bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Buffer Layers and Barrier Metals on Properties of (Ba, Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition
Authors: Kawahara Takaaki , Yamamuka Mikio , Tanimura Junji , Tarutani Masayoshi , Kuroiwa Takeharu , Tsuyoshi Horikawa Tsuyoshi Horikawa , Kouichi Ono Kouichi Ono
Published: October 2002

The characteristics, especially the electrical properties, of (Ba, Sr)TiO3 [BST]
films obtained by a two-step process of liquid source chemical vapor deposition (CVD)
on two types of substrates or Ru/Si and Ru/TiN/Ti/Si structures have been
investigated. First, the studies on the best deposition conditions for BST buffer layers
on Ru/Si substrates indicated that more crystallized buffer layers improved the
electrical properties of the two-step-deposited BST films. The reproducibility of the
measured thicknesses was 1.5% (1σ) and that for t
eq-values of equivalent SiO2
thicknesses was 5.4% (1σ) for seven consecutive two-step runs on Ru/Si substrates.
Moreover, the insertion of the barrier metals TiN/Ti between Ru and Si, which was
stable enough for back-end processing at high temperatures, increased the degree of
some crystal orientations of BST and Ru films; however, it hardly changed the
electrical properties of the BST films deposited in two-steps.
Residual Strain and Crystal Structure of BaTiO3–SrTiO3 Thin Films Prepared by Metal Organic Chemical Vapor Deposition
Authors: Funakubo Hiroshi , Nagano Daisuke , Saiki Atsushi , Inagaki Yoshiaki , Shinozaki Kazuo , Nobuyasu Mizutani Nobuyasu Mizutani
Published: October 2002

The lattice parameters of BaTiO3–SrTiO3 films prepared by chemcal vapor
deposition (CVD) were investigated. When the film thickness was 1500 nm, the
lattice parameters were mainly determined by the thermal stress due to the thermal
expansion difference between the film and the substrate. The lattice parameters of
epitaxially grown SrTiO3 films on (100)MgO substrates increased with decreasing
film thickness, while those of polycrystalline films were independent of the film
thickness down to 300 nm. They also increased with the Ti/(Sr+Ti) ratio for
epitaxially grown 500-nm-thick films, while those of polycrystalline films were
independent of Ti/(Sr+Ti) ratio. Large lattice parameters were also observed for
the epitaxially grown (Ba0.5Sr0.5)TiO3 film on a (100)MgO substrate but were not
observed for the epitaxially grown BaTiO3 film on (100)MgO substrate. These
occurrences were closely related to the epitaxial growth of the film.
Fatigue Characteristics of SrBi2Ta2O9 Thin Films by RF Magnetron Sputtering Method
Authors: Noboru Ichinose Noboru Ichinose , Masaru Watanabe Masaru Watanabe
Published: October 2002

Ferroelectric SrBi2Ta2O9 thin films were synthesized on various substrates, such
as MgO(100), glass, Pd/MgO(100) and Pd/glass by the rf magnetron sputtering
method. Single-phase thin films were prepared on these substrates using a target
with the starting chemical composition of SrCO3:Bi2O3:Ta2O5=0.7:1.2:1. At the
higher substrate temperature of 1073 K, (h 0 l) orientation was found. The
hysteresis loop of the thin film on Pd(100)/MgO(100) substrate did not change up to
109 switching cycles. These properties are very attractive for nonvolatile memory
application.
Key Technologies to Realize Magneto-Optical Storage of Over 7 Gbytes in CD-Sized Disk
Authors: Torazawa Kenji , Sumi Satoshi , Yonezawa Seiji , Suzuki Naomi , Tanaka Yasuhito , Takahashi Akira , Murakami Yoshiteru , Ohta Norio
Published: October 2002

Many types of recording technologies have been reported for future magneto-optical (MO) storage. However, they have not been well discussed from the viewpoint of total recording technology including the recording and readout methods, the pick-up technology and the signal processing technology. We propose key technologies for realizing MO storage of over 7 Gbytes in a CD-sized disk using a red laser, and describe the analytical and experimental results pertaining to each key technology.
Growth of BaTiO 3:Ce Single Crystals and Their Properties
Authors: Zhiming Chen Zhiming Chen , Masatoshi Adachi Masatoshi Adachi , Tadashi Shiosaki Tadashi Shiosaki , Akira Kawabata Akira Kawabata
Published: October 2002

BaTiO3 and BaTiO3:Ce single crystals were grown by the top-seeded solution
growth (TSSG) technique. Instead of mechanical poling, a thermal treatment
was developed to reduce the 90° domains in this work. After the thermal
treatment, the single crystals could be poled to the single-domain state under
an electrical field of 1 kV/cm near its Curie temperature for 3 h. Lightly doped
BaTiO3:Ce is light brown and its optical absorption increased with
increasing Ce content. Electrooptic coefficients r
T
13 and r
T
42
were measured. A heavily doped BaTiO3:Ce appeared dark and opaque in
visible light. Specific resistance ρ of the heavily doped crystal in
the <100 > direction at room temperature was about 80 Ω·m,
and a resonance change was observed at 120°C, which corresponds to the
Curie temperature. This crystal showed both ferroelectric and semiconductive properties.
The concentration of Ce in the crystal was found to be 2.6 times that in the melt.
Characteristics of TiN Films Sputtered under Optimized Conditions of Metallic Mode Deposition
Authors: Inoue Hirofumi Sumi , Taguchi Mitsuru , Sugano Yukiyasu , Masuya Haruko , Ito Naohiko , Kishida Satoru , Tokutaka Heizo
Published: October 2002

