bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration of Modified Plasma-Enhanced Chemical Vapor Deposited Tetraethoxysilane Intermetal Dielectric and Chemical-Mechanical Polishing Processes for 0.35 µm IC Device Reliability Improvement
Authors: Wang Ying-Lang , Tseng Wei-Tsu , Feng Ming-Shiann
Published: October 2002

The process of interlevel dielectrics (ILD) between poly-Si and metal is critical to device characteristics and reliability. Also, the shrinking design rules demand greater hot carrier reliability, which is strongly influenced by the ILD process. In this paper we describe a process for improving the reliability of 0.35 µ m devices by using modified plasma-enhanced chemical vapor deposited tetraethoxysilane (PECVD-TEOS) N2O-rich or O2-rich ILD films which contain less hydrogen concentration and excellent moisture resistance, and less mobile ion penetration after chemical-mechanical polishing (CMP), relative to standard PE-TEOS oxides. The hot carrier lifetime and the field isolation device threshold voltage are monitored and compared between devices with ILD layers based on different combinations of subatomespheric O3-TEOS borophosphorus silicate glass (BPSG), standard PE-TEOS, O2-rich and N2O-rich oxides. The material characteristics contributing to the reduction in post-CMP mobile ion levels and the improvement in device reliability will be discussed.
Charged Defects at the Interface between Directly Bonded Silicon Wafers
Authors: Laporte Angeline , Sarrabayrouse Gérard , Benamara Mourad , Claverie Alain , Rocher André , Peyre-Lavigne André
Published: October 2002

The interface between directly bonded hydrophobic silicon wafers is studied using the spreading resistance technique. It is found that this interface always contains positively charged defects. Possible origins of the defects are discussed on the basis of the morphology of the interface studied previously.
Revisit to the Anomaly in Dielectric Properties of (Ba1-xSrx)(Zn1/3Nb2/3)O3 Solid Solution System
Authors: Kim Jong Sam , Lee Jong Ho , Lim Yun-Soo , Jang Jin Wook , Kim In-Tae
Published: October 2002

In our present study, the anomalous variation in temperature coefficient and permittivity of (Ba1-
x

Sr

x

)(Zn1/3Nb2/3)O3 (BSZN) with chemical composition was investigated with respect to the order-disorder behavior of the system. It was observed that dielectric properties such as permittivity, temperature coefficient, and quality factor revealed systematic variation not only with composition but also with sintering temperature. The origin of the latter variation was ascribed to the change in bond character accompanied by the order-disorder behavior. With the aid of X-ray diffraction accompanied by a critical review of previous research, it is suggested that a short-range modulation of crystal structure rather than a change in long-range crystal structure is the origin of the temperature coefficient and permittivity anomalies apparent in the BSZN system.
Analysis of Dielectric Dispersion Property of Organic Monolayer Films on a Material Surface
Authors: Chen-Xu Wu Chen-Xu Wu , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: October 2002

Using the differential equation of the orientational order parameter representing the transient behavior of monolayers, which is derived from the Debye Brownian rotational motion equation, the dielectric dispersion of organic monolayers on a material surface was analyzed. It was found that the equations representing the dielectric dispersion of organic monolayers satisfy the relations by Debye, although the dielectric relaxation time depends on the spatial restriction of the monolayers, the Coulomb interaction between the molecules as well as the interaction between the molecules and the substrates. Finally, we discuss the dielectric relaxation of monolayers on the basis of the experimental results on L-α-dimyristoyl, phosphatidylcholine (DMPC) multilayers.
Hysteresis-Free Amorphous Chiral Nematic Reflective Guest-Host Liquid Crystal Displays
Authors: Sugiyama Takashi , Suzuki Hidehiko , Iimura Yasufumi , Kobayashi Shunsuke
Published: October 2002

An amorphous chiral nematic guest-host (a- N*-GH) liquid crystal display (LCD) characterized by high reflectivity due to a polarizer-free, wide viewing angle, and small hysteresis is demonstrated. The appearance of the hysteresis is investigated in detail by observing the textures of the cell. The hysteresis width depends on the domain size of the amorphous texture that can be controlled by the cooling rate after the injection of the liquid crystals at a high temperature above the nematic-isotropic phase transition temperature (T
NI).
Low-Temperature Heat Capacity of Wurtzite-Type Boron Nitride*1
Authors: Yoshiasa Akira Inaba
Published: October 2002

The heat capacity for wurtzite-type BN has been determined between 50 and 300 K. The difference from that of zinc blende-type BN, which was also measured between 15 and 300 K, indicates that the interatomic force constants of the wurtzite-type lattice are generally 4% weaker than those of the zinc blende-type one. This result is compatible with the fact that sp3-bonded BN is elongated along a unique axis to form the hexagonal lattice.
Modeling and Simulation of a Large-Area Plasma Source
Authors: Lee Jae Koo , Meng Lin , Shin Young Kyo , Chung Hae June Lee
Published: October 2002

A variant of transformer-coupled plasma, suitable for processing a large-area flat panel with good uniformity, is examined using various models and simulations. Using two-dimensional and one-dimensional fluid simulations, we present the detailed profiles of the plasma density, potential, electron temperature, electric field structure, and ion current density at the substrate. The average values compare reasonably well with those of a global (volume-averaged) model.
Vaporization Behavior of Cs in Plasma Melting of Simulated Low Level Miscellaneous Solid Wastes
Authors: Yasui Shinji , Kazuo Adachi Kazuo Adachi , Tadashi Amakawa Tadashi Amakawa
Published: October 2002

