bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma Conductivity Estimation in Inductively Coupled Electrodeless Discharge by Equivalent Circuit
Authors: Watanabe Yoshio , Yasuda Makoto , Tamura Kouyou
Published: October 2002

An equivalent distributed constant circuit model for inductively-coupled
electrodeless discharge, having a double tube structure, is introduced. The distribution
profile of plasma conductivity in the tube is calculated by means of the diffusion
equation for electron density. The obtained profile shows good agreement with the
measured profile of the excited mercury atom density. Then, plasma conductivity as a
function of the induced discharge current is estimated by comparing the experimental
results with the results calculated using the model. The estimated maximum plasma
conductivity, σmax
, is independent of operating frequency and is approximated by the
following expression for the employed discharge tube: σmax
=0.007814i
D
2+0.4836i
D,
where i
D is induced discharge current in A(rms)/m.
Relationship between Density and Magnetic Field Fluctuations in the Lower-Hybrid Range of Frequencies
Authors: Hojo Hitoshi
Published: October 2002

The relationship between the density and magnetic field fluctuations induced by
electromagnetic waves or instabilities in the lower-hybrid range of frequencies is studied
based on a kinetic theory.
Numerical Analysis of Localized Defect Modes in a Photonic Crystal: Two-Dimensional Triangular Lattice with Square Rods
Authors: Noriko Kawai Noriko Kawai , Mitsuo Wada Mitsuo Wada , Kazuaki Sakoda Kazuaki Sakoda
Published: October 2002

We report the results of numerical calculation for localized defect modes
in a two-dimensional triangular photonic crystal composed of square air-rods
formed in silicon.
The eigenfrequencies and eigenfunctions of the defect modes were
calculated by means of the numerical simulation of the radiation process
of a virtual oscillating dipole moment.
We found that a defect mode of the A
1 spatial symmetry appears when one of
the air-rods is missing.
We also found that defect modes with all possible symmetries appear when
the dielectric constant of the defect rod is varied.
The consequence of their spatial symmetry is discussed.
Effect of Oxide Precipitate Size on Slip Generation in Large Diameter Epitaxial Wafers
Authors: Akatsuka Masanori , Sueoka Koji , Katahama Hisashi , Koie Yasuo , Sadamitsu Shinsuke
Published: October 2002

The effect of oxide precipitate size on slip generation was investigated in Czochralski
(CZ), p/p-, p/p+ and p/p++ epitaxial wafers during device manufacturing. In high-temperature
processes where maximum temperature reaches 1100°C, the mechanical strength of epitaxial
wafers was far superior to that of CZ wafers. In contrast, the mechanical strength of all wafers
was sufficiently maintained in low-temperature processes where maximum temperature reaches
1050°C. The slip dislocation generation can be explained according to the size of oxide
precipitate formed in each wafer; precipitates larger than approximately 200 nm can generate
slip dislocations.
Comparison and Investigation of Ohmic Characteristics in the Ni/AuZn and Cr/AuZn Metal Schemes
Authors: Youn Doo-Hyeb , Hao Maosheng , Naoi Yoshiki , Mahanty Sourindra , Sakai Shiro
Published: October 2002

The Ni/AuZn and Cr/AuZn contacts for achieving a low resistance ohmic contact to moderately doped p-GaN(4.4×1017/cm3) have been reported. In order to determine the reasons for the difference in ohmic characteristics of both metals, we have compared the ohmic contact characteristics and investigated the interfacial reaction mechanism between metal and GaN. The specific contact resistance was measured to be ρc=3.6×10-3 Ωcm2 in Ni/AuZn and 2.3×10-2 Ωcm2 in Cr/AuZn. The interfacial reaction mechanism during annealing has been studied by secondary ion mass spectrometry (SIMS) measurement. From this measurement, it was observed that Ni and Cr interact with the p-GaN surface and these interfacial reactions promote the Zn diffusion upon thermal treatment. The electrical properties were studied using current–voltage (I–V) measurements at room temperature. The microstructure between the metal and p-GaN interface was investigated using transmission electron microscopy (TEM) before and after heat treatment.
Redistribution Process of Oxygen Atoms in Separation-by-Implanted-Oxygen (SIMOX) Substrates
Authors: Yoshino Akira , Kasama Kunihiko
Published: October 2002

To form separation-by-implanted-oxygen (SIMOX) substrates, oxygen ions were implanted into the conventional (100) single-crystal silicon substrates at 80 keV to a dose of 1.0×1018 cm-2, maintaining the substrate temperature at around 520°C. Before and after post implantation annealing at 650–1280°C for 2 h, we examined silicon-on-insulator (SOI) structures of the SIMOX substrates using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared absorption spectroscopy (FTIR), cross-sectional transmission electron microscopy (XTEM), and Rutherford backscattering spectroscopy (RBS). On the basis of the experimental results of the XPS measurements (depth profiles of oxygen concentration and Si2p spectrum at around the binding energy of 99–105 eV) and the FTIR measurements (the peak position and the full width at half-maximum of the absorption peak associated with the Si–O stretching mode at around 1080 cm-1), together with XTEM images and RBS spectra, we clarified that inward migration of the implanted oxygen atoms is one of the primary processes for the formation of the SOI structure, and discussed the redistribution process of the implanted oxygen atoms as a function of the annealing temperature.
Asymmetric Photocurrent Characteristics in GaAs/AlGaAs Phototransistors with Very Short Carrier-Diffusion Lengths
Authors: Ohsawa Jun , Saigoh Kaoru , Yamaguchi Satoshi , Migitaka Masatoshi
Published: October 2002