We prepared TiN films by metallic or nitride mode sputtering using a collimator, and investigated the characteristics of the films. Resistivity, density, thermal stress, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) measurements and transmission electron microscope (TEM) observation were carried out. The characteristics of the TiN films depended on the N2/Ar flow ratio. TiN deposition rates in the metallic mode with N2/Ar flow ratios from 0.2 to 0.5 were 3 times higher than those in the conventional nitride mode with N2/Ar ratios from 0.75 to 1.0. By depositing the film under the best metallic mode conditions with N2/Ar=0.5, the TiN film with a minimum resistivity and a maximum film density was formed. The TiN films, which were prepared under optimized conditions of metallic mode deposition, had a small concentration of oxide in the TiN, strong (111)-preferred orientation and good crystallinity.
90° Domain Reorientation and Electric-Field-Induced Strain of Tetragonal Lead Zirconate Titanate Ceramics
Authors: Tsurumi Takaaki , Kumano Yutaka , Ohashi Naoki , Takenaka Tadashi , Osamu Fukunaga Osamu Fukunaga
Published: October 2002

The effect of the reorientation of 90° domains on the electric-field-induced strains
was studied for tetragonal lead zirconate titanate (PZT) ceramics. An in situ X-ray diffraction (XRD) method
was used to evaluate the 90° domain reorientation under electric fields. The strains
caused by the reorientation were calculated and compared with the electric-field-induced
longitudinal strains measured with a laser displacement meter and the strains expected
from piezoelectric d-constants. It was experimentally confirmed that the electric-field-induced
strains of PZT ceramics were composed of strains due to the piezoelectric effect
and the 90° reorientation. After poling treatment, a small portion of the 90° domains
relaxed and reoriented, giving rise to a reversible reorientation of the 90° domains by
the electric field. These reversible reorientations contributed to the electric-field-induced
strains. In “soft” PZT ceramics, the degrees of 90° reorientation caused by poling and by
the subsequent application of an electric field had a close correlation with the
tetragonality of the crystal lattice rather than with the coercive field.
Electrical and Mechanical Characteristics of PbnBi4Tin+3O3n+12 Ceramics
Authors: Shoji Kazuo , Sakai Tomoharu , Sakata Yasuo Uehara
Published: October 2002

The electrical and mechanical characteristics of Pb

n

Bi4Ti

n
+3O3
n
+12
ceramics were examined. With increasing n, the dielectric constant ε
s
increased, and the temperature dependence of ε
s broadened. ε
s, at room
temperature, reached a value of approximately 750 at n=3 and n=4 at 100 kHz. The dielectric breakdown strength E
b and the three-point bending
strength σ decreased with increasing n. For example, σ of the sample at
n=4 was approximately a 70% value of the sample at n=0. On the other hand,
the examination of the characteristics of grain-oriented samples
clarified that E
b and σ can be improved in the direction perpendicular to
the polarization axis.
Ferroelectric Properties in Piezoelectric Semiconductor Zn 1-xMxO (M=Li, Mg)
Authors: Akira Onodera Akira Onodera , Norihiko Tamaki Norihiko Tamaki , Kazuo Jin Kazuo Jin , Haruyasu Yamashita Haruyasu Yamashita
Published: October 2002

Ferroelectric properties and the effect of Li+ and Mg2+
dopants in II–VI semiconductor ZnO were studied.
The ferroelectric D–E
loops were observed in Zn1-x
(Li0.02·Mg
x-0.02)O,
as well as in Zn1-x
LixO.
The transition temperature (T
c) increases in proportion to the
concentration of Mg2+ ions, while it is almost constant (330 K)
in Zn1-x
LixO above x > 0.1. T
c was 260 K for
Zn0.9(Li0.02Mg0.08)O and 360 K for
Zn0.7(Li0.02Mg0.28)O.
An additional 20% of Mg increases T
c by 100 K.
The ferroelectric phase transition is strongly influenced by
the introduction of small Li and Mg atoms instead of the host Zn atoms
in wurtzite ZnO.
Microwave Dielectric Properties of Ba 6- 3xSm 8+ 2xTi 18O 54 Solid Solutions with Sr Substituted for Ba
Authors: Motoaki Imaeda Motoaki Imaeda , Kiichiro Ito Kiichiro Ito , Makoto Mizuta Makoto Mizuta , Hitoshi Ohsato Hitoshi Ohsato , Susumu Nishigaki Susumu Nishigaki , Takashi Okuda Takashi Okuda
Published: October 2002

We have evaluated the effect of substituting Sr cations for Ba cations in solid solutions with a tungsten bronze-type structure used in microwave dielectric resonators.
Instead of
Ba6-3x
Sm8+2x
Ti18O54
solid solutions formula, the structure formula is presented as
(Sm8+2x
Ba2-3x
)(Ba4)Ti18O54
for the range of 0≤x≤2/3
and
(Sm9.33+2(x-2/3))(Ba4-3(x-2/3))Ti18O54
for
2/3 ≤x ≤1.
The quality factor Q \cdotpf has been improved based on the substitution of 0.2 Sr ions for 0.2 Ba ions in perovskite blocks in
(Sm9.2Ba0.2)(Ba4)Ti18O54
where x=0.6.
This composition has the best dielectric quality in the solid solution series,
because the substitution reduced the strain caused by the Ba ions.
The relationship between the lattice parameters and the microwave dielectric properties is also presented.
Effect of Y-Doping on Resistance Degradation of Multilayer Ceramic Capacitors with Ni Electrodes under the Highly Accelerated Life Test
Authors: Sato Shigeki , Nakano Yukie , Akira Sato Akira Sato , Takeshi Nomura Takeshi Nomura
Published: October 2002

