bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferrielectricity in Chiral Smectic Cβ of an Antiferroelectric Liquid Crystal
Authors: Tatemori Syuichi , Hiroyuki Uehara Hiroyuki Uehara , Jun Hatano Jun Hatano , Hideo Saito Hideo Saito , Shin'ichi Saito Shin'ichi Saito , Eiji Okabe Eiji Okabe
Published: October 2002

The switching current behavior and the complex dielectric constant under DC electric bias field and domain structures of
an antiferroelectric liquid crystal, 4-(1-methylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), were
investigated as a function of optical purity and cell thickness, and the ferrielectricity of the chiral smectic C
β
phase (SmC
β
*) was discussed. Optically pure samples show two-step decrease in the real part of complex dielectric constant with increasing DC bias field. The first decrease corresponds to the suppression of the ferroelectric Goldstone mode, which is also suppressed by decreasing cell thickness. The second step, which is observed even in the chiral smectic C
α
phase (SmC
α
*), corresponds to the suppression of a new relaxation mode induced by DC electric bias field. Three peaks of the switching current were observed in SmC
β
* and also in the lower-temperature region of SmC
α
*. Temperature dependence curves of the peak positions
are continuously connected together at the phase transition temperature between SmC
β
* and SmC
α
*. It can be said that the antiferroelectricity of SmC
α
* is conserved in SmC
β
*, and that the ferrielectricity of SmC
β
* may consist of the ferroelectricity
of SmC* and the antiferroelectricity of SmC
α
*. Striped domains observed in SmC
β
* after removing the DC electric bias field can be considered to be the SmC
α
* phase.
Optical and Transport Properties of CdSe/ZnSe Self-Organized Nanostructures: 1-Dimensional versus 3-Dimensional Quantum Confinement
Authors: Toropov Alexei A. , Ivanov Sergei V. , Shubina Tatiana V. , Sorokin SergeiV. , Lebedev Anton V. , Sitnikova Alla A. , Kop'ev Piotr S. , Pozina MagnusWillander , Bergman Peder , Monemar Bo
Published: October 2002

We present comprehensive studies of optical, structural and
transport properties of molecular beam epitaxy grown CdSe/ZnSe
self-organizing nanostructures, aimed at elucidation of the
intrinsic morphology of CdSe layers as a function of their nominal
thickness (w). Particular attention has been paid to the layer
thickness below the critical value (w < 3.0 monolayer (ML)). It is
found that the layer morphology is transformed from pure two-dimensional objects at w<0.7 ML to extended (15–40 nm) flat
islands formed in the thicker layers. The density of the islands
increases with w, which is accompanied by enhancement of the
luminescence quantum efficiency. An optically pumped green laser
is fabricated, taking advantage of the superior emission
characteristics of the single CdSe layer with w=2.8 ML, used as an
active region. The threshold power density of 3.9 kW/cm2 observed
at 300 K is fivefold less than that of the reference sample using
a conventional ZnCdSe quantum-well active region.
Low-Temperature Raman Studies of Pb(ZrxTi1-x)O3 and Pb1-3y/2NdyTiO3 Ceramics
Authors: Frantti Johannes , Lappalainen Jyrki , Lantto Vilho , Nishio Shigeru , Kakihana Masato
Published: October 2002

Raman scattering studies of lead zirconate titanate Pb(Zr
x
Ti1-x
)O3 (PZT),
0.10≤x≤0.80, and Nd-modified lead titanate Pb1-3y/2Nd
y
TiO3 (PNT),
y=0.02, 0.10, bulk ceramics were carried out at ambient temperatures
between 4.2 and 297 K. Our measurements reveal splitting of the
E⊕B
1
symmetry peak at low temperatures in both PZT and PNT samples. Splitting
or a very asymmetrical line shape of the three other E(TO) peaks in the PZT and PNT samples was also found. These findings are related to the precursor
effects. We also discuss the phase stability of lead titanate based perovskites
from the point of view of our experimental results and recent theoretical
calculations. A simple model explaining the differences between the low-frequency Raman spectra of tetragonal and trigonal PZTs is outlined.
Carbon in Grown-in Defects in Czochralski Silicon and Its Influence on Gate-Oxide Defects
Authors: Ueki Takemi , Itsumi Manabu , Takeda Tadao
Published: October 2002

We systematically investigated the impurities situated in the octahedral void defects in Czochralski silicon crystal by using electron energy-loss spectroscopy and Auger electron spectroscopy. As a result, we found that carbon cohesion was observed on the inner walls of the void defects. The carbon concentration on the inner walls was estimated to be about 2×1014/cm2. This result suggests that void defects with this amount of carbon could seriously affect the integrity of gate-oxides of metal-oxide-silicon integrated circuits.
Silicon Dioxide Film with Low Dielectric Constants using Liquid-Phase Deposition
Authors: Chanthamaly Phonekeo , Arakawa Taro , Haneji Nobuo
Published: October 2002

We propose a method which is advantageous for forming F bonds in the Si–O network without any external energy assistance. This method can be used to grow SiO2 films in supersaturated fluorosilicic acid (H2SiF6) at room temperature. The dissociation reaction between H2SiF6 and H2O leads to the formation of silica and the deposition of SiO2 films on the surface of substrates. Because the reaction involves an aqueous acid which contains fluorine, F bonds are formed in the films naturally. The percentage of F atoms increased from 3.5 to 4.75% according to X-ray photoelectron sectroscopy (XPS) survey, and the F1S
peak changed from 687.72 to 687.18 eV with an increase in concentration from 2.25 to 3.25 mol/l, respectively. In addition, due to the effect of F bonds inside the film, the dielectric constant also decreased from 3.7 to about 3. Atomic force microscopy (AFM) images showed that the surface roughness increased with increasing H2SiF6 concentration due to the attack of F; however, the maximum surface roghness was less than 0.5 nm.
Dependence of Grown-in Defect Behavior on Oxygen Concentration in Czochralski Silicon Crystals
Authors: Umeno Shigeru , Yanase Yoshio , Hourai Masataka , Sano Masakazu , Shida Yoshiaki , Tsuya Hideki
Published: October 2002

