bluuebunny/crossref_metadata_2025 huggingface dataset:
Collisional Quenching Rates by He, N2 and CH4 for the 4D3/2 State in SrII
Authors: Hirano Iku , Yoda Jun , Hong Feng-Lei , Okumura Kenichiro , Onae Atsushi
Published: October 2002

Sr+ ions were confined in a rf trap with buffer gases (He, N2 and CH4) at
several different pressures, and the fluorescence from 5p
2
P
1/2 to 5s
2
S
1/2 was detected.
Increasing in the fluorescence using a pump-back laser enabled the estimation of
collisional quenching rates for the 4d
2
D
3/2 state of Sr+. They are 0.27, 0.83 and 2.3 in
units of 10-16 m3 s-1 for He, N2 and CH4, respectively. The experimental collisional
quenching rates were compared with the Langevin reaction rates obtained by the
classical ion-molecule collision theory.
Many-Body States in a Quantum Dot under High Magnetic Fields
Authors: Mikio Eto Mikio Eto
Published: October 2002

Many-body electronic states in a quantum dot are studied
under high magnetic fields, using the exact diagonalization method.
The magnetic field dependence of low-lying excited states as well
as the ground state is calculated, which is in good agreement with
experimental results of Coulomb oscillation.
The maximum density droplet (MDD), in which all the
electrons are completely spin-polarized and accommodated in the lowest
levels, appears in a range of the magnetic field. The range is narrower
for larger number of electrons in the dot. Under higher magnetic fields,
the MDD state is replaced by a new ground state in which
electrons are strongly correlated to each other.
The correlation effect considerably reduces the peak heights of the
conductance.
Numerical Method for Local Density of States and Current Density Decomposed into Eigenchannels in Multichannel System
Authors: Nobuhiko Kobayashi Nobuhiko Kobayashi , Masaru Tsukada Masaru Tsukada
Published: October 2002

Scattering states in a multichannel quantum transport system are generally
decomposed into eigenchannels with no interchannel mixing,
which are a set of special channels
obtained by the unitary transformation of the original channels.
We present a numerical method of decomposing the local density of states
and the current density into eigenchannels
using the recursion-transfer matrix method.
The method is applied
to electron transport through
square prisms and single/double cubic dots between electrodes, and
it is shown, along with channel transmissions,
how the local density of states and the current density
are resolved into the eigenchannels for the systems.
Calculations of Scanning Tunneling Microscopic Images of Benzene on Pt(111) and Pd(111), and Thiophene on Pd(111)
Authors: Futaba Don Norimi , Chiang Shirley
Published: October 2002

We use a computational method, based on extended Hückel molecular orbital
theory, for calculating the scanning tunneling microscope (STM) images of benzene on
Pt(111), benzene on Pd(111), and thiophene on Pd(111). For each case, we calculated
images for both isolated and chemisorbed molecules. From binding energy calculations,
the low energy geometries for the three binding sites were determined. The calculated
images for benzene on Pt(111) agreed well with previously published experimental and
theoretical results. We found many similarities between the calculated images of benzene
on Pt(111) and on Pd(111). Calculated images of adsorbed thiophene showed marked
similarities with the previously calculated images of furan and
pyrrole.
Scanning Tunneling Spectroscopy Study of Fe(001) Using Nonmagnetic W- and Fe-Evaporated Probe Tips
Authors: Kondoh Takeshi Kawagoe , Jimma Yasuo , Kotaki Tomoyuki , Itoh Akiyoshi
Published: October 2002

The differential conductivity (dI/dV) spectra of Fe(001) film,
together with the topographic image,
were measured at room temperature
using ferromagnetic Fe and non-magnetic W probe tips.
A narrow peak was observed at 0.3 V in the dI/dV spectrum using a W tip,
which coincides with the surface state in the minority spin band predicted
by a theoretical calculation.
On the other hand, we found a pronounced peak at 0.7 V
in the tunneling spectra using a Fe-evaporated probe tip
with an intense and broad feature,
which cannot be explained by the calculation.
The enhancement of spin-polarized tunneling in an empty sample state
might occur in the case of a Fe tip.
Phase Relaxation and Non-Equilibrium Transport Properties through Multilevel Quantum Dot
Authors: Funabashi Yasuhiro , Ohtsubo Kazuhiko , Eto Mikio , Kawamura Kiyoshi
Published: October 2002

Phase relaxation of conduction electrons in transport through a
multilevel quantum dot in the Coulomb blockade region is studied
using the Anderson Hamiltonian.
Two types of currents are calculated separately, i.e., in the absence
and presence of the phase relaxation.
At low temperatures, the current without the phase relaxation is
considerably suppressed for an appropriate value of the Coulomb
interaction between electrons in the dot.
This is due to the interference between two virtual processes in the
transport of a electron.
At high temperatures, the two types of currents are almost identical
as a consequence of the thermal excitations.
Self-Assembly and Functional Group Effect of Asymmetric Disulfides on Graphite Studied by Scanning Tunneling Microscopy
Authors: Noh Jaegeun , Lee Dongsun , Hara Masahiko , Lee Haiwon , Sasabe Hiroyuki , Knoll Wolfgang
Published: October 2002

Well-ordered self-assembled monolayers of asymmetric disulfides on graphite were observed
by scanning tunneling microscopy (STM). STM images showed that the molecules are
oriented parallel to the graphite surface without dissociation of the sulfur-sulfur bond. The
adsorption phase of 11-hydroxyundecyl octadecyl disulfide (CH3(CH2)17SS(CH2)11OH)
molecules on graphite is governed by the formation of a hydrogen bond with a hydroxyl
group facing another hydroxyl group of adjacent molecules. Self-assembled monolayers of
octadecyl undecyl disulfide (CH3(CH2)17SS(CH2)10CH3) molecules, on the other hand,
showed different ordering periodicity compared to that of hydroxylated disulfide molecules.
Nanometer-Scale Photoelectric Property of Organic Thin Films Investigated by a Photoconductive Atomic Force Microscope
Authors: Sakaguchi Hiroshi , Iwata Futoshi , Hirai Atsushi , Sasaki Akira , Nagamura Toshihiko
Published: October 2002

