bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Ce-Substituted Yttrium Iron Garnet Films for Magneto-Optic Waveguide Devices
Authors: Toshihiro Shintaku Toshihiro Shintaku , Takehiko Uno Takehiko Uno
Published: October 2002

Ce-substituted yttrium iron garnet films are epitaxially grown in situ on (111)-oriented substrates of (Gd, Ca, Mg)3(Ga, Zr)5O12 garnet by conventional rf diode sputtering for application to magneto-optic waveguide devices in optical communication systems. Pure argon or argon containing a small amount of oxygen is used as the sputter gas. After sputtering, the films are annealed in a nitrogen atmosphere. By optimizing this process, film propagation loss can be reduced while maintaining a large Faraday rotation. A propagation loss of 13 dB/cm and a Faraday rotation of -3900°/ cm have been obtained at a wavelength of 1.55 µ m.
Effect of Powder Characteristics on Electrical Properties of (Ba, Bi, Nb)-Added TiO2 Ceramics
Authors: Jiann-Jang Cheng Jiann-Jang Cheng , Jenn-Ming Wu Jenn-Ming Wu
Published: October 2002

The effect of powder characteristics on the microstructures and electrical properties of (Ba, Bi, Nb)-added TiO2 ceramics was studied. Two powders were selected: one prepared by sol-precipitation using modified alkoxide precursors, and another prepared by mixing reagent-grade oxides. The fine grains and homogeneous distribution of additives in the sol-precipitated powder enhanced additive ( e.g. Ba, Bi, Nb) dissolution in the matrix during sintering, as well as solute segregation during cooling, which resulted in better varistor electrical properties.
Semi-Empirical Estimation of Thermal Expansion Coefficients of Oxides
Authors: Hideaki Inaba Hideaki Inaba
Published: October 2002

The thermal expansion coefficients of oxides have been estimated and analyzed using Ruffa's method by reevaluating the parameter used. The Morse potential and the Debye model have been used to evaluate the thermal expansion coefficient and the parameters of the Morse potential have been determined empirically. The Born repulsion parameter of oxides, which is necessary for determining the parameter of the Morse potential, has been determined empirically for metal atoms of oxides belonging to every period of the periodic table and the thermal expansion coefficients of various oxides at a wide range of temperatures have been calculated. The calculated thermal expansion coefficients thus obtained are in excellent agreement with the experimental ones except for the anomalous thermal expansion behaviors due to vacancy formation and phase transitions.
Crystallization Characteristics of LaNiO3 Layers and Their Effect on Pulsed Laser Deposited (Pb 1-xLax)(ZryTi 1-y)O 3 Thin Films
Authors: Tseng Tzu-Feng , Yang Ching-Chyuan , Liu Kuo-Shung , Wu Jenn-Ming , Lin Tai-Bar Wu
Published: October 2002

Crystallization characteristics of LaNiO3 (LNO) thin films prepared by either rf magnetron sputtering or pulsed laser deposition (PLD), and their effect on the ferroelectric properties of subsequently pulsed-laser-deposited (Pb1-
x

La

x

)(Zr

y

Ti1-
y

)O3 (PLZT) films were examined. Post-annealing of the amorphous LNO layers, which were prepared by room-temperature sputtering, revealed that the LNO crystallized at temperatures higher than 450° C, and the annealed LNO layers were randomly oriented. However, a substrate temperature of only 250° C was required to form crystalline LNO films in a high-temperature sputtering process and the resultant films were preferentially (100) oriented with low electrical resistivity (ρ S=0.55 m Ω·cm). On the other hand, a substrate temperature of 400° C was required in situ to grow crystalline LNO phase by the PLD process and the obtained films were predominantly (110) oriented with a high resistivity (ρ S=6.38 m Ω·cm). The Pt used as an underlay markedly reduced the resistivity (ρ S=0.05 m Ω·cm) without changing the texture characteristics of LNO layers. It was also found that a reduction of gas pressure in the deposition chamber could enhance the (100)-oriented crystallization of LNO in both sputtering or PLD process. PLZT films subsequently deposited by PLD on the LNO layers required a substrate temperature ≥500° C to completely eliminate the pyrochlore phase. The structural characteristics of the PLZT films inherit that of the underlying LNO layer. Ferroelectric and dielectric properties of PLZT films were optimized when using the (100) LNO-Pt double-layers were used as bottom electrodes. The remanent polarization and coercive field obtained were P
r=14.9 µ C/cm2 and E
c=3.5 kV/cm, respectively, and the dielectric constant was 950 with a loss of tan
δ<0.05 at 1 kHz.
Ionic Conduction and Photoisomerization in Azobenzene Langmuir-Blodgett Films Adsorbing Cyanine Dyes
Authors: Shinbo Kazunari , Kontani Tadashi , Watanabe Mitsuhiro , Fukami Tetsuo , Kato Keizo , Kaneko Futao , Kobayashi Satoshi
Published: October 2002

Azobenzene (Az) Langmuir-Blodgett (LB) films adsorbing cyanine dyes (NK-3) were deposited and the electrical properties were investigated in detail. The current vs electric field characteristics suggested ionic hopping conduction, and the transient current properties showed current peaks due to migration of mobile ions. The thermally stimulated currents (TSCs) were also due to the ionic space charge polarization, that is, displacement of mobile ions over long distances in the LB films. These results indicated that the electrical properties of the Az LB devices are strongly dependent on the mobile ions in the devices. In addition, the TSC and the short-circuit photocurrent properties due to the dyes were also changed by isomerization of the Az molecules. The results showed that the ionic space charge polarization and the aggregates of the dyes were affected by the isomerization.
Novel Impedance-Matching Method for Plasma Processing at Very High Frequency Band
Authors: Aoki Takeshi , Fukasawa Kazuaki , Mikoshiba Yasuo Nishikawa
Published: October 2002

