bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Moisture Absorption on Piezoresistance of Conducting Polymer Composite Thin Films
Authors: Hirano Shingo , Kishimoto Akira , Miyayama Masaru
Published: October 2002

This paper is devoted to the study of the piezoresistance of conducting composite thin films
consisting of epoxy resin and needle-like conductive fillers. The surface resistivity of the
thin films at room temperature depended on filler volume fraction and relative humidity (rh).
The effect of moisture absorption on the piezoresistance of the composite thin films was
studied under various rh values. At high rh values, strain dependence of resistance
was positive, and this positive coefficient decreased with decreasing rh value. At 30%rh, it
became negative and its absolute value increased with decreasing rh. These results suggest
that the piezoresistance effect of the conducting thin films is enhanced by moisture
absorption by the epoxy matrix that is relatively hydrophilic. From these observations,
the piezoresistance effect is considered to be based on the following two strains: one is
derived from a mechanical stress and the other is due to environmental stress induced by
moisture absorption.
Photocurrent Multiplication at Organic/Metal Interface and Morphology of Metal Films
Authors: Hiramoto Masahiro , Sato Ichiro , Nakayama Ken-ich , Yokoyama Masaaki
Published: October 2002

Characteristics of photocurrent multiplication phenomenon occurring
at an organic perylene pigment/metal interface were revealed to be
drastically influenced by the morphology of metal films. When a deposited
Au film formed an imperfect contact with a microscopically rough pigment
surface, the organic/Au junction exhibited a large photocurrent
multiplication exceeding 104-fold. In contrast, when an Au film closely
stuck to the pigment surface, the organic/Au junction exhibited slight
photocurrent multiplication. The present results support the existence of a
large number of blind alleys at organic/metal interfaces, acting as structural
traps which capture the photogenerated holes as a trapped space charge.
These traps build up an intense electric field at an organic/metal interface
and trigger tunneling electron injection from the Au electrode to yield the
large photocurrent multiplication.
Theoretical Investigation of the Adsorption Behavior of Si Adatoms on GaAs(001)-(2×4) Surfaces
Authors: Shiraishi Kenji , Ito Tomonori
Published: October 2002

We theoretically investigate the adsorption behavior of Si adatoms on GaAs(001)-(2×4) surfaces
by ab initio calculations. The calculated results show that Si adatoms tend to be incorporated in the
missing dimer trench when the Si coverage is small. Whereas favorable Si adsorption sites change
from the missing dimer trench to the upper As dimers as Si coverage increases. This coverage
dependence of Si adsorption sites is qualitatively consistent with recent experiments. Moreover, we
comment on the mechanism that governs the adsorption behavior of Si adatoms on GaAs surfaces.
Barium Titanate-Based Capacitors Buried into Ceramic Substrates
Authors: Chen Lih-Shan , Fu Shen-Li , Huang Kwan-Dar
Published: October 2002

Burying passive components into the multilayer ceramic substrate can
offer increased circuit surface area for IC. With the addition of LiF,
nonstoichiometric barium titanate BaTi0.975O3 can be well densified after
sintering at the temperature less than 1000°C. From X-ray diffraction pattern,
barium titanate is the main existing crystalline structure. Dielectric constant
about 1050 with the dissipation factor 2.3% was obtained for
BaTi0.975O3+2 wt% LiF embedded capacitor sintered at 900°C.
Optical Properties of a Polymer-Stabilized Liquid Crystal Microlens
Authors: Shin Masuda Shin Masuda , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

We propose and demonstrate, for the first time, the fabrication of a polymer-stabilized gradient-index-type microlens using a liquid crystalline composite system containing a UV curable liquid crystal (LC) that can be photopolymerized by UV irradiation. The gradient-distribution state of nematic LC molecules in the LC microlens can be stabilized by the polymer network formed by the UV curable LC, and the focusing property of the microlens is maintained without applying voltage. Furthermore, the optical property of the microlens can be varied by applying voltage after photopolymerization. As a result, it is confirmed that the polymer-stabilized LC microlens overcomes the drawback of conventional LC microlenses.
High Dielectric Dopants for Low Voltage Liquid Crystal Operation
Authors: Wu Shin-Tson , Zhang Qing T. , Marder Seth
Published: October 2002

Several linear polyene compounds with extraordinarily large dielectric anisotropy
and small elastic constant were synthesized and their physical properties
evaluated. The dielectric anisotropy of these compounds varies from 60 to 70,
depending on the detailed molecular structures. Adding 3% of these compounds
to a polar and a nonpolar liquid crystal mixtures significantly reduces their
threshold voltage while only causes a modest increase in viscosity.
Effects of Nitrogen Ion Beam Irradiation on a-C and CNx Thin Films
Authors: Jin Yun-Sik , Shibata Tetsuya , Matsuda Yoshinobu , Fujiyama Hiroshi
Published: October 2002

Amorphous carbon (a-C) and carbon nitride (CN
x
) thin films were irradiated with a nitrogen
ion beam (N+/N2
+) at different ion energies between 0.5–10 keV. The CN
x
film showed high
sputter erosion and a decrease in nitrogen concentration by ion bombardment. In a-C film,
nitrogen accumulation inside it due to nitrogen ion implantation was clearly observed. X-ray
photoelectron spectroscopy (XPS) depth profiles revealed that the ion implantation ranges of
nitrogen in the a-C films were consistent with TRIM calculation. The existence of C-N covalent
bonds was confirmed by XPS studies of the ion-implanted a-C film.
High-Resolution Magnetic Force Microscope Images of a Magnetic Particle Chain Extracted from Magnetic Bacteria AMB-1
Authors: Hitoshi Suzuki Hitoshi Suzuki , Tsuyoshi Tanaka Tsuyoshi Tanaka , Tomohito Sasaki Tomohito Sasaki , Noriyuki Nakamura Noriyuki Nakamura , Tadashi Matsunaga Tadashi Matsunaga , andShinro Mashiko andShinro Mashiko
Published: October 2002