Asymmetric optical gain was observed in a structure that was unusual for transistors.
Symmetric p-/n+/p- layers on p+-substrate were formed using selective overcompensation of
n--GaAs and n--AlGaAs by diffusion of deep acceptors of iron. Both GaAs homojunction and
AlGaAs/GaAs double-heterojunction (DH) devices demonstrated asymmetric photocurrent with
bias polarity; the current is larger and constant when the hole injection is along the carrier profile in
the base built up by photoabsorption, while for the reverse injection, the current is smaller and
increases with bias voltage. A gain of 10 was observed for the larger photocurrents of
homojunction devices. Since the hole diffusion length is greatly reduced due to recombination
centers of iron, and the absorption length is comparable to the base width of 0.8 µm, the
photocarrier profiles built up in the base region are believed to be responsible for the asymmetric
gain. Possible rapid response is also indicated.
Direct-Coupled High Tc DC Superconducting Quantum Interference Device Magnetometers on SrTiO3 Substrate: Theoretical Description and Comparison with Experiment
Authors: Enpuku Keiji , Minotani Tadashi , Kandori Atushi , Shiraishi Fumio , Beyer Joern , Drung Dietmar , Ludwig Frank
Published: October 2002

A comprehensive quantitative comparison between the measured performance of
direct-coupled high T
c superconducting quantum interference device (SQUID)
magnetometers with 30° bicrystal junctions and a numerical simulation is presented. It
is shown that the characteristics of the SQUID magnetometer are considerably affected by
resonances due to the large dielectric constant of the SrTiO3 substrate. In the realized
magnetometer layout, the strip line resonance occurring in the SQUID inductance
increases the voltage modulation depth and the output voltage noise of the SQUID, while
the flux noise of the SQUID is nearly unchanged. It is also shown that the distortion of
the voltage versus flux characteristic is caused by the LC resonance in the pickup loop of
the magnetometer in combination with a capacitive feedback. Good agreement between
experiment and simulation has been obtained.
Temperature Dependence of Negative Nonlinear Absorption Effect in an Erbium-doped Borate Glass
Authors: Maeda Yoshinobu , Konishi Akio , Hashima Hidekazu , Wakabayashi Hajimu , Yamada Toshikazu
Published: October 2002

The dependence of negative nonlinear absorption effect on sample temperature was investigated
in erbium-doped borate glass, using an 810.0 nm laser diode. Reversed-phase waveforms were
observed in the transmitted waveform in the temperature range of -200 to 750°C. The glass
transition temperature was measured to be 708°C by differential thermal analysis. It is suggested
that the effect can be obtained even when the glass is in the form of a supercooled liquid, because it
is formed by optical transitions of the erbium ion inner shell.
Electron Affinity Difference in CdS/Si Solar Cells
Authors: Kuhaimi Siham A. Al
Published: October 2002

The electron affinity difference ΔE
c=χ1-χ2, in CdS/Si solar cells fabricated
by four different processes is measured from observations of the variations of open
circuit voltage with temperature. For CdS/Si cells, the values of ΔE
c lie between 0.43
and 0.48 eV and are found to be independent of the process of cell fabrication. The
use of CdZnS in place of CdS decreases the value of ΔE
c to 0.3 eV. The method used
for the measurement of ΔE
c is very simple. The values of the saturation current I
0 for
different types of cells are estimated from the slopes of q
V
oc versus k
T characteristics
and compared with those obtained from ln I versus V curves. The values of I
0 found
for each cell by the two methods are in good agreement.
An Optical Deflector Using Collinear Acoustooptic Coupling Fabricated on Proton-Exchanged LiNbO3
Authors: Ito Kenchi , Kawamoto Kazumi
Published: October 2002

We fabricated a collinear acoustooptic deflector on proton-exchanged LiNbO3with the objective of achieving high-speed seeking and track-following in optical disk drives. In order to obtain a high-efficiency deflector, we studied the electromechanical coupling coefficientKeff2in proton-exchanged LiNbO3experimentally and found that proton exchange greatly reducesKeff2but annealing can gradually restore the value ofKeff2. The collinear acoustooptic deflectors fabricated under suitable annealing conditions had optimum properties for an optical pickup application. The other effects of the annealing are also discussed in detail.
Growth Kinetics of Hg1-xCdxTe Epilayers by Semiclosed Open-Tube Isothermal Vapor Phase Epitaxy
Authors: Koo Bonheun , Wang Jifeng , Ishikawa Yukio , Lee Chan-Gyu , Isshiki Minoru
Published: October 2002

Hg1-x
Cd
x
Te (MCT) epilayers were grown on (110) CdTe substrates by semiclosed
open-tube isothermal vapor phase epitaxy (ISOVPE). The effects of growth parameters
on the surface compositions (x) and thicknesses of the epilayers have been clarified and
discussed using the general ISOVPE model. It is found that the growth is limited by the
interdiffusion process. The growth kinetics in the interdiffusion control regime was also
studied. The growth rate followed the t
1/2 dependence expected for interdiffusion-limited
processes, and the growth rate constant (A) is given by the Arrhenius form with A
0=6.63×10-2 cm2/s and the activation energy Q=1.33 eV. The interdiffusion coefficients for
the composition (0.05<x<0.5) and temperature (698 K≤T≤ 773 K) are expressed as D(cm2/s)=550exp
(-9.27 x)exp
(-1.95 eV/κT) by Fleming-Stevenson analysis.
Quantum Chemical Study of the Oxidation Sites in Hydrogen- and Water-Terminated Si Dimers: Attempt to Understand the Si–Si Back-Bond Oxidation on the Si Surface
Authors: Sakata Ken , Tachibana Akitomo , Zaima Shigeaki , Yasuda Yukio
Published: October 2002