The behavior of grown-in voids in the as-grown state and during annealing was investigated for Czochralski silicon wafers using an atomic force microscope, Secco etching and an optical precipitate profiler. In previous reports, most grown-in voids have been found to consist of two octahedrons. In this report, it was shown that the percentage of the voids which consist of one octahedron increased as the oxygen concentration decreased. The annealing behavior of the voids was summarized as follows. In the case of supersaturated oxygen concentration, growth of the oxide films within the voids occurred and this reduced their ability to form flow patterns during Secco etching. The growth of oxide films within the voids was enhanced by excess interstitial silicon atoms injected during annealing in an oxygen ambient. In the case of undersaturated oxygen concentration, the annihilation of the voids was also enhanced due to the injection of interstitial silicon atoms during annealing in an oxygen ambient. Interstitial silicon atoms contributed to both of these phenomena.
Comparison of the Characteristics of Polyoxides Grown by Thermal, Rapid Thermal Oxidation, and Tetraethylorthosilicate Deposition Methods
Authors: Chang Kow Ming , Lee Tzyh Cheang , Sun Yong Long
Published: October 2002

The characteristics of polyoxides grown by different methods in
order to find the best way of growing high qualities of polyoxide were
investigated in this work. Thermal, rapid thermal oxidation (RTO), and
tetraethylorthosilicate (TEOS) deposition methods were used to grow
the polyoxides. RTO provided a smoother interface of
polyoxide/polysilicon than that of thermal furnace method. TEOS
deposition method resulted in a smooth polyoxide/poly-1 interface due
to no polysilicon consumption. The polyoxide grown by thermal method
had the worst characteristics, while the post-deposition RTO method
had the best qualities (low leakage current, high breakdown electric
field, low voltage shift, and high charge-to-breakdown). The high
qualities of polyoxide grown by post-deposition RTO method were due to
the smooth polyoxide/poly-1 interface and less electron trapping.
Optimization of Transparent Conductive Oxide for Improved Resistance to Reactive and/or High Temperature Optoelectronic Device Processing
Authors: Komaru Takashi , Shimizu Satoshi , Kanbe Mika , Maeda Yoshiteru , Kamiya Toshio , Fortmann Charles M. , Shimizu Isamu
Published: October 2002

Research on improved amorphous silicon-based devices has focused
on materials prepared at high temperatures and/or those grown under
very reactive conditions. The use of these conditions for device
applications requires the development of more robust transparent
conductive oxide (TCO) substrates. A thin (<10 nm) ZnO coating on
a SnO
x
-coated glass substrate could withstand RF (13.56 MHz) and
very high frequency (VHF: 144 MHz) hydrogen plasma treatments;
however, the TCO was strongly reduced by a higher density, higher
energy electron cyclotron resonance (ECR) hydrogen plasma or a higher
temperature. Ga-doped ZnO (GZO) TCO substrates exhibited greater
resistance to hydrogen plasma induced reduction. RF magnetron sputter
deposited crystalline GZO thin films were deposited and optimized at
temperatures higher than 150°C on glass substrates. The
electron mobility and the Ga doping efficiency were improved with
increasing GZO deposition temperature. The performance of a-Si:H
solar cells fabricated under standard conditions
(∼220°C) on these GZO substrates increased with
increased GZO deposition temperature. The performance of a-Si:H solar
cells prepared under more reactive and/or at higher deposition
temperatures on 250°C deposited GZO was also examined. Both
high temperature (280°C)-deposited narrow-bandgap
a-Si:H(Ar) and ECR hydrogen plasma deposited
a-Si:H(Cl) based solar cells were significantly
improved using high temperature deposited GZO substrates.
Exciton-Phonon Interaction and Phonon Frequency Renormalization in Semiconductor Quantum Dots
Authors: Selvakumar V. Nair Selvakumar V. Nair , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

We present a theory of LO phonon renormalization by coupling with the
exciton in semiconductor quantum dots. We find that the one phonon side
band of the exciton ground state shows an anticrossing with the excited exciton
states. Across such an anticrossing, the phonon-like and exciton-like modes
exchange their characters resulting in a redistribution of the oscillator
strengths of interband transitions. Even away from such a resonant coupling,
the phonon frequency shift is significant. For example, in CuCl quantum dots
in the weak confinement regime, the phonon frequency in the presence of a single
exciton is reduced by about 10% from its value in the ground state.
Consideration of Space Charge Effects and Effective Mass Non-parabolicity when Optimising Multi Quantum Barriers
Authors: Kestle Angela , Wilks Steve P.
Published: October 2002

