bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Orientation of Pb(Zr, Ti)O3 Thin Films Using PbTiO3 Buffer Layer
Authors: Shimizu Masaru , Sugiyama Masataka , Hironori Fujisawa Hironori Fujisawa , Tadashi Shiosaki Tadashi Shiosaki
Published: October 2002

The orientation of Pb(Zr, Ti)O3 (PZT) thin films grown by metalorganic chemical vapor deposition (MOCVD) using a two-step growth process was controlled by changing the orientation of the PbTiO3 buffer layer. The (111)-oriented and (100)-oriented PZT films were grown on the (111)-oriented and the (001) and (100) mixed-oriented PbTiO3 buffer layers, respectively. From the atomic force microscope (AFM) observations, it was found that in the initial growth stages of the (111)-oriented PbTiO3 layer, the main growth mechanism was two-dimensional growth. In the two-step growth process, the PbTiO3 buffer layer played the important role of providing dense nuclei in the succeeding growth of rhombohedral PZT thin films. The influence of the thickness of a buffer layer on the relative dielectric constants of PZT films was also investigated.
Device Simulation of a Thin-Film Silicon on Insulator Power Metal-Oxide- Semiconductor Field-Effect Transistor for Structure Optimization
Authors: Yoshino Satoshi Matsumoto
Published: October 2002

This paper proposes an optimised device structure based on the results of numerically simulating thin-film silicon on insulator (SOI) power metal-oxide-semiconductor field-effect transistors (MOSFETs) in the 50-V class. The dependence of the breakdown voltage and specific on-resistance on the doping concentration of the drain offset region, on the thickness of the superficiai silicon layer, on the thickness of the buried oxide layer, and on the drain offset length are compared for buried channel MOSFETs and surface channel MOSFETs.
Fabrication of Barium Titanate/Strontium Titanate Artificial Superlattice by Atomic Layer Epitaxy
Authors: Tsurumi Takaaki , Suzuki Toshimasa , Masayuki Yamane Masayuki Yamane , Masaki Daimon Masaki Daimon
Published: October 2002

Epitaxial growth of BaTiO3, SrTiO3 and their superlattices was carried out by the alternating evaporation method using an atomic-layer-epitaxy control system for molecular beam epitaxy (MBE). Stable and reproducible control of the chemical composition was achieved by layer-by-layer growth with this system. Both BaTiO3 and SrTiO3 were grown epitaxially on SrTiO3 substrates, and clear oscillations of reflection high-energy electron diffraction (RHEED) intensity were observed, corresponding to the alternating depositions of BaO and TiO2 in BaTiO3 growth. The artificial superlattice with the structure of [(BaTiO3)5/(SrTiO3)5]7 was fabricated, and the X-ray diffraction (XRD) pattern of the superlattice was simulated by a step model. Diffraction angles of satellite peaks and the shape of Laue peaks in XRD patterns were consistent with those calculated, indicating that the designed structure was fabricated in the superlattice.
Preparation and Properties of Ru and RuO2 Thin Film Electrodes for Ferroelectric Thin Films
Authors: Maiwa Hiroshi , Ichinose Noboru , Kiyoshi Okazaki Kiyoshi Okazaki
Published: October 2002

Ru and RuO2 thin films were prepared by RF magnetron sputtering. The crystalline structure and electrical properties of these films were investigated. Reactive sputtering of a ruthenium metal target was carried out in a mixed gas of argon and oxygen at 580° C. Total pressure (P
O2
+P
Ar) was controlled to maintain a constant pressure of 1 Pa. The RuO2 single phase could be obtained when P
O2
was 0.5 Pa and the deposition rate was about 30 nm/min. The resistivity of the 290 nm-thick RuO2 thin films deposited on SiO2(1000 nm)/Si was 54.9 µ Ω· cm. However, the resistivity increased with decreasing film thickness. Fatigue resistance of (Pb, La)TiO3 thin films with RuO2 as top and bottom electrodes was improved compared to the films on Pt electrodes.
Fabrication of PbTiO3 Thin Films on TiSi2/Si and Their Characterization
Authors: Yahagi Naohisa , Hatano Hitoshi , Okamura Soichiro , Takayama Koichi , Takeyo Tsukamoto Takeyo Tsukamoto
Published: October 2002

A titanium disilicide, TiSi2, layer was prepared on Si wafers by Ti evaporation on Si in vacuum and heat-treated above 800° C. The sheet electrical resistance of the TiSi2 layer was estimated to be 1.3 Ω/\Box at room temperature. The temperature dependence of the electrical resistivity of ceramics showed metallic behavior down to 10 K. Ferro-electric PbTiO3 thin films on TiSi2 were fabricated by the dipping pyrolysis method using metal naphthenates. The values of remanent polarization and coercive field of the PbTiO3 films were estimated to be 16.0 µ C/cm2 and 52.9 kV/cm, respectively. The applicability of the TiSi2 layer as electrodes for capacitors in a VLSI was confirmed.
Fabrication of Lead Titanate Thin Film by Laser Ablation with Alternate Deposition of Lead Oxide and Titanium Oxide Precursors
Authors: Funakoshi Hiroshi , Fumoto Keigo , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Preferentially oriented PbTiO3 thin films have been deposited on Si and Pt substrates by the laser ablation method using an ArF excimer laser. First, PbO and TiO2 ceramic targets are evaporated alternately, and PbTiO3 film is prepared on a Si substrate with natural oxide in a fixed stoichiometric ratio which was achieved by controlling the number of irradiation pulses. The obtained film shows a preferred a-axis orientation. Secondly, a TiO2 buffer layer is formed on Si a substrate with natural oxide. The lead lanthanum titanate (PLT) film deposited on this buffered layer has a preferred a-axis orientation.
Dielectric Properties of Multilayered Ferroelectric Thin Films Fabricated by Sol-Gel Method
Authors: Ohya Yutaka , Takashi Ito Takashi Ito , Yasutaka Takahashi Yasutaka Takahashi
Published: October 2002

