bluuebunny/crossref_metadata_2025 huggingface dataset:
Wavelength Router Using Bridged Planar Spectrographs
Authors: Okayama Hideaki , Kobayashi Masato , Xu Chang-Qing , Takemasa Keizo , Kamijoh Takeshi
Published: October 2002

We propose a device which has the same wavelength routing function as a conventional
arrayed-waveguide-grating and consists of two planar waveguide spectrographs connected by
waveguide array of equal-length. We fabricate the device using compound semiconductor for future
integration of many functions. The fabricated device shows a filter width of 1.7 nm and a sidelobe
level of -8 dB which is limited by the power distribution in the waveguide array. A device using the
whispering gallery mode is also demonstrated. The whispering gallery mode is expected to reduce
the phase error. The sidelobe level is reduced by over 5 dB as compared to a device using the
conventional channel waveguide. Finally, a design for compensating the effect of the radius of
curvature on the propagation constant is proposed.
Chlorine-Based Dry Etching of III/V Compound Semiconductors for Optoelectronic Application
Authors: Asakawa Kiyoshi , Yoshikawa Takashi , Kohmoto Shigeru , Nambu Yoshihiro , Sugimoto Yoshimasa
Published: October 2002

Chlorine-based dry etching of III/V compound semiconductors for optoelectronic applications has been reviewed. The advantages of the ultrahigh-vacuum (UHV)-based electron cyclotron resonance (ECR)-plasma reactive ion beam etching (RIBE) over conventional RF-plasma reactive ion etching (RIE) were emphasized as the capability to use carbon-free, chlorine (Cl2) gas plasmas, controllability of ion energies and compatibility with other UHV-based chambers such as a molecular beam epitaxy (MBE) chamber. The RIBE technique was shown to exhibit excellent laser diode performances, such as extremely low threshold-current, high polarization-controllability and a lifetime of more than 3000 h for structures with more than 1-µm-wide etched-mesa width. The degree of etching-induced damage was evaluated in terms of the nonradiative surface recombination velocitySrand the possibilities of practical applications of the dry-etched devices were discussed using theSrvalues.
A Scanning Tunneling Microscopy Investigation of Adsorption and Clustering of Potassium on the Si(111)7×7 Surface
Authors: Akihiko Watanabe Akihiko Watanabe , Masamichi Naitoh Masamichi Naitoh , Satoshi Nishigaki Satoshi Nishigaki
Published: October 2002

The adsorption process of potassium on the Si(111)7×7 surface is studied by scanning tunneling microscopy (STM).
At low coverages, an STM image reveals that potassium (K) atoms adsorb preferentially on the faulted-halves of the 7×7 unit cells rather ionically so that they do not appear in the filled-state image but present bright images in the empty-state mode.
The coverage at which both the faulted and the unfaulted regions are uniformly occupied by K is estimated to be about 6/49.
At coverages higher than this, the K atoms tend to form neutral clusters, preferentially in the faulted-regions.
The electronic structure around the clusters is modified markedly, which suggests a local charge redistribution.
Effects of Helicon-Wave-Plasma Etching on the Charging Damage of Aluminum Interconnects
Authors: Lin Wendy , Kang Tzong-Kuei , Perng Yean-Chyi , Dai Bau-Tong , Cheng Huang-Chung
Published: October 2002

The etching parameters of aluminum in the helicon wave plasma are characterized
to elucidate the mechanism of charging damage. By increasing the ion energy and
decreasing the plasma density via increase of the bias power and decrease of the source
power, respectively, we can significantly reduce charging damage. On the basis of this
concept, we develop a two-step etching technique to suppress the charging damage
without selectivity loss. Such a high-density plasma etching technique will be very
suitable for the formation of high-density, and narrow-line interconnects.
Defects in Ion Implanted Hg0.78Cd0.22Te Probed by Monoenergetic Positron Beams
Authors: Akira Uedono Akira Uedono , Hiroji Ebe Hiroji Ebe , Masahiro Tanaka Masahiro Tanaka , Ryoichi Suzuki Ryoichi Suzuki , Toshiyuki Ohdaira Toshiyuki Ohdaira , Shoichiro Tanigawa Shoichiro Tanigawa , Tomohisa Mikado Tomohisa Mikado , Kosaku Yamamoto Kosaku Yamamoto , Yoshihiro Miyamoto Yoshihiro Miyamoto
Published: October 2002

Defects and their annealing properties in ion implanted
Hg0.78Cd0.22Te were studied using monoenergetic positron beams.
Vacancy-type defects introduced by B+-implantation were
identified as open spaces associated with extended defects
such as dislocation loops and stacking faults. For an
Ar+-implanted specimen, the mean size of the open volume of
defects in the damaged region was estimated to be that of
divacancies. The observed difference between the species of
defects in the B+- and the Ar+-implanted specimens was
attributed to the suppression of the recombination between
vacancies and interstitials in the damaged region introduced
by Ar+-implantation. The annealing temperature of the
vacancy-type defects introduced by Ar+-implantation was determined to
be 300°C.
Spin Configuration of a Circular Quantum Dot in a Magnetic Field
Authors: Zhong Wang Zhong Wang , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

In this paper, we present an approach for modeling the spin configuration of a two-dimensional circular quantum dot in a magnetic field based on the interacting Green's functions on a tight-binding basis, where the electron-electron interaction is represented by the retarded self-energy. The quantum dot is composed of a circular lattice of tight-binding sites and has a cylindrically symmetric electrostatic confinement approximated by a harmonic potential. Using this approach, we were able to obtain the single electron energy spectrum and the spin state as a function of magnetic field up to the twentieth level.
We found that the shell structure in energy spectrum appears not only at zero magnetic field but also at a specific moderate magnetic field. The fine structures of energy levels in the shell are well identified by evaluating the mean radius of eigenfunction. At a strong magnetic field, we found that complete spin polarization progresses from lower level to higher level with the magnetic field. The subsequent state transition and the fine structures in energy levels are made clear as a function of magnetic field.
Effect of Strong Borrmann Absorption on X-Ray Fluorescence Yield Curves
Authors: Riichirou Negishi Riichirou Negishi , Tomoe Fukamachi Tomoe Fukamachi , Zhangcheng Xu Zhangcheng Xu , Masami Yoshizawa Masami Yoshizawa , Isao Matsumoto Isao Matsumoto , Takaaki Kawamura Takaaki Kawamura , Tetsuo Nakajima Tetsuo Nakajima
Published: October 2002