A DC transfer type plasma with a maximum output of 60 kW was used to melt 10 kg of carbon steel and 3 kg of granular oxide mixtures ( Fe2O3, Al2O3, SiO2 and CaO) containing non-radioactive cesium nitrate, for measuring Cs vaporization. These materials are the main components of low level miscellaneous solid wastes. The vaporization rate constant values obtained by approximating Cs vaporization by a first order reaction rate formula were in the range of (4.01–7.1)×10-6 (m/s). The vaporization rate constant of Cs did not depend on the initial Cs content, and increased with the increase of slag basicity ( %CaO/%SiO2). Since the vaporization rate constant was unaffected by the viscosity of the slag on which the Cs transfer rate in the slag depends, the Cs vaporization phenomenon from the slag can be estimated to be controlled by the vaporization step from the slag surface.
X-Ray Diffraction and Scanning Electron Microscopy Observation of Lead Zirconate Titanate Thick Film Formed by Gas Deposition Method
Authors: Ichiki Masaaki , Akedo Jun , Andreas Schroth Andreas Schroth , Ryutaro Maeda Ryutaro Maeda , Yuichi Ishikawa Yuichi Ishikawa
Published: October 2002

A lead zirconate titanate ( Pb(Zr, Ti)O3, PZT) thick film was produced using the Jet Molding System which was
developed from a gas deposition method. Some of the characteristics of the deposited lead zirconate titanate were determined
by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The dielectric constant was determined to be
760 after 500° C and 10 min of heat treatment for nonpolarized sample. Through scanning electron microscope observation,
some properties of the deposition of ultrafine particles of PZT were determined. A joining of the deposited particles could be
observed, which means a kind of sintering was caused by the deposition process. Crystal structure analysis was carried out using
X-ray diffraction for structural comparison before and after deposition. The perovskite structure of PZT was proved to be retained during the deposition process.
Retention Characteristics of a Ferroelectric Memory Based on SrBi2(Ta, Nb)2O9
Authors: Shimada Yasuhiro , Azuma Masamichi , Nakao Keisaku , Chaya Shigeo , Moriwaki Nobuyuki , Tatsuo Otsuki Tatsuo Otsuki
Published: October 2002

The polarization decay process in SrBi2(Ta, Nb)2O9 capacitors and retention
characteristics of a 288-bit ferroelectric memory device fabricated from SrBi2(Ta, Nb)2O9 were
studied. The remanent polarization decay at room temperature showed good linearity when
plotted against logarithmic retention time over a wide range of 10-3–105 s. The distribution of
times to failure of a 288-bit memory was fit to a model having a linear relationship between
log
(log
t
f) and 1/T for the period of infant failures and to the Arrhenius model having the form
log
t
f vs 1/T for the period of random failures, where t
f is the time to failure and T is the
temperature. The activation energy was found to be 0.35 eV for infant failures and 1.15 eV for
random failures. Possible causes for the difference in activation energies are discussed.
Atomic Force Microscopy Observation of the Initial Growth Stage and the Ferroelectric Properties of Bi2VO5.5 Films on SrTiO3(100), Si(100) Substrates
Authors: Yanagita Takeshi , Hitoshi Tabata Hitoshi Tabata , Tomoji Kawai Tomoji Kawai
Published: October 2002

The initial growth mechanism of Bi2VO5.5 thin films on SrTiO3(100) has been studied
using atomic force microscopy (AFM), and c-axis oriented ultra-thin films have been
prepared by laser ablation. The Bi2VO5.5 films are constructed at various growth
temperatures. The films deposited at 500° C grow by the step-flow mode, whereas the
films deposited at 400° C grow by homogeneous nucleation. From these results, it is
evident that Bi2VO5.5 grows in multiples of 0.8 nm as complete molecular units and that
the top-most layer is Bi2O2. The dielectric constant of Bi2VO5.5 thin films formed on
Si(100) is about 35, and a C-V plot of a Bi2VO5.5-SiO2 MIS capacitor subjected to dc
polarizing voltages shows memory windows of 0.1 V against a ±2 V gate bias.
Effect of Laser Energy Density on the Fabrication of Ba2NaNb5O15 Thin Films by Pulsed Laser Ablation
Authors: Ando Shizutoshi , Konakahara Kaoru , Okamura Soichiro , Takeyo Tsukamoto Takeyo Tsukamoto
Published: October 2002

Ferroelectric thin films of barium sodium niobate, Ba2NaNb5O15 (BNN), were prepared on Pt
substrates by pulsed laser ablation at O2 gas pressures of 0.01 and 0.1 Torr. We examined the effect
of laser energy density on the fabrication of BNN thin films. The laser energy density was changed
from 1.67 J/cm2 to 5.0 J/cm2. On increasing laser energy density, the chemical composition of thin
films approached the BNN stoichiometry. Crystallinity of BNN thin films fabricated at higher laser
energy densities developed a tendency to orient along the c-axis. Thin films of BNN deposited at an
O2 gas pressure of 0.1 Torr and a laser energy density of 5.0 J/cm2 have a stoichiometoric
composition and a prominent c-axis orientation with a remanent plarization P
r of 0.8 µ C/cm2 and a
coercive field E
c of 24.0 kV/cm at room temperature.
Characterization of Defects in Li2B4O7 Crystals Grown by Czochralski and Bridgman Methods
Authors: Vezin Vincent , Sugawara Tamotsu , Ryuichi Komatsu Ryuichi Komatsu , Satoshi Uda Satoshi Uda
Published: October 2002

Lithium tetraborate ( Li2B4O7) has attracted much attention as a surface acoustic wave substrate
for high-frequency use and its excellent nonlinear optical properties have been recently found. In the
present report, the main crystalline defects observed by X-ray topography in Li2B4O7 (110) wafers
grown by the Bridgman method and by the Czochralski method are presented. The main trends
observed are a majority of dislocations in {112} planes, a minority of dislocations in the {111} planes,
and low-angle grain boundaries in both {111} and {112} planes.
Microstructure of Pb(Zr, Ti)O3-Based Pyroelectric Ceramics HIPped with Glass Encapsulation
Authors: Sugiyama Osamu , Saito Shozo , Kato Kazuaki , Osumi Shuzo , Murakami Kenji , Kaneko Shoji
Published: October 2002

