bluuebunny/crossref_metadata_2025 huggingface dataset:
Very High Frequency Plasma Enhanced Chemical Vapor Deposition of TiSix/TiN1-xSix Barrier Films
Authors: Mizuno Shigeru , Tagami Manabu , Shinya Hasegawa Shinya Hasegawa , Youichirou Numasawa Youichirou Numasawa
Published: October 2002

Very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) of titaniumsilicide /titaniumnitride barrier films using the silane reduction process with a TiCl4 source is described. VHF plasma, which is denser than a conventional RF plasma, produces a large number of excited species. The silane reduction process, which supplies excited species such as SiH

x

radicals and SiH

x

+ ions as reductants in plasma, promotes dissociation of TiCl4 precursors more than a conventional hydrogen reduction process. Therefore, the VHF-PECVD with the silane reduction process forms high quality titaniumsilicide/titaniumnitride barrier films, which have a low Cl content (<0.2 at.%). In the silane reduction process, the Ti–Si bond is simultaneously formed into the bond structure, resulting in depositing Si-containing films of TiSi

x

or TiN1-
x

Si

x

. The resistivity of TiSi

x

or TiN1-
x

Si

x

is about 100 µ Ω· cm. The surface morphology of TiSi

x

films is very smooth and the structure of TiN1-
x

Si

x

films is amorphous.
Interfacial Abruptness in Si/SiGe Heteroepitaxy Grown by Ultrahigh Vacuum Chemical Vapor Deposition
Authors: Tsai Wen-Chung , Chang Chun-Yen , Jung Tz-Guei , Chang Ting-Chang , Lin Horng-Chih , Chen Liang-Po
Published: October 2002

High-quality Si/Si1-
x

Ge

x

strained-layer superlattices have been grown in the temperature range 525° C–550° C by ultrahigh vacuum chemical vapor deposition. We employed X-ray reflection and high-resolution double-crystal X-ray diffraction measurements to study the dimensional and compositional variations in a Si/Si1-
x

Ge

x

superlattice. From the X-ray reflection results, the interfacial roughness of Si layers on SiGe, and SiGe layers on Si, is 0.1 nm for growth at 525° C and 0.2 nm for growth at 550° C. A simple model for estimating the interfacial abruptness of Si/Si1-
x

Ge

x

heterojunctions is proposed. In this model, a transition region with a linearly graded Ge composition is assumed to exist at both Si/Si1-
x

Ge

x

interfaces. The Ge composition x of a Si/Si1-
x

Ge

x

superlattice is found to increase with the growth time at a constant gas phase composition. This phenomenon can be explained by this model, and the thickness of the transition region and the transition time can be extracted from these fitting results. The transition thicknesses are found to be about 0.3–0.7 nm for growth at 525° C and 1–1.5 nm for growth at 550° C.
Determination of the Tilt Angle of Langmuir Monolayers with Brewster Angle Autocorrelation Spectroscopy and Quantitative Image Analysis in Brewster Angle Microscopy: A Comparison between Two Different Methods
Authors: Carsten Lautz Carsten Lautz , Thomas M. Fischer Thomas M. Fischer
Published: October 2002

We have developed a method to determine the tilt angle of the aliphatic molecule chains of Langmuir monolayers on the water surface by combination of Brewster angle microscopy (BAM) and autocorrelation technique (Brewster angle autocorrelation spectroscopy). In this paper measurements of the surface pressure dependent tilt angle of stearic acid and arachidic acid monolayers on water will be presented. We compare our technique and the results with another previously presented method of quantitative image analysis in BAM. The comparison with X-ray diffraction data show that Brewster angle autocorrelation spectroscopy is an efficient tool for measuring the tilt angle in Langmuir monolayers with high accuracy.
Surface Phonon of MgO Layer on TiC(100) Surface
Authors: Hwang Yeon , Souda Ryutaro , Aizawa Takashi , Hayami Wataru , Otani Shigeki , Ishizawa Yoshio
Published: October 2002

The surface phonon of a hetero-epitaxial MgO layer on a TiC(100) surface has been investigated using high-resolution electron energy loss spectroscopy (HREELS). The Fuchs-Kliewer, Rayleigh and Wallis modes of MgO were detected. The vibration energy of the F-K wave in the MgO layer was higher than that of a MgO single crystal due to the two-dimensional character of the MgO layer. The Rayleigh mode having almost the same dispersion relationship with bulk MgO was measured at the non-zero wave vector. Among the microscopic surface phonons, the Wallis mode ( S2) has been detected, vibrational energy of which was the same as that of bulk.
Prototype Optical Tape Recorder
Authors: L. M. Put Paul , Gerard E. van Rosmalen Gerard E. van Rosmalen , Joost A. H. Kahlman Joost A. H. Kahlman
Published: October 2002

In 1994 a new concept for an optical tape recorder, based on a very fast spinning polygon, was presented. Since then, a prototype tape recorder has been developed on the basis of this technology. In order to reduce the complexity of the system, the optical configuration was redesigned. Also, a new polygon with 10 facets was developed. Finally, the tape transport mechanism was modified in order to further decrease the access time. The result is a smaller recorder consisting of fewer components and having better performance than the original one. Typically, a storage capacity on the order of 50–100 Gbyte is possible in a small cassette. Bit rates are up to 25 Mbit/s. An access time of less than 3 s was realized for 50 Gbytes of storage capacity.
Study of CF4, C2F6, SF6 and NF3 Decomposition Characteristics and Etching Performance in Plasma State
Authors: Koike Kunihiko , Fukuda Tatsuo , Fujikawa Shizuichi , Saeda Manabu
Published: October 2002

