.D* for specific detectivity (D*) of the specimen, doped with 0.5 mol% Y2O3, showed the highest value of 8.9 ×10-9 Ccm/J.
Principle of Photoconductive Ferroelectric Memory and Preliminary Experiments
Authors: Wang Wensheng , Karaki Tomoaki , Adachi Masatoshi
Published: October 2002

A novel concept called photoconductive ferroelectric memory (PFM) is proposed as a means to fabricate ferroelectric random access memories (FeRAMs). The memory device is based on the new operating principle that skillfully integrates the photoconductive effect of the semiconductor with the spontaneous polarization reversal and the pyroelectric effect of ferroelectrics. The entire multilayer structure of the device consists of indium-tin oxide (ITO)/a-Si:H/lead zirconate titanate (PZT)/bottom electrode. The operating principle of the PFM device is designed and theoretically calculated, and the device is then prepared by RF magnetron sputtering. The photoconductive effect of amorphous silicon due to the focused laser light is used for address. The remanent polarization directions of the PZT layer are used for “1” or “0” of memory. The pyroelectric current directions are used for readout. The write-read operation of PFM is proven by observing the hysteresis loop in a single cell and different pyroelectric current direction readouts by light beam illumination.
Development of Silver-Based Multilayer Coating Electrodes with Low Resistance for Use in Flat Panel Displays
Authors: Aoshima Yuki , Miyazaki Masami , Sato Kazuo , Akao Yasuhiko , Takaki Satoru , Adachi Kunihiko
Published: October 2002

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides were investigated from the view-point of low-resistance electrodes for use in flat panel displays. Optimization of the multilayer coatings resulted in a five-layer coating composed of indium and zinc oxide composite material (IZO) and silver containing 1 wt% of palladium (Ag–Pd). The coatings had satisfactory properties of low resistance, high transmittance, high moisture and alkali resistance, and good patterning.
Theory on High-Vacuum Planar Magnetron Discharge Incorporating the Effect of Escaping Electrons
Authors: Miura Tsutomu
Published: October 2002

A theory, which includes the case where B
A (magnetic flux density at the anode) is insufficient to confine the energetic electrons in the discharge space, has been developed. At a fixed E
a/B
A (E
a≡V
A/d
0, V
A: anode voltage and d
0: distance between the electrodes), I∝B
A
β (I: discharge current and β: const. ≧1). With increasing B
A, so that most of the energetic electrons are confined, β becomes 1. For d
0=42 mm, in E
a/B
A≧2.3×107/n V/(m·T) when B
A>5 mT and E
a>1.2×105/n V/m when B
A<5 mT (n: power index of the potential distribution), I becomes I∝E
a

M

B
A
1-M
(M: const.<1). The minimal conditions necessary to sustain the magnetron discharge are E
a/B
A>2.0×106/n V/(m·T) when B
A>10 mT and E
a>2.0×104/n V/m when B
A<10 mT for d
0=42 mm and E
a<(G
0/n)B
A
2 (G
0: const.). With decreasing d
0, the above conditions are modified by a corresponding increment in B
A. Experimental works have been carried out.
Observation of Terahertz Photon-Assisted Tunneling in Triple-Barrier Resonant Tunneling Diodes Integrated with Patch Antenna
Authors: Nobuo Sashinaka Nobuo Sashinaka , Yukio Oguma Yukio Oguma , Masahiro Asada Masahiro Asada
Published: October 2002

Terahertz (THz) photon-assisted tunneling was observed in GaInAs/InAlAs triple-barrier resonant tunneling diodes (RTDs) integrated with patch antennas on InP substrates. The conduction loss of the antenna was reduced by a structure that consists of an Au-coated ground plane, an Au antenna electrode and a thick benzo-cyclo-butane layer as a dielectric between them. Large THz voltages were induced across the RTD with this structure by THz irradiation (frequency f=1.4–3.1 THz), e. g. , 122 mV at an incident power of 76 mW at f=1.4 THz. Current changes due to photon-assisted tunneling with photon absorption and emission were determined. The peak voltage of the current change shifts due to the multiphoton process with increasing incident power. The multiphoton process was remarkable at low irradiation frequency. These measurements were in reasonable agreement with theory.
Optical Emission Spectroscopy of Arc Flame Plasma for Generation of Carbon Nanotubes
Authors: Akita Seiji , Ashihara Hiroshi , Nakayama Yoshikazu
Published: October 2002