The effect of Y-doping on the degradation behavior of insulation resistance for
multilayer ceramic capacitors with Ni electrodes has been studied using electrical
measurement techniques such as admittance spectroscopy, thermally stimulated current
(TSC), and electrical conductivity measurements. TSC measurements show that a strong
internal bias field remained after applying an electrical field at a high temperature, like during
highly accelerated life testing. This internal bias field originated from the migration of
positive carriers. Admittance spectroscopy indicated three types of relaxation, with activation
energies of 0.4, 0.8, and 0.8–1.0 eV. The intensity of the 0.4 eV relaxation peak increased
with Y3+ doping and disappeared at low oxygen partial pressure ( P
O2) annealing. The
existence of holes was also observed from the temperature dependence of insulation
resistance. The 0.4 eV relaxation is considered to be due to the transition of electrons from
the valence band to barium vacancy states. These results suggest that Y3+ acts as a donor and
creates barium vacancies, which compensate for the oxygen vacancies and thereby improve
the resistance to degradation.
Oxygen Gas Sensing Properties of Metal/Nb:SrTiO 3 Mechanical Contact
Authors: Jianxin Sheng Jianxin Sheng , Junichi Karasawa Junichi Karasawa , Tatsuo Fukami Tatsuo Fukami
Published: October 2002

An anomalous surface-barrier property of platinum on single-crystal Nb:SrTiO3 was investigated. The metal-semiconductor mechanical contact shows a
normal rectifying current-voltage characteristic in air, but a nonrectifying feature
in vacuum due to the adsorption/desorption of oxygen gas at the contact interface.
Considering that the depletion layer in a heavily doped semiconductor is usually very thin,
we tried to interpret this phenomenon from the viewpoint of the tunnelling effect on a Schottky barrier model with the adsorbed oxygen gas taken into account.
The experimental result that the depletion layer thickness decreased as oxygen gas was
gradually desorbed supports the proposed barrier model.
This type of diode seems promising for use in a device for
detecting oxygen gas at low temperatures.
Improved Growth of Large Lead Zinc Niobate Titanate Piezoelectric Single Crystals for Medical Ultrasonic Transducers
Authors: Kobayashi Tsuyoshi , Shimanuki Senji , Shiroh Saitoh Shiroh Saitoh , Yohachi Yamashita Yohachi Yamashita
Published: October 2002

Large piezoelectric single crystals of the Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZN-PT) binary
system have been successfully obtained using a conventional flux method and a suitable ratio
of PZN-PT: PbO flux. The largest crystal had dimensions of 43×42×40 mm and weighed
415 g. In order to improve growth behavior and reduce the number of nuclei, the
temperature gradient program of the crucible was optimized; that is, the bottom of the
crucible was made cooler (>50° C) than the top during cooling. A charged composition of
45 mol% PZN-PT and 55 mol% PbO showed good growth results. A large bar-mode
electromechanical coupling factor, k
33', (84%) for phased array ultrasonic transducers was
obtained. This confirms that large PZN-PT single crystals for phased-array ultrasonic
transducers can be grown using a flux method.
Anomalous Temperature Dependence of Positron Trapping due to Divacancies in Si
Authors: Atsuo Kawasuso Atsuo Kawasuso , Sohei Okada Sohei Okada
Published: October 2002

The temperature dependence of positron lifetime and trapping rate due to electrically neutral divacancies in Si has been determined for temperatures from 5.5 K to 210 K. The charge state of divacancies was verified through the Hall effect, electron spin resonance and infrared absorption measurements. The positron lifetime at neutral divacancies was 280 ps at low temperatures and increased to 295 ps at around 30 K. This is explained in terms of the lattice relaxation effect accompanying the positron trapping. The positron trapping rate due to neutral divacancies was found to increase upon cooling, to decrease after reaching a maximum at around 30 K and to increase again below 10 K. The observed temperature dependences of the trapping rate could not be explained by existing models. The temperature dependence was found to be reproduced by the Breit-Wigner formula for resonance phenomena. Possible reasons were discussed.
Effects of Aspect Ratio of Lead Zirconate Titanate on 1-3 Piezoelectric Composite Properties
Authors: Hirata Yoshihiro , Toshiyuki Numazawa Toshiyuki Numazawa , Hiroshi Takada Hiroshi Takada
Published: October 2002

An array of lead zirconate titanate (PZT) rods whose cross section is 25 µ m square was
fabricated using synchrotron radiation (SR) lithography, and the effects of the aspect ratio
(height/width) of the PZT rod on 1-3 piezoelectric composite properties were studied. The
aspect ratio was between 3 and 9. Mechanical quality factor and acoustic impedance were found
to depend weakly on the aspect ratio. However, electromechanical coupling coefficients were
found to increase as the aspect ratio increased. Based on the result of deformation simulation
by the finite element method (FEM), this dependence was found to be caused by the increase in
piezoelectric coefficients as the aspect ratio increased.
Phase Boundaries between Chiral Smectic Cα, Cβ and C Phases in an Antiferroelectric Liquid Crystal, MHPOBC
Authors: Hiroyuki Uehara Hiroyuki Uehara , Yoshinori Iino Yoshinori Iino , Jun Hatano Jun Hatano
Published: October 2002

The complex dielectric constant ε
* of 4-(1-methylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC) was measured as a function of temperature, optical purity and DC electric field, and switching current behavior was observed as a function of temperature and optical purity. A two-step change in the real part of complex dielectric constant ε
′ with DC electric field and several peaks in switching current were observed in high optical purity samples, but not in low optical purity ones. The phase diagram of temperature versus optical purity was obtained from the results.
The disappearance of the two-step decrease in ε
′ under DC electric field and the disappearance of the SmCα
* phase were observed at the same optical purity. It is suggested that antiferroelectric liquid crystals are classified into two types of phase sequence: (a) –SmCβ
*–SmCα
*–SmA–Iso. and (b) –SmC*–SmA–Iso.
Suppression of Parasitic Bipolar Action and Improvement of Hot-Carrier Reliability in Fully-Depleted Metal-Oxide-Semiconductor Field Effect Transistors on SIMOX (Separation by IMplanted Oxygen) Introducing Recombination Centers near Source Junction
Authors: Tsuchiya Toshiaki , Ohno Terukazu , Satoshi Tazawa Satoshi Tazawa , Masaaki Tomizawa Masaaki Tomizawa
Published: October 2002