We investigated the cluster model reactions of the oxidation sites in hydrogen- and
water-terminated Si dimers using ab initio molecular orbital calculations in order to obtain a
chemical insight of which bond in the Si surface network the oxidant prefers to attack. First,
we focused on the basic reaction enthalpies of Si2H6 with O2 and found that the Si–Si bond
in the cluster is more easily oxidized than the terminal Si–H bond. A similar oxidation trend
was also found in the reaction of SiH3SiH2(OH) with H. The transient reaction intermediate
that possesses a terminal oxygen radical was fully transferred with low activation energy to
the Si–Si bond but with much higher activation energy to the adjacent Si–H bond. These
results showed the ease of Si–Si back-bond oxidation, which is a key point in understanding
the microscopic character of the oxidation site on the Si surface.
Mechanism of Residue Formation in Silicon Trench Etching Using a Bromine-Based Plasma
Authors: Hayakawa Tetsuo , Suzuki Takashi , Uesugi Tsutomu , Mitsushima Yasuichi
Published: October 2002

The formation mechanism of residues observed in HBr-based Si trench etching has been investigated. The residues were characterized using an optical microscope and a scanning electron microscope (SEM), and the residue density dependence on the interstitial oxygen concentration in the Si substrate, the formation process of etching masks and the etching condition was examined. It was confirmed that needle-shaped silicon residues of various heights had a disorderly distribution at the trench bottom. The density of the silicon needles strongly depended on both the interstitial oxygen concentration in the Si substrate and the mask formation process: numerous needles were observed when the oxygen concentration was sufficiently high and the mask formation process included oxidation. It was also found that the residue density increased with etching depth and selectivity to silicon oxide controlled by the etching condition. All the experimental results were successfully explained by a model in which oxygen precipitates nucleate in the Si substrate during the mask formation process, acting as micromasks in trench etching.
A Dark Discharge Model of Earthquake Lightning
Authors: Takaki Shunji , Ikeya Motoji
Published: October 2002

A model of dark discharge in the atmosphere before a large earthquake was proposed to elucidate the mechanism of generation of earthquake lightning and related electroatmospheric phenomena. Change in seismic stress releases piezo-compensating, bound charges due to changes in the piezoelectric polarization of quartz grains in granitic rocks, which produces an intense electric field at the fault zone. The excited or ionized molecules by free electrons accelerated under the electric field produce luminous phenomena in the atmosphere. Both Maxwell and Druyvesteyn distributions of the electron energy under the induced electric field were considered to estimate the rate of ionization and excitation of N2 and O2 molecules. An electric field and spatial distribution of earthquake lightning (EQL) were calculated based on the induced charges in the piezoelectric process which accompanies an earthquake. The intensity of emission from the excitation state, B
3Πg of N2 molecule was estimated at 3×1020 photons/m3 close to the fault zone. A nucleus of precipitation might also be formed in a supercooled atmosphere leading to the appearance of earthquake fog and clouds.
Potential of High-purity Polycrystalline Silicon Carbide for Thermistor Applications
Authors: Vasconcelos Elder Alpes de , Zhang Wen Yi , Uchida Hidekazu , Katsube Teruaki
Published: October 2002

This report concerns with a new material for thermistors, which consists of an undoped, polycrystalline, ultrahigh-purity chemical vapor deposition silicon carbide wafer. The resistance-temperature characteristic was measured from 25°C to 365°C. A good fit to the thermistor equation was observed and the thermistor B constant was 4845 K. These wafers are thermally and chemically stable, homogeneous and pure. They might be useful for fabrication of sensitive thermistors with stability and reproducibility of characteristics.
Control of the Microstructure of (Pb,La)TiO3 Thin Films by Metal-Organic Chemical Vapor Deposition Using a Solid Delivery System for Ferroelectric Domain Memory
Authors: Shin Ju Cheol , Hong Jae Wan , Lee Jong Myeong , Hwang Cheol Seong , Kim Hyeong Joon , Khim Zheong-Gu
Published: October 2002

A model illustrating the fact that ferroelectric films with uniform grain size and columnar structure will exibit a suitable domain configuration for ferroelectric domain recording storage media is proposed. To verify this model, (Pb,La)TiO3 thin films are deposited by metal-organic chemical vapor deposition by a solid delivery technique to grow films with a columnar structure and granular structure. A slow source input rate results in a film with a columnar structure whereas a fast input rate produces a film with a granular structure. The film with a columnar structure exhibits a more adequate domain configuration as confirmed by electrostatic force microscope observation, and also exhibits a very stable write/read operation for the domain memory application.
γ-Ray Total Dose Radiation Effects of Pt/PbZr0.52Ti0.48/Pt and Au/PbTiO3/YBa2Cu3O7-δFerroelectric Capacitors
Authors: Gao Jianxia , Zheng Lirong , Zeng Jianming , Lin Chenglu
Published: October 2002

In order to investigate the total dose radiation effects of ferroelectric (FE) capacitors, Pt/PbZr0.52Ti0.48O3/Pt (Pt/PZT/Pt) and Au/PbTiO3/YBa2Cu3O7-δ(YBCO) capacitors were fabricated by pulsed excimer laser deposition (PLD) on Si(100) and SrTiO3(001) substrates, respectively. The capacitance-voltage (C-V) curve and hysteresis loops properties of the capacitors were measured before and after γ-ray irradiation. The results show that, with the increment of the total dose, the remanent polarization and the coercive field of the PZT capacitors did not decrease, but increased while the dielectric constantεdecreased; the degradation of theεof the PbTiO3capacitors is similar to that of the PZT capacitors, but the remanent polarization and the coercive field decreased gradually. The results have been interpreted by radiation-induced positive charges and the traps of defects theory.
Relationship between Pyroelectric Properties and Electrode Sizes in (Pb, La)(Zr, Ti)O3 (PLZT) Thin Films
Authors: Kobune Masafumi , Ishito Haruo , Mineshige Atsushi , Fujii Satoshi , Tomozawa RyoichiTakayama
Published: October 2002