The use of multi quantum barriers (MQBs) to enhance the barrier
height of n-i-n tunnelling diodes is demonstrated for a range of GaAs
based devices. In particular, a barrier height of 0.38 eV has been
measured for an Al0.3Ga0.7As/GaAs MQB, corresponding to a barrier
enhancement of 0.12 eV. The excellent agreement between experimental
measurement and theoretical prediction highlights the importance of
including space charge effects and the non-parabolicity of the
effective mass within the theoretical model. The In
x
Ga1-x
As/InP system
was studied theoretically for a range of In fraction, x. A barrier
height enhancement of 46% was predicted for a tensile strained
In0.4Ga0.6As/InP MQB when compared with a single barrier
structure. This was a larger enhancement than could be achieved using
a lattice matched In0.53Ga0.47As/InP MQB system. The presence of
strain was thus seen to provide an additional parameter for use within
MQB design and optimisation.
Focusing and Guiding Charged Particles by a Superconducting Tube: An Analytical Nonlinear Approach for the Complete Flux Expulsion Model
Authors: Buzea Calin , Agop Maricel , Rezlescu Nicolae
Published: October 2002

We give an analytical solution for the nonlinear equation of motion of an electron beam in the radial direction of a superconducting tube, for the case of electrons moving close to the tube axis, in the complete flux expulsion model. Hence, we deduce a general expression for the focusing length that is dependent on the parameters of the superconducting tube and electron stream. Our focusing length is inversely proportional to x
0, the width of the electron beam, and is in good agreement with experimental data.
Magnetic Isolation on a Superconducting Ground Plane
Authors: Yoshinao Mizugaki Yoshinao Mizugaki , Kiyoshi Yanagisawa Kiyoshi Yanagisawa , Takeshi Onomi Takeshi Onomi , Tsutomu Yamashita Tsutomu Yamashita , Koji Nakajima Koji Nakajima , Hirotake Yamamori Hirotake Yamamori , Akira Shoji Akira Shoji
Published: October 2002

We investigate the magnetic isolation on a superconducting ground plane (GP) by measuring the mutual inductance between two lines. We evaluate the shielding effect of three structures: a simple flat GP, a GP with a shielding wall, and a GP with a covering layer. The third structure reduces the mutual inductance as much as -13 dB compared with the first one. We also derive an expression of the mutual inductance for the first structure.
Ring Self-Pumped Phase Conjugator for High Energy Pulses at 1064 nm with Rhodium-Doped BaTiO3
Authors: Tei Kazuyoku , Niwa Yoshito , Kato Masaaki , Maruyama Yoichiro , Arisawa Takashi
Published: October 2002

An external loop phase conjugate mirror with a 45°-cut rhodium-doped BaTiO3 is constructed and characterized. The external loop is composed of an image-relay telescope, a 90°-image rotator and a phase modulator. The stable phase conjugation is achieved with nanosecond 20 mJ pulses at 1064 nm. Reflectivity of the mirror as high as 53% is obtained with a response time of 13 s at a repetition rate of 100 Hz. Wavefront compensation is applied to a laser beam whose quality is as poor as M
2 > 100.
Generation of 650-Femtosecond Optical Pulses from a Gain-Switched Laser Diode Using Second-Harmonic Generation
Authors: Ohta Hiroshi , Nogiwa Seiji , Kawaguchi Yoshikazu , Endo Yoshio
Published: October 2002

The frequency doubling and pulse compression of an optical pulse
is discussed. The optical pulse was generated from a gain-switched
laser diode, and its timing jitter was reduced to less than 210 fs by
the CW-light injection technique. The pulse width and the center
wavelength of the fundamental optical pulse were 4.8 ps and
1550 nm. By amplifying the fundamental pulse with two optical fiber
amplifiers, the waveform of the pulse was distorted, and the pulse
spectrum was spread by the Kerr effect in the amplifiers. In
periodically poled lithium niobate, high-efficiency second-harmonic
generation occurred with the high-peak power of the distorted
fundamental pulse. The generated second-harmonic optical pulse width
was 650 fs, and its waveform showed good agreement with the
sech2 shape. This optical pulse is useful as a sampling pulse
that can be used in electrical-optical or optical-optical sampling
because its repetition rate can be easily varied.
Simulation of Visible Light Induced Effects in a Tunnel Junction Array for Photonic Device Applications
Authors: Tabe Michiharu , Terao Yoichi , Ishikawa RatnoNuryadi , Asahi Noboru , Amemiya Yoshihito
Published: October 2002

We have studied visible light or near-infrared irradiation effects in voltage-biased tunnel junction arrays, where each node is connected not only to neighboring nodes but to a conducting substrate through a tunnel barrier. Major assumptions used in the simulation are: (i) that the photoexcitation of electrons occurs only in the substrate and (ii) the tunnel barrier is effectively lowered for the excited electrons, resulting in a reduced tunnel resistance. As a result, it was found that a U-shaped potential profile is formed by local irradiation and the potential of the irradiated area is clamped at the lowest value. Since the currents at both terminals reflect the left and the right potential slopes in the dark areas, respectively, the irradiated position is determined by measuring the currents. These results suggest that tunnel junction arrays can be applied to photonic devices such as position sensing detectors or image processing devices.
Interfacial Electronic Phenomena and Capacitance–Voltage Characteristics of Phthalocyanine Langmuir-Blodgett Films
Authors: Itoh Eiji , Iwamoto Mitsumasa
Published: October 2002

The capacitance–voltage (C–V) characteristics of ultrathin phthalocyanine (CuttbPc) Langmuir-Blodgett (LB) films were examined, taking into account the interfacial electrostatic phenomena. It was revealed that the electrical properties of CuttbPc LB film sandwiched between metal electrodes were dominated by negatively charged space-charge layers with a thickness of less than 10 nm. It was also shown that the density of charges in the electrostatic double layer of Al/CuttbPc LB film, determined from a low-frequency C–V measurement, is in good agreement with the space-charge density, obtained by the conventional surface- potential measurement.
Development of One-Dimensional Pyroelectric Infrared Array Detector with High Sensitivity
Authors: Hashimoto Kazuhiko , Tsuruta Tomohiro , Nishimura Koji , Morinaka Katsuya , Yoshiike Nobuyuki
Published: October 2002