Fully-depleted metal-oxide-semiconductor field effect transistors (MOSFETs) fabricated on a SIMOX (Separation by IMplanted Oxygen) wafer are very promising devices for next-generation low-power high-speed LSIs. However, it is essential to suppress parasitic bipolar action in order to improve source-drain breakdown voltage for practical use in LSIs except for extremely low-voltage-operated applications of less than around 1 V. In this paper, a new suppression method of parasitic bipolar action is proposed, which uses recombination centers near the source junction. Using a two-dimensional (2-D) device simulator, the effects of recombination centers are analyzed, and an effective and stable position for the region containing recombination centers is clarified. Moreover, the effectiveness of the new method is experimentally verified using Ar ion-implantation into the source/drain regions, to introduce the recombination centers. The new method is also remarkably effective in improving hot-carrier reliability, because a hot-carrier degradation mode peculiar to MOSFETs/SOI is able to be suppressed by it.
Modification of Heat and Mass Transfers and Their Effect on the Crystal-Melt Interface Shape of Si Single Crystal during Czochralski Crystal Growth
Authors: Watanabe Masahito , Kakimoto Koichi , Minoru Eguchi Minoru Eguchi , Taketoshi Hibiya Taketoshi Hibiya
Published: October 2002

The modification of heat transfer in molten silicon during Czochralski (CZ) crystal growth is discussed by focusing on the transition of the flow mode from axisymmetric to nonaxisymmetric, in order to clarify the mechanism of crystal-melt interface shape deformation. Heat transfer in silicon melt is observed by measuring the difference in temperature near the crucible wall and at the crystal-melt interface with simultaneous observation of molten silicon flow. We confirm that the heat transfer coefficient of silicon melt is reduced when the flow mode is changed from axisymmetric to non-axisymmetric. The crystal-melt interface shape changed as a result of the modified heat transfer, which is due to the flow mode transition from axisymmetric to non-axisymmetric.
A New Method for Transmission Electron Microscope Observation of Grown-in Defects in As-Grown Czochralski Silicon (111) Crystals
Authors: Yanase Yoshio , Ono Toshiaki , Kitamura Takafumi , Horie Hiroshi , Ochiai Takashi , Setsuo Okamoto Setsuo Okamoto , Hideki Tsuya Hideki Tsuya
Published: October 2002

A new technique for transmission electron microscope (TEM) observation of grown-in defects has been developed. The grown-in defects beneath the surface, at the “origin of crystal originated particles (COPs)”, are detected using a laser particle counter combined with an atomic force microscope (AFM). Subsequently, the position of the “origin of COP” using the above mentioned detection method is marked at the surface by applying the anodization technique using an AFM, and the TEM samples are prepared using this marking. Through this technique, we have succeeded in observing the “origin of COPs” using a TEM. It has been clarified that the “origin of COPs” are imperfect octahedron voids with thin oxide walls with no strain around them. These results have indicated that the “origin of COPs” are equivalent to the “laser scattering tomography defects (LSTDs)”.
Two-Terminal Monolithic In0.5Ga0.5P/GaAs Tandem Solar Cells with a High Conversion Efficiency of Over 30%
Authors: Takamoto Tatsuya , Ikeda Eiji , Kurita Hiroshi , Ohmori Masamichi , Yamaguchi Masafumi , Yang Ming-Ju
Published: October 2002

A world-record efficiency of 30.28% has been attained for two-terminal monolithic In0.5Ga0.5P/GaAs tandem solar cells under one-sun air-mass 1.5 global illumination. The cell area has a practical size of 4 cm2. At first, high efficiency In0.5Ga0.5P single junction cells had been developed by improving the minority carrier lifetime. Second, the GaAs single junction cells had been investigated to obtain higher open-circuit voltage. Third, the tandem cell performance had been improved by using an InGaP tunnel junction with AlInP barriers which constitute a double-hetero structure and increase the peak current of the tunnel junction. In addition, the AlInP barrier located beneath the InGaP top cell have been found to be effective for reflecting minority carriers in the top cell and for suppressing the diffusion of zinc from the highly doped tunnel junction toward the top cell during epitaxial growth.
Post Hydrogen Treatment Effects of Boron-doped a-SiC:H p-Layer of a-Si:H Solar Cell Using a Mercury-Sensitized Photo-Chemical Vapor Deposition Method
Authors: Jae Hoon Jang Jae Hoon Jang , Koeng Su Lim Koeng Su Lim
Published: October 2002

Post hydrogen treatment effects of boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) film used as a p-layer of p/i/n type amorphous silicon based solar cells using a mercury-sensitized photochemical vapor deposition method were investigated by measuring the thickness, electrical, and optical properties of the film before and after hydrogen treatment. It was found that the boron-doped a-SiC:H film was simultaneously etched and passivated by the treatment. The performance of the cell with a hydrogen treated p-layer was improved by ∼7% due to an increase in open circuit voltage (V
oc) and fill factor (F.F.), compared to that of the untreated cell, although the p-layer thickness was nearly identical in both cases. The increase in V
oc and F.F. could be explained by an increase in the built-in potential due to a decrease in the film activation energy. This electrical property improvement was well explained by the passivation effect of a SiH2/SiH ratio decrease of the film calculated by FTIR spectra. These film changes by post hydrogen treatment are considered to occur in the bulk of the boron-doped a-SiC:H film.
Optical Constants of ZnO
Authors: Hisashi Yoshikawa Hisashi Yoshikawa , Sadao Adachi Sadao Adachi
Published: October 2002