Highly c-axis-oriented PLZT films with compositions of (Pb0.925La0.075)(Zr
y
Ti1-y
)0.981O3,
where y=0.2–0.4, were deposited on Pt(100)/MgO(100) by the rf-magnetron sputtering,
applying an intermittent deposition comprised of the repetition of deposition and nondeposition.
It was confirmed that the highest figures of merit, F.M. and F.M.D* for the pyroelectric IR
sensors were obtained by using powders with excess PbO of 20 mol% added to PLZT, as
sputtering targets in the preliminary experiment. The PLZT film with y=0.2 exhibited the
highest F.M. for voltage responsivity Rv of approximately 5.3×10-13 C·m/J among the three
samples studied, which was around 1.8 times larger than that of PLZT ceramic with y=0.2.
The top-electrode sizes of around 500 and 250 µm diameters were suitable for the
measurement of pyroelectric properties, judging from the characteristics of the materials and the
accuracy of the measuring instruments.
Electric Fatigue in Antiferroelectric and Ferroelectric Pb(Zr, Sn, Ti)NbO3 Thin Films Prepared by Sol-Gel Process
Authors: Jang Jae Hyuk , Yoon Ki Hyun
Published: October 2002

The fatigue behavior in the sol-gel derived Pb0.99[(Zr0.6Sn0.4)0.97Ti0.03]0.98Nb0.02O3
(40/3/2) and Pb0.99[(Zr0.6Sn0.4)0.85Ti0.15]0.98Nb0.02O3 (40/15/2) thin films deposited on the
platinized silicon substrates was investigated. The thin film of the 40/3/2 composition
represented a double hysteresis loop, while the 40/15/2 composition represented a single
ferroelectric hysteresis loop. The thin film having the antiferroelectric phase showed less
fatigue than that having the ferroelectric phase. It can be explained that the
antiferroelectrics have less stress due to 180° domain switching compared to the
ferroelectrics.
Proposal of Optical Near-Field Probe Using Evanescent Field of Microdisk Laser
Authors: Atsushi Sakai Atsushi Sakai , Hiroshi Yamada Hiroshi Yamada , Masayuki Fujita Masayuki Fujita , Toshihiko Baba Toshihiko Baba
Published: October 2002

We propose an active optical near-field probe constructed of a semiconductor microdisk laser and a monitor detector. When a microdisk is placed close to an object, the evanescent field of the whispering gallery mode in the microdisk is scattered and the lasing characteristic is modulated. It was theoretically shown that a probe, made by using a circular disk with a diameter almost equal to the lasing wavelength λ and fixing the standing mode wave by a defect at the disk edge, shows a lateral resolution of 0.17λ × 0.23λ. Modulated light power by objects can be on the order of 100 µW with a bias current of 1 mA, which is sufficient for high-contrast imaging. Cleavage and selective wet etching were investigated as fabrication methods of such probes that project over the substrate edge. High-speed microscopy will be realized through the use of a large-scale array integration of this probe.
Effects of Morphological Changes of Pt/SrBi2Ta2O9 Interface on the Electrical Properties of Ferroelectric Capacitor
Authors: Suk Shin Dong , Nyung Lee Ho , Woo Lee Chang , Tae Kim Yong , Hoon Choi In
Published: October 2002

Morphological changes have been observed at the interface of Pt/SrBi2Ta2O9 (SBT) before and after annealing at 600 and 800°C after depositing Pt top electrode. We have investigated leakage currents, breakdown voltages, and capacitances of Pt/SBT/Pt /SiO2/Si capacitor and Pt/SBT/CeO2/Si gate structure. As a result, the leakage current density and capacitance are reduced from 10-7 to 10-8 A/cm2 and 1.3×10-10 to 8.5×10-11 F/cm2, respectively, and breakdown voltage increases from 5 to 14 V after post-annealing. The reduced leakage current density and increased breakdown voltage in the annealed samples are due to the smooth morphology of the interface of Pt/SBT. In the as-deposited Pt top electrode on SBT films, high electric field intensity is generated due to small arc of the valleys filled with fine Pt grains, resulting in higher leakage current density than the post-annealed Pt top electrode. Although the total gate capacitance of the post-annealed sample is reduced by the non-contact area due to voids at the interface of Pt/SBT, memory window of the ferroelectric gate is not influenced by such voids.
Imprint Characteristics of SrBi2Ta2O9 Thin Films with Modified Sr Composition
Authors: Hase Takashi , Noguchi Takehiro , Takemura Koichi , Miyasaka Yoichi
Published: October 2002

Imprint characteristics of SrBi2Ta2O9 (SBT) thin films with modified Sr composition
were investigated under elevated temperatures. A significant shift in readout charge was
observed after applying unipolar pulses (dynamic imprint test) at above 100°C, while only a
small shift was detected even when the capacitors were held at 150°C for up to 104 s without
any electrical signals (static imprint test). The charge shift was due to the internal voltage
formed by applying the unipolar pulses. Its increase, that is, degradation of dynamic imprint
endurance with increasing temperature is attributed to both an increase of the internal voltage
and a decrease of the coercive voltage (V
c). There was no significant difference in the
internal voltage between Sr deficient and Sr non-deficient SBT. SBT with a Sr deficient
composition had a relatively high dynamic imprint endurance compared to the Sr non-deficient films because of higher remanent polarization and larger V
c.
Cationic Ordering Structures of Lead Magnesium Niobates with Isovalent Dopants Having Different Ionic Radii
Authors: Kim Byung-Kook , Cha Seok-Bae , Park Jae-Hwan , Park Soon Ja
Published: October 2002

Pyrochlore-free lead magnesium niobate ceramics, the lead of which is partly replaced by lanthanum, and the magnesium of which is partly replaced by isovalent dopants such as nickel and cadmium, having different ionic radii <r
Ni2+
(0.69 Å)<r
Mg2+
(0.72 Å)<r
Cd2+
(0.95 Å)
Dielectric, Pyroelectric and Piezoelectric Properties of 0.4Pb(Mg1/3Nb2/3)O3-0.3Pb(Mg1/3Ta2/3)O3-0.3PbTiO3 Ceramics Modified with Cr2O3
Authors: Man Jung Jong , Won Choi Seong
Published: October 2002