The Ga K X-ray fluorescence yield from GaAs was measured around the 200 reflection peak in the symmetric Laue case, by tuning the incident X-ray energy from a synchrotron radiation source between the K-absorption edges of Ga and As.
It was found that the fluorescence yields from the crystal surface become minimum at the exact Bragg angle, when the diffraction is induced only by χ
h
i
, i.e., the imaginary part of the Fourier coefficient of the X-ray polarizability (χ
h
r
being the real part).
In the case of |χ
h
r
|=|χ
h
i
|, which occurs at two energy points, both yield curves are asymmetrical with respect to the exact Bragg angle and their asymmetries are opposite to each other.
Feasibility of Microelectronic Quartz Temperature and Pressure Sensors
Authors: Poplavko Yuri M. , Pereverzeva Larissa P. , Cho Nam-Ihn , You Young Soo , Nam Hyoung Gin
Published: October 2002

Under the non-isotropic boundary conditions, piezoelectric quartz crystal discovers
electrical response on scalar actions, the same as pyroelectric crystal. Thus, uniform
change of temperature causes a secondary-type artificial pyroelectricity, while
hydrodynamic change of pressure gives rise to a volumetric piezoelectric effect. Quartz
voltage responsivity and figure of merit are of the same values of magnitude as in
conventional pyroelectrics. Quartz type piezoelectric crystals, with their excellent
mechanical, chemical, thermal and electrical properties, extend the number of pyroelectric
materials and possibilities of their application.
Copper Oxide Thin Films Prepared from Copper Dipivaloylmethanate and Oxygen by Chemical Vapor Deposition
Authors: Maruyama Toshiro
Published: October 2002

Polycrystalline copper oxide thin films have been prepared from copper
dipivaloylmethanate and oxygen by an atmospheric-pressure chemical vapor deposition
method at a reaction temperature of 300°C. The deposition at oxygen partial pressure
(p
0) ≦2.13 kPa forms single-phase Cu2O with [100] oriented polycrystalline structure,
in which Cu+ is partially substituted by Cu2+ in proportion to the increase in oxygen
partial pressure from 1.06 kPa. The optical energy gap decreases from 2.5 to 1.8 eV with
the increasing Cu2+ fraction in the film. At p
0 ≧2.48 kPa, the crystalline CuO is formed
with nonoriented crystalline Cu2O. The content of the CuO phase markedly increase with increasing oxygen partial pressure.
Structure Analysis of SrTiO3 (111) Polar Surfaces
Authors: Sekiguchi Shoichi , Fujimoto Masayuki , Kang Min-Gu , Koizumi Satoshi , Cho Sung-Baek , Tanaka Junzo
Published: October 2002

The structure change of SrTiO3 (111) polar surfaces was studied as a function of
atmosphere, by atomic force microscopy, Auger electron spectroscopy (AES) and X-ray
photoelectron spectroscopy (XPS). The SrTiO3 (111) surfaces annealed in oxygen gas had a
trench structure, while the surfaces annealed in argon gas formed large triangular terraces.
The surfaces annealed in air, i.e., in intermediate oxygen partial pressure, consisted of
complicated self-similar triangles with different sizes, forming a fractal shape called Sierpinski's
gasket. The XPS analyses indicated that surface oxygen states were different depending on the
annealing atmosphere.
The Protrusion of Liquid Phase Oxide Deposition on Patterned Silicon Wafer with Silicon Nitride as Mask
Authors: Lee Ming-Kwei , Yang Ching-Nan , Lin Ching-Hsing , Lei Bo-Hsiung
Published: October 2002

In recent integrated circuit (IC) process development, planarization is an essential requirement. The low temperature growth, good step coverage and selective growth make the liquid phase deposition (LPD)-SiO2 have several applications in IC fabrications, such as completely planarized multilevel interconnections and trench isolation, etc. In the case of the selective growth of LPD-SiO2, there are spherical protrusions at the corners of silicon nitride mask. We propose a model to explain it and therefore control the planarized selective growth of LPD-SiO2.
High-Performance Low-Temperature Poly-Silicon Thin Film Transistors Fabricated by New Metal-Induced Lateral Crystallization Process
Authors: Kim Tae-Kyung , Ihn Tae-Hyung , Lee Byung-Il , Joo Seung-Ki
Published: October 2002

Effect of crystalline defects in metal-induced lateral crystallization (MILC) thin film transistors (TFTs) was
studied and a new MILC method was proposed to improve the electrical properties of poly-Si TFTs. Defects at
channel, which were formed by Ni in conventional MILC method, could be successfully removed by means of
asymmetric Ni-deposition. Since the crystalline defects were removed at the channel, field-effect electron mobility
increased by a large value up to 120 cm2/Vs, while the leakage current was reduced. Electrical properties of the
TFTs fabricated by the new MILC method were dependent on which side of the channel was deposited with Ni.
Characterization of CuInS 2 Thin Films Grown by Close-spaced Vapor Sulfurization of Co-sputtered Cu–In Alloy Precursors
Authors: Adurodija Frederick O. , Song Jinsoo , Kim Sang D. , Kim Seok K. , Yoon Kyung H.
Published: October 2002

