bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoluminescence and Electroluminescence from Polymer-Like Organic Thin Films Deposited by Plasma-Enhanced Chemical Vapor Deposition Using Para-Xylene as Precursor
Authors: Woo Park Donggeun Jung , Yongkeun Son Yongkeun Son
Published: October 2002

Photoluminescence (PL) and electroluminescence (EL) were observed from the polymer-like organic
thin films (POTFs) deposited by plasma-enhanced chemical vapor deposition (PECVD) using p-xylene as
the precursor. Absorption and PL spectra suggested that the film includes visible-light-luminescing species.
The PL spectrum had a peak around 460 nm. Current-voltage (I-V) and luminescence-voltage (L-V) were
measured from the aluminum/POTF/indium-tin-oxide light-emitting diode (LED). L-V curve follows the I-V curve
showing a turn-on voltage of ∼ 2.5 V. The EL spectrum from the LED was similar to the PL spectrum.
Estimation of the Life of Synthetic Silica Glass under Long Time Irradiation by ArF Excimer Laser
Authors: Shimbo Masaru , Nakajima Toshio , Tsuji Naoki , Kakuno Tsutomu , Obara Takashi
Published: October 2002

The life of synthetic silica glass under ArF excimer laser irradiation was
estimated in relation to the laser energy density by in-situ photoabsorption
measurements under exposure to more than 107 shots. Dissolved hydrogen
increases the life whereas OH in the glass scarcely influences it. Usual
photomask glass is found to be tolerable to more than 1011 shots at
0.1 mJ/cm2 of laser irradiation intensity.
Characterization of a GaN Bipolar Junction Transistor after Operation at 300 for over 300 h
Authors: Yoshida Seikoh , Suzuki Joe
Published: October 2002

GaN with an n-p-n structure was grown using gas-source molecular beam
epitaxy (GSMBE). We fabricated an n-p-n GaN bipolar junction transistor. The high-temperature reliability of the bipolar junction transistor (BJT) was investigated. That is,
the lifetime performance of the BJT at 300°C was examined during continuous current
injection at 300°C. We confirmed that the performance of the bipolar transistor at 300°C
did not change for over 300 h. No degradation of the metal-semiconductor interface
was observed by transmission electron microscopy (TEM). The reliability of the GaN
BJT at 300°C was thus confirmed.
Effect of Annealing on the Impurities of 6H–SiC Single Crystals
Authors: Shin Dong Hyuk , Vlaskina Svitlana I.
Published: October 2002

Heavily doped 6H–SiC crystals were annealed in vacuum at temperatures around
1900°C without Si vapor. The physical properties of the initial and the annealed crystals
have been studied using Hall effect measurements, optical transmission, and
photoluminescence. In the annealed crystals, the carrier concentration was reduced by three
orders of magnitude and mobility was increased by several times. It is supposed that the
reduction of carrier concentration is caused in part by the diffusion of the impurity atoms
from the bulk to the surface which are then removed by evaporation. It has been also observed
that the main donor level is changed from ∼0.1 eV to ∼0.7 eV after annealing.
The origin of the new deep donor level is not yet clear, but it may be due to the complex
related to the Si vacancy and N impurity.
Single-Mode Laser Oscillation in Semiconductor Gain Photonic Crystals
Authors: Nojima Shunji
Published: October 2002

A theory is presented for calculating the intensity of light emitted from
the two-dimensional photonic crystal with cylindrical gain rods at their
lattice points. The results obtained theoretically demonstrate for the
first time that an oscillation occurs in this kind of photonic crystal laser
with no ordinary external cavities, and, moreover, that it occurs in the
single mode in a certain frequency range studied. The light is found to
have a strong intensity toward the direction of the M-point in the Brillouin
zone.
Implantation of Organic Molecules into Biotissue by Pulsed Laser Irradiation
Authors: Goto Masahiro , Ichinose Nobuyuki , Kawanishi Shunichi , Fukumura Hiroshi
Published: October 2002

Zinc tetraphenyl porphyrin (ZnTPP) molecules were implanted into a piece of chicken
skin by irradiation with KrF laser pulses. The study of the implanted ZnTPP at the skin
surface using a fluorescence microscope indicated that the molecules are space-selectively
introduced at the irradiated area.
Role of PtO Electrode in Fatigue in Pb(Zr,Ti)O 3 Films
Authors: Soo Lee Byung , Young Lee Jeong
Published: October 2002

Two different structures of Pt/Pb(Zr,Ti)O3 (PZT)/Pt and PtO/PZT/PtO/Pt
capacitors were fabricated by rf magnetron sputtering followed by rapid
thermal annealing (RTA) in a N2 atmosphere. The ferroelectric properties
of these two capacitors were compared mainly in terms of fatigue. The
reduction of PtO to Pt after RTA was observed by X-ray diffraction (XRD)
and this resulted in degradation-free capacitors for 5.0×101
1 cycles
of polarization reversals. The Pt/PZT/Pt capacitor, however, showed a
sharp decrease in polarization in the range of 108 read and write cycles.
It is thought that the improvement was due to compensation for oxygen
vacancies in PZT, which are the source of fatigue during service,
by oxygen atoms reduced and separated from the PtO layer that then
diffuse to the dielectric layer to neutralize the vacancies.
Novel Design for Electromagnet with Wide Excitation Range
Authors: Yoshihisa Iwashita Yoshihisa Iwashita , Akira Noda Akira Noda , Toshiyuki Shirai Toshiyuki Shirai , Akio Morita Akio Morita , Masahiro Tadokoro Masahiro Tadokoro , Jun'ichi Hirota Jun'ichi Hirota , Masami Umezawa Masami Umezawa , Kazuo Hiramoto Kazuo Hiramoto
Published: October 2002