The decomposition characteristics and etching performances of CF4, C2F6, SF6 and NF3 in their plasma state were studied for use as self-cleaning gases in plasma-enhanced chemical vapor deposition (PE-CVD) equipment. The study revealed several important characteristics of these gases. The plasma decomposition ratios are in the order of C2F6>NF3≫SF6>CF4. A large amount of CF4 is formed as a result of the decomposition of C2F6. The decomposition ratio of these gases is strongly dependent on the plasma power density, but not appreciably on the temperature in the range of practical use. Moreover, the rate of F decrease of etchant through the plasma chamber appears to strongly correlate with the etch rate.
How Linearly Polarized Is the X-Ray Beam from the X-Ray Generator?
Authors: Sachiko Tanaka Sachiko Tanaka , Hiroshi Tsunemi Hiroshi Tsunemi , Kiyoshi Hayashida Kiyoshi Hayashida
Published: October 2002

We report the measurement result of the degree to which X-rays from a conventional X-ray generator in the energy range up to 60 keV are linearly polarized. The X-ray generator we used in which the accelerated electrons hit the water-cooled metal head is widely used commercially. We measured the degree of linear polarization by employing a Thomson scattering process. We found that the degree of linear polarization depends only on the ratio between the X-ray energy from 20 keV to 60 keV and the applied voltage to the electron. The higher the ratio is, the higher the degree of linear polarization we obtain, whereas the weaker the X-ray intensity is. By selecting an appropriate combination between the applied voltage and the X-ray energy, we confirmed that we would obtain a mono-energetic highly linear polarized X-ray beam with enough intensity for practical use.
Application of Chemical State Mapping Technique with Electron Probe X-Ray Microanalyzer for BiSrCaCuO Superconductor
Authors: Hideyuki Takahashi Hideyuki Takahashi , Toyohiko Okumura Toyohiko Okumura
Published: October 2002

High resolution O–Kα X-ray spectra obtained by electron probe X-ray microanalysis (EPMA) have been found to provide a detailed insight into the crystal structure of specimens. A practical approach for digital color mapping of the crystal structures is proposed, which uses the ratio of the intensities of two specific wavelengths to represent the spectral shape. An application of this approach to digital mapping for a BiSrCaCuO superconductor is presented. The results lead to a more comprehensive understanding of the micro-crystallinity of fine specimens.
Proposal for High-Current Bunched-Beam Acceleration in Electron Linac
Authors: Isamu Uetomi Isamu Uetomi , Koju Ueda Koju Ueda
Published: October 2002

A butterfly ring, in which a high current of a bunched beam is accumulated after a buncher system in an electron linac, is proposed. This beam is extracted from the ring, and can be bunched and accelerated to high energy at a succeeding buncher system and acceleration section. This high-energy beam is applicable as a high-current beam of nanosecond pulse duration.
Stability Control of Composition of RF-Sputtered Pb(Zr, Ti)O3 Ferroelectric Thin Film
Authors: Suu Koukou , Osawa Akira , Yutaka Nishioka Yutaka Nishioka , Noriaki Tani Noriaki Tani
Published: October 2002

The process stability of Pb(Zr, Ti)O3 (PZT) sputtering was
studied by observing film composition change as a function of the
process duration ( e.g. integrating sputtering time). A useful
method of controlling compositional stability was developed. It
was found that the existence of a potentially grounded anode was
effective to prevent the large variation of Pb contents in PZT thin
films and improve the process stability of PZT sputtering.
Effects of Excess Pb and Substrate on Crystallization Processes of Amorphous Pb(Zr, Ti)O3 Thin Films Prepared by RF Magnetron Sputtering
Authors: Yukio Fukuda Yukio Fukuda , Katsuhiro Aoki Katsuhiro Aoki
Published: October 2002

Effects of excess Pb and substrate on the crystallization processes of
amorphous lead-zirconate-titanate (a-PZT) thin films by post-annealing in
oxygen ambient were investigated to lower the crystallization temperature of
the films with a single perovskite phase. A-PZT films were prepared on Ir
and Pt substrates with a 2-nm-thick Ti buffer layer on their surfaces, and on
a SrRuO3 substrate by cosputtering Pb(Zr0.5Ti0.5)O3 and PbO targets.
Analyses by in situ heating X-ray diffraction revealed that the crystallization
processes strongly depend on the amount of excess Pb contained in the as-prepared
a-PZT and substrates. By controlling the rf power supplied to the
PbO target during the deposition, we obtained single perovskite phase PZT
films at 480° C, 520° C and 580° C on SrRuO3, Ir and Pt substrates,
respectively. The crystallized PZT films exhibited excellent ferroelectric
properties. For the 150-nm-thick PZT film, crystallized by rapid thermal
annealing at 600° C for 20 s, we obtained a coercive field of 40 kV/cm (0.6 V),
a remanent polarization density of 15 µ C/cm2 and polarization switching
endurance over 1×109 cycles with Ir top and bottom electrodes.
Synthesis of Ti(DPM)2(OCH3)2 and Evaluation of the TiO2 Films Prepared by Metal-Organic Chemical Vapor Deposition
Authors: Ando Fumio , Shimizu Hisashi , Kobayashi Ichizo , Masaru Okada Masaru Okada
Published: October 2002

Highly pure Ti(DPM)2(OCH3)2 was synthesized by an exchange reaction
of Ti(DPM)2(i-OC3H7)2 with CH3OH. The Ti(DPM)2(OCH3)2 is a
white crystalline material with a melting point of 80.1° C, having a high vapor
pressure the source temperature of 90° C, which enable its stable supply for a
long time. At the film deposition temperatures of PZT and BST (500° C–650° C),
no gas phase nucleation reaction was observed. The order of the performance of
the step coverage for several titanium source materials was
Ti(DPM)2(OCH3)2>Ti(DPM)2(i-OC3H7)2>Ti(DPM)2Cl2>Ti(i-OC3H7)4. In the case
of Ti(DPM)2(OCH3)2, the step coverage for the Si substrate with an aspect
ratio of 1.0 was 80% under the TiO2 film deposition conditions of 650° C and
1 Torr.
Synthesis of BaTiO3 Thin Films Substituted with Hafnium and Zirconium by a Laser Ablation Method Using the Fourth-harmonic Wave of a YAG Laser
Authors: Masuda Yoichiro , Fujita Shigetaka , Baba Akira , Masumoto Hiroshi , Nagata Kunihiro , Hirai Toshio
Published: October 2002