A one-dimensional pyroelectric array detector for use as a multielement infrared
sensor has been developed by using PbTiO3 bulk ceramics fabricated by a sheet-forming method. This one-dimensional infrared sensor consists of 16 elements. A pyroelectric detector responsivity of 3×104 V/W can be obtained at a 10 Hz chopping frequency, and a specific detectivity D
* of 1.2×108 cm·Hz1/2/W has been achieved. The time constant of this pyroelectric detector is about 5.2 ms, so the detector has a shorter response time compared with a commercially available conventional pyroelectric detector. The crosstalk, which influences the output for the adjacent elements, is less than 10%. The output voltage for the detector gradually decreased as the atmospheric temperature increased. Pyroelectric detector responsivity increases with decreasing electrode size. By using this high-performance pyroelectric array detector, the thermal sources at lower temperatures than that of the environment can be detected with high sensitivity, as much as in the case of the thermal sources at higher temperatures.
Red Light Emitting Injection Lasers with Vertically-Aligned InP/GaInP Quantum Dots
Authors: Hangleiter Thomas Riedl
Published: October 2002

In this paper, we demonstrate the first injection
lasers, using threefold-stacked
vertically-aligned InP/GaInP quantum dots (QD's) as the active medium. The lasers emit in the visible part of
the spectrum (690–710 nm) with a threshold current density
(j
th) of 172 A/cm2 at 90 K, increasing with temperature up
to j
th = 685 A/cm2 at 210 K. We identify the lasing being
due to QD ground state transitions. The temperature dependence of
j
th is investigated in detail. At low temperatures, the threshold
current density is almost independent of temperature while, towards
higher temperatures, a thermally activated increase is found, strongly
depending on QD size. The rise in j
th is accompanied by a decrease of the
integrated photoluminescence (PL) intensity, indicating that nonradiative
recombination of carriers plays a significant role with increasing
temperature. We assume thermal evaporation
of carriers out of the dots and into the wetting layer (WL), where they recombine
nonradiatively, to be the process responsible for the increase
in j
th.
Novel Ferroelectric Liquid Crystal Mode for Active Matrix Liquid Crystal Display Using Cholesteric–Chiral Smectic C Phase Transition Material
Authors: Asao Yasufumi , Togano Takeshi , Terada Masahiro , Moriyama Takashi , Nakamura Shinichi , Iba Jun
Published: October 2002

We propose a novel ferroelectric liquid crystal (FLC)
mode which is capable of gray-scale display with an active device
such as a thin-film transistor (TFT). This technology is based
on the monostable FLC mode, which is obtained from a material
with cholesteric–chiral smectic C (Ch–SmC*) phase transition
sequences and by applying a low DC voltage only near the phase
transition temperature from Ch to SmC* for making the layer
normal direction uniform. The electrooptical response of
liquid crystal molecules under AC voltage is asymmetric between
plus and minus voltages. It shows characteristics such as low
spontaneous polarization (P
S) value, short response time, small
temperature dependence and wide tolerance to cell gap
nonuniformity. Furthermore, we made TFT prototype panels using
this mode. We could confirm this mode, realizing high-quality
moving pictures without blurring based on the nonholding
display and good color reproducibility based on the field
sequential color method.
Simultaneous Calculation of Reflection, Physical Sputtering and Secondary Electron Emission from a Metal Surface due to Impact of Low-Energy Ions
Authors: Retsuo Kawakami Retsuo Kawakami , Jun Kawata Jun Kawata , Kaoru Ohya Kaoru Ohya
Published: October 2002

A computer simulation code which treats elastic and inelastic collision processes of low-energy ions in solids is presented. In the code, the direct excitation of electrons by a penetrating ion and recoiling atoms is simulated using the Monte Carlo technique, in addition to the simulation of elastic collisions of the moving particles with solid atoms. Electron cascades of the excited electrons and collision cascades of the recoil atoms are also taken into account, and as a result, the code allows us to simulate ion-solid interactions such as ion reflection, physical sputtering and secondary electron emission from the solids. This code is applied to calculations of the energy and angular distributions of emitted particles and the total particle yields of aluminum by impact of ions with the atomic numbers Z
1 of 1 to 17 and energies E
i of 10 eV to 10 keV at normal incidence. The calculated sputtering yield and ion reflection coefficient are in reasonable agreement with empirical formulae which have been recently presented. The calculated electron yield shows the clear dependence on Z
1 and E
i, but the E
i-dependence is different from that of the electronic stopping power at such low impact energies. The energy and angular distributions of emitted particles indicate the similarities of the secondary electron emission and the physical sputtering, as observed in recent experiments.
Drift Velocities of Electrons in Time Varying Electric Fields
Authors: Petrović Svetlan Bzenić , Raspopović Zoran M. , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

Monte Carlo simulations of electron transport have been performed in methane for time resolved rf fields under conditions where negative differential conductivity (NDC) occurs. It was found that the effect of NDC occurs for low frequencies as expected from the quasi stationary (temporally local) model. At higher frequencies the NDC disappears gradually but the NDC behavior is significantly different when field increases and when field decreases. In the latter case the NDC disappears while in the former it blends into one maximum occurring at the point of the maximum of the electric field with an intermediate frequency region with asymmetric time dependence.
Role of Reaction Products in F- Production in Low-Pressure, High-Density CF4 Plasmas
Authors: Daiyu Hayashi Daiyu Hayashi , Masahiko Nakamoto Masahiko Nakamoto , Noriharu Takada Noriharu Takada , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