Multilayered thin films of ferroelectric perovskites were fabricated by the sol-gel method. The investigated films were PbTiO3, PbZrO3, BaTiO3 and SrTiO3, and their multilayered films. The films were prepared by dipping and heating in air at 600–700° C. The microstructures and crystalline phases of the single component and their multilayered films were examined. The multilayered film of PbTiO3 and PbZrO3 has a very clear interface between the components, though that between PbTiO3 and SrTiO3 was not clear due to the diffusion of the lead component from the PbTiO3 layer into the SrTiO3 layer and the formation of a solid solution. The dielectric constant of the multilayered films and its dependence on temperature could not be explained by the series connection of those of the component films.
Preparation of Lead Zirconate Titanate Thin Films by Reactive Evaporation
Authors: Kazuyoshi Torii Kazuyoshi Torii , Sakae Saitoh Sakae Saitoh , Yuzuru Ohji Yuzuru Ohji
Published: October 2002

Lead zirconate titanate thin films have been successfully fabricated by reactive evaporation. Elemental Pb, Zr, and Ti were evaporated in ozone-oxygen mixture ambient. Excellent controls of uniformity of thickness and composition were achieved over a large area (within ±2% on 4-inch wafer). The electrical properties were examined as a function of Pb content in the films. High dielectric constant (ε∼1000) and low leakage current ( 1.7×10-7 A/cm2) were realized for the film with stoichiometric composition.
Piezoelectric Properties of Nanostructure-Controlled Lead-Perovskite-Based Ceramics
Authors: Takahashi Keiichi , Nishida Masamitsu , Syunichiro Kawashima Syunichiro Kawashima , Koichi Kugimiya Koichi Kugimiya
Published: October 2002

We studied the piezoelectric properties for structure-controlled ceramics of (Pb0.9Sr0.1)(Mg1/3Nb2/3)0.255Ti0.38Zr0.365O3 prepared by the ultrafine powder process called the “nanopowder process”. The dense and uniform fine-grained ceramics in this system, which had the relative density of 97.5% and the average grain size of 1.9 µ m, were obtained by this process. The sample prepared by this process showed the large dielectric constant of above 5300 and the high electromechanical coupling factor k
31 of 0.41. It was found that the nanopowder process is effective to improve the piezoelectric property. The maximum value of the piezoelectric constant |d
31| was 356×10-12 m/V.
Elevated Polycide Source/Drain Shallow Junctions with Advanced Silicidation Processing and Al Plug/Collimated PVD (Physical Vapor Deposition)-Ti/TiN/Ti/Polycide Contact for Deep-Submicron Complementary Metal-Oxide Semiconductors
Authors: Kotaki Hiroshi , Takegawa Yoshiyuki , Mori Yukiko , Katsunori Mitsuhashi Katsunori Mitsuhashi , Junkou Takagi Junkou Takagi
Published: October 2002

Low-resistivity shallow junctions and completely filled contact technologies have been developed. These were realized by forming the elevated polycide source/drain junction structure and Al plug/collimated PVD-Ti/TiN/Ti/Ti-polycide (APPOCIDE) contact structure through the use of advanced silicidation processes called AAS and BAS (arsenic ions doped into the polycide layer after silicidation and boron ions doped into the polycide layer after silicidation). About 2.0–2.1 Ω /square sheet resistances of n+-Ti-polycide and p+-Ti-polycide were reached at the same level as that of undoped Ti-polycide. Contact resistivities were 2–3×10-9 Ω cm2 for a 0.35-µm-diameter contact on both n+ and p+. These contact resistivities were two orders of magnitude lower than that of the conventional Al/TiN/Ti/n+ or p+-silicon structure. Furthermore, we proposed a unique consideration for the reasons for the relative difficulty in achieving silicidation with low sheet resistance of TiSi2 layer on n+- polysilicon as compared to that on undoped- polysilicon.
Large Electromechanical Coupling Factors in Perovskite Binary Material System
Authors: Yohachi Yamashita Yohachi Yamashita
Published: October 2002

Similarities of large electromechanical coupling factors (k
s) in perovskite binary material systems were studied. Five large-k
s material systems, PZT 53/47, PZNT 91/9, PMNT 67/33, PSTT 55/45 and PSNT 57/43, were compared. These five large-ks material systems were found to show four similarities: rhombohedral and tetragonal morphotropic phase boundary (MPB), large polarization (P
r>25 µ C/cm2), proper B1 ionic size (70–72 pm) and large B2 ion (64 pm) in Pb(B1, B2)O3 relaxors and proper B-site average ionic sizes of MPB composition (64.7–66.8 pm). For example, in this study, the maximum coupling factors (k
p=72 %, k
31=45 %, and k
33=77 %) were obtained in Pb[(Sc1/2Nb1/2)0.57Ti0.43]O3+0.005Nb2O5(PSNTN 57/43) piezoelectric ceramic materials.
Piezoelectric Linear Motors for Driving Head Element of CD-ROM
Authors: Akira Yabuki Akira Yabuki , Manabu Aoyagi Manabu Aoyagi , Yoshiro Tomikawa Yoshiro Tomikawa , Takehiro Takano Takehiro Takano
Published: October 2002

This paper deals with piezoelectric linear motors for driving an optical pickup element of CD-ROM. These linear motors have such merits in that they can be made thin because of their simple construction, and they are suitable for precise positioning owing to their operation principle of using ultrasonic vibrations of essentially very small displacements. We can expect that the input power of these motors will be economized due to their self-position-retention function. Therefore, in order to achieve such linear motors, we have already reported some piezoelectric linear motors of the self-moving type. On the other hand, in this paper, the authors investigated some stationary piezoelectric linear motors which could easily be constructed in a flat shape. Compared with the self-moving piezoelectric linear motors reported previously, the stationary piezoelectric linear motors have the merit that they easily generate a uniform pressing force. In this paper, the structure, operation principles, and characteristics of such stationary linear motors are described, and moreover, a method to lower the driving voltage of these linear motors is reported.
Hydrophone Sensitivity of Porous Pb(Zr, Ti)O3 Ceramics
Authors: Ina Katsuyoshi , Mano Toshimasa , Nagata Seiji Omura
Published: October 2002