For the first time to our knowledge, BaTi(Hf0.5Zr0.5)O3 (BTHZ) thin films have been
successfully synthesized using a laser ablation technique that employs the fourth
harmonic wave of a pulsed YAG (FHG-YAG) laser. The BTHZ thin film with a
preferred orientation in the c-axis was prepared under an oxygen gas pressure of 3 Pa
at 800° C. Chemical bonds in the BTHZ compounds can easily be broken by
irradiation at an optical energy of 7.47×10-19 J and an optical power density of
300 mJ/cm2. Crystallinity of the deposited films is dominated by the mean free path of
each element.
Properties of Bi 4Ti 3O 12 Thin Films Grown at Low Temperatures
Authors: Masaki Yamaguchi Masaki Yamaguchi , Takao Nagatomo Takao Nagatomo , Osamu Omoto Osamu Omoto
Published: October 2002

Bismuth titanate (Bi4Ti3O12) thin films have been deposited on a (100) silicon substrate with a buffer layer, using a rf planer magnetron sputtering technique.
The buffer layer was formed by the heat treatment of an amorphous layer at 550°C, and exhibits a pyrochlore phase with a smooth surface.
The amorphous layer consists of Bi, Ti and O atoms, which are the elements of the ferroelectric Bi4Ti3O12 thin film.
Ferroelectric Bi4Ti3O12 thin films were deposited on the buffer layer at a low substrate temperature of 500°C.
The Bi4Ti3O12 thin films have a dense and small grain structure.
A D–E hysteresis characteristic has been observed at room temperature.
The apparent remanent polarization and the apparent coercive field of this film at the measurement frequency of 50 Hz were estimated to be 2.4 µC/cm2 and 2.3 kV/cm, respectively.
Control of the Orientation of Ferroelectric Bi 4Ti 3O 12 Thin Films by Multi-step Metal Organic Decomposition Process
Authors: Soichiro Okamura Soichiro Okamura , Yukie Yagi Yukie Yagi , Katsumi Mori Katsumi Mori , Gaku Fujihashi Gaku Fujihashi , Shizutoshi Ando Shizutoshi Ando , Takeyo Tsukamoto Takeyo Tsukamoto
Published: October 2002

We have proposed a multi-step metal organic decomposition (MOD) process for Bi4Ti3O12 thin films in which some layers were formed in stages using precursor solutions including different amounts of Bi constituent. One step of the MOD process consisted of spin-coating at 3000–4000 rpm for 20 s, drying at 110°C for 5 min, calcination at 400°C for 5 min and sintering at 800°C for 30 min. The orientation index along the c-axis of Bi4Ti3O12 thin films was controlled in the range from 0 to 94% by changing the first coating solutions. Bi4Ti3O12 thin films with different orientation indexes were fabricated using precursor solutions including excess Bi atoms in ratios of 10 and 40 mol% and exhibited ferroelectric properties. The polarization values at zero field of the random orientated film and the strongly c-axis oriented one were 1.9 and 2.5 µC/cm2, respectively, when the same voltage was applied.
Preparation of SrBi2Ta2O9 Film at Low Temperatures and Fabrication of a Metal/Ferroelectric/Insulator/Semiconductor Field Effect Transistor Using Al/SrBi2Ta2O9/CeO2/Si(100) Structures
Authors: Hirai Tadahiko , Fujisaki Yoshihide , Nagashima Kazuhito , Hiroshi Koike Hiroshi Koike , Yasuo Tarui Yasuo Tarui
Published: October 2002

We report on the fabrication of an n-channel metal/ferroelectric/insulator/semiconductor
(MFIS)-Field Effect Transistor (FET) using
Al/SrBi2Ta2O9/CeO2/Si(100) structures and its characterization, as well as on the
preparation of SrBi2Ta2O9 ferroelectric films at low temperatures. SrBi2Ta2O9
ferroelectric films fabricated at about 650° C on a Pt/SiO2/Si substrate had a
remanent polarization (P
r) of 7.8 µ C/cm2. The drain current-gate voltage (I
D-V
G)
characteristics of MFIS-FET using the Al/SrBi2Ta2O9/CeO2/Si(100) structure
showed threshold hysteresis due to the ferroelectric properties of the SrBi2Ta2O9
film. Nonvolatile memory operations of the MFIS-FET were demonstrated by
observing its drain current (I
D) which was controlled by previously applied write
voltages.
Fabrication of YMnO3 Thin Films on Si Substrates by a Pulsed Laser Deposition Method
Authors: Yoshimura Takeshi , Fujimura Norifumi , Aoki Nobuaki , Hokayama Kouzo , Tsukui Shigeki , Kawabata Keisuke , Taichiro Ito Taichiro Ito
Published: October 2002

We have proposed ReMnO3 (Re: Rare earth elements) films for metal-ferroelectric-semiconductor
field effect transistor-(MFSFET) type ferroelectric random access memories
(Ferroelectric RAMs). For this kind of application, since ReMnO3 films must be fabricated
directly on Si substrates, this wrote focuses on the fabrication of YMnO3 films on Si substrates
with and without buffer layers. Although only amorphous YMnO3 films are obtained without
buffer layers, crystalline films are obtained using Y–Mn–O buffer layers deposited without
introducing oxygen. YMnO3 films can be epitaxially grown on the top of epitaxial Y2O3 on
(111)Si. For both crystalline YMnO3 films, although hysteresis behavior in D-E measurement is
observed, remanent polarizations are quite small. The role of buffer layers on the thin film
growth of YMnO3 on (111)Si is discussed.
Formation of BaTiO3 from a Barium Titanium Isopropoxide Complex
Authors: Suyama Yoko , Noritake Tatsuo , Nagasawa Mitsuru
Published: October 2002

