bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Properties of Cr-Doped β-FeSi2
Authors: Tani Jun-ichi , Kido Hiroyasu
Published: October 2002

The Hall effect and electrical resistivity of iron disilicide Fe1-x
Cr
x
Si2 (0.01≦x≦0.05) have been
measured in the temperature range between 80 and 300 K. The solid solution Fe1-x
Cr
x
Si2 is p-type over the
measured temperature range. The hole concentration of
Fe1-x
Cr
x
Si2 at 300 K ranges from 8.9×1018 cm-3 for
x=0.01 to 1.1×1020 cm-3 for x=0.05, which is one order of magnitude higher than that of Fe1-x
Mn
x
Si2. The
temperature dependence of the mobility of the composition range
0.03≦x≦0.05 can be explained by using
the small polaron model.
Second Harmonic Electroreflectance Study of AlGaAs–GaAs Asymmetric Triangular and Coupled Double Quantum Wells
Authors: Tiong Kwong-Kau , Lin Der-Yuh , Huang Ying-Sheng
Published: October 2002

Electroreflectance (ER) spectroscopy is used to study AlGaAs–GaAs asymmetric
triangular and coupled double quantum wells. The ER spectra are taken at both the
fundamental (1f ) and second harmonic (2f ) modulation frequencies. A detailed ER
lineshape analysis appropriate for a Lorentzian dielectric function is presented. The
experimental 1f and 2f spectra are, respectively, shown to be related to the first and
second order field induced changes in the dielectric function. A detail comparison of
the line shapes of the 1f, 2f and energy derivative of the 1f spectra and their respective
spectral forms enable a qualitative deduction of the dominant mechanism of the
experimental ER spectra. In particular, for the asymmetric triangular well structure,
the dominance of excitonic modulation mechanism can be inferred. Useful additional
information on the sample signature such as the features associated with the red and
blue shifts are obtained through such a comparative study. In addition, several weak
features are observed to be significantly enhanced in the 2f spectra and the
characteristics of these features are deduced.
Thermal Analysis for GaN Laser Diodes
Authors: Gen-ichi Hatakoshi Gen-ichi Hatakoshi , Masaaki Onomura Masaaki Onomura , Masahiro Yamamoto Masahiro Yamamoto , Shin-ya Nunoue Shin-ya Nunoue , Kazuhiko Itaya Kazuhiko Itaya , Masayuki Ishikawa Masayuki Ishikawa
Published: October 2002

Improvement in temperature characteristics of GaN laser diodes is important for realizing reliable devices operating at high temperatures. Thermal characteristics of GaN lasers have been analyzed by using a three-dimensional thermal conduction model. Maximum operation temperature has also been calculated. It was shown that the reduction in the stripe width as well as the reduction in threshold current density and operation voltage is very important for improving the temperature characteristics of GaN laser diodes.
Doping Mechanisms of Sn in In2O3 Powder Studied Using 119Sn Mössbauer Spectroscopy and X-Ray Diffraction
Authors: Yamada Naoomi , Yasui Itaru , Li YuzoShigesato , Nomura YusukeUjihira
Published: October 2002

The doping mechanism of Sn in In2O3 (ITO) powder was investigated using 119Sn transmission
Mössbauer spectroscopy (TMS) and X-ray diffraction (XRD) in view of the chemical state of Sn.
Deconvolution analyses of TMS spectra revealed that there was substitutional Sn4+ coordinated not
only by 6 oxygen atoms [SnIn
·] but also by 7 or 8 oxygen atoms, for the samples with doping
concentrations higher than 5 at.%. The amount of such electrically deactivated Sn4+ (coordination
number of 7 or 8) increased with increasing doping concentration, which was quantitatively
consistent with the decrease in doping efficiency. Precise XRD analyses indicated a systematic
increase in the lattice constant with increasing doping concentration from 0.5 to 7 at.%. The
increase in lattice constant was explained in terms of a repulsive
force among tetravalent [SnIn
·] (coordination number of 6) with higher effective charge than In3+, which was also consistent with
the results on the coordination of Sn4+ obtained through TMS
analyses.
A Study of Longitudinal and Transversal Range Parameters of Ion-Implanted 40–360 keV Molybdenum in Silicon
Authors: Liang J. H.
Published: October 2002

This paper presents an experimental and theoretical study of longitudinal and
transversal range parameters of molybdenum ions ranging from 40 to 360 keV
implanted in silicon. In the experimental part of this study, silicon wafers were tilted
by 7° and 55° at the time they were implanted with molybdenum ions. The
implanted-ion depth profiles were detected by means of secondary ion
mass specfroscopy (SIMS) measurements. The
measured range parameters were extracted from fitting the measured implanted-ion
depth profiles to a Pearson distribution. In addition, the transversal range straggling
measurements were obtained by using the Furukawa and Matsumura formula. Measured range parameters were also compared to the values calculated from the
Biersack theory. It was found that the calculated values of projected range,
longitudinal range straggling, skewness, kurtosis, and transversal range straggling
agreed to the corresponding measured values within (on average) 9%, 7%, 32%, 17%,
and 10%, respectively.
Structures of Self-Assembled Monolayers versus Vacuum Deposited Films of Terthiophene
Authors: Matsuura Toshihiko , Takamura Takumi , Shimoyama Yuhei
Published: October 2002