The microstructure of the system Pb(Zr, Ti)O3–Pb(Mn1/3Nb2/3)O3 ceramics prepared by
the hot isostatic pressing (HIP) method was investigated in terms of chemical bonding, etching
behavior, and morphology for the elucidation of its pyroelectric characteristics. As a result,
the concept model proposed previously (Sugiyama et al..: J. Ceram. Soc. Jpn., 1996), in which
the pyroelectric characteristics were composed of the overall integration of those of the two
starting materials and their serial solid solutions, was partly supported.
Effect of A-Site Substitution and Firing Temperature on Microstructure and Electrical Properties of BaTiO3 Semiconducting Ceramics Fired by Reduction-Reoxidation Method
Authors: Osonoi Akihiro , Shinjiro Tashiro Shinjiro Tashiro , Hideji Igarashi Hideji Igarashi
Published: October 2002

The effects of A-site substitution and firing temperature on the
microstructure and electrical properties of BaTiO3 semiconducting ceramics
fired by the reduction-reoxidation method were experimentally investigated.
Ba ions were substituted with Ca or (Sr0.5Pb0.5). Various microstructures were
obtained by varying the firing temperature in reducing atmosphere. Using
these samples, the recovery of the characteristics of positive temperature
coefficient of resistivity (PTCR) was evaluated. In particular, the minimum
grain size required for the reoxidation of only grain boundaries during
annealing in oxygen atmosphere in the cooling process was investigated.
Piezoelectric Properties of PbNi1/3Nb2/3O3–PbTiO3–PbZrO3 Ceramics
Authors: Kondo Masao , Hida Masaharu , Tsukada Mineharu , Kazuaki Kurihara Kazuaki Kurihara , Nobuo Kamehara Nobuo Kamehara
Published: October 2002

The longitudinal electromechanical coupling factor (k
33) was investigated as a function
of PbNi1/3Nb2/3O3– PbTiO3–PbZrO3 (PNN-PT-PZ) piezoelectric ceramic compositions close to
the morphotropic phase boundary (MPB). The k
33 was influenced by the grain size of PNN-PT-PZ
ceramics. The composition of the MPB determined by k
33 is slightly different from
that of the free permittivity. The maximum value of k
33 in PNN-PT-PZ system attained to 0.8
on the composition of 0.5PNN-0.345PT-0.155PZ.
Relationship between Mechanical Loss and Phases of Physical Constants in Lead-Zirconate-Titanate Ceramics
Authors: Sasaki Yasuhiro , Hirose Sadayuki Takahashi
Published: October 2002

Mechanical loss in lead-zirconate-titanate (PZT) based piezoelectric ceramics was studied
by introducing three complex physical constants: a complex elastic, a dielectric, and a
piezoelectric constant. The elastic and dielectric losses had finite values, while the
piezoelectric loss was negligibly small. More than 60% of the mechanical loss at resonance
under a relatively low vibration-velocity was the elastic-origin component, and the rest was
the dielectric-origin component. The dielectric-origin component rose sharply, however, as the
vibration-velocity increased and became dominant at high vibration-velocity. The mechanical
loss was reduced by doping Fe2O3 into the PZT, which was apparently caused by pinning of
the ferroelectric domain wall.
Preparation and Piezoelectric Property of Lead Titanate Thin Films for GHz-Band Resonators
Authors: Yamada Akira , Maeda Chisako , Umemura Toshio , Uchikawa Fusaoki , Misu Koichiro , Wadaka Shusou , Ishikawa Takahide
Published: October 2002

Film bulk acoustic wave resonators (FBAWRs) at the GHz band were
successfully fabricated using piezoelectric lead titanate, PbTiO3 (PT) films on GaAs
substrates by a process similar to that used in microwave integrated circuit (MIC)
fabrication. PT films deposited on Pt/Ti bottom electrodes by RF magnetron
sputtering oriented preferentially along the <111> crystal direction. Resonances of
the bulk acoustic mode were observed around 1.9 GHz. The effective
electromechanical coupling coefficient (k

t

2) and electrical Q were estimated to be
∼9.4% and ∼65, respectively. The relationship between residual stress in the PT
films and Q was investigated. It was found that stress in the PT film exerted a large
influence on Q.
Liquid Viscosity Measurement Using Plate Mode Shear Horizontal Waves on a Piezoelectric Ceramic Thin Plate
Authors: Hiroshi Moritake Hiroshi Moritake , Masaru Inoue Masaru Inoue , Kohji Toda Kohji Toda
Published: October 2002

Numerical analysis results of the propagation characteristics of multiple mode shear horizontal (SH) waves along a piezoelectric ceramic thin plate with liquid loading on one of two boundary surfaces are described. The fractional phase velocity changes for S0, A0 and S1 mode SH waves have linear dependences on the square root of liquid viscosity under the electrically shorted boundary condition of both surfaces of the substrate. The mechanical displacement in the liquid layer decays exponentially with the distance from the substrate-liquid interface. The existing depth of the displacement in the liquid layer increases with liquid viscosity in the form of a linear relationship to the square root of liquid viscosity.
The measurement of liquid viscosity using two modes of SH waves is carried out. The measured results for water solutions of glycerol using S0 and A0 mode SH waves show linear dependences between the fractional velocity change and the square root of liquid viscosity, and are consistent with the theoretical values.
Passive Damping Performance of an Adaptive Carbon-Fiber Reinforced Plastics/Lead Zirconate Titanate Beam
Authors: Tanimoto Toshio , Horiuchi Kiyoshi , Uchino Kenji
Published: October 2002

