bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Characterization of an Inductively Coupled Plasma Discharge Using a Shape-Adjustable Coil
Authors: Leou Keh-Chyang , Tsai Szu-Che , Chang Chai Hau , Chiang Whe-Yi , Lin Tsang-Lang , Tsai Chuen-horng
Published: October 2002

We report the results of experimental studies of an inductively
coupled plasma (ICP) source that employs a shape-adjustable coil to
maximize the source's operation window. With this novel concept,
the plasma density uniformity can be maintained over a wider
operation window as the system's parameters, such as gas pressure,
chemistry, and chuck RF bias power, are varied, as compared to the
conventional fixed coil design. To reduce the uneven shape
deformation, which may degrade the plasma's uniformity, the
adjustable coil design uses two sets of windings connected in
parallel. Experimental measurements using a 2D RF compensated
Langmuir probe show that the radial profile of the plasma density
changes as the coil is deformed. This effect is more evident at
higher gas pressures where the electron's mean free path becomes
shorter and the distribution of RF power plays a more dominant role
in determining the plasma density profile.
Ferrite Core Effects in a 13.56 MHz Inductively Coupled Plasma
Authors: Lloyd Shane , Shaw Denis M. , Watanabe Masahiro , Collins George J.
Published: October 2002

We investigate the effects of adding a ferrite core to the rf coil in a cylindrical inductively coupled plasma, thereby increasing the mutual inductance between the rf coil and the plasma at 13.56 MHz. This could reduce resistive power loss,Pcoil(loss)=Icoil2Rcoil, in the copper coil because of lower required rf drive current to ignite and sustain a plasma. The air core transformer circuit model of Piejaket al.. is modified to account for the effects of the ferrite core on the rf circuit. Specifically, circuit elements accounting for core power losses and the new primary inductance created by the addition of the core are included. The plasma electron density created by inductive drive, with and without the core was the same at the same total rf power. Any energy savings in the copper coils are offset by the large core losses at 13.56 MHz due to hysteresis and eddy currents.
Extensive Control of Plasma Parameters in the Afterglow Region of Electron-Cyclotron-Resonance Plasma for the Epitaxial Growth of Cubic Gallium Nitride
Authors: Yasui Kanji , Kikuchi Masaaki , Akahane AtushiUwabachi
Published: October 2002

In order to extensively control the plasma parameters in the afterglow region of
electron-cyclotron-resonance (ECR) plasma for the epitaxial growth of cubic gallium
nitride (c-GaN), magnetic and electric fields were applied in the afterglow region. The
lowest electron temperature and the smallest space potential were obtained at a large
negative mesh electrode bias under a mirror field condition. Under the mirror field
condition, the crystallinity of c-GaN was better at the negative mesh biases than that at the
positive ones. The integrated intensity ratio of c-GaN (200) to hexagonal GaN (10-11)
measured by the X-ray rocking curve also showed a large value under the conditions of
minimum electron temperature and minimum space potential.
Plasma Production and Wave Propagation in a Plasma Source Using Lower Hybrid Waves
Authors: Tetsuo Kikuchi Tetsuo Kikuchi , Keitaro Ohnishi Keitaro Ohnishi , Yasuyoshi Yasaka Yasuyoshi Yasaka , Kunihide Tachibana Kunihide Tachibana , Tohru Itoh Tohru Itoh
Published: October 2002

The lower hybrid wave, which is in the same frequency range as the
helicon wave, is resonant at the lower hybrid frequency and does not
penetrate into the higher density side of the plasma. This creates the
localized ionization region at the outer plasma radii and leads to uniform
plasma production. Typical plasma densities in the plasma source
designed to take advantage of this characteristic of the lower hybrid wave
are of the order of
1011cm-3 in the source region for 10 mTorr He and 1 kW radio
frequency (rf) power. The radial density profile can be controlled by
changing the location of the lower hybrid resonance by changing the magnetic
field B
0. We measured the radial dependence of rf electric and magnetic
fields to determine if
lower hybrid wave and helicon wave were present.
Plasma Diagnostics: Use and Justification in an Industrial Environment
Authors: Loewenhardt Peter , Zawalski Wade , Ye Yan , Zhao Allen , Webb Tim R. , Tajima Daisuke , Ma Diana X.
Published: October 2002

The importance of plasma diagnostics at semiconductor equipment manufacturers has
increased steadily over the past decade. The design and procurement of advanced etching
tools now require a full host of plasma diagnostics and modeling capability. Examples of
these activities at a semiconductor equipment manufacturer will be given, with specifics
of significant and useful results. Examples include the development and optimization of
an inductive plasma source, trend analysis and hardware effects on ion energy
distributions, and mass spectrometry influences on process development. Discussion will
focus on plasma diagnostics for in-house development and proliferation in an
environment with strong financial justification requirements.
Characteristics of Electron Density in Ablation Plasma Generated from Functionally Graded Material in Excimer Laser Processing
Authors: Yoshihisa Uchida Yoshihisa Uchida , Jun Yamada Jun Yamada , Hideo Furuhashi Hideo Furuhashi , Yoshiyuki Uchida Yoshiyuki Uchida
Published: October 2002

Functionally graded materials (FGMs), which possess the dual characteristics of two materials, are expected to be useful in industry in the near future. It is important to find a process of laser ablation when laser is used in the reprocessing of FGM such as cutting and drilling. The electron density is one of the important parameters needed to analyze the mechanism of the ablation plasma. The characteristics of electron density in ablation plasma were estimated. A XeCl excimer laser with a wavelength of 308 nm, a maximum pulse energy of 500 mJ and a pulse duration of 30 ns was used. A Mach-Zehnder interferometer was used to measure the electron density. The electron density dependence of the ablation plasma plumes on the ceramic-metal content of FGMs was observed. The temporal and spatial profiles of the electron density were also observed.
Effect of Gas Flow on RF Plasmas
Authors: Nobuyasu Sato Nobuyasu Sato , Yutaka Shida Yutaka Shida
Published: October 2002