Spatial distributions of plasma temperature and densities of carbon species in DC arc discharge for generating carbon nanotubes have been investigated by measuring the spatial distributions of optical emission spectra as a function of pressure, current density for arc discharge, and cooling rate of the cathode. It is found that the nanotube yield is high when the temperature at the axial center of the cathode is higher than 6000 K so that the dominant species is in the arc flame carbon monomer. The potential drop at the cathode sheath, calculated from the model proposed by Rethfeldet al.[J. Phys. D 29 (1996) 121], is high for the high nanotube yield in comparison to that under the low yield conditions.
Highly Anisotropic Etching of Polysilicon by Time-Modulation Bias
Authors: Ono Tetsuo , Mizutani Tatsumi , Goto Yasushi , Kure Tokuo
Published: October 2002

The improvement of selectivity for polysilicon (poly-Si) etching without lowering the selectivity to SiO2 is possible through the implementation of time-modulation (TM) bias. RF bias (800 kHz) applied to a substrate in an electron cyclotron resonant (ECR) etcher is pulse modulated with a repetition frequency of 1 kHz. The amplitude of RF voltage controls the energy of the ions accelerated toward the wafer. The flux of accelerated ions is controlled by the duty ratio of the pulse. The taper angle of the sidewall of line patterns is 89° for TM bias and 81° for conventional continuous-wave bias. The etch rate of the poly-Si is ∼300 nm/min and has a selectivity to SiO2 of 17. In addition, microtrenching at the bottom of the space is suppressed by the implementation of TM biasing. Modeling of the etch profile based on the competition of deposition and etching on the sidewall surface can explain the effects of TM bias.
Intrinsic and Extrinsic Excitonic Features in MgS/ZnSe Superlattices Revealed by Microspectroscopy
Authors: Kumano Hidekazu , Nashiki Hiroyuki , Suemune Ikuo , Suzuki Hideki , Uesugi Katsuhiro , He An-Qiang , Otsuka Nobuo
Published: October 2002

Microspectroscopy of luminescence and optical reflection properties was performed on
MgS/ZnSe superlattices with the spatial resolutions of ∼µm and ∼10 µm, respectively, to
examine the origin of excitonic transitions. C1-HH1 well-defined excitonic peaks which
originate from multi-monolayer (ML) variation of 4–5 ML height, formed predominantly at the
ZnSe surfaces of MgS/ZnSe heterointerfaces, were found to make a significant contribution to
the optical spectra. The detailed identification of these inhomogeneous C1-HH1 excitonic
peaks and intrinsic C1-LH1 excitonic peaks, which are close in energy levels, is discussed on
the basis of results of the present microspectroscopy studies and with respect to the temperature
dependence of the luminescence spectra.
Dynamic Three-Dimensional Echocardiography
Authors: Katsuhiko Matsusaka Katsuhiko Matsusaka , Motonori Doi Motonori Doi , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