Porous lead zirconate titanate ceramics exhibiting 3-3 connectivity for a considerably wide porosity range, i.e., 0 to more than 70%, were prepared by a unique method using spherical organic materials, poly-methyl methacrylate spheres and polystyrene foams, as pore-forming substrates. The hydrophone sensitivity was measured as well as dielectric and piezoelectric properties. Dielectric constants and 3-1 mode piezoelectric properties agreed with the theoretical predictions, while 3-3 mode properties did not. Hydrophone sensitivity increased around the resonant frequencies. Sensitivity depended slightly on frequency as the porosity increased. Porous PZT is thought to be suitable for a wide-frequency-range hydrophone.
Alkaline-Earth Complexes as Precursors for Metalorganic Chemical Vapor Deposition
Authors: Tasaki Yuzo , Sakamoto Ryo , Ogawa Yoshimitsu , Yoshizawa Shuji , Ishiai Junichi , Akase Shinichiro
Published: October 2002

The dipivaloylmethanato complexes of barium and strontium synthesized in anhydrous solvent were found to be more volatile and thermally stabler than those synthesized in aqueous solution. The pentamethylcyclopentadienyl complexes of barium and strontium vaporized at much lower temperatures than dipivaloylmethanato complexes, and they could be employed as precursors for metalorganic chemical vapor deposition (MOCVD) by using nitrous oxide as the oxidant.
High-Reflectivity Self-Pumped Phase Conjugation and Mechanisms for Improvement of Response Speed
Authors: Shiosaki Zhiming Chen
Published: October 2002

Using a BaTiO3 single crystal, about 70% stable self-pumped phase conjugation reflectivity has been obtained with angles of incidence of 62° to 72°. In order to improve the response speed of phase conjugate generation for a low-power signal, a pump beam, called the accelerating beam, which is coherent with the signal beam, has been used. Consequently, the response time becomes dependent on the intensity of the accelerating beam. Mechanisms for the improvement have been found to be those of four-wave mixing. The possibility of application to real-time optical associative memory is discussed.
Method for Separating Linear and Circular Photogalvanic Effects and Its Application to Ferroelectric Lead Germanate
Authors: A Strukov Yuichi Kamata
Published: October 2002

A new method for separating linear and circular parts in the photogalvanic effect is proposed. This method utilizes an optical phase plate which is inserted between a sample and a phase-modulator crystal. We successfully applied the method to determine the linear photogalvanic coefficient β36 and circular coefficient γ33 of Bi12SiO20 and γ33 of Pb5Ge3O11. In particular, the change of the sign of γ33 of Pb5Ge3O11 was observed by reversing the spontaneous polarization. This phenomenon originates from the fact that the ferroelectric 180° domains of Pb5Ge3O11 are related by mirror symmetry.
Proposal of a Modulator-Integrated Structure in Quasi-Phase-Matched Second Harmonic Generation
Authors: Sunao Kurimura Sunao Kurimura , Yoshiaki Uesu Yoshiaki Uesu
Published: October 2002

A quasi-phase-matched second-harmonic-generation (QPM-SHG) device integrated with an SH modulator is proposed to obtain modulated blue light, in which it is possible to avoid intensity modulation of the laser diode as a fundamental source. In the structure, the modulating voltage is independent of the domain inversion ratio which is difficult to controll precisely. Numerical results of the modulating voltage, the SH output and the extinction ratio are presented in the devices based on the nonlinear coefficient d
33 of LiNbO3, LiTaO3 and KTiOPO4.
Effect of Additives on Microstructure Development and Ferroelectric Properties of Sr0.3Ba0.7Nb2O6 Ceramics
Authors: Nishiwaki Shiro , Junichi Takahashi Junichi Takahashi , Kohei Kodaira Kohei Kodaira
Published: October 2002

Sr0.3Ba0.7Nb2O6 (SBN30) ceramics with ∼97% theoretical density were fabricated by pressureless sintering at 1400° C for 4 h. The sintered sample with homogeneous and small-grained (∼2 µ m) microstructure shows a broadened permittivity (ε
r)-temperature (T) curve with ε
max
=1600 at T
C≈175° C. The microstructure and ferroelectric properties of the SBN30 ceramics can be substantially modified by Nb2O5 or V2O5 additive (0.5 mol%). The Nb2O5-added sample with isotropic grains of ∼4 µ m has ε
max
=2400 at T
C≈165° C. Considerable coarsening and elongation of grains occur in the V2O5-added sample which has a markedly sharpened ε
r-T character with ε
max
=3500 at T
C≈220° C and improved spontaneous polarization of 6.4 µ C/cm2.
Microwave Dielectric Properties for Ba(Mg1/3Ta2/3)O3–A(Mg1/2W1/2)O3 (A=Ba, Sr, and Ca) Ceramics
Authors: Mitsuru Furuya Mitsuru Furuya , Atsushi Ochi Atsushi Ochi
Published: October 2002