Bacterial magnetic particles were observed by an atomic force microscope (AFM) and a
magnetic force microscope (MFM).
The chain of magnetic particles was extracted from the bacteria with little disturbance
to their alignment by a new preparation method.
Magnetic bacteria cells were broken using an NaOH/ethanol solution.
Cell debris was washed away in order to leave the magnetic particle chains, which were
held on the glass surface by a magnet.
In both AFM and MFM images, individual magnetic particles could be clearly observed.
The MFM image showed that the particles aligned their magnetized axes along the chain.
Investigation of Arsenic Desorption from GaAs(111)B Surface in Atmospheric Pressure Atomic Layer Epitaxy
Authors: Tetsuya Taki Tetsuya Taki , Koji Narita Koji Narita , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

Arsenic desorption from the GaAs (111)B surface is investigated under atmospheric pressure using an in situ gravimetric monitoring system, which is equipped with a halogen transport atomic layer epitaxy (ALE) reactor and a microbalance system.
It is shown that the growth rate decreases from > 1.0 to 0.5 molecular layer (ML)/cycle with increasing H2 purge time after AsH3 supply depending on the As coverage on the surface, and (111)B GaAs has three kinds of reconstructed surfaces in the atmospheric ALE.
The atomic force microscopy (AFM) images of 100 ML grown surfaces show that atomically smooth surfaces can be obtained on the reconstructions of (1×1)LT and (√19×√19).
Investigation of the Substrate-Patterning Effect on Morphological Instability in Selective Area Growth
Authors: Kim Jeong Soo , Jang Young Joo , Park Chan Yong , Choo Heung Ro , Kim Hong Man , Pyun Kwang Eui
Published: October 2002

The surface of selectively grown InP using metal-organic vapor phase epitaxy shows a corrugated morphology with of a striped shape. The morphological instability is shown to be caused by the presence of edge overgrowth. The corrugated morphology induced by the selective area growth deteriorates the optical quality of the multiple quantum well which is grown on the corrugated InP. The surface morphology of InP and the photoluminescence intensity of the multiple quantum well were improved by the method of patterned-selective growth which placed a dielectric mask at a lower region than that for the devices.
Improvement of SiO 2 Properties and Silicon Surface Passivation by Heat Treatment with High-Pressure H 2O Vapor
Authors: Toshiyuki Sameshima Toshiyuki Sameshima , Keiji Sakamoto Keiji Sakamoto , Yoshiyuki Tsunoda Yoshiyuki Tsunoda , Tadashi Saitoh Tadashi Saitoh
Published: October 2002

Heat treatment with high-pressure H2O vapor was applied to improve the properties of SiOx (x<2) films formed by vacuum evaporation, for passivation of the silicon surface. Heat treatment at 340–420 °C changed SiOx films into SiO2 films with an Si–O–Si bonding network similar to that of thermally grown SiO2 films. The densities of interface trap states and fixed positive charges were reduced to 6.5×1010 cm-2eV-1 and 2.5×1011 cm-2, respectively, after heat treatment at 340 °C with 2.4×106 -Pa–H2O vapor for 3 h. The heat treatment reduced the recombination velocity for the electron minority carriers from 1200 cm/s (as fabricated) to 140 cm/s.
Element-Specific Image and Local Work Function of Fe Submonolayer Film on Au(001) Studied by Scanning Tunneling Microscopy
Authors: Takeshi Kawagoe Takeshi Kawagoe , Yasuo Jimma Yasuo Jimma , Tomoyuki Kotaki Tomoyuki Kotaki , Nobuhiro Kondoh Nobuhiro Kondoh , Akiyoshi Itoh Akiyoshi Itoh
Published: October 2002

Spatially resolved maps of the local work function of Fe
submonolayer films
on an Au(001) surface, together with a topographic image,
were obtained using a scanning tunneling microscope with the gap
distance modulation technique.
A clearer element-specific contrast between Fe and Au was
observed compared with that of the topographic image.
The observed work function of ultrathin Fe films is larger than
that of Au(001) substrate,
which is in contrast with the bulk values of each element.
The effect of the decay rate of the wave function on the sample surface
is discussed. We also observed that the work function of the second Fe layer,
which exceeds the bulk value,
was larger than that of the first Fe layer.
All-Optical Inverter Operating up to 850°C in an Erbium-Doped Phosphate Glass
Authors: Maeda Yoshinobu , Akidzuki Yoshiki , Konishi Akio , Hashima Hidekazu , Wakabayashi Hajimu , Yamada Toshikazu
Published: October 2002

The dependence of an all-optical inverter on both sample temperature and modulation frequency was investigated in an erbium-doped
phosphate glass using a 809.5 nm laser diode. The reversed-phase waveforms were observed in the transmitted waveform in a temperature range of -220 to 875°C. The glass
transition temperature was measured to be 697°C by differential thermal analysis and the glass was in the form of supercooled liquid between 700 and 930°C. An all-optical
inverter which had a negative input-output characteristic was demonstrated in a temperature range of -200 to 850°C.
Silicon Crystal Growth under Equilibrium Condition of SiO2-Si–SiO System: Equilibrium Oxygen Segregation Coefficient
Authors: Huang Xinming , Nakazawa Tatsuo , Terashima Kazutaka , Hoshikawa Keigo
Published: October 2002

Single silicon crystals have been grown successfully under the equilibrium
condition of a SiO2–Si–SiO system in a closed silica ampoule with a vertical
directional freezing method. The oxygen concentration in the grown single crystals
was obtained using Fourier transform infrared spectroscopy (FT-IR) and secondary
ion mass spectroscopy (SIMS) techniques as 1.7±0.1 (×1018 atoms/cm3). The
equilibrium segregation coefficient of oxygen was obtained by comparing the
oxygen concentration of the silicon crystal to the oxygen solubility in the silicon
melt. The equilibrium oxygen segregation coefficient was, then, determined to be
0.8±0.1.
Generation of Novel Aluminum Nano Balls
Authors: Goto Masahiro , Murakami Junichi , Tai Yutaka , Igarashi Kazuo , Tanemura Sakae , Kusunoki Michiko
Published: October 2002