In this paper we report on the role of reaction products in F- production in low-pressure, high-density CF4 plasmas. The spatial distributions and temporal variations of F- density (n
-), and plasma parameters in the discharge phase and afterglow of helicon-wave CF4 plasmas which had an electron density (n
e) of 1011–1013 cm-3 were measured by the laser-photodetachment technique combined with a heated Langmuir probe. The relationship between the n
-/n
e ratio and the degree of ionization was investigated in the discharge phase. The n
-/n
e ratios in the plasma column of highly ionized plasmas were much higher than those expected from dissociative electron attachment to CF4, and n
-/n
e ratios were larger by several orders of magnitude in the outer region. The efficient increase in n
- was observed in the afterglow and n
-/n
e was enhanced by increasing the discharge duration. It is concluded that the attachment to the reaction products contributes greatly to F- production in low-pressure, high-density plasmas.
A Simple Model for Ar+–Ar, He+–He, Ne+–Ne and Kr+–Kr Collisions
Authors: Kenichi Nanbu Kenichi Nanbu , Go Wakayama Go Wakayama
Published: October 2002

A simple model for ion-atom collision with charge exchange is proposed to realize a computationally efficient particle simulation of plasmas. The model is a combination of isotropic scattering and charge switching, both occurring with the same probability. When an ion-atom collision cross section is chosen to be nearly twice as large as an atom-atom collision cross section, the measured ion drift velocities and transverse diffusion coefficients for Ar+ in Ar, He+ in He, Ne+ in Ne, and Kr+ in Kr can be reproduced with reasonable accuracy using the proposed model.
Magnetostatic Surface Wave Envelope Solitons in a Periodic Structure
Authors: Masahiro Uehara Masahiro Uehara , Ken'ichiro Yashiro Ken'ichiro Yashiro , Sumio Ohkawa Sumio Ohkawa
Published: October 2002

Nonlinear propagations of magnetostatic surface wave (MSSW)
envelope solitons are investigated quantitatively.
Both the dispersion and nonlinear coefficients are usually positive
for MSSW delay lines. Hence dark envelope solitons can propagate
and bright envelope solitons are forbidden.
In order to verify the possibility of MSSW bright solitons,
the uniformly layered structure with a metallic plate and the periodic
metallic array structure are considered.
Dispersion relations of MSSWs in a periodic metallic array structure
are obtained rigorously using the nonreciprocal Riemann-Hilbert technique.
In both structures, the obtained dispersion curves have highly dispersive regions
suitable for the formation of solitons of long duration,
which are convenient values for use in the experiments.
The nonlinear Schrödinger equation (NLSE) with third-order dispersion
and dissipation is used to describe MSSW envelope solitons.
The nonlinearity coefficient of the NLSE is determined by considering
the field distribution.
The numerical results of the NLSE show soliton-like behaviors
in which the waveforms are distorted due to the third-order dispersion.
Rewritable Near-Field Optical Recording on Photochromic Perinaphthothioindigo Thin Films: Readout by Fluorescence
Authors: Irie Masahiro , Ishida Hiroki , Tsujioka Tsuyoshi
Published: October 2002

Near-field optical recording on polystyrene thin films
containing photochromic perinaphthothioindigo (NTI) was carried out.
NTI underwent a reversible trans/cis photoisomerization in the
polystyrene film, and only the trans-form emitted fluorescence.
First, polystyrene film containing trans-form NTI molecules was used
as the recording medium. Upon irradiation with 633 nm light from a
fiber probe tip (aperture diameter ∼100 nm), the fluorescent
trans-forms in a small region were converted into non-fluorescent
cis-forms. The recorded small regions were detected as dark spots as
small as 110 nm by scanning across the written area. Second,
polystyrene film containing cis-form NTI molecules was used as the
recording medium. Upon irradiation with ultrasmall 488 nm light
(aperture diameter ∼80 nm), bright spots as small as 50 nm
were recorded and read out with scanning 633 nm light. The bright
spots were due to the fluorescence of the photogenerated trans-form
NTI molecules. Both the dark and bright spots were erased by
irradiation with 488 nm and 633 nm light, respectively. The bright
spot could also be recorded using a pulse
Nd3+: YAG laser (532 nm, pulse width 20 ns).
Beam-Profile Control Using an Octupole Magnet
Authors: Urakabe Eriko , Fujita Yuzo , Hiramoto Kazuo , Inoue Makoto , Iwashita Yoshihisa , Kanazawa Mitsutaka , Morita Akio , Nishi Masatsugu , Norimine Tetsuro , Noda Akira , Noda Koji , Ogawa Hirotsugu , Shirai Toshiyuki , Torikoshi Masami , Umezawa Masumi , Yamada Satoru
Published: October 2002

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system.
Simulation of High-Concentration Phosphorus Diffusion in Silicon Taking into Account Phosphorus Clustering and Pile-Up
Authors: Uematsu Masashi
Published: October 2002

We have simulated the transient enhanced diffusion (TED) of high-concentration phosphorus (P) in silicon during post-implantation annealing. Based on the models for P diffusion, for TED by self-interstitial clusters, and for end-of-range (EOR) dislocations as both a sink for and source of self-interstitials, a unified simulation is done, taking into account P clustering and P pile-up. P clustering is taken into account only beneath EOR dislocations, and P pile-up is estimated by a diffusion-segregation term in the diffusion equations. We have satisfactorily fitted P depth profiles at high doses (∼1015 cm-2) in a wide range of annealing conditions (700–1000°C).
Characterization of Photo Leakage Current of Amorphous Silicon Thin-Film Transistors
Authors: Yamaji Yoshimi , Ikeda Mitsushi , Akiyama Masahiko , Endo Takahiko
Published: October 2002