A novel design for an electromagnet with a wide excitation range is described. The magnetic field distribution of an electromagnet usually deforms as the excitation approaches the saturation level. This effect can be minimized if the saturation of the ferromagnetic material is uniform; the integrated magnetic field along a flux line \intH ·d
s in the pole is uniform for all flux lines crossing the gap area of interest. This condition can be realized by adding vacant portions into low flux density regions in iron poles, and thus the magnetic flux density in the iron region becomes uniform. This magnetic flux density equalizer can be applied to a variety of magnets: flat dipoles, n-indexed dipoles, quadrupoles and higher-order multipole magnets.
Electron Emission from a Heteroepitaxial Diamond Planar Emitter
Authors: Yamada Takatoshi , Maede Jun , Sawabe Atsuhito
Published: October 2002

Heteroepitaxial diamond (100) with relatively smooth surface morphology is grown on iridium
thin film by direct current plasma chemical vapor deposition, and its electron emission is
discussed by comparing the electron emission of polycrystalline diamond with the various surface
morphology. From the results of electron emission measurements, the emission property from
heteroepitaxial diamond is independent of the measurement point, while that from polycrystalline
diamond strongly depends on the measurement points. In addition, electron emission from
heteroepitaxial diamond was observed at lower voltage compared to that from polycrystalline diamond.
Development of Thermal Conductivity Measurement for Fluids Which is Convenient and Effective for Samples near the Critical Point
Authors: Chen Zai-hua , Tozaki Ken-ichi , Nishikawa Keiko
Published: October 2002

A method of thermal conductivity measurement was developed using a thermoelectric
module. The measurement is very convenient and simple, and has sufficient accuracy for
common gaseous samples and liquids that are not electrically conductive. Moreover, the
method is applicable to samples near the critical point and in the supercritical region. The
isotherm of the thermal conductivity of CO2 near the critical temperature was measured as an
example and the divergence of the values, the so-called “critical enhancement,” was observed.
New Growth Conditions for the c-Axis Oriented NdBa2Cu3Ox Films by Pulsed Laser Deposition: Lower Substrate Temperature and Higher Oxygen Pressure
Authors: Zama Hideaki , Ishikawa Kazuhiro , Suzuki Takeo , Morishita Tadataka
Published: October 2002

The substrate temperature at which the c-axis oriented NdBa2Cu3O
x
(NdBCO) film grows is 80–100°C higher than that for the c-axis oriented YBa2Cu3O
x
(YBCO). This is a drawback of
composing multilayers for device applications although NdBCO has crystalline and
superconductive properties superior to those of YBCO. We successfully grew the c-axis oriented
NdBCO films in the temperature range lower than that for the a-axis preferred oriented film at a
high oxygen pressure by pulsed laser deposition. The optimum c-axis oriented growth condition
was determined as follows: substrate temperature is 790°C, oxygen pressure 900 mTorr, and laser
energy density 0.5 J/cm2.
In-Plane Orientation Control of C-Axis Oriented YBa 2Cu 3O 7-δ Films on MgO Substrates by BaSnO 3 Buffer Layers
Authors: Masashi Mukaida Masashi Mukaida , Yoshinobu Takano Yoshinobu Takano , Kazuaki Chiba Kazuaki Chiba , Takuo Moriya Takuo Moriya , Masanobu Kusunoki Masanobu Kusunoki , Shigetoshi Ohshima Shigetoshi Ohshima
Published: October 2002

A new BaSnO3 buffer layer is proposed for controlling the in-plane orientation of YBa2Cu3O7-δ films grown on MgO substrates.
BaSnO3 buffer layers and YBa2Cu3O7-δ films are grown by pulsed laser deposition. 45° grain boundaries in YBa2Cu3O7-δ films grown on MgO (001) substrates, which are fatal defects for microwave device applications, are eliminated using the BaSnO3 buffer layer.
YBa2Cu3O7-δ films grown at an optimum growth temperature of 710°C on BaSnO3 buffer layers on MgO (001) substrates show lower surface resistance
(R

S
) than those on MgO (001) substrates without BaSnO3 buffer layers.
A 128×128-Pixel Artificial Retina LSI with Two-Dimensional Filtering Functions
Authors: Funatsu Eiichi , Nitta Yoshikazu , Tanaka Jun-ya , Kyuma Kazuo
Published: October 2002

Our artificial retina LSI executes image convolution on the focal plane with programmable 5×5
kernels consisting of the weight values of +1, 0 and -1 for each element. This function is
realized by simultaneous access to 5×5 pixels, and by employing interpixel current-mode
calculations. Each pixel of the fabricated 128×128-pixel artificial retina LSI is 60×60 µm2
with a 14.5% fill factor in a 0.8 µm complementary metal-oxide-semiconductor (CMOS)
process. We demonstrate image capture with some kernel patterns representing normal image
sensing, edge extraction, edge enhancement and orientation extraction.
Electron Probe Microanalysis of Second Phases via Acceleration Voltage Dependence
Authors: J. Fons Akimasa Yamada , Shigeru Niki Shigeru Niki , Hiroyuki Oyanagi Hiroyuki Oyanagi
Published: October 2002