For a high-Q dielectric resonator at microwave frequencies, complex perovskite-structured Ba(Mg1/3Ta2/3)O3–A(Mg1/2W1/2)O3 (A=Ba, Sr, and Ca) ceramics have been developed. A(Mg1/2W1/2)O3 effects on the crystal structure, microstructure, and microwave characteristic of Ba(Mg1/3Ta2/3)O3 (BMT) were investigated. Ba(Mg1/2W1/2)O3 (BMW) decreased the temperature coefficient of resonant frequency ( TCF) for BMT. Sr(Mg1/2W1/2)O3 (SMW) and Ca(Mg1/2W1/2)O3 (CMW) increased it. Zero TCF was obtained for the BMT/BMW=95/5 composition. With 0.5 mol% BMW content, dielectric loss quality, Q
d, reached a maximum (40000 at 10 GHz).
Anomalous Phase Sequence in Binary Mixture of 3MC2PCPOPB and TFMHPOBC
Authors: Moritake Hiroshi , Ozaki Masanori , Taniguchi Hiroki , Kazuo Satoh Kazuo Satoh , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Dielectric measurement, conoscopic observation and polarizing microscopic observation have been performed on the binary mixture of 4′-3(-methoxycarbonyl-2-propoxycarbonyl) phenyl 4-(4-(n-octyloxy) phenyl) benzoate (3MC2PCPOPB) and 4-(1,1,1-trifluoromethyl-heptyloxycarbonyl) phenyl 4′-octyloxybiphenyl-4-carboxylate (TFMHPOBC). The chiral smectic Cα ( SmCα
*) and chiral smectic Cγ ( SmCγ
*) phases have been observed between the smectic A (SmA) and chiral smectic C
A
( SmC
A

*) phases. Another SmCγ
* phase has been observed below the SmC
A

* phase and the appearance of reentrant SmCγ
* phase has been confirmed. An anomalous temperature (T)-electric field (E) phase diagram, in which two SmCγ
* phases observed above and below the SmC
A

* phase are connected to each other over the SmC
A

* phase, has been obtained.
Domain Nucleation During Polarization Reversal in Lead Germanate
Authors: Gruverman Alexei , Ponomarev Nikolai , Koichiro Takahashi Koichiro Takahashi
Published: October 2002

The kinetics of domain nucleation during polarization reversal in uniaxial ferroelectric lead germanate has been studied in detail using optical methods of visualization of the instantaneous domain configurations. Transient and steady-state regimes of nucleation have been discovered. The contribution of transient nucleation to polarization reversal essentially increases as the field is increased. Attention is drawn to the similarity between ferroelectric switching and a first-order phase transition. The obtained results can be used for the improvement of the description of switching behaviour in high fields.
Strain Relaxation Process of (InAs)m(GaAs)n Strained Short-Period Superlattices Grown by Molecular Beam Epitaxy
Authors: Kawai Takahiro , Yonezu Hiroo , Saito Daishiro , Mikihiro Yokozeki Mikihiro Yokozeki , Kangsa Pak Kangsa Pak
Published: October 2002

The strain relaxation process and crystalline quality of (InAs)

m

(GaAs)

n

strained short-period superlattices (SSPSs) grown on a GaAs(001) substrate were investigated
by transmission electron microscopy and double-crystal X-ray diffraction. The lattice
mismatch between the superlattice and the substrate was mainly accommodated by the
generation of misfit dislocations propagating parallel to the heterointerface with no
threading dislocations. However, the density of misfit dislocations was relatively low
in the single SSPS heterostructure. Moreover, the full width at half-maximum of X-ray
diffraction was markedly increased with the generation of misfit dislocations. It was
found that the residual strain of SSPS was effectively relieved by applying multiple SSPS heterostructures.
The Effect of Mesh Bias and Substrate Bias on the Properties of a-Si:H Deposited by Triode Plasma Chemical Vapour Deposition
Authors: Osborne Ian S. , Hata Nobuhiro , Gautam Ganguly Gautam Ganguly , Akihisa Matsuda Akihisa Matsuda
Published: October 2002

A new deposition parameter in the plasma enhanced chemical vapour deposition
(PECVD) technique for the control of the optoelectronic properties of hydrogenated
amorphous silicon (a-Si:H) is presented. The technique utilises a triode electrode
configuration with a wire mesh placed between the cathode and anode of a conventional
diode type PECVD system. A dc bias, applied to the mesh, affects the plasma-substrate
distance or the extent of plasma confinement between the mesh and the cathode, and
subtly alters the gas phase chemistry in the plasma. Using this technique, films of
undoped a-Si:H have been deposited with pure silane as the source gas. Our results
show that the defect density, hydrogen content, and hydrogen bonding configuration
are determined by the mesh bias. Measurement of the defect density of the as-grown
films by the constant photocurrent method (CPM) reveals that this technique can be
used to produce high quaility films with low defect density (<5× 1014 cm-3)
by application of an appropriate bias on the mesh during deposition.
Novel Field Reduction Structure at Tip of Electrode Fingers for Low On-Resistance High-Voltage Power Double-Diffused Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Fujishima Naoto , Tada Akio Kitamura
Published: October 2002

In this paper we report on a low on-resistance and high-voltage power double-diffused metal-oxide-semiconductor field-effect transistor (DMOSFET) with a newly proposed interdigitated form for power ICs, which is fabricated by a cost-effective standard complementary metal-oxide-semiconductor (CMOS) process. The basic structure with an extended p-base has a highly doped drift region. In an interdigitated form for high-current applications, the widely spread depletion layer fiom the drain side eliminates electric field concentration at the tip of the drain fingers. As for the tip of the source fingers, although the radius of curvature is only 15 µm, the newly proposed structure with a remainder p-substrate realizes a considerable decrease in electric field by the charge sharing effect. This structure realizes unlimited breakdown voltage at the corner. As a result of this technology, a 700 V power DMOSFET achieves more than 20% reduction of specific on-resistance.
Internal Stress of CoSi2 Films Formed by Rapid Thermal Annealing
Authors: Ito Tadashi , Hirozumi Azuma Hirozumi Azuma , Shoji Noda Shoji Noda
Published: October 2002