Carbon fiber reinforced plastics (CFRP) are widely used as structural materials
in applications such as spacecraft structures. However, although they have a high
stiffness and low density, these materials are considered to be unsuitable for
low-vibration structures because of their inherent low vibration damping (loss factor
η=0.001–0.01). This study examines the passive damping of CFRP cantilever
beams using resistively shunted, surface-bonded piezoelectric ceramic,
PbZrO3–PbTiO3 (PZT) sheets. The vibration damping of the CFRP beam is significantly
improved at the optimal shunting resistance which can be predicted theoretically.
The first three vibration modes are most effectively damped by locating the PZT
elements in areas of maximum strain as determined by a modal analysis of the
beam.
Silicon Oxynitridation with Inductively Coupled Oxygen–Nitrogen Mixed Plasma
Authors: Tetsuya Ito Tetsuya Ito , Daisuke Kitayama Daisuke Kitayama , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Oxynitridation of Si was performed using an inductively coupled nitrogen and oxygen mixed plasma with and without substrate heating up to 300°C. Fairly good capacitance-voltage characteristics were obtained for the film grown with an O2 flow-rate ratio of 80% (O2:N2=8:2) with substrate heating at 200–300°C and post-thermal annealing at 500°C for 30 min in an oxygen ambient. The current-voltage characteristics showed that the Fowler-Nordheim tunneling current was the main leakage current mechanism and the barrier height was estimated to be about 2.02–2.14 eV with an effective electron mass of 0.42–0.5 m
0 (m
0: free electron mass). X-ray photoelectron spectroscopic measurements showed that the Si oxide (including Si suboxide) and Si oxynitride (Si2N2O)/Si nitride (Si3N4) were formed, respectively, at or near the top surface, and at the interface of the grown film and Si substrate, i.e., Si oxide/Si oxynitride-nitride mixture/Si layered structures were always obtained. The growth kinetics were also speculated on.
Dielectric Breakdown in Polycrystalline System
Authors: Tomoyuki Nagaya Tomoyuki Nagaya , Yoshihiro Ishibashi Yoshihiro Ishibashi
Published: October 2002

The capacitance and the dielectric breakdown voltage in a polycrystalline system are investigated by adopting the Voronoi network model. In the present model the grain and the grain boundary are regarded as a perfect conductor and a capacitor, respectively. It is found that the capacitance of the system scales as C∼N
-1/2∼ξ, where N and ξ are the number of grains and the mean linear size of grains, respectively.
The distribution function of the breakdown voltage obtained in the simulation has the same functional form as the Duxbury form which describes the distribution of the breakdown voltage in the percolation model.
The relations among the breakdown voltage, the number of grains and the mean grain size are clarified.
Surface and Domain Structure of Pure PbTiO3, Mn-doped PbTiO3 and Pb(Zn1/2Nb1/2)0.91Ti0.09O3 Single Crystals by Atomic Force Microscopy
Authors: Yamamoto Takashi , Kawano Kenrou , Mitsuru Saito Mitsuru Saito , Shinobu Omika Shinobu Omika
Published: October 2002

Nanometer scale surface morphologies in pure PbTiO3, Mn-doped PbTiO3 and Pb(Zn1/2Nb1/2)0.91Ti0.09O3 single crystals prepared
by the flux method have been investigated by atomic force microscopy and discussed in connection with 90° and 180° domains.
Regular gradiants with angles of 3.4° to 3.6° at the domain boundary were measured on the (001) surface in as-grown crystals
with so-called typical 90° a-c domains. The angle of the gradiant is controlled by the crystal tetragonality ( c/a)
in the crystal and is 3.4° to 3.6° in pure PbTiO3 and Mn-doped PbTiO3 with c/a=1.063, and 0.5° to
0.8° in Pb(Zn1/2Nb1/2)0.91Ti0.09O3 with c/a=1.004. In pure PbTiO3 and Mn-doped PbTiO3,
the 180° c-c domains are constructed from the trapezoidal form with a step of 80 to 100 nm and confirmed by electric potential
measurements using Kelvin force microscopy.
Crystal Structure of the Metastable State of Ferroelectric Lead Germanate
Authors: Jun Hatano Jun Hatano , Tatsuya Kojima Tatsuya Kojima , Yoshio Matsui Yoshio Matsui , Yoichi Ishida Yoichi Ishida , Hiroyuki Uehara Hiroyuki Uehara , Koichiro Takahashi Koichiro Takahashi , Yutaka Adachi Yutaka Adachi
Published: October 2002

The crystal structure of the metastable state of ferroelectric lead germanate, Pb5Ge3O11, was investigated by high resolution transmission electron microscopy (HRTEM). It was concluded that the crystal structure of the metastable state is a result of the random piling up of isolated oxygen tetrahedra, GeO4, and double tetrahedra, Ge2O7, in layers perpendicular to the c-axis. Stacking faults between the layers with a relative shift parallel to them are included randomly in the structure.
Influence of Crystal-Originated “Particle” Microstructure on Silicon Wafers on Gate Oxide Integrity
Authors: Miyazaki Morimasa , Miyazaki Sumio , Kitamura Takafumi , Yanase Yoshio , Takashi Ochiai Takashi Ochiai , Hideki Tsuya Hideki Tsuya
Published: October 2002

To clarify the influence of crystal-originated “particles” (COPs) on gate oxide integrity (GOI), a new GOI evaluation method has been developed. This method compares the GOI of a metal oxide silicon (MOS) capacitor which includes a COP with a MOS capacitor that is COP-free by measuring the capacitors' I–V characteristics. Furthermore, to study the relationship between the shape of COP and GOI, the COP microstructure on the wafers was observed by atomic force microscopy (AFM) in the as-received state, after NH4OH/H2O2/H2O (SC-1) cleaning, high temperature annealing and repolishing. It was found that the presence of COP was the main cause of GOI failure and also that the shape of COP was closely related to the GOI yield. The microstructure of the original COP in a crystal is concluded to be an octahedral void and the same as an IR scattering defect.
High-sensitivity Defect Evaluation by a New Preferential Etching Technique for Highly As-doped Si Crystals
Authors: Majima Masaki , Takao Otogawa Takao Otogawa , Yutaka Kitagawara Yutaka Kitagawara
Published: October 2002