Using X-ray diffraction and Fourier-transform infrared (FT-IR) spectroscopy, we
elucidated the molecular orientation in self-assembled monolayers (SAM) and vacuum
deposited films of terthiophene. Terthiophene in the SAM aligns parallel to the gold
substrate. On the other hand, in the vacuum deposited films, the long axis of terthiophene
aligns along the normal to the surface. Although our results contradict the quantum
calculations, which predict that thiophene would not interact with gold significantly, we
experimentally demonstrated the interaction between terthiophene and gold. A theoretical
fitting of FT-IR signals, the out-of-plane –CH and –CH=CH– vibration at 680 cm-1,
revealed the SAM formation of terthiophene to be a Langmuir type of
adsorption.
Molecular Orientations in Langmuir-Blodgett and Vacuum-Deposited Films of VO-Phthalocyanine
Authors: Takamura Takumi , Moriyama Masaki , Komatsu Tomohiro , Shimoyama Yuhei
Published: October 2002

Langmuir-Blodgett (LB) and vacuum-deposited (VD) films of vanadyl tetra t-butyl
phthalocyanine (VOTBP) were investigated by X-ray diffraction (XRD), electron paramagnetic
resonance (EPR) and UV-visible spectroscopy to reveal their film structure and molecular
organization. Both types of films of VOTBP indicated a weaker intermolecular force than other
metal-phthalocyanine films, as determined by UV-visible spectroscopy. XRD data showed that
the LB films possessed a long-range order. VOTBP in the LB films were oriented
perpendicular to the glass substrate, as evaluated by the angular dependence of EPR spectra.
VOTBP in the VD films were oriented parallel to the substrate. The linewidth of EPR spectra
indicated a two-dimensional spin chain in the LB films and a three-dimensional spin chain in the
VD films. The order parameter evaluated from the magnetic parameters of EPR spectra
exhibited a moderate degree of ordering in both types of films. This evidence indicated that the
balance between the intermolecular force in VOTBP and the surface force from the substrate
determines the variety of molecular orientations. The moderate degree of ordering of both types
of the films is due to the weak intermolecular force as well as the dipolar interaction of
VOTBP.
Two-Dimensional In0.4Ga0.6As/GaAs Quantum Dot Superlattices Realized by Self-Organized Epitaxial Growth
Authors: Lan Sheng , Akahane Kouichi , Kawamura Kee-YounJang , Okada Yoshitaka , Kawabe Mitsuo , Nishimura Tetsuya , OsamuWada OsamuWada
Published: October 2002

We report on the realization of two-dimensional (2D)
In0.4Ga0.6As/GaAs quantum dot superlattices (QDSLs) by self-organized
epitaxial growth. The conditions for the formation of extended states
or minibands are analyzed by treating QD arrays as disordered
systems. Ordered quantum dot (QD) arrays are fabricated on GaAs (311)B
substrates. High density and small size are achieved by decreasing the
growth temperature. A large red shift of the photoluminescence (PL)
peak energy and a dramatic narrowing of the linewidth are found when
the dots become smaller and closer. The exciton coherence length in
the high-density ordered QD array is confirmed to be much larger than
the QD diameter by PL decay time measurements and by using beryllium
impurities as scattering centers. As a comparison, the incoherent
exciton motion dominated by nonresonant tunneling is discussed. The
transition from coherent to incoherent, including the intermediate
state, and the localization of excitons are demonstrated by various
mechanisms.
Study on Zr–Si/W(100) Surface at High Temperatures by Reflection High Energy Electron Diffraction
Authors: Kawano Takashi , Mitsuhashi Riichiro , Kimura Yoshihide , Shimizu Ryuichi
Published: October 2002

Reflection High Energy Electron Diffraction study has revealed that a Zr–Si/W(100) surface has an island structure at the operating temperature of ∼1300 K. The structure hardly changes when the sample temperature is lowered to room
temperature. This result has confirmed the previous work that the Zr–Si/W(100)
system does not undergo phase transition as does the Zr–O/W(100) system at
∼1000 K. The surface properties of the Zr–Si/W(100) system, so long as surface
characterization is concerned, hardly change in the range of sample temperature
between operating temperature and room temperature.
Does an X-Ray Photon Really Generate a Charge Cloud with an Asymmetric Shape?
Authors: Hiroshi Tsunemi Hiroshi Tsunemi , Junko Hiraga Junko Hiraga , Kumi Yoshita Kumi Yoshita , andEmi Miyata andEmi Miyata
Published: October 2002

An X-ray photon produces a finite-sized primary charge cloud
inside a charge-coupled device (CCD). Its shape is determined to be
asymmetric using a mesh experiment. It is elongated in the direction
perpendicular to the charge transfer direction. We checked whether or
not the asymmetry of the charge cloud shape was due to the experimental
setup. The geometrical shape of the mesh holes is confirmed to be
symmetric by a Scanning Electron Microscope (SEM). A new method is
introduced to quantitatively measure the effective size of the mesh
hole for the X-rays. The geometrical diameter of the mesh hole is
3.4 µm while the effective diameter of the mesh hole is 3.9±
0.3 µm for Al-K X-ray photons (1.5 keV) and 4.0±0.3 µm
for Mo-L X-ray photons (2.3 keV), respectively. These values are
consistent with that taking into account the diffraction of X-rays.
We conclude that the asymmetry of the primary charge cloud generated
inside the CCD is due not to the experimental setup but to the
asymmetry of the electric field inside the CCD.
Measuring Method for Mach Number in Tokamak Edge Plasma Using Probes
Authors: Maeda Mitsuru , Uehara Kazuya , Amemiya Hiroshi
Published: October 2002

A method for measuring the Mach number in tokamak edge plasmas using electric probes is
developed. The Mach number is deduced from the ratio of saturation currents of a Mach probe by
taking the ratio of the ion temperature to the electron temperature into account. The present method
of considering the effect of the finite ion temperature is applied to the edge plasma in the JFT-2M
tokamak.
Charge Transfer Cross Sections for Dysprosium and Cerium
Authors: Tamura Koji , Adachi Hajime , TakemasaShibata TakemasaShibata
Published: October 2002