The paper concerns a method of impedance matching between an rf generator and a plasma for material processing at the VHF band. Unlike the conventional methods for the case of low frequency, e.g., 13.56 MHz, in this method, a transmission line and two variable capacitors are adopted and the use of inductors is avoided. The ranges of line length and capacitances are shown graphically and formulated for easy calculation using an electronic calculator. The efficiency of the matcher is derived, including the losses of the network elements. Experiments in an ECR plasma demonstrate that the theoretical derivations are valid within experimental error, that the method is effective up to 190 MHz with the rf-bias voltage independent of network parameters and a factor of 3 greater compared with direct connection, and that VHF-biasing increases ion energy without significant broadening of the ion energy distribution.
Exchangeability Test on φ90 mm/600 MB Phase-Change Optical Disks for Common Specifications
Authors: Yamada Seiya , Kubo Takahiro , Takuya Ito Takuya Ito , Kouhei Yamauchi Kouhei Yamauchi
Published: October 2002

A common testing machine for φ90 mm phase-change (PC) optical disks is developed. The performance of the developed machine is tested by comparison with three manufacturers' experimental machines. The exchangeability test for these machines was done using disks made by the three companies. Six sample disks made by several different makers were also simultaneously evaluated with the developed machine. Items tested in this work are (1) read-write characteristics, (2) overwrite cycle performance, and (3) the influence of crosstalk on detrack, defocus and tilt angles.
Color-Variable Emission in Multilayer Polymer Electroluminescent Devices Containing Electron-Blocking Layer
Authors: Maki Hamaguchi Maki Hamaguchi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Color-variable emission in multilayer polymer electroluminescent (EL) devices has been obtained by the use of poly(N-vinylcarbazole) (PVCz) as an electron-blocking layer. The emissive polymers used were poly ( p-phenylenevinylene), poly(3-dodecylthiophene), and poly(2,5-dinonyloxy- p-phenylenevinylene), whose emission colors were green, red, and orange, respectively. When EL devices consisting of two emissive polymer layers separated by a PVCz layer were driven under either forward or reverse bias mode, emission from the negatively biased polymer was observed. PVCz is assumed to act as an electron-blocking layer due to its small electron affinity (2.3 eV) compared with those of the emissive polymers (2.7–3.5 eV), and to facilitate exciton confinement in the negatively biased polymer layer, where radiative recombination of the charge carriers occurs.
Temperature-Corrected Quartz-Crystal Microbalance for Real-Time Film Thickness Monitoring in Vacuum Evaporation
Authors: Hideki Yamamoto Hideki Yamamoto , Noriaki Saiga Noriaki Saiga
Published: October 2002

For a quartz-crystal microbalance system without thermocouples for monitoring thin film thickness, a computational method which corrects for the temperature variation in the quartz crystal is presented. This correction method eliminates the need for pipes and electrical wires, simplifying the conventional system. To avoid the use of electrical wires, both a laser diode and a microlens were used to transmit the signal of the change of resonant frequency of the quartz crystal. Using a 4.2 MHz resonant AT-cut quartz-crystal plate, the error in the measurement of Ti film thickness was <3.0% under the conditions of deposition time <230 s and the quartz-crystal temperature <160° C.
Preparation and Pyroelectric Characteristics of Pb(Zr, Ti)O3 Thin Films Grown by Metalorganic Chemical Vapor Deposition
Authors: Asakura Takao , Ishikawa Koji , Atushi Sato Atushi Sato , Masaru Okada Masaru Okada
Published: October 2002

Highly (001), (110) and (111)-oriented lead zirconate titanate (PZT)
thin films with a thickness of 2 µ m were grown on Pt(100)/MgO(100),
RuO2(110)/MgO(100) and Pt(111)/SiO2/Si(100) substrates, respectively,
by metalorganic chemical vapor deposition. The pyroelectric properties
of these films were investigated in relation to application to infrared
sensors. Pyroelectric currents were detected on three differently
oriented films without poling treatment. Pyroelectric coefficients of
(001), (110) and (111)-oriented films were 3.0, 1.0 and 0.5×10-8 C/cm2· K,
respectively, due to strong dependence on their crystalline orientations.
With poling treatment, these values were increased and attained values
3 times as large as those of as-grown films for (111)-oriented films.
Low-Temperature Processing of Ferroelectric Pb(Zr0.53Ti0.47)O3 Thin Film from Molecular-Designed Alkoxide Precursor Solution
Authors: Suzuki Hisao , Othman Mohamed Baijuri , Murakami Kenji , Hayashi Shoji Kaneko
Published: October 2002

A novel method is developed for the sol-gel preparation of Pb(Zr0.53Ti0.47)O3
(PZT) thin films. This method involves the insertion of an in situ crystallizing
interlayer film of perovskite lead titanate (PT) as a seeding layer that offers
nucleation sites which lower the activation energy for crystallization. Highly
crystallized PZT films with the perovskite structure were successfully obtained on
Pt-coated silicon wafers and even on silica-glass substrate. The formation
temperature of a perovskite single phase in the PZT thin film was effectively
lowered to 500° C in air and 450° C in a mixture of water vapor and oxygen. Relative permittivity, ε
r, of the resultant films annealed below 500° C increased
with increasing film thickness and leveled off at around 1.5 µ m thickness. ε
r
saturated at around 500 at 1 kHz. This behavior was compared with those of films
prepared by other methods at relatively high temperatures. It was concluded that the
molecular design of the alkoxide precursor solution and the use of an in situ
crystallizing PT seeding layer were essential for lowering the crystallization
temperature as well as for obtaining good electrical properties of the resultant PZT
thin films.
Chemical Processing and Dielectric Properties of Ferroelectric SrBi2Ta2O9 Thin Films
Authors: Hayashi Takashi , Hiroshi Takahashi Hiroshi Takahashi , Takuya Hara Takuya Hara
Published: October 2002