Conventional three-dimensional (3D) ultrasound imaging equipment for diagnosis requires much time to reconstruct 3D images or fix the view point for observing the 3D image. Thus, it is inconvenient for cardiac diagnosis. In this paper, we propose a new dynamic 3D echocardiography system. The system produces 3D images in real-time and permits changes in view point. This system consists of ultrasound diagnostic equipment, a digitizer and a computer. B-mode images are projected to a virtual 3D space by referring to the position of the probe of the ultrasound diagnosis equipment. The position is obtained by the digitizer to which the ultrasound probe is attached. The 3D cardiac image is constructed from B-mode images obtained simultaneously in the cardiac cycle. To obtain the same moment of heartbeat in the cardiac cycle, this system uses the electrocardiography derived from the diagnosis equipment. The 3D images, which show various scenes of the stage of heartbeat action, are displayed sequentially. The doctor can observe 3D images cut in any plane by pushing a button of the digitizer and zooming with the keyboard. We evaluated our prototype system by observation of a mitral valve in motion.
Reactive Ion Etching of Indium Nitride Using CH4 and H2 Gases
Authors: Guo Qixin , Matsuse Motoatsu , Nishio Mitsuhiro , Ogawa Hiroshi
Published: October 2002

We have studied the characteristics of reactive ion etching of indium nitride layers using CH4 and H2 gases. The effects of CH4/H2 gas composition, total gas pressure, and plasma power on the etching rates were investigated. It was found that variation of the CH4 concentration in gas mixtures leads to changes in both the etching rate and the surface morphology. A smooth etched InN surface was obtained in the range of 5–15% CH4 concentration and 25–55 Pa pressure. The etching rate of InN increases from 260 to 1310 Å/min with increasing the plasma power from 100 to 300 W at a 10% CH4 concentration and 45 Pa pressure.
Gate Orientation Dependence of InGaAs/AlGaAs High Electron Mobility Transistors Formed by Wet Recess Etching
Authors: Ohshima Tomoyuki , Yoshida Masaaki , Shigemasa Ryoji , Tsunotani Masanori , Kimura Tamotsu
Published: October 2002

The gate orientation dependence of InGaAs/AlGaAs high electron mobility transistors (HEMTs) formed by the wet-chemical recess etching has been evaluated. The short channel effect strongly depends on the gate orientation and is significant in the order of [011], [001] and [011] oriented devices. Such orientation dependence results from a difference of the side-etching lengths, which are 0.01 µm, 0.03 µm and 0.06 µm for the [011], [001] and [011] oriented devices, respectively. The other characteristics of HEMTs such BV
gd, gm and f
T also depend on the gate orientation because of a difference of the recessed shape.
Effect of Photon Recycling in Pixelless Imaging Device
Authors: Tsutsui Naoaki , Ikegami Irina Khmyrova
Published: October 2002

We present an analytical model for the photon recycling effect associated with the reabsorption of generated photons in a light-emitting diode (LED) driven by nonuniform current injected from a quantum well infrared photodetector (QWIP). The model is applied to the evaluation of the modulation transfer function and the external quantum efficiency in pixelless imaging devices based on the integration of a QWIP with a LED. The modulation transfer function and the signal external quantum efficiency of a QWIP-LED pixelless imager are calculated as functions of the structural physical and geometrical parameters. It is shown that photon recycling is a significant factor that limits the spatial resolution of images and increases the external quantum efficiency.
Focusing and Guiding Charged Particles Using a Superconducting Tube: An Analytical Nonlinear Approach
Authors: Buzea Calin , Agop Maricel , Rezlescu Nicolae , Matsuzawa Hidenori
Published: October 2002

We present an analytical solution for the nonlinear equation of motion of an electron beam in the radial direction of a superconducting tube, for the case of electrons moving close to the tube axis. Accordingly, we deduce a general expression for the focusing length dependence on the parameters of the superconducting tube and the electron stream. Our calculated focusing length is in good agreement with the experimental data.
Investigation of Negative Feedback Regimes for Generation of Compressed Pulses
Authors: Ganeev R. A. , Usmanov T.
Published: October 2002

The results of optimisation of active and passive negative feedback (NF) for generation of stable compressed picosecond pulse trains in Nd:glass and Nd:YAG lasers using a modulator driven by fast photomultiplier and a GaAs passive element are presented. Conditions of prolonged pulse trains generation with the duration of trains varied from 0.3 µs to 200 µs depending on parameters of active NF were investigated. Generation of long (1000 ns) pulse trains in passive NF regime was obtained. Pulse compression in active and passive NF regimes (from 8 ps to 1.4 ps and from 35 ps to 13 ps, respectively) was achieved.
A Volume Pinhole for Mode-filtering of the Femtosecond Laser for Use in the Generation of High-order Vibrational and Rotational Emissions by Four-wave Raman Mixing
Authors: Hirakawa Yasuyuki , Ogata Keiichi , Takeyasu Nobuyuki , Imasaka Totaro
Published: October 2002