Effects of gas flow on rf plasmas between parallel plates under plasma processing conditions are investigated using a Monte Carlo simulation (MCS) and a fluid model calculation. It has shown that the gas flow changes the ion density distribution in the bulk region of the rf plasma where the velocity of gas flow is faster than that of the ion diffusion motion. Comparison of the results of the MCS with those of the fluid model calculation has shown that the fluid model in which the velocity of gas flow is added to the drift and diffusion motion may be valid at a pressure above 1 Torr. Using the fluid model and Poisson's equation, self-consistent calculations of the argon and silane rf plasmas have been carried out. This indicates that the plasma structure including negative ions is sensitively changed by the gas flow.
Simulation of Variations in the Negative Ion Density in Time-Modulated Cl2 Plasmas
Authors: Yokozawa Ayumi , Samukawa Seiji
Published: October 2002

The variations in the negative ion density in a time-modulated (TM) Cl2 plasma with pulse duration
have been investigated. The behavior of electrons in the plasma is simulated by a model based on the Monte Carlo
method, and the variations in the negative ion density are deduced from attachment and detachment by electron
impact and recombination with positive ions. It is found that the negative ion density increases significantly while
electron density and temperature decrease when the microwave power is turned off. The time-averaged negative
ion density during the power-off period varies with the pulse duration, and this dependence of the negative ion
density on pulse duration is qualitatively the same as that of the etch rate obtained by the experiment. The present
results suggest that the impingement of negative ions on the substrate affects the etching performance in a TM Cl2
plasma.
Relationship between Intensity of Fullerene-Mass Spectrum and Carbon Vibrational Temperature in Microwave-Helium Plasmas
Authors: Kengo Ueda Kengo Ueda , Kiyoshi Kuwahara Kiyoshi Kuwahara , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

Soot containing fullerenes, such as C60 and C70,
was synthesized with He plasmas generated in a quartz tube by
microwave-glow discharge. A reticulated vitreous carbon (RVC) heated
by the microwave He plasmas with an electric field of TE10
mode was used as the carbon source. Swan bands of C2
molecules were observed during the synthesis by optical emission
spectroscopy (OES) in order to investigate the effect of the
vibrational temperature of C2 molecules on the formation of
the fullerenes. The soot deposited on the quartz tube was analyzed
by laser desorption time-of-flight mass-spectroscopy (LD-TOF-MS).
The intensities of the mass spectra of fullerenes were confirmed
to be maximum for the conditions as follows: the absorbed microwave
power P
ab=200 W and the He gas pressure P=100 Torr, while
the C2 vibrational temperature was approximately 7000 K.
Effects of Gas Flow on Particle Growth in Silane RF Discharges
Authors: Matsuoka Yasuhiro , Shiratani Masaharu , Fukuzawa Tsuyoshi , Watanabe Yukio , Kim Kyo-Seon
Published: October 2002

The effects of gas flow on particle growth in silane RF discharges in a plasma chemical vapor deposition (PCVD) reactor with a shower-type
powered electrode are studied using an in situ two-dimensional
polarization-sensitive laser-light-scattering method. Particle growth depends on both the production of short-lifetime radicals and the loss of neutral
clusters in the radical production region around the plasma/sheath boundary
near the powered electrode. Gas flow of a velocity above about 6 cm/s is
effective in suppressing particle growth because of increase in loss of
neutral clusters. Moreover, particles larger than 120 nm in size that flow to
the plasma/sheath boundary near the grounded electrode are found to pass
through the sheath. This implies that such particles may deposit on film
surfaces for PCVD reactors with the shower-type powered electrode.
Synthesis of β′′-Alumina from Powder Mixture Using Thermal Plasma Processing
Authors: Fukumasa Osamu , Sakiyama Satoshi , Esaki Hirotoshi
Published: October 2002

With the use of a thermal plasma reactor based on the forced
constricted type plasma jet generator, the synthesis of thermoelectric
materials (β′′-alumina) for the alkali metal thermoelectric
converter (AMTEC) has been studied. Under not only atmospheric
pressure but also low pressure, thin films of β′′-alumina are
successfully synthesized for the first time from powder mixtures of
α-Al2O3, Na2CO3 and MgO. The powder mixing
ratio, jet power and substrate position strongly affect the synthesis
of β′′-alumina, which is found to be correlated with jet
temperature.
High-Temperature Metalorganic Vapor Phase Epitaxial Growth of GaAs/AlGaAs Quantum Structures in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates
Authors: Tomoko Tsujikawa Tomoko Tsujikawa , Toshifumi Irisawa Toshifumi Irisawa , Hiroyuki Yaguchi Hiroyuki Yaguchi , Kentaro Onabe Kentaro Onabe , Yasuhiro Shiraki Yasuhiro Shiraki , Ryoichi Ito Ryoichi Ito
Published: October 2002

GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs {111}B substrates at temperatures above 800°C by metalorganic vapor phase epitaxy because quantum dots were expected to be formed at the bottom {111} regions of the TSRs.
Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at {100} edge regions, {110} and {111}A sidewalls and the {111} bottom and surface regions of the TSR.
Growth on the {111}B surface region between TSRs was clearly observed for the sample grown at 850°C.
As the growth temperature was raised above 850°C, the photoluminescence intensity on the {111}B surface increased whereas that on the {001} edge regions and {111}A sidewall regions decreased.
With an increase in well thickness, the luminescence from the bottom and edge regions was simultaneously observed.
A 50 Å-thick quantum well was formed on the small bottom region. From scanning electron microscope observation, the lateral size of the region was 550 Å.
Transmission Electron Microscopy and Photoluminescence Characterization of InAs Quantum Wires on Vicinal GaAs(110) Substrates by Molecular Beam Epitaxy
Authors: Satoshi Torii Satoshi Torii , Kazuki Bando Kazuki Bando , Byoung-Rho Shim Byoung-Rho Shim , Kenzo Maehashi Kenzo Maehashi , Hisao Nakashima Hisao Nakashima
Published: October 2002