Aluminum nano balls have been generated by the magnetron sputtering-gas aggregation method.
The analyses of transmission electron microscope (TEM) images and electron diffraction patterns
revealed that the balls are made of aluminum crystals covered with a thin layer of θ-type alumina.
The balls deposited on a copper substrate were observed by scanning tunneling microscopy (STM).
They were found to land softly on the substrate without decomposition.
Laser Compton Scattering as a Light Source from Vacuum Ultraviolet to Soft X-ray Wavelengths
Authors: Mamine Takayoshi , Ohgaki Hideaki
Published: October 2002

Features of laser Compton scattering are verified for its use as a light source covering the wavelength range from vacuum ultraviolet (VUV) to soft X-rays for future lithography. The wavelengths of scattered photons from typical solid-state or excimer lasers are well controlled in the range from 100 nm to less than 1 nm merely by varying the electron acceleration energy up to 10 MeV. It is also shown that the yield of photons could be of the order of 1010–1013/s by optimizing the pulse durations and beam spot sizes of photon and electron beams.
Transmission Electron Microscope Observation of Grown-in Defects Detected by Bright-Field Infrared-Laser Interferometer in Czochralski Silicon Crystals
Authors: Ikematsu Yoichi , Mizutani Toshiyuki , Nakai Katsuhiko , Fujinami Masanori , Hasebe Masami , Ohashi Wataru
Published: October 2002

Grown-in defects detected by a bright-field infrared-laser interferometer (known as Optical Precipitate Profiler: OPP) in Czochralski silicon (Cz–Si) have been investigated by means of transmission electron microscopy (TEM). The grown-in defects in Cz–Si grown at the pulling rate of 1.0 mm/min are identified as twin or triple polyhedral cavities faced by {111} and {100} planes, with a total size of 0.1–0.2 µm. These polyhedral cavities were observed to be attached to each other. It has been found that the grown-in defects in growth-held Cz–Si at 1080°C for 120 min remarkably grow as twin or triple polyhedral cavities with a total size of 0.4–0.7 µm. Further, the quantitative relation between the size of the grown-in defects and the OPP signal intensity is derived.
Two-Dimensional Visualization of Photoinduced Refractive Index Change in Photorefractive Lithium Niobate Crystal
Authors: Shiratori Akira , Aida Ryuji , Hagari Ryohei , Obara Minoru
Published: October 2002

We have demonstrated two-dimensional imaging of photoinduced index change in a photorefractive lithium niobate crystal using Mach-Zehnder interferometry. Refractive index changes induced by both ordinary and extraordinary Ar+ laser beams have been clearly visualized.
Thermal Quenching of the Photoluminescence of InGaAs/GaAs Single Quantum Wells Adjacent to a Selectively Oxidized AlAs Layer
Authors: Pratt Andrew Richard , Takamori Takeshi , Kamijoh Takeshi
Published: October 2002

The photoluminescence (PL) from InGaAs/GaAs single quantum wells (SQWs) adjacent to an oxidized AlAs layer is found to be thermally quenched for temperatures upwards of 100 K, depending on the proximity of the oxide-semiconductor interface. For a direct interface between the SQW and oxidized AlAs, the onset of the PL quenching occurs at a lower temperature than for the unoxidized material. Analysis of the temperature dependence reveals that the dominant loss mechanism is non-radiative recombination at the oxide-semiconductor interface, which is characterized by an eighteenfold increase in the non-radiative rate of carrier recombination. However, a 20 nm AlGaAs layer grown between the SQW and AlAs effectively blocks the carriers from the oxide interface, and results in a temperature dependence after oxidation approaching that of the as grown material.
Selective Enhancement of Coherent Optical Phonons Using THz-rate Pulse Train
Authors: Muneaki Hase Muneaki Hase , Tetsuya Itano Tetsuya Itano , Kohji Mizoguchi Kohji Mizoguchi , Shin-ichi Nakashima Shin-ichi Nakashima
Published: October 2002

Selective enhancement of coherent optical phonons in Bi-Sb mixed crystals has been performed using terahertz (THz) rate pulse trains generated by spatial phase modulation of femtosecond pulse with a liquid-crystal spatial light modulator. The profile of the shaped pulse train has a flat-toped shape. The Bi-Bi, Bi-Sb, and Sb-Sb vibrations can be enhanced and canceled selectively for pulse trains with a suitable repetition rate.
Study of Threading Dislocations in Wurtzite GaN Films Grown on Sapphire by Metalorganic Chemical Vapor Deposition
Authors: T. Romano Maosheng Hao , Shiro Sakai Shiro Sakai
Published: October 2002

The threading dislocations in GaN films grown on Al2O3 substrates were studied by plan view transmission electron microscopy (TEM). A pure edge dislocation and a mixed dislocation with different kinds of screw components, could be distinguished by taking the images near and far-away from the <0001> zone. The experimental results show that some pure edge dislocations form low-angle boundaries and other pure edge dislocations as well as mixed dislocations are randomly distributed in GaN films. The randomly distributed dislocations result from reactions of partial dislocations. Partial dislocations, on the other hand, is formed to eliminate the stacking disorder near the interface of GaN/Al2O3 films.
The Chaotic Oscillation of the Single-Mode He-Ne(6328 Å) Class A Laser
Authors: Iwasawa Fumiyoshi Kuwashima
Published: October 2002