This paper presents a discussion on internal stress generation in CoSi2
films formed by rapid thermal annealing (700–900° C). The internal
stress is measured by X-ray diffractometry. The internal stress is 1.1–1.3 GPa, and
is almost independent of the annealing temperature. This is in contrast with the fact
that the internal stress of TiSi2 films increases with the annealing temperature.
This contrast is attributed to the fact that thermal stress of CoSi2 films
relaxes during cooling, while in TiSi2 films the thermal stress contributes to
the internal stress without relaxing.
Bias Effect on Compositional Separation in Sputtered Co–Cr Films
Authors: Takei Koji , Rogers David J. , Maeda Yasushi
Published: October 2002

The effect of dc substrate bias on compositional separation (CS) in sputtered
Co–Cr films is examined using spin-echo 59Co NMR and transmission electron microscopy.
It is observed that the degree of CS decreases monotonically with increasing negative bias voltage.
Slight positive bias voltage, however, is found to enhance CS, resulting in increased
saturation magnetization and a higher anisotropy field. The elimination of Ar ion
bombardment at the film surface during deposition is thought to be effective in enhancing CS.
Characterization of Pb(Zr, Ti)O3 Thin Films Prepared by Multi-Ion-Beam Sputtering
Authors: Kanno Isaku , Hayashi Shigenori , Kamada Takeshi , Masatoshi Kitagawa Masatoshi Kitagawa , Takashi Hirao Takashi Hirao
Published: October 2002

Lead-zirconate-titanate (PZT) thin films with lead-lanthanum-titanate (PLT) buffer layer prepared by multi-ion-beam sputtering were characterized from the structural and electrical viewpoints. Cross-sectional transmission electron microscopy (TEM) observation demonstrated the epitaxial growth of the films without intermixing layers or misfit dislocations. Nominal interdiffusion of PZT/PLT/substrates was found in the depth profiles obtained from secondary ion mass spectroscopy (SIMS). The PZT films over the entire compositional range of Zr/Ti ratio exhibited relative dielectric constant which was consistent with the dependence of bulk PZT; however, obvious changes of lattice spacings at phase boundaries were not found from X-ray diffraction (XRD) measurement.
The Novel Capacitor Structure with Polysilicon Grain Hole for Advanced Dynamic Random Access Memory
Authors: Yee Youngjoo , Yu Sanggi , Kukjin Chun Kukjin Chun , Jong Duk Lee Jong Duk Lee
Published: October 2002

A simple and new technique to realize relatively large capacitance for high density dynamic random access memory (DRAM) is discussed. This technique adopts the surface modulation technology on bottom electrode polysilicon of stacked capacitor structure, and holes are created in the bottom polysilicon grains. The grain holes are achieved by reactive ion etching (RIE) using the oxide at the grain boundary as etch mask. The capacitance can be increased up to four times, while keeping the leakage current comparable to that of conventional stacked capacitors.
High-Efficiency Al0.2Ga0.8As/Si Stacked Tandem Solar Cells Using Epitaxial Lift-Off
Authors: Zahraman Khaled , Guillaume Jean-Claude , Nataf Gilles , Beaumont Bernard , Mathieu Leroux Mathieu Leroux , Pierre Gibart Pierre Gibart
Published: October 2002

In this paper, the potential of high conversion efficiency of solar energy through the
combination of Al0.2Ga0.8As and Si cells is illustrated by a mechanically
stacked tandem using, for the first time, the epitaxial lift-off (ELO) technique to
remove the top cell from its substrate. The selective etching of the GaAs substrate
provides efficient light transmission to the bottom cell. Photoluminescence decay
experiments show that substrate removal also enhances photon recycling effects. The
measured efficiency of the Al0.2Ga0.8As/Si tandem reaches 21% AM1.5.
Magneto-Optical Storage Media Using DyFeCo Film for Magnetic Field Modulation Direct Overwriting
Authors: Masahiro Tabata Masahiro Tabata
Published: October 2002

Amorphous DyFeCo films have been studied for use as magneto-optical (MO) storage
media for magnetic field modulation direct overwriting. The Dy-rich DyFeCo film has been
found to be suitable for magnetic field modulation recordings by applying small-modulation
magnetic field. The magnitude of the external recording magnetic field required for
direct overwriting has been considerably reduced through adjusting the Dy content in
DyFeCo film. In addition, the read-write characteristics have been improved by controlling
the content of Co in the film. The DyFeCo disk prepared for this study shows the carrier
to noise ratio (CNR) up to 49.5 dB when the modulation magnetic field is about 80 Oe
and the recording mark length is 0.83 µ m. Furthermore its reliability performance
has been examined by the accelerated test in humid environment at an elevated temperature for long periods of time.
Rewritable Capacitance Disk Memory with Ferroelectric-Semiconductor Structure
Authors: Ryoichi Yamamoto Ryoichi Yamamoto , Kazuo Sanada Kazuo Sanada , Shizuo Umemura Shizuo Umemura
Published: October 2002

This paper presents a new rewritable capacitance disk memory with a ferroelectric-semiconductor structure. The ferroelectric film of the medium was poled in the perpendicular direction to generate depletion capacitance for data recording. Capacitance between the stylus head and the medium was detected for data reproduction. The amount of change in capacitance due to the poling direction showed that the recording density of this memory system could be more than 1 Gbit/cm2. Evaluation equipment was constructed for dynamic bit recording and reproduction, in which the mobile stylus head was in contact with the medium surface. It was confirmed that data bits with 0.4 µm spatial wavelength could be recorded and reproduced. In our experiment, recording density was mostly determined by the stylus size, and its limit was also estimated by the numerical simulation of ferroelectric semiconductor structure.
Measurement of Steady-State Current Flowing in Nematic Liquid Crystal
Authors: Hitoshi Mada Hitoshi Mada , Hiroyuki Yamada Hiroyuki Yamada
Published: October 2002

Applied voltage dependence of steady-state current was measured for a nematic liquid crystal
(5CB). The current is proportional to the applied voltage in the low-voltage region.
However, for the high-voltage region, the voltage dependence becomes a square law or cubic law.
Transient Current Study of Ultraviolet-Light-Soaked States in n-Pentyl-p-n-Cyanobiphenyl
Authors: Hiroyoshi Naito Hiroyoshi Naito , Kazuyuki Yoshida Kazuyuki Yoshida , Masahiro Okuda Masahiro Okuda , Akihiko Sugimura Akihiko Sugimura
Published: October 2002