InAs quantum wires have been naturally formed on vicinal GaAs(110) surfaces with giant steps by molecular beam epitaxy. Transmission electron microscope observations reveal the high density of stacking faults and the moire fringe for thick wires (>4 ML) due to the large InAs–GaAs lattice mismatch. From the moire fringe separation, thick InAs wires are found to be completely relaxed. No defect is observed for thin wires (<4 ML). Strongly polarized photoluminescence (PL) observed for InAs wires confirms the carrier confinement to the quantum wire structures and the strain effect induced by the large lattice mismatch. A considerable energy shift is observed in the excitation intensity dependence of PL, indicating large nonuniformity.
Modeling of γ-Irradiation and Lowered Temperature Effects in Power Vertical Double-Diffused Metal-Oxide-Semiconductor Transistors
Authors: Golubovic Snezana , Stojadinovic SnezanaDjoric-Veljkovic
Published: October 2002

In this paper the results of investigation of γ-irradiation and lowered temperature effects on
commercial n-channel power vertical double-diffused metal-oxide-semiconductor (VDMOS)
transistors are presented. By analyzing obtained results, the mechanisms responsible for
observed effects are modeled.
Investigation of the Dopant Segregation Phenomenon in Nb-doped BaTiO3 Positive-Temperature-Coefficient-Resistor by Impedance Analysis
Authors: Yoon Seok Hyun , Kim Hwan
Published: October 2002

We sought evidence of the dopant segregation phenomenon and the formation of a dopant-segregation-induced insulating layer in Nb-doped BaTiO3, by impedance and modulus analyses. In a 0.05 mol% Nb-doped specimen in which dopant segregation is not expected to occur, impedance and modulus data over
the range of 30–400°C can be explained by the conventional positive-temperature-coefficient-resistor (PTCR) equivalent circuit of grain resistance (R) and grain boundary resistance and capacitance (C). In a
0.4 mol% Nb-doped specimen, however, impedance and modulus data can be described by introducing
another third RC component in addition to the grain and grain boundary component. This RC component
is assumed to have originated from the dopant segregation layer. Above 350°C, this RC component
associated with segregation layer begins to disappear. This phenomenon can be explained by the Fermi
level change and the valence change of the titanium vacancy in the dopant segregation layer with change
in temperature.
Influence of Microwave Application on Disintegration of Sodium Hydrogen Carbonate in Water
Authors: Jeon Jong Yeol , Kim Hee Young
Published: October 2002

The existence of microwave effects was reexamined for a
temperature-sensitive inorganic reaction, the disintegration of sodium
hydrogen carbonate in water, for which the microwave nonthermal
effects have been previously reported. Comparative experimental tests
were executed for microwave- and conventional infrared-heated
reactions, with their thermal conditions and apparatus being carefully
made similar. Their standard deviations in conversion were observed to
range between 2 and 6%, showing that there are no appreciable
microwave effects on the tested
reaction.
Observation of Thermal Phonon Resonance in Cylindrical Microcavities
Authors: Hattori Koichiro , Sakai Keiji , Takagi Kenshiro
Published: October 2002

Brillouin scattering measurements were made in small capillary
tubes filled with water with 1450 µm and 920 µm in inner
diameters. Hyper-resolution spectroscopy using an optical beating
technique revealed thermal phonon resonance in the cavity around
8 MHz and 30 MHz. The observed spectra have a complicated structure
with periodical main peaks and other subpeaks accompanying each main
peak. The resonance frequencies of the cylindrical phonon modes were
theoretically calculated and given through a series of n-th order
Bessel functions. Frequencies of the fundamental (n=0,1) modes were
in good agreement with those of the observed main peaks, and the
subpeaks were associated with higher modes with n≥2. The mode
assignment was successful. As the frequency increased, all the
sub-peaks gathered towards the relevant main peak and were
degenerated. This phenomenon was applied to measure the phonon
velocity of liquid confined in a small cavity. Measurement was made
for water over a temperature range from 20 to 28°C, and the
result demonstrated a high sensitivity for detecting velocity changes
smaller than 0.1%.
Distribution Profiles of B Atoms in Diborane Implanted Silicon Prepared Using an Ion Implantor without Mass Filters
Authors: Yokota Katsuhiro , Nakamura Kazuhiro , Nishimura Hidetoshi , Terada Kouichiro , Sakai Shigeki , Tanjou Masayasu , Takano Hiromichi , Kumagaya Masao
Published: October 2002

Ion species generated from a mixed gas of B2H6 and H2 were implanted
into silicon at 25 keV using an ion implantor without mass filters. Approximately
80% of the ions implanted into the silicon were B2H5
+ and H3
+ ions. The silicon
had distinct atom distribution profiles, corresponding to B and H atoms
decomposed from B2H5
+ ions and to H atoms dissociated from H3
+ ions. The
projected ranges of the distribution profiles of B and H atoms were the same as those for the B+ and H+ ions implanted into silicon at equivalent energies.
However, B and H atoms decomposed from molecular ions resulted in broad
exponential tails in the distribution profiles of the B and H atoms, and the
exponential tails depended slightly on the amount of H2 used for
diluting B2H6.
Facet Evolution of Al0.5Ga0.5As/GaAs Multilayers Grown on Mesa-Patterned GaAs Substrate
Authors: Jin Kim Hyo , K. Park Young , Kyu Kim Seong-Il Kim , Whan Kim Tae
Published: October 2002