Cu–In alloy films were prepared on bare or Mo-coated glass by co-sputtering from Cu and
In targets at ambient temperature. The formation of CuInS2 films was accomplished by
sulfurization within a graphite container under high S vapor pressure. X-ray diffraction
(XRD) analysis of the alloy films showed predominant variation of the phases from In→CuIn2→Cu11In9 as the Cu content in the films increased. The sulfurized In-rich films formed
the CuIn5S8 phase that steadily transformed into CuInS2 as film composition changed
toward the Cu-rich region. SEM analysis showed different morphologies for the CuIn5S8 and
CuInS2 films. Cu-rich films exhibited very dense crystal structures. EDX composition
measurements on the films showed Cu/(Cu+In) varying from 0.21 to 0.64 and S/(Cu+In)
from 0.80 to 1.36. Resistivities in the range of 2.36 to 1.7×108 Ω·cm were obtained. Studies
of the growth mechanism indicated formation of CuIn5S8 as the main secondary phase in
both Cu-rich and In-rich films at low temperatures before conversion into CuInS2 at
temperatures >400°C.
Conduction Band Spin Splitting in InxGa1-xAs/GaAs Quantum Wells
Authors: Kowalski B. , Zwiller V. , Wiggren C. , Varekamp P. R. , Miller M. S. , Pistol M. E. , Omling P. , Samuelson L.
Published: October 2002

Optically detected spin resonance (ODSR) was used to obtain the effective g-values (g
*) in type-I In
x
Ga1-x
As/GaAs quantum wells. The resonances were detected on the excitonic quantum well
luminescence that has an optical recombination time as short as 260 ps. Hence the present ODSR study addresses a regime far beyond the usual for magnetic resonance experiments, where the times of spin
transitions and of carrier recombination dynamics are on a microsecond scale. The resonances, exhibiting an anisotropic g-tensor with the two components g
∥
* and g
⊥
*, are assigned to electric
dipole-induced electron spin transitions. The g-values of the quantum wells differ from the bulk values, which is explained by strain and confinement.
Kinetic Analysis of the C49-to-C54 Phase Transformation in TiSi2 Thin Films by In Situ Observation
Authors: Tanaka Hiroyuki , Hirashita Norio , Sinclair Robert
Published: October 2002

The C49-to-C54 phase transformation of TiSi2 has been studied by in situ observation using a transmission electron microscope (TEM) and by
thermal desorption spectroscopy (TDS). In situ TEM observation reveals that
the interface of the transformation moves parallel to the Si substrate. The
results indicate that the transition is a diffusional transformation that occurs via
the short-distance diffusion of atoms, and is not a diffusionless shear
transformation. Through TDS study, H2 is found to be desorbed during the
transformation. The activation energy for the transformation is calculated to
be 4.1 eV from the relationship between the desorption temperature and the
heating rate of TDS. The phase transformation is thought to occur via lateral
and massive growth, and is not simply limited by the growth rate.
Interaction of Powerful Electromagnetic Wave with Integrated P-I-N Structures
Authors: Koshevaya Svetlana , Gutiérrez-D. Edmundo , Hayakawa Masashi , Tecpoyotl-T. Margarita , Grimalsky Vladimir , Kishenko Yaroslav
Published: October 2002

Theoretical and experimental analyze of surface-oriented silicon p-i-n structures for the
control of high power wideband devices, are introduced. The structure here studied show good
operating characteristics under the application of powerful electromagnetic waves. These surface-oriented
structures are very promising for applications in the millimeter- and submillimeter-wave range.
Gap-State Distributions in Hydrogenated Amorphous Silicon-Germanium Evaluated Using Capacitance–Voltage Method
Authors: Deki Hidenori , Nakagawa Kouji , Kohno Atsushi , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

The density of gap states in hydrogenated amorphous silicon-germanium (a-SiGe:H) alloys deposited at temperatures of 150–250°C has been evaluated by using a capacitance–voltage (C–V ) method. It was found that the gap-state distribution for a-SiGe:H deposited at 150°C has a broad bump around 0.6 eV below the conduction band edge E
c which is associated with Ge dangling bonds. In contrast, a 250°C-deposited film exhibits a peak density of 8×1018 cm-3·eV-1 around 0.75 eV below the conduction band edge E
c, which might originate from Ge and/or Si dangling bond states. After AM1 (200 mW/cm2) light soaking, the gap-state density above the midgap is increased for films deposited below 200°C, while at 250°C deposition, defect states near the midgap are increased.
Integrated Hologram Pickup with an Optical Waveguide Device for Magnetooptical Disk Players
Authors: Yoshida Yoshio , Minami Koji , Yoshimoto Akihito , Yamamoto Hiroyuki , Kurata Yukio
Published: October 2002

An integrated magnetooptical (MO) pickup is developed with an optical
waveguide device that can detect the MO signal. In this pickup, the optical waveguide
device is mounted in a package with a laser diode and a photodiode for servo signal
detection, so all optical functions are integrated into a unit except a light converging
function. The optical waveguide device is constructed with a prism coupler, a thin-film
bi-prism and four PIN photodiodes, on a 1 mm×2 mm Si substrate. The optical
utilization efficiency and the extinction ratio of the device are more than 50% and 1 : 10,
respectively. The carrier-to-noise ratio of the signal reproduced with this pickup
reaches up to 45 dB.
Imaging Photo-induced Reaction of poly(p-phenylenevinylene) Thin Films by a Spectrally Resolved Laser Scanning Microscope
Authors: Kao Fu-Jen , Chou Sen-Yi , Huang Sheng-Lung , Chen Show-An , Chuang Kuen-Ru , Fann Wunshain
Published: October 2002