Ultraviolet (UV)-light-soaked states in n-pentyl-p-n-cyanobiphenyl (5CB) have been investigated with transient current techniques. No change in the drift mobility of ions is detected, while the density of ions is increased after UV-light soaking because of the photochemical decomposition of 5CB. The origin of the impurity ions in 5CB is briefly discussed.
Chemical Composition of Al2O3/InP Metal-Insulator-Semiconductor Interfaces Improved by Plasma and Ultraviolet Oxidation
Authors: Matsuda Tetsuro , Yoshida Haruhiko , Nara Naoki , Hirohiko Niu Hirohiko Niu , Seigô Kishino Seigô Kishino
Published: October 2002

Plasma and ultraviolet (UV) oxidation are used to obtain insulating films for the
fabrication of an InP metal-insulator-semiconductor diode. A thin Al film is deposited
onto a UV-oxidized n-type InP wafer and the Al film is oxidized with the use of a
microwave-excited O2+N2 mixture plasma. The depth profile of the composition
of the oxidized film is measured by XPS with the aid of Ar ion sputtering. An annealing
procedure in N2-atmosphere followed by H2-atmosphere annealing was
applied to MIS diodes. Resultant InP MIS diodes show excellent C-V characteristics
with very small hysteresis. C-V measurements at 1 MHz yield a minimum interface
trap density of 6× 1010 cm-2 eV-1.
High-Resolution Patterning of Luminescent Porous Silicon with Photoirradiation
Authors: Nobuaki Noguchi Nobuaki Noguchi , Ikuo Suemune Ikuo Suemune
Published: October 2002

Selective formation of porous layers with micrometer dimensions was achieved with photoirradiation on a silicon surface with a patterned impurity distribution, and the mechanism was studied. Diffusion of photogenerated holes along an n-type silicon surface and the resultant accumulation of the holes in the potential well formed in p-type stripes embedded on the n-type surface were attributed to be the main factors for the selective formation. The saturation of the porous layer formation was observed at the depth of the p-n junction, and the resolution limit in the patterning was discussed from the viewpoint of trapping of the holes with the potential barrier at the p-n junctions.
Electron Linear Accelerator Using Phased Multi-Electromagnetic-Wave Beams
Authors: Otsuka Kazue , Yasushi Nishida Yasushi Nishida , Noboru Yugami Noboru Yugami
Published: October 2002

The motion of charged particles in a multi-electromagnetic-wave beam (multi-EM beam)
system has been investigated numerically. This system consists of many plane electromagnetic-wave
beams propagating parallel to each other, but the phase is delayed successively from
one beam to the next. The resultant electromagnetic field seems to be a slow wave
which can interact with the particle beam. When a static magnetic field is applied
parallel to the fluctuating magnetic field of the wave, it is concluded from numerical
calculations that the charged particles injected in this scheme are trapped in the apparent wave and accelerated stably to
high energy, close to the speed of light.
Electronic Chaos in Silicon Thyristor
Authors: Yasuda Koichiro Hoh
Published: October 2002

Deterministic chaos was observed in the ac response of the Si thyristor in relation to its S-shaped negative differential conductivity. Period-doubling and period-adding chaotic sequences appeared in the same device corresponding to the change of operating parameters. A simple device/circuit model reproduced experimental Lorenz plots qualitatively.
Influence of Aging on Classification of Partial Discharges in Cavities
Authors: Andrej Krivda Andrej Krivda , Edward Gulski Edward Gulski
Published: October 2002

In this work the effect of aging on discharge patterns from cavities
in polyethylene (PE) is investigated. Two aspects were taken into
account–aging due to discharges and the location of the cavity (dieletric or
electrode bounded). Discharge patterns were analyzed using a previously
developed technique involving statistical parameters. This tool
successfully discriminated various aging stages and cavity types.
No difference was found between discharge patterns of dieletric- and
electrode-bounded cavities in the first minutes from the beginning of
measurement. Clear recognition of dieletric- and electrode-bounded
cavities in the conditioned and aged stage was achieved. For discharge
patterns with asymmetry between the positive and the negative half of the
voltage cycle, the ability of statistical parameters to follow changes
in the defect location in a test object was proven.
Charge Damage Caused by Electron Shading Effect
Authors: Koichi Hashimoto Koichi Hashimoto
Published: October 2002

An antenna covered with photoresist patterns having high-aspect-ratio openings
caused charge damage to the gate oxide in various processing plasmas. This damage
increased with the pattern's aspect ratio, and occurred even when the test wafer was
cut into chips about 5 mm square and mounted on a wafer with insulation. These results
prove the electron shading model: the photoresist patterns shade the antenna from
electrons of oblique incidence, resulting in local charging occurring without a wafer-scale
voltage difference, which is essential for conventional charging. The damaging current
from this mechanism increased by a factor of more than ten with a decrease in the
gate oxide thickness only from 8 nm to 6 nm, implying that the degree of shading
depends on the gate charging voltage. An improved model is proposed to accommodate this strong dependence.
Influence of Reaction Products and Oxygen on Highly Selective Electron Cyclotron Resonance Ion Stream Etching of Si
Authors: Tsuchizawa Tai , Chiharu Takahashi Chiharu Takahashi , Seitaro Matsuo Seitaro Matsuo
Published: October 2002