The photo leakage current of amorphous silicon thin-film
transistors (a-Si TFTs) for switching elements in active-matrix liquid
crystal displays (AMLCDs) is studied to achieve high-image-quality
LCDs. The position dependence of photo leakage current generation in
the a-Si:H TFT is evaluated using a slit light from the channel
side. The generated photo leakage current is composed of a peak at the
junction region and a gradual part at channel region, both of which
are larger at the source electrode side than at the drain electrode
side. This large photo leakage current at the source electrode side
can be explained by the diffusion and tunnel current increase caused
by the variation of the quasi Fermi level by photogenerated carriers
in the reverse bias source junction and the larger electron mobility
than the hole, respectively. The results of this study indicate the
importance of the source junction for the TFT off-current, in contrast
to studies in the past which put forth that the off-current is limited
by the generation-recombination current at the drain junction. Our
results indicate the importance of front-side illumination by the
reflected-light illumination from the high brightness backlight of
AMLCD displays.
Effectively Blocking Copper Diffusion at Low-k Hydrogen Silsesquioxane/Copper Interface
Authors: Liu Po-Tsun , Chang Ting-Chang , Yang Ya-Liang , Cheng Yi-Fang , Shih Fu-Yung , Lee Jae-Kyun , Tsai Eric , Sze Simon M.
Published: October 2002

The interaction between copper and low-k hydrogen
silsesquioxane (HSQ) film was investigated using a Cu/HSQ/Si metal
insulation semiconductor capacitor and hydrogen plasma
posttreatment. Owing to serious diffusion of copper atoms in HSQ film,
degradation of the dielectric properties are significant with the
increase of thermal stress. By applying hydrogen plasma treatment to
the HSQ film, however, the phenomena of serious Cu penetration were
not observed by electrical characteristic measurements and secondary
ion mass spectroscopy (SIMS) analysis even in the absence of diffusion
barrier layers. Therefore, hydrogen plasma treatment can effectively
block the diffusion of copper in low-k HSQ film.
Effects of Methyl Silsesquioxane Electron-Beam Curing on Device Characteristics of Logic and Four-Transistor Static Random-Access Memory
Authors: Lin Chi-Fa , Tung I-Chung , Feng Ming-Shiann
Published: October 2002

The as-spun methyl silsesquioxane (MSQ) film cured by an electron beam (e-beam) did not show water absorption after a five-day exposure to ambient air. MSQ was applied to the triple-level metal (TLM) Logic and double-level metal (DLM) four-transistor (4-T) static random-access memory (SRAM) as intermetal dielectric by means of the non-etchback process. When MSQ treatment conditions were properly controlled, the top layer of the as-spun films was cured by e-beam exposure while the bottom layer of the film was thermally cured for a short period of time. The as-cured MSQ offered good surface planarity. In addition, neither via poisoning, bowing nor cracking was observed. The results showed that, by the application of the e-beam cured MSQ in the fabrication of interconnect structures, the cache time of DLM 4-T SRAM could be improved to 10 ns compared with 11.5 ns for the SRAM fabricated using the conventional furnace cure spin-on-glass (SOG) process (400°C annealing for one hour). E-beam exposure has little effect on n-channel metal-oxide-semiconductor (NMOS) device characteristics, such as saturation current, threshold voltage and channel length. In contrast, e-beam exposure has a significant effect on p-channel MOS (PMOS) device characteristics, resulting in a shift of the threshold voltage as well as an increase in the channel length. It is notable that the e-beam exposure almost did not affect NMOS device characteristics in the 4-T SRAM, since the polysilicon load resistor could serve as a shield against electron bombardment. In such a case, the resistance of the polysilicon load resistor was significantly decreased.
Static and Dynamic Characteristics of a 54 GHz fmax Implanted Base 0.35 µm Single-Polysilicon Bipolar Technology
Authors: Vincent Gilbert , Niel Stephan , Rozeau Olivier , Llinares Pierre , Chantre Alain
Published: October 2002

High performance single-polysilicon npn bipolar transistors
using a low cost 200 mm 0.35 µm bipolar technology have been
fabricated, and the electrical properties related to physical and
technological parameters. The devices feature record cut-off frequency
and maximum oscillation frequency of 35 GHz and 54 GHz respectively,
comparable to state-of-the-art results from more complex
double-polysilicon bipolar processes.
Magnetic Properties and Magnetoresistance of Granular Evaporated Fe/Si Films
Authors: Ihara Nobutaka , Narushima Shin , Kijima Tuyoshi , Abeta Hideto , Saito Toshiaki , Shinagawa Kiminari , Tsushima Tachiro
Published: October 2002

Fe (3.4 Å) and Si (6 Å) are evaporated alternately onto silica substrates to realize a
granular structure. The substrate temperature T
s during the evaporation is changed
from 100 K to 623 K to vary the film structures. The specimens of T
s≥room temperature (RT) are superparamagnetic at RT, which suggests a granular structure.
Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing
magnetic field H) for all specimens. It is thought that the negative MR is attributable to
the granular structure. On the other hand, at 77 K a positive MR linear with H (not H
2)
up to 50 kOe is observed for all specimens. The linear dependence on H of the positive
MR may be due to the nonuniformity in the granular structure. The positive MR itself
and the change of the sign of MR from negative to positive with decreasing
temperature have not been observed in conventional granular systems such as Co–Ag
and Co–Al–O.
Attosecond Pulse Generation in He Gas with Few-cycle KrF Driver Pulses
Authors: Shon Nguyen , Suda Akira , Katsumi Midorikawa Katsumi Midorikawa
Published: October 2002