A photoconductive atomic force microscope (AFM), which is a contact mode current-sensing AFM combined with an optical pumping laser, was developed in order to investigate the interaction between light and matter in a nanometer-scale tinny structure. The principle of the photoconductive AFM is the measurement of the photocurrent in an individual nanometer-scale structure, and also two-dimensional mapping of the photoelectric property by scanning the conductive cantilever on the surface of a sample. The photoelectric property of an organic thin film with copper phthalocyanine was demonstrated to test the performance of this system. Nanometer-scale point contact photocurrent, point contact current–voltage characteristics and photoconductive imaging could be attained using the system. Photoconductive AFM has the potential to be of use in various fields of nanometer-scale photonics.
Protein Stretching III: Force-Extension Curves of Tethered Bovine Carbonic Anhydrase B to the Silicon Substrate under Native, Intermediate and Denaturing Conditions
Authors: Tong Wang Tong Wang , Atsushi Ikai Atsushi Ikai
Published: October 2002

Atomic force microscope (AFM) was used to measure the
force-extension relationship of the globular protein, carbonic anhydrase B, having 259 amino acid residues, under
native, denaturing and intermediate solution conditions. For this
purpose, the protein was genetically engineered in order to
endow it with -SH groups at its N- and C- termini and was fixed to
the silanized surface of a silicon wafer using a covalent cross-linker with the reactive end to -SH and with a long spacer of polyethylene glycol. The silicon nitride tip of the AFM was covered with a cross-linker with the reactive end to -SH and was brought into contact with the protein on the silicon surface. Subsequent force curve measurements showed occasional stable bond formation, and the force extension relationship obtained from such curves showed distinct characteristics of the native, denatured and intermediate forms of carbonic anhydrase B.
Investigation of Surface Potential of Ferroelectric Organic Molecules by Scanning Probe Microscopy
Authors: Chen Xinqi , Yamada Hirofumi , Matsushige ToshihisaHoriuchi
Published: October 2002

The surface potential of ferroelectric copolymer films of vinylidene fluoride and trifluoroethylene was investigated by scanning probe microscopy. The results reveal that the as-deposited copolymer films on a graphite substrate show a negative surface potential. The surface potential is ascribed to the substrate-induced effect, which causes frozen dipoles in the copolymer films. We made locally poled areas in the films using a conductive cantilever tip and measured the piezoelectric response of the films with a modified scanning force microscope. The observed asymmetric behavior of the piezoelectric response of the thin films can be consistently explained by the frozen ferroelectric layer in the films. Both surface potential and piezoresponse images of locally polarized areas were also obtained. The results indicate that the charge transferred from the tip overcompensated for the oriented dipoles and that the surface potential of the poled regions was attributed to the excess charge.
Fabrication of Nano-Scale Point Contact Metal-Oxide-Semiconductor Field-Effect-Transistors Using Micrometer-Scale Design Rule
Authors: Hiroki Ishikuro Hiroki Ishikuro , Toshiro Hiramoto Toshiro Hiramoto
Published: October 2002

In this paper, we report the novel fabrication technique of Si
nano-scale point contact channels on the silicon-on-insulator substrate.
In our method, the width of the point contact channel is determined
only by the thickness of the surface Si layer and the nano-scale channels
can be fabricated without using any fine resolution lithography.
By applying the method to the point contact channel metal-oxide-semiconductor
field-effect-transistor (MOSFET), the electrical properties of the nano-scale
channels are investigated. The experimental results show that uniform
nano-scale point contact channels are successfully formed.
Analysis of Direct Tunneling for Thin SiO2 Film
Authors: Matsuo Naoto , Miura Takashi , Urakami Aki , Miyoshi Tadaki
Published: October 2002

The direct tunneling (DT) currents of the metal insulator metal
(MIM) structure is presented theoretically by considering the
relationship between the applied voltage to the oxide film (oxide
voltage: V
ox) and the Fermi energy (η) of the metal.
Using the newly obtained equation, the DT of a
poly-Si/SiO2/p-Si(100) stacked structure is analyzed. For
e
V
ox<η, the current component relating to the Fermi
energy of the electrode is added to Simmons' equation. The dependence
of each term for the present function, which is composed of the DT
current flowing from the high-potential electrode to the low-potential
one, reverse DT currents and the current component relating to the
Fermi energy on the oxide voltage was examined. For
e
V
ox>η, a new formula is introduced, since the DT
currents are not calculated by Simmons' equation theoretically. The
present calculation reproduces the large increase in ratio of the
currents for e
V
ox<η, and the accurate absolute value of the
currents for e
V
ox>η. The reason why the calculated
results are still large, one order of magnitude at the maximum, as
compared with the measured data from 0 to approximately -0.5 V is
also discussed from the viewpoints of the multifold valleys of Si,
inelastic scattering and Fermi distribution.
Linearity Study on Enhance/Depletion Dual-Gate High Electron Mobility Transitors using Gain Mapping Method
Authors: Tanimoto Takuma , Kawai Akie , Ohbu Isao , Takazawa Hiroyuki , Nakamura Tohru
Published: October 2002

Power gain linearity was studied using gain mapping method for
enhance/depletion (E/D) dual-gate high electron mobility transistors
(HEMTs). This method contains next steps; S-parameter and drain
current were measured for all drain and gate voltage where interested.
Maximum stable gain (MSG), maximum available gain (MAG) and H21
parameters were then calculated for frequency which is interested. These
parameters were plotted on drain-current and drain voltage plane. By
using this method into dual-gate HEMTs, it was found that threshold
voltage of the second gates are essential for gain linearity and have its
optimum value.
Characteristics of InGaN-Based UV/Blue/Green/Amber/Red Light-Emitting Diodes
Authors: Mukai Takashi , Yamada Motokazu , Nakamura Shuji
Published: October 2002