The confirmation of chaotic oscillation in a single-mode He-Ne(6328 Å) standing-wave class A laser, by means of delayed feedback with an external mirror is reported. Varying the reflectivity of the external mirror, the time series of the laser output power are observed. By constructing the phase portraits and estimating Lyapunov exponents, the transition from a point attractor to a strange attractor is confirmed by the positive Lyapunov exponents in the chaotic region.
Cathode Ray Tube Lighting Elements with Carbon Nanotube Field Emitters
Authors: Saito Yahachi , Uemura Sashiro , Hamaguchi Koji
Published: October 2002

We have manufactured cathode ray tubes (CRTs) equipped with field emitters composed of multiwalled carbon nanotubes. The fabricated CRTs (20 mm in diameter by 74 mm in length) are of a triode type, consisting of a cathode (nanotube field emitter arrays), a grid and an anode (phosphor screen). The manufactured CRTs are lighting elements, which are assembled to form a giant outdoor display. Stable electron emission, adequate luminance and long life are demonstrated. The CRT lighting elements presented here are the first practical products utilizing carbon nanotubes on an industrial scale.
Low Doped P-Type AlGaAs Buffer Layers Grown by Metalorganic Chemical Vapor Deposition Using Intrinsic Carbon Doping Method
Authors: Choi Seung June , Seo Jin Ho , Lee Jae Hak , Seo Kwang Seok
Published: October 2002

Low-doped (∼1016 cm-3) and low-compensated p-type AlGaAs layers grown by metalorganic chemical vapor deposition (MOCVD) were studied to determine the optimal growth conditions for p-type buffer layers in GaAs field-effect transistors (FETs). Good reproducibility of doping control was confirmed with the use of an intrinsic carbon doping method. As the growth conditions were varied, significant changes in the compensation ratio of p-type AlGaAs layers were observed. While the Al0.15Ga0.85As layer with a compensation ratio of 0.4 exhibited a hole mobility of 142 cm2/V·s, a larger hole mobility of 170 cm2/V·s was obtained for the sample with a compensation ratio of 0.1. The growth condition of high V/III ratio and a low growth temperature are preferable for the growth of low-doped and low-compensated p-type AlGaAs buffer layer.
Small-Angle Neutron Scattering Observation of Aqueous Suspension of Microcrystalline Cellulose
Authors: Masaaki Sugiyama Masaaki Sugiyama , Kazuhiro Hara Kazuhiro Hara , Nobuyasu Hiramatsu Nobuyasu Hiramatsu , Hideki Iijima Hideki Iijima
Published: October 2002

The aqueous suspensions of microcrystalline cellulose (the mean diameter using the laser scattering method, approximately 3µm) were observed with the small-angle neutron scattering method. The scattering profiles were almost independent of the microcrystalline cellulose concentration and showed a fractal structure with a dimension of 2.2. The small-angle neutron scattering results from the internal structure of the cellulose particle.
Spiral Growth of InGaN Nanoscale Islands on GaN
Authors: Keller Stacia , Mishra Umesh K. , Denbaars Steven P. , Seifert Werner
Published: October 2002

Spiral growth was found to be the dominant growth mechanism for InGaN single quantum wells grown under low trimethylgallium flow rates by metal-organic chemical vapor deposition on GaN-on-sapphire films. This spiral growth around threading dislocations with a screw component led to the formation of flat, 1–2 nm high, InGaN islands of diameters in the range of 100–400 nm. The diameter of the InGaN islands increased with decreasing trimethylgallium flow, i.e., decreasing InGaN growth rate. The formation of spatially separated islands could be enhanced by disilane pre-treatment of the GaN surface prior to InGaN deposition. The InGaN island formation is discussed as a possible contribution to the development of spatial inhomogeneities in InGaN layers.
Effects of Postannealing in Oxygen Ambient on Leakage Properties of (Ba, Sr)TiO3 Thin-Film Capacitors
Authors: Fukuda Yukio , Numata Ken , Aoki Katsuhiro , Nishimura Akitoshi , Fujihashi Gaku , Okamura Soichiro , Ando Shizutoshi , Tsukamoto Takeyo
Published: October 2002

Effects of postannealing in oxygen ambient on the leakage properties of sputter-deposited (Ba, Sr)TiO3 (BST) thin-film capacitors with Pt electrodes are investigated as a function of oxygen gas pressure, postannealing temperature and postannealing time. It is shown that the leakage properties can be improved by increasing these conditions. By comparing the leakage behavior with a Schottky emission model, it is concluded that the main effect of postannealing is an increase in the Pt/BST Schottky barrier height. It is also shown that the Fermi level of the BST film may be pinned at the Pt/BST interface because of oxygen vacancies in the film.
Production of Low-Pressure Planar Non-Magnetized Plasmas Sustained under a Dielectric-Free Metal-Plasma Interface
Authors: Morita Shin , Nagatsu Masaaki , Ghanashev Ivan , Toyoda Naoki , Sugai Hideo
Published: October 2002

Large-area Ar and CF4 non-magnetized plasmas were produced in an entirely metal (stainless steel) plasma chamber with a diameter of 220 mm by 2.45 GHz electromagnetic wave launched by slot antennas cut in the top circular metal lid. Dielectric (quartz) was used only for local vacuum sealing over the slot antennas, occupying less than 20% of the top metal area. At low pressure of 10 mTorr, overdense (>1011 cm-3) plasma was produced filling the whole chamber cross-section similarly to the known case of surface-wave plasmas produced below a large dielectric window covering 100% of the top chamber lid. The absence of this large dielectric suggests that this approach can be used for developing large-area non-magnetized plasma source with less impurities for thin-film processing.
New Approximant of Twelvefold Quasicrystal in Ta–Te: Electron Diffraction Study
Authors: Uchida Masaya , Horiuchi Shigeo
Published: October 2002