Ferroelectric SrBi2Ta2O9 (SBT) thin films were prepared on Pt/SiO2/Si
substrates at 800° C by MOD and sol-gel methods. SBT thin films prepared by the
MOD method using strontium 2-ethylhexanoate, bismuth 2-ethylhexanoate and
tantalum ethoxide showed a fine-grained structure with grain sizes of about 130 nm.
The SBT thin films with a thickness of 400 nm exhibited ε
r of about 180, P
r of
about 4.5 µ C/cm2 and E
c of 60 kV/cm. No fatigue was observed up to 109
switching cycles. On the other hand, in the sol-gel method, SBT thin films
crystallized with a high (105) diffraction intensity at 650° C, but with a highly (00l)
preferred orientation at 800° C. The thin films showed grain structure with grain
sizes of 100–300 nm. The sol-gel-derived 390 nm-thick SBT films with random
orientation exhibited ε
r of about 100, P
r of about 2.8 µ C/cm2 and E
c of
108 kV/cm.
Electron-Cyclotron-Resonance Sputtered SrTiO3 Thin Films
Authors: Itsumi Manabu , Shin-ichi Ohfuji Shin-ichi Ohfuji , Hideo Akiya Hideo Akiya
Published: October 2002

SrTiO3 thin films deposited by electron-cyclotron-resonance (ECR) plasma
sputtering at 400° C are investigated from the viewpoint of leakage current and
dielectric breakdown strength. 100-nm-thick SrTiO3 samples with 400° C
deposition followed by 400° C oxygen annealing show low leakage current
density (on the order of 10-9 A/cm2 at 5 V) and high dielectric breakdown
strength (>4 MV/cm). SrTiO3 thin films deposited by ECR sputtering at 400° C
are promised for capacitor dielectrics of future 1-giga-bit dynamic-random-access memories.
Preparation and Pyroelectric Properties of (Pb, La)(Zr, Ti)O3 (PLZT) Thin Films
Authors: Kobune Masafumi , Fujii Satoshi , Takayama Ryoichi , Tomozawa Atsushi
Published: October 2002

PLZT films around 3 µ m thick with compositions of
{(Pb0.925La0.075)(Zr

y

Ti1-
y

)0.981+0.5 mass% MnO2} where
y=0–0.10, which have an appropriately small relative dielectric constant
( ∼200) were deposited on Pt(100)/ MgO(100) by rf-magnetron
sputtering. The pyroelectric properties of PLZT films as element
materials for pyroelectric IR sensors were investigated in detail.
Assuming that the volume specific heat C
v of the present films is
3.2 J/cm3· K, the PLZT films exhibited the highest F.M. of 1.4×10-10 C· cm/J and F.M.D* of 1.6×10-8 C· cm/J, which were
around 1.8 times and 1.5 times larger than those of PLT films,
respectively. Consequently, the figures of merit for the
pyroelectric IR sensors could be improved by adding a small
amount of Zr to PLT.
Characterization of Niobium-Doped Lead Titanate Thin Films
Authors: Ibrahim Ricardo Cury , Sakai Takamitsu , Nishida Takashi , Horiuchi Toshihisa , Tadashi Shiosaki Tadashi Shiosaki , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Lead titanate ( PbTiO3) thin films were deposited on silicon substrates covered with
platinum by reactive sputtering using a single multicomponent-type target at high temperatures
(around 500° C). Small chips of metallic niobium were incorporated into the target for doping
purposes. Samples analyzed in this study were fabricated in such a way that the molar
concentration of niobium was kept at 0, 1, 2, 3, or 4%. X-ray diffraction (XRD) patterns
showed that samples doped with niobium tended to exhibit epitaxial growth on top of a (111)-oriented platinum electrode. At 2 mol% niobium doping, the tetragonality ratio (c/a) exhibited a
maximum value and the dielectric permittivity showed a local minimum. The dielectric loss and
leakage current characteristics of Nb-doped films were considerably improved. Electric
displacement-electric field (D-E) hysteresis loops were observed at all doping concentrations.
Some promising acoustic surface wave characteristics were also observed. Samples with 1 or 2 mol%Nb seem to be very promising candidates for integrated devices.
Magneto Optic Pick-Up Head Employing Interferometer Configuration
Authors: Zu Wen Chao Zu Wen Chao
Published: October 2002

A magneto optic pick-up head of interferometer configuration can not only produce a read-out signal proportional to Kerr rotation but also keep the laser diode free from feedback noise.
Formation of Tungsten Bronze-Type (Ba 6- 3xSm 8+ 2x)αTi 18-yAlyO 54 (α=1+y/36) Solid Solutions and Microwave Dielectric Properties
Authors: Makoto Mizuta Makoto Mizuta , Koji Uenoyama Koji Uenoyama , Hitoshi Ohsato Hitoshi Ohsato , Susumu Nishigaki Susumu Nishigaki , Takashi Okuda Takashi Okuda
Published: October 2002

The composition range of tungsten bronze-type Ba6-3x
Sm8+2x
Ti18O54 solid solutions, which are excellent microwave dielectric resonators, has been extended to (Ba6-3x
Sm8+2x
)αTi18-y
Al
y
O54 (α=1+y/36) with the B-site substituted by Al.
In this two-dimensional solid solution region, (Ba4.2Sm9.2)αTi18-y
Al
y
O54 (0≤y ≤1.61), which includes the best end member composition (x=0.6) of Ba6-3x
Sm8+2x
Ti18O54 solid solutions, was selected for study of solid solutions and their dielectric properties.
In the whole region of the solid solution formula, tungsten bronze-type solid solutions have been formed and the dielectric constants, Q·f values and τ f have been measured.
ε
r and τ f decreased as the amount of substituted Al increased.
The decrease in τ f with Al substitution is expected to be especially large for dielectric materials with large positive τ f.
These properties are discussed in terms of the structure.
Physical Properties of Composites
Authors: Yoshihiro Ishibashi Yoshihiro Ishibashi , Makoto Iwata Makoto Iwata
Published: October 2002