Highly efficient light-emitting diodes (LEDs) emitting ultraviolet (UV), blue, green, amber and red
light have been obtained through the use of InGaN active layers instead of GaN active layers. Red LEDs
with an emission wavelength of 675 nm, whose emission energy was almost equal to the band-gap energy of
InN, were fabricated. The dependence of the emission wavelength of the red LED on the current (blue shift)
is dominated by both the band-filling effect of the localized energy states and the screening effect of the
piezoelectric field. In the red LEDs, a phase separation of the InGaN layer was clearly observed in the
emission spectra, in which blue and red emission peaks appeared. In terms of the temperature dependence of
the LEDs, InGaN LEDs are superior to the conventional red and amber LEDs due to a large band offset
between the active and cladding layers. The localized energy states caused by In composition fluctuation in
the InGaN active layer contribute to the high efficiency of the InGaN-based emitting devices, in spite of the
large number of threading dislocations and a large effect of the piezoelectric field. The blue and green
InGaN-based LEDs had the highest external quantum efficiencies of 18% and 20% at low currents of 0.6 mA and 0.1 mA, respectively.
Improvement of Stabilized Efficiency of Amorphous Silicon Solar Cell by SiH2Cl2 Addition
Authors: Dairiki Koji , Yamada Akira , Konagai Makoto
Published: October 2002

The characteristics of mercury-sensitized photo-chemical vapor deposition (CVD) grown
a-Si:H films and solar cells in the case of dichrolosilane (SiH2Cl2) addition were investigated.
The films with a small amount of SiH2Cl2 addition exhibited high photosensitivity, low hydrogen
content and low defect density. However, the cells with an i-layer grown by SiH2Cl2 addition
showed a low fill factor. It was also observed by secondary ion mass spectroscopy (SIMS)
measurements that about 1019 atom/cm3 Cl was incorporated into a-Si:H films, even at the flow
rate ratio of 0.01 (SiH2Cl2 to SiH4). Furthermore, it was found that the excess Cl in a-Si:H films
was removed by H2 dilution. In the case of H2 dilution together with SiH2Cl2 addition to the i-layer of a-Si solar cells, a high fill factor and high quantum efficiencies, particularly in the
medium wavelength region was observed. From numerical analysis, it was determined that the
improvement was due to the increase of the electric field in the medium of the i-layer after light
soaking. As a result, we achieved a high stabilized efficiency of 9.0% for a 1 cm2 single-junction
a-Si:H solar cell.
Plasma Diagnostics of CH4/O2/H2 Electron Cyclotron Resonance Plasma with Permanent Magnets and Deposition of Amorphous Carbon
Authors: Yasui Toshiaki , Kodera Hidekazu , Oya Izumi , Tahara Hirokazu , Yoshikawa Takao
Published: October 2002

An electron cyclotron resonance (ECR) plasma source with permanent magnets was investigated for plasma-enhanced chemical vapor deposition of amorphous carbon. By using a mixture of CH4, O2 and H2 gases, this plasma source was used to successfully deposit amorphous carbon at a low pressure (2.7 Pa) and a low substrate temperature (500–600°C). At a 7.7 vol% CH4 concentration and 0.6 vol% O2 concentration, microcrystalline amorphous carbon with crystallites about 0.6 µm in diameter was deposited. Raman spectroscopic analysis showed that this deposit was diamond-like carbon. On increasing the O2 concentration slightly, the size of the deposit decreased. On the other hand, a slight decrease of O2 concentration changed the deposit to graphitic carbon. These deposition characteristics were explained by plasma diagnoses using optical emission spectroscopy and actinometry.
Pre-sheaths and Turbulent Flow in Electronegative Plasmas
Authors: Peter Vitello Peter Vitello
Published: October 2002

In electronegative plasmas Coulomb scattering between positive and
negative ions can lead to the formation of a pre-sheath boundary
layer containing the bulk of the negative ions. This boundary layer
may be unstable, showing time dependent turbultent behavior. The
negative ion boundary layer forms when collisional momentum transfer
for negative ions is dominated by Coulomb scattering between ions,
rather than ion scattering with neutrals. This condition is met in
Inductively Coupled Plasma reactors that operate at low pressure and
high plasma density. Numerical simulations of a chlorine discharge in
a Gaseous Electronics Conference reference cell modified for inductive
plasma operation are presented using the INDUCT95 2D model. The
behavior of the pre-sheath boundary layer structure as a function of
applied power and neutral pressure is shown.
Cylindrical DC Magnetron Sputtering Assisted by Microwave Plasma
Authors: Akira Yonesu Akira Yonesu , Takashi Kato Takashi Kato , Hiroki Takemoto Hiroki Takemoto , Naoki Nishimura Naoki Nishimura , Yasumasa Yamashiro Yasumasa Yamashiro
Published: October 2002

A new magnetron sputtering apparatus assisted by microwave plasma
has been developed to achieve high sputter deposition rates at low gas pressures.
In this apparatus, a microwave plasma is produced in a cylindrical multipolar magnetron arrangement and utilized for
DC magnetron sputtering deposition.
With the assistance of microwave plasma, operation of the magnetron discharge has been achieved at pressures on the order of 10-4 Torr.
Aluminum films are deposited in this apparatus at rates greater than 50 nm/min even at the low gas pressure of 2.5×10-4 Torr.
Characteristics of Scanning Mirror-type Magnetic Field Coaxial Electron Cyclotron Resonance Plasma for Inner Coating of Slender Glass Tubes
Authors: Teppei Nagano Teppei Nagano , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