A high-sensitivity preferential etching technique is presented to evaluate crystal defects in a highly As-doped silicon crystal with a resistivity lower than 0.01 Ω· cm. For highly doped n-type Si, a conventional preferential etching technique, such as Secco etching, Wright etching or Dash etching becomes less useful because of a significant decrease in defect detection sensitivity. The new method is quite sensitive to dislocations, stacking faults and oxygen precipitates in highly As-doped crystals with a surface of either (111) or (100). In this method, copper is first decorated at the defect site, then the defect is preferentially etched by a dilute alkaline solution. The technique thus offers us a sensitive and Cr-free method, attractive from an environmental aspect. A correlation between the laser scattering method is also obtained for the oxygen precipitate density.
Transmission Electron Microscopy Observation of CoSix Spikes in Si Substrates during Co-silicidation Process
Authors: Sukegawa Takae , Tomita Hirofumi , Fushida Atsuo , Goto Kenichi , Komiya Satoshi , Nakamura Tomoji
Published: October 2002

Needle-like spikes penetrating into Si substrates have been detected by cross-sectional transmission electron microscopy (TEM) studies of Co silicide/Si interfaces. The spikes are crystalline CoSi

x

and form at annealing temperatures of 400–425° C, when the transformations of Co→Co2Si and Co2Si→CoSi are both taking place. They sometimes extend to the p/n junction depth of 100 nm. During annealing at above 500° C, they become spherical and their density decreases. The temperature range in which CoSi

x

spikes are formed and extend to near the junction depth corresponds well with that for the onset of junction leakage. Therefore, this supports the conclusion that Co silicide junction leakage is caused by such spike formation.
Effects of Overcoat Materials on the Magnetic Properties of CoNi Alloy Heat-Treated Media
Authors: Motoharu Sato Motoharu Sato
Published: October 2002

The effects of overcoat materials such as C and Zr on magnetic properties of CoNi alloy heat-treated media were investigated. In the case of a C overcoat, coercivity decreased with an increasing heat treatment temperature because of the formation of Cr3C2 compounds at the interface between the CoNi alloy magnetic layer and the Cr underlayer, and the diffusion of C into the CoNi alloy magnetic layer. However, in the case of a Zr overcoat, coercivity increased with an increasing heat treatment temperature because of the diffusion of Cr from the Cr underlayer into the grain boundaries of the CoNi alloy magnetic layer. From the composition analysis of the heat-treated media, it is determined that coercivity increases with an increasing heat treatment temperature, if the nondiffusive element, which does not diffuse into the CoNi alloy magnetic layer, is used as the overcoat material for the heat-treated media.
Second-Harmonic Generation in C70 Film
Authors: Hoshi Hajime , Manaka Takaaki , Ken Ishikawa Ken Ishikawa , Hideo Takezoe Hideo Takezoe
Published: October 2002

Second-harmonic generation (SHG) spectrum was observed in a vacuum deposited C70 film. A remarkable resonant peak was observed at an SH energy of about 2.36 eV. The spectral feature was well described by the valence effective Hamiltonian theory under a magnetic dipole coupling mechanism. Possible assignment for the resonance was discussed.
Self-aligned TiN Formation by N2 Plasma Bias Treatment of TiSi2 Deposited by Selective Chemical Vapor Deposition
Authors: Kazuyoshi Kamoshida Kazuyoshi Kamoshida , Kunio Saito Kunio Saito
Published: October 2002

The titanium nitride (TiN) formation technology described here uses nitrogen plasma bias treatment to form self-aligned TiN only on the diffused layer from titanium silicide ( TiSi2) prepared by selective chemical vapor deposition (CVD). The nitriding was performed using magnetron sputtering equipment with an rf plasma source. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and etching in 1% HF were used to characterize the samples. The contacts fabricated with the Al-2%Si/TiN/TiSi2/Si barrier technology exhibit low resistivities of about 10-7 Ω·cm2. No excessive leakage of the 0.2-µm shallow junctions was observed even after thermally stressing the samples at 500°C for 30 min.
Sintering and Electrical Properties of (CeO2)0.9(Gd2O3)0.1 Powders Prepared by Glycine-Nitrate Process for Solid Oxide Fuel Cell Applications
Authors: Park In-Sik , Kim Sun-Jae , Byung-Ha Lee Byung-Ha Lee , Sung Park Sung Park
Published: October 2002

Doped CeO2–(CeO2)0.9(Gd2O3)0.1 pellets were prepared using the glycine-nitrate process with various sintering times and sintering temperatures. Compositional and structural characterizations were carried out using X-ray diffraction (XRD) with CuKα radiation, a scanning electron microscope (SEM) and a Transmission electron microscope (TEM). Sintering and electrical characteristics were investigated using dilatometer measurement and the AC impedance analyser. Powder characteristics were also investigated by the BET method. Polycrystalline (CeO2)0.9(Gd2O3)0.1 powders with specific surface areas of 19–23 m2/ g were obtained. Green bodies from the synthesized powders after milling shrunk up to about 1470° C, above which they expanded with heating temperature, whereas those before milling shrank continuously up to a temperature of 1600° C. This difference might be attributed to the change of the packing density of the synthesized powders upon milling: from 25% without milling to about 40% after milling. Therefore the sintered (CeO2)0.9(Gd2O3)0.1 bodies having a theoretical density of 7.25 g/cm3 were considered to be obtained from the as-milled powders by controlling the sintering time at a sintering temperature higher than 1470° C in air. In the AC impedance measurements, the electrical resistivity of the (CeO2)0.9–(Gd2O3)0.1 bodies, produced from as-milled powders, and sintered at 1500° C with increasing sintering time, showed the minimum total value at the sintering time of 10 h. The minimum total resistivity of the (CeO2)0.9(Gd2O3)0.1 bodies sintered at 1500° C for 10 h seems to be obtained when the sum of the activation energy for the resistivities in the grain and at the grain boundary.
Origin of Helix in Achiral Banana-Shaped Molecular Systems
Authors: Sekine Tomoko , Niori Teruki , Sone Masato , Watanabe Junji , Choi Suk-Won , Takanishi Yoichi , Takezoe Hideo
Published: October 2002