The effective medium approximation method was applied to estimate
physical quantities such as the dielectric constant and the resistivity of
composites. Regarding a relaxor as a composite in which the transition
temperature varies in different sections, the temperature and the frequency
dependences of the dielectric susceptibility were calculated.
Measurement System for Electric Field-Induced Strain by Use of Displacement Magnification Technique
Authors: Yasuyoshi Saito Yasuyoshi Saito
Published: October 2002

A new, simple, and precise method has been developed for the measurement of electric field-induced strain, which is based on the displacement magnification technique. This technique is stable
against environmental vibration noises, and is able to measure strains with 6 to 10 times higher resolution than that of a displacement sensor itself. Using this method, I constructed a novel measurement system which simultaneously collects data of field-induced strain, strain
rate, polarization, current and acoustic emission (AE) under high electric field drive for piezoelectric and electrostrictive materials. The system reveals, for soft tetragonal lead zirconate titanate (PZT) ceramics, that 180 deg domain walls move before 90 deg domain walls
move at around the coercive electric field strength under ±1500 V/mm electric field drive at a frequency of 0.05 Hz. AE is not generated around the coercive electric field, but is at high strain state. Some discussions are given about the origins of these phenomena.
Viscosity Measurement of Ferroelectric Liquid Crystal Using Shear Horizontal Wave
Authors: Hiroshi Moritake Hiroshi Moritake , Kuniaki Takahashi Kuniaki Takahashi , Katsumi Yoshino Katsumi Yoshino , Kohji Toda Kohji Toda
Published: October 2002

The characteristics of shear horizontal (SH) wave propagation on a piezoelectric ceramic plate having the poling axis along the horizontal direction are described. The zeroth-order symmetrical (S0) mode has a nearly nondispersive property and an interdigital transducer (IDT) for the S0 mode under the configuration of no counter electrode on the opposite surface of the plate has a high electromechanical coupling constant k
2 value exceeding 20% throughout the entire range of frequency times thickness (f
d) values. The viscosity of a ferroelectric liquid crystal (FLC) is measured using the S0 mode SH wave device which has two acoustic wave channels. In the smectic phase of FLC, the viscosity in the direction perpendicular to the smectic layer plane is larger than that parallel to it. The difference in the viscosity between the two directions of FLC alignment is detected by measuring the acoustical phase delay difference between two acoustic wave channels.
Electrical Characteristics of Ib/Undoped Diamond Junction Diode at High Temperature
Authors: Akiba Yukio , Toyokazu Sakata Toyokazu Sakata , Masamori Iida Masamori Iida
Published: October 2002

The electrical property of I
b diamond and characteristics of an I
b/undoped diamond (n–i) junction diode at high ambient temperature are studied. It is clear on examining the Seebeck effect that the I
b diamond shows n-type conduction at temperatures higher than 300° C. The distinct rectifying characteristic of the diamond n–i junction diode is obtained when temperature becomes higher than 700° C. At a low current level, forward current depends exponentially on the applied voltage and the n-value of the diode is 9.8. Ohm's law is dominant in the high current region of the forward characteristics. A band model of the n–i junction which explains the characteristics is proposed.
Resonant-Tunneling Bipolar Transistors with a Quantum-Well Base
Authors: Victor Ryzhii Victor Ryzhii , Irina Khmyrova Irina Khmyrova , Maxim Ryzhii Maxim Ryzhii , Magnus Willander Magnus Willander
Published: October 2002

Heterostructure bipolar transistors with a quantum-well base incorporated a resonant-tunneling structure in the collector are proposed and studied theoretically. Static characteristics of the transistors are evaluated using the proposed analytical model. It is shown that the current-voltage characteristics and the collector current versus base current dependences can be ambiguous corresponding to bistability operation. The bistability effect is associated with the mobile electron space charge in the collector region. Direct on–off switching by the collector voltage or base current pulses is discussed.
A Study of Damage Induced in In0.52Al0.48As Surface by Reactive Ion Etching
Authors: Gwo-Cherng Jiang Gwo-Cherng Jiang
Published: October 2002

Photoreflectance (PR), Raman scatter (RS), and photoluminescence (PL) experiments have been carried out to characterize the In0.52Al0.48As surface exposed to plasma with a gas of methane-hydrogen. PR spectra indicate that reactive ion etching (RIE) causes damage such as nonradiative recombination centers, scattering centers, and defects leading to the decrease of signal intensity, broaden linewidth and red shift of the transitions by increasing the rf power. In the Raman scattering study, RIE causes damage against InAs-like and AlAs-like longitudinal optic (LO) modes vibration. As the rf power increased, the maximum of two LO modes shifts towards lower frequency and the line shape becomes increasingly asymmetric. Also, the degraded intensity causes by disorder and point defects gradually with increasing rf power. Corresponding PL measurements showed that the transition energies red-shift with increasing the rf power. In addition, the spectral feature a broadens, and the intensity decreases with rf power more than 200 W. There is a good correlation of the PL, PR, and RS indicating that these methods can be used as sensitive evaluate for near surface damage of the epilayer.
Observation of <100> Dark Line Defects in Optically Degraded ZnSxSe 1-x-based Light Emitting Diodes by Transmission Electron Microscopy
Authors: Lourdes Salamanca-Riba Lourdes Salamanca-Riba , Li-Hsin Kuo Li-Hsin Kuo
Published: October 2002

