bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical and Smooth Etching of InP by Cl2/Xe Inductively Coupled Plasma
Authors: Matsutani Akihiro , Ohtsuki Hideo , Koyama Fumio , Iga Kenichi
Published: October 2002

We have demonstrated anisotropic and smooth etching of InP by an inductively coupled
plasma (ICP) using Cl2/Xe at high substrate temperatures. We investigated the etching
characteristics by varying the substrate temperature, gas pressure, Cl2 flow rate and rf power.
Vertical and smooth dry etching of InP was achieved under a low dc bias of -80 V. The ICP
etching process is an effective low-damage dry-etching technique for microfabrication of
InP-based optoelectronic devices.
Production of Inductively-Coupled Large-Diameter Plasmas with Internal Antenna
Authors: Setsuhara Yuichi , Miyake Shoji , Sakawa Yoichi , Shoji Tatsuo
Published: October 2002

Large-diameter RF plasmas at 13.56 MHz have been produced by
inductive coupling of an internal-type antenna in a discharge chamber
of 400 mm diameter and 200 mm height. For minimization of the
electrostatic coupling, (i) a double half-loop antenna of 360 mm
diameter was employed for the reduction of antenna inductance and (ii)
the antenna conductor was terminated by the insertion of a blocking
capacitor to satisfy the impedance balance condition where the
RF-voltage amplitude could be minimized to 1/2 the terminal voltage.
The plasma source could be operated stably at RF input powers of up to
3 kW to attain plasma densities as high as 1012 cm-3 at Ar
pressures around 1 Pa. Furthermore, (iii) full covering of the
antenna conductor with an insulator tubing exhibited a significant
effect on the suppression of the electrostatic coupling with
simultaneous achievement of plasma densities as high as 5×1011 cm-3.
Plasma Properties of a Negative Ion Plasma Reactive Ion Etching System
Authors: Keller John H. , Kocon W. Walter
Published: October 2002

In high density reactive ion etching (RIE) systems it has been found that there is an aspect ratio
charging effect which causes damage, RIE lag and loss of ion current to the bottom of high aspect
structures. It has been shown by a number of authors, that one way of reducing these effects is to reduce
the electron temperature of the plasma which is above the wafer. We have characterized the plasma
properties of a medium to high density plasma system which uses a magnetic filter in an inductively
coupled plasma (ICP) to produce a low temperature negative ion plasma above the wafer. At 4 mTorr,
the electron temperature of this negative ion plasma is 1/3 of that for the same system without the filter.
We present uniformity data and electron temperature data versus pressure and magnetic potential.
A Simple Model of a Single-Electron Floating Dot Memory for Circuit Simulation
Authors: Shuhei Amakawa Shuhei Amakawa , Kouichi Kanda Kouichi Kanda , Minoru Fujishima Minoru Fujishima , Koichiro Hoh Koichiro Hoh
Published: October 2002

A new simulation technique for a single-electron floating dot
memory based on a semiclassical single-electron transistor is
proposed. It is designed to be suitable for use in circuit
simulation and it uses a Monte Carlo method in combination with
the master equation. Current-voltage characteristics of the
sensing single-electron transistor are modeled on the
steady-state master equation. Stochastic charging and discharging
of the memory dot is simulated by the Monte Carlo method. Our model
is faster than the master equation method alone. In addition,
drain current of the transistor can be calculated accurately at
every instant in the transient simulation, which is time-consuming
with the conventional Monte Carlo method alone.
Studies on Magnetron Sputtering Assisted by Inductively Coupled RF Plasma for Enhanced Metal Ionization
Authors: Yamashita Masahiro , Setsuhara Yuichi , Miyake Shoji , Kumagai Masao , Shoji Tatsuo , Musil Jindrich
Published: October 2002

Planar magnetron discharge is assisted by inductively coupled plasmas, which are sustained by a helical RF antenna immersed in the plasma. Use of the technique significantly enhances the plasma density. The effects of antenna termination when grounded or floating have been investigated by a simple circuit analysis. The floating antenna configuration effectively suppresses the anomalous rise of the plasma potential and thus the plasma source can be stably operated at a higher input of RF power to generate plasmas with densities as high as >1012 cm-3.
Profile Control and Plasma Rotation by Biased Electrodes in Large Diameter RF Produced Plasma
Authors: Shinohara Shunjiro , Matsuoka Norikazu , Yoshinaka Toshiro
Published: October 2002

Control of the plasma profile has been carried out using three types of biased electrodes in
a large-diameter (45 cm), radio-frequency (RF)-produced plasma with a magnetic field in the
low-pressure region. The radial profile of the electron density changed from a hollow to a
peaked one, while the electron temperature distribution did not appreciably change. The
azimuthal rotation velocity was changed with this biasing. It decreased with a lower magnetic
field and/or in a high-pressure regime, and a localized velocity profile near the edge region was
obtained with a few kHz oscillation of the ion saturation current.
Behavior of F Atoms and CF2 Radicals in Fluorocarbon Plasmas for SiO2/Si Etching
Authors: Kamisugi Kunihide Tachibana , Takeshi Kawasaki Takeshi Kawasaki
Published: October 2002

Densities of F atoms and CF2 radicals were measured in CF4,
C2F6 and CHF3 plasmas by vacuum ultraviolet laser absorption and
laser-induced fluorescence techniques, respectively, using an RF (400 kHz) plasma source. In the measurement of source gas dependence, the F atom density became highest in CF4 and lowest in CHF3, while the tendency was reversed for the CF2 radical density. Dilution of the source gases with O2 caused increases in the F atom density and decreases in the CF2 density, but dilution with H2 brought about significant decreases in the F atom density. The density of CF2 radicals was largely affected by the chamber wall conditions, with or without polymer deposition. The decay time constants of these species were also measured
during the pulsed afterglow, and the results were qualitatively consistent with
the behavior of the densities. However, some quantitative disagreements remain,
suggesting that the loss rates of these species in active plasmas are different
from the rates in the afterglow.
Energy Distribution Functions of Ions Impacted on a Negatively Biased Substrate in an Electron Cyclotron Resonance Microwave Plasma
Authors: Yasunori Ohtsu Yasunori Ohtsu , Keiichi Mori Keiichi Mori , Hiroharu Fujita Hiroharu Fujita
Published: October 2002