The mechanism for the formation of BaTiO3 from a single-crystal
barium titanium isopropoxide complex with the presumed composition
BaTi[OCH(CH3)2]6·C6H6 was investigated in this study. When the
alkoxide complex was treated in Ar at 29° C for 2.5 h, 80 wt% of the
organic constituents in the crystal were eliminated as isopropanol,
propene and benzene, thus forming BaTiO3; 95 wt% of the organic
constituents were eliminated in the same manner at a temperature below
100° C. The remaining organic constituents were eliminated as alkyl
benzene at around 460° C in Ar. Crystalline BaTiO3 with ultrafine particles, ranging in size from 5 to 7.5 nm, formed even at room
temperature under these experimental conditions.
Growth of Potassium Lithium Niobate Single-Crystal Fibers by the Laser-Heated Pedestal Growth Method
Authors: Makoto Matsukura Makoto Matsukura , Zhiming Chen Zhiming Chen , Masatoshi Adachi Masatoshi Adachi , Akira Kawabata Akira Kawabata
Published: October 2002

Single crystals of potassium lithium niobate (KLN) are known
as useful materials for electrooptic applications.
KLN single-crystal fibers were grown by the halogen-lamp-assisted
laser-heated pedestal growth (LHPG) method and
both feed and seed ceramic rods consisting of 0.3K2O-0.17Li2O–0.53Nb2O5
were used for the growth. The growth conditions were a growth rate of 11 mm/h,
a laser power of 1.9 W, and a halogen lamp power of 350 W
for improvement of the thermal conditions around the crystallization point.
The fibers obtained were approximately 0.70 mm in diameter.
A transmission X-ray Laue photograph taken along the fiber growth axis
indicated that the fibers were single crystals and their c-axis corresponded
to the growth axis.
Temperature dependence of dielectric constant and tan
δ of fibers was measured.
Curie temperature T
c of 420°C of fibers grown
by the LHPG method corresponded to that of feed rods.
The Effect of MgO and Rare-Earth Oxide on Formation Behavior of Core-Shell Structure in BaTiO3
Authors: Kishi Hiroshi , Okino Yoshikazu , Honda Mutsumi , Iguchi Yoshiaki , Imaeda Motoaki , Takahashi Yoshinao , Ohsato Hitoshi , Okuda Takashi
Published: October 2002

The formation mechanism of the core-shell structure of a BaTiO3(BT)–MgO–Ho2O3-based system was studied.
Mg reacted with BT at low temperatures and showed poor diffusivity compared with Ho. The core-shell structure was considered to be
formed by the suppression of the diffusion of Ho into the core region by Mg. Also, replacement modes of Mg and Ho in perovskite
were investigated. Lattice parameters were determined at temperatures higher than the Curie temperature in order to avoid crystal
structure change. It was confirmed that Mg dissolved in Ti site, and Ho dissolved in both Ba and Ti sites. This indicates that Mg
ions act as acceptors and Ho ions act as both donors and acceptors in the shell phase.
Crystal Orientation of Tetragonal Lead Zirconate Titanate Ceramic Surface and Its Aging Behavior
Authors: Yamada Ayako , Chung Toshio Ogawa
Published: October 2002

A tetragonal lead zirconate titanate (PZT) ceramic surface fabricated by grinding and poling was evaluated by X-ray diffraction.
The crystal orientation in the direction of c axis increased as a result of grinding and poling. It was confirmed that an additional
domain switching occurred on the surfaces of ground and poled ceramics. We believe the surface alignment was due to the stress
during grinding and that the surface layer is easy to orient in the direction of c axis. The annealing effect of the surface
alignment at high temperatures depended on the surface conditions. It was difficult to release the crystal alignment of the ground
surface by grinding, even though the annealing temperature was far beyond the Curie point. After depoling the ceramics by annealing,
the c axis orientation increased with the aging time. Furthermore, the surface alignment increased greatly from an aging time of
15 days. The increase in the surface orientation was affected by the domain structures of the ceramic bulk. Evaluation of ceramic
surfaces is considered to be an effective tool for analyzing the domain structures of PZT thin films.
Hysteresis Curve of X-Ray Diffraction Peak Intensity in Lead Zirconate Titanate Ceramics
Authors: Yasuyoshi Saito Yasuyoshi Saito
Published: October 2002

A new system has been developed for the measurement of motion of
ferroelectric domains under high electric field driving in ferroelectric materials. This
system can simultaneously measure the hysteresis curves of (hkl) X-ray diffraction
peak intensity (I(hkl)), field-induced polarization (D), and switching current (I
current) as
a function of electric field. In a poled tetragonal lead zirconate titanate ceramic, it was
found that the peak of I
current occurs before the abrupt change in X-ray diffraction
intensity of I
002 (=I(002)/{I(002)+I(200)}) in the negative direction of the poling axis,
whereas the peak of I
current in the positive direction of the poling axis occurs at the
same electric field as the abrupt change in the X-ray diffraction intensity of I
002
under ±2000 V/mm triangular-waveform high electric field at a frequency of 1 mHz.
Domain motion is suggested as follows: 180 deg domain walls move before 90 deg
domain walls in the negative direction of the poling axis, and 180 deg domain walls
move together with 90 deg domain walls in the positive direction of the poling axis
near coercive electric fields. This is probably due to the existence of asymmetry of
internal bias electric/stress field. Several discussions are given on the relationships
among the hysteresis curves of X-ray diffraction peak intensity, field-induced strain,
dielectric coefficient, and piezoelectric d
33 coefficient in the tetragonal ceramics.
Preparation and Pyroelectric Properties of Mn-Modified (Pb, La)(Zr, Ti)O3 (PLZT) Ceramics
Authors: Kobune Masafumi , Mineshige Atsushi , Maeda Satoshi Fujii
Published: October 2002