We have used transmission electron microscopy to study the <100 > dark line defects (DLDs) produced during photodegradation of a ZnSxSe1-x
-based/GaAs heterostructure. Our results show that the DLDs are networks of elongated dislocation loops or half loops that originate in the quantum well region during device operation. The loops lie on { 111 } planes. Our results also show that after photodegradation the Frank-type stacking faults become networks of dislocations while the Shockley-type stacking faults remain unchanged indicating that the Frank-type stacking faults are the sources for the degradation under our experimental conditions. We propose a mechanism for the degradation process. The degradation starts by the accummulation of charge on the stacking faults from the electron-hole recombination in the quantum well followed by the emission of a mobile defect from the fault and along the <100 > directions. The mobile defect is probably a cluster of vacancies. As the mobile defect moves it leaves a trail of strained lattice along its path. Upon further electron-hole recombination dislocation loops form on the strained path left by the mobile defect. The loops elongate by glide and cross-slip mechanism on { 111} planes and become hair pin-like dislocation loops.
Hydrogenated Amorphous Silicon/Crystalline Silicon Double Heterojunction X-Ray Sensor
Authors: Guang-pu Wei Guang-pu Wei , Wen-biao Wu Wen-biao Wu , Takashi Kita Takashi Kita , Hiroshi Nakayama Hiroshi Nakayama , Taneo Nishino Taneo Nishino , Wen Ma Wen Ma , Hiroaki Okamoto Hiroaki Okamoto , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

With full utilization of the low-temperature process of hydrogenated amorphous silicon (a-Si) thin-film deposition and long carrier lifetime of high-purity crystalline silicon (c-Si) , we have developed a new type of a-Si/c-Si double heterojunction X-ray sensor. The sensor has the structure of Au/p a-SiC/n NTD c-Si/n a-Si/Al. High-purity NTD (neutron transmutation doping) crystalline silicon wafers were used as substrates. The high-purity NTD crystalline silicon has a long carrier lifetime (about 400 µs), and the low deposition temperature of a-Si has no adverse effects on the carrier lifetime. Therefore, high photogenerated carrier collection efficiency and high sensitivity can be obtained. The characteristics of this kind of X-ray sensor have been examined. The linearity of the relationship between output current and X-ray intensity was good, and the sensitivity was high.
Image Parallel Storage Technique Using Holographic Optical Disk
Authors: Zhai Jin-hui , Ruan Yu , Guofan Jin Guofan Jin
Published: October 2002

A novel method for implementing image parallel storage is presented, based on the theory of holographic optical disk storage. The required optical disk holograms are designed using an iterative search algorithm which we developed. The image readout architecture is proposed, and the search technique of specified optical disk holograms is described in detail. An experiment has been performed to demonstrate the optical comparison parallel encoding addressing technique.
High Brightness Liquid Crystal Projection Displays*
Authors: Shin-Tson Wu Shin-Tson Wu , Chiung-Sheng Wu Chiung-Sheng Wu
Published: October 2002

Three optical configurations for achieving high brightness liquid crystal projection displays are demonstrated. In both approaches, the two polarization components of unpolarized input light are effectively used resulting in an excellent light modulation efficiency. The advantages and disadvantages of each approach are analyzed.
Effect of F-Doping on Optical and Thermal Properties of Soda Magnesium Silicate Glasses for Ultralow-Loss Fibers
Authors: Shin-ichi Todoroki Shin-ichi Todoroki , Shigeki Sakaguchi Shigeki Sakaguchi
Published: October 2002

Rayleigh scattering, refractive index and viscosity were investigated for fluorine-doped soda magnesium silicate (NMS) glasses to evaluate their potential for use as a cladding material for NMS glass which is known to exhibit low Rayleigh scattering intensity. By substituting 5 mol% of MgF2 for MgO, the scattering intensity was increased and the refractive index decreased. The scattering increase was considered to be due to concentration fluctuation induced by F-doping. Some samples, however, exhibited lower scattering intensity than silica glass. Moreover, it was possible to match the viscosities of the core and cladding glasses by adjusting the F and SiO2 contents. These results imply that these F-doped glasses are suitable as cladding material for NMS glass fibers.
Lateral Force Modulation Atomic Force Microscopy of Langmuir-Blodgett Film in Water
Authors: Yamanaka Kazushi , Takano Hajime , Tomita Eisuke , Fujihira Masamichi
Published: October 2002

The mechanical properties of a Langmuir-Blodgett (LB) film in water were investigated using an atomic force microscope with lateral force modulation. During the force curve measurement, the dynamic friction force is measured by observing the amplitude and phase of the cantilever torsion vibration, as the sample is deformed by a tip with gradually increasing normal force. In contrast to conventional friction force microscopy, the friction measurement is performed without x–y scanning, and therefore is in real time. This method was applied to a LB film consisting of an arachidic acid (AA) single layer on top of a single layer of partially fluorinated ether of carboxylic acid (PFECA), and interesting results were obtained. In particular, the film was found to be stable for a short period (<120 min) and the structure and ratio of the friction forces between the AA and PFECA areas are identical with those observed in air. Moreover, a friction force transition was observed at a normal force of around 14 nN on loading and an almost reversible decrease was observed on unloading. This result indicates penetration of the AA film by the tip and recovery of the penetrated hole on unloading.
Investigation of Time-Resolved X-Ray Diffraction Analysis in Smectic A Liquid Crystal Cells
Authors: Hiroyuki Okada Hiroyuki Okada , Miki Shibata Miki Shibata , Hiroyoshi Onnagawa Hiroyoshi Onnagawa
Published: October 2002