Impacted ion energy distribution functions (IIEDFs) in Ar electron cycltron resonance(ECR) microwave plasma have been measured on a substrate biased negatively using a conventional retarding grid analyzer. With an increasing ion-neutral elastic collision probability, the IIEDFs were found to spread toward the low-energy side, forming two peaks. At the high collision probability (> 80 %) realized at high biased-voltage and gas pressure, the lower-energy ions formed higher peaks than the higher-energy ones. This result was caused by the charge-exchange collision. The impacted ion temperature estimated from the semilog plot of the analyzer current-voltage characteristics was roughly constant (≃ 0.6 eV) for collision probability < 80%.
A Numerical Study of a Collision-Dominated Inductively Coupled Plasma Using Particle-in-Cell/Monte Carlo Simulation
Authors: Jin-Sung Oh Jin-Sung Oh , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

The deposition of power into electrons and ions in a collision-dominated
inductively coupled plasma has been investigated in Ar in a cylindrical
reactor wound uniformly around it which has ribbon-shaped current coil
using particle-in-cell/Monte Carlo simulation.
Electrons obtain energy from the temporally varying
induced azimuthal field, while heavy ions are only slightly heated by the
electrostatic radial field caused by a wall sheath in front of the reactor
wall.
Kinetic and Steady-State Properties of Magnetron Sputter with Three-Dimensional Magnetic Field
Authors: Shon Chae Hwa , Park Jun Seong , Kang Bong Koo , Lee Jae Koo
Published: October 2002

A kinetic code is used to simulate kinetic plasma properties in
a planar magnetron system in a realistic magnetic field
in two and three dimensions.
We simulate the magnetron system in order to obtain
various plasma characteristics
and erosion profiles of a target material with these magnetic fields.
Scaling formulas are used to estimate the steady-state properties of
plasma particles and to reduce computation time.
Variations in the geometry and the magnetic field optimize
these erosion profiles and plasma characteristics.
For the plasma characteristics, we also calculate the plasma
temperature and the distribution function.
We found that electrons are nearly Maxwellian,
while ions are not, and that the electron temperature in the bulk
coincides well with the experimentally measured value.
Computational Studies of Plasma Generation and Control in a Magnetron Sputtering System
Authors: Shunji Ido Shunji Ido , Mieko Kashiwagi Mieko Kashiwagi , Mikihiko Takahashi Mikihiko Takahashi
Published: October 2002

The problems in plasma generation and erosion profiles are studied by tracing an electron in a cylindrical magnetron
sputtering system with a ferromagnetic target.
The magnetic field is analyzed using the finite-element method (FEM).
The magnetic fields in the basic reference model are generated by a permanent magnet in the center and
a yoke of soft iron around the central permanent magnet.
First, the yoke is moved to change the erosion profiles.
Second, the permanent magnet replaces the yoke.
In both systems, the erosion profiles and the configuration of the magnetic field
are examined when the yoke and the magnet in the outer are moved.
Formation of Diamond Films by Intermittent DC Plasma Chemical Vapor Deposition Using Subelectrode
Authors: Noda Mikio
Published: October 2002

Diamond films were formed by intermittent DC plasma chemical vapor deposition (CVD),
wherein the waveform of the power supply was half-wave-rectified and a subelectrode
located closely to the cathode was introduced to perform stable discharge at long electrode
distance. The crystalline quality of the films deposited on silicon substrate was superior
when the electrode distance was about 20 to 25 mm, in comparison with that of films
deposited when the electrode distance was 10 or 30 mm. This method was also effective in
changing the discharge current widely and in performing a stable discharge at a very low
discharge current.
Effect of Oxygen Component in Magneto-Active Microwave CH4/He Plasma on Large-Area Diamond Nucleation over Si
Authors: Jeon Hyeongmin , Wang Chunlei , Hatta Akimitsu , Ito Toshimichi
Published: October 2002

Nucleation-enhanced pretreatments have been studied for large-area diamond growth on Si
(100) substrates using magneto-active microwave plasma chemical vapor deposition (CVD) at
low pressures below 10 Pa. In this study, an optimal CO2 composition in the CH4/He plasma used
for the pretreatment was mainly examined for the case of a low substrate temperature of ∼600°C.
A two-hour subsequent growth using a CH4[5 sccm]/CO2[10 sccm]/H2[85 sccm] gas mixture after
the pretreatment resulted in <100>-oriented growth of diamond Particles with a high density (∼109/cm2) on Si substrates pretreated at CO2 concentrations of 1–2%. On the other hand, at CO2
concentrations higher than these, the carbon films deposited during the pretreatment were less
dense and were almost completely etched off after a 10-min treatment using the growth plasma. It
was found that quadrupole mass spectra, optical emission spectra and Raman scattering spectra
changed substantially when CO2 beyond 3.8% was added to the source gas.
Negative Ion Volume Production in Electron Cyclotron Resonance Hydrogen Plasmas
Authors: Fukumasa Osamu , Matsumori Masanori
Published: October 2002

Production and control of electron cyclotron resonance (ECR)
plasmas for negative ion sources have been studied. A new production
method using permanent magnets is proposed as one possibility for
generating a large-diameter high-density uniform microwave plasma.
The microwave power is launched by an annular slot antenna into the
circumference of a chamber with a ring-cusp or a line-cusp permanent
magnet, where a magnetic field can be applied in a local region and
plasmas can be efficiently generated if the ECR condition is
satisfied. In this paper, we report the structure of the ECR negative
ion source, the characteristics of the ECR plasmas, and the comparison
of the ECR plasmas with DC discharge plasmas from the viewpoint of a
negative ion source.
Accumulation of Negative Ions in Hollow-Type Electron Cyclotron Resonance CF4 Plasma Column
Authors: Mieno Tetsu , Ogawa Akira
Published: October 2002