Facet evolution of (511)A of Al0.5Ga0.5As/GaAs multilayers grown on a mesa-patterned GaAs substrate by metalorganic chemical vapor deposition has been investigated. The time development equation of the growth morphology together with the bond density model was introduced to analyze the facet evolution. The facets at the concave surface on the mesa-patterned GaAs substrate during the growth process were evolved toward the growth surface with the highest growth rate. The facets having the highest growth rate were analyzed as a function of the surface migration length. The calculated results show that the highest growth rate in the surface plane of (511)A occurred at the concave surface on a mesa-patterned GaAs substrate with a surface migration length of larger than 1.5 µm.
Ordering of Germanium Clusters During Epitaxy on Patterned Silicon Substrates
Authors: Hul'ko Oleksa , Zinke-Allmang Martin
Published: October 2002

Semiconductor surfaces have been patterned by a novel method based on the growth of metal clusters directly on the surface as masks for subsequent low energy ion beam modification. During subsequent wet etching, well-defined mesa structures were obtained. When these are overgrown with 5 to 50 monolayers of germanium, field emission scanning electron microscopy shows growth of crystallographically ordered Ge clusters not only on the substrate between the mesas but also on the slopes of the mesas. The latter clusters show a distinct orientational correlation, and ordering in size and nearest neighbor distance.
Analysis of Surface Photoabsorption Spectra of (001) InP Surfaces
Authors: Kim Young-Dong , Lee Tae-Wan , Hwang Heedon , Moon Youngboo , Yoon Euijoon , Nakamura Fumihiko
Published: October 2002

We present an in situ surface photoabsorption (SPA)
study on surface structures of (001) InP surfaces. Conventional
subtraction spectra of SPA on (001) InP showed two peaks at 430 nm
and 600 nm, which we assigned as P dimer and In dimer peaks,
respectively. By modifying the conventional subtraction equation to
separate contributions from In- and P-stabilized surfaces, we could
observe another structure at 400 nm which we interpret as related to
In-stabilized surface, showing possibility of complementary role of this modified equation. We also observed evolution of surface states from P- to In-stabilized surfaces at 600°C by the change of PH3 partial pressure.
Effects of the Initial Heat-Treatment Conditions on Microstructures of YbBa2Cu3O7-δ Superconducting Final Films Deposited on SrTiO3(001) Substrates by the Dipping-Pyrolysis Process
Authors: Shibata Junko , Yamagiwa Katsuya , Hirabayashi Izumi , Ma Xiuliang , Yuan Jun , Hirayama Tsukasa , Ikuhara Yuichi
Published: October 2002

We investigated by transmission electron microscopy the relationship between the initial heat-treatment conditions and the microstructures of YbBa2Cu3O7-δ superconducting final films deposited by a dipping-pyrolysis process on SrTiO3(001) single crystal substrates. An amorphous precursor film was prepared by heating rapidly up to 425°C. By heat-treating at 725°C, this film became a c-axis oriented YbBa2Cu3O7-δ film with a thickness of 100 nm, and showed a sharp resistive transition around the critical temperature (T
C). On the other hand, a polycrystalline precursor film was produced by heating slowly. This film did not give rise to an epitaxial film, but to a YbBa2Cu3O7-δ polycrystalline film with a grain size of about 200 nm, and exhibited a broad transition. Therefore, the initial heat-treatment conditions and the microstructures of the precursor films are important for the epitaxial growth and superconducting properties of the final YbBa2Cu3O7-δfilms.
Ba-Site Replacements of Ba2YCu3Oz-Type Cuprates and Superconductivity
Authors: Ono Akira
Published: October 2002

Superconducting Ba1.8R0.2*RCu3Oz(R*, R=La, Nd, Sm, Gd, Dy, Y) cuprates are prepared at 0.1 MPa and 2 GPa to study the relationships between composition, structure and superconducting critical temperature (Tc). The oxygen contents (z) of the cuprates annealed in oxygen range from 7.00 to 7.07 per formula unit.Tcvaries depending on the oxygen content and the kind of rare-earth elements on the Ba site. High La contents on the Ba site are favorable for highTcvalues, whereas Y, Dy and Gd on the Ba site suppressTc.Tctends to increase with increasing ionic radii of rare-earth elements. A similar result is obtained for cuprates withz≈7.10 annealed at 1.5 GPa. The results are explained in terms of the hole distribution between CuO2sheets and BaO–CuOxlayers. The large number of hole carriers in the CuO2sheets is reduced by the partial replacement of Ba with rare-earth elements that have smaller ionic radii.
Magnesium-Ion Indiffusion to Lithium Niobate Single-Crystal Fiber with MgF2 as Diffusion Source
Authors: Que Wenxiu , Zhou Yan , Lam Yeeloy , Chan Yuenchuen , Kam Chanhin , Zhang Liangying , Yao Xi
Published: October 2002

A study of the Mg-ion indiffusion to lithium niobate (LiNbO3) single-crystal fiber was carried out using MgF2 as the diffusion source. A core-cladding waveguide structure was obtained for a c-axis LiNbO3 single-crystal fiber with a diameter of 200 µm, and the optical characteristics of the cladded crystal fiber were given. By means of electron probe microanalysis, the activation energy for Mg-ion indiffusion was estimated to be 104 kJ/mol. It was also found by X-ray diffraction analysis that the Mg-diffused layer has serious lattice distortion and the LiNb3O8 compound appears beyond a certain extent of Mg-ion indiffusion. The appearance of the LiNb3O8 compound is related to Li-ion outdiffusion from the bulk of LiNbO3 and the large amount of F ions from MgF2 due to Mg-ion indiffusion to LiNbO3. It was indicated by scanning electron microscopy that F ions appear in the form of LiF particles and these particles volatilize from the surface of the Mg-diffused layer with increased diffusion.
Evaluation of n+a-Si Contact with Indium Tin Oxide by X-Ray Photoelectron Spectroscopy Valence Band Measurement
Authors: Yabuhara Hidehiko , Kataoka Yoshinori
Published: October 2002