Symmetric charge transfer cross sections between singly ionized ions and
their parent atoms were measured for dysprosium and cerium in the impact
energy range of 100–2000 eV. The primary ion beam was extracted from a
laser ion source in which the atoms were ionized by laser resonant photo-ionization. The slow ions produced in the charge transfer reaction and the fast
primary ions were detected with Faraday cups. The cross sections were
determined from the ratio between the number of ions produced in the charge
transfer reaction and that of the primary ion beam. Average values of obtained
cross sections were 1.8×10-14 cm2 for dysprosium and
0.9×10-14 cm2 for cerium
in the above energy range. The considerable difference between these values
was explained by considering the electronic configurations of related atoms and
ions.
Fractal Characters of 1/2-order Integration of White Noise and 1/f Resistance Fluctuation
Authors: Akabane Hideo , Agu Masahiro , Yoshida Atsushi
Published: October 2002

Four different types of 1/f time series are generated by computer simulations and the
analyses of their fractal characteristics are carried out. The numerical evaluation shows that the
differences in the generation mechanism results in a 1/f time series having different fractal
structures. The 1/f resistance fluctuation of a carbon fiber is observed and its fractal property is
analyzed in comparison with that of computer-generated 1/f fluctuations. It is found that the
fractal property of the resistance fluctuation is the same as that of the fluctuation generated by
1/2-order integration of white noise.
Underground Imaging Using Shear Waves –Study on Three Dimentional Underground Imaging–
Authors: Tsuneyoshi Sugimoto Tsuneyoshi Sugimoto , Naoki Yoshida Naoki Yoshida , Motoyoshi Okujima Motoyoshi Okujima
Published: October 2002

We proposed an underground imaging technique that uses shear waves and a method based on the stacking of reflected scattered waves.
In order to study a three-dimensional underground image, geophones were arranged in a plane and three targets were buried at different depths.
We tried to detect these targets using cross-sectional images.
From the experimental results, we were able to find the buried targets; however, improvements are necessary to make a three-dimensional image.
Carrier Concentration Dependence of Photoacoustic Signal Intensity of Silicon
Authors: Kuwahata Hiroshi , Muto Nobuo , Uehara Fumiya , Matsumori Tokue
Published: October 2002

Photoacoustic (PA) spectra near the energy gap of n- and p-type silicon were investigated
at various carrier concentrations. The PA signal intensity at energies lower than the energy gap
increased with increasing carrier concentration for both types. The increase is considered to be
due to the increase in the heat generated in the samples following free carrier absorption and
nonradiative relaxation processes. The PA signal intensity increased drastically above a carrier
concentration of 1017 cm-3 for n-type and above that of 1016 cm-3 for p-type silicon.
A Study on the Rectangular-Bar-Shaped Multilayer Piezoelectric Transformer Using Length Extensional Vibration Mode
Authors: Hu Junhui , Fuda Yoshiaki , Yoshida MasafumiKatsuno
Published: October 2002

The rectangular-bar-shaped multilayer piezoelectric transformer, which employs the length extensional
vibration mode and interdigital internal electrodes, has been suggested and developed by us for the application
to AC adapters. First, the methods of increasing the power-to-volume
ratio of the transformer are investigated
experimentally. As a result, it is found that using a high driving frequency and optimizing the positions of
input and output parts increase the power-to-volume ratio. Second, to prevent characteristic degradation
resulting from spurious vibrations in its driving frequency range, the methods of controlling such spurious
vibrations are studied theoretically and experimentally. It is found that controlling the size of the transformer
can widen the driving frequency range without spurious vibrations, and that using a low order length
extensional vibration mode can decrease the number of spurious vibrations in its driving frequency range. Also,
it is found that spurious vibrations can be eliminated or weakened by properly arranging the positions of input
and output parts according to the mode pattern of the spurious
vibrations.
Measurement of Distribution of Acoustic Radiation Force Perpendicular to Sound Beam Axis
Authors: Tuziuti Toru , Kozuka Teruyuki , Mitome Hideto
Published: October 2002

To clarify the range of force acting on a particle in the
direction perpendicular to the sound beam axis of an ultrasonic
standing wave for particle manipulation, the radiation force on a
polystyrene sphere of submillimeter size was measured through
observation of its movement in a 1.75 MHz ultrasonic standing
wave. The radiation force was estimated at some points by balancing
with the force from viscous drag proportional to the measured velocity
of a particle and the gravitational force, and its distribution was
determined. The measured distribution of the radiation force agreed
qualitatively with the theoretical distribution derived from
Nyborg's formula. The influence of gravitational force on a
stable position was also investigated. It was shown that the shift
from the stable position is marked for particles with large
radius. This effect should be considered in particle
manipulation.
A Real-Time Medical Ultrasound Image Sequence Transmission System with Narrow Integrated Service Digital Network
Authors: Toshiyuki Umeda Toshiyuki Umeda , Tomohiro Kuroda Tomohiro Kuroda , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

In this paper, a new telemedicine system which enables real-time
telediagnosis using medical ultrasound (US) image sequences on a
public digital network with a speed of up to 128 kbps, famed as narrow
integrated service digital network (N-ISDN) is proposed. This system
can be used to transmit two types of image sequences: one is the image
sequence of an entire region in low time/space resolution and the
other is a region of interests (ROI) in high time/space
resolution. Therefore, a medical doctor at a diagnosis site can
instruct the technician at the live acquisition site about the
location and angle of the probe, using the entire region image
sequences. When the appropriate slices are obtained, a medical doctor
can diagnose the high-resolution image sequences of the ROI. We
developed the prototype which compresses the US image sequences with
discrete cosine transform (DCT) and examined the system on a user
datagram protocol/Internet protocol (UDP/IP) communication
channel. The experimental results show that the image sequences of an
entire region, which holds 640 × 480 pixels, are transmitted
with 5.0 frames per second less than 112.5 kbps, and that the ROI,
which holds 90 × 90 pixels, are transmitted with 14.2 frames
per second less than 81.9 kbps.
Electrical Activity of Defects Induced by Oxygen Precipitation in Czochralski-Grown Silicon Wafers
Authors: Mchedlidze Teimouraz , Matsumoto Kei , Asano Eiichi
Published: October 2002