Accumulation of large amounts of F- negative ions in the
central region of magnetized plasma is realized by means of a
hollow-type electron cyclotron resonance plasma generated from a
CF4 gas source, where inhomogeneous distributions of plasma
species controlled by an applied magnetic field cause the production
of negative ions near the dense plasma region and their confinement
in the central region. This method should be a novel candidate for a
negative ion source at low gas pressures.
Fourier Transform Infrared Characterization of Moisture Absorption in SiOF Films
Authors: Chang Wai-Jyh , Houng Mau-Phon , Wang Yeong-Her
Published: October 2002

In this paper, the water absorption characteristics of as-deposited and annealed
liquid-phase-deposited fluorinated silicon oxide (LPD-SiOF) films were investigated to
clarify the film properties. The stability of moisture absorption was characterized under
an air-exposure environment of 23°C and 65% humidity. The as-deposited LPD-SiOF
film was found to easily absorb moisture from air and therefore to become unstable in
terms of the dielectric property. To obtain a highly stable dielectric film, a
hydrofluosilicic acid concentration of 2.2 M (with the corresponding fluorine content of
4.9 at.%) is suggested because it has a minimum water absorption change (<3%). The
related OH concentration was comparable (or even smaller) to those of other SiOF films
grown by chemical vapor deposition. Moreover, high-temperature annealing in nitrogen
ambient was utilized to drive out the moisture absorbed in an LPD-SiOF film. The
annealing process after deposition tends to render the film surface hydrophobic. The
resulting OH bonds were found to disappear after annealing and did not reappear even
after long time of air exposure.
Investigation on Base-Emitter Reverse Biasing: Light Emission, Junction Cross-Talk and Hot Carriers in Single-Polysilicon Quasi Self-Aligned Bipolar-Complementary Metal-Oxide Semiconductor Bipolar Transistors
Authors: Vendrame L. , Ailloud L. , Pontcharra J. De , Gravier T. , Niel S. , Kirtsch J. , Chantre A.
Published: October 2002

In this paper we investigate, in single-polysilicon quasi self-aligned bipolar transistors of an advanced 0.5 µm planar bipolar-complementary metal-oxide semiconductor (BiCMOS) technology, the base-emitter junction characteristics in reverse bias conditions and its influence on the behaviour of other neighbouring junctions, i.e. collector and substrate. We will show, due to the high emitter and base doping, the non negligible presence of impact-ionization effects superimposed over the well known reverse tunnel current even at moderate reverse bias. The related light emission coming from the energetic carriers in the impact-ionization regime can influence the collector and even the substrate junctions. These investigations are confirmed by temperature measurements and the results suggest that attention should be paid also to these secondary, higher order, effects during device scaling-down in BiCMOS circuitry.
Proposal on Temperature-Insensitive Semiconductor Lasers
Authors: Takahiro Numai Takahiro Numai , Natsuhiko Mizutani Natsuhiko Mizutani , Jun Nitta Jun Nitta
Published: October 2002

We propose temperature-insensitive semiconductor lasers which use compensation layers with negative refractive index temperature coefficients. It is theoretically shown that the maximum wavelength shift is -1.06 Å with temperature change within a range of 100 K. It is also expected that the characteristic temperature is high because the band gap of the compensation layer increases with temperature.
Modulation Characteristics of 1.53 µm Optical Inverter in Erbium-Lutetium Aluminum Garnets
Authors: Maeda Yoshinobu
Published: October 2002

An all-optical inverter derived from the negative nonlinear absorption effect was demonstrated in
erbium-lutetium aluminum garnet crystals using 1532 nm laser diode. By decreasing incident
modulation degree, a reversed-phase waveform was obtained in the transmitted laser at modulation
degrees smaller than 90% for sample lengths greater than 1.0 mm. The reversed-phase transmitted
waveforms were observed at modulation frequencies from 100 kHz to 1 GHz.
Coverage Properties of Nb/Al films made by Electron Cyclotron Resonance
Authors: Esposito Antonio , Nakagawa Hiroshi , Akoh Hiroshi , Takada Susumu
Published: October 2002

We perform growth of thin Al films using the electron cyclotron resonance
(ECR) technique on {100} Si wafer and bcc {110} Nb thin films at room temperature. The {110} Nb thin
films are also prepared by means of ECR. We carry out depositions using Xe plasma gas. We analyse the
surface structure of the films using reflection high-energy electron diffraction (RHEED) and atomic
force microscopy (AFM). The analyses show that Al films are polycrystalline on both Nb and Si
substrates. Moreover, very thin Al films on Nb show a remarkable match with Nb surfaces that in turn, exhibit
epitaxial behaviour and atomic scale flatness. This results in a good coverage of the Nb base itself.
Kinetics of Ferroelectric Phase Transition: Nonlinear Pyroelectric Effect and Ferroelectric Solar Cell
Authors: Itskovsky M. A.
Published: October 2002

Kinetics of a ferroelectric phase transition in thin ferroelectric layer (film), coated with metallic films [metal-ferroelectric-metal (MFM) system] and overheated with various heating rates through phase transition temperature by solar or laser irradiation impulse, is investigated. Dynamical nonlinear pyroelectric effect (pyroelectric current and polarization) as well as anomalies of dielectric permittivity and specific heat are calculated as functions of changing in time temperature for various heating rates. Conversion efficiency during heating of the MFM system (served as ferroelectric solar cell), operating due to the nonlinear pyroelectric effect in the ferroelectric phase transition region, ranges from a few percent for ferroelectrics of the triglycine sulphate (TGS) type to above 10% for the NaNO2 type ferroelectrics, reaching the order of efficiency of photovoltaic solar cell.
Thermoelectric Properties of and Dopant Distribution in SiC Thin Films
Authors: andToru Miyakawa Toshio Kawahara
Published: October 2002