The beam quality of a femtosecond dye/KrF excimer laser was improved using a pinhole, prepared from an acrylic plate. The pinhole acts as a volume light absorber that discriminates high-order transverse modes of the laser beam. A breakdown at the surface of the pinhole, which degrades the quality of the transmitted beam, can be avoided using this spatial filter. This approach was useful in minimizing self-phase modulation, which exhausts the limited laser energy and reduces the Raman output. A conversion efficiency of some vibrational and rotational emissions was improved, even though the laser pulse energy was substantially reduced by mode filtering.
Investigation of AlGaAs/GaAs V-grooved Quantum Wire Infrared Photodetector Structures
Authors: Liu X. Q. , Li N. , Li Z. F. , Lu W. , Shen S. C. , Fu Y. , Willander M. , Tan H. H. , Jagadish C. , Zou J.
Published: October 2002

An Al0.5Ga0.5As/GaAs quantum wires infrared photo-detectors (QWRIP) based on V-grooved substrate is fabricated. The inter-band transition in the quantum wires is characterized by spatially resolved micro-photoluminescence (micro-PL) measurement. The theoretical calculation of electronic structures is accomplished based on the Green function. The inter-subband transition is measured by photocurrent at 80 K, and the origin of the infrared response at 9 µm is from the inter-subband transition in quantum wire region, which is confirmed by the theoretical calculation results.
Study on the Optoelectronic Properties of Al/a-Si:H/a-As2Se3 Photoreceptor for Electrophotography
Authors: Chou Jung-Chuan , Yang Shu-Ying
Published: October 2002

Due to its superior photosensitivity in visible light, amorphous selenium-based photoreceptors are widely used on photoreceptor drums in copying machines. Hydrogenated amorphous silicon (a-Si:H), which has special homogeniety making it easily deposited on the substrate as well as excellent photosensitivity in visible light, is first applied as a blocking layer on photoreceptors. Because intrinsic a-Si:H film is an n-type semiconductor, this configuration generates Schottky contact and an np junction at the interfaces which could be regarded as an ideal photodiode. Therefore, we attempted to adopt a-Si:H thin film as a blocking layer, and combine it with amorphous arsenic selenide (a-As2Se3) to prepare two structures of Al/Al2O3/a-As2Se3 and Al/a-Si:H/a-As2Se3 photoreceptors. Using an electrostatic paper analyzer (model: EPA-8100) to measure the photoinduced discharge curve (PIDC), we discovered that the Al/a-Si:H/a-As2Se3 structure has a high initial surface potential (V
so∼214 V; 41.63 V/µm), excellent photosensitivity (E
1/2∼2.19 lx·s), a low residual potential (V
r∼4 V), and a high contrast voltage ratio (214 V/4 V\cong53.5). For a better understanding of photoreceptors, we investigated the photosensitivity at different incident wavelengths, the movement of carriers in the photoreceptors and the characteristics of photoreceptors during isothermal annealing.
Theory of Morphotropic Phase Boundary in Solid Solution Systems of Perovskite-Type Oxide Ferroelectrics: Engineered Domain Configurations
Authors: Iwata Makoto , Ishibashi Yoshihiro
Published: October 2002