The behavior of reaction products during Si etching by electron cyclotron resonance
(ECR) ion stream etching with Cl2 is investigated using the emission of SiCl
as a monitor of the reaction products. A strong correlation is found between the
emission intensity of SiCl and the SiO2 etch rate, and it is confirmed that an
increase in the reaction products promotes SiO2 etching. As the SiO2
etching mechanism, we propose the occurrrence of a reaction with a volatile compound,
(SiCl3)2O, on the SiO2 surface. When O2 is added to Cl2,
the concentration of reaction products in the plasma decreases. This is shown to occur
because the redesorption of the reaction products from the chamber wall is hindered by O2.
The suppression of SiO2 etching upon O2 addition is related not only
to the oxidation of the SiO2 surface but also to the decrease in reaction product concentration in the plasma.
Theoretical Analysis of Photoacoustic Displacement for Inhomogeneous Materials
Authors: Takamatsu Hiroyuki , Sumie Shingo , Morimoto Tsutomu , Kawata Yutaka , Nishimoto Yoshiro , Horiuchi Takefumi , Nakayama Hiroshi , Kita Takashi , Nishino Taneo
Published: October 2002

A method for theoretically analyzing photoacoustic displacement (PAD) induced
by a pump beam in a three-dimensional model is presented. The analysis is based on
rigorous methods in terms of temperature fields expanded by eigenmodes for an imaginary
bounded system, and it is formulated in matrix form so that calculations for inhomogeneous
materials can be performed systematically. It is shown that the theoretical calculations
are in good agreement with the experimental results for aluminum thin films and ion-implanted
silicon wafers, and that the theoretical model is experimentally verified. This method
is useful for characterizing materials' properties, including structural analysis
and subsurface defect detection of a sample.
Velocity Distribution by Time-of-Flight Measurement in an Optically Pumped Cs Beam Frequency Standard
Authors: Ohshima Shin-ichi , De Marchi Andrea , Oh Cha Hwan , Yasuhiro Nakadan Yasuhiro Nakadan
Published: October 2002

The velocity distribution of an optically pumped Cs fiequency standard was measured
by time-of-flight (TOF) measurement, and it agreed very well with the previous result
which was obtained by the long-pulse excitation method. We therefore conclude that the
TOF measurement is a very effective method to obtain the velocity distribution of optically pumped Cs standards.
Improvement of a-Si Solar Cell Fabricated by Mercury-Sensitized Photochemical Vapor Deposition Using H2 Dilution Technique
Authors: Siamchai Pavan , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai
Published: October 2002

The fabrication of hydrogen-diluted amorphous silicon (a-Si) film by the mercury-sensitized photochemical
vapor deposition (photo-CVD) method has been performed. The hydrogen content in the film along with the optical
bandgap was found to increase with the hydrogen/silane dilution ratio, while the dihydride/monohydride bond ratio
decreased at the substrate temperature of 150° C. As a result, a decrease in the defect density was
observed. Moreover, the photo- and dark conductivities were maintained in the range of 3×10-5 and
1×10-10 S/cm, respectively, in spite of the fact that the optical bandgap widened. The solar cells
with hydrogen diluted i-layers were fabricated and showed improvement in the open-circuit voltage and fill factor
(FF), resulting in the increase of both initial and stabilized efficiencies. The forward- and reverse-bias dark
I-V characteristics measurement of solar cells revealed improvement in quality and stability of the
hydrogen-diluted i-layers.
Photoluminescence Study of GaAs Grown on (001) Si
Authors: Vivian Alberts Vivian Alberts
Published: October 2002

The optical properties of GaAs epilayers grown by organometallic vapour phase epitaxy (OMVPE) on (001) Si substrates are reported. Low-temperature photolumniescence (PL) indicated that an increase in GaAs layer thickness led to an increase in PL intensity, a decrease in the full width at half-maximum (FWHM) of the excitomic transitions and an increase in the ratio of the exciton to carbon impurity peak heights. A comparison of PL spectra, obtained from layers grown on nominally (001) and 2? off (001) Si substrates, indicated that the carbon impurity concentration is higher in epitaxial layers grown on nominally (001) Si. PL studies also indicated that the optical quality of the top GaAs epilayer is critically dependent on the growth parameters of the nucleation layers. The best PL response (i.e., greatest intensity, smallest FWHM and lowest impurity concentration) was obtained from layers in which the initial Al0.2Ga0.8As nucleation layer was deposited at a low V/III ratio of 10. It was also shown in this study that postgrowth thermal annealing and the incorporation of AlGaAs/GaAs superlattices resulted in a dramatic improvement in the optical quality of GaAs/Si epilayers.
Numerical Simulation of Tunnel Effect Transistors Employing Internal Field Emission of Schottky Barrier Junction
Authors: Reiji Hattori Reiji Hattori , Junji Shirafuji Junji Shirafuji
Published: October 2002

Tunnel transistors employing internal field emission of the Schottky barrier junction (SBTT) are expected to be a promising component for high-density and low-cost integrated circuits. In order to characterize the performance of SBTT, we carried out 2-D numerical simulation on four typical device structures. The output characteristics of SBTT are basically triodelike; that is, the drain current increases exponentially with increasing gate voltage, having high and nonlinear transfer performance, as elucidated by the simulation. This triodelike characteristic is observed when the channel layer is thicker than the depletion layer width formed by gate bias near the drain. In the case of a thin channel layer, a saturation feature of the drain current with increasing gate bias appears due to a pinch-off effect, which is favorable for reducing the leakage current in the off state. A prototype n-channel SBTT of crystalline silicon was fabricated and its transistor action was confirmed.
Carbon and Indium Codoping in GaAs for Reliable AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Nittono Takumi , Watanabe Noriyuki , Ito Hiroshi , Sugahara Hirohiko , Koichi Nagata Koichi Nagata , Osaake Nakajima Osaake Nakajima
Published: October 2002