Majority and minority carrier traps introduced in p-type Czochralski-grown silicon (CZ-Si) wafers during two-step low-high temperature annealing procedures were investigated using deep level transient spectroscopy (DLTS). It was determined that the platelike silicon oxide precipitate surface and the punch-out dislocations introduce majority carrier traps having deep energy levels (EV+0.43 eV andEV+0.26 eV, repectively) in the Si band gap in concentrations proportional to the relevant defect density. The minority carrier traps are positioned atEC-0.42 eV andEC-0.22 eV. The majority carrier trap density on the surface of the platelike precipitate was estimated as ∼3×109cm-2and the linear trap density for the punch-out dislocations as ∼ 4×104cm-1.
Analysis of Local Lattice Strain Around Oxygen Precipitates in Czochralski-Grown Silicon Wafers Using Convergent Beam Electron Diffraction
Authors: Yonemura Mitsuharu , Sueoka Koji , KazuhitoKamei KazuhitoKamei
Published: October 2002

The local lattice strain field around oxygen precipitates in
Czochralski-grown silicon (CZ-Si) wafers has been measured
quantitatively using convergent beam electron diffraction (CBED). As a
result of the strain analysis from higher-order Laue zone patterns in
the CBED disk, strain of the silicon lattices was found in the
vicinity of oxygen precipitates, i.e., platelet type and polyhedral type.
The strain along the normal direction to the precipitate is
compressive, and the strain along the parallel direction to the
precipitate is tensile. The lattice strain field around the precipitate
decreases monotonically as a function of distance from the
precipitate/matrix interface. Further, the morphological change in the
growth process of the precipitate is important for the formation of
the local lattice strain.
Non-Linear Transports in Evaporated C60 Cluster Films
Authors: Xu Ying , Kondo Jun-ya , Shionoiri Yutaka , Ochiai Yuichi
Published: October 2002

We studied nonlinear transport in evaporated C60 films by means of the I-V
characteristics at room temperature. SET-like transport behavior was observed
in the results of studies of the C60 cluster films at room temperature. It is
especially thought to be related to a certain metal insulator transition in a low-dimensional system because of the large difference between the bulk and surface
transports of the small clusters of C60.
Enhancing the Oxygen Plasma Resistance of Low-k Methylsilsesquioxane by H2 Plasma Treatment
Authors: Liu Po-Tsun , Chang Ting-Chang , Mor Yi-Shian , Sze Simon M.
Published: October 2002

The organic silsesquioxane, methylsilsesquioxane (MSQ), has a low dielectric constant because of its low film density compared to
thermal oxide. However, the quality of the MSQ film is degraded by the damage caused by oxygen plasma and hygroscopic behavior during
photoresist stripping. In this work, we have studied the ability of H2 plasma treatment to improve the quality of MSQ. The leakage
current of MSQ decreases as the H2 plasma treatment time is increased. The dielectric constant of treated samples remains constant
(∼2.7). In addition, the thermal stability of MSQ film is significantly promoted. The H2 plasma treatment can provide additional
hydrogen to passivate the inner structure of porous MSQ film, and reduce the probability of moisture uptake. Therefore, H2 plasma
treatment can improve the quality of low-k MSQ film and reduce the issue of photoresist stripping in the integrated process.
Effect of Leakage Current on Pulse-Width Characteristic in Q-Switched Two-Section AlGaAs Multiple-Quantum-Well Semiconductor Lasers
Authors: Shimizu Mitsuaki , Suzuki Yoshihiro , Watanabe SeijiMukai , ToshifumiHasama ToshifumiHasama
Published: October 2002

We investigated the effect of leakage current on optical pulse width in Q-switched two-section AlGaAs multiple-quantum-well (MQW) lasers, employing numerical analysis using traveling-wave rate equations which include the effect of the carrier leakage. The analysis shows that the pulse width of Q-switched semiconductor lasers is broadened when carrier leakage current is present. This effect becomes significant and is one of the main reasons for the pulse-width broadening for short cavity. These numerical results agree with previously obtained experimental results. [1]
Manipulation of Laser Ablation Plume by Magnetic Field Application
Authors: Tachiki Minoru , Kobayashi Takeshi
Published: October 2002

Time- and wavelength-resolved observation of a laser ablation plume from a
strontium titanate target was performed under a dipole magnetic field applied
from the substrate side. In contrast to the conventional method, the present
method gave rise to increasing ionization of the growth species in the plume in
the vicinity of the substrate. Using this method, NiO films could be epitaxially
grown on (100)MgO substrates even at room temperature. When we placed a
shadow mask between the target and the substrate (eclipse method), the
deposition rate was increased to by 2.6-fold that under zero magnetic field.
Epitaxial Growth of HfN Film and Sequential Single-Oriented Growth of Al/HfN Bilayered Film on (001) and (111) Si
Authors: Satoko Shinkai Satoko Shinkai , Katsutaka Sasaki Katsutaka Sasaki
Published: October 2002