The complex dielectric functions, ε(E)=ε
1(E)+ iε
2(E), of ZnO have been measured by spectroscopic ellipsometry (SE) in the photon-energy range between 1.5 and 5.0 eV at room temperature. The SE measurements are carried out on the surface parallel to the optic axis c, which allows the determination of the optical constants for light polarized perpendicular (E⊥c) and parallel to the c -axis (E//c). The measured SE spectra show the exciton peaks at ∼3.4 eV (E
0 edge). These ε(E) spectra are analyzed on the basis of a simplified model of the interband transitions. Excellent agreement is achieved between the calculated and experimental results over the entire range of photon energies. Dielectric-function-related optical constants, such as the complex refractive index n
*(E)=n(E)+ ik(E), absorption coefficient α(E) and normal-incidence reflectivity R(E), of ZnO have also been reported.
Theory of Semiconductor Superjunction Devices
Authors: Fujihira Tatsuhiko
Published: October 2002

A new theory of semiconductor devices, called “semiconductor superjunction (SJ) theory”, is presented. To overcome the trade-off relationship between breakdown voltage and on-resistance of conventional semiconductor devices, SJ devices utilize a number of alternately stacked, p- and n-type, heavily doped, thin semiconductor layers. By controlling the degree of doping and the thickness of these layers, according to the SJ theory, this structure operates as a pn junction with low on-resistance and high breakdown voltage. Analytical formulas for the ideal specific on-resistance and the ideal breakdown voltage of SJ devices are theoretically derived. Analysis based on the formulas and device simulations reveals that the on-resistance of SJ devices can be reduced to less than 10-2 that of conventional devices.
The Gas Combustion of H2 with N2O Used for Rapid Thermal Annealing
Authors: Takashima Toshiyuki Sameshima , Akimitsu Tajima Akimitsu Tajima , Toshio Mohri Toshio Mohri
Published: October 2002

The gas combustion of H2 with N2O was investigated to develop a rapid thermal annealing method. Spectra of the light emission caused by the combustion show a gray body irradiation characteristic with a gas temperature of 2200 K with an initial total gas pressure of 500 Torr ([H2]/[N2O]=1). A transient thermometry with a 100-nm-thick Cr film as a temperature sensor formed on a quartz substrate was used to measure temperature changes at the surface during and after combustion. Heating to 800°C was achieved within 2 ms using a substrate preheated to 300°C. The increase of electrical conductivity was achieved from 4×10-7 S/cm to 7×10-4 S/cm by the combustion for 0.5% phosphorus-doped amorphous silicon films.
Improved Circuit Design of Multipeak Current–Voltage Characteristics Based on Resonant Tunneling Diodes
Authors: Gan Kwang-Jow , Su Yan-Kuin
Published: October 2002

Improved multipeak circuits with two or three special resonant tunneling diodes (RTDs) connected in series are analyzed and discussed. There are four to seven peaks in the combined current–voltage ( I–V ) characteristics with three series-connected RTDs under different conditions. These phenomena occur only when these diodes satisfy certain constraint conditions between their electrical parameters. We will investigate and derive these constraint conditions. Using these constraint conditions, improved multipeak I–V characteristics can be obtained, and will greatly reduce circuit material in comparison with the traditional structure that stacks identical RTDs on top of each other. Also, equations are derived to simulate the combined I–V characteristics to compensate the lack of RTD model in the SPICE program.
Time-Resolved Photoluminescence Study on a Hetero Interface Formed by Direct Regrowth of GaAs on an Al0.3Ga0.7As Surface Prepared by an In Situ HCl Gas Etching Process
Authors: Kizuki Hirotaka , Miyashita Motoharu , Yasutomo Kajikawa Yasutomo Kajikawa , Yutaka Mihashi Yutaka Mihashi
Published: October 2002

We have studied the quality of Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As double hetero (DH) structures, whose lower hetero interface is formed by regrowing GaAs directly on an etched Al0.3Ga0.7As surface. The Al0.3Ga0.7As surface is prepared by two-step in situ etching, which is comprised of a low temperature treatment and high temperature etching with HCl gas, just prior to the regrowth by metalorganic chemical vapor deposition. Time resolved photoluminescence measurements have revealed that the optical quality of the regrown DH structure is significantly improved by applying the two-step HCl gas etching process compared to the wet processed one. The PL decay curve of the in situ processed sample, however, shows a relatively shorter carrier lifetime than that of the continuously grown DH sample. An interface recombination velocity of 6.8×103 cm/s is obtained for the in situ processed AlGaAs interface. This value for the AlGaAs with a high Al content is comparable to the best results for the in situ processed GaAs and InGaAs surfaces reported so far. The relatively high recombination velocity compared to continuously grown interfaces is mainly due to residual oxygen at the in situ processed interface of concentrations as low as 2.2×1011 cm-2.
Carbon Diffusion Behavior in a GaAs Tunnel Junction with a Heavily Carbon Doped p+-Layer by Metalorganic Molecular Beam Epitaxy
Authors: Oh Je-Hwan , Nobuhiro Hayakawa Nobuhiro Hayakawa , Makoto Konagai Makoto Konagai
Published: October 2002