We have observed the enhancement of photoluminescence in poly(p-phenylenevinylene) thin films under laser beam irradiation by a spectrally resolved laser scanning microscope. The photoluminescence is found to increase at the very start of irradiation. However, extended exposure would also lead to decrement in photoluminescence and burned-out spots as reported previously. This enhancement effect may correspond to the many stages during the photo-induced reaction.
Direct Correlation between Space Charge and Conduction Characteristics of Low-density Polyethylene at Various Temperature
Authors: Hwangbo Seung , Kwon Yoonhyeok , Jeon Seungik , Han Minkoo
Published: October 2002

The space charge distribution and current in low-density polyethylene (LDPE) have been
measured by employing the pulsed-electro-acoustic (PEA) method. The measurement has been
performed simultaneously under the temperature of 20 to 70°C for electric fields up to
50 MV/m in order to clarify the direct correlation between dynamic and pre-formed space charges
and the conduction characteristics of LDPE. It was found that the conduction at high electric
fields should be explained by different conduction models as temperature varied. At higher
temperatures than 55°C, the conduction could be explained by diffusion-limited electrode
injection current, but at 20°C by a kind of space-charge-limited current (SCLC). The power-law
index of 4 was in reasonable agreement with the diffusion-limited electrode injection current
and was influenced by pre-formed space charge. In addition, the numerical calculation about
the experimental current and space charge distribution has been performed in order to correlate
them. It was found that the hopping conduction of injected carriers had a deep relation with the
formation of homo-space charge and the change of cathode field due to dynamic space charge
played an important role in determining the time characteristics of the experimental current at
high electric fields.
Effect of Spacer Layer Thickness on Energy Level Width Narrowing in GaInAs/InP Resonant Tunneling Diodes Grown by Organo-Metallic Vapor Phase Epitaxy
Authors: Takashi Oobo Takashi Oobo , Riichiro Takemura Riichiro Takemura , Ken Sato Ken Sato , Michihiko Suhara Michihiko Suhara , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

We studied the effect of spacer layer thickness on the resonant level width in resonant tunneling diodes (RTDs). GaInAs/InP RTDs were fabricated with various spacer layer thicknesses using organo-metallic vapor phase epitaxy, and the resonant level width was estimated. As a result, the resonant level width was found to decrease with increasing spacer layer thickness. To discuss this tendency, a theoretical model of the interface fluctuation between spacer layers and electrodes, caused by the random distribution of the impurity ions in electrodes, was proposed.
Observations of Silicon Surfaces Exposed to Inductively Coupled CHF3 and C4F8/H2 Plasmas Using Fourier Transform Infrared Ellipsometry
Authors: Ho-Jun Lee Ho-Jun Lee , Hideki Motomura Hideki Motomura , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

In situ Fourier transform infrared ellipsometry has been used to
investigate the characteristics of fluorocarbon films deposited in inductively coupled CHF3 and
C4F8/H2 plasmas.
Chemical composition and thickness of the films have been studied
as a function of process parameters.
For the CHF3 plasma, the mode strength of CF2 bond group increases
monotonically with pressure varying from 3 to 20 mTorr.
The mode strength ratio of hydrogen-containing fluorocarbon bond
groups (CHFx) to CF2 bond group increases with decreasing
pressure.
If He gas is admixed to CHF3, the
CHFx/CF2 ratio also increases.
Changes in the film structure have been discussed in terms of the
relationship between electron temperature and CHF3 dissociation.
As the discharge power is increased,
the deposition rate increases linearly without considerable changes in
the chemical composition of the film.
For the C4F8/H2 plasma, relative concentration of CHFx species
increases linearly with H2 mixing ratio.
Characteristics of a Partial-Coaxial Cavity-Type Holey-Plate Ion Source
Authors: Yoshida Yoshikazu
Published: October 2002

A low-pressure and high-density microwave ion source, created and
sustained by evanescent waves emitted from a holey-plate, and using a
partial-coaxial cavity resonator, has been newly developed for the production
of stable beams from gaseous feed materials. This source is called a holey-plate ion source. A microwave of 2.45 GHz is supplied from a coaxial cavity
and then converted into an evanescent mode through the use of a holey-plate.
The plate is made from a 0.5 mm thick, 54 mm diameter stainless steel sheet
with 2.5 mm diameter, 3.6 mm pitch holes, thus allowing high-density plasma
to be generated near the surface of the plate. A detailed source
description and beam properties are presented in this paper.
Reactions on Si(100) and Chemical Oxide Surfaces in Dissolved-Oxygen Controlled Deionized Water
Authors: Nakamori Masaharu , Aoto Nahomi
Published: October 2002

This paper discusses the characteristics of Si and chemical oxide surfaces rinsed with deionized (DI) water with dissolved oxygen (DO) concentration ranging from 0.08 ppm to 2.0 ppm, controlled by N2 bubbling, at temperatures ranging from 23°C to 80°C. From the aspect of electrochemistry, it is shown that the surface condition is determined by the balance of the simple reactions of oxidation and oxide etching, which proceed spontaneously and simultaneously on Si and chemical oxide surfaces. When the DO controlled DI water is used for rinsing after diluted HF (DHF) dipping before gate oxidation, the breakdown characteristics show no differences for different DI water conditions. Such surface sensitive control using DO controlled DI water, however, is thought to have other potential applications to surface treatment processes.
How Big Are Charge Clouds inside the Charge-Coupled Device Produced by X-Ray Photons?
Authors: Junko Hiraga Junko Hiraga , Hiroshi Tsunemi Hiroshi Tsunemi , Kumi Yoshita Kumi Yoshita , Emi Miyata Emi Miyata , Masayuki Ohtani Masayuki Ohtani
Published: October 2002