Dielectric, pyroelectric and piezoelectric properties of the
0.4Pb(Mg1/3Nb2/3)O3-0.3Pb(Mg1/3Ta2/3)O3-0.3PbTiO3
ceramics modified with Cr2O3 have been investigated. The dielectric constant and
loss of ceramic samples were determined. The pyroelectric coefficient and
spontaneous polarization were measured using the static Byer-Roundy method
as a function of temperature. Small amounts of Cr2O3 promoted
grain growth of the ternary base composition.
Dielectric, pyroelectric and piezoelectric
properties of the base composition were improved with the addition of small amounts
of Cr2O3.
Lead-Free Piezoelectric Ceramics of (Bi1/2Na1/2)TiO3–KNbO3–1/2(Bi2O3·Sc2O3) System
Authors: Nagata Hajime , Takenaka Tadashi
Published: October 2002

Bismuth sodium titanate, (Bi1/2Na1/2)TiO3 (BNT)-based solid solution, a(Bi1/2Na1/2)TiO3–bKNbO3–c1/2(Bi2O3·Sc2O3) (a+b+c=1), [KTNS(100a/100b/100c)], was studied for its
dielectric, ferroelectric and piezoelectric properties, as a new group of lead-free piezoelectric
ceramics. Electrical measurements such as dielectric and piezoelectric properties show that the
KTNS(100a/100b/100c) ceramics near the BNT side have a relatively high electromechanical
coupling factor, k
33 (=0.47). On particular, the amount of modified Bi ions has an effect on k
33.
These ceramics seem to be a candidate for lead-free piezoelectric ceramics.
Inharmonic Overtone Spurious Mode Suppression by Partial Mass-Loading onto the Electrode for Energy-Trapped-Type Thickness-Extensional-Mode Piezoelectric Ceramic Resonators
Authors: Yamashita Yoshinari , Oikawa Yasunobu , Sugimoto Masanobu
Published: October 2002

Experimental studies have been performed on the suppression of the inharmonic
overtone responses for realizing piezoelectric ceramic resonators with low resonance
impedance compatible with a wide-area electrode(>φ15λ). The circumferential mass-loading onto
the electrode is effective for the fabrication of an oscillator with a low oscillation
startup voltage, without any jump to spurious frequencies. In addition, this technique results in a wide rejection bandwidth for TV/VCR adjacent-channel sound-carrier-signal traps. This effect (stepped energy-trapping) is observed to
arise from the spatial vibration energy distribution dispersion by the additive weighting electrode using optical laser interferometry and finite- element-method analysis.
The Measurement of High-Power Characteristics for a Piezoelectric Transducer Based on the Electrical Transient Response
Authors: Umeda Mikio , Nakamura Kentaro , Ueha Sadayuki
Published: October 2002

In this paper, the theoretical and experimental considerations on the high-power characteristics of a piezoelectric transducer are presented. First, we propose a new measurement method for the large
vibration amplitude region using an electrical transient response to eliminate the effect of temperature rise. Then, a new loss mechanism concerning the piezoelectric effect is explained by observing the relationship between the vibration velocity
and the current and their harmonics. A `piezoelectric loss' is newly introduced in the equivalent circuit model to describe the real loss phenomena clearly.
Optical Recording in Ferroelectric Liquid Crystal Using N*-SmC* Phase Transition
Authors: Keizo Nakayama Keizo Nakayama , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Rewritable optical recording has been demonstrated in a ferroelectric liquid crystal (FLC) with the chiral nematic (N*)-chiral smectic C (SmC*) phase sequence. In a homogeneously aligned cell surface-treated for a unidirectional molecular alignment, there are two kinds of layer configurations in the SmC* phase which appears directly from the N* phase with decreasing temperature. The direction of the layer alignment can be controlled by selecting the polarity of the applied electric field at the phase transition from N* to SmC*. Due to these characteristics, by irradiating a laser beam on a spot in the FLC in the SmC* phase under a specific polarity of the applied field, the layer alignment in the irradiated spot can be switched to the desired direction. This recording of the laser spot is erasable. In this device, the subtraction function in a binary image has also been realized.
Overview of Silicon-Based Materials
Authors: Matsumoto Nobuo
Published: October 2002

A comprehensive review, including some recent results, of the structures,
properties and fabrication methods of inorganic and organic silicon-based materials with
backbone dimensions from 0 to 3 is presented. Quantum effects in low-dimensional
silicon structures are discussed using organosilicon materials, such as polyhedral
compounds and oligosilanes (quantum dots), polysilanes (quantum wires),
heterocopolymers (one-dimensional superlattices), and polysilynes (quantum planes).
The luminous properties of silicon-based materials are also summarized.
Thermoelastic Analysis of Slip Defect Generation on GaAs Wafers
Authors: Sawada Shin-ichi , Yoshida Hikari , Kiyama Makoto , Nakai Ryusuke
Published: October 2002