The diffusion behavior of a carbon-acceptor impurity in a p+-n+ GaAs tunnel junction with a heavily carbon doped p+-layer was investigated in detail. The diffusion coefficients of carbon were deduced from the degradation rates of the peak current density of the GaAs tunnel diodes. The current-induced diffusion coefficient of carbon under forward bias operations at 2 kA/cm2 was given by D
C,current\sevsize-induced=D
0exp
(-E
a/k
T), where D
0=1.5×10-13 cm2/ s and E
a=0.47±0.01 eV. In addition, the thermal diffusion coefficient was given by D
C,thermal=D
0exp
(-E
a/k
T), where D
0=1.1×10-9 cm2/ s and the activation energy E
a=1.47±0.01 eV.
Reliability of the Phase Change Optical Disk
Authors: Kusato Hirota Kusato Hirota , Gentaro Ohbayashi Gentaro Ohbayashi
Published: October 2002

Thermal stability of the Al-alloy reflective layer is essential for the archival life of a rewritable phase change optical disk. The new Al–Hf–Pd alloy reflective layer provides excellent thermal stability. A disk using this Al-alloy and a Pd–Ge–Sb–Te alloy recording layer is extremely stable. The bit-error-rate (BER) of the recorded signal did not change substantially after an acceleration test of 6,800 h under the conditions of 90° C, 80%RH. X-ray diffraction analysis showed that the new additive components (Hf, Pd) of the Al-alloy prevented the growth of the Al crystals.
Dielectric Confinement Effects on the Impurity and Exciton Binding Energies of Silicon Dots Covered with a Silicon Dioxide Layer
Authors: Masao Iwamatsu Masao Iwamatsu , Kenju Horii Kenju Horii
Published: October 2002

The binding energies of hydrogenic impurities and excitons in silicon (Si) dots modelled by a sphere covered with a silicon dioxide (SiO2) layer and embedded in various dielectric media, are calculated as a function of the sphere size and the thickness of the oxide. The strong-confinement limit was considered, so that all of the electrostatic interactions are treated as first-order perturbations considering the confined free-electron state as the unperturbed state. A recently proposed size correction for the dielectric constant of the Si dot is also taken into account. These calculations demonstrate the importance of the image-charge effect due to dielectric discontinuity. In addition, it is shown that the binding energies of the impurities and the excitons inside the silicon dots are greatly affected by alteration of the thickness of the oxides or the surrounding dielectric media.
AT-cut Quartz Resonators with Inverted-Mesa Electrodes
Authors: Hirama Koichi , Yuji Aoyama Yuji Aoyama , Matsutaro Naito Matsutaro Naito
Published: October 2002

This paper presents a theoretical analysis of trapped-energy AT-cut quartz resonators with an inverted-mesa electrode for obtaining a low capacitance ratio and inharmonic mode suppression. By decreasing the thickness of the electrode at its central region, the displacement distribution represents a single peak curve, a flat curve or a twin peak curve. The capacitance ratio has a minimum value in the region where the displacement distribution becomes flat. To suppress the inharmonic mode response, the energy trapping factor is located at the threshold point where the lowest symmetric inharmonic mode S1 is to be trapped. The calculated result confirms that there is a combination of design parameters which can achieve the minimum capacitance ratio and the inharmonic mode suppression simultaneously using the inverted-mesa electrode. The capacitance ratio of an AT-cut quartz resonator with the inverted-mesa electrode has a minimum value of 169.
Prebreakdown Density Change Streamer in Liquid Nitrogen
Authors: Kazuaki Yamazawa Kazuaki Yamazawa , Hisanao Yamashita Hisanao Yamashita
Published: October 2002

The prebreakdown density change streamers and the current pulses in liquid nitrogen were investigated. A needle-plane electrode system, consisting of a stainless steel plane and a tungsten needle whose tip radius is 1.0 µm, was used throughout the experiments. The streamers under impulse voltage conditions were observed using high-speed photography for both positive and negative polarities. Two structures of streamers, filamentary and bush-like, were found in both polarities. The mechanisms of these streamer structures are determined by analyzing the results.
Polymer-Stabilized Ferroelectric Liquid Crystal Devices with Grayscale Memory
Authors: Fujikake Hideo , Takizawa Kuniharu , Kikuchi Hiroshi , Fujii Takanori , Masahiro Kawakita Masahiro Kawakita , Tahito Aida Tahito Aida
Published: October 2002

A novel grayscale-memory ferroelectric liquid crystal device with polymer dispersion has been studied. The ferroelectric liquid crystal molecules are stabilized by a low-concentration doped polymer, which induces an enormous number of small liquid crystal domains with different threshold voltages for bistable switching. The polydomain has a spatial grayscale effect due to domain distribution. In forming the polymer-dispersion system with phase separation under ultraviolet light irradiation, a solution of liquid crystal and prepolymer was heated at the chiral nematic phase, and the directors of liquid crystal and prepolymer molecules were oriented parallel to the rubbing direction of alignment layers on substrates. A unique microscopic striped texture extending parallel to the rubbing direction was observed at a room temperature, and could be used to form the small domains. The 2-µ m-t
h
i
c
k device, fabricated by addition of 4 wt% polymer and strong ultraviolet irradiation of 40 mW/cm2, exhibited excellent grayscale memory according to applied voltage pulses of a few V. It has much potential for use in high-resolution matrix panel displays.
Stable Decagonal Quasicrystal in an Al–Mn–Fe–Ge System
Authors: Yokoyama Yoshihiko , Yamada Yoshihiro , Fukaura Kenzo , Sunada Hisakichi , Inoue Akihisa , Note Ryunosuke
Published: October 2002

A thermodynamically stable quasicrystalline phase with a decagonal structure was found to be formed in an Al40Mn25Fe15Ge20. The single phase was prepared by conventional solidification, followed by annealing for 100 h at 1050 K and then water quenching. The decagonal phase was identified to be the 6 layer (1.2 nm) Al4Mn-type decagonal structure. This alloy exhibits magnetization of 6.3 emu/g in an applied field of 10 kOe at 40 K.
Effects of Oxide Electrode on PbZrxTi1-xO3 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Kim Tae-Young , Daesig Kim Daesig Kim , Chee Won Chung Chee Won Chung
Published: October 2002