This paper reports a systematic study on C and In codoping in GaAs to form an AlGaAs/GaAs heterojunction bipolar
transistor (HBT) structure with minimized lattice strain. Carbon-doped layers were grown by metalorganic chemical
vapor deposition. The carbon concentration in the epitaxial layer can be controlled by adjusting the CCl4 flow
rate although it strongly depends on growth parameters such as substrate temperature and V/III ratio. We found the
CCl4 supply disturbs In incorporation into the epitaxial layer, while the In concentration changes in
proportion to trimethyl indium flow rate. The lattice mismatch of the In/C-doped layer can be explained by the
strained-layer model based on Vegard's law. Indium codoping does not deteriorate the electrical characteristics of
the C-doped layer or the current gains of the C-doped-base HBTs. The current gains of the In/C-doped-base HBTs were
stable for more than 1×104 h at a junction temperature of 250° C.
Linear and Nonlinear Optical Properties of Molecule and Crystal of N-(2,4-Dinitrophenyl)-1-Chloro-3-Phenyl-2-Propanamine
Authors: Komatsu Hiromi , Sugiyama Tsunetoshi , Shigemoto Takeo , Ukachi Takashi , Masahiro Niinomi Masahiro Niinomi
Published: October 2002

A new nonlinear optical material, N-(2,4-dinitrophenyl)-1-chloro-3-phenyl-2-propanamine was prepared. A
molecular hyperpolarizability value of 7.26×10-30 esu was obtained through electric-field-induced
second-harmonic (EFISH) measurement. The crystal structure and the linear and the nonlinear optical properties were
examined. Relatively low values of the effective nonlinear optical coefficient determined by angle-tuned SHG
experiments and Maker fringe experiments at 1064 nm were discussed with respect to the crystal structure.
Device Simulation with Quasi Three-Dimensional Temperature Analysis for Short-Channel Poly-Si Thin-Film Transistor
Authors: Tamio Shimatani Tamio Shimatani , Takuji Matsumoto Takuji Matsumoto , Takeshi Hashimoto Takeshi Hashimoto , Noriji Kato Noriji Kato , So Yamada So Yamada , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

A new poly-Si thin-film transistor (TFT) device simulator for quasi three-dimensional temperature analysis has been developed. In this simulator, the influences of the grain boundaries are incorporated into the mobility model when the basic semiconductor equations are solved. Furthermore, we have taken into account the self-heating effect owing to a small thermal conductivity of the insulating substrate using quasi three-dimensional temperature analysis. We could accurately analyse the temperature rise effect and the avalanche short-channel effect in the short-channel poly-Si TFT.
Defects Induced Enhancement of Eu3+ Emission in Yttria (Y2O3:Eu3+)
Authors: Jagannathan R. , Kutty T. R. N. , M. Kottaisamy M. Kottaisamy , P. Jeyagopal P. Jeyagopal
Published: October 2002

Bixbyite type Y2O3:Eu3+ apart from being the efficient red phosphor extensively used in
trichromatic fluorescent lamps, it is a typical system one can apply Jørgensen's refined electron spin pairing
theory. This can be used to explain the enhancement in Eu3+ emission intensity observed with the aliovalent
substitution in the yttria host matrix. Results based on these are explained qualitatively by considering a simple
configurational coordinate model. Futhermore, an insight into the different types of defects induced with the
aliovalent substitution in the yttria lattice has become possible with EPR probe.
Optical Constants of Amorphous Ga2Te3 and In2Te3
Authors: Ozaki Shunji , Kazuhiro Takada Kazuhiro Takada , Sadao Adachi Sadao Adachi
Published: October 2002

The optical response in amorphous (a-) Ga2Te3 and In2Te3 semiconductors in the
1.2–5.2-eV photon-energy range at room temperature has been measured by spectroscopic ellipsometry. These materials
were obtained directly from the melt. It is found that the dielectric functions,
ε(E)=ε
1(E)+ iε
2(E), of a- Ga2Te3 and a- In2Te3
have a strong resemblance to those of amorphous tetrahedrally bonded semiconductors. The optical energy gap estimated
from the plots of E
ε
2(E)1/2 versus E is 1.2 eV for both a- Ga2Te3 and
a- In2Te3. Dielectric-related optical constants, such as the complex refractive index, absorption
coefficient and normal-incidence reflectivity, of these amorphous semiconductors have also been presented.
Electric-Field-Induced Director-Field Transition of Nematic Liquid Crystal in a Closed Conical Cavity
Authors: Jong-Guang Wei Jong-Guang Wei , Shu-Hsia Chen Shu-Hsia Chen
Published: October 2002

Continuum theory and numerical method are utilized in this study to report the dependence of director-field transition induced by electric field on the elastic constants of nematic liquid crystal (NLC) with negative dielectric anisotropy in a closed conical cavity with perpendicular boundary conditions of NLC. Normal umbilic structure (NU), twisted umbilic structure (TU), normal hyperbolic point structure with a disclination ring (NH), twisted hyperbolic point structure with a disclination ring (TH), and normal Poincare structure (NP) are found to be stable structures in electric-field-induced transitions. Moreover, five typical sequences of transition, TNU→TU→TH, TNU→TU→NH→TH, TNU→TU→NH, TNU→NH, and TNU→NP→NHare found in the range of applied voltage less than 10 V. The transition sequences and the transition voltages are strongly dependent on the ratios of elastic constantsK11/K33andK22/K33.
Surface Disclinations on Modified Substrate
Authors: Okano Koji , Kenkichi Kitahara Kenkichi Kitahara , Eiji Ushizawa Eiji Ushizawa
Published: October 2002

A discontinuous change in the anchoring condition on a substrate of a nematic liquid crystal cell gives rise
to a disclination line attached to the substrate surface. We have analysed the distortion of the director field in the
presence of such surface disclinations by using the technique of conformal mapping. For a given (strong) anchoring
condition there exist several different director configurations. However, an analysis of the associated elastic free
energy revealed that among these configurations the director patterns in which neighboring disclination lines have
opposite sign have lowest free energy and only such configurations are stable. In these stable configurations the
distortion of the director extends along the direction of the substrate plane over a distance of the order of the
cell thickness from the position of the disclination line.