A new approximant of a twelvefold quasicrystal has been discovered in Ta62Te38.
Electron diffraction study reveals that it is basically composed of two modulated layers
rotated by 30° to each other. Structures of the twelvefold quasicrystal and the new
approximant can be related by modulation waves with same directions but with slightly
different wavelengths.
The Relation between Resonance Curves and Tip-Surface Interaction Potential in Noncontact Atomic-Force Microscopy
Authors: Naruo Sasaki Naruo Sasaki , Masaru Tsukada Masaru Tsukada
Published: October 2002

We present a perturbation theory which enables us to understand
the physics of the cantilever-forced vibration in noncontact-mode
atomic-force microscopy. Analytical expressions of the resonance
curve and frequency shift are given. This theory is applied to the
model system with a van der Waals tip-surface interaction potential.
Based on this case study, it is elucidated how the resonance
frequency shift is analytically described by an integral of the
tip-surface interaction force over the traverse of the tip around
the turning point. This quantity is rather sensitive to the
interaction potential. We can see by this method how the dynamical
instability occurs and significantly influences the observation of
the resonance peak. Calculated resonance curves and frequency shifts
agree fairly well with those obtained by a numerical integration of
equation of motion outside the bistable region.
Selective Etching of Silicon Native Oxide with Remote-Plasma-Excited Anhydrous Hydrogen Fluoride
Authors: Yutaka Nakazawa Yutaka Nakazawa , Yoji Saito Yoji Saito
Published: October 2002

We demonstrate to the acceleration of the moistureless etching reaction between the silicon native oxide and the anhydrous hydrogen fluoride (AHF) gas, using remote-plasma-excited Ar gas at room temperature.
The etching reaction is significantly enhanced by the remote-plasma-excitation for both the chemically grown native oxide films and the dehydrated oxide films. Then, we attempt to improve the selectivity
of the oxide etching with respect to silicon by introducing hydrogen into this system, and to realize the highly selective etching
of native oxide with respect to silicon. With the increase of the hydrogen partial pressure, the etch rate of silicon rapidly decreases due to the suppression of the density of fluorine radicals in the gas phase.
We have confirmed the value of the etch rate selectivity to be at least 4.
Electron Energy-Loss Spectroscopy and Energy-Filtered Imaging of C60 Thin Films
Authors: Shin Dong Hyuk
Published: October 2002

Electron energy-loss spectra and energy filtered images have been obtained from C60 film
deposited on Si(100) substrate using a serial electron energy loss spectrometer equipped on a
scanning transmission electron microscope. The electron energy loss spectra of the specimen
in the low loss region reveals the plasmon energies of C60 to be 6.6 eV and 25.3 eV. Energy-filtered images obtained at energy-losses corresponding to
zero-loss, plasmon energies
of Si and C60, and core loss energies of Si and C60 clearly demonstrate the elemental mapping
capabilities of the energy-filtered imaging technique. Energy-filtered selected area diffraction
pattern indicates that the film is amorphous, i.e., the C60 molecules are randomly arranged on
the Si substrate, with a mean intermolecular spacing of 9.9±0.2 Å.
Diamond Tip Arrays for Parallel Lithography and Data Storage
Authors: Watanabe Fumiya , Arita Makoto , Motooka Teruaki , Okano Ken , Yamada Takatoshi
Published: October 2002

We propose a device capable of massively parallel nanoscale lithography and
data storage due to a uniform array of diamond tips. A prototype device is
constructed and demonstrated by forming patterns on silicon wafer surfaces. In
our initial study, surface layers on silicon are selectively removed in parallel by
mechanical ablation and microsized carbon islands are deposited in air. Nearly
all the lithographic and data storage techniques derived from proximal probe
techniques are expected to benefit from the diamond tip array method.
Increased Size of Open Hexagonally Shaped Pits due to Growth Interruption and Its Influence on InGaN/GaN Quantum-Well Structures Grown by Metalorganic Vapor Phase Epitaxy
Authors: Uchida Kenji , Kawata Masahiko , Yang Tao , Miwa Atsuko , Gotoh Jun
Published: October 2002

We have investigated the influence of growth interruption when group-III
sources are temporarily shut off, and that of the number of quantum-well
(QW) layers, on the crystalline quality of InGaN/GaN QW structures grown
by metalorganic vapor phase epitaxy. Atomic force microscopy measurements
revealed that the size of the pits on the QW surface increased
dramatically as the interruption time increased. Through transmission
electron microscopy and energy dispersive x-ray microanalysis, we found
that the pit formation due to growth interruption induces fluctuation in
the In composition around the pits in the QW structure, which leads to
significant variation in the growth rate as the number of QW layers increases.
Nd:Glass Ring Regenerative Amplifier Using Telescopic Geometry for High Output Energy with Good Beam Quality
Authors: Moon Jeong Tae , Cheol Kang Eung , Tai Kim Byung , Hee Nam Chang
Published: October 2002

To achieve high output energy by generating a large gain mode volume, a Nd:phosphate glass
ring regenerative amplifier with a built-in 1:1 telescope was proposed as a part of a terawatt
chirped-pulse amplification Nd:glass laser, and its performance was characterized. In this ring
regenerative amplifier, an input energy of 80 pJ could be amplified up to 33 mJ, and the output
beam size was 2.3 mm in width and 2.0 mm in height. The amplified spectrum showed
that high amplification could be obtained without a noticeable gain narrowing from the injected
spectrum of 6 Å bandwidth.
Small Angle X-Ray Reflection and Conductivity of Ni Films Prepared by Ion Beam Sputtering and Electron Beam Deposition
Authors: Ryosaku Inamura Ryosaku Inamura , Kazushi Yamauti Kazushi Yamauti , Tadashi Mizoguchi Tadashi Mizoguchi
Published: October 2002