In this work we develop the thermoelastic analysis for prediction of slip defect
generation on (001) GaAs wafers, by means of the finite element method taking into
account the anisotropic structure and slip system of dislocation. The analysis for a
completely circular wafer predicts that longer slip defect lines are generated at the wafer
edge of θ=π/8+Δ+nπ/2, 3π/8-Δ+nπ/2 (Δ is about 3°) and the prediction well
agrees with the result of the wafer heating experiment. This demonstrates that our
anisotropic analysis is more accurate than simple isotropic analysis which predicts slip
defect generation at the wafer edge of θ=π/8+nπ/4. According to this thermoelastic
analysis, we can additionally confirm that longer slip defect lines are more prone to be
generated at the <110> orientation flat (OF) edge than at the circular edge. Finally, we
suggest the method of preventing slip defect generation.
Infrared Absorption Properties of Nanocrystalline Cubic SiC Films
Authors: Yong Sun Yong Sun , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Nanocrystalline cubic SiC films, in which SiC grain size depends
on film thickness, are prepared by hydrogen-plasma sputtering.
Infrared absorption properties of the films are studied by analyzing
the grain-size effects on the Si–C stretching absorption peak at 800 cm-1. Absorption intensity of the Si–C stretching mode depends
on both the SiC grain size and the content of the excess carbon in the
films. A compressive strain in the internal parts of the films shifts
the absorption peak to a higher wave number.
Heteroepitaxy and Multiquantum Well Structure of Layered Compound GaSe/GaSxSe1-x on (001)GaAs Substrate
Authors: Budiman Maman , Okamoto Tamotsu , Yamada Akira , Konagai Makoto
Published: October 2002

For the heterostructure with GaSe, the epitaxial growth of GaS
x
Se1-x
films on misoriented (001)GaAs substrate was investigated. We grew c-axis inclined GaS
x
Se1-x
/GaSe/GaS
x
Se1-x
heterostructure films on misoriented (001)GaAs substrate. The scanning electron microscopic (SEM) images and the photoluminescence spectra confirmed the existence of GaSe and GaS
x
Se1-x
layers. Furthermore, multiquantum well structure of the GaSe/GaS
x
Se1-x
system were fabricated for the first time.
Influence of Sulphidation Treatment on the Performance of Mid-Infrared InAsPSb/InAs Detectors
Authors: Gong Xiu Ying , Yamaguchi Tomuo , Kan Hirofumi , Makino Takamitsu , Iida Takefumi , Kato Takayoshi , Aoyama Mitsuru , Suzuki Yoshiko , Sanada Noriaki , Fukuda Yasuo , Kumagawa Masashi
Published: October 2002

The influence of sulphidation treatment on the performance of room temperature InAsPSb/InAs photodetectors was investigated. Measurements of photoresponsivity, external quantum efficiency and detectivity of the detectors with and without the sulphidation treatment showed that after the sulphidation treatment the sensitivity of the detectors improved 1.5 times. A study of the chemical state of sulphur on an (NH4)2S
x
-treated InAs(001) surface was performed by high-resolution X-ray photoelectron spectroscopy (XPS). The chemical state of sulphur bonded to indium (In) and arsenic (As) atoms for the as-treated surface was observed showing the termination of the dangling bonds at the surface by the sulphidation treatment. This gives rise to a remarkable decrease of surface recombination center density and results in the increase of photodetector sensitivity.
Counter-Doped Surface Channel Metal-Oxide-Semiconductor Field-Effect Transistor with High Current Drivability and Steep Subthreshold Slope
Authors: Koike Hidetoshi , Enda Toshiyuki , Matsuoka Fumitomo , Shigyo Naoyuki
Published: October 2002

A metal-oxide-semiconductor field-effect transistor (MOSFET) with a novel
channel structure called a counter-doped surface channel (CDSC) is proposed. A
unique characteristic of the CDSC MOSFET is that the channel current still exists
at the surface, even though the counter-doped layer is formed. Experimental
results confirm that the CDSC pMOSFET using an n+ poly-Si gate has the highest
current drivability and the steepest subthreshold slope while maintaining a good
short-channel-effect immunity compared with the surface channel (SC) and buried
channel (BC) pMOSFET. The delay time with the CDSC pMOSFET represents
1.34-fold improvement in comparison to that with the SC pMOSFET.
Degradation Modes of InGaAs p-n Diodes Operated at Forward Biases
Authors: Wada Yoshinori , Enoki Takatomo
Published: October 2002

Degradation modes under level-shift circuit operations of InP-based
lattice-matched InGaAs p-n diodes for InP-based ICs are studied. We conducted life
tests under forward-biased conditions, reverse-biased conditions, and elevated
temperature conditions to examine changes in electrical characteristics unique to
the stresses in level-shift circuit application. The operating current of the diodes
deceases with forward-bias aging, which is a serious mode for practical diodes
used in level-shift circuits. This operating current decrease becomes remarkable
with the current increase that is observed in the low-voltage forward-bias region
of the current–voltage (I–V ) characteristics. This current increase at low voltage
suddenly appears after a considerable aging time. The I–V characteristics were
monitored during the tests, and the changes were analyzed in detail to elucidate
the mutual interaction among the modes found in the tests. The degradation
modes are discussed in relation to reported failure modes for heterostructure
devices having p-n junctions.
Precise Control and Resizing of Polysilicon Gate Length by Hard-Mask Etching
Authors: Sato Masaaki , Kawai Yoshio
Published: October 2002

In this paper, we describe the etching of hard SiON/SiN masks for the reactive ion
etching (RIE) of gate polycrystalline silicon (polysilicon) to precisely control and reduce gate
length in order to transcend the resolution limit of lithography. A mixture of C3F8 and oxygen is
used to control gate length. To improve gate critical dimension (CD) accuracy in the wafer,
radical etch rate during hard-mask etching is controlled by changing the electrode gap and the
temperature distribution in the wafer. The amount of CD shift is successfully controlled by
optimizing the oxygen flow rate without increasing its deviation. Consequently, a 0.24-µm-wide
resist pattern can be successfully resized to a polysilicon gate electrode of 0.2 µm length.
Moreover, etching of both hard-mask and polysilicon does not increase the CD deviation of the
polysilicon gate electrode length at the least.
Analysis of Spherical Target Illumination with Partially Coherent Light through Random Phase Plate
Authors: Tsubakimoto Kouji , Nakatsuka Masahiro , Miyanaga Noriaki , Jitsuno Takahisa
Published: October 2002