We report here the charge cloud shape produced by an X-ray
photon inside the charge-coupled device (CCD) as well as a method to measure it. The
measurement is carried out by using a multi-pitch mesh which enables
us to specify the interaction position of X-rays with subpixel
resolution not only for single events but also for split events.
Split events are generated when the X-ray interaction position is
close to the pixel boundary. The width of this area depends on the
apparent charge size. Finally, we measured the signal output from the
pixel according to the interaction position of X-rays. By
differentiating this function, we obtain, in detail, the charge cloud
shape which can be well represented by an asymmetric Gaussian function.
The charge cloud size for Al-K X-rays is 0.7×1.4 µm2
while that for Mo-L X-rays is 0.8×1.4 µm2. The size of
the photoelectron in Si produced by these X-rays is about
0.04 µm. Taking into account the mean absorption length for
these X-rays in Si, diffusion process in the depletion region cannot
explain the charge cloud size. The asymmetry of the charge cloud
probably arises from the asymmetry of the electric field in the CCD.
Improvement in Semi-Insulating GaAs Material Quality: A Comparative Study of Defects with Deep Levels
Authors: Pavlović M. , Desnica U. V.
Published: October 2002

Thermally stimulated currents (TSC) spectra and photocurrent (I
PC)
measurements were used for detection and evaluation of defects with deep levels
in undoped semi-insulating (SI) GaAs crystals. Large number of liquid
encapsulated Czochralski (LEC) grown materials, produced from late 80's till
nowadays, provided from ten various sources were analysed. Deep levels were
characterised by a new analytical method-simultaneous multiple peak analysis
(SIMPA) of TSC spectra.
For each deep trap its unique and reliable signature was determined, comprising
activation energy, E
a, electron capture cross section, σn, as well as peak maxima, T
m, and trap's relative and absolute concentrations.
It has been found that all measured TSC spectra, even having dramatically
different shapes, can be excellently described with a limited set of 11
deep traps. Considerable improvement in quality of the SI GaAs materials
produced during last decade was found. It reflects in concentration
reduction of most defects and much better defect's distributional uniformity
along the same as well as among different wafers, and in similarity of I
PC
transients.
Substrate Reactivity and “Controlled Contamination” in Metalorganic Chemical Vapor Deposition of GaN on Sapphire
Authors: Golan Yuval , Fini Paul , DenBaars Steven P. , Speck James S.
Published: October 2002

Atomic force microscopy (AFM) and lateral force microscopy (LFM) have been
used to study the effect of common substrate surface pretreatments on the metalorganic
chemical vapor deposition (MOCVD) of GaN on sapphire. It appears that contaminants
play a major role in the surface chemistry and strongly influence the morphology of the
treated surfaces. To investigate the role of these contaminants, we have introduced the
concept of “controlled contamination” (CC), namely, exposure of the sapphire surfaces
to controlled amounts of potential contaminants and investigation of the resulting
sapphire morphology. The results showed that sapphire, considered to be a very stable
oxide surface, is clearly reactive under typical conditions employed in the high-temperature MOCVD growth of GaN.
Possibility of Simultaneous Monitoring of Temperature and Surface Layer Thickness of Si Substrate by In Situ Spectroscopic Ellipsometry
Authors: Jiang Zhong-Tao , Yamaguchi Tomuo , Aoyama Mitsuru , Hayashi Takahisa
Published: October 2002

The possibility of simultaneous monitoring of the temperature and the thickness of the surface layer of a crystalline silicon (c-Si) substrate by in situ spectroscopic ellipsometry (SE) is demonstrated using a surface adsorption layer (SAL) as an example. The model dielectric function (MDF) developed by Adachi and the tabular data of the dielectric function of fused silica were applied to a Si wafer and SAL, respectively. The best-fit curve has been obtained by fitting the measured \varPsi and Δ spectra simultaneously by adjusting the 12 MDF parameters and the thickness of SAL over the temperature range of 293–803 K. The best-fit MDF parameters indicate that the SAL thickness has almost no influence on the best-fit values of the MDF parameters. This fact can be used to monitor the temperature of a c-Si wafer independent of the thickness of surface layer by checking the shift of MDF parameters (e.g., E
2) using the SE and the MDF. The measurement errors in thickness and temperature are roughly estimated to be 0.1 nm and less than 10 K, respectively.
Real-time Incoherent Optical Pattern Recognition with Photorefractive Crystals
Authors: Yau Hon-Fai , Cheng Nai-Jen , Tsou Ren-Han , Lee Hsiao-Yi , Tong Yuh-Ping
Published: October 2002

Incoherent optical pattern recognition has been demonstrated with a simple setup
using photorefractive BaTiO3 crystals. The input patterns to be identified can be
transmitted into the system with completely incoherent (both temporal and spatial) light.
The setup does not require prefabricated filters for its operation and is thus a real-time
system. The working principles of the system involve the photorefractive beam fanning
effect and degenerate four-wave mixing.
Negative Pattern Generation Technique by Laser Beam Writing for Integrated Optics
Authors: Park Kyung Hyun , Kim Myong Wook , Byun Young Tae , Kim Sun Ho , Cho Wook Rae , Park Sung Han , Kim Ung , Choi Sang Sam
Published: October 2002

A novel technique for fabricating negative tone patterns for waveguide devices, using
laser beam writing is proposed. An optoelectronic device pattern with good contrast and a
smooth curve is generated. Our proposed technique can extend the applications of laser
beam writing to the fabrication of the optoelectronic devices.
Magnetic Domain Expansion Phenomena in a Double Mask Type Magnetically Induced Super Resolution Magneto-Optical Disk
Authors: Fujii Yoshio , Tokunaga Takashi , Yamada Koichi
Published: October 2002

The readout mechanism in a trilayer double mask type rear aperture detection (DRAD) magnetically induced super resolution (MSR) disk was studied by readout waveform analysis. A signal enhancement phenomenon was observed, which was ascribed to magnetic domain expansion. Two kinds of magnetic domain expansion mechanisms for the erase direction readout field (Hr) and for the write direction Hr were found. In the case of write direction Hr, a magnetic domain can expand toward the rear mask before the mark contacts with the rear mask from the estimation of mark size and mask position. Edge jitter was evaluated in each readout mode and characterized according to the readout mechanism. Both high-resolution power of MSR and signal amplitude enhancement due to magnetic domain expansion contributed to improvement of DRAD disk readout signal qualities.
Electronic Structures and Chemical Bonding of TiX2(X=S, Se, and Te)
Authors: Kim Yang-Soo , Mizuno Masataka , Tanaka Isao , Adachi Hirohiko
Published: October 2002