The acceleration voltage dependence of electron probe microanalysis
(EPMA) is discussed in relation to the determination of the
compositional profile of a thin film. It is shown that the
acceleration voltage dependence can be used to estimate the
composition of second phase(s) by means of parameter fitting of an
analytical model when the composition variation function is simple.
The feasibility of the method is demonstrated using the example of
molecular beam epitaxy grown CuGaSe2 with a second
phase. The composition of this phase is found to be
Cu3Se2 consistent with X-ray diffraction results.
Experimental Results of Laser Wakefield Acceleration Using a Femtosecond Terawatt Laser Pulse
Authors: Masaki Kando Masaki Kando , Hyeyoung Ahn Hyeyoung Ahn , Hideki Dewa Hideki Dewa , Hideyuki Kotaki Hideyuki Kotaki , Toru Ueda Toru Ueda , Mitsuru Uesaka Mitsuru Uesaka , Takahiro Watanabe Takahiro Watanabe , Hiroshi Nakanishi Hiroshi Nakanishi , Atsushi Ogata Atsushi Ogata , Kazuhisa Nakajima Kazuhisa Nakajima
Published: October 2002

Laser wakefield acceleration (LWA) experiments have been carried out in an
underdense plasma driven by a 2 TW, 90 fs laser
pulse synchronized with a 17 MeV RF linac electron injector at 10 Hz.
Around optimum plasma densities for LWA, we have observed electrons
accelerated to 35 MeV. Wakefield excitation has been confirmed by measuring
the electron density oscillation with a frequency domain interferometer. At
plasma densities higher than the optimum density, we have also observed high
energy electrons over 100 MeV up to 200 MeV.
Universal Theory of Si Oxidation Rate and Importance of Interfacial Si Emission
Authors: Kageshima Hiroyuki , Shiraishi Kenji , Uematsu Masashi
Published: October 2002

The essential role that Si atoms emitted from the interface play in determining the silicon-oxidation
rate is theoretically pointed out, and a universal theory for the oxide growth rate taking
account of the interfacial Si-atom emission is developed. Our theory can explain the oxide growth
rate for the whole range of the oxide thickness without any empirical modifications, while the rate
for an oxide thickness of less than 10 nm in dry oxidation cannot be explained with the Deal-Grove
theory.
Mosaic Structure of Ternary Al 1-xInxN Films on GaN Grown by Metalorganic Vapor Phase Epitaxy
Authors: Michihiko Kariya Michihiko Kariya , Shugo Nitta Shugo Nitta , Shigeo Yamaguchi Shigeo Yamaguchi , Hiroshi Amano Hiroshi Amano , Isamu Akasaki Isamu Akasaki
Published: October 2002

Al1-x
InxN heteroepitaxial films were grown on GaN by atmospheric pressure metalorganic vapor phase epitaxy. The films were characterized by X-ray diffraction and atomic force microscopy. In the case of Al0.50In0.50N, the crystallinity progressively degraded with increasing thickness. On the contrary, the crystallinity of Al0.83In0.17N, which is in-plane lattice-matched with GaN, remained almost unchanged irrespective of the thickness. The crystallinity of Al0.83In0.17N was strongly dependent on the quality of the underlying GaN layer, while that of Al0.50In0.50N was not as sensitive.
Effect of Back-Channel Plasma Etching on the Leakage Current of a-Si:H Thin Film Transistors
Authors: Yi Chung , Rhee Shi-Woo , Park Sae-Hwan , Ju Jin-Ho
Published: October 2002

The effects of back-channel plasma etching conditions and the amount of HCl and plasma power on the leakage current of a-Si:H thin-film transistors (TFTs) were studied. Atomic force microscopy (AFM) and secondary ion mass spectrometry (SIMS) analyses were performed to determine the optimal etching conditions which reduce the leakage current at the back channel. Etching with a HCl-rich gas mixture was found to be effective to reduce the leakage current and chlorine ions were believed to affect the back-channel surface characteristics and exhibit acceptor-like behavior in the lower subthreshold region. Chlorine is believed to suppress the electron generation in the back-channel region and trap electrons that are generated by thermal emission. The back-channel surface roughness was found to have no appreciable effect on the leakage current.
Formation of Shallow p+n Junctions Using Different Annealing Schemes with Low Thermal Budget
Authors: Juang Miin-Horng , Harn Sui-Chan
Published: October 2002

The formation of shallow p+n junctions by directly implanting BF2dopant into the Si substrates and then treating the samples by different annealing schemes with a low thermal budget has been studied. Nosignificant dopant diffusion is observed by using these annealing processes with a low thermal budget. After conventional furnace annealing (FA) at a medium temperature of 800°C for 30 min, the resulting junction characteristics are poor. A low-temperature long-time FA treatment at 600°C for 2 h, prior to the medium-temperature FA treatment, can considerably improve the junction formation. Furthermore, shallow p+n junctions with a leakage smaller than 10 nA/cm2can be achieved by an annealing scheme that employs low-temperature FA followed by medium-temperature rapid thermal annealing (RTA) at 800°C for 30 s. However, an annealing process that employs medium-temperature RTA at 800°C for 30 s followed by low-temperature FA treatment cannot produce good junctions. In addition, the low-temperature annealing time of 2–3 h is found to be sufficient for forming good shallow p+n junctions in the annealing scheme that employs low-temperature FA followed by medium-temperature RTA.
Reaction Analysis of Aluminum Chemical Vapor Deposition from Dimethyl-aluminum-hydride Using Tubular Reactor and Fourier-Transform Infrared Spectroscopy: Theoretical Process Optimization Procedure (1)
Authors: Sugiyama Masakazu , Itoh Hitoshi , Komiyama Jyun-ichi Aoyama , Shimogaki Yukihiro
Published: October 2002