An inner coating system has been developed with the use of scanning
coaxial electron cyclotron resonance (ECR) plasma.
In this system, plasma was generated by the ECR method inside a coaxial metallic or
insulated tubes under low
pressure and narrow gap conditions. ECR plasma was transported along the tube
axis by controlling the position of ECR points. By inserting the insulated tube
into the metallic tube, discharge at low pressure was realized.
We succeeded in coating titanium onto the inner surface of an insulated tube of 27 mm inner diameter
and 480 mm length. Using this coating system, titanium
nitride (TiN) films were deposited
in the metallic tube at an Ar flow rate of 0.1 sccm,
an N2 flow rate of 0.1 sccm and a total pressure of 0.14 mTorr.
Correlation between Charge Pumping Method and Direct-Current Current Voltage Method in p-Type Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Jie Bin-Bin , Ng Kok-Hooi , Lo Ming-FuLi
Published: October 2002

In this study, the correlation between the charge pumping (CP)
method and the direct-current current voltage (DCIV) method in p-type
metal-oxide-semiconductor field-effect transistors (pMOSFETs) is
investigated. We found that the two techniques probe essentially the
same interface traps in the channel (C) region as well as in the drain
(D) region. A good linear relationship is observed between the DCIV
signal and the CP signal. One obvious advantage of the DCIV method is
that it can clearly and directly distinguish the interface traps in
the C region and in the D region, respectively. This is possible in
the CP method only after complicated manipulation of raw experimental
data. The shift of V
cp shows the net effect of
compensating oxide charge and interface trapped charge, while the
shift of V
gb,max mainly shows the effect of the oxide
charge.
Reproducible Growth of Metalorganic Chemical Vapor Deposition Derived YBa2Cu3Ox Thin Films Using Ultrasonic Gas Concentration Analyzer
Authors: Shuu'ichirou Yamamoto Shuu'ichirou Yamamoto , Kouji Nagata Kouji Nagata , Satoshi Sugai Satoshi Sugai , Akio Sengoku Akio Sengoku , Yasunari Matsukawa Yasunari Matsukawa , Takeo Hattori Takeo Hattori , Shunri Oda Shunri Oda
Published: October 2002

We report, in detail, on precursor concentration monitoring in the metalorganic chemical vapor deposition (MOCVD) of YBa2Cu3O
x
(YBCO) by ultrasonic measurement and a newly developed feedback system to solve reproducibility problems. The fluctuation of the flow rate of dipivaloylmethanate (DPM) compounds has been clearly observed. We have proposed a feedback system using an ultrasonic concentration analyzer and two sets of mass flow controllers for each precursor, and have proven the validity of the operation.
On the AC Bias Readout Schemes for High-TC Superconducting Quantum Interference Devices
Authors: Kuriki Shinya , Hayashi Amane , Oyama Hiroshi
Published: October 2002

The ac bias method is used in the readout system of dc-superconducting quantum interference devices (SQUIDs) to suppress the low-frequency noise that originates in the fluctuation of parameters of two junctions in the SQUID. From the analysis of various schemes of the ac bias method, we propose a simple form which expresses the alternation of the operation variables, i.e., the bias current, modulation flux, and bias flux. We considered the modification of the previous schemes in the context of this form and have found a possible method to directly detect the noise component due to the parameter fluctuation. In the modified ac bias scheme, the low-frequency noise of the parameter fluctuation can either be detected or suppressed by manipulating a single variable. We fabricated the electronics to verify this function, and confirmed the versatility of this method from the measurements of the high-T
C SQUID.
Metal-Based Room-Temperature Operating Single Electron Devices Using Scanning Probe Oxidation
Authors: Matsumoto Kazuhiko , Gotoh Yoshitaka , Dagata TatsuroMaeda , Harris JamesS.
Published: October 2002

Coulomb oscillation was clearly observed at room temperature in the single
electron transistor fabricated by atomic force microscopy (AFM) nano-oxidation
process. In order to obtain a clear Coulomb oscillation at room temperature, new
and improved fabrication processes and measurement systems such as a pulse-mode
AFM nano-oxidation process and a triaxial active feedback measurement system are
introduced. The Coulomb oscillation peaks appear with the period of 1.9 V at the
drain bias conditions of 0.25 V and 0.3 V. The current modulation rate ranges from
20% to 30%.
Collective Resonance and Form-Factor of Homogeneous Broadening in Semiconductors
Authors: Sergey V. Zaitsev Sergey V. Zaitsev , Nikita Yu. Gordeev Nikita Yu. Gordeev , Leonid Ya. Karachinsky Leonid Ya. Karachinsky , Vladimir I. Kopchatov Vladimir I. Kopchatov , Innokenty I. Novikov Innokenty I. Novikov , Peter S. Kop'ev Peter S. Kop'ev
Published: October 2002

The concept of resonant carrier many body interaction during radiative recombination was applied to explain spectra of quantum well electroluminescence at 77 K. Extremely good (1%) agreement of the calculated and experimental spectra in the entire range of emission has been achieved. Estimations give a sub-picosecond characteristic time of such radiation process.
Al Adatom Migration on the Partly H-Terminated Si(111) Surface
Authors: Tadatsugu Hoshino Tadatsugu Hoshino , Nobuyuki Enomoto Nobuyuki Enomoto , Masayuki Hata Masayuki Hata , Minoru Tsuda Minoru Tsuda
Published: October 2002

Ab initio quantum chemical calculations using density functional theory have been performed to investigate the migration process of an Al adatom on the partly H-terminated Si(111) surfaces.
The diffusion of an Al adatom from the H-terminated monohydride area to the nonterminated bare Si area has been examined with two types of computational cluster models, both of which consistently indicate similar potential energy changes.
It has been revealed that the transfer of a single Al adatom from the H-terminated to the nonterminated area spontaneously proceeds without any activation energy barrier, and results in a very stable adhesion to the Si surface with an energy stabilization by 3.3 eV.
X-Ray Photoelectron Spectroscopy Study of Pt-Oxide Thin Films Deposited by Reactive Sputtering Using O2/Ar Gas Mixtures
Authors: Chun Kim Min-Cherl Jung
Published: October 2002