A systematic study of the electronic structures and chemical bonding of the titanium dichalcogenide TiX2(X=S, Se, and Te) layered structures is performed by a first-principles molecular orbital calculation using the discrete-variational (DV)-Xα cluster method. The intra- and interlayer chemical bonding properties are also investigated using the bond overlap population. Valence band structures obtained by the calculation are in good agreement with experimental results obtained by X-ray photoemission spectroscopy. Each peak in the density of states (DOS) is identified from the viewpoint of chemical bonding. There is a considerably strong covalent bonding between Ti and chalcogen atoms in TiX2. The covalency of chemical bonding is shown to increase and the ionicity to decrease in the series of TiS2–TiSe2–TiTe2. Both in intra- and interlayer chalcogen-chalcogen bonding and intralayer Ti–Ti bonding are much weaker than Ti-chalcogen intralayer bonding. However, interlayer interaction is found to be not purely of the van der Waals type.
Thermally Stimulated Current and Electrical Conduction Characteristics in Polychlorophenylacetylene
Authors: Dong Wook Kim Dong Wook Kim , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Thermally stimulated current (TSC) and electrical conduction characteristics of polychlorophenylacetylene (PCPA) film have been measured over wide ranges of temperature and electric fields. The experimental results of TSC show that the peak at the high-temperature region seems to be due to microbrownian motion of the PCPA backbone chain with continuous relaxation times, but the peaks at the low-temperature region are considered to originate from the depolarization of locally oriented dipole groups with a single relaxation time in the PCPA molecule. Three types of electrical conduction mechanisms were deduced depending on the region of the electric field. At low electric fields (≤25 MV/m), the ohmic current-voltage characteristic is observed due to the relaxation of dipole groups coupling with the motions of the PCPA backbone chain. However, at the middle electric fields (≤95 MV/m), it becomes nonlinear and the predominant conduction mechanism is interpreted to be controlled by the Schottky effect. At electric fields higher than 90 MV/m, the conduction may be due to the injection of carriers from the electrode and impact ionization.
Solid Solubility of Nitrogen in Amorphous Carbon Films Deposited in Electron Cyclotron Resonance Plasma
Authors: Hidetoshi Saitoh Hidetoshi Saitoh , Tohru Inoue Tohru Inoue , Shigeo Ohshio Shigeo Ohshio
Published: October 2002

Electron cyclotron resonance plasma is used in the formation of
nitrogen-containing carbon films with a CH4+N2 gas mixture.
To accelerate cations from the plasma room, rf-induced negative dc
bias voltage is applied to the Si substrate. An increase in
negative bias is effective for implantation of nitrogen, however,
the nitrogen fraction saturates at [N]/([N]+[C])=0.09 at 300 V.
The results of X-ray photoelectron spectroscopy suggests
that the films have the C–N–C bond or nitrogen terminates
the carbon dangling bond. In addition, ion acceleration causes
a G-band and a D-band to appear on IR spectrum, which would
normally appear on the Raman spectrum obtained from
typical diamond-like carbon films.
Furthermore, the hardness and maximum Young's modulus of
nitrogen-containing carbon films are comparable to those of
most diamond-like carbon films.
Use of Imaging Plates in Gas-Phase Electron Diffraction
Authors: Iijima Takao , Suzuki Wakana , Yano Yohko F.
Published: October 2002

In place of the photographic films used so far, imaging plates (IP) have been
tried for use in gas-phase electron diffraction. With the exposure conditions suitable for
photographic films, signal intensities of sufficient strength were obtained, and the
results of a least-squares analysis for carbon disulfide showed that standard deviations
of structural parameters were of similar magnitude as those obtained by photographic
films. By virtue of the wide dynamic range of IP, data of similar quality were obtained
even without rotating a sector.
Electrode Metal Dependence of Leakage Current Characteristics of Epitaxial BaTiO3 Films on p- and n-Type Electrodes
Authors: Okano Motochika , Sawamura Daisuke , Watanabe Yukio
Published: October 2002

BaTiO3 (BTO) films are grown on the bottom electrodes of Nb-doped SrTiO3 (STON) and
La2CuO4. The current through the BTO films exhibits diode properties having a reproducible
hysteresis at a forward bias with polarity determined by the bottom electrode. In BTO/La2CuO4 the
current intensity is almost independent of metal top-electrode materials, which is explicable by
regarding BTO/La2CuO4 as a pn junction [p: hole carrier, n: electron carrier]. The current through
BTO/STON is limited by the work functions of the metal and BTO, suggesting that it is suppressed by
an electrode metal with a high work function, e.g., Pt, in an n-type ferroelectric such as BTO. In a p-type ferroelectric such as PLZT, it is suppressed by an electrode metal with a low work function. The
relaxation current, the large leakage current in epitaxial ferroelectric films, and the effect of the
ferroelectric carrier type on fatigue are discussed.
Ferroelectric Properties of SrRuO3/(Ba, Sr)TiO3/SrRuO3 Epitaxial Capacitor
Authors: Kawakubo Takashi , Komatsu Shuichi , Abe Kazuhide , Sano Kenya , Yanase Naoko , Fukushima Noburu
Published: October 2002