We investigated the cause of the high resistance in a contact
structure of phosphorus-doped amorphous silicon (n+a-Si) with
indium tin oxide (ITO) for thin-film transistor liquid crystal
displays (TFT-LCDs). X-ray photoelectron spectroscopy (XPS) valence
band analysis for this interface was newly developed. TFT-LCD
fabrication processes could be simplified by using ITO in pixels as
the drain contact electrode. One problem of this drain structure was
the increase in electrical resistance associated with annealing. XPS
valence band measurements of the n+a-Si/ITO structure revealed
that the upper edge of the Si valence band shifted to a lower binding
energy after annealing at 250°C. These results suggest that
the increase in electrical resistance was mainly caused by the
increase in contact resistance. The above-mentioned result was also
confirmed by secondary ion mass spectrometry (SIMS) analysis and
resistance measurements.
A Blue Organic Light Emitting Diode
Authors: Kijima Yasunori , Asai Nobutoshi , Tamura Shin-ichiro
Published: October 2002

A blue organic light emitting diode (OLED) which has a structure like an SH-B type diode has
been developed. The blue OLED consists of a hole-injection layer (m-MTDATA), a hole-transporting
emissive layer, a hole-blocking layer and an electron-injection layer (Alq3) formed on an ITO anode
by vacuum vapor deposition. α-NPD was used for the hole-transporting emissive layer, which has
an emission peak at around 455 nm. For the hole-blocking layer, we found that 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine) is a very effective material. As Bathocuproine has a
good hole-blocking ability, the recombination area is in the α-NPD layer. The electroluminescence
peak from the new blue OLED is at around 455 nm. The color coordinate in CIE chromaticity is
(0.15, 0.16). The blue OLED has a potential of over 10,000 cd/m2 at 9.5 V under DC operation with
an AlLi cathode. When this OLED is driven under a 1/100 duty ratio, the peak luminance is over
54,000 cd/m2. The luminous efficiency was 1.1 lm/W at 150 cd/m2. The blue OLED device is also a
good green device without the Bathocuproine layer. The green OLED shows electroluminescence
from the Alq3 layer with luminance of 40,000 cd/m2 at 10 V under DC operation, and the color
coordinate in CIE chromaticity is (0.33, 0.55).
Two-Dimensional Effects on Measurement of Thermal Diffusivity by AC Calorimetric Method: II. Effects of Heat Loss
Authors: Takahashi Fumiaki , Hamada Yukihiro , Hatta Ichiro
Published: October 2002

In our previous paper [I. Hatta et al..: Jpn. J. Appl. Phys. 38 (1999) 2988.], the condition required for measuring thermal diffusivity along the surface of a thick plate-like sample using an ac calorimetric method was proposed in which the sample is subjected to an adiabatic condition. In measurement at high temperatures, we cannot avoid the effects of radiation heat loss. Therefore, it is important to extend the analysis to include a case where there is heat dissipation from the sample to surroundings. We analyze two-dimensional temperature wave propagation in a thick plate-like sample during heat loss between the plate-like sample and a thermal bath. In such a case, we propose the conditions for measuring thermal diffusivity to an accuracy of ±1%.
Fabrication of Slot-Antenna Coupled Warm Carrier Detectors for Submillimeter Wave Radiation
Authors: Yasuoka Yoshizumi , Shimizu Takashi , Abe Yasuhiko , Kirihata Atsushi , Gamo Kenji
Published: October 2002

Thin-film slot-antenna-coupled edge-type warm carrier devices with a contact area of about 8×10-10 cm2 were fabricated, and their detection properties were investigated at 700 GHz. The fabricated slot antenna operates as a one-wavelength slot antenna as designed on the basis of the experimental results obtained in the microwave region. In addition, the fabricated edge-type warm carrier device operates as a detector, and rectifies the 700 GHz signal received by the antenna. The sensitivity of the device at 700 GHz was about 100 V/W.
Influence of Current–Voltage Characteristics on Image-Sticking of Thin-Film-Diode Liquid-Crystal Displays
Authors: Hirai Takanori , Morita Hiroshi , Tasaka Masayasu
Published: October 2002

The origins of image-sticking in metal-insulator-metal type thin-film-diode (TFD) liquid-crystal displays have been identified. One of the origins is the current–voltage (I–V) characteristic asymmetry of the TFD element. The other is the I–V characteristic shift during element operation. A tandem TFD structure and intensive heat treatment were introduced to
reduce the asymmetry and shift of the I–V characteristics, respectively. By the combined
effect of both, the image-sticking time after display of a fixation pattern for 5 min could be
shortened from about 4 min to an almost negligible duration.
Large-Scale Ultrasonic Joining Tool for Joining Plastic Sheets Using a Rectangular Plate Face Vibrating in In-Plane-Mode
Authors: Watanabe Yuji , Shijo Yukihiro
Published: October 2002

This new tool is constructed using a rectangular plate having a large joining area. The plate vibrates in the in-plane-mode. Static pressure was applied using a metal stamp. The shape of the pressing face of the stamp can be arbitrary. Using the 19 kHz joining system, which has a 130 mm×180 mm joining area, we joined two polytetrafluoroethylene (PTFE; TeflonTM) sheets that were 0.4–0.8 mm thick. The joining face of the plate could rub the PTFE face vigorously. We found that the maximum load of the joint was determined by the product of the vibration velocity of the tool face and static pressure. Therefore, the joint strength distribution can be made uniform by adjusting the pressing face width according to the vibration velocity distribution of the tool face.
Bottom Electrode Structures of Pt/RuO2/Ru on Polycrystalline Silicon for Low Temperature (Ba,Sr)TiO3 Thin Film Deposition
Authors: Hwang Eun-Suck Choi , Soon-Gil Yoon Soon-Gil Yoon
Published: October 2002