Thin-film oxides of Pt were grown reactively by rf magnetron sputtering and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Oxygen incorporation of the films was adjusted by controlling the oxygen mixing ratio (OMR). XRD reflections indicated that these samples have an amorphous structure without crystalline ordering of the Pt–O phases. SEM pictures showed that the formation of protrusions appear under the condition of large OMR. The XPS spectra revealed chemical shifts of Pt 4f peaks, which are ascribed to two different oxidation states of Pt. The amounts of the energy shifts are 1.0 and 2.1 eV, implying that the Pt oxide thin films are composed of PtO grains and intermediate oxides of PtO and PtO2.
Self-Organization of High-Density III–V Quantum Dots on High-Index Substrates
Authors: Kawabe Mitsuo , Akahane Kohichi , Lan Sheng , Okino Kennji , Okada Yositaka , Koyama Hiromichi
Published: October 2002

Ordered In0.4Ga0.6As quantum dots (QDs), with the density of
109 cm-2–1011 cm-2, are fabricated on GaAs(311)B substrates by atomic-hydrogen
assisted molecular beam epitaxy. The density and the dot size are mainly
changed by the growth temperature between 460°C and 520°C. In sharp
contrast to InAs, where we can hardly observe any ordering, and
coalescence or merging of dots occurs beyond a thickness of 4 monolayers,
the high-density In0.4Ga0.6As QDs do not coalesce even when the QDs are
in contact with each other. The inhomogeneuos distribution of In and Ga in
the QDs which are In rich at the surface is found to be responsible for this unusual behavior by reflection high energy electron diffraction studies. The
atomic force microscope images show that a surface coverage of nearly 100%
can be achieved. It implies the existence of lateral coupling between QDs,
which is strongly supported by the photoluminscence measurements.
Mechanism of Highly Selective SiO2 to Si3N4 Etching Using C4F8 + CO Magnetron Plasma
Authors: Hayashi Hisataka , Sekine Makoto
Published: October 2002

Highly selective SiO2 to Si3N4 etching was
achieved using C4F8 + CO magnetron plasma when the CO gas-mixing ratio exceeded 75%. The analyses
of fluorocarbon radicals in the plasma showed a higher carbon-to-fluorine ratio
with increasing CO ratio. In particular, a drastic increase in the C radicals was
observed, which corresponded to the increase in electron density. The reaction
mechanism of CO in the C4F8 + CO plasma was investigated utilizing CO
composed of the 13C isotope. CO supplied the carbon by electron-impact
dissociation and scavenged fluorine by forming COF
x
. The carbon-implanted
Si3N4 film clarified the role of carbon on Si3N4 etching. The decrease in the
Si3N4 etching rate and the increase in the fluorocarbon film thickness on the
surface were observed with increasing carbon dose. CO addition thus realizes
the high selectivity to Si3N4 in SiO2 etching.
Atomic Structure of Faceted Planes of InAs Quantum Dots on GaAs(001) Studied by Scanning Tunneling Microscopy
Authors: Xue Qi-Kun , Hasegawa Yukio , Kiyama Hisashi , Sakurai Toshio
Published: October 2002

Three-dimensional island structure of the lattice mismatched InAs/GaAs(001)
system was prepared by molecular beam epitaxy (MBE) and its images showing atomic
structure on faceted planes were taken in situ by ultra-high vacuum scanning tunneling
microscopy (UHV-STM). (113), (114) and (215) faceted planes are observed on 3D
InAs islands. Based on high resolution STM images, atomic structural models of these
faceted planes surfaces are proposed. The structure of the (113) planes is found to be
different from those observed on nominal-flat InAs and GaAs (113) surfaces. The
structural information will be useful for characterization of surface energy/stress of the
islands, diffusion process on the surface, and interface properties. The result sheds a
light on the formation mechanism and self-organization process of quantum dots.
Analysis of Band Offset in GaNAs/GaAs by X-Ray Photoelectron Spectroscopy
Authors: Kitatani Takeshi , Kondow Masahiko , Kikawa Takeshi , Yazawa Yoshiaki , Okai Makoto , Uomi Kazuhisa
Published: October 2002

We used X-ray photoelectron spectroscopy (XPS) to measure the energy discontinuity in the
valence band (Δ
E
v) of Ga1-x
N
x
As/AlAs (x=0, 0.014, 0.034) and estimated Δ
E
v of GaNAs/GaAs by using
the Al2p energy level as a reference. The change in Δ
E
v for GaNAs/GaAs with an increasing nitrogen
content was -(0.019±0.053) eV/%N. This suggests that the valence-band edge (E
v) in GaNAs decreases in proportion to the nitrogen content. Based on the decrease in the bandgap energy of GaNAs, we found
that the energy discontinuity in the conduction band (Δ
E
c) of GaNAs/GaAs is -(0.175±0.053) eV/%N. This large effect of bandgap bowing on the conduction band indicates that an ideal carrier confinement in the
well can be obtained by using GaInNAs as an active layer in long-wavelength laser diodes.
Cleaning by Brush-Scrubbing of Chemical Mechanical Polished Silicon Surfaces Using Ozonized Water and Diluted HF
Authors: Kurokawa Yoshiaki , Hirose Harumichi , Moriya Takahiko , Kimura Chouichi
Published: October 2002