We have investigated epitaxial growth of HfN film and sequential single-oriented growth of Al/HfN bilayered film on (001) Si and (111) Si. Stoichiometric HfN film was prepared on Si by reactive sputtering using an ultrahigh-vacuum dc magnetron sputtering system. Orientational epitaxy and crystal structure of HfN film deposited on Si were investigated by X-ray pole figure measurement and X-ray diffraction analysis, respectively. Then, Al film was sputter-deposited on the HfN/Si system in the same sputtering chamber without breaking vacuum, and sequential single-oriented growth of Al/HfN bilayered film was examined by X-ray diffraction. It is revealed that the HfN films deposited on Si grow epitaxially with the directional relationships of HfN (001) [110] ∥Si (001) [110] and HfN (111) [002] ∥Si (111) [002], and (100) and (111) Al films also grow in a single-oriented state on epitaxial (001) and (111) HfN films.
Interface Structure of FeCo/Al Oxide/Fe Tunnel Junction
Authors: Lee Changho , Sato Yoshiyuki , Matsui MasaakiDoi
Published: October 2002

The magnetoresistance (MR) effect and interface structure of FeCo/Al Oxide/Fe tunnel
junctions were investigated. The highest value of the measured MR ratio was about 11% at
room temperature, however this value was not reproducible. To clarify the reasons for
nonreproducible characteristics of FeCo/Al Oxide/Fe tunnel junctions, atomic force
microscope (AFM) observation, X-ray photoelectron spectroscopy (XPS) study and
Mössbauer effect measurement have been performed. These results showed that Fe was not
covered with Al entirely and there remained many very small pinholes. Because of these
pinholes and the nonuniformly deposited Al, Fe oxide is formed at the interface. Eventually,
the interface of FeCo/Al Oxide/Fe junction consists of many phases, such as unoxidized Al,
Al2O3, Fe, Fe oxide and Fe3Al. The pinholes and the many phases, such as Fe oxide, Fe3Al, and nonoxidized Al, which
should not exist in an ideal tunnel junction, suppress the appearance
of the MR effect.
Thermal Stability of RuO2 Thin Films and Effects of Annealing Ambient on Their Reduction Process
Authors: Yukinao Kaga Yukinao Kaga , Yoshio Abe Yoshio Abe , Midori Kawamura Midori Kawamura , Katsutaka Sasaki Katsutaka Sasaki
Published: October 2002

RuO2 films prepared by reactive sputtering were annealed in air
and vacuum and the changes of their crystal structure, chemical binding
state and resistivity were studied.
In air, the RuO2 films maintain a rutile structure
below 800°C.
Crystal grain growth was found above 600°C and the minimum
resistivity of 46 µΩcm was obtained at 800°C.
The vacuum annealing was conducted with two types of annealing systems,
one using an oil diffusion pump and the other using a turbomolecular pump
as the main pump.
The RuO2 films annealed in the system using the turbomolecular pump
were not reduced below 500°C, however, the surface of the films
was reduced as low as 200°C in the system using the oil
diffusion pump.
The difference in the reduction processes was examined on the basis of the
thermodynamics of RuO2 and the influence of reducing residual gases in
vacuum.
Simultaneous Measurement of Size and Depth of Each Defect in a Silicon Wafer Using Light Scattering at Two Wavelengths: Principle, Limitation and Applications of Optical Shallow Defect Analyzer
Authors: Takeda Kazuo , Isomae Seiichi , Maeshima MakotoOhkura , ShigeruMatsui ShigeruMatsui
Published: October 2002

To inspect the quality of the silicon wafer surface region where
devices are to be fabricated, an instrument termed optical shallow
defect analyzer (OSDA) was developed [Takeda et al..:
Mater. Res. Soc. Symp. Proc. 442 (1997) 37]. The OSDA can measure the size
and depth of a defect by measuring light scattered from the defect at
two wavelengths having different penetration depths in Si. In this
paper, we describe the validity and the limitation of the method by
using a two-dimensional distribution analysis of the signal
intensities. This analysis clarifies that the detectable defect depth
depends on the defect size. The smaller the defect size is, the
shallower the detectable depth range is. As an application of the
OSDA, crystal originated particles (COPs) induced by thermal oxidation
of Czochralski silicon (CZ-Si) are analyzed. The COPs and the inner
defects are resolved by measurement using OSDA. The COPs are measured
as the defects whose depths are about zero, whose sizes are larger
than grown-in defects, and whose density increases with thermal
oxidation.
C-Terminated Reconstruction and C-Chain Structure on Mo2C(0001) Surface Studied by Low Energy Electron Diffraction and Scanning Tunneling Microscopy
Authors: Lo Rong-Li , Fukui Ken-ichi , Oyama ShigekiOtani , Iwasawa Yasuhiro
Published: October 2002

The structure of an α-Mo2C(0001) surface varies
depending on the annealing temperature. At
least three phases are observed by low energy electron diffraction
(LEED). A well-ordered (√3×√3)R30°
structure was observed on α-Mo2C(0001) at annealing
temperatures below 960 K, which was imaged as a honeycomb structure
by scanning tunneling microscopy (STM). A model
was proposed for the C-terminated structure where C atoms are located
on the threefold hollow
sites of a Mo layer, and each carbon atom is observed as a depression
of the honeycomb structure
by STM. An increase in carbon coverage on the surface transformed the
(√3×√3)R30° structure
to a c(2×4) structure where zigzag rows running parallel to
each other
were observed by STM.
Scanning Tunneling Microscopy Study of Surface Structure and Magnetism of Fe Thin Films Grown on MgO (001)
Authors: Subagyo Agus , Sueoka Kazuhisa , Mukasa Koichi , Hayakawa Kazunobu
Published: October 2002