Kinetic studies on the chemical vapor deposition (CVD) of
aluminum from dimethylaluminumhydride (DMAH) were carried out to
obtain the reaction model which is useful for the process
optimization. Fourier-transform infrared spectroscopy (FT-IR) was
used to monitor DMAH supplied to the reactor, which ensured the
reliability of precursor delivery by the bubbling method. FT-IR was
also used to identify the reaction product of DMAH. Aluminum
deposition from DMAH yielded only trimethylaluminum (TMA). The
analysis of aluminum deposition rate profile in the tubular reactor
revealed that the rate-limiting step was the surface reaction of
DMAH and that the surface reaction was almost of the first order
with respect to DMAH concentration. The analysis took account of the
monomer-dimer equilibrium of DMAH in the reactor whose existence was
suggested by quantum-chemical calculations. The activation energy of
approximately 80 kJ/mol was estimated from the relationship between
DMAH decomposition yield and the gas residence time in the tubular
reactor.
Radius Measurement of a Sonoluminescing Gas Bubble
Authors: Jeon Jin-Seok , Yang Ik-Jun , Karng Sarng-Woo , Kwak Ho-Young
Published: October 2002

Accurate measurement of the radius of a sonoluminescing gas
bubble by a light scattering method was suggested. This can be
achieved because of the remarkable stability of a sonoluminescing gas
bubble, which has the same shape variation sequence in every
oscillation cycle with only 50 ps jitter in the time between flashes,
which enables sequential measurement of the bubble radius by the light
scattering method and direct imaging technique for the first time. The
measured light scattering data with an appropriate proportionality
index value can be well fitted to the direct observation for the
bubble radius-time curve. However, the observed value of the
proportionality index is different from the one predicted by the Mie
scattering theory.
Self-Induced Transparency Phenomena of Single-Mode Pulse Laser Propagating in a Thick Ytterbium Vapor Column
Authors: Yi Jonghoon , Park Hyunmin , Rhee Yongjoo , Lee Jongmin
Published: October 2002

The variations in pulse shape of a single-mode pulse laser propagating through
ytterbium (Yb) atomic medium were investigated experimentally. The laser pulse shape
was changed as a function of pulse area and it could be explained well using the area
theorem. When the pulse area was close to 2π, the pulse shape was transformed to a
hyperbolic secant function after transmission. The transmission curve of the propagating
laser vs. the pulse area demonstrated self-induced transparency phenomena well.
However, the transmission was markedly reduced when the atomic density was
increased above ∼4×1010 atoms/cm3. Several causes; such as collision-induced
polarization relaxation, Doppler broadening, laser incoherence, and power broadening,
which could induce reduced transmission, were examined. It was the incoherence of the
laser that caused reduced transmission because the laser line width was broader than the
Fourier-transform limit, and the absorbed energy dissipated through spontaneous emission.
Analog Metal-Oxide-Silicon IC Implementation of Motion-Detection Network Based on a Biological Correlation Model
Authors: Masahiro Ohtani Masahiro Ohtani , Hiroo Yonezu Hiroo Yonezu , Tetsuya Asai Tetsuya Asai
Published: October 2002

In this paper, fabrication of a simple analog network for one-dimensional motion detection using the complementary metal-oxide-silicon (CMOS) process is described. The network is constructed with a number of local motion sensors based on biological elementary motion detectors. Experimental and simulation results indicate that the fabricated network computes the local velocity and direction of the moving object in the velocity range of 10-4 m/s to 3.2 ×102 m/s. The results also show that the velocity sensitivity of the network can be changed flexibly. The circuit structure of the network is compact and suitable for highly dense motion sensor arrays.
Optical Properties of Lead Lanthanum Zirconate Titanate Amorphous Ferroelectric-Like Thin Films
Authors: Li Huiqiu , Zhang Yueli , Wen Jinhui , Yang Shenghong , Mo Dang , Cheng Chih-Hsing , Xu Yuhuan , Mackenzie J. D.
Published: October 2002

Lead lanthanum zirconate titanate (PLZT) amorphous thin films, whose
composition is 5/50/50, have been prepared by the sol–gel technique. The optical
transmission property of the thin film was measured in the wavelength range of
200–820 nm. The ellipsometric spectra of the PLZT thin film on a glass substrate
were measured in the wavelength range of 200–670 nm, and their optical constant
(refractive index n and extinction coefficient k) spectra have been determined. The
dispersion of the refractive index is interpreted in terms of a single electric oscillator
at 9.64 eV. The direct band energy is found to be 3.67 eV.
Control of the Anchoring Energy of Rubbed Polyimide Layers by Irradiation with Depolarized UV-Light
Authors: Andrienko Denis , Kurioz Yuriy , Nishikawa Michinori , Reznikov Yuriy , West John L.
Published: October 2002

Exposure of rubbing polyimide (PI) film to depolarized ultraviolet (UV) light
suppressed the effective anchoring energy of liquid crystal (LC) with aligning surface.
Polarized light changed the orientational distribution of PI molecules obtained by
rubbing by changing both the anchoring energy and easy axis direction. These results
show that ultraviolet exposure can be effectively used to control anchoring
parameters.
Properties of TiN Films on Heated Substrate Below 550°C by 50 Hz Plasma-Enhanced Chemical Vapor Deposition
Authors: Yoshino Masaki , Shimozuma Mitsuo , Date Hiroyuki , Rodrigo Adolfo , Tagashira Hiroaki
Published: October 2002