Helical structures were confirmed for both the SmA
b
and SmBlue phases of banana-shaped molecular systems from observations of the microscopic fringe pattern and the selective reflection of blue color, respectively. X-ray and optical microscopy indicate that the helical axes in the SmA
b
and SmBlue phases are normal and parallel to the smectic layer, respectively. In these two helical phases, 13C NMR spectra show two C=O peaks, suggesting two different configurations of ester group, whereas only one C=O peak appears in the isotropic and crystal phases. This indicates that the two C=O groups in the mesogenic core are not in the same plane but are twisted. The addition of chiral dopant makes the dichroic ratio of the right- and left-circularly polarized scattered light positive or negative in the SmBlue phase, although the wavelength (∼430 nm) of the scattering peak does not change significantly. The origin of the helix will be discussed in view of the twisted molecular conformation (conformational chirality) and the escape from macroscopic polarization.
Photoregulated Liquid Crystal Alignment on Photoreactive Side-Chain Liquid-Crystalline Polymer
Authors: Kawatsuki Nobuhiro , Takatsuka Hirohumi , Ono Tohei Yamamoto
Published: October 2002

We describe the anisotropic photoreaction of photoreactive side-chain liquid-crystalline polymers (SLCPs), containing biphenyl mesogen and photoreactive cinnamoyl group, by irradiation with a linearly polarized (LP) UV light, and the alignment behavior of the low-molecular-weight (LMW) liquid crystal (LC) on them. The photo-crosslinked SLCP thin film photoreacted at room temperature showed very small negative dichroism, while that photoreacted in the LC temperature range of the film exhibited positive dichroism. The photoreacted SLCP film can align LMW-LC director \tilden both parallel and perpendicular to the incident \hatE vector of the LP-UV light. The alignment direction of the LMW-LC was controlled by the amount of photoreaction of the cinnamoyl group.
1.5 V Low-Voltage Microwave Power Performance of InAlAs/InGaAs Double Heterojunction Bipolar Transistors
Authors: Iwai Taisuke , Shigematsu Hisao , Yamada Hiroshi , Tomioka Takeshi , Kazukiyo Joshin Kazukiyo Joshin , Toshio Fujii Toshio Fujii
Published: October 2002

In this paper, we report the first demonstration of microwave power performance of InAlAs/InGaAs double heterojunction bipolar transistors (DHBTs) obtained at an extremely low operating voltage of 1.5 V. In order to obtain a high output power (P
out) at a low operating voltage, we used DHBTs rather than single heterojunction bipolar transistors (SHBTs) and thus reduced the offset voltage (V
CE,offset). We obtained a much lower V
CE,offset of 50 mV for the DHBT than that of 300 mV for a SHBT. At a low operation voltage of 1.5 V, the DHBT exhibited a P
out of 20.6 dBm with a power added efficiency (η add) of 36.6% and a power gain (G
a) of 8.5 dB biased for class-B operation at 1.9 GHz. The high-speed performance of the DHBT are a unity cutoff frequency (f
T) of 76 GHz and a maximum oscillation frequency (f
max) of 157 GHz. We also studied the reliability of DHBTs by conducting a 1000-hour accelerated life test. The InGaAs HBTs had a lifetime of 2×106 h at a junction temperature of 125°C with an activation energy of 0.95 eV.
Wave Motions in an Effective Chiral Composite: Dispersion Equations and Elastic Moduli
Authors: Hsia Shiuh-Kuang Yang
Published: October 2002

In this study, we investigate elastic wave propagation in an effective chiral (isotropic, noncentrosymmetric) composite. This composite is constructed by embedding the structural chiral microstructures or springs in a host medium. To ensure that the chiral effect can be found in the samples, a hypothesis about the material constants to characterize the effective chiral composites is proposed herein. Such a material is mirror asymmetric or chiral; therefore, six independent wave numbers can be found. Two of the wave numbers represent nondispersive longitudinal fields, the remaining four are dispersive circularity polarized transverse fields. According to the dispersion equations, two transition frequencies (90 Hz and 12 kHz) divide the frequency response of the transverse wave numbers into three different groups and the four transverse modes can only be distinguished in a specified frequency range. The above observation may account for why the microstructural size of the chiral composite should be sufficiently larger than the transverse wavelength so that an incident elastic shear wave can sense its chirality while the microstructural size should be adequately small that the composite is effectively chiral.
Growth and Characterization of Ferroelectric Pb(Zr, Ti)O3 Films on Interface-Controlled CeO2(111)/Si(111) Structures
Authors: Lee Myung Bok , Ohnishi Tsuyoshi , Maeda Tatsuro , Kawasaki Masashi , Mamoru Yoshimoto Mamoru Yoshimoto , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

Pb(Zr0.52Ti0.48)O3(PZT)/CeO2 films were grown on Si(111) substrates by the pulsed laser deposition method. Room-temperature (20° C) deposition of the CeO2 film on a hydrogen-terminated Si surface resulted in a sharp hetero-interface with no amorphous transition layer. PZT films were grown on the CeO2 layer in {101} orientation with in-plane three directions at substrate temperatures higher than 450° C. An Al/PZT(80 nm)/CeO2(24 nm)/Si structure showed a threshold voltage shift as large as 1.6 V (when bias voltage was 3 V) in a capacitance–voltage ( C–V ) curve due to the surface charges induced by ferroelectric polarization of the PZT film.
Non-Contact and Non-Destructive Measurement of Carrier Concentration of Nitrogen-Doped ZnSe by Reflectance Difference Spectroscopy
Authors: Jin Cheng-Guo , Yasuda Tetsuji , Kimura Kozo , Ohtake Akihiro , Kuo Li-Hsin , Wang Tai-Hong , Miwa Shiro , Yao Takafumi , Tanaka Kazunobu
Published: October 2002