The precise thickness of Ni films prepared by ion beam sputtering (IBS) and electron beam deposition (EBD) was measured by a small angle X-ray
reflection technique and the sheet resistance of these films was measured by
the van der Pauw method. It is concluded that the IBS films have a much
smaller crystalline grain size in growth structure and hence, a lower
conductivity (17 % of bulk value), and a slightly lower density
(87 % of X-ray density) as compared with the EBD films.
Widely-Chirped High-Repetition-Rate Continuous Wave FM Laser Oscillation in Erbium Fiber Ring Laser
Authors: Abedin Kazi Sarwar , Onodera Noriaki , Hyodo Masaharu
Published: October 2002

A widely chirped high-repetition-rate continuous wave (CW) FM laser
operation in an erbium fiber ring laser is demonstrated by intracavity phase
modulation at 3.3 GHz. Continuous wave FM spectrum as wide as 726 GHz at
1.56 µm is generated with a modulator phase retardation of 3.02 rad and a cavity
detuning of 24 kHz, corresponding to an FM modulation index of 109. This gives
an extremely large chirp rate of 7.51×1021 Hz/s of the output, highest of all
reported so far on FM laser oscillation. The effect of detuning and modulator
phase retardation on FM laser oscillation is investigated and compared with the
theoretical results.
650 nm AlGaInP/GaInP Compressively Strained Multi-Quantum Well Light Emitting Diodes
Authors: Chang Shoou-Jinn , Chang Chih-Sung
Published: October 2002

We have studied the optical properties of the AlGaInP/GaInP light emitting diodes (LEDs), with a compressively strained multiquantum well (CSMQW) active layer,
emitting at 650 nm. It was found that by introducing a compressive strain into the MQW active layer, we can significantly increase the output power of the MQW LEDs.
Furthermore, we have also found that a +0.33% compressive strain can reduce the 10–90% rise time and/or fall time of the AlGaInP/GaInP MQW LEDs from 50 ns to 15 ns.
Containerless Solidification of Si-Ge Binary Alloy by Means of Laser Heating Electromagnetic Levitation
Authors: Takamura Tomotsugu Aoyama , Kuribayashi Kazuhiko
Published: October 2002

Pure Si and Ge, and their alloys were stably levitated and
melted using an electromagnetic levitator combined with a laser
heating unit. A temperature measurement method using a mono- or
multicolor pyrometer for the semiconductor was discussed, and a
calibration method for a monocolor pyrometer was developed by
deriving their spectral emissivities at each melting point. The
maximum undercooling was measured as a function of composition. This
result corresponded well with the calculated value using the
classical theory of steady state nucleation in binary metallic melts.
Pd/GaN Schottky Diode with a Barrier Height of 1.5 eV and a Reasonably Effective Richardson Coefficient
Authors: Ishikawa Hiroyasu , Nakamura Kouichi , Egawa Takashi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

A Schottky diode of high quality Si-doped GaN grown on the c-face of a sapphire substrate by metalorganic chemical vapor deposition was investigated. Using conventional lift-off techniques, Ti/Al and Pd were evaporated as ohmic and Schottky contacts, respectively. The Pd/GaN Schottky diode showed excellent electronic properties. From the temperature dependence of current-voltage characteristics, a barrier height and a measured effective Richardson coefficient were obtained as 1.53 eV and 23.2 A·cm-2·K-2, respectively. The barrier height was much higher than reported values and the measured Richardson coefficient was almost equal to the calculated theoretical value of 26 A·cm-2·K-2.
Terminating Structure of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Surface Identified by Coaxial Impact Collision Ion Scattering Spectroscopy
Authors: Shimizu Saburo , Suzuki Yasumasa , Nishihara Takaharu , Hayashi Shigeki , Shinohara Makoto
Published: October 2002

Terminating structures of the GaN{0001} films grown on nitrided sapphire(0001) substrates by plasma-assisted molecular beam epitaxy (MBE) have been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). The analyses of incidence angle dependences of time of flight (TOF) spectra have shown that the surfaces of GaN films grown under both N-rich and Ga-rich conditions are (0001) N-planes terminated with Ga atoms. This implies that (0001), N-terminated surfaces of GaN films grown under these conditions are unstable and a Ga-rich condition is required to avoid the N-deficiency in the grown GaN film.
Properties of Josephson Junction Fabricated on Bicrystal Substrate with Different Misorientation Angles
Authors: Minotani Tadashi , Kawakami Satoru , Kuroki Yukinori , Enpuku Keiji
Published: October 2002

In order to develop YBa2Cu3O7-δ bicrystal junctions suitable for
high-performance superconducting quantum interference device (SQUID), the relationship
between the junction properties and the misorientation angle of the bicrystal substrate
is studied experimentally. Misorientation angles of 24°, 27°, 30°, 33° and 36.8° are used,
and the angular dependencies of junction resistance R
s and critical current I
o are
investigated. It is shown that values of R
s and I
o approximately follow the relation
I
o
R
s
1.5=const. in these junctions. The obtained results are analyzed in terms of the
direct and resonant tunneling mechanisms. It is also shown that values of R
s≈10 Ω
and I
o≈20 µA can be obtained rather reproducibly when we use the 30° junctions. The
properties of this junction are very promising for the development of
high-performance SQUID.
Efficient Production of Endohedral Metallofullerenes in Repetitive Gravitation-Free Arc Discharge Using a Vertical Swing Tower
Authors: Mieno Tetsu
Published: October 2002

Production of endohedral metallofullerenes in gravitation-free arc
discharge is investigated by means of a 12-m-high vertical swing tower to
confirm the effect of gravitation-free condition, which suppresses thermal
convection of hot gas in the arc region and enables long-duration hot reaction
of carbon molecules. As a result, production rate of lanthanum
metallofullerene (LaC82) in gravitation-free condition prominently increases
compared with that in steady-state gravitational condition.
Construction of the Sample Holder and Small-Angle X-ray Scattering Measurement for Supercritical Water
Authors: Morita Takeshi , Miyagi Hiroshi , Shimokawa Yuji , Matsuo Hitoshi , Nishikawa Keiko
Published: October 2002