We fabricated thin films of p-type SiC by the evaporation technique with metal dopants such as silver, nickel and copper, which acted as acceptors. The thermoelectric properties of SiC thin films were measured. These p-type dopants could reduce the resistance of SiC films and improve their performance as thermoelectric materials. For samples doped with 5 wt% Ag, the resistivity is very low compared with those of other samples. The thermoelectric power of the Ag-doped sample shows a temperature dependence in contrast to those of other samples.
A Thomson Scattering Measurement System based on an Infrared Laser
Authors: Bowden Mark D. , Kudo Hiroyasu , Uchino Kiichiro , Muraoka Katsunori , Noguchi Masanori
Published: October 2002

A new Thomson scattering measurement system, using a 1.064 µm YAG laser as the
radiation source, has been developed for the purpose of enabling measurement of
electron properties to be made in glow discharge plasmas containing reactive gases.
Initial measurements made using the new system in an inductively coupled plasma gave
results which were comparable with those obtained using previous Thomson scattering
systems that used visible lasers.
Sensitivity Enhancement for Acetylene Detection at 1.5 µm by Use of a High-Finesse Optical Cavity
Authors: Okazawa Rika , Kuze Hiroaki , Masusaki Hiroshi , Takeuchi Nobuo
Published: October 2002

We investigate the applicability of a high-finesse optical cavity to trace gas detection. An external-cavity diode laser is used to observe the absorption of acetylene at 1.5 µm. The detection sensitivity is enhanced by use of a 25 cm Fabry-Perot cavity of finesse ∼70 mounted inside a vacuum chamber. By locking the laser frequency to the peak of a cavity mode, which in turn is tuned to the peak of molecular absorption, an effective path length of 11 m is attained over a pressure range of 1 to 100 Pa.
Comparison of N-face and Ga-face AlGaN/GaN-Based High Electron Mobility Transistors Grown by Plasma-Induced Molecular Beam Epitaxy
Authors: Dimitrov R. , Mitchell A. , Wittmer L. , Ambacher O. , Stutzmann M. , Hilsenbeck J. , Rieger W.
Published: October 2002

Nominally undoped GaN/Al
x
Ga1-x
N/GaN high electron
mobility transistors were grown by plasma-induced molecular beam
epitaxy in order to study the formation and electric transport
properties of two-dimensional electron gases. By depositing an AlN
nucleation layer on sapphire substrates before the growth of the GaN
buffer layer, we were able to change the polarity of the wurtzite
films from N- to Ga-face. The change in polarity causes a change in
the sign of the spontaneous and piezoelectric polarization directed
along the c-axis of the strained AlGaN barrier. The sign and the
gradient in polarization at one of the GaN/AlGaN interfaces is mainly
responsible for the generation and confinement of the two-dimensional
electron gas. Ga- and N-face heterostructures with mobilities up to
1050 and 1200 cm2/Vs, respectively, and sheet
carrier concentrations of up to 1.2×1013 cm-2 at room temperature were realized. Transistors processed from heterostructures with both polarities show maximum source-drain currents between 800 and 850 mA/mm and a transconductance of up to 250 mS/mm.
Halogen-Transport Atomic-Layer Epitaxy of Cubic GaN Monitored by In Situ Gravimetric Method
Authors: Akinori Koukitu Akinori Koukitu , Yoshinao Kumagai Yoshinao Kumagai , Tetsuya Taki Tetsuya Taki , Hisashi Seki Hisashi Seki
Published: October 2002

In situ gravimetric monitoring (GM) of atomic-layer epitaxy (ALE) of cubic GaN on a GaN buffer layer/GaAs (001) is investigated using a halogen-transport system with GaCl and NH3 sources. The cubic GaN growth rate of one monolayer/cycle is obtained at a temperature ranging from 350 to 400°C. It is found that pure cubic GaN can be grown by halogen transport ALE. The growth rate decreases with increasing growth temperature, and a constant growth rate of about 0.45 is observed from 410 to 550°C. In this paper, it is shown that the in situ GM method is a powerful tool for understanding growth mechanism of the group III nitrides, as well as that of GaAs.
Properties of Cu(In,Ga)Se2 Thin Films Prepared by Chemical Spray Pyrolysis
Authors: Sho Shirakata Sho Shirakata , Yoshiaki Kannaka Yoshiaki Kannaka , Harufumi Hasegawa Harufumi Hasegawa , Tetsuya Kariya Tetsuya Kariya , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

Thin polycrystalline films of Cu(In,Ga)Se2 alloy with the single-phase chalcopyrite structure were successfully grown by the chemical spray pyrolysis (CSP) method on a glass substrate at 360 and 400°C. Alloy composition in the film was well controlled by that in the spray solution. The films were characterized by X-ray diffraction, optical absorption, Raman spectroscopy, van der Pauw measurement and scanning electron microscopy. It was found that lattice constants, the optical band-gap energy and the A
1 mode phonon frequency changed continuously with the alloy composition x. A grain size of about 1 µm was obtained for Cu-rich films.
Comprehensive Analysis of an Isolation Area Obtained by Local Oxidation of Silicon Without Field Implant
Authors: Fay Jean-Luc , Beluch Jean , Allirand Laurence , Brosset Dominique , Despax Bernard , Bafleur Marise , Sarrabayrouse Gerard
Published: October 2002