Electrode structures of Pt/RuO2/Ru on polysilicon and (Ba,Sr)TiO3(BST) thin films on
Pt/RuO2/Ru/poly-Si structures were prepared by metal-organic chemical vapor deposition
(MOCVD). The barrier layers of RuO2/Ru deposited by MOCVD showed a stable
interface and did not affect the surface morphology of the platinum bottom electrode
even at a high annealing temperature of 800°C in oxygen ambient. Contacts in the
annealed state up to 800°C exhibited linear current-voltage characteristics with a
constant specific contact resistance of 5.0 ×10-5 Ω·cm2.
The excellent leakage current characteristics and dielectric properties of 50-nm-thick BST films were due to the stable and
smooth morphologies of the bottom electrodes at BST deposition temperature.
Optical and Resonant Tunnelling Spectroscopy of Self-Assembled Quantum Dot Systems
Authors: Polimeni Antonio , Patanè Amalia , Thornton Andrew , Ihn Thomas , Eaves Laurence , Main Peter , Henini Mohamed , Hill Geoffrey
Published: October 2002

The electronic properties of self-assembled quantum dots have been studied by means of optical
and tunnelling spectroscopy. The effect of confining barrier composition and design on the thermal
behaviour of the dot optical properties is reported and exploited for the realisation of quantum dot
based lasers. Tunnel current spectroscopy through a single discrete quantum dot state is used to
investigate the electronic properties of an adjacent two-dimensional electron gas, including the
Landau level density of states and many-body enhanced g-factor in the presence of a magnetic field.
Improvement of Quality and Electrical Properties of Sputtered Pb(Zr, Ti)O3 Films by Wet-Oxidation Process
Authors: Nam Song-Min , Kimura Hiroyuki , Ohashi Naoki , Tsurumi Takaaki
Published: October 2002

A wet-oxidation process was proposed to improve the quality and
electrical properties of Pb(Zr, Ti)O3 (PZT) thin films prepared
by the RF-magnetron sputtering technique. For the oxidation of
metallic Pb in as-deposited PZT films, the wet-oxidation process was
carried out using hydrogen peroxide solutions prior to postannealing
for crystallization. In the case of PZT films on Pt/Ti/SiO2/Si
substrates, the density of defects observed using an optical
microscope was drastically decreased by means of the wet-oxidation
process, and the shape of polarization vs voltage hysteresis loops of
PZT films was also improved. In the case of PZT films on
Pt/IrO2/SiO2/Si substrates, microvoids were diminished by
means of the wet-oxidation process. For 70 nm-thick PZT films on
Pt/IrO2/SiO2/Si substrates, hysteresis loops could not be
measured without the wet-oxidation process. However, the films with
the wet-oxidation process exhibited the slim-type hysteresis loop with
a remanent polarization of over 23 µC/cm2 even at 2 V and a
coercive voltage of about 0.7 V.
Size Effects of Epitaxial and Polycrystalline Pb(Zr, Ti)O3 Thin Films Grown by Metalorganic Chemical Vapor Deposition
Authors: Fujisawa Hironori , Nakashima Seiji , Kaibara Kazuyuki , Shimizu Masaru , Niu Hirohiko
Published: October 2002

In order to distinguish the dependence of electrical properties on thickness
from that on grain size, the crystalline and electrical properties of
epitaxial and polycrystalline Pb(Zr, Ti)O3 (PZT) thin films grown on SrRuO3
(SRO)/SrTiO3(100) and SRO/SiO2/Si by metalorganic chemical vapor deposition
(MOCVD) were investigated. The tetragonality of our epitaxial PZT films
slightly increased with decreasing thickness. Relative dielectric
constant(ε
r) of PZT films decreased with decreasing thickness. The thickness
dependence of ε
r was stronger for polycrystalline PZT thin films than for
epitaxial films. The remanent polarization of both epitaxial and
polycrystalline films was not dependent on thickness. The coercive field of
both epitaxial and polycrystalline films increased markedly as the thickness
decreased. In our experiment, the minimum thickness of epitaxial PZT films
which showed D-E hysteresis was 40 nm.
Microstructure and Electrical Properties of Lead Zirconate Titanate (Pb(Zr52/Ti48)O3) Thick Films Deposited by Aerosol Deposition Method
Authors: Akedo Jun , Lebedev Maxim
Published: October 2002

Lead zirconate titanate (PZT) films with a thickness of more
than 10 µm were prepared by the aerosol deposition
method and their microstructure and chemical composition were
investigated by transmission electron microscopy (TEM) and energy
dispersive X-ray spectra (EDX) analysis. A damage layer was
observed at the interface between PZT and the Si substrate during
the deposition. The microstructure of the as-deposited film at room
temperature consisted of randomly oriented small crystallites with
sizes of less than 40 nm and large crystallites of 100 nm to
300 nm size, which were observed in the primary powder. The
Pb/Ti/Zr ratio along the film stacking direction and around the
grain boundaries was almost the same as that observed inside the
crystallites and the primary powder with a morphotropic phase
boundary composition of (Pb(Zr0.52Ti0.48)O3). The
marked improvement of the electrical properties observed in the
deposited films after annealing was mainly due to the crystal growth
of small crystallites.
Effect of Deposition Temperature and Composition on the Microstructure and Electrical Property of SrBi2Ta2O9 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Nukaga Norimasa , Ishikawa Katsuyuki , Funakubo Hiroshi
Published: October 2002