A high-temperature and high-pressure sample holder suitable for water under
supercritical conditions was constructed for small-angle X-ray scattering experiments, which
was designed to endure the temperature up to 750 K and the pressure up to 40 MPa. By use
of the holder, preliminary experiments for supercritical water were carried out along the
isotherm at 663 K with pressures from 22.5 to 29.5 MPa. Isothermal change of the correlation
length obtained from the scattering data showed maximum near the critical isochore. The
tendency is similar to other supercritical fluids, e.g., carbon dioxide, trifluorometane and
ethylene.
Degradation of Flash Memory Using Drain-Avalanche Hot Electron (DAHE) Self-Convergence Operation Scheme
Authors: Shen Shih-Jye , Yang Evans Ching-Song , Wong Wei-Jer , Wang Yen-Sen , Lin Chrong-Jung , Liang Mong-Song , Hsu Charles Ching-Hsiang
Published: October 2002

In this paper, the n-channel Flash memory device degradation by utilizing the drain-avalanche
hot electron (DAHE) self-convergence (S-C) scheme is demonstrated for the first time. The
injected hole originated by the channel electron induced avalanche hot hole generation is believed to
be responsible for this degradation. This hole injection phenomena not only result in the interface
state generation but also lead to the hole trapping in the tunnel oxide. The increased interface
states degrade the conduction of the channel current severely, which leads to abnormal
write/erase (W/E) endurance characteristics. The trapped holes in the tunnel oxide increase the
tunneling probability and cause the gate disturbance issue. From the concerns of long term
reliability, the self-convergence operation by utilizing the DAHE mechanism is not a proper scheme
for reliable Flash memory products.
Pattern Etching of Ta X-ray Mask Absorber on SiC Membrane by Inductively Coupled Plasma
Authors: Iba Yoshihisa , Kumasaka Fumiaki , Aoyama Hajime , Taguchi Takao , Yamabe Masaki
Published: October 2002

Patterning of an X-ray mask absorber after Si back-etching is desirable from the
viewpoint of the pattern placement accuracy. We investigated Ta X-ray absorber
etching on an SiC membrane equipped on a mask frame using a low-stress CrN
hard mask and an ICP etcher with a He cooling system. In this system, the
membrane temperature and the self-bias voltage could be controlled. A 40-nm-thick
CrN film was etched using a 200-nm-thick resist and Cl2 and O2 gases with a
selectivity of 0.72 and a vertical sidewall. A 400-nm-thick Ta film was etched using
Cl2 gas at an electrode temperature of -10°C and a low gas pressure of 0.1 Pa. A
high selectivity of Ta to CrN, 42, was obtained, and lines and spaces patterns below
0.1 µm with vertical sidewalls could be fabricated.
A 25-nm-pitch GaInAs/InP Buried Structure Using Calixarene Resist
Authors: Atsushi Kokubo Atsushi Kokubo , Tetsuya Hattori Tetsuya Hattori , Hiroo Hongo Hiroo Hongo , Michihiko Suhara Michihiko Suhara , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

To realize a fine periodical pattern by electron beam lithography, a stady for using calixarene as a resist was carried out. A 25-nm-pitch resist pattern was fabricated and transferred to a thin InP layer by two-step wet chemical etching. Precise slight O2 ashing, to eliminate residual matter was essential to transfer the pattern by wet etching. The controllability of the width was improved when using calixarene, when the period was 40 nm. Furthermore, a 25-nm-pitch InP pattern was buried in a GaInAs structure by organometallic vapor phase epitaxy. This technology could be applied to realize electron wave devices.
Selective Area Growth of GaN Using Tungsten Mask by Metalorganic Vapor Phase Epitaxy
Authors: Yasutoshi Kawaguchi Yasutoshi Kawaguchi , Shingo Nambu Shingo Nambu , Hiroki Sone Hiroki Sone , Takumi Shibata Takumi Shibata , Hidetada Matsushima Hidetada Matsushima , Masahito Yamaguchi Masahito Yamaguchi , Hideto Miyake Hideto Miyake , Kazumasa Hiramatsu Kazumasa Hiramatsu , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

We studied selective area growth (SAG) of GaN using a tungsten (W)
mask with an atmospheric metalorganic vapor phase epitaxy (MOVPE) system.
No GaN polycrystals were observed on the W mask regions, and the selectivity
of GaN growth on window regions proved to be excellent.
The GaN stripes developed into different shapes depending on the direction
of stripe mask patterns.
If the stripe was along <1120>, a triangular shape with {1101}
facets was formed.
If the stripe was along <1100>, a trapezoidal shape with a smooth
(0001) surface on top and rough surfaces on both sides was obtained.
The lateral overgrowth of GaN on the W mask occurred in both cases.
The growth mechanisms and the facet formation were similar to those
found in SAG using a SiO2 mask.
The Detection of Critical Micelle Concentration Based on the Adsorption Effect Using Optical Fibers
Authors: Ogita Masami , Yoshimura Kenji , Mehta Mary A. , Fujinami Tatsuo
Published: October 2002