Ferroelectric properties were investigated using SrRuO3/(Ba
x
, Sr1-x
)TiO3(BSTO)/SrRuO3 all-perovskite heteroepitaxial capacitors on strontium titanate substrates. The dielectric film had a composition with a Ba content
of x=0 to 1, i.e., the whole composition of the SrTiO3–BaTiO3 solid-solution system. The c-axis of the BSTO film was elongated depending on the Ba content, and reached 0.441 nm at the
BaTiO3 composition, which was 8.6% larger than the bulk c-axis. A peak relative dielectric constant of 870 and maximum remanent polarization (2P
r) of 58 µC/cm2 were obtained depending on the Ba content at a dielectric thickness of 20 nm. These are the highest storage
capacitance capacitor and the thinnest ferroelectric capacitor reported so far. Possibilities for deep submicron ferroelectric and dielectric memory applications are also discussed.
Influence of the Purity of Source Precursors on the Electrical Properties of Pb(Zr, Ti)O3 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Fujisawa Hironori , Yoshida Masahiro , Shimizu Masaru , Niu Hirohiko
Published: October 2002

Pb(Zr, Ti)O3 (PZT) thin films were prepared by metalorganic chemical
vapor deposition (MOCVD) using two types of Pb
precursors (tetra-ethyl lead: TEL) with different purities and the
influence of the purity of TEL on the electrical properties of PZT
thin films was investigated. While the difference in the purity
of TEL did not affect the crystalline properties and surface
morphology of PZT films, it influenced the electrical properties
of PZT films. Relative dielectric constants and D-E hysteresis loops
of PZT thin films were influenced slightly by the difference in
the purity of TEL. PZT films grown using high purity TEL showed
lower current densities and higher breakdown fields than those grown
using low purity TEL. High source purity PZT films also had higher
endurance against polarization fatigue than low source purity films.
From these results, it was concluded that the purification of source
materials led to the improvement of the electrical properties of
ferroelectric thin films.
Fabrication of PbZrxTi1-xO3 Films on Si Structures Using Y2O3 Buffer Layers
Authors: Byung-Eun Park Byung-Eun Park , Shigeto Shouriki Shigeto Shouriki , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Lead-zirconate-titanate (PbZr
x
Ti1-x
O3:PZT)
films were epitaxially grown on Si(111) substrates using Y2O3
buffer layers.
Y2O3 layers were prepared in a molecular beam epitaxy (MBE)
apparatus with a single electron beam gun, while PZT films were prepared
in a vacuum evaporation chamber with both a crucible and an electron beam gun.
It was found from in situ RHEED observation that Y2O3 layers
grew epitaxially on Si(111) substrates.
It was also found from X-ray diffraction analysis that strongly (101)-oriented PZT films grew on the Y2O3/Si(111) structures at a substrate temperature of 700°C.
Metal-ferroelectric-insulator-semiconductor(MFIS) capacitors were fabricated
using this structure, and capacitance-voltage (C–V) curves showed
a memory window of about 2.6 V, which is considered to be due to
the ferroelectric nature of the PZT film.
Effects of H2 Sintering and Pt Upper Electrode on Metallic Bi Content in Sr0.9Bi2.1Ta2O9 Thin Films for Ferroelectric Memories Prepared by Sol-Gel Method
Authors: Koiwa Ichiro , Kanehara Takao , Kato Hiroyo , Ono Sachiko , Sakakibara Akira , Osaka Tetsuya , Asami Katsuhiko
Published: October 2002

The effects of Pt electrode and H2 sintering on the metallic Bi content of
Sr0.9Bi2.1Ta2O9 (SBT) thin films for ferroelectric memories were studied using X-ray
photoelectron spectroscopy (XPS). Oxidic Bi in SBT films is reduced to
metallic Bi by H2 sintering. The degree of reduction depends on the structure of
the SBT film. The SBT film with a fluorite structure is more difficult to reduce
than that with a Bi-layered structure. Pt upper electrode formation also leads to
an increase of metallic Bi content. Both H2 sintering and the Pt upper electrode
work synergistically. In the combination of the pure Pt upper electrode and H2
sintering, over 80% of Bi on the SBT film surface was metallic. Pt films of 5 nm
thickness on the SBT film recrystallized during the heat treatment and were
broken up into particles. Pt electrode coverage was about 20% after the 2nd
annealing at 800°C for 30 min in O2 atmosphere. Electrical properties were
significantly affected by the presence of metallic Bi; in particular, SBT films with
higher metallic Bi content showed higher leakage current density. The metallic
Bi content must therefore be suppressed to obtain SBT films with low leakage
current density.
Study of the Valence State of the Manganese Ions in PbTiO3 Ceramics by Means of ESR
Authors: Hayashi Koichi , Ando Akira , Hamaji Yukio , Sakabe Yukio
Published: October 2002

ESR measurements have been carried out on Mn ions in PbTiO3 ceramics. Mn ions
in the PbTiO3 ceramics are incorporated at Ti4+ sites with mixed valence states of Mn2+
and Mn4+. The proportion of Mn2+ ions is the highest for the calcined powder and
changes during the firing process. After the firing it decreases with increasing the firing
temperature in the range from 800°C and 1100°C, and increases at temperatures above
1150°C. Additionally, the proportion changes with the amount of Mn ions. The
proportion of Mn2+ decreases with increasing Mn dopants up to 0.20 wt%. In the range
from 0.20 wt% and 0.25 wt% of MnO2 it increases steeply, and the Mn2+ and Mn4+ ratio is
not varied when more than 0.25 wt% MnO2 is doped. Piezoelectric properties of Mn
doped PbTiO3 can be explained by the changes of the valence states of Mn ions.
Optical Observation of Heterophase and Domain Structures in Relaxor Ferroelectrics Pb(Zn1/3Nb2/3)O3/9%PbTiO3
Authors: Fujishiro Kouji , Vlokh Rostislav , Uesu Yoshiaki , Yamada Yasusada , Kiat Jean-Michel , Dkhil Brahim , Yamashita Yohachi
Published: October 2002