SrBi2Ta2O9 (SBT) thin films were prepared by conventional thermal metalorganic
chemical vapor deposition (MOCVD) and subsequent heat treatment. The SBT film
deposited at 500°C had a smoother surface and better step coverage than that deposited
at 750°C. The degree of step coverage deposited at 500°C was 0.82. An almost
single phase of SBT was obtained for the film with a Bi/Ta mole ratio of 1.0 by heat
treatment at 750°C for 30 min in O2 atmosphere after MOCVD deposition at 500°C. 2P
r and E
C at an applied electric field of 620 kV/cm were 12.2 µC/cm2 and 87 kV/cm,
respectively, when the film was deposited at 500°C followed by heat treatment at
800°C for 30 min in O2 atmosphere, and its Bi/Ta ratio was 1.2.
Preparation and Characterization of Epitaxial LiNbO3 Thin Films by Metal-Organic Chemical Vapor Deposition
Authors: Shiratsuyu Kosuke , Sakurai Atsushi , Tanaka Katsuhiko , Sakabe Yukio
Published: October 2002

LiNbO3 thin films were prepared on sapphire substrates by the
metal-organic chemical vapor deposition (MOCVD) technique, using
lithium dipivaloylmethanate [Li(DPM)] and niobium pentaethoxide
[Nb(O–C2H5)5] precursors. LiNbO3 films were deposited on (001) and
(012) sapphire substrates and their crystalline structures were
investigated by X-ray diffraction and pole figure analyses. The
LiNbO3 films deposited on (001) sapphire substrates showed strong
(001) orientation involving twin structures, and highly
(100)-oriented films were obtained on the (012) sapphire substrates.
The full width at half maximum (FWHM) of the X-ray rocking curves of
(001)-oriented and (100)-oriented LiNbO3 films were, respectively,
0.16° and 0.21°. Field emission scanning electron
microscope (FE-SEM) analysis showed that highly (100)-oriented
LiNbO3 films had unique morphologies with long and narrow grains.
The grains align in plane on the (012) sapphire substrate, and the
c-axis of the LiNbO3 film is parallel to the short axis of the
grains.
Determination of Pb/(Zr+Ti) and Zr/(Zr+Ti) Ratios of Lead Zirconate Titanate Surface by X-Ray Photoelectron Spectroscopy
Authors: Sugiyama Osamu , Saito Shozo , Kato Kazuaki , Osumi Shuzo , Kaneko Shoji
Published: October 2002

The quantitative analysis of the surface of lead zirconate titanate (PZT) ceramics, the
compositions of which were in the ranges of 0.1<Zr/(Zr+Ti)<0.9 and 0.8<Pb/(Zr+Ti)<1.2, was
conducted using X-ray photoelectron spectroscopy (XPS). The linear relationship between
the corresponding XPS intensities and the atomic ratio Zr/(Zr+Ti) could be obtained as a
calibration equation. Here, the newly derived proportionality factor was introduced for the
cancellation of the systematic errors. The calibration equation for the atomic ratio Pb/(Zr+Ti)
was also obtained in the same way. The 99.9% confidence intervals of the calibration
equations for Zr/(Zr+Ti) and for Pb/(Zr+Ti) were all ±2% and ±3%, respectively, although they
narrowed to ±1% around the compositions of Zr/(Zr+Ti) = 0.5 and Pb/(Zr+Ti) = 1.0. This
analytical method was successfully applied to the follow-up of the compositional change of
the surface of the PZT ceramics through separate acid and heat
treatments.
Effect of Domain Switching and Rotation on Dielectric and Piezoelectric Properties in Lead Zirconate Titanate Ceramics
Authors: Ogawa Toshio , Nakamura Koji
Published: October 2002

Domain switching and rotation in soft lead zirconate titanate
(PZT) ceramics were investigated in comparison with those in hard
PZT ceramics by measuring the poling field dependence of the
dielectric and piezoelectric properties. The minimum dielectric
constant (ε
r) and maximum frequency constant
(f
c
p) were observed at the coercive fields, which
correspond to the poling fields required to obtain the minimum
planar coupling factor. These phenomena were due to the
180° domain clamping at these fields. The fields
of 90° (71° or
109°) domain rotation were estimated using the
relationships between the maximum ε
r and
minimum f
c
p. While minimum ε
r and
maximum f
c
p due to domain clamping were observed in the
compositions of tetragonal and rhombohedral soft PZT ceramics,
domain rotations which caused maximum ε
r and
minimum f
c
p were mainly observed in rhombohedral hard PZT
ceramics. It was thought that the reason why domain rotations which
caused maximum ε
r and minimum f
c
p
were not obtained in soft PZT was the mechanical softness of the
ceramics.
Electrical, Electromechanical and Structural Studies on Solid Solution Ceramic Pb(Fe1/2Nb1/2)O3–Pb(Zn1/3Nb2/3)O3
Authors: Yokosuka Masaru
Published: October 2002

Binary solid solutions of the system xPb(Fe1/2Nb1/2)O3–(1-x)
Pb(Zn1/3Nb2/3)O3 were synthesized by the conventional
ceramic process, where the constituent Pb(Zn1/3Nb2/3)O3 ceramic is not ferroelectric, having a
pyrochlore structure. For highly dense ceramic specimens with varying
compositions, various physical properties were investigated. As a result,
structural conversion from the pyrochlore to the perovskite phase was found
to occur in the range of x>0.1. Properties such as dielectric constant and
remanent polarization also exhibited anomalies corresponding to the
structural change. Maximum electromechanical factors k
P=0.26 and
k
33=0.44, and remanent polarization P
r=11.8 µC/cm2 were obtained for the
composition x=0.4.
Growth of 3-inch Langasite Single Crystal and Its Application to Substrate for Surface Acoustic Wave Filters
Authors: Uda Satoshi , Bungo Akihiro , Jian Chunyun
Published: October 2002