Substrate preparation procedure dependence of the growth morphology and magnetic
properties of 25 ML bcc-Fe(001) thin films epitaxially grown on MgO(001) substrates in a
wide range of growth temperature was investigated by means of scanning tunneling
microscopy (STM) and superconducting quantum interference device (SQUID). The growth
morphology of Fe thin films was uniform both on a polished and on an annealed substrate, but
nonuniform on a cleaved substrate. It was very difficult to obtain a flat Fe thin film on the
cleaved substrate, and the film became discontinuous at or above a growth temperature of 493 K. At a growth temperature of 550 K, atomically defined terraces of Fe thin films were
formed on the annealed substrate but were not formed on the polished substrate. A continuous
film grown on the annealed substrate at a temperature of 593 K has a less magnetic anisotropy.
The other continuous films have low coercivity of about 8 Oe and a biaxial magnetic
anisotropy. The dependency of the growth morphology and magnetic properties of Fe thin
films upon substrate preparation procedures concerning the presence of step-terraces on the
substrate surface is discussed.
Control of Surface Current on a Si(111) Surface by Using Nanofabrication
Authors: Seiji Heike Seiji Heike , Satoshi Watanabe Satoshi Watanabe , Yasuo Wada Yasuo Wada , Tomihiro Hashizume Tomihiro Hashizume
Published: October 2002

A scanning tunneling microscope (STM) is used to fabricate insulating trenches on a Si(111)-7×7 surface, and these trenches are used to control the current through the surface states.
When the STM tip is moved along the surface with a high current of approximately 100 nA, surface silicon atoms are extracted and a trench pattern is formed.
Tunneling-spectroscopy data indicate that the surface states are eliminated in the trench region.
Because the trench hinders conduction of electrons through the surface states, properly designed trench patterns can regulate the current path near the surface.
By surrounding the surface with the trench, the effects of the Schottky barrier between the surface states and the bulk are observed in the STM images.
The conduction path through the surface states is investigated by fabricating various trench patterns.
Scanning Tunneling Microscopy of Organic Molecules and Monolayers on Silicon and Germanium (001) Surfaces
Authors: Hamers Robert J. , Hovis Jennifer S. , Greenlief C. Michael , Padowitz David F.
Published: October 2002

High-resolution scanning tunneling microscopy has been used to
investigate the adsorption of a variety of unsaturated organic
molecules on the (001) surface of silicon and germanium. Results are
presented for a number of prototypical alkenes, conjugated and
non-conjugated dienes, and aromatic compounds. These include
cyclopentene, 1,5-cyclooctadiene, norbornadiene,
2,3-dimethyl-1,3-butadiene, and benzene on the Si(001) surface, and
for cyclopentene on the Ge(001) surface. Factors controlling the
selectivity of various reaction pathways and the consequences for
preparation of ordered organic overlayers are discussed.
Lateral Conduction Model for Intermolecular Interaction of Self-Assembled Monolayers
Authors: Wataru Mizutani Wataru Mizutani , Takao Ishida Takao Ishida , Hiroshi Tokumoto Hiroshi Tokumoto
Published: October 2002

We investigated binary-component
self-assembled monolayers (SAMs) and
fabricated small domains of a conjugated molecule in
preassembled n-alkanethiol SAM films using an implantation technique.
We measured the height of the domains by scanning tunneling microscopy
and found that, when the size is smaller than ∼5 nm, the observed height
of the conjugated molecular domains depends on their lateral size.
This size dependence of the domain height indicates that the vertical
conductance of the domains should depend on the domain size (number of molecules).
When many molecules are interacting, the molecular orbitals are affected,
which should cause changes in the electron tunneling and conductance.
The degree of the intermolecular interaction was
estimated by introducing an effective conductance between the molecules
using a classical model similar to a resistor network.
Observation of a Polystyrene Surface Modified by Ultrasonic Scratching Using Atomic Force Microscopy
Authors: Iwata Futoshi , Matsumoto Tarou , Ogawa Ryuhei , Sasaki Akira
Published: October 2002

Polymeric materials exhibit complicated microwear properties due to their viscoelasticity. Projections are formed on a polymer surface when scratched with the tip of an atomic force microscope. Ultrasonic scratching which can be realized with the combination of an atomic force microscope and a quartz crystal resonator have been applied for a polystyrene surface for modification without projection formation. The polystyrene surface oscillated laterally by the quartz crystal resonator is scan-scratched with a diamond tip for a progressive cutting force. Scratching parallel to the direction of the surface oscillation is the most effective for cutting the polystyrene surface. No projections are observed on the flat carved surface by ultrasonic scratching. With respect to the local elastic properties, although areas scratched without surface oscillation exhibit increased elasticity at the projections, ultrasonically scratched areas exhibit no change in elasticity. Furthermore, on an area previously modified by ultrasonic scratching, projections are not produced by scratching without surface oscillation.
Feasibility Studies on a Nanometric Oscillator Fabricated by Surface Diffusion for Use as a Force Detector in Scanning Force Microscopy
Authors: Kawakatsu Hideki , Saya Daisuke , deLabachelerie Michel , Hug Hans-J. , Güntherodt Hans-J.
Published: October 2002

A metal ball supported by a nanometric filiform neck, made by
surface diffusion in vacuum, has the potential to be used as an
oscillating force detector in scanning force microscopy. Although in
most cases, the oscillator is extremely fragile and does not survive
the transport from one vacuum chamber to the other, there still
remains the possibility that it can be used if fabricated and
utilized in situ. With the aim of characterizing the oscillator
without breaking the vacuum, we have made a scanning tunneling/force
microscope (STM, SFM) with a heating filament for fabrication of the
oscillator in a scanning electron microscope (SEM). The formation of
the oscillator was observed with the SEM, and then, the tip of the
STM/SFM was used for the application of force to verify its
feasibility as an oscillator.
A Silicon Based Nanometric Oscillator for Scanning Force Microcopy Operating in the 100 MHz Range
Authors: Kawakatsu Hideki , Toshiyoshi Hiroshi , Saya Daisuke , Fujita Hiroyuki
Published: October 2002