Isolation area, obtained by local oxidation of silicon (LOCOS) without field implant, naturally shows a high sensitivity of the leakage current to fixed charges in metal oxide semiconductor (MOS) parasitic transistors. It has been shown that during the deposition of the nitride capacitor insulator-layer, fixed charges are generated in the underlying plasma-deposited oxides. The behavior of the P-channel MOS (PMOS) parasitic transistor can be well accounted for by considering fixed charge creation in the thick part of the gate insulator. In the case of the N-channel MOS (NMOS) transistor, the leakage current is controlled by the bird's beak region where a high interface state density exists. The NMOS behavior has been explained taking into account the charge creation as well as a decrease in interface state density during nitride deposition. A new “recipe” for the nitride deposition based on a very low thermal budget has been established. Finally, a high threshold voltage and a reasonably low leakage current have been achieved for both the NMOS and PMOS parasitic transistors.
Synthesis of ZnO Bicrystals Doped with Co or Mn and Their Electrical Properties
Authors: Naoki Ohashi Naoki Ohashi , Yoshihiro Terada Yoshihiro Terada , Takeshi Ohgaki Takeshi Ohgaki , Shigeru Tanaka Shigeru Tanaka , Takaaki Tsurumi Takaaki Tsurumi , Osamu Fukunaga Osamu Fukunaga , Hajime Haneda Hajime Haneda , Junzo Tanaka Junzo Tanaka
Published: October 2002

Bicrystals of ZnO without intergranular additives were synthesized to elucidate the effect of Co and Mn doping on the varistor properties of ZnO ceramics. Nonlinear current-voltage (I–V) characteristics due to the formation of an interfacial barrier were observed in bicrystals doped with Co or Mn, while the nondoped bicrystals exhibited linearI–Vrelationship. Since the charge transport properties of bulk ZnO crystals were not changed, it is indicated that the energy dispersion and/or density of the interfacial states were changed by the Co and Mn doping.
Sharp Transmission Coefficient in GaAs/AlAs Resonant Tunneling Diodes with (411)A Superflat Interfaces Grown by Molecular Beam Epitaxy
Authors: Keisuke Shinohara Keisuke Shinohara , Satoshi Shimomura Satoshi Shimomura , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

In order to understand the improvedI–Vcharacteristics of GaAs/AlAs resonant tunneling diodes (RTDs) with (411)A superflat interfaces, transmission coefficient (T*T) was deduced from the second derivative (d2I/dV2) of the observedI–Vcurves. The peak width (full-width at half maximum, FWHM) of the transmission coefficient was found to be 8.6 meV, which was 18% smaller than that (10.5 meV) of the RTD simultaneously grown on a conventional (100) GaAs substrate. Photoluminescence (PL) measurements for the GaAs/AlAs double barrier structures of the RTDs themselves also showed a narrower linewidth for the (411)A sample (FWHM = 7.2 meV) than for the (100) sample (10.6 meV). This result suggests that electrons tunneling through the barriers are as sensitive to the interface roughness as excitons in the quantum well.
Three-Dimensional Intrinsic Josephson Junctions Using C-Axis YBa2Cu3O7-y Thin Film
Authors: Kim Sang-Jae , Yamashita Tsutomu
Published: October 2002

We report the successful fabrication of three-dimensional (3-D) intrinsic Josephson junctions (IJJs) using c-axis YBa2Cu3O7-y
(YBCO) thin films of 500–800 nm thickness. The stacks of IJJs were fabricated by the
lateral focused-ion-beam (FIB) etching method. The width depending on the required junction size and the full
depth of film thickness were patterned in a micro area from the normal direction etching. By tilting the sample
stage to 90°, two grooves of the bridge were etched from the lateral direction in accordance with the required
junction size. The junction did not show any degradation of the critical current density (J
c) down to an in-plane area of 0.5 m2.
Highly Uniform and Small InP/GaInP Self-Assembled Quantum Dots Grown by Metal-Organic Vapor Phase Epitaxy
Authors: Lee Hong-Wen Ren , Shigeo Sugou Shigeo Sugou , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

InP self-assembled quantum dots embedded in Ga0.51In0.49P were prepared by metal-organic vapor phase epitaxy. In order to reduce the dot diameter and improve the size uniformity, InP dots were grown at a low temperature using tertiarybutyl-phosphine instead of phosphine. Growth of 4 ML InP on a 4 ML GaP interface layer at 550°C resulted in InP islands of about 30 nm in base diameter and 7 nm in height that were remarkably uniform to within 10% deviation. The insertion of another 2 ML GaP interface layer between the InP islands and the GaInP cap-layer further reduced the half-width of the photoluminescence (PL) spectra from the InP dots to 29 meV at both 2 K and 77 K. It is necessary to grow the GaInP caplayer at higher than 630°C in order to alloy the undeveloped InP clusters and wetting layer with GaP interface layers.
Infrared Spectra of La0.67SrxMnO3-δ (x=0.33 and 0.23) around Curie Temperature
Authors: Zhou Zhou , Shengming Shengming , Zhou Zhou , Guien Guien , Zhang Zhang , Yuheng Yuheng
Published: October 2002

Infrared (IR) transmittance spectra were measured for La0.67Sr
x
MnO3-δ (x=0.33 and 0.23) samples in the temperature range 300–400 K. Large frequency shifts of the stretching mode of MnO6 octahedra were observed around the Curie temperature T
c. IR spectra showed that the local Jahn-Teller (JT) distortions persist in trigonal La0.67Sr
x
MnO3-δ and are partially removed below T
c. An extra absorption peak was detected for La0.67Sr0.23MnO3-δ due to the reduced symmetry of local MnO6 octahedra.
Demonstration of X-Ray Amplification in an X-Ray Laser Cavity Pumped by a Pulse-Train Yttrium Aluminium Garnet Laser
Authors: Yamaguchi Naohiro , Hara Tamio , Ohchi Tadayuki , Fujikawa Chiemi , Sata Toshio
Published: October 2002

X-ray lasings of a Li-like Al transition line at 15.47 nm in
the recombination scheme have been investigated using a tabletop
pulse-train yttrium aluminium garnet (YAG) laser system. A cavity
experiment has been carried out with a resonator consisting of a flat
and a concave Mo/Si multilayer mirrors. Clear enhancement of
the X-ray output from the cavity has been demonstrated. It was found
that the cavity output beam has a divergence of about 3 mrad and an
absolute intensity of about 1×108 photons/shot. The
temporal feature of the observed cavity output can be reproduced by a
simple ray-trace calculation with multiple times reflection and the
presence of a lasing medium.
Mechanism of Generation of Pretilt Angles on Polyimides with a Single Exposure to Polarized Ultraviolet Light
Authors: Nishikawa Michinori , West John L.
Published: October 2002