Time-resolved X-ray diffraction analysis of smectic A liquid crystal cells is investigated. Frequency and duty ratio dependence of smectic A layer motions is measured. From the experimental results, possible mechanisms of layer motions are discussed.
Transmission Electron Microscopy Observation of Polymorphic Epitaxial Growth of YSi2-x Layer in Al(001)/YSi2-x/Si(001) Systems
Authors: Noya Atsushi , Takeyama Mayumi , Sasaki Katsutaka , Aoyagi Eiji , Hiraga Kenji
Published: October 2002

The structures of compounds in the heteroepitaxial system Al/YSi2-
x

/Si have been examined by high resolution transmission electron microscopy. YSi2-
x

grown in two stages by a template method consists of two phases. Hexagonal YSi2-
x

(1*BAR*2*BAR*0) (low-temperature phase) grows on Si(001) when Y is deposited at 330° C and then annealed at 500° C for 10 min. Subsequent deposition of Y at 330° C followed by annealing at 330° C for 1 h results in the growth of tetragonal YSi2-
x

(001) (high-temperature phase) on the hexagonal phase. The growth of Al(001) on YSi2-
x

is confirmed. The epitaxial relationship Al[100]//tetragonal YSi2-
x

[100]//hexagonal YSi2-
x

[100]//Si[110] is found in this system. It is also revealed that in the formation process of YSi2-
x

, the tetragonal phase is nucleated first from a supercooled melt in the solid phase and then the hexagonal phase is formed by a polymorphic transformation during annealing at appropriate temperatures for the transition.
Surface Flatness of Transparent Conducting ZnO:Ga Thin Films Grown by Pulsed Laser Deposition
Authors: Akio Suzuki Akio Suzuki , Matsushita Tatsuhiko , Sakamoto Yoshiaki , Wada Naoki , Fukuda Tomoya , Fujiwara Hideki , Masahiro Okuda Masahiro Okuda
Published: October 2002

ZnO films doped with 4, 7 and 13 wt% Ga2O3 (GZO films) have been deposited on glass and quartz substrates using a pulsed laser deposition technique with an ArF laser (λ=193 nm). In all experiments, a repetition rate of 10 Hz, an energy density of 1 J/cm2, and an irradiation time of 20-30 min (12000-18000 shots) were used. An optical transmittance of more than 90% was obtained in the visible region of the spectrum for 150-200-nm-thick GZO (7 wt%) films deposited at substrate temperatures of 200-300° C. The lowest resistivity of 2.08×10-4 Ω⋅cm and the lowest sheet resistance of 14.5 Ω/sq were obtained for GZO (7 wt%) films grown at a substrate temperature of 200° C. It was found from AFM images that there were minute irregularities (50-70 nm in size, average roughness 0.8 nm) on the surfaces of GZO (7 wt%) films grown at substrate temperatures of 25-300° C.
The Optimization of Passivation Layout Structure for Reliability Improvement of Memory Devices
Authors: Seong-Min Lee Seong-Min Lee , Kwon-Woo Lee Kwon-Woo Lee
Published: October 2002

In the present study, a 3-dimensional finite element model has been adopted to characterize the thermal stress distribution in memory devices with multilayered passivation coating. The simulation results detail how the distribution of the interfacial stress along the passivation and die premolding coating interface correlates with occurrence of the passivation crack. Furthermore, it is shown how the stress component which causes the passivation crack is determined by the geometry and the mechanical properties of the passivation layer. The simulation result shows that an increase of the passivation thickness contributes to its thermomechanical stability. The experimental work also indicates that a thickening of the passivation layer composed of a silicon nitride film with an oxide layer coating is a highly effective way to retard crack initiation due to shear stress. Particularly, the passivation layer with a ductile underlayer such as PSG (phosphosilicate glass) is essential for the reliability improvement of high density memory devices because this construction allows sufficient elasticity to compensate for thermal expansion mismatch between packaging materials and improves the step coverage.
Characteristics of High-Current Pulsed Arc Discharge
Authors: Masugata Katsumi , Maekawa Hiroaki , Yoshida Masayuki , Ishii Tsutomu , Toshiyuki Suzuki Toshiyuki Suzuki , Kiyoshi Yatsui Kiyoshi Yatsui
Published: October 2002

Characteristics of high-current arc discharge in H2, N2, air and SF6 have been investigated to develop a high-efficiency, high-repetition pulse power switch. The discharge parameter was typically 5–50 kV, 12–16 kA, with pulse duration around 600 ns. Energy transfer efficiencies and the recovery characteristics of breakdown voltage have been evaluated using a charge transfer circuit. The energy transfer efficiency was found to be much higher for H2. The recovery times required to obtain 50% of initial breakdown voltage are evaluated to be 0.5 ms, 2 ms, and 3 ms for H2, SF6 and air, respectively. The arc column was observed to expand with a supersonic velocity which produced a strong shock wave. The volume of hot gas remaining after the discharge was found to be much smaller for H2, as compared with SF6.
Detection of Taste Substances Using Impedance Change of Phospholipid Langmuir-Blodgett Membrane
Authors: Hideyuki Akiyama Hideyuki Akiyama , Kiyoshi Toko Kiyoshi Toko , Kaoru Yamafuji Kaoru Yamafuji
Published: October 2002

Impedance changes in a phospholipid Langmuir-Blodgett (LB) membrane by several taste substances were measured. A recently developed multichannel taste sensor that uses lipid/polymer membranes responds to taste substances by the membrane potential change. The potential change is based on the change of a diffuse electric double layer near the membrane surface; the sensitivity to nonelectrolytes and weak electrolytes is lower than that to strong electrolytes. Although bitter substances include both electrolytes and nonelectrolytes, outputs of the taste sensor were quite different from each other. Therefore the “bitter" response of human gustatory sensation cannot be represented by the change of the diffuse electric double layer. In this work, most bitter substances were found to increase the resistance of the phospholipid LB membrane. This implies that the increase of membrane resistance is related to the generation of bitter taste in humans and that the sensing system based on impedance measurement is quite effective for the detection of bitterness.
Polarized Common Path Optical Heterodyne Interferometer for Measuring the Elliptical Birefringence of a Quartz Wave Plate
Authors: Chou Chien , Huang Yeu-Chuen , Chang Ming
Published: October 2002