The structure of a surfactant molecule consists of two groups, a hydrophilic and a hydrophobic group. The possibility of detection of the critical micelle concentration (CMC) was examined using optical fibers, plastic cladding silica fiber (PCS) and plastic optical fiber (POF), with hydrophilic and hydrophobic core properties, respectively. The cladding was removed at the sensing region and the core was exposed to the sample solution. The output from both the PCS and POF increased drastically at the CMC of 3×10-3 mol/l. This was due to the rapid increase in the reflectance at the interface between the core and the sample solution as the surfactant molecules in the saturated solution began to adsorb onto the sensing region of the core surface.
Electrical and Optical Properties of a Poly(p-Phenylenevinylene) Derivative with a Mesogenic Substituent
Authors: Masanori Ozaki Masanori Ozaki , Shoji Okazaki Shoji Okazaki , Mitsuyoshi Onoda Mitsuyoshi Onoda , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electrical and optical properties of a poly(p-phenylenevinylene) derivative substituted with a long side chain containing alkoxybiphenyl mesogenic unit have been studied. A liquid-crystalline molecular alignment and layer structure have been confirmed by optical microscopic observation and X-ray diffraction measurement, respectively. The dielectric constant changes in a stepwise manner at phase transition temperatures. The band gap of the new polymer in the liquid-crystalline phase has been evaluated to be 2.3 eV, which monotonously decreases with decreasing temperature. A photoluminescence peak was observed at around 560 nm, which corresponds to the emission originating from the poly(p-phenylenevinylene) main chain. An electroluminescnce device has been fabricated using this liquid-crystalline polymer and it has been found that the emission spectra depend on the polarity of the applied electric field.
Electroreflectance Spectrum of CdTe 1-xSx Mixed Crystal Layer in CdS/CdTe Thin-Film Solar Cell
Authors: Teruaki Yamamoto Teruaki Yamamoto , Toshihiko Toyama Toshihiko Toyama , Hiroaki Okamoto Hiroaki Okamoto
Published: October 2002

The electroreflectance (ER) spectrum of the CdS/CdTe thin-film
solar cell has been studied in conjunction with the results on
the atomic element depth profile. The ER spectrum occurs with three
spectral components with optical transition energies of 1.44 eV,
1.47 eV and 1.49 eV at 293 K. The mixed crystal layer of CdTe1-x
Sx,
∼2 µm thick (x>0.004), extends from the CdS/CdTe metallurgical interface
into the CdTe layer, and the n–p junction locates in the mixed crystal layer. The
dominant 1.47-eV ER component is assigned to the band gap of the
mixed crystal layer of CdTe0.95S0.05 at around the n–p junction.@keyword
CdTe1- x
S
x
, CdS/CdTe solar cell, mixed crystal, electroreflectance, SIMS, n–p junction
Spin-Dependent Electron Tunneling in Ferromagnetic Metal/Insulator/Semiconductor Junctions Using Optical Spin Orientation
Authors: Nakajima Kentaro , Okuno Shiho N. , Inomata Koichiro
Published: October 2002

We examined the spin-dependent tunneling of photoexcited electrons in FM/Al2O3/p-GaAs (FM=Ni and Co) junctions by using the optical spin orientation of p-GaAs. We have measured the phase-sensitive current modulation which corresponds to the polarization modulation of the excitation
light. The relative changes of conductance ΔG/G, with respect to the magnetization reversal of the
ferromagnet, were found to be 0.3 and 0.8% for Ni and Co, respectively. From bias-dependence of
ΔG/G, we assigned that the observed changes were responsible for the spin-dependent tunneling
where the photoexcited electrons in the conduction band of the GaAs enter into the unoccupied s,p-states of the ferromagnet.
Theory for Fringe Locking in a Laser Diode Interferometer
Authors: Liu Jiyuan , Yamaguchi Ichirou
Published: October 2002

A theoretical model that explains the fringe-locking phenomenon in a two beam laser diode
interferometer with optical feedback has been proposed. The dependence of wavelength on the
change of the optical path difference of the interferometer is calculated using the model, which
leads to results that agree well with those of experiments. The fringe locking is caused by the
change of lasing wavelength that suppresses the path difference change to much less than 2π.
The calculated rms phase fluctuations agree well with those measured experimentally.
Low Energy Electron Beam Stimulated Surface Reaction: Selective Etching of SiO 2/Si Using Scanning Tunneling Microscope
Authors: Nan Li Nan Li , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

We report here an experimental study of the low energy electron stimulated reaction (LEESR) carried out on a SiO2/Si surface using a scanning tunneling microscope (STM). By applying 100–150 V bias voltage and about 5 nA to below 1 µA current to the SiO2/Si surface, while the surface was kept at 700°C and 100-200 nm away from the STM tip, a surface reaction was induced by the low energy e-beam exposure. A surface of the Si substrate with clear atomic steps was observed within the exposed area, which indicates selective etching of SiO2 by which windows as small as 70 nm in diameter were cut through the SiO2 layer. This result demonstrates the possibility of fabricating a SiO2/Si surface by the LEESR etching and of performing a new type of well-controlled nanofabrication using STM.
Quality Improvement of GaInNAs/GaAs Quantum Well Growth by Metalorganic Chemical Vapor Deposition Using Tertiarybutylarsine
Authors: Pan Zhong , Miyamoto Tomoyuki , Koyama DietmarSchlenker , Iga Kenichi
Published: October 2002

A highly strained GaInNAs/GaAs quantum well (QW) was
investigated by low-pressure metalorganic chemical vapor deposition
(LP-MOCVD) using tertiarybutylarsine (TBAs) and dimethylhydrazine. The
V/III ratio was found to be an important parameter especially for
highly strained QW growth using TBAs based on MOCVD. The optimum V/III
ratio window of GaInNAs/GaAs QW growth was very narrow and located at
different temperatures and In contents. We propose a postgrowth
annealing procedure for improving the quality of GaInNAs/GaAs QW. The
photoluminescence intensity was significantly improved after annealing
at 640°C.
Growth of TlInGaAs on InP by Gas-Source Molecular Beam Epitaxy
Authors: Takenaka Keiichi , Asahi Hajime , Koh Hideki , Asami Kumiko , Gonda Shun-ichi , Oe Kunishige
Published: October 2002

TlInGaAs quaternary layers are grown on InP substrates by
gas-source molecular beam epitaxy (MBE) for the first time. The application of TlInGaAs was proposed
for long-wavelength optical devices as well as temperature-insensitive wavelength laser
diodes. During the growth, RHEED (reflection high-energy electron diffraction)
patterns show (2×2) reconstructions. Successful growth of TlInGaAs is confirmed with
X-ray diffraction measurements. PL emission is observed and the temperature variation
of PL peak energy is as small as 0.1 meV/K.