Behaviors of pretilt angles of liquid crystal (LC) cells were examined using polyimide (PI) films containing fluorine atoms by exposure to ultraviolet light (UV). Using a single obliquely polarized UV exposure, we obtained unidirectional LC alignment with any desired pretilt angles from 0° up to 90°. The pretilt angles depend on the concentration of fluorine atoms
in the PI and the UV exposure time and angle. The results of dichroic ratio and capacitance
measurements of the LC cells suggest that oblique polarized UV exposure breaks the surface
order degeneracy of the LC molecules, generating uniform pretilt angles along the optic axis of
the PI film.
Rigid Formation of Aligned Polymer Fiber Network in Ferroelectric Liquid Crystal
Authors: Fujikake Hideo , Aida Tahito , Yonai Jun , Kikuchi Hiroshi , Kawakita Masahiro , Takizawa Kuniharu
Published: October 2002

A rigid polymer fiber network for fastening two substrates and
anchoring a ferroelectric liquid crystal alignment was formed, for the
first time, by rapidly polymerizing aligned high-concentration acrylate
monomers. The µm-size polymer fibers segregated from a nematic
solution of the monomers and the ferroelectric liquid crystal under
high temperature and strong ultraviolet light irradiation are oriented
in the rubbing direction of the alignment layers. The free-standing
composite film having a concentration of the polymer of 20 wt%
exhibited a fast response time of 300 µs, a high contrast ratio of more
than 100:1, and grayscale capability. It is applicable to anti-shock
display devices.
CO2 Laser Annealing on Fluorinated Silicon Oxide Films
Authors: Wang Na-Fu , Houng Mau-Phon , Wang Yeong-Her
Published: October 2002

CO2 laser annealing of fluorinated silicon oxide films grown by liquid-phase deposition (LPD)
is proposed to improve the properties of the as-deposited films. It is found that the fluorinated
silicon oxide films after laser annealing become much denser and that the effective surface
charge density (Q
SS/q) is reduced significantly. However, the properties of the fluorinated silicon
oxide films after laser annealing depended on the power density of the laser beam. It is also
found that the effect of laser annealing is most prominent when the power density of the laser
beam is controlled at 12 KW/cm2. Based on the experimental results, it may be expected that the
structure of a fluorinated LPD-SiO2 film following CO2 laser annealing is similar to those of the
thermally grown layers. Thus, CO2 laser annealing is the best candidate for improving the
properties of LPD oxide films.
1.3 µm Room Temperature Emission from InAs/GaAs Self-Assembled Quantum Dots
Authors: Murray Ray , Childs David , Malik Surama , Siverns Philip , Roberts Christine , Hartmann Jean-Michel , Stavrinou Paul
Published: October 2002

We have investigated the growth conditions necessary to achieve strong room temperature emission at 1.3 µm for InAs/GaAs self-assembled quantum dots (QDs) using conventional solid source molecular beam epitaxy (MBE). A relatively high substrate temperature and very low growth rate (LGR) result in long wavelength emission with a small linewidth of only 24 meV. Atomic Force Micrographs obtained from uncapped samples reveal several differences between the LGRQDs and those grown at higher growth rates. The former are larger, more uniform in size and their density is lower by a factor of about 4. LGRQDs have been incorporated in p-i-n structures and strong room temperature electroluminescence detected. The light output of the QD p-i-n diodes is found to be significantly higher than a quantum well (QW) sample at least for current densities up to 0.5 kAcm-2.
Studies of the Ossicles from the Ciliate Protozoan Spirostomum ambiguum
Authors: Takagui Regina Reiko , Silveira Marina
Published: October 2002

Spirostomum ambiguum is able to concentrate intracellular deposits of calcium phosphate. This mineralization process is dependent on the age of the culture and can be stimulated by an applied piezoelectric potential. Crystalline deposits induced to form in laboratory cultures were analysed both in situ and after isolation from the cells, using transmission and scanning electron microscopies, energy dispersive microanalysis, and optical spectrophotometry. The ratio of Ca:P (1.57±0.01) fits with the expected value for hydroxyapatite.
Thickness Dependence of Ferroelectricity in Heteroepitaxial BaTiO3 Thin Film Capacitors
Authors: Naoko Yanase Naoko Yanase , Kazuhide Abe Kazuhide Abe , Noburu Fukushima Noburu Fukushima , Takashi Kawakubo Takashi Kawakubo
Published: October 2002

Heteroepitaxial BaTiO3 films of various thicknesses ranging from 12 nm to 79 nm were prepared on SrRuO3/SrTiO3 substrates by radio-frequency magnetron sputtering employing a two-step deposition technique, and the crystallographic and ferroelectric properties of the heteroepitaxial films were evaluated.
A ferroelectric hysteresis loop was clearly observed in the heteroepitaxial BaTiO3 films even when the thickness was reduced to 12 nm, probably due to improved crystallinity at the interface between the ferroelectric film and the electrodes through optimization of the preparation technique.
The observation of hysteresis at the temperature of 200°C was explained in terms of modification of the Curie temperature from the inherent 130°C to far above 200°C by lattice misfit strain.
A possible relationship between the artificially raised Curie temperature and the limited thickness dependence of ferroelectricity was discussed.
Low-Temperature Crystallization of Sol-Gel-Derived Pb(Zr, Ti)O3 Thin Films
Authors: Yoshikazu Fujimori Yoshikazu Fujimori , Takashi Nakamura Takashi Nakamura , Hidemi Takasu Hidemi Takasu
Published: October 2002