The detectable force resolution of a mechanical oscillator used
in scanning force microscopy can be improved by increasing its
natural frequency f
o, quality factor Q, and by
decreasing the spring constant k and the temperature of operation
T. For an oscillator having a structure that can be modeled as a
concentrated mass-spring model, decreasing the mass of the
oscillator is desirable, since high f
o can then be
obtained without increasing the spring constant k. We have
developed a novel fabrication technique for a head-neck shaped
nanometric oscillator by selective etching of a laminated silicon
substrate known as SIMOX. The oscillator head or mass measures
60 nm or 170 nm in thickness and 100 nm to 500 nm in diameter,
depending on the size of the mask. The neck, which serves as an
elastic support for the mass, measures 100 nm in length. The
oscillator could be tailored to have its natural frequency in the
range of 0.01 GHz to 0.5 GHz, and a spring constant between
10-1 N/m and 102 N/m.
Analysis of Phase-Breaking Effects in Triple-Barrier Resonant-Tunneling Diodes
Authors: Nobuya Machida Nobuya Machida , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

We analyze phase-breaking effects in triple-barrier resonant-tunneling diodes (TBRTDs) for estimations of hot-electron phase coherence. The method employed is the nonequilibrium Green's function (NEGF) formalism with a simple phase-breaking model. The NEGF formalism is found to improve a previously reported analysis for TBRTDs with respect to magnitudes of current densities. By comparing results of the present analysis with the experimental data, it is shown that the phase relaxation time is longer than 0.2 ps in GaInAs/InP TBRTD at the resonance level of 50 meV above the first well bottom and 100 meV above the second well bottom and at 4.2 K.
A Traveling-wave Time-division Demultiplexer
Authors: Koichi Narahara Koichi Narahara , Taiichi Otsuji Taiichi Otsuji
Published: October 2002

A novel design methodology is proposed for ultrafast time-division demultiplexers. The circuit consists of three stages: the retiming stage, the AND processing stage and the reshaping stage. None of them has any feedback, so the maximum speed of the circuit is not limited by the loopback delay, unlike the conventional transistor-based demultiplexer (DEMUX). Each circuit is configured in a distributed fashion and operates by managing the induced propagation modes. The authors discuss the design concept, the circuit configuration, an analytical estimation of circuit performance of the proposed DEMUX.
Pt/Ti Thin Film Adhesion on SiNx/Si Substrates
Authors: Kang Unbyoung , Lee Taegon , Young-HoKim Young-HoKim
Published: October 2002

The adhesion of Pt/Ti thin films on SiN
x
/Si substrates with
respect to the substrate pretreatment and annealing ambient was
investigated using the adhesive tape test, the peel test, and the
scratch test. Pt/Ti thin films were deposited a DC magnetron
sputtering system. The in situ Ar+ RF plasma treatment was more effective in enhancing adhesion between the Pt/Ti thin films and
the SiN
x
/Si substrate than chemical cleaning. After annealing in
an oxygen ambient, the adhesion of the Pt/Ti/SiN
x
/Si specimen was
degraded. This adhesion degradation was attributed to the depletion of the Ti adhesion layer due to the formation of the rutile TiO2 phase.
Accurate Thickness Determination of Both Thin SiO2 on Si and Thin Si on SiO2 by Angle-Resolved X-Ray Photoelectron Spectroscopy
Authors: Katayama Toshiharu , Yamamoto Hidekazu , Mashiko MasahikoIkeno , Kawazu Satoru , Umeno Masataka
Published: October 2002

Thicknesses of both ultrathin silicon oxide on silicon substrate and ultrathin silicon on silicon oxide are accurately determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The effective attenuation lengths of Si 2p photoelectrons in silicon oxide, λO, and silicon substrate, λS, are accurately determined by considering the photoelectron yields in both materials, which were obtained experimentally from the damping of intensities of the plasmon-loss peaks therein. Photoelectron yields for silicon oxide and silicon substrate are Y
O =
0.91 and Y
S = 0.74, respectively, and consequently the
relationship between λO and λS is
λO=1.4 λS. The value of
λS is accurately determined from the
silicon-on-insulator (SOI) sample with a thickness of 5 nm to be λS = 2.3 nm and the value of λO is subsequently determined to be 3.2 nm. Finally, the value of λO is confirmed by comparing the oxide thicknesses of SiO2 on Si(100) systems determined by AR-XPS with those determined by ellipsometry.
Single-Electron Devices Formed by Self-Ordering Metal Nanodroplet Arrays on Epitaxial CaF2 Film
Authors: Koji Kawasaki Koji Kawasaki , Marie Mochizuki Marie Mochizuki , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

Single-electron devices using a self-ordering metal nanodroplet array
as multitunneling junctions (MTJ) were fabricated.
The nanodroplet array was fabricated by sequential deposition of Al
and Ga on a epitaxial CaF2 film grown on Si substrate, so that
the Ga/Al droplets were aligned along the CaF2 step edges.
Current-voltage characteristics of an MTJ diode and an MTJ transistor
showed a Coulomb staircase at 55 K and 287 K, respectively.
A large Coulomb gap observed on a source–drain current
indicates that electrons tunnel a large number of nanodroplet arrays.
Plasma and Mode Rotations in a Reversed-Field Pinch Device, TPE-1RM20
Authors: Sakakita Hajime , Yagi Yasuyuki , Hirano Yoichi , Shimada Toshio , Sekine Shigeyuki , Hirota Isao , Maejima Yoshiki , Koguchi Haruhisa , Tariq JavaidBaig Tariq JavaidBaig
Published: October 2002