To improve the laser irradiation uniformity on a spherical target in inertial
confinement fusion research, partially coherent light (PCL) with an angular
spectral dispersion was introduced into a high power laser system. The calculation
procedure is presented to estimate the irradiation nonuniformity which depends on
the coherence of the beam pattern on the target plane. The theoretical analysis of
smoothing effect of PCL using a random phase plate is compared with the
experimental results. The reduction factor of irradiation nonuniformity is defined
as the ratio of the Legendre-mode amplitude of the intensity distribution of PCL to
that of the coherent laser. The mode structures predicted from reduction factors
were consistent with the experimental results for different values of spatial and
temporal coherence of PCL
Electro-Optic Intensity Modulator Using a Novel Urethane-Urea Copolymer
Authors: Watanabe Osamu , Tsuchimori Masaaki , Okada Akane , Ito Hiroshi
Published: October 2002

An electro-optic intensity modulator consisting of a waveguide
structure was fabricated using a novel urethane-urea copolymer that
exhibited high second-order optical nonlinearity and superior temporal
stability. Single-mode waveguides were defined by a photobleaching process,
and then the electro-optic effect of the polymer was induced by corona
poling. The intensity modulation for a propagation light at 830 nm was
observed when AC voltage was applied. A half-wave voltage of V
π=18 V
was measured at 1 kHz using a modulator that had a 13-mm-long electrode,
and the electro-optic coefficient (r
33) was estimated to be 12 pm/V. The
birefringence of the poled polymer and the r
33 of the modulator depended on
the poling voltage.
Development of Planar Optics for an Optical Tracking Sensor
Authors: Kawano Hiroyuki , Sasagawa Tomohiro
Published: October 2002

An optical tracking sensor for large-capacity flexible disk drive (FDD) is demonstrated. The
passive optics is compact and lightweight (5.4 mm length×3.6 mm width×1.2 mm height in size
and 18 mg weight). It comprises all passive optical elements necessary for optical tracking, e.g., a
focusing lens, a three-beam grating, an aperture and a beam splitter grating. Three beams were
focused to a predetermined spot size of 13 µm at designed intervals of 110 µm on a disk surface
and the reflected beams were successfully guided to photodiodes. This confirms that the application
of the planar optical technique is very useful for realizing a compact and light optical sensor.
An Improved Method for Wind Measurements with a Conical-Scanning Correlation Lidar
Authors: Sugimoto Nobuo , Matsui Ichiro , Pinandito Mego , Ishii Takakazu , Murata Shigeru , Yasuda Noboru
Published: October 2002

An improved method using a conical-scanning correlation lidar
was developed for wind measurements in the atmospheric boundary
layer. The method is based on temporal correlation of lidar
signals measured in multiple slant directions. In the new data
analysis method, the number of calculation steps is
approximately 1/8 of that of our previous method. The method was
demonstrated using a compact Mie scattering lidar with a wedge
prism conical scanner. The results were compared with
simultaneous rawinsonde measurements. The measured wind profiles show qualitative agreement with the sonde data at altitudes where aerosol density is high.
Optical Absorption Properties of Indium-Doped Thin Crystalline Silicon Films
Authors: Kasai Hiroto , Matsumura Hideki
Published: October 2002

The optical absorption of indium-doped thin crystalline silicon films is
investigated for photon energies from 1.24 to 2.75 eV (450 to 1000 nm) by
transmittance measurements. It is found that the optical absorption coefficient of
indium-doped silicon films increases not only in the infrared region but also in the
visible region of the spectrum by increasing the concentration of indium
impurities below the solid solubility limit of about 1018 cm-3. It is also revealed that
this enhancement is more dominant when the sample is thinner than 10 µm.
These results imply that In doping is effective in increasing the optical absorption
of indirect-band-gap materials such as crystalline silicon.
Optical and Electrical Properties of Sn-doped Indium Oxide Films Deposited on Polyester by Reactive Evaporation
Authors: Ma Jin , Zhang Dehang , Li Shuying , Zhao Junqing , Ma Honglei
Published: October 2002

Transparent conducting Sn-doped indium oxide (ITO) films have been prepared on
polyimide (PI) thin film substrate at low substrate temperature by reactive evaporation. The
structural, optical and electrical properties of the deposited films have been investigated.
High quality films with resistivity as low as 7×10-4 Ω·cm and transmittance over 80% have
been obtained. The temperature dependence of mobility and carrier concentration have been
measured over a temperature range 10–400 K. Corresponding scattering mechanism of
charge carriers in the films have been discussed.
Imprint of Oriented Pb(Zr, Ti)O 3 Thin Films with Oxygen Atmosphere in Cooling Process
Authors: Lee Hee-Soo , Auh Keun-Ho , Jeon Min-Seok , Um Woo-Sik , Lee In-Shik , Choi Gwang-Pyo , Kim Ho-Gi
Published: October 2002

Imprint properties of reactively sputtered Pb(Zr, Ti)O3 [PZT] thin films were studied as a function of oxygen pressure during cooling after deposition.
The well-oriented PZT films had a perovskite phase without any second phase regardless of the oxygen cooling ambient. The surface morphology of the PZT films became somewhat rough with decreasing oxygen
pressure because of the evaporation from the surface of the PZT films. Grain size, however, did not change significantly. As the oxygen cooling pressure increased, the hysteresis property of the PZT thin films improved and attained good squareness.
The decrease of remanent polarization, retained polarization and the coercive field was observed with decreasing oxygen pressure. It was observed that as the atmosphere in the cooling process of PZT films
becomes a reducing one, the P–E hysteresis loop shifts to a positive voltage asymmetrically. The direction of internal bias field was from the bottom to top electrode, which was confirmed by a field-accelerated retention test. In addition,
this field could be diminished by thermal treatment in oxygen atmosphere.
Dielectric Properties of PbTiO3Thin Films on CeO2/Si(100) and Y2O3/Si(100)
Authors: Wu Ye-Min , Lo Jyi-Tsong
Published: October 2002