Titanium nitride (TiN) films have been deposited on silicon substrates at low
substrate temperature (400–550°C) by 50 Hz plasma-enhanced chemical vapor
deposition (CVD) using a TiCl4+N2+H2 gas mixture. A
substrate bias circuit with two diodes was used to enhance the deposition through ion
processes. The Vickers hardness values of the deposited TiN films at T
sub
ranging from 450 to 550°C were above 2200 Hv, and resistivity was below
100 µΩ·cm at T
sub≧500°C. The
composition of the deposited films was investigated by the Rutherford backscattering
spectroscopy (RBS) method to determine that the at.% value of the Cl content
[=Cl/(Ti+N+O+C+Cl)] in the TiN films is
about 1% at T
sub=550°C. X-ray diffraction (XRD) spectra revealed
that the film has the preferred orientation of δ-TiN with (200) and (220) under
the deposition condition of T
sub≧500°C.
Modeling of Hysteresis Curves of Ferroelectric Capacitor with Inhomogeneous Charged Defect Density and Polarization Parameters in the Ferroelectric Film
Authors: Yong-Il Kim Yong-Il Kim , Won-Jong Lee Won-Jong Lee
Published: October 2002

A method for the modeling of polarization-electric field (P–E) hysteresis curves of the inhomogeneous ferroelectric thin film capacitor was developed, considering the local electric field histories. With the present modeling method, P–E hysteresis curves can be obtained from the ferroelectric film with any distributions of inhomogeneous charged defect density N(x) and local polarization parameters such as P
s(x), P
r(x), E
c(x) and ε
f(x), and the separate or combined effect of the parameters on the P–E hysteresis curve can be investigated. It was found that microscopic variations of the charged defect density in the ferroelectric film induce asymmetry and voltage shift in the hysteresis curve. How much and in which direction the voltage shift occurs are determined by the concentration distribution of the charged defects and their signs. Inhomogeneity of the other local polarization parameters in the ferroelectric film has no effects on the voltage shift of the P–E hysteresis curves. However, when they combined with the inhomogeneity of the charged defect density, the voltage shift induced by the inhomogeneous charged defect is generally enhanced. The effects of the model parameters on the apparent P
s and P
r values were also investigated.
X-Ray Photoemission Spectroscopy Study for the Flat YBa2Cu3Oy Single-Crystal Surface Prepared by Chemical Etching and O2 Annealing
Authors: Hiroshi Uchiyama Hiroshi Uchiyama , Nobue Tanaka Nobue Tanaka , Hideaki Zama Hideaki Zama , Setsuko Tajima Setsuko Tajima , Tadataka Morishita Tadataka Morishita , Koichiro Saiki Koichiro Saiki , Atsushi Koma Atsushi Koma
Published: October 2002

The effect of chemical etching with a HCl/methanol solution on a polished sample of single-crystal YBa2Cu3Oy (001) was investigated by emission-angle-dependent X-ray photoemission spectroscopy (XPS). By chemical etching, the extrinsic Ba state in the surface region was removed without the effect of halogen. The bulk state of Y was also restored in the surface by subsequent annealing in an oxygen atmosphere at 400°C.
X-Ray Diffraction from Low-Temperature-Grown Silicon Films with Small Surface Roughness
Authors: Kazuhiro Nakamura Kazuhiro Nakamura , Hirofumi Shimizu Hirofumi Shimizu , Jun Kodera Jun Kodera , Katsuhiro Yokota Katsuhiro Yokota
Published: October 2002

Silicon films were grown by molecular beam epitaxy (MBE) at temperatures below 350°C. The X-ray diffraction peaks from the (220) plane were observed only in the films grown at 300°C and 250°C, although they were not observed in the films grown above 350°C and below 200°C. The microroughness of the surface of the film was also examined by reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM). The relationship between the X-ray diffraction peak from the (220) plane and the microroughness of the surface of the film are discussed.
Electron Kinetics in the Hot-Cathode Negative Glow of a Helium Discharge
Authors: Sirghi Lucel , Ohe Kazuyuki , Costin Claudiu , Popa Gheorghe
Published: October 2002

The electron kinetics in the negative glow of a
thermionic-cathode discharge in helium is discussed based on the
results of Langmuir and emissive probe measurements performed in the
axial direction of a 5-cm-long discharge at 0.65 Torr helium
pressure and low discharge current. The electron energy distribution
function shows two groups of electrons: the primary ones, which are
emitted by the cathode and accelerated into the cathode fall, and
the secondary ones, which are produced by inelastic collisions
between primary electrons and neutral atoms. The cathode fall
voltage and primary-electron energy show a strong dependence on
thermionic current intensity. Based on the experimental results
obtained for a thermionic current corresponding to a cathode fall
voltage slightly above the helium ionization potential, a simplified
electron kinetic model using the Monte Carlo flux simulation is
proposed to obtain the secondary-electron energy distribution. Since
the axial profile of the measured plasma potential shows a potential
well, which corresponds to a maximum in the negative glow plasma
density, the simulated secondary-electron energy distribution can be
obtained mainly as a result of the accumulation of low-energy
electrons yielded from inelastic collisions.
Photodetachment Study of Capacitively-Coupled RF C4F8Plasma
Authors: Akihiro Kono Akihiro Kono , Yoshinobu Ohya Yoshinobu Ohya
Published: October 2002

Behaviors of electrons and negative ions in a capacitively coupled RF (13.56 MHz) plasma ofc-C4F8(perfluorocycrobutane) were studied using a laser-induced photodetachment technique in combination with a microwave cavity resonance technique. The results indicate that the negative ion formation process strongly depends on the RF power because of the dissociation ofc-C4F8even in the low power range (<100 W) studied in this work. The negative ion density estimated on the assumption that all negative ion species have the same photodetachment efficiency as that for F-is larger by a factor of ∼50 than the electron density in the typical condition in this work (100 mTorr C4F8, 10 W RF power). However, the electron attachment rate and ion recombination rate suggest that the actual negative ion density should be significantly higher than that derived on the above assumption; this discrepancy could be attributed to the low photodetachment efficiency for large molecular negative ions which may exist abundantly in the low RF power region.
Thermal Decomposition of Poly(methylphenylsilane)
Authors: Lujun Pan Lujun Pan , Mei Zhang Mei Zhang , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