The interaction of intense few-cycle KrF driver pulses with a gas of neutral He atoms is numerically investigated. Calculations are performed by solving the time-dependent Schrödinger equation within a framework of the single-active electron model. It is demonstrated that a single attosecond pulse as well as a train of bursts of subfemtosecond duration can be produced by Fourier synthesis of selected succsesive harmonics. The results are compared to those obtained by the strong field approximation model.
Enhancement of Nonlinear Optical Effect in One-Dimensional Photonic Crystal Structures
Authors: Tsurumachi Noriaki , Yamashita Shoichi , Muroi Norio , Fuji Takao , Hattori Toshiaki , Nakatsuka Hiroki
Published: October 2002

We observed the photonic band structure of one-dimensional photonic crystals using a white-light Michelson interferometer. In one-dimensional photonic crystals with a structural defect, there is a localized mode where the field is localized around the position of the defect. If the defect is made of nonlinear optical material, the effective nonlinearity of the photonic crystal is largely enhanced by the enhanced light intensity at the defect. In a one-dimensional photonic crystal with a defect, we observed a large enhancement of degenerate four-wave mixing efficiency. Since the total thickness of the whole structure is only a few micrometers, it was successfully used to form an optical phase-conjugated image.
Luminescence from the Thermally Treated Cerium Oxide on Silicon
Authors: Chel Choi Won , Nyung Lee Ho , Min Park Yong Kim , Kyu Kim Eun
Published: October 2002

As an efficient ultra violet/blue (UVB) luminescent material compatible with Si-based optoelectronics, we introduce thermally treated cerium oxide (CeOx) on silicon. UVB luminescence ranging from 358 nm to 450 nm is observed at room temperature for thermally treated CeOx thin films. The luminescence is attributed to Ce4.667(SiO4)3O and Ce2Si2O7 generated during thermal treatment.
Dependence of Seebeck Coefficient on Carrier Concentration in Heavily B- and P-Doped Si1-xGex (x≦0.05) System
Authors: Yamashita Osamu , Sadatomi Nobuhiro
Published: October 2002

The electrical resistivity ρ, the Seebeck coefficient S and the carrier mobility µ were
measured as a function of carrier concentration n for B- and P-doped Si, Si0.97Ge0.03 and
Si0.95Ge0.05 prepared by arc melting. It was found that at a high carrier concentration of
about 2×1020 cm-3, the S values of the Si0.97Ge0.03 and Si0.95Ge0.05 samples with dopant
segregations are about 50% higher than those measured previously on Si0.95Ge0.05, Si0.85Ge0.15
and Si0.7Ge0.3 samples with little segregation, although the differences between their ρ
values are very small. The most striking result is that the S curves of the doped Si samples
have a hump at a concentration of about 3×1019 cm-3, while no hump was observed for the
Si0.97Ge0.03 samples, as in the case of Si0.7Ge0.3 alloys. Such a hump is surprising because it
conflicts with the conventional theory that predicts a monotonic decrease of S with increasing n. This phenomenon is related to a change in the effective mass which results from dopant segregation.
A Study on Microstructure and Electrical Properties of Pb0.8La0.1Ca0.1Ti0.975O3 Thin Films Prepared by Metal-Organic Decomposition
Authors: Song Zhitang , Fu Xiaorong , Zeng Janming , Gong Jianxian , Lin Chenglu
Published: October 2002

In this paper, Ca modified (Pb, La)TiO3 (PLCT) films were deposited on Pt coated silicon substrates using metal-organic decomposition (MOD) process. The preferred orientations polycrystalline films were varied with heating treatment temperature. The PLCT films exhibit good ferroelectric and dielectric properties at room temperature. The large area PLCT thin films with (100) preferred orientation may be application for future non-volatile memory devices (NVFRAM's) and dynamic random access memories (DRAM's).
Pulsed Electric Breakdown and Destruction of Granite
Authors: Inoue Hirotoshi , Lisitsyn Igor V. , Akiyama Hidenori , Nishizawa Izumi
Published: October 2002

There are various methods of rock drilling and demolition. Recently, a method utilizing pulsed power technology has appeared. This method is based on the difference of the dynamic breakdown field strength of liquid and solid dielectrics. The applicability of this method was examined using a very hard rock–granite. The features of the rock destruction have been studied. The X-ray computer tomography was used to confirm the penetration of the electrical discharge into the rock. Well-resolved marks of the electric discharge channel could be observed using this technique. Destruction effectiveness was examined for various experimental conditions. The volume of the rock destroyed in a shot and the energy consumption in the destruction process are dependent on the
generator voltage. The distance between electrodes has the optimum
value for a given voltage.
Ultrasonic Attenuation Due to Localized Relaxation in Cubic Yttria-Stabilized Zirconia
Authors: Kirimoto Kenta , Nobugai Kohji , Miyasato Tatsuro
Published: October 2002

Longitudinal ultrasonic attenuation in yttria-stabilized zirconia [ZrO2(Y)] was measured at frequencies of 10 MHz and 120 MHz and at temperatures between 300 and 600 K. The temperature variation was strongly anisotropic, the maximum effect being observed in the <111 > direction. At 10 MHz a relaxation peak was observed from which an activation energy of 0.7 ±0.07 eV could be estimated. A similar figure was obtained from dielectric constant measurements, but the ionic conductivity yielded a higher value of 0.92 ±0.1 eV. Our conclusion is that there are two separate hopping processes for oxygen ions, one between Zr-related sites which can percolate the crystal and hence produce conduction, and another between Y-related sites which are localized.
Current–Voltage Characteristics of Thin-Film Diode Elements and Application of Poole-Frenkel Equation
Authors: Hirai Takanori , Morita Hiroshi , Tasaka Masayasu
Published: October 2002