High density lanthanum-modified lead zirconate titanate (PLZT)
ceramics with compositions of { (Pb0.925La0.075)(Zr

y

Ti1-
y

)0.981O3+0.5 mass% MnO2},
where y=0.1–0.9, were prepared by hot
iso-static pressing (HIP). After the relative dielectric constant ε
r at
room temperature increased gradually with increasing Zr content in
the tetragonal region, exhibiting a maximum in the vicinity of the
morphotropic phase boundary (MPB) between tetragonal and
rhombohedral structures, it decreased remarkably in the rhombohedral
region. For 0.2≦y≦0.5, the pyroelectric coefficient P at room
temperature showed relatively large values (≧3.0×10-4 C/m2· K).
The PLZT sample for y=0.2 exhibited the highest figures of merit
(F.M.) for voltage responsivity R
v of approximately 3.0×10-13 C· m/J
and ( F.M.D*) for specific detectivity D
* of approximately
10.5×10-11 C· m/J among the seven samples studied.
Dielectric Properties and Phase Transition of 0.5[( 1-x)PbYb 1/2Nb 1/2O 3–xPbTiO 3]–0.5PbZrO 3 Solid Solution
Authors: Ki Vin Im and Woong Kil Choo Ki Vin Im and Woong Kil Choo
Published: October 2002

The phase diagram of the 0.5[(1-x)PbYb1/2Nb1/2O3–(x)PbTiO3]–0.5PbZrO3 ceramic system has been determined.
A typical relaxor ferroelectric behavior with field dependent
hysteresis loops in 0.5PbYb1/2Nb1/2O3–0.5PbZrO3 (x=0)
was observed. As the PbTiO3[PT] content increases, however, the relaxor
behavior abruptly disappears. The phase at room temperature is a relaxor
between x=0 and 0.1, a pseudocubic ferroelectrics (FE) between x=0.1 and 0.4, a rhombohedral
FE between x=0.5 and 0.9 and a tetragonal FE between x=0.9 to 1.0.
In particular, a morphotropic phase boundary is found to exist between the
rhombohedral and tetragonal FE phases in the vicinity of x=0.9.
Temperature Coefficient Image of Dielectric Material
Authors: Yasuo Cho Yasuo Cho , Teruaki Kasahara Teruaki Kasahara
Published: October 2002

Two dimensional images of the distribution of the relative values of the temperature coefficient of the dielectric constant of a two phase composite ceramic composed of TiO2 and Bi2Ti4O11 are observed using a photothermal dielectric microscope. The images clearly show that each grain of TiO2 has a negative temperature coefficient and each of Bi2Ti4O11 a positive one, and that the macroscopic averaged temperature coefficient of the ceramic is relatively small due to the cancellation of the coefficients with opposite signs.
Dielectric and Piezoelectric Properties of the Solid Solution System Pb(Fe2/3W1/3)O3–PbZrO3
Authors: Masaru Yokosuka Masaru Yokosuka , Hidehiko Kojima Hidehiko Kojima
Published: October 2002

Solid solution ceramics having various ratios between
Pb(Fe2/3W1/3)O3 and PbZrO3 were synthesized by a conventional
solid state reaction. For well sintered specimens, dielectric,
piezoelectric and ferroelectric properties were studied as a
function of composition as well as of temperature. Maximum values
obtained at room temperature are: the remanent polarization
P
r=24.6 µ C/cm2, the electromechanical coupling coefficient k
33=0.32 and the piezoelectric constant d
33=56.0×10-12 C/N. Based on
these experimental results combined with an XRD study, the phase
diagram for the system of Pb(Fe2/3W1/3)O3–PbZrO3 was finally
determined, except for the narrow range near the end member
Pb(Fe2/3W1/3)O3.
Preparation of c-Axis Oriented Pb(Zr, Ti)O3 Thin Films by RF-Magnetron Sputtering and their Dielectric and Piezoelectric Properties
Authors: Fujii Satoru , Kanno Isaku , Takeshi Kamada Takeshi Kamada , Ryoichi Takayama Ryoichi Takayama
Published: October 2002

The c-axis oriented Pb(Zr, Ti)O3 (PZT) thin films, which have a tetragonal
structure and a composition near the morphotropic phase boundary, have been
obtained on (100)MgO substrates with (100)Pt electrodes by rf-magnetron sputtering.
These PZT thin films have a remarkably low relative dielectric constant of 240. The
intrinsic piezoelectric and mechanical properties of the thin films were evaluated. The
velocity of sound and the mechanical compliance s
11
E were measured by the
piezoelectric resonance of the cantilever. The piezoelectric coefficient d
31 was
measured directly from the transverse expansion of the cantilever beams. Even
without a poling treatment, d
31 of the PZT thin films was -100 pC/N and almost the
same as that of bulk ceramics. The extremely large piezoelectric coefficient g
31 of
-57×10-3 Vm/N was also estimated because of the large d
31 and remarkably low
dielectric constant. These PZT thin films are suitable for micro sensor and actuator
applications.
Frequency Characteristics of an Acoustooptic Modulator with Two Interdigital Transducers
Authors: Toda Michio Ohki
Published: October 2002

An acoustooptic (AO) modulator with two interdigital transducers (IDTs) is investigated from the
viewpoint of frequency characteristics of the modulation. The 1st IDT is used for driving an
acoustic wave in a piezoelectric substrate and the 2nd IDT is used for controlling the reflection
and the radiation of the acoustic wave propagating in the substrate. Light intensity modulation
using Raman-Nath diffraction is controlled by changing the electrical terminal condition at the
2nd IDT. The modulation characteristics are found to be periodic functions of the frequency of
acoustic wave, which suggests that the interference of acoustic waves in the substrate influences
the modulation. In the present AO modulator, the interference of fields is utilized effectively and
the electrical terminal condition with regard to not only the amplitude but also the phase can
control the modulation.
TE Harmonic Overtone Mode Energy-Trapped Ceramic Filter with Narrow Frequency Tolerance
Authors: Yamashita Yoshinari , Shigeru Sakano Shigeru Sakano , Isamu Toba Isamu Toba
Published: October 2002

Experimental studies have been made on the suppression of two major spurious
responses, i.e., inharmonic overtones and the 6th thickness-shear-mode harmonic overtone,
to realize a 3rd overtone thickness-extension double-mode bandpass filter using PbTiO3
ceramic substrates. Each leverage was found by investiging of low-symmetry electrode
shapes and implementing the nonpolarized portion of the region between terminal pads on
the piezoelectric substrate. The practical importance of the application of intermediate-frequency
filters (IF filters) used in wireless communication systems depends on how the
narrow frequency tolerance requirement is satisfied. A simple but accurate method of
adjusting the center frequency of these filters is shown here.
Ferroelectric Behavior of Thin Films of Vinylidene Fluoride/Trifluoroethylene/Hexafluoropropylene Copolymer
Authors: Tajitsu Yoshiro , Hirooka Ayumu , Yamagish Akira , Date Munehiro
Published: October 2002