A new process for scrubbing chemical-mechanical-polished silicon wafer
surfaces with a brush (brush-scrubbing process) was developed. The scrubbing is
performed in two stages; the first stage involves a wet treatment using ozonized
water and dilute HF. The second stage involves scrubbing with a Poly(vinyl
alcohol)(PVA) brush. After scrubbing, the number of residual particles, metal
and carbonaceous contamination, and surface roughness of the silicon wafer
surface were evaluated. It was determined that this new brush-scrubbing process
efficiently removed particles from chemical mechanical polished
silicon surfaces. Finally, a model explaining the new brush-scrubbing
process is constructed.
An In Situ Study on Phase Relation between Bi2SrO4 and SrCuO2 in the Bi2O3–SrO–CuO System
Authors: Mamiya Mikito , Suzuki Takuya , Takei Humihiko
Published: October 2002

A pseudobinary phase relation of Bi2SrO4–SrCuO2
in the Bi2O3–SrO–CuO ternary system between 850 and
1100°C has been investigated in situ using
an apparatus that combines high-temperature X-ray diffraction with an
optical microscopy. The liquidus temperatures increase with
decreasing Bi composition from 910°C to
1090°C. The lowest phase change temperature which
corresponds to the solidus line of this system is
910°C in the compositions below
Bi2Sr4Cu3O10. Above 910°C, the
decomposition to Bi4Sr8Cu5O
x
and liquefaction
occurs. On further heating above 925°C, a partially
molten phase with solid SrCuO2 appears in the Bi-deficient side.
The results are discussed in comparison with stabilities of the
Ca-added system of Bi2O3–SrO–CaO–CuO, in which Bi-based
cuprate superconductors are formed.
Giant Magnetoresistance in Granular Ferromagnetic Systems of Ni3Mn Alloy
Authors: Okazaki Teiko , Sugimoto Satoshi , Aono Yoshinori , Miyanaga Takafumi , Homma Motofumi
Published: October 2002

Giant magnetoresistance (GMR) phenomena were investigated in the inhomogeneous phase of Ni3Mn alloy, where magnetically ordered single-domain clusters are distributed in a disordered nonmagnetic matrix. The observed GMR varies with the long-range-order parameterSand has values ranging from -0.5% to -1.8% for 0.1 <S< 0.5. The GMR is proportional to [1 - (M/MS)2] with an applied magnetic field, whereMandMSare the global and saturation magnetizations, respectively. We found that the GMR is correlated with the average size  and the volume fraction ε of the ferromagnetic clusters. The GMR is maximized at ∼33nm3and ε∼0.25, these values being obtained from analysis using a superferromagnetic model.
Waveform Shaping of a Chemical Oxygen-Iodine Laser Utilizing the Zeeman Effect
Authors: Sugimoto Daichi , Kawano Takanori , Endo Masamori , Takeda Shuzaburo , Fujioka Tomoo
Published: October 2002

A laser power waveform shaping system for a chemical oxygen-iodine laser
(COIL) utilizing the Zeeman effect of iodine was developed. A feedback control
system based on the servomechanism was employed to modulate the laser power to
an arbitrary waveform. It was observed that the CW output is converted into a 20 Hz triangular waveform with a modulation depth of nearly 100%. The feedback
response of the power control system is theoretically analyzed and found consistent
with the experimental results. The analysis indicates that the response time of the
feedback system is limited by the inductance/resistance ratio of the electrical circuit,
and faster modulation can be realized at the expense of higher power consumption in an electrical circuit.
High Power GaInAsP/InP Strained Quantum Well Superluminescent Diode with Tapered Active Region
Authors: Yamatoya Takeshi , Mori Shota , Koyama Fumio , Iga Kenichi
Published: October 2002

High-power broadband superluminescent diodes (SLDs) have been studied for
spectrum-sliced multiwavelength light sources for use in wavelength division
multiplexing systems. We present the design and fabrication of high-power broadband
GaInAsP/InP strained quantum well SLDs with a tapered active region emitting in a
1.55 µm wavelength band. The fabricated device exhibited the high-power operation
of over 1 W. Also, the spectral width has been increased to over 60 nm by using
chirped multiquantum wells which have different well thicknesses.
Dielectric Properties in Polyamides of m-Xylylenediamine and Dicarboxylic Acids
Authors: Murata Yukinobu , Tsunashima Kenji , Koizumi Naokazu
Published: October 2002

Dielectric properties were investigated for polyamides consisting
of m-xylylenediamine and aliphatic dicarboxylic acids with the number
of carbon atoms from 6 to 11, over a frequency range of 25 Hz to
1 MHz, at temperatures from 200 to 400 K. The α relaxation
with a relaxation strength of 60 to 80 was observed at temperatures
above the glass transition temperature T
g in quenched
amorphous samples and was related to the micro-Brownian motion of
the molecular chains of these aromatic polyamides. The dipole moment
per repeating unit was 9 to 11 D for the α relaxation. The
β relaxation observed at temperatures below room temperature
exhibited a small relaxation strength, which was attributed to the
motion of carbonyl groups with water molecules bound by a hydrogen
bond. The space-charge polarization effects took place at high
temperatures and low frequencies. The crystallization occurring
during the heating process decreased the dielectric constant and
loss in the α relaxation and the space-charge polarization.
An Improved Method for Determining Densities and Energy Levels of Dopants and Traps by Means of Hall-Effect Measurement
Authors: Hideharu Matsuura Hideharu Matsuura
Published: October 2002

Using the temperature dependence p(T) of the majority-carrier concentration in a semiconductor, two graphical methods for determining the densities and energy levels of dopants and traps are compared. In the analysis proposed previously, the function to be evaluated is defined by S(T,E
ref) ≡p(T) exp
(E
ref/k
T)/k
T, where T is the temperature, k is the Boltzmann constant and E
ref is the parameter. However, it is sometimes difficult, particularly in high-resistivity semiconductors, to determine these values. This is why the function to be evaluated is introduced here as H(T,E
ref) ≡p(T)2 exp
(E
ref/k
T)/(k
T)2.5, and it is determined that H(T,E
ref) is superior to S(T,E
ref).
Dielectric Study on Ferri-like Ordering in Antiferroelectric Liquid Crystals during the Field-Induced Phase Transition
Authors: T. Nguyen Chang-Jae Yu
Published: October 2002