Phase boundary and domain structure in relaxor ferroelectrics Pb(Zn1/3Nb2/3)O3/9%PbTiO3
were observed using a (111) plate under a polarization microscope. The
dielectric constant was measured simultaneously to determine exact transition
temperatures and to connect the dielectric behavior with phase boundary movements.
Movement of the phase boundary between cubic and tetragonal phases was observed at
the temperature T
c where the dielectric constant changed abruptly. Below T
c,
tetragonal and rhombohedral phases coexisted over a wide temperature range. The
complicated domain/phase patterns are classified into two blocks according to
extinction position. The difference in extinction positions between the two blocks
deviated from 30° and manifested temperature dependence. This fact indicates that the
symmetry-lowering occurs in the heterophase. A small, but the distinct temperature
hysteresis of the dielectric constant was related to the nucleation and growth of one
phase into another phase.
Dielectric Properties and Microstructures of Solid Solutions of (1-x)Pb(Mg1/3Nb2/3)O3-xPb(In1/2Nb1/2)O3
Authors: Lee Kwang-Ho , Kim Hwan
Published: October 2002

The complete perovskite solid solutions of (1-x)Pb(Mg1/3Nb2/3)O3(PMN)-xPb(In1/2Nb1/2)O3(PIN), where x=0.1–0.9, were synthesized from the solid state reaction of columbite (MgNb2O6), wolframite (InNbO4) and PbO mixture and their dielectric properties and microstructures were investigated. Pure perovskite phase was obtained by the incorporation of PMN into PIN and an increase in PIN resulted in a linear increase in the lattice parameter and a gradual decrease in the grain size. With increasing x, the maximum permittivity (ε
rm
′), decreased and the temperature T
m, where ε
rm
′ appeared, shifted towards a higher temperature showing the presence of relaxor ferroelectricity.
Microscopic Examination of the Microwave Sintered (Pb0.6Sr0.4)TiO3 Positive-Temperature-Coefficient Resistor Materials
Authors: Chou Chen-Chia , Chang Hon-Yi , Lin I-Nan , Shaw Bin-Jen , Tan Jian-Tao
Published: October 2002

The (Pb0.6Sr0.4)TiO3 (PSrT) ceramics processed by the microwave sintering technique, exhibiting unique high-T
c behavior and low resistivity, were examined using a scanning electron microscope, scanning transmission electron microscope with energy dispersive spectroscopy, and electron diffraction in the present work. The results imply that different atomic species may interact differently with microwaves and produce a large strain field within materials, suggesting that domain mobility is restricted in the specimens due to lattice distortions. The Pb-species distribution and complicated domain arrangements induced by the strain field greatly influence the electrical properties of the materials.
Preparation and Properties of SrBi2Ta2O9 Ceramics
Authors: Shoji Kazuo , Aikawa Mizuka , Uehara Yasuo , Sakata Koichiro
Published: October 2002

The purpose of this paper is to investigate the preparation and
properties of SrBi2Ta2O9 ceramics as capacitors and/or piezoelectric
materials. Ordinarily fired (OF) samples were prepared by a conventional
ceramic technique. Grain-oriented (GO) samples were prepared by the
hot-forging method. High-density OF samples with density ratios of 95–96%
to theoretical X-ray density were easily obtained at the optimized
sintering temperature (1230°C). In this OF sample, the Curie temperature
existed at 322°C, and the dielectric constant at room temperature was 135.
SrBi2Ta2O9 ceramics did not deform smoothly at 1230–1250°C, and the maximum
reduction ratio was about 0.7. The X-ray grain orientation factor of the GO
sample was about 0.52. The coupling factor k
33 of the GO sample with f of 0.36 was 17.7%.
Growth and Optical Properties of Ferroelectric K3Li2Nb5O15 Single Crystals
Authors: Tomoaki Karaki Tomoaki Karaki , Kenya Miyashita Kenya Miyashita , Mayumi Nakatsuji Mayumi Nakatsuji , Masatoshi Adachi Masatoshi Adachi
Published: October 2002

Potassium lithium niobate (KLN) single crystals were grown from a melt
with potassium and lithium enriched composition using the rf-heating
Czochralski technique. The growth conditions were discussed. A crystal
with the composition of 0.315K2O–0.15Li2O–0.535Nb2O5
was grown from a melt of 0.348K2O–0.187Li2O–0.465Nb2O5.
The transparent crystal was pale-yellow with an absorption edge at 376 nm,
and showed a very small optical absorption in the 420–900 nm region.
The electrooptic and nonlinear optic coefficients were measured. The deviation
of composition in the crystals was investigated by measuring the change of
the Curie temperature and phase matching angle of the second harmonic generation.
A Simple Method for the Fast Elimination of Interference Fringes in the 4×4 Matrix Optics
Authors: Yoon Tae-Hoon , Kim Jae Chang
Published: October 2002

In this paper we propose an apodization method based on the structure of a Mach-Zehnder interferometer, by which we can eliminate the interference fringes in the 4×4 transfer matrix optics in negligible time. For a cell with k abrupt interfaces, the new apodization method can be implemented by simply, at maximum, k additional matrix multiplications of a 4×4 matrix in calculating the complete transfer matrix of the cell.
Effect of Hydrostatic Pressure on Dielectric Behavior and Phase Transition in Ferroelectric Polymers
Authors: Yuki Toshinao , Ito Shinji , Koda Tomonori , Ikeda Susumu
Published: October 2002

The effect of hydrostatic pressure on the dielectric behavior of ferroelectric
copolymers of vinylidene fluoride and trifluoroethylene is discussed to elucidate the roles of
intermolecular and intramolecular interactions in a ferroelectric-paraelectric phase transition
of the polymers. The phase transition temperature and temperature hysteresis of the phase
transition are influenced by the hydrostatic pressure. It is concluded that these effects of
hydrostatic pressure result from its selective working on the intermolecular interaction.