Polarization-field and strain-field hysteresis loops with field-induced transition in two types of engineered domain configurations in perovskite-type oxide ferroelectrics were calculated in terms of the Landau-Devonshire type free energy. Using the free energy function truncated at the fourth order with respect to the polarization, it was found that the field-induced transition from the tetragonal phase to the rhombohedral phase under the field along the [111] direction is of the first order, while the transition from the rhombohedral phase to the tetragonal phase under the field along the [001] direction is of the second order. Physical properties of the engineered domain configurations were discussed.
A Deposition Mechanism of SiO2 Chemical Vapor Deposition Using Tetra-Isocyanate Silane and Water
Authors: Akira Fujimoto Akira Fujimoto , Osamu Sugiura Osamu Sugiura
Published: October 2002

The deposition characteristic of SiO2 chemical vapor deposition (CVD) using tetra-isocyanate silane can be explained by the adsorption of source gases on the substrate surface. The deposition reaction occurs in the adsorbed layer. The deposition rate of the CVD was calculated under the assumption that source gases follow the BET isotherm theory independently. The dependence of deposition rate on temperature was well consistent with the experimental data by using a reaction constant V
SiO2
=1000 nm/min.
Cost-effective Driving Scheme for Bistable Cholesteric Displays
Authors: Yip W. C. , Kwok H. S.
Published: October 2002

For VLSI implementation, low operation voltage and switching current are the major concerns. Yet, none of the driving schemes published so far has addressed this combined issue. We studied the electro-optic characteristics of bistable cholesteric displays at the low transition voltage in this paper, and the effect of slew-rate on the maximum output current and average output power in a forthcoming paper. The dynamic responses were measured and an efficient scheme was devised accordingly. The most cost-effective addressing time was 4 ms/line using the low-end twist nematic (TN) or super twist nematic (STN) mixtures.
Determination of Quasi-Crystallographic Orientations of Al–Pd–Mn Icosahedral Phase by Means of Light Figure Method
Authors: Saito Kaichi , Sugawara Shigeo , Guo Jun Qing , Tsai An-Pang
Published: October 2002

The light figure method has been utilized for the determination of quasi-crystallographic orientations of a bulk single quasi-crystal of Al–Pd–Mn icosahedral phase. Prior to the light figure experiment, anodic etching was carried out in a solution of CH3OH+HNO3 (volume ratio 3:1), which revealed the occurrence of well-faceted micropits consisting of etch pits and microvoids on specific surface areas, showing approximately twofold, threefold or fivefold symmetry. The facet planes of the etch pits as well as those of the microvoids, when irradiated by a narrow light beam passing through a hole in the center of a screen, reflected the beam effectively, thus giving rise to a well-defined light figure with a specific symmetry on the screen. It is demonstrated that the light figure method functions effectively for the identification of principal symmetry directions of the quasi-crystal.
A Fictive Stress Model Calculation of Nonlinear Viscoelastic Behaviors in a Zr-Based Glassy Alloy: Stress Growth and Relaxation
Authors: Kato Hidemi , Kawamura Yoshihito , Chen Ho-Sou , Inoue Akihisa
Published: October 2002

Nonlinear viscoelastic behaviors of a Zr55Al10Ni5Cu30 glassy alloy are investigated experimentally and by theoretical modeling, based on the hypothesis of stress-induced structural relaxation and the concept of fictive stress. The model calculation curves agree well quantitatively with the experimental results. Structural changes of the nonlinear viscoelasticity during complex-step tests are expressed directly by the fictive stress. In addition, the critical condition under which the transition from linear to nonlinear viscoelasticity occurs is clarified on the basis of this model.
Nucleation and Spinodal Decomposition of Neutral Poly(N-isopropylacrylamide) Gels
Authors: Suzuki Atsushi , Yoshikawa Shinji
Published: October 2002