A novel method based on a polarized optical heterodyne interferometer with a common path feature was proposed and set up. This interferometer was used to measure the phase difference δ f of the fast wave of the elliptical polarized eigenstate in the directions of the P and S waves in an elliptical birefringence wave plate. The values of δ f are calculated on the basis of the phase difference and the ratio of the amplitude of input polarized light with the accuracy up to 10-3. The measurement results provide evidence of the existence of elliptical birefringence in both λ/4 and λ/2 quartz wave plates.
In Situ Electron-Beam Processing for GaAs/AlGaAs Nanostructure Fabrications
Authors: Tomonori Ishikawa Tomonori Ishikawa
Published: October 2002

The requirements for the fabrication technology of 2-dimensional and/or 3-dimensional nanometer-scale heterostructures with III–V compound semiconductors are described. In addition to a fabrication capability with nanometer accuracy, the processes must avoid both undesirable contaminations and any damage effect. To meet these requirements, we have developed in situ electron-beam (EB) processing in which all of the processes, including EB lithography, pattern etching and epitaxial overgrowth, are performed successively in an ultra-high vacuum-based environment. The present status of this technique, i.e. nanometer-scale patterning, cleanliness of the processed surfaces and damage-free characteristics, is discussed. It is also demonstrated that self-organized epitaxy, which is now being intensively studied, can be combined with in situ EB processing as an elemental process.
Ultrahigh-Speed InP/InGaAs Double-Heterostructure Bipolar Transistors and Analyses of Their Operation
Authors: Matsuoka Yutaka , Yamahata Shoji , Kurishima Kenji , Ito Hiroshi
Published: October 2002

Novel hexagonal emitters are proposed for heterostructure bipolar transistors (HBTs) with a base-metal-overlaid emitter-base self-alignment structure to reduce parasitic effects. Two different layer structures for InP/InGaAs double-heterostructure bipolar transistors (DHBTs) that can more fully utilize the inherent potential of the materials are used to enhance unity current gain cutoff frequency, f
T, and maximum oscillation frequency, f
max
. On a wafer with a 180-nm-thick collector, a transistor with a 20-µ m2 hexagonal emitter electrode shows an f
T of 230 GHz and an f
max
of 147 GHz, while with a 4-µ m2 hexagonal emitter electrode the corresponding values are 225 GHz and 241 GHz. f
max
of 300 GHz is achieved for a transistor with a 4-µ m2 emitter electrode and a 330-nm-thick collector. Transistor operation is analyzed using a simple but appropriate small-signal equivalent circuit model of a transistor that includes internal and external base/collector capacitances and yields good estimates of the measured scattering (s-) parameters. Even in these InP-based (D)HBTs, the internal collector capacitance increases with collector current density due to the Kirk effect which degrades performance. In thin-collector (D)HBTs, the increase in the internal collector capacitance is suppressed, which increases the collector current density at which the transistor can operate normally, and f
T is increased by both transit time reduction and high-collector-current operation.
Numerical Simulation and Experimental Realization of δ-doped Single Barrier Resonant Tunneling Diodes
Authors: Lin Jia-Chuan , Wang Shui-Jinn , Liou Wan-Rone , Ying-Che Luo Ying-Che Luo , Ching-Yuan Cheng Ching-Yuan Cheng
Published: October 2002

In this study, a new negative differential resistance (NDR) device based on a δ-doped single barrier resonant tunneling structure is presented. Numerical simulation is utilized to analyze the resonant tunneling mechanism of the proposed device. Calculated results reveal that the N-shaped NDR is due to the resonant tunneling through a quasibound state inside the V-shaped quantum well generated by the δ-doped layer. The peak doping concentration of the δ-doped layer in the barrier region plays a crucial role in determining both the onset and the peak-to-valley current ratio (PVCR) of the NDR. Preliminary experimental results based on the InGaAs/InP system grown by metalorganic chemical vapor deposition are reported for the first time. With a peak concentration of around 5×1018 cm-3 in the δ-doped layer, a strong NDR with a PVCR of about 1.11 at room temperature has been observed.
Effect of Thermal Curing on Molecular Orientation in Polyimide Films Having Rodlike Molecular Skeleton Formed on Substrates
Authors: Hideshi Nomura Hideshi Nomura , Masaya Asano Masaya Asano
Published: October 2002

Films of a single polyimide having a rodlike molecular skeleton of uniform thickness were prepared on silicon and quartz substrates under several different heating rates during the thermal curing cycle. The molecular orientation in the cured polyimide film was evaluated by polarizing infrared and visible light investigation. The molecular orientation in the film was very sensitive to the heating rate during the curing cycle at the interface with the substrate, but less sensitive to that at the surface. The rodlike molecules in the film which were slowly heated were highly oriented and nearly parallel to the film plane, whereas those which were quickly heated were randomly oriented at the interface. It was shown that the increase in thermal stress in the polyimide film with increasing heating rate reflected the degree of decrease of the in-plane orientation.
Formation Mechanisms of the Deformed Oxide Layer in a Tungsten Polycide Structure
Authors: Mashiko Yoji , Ohsaki Akihiko , Okamoto Tatsuo , Fukumoto Koji , Hirosi Koyama Hirosi Koyama
Published: October 2002