Macro defect-free langasite (La3Ga5SiO14) of 3′′ diameter was grown by the Czochralski technique. Thermal treatment of the melt and a uniform interface shape are important for langasite growth with a clear habit of faceting. The homogeneity in composition was two-dimensionally investigated by X-ray diffraction analysis and SAW (surface acoustic wave) velocity distribution on the wafer fabricated from the crystal. The deviation was sufficiently small for the use of langasite as a suitable substrate in SAW device applications. SAW properties were calculated based on the available material constants.
Energy Trapping Characteristics of Bismuth Layer Structured Compound CaBi4Ti4O15
Authors: Kimura Masahiko , Sawada Takuya , Ando Akira , Sakabe Yukio
Published: October 2002

Piezoelectric characteristics of bismuth layer structured compound CaBi4Ti4O15 ceramics were studied in terms
of the energy trapping phenomenon of the second harmonic thickness extensional (TE2) vibration mode. An
electrode-buried-type resonator was prepared by the co-firing technique to generate the TE2 mode, and frequency-lowering-type energy trapping was realized. Favorable resonant characteristics were obtained for piezoelectric
filter and oscillator applications with narrow frequency tolerances, which require a small electromechanical
coupling coefficient and a high mechanical quality factor. The electromechanical coupling coefficient for the TE2
vibration mode of the resonator was 13.9% and the mechanical quality factor Q
m was 2560. The temperature
coefficient of the resonance frequency was adequate for the applications. The microstructure of CaBi4Ti4O15
ceramic was also investigated. Marked shape anisotropy of the grain was observed; however, preferential grain
orientation was not recognized when the ceramic was prepared by the ordinary firing process.
Small Multilayer Piezoelectric Transformers with High Power Density –Characteristics of Second and Third-Mode Rosen-Type Transformers–
Authors: Sasaki Yasuhiro , Yamamoto Mitsuru , Ochi Atsushi , Inoue Takeshi , Takahashi Sadayuki
Published: October 2002

Low-profile inverter power sources are increasingly required for backlight systems of liquid crystal displays. A great deal of
attention has been focused on the application of miniaturized
piezoelectric transformers to such power sources. In this study,
the output performances of two types of piezoelectric transformers,
one operating in the second-order longitudinal vibration mode with
dimensions of 20 mm×6 mm×
0.9 mm, the other operating in a third-order longitudinal
vibration mode with dimensions of 27 mm×
4.5 mm×0.9 mm, are compared by means of
equivalent circuit analyses and experiments. The values of
efficiency for both reach a maximum when connecting a load
resistance of 50 kΩ to the output terminals. In terms of
output power, the latter, with seven ceramic layers in the driver
section, generates an output power of 3.3 W, which is twice as much
as that of the former with nine ceramic layers. It is concluded
that the difference is caused by mechanical losses which depend on
their vibration levels and multilayer structure and by the variation
of impedance at their output terminals.
Dielectric Property Change of Ferroelectrics and Electronic Structures
Authors: Fujita Masaki , Sekine Rika , Sugihara Sunao
Published: October 2002

Electronic structures were investigated in relation to the relative permittivity of ferroelectrics such
as the ABO3-type and A- and/or B-substituted materials, using a
molecular orbital method. The A-site ions were Ba, Pb, Sr and Ca, and
the B-site ion was Zr. Calculation was performed using the
DV-Xα (discrete variational Xα) method and the overlap
population, which is related to the covalent
bonding nature, was discussed together with the effective charge. As a result, the change from
ferroelectric to paraelectric was found to be associated with the covalency between the A-site ion and Ti
or Zr. Furthermore, the energy for π-bonding between O2p and Ti3d (or Zr4d in AZrO3) shifted
toward the lower energy level by substitution of the A site with Ca to give a lower relative permittivity.
Then, we studied the effect of quantitative changes of the amount (x = 0.25, 0.5, 0.75) of A-site ions in
the (Ba1-x
, Sr
x
)TiO3 system on the electronic structures, and suggested that the bonding nature
between O and Ti is related to the relative permittivity of the system.
Scanning Nonlinear Dielectric Microscopy with Contact Sensing Mechanism for Observation of Nanometer Sized Ferroelectric Domains
Authors: Yasuo Cho Yasuo Cho , Satoshi Kazuta Satoshi Kazuta , Kaori Matsuura Kaori Matsuura
Published: October 2002

A new scanning nonlinear dielectric microscope with very high
resolution for the observation of ferroelectric polarization was developed.
This microscope has a newly developed contact sensing mechanism for
detecting the exact contact point of a probe needle with respect to the
surface of a specimen.
This contact sensing mechanism enables us to use a probe needle with a very
thin pointed end.
Using the new microscope, domains in BaTiO3 single crystal and in
PbTiO3 thin film were observed.
By measuring the c-c domain wall of BaTiO3, the microscope was
confirmed to have nanometer-order resolution.
Low Surface Recombination Velocity on Silicon Wafer Surfaces due to Iodine-Ethanol Treatment
Authors: Kurita Kazunari , Shingyouji Takayuki
Published: October 2002

Negated
Two Kinds of Impurity-related Mark on Thermal Oxides Originating in Octahedral Void Defects
Authors: Itsumi Manabu , Maeda Masahiko , Ohfuji Shin-ichi , Ueki Takemi
Published: October 2002

We have found that thermal oxidation of Czochralski-silicon
substrates produces two kinds of impurity-related mark, both of which
are located on the oxides around an octahedral void defect. We believe
that both marks originate from the octahedral void defect. One mark
is circular and an octahedral void defect is situated in the center of
the mark. The other mark has an anisotropic shape and the octahedral
void defect is not situated in the center of the anisotropic mark.
The signal intensity of the circular mark became weak abruptly with
repeated observations, and, in many cases, the circular mark vanished
after two or three observations. The signal intensity of the
anisotropic mark, on the other hand, gradually became stronger and
then weaker with repeated observations. The thickness of the circular
mark and the anisotropic mark was estimated to be 0.5–1.0 nm and
15 nm, respectively. Analysis revealed that the concentration of
carbon was higher in the marks than in the surrounding region.