The shrinking phase separation of polymer gels was investigated using the neutral poly(N-isopropylacrylamide) gels prepared in a cylindrical shape with submillimeter diameter. The macroscopic conformation change was obtained on the isothermal processes after a step-like temperature increase beyond the transition point. The gel was quenched (super-heated) from three different initial temperatures to several final temperatures. It was observed that there exist three characteristic regions of transition velocity, which depend on the final temperature. The phase transition could be controlled by the nucleation mechanism in the shallow quenches (smaller super-heating; Stage I), which is characterized by a fine pattern: the gel remains transparent during the transition. On the other hand, in the deep quenches (larger super-heating; Stage III), the phase transition reaches the unstable region, which is characterized by a coarse pattern: the gel becomes transparent with time, from the surface layer to the core opaque portion. The transition velocity in Stage I or III does not depend on the initial temperature. The kinetics of the quenching into the intermediate temperature range (Stage II), however, is strongly affected by the initial temperature. The results were qualitatively discussed in terms of the macroscopic conformation changes resulting from the microscopic phase separation: nucleation and its growth (coarsening), spinodal decomposition and the transition-induced strain of networks.
Surface Modification of Poly(tetrafluoroethylene) Film Using Dielectric Barrier Discharge of Intermittent Pulse Voltage
Authors: Ishikawa Shinya , Yukimura Ken , Matsunaga Koichi , Maruyama Toshiro
Published: October 2002

The surface of a poly(tetrafluoroethylene) film was modified by using dielectric barrier (filament) discharge in air at atmospheric pressure. The discharge was produced by an intermittent one-cycle sinusoidal voltage with a duration of 10 µs and a voltage peak of 8 to 13 kV. The repetition rate was 5 to 100 kHz. The intermittent discharge at a duty cycle of 20% required a process time of 20 s for the entire surface to experience the discharge. The minimum contact angle of a water drop on the modified surface was about 70°. The quiet time of 40–90 µs was necessary to minimize the contact angle, and consequently, the stationary waveform was inappropriate for the modification. The immersion of the film in H2O and aqueous solutions of H3BO3 and H2O2 after plasma treatment in air drastically decreased the contact angle. However, the surface modification by the immersion was temporary, and the contact angle asymptotically approached that of the plasma-treated film.
Mechanism for Diamond Growth on Hydrogenated {111} Surfaces of Cubic Boron Nitride
Authors: Yanagihara Takashi , Yomogita Kazuo
Published: October 2002

Chemical reactions between hydrogen atoms or methyl radicals and hydrogenated {111} surfaces of cubic boron nitride clusters during diamond growth are investigated using the semiempirical molecular orbital method of AM1 approximation. The heat of formation (H.O.F.) estimated at the first stage of growth suggests product formation following the lowest energy path. Also, chemical interactions are discussed based on the calculated electronic energy levels of the fragments of clusters or methyl radicals. The results explain why diamond nuclei grow favorably on {111}B surfaces but not on {111}N ones, and the nucleation of diamond proceeds easily under the influence of alternating charge (+ and -), pulsed positive charge, or positive charge bias to the substrate.
A New Method for Size Control of Ultrafine Particles and Effect of Electric Field
Authors: Suzuki Hitoshi , Nakada Toshitaka , Saito Yoshio , Kaito Chihiro
Published: October 2002

A simple method to change the feature of smoke was found. Smokes of In2O3 and Al were used in the model experiment. The size of smoke particles is smaller, i.e., 0.6 (Al)–0.5 (In2O3), than those of ordinarily produced smoke particles. The oxide smoke curved in an electric field. In this case, various sizes of particles were obtained depending on the location of the collection point. Truncated In2O3 tetrahedron particles less than 100 nm in size were predominantly obtained. The oxygen defects in small In2O3 particles have been discussed as being due to a definite array of oxygen. The curve of oxide smoke in the electric field has been discussed in terms of being due to the structure of the oxide.
Theoretical Relation between Spatial Resolution and Efficiency of Detection in Scanning Hot Electron Microscope
Authors: Sakai Norio , Furuya Kazuhito , Zhang Bingyang , Karasawa Shinya
Published: October 2002