The thermal decomposition of poly(methylphenylsilane) was performed at constant heating rates and isothermal conditions. The evolved gases were studied by ionization-threshold mass spectroscopy. Pyrolysis under isothermal conditions reveals that the decomposition of poly(methylphenylsilane) is a type of depolymerization that has a first-order reaction. Kinetic analysis of the evolution spectra of CH3–Si–C6H5 radicals, phenyl and methyl substituents reveals the mechanism and activation energies of the decomposition reactions in main chains and substituents. It is found that the decomposition of main chains is a dominant reaction and results in the weight loss of approximately 90%. The effusion of phenyl and methyl substituents occurs in the two processes of rearrangement of main chains and the formation of stable Si–C containing residuals.
Characterization of Si(100) Surface after High Density HBr/Cl2/O2 Plasma Etching
Authors: Low Chun Hui , Chin Wee Shong , Tan Kuang Lee , Loh Foo Chan , Zhou Meisheng , Zhong Qing Hua , Chan Lap Hung
Published: October 2002

The nature of deposited film on unmasked Si(100) surface after
high density HBr/Cl2/O2 plasma etching has been investigated. The
as-etched surface was treated sequentially with HF for different
duration and monitored with atomic force microscopy (AFM) and X-ray
photoelectron spectroscopy (XPS). It was found that microscopic Si
pillars are formed on the etched surface and might be attributed to
the formation of micromasks. XPS surface analysis indicated the
passivation film consists mainly of silicon oxides and oxybromides.
Ab initio calculations using Si4 cluster model suggested the direct
attack of oxyhalide species on the surface as the energetically most
favored process. It is also shown that HF treatment for 40 s was
effective in the complete removal of the residual film.
Determination of the Density and the Thickness of SiO2 Films Using Extremely Asymmetric X-Ray Diffraction
Authors: Kudo Yoshihiro , Liu Kuang-Yu , Kawado Seiji , Kashiwagi Akihide , Hirano Keiichi
Published: October 2002

From a theoretical understanding of rocking curves of extremely asymmetric
X-ray diffraction from silicon crystals on which SiO2 films were thermally
grown, both of the density and the thickness of the films were determined. Inherent
measurement errors due to properties of the substrate were eliminated by dividing the
intensity of the diffracted X-rays from the substrate with the film by the intensity
without the film. The measurement results of the density indicated that the range of
structural imperfection in SiO2 films varies with the conditions of oxidation and
post-oxidation annealing.
Total Energy Estimation for Pd/Al Bimetallic Surfaces by a Parallel Computation Scheme
Authors: Noriko Watari Noriko Watari , Shuhei Ohnishi Shuhei Ohnishi , Hiroshi Onishi Hiroshi Onishi , Yasuhiro Iwasawa Yasuhiro Iwasawa
Published: October 2002

A numerical calculation scheme for the multicenter problem in large molecules and clusters is presented by applying the message-passing interface (MPI) in a massively parallel computer that uses the density functional method. The multicenter problem associated with the Coulomb singularity of an atom is efficiently treated by the parallel processors by allocating several atoms into each processor element (PE). The order N
2/P tuning is obtained for the Coulomb energy calculation by using the MPI which transfers Coulomb potential field between PE's. This method is applied to estimate the total energy of the reconstructed Al/Pd bimetallic surface. The energy estimation by the charge density of a superposition of isolated atomic charge fragments predict a stabilization caused by the reconstruction, being consistent with a self-consistent-field (SCF) cluster calculation of the bimetallic surface.
Wide Stop-Band Filter Consisting of Multiresonator Based on an Optical Directional Coupler
Authors: Furuta Hirosuke , Nishikawa Kenji
Published: October 2002

Recently, the wavelength range of wavelength division multiplex
(WDM) systems has been widening. Consequently, optical filters
require wide stop bands that can cover this range. Multiresonance
filters can have flat pass bands and relatively sharp cutoff
characteristics but have narrow stop bands because of the repeated
appearance of resonance. In this paper, an optical filter based on a
directional coupler is discussed. It may be suitable for integrated
optics because of its simple structure. The method of widening the
stop band is also reported.
Ink-Jet Fabrication of Polymer Microlens for Optical-I/O Chip Packaging
Authors: Ishii Yuzo , Koike Shinji , Arai Yoshimitsu , Ando Yasuhiro
Published: October 2002

We report on a simple and versatile method of fabricating
polymer microlenses
that can be easily integrated with optical devices. UV-curable epoxy
resin is dropped
onto optical devices by an ink-jet apparatus. When the droplets touch the surface,
they form into partial spheres due to their surface tension. UV light
irradiation for
less than five minutes can easily turn them into solid
microlenses. Various
microlenses, having a geometrical diameter from 20 to 140 µm with
F/1.0 to F/11.0,
were successfully produced by controlling the volume and viscosity of
the polymer
resin and their wettability to the substrate. Their uniformity in a
microlens array was
measured to be within ±1% in diameter and ±3 µm in
pitch. Hybrid
integration of an
ink-jetted microlens with a wire-bonded vertical-cavity
surface-emitting laser
(VCSEL) was also demonstrated. When an ink-jetted microlens (45-µm
diameter,
F/2.0) was formed on the aperture of an 850-nm VCSEL, the coupling
efficiency into a
single-mode fiber was 4 dB higher than without the microlens.
A High Performance Dichroic Glass Polarizer with A Thickness of 15–35 µm
Authors: Hasui Kenjiro , Grossman David G. , Mann Larry G. , Takahashi Hiroki , Borrelli Nicholas F.
Published: October 2002