The effect of the RuO

x

/Pt multilayer electrode on the microstructure and ferroelectric properties of PbZr

x

Ti1-
x

O3 (x=0.52) prepared by metalorganic chemical vapor deposition (MOCVD) were studied. The variation of RuO

x

thickness resulted in changes in the RuO

x

surface morphology. These modifications of RuO

x

surfaces caused changes in the texture, surface morphology and ferroelectric properties of lead zirconate titanate (PZT) thin films deposited on the multilayer electrodes. The improvements in the ferroelectric properties were attributed to the altered microstructure. Remanent polarization (P
r) and coercive voltage (V
c) of the multilayer PZT capacitors were estimated to be 22 µ C/cm2 and 0.7 V at 5 V, respectively. The multilayer PZT capacitors did not degrade up to 1012 cycles at 2 V. In this study, the factors of the deposition of PZT on RuO

x

/Pt multilayer electrode by MOCVD were investigated and the integration process of the Pt/RuO

x

/PZT/RuO

x

/Pt capacitor was also discussed.
Multiple Scattering Approach to Pt L3-edge X-Ray Absorption near Edge Structure Spectra of Small Pt Clusters with Hydrogen Adsorption
Authors: Ohtani Kunihiro , Fujikawa Takashi , Kubota Takeshi , Asakura Kiyotaka , Iwasawa Yasuhiro
Published: October 2002

Recent experimental studies on the Pt L-edge X-ray absorption near edge structure (XANES) spectra of Pt clusters show that the spectra are greatly influenced by hydrogen adsorption. In this paper the full multiple scattering method, which we developed, is applied to study the difference in measured XANES spectra before and after the hydrogen adsorption. Hydrogen atoms are more plausible on adsorbed sites out of the cluster than on absorbed sites inside the cluster though the calculated spectra are not so sensitive to the adsorption sites. The adsorbed hydrogen atoms have rather negative charge due to the charge transfer from Pt atoms. In the charge transfer process Pt 6s (or 6p) electrons play a more important role than 5d electrons. Furthermore the small difference in the XANES spectra for Pt foil and small cluster is studied, and we find that it is due to the large fraction of surface Pt atoms in the latter system.
Numerical Investigation of Vertical Mercury Arc Operating at Various Tube Radii
Authors: Hashiguchi Seishiro , Mori Shigeo , Tachibana Kunihide
Published: October 2002

Vertically standing mercury-arc discharge was investigated with a fluid model which treated radiation power due to optically thick lines precisely. Transport coefficients were determined using on electron-mercury atom collision cross section which was recently measured by England and Elford. The radiation power which was expressed as a function of temperature agreed with experiment for a 400-W operation. Variations of temperature and axial velocity were studied as a function of tube radius. At the central region, it was found that the input power almost transferred to radiation power for large tube radii and that it was mainly consumed as heat conduction loss for small tube radii. Normalized axial velocity profile along the radial direction was almost independent of the tube radius, although its maximum value increased with increase in the tube radius.
Analysis and Simulation of Stacked-Segment Electromechanical Transducers with Partial Electrical Excitation by PSPICE
Authors: Chen Yeong-Chin , Wu Long , Kuei-Kai Chang Kuei-Kai Chang , Cheng-Liang Huang Cheng-Liang Huang
Published: October 2002

A composite transducer is fabricated, by stacking certain segments of poled piezoelectric ceramic, to satisfy multiple, conflicting design specifications. An electromechanical equivalent circuit that substantially facilitates the analysis of segmented systems, based on the Mason model is derived. To obtain the optimal solution to a specific design formulation, PSPICE programming techniques can be applied. An example of the application of PSPICE programming in the segmented transducer analysis is presented and the simulation results are in good agreement with the experimental measurements.
Electronically Induced Instability of a Hydrogen-Carbon Complex in Silicon and Its Dissociation Mechanism
Authors: Yoichi Kamiura Yoichi Kamiura , Masao Hayashi Masao Hayashi , Yoshihide Nishiyama Yoshihide Nishiyama , Shigeki Ohyama Shigeki Ohyama , Yoshifumi Yamashita Yoshifumi Yamashita
Published: October 2002

We studied, by deep-level transient spectroscopy (DLTS), the dissociation mechanism of a hydrogen-carbon (H-C) complex, which has a donor level at E
c-0.15 eV and acts as an electron trap in crystalline silicon. On the basis of our results and a previously proposed atomic model of the H-C complex, in which the hydrogen atom resides inside a silicon-carbon bond, we have proposed the following dissociation mechanism. The complex is stable in the positive charge state, and to dissociate it needs a hydrogen jump with an activation energy of 1.3 eV to break the bond with carbon and silicon. The complex becomes neutral by capturing an electron from the conduction band or accepting an electron directly from the valence band under electronic excitation, and is consequently dissociated at an activation energy of 0.5 eV due to the loss of binding. Strong evidence for the existence of the negative charge state of hydrogen in crystalline silicon is also presented.
Formation of Grown-in Defects during Czochralski Silicon Crystal Growth
Authors: Nishikawa Hideshi , Tanaka Tadami , Yanase Yoshio , Hourai Masataka , Masakazu Sano Masakazu Sano , Hideki Tsuya Hideki Tsuya
Published: October 2002