Sol-gel derived Pb(Zr,Ti)O3 capacitors were prepared
by low-pressure annealing and the two-step annealing techniques.
Well-saturated D–E hysteresis was obtained at 650°C
with low-pressure rapid thermal annealing.
The low-pressure first anneal lowered the crystallization temperature
of sol-gel-derived Pb(Zr,Ti)O3 thin films.
Highly reliable and low-voltage operation Pb(Zr,Ti)O3 capacitors were
obtained using a two-step annealing techniques under low-pressure at 550°C.
BaTiO3-Based Non-Reducible Low-Loss Dielectric Ceramics
Authors: Nakamura Tomoyuki , Sano Harunobu , Konoike Takehiro , Tomono Kunisaburo
Published: October 2002

Dielectrics composed of BaTiO3-rare earth oxide-MgO have
been
studied to design a non-reducible low-loss dielectric
material. Curie temperatures of dielectrics composed of
BaTiO3–Gd2O3–MgO were lowered by Gd2O3, which provided the
dielectrics with low power loss. It was found that the addition of
BaZrO3 to BaTiO3–Gd2O3–MgO decreased the capacitance change with
temperature. Gd2O3 diffused easily into BaTiO3, but, it could not
easily diffuse into BaTiO3 to which BaZrO3 had been added. It was
considered that BaZrO3 prevented the Gd2O3 diffusion into BaTiO3,
resulting the remains of ferroelectricity and reduced capacitance
change. Thus non-reducible and low power loss X7R dielectric
ceramics were developed.
Hydrothermal Synthesis and Dielectric Properties of Lead Nickel Niobate Ceramics
Authors: Lu Chung-Hsin , Hwang Wen-Jeng
Published: October 2002

Lead nickel niobate (Pb(Ni1/3Nb2/3)O3) has been prepared by a newly
developed hydrothermal process. During the hydrothermal reaction at 250°C, a
pyrochlore phase is formed. After calcining the 250°C-hydrothermally derived
precursors at 750°C, a monophasic Pb(Ni1/3Nb2/3)O3 compound is successfully
produced. Increasing the hydrothermal temperature significantly facilitates the formation of the perovskite phase. In comparison with the solid-state reaction,
the hydrothermal process not only reduces the temperature for synthesizing
Pb(Ni1/3Nb2/3)O3, but also decreases its particle size to the submicron range. The
dielectric properties of Pb(Ni1/3Nb2/3)O3 strongly depend on the electric field
frequency. Increasing the field frequency results in an increase in the apparent
Curie temperature, which is associated with a decrease in the maximum
dielectric permittivity. The critical exponent and diffuseness calculated by a
modified permittivity-temperature equation verify the relaxor characteristics of
Pb(Ni1/3Nb2/3)O3.
Ferroelectric Properties of Bismuth Layer-Structured Compound SrxBi4-xTi3-xTaxO12 (0≦x≦2)
Authors: Nagata Hajime , Chikushi Naohito , Takenaka Tadashi
Published: October 2002

The ferroelectric and fatigue properties of bismuth layer-structured ferroelectrics (BLSF),
Sr
x
Bi4-x
Ti3-x
Ta
x
O12 (x=0–2) [SBTT-x] with m=3, are studied for the purpose of obtaining large
remanent polarization, P
r, and fatigue-free properties. From the measurement of D-E hysteresis
loops using a standard Sawyer-Tower circuit, the value of 2P
r for SBTT-0.3 ceramic was
found to be the largest (2P
r=24.6 µC/cm2) in the SBTT-x system. As a result of examining
fatigue properties, SBTT-0.3 ceramic displays fatigue-free behavior up to about 1010 cycles. It
is assumed that these results are caused by the substitiution of Ta and Sr ions.
Excitation Density and Temperature Dependent Photoluminescence of InGaAs Self-Assembled Quantum Dots
Authors: Chang Wen-Hao , Hsu Tzu-Min , Nee Kuei-FenTsai , Chyi Jen-Inn , Yeh Nien-Tze
Published: October 2002

In this paper, we shall report on the excitation density and temperature
dependent photoluminescence produced by discrete energy levels from
InGaAs self-assembled quantum dots. While increasing the photoexcitation
density, five peaks originating from discrete energy levels of quantum dot and
wetting layer are observed. By deconvoluting these spectra using multiple
Gaussian fit, the intensity of each state is saturated following its degeneracy.
We describe the lateral confinement of quantum dots using a parabolic
potential model. The saturated values are in good agreement with the
degeneracy of this potential type. From the temperature dependent
photoluminescence, we observed the thermally activated quenching of each
state. Our results suggest that the wetting layer acts as a barrier to the carrier
thermallization processes offering a two dimensional path for inter-dot
coupling.
Piezoelectric and Mechanical Properties of BaBi4Ti4O15/Ba4Ti13O30 Ceramics
Authors: Nakai Yasuhiro , Fukuoka Shuichi
Published: October 2002

This article presents the piezoelectric and mechanical
properties of bismuth layer-structured ferroelectrics
(BLSF)-based BaBi4Ti4O15 ceramics incorporating Ba4Ti13O30.
The ceramic compositions, (1-x)BaBi4Ti4O15–xBa4Ti13O30 with
x=0–100 vol%, are obtained through solid-state reaction
processes. The dielectric constant, ε
33
T/ε
0, decreases
exponentially from 220 to 97 with increasing x from 0 to 66 vol%. The electromechanical coupling factor, k
33, decreases
from 15 to 7% with increasing x from 0 to 66 vol%. The fracture
toughness, K
IC, and flexural strength, σ, of the compositions
with x≥39 vol% are almost identical to those of Ba4Ti13O30.
At x≥39 vol%, K
IC and σ are nearly 15 and 30% larger than those
of BaBi4Ti4O15, respectively. Ba4Ti13O30 particles dispersed
uniformly in the ceramics are capable of carrying an applied
load effectively and lead to further improvements of the
mechanical properties.
A Parallel-Bimorph-Type Piezoelectric Actuator for High-Resolution Imager
Authors: Tanuma Chiaki
Published: October 2002