A dichroic glass polarizer having good optical and thermal properties is
fabricated with a thickness of 15–35 µm. This polarizer has a contrast ratio
greater than 40 dB with 30 µm thickness at 1.54 µm wavelength. Insertion loss was
measured to be less than 0.06 dB. No difference in contrast ratio was confirmed
against incident angle shift from normal to 7°. Large aperture size as large as
10×10 mm square and good thermal durability were realized. This polarizer is
considered to be useful for lens-free and tilted configurations of
optical devices.
Cosintering of Ni–Zn–Cu Ferrite with Low-Temperature Cofired Ceramic Substrates
Authors: Chen Lih-Shan , Hsi Chi-Shiung , Fu Shen-Li , Lin Jiuun-Yih
Published: October 2002

Inserting a ferrite layer into a low-temperature cofired ceramic
substrate offers the potential of burying inductors in multilayer
ceramic substrates. To cofire a ceramic substrate at low temperatures,
ferrite must be densified at a low temperature. With the addition of
6 wt%Bi2O3, Ni–Zn–Cu ferrite can be densified at
900°C. The doped Bi2O3 not only lowers the sintering
temperature but also increases the permeability of Ni–Zn–Cu
ferrite. The “cordierite + borosilicate glass” system is very
compatible with Ni–Zn–Cu ferrite after cofiring, but the calcium
borosilicate crystallizable glass system is incompatible with
Ni–Zn–Cu ferrite. However, with the addition of 10 wt%SiO2
into the calcium borosilicate crystallizable glass system, the
incompatibility was resolved.
Reversed and Uniform Δβ Directional Coupler Optical Switch with Periodically Changing Coupling Strength
Authors: Okayama Hideaki , Kamijoh Takeshi , Tsuruoka Taiji
Published: October 2002

A new device structure for a reversed Δβ directional
coupler is
proposed to achieve the lower value of phase mismatch and device
length product (ΔβL) required for switching or
digital-like
response. By decreasing the coupling coefficient in the middle of
each electrode section, the ΔβL value required to drive
the device
is reduced to almost half of that for a conventional device. The
response curve of the device can be modified to obtain a wide range
of ΔβL values.
Switchable Zero-Order Diffraction Filters Using Fine-Pitch Phase Gratings Filled with Liquid Crystals
Authors: Sakata Hajime , Nishimura Michiyo
Published: October 2002

Zero-order transmission efficiency is controlled using electrically switchable liquid crystals
confined in periodic fine grooves. Trapezoidal grating profiles are designed in order to improve
the extinction ratio. Using the index matching and mismatching conditions of liquid crystals
with the grating grooves, we achieve a transparent window for the entire visible range in the
matching state, and a dark color filter in the mismatching state. Spectral transmittance is
changed through the frequency-dependent anisotropic permittivity of the liquid crystal.
Polarization-insensitive operation is performed using a two-stack
device with crossed grating directions.
A Bidirectional Optical Module Based on Stacked Planar Optical Circuit
Authors: Mizuno Rogerio Jun , Aoki Yasuhiko , Shimada Yuji , Iga Kenichi
Published: October 2002

In this paper, a bidirectional optical module based on a stacked
planar optical circuit (SPOC) concept to perform a wavelength
division multiplexing (WDM) function is described. The module
consists of an optical chip which incorporates planar microlens
(PML) arrays and nonpolarizing 1.31/1.55 µm WDM
dielectric-multilayer filters. Module design and theoretical
estimation of loss tolerance were conducted. From preliminary
experiments, the feasibility of SPOC modules was confirmed. A
fabricated WDM filter showed a small polarization-dependent loss
(PDL) of about 0.48 dB and 0.05 dB for the wavelengths of
1.31 µm and 1.55 µm, respectively. Channel crosstalk and
PDL for the SPOC module were characterized by means of discrete
filter devices. For the 1.55 µm downstream (1.31 µm
downstream/upstream) channel, a crosstalk as low as -40 dB
(-26 dB) and a PDL less than 0.23 dB (0.53 dB) were
achieved.
Micro-Optical Platform for All-Optical Demultiplexing Switch Array
Authors: Hainberger Rainer , Kamiya Takeshi
Published: October 2002

As it is free from electrical parasitics, the use of the all-optical switch array is an
attractive approach for achieving very high-speed signal processing for optical communication
and interconnection beyond the Gbit/s range. However, two incident beams and one outgoing beam
for each switch may require a complex geometry, thus the module assembly procedure remains a
serious obstacle for its realization. The present work reports the design, test fabrication, and
characterization of an optical platform dedicated to all-optical demultiplexing at 1.55 µm,
using asymmetric Fabry-Perot saturable absorber switches as active devices, and off-axis binary
Fresnel zone lenses as the focusing optics. Two different platform configurations were fabricated
by a substrate stacking technique achieving spot sizes of 13 µm and 22.5 µm at the switch
plane, with reasonable overlap between the pump and signal beams. The influence of wavelength
variation, fabrication tolerance and throughput are discussed.
Fabrication of Micro-Pyramidal Probe Array with Aperture for Near-Field Optical Memory Applications
Authors: Kim Young-Joo , Kurihara Kazuma , Suzuki Kazuhiro , Nomura Mitsuru , Mitsugi Satoshi , Chiba Masafumi , Goto Kenya
Published: October 2002