The current–voltage (I–V) characteristics of a metal-insulator-metal type thin-film diode
(TFD) could not be simply described by the Poole-Frenkel equation using the apparent
thickness of the oxide film. If the effective thicknesses of the oxide film for the determination
of terms α and β in the equation are appropriately estimated, the I–V characteristics of the
TFD element can be explained by the Poole-Frenkel equation. It was found that the optimum
design parameters could easily be estimated by this new formula for a liquid-crystal display
with the TFD element.
Fast Deposition of Microcrystalline Silicon Using High-Density SiH4 Microwave Plasma
Authors: Shirai Hajime , Sakuma Yoshikazu , Moriya Yoshimizu , Fukai Chisato , Ueyama Hiroyuki
Published: October 2002

A novel microwave discharge utilizing a spokewise antenna was
applied for the fast deposition of hydrogenated microcrystalline
silicon (µc-Si:H) film from SiH4 and Ar without the
H2 dilution method. Systematic deposition studies were employed
with total pressure, H2 dilution ratio and flow rate of
SiH4, Fr[SiH4], as variables, combined with optical
emission spectroscopy (OES) and Langmuir probe characterizations. It
was found that the deposition rate exhibits a maximum at 40–50 mTorr
at the axial distance of 10 cm from the quartz glass plate and the
film crystallinity strongly depend on the total pressure. Correlation
among OES signal intensity, SiH, the intensity ratio,
I
Hα
/I
Si*
, deposition rate and film
crystallinity were demonstrated. By combining the SiH4 depletion
and lower pressure conditions, a high deposition rate of 40 Å/s
was achieved in µc-Si:H growth with high crystallinity and
photosensitivity from SiH4 and Ar plasma.
High-Quality GaAsxP1-x/In0.13Ga0.87P Quantum Well Structure Grown on Si Substrate with a Very Few Threading Dislocations
Authors: Yasuhiro Fujimoto Yasuhiro Fujimoto , Hiroo Yonezu Hiroo Yonezu , Satoshi Irino Satoshi Irino , Katsuya Samonji Katsuya Samonji , Kenji Momose Kenji Momose , Naoki Ohshima Naoki Ohshima
Published: October 2002

We proposed a novel quantum well (QW) structure of GaAs
x
P1-x
/In0.13Ga0.87P grown on a GaP/Si substrate with a small lattice mismatch (1.4%) to the Si substrate, for a highly reliable laser diode (LD) on a Si substrate, and attempted to form the structure with a GaAs0.68P0.32 well and GaAs0.27P0.73 guiding layers. A two-dimensional (2D) growth mode was maintained during the growth of all layers. A cross-sectional image taken by transmission electron microscopy (TEM) revealed that the density of threading dislocations is the lowest in light-emitting device structures grown on Si substrates, as far as we know. The lattice mismatch of 1.4% was accommodated at the In0.13Ga0.87P-GaP and the GaP-Si heterointerfaces by introducing misfit dislocations. The quality and structural profile of GaAs
x
P1-x
epilayers was improved by varying the As4 flux in a short period. As a result, strong band-edge emission was observed from the GaAs0.68P0.32 QW at room temperature (RT). It was also found by secondary-ion mass spectroscopy (SIMS) that relatively abrupt heterointerfaces were formed in the QW structure of GaAs0.68P0.32/GaAs0.27P0.73/In0.13Ga0.87P.
Nanometer Level Resolving Near Field Optical Microscope under Optical Feedback in the Observation of a Single-String Deoxyribo Nucleic Acid
Authors: Maheswari Rajagopalan Uma , Yoshimoto Shuji Mononobe , Motoichi Ohtsu Motoichi Ohtsu
Published: October 2002

We present the observation results of a single string deoxyribo nucleic acid (DNA) obtained by a collection mode near field optical microscope (NOM) operated under constant distance mode with the optical near field intensity as the feedback signal. The observed width of the narrowest string is around 4 nm. To our knowledge, this is not only the successful optical observation of a single string DNA by purely optical means but also under such high resolving capability. This high resolution is mainly attributed to the special care taken during the preparation of the sample and of the probe to avoid unwanted scattered light. The probe efficiently picks up the high spatial frequency component of the scattered near field and simultaneously rejects out effectively the lower spatial frequency components.
High-Speed and High-Power 1.3 µm InGaAsP/InP Selective Proton-Bombarded Buried Crescent Lasers with Optical Field Attenuation Regions
Authors: Zhang Baijun , Yi Maobin , Song Junfeng , Gao Dingsan , Zhu Ninghua , Wu Ronghan , Wang Wei
Published: October 2002

High-speed and high-power InGaAsP/InP selective proton-bombarded
buried crescent (SPB-BC) lasers with optical field attenuation regions
were reported. The defect of proton bombardment can not affect the
lifetime of the SPB-BC laser because the optical field attenuation
region obstructs the growth and propagation of defects. A CW light
output over 115 mW was achieved at room temperature using a
500 µm long cavity SPB-BC laser. The 3 dB bandwidth was 8.5 GHz,
and the lifetime was about 8.5×105 h. The capacitance of
four kinds of current blocking structures was first measured in our
experiment, and the results shown that the capacitance of
proton-bombarded p
n
p
n structure was not only less than that
of p
n
p
n current blocking structure, but also less than that
of semi-insulating Fe–InP structure.