Ferroelectricity in vinylidene fluoride (VDF),
trifluoroethylene (TrFE) and hexafluoropropylene (HFP) copolymers
(P(VDF/TrFE/HFP)) with a low HFP content (lower than 11 mol%) has
been investigated primarily through switching measurements using
P(VDF/TrFE) as a comparison. Switching phenomena as a result of
ultimately 180° rotations of individual molecular chains around their
axes in crystalline regions were observed in P(VDF/TrFE/HFP) with an
HFP content lower than 2.5 mol%. With increasing HFP content in
P(VDF/TrFE/ HFP), the amount of reversed polarization decreases, and
the dielectric permittivity at the Curie point becomes smaller.
However, the switching times have very low dependence on the HFP
content of P(VDF/TrFE/HFP). These results suggest that
noncrystalline regions in P(VDF/TrFE/HFP) are similar to those in
P(VDF/TrFE), and the disorder in crystalline regions of
P(VDF/TrFE/HFP) increases compared to that in crystalline regions of
P(VDF/TrFE).
Optical Response in a Unique Circular Texture of Freely Suspended Ferroelectric Liquid Crystal Films
Authors: Tazoh Eisuke , Sadahito Uto Sadahito Uto , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electro-optic measurements on a freely suspended ferroelectric liquid crystal (FSFLC) film with a small spontaneous polarization have been carried out. The optical response depends on the magnitude of the applied electric field. The response to polarization reversal at intermediate field strength shows an anomaly, in which piled 2π-walls are observed. The electro-optic response in the FSFLC film in which the piled 2π-walls appear has been analyzed on the basis of a switching model with a distribution function for the molecular orientation. This theoretical model describes the essential features of our experimental observations of optical transmission during switching.
On Possibility of the Cubic-Orthorhombic Phase Transition in Perovskite-type Ferroelectrics
Authors: Ishibashi Kazuhiko Fujita
Published: October 2002

The ferroelectric phase transitions in perovskite-type ferroelectrics are
discussed phenomenologically on the basis of a Landau free energy.
Emphasis is placed on the possibility of the first order cubic-orthorhombic
transition, and the conditions required for it to take place are clarified.
Nonlinear Optical Properties of Langasite Crystal
Authors: Komatsu Ryuichi , Tamotsu Sugawara Tamotsu Sugawara , Satoshi Uda Satoshi Uda
Published: October 2002

The parameters in the Sellmeier equation for langasite are accurately obtained on the basis of
the measurement of the ordinary and extraordinary refractive indices in the region of 500 nm to 2500 nm,
and the phase-matching of langasite is investigated. The second harmonic generation
(SHG) of langasite is also examined by the Maker fringe method.
Post-stress Dual-trap Interaction in Hot-carrier Stressed Submicrometer N-channel Metal-Oxide-Semiconductor Field-Effect-Transistors
Authors: Wai Kin Chim Wai Kin Chim , Thiam Joo Chua Thiam Joo Chua
Published: October 2002

The interaction of fast and slow interface traps during the post-stress period after maximum substrate current hot-carrier stress in submicrometer n-channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) is investigated. Slow traps, initially present in the fresh device, are increased after the hot-carrier stress. Fast traps, which are negligible in the fresh device, are also generated by the electrical stress. For post-stress times less than 105 s, the density of the slow traps remains almost constant while there is a small increase in the density of the fast traps. However between post-stress times of 105 to 106 s, there is a noticeable decrease in the density of the slow traps which is correlated with an increase in the density of the fast traps. The capture cross-sections of the slow and fast traps tend to converge for post-stress times greater than 105 s. The results suggest that the slow traps are possibly evolving into fast traps.
Control of the Size and Position of Silicon Nanowires Grown via the Vapor-Liquid-Solid Technique
Authors: Westwater Jonathan , Dharam Pal Gosain Dharam Pal Gosain , Setsuo Usui Setsuo Usui
Published: October 2002

The diameter and position of vapor-liquid-solid (VLS) grown Si nanowires can be controlled by exploiting the difference in Au condensation coefficient on Si and SiO2 surfaces at elevated temperature. For low Au fluxes in the temperature range 520–700° C, Au condensation is completely selective to Si. Holes are etched through the surface oxide layer of a thermally oxidized Si(111) wafer to expose the Si. When Au is then evaporated onto the surface, the Au atoms condense selectively in the holes and form liquid Au/Si alloy balls. If the holes contain a small Si island protrusion formed by etching this acts as an alloy nucleation center and the alloy can agglomerate to form a single ball, the diameter of which is determined by the diameter of the hole and the total dose of Au. When silane gas is then introduced into the chamber as the Si source gas in the VLS reaction each alloy ball grows to form a Si wire of controlled diameter and position.
Effect of Collector-Base Barrier on GaInP/GaAs Double Heterojunction Bipolar Transistor and Further Improvement by Doping-Spike
Authors: Wen-Shiung Lour Wen-Shiung Lour , Wen-Lung Chang Wen-Lung Chang
Published: October 2002