A new optical memory system is urgently required to realize high
memory capacity and fast data transfer rates in the coming
multimedia era. To overcome the current capacity barrier of
far-field techniques, a novel near-field optical memory of
evanescent wave has been proposed using a vertical cavity surface
emitting laser (VCSEL) probe array, consisting of the VCSEL array as
a light source and the micro-pyramidal probe array as an evanescent
wave exit. The design and fabrication for the aperture probe array
were developed in this research. An array of up to 10,000 pieces was
prepared successfully using microfabrication processes, including
photolithography, silicon wet etching, thermal oxidation and thin
film deposition. The pyramidal probes in the array show little
variation in size and are sufficiently sharp to apply to the
near-field recording head. The probe tip has a small size of 100 nm
and the aperture has a diameter of around 150 nm. A smaller
aperture can be fabricated with more careful control of the
experimental procedures, including the etching process and thermal
wet oxidation.
Simultaneous Sensing of Temperature and Displacement Using a Multimode Fiber Bragg Grating
Authors: V. Djambova Tzvetanka , Toru Mizunami Toru Mizunami
Published: October 2002

We present an experimental method for the operation of a multimode fiber Bragg grating as a sensor of temperature and displacement. A Bragg grating in a multimode fiber has multiple reflection peaks. The bending of the multimode fiber induces the redistribution of modes and affects the measured reflection spectrum of a Bragg grating. The bending sensitivity is used for sensing of displacement. In the experiment, we bend a graded-index multimode fiber and observe the reflection and transmission spectra. As the fiber is bent, the number of reflection peaks decreases, and the center reflection wavelength shifts to the longer wavelength, toward the fundamental mode. We also measure the temperature dependence of the wavelength of each reflection peak. The bending and temperature dependence in transmission measurements is almost the same as that in the reflection measurements. Next, we present an experiment on the simultaneous sensing of temperature and displacement. The shift of each transmission or reflection wavelength of the fiber Bragg grating is only a function of temperature. The experimental results demonstrate the possibility of the practical application of this sensing approach.
Optical Pattern Recognition System Based on Parallel Spatial Filtering Using Synthetic Discriminant Function
Authors: Takahashi Takanori , Katayama Takeo , Iga Kenichi
Published: October 2002

In this paper, we propose an optical pattern recognition system
based on spatial filtering using a synthetic discriminant function
(SDF). In this system, the input image is multiplexed by a microlens
array under incoherent illumination, and then the optical inner
product of input images and SDF filters is optically conducted. The
image is recognized by thresholding the optical inner product
values. The present SDF filter was constructed with pseudogradation
transparent filters fabricated by electron-beam lithography. We
performed an experiment that involved the recognition of ten Arabic
numerals and evaluated the discriminating characteristics of
parallel pattern recognition. We confirm that the proposed system
can function as a parallel recognition system without the need to
scan images.
Optical Pattern Recognition Experiments of Walsh Spatial Frequency Domain Filtering Method
Authors: Takeo Katayama Takeo Katayama , Takanori Takahashi Takanori Takahashi , Kenichi Iga Kenichi Iga
Published: October 2002

An optical parallel processor for an image recognition system using
microoptical devices has been developed.
This system expands input images to coefficients of a two-dimensional
Walsh spatial frequency domain and discriminates them by performing
the inner product to the reference filter.
In this paper, we demonstrate parallel optical discrimination of
Arabic numerals using this method.
First, the mechanism of this recognition method is presented.
Next, the reference filter is designed.
In order to implement the reference filter by using the microoptical devices,
the fabrication problems were solved.
Finally, the recognition system is constructed and effects of deformation on the input image are experimentally evaluated.
Mechanism and Characteristics of Through-hole Formation on Si Wafer by Optical Excitation Electropolishing Method
Authors: Satoh Akinobu
Published: October 2002

Through-holes were formed by the optical excitation electropolishing method
(OEEM) in a 2.5 wt% HF electrolytic solution using an N-type (100) Si wafer as the
anode and a Pt plate as the cathode. The formation of through-holes occurs when the
positive holes important in this reaction converge only on the acute-angled portion
which is the three-dimensional element of the V-ditch which determines the positions
and diameters of through-holes. However, it was found that overall electropolishing
occurs at the initial stages there of the reaction when the positive holes also converge
on the acute-angled portion which is the two-dimensional element (Si surface) of the
V-ditch (due to the peripheral effect). The author investigated the OEEM reaction
mechanism through the analysis of gases generated in the reaction and proposed a
chemical equation for the reaction. In addition, he indicated that the dissolution of Si is
a reaction occurring in the presence of a charge followed by a slow chemical reaction
and that excessive current supply results in a reactive current.
Molecular Beam Epitaxial Growth and Characterization of the Vertically Aligned InAs Quantum Dots Embedded in Al0.5Ga0.5As
Authors: Kazuto Koike Kazuto Koike , Shuwei Li Shuwei Li , Mitsuaki Yano Mitsuaki Yano
Published: October 2002

In this paper we describe structural and optical properties of vertically aligned InAs quantum dots (QDs) embedded in Al0.5Ga0.5As. These aligned QDs were grown at 520°C in the Stranski-Krastanow growth mode of molecular beam epitaxy. Measurements by reflection high-energy electron diffraction and atomic force microscopy showed that both the size and density of these QDs increased with the number of stacking periods. The temperature dependence of the wavelength-integrated photoluminescence (PL) intensity revealed that the intense emission from excitons, which dominated the PL spectra at low temperatures, was easily thermally quenched by the large dots in the upper layers. To improve these unfavorable characteristics, we employed a size- and density-controlled growth procedure for the QDs in the upper layers, and succeeded in increasing the PL stability at high temperatures. We also studied a postgrowth annealing treatment for these aligned QD-structures, and found that it is effective to increase the PL intensity when the annealing is performed at around 570°C. By combining the controlled growth procedure with the postgrowth annealing treatment, we realized a strong excitonic emission of which the quenching temperature associated with an activation energy of 0.65 eV was as high as ∼300 K.