Destructive oxidation mechanisms in a tungsten polycide structure were investigated. In the experiments, the dependencies of the variation in the process flow, structural variations and annealing temperature application on the formation of destructive oxidation were examined. Surface and structural analyses were performed using a variety of analytical techniques such as transmission electron microscopy. The deformed oxide layer, having a pathological morphology of the oxide surface, was formed on the silicide layer during the oxide process after the removal of the surface layer of silicon oxide that initially covered the crystallized silicide film. It was revealed that destructive oxidation resulted from the formation of volatile metal-oxides, which originated during the process of low temperature annealing in ambient O2.
Characteristics of Two-Vibration-System Ultrasonic Plastic Welding with 90 kHz and 20 kHz Vibration Systems at Right Angles
Authors: Tsujino Jiromaru , Tamura Toshiki , Takako Uchida Takako Uchida , Tetsugi Ueoka Tetsugi Ueoka
Published: October 2002

The direct welding characteristics of an ultrasonic plastic welding system with an upper 90 kHz longitudinal welding tip with a small vibration amplitude and a lower 20 kHz low frequency torsional vibration welding tip with a large vibration amplitude at right angles are studied. By using a combination of high and low vibration frequency systems with small and large vibration amplitude welding tips, the welding characteristics are improved, resulting in a smaller required vibration amplitude and less damage to the specimens due to vibration than those using conventional systems. The two-vibration-system welding equipment consists of a 90 kHz upper longitudinal vibration source with six bolt-clamped Langevin-type piezoelectric ceramic (lead-zircon-titanate; PZT) transducers 15 mm in diameter, a 20 kHz torsional vibration system 40 mm in diameter and a welding frame. The total required velocity amplitude of the two-vibration-system welding equipment is decreased and the welding characteristics are improved significantly compared to those of conventional one-vibration-system for both soft and hard plastic sheet welding.
Suppression of Titanium Disilicide Formation on Heavily Arsenic-Doped Silicon Substrate
Authors: Kitano Tomohisa , Kodama Noriyuki , Tetsuya Sakai Tetsuya Sakai , Shuichi Saito Shuichi Saito
Published: October 2002

Titanium disilicide formation on heavily arsenic-doped silicon substrate was investigated. The suppression of disilicide formation was due to the existence of an incubation time, but not to the reduction of the disilicide formation rate. The incubation time for disilicide formation was induced when the amount of arsenic was above a critical concentration (5×1020 atoms/cm3) at the silicon surface. Arsenic concentration higher than the critical value induced the retardation of transformation from the titanium-rich silicides to the disilicide. When the arsenic concentration was lower than the critical value, the disilicide formation occurred without an incubation time.
Electroluminescence and Avalanche Multiplication at Electric Field Strength Exceeding 1 MV/cm in Hydrogenated Amorphous SiC Alloy
Authors: Toshihiko Toyama Toshihiko Toyama , Tetsuyuki Matsui Tetsuyuki Matsui , Kazuhiro Hiratsuka Kazuhiro Hiratsuka , Hiroaki Okamoto Hiroaki Okamoto , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

High electric field effects in hydrogenated amorphous silicon carbide alloy have been investigated employing a double insulating ac-driven electroluminescent device structure. The carbon content was systematically varied by changing the deposition conditions. Hot-electron-induced electroluminescence and avalanche multiplication occurred at an electric field of 1.4–2.3 MV/cm in amorphous silicon carbide as in hydrogenated amorphous silicon. From an analysis of the decay of the emission spectrum in terms of the lucky-drift model, the electron mean free path tends to be reduced with an increase in structural disorder due to carbon alloying.
AC Susceptibility Measurements for Superconducting Y–Ba–Cu–O Powder
Authors: Otabe Edmund Soji , Kitamura Ryouhei , Teruo Matsushita Teruo Matsushita
Published: October 2002

The effect of reversible motion of fluxoids was investigated by measuring fundamental and third harmonic AC susceptibilities in Y-based superconducting powder in which the intergrain current is eliminated. The peak values of AC susceptibilities decrease monotonically with increasing DC magnetic field and/or temperature, suggesting that the reversible fluxoid motion becomes significant. The AC magnetic field dependence of the AC susceptibilities of cylindrical superconductors were numerically calculated for simplicity based on the Campbell model which describes the reversible fluxoid motion. The critical current density and the AC penetration depth were estimated from the AC susceptibilities and compared with the results from DC magnetization. These results agree fairly well, and small differences between the two measurements may be attributed to the distribution of the particle size. It is concluded that the observed AC susceptibilities are well explained by the Campbell model.
The Influence of Boron on the Magnetic Properties of 2–17 and 2–14 Rare Earth Cobalt Compounds
Authors: Maruyama Fumio , Nagai Hiroyuki , Amako Yasushi , Adachi Hiroshi Yoshie
Published: October 2002

The influence of B atom on the magnetic properties of R2Co17-
x

B

x

(R=Y, Nd and Sm) with 0≤x≤1 and Y2Co14B

x

with 0.75≤x≤1 was studied by means of NMR and magnetic measurements. The 59Co NMR results for R2Co17-
x

B

x

show that the shorter the distance between Co and the nearest-neighbor (n.n.) B, the larger the decrease in the Co moment. The 59Co hyperfine fields at the 18f site in Sm2Co17-
x

B

x

decrease greatly and the Co orbital moments, µ orb, increase. Thus there is a possibility that the axial anisotropy strengthens. The 11B NMR results for R2Co17-
x

B

x

show that there are Co atoms with increased moments. The Co moment decreases in R2Co17-
x

B

x

with 0≤x≤1, while increases in Y2Co14B

x

with 0.75≤x≤1. This is explained in terms of the different distances between Co and B due to the different crystal structures. Therefore the moment of the first n.n. Co atom of B decreases and that of the second n.n. Co atom of B increases.