We report the effects of a collector-base barrier on GaInP/GaAs double heterojunction bipolar transistors (DHBT's). A potential barrier exists at the collector-base heterointerface due to a small yet finite conduction band discontinuity. The voltage-dependent barrier that blocks the electrons results in a large collector current saturation voltage (knee voltage). We found, through theoretical calculation, that the potential barrier is much higher and less sensitive to the external bias when the collector doping density is low. If the conduction band discontinuity of ΔE
c=0.2 eV is employed in the calculation, the collector-base voltage used to totally suppress the existing potential barrier varies from 2.5 V for N
C=1×1017 cm-3 to 17 V for N
C=2×1016 cm-3. Further improvement in eliminating the barrier was achieved using the doping spike located at the heterointerface. A zero potential barrier was obtained even if the base collector was forward biased. Experimentally, we have successfully fabricated GaInP/GaAs DHBT's with and without doping spikes at the B–C heterointerface. Large knee voltages are observed in DHBT's without a doping spike. The improved DHBT's exhibit a high current gain of 280 and a small knee voltage smaller than 1.8 V, supporting the very low potential barrier at the B–C junction.
The Instability Characteristics of Amorphous Silicon Thin Film Transistors with Various Interfacial and Bulk Defect States
Authors: Cheng Huang-Chung , Tsai Jun-Wei , Huang Chun-Yao , Luo Fang-Chen , Tuan Hsing-Chien
Published: October 2002

The instability characteristics of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) with various interfacial and bulk defect states were systematically investigated. It was found that, under positive bias stresses, the threshold voltage shifts of a-Si:H TFT's with the same interfacial defect states but with different bulk defect states exhibited similar threshold voltage shift characteristics. In contrast, a-Si:H TFT's with different interfacial defect states but the same bulk defect states showed threshold voltage shifts proportional to the interfacial defect states under positive bias stresses. Furthermore, both the above kinds of a-Si:H TFT under positive bias stresses exhibited that the subthreshold swing shift characteristics closely related to both the interfacial and bulk defect states.
High-Speed Response of Uni-Traveling-Carrier Photodiodes
Authors: Ishibashi Tadao , Kodama Satoshi , Naofumi Shimizu Naofumi Shimizu , Tomofumi Furuta Tomofumi Furuta
Published: October 2002

The photoresponse of a uni-traveling-carrier photodiode (UTC-PD), which is configured with a neutral narrow-gap light absorption layer and a depleted wide-gap carrier collecting layer, is investigated by small-signal analysis. Drift-diffusion model was used for analyzing carrier dynamics in the absorption layer. For accurately predicting the frequency response, a boundary condition at the edge of the absorption layer was carefully treated by taking into account the electron thermionic emission velocity. High electron mobility in the absorption layer and high drift velocity in the carrier collecting layer associated with the velocity overshoot effect are both essential for short response times. Calculations performed on InP/InGaAsP UTC-PDs with the same absorption and carrier collecting layer thicknesses show that the response can be dominated by the electron transport in the absorption layer provided that the significant velocity overshoot occurs in the carrier collecting layer. Furthermore, a UTC-PD with a quasi-field in the absorption layer can generate a several times broader bandwidth than conventional pin PDs, while maintaining a similar internal quantum efficiency.
Surface Corrugation of GaAs Layers Grown on (775)B-Oriented GaAs Substrates by Molecular Beam Epitaxy
Authors: Masanori Yamamoto Masanori Yamamoto , Masataka Higashiwaki Masataka Higashiwaki , Satoshi Shimomura Satoshi Shimomura , Naokatsu Sano Naokatsu Sano , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

Surface morphologies of GaAs layers grown on (775)B-oriented GaAs substrates by molecular beam epitaxy were studied using atomic force microscopy. The surface of a GaAs layer grown on a (775)B GaAs substrate is flat when it is grown at a substrate temperature (T
s) below 580°C, but corrugates regularly for T
s ≥640°C. Similar periodic corrugation of the (775)B GaAs surface formed during thermal annealing at T
s=640°C under As4 atmosphere (10-6 Torr), which is similar in shape to that of a GaAs layer in the early stage of growth (a GaAs layer thinner than 5 nm). As the thickness of a GaAs layer increases from 5 nm, the lateral period and step height of the corrugation increase and tend to saturate for thick GaAs layers (200 nm thick or more). The precise structure of the surface corrugation of a 3-nm-thick GaAs layer (the lateral period of 12 nm and step height of 1.2 nm) was observed as a corrugated AlAs-on-GaAs interface of a GaAs/(GaAs)5(AlAs)5 quantum well structure with an average well width of 3 nm by cross-sectional transmission electron microscopy observation.
Diamond Nucleation on Singlecrystalline 6H-SiC Substrates by Bias-Enhanced Nucleation in Hot Filament Chemical Vapor Deposition
Authors: Xi Li Xi Li , Tatsuru Shirafuji Tatsuru Shirafuji , Yasuaki Hayashi Yasuaki Hayashi , Stanislav Lilov Stanislav Lilov , Shigehiro Nishino Shigehiro Nishino
Published: October 2002

A bias-enhanced nucleation (BEN) technique in hot-filament chemical vapor deposition (HF-CVD) has been applied to singlecrystalline 6H-SiC substrates for diamond nucleation. The oriented diamond film has been grown on a 6H-SiC substrate. The experimental results have shown that the 6H-SiC substrate surfaces are etched by the reactive hydrogen species during the BEN process, and many inclined-pyramid crystals with {01\overline14} type faces are formed on the substrate surface. The array direction of the inclined-pyramid crystals is determined by the diffusion direction of the reactive hydrogen species existing in the plasma sheath and the specific free surface energy of the substrate. Diamonds nucleate on the top of the inclined-pyramid crystals. Diamond nucleation density is higher on the (0001)face than on the (000\overline1)face. The relationship between the inclined-pyramid crystals and the diamond nuclei is investigated using scanning electron microscopy.
Magnetic Properties and Structure of Nd–(Fe, B) Nanocomposite Alloys with Fixed Fe/B Ratios at 4–14
Authors: Fang Jau-Shiung , Hsieh Ming-Fu , Chen Shi-Kun , Tsung-Shune Chin Tsung-Shune Chin
Published: October 2002