In a reversed-field pinch (RFP) device, TPE-1RM20, the rotation velocities of impurity
ions and the magnetic modes are studied in connection to their roles on the dynamo activities.
It is observed that the deceleration of the plasma poloidal rotation synchronizes with the
deceleration of both poloidal and toroidal mode rotations at a discrete dynamo event. It is
shown that the plasma poloidal rotation velocity in the case of high-Θ discharges becomes
faster than that in the case of low-Θ discharges (Θ; pinch parameter). The radial electric field
is estimated to be positive around r/a∼0.52 under some assumptions. Measurements reveal
that the plasma poloidal rotation is in the electron diamagnetic direction around r/a∼0.52. This
indicates that the poloidal rotation does not simply depend on E
r×B flow. Through the
present experimental results, some new subjects in the RFP plasma
research are discussed.
New Electrodeless Light Source Excited by a Microwave Immersed in a Uniform Static Magnetic Field
Authors: Rui Zhang Rui Zhang , Yasushi Nishida Yasushi Nishida , Masato Kanno Masato Kanno , Noboru Yugami Noboru Yugami , Tomoyuki Yoshida Tomoyuki Yoshida
Published: October 2002

Low-pressure discharges excited by a microwave (f = 2.45 GHz) supplemented
with a static magnetic field are studied for possible use as new electrodeless
Light sources.
When the magnetic field strength is increased over the range of the electron
cyclotron resonance (ECR), the light intensity emitted from the mercury
lamp is more than 4.6 times that at B = 0 in high-power operation of the
microwave.
In the case of low-power operation of the microwave, the light intensity measured at the ECR point is increased to about three times that at B = 0,
although the total maximum intensity of the emitted light is weaker than that
in high-power case. The mechanism of the increment of light intensity in the
high-power case is discussed with using the model of a helicon wave excitation.
Charge Exchange Ion Energy Distribution at the RF Electrode in a Plasma Etching Chamber
Authors: Mizutani Naoki , Hayashi Toshio
Published: October 2002

Ar ion energy distribution affected by the charge exchange collision in a
sheath was measured by an ion energy analyzer in the rf mode at the rf electrode in a plasma etching chamber.
Dependence of the energy distribution on
Ar gas pressure ranging from 1.4 to 19.3 mTorr was measured. Under high
pressure, an extra peak in addition to the saddle-shaped peaks was observed,
and the energy distribution of the ions in the low-energy region increased.
These experimental features were adequately explained by a simple calculation model. We also calculated
energy distributions of neutrals that were
generated by the charge exchange collision, and suggested the connection of
the high-energy neutrals with the plasma etching process.
Propagation of Femtosecond White-Light Continuum Pulse in Polymer Latex Powder Investigated by Optical Kerr Gate and Time-Resolved Diffuse Reflectance Spectroscopy
Authors: Furube Akihiro , Asahi Tsuyoshi , Masuhara Hiroshi
Published: October 2002

Propagation of a femtosecond white-light continuum pulse
(350 fs) in poly (methyl methacrylate) (PMMA) latex powders with
particle diameters of 1, 5, 20, 60, and 100 µm was investigated
by means of an optical Kerr gate and time-resolved diffuse reflectance
spectroscopy, which is a pump-probe technique for multiple light
scattering materials. The temporal profile of a diffuse reflected light pulse from the powder and the temporal response
of transient absorption of the powder doped with an organic molecule were measured. The
Kubelka-Munk model was extended to address the propagation of a short light pulse, and its
numerical simulations reproduced both experimental results quite well. It is suggested that in
a dense scattering medium such as powder, an effect that light is confined or proceeds in a twisted manner is of importance. Fitting the experimental data with the diffusion theory was
unsuccessful, which is also discussed.
Formation of Artificial Twinning Quartz Plate with x-axis Inversion Area by Laser Beam Irradiation
Authors: Noge Satoru , Uno Takehiko
Published: October 2002

We have previously reported an artificial twinning (x-axis
inversion) technique by thermal treatment for a rotated Y-cut (RY-cut)
quartz plate. However, it is impossible to form an arbitrary x-axis
inversion pattern on a quartz plate using this technique. If the
x-axis inversion pattern is artificially controlled, it is possible to
produce new piezoelectric and/or optical devices. Twinning phenomenon
is induced as follows. A metal film (i.e., Cr or NiCr) is deposited on
the top surface of a rotated Y-cut quartz plate. Thermal treatment of
the plate at about 520–540°C produces x-axis inversion of
the quartz under the metal film. The x-axis inversion occurs due to
stress that results from the difference in the thermal expansion
between the quartz plate and the metal film. This paper presents a new
twinning technique using laser scanning that has the potential to form
an arbitrary twinning pattern. A quartz plate is placed on a movable
stage in a vacuum chamber. On the plate surface, a metal film is
deposited and the plate is heated at around 200–500°C. A laser
beam is irradiated onto the plate. The metal film on the quartz plate
absorbs the light energy and the plate is locally heated. This causes
strong mechanical strain and twinning occurs around the irradiated
area. As a result, a twinning area with an arbitrary pattern can be
produced by scanning the laser spot along the metal film deposited on
a RY-cut quartz plate. It was clarified that temperature gradient in
the quartz plate is an important factor for twinning. Large
temperature gradient produced in the plate by the laser beam
irradiation drastically reduces the treatment temperature.
Silicon Plate Thickness Measurement System Using Near-Infrared Optical Interferometry
Authors: Fujimoto Hiroyuki
Published: October 2002

A simple, noncontact silicon plate thickness measurement system that uses
infrared interferometry was demonstrated. Its applicability to samples with various
surface conditions was examined.