We report an optical technique to determine the net carrier concentration of nitrogen-doped ZnSe, N
a-N
d. An optical anisotropy induced by the built-in field was measured by reflectance difference spectroscopy (RDS). It has been shown that the energy derivative of the RD signal near 5 eV is proportional to (N
a-N
d)1/3 when N
a-N
d>5×1016 cm-3. The physical origin of the observed power law is discussed. We also address the origin of the surface roughness induced baseline in the RD spectra which affects the accuracy of the measurement.
Coulomb Blockade in a Laterally-Confined Double-Barrier Heterostructure with a Doped, Wide Well
Authors: Pawel J. A. Piotrowicz Pawel J. A. Piotrowicz , John R. A. Cleaver John R. A. Cleaver
Published: October 2002

Coulomb Blockade has been observed in a laterally-confined double-barrier heterostructure with a doped, wide well. The large-area characteristics exhibit only weak resonances, with no threshold voltage. When the device is laterally confined a plateau in I–V develops about zero bias, with weak structure either side. As the barriers are symmetric, no clear Coulomb Staircase is observed.
An Approach to Study Band-gap and Interface States in a-Si:H p-i-n Solar Cells
Authors: Viresh Dutta Viresh Dutta , R. V. R. Murthy R. V. R. Murthy
Published: October 2002

The defect states in bulk of i-layer and at p/i interface and their energy locations in a-Si:H p-i-n solar cells have been studied by using dark reverse current–voltage ( J–V ), capacitance–voltage–temperature–frequency (C–V–T–ω) and deep level transient spectroscopy (DLTS) measurements. The dark reverse currents as a function of voltage have been analyzed on the basis of thermal generation of the carriers. In current–voltage characteristics, it has been observed that at low reverse voltages (V<5 V) the defect states in the bulk of the i-layer and at high reverse voltages (V∼24 V) the defect states at p/i interface are contributing to the reverse current. Reverse bias annealing (RBA) treatment has been performed on these cells. It has been observed that RBA reduces the defect states more in the i-region near to the p-layer and at the p/i interface as compared to the deep regions in the bulk of i-layer. The calculated defect state density (DOS) is varying from its intrinsic value of 4.8×1016 cm-3 in the bulk of i-layer upto 1.8×1018 cm-3 near and at p/i interface. These values decrease to 1.8×1016 cm-3 and 6.6×1016 cm-3, respectively, in the samples annealed under reverse bias at 2 V. The capacitance as a function of temperature under fixed voltage of 0.5 V and frequency of 100 Hz is divided into three regions depend on the capacitance behavior. The RBA treatment has showed prominent changes only in the third region (T>350 K) which is due to the defects at p/i interface. The DOS in the bulk of i-layer and at p/i interface have been determined. The hole and electron trap states densities have been estimated to be 1.8×1016 eV-1 cm-3 and 1.6×1016 eV-1 cm-3, respectively, at 0.8 eV and 1.12 eV above the valence band from the DLTS measurements. The existence of interface states at 0.55 eV and 1.2 eV above the valence band, respectively, for p/i and i/n interfaces have also been observed. A good correlation has been observed in DOS estimation and their affect by RBA treatment in all the studies.
Heterojunction Bipolar Transistor with an Additional Minority Carrier Reflection Barrier in the Emitter
Authors: Eng Fong Chor Eng Fong Chor , Cai Jun Peng Cai Jun Peng
Published: October 2002

A heterojunction bipolar transistor (HBT) structure that provides an additional minority carrier reflection/confinement barrier within the quasi-neutral emitter region has been proposed and investigated by means of numerical simulations. The proposed device structure has been demonstrated to perform better than conventional HBTs–a higher current gain with better uniformity, which has been achieved without affecting the high frequency performance. In addition, the current gain was found to be relatively insensitive to temperature changes in the range of 250 K to 450 K, thus making the new device structure more suitable for high power applications.
Laser-Induced Reversion of Photodarkening in CdS-Doped Glass
Authors: Tadaki Miyoshi Tadaki Miyoshi , Koji Nitta Koji Nitta , Hiroyuki Ohkuni Hiroyuki Ohkuni , Fumihiko Ikeda Fumihiko Ikeda , Naoto Matsuo Naoto Matsuo
Published: October 2002

The effect of laser irradiation on photodarkened CdS-doped glass has been investigated as a function of the wavelength of laser light, using electron spin resonance (ESR) and time-resolved luminescence. When the wavelength of laser light is tuned to 500 nm, the intensity of the ESR signal associated with photodarkening decreases, as does the decay rate of luminescence. This indicates laser-induced reversion of photodarkening.
The Effect of Hydrogen on Refractive Index Profiles of Annealed Proton-Exchanged Z-Cut LiNbO3
Authors: Shen Chi-Yen , Shuming Tong Wang Shuming Tong Wang , Ren-Chang Chu Ren-Chang Chu
Published: October 2002

The effect of hydrogen ions ( H+) diffusion on refractive index profiles of annealed proton-exchanged z-cut LiNbO3 waveguides was investigated in this paper. The proton-exchanged samples were proton exchanged in phenylacetic acid and annealed in air at the temperature of 380° C to 420° C for 2 to 6 h. Optical prism-coupling measurements and numerical methods are performed to assess the refractive index profiles of the samples. Two kinds of diffusivities, i.e. substitutional and interstitial, were adopted to account for the extraordinary refractive index profile. The experimental data obtained from infrared spectroscopy and the calculated substitutional indices diffusant indicated that the annealing process resulted in the migration of free OH groups to the surface of the proton-exchange region. These subsequently turned into surface oxides and water.
KrF-Excimer-Laser Induced Absorption in Synthetic Fused Silica
Authors: Naoyoshi Kamisugi Naoyoshi Kamisugi , Nobu Kuzuu Nobu Kuzuu , Yoshinao Ihara Yoshinao Ihara , Takayuki Nakamura Takayuki Nakamura
Published: October 2002