Magnetic properties and nanostructure of pseudobinary Nd–(Fe, B) alloys with fixed Fe/B ratios of 4, 6, 8, 10, 14, respectively and Nd=3 to 11  at.%, prepared by melt-spinning and rapid thermal annealing (RTA), were investigated. Magnetic properties were found to depend on nanostructure, particularly the size and size distribution of hard and soft phases, which were in turn determined by Nd contents and Fe/B ratios together with RTA processing. The maximum energy products, (BH)max
, of the optimally RTA treated 11 at.%Nd flakes with Fe/B=10 and 14 are 19 MGOe and 18.8 MGOe, respectively. However, the remanence decreases with increasing Nd contents due to the decreasing amount of Fe nanocrystal. The Fe/B=6 alloys with Nd<6 at.% showed very low intrinsic coercivity (iHc) and (BH)max
, which were attributed mainly to impurity phases, typically Nd2Fe23B3 and Nd1.1Fe4B4. The reversible and irreversible magnetization behaviors were also studied in order to quantify the exchange coupling interaction between hard and soft phases of alloys. The variation in nucleation field at the same Fe/B ratio of 14 was found to depend on volume fraction of hard phase formation as well as the size distribution of the two phases.
Atomic Migration and Debye Temperatures in CuCrxFe2-xO4
Authors: Yun Kon Kim Yun Kon Kim
Published: October 2002

The Mössbauer spectrum and X-ray diffraction of CuCr

x

Fe2-
x

O4 (x=0.1–0.8) have been studied with special emphasis on the atomic distribution and Debye temperature. At room temperature, the crystal structures of CuCr

x

Fe2-
x

O4 are found to be cubic spinel for x=0.2–0.8 and tetragonal for x=0.1. The increasing intensity ratio of the tetrahedral (A) to octahedral (B) patterns at low temperatures, below 250 K, with increasing temperature is explained in terms of the large differences of the Debye temperatures between A- and B-sites, while the decreasing intensity ratio at high temperatures is due to atomic migrations of iron ions from A- to B-sites, which are found to increase drastically with increasing temperature and chromium concentration x. Even at 150 K, atomic migration starts near Cr-concentration x=0.2, and increases with increasing Cr-concentration x to such a degree that about 10% of the Fe3+ ions at the tetrahedral sites migrate to the octahedral sites for x=0.6. While, with increasing temperature, the atomic migration increases drastically to about 50% of the Fe3+ ions at A-sites for x=0.5 at 300 K.
Effect of Stabilizing Fields on Magnetization Process of Magnetoresistive Element
Authors: Hirata Yukinobu , Takashi Komine Takashi Komine , Kazuo Shiiki Kazuo Shiiki
Published: October 2002

Micromagnetic simulation using the Landau-Lifshitz-Gilbert equation is employed to study the magnetization process of a simple magnetoresistive (MR) element stabilized by a magnetic field at edges in the track width direction. The magnetization process of the MR element exhibits irreversible processes due to the presence of closure domains generated by an external field. In the absence of a stabilizing field, there exist two anomalous behaviors in the magnetization process. The closure domain generated at the track edge boundaries makes the magnetization complex and causes hysteresis, while the magnetization state at zero external field is reproducible when the closure domain is generated at the edges of the MR element. The stabilizing field suppresses the generation of closure domains and hysteresis even if closure domains appear at track width boundaries.
Effect of Laser Wavelength on the Generation Efficiency of Stimulated Raman Emission in the Femtosecond Regime
Authors: Keiichi Ogata Keiichi Ogata , Hiroyuki Kawano Hiroyuki Kawano , Yasuyuki Hirakawa Yasuyuki Hirakawa , Totaro Imasaka Totaro Imasaka
Published: October 2002

Rotational Raman lines are generated by stimulated Raman scattering and four-wave Raman mixing using the fundamental (810 nm) and second harmonic emission (405 nm) of a Ti:sapphire laser. The intensity of the Raman emission, measured at the different wavelengths, were compared and confirmed to be more pronounced when a second harmonic emission is used as a pump beam. This is attributed to a larger Raman gain coefficient at shorter wavelengths and better beam quality obtained by the second harmonic generation, as predicted from theory.
Optical Transitions of Interacting Electrons in Coupled Quantum Dots Modulated by an External Electric Field
Authors: Ryuichi Ugajin Ryuichi Ugajin
Published: October 2002

In a pair of quantum dots coupled by tunneling between adjacent quantum dots, several kinds of resonance due to electron-electron interaction produce rich structures in far-infrared absorption spectra. The optical transitions of three interacting electrons in a pair of coupled quantum dots are investigated using the effective mass approximation.
Free Spectral Range Variation of a Broadband, High-Finesse, Multi-Channel Fabry-Perot Filter using Chirped Fiber Bragg Gratings
Authors: Cho Sung-Hak , Isao Yokota Isao Yokota , Minoru Obara Minoru Obara
Published: October 2002

The free spectral range (FSR) variation of a broadband, high finesse, multi-channel Fabry-Perot (FP) filter using linearly chirped fiber gratings has been studied theoretically. It is found that the FSR variation of the FP filter using linearly chirped fiber gratings was determined by the relationship between the distance between two fiber gratings and the total transmitted phase change. The variation of the FSR of a FP filter using linearly chirped fiber gratings was explained by the equation obtained in this study. This simulation dealt with three types of FP filters using linearly chirped fiber gratings of different grating lengths for 1.3 µ m single mode fibers. These were 4.47 mm, 6.67 mm and 7.50 mm in grating length, which are easily obtainable using recent inscription technologies. The different behaviors of the spectral response of FP filters using fiber gratings and bulk FP etalon were also established.
Determination of Anomalous Scattering Factor by Using Transmitted Rocking Curves near the Absorption Edge
Authors: Shengming Zhou Shengming Zhou , Masami Yoshizawa Masami Yoshizawa , Tomoe Fukamachi Tomoe Fukamachi , Riichiro Negishi Riichiro Negishi , Takaaki Kawamura Takaaki Kawamura , Tetsuo Nakajima Tetsuo Nakajima , Zongyan Zhao Zongyan Zhao
Published: October 2002

The rocking curves of transmitted and diffracted beams for GaAs 200 reflection in the symmetric Laue case were measured near the Ga K-absorption edge, using X-rays from synchrotron radiation. The changes in the transmitted rocking curves become conspicuous as compared with those of the diffracted curves near the edge, which is used for determining anomalous scattering factors of Ga by a profile fitting method.