The lead titanate (PbTiO3) thin films were deposited on a Si(100) substrate with cerium oxide (CeO2) and yttrium oxide (Y2O3) buffer layers by the pulsed laser deposition technique. The CeO2/Si and Y2O3/Si thin films fabricated at 760°C in an oxygen pressure of 0.04 Torr showed CeO2(200) and Y2O3(222) preferential orientation, respectively. TheC–VandJ–Eanalyses of Au/CeO2/Si, Au/Y2O3/Si, Au/PbTiO3/CeO2/Si and Au/PbTiO3/Y2O3/Si thin films were carried out. The analyses results indicated that the dielectric constant of the PbTiO3layer increased with the thickness of buffered CeO2and Y2O3. The threshold voltage change (Vth) was about 3.6 V and 5 V for Au/PbTiO3(150 nm)/CeO2(100 nm)/Si and Au/PbTiO3(150 nm)/Y2O3(100 nm)/Si MIS capacitors, respectively. For the same current density of 100 nA/cm2, the applied fields were about 380 kV/cm and 400 kV/cm for PbTiO3(80 nm)/CeO2(20 nm)/Si and PbTiO3(80 nm)/Y2O3(20 nm)/Si thin films, respectively. The densities of surface states of Au/CeO2(100 nm)/Si and Au/Y2O3(100 nm)/Si interfaces estimated at 1 MHz were 6.6×1011/cm2eV and 3.7×1011/cm2eV, respectively.
Growth and Evaluation of Cd1-yZnyTe Epilayers on (100) GaAs Substrates by Hot Wall Epitaxy
Authors: Koo Bonheun , Wang Jifeng , Ishikawa Yukio , Isshiki Minoru
Published: October 2002

Growth of Cd1-y
Zn
y
Te (CZT) on (100) GaAs by hot wall epitaxy (HWE) is
reported for the first time. Nearly stoichiometric CZT epilayers of high quality with y≈0.045 are grown using y=0.2 source and Cd reservoir. Under determined optimum
growth conditions, the relationship between quality and thickness of CZT epilayers is
compared with that of CdTe epilayers. In the case of layers thicker than 4 µm, a broader
full width at half maximum (FWHM) is observed for CZT epilayers than for CdTe
epilayers. Also, the deep-level emission in 4.2 K photoluminescence does remains up to
12.8 µm. These results are thought to be due to structural defects that originate from
phase separation. The X-ray FWHM values of 150–180 arcsec are obtained at
thicknesses greater than 12 µm and are comparable to those obtained by another epitaxial
method.
Neutron Diffraction Measurements of Inner Local Strain of Fatigued Carbon Steel
Authors: Inoue Kazuko , Horikawa Takeshi , Nakamura Hiroshi , Arai Toshiaki , Minakawa Nobuaki , Tsuchiya Yoshinori , Morii Yukio , Yamaguchi Yasuo
Published: October 2002

The residual strain for three directions x, y, z at every 1 mm mesh
point on the notch root of a round fatigued steel bar with a diameter
of 8 mm was detected nondestructively, using a special neutron
diffraction apparatus, residual stress analyzer (RESA) at JRR-3M,
with a beam diameter of 2 mm. The residual stress for the three
directions calculated from the observed strain showed that the stress
was tensile and large near the surface of the specimen. This result is
consistent with the well-known phenomenon that the fracture starts
from the surface of the notch root. The residual stress near the center
of the notch root was also tensile in the axial direction of the round
bar.
Formation of F- and P-Type Icosahedral Quasicrystals in the Zn–Mg–Ho Alloy System*
Authors: Shimizu Takayuki , Ishimasa Tsutomu
Published: October 2002

Two types of icosahedral quasicrystals, F- and P-types, formed at 563°C in the
Zn60Mg40-x
Ho
x
alloy depending on Ho content. In the composition range of 6≦x≦10, F-type icosahedral quasicrystal formed as a major phase in these alloys. The intensity of
superlattice reflections which occurred due to F-type ordering became weaker in the
alloys with lower Ho content. At x=5, P-type icosahedral quasicrystal formed, coexisting
with MgZn2-type Laves phase at 563°C and 503°C. Some electron diffraction patterns of
the P-type icosahedral quasicrystal exhibited diffuse scattering intensity at positions
corresponding to F-type superlattice reflections. By annealing at 403°C, a mixture of the
P-type icosahedral quasicrystal and the MgZn2-type phase changed to a mixture of the F-type quasicrystal and a decagonal quasicrystal. The former state was reversibly obtained
by additional annealing at 503°C. These experimental results support the interpretation
that the three types of quasicrystals form as a thermodynamically stable state in the Zn–Mg–Ho alloy system.
Surface Structure of N/Pd(100)-c(2×2) Determined by Tensor Low Energy Electron Diffraction Analysis
Authors: Kayama Tomoyuki , Hamamatsu Hiroshi , Yokoyama Toshihiko , Ohta Toshiaki
Published: October 2002

The surface structure of N/Pd(100)-c(2×2) was investigated by means of the tensor low
energy electron diffraction I–V analysis. The N atom was found to adsorb at the fourfold hollow
site facing downward at a distance of 0.13±0.07 Å with respect to the first Pd layer. A slight
buckling of the second Pd layer was also noticed, and the buckled distance was estimated to be
0.08±0.07 Å. The N atom is consequently coordinated by one second-layer Pd atom with the
N–Pd distance of 2.02×0.07 Å as well as four first-layer Pd atoms with the N–Pd distance of
1.96±0.02 Å. Fivefold coordination observed in the present system is similar to the case of
N/Ni(100)-p4g(2×2), although no reconstruction takes place on Pd(100).