KrF-excimer-laser (5.0 eV) induced absorption in synthetic fused silica synthesized by flame hydrolysis of SiCl4 (type-III-fused silica) was measured. Induced absorption is a Gaussian absorption band peaking at 5.8 eV, which is different from that of ArF-excimer-laser induced absorption consisting of five absorption bands at 6.5, 5,8, 5.4, 5.0 and 4.8 eV. Peak intensities of the absorption band decrease with increasing OH content. When the OH content exceeds ≈1000 ppm in mass, the internal absorption at 5.0 eV approach a constant value ≈1 ×10-4 cm-1
Effect of Microwave Pulse on the Optical Properties of Hydrogenated Amorphous Silicon Thin Films Deposited by Electron Cyclotron Resonance Plasma
Authors: Lee Ju-Hyeon , Jung Il-Chae , Park Sang-Kook , Park Cheong-A Baek
Published: October 2002

Hydrogenated amorphous silicon(a-Si:H) thin films have been prepared by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. A pulse of 27.5 kHz was applied to the microwave power of the ECR PECVD during deposition. It was found that the pulse changed the total hydrogen content, its bonding configuration, substrate temperature, and the optical properties such as the refractive index (n), absorption coefficient (α) and the optical energy band gap. Using the present method, better quality a-Si:H films have been obtained as compared to those obtained by the conventional ECR PECVD method. It is ascertained that the properties of these films are good enough for device application even though the films are deposited without the intentional heating of the substrate. The results show the possibility of using plastic substrates for devices such as thin film transistor-liquid crystal displays.
Dielectric Properties of Pb(Zr,Ti)O 3 Heterolayered Films Prepared by Sol–Gel Method
Authors: Lee Sung-Gap , Park In-Gil , Bae Seon-Gi , Lee Young-Hie
Published: October 2002

Ferroelectric Pb(Zr,Ti)O3 (PZT) heterolayered thin films were fabricated by the alkoxide-based sol–gel method. PZT (20/80) and PZT (80/20) stock solutions were made and alternately spin-coated on the Pt/Ti/SiO2/Si substrate. Each layer was dried at 300°C for 30 min and sintered at 650°C for 1 h. The coating and heating procedure was repeated 6 times to form heterolayered films. PZT film thickness, obtained by one cycle of drying/sintering, was approximately 80 nm. The PZT heterolayered films showed dense and fine grain structures with a grain size of less than 0.2 µm. The relative dielectric constant and the dielectric loss of the 6-coated PZT heterolayered film(PZT-6) were approximately 1385 and 3.3%, respectively. As the number of coatings increased, remanent polarization increased, the coercive field decreased and the values for the PZT-6 film were 8.13 µC/cm2 and 12.5 kV/cm, respectively. The leakage current density of the PZT-6 film at 5 V was 8.8 ×10-13 A/cm2.
Preparation and Electrical Properties of Sol–Gel Derived Lead Zirconate Titanate Glass-Ceramic Thin Films on Metal Foil Substrates
Authors: Kunio Saegusa Kunio Saegusa
Published: October 2002

Thin film capacitors were prepared by depositing 0.835PbZr0.5Ti0.5O3 (PZT)–0.165(3PbO·SiO2·B2O3) glass-ceramic thin films of 0.5 to 1 µ m thickness on aluminum, titanium and stainless steel foils (0.05–0.2 mm thick) using a sol–gel process followed by firing at temperatures around 600° C. Materials suitable fot the composition of thin film capacitor included gold or nickel for the top electrode and Ti or Al foils for the substrate. The dielectric properties of the capacitors depended on the substrate materials. A relatively high capacitance (ε=300) with a high dielectric loss (tan
δ=5%) capacitor was obtained with the Ti foil, and a relatively low capacitance (ε=64) with a low dielectric loss (tan
δ=0.9%) capacitor was obtained with the Al foil. Excellent ultra-high frequency properties were shown in the case of Al foil capacitor.
Resonant Mode Characteristics of a Magnetostatic Resonator in Yttrium Iron Garnet (YIG) Films
Authors: Yan Hua , Awai Ikuo , Junji Yamagata Junji Yamagata , Qi Wang Qi Wang
Published: October 2002

In this paper, the performance of a magnetostatic surface wave straight edge resonator (MSSW-SER) is extensively studied, including the mode field distribution, the unloaded quality factor of the fundamental mode and coupling to the external circuit. Measurement of the magnetic field distribution on a MSSW-SER is found to be useful for identifying the mode number. The unloaded Q-value of the fundamental mode, which includes magnetic loss and conductor loss, and also the external Q are measured to give design data for tunable band-pass filters. Moreover, an equivalent circuit is set up to analyze the external Q, and verified by experiment. Under higher power excitation, a novel performance of the MSSW-SER is found in YIG films, that is, the resonant frequency shifts to the lower side and the unloaded quality factor tends to decrease. These phenomena caused by the nonlinear effect of a MSSW-SER are analyzed by means of the nonlinear MSSW dispersion relation. The above methods can be easily extended to study two other modes, magnetostatic forward volume wave (MSFVW) and magnetostatic backward volume wave (MSBVW) resonators.
Origin of (111) Twin Lamellae in BaTiO3 Thin Films on Platinum Substrates
Authors: Jang Jin Wook , Cho Woon Jo , Lee Jong Ho , Sang Sam Choi Sang Sam Choi , Taek Sang Hahn Taek Sang Hahn
Published: October 2002

The formation mechanisms of (111) twin lamellae in BaTiO3 thin films were examined using transmission electron microscopy. The voids in thin films were connected with (111) twin lamellae. These voids were formed due to the incomplete coalescence of islands, and it was found that (111) twin lamellae were produced in order to accommodate the small misfit between the growing islands during contact. With respect to planar defects, the cause of the formation of (111) twin lamellae could be explained by the maintenance of a TiO6 octahedron and the relationship with a hexagonal BaTiO3 structure. It could be understood that the very narrow width of the twin lamellae is due to the contact process of two growing islands as well as the very small grain size of thin films.