As minute positioning actuators for high-resolution imagers
using CCD(charge coupled device)-chip-shift operation, piezoelectric
bimorph actuators having low voltage drive and high-speed response
are required. In this study, a highly sensitive
parallel-bimorph-type piezoelectric actuator using both-ends support
with a U-shaped metal plate is proposed and developed. Firstly, the
effectiveness of the proposed actuator is confirmed from the
frequency and displacement characteristics in relation to the added
mass. Secondly, a parallel-bimorph-type piezoelectric actuator where
two bimorphs are arranged parallel to each other is fabricated for
use in a high-resolution imager that employs CCD-chip-shift
operation for practical applications. Through those experiments, the
optimal bimorph length and the U-shaped metal plate length are
experimentally obtained for stable and high performance of the
imager. A box-shaped package of imager, with a 22-pin, dual-in-line
format, and dimensions of 30(L)×20(W)×11(H) mm is
obtained. A demand displacement of 8.5×10-3 mm is obtained at a driving voltage of 13 Vp-p (30 Hz pulses).
Effect of BaO/WO3 on the Microwave Loss Quality of Ba(Mg1/3Ta2/3)O3
Authors: Yoon Ki Hyun , Yoo Seung Jong , Kim Woo Sup , Kim Jae Beom , Kim Eung Soo
Published: October 2002

Effects of BaO/WO3 ratio on the loss quality of complex perovskite Ba(Mg1/3Ta2/3)O3 were investigated as a function of the amount of (1-y)BaO-yWO3 (y=0.56, 0.8) from 0.3 wt.% to 7.0 wt.% at 10 GHz. The specimens with 1.5 wt.% of y=0.56 and/or with 1.0 wt.% of y=0.8 showed a maximum value of loss quality, respectively, and then decreased with an increase of additive content. The increase of loss quality with (1-y)BaO-yWO3, is resulted that the W6+ ions substitution of Ta5+ ions is enhanced the B-site ordering of Ba(Mg1/3Ta2/3)O3. The dielectric constant and temperature coefficient of resonant frequency (TCF) were decreased slightly with additives, which are due to the increase of BaWO4 phase as a secondary phase. The effects of additives on the intrinsic microwave losses of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000 cm-1.
Effect of Ba5Ta4O15Incorporation on Sintering Behavior and Microwave Dielectric Properties of Ba(Ma1/3Ta2/3)O3Materials
Authors: Liang Mei-Hui , Hu Chen-Ti , Chiou Chin-Gang , Tsai Yi-Nan , Lin I-Nan
Published: October 2002

The characteristics of Ba(Mg1/3Ta2/3)O3, BMT materials synthesized by a two-step process, consisting of the formation of B-site compounds,e.g., MgTa2O6, followed by the formation of a BMT perovskite, were compared with the properties of BMT powders prepared by the conventional single-step mixed-oxide route. BMT powders prepared by the two-step process exhibits superior reactivity compared to those synthesized by the single-step process. The single-phase perovskite can be formed at a lower calcination temperature (900°C) and high density ceramic materials can be obtained at a lower sintering temperature with a short period of time (1500°C, 2 h). When the Ba5Ta4O15is incorporated into pure BMT perovskite, the sintered density of BMT materials decreases significantly, and the dielectric constant (K) and temperature coefficient of resonance frequency (τf) are not altered significantly, but theQ-factor of the BMT materials decreases signicantly. These observations imply that the mechanism by which the two-step process significantly improves the densification process and the related microwave dielectric properties is the effective suppression of formation of the secondary phase, Ba5Ta4O15.
Crystal Structure and Microwave Dielectric Properties of CaTiO3–(Li1/2Nd1/2) TiO3–(Ln1/3Nd1/3)TiO3 (Ln=La, Dy) Ceramics
Authors: Kim Jeong-Seog , Cheon Chae-Il , Kang Hyun-Joo , Lee Chang-Hee , Kim Kyung-Yong , Nam Sahn , Byun Jae-Dong
Published: October 2002

Crystal structure and microwave dielectric properties of a xCaTiO3–y(Li1/2Nd1/2)TiO3–z(Ln1/3Nd1/3)TiO3 (Ln=La, Dy) ternary system were studied. Crystal structures were
refined by the Rietveld method using X-ray and neutron diffraction
data. (Li1/2Nd1/2)TiO3 and 0.2CaTiO3–0.8(La1/3Nd1/3)TiO3 ceramics showed the most reliable
R-values with a tetragonal structure with a space group P-4b2 and lattice constants of
a=b≈5.4 Å, and c≈7.6 Å. The A-site cations were ordered along the c-axis. When
x≥0.3, the crystal structure changed to an orthorhombic CaTiO3 type. The
xCaTiO3–y(Li1/2Nd1/2)TiO3–z(La1/3Nd1/3)TiO3
system showed microwave dielectric properties of
ε
r=133, Q·f=1,450 GHz and τf=-17 ppm/°C
at a composition of x=0.2, y=0.68, z=0.12. In
xCaTiO3–y(Li1/2Nd1/2)TiO3–z(Dy1/3Nd1/3)TiO3,
dielectric properties of ε
r=97.6, Q·f=5,150 GHz and τf=+0.4 ppm/°C were obtained at x=0.30, y=0.40, z=0.30. The effect of each ternary system component on the dielectric properties is discussed.
Ring Interferometric Voltage Sensor Using LiNbO3 Crystal
Authors: Kamada Osamu , Tamura Hitoshi
Published: October 2002

In this work, optical voltage sensors based on ring interferometry are studied to
enable the measurement of the DC voltage by introducing a phase modulation technique.
From experiments using z-cut LiNbO3 crystals as linear electrooptic elements for the
sensing element and the phase modulator, a high sensitivity of 1.5%/V and relative error
within ±1% were obtained for DC voltage up to 200 V. It was also clarified that these
characteristics satisfy the JEC1201-1PS standard accuracy.