To observe the spatial distribution of subsurface hot electrons (HEs) with a scanning probe, the relation between the spatial resolution and the hot electron current is investigated theoretically and the efficiency of HE detection is discussed. Using a sphere-plane model for the tip and the sample surface in a scanning hot electron microscope (SHEM), the electrostatic potential and the tunnel transmission are analyzed using the three-dimensional (3D) image charge method and quantum mechanical analysis, respectively, to simulate HE detection. The resolution and the hot electron current depend on the hot electron energy and the tip-sample space and are related. The efficiency of HE detection is defined and its dependence on the parameters is examined. For a given hot electron energy, the resolution is determined by the minimum hot electron current which is larger than the noise current.
Basic Experimental Simulation of a Traveling Wave Direct Energy Converter for a D–3He Fusion Reactor
Authors: Takeno Hiromasa , Ikeda Youichi , Yamada Takashi , Noda Kazuyuki , Yasaka Yasuyoshi
Published: October 2002

We simulated a traveling wave direct energy converter for application in a D–3He fusion reactor. The deceleration of a simulated ion beam was studied, and the dependence of the efficiency of the decelerator on its length was examined. The effectiveness of spatial variation in the phase velocity of the traveling wave was demonstrated experimentally. Optimization of the structure of the decelerator is discussed with the aid of numerical simulations. By employing the proper decelerator structure, the efficiency per unit length of about 0.2 with the normalized decelerator length of about 2.5 is expected.
Two-Photon Spectroscopy of the 6S–8S Transitions in Cesium using an Extended-Cavity Diode Laser
Authors: Sasaki Kaoru , Sugiyama Kazuhiko , Barychev Viatcheslav , Onae Atsushi
Published: October 2002

Two-photon spectroscopy of the 6S–8S transitions in cesium was conducted using an extended-cavity diode laser for the first time, to our knowledge. The signal-to-noise ratio of the signals obtained shows a potential use for the transitions as a secondary frequency standard at 822 nm.
Thermal Lens Microscope
Authors: Uchiyama Kenji , Hibara Akihide , Kimura Hiroko , Sawada Tsuguo , Kitamori Takehiko
Published: October 2002

We developed a novel laser microscope based on the thermal lens effect induced by a coaxial beam comprised of excitation and probe beams. The signal generation mechanism was confirmed to be an authentic thermal lens effect from the measurement of signal and phase dependences on optical configurations between the sample and the probe beam focus, and therefore, the thermal lens effect theory could be applied. Two-point spatial resolution was determined by the spot size of the excitation beam, not by the thermal diffusion length. Sensitivity was quite high, and the detection ability, evaluated using a submicron microparticle containing dye molecules, was 0.8 zmol/µm2, hence a distribution image of trace chemical species could be obtained quantitatively. In addition, analytes are not restricted to fluorescent species, therefore, the thermal lens microscope is a promising analytical microscope. A two-dimensional image of a histamine molecule distribution, which was produced in mast cells at the femtomole level in a human nasal mucous polyp, was obtained.
Arc Synthesis of Fullerenes from the Carbide of Waste Cloths
Authors: Hayashi Koichiro , Mieno Tetsu
Published: October 2002

A great many scraps of cotton cloth are disposed of as industrial waste through making clothes. The purpose of this study is to transform the waste into very valuable carbon compounds, that is, fullerenes. The scraps were piled and carbonized in air at 1050°C. By carbonization, the weight of the scraps decreased to 16–18%. Carbide from the scraps was used as the raw material for synthesizing fullerenes with the J×B arc discharge method. The soot that was deposited on the inside of the vacuum chamber contained C60 (>0.05 wt%), C70 and higher fullerenes.
√ω-Variation of AC Admittance in the Inhomogeneously Distributed RC Lines
Authors: Miura Michio Sugi , Kazuhiro Saito Kazuhiro Saito
Published: October 2002

The ac admittance Y(ω) has been analytically derived for the R
C lines with locally varying resistance R(x) and capacitance C(x) per unit length under the condition R(x)/C(x) = const. An R
C line of this type is found to obey the square-root law Y(ω) ∝√ω for higher frequencies, and to have the advantage of reducing the line length in comparison to the conventional R
C line with uniformly distributed R and C.