The formation behavior of grown-in defects in Czochralski silicon (CZ-Si) crystals was investigated using two crystals that were quenched during growth but in one case after crystal growth had been halted for 5 h. The distributions of grown-in defect density and size, and their micro-structures were analyzed as a function of temperature during crystal growth just before quenching by means of an optical precipitate profiler (OPP) and an atomic force microscope (AFM) coupled with a laser particle counter. The formation of grown-in defects, which are considered to be octahedral voids, was found to consist of two dominant processes. The first step involves rapid void growth in a narrow temperature range of about 30° C below 1100° C and the subsequent step consists of an oxide film growth on the inner surface of the void during the cooling process to about 900° C after void formation. It was also found that the growth of the oxide film in the voids is rate-limited by the diffusion rate of oxygen atoms in silicon. In addition, it is strongly suggested that void formation in such a narrow temperature range is due to a rapid agglomeration of vacancies.
Effects of the Addition of SiF4 to the SiH4 Feed Gas for Depositing Polycrystalline Silicon Films at Low Temperature
Authors: Syed Moniruzzaman , Inokuma Takao , Yoshihiro Kurata Yoshihiro Kurata , Seiichi Hasegawa Seiichi Hasegawa
Published: October 2002

Polycrystalline silicon films with a strong (110) texture were prepared on a corning 7059 glass substrate at 400° C by a plasma-enhanced chemical vapor deposition method using a mixture of gases with different SiF4 flow rates ( [SiF4] = 0–0.5 sccm) under a fixed SiH4 flow rate ( [SiH4] = 1 or 0.15 sccm). The effects of the addition of SiF4 to SiH4 on the structural properties of the films were studied by Raman scattering, X-ray diffraction (XRD), atomic force microscopy and stress measurements. For [SiH4] = 1 sccm, the crystallinity and the (110) XRD grain size monotonically increased with increasing [SiF4], and their respective maxima reach 90% and 900 Å. In contrast, for [SiH4] = 0.15 sccm, both the crystallinity and the grain size decreased with [ SiF4]. Mechanisms causing the change in crystallinity are discussed, and it was suggested that an improvement in the crystallinity, due to the addition of SiF4, is likely to be caused by the effect of a change in the surface morphology of the substrates along with the effect of in situ chemical cleaning. On the other hand, both the effect of in situ chemical etching on the growing surface and the effect of a change in the capability for surface migration of adsorbates may provide a minor contribution in determining the crystallinity.
ZnSe/ZnS Distributed Bragg Reflectors in the Blue Region Grown on (311)B GaAs Substrates
Authors: Takehiko Tawara Takehiko Tawara , Munetaka Arita Munetaka Arita , Katsuhiro Uesugi Katsuhiro Uesugi , Ikuo Suemune Ikuo Suemune
Published: October 2002

High-reflectivity distributed Bragg reflectors (DBRs) in the blue region consisting of II–VI semiconductors were grown on (311)B GaAs substrates for the first time using metalorganic vapor phase epitaxy. ZnSe/ZnS alternative layers were used as the DBR. To realize atomically flat surfaces, the conditions of the thermal cleaning and the growth of ZnSe and ZnS on (311)B GaAs surfaces were investigated using atomic force microscopy and X-ray diffraction. The supply of sufficient organic As flow during the thermal cleaning led to extremely-flat (311)B GaAs surfaces, and it was attributed to the suppression of As desorption from (311)B surfaces. Through the examination of the growth conditions for ZnSe and ZnS layers on (311)B GaAs substrates, a DBR with a high reflectivity was fabricated. The maximum reflectivity of the ZnSe/ZnS DBR grown on the (311)B GaAs substrate, measured at room temperature, was 94.5% with only 10 periods at a wavelength of 468 nm, which is in good agreement with the calculated reflectivity of 94.8%.
Performance of Single-Electron Transistor Logic Composed of Multi-gate Single-Electron Transistors
Authors: Moon-Young Jeong Moon-Young Jeong , Yoon-Ha Jeong Yoon-Ha Jeong , Sung-Woo Hwang Sung-Woo Hwang , Dae M. Kim Dae M. Kim
Published: October 2002

We have performed Monte Carlo studies of complementary capacitively coupled single-electron transistor (complementary C-SET) logic gates for single-electron digital logic circuits. The simulations carried out with various types of complementary C-SET logic gates showed that serial connections of single-electron transistors necessary for multi-input operations resulted in the degradation of the switching speed. It is pointed out that the multi-gate single-electron transistor configuration can provide a possible means to circumvent this problem. However, the associated nonsymmetric input-output characteristics could cause the operation failure of the circuit. It is shown that the multi-gate single-electron transistor circuits are the optimal choice from the standpoint of high speed operation and design simplicity, when confined to the input voltages not exceeding four terminals.
Positive Charge Generation at a SiO2/Si Interface due to Bombardment with Metastable Atoms
Authors: Ono Tetsuo , Itabashi Naoshi , Ochiai Isao , Yamamoto Seiji , Mochiji Kozou
Published: October 2002

The influence of metastable atoms on a SiO2/Si structure is examined to determine the source of damage in ULSI devices during plasma enhanced processes. Holes were generated at the SiO2 surface by the impact of metastable atoms of rare gases. Holes trapped at the interface formed positive charges, and the density of these positive charges increased with the increasing energy of the metastable atoms. The yields of the positive charge generation were between 0.01 and 0.1, which are on the same order as those caused by vacuum ultraviolet photons, and these values are not negligible. Thus, the influence of metastable atoms must be taken into consideration to control the damage that occurs during plasma enhanced processes.
Striations on Si Trench Sidewalls Observed by Atomic Force Microscopy
Authors: Yahata Akihiro , Satoshi Urano Satoshi Urano , Tomoki Inoue Tomoki Inoue
Published: October 2002

Atomic force microscopy (AFM) measurements revealed many striations on the Si trench sidewalls fabricated by reactive ion etching (RIE). The trench sidewall surface was rougher when a resist with a rougher surface was employed as a mask, whereas it was smoother when a resist with a smoother surface was employed. This result strongly suggests that the roughness of the resist is one of the causes of the roughness of the trench sidewalls.