We studied the field-induced ferri-like (FI) ordering in antiferroelectric (AF) liquid crystals based on a simple geometrical model which includes the electrostatic dipolar and quadrupolar interactions between the molecules in two adjacent layers. In this model, the stabilization of the FI ordering during the AF-ferroelectric (FO) transition results from the quadrupolar interactions between the molecules in the nearest neighbor layers. The experimental results for the dielectric behavior at various bias fields near the AF-FI transition temperature are consistent with the theoretical predictions made within the geometrical model.
Anisotropic Diamagnetic Susceptibility of AlNiCo Quasi-crystal
Authors: Yamada Yoshihiro , Yokoyama Yoshihiko , Matono Ken-ichi , Fukaura Kenzo , Sunada Hisakichi
Published: October 2002

We have carried out magnetization measurements of a single decagonal Al72Ni12Co16 quasi-crystal for the cases of the magnetic field parallel and perpendicular to the periodic axis with a torsion-type magnetic balance in various magnetic fields up to 10 kOe from 4.2 K to room temperature. Anisotropic diamagnetic susceptibility was observed, which is closely correlated to the electron motions in the quasi-crystal.
Controlling Microscopic Surface Structure, Crystalline Size and Crystallinity of CdS and ZnS Nanocrystallites
Authors: Hosokawa Kei Murakoshi Hiroji , Yanagida Shozo
Published: October 2002

Size controlled CdS and ZnS nanocrystallites with well-defined
crystallinity were simply prepared by reacting M2+
(M=Cd2+ or Zn2+) and S2-
(H2S or Na2S) in N,N-dimethylformamide (DMF) without adding any surface stabilizers. The mean diameter of CdS nanocrystallites can be rigorously controlled over a range from 1.8 to 4.2 nm maintaining the hexagonal crystalline structure by varying the sulfur source and by regulating the preparation temperature. The band-gap dependence estimated from the absorption peak wavelength on the size of the hexagonal CdS nanocrystallites was in good agreement with the pseudopotential calculation using lattice parameters of hexagonal CdS. In the system of ZnS nanocrystallites, crystallinity was controlled by changing the surface modifying reagent. Reactive organic molecules, which can bind onto the surface of ZnS nanocrystallites, induce phase transition of ZnS nanocrystallites from the hexagonal to the cubic phase, maintaining a crystalline size of 3 nm at ambient temperature and pressure.
Axial Structure of High-Vacuum Planar Magnetron Discharge Space
Authors: Miura Tsutomu
Published: October 2002

The spatial structure of high-vacuum planar magnetron discharge is
theoretically investigated taking into account the electron confinement. The
boundary x
es of the electron confinement region depends on B
A with E
a/B
A as the parameter (B
A: the magnetic flux density at the anode, E
a: the average electric field strength). The location at which the frequency of ionization events takes the maximum is expressed as C
nN
x
iep (C
nN: a factor related to the electron density distribution, x
iep: the distance of the location from the cathode at which the ionization is most efficient). With increasing E
a and B
A at a fixed E
a/B
A, the density of the confined energetic electrons increases. With increasing E
a, the region where ionization is efficient shifts to the cathode side to give a high efficiency of the magnet. The boundary x
es as determined by the probe method agreed with the theoretical prediction.
Annealing Effect of Pb(Zr, Ti)O3 Ferroelectric Capacitor in Active Ammonia Gas Cracked by Catalytic Chemical Vapor Deposition System
Authors: Minamikawa Toshiharu , Yonezawa Yasuto , Nakamura Takashi , Fujimori Yoshikazu , Masuda Atsushi , Matsumura Hideki
Published: October 2002

The effects of annealing treatments on Pb(Zr, Ti)O3 (PZT) film capacitors in
active ammonia gas are investigated as a function of substrate temperature. Since
active ammonia gas is generated by cracking of ammonia gas using a heated
catalyzer in catalytic chemical vapor deposition (Cat-CVD) apparatus, knowledge
of the effect of active ammonia gas on ferroelectric properties is important for the
application of Cat-CVD silicon nitride films for the passivation of ferroelectric
devices such as PZT. No degradation of ferroelectricity was detected for treatment
carried out below 200°C. It was revealed that the Cat-CVD method is a promising
candidate for the preparation of SiN
x
passivation films on ferroelectrics.
Effect of Hydrogen Anneals on Niobium-Doped Lead Zirconate Titanate Capacitors with Lanthanum Strontium Cobalt Oxide/Platinum Electrodes
Authors: Evans Joe T. , Boyer Jr. , Velasquez Geri , Ramesh Ramamoorthy , Aggarwal Sanjeev , Keramidas Vassillis
Published: October 2002

Ferroelectric capacitors, being oxide ceramics, are very sensitive to the effects of
hydrogen environments at elevated temperatures [H. Ashida et al..:
Integr. Ferroelectr. 21 (1998) 97]. After a capacitor has been exposed directly
to a annealing hydrogen environment at low hydrogen partial pressures, the
electrical properties of the device can deteriorate and leakage currents can
increase. At higher hydrogen concentration gradients, such as the formidable
forming gas annealing, physical failure of the inter-layer dielectric (ILD) and/or
top electrode adhesion can occur. The authors have examined various
structural approaches to mitigate the effects of hydrogen damage on integrated
ferroelectric lead zirconate titanate (PZT) capacitors. These approaches, including the use of a titanium
dioxide barrier layer above the PZT to impede the reducing effect of hydrogen on
the ceramic and the use of electrode layers other than platinum to eliminate the
generation of free hydrogen ions by catalyst action [S. Aggarwal et al..: Appl. Phys. Lett. 73 (1998) 1973]. The authors have found that niobium-doped PZT
capacitors using LSCO/platinum electrodes passivated with titanium dioxide will
recover from 1% forming gas annealing within 30 minutes at 450°C in nitrogen.
Ferroelectric Properties of La0.5Sr0.5CoO3/Pb(Zr0.4, Ti0.6)O3/RuO2 Capacitors
Authors: Atoh Hirokazu , Doi Hidekazu
Published: October 2002

As a continuation of the previous studies on
Pt/La0.5Sr0.5CoO3/Pb(Zr0.4, Ti0.6)O3/RuO2/SiO2/Si(100) capacitors, the effect of post-annealing conditions of the sputtered-deposited RuO2 bottom electrodes upon crystallization of the PZT(40/60) films and their ferroelectric properties was examined. The switchable polarization (d
P=P
*-P
∧) in the fatigue tests under comparatively low driving voltage amplitudes of 2.0–2.5 V of the PZT films grown on O2- or Ar-annealed RuO2 electrodes continued to be larger than 10 µC/cm2 up to 1010 switching cycles. The fatigue profile generally exhibited gradual degradation with increasing cycles. However, the rates of polarization degradations depended on post-annealing conditions of the bottom electrodes; in the case of O2 annealing, the degradation rate was the lowest (20%) when the annealing temperature was the lowest in the range of 700–800°C. On the other hand, in the case of Ar annealing, the opposite trend was noted. The leakage current density was in the range of 10-6 A/cm2 or less at 2 V, which appeared to be independent of the postannealing condition of the bottom electrode. A possible interpretation of the effectiveness of using the La0.5Sr0.5CoO3 top electrode for the Pb(Zr0.4, Ti0.6)O3 film in suppressing the polarization fatigue has been presented.
Electrical Properties of Highly Strained Epitaxial Pb(Zr,Ti)O3 Thin Films on MgO(100)
Authors: Hirotake Okino Hirotake Okino , Tomoki Nishikawa Tomoki Nishikawa , Masaru Shimizu Masaru Shimizu , Toshihisa Horiuchi Toshihisa Horiuchi , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

The film thickness (20–200 nm) dependence of the crystalline structure,
lattice parameters and electrical properties of
highly strained Pb(Zr,Ti)O3 (PZT) thin films on MgO(100) was investigated.
The PZT films were practically c-axis orientation.
As the film thickness decreased (< 100 nm),
the tetragonality ratio of PZT also decreased owing to
the inner expanding strain in the in-plane direction.
The dielectric constant decreased and
the structural phase transition temperature shifted to a lower temperature
corresponding with the decrease in the tetragonality ratio.
The electric displacement-electric field (D-E) hysteresis curves
for the thick (> 40 nm) films exhibited a certain amount of
remanent polarization in the in-plane direction,
implying the formation of a-domains.
The relationship between electrical properties and the inner strain is discussed.
A Study on a Metal-Ferroelectric-Oxide-Semiconductor Structure with Thin Silicon Oxide Film Using SrBi2Ta2O9 Ferroelectric Films Prepared by Pulsed Laser Deposition
Authors: Noda Minoru , Sugiyama Hideki , Okuyama Masanori
Published: October 2002

A preferentially (105)-oriented SrBi2Ta2O9 (SBT) thin film on
SiO2/n-Si(100) or on Pt is prepared by pulsed laser deposition (PLD)
at a low temperature of about 500°C. Polarization-electric
field (P–E) hysteresis is observed on the Pt/SBT/Pt diode, where 2P
r
is 5 µC/cm2 and E
c is 34 kV/cm, respectively. Counterclockwise
hysteresis appears in the C–V curve of the Al/SBT/SiO2/Si structure
only when a (105) peak is observed under various growth conditions
by PLD. This means that (105)-oriented perovskite SBT exhibits
counterclockwise hysteresis and noncrystalline SBT does not exhibit
hysteresis. The memory window has been increased from 2.7 V to 4.3 V
by changing the thickness ratio of SBT/SiO2 from 400 nm/27 nm to
400 nm/8 nm. This shows that an efficient electric field in SBT is
increased in the case of 8 nm SiO2 film; then E
c and the resulting
memory window are also increased. Positive shifts in the C–V curves
are observed when SiO2 thickness decreases down to about 10 nm. One
of the mechanisms of the shift is considered to be that a negative
charge is generated by electron tunneling through the SiO2 from the
conduction band of n-Si and is fixed at the SBT/SiO2 interface or in
the SBT bulk site. Also, the memory window starts to decrease when
the gate bias applied to the MFOS diode is sufficiently
increased. This indicates that the charge injection mode becomes
dominant then reduces dielectric counterclockwise hysteresis. The
retention time has been improved up to about 3×103 sec with an
optimized hold bias voltage in an MFOS diode with SiO2 thickness of
27 nm.
Effect of Occupational Sites of Rare-Earth Elements on the Microstructure in BaTiO3
Authors: Kishi Hiroshi , Kohzu Noriyuki , Mizuno Youichi , Iguchi Yoshiaki , Sugino Junichi , Ohsato Hitoshi , Okuda Takashi
Published: October 2002

The effect of rare-earth elements such as La, Ho and Yb on the microstructure in BaTiO3
(A
BO3) with various Ba/Ti ratios was studied. The grain size changed markedly depending on the
Ba/Ti ratio in the case of La- and Yb-doped BaTiO3. On the other hand, in the case of Ho-doped
BaTiO3, the grain size changed gradually in a wide range of Ba/Ti ratio. It is considered that Ho
ions occupy both A- and B-sites, depending on the Ba/Ti ratio, while La and Yb ions occupy A- and
B-sites, respectively. The solubility, the microstructure and the resistivity of rare-earth elements and
Mg-substituted BaTiO3 were also investigated. It was also confirmed that La ions occupied A-sites,
Yb ions occupied B-sites and Ho ions occupied both A- and B-sites. It appears that the drastic
change of the resistivity of Ho–Mg-substituted BaTiO3 is due to the change in the predominant
occupational site of Ho ions.